Abstract: An auto-focus laser incremental encoder for measuring linear or rotary motion or position of an object is described. An optical read head focuses three laser beams on the surface of a scaling grating. The grating is a reflection type grating where the height difference between adjacent pixels is one quarter of the wavelength of the laser light whereby the pitch of the grating can be detected by interferometric reflection. There are two sections of grating displaced with respect to each other so that a direction of movement can be readily determined. The third beam acts to provide an autofocus and is reflected from a smooth part of the grating between the two sections of reflective grating.

Abstract: A needle position detecting system for a circular knitting machine inputs the needle position to a computer which controls the needles to perform jacquard knitting. The knitting machine includes a needle cylinder carrying a plurality of needles, a driven gear fixedly mounted on the needle cylinder and driven to turn it by a motor driven gear. An optical encoder coaxially connected to the drive gear counts the number of rotations of the drive gear and the needle cylinder and sends a signal to the computer for calculating a respective needle position.

Abstract: An optical encoder is provided which is not affected by fluctuation of wavelength of a light beam due to temperature change, without sacrificing resolution of measurement. The optical encoder comprises a light source emitting a light beam, a first grating to which the light beam emitted by the light source is directed, and a second grating to which light beams exiting from the first grating is directed. Additionally, displacement information obtaining means is provided for obtaining information for the displacement of one of the first and second gratings, the information being obtained according to a twice-diffracted beam and a twice-transmitted beam at the second grating. The twice-diffracted beam is generated from a diffraction beam generated at the first grating, and the twice-transmitted beam is a transmission beam which has been transmitted through the first grating.

Abstract: The amount of the light beam passing through two diffraction gratings is output as an electrical signal by a photo detector. The amount of relative displacement of the diffraction gratings is detected according to the electric signal (output signal) that changes in proportion to the relative displacement. Groove portions and ridge portions are alternately arranged on the first diffraction grating, through which the light beam passes and undergoes wavefront modulation by mutual interference of the zeroth-order diffracted light. This eliminates interference of the zeroth-order diffracted light with a diffracted light of another order, and eliminates changes in the fundamental wave component of the output signal caused by changes in the gap between the two diffraction gratings. The output signal can be made not to include a high-order component by a predetermined modification to at least one of either the array pitch or width of a transparent portion in the second diffraction grating.

Abstract: Methods and apparatus are disclosed for performing detection of the position of a substrate, such as used in photolithography, with high precision by zero Nth-order detection. Alignment marks (grating marks) on the substrate are illuminated by coherent light beams comprising multiple wavelength components. Reflected light forms diffraction patterns that are detected by appropriate detectors. At least one level-difference detection circuit and at least one detected-position-correction circuit are provided, the former detecting grating-mark positions grating mark positions .DELTA.Xn' at respective wavelengths from light-quantity signals produced from the detectors, and the latter calculating relative level differences .delta..sub.n for the respective wavelengths at each grating mark, based on changes in the light-quantity signals accompanying relative scanning and based on design data for the grating marks.

Abstract: A scanning grating is provided in a photo-electric position measuring system and the scanning grating includes several grating areas. Each one of these grating areas has a transverse grating with a graduation period. The transverse gratings of the grating areas are disposed offset by TT/4 perpendicularly to the measuring direction, i.e., in the Y direction, with respect to each other. The partial light beams diffracted at the scanning grating in the +1st and -1st order lead to an intensity modulation at a defined scanning distance Z1. An amplitude grating is provided at the location of this intensity modulation, so that by means of downstream disposed photo-detectors a scanning signal is generated by the +1st diffraction order and a scanning signal, which is phase-shifted by 180.degree. with respect to the first, is generated by the -1st diffraction order.

