Mirror drive device and driving method thereof

Patent metadata

Field	Value
Publication number	US-9864189-B2
Application number	US-201414330452-A
Country	US
Kind code	B2
Filing date	Jul 14, 2014
Priority date	Jul 17, 2013
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

In a mirror drive device, a first and second actuator sections are arranged on both sides of a mirror supporting section that supports a mirror section so as to sandwich the mirror supporting section. Division of an upper and lower electrodes of each of the first and second actuator sections is performed correspondingly to stress distribution of principal stresses in a piezoelectric body in resonant mode vibration, and a piezoelectric body portion corresponding to positions of a first and third upper electrode sections, and a piezoelectric body portion corresponding to positions of a second and fourth upper electrode sections have stresses in opposite directions to each other. Division of the lower electrodes is performed similar to the upper electrodes, and drive voltages having the same phase can be respectively applied to the upper and lower electrode sections of the piezoelectric body portions that are different due to a division arrangement.

First claim

What is claimed is:

1. A mirror drive device comprising:
a mirror section that includes a reflective surface configured to reflect light;
a mirror supporting section that is connected to the mirror section, the mirror supporting section configured to support the mirror section so that the mirror section rotates around a rotating axis;
a piezoelectric actuator section that is connected to the mirror supporting section, the piezoelectric actuator section configured to generate a driving force that causes the mirror section to rotate around the rotating axis; and
a fixture section configured to support the piezoelectric actuator section,
wherein the piezoelectric actuator section has a lamination structure in which a diaphragm, a lower electrode, a piezoelectric body, and an upper electrode are laminated in this order, and includes a first actuator section and a second actuator section that are piezoelectric unimorph actuators that are deformed by an inverse piezoelectric effect of the piezoelectric body obtained by applying a drive voltage,
the first actuator section and the second actuator section are arranged on both sides of a direction perpendicular to the rotating axis so that the first actuator section and the second actuator section sandwich the rotating axis from the direction perpendicular to the rotating axis in a plan view,
from among the both sides the of the direction perpendicular to the rotating axis with respect to a connection portion with the mirror supporting section, the first actuator section is arranged on one side, and the second actuator section is arranged on another side,
a first base end section on an opposite side to the mirror supporting section in the first actuator section, and a second base end section on an opposite side to the mirror supporting section in the second actuator section are fixed to the fixture section,
tilting drive is performed on the mirror supporting section by bending the first actuator section and the second actuator section in opposite directions to each other,
the upper electrode of the first actuator section includes a first upper electrode section and a second upper electrode section that are insulated and separated from each other, and the first upper electrode section and the second upper electrode section are arranged in parallel along a longitudinal direction of a shape from the first base end section of the first actuator section to a connection portion with the mirror supporting section,
the lower electrode of the first actuator section includes a first lower electrode section that faces the first upper electrode section and a second lower electrode section that faces the second upper electrode section, and the first lower electrode section and the second lower electrode section are insulated and separated from each other,
the first actuator section includes a first piezoelectric conversion section that is constituted by the first upper electrode section and the first lower electrode section as an electrode pair, and a second piezoelectric conversion section that is constituted by the second upper electrode section and the second lower electrode section as an electrode pair,
the upper electrode of the second actuator section includes a third upper electrode section and a fourth upper electrode section that are insulated and separated from each other, and the third upper electrode section and the fourth upper electrode section are arranged in parallel along a longitudinal direction of a shape from the second base end section of the second actuator section to a connection portion with the mirror supporting section,
the lower electrode of the second actuator section includes a third lower electrode section that faces the third upper electrode section and a fourth lower electrode section that faces the fourth upper electrode section, and the third lower electrode section and the fourth lower electrode section are insulated and separated from each other,
the second actuator section includes a third piezoelectric conversion section that is constituted by the third upper electrode section and the third lower electrode section as an electrode pair, and a fourth piezoelectric conversion section that is constituted by the fourth upper electrode section and the fourth lower electrode section as an electrode pair,
an arrangement configuration of the first upper electrode section, the second upper electrode section, the third upper electrode section, and the fourth upper electrode section corresponds to stress distribution of a principal stress in an in-plane direction that is perpendicular to a film thickness direction of the piezoelectric body in a resonant mode vibration that is associated with tilting displacement of the mirror section due to the rotation around the rotating axis, and
stresses in opposite directions to each other are generated between a piezoelectric body portion that corresponds to positions of the first upper electrode section and the third upper electrode section, and a piezoelectric body portion that corresponds to positions of the second upper electrode section and the fourth upper electrode section, in the resonant mode vibration, and
wherein each of the first piezoelectric conversion section, the second piezoelectric conversion section, the third piezoelectric conversion section, and the fourth piezoelectric conversion section functions as a driving force generation section to which the drive voltage is applied, and at least one of the four upper electrode sections or the lower electrode sections of a piezoelectric conversion section which is nearer to the first base end section from among the first piezoelectric conversion section and the second piezoelectric conversion section of the first actuator section is divided to three electrodes, and at least one of another of the pairs of the four upper electrode sections and the lower electrode sections are undivided, and
one electrode of the three electrodes is used as an electrode section for detecting a voltage generated by a piezoelectric effect that is associated with a deformation of the piezoelectric body, and a drive voltage having a same phase is applied to other two electrodes of the three electrode.

2. The mirror drive device according to claim 1 ,
wherein the first actuator section and the second actuator section are connected to each other, and
the mirror supporting section is coupled to a coupling section of the first actuator section and the second actuator section.

3. The mirror drive device according to claim 1 , further comprising
a first mirror supporting section and a second mirror supporting section that support the mirror section from both sides of the rotating axis in an axial direction, as the mirror supporting section.

4. The mirror drive device according to claim 1 ,
wherein the first actuator section and the second actuator section include cantilever structures in which the first base end section and the second base end section that are fixed to the fixture section are used as fixture ends.

5. The mirror drive device according to claim 1 ,
wherein the first actuator section and the second actuator section are actuator sections having a tuning-fork shape in which two arm sections that are arranged so as to be divided on both sides of the mirror sections are provided, and the second base end section leading out of a portion at which the arm sections are joined and the fixture section are connected to each other at only one position,
the piezoelectric actuator section has a circular structure in which an arm section of the first actuator section is connected to an arm section of the second actuator section,
the mirror drive device has a first mirror supporting section and a second mirror supporting section that support the mirror section from both sides o

Assignees

• Fujifilm Corp

Inventors

• Naono Takayuki

Classifications

• B81B2201/032

  Bimorph and unimorph actuators, e.g. piezo and thermo · CPC title

• G02B26/105

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

• B81B2201/045

  Optical switches · CPC title

• B81B2201/042

  Micromirrors, not used as optical switches · CPC title

• B81B3/0043

  Increasing angular deflection · CPC title