WO2024180863A1 - Drive circuit, optical unit, and drive method - Google Patents

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

Driving circuit, optical unit and driving method

The present invention relates to a drive circuit, an optical unit, and a drive method.

A technique for driving a lens by a piezoelectric actuator is known (see, for example, Japanese Patent Application Laid-Open No. 2003-233663).
[Prior Art Literature]
[Patent Documents]
[Patent Document 1] JP 2005-354854 A

Problem to be solved

　Suppresses the generation of drive noise when the lens is driven by a piezoelectric actuator.

General Disclosure

In one aspect of the present invention, a drive circuit is provided that drives a piezoelectric actuator that moves an optical element. The drive circuit may include a drive section that generates a drive signal that controls the movement speed of the optical element based on the 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 drive circuit may include a filter section that suppresses the frequency of fluctuations in the movement speed due to the drive signal.

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 the operating frequency band of the piezoelectric actuator.

In any of the drive circuits described above, the filter unit may attenuate components in the fluctuation frequency of the movement speed that are greater than 100 Hz.

In any of the drive circuits described above, the drive unit may have a pulse signal generation unit that generates a pulse signal having a pulse train corresponding to the difference between the detection position and the target position. In any of the drive circuits described above, the drive unit may have 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 the frequency of changes to the pulse train in the pulse signal generation unit.

In any of the drive circuits described above, the filter unit 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.

In any of the drive circuits described above, the filter unit 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.

Any of the drive circuits described above may include a pre-processing unit that AD converts the signal indicating the detection position and inputs it to the drive unit. In any of the drive circuits described above, the filter unit may suppress the frequency at which the conversion result in the pre-processing unit is updated.

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

In any of the drive circuits described above, the filter section may adjust the filter characteristics for at least one of the frequency of change in the moving speed in a direction that decreases the moving speed and the frequency of change in the moving speed in a direction that increases the moving speed, based on a comparison result between the difference and a set reference value.

In any of the drive circuits described above, the drive unit may perform PID control based on the detected position and the target position to generate the drive signal.

Any of the above drive circuits may include a position detection unit that detects the position of the optical element and generates a signal indicative of the detected position.

Any of the drive circuits described above may include a boosting section that boosts the drive signal and supplies it to the piezoelectric actuator.

In any of the drive circuits described above, the drive unit may have a signal processing unit that generates a control signal to control the movement speed of the optical element based on the 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 drive circuits described above, the pulse signal generation unit may generate the pulse signal having the pulse train according to the control signal. In any of the drive circuits described above, 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 differing from the first pulses in at least one of the pulse width and amplitude.

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

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.

In any of the drive circuits described above, when the moving speed of the optical element is changed from a first speed to a second speed, the pulse signal generating unit may generate a pre-change pulse signal for the first speed, the pulse signal including a number of the first pulses corresponding to the first speed. In any of the drive circuits described above, the pulse signal generating unit may generate an intermediate pulse signal by adding one or more of the additional pulses to the pre-change pulse signal, after generating the pre-change pulse signal. In any of the drive circuits described above, the pulse signal generating unit may generate a post-change pulse signal including a number of the first pulses corresponding to the second speed, after generating the intermediate pulse signal.

In any of the drive circuits described above, the pulse signal generating section may have a first pulse generating section that generates one or more of the first pulses. In any of the drive circuits described above, the pulse signal generating section may have an additional pulse generating section that generates one or more of the additional pulses. In any of the drive circuits described above, the pulse signal generating section may have a logical OR circuit that outputs the logical OR of the pulse train of the first pulses generated by the first pulse generating section and the pulse train of the additional pulses generated by the additional pulse generating section.

In a second aspect of the present invention, a drive circuit is provided that drives a piezoelectric actuator that moves an optical element. The drive circuit may include a signal processing unit that generates a control signal that controls the movement speed of the optical element based on the 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. Any of the drive circuits may include a pulse signal generation 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 generation unit may be capable of generating 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 the pulse width and amplitude, for one of the movement speeds indicated by the control signal.

In a third aspect of the present invention, an optical unit is provided that includes 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.

In a fourth aspect of the present invention, there is provided a driving method for driving a piezoelectric actuator that moves an optical element. The above-mentioned activation method may generate a driving signal that controls the moving speed of the optical element based on the 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 above-mentioned driving method may suppress the frequency of fluctuations in the moving speed due to the driving signal.

The above summary of the invention does not list all of the features of the present invention. Also, subcombinations of these features may also be inventions.

