Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Polarity-responsive
Reexamination Certificate
2002-02-13
2004-10-12
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Polarity-responsive
C200S181000
Reexamination Certificate
active
06803843
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a movable-body apparatus with a movable body which can be reciprocally tilted about a twisting longitudinal axis, such as micro-actuators, and an optical deflector using an electromagnetic actuator, an optical instrument using the optical deflector, and a method of fabricating the movable-body apparatus.
2. Description of the Related Background Art
An optical deflector for defecting and scanning a light beam, such as a laser beam, is used in an optical instrument, such as a laser printer and a bar-code reader. As the optical deflector, there exist a polygonal mirror in which a polygon with side mirrors is rotated to reflect and deflect a light beam incident thereon, and a galvano-mirror in which a flat mirror is vibrated by an electromagnetic actuator.
However, an electromagnetic motor for rotating the mirror is needed in the polygonal mirror, and a driver coil formed by mechanical winding and a large-sized yoke for generating the magnetic field are needed in the galvano-mirror. Therefore, there exists the limitation to a decrease in the size of the mechanical elements mainly due to required output torque. Further, the size of an optical deflecting apparatus inevitably increases due to a required space in which component members are assembled.
Furthermore, where a light beam is scanned in a two-dimensional manner, a combination of the polygonal mirror and the galvano-mirror, or a combination of two polygonal mirrors is generally employed. However, when an accurate two-dimensional scanning should be attained, it is necessary to arrange the mirrors such that scanning directions are orthogonal to each other, and hence, their optical adjustment is very complicated.
Apparatuses disclosed in Japanese Patent Application Laid-Open Nos. 7(1995)-175005 and 7(1995)-181414 are known as optical deflectors proposed to solve the above-described disadvantages. In those apparatuses, semiconductor producing techniques are applied and micromachining techniques for integrally fabricating micro-machines on semiconductor substrates are used.
FIG. 1
illustrates an example disclosed in Japanese Patent Application Laid-Open No. 7(1995)-175005. In a galvano-mirror
1001
of
FIG. 1
, a planar movable plate
1005
with a light reflective mirror
1008
is rotatably supported relative to a silicon substrate
1002
by a pair of torsion springs
1006
formed of a monolithic silicon. There are further arranged an upper-side glass
1003
, a lower-side glass
1004
, a flat coil
1007
, contact pads
1009
, and permanent magnets
1010
A,
1011
A,
1010
B and
1010
C. In this structure, the driver coil
1007
for generating the magnetic field is disposed on the periphery of the movable plate
1005
, and paired permanent magnets
1010
A and
1010
B;
1011
A and
1010
C are disposed on upper and lower surfaces of the semiconductor substrate
1002
, respectively, through upper and lower glass substrates
1003
and
1004
, such that electrostatic fields are applied only to portions of the flat coil
1007
parallel to the twisting longitudinal axis of the torsion springs
1006
.
In this optical deflector, when a current is caused to flow through the flat coil
1007
, the Lorentz force appears in a direction determined by the Fleming's left-hand rule due to the current flowing through the flat coil
1007
and the magnetic flux generated by the magnets
1010
A and
1010
B;
1011
A and
1010
C. Thus, a moment for rotating the movable plate
1005
occurs. Upon rotation of the movable plate
1005
, a spring reaction force occurs due to the spring rigidity of the torsion springs
1006
. A static displacement of the movable plate
1005
is established based on an equilibrium relationship between the Lorentz force and the spring reaction force. When an alternate current is caused to continuously flow in the flat coil
1007
, the movable plate
1005
with the reflective mirror
1008
is reciprocally tilted in a vibratory manner, and a light beam reflected by the mirror
1008
is hence scanned.
The optical deflector of
FIG. 1
, however, has the following disadvantage. When a vibratory angle of the light beam is to be increased at the scanning time, distances between the upper and lower glass substrates
1003
and
1004
and the movable plate
1005
must be enlarged. Then, distances between the permanent magnets
1010
A and
1010
B;
1011
A and
1010
C and the flat coil
1007
increase, and hence, the magnetic flux by the permanent magnet weakens at the location of the flat coil
1007
. As a result, a large current is required to flow through the flat coil
1007
for the driving of the movable plate
1005
, and it hence becomes difficult to construct an optical deflector which can achieve a large deflection angle and reduce a consumption electric power. Further, since the permanent magnets
1010
A and
1010
B;
1011
A and
1010
C for generating the external magnetic field must be disposed outside the movable plate
1005
, an external size of the entire device inevitably increases. The movable plate
1005
provided with the flat coil
1007
also increases in size.
Further, in the deflector of
FIG. 1
, the wiring of the flat coil
1007
for driving the movable plate
1005
is formed on the torsion springs
1006
. Accordingly, there is a possibility that a metal material of the wiring is damaged and disconnected due to the repetitive torsional motion of the torsion springs
1006
at the time of driving the movable plate
1005
. Such disconnection of the wiring greatly limits the life of the device.
FIG. 2
illustrates an example disclosed in Japanese Patent Application Laid-Open No. 7(1995)-181414. In a structure of
FIG. 2
, a minute driving source
2006
for generating a minute vibration of a piezoelectric oscillator is provided at an end of an elastic support
2003
which has two elastic deformation modes of bending mode &thgr;
B
and torsion deformation mode &thgr;
T
. The other end of the elastic support
2003
is shaped into an oscillator
2002
with a light reflective surface
2007
. In this structure, there are further arranged a vibration input portion
2004
, a mirror support
2008
, and a plate
2009
.
In the optical deflector of
FIG. 2
, flexure vibration and torsional vibration of the elastic support
2003
are caused by the vibration from the driving source
2006
. Since there are characteristic resonance vibration modes of the flexure vibration and the torsional vibration in accord with the construction of the device, the elastic support
2003
resonates at the resonance frequency when the vibration source
2006
generates a vibration including frequency components of those two resonance frequencies. Thus, the oscillator
2002
with the reflective surface
2007
can scan a reflected light beam in a two-dimensional manner.
In the optical deflector of
FIG. 2
, however, scanning rate and waveform of the oscillated light beam are limited since the driving and optical scanning cannot be achieved at frequencies other than the resonance frequency. Further, the driving manner, in which the attitude of the reflective surface
2007
is maintained, cannot be performed.
Furthermore, in the optical deflector of
FIG. 2
, the elastic support
2003
is oscillated in two deformation modes of bending mode and torsion mode. Therefore, in the case of a two-dimensional scanning, a resultant force of bending stress and shear stress appears, and a large internal stress is hence generated in the elastic support
2003
, in contrast to the case of a single stress. As a result, the elastic support
2003
is easy to break, and the life of the device is greatly limited.
In addition to the above, the fabrication of an electromagnetic actuator on a substrate, such as silicon, has been recently tried by using semiconductor processes. When the electromagnetic actuator is fabricated using the semiconductor process, a unit of a stationary core, a moving core and an electromagnetic coil can be integrally fabricated. Accordingly, no joining and bonding pr
Hirose Futoshi
Kato Takahisa
Mizutani Hidemasa
Shimada Yasuhiro
Teshima Takayuki
Canon Kabushiki Kaisha
Donovan Lincoln
Fitzpatrick ,Cella, Harper & Scinto
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