Abstract: A vari-focal lens system comprising, in the order from the object side a movable front lens unit having negative refractive power and a movable rear lens unit having positive refractive power, said front lens unit consists of a negative lens component and a positive lens component or a single negative lens component, and said rear lens unit comprising at least one negative lens component. Said vari-focal lens system consists of a very small number of lens components, concretely specifically three or four lens components.

Abstract: A stereoscope for viewing two stereoscopically complementary pictures which are positioned one above the other. The stereoscope includes a housing which has left and right front openings at the front of the housing and upper and lower rear openings at the back of the housing. A passageway leads from the left front opening to one of the rear openings and from the right front opening to the other rear opening. Optical elements, such as mirrors, are located within the passageways for directing a light image from one of the pictures through one of the rear openings to the left front opening and for directing a light image from the other picture through the other rear opening to the right front opening so that the observer sees the two images as superimposed and perceives the superimposed images as a single 3-dimensional picture.

Abstract: A zoom lens has a compact and simple structure, with satisfactorily corrected aberration and with a zooming ratio exceeding 2.0. The lens has a first lens group G.sub.1 of a positive refractive power and a second lens group G.sub.2 of a negative refractive power arranged in this order from the object side and effecting zooming operation by varying the distance of the lens groups. The first lens group G.sub.1 has a front group G.sub.F of a positive refractive power and a rear group G.sub.R of a positive refractive power, arranged in this order from the object side. The front group G.sub.F comprises a positive meniscus lens L.sub.11 convex to the object side, a negative lens L.sub.12 concave to the object side, a positive lens component L.sub.13 and a positive lens component L.sub.14, arranged in this order from the object side. The rear group G.sub.R comprises a positive lens L.sub.15, and the second lens group G.sub.2 comprises a positive meniscus lens L.sub.21 convex to the image side, a negative lens L.sub.

Abstract: This image reading apparatus includes a light source for illuminating an object, a lens array for focusing reflected light from the object into a predetermined position, and an image sensor for reading an image formed by the focused light. The lens array includes a transparent base and a diffraction element provided on at least an incident plane and an emission plane of the base. The lens array includes an array having a plurality of lens areas. The employment of the diffraction element renders a shorter imaging distance of light from the object and thus a reduction in the size of the apparatus.

Abstract: A filter for reducing the glare of a viewing screen caused by ambient light and increasing the viewing area constructed of a substantially transparent sheet of material having first and second faces. The first face is substantially planar while the second face has a plurality of V-shaped grooves, each groove being formed by two walls. The geometry of the V-shaped grooves is such that ambient light enters the filter and becomes trapped therein due to internal reflection.

Abstract: An optical collimator having a collimator lens which is divided into front and rear collimator lenses. An inclined transparent parallel plate is located between the two collimator lenses, whereby the optical collimator is substantially free from comatic aberration and results in a collimator which can be reduced in size.

Abstract: A method for providing corrections of distortions of an imaging device. Initial corrections may be provided through the use of active optics, to apply forces to the imaging device, or to a compensator device in a common optical path with the imaging device, so as to introduce deformations that cancel out the distortions. This action, in turn, may induce undesirable, secondary aberrations. The method of the invention provides steps for identifying, isolating and removing the undesirable secondary aberrations, and computing new applied forces that cannot induce the secondary aberrations.

Abstract: A zoom lens comprising, from front to rear, a first lens group of positive power, a second lens group of negative power, and a third lens group of positive power, wherein the second and third lens groups are axially moved in differential relation to effect zooming, and the following conditions are satisfied:______________________________________ 0.9 < .vertline..beta.2T.vertline. < 1.1, .beta.2T < 0 0.5 < .vertline..beta.3T.vertline. < 1 .beta.3T < 0 0.4 < XIII/fw < 0.6 ______________________________________where .beta.2T and .beta.2T are the image magnifications at the telephoto end of the second and third lens groups respectively, XIII is the range of zooming movement of the third lens group, and fW is the shortest focal length of the entire lens system.

Abstract: A compact high zoom ratio lens comprising from the object end a front positive stationary lens unit, a negative variating lens unit, a positive variating lens unit and a compensate lens unit, the variating lens units and the compensator lens unit being axially moveable to vary the equivalent focal length of said lens, the compensator group having an object magnification change of less than twenty-five percent over the zoom range of the lens.

