Drive circuit, optical unit, and drive method

Abstract

Provided is a drive circuit that drives a piezoelectric actuator for driving an optical element, the drive circuit comprising: a drive unit that, on the basis of a detection position indicating the detected position of the optical element and a target position to which the optical element is to move, generates a drive signal for controlling the movement speed of the optical element; and a filter unit that suppresses the frequency of fluctuation of the movement speed due to the drive signal. The filter unit may dampen components higher than 100 Hz within the frequency of fluctuation of the movement speed.

Description

[Technical Field]

[0001] The present invention relates to a driving circuit, an optical unit, and a driving method. [Background technology]

[0002] Conventionally, a technique for driving a lens by a piezoelectric actuator is known (see, for example, Patent Document 1). [Prior art document] [Patent documents] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-354854 Problems to be Solved

[0003] The piezoelectric actuator suppresses the generation of driving noise when the lens is driven.

[0004] One aspect of the present invention provides a drive circuit for driving a piezoelectric actuator that moves an optical element. The drive circuit may include a drive unit that generates a drive signal to control the movement speed of the optical element based on the difference between a detected position indicating the position of the optical element and a target position to which the optical element should move. The drive circuit may include a filter unit that suppresses the frequency of fluctuations in the movement speed due to the drive signal.

[0005] In any of the drive circuits described above, the filter section may attenuate components of the fluctuation frequency of the movement speed that are equal to or higher than an operating frequency band of the piezoelectric actuator.

[0006] In any of the drive circuits described above, the filter section may attenuate components of the fluctuation frequency of the moving speed that are greater than 100 Hz.

[0007] In any of the drive circuits described above, the drive unit may include a pulse signal generation unit that generates a pulse signal having a pulse train corresponding to a difference between the detected position and the target position. In any of the drive circuits described above, the drive unit may include a driver that outputs the drive signal corresponding to the pulse signal. In any of the drive circuits described above, the filter unit may suppress a frequency of change of the pulse train in the pulse signal generation unit.

[0008] In any of the above drive circuits, the filter section may suppress the frequency of changes in the pulse train in a direction that decreases the moving speed more strongly than the frequency of changes in the pulse train in a direction that increases the moving speed.

[0009] In any of the drive circuits described above, the filter section may suppress the frequency of changes in the pulse train in a direction that decreases the moving speed, and may not suppress the frequency of changes in the pulse train in a direction that increases the moving speed.

[0010] In any of the above drive circuits, a pre-processing unit may be provided that performs AD conversion on the signal indicating the detection position and inputs the converted signal to the drive unit. In any of the above drive circuits, the filter unit may reduce the frequency of updating the conversion result in the pre-processing unit.

[0011] In any of the above drive circuits, the filter section may adjust filter characteristics based on a difference between the detected position and the target position.

[0012] In any of the above drive circuits, the filter section may adjust filter characteristics for at least one of the frequency of change in the movement speed in a direction to decrease the movement speed and the frequency of change in the movement speed in a direction to increase the movement speed, based on a comparison result between the difference and a set reference value.

[0013] In any of the above drive circuits, the drive section may perform PID control based on the detected position and the target position to generate the drive signal.

[0014] Any of the above drive circuits may further include a position detection section that detects the position of the optical element and generates a signal indicative of the detected position.

[0015] Any of the above drive circuits may further include a booster section that boosts the drive signal and supplies the boosted drive signal to the piezoelectric actuator.

[0016] In any of the above drive circuits, the drive unit may include a signal processing unit that generates a control signal to control a movement speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element is to move. In any of the above drive circuits, the pulse signal generation unit may generate the pulse signal having the pulse train according to the control signal. In any of the above drive circuits, the pulse signal generation unit may be capable of generating, for one of the movement speeds indicated by the control signal, the pulse signal including one or more first pulses and one or more additional pulses that differ from the first pulses in at least one of a pulse width and an amplitude.

[0017] In any of the drive circuits described above, the additional pulse may have a pulse width greater than that of the first pulse.

[0018] In any of the drive circuits described above, the additional pulse may have a pulse width that is at least twice as long as that of the first pulse.

[0019] In any of the above drive circuits, when changing the movement speed of the optical element from a first speed to a second speed, the pulse signal generation section may generate, for the first speed, a pre-change pulse signal including the number of first pulses corresponding to the first speed. In any of the above drive circuits, the pulse signal generation section may, after generating the pre-change pulse signal, generate an intermediate pulse signal by adding one or more additional pulses to the pre-change pulse signal. In any of the above drive circuits, the pulse signal generation section may, after generating the intermediate pulse signal, generate a post-change pulse signal including the number of first pulses corresponding to the second speed.

[0020] In any of the above drive circuits, the pulse signal generation section may include a first pulse generation section that generates one or more of the first pulses. In any of the above drive circuits, the pulse signal generation section may include an additional pulse generation section that generates one or more of the additional pulses. In any of the above drive circuits, the pulse signal generation section may include a logical OR circuit that outputs a logical OR of the pulse train of the first pulses generated by the first pulse generation section and the pulse train of the additional pulses generated by the additional pulse generation section.

[0021] A second aspect of the present invention provides a drive circuit for driving a piezoelectric actuator that moves an optical element. The drive circuit may include a signal processing unit that generates a control signal for controlling a movement speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element should move. Any of the drive circuits may include a pulse signal generating unit that generates a pulse signal having a pulse train according to the control signal and controls the movement speed according to the pulse train. In any of the drive circuits, the pulse signal generating unit may be capable of generating, for one of the movement speeds indicated by the control signal, the pulse signal including one or more first pulses and one or more additional pulses that differ from the first pulses in at least one of pulse width and amplitude.

[0022] In a third aspect of the present invention, there is provided an optical unit comprising an optical element, a piezoelectric actuator that moves the optical element, and a drive circuit according to the first aspect that drives the piezoelectric actuator.

[0023] A fourth aspect of the present invention provides a driving method for driving a piezoelectric actuator that moves an optical element. The driving method may generate a drive signal that controls a movement speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element should move. The driving method may suppress a frequency of fluctuations in the movement speed due to the drive signal.

[0024] The above summary of the invention does not list all of the features of the present invention, and subcombinations of these features may also constitute inventions. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a diagram showing an example of an optical unit 100 according to an embodiment of the present invention. [Figure 2] 3 is a diagram illustrating an example of a drive signal generated by a drive circuit 10. FIG. [Figure 3] 10 is a diagram illustrating an example of the operation of the booster 170. FIG. [Figure 4] 1 is a diagram showing an example of the relationship between the number of first pulses 14 included in a pulse train 12 and the position of an optical element 120. FIG. [Figure 5] 10 is a diagram showing an example of the relationship between the number of first pulses 14 included in a pulse train 12 and the sound pressure of the drive sound. FIG. [Figure 6] FIG. 2 is a diagram illustrating an example of the configuration of a drive circuit 10. [Figure 7] FIG. 2 is a diagram illustrating an example of the configuration of a pulse signal generating section 60. [Figure 8] 1 is a diagram showing an example of a first pulse 14, an additional pulse 15, and a pulse signal. [Figure 9] 10 is a diagram illustrating an example of the operation of the pulse signal generating section 60. FIG. [Figure 10]FIG. 10 is a diagram showing the relationship between the number of first pulses 14 included in a pulse train 12 and the sound pressure of the drive sound in a reference example. [Figure 11] FIG. 10 is a diagram showing the relationship between the number of pulses included in the pulse train 12 and the sound pressure of the driving sound in the embodiment. [Figure 12] FIG. 10 is a diagram showing an example of the timing at which an additional pulse 15 is inserted. [Figure 13] FIG. 10 is a diagram showing another example of the timing at which the additional pulse 15 is inserted. [Figure 14] FIG. 10 is a diagram showing another example of the timing at which the additional pulse 15 is inserted. [Figure 15] FIG. 10 is a diagram showing another example of the additional pulse 15. [Figure 16] FIG. 16 is a chart outlining a driving method for driving the piezoelectric actuator 110 described with reference to FIGS. [Figure 17] FIG. 2 is a diagram showing another example of the configuration of the drive circuit 10. [Figure 18] FIG. 2 is a diagram illustrating an example of the configuration of a pulse signal generating section 60. [Figure 19] 10A and 10B are diagrams illustrating an example of the operation of the filter unit 70. [Figure 20] 10 is a diagram showing an example of the position of the optical element 120 and the waveform of a control signal. FIG. [Figure 21] 10 is a diagram showing an example of the position of the optical element 120 and the waveform of a control signal. FIG. [Figure 22] 10 is a diagram showing another example of the arrangement of the filter section 70. FIG. [Figure 23] FIG. 23 is a chart outlining a driving method for driving the piezoelectric actuator 110 described with reference to FIGS. 17 to 22. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention as claimed. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0027] In this specification, one side in a direction parallel to the optical axis of the lens may be referred to as "upper" and the other side as "lower." The "upper" and "lower" directions are not limited to directions parallel to the direction of gravity.

