JP2005294899A - Optical transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmitter capable of easily aligning optical axes even for an optical radio transmitter using the transmission light of a narrow directional angle, and immediately re-adjusting even in the deviation of a currently used optical axes. <P>SOLUTION: The optical transmitter is provided with a storage medium 37 for storing a correction coefficient, a receiving means 10 composed of a plurality of receiving elements and receiving a second optical signal from an optical transmitter; a determining means 5 for determining whether or not the reception level of the second optical signal meets a predetermined condition; and an adjusting means 5 for adjusting the direction of the transmitting means and/or the receiving means if it does not meet the predetermined condition, and adjusting the direction of the transmitting means and/or the receiving means if it is determined that it meets the predetermined condition, and a reception error rate information for the first optical signal transmitted by the transmitting means is contained in the second optical signal in order to align the optical axes. When the deviation of optical axes occurs after the optical axes are aligned, the adjusting means adjusts the direction of transmitting means and/or the receiving means on the basis of the correction coefficient and the reception level of the second optical signal to align the optical axes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical transmitter for aligning an optical axis between an optical transmitter and an optical receiver constituting an optical wireless transmission apparatus.

Conventionally, there is an optical wireless transmission technology that performs spatial transmission of information using light. In general, optical wireless transmission uses infrared light, 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 a sufficient distance between transmission and reception is desired, it is necessary to sharply narrow the directivity angle of the light beam emitted from the transmitter so that a sufficient light level is incident on the receiver side. In this case, the optical axes of the transmitter and the receiver must be aligned. However, since a light beam with a narrow directivity angle is used or invisible infrared light is used for the light beam, the optical wireless transmission device The alignment of the optical axis is very troublesome. Therefore, an optical wireless transmission apparatus that can easily perform optical axis alignment is disclosed in Patent Document 1 below. The optical wireless transmission device disclosed in Patent Document 1 focuses the visible light from a transmission device to a pinpoint and sends it together with the same optical axis as a signal transmission infrared light or a parallel optical axis. This is applied to the visible light reflecting means provided on the side, and the operator adjusts the optical axis of the transmitting device while viewing the visible light reflected by the visible light reflecting means. As another technology, a sighting machine is installed in the transmitter, and an optical wireless transmission apparatus that aligns the optical axis while looking at the sighting machine, or a receiver for detecting the received light level is connected to the receiver. There is also an optical wireless transmission device that performs optical axis alignment in one set. Further, Patent Document 2 below discloses a technique in which a light source for adjusting the optical axis is used on the light receiving device side, and reception level information of transmitted light from the transmitting device is turned back and the optical axis is adjusted accordingly.
JP-A-62-110339 (FIGS. 1 and 2) JP-A-7-131422 (FIG. 1)

  However, the optical wireless transmission device disclosed in Patent Document 1 requires a configuration that causes the transmission device to generate visible light used for purposes other than optical wireless transmission. When a sufficient distance between the transmitting and receiving devices is desired, the visible light emission output must be made sufficiently large, and the configuration needs to be added, which increases the cost of the transmitting device. In addition, there is a problem that the apparatus becomes large. The same applies to the case where a sighting device is installed in the transmission device. In addition, it is necessary to precisely match the optical axis of visible light, the aiming of the sighting device, and the optical axis of infrared light for signal transmission. Further, even when the light receiving level detection measuring device is connected to the receiving device and performed by a pair of two people, it is necessary to prepare the light receiving level detecting measuring device, and there is a drawback that it requires manpower. As described above, the conventional optical wireless transmission device increases the cost and size of the transmission / reception device when trying to simplify the optical axis alignment, and reduces the optical axis alignment when trying to reduce the cost and size of the transmission / reception device. It had drawbacks such as time-consuming work.

  Further, in the technique disclosed in Patent Document 2, the above-described problems are solved, but transmission light as a pilot signal is transmitted to the transmitter from an optical axis adjustment optical transmission element attached to the receiver. Light is received by a single mounted light receiving element, and the optical axis is adjusted based only on the received light level and the reception level of the transmitted 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. However, when the optical axis is automatically adjusted, unnecessary operations are performed. It will increase. 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. For this reason, in order to automatically adjust the optical axis, it is necessary to move it once and to determine whether or not the direction in which it has moved is correct as compared with the light reception level, and to determine 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.

  In consideration of the above, there is also an idea of adjusting the optical axis based on the delivery information for the optical signal transmitted by the transmitter received from the receiver after adjusting in the rough (coarse) direction. In particular, when using transmission light with a narrow directivity angle, the accuracy of rough adjustment at the initial stage is important. However, in an actual optical wireless transmission device, optical axis adjustment errors caused by assembly errors and component variations, and light due to refraction of optical signals at the exterior of the exterior and the optical filter attached to the front of the optical transceiver An axis adjustment error occurs. In particular, when the transmitted light has a narrow directivity angle, the influence cannot be ignored, and there may be a case where transmission becomes impossible due to the deviation of the optical axis.

  Even if the transmitter adjusts the optical axis according to the delivery information transmitted from the receiver described above, the optical axis is readjusted if the transmitter moves during transmission and the optical axis slightly shifts. In this case, it is difficult to infer in which direction the transmitter should move the transmitter from the delivery information alone. For this reason, a position where the optical axes are matched is searched while the optical axes are readjusted at random, and it is not always possible to quickly return to the position where the optical axes are matched.

  The present invention is for solving the above problems, and it is possible to easily align the optical axis even in an optical wireless transmission device that uses transmission light with a narrow directivity angle. An object of the present invention is to provide an optical transmitter that can quickly readjust even in the case of deviation.

