Toshiyuki Sakamoto

High Quality Digital TV With Frame Store Processing

Though the existing TV standard (NTSC) is a highly sophisticated method to transmit a color television signal without a wide frequency bandwidth, it has some intrinsic problems as follows. (1) Cross-luminance (hanging dots) and cross-color interferences These are caused by the incompleteness of a luminance/ chrominance separation. Hanging dots interference is caused by the cross talk of the chrominance signal into the luminance signal. On the contrary, the cross-color interference is caused by the cross talk of the luminance signal into the chrominance signal. (2) Line flickering and coarse scanning line structure These are caused by interlace scanning. Line flickering is very obvious at the edge where the image changes its brightness in the vertical direction. The coarse scanning line structure can be observed in motion pictures very well because they have only 262.5 scanning lines a field.

A fully digital convergence system for projection TV

A high-precision fully digital convergence system for home-use PTVs (projection televisions) has been developed. The use of digital circuits and the curved-line interpolation technique can reduce the misconvergence to less than 2 mm (it is 4-6 mm in the conventional system). The use of time-division processing in the digital-to-analog converter and the newly developed gate array realizes a low-cost system and reduces the number of variable resistors to 6 (there are 30-45 in a conventional system). The system can handle nonstandard signals reproduced from VCRs, and can also be applied to EDTV, HDTV, and so on. >