Abstract: An eyepiece lens system comprising a first positive lens component and a second positive lens component: the first lens component being composed of a single positive lens element, and the second lens component being composed of a single cemented doublet consisting of a positive lens element and a negative lens element. This eyepiece lens system has distortion which is corrected favorably by selecting an adequate refractive power for a cemented surface of the cemented doublet and is configured so as to have a sufficiently long eyepoint distance.

Abstract: A photographing optical apparatus includes reflecting members for reflecting images transmitted along a plurality of optical paths having parallax; optical systems arranged on the plurality of optical paths behind the reflecting members; optical members for reducing vertically the images passing through the optical systems; and an image sensor disposed at or near the imaging plane of the images so that the images reduced by the optical members are formed on the image sensor. By moving the reflecting members, a convergent angle is changed and stereoscopic photography and panoramic photography become possible.

Abstract: A prismatic telescope optical system is available to include one of a plurality of optical systems different in magnification from one another, each having an objective system, an image erecting prism system, and an eyepiece system. Each of plurality of optical systems is constructed so that its respective overall length is are made practically equal by varying the refractive indices of an included image erecting prism system.

Abstract: A finder optical system including an objective system, an image erecting system for erecting an object image formed by the objective system, and an eyepiece system for observing the object image. These systems are constructed of low-hygroscopic organic materials. Thus, the finder optical system can prevent transient variations of optical properties caused by hygroscopicity.

Abstract: A wide field eyepiece lens system composed, in order from a side of an objective lens system, of a first lens unit which is composed of a plurality of lens elements and has a diverging function, and a second lens unit which is composed of a plurality of lens elements and has a converging function. The eyepiece lens system has an apparent field angle of 75.degree. to 80.degree., an eye relief of 0.95 f or longer and aberrations favorably corrected over an entire range of a visual field thereof including marginal portions, and is configured so as to satisfy the following conditions (1) and (2):-8.0<f.sub.1 /f<-4.8 (1)1.8<D/f<2.

Abstract: A real image type finder system comprising an objective lens system, a relay lens system and a field stop arranged at the location at which an image is to be formed by said objective lens system: and adapted to be changed into a panorama finder system by replacing the relay lens system with another relay lens system having a magnification different from that of said relay lens system and exchanging the field stop with another field stop having an aperture of a shape having an aspect ratio different from that of the aperture shape of said field stop.

Abstract: A compact zoom lens system comprising, in the order from the object side, a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power; and adapted so as to perform variation of focal length from the wide position to the tele position by moving the first lens unit and the third lens unit from the image side toward the object side, and displacing the second lens unit and the aperture stop so as to widen the airspace reserved between the first lens unit and the second lens unit, and narrow the airspace reserved between the second lens unit and the third lens unit. This zoom lens system has a total length shortened by thinning the first lens unit.

Abstract: A vari-focal photographic lens system of rear lens group exchange type comprising a front lens group and a rear lens group and arranged to vary the focal length of the lens system as a whole by exchanging the rear lens group for another rear lens group having a different lens configuration, the vari-focal photographic lens system being arranged so compactly and arranged that the variation of aberrations is small.

Abstract: A varifocal lens system equipped with an auxiliary lens group comprising a master lens system consisting of a front lens group having positive refractive power and a rear lens group having negative refractive power, and an auxiliary lens group arranged in such a manner that it can be freely inserted and removed, for varying focal length, between said front and rear lens groups. Said varifocal lens system is equipped with a simple mechanism capable of varying focal length of said lens system in a very short time.

Abstract: A zoom lens system comprising a vari-focal system and a relay lens system wherein the vari-focal system comprises a first lens group having positive refractive power and comprising a cemented doublet, a second lens group having negative refractive power and comprising a cemented doublet, and a third lens group having positive refractive power, and the relay lens system comprises a front lens group having positive refractive power, and a rear lens group having positive refractive power, the aperture ratio thereof being large and aberrations thereof being corrected favorably.

Abstract: A vari-focal photographic lens system of lens group exchange type comprising, in the order from the object side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, and a third lens unit having negative refractive power, the vari-focal photographic lens system being arranged to vary the focal length thereof by exchanging the second lens unit for another second lens unit having different lens configuration.

Abstract: A compact vari-focal photographic lens system comprising a master lens system and an auxiliary lens group wherein the master lens system comprises a front lens unit having positive refractive power and a rear lens unit having negative refractive power, the compact vari-focal photographic lens system being arranged to vary the focal length of the lens system as a whole by inserting and removing the auxiliary lens group to and from the image side of the master lens system and arranged that the overall length of the lens system is short, it is possible to vary the focal length without moving the stop mechanism, and aberrations are corrected satisfactorily favorably, the compact vari-focal photographic lens system being suitable for the use with popular cameras.

Abstract: A focusing method for a telephoto lens system comprising a front lens group having positive refractive power, an intermediate lens group having negative refractive power, and a rear lens group having positive refractive power, the focusing method for a telephoto lens system being arranged to focus the telephoto lens system by moving the intermediate lens group toward the image side and the rear lens group toward the object side.

Abstract: An endoscope provided with a light receiving device on the eyepiece side in respect of an image guide and with a driving means for moving an objective lens near an eyepiece, to make the whole endoscope slim and to make it simple in formation despite its being provided with an automatic focus detecting mechanism.

Abstract: A focusing method for a telephoto lens system comprising a front lens group having positive refractive power, an intermediate lens group having negative refractive power, and a rear lens group having positive refractive power, the focusing method for telephoto lens system being arranged to divide the intermediate lens group into two subunits and to focus the lens system by moving those subunits toward the image side by varying the distance between those subunits, the focusing method thereby enabling to attain focusing with satisfactorily favorable aberrations up to an object at a short distance.