JP4626231B2 - Lens barrel - Google Patents

Description

  The present invention relates to an inner focus (internal focus) type zoom lens barrel used for a camera or the like.

An example of a method for correcting a change in focus position during a zoom operation in an inner focus type zoom lens barrel is disclosed in Patent Document 1.
In the zoom lens disclosed in Patent Document 1, first, a plurality of focus curves are selected from different focus curves depending on the focal length of the zoom lens, and are continuously approximated so as to be within the depth of focus under a certain condition. A representative zoom focus curve is created by superimposing them. Then, a zoom correction curve for correcting the position of the focus lens on the optical axis when the zoom operation is performed along the zoom focus curve is created, and the focus operation and the zoom operation are performed using the two curves. This controls the amount of movement of the focus lens when
In the zoom lens disclosed in Patent Document 1, as shown in FIGS. 9 and 10 of Patent Document 1, a pin fixed to the focus lens frame is rotated to rotate the pin inside the zoom (magnification) focus cam. Moves and moves the focus lens back and forth to perform the focus operation.

  In the zoom lens disclosed in Patent Document 1 described above, a cam mechanism is used for driving the focus. However, if the close-up possible shooting distance is shortened with a high-power zoom lens having a zoom ratio of 5 times or more, the focus is reduced. As the lens feed amount increases, the maximum tilt angle of the focus cam (the maximum pressure angle of the cam) increases. For example, when trying to realize a close distance of 0.5 m or less with a zoom lens having a zoom ratio exceeding 10 times, the maximum tilt angle of the zoom focus cam is 72 in the configuration similar to that of the zoom lens disclosed in Patent Document 1. More than °.

However, in a configuration similar to that of the zoom lens disclosed in Patent Document 1, for example, when the friction coefficient is calculated as 0.2, if the maximum tilt angle of the zoom focus cam is 67 ° or more, the pin may be moved even if the cam is moved. There was a problem that would stop working. If the maximum tilt angle of the zoom focus cam is larger than the limit angle (67 ° in the above example), it becomes impossible to follow the pin along the cam no matter how great force is applied.
Therefore, a zoom lens with a short close distance that can be photographed at a high magnification such that the maximum tilt angle of the zoom focus cam is 72 ° or more cannot be realized by the technique disclosed in Patent Document 1. It was.
In addition, even if the above problem is solved by reducing the friction coefficient, it becomes possible to increase the width of the zooming focus cam in the optical axis direction, and the size of the lens barrel cannot be increased. It was.
JP-A-3-235908

An object of the present invention, there is provided a compact while facilitating the focus operation is that minimum shooting distance to provide a short high-magnification lenses barrel.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to the Example of this invention is attached | subjected and demonstrated, it is not limited to this.
The invention of claim 1 has a lens frame contactor (11a ), holds a focus lens (16) which is a part of the photographing optical system, and in the optical axis direction of the photographing optical system in accordance with a focus operation and a zoom operation. focus lens frame (11), and the rectilinear groove is formed along the optical axis direction to engage with the lens frame contacts (13b), the zoom ring contact to move the fixed cylinder relative to (12) along the (13a), a zoom ring (13) that engages with the fixed barrel so as to move along the optical axis direction while receiving a rotational driving force during zoom operation , and the imaging optical system has a straight groove formed along the optical axis (15a), a focus key to rotate about the optical axis during focusing operation (15), the engaging portion of the straight groove and the engagement of the focus key (20c ) and the zoom ring contact A first zoom focus cam portion which engages with the (20a), and a zoom focus ring (20) and a second zoom focus cam portion which engages with the lens frame contacts (20b), said first The combined movement amount obtained by combining the first movement amount determined by one zoom focus cam portion and the second movement amount determined by the second zoom focus cam portion is a zoom focus cam curve that determines the position of the focus lens frame. The zoom ring contactor moves the zoom ring contactor over the entire range in which the zoom ring contactor can move by engaging with the first zoom focus cam part during zoom operation and focus operation. The more the zoom ring contact is moved along the first direction around the axis, the more the zoom ring contact moves to the object side with respect to the zoom focus ring. And the lens frame contact is moved along the first direction in the entire range in which the lens frame contact engages with the second zoom focus cam portion during the focusing operation. The contact is a lens barrel that moves toward the image plane with respect to the zoom focus ring.
A second aspect of the present invention is the lens barrel according to the first aspect, wherein the zoom ring contact (13a) is engaged with the first zoom focus cam portion (20a) during a zoom operation and a focus operation. The angle around the optical axis that can be rotated together is such that the lens frame contactor engages with the second zoom focus cam portion (20b) during the zoom operation and the focus operation and rotates around the optical axis. This is a lens barrel characterized by being substantially equal to the angle.
The invention according to claim 3 is the lens barrel according to claim 1 or 2, wherein the first zoom focus cam portion (20a) and the second zoom focus cam portion (20b) are: It is a lens barrel formed on the same cylindrical surface of the zoom focus ring (20).

