Abstract: An optical imaging lens includes first, second, third, fourth, fifth, and sixth lens elements sequentially along an optical axis from an object side to an image side. Each of the first to the sixth lens elements includes an object-side surface facing the object side and allowing imaging rays to pass through and an image-side surface facing the image side and allowing the imaging rays to pass through. The optical imaging lens satisfies conditions of Gallmax/Fno?3.600 millimeters, EFL/ImgH?3.200, and Gallmax/Tavg?3.300; here, Gallmax represents a largest air gap along the optical axis between the first lens element and an image plane, Fno, EFL, and ImgH respectively represent an F-number, an effective focal length, and an image height of the optical imaging lens, and Tavg represents an average lens element thickness of all of the lens elements along the optical axis from the object side to the image plane.

Abstract: An optical system includes, disposed in sequence starting on an object side along an optical axis: a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a positive refractive power, wherein: the second lens group moves along the optical axis upon focusing from an infinity-distance object to a short-distance object; and a following conditional expression is satisfied: 1.00<f/(?f2)<2.40 where: f: a focal length of the optical system in an infinity in-focus state; and f2: a focal length of the second lens group.

Abstract: Innovations in the areas of hash table construction and availability checking reduce computational complexity of hash-based block matching. For example, some of the innovations speed up the process of constructing a hash table or reduce the size of a hash table. This can speed up and reduce memory usage for hash-based block matching within a picture (for block vector estimation) or between different pictures (for motion estimation). Other innovations relate to availability checking during block vector estimation that uses a hash table.

Abstract: The present disclosure discloses a camera optical lens, including, in an order from an object side to an image side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The first lens is made of glass material, the second lens is made of plastic material, the third lens is made of glass material, the fourth lens is made of plastic material, the fifth lens is made of plastic material, and the sixth lens is made of plastic material. The camera optical lens further satisfies specific conditions.

Abstract: The imaging lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. During focusing, only the second lens group moves in the direction of the optical axis. A lens closest to the object side in the first lens group has a positive refractive power. The second lens group includes two or three lenses, a lens closest to the object side is a meniscus lens which is concave toward the object side and has a positive refractive power, and a lens adjacent thereto on the image side has a negative refractive power. A lens closest to the image side in the third lens group is a single lens which is concave toward the object side and has a negative refractive power. Further, predetermined Conditional Expression (1) is satisfied.

Abstract: A wide-angle lens includes a first lens group, an aperture stop, a second lens group, and a third lens group. The first lens group has positive refractive power. The second lens group has negative refractive power. The third lens group has positive refractive power. The first lens group, the aperture stop, the second lens group, and the third lens group are disposed in order from the object side toward image side. The first lens group includes a negative lens and at least one cemented lens, the negative lens being disposed on most-object side and has a convex surface facing the object side. The following conditional expression is satisfied, 0.5<f1/f<1.0??(1) where f1 is a focal distance of the first lens group in a condition that infinite is in focus, and f is a focal distance of a whole system in the condition that the infinite is in focus.

Abstract: An optical system of a stereo video endoscope with lateral viewing direction. The optical system including: a sideways looking distal optical assembly; and a proximal optical assembly. Where the distal optical assembly includes, successively in a direction of light incidence on a common optical axis: an entrance lens configured as a raised negative meniscus, an optical deflection unit; and an exit lens configured as a hollow positive meniscus, Where the distal optical assembly has, at least in sections, a right and a left lens system channel of identical type and arranged parallel to one another, each of the right and left lens system channel having: a dedicated optical axis, and at least one first lens and an achromatic lens group in the direction of light incidence.

Abstract: An inner focus lens system comprising lens units each composed of at least one lens element, wherein a most object side lens unit is provided and is fixed with respect to an image surface in focusing, and the conditions: BF/Y<1.7 and (L×FNo)/f<2.2 (BF: a distance from an image side surface apex of a most image side lens element to the image surface, Y=f ×tan ?, L: an overall length of lens system, FNo: a F-number of lens system,f: a focal length of lens system, ?: a half view angle of lens system) are simultaneously satisfied, or only the condition: (L×FNo)/f<2.0 (L: the overall length of lens system, FNo: the F-number of lens system,f: the focal length of lens system) is satisfied.

