Drive apparatus, drive method, and optical device

Abstract

Noise produced during phase-difference changes is minimized without decreasing the responsiveness of a vibration-wave motor. A lens-side MCU for a lens barrel controls a drive apparatus that applies a drive voltage to the vibration-wave motor by outputting an A-phase drive signal and a B-phase drive signal thereto. The lens-side MCU uses, for example, a drive-voltage setting unit and a duty-cycle change unit to change the drive voltage. Also, the lens-side MCU is provided with a phase-difference change unit that changes the phase difference between the A-phase drive signal and the B-phase drive signal. When driving the vibration-wave motor, the lens-side MCU changes the drive voltage to V reg , and when the phase-difference change unit is changing the aforementioned phase difference, the drive voltage is changed to V 1 , V 1 being greater than zero and less than V reg .

1 . An optical device comprising:
 a vibration actuator that drives a lens using a drive force generated at a driving face by way of excitation of an electro-mechanical conversion element;   a drive control unit that provides two drive signals to the vibration actuator; and   a photography setting unit that can select a moving image photography mode, wherein   the drive control unit can change a speed of the vibration actuator, in a case of the photography setting unit selecting the moving image photography mode, by changing a phase difference of the two drive signals, and changing a frequency of the two drive signals to correspond to the phase difference thus changed, while maintaining a voltage of the two drive signals to be constant.   
     
     
         2 . The optical device according to  claim 1 , wherein
 the drive control unit can continuously change the phase difference of the two drive signals between 90°, −90° and 0°.   
     
     
         3 . The optical device according to  claim 1 , wherein
 the drive control unit performs a wobbling operation that is an operation to cause the lens to move back and forth in small motions to cause a focal position to follow a subject.   
     
     
         4 . The optical device according to  claim 3 , further comprising
 a contrast detection unit that detects contrast of a subject image, wherein   the drive control unit switches the frequency of the two drive signals in a subsequent one cycle to a predetermined one cycle so as to cause the focal position of the lens to follow the subject, based on the contrast of the predetermined one cycle in the wobbling operation, detected by way of the contrast detection unit.   
     
     
         5 . The optical device according to  claim 1 , wherein
 the drive control unit can switch the phase difference of the two drive signals between 90° and −90°, in a case of the photography setting unit selecting a still image photography mode.   
     
     
         6 . A drive apparatus comprising:
 a vibrating part having an electro-mechanical energy conversion element to which two drive signals having variable phase difference are inputted;   a relative motion part that relatively moves in relation to the vibrating part, by way of a drive force generate at the vibrating part by according to vibration of the electro-mechanical energy conversion element; and   a control unit that inputs the two drive signals to the electro-mechanical energy conversion element at a startup frequency that is higher than a drive frequency used in driving, while maintaining at phase difference at which the relative motion part is in a stopped state, and when gradually reducing the frequency of the two drive signals from the startup frequency and reaching the drive frequency, sets the phase difference to a phase difference that enables the relative motion part to relatively move in relation to the vibrating part.   
     
     
         7 . The drive apparatus according to  claim 6 , wherein
 the startup frequency is a frequency of at least a resonance frequency of a next higher-order vibration mode of a vibration mode including the drive frequency.   
     
     
         8 . The drive apparatus according to  claim 6 , wherein
 the phase difference at which the relation motion part maintains a stopped state is +/−15° from 0° or 180°.   
     
     
         9 . A method of driving a vibration actuator, wherein the vibration actuator comprises:
 a vibrating part having an electro-mechanical energy conversion element to which two drive signals having variable phase difference are inputted; and   a relative motion part that relatively moves in relation to the vibrating part, by way of a drive force generated at the vibrating part according to vibration of the electro-mechanical energy conversion element,   the method comprising the steps of:   during startup of the vibration actuator,   inputting the two drive signals to the electro-mechanical energy conversion element in a state maintaining a phase difference therebetween at a phase difference at which the relation motion part stays in a stopped state, and at a startup frequency that is higher than the drive frequency used in driving of the vibration actuator; and   setting the phase difference to a phase difference at which the relation motion part can relatively move in relation to the vibrating part, upon gradually reducing the frequency of the two drive signals from the startup frequency and reaching the drive frequency.   
     
