JP4737873B2 - Camera device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens barrel mounted movably, an ultrasonic motor connected thereto, and a motor control circuit for driving the ultrasonic motor in both forward and reverse directions to move the lens barrel forward and backward along the optical axis. The present invention relates to a camera device composed of More specifically, the present invention relates to a startup technique for an ultrasonic motor. In addition, the present invention relates to a technique of using an ultrasonic motor as a pseudo load for battery check.
[0002]
[Prior art]
In recent years, ultrasonic motors have begun to be used as actuators for lens barrels incorporated in camera devices. An ultrasonic motor (piezomotor) is divided into two types, a standing wave motor and a traveling wave motor, which are symmetrical excitation modes with a fixed center of gravity of the vibrator, and a disc or cylinder that is a vibrator divided into, for example, four parts. There is known an electrostrictive rotator type motor in which the center of gravity rotates around the center when excited by an asymmetric mode in which the amplitude of the rotation is reversed, and the outer periphery of the circle is eccentric like a hula hoop. Such an ultrasonic motor (hereinafter also referred to as a piezo motor) applies a high-frequency AC voltage to a piezoelectric element serving as a stator to generate ultrasonic vibration of about 20 kHz or more, thereby rotating the rotor pressed against the stator. ing. This type of piezo motor has the advantages that it is simple in structure and suitable for reduction in size and weight, and that it can obtain high torque even during low-speed rotation, and is quiet with little drive noise. In particular, the latter electrostrictive revolving rotator type motor generates 3D revolving torque in which axial mode is coupled in addition to the diameter and circumferential direction of the cylindrical revolving rotator as disclosed in Japanese Patent Laid-Open No. 10-272420. It has the feature that it can be used as a child. An ultrasonic motor control circuit for controlling the operation by applying a drive signal to such an ultrasonic motor is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-146258.
[0003]
FIG. 11 is a graph showing the operating characteristics of the ultrasonic motor described above. The horizontal axis represents the frequency f of the drive signal applied to the stator composed of the piezoelectric vibrator, and the vertical axis represents the drive current i flowing through the stator. As is apparent from the figure, the drive current i becomes maximum (imax) at the resonance frequency fp of the stator. When the frequency f of the drive signal is near fp, a sufficient drive current i flows through the stator. In response to this, revolution torque is generated in the stator. Generally, as the current i increases, the revolution torque increases. When the frequency f of the drive signal deviates from fp and the current i decreases, almost no revolution torque is generated.
[0004]
Therefore, in order to rotate the ultrasonic motor stably, it is preferable to drive the stator at an operating point D (fd, id) on the graph shown in FIG. 11, for example. The ultrasonic motor is driven so that id is substantially constant by controlling fd. On the other hand, the f / i characteristic of the stator has a property of shifting due to various factors such as temperature as shown in the figure. For example, the temperature of the stator not only changes depending on the environment, but also changes due to its own heat generated by exciting the stator. Since the piezoelectric resonator generally has a large Q value, the frequency range that can be used as an operating point is narrow, and the change of the current i with respect to the change of the frequency f is large. In order to control the current i, it is necessary to precisely adjust the frequency f. Further, since the shift amount of the f / i characteristic due to temperature is larger than the frequency range that can be used as the operating point D, when the ultrasonic motor is started, the frequency of the drive signal to be applied first can be devised. is necessary. As is apparent from the graph, when there is an f / i characteristic shift, the resonance frequency of the stator changes greatly from fp to fp ′. Accordingly, the optimum operating point shifts from D to D ′. This shift amount is greatly shifted compared to the fluctuation range (narrow width range centered on fd) allowed for the original operating point D.
[0005]
[Problems to be solved by the invention]
A piezo motor gives a driving waveform having a certain frequency, and a resonator called a stator resonates to generate a revolving torque, and a rotating part called a rotor is moved to drive. That is, the motor is started by determining a driving frequency and giving a driving waveform having the frequency. However, it is difficult to determine an appropriate starting frequency according to the f / i characteristics of each ultrasonic motor. If the starting frequency is greatly deviated from the f / i characteristic, the ultrasonic motor will not start. Accordingly, the present invention shall be the purpose of starting the ultrasonic motor stably in the camera apparatus.
