Patent ID: 8665418
Filing Date: 2014-03-04
Classification: G03F

Abstract:
1. A projection optical system for forming an image of a first surface and an image of a second surface on a third surface, comprising: a first imaging optical system disposed in an optical path between the first surface and a first conjugate point optically conjugate with a point on an optical axis of the first surface; a second imaging optical system disposed in an optical path between the second surface and a second conjugate point optically conjugate with a point on an optical axis of the second surface; a third imaging optical system disposed in an optical path between the third surface and, the first conjugate point and the second conjugate point; a first folding member which is disposed between the surface nearest to the third surface in the first imaging optical system and the surface nearest to the first surface in the third imaging optical system and which guides light from the first imaging optical system to the third imaging optical system; and a second folding member which is disposed between the surface nearest to the third surface in the second imaging optical system and the surface nearest to the second surface in the third imaging optical system and which guides light from the second imaging optical system to the third imaging optical system; wherein every optical element including a power in the third imaging optical system is a refractive element, wherein the first conjugate point is located between a surface nearest to the third surface in the first imaging optical system and a surface nearest to the first surface in the third imaging optical system, wherein the second conjugate point is located between a surface nearest to the third surface in the second imaging optical system and a surface nearest to the second surface in the third imaging optical system, and a ridgeline made by intersection of a reflecting surface of the first folding member with a reflecting surface of the second folding member is located on a point where the optical axes of the first, second, and third imaging optical systems intersect.