| 摘要 |
PURPOSE:To prevent an erroneous decision at the time of deciding a focusing detection by constituting a re-image forming lens so as to form two lenses in which the surface to an object side is a uniaxial spherical surface and turns the convex surface to the object side, and the surface to an image side has two pieces of optical axes being eccentric so as to become a symmetrical position relation against the optical axis of the object side face, and forms the spherical surface for turning the convex surface to the image side having an equal curvature. CONSTITUTION:The shape of a re-image forming lens 5 is constituted so that the surface of its object side has an optical axis 10 being common to a condenser lens 4, and also, turns the convex surface to the object side, and on the other hand, the surface of an image side has the respective optical axes being parallel to the optical axis, and also, having a symmetrical position relation, so as to be convex to the image side. That is, in order to make the eccentric quantity of the re-image forming lens 5 as large as possible, and also, to suppress small a distortion in the re-image formation, a special shape is given to the re-image forming lens 5. In such a way, a re-formed image whose distortion is small is obtained, and a focus detecting device which scarcely causes an erroneous decision can be manufactured without complicating the constitution of an optical system. |
