Abstract: A zoom lens system comprises, in order from an object side, a negative first lens group G1, a positive second lens group G2 and a positive third lens group that has positive refractive power. In the zoom lens system, zooming is carried out by moving the first lens group and the second lens group, the first lens group consists of two or three lenses that include a negative glass lens located closest to the object side, the second lens group consists, in order from the object side, of a cemented lens composed of a positive glass lens and a negative glass lens and a plastic meniscus lens that is convex on the object side and both surfaces of which are aspherical, the third lens group consists of one positive plastic lens, and a combined focal length f2 of the second lens group and a focal length Lf23 of the plastic meniscus lens in the second lens group satisfy the following condition 0<|f2/Lf23|<0.3.

Abstract: A lens unit according to the present invention is capable of varying power for forming an image onto an image pickup element. The lens unit includes: a plurality of lens groups, a diaphragm, and a shutter. In the plurality of lens groups, a distance between a k-th lens group counting from an object side and a (k+1)-th lens group arranged at an image side of the k-th lens group changes for varying power. The diaphragm is arranged between a position at an image side of the k-th lens group and a lens surface facing the object side of a lens closest to the image in the (k+1)-th lens group. The shutter is provided with an aperture in a noncircular shape and fulfills the predetermined conditional formulas.

Abstract: A fisheye lens system includes a negative first lens group and a positive second lens group, which are defined with respect to a maximum air-distance between lens elements constituting the fisheye lens system. The negative first lens group includes a first negative meniscus lens element having the convex surface facing toward the object, a second negative meniscus lens element having the convex surface facing toward the object, and a negative third lens element.

Abstract: An image forming device is provided with: a zoom lens system TL that performs magnification varying by changing the distance between the lens units; and an image sensor SR that converts an optical image formed by the zoom lens system TL into an electric signal. The zoom lens system TL comprises three lens units of negative, positive, positive configuration. The second lens unit Gr2 comprises three single lens elements of, from the object side, a positive lens element L21, a negative meniscus lens element L22 convex to the object side and a positive lens element L23. A condition 1.0<|P22/P21|<2.0 (P21 is the optical power of the object side positive lens element L21 in the second lens unit GR2, and P22 is the optical power of the negative meniscus lens element L22 in the second lens unit GR2) is satisfied.

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 third lens unit having a positive refractive power. The first, second, and third lens units are arranged in that order from an object side to an image plane side of the zoom lens. The first lens unit includes a first lens having a negative refractive power, the second lens unit includes a second lens having a positive refractive power and a third lens having a negative refractive power, and the third lens unit includes a fourth lens having a positive refractive power. During zooming from a wide-angle end to a telephoto end, the first lens unit is fixed, and the second lens unit and the third lens unit are moved.

Abstract: A zoom lens system having higher optical performance, a wide angle of view, a high zoom ratio, and compactness include, in order from an object, a first group having negative power, a second group having positive power, and a third group having positive power. At least the first and second lens groups are moved upon zooming. The first group has, in order from the object, a negative meniscus lens having a convex surface facing the object, and a positive lens. At least one surface of the negative meniscus lens is an aspherical surface. The second group has, in order from the object, a first positive lens, a second positive lens, a negative lens, and a third positive lens. At least one surface of the first positive lens is an aspherical surface. The third group has one positive lens, and at least one surface thereof is an aspherical surface.

Abstract: The invention relates to a zoom lens favorable for offering a tradeoff between slimming down a lens system upon received in an associated lens mount and making sure a small F-number. There is a zoom lens provided, which comprises, in order from its object side, a first lens group G1 having negative refracting power, a second lens group G2 having positive refracting power, and a third lens group G3 having positive refracting power. Upon zooming from a wide-angle end to a telephoto end, the first second and third lens groups G1, G2 and G3 each move along an optical axis while a spacing between the first lens group and the second lens group becomes narrow and a spacing between the second lens group and the third lens group becomes wide. The first lens group G1 comprises one single lens that is a double-concave negative lens or two lenses: a double-concave negative lens and a positive lens. The second lens group G2 comprises two positive lenses and one negative lens.

