JPH02282212A - Lens position controller for zoom lens - Google Patents

Abstract

PURPOSE:To rapidly and surely move the lens from a reset position set on the outside of a use range to a focal position by moving the lens first at a high speed, then moving the lens at an ordinary focusing speed at the time of moving the 2nd lens group from the initial set position thereof to the focal position. CONSTITUTION:The position of the focusing lens 2 is detected by the signal from a reset substrate 15 when the power source of a video camera is turned on. A pulse counter which counts the position of the focusing lens 2 is set at zero when the lens exists in the reset position. The position of a variable power lens 1 is then detected by a zoom encoder 13 and the position information of the focusing lens 2 is read out of a memory 18. The focusing lens 2 is then moved at the initial speed of the high speed. The controller 16 drives and controls the focusing lens 2 at the ordinary focusing speed to focus the lens at a subject when the count value of the pulse counter arrives at the position of the subject distance. The initial focusing operation ends in such a manner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lens position control device for a zoom lens, and particularly for a zoom lens in which a focusing lens group is provided behind a variable power lens group. .

[Prior Art] In a zoom lens in which a focus lens group is provided behind a variable power lens group, the position of the focus lens group changes depending on the subject distance, and also changes depending on the position of the variable power lens group, that is, the magnification. The distance also changes depending on the subject distance. Therefore, for example, in a zoom lens in which each lens group is arranged from the front in the order of focusing lens group → variator lens group → compensator lens group → relay lens group, for example, the variator lens group and compensator lens group are arranged as the cam barrel rotates. Unlike other formats that can maintain focus and change magnification by simply changing the relative distance to the lens group in the optical axis direction without moving the position of the focusing lens group. It is necessary to move the position of the focusing lens group, especially when the magnification is not changed like in a video camera, so blurring must not occur, and the distance to the subject changes. Then, complicated lens position control is performed in which the position of the focus lens group must be changed accordingly.

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

As shown in Figure 4, this lens position control method divides the zoom position (horizontal axis) from the telephoto end (T) to the wide-angle end (W) of the variable magnification lens group into multiple regions at equal distances. The trajectory of the focus lens group is stored in memory for each divided area, and when the variable power lens group is moved, the information in the memory is retrieved from the position information of the variable power lens group, and the focus lens group is moved along the trajectory. I'm trying to move it.

In such control, the position information of the variable magnification lens group is detected by a position detection means such as an encoder, and the position information of the focus lens group is detected by the pulse motor, since the focus lens group is driven by a pulse motor. Obtained by counting the number of drive pulses,
By driving the pulse motor within a range that does not cause step-out,
The position of the focus lens group is uniquely determined by counting the number of pulses that drive 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 focus is out of focus, in addition to the control based on the trajectory information in the memory described above. A suitable method is to receive the object light through a zoom lens with a light receiving means consisting of a photoelectric conversion element, and to control the focus lens group so that the high frequency components and sharpness of the output image signal reach their peaks. This is because when using a so-called active method that measures the subject distance externally using infrared light, etc., the focus lens group position differs depending on the zoom position (variable magnification lens group position). When performing detailed control, it is necessary to store in memory the position of the focus lens group corresponding to all zoom positions. This is due to the fact that the pitch has become extremely fine, and as a result, the amount of information that must be stored in the system becomes enormous, necessitating a large memory.

Therefore, if the system uses image signals, there is no need to use memory except for zoom operations, and it is possible to focus without following a trajectory for each subject distance as shown in FIG. 4.

However, with only this type of focusing method that uses image signals,
Driving and controlling the focus lens group while searching for the in-focus position during zooming is difficult, as described above, because, for example, in a video camera, images are picked up every 1/60 sec (NTSC), so the focus cannot follow the speed. The focus lens group is driven and controlled by the trajectory stored for each of the plurality of divided regions, and the focus lens group is controlled by the focusing system.

