Nikon Corporation

Nippon Kogaku K.k.

Kiyotaka Inadome

Toru Takayama

Kunihiro Fukino

Masahiro Nakatsuji

Hideo Kanno

Haruo Sato

Hiroshi Okano

Yoshiharu Shiokama

Hitoshi Imanari

Wataru Tatsuno

Naoto Ohta

In a zoom lens system in which the movement locus of a focusing lens unit is defined by synthesizing a focus cam and a zoom compensation cam, when the sensitivity of movement of an image point in association with the movement, in the direction of the optical axis, of the focusing lens unit in a closest in-focus state is larger than that in an infinity in-focus state, the ratio of the amount of rotation for focusing upon focusing from the infinity position to the closest distance position to the amount of rotation for zooming from the wide-angle end to the telephoto end in the focus cam is set to fall within a predetermined range, so that the sensitivity of movement of an image point in association with the movement, in the direction of rotation, of the focusing lens unit satisfies a specific condition.

Zoom lens system

In a zoom lens system in which the movement locus of a focusing lens unit is defined by synthesizing a focus cam and a zoom compensation cam, and the sensitivity of movement of an image point in association with the movement, in the direction of the optical axis, of the focusing lens unit in infinity and closest in-focus states does not vary so much, the ratio of the amount of rotation for focusing upon focusing from the infinity position to the closest distance position to the amount of rotation for zooming from the wide-angle end to the telephoto end in the focus cam is set to fall within a predetermined range, so that the sensitivity of movement of an image point in association with the movement, in the direction of rotation, of the focusing lens unit satisfies a specific condition.

A zoom lens system in which a movement locus of a focusing lens unit is defined by synthesizing a focus cam and a zoom compensation cam so as to achieve an in-focus state by a substantially constant amount of rotation for an identical object distance independently of a zooming state. In zooming, an amount of movement of the focusing lens unit is defined by a combination of the focus cam and the zoom compensation cam. An amount of movement of a non-focusing lens unit is defined by a combination of a zoom cam and the zoom compensation cam. In focusing, the amount of movement of the focusing lens unit is defined by the focus cam. The zoom lens system satisfies specified formulas so that the number of data of specific coefficients required for auto-focusing can be reduced, and an error upon calculation of the lens driving amount of the focusing lens unit using stored specific coefficients in correspondence with a detected defocus amount can be reduced.

There is provided a zoom lens of an inner focusing system which is capable of an auto-focusing operation and a manual focusing operation with a high precision. A zoom lens system in which a movement locus of a focusing lens unit is defined by synthesizing a focus cam and a zoom compensation cam is arranged such that a ratio of an amount of rotation for focusing from infinity to closest to an amount of rotation for zooming from wide angle to telephoto in the focus cam is set within a predetermined range so that, when the sensitivity of a movement of an imaging point with respect to a movement of the focusing lens unit in the direction of the optical axis in the closest in-focus state is larger than that in the infinity in-focus state, the sensitivity of the movement of the imaging point with respect to the movement of the focusing lens unit in the rotational direction satisfies specific conditions.

An internal focusing zoom lens comprises a first lens group of positive refracting power, a second lens group of negative refracting power, a third lens group of positive refracting power and a fourth lens group of positive refracting power disposed in the named order from the object side, in which at least the first lens group, the third lens group and the fourth lens group move toward an object along the optical axis during zooming from wide angle to telephoto such that an air gap increases between the first lens group and the second lens group, an air gap decreases between the second lens group and the third lens group and an air gap decreases between the third lens group and the fourth lens group, in which the second lens group moves toward the object along the optical axis during focusing, and which satisfies various conditions.

