Patent ID: 9465192
Filing Date: 2016-10-11
CPC Classification: G02B

Claim Text:
1. An imaging optical system, comprising: in the order from an object side to an image plane side, a first lens group having negative refracting power that includes a negative lens having a concave surface on the image plane side; a second lens group having positive refracting power that includes, in the order from the object side to the image plane side, a negative lens having a concave surface on the object side, and a cemented lens of a negative lens and a positive lens, said negative lens of the cemented lens being on the object side and said positive lens of the cemented lens being on the image plane side and having a convex surface on the object side; an aperture stop; a third lens group having positive refracting power that consists of a cemented lens of a positive lens and a negative lens; and a fourth lens group having negative refracting power that consists of a negative lens having a concave surface on the object side, wherein the imaging optical system does not have any other lenses other than the lenses of the first to fourth lens groups between the first lens group and the fourth lens group, and wherein the imaging optical system is configured to satisfy the following conditional expression (1): where a maximum image height of the imaging optical system is IY, and a distance on an optical axis from an image plane to an exit pupil position of the imaging optical system is AP.