Abstract: A zoom lens system comprising, at an image side location, a lens unit which has a negative refractive power and consists, in order from the object side, of a positive front subunit and a negative rear subunit: the front subunit being composed of a negative lens component consisting of a negative lens element and a positive lens element, the rear subunit being composed only of a single negative lens component, and the negative lens element having an aspherical surface which weakens a negative refractive power as portions of the aspherical surface are farther from an optical axis thereof.

Abstract: Disclosed is an image position correcting optical system, comprising sequentially from an object side, a first lens group having positive refracting power and a second lens group having negative refracting power. The first lens group is fixed. The second lens group is so provided as to be movable along an optical axis. A part of lens subunits of lens elements constituting the first lens group is so provided as to be movable in a direction across the optical axis. A positive lens element of the lens elements constituting the first lens group satisfies the following conditions:1.43.ltoreq.n.sub.d .ltoreq.1.6565.ltoreq..nu..sub.d .ltoreq.950.302.ltoreq..theta..sub.FCd .ltoreq.0.309where n.sub.d is the refractive index with respect to the d-line, n.sub.F is the refractive index with respect to the F-line, n.sub.c is the refractive index with respect to the C-line, .nu..sub.d is the Abbe number with respect to the d-line, and .theta..sub.FCd is the partial dispersion ratio expressed by (n.sub.d -n.sub.c) / (n.sub.

Abstract: A zoom lens having two units of lens components including from the object side a positive optical unit and a negative optical unit. The zoom lens satisfies the following relationship ##EQU1## where eW is the principal point separation of the zoom lens when said zoom lens operates at a wide angle position and eT is the principal point separation of the zoom lens when said zoom lens operates at the telephoto position.

Abstract: A zoom lens system using inexpensive lens materials and having a high magnification zoom ratio of more than 2 times and good aberration performance. A first lens group has a positive refractive power, and a second lens group has a negative refractive power. The distance between the first lens group and the second lens group varies during zooming. 0.37<f.sub.I /(f.sub.bT -f.sub.bw)<0.7; m.sub.2T /m.sub.2w >2.0, where f.sub.I is a combined focal length of the first lens group, f.sub.bT is a back focus distance at a telephoto position f.sub.bw is a back focus distance at a wide angle position, m.sub.2T is a magnification of the second lens group at a telephoto position, and m.sub.2w is a magnification of the second lens group at a wide angle position.

Abstract: A variable magnification lens system of the invention has from the object side a positive first lens unit and a negative second lens unit. The first lens unit includes a negative first lens element and a positive second lens element. The negative second lens unit includes a positive third lens element and a negative fourth lens element. At variable magnification from an equal magnification (1:1) state to an enlargement state, the overall lens system moves while the spacing between the two lens units is increased, and the distance between the object and the image remains constant. The object side surface of the first lens element and the image side surface of the fourth lens element are concave. Aspherical surfaces are provided on both surfaces of the first lens element and the image side surface of the third lens unit. The focal length of the first lens element and fourth lens element are suitable stipulated by a condition.

Abstract: There is provided a wide-angle zoom lens including in the following order from the object side: a first lens group having a positive refractive power, the first lens group consisting of, in the following order from the object side, a front lens subgroup which consists of a negative lens, and a rear lens subgroup which consists of at least one positive lens and at least one negative lens; and a second lens group having a negative refractive power, wherein an air gap between the first and second lens groups decreases upon zooming from a wide-angle end to a telephoto end, and the zoom lens satisfies the following conditions:0.09.ltoreq.D2/fW.ltoreq.0.4-0.6.ltoreq.Q1.ltoreq.0.

Abstract: A zoom lens system using inexpensive plastic lens materials and having a good aberration performance and good optical performance includes a first lens group having a positive refractive power and a second lens group having a negative refractive power, a distance between the first lens group and the second lens group being variable during zooming, wherein 37<(F.sub.I .multidot.f.sub.bT /D.sub.T .multidot.f.sub.bW)<48; and 2.5<D.sub.T /N.sub.nI <3.5 where f.sub.I is focal length of the first lens group, f.sub.bT is back focus distance at a telephoto position, f.sub.bW is back focus distance at a wide angle position, D.sub.T is distance between the first lens group and the second lens group at a telephoto position, and N.sub.nI is refractive ratio of the lens having a negative refractive power in the first lens group.

