Other

US Government As Represented by the Secretary of the Army

Matrix Instruments Inc.

Recognition Systems, Inc.

N Balasubramanian

Alan L Helgesson

A method for reading deformation images recorded on electrophotographic media involving scanning of an image surface and measuring microscopic surface tilt in a reflected beam. In one embodiment, the deformation image is scanned telecentrically and in another embodiment the surface is scanned with a beam at angles to the surface. By intercepting the retroflected beam and measuring the deviation of the reflected beam from the scanning center, a number of proportional-to-surface tilt is found. By then electrically integrating over neighboring regions, an electrical or optical pattern, reimaging the deformation image, may be constructed.

Method for reading deformation images on electrophotographic media

A servo system for a braked accelerative transport in which a signal representing velocity of a carriage within the transport is compared to a first reference signal representing desired carriage velocity. The comparison yields an error signal which is used to adjust the brake of the transport. A hydraulic valve having an adjustable needle is used as the brake. A second selectable reference signal is provided so that the first reference signal can be bypassed when the carriage is reset at high velocity or is at reset. The valve is also bypassed on reset so that the adjusted brake mechanism is left intact on reset.

Braked media transport for laser scanners

An optical leverage telecentric scanning apparatus for scanning a large fat film transparency at a given location is disclosed, wherein the scan pattern from the transparency is detected for optical power spectrum analysis. The scanning apparatus includes a collimated laser beam supply and a refraction device for laterally translating the collimated beam across the transparency. To magnify the collimated beam, an optical leverage device is provided including a first lens arranged between the laser beam supply device and the refraction device, and a scanning concave parabolic mirror arranged between the diffraction device and the transparency. The degree of magnification afforded by the optical leverage device is equal to the ratio of the focal lengths of the mirror to the first lens, respectively. A detector arranged on the opposite side of the transparency from the refraction device detects the scan pattern produced by the laser beam passing through the transparency.

Optical leverage telecentric scanning apparatus

An interferometric system for characterizing the surface of a test object, such as an aspheric surface. A white light interferogram is produced wherein the principal fringe indicates zero optical path difference between a test surface and a reference surface. Wavefronts from either of the test or reference surfaces are translated by incremental amounts. A multi-point detector array is used to make multi-point contrast readings. Points of contrast maxima for each detector point are computed by a statistical determination. A centroid function is preferred. By recording the points of maximum contrast and the incremental wavefront translation, two dimensional plots showing zero optical path differences for the two surfaces are obtained, thereby comparing the test and reference surfaces.

Optical system for surface topography measurement

A scanning laser measurement system for measuring depthwise variations of surfaces relative to a focal plane of an optical system. Laser light is directed to a test surface, generally aligned with the focal plane, through focusing optics having an optical axis. Some of the light from a beam spot is retro scattered from the test surface and reimaged along a path generally parallel to the optical axis. Depthwise variations in the test surface with respect to the focal plane cause spatial displacements in the retrobeam relative to the optical axis. The retrobeam is directed to a filter which is partially reflective and partially transmissive. A pair of photodetectors is used to intercept reflected and transmitted components of the retrobeam and the intensity of these components is measured and used to compute centroid values for the retrobeam on the filter for various beam spots on the test surface. The computed centroid values are directly proportional to depthwise surface deviations from the focal plane. The beam is directed to various points on the test surface by an optical scanner. If the deviations in the test surface from the focal plane are so great that a retrobeam cannot be formed, the entire optical system is translated until beam focus can be achieved and a retrobeam formed. The extent of translation is a coarse measurement of depthwise variations in the test surface relative to the focal plane, while the previously mentioned centroid values yield a fine measurement of depthwise variations relative to the focal plane.

Optical inspection device for measuring depthwise variations from a

An interferometric system for characterizing the surface of a test object, such as an aspheric surface. A white light interferogram is produced wherein the principal fringe indicates zero optical path difference between a test surface and a reference surface. Wavefronts from either of the test or reference surfaces are translated by incremental amounts and after each translation the position of the principal fringe is noted by observing the loci of points of maximum contrast. By recording the points of maximum contrast and the incremental wavefront translation, two dimensional plots showing zero optical path differences for the two surfaces are obtained, thereby comparing the test and reference surfaces.

