JPH1174844A - Slave set for optical radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slave set for optical radio communication system by which the optical axis of a light emitting means whose directivity characteristic is extremely narrow is aligned with a light receiving section of a master set with high accuracy. SOLUTION: The system uses a master set 5 consisting of a light emitting section where pluralities of light emitting elements 9 are arranged in a ring and a light receiving section 12 provided in the inside of the section, and a slave set 7 sending and receiving an optical signal. The slave set 7 is provided with an optical incoming direction detection means 15, a light receiving means 16 and a light emitting means 17 whose center axis is aligned with each optical axis with narrow directivity and a turning mechanism 18 that turns them in a horizontal and a vertical plane. After the optical incoming direction detection means 15 decides an optical incoming direction, the optical axis is aligned to the light emitting element 9 of the light emitting element section with a highest luminous quantity based on an output of the light receiving means 16 and the optical axis is deviated by a prescribed deviation angle θ and in matching with the light receiving section 12 to establish a communication path by a control section. Thus, the optical axis of the light emitting means 17 with an extremely narrow directivity is aligned with that of the light receiving section 12 of the master set 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slave unit of an optical wireless communication system for transmitting and receiving optical signals through space.
In particular, the present invention relates to a slave unit that can accurately perform optical axis alignment.

[0002]

2. Description of the Related Art Generally, in order to smoothly transmit and receive information in a limited space such as in an intelligence building, an optical LAN (Local Area Net) is used.
work). In this optical LAN, information is transmitted using light such as infrared light. For example, an optical signal is transmitted between a parent device provided on a ceiling and a child device as a node at each desk or the like. The master unit provided on the ceiling is linked to another master unit.

As described above, when performing optical communication between two points in space, it is necessary to first align the optical axes of the light emitting element and the light receiving element between the two points. In particular, when invisible light such as infrared light is used for communication, the optical axis adjustment is limited to a relatively narrow allowable range within several tens of degrees. One has to rely on automatic adjustment by a light arrival direction detector equipped with a detector for knowing the arrival direction. 20 and 21 are known as an example of the conventional optical axis alignment.

[0004] Reference numeral 1 denotes a master unit provided on a ceiling 2, which incorporates a light emitting element and a light receiving element. The optical device 3 emits an optical signal 3 from the master unit 1 in all directions in a space within a certain area, that is, downward from the ceiling, and the optical signal 3 is detected by a light arrival direction detecting device 4 placed on a desk, for example. I do. Then, with respect to the light arrival direction obtained by the detection device 4,
The photodetector of the optical transmitting / receiving device attached to the detecting device 4 or provided integrally with the detecting device 4 is oriented.

[0005] The detection device 4 is designed to stop down the optical signal 3 with a lens or a reflecting mirror and to detect the optical signal 3 with a photodetector such as a phototransistor or a photodiode. Output only when the optical signal 3 matches the optical axis. Therefore, the range that can be detected in one scan is very narrow, and the opening angle is 10 degrees or less. For this reason, as shown in FIG.
While rotating by degrees, the angle of the optical axis is changed in the elevation direction each time the rotation is made, as shown in FIG. 20, and by repeating this several times, a detection peak point is obtained to obtain a detection peak point between the main unit 1 and the ceiling unit. The optical axes are aligned with each other.

[0006]

The reason why the detector 4 must be reciprocated several times in the elevation direction every time the detector 4 is rotated in order to detect the direction of arrival of light is as follows.
That is, the detecting device 4 has a light receiving element for detecting information and detecting the direction of arrival of light near one focal point of a lens or a reflecting mirror. The light receiving range for detecting information is suitable for reducing disturbance light. The smaller is better, but the wider is better for detecting the direction of arrival of light. Since it is generally not possible to satisfy both requirements with a single lens or a reflecting mirror, the detection range is narrowed here, giving priority to increasing the accuracy of information detection. By increasing the number of scans in space, the object of detecting the direction of arrival of light is achieved. However, in this case, the number of scans on the space increases as described above, and there is a problem that the search time becomes longer.

Another example of the apparatus is disclosed in Japanese Patent Application No. 6-11 / 1994.
As disclosed in Japanese Patent No. 3897, a light emitting element for signal transmission is provided in an outer ring shape as a master unit so as to surround a central light receiving unit, and a data signal and a pilot signal for direction search of a slave unit are emitted from the light emitting element. Some are made to do so. In this case, the light emitting unit and the light receiving unit of the slave unit have a very narrow directional characteristic in order to reduce the size and weight of the slave unit. For example, a laser beam having a diameter of about several mm is transmitted from the light emitting unit. Output as

