| 摘要 |
PURPOSE:To always keep a white level of an original to a constant output by tracing an AGC output level after the level increase in the AGC input is consecutive for N picture elements so as to realize the AGC in following to the actual white level. CONSTITUTION:The level increase in the AGC input is compared with a count of an up-down counter 3 by a comparator 2 and an output is given to an N picture element consecution detection circuit 4 from the comparator 2. In giving an output of the comparator 2 to the circuit 4, an up signal is given to the counter 3 from the circuit 4. The count of the counter 3 is incremented by one. Then the AGC input and the count of the counter 3 are compared again. When the count is coincident, since the comparator 2 gives no output, the count of the counter 3 is made stable, and an arithmetic unit 1 calculates the count. Thus, the AGC in following to the actual white level is realized and the white level of an original is always kept to a constant output. |
