Image-erecting viewing optical system
An image-erecting viewing optical system includes a first prism having an incident surface and at least two reflection surfaces, a front lens group of an objective optical system, a second prism having an incident surface and at least two reflection surfaces, a rear lens group of the objective optical system, a field stop, and an eyepiece optical system, in this order from the object. One reflection surface of the first or second prism includes a roof-mirror surface. The following conditions are satisfied: sin(θ−ω′)>1/ n (1) 6°<ω<16° (2) wherein θ designates an angle between the incident surface and the first reflection surface of the first prism; ω designates a real field-of-view ω (half amount); ω′ designates an angle between a light ray of a real field-of-view ω (half amount) and the optical axis within the first prism; and n designates the refractive index of the first prism.
1. An image-erecting viewing optical system comprising a first prism having an incident surface and at least two reflection surfaces, a front lens group of an objective optical system, a second prism having an incident surface and at least two reflection surfaces, a rear lens group of said objective optical system, a field stop, and an eyepiece optical system, in this order from an object,
wherein one reflection surface of one of said first prism and second prism comprises a roof-mirror surface; and
wherein said first prism satisfies the following conditions:
sin(0−ω′)>1 /n
6°<ω<16°
wherein
θ designates an angle between said incident surface and a first reflection surface of said first prism;
ω designates a real field-of-view ω (half amount);
ω′ designates an angle between a light ray of a real field-of-view ω (half amount) and the optical axis in said first prism; and
n designates the refractive index of said first prism.
2. An image-erecting viewing optical system according to claim 1 , wherein at least one of said rear lens group of said objective optical system and said eyepiece optical system comprises a focusing lens group.