| 摘要 |
PURPOSE:To attain the focusing even with an object having a constant change of illumination intensity, by providing plural sets of the 1st and 2nd photodiodes of the same area and same form and the 3rd photodiode having a double area and a double side in the array direction and set between the 1st and 2nd photodiodes. CONSTITUTION:The photodetecting area, the form and the sensitivity are equal to each other among (n) units of photodiodes Q1-Qn. These diodes are disposed in a row with a fixed pitch. The continuous four photodiodes Qi, Qi+1, Qi+2 and Qi+3 (i=1, 5, 9...) are put in a set. Then the diodes Qi and Qi+3 and the diodes Qi+1 and Qi+2 are connected in parallel to each other, and the outputs P1+P4 and P2+P3 of these diodes are connected to a difference detecting circuit D1. These outputs are supplied to the diode loads to undergo the logarithmic compression respectively and then converted into absolute values after obtaining the difference. The sum of D1-Dm is obtained by an adder circuit E to obtain a contrast signal. The diode Qi+1 can be unified with the diode Qi+2. |