Abstract: 1. An electronic imaging apparatus comprises an imaging optical system, and an imaging device which converts an object image obtained via the imaging system to an electric signal. All of medium of optical elements which is disposed in a space between a most object side of the imaging system and the imaging device is constituted with optically isotropic medium. A diameter of a point image at the open F value of the imaging system is bigger than a pitch of a picture element. The following condition is satisfied; F>1.4·a(0<a?4) Where F represents the open F value of the imaging optical system, and a represents the pitch at a horizontal or a vertical direction of the imaging device.

Abstract: A negative first group G1 is fixed when a power of the projection zoom lens varies and has a focusing function. A positive second group G2, a positive or negative third group G3, a positive fourth group G4 and a positive or negative group G5 move with a mutual relationship. A sixth group G6 functions as a relay lens. The fifth group G5 includes a cemented lens formed by cementing a negative meniscus lens L10 having a convex surface directed to the magnification side, a negative lens L11 and a positive lens L12 in order from a magnification side, and a positive lens L13 having a convex surface directed to a reduction side. Also, an expression |F5|/F>4.5 is satisfied where F denotes a focal length of the projection zoom lens at a wide-angle end and F5 denotes a focal length of the fifth group.

Abstract: A compact zoom lens that include: 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, wherein the first through third lens groups are arranged sequentially from an object when zooming is performed from a wide angle position to a telephoto position, a distance between the first lens group and the second lens group decreases and a distance between the second lens group and the third lens group increases, and the zoom lens includes at least one plastic lens and satisfies the inequality 1 ? ( G ? ? 1 + G ? ? 2 + G ? ? 3 ) f w ? 1.8 where G1 denotes a thickness of the first lens group, G2 denotes a thickness of the second lens group, G2 denotes a thickness of the third lens group, and fw denotes an overall focal length at the wide angle position. Accordingly, the zoom lens can ensure a high zoom ratio, and be made compact and light at low manufacturing costs.

Abstract: At least one exemplary embodiment is directed to a zoom lens which includes, in order from the object side to the image side, a first lens unit having a negative refractive power, a second lens unit having a negative refractive power, a stop, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power. The distance between the first lens unit and the second lens unit changes during zooming. At least one of the second, third, and fourth lens units moves so that the distance between the second lens unit and the third lens unit at the telephoto end is smaller than that at the wide-angle end and so that the distance between the third lens unit and the fourth lens unit at the telephoto end is larger than that at the wide-angle end. The distance between the stop and the third lens unit changes during zooming.

Abstract: A compact zoom lens system providing a wide-range, ultra-wide angle optionally rotatable compound zoom is disclosed. In one embodiment, the optical design is comprised of an NPP kernel followed by a PP relay with four independently moving groups, two on each side of an intermediate image. The front group is stationary with respect to the image plane, as are two fold prisms. The kernel has a zoom ratio of about 2:1, and the zoom relay has a magnification ratio of about 4:1, giving a total zoom ratio of about 8.6:1. The PP relay is comprised of two independently moving positive groups. The focal lengths covered by the zoom range have a 35 mm still camera equivalent of about 21 mm to 180 mm. The aperture of the system ranges from about f/2.8 to f/6.3, but is constant at about f/2.8 from about 3 mm through 6.2 mm focal length.

Abstract: At least one exemplary embodiment is directed to a zoom lens which includes, in order from an object side to an image side, a first lens unit with a negative refractive power, a second lens unit with a positive refractive power, and a third lens unit with a positive refractive power. A first gap between the first and second lens units when the zoom lens is at a wide-angle end is smaller than the first gap when the zoom lens is at a telephoto end, where a second gap between the second and third lens units when the zoom lens is at the wide-angle end is larger than the second gap when the zoom lens is at the telephoto end. The second lens unit includes at least one positive cemented lens.

Abstract: A projection lens includes, in order from a magnification side, a first lens group, a second lens group and a third lens group. The first lens group includes, in order from the magnification side, a negative lens whose lens made of a non-resin, a plastic lens at least one surface of which is aspheric and a positive lens. The second lens group includes a plastic lens at least one surface of which is aspheric, a positive lens and a negative lens. The third lens group includes a positive lens. The following conditional expressions are satisfied. 1.0<Bf/f?1.8 2.0<f1/f 2.0<f2/f where Bf denotes a air-conversion back focus of the entire system, f denotes a focal length of the entire system, f1 denotes a focal length of the first lens group and f2 denotes a focal length of the second lens group.

