Abstract: A device for position encoding of a rotating shaft in which a polygonal mirror having a number of facets is mounted to the shaft and a monochromatic light beam is directed towards the facets. The facets of the polygonal mirror each have a low line density diffraction grating to diffract the monochromatic light beam into a number of diffracted light beams such that a number of light spots are created on a linear array detector. An analog-to-digital converter is connected to the linear array detector for reading the position of the spots on the linear array detector means. A microprocessor with memory is connected to the analog-to-digital converter to hold and manipulate the data provided by the analog-to-digital converter on the position of the spots and to compute the position of the shaft based upon the data from the analog-to-digital converter.

Abstract: The sensor has at least one sensor unit arranged opposite an incremental measurement scale (1) with reflecting graduation (2). The sensor unit comprises a photoemitter (3) and an adjacent photoreceiver (4), located in a printed circuit (6), with optical axes (xx') parallel to each other and perpendicular to the plane of the scale (1), and an optical group (9) with two focusing lenses (10, 12) and two deflection faces (11, 13) integrated by molding in a support of transparent synthetic material. In the optical group, one of the two lenses and one of the two deflection faces are aligned on each of the two said optical axes (x, x') in order to direct and deviate the light rays coming from the photoemitter (3) and to recover them on the photoreceiver (4) after their passage through a graduated sensing graticule (14).

Abstract: Apparatus for determining the three-dimensional shape of an object by projecting patterns onto the surface of the object, the patterns having fringes with a light intensity that varies sinusoidally in space, said apparatus comprising means (30, 34, 36) for changing the pattern centered on the projection optical axis (28), and cam means (54) for displacing the patterns (12a, 12b) transversely through distances equivalent to phase shifts of 2.pi./n.

Abstract: The amount of relative in-surface rotation between two scales of a position detector is precisely detected to thereby determine the deviation in longitudinal phase between tracks in one scale. Thus, positional data corresponding to signals from the tracks are made appropriate. The resultant positional data are used so that stable detection of an absolute position is performed.

Abstract: An optical absolute position encoder capable of obtaining absolute position data in a wide range utilizes the fact that the position of a transmitted or reflected light beam is shifted in accordance with the displacement of a grating window and the fact that the grating window can be specified depending upon the characteristics of the light beam which has passed through the grating window. Furthermore, precise position data is obtained by using two gratings which move relatively. The above-described data are combined with each other so that absolute position data revealing high resolution can accurately be obtained for a long stroke.

Abstract: A reflection type hologram scale, in which a hologram dry plate is bonded to a protecting base member in which a hologram grating formed on a scale base member forming the hologram dry plate and a reflecting film formed on a base member forming the protecting base member are opposed to each other. Therefore, the hologram grating and the reflecting film are both protected by the scale base member and the base member so that the hologram grating and the reflecting film are prevented from being exposed to the air, thereby preventing the hologram grating and the reflecting film from being smudged by fingermarks, dust and also from being scratched.

Abstract: A polarization diffraction element comprising two diffraction gratings formed on both faces of a substrate respectively. Both the diffraction gratings have grating lines which are arranged at the same grating pitch, and whose directions mutually form a predetermined minute angle. The grating lines may also be arranged parallel to each other. In this case, the relationship between grating pitches D.sub.1, D.sub.2 of the respective diffraction gratings and the wavelength .lambda. of an incident light is expressed as:0<.vertline..lambda.(1/D.sub.1 -1/D.sub.2)(1-(.lambda./2D.sub.1).sup.2).sup.-(1/2) .vertline..ltoreq.0.35; or0<.vertline..lambda.(1/D.sub.1 -1/D.sub.2)(1-(.lambda./D.sub.1 -.lambda./2D.sub.2).sup.2).sup.-(1/2) .vertline..ltoreq.0.35In a polarization detector employing this polarization diffraction element, a single converging lens of a small effective diameter separates one polarization from another polarization and converges them separately on different photodetectors.