Abstract: A compact zoom lens performs a zooming operation by changing a clearance between a first lens group having a positive focal length and a second lens group having a negative focal length. The first lens group is constructed by sequentially arranging first to fourth lenses from an object side. The second lens group is constructed by sequentially arranging fifth and sixth lenses from an object side. An aperture stop is arranged just after the first lens group. The following conditions(1) 0.60<f.sub.I /f.sub.W <0.75, (2) -1.10<f.sub.II /f.sub.I <-0.90, (3) EP/f.sub.W <0.25, (4) AP.sub.W /f.sub.T >-0.16are satisfied when f.sub.W is a focal length of an entire lens system at a short focal end; f.sub.T is a focal length of the entire lens system at a long focal end; f.sub.I is a focal length of the first lens group; f.sub.II is a focal length of the second lens group; EP is a distance from a lens front end to an entrance pupil; and AP.sub.

Abstract: A zoom lens system comprising, in order from the object side, a positive first lens group and a negative second lens group, with the focal length being changed by varying the distance between the first and second lens groups, which lens system is characterized in that said first lens group comprises, in order from the object side, a negative sub-group 1a and a positive sub-group 1b, said sub-group 1a comprising, in order from the object side, a negative first lens element having its smaller radius of curvature on the surface directed towards the object and a positive second lens element having a convex surface directed towards the image plane. The lens system satisfies a number of predetermined conditions.

Abstract: A zoom lens having two units of lens components including from the object side a positive optical unit and a negative optical unit. The positive optical unit includes two lens components, a weak power lens component, and a second positive power lens component, while the negative optical unit provides most of the magnification change during zooming. The zoom lens has reduced aspheric decenter sensitivity.

Abstract: A wide-angle zoom lens system includes a first lens group having a positive refractive power and a second lens group having a negative refractive power and spaced from the first lens group at a first distance, the first distance being variable during zooming. The first lens group includes a first lens having a positive refractive power and a convex surface toward an object, a second lens having a negative refractive power and concave surfaces, a third lens having a positive refractive power and convex surfaces, a fourth lens having a negative refractive power and convex surfaces, a fifth lens having a negative refractive power and a concave surface toward the object, and a sixth lens having a positive refractive power and one of convex and meniscus surfaces. The second lens group includes a seventh lens having a positive refractive power and a concave surface toward the object and at least one element of a negative refractive power lens. The zoom lens system having the following characteristics:0.5<f.sub.

Abstract: A zoom lens is disclosed, comprising, from front to rear, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, an air separation between the first and second lens units being varied to vary the focal length, wherein the first lens unit comprises, from front to rear, a front lens unit having a negative refractive power, a stop and a rear lens unit having a positive refractive power, satisfying the following condition:0.053<l/fw<0.1where l is an air separation between the stop and the rear lens unit when the zoom lens is focused on an infinitely distant object, and fw is the shortest focal length of the entire lens system.

Abstract: In a zoom lens in which a variable power is obtained by changing the distance between a first lens group having a positive focal length and a second lens group having a negative focal length, the first lens group includes a first lens embodied by a positive meniscus lens whose convex surface faces the object, a second lens embodied by a biconcave lens, a third lens embodied by a biconvex lens and a fourth lens embodied by a biconvex lens, the lenses being arranged in the stated order when viewed from the object side, the second lens group includes a fifth lens embodied by a positive meniscus lens whose convex surface faces the image, a sixth lens embodied by a negative lens and a seventh lens embodied by a negative meniscus lens whose convex surface faces the image, the lenses being arranged in the stated order when viewed from the object side, and providing, when the first and second lens groups are in an arrangement characterized by the longest focal length, that the focal length of the whole system is f.

