Abstract: This variable power optical system (ZL(1)) has a plurality of lens groups (G1-G7), and the intervals between the respectively adjacent lens groups change during power variation. The plurality of lens groups include a first focusing lens group (G6) that moves during focusing, and a second focusing lens group (G7) that is disposed closer to the image surface than is the first focusing lens group and moves so as to follow a track different from that of the first focusing lens group. The first focusing lens group (G6) and the second focusing lens group (G7) each have a negative refractive power and satisfy conditional expression: 0.40<MTF1/MTF2<1.

Abstract: Provided are: a zoom lens including, in order from an object side, a positive first lens group, a negative second lens group, an intermediate group as a whole, a negative lens group, and a rear group, wherein the intermediate group includes, in order from an object side, a first positive lens subgroup including one or two positive lenses, a first negative lens subgroup including only one cemented lens, a second negative lens subgroup including a negative lens with a concave surface facing an object, and a second positive lens subgroup including one or two positive lenses, the cemented lens constituting the first negative lens subgroup has at least one cemented surface with a convex surface facing an object, and a lens, closest to an image, of the second positive lens subgroup is a positive lens; and an imaging apparatus including the zoom lens.

Abstract: An objective optical system includes, in order from an object side: a positive first group; a negative second group; a negative third group; and a positive fourth group, in which the second group and the third group move together toward an image side to perform focusing from an object point at a long distance to an object point at a close distance, and the following conditional expression (2) is satisfied: 0.2<(t34f?t34n)/F<2 (2), where t34f is a distance between the third group and the fourth group at a time of focusing to the object point at the long distance, t34n is a distance between the third group and the fourth group at a time of focusing to the object point at the close distance, and F is a focal length of the overall objective optical system at a time of focusing to the object point at the long distance.

Abstract: A multifunctional ophthalmic instrument and method for assessing ocular surface health is disclosed. The instrument includes an illumination projector, which contains broadband light sources, covering visible and near infrared spectra, a zoom lens system with continuously variable magnification, a detection system to record said images, and a computer to display and analyze said images. Preferably, an eye alignment system with a beamsplitter is used to provide a fixation target for the eye under assessment. An optional thermal camera, operating in the long wave infrared spectrum is aligned paraxially to the zoom lens system. Further, an optional separate video camera is used to monitor the blink rate. Corneal topography and tear break up time could be evaluated with a low magnification, and microscopic features, such as tear meniscus height, meibomian gland orifices, are imaged at a high magnification. Meibomian glands and lipid layer thickness are analyzed with visible and near infrared spectra.

Abstract: Provided is a zoom lens consisting of, in order from an object side to an image side: a positive front lens unit configured not to move for zooming; a plurality of magnification-varying lens units including two magnification-varying lens units having negative refractive powers configured to move for zooming; and a positive rear lens unit configured not to move for zooming, in which a focal length of the front lens unit, a focal length of a magnification-varying lens unit having a negative refractive power and arranged closest to the object side in the plurality of magnification-varying lens units, a focal length of a magnification-varying lens unit having a negative refractive power and arranged closest to the image side in the plurality of magnification-varying lens units, and a focal length of the rear lens unit are suitably set.

Abstract: The zoom lens consists of, in order from an object side, a positive first lens group, a negative second lens group, a positive third lens group, a stop, and a negative fourth lens group. During zooming, the second and third lens groups move. The fourth lens group consists of, in order from the object side, a fourth A lens group, a negative fourth B lens group moving during image blur correction, a positive fourth C lens group, and a negative fourth D lens group moving during focusing, and a positive fourth E lens group. The zoom lens satisfies predetermined conditional expressions.

Abstract: Provided is a zoom lens including a plurality of lens units in which intervals between adjacent lens units are changed during zooming. The plurality of lens units consist of, in order from object side to image side, a positive first lens unit, a negative second lens unit and a rear lens group including at least one lens unit. A minimum F-number of zoom lens during zooming from wide angle end to telephoto end, an interval, at wide angle end, between a lens surface on object side of a lens arranged closest to object side of rear lens group and a lens surface on image side of a lens arranged closest to image side of rear lens group, a total lens length of zoom lens at wide angle end, and the widest lens interval at wide angle end among lens intervals included in rear lens group are each appropriately set.

