Abstract: An ultra-miniature interferometric fiber-optic encoder readhead for sensing displacement of a very fine pitch scale grating is disclosed. The readhead includes a source grating that diffracts diverging source light into +/? 1st order beams, a pair of mirrors that reflect the +/? 1st order beams to converge toward the scale grating. The +/? 1st order scale light beams are reflectively diffracted back from scale grating to return to the mirrors, and are then reflected to converge back toward the light source and a set of adjacent fiber-optic receiver channels. An interference field generating grating positioned in front of the receiver channels produces interference fringes having a desired pitch. Movement of the interference fringes is sensed by the fiber-optic receiver channels to provide displacement information. The readhead may be configured so that primarily or only +/? 1st order light reaches the receiver channels.

Abstract: When a convex lens 13 comes close to 0-th order transmitted light T0 with rotation of an optical scale 11, the 0-th order transmitted light T0 derived from a light beam L emitted from a light source 15 and transmitted through a diffraction grating 12 around is converged and incident on a reference position signal detection sensor 14. At that time, a large output is obtained from the reference position signal detection sensor 14. This signal constitutes a reference position signal. On the other hand, reflective diffracted light beams La, Lb having been reflected by the diffraction grating are detected by a diffraction light detection sensor 16 after interference, so that the speed and the angle etc. of the scale 11 are detected. In this way, the reference position signal and an incremental signal are detected at the same position on the optical scale.

Abstract: Disclosed is a displacement measuring apparatus that includes a composite scale having a magnetic pattern and a diffraction grating each aligned in a direction of measuring axis, and a detector head moving in a direction of measuring axis relative to the composite scale. The detector head has a magnetic detection unit detecting a magnetic field exerted by the magnetic pattern to generate first reproduced signals, a light source irradiating the diffraction grating with light, and an optical detection unit detecting the light diffracted by the diffraction grating to generate second reproduced signals. In composite scale, the magnetic pattern and the diffraction grating are arranged such that a pitch of the first reproduced signals is larger than that of the second reproduced signals.

Abstract: Optical sensors, and methods for operating optical sensors, are disclosed. One such sensor may include: a reflector positioned a distance from a reflective diffraction grating and a light source for providing light. A first portion of the light can be reflected from the reflective diffraction grating and a second portion of the light passes through the grating to the reflector and is reflected back through the diffraction grating. The sensor may further include a detector for sensing an intensity of light in an interference pattern formed by the first portion of the light reflected from the diffraction grating and the second portion of the light reflected from the reflector. The sensor includes a controller configured to modulate an emission of the light.

Abstract: A fixed-point detector is provided. The fixed-point detector includes a plurality of fixed-point detecting patterns, a fixed-point detecting light source, and a plurality of photoelectric conversion elements. The plurality of fixed-point detecting patterns each have a pair of diffraction gratings for diffracting incident light in different directions. The fixed-point detecting light source irradiates the pair of diffraction gratings with light while moving in the measurement-axis direction with respect to the plurality of fixed-point detecting patterns. The plurality of photoelectric conversion elements move together with the fixed-point detecting light source, while receiving light beams diffracted by the respective diffraction gratings of the plurality of fixed-point detecting patterns and converting the diffracted light beams into electric signals.

Abstract: A sensor head for use with a measurement grating is described. The sensor head comprises: a splitter grating configured to split a light beam into first and second measurement beams; a first retroreflector configured to retroreflect the first and second measurement beams toward the measurement grating; and a second retroreflector configured to retroreflect the first and second measurement beams toward the measurement grating. In one embodiment the second measurement beam is diffracted by the measurement grating to form first and second sub-beams and one of the first and second sub-beams comprises a zeroth order diffraction component and a first order diffraction component. In another embodiment, the first and second sub-beams each comprise a zeroth order diffraction component and a first order diffraction component.

Abstract: Indicating relative speed is disclosed. A first grating coupled to a first moving object is illuminated using a coherent light source to generate a first diffracted beam and a diffracted order beam. A second grating coupled to a second moving object is illuminated using the first diffracted beam and the second diffracted beam to generate a third diffracted beam and a fourth diffracted beam. The third diffracted beam and the fourth diffracted beam are measured. A relative speed of the first moving object with respect to the second moving object is indicated based at least in part on the measured third diffracted beam and the measured fourth diffracted beam.

