JP5614166B2 - Variable focal length lens, optical device, and variable focal length lens adjustment method - Google Patents

Description

  The present invention relates to a variable focal length lens, an optical apparatus having the same, and a method for adjusting the variable focal length lens.

  Conventionally, various variable focal length lenses suitable for photographic cameras, electronic still cameras, video cameras, and the like have been proposed (see, for example, Patent Document 1).

JP 2002-323655 A

  The conventional variable focal length lens has a problem that imaging performance deteriorates when an eccentric error occurs during manufacturing. In addition, in order to prevent deterioration in imaging performance, it was necessary to increase the shape accuracy of each lens, lens chamber, and mechanism parts to reduce the eccentric error. However, it is difficult to reduce the cost because the processing accuracy must be increased. It was.

  The present invention has been made in view of the above problems, and an object thereof is to provide a low-cost variable focal length lens capable of achieving good optical performance, an optical device having the variable focal length lens, and a variable focal length lens adjustment method. And

In order to solve the above problems, the present invention provides:
In order from the object side , the first lens group having a positive refractive power and the second lens group having a negative refractive power are composed of a front lens group having a negative refractive power as a whole, a central lens group having a positive refractive power, and a positive refractive power. It consists essentially of four lens groups depending on the rear lens group,
An air gap between the first lens group and the second lens group in the front lens group, an air gap between the front lens group and the central lens group, and an air gap between the central lens group and the rear lens group. By changing the focal length,
The rear lens group includes, in order from the object side, a 4A lens group having a positive refractive power and a 4B lens group.
After the assembly of the forward lens group and the central lens group and the rear lens group, an adjusting mechanism for adjusting the position of Ru is tilted decentered the second lenses group, position adjustment for shifting eccentrically the first 4A lens group an adjustment mechanism to perform possess, respectively,
Provided is a variable focal length lens that satisfies the following conditions .
2.0 <M2t / M2w
M4At / M4Aw <2.0
2.5 <(M2t / M2w) / (M4At / M4Aw)
However,
M2t: Composite imaging magnification of all the lens groups positioned between the second lens group and the image plane in the telephoto end state of the variable focal length lens
M2w: Composite imaging magnification of all the lens groups positioned between the second lens group and the image plane in the wide-angle end state of the variable focal length lens
M4At: Composite imaging magnification of all the lens units located between the fourth A lens unit and the image plane in the telephoto end state of the variable focal length lens
M4Aw: Composite imaging magnification of all lens groups positioned between the fourth A lens group and the image plane in the wide-angle end state of the variable focal length lens

  The present invention also provides an optical device comprising the variable focal length lens.

The present invention also provides:
In order from the object side , the first lens group having a positive refractive power and the second lens group having a negative refractive power are composed of a front lens group having a negative refractive power as a whole, a central lens group having a positive refractive power, and a positive refractive power. It consists essentially of four lens groups depending on the rear lens group,
The rear lens group includes, in order from the object side, a 4A lens group having a positive refractive power and a 4B lens group.
An air gap between the first lens group and the second lens group in the front lens group, an air gap between the front lens group and the central lens group, and an air gap between the central lens group and the rear lens group. the Rukoto varied a method for adjusting the variable focal length lens to change the focal length,
So that the following conditional expression is satisfied,
After the assembly of the forward lens group and the central lens group and the rear lens group, an adjusting mechanism for adjusting the position of Ru is tilted decentered the second lenses group, position adjustment for shifting eccentrically the first 4A lens group There is provided a variable focal length lens adjustment method characterized in that an adjustment mechanism for performing each is performed.
2.0 <M2t / M2w
M4At / M4Aw <2.0
2.5 <(M2t / M2w) / (M4At / M4Aw)
However,
M2t: Composite imaging magnification of all the lens groups positioned between the second lens group and the image plane in the telephoto end state of the variable focal length lens
M2w: Composite imaging magnification of all the lens groups positioned between the second lens group and the image plane in the wide-angle end state of the variable focal length lens
M4At: Composite imaging magnification of all the lens units located between the fourth A lens unit and the image plane in the telephoto end state of the variable focal length lens
M4Aw: Composite imaging magnification of all lens groups positioned between the fourth A lens group and the image plane in the wide-angle end state of the variable focal length lens

  According to the present invention, it is possible to provide a low-cost variable focal length lens that can achieve good optical performance, an optical apparatus having the variable focal length lens, and a variable focal length lens adjustment method.

It is sectional drawing which shows the lens structure of the variable focal distance lens which concerns on 1st Example-4th Example. The coma aberration figure with respect to d line | wire (wavelength (lambda) = 587.6nm) in the infinite point focusing state of the variable focal-length lens which concerns on 1st Example-4th Example when the eccentricity error does not generate | occur | produce at the time of manufacture is shown. , (A) shows the wide-angle end state, (b) shows the intermediate focal length state, and (c) shows the telephoto end state. The coma aberration diagram with respect to the d-line (wavelength λ = 587.6 nm) in the infinite focus state of the variable focal length lens according to the first embodiment to the fourth embodiment in the case where an eccentric error occurs at the time of manufacture is shown. a) shows the wide-angle end state, (b) shows the intermediate focal length state, and (c) shows the telephoto end state. It is sectional drawing which shows the mechanism of the variable focal distance lens which concerns on 1st Example. It is a figure which shows the mechanism for performing the position adjustment which tilts and decenters the 1st lens group of the variable focal distance lens shown by FIG. 4, and is the figure seen from the object side. It is a figure which shows the mechanism for performing the position adjustment which shift decenters the back lens group of the variable focal distance lens shown by FIG. 4, and is the figure seen from the image side. The variable focal length according to the first embodiment when the imaging performance is corrected by performing position adjustment for tilt decentering the first lens group and position adjustment for shift decentering the rear lens group when there is an eccentricity error during manufacturing. The coma aberration diagrams for the d-line (wavelength λ = 587.6 nm) in the infinitely focused state of the lens are shown, (a) is a wide-angle end state, (b) is an intermediate focal length state, and (c) is a telephoto end state. Respectively. It is sectional drawing which shows the mechanism of the variable focal distance lens which concerns on 2nd Example. It is a figure which shows the mechanism for performing the position adjustment which carries out the tilt decentering of the 2nd lens group of the variable focal distance lens shown by FIG. 8, and is the figure seen diagonally from the object side. It is a figure which shows the mechanism for performing the position adjustment which shift decenters the 4th A lens group of a part of back lens group of the variable focal distance lens shown by FIG. 8, and is sectional drawing perpendicular | vertical to an optical axis. When there is a decentration error at the time of manufacturing, the image forming performance is corrected by performing position adjustment for tilt decentering the second lens group and position adjustment for shifting decentering part of the 4A lens group of the rear lens group. The coma aberration figure with respect to d line | wire (wavelength (lambda) = 587.6nm) in the infinite point focusing state of the variable focal distance lens which concerns on 2nd Example is shown, (a) is a wide angle end state, (b) is an intermediate | middle focal distance state. , (C) show the telephoto end state, respectively. It is sectional drawing which shows the mechanism of the variable focal distance lens which concerns on 3rd Example. When there is a decentration error at the time of manufacturing, the first lens unit is tilted decentered, and the position adjustment is performed to shift and decenter a part of the 4A lens unit of the rear lens unit. The coma aberration figure with respect to d line (wavelength (lambda) = 587.6nm) in the infinite point focusing state of the variable focal-length lens which concerns on 3 Example is shown, (a) is a wide angle end state, (b) is an intermediate | middle focal distance state. , (C) show the telephoto end state, respectively. It is sectional drawing which shows the mechanism of the variable focal distance lens which concerns on 4th Example. The variable focal length according to the fourth embodiment in the case where the imaging performance is corrected by performing the position adjustment for tilt decentering the second lens group and the position adjustment for shift decentering the rear lens group when there is an eccentricity error during manufacturing The coma aberration diagrams for the d-line (wavelength λ = 587.6 nm) in the infinitely focused state of the lens are shown, (a) is a wide-angle end state, (b) is an intermediate focal length state, and (c) is a telephoto end state. Respectively. It is a figure which shows the structure of the camera provided with the variable focal distance lens which concerns on 1st Example.