[0006]
[Means for Solving the Problems]
In order to achieve the object of the present invention described above, the following measures were taken. That is, the present invention provides a movable lens barrel, an ultrasonic motor coupled to the lens barrel, and driving the ultrasonic motor in both forward and reverse directions to make the lens barrel an optical axis. A motor control circuit that moves forward and backward along the motor control circuit, which outputs a drive signal of a predetermined frequency to drive the ultrasonic motor, and detects a drive current flowing through the ultrasonic motor being driven. In the camera device comprising a detection unit that outputs current value data and a control unit that outputs frequency data based on the current value data and controls the frequency of the drive signal, the control unit is prior to activation. A drive signal for moving the lens barrel in the backward direction while sweeping the frequency while controlling the drive unit and holding the lens barrel in the backward direction limit position via the ultrasonic motor. Apply to On the other hand, to set the initial frequency data in accordance with the peak value of the current value data output from the detecting unit during the sweep, which is characterized by subjecting the activated ultrasonic motor by outputting to the drive unit. Preferably, the camera device includes connection means for connecting the ultrasonic motor to the lens barrel via a helicoid gear, and converts the rotational motion of the ultrasonic motor into a linear motion of the lens barrel. .
[0008]
According to the present invention, the f / i characteristic of the ultrasonic motor is measured in advance prior to activation, and an appropriate activation frequency is determined. That is, the current flowing through the stator is monitored while sweeping the frequency of the drive signal applied to the stator, the f / i characteristic is measured, and the starting frequency is determined based on this. By the way, if the frequency of the drive signal is swept so that the ultrasonic motor rotates in the direction in which the lens barrel moves forward, the lens barrel moves forward during the sweep, which may cause an error in position control. There is sex. Therefore, in the present invention, the drive signal is set so that the ultrasonic motor rotates in the backward direction of the lens barrel, and the frequency of the drive signal is further swept at the extreme position where the lens barrel hits the stopper, Measure f / i characteristics. Since the lens barrel keeps hitting the stopper during the sweep, there is no possibility of causing an error in the position control after activation. It is always possible to control the lens barrel extension position with reference to the extreme position that has been hit.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of a camera apparatus according to the present invention. As shown in the figure, the camera apparatus is composed of a lens barrel 3, an ultrasonic motor 100, and a motor control circuit. The lens barrel 3 is movably mounted on the front surface of the camera and is used for photographing a subject. The lens barrel 3 is moved forward and backward in the optical axis direction for zooming or automatic focusing. The ultrasonic motor 100 is connected to the lens barrel 3. The motor control circuit drives the ultrasonic motor 100 in both forward and reverse directions to move the lens barrel 3 forward and backward along the optical axis.
[0011]
Here, the motor control circuit includes a drive unit 110-140, a detection unit 150/160, and a control unit 170. The drive units 110-140 drive the ultrasonic motor 100 by outputting a drive signal having a predetermined frequency f. The detection unit 150/160 detects the drive current i flowing through the ultrasonic motor 100 being driven and outputs current value data. The control unit 170 outputs frequency data based on the current value data and controls the frequency f of the drive signal. In such a configuration, the control unit 170 controls the drive units 110 to 140 prior to activation, and sweeps the frequency f in a state where the lens barrel 3 is held at the backward limit position via the ultrasonic motor 100. A drive signal in the reverse direction is applied to the ultrasonic motor 100. Further, the control unit 170 sets initial frequency data according to the peak value of the current value data output from the detection unit 150/160 during the sweep, and outputs this to the driving unit 110-140 to start the ultrasonic motor 100. multiply.
