JPH07264135A - Direct optical communication system - Google Patents

Abstract

PURPOSE:To send information with sufficient quantity by allowing a laser ray from a sender side to be reflected by a receiver side and turned back and using a reflected light modulator to modulate even the reflected light for 2-way communication. CONSTITUTION:A laser ray (a) emitted from a transmitter A transmits through a reception window 36 of a receiver B and is reflected by a retro-reflector 33 to be a laser ray (b), it is emitted from the receiver B and is reflected in an opposite direction on the same path as the ray (a). The ray (b) is reflected upward by a Y axis deflection control mirror 24 and transmits through an X axis deflection control mirror 23 being a half mirror and is made incident onto a reflected light receiver. Then the signal of the transmitter A is superimposed on the ray (a) via a forward path signal modulator 22, and a signal detection section 35 of the receiver B detects and receives the signal. Furthermore, the signal of the receiver B is superimposed on the ray (b) via a reflected light modulator 32 to allow the receiver 27 of the transmitter A to receive the signal and to attain 2-way communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel direct optical communication system capable of bidirectional communication with a single light beam. This communication system can be used not only for communication between fixed stations but also for communication between mobile units and communication between fixed units of mobile units as well as automation of aiming. Such communication technology is considered to be important as a technology for ensuring traffic safety.

[0002]

2. Description of the Related Art Conventionally, when performing bidirectional direct optical communication (communication in which a laser beam skips a space), two laser light sources 1 for a forward path and a laser light source 2 for a backward path are used as shown in FIG. It was necessary to use the laser beams a and b. Therefore, in order to perform two-way communication, the transmitting device and the receiving device for the forward path and the returning apparatus need separate laser beam emitting devices 1 and 2, respectively, which increases the cost. Also, the task of aiming the laser beam from the transmitter to the receiver is troublesome, and when the receiver moves, it often causes troubles such as misalignment and disconnection of the line, and recovery work also takes a lot of time. There was a problem such as taking time. Therefore, direct optical communication is not generally accepted as a practical communication method, and its use has been limited to special cases.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above point, and by using the reflected light of the laser beam on the transmitting side in the return path, it is possible to economically perform bidirectional operation with a single light beam. It tries to make communication possible. Further, the problem to be solved by the present invention is to automate the necessary operation for aiming and eliminate the troublesome aiming. In other words, if the aim is off, this can be automatically corrected. As a result, for example, it becomes possible to easily communicate with a moving partner side, and it is possible to open up an application to communication between mobile bodies.

[0004]

According to the present invention, in a direct optical communication system using a free space medium of a light beam modulated by a signal, a reflector, a reflected light modulator and a photodetector are arranged on the receiving device side. A direct optical communication system in which a light beam from the transmitting device side is reflected by the receiving device side and returned, and at that time, reflected light is also modulated to perform bidirectional communication. Further, it is a direct optical communication system using a retro reflector as a reflector provided on the receiving device side for the purpose of opening a return line for bidirectional communication. Further, in a direct optical communication system using a free-space medium of light rays, a receiving target serving as a mark is arranged on the receiver side, and a device for recognizing the direction and distance of this mark on the transmitter side, and further, emitting a laser beam. It is a direct optical communication system that has a function to accurately aim a laser beam on a receiving target by providing a mirror angle control device for controlling the direction.

The receiving target provided on the receiving device side is
It has a distinguishable feature. For example, the illuminant is arranged in a specific shape, or blinks at a specific cycle, or is given a characteristic property such as a specific wavelength. This direct light is characterized by detecting this with the imaging device on the transmitter side, calculating the direction and distance using the detected information, and automatically aiming by controlling the mirror angle based on these values. It is a communication method.

[0006]

The optical communication is capable of large-capacity communication as compared with the wireless communication. Therefore, by applying the present invention, optical communication can be used for mobile communication, and it becomes possible to perform advanced information on the mobile. In addition, since one laser beam is folded back and bidirectional communication is performed, an economical direct optical communication system with a correspondingly low cost is provided. In addition, a highly reliable direct optical communication system will be realized by automating the aim.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The concept of bidirectional communication by reflection according to the present invention will be described below with reference to the drawings. In FIG. 1, a transmitter A on the left side is a laser light source 1 that oscillates a laser beam.
1, a modulation output device 12 for inputting a signal to be transmitted to the laser beam a oscillated from the laser light source 11, a receiver 13 for receiving the laser beam b from the receiving device B, and a transmitting device A for transmitting from the receiving device B. And an output device 14 for outputting the signal. On the other hand, the receiving device B on the right side receives the signal to be transmitted from the receiving device B to the transmitting device A, the reflected light modulator 15, the reflector 16, and the transmitting device A.
A photodetector 17 for receiving the laser beam a transmitted from the receiver B to the receiver B, an output device 18 for outputting a signal from the photodetector 17, and a reflected light modulator 15 for transmitting a signal from the receiver B to the transmitter A. And a transmitter 19 for inputting to the.

