Offset optical system including primary mirror and positionally-offset sub-mirror

Abstract

Provided is an optical system having a configuration capable of attaining a large light-gathering power while producing a maximum light-gathering power easily and inexpensively with a minimum material. An offset optical system according to the present invention comprises: a primary mirror composed of at least part of one of two optical element halves obtained by dividing an optical element having a concave shape curved only in one direction, in an intermediate position of a length along a curvature thereof, wherein the optical element is configured to reflect and focus light from an object, into a linear focus; a sub-mirror disposed between the primary mirror and the linear focus and configured to transmit or reflect light reflected by the primary mirror, thereby focusing the light into a point focus; wherein, when: a direction tangent to the curvature in the intermediate position of the optical element is defined as an x-axis; a direction which is perpendicular to the x-axis and in which the object is located is defined as a y-axis; and a direction orthogonal to the x-axis and the y-axis is defined as a z-axis, the sub-mirror is offset parallel to the x-axis by a given distance toward an edge of the primary mirror located distal to the y-axis.

Dependencies are inferred from the claim text.