JPH06130269A - Zoom lens barrel - Google Patents

Abstract

PURPOSE:To simplify the constitution of a lens group moving means which accurately realizes the linear and the non-linear movement of respective lens barrels and to facilitate plastic molding. CONSTITUTION:Plural lens groups G1 and G2 constituting a zoom lens system are disposed in a helicoid barrel 3 which is rotatable with respect to a fixed barrel 2 and the frame bodies 4 and 5 of the respective lens groups are screwed to an identical helicoid screw 3a formed on the inside circumferential surface of the barrel 3. Besides, respective straight advance guiding members 6 and 9 regulating the rotation of the frame bodies 4 and 5 of the respective lens groups around an optical axis are disposed and the frame body guiding parts 6b and 9b of the guiding members 6 and 9 are extended in parallel with the optical axis. By rotating the respective guiding members 6 and 9 around the optical axis as much as prescribed quantity, the moving quantity of the respective lens groups by the rotation of the barrel 3 is increased or decreased and the respective lens groups are moved to a focusing position and a variable power position.

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 for moving a lens group for focusing on the object side and a lens group moving with zooming by the same helicoid screw.

[0002]

2. Description of the Related Art Conventionally, a zoom lens barrel for mechanically changing the position of each lens unit constituting a lens system to adjust the magnification and focal position is provided with a plurality of cam grooves having different movement characteristics. The "cam barrel method" using a rotating cam barrel and the "helicoid method" utilizing a helicoid screw have been generally known. This has the advantage that the former cam cylinder method can relatively easily realize the non-linear movement of the lens group, and the latter helicoid method has the advantage that it can realize stable lens movement with a simple configuration. It is because each of them is used a lot.

[0003]

However, each of the above methods has various problems as described below. That is,
With the “cam barrel method”, when the cam barrel is manufactured by machining such as cutting, it takes a considerable amount of processing time, which inevitably leads to higher costs. When a cam barrel is manufactured by plastic molding, the wall surface (working surface) of the cam groove with which the cam pin slides is formed so as to include the normal line to the optical axis of photography, and moreover, it covers the area of the cam barrel outer circumference with a relatively large arc angle. Because it is formed
The wall surface constitutes an undercut portion for the core, and the mold structure is complicated. Since the cam barrel is arranged outside the lens frame, the outer diameter of the lens barrel becomes large, which in turn causes the camera body to become large. Further, in the "helicoid system", when two types of helicoid cylinders are used, one helicoid cylinder must be arranged outside the other, and the lens barrel becomes larger in diameter than the cam cylinder system. When a cam groove for nonlinearly moving the lens frame is formed in a proper place on the inner surface of the helicoid cylinder, it is difficult to mold the helicoid cylinder with plastic, and it is impossible to realize a large amount of nonlinear movement.

In view of the above, the present invention has been made to solve the above problems and provides a lens group moving means which is simple in construction, easy in plastic molding, and capable of realizing linear and non-linear movement of each lens barrel with high accuracy. An object is to provide a zoom lens barrel having the same.

[0005]

To achieve the above object, the lens barrel of the present invention has a plurality of lens groups constituting a zoom lens system in a helicoid cylinder rotatable with respect to a fixed barrel. Then, the frame body of each lens group is screwed into the same helicoid screw formed on the inner peripheral surface of the helicoid cylinder, and each straight line for restricting rotation of the frame body of each lens group around the photographing optical axis is advanced. A guide member is provided, a frame guide portion of the linear guide member extends in parallel with the photographing optical axis, and the frame of each lens group rotates around the photographing optical axis as the linear guide member rotates. Thus, the moving amount of each lens group in the photographing optical axis direction due to the rotation of the helicoid cylinder is increased or decreased, and each lens group is moved to the focal position and the variable power position.

Further, in the above construction, when the helicoid cylinder is stopped at a certain zoom position, the straight guide member of the lens group for adjusting the focal position of the lens group rotates around the photographing optical axis, and the helicoid is moved. It is characterized in that the helicoid female screw formed on the inner peripheral surface of the cylinder is used to move the focus position adjusting lens group back and forth in the optical axis direction to move to the focus position.

Further, a linear guide member for moving the lens group to the zoom magnification changing position is arranged so that the rotational force around the photographing optical axis is transmitted by the tangent screw, and the groove shape of the arm portion of the tangent screw is provided. Is formed into a predetermined curve, and the lens group is moved along the optical axis by rotation of the rectilinear guide member around the photographing optical axis.

