JPH07117638B2 - Lens drive device using vibration wave motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device for a camera, and more particularly, to a vibration wave motor used for driving a lens, which has substantially the same operating characteristics as high response. The present invention relates to a lens drive device which is modified so that drive control can be performed in accordance with a demand for a focus adjustment operation of a camera.

(Prior Art) Conventionally, in a mechanism (autofocus mechanism) configured for automatic adjustment of a focal length in a camera, a DC motor is often used for driving a lens, and it is possible to reduce a size by using a reduction gear. Is configured to obtain a high torque with the motor.

In place of the DC motor as described above, in recent years, a vibration wave motor that can obtain high torque without using a reduction gear and has high responsiveness is one of the examples used for driving the focusing lens. There is something.

In a servo mechanism such as a lens driving mechanism for performing the above focus adjustment, closed loop control is performed by feedback information using an electronic control unit including a computer (hereinafter, these may be collectively referred to as a microcomputer). Therefore, the above-mentioned lens drive mechanism detects changes in the rotational speed of the drive lens system, etc.
In the motor, this detected control amount is fed back to the change in the voltage applied to the motor, while in the latter vibration wave motor, it is usually fed back to the change in the frequency of the power supply applied to the motor.

When the drive control of the lens system of the camera as described above is changed by an electronic control device using a microcomputer, the degree of the change is determined by design depending on the type of camera, required performance, etc. As an example, it is often designed as one capable of selecting a rotation speed (rotation speed) of about 16 to 128 steps.

(Problems to be solved by the invention) By the way, the lens system driving mechanism such as the autofocus mechanism described above forms an image of a subject at the time of photographing with a camera by focusing on a film (or a CCD or the like). Since it is for the purpose of not only enabling accurate focusing necessary for displaying a photograph without blur, but also the operation viewpoint that the photographer holds the camera in his hand to take a focus adjustment. It can be said that it is desirable that the mechanical movement of the lens system at the time is smoothly given and does not cause vibration or the like that adversely affects the photographing operation.

Considering the lens system driving device using the DC motor among the above, this is the rotation speed (rotation speed) from the microcomputer.
Since the followability of the actual rotation speed of the motor to the change instruction is not high, there is an advantage that it is suitable for smooth drive control. However, on the other hand, there is a problem that the performance is inferior in obtaining accurate stop control to a predetermined position with high accuracy.

On the other hand, the lens driving device using the above vibration wave motor has the characteristic that the operation of the rotational speed control is relatively easy and the response to the speed control is high, but the change of the motor rotational speed in response to the rotational speed change instruction from the microcomputer. Since the response of the follower is high, it has an excellent advantage that it is suitable for obtaining an accurate stop suppression to a predetermined position with high response, but on the other hand, due to its high response, it is rather a rotation. There is a problem in the drive control in which vibration accompanying the follow-up response to the number change instruction is likely to occur, and therefore a smooth rotation speed (rotation speed) change is performed.

The problem in the lens system driving device using this vibration wave motor becomes more remarkable, for example, in the case where the camera is configured to include the power focus driving lens system driving mechanism together with the above-mentioned autofocus mechanism, and has high responsiveness. In view of this point, a lens system driving device using a vibration wave motor, which has an excellent characteristic as a camera driving mechanism for focus adjustment and the like, has become an issue to be improved.

(Means for Solving Problems) The present invention solves the above-described problems, substantially corrects the operation characteristic of high response of the vibration wave motor used for driving the lens system, and drives the lens system of the camera. With the aim of providing a lens drive device that realizes the demand for high-precision fixed position control and smooth drive control without vibration that are required in the operation of, in a device using a vibration wave motor. is there.

Thus, the lens driving device using the vibration wave motor according to the present invention, which has been made to realize such an object, is characterized in that the lens system is provided so as to be movable in the optical axis direction, and the lens system is driven. In a lens system drive device including a vibration wave motor and an electronic control device that drives and controls the vibration wave motor to move the lens system to a set target movement position, the electronic control device includes a movement of the lens system. A first control circuit for setting a speed, and a second control circuit for intermittently changing the moving speed of the lens system to the set moving speed.
Control circuit, drive remaining amount detecting means for sequentially detecting the drive remaining amount of the lens system up to the target moving position at every minute time, and the vibration wave depending on the detection information of the drive remaining amount detecting means. An interval adjusting unit that determines an interval of the change following operation of the motor is provided, and the interval adjusting unit lengthens the interval of the change following operation when the remaining driving amount of the lens system is large, and is small when the remaining driving amount is small. The configuration is such that the interval of the change tracking operation is shortened.

