Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06E—OPTICAL COMPUTING DEVICES; COMPUTING DEVICES USING OTHER RADIATIONS WITH SIMILAR PROPERTIES
  • G06E3/00—Devices not provided for in group G06E1/00, e.g. for processing analogue or hybrid data
  • G06E3/001—Analogue devices in which mathematical operations are carried out with the aid of optical or electro-optical elements
  • G06E3/005—Analogue devices in which mathematical operations are carried out with the aid of optical or electro-optical elements using electro-optical or opto-electronic means

Definitions

• the present invention generally relates to methods of operating optical computing and data processing systems and, in particular, to methods of operating a multistage lensless optical processor that is electrically programmable to perform a wide variety of complex computations on optical data.
• Images, or other spatially relatable data may be treated as matrices composed of rastor or vector scans of data elements that, at their real or effective resolution limit, are generally referred to as pixels.
• An ordinary image is typified by an analog picture frame taken as a cross section of an optical beam formed of a continuous series of such images. Each analog image frame typically contains an effectively continuous spatially distributed array of pixel data.
• discrete matrix data may be impressed onto a data beam by spat ially modulating the cross section of a data beam in terms of, for example, either its localized intensity or polarization vector.
• optical processing is of great potential value due to its fundamentally parallel processing nature.
• the parallelism arises due to the processing of complete images at a time.
• the volume of data processed in parallel is generally equivalent to the effective resolution of the image.
• optical processing has the virtue of processing data in the same format that it is conventionally obtained.
• the data to be processed is generally obtained as a single image or as a rastor scan of an image frame.
• an optical processor may receive data directly without conventional or other intermediate processing. Since the informative value of image data increases with the effective resolution of the image and the number of images considered, the particular and unique attributes of optical processing become quite desirable.
• optical processing is performed by projecting an image to be processed through a selected spatial mask onto an appropriate optical detector.
• the mask itself is, in its simplest form, only an image fixed in a film. Even as such, relatively complex optical processing computations may be performed.
• Optical processor projection systems generally require a variety of highly specialized components including arc lamps as illuminating point sources, collimating and focusing lenses, polarizing . and polarization rotation plates, beam splitters, and mirrors.
• arc lamps as illuminating point sources, collimating and focusing lenses, polarizing . and polarization rotation plates, beam splitters, and mirrors.
• these components must be assembled and maintained, often in critical alignment, spatially separated from one another. Consequently, the optical processing apparatus is large and bulky, sensitive to its environment, particularly in terms of vibration and contamination, and specifically limited to performing one or only a few quite closely related optical processing calculations.
• a temporally variable mask for optical processors has been realized as a two-dimensional spatial light modulator (SLM) that, through electronic activation, effects selective alteration of the spatially distributed data impressed on a data beam by the mask.
• SLM spatial light modulator
• a typical two-dimensional (2D) SLM is realized through the use of a photoelectrically activated reflective type liquid crystal light valve which may be coupled to a cathode ray tube.
• 2D SLM devices perform well for many applications within specific limits. Unfortunately, these performance limits include a relatively slow liquid crystal light valve response time of typically greater than 10 milliseconds. This naturally directly impacts the high speed processing capability of an optical processor.
• Two-dimensional SLM masks have also been realized in the form of a solid electro-optical element activated by a two-dimensional spatially distributed array of electrodes.
• the modulating image is effectively formed by separately establishing the voltage potential of each of the electrodes at an analog corresponding to their respective intended data values.
• the complexity level of such a two-dimensional SLM increases proportionally to the square of its pixel resolution (N).
• the current level of fabrication technology unfortunately, stands as a practical barrier to the reproducible fabrication of even moderately high resolution independent pixel addressable two-dimensional SLM devices. Alternately using a low effective resolution mask would directly impact the high speed data processing capabilities of the optical processor.
• a purpose for the present invention is, therefore, to provide methods of continuously, iteratively operating an optical data processor to perform a wide variety of complex data processing functions while avoiding or overcoming most, if not all, of the processing limitations incurred in the prior art.
• the methods of the present invention are preferably performed using an apparatus comprising a plurality of modulators for spatially modulating the optical data beam, means for the lensless interconnection of each of the modulators to provide for the focusless transfer of the optical data beam between the modulators, and means for controlling the plurality of modulators so as to permit the programmable processing of the optical data beam.
• an advantage of the present invention is that it can be utilized to perform a wide variety of optical data processing computations.
• Another advantage of the present invention is that it permits the continuously iterative processing of temporally changing optical data.
• a further advantage of the present invention is that it effectively provides for the dynamic modification and reconfiguration of the processing apparatus by data programming.
