Abstract: An apparatus includes an acquisition means for acquiring the displacement quantity in a time-series manner, the displacement quantity being generated at a measurement part of a structure by the weight of a vehicle that travels on the structure, a detection means for detecting the position and the clock time of the vehicle that travels a pre-passage area of the measurement part, an estimation means for estimating the arrival time that the vehicle arrives at the measurement part, from the position of the measurement part and the position and the clock time of the vehicle, and a control means for controlling the acquisition means on the basis of the estimated arrival time.

Abstract: A method of overlay error measurement includes disposing a reference pattern module over a substrate. The substrate includes first and second overlay measurement patterns in first and second locations. The reference pattern module includes first and second reference patterns. The method includes creating a first overlap of the first reference pattern with the first overlay measurement pattern and a second overlap of the second reference pattern with the second overlay measurement pattern. The method further includes determining a first overlay error between the first reference pattern of the reference pattern module and the first overlay measurement pattern of the substrate and determining a second overlay error between the second reference pattern and the second overlay measurement pattern. The method also includes determining a total overlay error between the first and second overlay measurement patterns of the substrate based on the first and second overlay errors.

Abstract: An article manufacturing method includes a first formation step of forming a focus compensation film on a substrate, a second formation step of forming a resist layer on the focus compensation film, and a transfer step of transferring a pattern of an original to the resist layer using an exposure apparatus. In the first formation step, the focus compensation film is formed such that the focus compensation film has a top surface shape corresponding to an image surface shape of the exposure apparatus.

Abstract: A difficulty of contamination interfering with a grid plate positional measurement system is addressed. In one embodiment contamination is prevented from coming into contact with the grating or the sensor. In an embodiment, surface acoustic waves are used to detach contamination from a surface of the grating or sensor.

Abstract: Disclosed is a system including: a beam projector module comprising a light source and an optical device configured to diffuse light output from the light source to reduce an intensity of the light; an image sensor configured to receive reflected light formed by the light reflected from an object; and a signal processing device configured to measure a distance from the object by analyzing a characteristic of the reflected light, wherein the signal processing device operates the beam projector module in an eye-safety mode when the characteristic of the reflected light corresponds to a crack characteristic.

Abstract: Spectrometer designs are provided. The spectrometer includes two planar diffraction gratings disposed in a cascade, without intervening optics therebetween. Advantageously, the described configurations may promote both a high throughput and a high resolution, enabling the design of a portable device having sufficient resolution for on-site use or in the laboratory. In some implementations, two different secondary diffraction channels may be provided.

Abstract: Systems and methods for imaging object velocity are provided. In an embodiment, at least one Time-of-Flight camera is used to capture a signal representative of an object in motion over an exposure time. Illumination and modulation frequency of the captured motion are coded within the exposure time. A change of illumination frequency is mapped to measured pixel intensities of the captured motion within the exposure time, and information about a Doppler shift in the illumination frequency is extracted to obtain a measurement of instantaneous per pixel velocity of the object in motion. The radial velocity information of the object in motion can be simultaneously captured for each pixel captured within the exposure time. In one or more aspects, the illumination frequency can be coded orthogonal to the modulation frequency of the captured motion. The change of illumination frequency can correspond to radial object velocity.

Abstract: In an optical position measuring device for the interferential determination of the relative distance of two objects which are movable relative to each other in at least one measuring direction, a bundle of rays emitted by a light source is split up into at least two partial bundles of rays, which fall on a grating or a plurality of gratings on separate optical paths and undergo distance-dependent phase shifts as a result. The partial bundles of rays are superpositioned at a mixing grating, whereupon at least three pairs of interfering partial bundles of rays propagate in different directions in space. Via the mixing grating, each pair of interfering partial bundles of rays is focused on a detector element so that at least three position-dependent, phase-shifted incremental signals are detectable via the detector elements.

Abstract: A metrology apparatus for and a method of determining a characteristic of interest relating to at least one structure on a substrate. The metrology apparatus comprises a sensor and an optical system. The sensor is for detecting characteristics of radiation impinging on the sensor. The optical system comprises an illumination path and a detection path. The optical system is configured to illuminate the at least one structure with radiation received from a source via the illumination path. The optical system is configured to receive radiation scattered by the at least one structure and to transmit the received radiation to the sensor via the detection path.

