Abstract: A main scale 11 and an index scale 12 are arranged in parallel with each other so as to be relatively movable. A light source 10 for irradiating collimated light on the main scale 11 is provided above the main scale 11. A light detecting devices 13a and 13b for detecting the amount of light which pass trough the index scale 12 are provided below the index scale 12. The main scale 11 has an uniform grating which consist of transmitting portions 14 and non-transmitting portions 15 which are formed with a uniform width and alternately arranged by uniform pitch P. The index scale 12 has non-uniform grating portions 12a and 12b whose phase are mutually shifted 90 degrees. Transmitting portions 16 and non-transmitting portions 17 of the non-uniform grating portions are arranged at the same pitch as the main scale 11.

Abstract: A method and apparatus for measuring thermally induced warpage in test elements such as printed wiring boards and printed wiring assemblies, including a heating chamber having a transparent window and support structure for supporting a printing wiring board in an observation orientation and position parallel to the transparent window. A glass grating placed adjacent the window and a light source shines through the window onto the printed wiring board under test. A camera is positioned for capturing images of shadow moire fringes formed over time as the oven heats up the printed wiring board or printed wiring assembly to simulate actual process conditions. A computer is used for controlling operation of the apparatus and for evaluating the captured images of the moire fringes in relation to the temperature as a function of time.

Abstract: A tank gauging system includes an improved level sensor float providing positional information to a level encoder unit having two slotted disks coupled to a gaugehead which alternately admit and interrupt light to optical sensors to provide relative incremental positional change and direction information as well as an error detection capability. The light optical sensors provide two signals, which are directly compared to provide a clock signal for an up/down counter. One of the two signals is delayed and this delayed signal is directly compared against the other signal to provide a direction signal for an up/down counter. A microprocessor converts this information to absolute data and provides it to a transmitter unit. The transmitter may also be provided with data from other gauging sensors, such as an error-compensated temperature measurement of the tank contents.

Abstract: The invention provides a device for shifting the phase of a projected grating by use of a grating generator comprising one or more clear substrates having a plurality of equally-spaced, equal width bands of liquid crystal. The liquid crystal bands are selectively activated to modulate, that is, to shift, the phase of the projection of the grating on a test surface.

Abstract: An encoding apparatus includes: a light source; a diffraction grating, including a number of fine grating portions orthogonally arranged in columns and rows in a diffraction grating surface, for producing first diffracted light rays and second diffracted light rays in accordance with light emitted from the light source, each of the first diffracted light rays having a direction cosine on a first plane, and each of the second diffracted light rays having a direction cosine on a second plane; an interference unit for producing a first interference light ray by subjecting two diffracted light rays of the first diffracted light rays to interference, and for producing a second interference light ray by subjecting two diffracted light rays of the second diffracted light rays to interference; a first detection unit for detecting a phase change of the first interference light ray when an object is moved relative to the light source; and a second detection unit for detecting a phase change of the second interference l

Abstract: A light source which emits light in strips is provided for illuminating a scale of a photoelectric position measuring system. The light modulated by the scale is converted into a sinusoidal scanning signal by a scanning plate. The scanning plate is a semiconductor substrate structured in strips. The width (A) of the light-emitting areas and the width (B) of the interspersed non-emitting areas of the light source is such that defined harmonics are filtered out of the scanning signal. The scanning plate is of such configuration that further harmonics are suppressed.

Abstract: An optical encoding apparatus 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 encoding apparatus includes a light source for emitting a light beam, a light beam condenser for condensing the light beam emitted by the light source, a first diffraction grating to which light beams condensed by the light beam condenser are directed, and a second diffraction grating to which light beams exiting from the first diffraction grating are directed. Additionally, a displacement information obtaining device is included for obtaining information regarding a displacement of one of the first and second diffraction gratings, the information being obtained according to a twice-diffracted beam and a twice-transmitted beam incident upon the second diffraction grating.

Abstract: A displacement detection apparatus has a light source 1, a first diffraction grating G1 for diffracting and dividing the light from the light source and applying O-order diffracted light and +1st-order diffracted light to a second diffraction grating G2, a third diffraction grating G3 for combining +1st-order reflected diffracted light created by the O-order diffracted light being reflected and diffracted by the second diffraction grating and -lst-order reflected diffracted light created by the +lst-order diffracted light being diffracted by the second diffraction grating, to thereby form interference light, and a light receiving element 3 for photoelectrically converting the interference light, the third diffraction grating including four diffraction gratings given a phase difference of .pi.

