The system is comprised of a projector and a high speed optical axis controller with high speed vision and mirrors.
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The rear screen is interesting: The 3.2-inch display use a mechanism that allows it to be viewed at different angles while always sitting on the lens' optical axis.
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The tilting screen design in particular stands out as unique, with a twisting mechanism that allows the 3.2-inch panel to be viewed at various angles while remaining on the lens' optical axis, and the screen also has a light on the rear so the camera's buttons can be seen in dark conditions.
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Optical axis gratings (OAGs) are gratings of optical axis of a birefringent material. In OAGs, the birefringence of the material is constant, while the direction of optical axis is periodically modulated in a fixed direction. In this way they are different from the regular phase gratings, in which the refractive index is modulated and the direction of the optical axis is constant. The optical axis in OAGs can be modulated in either transverse or the longitudinal direction, which causes it to act as a diffractive or a reflective component.
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In afocal systems an object ray parallel to the optical axis is conjugate to an image ray parallel to the optical axis. Such systems have no focal points (hence afocal) and also lack principal and nodal points. The system is focal if an object ray parallel to the axis is conjugate to an image ray that intersects the optical axis. The intersection of the image ray with the optical axis is the focal point F' in image space.
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Megaw H. D. (1952). The structure of afwillite. Acta Crystallographica, 5, 477. It is biaxial and its 2V angle, the measurement from one optical axis to the other optical axis, is 50 – 56 degrees.
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In fluid imaging particle analysis systems, the liquid is passed across the optical axis by use of a narrow flow cell as shown at right. Diagram showing the flow cell cross- section perpendicular to the optical axis in a dynamic imaging particle analyzer. Credit: Fluid Imaging Technologies, Inc.The flow cell is characterized by its depth perpendicular to the optical axis, as shown in the second diagram on right.
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Optical axis (coincides with red ray) and rays symmetrical to optical axis (pair of blue and pair of green rays) propagating through different lenses. An optical axis is a line along which there is some degree of rotational symmetry in an optical system such as a camera lens or microscope. The optical axis is an imaginary line that defines the path along which light propagates through the system, up to first approximation. For a system composed of simple lenses and mirrors, the axis passes through the center of curvature of each surface, and coincides with the axis of rotational symmetry.
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The optical axis is often coincident with the system's mechanical axis, but not always, as in the case of off-axis optical systems. For an optical fiber, the optical axis is along the center of the fiber core, and is also known as the fiber axis.
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The image location and size can also be found by graphical ray tracing, as illustrated in the figures above. A ray drawn from the top of the object to the mirror surface vertex (where the optical axis meets the mirror) will form an angle with the optical axis. The reflected ray has the same angle to the axis, but on the opposite side (See Specular reflection). A second ray can be drawn from the top of the object, parallel to the optical axis.
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The addition of a flat secondary mirror at 45° to the optical axis of the Schmidt design creates a Schmidt- Newtonian telescope.
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The orthocenter of the triangle with vertices in the three vanishing points is the intersection of the optical axis and the image plane.
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In standard FBGs, the grading or variation of the refractive index is along the length of the fiber (the optical axis), and is typically uniform across the width of the fiber. In a tilted FBG (TFBG), the variation of the refractive index is at an angle to the optical axis. The angle of tilt in a TFBG has an effect on the reflected wavelength, and bandwidth.
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An optical system is rotationally symmetric if its imaging properties are unchanged by any rotation about some axis. This (unique) axis of rotational symmetry is the optical axis of the system. Optical systems can be folded using plane mirrors; the system is still considered to be rotationally symmetric if it possesses rotational symmetry when unfolded. Any point on the optical axis (in any space) is an axial point.
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In optics, image/optical distortion is a divergence from rectilinear projection caused by a change in magnification with increasing distance from the optical axis of an optical system.
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If the pupil is centered on optical axis, it causes positive chromostereopsis. However, if the pupil is significantly off-center from the optical axis, negative chromostereopsis will ensue. Because most people have a point of maximum luminous efficiency that is off-center, the Stiles-Crawford Effects generally will have antagonistic chromostereoptic effects. Therefore, instead of seeing red in front of blue, blue will be seen in front of red and the effect will be reversed.
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In the Sénarmont prism the s-polarized ray (i.e., the ray with polarization direction perpendicular to the plane in which all rays are contained, called the plane of incidence) passes through without being deflected, while the p-polarized ray (with polarization direction in the plane of incidence) is deflected (refracted) at the internal interface into a different direction. Both rays correspond to ordinary rays (o-rays) in the first component prism, since both polarization directions are perpendicular to the optical axis, which is the propagation direction. In the second component prism the s-polarized ray remains ordinary (o-ray, polarized perpendicular to the optical axis), while the p-polarized ray becomes extraordinary (e-ray), with a polarization component along the optical axis.
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Light propagating in the direction of the optical axis will not be affected by the birefringence since the refractive index will be no independent of polarization. For other propagation directions the light will split into two linearly polarized beams. For light traveling perpendicularly to the optical axis the beams will have the same direction. This can be used to change the polarization direction of linearly polarized light or to convert between linear, circular and elliptical polarizations with waveplates.
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There are several designs that try to avoid obstructing the incoming light by eliminating the secondary or moving any secondary element off the primary mirror's optical axis, commonly called off-axis optical systems.
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OI can be created on any microscope by placing a piece of paper under one corner of the mount so that the plane-of- polish is no longer perpendicular to the optical axis.
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Acceptance angle The "acceptance angle" figure illustrates this concept. The concentrator is a lens with a receiver R. The left section of the figure shows a set of parallel rays incident on the concentrator at an angle α < θ to the optical axis. All rays end up on the receiver and, therefore, all light is captured. In the center, this figure shows another set of parallel rays, now incident on the concentrator at an angle α = θ to the optical axis.
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When looking at a point that is not perfectly aligned with the optical axis, some of the incoming light from that point will strike the mirror at an angle. This causes an image that is not in the center of the field to appear as wedge-shaped. The further off-axis (or the greater the angle subtended by the point with the optical axis), the worse this effect is. This causes stars to appear to have a cometary coma, hence the name.
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The plane in which an image produced by an optical system is formed; if the object plane is perpendicular to the optical axis, the image plane will ordinarily also be perpendicular to the axis.
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Focal systems also have an axial object point F such that any ray through F is conjugate to an image ray parallel to the optical axis. F is the object space focal point of the system.
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In Nikon and Canon's implementation, it works by using a floating lens element that is moved orthogonally to the optical axis of the lens using electromagnets.What is Optical Image Stabilizer? , Technology FAQ, Canon Broadcast Equipment Vibration is detected using two piezoelectric angular velocity sensors (often called gyroscopic sensors), one to detect horizontal movement and the other to detect vertical movement.Glossary : Optical : Image Stabilization, Vincent Bockaert, Digital Photography Review As a result, this kind of image stabilizer corrects only for pitch and yaw axis rotations, and cannot correct for rotation around the optical axis.
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"Collimation" refers to all the optical elements in an instrument being on their designed optical axis. It also refers to the process of adjusting an optical instrument so that all its elements are on that designed axis (in line and parallel). With regards to a telescope, the term refers to the fact that the optical axis of each optical component should be centered and parallel, so that collimated light emerges from the eyepiece. Most amateur reflector telescopes need to be re-collimated every few years to maintain optimum performance.
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Optical axis gratings can be implemented in various materials, including liquid crystals, polymers, birefringent crystals, magnetic crystals and subwavelength gratings. This new type of grating has broad potential in imaging, liquid crystal display, communication, and numerous military applications.
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A ray that goes from the top of the object through the focal point can be considered instead. Such a ray reflects parallel to the optical axis and also passes through the image point corresponding to the top of the object.