[0012]
As described above, in the present invention, the f / i characteristic is measured by performing sweeping before starting, and the starting frequency is determined based on this. Thereby, the ultrasonic motor 100 can always be started stably. When measuring the f / i characteristic, the ultrasonic motor 100 is reversely rotated in advance to hold the lens barrel 3 at the extreme position in the backward direction. Further, a driving current in the reverse direction is applied to the ultrasonic motor 100 during the frequency sweeping so that the lens barrel 3 itself cannot move. In this state, the f / i characteristic is measured to determine the starting frequency. Accordingly, at the stage of actual activation, the lens barrel 3 is in the limit position in the backward direction, and position control in the forward direction can be performed based on this. That is, after starting, the stop position in the forward direction of the lens barrel 3 can be accurately controlled by controlling the driving time or the number of driving pulses from the extreme position in the backward direction of the lens barrel 3 as a starting point. It is. Preferably, the camera apparatus includes connection means for connecting the ultrasonic motor 100 to the lens barrel 3 via a helicoid gear. This connecting means converts the rotational motion of the ultrasonic motor 100 into the linear motion of the lens barrel 3.
[0013]
2 is a schematic longitudinal sectional view showing a mechanical configuration of the camera apparatus shown in FIG. As shown in the figure, the camera apparatus basically includes an ultrasonic motor including a stator 1 and a rotor 2 and a lens barrel 3. These parts are assembled using the base 6. The stator 1 vibrates in response to application of a driving voltage from the outside, and generates a rotational driving force. The rotor 2 converts the rotational driving force generated in the stator 1 into its own rotational motion. For this reason, the rotor 2 is pressed against the stator 1 by the leaf spring 8. The leaf spring 8 is mounted between the base 7 and the rotor 2. The base 7 is fixed to the bottom of the base 6 with screws. On the other hand, the lens barrel 3 is equipped with camera lenses 33 and 34 and is attached to the base 6 so as to be linearly displaced in the optical axis Z direction of the lens. Specifically, a stopper 32 is formed on the lens barrel 3 and is engaged with a guide shaft 4 implanted in the pedestal 6. The lens barrel 3 is restricted in rotation by a stopper 32 and is linearly displaced along the guide shaft 4 in the optical axis Z direction. A stopper 41 engaged with the guide shaft 4 is provided with a spring 41 for loosening the lens barrel 3.
[0014]
Here, the rotor 2 has a ring shape, and a helicoid gear 21 is formed on the inner peripheral surface thereof. A helicoid gear 31 is also formed on the outer peripheral surface of the lens barrel 3. The helicoid gear 21 on the rotor 2 side and the helicoid gear 31 on the lens barrel 3 side are engaged with each other. When the rotor 2 rotates, the lens barrel 3 also tries to rotate by the connecting means including the engagement of the above-described helicoid gear. However, since the rotational displacement is restricted by the stopper 32, the optical axis Z extends along the guide shaft 4. It will be linearly displaced in the direction. Such a linear displacement along the optical axis Z direction of the lens barrel 3 is used for zooming or focusing of the camera.
[0015]
A stopper 61 is formed on the top of the base 6. When the lens barrel 3 is retracted along the optical axis Z, the tip of the stopper 32 of the lens barrel 3 stops at the extreme position where it comes into contact with the stopper 61 on the pedestal 6 side. As described above, when the ultrasonic motor composed of the stator 1 and the rotor 2 is activated, the lens barrel 3 is first moved to the above-mentioned backward position limit position. In this state, while applying a drive signal in the reverse rotation direction to the ultrasonic motor, the frequency is swept and the f / i characteristic is measured. Since the reverse rotation drive signal is applied to the ultrasonic motor, the lens barrel 3 tries to move in the backward direction along the optical axis Z, but it comes into contact with the stopper 61 and is held as it is. .
