JP2007184707A - Indoor optical wireless transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical wireless transmission system that is less affected by the sunlight incident indoors. <P>SOLUTION: Each of first and second optical wireless transmission apparatuses A1, A2 in the optical wireless transmission system includes: a first light emitting element 1 that emits data light with a wavelength band of 1350nm to 1400nm and the luminous intensity in compliance with the class 1 stipulated by the International Electrotechnical Commission IEC60825-1 to an opposite optical wireless transmission apparatus; a second light emitting element 9 that emits guide light with a wavelength band of 1350nm to 1450nm and the luminous intensity in compliance with the class 1 stipulated by the International Electrotechnical Commission IEC60825-1 to the opposite optical wireless transmission apparatus; and a detector 6A and a control section 8A that use the guide light emitted from the second light emitting element 9 of the opposite optical wireless transmission apparatus to particularize a direction of the opposite optical wireless transmission apparatus with respect to its own optical wireless transmission apparatus. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an indoor optical wireless transmission system for transmitting light (data light) modulated by data to be transmitted.

  Products that use laser light indoors are classified based on their output power according to the international safety standard (IEC60825-1) of the product, and various safety considerations are observed for each class. It is obliged to do. In addition, the international standard of the safety regarding the said laser product is applied mutatis mutandis about the product using a light emitting diode (LED).

  In class 1, which is the safest of the multiple classes and does not require safety considerations, the light output allowed is the lowest. In a conventional indoor optical wireless transmission device that automatically finds and communicates with a communication counterpart device under a condition in which the optical output power based on this class 1 is limited, light emitted from the counterpart device (hereinafter referred to as guide light) The direction of the counterpart device is detected based on the received guide light (see, for example, Patent Document 1).

In the partner device detection method described above, it is necessary to accurately receive the guide light. Therefore, the illumination light such as a fluorescent lamp, which is considered as light that interferes with the guide light, is cut by a visible light filter and converted into the guide light by the illumination light. In addition to removing the interference, and using the light modulated at a predetermined frequency as the guide light, the guide light is received separately from the other interference light by receiving the light using this modulation frequency.
Japanese Patent No. 3059870

  However, even when the above-described measures for distinguishing and receiving the guide light are performed, when sunlight enters the guide light receiving unit in the optical wireless transmission device as interference light, the sunlight is compared with the fluorescent lamp. Since the intensity of the near-infrared light component is orders of magnitude stronger than that of the guide light, there is a problem that the direction of the counterpart device cannot be detected due to the interference of the sunlight with the guide light. In addition, since a large S / N is required for data light when data is communicated at high speed, data communication with the counterpart device becomes difficult when interference light such as sunlight enters the guide light receiving unit. There was also a possibility.

  The present invention has been made in view of the above. The purpose of the present invention is to comply with the international safety standard class 1 of products using laser light, and the direction of the counterpart device even when sunlight is incident on the light receiving portion. It is an object of the present invention to provide an optical wireless transmission system capable of detecting

  In order to solve the above-mentioned problem, the invention according to claim 1 specifies the mutual direction between the first and second optical wireless transmission devices using the guide light, and the first and second directions are specified. An indoor optical wireless transmission system that performs data transmission by transmitting and receiving data light modulated by data to be transmitted between optical wireless transmission apparatuses, wherein each of the first and second optical wireless transmission apparatuses includes: The data light has a wavelength band of 1350 nm to 1400 nm with respect to the partner device between the first and second optical wireless communication devices, and conforms to Class 1 defined by the international safety standard IEC60825-1 Class 1 defined by the international safety standard IEC60825-1 with respect to the first light emitting element that emits data light having the light intensity and the guide device with the guide light having a wavelength band of 1350 nm to 1450 nm. Has light intensity conforming to A second light emitting element that emits guide light; and direction specifying means for specifying a direction of the counterpart apparatus relative to the self apparatus using the guide light emitted from the second light emitting element of the counterpart apparatus. Is the gist.

