Abstract: The present invention is connected with the holographic interferometry method and device that provides, to a very high precision, the reconstructing the original waveform of light emitted or reflected by an object. This method allows image resolution close to that of the wavelength of the light being used. The non-destructive method of holographic interferometry coupled with impulse heating of the test article to allow observation of its dynamic response to operating conditions, as described herein, is one of the most effective non-contact automated quality control methods available.

Abstract: A device for testing a test object in particular a tire (10) by means of a non-destructive measuring method is provided with at least one measuring head (20) by which the test object (10) can be scanned to produce a measurement result. The device is also provided with a positioning means (30) by which the measuring head (20) can be moved between a park position (I) and a measuring position (II). The device is also provided with a pressure chamber in which the test object (10) can be subjected to a prescribed pressure. The device is further provided with a sub-frame (60) on which the test object (10) can be mounted during the test. The sub-frame (60) is supported on a first bearing element (61) by means of which the transmission of vibrations from a base (70) to the sub-frame (60) can be reduced.

Abstract: A method of manufacturing an optical element (5) comprises testing an optical surface (3) of the optical element, using an interferometer 1a directing measuring light (23a) onto the optical surface wherein the measuring light traverses two successive holograms (44, 48) disposed in the beam path of the measuring light upstream of the optical surface.

Abstract: The present invention makes it possible to reliably hold a computer-generated hologram 17 and a sample surface 18a in ideal design positions and to perform interference measurements on the surface shape of the sample surface 18a by holding the computer-generated hologram 17 in a predetermined attitude by using a retaining member, and interposing a spacer 45 between this retaining member and the object so that relative positioning of both the computer-generated hologram 17 and the sample surface 18a is performed. Light transmission type targets used for alignment are respectively disposed on the four corners of the frame body of the CGH 17 and the four corners of the measurement mirror 18, and the system is devised so that images of these targets can be obtained by an image focusing lens 43 and CCD camera 44, thus making it possible to check the adjustment of the alignment of the CGH 17 and sample surface 18a.

Abstract: An aspheric surface measuring apparatus includes an interferometer which generates incident light; a test piece having an aspheric surface from which the incident light is reflected as test light; a first optical element disposed on an optical path of the incident light, having at least one surface with a hologram for diffracting the incident light toward the test piece; and a second optical element disposed after the first optical element, which transmits the incident light toward the aspheric surface and has a concave surface to reduce an incident angle of the test light entering the hologram after having been reflected from the aspheric surface. Alternatively, a single optical element with a hologram and a concave surface can be used instead of the separate first and second optical elements. An extremely aspheric lens can be precisely measured using the apparatus.

Abstract: Systems and methods are described for rapid acquisition of fused off-axis illumination direct-to-digital holography. A method of recording a plurality of off-axis object illuminated spatially heterodyne holograms, each of the off-axis object illuminated spatially heterodyne holograms including spatially heterodyne fringes for Fourier analysis, includes digitally recording, with a first illumination source of an interferometer, a first off-axis object illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis; and digitally recording, with a second illumination source of the interferometer, a second off-axis object illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis.

Abstract: A method of aligning an optical system and an optical system incorporating the method. A hologram element is installed in the optical system so that test beams diffracted by the hologram element travel along a same optical path as test beams incident on the optical system. Alignment errors in the optical system are measured using interference patterns formed on an image surface by test beams returned from the optical system and reference beams. At least one optical element of the system is aligned using measurements calculated from the interference patterns. The optical system may provide for temporarily installing the hologram element to perform the measurements or the optical system may be constructed with a hologram formed on any optical element which may require alignment. A direction and a magnitude of any misalignment are determinable based on an appearance of the pattern and a number of circles in the pattern, respectively.

Abstract: Methods for measuring the low spatial reflectivity uniformity of a DMD spatial light modulator. These methods are unique since they compensate for the non-uniformities introduced by the tilt angle of the DMD mirrors in addition to the normal system non-uniformities introduced by the illumination source and optics. These methods flatten the image and remove all but the low spatial non-uniformities from the DMD mirrors.

