JP3514245B2 - Zoom lens barrel - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens barrel, and more particularly to a zoom lens barrel for manually changing a focal length.

[0002]

2. Description of the Related Art Generally, there is a zoom lens as a photographic lens whose focal length can be changed. With a normal zoom lens, the position of the image plane does not change even if the focal length changes, so once you focus on the subject,
Focusing is not possible even if zooming operation is performed in that state, but in a so-called varifocal lens, the position of the image changes as the focal length changes, so it is necessary to focus each time zooming is performed.

By the way, in the varifocal lens, the lens barrel can be easily made compact and the shortest shooting distance can be easily shortened as compared with the zoom lens. It is also advantageous in terms of weight reduction. However, since the drive amount of the focus lens varies depending on the focal length, a structure corresponding to such an operation is required, and if there is no focus control function, interference will occur between the focus lens unit and other members. Will end up.

As a method of avoiding the interference between the focus lens unit and other members as described above, it is known to provide a mechanical stopper that limits the movement amount of the focus lens according to the change of the focal length. However, this mechanical stopper has a complicated structure, leading to an increase in the number of parts and an increase in cost.

A mechanism having the same effect as a mechanical stopper is also known, in which the cam groove for changing the focal length and the cam groove for adjusting the focus are constructed in accordance with predetermined conditions. However, the structure is also a complicated structure, and the above-mentioned predetermined conditions are severely restricted, which is a great restriction in optical design.

Further, it is also known to provide an electric stopper which detects an electric signal indicating focal length information and electrically controls the moving amount of the focus lens based on the electric signal. In this mechanism, the focal length changing means may be electric or manual. In the case of electric driving, it is generally difficult to finely control the focal length, which is unsuitable for severe framing, and a large amount of electric power is required for electric driving, which greatly restricts the entire camera system. Further, in the case of manual operation, there is no problem as in the case of electric operation, but interference occurs in an uncontrollable state such as when the power of the camera is off. Further, even if it is in a controllable state, if the focal length changing operation is performed at a very high speed, the focus adjustment control may not be able to follow, and interference may occur. This problem could be avoided by using a very powerful arithmetic system and a drive actuator, but it is obvious that the disadvantage is large in terms of cost and size.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in order to effectively solve the above-mentioned conventional technical problems. Therefore, an object of the present invention is a zoom lens barrel for manually changing the focal length, which prevents the focus lens from interfering with its adjacent members when the focus lens moves at high speed as described above. , The structure of the zoom lens barrel that can be prevented by a simple mechanical structure without using a complicated structure such as a mechanical stopper in the varifocal lens and without using an electric method such as an electric stopper. To provide.

[0008]

A zoom lens barrel according to the present invention has a varifocal type zoom having the following structure in order to solve the above-mentioned problems in the prior art and to achieve the object. It is a lens barrel. That is, a zoom optical system in which the focal length is manually changed, a focus optical system that is focus driven in the zoom optical system, a focus optical system holding member that holds the focus optical system and is movable, and the focus optical system. A first drive member for zoom-driving the zoom optical system and the focus optical system by a manual operation while holding the optical system holding member, and a focus drive for the focus optical system holding member provided on the first drive member. The focus drive amount of the focus optical system holding member differs depending on the focal length changed in the zoom optical system, and the focus movement of the focus optical system depends on the changed focal length. A varifocal type zoom lens in which other peripheral members of the above focus optical system exist within the range. In the lens barrel, the focusing optical
Provided between the system holding member and the first drive member,
The focus optical system holding member and the first driving member are used as an optical axis.
By urging them so that they are separated in the direction,
Rattling when the optical system holding member moves during focusing
Is absorbed, and the
When the focus optical system holding member moves, the peripheral members
The focus optical system holding member is attached to the contact surface provided on the
Holds the focus optical system in the direction in which it abuts and opposes the bias.
Focus movement based on the focal length by moving the member
Absorbs interference that occurs with the above-mentioned peripheral members due to the difference in amount.
A biasing member is provided.