  According to a second aspect of the present invention, in order to solve the above-described problem, the direction specifying means in each of the first and second optical wireless transmission devices receives a first light receiving unit that receives data light emitted from the counterpart device. A second light-receiving unit that receives the guide light emitted from the counterpart device, and a direction of the counterpart device based on the guide light received by the second light-receiving unit, with respect to the specified direction And means for directing data light emitted from the first light emitting element.

  In order to solve the above problem, the invention according to claim 3 specifies the mutual direction between the first and second optical wireless transmission devices using the guide light, and the first and second directions are specified. An indoor optical wireless transmission system that performs data transmission by transmitting and receiving data light modulated by data to be transmitted between optical wireless transmission apparatuses, wherein each of the first and second optical wireless transmission apparatuses includes: The first light emitting element that emits the data light to the partner device between the first and second optical wireless communication devices, and the guide light that emits the guide light to the partner device. And a first light-receiving unit that has high light-receiving sensitivity with respect to other wavelength ranges only for light in the wavelength range of 1350 nm to 1400 nm and receives data light emitted from the counterpart device For light in the wavelength range of 1350 nm to 1450 nm Has a high light receiving sensitivity to other wavelength ranges only hands, and summarized in that with a, a second light receiving portion for receiving the emitted guide light from the partner apparatus.

  According to a fourth aspect of the present invention, in order to solve the above problems, the first light receiving element has an lnP layer and a band gap energy corresponding to a wavelength of 1450 nm and is laminated on the lnP layer. The present invention includes a layer and a GalnAsP absorption layer having a band gap energy corresponding to a wavelength of 1350 nm and arranged on the opposite side of the undoped GalnAsP layer from the lnP layer.

  According to a fifth aspect of the present invention, in order to solve the above-mentioned problem, the second light receiving element has an lnP layer and an undoped GalnAsP layered on the lnP layer, having a band gap energy corresponding to a wavelength of 1400 nm. The present invention includes a layer and a GalnAsP absorption layer having a band gap energy corresponding to a wavelength of 1350 nm and arranged on the opposite side of the undoped GalnAsP layer from the lnP layer.

  According to the first and second aspects of the present invention, the guide light for detecting the direction of the counterpart device emitted from the first light emitting element of each of the first and second optical wireless communication devices is used as the international safety standard IEC60825-1. It has a light intensity that complies with Class 1 specified in, and the light in the wavelength range of 1350nm to 1450nm, where the power of sunlight is weak, so it is possible to reduce the interference caused by sunlight when receiving guide light, Even in the situation where sunlight is incident indoors, the guide light transmitted from the counterpart device can be received relatively strongly compared to the sun.

  In addition, according to the first and second aspects of the invention, the data light emitted from the second light emitting element of each of the first and second optical wireless communication devices is class 1 defined by the international safety standard IEC60825-1. In order to reduce the light interference during data reception, the light intensity is compliant with the above, the light reception power intensity is maintained to the maximum, and the light with a weak sunlight power is in the wavelength range of 1350 nm to 1400 nm. Even in a situation where sunlight is incident indoors, the data light sent from the counterpart device can be received relatively strongly compared to the sun.

  As a result, it is possible to suppress the influence of sunlight on the guide light and the data light, and it is possible to improve the reliability regarding data transmission between the first and second optical wireless transmission devices.

  Furthermore, according to the third to fifth aspects of the present invention, the first light receiving unit has a high light receiving sensitivity with respect to other wavelength ranges only for light in the wavelength range of 1350 nm to 1400 nm. The second light receiving unit is formed of a second light receiving element having high light receiving sensitivity with respect to other wavelength ranges only for light in the wavelength range of 1350 nm to 1450 nm. For this reason, the 1st light-receiving part of each optical wireless transmission apparatus can receive the guide light sent from the other party apparatus separately from sunlight even if it is a case where sunlight injects. Further, the second light receiving unit of each optical wireless transmission device distinguishes the data light transmitted from the counterpart device from the sunlight and maintains the maximum power of the data light even when sunlight is incident. Light can be received.

