JP2005026929A - Optical radio transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical radio transmitter in which the optical axis of an optical signal being transmitted from a transmitter with a relatively narrow exit angle can be directed toward a receiver easily while ensuring a reliable data transmission path. <P>SOLUTION: A receiver 16 calculates the error rate of a first optical signal being transmitted from a transmitter 1 with a relatively narrow exit angle and transmits error rate information by a second optical signal. The transmitter aligns the optical axis such that the second optical signal is received by a plurality of optical receiving means capable of receiving the optical signal at a level dependent on the direction of the receiver and the level difference is eliminated, and then aligns the optical axis to reduce the error rate based on the error rate information. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical wireless transmission apparatus that performs optical wireless transmission with an optical axis of an optical signal having a relatively narrow emission angle transmitted from a transmitter directed toward a receiver.
[0002]
[Prior art]
Conventionally, there is an optical wireless transmission technology that performs spatial transmission of information using light. In general, infrared light is used for the optical wireless transmission, and a semiconductor light emitting element such as a light emitting diode or a laser diode is used as the light emitting element. In such optical wireless transmission, when it is desired to provide a sufficient distance between transmission and reception, it is necessary to narrow the output angle of the light beam emitted from the transmission device sharply, that is, to narrow it so that a signal with a sufficient light level is incident on the reception device side. Therefore, the optical axes of the transmission device and the reception device must be aligned. Therefore, alignment of the optical axis of the optical wireless transmission apparatus is a very troublesome operation because a light beam having a narrow emission angle is used or infrared light whose light beam is invisible is used. Therefore, conventionally, there has been proposed an optical wireless transmission apparatus that can easily perform this optical axis alignment.
[0003]
As an example, Patent Document 1 below discloses that the visible light from the transmission device is focused on the same optical axis as the signal transmission infrared light or parallel optical axis and sent together to the reception device side. An optical wireless transmission device is disclosed in which an operator adjusts the optical axis of a transmission device while observing visible light reflected by the visible light reflection means and being applied to the provided visible light reflection means. As another technique, an optical sight transmitter is installed in the transmitter and the optical axis is adjusted while looking at the sight, or a measuring device for detecting the received light level is connected to the receiver side. There is also an optical wireless transmission device that performs optical axis alignment in one set. In addition, as disclosed in Patent Document 2 below, there is a type that uses a light source for adjusting the optical axis on the receiver side to fold back the reception level information of the transmitted light from the transmitter and adjust the optical axis accordingly. .
[0004]
[Patent Document 1]
JP-A-62-110339
[Patent Document 2]
JP-A-7-131422
[0005]
[Problems to be solved by the invention]
However, the optical wireless transmission device as disclosed in the above-described Patent Document 1 requires a configuration that causes the transmission device to generate visible light used for purposes other than optical wireless transmission. In addition, when it is desired to keep a sufficient distance between the transmitting and receiving devices, the visible light emission output must be made sufficiently large, and it is necessary to add the configuration, thereby increasing the cost of the transmitting device. In addition, the device becomes large. This is the same when a sighting machine is installed in the transmission device.
[0006]
Further, it is necessary to strictly match the optical axis of visible light, the aim of the sighting device, and the optical axis of infrared light for signal transmission. In addition, even when the measurement device for detecting the received light level is connected to the receiving device and the measurement is performed by one person, there are disadvantages such as the need to prepare the measured device for detecting the received light level and the need for manpower. As described above, when the conventional optical wireless transmission device attempts to simplify the optical axis alignment, the cost of the transmission / reception device increases and the size of the transmission / reception device increases. Conversely, the cost of the transmission / reception device decreases and the size of the transmission / reception device decreases. As a result, there is a drawback that it takes time and effort to align the optical axis.
[0007]
In Patent Document 2, the above-described problem is solved. However, a single light receiving device in which transmission light as a pilot signal from an optical axis adjusting optical transmission element attached to a receiver is mounted on a transmitter. Light is received by the element, and the optical axis is adjusted based only on the received light level and the reception level of the transmission light for signal transmission from the transmitter. For this reason, when a person adjusts the optical axis using a level display device or the like based on this information, the effort can be simplified sufficiently, but when the optical axis is adjusted automatically, unnecessary operations increase. End up.
[0008]
The reason is that it is impossible to determine whether the receiver is located on the top, bottom, left, or right only by the level of the transmission light for adjusting the optical axis obtained by a single light receiving element. Therefore, in order to automatically adjust the optical axis, it must always move once and it must be judged whether the direction of its movement is correct compared to the light reception level, and it must be judged after moving. . In this case, there is a problem in that unnecessary movement increases, and considering the time required for mechanical driving, it becomes a drag on high-speed automatic optical axis alignment. Furthermore, during automatic optical axis adjustment, the transmitter will transmit the transmitted light in an unspecified direction, which may adversely affect other peripheral optical systems, etc., or if a laser is used as the light source, I'm worried about the impact on people.
