Abstract: A zoom lens device has a zoom lens system having a plurality of lens units; and an image sensor converting an optical image formed by the zoom lens system, into electric image data. The zoom lens system has a first lens unit disposed on the most object side and consisting of a single negative lens element, a second lens unit having a positive optical power; and a diaphragm disposed on the object or the image side of the second lens unit, or in the second lens unit. Zooming is performed by varying the distances between the lens units. Focus adjustment by varying the object distance is performed by moving along the optical axis a positive lens unit or a single lens element disposed in a position on the image side of the diaphragm and not included in the most image side lens unit.

Abstract: A zoom lens device has a zoom lens system having a plurality of lens units; and an image sensor converting an optical image formed by the zoom lens system, into electric image data. The zoom lens system has, from the object side, a first lens unit disposed on the most object side and consisting of one negative lens element; and a second lens unit being overall positive power and including a positive lens element and a negative lens element independent of each other. Lens surfaces constituting the zoom lens system are all refracting surfaces. Zooming is performed by varying the distances between the lens units. The predetermined conditions are satisfied by the zoom lens system.

Abstract: A zoom lens includes, in order from the enlarging side: a first lens group that has negative refractive power, is movable for focusing, and is stationary during zooming; second, third, and fourth lens groups that are movable for zooming; and a fifth lens group that is stationary during zooming. The second and fifth lens groups have positive refractive power and the third and fourth lens groups have negative refractive power. The second and third lens groups move nearer the enlarging side when the zoom lens zooms toward the telephoto end and the fourth lens group is positioned nearer the reducing side when at the telephoto end than when at the wide-angle end. The ratios of the focal lengths of the first, second, fourth, and fifth lens groups to the focal length of the zoom lens satisfy four conditions. A projection display device uses the zoom lens.

Abstract: To obtain a small and thin zoom lens unit, the present invention includes a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole, arranged from an object side to an image side. The zoom lens zooms from a short-focal end to a long-focal end and corrects image surface changes required in accordance with the zooming by means of moving the second lens group and the third lens group, wherein the first lens group includes a first lens having a negative refractive power and a prism having a negative refractive power and changing an incident light path, arranged from the object side to the image side, the second lens group including a single second lens, said third lens group including a single third lens.

Abstract: A three-group zoom lens includes, in order from the object side, a first lens group of negative refractive power, and second and third lens groups, each of positive refractive power. The first and second lens groups include negative and positive components and the third lens group is a single lens component. All but one lens component may be a single lens element. When zooming from the wide-angle end to the telephoto end, the first and second lens groups move closer together while the second lens group moves farther from the third lens group. The third lens group remains stationary during zooming but moves for focusing. The second lens group includes a diaphragm on its object side. Aspheric lens surfaces are disclosed. The zoom lens satisfies certain conditions for the focal lengths of the zoom lens and a component of the zoom lens, and for Abbe numbers of two lens elements.

Abstract: An electronic picture taking apparatus comprises a zoom lens system and an image pickup device. The zoom lens system has a type of movement suitable for stable, high performance in the range from infinite to near distance and having a reduced thickness. The zoom lens system comprises at least four lens units. A foremost first lens unit on the object side of said zoom lens system has a negative refractive power. Each of three consecutive lens units has variable space on the image side thereof between an adjacent lens unit for performing a zooming operation. A rearmost lens unit of the zoom lens system consists of a single positive lens element having an aspherical surface and being fixed during the zooming operation. The zoom lens system includes an aperture stop moving incorporated with the second lens unit which is adjacent to the first lens unit.

Abstract: A zoom lens system has, in order from an enlargement side, a first lens unit having negative optical power, a second lens unit having positive optical power, a third lens unit having positive optical power, a fourth lens unit having negative optical power, including an aperture stop, a fifth lens unit having positive or negative optical power, and a sixth lens unit having positive optical power. Zooming is achieved by varying the first to fifth variable distances between the lens units. The third and fifth lens units move from the enlargement side to the reduction side during zooming from the telephoto end to the wide-angle end. The zoom lens system is substantially telecentric toward the reduction side.

