Focus detection device and method using a projection pattern material

摘要

A device and a method for focus detection that increases the amount of light projected on an object to capture the object without fail. Light rays are projected onto an object by a projection optical system using a projection pattern film that contains transparent and non-transparent parts, or semi-transparent parts with different light transmission rates. A pair of light rays from the object pass through the shooting lens and are guided onto a photo-electric converter by a focus detection optical system to compose a pair of object images. The focus adjustment state of the shooting lens is detected based on the image defocus amount of the pair of the object images.