[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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A still-picture radio transmission equipment, which is portable and used for remote observation, has been developed. Dither coding of half - tone pictures and progressive transmission of from coarse to fine resolution pictures has been effectively adopted to reduce the equipment memory size and to improve subjective transmission speed through the 2400 bps radio link. In the equipment, bi-level and multi-level dither codings are selectable with 512×512 and 256×256 resolutions, respectively. The 400 MHz radiofrequency band is used and a high-gain receiving antenna permits a lower radio radiation power than the range controlled by regulations.

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In order to clarify the self-sharpening effect on the resolution capability for camera tubes operated on a low-velocity electron beam landing, three major factors, storage capacitance, signal current and scanning line pitch, were investigated experimentally.
The theoretical method established by the author was also applied. It is concluded that theoretical results well agree with the measurements in regard to the following guiding principle for the camera tubes design :
(i) The self-sharpening effect enhances by several tens of percent the resolving power of widely used camera tubes with target storage capacitance of several hundred picofarads.
(ii) The enhancement disappears below a few 10 nA signal current.
(iii) The larger scanning line density results in a more enhanced vertical resolution capability, for example in the HDTV system because on effective vertical beam cross section is reduced due to “beam overlapping” adjacent scanning lines on each other.

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