Abstract: An encoder with signal conditioning of an emitter drive signal is described. In one embodiment, the encoder includes a peak comparator, a pulse generator, a threshold comparator, and digital circuitry. The peak comparator outputs a peak comparator signal based on a comparison of an input sinusoidal signal stored at a first time with the input sinusoidal signal stored at a second time. The pulse generator determines a peak of the input sinusoidal signal based on the peak comparator signal. The threshold comparator compares a differential signal amplitude with a differential signal amplitude window at approximately the peak of the input sinusoidal signal. The differential signal amplitude is associated with the input sinusoidal signal. The digital circuitry generates an emitter modification signal in response to a determination that the differential signal amplitude is outside of the differential signal amplitude window.

Abstract: Embodiments of an encoder are disclosed.

Abstract: A position-measuring device includes a code and a scanning unit. The code includes a sequence of code elements arranged one after the other in a measuring direction, at least two successive code elements in each case forming one code word having position information. The scanning unit includes a lighting unit for emitting directed light in the direction of the code for imaging at least the code elements forming code word onto a detector unit, the detector unit having in measuring direction at least two detector elements per code element forming code word, as well as an evaluation unit in which the code word having the instantaneous position information is ascertainable from the detector signals of the detector elements. The scanning unit and the code are arranged in a manner allowing movement relative to each other in measuring direction.

Abstract: A method for determining the position of one of two components in relative motion with respect to each other, using optical means, comprises: directing at least one light beam emitted by a light source attached to one component towards a diffractive support attached to the second component, calculated and manufactured for generating an optical signal indicative of the positioning of said support, the optical signal being produced by the diffractive support in transmission and/or in reflection; detecting and reading at least one optical code formed by said signal, which corresponds to a unique position of the diffractive support relatively to the beam; and assigning a position to each detected optical code.

Abstract: A method for absolute position measuring that includes scanning a code having code elements arranged one behind the other in a measuring direction, wherein the code elements include sequential first and second code elements which define a code word containing absolute position information. The method including generating scanning signals within the first code elements and the second code elements. The method further including forming information regarding the sequential first and second code elements from the scanning signals via a reference value and determining the reference value as a function of at least one of the scanning signals within the first code elements and the scanning signals within the second code elements.

Abstract: A fiber optic readhead and scale arrangement for measuring displacement provides a reference position indication. The scale includes a scale track comprising a first type of track portion providing first level of zero order reflectance, such as a grating, and a reference mark providing a second level of zero order reflectance, such as a mirror. The reference mark is configured with certain length or boundary spacing dimensions determined based on certain fiber optic receiver channel aperture dimensions in the readhead. In some configurations a fiber optic readhead and track that provides the reference position indication is separate from a fiber optic readhead and track that provides periodic incremental measurement signals. In some configurations an integrated fiber optic readhead and an integrated track structure provide both the reference position indication and the periodic incremental measurement signals.

Abstract: A method for determining the position of one of two components in relative motion with respect to each other, using optical means, comprises: directing at least one light beam emitted by a light source attached to one component towards a diffractive support attached to the second component, calculated and manufactured for generating an optical signal indicative of the positioning of said support, the optical signal being produced by the diffractive support in transmission and/or in reflection, and the optical signal including information indicative of its quality; detecting and reading at least one optical code formed by said signal, which corresponds to a unique position of the diffractive support relatively to the beam; and assigning a position to each detected optical code.

Abstract: An angle-measuring instrument including a cap defining an opening and a base body that is covered by the cap. A printed circuit board positioned on the base body and on which an electrical coupling element is fixed in place. A spacer that aids in positioning the cap in such a way relative to the printed circuit board so that the opening is aligned with respect to the electrical coupling element.

Abstract: An absolute linear encoder includes a plurality of absolute scales aligned in the detection direction with absolute calibrations, a plurality of detectors for detecting the calibrations on the absolute scales, absolute position data generating portions of each scale for generating absolute position data of each detector, and a calculator for outputting an absolute position over the whole length of connected whole absolute scales adding the absolute position data of each detector and the distance between the detectors. The detectors are fixed at such intervals as to simultaneously detect the calibrations of the two absolute scales adjoining in a scale connecting section. Thus, the long absolute linear encoder which is easy to use is realized at low costs.