Abstract: An optical system for monitor vibration, particularly applicable to power shafts in rotating power systems such as those found in trucks, naval vessels, turbogenerators, hydroelectric and nuclear generators, and helicopters, has an optical unit including IRLED radiation sources aimed at grid lines applied around the circumference of the shaft. The reflection of the radiation is imaged through lenses and a matching Ronchi grid onto a photodiode which produces a periodic wave signal from which indications of rotational irregularities can be derived. In one embodiment, duplicate radiation sources and imaging apparatus are arranged in diametric opposition across the shaft to permit compensation for pitch and plunge shaft vibration. In another preferred embodiment, a second, duplicate optical unit is located at a distance along the shaft from the first unit.

Abstract: An absolute encoder device comprises a code plate having a 1-track type absolute pattern whose minimum reading unit length is .lambda., a first incremental pattern with a pitch .lambda., and a second incremental pattern with pitch 2.sup.-n .lambda.. The device also comprises a detector section, which is movable relative to the code plate, which includes a detector detecting the absolute pattern and obtaining an absolute pattern signal, a detector detecting a first incremental pattern and obtaining a first incremental signal, and a detector detecting a second incremental pattern and obtaining a second incremental pattern signal. A shorter cyclic incremental signal is generated from the first incremental signal by interpolating and the shorter cyclic signal is synchronized with the second incremental signal. The absolute pattern signal, the second incremental signal and the synchronized first incremental signal represent the relative positional relationship between the code plate and the detector section.

Abstract: An optical apparatus for sensing the motion of an object. A light source transmits light through a first and second optical fiber. The first and second optical fiber are positioned on opposite sides of a modulator or code disk to face each other along an optical path. The modulator has alternating reflective regions and transmissive regions which modulate the light propagating along the optical path as the modulator moves across the optical path. The modulated light is received by the first and second and optical fibers and transported to a predetermined location for evaluation.

Abstract: A readhead 10 traverses along a scale 12, producing square wave signals in quadrature on lines 24,26. These are counted by an external counter 28 to indicate the position along the scale. The square waves cannot be used to monitor the orientation and stand-off of the readhead 10 relative to the scale 12. To achieve this, therefore, circuitry within the readhead 10 monitors the sinusoidal quadrature signals from which the square waves are produced, and gives a simple go/no-go indication on a LED 62 when these signals have an acceptable amplitude and are in an acceptable quadrature relationship.

Abstract: An optical sensor in which both analog and digital techniques are employed. The sensor comprises an encoder and a detector. The encoder includes a plurality of tracks extending along a sensing axis. Each track has a property that varies along the sensing axis, such that the property can have one of three or more distinguishable levels. The detector detects the levels of the tracks at a position along the sensing axis, and produces corresponding output signals. The levels vary in a manner such that the output signals encode the position of the encoder with respect to the detector. The levels may vary in steps or continuously. For stepwise variable tracks, preferably only one track changes its level at any given position, and all changes in level occur in single steps. Both optical and electrical implementations are described.

Abstract: The detector comprises an optoelectronic sensing unit (3) and a transparent rule (2) having two parallel graduation tracks (4, 5). One track (5) has incremental graduation of constant step and the other track (4) has pseudo-random graduation forming binary coding bits constituting a continuous sequence of words which are different from each other, the width of a bit being a function of the step of the incremental graduation. The incremental track (5) is read through a sensing graticule (9) by photodetectors (8) which are 90 electrical degrees out of phase in order to permit an interpolation in the step of said track. The track (4) with pseudo-random graduation is read by a CCD detector (11) through an image-enlarging lens (13). The signals generated are processed by circuits (15a, 15b) which assure the combining of the information taken from the two tracks of the rule.

Abstract: The invention provides a thin-profile displacement signal output device. The device comprises a first member having a periodic pattern consisting of alternating high-transmittance and low-transmittance regions, a second member having a periodic pattern consisting of alternating high-reflectance regions, a light emitting source for emitting a detection light beam and a light-receiver for receiving the reflected light, the first member and second member facing each other and spaced apart by a distance which is smaller than the pitch of the periodic pattern, the light-emitting source and light receiver means being both disposed on one side of said first member which is opposite to the side on which said second member is disposed, and the first and second member being displaceable relative to each other.

