Abstract: A distance measure between a beginning and an end of a material strip wound onto a body in a tangential direction can be determined by creating a height profile of a surface of the material strip, which covers the beginning and the end of the wound material strip in the tangential direction. If a position value of the beginning of the material strip is determined in the created height profile, the distance measure can be determined using this position value and the height profile covering the end of the material strip.

Abstract: A method and apparatus for dimensioning and, optionally, weighing an object. A platform with a surface is used for supporting an object. A user selects between two different dimensioning devices of the apparatus. The first device employs three distance sensors to determine a distance between each of the distance sensors and a side of an object. The second device includes a movable gate which is passed over and about an object or objects on the platform. Sensor arrays, such as paired, aligned light emitter and receiver arrays, are used in combination with a plurality of sensed gate positions to determine the dimensions of the objects(s) as the gate passes around the object(s) based on whether or not light from an emitter on one side of the gate reaches a light receiver on another, opposing side of the gate.

Abstract: A laser-based measuring apparatus for measuring a position of a distant target is disclosed. Some embodiments may include a laser tracker for detecting the position and the orientation of a measuring aid. The laser-based measuring apparatus may include a base, a support, a telescope unit, a first bearing apparatus, and a second bearing apparatus. In some embodiments the first bearing apparatus is in the form of a fixed/loose bearing apparatus, having a shaft, the longitudinal axis of which runs coaxially with the tilt axis, a fixed bearing and a loose bearing, and/or the second bearing apparatus is in the form of a fixed/loose bearing apparatus, having a shaft, the longitudinal axis of which runs coaxially with the vertical axis, a fixed bearing and a loose bearing.

Abstract: An apparatus which provides a multiplicity of test colors and neutral tones simultaneously within a microscope's optical system that may be used to align, and/or calibrate the microscope, and the light source and any associated recording devices, automatically or with input from an operator. The test colors and neutral tones may also be used as references against which to judge specimens being viewed in the microscope. Also disclosed is a method of operating a microscope using such a such pattern.

Abstract: Coordinate measurement device configured to send a first beam of light to a target includes first and second light sources configured to emit first and second lights having differing first and second wavelengths; fiber-optic coupler that includes three ports, a first port configured to accept a first portion of the first light, a second port configured to accept a second portion of the second light, a third port configured to transmit a third light which includes a portion of the first and second portions; first and second angle measuring devices configured to measure first and second angles of rotation; distance meter configured to measure a first distance from the device to the target based at least in part on a third portion of the second beam received by an optical detector; and a processor configured to provide 3D coordinates of the target.

Abstract: A scatterometry tool including an illumination source for directing a light beam into a first optical beam shaping and positioning element at an illumination pupil plane of the tool where the light beam is modulated and directed to an objective lens system having a high numerical aperture. The objective receiving the modulated light beam and directing it onto a target to generate a scattering signal. The objective lens collects the scattering signal and directs it to a second optical beam shaping and positioning element at a collection pupil plane where the signal is modulated and then directed to detectors for receiving and processing the signal to determine surface characteristics of the target.

Abstract: A method for measuring three-dimensional coordinates of a probe center includes: providing a spherically mounted retroreflector; providing a probe assembly; providing an orientation sensor; providing a coordinate measurement device; placing the spherically mounted retroreflector on the probe head; directing the first beam of light from the coordinate measurement device to the spherically mounted retroreflector; measuring the first distance; measuring the first angle of rotation; measuring the second angle of rotation; measuring the three orientational degrees of freedom based at least in part on information provided by the orientation sensor; calculating the three-dimensional coordinates of the probe center based at least in part on the first distance, the first angle of rotation, the second angle of rotation, and the three orientational degrees of freedom; and storing the three-dimensional coordinates of the probe center.

Abstract: The present invention relates to a distance measurement apparatus. The distance measurement apparatus according to the present invention has, mounted thereon, a light transmitting portion which emits light, and a light receiving portion including a light receiving element where a spot of the light is collimated. The present invention comprises: a tilting base; and a rotating reflector which reflects the light emitted by the light transmitting portion to an object, and reflects the light reflected or scattered by the object to the light receiving portion.

Abstract: The invention relates to a method for determining a set of optical imaging functions that describe the imaging of a measuring volume onto each of a plurality of detector surfaces on which the measuring volume can be imaged at in each case a different observation angle by means of detection optics. In addition to the assignment of in each case one image position (x, y) to each volume position (X, Y, Z), the method according to the invention envisages that the shape of the image of a punctiform particle in the measuring volume be described by shape parameter values (a, b, 100 , I) and that the corresponding set of shape parameter values be assigned to each volume position (X, Y. Z) for each detector surface.