Abstract: In order to make a ghost image appearing when projection light is projected using a phase-modulating spatial light modulation element difficult to visually recognize, a projection device includes a light source, a light-source driving means, a spatial light modulation element, a modulation element control means, a projection control means, and a projection optical system, wherein the projection control means controls the light-source driving means and the modulation element control means in such a way as to cause a phase distribution of an image including a ghost compensation image and a desired image to be displayed on a display part, the ghost compensation image being an image for which high brightness is set totally and in which a display information portion to be displayed on a projection surface is bright while a ghost image portion that appears in association with the display information is dark.

Abstract: In an exposure apparatus, on a substrate holder, a plurality of grating areas is arranged mutually apart in the X-axis direction, and a plurality of heads that irradiates a measurement beam with respect to the grating area and can move in the Y-axis direction is arranged outside of the substrate holder. A control system controls movement of the substrate holder in at least directions of three degrees of freedom within an XY plane, based on measurement information of at least three heads of the plurality of heads facing the grating area and measurement information of a measurement device that measures position information of the plurality of heads. The measurement beam of each of the plurality of heads, during the movement of substrate holder in the X-axis direction, moves off of one of the plurality of grating areas and switches to another adjacent grating area.

Abstract: A control system controls a drive system of a substrate holder, based on correction information to compensate for measurement error of a measurement system including an encoder system that occurs due to movement of at least one of a plurality of grating areas (scale), a plurality of heads and a substrate holder, and position information measured by the measurement system, and a measurement beam from a head of each of the plurality of heads moves off from one of the plurality of grating areas and switches to another adjacent grating area, during the movement of the substrate holder in the X-axis direction.

Abstract: An encoder head configured for use with a lithographic exposure tool. The head is devoid of the multiplicity of optical corner-cubes and includes, instead, a single, geometrically substantially perfect cuboid of optically-isotropic material complemented, in operation, with a birefringent lens to form a contraption that, as a unit, splits a single beam of light delivered to the contraption into four measurement (sub-)beams of light (two in xz-plane, two in yz-plane) and causes each of measurement sub-beams to interact with the wafer-stage diffraction grating at the same location twice: upon the first pass by the grating and upon the second pass by the grating.

Abstract: An optical encoder includes a scale including a diffraction grating, a light-receiving unit configured to receive light from a light source, and an optical element located between the scale and the light-receiving unit. The optical element includes a plurality of groove portions, which are a periodic structure portion formed periodically in one face of the optical element. The plurality of groove portions is configured to divide signal diffracted light and noise diffracted light into first splitted beams traveling at a predetermined travel angle and second splitted beams traveling at a travel angle greater than the travel angle of the first splitted beams, and make a diffraction efficiency of the first splitted beams of the noise diffracted light lower than a diffraction efficiency of the first splitted beams of the signal diffracted light.

Abstract: A liquid crystal exposure apparatus has a measurement system having scales arranged apart from each other in the X-axis direction provided at a substrate stage holding a substrate and heads each irradiating the scales with a measurement beam; and a measurement device that measures positions of head units in the Y-axis direction. The measurement system measures a position of the substrate holder in directions of three degrees of freedom within a plane, based on measurement information of at least three heads. Each of the heads move off of one scale while the substrate holder is moved in the X-axis direction and moves to irradiate another scale adjacent to the one scale, and correction information to control movement of the substrate holder using the head moving to irradiate another scale is acquired, based on measurements of at least three heads.

Abstract: An encoder head configured for use with a lithographic exposure tool.

Abstract: A displacement detecting device includes a first diffraction grating, a light source, a displacement detecting unit, and a light receiving unit. The displacement detecting unit includes a light flux dividing unit, a second diffraction grating, and a reference reflecting member. An incident angle of a first light flux to the first diffraction grating, a diffraction angle of the first diffraction grating, an incident angle of the first light flux to the second diffraction grating, and a diffraction angle of the second diffraction grating are angles at which a displacement amount in an optical path length of the first light flux from the light flux dividing unit to the first diffraction grating and a displacement amount in an optical path length of the first light flux from the first diffraction grating to the second diffraction grating become equal in a case where a measured member is displaced in a direction orthogonal to a measured surface.

Abstract: In an exposure operation, as a second stage is moved in a direction parallel to a predetermined plane, another head different from a plurality of heads faces a grating section instead of one head of the plurality of heads, and positional information of the second stage is measured by multiple heads including remaining heads and the another head, the remaining heads excluding the one head of the plurality of heads, and correction information is acquired for the positional information obtained from the another head, based on the positional information obtained from the plurality of heads including the one head.

