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A new light valve is described. The device is a cathode-ray tube (CRT) that incorporates a liquid-crystal cell as the electron-beam target. This light valve uses simple "slide projector" optics and has demonstrated initial (nonoptimized) performance of 512 × 512 line resolution and > 50:1 contrast ratio.

The voltage distribution in an electrooptic light-valve structure, consisting of an isotropic dielectric layer and a dielectrically anisotropic longitudinal electrooptic crystal sandwiched between conducting electrodes, has been analyzed in detail for the case where a spatial modulation in the charge density is introduced at the interface. The sensitivity of this sandwich structure is then defined as the reciprocal of the charge density necessary to produce the half-wave voltage across the electrooptic material. Several devices reported in the literature are then compared on a uniform plot of sensitivity versus spatial modulation frequency. The theoretical curves indicate graphically that, though the material characteristics alone determine the high-spatial-frequency sensitivity, the layer thicknesses drastically affect the low-spatial-frequency sensitivity. Since the electrooptic material and the isotropic dielectric material are usually chosen because certain characteristics (photoconductivity, optical perfection, low half-wave voltage, etc.) make them uniquely suited for a particular device, the major additional choice available in the design of the electrooptic light valve is this tradeoff of sensitivity for spatial bandwidth.

Aphotoactivated liquid-crystal projection display device that is based upon the field-effect mode of the liquid crystal has been built and tested. The device displays high-resolution dynamic color symbology by means of the optical birefringence of the liquid crystal. The colors that can be displayed simultaneously are white (with gray scale), blue, green, yellow, and magenta on a dark field. The imaging light power required to excite the device varies from 30-900 µW/cm2at 525 nm and the resolution obtained at an MTF of 50 percent is 40 lines/mm. The basic construction of the device is similar to the dynamic scattering photoactivated liquid-crystal light valve.

A new liquid-crystal phase-grating mode has been found. The grating is formed by the application of a spatially periodic electric field to a uniformly aligned liquid-crystal layer with dielectric and optical anisotropy. The fundamental diffraction characteristics of this liquid-crystal phase grating were measured by using a Schlieren optical system, and analyzed based on Fraunhofer diffraction theory with the assumption that the refractive indices vary periodically in the liquid-crystal layer. The incident light is diffracted under the electric field in particular directions determined by the spatial frequency of the periodic electrode, and the intensity of the diffracted light increases abruptly or gradually above the threshold depending on the cell thickness. The applicability of this liquid-crystal phase grating to a light valve in a projection display system is also considered.

A display system is described which uses a new high sensitivity a(amorphous)-Se-type Ruticon and projects TV-like images from a conventional 9-in diagonal monitor onto a 40 × 40-in screen. The a-Se-type Ruticon requires 200-400-V dc bias, f1.4 lens onto the photoconductor side of the Ruticon. The system uses no mechanical shutters, and image erasure is accomplished with exposure from a flash tube. Readout is performed with a schlieren system using an f2.0 projector lens, and a 360-W tungsten halogen lamp and a high gain screen. The readout optical system is capable of producing a maximum of 8.8 fc and 22:1 contrast ratio. Actual output brightness and contrast ratio in real-time operation are limited by the performance of the light valve. The image-storage characteristic of the Ruticon introduces brightness nonuniformity to the projected image.

A completely sealed-off electron beam-addressed light valve offering high reliability, low thermal impedance, and low-voltage operation is described. It is suitable for projection displays and is capable of producing bright high-contrast images with full gray-scale range and long-term storage. The light valve is contained as the faceplate in an otherwise standard, sealed-off 1½-in diameter vidicon tube and utilizes conventional focusing and deflection components. The target, which is fabricated of refractory materials using high-yield semiconductor-processing techniques, is composed of a dense matrix (500 elements/in) of aluminized silicon-dioxide membranes (~ 3000-A thickness) which are supported centrally on small silicon posts (4-5 µm high) above a transparent sapphire faceplate. These flat, stress-free oxide membranes can be deflected electrostatically (up to 4°) when addressed with the electron beam. Thus an intensity-modulated display of the deposited charge pattern on the "mirror matrix" is produced when this type of light valve is used in conjunction with reflective schlieren optical arrangement, Mechanical and optical considerations have led to a special 4-leaf geometry of the mirror elements, enabling operation at low-voltage levels (175 V) and a high optical gating efficiency (~ 50 percent) to be achieved. Large-screen (2½-by 3½-ft) displays with up to 35-fL highlight brightness ( ×5 screen gain), 15:1 contrast ratio, and 400 TV lines resolution have been demonstrated. In addition, single-frame displays (1/30-s writetime) with full gray scale storage (of many hours) have been achieved. Preliminary studies using higher density mirror matrices (1000 elements/in) show that the display resolution can be extended to 600 TV lines/picture height.