Abstract: A telephoto lens system and an electronic apparatus having the same are provided. The telephoto lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group. The third lens group includes a (3-1)-th lens group having a positive refractive power, a (3-2)-th lens group having a negative refractive power, and a (3-3)-th lens group having a positive refractive power.

Abstract: Projection lens having improved properties such as a high throughput are described. In one embodiment, a projection lens is described comprising in sequential order from a screen side a first lens group, a second lens group of positive refractive power, and a third lens group of positive refractive power. At least one lens group has an aspheric surface. The ratio of the focal length of the projection lens (F) to the focal length of each of the lens groups (F1, F2, and F3) is such that |F1/F|>5, 0.5<|F2/F|<0.9, and 1<F3/F<8. In another embodiment, a projection lens is described comprising in sequential order from a screen side a first lens group, a second lens group of positive refractive power, and a third lens group of positive refractive power. At least one lens group has an aspheric surface. The ratio of the focal length of the projection lens (F) to the focal length of each of the lens groups (F1, F2, and F3) is such that |F1/F|>5, 0.5<|F2/F|<2.0, and 1.4<F3/F<8.

Abstract: A telephoto lens system including a first lens group having a positive refractive power and including a negative lens that is disposed closest to an object side and has a meniscus shape that is convex toward the object side; a second lens group having a negative refractive power and including a single negative lens that moves along an optical axis and performs focusing; and a third lens group having a positive refractive power, wherein the first through third lens groups are disposed sequentially from the object side toward the image side, and the telephoto lens system satisfies the following condition, 0.5<|f2/f|<0.81, wherein, f2 denotes the focal length of the second lens group, and f denotes the focal length of the telephoto lens system.

Abstract: A first lens group having positive refractive power and a second lens group are arranged in this order from an object side, and only the first lens group moves in the optical axis direction while focusing. The first lens group substantially consists of a positive 1-1 lens, a positive 1-2 lens, a positive 1-3 lens, a negative 1-4 lens, an aperture stop, a negative 1-5 lens, a positive 1-6 lens, and a positive 1-7 lens. The 1-3 lens and the 1-4 lens are cemented to each other, and the 1-5 lens and the 1-6 lens are cemented to each other. The second lens group substantially consists of a negative 2-1 lens and a positive 2-2 lens. Only the first lens group moves in the optical axis direction while focusing.

Abstract: A telephoto lens system includes a first lens group having a positive refractive power, and comprising at least three positive lenses and one negative lens; a second lens group having a negative refractive power, and which moves along an optical axis to perform a focusing operation; a third lens group having a positive refractive power, and comprising a cemented lens in which a positive lens having a convex surface toward the object side and a positive lens having a convex surface toward the image side are bonded to each other, a bi-convex positive lens, and a negative lens having a concave surface toward the object side, and the first through third lens groups are disposed sequentially from the object side to the image side.

Abstract: An optical module (10) comprises a positive meniscus lens (16) having a focal length F1 and comprising a first convex optical surface (12) and a second concave optical surface (20), and a plano-convex lens (22) having a focal length F1 and comprising a third flat optical surface (24) and a fourth convex optical surface (26) from an object side (12) to an image side (14). The curvatures of the four optical surfaces (12, 20, 24, 26) are defined by the equation: Zi=CURViYi2/(1+(1+Ki)CURVi2Yi2)½)+(Ai)Yi2+(Bi)Yi4+(Ci)Yi6+(Di)Yi8, and the two lenses are defined by 0.35<F1/F2<0.90, 0.30<Conv2/Conv<0.70, and 0.50<M1/M2<1.