Abstract: A position detector for use in, for example, a robot hand can detect any of a plurality of positions on a movable element. The position detector includes a coding member having a first row of absolute codes and a second row of incremental codes both formed therein in a direction of movement thereof. Positional data in binary codes are serially recorded in the first row whereas regularly formed incremental codes corresponding to respective binary codes are recorded in the second row. The position detector further includes a plurality of light emitting and receiving elements for detecting the codes of the first and second rows and a serial-parallel converter for converting serially detected binary codes of the first row to parallel rows of binary codes based upon detection signals of the second row. The binary codes in each parallel row are equal in number to recording bits of the positional data.

Abstract: This specification discloses an apparatus which includes a detection unit body having light projecting means and light receiving means disposed in opposed relationship with and at a predetermined distance from the light projecting means, a mask member and a slit member each provided with a plurality of slit openings periodically in a direction orthogonal to the direction of opposition of the light projecting means and the light receiving means and interposed between the light projecting means and the light receiving means in such a manner that the directions of arrangement of the slits are the same direction and in which the mask member is mounted on the light receiving means and the slit member is disposed so as to be movable relative to the detection unit body, and of the light beam from the light projecting means, a light beam passed through the slit openings in both of the slit member and the mask member is detected by the light receiving means, and the relative positional information of the detection uni

Abstract: A rotary actuator data recording disk file is provided with a retro-reflective diffraction grating for use in measuring the angular position of the rotary actuator arm. The diffraction grating has a diffraction pattern whose pitch varies along the length of the diffraction grating. The variation in pitch is arranged such that, as the rotary actuator arm swings about its pivot axis and the diffraction grating moves across an incident light beam and simultaneously rotates with respect to it, the diffracted beam travels back along the incident path. Thus, the source and detector of a laser position measurement system can remain fixed while measuring the position of a rotary actuator arm to which the diffraction grating is affixed.

Abstract: The method of measuring the relative between submicron lithographic features on a wafer having thereon a reference characteristic associated with a reference submicron grating structure of periodicity p.sub.1 onto which there may be cast from a reticle the image of a projected submicron grating structure of different periodicity p.sub.2 comprising measuring the extent of change in a moire fringe pattern produced by the superposition of the two grating structures on the wafer.

Abstract: The present invention relates to a rotary encoder for detecting a rotational angle. A rotary encoder according to the present invention comprises a rotating body provided on its surface with a plurality of digital code patterns representative of absolute angle ranges and a plurality of relative angle patterns representative of relative angles, a high-order angle data producing means (1,2,5,7) for reading the absolute angle patterns to produce high-order angle data, and a low-order angle data producing means (1,2,5,7) for reading the relative angle patterns to produce low-order angle data. The rotary encoder according to the present invention ensures medium resolution by means of the digital code patterns and attains finer resolution by means of the relative angle patterns, whereby the rotational angle can be detected with superior resolution.

Abstract: In a photoelectric position detector a scanning movement of a scanning phase grating relative to a scale member which is provided with a reflective phase grating is detected, light emitted by at least one light source is diffracted by the scanning grating and as it is reflected by the scale member and then again by the scanning grating to form an interference pattern and only groups belonging to said interference pattern and being of a predetermined diffraction order are detected by respective photodetectors and are converted by them to phase-displaced photodetector signals, which are cyclically changed as the scanning grating is moved relative to the scale member.

Abstract: An automotive engine control system is provided for an automobile having a variable rotation speed engine which has a plurality of spark plugs served by respective spark plugs. The system includes an optical rotary encoder having a rotatable pulse scale having a row of code pattern with specific light-permeable or light-deflection slits each for outputting a reference position signal and other light-permeable or light-reflection slits each adapted to reduce the amount of light for outputting an angular signal, both of the optical signals being photoelectronically converted and the waveform of the resultant electric signals being shaped based on threshold voltages into electric pulse signals indicative of a reference angle of 0.degree.

