| 摘要 |
PROBLEM TO BE SOLVED: To provide an eyepiece for endoscope in which the entire length of an optical system is short despite a relatively small number of lenses composing the eyepiece (i.e., three), and satisfactory optical performance and high magnification are ensured. SOLUTION: The eyepiece includes in order from the object side: a first lens L<SB>1</SB>composed of a positive meniscus lens whose concave face is disposed on the object side; a second lens L<SB>2</SB>composed of a negative lens whose concave face is disposed on the eye side; and a third lens L<SB>3</SB>composed of convex lenses on both sides. The second lens L<SB>2</SB>and third lens L<SB>3</SB>form a positive cemented lens. The eyepiece satisfies the following expressions: (1) 0.5<(d-aBP+bFP)/f<0.8, (2) 1.4<¾R1F¾/f<1.9, and (3) 25.0<υ<SB>3</SB>-υ<SB>2</SB>, wherein f denotes the focal distance of the entire system, d denotes a spacial interval between the first and second lenses, aBP denotes a distance from the eye-side face of the first lens to the eye-side principal point of the first lens, bFP is a distance from the object-side face of the second lens to the object-side principal point of the cemented lens, R1F denotes the curvature radius of the object-side face of the first lens, andυ2 andυ3 denote the Abbe's numbers of the second lens and third lens respectively. COPYRIGHT: (C)2007,JPO&INPIT
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