JP2004015491A - Free-space optical transmission apparatus and system thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an emitted optical beam is waste if the number of mirrors in a free-space optical transmission apparatus do not match. <P>SOLUTION: The free-space optical transmission apparatus for transmitting information between a pair of multi-points by an optical beam to a plurality of the other apparatuses is provided with a light source 102 and a minute mirror array unit 104 composed of a plurality of minute mirrors arranged in the form of a matrix reflecting the optical beam emitted from the light source toward the plurality of the other apparatuses. The direction of the plurality of the minute mirrors can be individually set, the number of a plurality of mirror groups formed by the plurality of the minute mirrors is variable, and the optical beam from the light source is reflected by each mirror group toward each other apparatus. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an optical space transmission device that performs information transmission using a light beam emitted into space.
[0001]
[Prior art]
2. Description of the Related Art In a conventional optical space transmission apparatus for transmitting information between one-to-many points using a light beam, a plurality of remote apparatuses are illuminated with light over the entire range where the remote apparatuses exist, such as radio waves. In this case, in order for each partner device to receive a sufficient level of light, high-output light is required on the transmitting side.
[0002]
However, in the optical space transmission device, the output level of light on the transmission side is limited from the viewpoint of the life of the light emitting element and the like, so that it is possible to irradiate a sufficient level of light to the entire range where the partner device exists. Can not.
[0003]
In general, an optical space transmission device that transmits information to a plurality of remote devices by using a light beam with respect to a plurality of remote devices reflects an emission light from the own device and sends the reflected light to the plurality of remote devices, or a plurality of remote devices. It has a plurality of mirrors for reflecting the light transmitted from the partner device and taking the light into the light receiving unit of the own device. Then, since each of the plurality of mirrors is set at an appropriate angle so that the own device and each of the other devices can exchange light, the space optical transmission device at one-to-many points uses the mirrors. It is possible to transmit and receive light efficiently.
[0004]
In the case of an optical space transmission device that transmits information using a light beam, the optical axis of the received light transmitted from the partner device and the optical axis of the light receiving unit of the own device due to the effect of wind, sunlight, etc., or an artificial effect. , The S / N ratio of the signal may be degraded, and communication may not be performed normally. For this reason, it is necessary for the optical space transmission apparatus to have a margin for some deviation.
[0005]
The margin for this shift is increased by increasing the spread angle of the emitted light on the transmission side. In general, in order to give this divergent angle to the light beam output, the light emitted from the own device is reflected and transmitted to a plurality of partner devices, or the light transmitted from the plurality of partner devices is reflected. A plurality of mirrors for taking light into a light receiving section of the own device are made concave so as to form a beam divergence angle.
[0006]
Here, FIG. 9 shows a conventional optical space transmission apparatus. Reference numeral 901 denotes a transmission circuit, 902 denotes a light emitting element, 903 denotes a polarization beam splitter for separating transmission light and reception light, and 904 denotes a concave mirror unit for distributing light to a partner device. 905 is a light receiving element, and 906 is a receiving circuit.
[0007]
The transmission circuit 901 converts a signal to be transmitted into a signal that can be electro-optically converted, and the light emitting element 902 converts the signal into light to emit a light beam. Transmitted light emitted from the light emitting element 902 passes through the beam splitter 903, is reflected by the concave mirror unit 904, and travels to a plurality of partner devices, respectively.
[0008]
On the other hand, the light beam transmitted from the partner device is reflected by the concave mirror unit 904 and sent to the beam splitter 903. The light beam reflected by the beam splitter 903 is converted into an electric signal by the light receiving element 905, and information included in the signal is received by the receiving circuit 906.
[0009]
The concave mirror unit 904 has a configuration as shown in FIG. That is, four concave mirrors 910 are arranged as shown in the figure, and each concave mirror 910 is supported so that the angle can be freely moved.
[0010]
[Problems to be solved by the invention]
However, in the above conventional example, since the number of mirrors in the optical space transmission device is determined at the stage of manufacturing the device, when actually installing the device, the number of mirrors is always larger than the number of partner devices on site. It doesn't fit.
[0011]
When the number of partner devices is smaller than the number of mirrors, the mirrors are not used in a smaller number. At this time, since the mirror is constantly irradiated with light from the light source, the light output from the unused mirror is wasted.