Abstract: A method for writing or calibrating the scale of a scale-based position encoder. The scale is installed where it will be used to provide ongoing position measurements for a host system. The image correlation sensor is temporarily mounted proximate to the mounting position of the scale-based position encoder readhead on the host system, and is moved along the measuring axis relative to the scale, to provide corresponding displacement measurement information. The displacement measurement information is used to govern a scale writing process or a calibration process for the scale-based position encoder, such that the displacement measurement information at least partially governs the values of respective ongoing position measurements provided by the scale-based position encoder at respective positions along the measuring axis. A two-axis image correlation displacement sensor is advantageously used to detect and/or corrected various potential errors during the calibration or writing process.

Abstract: An optical encoder device for a small-sized motor has a code wheel attached to a motor shaft which extends to the exterior of the motor through a bearing accommodated in a bearing-retaining section provided on an end bell of the motor, and a board on which a photosensor module is mounted such that an optical modulation track portion of the code wheel is positioned and disposed in a gap of the photosensor module. While a spacer is sandwiched between the end bell and the board, the motor, the spacer, and the board are fixed together by soldering a pair of motor terminals to a printed wiring portion of the board. The spacer has a generally U-shaped structure so as to allow fitting in position thereof from a direction orthogonal to the motor shaft.

Abstract: A system for reproducibly measuring motion along surfaces of arbitrary or indeterminate length and of arbitrary curvature, using an opto-electronic sensor mounted to an object in motion along the surfaces. The system involves the detection of alternating reflective and non-reflective markings, on surfaces which can be curved in a certain dimension and can be of any length. Additionally, the system can be applied to measure the motion of camera carts or dollies along straight track, curved track, or any combination of straight and curved track.

Abstract: An optical encoder that includes an optical grating and a quadrature optical encoder sensor that move relative to each other. The optical grating includes a first encoder bar and a plurality of second encoder bars, wherein the first encoder bar is optically configured to change an amplitude of an output of the quadrature optical encoder sensor.

Abstract: In two phases signals (A, B) outputted from a scale or a scale having a discontinuous portion provided in its incidental member to a light receiving portion, a region in which amplitudes of the two phases signals (A, B) are small corresponds to outputs when a reflecting portion lies in the scale in terms of rotation position, and a region in which amplitudes of the two phases signals (A, B) are large corresponds to outputs when a nonreflecting portion lies in the scale in terms of rotation position. An optical encoder for discriminating positions of a reflecting portion and a nonreflecting portion of a scale using a threshold value (L) to detect an absolute position based on a reason that when the signals (A, B) are arithmetically operated by an arithmetic operation processing circuit to obtain a sum of squares of the signals (A, B), change points in the amplitudes of the signals (A, B) are steeply obtained.

Abstract: Optical encoders having one or more of a number of disclosed features are disclosed. The features of the optical encoder in accordance with the present invention include a symmetrical (for example, circular) emitter; baffle between the emitter and a detector; double-dome or single-dome encapsulant; multiple detector; and multiple (at least three) data channels.

Abstract: At least one exemplary embodiment is directed to an optical encoder which includes a first diffraction grating having a desired optical effective aperture ratio at an appropriate gap position so as to eliminate and/or reduce high-harmonic components from the light intensity distribution of interference fringes and reduce high-order spatial frequency components overlapped on a displacement signal of the interference fringes formed by the first diffraction grating.

Abstract: A position-measuring device for generating a reference-pulse signal at at least one reference position includes a scanning unit and also a reflection-measuring graduation displaceable relative thereto in at least one measuring direction. The scanning unit for generating the reference-pulse signal includes a plurality of optical elements, including at least one imaging optics as well as at least two diaphragm structures, which are disposed in a diaphragm plane and have a plurality of diaphragm openings in each case. Furthermore, a light source as well as at least two detector elements are assigned to the scanning unit. The reflection-measuring graduation has a reference marking at the at least one reference position. It includes at least one set of first structure elements, which is arranged in the plane of the reflection-measuring graduation, perpendicular to the measuring direction, periodically at a first transversal periodicity.

Abstract: There is provided a position detecting apparatus that has a high ability of detecting a correct position even if there is mechanical play in a moving mechanical member, a position of which is detected, and an image processing apparatus provided with the position detecting apparatus. In a position detecting apparatus 100 of the invention, even if there is a certain degree of play in a slide plate 11 that moves in a slide direction DN and reading by bit mark reading sensors 21 to 24 deviates from regular reading of binary numbers, since binary numbers appended to a surface of the slide plate is formed by gray codes, a position derived by a position deriving unit is more likely to be controlled to be as small as adjacent binary numbers with respect to a slide direction of the slide plate compared with the case of the conventional simple binary numbers.

