JP3022425B2 - Transmission / reception optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / reception optical device of an optical wireless communication device using light as communication means.

[0002]

2. Description of the Related Art In recent years, an indoor wireless LAN (local area network) has been developed by using an optical wireless communication device that performs wireless transmission using light.
Network) have been put to practical use. FIG. 4 shows a general example of a LAN system using an optical wireless communication device. A master station 512 that transmits and receives light to and from a plurality of slave stations 511 is attached to a ceiling 516, and the master station 512
Data is transmitted between the wired LA installed on the ceiling 517.
This is performed by an N cable 518. Since the communication between the master station 512 and the plurality of slave stations 511 is performed by light, in order to perform reliable light reception at all the slave stations 511, the transmitted light from the master station 512 is effective for receiving the entire room 513 as much as possible. It is necessary to satisfy with the light quantity of the level or more. In other words, it is necessary to emit light of sufficient power from the main station 512 in all directions of the room 513, which requires a large amount of power.
Light not received by the slave station becomes stray light and causes noise in the light receiving element.

As a method for solving these problems, Japanese Patent Application No. 8-251454 proposes a configuration in which a flat optical beam is radiated from a main station 512 in the horizontal direction as shown in FIG. In the drawing, A indicates the flow of the light beam from the master station to the slave station, and B indicates the flow of the light beam from the slave station to the master station. The flat light beam emitted in the horizontal direction from the master station 512 is guided to the slave station 511 by the reflecting mirror 519. According to this configuration, since it is not always necessary to spread light throughout the room, the required optical power is greatly reduced. This is also effective in that the amount of stray light is significantly reduced.

In such a configuration in which optical communication is performed using a flat light beam, a light receiving section having a flat visual field corresponding to the light beam is provided. As shown in FIG.
The 12 light receiving units include a cylindrical lens 601 and a photodetector 602. Since the cylindrical lens 601 does not have a light condensing power in the horizontal direction, it is necessary to use a light detector 602 that is elongated in the horizontal direction so as to maintain a light receiving sensitivity while having a wide field of view in a horizontal plane. In the vertical direction, since the cylindrical lens has a light condensing power, the photodetector may be a narrow one having a minimum necessary narrow visual field. In this way, the reception field of view is expanded horizontally into a flat plate shape.

[0005] Such a condensing system is not limited to the case using the cylindrical lens described above, and may be configured as a reflection optical system. In this case, too, as in the case of using the cylindrical lens, an elongated light detecting system is used. It is necessary to use a vessel.

Although a light emitting diode or a laser diode is used as a light emitting element for transmission, the light emitting element is not necessarily required to be elongated like the photodetector 602. If the light emitting element has a required divergence angle as a transmission light beam, a flat light beam can be projected on a horizontal plane by disposing the light emitting element such that the spreading direction is horizontal. As described above, regarding the transmission system, since the spread angle of the light emitting element can be used as it is, there is no need to use a cylindrical lens, and one element that is not as long as the photodetector 402 may be provided in the center.

[0007]

In the prior art, as a first problem, an elongated photodetector required for receiving a flat light beam using a cylindrical lens or the like is used for high-speed data communication. It is difficult to use and expensive. That is, this photodetector has a drawback in that it has a large shape due to its elongated shape, has a large light receiving area and a junction capacitance, and cannot respond to a high-speed signal. Further, the photodetector has a large light-receiving area and a special shape, and is generally inexpensive because of poor versatility and limited demand.

As a second problem, in an optical system using a cylindrical lens or the like, there is a limit in providing a wide-angle view in the horizontal direction. Specifically, in an optical system such as a cylindrical lens or the like, the viewing angle is limited to about 120 degrees even if it is in principle wide, and the sensitivity is greatly reduced at the end of the viewing field. Therefore, in order to obtain a 360-degree field of view, it is necessary to provide a plurality of receiving units in parallel and make the respective fields of view have a total of 360 degrees, which makes the apparatus expensive and complicated.

It is an object of the present invention to provide a single transmitting / receiving section for 360
An object of the present invention is to provide a transmission / reception optical device for a main station of an optical wireless communication device which is capable of emitting and receiving a flat plate-shaped light beam, has a simple configuration, and is low in cost.

[0010]

SUMMARY OF THE INVENTION A transmitting and receiving optical device according to the present invention comprises an optical transmitter for transmitting a substantially parallel light beam and an optical receiver coaxially arranged with the optical transmitter. A transmitting / receiving unit, and a reflecting conical portion disposed on an extension of the central axis of the transmitting / receiving unit and having an outer peripheral surface serving as a reflecting surface, wherein the central axis of the conical portion coincides with the central axis of the transmitting / receiving unit. And the angle between the generatrix of the conical portion and the central axis is substantially 45 degrees.

