JPH0943485A - Lens position control device - Google Patents

Abstract

(57) Abstract: In a device that vibrates a lens to detect a focus detection state of a photographing lens, to reduce focus movement when the autofocus mode is stopped. A first mode for moving a focus lens based on a focus detection signal obtained by slightly moving a part of a photographing lens in a front-back direction along an optical axis for focus detection. , A setting means for setting a second mode for moving the focus lens by a manual operation, and when the second mode is set by the setting means, a part of the lens is slightly moved. Stopped at the point position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens moving mechanism suitable for a photographing lens with an autofocus function for detecting a focused state by moving an optical lens group in the optical axis direction.

[0002]

[Prior art]

[Prior Art 1] Conventionally, as an autofocus device for a video camera, there is a hill-climbing system that detects the fineness of a photographic screen from high frequency components in a video signal and controls the lens position so that the fineness is maximized. Are known. This method is
The details are described in Japanese Patent Application Laid-Open No. 56-511164, and the method will be briefly described below with reference to FIG. In the figure, 100 is a lens, 101 is a signal processing unit, 10
2 is a motor.

The light of the subject entering the lens 100 is converted into an electric signal by the signal processing unit 101. The signal processing unit 101 uses the fact that the higher frequency components of the electric signal are less when the lens is in a poor focus state and are greater when the lens is in focus. A period for forming one screen after passing through the filter, that is, one field period (1/1 in the case of a television system)
The detection and integration are performed over 60 seconds to detect the focus condition.

Then, the focus lens is moved by the motor so that a high frequency signal can be obtained to obtain a focused state.

By the way, in order to detect the out-of-focus direction, it is common practice to slightly move (wobble) some lenses of the taking lens 100 in the front-back direction along the optical axis.

Conventionally, in such a zoom lens apparatus, a lens moving mechanism for slightly moving the lens group is shown in FIG.
The method shown in is generally used. In the figure, 103 is a lens group that moves slightly, 103a is a holding member that holds the lens 103, and 104 is a fixed portion (fixed lens barrel) of the lens apparatus main body. Lens holding member 103a
Is fitted in a hole (not shown) provided in the fixed portion and is supported in the direction of linear movement in the optical axis direction. Reference numeral 105a denotes a male screw of a feed screw directly connected to the motor, which is arranged parallel to the optical axis and which is provided on the lens holding member 103a.
3b is engaged.

Under such a configuration, the lens 103 is slightly moved by the rotation operation of the motor 105, and the focusing direction is detected by the signal processing unit.

[0008]

By the way, a manual operation for focusing is performed by an autofocus mode in which the focus lens is moved based on a focus detection signal obtained by slightly moving such a lens and a manual operation by a cameraman. There are cameras that can set the mode. Further, conventionally, when switching from the auto focus mode to the manual operation mode, the movement of the movable lens is merely stopped.

However, if the moving lens is not accurately stopped at the midpoint of vibration, the focus position may be slightly displaced. This shift is not a serious problem in the case of a dark photographing lens or a camera that does not require a high resolution, but it is a problem in a photographing apparatus that requires a high resolution. In particular, for a commercial device used in a television station or the like, there is a possibility that this out-of-focus is observed and the image becomes unsightly.

In some cases, even if the entire moving range of the focus lens is moved, accurate focusing may not be achieved.

[0011]

In order to solve this problem, the present invention is obtained by slightly moving a part of the photographing lens in the front-back direction along the optical axis for focus detection. Based on the focus detection signal thus obtained, there is provided a setting means for setting a first mode for moving the focus lens and a second mode for manually moving the focus lens, and the setting means sets the second mode. When the mode is set, some of the lenses are stopped at the midpoint position of the minute movement.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, FIG. 4 shows an overall view of a lens moving mechanism of the present invention. In the figure, reference numeral 51 is a focus lens group for focusing, 52 is a zoom lens group for zooming, 53 is a diaphragm section for adjusting exposure, and 5 is a zoom lens group.
Reference numeral 4 denotes a lens group that slightly moves in the optical axis direction for focus detection, 56 denotes a driving unit for driving the lens, 57 denotes a relay lens group for performing an image forming action, and 58 denotes a driving unit for driving the focus lens group 51. Is. Reference numeral 59 is an image pickup device, 60 is a control unit that controls the drive units 56 and 58 to operate the automatic focus adjustment function, and 61 is a circuit that executes control of the entire camera. Reference numeral 70 denotes a switch for setting an autofocus mode (first mode) for moving the focus lens and a manual mode (second mode) for manually moving the focus lens based on the obtained focus detection signal.