FIG. 1 is a diagram showing an example of an optical unit 100 according to an embodiment of the present invention. 3A to 3C are diagrams illustrating an example of a drive signal generated by a drive circuit 10. 4A to 4C are diagrams illustrating an example of the operation of the booster 170. 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. 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 sound pressure of the drive sound. FIG. 2 is a diagram illustrating an example of the configuration of a drive circuit 10. FIG. 2 is a diagram illustrating an example of the configuration of a pulse signal generating unit 60. 1A and 1B are diagrams showing an example of a first pulse 14, an additional pulse 15, and a pulse signal. 6A to 6C are diagrams illustrating an example of the operation of a pulse signal generating unit 60. 11 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 driving sound in a reference example. FIG. FIG. 11 is a diagram showing the relationship between the number of pulses included in a pulse train 12 and the sound pressure of the driving sound in the embodiment. FIG. 13 is a diagram showing an example of the timing for inserting an additional pulse 15. FIG. 11 is a diagram showing another example of the timing for inserting the additional pulse 15. FIG. 11 is a diagram showing another example of the timing for inserting the additional pulse 15. 13A and 13B are diagrams showing other examples of the additional pulse 15. FIG. 16 is a chart outlining a method for driving the piezoelectric actuator 110 described with reference to FIGS. 1 to 15. FIG. 4 is a diagram showing another example of the configuration of the drive circuit 10. FIG. 2 is a diagram illustrating an example of the configuration of a pulse signal generating unit 60. 10A to 10C are diagrams illustrating an example of the operation of a filter unit 70. 11 is a diagram showing an example of the position of the optical element 120 and the waveform of a control signal. 11 is a diagram showing an example of the position of the optical element 120 and the waveform of a control signal. 13A and 13B are diagrams illustrating other exemplary arrangements of the filter section 70. FIG. 23 is a chart outlining a method for driving the piezoelectric actuator 110 described with reference to FIGS. 17 to 22.

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.

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 directions of "upper" and "lower" are not limited to directions parallel to the direction of gravity.

In this specification, when size or quantity is described as "same" or "equal," this may include cases where there is an error due to manufacturing variations, etc. Such errors are within 5%, for example. In addition, when angles are described as "parallel," "perpendicular," or "orthogonal," this may also include cases where there is an error due to manufacturing variations, etc. Such errors are within 5 degrees, for example.

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 outgoing light in response to incident light, or an element that operates in response to incident light. Examples of elements that generate outgoing light in response to incident light include elements that change the direction of travel 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 image sensors that convert incident light into electrical signals.

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. The piezoelectric actuator 110 of this example moves the shaft 114. The optical element 120 is fixed to the shaft 114. Therefore, the optical element 120 can be moved by moving the shaft 114. The piezoelectric actuator 110 of this example moves the shaft 114 in the longitudinal direction of the shaft 114. In FIG. 1, the movement direction of the optical element 120 and the shaft 114 is indicated by an arrow. The piezoelectric actuator 110 of this example can move the optical element 120 and the shaft 114 in both the positive (+) direction and the negative (-) direction of the movement direction. As an example, the piezoelectric actuator 110 moves the optical element 120 to realize 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.

The drive circuit 10 drives the piezoelectric actuator 110. The drive circuit 10 generates a drive signal for driving the piezoelectric actuator 110. In this example, the drive circuit 10 is input with a detection 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 drive circuit 10 generates a drive signal for controlling the movement speed of the optical element 120 based on the difference between the detection 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 drive circuit 10 may generate a drive signal based on whether the target position is located in the positive or negative direction with respect to the detection position in the movement direction, and the absolute value of the difference between the detection position and the target position.

The optical unit 100 may include a boost section 170 that boosts the drive signal and supplies it to the piezoelectric actuator 110. The boost section 170 may boost the drive signal using an inductor and a capacitance section. The boost 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 boost section 170. The capacitance section may be provided in the boost 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.

The optical unit 100 may further include some or all of the image acquisition section 130, the display section 140, the image processing section 150, and the position detection section 160. The image acquisition section 130 receives light that has passed through the optical element 120 and generates image data according to the received light. For example, the image acquisition section 130 includes an imaging element that generates image data of a subject of the camera. The imaging element of the image acquisition section 130 is, for example, a CMOS image sensor, but is not limited to this. The image acquisition section 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 section 130, but the piezoelectric actuator 110 in other examples may move the image acquisition section 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 section 130.

The image processing unit 150 performs a predetermined process on the image data generated by the image acquisition unit 130. The image processing unit 150 in 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 the two images created by each light (so-called phase difference autofocus), or may calculate the target position using another method.

The image processing unit 150 may cause the display unit 140 to display an image corresponding to the image data. The 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.

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 the 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.

2 is a diagram for explaining 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 have a pulse train 12 for each 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 become H level at the same time. In other words, during a period in which 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 have a period in which they become L level at the same time. As an example, the periods of the pulse trains 12-1 and 12-2 may be shifted by half a period.

The drive circuit 10 may generate a drive signal corresponding to each pulse signal. 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 of the same pattern as the pulse signal. The drive signal may be a signal output by a driver to which a pulse signal is input. The drive signal may be a signal with a different amplitude from the pulse signal.