Abstract: A three-group zoom lens includes first, second, and third lens groups, of negative, positive, and positive or negative refractive power, respectively. The second lens group includes a stop and the third lens group moves for focusing. When zooming from the wide-angle end to the telephoto end, the first and second lens groups become closer together. The zoom lens preferably satisfies specified conditions that ensure compactness, ease of manufacture, and favorable correction of aberrations. The zoom lens includes aspheric lens elements with lens surfaces defined by an aspheric lens equation that: (a) includes at least one non-zero coefficient of an even power of Y, and at least one non-zero coefficient of an odd power of Y, where Y is the distance of a point on the aspheric lens surface from the optical axis, and/or (b) includes at least one non-zero coefficient of Yi, where i is even and 16 or greater.

Abstract: The invention provides a fisheye lens system having an angle of view of 170 degrees or more capable of being used with a plurality of cameras having different image formats in size. The lens system includes a first lens group G1 having negative refractive power disposed to the most object side and a second lens group G2 having positive refractive power disposed to an image side of the first lens group. A distance between the first lens group G1 and the second lens group G2 is variable. The lens system takes the maximum focal length state when the distance is minimum and the minimum focal length state when the distance is maximum. The maximum image height in the maximum focal length state is different from that in the minimum focal length state. In each focal length state, the fisheye lens system has an angle of view of 170 degrees or more.

Abstract: A wide-angle zoom lens system includes a negative first lens group, a positive second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group. Upon zooming from the short to the long focal length extremities, the first lens group moves toward the image and thereafter moves toward the object; the distance between the first and second lens groups decreases, the distance between the second and third lens groups decreases, the distance between the third and fourth lens groups increases, and the distance between the fourth and fifth lens groups decreases.

Abstract: An object is to provide a zoom lens system having compactness of about a normal lens, small number of lens elements, a zoom ratio about 2.9, good productivity, and high optical performance. The system includes, in order from the object, a first lens group with negative power and a second lens group with positive power. Zooming is performed by varying a distance between the first lens group and the second lens group. The first lens group includes at least a negative lens and a positive lens. The second lens group includes a front lens group with positive power and a rear lens group with positive power. The front lens group includes a positive lens and a cemented lens constructed by a positive lens cemented with a negative lens. The rear lens group includes a cemented lens constructed by a negative lens cemented with a positive lens. Given conditions are satisfied.

Abstract: A five-group zoom lens is formed of, in order from the enlarging side of the zoom lens, a negative first lens group that is movable for focusing and that is stationary during zooming, a positive second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group that is stationary during zooming. The second lens group, the third lens group, and the fourth lens group move relative to one another and relative to the first and fifth lens groups during zooming. The second lens group includes a negative lens component that has a concave lens surface on the reducing side of the zoom lens. The zoom lens satisfies various conditions and may be used in a projection display device or an image pickup device such as a camera.

Abstract: The invention relates to a high-performance, large-aperture yet wide-angle zoom lens system that can be used with an electronic image pickup device in particular, a method for focusing the same. In particular, the invention is concerned with a high-performance, large-aperture yet wide-angle zoom lens system which has a zoom ratio of the order of 3 at a diagonal field angle of 75° at its wide-angle end, so that it can be used with a single-lens reflex camera using an electronic image pickup device with the number of pixels being of the order of 6,000,000. The zoom lens system comprises a first lens group G1 having negative refracting power, a second lens group G2 having positive refracting power, a third lens group G3 having negative refracting power, a fourth lens group G4 having positive refracting power and a fifth lens group G5 having positive refracting power. Upon movement of an object point, focusing is carried out with the fifth lens group G5.

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 zoom lens with a slim and compact design has arranged in sequence from the object side to the image plane side 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. The first lens group is formed from a first lens having a negative refractive power and a second lens having a positive refractive power. The second lens group is formed from a third lens having a positive refractive power and a fourth lens and a fifth lens. The fourth and fifth lens are joined together and have a negative refractive power. The third lens group is formed from a sixth lens having a positive refractive power. The zoom lens has a short length when retracted and extended, and a design that is compact and thin.

Abstract: A zoom lens system includes at least two lens groups, and a negative first lens group is positioned at the most object-side of the zoom lens system. The negative first lens group includes a negative sub-lens group and a positive sub-lens group. The positive sub-lens group includes a positive lens element and a rearmost lens element of the negative first lens group. The rearmost lens element includes a plastic lens element having at least one aspherical surface.

