JPH0247614A - Lens barrel of automatic focusing zoom lens - Google Patents

Abstract

PURPOSE:To enable focusing in a short time when the focal length varies considerably by interposing a driving force transmitting mechanism which moves a compensating lens system at a constant rate to the movement of a power varying lens system between a power varying lens driving mechanism and a compensating lens driving mechanism. CONSTITUTION:A helicoid 132 which is cut in the screw direction from an internal-diameter side helicoid 132 is provided on the external diameter side of an intermediate helicoid member 13 and a holding member 8 which holds a compensating lens system 9 engages the helicoid 132 threadably. Then when a cylinder member 3 is rotated, a lens frame member 1 and the holding member 8 are moved linearly by a straight movement key 14 in the opposite directions at the constant rate. Therefore, when the power varying lens system 2 is driven, the compensating lens system 9 is driven associatively with such driving and the compensating lens system 9 is driven at the constant rate to the movement of the power varying lens system 2. Consequently, the focusing time at the time of zooming is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lens barrel for an autofocus zoom lens.

(Prior Art) Conventionally, when a variable power lens system moves due to zooming, a correction lens system is moved without using a cam based on a signal from a focus detection means that detects changes in subject distance or focus. An autofocus zoom lens that maintains the focus plane at a predetermined position is known (Japanese Patent Laid-Open No. 53
-66223, JP 53-116828, JP 55-40447, JP 56-475
Publication No. 33).

The structure of the lens barrel that drives the variable power lens system and correction lens system of such an autofocus zoom lens is as follows.
For example, there is one shown in FIG.

The lens barrel of the autofocus zoom lens includes a lens frame member 1, a variable magnification lens system 2, a barrel member 3', a linear key member 4, a fixed barrel member 5, a plate member 6, a zoom operation ring 7, a holding member 8, It is composed of a correction lens system 9 and a rotating tube member 11. The lens frame member 1 holds the variable magnification lens system 2, and
It is screwed into the cylindrical member 3' by a helicoid screw (referred to as a helicoid), and is moved in the rectilinear direction by a rectilinear key member 4 based on the rotation of the cylindrical member 3'. Further, the cylindrical member 3' is bayonet connected to the fixed cylindrical member 5, and is rotatable, but movement in the axial direction is restricted. The plate member 6 is located in a notch (not shown) of the fixed cylinder member 5, and the lower part of the plate member 6 is screwed to the cylinder member 3', and the upper part of the plate member 6 is formed in the axial direction of the zoom operation ring part 7. The groove is engaged with the groove. As a result, the plate member 6 allows the cylindrical member 3 to
' and the zoom operation ring 7 are configured to be integrally driven to rotate.

The holding member 8 holds the correction lens system 9 and is screwed onto the fixed cylinder member 5 by a helicoid.

A protrusion 10 is formed on the outer diameter side of the holding member 8, and the protrusion 10 engages the holding member 8 in a groove formed in the axial direction of the rotary cylinder member 11.

The rotary cylinder member 11 is rotatable, but its movement in the axial direction is restricted, and when driven to rotate, the holding member 8 is moved in the axial direction by the combination of the axial groove and the protrusion 1o. is being done.

A gear 12 is provided at one end of the rotating tube member 11, and the driving force of a focusing motor (not shown) is transmitted to this gear 12 via a gear (not shown).

The holding member 8 also has a correction lens system 9 between a tele infinity stopper (not shown) and a wide closest stopper (not shown) provided between the fixed barrel member 5 and the rotating barrel member 11. is configured to be able to move independently of the movement of the variable magnification lens system 2 and the like.

Next, the operation of the above structure will be explained.

First, when the autofocus zoom lens is in focus at a certain focal length, the zoom operation ring 7 is rotated by the user, and the variable magnification lens system 2 is moved to change the focus. The surface is shifted from the film surface. This amount of deviation is calculated as the amount of movement of the correction lens system 9 to the in-focus position by the focal length detection means provided inside the camera body, and the rotary tube member 11 is rotated by the driving means in accordance with this amount of movement. be done.

Due to this rotation of the rotary cylinder member 11, the holding member 8 moves in the axial direction, and the correction lens system 9 is moved to a position corresponding to the amount of movement.
Stop moving when reached.

[Problem to be Solved by the Invention] However, with the above-mentioned autofocus zoom lens barrel, for example, when focusing on a subject at infinity at the telephoto end, the user can zoom to wide-angle. When focusing on the closest subject at the edge, the correction lens system 9 starts moving to the focus position after zooming, so it takes time to focus, and even during 0-con scan, There is a problem that the amount of movement of the correction lens system 9 corresponding to the scan range is large, and the scan time is long.

An object of the present invention is to provide an autofocus zoom lens tliW4 that can focus in a short time even when the focal length changes significantly due to movement of a variable power lens system.

[Means to solve the problem]

In order to achieve the above object, claim 1 of the present invention provides an autofocus zoom having a variable power lens drive mechanism that moves a variable power lens system, and a correction lens drive mechanism that moves a correction lens system for focusing. In Mg2 of the lens,
A driving force transmission ridge structure is interposed between the variable power lens drive mechanism and the correction lens drive mechanism to move the correction lens system at a constant ratio with respect to the movement of the variable power lens system.

