JPH06160699A - Zoom lens device - Google Patents

Abstract

PURPOSE:To obtain a zoom lens device capable of simplifying an entire device by appropriately constituting a lens moving mechanism for controlling the movement of a lens in the case of performing focusing operation and zooming operation. CONSTITUTION:This zoom lens device is provided with a 1st group 1 which is fixed, a 2nd group 2 and a 3rd group 3 which execute variable power by changing a distance between them, a 4a-th group 4a for focusing, and a 4b-th group 4b which is fixed in order from an object side; and it is provided with a 1st mechanical cam member 14 moving the 2nd group 2 and the 3rd group 3 on an optical axis by changing mutual positions and moving the 4a-th group 4a on the optical axis, and a 2nd mechanical cam member 15 moving the 4a-th group 4a on the optical axis and moving the 2nd group 2 and the 3rd group 3 on the optical axis while keeping mutual positions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens device, and more particularly, to a drive mechanism simplified by appropriately constructing a lens moving mechanism for controlling lens movement during zooming and focusing operations. The present invention relates to a zoom lens device suitable for cameras, TV cameras and the like.

[0002]

2. Description of the Related Art Conventionally, focusing of a zoom lens is referred to as a front lens group in front of a zoom section, which is composed of a zoom lens group for zooming and a correction lens group for correcting an image plane variation due to zooming. Generally, the lens group is moved on the optical axis.

However, according to the focusing by the front lens group, as the distance object becomes closer, the moving distance of the front lens group increases, and at that time, in order to eliminate the vignetting of the light flux and maintain sufficient optical performance, There is a problem that the outer diameter of the ball lens group must be increased.

Therefore, this has been a major obstacle in simplifying the drive mechanism of the zoom lens device. See also M. O. D
The (shortest shooting distance) is also limited due to the above reasons.

Therefore, as a conventional method for solving such a problem, for example, a zoom lens adopting a so-called rear focus type in which a lens group other than the first group is moved on the optical axis to perform focusing is disclosed in, for example, Japanese Patent Laid-Open No. Hei 2 (1999) -211. It is proposed in Japanese Patent Publication No. 154216.

FIG. 8 is a schematic view of a main part of a zoom lens device proposed in the publication.

In the zoom lens shown in FIG. 1, the first lens group 1 having a positive refractive power, the second lens group 2 having a negative refractive power, the third lens group 3 having a positive or negative refractive power, and the positive refractive power are sequentially arranged from the object side. And a fourth group of forces. The second group 2 and the third group 3 constitute a zoom unit 30 which performs zooming by changing the mutual lens interval. Then, at the time of focusing, some of the lens groups 4a in the fourth group are moved so that the amount of movement on the optical axis increases from the wide-angle side to the telephoto side.

In such a zoom lens device, for example, when performing a focusing operation and a zooming operation, a lens provided with a plurality of members (three in the figure) such as a motor and a sensor for position detection as shown in the figure. This is performed by moving the target lens group in a predetermined direction on the optical axis by a moving mechanism.

That is, in the figure, the first group 1 is fixed during zooming and focusing, and the lens housing 6 is fixed.
It is fixed to. The second group 2, the third group 3, and the front group 4a of the fourth group 4 are incorporated in lens barrel members 7, 8 and 9, respectively, and can be moved in the optical axis direction by fitting to the lens housing 6 or the like. Is supported as. The second group 2 and the third group 3
Are connected to the cam grooves 14a and 14b of the mechanical cam member 14 by pin members 10 and 11, respectively.

Reference numeral 17 denotes a motor, which rotates (rotates) the mechanical cam member 14 based on a signal from the controller 21.
I am letting you. A sensor 18 detects the rotational position of the motor 17 and sends a detection signal to the controller 21.

Reference numeral 16 denotes a movable table, which is configured to be movable in the optical axis direction with respect to the lens housing 6 by a motor 52. The mechanical cam member 1 is mounted on the movable table 16.
4, members such as the motor 17 and the sensor 18 are attached. Further, the feed screw shaft 51 meshes with the female screw portion provided on the moving table 16.

