JP2005277596A - Optical transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmitter for determining the presence or absence of the deviation of an optical axis for automatically matching the optical axis. <P>SOLUTION: The optical transmitter comprises a reception means 130 that comprises a plurality of light reception elements and receives a light adjustment signal for adjusting an optical axis from an optical receiver 101; a control unit 125 for determining whether the reception level of the light adjustment signal received by each light reception element in a light reception means satisfies a prescribed condition; and a drive control unit 126 for adjusting the direction of itself so that prescribed conditions are met, when it is determined that prescribed conditions are not met by the determination means, and adjusting the direction of itself so that a reception error is lost, when it is determined that prescribed conditions are not met by the determination means, and when the light adjustment signal received by the reception means includes reception error rate information for indicating reception errors to the light transmission signal transmitted by itself. <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. Another technique is to install an sighting device in the transmitter and connect an optical wireless transmission device that aligns the optical axis while looking at the sighting device, or a measuring device for detecting the received light level on the receiving device side. However, there is also an optical wireless transmission device that performs optical axis alignment with a pair of two persons. 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 to receive reception level information of transmission light from the transmission device and adjust the optical axis 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 it is necessary to keep a sufficient distance between the transmitting and receiving devices, the visible light emission output must be sufficiently large, and it is necessary to add the configuration, which causes an increase in the cost of the transmitting device. In addition, the device 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. In addition, even when a measuring device for detecting the received light level is connected to the receiving device and the operation is performed by a set of two people, it is necessary to prepare the measuring device for detecting the received light level, which requires a 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 (light adjustment) signal is transmitted from an optical transmission element for optical axis adjustment attached to a receiver. The light beam is received by a single light receiving element mounted on the transmitter, 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. 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.

  Considering the above, the transmitter is provided with a plurality of light receiving elements for receiving pilot light from the receiver, thereby eliminating the waste of optical axis adjustment. However, the optical axis aligned at this time is between the pilot light of the receiver and the light receiving element of the transmitter, and the optical axes of the light emitting element of the transmitter and the light receiving element of the receiver are aligned. I don't know if it is. Ideally, the optical axis of the transmitter's light-emitting element and the receiver's light-receiving element are parallel, but in the actual manufacturing process, the light-emitting axis and the light-receiving axis There may be cases where these are not necessarily parallel. Further, depending on the shape of the exterior (cover), the optical axis may be shifted due to a difference in incident angle when the light emitting axis and the light receiving axis pass through the exterior.

  An object of the present invention is to solve the above-described problem, and an object of the present invention is to provide a transmitter capable of automatically adjusting the optical axis by determining the presence / absence of deviation of the optical axis.

  In order to achieve the above object, according to the present invention, an optical transmitter having a function of adjusting an optical axis of an optical transmission signal transmitted to an optical receiver is configured by a plurality of light receiving elements and adjusts the optical axis. And receiving means for receiving an optical adjustment signal for receiving from the optical receiver, and determining whether or not a reception level of the optical adjustment signal received by each light receiving element of the receiving means satisfies a predetermined condition A determination unit, and when the determination unit determines that the predetermined condition is not satisfied, adjusts its direction so as to satisfy the predetermined condition, and determines that the predetermined condition is satisfied. If the optical adjustment signal received by the receiving means includes reception error rate information indicating a reception error with respect to the optical transmission signal transmitted by the receiver, Optical transmitter is characterized in that an adjusting means for adjusting its orientation so there is no signal errors is provided.

  The optical transmitter of the present invention has the above-described configuration, and can determine the presence or absence of optical axis deviation and automatically align the optical axis.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an optical wireless transmission apparatus including an optical transmitter according to an embodiment of the present invention. FIG. 2 is a flowchart for explaining an operation flow for adjusting the optical axis of the optical transmitter according to the embodiment of the present invention.

  First, an optical receiver of an optical wireless transmission apparatus including an optical transmitter according to an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the optical wireless transmission device 100 includes an optical receiver 101 and an optical transmitter 121. In the optical receiver 101, the optical transmission signal spatially transmitted by the optical transmission unit 129 of the optical transmitter 121 is received by the optical reception unit 102 having a relatively narrow directivity angle, and the optical transmission signal received by the optical reception unit 102 is received. The light receiving circuit 103 performs electrical amplification processing, the binarization circuit 104 converts the amplified optical transmission signal into a digital signal, the symbol decoding circuit 105 performs decoding, and the external device such as an image receiving device (not shown). Send.

