Patent ID: 6545810
Filing Date: 2003-04-08
Classification: G02B

Abstract:
An image pickup optical system, for forming an image of an object on a surface of an image pickup device, said image pickup optical system comprising:at least a rear optical unit on an image side of a pupil plane, said rear optical unit having at least one reflecting surface decentered such that a whole of said surface is tilted with respect to an axial principal ray defined by a light ray emanating from a center of the object and passing through a center of a pupil to reach a center of the image, and said reflecting surface having a rotationally asymmetric surface configuration that corrects rotationally asymmetric decentration aberrations caused by decentration, thereby reducing rotationally asymmetric aberrations of said image of the object, wherein said rear optical unit further has at least a second reflecting surface disposed to face said reflecting surface, and assuming that a direction in which said axial principal ray travels until it reaches a first surface of said optical system is defined as a Z-axis direction, and a Y-axis direction is taken in a plane of decentration of the decentered surface, and further an axis constituting an orthogonal coordinate system in combination with the Y- and Z-axes is defined as an X-axis, and further that said axial principal ray and a light ray which is parallel to said axial principal ray at a slight distance d in the Y-axis direction are made to enter said optical system from an entrance surface side thereof, and a sine of an angle formed between the two rays in the YZ-plane at an exit side of said optical system is denoted by NAâ€²yi, and further that a value obtained by dividing said NAâ€²yi by said distance d between said parallel rays, i.e. NAâ€²yi/d, is defined as a power Py in the Y-axis direction of said optical system, and p is an optical path length from a point at which said axial principal ray enters a constituent element of said optical system disposed closest to said object and having said rotationally asymmetric surface to a point at which said axial principal ray exits from a constituent element of said optical system disposed closest to said image and having said rotationally asymmetric surface, the following condition is satisfied: 0.1<8.â€ƒâ€ƒ(1)