| 摘要 |
PURPOSE:To enable always correct focus judgement to be done by comparing the outputs of plural photoelectric photo detectors. CONSTITUTION:The luminous flux from an object 101 enters an intended focal plane 107, semi-transparent mirrors 113, 114 by way of the diagonally installed semi-transparent mirror 103 on the optical axis of a lens 100. The reflected and transmitted light of the mirrors 113, 114 enter photoelectric photo detectors 105, 106, 115. The photo detectors 105, 106 are disposed in the positions equivalent to the positions 108, 109 of nearly equidistances before and behind the focal plane 107 with said plane in-between. The photo detector 115 is disposed in the position equivalent to the position 117 behind the position 109. The outputs of the respective photo detectors are made to the specified signals having peaks by processing circuits 110, 116 and these signals are respectively compared in differential amplifiers 112, 118, 119. The detection of the focusing of the image is accomplished by the signal being the result of comparison. |
