| 摘要 |
PURPOSE:To detect a focus by a simple constitution, by forming a transmission or reflection image of an image on a diffraction grating, and an image of a spectral component, on the same photodetecting element, and comparing both the outputs. CONSTITUTION:On a diffraction grating 2, an object image is formed by an objective lens 1, and this image is formed on a photodetecting element 4 by an image formation lens 3. On a disk-like member 5 provided on the front of the photodetecting element, the first and second filters 6, 7 for transmitting a light beam of different spectral components are placed. Image positions of these first and second spectral components approach to each other as they approach a focused state, and coincide with each other at the time of focusing. Accordingly, the focused state is detected by separately detecting and comparing the images of the first and second spectral components by an output detecting circuit 8 and a storing and ratio detecting circuit 9 by a rotation of the disk-like member. |