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Kepler space observatory is curved to compensate for the telescope's Petzval curvature. Consider an "ideal" single-element lens system for which all planar wave fronts are focused to a point at distance f from the lens. Placing this lens the distance f from a flat image sensor, image points near the optical axis will be in perfect focus, but rays off axis will come into focus before the image sensor, dropping off by the cosine of the angle they make with the optical axis. This is less of a problem when the imaging surface is spherical, as in the human eye.
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The lens's optical axis sweeps in the plane of the nominal X and Y axes around the nominal optical Z axis, pivoting on the optical convergence point (out along the Z axis), so that it passes through positions having parallax in relation to the optical convergence point. The circular scanning of the lens's optical axis traces out a coaxial cone pattern with the convergence point as its apex. Early tests revealed that the brain will translate parallax scanned information into depth information at scanning frequencies of between 3–6 Hz, and that the ideal frequency is 4.31 Hz.
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Toroidal mirrors are used in Yolo telescopes and optical monochromators. In these devices, the source and detectors of the light are not located on the optical axis of the mirror, so the use of a true paraboloid of revolution would cause a distorted image.
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The front focal point of an optical system, by definition, has the property that any ray that passes through it will emerge from the system parallel to the optical axis. The rear (or back) focal point of the system has the reverse property: rays that enter the system parallel to the optical axis are focused such that they pass through the rear focal point. Rays that leave the object with the same angle cross at the back focal plane. The front and rear (or back) focal planes are defined as the planes, perpendicular to the optic axis, which pass through the front and rear focal points.
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An incident laser beam is deflected by grooved diffraction pattern into axial diffraction orders along its optical axis. The foci appear around the far field position. With an additional focusing lens, foci from multifocal lens will appear at certain distances from the focal point of the lens.
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Spherical aberration. A perfect lens (top) focuses all incoming rays to a point on the Optical axis. In spherical aberration (Bottom) peripheral rays are focused more tightly than central rays. There are numerous higher-order aberrations, of which only spherical aberration, coma and trefoil are of clinical interest.
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Securing the lens to the optical axis and transferring forces from the ciliary muscle in accommodation. When colour granules are displaced from the zonules of Zinn, caused by friction of the lens, the iris can slowly fade. These colour granules can clog the channels and lead to glaucoma pigmentosa.
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Planes that include the optical axis are meridional planes. It is common to simplify problems in radially-symmetric optical systems by choosing object points in the vertical ("y") plane only. This plane is then sometimes referred to as the meridional plane. The second special plane is the sagittal plane.
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A spherical lens has the same curvature in every direction perpendicular to the optical axis. Spherical lenses are adequate correction when a person has no astigmatism. To correct for astigmatism, the "cylinder" and "axis" components specify how a particular lens is different from a lens composed of purely spherical surfaces.
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Like the Wollaston prism, the Nomarski prism consists of two birefringent crystal wedges (e.g. quartz or calcite) cemented together at the hypotenuse (e.g. with Canada balsam). One of the wedges is identical to a conventional Wollaston wedge and has the optical axis oriented parallel to the surface of the prism.
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The paraxial approximation assumes that rays travel at shallow angles with respect to the optical axis, so that \sin\theta\approx\theta and \cos\theta\approx 1. Aperture effects are ignored: rays that do not pass through the aperture stop of the system are not considered in the discussion below.
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The Optical Unit is a dimensionless units of length used in optical microscopy. Because every diffraction limited system have their resolution proportional to wavelength / NA, it is convenient for comparison to use this unit. There are actually 2 units, one "axial" (along the optical axis of the objective) and one "radial".
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In astronomy, the term cophasing or phasing describes the process of controlling the individual segments in a segmented mirror or a telescope so that the segments form a larger composite mirroring surface. Cophasing implies precise, active control of three degrees of freedom of each individual segment mirror: translation along the optical axis (piston) and rotation about two axes perpendicular to the optical axis (tip-tilt). Each segment of the segmented telescope is a solid body having 6 degrees of freedom exposed to the gravitation force, wind blowing, and other mechanical forces. If the position of each segment is not controlled the resolution of the whole telescope will be the same as if telescope had the diameter equal to the size of one segment.
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Rotational symmetry greatly simplifies the analysis of optical systems, which otherwise must be analyzed in three dimensions. Rotational symmetry allows the system to be analyzed by considering only rays confined to a single transverse plane containing the optical axis. Such a plane is called a meridional plane; it is a cross-section through the system.
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Part 602 describes this type of non- contact profilometer, incorporating a single point white light chromatic confocal sensor. The operating principle is based upon the chromatic dispersion of the white light source along the optical axis, via a confocal device, and the detection of the wavelength that is focused on the surface by a spectrometer.
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A photograph of Christmas lights with significant defocus aberration. In optics, defocus is the aberration in which an image is simply out of focus. This aberration is familiar to anyone who has used a camera, videocamera, microscope, telescope, or binoculars. Optically, defocus refers to a translation of the focus along the optical axis away from the detection surface.
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The Rochon and Sénarmont prisms are similar, but use different optical axis orientations in the two prisms. The Sénarmont prism is air spaced, unlike the Wollaston and Rochon prisms. These prisms truly split the beam into two fully polarized beams with perpendicular polarizations. The Nomarski prism is a variant of the Wollaston prism, which is widely used in differential interference contrast microscopy.
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Visual astigmatism (not optical)There are two distinct forms of astigmatism. The first is a third-order aberration, which occurs for objects (or parts of objects) away from the optical axis. This form of aberration occurs even when the optical system is perfectly symmetrical. This is often referred to as a "monochromatic aberration", because it occurs even for light of a single wavelength.
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This plane often represents the best compromise image location in a system with astigmatism. The amount of aberration due to astigmatism is proportional to the square of the angle between the rays from the object and the optical axis of the system. With care, an optical system can be designed to reduce or eliminate astigmatism. Such systems are called anastigmats.
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Esprit 80ED, 100ED, 120ED and 150ED Super APO refractors have a doublet field flattener to get a flat field and minimize aberration and distortion. Their wide 48mm opener ensures a larger and clearer aperture and also extremely minimized halation. Connect the triplet and doublet field flattener with a high precision thin thread to keep the optical axis perpendicular to the image.
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A spring-loaded pressure plate functions to align the film in a consistent image plane, both flat and perpendicular to the optical axis. It also provides sufficient drag to prevent film motion during the frame display, while still allowing free motion under control of the intermittent mechanism. The plate also has spring-loaded runners to help hold film while in place and advance it during motion.
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An example of a transverse OAG, the so-called cycloidal OAG, is shown in Fig. 1. The optical axis in this grating is monotonously modulated in transverse direction. This grating is capable of diffracting all incident light into either +1st or −1st order in a micrometer-thick layer . The cycloidal OAGs have already been proven to be very efficient in beam steering and optical switching.
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In another type of OAG, the optical axis is modulated in the direction of light propagation (Fig. 2) with a modulation period equal to a fraction of the wavelength (200-3000 nm). This modulation prevents these frequencies from propagating within the grating, acting as a band-stop filter. As a result, any light with frequency within the matching range will be reflected from the OAG.
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Anisotropic crystals will have optical properties that vary with the direction of light. The direction of the electric field determines the polarization of light, and crystals will respond in different ways if this angle is changed. These kinds of crystals have one or two optical axes. If absorption of light varies with the angle relative to the optical axis in a crystal then pleochroism results.
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The second wedge of the prism is modified by cutting the crystal so that the optical axis is oriented obliquely with respect to the flat surface of the prism. The Nomarski modification causes the light rays to come to a focal point outside the body of the prism, and allows greater flexibility so that when setting up the microscope the prism can be actively focused.
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Good depth of focus requires diffracted light traveling at comparable angles with the optical axis, and this requires the appropriate illumination angle.H. J. Levinson, Principles of Lithography (2nd ed.), 2005, pp. 274-276. Assuming the correct illumination angle, OPC can direct more diffracted light along the right angles for a given pitch, but without the correct illumination angle, such angles will not even arise.
