Abstract: Methods and devices for calculating the position of a movable device are disclosed. A console and movable device may include light detector(s) and light sources. A light source of the console may emit light that is detected by light detector(s) of the movable device. The moveable device may respond by emitting light synchronous with the received light. The console may calculate the position of the movable device by calculating the time for the light emitted from the movable device to strike the light detector(s) of the console. The rotation of the movable device may be calculated using multiple light sources and/or multiple light detector(s). The movable device may calculate its position and transmit it to a console. Multiple light sources may be distinguished using encoding or modulation of time and/or frequency. The roles of the light detectors(s) and light sources may be switched.

Abstract: A triangulation system including a laser beam, optics focusing the laser beam on an object, a light detection unit detecting light reflected from the object due to impingement of the beam on the object, and an arrangement for determining, based on the detected light, object feature dimensions. The wavelength of the laser beam may be shorter than of infrared radiation, which allows for a reduced spot size without significant loss of depth of field. So as to reduce aberrations or a sensitivity to aberrations due to the shortened wavelength, the system may include (i) a polarization dependent coating matching the index of refraction of an element of the light detection unit to that of air for a range of angles, (ii) tilted projection optics, (iii) a prism wavefront corrector, and/or (iv) a positioning assembly, which provides for increased precision in positioning the laser diode with respect to a collimator lens.

Abstract: An optical triangulation measuring device includes an emmiter that emits two alternating light beams with different wavelengths along the same path; a beam splitter; an optical separator that directs the alternating split beams towards the surfaces from which they are reflected; an optical combiner that collects the beams and directs them along a path; optronic sensors that receive two light images and to deliver a signal indicating the position of the energy barycenter a time synchronizer for the two alternating beams and the two images on the optronic sensors; and a processor for processing the signals from the optronic sensors in order to supply information relating to the position and inclination of the surface.

Abstract: An apparatus and a method for semiconductor wafer bonding provide in-situ and real time monitoring of semiconductor wafer bonding time. Deflection of the wafer edges during the last phase of the direct bonding process indicates the end of the bonding process. The apparatus utilizes a distance sensor to measure the deflection of the wafer edges and the bonding time is measured as the time between applying the force (bonding initiation) and completion of the bonding process. The bonding time is used as a real-time quality control parameter for the wafer bonding process.

Abstract: A fragmented lens system for creating an invisible light pattern useful to computer vision systems is disclosed. Random or semi-random dot patterns generated by the present system allow a computer to uniquely identify each patch of a pattern projected by a corresponding illuminator or light source. The computer may determine the position and distance of an object by identifying the illumination pattern on the object.

Abstract: A three-dimensional position observation apparatus provided with a lens system having focusing and diaphragm mechanisms, for forming an image on an imaging plane by light from an observation object includes a beam steering member disposed in a light path extending from the observation object to the imaging plane, for changing a traveling direction of observation light into a plurality of different directions, and an image analyzing unit for analyzing a position of the observation object based on a positional relation between a plurality of images on the imaging plane formed by light passing through the beam steering member.

Abstract: The invention refers to a method for calibrating a camera-laser-unit (1) with respect to at least one calibration-object (12) disposed at a given position and orientation in a three-dimensional space (13). The camera-laser-unit (1) comprises a laser (4) and a camera (3), wherein the laser (4) and the camera (3) are disposed at a given distance with respect to each other. An optical axis (9) of the laser (4) and an optical axis (8) of the camera (3) subtend a given angle (?). The camera-laser-unit (1) is adapted to record the location, form and/or dimensions of a measurement-object (5). The method has the advantage that the same calibration-object (12) can be used for the calibration of the camera (3) and of the laser (4), wherein the camera (3) is first calibrated using a Tsai-algorithm and then the laser (4) is calibrated with respect to, and by making use of, the already calibrated camera (3).

Abstract: Briefly, in accordance with one or more embodiments, a proximity detector is placed proximate to projector to detect an obstruction disposed proximate to the projector. The proximity detector is capable of estimating the distance from an object to the projector. If an object is detected within a minimum distance, the projector operation may be altered, for example to cause the projector to turn off, or to reduce the intensity of emitted light so that the power of the emitted light the minimum distance will be reduced to below a selected range. Furthermore, if an object cannot be detected within or near a maximum distance, the projector operation may likewise be altered, for example the proximity detector may cause the projector to turn off.