  Hereinafter, a variable focal length lens and an adjustment method of the variable focal length lens according to an embodiment of the present application will be described.

  The variable focal length lens according to this embodiment includes, in order from the object side, a front lens group having a negative refractive power, a central lens group having a positive refractive power, and a rear lens group having a positive refractive power. The focal length is changed by changing at least one of the air intervals, the air interval between the front lens group and the central lens group, and the air interval between the central lens group and the rear lens group, and the front lens group and the central lens group After assembling the rear lens group, there is an adjustment mechanism that performs position adjustment that tilts and decenters some lens groups of the front lens group and shifts and decenters some or all of the rear lens groups.

  With this configuration, it is possible to correct the deterioration of the imaging performance due to the decentration aberration caused by the decentration error during manufacturing in the entire focal range from the wide angle end to the telephoto end. Note that if you try to correct with only one of the front lens group or only part or all of the rear lens group, it is possible to correct decentration aberrations only in a small part of the focal length range. However, decentration aberrations remain in other focal length ranges, and the deterioration in imaging performance cannot be corrected sufficiently. This problem becomes more prominent as the zoom ratio of the variable focal length lens increases.

In addition, it is desirable that the variable focal length lens according to the present embodiment satisfies the following conditional expressions (1), (2), and (3).
(1) 2.0 <MAT / MAw
(2) MBt / MBw <2.0
(3) 2.0 <(MAt / MAw) / (MBt / MBw)
However, MAt is a composite imaging magnification of all the lens units located between a part of the front lens unit and the image plane in the telephoto end state of the variable focal length lens, and MAw is a wide angle end of the variable focal length lens. The combined imaging magnification of all the lens units located between the lens unit and the image plane in the front lens unit in the state, MBt is a part or all of the rear lens unit in the telephoto end state of the variable focal length lens The combined imaging magnification of all the lens units located between the lens unit and the image plane, MBw is a part of the rear lens unit in the wide-angle end state of the variable focal length lens or between all the lens units and the image plane This is the combined imaging magnification of all the lens groups located. If there is no lens group between a part or all of the rear lens groups and the image plane, MBt = MBw = 1.0.

  Conditional expressions (1) to (3) are to perform position adjustment to tilt decenter a part of the front lens group of the variable focal length lens and shift decenter a part or all of the rear lens group. Thus, the lens group magnification relationship suitable for correcting the deterioration of the imaging performance due to decentration aberration in the entire focal range from the wide-angle end to the telephoto end of the variable focal length lens is defined. The change in the combined imaging magnification of all the lens groups located between some lens groups of the front lens group and the image plane is positioned between some or all of the rear lens groups and the image plane. By configuring the lens group so as to be larger than the change in the combined image forming magnification of all the lens groups, it is possible to realize good correction in the entire focal range from the wide angle end to the telephoto end.

When the lower limit of conditional expression (1) is not reached, it is difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
If the upper limit value of conditional expression (2) is exceeded, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
If the lower limit of conditional expression (3) is not reached, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (1) to 2.5.
In order to secure the effect of the embodiment, it is preferable to set the upper limit of conditional expression (2) to 1.5.
In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (3) to 2.5.

In the variable focal length lens according to the present embodiment, the front lens group includes, in order from the object side, a first lens group having a positive refractive power and a second lens group having a negative refractive power, and from the wide-angle end state to the telephoto end. During zooming to the state, the air gap between the first lens group and the second lens group is enlarged, the air gap between the second lens group and the central lens group is reduced, and the air gap between the central lens group and the rear lens group is reduced. It is desirable to do.
This configuration is advantageous for achieving a high zoom ratio.

In the variable focal length lens according to the present embodiment, it is desirable that the adjustment mechanism performs position adjustment for decentering the first lens group and position adjustment for shifting and decentering the entire rear lens group.
By adjusting the position for decentering the first lens group and adjusting the position for shifting and decentering the entire rear lens group, good correction of decentration aberrations can be realized in the entire focal range from the wide-angle end to the telephoto end.

In addition, it is desirable that the variable focal length lens according to the present embodiment satisfies the following conditional expressions (4), (5), and (6).
(4) 5.0 <M1t / M1w
(5) M4t / M4w <2.0
(6) 5.0 <(M1t / M1w) / (M4t / M4w)
Where M1t is the combined imaging magnification of all the lens units located between the first lens unit and the image plane in the telephoto end state of the variable focal length lens, and M1w is the first lens in the wide angle end state of the variable focal length lens. The combined imaging magnification of all the lens units located between the group and the image plane, M4t is the combined result of all the lens units located between the rear lens unit and the image plane in the telephoto end state of the variable focal length lens. The image magnification, M4w, is a combined image formation magnification of all the lens units positioned between the rear lens unit and the image plane in the wide-angle end state of the variable focal length lens. If there is no lens group between the rear lens group and the image plane, M4t = M4w = 1.0.

  Conditional expressions (4) to (6) are obtained by performing position adjustment for decentering the first lens group of the variable focal length lens and position adjustment for shifting and decentering the entire rear lens group from the wide angle end of the variable focal length lens. Defines the magnification relationship of the lens group suitable for correcting the deterioration of the imaging performance due to decentration aberration in the entire focal range up to the telephoto end. The change in the combined image magnification of all the lens groups positioned between the first lens group and the image plane is changed to the change in the combined image magnification of all the lens groups positioned between the rear lens group and the image plane. By constructing it to be larger than that, it is possible to achieve good correction in the entire focal range from the wide-angle end to the telephoto end.

When the lower limit of conditional expression (4) is not reached, it is difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
When the upper limit value of conditional expression (5) is exceeded, it becomes difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
If the lower limit value of conditional expression (6) is not reached, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (4) to 10.0.
In order to secure the effect of the embodiment, it is preferable to set the upper limit of conditional expression (5) to 1.5.
In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (6) to 10.0.

In the variable focal length lens according to the present embodiment, it is desirable that the adjustment mechanism performs position adjustment for decentering the second lens group and position adjustment for shifting and decentering a part of the rear lens group.
By adjusting the position for decentering the second lens group and adjusting the position for shifting and decentering a part of the rear lens group, a good correction of decentration aberration can be realized in the entire focal range from the wide-angle end to the telephoto end.

In addition, it is desirable that the variable focal length lens according to the present embodiment satisfies the following conditional expressions (7), (8), and (9).
(7) 2.0 <M2t / M2w
(8) M4At / M4Aw <2.0
(9) 2.0 <(M2t / M2w) / (M4At / M4Aw)
Where M2t is a composite imaging magnification of all the lens units positioned between the second lens unit and the image plane in the telephoto end state of the variable focal length lens, and M2w is a second lens in the wide angle end state of the variable focal length lens. The combined image forming magnification M4At of all the lens groups positioned between the lens group and the image plane is positioned between the partial lens group of the rear lens group and the image plane in the telephoto end state of the variable focal length lens. The combined imaging magnification of all the lens groups, M4Aw is the combined imaging magnification of all the lens groups positioned between the partial lens group of the rear lens group and the image plane in the wide-angle end state of the variable focal length lens. is there. Note that when there is no lens group between the partial lens group of the rear lens group and the image plane, M4At = M4Aw = 1.0.

  Conditional expressions (7) to (9) are obtained by performing position adjustment for tilt decentering the second lens group of the variable focal length lens and position adjustment for shifting decentering a part of the rear lens group. A lens group magnification relationship suitable for correcting deterioration in imaging performance due to decentration aberration in the entire focal range from the wide-angle end to the telephoto end of the lens is defined. Changes in the combined imaging magnification of all the lens groups positioned between the second lens group and the image plane are combined with all the lens groups positioned between a part of the rear lens groups and the image plane. By configuring to be larger than the change in imaging magnification, good correction can be realized in the entire focal range from the wide-angle end to the telephoto end.