Abstract: A compact zoom lens has two lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in this order from an object. The second lens group is provided with a first lens made of a positive meniscus lens with a concave surface located adjacent to an object to be photographed, and a second negative lens with a concave surface adjacent to the object. The compact zoom lens satisfies the relationships defined by:(1) 1.9<f.sub.w /r.sub.1(2) 3.4<f.sub.T /f.sub.1 <4, and(3) 0.5<f.sub.T /f.sub.2-1 <1.2,wherein f.sub.w designates the focal length of the whole lens system at a wide-angle extremity, r.sub.1 the radius of curvature of the surface of the first lens, f.sub.T the focal length of the whole lens system at a telephoto extremity, f.sub.1 the focal length of the first lens group, and f.sub.2-1 the focal length of the first lens of the second lens group.

Abstract: A zoom lens system according to the present invention comprises, from the object side to the image side, a first lens unit with a positive refractive power including a negative high dispersion lens element and a positive lens element; a second lens unit with a negative refractive power consisting of two or three lens elements including a positive high dispersion lens element and a negative lens element, and having at least one aspherical surface; and a third lens unit with a positive refractive power consisting of five or less lens elements including a negative high dispersion lens element and one or two positive lens elements located on the object side of the negative high dispersion lens element, and having at least one aspherical surface. With the lens arrangement, a compact high-zoom-ratio zoom lens system having a high aberration correction performance is realized.

Abstract: A camera zoom lens consists of five lens elements arranged in two groups, in which the first three elements form a front lens group with a positive refractive power and the last two elements form a rear lens group with a negative refracting power. In the lens system, the front lens group is composed of a negative first lens element having its concave surface directed toward the object side of the lens system, a negative second lens element, and a positive third lens element; the rear lens group consists of a positive fourth lens element having its concave surface directed toward the object side of the lens system and a negative fifth lens element having its concave surface directed toward the object side of the lens system. The zoom lens system is suitable for use in a 35 mm lens shutter camera.

Abstract: A low-cost, high-performance two-unit zoom lens system for use with a compact camera, which has a zoom ratio of about 2 to 2.5. The zoom lens system has a 1-st lens unit (G1) of positive power, and a 2-nd lens unit (G2) of negative power. The 1-st lens unit (G1) is composed of a plastic lens (L1) of extremely small power having an aspherical surface, and a positive lens group consisting of lens elements (L2) and (L3). The 2-nd lens unit (G2) is composed of a positive lens (L4), and a negative lens (L5) having an aspherical surface.

Abstract: A zoom lens system including, in order from the object side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power, in which zooming is effective by varying the spacing between the first lens unit and the second lens unit. The first lens unit has, in order from the object side, a negative meniscus lens element having a convex surface directed toward the object side, a negative lens element and a positive lens element. The second lens unit has, in order from the object side, a positive lens element having a convex surface directed toward the object side, a positive lens element, a cemented negative lens element composed of a positive lens element and a negative lens element, which are cemented together and a positive lens element. The first and second lens units and the elements thereof are positioned and arranged in prescribed relative positions.

Abstract: A zoom lens has a first group of a positive refractive power and a second group of a negative refractive power in sequence as seen from an object. The first group of the positive refractive power comprises a front group of a positive refractive power arranged to face the object and in front of an aperture iris and a rear group of a positive refractive power arranged between the aperture iris and an image plane. The rear group includes displacement means to drive it across an optical axis for vibration correction.

Abstract: A wide angle zoom lens system. A first lens group has a positive refractive power, while a second lens group has a negative refractive power. The distance between the first lens group and the second lens group is changed during zooming. The first lens group includes a front group having a negative refractive power and a rear group having a positive refractive power. The front group includes a meniscus lens which is concave toward the object and has a negative refractive power, and the rear group includes at least four lenses which have positive or negative refractive powers, wherein 4.5<.vertline.f.sub.F /f.sub.W .vertline.<13; 0.005<.vertline.K/f.sub.F .vertline.<0.07; and 20<.vertline.(f.sub.bW .multidot.f.sub.F)/f.sub.W .vertline.<100 where f.sub.F is the focal length of the front group of the first lens group, f.sub.

Abstract: A zoom lens having two groups of lens components including from the object side a positive group and a negative group. The positive group includes two lens units, a weak unit, and a positive unit, while the negative group has at least one negative lens component and provides most of the magnification change during zooming.

