JP4599847B2 - Optical wireless transmission device - Google Patents

Description

  The present invention relates to an optical wireless transmission apparatus that transmits an optical signal having a relatively narrow radiation angle from a transmitter to a receiver, and more particularly to an improvement in optical axis alignment between a transmitter and a receiver.

  Conventionally, there is an optical wireless transmission technology for performing spatial transmission of information using light. Infrared light is generally 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 a sufficient distance between transmission and reception is desired, it is necessary to sharply squeeze the light beam emitted from the transmission device so as to increase the directivity so that a sufficient light level is incident on the reception device side. . Therefore, the optical axes of the transmitting device and the receiving device must be aligned. However, the alignment of the optical axes is very troublesome because of using a light beam with low directivity or using an invisible infrared light beam. It becomes work. Therefore, conventionally, there has been proposed an optical wireless transmission device that can easily perform this optical axis alignment.

For example, an optical wireless transmission device that installs a sighting device in the transmitter and 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, and a pair of two Some optical wireless transmission devices perform axis alignment. Further, as disclosed in the following Patent Document 1 by the present applicant, a light source for adjusting the optical axis is provided on the light receiver side, and reception level information of the transmitted light from the transmitter is turned back, and the transmitter is accordingly transmitted. Some of them are adjusted on the side to adjust the optical axis.
JP-A-7-131422 (abstract)

  However, the conventional optical wireless transmission apparatus is intended to easily and accurately apply the transmission optical axis on the transmission side to the reception means on the reception side, and has a viewpoint of correctly facing the reception means on the reception side to the transmission side. It was missing. Even if the transmission light from the transmitter is applied to the receiving means such as the photodiode of the receiver, each receiving means has an angle within a range in which light can be received, and the transmission light must be received within this angle range. Even if the transmitted light hits the receiving means of the receiver, optical wireless transmission is not realized. In this regard, since the example of Patent Document 1 does not have a direction control means for causing the receiving side to face the transmitted light, it is necessary to move or tilt the receiver itself.

  The light receiving level information from the receiving side is received by the receiving means on the transmitter side, and the optical axis is adjusted in two stages, coarse and dense, by the driving means that can move the transmitting means and the receiving means of the transmitter integrally. Although this method can be considered, this method includes a light emitting element and a light receiving element having a relatively wide directivity angle as means for aligning the optical axis of both the transmitter and the receiver, and a more directivity angle on which information to be transmitted by optical radio is placed. However, since there is no means for making the receiver directly face the transmitted light, it is necessary to move or tilt the receiver itself.

  In addition, a structure is conceivable in which the receiving means on the receiving side is directly opposed to the transmitted light by the biaxial rotation driving means. Even if the transmission light spot hits the reception means before the reception side rotates to face the transmission light, the position of the reception means moves due to the rotation and the reception means deviates from the transmission light spot. In particular, when the directivity angle of the transmission light is narrowed down and the transmission light spot is small, it is a problem that the reception means is likely to be detached from the transmission light spot due to the positional variation of the reception means due to rotation.

  In view of the above-described problems, the present invention minimizes the positional fluctuation caused by the angle adjustment of the receiving means of the receiver and minimizes the positional variation between the transmitting light and the receiving means so that the optical axis can be reliably aligned with the optical axis. An object is to provide an apparatus.

The present invention, in order to achieve the above object, a first optical converting a first transmitter having an optical transmission means, an electric signal by receiving the first optical signal for transmitting a first optical signal An optical wireless transmission device comprising a receiver having a receiving means,
The transmitter is
Second optical transmission means for transmitting a second optical signal having a radiation angle wider than the radiation angle of the first optical signal;
Third optical receiving means for receiving third light having a radiation angle transmitted by the receiver wider than the radiation angle of the first optical signal;
An optical axis alignment unit configured to perform optical axis alignment of the first optical transmission unit based on the third optical signal received by the third optical reception unit;
The receiver
Second optical receiving means for receiving the second optical signal by a plurality of light receiving elements;
Display means for displaying optical axis alignment guides in the vertical and horizontal directions based on signals obtained by comparing the respective light reception levels detected by the plurality of light receiving elements;
Third optical transmission means for transmitting the third optical signal ;
Based on the optical axis alignment guide displayed on the display means, at least the first and second optical receiving means can be integrally rotated around two orthogonal rotation axes. In addition, the two axes are main signals and pass through a substantially light receiving center of the first optical receiving means for receiving the first optical signal having a radiation angle narrower than that of the second and third optical signals. Rotational drive means configured as described above is provided.