  As a result, it is possible to suppress the influence of sunlight on the guide light and the data light, and it is possible to improve the reliability regarding data transmission between the first and second optical wireless transmission devices.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the basic concept of the present invention will be described.

  FIG. 1 is a diagram illustrating an example of a measurement result of a wavelength spectrum of sunlight incident indoors. As shown in FIG. 1, in the sunlight wavelength spectrum, it can be seen that there is a wavelength region (wavelength range) where the power is weak due to water absorption between wavelengths 1350 nm and 1450 nm.

  Therefore, by adopting light in the above wavelength range as the guide light for detecting the direction between the optical wireless communication devices, it becomes possible to reduce the interference caused by sunlight, even in the situation where sunlight enters the room, The guide light sent from the counterpart device can be received relatively strongly compared to the interference light (sunlight). As a result, even when sunlight may enter the light receiving unit, the direction of the counterpart device by the received light guide light can be easily detected. It becomes possible to perform data communication in.

  FIG. 2 is a diagram showing exposure limits of a class 1 laser (spot diameter: 3.5 mm or less) in IEC60825-1: 2001, which is an international safety standard for laser light. As shown in FIG. 2, when a class 1 laser having a spot diameter of 3.5 mm or less according to IEC60825-1: 2001 is used as data light, the wavelength range of 1200 nm to 1400 nm is a range where the maximum power can be output.

  Therefore, in the optical wireless transmission system according to the first aspect of the present invention, light of 1350 nm to 1450 nm, which is the power reduction wavelength range of sunlight, is used as the guide light for detecting the direction between the optical wireless transmission devices, Moreover, as data light for data communication between optical wireless transmission devices, the above-mentioned solar power is within the maximum power wavelength range of 1200 nm to 1400 nm that satisfies the radiation exposure limit for lasers that comply with Class 1 of the international safety standard. Light having a wavelength range of 1350 nm to 1400 nm that matches the wavelength reduction range is employed. According to the optical wireless transmission system configured as described above, the guide light receiving unit of each optical wireless transmission device separates the guide light transmitted from the counterpart device from sunlight even if sunlight is incident. The data light receiving unit of each optical wireless transmission device can distinguish the data light transmitted from the partner device from the sunlight, even if sunlight is incident, and Since light can be received while maintaining the maximum light power, data communication with the counterpart device can be performed easily and reliably.

  In the optical wireless transmission system according to the second aspect of the present invention, the guide light receiving unit for detecting the direction between the optical wireless transmission devices is not affected by light (particularly sunlight) other than the guide light. In addition, a light receiving element having light receiving sensitivity only for light in a wavelength band of 1350 nm to 1450 nm, in other words, a light receiving element having no light receiving sensitivity for light in a wavelength band other than 1350 nm to 1450 nm is used. Further, in each optical wireless transmission device of the optical wireless transmission system according to the second aspect of the present invention, light other than data light (particularly sunlight) is used as a data light receiving unit for detecting data light sent from the counterpart device. In order to maintain the maximum power of the data light without being affected, the device has light receiving sensitivity only for light in the wavelength band of 1350 nm to 1400 nm, in other words, there is no light receiving sensitivity for light in the wavelength band other than 1350 nm to 1400 nm. An element is used.

  According to the optical wireless transmission system configured as described above, the guide light receiving unit of each optical wireless transmission device separates the guide light transmitted from the counterpart device from sunlight even if sunlight is incident. The data light receiving unit of each optical wireless transmission device can distinguish the data light transmitted from the partner device from the sunlight, even if sunlight is incident, and Since light can be received while maintaining the maximum light power, data communication with the counterpart device can be performed easily and reliably.

  FIG. 3 is a diagram showing an overall configuration of an optical wireless transmission system using the first and second optical wireless transmission apparatuses A1 and A2 according to the first embodiment corresponding to the first aspect of the present invention. FIG. 4 is a diagram showing a schematic configuration of the optical wireless transmission apparatus A1 shown in FIG.