Abstract: An optical system for endoscopes is provided with an inhomogeneous lens configured, as a relay lens, so that refractive index reduces progressively in going from a center portion toward a periphery and at least one of an entrance end face and an exit end face satisfies the following condition:0.15 P<C<0.35 Pwhere P is the pitch of the inhomogeneous lens and C is distance from the entrance end face or the exit end face of the inhomogeneous lens to the imaging position closest to the end face in the lens. The optical system for endoscopes is low in manufacturing cost and allows a favorable image of an object to be observed in a clear field of view without being adversely affected by dirt and burr.

Abstract: A modular optical system is provided in which a central element which carries an afocal variator optical system is provided, and to which central element both a front optical system and a rear optical system can be substantially permanently connected in optical series in combination. The modular optical system has the ability to vary the actual focal length of the front optical system in conjunction with the rear optical system without the need to physically change the length dimension or the lens position or the lenses of the front optical system. The afocal variator optical system includes in optical series a first positive lens, a negative lens, and a second positive lens.

Abstract: Optical systems with very long eye relief and large working distances (10) and (110) with four lenses (12), (14), (16), (18) and (20) and three lenses (112), (114) and (116), respectively, have lens surfaces shaped to focus upon an object such that a high resolution image is formed at infinity substantially over the entire field of view. High resolution and low distortion are substantially maintained independent of the user's eye location.

Abstract: An image pickup system using an objective lens system for endoscopes consisting of an objective lens system comprising a front lens unit having negative refractive power and a rear lens unit having positive refractive power, and an optical system comprising an image sensor, and so adapted as to permit disposing the image sensor obliquely or parallel relatively to the optical axis by prolonging back focal length of said objective lens system and arranging an optical path deflecting system between said objective lens system and said image sensor.

Abstract: A wide angle lens system having, from the object side, a first lens of a negative refractive power, a second lens of a positive meniscus lens, a third lens of a negative meniscus lens, a fourth lens of a positive meniscus lens, a diaphragm, a fifth lens being symmetrical with the fourth lens with respect to the diaphragm, a sixth lens being symmetrical with the third lens with respect to the diaphragm, a seventh lens being symmetrical with the second lens with respect to the diaphragm, and a eighth lens being symmetrical with the first lens. Each of the first and eighth lenses may have an aspherical surface in rotation symmetry with each other with respect to the diaphragm. Also, some of the lenses may be made of synthetic resin.

Abstract: A high zoom ratio zoom lens for a compact camera is disclosed which comprises in order from the object side, a first lens group having a positive focal length, a second lens group having a positive focal length, and a third lens group having a negative focal length. When zooming is carried out from a wide angle side to a telephoto side, the first, second and third lens group are all moved toward the object side so that a distance between the first and second lens groups is increased and a distance between the second and third lens groups is decreased.

Abstract: A zoom lens system comprising a first lens unit having negative refractive power and a second lens unit having positive refractive power, so adapted as to change focal length thereof by varying the airspace reserved between said first lens unit and said second lens unit, and using at least one radial GRIN lens in said first lens unit. Said zoom lens system comprises a very small number of lens elements, and has distortion and chromatic aberration corrected especially favorably.

Abstract: A chromatic aberration correcting lens assembly arranged on the image side of a photographic lens which is used in combination with a prism of a predetermined thickness on the image side thereof to correct the chromatic aberrations of the entire system, is constructed in the form of an assembly of three lens elements made of at least two different materials and cemented together at their adjoining surfaces, each of the cemented surfaces being made concave toward the image side.

Abstract: An optical device for varying magnification, having an object plane on which an object is to be located, a light receiving surface, and an imaging lens unit for focusing an image of the object located on the object plane onto the light receiving surface, so that upon varying the magnification, an optical distance between the object plane and the light receiving surface can be changed, wherein the imaging lens unit includes a main lens group and a correcting lens group that are movable relative to each other, the main lens group or the correcting lens group being fixed with respect to the light receiving surface, the correcting lens group or the main lens group being movable to the object plane and the light receiving surface to vary the magification.

Abstract: A refractive index distribution type meniscus-shaped single lens characterized in that it has a refractive index distribution in which the refractive index decreases along the optic axis thereof from a convex surface to a concave surface and the difference .DELTA.N in refractive index between the convex surface and the concave surface on the optic axis satisfies .DELTA.N.gtoreq.0.15.

Abstract: A shielding device for use on a color television screen has an electrically conductive mesh formed by knitting of black, anti-reflection conductive filaments, the diameter of the filaments being between 20-100 micrometer and the individual mesh being between 45-230 micrometer, and has a frame supporting the conductive mesh, the angle created between the filaments direction and the frame being in the range of 10-45 degree, and the conductive mesh lays over surface of a color television screen in a very close contact.