[0008]

[Operation] Therefore, the zoom lens barrel of the present invention is
A helicoid cylinder rotating on the inner circumference of the fixed barrel guides a plurality of lens groups to a linear guide member to move them linearly, and the linear guide members move the lens groups in a non-linear manner to adjust the focus position and perform zooming. It can be moved.

[0009]

Embodiments of the zoom lens barrel of the present invention will be described below.
An embodiment of a zoom lens barrel having a two-group type zoom optical system will be described with reference to the accompanying drawings. FIG. 1 shows an embodiment of the present invention, and is a longitudinal sectional view of an essential part showing a zoom lens barrel in a state where each lens unit is arranged at a long focal position.
FIG. 2 is a longitudinal sectional view of an essential part showing the zoom lens barrel in a state of being similarly arranged at the short focus position, and FIG. 3 is a view taken along the line III-III in FIG.

In the figure, a lens barrel 1 includes a front lens group G1 and a rear lens group G2 which move relative to each other on an optical axis.
It is equipped with a two-group type zoom optical system. The front lens group G1 of this zoom optical system is a linear lens group that moves based on a unique linear characteristic diagram during a zooming operation, and the rear lens group G2 forms a unit with the front lens group G1 according to a unique nonlinear characteristic diagram. It is a non-linear lens group that moves within a predetermined range while changing the relative distance. The rear portion of the fixed barrel 2 of the lens barrel 1, that is, the right end portion in FIGS. 1 and 2 is fixed to the body of the camera body. A helicoid cylinder 3 is rotatably provided in the fixed barrel 2. The helicoid cylinder 3 is formed with a helicoid female screw 3a on the inner peripheral surface thereof and a zoom drive gear 3b on the rear portion thereof, that is, on the outer periphery of the right end portion in FIGS.

Helicoid female screw 3 of the helicoid cylinder 3
a is a first lens frame body 4 that holds the front lens group G1.
And the second lens frame body 5 that holds the rear lens group G2 are screwed together by a helicoid. The helicoid male screws 4a and 5a formed on the outer peripheries of the first lens frame body 4 and the second lens frame body 5 and screwed into the helicoid female screw 3a have the same pitch.

The first linear guide member 6 for restricting the rotation of the first lens frame 4 around the optical axis for normal photographing and moving only in the optical axis direction is a ring-shaped base 6a surrounding the first lens frame 4. And a frame body guide portion 6b which is connected to the ring-shaped base portion 6a and extends parallel to the photographing optical axis. The ring-shaped base portion 6a of the first rectilinear guide member 6 is rotatably held on the inner surface of the fixed barrel 2 at the front portion of the helicoid cylinder 3 so as to be rotatable about the photographing optical axis, and the frame body guide portion 6b is the first lens. Frame 4
After engaging with the rectilinear guide hole 4b formed in the outer peripheral portion of the second lens frame body 5, it penetrates through the escape hole 5b formed in the outer peripheral portion of the second lens frame body 5. With this configuration, the first lens frame body 4 is
It rotates integrally with the linear guide member 6 and can move in the optical axis direction by the relative difference between this rotation speed and the rotation speed of the helicoid cylinder 3. It should be noted that a straight guide pin may be used instead of the straight guide hole.

Further, spur teeth 6c are formed on a part of the outer peripheral portion of the ring-shaped base portion 6a of the first rectilinear guide member 6, and the spur teeth 6c are provided on the outside of the lens barrel 1 for focusing. It meshes with the focus gear 8 of the drive motor 7.

The second rectilinear guide member 9 for restricting the rotation of the second lens frame body 5 around the optical axis of the normal photographing and moving it only in the optical axis direction is a ring-shaped member positioned behind the second lens frame body 5. It has a base portion 9a and a frame body guiding portion 9b that is connected to the ring-shaped base portion 9a and extends parallel to the photographing optical axis. Second
The ring-shaped base portion 9a of the linear guide member 9 is provided in the helicoid cylinder 3
The frame body guide portion 9b is rotatably held around the photographing optical axis in an attachment portion on the inner surface of the fixed barrel 2 in the rear portion, and the frame body guide portion 9b is engaged with a rectilinear guide hole 5c formed in the outer peripheral portion of the second lens frame body 5. After that, the escape hole 4c formed in the outer peripheral portion of the first lens frame 4
Penetrates through. With this configuration, the second lens frame body 5
Rotates integrally with the second linear guide member 9 and can move in the optical axis direction by the relative difference between this rotation speed and the rotation speed of the helicoid cylinder 3.