The motor 52 rotates (rotates) the feed screw shaft 51 based on a signal from the controller 21. 53
Is a sensor, which detects the rotational position of the motor 52 and sends a detection signal to the controller 21.

On the other hand, the front group 4a which constitutes a part of the fourth group 4
Is connected to the female screw member 55 by the pin member 13, and the female screw member 55 meshes with the screw shaft 54.

Reference numeral 56 denotes a motor, which rotates (spins) the feed screw shaft 54 based on a signal from the controller 21. Reference numeral 57 denotes a sensor, which detects the rotational position of the motor 56 and sends the detection signal to the controller 21.

Reference numeral 22 denotes a focus operation section, which indicates the focus position to the controller 21. A zoom operation unit 23 instructs the controller 21 on the zoom ratio. The controller 21 is a focus operation unit 22,
Zoom operation unit 23, and each sensor 18, 53, 57
The motors 17, 52 and 56 are controlled based on signals from the above.

In the zoom lens apparatus having such a configuration, in order to perform a focusing operation on a certain object using the focus operating section 22 under a certain fixed focal length, first, the rotational position of the motor 17 is detected by a sensor. Detect at 18. That is, based on the output signal from the sensor 18 for detecting the zooming position, the movement amount of the front group 4a of the fourth group 4 and the movement amount of the zoom unit 30 including the second and third groups 2 and 3 are adjusted according to the focusing operation amount. Is calculated by the controller 21. Based on the calculation result, the screw shafts 51, 54 are rotated by the motors 52, 56 to move the zoom unit 30 and the front group 4a on the optical axis for focusing.

Next, when performing a zooming operation in the in-focus state, the controller 21 is operated via the zoom operation section 23.
Calculates the amount of movement of the moving lens, rotates the mechanical cam member 14 by the motor 17, moves the second group 2 on the optical axis for zooming, and in order to correct the image plane variation caused by the second group 2, The third group 3 is moved on the optical axis.

On the other hand, the screw shafts 51, 54 are further driven by the respective motors 52, 56 so that the in-focus state is always maintained even if the focal length changes based on the output signal from the sensor 18.
By rotating the zoom unit 3 including the second group 2 and the third group 3.
0 is integrally moved on the optical axis and the front group 4a is also moved on the optical axis to correct the image plane variation due to zooming.

[0019]

The lens moving mechanism in the zoom lens device shown in FIG. 8 has the second and third groups 2 and 3.
A motor 17 for rotating the mechanical cam member 14 for moving the motor, and a motor 5 for moving the zoom unit 30.
2 and three motors 56 for moving the front group 4a of the fourth group 4 are used.
Sensors 18, 53, 57 associated with 7, 52, 56,
Further, an electric circuit (not shown), a holding member, and the like are also configured by using three each.

As a result, the number of drive members such as motors and the number of electric system parts increases, which tends to increase the size and complexity of the entire apparatus and further increase the weight. Further, there has been a tendency that the cost increases due to the increase in the number of parts.

The present invention has been proposed by the applicant of the present invention in Japanese Patent Laid-Open No.
By configuring the lens moving mechanism in the zoom lens according to Japanese Patent Laid-Open No. 154216 with two mechanical cam members having at least one cam groove, two members such as a motor and a sensor are provided to simplify the entire apparatus (small size and light weight). Object) and a cost reduction of the zoom lens device.

[0022]

A zoom lens device according to the present invention comprises a fixed first lens group in order from the object side, a second lens group and a third lens group for zooming by changing the mutual distance, and a fourth lens group for focusing. In a zoom lens device having a group and a fixed fourth group, a first mechanical system for moving the second group and the third group on the optical axis by changing the mutual positions and moving the fourth group on the optical axis. A cam member and a second mechanical cam member for moving the fourth group on the optical axis and moving the second group and the third group on the optical axis while maintaining the mutual positions. It has a feature.