Abstract: The invention provides a zoom lens that operates in such a zooming mode and zoom arrangement that the number of lens elements is reduced to make the total thickness of each lens group thin while stable yet high image-formation capability is maintained, thereby achieving thorough size reductions in video cameras or digital cameras, and an electronic imaging system using the same. The zoom lens comprises a first lens group G1 of negative refracting power, a second lens group G2 of positive refracting power and a third lens group G3 of positive refracting power. For zooming from the wide-angle end to the telephoto end of the zoom lens upon focused on an infinite object point, the second lens group G2 moves toward the object side alone of the zoom lens, and the third lens group G3 moves in a locus different from that of the second lens group while the spacing between adjacent lens groups varies. The second lens group G2 is composed of two lens components, i.e.

Abstract: There are provided a zoom lens system comprising, in order from a more distant conjugate point, a first lens unit of a negative refractive power, a second lens unit of negative refractive power which moves during zooming, third, fourth and fifth lens units, and at least one diffraction optical element.

Abstract: A zoom lens has a lens group of negative refractive power at the enlarging end and a lens group of positive refractive power at the reducing end, both of which are fixed during zooming. The lens group of negative refractive power includes two lens components of negative refractive power, and at least one of the lens groups includes a thin plastic lens element with a lens surface bonded to a lens surface of a glass lens element, with the other lens surface of the plastic lens element having an aspheric shape. The lens group of negative refractive power consists of lens elements of negative refractive power. One of the two lens components is at the enlarging end of the zoom lens and includes a meniscus lens element of negative refractive power. The other lens component is adjacent the one lens component and is a biconcave lens component.

Abstract: A optical device has a zoom lens system that is comprised of a plurality of lens units and that achieves zooming by varying unit-to-unit distances and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system is comprised of, from the object side, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power. The zoom lens system achieves zooming by varying the distances between the first to fourth lens units.

Abstract: The present invention is directed to provide a compact and light-weighted projection lens system that is capable of projecting an image at an angle as wide as 75 degrees with sufficient field angle and brightness as represented by F number of approximately 2.4, that is capable of effectively correcting chroic aberration of magnification and aberration of distortion and exhibiting optical stability against environmental variations, and that is suitable to obtaining an extraordinarily fine image by the magnification and projection.

Abstract: A lens optical system is provided with a cemented lens element formed by cementing two constituent lens elements made of different optical materials together, with a diffractive optical surface formed at the cementing interface between the two constituent lens elements. The two constituent lens elements have at their respective interfaces with air a radius of curvature different from the radius of curvature that they have at the cementing interface.

Abstract: The invention relates to a high-performance, large-aperture yet wide-angle zoom lens system that can be used with an electronic image pickup device in particular, a method for focusing the same. In particular, the invention is concerned with a high-performance, large-aperture yet wide-angle zoom lens system which has a zoom ratio of the order of 3 at a diagonal field angle of 75° at its wide-angle end, so that it can be used with a single-lens reflex camera using an electronic image pickup device with the number of pixels being of the order of 6,000,000. The zoom lens system comprises a first lens group G1 having negative refracting power, a second lens group G2 having positive refracting power, a third lens group G3 having negative refracting power, a fourth lens group G4 having positive refracting power and a fifth lens group G5 having positive refracting power. Upon movement of an object point, focusing is carried out with the fifth lens group G5.

Abstract: A zoom lens system discloses a zoom lens system which is small in size and exhibits favorable optical performance. The zoom lens system, according to the present invention includes, in order from the front to the rear: a first lens unit having negative optical power; a second lens unit having positive optical power; a third lens unit having positive optical power; a fourth lens unit having positive optical power; and a fifth lens unit having positive optical power. Of these five lens units, at least three lens units move at the time of zooming. Further, the fifth lens unit is provided with a positive lens element having a relatively high refractive index.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group. The negative first lens group includes a negative meniscus lens element having the convex surface facing toward the object, and the positive third lens group includes a positive biconvex lens element. Upon zooming, at least the negative first lens group and the positive second lens group are moved. A diaphragm is provided on the object side of the positive second lens group, and moves integrally therewith. The zoom lens system satisfies the following conditions: 0.25<R1/D1<0.55 . . . (1); 0.25<f2/TL<0.45 . . .

Abstract: A zoom lens includes: a negative first group optical system G1, a positive second group optical system G2 and a third group optical system G3, which are sequentially arranged in this order from an object side; and a aperture stop FA which is disposed on the object side of the second group optical system G2, and moves integrally with the second group optical system G2.

