| 摘要 |
PURPOSE:To obtain the threshold level based on the maximum and minimum levels selected properly by the luminance level and then ensure the steady threshold level process for the video signal based on the threshold level obtained above. CONSTITUTION:The pickup signal obtained through pickup device 5 receives the A/D conversion and then stored in shift to two-dimensional picture reproducing circuit 7 consisting of the shift register groups in order to reproduce the two-dimensional picture. Local memory 8 stores the picture element which corresponding to the local area of the two-dimensional picture. Dispersion deciding circuit 9 detects whether the size of the picture element stored in memory 8 has the dispersion under a certain level. And gate 10 is turned on in case the dispersion is under a certain level, and then the picture elements within memory 8 are supplied to maximum and minimum detecting circuits 11 and 12 each. Thus optimum threshold level 15 is obtained through threshold level deciding circuit 13. |
