Construction and electro-optic properties of liquid-crystal display doped by rhodium nanoparticles

We prepared 4'-pentylbiphenyl-4-carbonitrile (5CB)-stabilized rhodium (5CB-Rh) nanoparticles and poly(cyclodextrin) (PCyD)-stabilized rhodium (PCyD-Rh) nanoparticles. The average diameter of Rh nanoparticles stabilized by 5CB, PalphaCyD, PbetaCyD, and PgammaCyD are 1.2, 5.4, 6.8, and 5.2 nm, respectively. The nanoparticles were dispersed in liquid crystal 5CB to construct novel twisted nematic liquid crystal device (TN-LCD). Voltage holding ratio was measured for TN-LCD fabricated by doping PbetaCyD-Rh nanoparticles. The decrement of the voltage was very much reduced for that doped with PbetaCyD-Rh. The response time of this TN-LCD in the presence of PbetaCyD-Rh nanoparticles was faster than that in the absence.     

Optimizing the constant-channel chromaticity and color gamut of CRT color displays by control of brightness and contrast levels

Before a CRT color display is calibrated, the levels of the brightness and contrast controls should be considered. These levels have different effects on the relationship between the chromaticity coordinates of the red-green-blue (RGB) channels and the voltage applied to the gun as well as on the color gamut. Using three different CRT color displays, we measured both these relationships as well as the color gamut for different combinations of brightness and contrast levels. With respect to the luminance range of the white point provided by each display, the results show that the assumption of constant-channel chromaticity of the RGB channels is more valid at medium- to low-brightness levels in combination with high-contrast levels. In addition, this assumption holds at high contrast and medium- to low-brightness levels, the color gamut being optimized at these combinations of levels, with regard to the size of the triangle of primaries-the maximum luminance of the display white point.     

Unique measurement of the parameters of a twisted-nematic liquid-crystal display

The parameters of a twisted-nematic liquid-crystal display (TN-LCD) are measured with no ambiguity when we measure the intensity transmittance of a system that simply consists of a TN-LCD, two polarizers, a quarter-wave plate, and a monochromatic beam. First we show analytically that the director angle can have a 90 degree ambiguity and the twist angle of the liquid-crystal molecules a 180 degree ambiguity. Then we uniquely measure the parameters by fitting the theoretical predictions to the intensity transmittance measured with and without the quarter-wave plate and by using the quasi local-adiabatic condition. The birefringence of the TN-LCD is measured next as a function of the applied voltage. We design a phase spatial light modulator by using the measured parameters and measure the phase delay of the output beam to excellent agreement with the theoretical prediction.     

Adaptive correction to the speckle correlation fringes by using a twisted-nematic liquid-crystal display

An innovative technique for reducing speckle noise and improving the intensity profile of the speckle correlation fringes is presented. The method is based on reducing the range of the modulation intensity values of the speckle interference pattern. After the fringe pattern is corrected adaptively at each pixel, a simple morphological filtering of the fringes is sufficient to obtain smoothed fringes. The concept is presented both analytically and by simulation by using computer-generated speckle patterns. The experimental verification is performed by using an amplitude-only spatial light modulator (SLM) in a conventional electronic speckle pattern interferometry setup. The optical arrangement for tuning a commercially available LCD array for amplitude-only behavior is described. The method of feedback to the LCD SLM to modulate the intensity of the reference beam in order to reduce the modulation intensity values is explained, and the resulting fringe pattern and increase in the signal-to-noise ratio are discussed.     

Self-interferometric technique for visualization of phase patterns encoded onto a liquid-crystal display

We report a new self-interferometric technique for visualizing phase patterns that are encoded onto a phase-only liquid-crystal display (LCD). In our approach, the LCD generates both the desired object beam as well as the reference beam. Normally the phase patterns are encoded with a phase depth of 2pi radians, and all of the incident energy is diffracted into the first-order beam. However, by reducing this phase depth, we can generate an additional zero-order diffracted beam, which acts as the reference beam. We work at distances such that these two patterns spatially interfere, producing an interference pattern that displays the encoded phase pattern. This approach was used recently to display the phase vortices of helical Ince-Gaussian beams. Here we show additional experimental results and analyze the process.     