Abstract: A zoom lens comprising a first group of lenses (1) having negative focal length, a second group of lenses (2) having positive focal length, and a third group of lenses (3 having the positive focal length in order from an object side, in which the second group of lenses (2) moves monotonically from an image side to the object side and the first group of lenses 1 moves so as to correct shift in a position of an image surface, which is attended with a change in magnification, when the magnification is changed from an end of short focus to the end of long focus. The zoom lens is characterized in that the first group of lenses 1 has at least two lenses (L1) and (L2) and an air lens formed between the two lenses, both sides of the air lens are the aspheric surface, and the first group of lenses satisfies the following conditional expressions of no>1.50 and ni>1.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group. Zooming is performed by moving the first and second lens groups in the optical axis direction thereof. The most image-side lens element of the positive first lens group includes a positive lens element having at least one aspherical surface.

Abstract: A zoom leas includes a first lens unit of a negative optical power and a second and third lens unit each of a positive optical power. The second lens unit consists of a first and second lens sub unit, each of a positive optical power arranged respectively on an object side and an image side. Zooming is effected by moving the lens units such that the distance between the first and second lens unit is smaller at a telephoto end than at a wide-angle end and that the distance between the second and third lens unit is larger. Focusing is effected by moving the second lens sub unit or the third lens unit where, when focusing on an object at infinity, the distance between the first lens sub unit and the second lens sub unit and the focal length of the entire system satisfy a predetermined condition.

Abstract: An object of the present invention is to provide a super wide-angle zoom lens system having an angle of view of 2&ohgr;=100° or more, a zoom ratio of about 2, the f-number of about f/4, sufficient amount of peripheral light quantity, high optical performance, and aspherical surfaces capable of being manufactured easily. According to one aspect of the present invention, in order from an object, a first lens group G1 having negative refractive power, and a second lens group G2 having positive refractive power are provided. Zooming is carried out by varying a distance between the first lens group G1 and the second lens group G2. The first lens group G1 has a negative lens component Ln and a positive lens component Lp. The negative lens component Ln has at least one aspherical lens Lasp. The aspherical lens Lasp satisfies given conditional expressions.

Abstract: A zoom lens includes, in order from the enlarging side, a first lens group that has negative refractive power, is movable for focusing, and is stationary during zooming, second, third, fourth, and fifth lens groups that are movable for zooming, and a sixth lens group that is stationary during zooming. The second, fourth, and sixth lens groups have positive refractive power and the fifth lens group has negative refractive power. The second and fourth lens groups move nearer the enlarging side when the zoom lens zooms toward the telephoto end, and the fifth lens group is nearer the enlarging side at the zoom lens telephoto end than at the zoom lens wide-angle end. The ratios of the focal lengths of the first, third, and fifth lens groups to the focal length of the zoom lens satisfy three conditions. A projection display device uses the zoom lens.

Abstract: A zoom lens includes, in order from the enlarging side: a first lens group that has negative refractive power, is movable for focusing, and is stationary during zooming; second, third, and fourth lens groups that are movable for zooming; and a fifth lens group that is stationary during zooming. The second, third, fourth, and fifth lens groups have positive refractive powers. The second, third, and fourth lens groups move nearer the enlarging side when the zoom lens zooms toward the telephoto end. The ratios of the focal lengths of the first, first through third, fourth, and fifth lens groups to the focal length of the zoom lens satisfy four conditions. The fourth lens group is a biconvex lens element. A projection display device uses the zoom lens.

Abstract: The present invention provides a compact, thin zoom lens. The zoom lens according to the present invention includes, from an object side to an image plane side, a first lens group having an overall negative overall refractive power, a second lens group having an overall positive refractive power; and a third lens group having an overall positive refractive power. The first lens group includes a first lens and a second lens bonded together and having a negative refractive power. The second lens group includes a third lens with a positive refractive power, and a fourth lens and a fifth lens bonded together and having a negative refractive power. The third lens group includes a sixth lens having a positive refractive power. As a result, the total length is reduced, the retracted length can be reduced, and the zoom lens can be compact and thin.

Abstract: This specification discloses a zoom lens system provided, in succession from the front to the rear, with a first lens unit of negative optical power, a second lens unit of positive optical power and, a third lens unit of positive optical power.