Abstract: An optical system comprises, in order from an object side to an image side, a first lens group includes a first lens element with positive refractive power having a convex object-side surface; and a second lens group in order from the object side to the image side includes a second lens element with negative refractive power having a concave image-side surface, a third lens element with positive refractive power having a convex image-side surface, and a fourth lens element with negative refractive power having a concave object-side surface and a concave image-side surface, wherein the image-side surface of the fourth lens element changes from concave at a paraxial region to convex at a peripheral region, and both of the object-side surface and the image-side surface of the fourth lens element are aspheric.

Abstract: Provided is an imaging lens including a fixed first lens group having a positive refractive power and including a plurality of lenses, a second lens group serving as a focus group and including a negative lens, and a third lens group having a positive refractive power that are arranged sequentially from an object side to an image side. A stop is disposed between predetermined lenses of the first lens group, and, on an assumption that a lens group located closer to the object side than the stop of the first lens group is a 1ath lens group and a lens group located closer to the image side than the stop is a 1bth lens group, Condition Equation (1) below is satisfied: 0.7<f/f1b<2.0,??(1) where f is a focal distance of an entire system and f1b is a focal distance of the 1bth lens group.

Abstract: An imaging lens includes a first lens; a second lens; and a third lens arranged from an object side to an image plane side. The first lens has an object-side surface having a positive curvature radius R1f and an image plane-side surface having a negative curvature radius R1r. The second lens has an object-side surface and an image plane-side surface with negative curvature radii. The third lens has an object-side surface and an image plane-side surface with positive curvature radii and formed as aspheric surfaces having inflexion points. When the whole lens system has a focal length f, the first lens has a focal length f1, the second lens has a focal length f2, and the third lens has a focal length f3, the imaging lens satisfies the following conditional expressions: f1<f2<f3 1.0<f1/f<1.5 ?0.

Abstract: An embodiment of this invention provides a zoom lens that primarily comprises, in order from an object side to an image-forming side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power. The second lens group comprises several lenses, in which the focal length of the first lens from the object side is efl3, the focal length of the second lens from the object side is efl4, and efl3 and efl4 satisfy: 0<efl3/efl4<0.3.

Abstract: The disclosed internal focusing large-aperture medium telephoto lens has as lens groups a positive first lens group, a positive second lens group, and a third lens group, in that order from the object side. When focusing on nearby objects, the first lens group and the third lens group have a fixed position relative to the image surface, and the second lens group displaces toward the object side. The second lens group has only one negative lens, and, in order from the object side, has at least a positive lens, a negative lens, and a positive lens. The following expression is fulfilled: ?0.5<(R1+R2)(R1?R2)<?0.1 (wherein, R1: radius of curvature of the object side surface of the negative lens in the second lens group; R2: radius of curvature of the image side surface of the negative lens in the second lens group).

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming, wherein the second lens unit includes two positive lenses, a negative lens, a positive lens in order from the object side to the image side, and an average refractive index Nd2p for d-line of materials of the positive lenses in the second lens unit and a refractive index Nd2n for d-line of a material of the negative lens in the second lens unit are appropriately set.

Abstract: An image pickup optical system includes, in order from an object side to an image side, a first lens unit that does not move for focusing and has a positive optical power, a second lens unit that moves during focusing, an aperture diaphragm, and a third lens unit that does not move for focusing. The image pickup optical system includes a diffractive optical element, and an optical element NLF made of a solid material on the object side of an intersection between a paraxial chief ray and an optical axis. The predetermined conditional expressions are satisfied.

Abstract: An optical system includes a first lens unit fixed during a focusing operation and having a positive refractive power, a second lens unit moving in an optical axis direction during the focusing operation and having a negative refractive power, a third lens unit positioned at the image side relative to the second lens unit and having a positive or negative refractive power, the first lens unit is configured by first, second, and third partial lens units, the first partial lens unit is configured by two positive lens components, the second partial lens unit is configured by one cemented lens having a negative combined refractive power, the third partial lens unit is positioned between the second partial lens unit and the second lens unit and has a positive refractive power as a whole, and each lens unit is configured so as to meet an appropriate condition.