  As shown in FIG. 3, the optical wireless transmission system according to the present embodiment is installed indoors, for example, on a desk or the like, and can be connected to a plurality of terminals such as a personal computer, A second optical wireless communication device A2 installed on, for example, the ceiling C, which is an upper position relative to the first optical wireless transmission device A1 indoors, and between these optical wireless transmission devices A1 and A2. This system performs data communication (bidirectional data optical transmission).

  As shown in FIGS. 3 and 4, the first optical wireless transmission device A1 has a substantially prismatic or cylindrical casing (housing) H. The housing H has a longitudinal direction in the figure, for example, It is arranged so as to be parallel to the horizontal direction, and at the upper end in the figure, light is transmitted to a second optical wireless transmission apparatus (hereinafter also referred to as a partner apparatus) A2 for ease of description. For example, a rectangular or circular window W for transmitting and receiving signals is formed.

  The first optical wireless transmission device A1 supplies, to the first light emitting element 1, a first light emitting element 1 for data light transmission such as a laser diode and a signal (data signal) corresponding to data to be transmitted. The light emitting element 1 is attached to, for example, one end of the short side of the housing H so that the optical axis thereof is along the horizontal direction.

  The first light emitting element 1 emits data light in the wavelength range 1350 nm to 1400 nm modulated by the data signal sent from the data supply unit 7.

  The first optical wireless transmission device A1 includes a collimator lens or the like arranged coaxially with respect to the optical axis of the data light on the optical path of the data light from the first light emitting element 1 in the housing H. The light shaping optical element 2 and its light transmission / reflection surface with respect to the optical axis of the data light on the downstream side of the optical element 2 on the optical path of the data light from the first light emitting element 1 in the housing H Are arranged coaxially and inclined at a predetermined angle, for example, first and second beam splitting optical elements 3B and 3A such as half mirrors.

  Further, the first optical wireless transmission device A1 includes a reflection optical system 4 disposed on the optical path of the data light from the first light emitting element 1 in the housing H and on the downstream side with respect to the second beam splitting optical element 3A. It has. In the reflection optical system 4, for example, the center position of the rectangular reflection surface 4 a is located on the optical axis of the first light emitting element 1.

  The reflection optical system 4 has, for example, a predetermined inclination angle (for example, 45 ° with respect to the optical axis of the first light emitting element) such that the reflecting surface 4a faces the emission surface of the first light emitting element 1 and the window W, respectively. ). The optical wireless transmission device A1 is attached to the reflection optical system 4, and passes through the reflection optical system 4 (reflection surface 4a) through the center of the reflection surface 4a and the optical axis of the first light emitting element. An actuator AT that can be rotated in the clockwise and counterclockwise directions in the figure, for example, about an axis (X axis) orthogonal to a plane passing through the central direction of the window W is provided.

  That is, by setting the inclination angle in the reflecting optical system 4 so that the light reflected by the reflecting surface 4a passes through the window W, the data light incident on the reflecting surface 4a passes through the reflecting surface 4a. Thus, the light is deflected (reflected) according to the deflection angle corresponding to the tilt angle and sent out through the window W.

  On the other hand, the first optical wireless transmission device A1 includes a condensing optical system 5A such as a condensing lens disposed concentrically with the reflecting surface of the first beam splitting optical element 3A, and the condensing optical system 5A. A light receiving portion 6A such as a photodiode (PD) for receiving the light collected by the light and converting it into an electric signal, and a light collecting unit disposed concentrically facing the reflecting surface of the second beam splitting optical element 3B. A condensing optical system 5B such as an optical lens and a light receiving portion 6B such as a photodiode for receiving the light collected by the condensing optical system 5B and converting it into an electric signal are provided.

  The above-described components 1 to 6B and AT are accommodated in the housing H, respectively.

  Furthermore, the first optical wireless transmission device A1 is electrically connected to the light receiving unit 6A and the actuator AT, and controls the actuator AT based on the electric signal converted by the light receiving unit 6A. A control unit 8A for controlling the inclination angle (data light deflection angle) of the reflection surface 4a of the reflection optical system 4 is provided.

  Further, the first optical wireless transmission apparatus A1 includes a data signal processing unit 8B electrically connected to the light receiving unit 6B.