If the lower limit value of conditional expression (7) is not reached, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
When the upper limit value of conditional expression (8) is exceeded, it becomes difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
If the lower limit value of conditional expression (9) is not reached, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (7) to 2.5.
In order to secure the effect of the embodiment, it is preferable to set the upper limit of conditional expression (8) to 1.5.
In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (9) to 2.5.

In the variable focal length lens according to the present embodiment, it is desirable that the adjustment mechanism performs position adjustment for decentering the first lens group and position adjustment for shifting and decentering a part of the rear lens group.
By adjusting the position for decentering the first lens group and adjusting the position for decentering a part of the rear lens group, it is possible to achieve good correction of decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.

In addition, it is desirable that the variable focal length lens according to the present embodiment satisfies the following conditional expressions (10), (11), and (12).
(10) 5.0 <M1t / M1w
(11) M4At / M4Aw <2.0
(12) 5.0 <(M1t / M1w) / (M4At / M4Aw)
Where M1t is the combined imaging magnification of all the lens units located between the first lens unit and the image plane in the telephoto end state of the variable focal length lens, and M1w is the first lens in the wide angle end state of the variable focal length lens. The combined image forming magnification M4At of all the lens groups positioned between the lens group and the image plane is positioned between the partial lens group of the rear lens group and the image plane in the telephoto end state of the variable focal length lens. The combined imaging magnification of all the lens groups, M4Aw is the combined imaging magnification of all the lens groups positioned between the partial lens group of the rear lens group and the image plane in the wide-angle end state of the variable focal length lens. is there. Note that when there is no lens group between the partial lens group of the rear lens group and the image plane, M4At = M4Aw = 1.0.

  Conditional expressions (10) to (12) are obtained by performing position adjustment for tilt decentering the first lens group of the variable focal length lens and position adjustment for shifting decentering some lens groups of the rear lens group. A lens group magnification relationship suitable for correcting deterioration in imaging performance due to decentration aberration in the entire focal range from the wide-angle end to the telephoto end of the lens is defined. A change in the combined imaging magnification of all the lens groups located between the first lens group and the image plane is obtained by synthesizing all the lens groups located between a part of the rear lens groups and the image plane. By configuring to be larger than the change in imaging magnification, good correction can be realized in the entire focal range from the wide-angle end to the telephoto end.

When the lower limit value of conditional expression (10) is not reached, it is difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
If the upper limit of conditional expression (11) is exceeded, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
If the lower limit value of conditional expression (12) is not reached, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.

In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (10) to 10.0.
In order to secure the effect of the embodiment, it is preferable to set the upper limit of conditional expression (11) to 1.5.
In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (12) to 10.0.

  In the variable focal length lens according to the present embodiment, it is desirable that the adjustment mechanism performs position adjustment for decentering the second lens group and position adjustment for shifting and decentering the entire rear lens group.

  By adjusting the position for decentering the second lens group and adjusting the position for shifting and decentering the entire rear lens group, good correction of decentration aberration can be realized in the entire focal range from the wide-angle end to the telephoto end.

In addition, it is desirable that the variable focal length lens according to the present embodiment satisfies the following conditional expressions (13), (14), and (15).
(13) 2.0 <M2t / M2w
(14) M4t / M4w <2.0
(15) 2.0 <(M2t / M2w) / (M4t / M4w)
Where M2t is a composite imaging magnification of all the lens units positioned between the second lens unit and the image plane in the telephoto end state of the variable focal length lens, and M2w is a second lens in the wide angle end state of the variable focal length lens. The combined imaging magnification of all the lens units located between the group and the image plane, M4t is the combined result of all the lens units located between the rear lens unit and the image plane in the telephoto end state of the variable focal length lens. The image magnification, M4w, is a combined image formation magnification of all the lens units positioned between the rear lens unit and the image plane in the wide-angle end state of the variable focal length lens. If there is no lens group between the rear lens group and the image plane, M4t = M4w = 1.0.

  Conditional expressions (13) to (15) are obtained from the wide-angle end of the variable focal length lens by performing position adjustment for tilt decentering the second lens group of the variable focal length lens and position adjustment for shift decentering the entire rear lens group. Defines the magnification relationship of the lens group suitable for correcting the deterioration of the imaging performance due to decentration aberration in the entire focal range up to the telephoto end. The change in the combined image magnification of all the lens groups located between the second lens group and the image plane is changed to the change in the combined image magnification of all the lens groups positioned between the rear lens group and the image plane. By constructing it to be larger than that, it is possible to achieve good correction in the entire focal range from the wide-angle end to the telephoto end.

If the lower limit value of conditional expression (13) is not reached, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
If the upper limit value of conditional expression (14) is exceeded, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.
If the lower limit value of conditional expression (15) is not reached, it will be difficult to correct decentration aberrations in the entire focal range from the wide-angle end to the telephoto end.

In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (13) to 2.5.
In order to secure the effect of the embodiment, it is preferable to set the upper limit of conditional expression (14) to 1.5.
In order to secure the effect of the embodiment, it is preferable to set the lower limit of conditional expression (15) to 2.5.

Further, in the variable focal length lens according to the present embodiment, when the position adjustment for shifting and decentering a part of the rear lens group is performed, the rear lens group has the fourth refractive power 4A in order from the object side. It is preferable that the adjustment mechanism includes a lens group and a 4B lens group, and the adjustment mechanism performs position adjustment that shifts and decenters the 4A lens group.
By decentering the 4A lens group, good correction of decentration aberration can be realized.

  The variable focal length lens adjustment method according to the present embodiment includes, in order from the object side, a negative lens power front lens group, a positive power central lens group, and a positive power rear lens group. A variable focal length lens that changes a focal length by changing at least one air interval in the front lens unit, an air interval between the front lens unit and the central lens unit, and an air interval between the central lens unit and the rear lens unit. After assembling the front lens group, the central lens group, and the rear lens group, a part of the front lens group is tilt-decentered, and a part or all of the rear lens group is Adjust the position to shift eccentricity.

  By this adjustment method, it is possible to correct the deterioration of the imaging performance due to the decentration aberration caused by the decentration error at the time of manufacture in the entire focal range from the wide angle end to the telephoto end. Note that if only one lens group in the front lens group or part or all of the rear lens group is used for correction, decentration aberrations can be corrected satisfactorily only in the focal length range. In other focal length ranges, decentration aberrations remain and image quality deterioration cannot be corrected sufficiently. This problem becomes more prominent as the zoom ratio of the variable focal length lens increases.

(Example)
Hereinafter, each example according to the present embodiment will be described with reference to the drawings.

  The variable focal length lenses according to the first to fourth embodiments have a common lens configuration, and differ in an adjustment mechanism described later for satisfactorily correcting deterioration in imaging performance due to an eccentric error during manufacture. Therefore, overlapping portions will be described together here.

  FIG. 1 is a cross-sectional view showing a lens configuration of a variable focal length lens according to first to fourth embodiments.

  As shown in FIG. 1, the lens system of the variable focal length lens according to the first to fourth embodiments includes a front lens group GF having a negative refractive power and a positive refractive power in order from the object side along the optical axis. Center lens group GM and a rear lens group GR having a positive refractive power. The front lens group GF includes, in order from the object side along the optical axis, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power, and the central lens group GM is along the optical axis. In order from the object side, the third lens unit G3A having positive refractive power, the third lens group G3B having negative refractive power, and the third lens group G3C having negative refractive power are arranged on the object side of the central lens group GM. The rear lens group GR has a stop S, and is composed of a fourth refractive power 4A lens group G4A and a negative power fourth B lens group G4B in order from the object side along the optical axis.

  When zooming from the wide-angle end state W to the telephoto end state T, the air gap between the first lens group G1 and the second lens group G2 is enlarged, and the air gap between the second lens group G2 and the central lens group GM is reduced. Each lens group moves so that the air space between the central lens group GM and the rear lens group GR is reduced.

  The first lens group G1 includes, in order from the object side along the optical axis, a cemented positive lens of a negative meniscus lens L11 having a convex surface facing the object side and a biconvex positive lens L12, and a positive meniscus having a convex surface facing the object side. Lens L13.

