| 摘要 |
PROBLEM TO BE SOLVED: To provide a real image type finder optical system whose entire length in its back-and-forth direction is shortened. SOLUTION: This real image type finder optical system is constituted of an objective optical system 1, a 1st prism 2 having a 1st surface 2a as an incident surface opposed to the emitting surface of the optical system 1, a 2nd surface 2b forming the angle of 22.5 deg. with the 1st surface 2a and a 3rd surface 2c through which an optical axis bent by the 2nd surface 2b and the 1st surface 2a passes, a 2nd prism 4 having a 1st surface 4a as an incident surface opposed to the 3rd surface 2c of the prism 2 parallel and separately, a 2nd surface 4b opposed to the 1st surface 4a in the order to bend the optical axis to an object side on a horizontal plane, a 3rd surface 4c bending the optical axis bent by the 2nd surface 4b and the 1st surface 4a to a direction nearly coaxial with an ocular 5 and a 4th surface 4d through which the optical axis bent by the 3rd surface 4c passes, and the ocular 5 opposed to the 4th surface 4d of the prism 4 and arranged to be nearly coaxial with the optical axis in order from the object side.
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