Abstract: A zoom lens includes, sequentially from an object side, a first lens group that is negative; and a second lens group that is positive, where focal length is varied by varying a distance between the first lens group and the second lens group. The first lens group includes, from the object side, a first lens that is a negative biconcave lens having at least one aspherical surface, and a second lens that is a positive meniscus lens having a convex surface facing toward the object side and at least one aspherical surface, and a first condition 0.8<|f1/f2|<1.0 and a second condition 0.5<|r2/f1|<0.8 are satisfied, where f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, r2 is radius of curvature of a surface of the first lens in the first lens group, the surface facing toward an image.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein: the first lens unit comprises a first lens element having a concave surface at least on the image side and negative power and a second lens element having a convex surface at least on the object side and positive power; the second lens unit comprises a cemented lens element fabricated by two lens elements having optical power of mutually different signs and one single lens element; in zooming, all of the lens units move along an optical axis; and conditions (1): 5.0<?iW<20.0 and (I-2): n11?1.9 (where, 3.

Abstract: An zoom optical system comprises a prism component which comprises in order from an object side, an entrance surface having negative refracting power, and a reflecting surface, and movable groups which are movable when either of zooming or focusing is carried out. An image pickup apparatus is provided with the zoom optical system. Thereby, thinning of the image pickup apparatus can be attained sufficiently, and it is possible to shorten the full length of the optical system furthermore, while keeping a moderate zooming ratio.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in this order from the object. Upon zooming from the short focal length extremity to the long focal length extremity, the distance between the negative first lens group and the positive second lens group decreases, and the distance between the positive second lens group and the positive third lens group increases. The negative first lens group includes a negative first lens element, a negative second lens element having a weaker negative refractive power, and a positive third lens element, in this order from the object. The second lens element of the negative first lens group satisfies the following condition: 0<(ra?rb)/(ra+rb)<0.

Abstract: A zoom lens including a first lens group with a negative refractive power and a second lens group with a positive refractive power is provided. The first lens group is composed of a first lens, a second lens, and a third lens. Refractive powers of the first lens, the second lens, and the third lens are respectively negative, negative, and positive. Moreover, the second lens group is disposed between the first lens group and an image side. The second lens group is composed of a fourth lens, a fifth lens, and a sixth lens. Refractive powers of the fourth lens, the fifth lens, and the sixth lens are respectively positive, negative, and positive. The first lens group and the second lens group are capable of moving between an object side and the image side. The zoom lens has advantages of wide angle and small volume.

Abstract: A zoom lens and an image pickup apparatus having such a zoom lens are provided. The zoom lens includes a first lens group in which each lens has negative refractive power, a second lens group in which each lens has positive refractive power, a third lens group in which each lens has positive refractive power. These lens groups are arranged in this order from an object side to an image side. The first lens group includes a negative lens and a positive lens which are arranged in this order from an image side to an object side. The third lens group includes a positive lens. Both surfaces of the negative lens of the first lens group are aspherical surfaces, respectively. Both surfaces of the positive surfaces of the third lens group are aspherical surfaces, respectively.

Abstract: A projection zoom lens includes in order from an enlargement side: a first lens group with negative power; a second lens group with positive power; a third lens group with positive power; a fourth lens group with positive power; and a fifth lens group with positive power, wherein the first and fifth lens groups are fixed and the second, third, and fourth lens groups move when zooming from a wide angle side to a telescopic side, the second lens group includes only a positive lens which is convex toward the enlargement side, and assuming that the focal length at a wide angle end of a whole system including the first to fifth lens groups is F and the focal length of the second lens group is F2, the following conditional expression (1) is satisfied: 0.05<F/F2<0.23??(1).

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in this order from the object. Upon zooming from the short focal length extremity to the long focal length extremity, the distance between the negative first lens group and the positive second lens group decreases, and the distance between the positive second lens group and the positive third lens group increases. The negative first lens group includes a negative first lens element, a positive or negative lens element having a weaker refractive power, and a positive third lens element, in this order from the object. The zoom lens system satisfied the following condition: ?0.25<f1/fp<0.25(f1<0)??(1) wherein f1 designates the focal length of the negative first lens group; and fp designates the focal length of the positive second lens element.

Abstract: A wide angle zoom lens, includes, from an object side in the following order: a first lens group that has a negative refractive power; a second lens group that has a positive refractive power; and a third lens group. When variable magnification is carried out from a wide angle end to a telephoto end, the first and second lens groups move while the third lens group remains fixed, so that an air space between the first lens group and the second lens group becomes narrow and that a space between the second lens group and the third lens group becomes wide. The first and second lens groups each include at least one positive lens and one negative lens. The third lens group includes one positive or negative meniscus lens whose convex surface faces an image surface. The following conditional expressions (1) and (2) are satisfied: 1.4?|f1|/fw?1.8??(1); and 1.7?f2/fw?2.

