| 摘要 |
PROBLEM TO BE SOLVED: To arrange a focal point detection region at an optional region in the field with a simple structure by providing a mask selectively transmitting the light flux from multiple regions in the field with multiple light transmission sections. SOLUTION: The primary image of an object 14 is formed on a mask 8 by a photographing lens 1. The mask 8 is constituted of a liquid crystal optical element, and only the light flux from the region corresponding to the focal point detection region is selected by the mask 8. When focal point detection is made for a point A on the object 14, for example, the portion of the point A' on the mask 8 corresponding to the point A is made transparent, and the remaining portion is shielded. The light flux passing through the mask 8 is collected by a field lens 9, and the light fluxes passing through the openings 11a-11d of an aperture plate 11 form images on an area sensor 13 by separator lenses 12 a-12d respectively. The outputs of the area sensor are inputted to a microcomputer, and the focal point drift quantity of the photographing lens 1 is calculated. |
