| 摘要 |
PURPOSE:To obtain a focusing detector which has no mechanical moving parts and does not require any special photodetector and demultiplexing optical system for focusing detection by comparing the red signal and green signal from a solid state image pickup element and obtaining the focusing signal from the difference therebetween. CONSTITUTION:The R signal and G signal separated by acting a window signal to window circuits 19R, 19G take the average value of the intensity in the image screen and the standardized. These signals are passed through high-pass filters 22R, 22G, detection circuits 24R, 24G, and integrating circuits 28R, 28G by which the quantity of the incident light at the noticed part of the photodetector surface is obtd. The peak value thereof is slightly deviated with VR and VG with respect to the movement of a lens 18 in the optical axis direction. The position where the VR and VG are equal is the focusing stage viewed with white light or extremely approximate thereto and can be discriminated as a whole as the focusing state. The difference between the output VR of the integrating circuit 28R and the output VG of the integrating circuit 28G is, therefore, obtd. by a differential amplifier 30, then the output thereof is an AF signal 32 to indicate whether the focusing state or not and lens moving direction toward the focusing state. |