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 and second piezoelectric elements are formed of, for example, ceramic. The piezoelectric actuator 110 may have a stator portion provided in contact with the first and second piezoelectric elements. The stator portion deforms in response to the deformation of the first and second piezoelectric elements. Since the pulse trains applied to the first and second piezoelectric elements are shifted by half a period, a traveling wave in response to the deformation of the first and second piezoelectric elements is generated on one of the surfaces of the stator portion. The piezoelectric actuator 110 may move the shaft 114 by the traveling wave.

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 direction, and a pulse period (second period) when moving the optical element 120 in the negative direction.

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.

The driving circuit 10 in 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 and 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 as the period (first period or second 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.

The driving circuit 10 of this example generates a modulation signal. The modulation signal is a signal that exhibits an H level only for a predetermined period W in a modulation cycle T, and exhibits an L level in 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 the first oscillation signal, and generates a second pulse signal from the logical product of the modulation signal and the second oscillation signal.

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 in the modulation signal. For example, by lengthening the period W, the number of first pulses 14 included in the pulse train 12 increases. The driving circuit 10 may control the period W according to the absolute value of the speed at which the optical element 120 should 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 the pulse train 12-1 is the same as the number of first pulses 14 included in the 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 pulse 14.

FIG. 3 is a diagram illustrating an example of the operation of the boost unit 170. As described above, the boost unit 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.

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 period of the pulse signal is different.

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, when the detection position reaches the vicinity of target position 2, the number of first pulses 14 included in the pulse train 12 decreases. Note that the distance that the optical element 120 moves with one first pulse 14 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 almost the same at the rising edge and the falling edge, the absolute value of the number of first pulses 14 corresponding to the rising edge and the falling edge may differ.

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

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, the change in the number of first pulses 14 indicates the acceleration or deceleration of the optical element 120. As shown in FIG. 5, it can be seen that a drive sound with a relatively large sound pressure is generated when the optical element 120 accelerates or decelerates.

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

The driving unit 50 acquires the detected position of the optical element 120 and the target position to which the optical element 120 should move. The driving unit 50 in this example receives the detected position from the pre-processing unit 20. The pre-processing unit 20 may receive an analog signal indicating the detected position from the position detection unit 160, for example, and output a digital signal resulting from AD conversion of the analog signal. The driving unit 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 processing unit 150. The target position recorded by the setting unit 30 is updated appropriately by the image processing unit 150.

As described above, the drive unit 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. In this example, the pulse signal generation unit 60 suppresses the amount of change in one control when changing the movement speed of the optical element 120. This makes it possible to suppress the peak volume of the drive sound.

The driving unit 50 in this example has 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 that the difference between the detected position and the target position is small. 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.

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 differential control (D control). In P control, the absolute value of the moving 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 moving 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 that reduces the differential value of the control signal (that is, reduces the change over time in the moving speed of the optical element 120).

The pulse signal generating unit 60 generates a pulse signal having a pulse train 12 according to the difference between the detection position and the target position. In this example, the pulse signal generating unit 60 generates the pulse signal shown in FIG. 2 according to a control signal. The pulse signal generating unit 60 may control the period of the first pulses 14 in the oscillation signal or the pulse train 12 according to the movement direction of the optical element 120 indicated by the control signal. The pulse signal generating unit 60 controls the number of first pulses 14 in the pulse train 12 according to the absolute value of the movement speed of the optical element 120 indicated by the control signal. The pulse signal generating unit 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.

The driver 80 outputs a drive signal corresponding to the pulse signal generated by the pulse signal generating unit 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.

FIG. 7 is a diagram showing an example of the configuration of the pulse signal generating unit 60. The pulse signal generating unit 60 of this example suppresses the amount of change in the moving 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 unit 60 of this example has a first pulse generating unit 67, an additional pulse generating unit 68, and a logical OR circuit 69.

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 a first pulse 14. The first pulse generating unit 67 generates a pulse train 12 including one or more first pulses 14 for one moving speed indicated by the control signal. The first pulse generating unit 67 repeatedly outputs a pulse train 12 including the same number of first pulses 14 until the moving speed indicated by the control signal is changed. When the moving speed indicated by the control signal changes, the first pulse generating unit 67 outputs a pulse train 12 including a number of first pulses 14 according to the changed moving speed.

The first pulse generating section 67 of this example has a first modulation section 62, a second modulation section 64, and a logical product circuit 66. The first modulation section 62 generates the oscillation signal described in FIG. 2. The first modulation section 62 may generate a first oscillation signal and a second oscillation signal as described in FIG. 2. The first modulation section 62 of this example can change the period of the oscillation signal according to the moving direction of the optical element 120. A clock signal with a predetermined period is input to the first modulation 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 modulation 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.