[0009]

The second driving member is provided with a screw feed mechanism for screwing the focus optical system holding member along the optical axis, and the biasing direction of the biasing member is the driving direction of the screw feeding mechanism. It is preferable that the direction is to absorb the rattling.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a zoom lens barrel according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing a zoom lens barrel 10 according to the present invention in a wide-angle state. 2 shows the movement paths of the optical lenses in the lens barrel of FIG. 1. The upper part of the figure shows the state of each optical lens at wide angle, and the lower part of the figure shows the state of each optical lens at telephoto. Is shown. In the illustrated example, the optical system is composed of five components, a first group to a fifth group. In FIG. 1, 11 is a first group, 12 is a second group, 13
Is a third lens group, 14 is a fourth lens group, and 15 is a fifth lens group. Further, 21 is the first group, 22 is the second group.
Group, 23a and 23b are the third group, 24 is the fourth group, 25
Indicates the respective lens frames of the fifth group.

A zoom operation ring 16 is provided on the outermost front surface of the lens barrel 10. When the zoom operation ring 16 is rotated from the wide-angle state of FIG. 1, each lens group moves from the upper state of FIG. 2 to the lower state toward the telephoto side. First lens group 11, third lens group 13 and fourth lens group 14
Moves to the subject side by the respective movement amounts, and the second lens group 12 moves to the image plane side. The fifth lens group 15 is composed of one lens and is a fixed lens. In FIG. 1, reference numeral 17 denotes a zoom cam ring, and when the zoom operation ring 16 is rotated, the zoom cam ring 17 also rotates. 18 is a fixed cylinder. The zoom cam ring 17 is formed with a spiral cam groove (not shown) that guides the movement of each lens frame, and the fixed barrel 18 is formed with a linear guide groove. When the zoom operation ring 16 is rotated, the zoom cam ring 1
7 also rotates and the first group lens frame 21, the second group lens frame 22 and the third group lens frame 23 are guided by the cam groove and the straight guide groove, and as shown in FIG. Move to. The fourth group lens frame 24 is connected to the zoom cam ring 17 via the fourth group zoom moving frame 19, and is connected to the cam groove of the zoom cam ring 17, the straight guide groove of the fixed barrel 18, and the fourth group.
By being guided by the group zoom moving frame 19, it moves in the optical axis direction together with the fourth group zoom moving frame 19. These structures are conventionally adopted.

As described above, each movable lens group zooms for the purpose of changing the focal length in the zoom operation, but only the fourth lens group 14 needs to be driven for the purpose of focus adjustment. It is for this reason that the fourth group lens frame 24 is connected to the zoom cam ring 17 via the fourth group zoom moving frame 19 as described above.
The fourth group zoom moving frame 19 is driven independently (focus drive).

When the fourth lens group frame 24 is driven to focus, the fourth lens group frame 2 is used when the shooting distance approaches the near side with the position of the fourth lens group frame 24 corresponding to an infinite shooting distance as a reference.
4 is driven toward the image plane side. The drive amount changes when the focal length is different even if the shooting distance is the same, and the change is continuous, and the drive amount is small on the wide angle side and needs to be large on the telephoto side. In FIG. 2, the left line A showing the movement of the fourth lens group 14 shows the change in the driving amount when the shooting distance is infinity, and the right line B shows that the shooting distance is 0.
The change in the driving amount in the case of 5 m is shown.

FIG. 3 is a view showing the schematic arrangement of the fourth group focus drive section 20, showing a state in which the subject distance at telephoto is infinity. Focus drive motor 2
6 is fixed to the fourth group zoom moving frame 19 with screws 27. The focus drive motor 26 is connected to a circuit on the camera body side by a flexible printed circuit board (not shown), and is electrically controlled. Fourth group ball frame 24
Is the spring 2 mounted between the fourth group zoom moving frame 19 and
It is urged by 8 in the image plane direction (rightward in the figure).