  In order to achieve the above object, according to the present invention, an optical transmitter that adjusts the optical axis of a first optical signal that is optically transmitted from a transmitting unit to an optical receiver is constituted by a plurality of receiving elements, Receiving means for receiving a second optical signal for adjusting the optical axis from the optical receiver, and a memory for storing a correction coefficient serving as a reference when correcting a deviation of the optical axis of the second optical signal Means for determining whether or not the reception level of the second optical signal received by each receiving element of the receiving means satisfies a predetermined condition, and the predetermined condition is determined by the determining means. When it is determined that the predetermined condition is not satisfied, the direction of the reception unit and / or the transmission unit is adjusted so as to satisfy the predetermined condition, and the determination unit determines that the predetermined condition is satisfied. The reception When the second optical signal received by the stage includes reception error rate information indicating a reception error with respect to the first optical signal transmitted by the transmission means, the reception is performed so that the reception error is eliminated. And / or adjusting means for adjusting the orientation of the transmitting means and adjusting the optical axis, and the adjusting means stores in the storage means when the optical axis shifts after the optical axes are aligned. The direction of the receiving unit and / or the transmitting unit is adjusted based on the corrected correction coefficient and the reception level of the second optical signal received by the receiving unit after the optical axis shift occurs. An optical transmitter characterized by aligning the optical axes is provided. Here, the predetermined condition means that the reception levels of the second optical signals received by the receiving means including, for example, four receiving elements (hereinafter also referred to as light receiving elements) are the same. The transmission means corresponds to first optical transmission means 9 described later.

  According to the invention, in the optical transmitter that adjusts the optical axis of the first optical signal that is optically transmitted from the transmitting means to the optical receiver, the optical transmitter is configured by a plurality of receiving elements and adjusts the optical axis. Receiving means for receiving a second optical signal for receiving from the optical receiver, and a first storage for storing a first correction coefficient serving as a reference in correcting a deviation of the optical axis of the second optical signal Means for determining whether or not the reception level of the second optical signal received by each receiving element of the receiving means satisfies a predetermined condition, and the predetermined condition is determined by the determining means. When it is determined that the predetermined condition is not satisfied, the direction of the transmitting means and / or the receiving means is adjusted so as to satisfy the predetermined condition, and the predetermined condition is determined by the determining means. By the receiving means When the second optical signal received in this way includes reception error rate information indicating a reception error with respect to the first optical signal transmitted by the transmission unit, the transmission unit eliminates the reception error. And / or adjusting the direction of the receiving means to adjust the optical axis, and based on the information on the reception level of the second optical signal when the optical axis is adjusted by the adjusting means, the optical axis And a second storage means for storing the second correction coefficient calculated by the calculation means, the adjustment means comprising: If the second correction coefficient is stored in the second storage means when the optical axis shift occurs after the optical axes are aligned, the optical axis shift occurs after Received by the receiving means The reception level of the second optical signal is corrected based on the reception level of the second optical signal and the second correction coefficient, and the second correction coefficient is stored in the second storage means. If not, the reception level of the second optical signal based on the reception level of the second optical signal received by the reception unit and the first correction coefficient stored in the first storage unit The determination means determines whether or not the corrected reception level of the second optical signal satisfies the predetermined condition, and the adjustment means satisfies the predetermined condition by the determination means. If it is determined that the second optical signal is received, the second optical signal received by the receiving unit indicates a reception error with respect to the first optical signal transmitted by the transmitting unit after it is determined that the predetermined condition is satisfied. Receive error rate When information is included, an optical transmitter is provided that adjusts the direction of the transmission unit and / or the reception unit so as to eliminate the reception error and aligns the optical axis.

  The information display server of the present invention has the above-described configuration and can easily align the optical axis even in an optical wireless transmission device that uses transmission light with a narrow directivity angle. Can be readjusted promptly.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration of an optical transmitter and an optical receiver according to the first embodiment of the present invention. FIG. 2 is a schematic diagram showing an optical wireless transmission apparatus including the optical transmitter according to the first embodiment of the present invention. FIG. 3 is a diagram for explaining the principle of detecting the direction of the optical receiver in the optical transmitter according to the first embodiment of the present invention. FIG. 4A is a diagram for explaining the principle of detecting the direction of the optical receiver in the optical transmitter according to the first embodiment of the present invention. FIG. 4B is a table showing a relationship between received light levels used to detect the direction of the optical receiver in the optical transmitter according to the first embodiment of the present invention. FIG. 5 is a diagram for explaining the optical wireless transmission apparatus when there is no deviation of the optical axis between the optical transmitter and the optical receiver according to the first embodiment of the present invention. FIG. 6 is a diagram for explaining the optical wireless transmission device when there is a deviation of the optical axis between the optical transmitter and the optical receiver according to the first embodiment of the present invention. FIG. 7 is a diagram for explaining a deviation of the optical axis when the optical transmitter according to the first embodiment of the present invention has an exterior. FIG. 8 is a diagram illustrating a configuration of a control unit of the optical transmitter according to the first embodiment of the present invention. FIG. 9 is a flowchart showing an operation flow of optical axis adjustment in the optical transmitter according to the first embodiment of the present invention.

  First, an optical wireless transmission apparatus including the optical transmitter according to the first embodiment of the present invention will be described with reference to FIG. The optical wireless transmission device receives the digital video signal data transmitted by optical wireless from the optical transmitter 1 installed in the video control device 53 by the optical receiver 16 installed on the video display device 54 side, and displays the video. An image is displayed on the device 54. Here, the video display device 54 is a high quality display device such as a plasma display panel (PDP) television. The video control device 53 is, for example, a tuner.

