Showing papers on "Spatial light modulator published in 1989"

Nonlinear joint power spectrum based optical correlation.

Abstract: A nonlinear joint transform image correlator is investigated. The Fourier transform interference intensity is thresholded to provide higher correlation peak intensity and a better defined correlation spot. Analytical expressions for the thresholded joint power spectrum are provided. The effects of nonlinearity at the Fourier plane on the correlation signals at the output plane are investigated. The correlation signals are determined in terms of nonlinear characteristics of the spatial light modulator (SLM) at the Fourier plane. We show that thresholding the interference intensity results in a sum of infinite harmonic terms. Each harmonic term is envelope modulated due to the nonlinear characteristics of the device and phase modulated by m times the phase modulation of the nonthresholded joint power spectrum. The correct phase information about the correlation signal is recovered from the first-order harmonic of the thresholded interference intensity. We show that various types of autocorrelation signal can be produced simply by varying the severity of the nonlinearity and without the need to synthesize the specific matched filter. For example, the autocorrelation signal produced by a phase-only matched filter can be obtained by selecting the appropriate nonlinearity.

Standard independent digitized video system

Abstract: A video display system which can receive and display a number of different video signals having different formats utilizing a processor extract the image from a stream of digital signals to produce a digitized image to be displayed by a digital spatial light modulator.

Spatial light modulator system

Abstract: A linear spatial light modulator with two offset rows of pixels for slight overlap of images, and a printer system using such a spatial light modulator with dark field projection optics is disclosed The pixels include electrostatically deflectable elements which all bend in the same direction to permit use of dark field projection The addressing electrodes for the elements are beneath the reflecting surface and arranged perpendicular to the rows of pixels with half on each side of the rows The printer uses a xerographic engine for conversion of modulated light into print, and an entire row is printed without any scanning

Optical interconnection network

Abstract: A crossbar switch (500) with input optical fibers (571, . . . 586) and output optical fibers (511, . . . 526) having ends connected to transmitters (551, . . . 554) and receivers 561, . . . 564), respectively, and other ends in linear arrays (545, 546) that are adjacent to linear micro lens arrays (540, 542) and a linear spatial light modulator (530) with light emitted from an input fiber end reflected back into an output fiber end for pixels deflected in one direction in the spatial light modulator (530) and lost for pixels deflected in another direction. Other embodiments include reflection from a pixel directly back into the same fiber which is bifurcated.

Single spatial light modulator joint transform correlator

Abstract: We describe a joint Fourier transform image correlator that employs thresholding at both the input plane and the Fourier plane. This suggests using a single binary spatial light modulator (SLM) to read in sequentially the binarized input signal and the binarized Fourier transform interference intensity. The performance of the single SLM joint Fourier transform correlator (JTC) is compared with that of the classical JTC in the areas of correlation peak intensity, peak-to-sidelobe ratio, signal-to-noise ratio (SNR), and correlation width. We show that the single SLM JTC outperforms the classical JTC in all such areas. Using a single binary SLM results in significant reduction in cost, size and complexity of the system.

High-speed binary optically addressed spatial light modulator

Abstract: We describe the structure and operating characteristics of a high‐speed optically addressed spatial light modulator (OASLM) with a hydrogenated amorphous silicon (a‐Si:H) photosensor and a ferroelectric liquid‐crystal modulator. The photosensor is a p‐i‐n photodiode, which switches the liquid crystal into one of two stable states. Under a write‐light intensity of 6 mW/cm2, the OASLM exhibits a response time of 155 μs, a contrast ratio of 20:1, and a resolution of 40 lp/mm. The writing sensitivity per pixel is 0.1 pJ.

Transfer characteristics of the microchannel spatial light modulator.

Abstract: The microchannel spatial light modulator (MSLM) is a versatile optically addressed spatial light modulator for optical computing and the optical neural network. In this paper the transfer characteristics of the MSLM are presented. The addressability and readability of the device and their relationships are discussed theoretically and experimentally from the viewpoint of the device structure and performance.