In such a situation, the search operation of the slave unit functions to specify the position of the light emitting unit of the master unit where the pilot signal is emitted. As a result of the search, the optical axis of the transmission unit of the slave unit is changed. There is a problem that the laser light having a diameter of several mm emitted from the slave unit and not hitting the light receiving unit of the master unit but hitting the light emitting unit of the master unit. The present invention has been devised in view of the above problems and effectively solving them. SUMMARY OF THE INVENTION It is an object of the present invention to provide a slave unit of an optical wireless communication system capable of accurately aligning the optical axis of a light emitting unit having an extremely narrow directional characteristic with a student unit of a master unit.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a master unit comprising a light emitting unit in which a plurality of light emitting elements are arranged in a ring and a light receiving unit provided inside the light emitting unit. And a slave unit provided below the slave unit for transmitting / receiving an optical signal to / from the master unit, wherein the slave unit is used for coarse adjustment for determining the rough light arrival direction. Light arrival direction detecting means, light receiving means having a narrow directivity characteristic, light emitting means having a narrow directivity characteristic, the light arrival direction detecting means for coarse adjustment, the light receiving means, and the light emitting means in a horizontal plane and a vertical plane. After determining a rough light arrival direction based on the output of the turning mechanism for turning and the light arrival direction detecting means for the coarse adjustment, the light emission with the largest light emission amount among the light emitting units based on the output of the light receiving means Align the optical axis exactly with the element Is obtained by so and a by shifting the optical axis downward by a predetermined shift angle, control unit for establishing a communication path between said light emitting means and the light receiving portion.

[0010] Thereby, first, the slave unit determines the rough light arrival direction in which the master unit is located by rotating the light arrival direction detection means in the horizontal and vertical directions, and then,
By finely adjusting the optical axis of the slave unit based on the light receiving means having a narrow directional characteristic, the optical axis is accurately matched with the light emitting element closest to the light emitting unit of the master unit (the light emission amount is the largest for the slave unit). . When laser light is transmitted from the light emitting means of the slave unit in this state, the laser light hits the light emitting part of the master unit. Therefore, the optical axis of the slave unit is shifted downward by a predetermined shift angle, for example, to shift the optical axis of the master unit. Match with the light receiving part. Thus, the communication path can be established by accurately matching the optical axis of the light emitting means of the slave unit with the optical axis of the light receiving unit of the master unit. In this case, as the light receiving means of the slave unit, for example, a four-divided sensor in which four light receiving elements are arranged in a square shape can be used.

When the optical axis of the slave unit is shifted, for example, downward by a predetermined shift angle after aligning the optical axis with the light emitting element of the master unit which emits the most light, for example, The output may be shifted by an angle such that the output difference between the pair of light receiving elements arranged in the moving direction of the light spot becomes a predetermined value. Alternatively, a map of a shift angle determined from the relationship between the distance to the master unit and the elevation angle with respect to the master unit may be created in advance, and the shift angle may be determined based on the shift angle map. After the communication path with the master unit is established by shifting the optical axis of the slave unit, the output of only the light receiving element located in the direction in which the light spot has moved due to the shift (shift) of the optical axis receives the optical signal. By using the signal, the S / N can be improved.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an optical wireless communication system according to an embodiment of the present invention;
1 is a view showing an optical wireless communication system, FIG. 2 is a schematic plan view showing a master unit, FIG. 3 is a schematic sectional view showing a master unit, FIG. 4 is a block diagram showing a slave unit of the present invention, and FIG. FIG. 6 is a front view showing the turning mechanism, FIG. 6 is a side view showing the turning mechanism, FIG. 7 is a perspective view showing a main part of the slave unit, FIG.
10 is a top view of the main part of the slave unit, FIG. 10 is a perspective view showing the main part of the light arrival direction detecting means for coarse adjustment, and FIG.
It is a top view which shows a division | segmentation sensor.

In FIG. 1, reference numeral 5 denotes a master unit provided on a ceiling unit 2, which sends out an optical signal 3 in all directions below it, and receives an optical signal coming from below, as will be described later. I do. The master units 1 cover a predetermined area, and are arranged in large numbers on a ceiling (not shown). The slave unit 7 is arranged, for example, on a desk in a room, and detects the arrival direction of the optical signal 3 to transmit and receive the optical signal. A terminal 8 such as a personal computer is connected to the slave unit 7, and data can be transmitted between the slave unit 7 and another terminal (not shown) via the slave unit 7 and the master unit 5. And constitute an optical LAN as a whole.