The second modulation unit 64 generates the modulation signal described in FIG. 2. The second modulation unit 64 may receive a modulation setting signal for generating the modulation signal. The modulation setting signal may include, for example, information indicating the length of the modulation period T shown in FIG. 2. The second modulation unit 64 adjusts the period W in the modulation signal according to the control signal output by the signal processing unit 40. For example, the second modulation unit 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 unit 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 the first modulation unit 62 may be input to the second modulation unit 64. The second modulation unit 64 may determine the period W by counting the pulses of the clock signal. The second modulation unit 64 may generate a modulation signal with a pulse width W that is an integer multiple of the period of the clock signal.

The logical product circuit 66 generates a pulse signal by generating a logical product of the oscillation signal and the modulation signal. As a result, the first pulse generation unit 67 outputs a pulse train 12 including a number of first pulses 14 according to the period W of the modulation signal.

The additional pulse generating unit 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 unit 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 the control signal output by the signal processing unit 40. The additional setting signal may include information that controls whether or not the additional pulse generating unit 68 outputs an additional pulse.

A clock signal may be input to the additional pulse generating unit 68. The period of the clock signal input to the additional pulse generating unit 68 may be the same as or different from the period of the clock signal input to the first pulse generating unit 67. The additional pulse generating unit 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 unit 67 is input to the additional pulse generating unit 68. The additional pulse generating unit 68 may generate an additional pulse having the same pulse width as the first pulse 14 and a different amplitude from the first pulse 14. In another example, the additional pulse generating unit 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 unit 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, and an increase in circuit size can be suppressed.

The logical OR circuit 69 outputs the logical OR of the pulse train 12 of the first pulse 14 generated by the first pulse generating section 67 and the pulse train of the additional pulse generated by the additional pulse generating section 68. In other words, the output of the logical OR 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.

With this configuration, the pulse signal generating unit 60 can generate, for one moving 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 in 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.

FIG. 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.

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

The logical sum circuit 69 outputs the logical sum of the pulse train 12 of the first pulse 14 and the pulse train of the additional pulse 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.

The first pulse 14 has a constant pulse width. Therefore, if the speed of the optical element 120 is controlled only by 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 where the speed of the optical element 120 changes by only V1 when the number of first pulses 14 included in the pulse train 12 is changed by only one. In this case, if the speed of the optical element 120 is controlled only by the first pulse 14, the speed of the optical element 120 can only be controlled to an integer multiple of V1. Therefore, the change in the speed of the optical element 120 in one control is at least V1. In this example, an additional pulse 15 can be included in the pulse train 12. This allows the change in the speed of the optical element 120 in one control to be smaller than V1. Since the volume of the drive sound generated in one control can be suppressed, the peak value of the drive sound can be suppressed.

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 greater than the pulse width of the first pulse 14 is inserted, the change in the speed of the optical element 120 becomes smaller than V1. The pulse width of the additional pulse 15 may be greater than or equal to twice the pulse width of the first pulse 14, or greater than or equal to three times. 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 the speed of the optical element 120 due to the additional pulse 15 becomes 0.5 x V1. As the pulse width of the additional pulse 15 approaches the pulse width of the first pulse 14, the change in the speed 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 the speed 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 speed 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 movement speed of the optical element 120 can be obtained by measuring it in advance.

The signal processing unit 40 may generate a control signal indicating whether or not to insert an additional pulse 15. For example, the signal processing unit 40 may generate the speed 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 speed of the optical element 120 indicated by the control signal with a resolution of 0.5 x V1. In this case, the pulse signal generating unit 60 does not insert an additional pulse 15 into the pulse train 12 when the speed of the optical element 120 indicated by the control signal is an integer multiple of V1. Also, the pulse signal generating unit 60 inserts an additional pulse 15 into the pulse train 12 when the speed of the optical element 120 indicated by the control signal is a value obtained by adding 0.5 x V1 to an integer multiple of V1. By such control, the speed of the optical element 120 can be controlled with fine resolution, and the peak value of the drive sound can be suppressed. The pulse signal generating unit 60 may insert multiple additional pulses 15 into one pulse train 12.

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. In other words, 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 an additional pulse 15 when the speed of the optical element 120 indicated by the control signal changes.

FIG. 9 is a diagram showing an example of the operation of the pulse signal generating unit 60. In this example, an example is 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.

The pulse signal generating unit 60 in this example sequentially generates a pre-change pulse signal corresponding to the first speed, an intermediate pulse signal corresponding to a speed between the first speed and the second speed, and a post-change pulse signal corresponding to the second speed. The pre-change pulse signal includes a number of first pulses 14 (e.g., four) according to the first speed, and does not include additional pulses 15.

The pulse signal generating unit 60 generates an intermediate pulse signal after generating the pre-modified pulse signal and before generating the post-modified pulse signal. The intermediate pulse signal is a signal in which one or more additional pulses 15 are added to the pre-modified pulse signal.

After generating the intermediate pulse signal, the pulse signal generating unit 60 generates a modified pulse signal that includes a number of first pulses 14 (e.g., five) according to the second speed. The modified pulse signal does not include the additional pulses 15. By controlling in this way, when changing the movement speed of the optical element 120, the movement speed can be changed gradually, and the peak value of the drive sound can be suppressed.

