Abstract: A lens assembly, which is mounted on a digital still camera (DSC), comprises a fixed aperture, and a lens unit. The lens unit has a first lens, a second lens, a third lens, a fourth lens and a fifth lens in sequence. The first lens is a negative meniscus lens disposed at the front side of the lens unit. The second lens is a biconvex lens. The third lens is a biconcave lens. The fourth lens is a positive meniscus lens. The fifth lens is a positive lens having a surface, which has a larger curvature radius, facing the image side. The aperture is arranged between the second lens and the third lens.

Abstract: A lens assembly, which is mounted on a digital still camera (DSC), comprises a fixed aperture, and a lens unit. The lens unit has a first lens, a second lens, a third lens, a fourth lens and a fifth lens in sequence. The first lens is a biconcave lens disposed at the front side of the lens unit. The second lens is a biconvex lens. The third lens is a biconcave lens. The fourth lens is a positive meniscus lens. The fifth lens is a positive lens. The aperture is arranged between the first lens and the second lens.

Abstract: A standard photographic lens is disclosed that includes a front lens group, a diaphragm stop, and a rear lens group, in order from the object side. The front lens group is formed of a negative meniscus lens with its convex surface on the object side, and a positive meniscus lens with its convex surface on the object side. The rear lens group is formed of a third lens element of negative refractive power with a concave surface on the object side, a fourth lens element of positive refractive power with a convex surface on the image side, and a fifth lens element, of meniscus shape with its concave surface on the image side. Organic material is preferably used for the second and third lens elements. Various conditions are satisfied so as to provide a lens having a bright image with favorably corrected aberrations.

Abstract: A retrofocus wide-angle lens is formed of only three lens groups, in order from the object side, a first lens group of negative refractive power, a second lens group that includes a stop, and a third lens group of positive refractive power. The first lens group is at the object end of the retrofocus wide-angle lens and includes, in order from the object side, a plurality of negative lens components and a plurality of positive lens components. The first lens group includes three lens groups with particular lens features, the first of which, from the object side, also includes two lens groups with particular features. Various combinations of lens elements satisfy two conditions for ratios of absolute values of focal lengths for the various combinations of lens elements that assist in achieving excellent imaging.

Abstract: A wide angle imaging system for providing a wide angle field of view of an area exteriorly of a vehicle comprises an outer negative or wide angle group of lenses for receiving the wide angle field of view and directing a virtual image toward a positive, converging or focusing group of optics, which further refract and focus the image and provide a focused image to an image capture device. The focusing group of lenses preferably comprises three plastic optic elements, which include a diffractive element and aspheric surfaces to correct for color, distortion and other aberrations in the wide angle virtual image received from the wide angle group of lenses. The wide angle group of lenses are also preferably formed of a plastic material, such as polycarbonate or acrylic, and include a diffractive element on one of the elements. The imaging system thus provides a low cost, light weight and compact wide angle focusing system which does not include expensive and fragile precision optic and/or glass elements.

Abstract: In a wide-angle lens system having a long back focal length, the various types of aberration, particularly distortion, are kept small. The wide-angle lens system 100 is disposed in front of a ⅓″ CCD camera 40 and the focal length (f) for all lens groups is 3.0 mm, the F-number is 3.0 and the half-field angle is 46°.

Abstract: A wide angle projection lens consists of a Gnp lens group having positive refractive power and a Gf lens group having positive refractive power in the order from a large conjugate side toward a small conjugate side, and further the Gnp lens group consists of a Gn lens group having negative refractive power and a Gp lens group having positive refractive power in the order from the large conjugate side toward the small conjugate side, while satisfying −1.8<fn/f<−1.1, 3.2<fp/f<5.5, 1.2<Dnp/f<2.4 and 2.8<ff/fnp<4.4, where f: focal length of the whole lens system, fn: focal length of the Gn lens group, fp: focal length of the Gp lens group, Dnp: air spacing between the Gn lens group and the Gp lens group, fnp: focal length of the Gnp lens group and ff: focal length of the Gf lens group.