Abstract: Dismountable numerical control machine which comprises a first longitudinal bedplate (1), a base (2), a column (3) attached to the base (2), a secondary carriage or crosspiece (4) and an arm (5), in which the principal carriage or base (2) moves horizontally along the longitudinal bedplate (1), while the secondary carriage or crosspiece (4) can move vertically in relation to the column (3); and in which, also, the arm (5) can be moved horizontally in relation to the crosspiece (4), and which also comprises a transport tool (6) configured as an auxiliary longitudinal bedplate placed adjacent to the principal bedplate (1).

Abstract: In the method for geo-referencing of optical remote sensing images of an area of the earth's surface, the geo-referencing is corrected based on an SAR image which is geo-referenced.

Abstract: A method and system are provided for controlling a laser tracker remotely from the laser tracker through gestures performed by a user. The method includes providing a rule of correspondence between each of a plurality of commands and each of a plurality of user gestures. A gesture is performed by the user with the user's body that corresponds to one of the plurality of user gestures. The gesture performed by the user is detected. The gesture recognition engine determines a first command from one of the plurality of commands that correspond with the detected gesture. Then the first command is executed with the laser tracker.

Abstract: A method and apparatus for defining, from a first periodic signal, a second signal of same period, including the steps of: generating a third signal exhibiting detectable events; and synchronizing the second signal for each event.

Abstract: Methods and systems for enhancing metrology sensitivity to particular parameters of interest are presented. Field enhancement elements (FEEs) are constructed as part of a specimen to enhance the measurement sensitivity of structures of interest present on the specimen. The design of the FEEs takes into account measurement goals and manufacturing design rules to make target fabrication compatible with the overall device fabrication process. Measurement of opaque materials, high-aspect ratio structures, structures with low-sensitivity, or mutually correlated parameters is enhanced by the addition of FEEs. Exemplary measurements include critical dimension, film thickness, film composition, and optical scatterometry overlay. In some examples, a target element includes different FEEs to improve the measurement of different structures of interest. In other examples, different target elements include different FEEs.

Abstract: Various metrology systems and methods are provided. One metrology system includes a light source configured to produce a diffraction-limited light beam, an apodizer configured to shape the light beam in the entrance pupil of illumination optics, and optical elements configured to direct the diffraction-limited light beam from the apodizer to an illumination spot on a grating target on a wafer and to collect scattered light from the grating target. The metrology system further includes a field stop and a detector configured to detect the scattered light that passes through the field stop. In addition, the metrology system includes a computer system configured to determine a characteristic of the grating target using output of the detector.

Abstract: A first metrology method includes the steps of projecting a first image and a second image, aligning the first image and the second image to form an aligned image of a known size, and determining a dimension of a target object by comparing the aligned image to the target object. A second metrology method includes the steps of projecting a first image and a second image, aligning the first image and the second image to form an aligned image of a known size by synchronously adjusting a zoom factor for projecting the first image and an angle for projecting the second image, and determining a dimension of a target object by comparing the aligned image to the target object.

Abstract: The invention relates to a method and a device (20) for three-dimensional measurement of an object (6) using a confocal microscopy method comprising a laser source (21) for generating an illumination beam (3), a focusing optics (4) for focusing the illumination beam (3) on at least one measuring point (5, 23) on a surface of the object (6) to be measured, a detector (10) for detecting an observation beam (9) reflected by the surface of the object (6), a confocal observation optics (7), which allows only the observation beam (9) that is focused on the surface of the object (6) to pass through to the detector (10). The laser source (21) comprises multiple coherent laser elements (22), the laser elements (22) simultaneously emitting illumination beams (3) that are focused on multiple measuring points (5, 23) on the surface of the object (6), so that the laser elements (22) are arranged to reduce the speckle effect in the 3D-image data generated by the measurement.

Abstract: A method of categorizing the reliability of measurement data in a chromatic range sensor (e.g., an optical pen) which uses chromatically dispersed light to measure the distance to a surface. In one embodiment, the system performs a number of predetermined reliability checks which determine the reliability categories for the sets of measurement data. The reliability categories may be stored as metadata with the respective workpiece height measurements that are determined from the associated measurement data. The reliability categories may be reported to the user (e.g., as graphical reliability category indicators that accompany a graphical display of the measurement data). With these reliability categories, the user may make informed decisions regarding the measurement data (e.g., deciding to filter out data that is associated with certain reliability categories, making adjustments to the setup to achieve improved measurements, etc.).

