JPH11109212A - Rear focusing system zoom lens device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a mechanical cam and an electron cam in common for a driving part for a correction group and to increase a zooming speed, in a rear focusing system zoom lens device. SOLUTION: A follower pin 22 protrusively installed on the lens frame 20 of a variable power group 14 is engaged into the cam groove 24A of a columnar cam member 24. The correction group 14 is composed of a moving frame 26 which is engaged into the cam groove 24B of the member 24 through a follower pin 32 and a lens frame 28 supported inside the moving frame 26 so as to be freely moved, and the lens frame 28 is constituted so as to be moved along the moving frame 26 under the control of a motor. And, the cam grooves 24A and 24B are separately formed to a curved shape obtained when an object distance is infinite(∞), in the case the object distance is other than a point at infinity, the correction lens 30 is moved to an appropriate position by using the mechanical cam and the movement of the lens frame 28 driven by the motor (electronic cam) in common. Besides, it is preferable to use a voice coil type linear motor for the driving part for the correction group 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear focus type zoom lens apparatus, and more particularly to a rear focus type zoom lens apparatus used for a video camera or the like, in which the optical positional relationship between a zooming group and a correction group is controlled by a so-called electronic cam. The present invention relates to a zoom lens device.

[0002]

2. Description of the Related Art A rear focus type zoom lens apparatus having a lens group (correction group) having a focus adjustment function located behind a position of an iris (iris) has a feature that the mass of the correction group can be reduced, and the distance of the subject is reduced. It has the advantage that the amount of movement of the correction group due to the change is small, and enables high-speed focusing, so that it is widely used in consumer video cameras and the like.

A rear focus type zoom lens device has a zooming group (front lens) and a correction group (rear lens).
Zooming and focusing are performed by appropriately moving each lens group by a zoom motor and a focus motor. In the rear focus type zoom lens device, since the position of the correction group is determined by two parameters of the zoom magnification and the object-image distance (subject distance) due to its structure, the movement is performed by a mechanical cam (mechanical cam). It is impossible to achieve. Accordingly, such a zoom lens device generally employs an electronic cam that controls the position of the correction group in the optical axis direction by electrically controlling the zoom motor and the focus motor in association with each other.

[0004]

However, in the rear focus type zoom lens apparatus, even when the distance to the subject is constant, the correction group must be moved by zooming, and the amount of movement is large. However, there is a problem that the movement is not a linear movement. Therefore,
The conventional rear focus type zoom lens device has a disadvantage that the maximum speed of zooming is defined by the maximum speed of the correction group, and it is difficult to increase the zoom speed.

The present invention has been made in view of such circumstances, and has as its object to provide a rear focus type zoom lens device capable of increasing the maximum speed of zooming.

[0006]

In order to achieve the above object, the present invention provides a rear focus type zoom system having a variable power group and a correction group, wherein the correction group is moved in the optical axis direction to perform focus adjustment. In the lens device, a mechanical cam that regulates the positional relationship between the zooming group and the correction group in the optical axis direction and moves the correction group in accordance with the movement of the zooming group accompanying the zooming operation is controlled by the mechanical cam. For the positional relationship between the zooming group and the correction group, a driving unit that moves only the correction group in the optical axis direction by driving a motor, and a moving amount of the correction group by the driving unit based on a zoom magnification and a subject distance. Decide,
And control means for controlling the driving means so as to move the correction group to an appropriate position.

According to the present invention, a mechanical cam for interlocking a zooming group and a correction group via a mechanical mechanism and a so-called electronic cam for moving only the correction group by motor drive control are used together. Therefore, the amount of movement of the correction group by the driving means (electronic cam) can be reduced. Further, the movement of the correction group becomes linear, and the reversal operation of the motor can be avoided. Thereby, the moving time of the correction group can be shortened, the motor control process can be simplified, and the zooming can be speeded up.

Further, according to another aspect of the present invention, the correction group includes a first moving frame engaged with a mechanical cam, and the first group is slidably supported in the first moving frame. And a second moving frame movable by the driving means, wherein the lens member is held by the second moving frame. With this configuration, the correction group can be moved by the mechanical cam in conjunction with the zooming group, and can be independently moved by the driving means (electronic cam).

Further, by employing a voice coil type linear motor as a motor for driving the correction group, the size can be reduced. According to another aspect of the present invention, the mechanical cam is formed with a curve that regulates the position of the correction group when the subject distance is infinity. The driving means is controlled so as to correct the amount of movement of the correction group due to the following. Thereby, the motor control processing in the control means can be simplified.