First, the master unit 5 will be described. The master unit 5 has a plurality of, in the illustrated example, 16 light emitting diodes (LE).
D) a light emitting unit 10 in which light emitting elements 9 such as
And a light receiving section 12 formed by arranging a plurality of, in the illustrated example, four, phototransistors or the like in a certain area inside the light receiving elements 11. The numbers of the light emitting elements 9 and the light receiving elements 11 are not limited thereto. Each of the light emitting elements 9 emits an optical signal 3 modulated by data, and has a directional characteristic such that the optical signal 3 spreads and propagates in a certain range obliquely downward from the center. I have. Immediately inside the light emitting element 9, an umbrella-shaped reflecting plate 13 that is inclined downward so as to spread outward from the center is provided.
The corresponding optical signal 3 is reflected downward. Further, the reflection plate 13 functions as a partition for preventing the light signal 3 from the light emitting element 9 from being incident on the light receiving element 11.

The light receiving section 12 is provided with a substantially hemispherical transmission / scattering film 14 so as to cover the light receiving element 11. When the transmission light 47 is applied to the transmission / scattering film 14, the light is scattered while being transmitted inward as shown in FIG. 2, and the light is efficiently captured by the light receiving element 11.

Next, the slave unit 7 will be described. As shown in FIG. 4, the slave unit 7 includes a coarse-adjustment light arrival direction detecting means 15 for determining a rough light arrival direction, a light receiving means 16 having a narrow directional characteristic, and a light emitting means 17 having a narrow directional characteristic. A turning mechanism 18 (see FIG. 1) for turning each of the means 15, 16 and 17 in a horizontal plane and a vertical plane, and a control unit 19 composed of, for example, a microcomputer for controlling the operation of the slave unit 7 are mainly used. Is configured. The coarse-adjustment light arrival direction detecting means 15 has a pair of coarse-adjustment light receiving elements 35A and 35B provided to be inclined upward by 45 degrees in directions different from each other by 180 degrees.
Light can be introduced into the 35B through a slit as described later. Then, the light receiving elements 35A, 3
By turning 5B in a horizontal plane, a rough azimuth from which an optical signal arrives is detected. The light receiving means 16 includes a condensing lens 39 for condensing the optical signal 3 and four fine-adjustment light receiving elements A, B, C, and D arranged in a quadrilateral sensor 3.
6. The light emitting means 17 includes a semiconductor laser element 37 for emitting a modulated laser beam and the light transmitting lens 3 for condensing the laser beam on a laser beam having a diameter of about 1 mm.
Eight.

Although each of the above-mentioned means is shown in a separated state for the sake of explanation, in practice, it will be described in detail later.
Optical units 20 (see FIG. 5).
In addition, the central axis of the light arrival direction detecting means 15 for coarse adjustment is aligned with the optical axes of the light receiving means 16 and the light emitting means 17. In the present invention, first, the control unit 19 comprises the light arrival direction detecting means 15 and the light receiving means 16 for coarse adjustment.
The optical axis is aligned with the light emitting element 9 having the largest light amount of the master unit 5 by using the fine-adjustment four-divided sensor 36, and then the optical axis of the slave unit 7 is shifted downward by a predetermined shift θ (see FIG. 1). Operate to shift. As a result, the optical axis can be accurately aligned with the approximate center of the light receiving section 12 of the master unit 5.

Next, referring to FIG. 5 and FIG.
8 will be described. The turning mechanism 18 has a turning base 21 for mounting and fixing the optical unit 20 thereon. At both ends of the base 21, support shafts 22, 22 are provided.
Two columns 24, 24, which are provided upright, are rotatably supported in a vertical plane via bearings 25, 25. A ring-shaped vertical gear 26 forming a worm wheel is fixed to one of the support shafts 22, 22. The vertical gear 26 has a vertical worm gear 27 rotatably supported on the horizontal rotating table 23 side. Are meshed. The rotation shaft of a vertical drive motor 28 composed of, for example, a step motor is connected to the vertical worm gear 27 directly or indirectly via a speed reducer or the like.
The vertical worm gear 27 can be rotated.
Therefore, by rotating the worm gear 27,
The swivel base 21 can be rotated or swung up and down in a vertical plane.

On the other hand, the lower surface of the horizontal turntable 23 is fixedly mounted on the upper end of a turning column 29.
Is rotatably supported by a base 30 via a bearing 31 so that the horizontal turntable 23 can be rotated in a horizontal plane. A circular gear 32 forming a worm wheel is fixed in the middle of the turning column 29, and a worm gear 33 rotatably supported on the base 30 side meshes with the gear 32. The rotation shaft of a horizontal drive motor 34 composed of, for example, a step motor is directly or indirectly connected to the worm gear 33 via a speed reducer or the like, so that the worm gear 33 can rotate.

With the above structure, the turning base 21 turns in a vertical plane by driving the vertical drive motor 28,
Further, by driving the horizontal drive motor 34, the horizontal turntable 23 rotates in a horizontal plane, and as a result, the turning base 2
1 turns in a horizontal plane. Note that both motors 2
Needless to say, by providing a counter for counting the number of pulses, an encoder, or the like, the amount of rotation, the position of rotation, and the like can be detected.

