公开(公告)号：US4170025A

公开(公告)日：1979-10-02

申请号：US913187

申请日：1978-06-06

申请人： Fred G. Benkley ,  Gerhard O. Sauermann

发明人： Fred G. Benkley ,  Gerhard O. Sauermann

IPC分类号： H04N17/00 ,  H04N7/02

CPC分类号： H04N17/00

摘要： A low contrast measurement apparatus for electronically measuring video signal modulation under low contrast scene conditions. The measurement apparatus utilizes a low contrast periodic optical bar chart in conjunction with a filter-integrator processor to measure very low contrast ratios.The filter-integrator processor contains a filter which is tuned to the corresponding fundamental frequency of the bar chart, thereby reducing the noise bandwidth and consequently improving the signal-to-noise ratio. The filtered signal is integrated over one whole picture frame which results in an improved signal to noise ratio. The integrated output of the filtered video signal constitutes a linearly increasing ramp with a period equal to the frame time and whose height is proportional to the amplitude of the periodic signal.