Abstract: A pattern recognition apparatus and a method for operating same. The apparatus includes a volume holographic medium (4) having a plurality of Fourier-space volume holograms representing pattern templates stored within. The apparatus further includes a spatial light modulator (1) and a phase encoder (2). The phase encoder has an output optically coupled to the medium by a first Fourier transform lens (3). The spatial light modulator spatially modulates a spatially uniform laser beam (7) in accordance with an unknown pattern. The two-dimensional phase encoder causes the spatially modulated laser beam to be spatially distributed prior to application to the medium. The apparatus further includes a detector (6, 11) having an input optically coupled by a second Fourier transform lens (5) means to an angular spectrum of plane waves generated by the medium in response to the output of the spatial modulator, phase encoder, and first Fourier lens.

Abstract: An optical correlation system employing the degenerate four wave mixing uses cross-polarized pump and probe beams to prevent the writing of a volume transmission phase hologram in a photorefractive crystal having an applied electric field parallel to the optic axis of the system, so that system response does not depend on the time required to write or erase such a transmission hologram.

Abstract: A holographic optical correlator includes a matched optical filter and control means therefor including a memory. In use searching for occurrences of an item to be found is carried out by the control means controlling the input and Fourier transform planes of the filter and a coherent light source for parallel optical processing of the memory content and the output plane of the filter provides information to the control means as to the location in the memory of occurrences of said item. The complexity of the detector means in the output plane can be reduced in comparison with previous proposals by moving the item to be sought step-wise across the input plane. The detector means then may comprise a single column of detectors which are required to detect a peak correlation signal within a predetermined range.

Abstract: An optical associative identifier is disclosed which is used to determine the closest match between an image to be identified and a plurality of reference images. The identifier includes a display area for displaying the various images, the display area additionally functioning as a spatial light modulator. First and second optical Fourier transform devices are included which are used to compare the reference images to the image to be identified. The output light intensity of each of the reference images is modulated in accordance with a two-dimensional intensity distribution corresponding to the correlation between the image to be identified in each of the reference images. Based upon a comparison of these output light intensities, a match between the image to be identified and one of the reference images can be made.

Abstract: A method of performing image correlation in a Fourier transform correlator utilizes phase-encoding of the input image as a phase object with a normalized amplitude component. Phase-only reference image filters are used in conjunction with the phase-encoded input objects to improve the signal to clutter ratio. This technique can employ optical or digital implementation.

Abstract: An image processing apparatus having a third-order nonlinear stimulated photon echo medium (1). The photon echo medium (1) can store large numbers of images in the form of a Fourier transformed pattern by spectral modulation. The spectral modulation is carried out by sending optical pulses in an optical pulse train having (or not having) image information to the medium (1) so that the population in the ground and excited states are modulated after the passage of the pulse trains and pulses. The Fourier transformed pattern is converted back to temporal modulation, consisting of a sequence of echo pulses that reproduce the original data pulse train. By using the apparatus, ultrafast operation such as convolution and correlation between a number of reference images and a test image can be achieved.

Abstract: A multiple target correlation system for unambiguously detecting, locating and determining the orientation of an array of multiple targets or objects. The multiple target correlator provides a means for fabricating a matched filter array or multiple matched filter with multiple targets stored on a single plate and a method for interrogating this multiple target matched filter with multiple scene images thereby providing for the identification of each object or target and determining its location and orientation in coordinates that are user selectable. The multiple target correlator utilizes a multiple matched filter having two matched filters for each particular object or target stored thereon, and each matched filter is positioned at a unique angle.

Abstract: An optical pattern recognition method which can be applied to a joint transform correlator operative to effect correlation processing between a plurality of reference images and at least a single object image to produce correlation peaks corresponding to the respective reference images. The joint transform correlator is provided with a feedback system effective to regulate the intensity of the respective reference images according to the corresponding correlation peak value so as to noise-shape the correlation peaks to discriminate most-correlated reference images. The pattern recognition method is carried out in the correlator sequentially by first preparing a plurality of initial groups each containing a given number of individual reference images and carrying out the pattern recognition of the object image with respect to each of the initial groups to discriminate each of the most-associated reference images having a maximum correlation coefficient in each initial group.

