| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens for endoscope which is wide-angled, has a small outer diameter and in which maximum ray beam height of a first lens is low and which is suitable for a small-sized CCD (charge coupled device). SOLUTION: The objective lens for endoscopes is constituted of a front lens group and a rear lens group while holding a diaphragm therebetween. The front lens group is composed of the first lens of negative refracting power and a second lens of positive refracting power turning a face of small radius of curvature to an object side in order from the object side. The rear lens group is composed of a third lens of positive refracting power turning a face of small radius of curvature to an image side, a fourth lens of positive refracting power, and a fifth lens of negative refracting power and the fourth lens and the fifth lens are joined. The objective lens for endoscope is characterised in that, when (f) denotes composite focal length of whole system and (f<SB>3</SB>) denotes focal length of the third lens, the condition of 2.0 <¾f<SB>3</SB>/f¾<3.0 is satisfied. COPYRIGHT: (C)2005,JPO&NCIPI
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