Abstract: A lens system has the following components in order from an object side: one negative lens component; a positive lens component; a negative lens component having a concave surface of a large curvature on an image side; an aperture stop; a negative lens component having a concave surface of a large curvature on the object side; and a positive lens component; the lens system satisfies a condition of the following expression: 0.75<SF1<1.60, where SF1=(R1+R2)/(R1?R2), and where R1 is a radius of curvature of an object-side lens surface of the negative lens component located nearest to the object side, R2 is a radius of curvature of an image-side lens surface thereof, and SF1 is a shape factor thereof.

Abstract: Disclosed is an imaging lens having a small F number, a wide angle of view, and a low manufacturing cost and capable of obtaining a high-quality image. An imaging lens includes a first lens having a negative power and including a concave surface facing an image side, a second lens having a positive power, an aperture diaphragm, a third lens having a negative power, an aperture diaphragm, a fourth lens having a positive power, a fifth lens having a positive power and including a convex surface facing the image side, and a sixth lens having a negative power arranged in this order from an object side. When the curvature radius of an image-side surface of the third lens is R3r and the curvature radius of an object-side surface of the fourth lens is R4f, the imaging lens satisfies the following Conditional expression: |R3r/R4f|<1.0.

Abstract: An imaging lens includes, in order from an object side, a positive first lens group, a stop, and a positive second lens group. The first lens group includes, in order from the object side, a first lens, which is a negative meniscus lens having a convex object-side surface, and a second lens having a positive power and including a convex image-side surface. The second lens group includes, in order from the object side, a third lens having a negative power and including a concave object-side surface, a fourth lens having a positive power and including a convex image-side surface, a fifth lens, which is a biconvex lens, and a sixth lens, which is a meniscus lens having a negative power and including a convex surface facing an image side. Each of the first to sixth lenses is a single spherical glass lens.

Abstract: An imaging lens system in order from the object side to the image side includes a first lens with negative refractive power, a second lens with positive refractive power, a third lens with negative refractive power, a fourth lens with positive refractive power, a fifth lens with negative refractive power and a sixth lens with positive refractive. The imaging lens system satisfies the following formulas: Nd2>1.8 and Vd2<25, where Nd2 is the refractive index of the second lens, Vd2 is the Abbe number of the second lens.

Abstract: An image reading lens system of Example 1 includes six lenses having first to sixth lenses being arranged in order from an object side and an aperture diaphragm. In the image reading lens system, the first lens, the third lens, and the sixth lens are formed of negative lenses, and the second lens, the fourth lens, and the fifth lens are formed of positive lenses. The first lens, the second lens, the third lens, and the fifth lens are made of glass, and surfaces of all these lenses are formed of spherical surfaces. The fourth lens and the sixth lens are made of resin, and surfaces of the fourth lens and surfaces of the sixth lens are formed of aspheric surfaces. A cemented lens is formed of the second lens and the third lens with a cemented surface interposed therebetween, and is disposed adjacent to the aperture diaphragm.

Abstract: An imaging lens system in order from the object side to the image side includes a first lens with negative refractive power, a second lens with positive refractive power, a third lens with negative refractive power, a fourth lens with positive refractive power, a fifth lens with negative refractive power and a sixth lens with positive refractive. The imaging lens system satisfies the following formulas: Nd2>1.8 and Vd2<25, where Nd2 is the refractive index of the second lens, Vd2 is the Abbe number of the second lens.

Abstract: An endoscope objective lens includes, in order from an object side, a negative first lens, a first cemented lens, an aperture diaphragm, a positive fourth lens and a second cemented lens. The negative first lens has a concave surface directed to an image side. The first cemented lens is formed by cementing a second lens and a third lens. One of the second and third lenses is positive and. The other is negative. The positive fourth lens includes a flat surface or a surface having a larger absolute value in radius of curvature, directed to the object side. The second cemented lens is formed by cementing a positive fifth lens and a negative sixth lens in order from the object side. The second cemented lens has a positive refractive power as a whole. The endoscope objective lens satisfies the following conditional expressions (1) and (2). f 2 × ? v 5 - v 6 ? ? R A ? × ( Bf + d 6 / n 6 ) > 10 ( 1 ) Bf / f > 2.