Abstract: An encoder has a detector that detects displacement of a movable portion and a generator that generates multiple phase periodic signals with at least three different phases. The phase periodic signals change according to the displacement and a selector selects one of the multiple phase periodic signals to which a predetermined offset is added. In one encoder arrangement, a light beam is radiated toward a scale on which a grating is formed along a relative displacement direction. A light-receiving element receives light modulated by the grating to obtain relative displacement information between the light beam and the scale. The light receiving element has an opening width that changes in a direction perpendicular to the displacement direction.

Abstract: An apparatus for detecting a displacement of a diffraction grating set on a measured object, comprises a light-emitting device, a separation optical element for separating a beam from the light-emitting device into a plurality of beams, a multiplexing optical element for multiplexing light beams diffracted by the diffraction grating from two beams out of the plurality of beams, a first detecting unit for detecting interference light generated when the beams of diffracted light are multiplexed by the multiplexing optical element and outputting a signal related to relative displacement information to the diffraction grating, and a second detecting unit for outputting a signal related to different information from the relative displacement information to the diffraction grating, based on a change in a diffracted light quantity of diffracted light by the diffraction grating from another beam out of the plurality of beams and/or another diffracted light by the diffraction grating from the two beams.

Abstract: An absolute encoder having a coder in which an incremental pattern and an absolute pattern are arranged in parallel and a detector including sensors for detecting the incremental pattern and the absolute pattern respectively. The absolute encoder comprises a discriminater to discriminate a relative phase position of the coder and the detector in one pitch of the incremental pattern from an output of the sensor for detecting the incremental pattern, and a signal generator to generate a synchronizing signal when a discriminated phase position coincides with a predetemined phase position by means of an electric circuit in one pitch of the incremental pattern. The absolute pattern is read on the basis of the synchronizing signal at a position except for the boundary region between the minimum reading units.

Abstract: A rotation measuring apparatus has a grating disposed on a cylindrical surface along the circumferential direction thereof, an illuminating system for applying a light beam to a first location on the grating, light emerging from the first location by the application of the light beam from the illuminating system being incident on a second location on the grating, light beams for detection emerging in a plurality of directions from the second location on which the light is incident, a plurality of light receiving elements for detecting the light beams for detection, respectively, the relative rotation information of the grating and the light receiving elements being measured by the detection by the light receiving elements, and light intercepting means for preventing the light beam for detection which should enter at least one of the light receiving elements from entering a different light receiving element.

Abstract: The apparatus disclosed herein employs a grating or scale which concentrates light at a preselected wavelength into the positive and negative first orders while minimizing the zeroth order. The scale is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector has its sensing plane spaced from the scale a distance less than ##EQU1## where W is the width of the illuminated region of the scale. The period of the poly-phase detector is equal to P/2 so that each detector element or phase responds principally to 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 scale is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first.

Abstract: The detector comprises a disc-like reel table adapted to support a tape reel thereon, the reel table having a reflective underneath surface and an array of concentric spaced-apart cutouts uniformly disposed on the reflective surface along a common imaginary circle whose center coincides with a rotational axis of the tape reel, each of the cutouts having a light scattering surface capable of reducing the intensity of a light beam incident thereupon to an appreciable level. A light emitter is located in an opposing relationship with respect to the reel table for projecting the light beam toward the reflective underneath surface and the light scattering surface of the reel table. Positioned adjacent to the light emitter is a light receiver for receiving the light beam reflected back from the reel table to produce a pulse signal when the intensity of the received light beam varies over time in a pulse pattern.

Abstract: A holographic interferometry apparatus for inspecting cylindrical optical surfaces. Laser light is split into regular reflection light and diffraction light by a holographic optical element. A reference reflector plate receives the regular reflection light. An object with a cylindrical optical surface receives the diffraction light. The object is held on a specimen holder table which has a four-axis adjustment mechanism which allows adjustments in the X,Y,Z and .theta. directions. Interference fringes are formed by the interference of light reflected from the object and from the reflector plate.

