JP2008053849A - Optical wireless communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-way optical wireless communication device which tracks a light beam again by temporarily increasing the angle of projection of the light beam to be projected by a simple mechanism which need not have high-level position precision when a light beam to be received deviates from the optical wireless communiation device. <P>SOLUTION: The optical wireless communication device 1 includes: a receiving means of receiving a light beam from an opposite station; a transmitting means of transmitting a light beam to the opposite station; and a tracking means of controlling the direction of optical systems of the receiving means and transmitting means by detecting the position of the light beam from the opposite station. A parallel flat plate 18 which is transparent and has a larger refractive index than air, is disposed to be put in and off an optical path between a light source 10 for light beam transmission of the transmitting means and an optical lens 13 converging the light from the light source, and the transmitting means is increased in angle of projection of the light beam projected from an optical lens 11 for projection and reception when the parallel flat plate 18 is put in the optical axis. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical wireless communication apparatus that performs bidirectional optical wireless communication via a space.

  When communicating between two-way optical wireless communication devices equipped with a transmission / reception function over a long distance, transmit the light beam as a beam close to parallel light while suppressing the spread of the light beam so that the power efficiency of the light beam does not decrease. Is made. In that case, since the width of the light beam is narrow, if the position or angle of one of the optical wireless communication devices changes due to some factor, a situation occurs in which the optical beams transmitted to each other are separated from the optical wireless communication device of the counterpart station. It becomes easy. In order to prevent such a situation, an apparatus having a tracking mechanism that controls the direction of the optical system of the transmitting / receiving means in the optical wireless communication apparatus in accordance with the light beam from the optical wireless communication apparatus of the counterpart station has been developed. Yes.

On the other hand, means for widening the projection angle of the light beam to be transmitted has been developed as necessary so that the light beam to be transmitted does not deviate from the optical wireless communication apparatus of the counterpart station. In the invention described in Patent Document 1, an optical lens for condensing light from a light source for transmitting a light beam (corresponding to the optical lens 13 in FIG. 1) is moved along the optical axis, whereby optical wireless communication is performed. The angle of the light beam projected from the communication device is widened.
Japanese Patent Laid-Open No. 5-134207

By the way, even if the optical wireless communication apparatus includes the tracking mechanism as described above, when the position or angle of one of the optical wireless communication apparatuses changes drastically or when the tracking mechanism malfunctions, After all, the mutual light beams are separated from the optical wireless communication apparatus of the counterpart station. Therefore, in order to enable tracking again, it is conceivable to increase the projection angle of the light beam projected to the optical wireless communication apparatus of the counterpart station. However, at that time, as in the invention of Patent Document 1, in the means for moving the optical lens that collects the light from the light source along the optical axis, the optical lens is moved along with the movement in the optical axis direction. In addition to the axial direction, a slight misalignment occurs. In this case, even if the positional deviation is about several μm to 10 μm, for example, the optical path of the light beam projected from the optical wireless communication apparatus is greatly affected. Further, in order to obtain a precise moving device that does not cause such a positional shift, the manufacturing cost increases.
The present invention has been made to solve the above-described problem. When a light beam to be received is separated from the optical wireless communication apparatus, the light is projected by a simple mechanism that does not require high positional accuracy. It is an object of the present invention to provide a bidirectional optical wireless communication apparatus capable of temporarily expanding the light beam projection angle and enabling tracking of the light beam again.

  In order to achieve such an object, an optical wireless communication apparatus of the present invention is an optical wireless communication apparatus that performs bidirectional optical wireless communication through a space, and that receives a light beam from a counterpart station And a transmission means for transmitting the light beam to the counterpart station, and a tracking means for controlling the direction of the optical system in the reception means and the transmission means by detecting the position of the light beam from the counterpart station. A parallel plate that is transparent to the light from the light source and has a higher refractive index than air is inserted into and removed from the optical path between the light source for transmitting the light beam and the optical lens that collects the light from the light source. The transmission means is an optical system that expands the light projection angle of the light beam projected from the light projecting / receiving optical lens when a parallel plate is inserted into the optical path. It is characterized by The

