JP2960070B2 - Lens position control device for zoom lens - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens position control apparatus for a zoom lens, particularly a zoom lens of a type in which a focusing lens group is provided behind a variable power lens group. .

[Prior Art] In a zoom lens system in which a focusing lens group is provided behind a variable power lens group, the position of the focusing lens group changes depending on the subject distance, and the position of the variable magnification lens group, that is, the magnification varies. Also changes according to the subject distance. Therefore, for example, a variator lens group and a compensator lens according to the rotation of a cam barrel, such as a zoom lens in which each lens group is arranged from the front side in the order of a focusing lens group → a variator lens group → a compensator lens group → a relay lens group. By changing the relative distance in the optical axis direction with the group, it is possible to maintain the focused state without moving the position of the focusing lens group and perform zooming. It is necessary to move the position of the focusing lens group. Especially when taking a picture while changing the magnification as in a video camera, blurring must not occur. In addition, complicated lens position control such that the position of the focus lens group must be changed is performed.

As a conventional lens position control of such a zoom lens, for example, Japanese Patent Application Laid-Open No. 62-296110 is known.

In this lens position control method, as shown in FIG. 3, a zoom position (horizontal axis) from a telephoto end (T) to a wide-angle end (W) of a variable power lens group is divided into complex regions at equal distances. The trajectory of the focus lens group is stored in the memory for each of the divided areas, and the information of the memory is extracted from the position information of the variator lens group when the variator lens group moves, and the focus lens group is moved along the trajectory. To move.

In such control, the position information of the variable power lens group is detected by position detection means such as an encoder, and the position information of the focus lens group is driven by the pulse motor. It is obtained by counting the number of drive pulses, and by driving the pulse motor in a range where no step-out occurs, the position of the focus lens group is uniquely determined by counting the number of pulses for driving the pulse motor.

In such a lens position control method, the position control of the focus lens group is performed by determining whether or not the subject is out of focus, in addition to the control based on the trajectory information in the memory, and a focusing method for determining focus. As a suitable method, a method in which a subject is received by a light receiving unit including a photoelectric conversion element through a zoom lens, and a focus lens group is controlled such that a high-frequency component and sharpness of an output image signal have a peak. This is because, when a so-called active method of externally measuring a subject distance using infrared light or the like is used, a zoom lens in which the focus lens group position differs depending on the zoom position (magnification lens group position) is considered. When performing fine control, it is necessary to store the position of the focus lens group in the memory corresponding to all zoom positions. This is due to the fact that the pitch becomes so fine that the information to be systematically stored becomes enormous and a large memory is required.

Therefore, if the system uses an image signal, there is no need to use a memory other than the zoom operation.
Focusing can be performed without following the locus for each subject distance as shown in the figure.

However, driving and controlling the focus lens group while searching for the focus position during the zooming operation only by this type of focusing method using an image signal requires, for example, a video camera to pick up an (NTSC) image in 1/60 sec. For this reason, focusing cannot be performed in terms of speed, so that the focus lens group is controlled by the focusing system while driving and controlling the focus lens group based on the trajectory stored for each of the plurality of divided areas as described above.

That is, as shown in FIG. 3, the locus of the focusing lens group with respect to the subject distance in the region where the zoom position is divided into a plurality of regions has little difference in the inclination of the curve within the range of the close subject distance. The position (vertical axis) of the lens group is divided into a plurality of parts, the moving speed of the focus lens group is typically determined for each divided zone, and stored in a memory. Is driven at the representative speed. Then, the blur state is periodically checked, and when the blur becomes larger than a predetermined amount, the drive of the focus lens group at the representative speed is stopped, and the focus lens group is moved in a direction in which the blur is reduced by increasing or decreasing the moving speed. When the focus lens group is driven and then driven again at the representative speed, a fine focusing operation is performed while moving the focus lens group approximately on a locus, thereby performing a zoom operation without blur. Before the zoom operation is started, for example, when the power of the camera is turned on, the focus lens group moves to a focus position by a focusing system operation.

Therefore, this lens position control device can efficiently drive and control the focus lens group with a memory having a very small storage capacity, and can perform lens drive control with a very simple system.