Abstract: In measuring apparatus for detecting relative displacement of a diffraction grating, a light beam is separated in an optical unit such as polarizing beam splitter into a reflected light beam and a transmitted light beam which beams are projected onto the diffraction grating. The diffracted light of the reflected and transmitted light beams are deflected by a deflection unit to be projected again onto the diffraction grating for rediffraction. The rediffracted light of the reflected and transmitted light beams are combined in the polarizing beam splitter and a detector detects the interference state of the combined rediffracted light. The deflection unit deflects the diffracted light beams of the reflected light and transmitted light so that they reenter the diffraction grating after traveling along the same optical path in the directions opposite to each other.

Abstract: The optical displacement detecting device utilizes an encoder plate 2 mounted displaceably along a given first plane and having thereon a periodic slit pattern 1. A light source 4 is disposed behind the encoder plate 2 to illuminate the slit pattern 1 to form a primary fringe image 3 shifting along the first plane. A lens member 6 is utilized to project the primary fringe image 3 by a given magnification to form a secondary enlarged fringe image 5 shifting along a given second plane. A light receiving unit 8 is fixed in the secondary plane to optically detect the shifting secondary enlarged fringe image 5 through a periodic mask pattern to thereby output an electric signal 7 indicative of a displacement of the encoder plate 2.

Abstract: A rotation detecting apparatus includes a grating portion provided on one of two objects for which relative rotation is to be detected, a light-emitting portion provided on the other of the two objects, and a light-receiving portion provided on the other object. The grating portion has at least one multi-helix diffraction grating. The light-receiving portion receives a beam emitted from the light-emitting portion and then traveling by way of the multi-helix diffraction grating. Information of relative rotation of the two objects is detected through light reception of the light-receiving portion.

Abstract: In an optical displacement sensor for measuring a moving state of a moving object by projecting a light beam onto a diffraction grating provided on a surface of a scale connected to the moving object and utilizing diffracted light beams of specific orders from among diffracted light beams diffracted by the diffraction grating, a portion of the light beams incident upon the diffraction grating is reflected at a reflecting region provided on the back of the scale a plurality of times. A photosensor detects a change in the amount of light emanating from a transparent or a light-blocking reference position, formed on a region on the surface of the scale other than the region where the diffraction grating is formed. An output signal from the photosensor is utilized as a reference signal, which provides information relating to the moving state of the moving object.

Abstract: A method for detecting the point of origin of a position sensor such as an optical linear scale by first displacing an object member whose position is to be determined until it butts against a mechanical stopper, then determining the position of the object member at the mechanical stopper and using that position as a reference position for the point of origin, and thereafter detecting the position of the object member by means of the position sensor, thereby detecting the position of the object member relative to the point of origin. In another embodiment, a first point of origin signal is obtained from an optical linear scale used as a position sensor and stored in response to latching signal generated at an end point of travel of the object member. Subsequently, when a second point of origin signal from the optical linear scale is compared with the first point of origin signal, any deviation from the first point of origin signal may be corrected based on the result of the comparison.

Abstract: A rotary detector has a diffraction grating arranged circumferentially and a center at substantially the center of rotation. The rotary detector measures rotational information of a rotating object. The rotary detector is provided with a light source, an irradiating optical system for irradiating luminous flux from the light source to a first point on the diffraction grating, and an optical system for guiding two diffracted luminous fluxes emerging from the first point at an emerging angle and diffracted to have a same order but different signs to be incident at a second point on the diffraction grating at an incident angle relative to a rotational direction of the grating, with the second point positioned substantially opposite to the first point on the diffraction grating with respect to the center of the rotation, and the incident angle is the same angle as the emerging angle.

Abstract: A detector is described, intended for use in metrology systems of the type which produce interference fringe patterns which contain a phase which is characteristic of the parameter under measurement, particularly displacement or position. The detector is in the form of an array of elements whose outputs are electrically interconnected so as to form three or more signals displaced from one another in phase by a fixed amount. The detector is provided on a single monolithic, silicon substrate using microelectronics techniques.

Abstract: A method and apparatus for making measurements on light fringes such as are produced by interferometers or gratings wherein such measurements can include measurements of position and velocity of an object such as a step and repeat carriage or microscope stageThe fringe pattern is sensed with a linear array detector whose elements are repetitively time multiplexed. The resultant output signal is filtered, yielding an AC signal with a phase indicative of fringe position. Rapid, digital, submicron counting is made possible using a phase lock loop to control the multiplexor clock. The advantages of AC interferometry are realized without optical modulation.