Abstract: A reflection-type main scale G1 is disposed on a first member 10. A diffused light source 40, a transmission-type light source index scale G2, and a photodiode array PDA are disposed on a second member 20. The diffused light source 40 irradiates the main scale G1 through the index scale G2 for generating a reflected image pattern. The photodiode array PDA detects the reflected image pattern obtained from the main scale G1. The photodiode array PDA and the index scale G2 are integrally united in such a manner that the receiving surface of the photodiode array PDA and the grating surface of the index scale G2 are aligned in a plane.

Abstract: An optical device, such as a position measuring instrument, having a source of light and a diffraction element for receiving the light, creating partial light beams which interfere with one another, and producing from the interfering partial light beams a first beam of light projecting along a first direction and producing a second beam of light projecting along a second direction. The optical device further includes a first optical projecting element positioned to receive the first beam of light and producing a first focused beam of light and a second optical projecting element positioned to receive the second beam of light and producing a second focused beam of light. Furthermore, the optical device has a first photodetector to receive and detect the first focused beam of light and a second photodetector to receive and detect the second focused beam of light.

Abstract: A scale, which is provided for use with a displacement sensor, has a high degree of freedom and is capable of being manufactured at a low cost. The scale includes a graduation section and a base board which is formed separately from the graduation section and which is bonded to the graduation section. By bonding a graduation section to a separate base board, a single graduation section can be used for scales of varying lengths. Sufficient rigidity is provided by bonding a separate base board to the graduation section.

Abstract: A phase grating has a concave part of rectangular shape type substantially, of which grating depth is deeper in a specific range than depth d' calculated in a formula.vertline.n-n.sub.0 .vertline..times.(p-d'/e)/p.times.d'=(.lambda./2).times.(1+2m) (where m=0, .+-.1, .+-.2, . . . )in terms of center wavelength .lambda. of light having partial interference to be diffracted by the phase grating, pitch length p of the phase grating, refractive index n of base material of the phase grating, refractive index n.sub.0 of medium surrounding the phase grating, and shape ratio e as the ratio of grating depth to width of slope of the concave part.

Abstract: A displacement measuring apparatus is disclosed, one embodiment of which employs two diffractive code disks, attached to a shaft, and a sensing head which need not contact the shaft. The head includes a light source with beam shaping optics, which creates two individual beamlets and pre-cranks the beamlets so that they reach the first grating at proscribed angles. Two diffracted orders from the first grating are allowed, preferably through free space propagation, to strike the second grating and to be rediffracted by the second grating. A phased-array detector, or equivalent array of detecting elements, are positioned beyond the second grating and in a region of natural interference between rediffracted orders of the incident diffracted orders, to detect the interference fringes which are generated there. The change in phase of the fringes is proportional to the relative displacement between the first and second gratings.

Abstract: An optical encoder comprising a first scale and photo sensitive elements that shift relative to the first scale along the length of the first scale for determining a relative position based on a plurality of signals having a predetermined phase difference from the photo sensitive elements. The optical encoder comprises groups of photo sensitive elements, wherein each group comprising a plurality of photo sensitive elements arranged side by side in the direction of the length, and wherein each photo sensitive element has a width corresponding to the width of the pattern of the first scale. The groups of photo sensitive elements corresponds respectively to the plurality of signals. The photo sensitive elements belonging to one photo sensitive element group and the photo sensitive elements belonging to the other photo sensitive element group are arranged side by side in a mixed fashion in the direction of the length.

Abstract: A scale and encoder are capable of stably outputting a displacement signal with less distortion. The scale has grating pattern lines arranged successively, and the widths of the pattern lines of a second scale are not P/2 but are determined to remove high-order distortion components on the grating pattern. For example, for removing the third and fifth order distortion components, the scale is made to include two slits in which pattern line widths are 17P/30 and 23P/30.

Abstract: An optical type sensor has a light emitting element, a light receiving element, at least one optical element acting on a light beam emitted from the light emitting element, in an optical path till the light beam enters the light receiving element, and a spacer member disposed to define a spacing between the light emitting element and/or the light receiving element and the at least one optical element, the spacer member having a structure for being mounted to other member.

