Abstract: A zoom lens system of a relatively high zoom ratio about 2.5 to 3.5 ranging to a wide field angle such as 76 degrees is disclosed. The zoom lens system comprises, from the object to the image side, a first movable negative lens group, a second movable positive lens group, a third stationary negative lens group and a fourth movable positive lens group with a first to third variable air spaces formed therebetween, respectively.

Abstract: A zoom lens system with a focusing system other than a front group focusing system is provided. The lens system comprises a first lens group including at least two sub-groups with a variable air space therebetween to be varied during zooming, and a focusing lens group located at the image side of the first lens group, the lateral magnification .beta..sub.F with respect to the focusing lens group being continuously variable during zooming with a condition,.vertline..beta..sub.F .vertline.>1always fulfilled so that .vertline..beta..sub.F .vertline. is increased in accordance with the increase of the focal length of the whole lens system. The focusing lens group may be divided into two or three sub-groups with a variable air space therebetween to be varied during zooming. Further, an additional lens group may be located at the image side of the focusing lens group.

Abstract: An inverted-telephoto type wide angle lens system is provided which comprises from the object side to the image side: a first lens group of a negative refractive power; a second lens group of a positive refractive power; an aperture diaphragm; and a third lens group of a positive refractive power; wherein the second and third lens groups are shiftable to the object side along the optical axis of the lens system at different speeds from one another in a focusing operation to a closer object while the first lens group is stationary on the optical axis in the focusing operation.

Abstract: A focus detection apparatus for a camera comprising: a condensor lens being arranged close to or behind a predetermined focal plane of an objective lens of the camera. A pair of image separation members for separating the image of an object formed on the predetermined focal plane by use of light having been passed through the objective lens into two images which are arranged behind the condensor lens symmetrically with respect to the optical axis of the objective lens, wherein the correlation between the two images formed separately is measured in order to detect the focus condition of the objective lens. The image separating means including a mask for projecting the exit pupil of image separation member within an exit pupil of a cata-dioptric lens system as the objective lens.

Abstract: A telephoto lens system is provided having a first lens group of a positive refractive power, a second lens group of a negative refractive power with a variable air space, and a third lens group of a positive refractive power with a variable air space. All of the lens groups are shiftable during a focusing operation with the second lens group air space increasing and the third lens group air space decreasing when focusing is effected from infinity to a short distance.

Abstract: A zoom lens system of a relatively high zoom ratio about 2.5 to 3.5 ranging to a wide field angle such as 76 degrees is disclosed. The zoom lens system comprises, from the object to the image side, a first movable negative lens group, a second movable positive lens group, a third stationary negative lens group and a fourth movable positive lens group with a first to third variable air spaces formed therebetween, respectively.

Abstract: A zoom lens system with a focusing system other than a front group focusing system is provided. The lens system comprises a first lens group including at least two subgroups with a variable air space therebetween to be varied during zooming, and a focusing lens group located at the image side of the first lens group, the lateral magnification .beta..sub.F with respect to the focusing lens group being continuously variable during zooming with a condition,.vertline..beta..sub.F .vertline.>1always fulfilled so that .vertline..beta..sub.F .vertline. is increased in accordance with the increase of the focal length of the whole lens system. The focusing lens group may be divided into two or three sub-groups with a variable air space therebetween to be varied during zooming. Further, an additional lens group may be located at the image side of the focusing lens group.

Abstract: A zoom lens system of a relatively high zoom ratio about 2.5 to 3.5 ranging to a wide field angle such as 76 degrees is disclosed. The zoom lens system comprises, from the object to the image side, a first movable negative lens group, a second movable positive lens group, a third stationary negative lens group and a fourth movable positive lens group with a first to third variable air spaces formed therebetween, respectively.

Abstract: A zoom lens system comprising a first lens group of a negative refractive power, a second lens group of a positive refractive power located on the image side of the first lens group with a first variable air space, a third lens group of a negative refractive power located on the image side of the second lens group with a second variable air space and a fourth lens group or unit of a positive refractive power located on the image side of the third lens group with a third variable air space is provided. The first and third variable air spaces are reduced and the second variable air space is increased in accordance with the increase of the focal length of the whole lens system during the zooming. The absolute value of the focal length of the third lens group is greater than that of the second lens group.

Abstract: An optical projection system of unit magnification for transmitting a real erect image of an object from an object plane to an image plane, comprises a plurality of lenses having parallel optical axes and being arranged in one or more rows. Each lens comprises three or four lens elements arranged along a common optical path extending between the object and image planes, and includes at least two aperture masks which subtend light rays from the axial and off-axis object points in the object plane. These aperture masks are arranged in positions where the image-forming pencil of light rays passing through the lens has a relatively large cross-section.

Abstract: An inverted telephoto type wide angle lens system is provided. The lens system comprises an aperture stop, a first lens group located at the object side of the aperture stop, and a second lens group located at the image side of the aperture stop, the second lens group including at least two movable focusing lens groups, whereby the focusing is practiced by only the movement of the focusing lens groups with the remaining lens elements in the lens system stationary.

Abstract: The invention comprises an improvement to a compact copying apparatus of a slit exposure scanning type. A plurality of sheets of plastic lens elements provide an array of optical erecting lens systems that combine to provide overlapping images of an original on an image recording member. The optical system is designed to comply with predetermined parameters of distance between the original and the image recording planes, the magnification of the inverted real image, the maximum effective aperture of the lens system, and the distance between respective edges of maximum effective apertures of adjacent lens systems.

Abstract: An inverted telephoto type wide angle lens system of an aperture ratio, 1/2.0 and a field angle, 84 degrees is provided. The lens system consists, from the object to the image side, of: a first component of a positive meniscus lens element convex to the object side; a second component of a negative meniscus lens element convex to the object side; a third component of a negative meniscus lens element convex to the object side; a fourth component of a biconvex lens element; an aperture stop; a fifth component of a positive meniscus lens element convex to the object side; a sixth component of a biconvex lens element; a seventh component of a biconcave lens element; an eighth component of a positive meniscus lens element convex to the image side; and a ninth component of overall positive refractive power including at least one lens element.

Abstract: The present invention is directed to an inverted telephoto type wide angle lens system having eight lens groups and eight lens elements which fulfill the following conditions:______________________________________ 0.75f < .vertline.f.sub.1,2,3 .vertline. < 1.1f f.sub.1,2,3 < 0 0.89f < f.sub.1,2,3,4,5 < 2.3f 0.5 < d.sub.7 /d.sub.6 < 2.0 1.0 < d.sub.8 /d.sub.10 < 2.4 1.5 < d.sub.7 /d.sub.9 < 5.2 ______________________________________wherein f.sub.1,2,3 represents the total focal length of the first to third single lens elements; f.sub.1,2,3,4,5 represents the total focal length of the first to fifth single lens elements; f represents the focal length of the entire lens system, and d.sub.i represents the i-th axial distance numbered consecutively from the front of the lens system.

Abstract: A projection television system having a light emitting target and a screen for realizing a projected video image is provided with an improved reflecting optical system which provides enhanced resolution and uniform correction of aberrations across a projected image. The optical system includes a concave mirror, positioned adjacent the light emitting target, for reflecting the video image towards the display screen. An optical compensating plate having at least one aspherical surface is located on the optical path. A meniscus lens is also located in the optical path. Both the optical compensating member and the meniscus lens can be positioned outside the vacuum envelope of the target and the electron gun to simplify alignment and construction.