[0009]
In consideration of the above, the transmitter is provided with a plurality of receiving elements for receiving position notification light from the receiver, or the reception level on the receiver side of the transmission light from the transmitter is set. It is conceivable to align the optical axis based on the base. However, matching the optical axis at the reception level of the transmitted light on the receiver side does not necessarily guarantee the optical axis as an optimum condition. That is, in the optical wireless transmission system, the reception level is expected to change greatly depending on the distance between the transmitter and the receiver, and it is not easy to determine and adjust the optical axis at a certain level. In addition, what is actually required for optical axis adjustment is not the magnitude of the light reception level, but the purpose is that transmission data can be transmitted without error. It is not the best way to match.
[0010]
Therefore, the present invention has been made paying attention to the above points, and it is possible to easily direct the optical axis of an optical signal having a relatively narrow emission angle transmitted by a transmitter to a receiver, and more reliably. An object of the present invention is to provide an optical wireless transmission apparatus that can guarantee a data transmission path.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention finally finds the approximate position of the receiver quickly while suppressing unnecessary operations to the minimum necessary, and finally determines the error rate information sent from the receiver. The optical axis is adjusted so that there is no error.
That is, according to the present invention, a transmitter having first optical transmission means for transmitting a first optical signal having a relatively narrow emission angle, and a first for receiving the first optical signal and converting it into an electrical signal. An optical wireless transmission apparatus comprising a receiver having the optical receiving means of
The receiver
Error rate calculating means for calculating an error rate of the first optical signal received by the first optical receiving means;
A second optical transmission unit configured to transmit the error rate information calculated by the error rate calculation unit using a second optical signal;
The transmitter is
A plurality of second optical receiving means each capable of receiving the second optical signal at a level corresponding to the direction of the receiver;
Driving means for moving the first optical transmitting means and the plurality of second optical receiving means together in the direction of the receiver to perform alignment;
First optical axis alignment means for controlling the drive means so as to eliminate the difference in level received by the plurality of second optical reception means, and for aligning the optical axis;
After the first optical axis alignment unit aligns the optical axis, the drive unit is controlled so that the error rate is reduced based on the error rate information in the signal received by the second optical reception unit. Thus, an optical wireless transmission apparatus having a second optical axis alignment means for aligning the optical axis is provided.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of an optical wireless transmission apparatus that realizes the optical axis alignment method of the present invention.
[0013]
First, the transmitter 1 will be described. The transmitter 1 receives a signal (for example, a video signal) sent from an external data generation device not described here, and performs an optical wireless transmission on the signal to an encoding circuit (for example, an 8B10B conversion circuit 2). ), And then converted into a binary digital signal that can be optically transmitted by the binarization circuit 3 and sent to the light emitting element driver 4. The light emitting element driver 4 drives a first light transmitting means (for example, composed of an LED, an LD, a condensing lens, etc.) 9 to optically transmit a binarized signal, and has a relatively narrow emission angle. Data is transmitted spatially toward the receiver 16 as transmission light.
[0014]
The transmitter 1 also includes second light receiving means (a plurality of light receiving elements) for receiving a second optical signal transmitted by the second light transmitting means 29 mounted for adjusting the optical axis in the receiver 16. The second optical receiving means 10 and the first optical transmitting means 9 are integrated and can be tilted by the tilt driving means 8, and by the pan driving means 7. Bread is possible.
[0015]
Further, the transmitter 1 performs processing such as electrically amplifying the received signal of each light receiving element received by the second light receiving means 10 by the light receiving circuit 11, and each light receiving element processed by the light receiving circuit 11. From the received signals, only a specific received signal is selected using the signal select circuit 12. The reception level detection circuit 15 detects the reception level of the selected specific reception signal, and the detection result is sent to the control unit 5. Further, the reception signal selected by the signal selection circuit 12 is demodulated by the demodulation circuit 13. The demodulated signal is sent to the packet detection / analysis means 14 to obtain the reception error rate information of the first optical signal on the receiver 16 side, where the reception error rate information from the receiver 16 is detected, The result is sent to the control unit 5.
[0016]
Here, the control unit (for example, MPU, DSP, etc.) 5 receives the signal received by the second optical receiving means 10 necessary using the signal selection circuit 12 at an appropriate time to align the optical axis of the transmitter 1 with the receiver 16. The signal is selected, the reception error rate information sent from the reception level detection circuit 15 and the receiver 16 is obtained by the packet detection / analysis means 14, and the drive control unit 6 is controlled based on these information to drive the pan. The means 7 and the tilt driving means 8 (for example, a stepping motor) are controlled to adjust the directions of the first optical transmission means 9 and the second optical reception means 10. Further, the control unit 5 controls the light emitting element driver 4 to prevent the first optical transmission signal from being inadvertently emitted to the periphery during the optical axis alignment based on the information from the reception level detection circuit 15. I have control.
[0017]
Next, the receiver 16 will be described. First, the main body of the receiver 16 can be panned and tilted by manually moving the movable parts 22 and 23, respectively, and the rough direction with respect to the transmitter 1 can be adjusted. The receiver 16 receives first optical transmission signals spatially transmitted by the first optical transmission means 9 of the transmitter 1 at a relatively wide incident angle (for example, PD, APD and condenser lens). 17), a signal received by the first optical receiving means 17 is subjected to processing such as electrical amplification by a light receiving circuit 18, and converted into a digital signal by a binarization circuit 19, and a symbol decoding circuit Decoding is performed by (for example, the 10B8B conversion circuit 21), and is transmitted to an external device (for example, an image receiving device) not described here.