An arm 9c is extended to the ring-shaped base portion 9a of the second rectilinear guide member 9, and the arm 9c includes a non-linear movement component of the rear lens group G2 as shown in FIG. A groove portion 9d having a predetermined curve is formed. A bevel gear 11 having spur teeth 11a of a zooming drive motor 10 provided outside the lens barrel 1 is provided in the groove 9d.
The pin 15 of the driving piece 14 that is screwed into the fine movement shaft 13 of the bevel gear 12 that meshes with the bevel tooth 11b is engaged. Further, the zoom drive gear 3b formed on the outer circumference of the helicoid cylinder 3 has spur teeth 11a formed on the outer peripheral surface of the bevel gear 11.
Meshes with. The fine movement shaft 13 has a tangent screw on its outer circumference, and is supported by a U-shaped support fitting 16 so as to be rotatable integrally with the bevel gear 12. The drive piece 14
Has a female screw that is screwed into the tangent screw of the fine movement shaft 13.

Next, the operation of the zoom lens barrel constructed as above will be described. In FIG. 1, when the focusing drive motor 7 is stopped, the focus gear 8
Since it is also stopped, the first rectilinear guide member 6 does not rotate around the photographing optical axis and stops together with the fixed barrel 2. In this state, when the zooming drive motor 10 is operated and the helicoid cylinder 3 rotates, the rotation angle and the first lens frame 4 screwed into the helicoid cylinder 3 and the helicoid are moved forward and backward in the photographing optical axis direction. Further, when the drive motor 7 is operated while the helicoid cylinder 3 is stopped at the zoom position, the first linear guide member 6 is rotated by the focus gear 8, and the first lens frame body 4 is fixed to the helicoid female screw of the helicoid cylinder 3. Three
It is possible to move forward and backward in the optical axis direction of the image while rotating by using the lead a. That is, even if the helicoid cylinder 3 is stopped, by moving only the first lens frame body 4, normal focus position adjustment (focusing) is performed.
It can be performed.

When zooming is performed, the bevel gear 11 is rotated when the zoom drive motor 10 is operated by operating the zoom drive motor 10 to rotate the bevel gear 11 through the spur gear 11a and the zoom drive gear 3b. And the helicoid cylinder 3 rotates about the photographing optical axis. On the other hand, the rotation of the bevel gear 11 is also transmitted to the fine movement shaft 13 via the bevel gear 12 that meshes with the bevel teeth 11b of the bevel gear 11, and the fine movement shaft 1
3 also rotates. Drive piece 1 screwed onto the fine movement shaft 13
In No. 4, since the pin 15 is engaged with the groove 9d of the arm 9c, the rotation about the drive piece 14 is restricted, and the pin 15 moves in the axial direction of the fine movement shaft 13 at the screw pitch of the fine movement shaft 13, Along with the movement of 14, the pin 17 moves while slidingly contacting the groove 9d having a predetermined curve including the non-linear movement component of the rear lens group G2 of the arm 9c, and moves the second linear guide member 9 through the arm 9c. It rotates and the second lens frame 5
Can perform desired non-linear movement due to the relative difference between the rotation of the helicoid cylinder 3 and the rotation of the second rectilinear guide member 9 to perform zooming.

In the above embodiment, the fine movement shaft 1 for rotating the second lens frame body 5 of the rear lens group G2 in unison with the bevel gear 12.
3, the pin 15 of the driving piece 14 is connected to the groove 9d of the arm 9c.
This is a mechanical control method in which the second linear guide member 9 is non-linearly rotated by using the so-called fine movement of the Tangest screw, but a motor provided separately with the second linear guide member 9 is used. An electric control method in which the rotation of the motor is controlled by a microcomputer to perform an arbitrary non-linear rotation is also possible.

As described above, the present invention has been described with reference to the embodiments using the two-group type zoom optical system. However, the present invention is not limited to these, and various modifications can be made without departing from the scope of the invention. For example, it can be applied to a lens barrel for a zoom lens of a three-group type that is often used in high-end machines.
Further, both the first and second lens frame members can be non-linearly moved by nonlinearly rotating both linear guide members by mechanical or electrical means.