Abstract: An adaptive filter having a correlation weighting structue having a single Bragg cell, acting as a tapped delay line and having an input and an output, the Bragg cell intensity modulating a write laser beam for computing correlation values, and modulating a read laser field strength for multiplying the correlation values by delayed signal values. A photorefractive element is arranged such that substantial portions of diffracted and undiffracted light components from the single Bragg cell overlap within the photorefractive element. A write laser is intensity modulated by an error signal to produce an optical write signal that is received at the photorefractive element input and which writes correlation coefficients in the photorefractive element. A read laser produces a light signal, a portion of which is diffracted by the single Bragg cell, the portion of the light signal that is not diffracted by the single Bragg cell being partially diffracted by the photorefractive element.

Abstract: An optical correlator console for mounting and assembling the components of an optical correlator system in a unique stable, compact and functional configuration in which all of the components are mounted in a compact configuration on upper and lower sides of a base support plate. The components which do not ordinarily require accessibility are mounted below the support plate and the components which ordinarily require accessibility during operation and use of the optical correlator are mounted above the support plate. The lower side of the support plate mounts a laser source and a collimator along with several other incidental optical components, with the laser source providing a laser beam as an input to the collimator which provides an expanded and collimated optical beam. The additional incidental optical elements can include a spatial filter and a shutter mounted interposed between the laser source and the collimator.

Abstract: The Fourier transform optical processing system of the present invention includes generating an electrical signal in response to a first image and modulating a beam of coherent light with means that is responsive to the electrical signal. A Fourier transform image of the modulated coherent light beam is formed, an then detected. The detector provides a second electrical signal representative of the Fourier transformed image. Other aspects of the invention include comparing the second electrical signal to a reference electrical signal for producing an output signal representing any differences; optically preprocessing the image; detecting the Fourier transform image and generating signals representative of its Fourier transform characteristics; and modulating a coherent light beam using a liquid crystal or other spatial light modulating device.

Abstract: Glints (e.g., images of point sources attributable to specular reflections) are suppressed in the focal plane of an optical imaging system by:a) Fourier-transforming an image of the imaging system's object field (including glints), and dividing the resulting energy distribution into a first channel and a second channel;b) focussing the energy in the first channel onto a first diffraction grating so as to impose a periodic carrier on the image, thereby producing a first image signal;c) directing the energy in the second channel so as to illuminate a Fourier-transform hologram of the complex point response of the imaging system to which additional aberrations (preferably toroidal aberrations) have been added;d) focussing the energy distribution from the hologram onto a second diffraction grating that is 180.degree. out-of-phase with the first diffraction grating, and blocking higher diffracted orders, thereby producing a second image signal;e) superimposing the first and second image signals (which are 180.

Abstract: A transform digital optical processing system generates a transform signal of an image. Fourier or other well-known transforms may be employed. The transform signal may be generated in one of two ways: optically or electronically. In optical generation a two dimensional object is generated by modulating a beam of coherent light with an image of the object. A transform image of the modulated coherent light beam is formed, using an optical transform element. The optical transform is then stored in a two dimensional buffer. The transform signal may also be generated electronically by storing a digital video image of an object and generating a Fourier or other transform of the digital video image using vector processing chips or other commercially available digital transform generating computers. This digitally generated information may be analyzed and classified through a neural network type processor.

Abstract: An optical correlator according to the present invention generates a cross-correlation peak of two patterns of pictorial information to be compared. It generates pictorial patterns of a sum of the two patterns of pictorial information and of a difference between the two patterns of pictorial information by a phase conjugate waveform, transforms the pictorial patterns into first Fourier transform images, generates a pictorial pattern of a difference between an intensity distribution of the first Fourier transform images by the phase conjugate waveform, and transforms the pictorial pattern of a difference between an intensity distribution of the first Fourier transform images into second Fourier transform images. The optical correlator detects a cross-correlation peak of the two patterns of pictorial information for comparison at a high S/N ratio.

Abstract: Edge enhancement of an input image by four-wave mixing a first write beam with a second write beam in a photorefractive crystal, e.g., GaAs, achieved for VanderLugt optical correlation with an edge enhanced reference image by optimizing the power ratio of a second write beam to the first write beam, e.g., 70:1, and optimizing the power ratio of a read beam, which carries the reference image to the first write beam, e.g., 100:701. Liquid crystal TV panels are employed as spatial light modulators in order to change the input and reference images in real time.