Abstract: A variable focal length optical system comprises, in the following order from the object side, a first lens group having positive refractive power, the first lens group including, in succession from the object side, a first lens component having positive refractive power, a second lens component comprising a cemented lens consisting of a negative lens component and a positive lens component, and a third lens component having positive refractive power, and a second lens group having negative refractive power, the second lens group including, in succession from the object side, a fourth lens component having positive refractive power, and a fifth lens component having negative refractive power. The variable focal length optical system satisfies the following condition:-0.19<(r23-r32)/(r23+r32)<-0.

Abstract: A zoom camera lens for an inexpensive camera, for example, a single use camera, has two plastic elements including a positive element and a negative element and a stop. Each of the surfaces of each of the elements is concave to the stop. Preferably, the lens has a curved image plane.

Abstract: A zoom lens system for use with compact cameras which is compact and yet effectively corrects chromatic aberrations, includes, in order from the object side, a first lens group having a positive focal length and a second lens group having a negative focal length, the inter-group distance being varied to perform zooming. The first lens group includes, in order from the object side, a first subgroup having a small power and a second subgroup having a large positive power. At least one of the subgroups is a cemented lens having a divergent surface, with an aspheric surface being provided in the first subgroup. The first lens group satisfies the following conditions-0.7<fS/fla<0.31.2<fS/flb<2.3-1.7<fS/fc<0where:fS=the overall focal length at wide angle,fla=the focal length of the first subgroup,flb=the focal length of the second subgroup.

Abstract: The invention provides a two-unit or positive-negative type of zoom lens that has a zoom range of the order of 38-70 mm, comprises six lens groups or six lenses, and makes use of an aspherical plastic lens for cost reduction and for improving its performance as well. This zoom lens system is constructed from a first unit I of positive power and a second unit II of negative power and is designed to be variable in the air space between both the units for zooming. The first unit I includes a positive meniscus lens L1 convex on the object side, a negative lens L2, a positive lens L3 and a lens L4, and the second unit II includes a positive meniscus lens L5 convex on the image side and a negative meniscus lens L6 convex on the image side. At least L5 consists of a plastic lens having an aspherical surface.

Abstract: A zoom lens system for use with a compact camera comprises, in order from the object side, a first lens group having a positive focal length and a second lens group having a negative focal length and which performs zooming by changing the distance between the first and second lens groups. The first lens group comprises, in order from the object side, a subgroup 1a of a small power that is composed of a positive first lens and a negative second lens and a subgroup 1b of a large positive power that has a cemented surface of a negative power on the image side. The subgroup 1a has at least one aspheric surface that has a divergent amount of asphericity with respect to a paraxial radius of curvature.

Abstract: A zoom lens suitable for an inexpensive camera has a front positive lens group and a rear negative lens group. Both groups move for zooming with the rear negative group providing most of the variation in focal length. The front positive group includes a front negative component and a rear positive component while the rear negative group includes a rear negative component and a weak plastic element having at least one aspheric surface. The plastic element is sufficiently weak that it does not cause variation in focus with normal variations in temperature and relative humidity. All other elements in the zoom lens are glass.

Abstract: A varifocal lens system consists of first and second lens groups arranged in this order from the image forming side. The first lens group consists of four lenses and has a negative refracting power and the second lens group consists of three lenses and has a positive refracting power. The varifocal lens system satisfies the following conditions wherein R.sub.i represents the radius of curvature of the i-th lens surface as consecutively numbered from the image forming side, d.sub.i represents the axial surface separation between the i-th lens surface and the (i+1)-th lens surface as consecutively numbered from the image forming side, .upsilon..sub.i represents the Abbe's number of the i-th lens as consecutively numbered from the image forming side, and .sub.II D represents the thickness of the second lens group:44<(.upsilon..sub.1 +.upsilon..sub.2)/2 (1)(.upsilon..sub.3 +.upsilon..sub.4)/2<50 (2)0.4<d.sub.9 /.sub.II D<0.6 (3)1.0<.vertline.R.sub.3 /R.sub.4 .vertline.<2.