Shape measurement by use of liquid-crystal display fringe projection with two-step phase shifting

The use of an optical fringe projection method with two-step phase shifting for three-dimensional (3-D) shape measurement of small objects is described. In this method, sinusoidal linear fringes are projected onto an object's surface by a programmable liquid-crystal display (LCD) projector and a long-working-distance microscope (LWDM). The image of the fringe pattern is captured by another LWDM and a CCD camera and processed by a phase-shifting technique. Usually a minimum of three phase-shifted fringe patterns is necessary for extraction of the object shape. In this method, a new algorithm based on a two-step phase-shifting technique produces the 3-D object shape. Unlike in the conventional method, phase unwrapping is performed directly by use of an arccosine function without the need for a wrapped phase map. Hence, shape measurement can be speeded up greatly with this approach. A small coin is evaluated to demonstrate the validity of the proposed measurement method, and the experimental results are compared with those of the four-step phase-shifting method and the conventional mechanical stylus method.     

Fourier series analysis of fractal lenses: theory and experiments with a liquid-crystal display

We report on a Fourier series approach that predicts the focal points and intensities produced by fractal zone plate lenses. This approach allows us to separate the effects of the fractal order from those of the lens aperture. We implement these fractal lenses onto a liquid-crystal display and show experimental verification of our theory.     

Gray characteristics of a color liquid-crystal television in the beam of a He-Ne laser

Systems of coherent optics with cheaper spatial light modulators are discussed. The aim is toward the behavior differences of the color components of a color liquid-crystal television (CLCTV) screen illuminated by a He-Ne laser (633 nm) and white light. Several conclusions have been derived about (1) the summary effects of numerous components, (2) the response of single components, (3) the comparison of conversion from color to gray between laser and white light, and (4) the approach of encoding and addressing a CLCTV.     

Effective contrast of colored stimuli in the mesopic range: a metric for perceived contrast based on achromatic luminance contrast

Little is known about how color signals and cone- and rod-based luminance signals contribute to perceived contrast in the mesopic range. In this study the perceived contrast of colored, mesopic stimuli was matched with that of spatially equivalent achromatic stimuli. The objective was to develop a metric for perceived contrast in the mesopic range in terms of an equivalent achromatic luminance contrast, referred to here as effective contrast. Stimulus photopic luminance contrast, scotopic luminance contrast, and chromatic difference from the background all contributed to effective contrast over the mid-mesopic range, but their contributions were not independent and varied markedly with background luminance. Surprisingly, color made a significant contribution to effective contrast from 10 to approximately 0.003 cd m(-2). A model describing this relationship is introduced (R2 = 0.89) and compared with predictions of mesopic luminance contrast obtained from a number of models proposed as systems of mesopic photometry.     

Improvement of color reproduction in color digital holography by using spectral estimation technique

We propose a color digital holography by using spectral estimation technique to improve the color reproduction of objects. In conventional color digital holography, there is insufficient spectral information in holograms, and the color of the reconstructed images depend on only reflectances at three discrete wavelengths used in the recording of holograms. Therefore the color-composite image of the three reconstructed images is not accurate in color reproduction. However, in our proposed method, the spectral estimation technique was applied, which has been reported in multispectral imaging. According to the spectral estimation technique, the continuous spectrum of object can be estimated and the color reproduction is improved. The effectiveness of the proposed method was confirmed by a numerical simulation and an experiment, and, in the results, the average color differences are decreased from 35.81 to 7.88 and from 43.60 to 25.28, respectively.     

Luminance addition of a stack of multidomain liquid-crystal displays and capability for depth-fused three-dimensional display application

A stack of liquid-crystal displays is expected to reduce visual fatigue caused by a flat-panel three-dimensional (3D) display. We previously developed a compact depth-fused 3D (DFD) display by using a stack of two twisted-nematic (liquid-crystal) LC panels, but its viewing-angle characteristics and color reproducibility were not so good. Therefore recent wide-view LC panels should be used. We report calculated and measured luminance addition characteristics, which are essential for evaluating 3D display characteristics, of a stack of two multidomain LC panels. We found that LC panels with super in-plane switching, patterned vertical alignment, multiple vertical alignment, and continuous pinwheel alignment modes are suitable for DFD display application.     

