Abstract: A displacement detection device is capable of stably and accurately detecting an amount of displacement. A polarization maintaining fiber has a length not to be equal to a length obtained by dividing, a product of an integral multiple of twice a length of a resonator times a refractive index of the resonator and a beat length obtained from a difference between propagation constants of two polarization modes, by a wavelength of the light source, is selected from a range including a length equal to the above length. The polarization maintaining fiber includes multiple polarization maintaining fibers fitted to each other by removable connectors.

Abstract: In order to provide an optical encoder with high resolution, the optical encoder includes: a rotary scale provided with a grating pattern having a first radial pattern and a plurality of concentric circular patterns disposed at predetermined intervals; and a light receiving element which detects a first interference fringe formed by the first pattern having a first period in the circumferential direction, a second interference fringe which is diffracted in a direction of the first interference fringe by a grating pattern having a second period in the circumferential direction disposed at a different radial position so that the second interference fringe has a period closer to the first period than the second period.

Abstract: An apparatus and method for die defect detection are disclosed. The apparatus includes: a light source unit (10) for emitting light of at least two wavelengths; a beam splitter (40) for receiving the light emitted by the light source unit (10) and splitting it into a first portion and a second portion, the first portion of the light reflected by a die (60) surface under inspection and thereby forming a detection beam; a reference unit (70) for receiving the second portion of the light and processing it into a reference beam; and a detection unit (90) for receiving the detection beam and the reference beam. The reference beam crosses the detection beam at an angle and thus produces interference fringes on a sensing surface of the detection unit (90), based on which a defect parameter of the die (60) surface under inspection is determined. This apparatus is capable of measuring a die with improved accuracy and efficiency and is suitable for the measurement of large dies.

Abstract: An alignment system obtains the characteristics of the light coming back from a wafer stack. A beam analyzer measures changes in wavelength, polarization, and beam profile. This measured information allows for in-line process variation corrections. The correction provides optical monitoring of individual mark stack variations, and in turn provides information to reduce individual mark process variation-induced accuracy error.

Abstract: A position measurement system to measure a position of an object relative to a reference, the position measurement system including two interferometers, wherein each interferometer is configured to form a reference beam and a measurement beam from input radiation and to combine the reference beam and the measurement beam to provide output radiation to be delivered to a detector, wherein each interferometer is configured such that the reference beam is formed by reflection of input radiation from a reflective element, and such that the measurement beam is formed by diffraction of input radiation from a grating on the object, and wherein the reference beam and the measurement beam are parallel to each other.

Abstract: A displacement detection apparatus can reduce a measurement error even when a diffraction grating is displaced and/or tilted to a direction other than the measurement direction. A displacement detection apparatus includes a light source which emits light, a luminous flux-splitting section, a diffraction grating, a diffracted light-reflecting section, a correcting lens, a luminous flux-coupling section, and a light-receiving section. The diffracted light-reflecting section reflects a first luminous flux and a second luminous flux so as to be perpendicular to one of measuring planes of the diffraction grating and be parallel to each other. The correcting lens is arranged between the diffracted light-reflecting section and the diffraction grating.

Abstract: An integrated imaging spectrometer for hyperspectral imaging (HSI) system is disclosed. The integrated imaging spectrometer features photonic PLCs that include an array of input channel waveguides, one for each pixel of an image scene. Spectral grating filters are positioned along the length of each waveguide to extract the spectral components as the light propagates to the end of the waveguide. The filters route the optical energy to photodetectors and the detected electrical signals are captured by a read out integrated circuit (ROIC). Together the PLC, detectors, and ROIC form an imaging layer. Stacking imaging layers generates a device capable of recording an entire 3D high-resolution spatial/spectral image data cube in real-time.