Abstract: A photoelectric encoder includes a light source of an illumination light beam. The encoder also includes a movable grating which has grating lines and which is displaceable in a direction intersecting the grating lines. An index grating serves as a reference for displacement of the movable grating. A light-receiver receives the illumination light beam via the movable grating and the index grating. A modulator periodically changes a light beam outgoing from the index grating. A displacement detector detects the displacement of the movable grating based on the illumination light beam received by the light-receiver. Accordingly, a signal representing the displacement of a movable body can be accurately generated even when fluctuation of the attitude of the grating occurs.

Abstract: A photoelectric encoder that has a lens optical system including a lens inserted between a main scale and a light receiving element. In the photoelectric encoder, three planes extended from a surface of the main scale, a principal plane of the lens, and an image plane of the light receiving element are disposed so as to intersect at a single point and satisfy the Scheimpflug rule. Focus can thereby be obtained over the entire image plane, so that a reduction in contrast is prevented, even if the optical axis is inclined to make an optical system smaller.

Abstract: A reflection encoder is disclosed having a light emitting element in a light receiving element that are separated by a light shielding body that prevents unwanted light from entering the light receiving element. In variations of the invention, the light shielding body may be integrally formed with a mold resin portion that holds the light emitting element and light receiving element, formed by a sheet or plate, or formed using an opaque liquid resin that is poured between transparent resin bodies that encapsulate the light emitter and receiver. In operation, light radiated from the light emitting element is reflected by a code wheel and then received by a light receiving element. Other variations include varying the height at which the light receiving and detecting elements are disposed relative to the code wheel and tilting these elements towards each other so as to increase light efficiency.

Abstract: A system and method of measuring a rotational motion of a code wheel measures a rotational movement of the code wheel including an error component due to a non-rotational movement of the code wheel; measures the non-rotational movement of the code wheel; and produces an error-corrected measurement of the rotational movement of the code wheel by using the measured non-rotational movement of the code wheel to cancel the error component of the measured rotational movement of the code wheel. A signal can be produced indicating a need for maintenance when the non-rotational movement of the code wheel exceeds a threshold.

Abstract: A photodetector for an optical encoder has plural sets of segmented photodiodes, each set of which is made by two adjoining segmented photodiodes capable of coping with a scale slit having a reference resolution. Output lines of the two adjoining segmented photodiodes are connected together in each set of the photodiodes. These output lines are connected to output lines of the corresponding segmented photodiodes in the other sets. The two adjoining segmented photodiodes function like one segmented photodiode, and thereby, the resolution of the applied scale slit is made ½ of the reference resolution. Thus, this photodetector easily copes with a scale slit having a half resolution of the reference resolution at low cost only by modification of wiring without changing any configuration of the segmented photodiodes.

Abstract: An optical displacement-measuring instrument of a reflection type includes a sensor head movable above a scale in a direction of measurement. This instrument is of a three-grating type that comprises a first optical grating arranged close to a light source, a second optical grating arranged on the scale, and a third optical grating arranged in a photoreceptor. A light diffuser is arranged between the light source and the first optical grating. A collimated light from the light source is diffused at the light diffuser and led to the first optical grating.

Abstract: The invention relates to an apparatus, notably an X-ray apparatus, which comprises two components which are displaceable relative to one another. A position visualization unit is arranged on one component of the apparatus and the other component of the apparatus is provided with an image acquisition unit whose acquisition zone contains a segment of the position visualization unit which changes due to the motion. The image acquisition unit acquires images of the segment present in the acquisition zone and applies such images to an evaluation unit which extracts position information from the images.

Abstract: A signal adjusting apparatus includes a movable member, a setting device, and a prohibiting device. The movable member is movable in a movable range to have the electrical signal adjusted in accordance with a position of the movable member. The setting device sets a prohibition range in the movable range. The prohibition range is a range where a volume level of the electrical signal is to be constant. The prohibiting device prohibits the volume level from being adjusted under the state that the movable member is located in the prohibition range.