Abstract: A large aperture super wide-angle lens system has an angle of view of 2&ohgr;=94° or more, an f-number of about 1.4, small variation in close-range aberrations, compactness, and high optical performance. The lens system includes, in order from an object, a negative lens group GN having negative refractive power which is fixed upon focusing, and a positive lens group GP having positive refractive power as a whole which is moved upon focusing. The positive lens group GP includes a front lens group GF having an aperture stop and a rear lens group GR having positive refractive power. Focusing at a close object is carried out by moving the front lens group GF and the rear lens group GR to the object side with different moving amounts. Prescribed conditional expressions are satisfied.

Abstract: A telescopic lens system includes a positive first lens group, and a positive second lens group. The first lens group includes cemented lens elements having a positive lens element and a negative lens element. The second lens group includes cemented lens elements having a positive lens element and a negative lens element.

Abstract: Compactness of a projection type image display apparatus is realized by achieving miniaturization and wide-angle of a projection lens apparatus while various kinds of aberration are satisfactorily compensated. A first lens group having a negative refracting power, a second lens group having a positive refracting power, and a third lens group having a positive refracting power are positioned in this order, from a screen side, toward an image display element side, in the projection lens apparatus. When f, f1, f3, f23, and fb represent, respectively, a focal length of the whole lens system, a focal length of the first lens group, a focal length of the third lens group, a combined focal length of the second and third lens groups, and a back focus of the whole lens system, the projection lens apparatus satisfies the following conditions: 1.4<|f1|/f  (1) 2.8<f3/f  (2) 3.6<fb/f  (3) 0.1<|f1/f23|<0.3.

Abstract: A wide-angle lens system includes a negative first lens group, a positive second lens group, a diaphragm, and a positive third lens group. Upon focusing, the positive second lens group moves along the optical axis direction.

Abstract: A projection television system (10) is provided which has a CRT (16) and a projection lens system (13) for forming an image on a screen (14). The projection lens system (13) is characterized by a diffractive optical surface (DOS) which provides color correction for the lens system. The diffractive optical surface (DOS) can be formed as part of a diffractive optical element (DOE) or as part of an existing lens element of the lens system. The diffractive optical surface (DOS) is located between the object side (S2) of the lens' first lens unit (U1) and the image side (S11) of the lens' third lens unit (U3). The distance between the diffractive optical surface (DOS) and the lens' aperture stop (AS) is less than 0.1·f0, where f0 is the focal length of the projection lens (13).

Abstract: A zoom lens system having multiple lens units including, sequentially in a direction from an enlargement side thereof toward a reduction side thereof, a first lens unit having a negative optical power, a second lens unit having a positive optical power, a third lens unit having a positive optical power, a fourth lens unit having a negative optical power, and a fifth lens unit having positive optical power. Additionally, during a zoom operation from a longest focal length condition to a shortest focal length condition, the zoom lens system can function such that the first lens unit and the fifth lens unit can remain stationary, while the second, third and fourth lens units are able to move.

Abstract: Provided is a retrofocus imaging lens in which various aberrations are satisfactorily corrected, having a sufficient space from a mechanism viewpoint so that a focus group does not interfere with a lens shutter mechanism even at the time of focusing according to a rear-focus system. A retrofocus imaging lens has, in order from an object side, a first lens group and a second lens group. The first lens group is constructed of, in order from the object side, a front-side first lens group having a negative refractive power as a whole and a rear-side first lens group having a positive refractive power as a whole. The first lens group is basically constructed to have a positive refractive power as a whole. The second lens group includes one or more positive lens and one or more negative lens and has a positive refractive power as a whole. Each of the front-side first lens group and the rear-side first lens group includes, basically, one or more positive lens and two negative lenses.

Abstract: A wide-angle, single focus lens is disclosed that is formed of four lens elements of negative, positive, negative, and positive refractive power, in sequential order from the object side. The first lens element is concave on its object side, the second lens element has at least one surface that is aspheric, and the fourth lens element is convex on its image side and has at least one surface that is aspheric. Specified conditions are preferably satisfied in order to reduce aberrations and provide a bright image while maintaining a short overall lens length.

