Misplaced Pages

#465534

74-579: The DSC-RX1 was announced in September 2012. The DSC-RX1R , released in 2013, is a variant of the Sony DSC-RX1 without anti-aliasing filter in front of the image sensor. In 2015, both models were succeeded by the DSC-RX1R II . The DSC-RX1 was the world's first fixed-lens, full-frame digital compact camera , and as of its announcement, was the world's smallest full-frame digital camera but

148-431: A gouty joint will reveal negatively birefringent monosodium urate crystals . Calcium pyrophosphate crystals, in contrast, show weak positive birefringence. Urate crystals appear yellow, and calcium pyrophosphate crystals appear blue when their long axes are aligned parallel to that of a red compensator filter, or a crystal of known birefringence is added to the sample for comparison. The birefringence of tissue inside

222-715: A signal sampler to restrict the bandwidth of a signal to satisfy the Nyquist–Shannon sampling theorem over the band of interest . Since the theorem states that unambiguous reconstruction of the signal from its samples is possible when the power of frequencies above the Nyquist frequency is zero, a brick wall filter is an idealized but impractical AAF. A practical AAF makes a trade off between reduced bandwidth and increased aliasing . A practical anti-aliasing filter will typically permit some aliasing to occur or attenuate or otherwise distort some in-band frequencies close to

296-400: A 200 kHz band, then an appropriate anti-alias filter would be centered on 87.9 MHz with 200 kHz bandwidth (or passband of 87.8 MHz to 88.0 MHz), and the sampling rate would be no less than 400 kHz, but should also satisfy other constraints to prevent aliasing . It is very important to avoid input signal overload when using an anti-aliasing filter. If the signal

370-402: A compromise between filter complexity and performance. High-resolution audio uses a higher sample rate, providing both a higher passband edge and larger transition band, which allows better filter performance with reduced aliasing, reduced attenuation of higher audio frequencies and reduced time and phase domain signal distortion. Often, an anti-aliasing filter is a low-pass filter ; this

444-413: A few ways: The best characterized birefringent materials are crystals . Due to their specific crystal structures their refractive indices are well defined. Depending on the symmetry of a crystal structure (as determined by one of the 32 possible crystallographic point groups ), crystals in that group may be forced to be isotropic (not birefringent), to have uniaxial symmetry, or neither in which case it

518-415: A glass plate to generate an optical vortex and full Poincare beams (optical beams that have every possible polarization state across a cross-section). Birefringence is observed in anisotropic elastic materials. In these materials, the two polarizations split according to their effective refractive indices, which are also sensitive to stress. The study of birefringence in shear waves traveling through

592-491: A higher intermediate digital sample rate is used, so that a nearly ideal digital filter can sharply cut off aliasing near the original low Nyquist frequency and give better phase response , while a much simpler analog filter can stop frequencies above the new higher Nyquist frequency. Because analog filters have relatively high cost and limited performance, relaxing the demands on the analog filter can greatly reduce both aliasing and cost. Furthermore, because some noise

666-456: A less invasive method to diagnose Duchenne muscular dystrophy . Birefringence can be observed in amyloid plaques such as are found in the brains of Alzheimer's patients when stained with a dye such as Congo Red. Modified proteins such as immunoglobulin light chains abnormally accumulate between cells, forming fibrils. Multiple folds of these fibers line up and take on a beta-pleated sheet conformation . Congo red dye intercalates between

740-410: A living human thigh was measured using polarization-sensitive optical coherence tomography at 1310 nm and a single mode fiber in a needle. Skeletal muscle birefringence was Δn = 1.79 × 10 ± 0.18×10 , adipose Δn = 0.07 × 10 ± 0.50 × 10 , superficial aponeurosis Δn = 5.08 × 10 ± 0.73 × 10 and interstitial tissue Δn = 0.65 × 10 ±0.39 × 10 . These measurements may be important for the development of

814-437: A measure of the degree of order within these fluid layers and how this order is disrupted when the layer interacts with other biomolecules. For the 3D measurement of birefringence , a technique based on holographic tomography [1] can be used. Birefringence is used in many optical devices. Liquid-crystal displays , the most common sort of flat-panel display , cause their pixels to become lighter or darker through rotation of

SECTION 10

#1732802008466

888-535: A new Multi Interface Shoe that is physically compatible with the ISO 518 standard hot shoe , with electrical contacts for newer Sony shoe-mounted accessories as well as compatibility with the proprietary iISO flash shoe via the ADP-MAA adapter. Based on DxOMark Sensor Scores (performance), the Sony DSC-RX1 got the best overall score among high-end compact cameras and mirror-less cameras tested with 93 scored, and even