Abstract: A position measuring system having an illuminating device for generating a beam of light. A graduation support is provided with a graduation and a reference marker with a first set of graduation markings, where the graduation support receives the beam of light and generates a second beam of light. A scanning plate moves along a measuring direction and receives the second beam of light and generates a third beam of light, wherein the scanning plate has a second set of graduation markings for scanning the first set of graduation markings of the reference marker. A first photodetector and a second photodetector receive portions of the third beam of light and generate position-dependent electrical signals, wherein either the first set of graduation markings of the reference marker or the second set of graduation markings have a structure which deflects in the measuring direction.

Abstract: A scanning graduation that scans a scale along a measuring direction to produce a signal representative of a position measurement value. The scanning graduation includes a particular transmission function which generates a filtering function when scanning the scale, wherein the transmission function is determined by a quantity of harmonics to be suppressed in the signal. The scanning graduation includes at least one scanning element for scanning a graduation period of the scale. The at least one scanning elements have at least one track comprised of N sub-elements, which are offset from one another in a measurement direction within a graduation period of the scanning graduation and whose effective widths b.sub.i (i=1 to N) within the graduation period are matched to their position within the graduation period so that the Fourier coefficients of the transmission function associated with the harmonics to be suppressed are minimized.

Abstract: An opto-electronic scale reading apparatus includes a reflective scale (410) relative to which a readhead is movable. The readhead includes a light source in the form of the emission end of an optical fiber (300), which directs light via collimating lens (420), beam splitter (310), and deflecting optics (312,314) onto the scale. The light reflected from the scale passes through an index grating (416) to generate a series of spatial fringes in the plane of an analyzer (418). The analyzer comprises a series of elongate light transmitting color filters, extending substantially parallel to the fringes and arranged in a repeating pattern (e.g. red, blue, green, red, blue . . . ); like-colored elements are separated by a distance corresponding to an integer multiple of the fringe pitch. The array (418) encodes the fringes into a plurality of phase-shifted signals, which pass through the beam splitter (310), lens (420) and back along fiber (300).

Abstract: An interferometer arrangement has an adjustable optical path length difference in at least one interferometer arm and a photoelectric receiver for detecting the interference signals generated by the interferometer. An incremental grating transmitter is coupled to the arrangement with a device for changing the optical path length difference and for generating a reference signal which changes its frequency like that of the interference signal depending on the rate of change of the optical path difference.

Abstract: An apparatus for measuring the displacement of an object includes: a diffraction grating arranged on the object, a light source for irradiating a coherence light beam onto the diffraction grating, a first detector for causing two light beams whose phases relatively shift upon linear motion of the object of diffracted light diffracted by the diffraction grating to interfere with each other to detect the interference light beam, and a second detector for causing two light beams whose phases relatively shift upon rotary motion of the object of diffracted light diffracted by the diffraction grating to interfere with each other to detect the interference light beam.

Abstract: A dynamic and thermal mechanical analyzer incorporating a slide driven vertically in an air bearing guidance system with a large displacement capacity, very low friction and low mass. The position of the slide is measured by digitizing and interpolating two quadrature output signals generated by an optical encoder with very high spatial resolution and a long stroke. A force is applied to the slide using a linear permanent magnet motor with high force, high force linearity and low sensitivity to temperature variations. Position signals derived from the digitized and interpolated quadrature output signals are analyzed as a function of the applied force to calculate viscoelastic properties of a sample of material.

Abstract: A camera shutter and focus encoder assembly comprises an encoder mask fixed in a camera housing and having an arcuate window having alternating opaque and transmissive portions, and an encoder sheet mounted in the housing in abutting relationship with the encoder mask, the encoder sheet being movable with exposure blades and the focus lens of the camera and having an arcuate window having alternating opaque and transmissive portions therein. Means are provided for pressing the encoder mask and the encoder sheet together with the mask and sheet windows in registration with each other. A sensor passes pulses of light through the mask and sheet windows when the transmissive portions thereof are in registration and detects the pulses of light, converts the light pulses to electrical signals, and transmits the electrical signals.

