| 摘要 |
PROBLEM TO BE SOLVED: To provide a condensing optical system which has variable power is while contributing to the miniaturization of a confocal endoscope, and is suitable for the confocal endoscope. SOLUTION: The condensing optical system 10 is loaded to a scanning confocal optical system for observing an inspection surface by moving a point light source functioning as a confocal pin hole and scanning the inspection surface with a luminous flux emitted from the point light source. The condensing optical system 10 includes, in order from the point light source side, a first group, a second group having positive power, a third group having positive power and a fourth group, wherein the power is varied by moving the second group and the third group in the optical axis direction, and the following inequalities (1) and (2) are simultaneously satisfied: (1): -0.8<ms<-0.5 and (2): -1.8<mt<-1.2. In the inequalities (1) and (2), (ms) denotes the composite power of the second group and the third group at a low power end when the point light source is regarded as an object point, and (mt) denotes the composite power of the second group and the third group at a high power end when the point light source is regarded as an object point. COPYRIGHT: (C)2008,JPO&INPIT
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