Abstract: A three-group zoom lens includes, in order from the object side, a first lens group of negative refractive power, and second and third lens groups, each of positive refractive power. The first and second lens groups include negative and positive components and the third lens group is a single lens component. All the lens components may be single lens elements. When zooming from the wide-angle end to the telephoto end, the second and third lens groups move toward the object side and all three lens groups move such that the group spacings decrease. The second lens group includes a diaphragm on its object side. A constant axial spacing between the second and third lens groups is maintained when zooming while the zoom lens is focused at infinity, and the third lens group is moved toward the object side when focusing from infinity to a near point.

Abstract: An electronic picture taking apparatus comprises a zoom lens system and an image pickup device. The zoom lens system has a type of movement suitable for stable, high performance in the range from infinite to near distance and being thoroughly reduced the thickness. The zoom lens system comprises at least four lens units. A foremost first lens unit on the object side of said zoom lens system has a negative refractive power. Each of three consecutive lens units has variable space on the image side thereof between an adjacent lens unit for performing a zooming operation. A rearmost lens unit of the zoom lens system consists of a single positive lens element having an aspherical surface and being fixed during the zooming operation. The zoom lens system includes an aperture stop moving incorporated with the second lens unit which is adjacent to the first lens unit. The electronic picture taking apparatus satisfies the following condition: 1.5<L2/Y<3.

Abstract: A zoom lens system, covering a wide-angle range, includes a negative first lens group, a positive second lens group, and a negative third lens group.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group. Upon zooming from the short to long focal length extremities, the distance between the first and second lens groups decreases, and the distance between the second and third lens groups increases.

Abstract: It is an object of this invention to provide a zoom lens capable of projecting an original projection image displayed by a liquid crystal display element onto a screen surface with high optical performance, and an image projection apparatus using the zoom lens. A zoom lens includes a first lens unit having negative refractive power, a second lens unit having positive refractive power, a stop, a third lens unit having negative refractive power, a fourth lens unit having negative refractive power, and a fifth lens unit having positive refractive power, which are sequentially arranged from the enlargement side and having one or a plurality of lenses. When the magnification is to be changed from the wide angle end to the telephoto end, the second, third, and fourth lens units and the stop move.

Abstract: A projection lens of the following structure was invented for the purpose of providing a bright projection optical system with the F-number of approximately 2 or lower while maintaining good optical characteristics, in an image display apparatus. The projection lens is constructed of six lens units, a first lens unit L1 of a negative optical power, a second lens unit L2 of a positive optical power, a third lens unit L3 of a positive optical power, a fourth lens unit L4 of a negative optical power, a fifth lens unit L5, and a sixth lens unit L6 of a positive optical power, in the order named from the enlargement conjugate side, and four lens units (L2 to L5) out of the lens units move toward the enlargement conjugate side during zooming from the wideangle extreme to the telephoto extreme.

Abstract: The invention provides a zoom lens that operates in such a zooming mode and zoom arrangement that the number of lens elements is reduced to make the total thickness of each lens group thin while stable yet high image-formation capability is maintained, thereby achieving thorough size reductions in video cameras or digital cameras, and an electronic imaging system using the same. The zoom lens comprises a first lens group G1 of negative refracting power, a second lens group G2 of positive refracting power and a third lens group G3 of positive refracting power. For zooming from the wide-angle end to the telephoto end of the zoom lens upon focused on an infinite object point, the second lens group G2 moves toward the object side alone of the zoom lens, and the third lens group G3 moves in a locus different from that of the second lens group while the spacing between adjacent lens groups varies. The second lens group G2 is composed of two lens components, i.e.

Abstract: Disclosed is a zoom lens system. The zoom lens system comprises: a first lens group of a negative refractive power, the first lens group comprising at least one lens of a negative refractive power and at least one lens of a positive refractive power; a second lens group of a positive refractive power, the second lens group comprising a first lens of a positive refractive power, a second lens of a positive refractive power, and a third lens of a negative refractive power; and a third lens group of a positive refractive power, the third lens group comprising at least one lens of a positive refractive power; wherein the first, the second, and the third lens groups move along an optical axis, and the zoom lens system satisfies the following conditions: 1 0.4 ≤ t II f W ⁢ f T ≤ 0.

Abstract: A five-group zoom lens is formed of, in order from the enlarging side of the zoom lens, a negative first lens group that is movable for focusing and that is stationary during zooming, a positive second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group that is stationary during zooming. The second lens group, the third lens group, and the fourth lens group move relative to one another and relative to the first and fifth lens groups during zooming. The second lens group includes a negative lens component that has a concave lens surface on the reducing side of the zoom lens. The zoom lens satisfies various conditions and may be used in a projection display device or an image pickup device such as a camera.