Abstract: The variable magnification optical system includes, in order from an object side, a positive first lens group disposed at a position closest to the object side, a variable magnification lens group which is disposed at a position closest to the object side among negative lens groups and moves during changing magnification, an intermediate group including at least one lens group, and a positive final lens group which is disposed at a position closest to the image side. The variable magnification lens group, the intermediate group, and the final lens group are continuously disposed. The variable magnification optical system includes at least one LA lens. This LA lens satisfies predetermined conditional expressions relating to a refractive index, an Abbe number, and a partial dispersion ratio, and is located from the variable magnification lens group to the intermediate group.

Abstract: An otoscope includes an instrument head, a tip element and an optical system. The instrument head has a distal insertion portion for insertion into an ear of a human or veterinary subject. The distal insertion portion has a distal opening. The tip element is releasably attached to the distal insertion portion. The tip element has a distal opening. The optical system is contained within the instrument head. The optical system includes a plurality of optical components. The optical system further comprises a viewing component for viewing of an image of a target of interest aligned along an optical axis disposed within said distal opening. The optical system is configured to provide a field of having a diameter equaling at least 7 mm at a distance of at least 15 mm from a distal opening of said attached tip element. The optical system is further configured to simultaneously provide a distance range of optimal focus having a range of at least 8 mm.

Abstract: A lens assembly comprises sequentially from an object side to an image side along an optical axis a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. The first lens is with negative refractive power and includes a convex surface facing the object side and a concave surface facing the image side. The second lens is with refractive power. The third lens is a biconvex lens with positive refractive power. The fourth lens is with refractive power and includes a convex surface facing the image side. The fifth lens is a biconvex lens with positive refractive power. The sixth lens is with negative refractive power and includes a concave surface facing the object side. The seventh lens is a meniscus lens with refractive power.

Abstract: An otoscope includes an instrument head, a tip element and an optical system. The instrument head has a distal insertion portion for insertion into an ear of a human or veterinary subject. The distal insertion portion has a distal opening. The tip element is releasably attached to the distal insertion portion. The tip element has a distal opening. The optical system is contained within the instrument head. The optical system includes a plurality of optical components. The optical system further comprises a viewing component for viewing of an image of a target of interest aligned along an optical axis disposed within said distal opening. The optical system is configured to provide a field of having a diameter equaling at least 7 mm at a distance of at least 15 mm from a distal opening of said attached tip element. The optical system is further configured to simultaneously provide a distance range of optimal focus having a range of at least 8 mm.

Abstract: Compact narrow angle lens systems that may be used in small form factor cameras. The lens system may include six lens elements with refractive power, and may provide lower F-numbers while maintaining or improving imaging quality and package size when compared to other compact lens systems. Total track length of the lens system may be 6.5 millimeters or less, for example 5.9 or 6 millimeters. Focal length of the lens system may be 7.0 millimeters or less, for example 6.6 millimeters. The lens system may include an aperture stop located behind the front vertex of the lens system, for example between the first and second lens elements, that effectively moves the ideal principal point of the camera to in front of the front vertex. The lens system may provide a focal ratio of 2.8 or less, for example 2.6 or 2.4.

Abstract: A zoom lens is constituted by, in order from the object side to the image side: a positive first group which is fixed when changing magnification, a negative second lens group which moves when changing magnification, a negative third lens group which moves when changing magnification, and a positive fourth lens group which is fixed when changing magnification. The first lens group is constituted by a 1a lens of a negative meniscus shape, a positive 1b lens, and a positive 1c lens. The second lens group is constituted by a negative 2a lens, a biconcave 2b lens, a positive 2c lens, and a negative 2d lens. The third lens group is constituted by a negative 3a lens and a positive 3b lens. The fourth lens group includes a 4a lens, an aperture stop, and a positive 4b lens, which are consecutively provided from the most object side thereof.

Abstract: Provided is a zoom lens, including, in order from an object side to an image side: a positive first lens unit that does not move for zooming; a negative second lens unit that moves during zooming; and a positive N-th lens unit that does not move for zooming and is arranged closest to the image side. Among lenses constructing the second lens unit, two lenses closest to the image side are a positive lens and a negative lens, and partial dispersion ratios for g-line and F-line and Abbe numbers for a d-line of the positive and negative lenses, and an average value of refractive indices of all the lenses of the second lens unit are appropriately set.