962-449: A plane wave of angular frequency ω can be written in the general form: where r is the position vector, t is time, and E 0 is a vector describing the electric field at r = 0 , t = 0 . Then we shall find the possible wave vectors k . By combining Maxwell's equations for ∇ × E and ∇ × H , we can eliminate H = ⁠ 1 / μ 0 ⁠ B to obtain: With no free charges, Maxwell's equation for

1036-449: A polarization perpendicular to that of the ordinary ray, the polarization direction will be partly in the direction of (parallel to) the optic axis, and this extraordinary ray will be governed by a different, direction-dependent refractive index. Because the index of refraction depends on the polarization when unpolarized light enters a uniaxial birefringent material, it is split into two beams travelling in different directions, one having

1110-433: A sample is placed between two crossed polarizers, colour patterns can be observed, because polarization of a light ray is rotated after passing through a birefringent material and the amount of rotation is dependent on wavelength. The experimental method called photoelasticity used for analyzing stress distribution in solids is based on the same principle. There has been recent research on using stress-induced birefringence in

1184-441: Is a biaxial crystal. The crystal structures permitting uniaxial and biaxial birefringence are noted in the two tables, below, listing the two or three principal refractive indices (at wavelength 590 nm) of some better-known crystals. In addition to induced birefringence while under stress, many plastics obtain permanent birefringence during manufacture due to stresses which are "frozen in" due to mechanical forces present when

1258-413: Is a single direction governing the optical anisotropy whereby all directions perpendicular to it (or at a given angle to it) are optically equivalent. Thus rotating the material around this axis does not change its optical behaviour. This special direction is known as the optic axis of the material. Light propagating parallel to the optic axis (whose polarization is always perpendicular to the optic axis)

1332-459: Is also considerably more expensive than most other compact cameras. It was announced in September 2012. The DSC-RX1 features a 35 mm f/ 2 Zeiss Sonnar lens with leaf shutter capable of a minimum shutter speed of 1/2000 s (for apertures 2.0 to 4.0), 1/3200 s (for apertures down to 5.6), and even 1/4000 s (for smaller apertures down to 22). The camera is equipped with a 24.3- megapixel full-frame CMOS sensor , and it includes

1406-406: Is at a finite angle from the direction of the wave vector resulting in an additional separation between these beams. So even in the case of normal incidence, where one would compute the angle of refraction as zero (according to Snell's law, regardless of the effective index of refraction), the energy of the extraordinary ray is propagated at an angle. If exiting the crystal through a face parallel to

1480-475: Is averaged out, the higher sampling rate can moderately improve signal-to-noise ratio . A signal may be intentionally sampled at a higher rate to reduce the requirements and distortion of the anti-alias filter. For example, compare CD audio with high-resolution audio . CD audio filters the signal to a passband edge of 20 kHz, with a stopband Nyquist frequency of 22.05 kHz and sample rate of 44.1 kHz. The narrow 2.05 kHz transition band requires

1554-416: Is called "birefringent" because it will generally refract a single incoming ray in two directions, which we now understand correspond to the two different polarizations. This is true of either a uniaxial or biaxial material. In a uniaxial material, one ray behaves according to the normal law of refraction (corresponding to the ordinary refractive index), so an incoming ray at normal incidence remains normal to

SECTION 20

#1732802008466

1628-428: Is commonly used in biological tissue, as many biological materials are linearly or circularly birefringent. Collagen, found in cartilage, tendon, bone, corneas, and several other areas in the body, is birefringent and commonly studied with polarized light microscopy. Some proteins are also birefringent, exhibiting form birefringence. Inevitable manufacturing imperfections in optical fiber leads to birefringence, which

1702-400: Is governed by a refractive index n o (for "ordinary") regardless of its specific polarization. For rays with any other propagation direction, there is one linear polarization that is perpendicular to the optic axis, and a ray with that polarization is called an ordinary ray and is governed by the same refractive index value n o . For a ray propagating in the same direction but with

1776-460: Is involved. A material is termed uniaxial when it has a single direction of symmetry in its optical behavior, which we term the optic axis. It also happens to be the axis of symmetry of the index ellipsoid (a spheroid in this case). The index ellipsoid could still be described according to the refractive indices, n α , n β and n γ , along three coordinate axes; in this case two are equal. So if n α = n β corresponding to

