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 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 light-measuring system for single-lens reflex cameras wherein the light coming from an object to be photographed as reflected at the image-pickup surface is reflected once again by a partially reflecting means disposed in the photographing light path, so that this latter reflection light is measured on its own optical axis, to enable to perform the real-time measurement of light with a high precision.

Abstract: A finder optical system for single-lens reflex cameras comprising a screen on which an image by a photographing lens is to be formed through a half-mirror and a relay lens for forming the image formed on the screen in a focal position in front of a magnifying lens so that, when the focal distance of the magnifying lens is represented by f.sub.oc and the distance from the screen to the front principal point position of the magnifying lens is represented by L, the relation of 0.2.ltoreq.f.sub.oc /L.ltoreq.0.8 will satisfied, in order to make it easy to replace the photographing lens and to make the magnification high while keeping the eye point in a position sufficiently separated from the screen.

Abstract: An attachment lens system for single-lens reflex cameras capable of being interposed between an ordinary interchangeable lens system and camera body and formed with a negative lens component, a beam splitter arranged at the image side of the negative lens component and a positive lens component arranged at the image side of the beam splitter, in order to enable the use of an ordinary interchangeable lens system as an interchangeable lens system provided with a focus detection optical system for auto-focus. The light from an object which has passed a master lens is divided by the beam splitter so as to be guided onto the film face or finder screen and to the focus detection means.

Abstract: A shiftable lens hood for a camera includes a light-intercepting body which has its front end representing a sectional form taken on a plane inclined to the center axis thereof of which is secured to a lens barrel of the camera, in eccentric relationship with its mounting section, whereby even when a taking lens is shifted effective light rays within a photographing angle of view are not shaded, thus an effective light-intercepting effect being obtainable.

Abstract: Retro-focus type super wide angle lens system comprising a first positive meniscus lens component having the convex surface on the object side, a second negative meniscus lens component having the convex surface on the object side, a third negative meniscus lens component having the convex surface on the object side, a fourth positive lens component, a fifth negative meniscus lens component, a sixth positive cemented lens component, a seventh negative cemented lens component, an eighth positive meniscus lens component having the convex surface on the object side, a ninth positive lens component, and a filter disposed between the fifth and sixth lens components. In this lens system, aberrations are well corrected.

Abstract: A zoom lens system comprising a flare stop and so adapted as to favorably limit rays which will otherwise produce flare without making light intensity insufficient by displacing said flare stop independently of displacements of lens groups for zooming.

Abstract: A wide-angle zoom lens system consisting of a front lens group, a rear lens group and an aperture stop arranged therebetween, said front lens group comprising a first positive meniscus lens element having a convex surface on the object side, a second negative meniscus lens element having a strongly concave surface on the image side, a third positive meniscus lens element having a concave surface on the object side, a fourth biconcave lens element and a fifth biconvex lens element, and said rear lens group comprising a sixth biconvex lens element, a seventh positive meniscus lens element, an eighth positive meniscus lens element, a ninth biconcave lens element, a tenth negative meniscus lens element having a concave surface on the image side and an eleventh biconvex lens element. Said zoom lens system is so adapted as to permit changing forcal length of the entire lens system by changing the airspace reserved between said front and rear lens groups.

Abstract: A Gauss type lens system comprising a first, second, third and fourth lens components, the first lens component being a positive meniscus lens, the second lens component being a cemented doublet consisting of a positive lens and negative lens, the third lens component being a cemented doublet consisting of a negative lens and positive lens, the fourth lens component being a biconvex lens, the Gauss type lens system having the aperture ratio of 1.8 and field angle of 46.degree. and being made low in price by using high refractive-index high dispersion glass materials for many of lenses.

Abstract: A compact retrofocus type lens system having a first lens component of a positive meniscus lens with its convex surface facing the object side, second and third lens components of negative meniscus lenses with their convex surfaces both facing the object side, a fourth lens component of a positive meniscus lens with its convex surface facing the object side, a fifth lens component of a biconvex lens, a sixth lens component of a biconcave lens, a seventh lens component of a positive meniscus lens with its convex surface facing the image side and an eighth lens component of a positive meniscus lens with its convex surface facing the image side. This lens system is so arranged that the lateral chromatic aberration is made small by increasing the Abbe number of the first lens component and also that the Petzval sum which is deteriorated thereby is corrected by increasing the refractive index of the fourth lens component.

Abstract: A photographic lens system of modified Gauss type comprising a first, second, third fourth and fifth lens components in which the first and second lens components are positive meniscus lenses arranged convex toward the object side, the third lens component is a negative meniscus lens arranged convex toward the object side, the fourth lens component is a negative cemented meniscus doublet comprising a biconcave lens and biconvex lens, the fifth lens component is a biconvex lens, the photographic lens system being compact and light in weight and having a long back focal length and aberrations corrected favorably.

Abstract: A compact cata-dioptric objective lens system comprising a first, second, third and fourth lens components in which the first lens component is a positive meniscus lens, the second lens component has a primary mirror formed on its surface on the image side by leaving a transparent central portion, the third lens component has a secondary mirror formed on its surface on the object side and the fourth lens component is cemented to the second lens component. The cata-dioptric objective lens system is arranged so that the rays entered through the first lens component are reflected by the primary and secondary mirrors, pass through the transparent central portion of the second lens component and are imaged thereafter and so that the fourth lens component has a large thickness in order to eliminate detrimental rays.

Abstract: A wide-angle zoom lens system comprising a front negative lens group and rear positive lens group and arranged to be zoomed by varying the airspace between the front and rear lens groups and to minimize variation of aberrations to be caused at the time of zooming.

Abstract: A shift lens system having a correcting means for correcting aggravation of aberrations to be caused when the lens system is shifted in parallel with the image surface. The correcting means is arranged to decenter at least one lens component in the lens system when the lens system is shifted and to thereby obtain a favorable image.

Abstract: A gauss type photographic lens system having a large aperture ratio which comprises five components of six lens elements and wherein symmetry of coma is improved and curvature of field, spherical aberration, etc., are favorably corrected by enlarging the airspace comprising a stop and increasing refractive indices of the lens elements arranged on both the sides of said stop.

Abstract: A large-aperture telephoto lens system with high telephoto ratio wherein a negative thick meniscus lens is arranged in the rear lens group for correcting the negative spherical aberration and negative coma which are produced by the positive meniscus lenses with high refractive indices positioned on the object side.