• Still another advantage of the present invention is that it is readily adaptable to the performance of any desired optical computation.
• Yet another advantage of the present invention is that it can conveniently implement such computationally intensive optical data processing functions as multid imensional Fourier transform , cross correlation , and sliding window cross-ambiguity functions for example.
• FIG. 1 is a perspective block diagram of a preferred optical data processing system in accordance with the present invention
• FIG. 2 is a side view of a preferred generic embodiment of an optical data processor constructed for use in accordance with the present invention
• FIG. 3 is a perspective detail of an electro-optical spatial light modulator.
• FIG. 4 is a perspective view of another electro-optical spatial light modulator.
• FIG. 5 is an exploded perspective representation of a preferred embodiment of an optical processor for illustrating the preferred methods of operation in accordance with the present invention.
• the preferred system embodiment for use with the present invention is shown in FIG. 1.
• the preferred multistage optical data processor (ODP) is operatively supported by the microcontroller 12 and interface registers 18, 22, 24, 26, 30, 32 and 34. While the preferred structure of the ODP 20 will be described in greater detail below, the principle operative components of the ODP 20 are shown in FIG. 1 as including a flat panel light source 14, matrix array accumulator 16 and a plurality of spatial light modulators (SLMs) 36, 38, 40, 42, 44 and 46.
• SLMs spatial light modulators
• the light source 14, accumulator 16 and the SLMs 36, 38, 40, 42, 44, 46 are provided in closely adjacent parallel planes with respect to one another such that a relatively uniform beam sourced by the light source 14 travels through each of the spatial light modulators in succession and is ultimately received by the accumulator 16.
• the light beam is effectively used as a data transport mechanism acquiring data provided by each of the spatial light modulators that is subsequently delivered to the accumulator 16.
• the operation of each of the spatial light modulators can be explained in terms of their spatial transmissivity variation with respect to corresponding spatially distributed activating voltage potentials.
• the transmissivity of a spatial light modulator is directly proportional to the applied voltage potential.
• the combined transmissivity (T 0 ) of two serially coupled spatial light modulators is proportional to the product of the respective transmissivities of the spatial light modulators.
• the combined transmissivity T 0 can thus be written as:
• V 1 and V 2 are the respectively applied voltage potentials
• ⁇ and ⁇ are the transmissivity to applied voltage coefficients for the respective spatial light modulators.
• the combined transmissivity To of the multistage spatial light modulator stack is proportional to the product of the respective transmissivities of the individual spatial light modulators.
• a light beam sourced by the flat panel 14 can thus be directed to acquire spatially distributed data corresponding to the spatially distributed relative transmissivities of each of the spatial light modulators 36, 38, 40, 42, 44 and 46.
• spatially relatable data is provided to the spatial light modulators 36, 38, 40, 42, 44 and 46 via the interface registers 22, 24, 26 , 30, 32 and 34.
• These registers preferably operate as high speed digital data storage registers, buffers and digital-to-analog data converters.
• the stack of spatial light modulators preferably includes a plurality of one-dimensional spatial light modulators and one or more two-dimensional spatial light modulators. As shown in FIG. 1, onedimensional spatial light modulators 36, 38, 40, 42 and 44 are coupled to respective registers 22, 30, 24, 32 and 26 via interface data lines 60, 78, 62, 80 and 64.
• a two-dimensional spatial light modulator 46 receives data from register 34 via the interface data line 82.
• the interface registers 22, 24, 26, 30, 32 and 34 in turn preferably receive data in a parallel form provided by external sensors.
• the microcontroller 12 via the processor control buses 50, 70 provides the control signals. While the processor control buses 50, 70 are shown as separate and respectively connected to the registers by the register control lines 52, 54, 56, 72, 74 and 76, the interface registers may alternately be coupled via control multiplexers to a single, common control bus driven by the microcontroller 12. In either case, however, it is essential only that the microcontroller 12 possess sufficient control over the registers 22, 24, 26, 30, 32 and 34 to selectively provide its predetermined data thereto.
• the optical data processor system 10 is completed with the provision of the output register 18 coupled between the accumulator 16 and the processor output.
• the accumulator 16 itself is a matrix array photosensitive device capable of converting incident light intensity into a corresponding voltage potential representative of the data beam at an array resolution at least matching that of the spatial light modulators 36, 38, 40, 42, 44 and 46.
• the accumulator 16 accumulates light beam data that can then be shifted by means of a clock signal supplied by a clock generator 83 to the data output register 18 via the output interface bus 88.