Abstract: In an exposure operation, as a second stage is moved in a direction parallel to a predetermined plane, another head different from a plurality of heads faces a grating section instead of one head of the plurality of heads, and positional information of the second stage is measured by multiple heads including remaining heads and the another head, the remaining heads excluding the one head of the plurality of heads, and correction information is acquired for the positional information obtained from the another head, based on the positional information obtained from the plurality of heads including the one head.

Abstract: In an exposure operation, as a second stage is moved in a direction parallel to a predetermined plane, another head different from a plurality of heads faces a grating section instead of one head of the plurality of heads, and positional information of the second stage is measured by multiple heads including remaining heads and the another head, the remaining heads excluding the one head of the plurality of heads, and correction information is acquired for the positional information obtained from the another head, based on the positional information obtained from the plurality of heads including the one head.

Abstract: In an exposure operation of a substrate, a controller controls first and second drive systems based on correction information for compensating for a measurement error of an encoder system and measurement information of first and second measurement devices, so that scanning exposure is performed and a measurement error is compensated for. In the scanning exposure, a mask and the substrate are each moved relative to illumination light with a first direction serving as a scanning direction, the measurement error occurring due to a difference between a position of a reference plane and a position of a grating surface of a grating section in a third direction orthogonal to a predetermined plane that includes the first direction, and the reference plane being a reference plane for position control or positioning of a second stage or a reference plane with which the substrate coincides in the exposure operation.

Abstract: A detection head movable relative to a scale detects diffracted light and outputs a detection result. The diffracted light is diffracted by an incremental pattern. A signal processing unit calculates a relative displacement between the scale and the detection head. The detection head includes: a light source emitting the light to the scale; and a detection unit including a light-receiving unit receiving the diffracted light through an optical element, in which the light-receiving elements outputting detection signals are periodically arranged with a predetermined period. The number of the plurality of light-receiving elements is an even number. The predetermined period is a value obtained by multiplying a fundamental period by an odd-number. The fundamental period is a period of interference fringes formed on the light-receiving unit by +1st and ?1st order diffracted lights. A width of the light-receiving element is not equal to an integral multiple of the fundamental period.

Abstract: An opto-acoustic transducer may include a light source, a substrate, a top layer, an interstitial layer, a lens, and a detector array. The light source may generate light beams. The substrate may reflect the light beams generated by the light source. The top layer may modulate responsive to an acoustical wave impingent thereupon and may reflect the light beams generated by the light source. The interstitial layer may be between the substrate and the top layer and may include a cavity which acts as an optical collector. The lens may propagate the light beams reflected by the substrate and the light beams reflected by the top layer. The detector array may reconstruct the acoustical wave impingent on the top layer based on the light beams propagated by the lens.

Abstract: The present invention relates to an optical displacement sensor comprising a first at least partially reflective surface and a second surface having a diffractive pattern, the surfaces being provided on elements having a variable distance between them, each surface pair defining a cavity between them. The sensor also comprising at least one light source transmitting light at least one a chosen wavelength range into said cavities and at least one light detector receiving light from the cavities, wherein said diffractive patterns are adapted to direct light toward at least one detector provided in a known position relative to said diffractive surfaces.

Abstract: Positional information of a movable body in a Y-axis direction is measured using an interferometer and an encoder whose short-term stability of measurement values excels when compared with the interferometer, and based on the measurement results, a predetermined calibration operation for obtaining correction information for correcting measurement values of the encoder is performed. Accordingly, by using measurement values of the interferometer, correction information for correcting the measurement values of the encoder whose short-term stability of the measurement values excels the interferometer is obtained. Then, based on the measurement values of the encoder and the correction information, the movable body is driven in the Y-axis direction with good precision.

Abstract: An immersion exposure apparatus exposes a substrate with light via a projection system and liquid, and includes a first stage system having a first movable body to hold a mask, a first detection system that detects a mark of the mask or of the first movable body, a first encoder system having first heads, a second stage system having a second movable body to hold the substrate, a second detection system that detects a mark of the substrate or of the second movable body, and a second encoder system having second heads. In each of an exposure operation and a detection operation by the first detection system, positional information of the first movable body is measured by the first encoder system. In each of the exposure operation and a detection operation by the second detection system, positional information of the second movable body is measured by the second encoder system.

