| 摘要 |
<p>PURPOSE:To execute the photometry of a photographic field compactly and exactly, and to prevent a blur of a finder system, by constituting so that the image formation luminous flux incident surface of an optical separator using a relief type diffracted structure substance is made a diffusion surface and the optical separator and a focusing plate are formed in one body. CONSTITUTION:A lower surface 4 of an optical separator 6 having a relief type diffracted structure substance 9 is made a mat surface. An image formation luminous flux 1 which has been made incident to the optical separator is partially separated by the diffracted structure substance, a separated light beam 2 is propagated by total reflection in the optical separator, and is led to a photodetecor 8 of SPC, etc. On the other hand, a transmission light beam passes through an eye piece lens and forms an image on the mat surface. When an inclined surface alpha of the diffracted structure substance is decided in accordance with a condition shown in the expression, the separated light beam does not hit against the lower mat surface of the optical separator. Provided that, in the expression, T, (t), L and theta show length of the optical separator, the space between 4 and 9, a maximum distance up to the end of the diffracted structure substance, and an extended half angle of the luminous flux, respectively.</p> |