In the example of FIG. 9, an example of increasing the moving speed of the optical element 120 has been described, but the same applies when decreasing the moving speed of the optical element 120. When decreasing the moving speed of the optical element 120, the pulse signal generating unit 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 moving speed of the optical element 120, the pulse signal generating unit 60 inserts an additional pulse 15 in place of any of the first pulses 14 contained in the pulse signal before the speed reduction. Next, the pulse signal generating unit 60 can generate a pulse signal after the speed reduction by deleting the additional pulse 15.

FIG. 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 loud drive sound is generated.

FIG. 11 is a diagram showing the relationship between the number of pulses included in the pulse train 12 and the sound pressure of the drive sound in the embodiment. 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 moving speed of the optical element 120.

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

As shown in FIG. 8 etc., the additional pulse generating unit 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 etc., the additional pulse generating unit 68 may generate the additional pulse 15 in a period after the period in which one or more first pulses 14 are generated in the modulation period T. In another example, the additional pulse generating unit 68 may generate the additional pulse 15 in a period before the period in which one or more first pulses 14 are generated. In another example, the additional pulse generating unit 68 may generate the additional pulse 15 in a period that overlaps with any of the first pulses 14.

FIG. 12 is a diagram showing an example of the timing for inserting an additional pulse 15. In this example, the additional pulse generating unit 68 generates an 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.

FIG. 13 is a diagram showing another example of the timing for inserting an additional pulse 15. In this example, the additional pulse generating unit 68 generates an 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 a 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.

FIG. 14 is a diagram showing another example of the timing for inserting an additional pulse 15. In this example, the additional pulse generating unit 68 generates an 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.

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 FIG. 9. The pulse width of the additional pulse 15 may be the same as or different from that of the first pulse 14. The other processing is the same as any of the forms described in this specification. This type of processing can also gradually change the moving speed of the optical element 120, and suppress the peak value of the drive sound.

The ratio (A2/A1) of the amplitude A2 of the additional pulse 15 to the amplitude A1 of the first pulse 14 is R. The amount of change in the movement speed of the optical element 120 due to the additional pulse 15 is approximately R x 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 x V1. The ratio R may be less than 1 or may be greater than 1. If the ratio R is greater than 1, the pulse width of the additional pulse 15 may be made 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.

16 is a chart diagram outlining the driving method for driving the piezoelectric actuator 110 described in FIGS. 1 to 15. In this driving method, the detection position and 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 detection position and the target position (S1204). Then, a pulse signal (or 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 can be generated that includes 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 for one movement speed indicated by the control signal.

FIG. 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 in the examples described in FIGS. 1 to 16 in that it includes a filter unit 70. The configuration other than the filter unit 70 is the same as any of the aspects described in FIGS. 1 to 16. The filter unit 70 may be included in the drive unit 50, or may be provided outside the drive unit 50.

As described above, the drive unit 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. The filter unit 70 suppresses the frequency of fluctuations in the movement speed caused by the drive 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.

As explained in Figures 1 to 16, the drive noise can also be suppressed by reducing the amount of change in one 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 makes it possible to further suppress the drive noise. In the following, the operation of the filter unit 70 will be mainly explained, but the pulse signal generating unit 60 may combine the insertion process of the additional pulse 15 explained in Figures 1 to 16 with the processing by the filter unit 70. However, the pulse signal generating unit 60 does not have to perform the insertion process of the additional pulse 15 explained in Figures 1 to 16. The drive noise can be suppressed by only performing the processing by the filter unit 70 without performing the insertion process of the additional pulse 15.

The filter unit 70 may be provided at any position in the drive circuit 10 as long as the frequency of fluctuations in the moving speed of the optical element 120 can be reduced compared to when the filter unit 70 is not provided. For example, the filter unit 70 may be provided in front 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, and as a result, fluctuations in the number of first pulses 14 included in the pulse train 12 are suppressed, and the frequency of fluctuations in the moving speed of the optical element 120 is suppressed. In addition, the filter unit 70 may be provided inside the drive unit 50 to control the frequency of fluctuations in the number of first pulses 14 included in the pulse train 12 to be lower than the frequency of fluctuations in the relative position between the detection position and the target position. In addition, the filter unit 70 may be provided in the rear of the drive unit 50 to suppress the frequency of fluctuations in the number of first pulses 14 included in the modulation period T in the generated drive signal.

The filter unit 70 of this example suppresses the frequency of changes to the pulse trains 12 in the pulse signal generating unit 60. For example, the filter unit 70 suppresses the frequency of changes to the number of first pulses 14 included in one pulse train 12. Since the number of first pulses 14 included in one pulse train 12 corresponds to the moving speed of the optical element 120, the frequency of changes to the moving speed of the optical element 120 can be suppressed by suppressing the frequency of changes to the number of first pulses 14. The filter unit 70 may suppress the frequency of changes to the number of first pulses 14 included in one pulse train 12 by suppressing the frequency of changes to the period W of the modulated signal.

