等离子体显示技术的进展

概述了等离子体显示技术的研究进展,着重讨论了彩色等离子体显示中在提高发光效率和亮度、提高对比度等方面的最新技术。     

Fast polarization switching panel with high brightness and contrast ratio for three-dimensional display

We propose a polarization switching device using optically compensated pi cell for polarization-glass-type three-dimensional display. This device shows good optical properties such as high transmittance and low cross-talk ratio because of its fast dynamic response characteristics. To improve the brightness and contrast ratio on the right- and left-hand sides, we attach optical retardation films on each side of the polarization glasses instead of attaching the films on the polarization switching panel. From the calculation and experiment, we obtain high contrast ratios, over 200:1, on both sides and a high brightness using only one film on each side.     

Reflective liquid-crystal displays with asymmetric incident and exit angles

The 2 x 2 matrix methods are extended to calculate the optical behaviors of reflective liquid-crystal displays with asymmetric incident and exit angles. Both the unfolding method and the backward-eigenwave method are employed to derive the 2 x 2 matrix representations. The simulation results for symmetric incident and exit angles from these two methods are identical and agree well with those obtained from the 4 x 4 matrix method when the air-panel surface reflections are neglected. Further, the derived 2 x 2 matrix methods are applied to the asymmetric cases with different incident and exit angles. The simulated results on the normally black vertical alignment and normally white mixed-mode twisted nematic reflective displays show reasonably good agreement with the reported experimental data. In addition, a rubbing effect related to contrast values is observed and analyzed in asymmetric reflective cases. We also find that this effect has a significant influence on the contrast ratios once the difference between the incident and exit angles becomes large.     

Spatial light modulators for high-brightness projection displays

We fabricated polymer-dispersed liquid-crystal light valves (PDLCLV's) consisting of a 30-mum-thick hydrogenated amorphous-silicon film and a 10-mum-thick polymer-dispersed liquid-crystal (PDLC) film composed of nematic liquid-crystal (LC) microdroplets surrounded by polymer. The device can modulate high-power reading light, because the PDLC becomes transparent or opalescent independent of the polarization state of the reading light when either sufficient or no writing light is incident on the PDLCLV. This device has a limiting resolution of 50 lp/mm (lp indicates line pairs), a reading light efficiency of 60%, a ratio of intensity of light incident on the PDLC layer to intensity of light radiated from the layer, and an extinction ratio of 130:1. The optically addressed video projection system with three PDLCLV's, LC panels of 1048 x 480 pixels as input image sources, a 1-kW Xe lamp, and a schlieren optical system projected television (TV) pictures of 600 and 450 TV lines in the horizontal and the vertical directions on a screen with a diagonal length of 100 in. The total output flux of this system was 1500 lm.     

Microscopic three-dimensional topometry with ferroelectric liquid-crystal-on-silicon displays

When three dimensional measurements are conducted with fringe projection, the quality of the grating used for the generation of the fringes is important. It has a direct influence on the achievable depth resolution in a given measurement setup. In the past, Ronchi grating or gratings written in nematic liquid-crystal displays or in digital micromirror devices have been used. We report on the application of a reflective ferroelectric liquid-crystal-on-silicon display as the fringe-generating element in a setup based on a stereo microscope. With this device the depth resolution of measurements by use of phase-shifting algorithms can be significantly improved compared with the application of a Ronchi grating or a nematic liquid-crystal display.     

High-efficiency, liquid-crystal-based, controllable diffraction grating

We propose a new reflective liquid-crystal diffraction grating design attained by combining the use of a polymer wall to reduce the detrimental effect of the fringing electric field in a high-resolution grating and a quarter-wave plate to make the device polarization independent. This design could offer significant performance advantages in a projection display system. Results of calculations are compared with experimental data.     

Time-multiplexed three-dimensional displays based on directional backlights with fast-switching liquid-crystal displays

An autostereoscopic display using a directional backlight with a fast-switching liquid-crystal (LC) display was designed and fabricated to obtain a better perception of 3D images by enhanced resolution and brightness. A grooved light guide in combination with an asymmetric focusing foil was utilized to redirect the emitting cones of light to the left and right eyes, respectively. By designing the groove structures of the focusing foil with rotation from -1.5 degrees to 1.5 degrees in the gradient and having the pitch ratio of the grooved light guide to the focusing foil of less than 3, the boundary angle then shifts from normal viewing and the moiré phenomenon can be suppressed. Cross talk of less than 6% and a LC response time of faster than 7.1 ms further improve the stereoscopic image perception. Additionally, 2D-3D compatibility is provided.     

