| 摘要 |
PURPOSE:To make a focusing decision stably with a little malfunction again noises by detecting the difference between the output of one of integration devices and a mean value when the mean value of integration outputs of the output signal of a photodetecting device reaches a specific value, and obtaining a focus detection signal from the difference signal. CONSTITUTION:Outputs Va and Vb of two integration circuits 30 of signal processing circuits 23 and 24 are supplied to an adder 40, which outputs the output means value (Va+Vb)/2. A step signal ST is applied from a logic circuit 45 to a charging circuit 43 to which the mean value is inputted and the voltage obtained by adding the step signal to the voltage (Va+Vb)/2 stepwise is supplied to the negative input terminal of a comparator 46. This comparator 46 has two positive input terminals and receive the integration outputs Va and Vb. The output Va or Vb can be compared with the (Va+Vb)/2 stages of voltages, and consequently the potential difference between the integration outputs Va and Vb can be measured. For the purpose, a clock signal CLK, a mode signal MODE, and a gain signal GAIN are sent to the circuit 45 from a microcomputer 49 and the circuit 45 makes transition among four modes in one distance measurement period to detect focusing.
|
