JP2000286799A - Optical radio equipment and method for adjusting its optical axis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical radio equipment that automatically adjusts an optical axis with a simple and inexpensive configuration and adjusts the optical axis finely and to obtain its optical axis adjustment method. SOLUTION: The optical radio equipment 41 has a transmission reception section 30 where a light emitting means 10 and a light receiving means 20 are integrated to make optical axes of them parallel to each other to realize 2-way transmission, and the optical axis of a transmission parabolic reflector 11 and the optical axis of a reception parabolic reflector 21 are aligned to be in parallel in the case of the assembling. Furthermore, an array shaped corner cube 34 is provided on the light receiving means 20 over the entire circumference of the transmission reception section 30. Then a drive means 31 can vertically rotate the transmission reception section 30 consisting of the integration of the light emitting means 10 and the light receiving means 20, and a drive means 32 provided in a base 33 can laterally rotate the transmission reception section 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical wireless device for transmitting a signal by optical wireless and an optical axis adjusting method thereof.

[0002]

2. Description of the Related Art Generally, when a signal is transmitted via an optical radio, an LED (light emitting diode) or a laser diode is used as a light emitting element on the light transmitting side. Since it does not spread even if it is transmitted over a distance, it is used for transmission between buildings or across a river.

[0003] In addition, LEDs are not suitable for long-distance transmission because the LED has a wide directivity and a light beam spreads with distance.
The transmission distance can be extended by integrally forming the LED and the focusing lens or by using a plurality of LEDs arranged in parallel.

On the other hand, PDs (photodiodes) and avalanche PDs are used as light receiving elements for receiving light in optical wireless communication. Normally, PD is avalansh PD
Although the light receiving sensitivity is weaker than that of, the light receiving sensitivity can be increased by integrally forming the focusing lens or using a plurality of PDs in parallel. The avalanche PD is much more expensive than a normal PD.

[0005] Further, in the case of performing broadband transmission using optical wireless communication or performing optical communication on a plurality of transmission lines of the same band in the same space, it is necessary to narrow the light emission directivity and light reception directivity. However, as the directivity becomes narrower, it is more difficult to accurately adjust the optical axis at the time of installation, and at the time of communication, an error occurs due to slight deviation of the optical axis due to vibration or the like.

Accordingly, the present applicants have disclosed Japanese Patent Application Laid-Open No. 6-224.
No. 858 proposes a method for adjusting the optical axis. As a method of directing the optical axis toward the communication partner, there are an automatic method and a manual method. In either case, it is necessary to make the other party detect both positions. Specifically, the first optical wireless device emits search light, and the second optical wireless device emits search light.
Receives the signal, detects the position of the first optical wireless device, emits search light toward the first optical wireless device, and informs the first optical wireless device of the position. Have done that.

[0007]

SUMMARY OF THE INVENTION As described above, the first
In order to adjust the optical axis of the light emitting / receiving unit of the optical wireless device, it is necessary to receive search light from the second optical wireless device.
However, since the light emission from the LED has directivity,
The possibility that the search light from the second optical wireless device enters the light receiving unit was extremely low.

For example, as a light emitting unit for outputting search light of the second optical wireless device, a relatively wide LED having a directivity of 30 ° is used without using a focusing lens, and a light receiving portion of the first optical wireless device is used. When a PD having a relatively wide directivity of 60 ° is used, even if the first and second optical wireless devices are in the range of + 180 ° in the horizontal direction and + -30 ° in the vertical direction, the second and third optical wireless devices are in the second direction. The probability that the search light of the optical wireless device reaches the first optical wireless device is 1/24, and the probability that the search light is received by the light receiving unit is 1/6. Therefore, the probability of facing each other is 1/144, and it is extremely difficult to align the optical axes only by transmitting and receiving the search light.

Therefore, at present, a large number of LEDs are provided in the second optical wireless device in a hemispherical shape, and search light is emitted in all directions in the upper half, and a large number of LEDs are also provided in the first optical wireless device.
D is provided to receive the search light,
After transmitting and receiving the search light by manually adjusting the optical axis manually in advance, the optical axis alignment between the apparatuses is performed.

