Focus detection device

Abstract

A focus detection device for precisely mounting a deflection member in a module body with high reliability. A module body retains a focus detection optical system. A portion of a hollow portion, through which a focus detection light beam passes, is formed by an aperture in the exterior of the module body. A deflecting member, which deflects the optical path of the focus detection light beam, is located in the aperture. A biasing member bias the deflecting member and restrains the deflecting member in a fixed location on the module body. A lens aggregate which has multiple lenses formed into a single body on the same substrate is forced against a support member in the module body to touch at contact areas. The contact areas on either the lens aggregate or the support member includes first, second and third protuberances. A first contact area opposite the first protuberance is shaped such that the first protuberance is restrained from movement in all directions lying in a plane substantially perpendicular to the direction in which the force is exerted. A second contact area opposite the second protuberance permits movement ,along only one line within the aforementioned plane. A third contact opposite the third protuberance does not restrain movement within the aforementioned plane. In an alternative embodiment, only two contact areas are provided in holes in the support member. Only two protuberances protrude from the lens aggregate and are disposed in the holes. A curable liquid filler which hardens on exposure to air is introduced into the holes around the protuberances. One of the holes is shaped to restrict all movement in a plane perpendicular to the protuberances, while the other hole permits movement along a line in the plane after the filler hardens.