A lens system driving device using the vibration wave motor having the above-described structure according to the present invention includes a lens system movable in the optical axis direction for focus adjustment as described above, and a mechanical element of the vibration wave motor for driving the lens system. And an electronic control device for driving and controlling the vibration wave motor. The electronic control device is generally composed of a microcomputer or the like.

In the present invention, the setting of the target movement position for moving the lens system is given based on distance information detected by the distance measuring device of the AF mechanism mounted on the camera, for example, lens system drive information in the power focus mechanism, For example, it is given by input information to an input means such as a dial type or a button type.

(Operation) According to the present invention, with the configuration described above, the interval of the rotation speed change instruction given from the electronic control unit to the vibration wave motor for follow-up control is reduced when the required remaining drive amount of the lens system is still large. It can be considered that the vibration wave motor becomes longer and the response of the vibration wave motor is substantially lowered. Therefore, the generation of vibrations associated with lens driving is suppressed, and smooth lens driving control is performed.

On the other hand, when the remaining amount of drive required for the focus adjustment lens is sufficiently low, the interval of rotation speed change instructions for tracking control is shortened and the characteristic of the vibration wave motor's high responsiveness is fully demonstrated. Therefore, it is possible to ensure highly accurate positioning and stopping accuracy of the lens system, and it is possible to obtain a highly accurate focus adjusting action.

(Example) Hereinafter, the present invention will be described based on an example shown in the drawings.

FIG. 1 is a block diagram showing a hardware configuration of an embodiment of a lens system driving device for focus adjustment according to the present invention. In FIG. 1, reference numeral 1 is a microcomputer constituting a part of an electronic control unit ( Hereinafter referred to as a microcomputer),
A program for moving a known lens system 4 that is movable in the optical axis direction for focus adjustment according to distance measurement information from a distance measurement device (not shown) or input information of a power focus mechanism is provided. It is set in advance.

The output signal from the microcomputer 1 is input to the rotation speed changing means 2, a predetermined frequency signal corresponding to the signal from the microcomputer 1 is output to the vibration wave motor 3, and the lens system rotates in accordance with the vibration wave motor 3. Drive controlled.

Reference numeral 5 denotes a pulse encoder E1 which generates a pulse proportional to the rotational drive amount when the lens system 4 is rotationally driven by the vibration wave motor. The pulse generated by the pulse encoder E15 is counted by the pulse counter C1.

Further, in the camera of this example, in addition to the autofocus mechanism that detects the moving position information for driving the lens system by using a distance measuring device (not shown), a lens system drive signal arbitrarily set by the camera operator is used. Based on this, a power focus mechanism for driving the lens system using the vibration wave motor is provided, and reference numeral 7 in FIG. 1 denotes an electronic device as a means for inputting a signal for driving the lens system by the operator of the camera. Shows the dial.

The electronic dial 7 is for rotating the lens system by an amount according to the amount of rotation by rotating the rotary knob, for example.

Reference numeral 8 is a pulse encoder E2 that generates a pulse in proportion to the amount of rotation when the electronic dial 7 is rotated.
Is a pulse counter C2 for counting the pulses generated from this pulse encoder E28.

In the lens system driving device of the present embodiment having the above configuration, the distance measurement information signal from the distance measuring device (not shown) of the autofocus mechanism is input to the microcomputer or is input by operating the electronic dial which is the input means of the power focus mechanism. The position information signals thus generated are input to the microcomputer, and based on these input signals, the microcomputer 1 determines the rotational speed when the lens system is rotationally driven, the target position for moving the lens system, the control mode, etc. The vibration wave motor 4 is driven and controlled according to a programmed procedure.

The control operation of the lens driving device having the above configuration will be described below by taking the program of this example set in the microcomputer so as to correspond to the power focus mechanism as an example.

FIG. 2 is a flow chart showing programmed contents, and this flowchart is explained as a set of independent routines A to J. In addition, since the result of the length control of the rotation speed change instruction interval performed for the follow-up control can be evaluated in a broad sense as the difference in the response of the vibration wave motor, in the following description, the length control of the above interval is referred to as the response control. Will be explained.

The operation of each independent routine is as follows, and is repeatedly executed from the start to the stop of the vibration wave motor.

A) Pulse input routine By rotating the electronic dial 7, information on the target position of movement of the lens system is input. The information on the target position is taken into the microcomputer 1 as a count signal from the electronic dial pulse counter C2.