A fourth aspect of the present invention is the lens barrel according to any one of the first to third aspects, wherein the first zoom focus cam portion (20a) and the second zoom focus cam are provided. part (20b) are lenses mirrors, characterized in that it is a cam profile which gives a moving amount of the moving amount given by the zoom focus cam curve bisected in accordance with the rotation angle of the zoom focus ring (20) It is a cylinder.
A fifth aspect of the present invention is the lens barrel according to any one of the first to fourth aspects, wherein the first zoom focus cam portion (20a) and the second zoom focus cam are provided. The portion (20b) is a lens barrel characterized by cam grooves connected to each other.
A sixth aspect of the present invention is the lens barrel according to any one of the first to fourth aspects, wherein the first zoom focus cam portion (20a) and the second zoom focus cam are provided. the part (20b), the circumferential position of the zoom focus ring (20) on is a lenses barrel, characterized in that you are disposed offset from one another.
A seventh aspect of the present invention is the lens barrel according to any one of the first to sixth aspects, wherein the focus lens frame (11) rotates around the optical axis during a focusing operation. a lenses barrel and without features that you move in a direction along the optical axis.

According to the present invention, the following effects can be obtained.
(1) The zoom ring contactor moves along the first direction around the optical axis in the entire range in which the zoom ring contactor can engage and move with the first zoom focus cam portion during zoom operation and focus operation. As the zoom ring contact is moved, the zoom ring contact moves toward the object side with respect to the zoom focus ring, and the lens frame contact engages with the second zoom focus cam portion during the zoom operation and the focus operation. As the lens frame contact is moved along the first direction, the lens frame contact moves toward the image plane with respect to the zoom focus ring, so that the maximum tilt angle of the cam can be reduced, and the high magnification Even if the zoom lens barrel has a short close-up distance that can be photographed with the lens, it can be driven reliably and the required driving force can be reduced.

(2) The first zoom focus cam portion and the second zoom focus cam portion have cam shapes that give a movement amount obtained by dividing the movement amount given by the zoom focus cam curve into two equal parts according to the rotation angle of the zoom focus ring. As a result, the cam inclination angle can be evenly distributed and the required driving force can be minimized.

(3) Since the first zoom focus cam portion and the second zoom focus cam portion are arranged so that their circumferential positions on the zoom focus ring are shifted from each other, they are arranged in the optical axis direction of the zoom focus ring. The width can be reduced, and the zoom lens barrel can be reduced in size.

(4) Since the focus lens frame moves in the direction along the optical axis without rotating around the optical axis during the focusing operation, the optical axis can be prevented from shifting even if the focus lens is decentered. In particular, even in the focusing operation at the telephoto end where the optical axis is likely to be shifted due to abrupt driving, it is possible to minimize degradation of imaging performance and image shake.