Abstract: A compact zoom lens constituted of, from an object side, a first lens group having a positive refractive power and a second lens group having a negative refractive power, in which image magnification is varied by adjusting the distance between the two lens groups. The first lens group is composed of a front lens component having a negative refractive power including at least one aspherical surface and a rear lens component having a positive refractive power. The front lens component is composed of the first negative lens and the second meniscus lens. The convex surface of the meniscus lens is directed to the image side. The following inequality is satisfied: .upsilon.n<35 where .upsilon.n is the Abbe's number of the lens which has a stronger negative refractive power of the two lenses in the front component of the first lens group.

Abstract: A zoom lens system consists of five lens elements arranged in two groups. Counting from the object side, the first three elements form a front lens group with positive refracting power and the last two elements form a rear lens group with negative refracting power. An airspace is reserved between the front lens group and the rear lens group and it is made variable for zooming. The first lens element in the front lens group is a negative meniscus lens element having its concave lens surface directed toward the object side. Both the second and third lenses in the front lens group are positive lens element. The fourth lens in the rear lens group is positive meniscus lens element, and the fifth lens is a lens element with negative refracting power. In the lens composition, both the front lens group and the rear lens group at least include an aspherical surface respectively.

Abstract: A zoom lens is constructed by two lens groups in which a first lens group having a positive focal length is arranged on an object side and a second lens group having a negative focal length is arranged on an image side. A zooming operation is performed by changing a distance between the first and second lens groups. The first lens group has first to fourth lenses sequentially arranged from the object side toward the image side. The first lens is constructed by a positive meniscus lens having a convex face directed onto the object side. The second lens is constructed by a biconcave lens. The third lens is constructed by a positive lens. The fourth lens is constructed by a biconvex lens. The second lens group has fifth to seventh lenses sequentially arranged from the object side toward the image side. The fifth lens is constructed by a positive meniscus lens having a convex face directed onto the image side.

Abstract: The invention provides a zoom lens which comprises a first lens group G1 of positive refracting power and a second lens group G2 of negative refracting power, said first lens group comprising, in order from the object side, a first lens L.sub.1 formed of plastics having not substantially refracting power, a second lens L.sub.2 of negative refracting power and a third lens L.sub.3 of positive refracting power. This zoom lens, albeit using a plastic lens, is less likely to undergo a variation in the focal position due to temperature and humidity changes, inexpensive, compact and of good performance.

Abstract: A zoom lens system consists of a forward lens groups of a positive power comprising first to fourth lens groups and a rearward lens group of a negative power comprising fifth to seventh lens groups, and satisfies the following conditions:1.40<f.sub.w /f.sub.F <2.0Np<Nn-0.45<f.sub.67 /f.sub.w <-0.10.5<f.sub.6 /f.sub.7 <0.8-3<(f.sub.12 .times.f.sub.34)/f.sub.F.sup.2 <0.5wherein f.sub.w is the focal length of the zoom lens system in the wide-angle mode, f.sub.F is the focal length of the forward lens groups, Np is the refractive index of a convex lens of the third lens group, Nn is the refractive index of a concave lens of the third lens group, f.sub.67 is the resultant focal length of the sixth and seventh lens groups, f.sub.6 is the focal length of the sixth lens group, f.sub.7 is the focal length of the seventh lens group, f.sub.12 is the resultant focal length of the first and second lens groups, and f.sub.34 is the resultant focal length of the third and fourth lens groups.

Abstract: The invention provides an ultra-wide zoom lens system that has a very wide angle coverage, as indicated by a field angle change of about 92.degree. to about 65.degree., is bright, as indicated by an F-number of 4.5 at the telephoto end, and is relatively simple in lens unit construction, and consists of, in order from the object side, a first lens unit I of negative refracting power, a second lens unit II of positive refracting power and a third lens unit III of negative refracting power, all said lens units being moved toward the object side for wide angle to telephoto zooming. The zoom lens system then conforms to Conditional Formulae (1), (2) and (3):-6.5<f.sub.1 /f.sup.T <-1.5 (1)0.4<f.sub.2 /f.sup.T <1.0 (2)0.8<e.sub.1.sup.W /e.sub.1.sup.T <1.2 (3)where f.sub.1 and f.sub.2 are the focal lengths of the first and second lens units, respectively, f.sup.T is the focal length of the overall lens system at the telephoto end, and e.sub.1.sup.W and e.sub.1.sup.