Abstract: An FTIR touch panel (100) includes a light guide plate (11) and a prism (14) joined to the light guide plate (11). The prism (14) includes a side surface (14a), which is a joining portion that is joined to the light guide plate (11), and a groove (141) in which a light source (12) is inserted. Light emitted from the light source (12) is incident on the prism (14) through a wall surface of the groove (141), and travels from the prism (14) to the light guide plate (11) through the side surface (14a). Plating (200) is formed on a surface of the prism (14) over a region excluding the side surface (14a) and the wall surface of the groove (141). Accordingly, a touch panel having a high position detection accuracy can be provided.

Abstract: During the drive of a stage, positional information in a movement plane of a stage is measured by three encoders that include at least one each of an X encoder and a Y encoder of an encoder system, and a controller switches an encoder used for a measurement of positional information of a stage in the movement plane from an encoder to an encoder so that the position of the stage in the movement plane is maintained before and after the switching. Therefore, although the switching of the encoder used for controlling the position of the stage is performed, the position of the stage in the movement plane is maintained before and after the switching, and a correct linkage becomes possible.

Abstract: During the drive of a stage, positional information in a movement plane of a stage is measured by three encoders that include at least one each of an X encoder and a Y encoder of an encoder system, and a controller switches an encoder used for a measurement of positional information of a stage in the movement plane from an encoder to an encoder so that the position of the stage in the movement plane is maintained before and after the switching. Therefore, although the switching of the encoder used for controlling the position of the stage is performed, the position of the stage in the movement plane is maintained before and after the switching, and a correct linkage becomes possible.

Abstract: An optical element for generating diffraction orders for an encoder apparatus, in which the optical element includes an array of diffraction features arranged such that the spacing between the centers of adjacent diffraction features varies irregularly from one pair of adjacent features to the next.

Abstract: An automatic magnification adjusting method is applied to an optical navigation device. The optical navigation device has an illumination channel, a reference channel and an imaging channel. The reference channel has a reference feature with a known parameter. The automatic magnification adjusting method includes driving the illumination channel and the reference channel to alternatively output a detecting image and a reference image, capturing a series of navigation images consisting of the detecting image and the reference image by the imaging channel, analyzing the reference image to recognize the reference feature, calculating a compensating factor according to a detected parameter of the reference feature, and adjusting magnification of the detecting image by the compensating factor to output corresponding coordinate displacement.

Abstract: An optical position measuring instrument including a scale and a scanning unit, wherein the scanning unit and the scale are movable with respect to one another. The scanning unit includes a detector unit, and a reflector unit that has a first and second wave front correctors and a beam direction inverter. The reflector unit is disposed so that beams first pass through the scale and the first wave front corrector, then a back-reflection of partial beams is effected in a direction of the scale, and the partial beams then pass through the scale and the second wave front corrector before the partial beams then arrive at the detector unit, wherein it is ensured that wave front deformations of the partial beams are converted into wave front deformations that compensate for resultant wave front deformations of the partial beams upon a second diffraction at the scale.

Abstract: An encoder head includes one or more components arranged to: i) direct a first incident beam to the diffractive encoder scale at a first incident angle with respect to the encoder scale; ii) receive a first return beam from the encoder scale at a first return angle, the first return angle being different from the first incident angle; iii) redirect the first return beam to the encoder scale as a second incident beam at a second incident angle; and iv) receive a second return beam back from the encoder scale at a second return angle, the second return angle being different from the second incident angle, in which a difference between the first incident angle and second incident angle is less than a difference between the first incident angle and the first return angle and less than a difference between the second incident angle and the second return angle.

Abstract: A method determines a distance with a specified accuracy. The method transmits to an interferometer a test signal oscillating with a test frequency and receives, in response to the transmitting, an interferometric signal formed by interfering the test signal with a delayed signal produced by delaying a copy of the test signal over the distance equal to a path length difference in the interferometer. The test frequency is varying such that the test signal oscillates with different values of the test frequency. The method determines at least two values of the test frequency corresponding to particular values of the interferometric signal by beating the test signal with a reference signal having a reference frequency, wherein a value of the reference frequency is an absolute value predetermined with the specified accuracy. The method determines the distance using the two values of the test frequency.

Abstract: A measuring graduation includes a phase grating for a photoelectric position measuring device for measuring positions in a first direction and in a second direction extending orthogonally to the first direction. The phase grating has a periodic array of grating elements in the first direction and in the second direction. The grating elements each have an outer contour that is formed by a continuous line which includes two mutually opposing first straight edges, two mutually opposing second straight edges extending perpendicularly to the first straight edges, and connecting lines extending between the first straight edges and the second straight edges. The connecting lines form an obtuse angle with the first straight edges and with the second straight edges.