The zoom lens device according to the present invention comprises, in order from the object side, a fixed first lens group, a second lens group for zooming, a third lens group for correcting an image plane variation due to zooming, and a focus lens. No. 4a
In a zoom lens device having a group and a fixed fourth group for image formation, the second group and the third group are moved on the optical axis by changing their mutual positions, and the fourth group is moved on the optical axis. A first mechanical cam member and a second mechanical cam member for moving the fourth group a on the optical axis and moving the second group and the third group on the optical axis while maintaining the mutual positions are used. It is characterized in that the zooming operation and the focus operation are performed by the above.

[0024]

Embodiment 1 FIG. 1 is a schematic view of the essential portions of Embodiment 1 of the present invention. In the figure, the same elements as those shown in FIG. 8 are designated by the same reference numerals.

In this embodiment, the zoom lens disclosed in Japanese Patent Application Laid-Open No. 2-154216 previously proposed by the applicant (see FIG. 8).
2), the lens moving mechanism is composed of two mechanical cam members 14 and 15 having at least one cam groove, and a zooming operation and a focusing operation are performed.

In the figure, 1 is a fixed first lens group, 2 is a variable power lens group for zooming, 3 is a correction lens group for correcting image plane variation due to zooming, and 4 is for image formation. Lens group for focusing (front group) 4a and fixed lens group (rear group)
It consists of 4b. The second unit 2 and the third unit 3 form a zoom unit 30.

The first group 1 is fixed during zooming and focusing and is fixed to the lens housing 6. The second group 2, the third group 3, and the front group 4a of the fourth group 4 are incorporated in lens barrel members 7, 8 and 9, respectively, and can be moved in the optical axis direction by fitting to the lens housing 6 or the like. Is supported as. The second group 2 and the third group 3 are composed of the pin members 10, 11
The cam grooves 14a, 14b of the mechanical cam member 14
Are connected to each.

Reference numeral 17 denotes a motor, which rotates (rotates) the mechanical cam member 14 based on a signal from the controller 21.
I am letting you. A sensor 18 detects the rotational position of the motor 17 and sends a detection signal to the controller 21.

Reference numeral 15 denotes a mechanical cam member, which is a cam groove 15a of a movement locus of the zoom portion 30 by focusing.
And a cam groove 15b of the movement locus of the front group 4a in the fourth group 4. The front group 4a is connected to the cam groove 15b of the mechanical cam member 15 by a pin member 33.

Reference numeral 36 denotes a movable table, which is connected to the cam groove 15a of the mechanical cam member 15 by the pin member 12 and is configured to be movable in the optical axis direction with respect to the lens housing 6. Similar to the zoom lens device shown in FIG. 8, the movable base 36 has the mechanical cam member 14, the motor 17, and the sensor 18 mounted on the movable base 36.

A motor 19 rotates the mechanical cam member 15 based on a signal from the controller 21. Reference numeral 20 denotes a sensor, which detects the rotational position of the motor 19 and sends the detection signal to the controller 21.

In this embodiment, with such a configuration, first, the rotational position of the motor 17 is detected in order to perform a focusing operation on a certain object using the focus operating section 22 under different focal lengths. . That is, the front group 4a of the fourth group 4 is moved along the optical axis based on the output signal from the sensor 18 for detecting the zooming position, and the second group 2 and the third group 3 are integrally maintained while maintaining their mutual positions. It is moving.

That is, the controller 21 calculates the rotation angle of the mechanical cam member 15 according to the focusing operation amount. Based on the calculation result, the mechanical cam member 15 is rotated by the motor 19 to move the zoom unit 30 including the second group 2 and the third group 3 and the front group 4a on the optical axis for focusing.

Next, when performing a zooming operation in the in-focus state, the controller 21 calculates the amount of movement of the movable lens (the second group, the third group, and the fourth group a) via the zoom operation section 23. First, the mechanical cam member 14 is rotated by the motor 17 and moved on the optical axis while changing the mutual positions of the second group 2 and the third group 3. That is, during zooming from the wide-angle side to the telephoto side, the second lens group 2 is moved and the image plane variation due to zooming is also moved by moving the third lens group 3.

On the other hand, the mechanical cam member 15 is further rotated by the motor 19 so as to maintain the in-focus state at all times even if the focal length changes based on the output signal from the sensor 18, and the second group 2 and Zoom unit 30 including the third group 3
And the front group 4a of the fourth group 4 is moved on the optical axis. As a result, it is possible to excellently correct the image plane variation due to the magnification change.