Abstract: An alignment tool for a lithographic apparatus illuminates an alignment mark on a substrate with an alignment beam and measures the reflected spectrum. The reflected spectrum is compared with a reference mark to determine any misalignment. A blazed sub-wavelength grating is used to deflect the sub-beams created by diffracting the alignment beam from the alignment mark onto the reference mark.

Abstract: A position-measuring device includes a light source, a first grating, a second grating and photodetectors, light from the light source, which is split into partial beams of different directions at the first and second grating, being directed via a deflecting element to the detector. The deflecting element for incident partial beams having different directions has different regions, so that all partial beams directed from the deflecting element to the detector are approximately parallel.

Abstract: A vibration detection device capable of improving detection sensitivity when optically performing vibration detection is provided. A vibration detection device includes: a light source emitting a laser beam; an interferometer including a vibrating body and a first reflection body both capable of reflecting the laser beam, and a second reflection body capable of at least partially reflecting the laser beam, the interferometer splitting the laser beam emitted from the light source into beams traveling along first and second optical paths, the interferometer causing interference between a reference beam reflected by the first reflection body in the first optical path and reflected beams multiply reflected between the vibrating body and the second reflection body in the second optical path to form interference patterns; and a detection means for detecting the vibration of the vibrating body on the basis of the formed interference patterns.

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: Micron-scale displacement measurement devices having enhanced performance characteristics are disclosed. One embodiment of a micron-scale displacement measurement device includes a phase-sensitive reflective diffraction grating for reflecting a first portion of an incident light and transmitting a second portion of the incident light such that the second portion of the incident light is diffracted. The device further includes a mechanical structure having a first region and a second region, the mechanical structure positioned a distance d above the diffraction grating, the second portion of the incident light is reflected off of the first region of the structure such that an interference pattern is formed by the reflected first portion and the reflected second portion of the incident light. The device can further include an electrode extending toward, but spaced a distance away from, the second region of the mechanical structure.

Abstract: An apparatus and method for measuring displacement includes a light beam directed to an interferometer core that splits the light beam into first and second component beams. The first component beam is directed to a diffraction grating at approximately a Littrow angle. A diffraction is received by the interferometer core and is combined with the second component beam. The combination of the first and second component beams is measured to determine displacement of the diffraction grating.

Abstract: A wavefront aberration measuring device includes a mask which arranges a group of minute apertures for generating a group of point light sources at an object point as a measurement objective of an inspection-objective optical system, an illumination system which illuminates the mask with an illumination light, a diffraction grating which shears, into a plurality of light fluxes, a light flux exiting from the group of minute apertures and passing via the inspection-objective optical system, and a detecting portion which detects an interference fringe formed mutually by the plurality of sheared light fluxes, wherein a center spacing distance L between adjacent minute apertures which are adjacent in a shear direction in the group of minute apertures is defined to minimize the coherence degree.

Abstract: Interferometer systems for measuring displacement include a displacement interferometer. This interferometer includes a displacement converter responsive to a measuring beam of light. The displacement converter is configured to transform movement thereof in a direction orthogonal to the measuring beam of light into a change in path length between a reflective surface of the displacement converter and the measuring beam of light. The displacement converter may include a transmission grating and a displacement mirror or a reflecting grating.

Abstract: Measurement of a distance change between a reference surface and a target is provided. A substrate has a first surface facing the target and including a grating. The grating and target combine to form an optical interferometer responsive to changes in distance between the grating and the target. A second surface of the substrate coincides with the reference surface and faces away from the target. Thickness information pertaining to the substrate is combined with results from the optical interferometer to provide a measurement of distance change between reference surface and target. The substrate is preferably a rigid material having picometer level dimensional stability.

Abstract: The displacement detector includes: a light source 140; a beam splitter 170 for dividing the light, which is sent from the light source 140, into two beams of light; reflection mirrors 181, 182 provided for the two beams of light sent from the beam splitter 170, for reflecting these two beams of light and making them incident upon a scale 110; and corner cubes 191, 192 provided for the beams of diffracted light, which are generated when two beams of light incident upon the scale 110 are diffracted by the diffraction grating 111, wherein the corner cubes 191, 192 retroreflect the diffracted light and make the light incident upon the scale as retroreflected light. The incident angle to grating groove formed between the incident light and the normal line vector of the scale is larger than the diffraction angle formed between the retroreflected light and the normal line vector of the scale.