  The second lens group G2 includes, in order from the object side along the optical axis, a negative meniscus lens L21 having a convex surface directed toward the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a concave surface directed toward the object side. A negative meniscus lens L24 and a positive negative meniscus lens L25 having a concave surface facing the object side. The negative meniscus lens L21 has a thin resin layer on the object side and has a resin surface aspherical. It is.

  The third A lens group G3A is composed of, in order from the object side along the optical axis, a biconvex positive lens L31, a biconvex positive lens L32, and a cemented positive lens of a biconvex positive lens L33 and a biconcave negative lens L34. .

  The third lens group G3B is composed of, in order from the object side along the optical axis, a cemented negative lens of a biconcave negative lens L35 and a positive meniscus lens L36 having a convex surface directed toward the object side. The biconcave negative lens L35 is on the object side. This surface is an aspherical lens.

  The third C lens group G3C is composed of a negative meniscus lens L37 having a concave surface directed toward the object side.

  The fourth A lens group G4A is composed of a biconvex positive lens L41, and the biconvex positive lens L41 is a lens having an aspheric object side surface.

  The fourth lens group G4B is composed of a cemented negative lens composed of a biconcave negative lens L42 and a biconvex positive lens L43 in order from the object side along the optical axis.

  The image plane I is formed on an image sensor (not shown), and the image sensor is composed of a CCD, a CMOS, or the like.

  Table 1 below shows specifications of the lens system of the variable focal length lens according to the first to fourth embodiments.

  In (surface data) in the table, the object surface is the object surface, the surface number is the surface number from the object side, r is the radius of curvature, d is the surface spacing, and nd is the refraction at the d-line (wavelength λ = 587.6 nm). The ratio, νd represents the Abbe number in the d-line (wavelength λ = 587.6 nm), (variable) represents the variable surface interval, (diaphragm) represents the iris diaphragm S, and the image plane represents the image plane I. Note that the description of the refractive index nd of air = 1.000.000 is omitted. Further, “∞” in the radius of curvature r column indicates a plane.

In (Aspheric data), the aspheric surface is expressed by the following equation.
X (y) = (y ² / r) / [1+ [1-κ (y ² / r ² )] ^1/2 ]
+ A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y ¹⁰
Here, the height in the direction perpendicular to the optical axis is y, and the amount of displacement in the optical axis direction at the height y (the distance along the optical axis from the tangential plane of each aspheric surface to each aspheric surface) is X ( y) Let r be the radius of curvature (paraxial radius of curvature) of the reference sphere, κ be the conic coefficient, and An be the n-th aspherical coefficient. “En” represents “× 10 ⁻ⁿ ”, for example “1.234E-05” represents “1.234 × 10 ⁻⁵ ”. Each aspherical surface is indicated with “*” on the right side of the surface number in (surface data).

  (Various data), the zoom ratio is the zoom ratio of the lens system, W is the wide angle end state, M is the intermediate focal length state, T is the telephoto end state, f is the focal length, FNO is the F number, 2ω is the angle of view ( (Unit: “°”), Y is the image height, TL is the entire length of the lens system, Bf is the back focus, and di is the variable surface interval value at surface number i.

  (Zoom lens group data) indicates the start surface number of each lens group and the focal length of the lens group.

  In all the following specification values, “mm” is generally used as the focal length f, radius of curvature r, surface interval d and other lengths, etc. unless otherwise specified, but the optical system is proportional. Even if it is enlarged or proportionally reduced, the same optical performance can be obtained. Further, the unit is not limited to “mm”, and other appropriate units may be used.

(Table 1)

(Surface data)
Surface number rd nd νd
Object ∞ ∞
1 123.9595 2.0000 1.850260 32.35
2 65.8189 9.3000 1.497820 82.52
3 -679.8190 0.1000
4 66.6349 6.2000 1.593190 67.87
5 419.9308 (variable)

6 * 162.3242 0.1500 1.553890 38.09
7 146.0754 1.0000 1.834807 42.72
8 16.1304 6.5500
9 -35.2760 1.0000 1.882997 40.76
10 60.4450 0.1000
11 37.3723 5.2000 1.846660 23.78
12 -32.7279 0.8214
13 -23.9463 1.0000 1.882997 40.76
14 -252.4150 2.0000 1.808090 22.79
15 -72.4479 (variable)

16 (Aperture) ∞ 1.0000
17 36.7222 3.3000 1.593190 67.87
18 -118.1963 0.1000
19 41.3768 3.1500 1.487490 70.41
20 -92.3429 0.1000
21 42.3403 3.8000 1.487490 70.41
22 -41.0036 1.0000 1.805181 25.43
23 259.3609 3.8191
24 * -63.6485 1.0000 1.806100 40.94
25 22.0000 2.9000 1.805181 25.43
26 150.5781 4.2000
27 -45.8244 1.0000 1.882997 40.76
28 -215.9895 (variable)

29 * 77.1794 3.1500 1.589130 61.16
30 -37.1187 0.1000
31 -261.2949 1.0000 1.882997 40.76
32 39.9808 4.4000 1.518229 58.93
33 -48.5209 (Bf)
Image plane ∞

(Aspheric data)
6th surface κ = -5.7774
A4 = 6.79980E-06
A6 = -2.52730E-08
A8 = 8.26150E-11
A10 = -1.02860E-13
24th surface κ = 2.8196
A4 = 4.59750E-06
A6 = 4.28350E-09
A8 = 0.00000E + 00
A10 = 0.00000E + 00
29th surface κ = -6.5363
A4 = -1.95310E-05
A6 = 1.79050E-08
A8 = -1.55070E-10
A10 = 4.13770E-13

(Various data)
Zoom ratio 15.70
W M T
f = 18.54 50.00 290.99
FNO = 4.11 5.39 5.86
2ω = 78.00 30.78 5.48
Y = 14.20 14.20 14.20
TL = 160.01 187.27 237.80
Bf = 39.12 69.40 99.17

d5 2.15 25.00 65.69
d15 40.45 20.28 2.00
d28 8.85 3.15 1.50

(Zoom lens group data)
Group Start surface Focal length F 1 -20.11 (W) -28.50 (M) -110.68 (T)
1 1 103.25
2 6-15.13
M 17 44.77
3A 17 25.59
3B 24-54.94
3C 27-66.05
R 29 47.36
4A 29 42.98
4B 31-698.29

  FIG. 2 shows a coma with respect to the d-line (wavelength λ = 587.6 nm) in the infinitely focused state of the variable focal length lens according to the first to fourth embodiments when no eccentric error occurs during manufacturing. Aberration diagrams are shown, in which (a) shows a wide-angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state.

  FIG. 3 is a coma aberration diagram with respect to the d-line (wavelength λ = 587.6 nm) in the infinite focus state of the variable focal length lens according to the first to fourth embodiments when an eccentric error occurs during manufacturing. (A) shows the wide-angle end state, (b) shows the intermediate focal length state, and (c) shows the telephoto end state.

  In each aberration diagram, Y represents an image height (unit: “mm”), and coma aberration is shown at image heights of 10 mm, 0 mm (center), and −10 mm. The same applies to other aberration diagrams referred to in the following description.

(First embodiment)
Next, the variable focal length lens adjusting mechanism according to the first embodiment will be described. In the first embodiment, in order to satisfactorily correct the deterioration of the imaging performance due to the eccentric error during manufacturing, the position adjustment for tilt decentering the first lens group G1 and the position adjustment for shifting decentering the rear lens group GR are performed. It has a mechanism.

  FIG. 4 is a sectional view showing the mechanism of the variable focal length lens according to the first embodiment.

  FIG. 5 is a view showing a mechanism for adjusting the position of tilt decentering of the first lens group of the variable focal length lens shown in FIG. 4, and is a view seen from the object side.

  FIG. 6 is a diagram showing a mechanism for adjusting the position for shifting and decentering the rear lens group of the variable focal length lens shown in FIG. 4, and is a diagram seen from the image side.

