JPH1152209A - Lens driving device and optical equipment provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize zooming and focusing mechanisms by which focus moving amount at the time of zooming is kept in allowable range with simple structure by driving a lens along the synthetic line of three cam curves at the time of zooming. SOLUTION: When an operation ring for focusing is operated to be rotated, a focus pin 5 moves in an optical axis direction along both a key cam 4a and a focus cam 2b, that is, by the synthetic action of the key cam 4a and the focus cam 2b in a 6th lens group. When an operation ring for zooming is operated to be rotated, a zoom cam barrel 3 rotates and a focus cam barrel 2 is rotated in the same direction through a coupling pin 2a. At such a time, the cam barrel 2 moves in the optical axis direction by the fitting action of a correction cam 2c with a fixed pin 1a, and the 6th lens group moves in the optical axis direction by the fitting action of the focus cam 2b with the focus pin 5. Namely, the synthetic action of the focus cam 2b, the correction cam 2c and the key cam 4a exerts on the 6th lens groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device for driving a lens in a direction of an optical axis by a cam. The present invention relates to a lens driving device employing an inner focus method.

[0002] The present invention relates to a zooming and focusing mechanism of a zoom lens suitable for a single-lens reflex camera or a still camera, for example, which has a compact lens system and enables quick focusing.

[0003]

2. Description of the Related Art As a focus system of a zoom lens in a single-lens reflex camera or the like, a so-called front lens focus system in which focusing is performed by a first lens unit is generally used. In this method, the extension amount of the focus lens for the same object distance is constant regardless of the zoom position.
There is an advantage that the lens barrel structure can be simplified. However, when used in a high-magnification zoom lens, it is necessary to increase the outer diameter of the front lens in order to secure the peripheral light amount at the time of short-distance shooting, which has the disadvantage of hindering the miniaturization of the lens system. .

[0004] As other focus methods, a rear focus method and an inner focus method have been proposed. These methods have the advantage that a zoom lens and a focus lens can be configured to be relatively small and lightweight, so that when used in an autofocus camera, quick focusing becomes possible, and that the entire lens system can be downsized. There are advantages. However, in these focus methods, even when focusing on a specific object, in many cases, when zooming is performed, a focus movement occurs because the focus lens on the optical axis has a different position on the optical axis at each zoom position. For this reason, there is a disadvantage that the focus must be adjusted by moving the position of the focus lens in accordance with zooming.

Japanese Patent Application Laid-Open No. 58-202416 discloses a paraxial arrangement in which the amount of movement of a focus lens is optically constant over the entire zoom range, and corrects focus movement due to zooming. Zoom lenses have been proposed. However, in the method proposed in this publication, the restriction on the paraxial refractive power arrangement is severe, so that the size of the entire lens system tends to be increased.

In this respect, the focus method proposed in Japanese Patent Application Laid-Open No. 3-235908 prepares two cams, a focus cam and a correction cam, for moving the focus lens, and focuses on an arbitrary object distance. When zooming from a state in which the camera is in a moving state, the focus movement is corrected by moving on a curve synthesized by the focus cam and the correction cam. In this method, since the focus movement due to zooming is mechanically corrected, the degree of freedom of optically paraxial arrangement is increased optically, and downsizing of the lens system can be achieved.

Also, Japanese Patent Application Laid-Open Nos. Hei 2-2560011, Hei 4-293008, Hei 5-142475
JP, JP-A-6-175023 and JP-A-6-175023
Japanese Patent Publication No. -180423 and the like all propose a method of mechanically correcting a focus movement due to zooming.

[0008]

However, JP-A-3-235908, JP-A-2-256011, JP-A-4-293008 and JP-A-5-1
The method proposed in Japanese Patent No. 42475 corrects focus movement due to zooming using two cam curves, and it is difficult to keep the amount of focus movement during zooming within an allowable range depending on an optical system. There are cases.

[0009] Further, in the systems proposed in Japanese Patent Application Laid-Open Nos. 6-175023 and 6-180423,
This is to correct the focus movement due to zooming by using two cam curves for a so-called floating focus for moving a plurality of lens groups during focusing, and there is a problem that the structure tends to be complicated.

Therefore, the present invention is particularly suitable for a zoom lens in which the amount of movement for focusing of the focus lens for the same object distance differs depending on the focal length, and the amount of focus movement during zooming is simple with a simple structure. It is an object of the present invention to provide a lens driving device capable of realizing a zooming and focusing mechanism that can be accommodated.

