JP6332943B2 - Drive device and lens device for vibration actuator - Google Patents

Description

  The present invention relates to control of a vibration actuator such as an ultrasonic motor.

  As a method for controlling a vibration actuator, it is known to change the frequency of an AC signal applied to a vibrating body. FIG. 3A is an FN characteristic diagram showing the relationship between the applied frequency and the rotational speed of the vibration actuator, where the horizontal axis represents frequency and the vertical axis represents rotational speed. From the figure, it can be seen that the number of rotations can be changed by changing the frequency. The vibration actuator has a characteristic that the rotation speed increases when the frequency is scanned from the higher side to the lower side, and the rotation speed decreases again after passing through a certain frequency. The frequency at which this rotation speed is switched is defined as the resonance frequency of the vibration actuator. Call. In the control, the frequency is changed so that the current rotational speed becomes the target rotational speed (target speed).

  It is known that the FN characteristic diagram varies depending on the environmental temperature. FIG. 3B shows FN characteristics when the environmental temperature is 45 ° C., 25 ° C., and −20 ° C. Patent Document 1 proposes a method of maintaining such temperature characteristics, detecting the environmental temperature when driving the vibration actuator, and using an FN characteristic diagram corresponding to the detected environmental temperature. That is, the target rotational speed can be quickly obtained by scanning the vicinity of the frequency corresponding to the target rotational speed.

JP 2009-261173 A

  However, the FN characteristic diagram varies greatly due to individual differences and aging degradation. Since Patent Document 1 does not consider this, there is a case where the frequency corresponding to the target rotational speed and the frequency that actually gives the target rotational speed are separated from the FN characteristic diagram obtained from the environmental temperature. The target rotational speed cannot always be obtained quickly. For this reason, when the vibration actuator is applied to a drive unit for a focus lens or a zoom lens, there is a possibility that rapid focus adjustment or zooming cannot be acquired.

An exemplary object of the present invention is to provide a vibration actuator driving apparatus capable of causing a frequency of a signal applied to a vibration actuator to reach a frequency for setting the vibration actuator to a target rotational speed in a short time. Yes.

The drive device of the present invention is a drive device having a vibration actuator, a control unit for controlling the drive of the vibration actuator by giving a signal of a set frequency, and a temperature detection means for detecting the environmental temperature of the vibration actuator. each matching, the control unit, which drives a storage means for pre-Symbol vibration actuator stores the information indicating the start frequency is a frequency relationship environmental temperature of the vibrating actuator when starting driving, the vibration actuator in the acquired environmental temperature detected by the obtained and the temperature detecting means before KiOkoshi dynamic frequency by changing the frequency of the given El signals to the vibration actuator, the acquired starting frequency and the ambient temperature by the storage characterized in that it has an update means to update the information stored in the unit

According to the present invention, the frequency of the signal applied to the vibration actuator, it is possible to provide a driving apparatus of a vibration actuator capable of reaching in a short time the vibration actuator in frequency to the target rotational speed .

It is a block diagram of the camera system of this embodiment, and a block diagram of its lens microcomputer. It is a flowchart which shows the process of the lens microcomputer shown in FIG. It is a figure explaining the method to detect the starting frequency of the vibration actuator in this embodiment. It is a figure which shows the FN characteristic view of a vibration actuator, and its temperature fluctuation.

  FIG. 1A is a block diagram of a single-lens reflex digital camera system. The lens device 1 as an interchangeable lens is detachably attached to the camera body 20. This embodiment can also be applied to a lens-integrated camera.

  The lens device 1 forms an optical image of a subject and includes a focus lens 2. The focus lens 2 moves in the optical axis direction indicated by the alternate long and short dash line to adjust the focus. The focus lens 2 is held by a focus unit 3 that is a driven member. The driven member may be a zoom unit that holds a zoom lens.

  The lens device 1 includes a lens microcomputer 4, a driver circuit 5, a booster circuit 6, a vibration motor 7, a rotation amount detection unit (drive detection means) 8, a position detector 10, and a thermometer 11.

  A lens microcomputer (lens microcomputer, lens control means) 4 controls each part of the lens device 1. In particular, the lens microcomputer 4 controls the driving of the vibration motor 7 by giving a signal having a set frequency.

  As shown in FIG. 1B, the lens microcomputer 4 includes an internal timer 4a, an internal memory 4b, and a function (module) of the updating unit 4c. In the case of a lens-integrated camera, the camera microcomputer 22 described later may have these functions. The lens microcomputer 4 further includes a serial communication controller, an A / D converter, and an input / output port for communicating with the camera body 20 via the contact unit 25.

