| 摘要 |
PURPOSE:To make it possible to ensure sufficiently long eye relief even if a small-sized pentaprism is used by introducing aspherical surface in image side of a negative lens and thereby strengthening refracting power of each lens and correcting various aberrations nicely. CONSTITUTION:An eyepiece consisting of a negative lens L1 and a positive lens L2 is placed in emitting side of a pentaprism P. The image side surface r4 (surface opposite to the pentaprism P) is made to aspherical surface. Thus, by making the image side face r4 of the negative lens L1 aspherical surface having radius of curvature that becomes smaller with the distance from the optic axis, occurrence of astigmatism and distortion in the image side face of the negative lens is increased to cancel aberration occurred in the positive lens in good balance. Thus, aberration of the whole system can be corrected satisfactorily.
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