Abstract: A telephoto lens comprising; a front lens group comprising a positive lens, a negative lens and positive lens arranged in the written order from the object side, and having a positive refracting power, and a rear lens group arranged with a large space from the front group, in which the positive lens is made of an anomalous dispersion optical material, and the negative lens is made of lanthanum glass, and the telephoto lens satisfies the following conditions: ##EQU1## wherein F is the focal length of the whole system, .phi.i is the refracting power of the i-th lens from the object side, and ri is the curvature radius of the i-th lens surface of the lens from the object side.

Abstract: A compact wide angle zoom lens in order from the object side, of a divergent front lens group and a convergent rear lens group, the overall focal length being variable by mechanical movement of the front and rear lens groups. The divergent front lens group is composed, in order from the object side, of a first lens being a negative meniscus lens convex toward the object side, a second lens being a double convex positive lens or a positive cemented lens having positive and negative lenses, a third lens being a negative meniscus lens convex toward the object side, a fourth lens being a negative lens and a fifth lens being a positive lens. The convergent rear lens group is composed of a sixth lens being a positive lens, a seventh lens being a positive meniscus lens convex toward the object, an eighth lens being a double convex positive lens, a ninth lens being a double concave negative lens, the eighth and ninth lenses being cemented to each other, and the tenth lens being a positive lens.

Abstract: An objective for video disks comprising a first, second, third and fourth lenses in which the first lens is a biconvex lens, the second lens is a negative lens, the third lens is a positive lens, and the fourth lens is a positive lens and for which N.A. is large and aberrations such a spherical aberration, astigmatism, etc. are corrected favorably.

Abstract: A telephoto lens having a relatively short focal length compared to what is generally accepted as the focal length of a telephoto lens and corrected for aberrational deviations throughout the focusing range. The lens comprises a positive first (counting from the front) member, negative second and third members, and a positive fourth member. The first member consists of two positive components and one negative component, the frontmost and rearmost lens surfaces of each of said second, third and fourth members being convex and concave to the front and rear respectively, and said fourth member serving to cancel the residuals of spherical aberration and distortion. Focusing down to shorter object distances is performed either by forward axial movement of the entire system, or by rearward axial movement of the third member with the other members being stationary.

Abstract: A spectacle structure for wear during active sports where eye protection is desired includes a protective panoramic or wrap-around frame and portions snugly engaging spaced parts of the head to support the frame on the head of a person. Lenses, such as prescription lenses, are fitted into the frame with removable transparent guard lenses thereover and spaces are provided for ventilation of the lenses and the person's eyes to aid in remedying condensation and discomfort.

Abstract: An objective of the expanded Tessar type is disclosed. Five elements form four components of which the first counting from the front is positive and convex toward the front, the second is a bi-concave lens, the third is a positive doublet consisting of a negative lens element and a bi-convex lens element cemented together at their adjoining surfaces, and the fourth is a bi-convex lens. The objective fulfills the following conditions: ##EQU1## wherein f is the focal length of the entire lens system; Ri is the radius of curvature of the i-th surface counting from the front; Di is the axial thickness of the i-th glass or air lens element; and Ni is the refractive index of the material of the i-th lens element.

Abstract: A method of designing a telephoto type zoom lens having a convergent front member movable for focusing and capable of providing focusing down to as short an object distance as 6.5 times the longest focal length to achieve good stabilization of correction of spherical aberration on adjustment of the other aberrations within predetermined limits throughout the extended focusing range even when zooming is effected to the telephoto settings. This is accomplished by means of the formula:F(Ao, Lo) = .phi..sup.3 h.sup.4 Ao(1-.lambda..sup.4 -4a.beta.+6a.sup.2 .beta..sup.2) + 4.phi..sup.2 h.sup.2 Lo(-.beta.+3a.beta..sup.2) - .beta.(.alpha.').sup.2 + .beta..sup.2 {2.phi.(3+Po) + 3.alpha.'.alpha.'}In the case of the telephoto type zoom lens comprising, in addition to such front component, a divergent second component or variator, a convergent or divergent third component or compensator and a convergent fourth component or relay lens,-0.25.ltoreq.F(Ao, Lo).ltoreq.0.25is found as acceptable.

Abstract: The present invention relates to a large aperture zoom lens consisting of a positive focusing lens group, a negative variator, a negative compensator, an afocal lens group and an image forming lens in sequence from the object. The focusing lens group consists of a negative meniscus lens whose convex surface is directed toward the object, a bi-convex lens and a positive meniscus lens whose convex surface is directed toward the object, the variator of a negative meniscus lens whose convex surface is directed toward the object, the bi-concave lens and a positive lens cemented with each other, the compensator representing a negative lens of a bi-concave lens and a lens cemented with each other, the negative meniscus lens in the focusing lens group is distant from the bi-convex lens so as to form are air lens with weak divergence and the compensator is moved forwards and backwards at the same time with the movement of the variator for zooming.

Abstract: A light intensity filter for a telescope or other optical instrument viewed by the human eye is formed of an opaque material having a plurality of holes or windows. These windows transmit a reduced amount of light to the image-forming optical component. The area of the windows relative to the area of the optical component is selected to the light intensity being imaged. The filter is especially useful for telescopes and the like, wherein the image is viewed by a human observer and the light source is momentarily of great intensity. Under these conditions the filter prevents temporary blindness of the observer due to excessive illumination, for example, tracking a moving object across the sun.

