| 摘要 |
PURPOSE:To substantially prevent the exertion of adverse influence on a secondary image by setting the inclination of a pair of concave mirrors in the relation with the max. diameter R thereof in such a manner that the incident angles (radian) of the ray from the center of a primary image detecting region on the centers of the concave mirrors attain respectively about <=sq. rt. 0.04/R (R is the max. diameter of the concave mirrors). CONSTITUTION:The angles of inclination of the respective concave mirrors are so determined that the incident angles (radian units) of the light source from the center of the prescribed detecting region on the centers of the respective concave mirrors attain both about <=sq. rt. 0.04/R (R is the max. diameter of the concave mirrors and the unit thereof is mm). The inclinations and the max. diameters of the concave mirrors are so set that the deviating angles 2psi when, for example, the luminous fluxes are made incident on the center of the concave mirrors and the max. diameter Rm of the concave mirrors satisfy equation I. The astigmatism which is significantly affected by the inclination of the concave mirrors is sufficiently suppressed in this way and the focus detection with high accuracy is enabled. |
