Abstract: An image forming optical system comprising four or five lens groups in total, wherein during zooming from the wide angle end to the telephoto end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group changes, the first lens group comprises three lenses including a negative meniscus lens, a positive meniscus lens, and a positive lens, the second lens group includes a negative meniscus lens having a convex surface directed toward the object side and a concave surface directed toward the image side, the negative meniscus lens being located closest to the object side in the second lens group, the position of the second lens group at the telephoto end is closer to the object side than that at the wide angle end, the image forming optical system has an aperture stop that moves integrally with the third lens group, the third lens group includ

Abstract: A zoom optical system having a lens group I including two single lenses or one lens component, an aperture stop, and a lens group A disposed between the lens group I and the aperture stop, including a lens component made up of a positive lens LA and a negative lens LB that are cemented together, and having a negative refracting power as a whole. The distance between the lens group I and the lens group A on the optical axis changes for zooming, and the lens component has an aspheric cemented surface. When the shape of the aspheric surface is expressed by a certain equation, the shape of the air-contact surface of the positive lens LA and its aspheric components etc. satisfy conditional expressions (3a) and (3b).

Abstract: An image forming optical system of the present invention is characterized by comprising three groups having, in order from an object side to an image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, or four groups with one more lens group added to the image side, the first lens group comprises one lens component facing its concave surface toward the object side, the second lens group comprises a single lens having a positive refractive power and a cemented lens having a negative refractive power as a whole, and the third lens group comprises a lens component having a positive refractive power, wherein upon zooming from the wide-angle end toward the telephoto side, the amount of movement of the first lens group in the optical axis direction in an area, where the focal length of the entire image pickup optical system is 3.

Abstract: An optical system includes, in order from its object side a negative first lens unit, a positive second lens unit, a negative third lens unit, and a positive fourth lens unit. The air gaps between the lens units are variable during zooming. The first lens unit includes one positive lens, the second lens unit includes one negative lens, the third lens unit consists of one or two lens components, and the fourth lens unit consists of one lens component, where the term “lens component” refers to a single lens or a cemented lens. The system satisfies the condition “0<M3/M2<0.55”, where M2 and M3 are the amounts of movement of the second lens unit and the third lens unit respectively during zooming from the wide angle end to the telephoto end in the state in which the zoom lens is focused on an object point at infinity.

Abstract: The zoom lens of the invention comprises, in order from an object side thereof, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, a fourth lens group having positive refracting power, a fifth lens group having negative refracting power, and a sixth lens group having positive refracting power. The first lens group includes a reflective optical element, and the lens in and on the most image side of the fourth lens group comprises a negative lens concave on its image side.

Abstract: The zoom lens comprises, from an object side, a first lens group, a second lens group that includes an aperture stop moving integrally therewith, a third lens group, and a fourth lens group having, respectively, negative, positive, negative, and positive refracting power, and during zooming from a wide-angle end to a telephoto end, a spacing between the first and second lens groups becomes narrow, between the second and third lens groups changes, and between the third and fourth lens groups grows wide, and the first lens group includes a first lens having negative refracting power, a second lens having a reflective surface for bending a light ray coming out of an object and a third lens having positive refracting power, and in said second lens group, a most image-plane-side surface of a lens having negative refracting power is configured in a concave shape on an image plane side.

Abstract: A zoom lens includes, in order from the object side, a negative lens unit, a positive lens unit and a positive lens unit. During zooming from the object side, the second lens unit moves, the distance between the first lens unit and the second lens unit decreases, the distance between the second lens unit and the third lens unit increases. The second lens unit has two lens components including, in order from the object side, a positive front lens component and a rear lens component. The third lens unit is composes of two lens components including, in order from the object side, a front lens component and a positive rear lens component. An aperture stop is disposed closer to the image side than the first lens unit and closer to the object side than the rear lens component in the second lens unit, and the aperture stop moves integrally with the second lens unit along the optical axis direction during zooming from the wide angle end to the telephoto end.

Abstract: An electronic imaging apparatus has a zoom optical system in which the most object-side lens unit A includes one biconcave-shaped negative lens component, each of air-contact-surfaces of which is configured as an aspherical surface, and when the magnification of the zoom optical system is changed in the range from a wide-angle position to a telephoto position, the lens unit A is moved back and forth along the optical axis in such a way that the lens unit A is initially moved toward the image side, and an electronic imaging unit that has an electronic image sensor so that image data picked up by the electronic image sensor are electrically processed and can be output as image data whose format is changed. In this case, in nearly infinite object point focusing, the zoom optical system satisfies the following condition: 0.7<y07/(fw·tan ?07w)<0.94 where y07 is expressed by y07=0.

Abstract: The zoom lens of the invention comprises, in order from an object side thereof, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, a fourth lens group having positive refracting power, a fifth lens group having negative refracting power, and a sixth lens group having positive refracting power. The first lens group includes a reflective optical element, and the lens component in, and on the most image side of, the fourth lens group has negative refracting power.

Abstract: The zoom lens of the invention comprises, in order from an object side thereof, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, a fourth lens group having positive refracting power, a fifth lens group having negative refracting power, and a sixth lens group having positive refracting power. The first lens group includes a reflective optical element, and the lens in and on the most image side of the fourth lens group comprises a negative lens concave on its image side.

Abstract: An optical system includes, in order from its object side a negative first lens unit, a positive second lens unit, a negative third lens unit, and a positive fourth lens unit. The air gaps between the lens units are variable during zooming. The first lens unit includes one positive lens, the second lens unit includes one negative lens, the third lens unit consists of one or two lens components, and the fourth lens unit consists of one lens component, where the term “lens component” refers to a single lens or a cemented lens. The system satisfies the condition “0<M3/M2<0.55”, where M2 and M3 are the amounts of movement of the second lens unit and the third lens unit respectively during zooming from the wide angle end to the telephoto end in the state in which the zoom lens is focused on an object point at infinity.