  In the optical receiver 101, the pilot light emitting means 106 having a wide directivity angle transmits pilot light to the optical transmitter 121 so that the optical transmitter 121 adjusts the optical axis. Further, the pilot light emitting unit 106 also has a function of transmitting reception error rate information indicating a reception error of the optical transmission signal received by the optical receiving unit 102. The optical receiver 101 detects an error of an optical transmission signal (hereinafter also referred to as digitized data) received by the optical receiving means 102 and digitized by the binarization circuit 104.

  Error detection in the embodiment of the present invention is performed by the symbol error detection circuit 107. Further, there is a CRCC check circuit 108 that checks a CRCC (Cyclic Redundancy Check Code) added to a received optical transmission signal by a CRCC addition circuit 136 of the optical transmitter 121 described later in order to increase the accuracy of error detection. . Here, CRCC refers to an error detection code. The result detected by the symbol error detection circuit 107 and each error result detected by the CRCC check circuit 108 are counted in an error rate calculation circuit 109 for a predetermined time, and the result is transmitted to the pilot light emitting means 106 in order to transmit an error rate packet. The generation circuit 110 performs packetization, modulates the light emission signal to the pilot light emission means 106 in accordance with the packet by the modulation circuit 111, and sends the modulated signal to the light emitting element driver circuit 112, thereby using an optical transmitter using the pilot light. The reception state of the optical transmission signal transmitted from 121 is sent to the optical transmitter 121.

  Further, when detecting an error in the optical transmission signal received by the optical receiver 101, the symbol error detection circuit 107 detects the error rate when the optical transmission signal is not received at a certain level or higher. The reception level of the optical transmission signal received by the receiving means 102 and the light receiving circuit 103 is monitored by the signal level detection circuit 113, and when it is not received at a certain level or higher, the generation of the error rate packet is stopped.

  Next, an optical transmitter according to an embodiment of the present invention will be described with reference to FIG. The optical transmitter 121 receives a signal such as a video signal sent from an external data generation device (not shown), and the CRCC addition circuit 136 confirms the correctness of the optical transmission signal on the optical receiver 101 side after transmission. In addition, the optical transmission signal to be transmitted is divided into fixed sizes, and a CRCC code is added to each optical transmission signal. Further, in order to perform optical wireless transmission, the optical transmission signal is encoded by the encoding circuit 122, converted into a binary digital signal that can be optically transmitted by the binarization circuit 123, and sent to the light emitting element driver circuit 124. The light emitting element driver circuit 124 drives the optical transmission means 129 to optically transmit the binarized optical transmission signal, and the optical transmission signal is spatially transmitted to the optical receiver 101 as transmission light having a narrow directivity angle. Is done.

  The optical transmitter 121 has a pilot light receiving means 130 for receiving pilot light transmitted by the pilot light emitting means 106 mounted for adjusting the optical axis of the optical receiver 101. The pilot light receiving means 130 is composed of a plurality of light receiving elements. The light receiving circuit 131 performs processing such as electrically amplifying the received signal of each received light receiving element. Of the reception signals from the respective light receiving elements processed by the light receiving circuit 131, only a specific reception signal is selected by the control unit 125 in the signal selection circuit 132, and the reception level is detected in the reception level detection circuit 135 with respect to the selected reception signal. Is detected, and the result is delivered to the control unit 125. Further, the reception signal selected by the signal selection circuit 132 by the control unit 125 is demodulated by the demodulation circuit 133, and the packet detection analysis unit 134 receives the optical transmission signal on the optical receiver 101 side from the demodulated reception signal. Error rate information is detected, and the result is sent to the control unit 125.

  The control unit 125 selects a necessary reception signal by the pilot light receiving means 130 using the timely signal selection circuit 132 in order to align the optical axis of the optical transmitter 121 with the optical receiver 101, and in the reception level detection circuit 135. Based on the reception level of the received signal and the reception error rate information obtained by the packet detection analysis unit 134, the drive control unit 126 is controlled, and the drive units 127 and 128 are controlled, and the optical transmission unit 129 and the pilot light receiving unit 130 are controlled. Adjust the orientation. In addition, the control unit 125 constantly monitors the reception error rate information, so that even if the direction of the optical transmitter 121 changes for some reason, the control unit 125 controls the drive means 127 and 128 again. Then, the direction of the optical transmission means 129 is adjusted.