Abstract: A position detecting apparatus includes a light source, which supplies a detecting light; a light-collecting optical system which collects the detecting light onto a diffracted light generating portion provided on the object; a light guiding optical system which guides, to a predetermined position, a diffracted measuring light generated from the diffracted light generating portion by receiving the detecting light and a reference light generated from a reference surface by receiving the detecting light; and a photodetector which is arranged at the predetermined position and which detects interference fringes generated by the diffracted measuring light and the reference light. Three-dimensional positional information of, for example, a mask pattern surface or an exposure surface of a photosensitive substrate can be highly accurately detected by a relatively simple construction.

Abstract: The present invention provides an apparatus for highly accurate and real-time photoelectric glass substrate identification. The apparatus includes: a laser device for emitting a laser beam; a glass substrate that has a first surface and a second surface and is configured to receive the laser beam to generate a first laser beam point and a second laser beam point; and, a charged coupled device (CCD) camera inspecting equipment. The first laser beam point has a first point area, and the second laser beam point has a second point area. Once the first point area is moved for a glass distance number and is aligned with the second point area, the CCD camera inspecting equipment can obtain a thickness value of the glass substrate with a resolution value and the glass distance number. In addition, the present invention also provides a method for highly accurate and real-time photoelectric glass substrate identification.

Abstract: A measurement system (22) for measuring the position of a work piece (28) includes a measurement grating (34) and an encoder head (36). The encoder head (36) directs a measurement beam (252) at the measurement grating (34), the measurement beam (252) having an oval shaped cross-section. The encoder head (36) includes a beam shape adjuster (256) positioned in the path of an input measurement beam (240) having a substantially circular cross-sectional shape that transforms the input measurement beam (240) to provide the measurement beam (252) having the oval shaped cross-section.

Abstract: A method for determining information about changes along a degree of freedom of an encoder scale includes directing a first beam and a second beam along different paths and combining the first and second beams to form an output beam, where the first and second beams are derived from a common source, the first and second beams have different frequencies, where the first beam contacts the encoder scale at a non-Littrow angle and the first beam diffracts from the encoder scale at least once; detecting an interference signal based on the output beam, the interference signal including a heterodyne phase related to an optical path difference between the first beam and the second beam; and determining information about a degree of freedom of the encoder scale based on the heterodyne phase.

Abstract: A displacement detecting device has a diffraction grating, grating interferometers, and relative position information output sections. The grating interferometers have a light source, reflectors, a beam splitter, and light receiving sections. The reflectors reflect 1st-order diffracted lights diffracted by the diffraction grating, and cause the reflected 1st-order diffracted lights to be incident at a position substantially identical to the position at which the light from the light source is irradiated. Furthermore, the reflectors cause the 1st-order diffracted lights to be incident on the diffraction grating at an angle different to either the incidence angle of the light from the light source incident on the diffraction grating or the angle at which the 1st-order diffracted lights are transmitted through or reflected by the diffraction grating.

Abstract: Measurement of motion errors of a linear stage is performed to enable accurate measurement of motion errors in linear directions and a rotational direction in the linear stage using a diffraction grating. A first beam splitter splits a laser beam emitted from a light emitting unit. A first measurement unit measures a unidirectional linear motion error of the linear stage using one laser beam component split by the first beam splitter and a second measurement unit measures an angular motion error and another unidirectional linear motion of the linear stage error using a diffracted beam component obtained by diffracting another laser beam component split by the first beam splitter through the diffraction grating. A third measurement unit circularly polarizes the beam component diffracted through the diffraction grating to measure a third unidirectional linear motion error of the linear stage.

Abstract: A self-referencing interferometer includes an optical system to split an alignment beam to create a reference beam and a transformed beam. The optical system includes a beam splitter to combine the reference beam and the transformed beam so that the diffraction orders in the reference beam spatially overlap with their respective opposite orders in the transformed beam. A detector system receives the spatially overlapping reference beam and transformed beam from the optical system and determines a position signal. The detector system includes a polarizing system for manipulating the polarization of the beams so that they interfere, and for directing the interfering reference beam and transformed beam to a detector for determining a position signal from the variation of intensity of the interfering beams.