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The cardinal points of a thick lens in air. F, F' front and rear focal points, P, P' front and rear principal points, V, V' front and rear surface vertices. The cardinal points lie on the optical axis of the optical system. Each point is defined by the effect the optical system has on rays that pass through that point, in the paraxial approximation.
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For a thin lens in air, the principal planes both lie at the location of the lens. The point where they cross the optical axis is sometimes misleadingly called the optical centre of the lens. Note, however, that for a real lens the principal planes do not necessarily pass through the centre of the lens, and in general may not lie inside the lens at all.
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For an ideal concentrator, all rays are still captured. However, on the right, this figure shows yet another set of parallel rays, now incident on the concentrator at an angle α > θ to the optical axis. All rays now miss the receiver and all light is lost. Therefore, for incidence angles α < θ all light is captured while for incidence angles α > θ all light is lost.
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A Wollaston prism A Wollaston prism is an optical device, invented by William Hyde Wollaston, that manipulates polarized light. It separates light into two separate linearly polarized outgoing beams with orthogonal polarization. The two beams will be polarized according to the optical axis of the two right angle prisms. The Wollaston prism consists of two orthogonal prisms of birefringent material—typically a uniaxial material such as calcite.
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This is defined as the plane, orthogonal to the tangential plane, which contains the object point being considered and intersects the optical axis at the entrance pupil of the optical system. This plane contains the chief ray, but does not contain the optic axis. It is therefore a skew plane, in other words not a meridional plane. Rays propagating in this plane are called sagittal rays.
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It was ESRO's first 3-axis stabilized satellite, with one axis pointing to the Sun to within ±5°. The optical axis was maintained perpendicular to the solar pointing axis and to the orbital plane. It scanned the entire celestial sphere every 6 months, with a great circle being scanned every satellite revolution. After about 2 months of operation, both of the satellite's tape recorders failed.
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Schematic diagram of the human eye The binocular nature of the chromostereopsis was discovered by Bruecke and arises due to the position of the fovea relative to the optical axis. The fovea is located temporally to the optical axis and as a result, the visual axis passes through the cornea with a nasal horizontal eccentricity, meaning that the average ray bound for the fovea must undergo prismatic deviation and is thus subject to chromatic dispersion. The prismatic deviation is in opposite directions in each eye, resulting in opposite color shifts that lead to a shift in stereoptic depth between red and blue objects. The eccentric foveal receptive system, along with the Stiles-Crawford effect, work in opposite directions of one another and roughly cancel out, offering another explanation to why subjects may show color stereoscopy "against the rule" (a reversal of the expected results).
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The error associated with the paraxial approximation. In this plot the cosine is approximated by . In geometric optics, the paraxial approximation is a small-angle approximation used in Gaussian optics and ray tracing of light through an optical system (such as a lens). A paraxial ray is a ray which makes a small angle (θ) to the optical axis of the system, and lies close to the axis throughout the system.
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Field curvature: the image "plane" (the arc) deviates from a flat surface (the vertical line). Petzval field curvature, named for Joseph Petzval, describes the optical aberration in which a flat object normal to the optical axis (or a non-flat object past the hyperfocal distance) cannot be brought properly into focus on a flat image plane. It is not to be confused with flat-field correction, which refers to brightness uniformity.
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This ray is reflected by the mirror and passes through its focal point. The point at which these two rays meet is the image point corresponding to the top of the object. Its distance from the optical axis defines the height of the image, and its location along the axis is the image location. The mirror equation and magnification equation can be derived geometrically by considering these two rays.
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In the simplest form, uniaxial birefringence, there is only one special direction in the material. This axis is known as the optical axis of the material. Light with linear polarization perpendicular to this axis will experience an ordinary refractive index no while light polarized in parallel will experience an extraordinary refractive index ne. The birefringence of the material is the difference between these indices of refraction, Δn = ne − no.
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The Pentax K-1 is the first production Pentax full-frame digital SLR camera. As the flagship model of the Pentax K-mount system, it includes several new and improved features, including a five-axis SR II in-body image stabilization system, newly designed flexible tilt articulating screen mounted on four metal struts allowing for rotation about the optical axis in addition to upward and downward tilt, and improved autofocus and metering systems.
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It is however important to consider when mapping cliffs. Ideally aerial photographs are taken so the optical axis of the camera is perfectly perpendicular to the ground surface, thereby creating a vertical photograph. Unfortunately this is often not the case and virtually all aerial photographs experience tilt up to 3°. In this situation the scale of the image is larger on the upward side of the tilt axis and smaller on the downward side.
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The focus of the first lens is traditionally about 2mm away from the plane face coinciding with the sample plane. A pinhole cap can be used to align the optical axis of the condenser with that of the microscope. The Abbe condenser is still the basis for most modern light microscope condenser designs, even though its optical performance is poor.Royal Microscopical Society,"Journal of the Royal Microscopical Society", Williams and Norgate, London (1882), p.
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The principal points are the points where the principal planes cross the optical axis. If the medium surrounding the optical system has a refractive index of 1 (e.g., air or vacuum), then the distance from the principal planes to their corresponding focal points is just the focal length of the system. In the more general case, the distance to the foci is the focal length multiplied by the index of refraction of the medium.
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The surface vertices are the points where each optical surface crosses the optical axis. They are important primarily because they are the physically measurable parameters for the position of the optical elements, and so the positions of the cardinal points must be known with respect to the vertices to describe the physical system. In anatomy, the surface vertices of the eye's lens are called the anterior and posterior poles of the lens.
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The image's handedness is not changed by the Schmidt-Pechan. The design of the two prisms is such that the entrance beam and exit beam are coaxial, i.e. the Schmidt–Pechan prism does not deviate the beam if centered on the optical axis. The "roof" section of the upper prism flips (reverts) the image laterally with two total internal reflections in the horizontal plane from the roof surface: once on each side of the roof.
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Rays that move closer to the optical axis as they propagate are said to be converging, while rays that move away from the axis are diverging. These imaginary rays are always perpendicular to the wavefront of the light, thus the vergence of the light is directly related to the radii of curvature of the wavefronts. A convex lens or concave mirror will cause parallel rays to focus, converging toward a point. Beyond that focal point, the rays diverge.
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A second polarization controller is similarly used to control the polarization of the light passing through the reference path. The output of the fiber on the right is collimated using lens L1 and illuminates the tissue. But because the delivery fiber is offset from the optical axis of the lens, the beam is delivered to the sample at an oblique angle. Backscattered light is then collimated by the same lens and collected by the fiber bundle.
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A Glan–Foucault prism deflects p-polarized light, transmitting the s-polarized component. The optical axis of the prism material is perpendicular to the plane of the diagram. A Glan–Foucault prism (also called a Glan–air prism) is a type of prism which is used as a polarizer. It is similar in construction to a Glan–Thompson prism, except that two right-angled calcite prisms are spaced with an air gap instead of being cemented together.
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The telescope converts a bundle of parallel rays to make an angle α, with the optical axis to a second parallel bundle with angle β. The ratio β/α is called the angular magnification. It equals the ratio between the retinal image sizes obtained with and without the telescope.Stephen G. Lipson, Ariel Lipson, Henry Lipson, Optical Physics 4th Edition, Cambridge University Press, Refracting telescopes can come in many different configurations to correct for image orientation and types of aberration.
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Original holographic scheme by Dennis Gabor is inline scheme, which means that reference and object wave share the same optical axis. This scheme is also called point projection holography. An object is placed into divergent electron beam, part of the wave is scattered by the object (object wave) and it interferes with the unscattered wave (reference wave) in detector plane. The spatial coherence in in-line scheme is defined by the size of the electron source.
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Binocular stereo vision method requires two identical cameras with parallel optical axis to observe one same object, acquiring two images from different points of view. In terms of trigonometry relations, depth information can be calculated from disparity. Binocular stereo vision method is well developed and stably contributes to favorable 3D reconstruction, leading to a better performance when compared to other 3D construction. Unfortunately, it is computationally intensive, besides it performs rather poorly when baseline distance is large.
