| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens for an endoscope, of which the magnification chromatic aberration is excellently corrected while securing back focus having a sufficiently long length allowing an optical path conversion prism to be inserted and arranged on an image surface side. SOLUTION: In the objective lens for the endoscope, in which the back focus Bf of the whole system is longer than twice the composite focal distance f of the whole system; a negative first lens L1, a positive second lens L2, a brightness stop St, a positive third lens L3, and a cemented lens L45 composed of a positive forth lens L4 and a negative fifth lens L5 are arranged successively from the object side and a formula (1): (ν<SB>2</SB>+ν<SB>5</SB>)<45 is satisfied (in the formula (1),ν<SB>2</SB>is the a Abbe's number of the second lens L2 andν<SB>5</SB>is the Abbe's number of the fifth lens L5). COPYRIGHT: (C)2007,JPO&INPIT
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