Abstract: First and second signal detecting element groups are respectively arranged to face first and second signal detecting tracks that are provided on a first code wheel. In addition, third and fourth signal detecting element groups are respectively arranged to face third and fourth signal detecting tracks that are provided on a second code wheel. A code string is output from the first and second signal detecting element groups to obtain a circular gray-code for detecting the rotation of the first code wheel within one revolution. Further, a code string is output from the third and fourth signal detecting element groups to obtain a circular gray-code for detecting the rotation of the first code wheel over one revolution.

Abstract: A signal adjusting apparatus comprises a movable member, a first detecting device, a second detecting device, and a correction device. The member is movable in a movable range composed of a plurality of intervals. The first detecting device detects one of the intervals where the member is located. The first detecting device is constituted by a first movable portion mounted on the member and a first fixed portion spaced apart from the first movable portion. The one of the intervals is an absolute position. The second detecting device detects a relative position of the member within the detected interval. The second detecting device is constituted by a second movable portion mounted on the member and a second fixed portion spaced apart from the second movable portion. The correction device corrects the detected relative position based on a relationship between the absolute position and the relative position stored in a memory.

Abstract: An angular offset sensing device includes an optical encoder having a light generating element and a light sensor. An armature includes a reflective surface having a generally semicircular shape and a surface height continuously increasing from a first end of the surface to a second end of the surface. A housing encloses both the optical encoder and the armature and rotationally supports the armature. An electrical voltage is generated when light from the light generating element is reflected back to the sensor from the reflective surface. The voltage is proportional to a wavelength of the reflected light and is indicative of an angular rotation of the armature relative to the optical encoder. The voltage is corrected for linearity and used for example to signal a vehicle transfer case shift.

Abstract: A method for position measurement that includes scanning a plurality of graduation periods of one incremental graduation by a detector arrangement extending over a length of one measurement range, a reference marking being integrated with one of the graduation periods, and generating a plurality of periodic scanning signals, of which at least one is locally modified by the reference marking. The method includes detecting the at least one scanning signal, modified by the reference marking, from among the plurality of periodic scanning signals. The method further includes determining an absolute position of the reference marking within the length of said measurement range as a function of the scanning signal detected.

Abstract: An angle absolute encoder comprises an encoded code rod that has code marks, such as pairs of fine code lines and coarse code lines. Light is reflected from or transmitted through the code marks and detected by a light detector to determine absolute angle position.

Abstract: A main scale of an optical displacement measuring apparatus has slits arranged on it at regular intervals, a part of which is a missing slit that does not allow light to pass through used for detecting the original point. An index scale has four sets of windows formed on it. The four windows are arranged with mutual phase differences of ¼ P, where P is the pitch of the arrangement of the slits. When a part of the missing slit overlaps with the index scale, no light reaches to photodiodes from the missing slit and only a partial light flux passes through a window, so that the light quantity decreases. An original point signal associated with the missing slit can be obtained by adding up the outputs of all the photodiodes.

Abstract: An optical position measuring system including a scale and a scanning unit. The scanning unit includes a light source that emits light beams and a periodic scanning graduation having scanning graduation marks arranged periodically at a scanning graduation period along a measuring direction. The scanning unit further including a detector arrangement. The scanning graduation or the scale graduation includes at least three partial tracks, which adjoin perpendicularly with respect to the measuring direction, and graduation marks associated with each of the at least three partial tracks have a defined and constant offset spacing from their nominal positions, wherein the offset spacings associated with adjoining ones of the at least three partial tracks differ, so that filtering of undesired harmonic waves out of the at least one periodic scanning signal results from said offset spacings.

Abstract: Reflective image encoder. A reflective image encoder has an emitter such as one or more light emitting diodes, a diffuse reflective coder such as a code wheel or code strip reflecting a portion of the light from the emitter, an imaging lens forming an inverted image on to a detector. The reflective image encoder may include apertures on either or both sides of the imaging lens, and may include baffles to minimize stray light reaching the detector.

Abstract: A photoelectric encoder includes an optical receipt chip on which a plurality of photodiodes (PDs) are laid out along a measurement axis “X” so that these are organized into an array. The layout pitch of PDs disposed at end portions of the array is made less than the pitch of those at a central portion of the array. Similarly the width of a light acceptance surface of the former is less than that of the latter.