However, in this method, the search light needs to be emitted in a wide range, and the directivity cannot be narrowed using a lens. For this reason, in order to extend the light emission distance, it is necessary to direct many LEDs in the same direction,
Including light emission over a wide area, the circuit scale and power consumption increase, making it difficult to reduce the size and cost.
In addition, in the above method, it is necessary to rely on manual operation, and wide directivity is required in consideration of the accuracy of manual optical axis alignment. In this case, a light-emitting unit having a wide directivity dedicated to search is required separately. As a result, the circuit scale increases, and also in this case, miniaturization becomes difficult, and the cost also increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical wireless device capable of automatically and finely adjusting the optical axis with a simple and inexpensive configuration, and an optical axis adjusting method therefor.

[0012]

SUMMARY OF THE INVENTION As means for achieving the above object, an object of the present invention is to provide an optical wireless device having the following configuration and an optical axis adjusting method thereof.

1. An optical wireless transmission unit having a light emitting unit for outputting a narrow band light beam, a driving unit for driving the light emitting unit with information to be transmitted, a light receiving unit for receiving signal light, and an output from the light receiving unit An optical wireless receiving unit having information receiving means for extracting received information from a signal, and integrating the optical axis of the light beam output from the light emitting means and the optical axis of the signal light received by the light receiving means in parallel. And
An optical wireless device further comprising a transmitting / receiving unit provided with a large number of small corner cubes for reflecting a beam light.

2. For directing a transmission / reception unit of the first optical wireless device in a direction in which the second optical wireless device exists in order to perform optical wireless communication between the first optical wireless device and the second optical wireless device. An optical axis adjusting method for an optical wireless device, wherein the transmitting and receiving unit of the first optical wireless device includes a light emitting unit that outputs a narrow band light beam, and a driving unit that drives the light emitting unit with information to be transmitted. An optical wireless transmission section having an optical wireless transmission section having: a light receiving section for receiving signal light; and an information receiving section for extracting received information from a signal output from the light receiving section. The optical axis of the beam light and the optical axis of the signal light received by the light receiving unit are integrated so as to be parallel, and the second optical wireless device is provided with a large number of small corner cubes that reflect the beam light. In front of the first optical wireless device. The transmitting and receiving unit of the first optical wireless device is displaced while outputting the light beam from the light emitting unit, and the optical axis is aligned based on the light receiving level of the light beam reflected by the corner cube of the second optical wireless device. A method for adjusting the optical axis of an optical wireless device.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram illustrating an example of a light emitting unit of the optical wireless device of the present invention, FIG. 2 is a configuration diagram illustrating an example of a light receiving unit of the optical wireless device of the present invention, and FIG. FIG. 3B is a configuration diagram showing an optical wireless device having a transmitting / receiving unit in which the means and the light receiving unit of FIG. 2 are integrated, FIG. 3B is a configuration diagram showing an optical wireless device having a transmitting / receiving unit of another configuration, and FIG.
FIG. 5A is a diagram for explaining an example of optical wireless communication between optical wireless devices shown in FIG. 5A, FIG. 5 is a configuration diagram showing an embodiment of the optical wireless device of the present invention, and FIGS. () Is a configuration diagram showing an example of a corner cube.

In the light emitting means 10 shown in FIG. 1, the LED 1 is located at or near the focal point of the parabolic reflector 11.
2 are arranged and reflected by the reflecting surface of the parabolic reflector 11 so that the emitted light of the LED 12 becomes parallel light.
In this case, it is preferable that the focal length of the parabolic reflector 11, the size (diameter) of the reflecting surface, and the opening angle be configured such that all the light emitted from the LED 12 is reflected by the parabolic reflector 11.

The diameter of the reflecting surface may be, for example, 10 cm. The parabolic reflector 11
It is manufactured by cutting out an aluminum block and polishing the surface, or by plating metal on the surface of a synthetic resin parabola, so that the reflection surface becomes a metal surface including those for reception described below I do.