Abstract: A zoom lens includes, in order from a magnification side, a negative first lens group for focus adjustment adapted to be fixed during power-varying, a positive second lens group adapted to move during power-varying, a negative third lens group, a positive fourth lens group, and a positive fifth lens group, and a positive sixth lens group adapted to be fixed during power-varying, the sixth lens group having a stop arranged nearest to the magnification side. Each lens is a single lens. A ratio of a back focal length of the entire system to a focal length at a wide-angle end of the entire system is larger than 2.5, and Fno. is set constant over the whole region of power-varying.

Abstract: An imaging lens includes a first lens having a negative power and including a concave surface facing an image side, a second lens having a positive power, a third lens having a positive power, an aperture diaphragm, a fourth lens, which is a biconvex lens having a negative power, a fifth lens having a positive power and including a convex surface facing the image side, and a sixth lens having a positive power and including a convex surface facing an object side, which are arranged in this order from the object side. The Abbe number of a material forming the fourth lens with respect to the d-line is 30 or less. When the focal length of the entire lens system is f and a composite focal length from the fourth lens to the sixth lens is f456, the imaging lens satisfies following conditional expression: 1.00<f456/f<1.88.

Abstract: A zoom lens system includes, in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. During zooming from a wide-angle end to a telephoto end, a space between the first lens unit and the second lens unit narrows, at least the second lens unit moves only toward the object side, and the third lens unit is constituted of one positive lens.

Abstract: The projection zoom lens system includes a negative first lens group, a positive second lens group, a third lens group, a positive fourth lens group, a fifth lens group, and a positive sixth lens group. The lens system is nearly telecentric on a reduction side. During zooming, the second to fifth lens groups are moved while the first and six lens groups remain stationary. The third lens group includes a positive lens LP having a convex surface directed to a magnification side, and a negative lens LN having a concave surface which is directed to the reduction side and has a curvature stronger than a magnification-side surface of the negative lens LN. The conditional expression of 5.0?|fG3/RLN-2| is satisfied. Here, fG3 denotes a focal length of the third lens group, and RLN-2 denotes a radius of curvature of the reduction-side surface of the negative lens LN.

Abstract: An imaging lens includes a first lens having a negative power and including a concave surface facing an image side, a second lens having a positive power, a third lens having a positive power, an aperture diaphragm, a fourth lens, which is a biconvex lens having a negative power, a fifth lens having a positive power and including a convex surface facing the image side, and a sixth lens having a positive power and including a convex surface facing an object side, which are arranged in this order from the object side. The Abbe number of a material forming the fourth lens with respect to the d-line is 30 or less. When the focal length of the entire lens system is f and a composite focal length from the fourth lens to the sixth lens is f456, the imaging lens satisfies following conditional expression: 1.00<f456/f<1.88.

Abstract: A small projection lens includes a first lens, which is a biconvex lens, an aperture, an aperture diaphragm (or an aperture), a second lens, which is a negative meniscus lens having a concave surface facing a magnification side, a third lens, which is a positive meniscus lens having a convex surface facing a reduction side, and a fourth lens, which is a biconvex lens having aspheric surfaces at both sides on an optical axis, arranged in this order from the magnification side. A minimum portion of the length of all lens elements of the small projection lens in a diametric direction vertical to the optical axis is equal to or less than 15 mm, and the small projection lens satisfies the following conditional expression: 2.5<?/S<10.0 (where S indicates the maximum length of a magnification-side image (inch) and ? indicates a magnifying power).

Abstract: The imaging lens system includes a negative first lens disposed on a most object side, having a concave surface directed toward the object side and having a meniscus shape, a cemented lens LC disposed on a most image side and having a convex surface on its most object side, and an aperture diaphragm disposed just in front of the object side of the cemented lens. The system satisfies the following conditional expressions: 0.05<(R2?R1)/(R1+R2)<0.25 vd1 ?vd2 >15 where R1 and R2 denote radius of curvatures of object side and image side surfaces of the first lens, respectively, and vd1 and vd2 denote Abbe numbers of lenses, which are located on the most object side and on the most image side among lenses constituting the cemented lens, at the d-line, respectively.