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Fig. 3a: Barrel distortion Fig. 3b: Pincushion distortion Even if the image is sharp, it may be distorted compared to ideal pinhole projection. In pinhole projection, the magnification of an object is inversely proportional to its distance to the camera along the optical axis so that a camera pointing directly at a flat surface reproduces that flat surface. Distortion can be thought of as stretching the image non-uniformly, or, equivalently, as a variation in magnification across the field.
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An optic axis of a crystal is a direction in which a ray of transmitted light suffers no birefringence (double refraction). An optical axis is a direction rather than a single line: all rays that are parallel to that direction exhibit the same lack of birefringence. Crystals may have a single optic axis, in which case they are uniaxial, or two different optic axes, in which case they are biaxial. Non-crystalline materials generally have no birefringence and thus, no optic axis.
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In some applications it is important to achieve a given irradiance (or illuminance) pattern on a target, while allowing for movements or inhomogeneities of the source. Figure "Köhler integrator" on the right illustrates this for the particular case of solar concentration. Here the light source is the sun moving in the sky. On the left this figure shows a lens L1 L2 capturing sunlight incident at an angle α to the optical axis and concentrating it onto a receiver L3 L4.
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The image recorded by a photographic film or image sensor is always a real image and is usually inverted. When measuring the height of an inverted image using the cartesian sign convention (where the x-axis is the optical axis) the value for hi will be negative, and as a result M will also be negative. However, the traditional sign convention used in photography is "real is positive, virtual is negative". Therefore, in photography: Object height and distance are always real and positive.
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The cross-section through the optical axis shows the grooves that limit the aberration. A Coddington magnifier is a magnifying glass consisting of a single very thick lens with a central deep groove diaphragm at the equator, thus limiting the rays to those close to the axis, which minimizes spherical aberration. This allows for greater magnification than a conventional magnifying glass, typically 10× up to 20×. Most single lens magnifiers are limited to 5× or so before significant distortion occurs.
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Coma is an inherent property of telescopes using parabolic mirrors. Unlike a spherical mirror, a bundle of parallel rays parallel to the optical axis will be perfectly focused to a point (the mirror is free of spherical aberration), no matter where they strike the mirror. However, this is only true if the rays are parallel to the axis of the parabola. When the incoming rays strike the mirror at an angle, individual rays are not reflected to the same point.
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This terminology may be misleading, however, as the amount of aberration can vary strongly with wavelength in an optical system. The second form of astigmatism occurs when the optical system is not symmetric about the optical axis. This may be by design (as in the case of a cylindrical lens), or due to manufacturing error in the surfaces of the components or misalignment of the components. In this case, astigmatism is observed even for rays from on-axis object points.
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The mounted lenses were centered in such a way that the axis of rotation of the machine and the optical axis of the lenses matched exactly. Thus, the lens frames could be reworked with highest accuracy and then arranged in tubes of precise interior diameter. Parallel to the MKF-6, a multispectral projector, the MSP-4 was developed. With it, several spectral images, on top of each other and under various filters can be projected on a screen or photographic film.
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This CLSM design combined the laser scanning method with the 3D detection of biological objects labeled with fluorescent markers for the first time. In 1978 and 1980, the Oxford-group around Colin Sheppard and Tony Wilson described a confocal microscope with epi-laser-illumination, stage scanning and photomultiplier tubes as detectors. The stage could move along the optical axis (z-axis), allowing optical serial sections. In 1979 Fred Brakenhoff and coworkers demonstrated that the theoretical advantages of optical sectioning and resolution improvement are indeed achievable in practice.
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Other arrangements involve the laser passing at 90° with respect to the optical axis. Detection angles of 90° and 0° are less frequently used. The collected scattered radiation is focused into a spectrograph, in which the light is first collimated and then dispersed by a diffraction grating and refocused onto a CCD camera. The entire spectrum is recorded simultaneously and multiple scans can be acquired in a short period of time, which can increase the signal-to-noise ratio of the spectrum through averaging.
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The event location, energy, and depth of interaction in the detector are computed from the nine- pixel signals. The focal planes are shielded by cesium iodide (CsI) crystals that surround the detector housings. The crystal shields, grown by Saint- Gobain, register high energy photons and cosmic rays which cross the focal plane from directions other than the along the NuSTAR optical axis. Such events are the primary background for NuSTAR and must be properly identified and subtracted in order to identify high energy photons from cosmic sources.
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Item #6. Panoramic photographers often incorrectly refer to the entrance pupil as a nodal point, which is a different concept. Depending on the lens design, the entrance pupil location on the optical axis may be behind, within or in front of the lens system; and even at infinite distance from the lens in the case of telecentric systems. In photography, the size of the entrance pupil (rather than the size of the physical aperture itself) is used to calibrate the opening and closing of the diaphragm aperture.
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The f-number ("relative aperture"), N, is defined by N = f/EN, where f is the focal length and EN is the diameter of the entrance pupil. p.49 Increasing the focal length of a lens (i.e., zooming in) will usually cause the f-number to increase, and the entrance pupil location to move further back along the optical axis. The entrance pupil of the human eye, which is not quite the same as the physical pupil, is typically about 4 mm in diameter.
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The Pfund telescope, originated by A.H. Pfund, provides an alternative method for achieving a fixed telescope focal point in space regardless of where the telescope line of sight is pointed. Pfund's configuration uses a two-axis flat feed mirror that reflects starlight into a fixed paraboloidal mirror, usually with a horizontal optical axis. The paraboloid focuses through a central hole in the feed flat to a convenient location some distance behind the flat. No spider vanes or Newtonian secondary fold mirrors are required in this configuration.
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This can be tested by aligning the tubular spirit bubble parallel to a line between two footscrews and setting the bubble central. A horizontal axis error is present if the bubble runs off central when the tubular spirit bubble is reversed (turned through 180°). To adjust, the operator removes half the amount the bubble has run off using the adjusting screw, then re-level, test and refine the adjustment. ; Collimation error: The optical axis of the telescope, must also be perpendicular to the horizontal axis.
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Since these systems can be made from any standard optical microscope, they may be a lower cost approach for people who already have microscopes. More important, though, is that microscope-based systems have less depth of field issues generally versus dynamic imaging systems. This is because the sample is placed on a microscope slide, and then usually covered with a cover slip, thus limiting the plane containing the particles relative to the optical axis. This means that more particles will be in acceptable focus at high magnifications.
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Gaussian optics is a technique in geometrical optics that describes the behaviour of light rays in optical systems by using the paraxial approximation, in which only rays which make small angles with the optical axis of the system are considered.A. Lipson, S.G. Lipson, H. Lipson, Optical Physics, 4th edition, 2010, University Press, Cambridge, UK, p. 51. In this approximation, trigonometric functions can be expressed as linear functions of the angles. Gaussian optics applies to systems in which all the optical surfaces are either flat or are portions of a sphere.
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Standard ellipsometry (or just short 'ellipsometry') is applied, when no s polarized light is converted into p polarized light nor vice versa. This is the case for optically isotropic samples, for instance, amorphous materials or crystalline materials with a cubic crystal structure. Standard ellipsometry is also sufficient for optically uniaxial samples in the special case, when the optical axis is aligned parallel to the surface normal. In all other cases, when s polarized light is converted into p polarized light and/or vice versa, the generalized ellipsometry approach must be applied.
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Coma, or comatic aberration, derives its name from the comet-like appearance of the aberrated image. Coma occurs when an object off the optical axis of the lens is imaged, where rays pass through the lens at an angle to the axis θ. Rays that pass through the centre of a lens of focal length f are focused at a point with distance from the axis. Rays passing through the outer margins of the lens are focused at different points, either further from the axis (positive coma) or closer to the axis (negative coma).