[Problems to be Solved by the Invention] In a zoom lens in which such lens position control is performed, a focus lens group is driven at the representative speed for each divided zone in synchronization with a zooming operation. When the focusing drive control is not performed based on the focus determination by the focusing system and the focusing is performed by manual operation (the above-mentioned mode is referred to as a manual focus mode), when the zooming operation is performed, the focus lens is changed. Since the focus position of the group moves greatly, for example, even if the focus is adjusted manually by a manual operation to focus on a certain subject, the focus is immediately blurred when the zoom operation is performed. When the operation of performing focusing is selected by the operation, the zooming operation must be prohibited.

Japanese Patent Application Laid-Open No. 63-83711 discloses a system which enables a manual focus mode without prohibiting a zoom operation of such a type of zoom lens. This involves moving the variable power lens and the compensator lens using a mechanical cam ring so that the movement trajectory of the focus lens accompanying the variable power operation can be approximated in an exponential manner. The encoder for detecting the position of the zoom lens and the encoder for detecting the position of the variable power lens are of a capacitance type, and the time variation coefficient and timing are used to prevent blur even during manual focusing.

However, the lens position control device of this type requires a mechanical cam ring, a capacitance type encoder, and the like, and the mechanism becomes complicated, and high precision is required, resulting in an expensive and large system. There were difficulties.

An object of the present invention is to provide a lens position control device of a zoom lens that enables a zoom operation without blurring even in a manual focus mode without using a mechanical cam ring or the like.

[Means for Solving the Problems] A configuration for realizing the object of the present invention according to the present application includes a first lens that moves along the optical axis direction to perform a zooming operation, and corrects and focuses during zooming. A second lens for performing a matching operation, and a first lens for detecting a position of the first lens.
Lens position detecting means, second lens position detecting means for detecting the position of the second lens, first driving means for driving the first lens, and second driving means for driving the second lens. 2 lens driving means, and driving control means for controlling the moving speed of the second lens in accordance with the driving of the first lens, wherein the driving control means changes the moving position of the first lens. Speed setting means for setting a speed at which the second lens is correspondingly moved to maintain the in-focus state using information stored in advance based on the positions of the first and second lenses; and Storage means for storing a movement history of the second lens at a movement speed set by the speed setting means when moving from the long focal length side to the short focal length side of the first lens. Wherein the first lens is When moving from the focal length side to the long focal length side, a lens position control device for a zoom lens that drives and controls the moving speed of the second lens using the movement history information stored in the storage means. When the first lens moves from the short focal length side to the long focal length side, if the movement history is not stored in the storage unit, the moving speed set by the speed setting unit Driving control of the second lens.

[Action] When zooming from the short focal length side to the long focal length side, the second
Move at a speed set by speed setting means using information stored in advance, and the movement history of the second lens at the set movement speed is stored in the storage means. When the magnification is changed from the short focal length side to the long focal length side, the driving speed of the second lens is controlled based on the movement history stored in the storage means. If is not stored, the second lens is moved at the moving speed set by the speed setting means.

[Embodiment] Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of a lens position control device for a zoom lens according to the present invention, which is an example used for a video camera.

1 is a variable power lens for changing the magnification of an image, 2 is a variable power lens 1
A focus lens that functions as a compensator and a focusing function in accordance with the movement of the lens, 3 is a so-called relay lens that indicates an imaging system lens, 4 is an optical low-pass filter, and a fixed lens 20 fixed at the forefront position.
Form a zoom lens, and form an image of the subject on the imaging means 5 such as a CCD.

Reference numeral 9 denotes a guide bar extending along the optical axis direction. A pulley 10a is fixed to one end and a screw 9a is
And is supported by a fixed cylindrical portion (not shown) so that the shaft can rotate and cannot move in the axial direction. Reference numeral 11 denotes a variable power drive motor (hereinafter referred to as a zoom motor), and reference numeral 10 denotes a reduction mechanism that connects a motor pulley 10b and a pulley 10a of the zoom motor 11 via a belt 10c. Through the guide bar 9. Guide bar 9 screw
A screw hole 1b formed in a support frame 1a for holding the variable power lens 1 is screwed into the 9a, and by driving the zoom motor 11, the guide bar 9 is rotated to move the variable power lens 1 in the optical axis direction. To change the magnification.