[0011]

In order to achieve the above object, according to the present invention, in a lens driving device for driving a lens in the direction of an optical axis, especially when zooming, the above lens is used.
By driving by the combined action of two cams, that is, along the combined line of the three cam curves, compared to driving by the combined action of two cams (along the combined line of the two cam curves) Defocusing during zooming can be corrected better, and the amount of focus movement during zooming can be kept within an allowable amount with a relatively simple structure.

Specifically, when an amount proportional to the rotation angle of the lens driving operation means is a parameter p and a position of the lens in the optical axis direction is a parameter x, a first function g (p) represented by a function g (p) is given. A cam curve, a second cam curve represented by a function gz (p), and a third cam curve represented by a function k (x) are set. Where Δf is the variation of the parameter P and Δz is the variation of the parameter P from the wide-angle end to the telephoto end, the lens driving device is configured to satisfy the following condition: 0.5 <| Δf / Δz | <2. ing.

The above-described invention is suitable for a rear focus or inner focus type zoom lens in which the amount of movement of the lens for focusing on the same object distance differs depending on the focal length.

In the above invention, it is preferable that the lens is monotonously driven to one of the object side and the image side during zooming so that the focus movement during zooming can be corrected well.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) (Numerical Example 1) FIGS. 1 and 2 show a zoom lens (optical apparatus) according to a first embodiment of the present invention.
FIG. 1 shows a cross section of each lens at the wide-angle end,
FIG. 2 shows the locus of movement of each lens group during zooming from the wide-angle end to the telephoto end. The first to sixth lens units I to VI used in this embodiment are made corresponding to Numerical Example 1 shown in FIG.

In Numerical Example 1, ri (1,
2, 3 ...) are the radii of curvature of the i-th lens surface from the object side, di is the i-th lens thickness or air gap from the object side, and ni and vi are the refractive index and Abbe number of the i-th lens. is there. A, b, c, d,... Are aspherical coefficients,
The shape of the aspheric surface was such that the traveling direction of light was positive, the height perpendicular to the optical axis was Y, and the length parallel to the optical axis from the optical axis center of the lens surface to the lens surface was X. When

[0017]

(Equation 1)

## EQU1 ##

In FIGS. 1 and 2, S is a stop and SP is a flare cut stop. The flare-cut aperture moves toward the object side during zooming while changing the aperture.

In this embodiment, as shown in FIG. 2, during zooming from the wide-angle end to the telephoto end, the first to sixth lens units I to VI are each provided with a zoom operation member (not shown).
Moves in a non-linear manner to the object side with respect to the rotation amount of the third lens group III and the fifth lens group V move integrally.

Focusing from the object distance infinity to the close distance is performed by moving the sixth lens group VI to the image side. In the present embodiment, the moving amount for focusing to the same object distance changes depending on the focal length. FIG. 6 shows the amount of movement of each lens group at an object distance of infinity.

Next, a lens driving mechanism (lens driving device) for performing focusing driving and zooming driving of the sixth lens group VI will be described.

FIG. 3 schematically shows the structure of the lens driving mechanism in a side view. In this figure, the sixth lens group VI moves in the optical axis direction during zooming and during focusing. FIG. 4 shows the lens driving mechanism in a developed state in plan view.

In these figures, 1 is a fixed cylinder,
Reference numeral 2 denotes a focus cam cylinder that can move in the optical axis direction and rotate around the optical axis. The focus cam cylinder 2 is formed with a focus cam 2b having a cam curve g and a correction cam 2c having a cam curve gz. A focus pin 5 formed on a lens holding frame that moves in the optical axis direction integrally with the sixth lens group VI is fitted to the focus cam 2b, and formed on the fixed barrel 1 to the correction cam 2c. The fixed pin 1a is fitted.

Reference numeral 3 denotes a zoom cam barrel which is rotatable around the optical axis toward the tele (T) side and the wide (W) side at a fixed position in the optical axis direction in accordance with a rotation operation of a zoom operation ring (not shown). The zoom cam barrel 3 has a linear guide groove 3a extending in the optical axis direction.
Are formed. A connecting pin 2a formed on the focus cam barrel 2 is fitted into the straight guide groove 3a.

Reference numeral 4 denotes a focus key which is rotatable around the optical axis at infinity (∞) and the closest side at a fixed position in the optical axis direction in accordance with a rotation operation of a focus operation ring (not shown).
A key cam 4a having a cam curve k is formed on the focus key 4, and the focus pin 5 fitted on the focus cam 2b is fitted on the key cam 4a as described above.