Abstract: An image forming optical system of the present invention is characterized by comprising three groups having, in order from an object side to an image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, or four groups with one more lens group added to the image side, the first lens group comprises one lens component facing its concave surface toward the object side, the second lens group comprises a single lens having a positive refractive power and a cemented lens having a negative refractive power as a whole, and the third lens group comprises a lens component having a positive refractive power, wherein upon zooming from the wide-angle end toward the telephoto side, the amount of movement of the first lens group in the optical axis direction in an area, where the focal length of the entire image pickup optical system is 3.

Abstract: A zoom lens has a negative object side lens unit (or first lens unit G1), a positive image side lens unit (or third lens unit G3), a positive intermediate lens unit (or second lens unit G2), and an aperture stop. The distance between the object side lens unit and the intermediate lens unit is smaller at the telephoto end than at the wide angle end, the distance between the intermediate lens unit and the image side lens unit is larger at the telephoto end than at the wide angle end, the intermediate lens unit moves in such a way that it is located closer to the object side at the telephoto end than at the wide angle end, the image side lens unit moves in such a way that it is located closer to the image side at the telephoto end than at the wide angle end, the aperture stop moves integrally with the intermediate lens unit. The image side lens unit is composed of two lens component including a front lens component and a positive rear lens component arranged in the mentioned order from the object side.

Abstract: An image forming optical system comprising four or five lens groups in total, wherein during zooming from the wide angle end to the telephoto end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group changes, the first lens group comprises three lenses including a negative meniscus lens, a positive meniscus lens, and a positive lens, the second lens group includes a negative meniscus lens having a convex surface directed toward the object side and a concave surface directed toward the image side, the negative meniscus lens being located closest to the object side in the second lens group, the position of the second lens group at the telephoto end is closer to the object side than that at the wide angle end, the image forming optical system has an aperture stop that moves integrally with the third lens group, the third lens group includ

Abstract: A zoom lens includes, in order from the object side, a first lens unit with negative power, a second lens unit with positive power, a third lens unit with positive power, and a fourth lens unit. When the magnification of the zoom lens is changed in the range from a wide-angle position to a telephoto position, spacing between the first lens unit and the second lens unit is narrowed and spacing between the second lens unit and the third lens unit is widened. An aperture stop moved integrally with the second lens unit is interposed between the most image-side lens element of the first lens unit and the most image-side lens element of the second lens unit. The first lens unit has, in order from the object side, a negative lens element and a positive lens element and satisfies the following conditions: 0.15<?1MF/?1MR<1.0 ?3.0<?1PF/?1PR<?1.

Abstract: An image forming optical system according to the present invention is characterized in that, in an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the positive lens group is disposed at an object side of the aperture stop, the positive lens group has a cemented lens which is formed by cementing a plurality of lenses, in a rectangular coordinate system in which a horizontal axis is let to be Nd and a vertical axis is let to be ?d, when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens is included in both of areas namely, an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1a), and a line when an upper limit value is in a range of the following conditional expression (1a), and of an area determined by following conditional expressions (2a) and (3a). 1.45<?<2.15??(1a) 1.30<Nd<2.

Abstract: A zoom optical system having a lens group I including two single lenses or one lens component, an aperture stop, and a lens group A disposed between the lens group I and the aperture stop, including a lens component made up of a positive lens LA and a negative lens LB that are cemented together, and having a negative refracting power as a whole. The distance between the lens group I and the lens group A on the optical axis changes for zooming, and the lens component has an aspheric cemented surface. When the shape of the aspheric surface is expressed by a certain equation, the shape of the air-contact surface of the positive lens LA and its aspheric components etc. satisfy conditional expressions (3a) and (3b).

Abstract: An image forming optical system according to the present invention is characterized in that, in an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the positive lens group is disposed at an object side of the aperture stop, the positive lens group has a cemented lens which is formed by cementing a plurality of lenses, in a rectangular coordinate system in which a horizontal axis is let to be Nd and a vertical axis is let to be ?d, when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens is included in both of areas namely, an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1a), and a line when an upper limit value is in a range of the following conditional expression (1a), and of an area determined by following conditional expressions (2a) and (3a). 1.45<?<2.15??(1a) 1.30<Nd<2.

Abstract: In an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the positive lens group being disposed at an image-plane side of the aperture stop and having a cemented lens, and when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens are included in both an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1), and a line when an upper limit value is in a range of the following conditional expression (1), and in an area determined by following conditional expressions (2) and (3) 1.45<?<2.15??(1) 1.30<Nd<2.20??(2) 3<?d<25??(3) Here, Nd denotes a refractive index, and ?d denotes an Abbe's number.

Abstract: The first lens group comprises a positive lens and a negative lens, and the total number of lenses in the first lens group is 2. The second lens group consists of, in order from the object side, a front unit of negative refracting power and a rear unit of positive refracting power. The third lens group consists of, in order from the object side, a front unit of positive refracting power and a rear unit of negative refracting power. The fourth lens group comprises a positive lens component, and the total number of lens components in the fourth lens group is 1. The front unit of the second lens group comprises a negative lens component, and the total number of lens components in the front unit of the second lens group is 1. The rear unit of the second lens group comprises, in order from the object side to the image side, a negative lens and a positive lens, and the total number of lenses in the rear unit of the second lens group is 2.