In such a configuration, under the first mode condition, the lens group 54 for focus detection is such that even if the lens group 54 is slightly moved in the optical axis direction, the image magnification hardly changes and only the focus is blurred. It has become. Therefore, by slightly moving the lens group 54 in the optical axis direction by the driving unit 56, the focus position on the image pickup surface of the image pickup device 59 changes slightly, which can be detected as a change in the video signal. This signal change is sent to the circuit 61 on the camera side for signal processing, and a focus detection signal obtained by calculating the amount and direction of out-of-focus is output to the control unit 60. The control unit 60 outputs a drive signal according to the amount and direction of out-of-focus, and the drive unit 58 drives the focus lens 51 to perform autofocus. On the other hand, in the manual mode, the focus lens is moved manually or by remote operation.

Next, FIG. 1 shows a specific lens moving mechanism. Reference numeral 1 is a lens unit that moves slightly, and 2 is a holding member that holds the lens unit 1, which is fitted in a fixed unit 3 (fixed lens barrel) and is movable in the optical axis direction. Reference numeral 4 denotes a disc cam having a cam surface machined on its outer periphery, which is connected to the output shaft of a stepping motor 5 attached to the fixed portion 3 and is arranged so that the cam surface is in contact with the end surface of the lens holding member 2. Has been done. The motor 5 is controlled to repeat forward rotation and reverse rotation.

Further, although the disk cam 4 is directly connected to the output shaft of the motor 5 in the same drawing, it may be connected via an appropriate speed reducing mechanism. Reference numeral 6 denotes a ring-shaped member having a spring property, which is incorporated between the lens holding member 2 and the fixing portion 3,
So that the holding member 2 is always in contact with the cam surface of the disc cam 4,
Pressing is urging. 10 is a photo sensor, which is a cam 4
The rotational position of the cam 4 is detected by detecting the light reflected from the light reflecting portion 40 provided with.

FIG. 2 is a graph showing the cam shape of the disc cam 4 and the relationship between the rotational angle and the cam displacement. In FIG. 2, the center of rotation of the disc cam 4 is taken as the z-axis, and when wobbling is not performed, that is, when the lens portion 1 is at the reference position, the position of the cam surface with which the lens holding member 2 is in contact or the normal rotation direction. Assuming that the angle when the action center of the reversed cam surface is the reference is θ = 0 and the cylindrical coordinate system r-θz is taken, the cam shape is centered on θ = 0 as is clear from the characteristic diagram. range (-θ ₁ ~θ ₁₎
Up to the above, the lens portion 4 is slightly moved back and forth, and when it exceeds the range, the lens portion 4 is suddenly largely moved. The amount of change in the position (distance) r of the cam surface with respect to the angle θ in the range of use of the cam is specifically this disc-shaped cam shape. In θa to θa, in the range of −θa to 0

[0017]

[Outside 1] In the range of 0 to θ _a

[0018]

[Outside 2] Is formed so as to satisfy the above condition, and the moving distance of the lens portion is increased as the distance from the center of rotation increases.

In the above structure, when the motor 5 is repeatedly rotated in the forward and reverse directions, the disc cam 4 connected to the output shaft of the motor 5 also rotates. At this time, since the lens holding member 2 is pressed against the disc cam 4 by the spring 6, when the disc 4 rotates and the displacement of the cam surface in contact with the lens holding member 2 changes, the lens holding member 2 Following this, the lens unit 1 moves forward and backward in the optical axis direction, and the lens unit 1 moves back and forth in the optical axis direction. In this way, wobbling is achieved.