  The first optical wireless transmission device A1 is installed in the vicinity of the window W in the housing H. In order to inform the counterpart device A2 of the direction of the own device (optical wireless transmission device), a predetermined communicable area (service A second light emitting element 9 for irradiating guide light (pilot light) in the area R1 is provided.

  In the present embodiment, the range of the service area R1 of the second light emitting element 9 in the first optical wireless transmission device A1 is set as a light emission directivity angle (field angle) of the second light emitting element 9 (FIG. 3). ).

  In the present embodiment, as the second light emitting element 9, an edge emitting semiconductor laser, a surface emitting laser, a light emitting diode, or the like that emits light in a wavelength region of 1350 nm to 1450 nm is used.

  On the other hand, as shown in FIG. 3, the second optical wireless transmission device A2 is configured by an optical transmission / reception module having substantially the same configuration as the first optical wireless transmission device A1 shown in FIG. In the optical wireless transmission device A2, the window W and the guide light exit surface of the second light emitting element 9 face downward, that is, the first optical wireless transmission device A1 side. Further, in the present embodiment, the range of the service area R2 of the second light emitting element 9 in the second optical wireless transmission device A2 is set as a wide range (see FIG. 3) as the light emission directivity angle of the second light emitting element 9. ing.

  As the second light emitting element 9 in the second optical wireless transmission apparatus A2, an edge emitting semiconductor laser, a surface emitting laser, a light emitting diode, or the like that emits light in a wavelength region of 1350 nm to 1450 nm is used.

  Next, the overall operation of this embodiment will be described.

  In the present embodiment, the guide light (incident from the second light emitting element 9 of the counterpart device (second optical wireless transmission device) A2 through the window W of the housing H in the first optical wireless transmission device A1 ( 3R2) is reflected through the reflecting surface 4a of the reflecting optical system 4 and is incident on the reflecting surface of the beam splitting optical element 3A.

  The guide light is reflected by the reflecting surface of the beam splitting optical element 3A and is received by the light receiving unit 6A through the condensing optical system 5A.

  Guide light data received by the light receiving unit 6A and converted into an electrical signal in proportion to the received light intensity is sent to the control unit 8A. In the control unit 8A, based on the transmitted guide light data, the reflection optical system for irradiating the light receiving unit 6B of the communication counterpart device A2 with the data light emitted from the first light emitting element 1 of the own device A1. 4 (reflection surface 4a) is obtained. The reflection surface 4a of the reflection optical system 4 is rotated by driving the actuator AT based on the control of the control unit 8A according to the obtained inclination angle (deflection angle). As a result, the light is emitted from the first light emitting element 1 of the device A1. The received data light is irradiated to the light receiving unit 6B of the counterpart apparatus A2.

  At this time, in the present embodiment, an element that outputs guide light in a wavelength region of 1350 nm to 1450 nm is used as the second light emitting element 9 in the counterpart apparatus A2, so that sunlight is incident on the light receiving unit 6A. Even in this case, as shown in FIG. 1, since the power of sunlight is significantly reduced in the wavelength band, the light receiving unit 6A can receive the guide light from the counterpart device A2 separately from the sunlight. It becomes. As a result, the direction detection process for the counterpart device A2 of the first optical wireless transmission device A1 through the actuator AT by the control unit 8A described above can be performed with high accuracy.

  Similarly, also in the second optical wireless transmission device A2, guide light (see R1 in FIG. 3) emitted from the second light emitting element 9 of the first optical wireless transmission device A1, or data light described later (FIG. 3, the direction detection process described above is executed. As a result, data light can be transmitted and received between the devices A1 and A2, and in other words, a data transmission path is established between the devices A1 and A2. Note that after the data transmission path is established, the communication path can be maintained even when the guide light output from the second light emitting element 9 is turned off.