  According to the optical wireless transmission apparatus of the present invention, since the rotation axis of the receiving means of the receiver is configured to pass through the light receiving center, when rotating the receiving means with respect to transmission light having a narrow radiation angle, It is possible to prevent the receiving means from being removed from the spot of the transmitted light by moving either of the two rotation axes.

Embodiments of the present invention will be described below with reference to the drawings.
<Overall configuration of device>
FIG. 1 is a schematic configuration diagram showing an embodiment of an optical wireless transmission apparatus for realizing the optical axis alignment method of the present invention. As shown in FIG. 1, the optical wireless transmission apparatus according to the present invention performs video control in order to optically wirelessly transmit a video signal of the video control unit 3 located at a location away from the video display unit 4 to the video display unit 4 for display. It comprises a transmitter 1 provided on the unit 3 side and a receiver 2 provided on the video display unit 4 side.

  From the transmitter 1, the video signal is converted into an optical signal (L1 to be described later) and output, and the output optical signal is received within a certain radiation angle range B (= −B / 2 to + B / 2). Keep the given strength possible. On the other hand, the receiver 2 has a received light directivity angle A (= −A / 2 to + A / 2) that can be received by the light receiving element that receives the optical signal output from the transmitter 1. In order to realize the optical transmission, the light receiving element of the receiver 2 is caught within the range of the transmission light radiation angle B of the optical signal from the transmitter 1, and the light receiving element of the receiver 2 can receive the transmitted light. It is necessary to receive transmission light within the range of the light directivity angle A. Optical axis alignment in optical wireless transmission is to create the state as described above. In this embodiment, an LD (laser diode) is used as an optical transmission means for optically transmitting a video signal, and a PD (photodiode) is used as an optical reception means.

<Internal configuration of transceivers 1 and 2>
FIG. 2 is a schematic configuration diagram of the transmitter 1 and the receiver 2 of the optical wireless transmission apparatus of the present invention. Each of the transmitter 1 and the receiver 2 is provided with a first optical transmitter 11 and a first optical receiver 21 for transmitting and receiving the first optical signal L1 obtained by converting the video signal. Separately, in order to align the optical axis for transmitting the video signal, the transmitter 1 is provided with the second optical transmission means 12 and the third optical reception means 13, and the receiver 2 is provided with the second optical transmission means 12. An optical receiver 22 and a third optical transmitter 23 are provided. Finally, the optical axis alignment of the first optical signal L1 having a narrow radiation angle on the transmitter 1 side to the corresponding first optical receiving means 21 on the receiver 2 side from the front can be easily performed manually on the receiver 2 side. In order to do this, the second optical signal L2 having a wide radiation angle is transmitted from the second optical transmitter 12 on the transmitter 1 side, and the received light quantity is obtained by the second optical receiver 22 on the receiver 2 side. The direction of the transmitter 1 is detected and used for optical axis alignment for optical transmission of video signals.

  Here, in the transmitter 1, the first optical transmission unit 11, the second optical transmission unit 12, and the third optical reception unit 13 are integrated in the transmission side optical unit 14. The vertical rotation drive means 15 and the horizontal rotation drive means 16 can automatically rotate in the vertical and horizontal directions, respectively. In the receiver 2, the first optical receiving means 21, the second optical receiving means 22, and the third optical transmitting means 23 are integrated in the receiving optical unit 24, and the receiving optical unit 24 is manually operated. It can be rotated in the vertical and horizontal directions. Further, as shown in FIGS. 3 to 7, the vertical rotation shaft 31 v and the horizontal rotation shaft 31 h of the reception-side optical unit 24 are configured to pass through the center O of the first optical reception means 21.