Abstract: A zoom lens comprises, in order from an object side to an image side, a lens group having negative refracting power, and a lens group having positive refracting power. Zooming is carried out with a change in a space between at least said two lens groups. The lens group having negative refracting power comprises a plurality of aspheric surfaces. The lens group having positive refracting power comprises at least one aspherie surface. The lens group having negative refracting power comprises at least three negative lenses, with satisfaction of the following condition: 2.3<|f2/f1<3.1, where f1 is a focal length of said lens group having negative refracting power, and f2 is a focal length of said lens group having positive refracting power.

Abstract: A projection lens includes three lens groups, arranged as follows from the magnification side: a first lens group of negative refractive power, a second lens group of positive refractive power, and a third lens group of positive refractive power. The first lens group includes three lens elements, each of negative refractive power, and two of these lens elements each have a meniscus shape with its convex surface on the magnification side. The second lens group includes a lens element having positive refractive power, a meniscus shape, and a convex surface on the magnification side. The third lens group includes: a lens element of positive refractive power and a meniscus shape with its convex surface on the reduction side; a cemented lens component; and at least one aspheric surface. The projection lens satisfies specified conditions regarding focal lengths and spacings of lens surfaces. A projection display device uses the projection lens.

Abstract: The invention relates to a small-format yet high-performance two units or three units type zoom lens with a negative unit at the front, which has a zoom ratio of about 3, an angle of view of as wide as 60° at the wide-angle end and high image-formation capability, and is much less susceptible to chromatic blurring, with a compact lens barrel. The zoom lens comprises a first lens unit G1 of negative refracting power and a second lens unit G2 of positive power, wherein zooming is implemented by varying the space between the lens units. The first lens unit G1 is made up of one negative lens L11 and one positive lens L12, two in all, and satisfies specific conditions with respect to their refractive index and Abbe constant.

Abstract: A five-element 3:1 zoom lens system in which the first lens group has a negative power and includes two lens elements and the second lens group has a positive power and includes a pair of lens sub-groups, the first sub-group having a positive power and including a pair of lens elements and the second sub-group having a positive power and including a single lens element. In one embodiment the second sub-group remains stationary relative to the location of the image plane and in another embodiment the second sub-group remains stationary relative to the first sub-group while they are moved relative to the location of the image plane. Several of the lens element surfaces are aspherical. The second lens element of the first sub-group is relatively thick and has a relatively high optical power. The overall length of the lens system is relatively short.

Abstract: A zoom lens system comprising a first lens unit of negative power, a second lens unit of positive power and a third lens unit of positive power, wherein in zooming, the lens units move respectively along an optical axis so that an interval of first lens unit and second lens unit decreases while an interval of second lens unit and third lens unit changes with variable magnification, the first lens unit comprises one object side negative lens element and one image side positive lens element, which have an aspheric surface, and the conditions: n 12>1. 88, ?12<26 and 5.0<?iW<20.0 (?W>30, n12 and ?12 are refractive index and Abbe number, respectively, of the image side positive lens element of the first lens unit, ?i W is an incident angle of the principal ray onto the image sensor at the maximum image height at a wide-angle limit) are satisfied.

Abstract: A magnifying optical system for endoscope which can be set at least in a usual observing condition (at a wide position) and a condition for observing a magnified image of an object at a short distance (at a tele position) by moving any of one of lens units, and is configured so as to satisfy a condition mentioned below, thereby providing a sufficient observation depth in each observing condition: f(W)/F(T)>0.

Abstract: A magnification varying optical system that directs light from an object to an image sensor includes in order from the object side: a first lens unit having negative optical power and including an optical axis changing element that changes the optical axis; a second lens unit having positive optical power and including three lens elements; a third lens unit having negative optical power; and a fourth lens unit having positive optical power. In this magnification varying optical system, in magnification varying from the wide-angle end to the telephoto end, the first lens unit is stationary, the distance from the first lens unit to the second lens unit decreases, and the distance from the third lens unit to the fourth lens unit increases. The magnification varying optical system satisfies the specified conditions.

