Patent ID: 9395525
Filing Date: 2016-07-19
CPC Classification: G02B

Claim Text:
1. A catadioptric imaging lens, comprising: a first reflecting mirror, a second reflecting mirror and a lens group, with the first reflecting mirror disposed closest to an object side where an object is present, the second reflecting mirror disposed second closest to the object and the lens group disposed furthest away from the object in a positional arrangement along an optical path whereby light reflected at the first reflecting mirror is reflected at the second reflecting mirror and then travels through the lens group to form an object image at a predetermined image plane; wherein when a straight line connecting a center of the object and a center of the first reflecting mirror is designated as a first reference axis, a straight line connecting a center of the second reflecting mirror and a center of the image plane is designated as a second reference axis, a plane that contains the first reference axis and the second reference axis is designated as a reference plane, a plane that ranges through the center of the first reflecting mirror, is perpendicular to the reference plane and forms a first predetermined angle with the first reference axis is designated as a first orthogonal plane, a plane that ranges through the center of the second reflecting mirror, is perpendicular to the reference plane and forms a second predetermined angle with the second reference axis is designated as a second orthogonal plane, and a plane that ranges through a center of a surface in the lens group located closest to the second reflecting mirror, is perpendicular to the reference plane and is parallel to the second reference axis is designated as a third orthogonal plane: the first reflecting mirror and the second reflecting mirror are decentered within the reference plane; a reflecting surface of the first reflecting mirror is a rotationally asymmetrical aspherical surface, having a contour that manifests concavity on the object side within the reference plane and also within the first orthogonal plane; a reflecting surface of the second reflecting mirror is a rotationally asymmetrical aspherical surface, having a contour that manifests convexity on a side further toward the first reflecting mirror within the reference plane and also within the second orthogonal plane; and the surface in the lens group located closest to the second reflecting mirror is a rotationally asymmetrical aspherical surface, having a contour that manifests concavity on a side further toward the second reflecting mirror within the reference plane and manifests convexity on the side further toward the second reflecting mirror within the third orthogonal plane; each aspherical surface among the rotationally asymmetrical aspherical surfaces is defined as expressed in (1) below, when a direction along which a normal line extends at an origin point of a tangent plane to the aspherical surface is designated as a z direction, two directions extending orthogonally to each other within the tangent plane are designated as an x direction and a y direction, respectively, s represents a sag quantity indicating an extent of sagging of the aspherical surface manifesting along the z direction, c represents a curvature at the origin point, r represents a distance from the origin point, k represents a conic constant, m and n each represent an integer equal to or greater than 0, and C(m, n) represents a coefficient for a monomial x and α3 representing a sum of the coefficient C(2, 0) of x