Abstract: A photographic optical system includes, in order from an object side to an image side, a first lens unit, a second lens unit for focusing, and a third lens unit. The first lens unit includes a first lens sub-unit having a positive refractive power and a second lens sub-unit. The first lens unit includes a diffractive optical element and an aspheric surface. A length on an optical axis from a lens surface furthest on the object side of the first lens sub-unit to an image plane, an air space between the first lens sub-unit and the second lens sub-unit, a focal length of the first lens sub-unit, a focal length of the second lens sub-unit, a focal length of the diffractive optical element by only a diffractive component, a focal length and an F-number of the entire photographic optical system are appropriately set to satisfy predetermined conditions for optimal focusing.

Abstract: An optical system, in order from an object side to an image side, includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive or negative refractive power. The first lens unit is configured by a first partial lens unit and a second partial lens unit each having a positive refractive power. The first partial lens unit is configured by a positive single lens, and has at least one aspherical surface. The second partial lens unit is configured by a positive lens and a negative lens, and has a diffraction optical surface of a diffraction optical element rotationally symmetric with reference to an optical axis direction. The second lens unit is a focus lens unit that is movable in the optical axis direction. And a paraxial lateral magnification ?asph meets a predetermined condition.

Abstract: Provided is a small-sized five-element image pickup lens which ensures a sufficient lens speed of about F2 and exhibits various aberrations being excellently corrected. The image pickup lens is composed of, in order from the object side, a first lens with a positive refractive power, including a convex surface facing the object side; a second lens with a negative refractive power, including a concave surface facing the image side; a third lens with a positive or negative refractive power; a fourth lens with a positive refractive power, including a convex surface facing the image side; and a fifth lens with a negative refractive power, including a concave surface facing the image side. The image-side surface of the fifth lens has an aspheric shape, and includes an inflection point at a position excluding an intersection point with the optical axis.

Abstract: Provided is a small-sized five-element image pickup lens which ensures a sufficient lens speed of about F2 and exhibits various aberrations being excellently corrected. The image pickup lens is composed of, in order from the object side, a first lens with a positive refractive power, including a convex surface facing the object side; a second lens with a negative refractive power, including a concave surface facing the image side; a third lens with a positive or negative refractive power; a fourth lens with a positive refractive power, including a convex surface facing the image side; and a fifth lens with a negative refractive power, including a concave surface facing the image side. The image-side surface of the fifth lens has an aspheric shape, and includes an inflection point at a position excluding an intersection point with the optical axis.

Abstract: A telephoto lens system including a first lens group having a positive refractive power and including at least three positive lenses and one negative lens; a second lens group having a negative refractive power and for performing focusing by moving along an optical axis; and a third lens group having a positive refractive power and including a 3a sub-lens group with positive refractive power and a 3b sub-lens group), wherein the 3a sub-lens group includes a negative lens and a positive lens sequentially arranged from an object side d, the 3b sub-lens group includes a positive lens and a negative lens sequentially arranged from the object side, and the telephoto lens system satisfies a condition, 0.17<fb/f<0.

Abstract: An optical system includes, in order from its object side a negative first lens unit, a positive second lens unit, a negative third lens unit, and a positive fourth lens unit. The air gaps between the lens units are variable during zooming. The first lens unit includes one positive lens, the second lens unit includes one negative lens, the third lens unit consists of one or two lens components, and the fourth lens unit consists of one lens component, where the term “lens component” refers to a single lens or a cemented lens. The system satisfies the condition “0<M3/M2<0.55”, where M2 and M3 are the amounts of movement of the second lens unit and the third lens unit respectively during zooming from the wide angle end to the telephoto end in the state in which the zoom lens is focused on an object point at infinity.

Abstract: A telephoto lens system and a photographing device including the telephoto lens system. The telephoto lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are sequentially disposed from an object side, wherein the second lens group performs focusing, and the third lens group includes a front lens group having a negative refractive power and a back lens group having a positive refractive power, and vibration correction is performed by moving the front lens group of the third lens group in a perpendicular direction to the optical axis.