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The emission light is either detected from one side only or in an incoherent superposition from both sides. In a 4Pi microscope of type B, only the emission light is interfering. When operated in the type C mode, both excitation and emission light are allowed to interfere, leading to the highest possible resolution increase (~7-fold along the optical axis as compared to confocal microscopy). In a real 4Pi microscope light cannot be applied or collected from all directions equally, leading to so-called side lobes in the point spread function.
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133–136; , Theorem 10.3, p. 149. A more general fact is that every simple closed space curve which lies on the boundary of a convex body, or even bounds a locally convex disk, must have four vertices.; If a planar curve is bilaterally symmetric, it will have a vertex at the point or points where the axis of symmetry crosses the curve. Thus, the notion of a vertex for a curve is closely related to that of an optical vertex, the point where an optical axis crosses a lens surface.
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Although scattered light leaves the sample in all directions the collection of the scattered light is achieved only over a relatively small solid angle by a lens and directed to the spectrograph and CCD detector. The laser beam can be at any angle with respect to the optical axis used to collect Raman scattering. In free space systems, the laser path is typically at an angle of 180° or 135° (a so-called back scattering arrangement). The 180° arrangement is typically used in microscopes and fiber optic based Raman probes.
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It has a density of 2.6. Dickite is biaxial, its birefringence is between 0.0050-0.0090, its surface relief is low and it has no dispersion. The plane of the optical axis is normal to the plane of symmetry and inclined 160, rear to the normal to (0,0,1). The atomic structure of dickite, being very similar to that of kaolinite and other kaolin type minerals, has a very specific arrangement that differs slightly enough to set its physical appearance and other physical properties apart from that of its family members kaolinite and nacrite.
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However, very good results can be obtained only with a flash unit that is separated from the camera, sufficiently far from the optical axis, or by using bounce flash, where the flash head is angled to bounce light off a wall, ceiling or reflector. On some cameras the flash exposure measuring logic fires a pre-flash very quickly before the real flash. In some camera/people combinations this will lead to shut eyes in every picture taken. The blink response time seems to be around 1/10 of a second.
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As in ABI an additional signal coming from Ultra-small-angle scattering by sub-pixel microstructures of the sample, called dark-field contrast, can also be reconstructed. This method provides high spatial resolution, but also requires long exposure times. An alternative approach is the retrieval of the differential phase by using Moiré fringes. These are created as a superposition of the self-image of G1 and the pattern of G2 by using gratings with the same periodicity and inclining G2 against G1 regarding to the optical axis with a very small angle(<<1).
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An object infinitely far from the optical system forms an image at the rear focal plane. For objects a finite distance away, the image is formed at a different location, but rays that leave the object parallel to one another cross at the rear focal plane. Angle filtering with an aperture at the rear focal plane. A diaphragm or "stop" at the rear focal plane can be used to filter rays by angle, since: #It only allows rays to pass that are emitted at an angle (relative to the optical axis) that is sufficiently small.
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N, N' The front and rear nodal points of a thick lens. The front and rear nodal points have the property that a ray aimed at one of them will be refracted by the lens such that it appears to have come from the other, and with the same angle with respect to the optical axis. (Angular magnification between nodal points is +1.) The nodal points therefore do for angles what the principal planes do for transverse distance. If the medium on both sides of the optical system is the same (e.g.
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An ideal, rotationally symmetric, optical imaging system must meet three criteria: #All rays "originating" from any object point converge to a single image point (Imaging is stigmatic). #Object planes perpendicular to the optical axis are conjugate to image planes perpendicular to the axis. #The image of an object confined to a plane normal to the axis is geometrically similar to the object. In some optical systems imaging is stigmatic for one or perhaps a few object points, but to be an ideal system imaging must be stigmatic for every object point.
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The spherical secondary can be fringe tested against a spherical concave surface or tested from behind. This is markedly an advantage over the hyperbolic secondary of the Ritchey-Chrétien design. Another advantage of either the basic Dall-Kirkham or the Modified Dall-Kirkham design is that collimation of the convex spherical secondary mirror with respect to the optical axis of the primary mirror is almost trivial, because there is no single defined axis of a sphere. Any line that runs through the center of the sphere can be an axis.
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In order to keep the particles in focus, the flow depth is restricted so that the particles remain in a plane of best focus perpendicular to the optical axis. This is similar in concept to the effect of the microscope slide plus cover slip in a static imaging system. Since depth of field decreases exponentially with increasing magnification, the depth of the flow cell must be narrowed significantly with higher magnifications. The major drawback to dynamic image acquisition is that the flow cell depth must be limited as described above.
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First, the nematic phase he characterized as having microscopic threads (these threads are today interpreted as disclinations in the director-field in the mesophase). Second, Friedel coined the term smectic phase for a layered mesophase having the structure of neat soap. Third, Friedel use the term cholesteric phase for materials like cholesteryl benzoate, and noted that such mesophases "involve strong twists around a direction normal to the positive optical axis".David Dunmur and Tim Sluckin (2011) Soap, science, and flat- screen TVs: a history of liquid crystals. pp.
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An off-axis optical system is an optical system in which the optical axis of the aperture is not coincident with the mechanical center of the aperture. The principal applications of off-axis optical systems are to avoid obstruction of the primary aperture by secondary optical elements, instrument packages, or sensors, and to provide ready access to instrument packages or sensors at the focus. The engineering tradeoff of an off-axis optical system is an increase in image aberrations. There are various theoretical models for aberration in off-axis optical systems.
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In fiber optics, a graded index is an optical fiber whose core has a refractive index that decreases with increasing radial distance from the optical axis of the fiber. Because parts of the core closer to the fiber axis have a higher refractive index than the parts near the cladding, light rays follow sinusoidal paths down the fiber. The most common refractive index profile for a graded-index fiber is very nearly parabolic. The parabolic profile results in continual refocusing of the rays in the core, and minimizes modal dispersion.
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For technological applications the divergent beam has to be focused, which is realized by the magnetic field of a coil, the magnetic focusing lens. For proper functioning of the electron gun, it is necessary that the beam be perfectly adjusted with respect to the optical axes of the accelerating electrical lens and the magnetic focusing lens. This can be done by applying a magnetic field of some specific radial direction and strength perpendicular to the optical axis before the focusing lens. This is usually realized by a simple correction system consisting of two pairs of coils.
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Single axicons are usually used to generate an annular light distribution which is laterally constant along the optical axis over a certain range. This special feature results from the generation of (non-diffracting) Bessel-like beams with properties mainly determined by the Axicon angle α. Creation of Bessel beams through an axicon There are two areas of interest for a variety of applications: a long range with an almost constant intensity distribution (a) and a ring-shaped distant field intensity distribution (b). The distance (a) depends on the angle α of the Axicon and the diameter (ØEP) of the incident beam.
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Thus it is also called a stop (an aperture stop, if it limits the brightness of light reaching the focal plane, or a field stop or flare stop for other uses of diaphragms in lenses). The diaphragm is placed in the light path of a lens or objective, and the size of the aperture regulates the amount of light that passes through the lens. The centre of the diaphragm's aperture coincides with the optical axis of the lens system. Most modern cameras use a type of adjustable diaphragm known as an iris diaphragm, and often referred to simply as an iris.
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Geometrical optics provides further matrix applications. In this approximative theory, the wave nature of light is neglected. The result is a model in which light rays are indeed geometrical rays. If the deflection of light rays by optical elements is small, the action of a lens or reflective element on a given light ray can be expressed as multiplication of a two-component vector with a two- by-two matrix called ray transfer matrix analysis: the vector's components are the light ray's slope and its distance from the optical axis, while the matrix encodes the properties of the optical element.