  The optical wireless transmission apparatus transmits data to the optical receiver 16 by a first optical transmission signal (hereinafter also referred to as transmission light) 40 emitted from the optical transmitter 1, and is efficient with limited optical power. In order to transmit data, the transmission light 40 is performed at a narrow transmission directivity angle, and it is an important transmission condition that the transmission light 40 is accurately applied to the optical receiver 16. For this reason, the concept (function) of optical axis adjustment is required in an optical wireless transmission apparatus that is required to match the transmission light 40 to the optical receiver 16. Further, since the optical transmitter 1 is installed on the side of the video control device 53 such as a tuner, the position (optical axis) may be shifted due to an impact in daily life, for example, cleaning. In addition, the precise adjustment of the optical axis by the user significantly hinders the comfort level of use. Therefore, it is desirable that the optical transmitter 1 has a function of automatically adjusting the optical axis, and it is desirable that the optical axis can be readjusted quickly and automatically even if the optical axis shifts during use. In order to provide such an optical transmitter 1 with an automatic optical axis adjustment function, a second optical transmission signal for the optical transmitter 1 to adjust the optical axis, such as a pilot, is provided on the optical receiver 16 side. Means for emitting light 41 will be provided.

  Next, the configuration of the optical transmitter and the optical receiver according to the first embodiment of the present invention will be described with reference to FIG. First, the configuration of the optical receiver 16 will be described. In the optical receiver 16, the first optical receiver 17 having a relatively wide directivity angle for receiving the first optical transmission signal 40 spatially transmitted by the first optical transmitter 9 of the optical transmitter 1 is provided. The first optical transmission signal 40 is received, the first optical transmission signal 18 received by the light receiving circuit 18 is subjected to processing such as electrical amplification, and the binarization circuit 19 amplifies the first optical transmission. The signal 40 is converted into a digital signal, the symbol decoding circuit 21 performs decoding, and transmits the decoded signal to an external device such as an image receiving device (not shown). Here, the first light receiving means 17 is composed of, for example, a PD (Photo Diode), an APD (Advanced Photo Diode), a condenser lens, and the like. The symbol decoding circuit 21 is, for example, a 10B8B conversion circuit.

  In the optical receiver 16, the second optical transmission unit 29 having a wide directivity angle for the optical transmitter 1 to adjust the optical axis transmits the second optical transmission signal 41 to the optical transmitter 1. . Here, the second light transmitting means 29 is, for example, an LED (Light Emitting Diode) or an LED in which a lens is added. Further, the second optical transmission signal 41 is, for example, pilot light. Further, the second optical transmission unit 29 also has a function of transmitting reception error rate information indicating a reception error with respect to the first optical transmission signal 40 received by the first optical reception unit 17. Then, error detection is performed on the first optical transmission signal 40 received by the first optical receiver 17 and digitized by the binarization circuit 19. A symbol error detection circuit 24 is used for this error detection. The error rate calculation circuit 25 monitors (counts) the error detected here for a certain period of time. In order to transmit the result by the second optical transmission means 29, the error rate packet generation circuit 26 packetizes, and the modulation circuit 27 Modulation is performed in accordance with the packet and sent to the light emitting element driver 28. Thus, the reception status of the first optical transmission signal 40 transmitted from the optical transmitter 1 is sent to the optical transmitter 1 using the second optical transmission means 29.

  In addition, when detecting the error of the first optical transmission signal 40 received by the optical receiver 16, if the first optical transmission signal 40 is not received at a certain level or higher, the error detection is postponed. Therefore, the signal level detection circuit 20 monitors the reception level of the optical signal received by the first light receiving means 17 and the light receiving circuit 18 and stops the generation of the error rate packet.

  Next, an optical transmitter according to the first embodiment of the present invention will be described. In the optical transmitter 1, a signal such as a video signal transmitted from an external data generator (not shown) is received, the signal is encoded by the encoding circuit 2, and the encoded signal is optically transmitted by the binarization circuit 3. It is converted into a binary digital signal that can be transmitted and sent to the light emitting element driver 4. The light emitting element driver 4 drives the first optical transmission means 9 to optically transmit the binarized signal, and spatially transmits data to the optical receiver 16 as transmission light with a narrow directivity angle. Here, the encoding circuit 2 is, for example, an 8B10B conversion circuit. The first light transmitting means 9 is constituted by, for example, an LED, an LD (Laser Diode), a condenser lens, or the like.

  Further, the optical transmitter 1 receives the second optical reception signal for receiving the second optical transmission signal 41 transmitted by the second optical transmission means 29 mounted for adjusting the optical axis of the optical receiver 16. Means 10 are present. Here, the second light receiving means 10 is composed of, for example, a plurality of light receiving elements. The light receiving circuit 11 performs processing such as electrically amplifying the reception signal received by each light receiving element. The control unit 5 selects only a specific reception signal from the reception signal processed by the light receiving circuit 11 by using the signal selection circuit 12, and the reception level detection circuit 15 detects the reception level, and the result is sent to the control unit 5. Hand over. Further, the reception signal selected by the signal selection circuit 12 by the control unit 5 is demodulated by the demodulation circuit 13, and the packet is received in order to obtain the reception error rate information of the first optical transmission signal 40 on the optical receiver 16 side. The detection / analysis means 14 detects the reception error rate information from the optical receiver 16 and sends the result to the control unit 5.

  Here, the control unit 5 selects a necessary received signal by the second optical receiving means 10 by using the signal selection circuit 12 and receives a signal when appropriate in order to align the optical axis of the optical transmitter 1 with the optical receiver 16. Reception error rate information sent from the level detection circuit 15 and the optical receiver 16 is obtained by the packet detection / analysis means 14, the drive control unit 6 is controlled based on these information, and the drive means 7, 8 are controlled. Then, the orientations of the first optical transmitter 9 and the second optical receiver 10 are adjusted. Further, the control unit 5 controls the light emitting element driver 4 so as to prevent the first optical transmission signal 40 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. Here, the control unit 5 is, for example, an MPU or a DSP (Digital Signal Processor). The driving means 7 and 8 are, for example, stepping motors.