Abstract: An optical encoder including a light source and a first grating plate having a first diffraction grating for diffracting a light beam emitted from the light source. The optical encoder further includes a second grating plate having a second diffraction grating including a blazed diffraction grating for further diffracting the light beam diffracted by the first diffraction grating so as to allow the light beam to be incident on the first grating plate. The optical encoder also includes a light-receiving portion for receiving the light beam reentering the first grating plate and diffracted by the first grating plate.

Abstract: An uncovered unprotected phase grating includes a substrate which has a relief structure. The relief structure includes a high-refraction material so that even if soiled with impeding ambient media an adequate difference in the index of refraction exists and the diffraction effect is preserved.

Abstract: An optical encoder includes: a light source; a first grating plate having a first diffraction grating for diffracting a light beam emitted from the light source; a second grating plate having a second diffraction grating for further diffracting the light beam diffracted by the first diffraction grating; a reflector for reflecting the light beam from the second grating plate so as to allow the light beam to reenter the second grating plate; and a light-receiving portion for receiving the light beam reflected by the reflector and successively diffracted by the second and first grating plates, wherein a diffraction angle of plus and minus first-order diffracted light beams of the first diffraction grating is substantially equal to that of the plus and minus first-order diffracted light beams of the second diffraction grating, and the light-receiving portion generates an electric signal in accordance with the amount of the plus and minus first-order diffracted light beams of the first diffraction grating.

Abstract: An optical encoder has a light source and a diffracted light interference device including at least first and second diffraction gratings confronting each other, producing diffracted light beams in specific orders by passing light emitted from the light source through the first and second diffraction gratings, and making the diffracted light beams in the specific orders, which have passed through the diffraction gratings, interfere with each other to produce on-axis interference light beams in which the sum of the orders of the diffraction at the diffraction gratings is zero and off-axis interference light beams in which the sum of the orders of the diffraction is not zero. A phase device is adjusting the phases of the on-axis interference light beams and the off-axis interference light beams emitted from plural portions of the diffracted light interference device. A plurality of light sensors receive and detect the on-axis interference light beams and the off-axis interference light beams device.

Abstract: A scanning grating is provided in a photoelectric position measuring system which has three areas per graduation period (d) arranged behind each other in the measuring direction. These areas B.sub.1, B.sub.2, B.sub.3 are structured transversely with respect to the measuring direction X in such a way that transversely diffracted light beams are directed on detectors D.sub.0, D.sub.1, D.sub.2 which are arranged transversely to the measuring direction X. The detectors generate signals which are phase-shifted with respect to each other.

Abstract: A displacement detection apparatus includes a light source (1), a first diffraction grating (G1) which is arranged on the same substrate as a second diffraction grating (G2) so as to diffract and split light emitted from the light source and to irradiate .+-.1st-order diffracted light beams onto the second diffraction grating (G2), a third diffraction grating (G3) for synthesizing a +1st-order reflectively diffracted light beam generated by reflectively diffracting the +1st-order diffracted light beam by the second diffraction grating, and a -1st-order reflectively diffracted light beam generated by reflectively diffracting the +1st-order diffracted light beam by the second diffraction grating to form interference light, and a light-receiving element (3) for converting the interference light into a signal representing a displacement of the substrate.

Abstract: An encoder including a scale and a light source for illuminating the scale, and a sensing device displaceable relative to the scale in a measuring direction for generating measuring signals, with the sensing device including a transparent carrier provided with a scanning grating, photosensors for converting a position-dependent modulated light into electrical scanning signals defining the measuring signals, and strip conductors provided on a surface of the transparent carrier for forming an electrical connection with the photosensors.

Abstract: An apparatus for optically detecting information relating to the relative displacement of an object on which a diffraction grating, arranged in two axial directions with a predetermined pitch. The apparatus includes a light-emitting device configured to emit a light beam, and a first optical element configured to divide the light beam from the light-emitting device into a plurality of light beams directed in each of the two axial directions to the diffraction grating on the object which produces a plurality of diffracted light beams for each of the two axial directions.

