| 摘要 |
PROBLEM TO BE SOLVED: To provide an ocular optical system whose diopter scale is adjusted, where sufficient eye relief is secured even when the diopter scale is adjusted and which is compact as a whole including a pentagonal mirror as an ocular optical system for a single lens reflex camera provided with a pentagonal mirror and using 135 type film. SOLUTION: This optical system is composed of a 1st meniscus lens L1 having negative power, whose concave surface faces to the pentagonal mirror side, a 2nd lens L2 having positive power, a 3rd lens L3 having positive power, and a 4th lens L4 having negative power, whose concave surface faces to an eye side in order from the pentagonal mirror side; and is the ocular optical system for the single lens reflex camera where at least either the 2nd lens L2 or the 3rd lens L3 is set as a diopter adjustable lens which can be positionally adjusted in an optical axis direction.
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