| 摘要 |
PURPOSE:To easily regulate the assembly of an optical system and to correctly and stably detect a focus by forming an optical member which applies the abration approximate to the coma abration to a light beam with a simple shape. CONSTITUTION:Since an optical path length converting means 14 can change the pattern of a light beam spot on a photo detecting means 16 only by applying optical path length different at every ray constituting the light beams from a picture recording medium 12, the optical path length converting means 14 can be made into a mechanically simple shape. Consequently the optical path length converting means 14 can be arranged in an arrangement relation at comparatively large allowable level in the optical system. Thus the focus detector, which has a stable detecting characteristic, a simple constitution and whose assembly regulation is facilitated, can be obtained. |