Abstract: In an optical apparatus utilizing moire fringes to inspect surface irregularities of a test object, a single light beam forms a light beam network in an optical sensor (28) such that the test object can be two-dimensionally detected, thereby preventing the test object from abnormally approaching a moire grating (12). The light beam is reflected between a pair of mirrors (50, 52) a plurality of times within an identical plane and then the optical sensor (28) detects the intensity of the light beam. The optical sensor (28) is disposed such that the light beam network is positioned directly below the moire grating (12). Accordingly, a test object (2) abnormally approaching the moire grating (12) can be two-dimensionally detected by the light beam network, thereby improving the accuracy in detection.

Abstract: An apparatus for detecting displacement information is disclosed. The apparatus is provided with a scale arranged on the side of an object of which relative displacement information is to be detected, a periodic signal generation diffraction grating formed at a predetermined pitch, and a predetermined data recording portion formed independently of the periodic signal generation and diffraction grating for detecting displacement information, a first detection system for irradiating a light beam onto the periodic signal generation diffraction grating to generate diffracted light, the first detection system forming a periodic signal corresponding to a displacement relative to the scale by detecting interference light of the diffracted light generated by the periodic signal generation diffraction grating, and a second detection system for optically detecting the predetermined data recording portion. The predetermined data recording portion also has a diffraction grating.

Abstract: An optical encoder includes: a light source; a first grating plate having a first diffraction grating for diffracting a light beam emitted from the light source; a second grating plate having a second diffraction grating for further diffracting the light beam diffracted by the first diffraction grating; a reflector for reflecting the light beam from the second grating plate so as to allow the light beam to reenter the second grating plate; and a light-receiving portion for receiving the light beam reflected by the reflector and successively diffracted by the second and first grating plates, wherein a diffraction angle of plus and minus first-order diffracted light beams of the first diffraction grating is substantially equal to that of the plus and minus first-order diffracted light beams of the second diffraction grating, and the light-receiving portion generates an electric signal in accordance with the amount of the plus and minus first-order diffracted light beams of the first diffraction grating.

Abstract: A rotary encoder has a disk with fine gratings comprising diffraction gratings of small diameters and a high density. Two diffraction lights of predetermined orders which are obtained when a light beam is irradiated to the fine gratings, are interfered properly with each other, thereby enabling rotational information of a rotary object to be detected at a high resolution while realizing a small and thin size of the overall apparatus.

Abstract: An apparatus for detecting information relating to displacement of an object on which a grating scale is affixed. The apparatus includes a beam-emitting system for irradiating the grating scale with a beam. The apparatus also includes a light-detecting element having a light-receiving surface. A grating portion is integrally formed on at least a part of the light-receiving surface for detecting a beam from the grating scale which is irradiated by the beam from the beam-emitting system. Information relating to displacement of the object is detected on the basis of the detection by the grating portion of the light-detecting element.

Abstract: Remote positioning to submicron accuracy is based on comparison of two interference gratings, the first of constant phase, and the second segmented. Positioning corresponds with equal segment-by-segment overlap of an image of one grating superimposed on the other.

Abstract: An optical encoder is provided which is not affected by fluctuation of wavelength of a light beam due to temperature change, without sacrificing resolution of measurement. The optical encoder comprises a light source emitting a light beam, a first grating to which the light beam emitted by the light source is directed, and a second grating to which light beams exiting from the first grating is directed. Additionally, displacement information obtaining means is provided for obtaining information for the displacement of one of the first and second gratings, the information being obtained according to a twice-diffracted beam and a twice-transmitted beam at the second grating. The twice-diffracted beam is generated from a diffraction beam generated at the first grating, and the twice-transmitted beam is a transmission beam which has been transmitted through the first grating.

