Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-07-30
2003-09-09
Mullen, Thomas (Department: 2632)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200
Reexamination Certificate
active
06618177
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a light space-transmission device, and more particularly, is suitably applicable to, for instance, a light space-transmission device for enlarging the luminous-flux-diameter of the light beam by means of a light beam expander and for transmitting a light beam.
2. Description of the Related Art
A light space-transmission device has been conceived wherein information signals are transmitted via a light beam. In such a light space-transmission device, a laser diode is driven with the stated information signal, and the luminous-flux-diameter of a light beam that is emitted from the laser diode is enlarged by means of a light beam expander, and the light beam is transmitted to an opposed other light space-transmission device that is the partner of the communication. Then, the other light space-transmission device receives this light beam with a light receiving element, and demodulates the output signal of the light receiving element to obtain the information signal; in this way, the information signal is transmitted via the light beam. In the same way, information signals can be transmitted from the other light space-transmission device via light beams.
In such a light space-transmission device, it is required to perform optical-axis correction so as to match the optical axis of the light beam that is beamed toward the light space-transmission device of the partner to the light space-transmission device of the partner; various methods are conceivable for performing this optical-axis correction.
For instance, such an optical-axis correcting method can be conceived that the light space-transmission device is supported with a gimbal that is movable upwards, downwards, leftward and rightward and the direction of the entire light space-transmission device is varied; but, in this case, there are such problems that whole device becomes larger and more complex one, and the speed of response of the optical-axis correction becomes slower, because it is needed to move the entire light space-transmission device.
Besides, such a method for correcting the optical-axis of the light beam can be conceived that the light beam emitted from a light beam expander is reflected with a servo mirror, and the angle of this servo mirror is controlled; but, in this case, there are such problems that the reflecting surface of the servo mirror becomes larger, and the speed of response of the optical-axis correction becomes slower, because the servo mirror is required to reflect the entire light beam whose luminous-flux-diameter has been enlarged by the light beam expander.
Besides, such a method can be conceived that the optical axis of a light beam that is not yet thrown into the light beam expander is corrected by means of a servo mirror, and this light beam whose optical axis has been corrected is expanded with the light beam expander and then emitted. Referring to
FIG. 1
, a light space-transmission device generally designated as
1
is comprised of an optical block
10
for transmitting and receiving light beams, a light beam expander
30
for enlarging or diminishing the luminous-flux-diameter of the light beam, and a servo mirror
20
for controlling the angle of the optical axis of the light beam.
The light space-transmission device
1
receives a reception light beam L
2
that comes from a light space-transmission device (not shown) of the partner with the light beam expander
30
, diminishes the luminous-flux-diameter of the reception light beam L
2
by the use of lenses
32
and
31
, and sends it to the optical block
10
via a mirror
21
of the servo mirror
20
.
In the the optical block
10
, the reception light beam L
2
is passed through a beam splitter M
1
, and then a part of the reception light beam L
2
is reflected by a beam splitter M
2
and brought into convergence on a position detecting element
13
via a lens
16
; the rest of the reception light beam L
2
is passed through the beam splitter M
2
, and converged on a light receiving element
12
via a lens
15
. And, the light space-transmission device
1
performs photoelectric conversion of the converged reception light beam L
2
into an electric signal by means of the light receiving element
12
, and then decodes the electric signal with a signal processing circuit (not shown) of the subsequent stage, thereby restoring the information signal.
In transmitting light beams, the light space-transmission device
1
drives a laser diode
11
of the optical block
10
with the information signal that is supplied from the exterior, transforms a transmission light beam L
1
that is emitted from the laser diode
11
into a parallel ray by means of a lens
14
, reflects the transmission light beam L
1
with a beam splitter M
1
, and further reflects the transmission light beam L
1
with the servo mirror
20
, so as to throw it to the light beam expander
30
. The light beam expander
30
enlarges the luminous-flux-diameter of the transmission light beam L
1
by the use of the lenses
31
and
32
, and throws the transmission light beam L
1
toward the light space-transmission device of the partner. In this manner, the light space-transmission device
1
transmits and receives the information signals through the medium of the transmission light beam L
1
and the reception light beam L
2
.
At this time, the light space-transmission device
1
aligns the optical axes of the transmission light beam L
1
and the reception light beam L
2
, so as to perform optical-axis correction for adjusting the optical axis of the transmission light beam L
1
to the optical wireless device of the partner. The position detecting element
13
sends the light receiving position information of the reception light beam L
2
at the light receiving plane of the position detecting element
13
to a controlling division (not shown). The controlling division calculates the difference between the actual light receiving position and the light receiving position (reference position) of the reception light beam L
2
that is in such a state that the optical axes of the transmission light beam L
1
and the reception light beam L
2
have been aligned, drives the mirror
21
on the basis of this difference, and adjusts the light receiving position of the reception light beam L
2
such that it coincides with the reference position, thereby achieving the optical-axis correction.
By locating the servo mirror
20
between the optical block
10
and the light beam expander
30
, the mirror
21
, as a result, the speed of response can be improved.
The angle of light which is emitted from the light beam expander becomes a value that is given by dividing the angle of the light thrown into the light beam expander by the enlargement ratio of the light beam expander. That is, as shown in
FIG. 2
, in the case where the angle of the mirror
21
is increased by a degree, the optical axis of the light beam that is thrown into the light beam expander
30
increases by 2&agr; degrees, and, provided that the enlargement ratio of the light beam expander
30
is X, the change of angle of the optical axis of the light beam that is emitted from the light beam expander
30
becomes 2&agr;/X degrees. For instance, if the enlargements ratio of the light beam expander
30
is 16 times, and the optical axis correcting angle range that is required for the light space-transmission device
1
is ±1 degree, then ±8 degrees is required for for the rotational range of the mirror
21
. In the case where the servo mirror
20
is placed between the optical block
10
and the light beam expander
30
in this way, such problems still exist that the required rotational-range of the mirror
21
becomes wider and, therefore, the servo mirror
20
becomes larger and more complex.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the invention is to provide a light space-transmission device which has a simple constitution and a wide range of optical-axis correction.
The foregoing object and other objects of the i
Ito Yujiro
Kato Tetsuro
Bell Boyd & Lloyd LLC
Mullen Thomas
Sony Corporation
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