In the present embodiment, the disc cam having the above-described shape is used to control the rotation of the cam up to the maximum angle θ ₂ of one rotation or less when the depth of focus is deep, so that wobbling can be performed at high speed. I am trying. On the other hand, as shown in FIG. 2, when the depth of focus is shallow, the cam surface where the displacement of the cam is small (-θ _{1 to} θ ₁ ) is used. The number of rotations does not become too low, and the lens group can be wobbled with high accuracy.

As described above, with the lens moving mechanism of this embodiment, even when the depth of focus is deep and the amount of lens movement is large, wobbling can be performed at high speed, and even when the depth of focus is shallow and the amount of lens movement is small, It is possible to perform wobbling with high accuracy. Of course, these turning angle controls are the zoom position information that determines the depth of focus, and
It will be performed based on the aperture value.

FIG. 3 shows the cam shape of the disc cam of the second embodiment of this embodiment. However, the parts other than the disc cam have the same structure as in the first embodiment.

In FIG. 3, a cylindrical coordinate system r similar to that in FIG.
If θz is taken, in the disc cam of the present embodiment, the z-axis and the cam surface are separated from each other within a minute angle Δθ in the vicinity of the position of θ = 0 corresponding to the wobbling lens group at the reference position. Given that the distance r is constant and within the range of Δθ,

[0024]

[Outside 3] Other than that

[0025]

[Outside 4] It is characterized in that the shape of the cam is set so as to satisfy the relationship.

According to the present embodiment, when the wobbling process is not performed and the stop position of the disc cam deviates from the position of θ = 0 due to the stop accuracy of the motor or the like, the wobbling lens group moves from the reference position. , The problem that the focus is out of focus is solved. In the present embodiment as well, the same effect as in the first embodiment can be obtained by rotating the motor so as to rotate the disc cam outside the range of Δθ during wobbling.

In the present embodiment, while devising the shape of the cam, a disc-shaped cam is further provided with a detection section for position detection as shown in FIG. The control is performed so as to return to the origin position (reference position) so that a slight focus shift does not occur when switching to the operation mode.

Specifically, as shown in FIG. 1 (B), a reflecting portion 4a for reflecting light is provided on a part of the cam 4, and the photo sensor 10 receives light emitted from the light emitting portion of the photo sensor. It is fixed so that the light is reflected by the reflecting portion 4a and enters the light receiving portion of the photo sensor. Then, when the mode setting unit 70 switches from the auto focus mode to the manual mode, the reference position is confirmed by detecting the output of the photo sensor by receiving the output of the photo sensor without stopping the moving lens at that time, and the middle point The processing is performed so as to stop at the position, that is, the origin.

In the above, the embodiment in which the movement of the lens holding portion is directly controlled by the cam has been shown. Next, FIG. 5 shows another embodiment.

In the figure, 1 is a moving lens group, 2 is a lens holding member for holding the moving lens, and 3 is a fixed portion (fixed lens barrel) of the lens barrel main body. Reference numeral 20 denotes a metallic thin elastic disk having copper as a main component, which holds the lens holding member 2 in its inner diameter and is fixed to the fixing portion 3 in its outer diameter. However, the lens holding member 2 and the elastic disk 20 do not rotate with respect to the fixed portion 3. 4 is a cam similar to that described above.

Reference numeral 11 denotes a ring-shaped plate, and pin members 11a and 11b having sharp tips are attached to one surface of the plate at two positions symmetrical with respect to the optical axis center. A conical hole 13 and a V-shaped groove 14 are formed at a position deviated from the position of 11b by 90 °. However, the positions of the conical hole 13 and the V-shaped groove 14 are assumed to be shifted by 180 °. The tip ends of the pin members 11 a and 11 b are in contact with the end surface of the lens holding member 2. Incidentally, FIG.
5A shows a main part of the lens seen from above, and FIG. 5B shows a main part seen from the side.