Abstract: There is provided a zoom lens of variable power ratio of the order of 3 in which the whole of the zoom lens is made up of three lens elements groups and the power configuration of each of the groups has an arrangement of negative, positive and negative, whereby the reduction in overall length of its optical system is enabled, so that a compact zoom lens and a camera with it can be provided. The zoom lens comprising, sequentially from an object side thereof, a first lens elements group has a negative refraction power as a whole, a second lens elements group has a positive refraction power as a whole and the third lens element group has a negative refraction power as a whole, and a variable power is realized by shifting the positions of the first and second lens elements group in the direction of an optical axis thereof.

Abstract: A wide-angle lens system includes a negative front lens group and a positive rear lens group, in this order from the object. The negative front lens group includes a negative first sub-lens group and a positive second sub-lens group, in this order from the object. The positive rear lens group includes cemented lens elements having a positive R1 lens element and a negative R2 lens element, a positive R3 lens element having a convex surface facing toward the image, and a positive R4 lens element, in this order from the object. The wide-angle lens system satisfies the following conditions: ?0.8<f1a/f1b<?0.1 ??(1) 0.6<f/fR<1.1 ??(2) wherein f1a designates the focal length of the negative first sub-lens group; f1b designates the focal length of the positive second sub-lens group; f designates the focal length of the entire wide-angle lens system; and fR designates the focal length of the positive rear lens group.

Abstract: A wide-angle lens system includes a negative front lens group and a positive rear lens group, in this order from the object. The negative front lens group includes a negative first sub-lens group and a positive second sub-lens group, in this order from the object. The positive rear lens group includes cemented lens elements having a positive lens element, a negative lens element and a positive lens element. The wide-angle lens system satisfies the following conditions: ?0.8<f1a/f1b<?0.2 ??(1) 0.7<f/fR<1.1 ??(2) wherein f1a designates the focal length of the negative first sub-lens group; f1b designates the focal length of the positive second sub-lens group; f designates the focal length of the entire wide-angle lens system; and fR designates the focal length of the positive rear lens group.

Abstract: A zoom lens having an effective focal length fw for the wide angle mode comprises a first lens group, a second lens group and a third lens group. The first lens group has a negative effective power and an effective focal length f1, wherein 2.1<|f1/fw|<2.6. The first lens group comprises a first lens and a second lens. The first lens has a first negative power and at least a first concave aspheric lens surface. The second lens has a first positive power. The second lens group has a first positive effective power and an effective focal length f2, wherein 1.5<|f2/fw|<1.8. The second lens group comprises a third lens and a fourth lens. The third lens has a second positive power and at least a second aspheric lens surface. The fourth lens has a third positive power. The third lens group has a second positive effective power.

Abstract: There is provided a zoom lens of variable power ratio of the order of 3 in which the whole of the zoom lens is made up of three lens elements groups and the power configuration of each of the groups has an arrangement of negative, positive and negative, whereby the reduction in overall length of its optical system is enabled, so that a compact zoom lens and a camera with it can be provided. The zoom lens comprising, sequentially from an object side thereof, a first lens elements group has a negative refraction power as a whole, a second lens elements group has a positive refraction power as a whole and the third lens element group has a negative refraction power as a whole, and a variable power is realized by shifting the positions of the first and second lens elements group in the direction of an optical axis thereof.

Abstract: An inner-focus type zoom lens system used for a camera module having an image sensor and using an LC lens is provided. The inner-focus type zoom lens system includes an objective lens group, a condensing lens group, at least one moving lens group, and an LC lens. The objective lens group is located most closely to an object side and fixed, and the condensing lens group is located most closely to an image side and fixed. The moving lens group is located between the objective lens group and the condensing lens group and moved for zooming. The LC lens includes an inner space filled with an LC material whose refractive index and abbe number change according to an applied voltage. The LC lens compensates for an image plane using the changes of the refractive index and the abbe number of the LC material when the zooming is performed by the moving of the moving lens.