  Next, the second optical transmission signal 41 emitted from the second optical transmission means 29 as shown in FIG. 2 described above is used as pilot light, and the optical transmitter 1 uses the second optical reception means 10 to perform optical reception. An example of the basic principle for detecting the direction of the machine 16 will be described with reference to the tables of FIGS. 3, 4A and 4B. First, the case where the second optical receiving means 10 included in the optical transmitter 1 includes four PD elements as shown in FIG. 3 and these are enclosed by one lens will be described. As shown in FIG. 3, the four-segment PD includes four PD1, PD2, PD3, and PD4 in one optical lens. In this element, the light receiving level of each of the light receiving elements PD1, PD2, PD3, and PD4 (hereinafter also referred to as a reception level) varies depending on the incident direction of light. In FIG. 3, the principle is divided into three patterns (a), It is divided into (b) and (c).

  In the case of FIG. 3A, the light source 300 is located on the left side (PD1 and PD3 side) with respect to the quadrant PD. In this case, the incident light is transmitted by the lens in which each PD is enclosed. The light is condensed on the PD2 and PD4 sides, and as a result, the relationship between the respective light reception levels is PD1 <PD2 and PD3 <PD4. In the case of (b) in FIG. 3, the light source 300 is located in front of the quadrant PD. In this case, since the light is condensed at the center where each PD is located, the relationship between the respective light reception levels is PD1 = PD2, PD3 = PD4. In the case of FIG. 3C, the light source 300 is positioned on the right side (PD2, PD4 side) with respect to the four-divided PD. In this case, the incident light is transmitted by the lens in which each PD is enclosed. The light is condensed to the PD1 and PD3 sides, and as a result, the relationship between the respective light reception levels is PD1> PD2 and PD3> PD4.

  From this, it is possible to know the direction in which the light source 300 is located by comparing the light receiving levels of the light receiving elements by using the characteristics of the light receiving elements such as the 4-part PD. An example of the operation for direction alignment using this fact will be described with reference to the tables of FIGS. 4A and 4B. FIG. 4A shows the second optical receiving means 10 including the light receiving elements PD1, PD2, PD3, and PD4 mounted on the optical transmitter 1, and the optical receiver 16 as viewed from the second optical receiving means 10. Is where it is. In FIG. 4A, the position of the optical receiver 16 is expressed as “light source” as the position of the second optical transmission means 29.

  Here, when the optical receiver 16 is in the direction of the position A of the light source 300 shown in FIG. 4A when viewed from the optical transmitter 1, the reception level of the PD1 of the second optical receiving means 10 of the optical transmitter 1 is SL1, When the reception level of PD2 is SL2, the reception level of PD3 is SL3, and the reception level of PD4 is SL4, the relationship is approximately SL1 = SL2 <SL3 = SL4 as shown in the table of FIG. 4B. From this, the control unit 5 compares the reception levels obtained from these second optical receiving means 10, determines that the optical receiver 16 is in the upward direction from the relationship of SL1 = SL2 <SL3 = SL4, and drives A control signal is output to the control unit 6 so that the first optical transmission unit 9 and the second optical reception unit 10 face upward. Similarly, when there is the optical receiver 16 from the position A to B, the relationship shown in the table of FIG. 4B occurs between SL1 and SL4, and the control unit 5 checks the relationship between the first and the first. Positions at which the reception levels SL1 to SL4 of the second optical receiver 10 of the optical transmitter 1 all become the same value by controlling the optical transmitter 9 and the second optical receiver 10 and repeating such control. By moving the optical transmitter 1 to the optical transmitter 1, the optical transmitter 1 has roughly caught the optical receiver 16.

  However, in an actual optical wireless transmission apparatus, accurate optical axis alignment is difficult with only the information on the light reception level of the second optical transmission signal 41 (pilot light) by the second optical receiving means 10 as described above, and mass production is difficult. There is a big burden in the assembly adjustment at the time. In particular, when it is desired to increase the data transmission speed and increase the transmission distance, it is necessary to narrow the radiation directivity angle of the first optical transmission signal 40, and more accurate optical axis alignment is required. Therefore, in such an optical wireless transmission device, the optical axis adjustment based only on the information on the light reception level of the pilot light described above is not sufficient. That is not sufficient will be described with reference to FIGS.

  First, as shown in FIG. 5, the first optical transmission means 9 and the second optical reception means 10 of the optical transmitter 1 are installed on a single substrate 44, and the transmission axis and the reception axis are kept parallel. I'm leaning. Further, the first optical receiving means 17 and the second optical transmitting means 29 of the optical receiver 16 are installed on the substrate 45, and the transmission axis and the reception axis are kept in parallel. When the transmission / reception axes of the optical elements of the optical transmitter 1 and the optical receiver 16 are secured in parallel, the light receiving axis 50 in the second optical receiving means 10 of the optical transmitter 1 is connected to the second optical receiver 16. To the optical transmission means 29 (that is, the received light levels of the four-divided PDs are matched), the first light transmission means 9 of the optical transmitter 1 as a result is emitted first. The optical transmission signal 40 can be applied to the first optical receiving means 17 of the optical receiver 16, and the first optical transmission signal 40 can be received by the first optical receiving means 17. That is, this state is a state where the optical axes of the optical transmitter 1 and the optical receiver 16 are aligned.

  However, as described above, it is very difficult to make the light receiving and emitting axes of each optical element as shown in FIG. 5 exactly parallel, and the axis of the optical element varies depending on variations in the axis misalignment of each element and assembly errors during assembly. Ensuring parallelism is a major burden in the mass production process. Therefore, a case where the parallelism of each axis is not generally secured will be described with reference to FIG. FIG. 6 shows a case where the light receiving axis 50 of the second light receiving means 10 and the light emitting axis 51 of the first light transmitting means 9 are not secured in parallel when the element is attached to the substrate 44. The state of the optical axis deviation between the optical transmitter 1 and the optical receiver 16 when the light receiving axis 50 of the receiving means 10 is aligned with the second optical transmitting means 29 of the optical receiver 16 is shown. FIG. 6A shows a case where the first optical transmission signal 40 is emitted with a relatively wide directivity angle, and FIG. 6B shows the first optical transmission signal. The case where 40 is emitted with a narrow directivity angle is shown.

