Optical scanner

Details Optical scanner Optical scanner

2001-07-25

2003-04-29

Phan, James (Department: 2872)

Optical: systems and elements

Deflection using a moving element

By moving a reflective element

C359S223100, C359S199200, C359S198100

Reexamination Certificate

active

06556333

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-227482, filed Jul. 27, 2000; the entire content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanner of a type having a movable plate supported at a support body by means of torsion bars, and scanning light by turning the movable plate with the torsion bars being a turning axis.
The optical scanner of such type as described above is widely known in Jpn. Pat. Appln. KOKAI Publication No. 10-123449.
In an optical scanner
1
disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-123449, as shown in
FIG. 12
, a movable plate
2
, torsion bars
3
, and a support body
4
are integrally configured by utilizing a semiconductor process.
The movable plate
2
has a front portion provided with a coil
5
and a back portion having a reflection face. The front portion and back portion are configured in parallel to each other. The movable plate
2
is positioned at a neutral position in a stop state (in a non-driven state). The neutral position denotes a state in which the movable plate
2
is supported so that the front portion of the movable plate
2
and the front portion of the support body
4
(a face at the same side as the front portion of the movable plate
2
) are substantially disposed on the same plane.
At this neutral position, the front portion of the pair of torsion bars
3
(a face at the same side as the front portion of the movable plate
2
) as well is disposed at the substantially same plane as the front portions of the movable plate
2
and support body
4
. In addition, at this neutral position, the mutually longitudinal center axis lines of the pair of torsion bars
3
are kept in a state in which these axis lines coincide with each other.
The torsion bars
3
are configured in the shape of a pair of plates, each of which is connected to the movable plate
2
at one end, and is connected to the support body
4
at the other end. A pair of torsion bars
3
has a longitudinal center axis lines, and is disposed in a straight line manner so that the mutually longitudinal center axis lines coincide with each other. The longitudinal center axis lines do not pass through the gravity of the movable plate at the neutral position.
The support body
4
supports the movable plate
2
so that the plate can be swung by means of the torsion bars
3
. In addition, a pair of permanent magnets
6
is fixed to a face at the same side as the front portion of the movable plate
2
.
The coil
5
is provided along the outer periphery at the front portion of the movable plate
2
. Both ends of the coil
5
are pulled out onto the support body
4
over a pair of the torsion bars
3
. One end and the other end of the coil
5
pulled out onto the support body
4
configure a power supply pad
5
a
. The power supply pad
5
a
is connected to a power source (not shown).
When a current is applied from the power supply pad
5
a
to the coil
5
, the optical scanner
1
causes the movable plate
2
to swing (turn) with the torsion bars being a turning axis due to the Lorentz force (electromagnetic force) generated by a magnetic field formed by the permanent magnets
6
and the current. That is, the movable plate
2
is such that the longitudinal center axis lines of a pair of torsion bars
3
and the turning center line of the plate itself coincide with each other. The optical scanner
1
causes light to be externally incident to the reflection face of the back portion of the movable plate
2
, and the thus incident light is reflected, thereby scanning light.
The above described optical scanner
1
makes the following operation when the scanner is subjected to strong shock due to a drop or is subjected to vibration.
Hereinafter, a force to which torsion bars
3
are subjected when the optical scanner
1
drops and is subjected to shock will be described with reference to FIG.
13
.
First, referring now to
FIG. 13A
, a description is given with respect to a case in which the optical scanner
1
having the movable plate
2
set at the neutral position drops on a horizontal floor face while the back portion of the movable plate
2
is horizontal. In the specification, the drop is defined as a first state drop.
The first state drop denotes a drop in a vertical direction (a drop downward on a paper face) while the back portion of the movable plate
2
is horizontal. Thus, this drop can be referred to as a drop in a direction orthogonal to the back portion.
When the first state drop is carried out, at a moment when the optical scanner
1
collides with the floor face, an inertial force caused by multiplying acceleration due to such drop for the mass of the movable plate
2
is applied to the movable plate
2
. At this time, the movable plate
2
, as shown in
FIG. 13A
, is displaced in a direction (downward) orthogonal to the back portion of the movable plate
2
. In the case where the inertial force is excessive, a stress equal to or greater than a permissible stress generates with a pair of torsion bars
3
. In this case, the torsion bars
3
extend downwardly or are bent, and a permanent deformation generates. Due to this permanent deformation, there is a possibility that a damage or characteristic change generates with the torsion bars
3
. In the case where such a damage or characteristic change generates with the torsion bars
3
, the optical scanner
1
cannot cause the movable plate
2
to perform desired swinging, and desired optical scanning cannot be performed. That is, the optical scanner
1
is damaged or is changed in characteristics.
In addition, at the first state drop, although the back portion is positioned downwardly, the front portion may be positioned downwardly. In the case where the optical scanner drops when the front portion is positioned downwardly, the scanner is displaced in a direction orthogonal to the front portion. In this case as well, as in the case where the above described back portion is positioned downwardly, the torsion bars
3
extend downwardly or is bent, and there is a possibility that a permanent deformation generates.
In the specification, a displacement of the movable plate in a direction orthogonal to the front portion and/or back portion is defined as an orthogonal displacement.
Now, a description will be given with respect to a drop of the optical scanner at a disposition at which the surfaces (front portion and back portion) of the movable plate
2
are vertical, in the optical scanner
1
having a movable plate
2
set at a neutral position. In the specification, the above described drop is defined as a second state drop.
The second state drops include a second state horizontal drop in a state in which torsion bars
3
are horizontal (more precisely, the longitudinal center axis lines of the torsion bars are horizontal) and a second state vertical drop in a state in which the torsion bars
3
are vertical.
Now, the second state horizontal drop will be described hereinafter.
With respect to the second state horizontal drop, in
FIG. 13B
, the drop direction is schematically indicated by the arrow F. When the second state horizontal drop is carried out, at a moment when the optical scanner
1
collides with a floor face H, an inertial force is applied to the movable plate
2
as in the first state drop. Here, the gravity of the movable plate
2
does not coincide with the longitudinal center axis lines of the torsion bars
3
. Thus, the inertial force acts as a moment relevant to the rotation axis. Therefore, a deformation due to expansion and torsion generates with the torsion bars
3
. As indicated by the arrow R shown in FIG.
13
B′, the movable plate
2
turns around the turning axis with the torsion bars
3
being the turning axis. In the specification, this turning movement is defined as a turning displacement. In the case where the inertial force is excessive, a permanent deformation due to expansion and torsion ge

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