Abstract: Provided is a zoom lens, including, in order from an object side to an image side: a positive first lens unit that does not move for zooming; a negative second lens unit that moves during zooming; and a positive N-th lens unit that does not move for zooming and is arranged closest to the image side. Among lenses constructing the second lens unit, two lenses closest to the image side are a positive lens and a negative lens, and partial dispersion ratios for g-line and F-line and Abbe numbers for a d-line of the positive and negative lenses, and an average value of refractive indices of all the lenses of the second lens unit are appropriately set.

Abstract: Provided is a zoom lens, comprising, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power. The second lens unit and the third lens unit are configured to move along loci different from each other during zooming. At least one lens unit of the first lens unit, the second lens unit, the third lens unit, or the fourth lens unit includes a positive lens and a negative lens that are arranged adjacent to each other, and materials for the positive lens and the negative lens are appropriately set, respectively.

Abstract: A zoom lens unit comprises a first and fourth lens groups with positive refractive power, a second and third lens groups with negative refractive power. The first and the fourth lens groups are fixed, the second lens group moves toward an image side and the fourth lens group moves when changing a magnification ratio from a wide-angle end to a telephoto end. The fourth lens group includes a negative resin lens and at least one positive lens. At least one of said positive lenses fulfills following conditions: 1.40<nd<1.65 65.0<?d<100.0 0.015<Pg, F?(?0.001802×?d+0.6483)<0.060 where nd, ?d, and Pg, F, each represents a refractive index, an Abbe number, a partial dispersion ratio of the positive lens. Pg, F is (ng?nF)/(nF?nC), where ng, nF, and nC represent refractive indexes at g-line, F-line, and C-line of the positive lens.

Abstract: An otoscope includes an instrument head, a tip element and an optical system. The instrument head has a distal insertion portion for insertion into an ear of a human or veterinary subject. The distal insertion portion has a distal opening. The tip element is releasably attached to the distal insertion portion. The tip element has a distal opening. The optical system is contained within the instrument head. The optical system includes a plurality of optical components. The optical system further comprises a viewing component for viewing of an image of a target of interest aligned along an optical axis disposed within said distal opening. The optical system is configured to provide a field of having a diameter equaling at least 7 mm at a distance of at least 15 mm from a distal opening of said attached tip element. The optical system is further configured to simultaneously provide a distance range of optimal focus having a range of at least 8 mm.

Abstract: A zoom lens and a photographing apparatus including the same. The zoom lens includes, in an order from an object side to an image side: a front lens group having a negative refractive power; an aperture stop; and a rear lens group having a positive refractive power, wherein the front lens group 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 negative refractive power, and the third lens group includes at least one positive lens and one negative lens and performs focusing, and the rear lens group includes at least two lens groups that are moved during zooming and have a positive refractive power, wherein at least one of the lenses of the two lens groups perform hand shake correction.

Abstract: A zoom lens includes, sequentially from an object side, a positive first lens group, a negative second lens group, a positive third lens group, and a positive rear lens group. During zooming from a wide angle position to a telephoto position, an interval between the first lens group and the second lens group increases, and an interval between the second lens group and the third lens group decreases. The rear lens group includes a positive first sub-group, a negative second sub-group, and a positive third sub-group, and focusing is performed by moving the second sub-group toward an image surface side. The zoom lens satisfies the following conditions: 0.2<frt/ft<1.8 and 0.2<|fb|/frt<1.0, where “frt” denotes a focal length of the rear lens group at the telephoto position, “fb” denotes a focal length of the second sub-group, and “ft” denotes a focal length of the zoom lens at the telephoto position.

Abstract: A zoom lens includes, sequentially from an object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power; and a fourth lens group having positive refractive power. When zoom is varied from a wide-angle end to a telephoto end, positions of the first lens group and the fourth lens group are fixed on an optical axis. The second lens group includes, sequentially from the object side, a second A lens group having positive refractive power and a second B lens group having positive refractive power, and the second B lens group is moved in the optical axis direction to perform a focusing function from an object disposed in a close range to an object disposed at infinity. The third lens group is shifted in a direction perpendicular to the optical axis to correct image blur.