Abstract: A zoom lens includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a rear unit including one or more lens units, which are arranged in order from the object side to the image side. The zoom lens performs zooming by changing distances between the first, second, and rear lens units. A first focusing unit and a second focusing unit which move independently of each other during focusing are provided. The first and second focusing units are adequately set.

Abstract: A zoom lens ZL installed in an electronic still camera 1 includes, in order from an object side, a first lens group G1 having negative refractive power, and a second lens group G2 having positive refractive power. A distance between the first lens group G1 and the second lens group G2 varies upon zooming from a wide-angle end state to a telephoto end state. The second lens group G2 has a front lens group G2F and a rear lens group G2R, and the front lens group G2F is moved along the optical axis upon focusing on a close object, thereby providing a compact zoom lens having excellent optical performance, an optical apparatus equipped with the zoom lens, and a method for manufacturing the zoom lens.

Abstract: A zoom optical system that comprising: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power which are arranged in order from an object side, a space between the lens units being changed to perform variation of magnification, the first lens unit includes a negative lens, the second lens unit includes a positive lens and a negative lens in order from the object side, the third lens unit includes a positive lens, and an electronic equipment provided with the zoom optical system.

Abstract: There is provided a zoom optical system having lens elements produced with less difficulty i.e. with substantially the same skill level as the conventional arrangement, with sufficient miniaturization. The zoom optical system includes a first lens group having a negative optical power, and a second lens group having a positive optical power in the order from the object side, the distance between the first lens group and the second lens group being decreased in zooming from a wide angle end to a telephoto end. The first lens group is constituted of a negative lens element and a positive meniscus lens element. The second lens group is constituted of a biconvex positive lens element and a negative meniscus lens element.

Abstract: On condition that a first lens group adopts at least one plastic lens; a second lens group adopts at least any two adjacent plastic lenses; the first lens group monotonously moves from an object side to an image plane side in a zooming; the second lens group monotonously moves from the image plane side to the object side; wherein fw/fpi represents a ratio of refractive power of the entire system achieved at a wide angle end to refractive power of the respective lenses; P1 represents a total of fw/fpi of the plastic lenses of the first lens group; and P2 represents a total of fw/fpi of the plastic lenses of the second lens group, conditional expressions (1) and (2) provided below are fulfilled. ?0.22<P1<?0.01??(1) ?0.15<P2<?0.

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

Abstract: An observation optical system has a negative lens unit including a cemented lens, arranged at the most object-side position; an annular reflecting mirror placed on the image side of the negative lens unit, with a reflecting surface facing the image side; and an imaging lens unit arranged on the image side of the negative lens unit and the annular reflecting mirror.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein: the first lens unit comprises a first lens element having a concave surface at least on the image side and negative power and a second lens element having a convex surface at least on the object side and positive power; the second lens unit comprises a cemented lens element fabricated by two lens elements having optical power of mutually different signs and one single lens element; in zooming, all of the lens units move along an optical axis; and conditions (1): 5.0<?iW<20.0 and (I-2): n11?1.9 (where, 3.

Abstract: A zoom lens includes, in order from an object side, a first lens group having a negative power, a second lens group having a positive power, and a third lens group having a positive power. At least the first and second lens groups are movable during a change from a wide-angle end state in which a focal length becomes shortest to a telephoto end state in which the focal length becomes longest. The first lens group is constructed of a glass lens and a plastic lens, the glass lens being positioned on the object side and having a negative power, the plastic lens being positioned on an image side and having a positive power. The second lens group includes a single plastic lens having a negative power. The third lens group includes at least one plastic lens having a positive power. The lenses are satisfied predetermined conditions.

Abstract: Provided is a zoom lens in which both higher-order components of distortion and lateral chromatic aberration are corrected in a retrofocus type optical system. The zoom lens includes, in order from a magnifying side, a first lens unit which is negative, a second lens unit which is positive, and a rear lens group which is positive. A solid material having high dispersion and high extraordinary dispersion is used for a negative lens included in the first lens unit to provide a suitable shape and refractive power.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, the second lens unit including a positive lens, and a third lens unit having a positive refractive power. In the zoom lens, intervals between adjacent ones of the first lens unit, the second lens unit, and the third lens unit are variable during zooming. In the zoom lens, a refractive power of a material of the positive lens included in the second lens unit (Nd2P) and an Abbe number of the material of the positive lens included in the second lens unit (?d2P) satisfy the following conditions: Nd2P+0.01×?d2P>2.3 1.65<Nd2P<2.7 ?d2P>45.