The driving state of the lens system is taken into the microcomputer 1 as a count signal from the pulse counter C1, and the driving amount necessary for the lens system to move to the target position due to the difference between these count signals (hereinafter referred to as the relative drive remaining amount). referred) X ₁ is calculated.

The driving of the lens system may be started immediately when an input operation is performed on the electronic dial 7, and the input operation and the driving of the lens system may be performed in parallel.
The lens system may be driven after the input operation to is completed. The latter case is similar to the case of driving the lens system based on the distance information from the distance measuring device of the AF mechanism.

B) Remaining drive amount comparison / branching routine Based on the relative drive remaining amount X ₁ of the lens system calculated in the pulse input routine (A), the drive mode of the vibration wave motor is determined and the process routine for each mode is branched. .

For example, if the relative drive remaining amount X ₁ is X ₁ = 0, branch to the motor stop routine, and if the relative drive remaining amount X ₁ is positive (X ₁ > 0), branch to the motor forward rotation routine. Drive remaining X ₁
If is negative (X ₁ <0), each branch to the motor reverse rotation routine. In the motor reverse rotation routine, the absolute value of the relative drive remaining amount X ₁ calculated above is calculated.

This routine (B) constitutes a drive remaining amount detecting means of the lens system.

C ₁ ) Motor stop routine A drive signal is output to the vibration wave motor to stop the vibration wave motor.

That is, this branch routine means that the lens system is already at the position corresponding to the predetermined target position and, for example, the focus adjustment control is completed, and therefore the process returns to the initial state.

Responsiveness flag F is zero (mode without responsiveness control)
And

C ₂ ) Motor forward rotation routine The rotation direction of the vibration wave motor is set to the forward rotation direction, and a forward rotation drive signal to the vibration wave motor is output to the vibration wave motor.

Further, the relative drive remaining amount X ₁ from the pulse input routine (A) is directly substituted for the absolute drive remaining amount X ₂ .

C ₃ ) Motor reverse rotation routine The rotation direction of the vibration wave motor is set to the reverse rotation direction, and a reverse rotation drive signal to the vibration wave motor is output to the vibration wave motor.

Further, the relative drive remaining amount X ₁ from the pulse input routine (A) is substituted for the absolute drive remaining amount X ₂ with its positive and negative signs reversed.

D) Responsiveness change routine This routine decreases the responsiveness by increasing the interval of the vibration wave motor follow-up control when X ₂ becomes large according to the magnitude of the absolute drive remaining amount X ₂ , and makes the response substantially lower. _{When 2} becomes small, the follow-up control of the vibration wave motor is frequently performed to substantially improve the responsiveness, and forms a part of the interval adjusting means.

That is, in the case of the motor forward rotation routine (C ₂ ) and the motor reverse rotation routine (C ₃ ), the responsiveness flag F is checked, and if F = 0 (mode without responsiveness control), the motor is started (started). It branches to the acceleration / deceleration control routine as it is.

If F = 1 (mode with response control), the response comparison value N ₂ according to the absolute drive remaining amount X ₂ is obtained by the function fa (X ₂ ). The function fa (X ₂ ) in the present example is a function proportional to the absolute drive remaining amount X ₂ as shown in FIG. 3, and therefore has a large value if the required movement amount to the target position is large.

The responsiveness comparison value N ₂ is compared with the responsiveness counter N ₁ ,
If N ₁ ≧ N ₂ , N ₁ is cleared and the process branches to the target pulse interval calculation routine in the previous stage of acceleration / deceleration control.

If N ₁ <N ₂ , the routine branches to the N ₁ count-up processing routine, and acceleration / deceleration control is not performed. Note that the responsiveness counter N ₁ is incremented by 1 for each execution count of this flow by the responsiveness counter count-up routine (I) described later, and therefore N ₁ is gradually increased by repeated executions. Becomes

E) Target pulse interval calculation routine This routine is for setting the optimum rotation speed of the vibration wave motor, and is a part of the first control circuit for setting the movement (rotation) speed of the lens system. .

That is, in this routine of this example, the rotation speed of the vibration wave motor is expressed by the time T of the pulse interval, and its target value
Calculate T ₂ by the function fs (X ₂ ) of the absolute drive remaining amount X ₂ . This fs
(X ₂ ) is a function that is inversely proportional to X ₂ as shown in FIG. 4 in order to obtain the characteristic of accelerating when the remaining amount X ₂ is large and decelerating when the remaining amount is small. However, in this example, the target pulse interval is fixed when the absolute drive remaining amount X ₂ is a certain value or more.