等离子体显示器件中氧化镁膜的制备和测试

等离子体显示器（PDP）是最有发展前景的新一代显示器件，MgO膜是其制造工艺中的一个瓶颈。本文结合PDP的发展，综述了近年来MgO膜层镀制与测试工艺的进展，讨论了PDP对保护膜性能的要求。PDP市场的进一步扩大亟需在生产上建立一个能取得共识的对MgO膜层性能进行评价的标准。     

Polarization-modulated differential-interference contrast microscopy with a variable retarder

A liquid-crystal variable retarder inserted into a differential-interference contrast video microscope switches image highlights into shadows and vice versa in alternate frames. Synchronous computation and display of the difference between alternate frames yield a stream of images with doubled contrast and reduced fixed-position noise because of the automatic background subtraction. The measured signal-to-noise ratio (SNR) peaks when the modulation +/- Gamma of the retarder equals the phase shift delta of the sample. A Jones calculus model of the central ray in the polarization-modulated differential-interference contrast microscope yields SNR = (sin Gamma sin delta)/((1 - cos Gamma cos delta)N), where N is the rms time-dependent photon noise. This expression fits the experiments closely for 1.8 degrees < or = Gamma < or = 115 degrees.     

Profile measurement taken with liquid-crystal gratings

Profile measurement taken with liquid-crystal gratings and a phase-shifting technique is proposed, and its effectiveness is verified by experiment. The surface profile is obtained by measurement of the phase distributions of the sinusoidal gratings deformed by an object's surface. The liquid-crystal grating gives an accurate phase shift, an arbitrary projection pitch, and a constant surface brightness compared with conventional gratings such as a laser interference fringe grating and a Ronchi grating. Therefore a flexible measuring system may be developed with it. Two gratings with different pitches are used to measure an object with large steps. A two-color projection system can be used to produce such gratings simultaneously. Locally varying reflectivity on a surface can also be compensated by adjustment of the color component of the projected grating with a liquid-crystal grating. Thus the contrast in the projected grating can be made uniform, and a good profile measurement can be accomplished.     

Measurement of valence band structure in arbitrary dielectric films

A new way of measuring the band structure of various dielectric materials using the secondary electron emission from Auger neutralization of ions is introduced. The first example of this measurement scheme is the magnesium oxide (MgO) films with respect to the application of the films in the display industries. The density of state in the valence bands of MgO film and MgO film with a functional layer (FL) deposited over a dielectric surface reveals that the density peak of film with a FL is considerably less than that of film, thereby indicating a better performance of MgO film with functional layer in display devices. The second example of the measurement is the boron-zinc oxide (BZO) films with respect to the application of the films to the development of solar cells. The measurement of density of state in BZO film suggests that a high concentration of boron impurity in BZO films may enhance the transition of electrons and holes through the band gap from the valence to the conduction band in zinc oxide crystals; thereby improving the conductivity of the film. Secondary electron emission by the Auger neutralization of ions is highly instrumental for the determination of the density of states in the valence band of dielectric materials.     

Speckle-noise reduction on kinoform reconstruction using a phase-only spatial light modulator

Random-phase distributions that are statistically independent individually are used for computing kinoforms. These uncorrelated kinoforms are recorded and read out sequentially by a phase-only liquid-crystal spatial light modulator, and reconstructed images with well-developed speckles are added. The fidelity of the resultant image to an original is improved as the number of additions increases. The dependence of the speckle contrast on the initial random phase and the influence of the liquid-crystal spatial light modulator's display performance on the image quality are discussed.     

(2 0 0)-Texture and microstructure of MgO films by rf-magnetron sputtering in Ar plus N2 atmosphere

Intensity of the (2 0 0) peak in the X-ray diffraction pattern of the MgO film increases as N₂ is added to Ar gas during MgO deposition. The optimum flow rate ratio of N₂ to Ar in order to obtain maximum intensity of the MgO (2 0 0) peak is 2:5. As introducing N₂ gas, no residual nitrogen atoms are found in the MgO films, which are confirmed by AES and ESCA analysis. On the other hand, the TEM dark field image shows that the average grain size of MgO film increases with increasing the flow rate ratio of N₂ to Ar. This is due to that the deposition rate of MgO film is decreased with increasing the flow rate ratio of N₂ to Ar.     

