Patent ID: 9097883
Filing Date: 2015-08-04
Classification: G02B

Abstract:
1. A catadioptric optical system comprising: a first imaging optical system configured to condense a light flux from an object and to form an intermediate image of the object; and a second imaging optical system configured to form an image of the intermediate image on an image surface, wherein the first imaging optical system includes: a first optical element including a light transmission part located around an optical axis, and a backside reflection part located closer to an outer circumference of the first optical element than the light transmission part of the first optical element and having a reflective surface on an object side; a second optical element including a light transmission part located around the optical axis, and a backside reflection part located closer to an outer circumference of the second optical element than the light transmission part of the second optical element and having a reflective surface on an image surface side; and a negative lens located on an optical path between the first optical element and the second optical element, wherein the light flux from the object passes through the light transmission part of the first optical element and the negative lens, is reflected on the backside reflection part of the second optical element, passes through the negative lens, is reflected on the backside reflection part of the first optical element, and passes through the negative lens and the light transmission part of the second optical element, in this order, and is emitted to the second imaging optical system, and wherein an Abbe number of a material of the negative lens is larger than that of a material of the second optical element.