Abstract: Each of beams originated from a light source to be measured and a white light source is branched by a beam splitter into two beams, which are reflected by a fixed and a movable mirrors respectively to meet each other again so as to generate interfering light, the white light being maximum in interfering efficiency when the optical path reaching the movable mirror is equal in length to that reaching the fixed mirror. The interfering light originated from the light source is converted into an electric signal by a first light receiver and further into pulses by a first converter. A length measuring machine outputs a pulse signal corresponding to the moving length of the movable mirror. A second light receiver converts the interfering light originated from the white light source into an electric signal.

Abstract: An optical arrangement or length- or angle-measuring device comprising an illumination device for generating partial ray beams and an image lens to receive and transmit the partial ray beams, wherein each of the received partial ray beams defines an angle of inclination with respect to the image lens. The optical arrangement further comprises a plurality of detectors to receive the transmitted partial ray beams and the detectors are positioned so that the distance between the image lens and the individual photodetectors is a function of the angle of inclination of the partial ray beams received by the image lens.

Abstract: Apparatus for surface measurement has a grating interferometer with a curved diffraction grating carried on a pivotal support arm of a probe for contacting a surface. The probe is biased into contact with a surface by an electromagnetic coil acting on an armature, or a pair of such biasing arrangements. A laser diode illuminates the grating to produce a pair of first order diffracted beams of opposite sign which are reflected from internal faces of a prism, and combined by a diachronic central layer of the prism and a pair of beam splitters. Output signals from the beam splitters are supplied to a signal processing circuit having a fringe counter and an interpolator. The fringe counter detects zero crossings of the signals and the interpolator maintains a digital estimate of the phase of the signals and updates the estimate when the phase difference between the estimate and the input signals exceeds a predetermined threshold.

Abstract: A displacement detector includes a light generation source for generating light, a scale to be irradiated by the generated light and displaceable relative to the irradiated light, a first detection device having a photo-sensing element for detecting light transmitted through the scale for detecting displacement information of the scale, a mark having a focusing or light-condensing function formed integrally with the scale, and a second detection device having a photo-sensing element for sensing the light-condensed by the mark for detecting a reference position of the scale.

Abstract: An integrated optical interferometer is provided having a substrate located on one object and a measuring reflector or measuring diffraction grating located on another object. A beam impinging upon the substrate is split into two partial beams by a coupling grating and is coupled into a beam waveguide and supplied to another coupling grating. A second partial beam is routed by the measuring reflector to the second coupling grating and there interferes with the first partial beam. The second coupling grating is divided into a plurality of gratings which are phase-shifted with respect to each other so that signals that are phase-shifted with respect to each other can be generated by a plurality of detectors.

Abstract: An apparatus for detecting information as for the rotation of a scale having a diffraction grating arranged thereon along a direction of detection of the rotation is constituted by a light source portion for irradiating a light beam onto a first point on the diffraction grating of said scale wherein said light source portion emitting two diffracted lights having a predetermined order from the first point by the irradiation of the light beam, a transparent substrate to be parallelly arranged in the vicinity of the surface of said scale and having a plurality of optical elements arranged thereon, said plurality of optical elements directing the two diffracted lights of the predetermined order to a second point other than said first point on the diffraction grating of said scale and a photo-detector for detecting an interference light beam of the diffracted lights generated out of said second point on which the two diffracted lights of the predetermined order are incident whereby the information on the rotation

Abstract: A position measuring system with compensation for variable distance between the light source and the index disk. The index disk has a plurality of index lines separated by masked areas. The light source emits beams of light that impinge upon the plane of the index disk at an angle and yet are parallel to the direction of the index lines. The masked areas on the index disk along with the light source positioned at an angle with respect to the axis of the index disk allow the detectors located downstream of the index disk to be maximally illuminated when the index disk is located at its maximum permissible distance from the light source and the detectors are minimally illuminated when the index disk is located at its minimum permissible distance from the light source.

