信息显示技术课件-03-Transmission principle of TV images.ppt

Characteristics of NTSC system simple system, good compatibility； Because the phase angle of chroma wave corresponds hue information, if the transmission channel of chroma wave causes phase distortion, the reproduction image will have tonal distortion； Because two color difference signals are modulated with two orthogonal carriers, when the characteristics of transmission channel are not good, chromaticity distortion will be produced due to orthogonal cross color. Color television systems Entire signal for monochrome television Shooting and reproducing of color images Basic characteristics of TV image Image size and geometry Contrast ratio and brightness level of image Image color (hue and saturation) Image definition Image continuity (i.e., flicker sense) Choice of scanning parameters Choice of system frequency bandwidth Determination of system gamma correction coefficient Determination of various nonlinear distortion coefficient Determination of phosphor chromaticity coordinates and reference white Determination of color television system Basic parameters of TV images Geometric characteristic of image Standard pattern in the case of good linearity of line, field scanning current Basic parameters of TV images Image distortion caused by deterioration of linearity of line scanning current Image distortion caused by deterioration of linearity of field scanning current Requirements to field scanning frequency no raster flickering, not susceptible to interference, continuous feeling for transmitting activity images, not too wide bandwidth of image signal. Selection of field scanning frequency Influence factors of critical flicker frequency: screen brightness, image content, viewing conditions and afterglow time of phosphors, etc.. In general, to avoid flicker feeling of human eyes caused by raster, field frequency should be higher than 48Hz. With increasing of screen size and brightness, approaching of viewing distance, field frequenc