  Thus, after the data transmission path establishment process between the first and second optical axis wireless transmission apparatuses A1 and A2 by the guide light (and data light) is completed, the second optical wireless transmission apparatus A2 The data light D2 (see FIG. 3) emitted from one light emitting element 1 and shaped into a beam close to a parallel light beam (collimated light) via the optical element 2 is transmitted through the beam splitting optical elements 3B and 3A, respectively. The light is transmitted toward the first optical wireless transmission apparatus A1 through the reflection surface 4a of the reflection optical system 4 and the window W.

  At this time, the data light D2 that has entered through the window W of the housing H in the first optical wireless transmission device A1 is reflected through the reflecting surface 4a of the reflecting optical system 4 and reflected by the beam splitting optical element 3A. The light passes through the surface and enters the beam splitting optical element 3B.

  The data light D2 is reflected by the reflecting surface of the beam splitting optical element 3B and is received by the light receiving unit 6B through the condensing optical system 5B.

  The data signal received by the light receiving unit 6B and converted into an electrical signal in proportion to the received light intensity is sent to the data signal processing unit 8B. In the data signal processing unit 8B, the data to be transmitted is demodulated from the transmitted data signal, and as a result, transmission of the transmission target data from the counterpart device A2 to the first optical wireless transmission device A1 is completed.

  At this time, in the present embodiment, an element that outputs data light in a wavelength region of 1350 nm to 1400 nm is used as the first light emitting element 1 in the counterpart apparatus A2, so that sunlight is incident on the light receiving unit 6B. Even in this case, as shown in FIG. 1 and FIG. 2, in the wavelength band, the power of sunlight is significantly reduced and the power of received data light is maintained at the maximum. The data light from the counterpart device A2 can be distinguished from sunlight and received with high sensitivity. As a result, the influence of sunlight interference on the reception of data light can be alleviated to the maximum.

  Similarly, the second optical wireless transmission device A2 can receive the data light D1 (see FIG. 3) emitted from the first light emitting element 1 of the first optical wireless transmission device A1, so that the data The influence of sunlight interference on light reception can be reduced to the maximum.

  Therefore, the reliability with respect to the influence of sunlight concerning the data transmission between the first and second optical wireless transmission devices A1 and A2 can be greatly improved.

  FIG. 5 is a diagram illustrating an example of the configuration of the light receiving unit 6A1 in each optical wireless transmission device according to the second embodiment corresponding to the second aspect of the present invention. Note that the configuration of each optical wireless transmission apparatus according to the second embodiment is substantially the same as the configuration shown in FIGS. In the present embodiment, the first light emitting element 1 in each optical wireless transmission device does not necessarily need to emit light in the wavelength band of 1350 nm to 1400 nm, and similarly, the first light emitting element 1 in each optical wireless transmission device. The second light emitting element 9 is not necessarily required to emit light having a wavelength band of 1350 nm to 1450 nm.

  As the light receiving unit 6A1 in the present embodiment, an element having light receiving sensitivity only for light in the wavelength band of 1350 nm to 1450 nm, in other words, 1350 nm to 1450 nm, so as not to be affected by light other than guide light (particularly sunlight). It is configured using an element having no (or very low) light receiving sensitivity to light in a wavelength band other than.

  For example, the light receiving section 6A1 shown in FIG. 5 includes an n-type lnP substrate 11, an n-lnP layer 12 having the same conductivity type grown on the substrate 11, and a predetermined on the n-lnP layer 12. And an undoped GalnAsP layer 13 having a band gap corresponding to a wavelength of 1450 nm grown by a thickness (layer thickness).

  The light receiving portion 61A1 has a p-lnP block layer 14 having the opposite conductivity type grown on the undoped GalnAsP layer 13, and 1350 nm grown on the p-lnP block layer 14 by a predetermined thickness (layer thickness). P-GalnAsP absorption layer 15 having a band gap corresponding to the wavelength of.

  Further, the light receiving portion 61A1 includes an n-electrode 10 and a p-electrode 11 that are attached to the outer surface of the n-type lnP substrate 11 and the outer surface of the GalnAsP absorption layer 15, that is, the lower upper surface of the multilayer structure including the constituent elements 11 to 15, respectively. It has.