  The lens microcomputer 4 functions as a control device (control unit) that controls the driving of the vibration motor 7 by itself, but includes a thermometer 11 that detects the environmental temperature, a rotation amount detection unit 8 that detects the rotation of the vibration motor 7, and the like. A control device (control unit) may be considered.

  The output of the lens microcomputer 4 is connected to a driver circuit 5 and a booster circuit 6, and the output of the driver circuit 5 is connected to a vibration motor 7 that drives the focus unit 3. The driver circuit 5 performs power amplification for driving the vibration motor 7. The booster circuit 6 is a driving power source for the vibration motor 7, and the output of the booster circuit 6 is supplied to the driver circuit 5. The booster circuit 6 is a circuit (DC / DC converter) that generates a reference voltage to be applied to the vibration motor 7 and boosts the battery voltage up to about five times. The vibration motor 7 is an example of a vibration actuator that is driven by giving a signal having a set frequency. In this embodiment, the vibration motor 7 is an ultrasonic motor, but the drive frequency is not limited to an ultrasonic wave.

  The rotation amount detection unit 8 detects the rotation amount of the vibration motor 7, and the output (signal corresponding to the rotation) of the rotation amount detection unit 8 is supplied to the lens microcomputer 4. The rotation amount detection unit 8 includes a small disk that rotates in synchronization with the rotation of the vibration motor 7 and a photo interrupter element. The circular plate is cut out at the same pitch on the circumference, and a change in signal is detected depending on whether light projected from the LED of the photo interrupter element reaches the light receiving element or is blocked. Further, the time interval of one pulse of the signal from the photo interrupter element is measured, and the speed of the vibration motor 7 and the focus unit 3 is detected.

  The lens microcomputer 4 determines each control constant using one change of the signal from the photo interrupter element as one pulse. Since the movement amount of the focus unit 3 is proportional to the rotation amount of the vibration motor 7, the movement amount of the focus unit 3 can also be detected by counting the number of pulses.

  The absolute position detector 10 is position detection means for detecting the absolute position of the focus unit 3, and the output of the absolute position detector 10 is supplied to the lens microcomputer 4. The thermometer 11 is a temperature detection unit that is connected to the lens microcomputer 4 and detects the environmental temperature of the vibration motor 7.

  The camera body (imaging device) 20 is provided with an imaging device 21, a camera microcomputer (camera control means) 22, a release button (SW) 23, and a focus detection unit 24. The lens microcomputer 4 and the camera microcomputer 22 are connected via the contact unit 25 and can communicate with each other.

  The image sensor 21 photoelectrically converts an optical image formed by the photographing optical system, and is arranged on the optical axis of the focus lens 2 and is composed of a CCD or a CMOS. The camera microcomputer 22 controls each part of the camera body. An image sensor 21, a release button 23, and a focus detection unit 24 are connected to the camera microcomputer 22.

  The photographer generates a SW1 signal for starting autofocus (automatic focus adjustment) AF and photometry by pressing the release button 23 halfway, and generates a SW2 signal for instructing exposure by pressing the release button 23 halfway. The focus detection unit 24 detects the current position of the focus unit 3 with respect to the subject distance and the amount of focus deviation at the image sensor 21 from the output of the position detector 10 of the focus unit 3 or the output value from the above-described photo interrupter. . The focus detection unit 24 of the present embodiment employs a phase difference method that performs focus detection based on the phase difference between a pair of subject images.

  The camera microcomputer 22 stands by until there is an AF start instruction by the SW1 signal, and when there is an instruction, the detection result of the focus detection unit 24 is captured. The camera microcomputer 22 calculates the amount of movement of the focus unit 3 for obtaining focus from the amount of focus deviation, and communicates with the lens microcomputer 4 through the contact unit 25.

  The contact unit 25 has a plurality of metal contacts, and the lens apparatus 1 and the camera body 20 perform electrical communication and supply power from the camera body 20 to the lens apparatus 1.