Abstract: In the interferometric system, the image plane is imaged by an output imaging setup via a transmission system of reflectors to the output plane and a reflection type diffraction grating is located in the image plane of an imaging setup of a reference branch. The transmission systems of reflectors are adjusted so that axes of both branches coincide at an entrance to the output plane and parallel with a normal line of the output plane, and an axial beam, diffracted by the reflection type diffraction grating at an angle ?, enters into the output plane at an angle ?, and the relation between angle ? and ? is sin(?)=sin(?)/m, where m is a magnification of the output imaging setup. The system enables the achievement of a holographic imaging of an object by low-coherence waves. Incoherent waves allow the imaging of objects immersed in scattering media.

Abstract: A congruence reduction algorithm that forms composite lenslets by reducing data of a plurality of focal spot locations using linear transformations. Use of the congruence reduction algorithm increases the speed of calculations by which corrective elements such as deformable mirrors function, reduces the number of lenslets in an array and improves reconstruction time and focal spot quality.

Abstract: A method and a device for dynamic measurement of the radial deformation of a bearing ring (12) of a rolling bearing (10) for a rotating element (16), a glass fiber segment (22) of a fiber optic sensor (24) that is fixed in or to the periphery of the bearing ring, a light signal which has been generated by the light source (30) being injected into the glass fiber segment, and the light signal passing through the glass fiber segment being detected by a detector (34), the longitudinal deformation of the glass fiber segment being determined from the change of at least one parameter of the light signal, when the light signal passes through the glass fiber segment, in order to determine the corresponding radial deformation of the bearing ring.

Abstract: A self-referencing interferometer includes an optical system to split an alignment beam to create a reference beam and a transformed beam. The optical system includes a beam splitter to combine the reference beam and the transformed beam so that the diffraction orders in the reference beam spatially overlap with their respective opposite orders in the transformed beam. A detector system receives the spatially overlapping reference beam and transformed beam from the optical system and determines a position signal. The detector system includes a polarizing system for manipulating the polarization of the beams so that they interfere, and for directing the interfering reference beam and transformed beam to a detector for determining a position signal from the variation of intensity of the interfering beams.

Abstract: A laser beam emitted by an encoder main body enters a wafer table via a PBS from the outside, and reaches a grating at a point that is located right under exposure area, and is diffracted by the grating. Then, by receiving interference light of a first polarized component that has returned from the grating and a second polarized component reflected by the PBS, positional information of the wafer table is measured. Accordingly, because the first polarized component, which has passed through PBS passes through the wafer table until it is synthesized with the second polarized component again, does not proceed through the atmosphere outside, position measurement of the wafer table can be performed with high precision without the measurement beam being affected by the fluctuation of the atmosphere around the wafer table.

Abstract: An optical displacement measuring device includes a diffraction grating, a reflecting optical system configured to irradiate two one-time diffracted beams diffracted at the diffraction grating on the diffraction grating again, and the reflecting optical system includes a first imaging element, a second imaging element, a first reflector, and a second reflector, wherein the focal length of the first imaging element and the focal length of the second imaging element are the same, the diffraction grating and first reflector are disposed around the focal position of the first imaging element, and the diffraction grating and second reflector are disposed around the focal position of the second imaging element, thereby suppressing influence of displacement of the diffraction grating as to other than a direction where a movement position is detected.

Abstract: A device has a scale on which a grating pattern is formed, a light source to irradiate light on the scale, a wavelength plate to transform multiple diffracted lights from the light source into circular polarized light, respectively, an optical element to superposition and cause interference of the multiple diffracted lights, and a photodetector to receive the interfered light. Also, a generating unit to generate linearly polarized light by the light from the light source, so that the multiple diffracted lights input to the wavelength plate become linearly polarized light with a same mutual polarization direction.