Abstract: An image forming optical system which comprises a negative lens unit and a positive lens unit arranged in order from an object side. The negative lens unit includes, in order from the object side, a first negative lens and a second negative lens, or a first negative lens, a second negative lens and a third negative lens. The positive lens unit includes, in order from the object side, a third positive lens, a fourth negative lens, a fifth positive lens and a sixth positive lens, or a fourth positive lens, a fifth negative lens, a sixth positive lens and a seventh positive lens.

Abstract: A projection zoom lens is provided and includes: in order from the magnification side, a negative first lens group performing focusing with being fixed during power-varying; a positive second lens group, a positive third lens group, a positive fourth lens group, a positive fifth lens group, which are moved with correlation; and a positive sixth lens group fixed during the power-varying. An aperture diaphragm is moved between the fourth lens group and the fifth lens group during the power-varying to keep Fno constant in the whole power-varying region. In addition, the expression of 1.7<Bf/f<3.0 is satisfied, where f is a focal length of the whole system, and Bf is a back focal length (air conversion distance) of the whole system.

Abstract: A lens system has the following components in order from an object side: one negative lens component; a positive lens component; a negative lens component having a concave surface of a large curvature on an image side; an aperture stop; a negative lens component having a concave surface of a large curvature on the object side; and a positive lens component; the lens system satisfies a condition of the following expression: 0.75<SF1<1.60, where SF1=(R1+R2)/(R1?R2), and where R1 is a radius of curvature of an object-side lens surface of the negative lens component located nearest to the object side, R2 is a radius of curvature of an image-side lens surface thereof, and SF1 is a shape factor thereof.

Abstract: A zoom lens includes a first lens group having a negative optical power and including a reflection optical element; a second lens group having a positive optical power; a third lens group having a negative optical power; a fourth lens group having a positive optical power; and, a fifth lens group. At least the second lens group and the fourth lens group move to the object side of the zoom lens for varying a power of the zoom lens from a wide-angle end to a telephoto end. The zoom lens further includes a diaphragm and the diaphragm moves to the object side for varying the power of the zoom lens from the wide-angle end to the telephoto end.

Abstract: A lens system comprises a first lens negative in power, a second lens positive in power, a third lens negative in power, a fourth lens positive in power, a fifth lens negative in power, and a sixth lens positive in power. The lens system meets a criteria of TT/f?1.68 and 0.3<f/f23<0.4, wherein TT denotes a distance between an object-side surface of the first lens and an image plane of the lens system; f23 denoting an effective focal length of a combination of the second lens and the third lens; f denoting an effective focal length of the entire lens system.

Abstract: The imaging lens system includes a negative first lens disposed on a most object side, having a concave surface directed toward the object side and having a meniscus shape, a cemented lens LC disposed on a most image side and having a convex surface on its most object side, and an aperture diaphragm disposed just in front of the object side of the cemented lens. The system satisfies the following conditional expressions: 0.05<(R2?R1)/(R1+R2)<0.25 vd1?vd2>15 where R1 and R2 denote radius of curvatures of object side and image side surfaces of the first lens, respectively, and vd1 and vd2 denote Abbe numbers of lenses, which are located on the most object side and on the most image side among lenses constituting the cemented lens, at the d-line, respectively.

Abstract: An inverse telephoto with correction lenses comprises five lens elements with refractive power, from the object side to the image side: a first lens element with negative refractive power having a concave image-side surface; a second lens element with positive refractive power having a convex image-side surface; a third lens element with a convex object-side surface; a fourth lens element with a concave image-side surface; a fifth lens element with positive refractive power having a convex image-side surface, at least one of an object-side surface and the image-side surface of the fifth lens element being aspheric; and an aperture stop located between the first lens element and the second lens element. At least three of the surfaces of the first, second, third, fourth and fifth lens elements are aspheric.

Abstract: A zoom lens comprises a first lens group G1, which includes a negative focal length, a second lens group G2, which includes a positive focal length, a third lens group G3, which includes a negative focal length, a fourth lens group G4, which includes a positive focal length, and a fifth lens group G5, which includes a positive focal length, in order from nearest to furthest from a photographic subject, or with a sixth lens group G6, which includes a negative focal length, installed as an anchored lens group between the fifth lens group and an image site of the camera apparatus.