Abstract: In order from a magnification side of the projection zoom lens system, five lens groups are arranged. The fourth lens group includes, in order from the magnification side, a negative lens having at least one aspheric surface, a positive lens, a negative lens concave toward the magnification side, a positive lens convex toward the reduction side, and a positive lens. The fifth lens group is formed of one lens, and is configured so that a ratio of a focal length of the fifth lens group to a focal length of the whole system at a wide-angle end is within a numerical range of 3 to 8.

Abstract: A wide angle zoom lens system in a three lens group N-P-P configuration wherein the first lens group, the second lens group, and the third lens group are arranged in an order from an object side to an image side, and wherein, when variable power operation is performed from a wide angle to a telephoto position, the distance between the first lens group and the second lens group is reduced, and the second lens group is moved toward the object side, and the distance between the second lens group and the third lens group is increased, and wherein the zoom lens has a large view angle at the wide angle position.

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

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

Abstract: A rear focus wide-angle lens system includes a first lens group, a diaphragm, and a second lens group, in this order from the object; the second lens group is moved along the optical axis thereof when focusing is performed from infinity to an object at a closer distance; and, the rear focus wide-angle lens system satisfies the following condition: 1.5<F1/F2<3.0??(1) wherein F1 designates the focal length of the first lens group; and F2 designates the focal length of the second lens group.

Abstract: A projection zoom lens includes a first lens group having a negative reflecting power and a second to fifth lens groups each having a positive reflecting power are provided in the order from the magnification side. Nine lenses are distributed in a manner that the first lens group has one lens, the second lens group has one lens, the third lens group has two lenses, the fourth lens group has four lenses and the fifth lens group has one lens. Since the second lens group, the third lens group and the fourth lens group are moved at the time of the power-varying operation, various kinds of aberrations may be made despite of simple configuration. The first lens group is an aspherical lens which concave surface is directed to the reduction side.

Abstract: The zoom lens system is used for forming an optical image of an object with a variable magnification, and, in order from the object side, comprises a first lens unit G1 of negative optical power, a second lens unit G2 of positive optical power and a third lens unit G3 of positive optical power. The lens units move respectively along the optical axis so that a magnification is changed with changing a distance between the respective lens units. The second lens unit G2 comprises at least three lens elements including an object side lens element of the second lens unit which is a positive lens element arranged on the most object side with the surface of strong curvature facing the object side, and an image side lens element of the second lens unit which is a positive lens element arranged on the most image side with the convex surface facing the object side.

Abstract: A zoom lens includes a first negative lens group, a second negative lens group, a third positive lens group, an aperture diaphragm, and a fourth positive lens group arranged in this order from an object side. When power varies from a wide angle end to a telephoto end, the first and second lens groups are moved to an image surface along an optical axis and then moved to the object side. The third and fourth lens groups are moved to only the object side along the optical axis. The first lens group includes at least one aspheric lens, and the aspheric lens has an aspheric shape in which a positive refractive power is increased toward the periphery of the lens when a paraxial refractive power is positive and a negative refractive power is decreased toward the periphery of the lens when the paraxial refractive power is negative.

Abstract: An zoom optical system comprises a prism component which comprises in order from an object side, an entrance surface having negative refracting power, and a reflecting surface, and movable groups which are movable when either of zooming or focusing is carried out. An image pickup apparatus is provided with the zoom optical system. Thereby, thinning of the image pickup apparatus can be attained sufficiently, and it is possible to shorten the full length of the optical system furthermore, while keeping a moderate zooming ratio.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein in zooming from a wide-angle limit to a telephoto limit, the lens units move respectively along an optical axis in such a manner that an interval between the first lens unit and the second lens unit decreases while an interval between the second lens unit and the third lens unit changes so that variable magnification is achieved, the first lens unit comprises one object side negative lens element and one image side positive lens element with a convex surface facing the object side, which have an aspheric surface, and the conditions: n12>1.88 and ?12<26 (n12 and ?12 are refractive index and Abbe number, respectively, of the image side positive lens element of the first lens unit) are satisfied.

Abstract: A zoom lens system comprising, in order from an object along an optical axis: 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 following conditional expression being satisfied: 0.6<Ymax×ft/f12<1.0 where Ymax denotes the maximum image height of the zoom lens system, ft denotes a focal length of the zoom lens system in a telephoto end state, and f1 denotes a focal length of the first lens group.