Abstract: A displacement detection apparatus includes a light source for emitting light and an extinction ratio conversion element which raises an extinction ratio of the light to 20 dB or more. A condenser lens condenses the light having the increased extinction ratio and a polarization maintaining type optical fiber transmits the condensed light which is subsequently transferred to a diffraction grating that is attached to an object to be measured. The displacement detection apparatus adjusts a polarization axis of the light having increased extinction ratio.

Abstract: A reflective metrological scale has a metal tape substrate and a scale pattern of elongated side-by-side marks surrounded by reflective surface areas of the substrate. Each mark has a furrowed cross section and may have a depth in the range of 0.5 to 2 microns. The central region of each mark may be rippled and darkened to provide an enhanced optical reflection ratio with respect to surrounding surface areas. A manufacturing method includes the repeated steps of (1) creating a scale mark by irradiating the substrate surface at a mark location with overlapped pulses from a laser, each pulse having an energy density of less than about 1 joule per cm2, and (2) changing the relative position of the laser and the substrate by a displacement amount defining a next mark location on the substrate at which a next mark of the scale is to be created.

Abstract: A displacement detection apparatus, polarization beam splitter, and diffraction grating are provided. A displacement detection apparatus configured to detect a displacement includes a light source, a reflective diffraction grating configured to receive the two polarized beams, two polarization altering elements configured to alter the polarization states of two diffracted beams of the two polarized beams obtained at the diffraction grating, two mirrors configured to reflect the beams whose polarization states have been altered at the two polarization altering elements and to guide the reflected beams to the two polarization altering elements, each of the mirrors corresponding to the polarization altering elements, and a polarization beam splitter provided as a unit with at least the two polarization altering elements, the polarization beam splitter including a polarizing and splitting surface and a transmissive area.

Abstract: A Littrow encoder is disclosed. The encoder includes first and second interferometers and a beam splitter assembly that splits a first instrument light beam into first and second interferometer input beams and directs these beams into the first and second interferometers, respectively. Each interferometer generates a measurement beam and a reference beam and directs the measurement beam toward a grating on a surface from which the measurement beam is diffracted, the measurement beam from the first interferometer striking the surface at a Littrow angle that is the negative of the angle at which the measurement beam from the second interferometers strikes that surface. Each interferometer includes at least one intensity detector that generates a signal related to an intensity of light in a combined light beam that includes the reference and measurement beams from that interferometer.

Abstract: An optical displacement measuring device includes a diffraction grating, a reflecting optical system configured to irradiate two one-time diffracted beams diffracted at the diffraction grating on the diffraction grating again, and the reflecting optical system includes a first imaging element, a second imaging element, a first reflector, and a second reflector, wherein the focal length of the first imaging element and the focal length of the second imaging element are the same, the diffraction grating and first reflector are disposed around the focal position of the first imaging element, and the diffraction grating and second reflector are disposed around the focal position of the second imaging element, thereby suppressing influence of displacement of the diffraction grating as to other than a direction where a movement position is detected.

Abstract: In a position-measuring device for recording the relative position of a scanning unit and a measuring graduation that is movable with respect to the latter in at least one measuring direction, the scanning unit includes a plurality of grating structures as well as at least one reflector element. The elements in the scanning unit are arranged such that the beams of rays diffracted by the measuring graduation pass through first grating structures in the scanning unit, subsequently impinge on the reflector element, from which there takes place a retroreflection in the direction of the measuring graduation, and the partial beams of rays then pass through second grating structures and then once again impinge upon the measuring graduation. The first and the second grating structures are arranged such that, upon the first and second passing through of the partial beams of rays, a defined lens effect on the partial beams of rays results.

Abstract: A measuring instrument, in particular for transmission measurement with transparent substrates, comprises a measuring head with a light emitting element for emitting a light beam and a light receiver element for recording an incident light beam, and a retro-reflector for reflection of the emitted light beam. The measuring instrument allows transmission measurements to be carried out on transparent substrates with only one reflection measuring head. The measuring instrument also allows reflection measurements to be carried out, for example on non-transparent substrates or by tilting the measuring head and covering the retro-reflector. The measuring instrument only requires one measuring head and can therefore be produced more cost-effectively. It does not require calibration, as the retro-reflector also reflects the light in the original direction in the case of oblique incidence and in the event of positional changes caused by process or operational factors (vibrations etc.).