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Optoform is an optical bench system or cage system that provides multiple opto-mechanical components that may be assembled in various configurations to construct a variety of optical instruments. Unlike traditional cubic optical systems, Optoform employs a concentric bore pattern that allows interconnection between mounts using rods along their optical axis, or at right angles via corner connectors. The circular patterns allow for easier assembly of optical components in a more natural fashion with other optical components, such as lenses. These bores could also utilize linear bearings, and micrometers for precise linear, and X-Y positioning of optical elements.
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The concentrator is then said to have a (half) acceptance angle θ, or a total acceptance angle 2θ (since it accepts light within an angle ±θ to the optical axis). Transmission curves Ideally, a solar concentrator has a transmission curve cI as shown in the "transmission curves" figure. Transmission (efficiency) is τ = 1 for all incidence angles α < θI and τ = 0 for all incidence angles α > θI. In practice, real transmission curves are not perfect and they typically have a shape similar to that of curve cR, which is normalized so that τ = 1 for α = 0\.
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In visual perception, the far point is the farthest point at which an object can be placed (along the optical axis of the eye) for its image to be focused on the retina within the eye's accommodation. It is sometimes described as the farthest point from the eye at which images are clear. The other limit of eye's accommodation is the near point. For an unaccommodated emmetropic eye, the far point is at infinity, but for the sake of practicality, infinity is considered to be because the accommodation change from 6 m to infinity is negligible.
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Many sights utilize a type of mangin mirror system, consisting of a meniscus lens corrector element combined with the semi-reflective mirror (what Aimpoint's advertising calls a "two lens" or "double lens" systemBATTLESPACE Exhibition News, SHOT SHOW OPENS WITH A BANG! by Julian Nettlefold), that compensates for spherical aberration, an error that can cause the dot position to diverge off the sight's optical axis with change in eye position.Note: a setup Aimpoint calls "parallax free"ar15.com, How Aimpoints, EOTechs, And Other Parallax-Free Optics WorkGunsight - Patent 5901452 - general description of a mangin mirror system Aimpoint markets their sights as "parallax free",Aimpoint's parallax-free, double lens system... AFMO.
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In contrast, if multiple feeds are used with a parabolic reflector, all must be within a small angle of the optical axis to avoid suffering coma (a form of de-focussing). Apart from offset systems, dish antennas suffer from the feed and its supporting structure partially obscuring the main element (aperture blockage); in common with other refracting systems, the Luneburg lens antenna avoids this problem. A variation on the Luneburg lens antenna is the hemispherical Luneburg lens antenna or Luneburg reflector antenna. This uses just one hemisphere of a Luneburg lens, with the cut surface of the sphere resting on a reflecting metal ground plane.
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They show explicitly that the necessary condition to realize a negative (pulling) optical force is the simultaneous excitation of multipoles in the particle and if the projection of the total photon momentum along the propagation direction is small, attractive optical force is possible. The Chinese scientists suggest this possibility may be implemented for optical micromanipulation. Functioning tractor beams based on solenoidal modes of light were demonstrated in 2010 by physicists at New York University. The spiraling intensity distribution in these non-diffracting beams tends to trap illuminated objects and thus helps to overcome the radiation pressure that ordinarily would drive them down the optical axis.
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Citrus Swallowtail Papilio demodocus Chromostereopsis may also have evolutionary implications for predators and prey, giving it historical and practical significance. Possible evidence for the evolutionary significance of chromostereopsis is given in the fact that the fovea has developed in the lateral eyes of hunted animals to have a very large angle between the optical axis and visual axis to attain at least some binocular field of view. For these hunted animals, their eyes serve to detect predatory animals, which explains their lateral position in order to give them a full panoramic field of view. In contrast, this observed foveal development is opposite in predators and in primates.
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The process of inspections are designed to remove weakened drill pipe, so that pipe will not fracture during drilling. Tool pipe with thicker than 1" walls for a 4" diameter tube of hardened steel, fitted with tapered thread collars are re- used after drilling is complete, and thinner-walled tubular oil-well casing is in place. Electronic instrumentation similar to the spherometer in design are modified at inspection plants for casing, tubing, and drill pipe. The equivalent measurements in optics would be for a cylinder, or lens with a cylindrical component having an optical axis, where a plane through the lens would produce an oval circumference.
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Gaussian optics is a technique in geometrical optics that describes the behaviour of light rays in optical systems by using the paraxial approximation, in which only rays which make small angles with the optical axis of the system are considered. In this approximation, trigonometric functions can be expressed as linear functions of the angles. Gaussian optics applies to systems in which all the optical surfaces are either flat or are portions of a sphere. In this case, simple explicit formulae can be given for parameters of an imaging system such as focal distance, magnification and brightness, in terms of the geometrical shapes and material properties of the constituent elements.
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With Weiss he studied the magnetic splitting of the blue lines of the zinc atom and in 1907 they were able to determine the ratio of the electron's charge to its mass (e/m) with better precision than the method of J.J. Thomson. Cotton then became interested in the Faraday effect near absorption lines and demonstrated magnetic circular dichroism. At the same time, he worked with his former classmate Henri Mouton, a biologist at the Pasteur Institute, on magnetic birefringence in colloïdal solutions of magnetic particles. In 1907 the two discovered the Cotton-Mouton effect, an intense magnetic birefringence with optical axis perpendicular to the magnetic field lines.
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As phase values can only vary from zero to 2π, then repeat in either direction (termed phase wrapping), changing the piston coefficient changes the zero phase value contour locations across the wavefront. This property is critical to the operation of phase-measuring interferometers, which give not only the magnitude but also the sign (convexity or concavity) of a wavefront under test. Piston is physically created in the interferometer by piezoelectric actuators that translate the Fizeau interferometer reference surface along the optical axis by precise fractions of the test wavelength, usually by one quarter of a wavelength. This changes the interferometric fringe patterns and allows direct calculation of the exact wavefront error.
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In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the focal points, the principal points, and the nodal points. For ideal systems, the basic imaging properties such as image size, location, and orientation are completely determined by the locations of the cardinal points; in fact only four points are necessary: the focal points and either the principal or nodal points. The only ideal system that has been achieved in practice is the plane mirror, however the cardinal points are widely used to approximate the behavior of real optical systems.
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Since the collimated image produced by the sight is only truly parallax free at infinity, the sight has an error circle equal to the diameter of the collimating optics for any target at a finite distance. Depending on the eye position behind the sight and the closeness of the target this induces some aiming error. For larger targets at a distance (given the non-magnifying, quick target acquisitions nature of the sight) this aiming error is considered trivial. On small arms aimed at close targets this is compensated for by keeping the reticle in the middle of the optical window (sighting down its optical axis).
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An LED-based ring flash A ring flash is a circular photographic electronic flash that fits around a camera lens. Unlike point light sources, a ring flash provides even illumination with few shadows visible in the resulting photographs because the origin of the light is very close to (and surrounds) the optical axis of the lens. It was invented by Lester A. Dine in 1952 for use in dental photography, but now is commonly used in applications such as macro, portrait and fashion photography. As the efficiency of light sources, and the sensitivity of photographic imaging sensors, increased, the use of a continuous ring light instead of a flash increased.
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Conventional concave reflectors are practically inapplicable to the high-concentrating geometry in the case of a giant shadowing space target, which is located in front of the mirrored surface. This is primarily because of the dramatic spread of the mirrors' focal points on the target due to the optical aberration when the optical axis is not aligned with the Sun. On the other hand, the positioning of any collector at a distance to the target much larger than its size does not yield the required concentration level (and therefore temperature) due to the natural divergence of the sunrays. Such principal restrictions are inevitably at any location regarding the asteroid of one or many unshaded forward-reflecting collectors.
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Discrete frames are formed as each successive face of the mirror passes through the optical axis. Rotating drum cameras are capable of speed from the tens of thousands to millions of frames per second, but since the maximum peripheral linear speed of the drum is practically around 500m/s, increasing the frame rate requires decreasing the frame height and/or increasing the number of frames exposed from the rotating mirror. In both types of rotating mirror cameras, double exposure can occur if the system is not controlled properly. In a pure rotating mirror camera, this happens if the mirror makes a second pass across the optics while light is still entering the camera.
