| 摘要 |
PURPOSE:To reduce flickers by obtaining the same flicker waveform in every cycle by synchronizing the field frequency of TV at cycles (n) types flickers under illumination conditions, and by applying it to an AGC circuit control terminal. CONSTITUTION:When an illumination light source is of 50Hz, photoelectric element 10 detects fluctuations of the quantity of light of 100Hz and through BPF14, only a component of 100Hz is extracted. Output 4b of BPF14 is multiplied by six by PLL circuit 15 and 1/6 frequency divider 16 and frequency-divided by 1/10 frequency divider 17 to 60Hz, but the output of frequency divider 16 is frequency-divided by 1/10 frequency divider 18 as reference frequency division to generate reset pulse 7b' for resetting. Next, 1/3 frequency divider 19 frequency-divides 60Hz signal 8b on the basis of signal 7b'. Then, output signal 9b of frequency divider 19 is a control voltage for AGC circuit 4. This circuit 4 increases the amplification factor as the control voltage rises, reducing flickers greatly. |