  As shown in FIG. 4, in the variable focal length lens 1 according to the first example, the first lens group G1 is held by an annular first holding member 3, and the second lens group G2 is a second holding part having a substantially cylindrical shape. The central lens group GM is held by a substantially cylindrical third holding member 39, and the rear lens group GR is held by an annular fourth holding member 41.

  The first holding member 3 is fixed to the annular first sliding member 17 by the first screw 13 and the second screw 15, and the second holding member 5 is fixed to the annular second sliding member 19 for the third holding The member 39 is fixed to the annular third sliding member 43, and the fourth holding member 41 is fixed to the annular fourth sliding member 47 by the third screw 45.

  The lens system of the variable focal length lens 1 of the first embodiment is housed inside a cylindrical fixed tube 29 and a cylindrical cam tube 31 that is rotatably fitted in the fixed tube 29. Cam pins (not shown) are provided on the outer peripheral edges of the first sliding member 17, the second sliding member 19, the third sliding member 43, and the fourth sliding member 47. These cam pins are cams. A cam groove (not shown) formed in the cylinder 31 is engaged. By rotating the cam cylinder 31 with respect to the fixed cylinder 29 by a mechanism (not shown), the first sliding member 17, the second sliding member 19, the third sliding member 43, and the fourth sliding member 47 are used as the optical axis. It can be moved back and forth along.

  A mount member 33 is fixed to the fixed cylinder 29, and the fixed cylinder 29 is fixed to an imaging device such as a camera (not shown) via the mount member 33. The iris diaphragm S is opened and closed by a diaphragm mechanism 35 fixed to the third sliding member 43.

  The first holding member 3 includes a cylindrical portion 3a that holds the first lens group G1, and a flange portion 3b that extends radially outward of the cylindrical portion 3a. Three flange holes 3c that penetrate the flange portion 3b in the optical axis direction are formed in the flange portion 3b at substantially equal intervals in the circumferential direction, and three screw holes 3d that penetrate the flange portion 3b in the optical axis direction. Are formed at substantially equal intervals in the circumferential direction. The total of these six holes 3c and screw holes 3d are alternately formed at substantially equal intervals in the circumferential direction. The diameter of the fool hole 3 c is formed larger than the shaft diameter of the first screw 13. The first sliding member 17 is formed with three screw holes 17a at positions corresponding to the three fool holes 3c when viewed in the optical axis direction.

  As shown in FIGS. 4 and 5, the three first screws 13 are respectively inserted into the three burr holes 3 c and screwed into the three screw holes 17 a. The three second screws 15 are screwed into the three screw holes 3d, respectively.

  By tightening or loosening the first screw 13, the force by which the head of the first screw 13 pushes the first holding member 3 toward the optical axis direction image side is adjusted, and by tightening or loosening the second screw 15, By adjusting the force with which the screw 15 pulls the first holding member 3 toward the object side in the optical axis direction, the inclination of the first holding member 3 with respect to the first sliding member 17 can be adjusted and fixed. That is, it is possible to adjust the position of tilting the first lens group G1 with respect to the optical axis.

  The fourth holding member 41 includes a cylindrical portion 41a that holds the rear lens group GR, and a flange portion 41b that extends radially outward of the cylindrical portion 41a. Three flange holes 41c that penetrate the flange portion 41b in the optical axis direction are formed in the flange portion 41b at substantially equal intervals in the circumferential direction. The diameter of the hole 41c is formed larger than the shaft diameter of the third screw 45. The fourth sliding member 47 is formed with three screw holes 47a at positions corresponding to the three fool holes 41c when viewed in the optical axis direction.

  As shown in FIGS. 4 and 6, the three third screws 45 are respectively inserted into the three fool holes 41c and screwed into the three screw holes 47a. The holding member 41 is fixed to the fourth sliding member 47 from the image side.

  Since the diameter of the burr hole 41 c is more than the shaft diameter of the third screw 45, the fourth holding member 41 is optically moved with respect to the fourth sliding member 47 by once loosening the tightened third screw 45. Can move in a direction perpendicular to the axis. And after moving the 4th holding member 41 to the optimal position, the 4th holding member 41 can be fixed to the optimal position by fastening the 3rd screw 45 again. That is, it is possible to adjust the position by shifting the rear lens group GR with respect to the optical axis.

  Table 2 below lists corresponding values of the conditional expressions (1) to (6) in the variable focal length lens 1 according to the first example.

  In the first example, MAt is a composite imaging magnification of the second lens group G2, the central lens group GM, and the rear lens group GR in the telephoto end state, and MAw is the second lens group G2 and the central lens in the wide-angle end state. The combined imaging magnification of the group GM and the rear lens group GR, and since there is no lens group between the rear lens group GR and the image plane I, MBt = MBw = 1.0, and M1t is the second lens group in the telephoto end state. G2 is a composite image magnification of the central lens group GM and the rear lens group GR, M1w is a composite image magnification of the second lens group G2, the central lens group GM and the rear lens group GR in the wide-angle end state, and the rear lens group GR. M4t = M4w = 1.0 because there is no lens group between the image plane I and the image plane I.

(Table 2)
(Values for conditional expressions)
(1) MAt / MAw = 15.70
(2) MBt / MBw = 1.000
(3) (MAt / MAw) / (MBt / MBw) = 15.70
(4) M1t / M1w = 15.70
(5) M4t / M4w = 1.000
(6) (M1t / M1w) / (M4t / M4w) = 15.70

  FIG. 7 shows a first embodiment in which the imaging performance is corrected by performing position adjustment for tilt decentering the first lens group and position adjustment for shifting decentering the rear lens group when there is an eccentricity error during manufacturing. The coma aberration figure with respect to d line | wire (wavelength (lambda) = 587.6nm) in the infinite point focusing state of such a variable focal length lens is shown, (a) is a wide angle end state, (b) is an intermediate | middle focal length state, (c). Indicates the telephoto end state.

  Comparing the aberration diagrams of FIGS. 2, 3, and 7, it can be seen that in FIG. 7, the deterioration of the imaging performance due to the decentration error at the time of manufacture is well corrected from the wide-angle end state to the telephoto end state.

(Second embodiment)
Next, a variable focal length lens adjusting mechanism according to the second embodiment will be described. In the second embodiment, in order to satisfactorily correct deterioration in imaging performance due to a decentration error at the time of manufacture, position adjustment for tilt decentering the second lens group G2 and a part of a fourth A lens group G4A of the rear lens group GR are performed. And an adjustment mechanism for adjusting the position for shifting eccentricity. Parts having the same structure as the first embodiment will be described using the same reference numerals.

  FIG. 8 is a sectional view showing the mechanism of the variable focal length lens according to the second embodiment.

  FIG. 9 is a view showing a mechanism for performing position adjustment for tilt decentering the second lens group of the variable focal length lens shown in FIG. 8, and is a view seen obliquely from the object side.

  FIG. 10 is a diagram showing a mechanism for performing position adjustment for shifting and decentering a part of the 4A lens group of the rear lens group of the variable focal length lens shown in FIG. 8, and is a cross-sectional view perpendicular to the optical axis. is there.

  As shown in FIG. 8, in the variable focal length lens 61 according to the second example, the first lens group G1 is held by a substantially cylindrical first holding member 51, and the second lens group G2 is a substantially cylindrical first lens. 2 is held by the holding member 53, the central lens group GM is held by the substantially cylindrical third holding member 39, and a part of the fourth lens group G4A of the rear lens group GR is held by the annular fourth holding member 7. The remaining fourth B lens group G4B of the rear lens group GR is held by a substantially cylindrical fifth holding member 11.

  The first holding member 51 is fixed to the annular first sliding member 55, the second holding member 53 is fixed to the annular second sliding member 57, and the third holding member 39 is the annular third sliding member 43. The fourth holding member 7 is fixed to the annular fourth sliding member 23 by the fourth screw 21, and the fifth holding member 11 is also fixed to the annular fourth sliding member 23.