[0018]
The receiver 16 transmits a second optical signal (generally referred to as pilot light or the like) to the transmitter 1 so that the transmitter 1 adjusts the optical axis. (For example, an LED or a lens added to the LED) 29 is transmitted with a relatively wide emission angle. Further, the second optical transmission unit 29 also has a purpose of transmitting the reception error rate information of the signal received by the first optical reception unit 17. For this reason, the receiver 16 has the first optical reception unit. 17, error detection is performed on the data received by the first optical signal received by the binarization circuit 19.
[0019]
In the example of FIG. 1, a data reception error is detected using a symbol error detection circuit 24 for detection of a reception error, and the error detected here is monitored (counted) for a certain period of time by an error rate calculation circuit 25. For transmission by the second optical transmission means 29, packetization is performed by the error rate packet generation circuit 26, and the light emission signal to the second optical transmission means 29 is modulated by the modulation circuit 27 in accordance with this packet, and light emission By transmitting to the element driver 28, the reception state of the first optical transmission signal transmitted from the transmitter 1 in the receiver 16 is transmitted to the transmitter 1 using the second optical signal.
[0020]
In addition, when detecting a data error of the first optical signal received by the receiver l6, the first optical signal is used to cancel the error rate detection when the first optical signal is not received at a certain level or higher. The signal level detection circuit 20 monitors the reception level of the signals received by the light receiving means 17 and the light receiving circuit 18 to stop the generation of the error rate packet.
[0021]
Next, referring to FIG. 2, as an example of a light receiving element used as the second optical receiving means 10 of the transmitter 1, light reception in which four (= left and right x 2 up and down) PD elements are enclosed by one lens. A case where an element (4-division PD) is used will be described. The principle of this quadrant PD will be briefly described. As shown in FIG. 2, the divided PD is one in which four PDs (light receiving elements: PD 1, PD 2, PD 3, PD 4) are housed in one optical lens 10. In this element, the light receiving level of each light receiving element (PD1, PD2, PD3, PD4) varies depending on the incident direction of light, and the principle is shown in FIGS. 2 (a), 2 (b), and 2 (c). Three patterns are shown as examples.
[0022]
The case of FIG. 2A is a case where the light source 29 corresponding to the second optical transmission means in FIG. 1 is located on the left side (PD1, PD3 side) with respect to the 4-split PD. Incident light is condensed on the PD2 and PD4 side by the optical lens 10 in which each PD is enclosed, and as a result, the relation of PD1 <PD2 and PD3 <PD4 is obtained for each light receiving level. In the case of FIG. 2B, the light source is located in front of the 4-split PD. In this case, since the light is condensed at the center where each PD is located, the relationship between the reception levels is PD1 = PD2, PD3. = PD4. In the case of FIG. 2C, the light source 29 is positioned on the right side (PD2, PD4 side) with respect to the four-divided PD. In this case, the incident light is transmitted to the PD1 by the lens 10 in which each PD is enclosed. As a result, the light receiving levels have a relationship of PD1> PD2 and PD3> PD4.
[0023]
Based on such a principle, the quadrant PD can know the direction in which the light source is located by comparing the reception levels of the light receiving elements. An example of the operation will be described with reference to FIGS. In FIG. 3, the second light receiving means 10 mounted on the transmitter 1 has four light receiving elements (PD1, PD2, PD3, PD4) arranged in two left and right and two above and below as shown in FIG. It is assumed that the receiver 16 is located when viewed from the second optical receiving means 10 (in FIG. 3, the position of the receiver 16 is represented as a light source 29).
[0024]
Here, when the receiver 16 is positioned in the direction of the position A of the light source 29 shown in FIG. 3 when viewed from the transmitter 1, the reception level of the PD1 of the second optical receiving means 10 of the transmitter 1 is SL1. The reception level of PD2 is SL2, the reception level of PD3 is SL3, the reception level of PD4 is SL4, and the relationship is approximately SL1 = SL2 <SL3 = SL4 as shown in FIG. From this, the control unit 5 compares the reception levels obtained from the second optical receiving means 10, and when the relationship of SL1 = SL2 <SL3 = SL4 is obtained, the receiver 16 is in the upward direction. And a control signal is output to the driving means 7 and 8 so that the first optical transmission means 9 and the second optical reception means 10 face upward. Similarly, when there is a receiver 16 at each of the positions A to H, the relationship shown in FIG. 4 is roughly generated between SL1, SL2, SL3, and SL4, and the control unit 5 examines this relationship while checking FIG. The first optical transmitter 9 and the second optical receiver 10 are controlled so as to face each direction shown in FIG.
[0025]
By repeating such control several times, the reception levels SL1 to SL4 of the second optical reception signal of the transmitter 1 are all moved to the same value, and such a state is obtained. By the way, the transmitter 1 roughly grasps the position of the receiver 16.