Abstract: Various metrology systems and methods for high aspect ratio and large lateral dimension structures are provided. One method includes directing light to one or more structures formed on a wafer. The light includes ultraviolet light, visible light, and infrared light. The one or more structures include at least one high aspect ratio structure or at least one large lateral dimension structure. The method also includes generating output responsive to light from the one or more structures due to the light directed to the one or more structures. In addition, the method includes determining one or more characteristics of the one or more structures using the output.

Abstract: The invention is directed to a method and an apparatus for air-borne or space-borne radiometric measurement of object points present in an object scene on the surface of an astronomical body which are assigned to rows and columns of an object matrix during a scanning progressing systematically in a first scanning direction and a second scanning direction, wherein the object matrix points are imaged on a detector in an image plane generated by optics, and the image inside the image plane is recorded by at least one radiation-sensitive detector element of the detector.

Abstract: A system for sizing and fitting an individual for apparel, accessories, or prosthetics includes at least one energy emitter configured to emit energy onto a field-of-view that contains an individual, and at least one energy sensor configured to capture reflected energy from within the field-of-view. A spatial measurement module calculates spatial measurements of a surface portion of the body of the individual when the individual is either stationary or moving about in real-time, based on data from the energy sensor.

Abstract: A target space ratio of a monitor pattern on a substrate for inspection is determined to be different from a ratio of 1:1. A range of space ratios in a library is determined to include the target space ratio and not include a space ratio of 1:1. The monitor pattern is formed on a film to be processed by performing predetermined processes on the substrate for inspection. Sizes of the monitor pattern are measured. The sizes of the monitor pattern are converted into sizes of a pattern of the film to be processed having a space ratio of 1:1, and processing conditions of the predetermined processes are compensated for based on the sizes of the converted pattern of the film to be processed. After that, the predetermined processes are performed on a wafer under the compensated conditions to form a pattern having a space ratio of 1:1 on the film to be processed.

Abstract: A new and useful method is provided for Goos-Hanchen compensation in an optical autofocus (AF) system that uses light reflected from a substrate to determine changes in the z position of a substrate. According to the method of the invention reflected light from the substrate is provided at a plurality of wavelengths and polarizations, detected and used to make corrections that compensate for the errors due to the Goos-Hanchen effect.

Abstract: A gap and height difference measurement module may include a mounting frame with a flange mounted on a first end thereof and a connecting frame mounted on a second end of the mounting frame, first and second housings mounted on both sides of the connecting frame respectively, a first light source mounted on a lower end of the first housing and emitting light onto the panels, a second light source mounted on a lower end of the second housing and emitting light onto the panels, first and second sensors respectively mounted on front ends of the first and second housings, and first and second filters that are respectively mounted to the first and second sensors so as to allow the first and second sensors to each extract straight-line elements from cross sections formed as the lights emitted from the first and second light are irradiated onto the panels.

Abstract: A handheld measuring device for optical distance measurement includes a transmitting device, a receiving device, an evaluation device, and a homogenizing device. The transmitting device is configured to transmit periodically modulated optical measurement radiation toward a target object. The receiving device is configured to detect optical measurement radiation returning from the target object. The evaluation device is configured to receive and evaluate detection signals of the receiving device. The evaluation device comprises a plurality of accumulation devices configured to accumulate detection signals. The evaluation device conducts detection signals during a sampling time window from a plurality of sampling time windows temporally schematically changeably to an assigned accumulation device from the plurality of accumulation devices, such that the accumulation device accumulates the detection signals during the sampling time window.

Abstract: A method is provided for measurement of the thickness of any deposit of material on the inner wall of a pipeline at least partly filled with a medium including hydrocarbons, the medium being for instance oil or natural gas, wherein the method includes: projecting infrared light onto the inner wall of the pipeline along a line corresponding to the intersection between the inner wall of the pipeline and a cross-sectional plane of the pipeline; registering an image of the infrared light projected on the inner wall of the pipeline; and determining the thickness of any deposit of material on the inner wall of the pipeline based on the registered image.

