| 摘要 |
An optical system for observation of a front-direction object and a substantially-lateral-direction object includes, in order from the front-direction-object side, a front group with a negative refracting power having a reflecting/refracting optical element, an aperture stop, and a rear group with a positive refracting power having a moving lens component movable along the optical axis. The reflecting/refracting optical element has a first face formed on the front-direction-object side, a second face formed on the image side, and a third face formed as a transmitting surface between the first face and the second face. The first face has a first transmitting surface formed with the optical axis being at a center thereof and a first reflecting surface annularly formed around the first transmitting surface and directed toward an image side. The second face has a second transmitting surface formed with the optical axis being at a center thereof and a second reflecting surface annularly formed around the second transmitting surface and directed toward the front-direction- object side. A movement of the moving lens component changes the refracting power ratio of the front group to the rear group, to enlarge or shrink, in the entire observation region, a region in which an image of the front-direction object is formed. |