Next, an optical unit 20 in which the light arrival direction detecting means 15, the light receiving means 16, and the light emitting means 17 for coarse adjustment are integrally connected will be described with reference to FIGS.
The light receiving means 16 of the optical unit 20 includes a double reflection type condensing lens 39 made of, for example, a resin having an upper surface serving as a light receiving surface 40 that is substantially horizontal and a lower surface formed into a curved surface having, for example, an arc-shaped cross section.
(See FIG. 4). The lower surface of the condensing lens 39 having an arc-shaped cross section is formed as a concave first reflecting surface 41 by coating the reflecting film in a ring shape. The central part of the upper surface of the condensing lens 39 is formed with a plane part 42 having a planar cross section, and the surface of the plane part 42 is coated with a reflection film to form a plane second reflection surface 43. Make up.

The double reflection type condenser lens 39
Immediately below the central portion of the lower surface of the device, fine-adjustment light-receiving elements A, B,
A four-divided sensor 36 (see FIG. 4) composed of C and D is arranged. Accordingly, the first and second reflecting surfaces 41 and 43 are coaxially opposed to each other, and the respective curvatures are such that the optical signal 3 incident from the light receiving surface 40 as shown in FIG. , Are sequentially reflected by the first and second reflecting surfaces 41 and 43 and then condensed on the four-divided sensor 36. The diameter of this condenser lens 39 is 2-3 c.
m, so that the optical system has a relatively narrow directivity. This double reflection type condenser lens 39
Is mounted and fixed on the revolving base 21 with the light receiving surface 40 as the upper surface and the support frame 44 and screws.

Further, from the support frame 44, four support arms 45 extend above the central axis (optical axis) of the condenser lens 39, and the tip of each arm 45 holds the element mounting base 46. I support it. And, this element mounting base 46
As the light emitting means 17, for example, a semiconductor laser element 37
And a light transmitting lens 3 for converging laser light emitted from the light into a light beam having a diameter of about 1 mm and emitting the light as transmission light 47.
8 (see FIG. 4). In this case, the element mounting base 46 is provided coaxially with the first and second reflection surfaces 41 and 43 to minimize the loss of an incoming optical signal.

The double reflection type condenser lens 39
A pair of slit-shaped notches 48, 48 having a predetermined thickness are formed along the diametric direction, and a pair of the coarse-adjustment light arrival direction detecting means 15 described with reference to FIG. The light receiving elements 35A and 35B are arranged to be back to back. The light receiving elements 35A and 35B for the coarse adjustment detect a rough light arrival direction.

FIG. 10 is a diagram showing the arrangement of the coarse adjustment light receiving elements 35A and 35B of the coarse adjustment light arrival direction detecting means. The detecting means 15 has two slits 50 formed on the vertical rotation center 49 toward the opposite sides.
A, 50B, and these slits 50A, 5B
OB is formed, for example, by joining a plastic plate member 51 having a substantially square shape, as if one upper end portion has been cut away, by the width of the slit, and joining the bottom surface and the inner central portion side. Two plate-like members 51 are used to form one slit. Therefore, four slits 50A and 50B are used here to form a single slit.

The slits 50A, 50B
At the bottom or back, the inclination angle with respect to the horizontal direction is approximately 4
A pair of light receiving elements 35A and 35B for coarse adjustment are provided that are oriented 180 degrees in opposite directions so as to be 5 degrees. In this case, when the corresponding slits 50A and 50B are viewed from the respective elements 35A and 35B, the divergence angle in the vertical direction, or the elevation angle in this case, is set to be approximately 90 degrees. A space in a region extending in the vertical direction with a width of can be seen through a slit. These elements 35A and 35B are composed of a phototransistor, a photodiode and the like. The member thus configured is inserted into the notches 48, 48.

On the other hand, as shown in FIG. 11, the four-division sensor 36 comprises fine adjustment light receiving elements A, B, C, and D, and a pair of light receiving elements on any one of the diagonal lines, for example, the light receiving elements B and D. The difference between the outputs is obtained by the comparator 52, and this output is used as a horizontal rotation signal S1 for rotating the horizontal drive motor 34. On the other hand, the difference between the outputs of the light receiving elements A and C is obtained by the comparator 53, and this output is used as a vertical rotation signal S2 for rotating the vertical drive motor 28. Then, two light receiving elements A arranged in a direction orthogonal to the extending direction of the support shaft 22 (see FIGS. 5 and 6),
The output of C is introduced into the selection unit 54, and the output of one of the elements is changed by the instruction from the control unit 19 to the reception signal S3.
Used as Here, the arrangement direction of the pair of elements B and D is the extending direction of the support shaft 22.