Abstract: An optical inspection system (10) for comparing surface structures of test and reference objects comprises a laser (12), a photorefractive crystal (24) and a detector (30). A refractive index grating corresponding to a diffraction pattern of a surface structure of the reference object is present within the photorefractive crystal (24) and acts as a spatial filter for light diffracted by surface structures of the test objects. If a surface structure of a test object matches that of the reference object, little or no light reaches the detector (30). If the surface structure of a text object differs from that of the reference object, light of greater power reaches the detector (30). The system (10) provides a simple pass/fail comparison test and light incident on the detector (30) requires no interpretation or other processing. The system (10) may be adapted to allow simple imaging of an edge of an object.

Abstract: An apparatus and method for acquiring an image of a patterned object such as a fingerprint including a light refracting device, a focusing lens, a light source, and a biometric circuit for detecting the presence of a patterned object such as a fingerprint at the light refracting device. Incident light from the light source is projected through a light receiving surface of the light refracting device and is directly reflected off an imaging surface. The resulting image is projected through the focusing lens. The focusing lens has a diameter which is larger than the projection of the patterned object through the light refracting device.

Abstract: Systems and methods are described for faster processing of multiple spatially-heterodyned direct to digital holograms.

Abstract: The invention relates to an apparatus for performing electronic shearography on a test object, especially a tire or retread tire. The apparatus uses a laser light source to illuminate the test object. An optical element through which electromagnetic radiation is reflected from the test object is transmitted and forms a random interference image. The random interference image can be electronically processed to provide a video animation of the effects of stress on the test object. An archive memory can be provided for retaining the animation data which can be compressed such that it includes only preselected individual shearogram images from the set of sequential shearogram images and less than all of the image data associated therewith. An air handling system can be provided for changing the ambient pressure in a pressure chamber within which the test object is supportable. The air handling system can include a humidity reducing mechanism.

Abstract: A system for interferometric fit testing of a specimen having an aspherical surface in reflection, the specimen being a segment (2) (footprint) of a rotationally symmetrical basic body (1) (parent), comprises an interferometer (3) and a diffractive optical element (DOE) (5). An optical axis of the interferometer (3) in the beam direction behind the diffractive optical element (5) and an axis of rotation of the basic body (1) form an angle that differs from zero. The diffractive optical element (5) is designed in such a way that the rays produced by the interferometer (3) and falling into the diffractive optical element (5) strike the specimen (2) perpendicularly and from there run back in themselves.

Abstract: Systems and methods are described for reduction of reference hologram noise and reduction of Fourier space smearing, especially in the context of direct-to-digital holography (off-axis interferometry). A method of reducing reference hologram noise includes: recording a plurality of reference holograms; processing the plurality of reference holograms into a corresponding plurality of reference image waves; and transforming the corresponding plurality of reference image waves into a reduced noise reference image wave.

Abstract: This invention relates to a method and device for performing non-destructive measurements of residual stresses in an investigation area of an object based on use of optical holographic interferometry technique. The holographic interferometer is divided into a holographic probe which contains means for illuminating the investigation area of the object by coherent light, collecting the coherent light that scatters off this investigation area and means for performing a non-destructive dislocation release pulse of the residual stresses in a small region of the investigation area by exposing the object to an electric high currency, and a holographic camera which contains means for formation, registration, and development of a hologram and for formation of an interferogram of the investigation area of the object.

Abstract: A method is for three-dimensionally, optically measuring measuring objects by comparison with a reference object, where image data of the measuring object are acquired and compared to image data of the reference object, and the measuring object is directly or indirectly assessed with regard to deviations from the reference object. A quick and, at the same time, reliable assessment of the measuring object is achieved in that the measuring object and/or the reference object or a holographic recording of the measuring object and/or of the reference object are/is rotated relative to one another about at least one axis, the image data of the measuring object being acquired and the comparison being performed in various, relative rotational positions, in that an evaluation regarding a maximum agreement of the measuring object with the reference object is performed in the different comparisons, and in that the deviation is assessed in the rotational position determined by the maximum agreement.

Abstract: With interferometric test systems, the test object is frequently measured over several sections in order to realize a complete test. If special structural features are found, in particular defects, it is usually difficult to localize the structural features shown on the result images on the object. It is the object of the present method to transfer the interferometrically measured data from the various sections to a joint object coordinate system. To achieve this object, the shape of the object is measured and the spatial coordinates for the deformation data on the object surface are determined from this measured. Thus, a method is realized which permits determining the exact spatial orientation and position of the discovered structural features on the object. On the one hand, the defects on the object can thus be localized precisely while, on the other hand, an exact quantitative evaluation of the results is possible.