Abstract: A measurement method measures a wavefront aberration of a target optical system using an interference pattern formed by lights from first and second image side slits. The first image side slit has a width equal to or smaller than a diffraction limit of the target optical system. The measurement method includes the steps of obtaining a first and second wavefronts having wavefront aberration information of the target optical system in ±45° directions relative to the polarization direction of the light, and calculating wavefront aberration of the target optical system based on the first and second wavefronts of the target optical system obtained by the obtaining step.

Abstract: Interference measuring apparatus having an optical system for dividing a coherent light beam into two light beams, and causing the divided two light beams to pass along discrete optical paths. The light beams are made into linearly polarized light beams orthogonal to each other and given modulation to the phase of the wave front of at least one of them. The wave fronts of the linearly polarized light beams are superposed one upon the others. A light dividing member divides the light beams superposed one upon the other by the optical system into a plurality of light beams. A polarizing plate takes out each light beam with a 45° polarized component, and a plurality of light receiving elements individually receive the light beams taken out by the polarizing plate.

Abstract: A device according to one embodiment of the invention may be applied to measure the overlay (e.g. as a machine performance number) quickly and over an expanded range of locations (possibly everywhere) on a wafer. One method using such a device includes measuring the amplitude of a diffraction order of a diffraction pattern that results from interference between a pattern on wafer level and a pattern that is projected on the pattern on wafer level. The pattern that is projected may be present, for example, at reticle level.

Abstract: A displacement detection device having excellent stability with the lapse of time and suitable for reduction in size and weight includes: a light source for emitting light; polarizing light splitting unit for splitting the light emitted from the light source into two light beams having difference polarized components, radiating the two light beams to an external optical system, and combining the two light beams reflected by the external optical system to generate combined light; a phase plate provided between the light source and the polarizing light splitting unit and adapted for changing the polarization state of the light emitted from the light source and leading the light to the polarizing light splitting unit; light splitting films for splitting the combined light generated by the polarizing light splitting unit into plural light beams; polarizing units for transmitting only a predetermined polarized components of the split combined light beams; and light-receiving elements for photoelectrically converti

Abstract: A point diffraction interferometer measures optical performance of a target optical system based on a light intensity distribution of an interference fringe through an interference between a wave front that passes the target optical system and a reference wave front generated from a pinhole, wherein the pinhole satisfies 1.05?ellipticity?1.16, where the ellipticity is defined as a diameter of a pinhole in a direction perpendicular to a linear polarization direction of light incident upon the pinhole, divided by a diameter of the pinhole in the linear polarization direction.

Abstract: A method and an apparatus for determining the influencing of the state of polarization of optical radiation by an optical system under test, wherein radiation with a defined entrance state of polarization is directed onto the optical system, the exit-side state of polarization is measured, and the influencing of the state of polarization is determined by the optical system with the aid of evaluation of the exit state of polarization with reference to the entrance state of polarization. An analyser arrangement which can be used for this purpose is also disclosed. The method and the apparatus are used, e.g., to determine the influencing of the state of polarization of optical radiation by an optical imaging system of prescribable aperture, the determination being performed in a pupil-resolved fashion.

Abstract: A device for polarization-specific examination of an optical system having a detector part that has polarization detector means for recording the exit state of polarization of radiation emerging from the optical system. Also, an associated optical imaging system, and a calibration method for the device. The device includes a polarization detector with a polarizing grating structure. Provided as an alternative is a device for snapshot polarimetry having a birefringent element and downstream polarizer element that adequately polarizes nonquasi-parallel radiation. The device may be used for determining the influence on the state of polarization of UV radiation by a microlithographic projection objective.