Abstract: A position measuring device having a scanning device and a scale, wherein the scanning device is movable in relation to the scale in a measuring direction. The scale including a measuring graduation, wherein periodic measuring signals are generated when the scanning device scans the measuring graduation and a reference marking, wherein a reference marking signal is generated when the scanning device scans the reference marking with a scanning beam bundle. The scale further includes a first optically scannable area marking next to the reference marking and a second optically scannable area marking next to the reference marking and which has a different optical deflection property than the first optically scannable area marking, wherein photoelectric scanning of the first and second optically scannable area markings with the scanning beam bundle from the scanning device generates an area signal that differentiates characteristics of the first and second optically scannable area markings.

Abstract: An apparatus and a method of the present invention positions an optical component among several optical components, which are arranged in a receiving device. The receiving device is rotatable about an axis or movable along a direction in such a way that an optical component is positionable and the receiving device is retainable in a retention position. A coding device having first and second coders and two detectors are also provided. Either the coding device or the two detectors are associated with the receiving device and the two detectors detect the first and second coders at spatially different points. The coding device is embodied in such a way that the two detectors detect the first coder simultaneously when the receiving device is in a retention position and no more than one detector detects the second coder when the receiving device is in a region between two adjacent retention positions.

Abstract: An optical rotary encoder for acquiring rotation information regarding a shaft includes a light source located on or in the vicinity of the axis of rotation of the shaft for emitting light rays and a code wheel mounted on the shaft for rotation about the axis of rotation. The code wheel has a plurality of alternating light transmissive and non-light transmissive areas in a circumferential direction. A reflector is spaced a distance from the code wheel for reflecting the light rays emitted from the light source so that they are turned into a parallel beam of light. The parallel beam of light illuminates the light transmissive areas of the code wheel so that light passing through the light transmissive areas is directed toward a peripheral region of the light source. The encoder also includes one or more light-detecting element for detecting the light passing through the light transmissive areas.

Abstract: A position encoder uses a track encoded with a pattern of bit-widths in accordance with a sequence. The sequence may be any sequence having unique subsequences, and may be a pseudo-random noise (PRN) sequence such that each N-bit subsequence occurs only once on the track. Sensors detect transitions between the bits and bit-widths as the track moves with respect to the sensors to provide in-phase and quadrature-phase pick-off signals. The pickoff signals are summed and absolute value thresholded. The absolute value thresholded sum signal is sampled when the quadrature pairs are in the “00” or “11” quadrants, and latched when the sum signal goes high to distinguish between wide and narrow bit widths. The latch is shifted into a shift data register for use in determining the position of the encoder track. In the case of a PRN sequence having a length of 2N bits, the position may be an absolute position when the number of valid bits in the shift data register is at least N.

Abstract: A position detecting device in which a count value is incremented or decremented on the basis of a pulse output from an encoder every predetermined shift amount of a control target to thereby detect a current value representing a current position of the control target as the count value, is characterized by comprising: initialization signal output means for outputting an initialization signal representing an initialization position at plural positions of a movable range of the control target when the movable range of the control target is restricted, or at plural positions of an operating range of integer times of a period when the movable range of the control target is not restricted and the same state is repeated at the period concerned; current value storing means for storing, in association with identification information for identifying each initialization signal, the current value of the control target at each position where the initialization signal is output by each initialization signal output means;

Abstract: An optical encoder that includes an optical grating and a quadrature optical encoder sensor that move relative to each other. The optical grating includes a first encoder bar and a plurality of second encoder bars, wherein the first encoder bar is optically configured to change an amplitude of an output of the quadrature optical encoder sensor.

Abstract: An absolute 2D position-sensing device is usable to measure the position of a first element with respect to a second element. A 2D absolute scale includes an integrated 2D absolute scale pattern extending over the 2D scale area along each measuring axis of the scale. The integrated 2D absolute scale pattern includes a predetermined quasi-random pattern repeatedly interleaved with a plurality of code portions along each axis. Each code portion includes a plurality of code elements indicative of an absolute measurement value. The offset of the quasi-random pattern relative to a readhead of the device is combined with the absolute measurement value to determine an absolute position to a very high resolution over a relatively large 2D range.

Abstract: A device for position indication and the detection of guidance errors that includes a scale that has a position measuring graduation arranged in a position measurement direction. A first guidance error measuring graduation which is arranged perpendicularly with respect to the position measurement graduation and a second guidance error measuring graduation which is arranged perpendicularly with respect to the position measurement graduation, wherein the first guidance error measuring graduation and the second guidance error measuring graduation are arranged on both sides of and adjacent to the position measuring graduation. A position indication scanning unit movable with respect to the scale, wherein the position indication scanning unit scans the position measuring graduation for generating position measurement signals.

