| 摘要 |
PROBLEM TO BE SOLVED: To prevent the deterioration of image quality by assembling condition and to improve the assembling easiness in a hard mirror whose insertion part has a comparatively small outside diameter, <= about 3mm, especially. SOLUTION: The objective lens is composed of a cover glass 31, a plane- concave lens 32, a 30 deg. prism 33, a plane-convex positive lens 34 and a bonded lens 35; and the cover glass 31 has a concave surface on an image side and is fixed on a leading end frame 30 integrally formed with an outer tube 21 by means of adhesion. In such a case, the outside diameter of the lens 35:ϕ=2.000; the thickness of the lens 35: d=6.499; d/ϕ=3.250; the glass path length of the positive lens of the lens 35: d1=1.633; and the glass path length backward from the positive lens of the lens 35: d2=4.866.
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