[0016]
FIG. 3 is a schematic circuit diagram showing a specific configuration example of an ultrasonic motor control circuit incorporated in the camera apparatus shown in FIG. As shown in the figure, this ultrasonic motor control circuit applies a drive signal to the ultrasonic motor 100 to control its operation. The direct digital synthesizer DDS 110, the oscillator 120, the pre-driver 130, the power driver 140, the current A monitor 150, an analog / digital converter (A / D converter) 160, and a CPU 170 are included. The DDS 110 operates in accordance with the clock signal fc, and outputs a basic waveform fd0 having a frequency that changes according to control data df given as a numerical value. The basic configuration of DDS is disclosed in, for example, Japanese Patent Laid-Open No. 2000-151284. The oscillator 120 supplies the clock signal fc to the DDS 110 described above. The pre-driver 130 processes the basic waveform fd0 output from the DDS 110 to generate a multiphase drive signal fd. The power driver 140 sends a drive current id to the ultrasonic motor 100 in accordance with the drive signal fd output from the pre-driver 130 and drives it. The current monitor 150 sequentially detects the drive current id flowing through the ultrasonic motor 100 and outputs the result as a detection voltage Vid. The A / D converter 160 converts Vid representing the detected amount of drive current into digital current value data di. The CPU 170 obtains the control data df based on the digital current value data di output from the A / D converter 160 and sequentially inputs it to the DDS 110.
[0017]
The CPU 170 performs feedback control based on a predetermined program, and outputs frequency control data df to the DDS 110 side according to the current value data di. For example, the CPU 170 can adjust the control data df so that the drive current flowing through the ultrasonic motor 100 becomes a constant current value Vid by the feedback control. By making the drive current id flowing through the ultrasonic motor 100 constant, the output torque and the rotational speed of the ultrasonic motor 100 become constant, and the steady operation of the ultrasonic motor 100 can be stabilized.
[0018]
In addition to the above-described steady operation control, the CPU 170 also performs startup control according to the present invention. That is, the CPU 170 calculates the numerical value of the control data df given to the DDS 110 when the ultrasonic motor 100 is started so that the frequency of the drive signal fd applied to the ultrasonic motor 100 enters the optimum operating point from the start. To do. Thus, the ultrasonic motor 100 is prevented from being disabled. Specifically, the CPU 170 applies a drive signal to the ultrasonic motor 100 while sweeping the frequency at high speed, while setting initial frequency data according to the peak value of the current value data output from the current monitor 150 during sweeping, This is output to the pre-driver 130 to activate the ultrasonic motor 100.
[0019]
FIG. 4 is a schematic perspective view showing a specific configuration example of the ultrasonic motor (piezomotor) 100 shown in FIG. As shown in the figure, a piezo motor 100 is an electrostrictive revolution rotator type motor comprising a 3D revolution torque resonator disclosed in Japanese Patent Laid-Open No. 10-272420 described above, and is in pressure contact with a cylindrical stator 1 and its rear end. And the annular rotor 2 formed. Electrodes 11, 12, 13, and 14 are formed on the outer peripheral surface of the cylindrical stator 1. Although not shown, electrodes are also formed on the inner peripheral surface of the cylinder. The electrodes formed on the outer peripheral surface of the cylinder are divided into four parts, and AC driving currents I (A), I (B), I (AX), and I (BX) having different phases are supplied. A phase current and B phase current are 90 degrees out of phase with each other. Further, the phase of the A-phase current and the AX-phase current are different by 180 degrees. In other words, the A phase and the AX phase have opposite polarities. Similarly, the B phase and the BX phase have opposite polarities.
[0020]
FIG. 5 is a schematic cross-sectional view of the stator shown in FIG. As shown in the drawing, an electrode 10 for applying a reference potential is formed on the entire inner peripheral surface of a cylindrical stator 1 made of a piezoelectric element such as ceramic. Four driving electrodes 11 to 14 are formed on the outer circumferential surface of the cylinder. Four-phase AC drive currents I (A), I (B), I (AX), and I (BX) whose phases are shifted by 90 degrees from each other are supplied to the four-divided electrodes 11 to 14.