[0028] In this specification, when size or quantity is described using terms such as "same" or "equal," this may include cases where there is an error due to manufacturing variations, etc. The error is, for example, within 5%. Furthermore, when angles are described using terms such as "parallel," "perpendicular," or "orthogonal," this may also include cases where there is an error due to manufacturing variations, etc. The error is, for example, within 5 degrees.

[0029] FIG. 1 is a diagram showing an example of an optical unit 100 according to an embodiment of the present invention. The optical unit 100 includes an optical element 120, a piezoelectric actuator 110, and a drive circuit 10. The optical element 120 is, for example, a lens, but is not limited to this. The optical element 120 may be an element that generates output light in response to incident light, or an element that operates in response to the incident light. Examples of elements that generate output light in response to incident light include elements that change the propagation direction of light, elements that change the polarization direction of light, elements that change the wavelength components of light, and elements that change the intensity of light. Examples of elements that operate in response to incident light include an image sensor that converts incident light into an electrical signal.

[0030] The piezoelectric actuator 110 moves the optical element 120 by deforming or vibrating in response to an input electrical signal. The piezoelectric actuator 110 may include a piezoelectric portion that deforms or vibrates in response to an electrical signal. In this example, the piezoelectric actuator 110 moves a shaft 114. The optical element 120 is fixed to the shaft 114. Therefore, moving the shaft 114 moves the optical element 120. In this example, the piezoelectric actuator 110 moves the shaft 114 in the longitudinal direction of the shaft 114. In FIG. 1, the movement directions of the optical element 120 and the shaft 114 are indicated by arrows. In this example, the piezoelectric actuator 110 can move the optical element 120 and the shaft 114 in both the positive (+) direction and the negative (-) direction. As an example, the piezoelectric actuator 110 moves the optical element 120 to achieve an autofocus function in a camera. However, the use of the piezoelectric actuator 110 is not limited to this. Furthermore, the movement direction of the optical element 120 etc. is not limited to a linear direction.

[0031] The driving circuit 10 drives the piezoelectric actuator 110. The driving circuit 10 generates a driving signal for driving the piezoelectric actuator 110. In this example, the driving circuit 10 receives a detected position indicating the current position of the optical element 120 in the movement direction and a target position to which the optical element 120 should move. The driving circuit 10 generates a driving signal for controlling the movement speed of the optical element 120 based on the difference between the detected position and the target position. The movement speed of the optical element 120 may include the direction of movement (positive or negative) and the absolute value of the speed. The driving circuit 10 may generate the driving signal based on whether the target position is located in the positive or negative direction relative to the detected position in the movement direction and the absolute value of the difference between the detected position and the target position.

[0032] The optical unit 100 may include a boosting section 170 that boosts the drive signal and supplies it to the piezoelectric actuator 110. The boosting section 170 may boost the drive signal using an inductor and a capacitance section. The boosting section 170 may boost the drive signal by resonating the drive signal between the inductor and the capacitance section. The inductor may be provided in the boosting section 170. The capacitance section may be provided in the boosting section 170 or in the piezoelectric actuator 110. The capacitance section may be a capacitor element or may be a parasitic capacitance in the piezoelectric actuator 110, etc.

[0033] The optical unit 100 may further include some or all of the image acquisition unit 130, the display unit 140, the image processing unit 150, and the position detection unit 160. The image acquisition unit 130 receives light that has passed through the optical element 120 and generates image data corresponding to the received light. For example, the image acquisition unit 130 includes an imaging element that generates image data of a subject of the camera. The imaging element of the image acquisition unit 130 is, for example, a CMOS image sensor, but is not limited to this. The image acquisition unit 130 is also an example of an optical element. In the example of FIG. 1, the piezoelectric actuator 110 moves the lens (optical element 120) relative to the image acquisition unit 130. However, in other examples, the piezoelectric actuator 110 may move the image acquisition unit 130 relative to the lens (optical element 120). In other words, the piezoelectric actuator 110 may control the relative position between the lens and the image acquisition unit 130.

[0034] The image processing unit 150 performs predetermined processing on the image data generated by the image acquisition unit 130. The image processing unit 150 of this example may calculate a target position to which the optical element 120 should move, based on the image data. For example, the image processing unit 150 may calculate the target position based on the contrast of the image data (so-called contrast autofocus), may split the light that has passed through the optical element 120 into two, and calculate the target position based on the distance between two images formed by each light (so-called phase difference autofocus), or may calculate the target position using another method.

[0035] Image processing unit 150 may display an image corresponding to the image data on display unit 140. Display unit 140 may be a display such as a liquid crystal display or an organic EL display provided in the camera, or may be another display.

[0036] The position detection unit 160 detects the position of the optical element 120 in the movement direction. The position detection unit 160 may detect the position of the optical element 120 based on a magnetic field between the optical element 120 and the position detection unit 160. For example, a magnetic field generation unit such as a magnet may be provided in the fixed unit 122, and a magnetic field detection unit such as a Hall element may be provided in the position detection unit 160. In another example, a magnetic field detection unit may be provided in the fixed unit 122, and a magnetic field generation unit may be provided in the position detection unit 160. The magnetic field generation unit and the magnetic field detection unit are provided so that the strength of the detected magnetic field changes depending on the relative positions of the position detection unit 160 and the fixed unit 122 in the movement direction. The position detection unit 160 may calculate the position of the optical element 120 based on the strength of the magnetic field detected by the magnetic field detection unit.

[0037] FIG. 2 illustrates an example of a drive signal generated by the drive circuit 10. FIG. 2 shows the time waveforms of each signal, such as the drive signal. The drive circuit 10 of this example generates a first pulse signal and a second pulse signal. The first pulse signal and the second pulse signal each have a pulse train 12 at a predetermined modulation period T. In the example of FIG. 2, the first pulse signal includes a pulse train 12-1, and the second pulse signal includes a pulse train 12-2. Each pulse train 12 includes one or more first pulses 14. The pulse trains 12-1 and 12-2 are out of phase with each other so that they do not simultaneously reach the H level. In other words, during a period when one pulse train 12 has a first pulse 14, the other pulse train 12 does not have a first pulse 14. The pulse trains 12-1 and 12-2 may simultaneously reach the L level. As an example, the periods of the pulse trains 12-1 and 12-2 may be shifted by half a period.

[0038] The drive circuit 10 may generate drive signals corresponding to the respective pulse signals. In this example, the drive circuit 10 generates a first drive signal corresponding to the first pulse signal and a second drive signal corresponding to the second pulse signal. The drive signal has a pulse train with the same pattern as the pulse signal. The drive signal may be a signal output by a driver to which the pulse signal is input. The drive signal may be a signal with a different amplitude from the pulse signal.

[0039] The piezoelectric actuator 110 may include a first piezoelectric element to which a first drive signal is applied and a second piezoelectric element to which a second drive signal is applied. The first piezoelectric element and the second piezoelectric element may be formed of, for example, ceramic. The piezoelectric actuator 110 may have a stator portion provided in contact with the first piezoelectric element and the second piezoelectric element. The stator portion deforms in response to the deformation of the first piezoelectric element and the second piezoelectric element. Because the pulse trains applied to the first piezoelectric element and the second piezoelectric element are shifted by a half period, traveling waves are generated on one surface of the stator portion in response to the deformation of the first piezoelectric element and the second piezoelectric element. The piezoelectric actuator 110 may move the shaft 114 using the traveling waves.