Abstract: A system and method for determining parameters such as critical dimension of a patterned structure and best focus condition of a lithographic apparatus, based on measurment of the intensity of a non-zero order of light diffracted from an experimental structure. The experimental structure includes a first array of lines and partially filled spaces having a period longer than the wavelength of the diffracted light. The experimental structure also includes a second array of lines and spaces, where the second array of lines and spaces comprise the partially filled spaces.

Abstract: A measurement unit to determine a position in a first and second dimension includes a diffraction type encoder and an interferometer. The diffraction type encoder determines by means of a diffraction on a first and a second diffraction grating the position in the first dimension of the second grating with respect to the first grating, The interferometer determines the position in the second dimension of a mirror. The measurement unit includes a combined optical unit to transfer an encoder measurement beam as well as an interferometer measurement beam. Further, the measurement unit may include a combined light source for the encoder as well as the interferometer. One of the first and second diffraction gratings may further show some degree of zero order reflection to provide the mirror of the interferometer.

Abstract: An optical displacement sensor is disclosed which uses a vertical-cavity surface-emitting laser (VCSEL) coupled to an optical cavity formed by a moveable membrane and an output mirror of the VCSEL. This arrangement renders the lasing characteristics of the VCSEL sensitive to any movement of the membrane produced by sound, vibrations, pressure changes, acceleration, etc. Some embodiments of the optical displacement sensor can further include a light-reflective diffractive lens located on the membrane or adjacent to the VCSEL to control the amount of lasing light coupled back into the VCSEL. A photodetector detects a portion of the lasing light from the VCSEL to provide an electrical output signal for the optical displacement sensor which varies with the movement of the membrane.

Abstract: A position measuring arrangement for detecting a relative position. The position measuring arrangement includes a reflection scale graduation and a scanning unit having a plurality of optical elements. The plurality of optical elements include a combining grating, a retro-reflector element, a scanning grating and detector elements. The optical elements are arranged so that: 1) light beams and/or partial light beams of a scanning beam path act on the reflection scale graduation at least twice, 2) a directional reversal of the incident partial light beams impinging on the reflection scale graduation perpendicularly with respect to the measuring direction takes place by the retro-reflector element; and 3) a pair of partial light beams impinges in a non-parallel manner on the combining grating, and the combining grating brings the partial light beams impinging on the combining grating to interference, so that phase-shifted signals are detected by the plurality of detector elements.

Abstract: An optical position encoder employs spatial filtering of diffraction orders other than +/?1st diffraction orders for greater accuracy. The encoder includes a light source, a scale including a diffractive scale pattern, an optical detector adjacent to the scale, and first and second spaced-apart diffraction gratings between the light source and the scale. The gratings and scale are configured to spatially separate +/?1st diffraction orders from other diffraction orders and to direct the +/?1st diffraction orders along respective optical paths. The optical paths diverge from the first grating to respective locations on the second grating that are separated by more than the beam width of the source light beam. The optical paths further converge from the locations on the second grating to an area of the scale adjacent to the detector, and then extend from the area of the scale to the detector to create an interference pattern as a function of the relative position between the scale and the light source.

Abstract: An optical encoder includes a source of a light beam, an optical grating that generates a spatial pattern of interference fringes, and an optical detector which includes generally elongated detector elements that sample the interference fringe pattern at spatially separated locations along the direction of motion of the grating. Each detector element has one or more segments slanted along the direction of motion of the grating by an integer multiple of the period of an undesirable harmonic component of the fringe pattern, thereby spatially integrating the harmonic component and suppressing its contribution to an output of the detector. One specific detector type includes parallel elongated rectangular elements in a rectangular array that is rotated slightly about a Z axis; another type includes detector elements arranged to form a non-rectangular parallelogram.