In this embodiment, the focusing operation and the zooming operation are performed by using the two mechanical cam members 14 and 15 having the two cam grooves forming a part of the lens moving mechanism. ing.

In particular, the difference from the lens moving mechanism of the zoom lens device shown in FIG. 8 is that the zoom section 30 and the front group 4a.
2 cam grooves 15 to change the position due to focusing
By using the mechanical cam member 15 having a and 15b, the number of each member such as the motor and the sensor is reduced from three to two. As a result, in this embodiment, the entire apparatus is simplified.

Next, the shapes of the two cam grooves 15 and 15b provided in the mechanical cam member 15 will be described.

Mechanical cam member 15 in this embodiment
The shapes of the cam grooves 15a and 15b to be machined are formed so as to satisfy the following conditions.

That is, JP-A-2-
In the zoom lens disclosed in Japanese Patent No. 154216, as shown in FIG.
It is shown that the following relational expression (1) is established in the optical (paraxial refractive power) arrangement diagram ((A) when an object is at infinity and (B) is focused on a near object) shown in (B). There is.

[0041]

[Equation 1] The above equation (1) shows the relationship between the movement amount Δ of the object point, the movement amount x of the zoom unit 30 and the movement amount y of the front group 4a of the fourth group 4 based on FIG.

In the figure, f _R is the focal length of the fourth lens unit 4,
M is the distance between the image point of the fourth group 4 and the principal point of the fourth group 4 when the object distance is infinity, f _VC is the composite focal length of the zoom unit 30, and e ₁ is the first group 1 and the zoom The distance between the principal points of the unit 30, Δ is the amount of movement of the image point made by the first group 1 when the object distance becomes finite from infinity, and L is from the image point of the zoom unit 30 to the principal point of the zoom unit 30. The distance, f _F, is the focal length of the first lens unit 1.

In the present embodiment, the fourth group 4 shown in FIG. 2 is composed of two lens groups, a front group 4a and a rear group 4b, as shown in FIG. 3, and the front group 4a and the rear group 4b. Between them forms an afocal.

That is, when the object distance is infinity, the distance M between the image point of the fourth lens group 4 and the principal point of the fourth lens group 4 becomes M → ∞, and, for example, from the first lens group 1 to the fourth lens group 4. When the above equation (1) is applied to the lens system up to the front lens group 4a, the following equation is obtained.

[0045]

[Equation 2] However, in the equation (2), when the object distance becomes finite from infinity, the moving amount Δ of the image point created by the first group 1 is S (<0) as the distance from the principal point of the first group 1 to the subject. Then, Δ = −f _F ² / S (3), and if the subject distance S is determined, the movement amount Δ is uniquely determined.

Further, since the focal length f _F of the first group 1 and the principal point interval e ₁ of the first group 1 and the zoom section 30 are constant values determined by the lens system, the subject distance S and the zoom section 30 are combined. If the focal length f _VC is given, the relationship between the movement amount y of the front unit 4a and the movement amount x of the zoom unit 30 can be obtained from the equation (2).

The values of the movement amounts y and x can be arbitrarily selected if the equation (2) is satisfied. In addition, this movement amount y and x
The value of must be selected from an optical point of view, but for example, if y = x ² is selected, focusing can be performed as shown below.

That is, the mechanical cam member 1 shown in FIG.
5, when the rotation angle of the mechanical cam member 15 is θ, a cam groove giving a locus of x, that is, the pin member 12
When the shape of the cam groove 15a fitted with is a continuous function x = g (θ) with a rotation angle θ, the shape of the cam groove giving a locus of y, that is, the shape of the cam groove 15b with which the pin member 33 is fitted. Is constructed as follows.

Y = x ² = {g (θ)} ² (4) By using the equations (2) and (4) shown above, the zoom unit 30 and the front group for each object distance and focal length are obtained. 4a
The values of the movement amounts x and y can be obtained.

