Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2001-03-09
2003-09-23
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S328000
Reexamination Certificate
active
06624549
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive device having a light modulation mechanism for use in an image display unit, an image printing unit, an exposure unit, an optical switch, or a like apparatus.
2. Description of the Related Art
Recently, various devices having light modulation mechanisms have been developed. For example, Japanese Patent Application Laid-Open (kokai) No. 5-196880 discloses a deformable mirror device (hereinafter called a DMD). As shown in the schematic perspective view of
FIG. 33
, the DMD includes a CMOS substrate
200
; two support elements
202
disposed on the substrate
200
; a pair of torsion hinges
204
supported by the support elements
202
; a yoke
206
supported by the support elements
202
via the torsion hinges
204
; and a mirror
208
supported by the yoke
206
. The torsion hinges
204
are twisted through utilization of electrostatic attraction, to thereby change the angle of the mirror
208
. For easy understanding, the mirror
208
in
FIG. 33
is represented as being transparent.
The DMD is said to enable reduction in device size and highly dense arrangement of pixels. However, since the torsion hinges
204
are twisted so as to drive the mirror
208
, the torsion hinges
204
tend to suffer fatigue. Also, since electrostatic attraction is utilized for driving the mirror
208
, the mirror
208
may be stuck during operation.
As shown in the schematic sectional view of
FIG. 34
, a thin-film actuated mirror array (hereinafter called AMA) disclosed in Japanese Patent Application Laid-Open (kokai) No. 11-72724 includes an actuating portion
312
supported by an anchor
302
formed on a substrate
300
. The actuating portion
312
consists of a support layer
304
supported by the anchor
302
, a bottom electrode
306
formed on the support layer
304
, a deformable layer
308
containing a piezoelectric substance and formed on the bottom electrode
306
, and a top electrode
310
formed on the deformable layer
308
. A stress balance layer
316
is supported on the actuating portion
312
via the post
314
, and a light-reflecting member
318
is formed on the stress balance layer
316
. Voltage is applied between the bottom electrode
306
and the top electrode
310
so as to deform the deformable layer
308
. Through deformation of the deformable layer
308
, the actuating portion
312
is inclined, to thereby incline the light-reflecting member
318
. For changing the angle of the light-reflecting member
318
the AMA utilizes deformation of the deformable layer
308
containing a piezoelectric material instead of torsional movement of a torsion hinge. As a result, a drive part is less likely to suffer fatigue. Also, since the AMA does not employ electrostatic attraction, the light-reflecting member
318
is unlikely to become stuck.
However, the AMA involves the following drawbacks. Since the light-reflecting member
318
is formed in parallel with the deformable layer
308
, the length of the deformable layer
308
must be increased when a large deflection angle (the angle of tilt of reflective surface) is required. As a result, the size of the element increases. Also, since the light-reflecting member
318
is formed of a thin metal film, whose rigidity is low, the reflective surface implemented by the light-reflecting member
318
encounters difficulty in maintaining flatness. Since the flatness of the reflective surface changes with time as a result of operation of the AMA, the operation of deflecting the reflective surface cannot be performed stably over a long period of time.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problems involved in the DMD and the AMA and to provide a piezoelectric/electrostrictive device enabling an increase of deflection angle without involvement of an increase in the size of an element and which is less susceptible to time-course deterioration in a drive part, as well as to provide a method for fabricating the device.
To achieve the above object, the present invention provides a piezoelectric/electrostrictive device comprising a functional element, which, in turn, comprises a base portion; a deformable portion assuming the form of a thin plate and extending from the base portion to thereby form a plane; a piezoelectric/electrostrictive element tightly fixed to at least the deformable portion; and a reflective portion extending from the deformable portion so as to form an active plane intersecting with the plane of the deformable portion, and having a light-reflecting member disposed on the active plane. Upon operation of the piezoelectric/electrostrictive element, the deformable portion deforms in a direction substantially perpendicular to the plane of the deformable portion to thereby change a reflection angle of light reflected from the reflective portion.
In order to change the reflection angle of light reflected from the light-reflecting member disposed on the reflective portion, the piezoelectric/electrostrictive element causes the thin deformable portion to be deformed in a direction substantially perpendicular to the plane of the deformable portion. Thus, no torsion is exerted on the deformable portion, which serves as a drive portion. Therefore, the deformable portion is unlikely to deteriorate with time. Also, since the active plane of the reflective portion on which the light-reflecting member is disposed is arranged in such a manner as to intersect with the plane of the deformable portion, even when the length of the deformable portion is increased in order to increase the deflection angle (the angle of tilt of reflective surface), there is no need to increase the length of the light-reflecting member in association with the increase in the length of the deformable portion. Accordingly, the above-described configuration enables provision of a piezoelectric/electrostrictive device of small size and high reliability, thereby enabling highly dense arrangement of pixels in application to, for example, an image display unit. Notably, the degree of reduction in the size of the piezoelectric/electrostrictive device becomes greatest when the active plane of the reflective portion and the plane of the deformable portion intersect at right angles.
In the above piezoelectric/electrostrictive device, the reflective portion preferably extends from an end part of the deformable portion while having a width substantially equal to that of the deformable portion.
Since the conventional AMA mentioned previously has the light-reflecting member supported at a single point by means of the post, the light-reflecting member tends to be deformed (twisted or warped) under its own weight. Thus, the AMA encounters difficulty in maintaining good flatness of the reflective surface over a long period of time. By contrast, the piezoelectric/electrostrictive device of the present invention is configured such that the reflective portion extends from an end part of the deformable portion while having a width substantially equal to that of the deformable portion. Thus, the reflective portion is supported over a long distance and can be enhanced in rigidity. Therefore, the reflective portion is unlikely to be deformed and can maintain good flatness of the reflective surface.
The piezoelectric/electrostrictive device of the present invention may be configured such that a plurality of functional elements are arranged linearly adjacent to one another, to thereby enable application to an optical switch, an exposure unit, or a like unit. In this case, the plurality of functional elements preferably have the respective base portions formed into a common base portion.
The piezoelectric/electrostrictive device of the present invention can be configured such that a plurality of functional elements are arranged in a matrix and adjacent to one another, to thereby enable application to an optical switch, an image display unit, an exposure unit, or a like unit. In this case, at least a column of functional elements in t
Kimura Koji
Nanataki Tsutomu
Takeuchi Yukihisa
Addison Karen
Burr & Brown
NGK Insulators Ltd.
Ramirez Nestor
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