Showing papers on "Spatial light modulator published in 1983"

Two-Dimensional Magneto-Optic Spatial Light Modulator For Signal Processing

Abstract: This electrically alterable magneto-optic device can be used as a two-dimensional spatial light modulator in an optical image processor or a display system. A thin magnetic garnet film is epitaxially deposited on a transparent nonmagnetic garnet substrate, in the manner of magnetic bubble memory films. Semiconductor photolithographic techniques are used to etch the film into a two-dimensional array of mesas and to deposit X-Y drive lines for matrix-addressed current switching of the mesa magnetization. Electromagnetic switching provides higher speed switching than a previously reported thermal switching method. The axis of polarization of polarized light transmitted through the film is rotated by the Faraday effect in opposite directions where opposite magnetic states have been written, and a polarization analyzer converts this effect into image brightness modulation. The resulting high speed random access light modulator is applicable to all three planes of the classic coherent three-plane correlator. Although the basic effect is binary, there are at least four possible configurations which achieve gray scale rendition.

Characteristics Of The Deformable Mirror Device For Optical Information Processing

Abstract: A new two-dimensional, fast, analog, electrically addressable, silicon-based membrane spatial light modulator (SLM) has been developed for optical information processing applications. This SLM, the deformable mirror device (DMD), consists of a 128x128 array of deformable mirror elements addressed by an underlying array of metal-oxide-semiconductor (MOS) transistors. Coherent light reflected from the mirror elements is phase modulated producing an optical Fourier transform of an analog signal input to the device. The DMD architecture and operating parameters related to this application are presented. A model is developed that describes the optical Fourier transform properties of the DMD. The calculated peak first-order diffraction efficiency of 8.2% is in good agreement with the value of 8.4% obtained from experimental optical Fourier transform measurements.

Spatial light modulator drive system

Abstract: The spatial light modulator drive system of the present invention permits useful light modulation, such as employed in a projection display device, with a minimum of required data input. A plurality of charge storage cells with associated charge dependent light modulator cells are disposed at the intersection of row and column conductors. The drive system alternately refreshes the data stored in a particular row and responds to external commands. The automatic refresh involves selecting a particular row via a dedicated refresh counter, reading the column data in that row, storing this data in a column latch and rewriting this data to the same row. The generation of a new display is achieved in a number of steps. A particular row is selected by externally applied data. The data type, such as number of bits and variations in shade, is also specified. The starting column for application of new display data enables this new data to be entered into the desired portion of the column latch for application to the desired light modulator cells.

Operating Modes Of The Microchannel Spatial Light Modulator

Abstract: The fundamental operating characteristics and materials limitations of the optically addressed microchannel spatial light modulator (MSLM) are discussed. The role of secondary electron emission in the operation of the device is stressed, and some of the write, cycling, and readout modes, and their limitations, are described. In addition, the limitations of the inherent space-domain image processing operations of the device are discussed.

Technique for real-time high-resolution adaptive phase compensation

Abstract: An “all-optical” approach for the realization of adaptive optical systems potentially containing in excess of a million spatial-resolution elements is reported. A phase-measurement and -compensation technique called an interference phase loop is employed in conjunction with a monolithic optically addressed spatial light modulator (SLM). Wave-front phase compensation and shaping, and the ability to ignore amplitude fluctuations and compensate phase in real time over multiple π radians of dynamic range, were demonstrated in two discrete-channel laboratory test systems containing one and nineteen resolution elements. All-optical phase compensation with a monolithic SLM was also successfully demonstrated.