Abstract: A lens system comprises a first lens negative in power, a second lens positive in power, a third lens negative in power, a fourth lens positive in power, a fifth lens negative in power, and a sixth lens positive in power. The lens system meets a criteria of TT/f?1.68 and 0.3<f/f23<0.4, wherein TT denotes a distance between an object-side surface of the first lens and an image plane of the lens system; f23 denoting an effective focal length of a combination of the second lens and the third lens; f denoting an effective focal length of the entire lens system.

Abstract: The invention relates to a zoom lens favorable for offering a tradeoff between slimming down a lens system upon received in an associated lens mount and making sure a small F-number. There is a zoom lens provided, which comprises, in order from its object side, a first lens group G1 having negative refracting power, a second lens group G2 having positive refracting power, and a third lens group G3 having positive refracting power. Upon zooming from a wide-angle end to a telephoto end, the first second and third lens groups G1, G2 and G3 each move along an optical axis while a spacing between the first lens group and the second lens group becomes narrow and a spacing between the second lens group and the third lens group becomes wide. The first lens group G1 comprises one single lens that is a double-concave negative lens or two lenses: a double-concave negative lens and a positive lens. The second lens group G2 comprises two positive lenses and one negative lens.

Abstract: A projection system includes a cabinet having a surface with an aperture therein, a projector disposed within the cabinet, adapted to project light through the aperture in the surface of the cabinet, and a lens disposed in the aperture to project the light onto a screen disposed generally non-parallel to the cabinet surface having the aperture.

Abstract: To provide a high-brightness, small, low-cost optical apparatus which covers a wide-angle to super-wide-angle region and which reliably corrects various aberrations with a small number of lenses. At least one negative lens unit 1, a meniscus lens 2 that is convex on an object side, an aperture stop S, and a double-convex positive lens 3 are arranged in order from the object side. At least one of the lenses positioned on the object side of the aperture stop S and the positive lens 3 include respective aspherical surfaces.

Abstract: In a three-group zoom lens having negative power, positive power, and positive power in order from an object side, a first lens group is built from a first negative lens and a second positive biconvex lens which is formed from a plastic material and which has at least one aspherical surface; a second lens group G2 is built from a positive, a negative cemented lens and a fifth lens L5 assuming a meniscus shape; and a third lens group is built from a sixth lens L6 which is a positive single lens. The zoom lens fulfills conditional expressions provided below: 3.2<fg2/fw ??(1) 26<?1??2<30 ??(2) D1/fw<0.75 ??(3) (fg2: a focal length of the second lens, fw: a focal length of an entire system achieved at a wide-angle end, ?1: Abbe number of the first lens, ?2: Abbe number of the second lens, and D1: Axial distance from a lens surface most closely positioned to the object side to a lens surface most closely positioned to an image side in the first lens group).

Abstract: The imaging lens is provided and includes: in order from the object side, a negative first lens whose concave surface is directed toward the image side; a second lens of a planoconcave lens whose flat surface is directed toward the object side or a biconcave lens whose surface having a larger absolute value of radius of curvature is directed toward the object side; a third biconvex lens; a stop; a positive fourth lens whose surface having a smaller absolute value of radius of curvature is directed toward the image side; and a cemented lens of a positive fifth lens of biconvex shape and a negative sixth lens of meniscus shape, the cemented lens having a positive refractive power, and an Abbe number v3 at d-line of the third lens satisfies a conditional expression (1) v3<43.

Abstract: A zoom lens includes, in sequence from the object side: a first lens group with an overall negative refractive power; and a second lens group with an overall positive refractive power. A zoom factor changes by moving the second lens group. Focal adjustments are made by moving the first lens group accompanied by the change of the zoom factor made by the movement of the second lens group. The first lens group includes a first lens having a negative refractive power and a second lens having a positive refractive power. The second lens group includes a third lens having a positive refractive power, a fourth lens with a positive refractive power and a fifth lens with a negative refractive power bonded together, and a sixth lens with a positive refractive power. The bonded lenses form a meniscus shape with a convex surface facing the object side. The resulting lens is short in length, compact, thin, and suitable for digital still cameras.