Abstract: A seal for a container opening includes a backing layer and a seal layer for connecting to and covering an opening of the container. A pull-tab forming layer is sandwiched between the backing layer and the seal layer. The pull-tab forming layer has a heat sealable surface joined to the backing layer. An opposite heat resistant surface is joined to the seal layer. A hinge is disposed near the center of the seal that joins the backing layer and the sealed layer wherein the backing layer and at least a portion of the pull-tab forming layer define a pair of pull-tabs extending from the hinge. A method of forming the seal including the pull-tab forming layer and a material blank for forming a plurality of the seals are also described.

Abstract: Projection lenses (13) for use with pixelized panels (PP) are provided. The projection lenses have a negative first unit (U1) which has at least one aspheric surface and a positive second unit (U2) which has three subunits (US1, US2, US3) which have a positive/negative/positive configuration. The lens' aperture stop (AS) is located at the short conjugate end of the lens and is either in the third subunit (US3) or close to that subunit. The lenses are particularly well-suited for use in the manufacture of compact projection systems which employ side illumination of a reflective pixelized panel.

Abstract: A retrofocus lens system has a negative first, a positive second and a positive third lens group. The first lens group includes an aspheric first lens, a negative meniscus second and third lenses that are convex on the large conjugate side, and a negative meniscus fourth lens being convex on the small conjugate side. The second lens group includes a positive fifth lens and a sixth lens joined to the fifth lens. The third lens group includes a positive meniscus seventh lens being convex on the small conjugate side, a biconcave eighth lens, a positive ninth lens joined to the eighth lens, a biconvex tenth and eleventh lenses, and an aspheric twelfth lens. The system satisfies 0.8<f2/f3<1.5, 1.6<|f1|/f<2.

Abstract: An image pickup lens system includes a first lens, a stop, and a second lens arranged in a row from an object side to an image side. The first lens is a meniscus resin lens having negative power and oriented such that a convex surface thereof faces the object side. The second lens is a meniscus resin lens having positive power and oriented such that a convex surface thereof faces the image side. The image pickup lens system has at least two aspheric lens surfaces such that the first lens has at least one aspheric surface and such that the second lens has at least one aspheric surface, and is configured so as to satisfy conditions represented by: 3.2f≦|r3|≦50f; 0.9f≦d≦1.5f; and 0.1<|f2|/|f1|<0.

Abstract: A taking lens system has, from the object side, a front lens unit including a first lens element and a second lens element, an aperture stop, and a rear lens unit including a third positive lens element, a fourth negative lens element, and a fifth positive lens element. In the taking lens system, the following condition is fulfilled: 0.3<F/F345<0.9 where F represents the focal length of the entire taking lens system; and F345 represents the composite focal length of the third to fifth lens elements.

Abstract: Objective lenses employing three lens units U1, U2, U3 having a negative (or weak positive); positive; negative optical power configuration are disclosed. The lenses have a total field coverage of at least 50 degrees with a relative aperture of less than f/5. They employ small lens elements having aspherical surfaces and are designed for mass production, particularly using plastic optical materials. Designs for these lenses do not exist in all-spherical form, because the aberrations, particularly distortion, cannot be sufficiently corrected; however, by using a sufficient number of aspherical surfaces, not only can the aberrations be corrected to a higher degree than a conventional aspherized triplet design, but the sensitivity of the design to manufacturing deviations can also be minimized.

Abstract: A wide-angle lens system includes a negative first lens group, and a positive second lens group, in this order from the object. The second lens group includes a positive 2F sub-lens group and a positive 2R sub-lens, in this order from the object. Upon focusing from infinity to a closer object distance, an Fa lens group constituted by the first lens group and the positive 2F sub-lens group which are arranged to move integrally, and an Fb lens group constituted by the positive 2R sub-lens group are independently moved from the image side toward the object side so that the distance between the Fa lens group and the Fb lens group are made shorter.

