| 摘要 |
PURPOSE:To obtain the finder optical system with a high visual field rate and high visual field magnification which suits to an electronic camera, etc., with a relatively small photographic image plane by using two prisms in a specific shape in combination as a substitute for the conventional pentagonal roof prism. CONSTITUTION:The (x) axis is set on the incidence surface S1 of the 1st prism 10 in the optical-axis direction of a photographic lens 1, the (y) axis is set at right angles to the (x) axis, and the (z) axis is set at right angles to the incidence surface S1. A light beam E on the optical axis of a finder is incident on the incidence surface S1 of the 1st prism 10 nearly at right angles and reflected by the 1st reflecting surface S2 on which a reflecting film is vapor-deposited, reflected totally by the 2nd reflecting surface S1' almost in the same plane with the incidence surface S1, and then projected from the projection surface S3 of the 1st prism 10. Then, the light beam E is incident on the incidence surface S4 of the 2nd prism 11 and reflected by the roof surface S55' consisting of two reflecting surfaces S5 and S5' where a reflecting film is vapor-deposited, further reflected by the 4th reflecting surface S4' nearly on the same plane with the incidence surface S4, and then projected from a projection surface S6 nearly at right angles. Then, the light beam E projected from the projection surface S6 is incident on an ocular lens 12.
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