Therefore, according to the transmitting device 10,
Since the beam can be transmitted with the same beam diameter as the diameter of the parabolic reflector 11, the spread of the beam diameter and the decrease in the optical power on the receiving side at a long distance can be minimized. Further, since the spread of the beam diameter can be suppressed to a minimum, interference can be prevented when a plurality of devices are used in parallel, and long-distance transmission can be realized.

Next, the light receiving means 20 will be described with reference to FIG. 2. Similar to the light emitting means 10, a pin photodiode (PD) 22 is disposed at or near the focal position of the parabolic reflector 21, and the parabolic reflector 21 is provided. 2
The light reflected by 1 is focused at or near the focal position and received by PD 22. Therefore, according to this receiving device, since it has narrow directivity, it is possible to greatly reduce the influence of interference light. It is not always necessary to focus the light with the parabolic reflector 21 as long as the PD 22 can secure a sufficient amount of light.

FIG. 3 shows an example of an optical radio apparatus in which the light emitting means 10 shown in FIG. 1 and the light receiving means 20 shown in FIG. 2 are integrated.
FIG. 3A shows another example of the optical wireless device shown in FIG. The optical wireless devices 40 and 40a shown in the respective drawings have the light emitting means 1 so that the optical axes are parallel to realize bidirectional transmission.
0, 10a and the light receiving means 20, 20a are integrated, and in the optical wireless device 40, the assembling is performed such that the optical axis of the parabolic reflector 11 for transmission and the optical axis of the parabolic reflector 21 for reception are parallel. Adjusted. In the optical wireless device 40a, the light axis of the parallel light that is output after the light emitted from the LED 11 of the light emitting unit 10a is converted by the light emitting lens 14 and the optical axis of the parallel light that enters the light receiving unit 20a Are adjusted at the time of assembly so that are parallel. In addition,
The parallel light entering the light receiving means 20a is focused on the PD 22 by the light receiving lens 24.

The transmitting / receiving sections 30, 30a in which the light emitting means 10, 10a and the light receiving means 20, 20a are integrated.
Is rotatable in a vertical direction by a driving means 31, and is rotatable in a horizontal direction by a driving means 32 provided in a table 33.

In order to perform optical wireless communication between such optical wireless devices 40, as shown in FIG. 4, the transmission signals transmitted from the respective light emitting means 10 are received by the light receiving means 20 so as to be received. It is necessary to operate the driving units 31 and 32 to perform optical axis alignment. And in this embodiment,
As shown in FIG. 5, an optical wireless device 41 having a corner cube 34 provided near the light receiving means 20 is used to facilitate optical axis alignment. The configuration other than the corner cube 34 is substantially the same as that of the optical wireless device 40 shown in FIG.

The corner cube 34 is shown in FIG.
As shown in (B), the mirror has a structure in which three mirrors are combined at an angle of 90 degrees, so that light incident from a certain range is reflected in the incident direction. When the reflection area is increased, the volume required for the configuration also increases. Therefore, an array of corner cubes 34 in which a number of small corner cubes are arranged is used. By providing the arrayed corner cubes 34 around the transmission / reception unit 30, search light emitted from the light emitting means 10 can be reflected in the incident direction from any position along the entire circumference in the horizontal direction. In addition, this array-shaped corner cube 3
By using translucent plastic corner cubes used for reflectors of bicycles as 4,
It can be realized at low cost.

Here, an array shape when the corner cube 34 made of plastic is used will be described. The reflectance of the plastic corner cube 34 was measured as shown in FIG. Specifically, while rotating the corner cube 34 made of plastic to change the reflection angle, the amount of light emitted from the LED and the amount of light received by the power meter were compared to determine the reflectance at each angle. The results are shown in the graph of FIG.

As shown in FIG. 8, since the reflectance decreases as the angle Θ increases, the plastic cube cube 34 is incident on the light incident on the reflection surface at an angle almost perpendicular to the reflection surface. It can be seen that there is no reflection. Therefore, when such a plastic corner cube 34 is used, it is preferable to prevent the non-reflection phenomenon in a specific direction by using an array on the side surface of a polygonal pyramid or a cylinder.