• the accumulator 16 also includes circular shift bus 86 and lateral shift bus 84 to permit a wide variety of shift and sum operations to be performed within the accumulator 16 during the operation of the optical data processor 20.
• the data output register 18 is preferably a high speed analog-to-digital converter, shift register and buffer that channels the shifted output data from the accumulator 16 to the processor output via the processor data output bus 90.
• the microcontroller 12 possesses full control over the optical data processor 20.
• Any desired data can be provided to any specific combination of spatial light modulators to implement a desired data processing algorithm.
• Spatial light modulators within the optical data processor 20 may be provided with appropriate data via their respective data registers to uniformly maintain the spatial light modulators at their maximum transmissivity. Consequently, selected spatial light modulators may be effectively removed from the optical data processor by their appropriate data programming.
• the optical data processing system 10 provides an extremely flexible environment for the performance of optical data processing computations.
• the structure of an exemplary optical data processor 20 fabricated in accordance with the preferred optical processor embodiment of the present invention is shown in FIG. 2.
• the embodiment shown is exemplary as including substantially all of the principle components that may be incorporated into any preferred embodiment of the optical processor.
• the components of the optical data processor may be functionally grouped as parts of a light source 91, SLM stage 92 and data beam receiver 93.
• the light source 91 essentially includes the flat panel light source 14 and, optionally, a light beam buffer component 94.
• the flat panel light source 14 is preferably an electroluminescent display panel or, alternately, a gas plasma display panel or LED or LED array or laser diode or laser diode array.
• the buffer component 94 is preferably utilized to grade the light produced by the flat panel display panel into a spatially uniform optical beam. Where a gas plasma display is utilized, the buffer component 94 may further function to insulate the remainder of the optical data processor 20 from any heat generated by the plasma display 14. In either case, the buffer component 94 is preferably an optical glass plate having a thickness of approximately 0.25 inch.
• the bulk of the optical data processor 10 is formed by a serial stack of SLM stages, of which SLM stage 92 is representative. While each stage is preferably identical in terms of their component composition, the SLM of each is the only essential component. Preferably, the SLM is a rigid structure requiring no additional support. In such embodiments, the SLMs may be placed immediately adjacent one another, separated only by a thin insulating optically transparent layer, yielding an optimally compact multistage stack of spatial light modulators. However, where the spatial. light modulators are, for example, of a material possessing insufficient structural strength to provide for their own support, the stage 92 preferably further includes a supporting fiber optic plate 102.
• the fibers of the fiber optic plate 102 are, of course, aligned with their cylindrical axes parallel the major axis of the optical data processor 20.
• a polarizer 64 is preferably interposed between the SLM 44 and fiber optic plate 102.
• the polarizer 64 further permits the utilization of an unpolarized optical data beam source 14 in local polarization vector data representation embodiments of the present invention. If the principle of operation of the spatial light modulation is light absorption (instead of polarization rotation), then there is no need for the polarizers.
• the data beam receiver 93 essentially includes an accumulator component 16.
• the accumulator 16 is preferably a solid state matrix array of optical detectors.
• the optical detector array is preferably a two-dimensional shift register array of conventional charge coupled devices (CCDs) provided at an array density equivalent to the effective resolution of the optical data processor 20.
• CCDs charge coupled devices
• the use of a CCD array is preferred both for its charge accumulation, i.e., data summing, capability as well as for the ease of fabricating CCD shift register circuitry that can be directly controlled by the microcontroller 12. Further, the use of the CCD array permits substantial flexibility in the operation of the accumulator 16 by permitting data shifted out of the accumulator 16 and onto the data return bus 88 to be cycled back into the accumulator 16 via the circular shift data bus 86.
• the accumulator 16 possesses the desirable flexibility through the use of adjacent register propagation path interconnections to permit lateral cycling of the data contained therein via the lateral shift data bus 84 generally as indicated in FIG. 1. Consequently, the accumulator 16 can be effectively utilized in the execution of quite complex optical data processing algorithms involving shift and sum operations under the direct control of the microcontroller 12.
• the data beam receiver 93 may optionally include a fiber optic plate 122 as may be desirable in interconnecting the accumulator 16 with the SLM 44 of the last stage 92 of the optical data processor 20.
• the preferred embodiments of the two one-dimensional spatial light modulators are shown in FIGS. 3 and 4.
• the spatial light modulator 130 shown in FIG. 3 includes an electro-optic element 132 preferably having two major parallel opposing surfaces upon which stripe electrodes 136 and potential reference plane 140 are provided respectively.