Optical correlator using electronic image preprocessing

Abstract: An optical processing system uses spatial filtering to recognize two-dimensional functions and images. Images of real objects are captured with a television camera. The electronic signals representing the two-dimensional function or image are electronically preprocessed, such as by edge enhancement techniques or by applying a curvature function, and displayed on a narrow-band-phosphor cathode ray tube or television monitor. The monitor image is used directly as the input to an incoherent holographic correlator. Alternatively, the monitor image is used to modulate a source of coherent radiation such as a laser via a spatial light modulator to generate a modulated optical signal which is the input to a coherent holographic correlator. Analyzer circuitry with an optical detector at the correlation plane analyzes the shape of the correlation function to determine the intensity and position of its peak. The input to the CRT or monitor may also be in the form of non-optically generated electronic signals representative of a two-dimensional function for display in graphic form by the CRT or monitor.

Design and performance of an integrated optical digital correlator

Abstract: We describe an integrated optical correlator capable of performing ordinary binary or bipolar correlations. The device consists of two surface-acoustic-wave (SAW) transducers and an electrooptic spatial light modulator in a planar Ti in-diffused LiNbO 3 waveguide. It is designed to correlate a 32-bit word at a 32-Mbit/s data rate.

Fundamental Characteristics Of The Litton Iron Garnet Magneto-Optic Spatial Light Modulator

Abstract: This electrically alterable magneto-optic device can be used as a two-dimensional spatial light modulator (SLM) in an optical image processor or a display system. A thin magnetic garnet film is epitaxially desposited on a transparent nonmagnetic garnet substrate, in the manner of magnetic bubble memory films. Semiconductor photolithographic techniques are used to etch the film into a two-dimensional array of mesas and to deposit X-Y drive lines for matrix-addressed current switching of the mesa magnetization. Electromagnetic switching provides higher speed switching than previously reported thermal switching methods. The axis of polarization of polarized light transmitted through the film is rotated by the Faraday effect in opposite directions where opposite magnetic states have been written, and a polarization analyzer converts this effect into image brightness modulation. The resulting high speed random access light modulator is applicable to all three planes of the classic coherent three-plane correlator. Although the basic effect is binary, there are at least four possible configurations which achieve gray scale rendition. This reusable transparency has non-volatile image storage and a relatively modest projected cost expected to be comparable to that of integrated circuits of the same size. Evaluation of prototype units has shown the material to be well behaved, exhibiting excellent uniformity and readily engineered into devices suitable for numerous applications.

Characteristics Of The Linear Array Total Internal Reflection (TIR) Electrooptic Spatial Light Modulator For Optical Information Processing

Abstract: A first order analytical model which describes the imaging performance of the total internal reflection (TIR) linear array spatial light modulator is presented. Two modulator configurations are identified, each with a distinct imaging response. The modulator crystal orientation defines which image response model applies. Several optical readout techniques for converting the optical phase modulation into an intensity modulation are described.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Fourier transformation using an electroabsorptive CCD spatial light modulator

Abstract: The use of a GaAs CCD as a spatial light modulator is described and its application to coherent optical Fourier transformation is analyzed. In this device, the transmission through the two-dimensional buried-channel CCD may be electroabsorption modulated near the GaAs cutoff wavelength since the electric field in each storage well is controlled by the transferred charge. One of the primary advantages of this modulator is the ability to electrically address the device at high speed. Analysis of the two-dimensional modulator with a silicon CCD detector array yields a projected dynamic range approximately equal to the number of modulator array elements. For arrays containing greater than 1000 elements, detector performance and nonuniformities can limit the maximum range to 30-40 dB. The device can also be optically addressed, and in this mode of operation it has a comparable dynamic range to the electrically addressed structure with an optical write energy an order of magnitude lower than liquid crystal or photorefractive light valves. An alternative mode of device operation is a waveguide mode in which the light propagates along an epitaxial layer and is modulated as it passes under a one-dimensional CCD. The detection is done by a second linear CCD. The higher modulation efficiency results in a dynamic range approximately one hundred times the number of elements but is again limited to 30-40 dB because of detector response and nonuniformities.