1850-403: Is just a scalar (and equal to n ε 0 where n is the index of refraction ). In an anisotropic material exhibiting birefringence, the relationship between D and E must now be described using a tensor equation: where ε is now a 3 × 3 permittivity tensor. We assume linearity and no magnetic permeability in the medium: μ = μ 0 . The electric field of

1924-557: Is not a requirement, however. Generalizations of the Nyquist–Shannon sampling theorem allow sampling of other band-limited passband signals instead of baseband signals. For signals that are bandwidth limited, but not centered at zero, a band-pass filter can be used as an anti-aliasing filter. For example, this could be done with a single-sideband modulated or frequency modulated signal. If one desired to sample an FM radio broadcast centered at 87.9 MHz and bandlimited to

1998-491: Is one cause of pulse broadening in fiber-optic communications . Such imperfections can be geometrical (lack of circular symmetry), or due to unequal lateral stress applied to the optical fibre. Birefringence is intentionally introduced (for instance, by making the cross-section elliptical) in order to produce polarization-maintaining optical fibers . Birefringence can be induced (or corrected) in optical fibers through bending them which causes anisotropy in form and stress given

2072-492: Is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by Danish scientist Rasmus Bartholin in 1669, who observed it in Iceland spar ( calcite ) crystals which have one of the strongest birefringences. In the 19th century Augustin-Jean Fresnel described

2146-422: Is similar to the mathematics of time-domain sampling, but the filter implementation technologies are different. The typical implementation in digital cameras is two layers of birefringent material such as lithium niobate , which spreads each optical point into a cluster of four points. The choice of spot separation for such a filter involves a tradeoff among sharpness, aliasing, and fill factor (the ratio of

2220-427: Is strong enough, it can cause clipping at the analog-to-digital converter , even after filtering. When distortion due to clipping occurs after the anti-aliasing filter, it can create components outside the passband of the anti-aliasing filter; these components can then alias, causing the reproduction of other non- harmonically related frequencies. Birefringent Birefringence means double refraction. It

2294-484: Is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light . These optically anisotropic materials are described as birefringent or birefractive . The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress . Birefringence

Sony Cyber-shot DSC-RX1 - Misplaced Pages Continue

2368-488: Is the component for which the material has the higher effective refractive index (slower phase velocity), while the fast ray is the one with a lower effective refractive index. When a beam is incident on such a material from air (or any material with a lower refractive index), the slow ray is thus refracted more towards the normal than the fast ray. In the example figure at top of this page, it can be seen that refracted ray with s polarization (with its electric vibration along

2442-498: The Pentax K-3 's anti-aliasing filter, which applies small vibrations to the sensor element. Anti-aliasing filters are used at the input of an analog-to-digital converter . Similar filters are used as reconstruction filters at the output of a digital-to-analog converter . In the latter case, the filter prevents imaging, the reverse process of aliasing where in-band frequencies are mirrored out of band. With oversampling ,

2516-441: The x and y axes, then the extraordinary index is n γ corresponding to the z axis, which is also called the optic axis in this case. Materials in which all three refractive indices are different are termed biaxial and the origin of this term is more complicated and frequently misunderstood. In a uniaxial crystal, different polarization components of a beam will travel at different phase velocities, except for rays in

2590-437: The 3 axes) where the refractive indices for different polarizations are again equal. For this reason, these crystals were designated as biaxial , with the two "axes" in this case referring to ray directions in which propagation does not experience birefringence. In a birefringent material, a wave consists of two polarization components which generally are governed by different effective refractive indices. The so-called slow ray

2664-544: The Nyquist limit. For this reason, many practical systems sample higher than would be theoretically required by a perfect AAF in order to ensure that all frequencies of interest can be reconstructed, a practice called oversampling . In the case of optical image sampling, as by image sensors in digital cameras , the anti-aliasing filter is also known as an optical low-pass filter ( OLPF ), blur filter , or AA filter . The mathematics of sampling in two spatial dimensions

2738-436: The Sony DSC-RX1's overall score is just behind the full-frame DSLR of Nikon D800, Nikon D800E and Nikon D600 , with 96 and 94 respectively. The Sony Cyber-shot DSC-RX1R, released in 2013, is a variant of the Sony DSC-RX1 without anti-aliasing filter in front of the image sensor. This can slightly increase the effective resolution at the expense of possibly more moiré in areas with fine repeating textures. The DSC-RX1R II