  According to the light receiving unit 6A1 configured as described above, since an electric field is applied only to the undoped GalnAsP layer 13, only light (guide light) absorbed by the undoped GalnAsP layer 13 becomes an electric signal as a photocurrent.

  For example, when light having a wavelength shorter than 1350 nm is incident from the upper side (p electrode 16) side in FIG. 5, this incident light is absorbed by the p-GalnAsP absorption layer 15 and therefore does not reach the undoped GalnAsP layer 13. Therefore, no photocurrent is generated in the undoped GalnaP layer 13.

  Here, the P-lnP block layer 14 in the light receiving portion 6A1 functions to prevent carriers generated by absorption in the P-GalnAsP layer 15 on the surface from leaking into the undoped GalnAsP layer 13 and generating a photocurrent. It works as a layer.

  On the other hand, when light (guide light) having a wavelength in the band of 1350 nm to 1450 nm is incident from the upper side (p electrode 16) side in FIG. 5, this guide light is not absorbed by the P-GalnAsP layer 15 and is undoped GalnAsP. The light enters the layer 13 and is absorbed in the undoped GalnaP layer 13 to become a photocurrent.

  In addition, light having a long wavelength of 1450 nm or more is not absorbed by the undoped GalnAsP layer 13 because its energy is smaller than the band gap energy of the undoped GalnAsP layer 13, so that no photocurrent is generated in the undoped GalnAsP layer 13.

  As described above, the light receiving section 6A1 having the structure shown in FIG. 5 is configured as a light receiving element that is sensitive only to light (guide light) in the wavelength range of 1350 nm to 1450 nm.

  In addition, the configuration of the light receiving unit 6B1 in each optical wireless transmission device and communication counterpart device according to the second embodiment corresponding to the second aspect of the present invention is substantially the same as the configuration of the light receiving unit 6A shown in FIG. Therefore, the description is omitted.

  That is, the light receiving unit 6B1 in the present embodiment has a wavelength band of 1350 nm to 1400 nm so as not to be affected by light other than the guide light (particularly sunlight) and to maintain the received light power to the maximum. An element having light receiving sensitivity only for light, in other words, an element having no (or very low) light receiving sensitivity for light in a wavelength band other than 1350 nm to 1400 nm.

  Specifically, in the configuration shown in FIG. 5, the P-GalnAsP layer 15 can be realized by changing from a layer having a band gap corresponding to 1350 nm to a layer having a band gap corresponding to 1400 nm.

  As described above, according to the present embodiment, as the light receiving unit 6A1 in each optical wireless transmission device, an element having higher sensitivity to light in the wavelength band of 1350 nm to 1450 nm than light in other wavelength bands is used. Therefore, even if sunlight is incident on the light receiving unit 6A, as shown in FIG. 1, since the power of sunlight is significantly reduced in this wavelength band, the light receiving unit 6A is connected to the counterpart device A2. Can be received separately from sunlight. As a result, the direction detection process for the counterpart device A2 of the first optical wireless transmission device A1 through the actuator AT by the control unit 8A described above can be performed with high accuracy.

  Similarly, according to the present embodiment, the light receiving unit 6B1 in each optical wireless transmission device uses an element having higher sensitivity to light in the wavelength band of 1350 nm to 1400 nm than light in other wavelength bands. Even if sunlight is incident on the light receiving unit 6B, as shown in FIG. 1, the power of sunlight is significantly reduced in this wavelength band, and as shown in FIG. Since the light receiving intensity in class 1 can be maintained to the maximum, the light receiving unit 6B can distinguish the data light from the counterpart device A2 from sunlight and receive it with high sensitivity. As a result, the influence of sunlight interference on the reception of data light can be alleviated to the maximum, and the reliability of data transmission can be improved.

  In addition, it is naturally possible to adopt both the configuration of the first embodiment and the configuration of the second embodiment, and the reliability of data transmission between optical wireless transmission devices can be further improved.

  Note that it is naturally possible to employ both the configuration of the first embodiment and the configuration of the second embodiment, and the reliability of data transmission of the optical wireless transmission apparatus can be further improved.