Next, the operation of the slave unit configured as described above will be described. First, as shown in FIGS. 2 and 3, a large number of light emitting elements 9 arranged in an annular shape of the light emitting section 10 of the base unit 5 provided on the ceiling 2 cover a certain area obliquely downward. The optical signal 3 is emitted with such directivity. As shown in FIG. 1, among the many light-emitting elements 9, the light-emitting element having the largest light quantity for the slave unit 7, that is, the light-receiving signal level being the maximum is the element located closest to the slave unit 7. When the communication path securing operation of the slave unit 7 is started, first, the control unit 19 (see FIG. 4) firstly performs the fine adjustment light receiving elements A to of the four-division sensor 36 of the light arrival direction detecting means 15 and the light receiving means 16 for coarse adjustment. The optical axis of the master unit 5 is
The light receiving signal level is directed to the maximum. In FIG. 1, the optical axis 60 is the optical axis at which the light receiving signal level is maximum, and the direction of the light emitting element 9 closest to the slave unit 7 among the many light emitting elements of the master unit 5 is the optical axis direction.

Next, the control unit 19 shifts the optical axis of the slave unit 7 downward by a predetermined slight shift angle θ to shift the optical axis.
The optical axis of the slave unit 7 is positioned substantially at the center of the light receiving unit 12 of the master unit 5 as viewed from the slave unit 7. In FIG. 1, an optical axis 61 is an optical axis that coincides with substantially the center of the light receiving unit 12 as viewed from the slave unit 7. Then, a communication path is established along the optical axis 61. The reason that the optical axis of the slave unit 7 is shifted downward from the optical axis 61 by the predetermined shift angle θ in this manner is that if the optical axis of the slave unit 7 is
When a communication path is established in a state where the transmission path coincides with 0, the transmission light from the slave unit 7 is a laser beam having a very narrow directivity of about 1 mm in diameter. This is because it may hit the element 9 and make communication impossible. In this case, since the diameter of the light receiving unit 12 is usually about 10 cm, the shift angle is about several degrees depending on the installation location of the slave unit 7.

The above operation will be specifically described. First, in order to roughly detect the light arrival direction, the horizontal turntable 23 of the turning mechanism 18 shown in FIGS. 5 and 6 is driven to rotate the optical unit 20 in a horizontal plane by 180 degrees. At this time, the pair of light receiving elements 3 for coarse adjustment of the light arrival direction detecting means 15 for coarse adjustment is used.
The outputs of 5A and 35B are monitored, and the horizontal turntable 23 is stopped at the azimuth at which the reception level becomes the highest. At this time, the elevation angle of the master unit 5 is still unknown. Next, the turning base 21 is gradually turned in the vertical plane to tilt the turning base 21. At this time, the inclination of the turning base 21 is stopped when the outputs of the coarse adjustment light receiving elements 35A and 35B become the same. At this point, the light emitting element 9 having the highest light receiving signal level is substantially located on the extension of the vertical rotation center 49 shown in FIG.

As a result, a rough light arrival direction (including an elevation angle) is determined. Here, slits 50A, 5
The resolution of the light arrival direction detecting means 15 including the light receiving elements 35A and 35B (see FIG. 10) is not so high.
The control is switched to the control based on the output of No. 6. That is, as shown in FIG. 1 or FIG. 11, the optical signal 3 from the light emitting element 9 closest to the slave unit 7 is condensed by the condensing lens 39 of the light receiving means 16 to form the light spot 62 on the four-division sensor 36. The turning mechanism 18 is finely adjusted so that the light spot 62 is located at the center of the four-divided sensor 36. Thereby, the optical axis of the optical unit 20 of the slave unit 7 (see FIG. 5) is
This means that the light-receiving element 9 is accurately directed to the light-emitting element 9 having the maximum light-receiving signal level. The optical axis of the optical unit 20 at this time coincides with the optical axis 60 in FIG.

Next, the vertical drive motor 28 of the turning mechanism 18
Is mainly driven to move the optical axis of the optical unit 20 downward by a predetermined shift angle θ so that the optical axis is positioned substantially at the center of the light receiving unit 12 of the master unit 5 as viewed from the slave unit 7. In this state, a communication path is established. The optical axis of the optical unit 20 at this time coincides with the optical axis 61 in FIG. FIG. 12 is a diagram schematically showing the movement of the optical axis of the slave unit 7 with respect to the master unit at this time. Here, the radius R1 of the light receiving unit 12 of the master unit 5 is 85 m.
m. The opening angle when the light receiving section 12 is viewed from the slave unit 7 is represented as α1, and the angle difference between the optical axis 61 and the optical axis 60, which is the center, becomes the shift angle θ. Further, the optical axis of the optical unit 20 is changed from the optical axis 60 to the optical axis 61.
The state of movement of the light spot 62 on the four-division sensor 36 when the light spot 62 is shifted to is shown in FIG. 13, and moves from the light spot 62 shown by a solid line to the light spot 62 shown by a broken line. In the illustrated example, the light spot 62 moves from the center of the four-divided sensor 36 toward the light receiving element B. At this time, needless to say, the optical axis is finely adjusted so that the output difference between the light receiving elements B and C becomes zero.