[0012]
In addition, since mirrors having the same curvature are used, there are problems when the distance to the partner device is short and when the distance is long. The beam diameter becomes small for the partner device at a short distance, and the light entering the light receiving element becomes too strong, which may cause a failure of the light receiving element. In addition, since the beam diameter becomes too large for the remote device at a long distance, the received light amount at the remote device decreases, and the margin for rainfall decreases, so that communication can be interrupted even by a little rain or fog. Sex comes out. For this reason, conventionally, the range of the transmission distance has been limited.
[0013]
Therefore, when there are more partner devices than the number of mirrors, another device is installed, and when the number of partner devices is small, extra light output from the mirror is wasted. In addition, the transmission distance can be used with a limited transmission distance range.
[0014]
[Means for Solving the Problems]
In the present invention, in order to solve the above-mentioned problems, in a spatial light transmission device for transmitting information between one and many points by a light beam to a plurality of partner devices, a light source and a plurality of micromirrors arranged in a matrix. A micromirror array unit configured to reflect a light beam emitted from the light source toward a plurality of partner devices. The directions of the plurality of micromirrors can be individually set, the number of the plurality of mirror groups formed by the plurality of micromirrors is made variable, and each mirror group directs the light beam from the light source to each partner device. To reflect.
[0015]
Further, in the present invention, it is possible to receive light beams emitted from a plurality of partner devices, and in a spatial light transmission device for transmitting information between one and many points by using the light beams, the light receiving elements are arranged in a matrix. A plurality of micromirrors, and a micromirror array unit that reflects the light beam emitted from the partner device toward the light receiving element. Then, the directions of the plurality of micro mirrors can be individually set, the number of the plurality of mirror groups formed by the plurality of micro mirrors is made variable, and each mirror group directs the light beam from each partner device to the light receiving element. I try to reflect.
[0016]
In each of the above inventions, the number of micromirrors constituting each mirror group may be larger when the distance to the counterpart device is longer than when the distance to the partner device is shorter.
[0017]
Further, the degree of condensing the light beam by each mirror group may be changed according to the distance to the partner device.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a schematic configuration of an optical free space transmission apparatus according to an embodiment of the present invention. Although not shown, the optical space transmission device serving as the partner device has the same configuration as the optical space transmission device in FIG. Then, the free space optical transmission system is configured by the free space optical transmission device shown in FIG. 1 and a plurality of partner devices.
[0019]
In FIG. 1, 101 is a transmission circuit, 102 is a light emitting element (light source), 103 is a polarization beam splitter for separating transmission light and reception light, and 104 is a micro mirror array unit. 105 is a photoelectric conversion element, and 106 is a receiving circuit.
[0020]
The transmission circuit 101 converts a signal containing information to be transmitted into a signal that can be electro-optically converted by the light emitting element 102. The light emitting element 102 converts the signal into light and emits the light.
[0021]
The light beam emitted from the light emitting element 102 passes through the beam splitter 103, is reflected by the minute mirror array unit 104, and is emitted toward a plurality of partner devices (not shown).
[0022]
On the other hand, the light beam transmitted from each partner device is reflected by the minute mirrors arranged in a matrix forming the minute mirror array unit 104 and sent to the beam splitter 103. The light beam reflected by the beam splitter 103 and guided to the light receiving element 105 is converted into an electric signal by the light receiving element 105, and information included in the electric signal is received by the receiving circuit 106.
[0023]
FIG. 6 shows details of the micro mirror array unit 104. The micromirror array unit 104 includes a large number of micromirrors arranged in a matrix, and the angle of each micromirror can be freely set by an electric signal.
[0024]
For this reason, as shown in FIG. 5, by setting each of a certain number of mirrors at an appropriate angle, a part of the mirror group of the micro mirror array unit 104 can function as a condensing mirror. (Hereinafter, this mirror group is referred to as a pseudo focusing mirror).
[0025]
Therefore, any number of pseudo focusing mirrors can be formed in the micro mirror array unit 104. Further, by changing the number of micro mirrors constituting the pseudo condensing mirror, the reflection area of one pseudo condensing mirror can be changed.
[0026]
Further, by adjusting the angle of the micro mirrors constituting the pseudo focusing mirror, the degree of focusing of the pseudo focusing mirror can be changed. Since this corresponds to the curvature of the concave mirror, it is expressed as “the curvature of the pseudo focusing mirror” in the following description.
[0027]
By using the micromirror array unit 104 configured as described above for optical space transmission between one and many points and forming a plurality of pseudo condensing mirrors in the micromirror array unit 104, the following operational effects can be expected. .