Correlation with a spatial light modulator having phase and amplitude cross coupling.

Abstract: In correlation filtering a spatial light modulator is traditionally modeled as affecting only the phase or only the amplitude of light. Usually, however, a single operating parameter affects both phase and amplitude. An integral constraint is developed that is a necessary condition for optimizing a correlation filter having single parameter coupling between phase and amplitude. The phase-only filter is shown to be a special case.

Motivations for using ferroelectric liquid crystal spatial light modulators in neurocomputing.

Abstract: Spatial light modulators can be used in neurocomputing as input and output display devices and storage media for the synaptic weights. We discuss the operating characteristics of a new class of spatial light modulator that utilize ferroelectric liquid crystals and their application to building optical neural network architectures.

Pointer for three dimensional display

Abstract: A pointer for a three dimensional display utilizes sensors on the display for the user to communicate with the display by means of a hand held device. The three dimensional display can have a spatial light modulator with a plurality of deformable mirror cells each with several memory cells.

Implementation of ternary phase amplitude filters using a magnetooptic spatial light modulator.

Abstract: Ternary modulation can be achieved with a single SLM and improvedc orrelationd iscriminationc an bee xperimentally realized.

Deformable mirror device spatial light modulators and their applicability to optical neural networks

Abstract: All neural networks are characterized by a large number of interconnections between processor nodes. In general, the value of these interconnections (weights) must be modifiable. However, current semiconductor technology does not lend itself well to modifiable interconnection technology. A novel type of spatial light modulator, the deformable mirror device, is proposed as the breakthrough needed to solve the neural network interconnect problem.

Development of a spatial light modulator: a randomly addressed liquid-crystal-over-nMOS array.

Abstract: The construction of a 50- × 50-pixel spatial light modulator based on an active silicon backplane and using the hybrid field effect in nematic liquid crystals as the light modulating process is described. The design and electrical evaluation of the pixel array, which is fabricated in 1.5-μm nMOS and has an individual memory cell within each pixel, are discussed. The performances of a 16 × 16 prototype SLM and the new 50- × 50-pixel device are compared to provide an indication of progress toward high performance spatial light modulators with onboard pixel memory.

Viscoelastic spatial light modulator with active matrix addressing

Abstract: Thin metallized viscoelastic layers, addressed by an active matrix of MOSFETs and used in a schlieren-optical light valve, are described. The time behavior and spatial frequency response of these incompressible deformable spatial light modulators are evaluated on the basis of a detailed theoretical analysis which takes into account the electrostatic field distribution, viscoelasticity of the elastomer material, and elasticity of the thin mirror electrode. Some of the theoretical predictions are compared to corresponding experimental results. The findings indicate satisfactory deformation properties of viscoelastic spatial light modulators for such applications as high resolution light valve projectors and optical information processing devices.

Deformation Behavior Of Thin Viscoelastic Layers Used In An Active-Matrix-Addressed Spatial Light Modulator

Abstract: Thin viscoelastic layers with active-matrix addressing are proposed as high-resolution spatial light modulators (SLM's) for eventual use in a reflective schlieren light valve. Light modulation is achieved by diffraction from the periodically deformed mirror electrode covering the SLM layer. A two-dimensional array of Si-MOS transistors will be employed for addressing the viscoelastic SLM. Orthogonal and diagonally offset arrangements of pixels with two grating periods each are suggested for this active matrix. For measuring the deformation behavior of viscoelastic layers with a reflective top electrode, a standard microscope interferometer was modified so that the phase-shift technique could be employed. The deformation profile is recorded by means of a CCD image sensor, while the temporal development of the deformation is detected with a photomultiplier tube. Qualitatively, the experimental results agree with previously obtained predictions from an extensive theoretical analysis of the SLM's time behavior and spatial-frequency response.

Content-addressable-memory-based single-stage optical modified-signed-digit arithmetic

Abstract: Using a novel nonholographic optoelectronic content-addressable memory in a free-space angular multiplexing geometry, a single-optical-stage compact parallel optical modified-signed-digit arithmetic processing architecture is proposed. Some spatial light modulator based experimental results are also presented.