Abstract: A displacement detection apparatus (100) includes a main scale (110) and a detection head (120). The detection head (120) includes a light emission/reception unit (130) and an optical device unit (140). The optical device unit (140) has a first diffraction scale (141) and a second diffraction scale (143). The first diffraction scale (141) has a transmission type first diffraction grating (142). The second diffraction scale (143) has a diffraction grating. The second diffraction scale (143) has a transmission type second diffraction grating (144) on both sides of a metal film (146). Furthermore, the metal film (146) configures a reflection type third diffraction grating (145) when the second diffraction scale (143) is viewed from the side of the main scale (110).

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: In an acoustoelectric converter element, a light wave from a light source is introduced into a first optical waveguide of a vibration substrate, and diffracted by a diffraction grating disposed on the first optical waveguide. The diffracted light is directed to and detected by a photo detector. Here, the vibration substrate is so supported as to vibrate with respect to an acoustic wave. Therefore, the diffracted light detected by the photo detector is modulated by the acoustic wave, and a signal is output from the detector in accordance with the acoustic wave.

Abstract: A position measuring device for detecting the spatial position of a movable element in relation to a base body, the device including a linear measuring device that measures a distance between a movable element and a base body and an angle-measuring apparatus that measures an angle between the movable element and the base body. A light source that directs light along a beam path, a detector within the beam path and a grating within the beam path between the light source and the detector. For measuring the angle, the beam path extends between the movable element and the base body so that an intensity strip pattern is created by illuminating the grating by the light source, whose position relative to the detector is a measure of the angle.

Abstract: A position-measuring device includes: a measuring graduation provided on a material measure going around in ring-like fashion; a scanning unit for optically scanning the measuring graduation using electromagnetic radiation; a scanning plate with a periodic scanning graduation which is arranged in the beam path of the electromagnetic radiation used for scanning the measuring graduation, so that the radiation interacts both with the scanning graduation and with the measuring graduation; and a detector of the scanning unit, the detector surface of which is used for detecting the electromagnetic radiation after interaction with the scanning graduation and the measuring graduation and which is arranged with a period (PD) for detecting electromagnetic radiation in the form of a stripe pattern. The period PM of the measuring graduation and the period PA of the scanning graduation may be coordinated so that 1/(1/PA?1/PM)<PD.

Abstract: An optoelectronic detector system is for generating a plurality of periodic, phase-shifted scanning signals from the scanning of a periodic fringe pattern. The fringe pattern extends in a detection plane with fringe-pattern period P in a fringe-displacement direction. The detector system is made up of a plurality of detector elements, the geometrical shape of the detector elements being selected such that a defined filtering of unwanted harmonics from the scanning signals thereby results. Within one fringe-pattern period P, a total of N detector elements of the same geometrical shape are arranged one immediately after the other in measuring direction x.

Abstract: A grating interference type optical encoder has 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: A first luminous flux emitted from the front end face of a LD is reflected by a mirror to be made incident on a detection point on the surface of a measuring object, and a second luminous flux emitted from the rear end face of the LD is reflected by another mirror to be made incident on the detection point. Scattered light from the first detection point is received in a photodiode. A signal processing circuit part calculates the frequency shift quantity of the scattered light based on output from the photodiode. As a result, a velocimeter is provided which detects the moving speed of a measuring object highly precisely.

Abstract: A light modulator incorporates a polarization sensitive prism and a novel MEMS ribbon device to impart a relative phase shift to polarization components of an incident light beam. A linear array of phase shifting elements in the MEMS device creates a linear image which is scanned to form a two dimensional scene. Alternatively the deflection of each cantilever in a linear array of atomic force microscope cantilevers may be measured simultaneously.

Abstract: An apparatus for measuring a two-dimensional displacement is disclosed and includes a laser light source, a collimator lens, a beam splitter, a plurality of staggered conjugate optic lens and a plurality of interference optical dephasing modules. The laser light source provides a laser light incident on the collimator lens to generate collimated laser beams. Each of the collimated laser beams are incident on the beam splitter to be separated into two incident beams and incident on a two-dimensional diffraction unit to generate a plurality of first diffracted beams and a plurality of second-order diffracted beams. The staggered conjugate optic lens are used to reflect the first diffracted beams so that the first diffracted beams return to the two-dimensional diffraction unit to generate a plurality of second diffracted beams where the second diffracted beams and the second-order diffracted beams generated as a result of the first diffraction of the beams stagger.

