| 摘要 |
PURPOSE:To precisely detect the true life of a photosensitive body by detecting the surface roughness of the photosensitive body from the reflection of light. CONSTITUTION:A surface roughness detecting device 11 composed of a light emitting element 20 which emits light to the surface of a photosensitive body 1 and light receiving element 21 which receives the reflected light of the light emitted from the element 20 from the surface of the photosensitive body 1 is provided opposed to the photosensitive body 1. Then the surface roughness of the photosensitive body 1 which changes with lapse of time is optically detected with the device 11. |