Effects of luminance and stimulus distance on accommodation and visual resolution.

Measurements of accommodation and visual resolution were obtained at a number of luminance levels and stimulus distances. With reductions in luminance the eye approached a "fixed-focus" condition of accommodation for intermediate distances, resulting in successively larger errors in accommodation for both near and far stimuli. The visual resolution values were initially affected by both the luminance and distance of the stimulus. Subsequent measurements of resolution, following the correction of accommodative errors, were found to be independent of the stimulus distance. The findings are discussed with regard to the problems of "night myopia" and variations in visual resolution with stimulus distance.     

Programmable color tuning of a multiline laser by means of a twisted nematic liquid crystal display

An optical system useful to tune in a controlled way the color of a triline argon krypton (Ar-Kr) laser by means of a twisted nematic liquid crystal display (TNLCD) is presented. The optical setup employs a 4f system and two blazed gratings to first separate and then recombine the spectrum of the light beam. The TNLCD is included in the intermediate focal plane operating in the amplitude modulation mode to control the relative transmission of each spectral line. The resulting color is accurately predicted by using a previously developed physical model of the spectral and voltage dependence of the TNLCD birefringence. By simply changing the gray level image addressed to the display, the Ar-Kr laser is color modulated at a video rate, thus becoming an interesting, reconfigurable, coherent light source for applications such as multicolor holography or color inspection.     

Surface segmentation based on the luminance and color statistics of natural scenes

The luminance and color of surfaces in natural scenes are relatively independent under certain linear transformations, with the luminance of a surface providing little information about the color of that surface, and vice versa. However, differences in luminance between two locations in a natural scene remain strongly associated with differences in color. We used the statistics of the spatiochromatic structure of natural scenes as the priors for a Bayesian model that decides whether or not two points within an image fall on the same surface. This model provides a biologically plausible algorithm for surface segmentation that models observer segmentations well.     

Fabrication of color electronic paper display by using the charged particles

We fabricated a color electronic paper display (EPD) by using the charged particles. The display has 160 (xRGBW) x 480 array of pixels and four inch diagonal viewing area. Color filter technology was applied for coloration of the EPD. The fabrication process was as follows. First, ITO electrodes were patterned on top and bottom substrates. Ribs were formed to define pixels on the bottom substrate, and color filters were deposited on the ITO of top substrate. The charged particles were put into the pixel arrays defined by the ribs. Finally, the top substrate having the color filters was assembled on the bottom substrate. The resolution was 160 (xRGBW) x 480 with 4 x 4 inch area. The color gamut was about 2.49%, and the response time was 0.25 msec at 90 V. The contrast ratio was 2.36. The color EPD successfully demonstrated to display some images.     

Amplitude,phase, and hybrid ternary modulation modes of a twisted-nematic liquid-crystal display at approximately 400 nm

Applicability of a commercial twisted-nematic liquid-crystal display is examined at approximately 400 nm. Different modulation modes predicted by Jones-matrix calculus are experimentally tested. High contrast amplitude modulation with negligible loss, high contrast and low loss hybrid ternary modulation, and 1.5pi continuous phase delay without intensity modulation and with low loss are presented. Simulation results of a 4f holographic system prove the usefulness of the high contrast for amplitude modulation, and the importance of pi phase difference between high transmission white levels in a hybrid ternary modulation.     

Moire fringe reduction by optical filters in integral three-dimensional imaging on a color flat-panel display

We propose a method to reduce the color moire fringes that are attributable to the structure of a color flat-panel display in integral three-dimensional imaging. The method uses two types of optical low-pass filter, diffuser and defocus. The effectiveness of the method was confirmed in an experiment. We describe a way to design these filters with moire's residual energy and video signal energy as indices and demonstrate the validity of the model, which combines two filters to reduce moire fringes.