| 摘要 |
PURPOSE:To achieve direct photometry and to obtain an optical low pass filter function by arranging a specific optical filter in an optical path between an image pickup optical system and an image pickup element. CONSTITUTION:The optical filter 10 is arranged in the optical path of an objective light between the image pickup optical system and the image pickup element 9, so as to be perpendicular to an optical axis. In the optical filter 10, the surface 14a of a diffusing plate 14 made of a transparent glass on the side of the image pickup optical system is a flat plane perpendicular to the optical axis and the cross-section on the side of the image pickup element 9 is a sine- curved diffusing surface 14b. The diffusing surface 14b has a metallic thin film 15 which is made of coated silver, etc. a half transmitting and reflecting member and a transparent diffusing plate 16 which is joined to the metallic thin film 15 and is made of acrylic plastic resin, etc. having a reflective index different from the diffusing plate 14. The surface 16a on the side of the image pickup 9 is the flat plane perpendicular to the optical axis. Thus, direct photometry can be achieved, and also a function as an optical low pass filter is obtained. Furthermore, a device is made compact. |
