Variable focal length optical system capable of shifting image

Claim 2

A variable focal length optical system comprising a plurality of lens units and capable of shifting an image by shifting a shift lens unit, which constitutes a portion of the optical system, in a direction substantially perpendicular to an optical axis, wherein said shift lens unit is moved based on focal length information of the optical system to correct any variation in image position due to vibration of the optical system, and said optical system satisfies the following condition: 1<Xt/Xw<Z where: Xt=-f.sub.t /βb.sub.t (1-βa.sub.t); Xw=-f.sub.w /βb.sub.w (1-βa.sub.w); and where: Z: a zoom ratio of the optical system; f t : the focal length of the entire optical system at a maximum focal length state; f w : the focal length of the entire optical system at a minimum focal length state; βa t : the lateral magnification of the shift lends unit at the maximum focal length state; βb t : the lateral magnification of an entire lens unit disposed on the image side of the shift lens unit at the maximum focal length state; βa w : the lateral magnification of the shift lens unit at the minimum focal length state; βb w : the lateral magnification of the entire lens unit disposed on the image side of the shift lens unit at the minimum focal length state.

Claim 3

A variable focal length optical system capable of shifting an image according to claim 1, wherein a focusing lens unit movable along the optical axis during focusing on an object positioned at a closest distance is disposed on an object side of said shift lens unit, and a required amount of movement of said shift lens unit is calculated based on said focal length information and a predetermined coefficient.

Claim 4

A variable focal length optical system capable of shifting an image according to claim 2, wherein, when said focal length information is defined as Δ, vibration information of said optical system is defined as ε, and said predetermined coefficient is defined as a i , the required amount of movement δ of said shift lens unit is calculated based on the following relational expression: δ=ε·Σa.sub.i Δ.sup.i (i=0, 1, 2, 3, . . . ).

Claim 5

A variable focal length optical system capable of shifting an image according to claim 1, wherein a focusing lens unit movable along the optical axis during focusing on an object positioned at a closest distance is disposed on an image side of said shift lens unit, and a required amount of movement of said shift lens unit is calculated based on said focal length information, photographing distance information, and a predetermined coefficient.

Claim 6

A variable focal length optical system capable of shifting an image according to claim 4, wherein, when said focal length information is defined as Δ, said photographing distance information is defined as R, vibration information of said optical system is defined ε, and said predetermined coefficient is defined as a ij , the required amount of movement δ of said shift lends unit is calculated based on the following relational expression: δ=ε·Σa.sub.ij Δ.sup.i R.sup.-j (i=0, 1, 2, 3, . . . j=0, 1, 2, 3, . . . ).

Claim 7

A variable focal length optical system comprising: a plurality of lens units including a shift lends unit which is shifted in a direction substantially perpendicular to an optical axis of the optical system so as to shift an image position on a plane on which the image is formed; said shift lens unit being driven based on focal length information of the optical system to correct any variation in image position due to vibration of the optical system, wherein said optical system satisfies the following condition: 1<Xt/Xw<Z where: Xt=-f.sub.t /βb.sub.t (1-βa.sub.t); Xw=-f.sub.w /βb.sub.w (1-βa.sub.w); and where: Z: a zoom ratio of the optical system; f t : the focal length of the entire optical system at a maximum focal length state; f w : the focal length of the entire optical system at a minimum focal length state; βa t : the lateral magnification of the shift lends unit at the maximum focal length state; βb t : the lateral magnification of an entire lens unit disposed on the image side of the shift lens unit at the maximum focal length state; βa w : the lateral magnification of the shift lens unit at the minimum focal length state; βb w : the lateral magnification of the entire lens unit disposed on the image side of the shift lens unit at the minimum focal length state.

Claim 8

A variable focal length optical system comprising: a plurality of lens units including a shift lends unit which is shifted in a direction substantially perpendicular to an optical axis of the optical system so as to shift an image position on a plane on which the image is formed; said shift lens unit being driven based on focal length information of the optical system to correct any variation in image position due to vibration of the optical system, wherein said optical system satisfies the following condition: 1<Xt/Xw<Z where: Xt=-f.sub.t /βb.sub.t (1-βa.sub.t); Xw=-f.sub.w /βb.sub.w (1-βa.sub.w); and where: Z: a zoom ratio of the optical system; f t : the focal length of the entire optical system at a maximum focal length state; f w : the focal length of the entire optical system at a minimum focal length state; βa t : the lateral magnification of the shift lends unit at the maximum focal length state; βb t : the lateral magnification of an entire lens unit disposed on the image side of the shift lens unit at the maximum focal length state; βa w : the lateral magnification of the shift lens unit at the minimum focal length state; βb w : the lateral magnification of the entire lens unit disposed on the image side of the shift lens unit at the minimum focal length state.

Claim 9

A variable focal length optical system according to claim 6, wherein a focusing lens unit movable along the optical axis during focusing on an object positioned at a closest distance is disposed on an object side of said shift lends unit, and a required amount of movement of said shift lens unit is calculated based on said focal length information and a predetermined coefficient.

Claim 10

A variable focal length optical system according to claim 7, wherein, when said focal length information is defined as Δ, vibration information of said optical system is defined as ε, and said predetermined coefficient is defined as a i , the required amount of movement δ of said shift lens unit is calculated based on the following relational expression: δ=ε·Σa.sub.i Δ.sup.i (i=0, 1, 2, 3, . . . ).

Claim 11

A variable focal length optical system according to claim 6, wherein a focusing lens unit movable along the optical axis during focusing on an object positioned at a closest distance is disposed on an image side of said shift lens unit, and a required amount of movement of said shift lens unit is calculated based on said focal length information, photographing distance information, and a predetermined coefficient.

Claim 12

A variable focal length optical system according to claim 9, wherein, when said focal length information is defined as Δ, said photographing distance information is defined as R, vibration information of said optical system is defined as ε, and said predetermined coefficient is defined as a ij , the required amount of movement δ of said shift lens unit is calculated based on the following relational expression: δ=ε·Σa.sub.ij Δ.sup.i R.sup.-j (i=0, 1, 2, 3, . . . ).