Abstract: A wide-angle zoom lens system includes a negative first lens group, a positive second lens group, a negative third lens group and a positive fourth lens group), in this order from the object. Upon zooming from the short focal length extremity to the long focal length extremity, a distance between the negative first lens group and the positive second lens group decreases, a distance between the positive second lens group and the negative third lens group increases, and a distance between the negative third lens group and the positive fourth lens group decreases. The wide-angle zoom lens system satisfies the following conditions: 1.3<|f1|/fw<1.7 (f1<0)??(1) 2.5<f4/fw<3.3??(2) wherein f1 designates the focal length of the negative first lens group; f4 designates the focal length of the positive fourth lens group; and fw designates the focal length of the entire wide-angle zoom lens system at the short focal length extremity.

Abstract: A two-unit zoom lens system which comprises a negative first lens unit G1 and a positive second lens unit G2, during change of magnification from a wide-angle end to a telephoto end, the first lens unit and the second lens unit are moved so as to reduce a space between the first lens unit and the second lens unit, the first lens unit includes a negative sub-unit G1a and a positive sub-unit G1b, the second lens unit has a first positive lens L21, a second negative lens L22, and a third positive lens L23, and the system further has an aperture stop S disposed in an air space which comes into contact with the first positive lens L21.

Abstract: A zoom lens system comprising, a first negative lens unit; a second positive lens unit; and a third negative lens unit, wherein a space between the second and third lens units changes during magnification change or focusing operation; the second lens unit and the third lens unit move only to the object side during the magnification change from a wide-angle end to a telephoto end so that a space between the first and second lens units is narrower in the telephoto end than in the wide-angle end; the first lens unit comprises a negative lens and a positive lens; the second lens unit comprises at most three lenses; the third lens unit comprises a negative lens; and the following condition (1) is satisfied: 0.7<Cj(t)/Cj(w)<1.2 .

Abstract: A zoom lens for a projection display device includes, in order from the long conjugate length side, a first lens group having negative refractive power and including at least one aspheric surface, a second lens group having positive refractive power and including at least two lens components, a third lens group, a fourth lens group having positive refractive power, and fifth and sixth lens groups. The second, third, fourth, and fifth lens groups move with coordinated movements during zooming. Preferably, the zoom lens satisfies three conditions related to the wide-angle and telephoto focal lengths and the focal lengths of the third and fifth lens groups, the fifth lens group has positive refractive power, and the first and fifth lens groups have particular lens element and lens component constructions. A projection display device uses the zoom lens.

Abstract: The invention relates to a zoom optical system that can offer an effective tradeoff between size reductions and cost reductions and electronic equipment incorporating it. The zoom optical system comprises, in order from its object side, 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 and a fourth lens group G4 having positive refracting power. The second lens group G2 consists of one positive lens. The positive lens satisfies a condition regarding the temperature coefficient of refractive index.

Abstract: A wide-angle zoom lens system includes a negative first lens group, a positive second lens group, a negative third lens group and a positive fourth lens group, in this order from the object. Upon zooming from the short focal length extremity to the long focal length extremity, a distance between the negative first lens group and the positive second lens group decreases, a distance between the positive second lens group and the negative third lens group increases, and a distance between the negative third lens group and the positive fourth lens group decreases. The wide-angle zoom lens system satisfies the following conditions: 1.1<|f1|/fw<2.0(f1<0) ??(1) 2.0<f4/fw<3.5 ??(2) 2.5<fBw/fw<3.

Abstract: An image-taking lens apparatus has an image sensor for converting an optical image of a subject into an electrical signal and an image-taking lens system for forming the optical image on the image sensor. The image-taking lens system includes a prism for bending the optical path, and the refractive index of the prism fulfills a prescribed conditional formula.

Abstract: A zoom lens, comprising, in order from an object side to an image side: (a) a first lens unit of negative optical power; (b) a second lens unit of positive optical power; and (c) a third lens unit of positive optical power, wherein a separation between the first lens unit and the second lens unit and a separation between the second lens unit and the third lens unit are varied during zooming, and wherein, during zooming from a wide-angle end to a telephoto end, the first lens unit moves so that its motion comprises (a) moving toward the image side and (b) moving thereafter toward the object side, and the third lens unit moves so that its motion comprises (a) moving toward the image side and (b) moving thereafter toward the object side.