Abstract: A front group is formed of a negative first lens as a meniscus lens which is convex at the object side and a negative second lens, and a rear group is formed of a biconvex positive third lens, an aperture stop, a negative fourth lens and a biconvex positive fifth lens. The first lens is a glass lens, and the second lens is a plastic aspherical lens. The following conditions are satisfied: ?2.4<fI/f<?1.55, 0.15<f2/f1<0.35, va<29, and vb>50, where f denotes a focal distance of a whole system, f1 denotes a focal distance of the first lens, f2 denotes a focal distance of the second lens, fI denotes a focal distance of the front group, va denotes an average value of abbe numbers of the third and the forth lenses, and vb denotes an average value of abbe numbers of the rest of the lenses.

Abstract: A zoom lens formed in a small size adaptable to a thin and portable device, having three lens groups, including, from the object plane to the image forming plane: a first lens group with a negative power, a second lens group with a positive power and a third lens group with a positive power. By controlling the ratio of the focal length of the second lens group and the focal length of the tele-photo end, image distortion may be controlled, and the total length of the lens may be reduced to shrink the size of the lens. Hence production costs may be reduced, which is important to mass production.

Abstract: A zoom lens having at least a first lens group including a reflection member for bending an optical axis fixedly during zooming and having a negative refractive power, a second lens group having a negative refractive power, and a third lens group arranged in the order from an object side is provided. In the zoom lens, an image can be shifted into a direction perpendicular to the optical axis by moving either of the second and the third lens groups (“shift lens group”) in a direction perpendicular to the optical axis, and a following conditional expression (1) is satisfied, 0.5<(1???)×?b<3.0,??(1) where: ??: a magnification of the shift lens group in a maximum telephoto state, and ?b: a magnification of a lens group arranged on an image surface side of the shift lens group in the maximum telephoto state.

Abstract: Provided is a projection lens, including: a plurality of moving lens units that move on an optical axis for zooming; and a plurality of plastic lenses containing plastic, in which when a focal distance of an i-th positive lens from a predetermined plane side of N positive lenses of the plurality of plastic lenses is given by fpi, a focal distance of a j-th negative lens from the predetermined plane side of M negative lenses of the plurality of plastic lenses is given by fnj, and fp and fn are defined by 1 fp = ? i = 1 N ? 1 fpi 1 fn = ? j = 1 M ? 1 fnj (N and M each are a natural number, that is, an integer equal to or larger than 1), ?0.56<fn/fp<?0.05 is satisfied.

Abstract: A taking lens system includes, in order from an object side thereof, a first lens group (negative refracting), a second lens group (positive refracting), an aperture stop and a third lens group (positive refracting). Focusing from an infinite distance to a finite distance is performed by setting the second lens group and the third lens group such that the position of the second lens group upon focusing on a finite distance is located on an image side of the taking lens system with respect to the position of the second lens group upon focusing on an infinite distance and the position of the third lens group upon focusing on a finite distance is located on an object side of the taking lens system with respect to the position of the third lens group upon focusing on an infinite distance, while the first lens group remains fixed.

Abstract: A Fourier transform lens system includes: a first lens group having negative power and a second lens group having positive power disposed at one side of the first lens group with the first lens group and the second lens group being arranged on a common optical axis. The first lens group includes two negative meniscus lenses each having negative power, and each of the negative meniscus lenses has a concave lens surface facing toward a concave lens surface of the other negative meniscus lens. The second lens group includes a positive lens having a convex lens surface facing toward the first lens group. The Fourier transform lens system satisfies the following conditions: (1) 0.1<R1R/f<0.4; (2) ?0.4<R2F/f<?0.1; and (3) 0.1<d12/f<0.3. A holographic storage system using a Fourier transform lens system is also provided.

Abstract: A zoom lens system, with a new structure that exhibits high optical performance over the entirety of a zoom range and the entirety of a focusing range, is disclosed. This zoom lens system comprises, in order from an object side to an image side: a front lens group which includes a plurality of lens units that move during zooming; a lens unit with negative optical power which moves during zooming and moves towards the object side during focusing from an infinity object to a close-distance object; and a lens unit with positive optical power which does not move for zooming.