[0040] The direction of movement of the shaft 114 varies depending on the pulse periods of the first pulse train 12-1 and the second pulse train 12-2. The drive circuit 10 may change the pulse periods of the first pulse train 12-1 and the second pulse train 12-2 depending on the direction in which the shaft 114 should be moved. The drive circuit 10 may be preset with a pulse period (first period) when moving the optical element 120 in the positive direction of the movement, and a pulse period (second period) when moving the optical element 120 in the negative direction.

[0041] The absolute value of the movement speed of the shaft 114 can be controlled by the number of first pulses 14 included in the pulse train 12 in the modulation period T. The greater the number of first pulses 14 included in the pulse train 12, the greater the absolute value of the movement speed of the shaft 114. The drive circuit 10 may control the number of first pulses 14 included in the pulse train 12 according to the absolute value of the speed at which the optical element 120 should be moved.

[0042] The driving circuit 10 of this example generates a first oscillation signal and a second oscillation signal. The first oscillation signal and the second oscillation signal have the same period but differ in phase by half a period. The driving circuit 10 generates the first oscillation signal and the second oscillation signal with the same period (first period or second period) as the period that the pulse train 12 should have. The driving circuit 10 may control the periods of the first oscillation signal and the second oscillation signal depending on the direction in which the optical element 120 should be moved.

[0043] The driving circuit 10 of this example generates a modulation signal. The modulation signal is a signal that exhibits an H level for a predetermined period W in a modulation cycle T and exhibits an L level for other periods. The modulation signal may have a single pulse with a pulse width W in the modulation cycle T. The driving circuit 10 generates a first pulse signal from the logical product of the modulation signal and a first oscillation signal, and generates a second pulse signal from the logical product of the modulation signal and a second oscillation signal.

[0044] The driving circuit 10 of this example controls the number of first pulses 14 included in the pulse train 12 of each pulse signal by controlling the period W of the modulation signal. For example, increasing the period W increases the number of first pulses 14 included in the pulse train 12. The driving circuit 10 may control the period W according to the absolute value of the speed at which the optical element 120 is to be moved. Note that in this specification, the first modulation signal and the second modulation signal may be simply referred to as modulation signals, the first pulse signal and the second pulse signal may be simply referred to as pulse signals, and the first drive signal and the second drive signal may be simply referred to as drive signals. The period W of the modulation signal may be set so that the number of first pulses 14 included in pulse train 12-1 is the same as the number of first pulses 14 included in pulse train 12-2. The timing of the falling edge of the modulation signal may be controlled to be the same as the timing of the falling edge of any of the first pulses 14. The period W of the modulation signal may be set to be an even multiple of the pulse width of the first pulses 14.

[0045] 3 is a diagram illustrating an example of the operation of the booster 170. As described above, the booster 170 boosts and outputs the drive signal. The amplitude of the boosted drive signal is greater than the amplitude of the drive signal before boosting. The period of the drive signal may be the same before and after boosting.

[0046] Fig. 4 is a diagram showing an example of the relationship between the number of first pulses 14 included in the pulse train 12 and the position of the optical element 120. The vertical axis in Fig. 4 indicates the number of first pulses 14 included in the pulse train 12. The sign on the vertical axis indicates the direction in which the optical element 120 is moved. In other words, when the signs on the vertical axis are different, the periods of the pulse signals are different.

[0047] FIG. 4 shows an example in which the optical element 120 is moved from target position 1 to target position 2 and then to target position 3. The number of first pulses 14 included in the pulse train 12 changes depending on the direction and distance of movement. As described in FIG. 2, the number of first pulses 14 can be controlled by controlling the period W of the modulation signal. In this example, when moving from target position 1 to target position 2, the number of first pulses 14 included in the pulse train 12 decreases when the detection position reaches the vicinity of target position 2. Note that the distance traveled by one first pulse 14 of the optical element 120 may differ depending on the direction of movement of the optical element 120. In this case, as shown in FIG. 4, even if the slope of the waveform at the detection position of the optical element 120 is approximately the same at the rising edge and the falling edge, the absolute values ​​of the numbers of first pulses 14 corresponding to the rising edge and the falling edge may differ.

[0048] Driving noise may occur as the optical element 120 moves. Driving noise is likely to occur when the optical element 120 accelerates or decelerates.

[0049] Fig. 5 is a diagram showing an example of the relationship between the number of first pulses 14 included in the pulse train 12 and the sound pressure of the drive sound. The change in the number of first pulses 14 is similar to the example in Fig. 4. Since the number of first pulses 14 included in the pulse train 12 corresponds to the moving speed of the optical element 120, a change in the number of first pulses 14 indicates acceleration or deceleration of the optical element 120. As shown in Fig. 5, it can be seen that drive sound with a relatively high sound pressure is generated when the optical element 120 accelerates or decelerates.

[0050] 6 is a diagram showing an example of the configuration of the drive circuit 10. The drive circuit 10 includes a drive section 50. The drive circuit 10 may further include a pre-processing section 20 and a part or all of a setting section 30.

[0051] The driver 50 acquires the detected position of the optical element 120 and the target position to which the optical element 120 should move. The driver 50 in this example receives the detected position from the pre-processor 20. The pre-processor 20 may receive, for example, an analog signal indicating the detected position from the position detector 160 and output a digital signal obtained by AD converting the analog signal. The driver 50 in this example may receive a digital signal indicating the target position from the setting unit 30. The setting unit 30 may have a register that records the target position received from, for example, the image processor 150. The target position recorded by the setting unit 30 is updated as appropriate by the image processor 150.

[0052] As described above, the driver 50 generates a drive signal that controls the movement speed of the optical element 120 based on the difference between the detected position and the target position. When changing the movement speed of the optical element 120, the pulse signal generator 60 of this example limits the amount of change in one control. This makes it possible to reduce the peak volume of the drive noise.

[0053] The driving unit 50 of this example includes a signal processing unit 40, a pulse signal generating unit 60, and a driver 80. The signal processing unit 40 generates a control signal based on the detected position and the target position. The control signal is a signal for controlling the movement speed of the optical element 120 so as to reduce the difference between the detected position and the target position. The control signal may include information indicating the direction in which the optical element 120 should be moved and the absolute value of the movement speed.

[0054] The signal processing unit 40 may perform PID control based on the detected position and the target position to generate a control signal. That is, the signal processing unit 40 may perform a process that combines proportional control (P control), integral control (I control), and derivative control (D control). In P control, the absolute value of the movement speed of the optical element 120 is increased in proportion to the magnitude of the difference between the detected position and the target position. In I control, the movement speed of the optical element 120 is adjusted according to the magnitude of the time integral of the difference between the detected position and the target position. In D control, a process is performed to reduce the derivative value of the control signal (that is, to reduce the time change in the movement speed of the optical element 120).

[0055] The pulse signal generating section 60 generates a pulse signal having a pulse train 12 corresponding to the difference between the detected position and the target position. The pulse signal generating section 60 of this example generates the pulse signal shown in FIG. 2 in response to a control signal. The pulse signal generating section 60 may control the period of the first pulses 14 in the oscillation signal or the pulse train 12 in response to the movement direction of the optical element 120 indicated by the control signal. The pulse signal generating section 60 controls the number of first pulses 14 in the pulse train 12 in response to the absolute value of the movement speed of the optical element 120 indicated by the control signal. The pulse signal generating section 60 may control the number of first pulses 14 included in the pulse train 12 by adjusting the period W of the modulation signal shown in FIG. 2.

[0056] The driver 80 outputs a drive signal corresponding to the pulse signal generated by the pulse signal generating section 60. As described above, the drive signal may include a pulse train 12 having the same pattern as the pulse signal. The amplitude of each pulse of the drive signal may be the same as or different from the amplitude of each pulse of the pulse signal. The driver 80 may supply a current to drive the piezoelectric actuator 110.

[0057] Fig. 7 is a diagram showing an example of the configuration of the pulse signal generating section 60. The pulse signal generating section 60 of this example suppresses the amount of change in the movement speed of the optical element 120 that is changed in one control by inserting an additional pulse into the pulse signal shown in Fig. 2. The pulse signal generating section 60 of this example has a first pulse generating section 67, an additional pulse generating section 68, and a logical OR circuit 69.