Abstract: A single-, two- or three-axis opto-electronic encoder, or error-inputting device, with an optical scale which is overall cylindrical, spherical or volumetric, as opposed to extant planar, circular optical scales; mostly parallel rays of light enter from the cylindrical or spherical surface of the scale, travel, with or without being modulated in intensity due to rotation/rotations of, or distortion/distortions in, the scale, along elliptical and/or circular sectional planes of the scale and exit to fall upon an obstructing opto-electronic sensor or a plurality of such sensors.

Abstract: An interferential position measuring arrangement including a light source, which emits a beam of rays and an optical element, which converts the beam of rays emitted by the light source into an incoming beam of rays. A scale grating which splits the incoming beam of rays into a first partial beam of rays and a second partial beam of rays. A first scanning grating that causes splitting of the first partial beam of rays and a second scanning grating that causes splitting of the second partial beam of rays, wherein a periodically modulated interferential fringe pattern with definite spatial interferential fringe pattern period results in a detection plane. A detection arrangement which causes splitting of light entering through the detection arrangement into at least three different spatial directions and optoelectronic detector elements arranged in the at least three spatial directions for detecting phase-shifted scanning signal.

Abstract: An opto-acoustoelectric device encompasses a diaphragm having a diffraction grating, the diaphragm is susceptible to a vibration driven by an external force; a light source oriented to irradiate the diffraction grating; and a photo detector configured to detect the light diffracted by the diffraction grating and to convert the detected light into an electric signal. The electric signal corresponds to a displacement of the vibration in the diaphragm.

Abstract: Diffraction grating based fiber optic interferometric systems for use in optical coherence tomography, wherein sample and reference light beams are formed by a first beam splitter and the sample light beam received from a sample and a reference light beam are combined on a second beam splitter. In one embodiment, the first beam splitter is an approximately 50/50 beam splitter, and the second beam splitter is a non 50/50 beam splitter. More than half of the energy of the sample light beam is directed into the combined beam and less than half of the energy of the reference light beam are directed into the combined beam by the second beam splitter. In another embodiment, the first beam splitter is a non 50/50 beam splitter and the second beam splitter is an approximately 50/50 beam splitter. An optical circulator is provided to enable the sample light beam to bypass the first beam splitter after interaction with a sample.

Abstract: An interferometric fiber optic encoder readhead for sensing the displacement of a scale grating is disclosed. The detector channels of the readhead are fiber optic detector channels having respective phase grating masks. The fiber optic encoder readhead is configured to detect the displacement of interference fringes arising from the scale grating. In various exemplary embodiments, the fiber optic readhead is constructed and operably positioned according to various design relationships that insure a compact mounting and a relatively ideal sinusoidal signal as a function of displacement. Accordingly, high levels of displacement signal interpolation may be achieved, allowing sub-micrometer displacement measurements. The fiber optic encoder readhead may be assembled in a particularly accurate and economical manner and may be provided in a package with dimensions on the order of 1–2 millimeters.

Abstract: An optical displacement sensor comprises a surface emitting laser light source, a scale and a photosensor. The surface emitting laser light source emits a light beam having a predetermined shape. The scale is displaceable in such a manner as to cross the light beam emitted from the surface emitting laser light source and has a diffraction grating of a predetermined period formed thereon for forming a diffraction interference pattern from the light beam. The photosensor receives a predetermined portion of the diffraction interference pattern.

Abstract: An optical displacement sensor comprises a surface emitting laser light source, a scale and a photosensor. The surface emitting laser light source emits a light beam having a predetermined shape. The scale is displaceable in such a manner as to cross the light beam emitted from the surface emitting laser light source and has a diffraction grating of a predetermined period formed thereon for forming a diffraction interference pattern from the light beam. The photosensor receives a predetermined portion of the diffraction interference pattern.

Abstract: An optical displacement sensor comprises a surface emitting laser light source, a scale and a photosensor. The surface emitting laser light source emits a light beam having a predetermined shape. The scale is displaceable in such a manner as to cross the light beam emitted from the surface emitting laser light source and has a diffraction grating of a predetermined period formed thereon for forming a diffraction interference pattern from the light beam. The photosensor receives a predetermined portion of the diffraction interference pattern.