Abstract: A wide-angle projection lens is disclosed having three lens groups of negative, positive, and positive refractive power, respectively, in order from the enlarging side, and that favorably corrects both distortion and lateral color. The wide-angle projection lens includes a diaphragm positioned between the second lens group and the third lens group, and is especially suitable for use in a rear-projection-type image display device that uses a multi-display technique wherein multiple projection lenses arranged in an array, with each projection lens displaying image information for a particular segment of the image to be displayed. By satisfying specified conditions, the wide-angle projection lens, when used in a projection-type image display device, enables the image display device to be more compact.

Abstract: In order to provide a large relative-aperture super wide-angle lens having the inclusive angle of 2&ohgr;=115° or more with the conventional projection method (y=f·tan &thgr;) having the relative-aperture of about F 2.8, having compactness and high optical performance, and having small variation of aberration in relatively closed object distance, the lens includes, in order from the object, a divergent lens group Gn having negative refractive power and a convergent lens group Gp having positive refractive power, and the divergent lens group Gp includes at least one aspherical negative lens, and the aspherical lens satisfies predetermined conditional expressions.

Abstract: A wide-angle lens system includes a negative first lens group, and a positive second lens group with a diaphragm, in this order from the object. The wide-angle lens system satisfies the following condition: −1.4<f1/f<−1.1  (1) wherein f1 designates the focal length of the first lens group, and f designates the focal length of the entire lens system.

Abstract: A wide-angle lens system includes a negative first lens group, and a positive second lens group. The first lens group includes a positive lens element, and a negative lens element. The wide-angle lens system satisfies the following conditions: 0<(&phgr;1-2+&phgr;2-1)/&phgr;<0.3 . . . (1); 0.5<HF/HL<0.9 . . .

Abstract: An optical system includes a window, an optical corrector formed of a curved piece of a transparent material having a front surface and a back surface, and a sensor system with a sensor positioned such that the optical corrector is between the window and the sensor. At least one of the front surface and the back surface of the optical corrector is a segment of a convex aspheric curve rotated about a center, otherwise known as a torus.

Abstract: A retrofocus lens system has a negative first, a positive second and a positive third lens group. The first lens group includes an aspheric first lens, a negative meniscus second and third lenses that are convex on the large conjugate side, and a negative meniscus fourth lens being convex on the small conjugate side. The second lens group includes a positive fifth lens and a sixth lens joined to the fifth lens. The third lens group includes a positive meniscus seventh lens being convex on the small conjugate side, a biconcave eighth lens, a positive ninth lens joined to the eighth lens, a biconvex tenth and eleventh lenses, and an aspheric twelfth lens. The system satisfies 0.8<f2/f3<1.5, 1.6<|f1|/f<2.

Abstract: Very compact, high numerical aperture, high resolution, ultra-wide field of view concentric optical apparatus. The concentric optical apparatus comprises a concentric lens and a focal surface array disposed along a focal surface of the concentric shell outer lens. The optical apparatus may further comprise an image intensifier tube optically coupled to the concentric lens by way of a curved fiber optic relay having an input surface that is concentrically disposed with respect to the concentric lens. The optical apparatus may also comprise a dewar that houses the focal surface array, and wherein the concentric lens comprises a cold stop for the focal surface array.

Abstract: An optical system includes a curved window, an optical corrector adjacent to a curved inner surface of the window, an optical train positioned such that the optical corrector lies between the curved window and the optical train, a movable optical train support upon which the optical train is mounted, and a sensor disposed to receive an optical ray passing sequentially through the window, the optical corrector, and the optical train. The optical corrector has an inner surface and an outer surface, at least one of which has a shape described by a modified Zernike polynomial surface.

Abstract: An optical system includes a curved window, an asymmetric, scoop-shaped optical corrector adjacent to a curved inner surface of the window, an optical train positioned such that the optical corrector lies between the curved window and the optical train, a movable optical train support upon which the optical train is mounted, and a sensor disposed to receive an optical ray passing sequentially through the window, the optical corrector, and the optical train. The optical corrector has an inner surface and an outer surface, at least one of which has a shape defined by an asymmetric polynomial.