Therefore, the laser beam a from the transmitter A is
Is reflected by the reflector 16 of the receiver B and folded back, and at this time, the reflected light b can also be modulated by the reflected light modulator 15 to perform bidirectional communication. At this time, if a retro-reflector is used as a reflector, the laser beam a from the transmitter A will follow the optical path just opposite to the laser beam a from the transmitter A by the retro-reflector 16 on the receiver B side, and always return to the transmitter A. This makes the aiming extremely easy. In other words, if the transmitter A side aims, it is not necessary to aim the receiver B side. Further, the signal from the receiving device B to the transmitting device A is used by time division in the first half and the second half as shown by a signal waveform d on the outward path and a signal waveform e on the return path as shown in FIG. By
Two-way communication will be performed with only one laser beam.

Next, an embodiment of the direct optical communication system will be described with reference to FIG. FIG. 3 is a configuration diagram showing the configuration of the direct optical communication system of the embodiment. That is, on the left side transmitter A side,
Light from the 1.55 μm laser light source 21 is reflected downward by the X-axis shake control mirror (semi-transmissive mirror) 23 arranged at an angle of 45 degrees through the forward path signal modulator 22, and the X-axis shake control is performed. The Y-axis shake control mirror 24 arranged at an angle of 45 degrees in a direction orthogonal to the mirror 23 reflects the light on the right side and transmits. The X-axis shake control mirror 23 and the Y-axis shake control mirror 24 are connected to a mirror angle control device 25, and the angles of the X-axis direction and the Y-axis direction are controlled respectively, and it is possible to transmit in any direction. is there. This is because the laser beam of 1.55 μm has a wavelength that is difficult to be absorbed by the human eye, and therefore, it is safe to enter the human eye if it goes out of the target.

The receiving device B on the right side mainly receives the reception target mark 3
1, a reflected light modulator 32, a retroreflector (retroreflector) 33, and a signal detector 35. The details of the reception target 31 are shown in the front view of FIG. That is, as a mark, the infrared light LED mark 31 is provided around the reception window 36 in the central portion.
Are arranged.

A laser beam a emitted from the transmitter A
Is transmitted through the receiving window 36 of the receiving device B, reflected by the retro-reflector 33, becomes a laser beam b, is emitted from the receiving device B, and is reflected in the same direction as the laser beam a in the opposite direction. Then, the light is reflected upward and transmitted through the X-axis shake control mirror 23, which is a semi-transmissive mirror, as it is and enters the reflected light receiver 27. Therefore, by placing the signal d on the transmitter A side on the laser beam a via the outward signal modulator 22, the signal detector 35 of the receiver B can detect and receive the signal d. Further, by placing the signal e on the receiving device B side on the laser beam b via the reflected light modulator 32, it becomes possible for the reflected light receiver 27 on the transmitting device A side to receive the signal e from the transmitting device A side. Two-way communication is possible only with the laser beam of a book. For this reason, the light beam emitted from the transmitter A is
As shown in FIG. 2, there is a margin for only the return path signal e for carrying the signal from the receiver B.

Two reflectors are used to control the direction of the laser beam a of the transmitter A, and one Y-axis shake control mirror 24 is a high-reflectance total reflector and the other X-mirrors.
The axis shake control mirror 23 is a semitransparent mirror. The two mirrors are mounted on a rotary stage whose axes are orthogonal to each other in order to swing the laser beam a in the X-axis direction and the Y-axis direction, and these are controlled by the computer of the mirror angle control device 25.

The transmitter A has a CCD camera 29.
The camera 29 receives an image of the reception target 31 of the receiving device B with the camera 29, forms an image of the image, and takes it into the computer. An example of the target detection monitor screen is shown in FIG.
That is, the direction is calculated from the position of the image 31 ′ of the receiving target in the image 30, and the distance is calculated from the size of the image of the image 31 ′ of the receiving target. Based on this value, the mirror degrees of the X-axis shake control mirror 23 and the Y-axis shake control mirror 24 of the transmitter A are controlled via the computer of the mirror angle controller 25, and the laser beam a is accurately directed to the receiver B. Will fire. By repeating this automatically and continuously, even if the receiving device B moves, the bidirectional communication line can be opened as long as it is within the field of view of the CCD camera 29 of the transmitting device A.