In the lens driving mechanism configured as described above, when the focus operation ring is rotated to perform focusing at an arbitrary zoom position, the focus key 5 is rotated accordingly (at this time, the focus operation is performed). The cam cylinder 2 is in a fixed state). Thus, the focus pin 5 (the sixth lens group VI) moves along both the key cam 4a and the focus cam 2b, that is, the key cam 4a.
The focus cam 2b moves in the optical axis direction due to the combined action. In other words, the sixth lens group VI moves along a curve (composite line) connecting the intersections of the two cam curves g and k.

Next, a case where zooming is performed from a state in which an object is focused on an arbitrary object distance will be described. When the zoom operation ring is rotated, the zoom cam barrel 3 is rotated accordingly (at this time, the focus key 4 is in a fixed state).
The rotation of the zoom cam barrel 3 is transmitted to the focus cam barrel 2 via the connecting pin 2a, and rotates the same in the same direction. At this time, the focus cam cylinder 2 moves in the optical axis direction due to the fitting action between the correction cam 2c and the fixed pin 1a. Then, when the focus cam barrel 2 moves in the optical axis direction, the sixth group lens group VI moves in the optical axis direction due to the fitting action between the focus cam 2b and the focus pin 5. That is,
During zooming, the sixth lens group VI moves in the optical axis direction due to the combined action of the focus cam 2b, the correction cam 2c, and the key cam 4a. In other words, the sixth lens group VI is a curve obtained by adding another cam curve gz to a curve connecting the intersections of the two cam curves g and k (synthetic line).
Move along.

In the present embodiment, the sixth lens group VI moves monotonously to the object side or the image side along the key cam 4a during zooming, so that the focus movement during zooming can be corrected well.

In this embodiment, the focus movement by zooming is set to a practically acceptable size.
The cam curve g of the focus cam 2b, the cam curve gz of the correction cam 2c, and the cam curve k of the key cam 4a are calculated.

FIG. 7 shows the sixth lens unit at each focal length and each object distance based on the position of the sixth lens unit VI at the wide-angle end and at object infinity calculated from the paraxial arrangement of the optical system.
The position of the VI in the optical axis direction is shown, and the sign is positive in the traveling direction of light. A cam curve g for realizing this movement,
gz, k is an amount proportional to the rotation angle of the zoom operation ring and the focus operation ring as a parameter p.
When the position of the VI in the optical axis direction is a parameter x, g (p) = a1 × p + a2 × p ² +... Gz (p) = b1 × p + b2 × p ² +... K (x) = c1 × x + c2 × x ² It is represented by the function + ...

Here, the parameter p is based on the assumption that the object is infinite at the wide angle end and the rotation angle of the zoom operation member from the wide angle end to the telephoto end is normalized to one. The parameter x is the sixth lens group VI when the reference is at the wide-angle end and the object is infinite.
In the figure, the sign indicates that the traveling direction of light is positive. Further, k (x) is a quantity of the same dimension as the parameter p.

In the above function, a1, a2, b1,
, c1, c2... are coefficients, and specific numerical values are shown in FIG.
Shown in FIG. 9 shows the amount of movement at each focal length and each object distance of the sixth lens group VI along the composite line of the three cam curves. Further, FIG. 10 shows the parameter p, the focal length, and the amount of defocus at the time of zooming of each lens group at each object distance.

In the present embodiment, the following conditional expression (1) is satisfied in order to more favorably correct the amount of defocus.

0.5 <| Δf / Δz | <2 (1) (where, Δf is a change amount of the parameter P from an infinite object to a close object, and Δz is a change amount of the parameter P from a wide-angle end to a telephoto end. Here, if the lower limit value of the above conditional expression is exceeded, the ratio of the focus amount to the shift amount at the time of zooming decreases, and the operating point of the cam greatly changes due to the zooming. And the amount of defocus tends to increase. If the upper limit is exceeded, the deployed length of the focus cam 2a becomes longer, and the focus cylinder 2
It is difficult to form a cam groove on the surface.

(Numerical Embodiment 2) FIGS. 11A and 11B show the first to sixth lens units I to VI corresponding to Numerical Embodiment 2 shown in FIG.
4 shows a cross section of each lens at the wide-angle end when the image is formed, and a movement locus of each lens group during zooming from the wide-angle end to the telephoto end.

FIG. 13 shows the amount of movement of each lens unit at infinity of the object distance. FIG. 14 shows the sixth lens unit at the wide-angle end and at object infinity calculated from the paraxial arrangement of the optical system. The optical axis direction position of the sixth lens group VI at each focal length and each object distance with reference to the position of VI is shown. FIG. 15 shows the amount of movement at each focal length and each object distance of the sixth lens group VI along the composite line of the three cam curves. FIG. 16 shows a parameter p at each object distance.
And the focal length and the amount of defocus during zooming of each lens unit.