Abstract: Disclosed are a projection lens that has a small size, a simple inner focus structure, a high optical performance, and a wide angle of view of about 75 degrees or more, and a projection display device. A projection lens includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power arranged in this order from a magnification side. A fifth lens arranged closest to a reduction side in the first lens group is moved along an optical axis to adjust focus. The projection lens satisfies the following conditional expression: 3.0<DG12/f<6.0 where DG12 indicates a distance between the first lens group and the second lens group and f indicates the focal length of the entire lens system.

Abstract: A telephoto lens system including a first lens group having a positive refractive power and including at least three positive lenses and one negative lens; a second lens group having a negative refractive power and for performing focusing by moving along an optical axis; and a third lens group having a positive refractive power and including a 3a sub-lens group with positive refractive power and a 3b sub-lens group), wherein the 3a sub-lens group includes a negative lens and a positive lens sequentially arranged from an object side d, the 3b sub-lens group includes a positive lens and a negative lens sequentially arranged from the object side, and the telephoto lens system satisfies a condition, 0.17<fb/f<0.

Abstract: Provided is a small-sized five-element image pickup lens which ensures a sufficient lens speed of about F2 and exhibits various aberrations being excellently corrected. The image pickup lens is composed of, in order from the object side, a first lens with a positive refractive power, including a convex surface facing the object side; a second lens with a negative refractive power, including a concave surface facing the image side; a third lens with a positive or negative refractive power; a fourth lens with a positive refractive power, including a convex surface facing the image side; and a fifth lens with a negative refractive power, including a concave surface facing the image side. The image-side surface of the fifth lens has an aspheric shape, and includes an inflection point at a position excluding an intersection point with the optical axis.

Abstract: A telephoto lens system and a photographing device including the telephoto lens system. The telephoto lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are sequentially disposed from an object side, wherein the second lens group performs focusing, and the third lens group includes a front lens group having a negative refractive power and a back lens group having a positive refractive power, and vibration correction is performed by moving the front lens group of the third lens group in a perpendicular direction to the optical axis.

Abstract: Provided is a telephoto lens system. The telephoto lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are arranged sequentially from an object side to an image side. Focusing is performed by moving the second lens group along an optical axis. The first lens group comprises (from object to image side) a positive lens having an object side surface whose radius of curvature is greater than that of an image side surface, a positive meniscus lens having a convex surface at the object side, a negative meniscus lens having a convex surface at the object side, and a positive lens having an object side surface whose radius of curvature is greater than that of an image side surface.

Abstract: Provided is a telephoto lens system. The telephoto lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are arranged sequentially from an object side to an image side. Focusing is performed by moving the second lens group along an optical axis. The first lens group comprises (from object to image side) a positive lens having an object side surface whose radius of curvature is greater than that of an image side surface, a positive meniscus lens having a convex surface at the object side, a negative meniscus lens having a convex surface at the object side, and a positive lens having an object side surface whose radius of curvature is greater than that of an image side surface.

Abstract: A telephoto lens having a vibration proof function is provided and includes: in order from an object side of the telephoto lens, a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a positive refractive power. The second lens group is moved along an optical axis thereof to perform focusing. The third lens group includes a 3a-th group having a positive refractive power and a 3b-th group having a negative refractive power in the order from the object side. The 3a-th group is moved in a direction orthogonal to the optical axis to correct an image vibration of a taken image. The telephoto lens satisfies a specific conditional expression.

Abstract: An intermediate telephoto lens system includes a positive front lens group, a variable-aperture diaphragm, and a positive rear lens group, in this order from the object. The positive front lens group includes a positive first lens element L1, a positive second lens element L2 and a negative third lens element L3, in this order from the object. The positive rear lens group includes cemented lens elements having a negative fourth lens element L4 and a positive fifth lens element L5, and a positive sixth lens element L6, in this order from the object. The intermediate telephoto lens system satisfies the following condition: 2.0<f/f12<3.0??(1) wherein f designates the focal length of the entire intermediate telephoto lens system; and f12 designates the combined focal length of the positive first lens element L1 and the positive second lens element L2.