  The objective of providing a zoom lens barrel that has a short close-up distance and a high magnification is realized by providing a plurality of cam portions that determine the amount of movement of the focus lens frame, thereby facilitating the focusing operation and reducing the size.

FIG. 1 is a diagram showing a main part of a zoom lens barrel according to a first embodiment of the present invention. FIG. 1A is an expanded view of the focus driving of the zoom lens barrel, and FIG. 1B shows an A1-A2 cross section shown in FIG. FIG. 1 shows a case where the zoom position is at the wide-angle end (Wide) and the focus position is close.
The zoom lens barrel in the first embodiment includes a focus lens frame 11, a fixed barrel 12, a zoom ring 13, a focus key 15, a zoom focus ring 20, and the like, and is an interchangeable lens that is detachable from a camera body (not shown). is there. In addition, the zoom lens barrel in this embodiment employs an inner focus method (inner focus method) in which the focus state does not change by a zoom operation.

  The focus lens frame 11 is a member that holds a focus lens 16 that is a focusing optical system, and is provided with a pin 11a. The focus lens frame 11 is provided with a pin 11a which is a lens frame contact that engages with a later-described second zoom focus cam portion 20b and a rectilinear groove 13b.

  The fixed cylinder 12 is a member that is integrally fixed to a mount portion (not shown) connected to the camera body, and does not move by any of the focus operation and the zoom operation, and the base of the zoom lens barrel. It is the member which becomes. The fixed cylinder 12 is formed with a focus correction cam 12a.

  The zoom ring 13 is a member that rotates in response to a rotational driving force generated when a photographer rotates a zoom operation member (not shown) during a zoom operation. The zoom ring 13 includes a pin 13a that is a zoom ring contact that engages with a first zoom focus cam portion 20a described later, a rectilinear groove 13b that extends in a direction along the optical axis of the photographing optical system, and a focus. A pin 13c that engages with the correction cam 12a is provided.

The focus key 15 is a member that rotates around the optical axis in response to a rotation operation of a photographer or a rotation drive force from a focus drive source (not shown) during a focus operation. The focus key 15 is formed with a rectilinear groove 15a extending along the optical axis direction, and a pin 20c is engaged with the rectilinear groove 15a.
The focus lens 16 is a lens that constitutes a middle group or a rear group of a photographing optical system (not shown), and is a focusing optical system that moves along the optical axis direction during a focusing operation to change the focal position.

  The zoom focus ring 20 includes a first zoom focus cam portion 20a that engages with the pin 13a, a second zoom focus cam portion 20b that engages with the pin 11a, and a pin 20c that engages with the rectilinear groove 15a. have. The first zoom focus cam portion 20a and the second zoom focus cam portion 20b are symmetrical with respect to a plane orthogonal to the optical axis.

FIG. 2 shows one zoom focus cam curve optimized from the photographing optical system used in the first embodiment.
The zoom focus cam curve is calculated so that the position of the focus lens frame 11 is determined so that the relationship between the rotation angle of the focus key 15 and the subject distance is the same at any focal distance during the focus operation. In the zoom focus cam curve shown in FIG. 2, it is necessary to move the focus lens by 15 mm in the optical axis direction by rotating the frame member forming the cam according to this curve by about 130 °. Since the maximum tilt angle of the focus cam is 72 °, which is larger than the limit angle 67 ° described above, it is expected that the focus operation becomes difficult.

Therefore, in this embodiment, the movement amount corresponding to the movement amount given by the zoom focus cam curve is equally divided into two parts, the first zoom focus cam part 20a and the second zoom focus cam part 20b. Formed in ring 20.
FIG. 3 is a diagram illustrating the cam shapes of the first zoom focus cam portion 20a and the second zoom focus cam portion 20b.