2812-445: The active refracting area of a microlens array to the total contiguous area occupied by the array). In a monochrome or three-CCD or Foveon X3 camera, the microlens array alone, if near 100% effective, can provide a significant anti-aliasing function, while in color filter array (e.g. Bayer filter ) cameras, an additional filter is generally needed to reduce aliasing to an acceptable level. Alternative implementations include

2886-420: The angle of incidence, the effective refractive index of the extraordinary ray can be tuned in order to achieve phase matching , which is required for the efficient operation of these devices. Birefringence is utilized in medical diagnostics. One powerful accessory used with optical microscopes is a pair of crossed polarizing filters. Light from the source is polarized in the x direction after passing through

2960-565: The axis around which it is bent and radius of curvature. In addition to anisotropy in the electric polarizability that we have been discussing, anisotropy in the magnetic permeability could be a source of birefringence. At optical frequencies, there is no measurable magnetic polarizability ( μ = μ 0 ) of natural materials, so this is not an actual source of birefringence. Birefringence and other polarization-based optical effects (such as optical rotation and linear or circular dichroism ) can be observed by measuring any change in

3034-407: The birefringence of the optic nerve fiber layer to indirectly quantify its thickness, which is of use in the assessment and monitoring of glaucoma . Polarization-sensitive optical coherence tomography measurements obtained from healthy human subjects have demonstrated a change in birefringence of the retinal nerve fiber layer as a function of location around the optic nerve head. The same technology

Sony Cyber-shot DSC-RX1 - Misplaced Pages Continue

3108-410: The change in polarization state using such an apparatus is the basis of ellipsometry , by which the optical properties of specular surfaces can be gauged through reflection. Birefringence measurements have been made with phase-modulated systems for examining the transient flow behaviour of fluids. Birefringence of lipid bilayers can be measured using dual-polarization interferometry . This provides

3182-453: The crystal is positive (or negative, respectively). In the case of biaxial crystals, all three of the principal axes have different refractive indices, so this designation does not apply. But for any defined ray direction one can just as well designate the fast and slow ray polarizations. While the best known source of birefringence is the entrance of light into an anisotropic crystal, it can result in otherwise optically isotropic materials in

3256-422: The crystal. For most ray directions, both polarizations would be classified as extraordinary rays but with different effective refractive indices. Being extraordinary waves, the direction of power flow is not identical to the direction of the wave vector in either case. The two refractive indices can be determined using the index ellipsoids for given directions of the polarization. Note that for biaxial crystals

3330-424: The direction of the wave vector . This causes an additional shift in that beam, even when launched at normal incidence, as is popularly observed using a crystal of calcite as photographed above. Rotating the calcite crystal will cause one of the two images, that of the extraordinary ray, to rotate slightly around that of the ordinary ray, which remains fixed. When the light propagates either along or orthogonal to

3404-446: The direction of the optic axis, thus called the extraordinary ray ) is the slow ray in given scenario. Using a thin slab of that material at normal incidence, one would implement a waveplate . In this case, there is essentially no spatial separation between the polarizations, the phase of the wave in the parallel polarization (the slow ray) will be retarded with respect to the perpendicular polarization. These directions are thus known as

3478-509: The direction of what we call the optic axis. Thus the optic axis has the particular property that rays in that direction do not exhibit birefringence, with all polarizations in such a beam experiencing the same index of refraction. It is very different when the three principal refractive indices are all different; then an incoming ray in any of those principal directions will still encounter two different refractive indices. But it turns out that there are two special directions (at an angle to all of

3552-517: The divergence of D vanishes: We can apply the vector identity ∇ × (∇ × A ) = ∇(∇ ⋅ A ) − ∇ A to the left hand side of eq. 3a , and use the spatial dependence in which each differentiation in x (for instance) results in multiplication by ik x to find: The right hand side of eq. 3a can be expressed in terms of E through application of the permittivity tensor ε and noting that differentiation in time results in multiplication by − iω , eq. 3a then becomes: Applying

3626-556: The first polarizer, but above the specimen is a polarizer (a so-called analyzer ) oriented in the y direction. Therefore, no light from the source will be accepted by the analyzer, and the field will appear dark. Areas of the sample possessing birefringence will generally couple some of the x -polarized light into the y polarization; these areas will then appear bright against the dark background. Modifications to this basic principle can differentiate between positive and negative birefringence. For instance, needle aspiration of fluid from

