PRISM TELESCOPIC OPTICAL SYSTEM

PURPOSE:To constitute plural prism telescopic optical systems so that the entire length may be equal by improving the constitution of an image inverting prism system in plural prism telescopic optical systems having different observation magnification. CONSTITUTION:In the prism telescopic optical system having observation magnification of 7; an objective lens system 11, the image inverting prism optical system 12 and an ocular system 13 are arranged in this order from an object side. In the prism telescopic optical system having the observation magnification of 9; the objective lens system 15, the image inverting prism optical system 16 and the ocular system 13 are arranged in this order from the object side. The two optical systems are constituted so that the length of the prisms may be common, only refractive indexes may be different from each other, and the entire length of the systems may be nearly equal with each other. By such constitution, mechanical parts are used in common between the optical systems, thereby designing the optical systems in common. Furthermore, since the focal distance of the ocular system is optimally set, the position of an eye point does not become low. Thus, the prism telescopic optical system excellent in handleability is obtained.