Patent ID: 7885017

Claim:
An objective lens system for endoscope comprising in order from the object side at least: a first negative lens element; a second positive lens element; an aperture stop; and a cemented lens component consisting of a third negative lens element and a fourth positive lens element, wherein said objective lens system satisfies the following conditions (1), (2), (5) and (4): 0.5< D 1/ f< 1.8 (1) D 2/ f< 0.9 (2) | f /( f 1 ×ν 1 )+ f /( f 2 ×ν 2 )|<0.025 (5) 1.5<|( f 4 ×ν 4 )/( f 3 ×ν 3 )| (4) wherein a reference symbol D 1 represents an air reduction optical path length from an object side of the first lens element to the aperture stop, a reference symbol D 2 designates an air reduction optical path length from the aperture stop to an image side surface of the fourth lens element, a reference symbol f denotes a total focal length of the objective lens system as a whole, reference symbols f 1 , f 2 , f 3 and f 4 represent focal lengths of the first lens element, the second lens element, the third lens element and the fourth lens element respectively, and reference symbols ν 1 , ν 2 , ν 3 and ν 4 designate Abbe's numbers of the first lens element, the second lens element, the third lens element and the fourth lens element respectively.