  As can be seen from these, in the situation 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 not secured in parallel, the light receiving axis of the second light receiving means 10 can be obtained. 50 is adjusted to the second optical transmission means 29 of the optical receiver 16, the light emission axis 51 of the first optical transmission means 9 of the optical transmitter 1 is changed from the first optical reception means 17 of the optical receiver 16. End up. As shown in FIG. 6 (a), when the radiation directivity angle of the first optical transmission signal 40 is relatively wide, the first optical transmission signal 40 is the first optical receiving means even if each axis is slightly deviated. You might be able to catch 17. However, as shown in FIG. 6B, in the optical wireless transmission apparatus in which the transmission speed and the transmission distance are required, it is necessary to narrow the radiation directivity angle of the first optical transmission signal 40. Such optical wireless transmission In the apparatus, the first optical transmission signal 40 is deviated from the first optical receiving means 17 even with a slight misalignment, and a transmission path cannot be secured.

  In addition to the optical axis misalignment between the optical transmitter 1 and the optical receiver 16 caused by the axis misalignment of each optical element as described above, a transmission optical filter is considered in consideration of an actual optical wireless transmission device. The problem of misalignment of the axis due to light refraction at the exterior is also mentioned. This will be described with reference to FIG. In FIG. 7, a case will be described in which a transmission plate 42 attached as an exterior or the like exists between the optical light emitting and receiving units of the optical transmitter 1 and the optical receiver 16. When there is a transmission plate 42 such as an optical filter for the purpose of removing unnecessary disturbance light between the optical transmitter 1 and the optical receiver 16, the second optical transmission signal 41 from the optical receiver 16 is transmitted. The second optical receiving means 10 of the optical transmitter 1 releases the second optical transmission signal 41 from the position of the virtual image 39 of the second optical transmitting means 29 shown in FIG. Recognize as if leaning. As a result, the optical transmitter 1 orients the light receiving axis 50 of the second optical receiver 10 in the direction of the virtual image 39, and the first optical transmission emitted from the first optical transmitter 9 of the optical transmitter 1. The signal 40 cannot be applied to the first optical receiving means 17 of the optical receiver 16, and the first optical transmission signal 40 is emitted in a different direction.

  As described above, in order to align the optical communication optical axes of the optical transmitter 1 and the optical receiver 16, as described with reference to the tables of FIG. 3, FIG. 4A and FIG. On the other hand, it is difficult to accurately adjust the optical axis simply by receiving light with a four-divided PD element and aligning the direction based on the level information. It is enough. For this reason, in the optical wireless transmission device using light with a narrow directivity angle, as described in FIG. 2, the optical receiver 16 side transmits the delivery information on the reception state of the first optical transmission signal 40 from the optical transmitter 1. By returning the reply, the optical transmitter 1 finally has a mechanism for matching the optical axis with the optical receiver 16 based on the delivery information from the optical receiver 16.

  In other words, in order to align the communication optical axis with the optical receiver 16, the optical transmitter 1 first quickly uses the second optical receiver 10 and / or the first optical transmitter based on the information on the reception level of the pilot light. 9 is directed to the optical receiver 16, and then the first optical receiving means 17 of the optical receiver 16 determines the first optical receiving means 17 based on the delivery information that informs the reception status of the first optical transmission signal 40 from the optical receiver 16. The optical axis of communication with the optical receiver 16 is adjusted until the one optical transmission signal 40 can be correctly received.

  Here, in order for the optical transmitter 1 to finally align the communication optical axis with the optical receiver 16, optical axis adjustment based on the reception status (delivery information) from the optical receiver 16 is necessary. However, with such optical axis adjustment (hereinafter also referred to as delivery confirmation optical axis adjustment), the direction of the optical receiver 16 cannot be known, and it is difficult to quickly adjust the deviation of the communication optical axis, I have to spend some time. Here, the delivery information includes the above-described reception error rate information. In addition, in the delivery confirmation optical axis adjustment, since the direction of the optical receiver 16 is unknown as described above, there are cases where the direction is adjusted in the opposite direction to the correct direction depending on the case. The position where the final optical axis coincides will be found. Of course, by devising the direction adjustment movement algorithm, etc., it is expected that the delivery confirmation optical axis can be adjusted to a certain degree of smoothness. However, the processing becomes heavy and results due to the burden on the control unit 5 and the processing speed. It is also possible that high-speed adjustment cannot be expected.

  Further, in the optical wireless transmission apparatus as shown in FIG. 2, it is possible that the optical transmitter 1 is slightly shifted during use and a part of the image is disturbed. In such a case, if the transmission optical axis is readjusted by the delivery confirmation optical axis adjustment, the initial operation, which is the first adjustment, is not necessarily adjusted in a direction in which the disturbance of the image can be recovered. The image may move in a more disturbing direction, which is uncomfortable for the user.

  Therefore, in the present invention, after the transmission optical axis between the optical transmitter 1 and the optical receiver 16 is once adjusted using the delivery confirmation optical axis adjustment, the optical transmitter 1 is shifted due to an impact or a signal and the optical axis is shifted. In the case of deviation, the optical axis is not readjusted by the delivery confirmation optical axis adjustment, but the optical axis is adjusted relatively quickly by performing the optical axis adjustment based on the light reception level of the second optical transmission signal 41. To restore the transmission path. Thus, the user can wait for the recovery of the optical axis without discomfort even if the optical axis is readjusted during use as described above.