Abstract: A displacement detection device having excellent stability with the lapse of time and suitable for reduction in size and weight includes: a light source for emitting light; polarizing light splitting unit for splitting the light emitted from the light source into two light beams having difference polarized components, radiating the two light beams to an external optical system, and combining the two light beams reflected by the external optical system to generate combined light; a phase plate provided between the light source and the polarizing light splitting unit and adapted for changing the polarization state of the light emitted from the light source and leading the light to the polarizing light splitting unit; light splitting films for splitting the combined light generated by the polarizing light splitting unit into plural light beams; polarizing units for transmitting only a predetermined polarized components of the split combined light beams; and light-receiving elements for photoelectrically converti

Abstract: Provided is a grating interference type optical encoder including a scale board, a diffraction grating located on the scale board, a light receiving element, an illumination optical system for emitting a coherent light fluxes to the diffraction grating on the scale board that relatively moves, to produce two diffraction light fluxes having different orders, an arc-shaped grating for re-emitting to the diffraction grating the two diffraction light fluxes having the different orders which are produced in the diffraction grating portion through a deflection unit, and a light guiding unit for superimposing rediffraction light fluxes produced by rediffracting the diffraction light fluxes re-emitted to the diffraction grating and guiding the superimposed rediffraction light fluxes to the light receiving element.

Abstract: Interference measuring apparatus for detecting a plurality of different interference phase signals. The apparatus has a light dividing member for dividing linearly polarized light beams superposed one upon another into a plurality of light beams. The apparatus also includes a light transmitting member with a plurality of light passing portions having different light transmitting properties in conformity with the incidence positions of the plurality of light beams divided by the light dividing member. In addition, the apparatus has a polarizing plate to receive the plurality of light beams that passed through the light transmitting member.

Abstract: A position measuring device for detecting the relative position of a scanning unit and a scale. The position measuring device includes a scale and a scanning unit that is displaced with respect to the scale in a measuring direction. The scanning unit includes a scanning grating, a ridge prism and an optoelectronic detector element. The ridge prism having a ridge that is oriented parallel with the measuring direction, the ridge prism acts as a retro-reflector in a second direction which is aligned in a plane of the scale vertically with respect to the measuring direction.

Abstract: A displacement measuring device allows a plurality of light beams to be incident at positions on a scale or diffracted at points on a scale grating, which are farther spaced away from each other than the diameter of the light beams on the scale grating, and makes an angle of incidence of each light beam on the scale equal generally to an angle of transmission of the diffracted light beam of each light beam. This makes the strength of a detection signal impervious to variations in pitch angle and allows for providing good signals. Accordingly, it is possible to attach the device easily to an apparatus and provide improved ease of use for the device.

Abstract: The invention comprises methods and apparatus for reducing sub-harmonic cyclic errors by rotating by a small angle an interferometer or elements thereof. The rotation of the interferometer or selective elements thereof introduces a corresponding small angle between a sub-harmonic type spurious beam that subsequently interferes with either the reference or measurement beam so that the fringe contrast of the interference terms between the subharmonic spurious beam and either the reference or measurement beam is reduced by a required factor for a given use application thereby reducing nonlinearities in the phase signal.

Abstract: A scale (10) is illuminated by a light source (18). After interaction with an index grating (12), fringes (F) are formed in a Talbot plane and analyzed by an analyzer grating (14). To decrease the sensitivity to changes in the ride height of the index grating above the scale, the light source is restricted to a small but finite size, and positioned so that it subtends a small angle Ø at the analyzer grating (or, if a collimating lens (24) is used, positioned so that it subtends a small angle Ø at the lens). The size of the light source should preferably be smaller than a predetermined value such that the extent of a geometric fringe visibility envelope exceeds the extent of a Talbot fringe visibility envelope.