  According to this apparatus, by detecting the position of the light beam from the counterpart station, bidirectional optical wireless communication can be performed through the space while performing the tracking operation for controlling the direction of the optical system. When the mutual light beams are separated from the optical wireless communication apparatus of the counterpart station and cannot be tracked, the optical path between the light source for transmitting the light beam in the transmitting means and the optical lens for collecting the light from the light source On the other hand, by inserting a parallel plate that is transparent to the light from the light source and has a refractive index greater than that of air, a simple mechanism that does not require a high degree of positional accuracy, and that the projected light beam The projection angle of the light beam projected from the light projecting / receiving optical lens can be expanded without causing any deviation in the optical path. Therefore, the optical beam is detected by the optical wireless communication apparatus of the other station, and tracking can be performed again. After that, by separating the parallel plate from the optical path between the light source and the optical lens that collects the light from the light source, the projection angle of the light beam projected from the light projecting / receiving optical lens is expanded. It is possible to return to a light projection state with excellent power efficiency.

  In addition, when the parallel plate is configured so that one parallel plate can be moved back and forth, the parallel plate can be easily moved forward and backward when it is arranged to be able to be inserted and removed from the optical path. With this configuration, it is possible to change the light projection angle of the light beam in two stages when the parallel plate is inserted and when the parallel plate is detached.

  Further, the parallel plate is composed of a plurality of parallel plates having different refractive indexes or thicknesses, and each of them is selectively disposed so as to be able to be inserted into and removed from the optical path. In this case, the spread of the projection angle of the light beam when the parallel plate is inserted can be selected in a predetermined multistage.

  The apparatus of the present invention is an optical wireless communication apparatus that performs two-way optical wireless communication through a space, and includes a receiving unit that receives a light beam from a partner station and a transmission that transmits the light beam to the partner station. And a tracking means for controlling the direction of the optical system in the receiving means and the transmitting means by detecting the position of the light beam from the counterpart station, and collecting light from the light beam transmitting light source in the transmitting means. The optical lens that illuminates consists of a plurality of lenses, and is transparent to the light from the light source and has a refractive index higher than that of air with respect to the optical path between the lenses and the light beam in that part is not a parallel beam. A large parallel plate is arranged so that it can be inserted and removed, and the transmitting means expands the projection angle of the light beam projected from the light projecting / receiving optical lens when the parallel plate is inserted into the optical path. Optical system And characterized in that it is.

  According to this apparatus, by detecting the position of the light beam from the counterpart station, bidirectional optical wireless communication can be performed through the space while performing the tracking operation for controlling the direction of the optical system. When the mutual light beams are separated from the optical wireless communication apparatus of the counterpart station and cannot be tracked, between the plurality of lenses for condensing the light from the light source for light beam transmission in the transmission means, and By inserting a parallel plate that is transparent to the light from the light source and has a refractive index greater than that of air into the optical path where the light beam of that part is not a parallel beam, a simple mechanism that does not require a high degree of positional accuracy is used. In addition, the projection angle of the light beam projected from the light projecting / receiving optical lens can be expanded without causing a deviation in the optical path of the projected light beam. Therefore, the optical beam is detected by the optical wireless communication apparatus of the other station, and tracking can be performed again. After that, by removing the parallel plate from the optical path, it is possible to suppress the spread of the light projection angle of the light beam projected from the light projecting / receiving optical lens and to return to the light projection state with excellent power efficiency. it can. In this apparatus, even if it is difficult to arrange the parallel plate at a position close to the light source, the parallel plate can be arranged at an appropriate position in the lens group that collects light from the light source.

  According to the present invention, when the light beam to be received deviates from the optical wireless communication apparatus, the light projection angle of the light beam to be projected is temporarily expanded by a simple mechanism that does not require high positional accuracy. Thus, it is possible to provide a bidirectional optical wireless communication apparatus capable of tracking the light beam again.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an optical wireless communication apparatus according to the present invention will be described in detail with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted. FIG. 1 is a conceptual diagram showing the overall configuration of an optical wireless communication apparatus according to an embodiment of the present invention. The movable base 2 in the optical wireless communication apparatus 1 is provided with an optical system for transmission and reception inside, and the control means 3 is driven to rotate up and down so that the optical system can track the light beam from the counterpart station. The direction can be automatically adjusted by means 4 and horizontal rotation drive means 5. In the tracking operation of the movable base 2, the control means 3 drives and controls the vertical rotation driving means 4 and the horizontal rotation driving means 5 in accordance with a signal from the position detector 8 that detects the position of the light beam from the counterpart station. Made in Note that the vertical rotation of the movable base 2 by the vertical rotation drive means 4 is shown in FIG. 1 in order to avoid complication of the drawing. However, the center of the vertical rotation is not limited to the end side of the movable base 2 and is preferably approximately the center in the longitudinal direction of the movable base 2 from the viewpoint of force balance and space efficiency. . Similarly, the horizontal rotation driving means 5 enables the movable base 2 to rotate as indicated by an arrow b in the horizontal direction at a substantially central portion in the longitudinal direction.