[0020]

As described above, in the zoom lens barrel of the present invention, a plurality of lens groups are screwed onto the inner peripheral surface of the helicoid cylinder rotatable with respect to the fixed barrel, and the linear guide of each lens group is provided. By rotating the member linearly or non-linearly in synchronization with the rotation of the helicoid cylinder, the amount of movement of the lens group due to the rotation of the helicoid cylinder is increased or decreased so that a predetermined linear or non-linear zooming movement can be achieved. With a single-lead helicoid tube that is easy to mold plastic,
The lens movement can be realized with high accuracy. Therefore, it is possible to provide a lens barrel having a small diameter, a light weight, and an ideal price, which is ideal for a compact camera or a video camera.

Further, when the helicoid cylinder is stopped at a certain zoom position, by rotating a certain linear guide member, only a certain lens group can be moved back and forth to adjust the focus position (focusing). You can Therefore, autofocus photography, macro photography, and the like are possible, and since the helicoid screw for zoom movement can be used as it is for the moving mechanism for focusing, the cost can be greatly reduced.

Further, the rotary drive mechanism for the linear guide member,
The tangent screw fine movement, which has a simple structure, is used, and the linear guide member having the arm used for the tangent screw can be formed by press processing or the like at low cost, so that the cost can be significantly reduced. Moreover, since the groove shape of the arm of the general tangent screw fine movement is a straight line, the rotation accuracy is fast when the distance between the rotary shaft and the pin of the drive piece is short, and slow when the distance is far. The angular velocity ω of the rotation axis has a relationship of cos ² θ, but in the present invention, the linear guide member can be rotated at a constant speed or non-linearly by making the groove shape of the arm an arbitrary curve.

As described above, the present invention has a small diameter and a light weight,
Moreover, it has the outstanding effect that a highly functional camera lens and video lens can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing a zoom lens barrel in a state where each lens unit is arranged at a long focal position, showing an embodiment of the present invention.

FIG. 2 is a longitudinal cross-sectional view of a main part of the zoom lens barrel, which is also arranged in the short focus position.

FIG. 3 is a view taken along the line III-III in FIG.

[Explanation of symbols]

G1 ... Front lens group, G2 ... Rear lens group, 1 ... Lens barrel, 2 ... Fixed barrel, 3 ... Helicoid cylinder, 3a ... Helicoid female screw, 3b ... Zoom drive gear, 4 ... First lens frame,
4a ... Helicoid male screw, 4b ... Straight guide hole, 4c ... Escape hole, 5 ... Second lens frame body, 5a ... Helicoid male screw,
5b ... Escape hole, 5c ... Straight advance guide hole, 6 ... 1st straight advance guide member, 6a ... Ring base, 6b ... Frame guide part, 6c ... Spur tooth, 7 ... Focusing drive motor, 8 ... Focus gear, 9 ... Second straight guide member, 9a ... Ring-shaped base portion, 9b
... frame body guide part, 9c ... arm, 9d ... groove part, 10 ... zooming drive motor, 11 ... bevel gear, 11a ... spur teeth, 11
b ... Bevel teeth, 12 ... Bevel gears, 13 ... Fine movement shaft, 14 ... Driving piece, 15 ... Pin, 16 ... Support metal fittings

Claims (3)

[Claims] 1. A plurality of lens groups constituting a zoom lens system are arranged in a helicoid cylinder rotatable with respect to a fixed barrel, and a frame body of each lens group is formed on an inner peripheral surface of the helicoid cylinder. Screwed to the same helicoid screw, and each straight guide member for restricting the rotation of the frame body of each lens group around the photographing optical axis is arranged, and the frame guide portion of the straight guide member is used for photographing light. The frame of each lens group extends around the photographing optical axis as the linear guide member extends in parallel with the axis, and the helicoid cylinder rotates to move each lens group in the photographing optical axis direction. A zoom lens barrel characterized by increasing or decreasing the amount and moving each lens group to a focal position and a zoom position. 2. A straight guide member of the lens group for adjusting the focus position of the lens group rotates around the photographing optical axis, and a helicoid screw formed on the inner peripheral surface of the helicoid cylinder is used to adjust the focus position. The zoom lens barrel according to claim 1, wherein the lens unit is moved back and forth in the optical axis direction to move to the focal position. 3. A linear guide member for moving the lens group to a zoom variable power position is arranged so that a rotational force around the photographing optical axis is transmitted by a tangent screw, and a groove shape of an arm portion of the tangent screw. 2. The zoom lens barrel according to claim 1, wherein the lens group is moved along the optical axis by forming a curved line, and rotating the straight guide member around the optical axis of the photographing.