The filter unit 70 may suppress fluctuations in parameters other than the number of first pulses 14 in the pulse train 12. For example, if the driver 50 changes the moving 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. Also, if the driver 50 changes the moving 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.

FIG. 18 is a diagram showing an example of the configuration of the pulse signal generating unit 60. The pulse signal generating unit 60 of this example differs from the example of FIG. 7 in that it further includes a filter unit 70. The other structures are similar to the example of FIG. 7. If the pulse signal generating unit 60 does not perform the process of inserting the additional pulse 15 described in FIG. 1 to FIG. 16, the pulse signal generating unit 60 does not need to include the additional pulse generating unit 68.

The filter unit 70 suppresses fluctuations in the control signal output by the signal processing unit 40, and inputs the control signal after the fluctuations have been suppressed 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 the 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 in the filter unit 70.

The filter unit 70 attenuates components in 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 in this example attenuates components in the control signal that are equal to or higher than the operating frequency band of the piezoelectric actuator 110. The filter unit 70 may attenuate components in 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 in 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 use the specification value provided by the manufacturer of the piezoelectric actuator 110. This type of control makes it possible to suppress the drive noise while maintaining the operating speed of the piezoelectric actuator 110 at a constant level or higher.

The filter unit 70 may attenuate components greater than 100 Hz in the frequency of fluctuation 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 constant level.

The pulse signal generating unit 60 in this example has a first modulation unit 62 and a second modulation unit 64, but the pulse signal generating unit 60 in other examples may have the first modulation unit 62 and 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 according to the 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 the fluctuation of the control signal, thereby suppressing the fluctuation of the moving speed of the optical element 120 and suppressing the drive noise.

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

The filter unit 70 of this example suppresses the frequency of fluctuations in the movement speed in the direction that decreases the movement speed of the optical element 120. 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 greater than the operation period (PID cycle) of the signal processing unit 40. The operation period of the signal processing unit 40 refers to the minimum period in 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 more. In other words, the filter unit 70 may delay the falling edge of the control signal by a delay time that is twice or more the operation period of the signal processing unit 40. The filter setting value may be a value of 3 or more, 5 or more, or 10 or more. By delaying the falling edge of the control signal, it is possible to suppress the rising edge and the falling edge of the control signal from vibrating repeatedly in a short period of time. This makes it possible to suppress the generation of drive noise.

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.

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. A strong degree of suppression of the fluctuation frequency may also mean that the cutoff frequency in the filter section 70 is low.

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 moving speed increases) may be shorter than the delay time of the falling edge (in the direction in which the moving speed decreases). In another example, the filter unit 70 may not delay the rising edge. That is, the filter unit 70 may suppress the frequency of fluctuations in the moving speed of the optical element 120 in the direction in which the moving speed decreases, while not suppressing the frequency of fluctuations in the moving speed of the optical element 120 in the direction in which the moving speed increases. This type of control prevents the movement of the optical element 120 from slowing down. Therefore, operations such as autofocus can be completed quickly and the operating noise can be suppressed.

In another example, 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 of the optical element 120 more than 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. In this case, it becomes easier to decelerate the optical element 120. This makes it possible to suppress overshooting, 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 of the optical element 120, but may not 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.

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 section 70 is not used. In the upper part of FIG. 20, the detection 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 detection position of the optical element 120 gradually approaches the target position.

Immediately after the target position is changed, the difference between the target position and the detection position is large, so the drive unit 50 attempts to increase the movement speed of the optical element 120. As the detection position approaches the target position, the drive unit 50 decelerates the optical element 120.

When changing the moving speed of the optical element 120, for example in the PID control described in FIG. 17, the value of the control signal may oscillate within a short period of time. In the time waveform of the control signal in FIG. 20, the value of the control signal oscillates every time the moving speed of the optical element 120 is changed. When such oscillation occurs, it becomes easy for a loud drive noise to occur.

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 the control signal output by the filter unit 70. The filter unit 70 in this example suppresses fluctuations in the waveform of the control signal. As a result, the waveform of the control signal in this example does not have vibrations as shown in FIG. 20. This makes it possible to suppress drive noise. Also, even if the filter unit 70 is provided, the transition of the detection position of the optical element 120 is almost the same as the example in FIG. 20.