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This allows flexibility in mounting and shooting position. The CompM4 uses Aimpoint's "parallax-free" optical correction system, meaning there is minimal induced optical error that would shift the point of aim relative to the sight's optical axis as the user's eye moves off-center in relation to the sight. The sight itself is parallax-free at around 50 yards, meaning that the red dot will not change position relative to the target based on eye position at that range. As in other reflex sights, the point of aim will change position based on eye position at other ranges with the maximum error being equal to the diameter of the sight's optical window at short range.
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In 1815 he demonstrated that "polarized light, when passing through an organic substance, could be rotated clockwise or counterclockwise, dependent upon the optical axis of the material."Biot, J. B. (1815) "Phenomene de polarisation successive, observés dans des fluides homogenes" (Phenomenon of successive polarization, observed in homogeneous fluids), Bulletin des Sciences, par la Société Philomatique de Paris, 190–192.Jean-Baptiste Biot - Florida State University His work in chromatic polarization and rotary polarization greatly advanced the field of optics, although it was later shown that his findings could also be obtained using the wave theory of light (Frankel 2009). Biot's work on the polarization of light has led to many breakthroughs in the field of optics.
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Schematic of STEM mode An ultrahigh-vacuum STEM equipped with a 3rd-order spherical aberration corrector Inside the aberration corrector (hexapole- hexapole type) A scanning transmission electron microscope (STEM) is a type of transmission electron microscope (TEM). Pronunciation is [stɛm] or [ɛsti:i:ɛm]. As with a conventional transmission electron microscope (CTEM), images are formed by electrons passing through a sufficiently thin specimen. However, unlike CTEM, in STEM the electron beam is focused to a fine spot (with the typical spot size 0.05 – 0.2 nm) which is then scanned over the sample in a raster illumination system constructed so that the sample is illuminated at each point with the beam parallel to the optical axis.
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However, to simplify the calculation, images are drawn in front of the optical center of the lens by f. The u-axis and v-axis of the image's coordinate system O1uv are in the same direction with x-axis and y-axis of the camera's coordinate system respectively. The origin of the image's coordinate system is located on the intersection of imaging plane and the optical axis. Suppose such world point P whose corresponding image points are P1(u1,v1) and P2(u2,v2) respectively on the left and right image plane. Assume two cameras are in the same plane, then y-coordinates of P1 and P2 are identical, i.e.,v1=v2.
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Holographic weapon sights use a holographic image of a reticle at finite set range built into the viewing window and a collimated laser diode to illuminate it. An advantage to holographic sights is that they eliminate a type of parallax problem found in some optical collimator based sights (such as the red dot sight) where the spherical mirror used induces spherical aberration that can cause the reticle to skew off the sight's optical axis. The use of a hologram also eliminates the need for image dimming narrow band reflective coatings and allows for reticles of almost any shape or mil size. A downside to the holographic weapon sight can be the weight and shorter battery life.
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Low-dose imaging is performed by deflecting illumination and imaging regions simultaneously away from the optical axis to image an adjacent region to the area to be recorded (the high-dose region). This area is maintained centered during tilting and refocused before recording. During recording the deflections are removed so that the area of interest is exposed to the electron beam only for the duration required for imaging. An improvement of this technique (for objects resting on a sloping substrate film) is to have two symmetrical off-axis regions for focusing followed by setting focus to the average of the two high-dose focus values before recording the low-dose area of interest.
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Eye movement perpendicular to the device's optical axis will make the reticle image move in exact relationship to eye position in the cylindrical column of light created by the collimating optics.American rifleman: Volume 93, National Rifle Association of America - THE REFLECTOR SIGHT By JOHN B. BUTLER, page 31 A common type (used in applications such as aircraft gun sights) uses a collimating lens and a beam splitter. This type tends to be bulky since it requires at least two optical components, the lens and the beam splitter/glass plate. The reticle collimation optics are situated at 90° to the optical path making lighting difficult, usually needing additional electric illumination, condensing lenses, etc.
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While a majority of people will view red as "floating" in front of blue, others experience a reversal of the effect in which they see blue floating in front of the red, or no depth effect at all. While this reversal may appear to discredit chromostereopsis, it does not and instead, as originally proposed by Einthoven, can be explained by an increase in the effect and subsequent reversal via blocking of the eccentric position of the pupil with respect to the optical axis. The diverse nature of the chromostereoptic effect is because the color depth effect is closely intertwined with both perceptual and optical factors. In other words, neither the optical nor the perceptual factors can be taken in insolation to explain chromostereopsis.
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More complex reticle patterns such as crosshairs or concentric circles can be used but need more complex aberration free optics. Like other reflector sights, the collimated image of the red dot is truly parallax free only at infinity, with an error circle equal to the diameter of the collimating optics for any target at a finite distance.Encyclopedia of Bullseye Pistol This is compensated for by keeping the dot in the middle of the optical window (sighting down the sight's optical axis).Tony L. Jones, The police officer's guide to operating and surviving in low-light and no-light conditions, page 86 Some manufacturers modify the focus of the LED/optical collimator combination, making models with the optical collimator set to focus the dot at a finite distance.
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Bi-telecentric lens with 208mm diameter and C mount Bi-telecentric lens Comparison of a conventional lens (1), object-space telecentric lens (2), image-space telecentric lens (3) and bi-telecentric lens (4) A telecentric lens is a compound lens that has its entrance or exit pupil at infinity; in the prior case, this produces an orthographic view of the subject. This means that the chief rays (oblique rays that pass through the center of the aperture stop) are parallel to the optical axis in front of or behind the system, respectively. The simplest way to make a lens telecentric is to put the aperture stop at one of the lens's focal points. An entrance pupil at infinity makes the lens object-space telecentric.
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If the surface is paraboloidal, the mirror usually looks like a doughnut or lozenge although the exact appearance depends on the exact position of the knife edge. It is possible to calculate how closely the mirror surface resembles a perfect parabola by placing a Couder mask,Designing and calculating Couder screens for Foucault testing Ken Slater and Nils Olof Carlin Everest pin stick (after A. W. Everest)Stellafane ATM Build a Couder Mask; Build an Everest Pin Stick or other zone markerHarbour 2008 pp 49-51 over the mirror. A series of measurements with the tester, finding the radii of curvature of the zones along the optical axis of the mirror (Y-axis). These data are then reduced and graphed against an ideal parabolic curve.
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Most LOM observations are conducted using bright-field (BF) illumination, where the image of any flat feature perpendicular to the incident light path is bright, or appears to be white. But, other illumination methods can be used and, in some cases, may provide superior images with greater detail. Dark- field microscopy (DF), is an alternative method of observation that provides high-contrast images and actually greater resolution than bright-field. In dark-field illumination, the light from features perpendicular to the optical axis is blocked and appears dark while the light from features inclined to the surface, which look dark in BF, appear bright, or "self-luminous" in DF. Grain boundaries, for example, are more vivid in DF than BF.
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This technique, as described below, is derived using the paraxial approximation, which requires that all ray directions (directions normal to the wavefronts) are at small angles θ relative to the optical axis of the system, such that the approximation \sin \theta \approx \theta remains valid. A small θ further implies that the transverse extent of the ray bundles (x and y) is small compared to the length of the optical system (thus "paraxial"). Since a decent imaging system where this is not the case for all rays must still focus the paraxial rays correctly, this matrix method will properly describe the positions of focal planes and magnifications, however aberrations still need to be evaluated using full ray-tracing techniques.Extension of matrix methods to tracing (non-paraxial) meridional rays is included here.