  The optical system in the receiving means includes a light projecting / receiving optical lens 11, an optical lens 12, a beam splitter 16, a beam splitter 17, and an optical lens 14. The received light A from the partner station received by the light projecting / receiving optical lens 11 passes through the optical lens 12 and the beam splitters 16 and 17 and is condensed on the signal receiver 9 by the optical lens 14. Then, the reception signal from the signal receiver 9 is sent to the transmission / reception circuit 7. A part of the received light A is reflected by the beam splitter 17 and is condensed on the position detector 8 by the optical lens 15. The position detector 8 is constituted by, for example, a sensor such as a four-division photodiode, and transmits the collected position signal of the received light A to the control unit 3 so that the optical axis of the light projecting / receiving optical lens 11 is received. The tracking operation of the movable base 2 is performed so as to coincide with the optical path center of the light A.

  The optical system in the transmission means includes a light projecting / receiving optical lens 11, an optical lens 12, a beam splitter 16, and an optical lens 13 that condenses light from the light source 10. The light source 10 is configured by a laser diode or the like that generates light modulated by a transmission signal from the transmission / reception circuit 7. The light beam condensed by the optical lens 13 and made almost parallel is reflected by the beam splitter 16, passes through the optical lens 12, and is transmitted from the light projecting / receiving optical lens 11 as transmission light B to the optical wireless communication apparatus of the counterpart station. Sent to.

  Note that when performing bidirectional communication, the wavelengths of the transmitted light and the received light can be made different. In this case, the beam splitter 16 reflects the light beam having the wavelength of the transmitted light, and the light having the wavelength of the received light is reflected. By using a dichroic mirror that transmits the beam, transmission light and reception light can be separated. Also, the polarization of the transmission light and the reception light can be made different. In this case, a polarization beam splitter (PBS) that reflects the polarization beam of the transmission light and transmits the polarization beam of the reception light is used as the beam splitter 16. By doing so, transmission light and reception light can be separated.

  In the present embodiment, the light path between the light source 10 and the optical lens 13 that collects the light from the light source 10 is transparent to the light from the light source 10, that is, the light can be transmitted, and the refractive index. A parallel plate 18 having a larger diameter than that of air is disposed so as to be inserted and removed. The parallel plate 18 is, for example, a glass plate, but is not limited to a glass plate as long as it is a parallel plate that transmits light from the light source 10 and has a refractive index larger than that of air. The parallel plate 18 can be advanced and retracted by parallel plate insertion means 6 including an actuator 61 that is electromagnetically driven, for example. The parallel plate insertion means 6 is controlled by the control means 3 when the position detector 8 does not detect the position of the received light A from the counterpart station and the tracking operation cannot be performed. It is inserted into the optical path between the light source 10 and the optical lens 13. In this case, the light beam is projected from the light projecting / receiving optical lens 11 through a path as indicated by a broken line after the parallel plate 18 by the same action as the position of the light source 10 is brought closer to the optical lens 13. The light beam becomes the transmission light C having a projection angle larger than that of the transmission light B in a state where the parallel plate 18 is not inserted.

  Here, the parallel plate 18 does not have an optical axis like a lens, and the degree of light collection does not change depending on the position along the optical path. Therefore, the parallel plate 18 is disposed substantially perpendicular to the optical axis of the optical lens 13. Therefore, even if the position control is not performed accurately in the direction perpendicular to the optical axis or in the optical axis direction, the optical path of the transmission light is not deviated (varied). Then, the projection angle of the transmission light C projected from the light projecting / receiving lens 11 is expanded by a predetermined amount determined by the thickness and refractive index of the parallel plate 18.