Abstract: A zoom lens system consisting of three groups, wherein intervals between the groups are varied to thereby change a focal length. In this zoom lens system, the number of lenses constituting the groups is one, respectively. That is, a first group is constituted by a convex meniscus lens 11, a second group is constituted by a negative meniscus lens 12 directing a strong positive surface thereof toward an object and a third group is constituted by a negative meniscus lens 13 directing a strong convex surface thereof toward the object, whereby the number of the constituting lenses can be minimized to be three, and, because of the zoom lens system consisting of the three groups, the movement of the lens is scattered, so that the movement value of the lens for obtaining a desirable zooming ratio can be decreased.

Abstract: A wide-angle zoom lens has a first lens group having a positive refracting power and a second lens group having a negative refracting power, which are moved relative to each other along the optical axis so as to attain zooming. The first lens group is constituted in turn from the object side by a front group having a negative refracting power and a rear group having a positive refracting power. The front group has at least one negative lens. The rear group has at least two positive lenses. The zoom lens is constituted to satisfy the following conditions:0.75<.vertline.f.sub.F /f.sub.W .vertline.<4, f.sub.F <00.1<K/f.sub.W <0.40.1<L/f.sub.W <0.7wherein f.sub.F is the focal length of the front group in the first lens group, f.sub.

Abstract: A zoom lens system having a zoom ratio of approximately 2 that is used with a compact camera. The system's overall lens length at the telephoto end is shorter than its focal length at the telephoto end, and it experiences small variations in aberrations during zooming. The present zoom lens system comprises, in order from the object side, a positive first lens group and a negative second lens group, which adjust the magnification by varying the distance therebetween. This lens system satisfies the following conditions:1.59<fw/f1<2.0 (1) and1.79<fw/f2<2.5 (2);where fw represent the focal length of the overall system at the wide-angle end; f1 represents the focal length of the first lens group and f2 represents the focal length of the second lens group (f2<0).

Abstract: A zoom lens system consists of five lens elements arranged in two groups, in which the first three elements form a front lens group with positive refracting power and the last two elements form a rear lens group with negative refracting power. In the lens system of the present invention, the front lens group is composed of a positive first lens element, a negative second lens element, and a positive third lens element; the rear lens group consists of a positive fourth lens element and a negative fifth negative lens element. The airspace between the front lens group and the rear lens group is variable for zooming operation. Both the front lens group and rear lens group comprise at least an aspheric lens elements.

Abstract: A new compact-size, light-weight and low-cost zoom lens system having a high optical quality with a very simple structure including, from the object side to the image side, a front lens group having a positive refractive power and a rear lens group having a negative refractive power. The zoom lens system is operated by changing the axial air distance between the front and rear lens groups during a zooming operation. The zoom lens system uses aspherical surfaces whose low-cost manufacturing has been enabled by the recent progresses in plastic molding technology and glass molding technology. Many embodiments of the lens compositions according to the present invention, and further more specific examples of the embodiments are described with figures and data that show compactness and high optical performance.

Abstract: An optical system comprising a plural number of lens elements at least one of which is designed as a graded refractive index lens element having refractive index distribution in the radial direction, and has aberrations favorably corrected in said optical system as a whole by making most of the correcting functions of the graded refractive index lens element for Petzval's sum and chromatic aberration.

Abstract: A zoom lens system for use with a compact camera comprises, in order from the object side, a first lens group having a positive focal length and a second lens group having a negative focal length and which performs zooming by changing the distance between the first and second lens groups. The first lens group comprises, in order from the object side, a subgroup 1a of a small power that is composed of a positive first lens and a negative second lens and a subgroup 1b of a large positive power that has a cemented surface of a negative power on the image side. The subgroup 1a has at least one aspheric surface that has a divergent amount of asphericity with respect to a paraxial radius of curvature.

Abstract: A zoom lens system consists of four lens elements arranged in two groups. Counting from the object side, the first two elements form a front lens group with positive refracting power and the last two elements form a rear lens group with negative refracting power. An airspace is reserved between the front lens group and the rear lens group and it is made variable for zooming. The first lens element in the front lens group is a negative lens element and has its concave lens surface directed toward the object side. Both the two lens elements in the rear lens group are negative lens element. In the lens composition, both the front lens group and the rear lens group at least include an aspherical lens surface respectively for aberration correction.

