| 摘要 |
PURPOSE:To obtain a focus detector capable of measuring so long as a prescribed lightness is available, by judging fucusing in accordance with the sum of output change amts. of photodetectors depending upon forward and backward movement of an objective lens. CONSTITUTION:An image is focused on a diffracting element or an optical element with an objective lens, this image is focused on many photodetectors elements 1a-8a with a focusing lens, and outputs V1-V8 are taken out through electrode plates 1b-8b. The front focus and the rear focus are judged in accordance with the positive or negative sum DELTAVt of output change DELTAV1-DELTAV8 of each element 1a-8a due to the forward and backward movements of the objective lens, and focusing can be detected from the time of DELTAVt=0. Since detection of contrast or phase difference or the like is dispensable, the measurement is made possible so long as a prescribed lightness is available. |
