| 摘要 |
PURPOSE:To decide the state of an optical imaging system over a wide defocusing range, and to decrease the probability of a failure in decision by finding output differences between two out of different photodetectors with regard to all combinations, and then performing arithmetic for focus detection. CONSTITUTION:Photocurrents which correspond to the light and shade levels of images are generated by photodetectors S1 - S6, and supplied to logarithmic amplifiers LA1 - LA6, which perform logarithmic compression and amplification respectively. Their outputs are passed through analog switches AS1 - AS10 to obtain 6C2 combinations, which are inputted successively to buffer amplifiers BA1 and BA2. The output of the BA1 is supplied to the inverted input terminal of a differential amplifier DA, and the output of the BA2 and a reference voltage from a reference voltage generating circuit RG are supplied to the uninverted input terminal of the DA. Thus, the arithmetic between output differences between adjacent photodetectors and those between two other photodetectors is carried out. |