  Next, the operation of the optical wireless communication apparatus of this embodiment will be described with reference to FIGS. FIG. 2 is a conceptual diagram in a case where the optical wireless communication apparatus 1 of FIG. FIG. 2 (1) shows that the optical base station 1-1, the optical wireless communication apparatus 1-2 of the local station, and the optical wireless communication apparatus 1-2 of the other station detect the light beams transmitted from the other party to detect the movable bases 2-1, 2. 2 shows normal two-way communication in which a tracking operation for driving and controlling -2 is possible. In this case, the light beams A and B that are projected to each other are prevented from spreading in a state that is substantially close to parallel light so that the power efficiency does not decrease. In FIG. 1, the received light A received by the light projecting / receiving optical lens 11 is collected by the signal receiver 9, and the received signal is sent to the transmission / reception circuit 7, while the transmission signal is transmitted as a light beam from the light source 10. The light is condensed by the optical lens 13 and transmitted as the transmission light B from the light projecting / receiving optical lens 11. Further, a part of the received light A is condensed on the position detector 8 to detect the position, and based on this, the control means 3 drives the up / down rotation driving means 4 and the horizontal rotation means 5 to move. A tracking operation is performed on the received light of the optical system in the transmission / reception means arranged in the base 2.

  However, as shown in FIG. 2 (2), when the direction and position of the movable base 2-2 of one optical wireless communication device 1-2 change greatly, both the light beams A and B are narrow, The positions of the other party's transmission lights cannot be detected, and tracking is impossible. Therefore, in FIG. 1, when the position detector 8 cannot detect the position of the received light to be received, the control means 3 drives the parallel plate insertion means 6 so that the parallel plate 18 is replaced with the light source 10 and the optical lens 13. Insert into the light path between. As a result, the light beam projected from the light projecting / receiving optical lens 11 has a wider light projection angle like the transmission light C. As shown in FIG. 2 (3), the optical wireless communication apparatus 1-2 of the counterpart station can detect the transmission light C by the expanded transmission light C transmitted from the optical wireless communication apparatus 1-1. By the tracking function, the movable base 2-2 rotates, and it becomes possible to detect and track each other light beam again. In this case, the optical wireless communication device 1-2 of the counterpart station does not necessarily need to include the parallel plate 18 and the parallel plate insertion means 6. However, when both optical wireless communication devices are provided, in either device Needless to say, the transmission light can be expanded. When the tracking function is restored, the control plate 3 causes the parallel plate insertion unit 6 to remove the parallel plate 18 from the optical path between the light source 10 and the optical lens 13, thereby again transmitting the transmitted light to a power efficient beam. A narrow transmission light B is assumed.

  As described above, in the present embodiment, the optical lens is obtained by a simple mechanism that simply inserts the parallel plate 18 into the optical path between the light source 10 and the optical lens 13 that collects light from the light source 10 so as to be able to advance and retract. When the received light cannot be detected without requiring accurate alignment in the direction perpendicular to the optical axis 13 or in the optical axis direction, the projection angle of the transmitted light can be expanded.

  In the present embodiment, the number of the parallel plate 18 is one, and it is advanced and retracted by the actuator 61 of the parallel plate insertion means 6, but it may be multi-stage as shown in FIGS. FIG. 3 is a conceptual diagram showing a vertical cross section when the parallel plate inserting means 6 is constituted by the rotary motor M and the rotary disc 63, and FIG. 4 is a IV-IV cross sectional view thereof. In the rotating disc 63, a plurality of parallel flat plates 18-1 to 18-7 having different refractive indexes or thicknesses and a window portion 64 having no parallel flat plate are arranged along the circumference. In the case of this apparatus, when the control means 3 controls the rotational position of the motor 62 so that the window 64 is positioned in the optical path where the light from the light source 10 is collected by the optical lens 13, FIG. As shown by the transmitted light B, the light beam is projected as a narrow-width light beam. When the position detector 8 cannot detect the light received from the other station, the rotary motor 62 is driven so that the parallel plate 18-1 is positioned in the optical path. For example, the thickness or refractive index of the parallel plate 18 can be set so that the projection angle of the transmission light sequentially increases from 18-1 to 18-7. Then, for example, depending on the parallel plate 18-1, if the tracking function is not recovered, the parallel plate 18-2 is sequentially placed in the optical path, such as the parallel plate 18-2, and if not, the parallel plate 18-3. By performing control that is positioned, the tracking function can be restored by expanding the projection angle of the transmitted light according to the deviation of the light beam from the partner station without expanding the transmitted light too much from the beginning. Can do.

