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We describe the operation of a wire-grid-mirror liquid-crystal light valve and its use for optical pattern recognition. The nonlinear characteristic of the wire-grid-mirror liquid-crystal light valve is used to implement the nonlinear joint transform correlator. Experimental results and computer simulations show that the nonlinear characteristic of the wire-grid-mirror liquid-crystal light valve can produce a well-defined correlation peak and low output background. The performance of the nonlinear joint transform correlator obtained when the wire-grid-mirror liquid-crystal light valve is used is compared with that of the binary joint transform correlator.

We demonstrate experimentally the concept of the digital optical cellular image processor architecture by implementing one processing element of a prototype optical computer that includes a 54-gate processor, an instruction decoder, and electronic input–output interfaces. The processor consists of a two-dimensional (2-D) array of 54 optical logic gates implemented by use of a liquid-crystal light valve and a 2-D array of 53 subholograms to provide interconnections between gates. The interconnection hologram is fabricated by a computer-controlled optical system.

We show novel experimental results for an all-optical cascadable module that consists of a spatial light rebroadcasters, an image intensifier, and a liquid-crystal light valve. The module may be used for all-optical logic, memory, or arithmetic. Previous experimental systems involving spatial light rebroadcasters use a video camera and computer to overcome their lack of cascadability. The results of laboratory experiments show correct operation for a half-adder constructed from the cascadable module. Optical setups are proposed for constructing all-optical parallel ripple-carry and bit-slice full adders by using a single optical half-adder.

Programmable coherent source arrays are generated by using addressable liquid-crystal spatial light modulators and two-dimensional arrays of Fresnel lenses. The modulators used are an optically addressed liquid-crystal light valve, a matrix-addressed pixelated display, and two devices that have individually addressable elements with specially designed patterned electrodes. One such device has a transparent electrode patterned as a Fresnel zone plate array; the other is a gate array used in a hybrid implementation with a Fresnel lens array etched on a glass substrate. The operation of devices that use binary-amplitude and binary-phase Fresnel lenses is described, identifying programmable features, resolution limits, and applications.

In recent papers the authors described a liquid crystal (LC) device, operated in the transmission mode, that had response times of the order of 0.2-0.4 msec and contrasts of 6%. These response times are considerably faster than the 20-50 msec normally associated with cells using the twisted nematic configuration. The improvement in response time results from (1) the addition of a small amount of a cholesteric to a binary nematic, and (2) operation of the cell with the signal voltage superimposed on a square-wave pedestal voltage whose polarity is reversed at a 20-Hz rate. With an aim toward incorporating these features into a light valve of the type described by Beard et al., which uses a photoconductor-LC sandwich configuration, we have carried out experiments similar to those described earlier but on a cell in the reflection mode.

The optical modulator in a flying spot scanner converts the electronic video signal into a corresponding temporal modulation of a light beam. An alternative configuration, which directly exploits the spatial modulation of an acoustooptic cell, is the Scophony scanner, first developed by the Scophony Laboratories of London during the 1930s. The Scophony scanner responds like a coherent imaging system, whereas the flying spot scanner performs like an incoherent imaging system, when the light source is spatially coherent. The Scophony response is intimately linked to the concepts of FM blur and the deflector as video spectrum bandpass filter.

The application of shape memory alloy (SMA) thin films in optical devices is introduced and explored for the first time. Physical and optical properties of titanium-nickel (TiNi) SMA thin films change as these films undergo phase transformation on heating. An optical beam can be modulated either mechanically with a TiNi actuator or by the changes that occur in TiNi's optical properties upon heating and phase transformation. Reflection coefficients of TiNi films were measured in their so-called martensitic (room-temperature) and austenitic (elevated-temperature) phases. The reflection coefficients of the austenitic phase were higher than those of the martensitic phase by more than 45% in the wavelength range between 550 and 850 nm. Also, a microfabricated TiNi diaphragm with a 0.26-mm-diameter hole was used as a prototype light valve. The intensity of the transmitted light through the hole was reduced by 10%-17% when the diaphragm was heated. A novel TiNi light valve fabricated by using silicon micromachining techniques is also proposed and discussed. We present both optical data and structural data obtained by using transmission electron microscopies.

We present a multiple-input, single-output, weakly nonlinear model of spatial light modulators by use of a second-order Volterra series and describe an experimental method to measure the nonlinear transfer functions by means of sinusoidal perturbation and synchronous detection with a lock-in amplifier. We also present an application of this method to a liquid-crystal light valve.