Optical-Hybrid Backprojection Processing

Abstract: In some synthetic aperture systems the data gathered from a single transmitted pulse samples the 3-D frequency space of the object. A 3-D image can be formed by taking a 3-D FT of this data. However, the data are often in a form that allows backprojection techniques to be effi-ciently used to generate the image. We describe an optical hybrid coherent backprojection proces-sing technique that uses a 1-D spatial light modulator, a coherent optical processor, a 2-D detector array, and some simple computer post-processing to produce the image.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser Printing With The Linear TIR Spatial Light Modulator

Abstract: A linear spatial light modulator has been developed for laser printing. It provides capability for parallel modulation of several thousand points across a line of illumination, which is then imaged onto a photosensitive medium. The spatial light modulator, which has been described previously, utilizes a VLSI silicon chip containing addressing electronics, drive transistors, and a series of metal lines. This chip is pressed against a single crystal piece of lithium niobate, so that flinging fields created by voltage differences between metal lines are proximity coupled into the crystal and generate locally controllable changes in the index of refraction. The device is read out in total internal reflection off the proximity coupling interface, with schlieren readout imaging optics used to convert the phase modulation of the wavefront to a modulated line image. This paper will review the basic device concept, describe some of the device design and operating parameters, discuss printer application considerations, and show results from a breadboard level printer.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

High Accuracy Matrix Multiplication With A Magnetooptic Spatial Light Modulator

Abstract: High accuracy matrix multiplication with a magnetooptic spatial light modulatorRavindra A. Athale, Huy Q. Hoang*and John N. LeeNaval Research LaboratoryWashington, D.C. 20375AbstractOuter product optical processors can perform high accuracy matrix multiplication usingbinary representations of input matrices. It has been discovered that the outer productmatrix between a binary column vector and a binary row vector is formed naturally in a 2 -Dmatrix -addressed display if the components of the column vector and the row vector areapplied in parallel to the row and column electrodes, respectively, of the display. Onematrix -addressed display device is the Litton magneto -optic Spatial Light Modulator. Thedesign and operational parameters of an outer product optical processor based on thisdevice will be discussed. Initial experimental results will be presented. This outerproduct optical processor has the potential for compact, rugged design and high speedoperation.

Elementary Spatial Filtering With Magneto-Optic Light Modulators

Abstract: The application of a newly developed transmission-mode magneto-optic spatial light modulator to optical image processors is being examined. This high speed, reusable, electrically addressable spatial light modulator can provide a non-volatile random access interface for optical processor input and output. The light modulator employs a magnetic irongarnet thin film on a transparent nonmagnetic substrate. The magnetic film is divided into an array of separate magnetically bistable mesas. Plane polarized light transmitted through the array of mesas and the polarization analyzer is spatially modulated by the Faraday effect. This paper describes the operation of the new magneto-optic spatial light modulator in simple tests in the input plane, transform plane and output plane of optical image processors. Test patterns written into the object input plane produce Fourier transforms having most of their energy. lying near the X and Y axes. Operation of the spatial light modulator in the Fourier plane was demonstrated by reproducing the classic Abbe-Porter mesh component deletion experiment, and by obtaining edge-enhancement images. The spatial light modulator. was also tested as a compact output image scanner in the output plane. Image addressing is particularly straightforward in applications requiring only binary light modulation.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Real-time synthetic aperture radar image formation utilizing an electrooptic spatial light modulator

Abstract: The development of novel electro-optic spatial light modulators (both one and two dimensional) which allows real-time coherent optical SAR processors to be implemented is outlined It is suggested that the availability of such processors may initiate new mission applications not presently envisioned due to current digital processor limitations

Materials Limitations Of The Microchannel Spatial Light Modulator

Abstract: The fundamental operating characteristics and materials limitations of the optically addressed microchannel spatial light modulator (MSLM) are discussed. The role of secondary electron emission in the operation of the device is stressed and some of the write, cycling and readout modes and their limitations are described. In addition, the limitations of the inherent space-domain image-processing operations of the device are discussed.