  The lens microcomputer 4 activates the booster circuit 6 and applies a voltage of about 30 V to the driver circuit 5. When a voltage is applied to the driver circuit 5, the lens microcomputer 4 outputs a drive waveform having a predetermined frequency using the internal timer 4 a and drives the vibration motor 7 to start the movement of the focus unit 3. The lens microcomputer 4 gradually decreases the frequency and increases the rotation speed of the vibration motor 7 every time a predetermined time elapses in the internal timer 4a. The lens microcomputer 4 monitors the rotation amount detection unit 8 and compares it with the movement amount transmitted from the camera microcomputer 22. If they match as a result of the comparison, it is determined that the focus unit 3 has moved by a predetermined movement amount, and the drive of the vibration motor 7 is stopped.

  Further, the lens microcomputer 4 measures the output change time of the rotation amount detection unit 8 by the internal timer 4a, and compares it with a time value corresponding to the target speed (target rotational speed) set in the internal memory 4b. If so, change the frequency. As a result, the rotational speed of the vibration motor 7 is controlled to control the moving speed of the focus unit 3.

  The internal timer 4a is a time measuring means. The internal memory 4b is constituted by a ROM, a RAM, and the like, and is a storage unit that stores information indicating the relationship between the environmental temperature of the vibration actuator and the startup frequency shown in Table 1. In addition, the expression method of a relationship is not limited, A table | surface, numerical formula, or a graph can be utilized.

  The update means 4c acquires the starting frequency at which the vibration actuator actually starts from the acquired environmental temperature and the initial frequency obtained from the information stored in the internal memory 4b by scanning (or sweeping). That is, the update unit 4c acquires the current activation frequency of the vibration actuator by changing the frequency of the signal applied to the vibration actuator.

  FIG. 4 is a diagram illustrating a method for acquiring the activation frequency by scanning. Here, since the activation frequency is unknown at the time of the first drive, an example is shown in which scanning of the frequency is started from the maximum frequency (maximum value) that can be set. Gradually lower the frequency until activation is confirmed. Then, the output of the photo interrupter of the rotation amount detection unit 8 is monitored, and the frequency at the time when rotation is detected is stored in the internal memory 4b as activation frequency information. At that time, as shown in Table 1, it is stored in association with the environmental temperature.

  The updating unit 4c acquires the activation frequency corresponding to the acquired environmental temperature from the internal memory 4b. In the present embodiment, the update unit 4 c acquires the environmental temperature of the vibration motor 7 from the thermometer 11.

  The updating unit 4c acquires the activation frequency corresponding to the environmental temperature from the storage unit, and based on the activation frequency corresponding to the environmental temperature, is the frequency of the initial signal given to the vibration actuator to acquire the current activation frequency. Set the initial frequency. The updating unit 4c sets a frequency that is higher than the acquired activation frequency by a predetermined frequency as an initial frequency. In this way, the initial frequency is obtained from the acquired starting frequency. The predetermined frequency is not limited.

  In this way, at the time of the next drive, first, the ambient temperature at that time is first detected, the frequency corresponding to the ambient temperature at that time is searched from the startup frequency information stored in the internal memory 4b, and a predetermined amount higher than that frequency. Scanning starts at the frequency of. Thereby, a vibration actuator can be started in a short time.

  If the startup frequency information corresponding to the ambient temperature is not stored (if this is the first time driving at that ambient temperature), the current startup frequency is obtained by interpolation from the startup frequencies corresponding to the previous and next stored ambient temperatures. Alternatively, scanning may be started from the maximum frequency. Alternatively, scanning may be started from a representative value of the starting frequency at each temperature separately stored as initial value data (not an actual measurement value but an average value obtained from a simulation or other same device).

  The updating unit 4c updates the information stored in the internal memory 4b with the acquired activation frequency. Thereby, the influence of aged deterioration can be reflected in Table 1.

  FIG. 2 is a flowchart showing a vibration motor control method executed by the lens microcomputer 4 of this embodiment, where “S” represents a step. The flowchart shown in FIG. 2 can be embodied as a program for causing a computer to execute the function of each step. In the control method shown in FIG. 2, the communication sent from the camera body 20 through the contact unit 25 is analyzed and necessary processing is performed.

  First, in S101, the lens microcomputer 4 initializes the internal memory 4b, activates the booster circuit 6, activates the position detector 10, and prepares to receive communication from the camera microcomputer 22 (initialization process). In S102, the lens microcomputer 4 analyzes the communication from the camera microcomputer 22 and determines whether it is related to the focus drive command. If it is not a focus drive command (NO in S102), other processing is performed (S111), and the process returns to S102.

  On the other hand, if the communication is a focus drive command (YES in S102), the analog signal from the thermometer 11 is digitized by an A / D converter built in the lens microcomputer 4 and stored in the internal memory 4b as current temperature information. (S103).