Abstract: A zoom lens system includes a negative first lens group, a diaphragm, a positive second lens group, and a positive third lens group, in this order from the object. Zooming is performed by moving the negative first lens group and the positive first lens group in the optical axis direction. The zoom lens system includes six lens elements divided into lens group as follows: a negative first lens element and a positive second lens element, in this order from the object, constitute the negative first lens group; a positive third lens element, a negative fourth lens element and a positive fifth lens element, all of which are bonded to each other, in this order from the object, constitute the positive second lens group; and a positive sixth lens element constitutes the positive third lens group.

Abstract: A large aperture wide-angle lens includes first and second lens groups separated by a stop. The first lens group includes more than one lens element and the second lens group includes, in order from the object side, a first lens component having at least one aspheric surface, having negative refractive power, and having increasingly negative refractive power toward the periphery, a second lens component having a convex surface on the image side, and a third lens component having at least one aspheric surface and having decreasingly positive refractive power or increasingly negative refractive power toward the periphery. The large aperture wide-angle lens includes six or seven lens components and seven lens elements, and preferably satisfies specified conditions related to f-number and focal length of the wide-angle lens, the maximum image height at the image surface, and the index of refraction of the object-side lens element of the second lens group.

Abstract: A zoom lens system includes a frontmost first lens unit having a negative optical power and a plurality of lens units on the rear side thereof. The first lens unit consists of a negative lens element. The zoom lens system includes five or less lens elements in total. The Abbe number of the negative lens element and the exit pupil distance of the zoom lens system at a wide-angle end are appropriately adjusted.

Abstract: An image forming device is provided with: a zoom lens system TL that performs magnification varying by changing the distance between the lens units; and an image sensor SR that converts an optical image formed by the zoom lens system TL into an electric signal. The zoom lens system TL includes at least a negative first lens unit GR1 and a positive second lens unit GR2, and at least the first lens unit GR1 and the second lens unit GR2 move in zooming from the wide angle end (W) to the telephoto end (T). The second lens unit GR2 includes three lens elements of, from the object side, a positive meniscus lens element L21 convex to the object side, a negative lens element L22 and a positive lens element L23, and the following condition is satisfied: ?1.0<(CR1?CR2)/(CR1+CR2)<0.0 (CR1 is the front radius of curvature of the most object side lens element L21 in the second lens unit GR2, and CR2 is the rear radius of curvature of the most object side lens element L21 in the second lens unit GR2).

Abstract: A zoom lens having at least a first lens group including a reflection member for bending an optical axis fixedly during zooming and having a negative refractive power, a second lens group having a negative refractive power, and a third lens group arranged in the order from an object side is provided. In the zoom lens, an image can be shifted into a direction perpendicular to the optical axis by moving either of the second and the third lens groups (“shift lens group”) in a direction perpendicular to the optical axis, and a following conditional expression (1) is satisfied, 0.5<(1???)×?b<3.0,??(1) where: ??: a magnification of the shift lens group in a maximum telephoto state, and ?b: a magnification of a lens group arranged on an image surface side of the shift lens group in the maximum telephoto state.

Abstract: At least one exemplary embodiment is directed to a zoom lens system which includes, in order from an object side to an image side a first lens unit having negative optical power, a second lens unit having positive optical power, and a third lens unit having positive optical power. In zooming, a distance between the first lens unit and the second lens unit and a distance between the second lens unit and the third lens unit are changed.

Abstract: There are provided a first lens group having a negative optical power as a whole, second and third lens groups having positive optical powers as a whole, which are located in this order from the object side. These lens groups are all configured to be movable in the optical axis direction during magnification. The first lens group is constituted by a bi-concave lens having a negative optical power and a positive meniscus lens which is convex at the object side thereof, which are located in this order from the object side. The second lens group is constituted by a bi-convex lens having a positive optical power and a bi-concave power having a negative optical power, which are located in this order from the object side and bonded to each other to constitute a cemented lens. The third lens group is constituted by a bi-convex lens having a positive optical power. The first and fifth lenses are double-aspherical lenses formed from resin and the third and fourth lenses are single-aspherical lenses.

