Abstract: An object is to provide an aspherical lens having compactness in dimension, large degree of freedom in design, and good optical performance, with increasing in productivity, and lowering production cost. The aspherical lens constructed by a substrate member A and a member B having different composition formed on the substrate member A. A boundary between the substrate member A and the member B having different composition is formed by a first aspherical surface RAB, and a surface of the member B having different composition opposite to the boundary being formed by a second aspherical surface RB having higher fabrication accuracy than that of the first aspherical surface RAB, and given conditional expressions are satisfied.

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

Abstract: In order to provide a fast super wide-angle lens system having the f-number of f/2.8 and a wide angle of view of 2?=100° or more in an imaging area of a digital camera and an image-capturing device equipped with the super wide-angle lens system. The lens system includes, in order from an object, a first lens group G1 having negative refractive power, an aperture stop S, and a second lens group G2 having positive refractive power, and the lens system satisfies predetermined conditional expressions.

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

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

Abstract: A large aperture super wide-angle lens system has an angle of view of 2&ohgr;=94° or more, an f-number of about 1.4, small variation in close-range aberrations, compactness, and high optical performance. The lens system includes, in order from an object, a negative lens group GN having negative refractive power which is fixed upon focusing, and a positive lens group GP having positive refractive power as a whole which is moved upon focusing. The positive lens group GP includes a front lens group GF having an aperture stop and a rear lens group GR having positive refractive power. Focusing at a close object is carried out by moving the front lens group GF and the rear lens group GR to the object side with different moving amounts. Prescribed conditional expressions are satisfied.

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

Abstract: The object is to provide a zoom lens system with an angle of view 2&ohgr; of about 74.1° to 11.8°, a zoom ratio of about 6.6, ultimately small in diameter and compact, being composed of less number of elements, and having high cost performance and superb optical performance. The system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, at least one lens group, and a lens group Gm having positive refractive power as a whole. Zooming is carried out by changing an air space between the first lens group and the second lens group. The lens group Gm consists of, in order from the object, a positive lens component having a convex surface facing to an image side and a negative lens component having a concave surface facing to the object side. Particular conditions are satisfied.

Abstract: In order to provide a large relative-aperture super wide-angle lens having the inclusive angle of 2 &ohgr;=115° or more with the conventional projection method (y=f·tan &thgr;) having the relative-aperture of about F 2.8, having compactness and high optical performance, and having small variation of aberration in relatively close object distance, the lens includes, in order from the object, a divergent lens group Gn having negative refractive power and a convergent lens group Gp having positive refractive power, and the divergent lens group Gn includes at least one aspherical negative lens, and the aspherical lens satisfies predetermined conditional expressions.

Abstract: A large aperture super wide-angle lens system has an angle of view of 2&ohgr;=94° or more, an f-number of about 1.4, small variation in close-range aberrations, compactness, and high optical performance. The lens system includes, in order from an object, a negative lens group GN having negative refractive power which is fixed upon focusing, and a positive lens group GP having positive refractive power as a whole which is moved upon focusing. The positive lens group GP includes a front lens group GF having an aperture stop and a rear lens group GR having positive refractive power. Focusing at a close object is carried out by moving the front lens group GF and the rear lens group GR to the object side with different moving amounts. Prescribed conditional expressions are satisfied.

Abstract: The object is to provide a zoom lens system with an angle of view 2&ohgr; of about 74.1° to 11.8°, a zoom ratio of about 6.6, ultimately small in diameter and compact, being composed of less number of elements, and having high cost performance and superb optical performance. The system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, at least one lens group, and a lens group Gm having positive refractive power as a whole. Zooming is carried out by changing an air space between the first lens group and the second lens group. The lens group Gm consists of, in order from the object, a positive lens component having a convex surface facing to an image side and a negative lens component having a concave surface facing to the object side. Particular conditions are satisfied.

Abstract: The object of the present invention is to provide a negative-positive, two-group type zoom lens system having a uniquely high zoom ratio of about 3.5, and having relatively small diameter and compactness with small number of lens element. According to one aspect, a zoom lens system includes, in order from an object-side, a first lens group having negative refractive power and a second lens group having positive refractive power. Zooming is carried out by varying the space between the first lens group and the second lens group. The first lens group includes, in order from the object side, a negative lens group G1F composed of one or two negative lens element, and a positive lens group G1R. The following conditional expressions are satisfied: 4.5≦|X2|·ft/fw2≦15  (1) 0.7≦|f1|/(fw·ft)½≦1.

