Control unit, optical deflection system, image projection apparatus, and control method

Patent metadata

Field	Value
Publication number	US-2017269352-A1
Application number	US-201715459208-A
Country	US
Kind code	A1
Filing date	Mar 15, 2017
Priority date	Mar 17, 2016
Publication date	Sep 21, 2017
Grant date	—

Abstract

A control unit to control a movement of a reflector includes a drive signal output unit to apply a drive voltage having a minimum value and a maximum value in one cycle to a piezoelectric element to deform the piezoelectric element, the deformation of the piezoelectric element causing the reflector to move, and circuitry to control the drive voltage to have the minimum value greater than a zero voltage by a given difference value.

First claim

What is claimed is:

1 . A control unit to control a movement of a reflector, comprising:
a drive signal output unit to apply a drive voltage having a minimum value and a maximum value in one cycle to a piezoelectric element to deform the piezoelectric element, the deformation of the piezoelectric element causing the reflector to move; and circuitry to control the drive voltage to have the minimum value greater than a zero voltage by a given difference value.

2 . The control unit of claim 1 , wherein the difference value is set such that a change rate of a piezoelectric constant value of the piezoelectric element in the one cycle of the drive voltage having the minimum value greater than the zero voltage by the given difference becomes smaller than a change rate of the piezoelectric constant value of the piezoelectric element in the one cycle of the drive voltage having the minimum value of zero voltage.

3 . The control unit of claim 2 , wherein the given difference is set such that the change rate of the piezoelectric constant value of the piezoelectric element in the one cycle of the drive voltage or a half cycle of the drive voltage starting from an application of the drive voltage becomes within 20%.

4 . The control unit of claim 2 , wherein the given difference is set such that the change rate of the piezoelectric constant value of the piezoelectric element in the one cycle of the drive voltage or a half cycle of the drive voltage starting from an application of the drive voltage becomes within 10%.

5 . The control unit of claim 2 , wherein the given difference is set such that the change rate of the piezoelectric constant value of the piezoelectric element in the one cycle of the drive voltage or a half cycle of the drive voltage starting from an application of the drive voltage becomes from 5% to 10%.

6 . The control unit of claim 1 , wherein the given difference is set to a voltage value smaller than a voltage value where the piezoelectric constant value of the piezoelectric element becomes a local maximum in the one cycle of the drive voltage.

7 . The control unit of claim 6 , wherein the given difference is set with 30% or more of the voltage value where the piezoelectric constant value of the piezoelectric element becomes the local maximum in the one cycle of the drive voltage.

8 . The control unit of claim 6 , wherein the given difference is set with 70% or more of the voltage value where the piezoelectric constant value of the piezoelectric element becomes the local maximum in the one cycle of the drive voltage.

9 . The control unit of claim 1 , wherein the minimum value of the drive voltage is 2 V or more.

10 . The control unit of claim 1 , wherein the minimum value of the drive voltage is from 4.5V to 7V.

11 . The control unit of claim 1 , wherein when the piezoelectric element including the first piezoelectric element and the second piezoelectric element, the drive signal output unit applies a first drive voltage having a first waveform to the first piezoelectric element, and a second drive voltage having a second waveform to the second piezoelectric element, and the circuitry sets a first minimum value of the first drive voltage having the first waveform differently from a second minimum value of the second drive voltage having the second waveform.

12 . The control unit of claim 1 , wherein the control unit controls a moveable device having the piezoelectric element and the reflector, the piezoelectric element including the first piezoelectric element and the second piezoelectric element,
wherein the drive signal output unit applies a first drive voltage having a first waveform to the first piezoelectric element, and a second drive voltage having a second waveform to a second piezoelectric element, the first waveform having a sawtooth waveform having a first rising time and a first falling time in one cycle, and the second waveform having a sawtooth waveform having a second rising time and a second falling time in one cycle, wherein the circuitry controls a ratio of the first rising time and the one cycle of the first drive voltage or a ratio of the second falling time and the one cycle of the second drive voltage such that a mechanical resonance frequency of the moveable device matches at least one frequency band of a frequency spectrum of the first drive voltage or one frequency band of a frequency spectrum of the second drive voltage where a higher harmonic wave component becomes low.

13 . An optical deflection system comprising:
the control unit of claim 1 ; a mirror unit having the reflector; and a plurality of piezoelectric drivers each having the piezoelectric element, wherein the piezoelectric drivers deform the corresponding piezoelectric element to move the mirror unit about one axis under a control of the control unit.

14 . An image projection apparatus comprising
a light source unit to emit light; and the optical deflection system of claim 13 to deflect the light emitted from the light source unit and modulated based on image information to scan an image formation face to form an image on the image formation face.

15 . A method of controlling a movement of a reflector comprising:
applying a drive voltage having a given waveform with a minimum value and a maximum value to the piezoelectric element; controlling the drive voltage to have the minimum value greater than a zero voltage by a given difference value; and applying the drive voltage having the minimum value set greater than the zero voltage to the piezoelectric element to control the movement of the reflector through deforming the piezoelectric element.

Assignees

• Hashiguchi Tsuyoshi
• Nakagawa Jun
• Suzuki Shuichi
• Ricoh Co Ltd

Inventors

• Hashiguchi Tsuyoshi
• Nakagawa Jun
• Suzuki Shuichi

Classifications

• G02B26/0858 Primary

  the reflecting means being moved or deformed by piezoelectric means · CPC title

• G02B26/105

  with one or more pivoting mirrors or galvano-mirrors (G02B26/101 takes precedence) · CPC title

• G02B26/101

  with both horizontal and vertical deflecting means, e.g. raster or XY scanners (colour television using laser beams scanning a display screen H04N9/3129) · CPC title

• G03B21/008

  using micromirror devices · CPC title

• H04N3/08

  having a moving reflector · CPC title