Abstract: An optical triangulation measuring device includes an emmiter that emits two alternating light beams with different wavelengths along the same path; a beam splitter; an optical separator that directs the alternating split beams towards the surfaces from which they are reflected; an optical combiner that collects the beams and directs them along a path; optronic sensors that receive two light images and to deliver a signal indicating the position of the energy barycenter a time synchronizer for the two alternating beams and the two images on the optronic sensors; and a processor for processing the signals from the optronic sensors in order to supply information relating to the position and inclination of the surface.

Abstract: Dual mode depth imaging system and method is provided, the system comprising a first and second image sensors and a processor able to switch between a first mode of depth imaging and a second mode of depth imaging according to at least one predefined threshold. The method comprising providing depth sensing by Time of Flight if the distance of the sensed object from the camera is not below a first threshold and/or if a depth resolution above a second threshold is not required, and providing depth sensing by triangulation, if the distance of the sensed object from the camera is below the first threshold and/or if a depth resolution above the second threshold is required.

Abstract: An optical translation technique for moving the interrogation spot at which a triangulation system measures the displacement of a target is disclosed. In normal operation of the laser triangulation sensor, an incident laser beam is projected from a sensor head onto a surface of a web that is facing the sensor head. Radiation is reflected from the surface and detected by the sensor. The distance from the sensor head to the web surface is calculated by triangulation. With optical translation, both the incident ray path and the captured ray path are translated with a plurality of high refractive index geometries such that the nominal functioning of the triangulation sensor remains undisturbed. The optimal position on the sheet wherein the interrogation spot will be located can be ascertained.

Abstract: A system for controlling and monitoring a position of a holding element, which is provided to hold a sample to be examined, is disclosed. The system may use a beam device, such as an electron microscope. The system provides for controlling and monitoring a position of a holding element taking into account any errors with respect to irregularities and may include interpolation of possible errors.

Abstract: A system for measuring an object and for monitoring the surface of the object. The system comprises at least a first subsystem for determining one or more dimensions of the object and a position of the object within the first subsystem, and at least a second subsystem for determining a surface structure of the object. Further, the system comprises a control unit generating control signals (iii) for operation of the second subsystem as a function of data (i) of the first subsystem with respect to a position of the object in the first subsystem and/or the dimension of the object, and of data (ii) of the second subsystem with respect to a position of the camera device in the second subsystem.

Abstract: An apparatus and a method for semiconductor wafer bonding provide in-situ and real time monitoring of semiconductor wafer bonding time. Deflection of the wafer edges during the last phase of the direct bonding process indicates the end of the bonding process. The apparatus utilizes a distance sensor to measure the deflection of the wafer edges and the bonding time is measured as the time between applying the force (bonding initiation) and completion of the bonding process. The bonding time is used as a real-time quality control parameter for the wafer bonding process.

Abstract: An apparatus for determining an elevation of a working tool relative to a reference plane, includes a rotary laser system, a radio unit and a detector. The rotary laser system emits a rotating laser beam in a plane inclined relative to the reference plane. The radio unit is configured to measure a distance between the working tool and the rotary laser system and the detector is mounted on the working tool for detecting the laser beam. The elevation of the working tool can be determined on a basis of the inclination angle and the distance between the working tool and the rotary laser system.

Abstract: A method for global calibration of a multi-view vision-based touch probe measurement system is provided which encompasses calibrating camera frame distortion errors as well as probe form errors. The only required features in the calibration images are the markers on the touch probe. The camera frame distortion calibration comprises a process that depends on a portable calibration jig and the touch probe, but that process is unaffected by probe form distortion errors in the touch probe and/or tip. The probe tip position calibration depends on applying the results of the camera, frame distortion calibration. When the same probe tip is used throughout the global calibration, the probe tip position calibration uses images from the set of images used by the camera frame distortion calibration. The global calibration method is particularly advantageous for low cost portable versions of multi-view vision-based touch probe measurement systems.

Abstract: The invention relates to a method for optically measuring a chassis at a testing station. According to said method, radiation that is reflected by several optically distinguishable characteristic structures on a vehicle, comprising at least one wheel and a surrounding bodywork section, is detected by a measuring device with the aid of an image capture unit and at least the wheel plane and the wheel centre point are determined by an evaluation of the positional data obtained by means of the detected radiation.