In other words, as shown in Fig. 4, in the area where the zoom position is divided into multiple areas, the trajectory of the focus lens group relative to the subject distance does not differ much in the slope of the curve in the range of close subject distances, so the focus lens group The position of the lens group (vertical axis) is divided into multiple zones, the moving speed of the focus lens group is determined representatively for each divided zone and stored in memory, and the focus lens group is moved according to the position information of the variable power lens group. is driven at the representative speed. Then, the blur state is checked periodically, and if the blur exceeds a predetermined amount,
Stop driving the focus lens group at the representative speed,
The focus lens group is driven in a direction that reduces blur by increasing or decreasing the moving speed, and when it is in focus, it is driven again at the representative speed. A focus operation is performed to perform a zoom operation without blur. Note that before starting the zoom operation, for example, when the power of the camera is turned on, the focus lens group is moved to the in-focus position by the operation of the focusing system.

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

On the other hand, in such a lens position control device, the lens position, especially the position information of the focus lens group driven by the pulse motor, is obtained by counting the number of driving pulses of the pulse motor, and therefore, for example, When the main power of the camera is turned on, the focus lens group must be located at the reference position for pulse counting, and the number of pulses when the focus lens group is moved from this reference position to the position where the focus lens group is After obtaining the position information, the division zone stored in the memory is specified from the position information of the variable magnification lens group, and the representative speed during the zoom operation is determined.

The method for positioning the focus lens group at the reference position (reset position) is to return it to the reset position when the power is turned off, or return it to the reset position when the power is turned on, and then clear the focus or zoom position memory to zero. In other words, there is a method of resetting.

[Problems to be Solved by the Invention] By the way, if the reset position, which is the reference for the positional information of the focus lens group position, is within the normal drive range of the focus lens group, temperature errors, focusing errors, etc. may cause problems during use. Since the focus lens group is at the reset position, which causes inconvenience in terms of load and system, the reset position is provided outside the use range of the focus lens group.

For this reason, when the power is turned on, the focus lens group is located at a reset position outside the usable range, and autofocus operation begins from there, which poses a problem in that it takes time to achieve focus. In particular, with focusing methods that use image signals to find the peak position of high-frequency components in an image, if the focusing speed is too fast, there is a risk that the focus lens group will stop after passing the peak position. Focusing speed is slower than distance-based focusing systems.

Furthermore, since the reset position falls within the super-region of the focus lens group movement locus, the focus operation is slow due to the extremely blurred state.

An object of the present invention is to solve such conventional problems and to provide a zoom lens that can quickly and reliably move a focus lens group from a reset position set outside the usage range to a focus position. An object of the present invention is to provide a lens position control device.

[Means for Solving the Problems] The gist of the present invention to achieve the object is to provide a first lens group that moves along the optical axis to perform a zooming action, and a correction during zooming. and a second lens group that performs a focusing action, a first lens position detection means that detects the position of the first lens group, and a second lens position that detects the position of the second lens group. The detection means detects the position of the first lens group and the second lens group.
drive control means for controlling the position and moving speed of the lens group based on the degree of focus obtained from the information from the focus detection means; It has a storage unit that stores position information of the lens group, and an initial focus drive control unit that drives and controls the second lens group from its initial setting position to a focus position,
The initial focus drive control section moves the second lens group from its initial setting position to a second lens group position corresponding to the first lens group position stored in the storage section, by the focus detection means. A control operation based on the first movement speed is prohibited, and the first movement speed is
A lens position control device for a zoom lens is characterized in that drive control is performed at a second movement speed that is faster than the movement speed of the zoom lens.

[Function] The zoom lens lens position control device configured as described above initially moves at high speed when, for example, the camera is turned on and the second lens group is moved from the initial position to the in-focus position. , then moves at normal focusing speed and stops at the focused position.

[Example] The present invention will be described in detail below based on an example shown in the drawings.

