| 摘要 |
PURPOSE:To attain the automatic control of the photodetecting level at an approximately fixed value regardless of the brightness on the surface of an original, by controlling the timing cycle to read the detection signal out of a 1-dimensional or 2-dimentional array of storage-type photodetecting elements in response to the brightness on the original surface. CONSTITUTION:A shift register 17 functions to control the output timing of the detection signal of a photodetecting element array 5b and is shifted by the timing of the clock pulse CP delivered from a VCO 18 to deliver the output signal from the corresponding element of the array 5b. Then the natural light L1 is made incident on a luminous intensity sensor 3 consisting of a phototransistor PTO and therefore the voltage VO is produced at the terminal of a resistance RO in response to the quantity of the light L1. The VO is increased as the light quantity is increased and the originating frequency of the VCO 18 is increased with the cycle of the pulse CP shortened respectively. Thus the shifting time interval of the register 17 is shortened. Then the voltage VO is reduced when the luminous intensity is reduced. Thus the originating frequency of the VCO 18 is reduced and the register 17 is shifted at a long time interval.
|