[0011] According to this, a single plate-shaped light beam can be emitted in a direction of 360 degrees, and a flat reception field of 360 degrees is provided, so that it is possible to reduce the size and weight with a simple structure. It is. Further, since a large number of light emitting elements are not required and a circuit for coupling a large number of transmission / reception optical units is not required, power consumption can be reduced.

[0012] The generatrix of the conical portion may be curved.

Further, a configuration may be provided in which a flat reflecting portion provided outside the transmitting / receiving portion and the conical portion and having a reflecting surface parallel to the central axis is provided.

The plane reflecting portion may be an orthogonal plane mirror having an intersection line parallel to the central axis.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the transmission / reception optical device of the present invention comprises an optical transmitter 104 and an optical receiver 1 arranged coaxially.
And a reflecting cone 102 arranged so that the central axis of the transmitting / receiving unit 101 coincides with that of the transmitting / receiving unit 101.
And a holding mechanism 103 for holding these. The reflecting cone 102 has an angle θ between the central axis a and the generating line b of 45 degrees (the vertex angle 2θ of the cone is 90 degrees), and the outer peripheral surface of the cone is a reflecting mirror surface. The optical receiver 105 of the transmission / reception unit 101 includes the lens 106 and the photodetector 1
07. The optical transmitter 104 of the transmitting / receiving unit 101 includes a light emitting element 111 such as a light emitting diode and a lens 112. The holding mechanism 103 includes a substrate 108 and a transparent cylinder 109, and the substrate 108 is fixed to a ceiling 114. In the present embodiment, the substrate 109
The reflection cone 102 is held inside a transparent cylinder 108 attached to the transparent cylinder 108, and the optical receiver 105 is accommodated in a transmitting / receiving unit frame 110 attached below the transparent cylinder 108. Further, the optical transmitter 104 is accommodated in an inner cylinder 113 embedded in the lens 106 of the optical receiver 105. The lenses 106 and 112, the light emitting element 111, and the photodetector 107 all have the same central axis, and are denoted by a in the drawings.

Next, transmission and reception of light in this embodiment will be described. Regarding transmission, the signal light emitted from the light emitting element 111 becomes a substantially parallel light beam by the lens 112, and this light beam is reflected by the reflecting cone 102, and is perpendicular to the central axis of the cone 102. Direction 3
It is emitted evenly over the entire circumference of 60 degrees. In this way, the signal light is converted into a flat beam and emitted. If the flat beam needs to have a slight divergence angle, the necessary divergence angle may be given to the light beam transmitted from the optical transmitter 104 in advance.

The optical receiver 105 of this transmission / reception optical device has:
Lens 10 substantially perpendicular to the central axis of reflective cone 102
6, and a photodetector 107 is disposed at the focal position of the lens 106. The reception field of view of the photodetector 107 lies in a plane substantially perpendicular to the central axis of the reflection cone 102. Then, light incident from the outside is reflected by the reflecting conical portion 102, travels downward in the drawing toward the lens 106, is condensed by the lens 106, and enters the photodetector 107. The divergence angle required for the reception field of view can be obtained by appropriately setting the focal length of the lens 106 and the size of the photodetector 107 in advance.

As described above, the transmission / reception optical device of the present embodiment has a simple configuration, is low in cost, and can transmit and receive a flat light beam over the entire 360-degree circumference. It is very effective to use this transmission / reception optical device as the main station of a LAN system as shown in FIG. In this case, the slave station can use the same one as the conventional one, and the divergence angle of the transmission light beam is as small as several degrees, and the reception viewing angle is also small enough to match. It may have a photodetector.

In the present embodiment, as shown in FIG. 1, the reflecting cone 102 having a downward apex angle is located above the apparatus. However, the reflecting cone 102 is turned upside down so that the apex angle is upward. It is also possible to adopt a configuration in which 102 is located below the apparatus. In this case, the transmitting / receiving unit 101 is provided with the reflecting cone 102.
Is provided at the tip of the apex angle. The angle θ formed between the center axis a of the reflecting cone 102 and the generatrix b is 45 degrees, but an error of about ± 0.1 degrees is allowed. Furthermore, in the present embodiment, the generating line b of the reflecting conical portion 102 is a straight line, but may be a curved line. By making the outer peripheral surface of the conical portion 102 bulge, it becomes possible to increase the flat plate-like reception viewing angle and the transmission beam divergence angle.

The transmitting / receiving section 101 of this embodiment has a configuration in which an optical transmitter 104 is coaxially arranged at the center and an optical receiver 105 is coaxially arranged at the outer side. However, this is an example, and conversely, the optical receiver 104 is arranged at the center. Obviously, the configuration of the transmission / reception unit 101 in which the optical transmitter 104 is disposed on the outside can be adopted.

In the present embodiment, the lenses 112 and 106 are used as light collecting means of the optical transmitter 104 and the light receiver 105. However, a reflecting mirror can be used as the light collecting means.