[0026]
Here, if the optical transmission angle of the first optical transmission means 9 of the transmitter 1 is sufficiently wide (the directivity is sufficiently low), the transmitter 1 sends a signal to the receiver 16 in this state. It is possible to transmit using means 9. However, if the emission angle of the first optical transmission means 9 is widened, the optical power (light quantity) decreases, and it often happens that the transmission distance cannot be taken sufficiently, so that a sufficient transmission distance is secured. Therefore, it is required to narrow the emission angle of the first optical transmission means 9. However, in the case of the technique for searching for the position of the second optical signal from the receiver 16 using the second optical receiving means 10 described above, the first optical transmitting means 9 having a narrow emission angle is used in this technique. In order for the emitted first optical transmission signal to accurately capture the first optical receiving means 17 of the receiver 16, the emission axis of the first optical transmitting means 9 and the second optical receiving means of the transmitter 1 are used. The 10 light receiving axes must be parallel. This will be described with reference to FIG.
[0027]
FIG. 5A shows an ideal case where the light emitting axis 51 of the first light transmitting means 9 and the light receiving axis 50 of the second light receiving means 10 are in a parallel state. In such a case, the second light receiving means 10 finds the position of the light source 29 and is emitted from the first light transmitting means 9 to the first light receiving means 17 placed adjacent to the light source 29. A first optical signal can be applied. However, in the actual manufacturing process, there may occur a case where the light emitting shaft 51 and the light receiving shaft 50 are not necessarily parallel when the components are dispersed or assembled / attached. Rather, it seems that there are more cases where the optical axes are not parallel.
[0028]
FIG. 5B shows a case where the light emitting axis 51 of the first light transmitting unit 9 and the light receiving axis 50 of the second light receiving unit 10 are not in a parallel state but in an off-axis state. In such a case, even if the position of the light source 29 is found by the second light receiving means 10, the light is emitted from the first light transmitting means 9 to the first light receiving means 17 adjacent to the light source 29. The first optical signal cannot be accurately applied, and data transmission cannot be realized.
[0029]
Therefore, in the present invention, after the position of the light source 29 is found by the second optical receiver 10 as described above, the reception error rate information of the first optical reception signal is received from the receiver 16 by the second optical transmitter 29. Using this information, the transmitter 1 aligns the optical axis based on this information, thereby realizing accurate and high-speed automatic optical axis alignment.
[0030]
Next, in the present invention, error rate information packetized by the second optical transmission signal is transmitted from the receiver 16 to the transmitter 1, and an example of the packet configuration is introduced in FIG. As shown in FIG. 6, a command header 40 for identifying data for transmitting error rate information, a data length 41 to be transmitted, error rate data (information) 42, and a data end 43 are included. Packetization is performed and the second optical signal is transmitted.
[0031]
Of course, the configuration example here is a very simple configuration, and it goes without saying that a CRC code can be added or other information can be incorporated as in the second embodiment to be described later. . In actual transmission, a series of data having the structured packet structure can be transmitted continuously, or can be divided (for example, one byte) and transmitted. That is, these sending methods may be determined as a promise on the transmitting side and the receiving side.
[0032]
Next, the operation of the transmitter 1 will be described with reference to FIG. First, in the transmitter 1, the control unit 5 controls the signal selection circuit 12 in step S101 to sequentially select the second optical reception signals, and the second detected by the reception level detection circuit 15 in step S102. Check the optical signal reception level. If this level does not exceed the first determination level (a level that can be determined as the second optical signal from the receiver 16), it is determined that the receiver is not facing the receiver 16, and the first light is detected in step S103. The signal is stopped to prevent unnecessary transmission of the first optical transmission signal to the surroundings, and the occurrence of adverse effects on the surrounding environment such as surrounding devices and people is prevented. In step S104, the second optical receiving means The driving means 7 and 8 are controlled in accordance with the light receiving level obtained by each of the ten light receiving elements, and the first optical transmitting means 9 and the second optical receiving means 10 are directed to the receiver.
[0033]
If there is a signal exceeding the first determination level in step S102, the reception levels of all these second optical reception signals coincide with each other in step S105 (actually, they are within a predetermined range where there is a difference). In step S106, the second optical receiver 10 is driven to change the direction of the second optical receiver 10 up, down, left, and right according to each level of the second optical received signal. The reception levels of the optical reception signals are matched. Since the second optical receiving means 10 is integrated with the first optical transmitting means 9, the direction of the first optical transmitting means 9 is similarly changed.
[0034]
At this time, the transmitter 1 is driven to change the direction of the first optical transmission unit 9 and the second optical reception unit 10 so that the reception levels of the second received light coincide with each other. As described with reference to FIGS. 3 and 4, the second optical receiver 10 is driven in accordance with each reception level of the receiving element.
[0035]
If all the received signal levels of the second received light match in step S105, the control unit 5 controls the light emitting element driver 4 to be turned ON in step S107 for the signal subjected to the 8B10B conversion and binarization processing. To start transmission as the first optical transmission signal, receive the reception error rate information of the first optical signal on the receiver 16 side transmitted by the second transmission light in step S108, and obtain the error obtained in step S109. The rate information is analyzed, and if information indicating that there is an error is received, in step S110, the direction of the first optical transmission means 9 is slightly changed so as to be slightly changed. At this time, the second optical receiver 10 integrated with the first optical transmitter 9 is also finely moved. After the completion of step S110, steps S107 to S110 are repeated as necessary, and the error rate information from the receiver 16 is again determined in step S109.
