RETROFOCUS LENS

摘要

PROBLEM TO BE SOLVED: To provide a wide-angle retrofocus lens that exhibits high imaging performance despite its sufficiently compact configuration. SOLUTION: The retrofocus lens includes, in order from the object side: a front group G1 composed of lenses L1 to L3 and having negative refractive power as a whole; and a rear group G2 including a diaphragm St, a cemented lens L56 disposed on the image side of the diaphragm St, and a positive lens L7 disposed closest to an image and having positive refractive power as a whole. The retrofocus lens satisfies the following conditional formula (1) 2.00≤NdG2_LAST≤2.50 (wherein NdG2_LASTis a refractive index to the line d of the lens L7). This restrains astimatic, which is an aberration depending on a field angle, image face curvature, and distortion, and relatively facilitates adjustment (reduction) of the Petzval sum of the entire system. Further, this is effective to make the retrofocus lens compact. COPYRIGHT: (C)2008,JPO&INPIT