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: A position measuring arrangement for determining a relative position between a first object and a second object. The arrangement includes a light source having a single-mode laser light source that generates radiation and a signal generator that receives the radiation and generates displacement-dependent output signals that determine a relative position between a first object and a second object. A feedback device, wherein the laser light source interacts with the feedback device in such a way that an excitation of several modes takes place in the single-mode laser light source, and a multi-mode operation of the single-mode laser light source results.

Abstract: A displacement pickup is provided which includes a displaceable scale (12) having defined therein a first area (12a) where positional information is recorded with a predetermined pitch and a second area (12b) where positional information is recorded with a predetermined pitch different from that in the first area (12a), a first reading system (10) to read the positional information recorded in the first area (12a), a first phase detector (14) to detect a first phase on the basis of the positional information read by the first reading system (10), a second reading system (11) to read the positional information recorded in the second area (12b), a second phase detector (15) to detect a second phase on the basis of the positional information read by the second reading system (11), a phase comparator (16) to make a comparison between the first and second phases, and an origin signal generator (17) to generate an origin signal according to the result of comparison from the phase comparator (16).

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: Diffraction grating based fiber optic interferometric systems for use in optical coherence tomography, wherein sample and reference light beams are formed by a first beam splitter and the sample light beam received from a sample and a reference light beam are combined on a second beam splitter. In one embodiment, the first beam splitter is an approximately 50/50 beam splitter, and the second beam splitter is a non 50/50 beam splitter. More than half of the energy of the sample light beam is directed into the combined beam and less than half of the energy of the reference light beam are directed into the combined beam by the second beam splitter. In another embodiment, the first beam splitter is a non 50/50 beam splitter and the second beam splitter is an approximately 50/50 beam splitter. An optical circulator is provided to enable the sample light beam to bypass the first beam splitter after interaction with a sample.

Abstract: The object of the present invention is to quickly and easily recognize the position, quantity, and kind of the object, which takes unspecified forms according to the angle in which the object is positioned. Points are arranged at regular intervals on an image. For each respective point, a fundamental wave Fourier transformation is calculated on the respective pixel values on the circumference of a circle whose center is at the point. The phase obtained by the fundamental wave Fourier transformation is a normal vector of the point. From the normal vector groups of every point arranged at regular intervals the object is recognized.

Abstract: A light beam emitted from a semiconductor-laser light source is projected onto a diffraction-grating scale after passing through a collimator lens, a beam splitter and a central portion of an annular reflection grating. Two diffracted light beams reflected from the diffraction-grating scale are projected onto the annular reflection grating. The annular reflection grating diffracts the light beams projected onto all portions thereon to a substantially original direction to be projected onto and diffracted from the same position on the diffraction-grating scale. The diffracted light beams are superposed and the resultant light beam is returned to the beam splitter. The light beam is guided by the beam splitter in a direction different from the semiconductor-laser light source, and is detected by a photosensor as an interference light beam.

Abstract: A surface-emitting laser is disposed on a photodetector disposed in parallel with a scale, so that an optical pattern surface of the scale can be irradiated with a light beam having a desired shape. A major axis of the light beam emitted from the surface-emitting laser is vertical to the photodetector, and forms a beam spot on the optical pattern surface of the scale. A light emission portion of the light source is disposed in a 0-order diffracted light region from the scale and other than a region in which only a 0-order diffracted light and 1st-order diffracted light or a 0-order diffracted light and ?1st-order diffracted light interfere. A light shield metal and/or a dummy light receiving portion are/is disposed to surround a light receiving portion outer periphery, and is disposed in a region between an inner periphery of the light receiving portion and the surface-emitting laser.

Abstract: The device for measuring translation, rotation or velocity includes at least a light source, a light detector, a first grating and a second grating, the first grating being mobile relative to the second grating. A incident beam reaches the first grating where it is diffracted in two beams whose directions are interchanged by the second grating, the resulting beams being then again diffracted by the first grating in an output diffraction direction where they interfere together. Both gratings are used in reflexion.