FIG. 2 is a block diagram showing an embodiment of a lens position control device for a zoom lens according to the present invention, and is an example used in a video camera.

1 is a variable magnification lens that changes the magnification of an image; 2 is a focus lens that serves both as a compensator and a focusing function as the variable magnification lens 1 moves; and 3 is a so-called relay lens that is an imaging system lens; 4 is an optical low-pass filter, and a fixed lens 20 is fixed at the forefront position.
This constitutes a zoom lens, and forms a subject image on an imaging means 5 consisting of CG, D, etc.

Reference numeral 9 denotes a guide bar extending along the optical axis direction, to which a pulley 10a is fixed at one end and a threaded portion 9 at the other end.
a is formed, and is supported by a fixed cylindrical portion (not shown) so as to be rotatable and immovable in the axial direction. 11 is a variable power driving motor (hereinafter referred to as a zoom motor); 10 is a zoom motor 11;
Bell l□ motor pulley 10b and pulley 10a
The zoom motor 11 is a speed reduction mechanism connected via 10c.
The rotation is transmitted to the guide bar 9 via the deceleration mechanism 10. A screw hole ib formed in the support frame 1a that holds the variable magnification lens 1 is screwed into the threaded portion 9a of the guide bar 9, and by driving the zoom motor 11, the guide bar 9 is rotated to change the magnification. The lens 1 is moved along the optical axis direction to change the magnification.

A brush 12 is fixed to the support frame 1a of the variable power lens 1,
A conductive brush portion formed at the tip of this brush 12 on the encoder pattern formed on the encoder substrate 13]
, 2a are in contact with each other, and the position of the variable power lens 1 is encoded as an absolute value, and the variable power lens position information is output to a control unit 16, which will be described later. The encoder pattern of this embodiment allows position detection of 4 bits and 16 zones. Reference numeral 17 denotes a zoom switch, which outputs the movement direction to the telephoto side (T) and the wide-angle side (W) and a drive signal to the zoom motor driver 11a to rotate the zoom motor 11 in the forward or reverse direction. It also outputs a moving direction signal.

On the other hand, as for the focus lens 2, the support frame 2a of the focus lens 2 is connected to the guide bar 6, similarly to the variable magnification lens.
A pulley 7a, a motor pulley 7b, and a pulley 7a are screwed into the threaded portion 6a of the guide bar 6 and fixed to the guide bar 6.
The rotation of the pulse motor 8 for driving the focus lens is transmitted to the guide bar 6 through the transmission mechanism 7, which includes a belt 7c that is rotated by a motor pulley 7b, and the focus lens 2 is moved along the optical axis direction. A focusing operation is performed by moving the lens. Note that the transmission mechanism 7 sets the gear ratio or the diameter ratio of the pulley so that the pitch has a predetermined image blur amount with respect to a predetermined focus drive pulse.

A normal focusing operation is performed by a control unit 16 that performs system control and image processing based on image information from the imaging means 5, and as shown in FIG. Since the peak value changes, the pulse motor 8 is driven to move the focus lens 2 so that the peak appears clearly. The pulse motor 8 is driven by inputting drive pulses from the control unit 16 to the pulse smoke driver 8a, and the number of output pulses is determined by a pulse counter within the control unit 16. Note that the focus detection based on the high-frequency components of the image may be performed using a method based on the above-mentioned definition, that is, sharpness, a method that takes the slope of the brightness change portion, or the like.

A brush 14 is attached to the support frame 2a of the focus lens 2, and a reset substrate 15 on which a reset position is patterned is provided opposite to the brush 14. Part 1
4 a comes into contact with the pattern on the reset board 15 , so that a focus lens reset signal is output from the reset board 15 to the control section 16 .

On the other hand, the driving 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 explanation of the conventional technology.For example, the variable power lens 1 is driven at a constant speed, and the focus lens 2 is driven at a representative speed determined for each divided zone divided into a matrix as shown in FIG. 4, and a focusing operation from a focusing means that performs focus detection based on high frequency components of an image is superimposed.