Abstract: The relative position (M) of two members (33, 34) is sensed by scanning (S) an optical beam (25) over an encoded pattern (20) carried by one of the members, and by using a read head (21) secured to the other member to receive an optical signal transmitted from the encoded pattern (20). This optical signal is received by an optical position sensor to discriminate from the frequency of the signal, the position of the read head (21) relative to the encoded pattern (20). As the relative position is detected from the frequency of the signal rather than its intensity, components can be replaced without recalibration. The optical beam (25) is scanned by using a light source of variable wavelength which is passed through a device, such as a diffraction grating or a gradient index lens, for deflecting the beam (25) dependent on its wavelength.

Abstract: A position measuring apparatus includes an optical instrument placed in a first plane, a first diffraction grid placed in a second plane, parallel to the first plane, a retro-reflecting element, a second diffraction grid, and an optical element, preferably placed in the first plane. The optical instrument splits a beam of light into at least two divergent partial beams which are diffracted by the first diffraction grid into parallel partial beams. The parallel partial beams are conducted through the retro-reflecting element and then impinge onto the second diffraction grid. The second diffraction grid diffracts the partial beams and causes them to interfere with each other at the optical element. A detection device measures a change (.DELTA.OPD) of path difference of the partial beams which is directly proportional to the change in distance between the first and second planes. This change (.DELTA.

Abstract: A first grating is formed on a main scale, and a second and third gratings on an index scale. The first grating generally assumes a cruciform shape, and consists of a grating having grating lines arranged in the X-direction and another grating having grating lines arranged in the Y-direction. The second grating is formed in a square central area of the index scale, and consists of two gratings having grating lines arranged in the X-direction and divided at the center and another two gratings having grating lines arranged in the Y-direction and divided at the center. The third grating consists of four gratings having grating lines arranged in the X-direction with different phases and another four gratings having grating lines arranged in the Y-direction with different phases. A light-emitting element and eight photodetectors that are arranged corresponding to the respective gratings of the third grating are fixed to a movable member on which the index scale is attached.

Abstract: A position detector for a scanning beam comprising a plurality of rows of spaced apart sensors. Each row of sensors includes a plurality of logic zero sensors and a plurality of logic one sensors which are arranged in alternating logic order. Each row is arranged such that it is symmetrical about its center. Equal areas of logic zero sensors on each side of the center are equal distances away from the center and equal areas of logic one sensors on each side of the center are equal distances away from the center to substantially cancel out any background light effects on the sensors.

Abstract: The object of the invention is a process for observing moire patterns of surfaces to be tested, wherein the object gratings to be observed are pictured onto auxiliary gratings and the moire patterns generated thereby are detected, stored and/or processed by computer, wherein for each observation at least phase-shifted moire patterns are respectively evaluated. Furthermore, the invention relates to a device for observing moire patterns of the surfaces to be tested by applying the moire method using phase shifting. For an observation of the phase-shifted moire patterns associated with the object grating are simultaneously generated, pictured and detected by superposition of the object grating image with auxiliary gratings which are disposed in a phase-shifted manner.

Abstract: An interferometer for measuring the displacement of a diffraction grating includes a multi-mode semiconductor laser for generating a laser beam; a device for supplying a predetermined current to the laser so that at least five vertical modes occur in an oscillation spectrum of the laser beam generated by the laser at an intensity ratio of at least 0.05; and an optical system for splitting the laser beam generated by the laser into first and second beams. The optical system also directs the first and second beams to the diffraction grating and effects interference between a first diffracted light beam generated by the diffraction of the first beam at the diffraction grating and a second diffracted light beam generated by the diffraction of the second beam at the diffraction grating to produce an interference light beam. Also provided is a photoelectric convertor for converting the interference light beam into an electrical signal.