The mechanical cam may have various configurations. For example, a first cam groove for regulating the position of the variable power unit and a second cam groove for regulating the position of the correction unit are formed. By using the cylindrical cam member, the variable power unit is engaged with the first cam groove, and the correction unit is engaged with the second cam groove.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a rear focus type zoom lens device according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a side sectional view showing a configuration example of a rear focus type zoom lens device according to the present invention. The optical system of the rear focus type zoom lens device 10 shown in FIG. 1 includes a zooming group 12 and a correction group 1 having a focusing function.
4, the subject image is composed of the variable magnification group 12 and the correction group 14
The image is formed on the image forming surface of the CCD 16 or the like of the television camera through. An aperture (not shown) is arranged between the zooming group 12 and the correction group 14.

A lens (magnifying lens) 18 of the zooming group 12 is mounted on a lens frame 20, and this lens frame 20 is supported in a fixed cylinder (not shown) so as to be movable back and forth. A driven pin 22 protrudes from an outer peripheral portion of the lens frame 20, and the driven pin 22 is engaged with a cam groove 24 </ b> A of a cylindrical cam member (hereinafter, referred to as a cylindrical cam member) 24.

The cylindrical cam member 24 is rotatably supported via a support mechanism (not shown), and rotational driving force from a motor (not shown) is transmitted via a gear transmission mechanism. The correction group 14 includes a movable frame 26 supported in the fixed cylinder so as to be movable back and forth, and a lens frame 28 supported inside the movable frame 26, and a lens (correction lens) is provided on the lens frame 28.
30 is mounted. A driven pin 32 protrudes from an outer peripheral portion of the moving frame 26, and the driven pin 32 is engaged in the cam groove 24 </ b> B of the cylindrical cam member 24.

The lens frame 28 of the correction group 14 is
The lens frame 28 is driven back and forth in the optical axis direction by a motor (driving means) (not shown).
The motor that drives the cylindrical cam member 24 to rotate and the motor that drives the lens frame 28 of the correction group 14 back and forth are controlled by a motor control device (control means) (not shown).

The configuration of the driving section of the lens frame 28 is not limited to this, and various modes are possible. FIG. 2 shows an example in which a voice coil type linear motor is used as a driving unit of the correction group 14. As shown in FIG. 2, the voice coil linear motor 35 includes a voice coil 36, a magnet 38, a yoke 40, and the like, as is well known. Although not shown in detail, a movable part integral with the lens frame 28 'holding the correction lens 30 is slidably supported by a guide shaft. The movable part has a position detection sensor and a speed detection for position control. A sensor is provided. Note that, for example, a magnetoresistive element (MR element) is applied to the position detection sensor, and the speed detection sensor includes a speed detection coil and a permanent magnet. With this configuration, it is possible to move the lens 30 of the correction group 14 at high speed and with high accuracy along the optical axis.

FIG. 3 shows the relationship between the position of the variable power lens and the position of the correction lens of a general rear focus type zoom lens device. The horizontal axis in the figure represents the zoom magnification corresponding to the position of the variable power lens, and the vertical axis represents the position of the correction lens. The position of the correction lens is determined by two parameters, zoom magnification and subject distance. When the subject distance is infinity, the movement of the correction lens is as shown by the curve in the figure, and when the subject distance is 1 m, the movement of the correction lens Becomes like a curve.

As shown in FIG. 2, the moving distance of the correction group when the object distance is changed from infinity to 1 m is smaller than that of the correction group.
Zoom magnification from minimum (1x) to maximum (10x, for example)
The amount of movement of the correction lens when changed to is much larger. The embodiment of the present invention focuses on this point, moves the correction lens 30 by changing the zoom magnification with a mechanical cam using the cylindrical cam member 24, and moves the correction lens 30 with the change of the subject distance. The control is performed by electric control (electronic cam) using a motor.

That is, the cam groove 24A of the cylindrical cam member 24,
The shape of 24B is formed as a curve when the subject distance is infinity (∞), and in photographing at infinity, the lens frame 28 of the correction group 14 is moved to a predetermined reference position (for example, the moving frame 26) with respect to the moving frame 26. At the rear end position). In cases other than infinity, the motor moves the lens frame 28 with respect to the moving frame 26 to correct the position of the correction lens 30.