[0028]
For one thing, even if the number of partner devices changes, it is possible to configure the pseudo condensing mirrors (pseudo diverging mirrors in some cases) by the number of partner devices, and to improve the efficiency of each partner device. It becomes possible to receive a light beam well.
[0029]
Also, by changing the number of micro mirrors constituting the simulated focusing mirror, the reflection area of the simulated focusing mirror can be changed, so that the amount of transmitted light can be arbitrarily distributed according to the distance to the partner device. Will be possible. That is, the number of mirrors constituting the pseudo focusing mirror when the distance to the partner device is long is larger than the number of mirrors when the distance is short.
[0030]
Furthermore, by adjusting the angle of the micro mirrors constituting the simulated focusing mirror, the curvature of the simulated focusing mirror can be changed, so that an appropriate beam diameter can be set for the partner device.
[0031]
Next, a transmission method in a case where there are four partner devices and a case where there are two partner devices will be described. When there are four partner devices, four pseudo focusing mirrors are formed in the micro mirror array unit 104 as shown in FIG. Here, the pseudo focusing mirror formed at the upper right in the micromirror array unit 104 is group A, the pseudo focusing mirror formed at the upper left is group B, and similarly, the lower left is group C and the lower right is group D. And
[0032]
In this way, a pseudo condensing mirror is formed for each group, and the micromirrors are controlled by electric signals so that the groups A, B, C, and D emit light emitted from the light emitting elements 102 toward the corresponding partner devices. The angles of the micromirrors of each group are set so as to reflect the beam or reflect the light beam emitted from the partner device toward the polarizing beam splitter 103 and the light receiving element 105.
[0033]
In the case where there are two partner devices, two pseudo condensing mirrors are formed in the micro mirror array unit 104 as shown in FIG. Here, the pseudo condensing mirror formed on the upper side in the micromirror array unit 104 is referred to as an A group, and the pseudo condensing mirror formed on the lower side is referred to as a B group.
[0034]
In this way, a pseudo condensing mirror is formed for each group, and the micromirrors are controlled by electric signals so that the groups A and B reflect the light beams emitted from the light emitting elements 102 toward the corresponding partner devices. The angles of the micromirrors in each group are set so that the light beam emitted from the partner device is reflected toward the polarization beam splitter 103 and the light receiving element 105.
[0035]
Here, when comparing FIG. 2 with FIG. 3, even if the number of partner devices changes, all the emitted light from the own device side can be assigned to the partner device, which is very efficient. .
[0036]
Further, when communicating with a remote device at a long distance, the amount of light attenuation increases in proportion to the distance. For example, when comparing the attenuation amount at the time of rainfall of 1 km and 2 km, the attenuation amount of 2 km is the square of the attenuation amount of 1 km. That is, when transmitting to a remote device at a long distance, in order to obtain the same margin for light attenuation as that at the remote device at a short distance, it is necessary to increase the emission light amount on the transmission side more than at a short distance. On the other hand, when transmitting to a short distance partner device, the amount of emitted light may be small because the amount of attenuation is small.
[0037]
Therefore, the transmission method when the partner device is at a long distance and when it is at a short distance will be described below. When two opponent devices are installed at a long distance and a short distance, the mirror group A corresponding to the opponent device located at a long distance and the opponent device located at a short distance in the micro mirror array unit 104. FIG. 4 shows the allocation of micro mirrors to the mirror group B corresponding to. That is, the number of micro mirrors forming the mirror group A is larger than the number of micro mirrors forming the mirror group B.
[0038]
As a result, many light components of the light beam incident on the micromirror array unit 104 are sent to the long-distance partner device, and the minimum necessary light components are sent to the short-distance partner device. Therefore, it is possible to obtain a margin for attenuation equivalent to that of a short-distance partner with respect to a long-distance partner device, and to prevent unnecessary light from being sent to a short-distance partner device. Light distribution.
[0039]
The setting of the divergence angle of the light beam suitable for long- and short-distance partner devices will be described below.
[0040]
For example, consider the case where the divergence angle of a light beam is the same for a long-distance partner device and a short-distance partner device. When light with sufficient margin for attenuation due to rainfall is output to a remote device at a long distance, the divergence angle is constant.Because the beam diameter becomes small at short distances, the light energy is concentrated and more than necessary. Is received by the light receiving element.