Abstract: The object of the present invention is to provide a zoom lens system being extremely reduced size such as a standard single focal length lens, having very few number of lens elements, being ultimately reduced cost, having a zoom ratio about 2.2, and also having high optical performance without using any aspherical surface. The zoom lens system has, in order from an object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power, and performs zooming by changing an air space between the first lens group G1 and the second lens group G2. The first lens group comprises, in order from the object side, a negative lens group Ln consisting of one or two negative lens elements and a positive lens L12 having a convex surface facing to the object side. All surfaces consisting of the first lens group G1 are spherical or plane surfaces. Predetermined conditional expressions are satisfied.

Abstract: In order to provide a large relative-aperture super wide-angle lens having the inclusive angle of 2&ohgr;=115° or more with the conventional projection method (y=f·tan &thgr;) having the relative-aperture of about F 2.8, having compactness and high optical performance, and having small variation of aberration in relatively closed object distance, the lens includes, in order from the object, a divergent lens group Gn having negative refractive power and a convergent lens group Gp having positive refractive power, and the divergent lens group Gp includes at least one aspherical negative lens, and the aspherical lens satisfies predetermined conditional expressions.

Abstract: The object of the present invention is to provide a negative-positive, two-group type zoom lens system having a uniquely high zoom ratio of about 3.5, and having relatively small diameter and compactness with small number of lens element. According to one aspect, a zoom lens system includes, in order from an object-side, a first lens group having negative refractive power and a second lens group having positive refractive power. Zooming is carried out by varying the space between the first lens group and the second lens group. The first lens group includes, in order from the object side, a negative lens group G1F composed of one or two negative lens element, and a positive lens group G1R.

Abstract: The object of the present invention is to provide a zoom lens system being extremely reduced size such as a standard single focal length lens, having very few number of lens elements, being ultimately reduced cost, having a zoom ratio about 2.2, and also having high optical performance without using any aspherical surface. The zoom lens system has, in order from an object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power, and performs zooming by changing an air space between the first lens group G1 and the second lens group G2. The first lens group comprises, in order from the object side, a negative lens group Ln consisting of one or two negative lens elements and a positive lens L12 having a convex surface facing to the object side. All surfaces consisting of the first lens group G1 are spherical or plane surfaces. Predetermined conditional expressions are satisfied.

Abstract: To provide a zoom lens having wide field angle coverage, a zooming ratio of 3.5.times. or greater, and a large aperture such that F-number is on the order of F 2.

Abstract: Zoom lens system having a high zoom ratio including, in order from the object end: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power; and a fifth lens group having a positive refractive power. When the zoom lens system is operated from its maximum wide-angle state to its maximum telephoto state, the air-space separation between the first lens group and the second lens group is increased, the air-space separation between the second lens group and the third lens group is decreased, the air-space separation between the third lens group and the fourth lens group is increased, and the air-space separation between the fourth lens group and the fifth lens group is decreased, and the following condition (1) is satisfied:2.3<D.sub.IT -D.sub.IW /fw<10 (1)where D.sub.

Abstract: A large high zoom ratio lens system having a large field angle with a zoom ratio of over 3.5 and an F number of about 2.8 to about 3.5 which includes at least a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power. The second lens group G2 includes a negative lens component L2A having at least one aspherical surface, a positive composite lens component L2B, and a negative lens component L2C having a concave surface facing toward the object end wherein the positive cemented lens component L2B is preferably formed of a positive lens having a convex surface facing toward the object end and a negative lens.

Abstract: An aberration-controllable optical system has a large angle of view and is capable of continuously varying spherical aberrations from negative values to positive values, including a point at which a sharp image can be produced. A master lens group includes a first sub lens group having a positive refractive power, a second sub lens group having a negative refractive power, and a third sub lens group having a positive refractive power in this order from the object side of the system. The converter lens group includes a positive lens element and a negative lens element in this order from the object side. The on-axis distance of the air gap which is formed between the positive lens element and the negative lens element can be controlled to mainly change the spherical aberrations in this system. When f.sub.m is a master lens group focal length and f.sub.C is a converter lens group focal length, the aberration-controllable optical system satisfies a condition:-1<f.sub.M /f.sub.C <0.