A conical hole 15 is formed on the wall surface of the fixing portion 3 facing the conical hole 13, and between the conical holes 13,
The ball member 16 is sandwiched. Further, a through hole 17 is provided on the wall surface of the fixed portion 3 facing the V-shaped groove 14. A ball member 18 is fitted in the through hole 17 so as to project to both sides of the hole 17. One surface of the ball 18 is fitted in the V-shaped groove 14, and the opposite side is in contact with the cam surface of the cam member 4. The cam member 4 is rotatably supported with respect to the fixed portion 3, and can be electrically driven by a motor or the like.

Reference numeral 4b is a disc having a slit, which is attached so as to rotate in synchronization with the cam member 4. Reference numeral 21 denotes a photo interrupter, which is arranged so as to sandwich the disc 4b, and detects when the slit of 4b passes between the two when the cam member 4 and the disc 4b rotate.

In such a structure, when the cam member 4 is electrically rotated, the spherical member 18 is pushed by the cam surface and moves in the through hole 17 toward the ring-shaped plate 11 so that the ring-shaped plate 11 is moved. Push. The plate 11 has opposite grooves 13 and 15
The movement in the direction perpendicular to the optical axis is restricted by the effect of the spherical member 16 sandwiched between the conical holes and the spherical member 16 fitted in the V-shaped groove 14 and the through hole 17, so that 16 is a fulcrum. Inclining to the lens holding member 2 side. Then, the pin members 11a, 1
1b pushes the lens holding member 2, and the holding member 2 moves in the optical axis direction.

On the other hand, by reversing the cam member 4, when the displacement of the cam surface contacting the spherical member 18 decreases, the elastic force of the elastic disc 20 causes the lens holding member 2 to move in the opposite direction. . In autofocus mode,
This operation is repeated to detect the focus state.

In particular, in this embodiment, since the ring-shaped plate 20 for pushing the lens holding member 2 is tilted with the spherical member 16 as a fulcrum, the lever members serve as the pin members 11a and 11b.
The ratio of the displacement amount that pushes the holding member 2 at the position of and the displacement amount that is given from the disc cam member 4 to the ring-shaped plate 11 through the spherical member 18 is from the spherical member 16 serving as a fulcrum to the pin member 11a
It is equal to the ratio of the distance of 11b and the distance of the ball member 16 to the ball member 18. That is, the displacement amount of the cam increases by the distance ratio times the lens movement amount. As a result, when you want to move the lens group by a very small amount, the effect of cam processing error is less than when the cam displacement and lens group movement amount are the same, and cam processing is easier and lens position accuracy is better. The effect of improving is also obtained.

On the other hand, when the auto focus mode is switched to the manual operation mode by the setting means 70 shown in FIG. 4, the output state of the photo interrupter is detected, and the cam is controlled to return to the reference position, that is, the midpoint position. It will be.

[0038]

As described above, according to the present invention, it is possible to obtain an image without deterioration when the mode is changed from the autofocus mode to the manual operation mode.

Further, the focusing operation can be performed accurately over the entire moving area of the focus lens.

[Brief description of drawings]

FIG. 1 is a diagram showing a lens moving mechanism according to the present invention.

FIG. 2 is a view showing the shape of a disk-shaped cam according to the present invention.

FIG. 3 is a diagram showing the shape of a disk-shaped cam according to the present invention.

FIG. 4 is a block diagram of an entire camera equipped with a lens moving mechanism according to the present invention.

FIG. 5 is a diagram showing a second embodiment of the lens moving mechanism according to the present invention.

FIG. 6 is a control block diagram of a conventional zoom lens.

FIG. 7 is a view showing a conventional lens moving mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Moving lens group 2 Lens holding member 4 Disc-shaped cam member 5 Motor 6 Spring member

Claims (2)

[Claims] 1. A first mode in which a focus lens is moved based on a focus detection signal obtained by slightly moving a part of lenses of a photographing lens in a front-back direction along an optical axis for focus detection. And a setting means for setting a second mode for moving the focus lens by manual operation. When the second mode is set by the setting means, a part of the lens is slightly moved. A lens position control device characterized by being stopped at a midpoint position. 2. In the first mode, the part of the lenses has a surface cam and is rotated about a predetermined axis and is slightly moved by the rotating operation of a disc-shaped cam member. The lens position control device according to claim 1.