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Masaru KANAZAWA,
Senior Research Engineer,
Three-Dimensional Audio-Visual Systems |
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As a candidate for future broadcasting services, the Science & Technical Research Laboratories has been studying an ultrahigh-definition image system, which will become a medium supplying wide-view/large-display images with a definition equivalent to that of gravure printing. To establish a standard for ultrahigh-definition images, it was necessary to clarify various system requirements. To that end, we constructed an image system with 4000 scanning lines, which is four times the number of Hi-Vision (HDTV).
Regarding human visual characteristics, past studies reported that the sensation of reality constantly increases in correspondence to the visual field angle from which a viewer watches a screen, saturating at approximately 100 degrees of visual field angle. To have a pixel structure invisible to the human eye, one degree of visual field angle requires 60 pixels. This value corresponds to a standard HDTV screen viewing distance of 3H (H: height of display). The horizontal visual field angle expands to approximately 100 degrees when HDTV screens are arrayed in a four by four arrangement, for a total of 16 screens, while maintaining the viewing distance. This value corresponds to the visual field angle at the sensation of reality saturation point, with a viewing distance of 0.75H. These conditions have led to the choice of an image display system with 4000 scanning lines.
Realization of a 4000-scanning-line display system requires
a display device with approximately 32 million pixels (approx.
4000 8000
pixels). However, a display device that can present an image
with such a large number of pixels has yet to be developed.
For this reason, we fabricated the display system with a four
CCD panel color scheme (2 green CCDs, 1 each for red and green)
using 8-million pixel liquid crystal devices (the maximum
number currently available).
This system has the following characteristics:
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It produces an ultrahigh definition level with a smaller number of devices by considering human visual characteristics. |
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Composition compliance with a 4000-scanning-line camera system makes direct display of a camera image feasible. |
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Figure 1: Projector's external appearance and optical system block chart
(Upper: for RB, Lower: for G) |
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Figure 2: Display in the laboratory
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Figure 1 shows the external appearance of a recently fabricated
projector and a block chart for its optical system. Since
installing four CCDs in a single unit requires complicated
optical system engineering, we employed two units (lower system
for green light, upper for red and blue light) in the system.
We also constructed a convergence correction system that positions
the light from the two projectors on the screen. Combining
these systems to present a 4000-scanning-line image on a 320-inch
screen (approx. 4 m (H)7
m (W)) attains a horizontal visual field angle of 110 degrees
at 3 m from the display. The luminance on the screen is 50
cd/m2, which is a level equivalent to that of a movie theatre.
Figure 2 shows a display example.
Through a study of the psychological effects on a viewer from wide-view/ultrahigh-definition images using this display system, we are going to examine parameters such as the resolution required for future broadcasting conveying a heightened sensation of reality. We will also enhance the picture quality by developing the highly accurate equipment control functions required to present ultrahigh-definition images. |
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2002/10
