Search

We have developed a projector which can display high-resolution images of Super Hi-Vision (7680 x 4320pixels) and has a high dynamic range of 1.1 million to 1. This projector features a serial combination of two modulation blocks: the first for chrominance and the second for luminance. While a conventional projector has one modulation block that contains three devices to modulate red, green, and blue light, our projector has another modulation block that contains a device for luminance to further modulate the combined RGB modulated light. We measured some characteristics of the projector, which are modulation transfer function, dynamic range, and tone reproduction. We found that the projector can resolve Super Hi-Vision images and that it has an extremely high dynamic range and a fine 12-bit tone reproduction. We did two types of subjective evaluations with the projector to research the effect of the resolution of the chrominance component and that of the limited dynamic range of the display on the total image quality. The results of the first evaluation indicate viewers do not notice the image degradation when the resolution of the chrominance component is degraded to a half of that of the luminance component. The results of the second evaluation indicate the dynamic range of at least 1000:1 is necessary for displaying natural images and the dynamic range of about 30000:1 is necessary for displaying special images which have low average picture levels.

We have developed an extremely high-resolution display (Super Hi-Vision display) system that has quadruple the amount of the horizontal and vertical resolution of HDTV. The extremely high-resolution display consists of two LCD projectors, for green and another for red and blue, so convergence errors between green and red/blue images exist on the screen. We introduce a method for automatically adjusting the convergence that detects convergence errors by displaying mountain-like patterns using a digital-camera. The projector for green images has a resolution equivalent to 7680×4320 pixels with a spatial pixel-offset method using two 3840×2160 LCD panels. In this case, two green panels must be located at an exact spatial offset of 0.5 pixel. We developed a method for detecting a misalignment of spatial offset by using two sine-wave patterns with different phases.

We studied the synergism of resolution and gray-scale levels in image recognition in relation to the precise phase detection in vernier acuity. Humans who have a 1.0 visual acuity candetect 1.0 minute-size (1/60 degree) objects. Video systems are designed based on this data. On the other hand, it has been reported that human can detect an approximately 2.0-second (2/60/60 degree) phase shifts. We found that precise position detection is possible with a low resolution detector if the number of gray-scale levels is sufficient. We applied this principle to the position adjustment on a multi-screen display system.

Modulation transfer function (MTF) quantitatively describes a display' s resolution characteristics. It involves two measurement methods : the impulse method and the sinusoidal method. The authors compared the two methods and showed that the sinusoidal method is the best of the two because the video circuit characteristics are involved in the results. The MTF measurement method for moving images is also investigated.

This paper describes an investigation results of optimum screen size and viewing distance (angle) for viewing ultra high-definition and wide-screen television (UDW), and the psychological effects of UDW images. First, it is found that a shorter relative viewing distance is preferable to that of the HDTV system and that the preferred viewing distance for UDW images depends not on relative figures using the image height, but instead screen size. Second, it is found that the preferred viewing angles coincide with the positions where the maximum combined effects of “potency” and “comfortableness” are obtained, and that, compared with the HDTV system, UDW images, when viewed at the preferred viewing angles, can give much higher level of emotional feeling with regard to both “potency” and “comfortableness”.

The effectiveness of using a PLUGE (picture line-up generating equipment) signal to improve a display's grayscale reproduction under ambient illumination was investigated using two new metrics. Experimental results showed that adjusting a display's brightness with a PLUGE signal enables more precise adjustment than with a general image. A metric for the volume of reproducible color space was used to describe the area that a display can reproduce in the color space. A metric for the color reproduction reduction rate was used to describe how gray-scale reproduction deteriorates under ambient illumination. The values obtained for these metrics showed that adjusting the brightness with a PLUGE signal improves grayscale reproduction.

We have produced digital pictures to be used in subjective assessments of HDTV picture quality.A drum scanner is used as the input device, to assure useful quality for the assessments, and a series of signal processes are performed by computer. Some technical factors, such as resolution, aliasing, color reproduction, gray scale characteristics and precision of quantization are taken into account in producing the digital pictures.To reduce the alias component, 16-times over-sampling is employed and sub-sampling with filtering is performed by computer. Gray scale characteristics are corrected by polynomial approximation, and color reproduction is compensated for by linear matrixing. After signal processing, precision of quantization becomes equivalent to that of the 10-bit linear quantization applied to the gamma pre-corrected video signal.

A 50-inch diagonal rear-projection display for HDTV has been developed. The resolution on the screen is more than 1000 TV lines, and the contrast ratio is improved by the optical coupling between the CRTs and the projection lenses. The display contains two mirrors in order to make the depth of the display smaller. One of the mirrors contains three photodiodes in order to allow the detection of the convergence error that occurs on the screen. Examining the outputs of the photodiodes, a CPU, located within the display, can detect and correct the convergence error.