A brush 12 is fixed to a support frame 1a of the variable power lens 1, and a conductive brush portion 12a formed at a tip end of the brush 12 contacts an encoder pattern formed on an encoder substrate 13, so that the position of the variable power lens 1 is adjusted. Encoding is performed as an absolute value, and the variable power lens position information is output to the control unit 16 described later. The encoder pattern of the present embodiment can detect the position of 4 bits and 16 zones. Reference numeral 17 denotes a zoom switch which outputs a moving direction to the telephoto side (T) and a wide-angle side (W) and a drive signal to the zoom motor driver 11a to rotate the zoom motor 11 in a forward or reverse direction. Also outputs the moving direction signal.

On the other hand, similarly to the variable power lens, the support frame 2a of the focus lens 2
The focus lens is driven via a transmission mechanism 7 including a pulley 7a, a motor pulley 7b, a pulley 7a, and a belt 7c wound around the motor pulley 7b. The focusing operation is performed by transmitting the rotation of the pulse motor 8 to the guide bar 6 and moving the focus lens 2 along the optical axis direction.
The transmission mechanism 7 sets the gear ratio or the pulley diameter ratio such that the pitch is a predetermined amount of image blur for a predetermined focus drive pulse.

The normal focusing operation is performed by the control unit 16 which performs system control and image processing based on the image information from the imaging means 5, and as shown in FIG. The pulse motor 8 changes so that the peak appears clearly.
To move the focus lens 2. The pulse motor 8 is driven by inputting a drive pulse from the control unit 16 to the pulse driver 8a.
It is performed by the pulse counter inside. The focus detection based on the high-frequency component of the image may be based on the above-described method using the sharpness, that is, the method using the sharpness, the method using the inclination of the light-dark change portion, or the like.

A brush 14 is attached to a support frame 2a of the focus lens 2, and a reset position is formed in a pattern opposite to the brush 14 and a reset substrate 15 is provided.
When the conductive brush portion 14a of the brush 14 is connected to the pattern of the reset board 15 at a position outside the use range, a reset signal of the focus lens is output from the reset board 15 to the control section 16.

On the other hand, the drive control of the variable power lens 1 and the focus lens 2 during the zoom operation is performed in the same manner as described in the description of the related art. For example, the variable power lens 1 is driven at a constant speed, and the focus lens is driven. 2 is driven at the representative speed determined for each of the divided zones as shown in FIG. 3, and a focusing operation from a focusing means for performing focusing detection based on a high-frequency component of an image is performed in a superimposed manner.

In the present embodiment, as shown in FIG. 3, since the detection performance of the zoom encoder 13 is 16 zones, the zoom position is divided into 16 according to this, and the range of use of the focus lens is divided into 5, The representative speed and inclination of the focus lens 2 for each of the 80 divided zones (shown by arrows in the figure)
Is determined and stored in the memory 18.

When the zoom switch 17 is turned on to the T or W side, the control unit 16 controls the focus lens 2 including the direction.
From the position information of the variable power lens 1, the corresponding divided zone is determined, and the representative speed is read from the memory 18.

In the lens position control device having such a configuration, when the variable power operation is performed in the manual focus mode in which the focusing is manually performed without performing the focus detection of the focusing system, the movement of the variable power lens 1 is adjusted. Thus, the focus lens 2 moves at the representative speed of each zone read from the memory 18.

Here, the trajectory of the focus lens with respect to the subject distance shown in FIG. 3 has an interval between the adjacent trajectories (moving direction of the focus lens) much smaller on the short focus (W) side than on the long focus (T) side. ing.

In addition, when focusing on the T side, the diameter of the confusion circle expressing the amount of blur is generally proportional to the square of the infinite distance for the same focus movement, so that the focusing accuracy is relatively strict. . That is, even a slight shift of the focus lens position appears as blur.

From these facts, when the magnification is changed from the T side to the W side, the focus lens is substantially positioned on the trajectory at the time of manual focusing, so that the accuracy of the start focus lens position is good, Further, since the blur goes in a less noticeable direction, at the time of zooming from the T side to the W side in the manual focus mode, a sufficient image can be obtained even if the focus lens 2 is driven only by the representative speed in each divided zone read from the memory 18. can get.

