Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-08-31
2001-06-19
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S212100, C359S223100, C359S813000, C359S872000
Reexamination Certificate
active
06249367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical apparatus such as a galvanometer mirror actuator or the like for rotationally driving an optical member to reflect or diffractively deflect light.
2. Related Background Art
In recent years there have been increasing needs for the machining technology for scanning with a light beam, such as a laser or the like, or for positioning it with high accuracy to utilize the laser energy such as in a laser marker or a stereo lithography device, and there are also known devices for deflecting a laser beam at high speed to draw an image, such as laser displays.
These devices are arranged to rotationally drive an optical member such as a reflection mirror or a diffraction grating to deflect or move the optical axis of the beam to a desired position, and various galvanometer mirror actuators may be used as driving devices for rotationally driving the optical member. Among these galvanometer mirror actuators, there are actuators for rotationally rocking the optical member only in a certain angular range according to use, and there are increasing demands for higher drawing or positioning accuracy and for quicker operation performance.
A conventional galvanometer mirror actuator has the structure as illustrated in
FIGS. 5A
,
5
B to FIG.
7
. In
FIGS. 5A
,
5
B to
FIG. 7
, a reflection mirror
101
is supported on a plate spring
102
held on a base member
105
so as to be rotatable via neck portions
102
a
of the spring
102
, and a pair of magnets
103
and a yoke
104
are attached to the lower surface of the reflection mirror
101
. The magnets
103
, together with the yoke
104
and base member
105
, constitute a magnetic circuit. Attached to the base member
105
is a coil
106
for rotationally driving the reflection mirror
101
in cooperation with the magnets
103
.
In this structure, when a current is supplied to the coil
106
, a rotation movement is generated to twist the neck portions
102
a
of the plate spring
102
supporting the reflection mirror
101
to rotate the reflection mirror
101
, thereby deflecting a beam incident to the reflection mirror
101
. The center of rotation at this time is a point P in the neck portions
102
a
of the plate spring
102
as illustrated in FIG.
7
.
In addition to the above structure, there are also known galvanometer mirror actuators using antifriction bearings such as ball bearings or the like as holding and rotation guiding means for the reflection mirror.
The conventional galvanometer mirror actuators described above, however, have the following issues to be solved.
(1) In the galvanometer mirror actuators having the structure for supporting the driven part by the plate spring, because the neck portions of the plate spring have a certain width, variations in the width and plate thickness make it hard to define the center of rotation of the driven part at a predetermined position. Since the plate spring undergoes twist deformation, the rigidity thereof is also degraded in directions except for the twist rotation directions. If the center of gravity of the driven part moves during the rotation because of the degradation of rigidity, the center of rotation will also move under the influence thereof, so as to produce such errors as an angular error of the reflected beam, offset deviation thereof, and so on, thereby degrading the positioning performance.
(2) In the galvanometer mirror actuators having the structure for supporting the driven part by antifriction bearings, while the radial rigidity can be kept high, continuous execution of fine feed operations will induce a shift in the positional relation between balls and a retainer of the bearing to increase a rotational friction torque suddenly, thereby degrading controllability. Since continuous execution of rotational rocking operations in a fixed angular range will bring about local deficiency of oil film in the bearing and tend to damage the bearing, this structure will need an oil feeding mechanism, periodic oil feeding, etc. and the apparatus will increase its scale and necessitate maintenance.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the unsolved issues in the prior art as described above, and an object of the invention is to provide an optical apparatus capable of implementing high-accuracy and high-speed operation in a maintenance-free and compact structure.
For solving the above problems, an optical apparatus of the present invention comprises a stationary portion, a movable portion having an optical member and a semi-cylindrical shape, said movable portion being rotationally movable relative to the stationary portion, a non-contact static bearing for supporting a semi-cylindrical surface of the movable portion, and a non-contact actuator for actuating the movable portion relative to the stationary portion therewith in a direction of rotation.
The actuator desirably comprises a magnet and a coil. In this case, it is preferable to dispose the magnet on the movable portion side and the coil on the stationary portion side. The semi-cylindrical shape provided in the movable portion is better formed on a surface of the magnet disposed on the movable portion side.
The stationary portion is desirably comprised of a magnetic material and the magnet disposed on the movable portion side desirably generates an attraction force between the movable portion and the stationary portion.
The apparatus desirably further comprises a preload mechanism for generating an attraction force between the movable portion and the stationary portion.
The optical member is desirably a mirror for reflecting or diffractively deflecting a light beam and a center axis of the rotation is better located substantially on a surface of the mirror.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
REFERENCES:
patent: 4436260 (1984-03-01), Donelan
patent: 5430571 (1995-07-01), Witteveen
patent: 5779187 (1998-07-01), Dulat et al.
patent: 8-229759 (1996-09-01), None
Canon Kabushiki Kaisha
Cherry Euncha
Fitzpatrick ,Cella, Harper & Scinto
Spyrou Cassandra
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