In this embodiment, the case where the focus lens is only the sixth lens group VI has been described.
The present invention is also effective when there are a plurality of focus lenses, that is, in a floating focus type zoom lens. Further, it is also possible to partially change the cam curve in the present embodiment and to configure a cam for macro photographing while ignoring a focus shift during zooming.

[0039]

As described above, according to the present invention,
Since the lens is driven by the combined action of the three cams, that is, along the combined line of the three cam curves, especially when the amount of lens movement for focusing at the same object distance is different, the two Compared to the case of driving by the combined action of cams (along the combined line of the two cam curves),
Defocusing during zooming can be better corrected, and the amount of focus movement during zooming can be kept within an allowable range with a relatively simple structure.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens (Numerical Example 1) at a wide-angle end according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a paraxial arrangement of the zoom lens and a movement locus of each group lens when zooming from a wide-angle end to a telephoto end.

FIG. 3 is a schematic sectional view of a lens driving mechanism of the zoom lens.

FIG. 4 is a schematic development plan view of the lens driving mechanism.

FIG. 5 is a table showing specific numerical values of Numerical Example 1;

FIG. 6 is a table showing movement amounts of each group lens in the zoom lens during zooming.

FIG. 7 is a table showing the amount of movement of the sixth lens group calculated from the paraxial arrangement of the optical system at each focal length and each object distance in the zoom lens.

FIG. 8 is a table showing a focus cam curve coefficient, a correction cam curve coefficient, and a focus key curve coefficient in the lens driving mechanism.

FIG. 9 is a table showing the amount of movement of a sixth lens group combined by a cam at each focal length and each object distance in the zoom lens.

FIG. 10 is a table showing the amount of defocus during zooming in the zoom lens.

FIG. 11 is a schematic diagram illustrating a cross-sectional view of a zoom lens (numerical example 2) according to the first embodiment at a wide-angle end and a movement locus of each lens group when zooming from the wide-angle end to a telephoto end. FIG.

FIG. 12 is a table showing specific numerical values of Numerical Example 2;

FIG. 13 is a table showing the amount of movement of each group lens during zooming in the zoom lens (Numerical Example 2).

FIG. 14 is a table showing the amount of movement of the sixth lens group calculated from the paraxial arrangement of the optical system at each focal length and each object distance in the zoom lens (Numerical Example 2).

FIG. 15 is a view showing a sixth example obtained by combining a cam at each focal length and each object distance in the zoom lens (Numerical embodiment 2).
FIG. 5 is a table showing the amount of movement of a group lens.

FIG. 16 is a table showing the amount of defocus during zooming in the zoom lens (Numerical Example 2).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed cylinder 2 Focus cam cylinder 2b Focus cam 2c Correction cam 3 Zoom cam cylinder 4 Focus key 4a Focus key cam 5 Focus pin I-VI 1st-6th lens

Claims (9)

[Claims] 1. A lens driving device for driving a lens in an optical axis direction, wherein the lens is driven by a combining action of three cams. 2. The zoom lens according to claim 1, wherein said lens is driven by a combining action of said three cams during zooming, and said lens is driven by a combining action of two of said three cams during focusing. The lens driving device as described in the above. 3. The lens driving device according to claim 1, wherein an amount of movement of the lens for focusing on the same object distance differs depending on a focal length. 4. The lens driving device according to claim 1, wherein said lens is monotonously driven to one of an object side and an image side during zooming. 5. A lens driving device for driving a lens in an optical axis direction, wherein the lens is driven along a composite line of three cam curves. 6. The method of driving the lens along a composite line of the three cam curves during zooming, and driving the lens along a composite line of two of the three cam curves during focusing. The lens driving device according to claim 5, wherein 7. The lens driving device according to claim 5, wherein an amount of movement of the lens for focusing on the same object distance differs depending on a focal length. 8. The lens driving device according to claim 5, wherein the lens is monotonously driven to one of an object side and an image side during zooming. 9. A first cam curve represented by a function g (p), where an amount proportional to the rotation angle of the lens driving operation means is a parameter p and a position of the lens in the optical axis direction is a parameter x. And a second cam curve represented by a function gz (p) and a third cam curve represented by a function k (x), wherein the parameter P changes from an object at infinity to a close object. The condition of 0.5 <| Δf / Δz | <2 is satisfied when the amount is Δf and the amount of change of the parameter P from the wide-angle end to the telephoto end is Δz. The lens driving device according to any one of the above.