  The lens system of the variable focal length lens 61 of the second embodiment is housed inside a cylindrical fixed tube 29 and a cylindrical cam tube 31 that is rotatably fitted in the fixed tube 29. Cam pins (not shown) are provided on the outer peripheral edges of the first sliding member 55, the second sliding member 57, the third sliding member 43, and the fourth sliding member 23, respectively. A cam groove (not shown) formed in the cylinder 31 is engaged. The cam pin 57d provided on the second sliding member 57 is shown in FIG. By rotating the cam cylinder 31 with respect to the fixed cylinder 29 by a mechanism (not shown), the first sliding member 55, the second sliding member 57, the third sliding member 43, and the fourth sliding member 23 are used as the optical axis. It can be moved back and forth along.

  A mount member 33 is fixed to the fixed cylinder 29, and the fixed cylinder 29 is fixed to an imaging device such as a camera (not shown) via the mount member 33. The iris diaphragm S is opened and closed by a diaphragm mechanism 35 fixed to the third sliding member 43.

  As shown in FIGS. 8 and 9, the second sliding member 57 has a double annular structure centered on the optical axis, an inner annular portion 57 a that holds the second holding member 53, and an outer side. The annular portion 57b is connected by three coupling portions 57c formed at substantially equal intervals along the outer periphery of the inner annular portion 57a. Three cam pins 57d described above are fixed to the outer periphery of the outer annular portion 57b at substantially equal intervals in the circumferential direction.

  In the outer annular portion 57b, three elongated holes 57e extending in the circumferential direction are formed at substantially equal intervals in the circumferential direction. At both ends of each elongated hole 57e, a notch 57f extending substantially toward the object side in the optical axis direction is formed. Further, an immobilizer 59 is fitted in the center of each elongated hole 57e, and the immobilizer 59 is screwed inwardly in the radial direction of the cam cylinder 31 into the object side surface of the elongated hole 57e. A tapered surface 57g is formed to push 57e in the optical axis direction. When the second sliding member 57 is viewed in the optical axis direction, each immobilizer 59, the coupling portion 57c in the vicinity thereof, and the optical axis are on substantially the same straight line.

  Three holes 29b are formed in the fixed cylinder 29 at positions corresponding to the three immobilizers 59 when viewed in the radial direction, and the cam cylinder 31 is positioned at a position corresponding to the three immobilizers 59 when viewed in the radial direction. Three holes 31b are formed. A hexagonal hole 59a is formed in the head of each immobilizer 59, and each immobilizer 59 can be rotated by inserting a hex key from the outside through the hole 29b and the hole 31b. . In order to prevent dust and the like from entering the inside of the fixed cylinder 29 and the cam cylinder 31, the holes 29b and 31b are closed with a rubber ring (not shown) except when the immobilizer 59 is rotated.

  By screwing the immobilizer 59 into the elongated hole 57e, the elongated hole 57e is expanded to elastically deform the outer annular portion 57b, and the inner annular portion 57a connected to the outer annular portion 57b via the coupling portion 57c is connected to the cam pin 57d. Can be tilted against. In addition, since the notch 57f is formed in the long hole 57e, the outer annular portion 57b can be easily deformed by screwing the immobilizer 59.

  By tightening or loosening the immobilizer 59, the inclination of the second holding member 53 held by the inner annular portion 57a with respect to the cam pin 57d can be adjusted and fixed. In other words, it is possible to adjust the position of tilting the second lens group G2 with respect to the optical axis.

  The fourth holding member 7 includes a cylindrical portion 7a that holds the fourth A lens group G4A, and a flange portion 7b that extends radially outward of the cylindrical portion 7a. The flange portion 7b is the fourth sliding member 23. Is fitted into an annular groove 23a. In the fourth sliding member 23, three screw holes 23b penetrating the fourth sliding member 23 in the radial direction of the cylindrical portion 7a are formed at substantially equal intervals along the groove 23a. The fixed cylinder 29 is formed with three holes 29a at positions corresponding to the three screw holes 23b when viewed in the radial direction of the cylindrical part 7a, and the cam cylinder 31 has a radial direction of the cylindrical part 7a. Three holes 31a are formed at positions corresponding to the three screw holes 23b as viewed.

  As shown in FIGS. 8 and 10, the three fourth screws 21 are respectively screwed into the three screw holes 23b, and the tips thereof are in contact with the edges of the flange portion 7b. Each fourth screw 21 can be rotated by inserting a screwdriver from the outside through the hole 29a and the hole 31a. In order to prevent dust and the like from entering the inside of the fixed cylinder 29 and the cam cylinder 31, the holes 29a and 31a are closed with a rubber ring (not shown) except when the fourth screw 21 is rotated.

  By tightening or loosening the fourth screw 21, the fourth screw 21 is advanced or retracted in the radial direction of the cylindrical portion 7 a, thereby moving the fourth holding member 7 in a direction perpendicular to the optical axis with respect to the fourth sliding member 23. Can be moved and fixed. That is, it is possible to adjust the position by shifting the 4A lens group G4A with respect to the optical axis.

  Table 3 below lists corresponding values of the conditional expressions (1) to (3) and the conditional expressions (7) to (9) in the variable focal length lens 61 according to the second example.

  In the second embodiment, MAt is a composite image magnification of the central lens group GM and the rear lens group GR in the telephoto end state, and MAw is a composite image formation of the central lens group GM and the rear lens group GR in the wide-angle end state. Magnification, MBt is an imaging magnification of a part of the fourth B lens group G4B of the rear lens group GR in the telephoto end state, MBw is an imaging magnification of a part of the fourth B lens group G4B of the rear lens group GR in the wide angle end state, M2t is a composite imaging magnification of the central lens group GM and the rear lens group GR in the telephoto end state, M2w is a composite imaging magnification of the central lens group GM and the rear lens group GR in the wide-angle end state, and M4At is in the telephoto end state. The imaging magnification of a part of the fourth lens group G4B in the rear lens group GR, M4Aw is the imaging magnification of a part of the fourth lens group G4B in the rear lens group GR in the wide-angle end state. It is.

(Table 3)
(Values for conditional expressions)
(1) MAt / MAw = 2.85
(2) MBt / MBw = 0.927
(3) (MAt / MAw) / (MBt / MBw) = 3.07
(7) M2t / M2w = 2.85
(8) M4At / M4Aw = 0.927
(9) (M2t / M2w) / (M4At / M4Aw) = 3.07

  FIG. 11 shows correction of imaging performance by performing position adjustment for tilt decentering of the second lens group and position adjustment for shift decentering part of the 4A lens group of the rear lens group when there is an eccentricity error during manufacturing. The coma aberration diagram with respect to the d-line (wavelength λ = 587.6 nm) in the infinitely focused state of the variable focal length lens according to the second example is shown, (a) is in the wide-angle end state, and (b) is in FIG. Intermediate focal length state, (c) shows the telephoto end state.

  Comparing the aberration diagrams of FIGS. 2, 3, and 11, it can be seen that in FIG. 11, the deterioration of the imaging performance due to the decentration error at the time of manufacture is well corrected from the wide-angle end state to the telephoto end state.

(Third embodiment)
Next, a variable focal length lens adjusting mechanism according to the third embodiment will be described. In the third embodiment, in order to satisfactorily correct deterioration in imaging performance due to a decentration error at the time of manufacturing, position adjustment for tilt decentering the first lens group G1 and a fourth A lens group G4A of a part of the rear lens group GR are performed. And an adjustment mechanism for adjusting the position for shifting eccentricity. Parts having the same structure as those of the first embodiment and the second embodiment will be described using the same reference numerals, or the same reference numerals are shown in the drawings and description thereof is omitted.

  FIG. 12 is a sectional view showing the mechanism of the variable focal length lens according to the third embodiment.

  As shown in FIG. 12, in the variable focal length lens 37 according to the third example, the first lens group G1 is held by the annular first holding member 3, and the second lens group G2 is a second holding part having a substantially cylindrical shape. The central lens group GM is held by the substantially cylindrical third holding member 39, and a part of the fourth lens group G4A of the rear lens group GR is held by the annular fourth holding member 7, and is held by the member 5. The remaining fourth B lens group G4B of the lens group GR is held by a substantially cylindrical fifth holding member 11.