Abstract: An imaging apparatus including a first lens unit with positive power in which the most object-side surface is concave and the most image-side surface is convex, an aperture stop, a second lens unit with positive power in which the most object-side surface is convex and the most image-side surface is concave, and a third lens unit with positive power; and an image sensor. Air spacing between the second lens unit and the third lens unit assumes the shape of a biconvex air lens. The imaging apparatus satisfies the following condition: 1.4?|r 2R|/IH?15.0 where IH is the maximum photographic image height, which is a half of the diagonal length, in an effective imaging area, of the image sensor, and r 2R is the radius of curvature, measured along the optical axis, of the most image-side surface of the second lens unit.

Abstract: A bifocus lens system that is particularly suitable for being used in the portable machine, which not only can improve the incident angle but also can ensure miniaturization. The bifocus lens system comprises: a first lens group, a second lens group at wide angle side, and a second lens group at telephoto side, wherein the focal length can be changed by selectively arranging either of the first lens group and the second lens group on optical axis. A focal length of the first lens group is f1, a focal length of the second lens group at wide angle side is fw, and they satisfy the relation as: 1.0<f1/fw<1.4. A focal length of the second lens group at telephoto side is f2t, a total focal length of the whole lens groups at telephoto side is ft, they satisfy the relation: 0.8<|f2t/ft |<2.

Abstract: A front teleconverter lens system having superb optical performance with less production of aberration in spite of its compactness. The front teleconverter lens system includes, in order from an object, a first lens group having positive refractive power, and a second lens group having negative refractive power, and forming an afocal optical system. A diffractive optical surface is arranged in at least one of the first lens group and the second lens group. The conditional expression 1.2<?F/?R<10 is satisfied, where ?F denotes the effective diameter of the most object side lens surface of the first lens group, and ?R denotes the effective diameter of the most image side lens surface of the second lens group.

Abstract: A method of manufacturing a large double-sided curved Fresnel lens. The method includes a machining step (A) of performing ultra-precise three-dimensional machining on an upper mold and a lower mold to each have an upper transfer surface and a lower transfer surface engaging an upper surface and a lower surface of a thermoplastic resin plate, respectively. Further, the method includes a hot press molding step (B) of pressing the thermoplastic resin plate between the upper and lower molds by a predetermined pressure with the resin plate being held at a temperature higher than a softening temperature thereof and lower than a melting temperature thereof so that the thermoplastic resin plate is curved, and both lens surfaces for the double-sided Fresnel lens are respectively transferred to an upper surface and a lower surface of the thermoplastic resin plate.

Abstract: A projection objective having a variable focal length, preferably serving to image tilting mirror matrices or reflecting and/or transmitting LCDs, said projection objective comprising three groups of lenses (G1, G1, G3) arranged on a common optical axis, wherein, starting from the side facing the projection screen, the first lens group (G1), serving the purpose of focussing, and the second lens group (G2), serving the purpose of varying the focal length, are arranged on the optical axis in a variably positioned manner, and the third lens group (G3) is stationary. According to the invention, the following condition is met: 1.0 h max<dG2-G3<1.5 h max and s?10 mm, wherein h max is the maximum object height, dG2-G3 is the distance between the lens group G2 and the lens group G3 in a first position, and s is the object-side intercept distance or distance from the vertex to the object.

Abstract: The present invention discloses a dual-lens hybrid diffractive/refractive imaging system comprising: a first lens including a concave surface and a convex surface; and the second lens including a convex surface and a concave surface. The concave surface of the first lens is an objective surface facing the object. The convex surface faces the convex surface of the second lens, while the concave surface of the second lens faces the charge-coupled device (CCD) through a filter. Any surface of the first lens and the second lens is spheric or aspheric. Moreover, the imaging system comprises at least one diffractive surface, referred to as a hybrid diffractive/refractive surface, formed on any surface of the two lenses. Therefore, aberration is eliminated and image quality is improved without increasing the number of lenses.