[0058] The first pulse generating unit 67 generates a signal similar to the pulse signal shown in FIG. 2. In this specification, one or more pulses included in the pulse signal output by the first pulse generating unit 67 are referred to as first pulses 14. The first pulse generating unit 67 generates a pulse train 12 including one or more first pulses 14 for one movement speed indicated by the control signal. The first pulse generating unit 67 repeatedly outputs the pulse train 12 including the same number of first pulses 14 until the movement speed indicated by the control signal is changed. When the movement speed indicated by the control signal changes, the first pulse generating unit 67 outputs the pulse train 12 including the number of first pulses 14 according to the changed movement speed.

[0059] The first pulse generating section 67 of this example has a first modulating section 62, a second modulating section 64, and an AND circuit 66. The first modulating section 62 generates the oscillation signal described in FIG. 2. The first modulating section 62 may generate the first oscillation signal and the second oscillation signal as described in FIG. 2. The first modulating section 62 of this example is capable of changing the period of the oscillation signal depending on the movement direction of the optical element 120. A clock signal with a predetermined period is input to the first modulating section 62 of this example. The period of the clock signal is, for example, the first period or the second period described above. The first modulating section 62 may generate each oscillation signal based on the clock signal. The period of the oscillation signal may be the same as the period of the clock signal.

[0060] The second modulation section 64 generates the modulated signal described in FIG. 2. A modulation setting signal for generating the modulated signal may be input to the second modulation section 64. The modulation setting signal may include, for example, information indicating the length of the modulation period T shown in FIG. 2. The second modulation section 64 adjusts the period W of the modulated signal in accordance with the control signal output by the signal processing section 40. For example, the second modulation section 64 lengthens the period W when a control signal for increasing the moving speed is input, and shortens the period W when a control signal for decreasing the moving speed is input. In the second modulation section 64 of this example, the length that can be set as the period W (or pulse width W) may be a discrete value, such as an integer multiple of the period of the oscillation signal. A clock signal having the same period as that of the first modulation section 62 may be input to the second modulation section 64. The second modulation section 64 may determine the period W by counting the pulses of the clock signal. The second modulation section 64 may generate a modulated signal having a pulse width W that is an integer multiple of the period of the clock signal.

[0061] The AND circuit 66 generates a pulse signal by calculating the AND of the oscillation signal and the modulation signal, and the first pulse generator 67 outputs a pulse train 12 including first pulses 14, the number of which corresponds to the period W of the modulation signal.

[0062] The additional pulse generating section 68 generates one or more additional pulses that differ from the first pulse 14 in at least one of the pulse width and amplitude. The additional pulse generating section 68 may receive an additional setting signal that specifies at least one of the pulse width and amplitude that the additional pulse should have. The additional setting signal may be included in a control signal output by the signal processing section 40. The additional setting signal may include information that controls whether the additional pulse generating section 68 outputs an additional pulse.

[0063] A clock signal may be input to the additional pulse generating section 68. The period of the clock signal input to the additional pulse generating section 68 may be the same as or different from the period of the clock signal input to the first pulse generating section 67. The additional pulse generating section 68 may generate an additional pulse based on the input clock signal. In this example, a clock signal having the same period as the clock signal input to the first pulse generating section 67 is input to the additional pulse generating section 68. The additional pulse generating section 68 may generate an additional pulse having the same pulse width as the first pulse 14 but a different amplitude from the first pulse 14. In another example, the additional pulse generating section 68 may generate an additional pulse having a pulse width that is an integer multiple of the period of the input clock signal. The additional pulse generating section 68 may generate an additional pulse having a pulse width that is an integer multiple of the pulse width of the first pulse 14. With this configuration, the first pulse 14 and the additional pulse can be generated based on a single clock signal, thereby suppressing an increase in circuit size.

[0064] The logical sum circuit 69 outputs the logical sum of the pulse train 12 of first pulses 14 generated by the first pulse generating section 67 and the pulse train of additional pulses generated by the additional pulse generating section 68. That is, the output of the logical sum circuit 69 is at H level during a period when at least one of the outputs of the first pulse generating section 67 and the additional pulse generating section 68 indicates H level, and is at L level during a period when both the output of the first pulse generating section 67 and the output of the additional pulse generating section 68 indicate L level.

[0065] With this configuration, the pulse signal generating unit 60 can generate, for one movement speed indicated by the control signal, a pulse signal including one or more first pulses 14 and one or more additional pulses that differ from the first pulses 14 in at least one of the pulse width and amplitude. The pulse signal generating unit 60 of this example can generate a pulse signal including one or more first pulses 14 and one or more additional pulses in each modulation period T.

[0066] 8 is a diagram showing an example of a first pulse 14, an additional pulse 15, and a pulse signal. In this example, the additional pulse 15 has a different pulse width from the first pulse 14. The amplitudes of the additional pulse 15 and the first pulse 14 may be the same or different.

[0067] As described above, the first pulse generating section 67 outputs a pulse train 12 including one or more first pulses 14 in each modulation period T. The additional pulse generating section 68 may output a pulse train including one or more additional pulses 15 in each modulation period T. The additional pulse generating section 68 may output an additional pulse 15 in one modulation period T and not output an additional pulse 15 in other modulation periods T.

[0068] The logical sum circuit 69 outputs the logical sum of the pulse train 12 of the first pulses 14 and the pulse train of the additional pulses 15 as the pulse train 12 of the new pulse signal. This allows the pulse signal generating unit 60 to output multiple types of pulses with different pulse widths or amplitudes within one modulation period T.

[0069] The first pulse 14 has a constant pulse width. Therefore, if an attempt is made to control the speed of the optical element 120 using only the first pulse 14, the speed of the optical element 120 can only be controlled in speed units corresponding to one first pulse 14. For example, consider a case in which the speed of the optical element 120 changes by V1 when the number of first pulses 14 included in the pulse train 12 is changed by just one. In this case, if an attempt is made to control the speed of the optical element 120 using only the first pulse 14, the speed of the optical element 120 can only be controlled to a value that is an integer multiple of V1. Therefore, the minimum amount of change in the speed of the optical element 120 in one control is V1. In this example, an additional pulse 15 can be included in the pulse train 12. This allows the amount of change in the speed of the optical element 120 in one control to be smaller than V1. Since the volume of the drive noise generated in one control can be reduced, the peak value of the drive noise can be suppressed.

[0070] The pulse width of the additional pulse 15 may be greater than the pulse width of the first pulse 14. When an additional pulse 15 having a greater pulse width than the first pulse 14 is inserted, the change in velocity of the optical element 120 becomes smaller than V1. The pulse width of the additional pulse 15 may be at least twice, or even three times, the pulse width of the first pulse 14. Experimentally, when the pulse width of the additional pulse 15 is approximately three times the pulse width of the first pulse 14, the change in velocity of the optical element 120 due to the additional pulse 15 becomes 0.5 × V1. As the pulse width of the additional pulse 15 approaches the pulse width of the first pulse 14, the change in velocity of the optical element 120 due to the additional pulse 15 approaches V1, and as the pulse width of the additional pulse 15 increases, the change in velocity of the optical element 120 due to the additional pulse 15 approaches 0. The pulse signal generating unit 60 may control the pulse width of the additional pulse 15 according to the change in the moving velocity of the optical element 120 to be set. The relationship between the pulse width of the additional pulse 15 and the amount of change in the moving speed of the optical element 120 can be obtained by measuring in advance.

[0071] The signal processing unit 40 may generate a control signal indicating whether to insert an additional pulse 15. For example, the signal processing unit 40 may generate the velocity of the optical element 120 indicated by the control signal with a resolution finer than V1. For example, the signal processing unit 40 may control the velocity of the optical element 120 indicated by the control signal with a resolution of 0.5 × V1. In this case, the pulse signal generating unit 60 does not insert an additional pulse 15 into the pulse train 12 when the velocity of the optical element 120 indicated by the control signal is an integer multiple of V1. Furthermore, the pulse signal generating unit 60 inserts an additional pulse 15 into the pulse train 12 when the velocity of the optical element 120 indicated by the control signal is an integer multiple of V1 plus 0.5 × V1. This control allows the velocity of the optical element 120 to be controlled with fine resolution, thereby suppressing the peak value of the drive noise. The pulse signal generating unit 60 may insert multiple additional pulses 15 into one pulse train 12.