High‐speed analog spatial light modulator using a hydrogenated amorphous silicon photosensor and an electroclinic liquid crystal

Abstract: A high‐speed optically addressed spatial light modulator is described which uses the electroclinic effect in chiral smectic A liquid crystals with a p‐i‐n photodiode of hydrogenated amorphous silicon (a‐Si:H). The near microsecond response time is a function of the liquid‐crystal mixture and temperature. We present and analyze optical modulation measurements of a device which exhibits a response time of 40 μs at 29 °C and 4 μs at 50 °C. The optical response is continuous and linear with electric field and write‐light intensity, allowing for grey level applications.

Hydrogenated amorphous-silicon photosensor for optically addressed high-speed spatial light modulator

Abstract: A high-speed, optically addressed spatial light modulator (OASLM) which incorporates a hydrogenated amorphous silicon (a-Si:H) photosensor and a ferroelectric liquid-crystal (FLC) modulator is discussed. The device operates with an applied square-wave voltage such that read and write operations occur under reverse bias, while the erase operation occurs under forward bias. The OASLM exhibits a response time of 155 mu s and a spatial resolution of >33 1p/mm. The capacitance and resistance of both the a-Si:H and FLC have been measured and are shown to influence the response of the device strongly. >

Robotic vision, optical correlation system

Abstract: A robotic vision, optical correlation system optically analyzes an input image (10) to provide identification and aspect information. The input image (10) is incident upon a spatial light modulator (14). A multiple holographic lens (22) then performs a multiple number of Fourier transformations upon the image (10). An array of matched filters (24) has the array of Fourier transforms incident thereon. Each matched filter (24) comprises a Fourier transform hologram of different aspect view of the object and passes an optical correlation signal indicative of the degree of correlation. The signal is then transformed by an inverse Fourier transform lens (26). A detector (28) then detects the signal. A processing circuit (30) compares the relative magnitudes of the signals to determine aspect information about the input image (10). The present invention includes a normalizing means (electronic (30) or optical) for each matched filter. This normalizing means operates on the basis of separate angular response curves for each matched filter.

Neural processor with holographic optical paths and nonlinear operating means

Abstract: An optical apparatus for simulating a highly interconnected neural network is disclosed as including a spatial light modulator (SLM), an inputting device, a laser, a detecting device, and a page-oriented holographic component. The inputting device applies input signals to the SLM. The holographic component optically interconnects N 2 pixels defined on the spatial light modulator to N 2 pixels defined on a detecting surface of the detecting device. The interconnections are made by N 2 patterns of up to N 2 interconnection weight encoded beams projected by N 2 planar, or essentially two-dimensional, holograms arranged in a spatially localized array within the holographic component. The SLM modulates the encoded beams and directs them onto the detecting surface wherein a parameter of the beams is evaluated at each pixel thereof. The evaluated parameter is transformed according to a nonlinear threshold function to provide transformed signals which can be fed back to the SLM for further iterations.

Reconfigurable substrate-mode holographic interconnect apparatus and method

Abstract: The present invention discloses a reconfigurable optical interconnect apptus that redirects an optical beam through embedded holographic elements of a substrate-mode hologram to connecting information processors or to photonic switching devices. The apparatus includes a substrate-mode hologram, including a polarization insensitive input hologram member, one or more embedded polarization sensitive hologram members that couple transmitted diffracted or non-diffracted light to respective optical receivers. The optical receivers further couple the light out of the substrate-mode hologram or to cascaded similar apparatus. The method includes processing an incident beam of polarized light through a controlled polarization modulator, through an optical information encoder, such as a spatial light modulator, then further processing the polarized light through the substrate-mode hologram. The apparatus has advantages of being compact and expandable into larger systems.

Spatial light modulation using surface plasmon resonance

Abstract: A new type of spatial light modulator has been demonstrated, operating by the surface plasmon resonance effect. Devices have been constructed using nematic liquid crystal as the active material, and the operation of these devices is 50 times faster than the bulk switching of the liquid‐crystal cells. We have obtained resolution of 10–20 μm and contrast ratios better than 100:1.