  Next, an operation flow for adjusting the optical axis of the optical transmitter according to the embodiment of the present invention will be described with reference to FIG. It is assumed that the optical axis of the optical receiver 101 is the same. For example, the pilot light receiving means 130 composed of four light receiving elements receives the pilot light from the optical receiver 101 (step S201). The control unit 125 controls the signal selection circuit 132 to sequentially select the reception signals included in the received pilot light, and checks the reception level of the reception signal whose level is detected by the reception level detection circuit 135 (step) S202). The control unit 125 determines whether or not the light reception levels of the light reception signals received by the four light receiving elements match (step S203). If it is determined that the received light levels of the received signals all match, the control unit 125 determines whether the received signal has received error rate information based on detection of the received error rate information by the packet detection analysis unit 134. Is determined (step S204). When it is determined that there is no reception error rate information, the control unit 125 controls the drive control unit 126 to stop the drive units 127 and 128 and fix the direction of the optical transmitter 121 (step S205). At this time, it can be said that the optical axes of the optical transmitters 121 are in alignment.

  If it is determined in step S203 that the received light levels of the received light signals do not all match, the control unit 125 controls the drive control unit 126 to drive the drive units 127 and 128 so that the received levels match. Thus, the direction of the optical transmitter 121 is adjusted (step S206), and then the process returns to step S202. In step S204, when it is determined that there is reception error rate information, that is, there is an error, the control unit 125 controls the drive control unit 126 to drive the drive units 127 and 128 minutely, and the error is detected. The direction of the optical transmitter 121 is adjusted so as to disappear (step S207), and the process returns to step S204.

  In step S205, the control unit 125 always receives the reception error rate in order to cope with a case where the optical axis of the optical transmitter 121 is shifted due to some external factor after the optical axis of the optical transmitter 121 is aligned. The presence or absence of information is monitored, and when there is reception error rate information, the above-described control is performed to align the optical axis of the optical transmitter 121. As described above, the optical transmitter 121 can always automatically align the optical axis.

  The optical transmitter according to the present invention can automatically determine the optical axis by determining whether or not there is a deviation of the optical axis. Therefore, the optical axis between the optical transmitter and the optical receiver constituting the optical wireless transmission device. This is useful for optical transmitters that match.

It is a figure which shows the optical wireless transmission apparatus containing the optical transmitter which concerns on embodiment of this invention. It is a flowchart for demonstrating the operation | movement flow of adjustment of the optical axis of the optical transmitter which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical wireless transmission device 101 Optical receiver 102 Optical receiving means 103, 131 Light receiving circuit 104, 123 Binarization circuit 105 Symbol decoding circuit 106 Pilot light emitting means 107 Symbol error detection circuit 108 CRCC check circuit 109 Error rate calculation circuit 110 Error Rate packet generation circuit 111 Modulation circuit 112, 124 Light emitting element driver circuit 113 Signal level detection circuit 121 Optical transmitter 122 Coding circuit 125 Control unit (determination means)
126 Drive control unit (adjustment means)
127, 128 Driving means 129 Optical transmitting means 130 Pilot light receiving means (receiving means)
132 signal selection circuit 133 demodulation circuit 134 packet detection analysis means 135 reception level detection circuit 136 CRCC addition circuit

Claims (1)

In an optical transmitter having a function of adjusting the optical axis of an optical transmission signal transmitted to an optical receiver,
A receiving unit configured by a plurality of light receiving elements and receiving an optical adjustment signal for adjusting the optical axis from the optical receiver;
Determining means for determining whether or not a reception level of the light adjustment signal received by each light receiving element of the receiving means satisfies a predetermined condition;
When it is determined by the determining means that the predetermined condition is not satisfied, the orientation is adjusted so as to satisfy the predetermined condition, and when the predetermined condition is determined to be satisfied, When the optical adjustment signal received by the receiving means includes reception error rate information indicating a reception error with respect to the optical transmission signal transmitted by itself, the direction of the optical adjustment signal is adjusted so that the reception error is eliminated. Adjusting means,
An optical transmitter characterized by comprising.

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