In FIG. 3, a curve K1 indicated by a solid line is a cam curve obtained from the zoom focus cam curve shown in FIG. 2, and a curve K2 indicated by a two-dot chain line indicates the first zoom focus cam portion 20a, the second curve K2. This is a cam curve of the zoom focus cam portion 20b. The curve K2 is set so that the movement amount is ½ of the curve K1 with respect to the same amount of rotation angle. Therefore, the combined movement amount obtained by combining the first movement amount determined by the first zoom focus cam portion 20a and the second movement amount determined by the second zoom focus cam portion 20b is in a predetermined focus state during the focusing operation. The amount of movement is such that the position of the focus lens frame 11 is determined so that the rotation angle of the focus key 15 (zoom focus ring 20) that causes a change is substantially the same rotation angle at any focal length.
In this embodiment, by doing so, the focus lens frame 11 can be reliably driven with a light driving force by securing the necessary amount of movement and setting the maximum inclination angle of the cam to 32 °. I can do it.

Next, the operation of the focus lens frame 11 in the zoom lens barrel according to the first embodiment will be described.
FIG. 4 is a diagram illustrating operations during zooming and focusing according to the first embodiment. FIG. 4A shows a case where the zoom position is the wide-angle end (Wide) and the focus position is close, and FIG. 4B is a view where the zoom position is the telephoto end (Tele) and the focus position is close. FIG. 4C shows a case where the zoom position is at the telephoto end (Tele) and the focus position is infinite (∞). FIG. 4A shows the same state as FIG.

First, as a zoom operation, a case will be described in which the zoom ring 13 is moved to the telephoto side (downward in FIG. 4) from the state of FIG. 4 (a) to the state of FIG. 4 (b). . In this case, due to the engagement relationship between the pin 13a and the focus correction cam 12a, the zoom ring 13 moves toward the subject along the optical axis while rotating.
Then, since the zoom focus ring 20 is restricted in rotation by the focus key 15 and the pin 13a and the first zoom focus cam portion 20a are engaged, the zoom focus ring 20 has the first zoom focus cam portion. The first moving amount determined by 20a and the corrected moving amount determined by the focus correction cam 12a are moved along the optical axis direction by a combined moving amount. In this embodiment, the movement component due to the first movement amount is movement toward the main body, the movement component due to the correction movement amount is movement toward the subject side, and the zoom focus ring 20 moves toward the subject side. .

  On the other hand, the focus lens frame 11 is rotationally driven by the rotation of the zoom ring 13 because the pin 11a is engaged with the rectilinear groove 13b. Since the pin 11a is also engaged with the second zoom focus cam portion 20b, the focus lens frame 11 is determined by the second zoom focus cam portion 20b with the zoom focus ring 20 as a reference while rotating. It moves along the optical axis direction by a movement amount of 2. Here, as described above, since the zoom focus ring 20 is moved along the optical axis direction by the movement amount obtained by combining the first movement amount and the correction movement amount, the focus lens frame 11 is a fixed frame. Taking 12 as a reference, the movement is made by the first movement amount + second movement amount + correction movement amount.

  In this example, the movement component due to the first movement amount is movement toward the main body side, the movement component due to the correction movement amount is movement toward the subject side, and the movement component due to the first movement amount toward the main body side. Is a move. Since the movement component due to the corrected movement amount is larger than the sum of the other movement components (see FIG. 4), the focus lens frame 11 moves to the subject side, but the first movement amount and the second movement amount are combined. The moving component corresponds to the moving amount determined by the zoom focus cam curve shown in FIGS.