RF Spectral And Temporal Analysis With A Real Time Tunable Frequency Filter

Abstract: RF spectral and temporal analysis with a real time tunable frequency filter Jean-Michel Guerin and Michael B. ChangXerox Corporation 1500 Shamrock Avenue, Monrovia, California 91016AbstractThis paper reports on a set of experiments involving an acousto-optic RF spectrum analyzer, an electro-optic tunable frequency filter, and a slit detection configuration. The system extracts in real time any wanted signal out of a multifrequency RF population and recovers its temporal modulation information. Its rise time is faster than the acoustic pulse transit time through the optical beam in the Bragg cell, yet its frequency resolution remains as fine as its A/0 spectrum analyzer parameters dictate. The E/0 tunable frequency filter operates as a real time optical processor, hence significantly reducing digital processing of the RF spectrum. First, a conceptual system using the 5376 electrode Xerox linear Total Internal Reflection (TIR) spatial light modulator is described. Experimental results using a 10 channel TIR spatial light modulator are then presented which verify the concepts, demonstrate the retrieval of a weak signal, > 20 dB dynamic range, and real time selection of desired frequency signals. The recovery of temporal information is demonstrated using an imaging technique showing ^ 1 M.S modulation pulse rise time using a narrow slit at the photodetector. Tradeoffs exist between dynamic range, recovered rise time, laser power, Bragg cell efficiency, TIR efficiency and channels cross-talk, and photodetector/amplifier noise. These aspects will be discussed.IntroductionReal time signal processing has evolved from the single stage of acousto-optic spectrum analysis in one dimension to the many stages of 3D optical processors.1 This paper will present a three-stage optical processor of pulse modulated RF signals by frequency separation and real time filtering.System ConceptThere are three basic parts to this system. The first consists of an acousto-optic spectrum analyzer. Such systems have been extensively covered earlier.2 > 3,4 Usually a CCD detector array is positioned at the frequency plane and its output is processed digitally. Other schemes preprocess this frequency spectrum optically to reduce digital processing time. Various applications call for different configurations and components.5 in our application, a filtering function was implemented. This second part requires a device which can selectively let through wanted frequencies in real time and block the undesired frequencies.Such an ideal device is the Xerox integrated Total Internal Reflection (TIR) spatial light modulator.6 Figure l(a) illustrates the component architecture. The driver chip consists of 5376 individually addressable electrodes. This 1C unit is pressed against the LiNb03 crystal which undergoes local changes in refraction indices due to the electric fields, as shown in Figure l(b). Light is then passed through the crystal as in Figure He) in such a way that it totally internally reflects off of the index perturbed surface. The electrically-induced refractive grating causes the incident beam to diffract into numerous orders as illustrated in Figure l(d).

R.F. filter whose characteristics can be rapidly changed

Abstract: An RF input signal at 1 is applied to an electro-acoustic transducer (Bragg cell) 2 which launches surface acoustic waves along a lithium niobate block 3 which interact with light from a laser 4 to deflect the light by an angle depending on their frequency The deflected light is incident on a spatial light modulator 7, controlled by control signals on lines 7A so as to determine the relationship between the electric field and hence the translucency of the filter 7 and the position in a direction perpendicular to the optical path This relationship can be a simple one such that light is transmitted only through certain parts of the filter or can be more complex The filter thus filters by different amounts light modulated by input signals on different carrier frequencies The light, thus filtered is heterodyned with an undeflected portion of the light, at 8, and converted back, at 9, into electrical signals Alternative optical light modulators use electric fields to change the voltage phase of light divided between two light guides to cause distinctive interference on recombination, or to modify the coupling between two light guides

Coherent-optical signal processor based on a spatial light modulator with multichannel optical addressing

Abstract: A study was made of the use of a combined coupling-in device in a coherent-optical processor for signals from antenna arrays. This device included a multichannel electrooptic light modulator made of lithium tantalate, a mechanical deflector, and an optically controlled transparency in the form of a Fockels readout optical memory (PROM).