Abstract: A telephoto zoom lens system comprises a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. In a zooming operation, the first lens group moves arithmetically, the second lens group moves from the objective side toward the image side in the first half of the movement and then from the image side toward the objective side in the latter half of movement, and the third lens group moves so as to maintain the image side focal point thereof in a fixed position in conjunction with the first and second lens groups.

Abstract: A reflecting apparatus in an optical system in which, in order to transmit image light effectively to a light receiving body having a given spectral sensitivity characteristic, either a single or plural reflecting film layer, having a spectral sensitivity characteristic approximately equal to that of the light receiving body, is formed on a polished surface which forms one face of a light absorbing substance.

Abstract: A prism system is utilized in tricolor separation in order to obtain three images of separated colors by passing through the prism a light beam from a single objective lens system. The prism system includes first, second and third prisms, each having the same refractive index. First and second interference filters are utilized in conjunction with the prisms in order to provide reflecting lights and transmitted lights that are complementary to each other. The first prism is a right-angled triangular prism having a vertical angle of 30.degree., with its oblique surface being disposed at a right angle to the optical axis of the objective lens system. The second and third prisms are each of a trapezoidal shape, having the identical size. Two adjoining angles of the trapezoidal prisms are 90.degree. and the other two angles are 60.degree. and 120.degree., respectively as viewed in their cross sections.