Abstract: A moire contouring imaging device for small field moire imaging in which both the illumination and viewing optical beam paths pass through a common primary lens and optical grating. The use of such common optical elements improves optical stability and accuracy since magnification and focal length and other mismatching between discrete optical elements in the viewing and illumination paths are avoided. The device is assembled in a rugged elongated housing. The device further incorporates mechanisms for either translating the grating to generate a moire phase shift, or translating the folding mirror of the system to provide a moire field shift.

Abstract: A position detecting method and apparatus for detecting the relative position of a particular grating pattern with respect to a predetermined reference grating pattern, includes a signal forming step for forming first and second signals corresponding to moire fringes provided or to be provided by the patterns, the first and second signals having phases shiftable in opposite directions in accordance with the position of the particular grating pattern; and a position detecting step for detecting the position of the particular grating pattern on the basis of any difference in phase between the first and second signals.

Abstract: An opto-electronic scale reading apparatus comprises a light source (20) which projects light via an index grating (22) onto a reflective scale (10). Light is reflected from the scale (10), passes through an auxiliary grating (36) and is incident upon an analyser grating (28), at which a plurality of periodic light patterns are formed. Light from the light source (20) travels initially parallel to the scale plane, and is subsequently deflected through 90.degree. by a beam splitter cube (26); the light is thus incident upon and reflected and off the scale (10) at 90.degree. to the scale plane. This arrangement enables large movements of the readhead in a direction perpendicular to the scale.

Abstract: The invention comprises a sensor system in a printhead scanner which is capable of achieving accurate pixel to pixel registration. A plastic film strip with alternating fiducial bars and spaces is scanned. A voltage pattern is triggered by the zero slope points of the voltage induced by a sensing mechanism being moved along the plastic film strip.

Abstract: A displacement detecting device generates first and second periodic signals in accordance with a displacement of a relatively movable object. The first and second periodic signals have differing phases relative to each other and each include a third harmonic component and a fifth harmonic component which are approximately equal to each other. The third and fifth harmonic components are equalized by setting a distance between first and second gratings of the position detection device. By equalizing the third and fifth harmonic components of the periodic detection signals, detection errors are reduced.

Abstract: The present invention relates to position detection, and aligning structure utilizing optical heterodyne method in semiconductor ultra fine processing or ultra accurate measuring. This is to provide a structure which contains pitches of not less than two kinds with respect to grating pitches of diffraction gratings which directly give influences to signal detecting range and detecting resolution, or which contains different values of not less than two kinds with respect to absolute values n of an order of .+-.n-th order injecting directions (or .+-.n-th order diffraction directions) to be determined by said grating pitches, so as to enable to enlarge a detecting range as maintaining a required detecting resolution (or a structure which can take out diffracted lights in different diffraction directions of not less than two).

Abstract: A reflected light barrier is provided which includes a light source and a transmitting lens located for transmitting light from the light source along a beam path having a transmitting axis. A retroreflector is positioned for receiving the light transmitted by the transmitting lens and retroreflects the transmitted light. A light detector is disposed on the same side of the retroreflector as the light source. A receiving lens having a receiving optical axis is disposed in front of the light receiver for collecting a portion of the retroreflected light and focusing the portion of retroreflected light onto the light detector. The transmitting lens and the receiving lens are arranged next to one another. An optical device is disposed along the beam path between the transmitting lens and the receiving lens for transmitting and redirecting the transmitted and retroreflected light so that an increased portion of retroreflected light is oriented onto the receiving optical axis of the receiving lens.

Abstract: An optical encoder irradiating light emitted from a light emitting unit includes a rectangular collimator lens having a rectangular face onto a main scale which moves in the longitudinal direction, receives the collimated light beam passing the main scale in a light receiving unit, and optically reads the displacement of the main scale. Since the collimator lens is rectangular, the light emitting unit can be made compact without decreasing the irradiation area of a light beam which is effective in the detection of the displacement. Furthermore, it is possible to increase the irradiation area of the light beam by dividing a collimated light beam from the collimator lens into a plurality of diffracted light beams by a transmitting or reflecting diffracton grating.