Abstract: Method of producing an averaged amplitude mask, for use in conjunction with a phase only filter (pOF) to provide an averaged amplitude matched filter (AAMF) in a Fourier transform optical correlator, involves intensity normalizing a plurality of reference images within a given class of objects, averaging the intensities of the reference images, Fourier transforming the resulting data, and utilizing the resultant amplitude function, exclusive of phase, of the Fourier transform to produce the averaged amplitude filter. A number of such masks are sequentially positioned adjacent the POF to very rapidly determine whether an input image falls within a particular class of objects, or whether the input image is of a particular object within the class.

Abstract: A discoid optical correlator system having a plurality of reflective optical components, a source of electromagnetic radiation, such as visible light, and an output detector which are positioned around the rim region of a solid disk body to develop a symmetrically folded optical axis traversed by a beam of electromagnetic radiation so that an unknown object is optically detected and identified.

Abstract: An incoherent holographic correlator comprising a two-dimensional array of surface-emitting lasers which are selectable in an arbitrary pattern so as to emit a beam containing the pattern. The pattern is spatially incoherent because the lasers are not phase-locked but it is temporally coherent. The beams are collimated onto a recorded hologram, and each of the beams produces a diffracted beam from the recording. All the diffracted beams are focused onto an imaging plane. A high-intensity spot represents a strong correlation between the selected pattern on the laser array and the image previously recorded in the hologram.

Abstract: A keyless holographic locking device that uses a matched optical filter to store in form of a hologram a unique identificaton such as a fingerprint of an authorized user, a source of coherent light that provides the illumination, and an input element for providing angle-invariance possessing the form of a transparent window against which the user places and rotates the same fingerprint, and a registering device for registering the correlation optical signal between the stored fingerprint and the presented fingerprint to generate a signal to unlock the device when, and only if, a positive correlation exists between the presented and the stored fingerprints.

Abstract: A holographic apparatus has an inferometer for concurrently irradiating an image recording medium by a writing reference light of spherical or plane wave form and a signal light containing image information which interfere with each other to form a hologram, and means for irradiating the hologram by a reading reference light in the opposite direction of the reference light to thereby reconstruct the image information. The image recording medium is comprised of a photoconductive layer, an optical reflective layer, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristic between its optical reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates.

Abstract: An analog optical processor for performing affine transformations and constructing fractal objects. An optical processor for optically performing an iterated affine transformation includes a rotating prism, an imaging lens and a translatable mirror, together with a pulsed laser as an input light source and an image detector array to record the final transformed image. The amount of rotation is determined by the setting of the rotating prism. The imaging lens provides the required magnification or demagnification. The translating mirror is shifted to provide the necessary translation. The pulsed image passes through the optical loop many times to perform the transformation. An optical Iterated Function System is implemented by connecting a plurality of the optical loops in parallel, together with shutters or beamsplitters for guiding the pulsed image to different loops according to the probabilities assigned by the Iterated Function System.

Abstract: An optical system is provided for the transformation of input images to be correlated by a pattern recognition system. A pulse of light from a laser carries an input image to a beam splitter. The beam splitter divides the input pulse into an output pulse and a thoughput pulse that is directed through an optical ring resonator. The ring resonator is an optical reimaging system that transforms the input image in scale or orientation. The transformed version of the input image is then directed to the beam splitter where it is split into a modified output pulse and a modified throughput pulse that reenters the ring resonator. The transformation process is self-repeating to generate a series of successively modified output images that are equally spaced in time. The series of output images can be provided to an optical pattern recognition system for correlation with a stored reference.

Abstract: An optical system for auto-associative and hetero-associative recall utilizing Hamming distance as the similarity measure between a binary input image vector V.sup.(k) and a binary image vector V.sup.(m) in a first memory array using an optical Exclusive-OR gate for multiplication of each of a plurality of different binary image vectors in memory by the input image vector. After integrating the light of each product V.sup.(k) .times.V.sup.(m), a shortest Hamming distance detection electronics module determines which product has the lowest light intensity and emits a signal that activates a light emitting diode to illuminate a corresponding image vector in a second memory array for display. That corresponding image vector is identical to the memory image vector V.sup.(m) in the first memory array for auto-associative recall or related to it, such as by name, for hetero-associative recall.