FIG. 4 is a view showing a schematic structure of the fourth group of focus drive units 20 in the state of FIG. 3 at a sectional position different from that of FIG. 3 (for convenience of explanation, a central angle is appropriately set around the optical axis. It is shown in a closed position). However, although the focus driving motor 26 is at the same position as in FIG. 3, it is depicted to show the output shaft of the motor in FIG. 4, and FIG. 3 shows a screw fastening portion for the fourth group zoom moving frame 19. It is a description for. The output shaft 29 of the focus drive motor 26 is extended, a screw is formed on the outer peripheral surface of the output shaft 29, and a nut 30 is screwed into the screw. A pin 31 is provided on the nut 30 so as to project radially outward. The pin 31 of the nut 30 has its tip end fitted in a groove 32 formed along the optical axis direction in the fourth group lens frame 24, and the fourth group lens frame is attached to the end surface of the nut 30 on the object side. The image-side end surface of 24 is in contact. Nut 30
Has the pin 31 and the groove 32 fitted together, the motor 2
Even if the output shaft 29 of No. 6 rotates, it is restricted from rotating with it, but it is guided and moved in the direction in which the groove 32 extends in accordance with the screw pitch of the output shaft 29 and the nut 30. That is, the fourth group zoom moving frame 19 is driven by the screw feeding mechanism.

Two guide shafts 33 and 34 (only 33 is shown) which are parallel to the optical axis are fixed to the fourth group zoom moving frame 19, and the fourth group lens frame 24 is extendedly fitted therein. Since the portion 35 is fitted, the movement of the fourth group lens frame 24 in the optical axis direction is guided, but the rotation around the optical axis is restricted.

FIG. 5 shows the fourth group of focus drive units 20.
Is shown in a state in which the subject distance at the time of telephoto is 0.5 m. The upper half of the optical axis is shown at the same sectional position as in FIG. 4, and the lower half of the optical axis is shown at the sectional position passing through a guide shaft 34 different from the guide shaft shown in FIG. The fourth group frame 24,
From the state where the subject distance is infinite as shown in FIG. 4, the object is moving toward the image plane side (to the right in the drawing) with respect to the fourth group zoom moving frame 19.

FIG. 6 shows the focus driving unit 20 of the fourth group in the state of FIG. 5 at a sectional position different from that of FIG. 5 (the upper half of the optical axis is shown at the same sectional position as FIG. (The lower half of the shaft is shown at a cross-sectional position passing through the guide shaft 33 shown in FIG. 4)
It is a figure.

When only the focal length is changed from the telephoto state to the wide-angle state of FIG. 5 or 6, if the focus drive is properly controlled, the state of FIG. If the focal length changing operation is performed in an uncontrollable state such as when the power is turned off, or even if the control operation can be performed, the focal length changing operation can be performed manually at a very high speed. When an operation is performed, the focus control operation cannot follow up.
FIG. 7 shows this state, and the fourth group zoom movement frame 19
And the motor 26 are moving toward the image side at high speed.
The group lens frame 24 is only urged toward the image side by the spring 28 shown in FIG. 3, and the image plane side end of the extension fitting portion 35 of the fourth group lens frame 24 is the fifth group lens. It contacts the frame 25, that is, it interferes with the fifth group. The nut 30 cannot return to the position shown in FIG. 4, or the follow-up operation is in a state where it cannot catch up, but if the control operation starts when the power of the camera is turned on, or the control operation starts after a while. Catches up with the situation shown in FIG. In this way, the interference is absorbed by the nut 30 moving away from the image-side end surface of the fourth lens group frame 24 by the stroke in which the interference has occurred. When absorbing this interference, it is preferable that the surfaces where the fourth group and the fifth group contact each other are not the lens surfaces but the surfaces of the structural parts as shown in FIG. 7.
By making it possible to absorb the interference in this way, it is not necessary to increase the movable distance of the fourth lens unit, and it is possible to reduce the size of the lens barrel even with a zoom lens in which the focal length is changed manually.