In this embodiment, as shown in FIG. 4, since the detection performance of the zoom encoder 13 is 16 zones, the zoom position is divided into 16 zones, and the range of use of the focus lens is divided into 5 zones. The representative speed of the focus lens 2 is determined for each of a total of 80 divided zones and is stored in the memory 18.

In the zoom operation, when the zoom switch 17 is turned on to the T or W side, the control unit 16 determines the representative speed of the corresponding division zone from the memory 18 based on the position information of the focus lens 2 and variable magnification lens 1, including the direction. read out.

In such a type of lens position control device, in consideration of reading the subject image, the movement speed of the focus lens during zoom operation must be faster than the movement speed during normal focusing operation, and As shown in Fig. 4, the speed near the object ω distance on the T side is the fastest, and in order to enable focusing during zooming at this position, a faster action than normal focusing is required. It is necessary that this is possible. Here, this fastest representative speed ■ is taken as the focus initial speed.

In this embodiment, point A in FIG. 4 is the reset position of the focus lens 2, and the subject (3) in each zoom zone is
The focus lens position at each distance is stored in the memory 18 as a representative value, and when moving the focus lens from the reset position to the focus position, the control unit 16 adjusts the focus initial speed ■ or higher to the subject ω position at the zoom position. The focus lens 2 is driven at a speed of Counting of drive pulses starts from the start of movement.

The driving control operation of the focus lens from the above-mentioned reset position to the focus position by the control unit 16 will be explained based on the flowchart shown in FIG.

First, when the power of the video camera is turned on, whether or not the focus lens 2 is located at the reset position A is detected by a signal from the reset board 15, and if the focus lens 2 is not located at the reset position, , forcibly drives the focus lens 2 to the reset position. Then, when the focus lens 2 is located at the reset position or when it reaches the reset position, a pulse counter that counts the focus lens position is reset to zero. Next, adjust the position of the variable magnification lens 1 using the zoom encoder 13.
From the position of the variable magnification lens 1 detected here, the position information of the focus lens 2 corresponding to the distance to the subject (2) is read out from the memory 18, and the focus lens 2 is driven at the initial focus speed (2).

Then, when the focus lens 2 moves at the initial focus speed V and reaches the object distance position, that is, when the count value of the pulse counter reaches the object (3) distance position, the focus lens 2 moves at the initial focus speed V. , and the focus lens 2 is driven and controlled at a normal focusing speed that is slower than this initial focusing speed (2) to focus on the object to be focused, and the initial focusing operation is completed. Note that the magnification changing operation is prohibited during the operation of driving the focus lens 2 to this initial focus position.

In other words, when the camera is turned on and the focus lens moves from the reset position to the focusing position,
The camera moves at the fastest speed set for driving the focus lens 2 to the object (2) position, and then moves at the normal focusing speed to perform focusing, so rapid focusing is possible.

Further, since the movement speed of the focus lens during initial focusing is very fast, it is desirable to mute the audio signal of the microphone and prohibit transition to the recording mode in the camcorder in consideration of noise.

In the above embodiment, the focus lens 2 is driven at the fastest speed (V) of the focus lens 2 during the zoom operation during initial focusing, but the focus lens 2 is driven at a speed even faster than this speed V. An initial focusing operation may also be performed.

In addition, in the above embodiment, the focus lens is
Although the robot is moved at a high speed to the desired position, it may be moved to an arbitrary position such as 5 m, for example.

Furthermore, what is the point regarding the subject distance? For example, 0.3.1
, 3, and 5.00, and store the focus lens positions at these subject distances in memory in correspondence with each zoom zone, and manually input information on subject distances measured by other distance measuring devices. By doing so, it is possible to similarly start from a predetermined distance at the time of initial focusing.