This article demonstrates a bistable optical valve in a photonic liquid crystal fiber using the thermal hysteresis effect of the phase transition between the cholesteric phase and the blue phase (BP). The attenuation is due to various scattering losses in different phases. Both cholesteric and BPs can exist stably at room temperature (RT) and can also be switched to each other using temperature-control processes. The transmission spectrum and the intensity of the guided light can be controlled with various extents of scattering loss. For optical communications, this device can be manipulated over a loss difference of 10 dB at RT and insensitive to the polarization of light.

We report on the physics, design, characterization, and demonstration of five viable techniques for switchable retroreflectors, including integrated electrowetting scattering, integrated and external electrowetting light valves, external liquid crystal light valve, and external liquid crystal scattering. All techniques were evaluated for use in conspicuity applications spanning wavelengths in the visible and IR (night vision). Achieved performance includes high optical efficiencies up to nearly 30% (out of a maximum 35%), visibly fast switching speeds of

The optical masks prepared by using a LCLV liquid-crystal light valve are first proposed for light-induced photorefractive waveguides in photorefractive materials. Employing this technique, various waveguide structures can be fabricated, e.g., Y- or multiple-branches waveguides, fiber-like waveguides, and Mach–Zehnder-like switches, and even whole optical circuits may be formed. A Y-branches waveguide and a fiber-like waveguide were demonstrated in a LiNbO3:Fe crystal. Several technical problems, such as intensities, resolutions, writing speed, and so on, were also discussed in detail. Using a LCLV with a fast response and a writing beam with a high intensity, the waveguide structures may be changed in real time.

We present an all-optical three-dimensional integral imaging projector. An optically addressed spatial-light modulator is used, which potentially provides better image resolution than the conventional CCD and liquid-crystal display pair. We present experimental results using a liquid-crystal light valve.

The photoexcitation transport and the reversible photochemical reaction in Langmuir-Blodgett film is studied and shows its applicability to an optical parallel processor. The excitation transport is switched depending on UV or visible irradiation, which controls the photochromic reaction. The performance of this photochromic Langmuir-Blodgett multilayer is 10(12) NOT operations s(-1) and is comparable with other types of optical processors, such as a liquid-crystal light valve.

We report an optically controlled Fabry-Perot interferometer which uses a liquid crystal light valve (LCLV) for one of the mirrors. The light valve rotates the plane of polarization for light incident on its read side through an angle dependent on the intensity of a write beam incident on its other side. The Fabry-Perot interferometer is constructed using a polarizing cube beam-splitter and a second mirror. The finesse of this Fabry-Perot varies sharply with the rotation angle introduced by the LCLV. The dependence of this rotation angle on the incident write beam intensity varies with the frequency of the voltage applied to the LCLV, the bias voltage, and the orientation angle of the LCLV. Experimental performance is examined using a single mode He-Ne laser beam and compares well with theoretical predictions: This device has potential uses in optical computing and optical neural networks.

Thin metallized viscoelastic layers, addressed by an active matrix of MOSFET(s) and used in a schlierenoptical 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.

Effects of MTF limitations of projecting lenses are investigated. A theory of optical imaging is summed up for adjusted calculations. Imaging by the lens system in a special schlieren-optical arrangement of a color TV projector is simulated by spatial frequency filtering. A sinus modulation of carrier gratings is written into the control layer of a single light valve. The dark field image of this phase object is considered as an example of signals to be transmitted. A modification of the power spectrum of the object intensity is proposed to estimate the influence of an optical arrangement to be designed for a high-definition TV projector. Test functions in the spatial frequency plane shaped to an experimental MTF curve are used for calculations. The demands on the projection lenses are found to be independent of the chosen carrier gratings. The effect of wave aberration on signal transmittance is outlined.

Various real-time optical data processing experimentst using the photo-DKDP spatial light modulator are described. These include the performance of image subtraction and contrast reversal directly on the light valve and their application to practical pattern recognition situations in which the input and reference objects differ. Examples of real-time optical correlation on coded waveforms for signal processing are presented, and the accuracy of the optically produced ambiguity function outputs are compared to the theoretically expected ones. Real-time optical image pattern recognition experiments are also presented, together with comparative data obtained with off-line correlations performed using film.

A new television projection system is described. The heart of this light valve is a deformable reflective target consisting of a thin (~2000–6000 A)metal film supported in close proximity to a glass substrate. In operation a video-modulated electron beam scans the target and deforms the metal film analogously to the intensity of the video signal. These deformations control the amount of light from the schlieren projector that falls on the screen. The mechanical and electrical performance of the deformable targets and operation of a specially designed off-axis, reflective schlieren projector are discussed. Display results for the total system are presented.