The equations (2) and (4) shown above are applied to the first numerical example of the zoom lens proposed in Japanese Patent Laid-Open No. 2-154216 (Table-1 shown below). However, the subject distance and the zoom unit 30 at each focal length
The relationship between the movement amounts x and y of the front group 4a is obtained as shown in FIGS.

4 and 5 are graphs showing the relationship between the subject distance S and the movement amount x of the zoom unit 30 and the movement amount y of the front lens group 4a. The horizontal axis is the reciprocal of the distance S to the subject distance. ,
The vertical axis shows the position of the lens when the subject is at the distance S as 0 when it is at ∞.

[0052]

【table 1】 That is, according to the present embodiment, the zoom unit 3 is provided at each focal length.
Focusing can be satisfactorily performed by changing the movement amounts x and y of the front lens group 4a and the front lens group 4a in accordance with the subject distance S as shown in FIGS.

Further, the shape of the cam groove giving the locus of y, that is, the shape of the cam groove into which the pin member 33 is fitted is constituted by, for example, y = 3x = 3g (θ) (5) instead of the expression (4). Then, when the above formulas (2) and (5) are applied to the first numerical example (Table-1) of the zoom lens in JP-A-2-154216 in the same manner as described above, at each focal length,
The subject distance S and the movement amount x of the zoom unit 30 and the front group 4a,
The relation with y is as shown in FIG. 6 and FIG. 7, and the lens moving mechanism capable of performing good focusing as described above is obtained.

Although the present embodiment is applied to the zoom lens device previously proposed by the applicant, the present invention can be applied to any zoom lens having the above-described structure.

[0055]

According to the present invention, the lens moving mechanism of the zoom lens device according to Japanese Patent Application Laid-Open No. 2-154216 previously proposed by the applicant of the present invention includes two mechanical cam members having at least one cam groove as described above. In particular, one of the two mechanical cam members is used to change the position of the zoom unit including the second and third lens units and a part of the lens units forming the fourth lens unit by focusing. The number of members such as and sensors can be reduced from three to two as compared with the conventional zoom lens device, and thus a zoom lens device that can simplify the entire device can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an optical layout diagram of a zoom lens previously proposed by the applicant.

FIG. 3 is an optical layout diagram of a zoom lens previously proposed by the applicant.

FIG. 4 is an explanatory diagram showing a relationship between a subject distance and a movement amount x of a zoom unit according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing the relationship between the subject distance and the movement amount y of the front unit of the fourth unit according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing the relationship between the subject distance and the movement amount x of the zoom unit according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram showing the relationship between the subject distance and the movement amount y of the front unit of the fourth unit according to the first embodiment of the present invention.

FIG. 8 is a schematic view of a main part of a zoom lens device previously proposed by the applicant.

[Explanation of symbols]

 1 1st group 2 2nd group 3 3rd group 4 4th group 4a Front group 4b Rear group 30 Zoom part 6 Lens housing 7,8,9 Lens barrel member 10,11,12,13 Pin member 14,15 Mechanical cam Member 16 Mobile stand 17,19 Motor 18,20 Sensor 21 Controller 22 Focus operation part 23 Zoom operation part

Claims (2)

[Claims] 1. A zoom lens having a fixed first group in order from the object side, a second group and a third group for changing the magnification by changing the mutual distance, a focusing fourth group and a fixed fourth group. In the apparatus, a first group for moving the second group and the third group on the optical axis by changing their mutual positions and a group for moving the fourth group on the optical axis.
Mechanical cam member, and a second mechanical cam member that moves the fourth group on the optical axis and moves the second group and the third group on the optical axis while maintaining the mutual positions. A zoom lens device characterized in that 2. A first group which is fixed in order from the object side, a second group for zooming, a third group for correcting an image plane variation due to zooming,
In a zoom lens device having a focusing 4a group and a fixed 4b group for imaging, the second group and the third group are moved on the optical axis while changing their mutual positions, and the fourth group is moved. A first mechanical cam member for moving on the optical axis, and a second mechanical cam for moving the fourth group on the optical axis and moving the second group and the third group on the optical axis while maintaining mutual positions. A zoom lens device characterized in that a zooming operation and a focusing operation are performed using a member.