Image-forming optical system

摘要

A high-performance and low-cost image-forming optical system made compact and thin by folding an optical path using reflecting surfaces having power. The optical system has a plurality of reflecting surfaces having power. Among the reflecting surfaces, a reflecting surface (12) of negative power is placed closest to the object side, and a reflecting surface (22) of positive power is placed closer to the image side than the reflecting surface (12). At least one reflecting surface (13) is provided between the reflecting surface (12) and the reflecting surface (22). An axial principal ray (1) incident on the reflecting surface (13) satisfies the condition of 45 DEG <| theta |, where theta is the angle formed between the axial principal ray and a line normal to the reflecting surface (13) in the decentration direction at a point where the axial principal ray (1) intersects the reflecting surface (13).