Abstract: A wide-angle zoom lens is disclosed having only two lens groups, of negative and positive refractive power in order from the object side, respectively, and which provides an image angle at the wide-angle end of at least 100°. Zooming is performed by moving the first lens group and the second lens group along the optical axis. The first lens group is formed of, in sequential order from the object side, a negative meniscus lens element with its convex surface on the object side, two negative lens elements, and a positive lens element. The second lens group is formed of, in sequential order from the object side, two positive lens elements, a biconcave lens element, and two positive lens elements. Various conditions are preferably satisfied so as to minimize aberrations and make the zoom lens compact and easy to manufacture.

Abstract: A fixed focal length, wide-angle lens includes, in order from the object side, a negative first lens group that includes a plastic negative lens element, a positive second lens group that includes a plastic positive lens element, a positive third lens group that includes a positive lens element joined on its image side to another lens element, and a positive fourth lens group. In the preferred embodiments, all lens groups except the third lens group are single lens elements that each include an aspheric lens surface. Also, the wide-angle lens preferably satisfies specified conditions that, together with the use of plastic lenses, joined lens elements, and aspheric surfaces, enables a high performance, compact, wide-angle lens of relatively simple construction to be produced.

Abstract: A retro-focus-type camera lens is disclosed that is formed of, in order from the object side: a front lens group having negative refractive power, a diaphragm, and a rear lens group having positive refractive power. The front lens group is formed of, in order from the object side, a positive lens element and two negative lens elements, and the rear lens group is formed of, in order from the object side, a positive lens element, two sets of lens elements that are cemented together to form two joined lenses, and a positive lens element. Various conditions are preferably satisfied in order to provide a lens having an image angle of about 38°, an F number of about 1.4, and which suppresses the occurrence of color shading while providing a sufficient back focus to insert a color separation optical system between the retro-focus-type camera lens and the image plane.

Abstract: A three-group zoom lens includes, in order from the object side, a first lens group of negative refractive power, and second and third lens groups, each of positive refractive power. The first and second lens groups include negative and positive components and the third lens group is a single lens component. All the lens components may be single lens elements. When zooming from the wide-angle end to the telephoto end, the second and third lens groups move toward the object side and all three lens groups move such that the group spacings decrease. The second lens group includes a diaphragm on its object side. A constant axial spacing between the second and third lens groups is maintained when zooming while the zoom lens is focused at infinity, and the third lens group is moved toward the object side when focusing from infinity to a near point.

Abstract: The invention has for its object to use a zoom system that comprises a reduced number of lens elements, is compact and simplified, and has high image-formation capability, thereby achieving thorough size reductions in video cameras or digital cameras. A zoom lens for use on an image pickup system comprises a first lens group G1 negative power comprising an aspheric negative lens element and a positive lens element, a second lens group G2 comprising a positive single lens element, a positive doublet wherein a positive and a negative lens element are cemented together in this order and which is in a meniscus form convex toward an object side of the zoom lens and a positive single lens element, wherein two or more surfaces except the cementing surface of the doublet are each defined by an aspheric surface, and a third lens group G3 comprising one positive lens component.

Abstract: The invention provides a zoom lens that comprises a reduced number of lens elements, is compact and simplified, and has high image-formation capability, thereby achieving thorough size reductions in video cameras or digital cameras, and an electronic imaging system using the same. The zoom lens comprises a first lens group G1 of negative refracting power, a second lens group G2 of positive refracting power and a third lens group G3 of positive refracting power. Upon zooming from the wide-angle end to the telephoto end of the zoom lens, the second lens group G2 moves toward the object side alone of the zoom lens, and the third lens group G3 moves while the spacing between the third lens group G3 and the second lens group G2 varies. The second lens group G2 is composed of a front subgroup and a rear subgroup.

Abstract: A zoom lens system has a zoom ratio of about 3, a wide field angle on the wide-angle end and a small F-number. The system includes a negative power lens group Gi, an aperture stop, a positive power lens group G2 and a positive power lens group G3. For zooming, Gi and G2 move on the optical axis with a varying spacing between adjacent lens groups while G3 remains fixed. The stop moves in unison with the second lens group.