Abstract: An optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power. In the optical system, an aperture stop is located closer to the reduction conjugate side than the first lens unit, one or more positive lenses are located closer to the reduction conjugate side than the aperture stop, and the one or more positive lenses include a P-th positive lens located closest to the reduction conjugate side.

Abstract: A variable-power optical system includes, in order from an object side thereof: a first lens group with a negative optical power; a second lens group with a positive optical power; and a third lens group with a negative optical power, where an interval between the first lens group and the second lens group decreases when a power of the variable-power optical system varies from a wide-angle end to a telephoto end. The first lens group comprises a negative lens and a positive lens. The second lens group consists of a positive lens and a negative lens, and includes at least one aspheric surface. The variable-power optical system satisfies the predetermined conditional expressions.

Abstract: A zoom lens suitable for imaging an object on a photosensitive device is provided. The zoom lens includes a first lens group, a second lens group, a third lens group and a fourth lens group, which are arranged in series. The fourth lens group is disposed near the photosensitive device. The second lens group and the third lens group are suitable for moving between the first lens group and the fourth lens group. The first lens group, the second lens group, the third lens group and the fourth lens group include at least a glass lens and a plurality of plastic lenses. The number of the plastic lenses is more than the number of glass lenses. Thus, overall cost of producing the zoom lens is lower.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein: the first lens unit comprises a first lens element having a concave surface at least on the image side and negative power and a second lens element having a convex surface at least on the object side and positive power; the second lens unit comprises a first cemented lens element of two lens elements having power of mutually different signs and a second cemented lens element of two lens elements having power of mutually different signs; in zooming, all of the lens units move along an optical axis; and conditions (1): 5.0<?iW<20.0 and (I-2): n11?1.9 (where, 3.

Abstract: A three-unit zoom lens includes, in order from the object side, a negative first lens unit G1, a positive second lens unit G2 and a third lens unit G3, wherein during zooming from the wide angle end to the telephoto end the distance between the first lens unit G1 and the second lens unit G2 decreases and the distance between the second lens unit G2 and the third lens unit G3 changes. The first lens unit G1 is composed of one negative lens component including, in order from the object side, a negative lens having a concave surface directed toward the image side and a positive lens having a convex surface directed toward the object side. The second lens unit G2 includes at least one negative lens and a plurality of positive lenses, wherein at least three lenses among these lenses are cemented to adjacent lenses, the total number of lens components included in the second lens unit G2 is two or less. The third lens unit is composed of one lens component composed of two or less lenses.

Abstract: A zoom lens comprises a first lens unit that does not move for zooming and that has a positive refractive power, a second lens unit that is configure to move to an image side during zooming from a wide angle end to a telephoto end and that has a negative refractive power, a third lens unit that is configured to reduce image plane variation due to zooming, and a fourth lens unit that does not move for zooming. The fourth lens unit comprises a fourth-F unit, a fourth-B1 unit, and a fourth-B2 unit. The average Abbe number of positive lens and negative lenses in the fourth-B1 unit and the average Abbe number of positive negative lenses in the fourth-B2 unit are set appropriately.

Abstract: A zoom optical system comprising, in order from an object side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, a space between the lens units being changed to thereby perform zooming and focusing, wherein the first lens unit is constituted of a negative lens.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein in zooming from a wide-angle limit to a telephoto limit, the lens units move respectively along an optical axis in such a manner that an interval between the first lens unit and the second lens unit decreases while an interval between the second lens unit and the third lens unit changes so that variable magnification is achieved, the first lens unit comprises one object side negative lens element and one image side positive lens element with a convex surface facing the object side, which have an aspheric surface, and the conditions: n12>1.88 and ?12<26 (n12 and ?12 are refractive index and Abbe number, respectively, of the image side positive lens element of the first lens unit) are satisfied.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein in zooming from a wide-angle limit to a telephoto limit, the lens units move respectively along an optical axis in such a manner that an interval between the first lens unit and the second lens unit decreases while an interval between the second lens unit and the third lens unit changes so that variable magnification is achieved, the first lens unit comprises one object side negative lens element and one image side positive lens element with a convex surface facing the object side, which have an aspheric surface, and the conditions: n 12>1.88 and ? 12<26 (n12 and ?12 are refractive index and Abbe number, respectively, of the image side positive lens element of the first lens unit) are satisfied.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein in zooming from a wide-angle limit to a telephoto limit, the lens units move respectively along an optical axis in such a manner that an interval between the first lens unit and the second lens unit decreases while an interval between the second lens unit and the third lens unit changes so that variable magnification is achieved, the first lens unit comprises one object side negative lens element and one image side positive lens element with a convex surface facing the object side, which have an aspheric surface, and the conditions: n12>1.88 and ?12<26 (n12 and ?12 are refractive index and Abbe number, respectively, of the image side positive lens element of the first lens unit) are satisfied.

