| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a camera head optical system used for photographing by being attached to the eyepiece part of an endoscope, which is optimized to a compact imaging element having a negative oblique incident characteristic and a short exit pupil distance without using a relay lens. Ž<P>SOLUTION: In the optical system 30 for the camera head, which has an imaging lens 32 used for photographing by being attached to the eyepiece part 20 of an endoscope, the small imaging element 33 with the short exit pupil distance is optimized using a field lens 34 of negative power. As a range in which high effectiveness is achieved when a field lens 34 of a negative power is used for oblique incidence, the imaging lens 32 satisfies expression (1) given below: f×tan(-tw)/h>1.0 ... (1), wherein f is a focal distance of an imaging lens, h is the maximum image height on an imaging face, and tw is an angle at which the light ray of the center of an oblique luminous flux enters an imaging face at the maximum image height. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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