3700-591: The folds and, when observed under polarized light, causes birefringence. In ophthalmology , binocular retinal birefringence screening of the Henle fibers (photoreceptor axons that go radially outward from the fovea) provides a reliable detection of strabismus and possibly also of anisometropic amblyopia . In healthy subjects, the maximum retardation induced by the Henle fiber layer is approximately 22 degrees at 840 nm. Furthermore, scanning laser polarimetry uses

3774-415: The image from light of either polarization, simply a relative phase shift between the two light waves. Much of the work involving polarization preceded the understanding of light as a transverse electromagnetic wave , and this has affected some terminology in use. Isotropic materials have symmetry in all directions and the refractive index is the same for any polarization direction. An anisotropic material

SECTION 50

#1732802008466

3848-426: The incoming face, the direction of both rays will be restored, but leaving a shift between the two beams. This is commonly observed using a piece of calcite cut along its natural cleavage, placed above a paper with writing, as in the above photographs. On the contrary, waveplates specifically have their optic axis along the surface of the plate, so that with (approximately) normal incidence there will be no shift in

3922-540: The index ellipsoid will not be an ellipsoid of revolution (" spheroid ") but is described by three unequal principle refractive indices n α , n β and n γ . Thus there is no axis around which a rotation leaves the optical properties invariant (as there is with uniaxial crystals whose index ellipsoid is a spheroid). Although there is no axis of symmetry, there are two optical axes or binormals which are defined as directions along which light may propagate without birefringence, i.e., directions along which

3996-503: The optic axis). In addition, a distinct form of double refraction occurs, even with normal incidence, in cases where the optic axis is not along the refracting surface (nor exactly normal to it); in this case, the dielectric polarization of the birefringent material is not exactly in the direction of the wave's electric field for the extraordinary ray. The direction of power flow (given by the Poynting vector ) for this inhomogenous wave

4070-448: The optic axis, such a lateral shift does not occur. In the first case, both polarizations are perpendicular to the optic axis and see the same effective refractive index, so there is no extraordinary ray. In the second case the extraordinary ray propagates at a different phase velocity (corresponding to n e ) but still has the power flow in the direction of the wave vector . A crystal with its optic axis in this orientation, parallel to

4144-475: The optical surface, may be used to create a waveplate , in which there is no distortion of the image but an intentional modification of the state of polarization of the incident wave. For instance, a quarter-wave plate is commonly used to create circular polarization from a linearly polarized source. The case of so-called biaxial crystals is substantially more complex. These are characterized by three refractive indices corresponding to three principal axes of

4218-414: The ordinary ray is simply described by n o as if there were no birefringence involved. The extraordinary ray, as its name suggests, propagates unlike any wave in an isotropic optical material. Its refraction (and reflection) at a surface can be understood using the effective refractive index (a value in between n o and n e ). Its power flow (given by the Poynting vector ) is not exactly in

4292-412: The phenomenon in terms of polarization, understanding light as a wave with field components in transverse polarization (perpendicular to the direction of the wave vector). A mathematical description of wave propagation in a birefringent medium is presented below . Following is a qualitative explanation of the phenomenon. The simplest type of birefringence is described as uniaxial , meaning that there

4366-420: The plastic is molded or extruded. For example, ordinary cellophane is birefringent. Polarizers are routinely used to detect stress, either applied or frozen-in, in plastics such as polystyrene and polycarbonate . Cotton fiber is birefringent because of high levels of cellulosic material in the fibre's secondary cell wall which is directionally aligned with the cotton fibers. Polarized light microscopy

4440-494: The polarization (circular birefringence) of linearly polarized light as viewed through a sheet polarizer at the screen's surface. Similarly, light modulators modulate the intensity of light through electrically induced birefringence of polarized light followed by a polarizer. The Lyot filter is a specialized narrowband spectral filter employing the wavelength dependence of birefringence. Waveplates are thin birefringent sheets widely used in certain optical equipment for modifying

4514-460: The polarization component normal to the optic axis (ordinary ray) and the other linear polarization (extraordinary ray) will be refracted toward somewhat different paths. Natural light, so-called unpolarized light , consists of equal amounts of energy in any two orthogonal polarizations. Even linearly polarized light has some energy in both polarizations, unless aligned along one of the two axes of birefringence. According to Snell's law of refraction,