Abstract: Provided is a projection lens, including: a plurality of moving lens units that move on an optical axis for zooming; and a plurality of plastic lenses containing plastic, in which when a focal distance of an i-th positive lens from a predetermined plane side of N positive lenses of the plurality of plastic lenses is given by fpi, a focal distance of a j-th negative lens from the predetermined plane side of M negative lenses of the plurality of plastic lenses is given by fnj, and fp and fn are defined by 1 fp = ? i = 1 N ? 1 fpi 1 fn = ? j = 1 M ? 1 fnj (N and M each are a natural number, that is, an integer equal to or larger than 1), ?0.56<fn/fp<?0.05 is satisfied.

Abstract: An image taking optical system which comprises, 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 negative refractive power, wherein the second lens unit moves toward the object side so that a space between the first lens unit and the second lens unit decreases, and the third lens unit moves so that a space between the second lens unit and the third lens unit changes, in a case where zooming is performed from a wide-angle end to a telephoto end, the first lens unit includes at least one lens, among which there exists only one lens that has a negative refractive power, and the second lens unit includes at least one positive lens and at least one negative lens.

Abstract: A compact zoom lens system includes, from the object side to the image side, a negative first lens group (1), a positive second lens group (2), a positive third lens group (3) and a positive fourth lens group (4). The first lens group is stationary, and both the second and third lens groups are movable for effecting focal length change. The fourth lens group is also movable to compensate for image plane shift due to focal length change and thereby maintain the position of the image plane. The compact zoom lens system has a significantly reduced lens count and thus has an overall length of only 20 mm while achieving an approximately 3× zoom ratio. Sufficient back focal length is ensured even for such a short overall length. By employing aspheric lenses (10, 20, 301, 31, 41) for aberration correction, a high level of optical performance can be ensured.

Abstract: A zoom lens having a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power arranged in the order from an object side, wherein the first lens group includes a negative lens and a positive lens having at least one aspherical surface arranged from the object side and satisfies the following condition: 0.4<D1/fw<0.66 where D1 represents a distance, inside the first lens group, between a lens surface closest to an object and a lens surface closest to an image, and fw represents a focal distance with the zoom lens set to a wide-angle position.

Abstract: The invention relates to a wide-angle zoom lens system easy to ensure telecentricity particularly suited for digital single-lens reflex cameras. The wide-angle zoom lens system comprises a first group G1 of negative power, a second group G2 of positive power and a third group G3 of positive power. Upon zooming from a wide-angle end to a telephoto end, at least the first group G1 and the second group G2 move such that a spacing between the first group G1 and the second group G2 becomes narrow and a spacing between the second group G2 and the third group G3 becomes wide. The first group G1 comprises, in order from its object side, a first lens subgroup SG1a of negative refracting power and a second lens subgroup SG1b of negative refracting power. Upon focusing from a far object point to a near object point, the first lens subgroup SG1a and the second lens subgroup SG1b move toward the object side with a narrowing spacing between them.

Abstract: A zoom lens system includes four lens units having, from an object to an image side, negative, positive, negative and positive optical powers, respectively. During zooming, the intervals between the first and second lens units, and also the third and fourth lens units at the telephoto end are smaller than that at the wide angle end. Also, an interval the second and third lens units at the telephoto end is larger than that at the wide angle end. A zoom ratio is about 2.5 to 4.0. The following condition is satisfied: 2.2<bfw/H<3.0, where bfw represents a back focus at the wide angle end, and H represents a maximum image height.

Abstract: At least one exemplary embodiment is directed to a zoom lens which includes, in order from an object side to an image side, a first lens unit, which can have a negative refractive power; a second lens unit, which can have a positive refractive power; and a third lens unit, which can have a negative refractive power. The second and third lens units can move in zooming. The first, second, and, third lens units can satisfy the following conditions: 1.2<|?1/?T|<2 0.9<?2/?T<2.2 0.75<?3/?1<1.2 wherein ?1, ?2, and ?3 are the refractive powers of the first, second, and third lens units, respectively, and ?T is the refractive power of the zoom lens at a telephoto end.

Abstract: A zoom lens comprises a plurality of lens units including a first lens unit disposed most adjacent to an enlargement side and having negative refractive power, wherein one or more lens units of the plurality of lens units are moved in the direction of the optical axis thereof during magnification change, and wherein the first lens unit includes a 1-1st lens unit comprising at least one lens of negative refractive power and moved during focusing and a 1-2nd lens unit having positive refractive power, and fixed during focusing.