Abstract: A method and an electronic slide caliper serve for measuring a length. The slide caliper comprises a rule and a slide which is arranged on the rule for longitudinal displacement and which is provided with two sensors which are offset relative to each other in the longitudinal direction in such a way that the zero passages of the signals generated by the sensors will not coincide. In order to be able to measure the lengths even in the presence of considerable drifts, the zero passages (ND) of the signals are determined by determining first maximum values (MX) and minimum values (MN) of the signal values (U) and deriving thereafter the zero passages (ND) as arithmetic mean value. By taking the average of a larger number of zero passages one then determines the respective zero level (U.sub.N).

Abstract: This invention relates to an apparatus and method for 3-D vision sensing or measurement to rapidly collect X-Y-Z surface data to support dimensional measurement, surface inspection and Reverse-CAD functions. The high-speed three-dimensional surface measurement system for use in determining the surface of an object from at least two electronic signals, has at least a first source for illuminating at least a surface area of the object with at least one fringe pattern.

Abstract: The present invention consists of a photocell array to determine the cross-scan position of a laser beam. The array consists of multiple rows of elongated photocells oriented perpendicular to the main scan direction of the laser beam with each row of photocells representing one bit of data. Furthermore, each row consists of alternating types of photocells, one type representing a logic 1 and the other type representing a logic 0. As the laser beam crosses this array, it energizes certain photocells on each row such that its output is a binary number that identifies the position at which the laser beam crosses the array. To improve the accuracy of the binary output, the pitch between the photocells of each row should not be reduced to less than 1/4 of the width of the laser beam. If greater accuracy is needed, the photocells should be offset while keeping the pitch between the photocells constant at a pitch not less than 1/4 of the width of the laser beam.

Abstract: An interference type angle measuring device has a graduated disk with a circular graduation. This circular graduation is scanned by a scanning device, which is constructed as a monolithically integrated optical circuit with two diametrical scanning areas. Simply structured coupling and decoupling grids are used as coupling elements, which have also simply constructed correction grids placed upstream or downstream thereof.

Abstract: A tomograph makes use of phase information obtainable from a radiation beam having transmitted a to-be-inspected object. In one embodiment, the tomograph has an interferometer for producing interference infringes between a signal beam having transmitted through the object and a reference beam and eventually producing Moire fringes a detector for detecting the Moire fringes, and a signal processing unit for processing outputs of the detector.

Abstract: A parallel light ray measuring apparatus invention measures the parallelism of a light beam by: receiving a light beam which has passed through two gratings having the same grating period by means of at least two photoelectric converting elements, and by detecting the light intensity obtained from those aforementioned photoelectric converting elements and the phase difference between the periodic signals obtained when either of the gratings is moved, using the at least photoelectric converting elements. Further, the parallel light ray measuring apparatus includes: a first grating; a second grating having the same grating period as that of the first grating, and being disposed such that the grating lines of the second grating are in parallel with those of the first grating; a light pick-up screen for receiving a light beam which has passed through both gratings, whereby the light intensity distribution appearing on the light pick-up screen is detected so as to measure the parallelism of the light beam.

Abstract: A method and apparatus for generating and detecting changes in interference patterns such as may be used to measure small displacements. A collimated beam is diffracted to produce a standing wavefront along a surface. The surface is coincident with the surface of a device which emits a signal in response to changes in the intensity of the wave front. In one embodiment, the diffracting means is a grating and the signal emitting means includes a beam splitter that generates an interference pattern responsive to the intensity of the wave front. In another embodiment, the signal emitting means is a membrane that emits a signal in response to changes in the wavefront. The apparatus and method can be used in applications which include measurement of displacement and measurement of force in which no displacement takes place.