Abstract: A system for accurate determination of target orientation in a laser tracking system. A target aperture is configured to produce spatially distinct laser beam and background images. A processing unit is configured to determine a centroid of the laser beam image position using information collected from detected images, such as laser beam and background images. The laser beam image centroid position is used to determine an accurate target orientation. In one example, a process for determining target orientation includes the steps of collecting a background image passing through a first retro-reflector at a first laser light sensor; 2) collecting a measurement image passing through a second retro-reflector at a second laser light sensor; 3) establishing a common positional reference point for the measurement image and the background image; 4) subtracting the background image from the measurement image based on the common positional reference point.

Abstract: An electro-optical distance measuring method for measuring a distance to an object to be measured by receiving a reflected light from the object to be measured, comprising a step of projecting a pulsed laser beam with a predetermined spreading angle from each of two or more known positions so that two or more objects to be measured are commonly included, a step of detecting reflected lights from the two or more objects to be measured for each pulsed laser beam by discriminating the reflected lights for each emitted pulse, a step of measuring distances to the two or more objects to be measured from each of the known points based on the results of detection of the discriminated reflected lights, and a step of measuring coordinate positions of the two or more objects to be measured based on the measured distances.

Abstract: The present invention provides an optical displacement meter in which light receiving elements are disposed two-dimensionally, capable of stably obtaining a reception light amount in accordance with a work.

Abstract: In a device for location positioning, and more particularly, in a system for identifying an environmental source emitting a base frequency and waveform signal, a sensor (101) records an environmental source (105) emitting a base frequency and waveform signal, the signal being amplified (102), digitized (103), processed and compared (104) with a stored unique waveform characteristic. On the basis of the comparison result(s), location positioning and/or a device orientation may be determined.

Abstract: An optical position-tracking system comprises a first light beam steering device for sweeping a first light beam through a first angular range to cause a reflection of the first light beam by a target. Additionally, the optical position-tracking system further comprises a second light beam steering device for sweeping a second light beam through a second angular range to cause a reflection of the second light beam by the target. Moreover, the optical position-tracking system enables determination of a position of the target using a triangulation technique utilizing a first angular value of the first light beam and a second angular value of the second light beam. The first angular value and the second angular value depend on the existence of the respective reflection.

Abstract: Device and method of measuring a position of an irregular surface. The method includes projecting a spot along a first axis onto the irregular surface, focusing an image of the spot along a second axis onto a detector, wherein the second axis is non-coaxially arranged with respect to the first axis, processing signals from the detector, and calculating the position of the irregular surface based on at least one isolated desired frequency component of the signals.

Abstract: A probe control interface is provided for a structured light non-contact coordinate measuring machine probe. Portions of a video control signal for controlling the grey level of selected rows of pixels of a spatial light modulator of the probe can be decoded into control signals for additional probe components or functions that have been added to increase the measuring capabilities or versatility of the non-contact probe. By providing the additional probe component control signals in this manner, a versatile structured light non-contact probe system can be made compatible with a standard probe head autojoint system (e.g. a Renishaw™ type system), thus allowing the probe to be automatically exchanged with other standard probes and allowing existing systems to use the non-contact probe more easily. Various aspects of the probe control interface allow for relatively simple, compact, lightweight and robust implementation.

Abstract: In a position sensitive photoelectric sensor that calculates a distance to a target based on a triangular range finding using a light and outputs a result compared with a reference distance, first the reference distance Dref is set roughly by using a light receiving portion adjusting mechanism that changes an angle of a light receiving portion including a reception lens and a light receiving device. Then, the change adjustment of the reference distance is performed by teaching. In addition, the user performs a fine adjustment of the reference distance by a manual adjustment using an increase/decrease key if necessary.

Abstract: The radar apparatus includes a transmit/receive section having a function of emitting a transmission wave, receiving the transmission wave reflected from a reflecting object, and outputting a reception signal having a signal level depending on the intensity of the received transmission wave, a control section controlling the transmit/receive section to transmit the transmission wave a predetermined number of times in the same direction, an integrating section successively integrating the reception signal successively outputted from the transmit/receive section to thereby successively form an integrated signal while the transmit/receive section repeatedly emits the transmission wave in the same direction, and a detector section judging whether or not the integrated signal enables detection of the reflecting object.