Abstract: An encoder (100) includes a cylindrical body (10), a sensor unit (7) configured to detect a displacement of the cylindrical body (10) in a circumferential direction of the cylindrical body (10), and a scale (2) that is attached to the cylindrical body (10) using a holder (12) and a holder (13) and that has a signal detection effective region (14) used to detect the displacement by the sensor unit (7), and a region (17) that has a stiffness smaller than a stiffness of the signal detection effective region (14) in the circumferential direction of the cylindrical body (10) is provided on an outside of the signal detection effective region (14) and on at least one side of the first holder (12) and the second holder (13).

Abstract: An exposure apparatus can mitigate the impact of fluctuations in the refractive index of ambient gas, and improve, for example, stage positioning accuracy. An exposure apparatus radiates an exposure illumination light to a wafer on a wafer stage through a projection optical system, and forms a prescribed pattern on the wafer, and comprises: a scale, which is provided to the wafer stage; a plurality of X heads, which detect information related to the position of the scale; a measurement frame that integrally supports the plurality of X heads and has a coefficient of linear thermal expansion that is smaller than that of the main body of the wafer stage (portions excepting a plate wherein the scale is formed); and a control apparatus that derives information related to the displacement of the wafer stage based on the detection results of the plurality of X heads.

Abstract: A first light flux serving as object light is caused to enter a member to be measured, and reflected light thereof is caused to enter again the member to be measured after being diffracted by a first diffraction grating. Then, the second-time reflected light of the first light flux by the member to be measured is diffracted by a second diffraction grating. By diffracting the first light flux by the second diffraction grating, a change of the optical path length caused by tilting of the member to be measured is cancelled.

Abstract: Micro pick up arrays and methods for transferring micro devices from a carrier substrate are disclosed. In an embodiment, a micro pick up array alignment encoder detects relative position between a micro pick up array having an encoder scale and a target substrate having a corresponding reference scale. In an embodiment, the micro pick up array alignment encoder facilitates alignment of the micro pick up array with the target substrate.

Abstract: An interferometer includes a light source, beam splitter, measuring reflector, reference retroreflector, detector system, and two transparent plane plates. The beam splitter splits a first beam of rays, emitted by the light source, into at least one measuring beam and at least one reference beam, defining a first splitting plane. The measuring beam propagates in a measuring arm and the reference beam propagates in a reference arm until being recombined at a recombining location, which is oriented parallel to the first splitting plane. The measuring reflector is disposed in the measuring arm, and the reference retroreflector is disposed in the reference arm. The first and second transparent plane plates are disposed parallel to each other in the beam path between the light source and the detector system. The reference retroreflector is formed in the first plane plate and the beam splitter is disposed on the second plane plate.

Abstract: A distance measurement apparatus includes: an imaging device which captures an image; a diffractive optical device which diffracts a subject image; an optical system which forms, on the imaging device, the image from the subject image diffracted by the diffractive optical device; and a distance measurement unit which measures a distance to a subject using the image captured by the imaging device. The distance measurement unit measures the distance to the subject based on an interval between diffraction figures of the subject image which are created by the diffractive optical device. The interval is on the image captured by the imaging device.

Abstract: A displacement detecting device includes: a diffraction grating having a relief shape; an irradiation optical system adapted to irradiate two beams onto the diffraction grating as p-polarized light; a reflection optical system adapted to reflect two first diffracted lights generated when the two beams is diffracted by the diffraction grating, and cause the first diffracted lights to be incident again on the diffraction grating as p-polarized light so as to generate two second diffracted lights; an interference optical system adapted to cause the two second diffracted lights to interfere with each other to obtain interference light; a light receiving section adapted to receive the interference light; and a position information detecting section adapted to detect position information of the diffraction grating based on an interference signal. The period of the relief of the diffraction grating is no more than 1.5 times the wavelength of coherent light.

Abstract: A flexible optical displacement encoder configuration uses a source grating to illuminate a scale with structured light such that light from the scale is modulated with a beat frequency envelope, which may have a relatively coarse pitch that matches a desired detector pitch. An imaging configuration provides spatial filtering to remove the high spatial frequencies from the modulation envelope to provide a clean signal in the detected fringe pattern. This combination of elements allows an incremental scale track pattern with a relatively finer pitch (e.g., 4, 5, 8 microns) to provide fringes with a coarser pitch (e.g., 20 microns) at a detector. Various scale resolutions can use a corresponding source grating such that all combinations can produce detector fringes that match the same economical detector component.

