| 摘要 |
PURPOSE:To detect the reduction of a light beam due to its scattering caused by cracks or other defects of an optical member by detecting the quantity of passing light transmitted or reflected by an optical member. CONSTITUTION:The light beam 4a emitted by a light source 4 is transmitted through the optical member 2. Its transmitted light 4b is detected by a light quantity detector 5. In this case, if the optical member 2 has a crack, the light is scattered at the crack, so the quantity of logical light 14b detected by the light quantity detector 5 decreases. The output of this light quantity detector 5 is compared by a comparator 6 and a decision result is outputted. The same effect can be expected even when the light beam 4a is reflected by the surface of the optical member 2. |