Abstract: Projection lens systems (13) for use in CRT projection televisions (10) are provided. From the screen side, the systems have three lens units (U1, U2, U3), the first two units (U1, U2) forming a retrofocus lens and the third unit (U3) being associated with the CRT during use and serving to correct field curvature. At its screen end, the first lens unit (U1) has a negative element (E1) which has a screen surface (S1) which is concave to the screen. The second lens unit (U2) has two positive subunits (US1, US2), the first subunit (US1) being a color correcting doublet composed of glass and the second subunit having a positive lens element (E2) at its screen end. The projection lens systems are fully color corrected, have f/#'s of 1.0 for an infinite conjugate, have half fields of view of at least 25°, and are economical to manufacture.

Abstract: A wide-angle lens of fixed focal length formed of four lens groups of negative, positive, positive and positive refractive power, respectively, in order from the enlarging side is disclosed. The fourth lens group as well as one of the lens groups of among the first lens group, the second lens group and the third lens group are fixed in position. The other two lens groups of among the first lens group, the second lens group and the third lens group are moved during focusing, and specified conditions are satisfied in order to: (1) insure that the wide-angle lens is nearly telecentric on its reducing side, (2) maintain favorable correction of aberrations, (3) maintain a sufficiently large back focus for insertion of necessary components, and (4) enable the wide-angle lens to be compact. Preferably, the movement amount during a given focus adjustment of one of the two moveable lens groups is directly proportional to the movement amount of the other moveable lens group.

Abstract: A photographic lens for an electronic still camera having five lens components, with refractive powers in sequential order from the most object side, as follows: negative, positive, positive, negative and positive. A stop is positioned between the second lens component and the third lens component. The photographic lens has a short overall length, a wide angle of view, a large numerical aperture, and high resolution as a result of the lens being favorably corrected for aberrations. The first lens component includes at least one ashperical surface, the second lens component has a convex surface on the image side, the third lens component has at least one aspherical surface, and has a convex surface on the image side. The fourth lens component has a concave surface on the object side, and the fifth lens component has a convex surface on the image side.

Abstract: A wide-angle lens of fixed focal length formed of four lens groups of negative, positive, positive and positive refractive power, respectively, in order from the enlarging side is disclosed. The fourth lens group as well as one of the lens groups of among the first lens group, the second lens group and the third lens group are fixed in position. The other two lens groups of among the first lens group, the second lens group and the third lens group are moved during focusing, and specified conditions are satisfied in order to: (1) insure that the wide-angle lens is nearly telecentric on its reducing side, (2) maintain favorable correction of aberrations, (3) maintain a sufficiently large back focus for insertion of necessary components, and (4) enable the wide-angle lens to be compact. Preferably, the movement amount during a given focus adjustment of one of the two moveable lens groups is directly proportional to the movement amount of the other moveable lens group.

Abstract: An objective optical system is disclosed having, in a first construction, in relative order from the object side, a first lens element of negative refractive power, a visual field conversion optical element which folds light rays incident thereon, a stop, and either one or two additional lens elements of positive refractive power which form an objective optical system. Certain prescribed conditions are satisfied in order that the objective optical system be compact and have acceptably small aberrations to thereby enable a high quality image to be formed. In a second alternative construction, the stop is positioned after the second lens element and the third lens element includes a convex surface on the image side and satisfies a prescribed condition.

Abstract: A taking lens system has, from the object side, a front lens unit, an aperture stop, and a rear lens unit. The front lens unit is composed of two lens elements that are, from the object side, a positive glass element and a negative plastic lens element. The rear lens unit has a positive plastic lens element disposed at the image-side end thereof. On the object side of this positive plastic lens element is disposed solely a lens element made of glass.

Abstract: An imaging lens comprises a front group constituted by a first lens L1 made of a negative meniscus lens having a convex surface directed onto the object side, the object-side surface thereof being made aspheric, and a second lens L2 made of a biconvex lens having a surface with a larger curvature directed onto the object side; and a rear group constituted by a third lens L3 made of a biconcave lens and two biconvex lenses L4, L5. Letting d be the distance from the object-side surface of the first lens L1 to the image-side surface of the second lens L2, f be the focal length of the whole lens system, and nA and &ngr;A be average values of refractive index and Abbe number, respectively, in the two biconvex lenses L4, L5, the imaging lens satisfies 1.0<d/f<2.0, nA>1.76, and &ngr;A>45.0.