  The first holding member 3 is fixed to the annular first sliding member 17 by the first screw 13 and the second screw 15, and the second holding member 5 is fixed to the annular second sliding member 19 for the third holding The member 39 is fixed to the annular third sliding member 43, the fourth holding member 7 is fixed to the annular fourth sliding member 23 by the fourth screw 21, and the fifth holding member 11 is also the annular fourth sliding member. It is fixed to the moving member 23.

  The lens system of the variable focal length lens 37 of the third embodiment is housed inside a cylindrical fixed tube 29 and a cylindrical cam tube 31 that is rotatably fitted in the fixed tube 29. Cam pins (not shown) are provided on the outer peripheral edges of the first sliding member 17, the second sliding member 19, the third sliding member 43, and the fourth sliding member 23. These cam pins are cams. A cam groove (not shown) formed in the cylinder 31 is engaged. By rotating the cam cylinder 31 with respect to the fixed cylinder 29 by a mechanism (not shown), the first sliding member 17, the second sliding member 19, the third sliding member 43, and the fourth sliding member 23 are used as the optical axis. It can be moved back and forth along.

  A mount member 33 is fixed to the fixed cylinder 29, and the fixed cylinder 29 is fixed to an imaging device such as a camera (not shown) via the mount member 33. The iris diaphragm S is opened and closed by a diaphragm mechanism 35 fixed to the third sliding member 43.

  Since the structure for fixing the first holding member 3 to the first sliding member 17 is the same as that of the first embodiment, the same reference numerals are shown in FIG. By this method, the inclination of the first holding member 3 with respect to the first sliding member 17 can be adjusted and fixed. That is, it is possible to adjust the position of tilting the first lens group G1 with respect to the optical axis.

  Since the structure for fixing the fourth holding member 7 to the fourth sliding member 23 is the same as that of the second embodiment, the same reference numerals are shown in FIG. By this method, the fourth holding member 7 can be moved and fixed to the fourth sliding member 23 in the direction perpendicular to the optical axis. That is, it is possible to adjust the position by shifting the 4A lens group G4A with respect to the optical axis.

  Table 4 below lists corresponding values of the conditional expressions (1) to (3) and the conditional expressions (10) to (12) in the variable focal length lens 37 according to the third example.

  In the third example, MAt is a composite imaging magnification of the second lens group G2, the central lens group GM, and the rear lens group GR in the telephoto end state, and MAw is the second lens group G2 and the central lens in the wide-angle end state. The combined imaging magnification of the group GM and the rear lens group GR, MBt is the imaging magnification of a part of the fourth B lens group G4B of the rear lens group GR in the telephoto end state, and MBw is one of the rear lens group GR in the wide angle end state. The image forming magnification of the fourth B lens group G4B, M1t is the combined image forming magnification of the second lens group G2, the central lens group GM and the rear lens group GR in the telephoto end state, and M1w is the second lens group in the wide angle end state G2 is a combined image forming magnification of the central lens group GM and the rear lens group GR, M4At is an image forming magnification of a part of the fourth B lens group G4B of the rear lens group GR in the telephoto end state, M4Aw Is a magnification of the part of the 4B lens group G4B the rear lens group GR in the wide-angle end state.

(Table 4)
(Values for conditional expressions)
(1) MAt / MAw = 15.70
(2) MBt / MBw = 0.927
(3) (MAt / MAw) / (MBt / MBw) = 16.94
(10) M1t / M1w = 15.70
(11) M4At / M4Aw = 0.927
(12) (M1t / M1w) / (M4At / M4Aw) = 16.94

  FIG. 13 shows correction of imaging performance by performing position adjustment for decentering the first lens group and position adjustment for shifting and decentering part of the 4A lens group in the rear lens group when there is an eccentricity error during manufacturing. The coma aberration figure with respect to d line | wire (wavelength (lambda) = 587.6nm) in the infinite point focusing state of the variable focal-length lens which concerns on 3rd Example at the time of doing is shown, (a) is a wide-angle end state, (b) is Intermediate focal length state, (c) shows the telephoto end state.

  Comparing the aberration diagrams of FIGS. 2, 3, and 13, it can be seen that in FIG. 13, the deterioration of the imaging performance due to the decentration error at the time of manufacture is well corrected from the wide-angle end state to the telephoto end state.

(Fourth embodiment)
Next, a variable focal length lens adjusting mechanism according to the fourth embodiment will be described. In the fourth embodiment, in order to satisfactorily correct deterioration in imaging performance due to decentration error during manufacturing, adjustment is performed to adjust the position where the second lens group G2 is tilted and to adjust the position where the rear lens group GR is shifted. It has a mechanism. Parts having the same structure as those of the first embodiment and the second embodiment will be described using the same reference numerals, or the same reference numerals are shown in the drawings and description thereof is omitted.

  FIG. 14 is a sectional view showing the mechanism of the variable focal length lens according to the fourth embodiment.

  As shown in FIG. 14, in the variable focal length lens 49 according to the fourth example, the first lens group G1 is held by a substantially cylindrical first holding member 51, and the second lens group G2 is a substantially cylindrical first lens. 2, the central lens group GM is held by a substantially cylindrical third holding member 39, and the rear lens group GR is held by an annular fourth holding member 41.

  The first holding member 51 is fixed to the annular first sliding member 55, the second holding member 53 is fixed to the annular second sliding member 57, and the third holding member 39 is the annular third sliding member 43. The fourth holding member 41 is fixed to the annular fourth sliding member 47 by the third screw 45.

  The lens system of the variable focal length lens 49 of the fourth embodiment is housed inside a cylindrical fixed tube 29 and a cylindrical cam tube 31 that is rotatably fitted in the fixed tube 29. Cam pins (not shown) are provided on the outer peripheral edges of the first sliding member 55, the second sliding member 57, the third sliding member 43, and the fourth sliding member 47, respectively. A cam groove (not shown) formed in the cylinder 31 is engaged. By rotating the cam cylinder 31 with respect to the fixed cylinder 29 by a mechanism (not shown), the first sliding member 55, the second sliding member 57, the third sliding member 43, and the fourth sliding member 47 are used as the optical axis. It can be moved back and forth along.

  A mount member 33 is fixed to the fixed cylinder 29, and the fixed cylinder 29 is fixed to an imaging device such as a camera (not shown) via the mount member 33. The iris diaphragm S is opened and closed by a diaphragm mechanism 35 fixed to the third sliding member 43.

  Since the structure of the second sliding member 57 is the same as that of the second embodiment, the same reference numerals are shown in FIG. 14 and the description thereof will be omitted. However, as with the second embodiment, by tightening or loosening the immobilizer 59, The inclination of the second holding member 53 held by the annular portion 57a with respect to the cam pin 57d (see FIG. 9 of the second embodiment) can be adjusted and fixed. In other words, it is possible to adjust the position of tilting the second lens group G2 with respect to the optical axis.

  Since the structure for fixing the fourth holding member 41 to the fourth sliding member 47 is the same as that of the first embodiment, the same reference numerals are shown in FIG. By this method, the fourth holding member 41 can be moved and fixed to the fourth sliding member 47 in the direction perpendicular to the optical axis. That is, it is possible to adjust the position by shifting the rear lens group GR with respect to the optical axis.

  Table 5 below lists corresponding values of the conditional expressions (1) to (3) and the conditional expressions (13) to (15) in the variable focal length lens 49 according to the fourth example.

  In the fourth embodiment, MAt is a composite image magnification of the central lens group GM and the rear lens group GR in the telephoto end state, and MAw is a composite image formation of the central lens group GM and the rear lens group GR in the wide-angle end state. Magnification, since there is no lens group between the rear lens group GR and the image plane I, MBt = MBw = 1.0, M2t is a composite imaging magnification of the central lens group GM and the rear lens group GR in the telephoto end state, M2w is a composite imaging magnification of the central lens group GM and the rear lens group GR in the wide-angle end state, and M4t = M4w = 1.0 because there is no lens group between the rear lens group GR and the image plane I.