Next, as a focus operation, from the state of FIG. 4B, the focus key 15 rotates around the optical axis in response to a photographer's operation or a rotational drive force from a focus drive source (not shown), and is infinite from the closest side. A case in which the state moves to the side (upward in FIG. 4) and becomes the state of FIG. 4 (c) will be described. In this case, since the pin 20c is engaged with the rectilinear groove 15a, the rotational driving force is transmitted to the zoom focus ring 20. Since the first zoom focus cam portion 20a and the pin 13a are engaged and the zoom ring 13 does not rotate during the focus operation, the zoom focus ring 20 is moved in the first movement determined by the first zoom focus cam portion 20a. Move while rotating toward the camera body by the amount.
In addition, since the second zoom focus cam portion 20b is engaged with the pin 11a and is guided straight by the straight advance groove 13b, the focus lens frame 11 is moved by the rotation of the zoom focus ring 20 with the zoom focus ring 20 as a reference. The second movement amount determined by the second zoom focus cam portion 20b (in this embodiment, the first movement amount = the second movement amount) is moved.

Here, as described above, the zoom focus ring 20 moves while rotating to the camera body side by the first movement amount determined by the first zoom focus cam portion 20a. Then, it moves in the direction along the optical axis by the amount of movement obtained by combining the first movement amount and the second movement amount without rotating around the optical axis. The combined movement amount obtained by combining the first movement amount and the second movement amount corresponds to the movement amount determined by the zoom focus cam curve shown in FIGS.
It should be noted that the first and second movement amounts in the focus operation are described above because the positions of the first zoom focus cam portion 20a and the second zoom focus cam portion 20b are different from those in the zoom operation. This is a value different from the first and second movement amounts during the zoom operation.

  According to the present embodiment, the two zoom cams, the first zoom focus cam portion 20a and the second zoom focus cam portion 20b, perform an operation corresponding to a zoom focus cam curve that has been conventionally formed by one cam. Therefore, even in a zoom lens barrel having a short close-up shooting distance and a high magnification, the relationship between the rotation angle of the zoom focus ring 20 and the subject distance is substantially the same at any focal length, and the focusing operation is performed. It can be done easily.

FIG. 5 is a diagram showing a main part of a second embodiment of the zoom lens barrel according to the present invention. FIG. 2A shows an expanded view of the focus driving of the zoom lens barrel, and FIG. 2B shows a B1-B2 cross section shown in FIG.
In this embodiment, the arrangement of the first zoom focus cam portion 20a and the second zoom focus cam portion 20b in the first embodiment is improved, and the first zoom focus cam portion 220a, the second zoom focus cam portion 220b, Since only the point which was done differs from Example 1, the part which performs the same function as Example 1 mentioned above attaches | subjects the same code | symbol, and abbreviate | omits the overlapping description suitably.

In the zoom focus ring 220, a first zoom focus cam portion 220a and a second zoom focus cam portion 220b are arranged with their circumferential positions shifted from each other. Accordingly, the zoom focus ring 220 can be narrower in the optical axis direction than the zoom focus ring 20 in the first embodiment.
As in this embodiment, when the first zoom focus cam portion 220a and the second zoom focus cam portion 220b are arranged so that the positions in the circumferential direction are shifted, the movement of one zoom focus cam curve is performed. By dividing the amount into two equal parts, the first zoom focus cam unit 220a and the second zoom focus cam unit 220b can be efficiently arranged on the zoom focus ring 220, and a compact zoom lens barrel is obtained. be able to.

The functions and the like of the first zoom focus cam unit 220a and the second zoom focus cam unit 220b are the same as those of the first zoom focus cam unit 20a and the second zoom focus cam unit 20b in the first embodiment. .
According to the present embodiment, the zoom lens barrel can be made smaller while exhibiting the same effects as the first embodiment.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the equivalent scope of the present invention.
For example, in each embodiment, the first zoom focus cam portion (20a, 220a) and the second zoom focus cam portion (20b, 220b) divide the movement amount of one zoom focus cam curve into two equal parts. Although the example which is a shape was shown, it is not restricted to this, For example, you may change the ratio to divide | segment appropriately, such as 3 to 7.

  In each embodiment, the zoom lens barrel is an interchangeable lens. However, the present invention is not limited to this. For example, the zoom lens barrel may be a non-replaceable zoom lens barrel.