Abstract: A zoom lens includes, in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power. During change of magnification from a short focal end to a long focal end, the first lens group is fixed, the second lens group is moved to an image side, the third lens group is moved, and the fourth lens group is fixed. The first lens group and the fourth lens group include diffraction surfaces and satisfy the Condition Expressions 50<f1doe/f1<200 (1) and 100<f4doe/f4<300 (2).

Abstract: A zoom lens includes first, second, third, and fourth lens groups respectively having positive, negative, negative, and positive powers. The first lens group includes an 11 lens group having a negative power, which is fixed during focusing operations, a lens group having a positive power, which moves during focusing operations, and a lens group having a positive power, which is fixed during focusing operations. The 11 lens group includes two negative meniscus lenses having concave surfaces toward an image side, and a cemented lens constituted by a biconcave lens toward an object side and a biconvex lens toward the image side. A distance D4 between the second meniscus lens and the cemented lens and the focal distance f1 of the first lens group satisfy the relationship: 0.60<D4/f1<2.0. Thereby, variations in angles of view while changing magnification are suppressed, sufficient reductions in size and weight, and high performance are achieved.

Abstract: A zoom lens includes first, second, third, and fourth lens groups respectively having positive, negative, negative, and positive powers. The first lens group includes a first lens subgroup having a negative power, which is fixed while focusing, a second lens subgroup having a positive power, which moves while focusing, and a third lens subgroup having a positive power, which is fixed while focusing. The second lens subgroup includes a positive lens having a surface having a radius of curvature with a smaller absolute value toward the image side; and a cemented lens constituted by a negative lens toward the object side and a positive lens toward the image side, cemented together at a joint surface having a convex surface toward the object side. The focal distance f12 of the second lens subgroup and the focal length fw of the entire system at the wide angle end satisfy the relationship: 3.0<f12/fw<20.0.

Abstract: A zoom lens includes a first lens group with a diffraction optical element and having positive refractive power, a second lens group having negative refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, which are sequentially arranged from an object side to an image side. The second lens group and the third lens group are moved in accordance with zooming between a wide angle end and a telephoto end such that the second lens group is positioned to the object-most side at the wide angle end, and the third lens group is positioned to the image-most side at the telephoto end. At least one of the second lens group and the third lens group includes a negative lens satisfying the conditional expressions: 1.50<nd<1.75; 60.0<?d<75.0; and ?C,A??0.0015×?d<0.2550.

Abstract: A zoom lens includes, in order from an object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power. During change of magnification from the short focal end to the long focal end, the first lens unit is stationary, the second lens unit is moved to an image side, the third lens unit is moved, and the fourth lens unit is stationary. A positive lens, included in the fourth lens unit or the first lens unit, satisfies the condition formulas: 1.40<nd<1.65; 65.0<?d<100.0; and 0.015<Pg,F?(?0.001802×?d+0.6483)<0.060, and the first lens unit includes a diffraction plane and satisfies the condition formula: 50<fdoe/f1<200.

Abstract: The endoscope objective lens is configured such that focusing from the farthest object to the nearest object is achieved by moving at least one lens group other than the most object-side lens group along the optical axis. One of the at least one lens group to be moved during focusing is a negative lens group. The one negative lens group that is moved during the focusing consists of a cemented lens that is formed by a positive lens and a negative lens cemented together in this order from the object side. The cemented surface of the cemented lens is oriented such that the concave surface faces the object side. Given conditional expressions are satisfied.

Abstract: A zoom-lens substantially consists of a positive-first-lens-group, fixed during magnification-change, a negative-second-lens-group, which moves from object-side toward image-side during magnification change from wide-angle-end to telephoto-end, a negative-third-lens-group, which corrects movement of an image-plane during magnification-change, and a positive-fourth-lens-group, which is fixed during magnification-change and includes a stop, in this order from object-side. The first-lens-group substantially consists of a negative-1a-th-lens-group, fixed during focusing, a positive-1b-th-lens-group, which moves during focusing, and a positive-1c-th-lens-group, fixed during focusing, in this order from object-side. The second-lens-group substantially consists of a negative-2a-th-lens-group and a positive-2b-th-lens-group, and a distance therebetween is changed during magnification-change.