[0021]
The operation of the piezo motor shown in FIGS. 4 and 5 will be described with reference to FIG. Needless to say, the present invention is not limited to the piezo motor (ultrasonic motor) shown in FIGS. 4 to 6 and can be applied to ultrasonic motors having various other configurations. In the piezo motor, since the ultrasonic vibration as a power source has a constant resonance frequency, the current has a substantially constant value. The resonator has a high Q, and the rise of the vibration amplitude is considered to be within one cycle, and can be regarded as a non-inertia mechanism. The current changes only within the range where the inertia of the load affects. Various configurations of piezo motors having such characteristics have been developed, but the electrostrictive revolution type is particularly effective. The electrostrictive revolution type uses a resonator that can directly excite a uniform revolution torque over the entire peripheral surface, instead of changing the vibration into torque as in the prior art. There are two types of conventional ultrasonic transducers, standing wave type and traveling wave type, but both can be excited only in a symmetric mode with a fixed center of gravity. On the other hand, when the cylinder is excited in a mode in which left and right expansion and contraction are reversed, the center of gravity vibrates away from the center. When this asymmetric excitation is performed, a cylindrical resonance mode that cannot be observed with the conventional symmetrical excitation can be obtained. Therefore, when the electrodes of the stator cylinder are divided into, for example, four parts and excited by rotating electric fields having different phases by 90 degrees, resonance in a mode in which the center of gravity rotates around the center can be seen as shown in FIG. At this time, the outer periphery of the cylinder is decentered like a hula hoop while maintaining the original shape, so that the vibrator rotates and revolves. The electrostrictive revolving rotator type motor having such a configuration can be used as a 3D revolving torque generator in which a direct rotation mode is excited and an axial mode is combined in addition to the diameter and circumferential direction of the cylindrical revolving element. This revolution torque is extracted directly as the rotation of the rotor.
[0022]
FIG. 7 is a schematic block diagram illustrating a specific configuration example of the DDS 110 illustrated in FIG. 3. The DDS 110 is composed of an adder and a latch. The adder sequentially adds 16-bit control data df given as a numerical value from the CPU, and sends the result to the latch. The latch operates according to the clock signal fc and feeds back the latched addition result to the adder side. The latch outputs the most significant bit MSB as fd0 when an overflow (carry) occurs due to addition by the adder. In this way, the DDS 110 generates a basic waveform of the frequency fd0 expressed by the following equation in accordance with the frequency setting data df given from the CPU and the clock frequency fc from the oscillator.
fd0 = df × fc / 2 ^N (N: number of bits of data)
[0023]
In the normal DDS, the latched output data is converted into waveform data such as a sine wave by the search table LUT, and then digital / analog is converted into an output waveform. However, the ultrasonic motor can be basically driven by a rectangular wave drive signal. For this reason, since the DDS of this example may output a rectangular wave, the most significant bit MSB of the latched data can be used as it is as an output waveform. Therefore, the LUT and the digital / analog converter are omitted from this DDS.
[0024]
FIG. 8 is a waveform diagram showing the multiphase drive signal fd output from the pre-driver 130 shown in FIG. As described above, the pre-driver is based on the basic waveform fd0 output from the DDS, and the multi-phase drive signals fd (A), fd (B), fd (AX), fd (BX) for driving the stator. ) Is generated. The frequency of each drive signal fd is equal to the basic waveform fd0 or a frequency obtained by dividing the frequency. In the illustrated example, each drive signal fd has a waveform obtained by dividing the basic waveform fd0 by half. As shown in the figure, the B phase is shifted by 90 degrees relative to the A phase, the AX phase is shifted by 180 degrees, and the BX phase is shifted by 270 degrees. In this way, a rotating electric field is formed by applying AC driving signals having different phases by 90 degrees to the stator, and the stator directly excites the rotation mode in response to this. As a result, the rotor rotates in the positive direction. If the phase relationship of each drive signal fd is reversed, the rotor rotates in the opposite direction. As described above, the pre-driver generates four types of drive waveforms having different phases by 90 degrees. The frequency fd of the drive waveform is ½ of the basic frequency fd0. These waveforms can be easily created from the basic waveform fd0 by a logic IC such as a counter or an inverter.