It is a figure which shows the principal part of Example 1 of the zoom lens barrel by this invention. FIG. 3 is a single zoom focus cam curve calculated from the photographing optical system used in Embodiment 1 and optimized. FIG. It is a figure explaining the cam shape of the 1st zoom focus cam part 20a and the 2nd zoom focus cam part 20b. FIG. 6 is a diagram illustrating operations during zooming and focusing according to the first exemplary embodiment. It is a figure which shows the principal part of Example 2 of the zoom lens barrel by this invention.

Explanation of symbols

11 focus lens frame 11a pin 12 fixed cylinder 12a focus correction cam 13 zoom ring 13a pin 13b rectilinear groove 15 focus key 15a rectilinear groove 16 focus lens 20 zoom focus ring 20a first zoom focus cam section 20b second zoom focus cam section 20c pin

Claims (7)

A focus lens frame that has a lens frame contact , holds a focus lens that is a part of the photographic optical system, and moves relative to a fixed cylinder along the optical axis direction of the photographic optical system in accordance with a focus operation and a zoom operation When,
A linear groove formed along the optical axis direction and engaged with the lens frame contactor, and a zoom ring contactor , along the optical axis direction while rotating by receiving a rotational driving force during a zoom operation. A zoom ring that engages the fixed barrel to move;
A focus key having a rectilinear groove formed along the optical axis direction of the photographing optical system, and rotating around the optical axis during a focusing operation;
An engaging portion for rectilinear groove engage with the focus key, and a first zoom focus cam portion for engagement with the zoom ring contact, and a second zoom focus cam portion which engages with the lens frame contacts and a zoom focus ring having,
The combined movement amount obtained by combining the first movement amount determined by the first zoom focus cam portion and the second movement amount determined by the second zoom focus cam portion is a zoom focus that determines the position of the focus lens frame. It corresponds to the movement amount given by the cam curve ,
The zoom ring contactor is moved along the first direction around the optical axis in the entire range in which the zoom ring contactor can move by engaging with the first zoom focus cam part during zoom operation and focus operation. The more the zoom ring contact is moved, the more the zoom ring contact moves to the object side with respect to the zoom focus ring,
When the lens frame contactor is moved along the first direction in the entire range in which the lens frame contactor can move by engaging with the second zoom focus cam part during zoom operation and focus operation, The lens barrel according to claim 1, wherein the lens frame contact moves toward the image plane with respect to the zoom focus ring.   The lens barrel according to claim 1,
  The angle around the optical axis at which the zoom ring contactor can rotate by engaging with the first zoom focus cam unit during zoom operation and focus operation is such that the lens frame contactor can rotate during zoom operation and focus operation. A lens barrel characterized by being substantially equal to an angle around the optical axis that can be rotated by engaging with the second zoom focus cam portion.   The lens barrel according to claim 1 or 2, wherein
  The lens barrel characterized in that the first zoom focus cam portion and the second zoom focus cam portion are formed on the same cylindrical surface of the zoom focus ring. A lens barrel according to any one of claims 1 to 3, wherein
The first zoom focus cam portion and the second zoom focus cam portion each have a cam shape that gives a movement amount obtained by dividing the movement amount given by the zoom focus cam curve into two equal parts according to the rotation angle of the zoom focus ring. A lens barrel characterized by that.   A lens barrel according to any one of claims 1 to 4, wherein
  The lens barrel according to claim 1, wherein the first zoom focus cam portion and the second zoom focus cam portion are cam grooves connected to each other. A lens barrel according to any one of claims 1 to 4, wherein
The lens barrel according to claim 1, wherein the first zoom focus cam portion and the second zoom focus cam portion are arranged such that their circumferential positions on the zoom focus ring are shifted from each other . A lens barrel according to any one of claims 1 to 6, wherein
The lens barrel, wherein the focus lens frame moves in a direction along the optical axis without rotating around the optical axis during a focusing operation .

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