Abstract: A telephoto lens system includes a positive first lens group, a negative second lens group and a positive third lens group. Upon focusing, the second lens group moves toward the image, and the telephoto lens system satisfies the following conditions: 1.35<f/f1<1.80 . . . (1); 1.30<|f/f2|<1.85 . . . (2); 0.48<f/f3<0.75 . . . (3) and 0.10<|L2/f2|<0.22 . . . (4); wherein f designates the focal length of the entire telephoto lens system; f1 designates the focal length of the first lens group; f2 designates the focal length of the second lens group; f3 designates the focal length of the third lens group; and L2 designates the distance between the second lens group and the third lens group when an object at an infinite photographing distance is in an in-focus state.

Abstract: A photographing lens system including a first lens group, a second lens group, and a third lens group. The negative second lens group is moved to the image, upon focusing. The positive first lens group includes a biconvex lens element, another biconvex lens element, and a biconcave lens element. The second lens group includes cemented lens elements constituted by a meniscus lens element having the concave surface facing toward the object and a biconcave lens element. The photographing lens system satisfies the following conditions: 0.020<dX/f<0.20 . . . (1); (n1+n2)/2>1.52 . . . (2); (&ngr;1+&ngr;2)/2>55 . . .

Abstract: An image-capturing lens is formed of front and rear lens groups having negative and positive refractive power, respectively, in order from the object side. The rear lens group is formed of, in relative sequential order from the most object side of the rear lens group, a biconvex lens element that is cemented to a biconcave lens element, a biconvex lens element, and a biconvex lens element. A specified condition is satisfied so as to make the cemented lens of the rear lens group insensitive to de-centering errors which may occur either in making the cemented lens or in assembling the image-capturing lens.

Abstract: An inner-focus-type lens is formed of three lens groups of positive, negative and positive refractive power, respectively, in order from the object side. The first lens group is formed of four lens elements of positive, positive, negative and negative refractive power, in order from the object side. The second lens group has at least one each of a positive lens element and a negative lens element and is moved along the optical axis in order to focus the inner-focus-type lens. The third lens group has a stop and at least one each of a positive lens element and a negative lens element. Preferably, various conditions are satisfied in order to provide a compact lens that has a large back focus and which favorably corrects various aberrations so as to provide a high quality image.

Abstract: An optical system includes, in order from an object side to an image side, a first lens unit of positive optical power, and a second lens unit of negative refractive power, wherein focusing from an infinitely distant object to a closest object is effected by moving the second lens unit toward the image side along an optical axis, and the second lens unit consists of one negative lens. Further, it is desirable that the following conditions are satisfied: d2 L1(&lgr;)/d &lgr;2>0 d2 T1(&lgr;)/d &lgr;2<0 &ngr;2>30 where L1(&lgr;) is an aberration coefficient of longitudinal chromatic aberration of the first lens unit, T1(&lgr;) is an aberration coefficient of lateral chromatic aberration of the first lens unit, &lgr; is a wavelength of light, and &ngr;2 is an Abbe number of material of the negative lens of the second lens unit.

Abstract: An intermediate telephoto lens system includes a first lens group 1, and a second lens group 2. The first lens group 1 includes a first lens element, a second lens element, a third lens element, an aperture stop, cemented lens elements constituted by a fourth lens element and a fifth lens element, and a sixth lens element. The second lens group 2 includes a seventh lens element, and an eighth lens element. Upon focusing, only the first lens group 1 moves along the optical axis. The intermediate telephoto lens system satisfies the following condition: (&ngr;′1-1 +&ngr;′1-2)/2>102 . . . (1); &ngr;′1-1: the dispersion ratio of the first lens element; &ngr;′1-2 the dispersion ratio of the second lens element; &ngr;′=(nd-1)/(ng-nF); nd: the refractive index of the d-line for each lens element; ng: the refractive index of the g-line for each lens element; nF: the refractive index of the F-line for each lens element.

Abstract: A telephoto lens system includes a positive first lens group, a negative second lens group and a positive third lens group.