Abstract: An image input/output apparatus which can reproduce an image having a large focal depth, without decreasing the resolution and luminance. The apparatus has a wide range of practical applications, and can be, easily, quickly and exactly put to practical use. The apparatus includes a mechanism for inputting a plurality of images focused on different object planes, circuitry for Fourier-transforming the images input by the inputting mechanism circuitry for weighting and adding the images Fourier-transformed by the Fourier-transforming circuitry, and circuitry for performing an inverse Fourier transform of Fourier spectrum images obtained by the weighting and adding circuitry.

Abstract: A holographic learning machine comprising a volume holographic recording medium, 2N photo-detectors receiving light diffracted from the medium, and N electrical circuits subtracting respective pairs of outputs of the photo-detectors, thresholding the differences and comparing them to target values. During training, a coherent image beam shines on the recording medium and corresponding target values are supplied to the circuits. Depending on whether the comparison between the thresholded difference and the target is positive or negative, a positive error or negative error amplitude modulator in a 2N array is turned on to transmit to the recording medium light coherent with the image beam. Thereby, the full bipolar perceptron algorithm is implemented. The implementation may be integrated into a rugged, integral unit.

Abstract: In a nonlinear joint transform image correlator, the Fourier transform interference intensity is nonlinearly transformed to provide higher correlation peak intensity and a better defined correlation spot. The correlation signals are determined, for example, in terms of nonlinear characteristics of a spatial light modulator (SLM) at the Fourier plane. The correct phase information of the correlation signal is recovered from the first-order harmonic of the nonlinearly transformed interference intensity, and various types of autocorrelation signals can be produced simply by varying the severity of the nonlinearity and without the need to synthesize specific matched filters. For example, the autocorrelation signal produced by a phase-only matched filter can be obtained by selecting the appropriate nonlinearity.

Abstract: Optical correlator technology is applied to optical computing in the form of an optical interconnect utilizing multiple Fourier transforms in a hologram-based design.

Abstract: A fingerprint recognition device is disclosed which is capable of making a more definite fingerprint recognition by using a hologram. The device includes a laser for emitting light, a collimator for making the light travel in parallel, and a tetragonal prism for forming a fingerprint image on it all of which are arranged along the first optical axis. A hologram is provided for shifting the position of the fingerprint image to a second optical axis, an image-forming lens for forming the fingerprint image, and an area CCD for converting the fingerprint image to electrical signals are arranged along the second optical axis. The area CCD is connected to a circuit which amplifies and analyzes the electrical signals. Accordingly, a virtual image of a fingerprint is shifted onto the optical axis of the image-forming lens by the hologram so as to be formed as a virtual image, the virtual image is formed on the area CCD by the image-forming lens to generate electrical signals according to the fingerprint image.

Abstract: An image enhanced optical correlator system providing for optical preprocessing of an input image prior to processing thereof in an optical correlator. The optical preprocessing is provided to enhance the image and/or image related characteristics such that the probability of detection of prescribed targets therein in the optical correlator is increased. In the system, an input image beam is split into orthogonally polarized image inputs, processed to enhance targets therein, and then the algebraic result (addition and/or subtraction) thereof is processed through an optical correlator. Techniques are used in the feedback systems to enhance the output plane correlation signal detection by an adjustment in phase, spatial frequency filtering and/or threshold setting optimization.

Abstract: For inputting a two-dimensional image into an optical neural network apparatus, a primary processing device is used to extract the characteristic feature of an object pattern. Thereafter, compressed information as a result of the above processing is inputted into the input of the all-optical type optical neural network apparatus, that implements parallel processings adaptively through optical computing, at individual points on the input of the same. Therefore, the primary processing device that was capable of dealing with only logical input information until now can process even vague input information by the use of the optical neural network apparatus located on the later stage.

Abstract: The conformance of an unknown object to predetermined characteristics is evaluated through a characteristic signature, using its transform image. The presence at an inspection station of each successive one of the objects to be inspected is detected. The inspection system includes a rotatable disk having mask apertures that move into the line of sight of a light detector. Signals produced by scanning of timing marks upon the disk reflect which one of the plurality of masks is present in the optical path, and the photodetector determines the intensity of the transform image sampled by said mask means. The signals representing these intensities, correlated to the domain from which they emanate, are collected to form a signature for the object. This signature is compared to a known signature.