[0036]
If information indicating that there is no error is received in step S109, the orientations of the first optical transmission means 9 and the second optical reception means 10 are fixed in step S111, and the first signal from the receiver 16 is received in step S112. Whether or not the optical signal transmission time 2 is stopped is monitored (detected) for a predetermined time or more. This is because when the first optical signal can be received without error on the receiver 16 side, the transmission of the second optical signal is stopped so that the first optical signal can be transmitted without error. It is finally confirmed whether or not the optical axis is correct. If the stop of the second optical signal is not recognized in step S112, the optical axis adjustment is performed again from step S107 (or step S101). Is to do.
[0037]
Next, the operation of the receiver 16 will be described with reference to FIG. In the receiver 16, as the step S <b> 201, the first optical receiver 17 and the second optical transmitter 29 are directed to the general direction of the transmitter 1 by manually adjusting the movable parts 22 and 23. The receiver 16 directed in the general direction of the transmitter 1 checks the reception level received by the first optical receiving means 17 in step S202, and recognizes it as the first optical signal sent from the transmitter 1. If it is not higher than a certain level (a certain level), a signal (pilot light) for notifying the transmitter 1 of the position is transmitted from the second optical transmission means 29 in step S203.
[0038]
If it is confirmed in step S202 that the reception level of the first optical signal (also referred to as first received light) is equal to or higher than a certain level, the reception level of the first optical signal is further transmitted in step S204. Wait until it is close to a possible level. If the reception level reaches a level at which data can be transmitted with the first optical signal to some extent, the second optical transmission means 29 is stopped and the second optical signal (pilot light) is stopped in step S205. . Next, the data of the first optical signal received in step S206 is binarized and 10B8B converted (decoded). In step S207, a symbol error of the data received by the first optical signal is detected, and in step S208. The number of errors until the fixed time elapses is counted. In step S209, the error rate is calculated from the number of errors detected in the fixed time. In step S210, whether there is an error is determined. If there is an error, an error packet indicating the error rate is generated in step S212. In step S213, the second optical signal is modulated and loaded, and then transmitted to the transmitter 1. To transmit.
[0039]
<Second Embodiment>
Next, a transmitter 1 in the optical wireless transmission apparatus shown in FIG. 9 will be described as a second embodiment of the present invention. The transmitter 1 receives a signal (for example, a video signal) sent from an external data generation device not described here, and checks the correctness of the data on the receiver 16 side after transmission, in order to confirm the correctness of the data. The transmission data is divided by a predetermined size and a CRC code is added to each data. Further, this signal is encoded by an encoding circuit (for example, 8B10B conversion circuit 2) for optical wireless transmission, and then converted into a binary digital signal that can be optically transmitted by the binarization circuit 3, and the light emitting element driver 4 Send to. The light emitting element driver 4 drives a first light transmission means 9 (for example, composed of an LED, an LD, a condensing lens, and the like) 9 to transmit a binarized signal to transmit a narrow emission angle. Data is spatially transmitted to the receiver 16 as light.
[0040]
The transmitter 1 has a second optical receiving means 10 for receiving a second optical signal transmitted by the second optical transmitting means 29 mounted for adjusting the optical axis of the receiver 16, and this Processing such as electrically amplifying the received signal of each light receiving element received by the second light receiving means 10 by the light receiving circuit 11 is added. From the received signals from the respective light receiving elements processed by the light receiving circuit 11, only a specific received signal is selected by the control unit 5 using the signal select circuit 12, and the received level is detected by the received level detecting circuit 15, The result is passed to the control unit 5. Further, the reception signal selected by the signal selection circuit 12 according to the control signal from the control unit 5 is demodulated by the demodulation circuit 13, and packet detection is performed to obtain the reception error rate information of the first optical signal on the receiver 16 side. The analysis unit 14 detects reception error rate information from the receiver 16 and sends the result to the control unit 5.
[0041]
The control unit (for example, MPU, DSP, etc.) 5 selects a signal received by the second optical receiving means 10 necessary using the signal selection circuit 12 when appropriate to align the optical axis of the transmitter 1 with the receiver 16. Then, the reception error rate information sent from the reception level detection circuit 15 and the receiver 16 is obtained by the packet detection / analysis means 14, and the drive control unit 6 is controlled based on these information, and the drive means 7, 8 (For example, a stepping motor or the like) is controlled to adjust the directions of the first optical transmitter 9 and the second optical receiver 10. Further, the control unit 5 controls the light emitting element driver 4 to prevent the first optical transmission signal from being inadvertently emitted to the periphery during the optical axis alignment based on the information from the reception level detection circuit 15. I have control.