Abstract: Systems and methods are disclosed for focusing a beam for an interaction with a film deposited on a substrate wherein the focused beam defines a short axis and a long axis. In one aspect, the system may include a detecting system to analyze light reflected from the film on an image plane to determine whether the beam is focused in the short axis at the film. In still another aspect, a system may be provided for positioning a film (having an imperfect, non-planar surface) for interaction with a shaped line beam.

Abstract: Methods for acquiring an approximation of the surface geometry of a 3-dimensional object include projecting pattern of structured light on the object, moving the pattern with respect to the object, acquiring images of the intersection of the light on the object over time, determining local coordinates of points on the intersection with respect to the pattern, tracking the position of the pattern, transforming the local coordinates to object coordinates, and accumulating the points as a model of the surface of the object. The methods include a step for wirelessly and possibly compactly transmitting geometrical data which characterizes an intersection for a given position of the scanner with respect to the object. Systems for embodying the method include a self-powered wireless, non-contact optical scanner, the location and orientation of which may be tracked with respect to an object coordinate system.

Abstract: A device for measuring one or more dimensions of an object. One or more light emitters direct light towards the object. At least one light blocking element, arranged between the light emitters and the object, blocks all but a bundle of light to form a light edge on the object. At least one sensor captures an image of the light edge, wherein the dimensions may be determined from image data of the sensor. The object and/or device may move relative to one another, along an axis, to change measurement location of the object.

Abstract: A method and apparatus for optically examining an object in a contactless manner, in which light successively impinges upon the surface of an object being examined. The different sources of light strike the object surface at different angles of incidence and reflect off the surface and are then able to be measured by an image sensor which produces a plurality of image data sets having different contents. In this way, a first image data set is produced with the incident light from which form-independent or non-topographical characteristics, such as color errors, can be derived. Form-dependent or topographical characteristics, such as scratches, are derived from a second image data set formed with glancing light or oblique light. Before the form characteristics are derived from the first image data set, it is essential that the distorting influences of form-independent characteristics are eliminated from the first image data set via the second image data set.

Abstract: Optical displacement sensor may possess light-emitting element(s) for projecting light onto distance measurement target(s), and light-receiving element(s) capable of receiving light reflected from distance measurement target(s) and disposed such that light-receiving surface(s) thereof is or are substantially perpendicular to optical axis or axes R1 of projected light. Furthermore, such optical displacement sensor(s) may be equipped with slit(s) capable of narrowing light beam(s) projected toward distance measurement target(s), and slit(s) capable of narrowing light reflected from distance measurement target(s).

Abstract: A method and apparatus for measuring the location of objects arranged on a convex surface. A plurality of cameras is arranged in a stationary array about the surface, and is used to capture images of the objects. A parameterized model of the surface is developed using optimization techniques, and then the locations of the objects are established by triangulation. The method is applied to location of electrophysiological sensors on the head, for purposes of electroencephalographic source analysis, or for registration with other imaging modalities such as MRI (magnetic resonance imaging).

Abstract: A measurement sensor comprising a PSD (30) as an optoelectronic receiver, a transmitter (10, 12) for generating spots (22, 26), optics (14, 32) for reproducing the spots (22?, 26?) on the PSD (30) and means (44, 46, 48, 50, 52) for processing output signals (I1, I2) generated by said PSD (30) and for controlling the transmitter (10, 12) depending on the processed output signals (I1, I2) in order to measure the distance between the target (24) and the sensor by a triangulation technique is disclose closed. The transmitter comprises at least two optoelectronic signal sources (10, 12) for projecting at least two spots (22, 26) independent from each other on a target (24), the means (44, 46, 48, 50, 52) comprising a digitally controlled potentiometer (48) for balancing the output signals (I1, I2) and a digital processor (52) adapted for controlling the potentiometer (48).

Abstract: A remote pointing apparatus including a remote control that generates an optical signal that is periodically expanded and/or reduced around the origin and an optical sensor that detects whether the optical signal is received, and a remote pointing method therefor. The remote pointing method includes projecting an optical signal that is periodically expanded and/or reduced around an origin; detecting whether the optical signal is received using a plurality of optical sensors that are two-dimensionally disposed; and detecting the position of the origin, which exists within a position recognition range including at least a polygon having the optical sensors as vertexes, based on the results of detection of the optical sensors. Since the remote pointing apparatus and method do not need a light receiving panel that is installed to fully cover a display screen or installed in vertical and horizontal directions of the display panel in order to receive a laser beam, a manufacturing cost thereof can be reduced.