[0072] In another example, the signal processing unit 40 may control the speed of the optical element 120 indicated by the control signal with a resolution of V1. That is, the speed of the optical element 120 indicated by the control signal is an integer multiple of V1. The pulse signal generating unit 60 may automatically perform a process of inserting additional pulses 15 when the speed of the optical element 120 indicated by the control signal changes.

[0073] FIG. 9 is a diagram showing an example of the operation of the pulse signal generating unit 60. In this example, an example will be described in which the speed of the optical element 120 is changed from a first speed to a second speed. In FIG. 9, the first speed is 4×V1, and the second speed is 5×V1. In other words, the first speed and the second speed are integer multiples of the speed V1 corresponding to one first pulse 14. The control signal output by the signal processing unit 40 in this example transitions from a control signal indicating the first speed to a control signal indicating the second speed.

[0074] The pulse signal generating unit 60 of this example sequentially generates a pulse signal before the change corresponding to the first speed, an intermediate pulse signal corresponding to a speed between the first speed and the second speed, and a pulse signal after the change corresponding to the second speed. The pulse signal before the change includes a number of first pulses 14 (for example, four) according to the first speed, but does not include additional pulses 15.

[0075] The pulse signal generating unit 60 generates an intermediate pulse signal after generating the unmodified pulse signal and before generating the modified pulse signal. The intermediate pulse signal is a signal obtained by adding one or more additional pulses 15 to the unmodified pulse signal.

[0076] After generating the intermediate pulse signal, the pulse signal generating section 60 generates a changed pulse signal that includes a number (e.g., five) of first pulses 14 according to the second speed. The changed pulse signal does not include the additional pulse 15. By such control, when changing the movement speed of the optical element 120, the movement speed can be changed gradually, and the peak value of the drive noise can be suppressed.

[0077] 9 has been described as an example in which the movement speed of the optical element 120 is increased, the same applies when the movement speed of the optical element 120 is decreased. When decreasing the movement speed of the optical element 120, the pulse signal generating section 60 may generate pulse signals in the order of the changed pulse signal, the intermediate pulse signal, and the pulse signal before the change shown in FIG. 9. In other words, when decreasing the movement speed of the optical element 120, the pulse signal generating section 60 inserts an additional pulse 15 in place of any of the first pulses 14 included in the pulse signal before the speed reduction. Next, the pulse signal generating section 60 can generate a pulse signal after the speed reduction by deleting the additional pulse 15.

[0078] 10 is a diagram showing the relationship between the number of first pulses 14 included in the pulse train 12 and the sound pressure of the drive sound in a reference example. In the reference example, the additional pulses 15 are not used. In this case, each time the number of first pulses 14 included in the pulse train 12 is changed, a relatively large drive sound is generated.

[0079] 11 is a diagram showing the relationship between the number of pulses included in the pulse train 12 and the sound pressure of the driving sound in this example. In this example, one first pulse 14 is counted as a pulse number of "1," and one additional pulse 15 is counted as a pulse number of "0.5." The pulse number corresponds to the movement speed of the optical element 120.

[0080] In this example, the use of additional pulse 15 can improve the resolution of the number of pulses included in pulse train 12 (movement speed of optical element 120). This makes it possible to reduce the volume of drive noise generated by one speed change, and suppress the peak value of the drive noise.

[0081] As shown in FIG. 8 and other figures, the additional pulse generating section 68 may generate the additional pulse 15 in a period that does not overlap with any of the first pulses 14. As shown in FIG. 8 and other figures, the additional pulse generating section 68 may generate the additional pulse 15 in a period that follows a period in the modulation cycle T in which one or more first pulses 14 are generated. In another example, the additional pulse generating section 68 may generate the additional pulse 15 in a period that precedes a period in which one or more first pulses 14 are generated. In another example, the additional pulse generating section 68 may generate the additional pulse 15 in a period that overlaps with any of the first pulses 14.

[0082] 12 is a diagram showing an example of the timing at which the additional pulse 15 is inserted. The additional pulse generating section 68 in this example generates the additional pulse 15 at a timing that overlaps with the earliest first pulse 14 among one or more first pulses 14 included in the modulation period T. The additional pulse 15 may overlap with multiple first pulses 14.

[0083] 13 is a diagram showing another example of the timing at which the additional pulse 15 is inserted. The additional pulse generating section 68 of this example generates the additional pulse 15 at a timing that does not overlap with either the earliest or latest first pulse 14 among one or more first pulses 14 included in the modulation period T. The additional pulse 15 may overlap with the first pulse 14 that is located in the center on the time axis among the one or more first pulses 14. The additional pulse 15 may overlap with multiple first pulses 14.

[0084] 14 is a diagram showing another example of the timing at which the additional pulse 15 is inserted. In this example, the additional pulse generating section 68 generates the additional pulse 15 at a timing that overlaps with the latest first pulse 14 among one or more first pulses 14 included in the modulation period T. The additional pulse 15 may overlap with multiple first pulses 14.

[0085] FIG. 15 is a diagram showing another example of the additional pulse 15. The additional pulse generating unit 68 in this example generates an additional pulse 15 having a smaller amplitude than the first pulse 14. FIG. 15 shows an example in which the additional pulse 15 is automatically inserted, similar to the example shown in FIG. 9. However, the additional pulse 15 in this example can also be applied to examples other than that shown in FIG. 9. The pulse width of the additional pulse 15 may be the same as or different from that of the first pulse 14. Other processing is the same as any of the embodiments described in this specification. This processing also makes it possible to gradually change the moving speed of the optical element 120 and suppress the peak value of the driving noise.

[0086] The ratio (A2 / A1) of the amplitude A2 of the additional pulse 15 to the amplitude A1 of the first pulse 14 is defined as R. The amount of change in the movement speed of the optical element 120 due to the additional pulse 15 is approximately R×V1. The amplitude of the additional pulse 15 may be 50% of that of the first pulse 14. In this case, the amount of change in the movement speed of the optical element 120 due to the additional pulse 15 is 0.5×V1. The ratio R may be less than 1 or may be greater than 1. When the ratio R is greater than 1, the pulse width of the additional pulse 15 may be set smaller than the pulse width of the first pulse 14. This allows for fine control of the amount of change in the movement speed of the optical element 120.

[0087] 1 to 15. In this driving method, a detected position and a target position of the optical element 120 are acquired (S1202). Then, a control signal for controlling the movement speed of the optical element 120 is generated based on the difference between the detected position and the target position (S1204). Then, a pulse signal (or a drive signal) for driving the piezoelectric actuator is generated based on the control signal (S1206). As described in FIGS. 1 to 15, in the driving method of this example, in the step of generating a pulse signal (S1206), a pulse signal including one or more first pulses 14 and one or more additional pulses 15 that differ from the first pulses 14 in at least one of the pulse width and amplitude can be generated for one movement speed indicated by the control signal.

[0088] 17 is a diagram showing another example of the configuration of the drive circuit 10. The drive circuit 10 of this example differs from the drive circuit 10 of the example described with reference to FIGS. 1 to 16 in that it includes a filter section 70. The configuration other than the filter section 70 is the same as that of any of the embodiments described with reference to FIGS. 1 to 16. The filter section 70 may be included in the drive section 50, or may be provided outside the drive section 50.

[0089] As described above, the driving unit 50 generates a driving signal that controls the movement speed of the optical element 120 based on the difference between the detected position and the target position. The filter unit 70 suppresses the frequency of fluctuations in the movement speed caused by the driving signal. In other words, the filter unit 70 reduces the frequency of fluctuations in the movement speed of the optical element 120 compared to when the filter unit 70 is not provided. This makes it possible to suppress the generation of drive noise as described in FIG. 5. In this specification, frequency refers to the number of times per unit time. The frequency of fluctuations in the movement speed refers to the number of times the movement speed is changed per unit time.