  However, as described above, in the direction alignment based on the light reception level information of the second optical transmission signal 41 at the time of readjustment of the transmission optical axis between the optical transmitter 1 and the optical receiver 16, FIGS. As described above, the second optical transmission signal 41 in each light receiving element of the second light receiving means 10 is not necessarily affected by the shift of the transmission / reception shaft of each optical element during assembly or the influence of light refraction at the exterior. The positions where the received light levels coincide are not necessarily the positions where the optical axes coincide. Therefore, in the present invention, once the optical axis is matched by adjusting the delivery confirmation optical axis, the received light level of the pilot light is corrected using the first correction coefficient stored in the optical transmitter 1 in advance, so that it can be quickly and accurately performed. It is possible to align the optical axis. Here, the first correction coefficient is, for example, a coefficient set at the initial time for multiplying the received light level received after the optical axis is shifted so that the optical axis is approximately aligned after the optical axis is shifted. It is not limited to this.

  FIG. 8 shows a part of the configuration of the optical transmitter 1 according to the first embodiment of the present invention. As shown in FIG. 8, the control unit 5 uses the second light receiving means 10 based on the received light level of each PD element in the second light receiving means 10 of the pilot light 41 that is the second light transmission signal. And / or after adjusting the direction of the first optical transmission means 9 and accurately aligning the communication optical axis based on the reception status (delivery information) from the optical receiver 16, the communication optical axis for some reason during use Is shifted, the light receiving level of each PD element of the second light receiving means 10 is corrected by the first correction coefficient.

  In addition, the control unit 5 includes an optical axis adjustment control unit 35 for driving and controlling the directions of the second optical receiving unit 10 and the first optical transmission unit 9. Each time the direction of the second light receiving means 10 and / or the first light transmitting means 9 is changed, the optical axis adjustment control unit 35 sequentially receives signals received by the respective light receiving elements of the second light receiving means 10. In order to make the selection, the signal selection circuit 12 is controlled, and the first correction coefficient is read from the first correction coefficient recording memory 37 and transferred to the level correction calculation unit 36. The level correction calculation unit 36 multiplies (calculates) the light reception level of each light receiving element (PD1, PD2, PD3, PD4) sent from the reception level detection circuit 15 by the first correction coefficient obtained from the first correction coefficient recording memory 37. ) And sent to the optical axis adjustment control unit 35.

  The optical axis adjustment control unit 35 compares the received light levels of the corrected light receiving elements (PD1, PD2, PD3, PD4) sent from the level correction calculation unit 36, and controls the driving means 7 and 8 accordingly. Thus, the direction in which the second optical receiver 10 and / or the first optical transmitter 9 is directed is changed. The optical axis of the optical transmitter 1 is aligned with the optical receiver 16 by repeating such an operation until the corrected light receiving levels of the respective light receiving elements of the second optical receiving means 10 match.

  Next, an operation flow of optical axis adjustment in the optical transmitter according to the first embodiment of the present invention will be described with reference to FIG. First, the control unit 5 controls the signal selection circuit 12 to sequentially select the second optical transmission signal (pilot light) 41 (step S1). The control unit 5 reads the first correction coefficient from the first correction coefficient recording memory 37 (step S2). The level correction calculation unit 36 of the control unit 5 multiplies (calculates) the light reception level of the second optical transmission signal 41 sent from the reception level detection circuit 15 by the read first correction coefficient, and calculates the light reception level. Correction is performed (step S3). The control unit 5 determines whether or not the corrected light reception level is a light reception level equal to or higher than a certain level (step S4). This is for avoiding erroneous determination due to reception of noise such as ambient light by determining whether the optical receiver 16 is within the directivity angle of the second optical receiver 10. If there is no reception exceeding a certain level in this determination, the control unit 5 stops the light emission of the first optical transmission means 9 (step S5), and avoids unnecessary emission of the first optical transmission signal 40. Consider the surrounding environment. The optical axis adjustment control unit 35 of the control unit 5 controls the drive control unit 6 to drive the drive units 7 and 8 to drive the direction of the second optical reception unit 10 and / or the first optical transmission unit 9. (Step S6).

  Further, when it is determined in step S4 that the light reception level is equal to or higher than a certain level, the control unit 5 determines whether or not all the light reception levels match (step S7). If it is determined that they do not match, the process of step S6 described above is performed. If it is determined that all the received light levels match, the first optical transmission means 9 transmits the first optical transmission signal 40 to the optical receiver 16 (step S8), and the second optical reception. The means 10 receives the delivery information for the first optical transmission signal 40 from the optical receiver 16 (step S9). The control unit 5 determines whether or not there is an error in the received delivery information (step S10), and when it is determined that there is no error, the control unit 5 ends when the optical axes are matched. On the other hand, when it is determined in step S10 that there is an error, the optical axis adjustment control unit 35 of the control unit 5 searches the second optical receiving unit 10 and / or the first optical transmission in order to search for a position where there is no error. The means 9 is driven in a direction (step S11). In addition, embodiment mentioned above is an example and the structure can be changed suitably.

<Second Embodiment>
Next, an optical transmitter according to a second embodiment of the present invention will be described with reference to FIGS. Since the optical transmitter 1 according to the second embodiment of the present invention has almost the same configuration and function as those of the above-described optical transmitter 1 according to the first embodiment of the present invention, overlapping portions will be described. Will be omitted, and different parts will be described. The difference in configuration is that it has a second correction coefficient recording memory 38 for storing the second correction coefficient. First, a part of the configuration of the optical transmitter 1 according to the second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 10, the control unit 5 uses the second optical receiving means 10 based on the light reception level of each PD element in the second optical receiving means 10 of the second optical transmission signal (pilot light) 41. And / or after adjusting the direction of the first optical transmission means 9 and accurately aligning the communication optical axis based on the reception status (delivery information) from the optical receiver 16, the communication optical axis is accurately aligned. The second correction coefficient calculated from the reception level of each PD element of the second light receiving means 10 in the state is stored in the second correction coefficient recording memory 38, and the communication optical axis is shifted for some reason during use. The light receiving level of each PD element of the second light receiving means 10 is corrected by the second correction coefficient stored in the second correction coefficient recording memory 38. Here, the second correction coefficient is a coefficient that equalizes the reception level of each PD element of the second light receiving means 10 in a state where the communication optical axis is accurately aligned, for example, but is not limited thereto. is not.