[0042]
Next, the receiver 16 shown in FIG. 9 will be described. The receiver 16 receives the first optical transmission signal spatially transmitted by the first optical transmission unit 9 of the transmitter 1 by the first optical reception unit 17 having a relatively wide incident angle for receiving the first optical transmission signal. 18 is added to a digital signal by a binarization circuit 19 and decoded by a symbol decoding circuit (for example, 10B8B conversion circuit 21), and an external device (for example, not described here) To the image receiving device).
[0043]
The receiver 16 is connected to the transmitter 1 by a second light transmitting means (for example, an LED or a lens added thereto) 29 having a wide emission angle so that the transmitter 1 can adjust the optical axis. Two optical signals (generally, such light is also referred to as pilot light) are transmitted. Further, the second optical transmission unit 29 also has a purpose of transmitting the reception error rate information of the signal received by the first optical reception unit 17. For this reason, the receiver 16 has the first optical reception unit. 17, error detection is performed on the data received by the first optical signal received by the binarization circuit 19.
[0044]
In the example of FIG. 9, a symbol error detection circuit 24 is used to detect a reception error to detect a data reception error, and further, CRCC (cyclic) added to the received first optical signal data to improve error selection accuracy. The CRC circuit 31 checks the redundancy check code (hereinafter also referred to as CRC code). The error rate calculation circuit 25 monitors (counts) the result detected by the symbol error detection circuit 24 and each error result detected by the CRC circuit 31, and transmits the result by the second optical transmission means. The error rate packet generation circuit 26 performs packetization, modulates the light emission signal to the second optical transmission means 29 according to this packet by the modulation circuit 27, and sends the modulated signal to the light emitting element driver 28. The reception state of the first optical transmission signal sent from the transmitter 1 at the receiver 16 is sent to the transmitter 1 using the optical signal of FIG.
[0045]
In addition, when the data error of the first optical signal received by the receiver 16 is detected, the first optical signal is not received at a certain level or more. The signal level detection circuit 20 monitors the reception level of the signal received by the light receiving means 17 and the light receiving circuit 18 to stop the generation of the error rate packet.
[0046]
Here, the features of the two types of embodiments shown in FIGS. 1 and 9 described above will be described. In each of these two embodiments, whether or not the optical axes of the transmitter 1 and the receiver 16 are correctly facing each other, whether the first optical signal sent from the transmitter 1 is received at the receiver 16, and the data error. Judgment is made by monitoring the presence or absence. On the other hand, in an optical transmission system such as the present invention, the transmission rate (amount) of data that can be transmitted has an upper limit depending on the performance of the optical element and the performance of the electrical signal processing circuit. The transmission performance of the system is determined by appropriately selecting the performance. If an attempt is made to increase the transmission speed, this will naturally be reflected in the cost. In addition, in order to perform error detection during transmission as in the present invention, the information must be added to the transmission data so that the occurrence of an error can be detected in some form.
[0047]
However, as described above, since there is an upper limit on the transmission performance (speed) of the transmission path, it is desirable to avoid the amount of transmission data from becoming larger than the original data as much as possible. Therefore, the present invention is characterized in that simple error detection means is used for adding a symbol error and a CRC code. In particular, the example of FIG. 1 mainly monitors symbol errors, which is realized without adding codes to the transmission data for error detection.
[0048]
On the other hand, in the second embodiment, a CRC error is simultaneously monitored in addition to a symbol error. This is because not all errors can be detected by symbol error detection, and error detection using a CRC code is also used in order to improve the detection accuracy. In other words, the symbol error is, for example, to prevent four or more identical bits (1 or 0) from occurring continuously by replacing 8 bits (bits) of data with specific symbols (bit patterns) of 10 bits. For this reason, even if an error occurs in the transmission data, it cannot be detected as an error if it is converted into a defined symbol. Therefore, by using together with an error check using a CRC code, the error detection accuracy is increased, thereby realizing higher-precision optical axis alignment.
[0049]
Further, in order to calculate the error rate of the first optical reception signal in the receiver 16 in the first and second embodiments, it is necessary to monitor the error occurrence state for a certain period of time. However, the long time monitoring leads to enlargement of the monitoring means, and it takes time until the transmitter 1 returns the result when the direction is adjusted. For this reason, it is desirable to monitor the monitoring time for calculating the error rate with an appropriate length according to the system. For example, when transmission of video data is considered, an error occurrence at a level in which the image quality is visually disturbed in reproduction of the transmission data is not allowed in the system. In such a system, the presence / absence of the visual influence of the error is one judgment material, and it becomes possible to visually detect when an error of about 10 −9 bits or more occurs at the level of high-definition data. In other words, when such video data is used for transmission, no further errors are allowed, so this accuracy is also required for error detection. It is desirable to monitor.
[0050]
An outline of an optical axis alignment method in such an optical wireless transmission apparatus will be described. Here, it demonstrates using FIG. 1 among two above-mentioned embodiment. When optical transmission is performed indoors or the like by the example shown in this example, the distance between the transmitter 1 and the receiver 16 is at most about several tens of meters. Therefore, first, the first optical receiver 17 of the receiver 16 is used. The light receiving element has a relatively wide incident angle, and is assumed to be adjusted in the direction of the transmitter 1 with a scale. The transmitter 1 converts a video signal or the like into an optical signal and outputs a first optical signal. The receiver 16 receives this first optical signal, converts it into an electrical signal, outputs it to the outside as data such as a video signal, and detects a reception error of this first optical signal.