Abstract: A laser distance measuring device comprising a transmitter channel (1), a receiver channel (2) and a dimensionally stable multilayer base printed circuit board (3), with the transmitter channel (1) and the receiver channel (2) being mounted and symmetrically disposed one on each side of the base printed circuit board (3), with the base printed circuit board (3) serving as a mechanical foundation, as an optical and electrical shield, as a carrier of electrical and optical connections and, optionally, as a heat conductor.

Abstract: A method for decomposing design shapes in a design level into a plurality of target design levels is provided. Design shapes including first-type edges and second-type edges having different directions is provided for a design level. Inner vertices are identified and paired up. Vertices are classified into first-type vertices and second-type vertices. First mask level shapes are generated so as to touch the first-type vertices, and second mask level shapes are generated so as to tough the second-type vertices. Cut mask level shapes are generated to touch each first-type edges that are not over a second-type edge and to touch each second-type edges that are not over a first-type edge. Suitable edges are sized outward to ensure overlap among the various shapes. The design shapes are thus decomposed into first mask level shapes, the second mask level shapes, and the cut mask level shapes.

Abstract: An apparatus and methods for scanning and measuring transparent fibers. One example method includes placing the transparent fibers on a platen of a flat-bed style scanner and compressing the transparent fibers to the platen with a cover including a non-reflective surface adjacent to the transparent fibers. The method also includes spacing an image sensor apart from a light source on a carriage below the platen and transmitting light from the light source through the platen. The light refracts within the transparent fibers and reflects from the transparent fibers to the image sensor and is absorbed by the non-reflective surface of the cover. The method also includes capturing an image of the transparent fibers with the image sensor.

Abstract: A LIDAR device may transmit light pulses originating from one or more light sources and may receive reflected light pulses that are then detected by one or more detectors. The LIDAR device may include a lens that both (i) collimates the light from the one or more light sources to provide collimated light for transmission into an environment of the LIDAR device and (ii) focuses the reflected light onto the one or more detectors. The lens may define a curved focal surface in a transmit path of the light from the one or more light sources and a curved focal surface in a receive path of the one or more detectors. The one or more light sources may be arranged along the curved focal surface in the transmit path. The one or more detectors may be arranged along the curved focal surface in the receive path.

Abstract: The invention provides a structure for critical dimension and overlay measurement including a measuring unit, a first measurement pattern for measuring overlay and a second measurement pattern for measuring linewidth, line density and/or line semi-density. The first target pattern includes an outer bar structure disposed on a first layer and an inner bar structure disposed on a second layer; the outer bar structure and/or the inner bar structure has a same shared pattern structure with the second target pattern. The pattern structure includes four bars with the same shape positioned orthogonally and closely to each other, and at least two orthogonally positioned bars include N equally spaced rectangular lines of the same width, wherein, N is an odd number; the N rectangular lines include one central rectangular line and N?1 auxiliary rectangular lines.

Abstract: Systems, methods, and apparatuses for gathering data are disclosed. For example, a plant matter sensor includes a pair of parallel spaced apart sensor arms and a control console, a first of the arms having a plurality of emitter spaced along its length, each emitter configured to emit a signal substantially perpendicularly to the arm to be received by a corresponding receiver on the second arm. The console contains controller means to control the rate, strength and regularity of the signal emitted by each of the emitters, collectors to collect data from each receiver as to the existence or absence of receipt of a signal, a processor to process data received from the controllers and the collectors and determine the height of any plant matter traversed by the plant matter sensor and predetermined intervals, and storage to store the plant matter height data generated by the processor for subsequent download or analysis.

Abstract: A low coherence enhanced backscattering tomography (LEBT) method is disclosed for depth-selective sensing of the superficial layer of tissue. 3D images of the microarchitecture and molecular conformation of the superficial layer of tissue are obtained. The method combines the high resolution advantage of low coherence light and the high sensitivity advantage of light scattering to tissue structure and composition. Intact tissue can be examined without the need of excision or processing. The method can be applied in in situ measurements. According to the method, 3D images of the nuclear morphology and cellular structure for the superficial layer of the tissue are generated; this is particularly useful in detecting cancer and precancer at the earliest stage of carcinogenesis.

Abstract: A method includes passing an interrogating light beam through a Fourier transform lens and onto the surface of a material to form a Fraunhofer diffraction pattern of one or more surface features of the material. An image of the diffraction pattern is processed to determine the dimensions of the feature.