Abstract: The invention relates to a method for determining the spatial co-ordinates of an object, whereby the object is illuminated with patterns of light from at least two directions by means of a projection device. A calibrating camera and at least one measuring camera at least partially record the patterns of light projected onto the object, the calibrating camera being fixed in relation to the object. The projection device is calibrated by means of at least four phase measuring values, the measuring camera is calibrated using at least two phase measuring values, the three-dimensional co-ordinates of the object are calculated using at least one phase measuring value. The projection device and the measuring camera are thus transferred together into the desired positions.

Abstract: A ranging sensor includes: a light emitting element; a projection lens for projecting light emitted from the light emitting element to an object; a condenser lens for condensing light reflected from the object; and a light receiving element, provided at the light condensing position of the condenser lens, for transmitting an output signal which varies according to the position of the object by receiving the reflected light at the light receiving surface thereof, wherein the condenser lens is held by a holding member so that the condenser lens is movable in a predetermined direction. Consequently, it becomes possible to easily adjust the output.

Abstract: In a lithographic projection apparatus, a measuring system configured to measure the position of the projection system relative to a reference frame includes sensors rigidly mounted in relation to counterpart sensors of a measuring system measuring the substrate table position. An angular encoder which sends light from a target down two optical paths having opposite sensitivities to tilt is used to measure rotation of the projection system about its optical axis.

Abstract: A method for measurement of the distance between a component which is moved past a reference surface and that reference surface is intended to be suitable in particular for use for the measurement of radial gaps in a turbine, while having particularly high measurement accuracy. To this end, a method based on a triangulation measurement be combined with a reference measurement for determination of the actual speed of the component. In this case, two light beams aligned essentially parallel to one another as well as at least one further light beam, aligned at an angle to the parallel light beams in the movement direction of the component, are monitored for a respectively associated reflection signal which is caused by the component.

Abstract: A laser receiver for detecting the position of incidence of a beam of laser light thereon includes a first photodetector and a second photodetector aligned in series with each other and spaced apart from each other by a gap. If the laser is evenly distributed between the two photodetectors, then the laser position will be set as the correct position and a corresponding signal will be displayed. However, if the first photodetector detects more light than the second photodetector, then a signal will also be displayed to inform the user that more laser is being projected onto the first photodetector. On the other hand, if the second photodetector detects more light than the first photodetector, then a signal will be displayed to inform the user that more laser being projected onto the second photodetector. These signals will assist users to adjust the laser receiver to accurately position the laser.

Abstract: A position measuring device including a detector unit that generates position-dependent scanning signals and a transmitting unit that transmits instantaneous values of the position-dependent scanning signals in a preset scanning clock pulse. A processing unit that establishes a resulting measured position value by filtering instantaneous values of several scanning clock pulses and an interface which, on the basis of a transmission clock pulse transmits the resulting measured position value to a sequential electronic unit via a serial data line.

Abstract: An optical reflection sensor emits light and its reflection from a target object is received. A signal processor carries out a measurement on the received reflected light such as the distance to the target object each time the reflected light is received. Repeatability of measured values is calculated and displayed on a display device incorporated into the housing of the sensor. The display device may have two display areas such that the calculated repeatability and the measured value can be displayed simultaneously. The calculated repeatability may be compared with a specified threshold value, with the result of the comparison displayed. The housing may also incorporate an input device through which a required level of accuracy may be set.

Abstract: An apparatus for sensing position data of a light pattern created by a known light source on an object, comprising an optical system for collecting an incident light beam of the light pattern and transmitting the incident light beam to a beam splitter. The beam splitter has a known reflection/transmission ratio, such that the incident light beam from the light pattern received on the surface of the beam splitter results in a transmission channel, transmitted through the beam splitter, and a reflective channel, reflected from the beam splitter, with intensities of the transmission channel and the reflective channel varying as a function of a position of the incident light beam on the surface of the beam splitter. Detectors detect the intensities of the reflective channel and of the transmission channels. Dimensions of points of the light pattern on the object are calculable as a function of the intensity of the reflective channel and of the intensity of the transmission channel.