Abstract: An electro-optical system that implements the self-tiling process of fining proper Iterated Function Systems for modeling natural objects. The system can operate in two different modes, a real-time interactive mode and an automated mode. The purpose of the system is to speed up the process of finding a proper IFS for a given object to be modeled. The system makes use of optical processing, including optical means for rotating, magnifying/demagnifying and translating an input image. Optical beamsplitters are used to combine transformed images to produce a tiled output image. In one embodiment, an automated controller evaluates the goodness of the match between the tiled image and the input image and generates control signals which cause adjustment of the settings of the optical means. The process is repeated automatically until the match is sufficiently good. The invention can also be operated in a manual, man-in-the-loop mode.

Abstract: A 2f Fourier transform optical correlator uses two simple, single element lenses, with the second lens performing both quadratic phase term removal and the inverse Fourier transform operation in a compact two-focal-length space. This correlator performs correlations quite well and uses three less lens elements than a prior 2f system, is shorter by a factor of two compared to the standard 4f system, and uses one less lens than the 3f system, while still retaining the variable scale feature.

Abstract: In an image correlation calculation apparatus for optically calculating correlations between reference patterns and an image such as a character or any other figure, the image such as the character or any other figure subjected to correlation calculations is optically multiplied by a multiplier to form simultaneously in parallel a plurality of optical pattern images of a substantially identical shape, and optical correlation calculation between the plurality of optical pattern images and the reference patterns formed on various types of reference masks is performed individually and instantaneously, the various type of reference masks being arranged at a position spaced apart by a predetermined distance from the plurality of optical pattern image, thereby detecting beams emitted through the various types of reference masks.

Abstract: An optical architecture implementing the mean-square error correlation algorithm,MSE=.SIGMA.[I-R].sup.2for discriminating the presence of a reference image R in an input image scene I by computing the mean-square-error between a time-varying reference image signal s.sub.1 (t) and a time-varying input image signal s.sub.2 (t) includes a laser diode light source which is temporally modulated by a double-sideband suppressed-carrier source modulation signal I.sub.1 (t) having the formI.sub.1 (t)=A.sub.1 [1+.sqroot.2m.sub.1 s.sub.1 (t)cos (2.pi.f.sub.o t)]and the modulated light output from the laser diode source is diffracted by an acousto-optic deflector. The resultant intensity of the +1 diffracted order from the acousto-optic device is given by:I.sub.2 (t)=A.sub.2 [+2m.sub.2.sup.2 s.sub.2.sup.2 (t)-2.sqroot.2m.sub.2 (t) cos (2.pi.f.sub.o t]The time integration of the two signals I.sub.1 (t) and I.sub.2 (t) on the CCD deflector plane produces the result R(.tau.) of the mean-square error having the form:R(.tau.

Abstract: A high-speed optical fingerprint correlator. The invention uses the unknown ingerprint to produce a matched filter for autocorrelation and detecting and displaying the resultant indicia of correlation, the correlation peaks produced. The matched filter is produced by performing digital Fourier transform on the optically scanned digitized image input of the unknown print. The matched filter is then multiplied with the optically performed Fourier transforms on the reconstructed known fingerprint images provided in digital format from visual or digital storage.

Abstract: A device for the correlation between optical beams having spatially modulated intensities has an active glass window, which on one side is illuminated at the same time by a reading and a pumping beam through one or a plurality of semitransparent mirrors. The reading beam has radiations with a wavelength equal to that of a transition between an intermediate and fundamental energy level. The pump beam has radiations with a wavelength corresponding to the energy of the highest power level of the material forming the active glass, obtaining on the other side of the window a light beam representing the correlation betwen the pumping and reading beams.

Abstract: A simple, low cost, high performance joint Fourier transform correlator, which requires only a single spatial light modulator, is disclosed. Input and reference images are recorded upon a single phase modulating SLM, and a lens produces a first joint Fourier transform of the images upon an electro-optic sensor. The first Fourier transform is binarized and recorded upon the single SLM electronically, and the same lens produces a second Fourier transform to form an image correlation signal at a correlation plane. Also, recordation of the input and reference images and recordation of the joint Fourier transform upon the single SLM may be performed optically rather than electronically.