Further, in a second aspect of the present invention, the correction lens drive mechanism includes a helicoid screw, and the lead thereof is set between a maximum value and a minimum value of the lead for focusing over the entire zoom range.

Roughly speaking, in claim 3, the correction lens drive mechanism includes a helicoid screw, and the lead thereof is represented by a straight line connecting points such that the image point is corrected and brought into focus at the telephoto end and the wide end. It is something.

[Effect]

According to the use of the autofocus zoom lens having the above configuration, when the variable power lens system is driven, the correction lens system is driven so as to move at a constant ratio to the amount of movement thereof.

(Example) FIG. 1 is a side sectional view of a lens barrel of an autofocus zoom lens according to the present invention. In addition, in the figure, the same number as in FIG. 2 indicates the same thing. In the figure, a lens frame member 1, a variable magnification lens system 2, a cylinder member 3, a linear key member 4, a fixed cylinder member 5, a plate member 6
, zoom operation ring 7, holding member 8, correction lens system 9, rotating tube member 11, middle helicoid member 13, and linear key member 1
It consists of 4. Note that although the explanation here assumes that the zoom lens is replaceably attached to the camera body and has a focus detection means and a focusing motor on the camera body side, it also applies when the zoom lens is integrally built into the camera. It goes without saying that the present invention is applicable.

The cylindrical member 3 is screwed into the ball crushing member 1 that holds the variable magnification lens system 2 by means of a helicoid provided on its inner diameter side, and is provided on the inner diameter side of a middle helicoid member 13 by means of a helicoid provided on its outer diameter side. The helicoid 131 is screwed onto the helicoid 131.

Further, a helicoid 132 is provided on the outer diameter side of the middle helicoid member 13 so that the screw direction is opposite to that of the helicoid 131 on the inner diameter side. The members 8 are screwed together.

When the cylinder member 3 is rotated, the lens frame member 1 and the holding member 8 are moved straightly in opposite directions at a constant ratio by the straight key member 14.

Although not shown, the tube member 3 and the fixed tube member 5 have a rotation range of the tube member 3 (i.e., an optical axis movement range of the variable magnification lens system 2 and an optical axis movement range of the correction lens system 9 that follows it). ), and the rotating barrel member 11 and the fixed barrel member 5 each have a stopper that regulates the rotation range of the holding member 8 (i.e., the optical axis movement range of the correction lens system 9 for focusing). It is provided.

Next, the operation of the lens barrel of such an autofocus zoom lens will be explained.

When the autofocus zoom lens is in focus,
When the variable magnification lens system 2 is moved by the user, that is, when the cylinder member 3 is rotated, the middle helicoid member 13 moves straightly toward the key member 1.
4 to move in the axial direction.

In addition, since the protrusion 10 of the holding member 8 is engaged with the straight groove of the rotating cylinder member 11, the holding member 8 and the middle helicoid member 1
3 moves straight in a direction opposite to the moving direction of the ball crushing member 1 and at a constant ratio to the movement l of the ball frame member 1, that is, the amount of movement of the variable magnification lens system 2.

Next, the amount of movement of the correction lens system 9 is calculated by the focus detection means on the camera body side, and the rotary tube member 11 is rotationally driven via the drive shaft of the focusing motor of the camera body so as to correspond to this movement. Ru.

Due to this rotation of the rotary cylinder member 11, the holding member 8 moves in the axial direction and stops moving when it reaches the in-focus position.

In addition, the middle helicoid member 13 is arranged so that the rotational force from the rotating cylinder member 11 is not transmitted to the cylinder member 3.
Since the rotation of the middle helicoid member 13 is prevented by the rectilinear groove 3 and the rectilinear key material 14, the focusing operation by the correction lens system 9 can be performed without moving the variable power lens system 2.

Next, the relationship between the locus of movement of the variable magnification lens system 2 and the locus of movement of the correction lens system 9 and the movement of the correction lens system 9 to the in-focus position will be explained using FIG.

First, let A be the position of the variable magnification lens system 2 and C be the position of the correction lens system 9 when focusing on an object at infinity at the telephoto end. At this time, when the user starts zooming and moves the variable magnification lens system 2 from position A to position B, which is the wide end, the correction lens system 9 moves while always focusing on the subject at infinity. To do this, draw a solid line 1 from position @C to position
must move along.

When the variable magnification lens system 2 is moved from position B to position A, the dashed line 11 must be drawn from position WE to position F in order for the correction lens system 9 to move while always focusing on the closest subject.
must move along.

The shaded area surrounded by the solid line 1 and the broken line 11 is the range where the correction lens system 9 is always in focus for all subject distances during zooming.

On the other hand, in the case of a conventional autofocus zoom lens barrel, the correction lens system 9 is configured to be able to move independently between the telephoto infinity stopper and the wide closest stopper. When the variable magnification lens system 2 is moved from position A to position B while focusing on an object at infinity, the correction lens system 9 changes the magnification lens system 2 to position 1.
Since it moves after reaching position B, the correction lens system 9 must move a distance 1b from position C' to position IE in order to focus on the closest object.