Abstract: A wide angle imaging system for providing a wide angle field of view area exteriorly of a vehicle comprises an outer negative or wide angle group of lenses for receiving the wide angle field of view and directing a virtual image toward a positive, converging or focusing group of optics, which further refract and focus the image and provide a focused image to an image capture device. The focusing group of lenses preferably comprises three plastic optic elements, which include a diffractive element and aspheric surfaces to correct for color, distortion and other aberrations in the wide angle virtual image received from the wide angle group of lenses. The wide angle group of lenses are also preferably formed of a plastic material, such as polycarbonate or acrylic, and include a diffractive element on one of the elements. The imaging system thus provides a low cost, light weight and compact wide angle focusing system which does not include expensive and fragile precision optic and/or glass elements.

Abstract: A retro focus lens having three lens groups arranged, in order from the longer conjugate length side of the lens, as follows: a negative first lens group G.sub.1, a positive second lens group G.sub.2, and a positive third lens group G.sub.3. The first group G.sub.1 includes, in order from the longer conjugate length side of the lens, a first lens element L.sub.1 of small positive refractive power and made of plastic with an aspherical surface, a second lens element L.sub.2 of negative refractive power that is made of glass and has a concave surface facing the shorter conjugate length side of the lens, and a third lens element L.sub.3 of negative refractive power with a concave surface facing the shorter conjugate length side of the lens, there being no additional lens elements between the first lens element L.sub.1 and the third lens element L.sub.3.

Abstract: An objective lens system for endoscopes comprising a first lens component (L.sub.1) which has no or a negative refractive power, a second lens component (L.sub.2) which has a convex image side surface and a third lens component (L.sub.3) which has a convex object side surface, wherein a radius of curvature r.sub.3F on the object side surface of the third lens component and a thickness of the third lens component satisfy the following condition:3<r.sub.3F /D.sub.3 <10.

Abstract: A close-up photographing lens (10) having a long back focus and a large aperture, thus making the lens suitable for use with high-performance electronic imaging equipment. The lens comprises, objectwise to imagewise, a first lens group (G1) having positive refractive power, a second lens group (G2) having positive refractive power, and a relay optical system (GL) having positive refractive power. The relay optical system includes a third lens group (GLN) having negative refractive power and a fourth lens group (GLP) having positive refractive power. The first lens group and the second lens group are separated by an axial air space (D12) and move objectwise on different trajectories (16,18) when changing focus from an infinite focus state to a most close-up focus state. The axial air space is narrower in the most close-up focus state than in the infinite focus state. The lens preferably satisfies at least one of a number of design conditions.

Abstract: A wide-angle zoom lens is disclosed having four lens groups of negative, positive, positive, and positive refractive power, in order from the object side. By satisfying prescribed conditions, the overall length as well as the outer diameter of the wide-angle zoom lens can be kept small, the number of lens elements required can be minimized so as to keep manufacturing costs low, yet a high-quality image is provided over the entire range of zoom. During zooming, the first and fourth lens groups remain in a fixed position while the second and third lens groups are moved along the optical axis. The first lens group G.sub.1 includes at least one negative lens element with a concave surface of strong curvature on the image side. The second lens group G.sub.2 has at least one biconvex lens. The third lens group G.sub.3 may consist of a single positive lens. The following conditions are satisfied:-2.5<f.sub.1 /f.sub.w <-1.52.0<f.sub.2 /f.sub.w <4.0wheref.sub.