Abstract: A multi-coordinate measuring system having a diffraction element that receives light emitted by a light source and diffracts the light into at least a first, second, third and fourth partial beam bundles where the first, second, third and fourth partial beam bundles are directed in different coordinate directions onto a substrate. The substrate has first, second, third and fourth waveguides located thereon. The substrate has a coupling element that directs the first, second, third and fourth partial beam bundles into the first, second, third and fourth waveguides, respectively. The substrate also has a first coupling element for bringing the first and second partial beam bundles into interference and a second coupling element for bringing the third and fourth partial beam bundles into interference. A detector system then detects the interference of the first and second partial beam bundles and the third and fourth partial beam bundles.

Abstract: A Fourier-transform (FT) infrared (IR) spectrometer includes a Michelson interferometer without an IR beam compensator. An input IR beam is directed through a substrate and a beamsplitter attached to the substrate for support, with the input IR beam divided by the beamsplitter into a first beam portion incident upon a fixed retroreflector and a second beam portion incident upon a movable retroreflector. The first and second beam portions are then recombined to provide an uncompensated output IR beam with an interference pattern which is directed onto a sample to provide an uncompensated interferogram. The uncompensated interferogram is converted from a time domain to a frequency domain via a Fourier-transform to provide a complex intermediate spectrum, followed by a calculation of a corrected phase angle in terms of wavenumber arising from the substrate's optical thickness. The complex intermediate spectrum is then rotated by a negative of the corrected phase angle.

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: The purpose of the present invention is to provide a highly accurate optical wavelength meter in which the accurate starting and stop points of the measurement are detected. In accordance with the present invention, a detector which detects the back-shift of the moving mirror due to elastic force of the belt and an up-down counter which measures the amounts of the overshoot and the back-shift of the moving mirror so as to cancel the overshoot and the back-shift are provided, by which the accurate starting and stop points of the measurement can be detected.

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 direct the light beam to a stand-alone 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: There are disclosed a signal processing method, and a displacement information measuring apparatus utilizing such method, capable of providing highly reliable binary signals even in the presence of a time-dependent variation in the light emission intensity of the light source, a variation in the emission intensity resulting from a variation in the external temperature, or a variation in the optical transmittance resulting from smear on the optical scales, thereby enabling highly precise detection of the displacement information of the movable member.

Abstract: A displacement detection apparatus comprises a light source 1, a first diffraction grating including a blazed grating for diffracting and splitting light from the light source to irradiate a 0-order diffraction light and a +1-order diffraction light to a second diffraction grating, a third diffraction grating including a blazed grating for combining a +1-order reflected diffraction light produced by the reflection and diffraction of the 0-order diffraction light by the second diffraction grating and a -1-order reflected diffraction light produced by the diffraction of the +1-order diffraction light by the second diffraction grating to produce an interference light, and a photo-sensing element for converting the interference light to a signal representing a change in the second diffraction grating.

Abstract: An encoder capable of detecting movement information on a moving body with high accuracy without being affected by environmental changes, wherein movement information on a moving body is detected by causing a luminous flux to impinge upon a first scale section of an optical scale which is provided on the moving body and which consists of gratings of a fixed pitch, causing the luminous flux to impinge upon a second scale section of the optical scale, and receiving the luminous flux which has undergone light modulation at the second scale section, and wherein a light adjustment device for intercepting or attenuating a +1st order or -1st order diffracted ray of diffracted rays of light from the first scale section is provided in the optical path extending from the first scale section, an optical image having an intensity distribution of the same grating pitch as the first scale section being formed on the second scale section mainly by the zero order and the -1st order diffracted rays or by the zero order and th

Abstract: The invention provides a device for shifting the phase of a projected grating by use of a plurality of transparent plates, each disposed at a different angle with respect to the angle of the grate, which plates may be selectively placed between the grating and the projecting lens of a projecting system to modulate, that is, to shift, the phase of the projection of the grating on a test surface.

Abstract: A scale comprising a regular arrangement of optically or magnetically different response characteristics such as light reflection and light diffusion portions or light reflection and absorption portions is attached to a moving object either directly or by way of an intermediate member. The scale can be attached to a motor or the like even after assembling with associated mechanical components, thereby enabling easy measurement of the mode of operation of the motor or similar movable objects. The light beam from the light emitting device is directed to the label media and the reflected light beam is received by a light receiving device to identify the individual object or product based on the label.