     
         10 . An optical device comprising the drive apparatus according to  claim 6 . 
     
     
         11 . A drive apparatus for controlling driving of a vibration actuator that generates a drive force, by applying two-phase alternating signals having different phases to a piezeoelectric body provided to a vibrating body to cause the vibrating body to vibrate, the drive apparatus comprising:
 a speed control unit that controls a drive speed of the vibration actuator, by causing a frequency of the two-phase alternating signals applied to the piezoelectric body to change;   a frequency storage unit that stores a predetermined frequency; and   a stop determination unit that determines whether the vibration actuator is stopped, wherein   the speed control unit causes the frequency of the alternating signals applied to the piezoelectric body to change to the predetermined frequency stored in the frequency storage unit, in a case of the stop determination unit having determined that the vibration actuator is stopped.   
     
     
         12 . A drive apparatus that controls driving of a vibration actuator that generates a drive force, by applying two-phase alternating signals having different phases to a piezeoelectric body provided to a vibrating body, the drive apparatus comprising:
 a speed control unit that controls a drive speed of the vibration actuator, by causing a frequency of the two-phase alternating signals applied to the piezoelectric body to change; and   a stop determination unit that determines whether the vibration actuator is stopped, wherein   the speed control unit causes the frequency of the alternating signals applied to the piezoelectric body to change so as to approach an electrical resonance frequency, in a case of the stop determination unit having determined that the vibration actuator is stopped.   
     
     
         13 . The drive apparatus according to  claim 12 , wherein
 the speed control unit causes the frequency of the alternating signals applied to the piezoelectric body to change to a rising direction, in a case of the stop determination unit having determined that the vibration actuator is stopped.   
     
     
         14 . The drive apparatus according to  claim 12 , wherein
 the speed control unit causes the frequency of the alternating signals applied to the piezoelectric body to change to a frequency at which the vibration actuator begins driving from a stopped state, in a case of the stop determination unit having determined that the vibration actuator is stopped.   
     
     
         15 . The drive apparatus according to  claim 12 , wherein
 the speed control unit causes the frequency of the alternating signal applied to the piezoelectric body to change to the electrical resonance frequency, in a case of the stop determination unit having determined that the vibration actuator is stopped.   
     
     
         16 . The drive apparatus according to  claim 12 , wherein
 the electrical resonance frequency is a resonance frequency of a capacitance of the piezoelectric body and an inductance of a drive circuit applying the alternating signal to the piezoelectric body.   
     
     
         17 . The drive apparatus according to  claim 11 , further comprising a speed detection unit that detects a drive speed of the vibration actuator, wherein
 the speed control unit controls the drive speed of the vibration actuator by causing a phase difference of the two-phase alternating signals applied to the piezoelectric body to change, and wherein   the stop determination unit determines whether the vibration actuator stopped, based on a state of the phase difference of the two-phase alternating signals applied to the piezoelectric body, and information of the drive speed detected by way of the speed detection unit.   
     
     
         18 . An optical device comprising:
 the drive apparatus for a vibration actuator according to  claim 11 ;   a vibration actuator that is driven by way of the drive apparatus for a vibration actuator; and   an optical member that is driven by way of the vibration actuator.   
     
     
         19 . An optical device comprising:
 an electro-mechanical energy conversion element to which a drive signal is applied from a drive circuit;   a vibrating body that generates a drive force by way of the electro-mechanical energy conversion element;   a moving body that is driven by the drive force of the vibrating body; and   a control unit that performs first control to control so that the drive signal becomes a first frequency when causing the moving body to drive, and performs second control to control so that the drive signal becomes a second frequency when the moving body is stopped, wherein   the drive circuit has a smaller amount of power consumption when the drive signal is the second drive signal than when the drive signal is the first drive signal.