Abstract: Phase noise is at least partially cancelled for an interferometric system by using a delay/phase cross-correlation approach for two interferometers within the system. The cross-correlation approach may be used in measuring group delay of a device under test and includes determining the differences between the phase of the output of each interferometer at time t and the phase of the same output at the time t minus the delay of the other interferometer. In one embodiment, the first phase difference is the difference between the phase of a test interferometer output at time t and the phase of the test interferometer output at the time t offset by the known delay of a reference interferometer. The second phase difference is calculated using the same technique, but the time offset is a delay representative of the relative delay of two light propagations within the test interferometer.

Abstract: An absolute position-sensing device is usable to measure the relative position of two elements. An absolute scale includes an integrated track extending along a measuring axis of the scale. The integrated track includes a plurality of code portions interleaved with, or embedded in, a plurality of periodic portions. Each periodic portion includes a plurality of periodically-placed incremental scale elements. Each code portion includes a plurality of code elements indicative of an absolute measurement value. The code elements are arranged in code element zones along the direction perpendicular to the motion axis, and are detectable by associated variations along the direction perpendicular to the motion axis. The offset of the periodically placed elements relative to a readhead of the device is combined with the absolute measurement value to determine an absolute position.

Abstract: An absolute angular position sensor assembly for use with a vehicle steering column that generally includes a digitally encoded disk, an optical output device and an optical input device. The encoded disk has numerous circumferentially extending, concentric data tracks; some of these tracks include cutouts representing absolute angular position bits and some include cutouts representing error correcting bits. Preferably, the absolute angular position bits are arranged according to a grey-code type arrangement, while the error correction bits include Reed-Solomon error detecting and correcting information. The optical output device shines light against the encoded disk such that a pattern, generally determined by the cutouts, is formed on the optical input device. The optical input device, in turn, utilizes that pattern to generate an angular position signal representative of the absolute angular position of the steering wheel and having error correction information.

Abstract: This invention presents a two-dimensional absolute optical encoder and a method for determining position of an object in accordance with information from the encoder. The encoder of the present invention comprises a scale having a pattern being predetermined to indicate an absolute location on the scale, means for illuminating the scale, means for forming an image of the pattern; and detector means for outputting signals derived from the portion of the image of the pattern which lies within a field of view of the detector means, the field of view defining an image reference coordinate system, and analyzing means, receiving the signals from the detector means, for determining the absolute location of the object. There are two types of scale patterns presented in this invention: grid type and starfield type.

Abstract: In a projection encoder based on a triple-grating concept, a light-transmitting grating group 3 for detecting A- and B-phase signals, a photodiode group 4 for detecting A- and B-phase signals, and a photodiode group 5 for detecting a home position are formed on a movable grating plate 6 of a projection linear encoder 1; and a reflecting grating group 7 for detecting A- and B-phase signals, and a reflecting grating group 8 for detecting the home position are formed on a reflecting grating plate 9.

Abstract: A control part 7 detects pulse widths of four continuous pulses, and a pulse width w1 of a pulse detected first is compared in size with a pulse width w2 of a pulse detected second and when w2 is larger, normality is determined. The pulse width w2 of the pulse detected second is compared in size with a pulse width w3 of a pulse detected third and when w3 is larger, normality is determined. The pulse width w3 of the pulse detected third is compared in size with the pulse width w1 of the pulse detected first and when w1 is larger, normality is determined. In the above first to fourth determinations, when the number of cases determined as normality is two times or more, normal rotation is determined, and otherwise, reverse rotation is determined.

Abstract: An absolute position-sensing device is usable to measure the relative position of two elements. An absolute scale includes an integrated track extending along a measuring axis of the scale. The integrated track includes a plurality of periodic portions interleaved with a plurality of non-periodic portions. Each periodic portion includes a plurality of periodically-placed scale elements. Each non-periodic portion includes a plurality of code elements indicative of an absolute measurement value. The code elements may have a length that is narrower along the measuring axis than the length of the periodic scale elements. The offset of the periodic-placed elements relative to a readhead of the device is combined with the absolute measurement value to determine an absolute position.