  In addition, the control unit 5 includes an optical axis adjustment control unit 35 for driving and controlling the directions of the second optical receiving unit 10 and the first optical transmission unit 9. The optical axis adjustment control unit 35 sequentially selects a signal received by each light receiving element of the second light receiving means 10 every time the direction of the second light receiving means 10 and the first light transmitting means 9 is changed. For this purpose, the signal selection circuit 12 is controlled to read out each correction coefficient from the first correction coefficient recording memory 37 or the second correction coefficient recording memory 38 and deliver it to the level correction calculation unit 36. Here, if there is a second correction coefficient in the second correction coefficient recording memory 38, the optical axis adjustment control unit 35 passes the second correction coefficient to the level correction calculation unit 36, and if not, the first correction coefficient is transferred to the level correction calculation unit. Deliver to 36. The level correction calculation unit 36 obtains the light reception level of each light receiving element (PD1, PD2, PD3, PD4) sent from the reception level detection circuit 15 from the first correction coefficient recording memory 37 or the second correction coefficient recording memory 38. It is multiplied (calculated) by the correction coefficient and sent to the optical axis adjustment control unit 35.

  The optical axis adjustment control unit 35 compares the received light levels of the corrected light receiving elements (PD1, PD2, PD3, PD4) sent from the level correction calculation unit 36, and controls the driving means 7 and 8 accordingly. Thus, the direction in which the second optical receiver 10 and / or the first optical transmitter 9 is directed is changed. The optical axis of the optical transmitter 1 is aligned with the optical receiver 16 by repeating such an operation until the corrected light receiving levels of the respective light receiving elements of the second optical receiving means 10 match.

  Next, an operation flow of optical axis adjustment in the optical transmitter according to the second embodiment of the present invention will be described with reference to FIG. First, the control unit 5 controls the signal selection circuit 12 to sequentially select the second optical transmission signal (pilot light) 41 (step S1). The controller 5 determines whether or not there is a second correction coefficient in the second correction coefficient recording memory 38 (step S2). If it is determined that there is a second correction coefficient, the control unit 5 reads the second correction coefficient recording memory 38 from the second correction coefficient recording memory 38. Two correction coefficients are read out (step S3). The level correction calculation unit 36 of the control unit 5 corrects the light reception level using the second correction coefficient (step S4). Next, the control unit 5 determines whether or not the corrected light reception level is a light reception level equal to or higher than a certain level (step S5). This is to avoid erroneous determination due to noise reception such as disturbance light by determining whether or not the optical receiver 16 is within the directivity angle of the second optical receiving means 10. If there is no reception exceeding a certain level in this determination, the control unit 5 stops the transmission of the first optical transmission means 9 (step S6), and avoids unnecessary emission of the first optical transmission signal 40. Consider the surrounding environment. The optical axis adjustment control unit 35 of the control unit 5 controls the drive control unit 6 to drive the drive units 7 and 8 to drive the direction of the second light reception unit 10 and / or the first light transmission unit 9. (Step S7).

  If it is determined in step S5 that the received light level is equal to or higher than a certain level, the control unit 5 determines whether or not all the received light levels match (step S8). If it is determined that they do not match, the process of step S7 described above is performed. If it is determined that all the received light levels match, the first optical transmission means 9 transmits the first optical transmission signal 40 to the optical receiver 16 (step S9), and the second optical reception. The means 10 receives the delivery information for the first optical transmission signal 40 from the optical receiver 16 (step S10). The control unit 5 determines whether or not there is an error in the received delivery information (step S11), and when it is determined that there is no error, the control unit 5 controls the signal selection circuit 12 to control the second light. The transmission signal (pilot light) 41 is sequentially selected (step S12).

  The control unit 5 calculates a second correction coefficient that is a coefficient that makes all the selected light reception levels equal (step S13), and registers and updates the second correction coefficient (step S14). On the other hand, when it is determined in step S11 that there is an error, the optical axis adjustment control unit 35 of the control unit 5 searches the second optical receiving unit 10 and / or the first optical transmission in order to search for a position without an error. The means 9 is driven in a direction (step S15). In addition, embodiment mentioned above is an example and the structure can be changed suitably. If it is determined in step S2 that there is no second correction coefficient, the first correction coefficient is read from the first correction coefficient recording memory 37 (step S16), and the level correction calculation unit 36 of the control unit 5 is a reception level detection circuit. The received light level of the second optical transmission signal 41 sent from 15 is multiplied (calculated) by the read first correction coefficient to correct the received light level (step S17). And it continues after step S5.

  Note that after step S 12, the level correction calculation unit 36 of the control unit 5 reads the first received light level of the second optical transmission signal 41 sent from the reception level detection circuit 15 from the first correction coefficient recording memory 37. Step S13 and subsequent steps may be performed after the light reception level is corrected by multiplying (calculating) 1 correction coefficient.

  The optical transmitter according to the present invention can easily align the optical axis even in an optical wireless transmission apparatus that uses transmission light with a narrow directivity angle. Since it can be adjusted, it is useful for an optical transmitter that aligns the optical axis between an optical transmitter and an optical receiver constituting the optical wireless transmission apparatus.

