Abstract: A focus detecting device which performs a temperature compensating action on the basis of an output of a temperature sensor includes a focus detecting sensor, a reimaging lens which reimages a light flux to be used for focus detection, a support member on which the focus detecting sensor and the reimaging lens are mounted, and the temperature sensor disposed in the vicinity of a mounting surface of the support member on which the reimaging lens is mounted.

Abstract: There is disclosed a focus detecting apparatus capable of detecting the focus state of an objective lens in a wide viewing field, comprises a view finder optical unit for observing the image formed by the objective lens, an optical unit for forming a pair of optical amount distributions, based on light beams passing through different areas of the pupil of the objective lens, wherein the optical unit being provided, at the light incident side, with a concave face directed to the light incident side, and, at the light exit side, with a convex face directed to the light exit side, a sensor unit for received said pair of the optical amount distributions, a main mirror positioned in the optical path from the objective lens to the optical unit and adapted to reflect the light beams from the objective lens toward the finder optical unit, and a reflecting mirror having a concave curved face directed to the light entrance side and adapted to reflect the light beams, transmitted by the main mirror, in a direction oppos

Abstract: An apparatus which has a finder optical unit for observing therethrough an image formed by an objective lens, an optical unit for forming a pair of distributions of light quantity on the basis of light beams transmitted through the different pupils of the objective lens, a sensor unit for receiving the pair of distributions of light quantity, a main mirror disposed in an optical path leading to the objective lens and the optical unit for reflecting the light beam from the objective lens to the finder optical unit, and a reflecting mirror having a curved surface having its concave surface facing the light incidence side for reflecting the light beam transmitted through the main mirror in the direction of the optical unit which is opposite to the finder optical unit, and which well makes focus detection possible for a wide field area formed by the objective lens.

Abstract: A focus detecting apparatus includes an optical unit provided on an image plane side of an objective lens for detecting a focus state of the objective lens, the optical unit forming a plurality of light quantity distributions, a photoelectrical changing unit having a plurality of elements for outputting a relative positional signal between the plurality of light quantity distributions, and a circuit for detecting a focus state of the objective lens. The optical unit includes a reflecting mirror having a light condensing property for reflecting a light beam from the objective lens to form an object image on a predetermined surface, a secondary imaging lens having at least a pair of lenses for causing the object image formed on the predetermined surface to be reimaged on the photoelectrical changing unit and a pair of apertures having aperture portions respectively corresponding to the pair of lenses.