An apparatus is described which provides optical scanning with both high resolution and high speed. A low resolution acousto-optic deflector is scan-center coupled with a rotating scanner to allow high scanning speed without degrading the resolution characteristics associated with a rotating scanner. A mirror having a parabolic reflective surface exhibiting spherical aberration cooperates with a rotating multi-faceted cylindrical mirror to maintain the imaging focal point of the beam provided by the apparatus in a flat image field as the beam is caused to scan the field.

Apparatus for optical scanning

A method and system for determining interferometric optical path length difference including: varying the interferometric optical path length difference between a first and a second surface in three steps at one-quarter wavelength intervals; sensing the intensity of the interferogram radiation at at least one position of the interferogram at each of the steps; storing the intensity sensed at each position at each step; for each of the positions adding the intensity of the first and third steps to produce a d.c. spatial frequency amplitude, subtracting the intensity of the third step from that of the first to obtain the cosinusoidal spatial frequency amplitude, and subtracting the intensity of the second step from the d.c. amplitude to produce the sinusoidal spatial frequency amplitude; combining the sinusoidal and cosinusoidal amplitudes to produce a trigonometric function of the phase angle of the radiation reflected from each position of the first and second surfaces and generating from the trigonometric function of the phase angle an output representative of the optical path length difference at each position.

Method and system for determining interferometric optical path length

A laser projection and printing system wherein a laser beam is focused on e scan center of an X-Y galvo-deflector, passes through a condensing lens to a transparency to be projected, and is transmitted to an imaging lens for projection to a large format plate. The scanning galvinometer, condenser, and imaging lens render the laser beam effective to project the small transparency to a large format plate.

Process and apparatus for laser illumination of printing plates

A method and system for surface contouring including: projecting a sinusoidal pattern on a surface to be tested; shifting the pattern in three steps at one-quarter period intervals of the sinusoidal pattern; sensing the intensity of the radiation from the test surface through a mask containing the same sinusoidal pattern at at least one position of the surface at each of the steps; storing the intensity sensed at each position at each step; for each of the positions adding the intensity of the first and third steps to produce a d.c. spatial frequency amplitude, subtracting the intensity of the third step from that of the first to obtain the cosinusoidal spatial frequency amplitude, and subtracting the intensity of the second step from the d.c. amplitude to produce the sinusoidal spatial frequency amplitude; combining the sinusoidal and cosinusoidal amplitudes to produce a trigonometric function of the phase angle of the projected sinusoidal pattern on the test surface and generating from the trigonometric function of the phase angle an output representative of the height of the surface at each position.

Method and system for surface contouring

A non-contacting optical probe incorporates an optical system designed to measure distances between various surfaces which may be internal or external such as exists in molds and the like. A collimated light beam is passed off-center through a first lens and focused to a first point on a first surface coplanar with the focal plane of the lens. When the distance between the first surface and the optical probe carrying the collimated beam changes so that a second surface is presented, this second surface is no longer in the focal plane with the result that a laterally displaced image of the point of interception of the collimated beam with the point of the intersection of the optical axis of the system occurs. This lateral displacement is imaged back through the optical system to a sensing surface. The primary focusing lens is then physically shifted along its optical axis to bring the focal plane into coplanar relationship with the second surface, the amount of lens movement being readily determined when the laterally displaced image point on the sensor surface is brought into coincidence with the center optical axis of the lens system on the sensor surface. The distance through which the lens is physically moved then corresponds precisely to the distance between the first and second surfaces.

Optical measuring system

A heterodyne optical correlator allows a correlation function to be computed for plural portions of a stereo pair of transparencies which is normalized to thus reduce the possibility of false correlation peaks. To obtain the correlation function, a pair of stereo transparencies are illuminated by an intense monochromatic light source producing an image at a common image plane in which a detector array is located. The relative path length, between source and transparencies, is periodically modulated producing at plural locations of the detector array plural alternating current signals representing the correlation between the amplitude transmittances at various corresponding locations on the transparencies for a given relative displacement between the transparencies. To normalize this correlation coefficient a second signal is produced by illuminating only one transparency and a corresponding third signal is produced by illuminating only the other transparency. The ratio between the correlation coefficient and twice the square root of the product of the second and third signals is a normalized correlation coefficient. Plotting the normalized correlation coefficient at each of the plurality of points in the transparencies as the relative positioning of the transparencies is shifted allows the correlation function and its peak to be determined. The relative positioning between the transparencies at the correlation peak is a measure of parallax.

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Saratoga, CA, United States of America

N Balasubramanian