Patent ID: 7697220
Filing Date: 2010-04-13
Classification: G02B

Abstract:
1. An image forming optical system comprising, in order from an object side, a front lens group having negative refracting power, and a rear lens group having positive refracting power, wherein the front group comprises, in order from the object side, a first lens element having the negative refracting power, and a second lens element of a meniscus form having a convex surface directed toward an image side; wherein the first lens element has an aspherical surface that is a concave surface directed toward the object side in the vicinity of the optical axis, and negative refracting power at a position on the aspherical surface becomes weak as a distance between the position and the optical axis becomes large; and a surface that is a concave surface directed toward the image side at least in the vicinity of the optical axis; and further the following conditions (1) and (2) are satisfied: where F