Abstract: A zoom lens includes a positive first lens group fixed during zooming, a negative second lens moved to the image side upon zooming from the wide angle end to the telephoto end, a negative third lens group for image plane correction during zooming, and a positive fourth lens group fixed during zooming. The first lens group is composed of a negative first lens group front group, a positive first lens group middle group, and a positive first lens group rear group, disposed in order from the object side. The first lens group front group is composed of two negative lenses and one positive lens, disposed in order from the object side. Focusing is performed by moving only the first lens group middle group in an optical axis direction. The zoom lens satisfies a predetermined conditional expression.

Abstract: A zoom lens system has, in order from the enlargement side, a first lens group that remains stationary during zooming and that has a negative optical power and a plurality of lens groups that move during zooming. The first lens group includes three lens groups each having a negative optical power, namely a 1a-th lens group, a 1b-th lens group, and a 1c-th lens group. The 1a-th lens group remains stationary during focusing and includes at least one positive lens element. The 1b-th lens group moves toward the reduction side during focusing from infinity to a close distance. The 1c-th lens group moves toward the enlargement side during focusing from infinity to a close distance.

Abstract: A compact and lightweight zoom lens system having excellent imaging performance, which is favorably applicable to an interchangeable-lens type digital camera system, is provided. The zoom lens system of the present invention includes, in order from an object side to an image side, a first lens unit having positive optical power and composed of not more than two lens elements, a second lens unit having negative optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power. In zooming from a wide-angle limit to a telephoto limit, the fourth lens unit moves along an optical axis. Further, the following conditions are satisfied: 1.50<nd1<1.72, 50<vd1<75 (nd1: a refractive index to the d line of a positive lens element constituting the first lens unit, vd1: an Abbe number of a positive lens element constituting the first lens unit).

Abstract: A zoom lens consists of positive first lens group, which is fixed during changing magnification, negative second lens group, which is moved during changing magnification, negative third lens group for correcting a fluctuation of an image plane caused by changing magnification, and positive fourth lens group, which is fixed during changing magnification, which are in this order from an object side. The first lens group consists of negative lens and positive lens group consisting of three or less positive lenses in this order from the object side. Each of the negative lens and at least one of the positive lens or lenses in the first lens group has at least an aspherical surface. A predetermined formula is satisfied.

Abstract: A zoom lens includes first, second, third, and fourth lens groups respectively having positive, negative, negative, and positive powers. The first lens group includes an 11 lens group having a negative power, which is fixed while focusing, a 12 lens group having a positive power, which moves while focusing, and a 13 lens group having a positive power, which is fixed while focusing. The 12 lens group includes a positive lens having a surface having a radius of curvature with a smaller absolute value toward the image side; and a cemented lens constituted by a negative lens toward the object side and a positive lens toward the image side, cemented together at a joint surface having a convex surface toward the object side. The focal distance f12 of the 12 lens group and the focal length fw of the entire system at the wide angle end satisfy the relationship: 3.0<f12/fw<20.0.

Abstract: A zoom lens includes first, second, third, and fourth lens groups respectively having positive, negative, negative, and positive powers. The first lens group includes an 11 lens group having a negative power, which is fixed during focusing operations, a lens group having a positive power, which moves during focusing operations, and a lens group having a positive power, which is fixed during focusing operations. The 11 lens group includes two negative meniscus lenses having concave surfaces toward an image side, and a cemented lens constituted by a biconcave lens toward an object side and a biconvex lens toward the image side. A distance D4 between the second meniscus lens and the cemented lens and the focal distance f1 of the first lens group satisfy the relationship: 0.60<D4/f1<2.0. Thereby, variations in angles of view while changing magnification are suppressed, sufficient reductions in size and weight, and high performance are achieved.

Abstract: A zoom lens includes, in order from object side, a positive first lens unit which does not move for varying magnification, a negative second lens unit which moves for varying magnification, a negative third lens unit which moves for varying magnification, and a positive fourth lens unit which does not move for varying magnification, wherein the first lens unit includes a positive lens which satisfies the following conditions: 70<?p<85; 2.31<Np+0.01×?p<2.58; and 1.6<Np<1.85, where Np is refractive index of the positive lens, and ?p is Abbe constant of the positive lens, and 1.25<|fp/fna|<1.7 is satisfied, where fp is focal length of the positive lens, and fna is combined focal length of negative lenses in the first lens unit defined by the equation: fna = 1 ? i = 1 n ? 1 fn i , where n is a number of the negative lenses in the first lens unit, and fni is focal length of the i-th negative lens.