[0041]
In general, when communicating with long-distance and short-distance partner devices using an optical space transmission device, the divergence angle of the light beam on the transmitting side is adjusted so that the beam diameter is constant at the partner device regardless of the distance. Is done.
[0042]
Therefore, in the present embodiment, when communicating with a remote device at a long distance and a short distance, the curvature of the pseudo focusing mirror should be changed so that the beam diameter becomes the same at the transmission destination regardless of the long distance and the short distance. Accordingly, the divergence angle of the light beam can be adjusted, and light having an appropriate beam diameter can be transmitted widely from a long distance to a short distance.
[0043]
In the present embodiment, a case has been described in which the pseudo condensing mirrors (mirror groups) are formed so as to be united in the micro mirror array unit 104. For example, as shown in FIG. In the unit 104 ', the micromirrors constituting each mirror group may be dispersedly arranged.
[0044]
Further, in the above embodiment, the optical space transmission apparatus having both the transmission function and the reception function of the optical signal (light beam) has been described. May be combined to form a system.
[0045]
【The invention's effect】
As described above, according to the present invention, in performing one-to-many optical space transmission, it is possible to arbitrarily form a mirror group corresponding to the number of partner devices. Therefore, one device can handle various numbers of partner devices, and the emitted light beam can be used without waste.
[0046]
Further, the number of micromirrors constituting the mirror group can be changed or the curvature of the mirror group can be changed in accordance with the distance between the partner devices, so that there is no waste between the partner devices having various distances. It is possible to perform information transmission without fail and reliably.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an optical space transmission apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a mirror group configuration of a micro mirror array unit in the case where the number of partner devices in the optical space transmission apparatus is four.
FIG. 3 is a diagram showing a mirror group configuration of a micro mirror array unit in the case where there are two partner devices in the optical space transmission apparatus.
FIG. 4 is a diagram showing a mirror group configuration of a micro mirror array unit in a case where two opposing devices in the optical space transmission device are arranged at a long distance and a short distance.
FIG. 5 is a sectional view of the mirror group.
FIG. 6 is a configuration diagram of the micro mirror array unit.
FIG. 7 is a configuration diagram of another micro mirror array unit.
FIG. 8 is a configuration diagram of a concave mirror unit in a conventional optical space transmission device.
FIG. 9 is a configuration diagram of a conventional optical space transmission device.
[Explanation of symbols]
Reference Signs List 101 Transmitting circuit 102 Light emitting element 103 Polarizing beam splitter 104 Micro mirror array unit 105 Light receiving element 106 Receiving circuit

Claims (7)

An optical space transmission apparatus for transmitting information between one and many points by a light beam to a plurality of partner apparatuses,
A light source,
A micromirror array unit configured by a plurality of micromirrors arranged in a matrix and reflecting a light beam emitted from the light source toward the plurality of partner devices,
The directions of the plurality of micro mirrors can be individually set, the number of a plurality of mirror groups formed by the plurality of micro mirrors is made variable, and the light beam from the light source is transmitted by the respective mirror groups to each of the partner devices. An optical space transmission device, which reflects light toward a light source. 2. The optical space transmission apparatus according to claim 1, wherein the number of micromirrors constituting each of the mirror groups is larger when the distance to the counterpart device is long than when the distance to the counterpart device is short. 2. The optical space transmission apparatus according to claim 1, wherein a degree of focusing of the light beam by each of the mirror groups is changed according to a distance to the partner apparatus. An optical space transmission device capable of receiving light beams emitted from a plurality of partner devices and transmitting information between one and many points by using the light beams,
A light receiving element,
A micromirror array unit configured by a plurality of micromirrors arranged in a matrix and reflecting a light beam emitted from the partner device toward the light receiving element,
The directions of the plurality of micromirrors can be individually set, the number of the plurality of mirror groups formed by the plurality of micromirrors is made variable, and each mirror group reflects a light beam toward the light receiving element. An optical space transmission device characterized by the above-mentioned. The optical space transmission apparatus according to claim 4, wherein the number of micromirrors constituting each of the mirror groups is larger when the distance to the counterpart device is long than when the distance is small. The optical space transmission apparatus according to claim 4, wherein a degree of focusing of the light beam by each of the mirror groups is changed according to a distance to the partner apparatus. A space optical transmission system comprising the space optical transmission device according to claim 1 and the space optical transmission device according to claim 4.

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