<Optical axis alignment procedure: Transmitter 1 side automatic>
In order to optically transmit a video signal, a user first installs the transmitter 1 and the receiver 2 so as to face each other, and the third optical receiving means 13 of the transmitter 1 uses the third optical of the receiver 2. The direction of the receiver 2 can be detected by the optical signal L3 from the transmission means 23. In the present embodiment, an LED (light emitting diode) having a relatively wide radiation angle is used as the third optical transmission means 23 for aligning the optical axis, and a plurality of PDs having a relatively wide light receiving angle are used as the third optical reception means 13. By simply using the transmitter 1 and the receiver 2 facing each other, the user can install the light receiving element and the light emitting element within the range of the directivity angle.

  The third optical receiver 13 of the transmitter 1 that has received the optical signal L3 from the third optical transmitter 23 of the receiver 2 performs processing such as amplifying received signals from a plurality of PDs. The reception signal is detected by a reception level detection circuit (not shown), the reception level from each PD is compared, the drive control unit is controlled, and the transmission side optical unit 14 is driven by driving means 15 and 16 such as a stepping motor. The first optical signal L1 having a narrow emission angle on which the video signal is carried is applied to the first optical receiving means 21 of the receiver 2 by rotating and driving in the vertical direction and the horizontal direction, respectively.

<Optical axis alignment procedure: manual on receiver 2 side>
Next, in a state where the optical signal L1 hits the first optical receiving means 21 of the receiver 2, the direction of the receiving side optical unit 24 of the receiver 2 is manually adjusted so as to face the optical signal L1. The receiver 2 receives the optical signal L2 by a plurality of, for example, 2 × 2 PDs of the second optical receiving means 22, detects each received light level, and shows the result shown in FIG. Such optical axis alignment guides in the vertical and horizontal directions are displayed on the optical axis adjustment direction display unit 30. When aligning the optical axis, a human (operator) adjusts the receiving-side optical unit 24 in the vertical and horizontal directions while viewing the display information.

<Optical axis for video signal transmission matches>
Since the transmission side optical unit 14 and the reception side optical unit 24 can be directly opposed in the previous steps, the first optical transmission means 11 for transmitting the optical signal L1 carrying the video signal and the first optical transmission unit 11 The optical axes of the optical receiving means 21 are aligned.

  FIG. 4 is a diagram showing the first optical receiving means 21 on the receiver 2 side that receives the first optical signal L1 having a narrow radiation angle and the rotation axes 31v and 31h of the receiving optical unit 24. As the light receiving means of the first optical receiving means 21, a plurality of PDs, for example, 2 × 2 light receiving elements 21a are used, and the reference position when detecting the optical signal L1 by receiving light is a plurality of light receiving elements. It is the center O of 21a. This center O is the light receiving center, and if the intersection of the light receiving center O and the rotation axes 31v, 31h of the receiving optical unit 24 is made coincident, the position of the light receiving center O will be able to rotate around any axis 31v, 31h. Is immutable. In the present embodiment, the two orthogonal rotation axes are the vertical and horizontal rotation axes 31v and 31h. However, any axis can be used as long as it is a rotation axis passing through the light receiving center O. The light receiving center O is not displaced during the adjustment.

  FIGS. 5A and 5B respectively show the light receiving element of the first optical receiving means 21 corresponding to the first optical transmitting means 11 for video signal transmission in the receiver 2 of the optical wireless transmission apparatus according to the present invention. It is the side view and front view which show the example of the positional relationship of the light reception center O and rotating shaft 31v, 31h. The light receiving center O of the first optical receiving means 21 corresponding to the first optical signal L1 having a narrow radiation angle is configured such that the intersection of the two rotational axes 31v and 31h coincides. The positional displacement due to the rotation of the first optical receiving means 21 increases as the distance from the rotation center increases. However, if the biaxial rotation center and the light receiving center O of the first optical receiving means 21 coincide, The position variation due to the rotation of 24 can be ignored.