Abstract: The present invention provides an apparatus and method for measuring two- dimensional displacement by moire fringes of concentric circle gratings which two-dimensional displacement can be precisely measured by a pair of grating and the measurement resolution can be improved by the image processing using the characteristics of moire fringes without noises.

Abstract: An apparatus and method for measuring displacement by determining the relative speed between a scale and a scanning plate from reading out a first track twice at different times. From this, correction values for the other tracks are calculated, which represent values from those tracks that would have been read out if all those tracks had been read out at the same time the first track was read out instead of sequentially.

Abstract: An optoelectronic measuring scale for determining and indicating position of light emitted from a beam source is provided. The measuring scale comprises a composite unit including a profiled body, a number of discrete photoelements fixedly mounted on a circuit board or similar device in the body and connected to a microprocessor attached to the circuit board. Mounted in the measuring scale is a diffusor for distributing incident light such that the intensity of such incident will be distributed over a plurality of mutually adjacent photoelements. The microprocessor detects and compares the intensity of light detected by respective photoelements and, based on the intensity of light detected by the photoelements, produces output currents for causing the exact position of the light beam to be indicated on a display connected to the scale.

Abstract: A photoelectric position indicator comprises a scale phase grating, and a scanning unit movable along a measuring direction and comprising a scanning phase grating, which is movable relative to the scale phase grating, a light source, a collimator, and photodetectors, which from the interference patterns formed by the light diffracted by the gratings receive groups having a predetermined order of diffraction and produce periodic phase-displaced actual-value signals in dependence on the orders of diffraction of said groups during a movement of the scanning unit relative to the scale phase grating. To ensure a generation of signals which can easily be evaluated and to permit larger assembling tolerances, the scanning unit comprises a light-directing phase grating arranged to fan the light from the light source transverse to the measuring direction so as to form component light beams, and the photodetectors receive the groups of the interference patterns generated by one of the component light beams.

Abstract: A device for detecting the displacement of an object is provided with a semiconductor laser having an active layer for emitting laser beams in two directions, mirrors for directing the laser beams toward a diffraction grating provided on the object, and a detector for receiving the interfering lights diffracted by the diffraction grating. The active layer of the semiconductor laser is arranged substantially parallel to the diffraction grating, to save space, also to enable light deflection such that the spreading direction of the light beams from the semiconductor laser coincides with the direction of pitch of the diffraction grating. The diffraction grating is irradiated with an improved efficiency, giving diffracted lights with higher intensity to the detector and improving the S/N ratio of detection. The space between the semiconductor laser and the object is reduced, thus reducing the entire volume of system.

Abstract: A system used for measuring the tilt of an image formed by a lens. The measuring system has a light source, a diffraction grating, a reflection surface and a detector for detecting an interference pattern that is formed by the light after passing through the diffraction grating reflection surface and the lens.

Abstract: A known method of measuring angular displacement of a shaft (11) using an optical grating mounted for rotation with the shaft is applied at two or more angularly spaced locations (16, 17 and 18) and the resulting measurements are process to produce a measurement of relative displacement of the shaft in a direction transverse to the shaft. Two locations are needed to measure displacement in a given direction. Three or more locations are necessary to provide full information about the displacement of the shaft.

Abstract: A position detecting apparatus with a sampling function, comprises a waveform generator for generating repetitive periodic waveforms in relation to a moving object to be measured. A processor samples the output of the waveform generator and, after digitizing the same, processes the digital data to detect the position of the object. The processor first estimates the current position from the data obtained in the preceding detection and then determines the current position on the basis of the estimated position. The apparatus can be incorporated in a system for driving an optical unit in a video camera, wherein the object to be measured is a moving focus lens member and is actuated by a direct drive motor.

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: An optical pickup device in which a main beam and a pair of sub-beams are used and a diffraction device is disposed between a recording medium and a light receiving device such as a photodetector is disclosed. The diffraction device comprises first to third diffraction regions. The second and third regions receive light beams from the recording medium which are substantially identical in amount to each other. The light receiving device comprises a first to a fourth light receiving regions. The first and second light receiving regions are juxtaposed, and separated by a line. The main beam which has been diffracted by the first diffraction region is focused onto said line. The main beam which has been diffracted by the second diffraction region is focused onto the first light receiving region. The main beam which has been diffracted by the third diffracting region is focused onto the second light receiving region.