(Table 5)
(Values for conditional expressions)
(1) MAt / MAw = 2.85
(2) MBt / MBw = 1.000
(3) (MAt / MAw) / (MBt / MBw) = 2.85
(13) M2t / M2w = 2.85
(14) M4t / M4w = 1.000
(15) (M2t / M2w) / (M4t / M4w) = 2.85

  FIG. 15 shows a fourth embodiment in which imaging performance is corrected by performing position adjustment for tilt decentering of the second lens group and position adjustment for shift decentering of the rear lens group when there is an eccentricity error during manufacturing. The coma aberration figure with respect to d line | wire (wavelength (lambda) = 587.6nm) in the infinite point focusing state of such a variable focal length lens is shown, (a) is a wide angle end state, (b) is an intermediate | middle focal length state, (c). Indicates the telephoto end state.

  Comparing the aberration diagrams of FIGS. 2, 3, and 15, it can be seen that in FIG. 15, the deterioration of the imaging performance due to the decentration error at the time of manufacture is well corrected from the wide-angle end state to the telephoto end state.

  The variable focal length lens according to the present embodiment performs position adjustment for tilt decentering a part of the front lens group and position adjustment for shifting decentering a part or all of the rear lens group. In addition to this, it is also possible to perform a position adjustment that shifts and decenters some lens groups of the central lens group. By decentering a part of the central lens group, it is possible to achieve better correction of decentration aberrations. In particular, the central lens group is composed of a 3A lens group having a positive refractive power, a 3B lens group having a negative refractive power, and a 3C lens group having a negative refractive power in order from the object side, and a 3C lens. It is desirable to perform a position adjustment that shifts and decenters the group. By shifting and decentering the third C lens group, better correction of decentration aberration can be realized.

  Further, the variable focal length lens according to the present embodiment performs position adjustment for tilt decentering a part of the front lens group and position adjustment for shifting decentering a part or all of the rear lens group. In addition to this, it is also possible to perform a position adjustment that tilts and decenters some lens groups of the central lens group. By decentering a part of the central lens group, tilt aberration can be corrected more satisfactorily. In particular, the central lens group is composed of a 3A lens group having a positive refractive power, a 3B lens group having a negative refractive power, and a 3C lens group having a negative refractive power in order from the object side. It is desirable to perform a position adjustment for decentering the group, and by further decentering the third B lens group, it is possible to achieve better correction of decentration aberrations.

  As described above, according to this embodiment, it is possible to provide a low-cost variable focal length lens that can achieve good optical performance and an adjustment method thereof. Furthermore, in a variable focal length lens having a large zoom ratio, good optical performance can be achieved over the entire variable focal length from the wide-angle end state to the telephoto end state.

  Next, a camera equipped with the variable focal length lens according to the present embodiment will be described. Although the case where the variable focal length lens 1 according to the first embodiment is mounted will be described, the same applies to other embodiments.

  FIG. 16 is a diagram illustrating a configuration of a camera including the variable focal length lens according to the first example.

  In FIG. 16, a camera 63 is a digital single-lens reflex camera provided with the variable focal length lens 1 according to the first embodiment as a photographing lens. In the camera 63, light from an object (subject) (not shown) is collected by the taking lens 1 and focused on the focusing screen 67 through the quick return mirror 65. The light imaged on the focusing screen 67 is reflected a plurality of times in the pentaprism 69 and guided to the eyepiece lens 71. Thus, the photographer can observe the subject image as an erect image through the eyepiece lens 71.

  When the release button (not shown) is pressed by the photographer, the quick return mirror 65 is retracted out of the optical path, and light from the subject (not shown) reaches the image sensor 73. As a result, light from the subject is picked up by the image sensor 73 and recorded as a subject image in a memory (not shown). In this way, the photographer can shoot the subject with the camera 63.

  By mounting the variable focal length lens 1 according to the first embodiment as a photographing lens on the camera 63, a camera having high performance can be realized.

  In addition, in order to explain the present invention in an easy-to-understand manner, the configuration requirements of the embodiment have been described, but the present invention is not limited to this.

GF Front lens group S Iris stop GM Central lens group GR Rear lens group G1 First lens group G2 Second lens group G3A Third A lens group G3B Third B lens group G3C Third C lens group G4A Fourth A lens group G4B Fourth B lens group I Image plane 1 Variable focal length lens 13 First screw 15 Second screw 21 Fourth screw 45 Third screw 59 Immobilis 63 Camera

Claims (4)

In order from the object side , the first lens group having a positive refractive power and the second lens group having a negative refractive power are composed of a front lens group having a negative refractive power as a whole, a central lens group having a positive refractive power, and a positive refractive power. It consists essentially of four lens groups depending on the rear lens group,
An air gap between the first lens group and the second lens group in the front lens group, an air gap between the front lens group and the central lens group, and an air gap between the central lens group and the rear lens group. By changing the focal length,
The rear lens group includes, in order from the object side, a 4A lens group having a positive refractive power and a 4B lens group.
After the assembly of the forward lens group and the central lens group and the rear lens group, an adjusting mechanism for adjusting the position of Ru is tilted decentered the second lenses group, position adjustment for shifting eccentrically the first 4A lens group an adjustment mechanism to perform possess, respectively,
A variable focal length lens characterized by satisfying the following conditions .
2.0 <M2t / M2w
M4At / M4Aw <2.0
2.5 <(M2t / M2w) / (M4At / M4Aw)
However,
M2t: Composite imaging magnification of all the lens groups positioned between the second lens group and the image plane in the telephoto end state of the variable focal length lens
M2w: Composite imaging magnification of all the lens groups positioned between the second lens group and the image plane in the wide-angle end state of the variable focal length lens
M4At: Composite imaging magnification of all the lens units located between the fourth A lens unit and the image plane in the telephoto end state of the variable focal length lens
M4Aw: Composite imaging magnification of all lens groups positioned between the fourth A lens group and the image plane in the wide-angle end state of the variable focal length lens Upon zooming from the wide Kakutan state to the telephoto end state, the air gap of the second lens group and the third lens group is expanded, the air interval between the second lens the middle lens group and group is reduced, the The variable focal length lens according to claim 1, wherein an air space between the central lens group and the rear lens group is reduced. Optical apparatus characterized by having a variable focal length lens according to any one of claims 1 or 2. In order from the object side , the first lens group having a positive refractive power and the second lens group having a negative refractive power are composed of a front lens group having a negative refractive power as a whole, a central lens group having a positive refractive power, and a positive refractive power. It consists essentially of four lens groups depending on the rear lens group,
The rear lens group includes, in order from the object side, a 4A lens group having a positive refractive power and a 4B lens group.
An air gap between the first lens group and the second lens group in the front lens group, an air gap between the front lens group and the central lens group, and an air gap between the central lens group and the rear lens group. the Rukoto varied a method for adjusting the variable focal length lens to change the focal length,
So that the following conditional expression is satisfied,
After the assembly of the forward lens group and the central lens group and the rear lens group, an adjusting mechanism for adjusting the position of Ru is tilted decentered the second lenses group, position adjustment for shifting eccentrically the first 4A lens group An adjustment method for a variable focal length lens, characterized in that an adjustment mechanism for performing each is performed.
2.0 <M2t / M2w
M4At / M4Aw <2.0
2.5 <(M2t / M2w) / (M4At / M4Aw)
However,
M2t: Composite imaging magnification of all the lens groups positioned between the second lens group and the image plane in the telephoto end state of the variable focal length lens
M2w: Composite imaging magnification of all the lens groups positioned between the second lens group and the image plane in the wide-angle end state of the variable focal length lens
M4At: Composite imaging magnification of all the lens units located between the fourth A lens unit and the image plane in the telephoto end state of the variable focal length lens
M4Aw: Composite imaging magnification of all lens groups positioned between the fourth A lens group and the image plane in the wide-angle end state of the variable focal length lens

Images