Abstract: A zoom lens substantially consists of, in order from the object side: a first lens group that has a positive refractive power and is fixed during magnification change; a second lens group that has a negative refractive power and is moved along the optical axis during magnification change; a third lens group that has a negative refractive power and corrects for fluctuation of the image plane along with magnification change; and a fourth lens group that has a positive refractive power and is fixed during magnification change. Focusing of an object at a distance between infinity and a predetermined distance is achieved by moving a first-group second lens sub-group, which is a part of the first lens group, along the optical axis, and focusing of an object at a closer distance than the predetermined distance is achieved by moving the third lens group along the optical axis.

Abstract: a zoom lens includes, in order from object side: a positive first unit immovable for zooming; a negative second unit moving during zooming; a third unit moving during zooming; a stop; and a positive fourth unit immovable for zooming. The first unit includes, in order from object side, a fixed negative front first unit, a positive middle first unit moving for focusing, and a fixed positive rear first lens unit. Each of the front first and the second units includes at least one positive lens and two negative lenses. Average of Abbe constants and average of partial dispersion ratios of positive lenses in the front first unit, average of Abbe constants and average of partial dispersion ratios of negative lenses in the front first unit, combined focal length of the positive lenses in the front first unit and focal length of the front first unit are appropriately set.

Abstract: A zoom lens includes a first lens unit with positive refraction that is stationary for zooming, a second unit with negative refraction that moves during zooming, a third unit that moves on the optical axis along with movement of the second unit, and a fourth unit with positive refraction that is stationary during zooming, arranged in order from the object to image planes. The first unit includes a negative meniscus element G1 convex towards the object plane, a positive element G2, a positive element G3, and a positive meniscus element G5 convex towards the object plane, arranged in order from the object to image planes. The respective curvature radii G1R1, G1R2, G5R1, and G5R2 of surfaces of the elements G1 and G5 and the respective focal lengths fG1, fG2, and f1 of the elements G1 and G5 and the first unit are set appropriately.

Abstract: A zoom lens consists of positive first lens group, which is fixed during changing magnification, negative second lens group, which is moved during changing magnification, negative third lens group for correcting a fluctuation of an image plane caused by changing magnification, and positive fourth lens group, which is fixed during changing magnification, which are in this order from an object side. The first lens group consists of negative lens and positive lens group consisting of three or less positive lenses in this order from the object side. Each of the negative lens and at least one of the positive lens or lenses in the first lens group has at least an aspherical surface. A predetermined formula is satisfied.

Abstract: A zoom lens system includes, in order from object-side to image-side a positive first lens unit, a second negative lens unit, a third lens unit, and a fourth positive lens unit. The fourth unit includes a front subunit having positive power and a rear subunit having positive power. The following conditions are satisfied: ?2.100×10?3×?d+0.693<?gF; 0.555<?gF<0.900; 0.8<(?fp/?fn)/(?rp/?rn)<4.0; 0.

Abstract: Provided is a zoom lens system including a compact focusing lens unit and having a suppressed change in image magnification at the time of movement of the focusing lens unit. The zoom lens system of the present invention, in order from an object side to an image side, includes, a first lens unit G1 having positive optical power, a second lens unit G2 having negative optical power, a third lens unit G3 having negative optical power, and a fourth lens unit G4. Further, condition: 1.88<nd2 is satisfied (where, nd2 is an average refractive index of a lens element (a portion excluding a resin layer in the case of a hybrid lens) included in the second lens unit G2).

Abstract: An optical system includes at least one lens unit having a negative refractive power disposed closer to an object side than an aperture portion. The lens unit having a negative refractive power includes at least one positive lens and one negative lens. The ratio between the numbers of positive lenses and negative lenses included in the lens unit having a negative refractive power is appropriately set. The lens unit having a negative refractive power includes a plurality of negative lenses each having an appropriate Abbe number and relative partial dispersion and a positive lens having an appropriate Abbe number. A negative lens having the highest dispersion among the negative lenses is located in an appropriate position.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, which does not move for zooming, a second lens unit having a negative refractive power, which moves during zooming, a third lens unit having a negative refractive power, which moves during zooming, an aperture stop, and a fourth lens unit having a positive refractive power, which does not move for zooming. The fourth lens unit includes a first lens sub-unit, a focal length conversion optical system configured to be inserted into or removed from an optical path, and a second lens sub-unit. A focal length of the second lens sub-unit, a distance from the aperture stop to a lens surface at the most object side of the second lens sub-unit, and an F-number of the entire zoom lens at a wide-angle end are appropriately set.