However, when zooming from the W side to the T side, since the depth of focus is deep and the circle of confusion is large on the W side, focusing is performed while looking through the viewfinder even if the focus lens is not located on the track. Person is determined to be in focus. That is, at the start of the zooming operation, the focus lens 2 starts from a position shifted from the locus, and the deviation is large.

Therefore, in the manual focus mode, if the focus lens starts shifting from the W side to the T side with a deviation from the ideal focusing position, the focusing accuracy on the T side is severe as described above. Therefore, the more the blur of the image moves to the T side, the more noticeable it becomes.

In other words, when performing a scaling operation to adjust the angle of view,
Even if the focus is slightly out of focus, there is no practical problem by manually operating the focus lens again, but when aiming at the effect of moving the angle of view, it is necessary to avoid noticeable defocus.

Therefore, in the present embodiment, in the manual focus mode, when the magnification is changed from the T side to the W side, the focus lens is driven only at the representative speed in each divided zone. a movement amount ΔX of the focus lens, a moving speed V _M is stored in the focus memory (not shown) in each divided zone, the time of zooming from the W side T side direction, within the range of moving amount ΔX stored By driving at a speed opposite to the stored moving speed (negative if T → W is positive), double tracing is performed in the W → T direction while tracing the movement trajectory in the T → W direction in reverse. In this way, the effect of moving the angle of view without blurring is possible during manual focusing.

The operation procedure of the control unit 16 for performing such an operation will be described below with reference to the flowchart shown in FIG.

First, in the manual focus mode, a manual (M) focus operation, for example, one drive pulse is generated each time a manual focus switch button is pressed once, the pulse motor 8 is driven, and the focus lens 2 is moved. It is detected whether or not the focusing operation has been performed while looking through the viewfinder, that is, whether or not the focus lens 2 has moved (S-1). If the focus lens 2 has moved, it is stored in the focus (F) memory. focus lens movement amount [Delta] X, and resets the value of the focus speed V _M (S-2).

When the zoom switch 17 is operated in (S-3), the direction of the zoom movement is detected (S-4).

In (S-4), if the zoom direction is the T → W direction, the position information of the variable power lens 1 from the encoder substrate 13 and the information from the focus encoder that detects the position of the focus lens 2 by pulse counting are read ( S-
5) The focus speed is read from the memory 18 (S-
6). Then, the zoom motor 11 and the pulse motor 8 are driven (S-7). With the zoom operation, it is checked whether or not the variable power lens 1 and the focus lens 2 have moved based on signals from the zoom encoder and the focus encoder (S-8). Then, if the movement is a variable power lens 1 and the focusing lens 2, a moving speed V _M and the moving amount ΔX of the focus lens 2 until it is input to the F memory when the change of the division zone (S-9). Zoom encoder 13 is 16
Since the output is not changed while the variable power lens is moving in one divided area because of the division, (S
At -10), it is checked whether or not the zoom switch 17 is on. If it is on, the zoom motor and the pulse motor are continuously driven, the zoom and focus encoder are read again, the zone is determined, and the focus in that zone is determined. The focus lens is driven by the speed, and if the zone changes, the same operation is repeated until the zoom switch 17 is turned off. When the zoom switch 17 is turned off, the driving of the zoom motor and the pulse motor is stopped (S-11). At that time, the focus lens moving amount ΔX and the speed from the zone switching are changed.
The V _M is input to the F memory (S-12). Incidentally, F memory are provided the same number as the divided zone, the amount of movement ΔX and velocity V _M is inputted to each separate memory for each zone Setsu換Ri.

On the other hand, in (S-4), if the zooming direction is the W → T direction, the moving amount Δ of the focus lens 2 from the F memory
And X, reads the moving velocity V _M (S-13).

Here, when the zooming operation in the T → W direction is completed before switching from the W → T direction, and the focus lens 2 is manually moved at that zooming position to perform focusing (S-1). ),
Since the memory contents of the F memory have been reset, (S
In -14), the F memory is determined to be 0 and the process proceeds to (S-5). Also, when the zooming direction at the start of photographing is set to the W → T direction, no data is stored in the F memory, so that the F memory is also determined to be 0.

