Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-03-23
2001-02-13
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S212100, C359S220100, C359S221200, C359S224200
Reexamination Certificate
active
06188502
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser pointing apparatus and in particular, to a laser pointing apparatus having a small size and small weight and capable of controlling a high-accuracy positioning. Moreover, the present invention relates to an on-fulcrum movement drive apparatus for use in the laser pointing apparatus and an antenna and a mirror which are located in an outer space.
2. Description of the Related Art
[A] Firstly, explanation will be given on a conventional laser pointing apparatus.
A laser beam machining apparatus and a laser display apparatus, a laser scan apparatus, and the like, in general, employ a laser pointing apparatus for controlling a laser beam emission angle or a laser beam incident angle.
In most of the conventional laser pointing apparatuses, two mirrors are used in combination for scanning a two-dimensional plane with a laser beam. However, there is a strong desire for reduction in the apparatus size and production cost as well as for simplification of a procedure for optical axis matching and positioning.
In order to satisfy these requirements, for example, Japanese Patent Publication (Unexamined) A-7-185866 discloses an apparatus including a single mirror, a rotary support member which can rotate around a normal axis of the mirror, and a mirror positioning mechanism supported by the support member. In this apparatus, a two-dimensional plane can be scanned by a laser beam using the single mirror.
Hereinafter, explanation will be given on some examples of conventional laser pointing apparatus with reference to the attached drawings.
FIG. 21
is a side cross sectional view of a conventional laser pointing apparatus including: a mirror
101
; an electromagnetic exciter
105
for moving the mirror
101
; a rotary support member
106
for supporting the mirror
101
and the electromagnetic exciter
105
; and a motor rotating the rotary support body
106
.
The mirror
101
can be deflected around the Z axis by rotation of the rotary support member
106
driven by the motor
109
and also deflected around the oscillation center
103
. This enables a laser beam to scan any position on a two-dimensional plane with the single mirror.
[B] Next, explanation will be given on a conventional on-fulcrum movement drive apparatus.
An antenna mounted on an artificial satellite or other space object is positioned by an on-fulcrum movement drive apparatus so as to assure a preferable communication with an earth station. The on-fulcrum movement drive apparatus moves the antenna around the X axis and Y axis which vertically intersects the X axis. Conventionally, this positioning around two axes has been effectuated by using a support mechanism having two bearings arranged vertical to each other. Moreover, this type of on-fulcrum movement drive apparatus is employed not only for an antenna but also for positioning a mirror and driving a positioning table.
In general, for the apparatuses to be mounted on an artificial satellite, there is a strong requirement for reduction in size and weight. The on-fulcrum movement drive apparatus has also been improved in various ways to satisfy the aforementioned requirement. For example, Japanese Patent Publication (Unexamined) A-53-34499 discloses an on-fulcrum movement drive apparatus in which an object to be driven is supported at a single point of a spherical bearing.
FIG. 22
is a cross sectional view of such a conventional on-fulcrum movement drive apparatus. The on-fulcrum movement drive apparatus shown in
FIG. 22
includes: an antenna
301
as an object to be positioned; a spherical bearing
302
for movably supporting the antenna
301
; a piston
303
for driving the antenna
301
; a linear motor
304
for driving the piston
303
; a sensor
305
for detecting displacement of the linear motor
304
; and a spring
306
for pushing the antenna
301
toward the piston
303
.
According to a detection result of displacement detected by the sensor
305
, the linear motor
304
drives the piston
303
and the antenna
301
is moved around the spherical bearing
302
as a fulcrum.
Although not depicted, another set of a piston, a linear motor, and a sensor is arranged in a direction vertically intersecting the drive direction of the piston
303
. Thus it is possible to obtain a movement around two axes.
However, the conventional laser pointing apparatus and the conventional on-fulcrum movement drive apparatus have following problems.
[A] Firstly, explanation will be given on the problems involved in the conventional laser pointing apparatus.
The first problem is that the conventional laser pointing apparatus is too large in size because it employs an electromagnetic exciter and a motor having a large volume.
The second problem is that the apparatus is too heavy because the rotary support member requires a comparatively high support strength and becomes heavy. Accordingly, the motor for driving the rotary support member also becomes heavy.
The third problem is that a large power consumption is required. This is because rotation of the mirror around the normal requires rotation of not only the mirror but also the large-mass positioning mechanism constituted by the electromagnetic exciter and the rotary support member.
The fourth problem is that it is difficult to control a pointing position with a high accuracy. This is because the rotation is driven by a motor and a belt. That is, non-linear elements such as the motor torque ripple and the belt expansion/shrinking are involved in the control system.
[B] Next, explanation will be given on the problems involved in the conventional on-fulcrum movement drive apparatus.
The first problem is that it is difficult to control positioning with a high accuracy. That is, the spherical bearing
302
cannot eliminate fluctuation and friction. During a drive, non-linear external components are involved in the control system, lowering the positioning accuracy.
The second problem is that the conventional on-fulcrum movement drive apparatus cannot be used in an outer space. In order to maintain a predetermined sliding characteristic on the spherical bearing
302
, a certain amount of lubricant should be present. However, this is difficult in an outer space where a lubricant easily volatilizes.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a laser pointing apparatus small in size and weight and capable of a highly accurate positioning with a reduced power consumption.
Another object of the present invention is to provide an on-fulcrum movement drive apparatus which can perform positioning with a highly accurate angle and which can also be used in an outer space.
The laser pointing apparatus according to the present invention is for pointing a laser beam on a predetermined position and comprises: a mirror extending on a X-Y plane and having a mirror surface for reflecting the laser beam; a mirror holder arranged so as to be displaceable and having a mirror holder main body for holding the mirror and at least three arms extending outwardly from the mirror holder main body; an elastic support mechanism for supporting the mirror holder main body according to the displacement of the mirror holder around a point on a Z axis passing through the center of the mirror and vertically intersecting the X-Y plane; a base for supporting the elastic support mechanism;
coil type electromagnets (hereinafter, referred to as coil magnets) arranged on the respective arms so as to generate a line of magnetic force in the Z axis direction; and permanent magnets provided on the base facing the corresponding coil magnets so as to generate a line of magnetic force in the Z axis direction,
wherein a magnetic force generated by interaction between the permanent magnets and the coil magnets supports the mirror holder in such a manner that the mirror holder can be translated in the Z axis direction and also rotated around the mirror center.
According to another aspect of the present invention,
NEC Corporation
Phan James
Sughrue Mion Zinn Macpeak & Seas, PLLC
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