| 摘要 |
An objective lens for use in a variable field angle endoscope which enables its field angle without increasing the diameter of the front end of the endoscope or complicating the shape of the same by moving a rear set of lenses between two positions where a conjugate distance of the rear set of lenses for image formation becomes substantially the same. Release lenses of a third group lens group are movable between two positions in the direction of the optical axis. When the relay lenses are situated at a first position, i.e., a wide angle position, the field angle of the objective lens becomes large. However, when the relay lenses are situated at a second position, i.e., a telephoto position, the field angle of the same becomes small. When the relay lenses are switched from one position to the other position, a focused image of a subject is formed at a second image formation position without changing a distance between first and second image formation positions, i.e., without changing a conjugate distance or the positions of other lenses.
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