If it is determined in step (S-14) that data is stored in the F memory, that is, the zooming operation in the T → W direction is completed, and the zooming direction is changed in the W → T direction without moving the focus lens. Assuming that, the moving speed of the last F memory stored in the T → W direction read in (S-13)
Performing a zoom operation of driving the focusing lens 2 in the reversed V _M (S-15). If the zoom switch 17 is on (S-17), the F memory is sequentially read each time the amount of movement of the focus lens reaches ΔX, and the same operation is performed to move the trajectory when moving in the T → W direction. Move the focus lens in the reverse direction.

The storage contents ΔX of F memory in the middle, if V _M becomes 0, the process proceeds (S-14) from the (S-5), the zoom operation is performed by the content stored in the memory 18.

When the zoom switch 17 is turned off, the driving of the zoom motor and the pulse motor is stopped (S-18), and this routine ends.

In the above embodiment, the DC motor and the absolute encoder are used for driving and position detection of the variable power lens. However, similar effects can be obtained by using an incremental encoder or a pulse motor.

Although a pulse counter that counts driving pulses is used for detecting the position of the focus lens, an absolute encoder may be used separately, or a combination of a DC motor and an encoder may be used.

Although the lens of the first group on the front surface is fixed, the same control can be performed with a zoom lens using a relay system of the rear group as a focus lens, and the first group moves with a certain locus with the second group during zooming. However, the same operation can be performed by relatively moving the two with a cam or the like.

[Effects of the Invention] As described above, according to the invention of claim 1,
When moving the first lens for performing the zooming operation from the long focal length side to the short focal length side, the second lens for performing the zooming correction and focusing operations so as to maintain the in-focus state. Performing the speed control using the moving speed set by the speed setting means using the information stored in advance,
The movement history is set in advance, and when the first lens moves from the short focal length side to the long focal length side, the second lens
By controlling the movement speed of the lens using the history information, for example, in a lens position control device that can increase the focusing accuracy even in manual focus, even when the movement history is not stored, from the short focal length side Since the speed of the second lens can be controlled at the time of zooming to the long focal length side, the speed of the second lens can be controlled while maintaining a substantially focused state in any state. .

According to the second aspect of the invention, for example, when the second lens is moved by manual focus to focus on a new subject, the movement history stored in the storage unit is erased. Speed control of an erroneous second lens can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a lens position control device for a zoom lens according to the present invention, FIG. 2 is a diagram showing a relationship between a high frequency component of an image and a focus lens position, and FIG. FIG. 4 is a flow chart for explaining the operation of the embodiment shown in FIG. 1, showing the relationship between the lens position and the zoom lens position. DESCRIPTION OF SYMBOLS 1 ... Magnification lens 2 ... Focus lens 3 ... Relay lens 4 ... Low-pass filter 5 ... Photographing means 8 ... Pulse motor 11 ... Motor 12, 14 ... Brush 13 ... Encoder board 15 ... Reset board, 16 ... Control unit 18 ... Memory

Continuation of front page (72) Inventor Masahide Hirasawa 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Prefecture Tamagawa Works of Canon Inc. (56) References JP-A-62-62313 (JP, A) (58) Fields investigated ( Int.Cl. ⁶ , DB name) G02B 7/02-7/16

Claims (2)

(57) [Claims] 1. A first lens which moves along an optical axis direction to perform a zooming operation, a second lens which performs a correction and focusing operation during zooming, and said first lens. First lens position detecting means for detecting the position of
Second lens position detecting means for detecting the position of the first lens, first driving means for driving the first lens, second lens driving means for driving the second lens, Drive control means for controlling the movement speed of the second lens in accordance with the movement of the lens, wherein the drive control means maintains a focused state in response to a change in the movement position of the first lens Speed setting means for setting the speed at which the second lens is moved using information stored in advance based on the positions of the first and second lenses, and at least a short distance from the long focal length side of the first lens. Storage means for storing the movement history of the second lens at the movement speed set by the speed setting means when moving to the focal length side, wherein the first lens has the short focal length From the distance side to the long focal length side When moving to the lens position control device of the zoom lens that drives and controls the moving speed of the second lens using the information of the movement history stored in the storage means, When moving from the focal length side to the long focal length side, if the movement history is not stored in the storage means, the second lens is driven and controlled by the movement speed set by the speed setting means. A lens position control device for a zoom lens. 2. The zoom lens according to claim 1, wherein said drive control means erases the storage contents of said storage means when detecting the movement of said second lens other than the zooming operation. Lens position control device.