Abstract: A zoom lens includes a first lens group having negative refractive power and a second lens group having positive refractive power, each including at least one plastic aspherical lens. The zoom lens satisfies the following Conditional Expressions (1) and (2), 0.40<fw/bkw<0.60 (1) 0.01<|(X1?X0)/h0|<0.022 (2) where, fw: focal length of the entire zoom lens in focus at infinity in a wide-angle end state; bkw: back focus when the entire zoom lens is in focus at infinity in the wide-angle end state; X1: thickness at an image-side effective diameter position of the plastic aspherical lens of the first lens group; X0: thickness at the center of the plastic aspherical lens of the first lens group; and h0: image-side effective radius of the plastic aspherical lens of the first lens group.

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

Abstract: An exemplary zoom lens comprises, in order from an object side of the zoom lens, a first lens module having a negative refractive power, a second lens module having a positive refractive power and a third lens module having a positive refractive power. When the zoom lens is adjusted from wide-angle to telephoto, the first lens module remain fixed in place, the second group is moved toward the object side thereof along an optical axis so as to perform the zooming, while the third group is moved along the optical axis so as to compensate for any fluctuation of in position of an image on the image plane caused by the movement of the second lens module.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens group of negative refracting power, a second lens group of positive refracting power and a third lens group of positive refracting power, wherein the first and second lens groups are configured to move during a zooming operation, and wherein a focal length of the whole system at a wide-angle end, a focal length of the whole system at a telephoto end, focal lengths of the first, second, and third lens groups, the lateral magnification of the second lens group at the wide-angle end, and the lateral magnification of the second lens group at the telephoto end are appropriately set to assure a zoom lens which is small in the lens whole system size and which provides good optical performance throughout the whole zoom range.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein: the first lens unit comprises a first lens element having a concave surface at least on the image side and negative power and a second lens element having a convex surface at least on the object side and positive power; the second lens unit comprises a first cemented lens element of two lens elements having power of mutually different signs and a second cemented lens element of two lens elements having power of mutually different signs; in zooming, all of the lens units move along an optical axis; and conditions (1): 5.0<?iW<20.0 and (I-2): n11?1.9 (where, 3.

Abstract: A three-unit zoom lens system includes in order from an object side thereof, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, and a third lens unit having a refracting power. The first lens unit includes a biconcave negative lens component nearest to the object side, and the biconcave negative lens component is the only negative lens component in the first lens unit. The second lens unit includes a cemented lens component which includes in order from the object side thereof, at least three lenses cemented mutually on an optical axis, namely a first positive lens, a negative lens, and a second positive lens. A surface on the image side of the negative lens is a concave surface, and the negative lens has an Abbe's number smaller than the Abbe's number for the first positive lens and the second positive lens, and has a refractive index higher than a refractive index of the second positive lens.

Abstract: A zoom lens system is provided that can be used as an optical system for an image pick-up device, which can have improved shading characteristics using multiple lens units, for example three lens units.

Abstract: A zoom lens system includes, in order from an object side: a first lens group having a negative optical power, a second lens group having a negative optical power, and, a third lens group having a positive optical power. The position of the first lens group is fixed during zooming, and the third lens group includes three single lenses including, in order from the object side, a third-first lens being a single lens having a positive optical power, a third-second lens being a single lens having a negative optical power and a third-third lens being a single lens having a positive optical power. The zoom lens system satisfies the following conditional expression: 0.35<L3/f3<1.5 where L3 represents the axial air gap distance between the third-second lens and the third-third lens and f3 represents the focal length of the third lens group.

Abstract: An image pickup apparatus having a plurality of image pickup modes and a zoom lens for use with the image pickup apparatus is configured such that, even if the dimension of an effective screen region of an image pickup element changes as a result of changeover of the image pickup mode, the change of the angle of view is moderated and good aberration correction can be achieved in any of the image pickup modes. In an image pickup apparatus (1), an additional lens set (G5) having a positive refractive power is positioned most adjacent the image side with respect to a zoom lens (2) for movement to and from a position on an optical axis of the zoom lens.