In the above-mentioned example, the case where the fourth group and the fifth group interfere with each other has been described. In short, the fourth group, which is focus-driven, is within the movable range and is adjacent to the fourth group. It will be easily understood by those skilled in the art that, if it is a member (for example, other member configuration such as a shelter), the same action and effect can be obtained by providing the interference absorbing means between the member and the member.

[Brief description of drawings]

FIG. 1 is a sectional view showing a lens barrel according to the present invention.

FIG. 2 is a diagram showing a movement path of each optical lens in the lens barrel of FIG.

FIG. 3 is a diagram showing a schematic configuration of a focus driving unit of a fourth group, showing a state in which the subject distance is infinity at the time of telephoto.

FIG. 4 is a diagram showing the fourth group of focus drive units in the state of FIG. 3 at a sectional position different from that in FIG. 3;

FIG. 5 is a diagram showing a schematic configuration of a focus driving unit of a fourth group, showing a state in the case of a telephoto state and a subject distance of 0.5 m.

6 is a view showing the fourth group of focus drive units in the state of FIG. 5 at a sectional position different from that in FIG.

FIG. 7: The focal length changing operation is performed when the camera is turned off and cannot be controlled, or the focal length changing operation is manually performed at an extremely high speed, and the focus control operation cannot follow up. FIG.

[Explanation of symbols]

10 lens barrel 11 First lens group 12 Second lens group 13 Third lens group 14 4th lens group 15 5th lens group 16 Zoom operation ring 17 Zoom cam ring 18 Fixed tube 19 Fourth group zoom movement frame 20 4th group focus drive section 21 First Ball Frame 22 Second ball frame 23 Third Ball Frame 24 Fourth Ball Frame 25 5th frame 26 Focus drive motor 27 screws 28 spring 29 Output shaft 30 nuts 31 pin 32 grooves 33 Guide shaft 34 Guide shaft 35 Extension fitting part of 4th lens group frame

─────────────────────────────────────────────────── --- Continued from the front page (56) References JP-A-4-345116 (JP, A) JP-A-9-203849 (JP, A) JP-A-2002-296480 (JP, A) JP-A-2-89012 (JP, A) Actual development 2-107115 (JP, U) Actual development 4-50810 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 7/02-7 / Ten

Claims (2)

(57) [Claims] 1. A zoom optical system in which a focal length is manually changed, a focus optical system which is focus driven in the zoom optical system, and a focus optical system holding member which holds the focus optical system and is movable. A first drive member for driving the zoom optical system and the focus optical system to zoom by a manual operation while holding the focus optical system holding member; and the focus optical system holding member provided on the first drive member. And a second drive member for focus-driving, and the focus drive amount of the focus optical system holding member is
Depending on the focal length changed in the zoom optical system, depending on the changed focal length, a varifocal type zoom lens in which other peripheral members of the focus optical system exist within the focus movable range of the focus optical system. In the lens barrel, the focus optical system holding member and the first driving member
Is provided between the focus optical system holding member and the first
(1) biasing the driving member so as to separate it from the driving member in the optical axis direction.
And the focusing optical system holding member is focused.
Absorb rattling when moving, and also by manual operation
The focus optical system holding member moves along with the zoom drive
The focus on the contact surface provided on the peripheral member.
The optical system holding member comes in contact with the above-mentioned flap in the direction opposite to the bias.
By moving the focus optical system holding member,
Due to the difference in focus drive amount due to
A zoom lens barrel including a biasing member for absorbing generated interference . 2. The second drive member comprises a screw feed mechanism for screwing the focus optical system holding member along the optical axis, and the urging direction of the urging member is the screw feed mechanism. 2. A direction for absorbing rattling in the driving direction.
The zoom lens barrel described.