Patent ID: 7414664

Claim:
An image taking apparatus comprising: a light splitting unit which splits a light flux from an image-taking lens into a plurality of light fluxes; a view finder optical system configured and positioned to observe an object image formed by the light flux from the image-taking lens; an image pickup element which photoelectrically converts the object image to an electrical signal; and a focus detection unit configured and positioned to detect the focusing state of the image-taking lens according to a phase difference detection system, wherein the light splitting unit changes its state among a first state in which the light flux is directed to the view finder optical system and the focus detection unit, a second state in which the light flux is directed to the image pickup element and the focus detection unit and a third state in which the light flux is directed only to the image pickup element, wherein the light splitting unit has a half mirror and a reflection mirror which prevents an incident light flux from passing through the reflection mirror wherein in the first state, the half mirror and the reflection mirror are positioned in an image-taking optical path so that part of the light flux is reflected by the half mirror and directed to the view finder optical system, and the rest of the light flux a) passes through the half mirror, b) is reflected by the reflection mirror, and c) is directed to the focus detection unit, and wherein in the second state, the reflection mirror is withdrawn from the image-taking optical path and the orientation of the reflecting surface of the half mirror is changed in the image-taking optical path with respect to the first state so that part of the light flux is reflected by the half mirror and directed to the focus detection unit, and the rest of the light flux passes through the half mirror and is directed to the image pickup element, and wherein in the third state, the half mirror and the reflection mirror are withdrawn from the image-taking optical path so that the light flux is directed only to the image pickup element.