Furthermore, when the variable magnification lens system 2 is returned from position B to the position B, the correction lens system 9 focuses on the subject at infinity.
must be moved from position E' to position 1c.

Furthermore, during low-contrast scanning, since scanning is performed in a range from infinity to the closest approach, the amount of movement of the correction lens system 9 becomes longer as the distance increases.

In the case of the autofocus zoom lens barrel of the present invention,
The lead of the vericoid 131 provided on the inner diameter side of the middle helicoid member 13 (the amount by which the correction lens system 9 is moved in the optical axis direction per one revolution of the helicoid) is indicated by the two-dot broken lines iii, iv, and v in FIG. As shown, it has the same slope as the straight line connecting the telephoto end position C and the wide end position 10 on the solid line 1, for example.

In other words, at the tele end and wide end, the image point is corrected to form a straight line with a slope that brings it into focus, and the slope is the lead (minimum value) at the tele end and the lead (minimum value) at the wide end. maximum value). By setting the lead of the helicoid 131 in this way,
When the variable magnification lens system 2 is moved from position 11A to position IB while focusing on an object at infinity at the telephoto end, the correction lens system 9 changes from position 1c to position 1c at a constant ratio to the above movement amount. and move along the two-dot dashed line ii1. At this time, when focusing on the closest object, the correction lens system 9 only needs to be moved by a distance a from the position to the position E, and the moving layer of the correction lens system 9 can be reduced compared to the conventional case.

Also, when the variable power lens system 2 is returned from position 8 to position A, the correction lens system 9 moves from position E to position F along the two-dot broken line iv.
move along. Further, when the correction lens system 9 focuses on a subject at infinity when the variable power lens system 2 is at position I, and then moves to position A, the correction lens system 9 moves from position [J to Move to position G along the two-dot broken line V. Further, when the variable power lens system 2 moves from the position I to the position B, the correction lens system 9 moves from the position J to the position IiH along the two-point break 1v.

Therefore, since the correction lens system 9 moves only within the range of the parallelogram EFGH formed by the two-dot broken lines iv and v, the amount of movement of the correction lens system 9 for focusing after zooming is also conventional. less. Also,
Even during low contrast scanning, the correction lens system 9 only needs to move by a distance 11c within the range of the parallelogram EFGH.

In the above embodiment, an optical system in which the variable power lens system and the correction lens system move in opposite directions at a constant ratio is described, but the invention is not limited to this. The present invention can also be applied to a zoom lens using an optical system that moves in the same direction.

Further, although a helicoid was used as the correction lens system in the above embodiment, substantially the same effect as the present invention can be obtained by using a cam instead.

At this time, the shape of the cam may be determined so that it is equivalent to the lead of the helicoid shown in FIG.

〔Effect of the invention〕

In the present invention, when the variable power lens system is driven, the correction lens system is driven in conjunction with the drive, and the correction lens system is driven at a constant ratio with respect to the movement of the variable power lens system. This makes it possible to reduce the focusing time associated with zooming. Additionally, an autofocus zoom lens with good tracking performance can be achieved. Furthermore, since the scan range during low-contrast scanning can be shortened, the scan time can be shortened.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of the lens barrel of an autofocus zoom lens according to the present invention, Fig. 2 is a side sectional view of the lens barrel of a conventional autofocus zoom lens, and Fig. 3 is a trajectory of movement of the variable magnification lens system. FIG. 6 is a diagram illustrating the relationship with the movement trajectory of the correction lens system and the amount by which the correction lens system should move to the in-focus position. DESCRIPTION OF SYMBOLS 1... Ball crushing member, 2... Variable power lens system, 3... Tube material, 4... Straight key material, 5... Fixed tube material, 6...
Plate member, 7... Zoom operation ring part, 8... Holding member,
9... Correction lens system, 11... Rotating cylinder material, 13...
・Medium helicoid member, 14...straight key material, 131・
・Helicoid on the inner diameter side of the middle helicoid member.

Claims (1)

[Claims] 1. A variable power lens drive mechanism that moves a variable power lens system;
In a lens barrel of an autofocus zoom lens having a correction lens drive mechanism that moves a correction lens system for focusing, a variable power lens drive mechanism and a correction lens drive mechanism are provided with a lens barrel for moving the variable power lens system. A lens barrel for an autofocus zoom lens, characterized in that a driving force transmission mechanism for moving the correction lens system at a constant ratio is interposed. 2. The autofocus zoom lens mirror according to claim 1, wherein the correction lens drive mechanism includes a helicoid screw, and the lead thereof is set between a maximum value and a minimum value of the lead for focusing over the entire zoom range. Torso. 3. The correction lens drive mechanism includes a helicoid screw, and the lead thereof is indicated by a straight line connecting points such that the image point is corrected and brought into focus at the telephoto end and the wide end.
The lens barrel of the autofocus zoom lens described.