Patent ID: 6181483
Filing Date: 2001-01-30
Classification: G02B

Abstract:
A wide-angle lens having a long back focus comprising, successively from an object side, a first lens group having a negative refracting power and a second lens group having a positive refracting power; wherein said first lens group comprises, successively from the object side, a first-a lens group having a negative refracting power and a first-b lens group having a positive refracting power; said wide-angle lens satisfying the following conditional expressions (1) and (2):5.0<Bf/f (1)-0.05<tan .theta.<0.05 (2)wheref is the focal length of the whole system;Bf is the back focus of the whole system; and.theta. is an angle formed between a principal ray directed to a screen corner portion and an optical axis.