The change in the output of the light receiving elements A and C at this time is shown in FIG. 14. When the optical axis is shifted, the output of the light receiving element A gradually decreases. The output gradually increases. When the shift of the shift angle θ is completed, the driving of the turning mechanism 18 is stopped, and the communication path is established. Thereafter, the optical axis is constantly controlled so as to maintain this state. As described above, if the communication path is established, the reception signal of the optical signal 3 from the master unit 5 is not an addition of the reception signals of the light receiving elements A to D of the four-split sensor 3 but an optical signal. Only the output of the light receiving element in the direction in which the spot 62 has moved, in FIG. 13, only the output of the light receiving element C is used as the received signal. Thereby, S of the received signal is
/ N can be improved. The switching of the output of the reception signal is performed by the selection unit 54 according to a command from the control unit 19 as shown in FIG.

The reason is that the received signals of the light receiving elements A to D contain uncorrelated noise, and when these signals are simply added, the sum signal becomes as shown by a curve 63 in FIG. Increase and the S / N decreases. On the other hand, if only the output signal of the light receiving element in the direction in which the light spot 62 is moved is used as the reception signal, the noise component is reduced to 理論 theoretically, and the gain of the output signal can be improved by about 6 dB. it can. As described above, according to the present invention, it is possible to quickly and accurately align the optical axis of the light emitting unit of the slave unit having an extremely narrow directivity.

The above series of operations will be described generally with reference to the flowchart shown in FIG. First, when the communication path establishment operation is started, the optical unit 20 (see FIG. 5) is horizontally turned, and at this time, a pair of light receiving elements 35A and 35B for coarse adjustment of the light arrival direction detecting means 15 for coarse adjustment (see FIG. 4) is monitored (S1), and the optical unit 20 is oriented to the direction in which the amount of light is maximum (S2). next,
The optical unit 20 is turned in the vertical plane, and the turning is stopped at the position where the outputs of the light receiving elements 35A and 35B for coarse adjustment at this time become the same. Thereby, the optical unit 20
Is substantially directed to the light-emitting element closest to the slave unit 7 among the many light-emitting elements 9 of the master unit 7, and it is possible to determine a rough light arrival direction (S3).

Next, a signal serving as a reference for control is converted from the output signals of the light receiving elements 35A and 35B for coarse adjustment to the four-divided sensor 3
6 based on the output of each of the light receiving elements A to D of the four-divided sensor 36, the light spot 62 (FIG. 1).
3) is finely adjusted so that the turning mechanism 18 is positioned at the center of the four-division sensor 36, and the optical axis is aligned with high accuracy (S4). Next, the optical axis of the optical unit 20 is shifted downward by a predetermined shift angle θ, and the optical axis is positioned substantially at the center of the light receiving section 12 of the master unit 5 as viewed from the slave unit 7 (S5).

When the shifting is completed, a communication path is established (S6). If the communication path is established, the output signal of only the light receiving element located in the direction in which the light spot 62 has moved is used as a reception signal to improve the S / N (S7). In the above embodiment, the optical unit 20
When the optical axis is shifted downward by the predetermined shift angle θ, the control is performed by the number of pulses of the step motor. However, the shift angle θ may be less than 1 degree, and the accuracy is degraded due to play or play of the motor or the like. In some cases, the optical axis does not hit the light receiving unit 10 of the master unit 5. Therefore, in order to prevent this, as shown in FIGS. 13 and 14, the output difference between the two light receiving elements arranged in the moving direction of the light spot 62, here, the two light receiving elements A and C has a predetermined value. What is necessary is just to shift an optical axis so that it may become. That is, the difference between the light receiving elements A and C is obtained by the comparator 53 in FIG. 11, and the light spot 62 is shifted until the absolute value becomes a predetermined value 64 in FIG. According to this, control can be performed in a closed loop, and the optical axis of the optical unit 20 can be made to coincide with the light receiving section 12 of the master unit with higher accuracy.

The control flow at this time will be described generally with reference to FIG. The nodes in FIG. 16 correspond to those in FIG.
Corresponding to the middle node. First, S4 shown in FIG.
When the high-precision optical axis alignment is completed in step (2), the optical axis of the optical unit 20 is gradually shifted downward (S2).
1) At the same time, an output difference between the light receiving elements A and C in the moving direction of the light spot 62 is obtained (S22). The shift of the optical axis is continued until the output difference reaches a predetermined value 64 (see FIG. 14) (NO in S23). If the output difference reaches a predetermined value (YES in S23), the optical axis is shifted. The shifting is stopped (S24). The subsequent control moves to S6 in FIG.
According to this, the optical axis of the optical unit 20 is surely aligned with the master unit 5.
Can be directed to the light receiving section 12.