A display device, e.g., projection TV, can be made by scanning, with an electron beam, a large sheet of electrooptic crystal in a light valve configuration. The design equations indicate the following. 1) The transfer function will be reasonably linear. 2) The resolution measured at the crystal will be the order of two TV lines per crystal thickness at 15 percent sine; wave response. 3) The output light spectrum can be nearly white. 4) Writing rates of the order of 10 MHz are feasible with conventional high-resolution CRT electron guns. 5) Large screen image brightnesses of the order of 40 to 50 fL are obtainable with xenon arc lamps and f/l collimator lenses. 6) Image contrast will generally be limited by the polarizer-analyzer quality. The electrooptic crystals must be several hundred millimeters in diameter and several tenths of a millimeter thick. Obtaining such crystals is the most serious obstacle to device construction.

An electrooptic light valve is described, using the Pockels effect in a KD 2 PO 4 crystal cooled close to its Curie temperature and addressed by photoconduction in an amorphous selenium layer. The preliminary performance levels obtained are: resolution 40 lp/mm, maximum contrast ratio 70/1, writing time 10 µs, sensitivity 2 PO 4 plate prevents all loss of coherence in coherent optical data processing. Furthermore, suppression of the zero order in the Fourier transform of an image has been obtained by subtracting from that image a uniform one whose amplitude is equal to the average amplitude of the initial image; this results in the suppression of the optical noise introduced by the scattering of the zero-order term in coherent filtering experiments. Character-recognition experiments are described employing a filter hologram previously made using the same device. The high-speed capability of the device would permit the construction of automatic reading systems at least ten times faster than those generally available.

Recent developments in the solid-state light valve promise a high-quality projection display. The heart of the solid-state light valve is a cathode-ray tube which operates with a modulated and scanning write beam depositing charge on an electrooptic crystal target. The charge pattern on the target causes optical changes which result in modulation of an external light source. The tube incorporates an erase flood gun to control persistence of the display. This paper discusses an unique reflected light configuration with the target operating at reduced temperature and illustrates the resulting image performance. Accomplishments of contracts with Isomet Corporation on crystal targets of KD 2 P (potassium dideuterium phosphate) and with EDO, Ltd., on isomorphs of KDP (potassium dihydrogen phosphate) are included. Work being performed by the National Bureau of Standards on crystal perfection and electrode interaction is also presented. The paper concludes with a brief summary of various applications of the solid-state light valve concept, and a short synopsis of results obtained by others that support our enthusiasm for the device.

A new method of providing artificially well-defined threshold characteristics in the domain switching of ferroelectric-ferroelastic Gd 2 (MoO 4 ) 3 single crystals is presented and experimentally confirmed. The essence of the idea lies in the utilization of a coupling effect between the strain and the polarization which is a characteristic of ferroelectric-ferroelastic crystals. The potential barrier required for electrical switching with a definite threshold is produced by the strain due to locally deposited surface films, which results in strain-induced multidomain regions beneath the films and stabilizes the domain wall at the end of strain-free switching regions. The measured characteristics of the threshold switching elements were as follows; threshold voltage V_{t}=190 V and switching time t_{s} = 0.6 ms at applied full voltage V_{f} = 250 V. These threshold switching elements have potential applications to a ferroelectric light valve array and a ferroelectric memory device.

A multilayer color display device employs two kinds of liquid-crystal films, One is a field-effect nematic liquid crystal; the other comprises a mixture of cholesteric and nematic liquid crystals that have the same function as circular polarizers used in place of crossed polarizers. Three colors (red, green, and blue) can be modulated independently by changing three voltages.