| 摘要 |
PURPOSE:To attain rapidly focus detection even if a difference between a pair of integrated outputs is large by gradually increasing the capacity of electrostatic discharge or charge with the passage of time. CONSTITUTION:The whole current (i) is grounded to the ground through a switch 43h during the close of the switch 43h, but when the switch 43h is opened by a step signal ST, the current (i) flows into a current mirror and the equal current value is taken out from a capacitor 43d. Thereby, the voltage of the capacitor 43d is dropped at a drop speed proportional to the integrated value from the (Ve+Vb)/2. When the width of the step signal ST for driving the switch by a transistor 43h is gradually increased, the drop speed is gradually increased and non-linearly changed. Even if the differences between the average value (Va+Vb)/2 and the integrated values Ve, Vb are large, the drop speed of the voltage Vc is gradually increased, so that the difference can be measured within a comparatively short period. |
