| 摘要 |
A contrast control circuit (54) develops a video gain control signal for continuously varying the video gain of a video signal to adjust the contrast of the video signal and limit beam current. The contrast control circuit may comprise an auto contrast control (24) responsive to video signal peaks, a contrast limiter (70) responsive to a beam current control signal related to average picture intensity and a manual control (20). A brightness modulator (72) is also responsive to the contrast control signal for continuously adjusting the brightness of the video signal inversely with the contrast. The brightness modulation is especially useful as part of a pix-in-pix video control circuit, further comprising video sources (30, 32) for first and second video signals and a selector (34) for alternatively feeding the first and second video signals to a video amplifier (52) to form a primary picture with an inset secondary picture. |