Abstract: An optical displacement sensing device is provided for determining the relative displacement of a diffraction scale grating that may have a grating pitch less than the wavelength of the light of the sensing device. The sensing device includes a split light beam input portion for inputting two split light beams along respective light paths, and light beam directing elements for directing the two split beams along converging light paths toward a first zone on the scale grating to give rise to two diffracted beams along light paths which diverge. The sensing device further includes retroreflector elements for receiving the two diverging diffracted beams and retroreflecting them along light paths which converge toward a second zone on the scale grating to give rise to two later-diffracted light beams that are then directed to a shared zone. The retroreflectors may be positioned to eliminate cross-over beams and the need for polarizers.

Abstract: A laser beam is irradiated onto a moving object, and scattered light reflected from the moving object is split into two beams, which are then received through respective spatial filters that are 90° out of phase with each other, thereby providing two signals. The signals are processed to determine the movement direction of the moving object.

Abstract: A laser beam irradiation device, comprising a light source for emitting a laser beam, a cylindrical lens, an optical system for entering the laser beam to the cylindrical lens perpendicularly with respect to a center line of the cylindrical lens, and a luminous flux rotating means for rotating the incident laser beam around an optical axis of the laser beam.

Abstract: A displacement detection device having excellent stability with the lapse of time and suitable for reduction in size and weight includes: a light source for emitting light; polarizing light splitting unit for splitting the light emitted from the light source into two light beams having difference polarized components, radiating the two light beams to an external optical system, and combining the two light beams reflected by the external optical system to generate combined light; a phase plate provided between the light source and the polarizing light splitting unit and adapted for changing the polarization state of the light emitted from the light source and leading the light to the polarizing light splitting unit; light splitting films for splitting the combined light generated by the polarizing light splitting unit into plural light beams; polarizing units for transmitting only a predetermined polarized components of the split combined light beams; and light-receiving elements for photoelectrically converti

Abstract: A method and device is capable of amplitude, phase, polarization shear, wavelength, and diversity measurement along a common path by using a sampling device to get a sparse sampled optical field. The sampled field is fed to a diversity generator device. The diversity generator device generates the diversity information associated with each sample/element of the sparse input in empty space provided by sampling. The diversity information may consist of phase-shifted copies of the input sample having known/device dependent relative phases, amplitudes, polarization, shear, or wavelength with respect to their originating sample. The geometry of the fan out allows overlap between part or all different diversity copies (originating from the same or from different samples) thus making the method interferometric.

Abstract: An apparatus having a first system for forming a composite light beam of two light beams to be made to interfere with each other, a splitting member for amplitude-splitting the composite light beam into three or more split light beams in the same area, and a second system for obtaining interference light beams of different phases from the plurality of split light beams.

Abstract: Light of multiple wavelengths passes through, in order, a plane polarizer, a ½ wave plate, a means for attenuating polarized light in a selected plane, and a ¼ wave plate. The ¼ wave plate and the ½ wave plate are selected for green light. The ½ wave plate induces an error for nongreen light which is twice the error which the ¼ wave plate would induce for a particular light wavelength but of opposite sign. The errors are reduced by ½ by attenuation by passing all wavelengths of light through glass air interfaces defined by a plurality of glass plates, angled at between about 45 and 55 degrees with respect to the optical axis. Light which is plane polarized for green light, and precorrected for every other wavelength is passed through the ¼ wave plate and all wavelengths are converted to circularly polarized light.

Abstract: A light wave measuring instrument has a small optical system. Beams from a laser light source illuminate a grating scale and plus-first-order-diffracted and minus-first-order-diffracted beams from the grating scale are diffracted and reflected so as to travel through their original optical paths. The beams are returned to a non-polarization beam splitter, transmitted through a quarter wavelength plate and converted into one straight polarized beam having a polarization direction varying with the phase difference between the two beams. The straight beam is then separated. The separate beams are separated into P and S polarized beams. The S polarized beams are reflected by a polarization film, while the P polarized beams are reflected by a parallel glass plate. These beams are transmitted through the polarization film again to become coherence signal beams having reverse phases of fringes, which are then emitted in the same direction.