Abstract: A three-dimensional laser scanner instrument for acquiring three-dimensional geometric data of a scene (1) comprises an illumination system (3) for generating a light beam (2) and for scanning an illumination point of said light beam (2) through said scene (1), a light detection system (6-9) comprising at least one light detector (8), said light detection system being arranged to receive light from said scene (1), and an optical system (4) for imaging light scattered in or reflected from said scene (1) onto said light detection system (6-9).

Abstract: Dimensions of a surface feature are determined by capturing an image of the surface feature and determining a scale associated with the image. Structured light may be projected onto the surface, such that the position of structured light in the captured image allows determination of scale. A non-planar surface may be unwrapped. The surface may alternatively be projected into a plane to correct for the scene being tilted with respect to the camera axis. A border of the surface feature may be input manually by a user. An apparatus and system for implementing the method are also disclosed.

Abstract: A real-time measurement of relative position data and/or of geometrical dimensions of a moving body by lighting unit and a detector unit, wherein the moving body is movably guided relative to both of the units. Light beams are transmitted from the lighting unit towards the detector unit; the moving body protrudes between the lighting unit and the detector unit into the volume flooded by the light beams, so that the shadow border of the shadow thrown by the moving body extends over the detector unit. The detector unit includes a two-dimensional optical position detector, which is designed as a two-dimensional optical waveguide containing photo-luminescent particles. Signals from the two-dimensional optical waveguide are read out by a plurality of small-area photoelectric sensors spaced apart from one another, the strength of the signals correlating with the intensity of the light at the sensor location in waveguide mode.

Abstract: Methods of optimizing the diameters of nanowire photodiode light sensors. The method includes comparing the response of nanowire photodiode pixels having predetermined diameters with standard spectral response curves and determining the difference between the spectral response of the photodiode pixels and the standard spectral response curves. Also included are nanowire photodiode light sensors with optimized nanowire diameters and methods of scene reconstruction.

Abstract: A height-measuring device (100) in which the focal position of an image-forming optical system (20) is moved in relative fashion in the direction of an optical axis with respect to an object (10) to be measured; scanning is performed; images of the object (10) to be measured, which are formed by the image-forming optical system (20), are obtained in order; and the focal position for individual pixels of the images is found, thereby yielding a relative height value of the object to be measured (10) at positions corresponding to the pixels; wherein a second function (g) is defined on the basis of a first function (f) fitted to a numerical value sequence comprising a coordinate value on the optical axis and a light intensity value for the pixels of a plurality of the images obtained by the scanning, or the coordinate value and a numerical value obtained by processing the light intensity value; and positions on the optical axis at which a correlation value between the numerical value sequence and the second funct

Abstract: A coating dimension measuring apparatus may include: a camera that is positioned at a prescribed position distanced from a sheet to capture an image of a coating dimension of the sheet; a roller configured to transport the sheet; a scale that is disposed along a lengthwise direction of the roller to perform numerical calibration of the coating dimension; a scale holding unit configured to hold the scale over the roller, the scale holding unit being disposed so as to enable free insertion and removal of the scale.

Abstract: Method for determining wheel alignment of a vehicle, which vehicle comprises at least one wheel axle (12, 13, 14) having an axle end with at least one wheel member (2a-b, 3a-b, 4a-b) at a respective longitudinal side of the vehicle. The method comprises steps for determining the out of square of the wheel axle in relation to the longitudinal geometric centerline of the vehicle. A system for carrying out the method is also described.

Abstract: A method of determining a structural parameter related to process-induced asymmetry, the method including: illuminating a structure, having an asymmetry property and a sub-structure susceptible to process-induced asymmetry, with radiation with a plurality of illumination conditions, at a first location of a substrate, determining a difference between measured asymmetry properties of the structure obtained with each of the plurality of illumination conditions, calculating a differential dependence of a difference between modeled asymmetry properties simulated for illumination by each of the plurality of illumination conditions on a structural parameter representing process-induced asymmetry of the sub-structure, and determining a value of the structural parameter using the determined difference and the calculated differential dependence.

Abstract: A method of characterizing and correcting effective radius variations in a surface nanoscale axial photonic (SNAP) device that comprises a plurality of separate optical microdevices includes the steps of characterizing an as-fabricated SNAP device to determine local effective radius values of the plurality of separate optical microdevices, calibrating the as-fabricated SNAP device to determine a correction factor defined as a change in effective radius associated with a predetermined corrective treatment and then correcting individual microdevices by the application of a number of refractive index-changing treatments, the number of treatments applied to individual microdevices determined by the amount of correction required and the correction factor determined in the calibrating step. A number of iterations of the characterizing and correcting operations can be performed, achieving less than an Angstrom variation in effective radius variation. An apparatus for performing the method is also disclosed.