F) Pulse interval comparison / branching routine This routine is for determining the conditions for making the actual rotation speed of the vibration wave motor (detected at the actual pulse interval) follow the rotation speed given by the target pulse interval set in the above routine (E). Routine, which constitutes a part of the second control circuit.

That is, the target pulse interval T ₂ given in the target pulse interval calculation routine (E) is compared with the actual pulse interval T _1, and according to the comparison result, the routine branches to the following routines.

If T ₂ = T ₁ , the acceleration / deceleration processing is not performed because the actual pulse interval matches the target pulse interval.

If T ₂ > T ₁ , the actual pulse interval is shorter than the target pulse interval, so the routine branches to the deceleration instruction routine.

If T ₂ <T ₁ , the actual pulse interval is longer than the target pulse interval, and the process branches to the acceleration instruction routine.

The actual pulse interval T ₁ is calculated by a T ₁ measurement subroutine (not shown) based on the signal from the pulse counter C ₁ . In this example, as will be described later, the execution of this T ₁ measurement subroutine is interrupted during the execution of the main routine of FIG.

G ₁ ) Acceleration instruction routine In the pulse interval comparison branch routine (F), T ₂ <T ₁
When is detected, the routine branches to this routine, and when the rotation speed of the vibration wave motor does not reach the maximum specifiable level, the drive frequency instruction applied to the vibration wave motor is lowered by one step. When the rotation speed of the vibration wave motor reaches the maximum specifiable level, that speed is maintained.

G ₂ ) Deceleration instruction routine In the pulse interval comparison branch routine (F), T ₂ > T ₁
When is detected, the process branches to this routine, and when the rotation speed of the vibration wave motor does not reach the lowest level that can be specified, the drive frequency instruction applied to the vibration wave motor is increased by one step. When the rotational speed of the vibration wave motor reaches the minimum specifiable level, that speed is maintained.

H) Routine flag setting routine This routine sets the control state to the mode with responsiveness control of F = 1 when the rotation speed of the vibration wave motor reaches the target speed or when deceleration processing is performed. It is for.

After that, this mode is continued until the vibration wave motor is stopped.

I) Count-up routine of responsiveness counter The responsiveness counter N ₁ is incremented by 1.

J) Pulse Interrupt Processing Subroutine The role of this subroutine is to calculate the time from the occurrence of the previous interrupt to the present interrupt and substitute it for the actual pulse interval T ₁ .

That is, in this routine, an interrupt signal is generated by the pulse from the pulse counter C1 detected from the lens system, and the T ₁ measurement subroutine is executed.

An example of a specific operation of the lens system driving device of this example having an electronic control device that performs the control described in the above flowchart will be described.

Now, it is assumed that the position information for rotating the lens system in the forward direction by a certain amount is input by operating the electronic dial 7.

By inputting this position information, the pulse counter C2 counts a predetermined number of pulses.

Along with this, execution of the main routine of the flow in FIG. 2 is started, and X ₁ is _first detected in routine (A).
Since X ₁ is positive, the motor is branched to the normal rotation mode to reach the routine (C).

Here the flag F is checked, initially F = 0.
R is cleared by clearing N ₁ because it is set to (E)
The target pulse interval T ₂ is calculated as a function fs (X ₂ ) of the absolute drive remaining amount X ₂ . In this example, this target pulse interval T ₂ is given as a value inversely proportional to the absolute drive remaining amount X ₂ as shown in FIG.

Next, in routine (F), the actual pulse interval T ₁ indicating the actual rotational speed of the lens system obtained as described in the above-mentioned subroutine (J) is compared with the target pulse interval T ₂ . Since T ₁ is smaller than T ₂ in the initial stage of the vibration wave motor start, the routine branches to the acceleration instruction mode of the routine (G). This returns through the N ₁ increment routine.

When the vibration wave motor is gradually accelerated and the rotational speed of the lens system is increased in accordance with the above repetitions, T ₁ = T ₂ is detected in routine (F). In this case, acceleration / deceleration is performed from routine (F). The routine is skipped, the routine jumps to the routine (H), the flag F is set to 1, and the routine returns.

In the next execution cycle, F = 1 in routine (D)
Therefore, the response comparison value according to the absolute drive remaining amount X ₂
N ₂ is calculated by the function fa (X ₂ ). This N ₂ is a value proportional to the absolute drive remaining amount X ₂ as shown in FIG. 3, and becomes a large value if the required amount of lens system drive up to the target position is still large.