Abstract: An aspheric surface measuring apparatus includes an interferometer which generates incident light; a test piece having an aspheric surface from which the incident light is reflected as test light; a first optical element disposed on an optical path of the incident light, having at least one surface with a hologram for diffracting the incident light toward the test piece; and a second optical element disposed after the first optical element, which transmits the incident light toward the aspheric surface and has a concave surface to reduce an incident angle of the test light entering the hologram after having been reflected from the aspheric surface. Alternatively, a single optical element with a hologram and a concave surface can be used instead of the separate first and second optical elements. An extremely aspheric lens can be precisely measured using the apparatus.

Abstract: This invention relates to a method and device for non-destructive testing of details, machine units and mechanisms, various materials, and in particular, to a method and device for non-destructive determination of residual stresses which are based on the optical holographic interferometry technique. First, a hologram of the investigation area of the object in its initial state is registered. Then the release of the residual stresses in an investigation point in the investigation area is performed by exposing the surface of the object to a high-current electric pulse with rectangular shape. Finally, an interferogram of the exact same area of the object is made, and the residual stresses at the investigation area are determined from the shape and size of the fringes in the interferogram.

Abstract: A structure (22) is located relative to a reference surface (26a, 42) using an optical target (28) affixed to the structure (22) and having a reflective angular-reference hologram (30) thereon with an effective angular orientation. An alignment light beam (38) is directed perpendicular to the reference surface (26a, 42) and incident upon the angular-reference hologram (30) on the optical target (28), and a signal return of the alignment light beam (38) is received at a measurement location. The angular orientation of the structure (22) is adjusted to achieve a signal return of the alignment light beam (38) corresponding to an alignment of the alignment light beam (38) to the effective angular orientation of the reflective angular-reference hologram (30). Multiple reflective angular-reference holograms (30) may be spatially superimposed upon each other in the optical target (28) or spatially separated from each other on the optical target (28).

Abstract: A holographic particle-measuring apparatus is provided that can improve the precision of measurement by photographing only particles through the elimination of noise. In an off-axis holographic optical image pick-up device (100), object beams (L1) that is a flux of parallel beams are irradiated onto particles (114) as a subject. At the same time, reference beams (L2) are incident, with an inclination, onto the object beams (L1) after being irradiated onto the particles (114). An interference fringe generated as a result of the interference between the object beams (L1) and the reference beams (L2) is recorded onto a recording material Noise elimination relay lenses (116a and 116b) are installed between the particles (114) and the recording material (115). Further, a noise elimination pinhole plate (117) having a pinhole (118) is installed between the lenses (116a and 116b) constituting the relay lens.

Abstract: An interferometric testing system for testing an optical system includes an interferometer which outputs a light beam and analyzes the returned light beam, and a multiple plane reference mirror which reflects the light beam corresponding to the image point transmitted by the optical system back through the optical system to thereby generate the interference. According to one aspect of the invention, the multiple plane reference mirror reflects the light beam back along the arrival path of the light beam. According to another aspect of the invention, the multiple plane reference mirror comprises a holographic multiple plane reference mirror. The interferometric testing method is also described.

Abstract: An interferometric testing system and method employing a multiple-aperture hologram. In an illustrative embodiment, the inventive optical testing system includes an interferometer which outputs a planar light beam and analyzes a reflected selected light beam. A multiple-aperture hologram generates N image points in an image plane of the optical system responsive to the planar light beam. A retro-reflector reflects a selected one of N light beams corresponding to the N image points transmitted by the optical system back through the optical system to generate the selected light beam. According to one aspect of the present invention, the multiple-aperture hologram includes N apertures generating the N image points and one of the N apertures overlaps at least one other of the N apertures. According to another aspect of the invention, the multiple-aperture hologram intersects a plane perpendicular to an axis defined by the centers of the interferometer and the retro-reflector.

Abstract: The invention relates to an apparatus for performing electronic shearography on a test object, especially a tire or retread tire. The apparatus uses a laser light source to illuminate the test object. An optical element through which electromagnetic radiation is reflected from the test object is transmitted and forms a random interference image. The random interference image is electronically processed to provide a video animation of the effects of stress on the test object.