Abstract: A conversion lens system to be attached to an objective lens system at the image side thereof for converting the focal length of the objective lens system into a greater value is provided. The conversion lens system has a negative focal length and comprises seven single lens elements consisting of a first negative meniscus lens element convex to the object side, a second biconvex lens element, a third biconcave lens element, a fourth biconvex lens element, a fifth negative lens element having a concave front surface, a sixth positive lens element having a convex rear surface and a seventh biconcave lens element. All of the seven lens elements may be separated from the others, or alternatively, at least two of the second to fourth lens elements may be cemented to each other.

Abstract: First and second electro-optical display devices for displaying visual acuity targets, one of which is adapted to be viewed by a patient and the other of which is adapted to be viewed by an examiner. An electronic memory is connected to the display devices containing a plurality of acuity targets stored in various orientations for presentation to the display devices. Controls are provided in an examiner's console for selecting one of a plurality of available target sizes, "zoom" increasing size or decreasing size, selecting a single or a line of multiple target characters, providing normal or reverse video presentation, changing the orientation of the target characters, and providing a blank screen. The size of the targets is varied by changing the dimensions of each of the targets about its own center and in the case of multiple targets, maintaining proportional spacing between the targets as the size of the targets vary.

Abstract: The disclosed camera objective has a fixed rear lens group preceded by a four-component front group with negatively refracting second and third components which are axially shiftable between positively refracting first and fourth components to establish a minimum overall focal length F.sub.min and a maximum overall focal length F.sub.max with a ratio of about 1:2. The substantially stationary first component consists of a negative front lens (which may be limitedly shiftable for focusing purposes) followed by three positive lenses while the movable second component consists of two negative lenses followed by a positive lens; the movable third component and the fixed fourth component are constituted by a negative and a positive lens, respectively.

Abstract: An optical system projects information recorded onto a record carrier on a projection plane. In the system a plurality of projecting lenses include a long focal length lens group composed of five lenses. As viewed from the projection plane there are two positive meniscus lenses (I and II) having their convex faces facing the projection plane, a concavo-concave lens (III), a convexo-convex lens (IV) and a negative meniscus lens having its convex face facing the record carrier.

Abstract: Dual projection lens systems are housed together to project adjacent stereo images onto a screen in stereoscopic position relationship. An ultra-violet filter is positioned on the optical axis of each lens system, and toward the screen a separate polarizer is positioned on each axis to provide polarized images to be seen by the viewer through binocular-polarized eyepieces. Heat sinks are attached to the filters for removing heat.

Abstract: A photographic lens system for use in a compact camera, having an angular field of view of 60.degree. to 70.degree. and aperture ratio of F/2.8 and comprising a first lens component of a positive meniscus lens with its convex surface on the object side, a second lens component of a biconcave lens, a third lens component of a single or cemented positive lens, a fourth lens component of a negative meniscus lens with its convex surface on the image side and a fifth lens component of a positive meniscus lens with its convex surface on the image side.

Abstract: An optically compensated zoom lens particularly suited for use in a still camera. This lens system comprises positive first, negative second and positive third lens groups counting from the front of which the first and third ones are axially movable in fixedly spaced relation to each other during zooming, while the second one remains stationary together with a relay lens group that follows the third lens group, the relay lens group consisting of a negative lens with its front surface of strong divergence, and bi-convex, bi-concave and bi-convex lenses. In said first and said second lens groups, there are provided individual divergent contact surfaces configured in opposite direction of curvature to each other so as to facilitate good correction of astigmatism and distortion.

Abstract: A standard photographic lens system comprising a first positive meniscus lens component, a second meniscus cemented doublet lens component, a third meniscus cemented doublet lens component and a fourth positive lens component. In said lens system, large radii of curvature are selected on the cemented surfaces of the second and third lens component respectively for facilitating to manufacture the respective elements of these two lens components, glass materials having low refractive indices are used for the respective lens elements for making it possible to manufacture said lens system at low cost, and various aberrations are favorably corrected.

Abstract: An apochromat type high magnification objective lens system for microscopes comprising a first cemented semispherical lens component, a second positive meniscus lens component, a third cemented lens component consisting of three lens elements, a fourth cemented lens component consisting of three lens elements, a fifth cemented meniscus lens component and sixth cemented meniscus lens component. Said lens system is so designed as to assure favorably corrected aberrations by improving the fourth, fifth and sixth lens components so as to have enhanced functions to correct chromatic aberration and other aberrations.

Abstract: An objective lens system for microscopes which has a large numerical aperture and a long working distance and wherein the secondary spectrum is sufficiently minimized and curvature of field, coma, etc. are favorably corrected over a wide range of visual field. Said objective lens system comprises a first single-element or cemented doublet lens component and at least three lens components, i.e., two cemented meniscus lens components so arranged as to face their concave surfaces each other and a cemented three-element lens component.

Abstract: A behind-stop type photographic camera lens system designed for an aperture ratio of F/2.8, a field angle of 60.degree., a short total length less than 0.37 f and favorably corrected aberrations, and comprising a first positive meniscus lens component, a second positive meniscus lens component, a third negative lens component, a fourth cemented lens component consisting of a biconvex lens element and a negative lens element.