The calculated responsiveness comparison value N ₂ is compared with the responsiveness counter N ₁ to detect whether or not the rotation speed of the lens system needs to follow the target speed. That is, when N ₁ ≧ N ₂ , it is determined that there is a need for tracking, and in routines (E), (F), and (G), the additional response for the tracking response of the vibration wave motor to the target pulse interval T ₂ at that time is added. Deceleration control or speed maintenance is discriminated, and a signal resulting from the deceleration control is output from the microcomputer 1 to the rotation speed changing means 2 to perform follow-up control of the vibration wave motor 3. On the other hand, when N ₁ <N ₂ , it is determined that the timing at which follow-up control is necessary has not been reached, and the routine returns after going through the increment routine of N ₁ .

When the follow-up control is performed by N ₁ ≧ N ₂ above, in order to newly determine the time of the next follow-up control based on the absolute drive remaining amount X ₂ , clear N ₁ in routine (D). Is done.

After the above control is performed as needed, when the lens system reaches the target position, X ₁ = 0 is detected in routine (B), the motor is stopped and the stop signal is output to the vibration wave motor. . At this time, the flag F = 0 is set, and the preparation for driving the next lens system is given.

In the above control, two characteristic actions are obtained.

That is, in the routine (E), since the target pulse interval T ₂ is calculated (inversely proportional) depending on the absolute drive remaining amount X ₂ at that time, the vibration wave set as the lens system approaches the target position. The rotation speed of the motor becomes slower, and therefore smooth deceleration control is performed.

Further, the interval at the time of controlling the actual pulse interval T ₁ to follow the target pulse interval T ₂ is given by the routines (D) and (I) depending on (proportional to) the magnitude of the absolute drive remaining amount X _2. For this reason, when the lens system is distant to the target position and is rotating quickly, tracking control is given by extending it. Conversely, when the lens system is slowly rotating toward the target position, frequent tracking control is performed. Therefore, the responsiveness change control that is substantially preferable as the camera lens system drive control is performed.

The present invention is not limited to the above-described embodiment, and the response change control is made to depend on the remaining drive amount to the target position in a stepwise manner, or a response is made according to the current motor rotation speed. It is of course possible to make the sex change control dependent.

(Effects of the Invention) As described above, according to the lens system driving device using the vibration wave motor of the present invention, the following effects are obtained.

Immediately after the vibration wave motor is started, the response is the highest and the rising characteristic is good until the target speed is reached or deceleration is performed.

After the motor starts up, if the absolute drive remaining amount is large, the response becomes low, the vibration generated by changing the rotation speed can be reduced, and the unnecessary rotation speed due to the rotation speed measurement error due to manufacturing error etc. Changes can be prevented and unpleasant vibrations can be reduced.

As the absolute drive remaining amount decreases, the responsiveness increases, and it becomes possible to accurately stop at a predetermined position.

[Brief description of drawings]

Drawing FIG. 1 is a block diagram showing an example of an outline of a hardware configuration of a lens system driving device using an oscillatory wave motor according to the present invention, and FIG. 2 is a diagram showing an example of a drive control flowchart in the embodiment. FIG. 3 is a diagram showing the relationship between the absolute drive remaining amount and the response comparison value, and FIG. 4 is a diagram showing the relationship between the absolute drive remaining amount and the target pulse interval. 1: Microcomputer, 2: Rotational speed changing means 3: Vibration wave motor 4: Lens system 5: Pulse encoder E1 6: Pulse counter C1 7: Electronic dial 8: Pulse encoder E2 9: Pulse counter C2

Claims (1)

[Claims] 1. A lens system movably provided in the optical axis direction, a vibration wave motor for driving the lens system, and drive control of the vibration wave motor for moving the lens system to a set target position. In the lens system driving device including the electronic control device, the first control circuit that sets the moving speed of the lens system and the actual moving speed of the lens system are intermittent with respect to the set moving speed. A second control circuit for changing and following the change, a drive remaining amount detecting means for sequentially detecting the drive remaining amount of the lens system up to the target position at every minute time, and the detection information of the drive remaining amount detecting means. And an interval adjusting unit that determines an intermittent interval of the change following operation of the vibration wave motor, and the interval adjusting unit lengthens the intermittent interval of the change following operation when the remaining drive amount of the lens system is large. Same drive remaining amount Lens system driving apparatus using the vibration wave motor, characterized in that when the small becomes is to shorten the intermittent interval of variation follow-up operation.