In-focus state detecting device for camera

摘要

An in-focus state detecting device which is provided with erroneous signal discriminating means is arranged such that: The lens cap of a photo-taking lens has the whole surface or a part of the surface thereof formed into a diffuse transmission face. With this lens cap put on the photo-taking lens, a light flux is allowed to be diffused by the diffuse transmission face to obtain a uniform brightness face at the cap. Then, a light flux from the uniform brightness face of the cap is guided to the in-focus detecting device to perform a checking operation with the discriminating means to check for an erroneous action of the device.