Abstract: In this apparatus, which serves preferably to generate reference pulses, graduations are provided on the scanner plate (A), whose graduation period varies steadily as a function of location (chirped grating). The various graduation markings (GS) are embodied in turn as periodic phase gratings, whose graduation scores extend parallel to the measurement direction (X).

Abstract: A method and system are provided including an optical head which moves relative to an object at a vision station to scan a projected pattern of imagable electromagnetic radiation across the surface of an object to be inspected at a relatively constant linear rate to generate an imagable electromagnetic radiation signal. In one embodiment, the electromagnetic radiation is light to develop dimensional information associated with the object. The optical head includes at least one projector which projects a grid of lines and an imaging subsystem which includes a trilinear array camera as a detector. The camera and the at least one projector are maintained in fixed relation to each other. Three linear detector elements of the array camera extend in a direction parallel with the grid of lines. The geometry of the optical head is arranged in such a way that each linear detector element picks up a different phase in the grid pattern.

Abstract: The apparatus disclosed herein employs a grating (13) which concentrates light at a preselected wavelength into the positive (33) and negative (35) first orders while minimizing the zeroth order (31). The grating (13) is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector (25) has its sensing plane spaced from the grating a distance less than ##EQU1## where W is the width of the illuminated region of the grating. The period of the poly-phase detector is equal to P/2 so that each detector element (51) or phase responds principally to the natural interference between the positive and negative first orders without requiring magnification or redirection of the diffracted light. Preferably, the distance of the sensing plane from the grating (13) is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first.

Abstract: A measuring device for determining the displacement of a movable object includes a graduation element which is mechanically connected to the object whose displacement is to be determined. The graduation element comprises at least a track which is formed by a plurality of successive grating strips located transversely to the direction of movement of the object. The measuring device also includes a radiation source, a detector and a reflective optical system which comprises at least a beam collimating element. The reflective optical system guides the radiation from the radiation source to the graduation element and changes it to an elongate radiation beam which is parallel on average in the cross-section perpendicular to the grating strips.

Abstract: A fixed point detecting device comprises a light source, a hologram disposed therebelow and having two portions, and two light receivers for detecting lights diffracted by the two portions of the hologram, wherein an angle of diffraction of light diffracted by one of the two portions of the hologram and an angle of diffraction of light diffracted by another of the two portions of the hologram have opposite signs and the same absolute value and are constant along the axis of measurement, and a difference in luminous intensity is great between positive and negative homogeneous lights diffracted by the two portions of the hologram.

Abstract: An optical measuring system comprises an illumination arrangement including a light source, grating, and lens, and an image acquisition arrangement, including a lens, grating, and camera. A mechanical translation device moves the grating in a plane parallel to a reference surface to effect a phase shift of a projected image of the grating on the contoured surface to be measured. A second mechanical translation device moves the lens to effect a change in the contour interval. A first phase of the points on the contoured surface is taken, via a four-bucket algorithm, at a first contour interval. A second phase of the points is taken at a second contour interval. A controller, including a computer, determines a coarse measurement using the difference between the first and second phases. The controller further determines a fine measurement using either the first or second phase.

Abstract: In a scanner unit for An overhead image scanner, a rotatably mounted mirror reflects light from a surface to be scanned off to a focusing lens to form an optical image of a scanned line on a linear image sensor. An extension arm is connected to the minor for rotation therewith. To one end of the arm is attached an electromagnetic drive system and to the other end a light reflecting member which is formed with a multiplicity of microscopically spaced apart tracks running parallel to the length of the extension arm. A laser beam spot is formed on the reflecting member and a photodiode array detects reflections therefrom to produce a plurality of output signals representative of the amounts of reflections incident on different areas of the array.

Abstract: An optical type encoder is comprised of a gauge member and a sensor portion moved relative to each other with the movement of an object to be detected. The gauge member has a plurality of slit rows comprising a plurality of slits formed at intervals along the direction of movement of the object to be detected, and a plurality of slit intervals formed by the corresponding slits in the slit rows are made partly equal. The sensor portion has at locations corresponding to the slit rows position detecting type light receiving means for receiving light beams from light projecting means passed through the plurality of slits rows of the gauge member, and the position information of the object to be detected is detected by the utilization of signals from these light receiving means.