FIG. 5 shows a detailed sectional structure of the receiver B. The laser beam b that passes through the reception window 36 and the reflected light modulator 32 and is reflected by the retro-reflector 33 is modulated when passing through the reflected light modulator 32. A part c of the laser beam is extracted by the evanescent wave on the reflecting surface of the retro reflector 33. If this is not enough, if adhesive or the like is attached to a part of the reflecting surface to impair the flatness, light leaks from it, and this is used to make it incident on the signal detector 35 for reception. Alternatively, the signal from the transmitter A may be received.

As shown in the front view of FIG. 4, the receiving target 31 of the receiving apparatus B has eight infrared light LEDs 31 in a circular shape around the receiving window 36 for guiding the light to the signal detector 35. It is arranged and configured. The infrared light b ′ is used here because it can be easily separated from the surrounding image by the infrared transmission filter. In addition, this arrangement is characteristic, and even if there is light emission in the same wavelength band, it is possible to separate and identify. Then, the distance can be measured from the size of the arrangement circle.

In the above example, the light b'from the infrared LED is used as the mark of the reception target 31, but it may be possible to use the light emission of the visible light lamp. Further, it is needless to say that the LED and the lamp may be blinked at a specific cycle to increase the discrimination power, and further, the reflected light of the specific wavelength may be used for the discrimination.

The retroreflector is manufactured by using a glass or plastic material, a mold having a front surface which is flat, and a back surface having three right-angled pyramid projections which form 90 degrees with each other. Create. Alternatively, the mirrors can be joined by facing each other so that the three surfaces are perpendicular to each other. In this case, the mirror surface is coated with a reflective film such as aluminum and a part thereof is removed to obtain the leaked light c.

[0018]

As described above, according to the direct optical communication system of the present invention, it is possible to perform two-way communication by using one laser beam on the transmitting side, it is economical, and the aiming is automated. It can be expected to increase its reliability and expand its field of use. In particular, in mobile-to-mobile communication, the communication capacity has been insufficient until now, but it becomes possible to transmit a sufficient amount of information, and it becomes possible to construct an advanced information network.

[Brief description of drawings]

FIG. 1 is a block diagram showing the concept of a direct optical communication system of the present invention,

2 is a waveform diagram of a signal wave applied to the direct optical communication system of FIG.

FIG. 3 is a configuration diagram showing a configuration of a direct optical communication system according to an embodiment,

4 is a front view of the receiving device of FIG. 3,

5 is a cross-sectional view of the receiving device of FIG. 3,

FIG. 6 is an explanatory diagram showing a target detection monitor screen,

FIG. 7 is an explanatory diagram of a conventional direct optical communication system.

[Explanation of symbols]

 21 laser light source 22 forward path signal modulator 23 X-axis deflection mirror 24 Y-axis deflection mirror 25 mirror angle control device 27 reflected light receiver 28 image analysis device 29 CCD camera 31 reception target 32 reflected light modulator 33 retroreflector 35 photodetector 36 reception window

Claims (4)

[Claims] 1. In a direct optical communication system using a free space medium of a light beam modulated by a signal, a reflector, a reflected light modulator and a photodetector are arranged on the receiving device side, and a laser beam from the transmitting device side is arranged. A direct optical communication system characterized in that the reflected light is reflected back at the receiving device side, and at that time, reflected light is also modulated by a reflected light modulator to perform bidirectional communication. 2. The direct optical communication system according to claim 1, wherein a retro-reflector is used on the receiving device side for the purpose of opening a return line for bidirectional communication. 3. The bidirectional direct optical communication system according to claim 1, wherein a receiving target having a characteristic of a mark is arranged on the receiving device side, and the direction and distance of this mark are recognized on the transmitting device side. The device further comprises a mirror angle control device for controlling the emission direction of the light beam, and the mirror angle is controlled based on the information of the recognition device of the mark so that the light beam is accurately applied to the receiving target. Direct optical communication system. 4. The direct optical communication system according to claim 1 or 3, wherein the receiving target provided on the receiving device side has a light emitter arranged in a specific shape, blinking at a specific cycle, or a specific wavelength. And the like, and recognize the mark from the receiving target by signal processing or feature extraction from the image captured using the CCD image pickup device on the transmitting device side using the reflected light from the receiving target, and determine its position. A direct optical communication system characterized in that it has a function of finding the direction and distance of the receiving side from the size.