As a control method at the time of shifting the optical axis,
A map of the shift angle θ may be determined in advance, and an appropriate shift angle θ may be selected from this map. That is,
As shown in FIG. 17, the optimum shift angle changes according to the position of the child device with respect to the parent device 5. In the figure, the position ~ indicates the position of the slave unit, and the position ~ indicates that the elevation angle with respect to the base unit 5 is 90.
Degree, position ~ has an elevation angle of 31 degrees, position ~ has an elevation angle of 1
The case of 5 degrees is shown. Further, the position, is located at the same horizontal level, for example, 1 m away from the ceiling 2, and the position,
Are at the same horizontal level, for example, 1.5 m from the ceiling 2
Remote, location, is at the same horizontal level, for example, 2 m from ceiling 2. And each position ~
Then, an optimum shift angle θ as shown in FIG. 12 is obtained, and a map of the shift angle θ is created. An example of such a shift angle map is shown in Table 1.

[0040]

[Table 1]

Incidentally, the opening angle α1 of the light receiving section in Table 1 is shown for reference, and is not required during the actual operation. As is clear from Table 1, even when the elevation angle of the slave unit 7 with respect to the master unit 5 is the same, as the distance from the master unit 5 increases, the optimum shift angle θ gradually decreases. Is less than once. When selecting the shift angle θ, the position can be specified if the elevation angle and the distance to the master unit 5 are known. The elevation angle with respect to the base unit 5 can be determined by, for example, the amount of rotation of the vertical drive motor 28, and the distance to the base unit 5 is reduced by a quadruple sensor because the amount of received light decreases in inverse proportion to the square of the distance. It can be obtained by recognizing 36 light receiving levels.

FIG. 18 shows a configuration diagram of the embodiment at this time. In addition to the configuration shown in FIG. 4, a shift angle storage unit 6 such as a ROM for storing a map of the shift angle θ shown in Table 1 above.
A distance determination unit 67 is provided for determining the distance to the base unit 5 based on the outputs of the 6 and 4 split sensors 36. According to this, the optimum shift angle θ can be obtained from the shift angle storage unit 66 based on the output of the distance determination unit 67 and the elevation angle obtained by the encoder or the like of the vertical drive motor 28. For example, as a result of the above determination, if it is determined that the slave unit 7 is located at the position, the shift angle θ is 0.4 degrees, and the optical axis of the optical unit 20 is shifted downward by this angle.

The number of positions mapped in Table 1 is as follows:
Here, only an example is shown.
Can be increased or decreased in accordance with the magnitude of the directional angle of. Also, as the shift angle θ decreases, the mapping density increases,
That is, the control of higher accuracy may be performed by reducing the increment of the elevation angle. Further, in the case where a slave unit exists between the positions in Table 1, the values before and after may be determined, for example, proportionally to determine the shift angle θ.

The above operation will be described generally with reference to the flowchart shown in FIG. In the figure, nodes,
Corresponds to the node in FIG. First, FIG.
If the highly accurate optical axis alignment is completed in S4 shown in (4), the distance determination unit 67 obtains the distance to the parent device 5 with reference to the light receiving level of the four-divided sensor (S31). next,
An elevation angle of the vertical drive motor 28 with respect to the parent machine 5 is obtained from an encoder or the like (S32). Next, an optimum shift angle θ is obtained from the shift angle storage unit 66 based on the obtained distance and elevation angle (S33). Then, the optical axis of the optical unit 20 is shifted downward by the calculated shift angle (S34). The subsequent control moves to S6 in FIG. According to this, the optimum shift angle θ according to the position of the slave unit 7 with respect to the master unit 5 can be determined, and the optical axis of the optical unit 20 of the slave unit can be more accurately set to the light receiving unit 12 of the master unit. Can be matched.
Here, the configuration of the optical LAN has been described as an example, but the present invention is not limited to this, and the present invention can be applied to various optical wireless communication systems.

[0045]

As described above, according to the slave of the optical wireless communication system of the present invention, the following excellent operation and effect can be exhibited. According to the invention defined in claim 1, after the optical axis is aligned with the light emitting element of the master unit, the optical axis is shifted downward, for example, by a predetermined shift angle, so that the directivity is extremely narrow. The optical axis of the light emitting means of the machine can be accurately directed to the light receiving section of the master machine. Further, when the optical axis is shifted by a predetermined shift angle, the output difference of the light receiving elements arranged in the moving direction of the light spot of the quadrant sensor used as the light receiving means is shifted until the output difference becomes a predetermined value. Thus, the optical axis of the light emitting means of the slave unit can be more accurately directed to the light receiving unit of the master unit.