  6 and 7 respectively, the receiving-side optical unit 24 of the optical wireless transmission apparatus according to the present invention rotates around the light receiving center O of the first optical receiving means 21 that receives the first optical signal L1 having a narrow emission angle. It is a figure before and after. Even if the receiving side optical unit 24 rotates, the position of the light receiving center O of the first optical receiving means 21 does not change, so that the first optical receiving means 21 does not deviate from the transmission light spot S1 of the optical signal L1. No. Similarly, the optical signal L2 by the second optical transmission means 12 sent to the receiver 2 side is originally for matching the first optical signal L1 with the first optical reception means 21, and is sufficiently radiated. Since the angle is wide, the second optical receiving means 22 corresponding to the second optical signal L2 does not deviate from the transmission light spot S2 of the second optical signal L2 due to the rotation of the receiving optical unit 24.

  In FIG. 8, the rotation axis of the reception-side optical unit 24 is at a position away from the first optical reception means 21, and when the reception-side optical unit 24 rotates, the first optical reception means 21 changes to the first optical signal L1. In this case, the transmission light spot S1 is deviated. The state shown in the figure is more likely to occur when the first optical signal L1 is barely hitting the first optical receiving means 21.

It is a schematic block diagram which shows one Embodiment of the optical wireless transmission apparatus for implement | achieving the optical axis alignment method of this invention. It is a schematic block diagram of the transmitter and receiver of the optical wireless transmission apparatus of the present invention. It is a figure which shows the optical axis adjustment direction display part for the optical axis alignment of the receiver by this invention. It is a figure which shows the positional relationship of the rotating shaft of the 1st optical receiving means by the side of the receiver which receives the 1st optical signal with a narrow radiation angle, and a receiving side optical unit. FIG. 5 is an overall view of a receiver on which the receiving side optical unit of FIG. 4 is mounted. It is a figure before the receiving side optical unit of the optical wireless transmission apparatus by this invention rotates. It is a schematic diagram which shows a mode after the receiving side optical unit of the optical wireless transmission apparatus by this invention rotates. It is a schematic diagram which shows a mode that the receiving side optical unit of the optical wireless transmission apparatus which does not have the structure of this invention rotates.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Receiver 3 Image | video control part 4 Image | video display part 11 1st optical transmission means 12 2nd optical transmission means 13 3rd optical reception means 14 Transmission side optical unit 15 Vertical direction rotation drive means 16 Horizontal direction rotation Driving means 21 First optical receiving means 21a Light receiving element 22 Second optical receiving means 23 Third optical transmitting means 24 Receiving side optical unit 30 Optical axis adjustment direction display unit 31h Horizontal rotation axis 31v Vertical rotation axis O Light reception Center S1, S2 Transmitted light spot

Claims (1)

First a transmitter having a first optical transmission means for transmitting an optical signal, the light and a receiver having a first optical receiver means for converting into an electric signal by receiving the first optical signal A wireless transmission device,
The transmitter is
Second optical transmission means for transmitting a second optical signal having a radiation angle wider than the radiation angle of the first optical signal;
Third optical receiving means for receiving third light having a radiation angle transmitted by the receiver wider than the radiation angle of the first optical signal;
An optical axis alignment unit configured to perform optical axis alignment of the first optical transmission unit based on the third optical signal received by the third optical reception unit;
The receiver
Second optical receiving means for receiving the second optical signal by a plurality of light receiving elements;
Display means for displaying optical axis alignment guides in the vertical and horizontal directions based on signals obtained by comparing the respective light reception levels detected by the plurality of light receiving elements;
Third optical transmission means for transmitting the third optical signal ;
Based on the optical axis alignment guide displayed on the display means, at least the first and second optical receiving means can be integrally rotated around two orthogonal rotation axes. In addition, the two axes are main signals and pass through a substantially light receiving center of the first optical receiving means for receiving the first optical signal having a radiation angle narrower than that of the second and third optical signals. An optical wireless transmission apparatus comprising a rotation driving unit configured as described above.

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