When the optical axes of the optical wireless devices 41 having such corner cubes 34 are aligned with each other, the light emitting means 10 emits search light having the same narrow directivity as that during communication while driving. By operating the means 31 and 32 and searching for the other optical wireless device 41,
As shown in FIG. 9, the light emitting means 1 of one optical wireless device 41
Even if the search light emitted from 0 is not incident on the light receiving means 20 of the other optical wireless device 41, the other optical wireless device 41
Since the search light is reflected by the corner cube 34 from the position where is present, it is possible to easily specify the position where the optical wireless device 41 of the partner is present.

When the optical axis is adjusted by using such a method, since the reflected light from the corner cube 34 is used, the communication distance is twice as long as that in the conventional case where communication is performed from both sides. Even if there is no attenuation due to the reflection of the cube 34, the amount of returning light is の of the case where the other party transmits. However, since the search is performed using the light beam having the same narrow directivity as in communication, it is possible to obtain a light amount substantially equal to that in the case of directly receiving the conventional search light having the wide directivity. Does not occur. In addition, when light emission is performed by an LED in high-frequency optical wireless communication such as 100 MHz, the light emission amount of the LED is reduced to a fraction of that in the case of several tens of MHz, but the oscillation frequency is reduced when the search light is emitted. Thus, it is possible to prevent a decrease in the amount of search light emitted.

Further, since the reflected light is used, it is necessary to determine the reflected light from the corner cube 34 of the communication partner and the reflected light from the obstacle. Here, the communication partner is specified using the pattern of the reflected light. For example, as shown in FIG. 15, when the driving means 31 and 32 are driven to search for a communication partner while emitting search light having a directional angle か ら from the light emitting unit 10 of an optical wireless device 41, a corner cube of the communication partner is determined. Assuming that the angle at which the search light is reflected from 34 is α, the level of the reflected light has a distribution as shown in FIG. 16, and the reflected light from the corner cube 34 of the communication partner is (2
Θ + α). In addition, corner cube 34
Reflects the incident light in the direction of incidence, whereas most ordinary objects diffusely reflect. Therefore, most obstacles can be removed by detecting the peak width and level of the reflected light, and it is possible to correctly determine the position of the communication partner by using the presence or absence of communication light only in special cases. it can.

Specifically, the pattern of the reflected light from the obstacle can be roughly classified into the following four patterns. 1) A large object at a short distance: peak width is 2θ + α
And can be excluded. 2) A large object at a long distance: Although the peak width may be approximately 2θ + α, the peak height is generally low due to poor reflectivity and can be excluded. 3) A small object at a short distance: the peak width may be approximately 2θ + α, and the height of the peak is also high (cannot be excluded). 4) A small object at a long distance: the peak width becomes smaller than approximately 2θ + α, and the peak height becomes lower, so that it can be excluded.

As described above, the patterns 1), 2) and 4) can be removed. The pattern 3) can be excluded by waiting for a while with the optical axis actually aligned and confirming that communication light from the other party cannot be received.

FIG. 11 shows an example of the light receiving characteristics of the light receiving means 20 when the driving means 31 and 32 are driven to search for a communication partner while emitting the search light from the light emitting means 10 of an optical wireless device 41. Suppose it was as shown. In the example of FIG. 11, since the peak a has a low light receiving level, the peak a is applicable to the pattern 2) and can be excluded. Peak b
Since the peak width is wide and the light receiving level is low, this applies to the pattern 1) above, and is considered to be not a communication partner.
On the other hand, the peak c has a peak width close to (2Θ + α) and has a high light receiving level. At this time, if the communication partner is also searching at the same time, the search light from the communication partner can be received within a certain time after the optical axis is directed to the peak c, so that the communication partner can move in the direction of the peak c. You can confirm that it is located. On the other hand, if the search light cannot be received within a certain period of time, it is determined that it is not the communication partner, and another peak is recognized as the communication partner or the search is performed again.