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To determine the zenith point of the circle, the telescope was directed vertically downwards at a basin of mercury, the surface of which formed an absolutely horizontal mirror. The observer saw the horizontal wire and its reflected image, and moving the telescope to make these coincide, its optical axis was made perpendicular to the plane of the horizon, and the circle reading was 180° \+ zenith point. In observations of stars refraction was taken into account as well as the errors of graduation and flexure. If the bisection of the star on the horizontal wire was not made in the centre of the field, allowance was made for curvature, or the deviation of the star's path from a great circle, and for the inclination of the horizontal wire to the horizon.
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Even an expensive star diagonal will deliver poor performance if it is not in alignment with the optical axis of the telescope. A telescope in perfect collimation will be thrown out of collimation by a misaligned star diagonal and often this misalignment will determine the image quality of the telescope to a larger extent than the surface accuracy of the prism or mirror. Since the mirror or prism of the star diagonal is located nearly at the focal plane of the instrument, surface accuracy of greater that 1/4 wave is more in the line of advertising than any increase in optical performance. A 1/10 wave mirror or prism star diagonal that throws off the collimation of the telescope will perform worse than a 1/2 wave star diagonal that is in proper alignment.
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At the same time, the interaction between the electron wave in different atom columns leads to Bragg diffraction. The exact description of dynamical scattering of electrons in a sample not satisfying the weak phase object approximation (WPOA), which is almost all real samples, still remains the holy grail of electron microscopy. However, the physics of electron scattering and electron microscope image formation are sufficiently well known to allow accurate simulation of electron microscope images. As a result of the interaction with a crystalline sample, the electron exit wave right below the sample φe(x,u) as a function of the spatial coordinate x is a superposition of a plane wave and a multitude of diffracted beams with different in plane spatial frequencies u (spatial frequencies correspond to scattering angles, or distances of rays from the optical axis in a diffraction plane).
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This intrinsic physical property of the setup is utilized to extract orientational information about the angular variation of the local scattering power of the sample by rotating the sample around the optical axis of the set-up and collecting a set of several dark-field images, each measuring the component of the scattering perpendicular to the grating lines for that particular orientation. This can be used to determine the local angle and degree of orientation of bone and could yield valuable information for improving research and diagnostics of bone diseases like osteoporosis or osteoarthritis. The standard configuration as shown in the figure to the right requires spatial coherence of the source and consequently is limited to high brilliant synchrotron radiation sources. This problem can be handled by adding a third grating close to the X-ray source, known as a Talbot-Lau interferometer.
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For example, because it is not practical to locate the principal planes of such small lenses, measurements are often made with respect to the lens or substrate surface. Where a lens is used to couple light into an optical fibre the focused wavefront may exhibit spherical aberration and light from different regions of the microlens aperture may be focused to different points on the optical axis. It is useful to know the distance at which the maximum amount of light is concentrated in the fibre aperture and these factors have led to new definitions for focal length. To enable measurements on micro-lenses to be compared and parts to be interchanged, a series of international standards has been developed to assist users and manufacturers by defining microlens properties and describing appropriate measurement methods.ISO 14880-1:2001.
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The EF mount also changed the logical clamping action of the bayonet receptacle to improve the tactical operation. Attaching an FD lens to a camera body required two hands: one to hold the lens in position, and a second to twist the breech- lock ring to rigidly lock the lens to the camera. The EF mount instead provides leaf springs in the receptacle, which hold the registration surfaces of the lens and receptacle together along the optical axis, while the manual twisting action engages a spring-loaded registration pin in the receptacle which drops into a recess provided on the bayonet fitting, locking the rotation. This EF mount feature provided the convenience of attaching EF lenses with one hand (holding the lens and twisting), versus two hands (one to hold the lens, one to twist the breech-lock) required for the FD attachment.
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Both mirror are flat and have a diameter of 2.65 metres and form a 45 degree angle with the optical axis of the telescope. The primary function of these mirrors is to ensure a continuous illumination of the tertiary optical system. Currently only the M4 branch is furnished with receivers with M4’ reserved for future high frequency and/or multi-beam receivers Tertiary Optics :The tertiary optics are responsible for the efficient coupling of the sky to the horn antennas of the 5 frequency bands of ARIESXXI. The first element encountered is an offset-parabolic with a focal length of 1.36 metres which converts the incoming quasi-plane wave to a converging beam which is then incident on a shaped dichroic lens that passes S/C/CH frequency for coupling to their respective feeds and reflects the X-band radiation towards the X-band feed.
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On one of the straight edges of the non maritime quadrant (solid sheet form) there are two sighting plates which are called “Hadafatani”. Each of the alignment plates having a small, centrally placed aperture or "pinhole", the two apertures (front and back) forming the optical axis through which one sights an incline object or Sun. The light rays from the Sun passing through both apertures, the spot image of the Sun being concentric with the center of the rear plate pinhole, imaging on to a finger (project screen) if desired but not necessary or less frequent the eye at night. The hanging plum line serving two functions the first being to provide a means (indicator) to reading the angular orientation of the instrument, the second function ensuring that the instrument when optically aligned with the object of interest is situated parallel with the vertical plane (perpendicular with the ground).
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Light path in a Cassegrain Reflector The Cassegrain reflector is a reflecting telescope design that solved the problem of viewing an image without obstructing the primary mirror by using a convex secondary mirror on the optical axis to bounce the light back through a hole in the primary mirror thus permitting the light to reach an eyepiece. It first appeared in the eighth edition of the 17th-century French science journal Recueil des mémoires et conférences concernant les arts et les sciences, published by Jean-Baptiste Denys on April 25, 1672. In that edition is found an extract from a letter written by M. de Bercé, writing from Chartres, where he acted as a representative for the Académie des sciences --scholars of Chartres. M. de Bercé reported on a man named Cassegrain who had written a letter on the megaphone with an attached note describing a new type of reflecting telescope, the Cassegrain reflector, where a secondary convex mirror is suspended above a primary concave mirror.
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The specimen goniometer of a TEM is thereby employed analogously to the goniometer head of an optical goniometer. The optical axis of the TEM is then analogous to the reference direction of an optical goniometer. While in optical goniometry net- plane normals (reciprocal lattice vectors) need to be successively aligned parallel to the reference direction of an optical goniometer in order to derive measurements of interfacial angles, the corresponding alignment needs to be done for zone axes (direct lattice vector) in transmission electron goniometry. (Note that such alignments are by their nature quite trivial for nanocrystals in a TEM after the microscope has been aligned by standard procedures.) Since transmission electron goniometry is based on Bragg’s Law for the transmission (Laue) case (diffraction of electron waves), interzonal angles (i.e. angles between lattice directions) can be measured by a procedure that is analogous to the measurement of interfacial angles in an optical goniometer on the basis of Snell’s Law, i.e.
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Light path in a Cassegrain reflecting telescope The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and radio antennas, the main characteristic being that the optical path folds back onto itself, relative to the optical system's primary mirror entrance aperture. This design puts the focal point at a convenient location behind the primary mirror and the convex secondary adds a telephoto effect creating a much longer focal length in a mechanically short system.Raymond N. Wilson, Reflecting Telescope Optics I: Basic Design Theory and its Historical Development, Springer Science & Business Media - 2013, pages 43-44 In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the centre, thus permitting the light to reach an eyepiece, a camera, or an image sensor. Alternatively, as in many radio telescopes, the final focus may be in front of the primary.
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Spherical aberration is a blurring effect arising when a lens is not able to converge incoming rays at higher angles of incidence to the focus point, but rather focuses them to a point closer to the lens. This will have the effect of spreading an imaged point (which is ideally imaged as a single point in the gaussian image plane) out over a finite size disc in the image plane. Giving the measure of aberration in a plane normal to the optical axis is called a transversal aberration. The size (radius) of the aberration disc in this plane can be shown to be proportional to the cube of the incident angle (θ) under the small-angle approximation, and that the explicit form in this case is : r_s = C_s\cdot\theta^3\cdot M where C_s is the spherical aberration and M is the magnification, both effectively being constants of the lens settings.
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