[0090] As explained in FIGS. 1 to 16, the drive noise can also be suppressed by reducing the amount of change in each change in the movement speed. In this example, the frequency of fluctuations in the movement speed is also suppressed by providing a filter unit 70. This allows for further suppression of the drive noise. The operation of the filter unit 70 will be mainly explained below, but the pulse signal generation unit 60 may combine the insertion process of the additional pulse 15 explained in FIGS. 1 to 16 with the processing by the filter unit 70. However, the pulse signal generation unit 60 does not have to perform the insertion process of the additional pulse 15 explained in FIGS. 1 to 16. The drive noise can be suppressed by simply performing the processing by the filter unit 70 without performing the insertion process of the additional pulse 15.

[0091] The filter unit 70 may be provided at any position in the drive circuit 10 as long as it can reduce the frequency of fluctuations in the movement speed of the optical element 120 compared to when the filter unit 70 is not provided. For example, the filter unit 70 may be provided upstream of the drive unit 50 to suppress fluctuations in the detection position. In this case, fluctuations in the relative position between the detection position and the target position are suppressed, which in turn suppresses fluctuations in the number of first pulses 14 included in the pulse train 12 and reduces the frequency of fluctuations in the movement speed of the optical element 120. Alternatively, the filter unit 70 may be provided inside the drive unit 50 to control the number of first pulses 14 included in the pulse train 12 to be less frequent than the frequency of fluctuations in the relative position between the detection position and the target position. Alternatively, the filter unit 70 may be provided downstream of the drive unit 50 to suppress fluctuations in the number of first pulses 14 included in the modulation period T in the generated drive signal.

[0092] The filter section 70 of this example suppresses the frequency with which the pulse trains 12 in the pulse signal generating section 60 are changed. For example, the filter section 70 suppresses the frequency with which the number of first pulses 14 included in one pulse train 12 is changed. Since the number of first pulses 14 included in one pulse train 12 corresponds to the moving speed of the optical element 120, suppressing the frequency with which the number of first pulses 14 changes can suppress the frequency with which the moving speed of the optical element 120 is changed. The filter section 70 may suppress the frequency with which the number of first pulses 14 included in one pulse train 12 is changed by suppressing the frequency with which the period W of the modulated signal is changed.

[0093] The filter unit 70 may suppress fluctuations in parameters other than the number of first pulses 14 in the pulse train 12. For example, when the driver 50 changes the movement speed of the optical element 120 by changing the amplitude of the first pulses 14, the filter unit 70 may suppress the frequency of fluctuations in the amplitude of the first pulses 14. Furthermore, when the driver 50 changes the movement speed of the optical element 120 by changing the pulse width of one first pulse 14, the filter unit 70 may suppress the frequency of fluctuations in the pulse width of the first pulse 14.

[0094] Fig. 18 is a diagram showing an example of the configuration of pulse signal generating section 60. Pulse signal generating section 60 of this example differs from the example of Fig. 7 in that it further includes a filter section 70. Other structures are similar to the example of Fig. 7. If pulse signal generating section 60 does not perform the process of inserting additional pulse 15 described with reference to Figs. 1 to 16, pulse signal generating section 60 does not need to include additional pulse generating section 68.

[0095] The filter unit 70 suppresses fluctuations in the control signal output by the signal processing unit 40, and inputs the fluctuation-suppressed control signal to the second modulation unit 64. The filter unit 70 may remove high-frequency components from the control signal, and input the remaining low-frequency components of the control signal to the second modulation unit 64. A filter setting signal for setting filter characteristics may be input to the filter unit 70. For example, the filter unit 70 is a low-pass filter, and the filter setting signal is a signal that sets the cutoff frequency of the filter unit 70.

[0096] The filter unit 70 attenuates components of the fluctuation frequency of the movement speed of the optical element 120 that are equal to or higher than the operating frequency band of the piezoelectric actuator 110. The filter unit 70 of this example attenuates components of the control signal that are equal to or higher than the operating frequency band of the piezoelectric actuator 110. The filter unit 70 may also attenuate components of the fluctuation frequency of the movement speed of the optical element 120 that are equal to or higher than the lower limit of the operating frequency band of the piezoelectric actuator 110. The cutoff frequency of the filter unit 70 may be the upper limit or lower limit of the operating frequency band of the piezoelectric actuator 110. The operating frequency band of the piezoelectric actuator 110 may be the specification value provided by the manufacturer of the piezoelectric actuator 110. Through this control, it is possible to suppress the drive noise while maintaining the operating speed of the piezoelectric actuator 110 at a constant level or higher.

[0097] The filter unit 70 may attenuate components greater than 100 Hz in the frequency of fluctuations in the movement speed of the optical element 120. In this example, the filter unit 70 attenuates components greater than 100 Hz in the control signal. The filter unit 70 may attenuate components greater than 80 Hz, or may attenuate components greater than 60 Hz. This type of control makes it possible to suppress drive noise while maintaining the operating speed of the piezoelectric actuator 110 at or above a certain level.

[0098] Although the pulse signal generating unit 60 of this example includes a first modulation unit 62 and a second modulation unit 64, the pulse signal generating unit 60 of other examples may include the first modulation unit 62 but not the second modulation unit 64. In this case, the first modulation unit 62 adjusts the pulse width of each pulse of the oscillation signal in response to a control signal. Specifically, when a control signal for accelerating the optical element 120 is input, the first modulation unit 62 increases the pulse width of the oscillation signal, and when a control signal for decelerating the optical element 120 is input, the first modulation unit 62 decreases the pulse width of the oscillation signal. Even in this case, the filter unit 70 suppresses fluctuations in the control signal, thereby suppressing fluctuations in the movement speed of the optical element 120 and reducing drive noise.

[0099] Fig. 19 is a diagram illustrating an example of the operation of the filter unit 70. The vertical axis in Fig. 19 represents the moving speed of the optical element 120 in response to the control signal. The horizontal axis in Fig. 19 represents time. In Fig. 19, the solid line represents the time waveform of the control signal when the filter unit 70 is used, and the dashed line represents the time waveform of the control signal when the filter unit 70 is not used.

[0100] The filter unit 70 of this example suppresses the frequency of fluctuations in the movement speed of the optical element 120 in a direction that decreases the movement speed. For example, the filter unit 70 delays the falling edge of the control signal by a predetermined time. The delay time may be set by a filter setting value included in the filter setting signal. The delay time may be longer than the operating period (PID cycle) of the signal processing unit 40. The operating period of the signal processing unit 40 refers to the minimum period during which the value of the control signal output by the signal processing unit 40 can fluctuate. The delay time may be the product of the filter setting value and the PID cycle. The filter setting value may be a value of 2 or greater. In other words, the filter unit 70 may delay the falling edge of the control signal by a delay time that is at least twice the operating period of the signal processing unit 40. The filter setting value may be a value of 3 or greater, 5 or greater, or even 10 or greater. Delaying the falling edge of the control signal can suppress repeated oscillations of the rising and falling edges of the control signal within a short period of time. This reduces the generation of drive noise.

[0101] The filter section 70 may suppress the frequency of fluctuations in the movement speed of the optical element 120 to a greater extent in a direction that decreases the movement speed of the optical element 120 than in a direction that increases the movement speed of the optical element 120. In the example shown in Fig. 18 , the filter section 70 suppresses the frequency of changes in the pulse train 12 to a greater extent in a direction that decreases the movement speed of the optical element 120 than in a direction that increases the movement speed of the optical element 120.

[0102] The degree of suppression of the fluctuation frequency may be the ratio of the fluctuation frequency after suppression to the fluctuation frequency before suppression. A strong degree of suppression means that the ratio of the fluctuation frequency after suppression to the fluctuation frequency before suppression is small. Alternatively, a strong degree of suppression of the fluctuation frequency may mean that the cutoff frequency in the filter unit 70 is low.

[0103] The filter unit 70 may also delay the rising edge of the control signal as shown in FIG. 19 by a predetermined delay time. In this case, the delay time of the rising edge (in the direction in which the movement speed increases) may be shorter than the delay time of the falling edge (in the direction in which the movement speed decreases). In another example, the filter unit 70 does not need to delay the rising edge. That is, the filter unit 70 may suppress the frequency of fluctuations in the movement speed of the optical element 120 in the direction in which the movement speed decreases, but may not suppress the frequency of fluctuations in the movement speed of the optical element 120 in the direction in which the movement speed increases. Such control prevents the movement of the optical element 120 from slowing down. Therefore, operations such as autofocusing can be completed quickly and operating noise can be suppressed.