Japanese Patent Application Laid-Open No. 5-332822 discloses a wide-angle condenser lens having a conical anti-slope surface, which collects incident light from a hemispherical space in front of a photodetector. For the purpose of light, a conical anti-sloping surface is formed as a part of the wide-angle lens, and the wide-angle lens is an essential component. The present invention, which has only a light receiving field within a plane perpendicular to the central axis a of the reflecting conical portion 102 and does not have a wide-angle lens, is completely different from JP-A-5-332822 in terms of the function and effect.

A second embodiment of the present invention is shown in FIG. In this embodiment, in addition to the transmitting / receiving optical device main body 201 having the same configuration as that of the first embodiment (see FIG. 1), the transmitting / receiving optical device main body 20 is brought as close as possible to this.
1 is a configuration in which a plane reflecting portion (plane mirror) 202 having a reflecting surface (mirror surface) 202a parallel to the central axis is provided. When the transmission / reception optical device of the present embodiment is installed near a wall in a room where optical wireless communication is performed and used as a master station of a LAN system, communication with a slave station farther than the transmission / reception optical device of the first embodiment becomes possible. Become.

Further, a third embodiment of the present invention is shown in FIG. This embodiment uses an orthogonal plane mirror 302 as a plane reflection section. This direct light plane mirror 302
Is arranged so that the intersection line is parallel to the central axis of the transmission / reception optical unit main unit 301, and is installed at a corner in a room where optical wireless communication is performed and is used as a main station of a LAN system. It is possible to extend the communication distance with the slave station.

[0026]

According to the transmitting / receiving optical device of the present invention, the reflecting cone is arranged so that the central axis coincides with the transmitting / receiving section comprising the optical transmitter and the optical receiver arranged coaxially. A flat light beam can be transmitted over 360 degrees in a plane perpendicular to the axis, and a reception field of view can be provided over 360 degrees in this plane, so that it can be easily used as a main station of a LAN system using an optical wireless device. Transmission and reception optics can be made. Moreover, the structure is simple and the cost can be kept low.

When the generatrix of the conical portion is formed in a curved shape, it is possible to enlarge the flat plate-like reception viewing angle and the transmission beam divergence angle by making the outer peripheral surface of the conical portion bulge.

Further, when a flat reflecting portion having a reflecting surface parallel to the central axis thereof is provided outside the transmitting / receiving portion and the conical portion, the optical wireless communication distance can be extended. Further, when the plane reflecting portion is formed of an orthogonal plane mirror having an intersection line parallel to the central axis, the optical wireless communication distance can be further lengthened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a first embodiment of a transmission / reception optical device of the present invention.

FIG. 2 is a perspective view showing a second embodiment of the transmitting and receiving optical device of the present invention.

FIG. 3 is a perspective view showing a third embodiment of the transmitting and receiving optical device of the present invention.

FIG. 4 is a schematic diagram of an entire LAN system using conventional optical wireless communication.

FIG. 5 is a schematic diagram of another overall LAN system using conventional optical wireless communication.

FIG. 6 is a perspective view showing a light receiving section of a conventional transmission / reception optical device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 101 transmitting / receiving section 102 reflecting cone section 103 holding mechanism 104 optical transmitter 105 optical receiver 106, 112 lens 107 photodetector 108 substrate 109 transparent cylinder 110 transmitting / receiving section frame 111 light emitting element 201, 301 transmitting / receiving optical apparatus main body section 202 plane mirror (Plane reflection part) 202a Reflection surface (mirror surface) 302 Orthogonal plane mirror (plane reflection part) a Central axis b Generating line θ Angle between the generating line of the conical part and the central axis

Continuation of the front page (56) References JP-A-9-230281 (JP, A) JP-A-7-283790 (JP, A) JP-A-5-347591 (JP, A) JP-A-5-252115 (JP) JP-A-62-110743 (JP, A) JP-A-10-98434 (JP, A) JP-A-6-58636 (JP, U) (58) Fields studied (Int. Cl. ⁷ , DB Name) H04B 10/00

Claims (4)

(57) [Claims] 1. A transmitting / receiving unit comprising an optical transmitter for transmitting a substantially parallel light beam, an optical receiver coaxially arranged with the optical transmitter, and an extension of a central axis of the transmitting / receiving unit. A reflection cone portion disposed and having an outer peripheral surface serving as a reflection surface, wherein a central axis of the cone portion coincides with a central axis of the transmission / reception portion, and a generatrix of the cone portion and the central axis. A transmission / reception optical device whose angle is substantially 45 degrees. 2. The transmitting and receiving optical device according to claim 1, wherein a generating line of the conical portion is curved. 3. The transmission / reception optical device according to claim 1, further comprising a plane reflection portion provided outside the transmission / reception portion and the conical portion and having a reflection surface parallel to the central axis. 4. The transmission / reception optical device according to claim 3, wherein said plane reflecting portion is formed of an orthogonal plane mirror having an intersection line parallel to said central axis.