Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
1999-07-16
2001-01-16
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S629000, C359S823000, C359S199200, C359S199200
Reexamination Certificate
active
06175451
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical axis correcting apparatus and a method of correcting an optical axis, and more particularly, is suitably applied to an optical axis correcting apparatus of an optical space transmission system that spatially transmits light beams.
2. Description of the Related Art
A transmission system transmits data from the transmitting side to the receiving side through a cable circuit or by radio. A construction to transmit data from transmitting side to receiving side through a cable circuit has ways in which the cable circuit is provided virtually and underground. However, both methods require troublesome procedure and large-scale construction. On the other hand, to transmit data from the transmitting side to the receiving side by radio, a prescribed frequency band must be allocated out of a limited electric wave source, and realizing it is difficult because practically there is limitation in the number of circuits.
Then, in recent years, an optical space transmission system that transmits various data in optical space with an optical circuit using light beams has been developed. However, an optical space transmission system having sufficient performance to transmit data to a long distance without error has not been developed yet.
For example, as shown in
FIG. 1
, the optical system
100
of an optical space transmission system capable of the bi-directional communication converts a laser beam from a semiconductor laser
101
that has been modulated in intensity based on a transmission signal into a parallel beam with a lens
102
, and makes the parallel beam be incident into a beam splitter
103
. The beam splitter
103
reflects the parallel beam and makes it be incident on a concave lens
104
to magnify the parallel beam. Then, the magnified beam is converted into a parallel beam again through a convex lens
105
and is emitted as an emitted light L
out
.
Furthermore, the optical system
100
brings an incident light L
in
which is transmitted from the communicating party of an optical space transmission system into convergence on the concave lens
104
with the convex lens
105
. The converged light is converted into a parallel beam by the concave lens
104
, and then the parallel beam is incident into a beam splitter
106
through the beam splitter
103
. The beam splitter
106
reflects the parallel beam and brings it into convergence on the light receiving surface of a position detecting sensor
108
through a lens
107
. At the same time, the beam splitter
106
makes the parallel beam pass through the sensor
108
and brings it into convergence on the light receiving surface of a light receiving device
110
through a lens
109
.
In such an optical system
100
, the optical axes must be identical with each other between that system and the optical system of the optical space transmission system of the communicating party. However, deviation unfortunately occurs between their optical axes because the optical system receives influences such as external causes, such as fog, rain, etc., an oscillation occurred inside the system, the change of a temperature of a setting place, or the like. In this case, in the optical space transmission system, even a slight deviation of optical axis causes an error in optical space transmission to a long distance, and it obstructs the communication.
To correct such the deviation of the optical axis, various optical axis correcting apparatuses have been provided. For example, as shown in
FIG. 2
, in an optical axis correcting apparatus
120
, the aforementioned optical system
100
is integrally provided in a body tube
121
. The above body tube
121
is supported by an intermediate ring
122
with two bearings for X-axis
123
so as to freely rotate on the X-axis in a rotary-direction.
A motor for X-axis
124
is fixed to the intermediate ring
122
. The above motor for X-axis
124
transmits its rotary driving power via a driving gear
125
to a driven gear
126
that is integrated with the bearing for X-axis
123
. This makes the body tube
121
rotate on X-axis in the rotary-direction.
Furthermore, the intermediate ring
122
is supported by a pedestal
127
with a bearing for Y-axis
128
so as to freely rotate on Y-axis in the rotary-direction. A motor for Y-axis
129
is fixed to the pedestal
127
. The motor for Y-axis
129
transmits its rotary driving power via a driving gear
130
to a driven gear
131
which is integrated with the bearing for Y-axis
128
. This makes the intermediate ring
122
and the body tube
121
integrally rotate on Y-axis in the rotary-direction.
The motor for X-axis
124
and the motor for Y-axis
129
make the body tube
121
rotate by a prescribed amount based on the detected result of the position detecting sensor
108
(
FIG. 1
) with a control part (not shown in figure) such that the optical axis of the emitted beam L
out
in transmission and the optical axis of the incident beam L
in
in reception are identical with each other.
On the other hand, as shown in
FIG. 3
in which the same reference numerals are applied to corresponding parts of
FIG. 1
, the optical axis correcting apparatus
140
is composed of a mirror for X-axis
141
provided on the optical path of the optical system
100
, a motor for X-axis
142
which makes the mirror for X-axis
141
rotate on X-axis in the rotary-direction, a mirror for Y-axis
143
provided at a position opposite to the mirror for X-axis
141
, and a motor for Y-axis
144
which makes the mirror for Y-axis
143
rotate on Y-axis in the rotary-direction.
In this case, the optical axis correcting apparatus
140
makes each of the motor for X-axis
142
and the motor for Y-axis
144
rotate by the prescribed amount based on the detected result of the position detecting sensor
108
with the control part (not shown). This adjusts the rotary angles of the mirror for X-axis
141
and the mirror for Y-axis
143
such that the optical axis of the emitted beam L
out
in transmission and the optical axis of the incident beam L
in
in reception are identical with each other.
In the-mentioned optical axis correcting apparatus
120
(FIG.
2
), since the optical axes are corrected by moving the whole body tube
121
, there is a problem that a response to a command to correct an optical axis deteriorates by the inertia mass of the whole body tube
121
.
Furthermore, the optical axis correcting apparatus
120
has problems that accurate bearings and motors for generating large driving power are needed and that the optical axis cannot be accurately corrected because of various influence of its transmission mechanism owing to the motor for transmit rotary power and backlash of gears.
Also the optical axis correcting apparatus
140
(
FIG. 3
) requires a mirror and a motor for each of X-axis direction and Y-axis direction. This causes problems that its configuration is complicated and enlarged and that the optical axis cannot be accurately corrected owing to backlash in its transmission mechanism.
Furthermore, in the optical axis correcting apparatus
120
and the optical axis correcting apparatus
140
, in the case where the rotary angles of the body tube
121
, the mirror for X-axis
141
and the mirror for Y-axis
143
are controlled only by their positional information (i.e., angles), the body tube
121
, the mirror for X-axis
141
and the mirror for Y-axis
143
unfortunately move from the stop positions when given some large oscillation from outside. Thus, stable control cannot be performed.
The optical axis correcting apparatus
120
and optical axis correcting apparatus
140
are provided with speed sensors which respectively detect an angular velocity component having a high frequency of the time when oscillation leads to movements of the body tube
121
, the mirror for X-axis
141
and the mirror for Y-axis
143
. The angular velocity component which represents the actual movement detected by the speed sensor is fed back to restrain the movement owing to the oscillation component. Th
Iriyama Toshihisa
Ito Yujiro
Epps Georgia
Limbach & Limbach L.L.P.
Seyrafi Saeed
Sony Corporation
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