[0025]
FIG. 9 is a circuit diagram showing a specific configuration example of the power driver 140 and the current monitor 150 included in the ultrasonic motor control circuit shown in FIG. As shown in the figure, the power driver connected to the ultrasonic motor 100 includes a pair of H bridge 140A and H bridge 140B. Here, the pair of drive signals fd (A) and fd (AX) are applied to a pair of electrodes facing each other of the ultrasonic motor 100 via the H bridge 140A. Similarly, another pair of drive signals fd (B) and fd (BX) are also applied to another pair of stator electrodes facing each other via another H bridge 140B. H bridges 140A and 140B are power amplifiers for supplying sufficient output currents I (A), I (B), I (AX), and I (BX) to the stator electrodes in response to input signals, respectively. ing. As described above, the power driver is composed of a pair of H bridges. As an element constituting the bridge, a MOSFET is used because it needs to be switched at high speed.
[0026]
On the other hand, the current monitor 150 includes a differential amplifier OP, a smoothing capacitor C, and a plurality of resistors R1 to R3. The current monitor 150 basically has a low-pass filter configuration, and outputs a voltage value Vid corresponding to the drive current flowing through the H bridges 140A and 140B via the resistor R1. The drive current is detected by smoothing the voltage generated in the resistor R1 having a low resistance value (for example, 1Ω) by the capacitor C and amplifying it by the amplifier OP. As described above, this output voltage Vid is sent to the A / D converter side.
[0027]
FIG. 10 is a schematic diagram showing another embodiment of the camera device according to the present invention. As shown to (A), this camera apparatus is comprised by the lens-barrel 3, the ultrasonic motor 100, the motor control circuit, and the battery 200. FIG. The lens barrel 3 is movably mounted on the front side of the camera device. The ultrasonic motor 100 is connected to the lens barrel 3. The motor control circuit applies a drive signal to the ultrasonic motor 100 and drives it in both forward and reverse directions to move the lens barrel 3 forward and backward along the optical axis. The battery 200 supplies power to the ultrasonic motor 100 and the motor control circuit described above. Specifically, the battery 200 is connected between the power supply line VBAT and the ground line GND. The ultrasonic motor 100 and the motor control circuit described above are also connected between VBAT and GND although not shown. In this way, the battery 200 supplies power to the ultrasonic motor 100 and the motor control circuit via the power supply line VBAT and the ground line GND.
[0028]
Here, the motor control circuit includes a drive unit 110-140, a detection unit 150/160, and a control unit 170. The driving units 110 to 140 output a driving signal having a predetermined frequency to drive the ultrasonic motor 100. The detection unit 150/160 detects the drive current flowing through the ultrasonic motor 100 being driven and outputs current value data. The controller 170 outputs frequency data based on the current value data and controls the frequency of the drive signal.
[0029]
The controller 170 further has a battery check function, and detects the output current of the battery 200 using the ultrasonic motor 100 as a pseudo load. Specifically, a voltage dividing resistor R is connected in series between the power supply line VBAT and the ground line GND via a transistor Tr. The base of the transistor Tr is connected to the control unit 170. The middle point of the voltage dividing resistor R is connected to the control unit 170. In such a configuration, a drive signal is supplied to the ultrasonic motor 100 in a state where the lens barrel 3 is in the forward or backward extreme position, and the current output from the battery 200 at this time is divided by the voltage dividing resistor R and detected. is doing. That is, only when the battery check is performed, the control unit 170 turns on the transistor Tr and detects the power supply voltage divided by the resistor R.