Abstract: A fisheye lens system with a half angle-of-view of 90° includes a negative front lens group, a diaphragm, and a positive rear lens group. The negative front lens group includes at least three negative meniscus lens elements each of which has the convex surface facing toward the object; and the three negative meniscus lens elements satisfy the following conditions: 0.2<SF(i=1)<0.6??(1) 0.8<SF(i=2)/SF(i=1)<1.5??(2) 0.8<SF(i=3)/SF(i=1)<2.0??(3) wherein SFi designates the shaping factor of the ith (1?i?3) negative meniscus lens element (SFi=(R1i?R2i)/(R1i+R2i)); R1i designates the radius of curvature of the object-side surface of the ith (1?i?3) negative meniscus lens element; and R2i designates the radius of curvature of the image-side surface of the ith (1?i?3) negative meniscus lens element.

Abstract: An eyepiece lens includes first lens group G1 having a negative refracting power including a negative meniscus lens with a concave surface facing eyepoint E.P side, second lens group G2 having a positive refracting power including a lens with both convex surfaces on both ends, and third lens group G3 having a negative refracting power including a negative lens. The first–third lens groups are arranged in an order from eyepoint E.P side, and the eyepiece lens is capable of varying a diopter by moving the second lens group along an optical axis. The eyepiece lens is configured by aspherical surfaces to make the positive refracting power weak while at least one surface of the convex surfaces of the lens deviates from the optical axis. Further, conditions of a following formula are satisfied: 1.6<f1/f3<2.5 ?0.

Abstract: A zoom lens includes a plurality of lens groups including a first lens group arranged on the foremost side and having negative optical power. Zooming is performed by moving at least one of the plurality of lens groups along a direction parallel to an optical axis of the zoom lens. The first lens group is fixed during the zooming. A first lens arranged on the foremost side, of the first lens group has negative refractive power. When an Abbe constant and a partial dispersion of a material configuring the first lens are respectively represented by ?dn and ?g,Fn, a focal distance of the first lens group is represented by f1, and an air-equivalent back focus upon focusing on an infinity object is represented by bf, the following conditions are satisfied: ?dn<32, 0.008<?g,Fn?(0.644?0.00168×?dn)<0.040, and |f1/bf|<0.9.

Abstract: A fixed-focus projection lens 2 comprises practically six lenses; a single lens having negative refracting power serving as a first lens 10, a single lens having positive refracting power serving as a second lens 20, a single lens having negative refracting power serving as a third lens 30, a compound lens having positive refracting power, consisting of a first component lens 41 and a second component lens 42, and serving as a fourth lens 40, and a single lens having positive refracting power serving as a fifth lens 50, arranged in that order from the side of a screen toward a display device. A surface 11, on the side of the display device, of the first lens 10, and a surface 41, on the side of the display device, of the second component lens 42 of the fourth lens 40 are aspherical.

Abstract: Projection lenses for use with pixelized panels (PP) are provided. The projection lenses have first and second lens units (U1,U2), with the first lens unit having a negative or weakly positive power and the second lens unit having a positive power. The second lens unit has first and second subunits (U2S1 and U2S2) which provide positive power followed by negative power. The second subunit (U2S2) of the second unit (U2), in turn, has negative power followed by positive power. In this way, an overall short projection lens (e.g., BRL/f0?0.9) along with small lens elements (e.g., CAmax/f0?0.8) can be achieved.

Abstract: Disclosed is a variable-power optical system, including, sequentially from a front side to a rear side, a negative-refractive-power first lens unit that does not move for zooming, a positive-refractive-power second lens unit, a negative-refractive-power third lens unit, a fourth lens unit, a negative-refractive-power fifth lens unit, and a positive-refractive-power sixth lens unit that does not move for zooming, in which the following conditional expression is satisfied: 1.7<bf/(|f1|·fw)1/2<2.3 where f1 represents a focal length of the first lens unit, bf represents a back focus in air, and fw represents a focal length of an overall system at a wide angle end, whereby, while downsizing of an overall lens system is achieved, various aberrations accompanying zooming are well corrected, good optical performance is attained over an entire screen, and a wide angle of view and a long back focus are also attained.

Abstract: A zoom lens includes three lens groups. The first lens group from the object side has negative refractive power and is formed of a lens component having negative refractive power and a lens element having positive refractive power. The second lens group from the object side has positive refractive power and is formed of two lens components, an object-side lens component that is a glass lens element with a convex surface on the optical axis on the object side and having an aspheric surface and an image-side lens component that includes a cemented surface and an image-side concave surface. The third lens group consists of a biconvex lens component. Only the first and second lens groups move along the optical axis for zooming. The zoom lens may be formed of only six lens elements, includes at least one aspheric surface, and satisfies specified conditions for compactness and aberration correction.