Abstract: Multi-domain, phase-compensated, differential-coherence detection of photonic signals for interferometric processes and devices may be manufactured holographically and developed in situ or with an automatic registration between holograms and photonic sources in a single frame. Photonic or electronic post processing may include outputs from a cycling or rotation between differently phased complementary outputs of constructive and destructive interference. A hyper-selective, direct-conversion, expanded-bandpass filter may rely on an expanded bandpass for ease of filtering, with no dead zones for zero beat frequency cases. A hyper-heterodyning, expanded bandpass system may also provide improved filtering and signal-to-noise ratios. An ultra-high-resolution, broadband spectrum analyzer may operate in multiple domains, including complex “fingerprints” of phase, frequency, and other parameters.

Abstract: Wavefront information for an optical system is calculated based on the intensity of an image of a plurality of gratings having different periods and orientations taken from at least two different planes a predetermined distance apart. The image of a plurality of gratings having different spatial frequencies or periods and orientations, the location of which are precisely known, are imaged in a nominal focal plane of the optical system, and, preferably, in two additional planes displaced a predetermined distance from the nominal focal plane. The phase shift, if any, from a fundamental frequency of the image intensity, is determined based on the known location of the grating and the grating image intensity. The grating image intensity is detected and measured in a first detection plane in a nominal focal plane and in a second detection plane a predetermined distance from the nominal focal plane. From these measurements wavefront information is calculated.

Abstract: Systems and methods for determining the position and classification of an object and which may provide signals that control deployment of an active restraint device, for example. Using a pulsed laser light beam from a laser source that is spread and preferably diffused to avoid ocular damage, an interference pattern is returned to a sensing module through a spectral filter. There it is optionally combined with a reference beam from the laser source, modified to emulate coherence length effects, and incident upon a phase transmission holographic template that may be segmented into regions for example. Each region of the holographic template contains Fourier transform images of occupant types. Behind the holographic template is a detector array that is sensitive to the laser light. An interference pattern derived from the object is convoluted or cross-correlated with the template. When an match occurs, a bright spot appears on the detector array.

Abstract: A method for determining the thickness of a thin sample is described. The method includes the step of exciting time-dependent acoustic waveguide modes in the sample with an excitation radiation field. The acoustic waveguide modes are detected by diffracting probe radiation off a ripple morphology induced on the sample's surface by the acoustic waveguide modes. The diffracted probe radiation is then analyzed to measure phase velocities or frequencies of the acoustic waveguide modes. A thickness of the thin sample is determined by comparing the measured phase velocities or frequencies to the phase velocities or frequencies calculated from a mathematical model.

Abstract: In a phase-shifting point diffraction interferometer, different image-plane mask designs can improve the operation of the interferometer. By keeping the test beam window of the mask small compared to the separation distance between the beams, the problem of energy from the reference beam leaking through the test beam window is reduced. By rotating the grating and mask 45°, only a single one-dimensional translation stage is required for phase-shifting. By keeping two reference pinholes in the same orientation about the test beam window, only a single grating orientation, and thus a single one-dimensional translation stage, is required. The use of a two-dimensional grating allows for a multiplicity of pinholes to be used about the pattern of diffracted orders of the grating at the mask. Orientation marks on the mask can be used to orient the device and indicate the position of the reference pinholes.

Abstract: The invention relates to an apparatus for performing electronic shearography on a test object, especially a tire or retread tire. The apparatus uses a laser light source to illuminate the test object. An optical element through which electromagnetic radiation is reflected from the test object is transmitted and forms a random interference image. The random interference image is electronically processed to provide a video animation of the effects of stress on the test object.

Abstract: The invention relates to an apparatus for performing electronic shearography on a test object, especially a tire or retread tire. The apparatus uses a laser light source to illuminate the test object. An optical element through which electromagnetic radiation is reflected from the test object is transmitted and forms a random interference image. The random interference image is electronically processed to provide a video animation of the effects of stress on the test object.

Abstract: A spectrum analyzer for producing a first two-dimensional array of time varying spectral analysis image input signals, a reference image generator for producing a second two-dimensional array of spectral analysis image reference signals, and a time-integrative correlator, which can be non-coherent or coherent, or correlating the two groups of image representitive signals to determine the degree of matching between an input image and a library reference image. The spectrum analyzer can include an interferometer, a tunable optical filter, or a time-wavelength-multiplexing holographic lens for viewing the input image. A monolithic non-holographic version provides a rugged, compact and portable image analyzer for examining many types of images.