Next, the operation of the rear focus type zoom lens apparatus having the above-described configuration will be described. The lens frame 28 of the correction group 14 is located at a predetermined reference position with respect to the moving frame 26 in the initial state. When the subject distance is infinity, the movement of the correction lens 30 accompanying zooming is performed by the cylindrical cam member 22. When the subject distance is other than infinity, the correction lens 30 is moved in conjunction with the mechanical cam by the cylindrical cam member 22 and the electronic cam when changing the zoom magnification.

FIG. 4 shows the relationship between the zoom magnification and the amount of movement of the correction group by the electronic cam. Cylindrical cam member 24
When the curve at infinity is used as the shape of the cam, the movement amount of the correction group 14 (movement amount of the correction lens 30 with respect to the moving frame 26) by the electronic cam when the subject distance is 1 m is as shown by the curve in FIG. become. That is, when the distance is infinity, the amount of movement of the correction group 14 by the electronic cam is “0”, so that the position of the correction lens 30 is corrected by changing the distance with respect to infinity (see FIG. (The difference between the curved line and the curved line) by the electronic cam.

By doing so, the amount of movement of the correction lens 30 by the electronic cam can be reduced, and the movement of the lens frame 28 with respect to the movement frame 26 becomes linear, so that the reversing operation of the motor can be avoided. This makes it possible to realize high-speed zooming. Further, in the above-described embodiment, the case where the curve at infinity is used as the shape of the mechanical cam has been described as an example. However, the shape between the infinity and the minimum shooting distance (MOD) (for example, 2 m) is used. ) Can also be used as the shape of the mechanical cam.

[0022]

As described above, according to the rear focus type zoom lens apparatus of the present invention, as a means for regulating the position of the correction unit, a mechanical cam interlocked with the variable power unit and a so-called electronic cam are used in combination. Therefore, the amount of movement of the correction group by the electronic cam can be reduced, and the movement becomes linear, thereby realizing a high-speed zooming.

In particular, by employing a voice coil type linear motor for the drive unit of the correction group, the correction group can be moved at high speed and with high accuracy, and the size can be reduced.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a configuration example of a rear focus type zoom lens device according to the present invention.

FIG. 2 is a sectional view showing a configuration example of a voice coil type linear motor.

FIG. 3 is a graph showing the relationship between the zoom magnification of a general rear focus type zoom lens device and the position of a correction lens.

FIG. 4 is a graph showing the relationship between the zoom magnification of the rear focus type zoom lens device shown in FIG. 1 and the amount of movement of the correction group.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Rear focus type zoom lens apparatus 12 ... Magnification group 14 ... Correction group 16 ... CCD 18 ... Magnification lens 24 ... Cylindrical cam member (mechanical cam) 26 ... Moving frame (first moving frame) 28 ... Lens frame (Second moving frame) 30: Correction lens (focus lens) 35: Voice coil type linear motor

Claims (5)

[Claims] 1. A rear focus type zoom lens device having a zooming group and a correction group, and performing focus adjustment by moving the correction group in the optical axis direction. A mechanical cam that regulates the positional relationship and moves the correction group in accordance with the movement of the zooming group accompanying the zooming operation, and the positional relationship between the zooming group and the correction group regulated by the mechanical cam, A driving unit for moving only the correction group in the optical axis direction by driving a motor; and determining a moving amount of the correction group by the driving unit based on a zoom magnification and a subject distance, and moving the correction group to an appropriate position. A rear focus zoom lens device, comprising: control means for controlling a driving means. 2. The correction group includes a first group engaged with a mechanical cam.
, And a second moving frame supported inside the moving frame and movable by the driving means, wherein a lens member is held by the second moving frame. The rear focus type zoom lens device according to claim 1, wherein 3. The rear focus type zoom lens device according to claim 1, wherein said driving means comprises a voice coil type linear motor. 4. The mechanical cam uses a curve that regulates the position of the correction group when the subject distance is infinity, and the control means uses the mechanical cam when the subject distance is other than infinity. 2. The rear focus type zoom lens device according to claim 1, wherein the driving unit is controlled so as to correct the amount of movement of the correction group. 5. The mechanical cam includes a cylindrical cam member having an outer peripheral surface formed with a first cam groove for regulating a position of a zooming group and a second cam groove for regulating a position of a correction group. The rear focus type zoom lens according to claim 1, wherein a zooming group is engaged with the first cam groove, and a correction group is engaged with the second cam groove. apparatus.