18 and 19, the filter characteristics of the filter unit 70 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 moving speed of the optical element 120 in the direction of decreasing the moving speed of the optical element 120 may be stronger than the degree of suppression of the frequency of fluctuations in the moving speed of the optical element 120 in the direction of increasing the moving 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 moving speed of the optical element 120 in the direction of increasing the moving speed of the optical element 120 may be stronger than the degree of suppression of the frequency of fluctuations in the moving speed of the optical element 120 in the direction of decreasing the moving speed of the optical element 120. As a result, when the detection position of the optical element 120 is far from the target position, the optical element 120 can be moved to the target position at high speed by prioritizing the acceleration of the optical element 120. Furthermore, when the detection position of the optical element 120 approaches the target position, priority is given to decelerating the optical element 120, and overshooting of the movement of the optical element 120 can be suppressed. Therefore, the optical element 120 can be moved at high speed and with high accuracy while suppressing drive noise.

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 moving speed in the direction to decrease the moving speed of the optical element 120 and the frequency of change in the moving speed in the direction to increase the moving 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 separated 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.

FIG. 22 is a diagram showing another example of the arrangement of the filter section 70. The filter section 70 may be provided at least in 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 detection position of the optical element 120 detected by the position detection section 160. This type of processing can also suppress fluctuations in the movement speed of the optical element 120.

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

The filter unit 70 may be provided between the signal processing unit 40 and the pulse signal generating unit 60. In this case, the filter unit 70 suppresses fluctuations in the control signal output by the signal processing unit 40, similar to the example of FIG. 18.

The filter unit 70 may be provided between the pulse signal generating unit 60 and the driver 80. In this case, the filter unit 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 unit 60.

The filter unit 70 may be provided after the driver 80. In this case, the filter unit 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.

FIG. 23 is a chart outlining the driving method for driving the piezoelectric actuator 110 described in FIGS. 17 to 22. In this driving method, the detected position and target position of the optical element 120 are acquired (S1102). Then, a driving signal for controlling the moving speed of the optical element 120 is generated based on the difference between the detected position and the target position (S1106). As described in FIGS. 1 to 22, the driving method of this example includes a filtering step S1104 that suppresses the frequency of fluctuations in the moving 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.

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 a position of the optical element that has been detected and a target position to which the optical element should be moved;
a pulse signal generating unit that generates a pulse signal having a pulse train corresponding 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 having at least one of a pulse width and an amplitude different from that of the first pulses.
(Item 2)
2. The drive circuit according to item 1, wherein the additional pulse has a pulse width greater than that of the first pulse.
(Item 3)
3. The drive circuit according to item 2, wherein the additional pulse has a pulse width that is at least twice as long as that of the first pulse.
(Item 4)
When changing the moving speed of the optical element from a first speed to a second speed,
The pulse signal generating unit
generating a pre-change pulse signal including the first pulses in a number corresponding to the first speed, for the first speed;
generating an intermediate pulse signal by adding one or more of the additional pulses to the unaltered pulse signal after generating the unaltered pulse signal;
3. The drive circuit according to claim 2, further comprising: a drive circuit for generating a changed pulse signal including a number of the first pulses according to the second speed after generating the intermediate pulse signal.
(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 a pulse train of the first pulses generated by the first pulse generating unit and a pulse train of the additional pulses generated by the additional pulse generating unit.
(Item 6)
The first pulse generating unit is
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;
and a logical product circuit that outputs a logical product of the oscillation signal and the modulation signal.
(Item 7)
7. The drive circuit according to item 6, wherein the additional pulse generating section generates the additional pulse in a period that does not overlap with any of the first pulses.
(Item 8)
7. The drive circuit according to item 6, wherein the additional pulse generating section generates the additional pulse during a period overlapping with at least one of the first pulses.
(Item 9)
2. The drive circuit of claim 1, wherein the additional pulse has a smaller amplitude than the first pulse.
(Item 10)
5. The drive circuit according to claim 1, further comprising a filter unit that suppresses a frequency of fluctuations in the moving speed of the optical element.
(Item 11)
5. The drive circuit according to claim 1, wherein the signal processing unit performs PID control based on the detected position and the target position to generate the control signal.
(Item 12)
5. The drive circuit according to claim 1, further comprising a boosting unit that boosts a drive signal supplied to the piezoelectric actuator.
(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 includes:
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 a position of the optical element that has been detected and a target position to which the optical element should be moved;
a pulse signal generating unit that generates a pulse signal having a pulse train corresponding to the control signal and controls the moving speed according to the pulse train;
having
the pulse signal generating unit is capable of generating, for one of the moving speeds indicated by the control signal, the pulse signal including one or more first pulses and one or more additional pulses having at least one of a pulse width and an amplitude different from that of the first pulses.
(Item 14)
A method for driving a piezoelectric actuator that moves an optical element, comprising the steps of:
generating a control signal for controlling a moving speed of the optical element based on a difference between a detected position indicating a position of the detected optical element and a target position to which the optical element should be moved;
generating a pulse signal having a pulse train corresponding to the control signal, and controlling the moving speed corresponding to the pulse train;
In generating the pulse signal, the driving method is capable of generating the pulse signal including one or more first pulses and one or more additional pulses having at least one of a pulse width and an amplitude different from that of the first pulses for one of the moving speeds indicated by the control signal.