Abstract: An imaging lens is disclosed having two lens groups, both of positive refractive power, a diaphragm positioned between the lens groups, and five or fewer lens elements with no aspherical surfaces. The imaging lens provides a high resolution over a wide image angle. During focusing, only the position of the rear lens group is adjusted relative to the image surface, enabling a low-cost shutter mechanism to be employed as the diaphragm. The front lens group includes, in order from the object side, either a plano-concave or a biconcave lens element and, in addition, a biconvex lens element. The rear lens group includes, in order from the object side, a positive meniscus lens element with its convex surface on the image side, a negative meniscus lens element with its concave surface on the image side, and a biconvex lens element. By having the ratio of the focal length of the positive meniscus lens element of the rear lens group divided by the focal length of the imaging lens be greater than 1.4 and less than 4.

Abstract: The invention provides a compact and simple wide-angle lens system composed of a reduced number of lenses and having high productivity, which is well suited for use on digital cameras, while making sure of the space necessary for edge, and middle thicknesses, and constructing the system and, at the same time, having a given back focus and exit pupil position, and good-enough image-forming capability, and which comprises two lens groups or, in order from the object side thereof, a negative lens group GN and a positive lens group GP with an aperture stop D midway between them and a lens located nearest to the object side thereof being defined by a positive lens, said positive lens conforming three conditions in terms of focal length, shape factor, and making sure of sufficient edge thickness.

Abstract: An image-forming lens having four lens elements of refractive power, in order from the object side, of: negative, positive, positive, and negative. By making the distance from image-side surface of the first element to the image-side surface of the second lens element to be greater than or equal to 0.3 f and less than or equal to 1.5 f, where f is the focal length of the image-forming lens, an image-forming lens having an F# of approximately 2.8 and a picture angle of about 60 degrees is obtained. A diaphragm may be positioned such that the distance along the optical axis from the diaphragm to the object side of the fourth lens is less than or equal to the focal length of the image-forming lens.

Abstract: A super wide angle lens, having a viewing angle greater than 120 degrees, and an F-number of about 1.2 is disclosed. The lens is formed of a first lens group G.sub.1 of negative refractive power, a second lens group G.sub.2 of positive refractive power, and a third lens group G.sub.3 of positive refractive power. The lens is designed so that the lens elements used in the lens groups may be easily and economically manufactured. The first lens group has a first lens element L.sub.1 composed of a negative meniscus lens with its convex surface on the object side, and a second lens element L.sub.2 composed of a negative meniscus lens with its convex surface on the object side. The second lens group includes a third lens element L.sub.3, that is biconcave, cemented to a fourth lens element L.sub.4 that is biconvex. The third lens group has four lens elements: a fifth lens element L.sub.5 composed of a negative meniscus lens, with its convex surface on the object side; a sixth lens element L.sub.

Abstract: The invention comprises a real image zoom finder including an objective lens group, an erecting group, and an eyepiece lens group. The objective lens group includes a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a positive refractive power, and a fourth lens having a positive refractive power. The surface of the fourth lens closest to the image side of finder is convex and the second lens is biconvex. The real image zoom finder has a simple structure and good performance for all magnification ranges.

Abstract: An optical system includes a housing having an axis of elongation, and a non-spherical window affixed to the housing. An optical corrector, preferably in the form of an aspherical strip of transparent material, is positioned adjacent to the curved inner surface of the window. The optical corrector is mounted on an optical corrector support, which is rotatable about the axis of elongation. An optical rain is positioned such the the optical corrector lies between the window and the optical train. The optical train includes at least one optical element operable to alter an optical ray incident thereon, and a gimbal upon which the at least one optical element is mounted. The gimbal is pivotable about a transverse axis perpendicular to the axis of elongation. The optical train is mounted on an optical train support, which is movable independently of the optical corrector support. A sensor is positioned to receive the optical ray passing sequentially through the window, the optical corrector, and the optical train.

Abstract: A low-cost wide-angle lens assembly being comprised of a decreased number of lenses yet capable of properly correcting optical aberrations. The second lens in each lens group from the minimum to the maximum horizontal viewing angle is commonly used, and the first lens in each lens group from a reference angle to the maximum horizontal viewing angle is commonly used, thus reducing the total number of required lenses. Aberrations are favorably corrected by satisfying predetermined conditions as to focal distances and back focuses of the lenses.