Effect of CaO addition on the firing voltage of MgO films in AC plasma display panels

In order to improve both operating voltage and memory coefficient of a protective layer for AC plasma display panels, controlled amount of alkaline earth oxide (CaO) was added to the pure MgO to replace the conventional pure MgO protective layer. The effects of CaO addition on both the electrical properties (V_f and V_s) and the microstructure of the Mg_1−xCa_xO thin films deposited on slide glass substrates by e-beam evaporation were investigated. Distinct changes in both peak intensity and diffraction peak positions of Mg–Ca–O films were observed with increasing [CaO/(MgO+CaO)] ratio owing to the strong atomic interaction between Mg and Ca. When the [CaO/(MgO+CaO)] ratio was increased to 0.1, the intensities of both (111) and (200) peaks were observed to increase with corresponding peak shift to lower diffraction peak positions as a result of the strong interdiffusion from the Ca and Mg atomic interactions. When the [CaO/(MgO+CaO)] ratio of 0.1 was used, the deposited films exhibited an enhanced operating performance with an improved memory coefficient. By adding a controlled amount of CaO, the deposited Mg–Ca–O films showed a firing voltage of 176 V that is lower than that of the conventional 100% MgO film.     

Image Upconversion from the Visible to the UV Domain: Application to Dynamic UV Microstereolithography

We present what to our knowledge is a new application of optical frequency upconversion of images in quadratic materials to dynamic UV microstereolithography. A 150 x 150 point visible image transmitted by a liquid-crystal display was upconverted in a lithium triborate crystal, and the UV image was successfully used to polymerize a commercial stereolithographic resin.     

Hadamard transforms of images by use of inexpensive liquid-crystal spatial light modulators

Incoherent light imaging by Hadamard transformations by use of an inexpensive spatial light modulator from a liquid-crystal display television is demonstrated. The transforms are implemented by means of S matrices. Good-fidelity 31 x 33 pixel images are obtained. The image distortions caused by the limitations of the spatial light modulator are discussed.     

Viewing angle of liquid-crystal displays: representation on the Poincaré sphere

Using the extended Jones calculus for oblique incidence, we have succeeded in representing light propagation through birefringent media on the Poincaré sphere for arbitrary propagation directions. The situation is far more complicated than for the case of perpendicular transmission. To achieve a simple representation method we had to define appropriate conventions. One can use the method to evaluate the efficiency of existing viewing-angle compensation foils. The Poincaré sphere turns out to be a valid geometrical method for the design of new compensation foils that optimize the contrast ratio. The different parameters of a homogeneous compensation foil that is applied to a liquid-crystal display to improve the viewing-angle properties can be systematically determined.     

Computer-generated holograms with optimum bandwidths obtained with twisted-nematic liquid-crystal displays

We discuss a computer-generated hologram for encoding arbitrary complex modulation based on a commercial twisted-nematic liquid-crystal display. This hologram is implemented with the constrained complex modulation provided by the display in a phase-mostly configuration. The hologram structure and transmittance are determined to obtain on-axis signal reconstruction, maximum bandwidth, optimum efficiency, and high signal-to-noise ratio. We employed the proposed holographic code for the experimental synthesis of first-order Bessel beams.     

High efficiency pocket-size projector with a compact projection lens and a light emitting diode-based light source system

We present a light emitting diode (LED)-based ultramini digital micromirror device projector with a size of 75 mm x 67 mm x 42 mm and a weight of 338 g. The LED illuminator inside this projector makes it possible to achieve a volume of 18 cm(3) by using a dichroic filter and a collimating lens. The illumination system consists of high uniformity of 93% through a microlens array as a homogenizer. A total internal reflection prism is also used to reduce the size of both the illumination system and the telecentric projection lens. A projection lens system with an ultrasmall track of 42 mm, including a high modulation transfer function value of 0.4 at 46.2 line pairs/mm, an optical distortion of only 0.25 %, and a television distortion of 0.01%, is designed. Through the above superior specification, we can produce a 20 in. (51 cm) color display comparable in brightness to a laptop with a contrast of 3700:1. The device is compact and suitable for personal use.