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 biconvex lens disposed at the front side of the lens unit. The second lens is a biconcave lens. The third lens is a positive lens with having a larger curvature radius facing the objective side. The fourth lens is a negative meniscus lens. The fifth lens is a positive lens with a surface having a larger curvature radius facing the image side. The fourth lens and the fifth lens are attached together to form a compound lens. The aperture is disposed in front of the first lens.

Abstract: According to one exemplary embodiment, a projection lens having an object plane and an image plane is provided and includes the following lens groups listed objectwise to imagewise: (1) a first lens group having negative refractive power; and (2) at least three other lens groups having a positive refractive power and at least one other lens group having a negative refractive power. In one embodiment, the projections lens includes a second lens group having a positive refractive power; a third lens group having a negative refractive power; and fourth, fifth and sixth lens groups having overall positive refractive power. The projection lens having a numerical aperture of at least about 0.85 and is of a 1½ waist construction, with the ½ waist defined in the first lens group and a primary waist is defined in the third lens group.

Abstract: A real image type finder optical system includes an objective lens group having positive refracting power and an eyepiece lens group having a positive refracting power. The objective lens group includes a first group consisting of a negative lens, a second group consisting of a positive lens, a third group consisting of a positive lens and a fourth group having a negative refracting power and forming part of an image inverting optical system. Upon zooming from a wide-angle end to a telephoto end, the first and fourth groups remain fixed and the second and third groups move. The eyepiece lens group comprises a fifth group that forms part of the image inverting optical system and a sixth group having positive refracting power. The resulting real image type finder optical system satisfies specific conditions with respect to the back focus of the first to third groups at the wide-angle end.

Abstract: A lens assembly comprising nine lenses. Each lens includes u greater than or equal to about 12.8°, LEP equal to or from about 100 mm to about 400 mm, &agr; Rba greater than or equal to about 1°, and &agr; Rbi less than or equal to about −14°. The outward ray angle tilt and the inward ray angle tilt are positive if the outward ray and the inward ray intersect the optical axis at a location which, when seen from the object, is in an opposite direction to projection. The outward ray angle tilt and the inward ray angle tilt are negative if the outward ray and the inward ray intersect the optical axis at a location which, when seen from the object, is in the direction of projection.

Abstract: A reference lens for an interferometer is constructed so that light transmitted by a partially reflecting reference spherical surface may be converged, toward a focal point that coincides with the center of curvature of the reference spherical surface, and reflected from a subject spherical surface that also has its center of curvature at the focal point. Measurement of the shape of the subject spherical surface is possible based on the interference of two light beams, one reflected by the subject spherical surface and one reflected by the reference spherical surface. The reference lens, which may include five or six lens components or lens elements, includes a negative meniscus lens component, a positive lens group, and a positive lens component. Specified conditions are satisfied to provide a reference lens that has favorable correction of aberrations, is compact, and can measure the surface accuracy of a wide range of convex spherical surfaces.

Abstract: A zoom lens system which allows a reduction in size. This zoom lens makes two points at different distances have an optically conjugate relationship, and sequentially includes, from a first conjugate point side at a longer distance to a second conjugate point side at a shorter distance, a first lens unit having a negative optical power, a second lens unit, a third lens unit, a fourth lens unit, a fifth lens unit, and a sixth lens unit. A plurality of lens units of the first to sixth lens units move for zooming, and at least one lens unit of the first to sixth lens units has a diffractive optical element.

Abstract: A retro focus type wide-angle lens comprises a front group having a negative refracting power and a rear group having a positive refracting power. The front group comprises a first lens made of a negative meniscus lens, a second lens made of a biconvex lens, a third lens made of a negative meniscus lens, and a fourth lens made of a positive meniscus lens. The rear group comprises a cemented lens in which a fifth lens made of a negative lens and a sixth lens made of a positive lens are cemented together, and a seventh lens made of a positive lens. This wide-angle lens further satisfies predetermined conditional expressions.