Further, as another embodiment, the variable power lens l may be driven by a pulse motor in the same manner as the focus lens 2, and the position of the variable power lens may be detected by counting the number of drive pulses in the same manner. At that time, the power is turned on to return the variable power lens to the reset position, but in this case as well, the variable power lens is driven at a speed faster than the normal speed when changing the power, so that it can be quickly changed to the W end, for example. You can return the double lens.

The above embodiments have been explained using a pulse smoke motor as a motor for driving a focus lens, but a similar method can be used to drive a focus lens from a reset position using a combination of an incremental encoder and a normal DC motor. Initial focusing operation is possible. in this case,
The speed of the DC motor is usually controlled by pulse width, and the duty is set to -100% at the time of initial focusing to increase the speed.

In addition, the zoom lens structure may include a focus lens attached to the imaging lens system (such as a type in which the frontmost lens moves along a certain trajectory when changing magnification, the total length of the lens becomes shorter on the W side). , easy storage, and portability.In this latter type, when the power is turned off, the focus lens is returned to the reset position, and then the power is turned off. With a zoom lens, when the power is turned on, the focus will be on the W side (to) position.However, if you specify the zoom position using the zoom preset switch, etc., the zoom lens will focus at the preset zoom position from the reset position. You can specify the position.In this case, if you have a memory backup power source, you can store the variable magnification lens position and focus lens position in memory when the power is turned off, reset them when the power is turned on, and then restore them to the memory. The variable magnification lens and focus lens can be quickly returned to their respective positions.

[Effects of the Invention] As described above, according to the present invention, the second lens group can be moved to the in-focus position accurately and quickly without overrun before performing a zooming operation. ,
In particular, if the initial setting position of the second lens group is set to a super-infinite position, it is possible to quickly pass through the super-infinite region where absolutely no focusing occurs and smoothly enter autofocus operation.

[Brief explanation of drawings]

FIG. 1 is a flowchart illustrating the operation of an embodiment of the lens position control device for a zoom lens according to the present invention, FIG. 2 is a block diagram showing an embodiment of the lens position control device for a zoom lens according to the present invention, and FIG. FIG. 4 is a diagram showing changes in high frequency components of an image depending on the position of the focus lens, and FIG. 4 is a diagram showing a locus of the focus lens position that changes depending on the subject distance with respect to the zoom lens position. : Variable magnification lens, focus lens: Relay lens: Low pass filter: Imaging means 8: Pulse motor 11 ・ 16: Motor 12.14: Brush encoder board reset board control section 18: Memory Hessei 9! , be∆hebe≧chi

Claims (1)

[Claims] 1. A first lens group that moves along the optical axis to perform a magnification change function, a second lens group that performs a correction and focusing function during magnification change; A first lens position detection means for detecting the position of the first lens group, a second lens position detection means for detecting the position of the second lens group, and an operation for changing the position of the first lens group. and a drive control means for controlling the position, moving speed, etc. of the first and second lens groups based on the degree of focus obtained from the information from the focus detection means upon detection, the drive control means , a storage unit that stores position information of the second lens group with respect to at least one subject distance;
and an initial focusing drive control section that drives and controls the second lens group from its initial setting position to the focus position, and the initial focusing drive control section controls driving of the second lens group from its initial setting position to the stored focus position. Prohibiting the control operation based on the first movement speed by the focus detection means to a second lens group position corresponding to the first lens group position stored in the section, and moving the control operation faster than the first movement speed. 1. A lens position control device for a zoom lens, characterized in that drive control is performed at a second moving speed. 2. The initial focus drive control section of the drive control means sets the second movement speed to be higher than the highest second lens group drive speed during the zooming operation. Item 1. A lens position control device for a zoom lens according to item 1. 3. The zoom lens according to claim 1 or 2, wherein the drive control means prohibits a magnification change operation during an initial focusing operation of the second lens group by the initial focus drive control section. Position control device.