Programmable optical interconnections with large fan-out capability using the magneto-optic spatial light modulator.

Abstract: We report the use of two-dimensional, binary phase-only diffraction gratings written on a programmable magneto-optic spatial light modulator to interconnect optically an input laser beam to multiple output locations. We show that we can achieve programmable weighted interconnects between the source and two output locations as well as a fan-out capability to as many as 128 separate output locations.

Single SLM joint transform correaltors

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.

Filter having adjustable spectral transmittance function

Abstract: An optical filter having a variable spectral transmittance function of selectable shape is described which includes a spectrum forming element for dispersing a light beam into a characteristic spectrum, an optical system for forming an image of the spectrum and directing the image into a multi-element electronic spatial light modulator, such as a liquid crystal display or electrophoretic display, and an optical system for projecting the spectrally filtered light as a directed beam.

Spatial light modulating element and neural network circuit

Abstract: A spatial light modulator and a neural network circuit are disclosed. The modulator is used in pattern recognition and has an arrangement in which a photoconductive layer held between conductive electrodes is connected in series to a liquid crystal cell including a liquid crystal layer held between two opposite electrodes. Setting the rate between the area of the photoconductive layer and the area of at least one of the opposite electrodes between which the liquid crystal layer is disposed, provides a highly efficient reflective and transmissive spatial light modulator of a simple structure. Both reflective and transmissive spatial light modulating elements are applied to a neurocomputer or the like.

Real-time optical holographic tracking of multiple objects.

Abstract: A coherent optical correlation technique for real-time simultaneous tracking of several different objects making independent movements is described, and experimental results are presented. An evaluation of this system compared with digital computing systems is made. The real-time processing capability is obtained through the use of a liquid crystal television spatial light modulator and a dichromated gelatin multifocus hololens. A coded reference beam is utilized in the separation of the output correlation plane associated with each input target so that independent tracking can be achieved.

Spatial light modulation by nonlinear absorbers

Abstract: A novel spatial light modulator (SLM) based on nonlinear absorption of light by excited molecules is suggested. A kinetic analysis is applied to calculate the relative populations of molecular levels in singlet and triplet manifolds. It is shown that for many actual cases a probe light can be modulated by propagating through a medium excited by another light source. The dependence of the molecular SLM on the photophysical parameters of the SLM medium is discussed.

Associative memory system with spatial light modulator

Abstract: An associative memory system is provided which incorporates a spatial light modulator (SLM) and thresholding components. In the preferred embodiment, a Fourier transform hologram is used to convolve a reference beam with correlated input images and stored object images. An iteration and feedback loop is provided which is used to derive an enhanced reference beam for use in matching and enhancing the associative memory of the hologram with the object input plane image. The iteration loop of SLM and optical amplifying components comprises a liquid crystal light valve (LCLV) which receives the correlation plane image and provides that image in the form of a spatially phase-modulated and amplitude modulated signal to a polarizing thresholding analyzer device. The analyzer/polarizer is adjustable and threshold limits the data at fast rates and, is used in the preferred embodiment to threshold the data with reference to the greatest amplitude portion of the correlation spot provided to the LCLV. After the optical analyzer/polarizer threshold has processed the signal, an improved signal is provided to the writing photoconductor side of the LCLV. This processed signal is used to phase-modulate a projection light readout beam. A polarizing beam splitter converts the phase modulation of the readout beam to an amplitude modulation wherein an enhanced reference beam is derived which is processed back to the hologram for readout at the output plane of the system. In this manner a variable-gain fast response spatial light modulator component system is provided for use as an associative memory.

Amplitude encoded phase-only filters for optical correlators

Abstract: Method allows a first phase-only optical correlator filter function to be written on an amplitude modulating device such as a spatial light modulator (SLM) by applying a bias term to the phase only filter function great enough to obtain a second amplitude encoded filter function, for use with a more economical amplitude responsive SLM