Further, a map of an optimum shift angle corresponding to the position of the slave unit with respect to the master unit is stored in advance, and an optimum shift angle is obtained from this map to perform control. Can be more accurately directed to the light receiving section of the master unit. In addition, the S / N can be improved by using the output signal of the light receiving element located in the direction in which the light spot has moved as the reception signal. Further, since the data optical signal from the master unit can be used as the pilot signal, it is not necessary to use a light emitting element for the pilot signal in the master unit.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an optical wireless communication system.

FIG. 2 is a schematic plan view showing a master unit.

FIG. 3 is a schematic sectional view showing a master unit.

FIG. 4 is a block diagram showing a slave unit of the present invention.

FIG. 5 is a front view showing a turning mechanism.

FIG. 6 is a side view showing a turning mechanism.

FIG. 7 is a perspective view showing a main part of the slave unit.

FIG. 8 is a sectional view of a main part of the slave unit.

FIG. 9 is a top view of a main part of the master unit.

FIG. 10 is a perspective view showing a main part of a light arrival direction detecting means for coarse adjustment.

FIG. 11 is a plan view showing a four-divided sensor of the light receiving means.

FIG. 12 is a diagram schematically showing movement of the optical axis of the slave unit.

FIG. 13 is a diagram showing a state of movement of a light spot on a four-division sensor.

FIG. 14 is a diagram illustrating an output state of some light receiving elements of the four-divided sensor.

FIG. 15 is a flowchart showing an example of the operation of the present invention.

FIG. 16 is a flowchart showing another example of the operation of the present invention.

FIG. 17 is a diagram showing an aspect of a position of a child device with respect to a parent device.

FIG. 18 is a block diagram showing another configuration of the present invention.

FIG. 19 is a flowchart showing yet another example of the operation of the present invention.

FIG. 20 is a diagram showing a relationship between a parent device and a conventional light arrival direction detection device.

21 is a diagram showing a scanning method of the detection device shown in FIG.

[Explanation of symbols]

3: optical signal, 5: master unit, 7: slave unit, 9: light emitting element of master unit, 10: light emitting unit, 11: light receiving element, 12: light receiving unit, 1
5 ... Light arrival direction detecting means for coarse adjustment, 16 ... Light receiving means, 1
7 ... Light emitting means, 18 ... Swing mechanism, 19 ... Control unit, 20 ...
Optical unit, 35 ... Light receiving element for coarse adjustment of slave unit, 36 ...
4-split sensor, 47: transmission light, 62: light spot, 66
... Shift angle storage unit, 67 ... Distance determination unit, A, B, C, D
... Light receiving element for fine adjustment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 33/00 // H01Q 3/08

Claims (5)

[Claims] A master unit comprising: a light emitting unit in which a plurality of light emitting elements are arranged in a ring; and a light receiving unit provided inside the light emitting unit;
In an optical wireless communication system using a slave unit that transmits and receives an optical signal to and from the master unit, the slave unit includes a light arrival direction detection unit that detects a rough light arrival direction of an optical signal,
The central axis of the light arrival direction detecting means coincides with each optical axis, and the light receiving means and the light emitting means having narrow directivity characteristics. The light arrival direction detecting means, the light receiving means, and the light emitting means are arranged in a horizontal plane and a vertical plane. After determining a rough light arrival direction of an optical signal based on an output of the light arrival direction detection means, a turning mechanism for turning the light into the light emission unit having the largest light emission amount based on an output of the light reception means. A control unit for establishing a communication path between the light receiving unit and the light emitting unit by aligning the optical axis with the element, and thereafter adjusting the optical axis by a predetermined shift angle to match the light receiving unit. A slave unit of the optical wireless communication system, characterized in that: 2. The handset of an optical wireless communication system according to claim 1, wherein said light receiving means comprises a four-divided sensor in which four light receiving elements are arranged in a square shape. 3. The apparatus according to claim 2, wherein the predetermined shift angle is an angle such that an output difference between the pair of light receiving elements becomes a predetermined value when the optical axis of the slave unit is shifted. Slave unit of the optical wireless communication system. 4. A shift angle determining unit for obtaining a distance to the master unit from an output of the light receiving means, and a shift angle storing a shift angle map corresponding to an elevation angle with respect to the master unit and a distance to the master unit in advance. 4. The slave unit of the optical wireless communication system according to claim 2, further comprising a storage unit, wherein a shift angle is obtained from the shift angle storage unit based on an output of the distance determination unit and the elevation angle. 5. After the communication path is established, an output of only the light receiving element located in a direction in which a light spot moves when the optical axis is shifted is used as a reception signal of an optical signal. A slave unit of the optical wireless communication system according to claim 2.