It is a figure which shows the structure of the optical transmitter and optical receiver which concern on the 1st Embodiment of this invention. 1 is a schematic diagram showing an optical wireless transmission device including an optical transmitter according to a first embodiment of the present invention. It is a figure for demonstrating the principle which detects the direction of the optical receiver in the optical transmitter which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the principle which detects the direction of the optical receiver in the optical transmitter which concerns on the 1st Embodiment of this invention. It is a table | surface which shows the relationship of the light reception level used in order to detect the direction of the optical receiver in the optical transmitter which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the optical wireless transmission apparatus when there is no shift | offset | difference of the optical axis between the optical transmitter which concerns on the 1st Embodiment of this invention, and an optical receiver. (A) In the case where there is a shift of the optical axis between the optical transmitter and the optical receiver according to the first embodiment of the present invention, (a) a diagram regarding a case where the first optical transmission signal is emitted with a wide directivity angle. is there. (B) It is a figure about the case where the 1st optical transmission signal is emitted with a narrow directivity angle. It is a figure for demonstrating the shift | offset | difference of an optical axis when the optical transmitter which concerns on the 1st Embodiment of this invention has an exterior. It is a figure which shows the structure of the control part of the optical transmitter which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the operation | movement flow of the optical axis adjustment in the optical transmitter which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the control part of the optical transmitter which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the operation | movement flow of the optical axis adjustment in the optical transmitter which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical transmitter 2 Encoding circuit 3, 19 Binary circuit 4, 28 Light emitting element driver 5 Control part (judgment means, adjustment means, calculation means)
6 Drive control unit 7, 8, 23 Drive means 9 First optical transmission means (transmission means)
10 Second optical receiving means (receiving means)
DESCRIPTION OF SYMBOLS 11, 18 Light reception circuit 12 Signal selection circuit 13 Demodulation circuit 14 Packet detection and analysis means 15 Reception level detection circuit 16 Optical receiver 17 1st optical reception means 20 Signal level detection circuit 21 Symbol decoding circuit 22 Horizontal movable part 23 Vertical movable Unit 24 symbol error detection circuit 25 error rate calculation circuit 26 error rate packet generation circuit 27 modulation circuit 29 second optical transmission means 30 refraction angle 35 optical axis adjustment control unit 36 level correction calculation unit 37 first correction coefficient recording memory (memory) Means, first storage means)
38 Second correction coefficient recording memory (second storage means)
39 Virtual Image 40 First Optical Transmission Signal (Transmission Light)
41 Second optical transmission signal (pilot light)
42 Transmission plate (optical filter)
44, 45 Substrate 50 Light receiving axis of second light receiving means 51 Light emitting axis of first light transmitting means 52 Light emitting axis of second light transmitting means 53 Video control device 54 Video display device 300 Light source PD1, PD2, PD3, PD4 light receiving element

Claims (2)

In the optical transmitter for adjusting the optical axis of the first optical signal to be optically transmitted from the transmission means to the optical receiver,
Receiving means configured by a plurality of receiving elements and receiving a second optical signal for adjusting the optical axis from the optical receiver;
Storage means for storing a correction coefficient serving as a reference when correcting a deviation of the optical axis of the second optical signal;
Determining means for determining whether or not the reception level of the second optical signal received by each receiving element of the receiving means satisfies a predetermined condition;
When the determination means determines that the predetermined condition is not satisfied, the direction of the receiving means and / or the transmission means is adjusted so as to satisfy the predetermined condition, and the predetermined condition is determined by the determination means. The second optical signal received by the receiving means includes reception error rate information indicating a reception error for the first optical signal transmitted by the transmitting means. Adjusting the direction of the receiving means and / or the transmitting means so that the reception error is eliminated, and an adjusting means for adjusting the optical axis,
When the optical axis shift occurs after the optical axes are aligned, the adjustment unit is received by the receiving unit after the correction coefficient stored in the storage unit and the optical axis shift have occurred. An optical transmitter characterized in that, based on the reception level of the second optical signal, the direction of the receiving means and / or the transmitting means is adjusted to align the optical axis. In the optical transmitter for adjusting the optical axis of the first optical signal to be optically transmitted from the transmission means to the optical receiver,
Receiving means configured by a plurality of receiving elements and receiving a second optical signal for adjusting the optical axis from the optical receiver;
First storage means for storing a first correction coefficient serving as a reference when correcting a deviation of the optical axis of the second optical signal;
Determining means for determining whether or not the reception level of the second optical signal received by each receiving element of the receiving means satisfies a predetermined condition;
When the determination means determines that the predetermined condition is not satisfied, the direction of the transmission means and / or the reception means is adjusted so as to satisfy the predetermined condition, and the predetermined condition is determined by the determination means. The second optical signal received by the receiving means includes reception error rate information indicating a reception error for the first optical signal transmitted by the transmitting means. Adjusting means for adjusting the direction of the transmitting means and / or the receiving means so as to eliminate the reception error, and aligning the optical axis;
Calculation means for calculating a second correction coefficient serving as a reference for correcting the deviation of the optical axis based on information on the reception level of the second optical signal when the optical axis is adjusted by the adjusting means. When,
Second storage means for storing the second correction coefficient calculated by the calculation means;
When the optical axis shift occurs after the optical axes are aligned, the adjusting means may cause the optical axis shift if the second correction coefficient is stored in the second storage means. Correcting the reception level of the second optical signal based on the reception level of the second optical signal received by the receiving means and the second correction coefficient after the occurrence, and storing the second optical signal in the second storage means; If the second correction coefficient is not stored, based on the reception level of the second optical signal received by the receiving means and the first correction coefficient stored in the first storage means. Correcting the reception level of the second optical signal;
The determination means determines whether the corrected reception level of the second optical signal satisfies the predetermined condition,
When the determination unit determines that the predetermined condition is satisfied by the determination unit, the adjustment unit determines that the second optical signal received by the reception unit satisfies the predetermined condition and then transmits the transmission unit. If the reception error rate information indicating a reception error with respect to the first optical signal transmitted by the receiver is included, the direction of the transmission unit and / or the reception unit is adjusted so that the reception error is eliminated, and the optical axis An optical transmitter characterized by combining.

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