  Next, in S <b> 104, the lens microcomputer 4 sets an initial frequency for starting scanning of the drive signal applied to the vibration motor 7. Specifically, the startup frequency data corresponding to the current ambient temperature is searched from the past startup frequency stored in the internal memory 4b and the ambient temperature data at that time, and the frequency is lowered by a predetermined amount from the frequency. Start scanning on the frequency side.

  Next, in S105, the lens microcomputer 4 detects the speed of the vibration motor 7 from the output of the rotation amount detection unit 8, and determines whether the current speed is faster or slower than the target speed. The lens microcomputer 4 performs an acceleration process when it is determined that it is slower than the target speed based on the output signal of the rotation amount detection unit 8 (S106), and performs a deceleration process when it is determined that it is faster than the target speed. Perform (S107).

  Next, in S108, the lens microcomputer 4 performs a process for confirming whether the vibration motor 7 is activated. Specifically, the output signal of the rotation amount detection unit 8 is monitored, and when the first signal is detected in the current drive, the ambient temperature at that time and the frequency of the drive signal applied to the vibration motor are determined as the startup frequency. Information is stored in the internal memory 4b. In other words, the activation frequency is detected every time it is driven, and is overwritten and stored together with the environmental temperature in the internal memory 4b.

  Next, in S109, the lens microcomputer 4 counts the number of pulses output from the rotation amount detection unit 8, and determines whether the focus unit 3 has been driven to the target position. If the target position has not been reached (NO in S109), the process returns to S105, and speed control and confirmation of arrival at the target position are repeated. If the target position has been reached (YES in S109), the lens microcomputer 4 performs a vibration motor stop process.

According to this embodiment, since the individual difference of the vibration actuator are taken into account, which can be reached in a short time the frequency of the signal applied to the vibration actuator, the frequency for the vibration actuator to the target rotational speed A control device for a vibration actuator can be provided. Thereby, quick focus adjustment can be performed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, A various deformation | transformation and change are possible within the range of the summary.

  The present invention can be applied to an application for controlling driving of a vibration actuator.

4 ... lens microcomputer, 4b ... internal memory (storage means), 4c ... update means

Claims (8)

A vibration actuator;
A control unit for controlling the driving of the vibration actuator by giving a signal of a set frequency;
A drive device having temperature detection means for detecting an environmental temperature of the vibration actuator,
The control unit is
Storage means for pre-Symbol vibration actuator stores the information indicating the start frequency is a frequency relationship environmental temperature of the vibrating actuator when starting driving,
Each of driving the vibration actuator, the acquired environmental temperature detected by the obtained and the temperature detecting means before KiOkoshi dynamic frequency by changing the frequency of the given El signals to the vibration actuator, and the obtained activated drive device, characterized in that it comprises an update hands stage by the frequency and the ambient temperature to update the information stored in the storage means. Said updating means, the initial frequency is the frequency of the given el initial signal to obtain the starting frequency of the detected ambient temperature by said temperature detecting means, stored in said detected ambient temperature and the storage means drive device according to claim 1, characterized in that set on the basis of the information. It said updating means include a drive device according to claim 2, wherein setting the predetermined amount higher frequency than the starting frequency corresponding to the storage environment temperature in the storage means as the initial frequency.   The update means, when the activation frequency corresponding to the environmental temperature detected by the temperature detection means is not stored in the storage means, the relationship between the environmental temperature stored in the storage means and the activation frequency. 4. The driving device according to claim 1, wherein the starting frequency corresponding to the environmental temperature is obtained by interpolation using information that is indicated. 5.   When the activation frequency corresponding to the environmental temperature detected by the temperature detection unit is not stored in the storage unit, the updating unit sets a representative value corresponding to the environmental temperature stored in the storage unit, The drive device according to claim 1, wherein the drive frequency is acquired as the start-up frequency corresponding to the environmental temperature.   The update means uses, as the initial frequency, the maximum value of the frequency that can be given to the vibration actuator when the activation frequency corresponding to the environmental temperature detected by the temperature detection means is not stored in the storage means. The driving device according to claim 1, wherein the driving device is set. Drive detection means for detecting the drive of the vibration actuator;
Said updating means include a drive device according to any one of claims 1 to 6, characterized in that to obtain the pre KiOkoshi dynamic frequency based on a detection result of the drive detection means.   A lens apparatus comprising: the driving device according to claim 1; and an optical member driven by the driving device.