• the electro-optic element 132 may be a transmission mode liquid crystal light valve though preferably it is a solid state electro-optic material, such as KD 2 PO 4 or BaTiO 3 . This latter material polarization modulates light locally in proportion to the longitudinal and transverse voltage potential applied across that portion of the material that the light passes through.
• Electrodes 136, 140 are preferably of a highly conductive transparent material such as indium tin oxide. Contact to the electrodes 136, 140 is preferably accomplished through the use of separate electrode leads 134, 138, respectively, that are attached using conventional wire bonding or solder bump interconnect technology.
• a variation of the spatial light modulator 130 provides a zero dimensional, or uniform, spatial light modulator that is of particular utility in the present invention.
• the transmissivity of the electro-optic material 132 will be uniformly modulated at all pixel locations.
• a single electrode covering the entire major surface of the electro-optic material 132 may be substituted for the stripe electrodes 136.
• FIG. 4 illustrates an alternate one-dimensional spatial light modulator. This spatial light modulator significantly differs from that of FIG. 3 by the relative placement of the signal 156 and potential reference 158 electrodes on the two major surfaces of the electro-optic element 152.
• a reference potential electrode 158 is interposed between pairs of the signal electrodes 156 to form an interdigitated electrode structure that is essentially identical on both major surfaces of the electro-optic element 152.
• the active portions of the electro-optic element 152 lie between each of the signal electrodes 156 and their surface neighboring reference potential electrodes 158.
• the achievable electro-optic effect is enhanced through the utilization of both surfaces of the electro-optic element 152.
• all of the electrodes 156, 168 may be of an opaque conductive material, such as aluminum, that may be further advantageously utilized to effectively mask the active regions of the electro-optic element 152. That is, the electrodes 156, 158 may be utilized to block the respective pixel edge portions of the data beam as they diverge while passing through the electro-optic element 152.
• the electro-optic element 152 may be either a liquid crystal light valve or a solid state electro-optic material.
• transverse field polarization modulation electro-optic materials such as represented by LiNbO 3 , LiTaO 3 , BaTiO 3 , Sr x Ba (1-x) NbO 3 and PLZT are preferred. These materials are believed to possess the generally equivalent structural strength characteristics as the polarization modulation material KD 2 PO 4 described above.
• Electrode leads to the electrode strips 156, 158 are again preferably attached using conventional wire bonding or solder bump interconnect technology.
• optical data processor 20 is functionally illustrated as a series of planes A, B, C, D, E and F, each plane parallel to the X and Y axis and distributed along the Z axis of the coordinate system 200.
• the optical data processor 20 is shown as having an effective resolution of three by three pixels.
• planes A, B and C contain registers 212, 214, 218 interconnected by buses 234, 236, 238 to one-dimensional spatial light modulators 202, 204, 206 and to the microcontroller 12 by buses 222, 224, 226, respectively.
• the registers 212, 214, 216 each preferably includes a three by three pixel buffer array.
• the A and B plane one-dimensional spatial light modulators 202, 204 provide for the modulation of three pixel rows (parallel to the X axis).
• the spatial light modulator 206 of plane C is distinguished as providing for the modulation of three pixel columns (parallel to the Y axis).
• a two-dimensional spatial light modulator 208 driven by register 218 via bus 240 is provided in plane D with both being interconnected with the microcontroller 12 by the bus 230. Since, as will be demonstrated below, the operation of the two-dimensional spatial light modulator is effectively static with respect to the other planes of the optical data processor, the necessity of high speed independent addressing of the array electrodes is substantially obviated. Rather, simpler shift register mode propagation of data may be utilized in the operation of the two-dimensional spatial light modulator 208. Consequently, the construction constraints and complexity limitations in the reliable fabrication of high resolution matrix spatial light modulators are greatly eased for purposes of the present invention.
• Plane E includes the three by three pixel register 220 that is interconnected with a uniform, zero-dimensional spatial light modulator 210 via the single pixel bus 242 and both with the microcontroller 12 via the bus 232.
• a matrix array accumulator 14 is provided in plane F.
• circular 86 and lateral 84 shift buses are provided to permit flexible sum and shifting operations to be performed under the control of the microcontroller 12.
• a two-dimensional Fourier transform of two-dimensional data is performed by: Initialize
• a two-dimensional cross correlation of two-dimensional data, appropriate for image recognition, is performed by:
• a one-dimensional sliding window cross ambiguityfunction calculation with respect to one-dimensional data is performed by: Initialize

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• 1985
  • 1985-12-05 DE DE8686900432T patent/DE3582329D1/de not_active Expired - Fee Related
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  • 1985-12-05 EP EP86900432A patent/EP0215008B1/de not_active Expired
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