| 摘要 |
PROBLEM TO BE SOLVED: To obtain an endoscopic objective lens having a small diameter, short overall length and high optical performance as an objective lens of a type to align the final face of the lens on an image side to the end face of a fiber bundle. SOLUTION: This endoscopic objective lens is composed, successively from an object side, of three single lenses; a first lens 10 having zero or negative refracting power, a second lens 20 having positive refracting power and a third lens 30 having positive refracting power and satisfies the following condition equations: (1) 0<=|f/f1|<0.5(f1 0). (2) 0<=|f2 /f1|<0.5. (3) 1.8<f3 /f2<8. (4) 0.15<d/f<0.55. In the equations, (f): the focal length of the entire system of the objective lens, f1 : the focal length of the first lens, f2 : the focal length of the second lens, f3 : the focal length of the third lens, (d): the spacing between the second lens and the third lens.
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