Abstract: A mode-locked fiber laser has a resonator including a gain-fiber, a mode-locking element, and a spectrally-selective dispersion compensating device. The resonator can be a standing-wave resonator or a traveling-wave resonator. The dispersion compensating device includes only one diffraction grating combined with a lens and a mirror to provide a spatial spectral spread. The numerical aperture of the gain-fiber selects which portion of the spectral spread can oscillate in the resonator.

Abstract: An encoder head includes one or more components arranged to: i) direct a first incident beam to the diffractive encoder scale at a first incident angle with respect to the encoder scale; ii) receive a first return beam from the encoder scale at a first return angle, the first return angle being different from the first incident angle; iii) redirect the first return beam to the encoder scale as a second incident beam at a second incident angle; and iv) receive a second return beam back from the encoder scale at a second return angle, the second return angle being different from the second incident angle, in which a difference between the first incident angle and second incident angle is less than a difference between the first incident angle and the first return angle and less than a difference between the second incident angle and the second return angle.

Abstract: An optical position-measuring device for detecting the relative position of two objects includes a measuring standard connected to one object, and a scanning unit connected to the other object and including a light source, one or more grating(s), and a detector system. The detector system includes a plurality of detector element groups arranged in a detection plane, via which a plurality of position-dependent, phase-shifted scanning signals is able to be generated by scanning a periodic fringe pattern that results in the detection plane, the detector elements that have in-phase scanning signals forming a group in each case. The sum of the areas and the centroid of the detector elements of a group is identical to the sum of the areas and the centroid, respectively, of the detector elements of each other group. Periodic diaphragm structures are arranged in front of the light-sensitive areas of the detector elements.

Abstract: An encoder head includes one or more components arranged to: i) direct a first incident beam to the diffractive encoder scale at a first incident angle with respect to the encoder scale; ii) receive a first return beam from the encoder scale at a first return angle, the first return angle being different from the first incident angle; iii) redirect the first return beam to the encoder scale as a second incident beam at a second incident angle; and iv) receive a second return beam back from the encoder scale at a second return angle, the second return angle being different from the second incident angle, in which a difference between the first incident angle and second incident angle is less than a difference between the first incident angle and the first return angle and less than a difference between the second incident angle and the second return angle.

Abstract: A detector includes an illumination optical system that illuminates a first diffraction grating having a period in each of a first direction and a second direction different from the first direction, and a second diffraction grating having a period in the second direction different from the period of the first diffraction grating in the second direction. A detection optical system detects diffracted light diffracted by the first diffraction grating and the second diffraction grating. The detection optical system includes a photoelectric conversion element and a guide portion arranged on a pupil plane of the detection optical system. The guide portion guides, to the photoelectric conversion element, the light diffracted by the first diffracting grating and the second diffraction grating. The diffracted light diffracted by the second diffraction grating enters a position different from the guide portion on the pupil plane of the detection optical system.

Abstract: A technique for measuring displacement involves passing parallel laser light from a laser light source through a first diffraction grating to a semi-transparent semi-reflective mirror. A portion of the laser light is reflected as first reversed light, which passes through the first diffraction grating. The remainder of the parallel laser light proceeds to a total reflection mirror and is reflected as second reversed light that passes through the semi-transparent semi-reflective mirror and the first diffraction grating. The amount of refracted light of a predetermined order that is of the first and second reversed light and that results from the first diffraction grating is detected by a first optical sensor, and the amount of displacement is obtained from the interference band or a signal thereof corresponding to the amount of relative motion in the axial direction of the total reflection mirror with respect to the semi-transparent semi-reflective mirror.

Abstract: An encoder interferometry system includes an interferometer positioned to receive first and second beams having different frequencies, in which the interferometer has at least one polarizing beam splitting element for directing the first beam along a measurement path to define a measurement beam and the second beam along a reference path to define a reference beam. The encoder interferometry system further includes a encoder scale positioned to diffract the measurement beam at least once, a detector positioned to receive the measurement and reference beams after the measurement beam diffracts from the encoder scale, and an output component positioned to receive the measurement and reference beams before they reach the detector and deflect spurious portions of the first and second beam away from the detector.