[0104] In another example, the filter unit 70 may suppress the frequency of fluctuations in the movement speed of the optical element 120 to a greater extent in a direction that increases the movement speed of the optical element 120 than in a direction that decreases the movement speed of the optical element 120. In this case, it becomes easier to decelerate the optical element 120. As a result, it is possible to suppress overshoot, in which the optical element 120 moves past the target position, while suppressing operation noise. The filter unit 70 may suppress the frequency of fluctuations in the movement speed of the optical element 120 in a direction that increases the movement speed, but may not need to suppress the frequency of fluctuations in the movement speed of the optical element 120 in a direction that decreases the movement speed of the optical element 120.

[0105] Fig. 20 is a diagram showing an example of the position of the optical element 120 and the waveform of a control signal. Fig. 20 shows an example in which the filter unit 70 is not used. In the upper part of Fig. 20, the detected position of the optical element 120 is shown by a solid line, and the target position is shown by a dashed line. When the target position changes as shown by the dashed line, the drive circuit 10 moves the optical element 120 toward the target position. As a result, the detected position of the optical element 120 gradually approaches the target position.

[0106] Immediately after the target position is changed, the difference between the target position and the detected position is large, so the driver 50 attempts to increase the moving speed of the optical element 120. As the detected position approaches the target position, the driver 50 decelerates the optical element 120.

[0107] When the movement speed of the optical element 120 is changed, for example, in the PID control described in Fig. 17, the value of the control signal may oscillate within a short period. In the time waveform of the control signal in Fig. 20, the value of the control signal oscillates every time the movement speed of the optical element 120 is changed. When such oscillation occurs, a loud drive noise is likely to occur.

[0108] FIG. 21 is a diagram showing an example of the position of the optical element 120 and the waveform of the control signal. FIG. 21 shows an example in which a filter unit 70 is used. The control signal shown in FIG. 21 is a control signal output by the filter unit 70. The filter unit 70 of this example suppresses fluctuations in the waveform of the control signal. As a result, the waveform of the control signal of this example does not exhibit vibrations such as those shown in FIG. 20. This makes it possible to suppress drive noise. Furthermore, even when the filter unit 70 is provided, the transition of the detection position of the optical element 120 remains almost the same as in the example of FIG. 20.

[0109] The filter characteristics of the filter unit 70 described in FIGS. 18 and 19 are constant regardless of the passage of time. In another example, the filter characteristics of the filter unit 70 may be dynamically changed. The filter unit 70 may adjust the filter characteristics based on the difference between the detection position of the optical element 120 and the target position. For example, when the detection position of the optical element 120 is far from the target position, the degree of suppression of the frequency of fluctuations in the movement speed of the optical element 120 in a direction to decrease the movement speed of the optical element 120 may be stronger than the degree of suppression of the frequency of fluctuations in the movement speed of the optical element 120 in a direction to increase the movement speed of the optical element 120. When the detection position of the optical element 120 approaches the target position, the degree of suppression of the frequency of fluctuations in the movement speed of the optical element 120 in a direction to increase the movement speed of the optical element 120 may be stronger than the degree of suppression of the frequency of fluctuations in the movement speed of the optical element 120 in a direction to decrease the movement speed of the optical element 120. In this way, when the detection position of the optical element 120 is far from the target position, priority is given to acceleration of the optical element 120, and the optical element 120 can be moved to the target position at high speed. Furthermore, when the detection position of the optical element 120 approaches the target position, priority is given to decelerating the optical element 120, thereby suppressing overshoot in the movement of the optical element 120. Therefore, the optical element 120 can be moved at high speed and with high accuracy, while suppressing drive noise.

[0110] The filter unit 70 may compare the difference between the detected position and the target position of the optical element 120 with a set reference value and adjust the filter characteristics according to the comparison result. Based on the comparison result, the filter unit 70 adjusts the filter characteristics for at least one of the frequency of change in the movement speed in a direction to decrease the movement speed of the optical element 120 and the frequency of change in the movement speed in a direction to increase the movement speed. If the difference is greater than the reference value, the filter unit 70 may determine that the detected position of the optical element 120 is far from the target position and perform the above-mentioned control, and if the difference is equal to or less than the reference value, may determine that the detected position of the optical element 120 has approached the target position and perform the above-mentioned control.

[0111] 22 is a diagram showing another example of the arrangement of the filter section 70. The filter section 70 may be provided at least at one of the positions indicated by the dotted lines in FIG. 22. For example, the filter section 70 may be provided before or after the pre-processing section 20. In this case, the filter section 70 suppresses fluctuations in the detected position of the optical element 120 detected by the position detection section 160. This type of processing can also suppress fluctuations in the moving speed of the optical element 120.

[0112] As described above, the preprocessing unit 20 converts the analog signal of the detected position detected by the position detection unit 160 into a digital signal. For example, the preprocessing unit 20 samples the analog signal at a predetermined period, converts the sampled analog value into a digital value, and records it. The preprocessing unit 20 updates the recorded digital value every time it obtains a new conversion result. The preprocessing unit 20 outputs the recorded digital value as the detected position. The filter unit 70 may reduce the frequency at which the conversion result in the preprocessing unit 20 is updated. In other words, the filter unit 70 may reduce the frequency of fluctuations in the digital signal output by the preprocessing unit 20.

[0113] The filter section 70 may be provided between the signal processing section 40 and the pulse signal generating section 60. In this case, the filter section 70 suppresses fluctuations in the control signal output by the signal processing section 40, similar to the example of FIG.

[0114] The filter section 70 may be provided between the pulse signal generating section 60 and the driver 80. In this case, the filter section 70 suppresses fluctuations in the number of first pulses 14 included in the pulse train 12 in the pulse signal output by the pulse signal generating section 60.

[0115] The filter section 70 may be provided after the driver 80. In this case, the filter section 70 suppresses fluctuations in the number of first pulses 14 included in the pulse train 12 in the drive signal output by the driver 80.

[0116] FIG. 23 is a chart outlining the driving method for driving the piezoelectric actuator 110 described with reference to FIGS. 17 to 22. In this driving method, a detected position and a target position of the optical element 120 are acquired (S1102). Then, a drive signal for controlling the movement speed of the optical element 120 is generated based on the difference between the detected position and the target position (S1106). As described with reference to FIGS. 1 to 22, the driving method of this example includes a filtering step S1104 for suppressing the frequency of fluctuations in the movement speed of the optical element 120 due to the driving signal. The filtering step S1104 may be performed between S1102 and S1106, after S1106, or during the processing of S1106.