Internal focusing zoom lens system

A zoom lens system, with both zooming and focusing functions, has a plurality of lens groups including at least two focusing lens groups which move differently from each other either in zooming or in focusing, wherein when a certain movement trace for zooming is expressed with a variable of rotation angle of a rotating barrel for defining a displacement amount of a lens group along an optical axis, a movement trace of the first focusing lens group is formed by a combination of a first focus cam with a first compensating zoom cam, a movement trace of an n-th focusing lens group is formed by a combination of an n-th focus cam with an n-th compensating zoom cam, and a movement trace of each movable non-focusing lens group taking no part in focusing is formed by a combination of one of the first to n-th compensating zoom cams with a zoom cam for the non-focusing lens group.

In a zoom lens system having a plurality of lens units including a focusing lens unit movable during zooming and having the zooming and focusing functions, when a predetermined movement locus for zooming is expressed with the angle of rotation of a rotatable lens barrel for prescribing the amount of movement of the lens units in the direction of the optical axis thereof as a variable, the movement locus of the focusing lens unit is formed by the combination of a focus cam and a zoom compensation cam, and the movement locus of the movable non-focusing lens units which are not concerned in focusing is formed by the combination of the zoom compensation cam and a zoom cam corresponding to each non-focusing lens unit.

A zoom lens barrel has a lens unit with both functions of zooming and focusing, comprises a first cyindrical member having a zoom guide groove (or zoom cam) corresponding to a zooming orbit of displacement of the lens unit with both the functions of zooming and focusing and a second cylindrical member having a focus guide groove (or focus cam) for displacing the lens unit with the functions of zooming and focusing along an optical axis for focusing. The focus guide groove or focus cam is non-linear and has an area inclined with respect to the optical axis to permit the relative displacement of the first and second cylindrical members to each other in the optical axis direction necessary for the focusing of a given object to be held substantially constant irrespective of the status of zooming and also permit the displacement of the lens unit with both the functions of zooming and focusing for focusing to be varied according to the status of zooming.

Zoom lens apparatus with lens units for zooming and focusing

A zoom lens includes a plurality of lens units movable along the optic axis, and a mechanism for prescribing the movements of the plurality of lens units along the optic axis and making the focal length of the zoom lens adjustable within a desired range. At least one of the plurality of lens units is moved along the optic axis to form the image of an obect lying at any distance from the zoom lens on a predetermined surface. The mechanism has a member formed with at least one slot which prescribes the movement of the at least one lens unit along the optic axis. The at least one lens unit is moved in accordance with the at least one slot both when it is moved along the optic axis to change the focal length of the zoom lens and when it is moved along the optic axis to form the image of the object on the predetermined surface.

Zoom lens with inner or rear focusing system

In a zoom lens a zoom operating ring is rotatable to vary the focal length of an optical system between a first focal length and a second focal length. A distance ring is rotatable to effect focusing of the optical system with respect to an object to be photographed which is positioned in a normal photographing distance range including infinity. A macro operating ring is rotatable to effect focusing of the optical system with respect to an object to be photographed which is positioned in a macro photographing distance range including an area of a shorter distance than a close distance in the normal photographing distance range. The optical system has a maximum magnification when the focal length is equal to the first focal length. In response to rotation of the macro operating ring, the zoom operating ring is rotated when the focal length of the optical system is equal to a given focal length different from the first focal length and the macro operating ring is in a position of rotation corresponding to a shortest distance within the macro photographing distance range conforming to the given focal length.

Zoom lens capable of macro photography

A zoom lens having a change-magnification range ranging from wide angle to telephoto comprises, in succession from the object side, first lens group of positive refractive power movable on the optical axis, a second lens group of negative refractive power fixed relative to the image plane at a determined position, a third lens group of negative refractive power movable on the optical axis, and a fourth lens group of positive refractive power movable on the optical axis. The first and fourth lens groups are moved toward the object side in linear fashion to change magnification from the wide angle end to the telephoto end while the third lens group is moved toward the object side at the same time in non-linear fashion to keep the image plane at the determined position.

Growing community of inventors

Kawasaki, Japan

Kiyotaka Inadome