| 摘要 |
PURPOSE:To always stabilize the white balance, by varying the DC level of a color difference signal after an integration of the output of a comparator in order to ensure the automatic follow-up of a control shift to the change with time. CONSTITUTION:The white balance can always be kept stably by selecting small offset of a comparator 9 with increased loop gain. The white balance is stable even if the loop is opened as long as the output of an integrator 10 is stored by a storing circuit 11. Both a beam current and the light emitting intensity are usually are unstable owing to the unsteady efficiency of light emission of a fluorescent matter. In this connection, a fine adjustment is secured with each color for the offset of the comparator 9 in response to the variance of cathode- ray tubes. Thus the white balance free from a change with time is obtained. Then an extremely small amount of beam current flown in a blanking period may sometimes affect the watching capability to normal pictures. Therefore the circuit 11 stores the output of the integrator 10 which is obtained when the loop is steady. Thereafter the pulse is cut off to cut the loop. Thus the white balance can be kept. |