[0051]
An error rate is calculated from the frequency of occurrence of this reception error, and is output to the transmitter 1 as error rate information on a second optical signal that also serves as a pilot signal. In the transmitter 1, the pilot signal is received by the second optical receiving means 10 of the transmitter 1 and converted into an electric signal, and is put on the reception level of the signal itself and the second optical reception signal. The error rate information of the first optical reception signal at the receiver 16 is taken out, and the transmitter 1 controls the drive means 7 and 8 by the control unit 5 according to these information, thereby changing the optical axis of the transmitter 1. Automatic adjustment to the receiver 16.
[0052]
As described above, the optical wireless transmission apparatus of the present invention is characterized in that the transmitter 1 automatically aligns the optical axis with the receiver 16, and for this purpose, the signal selection circuit 12, the demodulation circuit 13, the packet detection / analysis means. 14, a reception level detection circuit 15, etc., from which the control unit 5 obtains various information, adjusts the optical axis by controlling the drive control unit 6 and the light emitting element driver 4, and between the receiver 16 The optical transmission is realized.
[0053]
FIG. 10 shows the operation of the transmitter 1 of the optical transmission apparatus according to the second embodiment. As shown in FIG. 10, in the transmitter 1, as the first step S101, the control unit 5 controls the signal selection circuit 12 to sequentially select the second optical reception signals, and the reception level detection circuit 15 in step S102. The detected second optical signal reception level is checked. If this level does not exceed the first determination level (a level that can be determined as the second optical signal from the receiver 16), the first optical signal is determined not to be directed toward the receiver 16 in step S103. The transmission is stopped and unnecessary transmission of the first optical signal to the surroundings is prevented to prevent the adverse effects on the surrounding environment such as surrounding devices and people, and each light reception of the second light receiving means 10 is performed in step S104. The drive means 7 and 8 are controlled according to the received signal level obtained by the element, and the first optical transmission means 9 and the second optical reception means 10 are directed to the receiver 16.
[0054]
If there is a signal exceeding the first determination level in step S102, it is determined in step S105 whether the reception levels of all these second optical reception signals match (actually, the difference is within a predetermined range). If they do not coincide with each other, in step S106, the second optical receiving means 10 is driven so as to change the direction of the second optical receiving means 10 up, down, left and right in accordance with each level of the second optical reception signal. Signal reception levels are made to match. Since the second optical receiving means 10 is integrated with the first optical transmitting means 9, the direction of the first optical transmitting means 9 is similarly changed.
[0055]
At this time, the transmitter 1 is driven to change the direction of the first optical transmission unit 9 and the second optical reception unit 10 so that the reception levels of the second received light coincide with each other. The second optical receiver 10 is driven in accordance with each reception level of the receiving element.
[0056]
If all received signal levels of the second received light match in step S105, CRC data is added to the transmission data in step S113, and the 8B10B converted and binarized signal is added to the first signal in step S107. Transmission is started as an optical transmission signal, the error rate information of the first optical signal reception on the receiver 16 side transmitted by the second transmission light is received in step S108, and the error rate information obtained in step S109 is received. If it is analyzed, and information indicating that there is an error is received, in step S110, the direction of the first optical transmission means 9 is slightly changed so as to be slightly changed. At this time, the second optical receiver 10 integrated with the first optical transmitter 9 is also finely moved. After the completion of step S110, steps S107 to S110 are repeated as necessary, and the error rate information from the receiver 16 is again determined in step S109.
[0057]
If information indicating that there is no error is received in step S109, the orientations of the first optical transmission means 9 and the second optical reception means 10 are fixed in step S111, and the first signal from the receiver 16 is received in step S112. Whether the optical transmission time of 2 is stopped is monitored (detected) for a predetermined time or more. This is because when the first optical signal can be received without error on the receiver 16 side, the transmission of the second optical signal is stopped so that the first optical signal can be transmitted without error. It is finally confirmed whether the optical axis is correct. If stop of the second optical signal is not recognized in step S112, the optical axis is adjusted again from step S101. is there.
[0058]
Next, the operation of the receiver 16 according to the second embodiment will be described with reference to FIG. In the receiver 16, as the step S <b> 201, the first optical receiver 17 and the second optical transmitter 29 are directed to the general direction of the transmitter 1 by manually adjusting the movable parts 22 and 23. The receiver 16 directed in the general direction of the transmitter 1 checks the received light level received by the first optical receiving means 17 in step S202, and the first optical signal sent from the transmitter 1 If the level is not higher than the permissible level (a certain level), a signal (pilot light) for notifying the transmitter 1 of the position is transmitted from the second optical transmission means 29 in step S203.
[0059]
If it is confirmed in step S202 that the received light level of the first optical signal is equal to or higher than a certain level, it waits in step S204 until the received level of the first optical signal is close to a level at which data transmission is possible. To do. If the reception level reaches a level at which data can be transmitted with the first optical signal, the second optical transmission means 29 is stopped and the second optical signal (pilot light) is stopped in step S205. To do. Next, the data of the first optical signal received in step S206 is binarized and 10B8B converted (decoded), a symbol error in the first received signal is detected in step S207, and an error is detected by CRC in step S214. To check.