SECTION 60

#1732802008466

4588-511: The polarization of light passing through the material. These measurements are known as polarimetry . Polarized light microscopes, which contain two polarizers that are at 90° to each other on either side of the sample, are used to visualize birefringence, since light that has not been affected by birefringence remains in a polarization that is totally rejected by the second polarizer ("analyzer"). The addition of quarter-wave plates permits examination using circularly polarized light. Determination of

4662-464: The polarization of the ordinary ray and the other the polarization of the extraordinary ray. The ordinary ray will always experience a refractive index of n o , whereas the refractive index of the extraordinary ray will be in between n o and n e , depending on the ray direction as described by the index ellipsoid . The magnitude of the difference is quantified by the birefringence The propagation (as well as reflection coefficient ) of

4736-549: The polarization state of light passing through it. To manufacture polarizers with high transmittance, birefringent crystals are used in devices such as the Glan–Thompson prism , Glan–Taylor prism and other variants. Layered birefringent polymer sheets can also be used for this purpose. Birefringence also plays an important role in second-harmonic generation and other nonlinear optical processes . The crystals used for these purposes are almost always birefringent. By adjusting

4810-409: The refracting surface. As explained above, the other polarization can deviate from normal incidence, which cannot be described using the law of refraction. This thus became known as the extraordinary ray . The terms "ordinary" and "extraordinary" are still applied to the polarization components perpendicular to and not perpendicular to the optic axis respectively, even in cases where no double refraction

4884-451: The selection of spermatozoa for intracytoplasmic sperm injection . Likewise, zona imaging uses birefringence on oocytes to select the ones with highest chances of successful pregnancy. Birefringence of particles biopsied from pulmonary nodules indicates silicosis . Dermatologists use dermatoscopes to view skin lesions. Dermoscopes use polarized light, allowing the user to view crystalline structures corresponding to dermal collagen in

4958-403: The skin. These structures may appear as shiny white lines or rosette shapes and are only visible under polarized dermoscopy . Isotropic solids do not exhibit birefringence. When they are under mechanical stress , birefringence results. The stress can be applied externally or is "frozen in" after a birefringent plastic ware is cooled after it is manufactured using injection molding . When such

5032-401: The slow axis and fast axis of the waveplate. Uniaxial birefringence is classified as positive when the extraordinary index of refraction n e is greater than the ordinary index n o . Negative birefringence means that Δ n = n e − n o is less than zero. In other words, the polarization of the fast (or slow) wave is perpendicular to the optic axis when the birefringence of

5106-459: The solid Earth (the Earth's liquid core does not support shear waves) is widely used in seismology . Birefringence is widely used in mineralogy to identify rocks, minerals, and gemstones. In an isotropic medium (including free space) the so-called electric displacement ( D ) is just proportional to the electric field ( E ) according to D = ɛ E where the material's permittivity ε

5180-411: The top of this page, with the optic axis along the surface (and perpendicular to the plane of incidence ), so that the angle of refraction is different for the p polarization (the "ordinary ray" in this case, having its electric vector perpendicular to the optic axis) and the s polarization (the "extraordinary ray" in this case, whose electric field polarization includes a component in the direction of

5254-459: The two angles of refraction are governed by the effective refractive index of each of these two polarizations. This is clearly seen, for instance, in the Wollaston prism which separates incoming light into two linear polarizations using prisms composed of a birefringent material such as calcite . The different angles of refraction for the two polarization components are shown in the figure at

5328-415: The wavelength is independent of polarization. For this reason, birefringent materials with three distinct refractive indices are called biaxial . Additionally, there are two distinct axes known as optical ray axes or biradials along which the group velocity of the light is independent of polarization. When an arbitrary beam of light strikes the surface of a birefringent material at non-normal incidence,

5402-421: Was announced by Sony on October 14, 2015. It is the first camera in mass production featuring a continuously variable optical low pass filter . In contrast with conceptually related technology debuted in the Pentax K-3 and subsequently carried by other Pentax models, Sony's technology works at any shutter speed. Anti-aliasing filter An anti-aliasing filter ( AAF ) is a filter used before

5476-501: Was recently applied in the living human retina to quantify the polarization properties of vessel walls near the optic nerve. While retinal vessel walls become thicker and less birefringent in patients who suffer from hypertension, hinting at a decrease in vessel wall condition, the vessel walls of diabetic patients do not experience a change in thickness, but do see an increase in birefringence, presumably due to fibrosis or inflammation. Birefringence characteristics in sperm heads allow

#465534