Abstract: A zoom lens system includes, in order from the object side, the first lens group having a positive focal length and the second lens group having a negative focal length. The system performs zooming by changing the distance between the first and second lens groups. The first lens group has a negative lens element on the side closest to the object that has a concave surface of large curvature directed towards the image plane and the first lens group satisfies the specific conditions.

Abstract: A zoom lens system for a compact camera, having a zoom ratio of approximately 2 or 3 and a smaller overall lens length at the telephoto end than the focal distance at the telephoto end, and which optically experiences only a small focus shift due to environmental changes such as temperature or humidity. The zoom lens system includes a positive lens group and a negative lens group. A positive plastic lens element is disposed in either the positive lens group or the negative lens group. The magnification of the system is adjusted by varying the distance between the positive and negative lens groups. The zoom lens system satisfies the following conditions:0.9<f.sub.t /f.sub.p <1.6 (1)0.6<m.sub.p '-m.sub.p <1.2 (2)2.9<m.sub.MAX <4.0 (3)where f.sub.t is the focal length of the overall system at the telephoto end, f.sub.p is the focal length of the positive plastic lens element, m.sub.

Abstract: A zoom lens system including a first lens unit of positive power and a second lens unit of negative power with the axial separation therebetween varies to bring about zooming. The first lens unit includes at least one positive lens element and at least one negative lens element and the second lens unit consists of a biconcave negative lens element having a strong curvature towards the front.

Abstract: A zoom lens having two units of lens components including from the object side a positive optical unit and a negative optical unit. The positive optical unit includes two lens subunits, a weak power subunit, and a positive power subunit, while the negative optical unit consists of a negative lens component and provides most of the magnification change during zooming.

Abstract: A lens system comprising a positive power lens assembly and a negative power lens assembly, in which the positive power lens assembly includes a cemented doublet and a two-surface aspheric lens. The present invention discloses a zoom lens with a 2.57.times.zoom ratio.

Abstract: A zoom lens is disclosed comprising a front lens group having a positive lens unit, a negative lens unit and a positive lens unit and whose overall refractive power is positive, and a rear lens group having a positive lens unit and a negative lens unit and whose overall refractive power is negative, wherein zooming is performed by varying all the lens separations between the successive two of the lens units and focusing is performed by varying at least the lens separation between the positive lens unit and the negative lens unit of the rear lens group.

Abstract: A zoom lens comprises a first lens group having the positive refractivity which relatively travels along the optical axis to change the distance between the groups for varying powers, and a second lens group having negative refractivity. The first lens group has sequentially from an object side a first positive lens component, a second negative lens component, a third lens component having positive refractivity, a fourth positive lens component, and fifth lens component having positive refractivity, and the second lens group has sequentially from the object side a sixth positive lens component, a seventh negative lens component, and an eighth negative lens component. Further, the first lens group includes a diaphragm adjacent to the fifth lens component, and the zoom lens is characterized in being structured to satisfy conditions given below.78<f.sub.1 .multidot.Z<90-1.60<f.sub.L2a /D.sub.S <-1.10wheref.sub.1 : The focal length of the first lens group.Z: Zooming ratio.f.sub.

Abstract: A compact zoom lens, which can attain a compact lens system while maintaining a simple lens arrangement including six lenses, and can minimize deterioration of performance caused by a variation upon assembling, is disclosed. The compact zoom lens includes a positive first lens group G.sub.1 and a negative second lens group G.sub.2. The first lens group G.sub.1 has, in turn from the object side, a positive meniscus lens component L.sub.1 with the convex surface facing the object side, a meniscus-shape junction negative lens component L.sub.2 constituted by a double-concave negative lens component L.sub.2n and a double-convex positive lens component L.sub.2p, and a double-convex positive lens component L.sub.3. The second lens group G.sub.2 has, in turn from the object side, a positive meniscus lens component L.sub.4 with the convex surface facing the image side, and a negative meniscus lens component L.sub.