Abstract: Provided is a displacement sensor which allows at least part of the data used from the time of obtaining an image until the time of computing the displacement can be readily verified. In a displacement sensor for automatically extracting a coordinate of a measuring point from an image obtained by using an imaging device according to a prescribed measuring point extraction algorithm, and computing a desired displacement from the automatically extracted measuring point coordinate, the sensor is further provided with the function to edit data used from the time of obtaining the image until the time of computing the displacement for use as display data for an image monitor.

Abstract: An optical reflection sensor emits light and its reflection from a target object is received. A signal processor carries out a measurement on the received reflected light such as the distance to the target object each time the reflected light is received. Repeatability of measured values is calculated and displayed on a display device incorporated into the housing of the sensor. The display device may have two display areas such that the calculated repeatability and the measured value can be displayed simultaneously. The calculated repeatability may be compared with a specified threshold value, with the result of the comparison displayed. The housing may also incorporate an input device through which a required level of accuracy may be set.

Abstract: A system and method for measuring the profile of an external surface of a part is provided. The system includes a source of light that directs light onto a region of the external surface of the part. The system also includes a linear, light-sensitive sensor, and a lens used to image locations within the region onto the sensor. The source of light and the sensor are located substantially within the same plane such that the sensor detects substantially only light scattered, diffracted, or reflected from the region and travelling substantially within the plane. The system additionally includes a re-positionable mirror that re-directs the light emitted from the source of light to the plurality of locations within the region and re-directs light scattered, diffracted, or reflected from the plurality of locations within the region to the lens and the sensor.

Abstract: A system, method, and computer-readable medium for detecting and eliminating correspondence errors associated with image occlusions. In a first embodiment of the invention, the method applies traditional correspondence methods for matching points in two images, a left image (FIG. 1A) and a right image (FIG. 1B), taken of the same scene. The method applies the correspondence method to locate a matching a point (310) in the right image (FIG. 1B) with a “best match” point (320) in the left image (FIG. 1A). A set of matching points (310, 320) is generated. A second search is then performed by using the best match point (320) in the right image (FIG. 1B) as the basis for an additional correspondence search in the left image (FIG. 1A). The range of match candidates in the second search is such that points to the left of the starting point (310) are not tested as match candidates.

Abstract: Apparatus for measuring displacement that measures the displacement (the irregularities) of the surface of a measuring object precisely and at high speed is provided. The apparatus for measuring displacement scans light radiated toward the surface of the measuring object and measures the amount of displacement of the surface of the measuring object without contact based upon the position of an image formation point formed on the light receiving plane of a light receiving element. Light receiving means is provided with a lens array composed of plural condenser lenses which converges measuring beams and an imaging lens for forming an image formation point on the light receiving plane by converged measuring beams. Reflected light from an irradiation point is converged by the lens array. The converged reflected light is imaged on the light receiving plane by the imaging lens.

Abstract: The start of the displacement movement is initiated by a software instruction when measuring surface topologies with microscopic resolution. Trigger pulses which serve to trigger the recording of measured values on the sensor are generated in discrete local intervals by a position transmitter. The measured values obtained are stored and then asynchronously transmitted to the controller.

Abstract: An image capturing apparatus for obtaining information regarding a depth of a subject includes: an illumination unit operable to cast a first illumination light beam that mainly contains a first wavelength and has a first intensity distribution on a plane perpendicular to an optical axis of the first illumination light beam and a second illumination light beam mainly containing a second wavelength and a third wavelength and having a second intensity distribution on a plane perpendicular to an optical axis of the second illumination light beam onto the subject, the second and third wavelengths being different from the first wavelength, the second intensity distribution being different from the first intensity distribution; and a depth calculation unit operable to calculate a depth-direction distance to the subject based on outgoing light beams from the subject.

Abstract: Disclosed is a position system and method for correcting the position of a workpiece during a manufacturing process. The system includes a light generating means for projecting a light beam onto the top surface of the workpiece at a predetermined angle and a video capturing means for detecting the light received by the workpiece. The light projected on the workpiece is scanned to determine the deviation direction and the deviation amount from a predetermined reference point, then the position of the work piece is adjusted based on a positional relationship between a digital image of the projected light on the surface of said workpiece and the predetermined reference image.