Abstract: It is preferable that an image forming optical system includes in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a subsequent lens group having a positive refractive power as a whole, and that the third lens group includes only a cemented lens having a negative refractive power, which includes a positive lens and a negative lens in order from the object side. Moreover, it is preferable that a cemented surface of the cemented lens in the third lens group has a shape which is convex toward an image side.

Abstract: A zoom lens includes, in order from an enlargement side to a reduction side, a first lens unit having a positive refractive power, which is stationary for variation of magnification, a second lens unit having a negative refractive power, which moves for variation of magnification, a third lens unit having a negative refractive power, which moves for variation of magnification, a fourth lens unit having a positive refractive power, which includes a stop and which moves for variation of magnification, and at least one lens unit. In the zoom lens, for variation of magnification from a wide-angle end to a telephoto end, the second lens unit and the third lens unit move towards the reduction side and the fourth lens unit move towards the enlargement side. The zoom lens satisfies an appropriate condition.

Abstract: An image pickup apparatus having a simple configuration and being capable of performing switching between an image pickup mode based on a light field photography technique and a normal high-resolution image pickup mode is provided. The image pickup apparatus includes an image pickup lens 11, a microlens array section 12 where light passing through the image pickup lens 11 enters, and an image pickup device 13 sensing light emitted from the microlens array section 12, and the focal length of each of microlenses constituting the microlens array section 12 is variable in response to an applied voltage.

Abstract: A zoom lens, including: a first lens unit and a second lens unit, in which the first lens unit includes: a first lens sub unit which does not move; a second lens sub unit which moves for focusing; and a third lens sub unit which does not move; and in which the following expression is satisfied, ?2.27×10?3<(?p??na)/(?p??na)<?1.9×10?3, where ?na and ?na represent an average value of an Abbe number ? and an average value of a partial dispersion ratio ? of negative lenses included in the first lens sub unit, respectively, ?p and ?p represent an Abbe number and a partial dispersion ratio of a positive lens having a smallest Abbe number among lenses constituting the first lens sub unit, respectively, ?=(Ng?NF)/(NF?NC), and Ng, NF and NC denote refractive indexes at the g-line, the F-line and a C-line, respectively.

Abstract: A zoom lens system is provided that includes a compactly constructed focusing lens unit and that has a suppressed change in the image magnification at the time of movement of a focusing lens unit and further that can compensate an image blur caused by vibration applied to the entire system. The zoom lens system according to the present invention comprises a plurality of lens units and an aperture diaphragm arranged in the lens unit.

Abstract: A zoom lens includes, in order from object side, a positive first lens unit which does not move for varying magnification, a negative second lens unit which moves for varying magnification, a negative third lens unit which moves for varying magnification, and a positive fourth lens unit which does not move for varying magnification, wherein the first lens unit includes a positive lens which satisfies the following conditions: 70<?p<85; 2.31<Np+0.01×?p<2.58; and 1.6<Np<1.85, where Np is refractive index of the positive lens, and ?p is Abbe constant of the positive lens, and 1.25<|fp/fna|<1.7 is satisfied, where fp is focal length of the positive lens, and fna is combined focal length of negative lenses in the first lens unit defined by the equation: fna = 1 ? i = 1 n ? 1 fn i , where n is a number of the negative lenses in the first lens unit, and fni is focal length of the i-th negative lens.

Abstract: A zoom lens comprises first and fourth units which don't move for zooming, and second and third units moved during zooming. The first unit includes a front side partial unit which don't move for focusing, a movable partial unit moved for focusing, and a rear side partial unit which don't move for focusing, the rear side partial unit includes positive lenses and one or more negative lenses, and the following conditions are satisfied: ?1.2×10?3<(?pa??n)/(?pa??n), and ?n<30, where ?n is the smallest Abbe number of the material of the negative lenses, ?n is the partial dispersion ratio of the material of the negative lens of the smallest Abbe number, ?pa is the average of the Abbe numbers ? of the materials of positive lenses, and ?pa is the average of the partial dispersion ratio ? of the materials of the positive lenses.