[0117] This specification also discloses inventions relating to the following items. (Item 1) A drive circuit for driving a piezoelectric actuator that moves an optical element, a signal processing unit that generates a control signal for controlling a moving speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element should move; a pulse signal generating unit that generates a pulse signal having a pulse train according to the control signal and controls the moving speed according to the pulse train; Equipped with The pulse signal generating unit is capable of generating the pulse signal including, for one of the movement speeds indicated by the control signal, one or more first pulses and one or more additional pulses that differ from the first pulses in at least one of pulse width and amplitude. Drive circuit. (Item 2) The additional pulse has a pulse width greater than that of the first pulse. Item 1. The drive circuit according to item 1. (Item 3) The additional pulse has a pulse width that is at least twice as long as that of the first pulse. Item 2. The drive circuit according to item 2. (Item 4) When the moving speed of the optical element is changed from a first speed to a second speed, The pulse signal generating unit generating a pulse signal before the change that includes the first pulses in a number corresponding to the first speed, for the first speed; After generating the unmodified pulse signal, generate an intermediate pulse signal by adding one or more of the additional pulses to the unmodified pulse signal; After generating the intermediate pulse signal, a modified pulse signal including the number of first pulses corresponding to the second speed is generated. Item 2. The drive circuit according to item 2. (Item 5) The pulse signal generating unit a first pulse generating unit that generates one or more of the first pulses; an additional pulse generating unit that generates one or more of the additional pulses; a logical OR circuit that outputs a logical OR of the pulse train of the first pulses generated by the first pulse generating unit and the pulse train of the additional pulses generated by the additional pulse generating unit; 5. The drive circuit according to any one of items 1 to 4, comprising: (Item 6) The first pulse generating unit a first modulation unit that generates an oscillation signal including one or more of the first pulses; a second modulation unit that generates a modulation signal having a pulse width that is an integer multiple of the period of the oscillation signal; a logical product circuit that outputs a logical product of the oscillation signal and the modulation signal; Item 6. The driving circuit according to item 5, comprising: (Item 7) The additional pulse generating unit generates the additional pulse during a period that does not overlap with any of the first pulses. Item 7. The drive circuit according to item 6. (Item 8) The additional pulse generating unit generates the additional pulse during a period overlapping with at least one of the first pulses. Item 7. The drive circuit according to item 6. (Item 9) The additional pulse has a smaller amplitude than the first pulse. Item 1. The drive circuit according to item 1. (Item 10) a filter unit that suppresses fluctuations in the moving speed of the optical element; 5. A drive circuit according to any one of items 1 to 4. (Item 11) The signal processing unit performs PID control based on the detected position and the target position, and generates the control signal. 5. A drive circuit according to any one of items 1 to 4. (Item 12) The piezoelectric actuator further includes a booster that boosts the drive signal supplied to the piezoelectric actuator. 5. A drive circuit according to any one of items 1 to 4. (Item 13) An optical unit comprising: an optical element; a piezoelectric actuator that moves the optical element; and a drive circuit that drives the piezoelectric actuator, The drive circuit a signal processing unit that generates a control signal for controlling a moving speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element should move; a pulse signal generating unit that generates a pulse signal having a pulse train according to the control signal and controls the moving speed according to the pulse train; and The pulse signal generating unit is capable of generating the pulse signal including, for one of the movement speeds indicated by the control signal, one or more first pulses and one or more additional pulses that differ from the first pulses in at least one of pulse width and amplitude. An optical unit having: (Item 14) A driving method for driving a piezoelectric actuator that moves an optical element, comprising: generating a control signal for controlling a moving speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element should be moved; generating a pulse signal having a pulse train according to the control signal, and controlling the moving speed according to the pulse train; In generating the pulse signal, the pulse signal can be generated to include one or more first pulses and one or more additional pulses that are different from the first pulses in at least one of pulse width and amplitude for one of the movement speeds indicated by the control signal. Drive method.

[0118] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0119] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[0120] 10 Drive circuit, 12 Pulse train, 14 First pulse, 15 Additional pulse, 20 Pre-processing unit, 30 Setting unit, 40 Signal processing unit, 50 Drive unit, 60 Pulse signal generating unit, 62 First modulation unit, 64 Second modulation unit, 66 AND circuit, 67 First pulse generating unit, 68 Additional pulse generating unit, 69 OR circuit, 70 Filter unit, 80 Driver, 100 Optical unit, 110 Piezoelectric actuator, 114 Shaft, 120 Optical element, 122 Fixing unit, 130 Image acquisition unit, 140 Display unit, 150 Image processing unit, 160 Position detection unit, 170 Voltage boost unit

Claims

1. A drive circuit for driving a piezoelectric actuator that moves an optical element, a drive unit that generates a drive signal to control a moving speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element should move; a filter unit that suppresses the frequency of fluctuations in the moving speed due to the drive signal; Equipped with The drive unit is a pulse signal generating unit that generates a pulse signal having a pulse train corresponding to a difference between the detected position and the target position; a driver that outputs the drive signal in response to the pulse signal; and the filter unit suppresses the frequency of change of the pulse train in the pulse signal generation unit; the driving unit further includes a signal processing unit that generates a control signal for controlling a moving speed of the optical element based on a difference between the detected position and the target position, the pulse signal generating unit generates the pulse signal having the pulse train in accordance with the control signal; The pulse signal generating unit is capable of generating the pulse signal including, for one of the moving speeds indicated by the control signal, one or more first pulses and one or more additional pulses that differ from the first pulses in at least one of pulse width and amplitude. Drive circuit.

2. The additional pulse has a pulse width greater than that of the first pulse. The drive circuit of claim 1 .

3. The additional pulse has a pulse width that is at least twice as long as that of the first pulse.

3. The drive circuit according to claim 2.

4. When the moving speed of the optical element is changed from a first speed to a second speed, The pulse signal generating unit generating a pulse signal before the change that includes the first pulses in a number corresponding to the first speed, for the first speed; After generating the unmodified pulse signal, generate an intermediate pulse signal by adding one or more of the additional pulses to the unmodified pulse signal; After generating the intermediate pulse signal, a modified pulse signal including the number of first pulses corresponding to the second speed is generated.

3. The drive circuit according to claim 2.

5. The pulse signal generating unit a first pulse generating unit that generates one or more of the first pulses; an additional pulse generating unit that generates one or more of the additional pulses; a logical OR circuit that outputs a logical OR of the pulse train of the first pulses generated by the first pulse generating unit and the pulse train of the additional pulses generated by the additional pulse generating unit; 2. The drive circuit of claim 1, comprising:

6. A drive circuit for driving a piezoelectric actuator that moves an optical element, a signal processing unit that generates a control signal for controlling a moving speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element should move; a pulse signal generating unit that generates a pulse signal having a pulse train according to the control signal and controls the moving speed according to the pulse train; Equipped with The pulse signal generating unit is capable of generating the pulse signal including, for one of the moving speeds indicated by the control signal, one or more first pulses and one or more additional pulses that differ from the first pulses in at least one of pulse width and amplitude. Drive circuit.

7. The filter unit attenuates components of the fluctuation frequency of the moving speed that are equal to or higher than the operating frequency band of the piezoelectric actuator. The drive circuit of claim 1 .

8. The filter unit attenuates components of the fluctuation frequency of the moving speed that are greater than 100 Hz. The drive circuit of claim 1 .

9. The filter unit suppresses the frequency of changes in the pulse train in a direction that decreases the moving speed more strongly than the frequency of changes in the pulse train in a direction that increases the moving speed. The drive circuit of claim 1 .

10. The filter unit suppresses a frequency of change in the pulse train in a direction that decreases the moving speed, and does not suppress a frequency of change in the pulse train in a direction that increases the moving speed.

10. The drive circuit of claim 9.

11. a pre-processing unit that performs AD conversion on a signal indicating the detected position and inputs the converted signal to the driving unit; The filter unit reduces the frequency with which the conversion result in the preprocessing unit is updated. The drive circuit of claim 1 .

12. The filter unit adjusts the filter characteristics based on the difference between the detected position and the target position. The drive circuit of claim 1 .

13. The filter unit adjusts filter characteristics for at least one of a frequency of change in the moving speed in a direction to decrease the moving speed and a frequency of change in the moving speed in a direction to increase the moving speed, based on a comparison result between the difference and a set reference value.

13. The drive circuit of claim 12.

14. The drive unit performs PID control based on the detected position and the target position, and generates the drive signal. The drive circuit of claim 1 .

15. a position detection unit that detects the position of the optical element and generates a signal indicating the detected position; The drive circuit of claim 1 .

16. The piezoelectric actuator further includes a booster that boosts the drive signal and supplies the boosted drive signal to the piezoelectric actuator. The drive circuit of claim 1 .

17. An optical unit comprising: an optical element; a piezoelectric actuator that moves the optical element; and a drive circuit according to claim 6 that drives the piezoelectric actuator.

18. A driving method for driving a piezoelectric actuator that moves an optical element, comprising: generating a drive signal for controlling a moving speed of the optical element based on a difference between a detected position indicating the detected position of the optical element and a target position to which the optical element should be moved; suppressing the frequency of fluctuations in the moving speed due to the drive signal; When generating the drive signal, generating a pulse signal having a pulse train corresponding to a difference between the detected position and the target position; outputting the drive signal in response to the pulse signal; When suppressing the fluctuation frequency, suppressing the change frequency of the pulse train; When generating the drive signal, a control signal is generated based on a difference between the detected position and the target position, the control signal controlling the movement speed of the optical element; When generating the pulse signal, the pulse signal having the pulse train according to the control signal is generated, and the pulse signal including one or more first pulses and one or more additional pulses that differ from the first pulses in at least one of pulse width and amplitude can be generated for one of the movement speeds indicated by the control signal. Drive method.

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