[0060]
The number of errors detected in step S207 and step S214 is counted until a predetermined time elapses in step S208, and an error rate is calculated from the number of errors detected in this predetermined time in step S209, and whether or not there is an error is determined in step S210. If there is no error, an error-free packet is generated in step S211, and if there is an error, an error packet indicating the error rate is generated in step S212, and the second optical signal is generated in step S213. The received packet is modulated and transmitted to the transmitter 1.
[0061]
Note that the configurations of the transmitting device and the receiving device of the optical wireless transmission device described in the above embodiment are examples for explaining the technical idea of the present invention, and the configurations can be changed as appropriate. is there.
[0062]
【The invention's effect】
As described above, according to the present invention, after the transmitter quickly finds the approximate position of the receiver while minimizing unnecessary operations, it is finally determined according to the error rate information sent from the receiver. Since the optical axis alignment is performed so that there is no error, the automatic optical axis alignment can be performed at high speed and accurately.
Also, in the present invention, the optical axis alignment for ensuring a transmission path in which no transmission error occurs is performed by using the error occurrence state during actual data transmission instead of referring to the optical reception level at the receiver side. Regardless of performance variations of the first optical receiving means on the receiver side or performance deterioration due to long-term use, optical axis adjustment capable of data transmission is possible, and a highly stable optical transmission device can be realized. .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a first embodiment of an optical wireless transmission apparatus according to the present invention.
FIG. 2 is an explanatory diagram showing a relationship between a light source position and a reception level of a 4-split PD.
FIG. 3 is an explanatory diagram showing a first optical axis alignment method of the present invention.
FIG. 4 is an explanatory view showing in detail the first optical axis alignment method of the present invention.
FIG. 5 is an explanatory diagram showing optical axis misalignment.
FIG. 6 is an explanatory diagram showing a configuration example of an error information transmission packet.
7 is a flowchart showing an outline of an optical axis alignment operation of the transmitter of FIG. 1;
FIG. 8 is a flowchart showing an outline of an optical axis alignment operation of the receiver of FIG. 1;
FIG. 9 is a schematic configuration diagram illustrating a second embodiment of an optical wireless transmission apparatus according to the present invention.
10 is a flowchart showing an outline of an optical axis alignment operation of the transmitter of FIG. 9;
11 is a flowchart showing an outline of an optical axis alignment operation of the receiver of FIG. 9;
[Explanation of symbols]
1 Transmitter
2 8B10B conversion circuit (encoding circuit)
3, 19 Binarization circuit
4, 28 Light emitting device driver
5 Control unit
6 Drive controller
7 Pan drive means
8 Tilt drive means
9 First optical transmission means
10 Second light receiving means (optical lens)
11, 18 Light receiving circuit
12 signal select circuit
13 Demodulator circuit
14 Packet detection / analysis means
15 Reception level detection circuit
16 Receiver
17 First optical receiving means
20 Signal level detection circuit
21 10B8B conversion circuit (symbol decoding circuit)
22, 23 Movable parts
24 Symbol error detection circuit
25 Error rate calculation circuit
26 Error rate packet generation circuit
27 Modulation circuit
28 Light Emitting Element Driver
29 Second optical transmission means (light source)
30 CRC addition circuit
31 CRC circuit
40 Command header
41 Data length
42 data (error rate data)
43 Data End
50 Light receiving axis
51 Light emission axis

Claims (3)

A transmitter having first optical transmission means for transmitting a first optical signal having a relatively narrow emission angle, and reception having first optical reception means for receiving the first optical signal and converting it into an electrical signal. An optical wireless transmission device equipped with a machine,
The receiver
Error rate calculating means for calculating an error rate of the first optical signal received by the first optical receiving means;
A second optical transmission unit configured to transmit the error rate information calculated by the error rate calculation unit using a second optical signal;
The transmitter is
A plurality of second optical receiving means each capable of receiving the second optical signal at a level corresponding to the direction of the receiver;
Driving means for moving the first optical transmitting means and the plurality of second optical receiving means together in the direction of the receiver to perform alignment;
First optical axis alignment means for controlling the drive means so as to eliminate the difference in level received by the plurality of second optical reception means, and for aligning the optical axis;
After the first optical axis alignment unit aligns the optical axis, the drive unit is controlled so that the error rate is reduced based on the error rate information in the signal received by the second optical reception unit. And second optical axis alignment means for aligning the optical axis,
An optical wireless transmission apparatus. The transmitter further transmits a CRC added to the first optical signal,
The receiver further detects and transmits the number of symbol errors and the number of CRC errors of the first optical signal received by the first optical receiving means as the error rate information,
The optical wireless transmission apparatus according to claim 1, wherein the transmitter performs optical axis alignment based on the number of symbol errors and the number of CRC errors. The optical wireless transmission device according to claim 1, wherein the error rate calculation unit calculates an error rate of received data for a predetermined time or more.

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