Abstract: An illuminating apparatus is for use with a visual sensory apparatus, for projecting a light pattern onto a surface to be viewed by the sensory apparatus. The illuminating apparatus comprises: a light source; a patterniser for constraining light emitted from the source to produce on the surface, a light pattern having a light interface, the interface having an extended dimension. The light pattern is caused to move relative to the surface, parallel to the extended dimension of the light interface. The pattern may comprise a plurality of extended straight line interfaces, each interface being parallel to the other interfaces of the plurality. Rather than straight, the plurality may be circular and concentric. Rather than a plurality, the pattern may comprise a single straight line or circular light interface.

Abstract: An apparatus for measuring the relative displacement information between it and a scale on which a diffraction grating is formed has a light source, a separating device for separating a light beam from the light source into a plurality of light beams, a wave combining device for wave-combining the diffracted lights of the plurality of light beams separated by the separating device which are diffracted by the diffraction grating, a light receiver for receiving the interfering lights by the plurality of light beams wave-combined by the wave combining device, the relative displacement information between the apparatus and the scale being measured by the light reception of the light receiver, and an optical device adapted to collimate the plurality of light beams or to form a spherical wave having so large a radius of curvature that it can be regarded as a plane wave of the plurality of light beams in the direction of light beam separation of the separating device and to condense the plurality of light beams in t

Abstract: A device for measuring an angle between pivotally connected, intersecting sides of a parallelogram includes a grating having a pattern of parallel, straight grating lines formed on a substrate, and a read head. The grating is mounted in a fixed position with respect to a first side of the parallelogram. The read head includes a sensor positioned for sensing displacement of the grating lines in response to an angular change between the intersecting sides of the parallelogram and generating a scale reading. The read head is mounted in a fixed position with respect to a second side of the parallelogram that is parallel to the first side. In one embodiment, the grating includes a single pattern of grating lines and is used to measure an angular change relative to a reference angle. In a second embodiment, the grating includes first and second grating patterns and is used to measure an absolute value of the angle between the intersecting sides of the parallelogram.

Abstract: A method for measuring the contours (30) of a three-dimensional object (4); and a method for calibrating an optical system (2, 8). The object (4) is placed into the field of view of the optical system (2, 8). The optical system (2, 8) is activated to obtain a set of data giving a phase (x.sub.t) at each of a plurality of pixels corresponding to the object (4). The phases (x.sub.t) are unwrapped, e.g., by a method of ordered phase unwrapping. The unwrapped phases are converted into a set of three-dimensional coordinates (x.sub.s, y.sub.s, z.sub.s) of the object (4) for each of the pixels. These coordinates (x.sub.s, y.sub.s, z.sub.s) can be portrayed on a display of a computer (10). The method for calibrating the optical system (2, 8) shares several common steps with the above method. In addition, coordinates of a test calibration fixture (38, 46) are first mechanically measured.

Abstract: An interferometer delay line includes an optical payload displaced along a guide track under the control of a control device including at least one sensing device which senses the position of the payload along the guide track and a drive device acting on the payload. The sensing device includes a linear succession of fixed optical read heads parallel to the guide track and a graduated rule carried by the optical payload in any position on the latter facing at least one of the optical read heads. The sensing device also includes a synchronizing/switching unit causing a counter to count pulses from the heads in succession, the pulses representing distance increments.

Abstract: A system for detecting displacement of a surface in a direction normal to the surface, the system including a first grating; a second grating; an optical subsystem for projecting an image of the first grating onto the surface and for directing a secondary image of the first grating reflected off the surface onto the second grating; and a detector, responsive to the fringe pattern formed after the secondary image passes through the second grating, for detecting displacement of the surface in a direction normal to the surface.