[0030]
Currently, a fixed resistor is used as a pseudo load of the camera device, and a current is passed through it. For this purpose, a circuit that switches a fixed resistor only at the time of battery check is required, which complicates the configuration and increases the cost. Therefore, in the present invention, attention is paid to the ultrasonic motor incorporated in the camera device, and this is reversely rotated and held in a state where it hits the stopper, and this is used as a pseudo load so that a current flows. Here, (B) schematically represents the relationship between the current i and the frequency f of the ultrasonic motor. As apparent from the graph, since the current i can be variably controlled by the frequency f, a necessary load current can be passed without using an additional circuit, and this can be used as a pseudo load. This eliminates the need for a fixed resistor and can reduce the cost. Since the camera device is powered by a battery as described above, a battery check is required. Conventionally, a battery check is performed after a predetermined current is passed using a pseudo load using a fixed resistor in consideration of a driving voltage such as a shutter. On the other hand, in the present invention, it is possible to flow a desired load current by using an ultrasonic motor as a pseudo load and selecting a desired frequency. Since a circuit dedicated to the pseudo load is not required, the cost can be reduced. In addition, the mounting board can be downsized.
[0031]
【The invention's effect】
As described above, according to the present invention, the frequency is swept before starting the ultrasonic motor to measure the f / i characteristic, and the starting frequency is determined based on this. Thereby, an ultrasonic motor can be started stably. At this time, since the lens barrel maintains a state where it hits the limit position in the backward direction, the amount of advancement of the lens barrel in the forward direction after starting is determined from this as the starting time, the drive signal application time or the number of drive signal pulses It is possible to control accurately based on this. This makes it possible to accurately control the forward movement position of the lens barrel driven by the ultrasonic motor. Further, according to another aspect of the present invention, an ultrasonic motor can be used for a pseudo load for battery check, and a fixed resistor and a circuit for controlling the switching, which are conventionally required as a pseudo load, are not required. It is possible to reduce the overall cost of the camera device.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a camera device according to the present invention.
FIG. 2 is a cross-sectional view showing a mechanical configuration of the camera apparatus shown in FIG.
3 is a block diagram showing a specific configuration example of an ultrasonic motor control circuit included in the camera apparatus shown in FIG. 1. FIG.
FIG. 4 is a schematic perspective view of an ultrasonic motor.
FIG. 5 is a cross-sectional view of an ultrasonic motor.
FIG. 6 is an operation explanatory diagram of an ultrasonic motor.
7 is a block diagram illustrating a specific configuration example of a DDS included in the ultrasonic motor control circuit illustrated in FIG. 3;
FIG. 8 is a waveform diagram for explaining the operation of a pre-driver included in the ultrasonic motor control circuit shown in FIG.
9 is a circuit diagram showing a specific configuration example of a power driver and a current monitor included in the ultrasonic motor control circuit shown in FIG. 3;
FIG. 10 is a block diagram showing another embodiment of a camera device according to the present invention.
FIG. 11 is a graph showing operating characteristics of an ultrasonic motor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 ... Lens barrel, 100 ... Ultrasonic motor, 110-140 ... Drive part, 150/160 ... Detection part, 170 ... Control part

Claims (2)

A lens barrel mounted movably, an ultrasonic motor coupled to the lens barrel, and a motor that drives the ultrasonic motor in both forward and reverse directions to move the lens barrel forward and backward along the optical axis. A control circuit,
The motor control circuit outputs a drive signal of a predetermined frequency to drive the ultrasonic motor, and a detection unit to detect a drive current flowing in the ultrasonic motor being driven and output current value data In a camera device comprising a control unit that outputs frequency data based on the current value data and controls the frequency of the drive signal,
Wherein, in a state in which prior to the start and kept in the backward limit position of the lens barrel via the ultrasonic motor by controlling the drive unit, the lens barrel in a backward direction while sweeping frequency While applying the drive signal to be moved to the ultrasonic motor, initial frequency data is set according to the peak value of the current value data output from the detection unit during the sweep, and this is output to the drive unit to be super A camera apparatus characterized by activating a sonic motor.   The camera device includes connection means for connecting the ultrasonic motor to the lens barrel via a helicoid gear, and converts the rotational motion of the ultrasonic motor into linear motion of the lens barrel. The camera device according to claim 1.

Images