This optical axis adjusting method will be described with reference to FIG. 9. First, the transmitting / receiving section 3 of the optical wireless device 41 on the left side of FIG.
Scanning is performed by controlling the drive means 31 and 32 by a controller having a microcomputer (not shown) and swinging them in the horizontal and vertical directions. This scanning is the same as one-field scanning in television, for example, scanning horizontally from left to right with respect to the vertical section of the optical path, and then moving down one step vertically and scanning from left to right. Can be done in any way.

By this scanning, the optical wireless device 4 on the right side in FIG.
1 is detected by the receiving means 20 of the optical wireless device 41 on the left side of the figure while scanning the optical signal reflected and transmitted from the corner cube 34 provided in the transmission / reception unit 30 of FIG. The level detected by the level detector (not shown) is stored in the memory of the microcomputer using the scanning point as an address. After the scanning is completed, the microcomputer searches the scanning point at which the maximum level is obtained, and controls the driving units 31 and 32 so that the optical axis is aligned with the scanning point. In this manner, the optical axis alignment of the optical wireless device 41 on the left side in the figure is completed. Thereafter or simultaneously, the optical axis alignment can be performed in the optical wireless device 41 on the right side in the figure by performing the same operation as described above. In the case where the correction is intended, a good communication state can be maintained at all times by configuring to operate each time the power is turned on.

Next, FIG. 10 shows an example of a configuration required for optical axis alignment of the optical wireless device 41. In the figure, LED1 for search is used.
5 and the PD 25 are used, but the communication signal LED 12 and the PD 22 may be shared. In the figure, a microcomputer 56 is a controller that controls the entire optical axis alignment, and drives a pan motor (drive unit) 31 and a tilt motor (drive unit) 33 by a motor drive circuit 59 to move the transmission / reception unit 30 up, down, left, and right. Scanning (see FIG. 13). At the same time, a search signal is emitted from the LED 15 via the amplifier 58 from the search signal generation unit 57 and the four-divided PD 25
At the same time. The signal received by the four-divided PD 25 is amplified by an amplifier 52 at a portion of the light received by the PD 25 by a switch 51, extracted by a bandpass filter (BPF) 53, and converted into a DC voltage by a rectifier circuit 54. A / D converter 55 converts the digital signal into a digital signal and supplies the digital signal to the microcomputer 56 to store the light receiving level at each scanning position.

FIG. 11 is a flowchart illustrating the operation of the optical axis adjusting method. First, when the power of the optical wireless device 41 is turned on, the optical axis of the transmission / reception unit 30 is moved to the start position of the movable range in the horizontal and vertical directions, and the position is stored (step 61). While the light receiving level L
And a light receiving pattern table 75 in the microcomputer 56
(Step 62). When the detection of the light receiving level L in the horizontal direction of 360 degrees (one round) is completed (step 63)
→ Θh = 360), the angle in the vertical direction is increased by 5 degrees (step 64), and the light receiving level L for one round in the horizontal direction is detected again and stored in the light receiving pattern table 75 (step 65).
→ Step 62). When the angle in the vertical direction becomes 20 degrees (step 65 → Δv = 20), the value of the light receiving level L stored in the light receiving pattern table 75 is set to a value equal to or less than the threshold T to 0 to facilitate the light receiving pattern recognition. (Step 66), the light receiving pattern is recognized (Step 67).

Then, a specific light receiving pattern (for example, FIG. 1)
The location (@h, @v) indicating the 1st peak c) and its light receiving level L are separately stored (step 68), and the transmitting / receiving unit 30 is rotated to the storage position (step 69). At this time, since the communication partner is also performing the same search, if the search light cannot be received (step 70 → step 71), it waits for a predetermined time (step 71) and receives the search light within that time. If not possible (Step 7
2 → Step 69), the transmitting / receiving unit 30 is rotated to the next storage position (Step 69). By repeating this, if the search light from the communication partner can be received (step 70 or 72 → step 73), the optical axis is finely adjusted using the 4-split PD 73 (step 73), and the optical axis adjustment is performed. Is completed (step 74).

The four-divided PD 73 in step 73
The fine adjustment of the optical axis using is to finely adjust the light receiving spot when receiving the search light from the communication partner as shown in FIG. 14A as shown in FIG. This enables optimal optical wireless communication.