  Further, in the present embodiment, the parallel plate 18 is disposed so as to be insertable between the light source 10 and the optical lens 13 that condenses the light. However, as shown in FIG. When comprised by 13-1, 13-2, the parallel plate 18 can also be arrange | positioned so that insertion is possible among those lenses. Similarly, as shown in FIG. 6, the optical lens 13 is composed of a plurality of lenses 13-1, 13-2, and 13-3, and a parallel plate 18 is disposed so as to be insertable at one place between these lenses. You can also Since the parallel plate 18 is inserted, even if it is arranged in the parallel light beam portion, the projection angle of the transmitted light cannot be changed, but the light beam is expanded as shown in FIGS. If the optical system shown in FIG. 1 is arranged so that it can be inserted into the portion to be inserted, the projection angle of the transmitted light can be expanded. If the optical system in the transmission means is changed as appropriate, the transmission light from the light projecting / receiving optical lens 11 can be transmitted by inserting the parallel plate 18 into the optical path where the light beam between the lenses constituting the optical lens 13 is reduced. It can also be enlarged. Further, the parallel plate 18 and the parallel plate insertion means 6 shown in FIGS. 5 and 6 may be those shown in FIGS. As described above, when the parallel plate 18 is arranged so as to be inserted between the lenses constituting the optical lens 13, even if it is difficult to arrange the parallel plate 18 at a position close to the light source 10, the parallel plate 18 can be inserted by inserting the parallel plate. The projection angle of the transmitted light can be expanded.

It is a conceptual diagram which shows the structure of the optical wireless communication apparatus 1 of embodiment of this invention. It is a conceptual diagram which shows the bidirectional | two-way communication of the optical wireless communication apparatus 1 in embodiment of this invention. It is explanatory drawing which shows another form of the parallel plate 18 and the parallel plate insertion means 6 in this invention. It is IV-IV sectional drawing in FIG. It is explanatory drawing which shows another form about arrangement | positioning of the parallel plate 18 in this invention. It is explanatory drawing which shows another form about arrangement | positioning of the parallel plate 18 in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical wireless communication apparatus, 2 ... Movable base | substrate, 3 ... Control means, 4 ... Vertical rotation drive means, 5 ... Horizontal rotation drive means, 6 ... Parallel plate insertion means, 7 ... Transmission / reception circuit, 8 ... Position detector , 9 signal receiver, 10 light source, 11 light projecting / receiving optical lens, 12 optical lens, 13 optical lens, 14 optical lens, 15 optical lens, 16 beam splitter, 17 beam splitter, 18 ... Parallel plate, A ... Received light, B ... Transmitted light (when no parallel plate is inserted), C ... Transmitted light (when a parallel plate is inserted)

Claims (4)

An optical wireless communication device that performs bidirectional optical wireless communication through a space,
Receiving means for receiving the light beam from the other station;
A transmission means for transmitting a light beam to a partner station;
A tracking unit that controls the direction of the optical system in the receiving unit and the transmitting unit by detecting the position of the light beam from the counterpart station;
A parallel plate that is transparent to the light from the light source and has a refractive index larger than that of air with respect to the optical path between the light source for transmitting the light beam in the transmission means and the optical lens that collects the light from the light source. Placed so that it can be inserted and removed,
The transmitting means is an optical system that expands a light projection angle of a light beam projected from a light projecting / receiving optical lens when the parallel plate is inserted into the optical path. Optical wireless communication device.   The optical wireless communication apparatus according to claim 1, wherein the parallel plate is configured such that a single parallel plate can be moved forward and backward, so that the parallel plate can be inserted into and removed from the optical path.   The parallel plate is composed of a plurality of parallel plates having different refractive indexes or thicknesses, and each of the parallel plates is selectively disposed so as to be inserted into and removed from the optical path. The optical wireless communication apparatus according to claim 1. An optical wireless communication device that performs bidirectional optical wireless communication through a space,
Receiving means for receiving the light beam from the other station;
A transmission means for transmitting a light beam to a partner station;
A tracking unit that controls the direction of the optical system in the receiving unit and the transmitting unit by detecting the position of the light beam from the counterpart station;
The optical lens for condensing the light from the light source for transmitting the light beam in the transmission means is composed of a plurality of lenses, and the light beam between the lenses and the light beam of the portion is not a parallel beam, A parallel plate that is transparent to the light from the light source and has a refractive index larger than that of air is arranged so that it can be inserted and removed,
The transmitting means is an optical system that expands a light projection angle of a light beam projected from a light projecting / receiving optical lens when the parallel plate is inserted into the optical path. Optical wireless communication device.

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