Abstract: A rotary encoder and a scanning system using the same for detecting rotation of a galvano scanner which comprises a rotary scale coupled to a rotating driver, a scale with slits formed at a non-uniform pitch circumferentially on the rotary scale within a limited rotation angle and detection means for detecting a rotation status by reading the slits.

Abstract: A photoelectric encoder characterized in that the grating substrate on the light emission side is composed of a plate-like light emitting element and in that light shielding members in the form of a thin film are arranged at regular intervals on the surface of the substrate which faces the reference grating. Since the light emitting element and the grating substrate on the light emission side are integrally provided with each other, reducing in the size and the weight of the apparatus and the number of parts is enabled.

Abstract: The invention provides an optical encoder for encoding the position of a rotatable shaft. The encoder generates an index pulse having the same logic level regardless of the direction of rotation of the shaft. The encoder includes a light source; a code wheel having plural alternating windows and spokes which respectively transmit or block light from the light source; and first, second, and third photodetectors in alignment with the light source. The code wheel is mounted between the light source and the photodetectors. The first photodetector has a unit width and is mounted between the second and third photodetectors which each have a one-half unit width. The index window has a three-unit width. The encoder also includes a buffer circuit having a first input connected to the output of the second and third photodetectors, and a second input connected to the output of the first photodetector.

Abstract: In a method for detecting a moving amount of a detected body, light emitted from a light source is irradiated onto the detected body and light reflected from the detected body or light transmitted therethrough is detected by a photodetector. This method has the steps of emitting incoherent light from the light source through a small opening of a light-interrupting plate; irradiating the incoherent light onto the detected body having a monoperiodic structure to obtain a divergent transmitting or reflecting light beam; forming a shadow picture diffraction-interference pattern by the divergent transmitting or reflecting light beam; and detecting a moving amount of the shadow picure diffraction-interference pattern caused by a movement of the detected body in a direction crossing the irradiated light beam by the photodetector to detect the moving amount of the detected body.

Abstract: A light beam is incident on a first position on a scale at such an angle that diffracted lights substantially coincide with an incident optical path, and two diffracted lights are directed along a substantially common optical path and are incident on a second position symmetrical with the first position. An interference light formed by rediffracted lights reflected from the second position is detected to thereby detect the displaced state of the scale.

Abstract: The present invention is directed to a rotary code disk mounting structure for an optical encoder. A rotary code disk (3) with no center hole is fastened to a spindle (2) by an adhesive (J) that a is put in a recess (21) formed in a mounting surface (20). The mounting surface (20) is formed on the top surface of the spindle (2) with the central portion of the backside of the rotary code disk (3) in contact with the mounting surface (20). The rotary code disk mounting structure is applied to optical encoders for use in combination with servometers, machine tools and measuring apparatuses.

Abstract: A high-accuracy position comparator includes a length-measuring grating having a ruling extending two-dimensionally, a reflecting device, an index grating having the ruling following the same direction as that of the length-measuring grating, a grating overlapping optical system comprised of a projecting device for projecting an image of one of these two gratings and an imaging device for forming the image through the reflecting device, a fringe detecting device for detecting interference fringes produced by the optical system, and a measuring position detecting device. Thus, the comparator has practically important advantages of being able to make two-dimensional measurement and positional comparison without resetting an object being measured.

Abstract: Several bar patterns are projected in sequence on the object (O) to be measured by time-division multiplexing, and images of the bar patterns are recorded by a camera (K). The phases of each bar pattern, as distorted by the object, are calculated for preselected image points by a computer connected with the camera. For each image point, the calculated phases for one of said bar patterns are compared to the phases calculated for at least one other of said bar patterns, thereby producing a beat frequency which can be used to determine height measurements in the direction of the camera axis (z). In order to increase the range of the height measurements, at least two beat frequencies of quite different effective wavelengths are generated and evaluated. Different systems are disclosed for generating the different beat frequencies. In one embodiment, the bar patterns are projected by three different projectors (P.sub.1, P.sub.2, P.sub.3) which are inclined at different angles relative to each other (.alpha..sub.