The present invention has been described above using an embodiment, but the technical scope of the present invention is not limited to the scope described in the above embodiment. It will be clear to those skilled in the art that various modifications and improvements can be made to the above embodiment. It is clear from the claims that forms incorporating such modifications or improvements can also be included in the technical scope of the present invention.

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" or "prior to," and it should be noted that the processes can be performed in any order, unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is necessary to perform the processes in that order.

10: drive circuit, 12: pulse train, 14: first pulse, 15: additional pulse, 20: pre-processing section, 30: setting section, 40: signal processing section, 50: drive section, 60: pulse signal generating section, 62: first modulation section, 64: second modulation section, 66: logical product circuit, 67: first pulse generating section, 68: additional pulse generating section, 69: logical sum circuit, 70: filter section, 80: driver, 100: optical unit, 110: piezoelectric actuator, 114: shaft, 120: optical element, 122: fixing section, 130: image acquisition section, 140: display section, 150: image processing section, 160: position detection section, 170: boost section

Claims (20)

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 a position of the optical element that has been detected and a target position to which the optical element should be moved;
   a filter unit that suppresses a frequency of fluctuations in the moving speed due to the drive signal.
2. The drive circuit according to claim 1 , wherein the filter section attenuates components of the fluctuation frequency of the moving speed that are equal to or higher than an operating frequency band of the piezoelectric actuator.
3. The drive circuit according to claim 1 , wherein the filter section attenuates components of the fluctuation frequency of the moving speed that are greater than 100 Hz.
4. 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;
   The drive circuit according to claim 1 , wherein the filter section suppresses a frequency of change of the pulse train in the pulse signal generating section.
5. The drive circuit according to claim 4 , wherein the filter section suppresses a frequency of change in the pulse train in a direction that decreases the moving speed more strongly than a frequency of change in the pulse train in a direction that increases the moving speed.
6. The drive circuit according to claim 5 , wherein the filter section 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.
7. a pre-processing unit that performs AD conversion on a signal indicating the detected position and inputs the signal to the driving unit;
   The drive circuit according to claim 1 , wherein the filter section reduces a frequency at which the conversion result in the pre-processing section is updated.
8. The drive circuit according to claim 1 , wherein the filter section adjusts a filter characteristic based on a difference between the detected position and the target position.
9. 9. The drive circuit according to claim 8, wherein the filter section adjusts a filter characteristic 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 result of comparing the difference with a set reference value.
10. The drive circuit according to claim 1 , wherein the drive section performs PID control based on the detected position and the target position to generate the drive signal.
11. The drive circuit according to claim 1 , further comprising a position detector configured to detect a position of the optical element and generate a signal indicative of the detected position.
12. The drive circuit according to claim 1 , further comprising a boosting section that boosts the drive signal and supplies the boosted signal to the piezoelectric actuator.
13. 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 a detected position indicating a position of the detected optical element and a target position to which the optical element should be moved,
    the pulse signal generating unit generates the pulse signal having the pulse train in response to the control signal;
    5. The drive circuit according to claim 4, wherein 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 having at least one of a pulse width and an amplitude different from that of the first pulses.
14. The drive circuit according to claim 13 , wherein the additional pulse has a pulse width greater than that of the first pulse.
15. The drive circuit according to claim 14 , wherein the additional pulse has a pulse width at least twice as long as that of the first pulse.
16. When changing the moving speed of the optical element from a first speed to a second speed,
    The pulse signal generating unit
    generating a pre-change pulse signal including the first pulses in a number corresponding to the first speed, for the first speed;
    generating an intermediate pulse signal by adding one or more of the additional pulses to the unaltered pulse signal after generating the unaltered pulse signal;
    The drive circuit according to claim 14 , further comprising: a drive circuit configured to generate, after generating the intermediate pulse signal, a modified pulse signal including a number of the first pulses corresponding to the second speed.
17. 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;
    14. The drive circuit according to claim 13, further comprising: a logical OR circuit that outputs a logical OR of the pulse train of the first pulses generated by the first pulse generating section and the pulse train of the additional pulses generated by the additional pulse generating section.
18. 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 a position of the optical element that has been detected and a target position to which the optical element should be moved;
    a pulse signal generating unit that generates a pulse signal having a pulse train corresponding 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 having at least one of a pulse width and an amplitude different from that of the first pulses.
19. 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 includes:
    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 a position of the optical element that has been detected and a target position to which the optical element should be moved;
    and a filter unit that suppresses a frequency of fluctuations in the moving speed due to the drive signal.
20. A method for driving a piezoelectric actuator that moves an optical element, comprising the steps of:
    generating a drive signal for controlling a moving speed of the optical element based on a difference between a detected position indicating a position of the detected optical element and a target position to which the optical element should be moved;
    The driving method suppresses a frequency of fluctuations in the moving speed due to the driving signal.

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