As described above, according to the optical axis adjusting method of the optical wireless device of the present invention, even when light having a narrow directivity is used, the light is reflected by the corner cube 34 during initial installation. The direction can be roughly adjusted, and by performing fine adjustment automatically, communication can be performed by adjusting the optical axis without human intervention.

[0039]

According to the optical wireless apparatus and the optical axis adjusting method of the present invention, the optical axis can be aligned without using any light emitting means for search for performing a wide area light emission and without any manual operation. effective.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a light emitting unit used in an optical wireless device of the present invention.

FIG. 2 is a configuration diagram illustrating an example of a light receiving unit used in the optical wireless device of the present invention.

FIG. 3 is a configuration diagram illustrating an example of an optical wireless device.

FIG. 4 is a configuration diagram illustrating an example of optical wireless communication between optical wireless devices.

FIG. 5 is a configuration diagram illustrating an optical wireless device according to an embodiment of the present invention.

FIG. 6 is a configuration diagram showing an example of a corner cube used in the optical wireless device of the present invention.

FIG. 7 is a diagram for explaining an example of measuring the reflectance of a corner cube used in the optical wireless device of the present invention.

FIG. 8 is a graph showing an example of the reflectance of a corner cube used in the optical wireless device of the present invention.

FIG. 9 is an explanatory diagram illustrating an example of optical axis alignment between optical wireless devices according to the present invention.

FIG. 10 is a configuration diagram for explaining an optical axis adjustment portion of the optical wireless device of the present invention.

FIG. 11 is a graph showing an example of a search light reception level.

FIG. 12 is a flowchart for explaining an optical axis adjusting method of the optical wireless device of the present invention.

FIG. 13 is a diagram for explaining an example of a rotation direction of the optical wireless device of the present invention.

FIG. 14 is a diagram for explaining an optical axis adjusting method of the optical wireless device of the present invention.

FIG. 15 is a diagram for explaining a directional angle of search light output from a light emitting unit of the optical wireless device of the present invention.

FIG. 16 is a graph showing the level of light reflected from a corner cube.

[Explanation of symbols]

 10, 10a Light emitting means 11, 21, Parabolic reflector 12, 15 LED (light emitting diode) 14 Light emitting lens 20, 20a Light receiving means 22, 25 PD (photodiode) 23 Reflecting mirror 24 Light receiving lens 30, 30a Transmitting and receiving unit 31, 32 Driving means 33 units 34 Corner cubes 40, 40a, 41 Optical wireless device

Claims (2)

[Claims] A light emitting means for outputting a narrow band light beam;
An optical wireless transmission unit having a driving unit for driving the light emitting unit with information to be transmitted, a light receiving unit for receiving signal light, and an information receiving unit for extracting reception information from a signal output from the light receiving unit An optical wireless receiving unit is integrated such that the optical axis of the beam light output from the light emitting unit and the optical axis of the signal light received by the light receiving unit are parallel to each other. An optical wireless device comprising a transmitting / receiving unit provided with a corner cube. 2. The transmission / reception unit of the first optical wireless device is provided with the second optical wireless device in order to perform optical wireless communication between the first optical wireless device and the second optical wireless device. An optical axis adjusting method for an optical wireless device for directing light in a direction, wherein the transmitting and receiving unit of the first optical wireless device includes: a light emitting unit that outputs a narrow band light beam; and the light emitting unit that outputs information to be transmitted. An optical wireless transmitting unit having a driving unit for driving the optical wireless receiving unit, a light receiving unit for receiving signal light, and an information wireless receiving unit having an information receiving unit for extracting received information from a signal output from the light receiving unit; The optical axis of the light beam output from the light emitting means and the optical axis of the signal light received by the light receiving means are integrated so as to be parallel to each other. Is provided, and the first The transmitting and receiving unit of the first optical wireless device is displaced while outputting the light beam from the light emitting unit of the optical wireless device, and the light receiving level of the light beam reflected by the corner cube of the second optical wireless device is changed to An optical axis adjustment method for an optical wireless device, comprising: performing optical axis alignment based on the optical axis.