Abstract: The present invention provides multiple improvements to optical-based laser scanning micrometers and providing a small handheld version laser scanning micrometer based on the these improvements. For added accuracy and reduction in unit size, a double sided coated mirror receiver reflects the beam back into the transmitter light source. For added accuracy, a Ronchi rule is repositioned one or more times to calibrate additional lookup table correction values. To compensate for barometric pressure change and temperature, two additional reference edges are added to be combined with the reference edges in the transmitter to generate to null out pressure and temperature at the passline measurement area. To minimize beam errors and for part locating, a third derivative is detected. Two or more parallel scanning beams are generated to null out cosine errors and to measure, taper and spherical parts.

Abstract: A multifunctional detector for emitting and receiving optical signals in order to determine the presence, location, and range movement of a player within a field of regard is disclosed. The detector generally includes a laser module operable for emitting an optical signal; an optional fiber optical delay line; a microcontroller/processor; a faceted scanning mirror pattern having multiple facets with each facet being tilted downward to allow for unique depressions for reflecting and scattering optical signals emitted by the laser module; a spinner/motor for driving and rotating the faceted mirror pattern; an optional combiner for separating emitted optical signals from the laser module or combining reflected optical signals from an reflective source; and a transceiver with an integrated APD receiver for receiving reflected optical signals combined from the combiner and transmitting reflected optical signal data to a central controller or other players. A method of using the detector is also disclosed.

Abstract: A profile measurement system includes a light source configured to generate light. A beam shaper configured to shape the light generated from the light source. A beam splitter configured to partially transmit and reflect the light shaped by the beam shaper. An object lens configured to receive the light from the beam splitter and irradiate the light to a stage in which a workpiece is mounted. A profile estimating part has a plurality of continuously varying focal points. The profile estimating part includes a focusing lens and a light detector configured to receive the light transmitted through the focusing lens.

Abstract: A first metrology method includes the steps of projecting a first image and a second image, aligning the first image and the second image to form an aligned image of a known size, and determining a dimension of a target object by comparing the aligned image to the target object. A second metrology method includes the steps of projecting a first image and a second image, aligning the first image and the second image to form an aligned image of a known size by synchronously adjusting a zoom factor for projecting the first image and an angle for projecting the second image, and determining a dimension of a target object by comparing the aligned image to the target object.

Abstract: A method and configuration to estimate the dimensions of a cuboid. The configuration includes two image acquisition units offset from each other with at least one of the units positioned at a defined acquisition height above a background surface. Image processing techniques are used to extract a perimeter of a top surface of the cuboid, placed on the background surface, from pairs of acquired images. A height estimation technique, which corrects for spatial drift of the configuration, is used to calculate an absolute height of the cuboid. The absolute height of the cuboid is used, along with the extracted perimeter of the top surface of the cuboid, to calculate an absolute length and an absolute width of the cuboid. The height, length, and width may be used to calculate an estimated volume of the cuboid.

Abstract: An optical beam scanner includes a light source, an optical scanner configured to scan a light beam irradiated from the light source, and an input optical system configured to direct the light beam irradiated from the light source to the optical scanner, wherein the optical scanner includes a rotating mirror configured to rotate around a rotational axis and reflect the light beam irradiated from the light source; the rotating mirror is rotated around the rotational axis so that the light beam is irradiated on differing positions of a mirror surface of the rotating mirror; and the mirror surface of the rotating mirror has a mirror surface inclining angle with respect to a direction parallel to the rotational axis that is arranged to gradually increase from a first side to a second side of the rotating mirror in a direction parallel to a plane perpendicular to the rotational axis.

Abstract: An industrial truck has a lifting mast and vertically movable load handling device located on the lifting mast. The lifting mast has a lifting height measurement system having a light emitter that emits a light beam, a receiving element, an optical alignment element, a target element, and a measurement path located between them, the length of which measurements path varies with the lifting height. The alignment element and/or the light emitter has a beam-forming optical system, in particular a beam-expanding optical system, so that at the maximum lifting height the reflecting target is inside the expanded light beam of the light emitter in all positions of the allowable maximum bending of the lifting mast.