  It is also possible to limit the guide light and data light to a narrower area within the specified range. In this case, the light receiving element that receives the light has sensitivity only in the range corresponding to the area. Therefore, it is possible to further improve the reliability.

  Furthermore, in this embodiment, an element having sensitivity only in a certain wavelength range is used due to the structure of the light receiving element. However, a combination with a wavelength cut filter or a filter that transmits only a predetermined wavelength is placed in front of the light receiving element. Can produce similar effects.

It is a figure which shows an example of the measurement result of the wavelength spectrum of the sunlight which entered indoor. It is a figure which shows the radiation limit of exposure of the class 1 laser (spot diameter: 3.5 mm or less) in IEC60825-1: 2001 which is an international standard for laser light safety. 1 is a diagram illustrating an overall configuration of an optical wireless transmission system using an optical wireless transmission apparatus and a communication partner apparatus according to a first embodiment of the present invention. It is a figure which shows schematic structure of the optical wireless transmission apparatus shown in FIG. It is a figure showing an example of the structure of the light-receiving part for guide light reception in each optical wireless transmission apparatus and communication partner apparatus concerning the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st light emitting element 2 Optical element 3A, 3B Beam splitter optical element 4 Reflective optical system 4a Reflecting surface 5A, 5B Condensing optical system 6A, 6A1, 6B Light receiving part 7 Data supply part 8A Control part 8B Data signal processing part 9 second light emitting element 10 n electrode 11 n-lnP substrate 12 n-lnP layer 13 undoped GalnAsP layer 14 p-lnP blocking layer 15 p-GalnAsP absorption layer 16 P electrode

Claims (5)

A mutual direction is specified between the first and second optical wireless transmission apparatuses using the guide light, and the first and second optical wireless transmission apparatuses whose directions are specified are modulated by data to be transmitted. An indoor optical wireless transmission system that transmits data by transmitting and receiving data light,
Each of the first and second optical wireless transmission devices includes:
Between the first and second optical wireless communication apparatuses, the data light has a wavelength band of 1350 nm to 1400 nm and complies with Class 1 defined by the international safety standard IEC60825-1 with respect to the partner apparatus. A first light emitting element that emits data light having light intensity;
A second light emitting element that emits guide light having a wavelength band of 1350 nm to 1450 nm and having light intensity conforming to class 1 defined by the international safety standard IEC60825-1 with respect to the counterpart device When,
Direction specifying means for specifying the direction of the counterpart device relative to the own device using guide light emitted from the second light emitting element of the counterpart device;
An indoor optical wireless transmission system comprising: The direction specifying means in each of the first and second optical wireless transmission devices includes a first light receiving unit that receives data light emitted from the counterpart device;
A second light receiving unit for receiving the guide light emitted from the counterpart device;
Means for specifying the direction of the counterpart device based on the guide light received by the second light receiving unit, and directing the data light emitted from the first light emitting element to the specified direction;
The indoor optical wireless transmission system according to claim 1, further comprising: A mutual direction is specified between the first and second optical wireless transmission apparatuses using the guide light, and the first and second optical wireless transmission apparatuses whose directions are specified are modulated by data to be transmitted. An indoor optical wireless transmission system that transmits data by transmitting and receiving data light,
Each of the first and second optical wireless transmission devices includes:
A first light emitting element that emits the data light to a mutual partner device between the first and second optical wireless communication devices;
A second light emitting element that emits the guide light to the counterpart device;
A first light-receiving unit that has high light-receiving sensitivity with respect to other wavelength ranges only for light in the wavelength range of 1350 nm to 1400 nm, and that receives data light emitted from the counterpart device;
A second light-receiving unit that has high light-receiving sensitivity with respect to other wavelength ranges only for light in the wavelength range of 1350 nm to 1450 nm, and that receives the guide light emitted from the counterpart device;
An indoor optical wireless transmission system comprising: The first light receiving element is:
an lnP layer, having an band gap energy corresponding to a wavelength of 1450 nm, an undoped GalnAsP layer stacked on the lnP layer, and having a band gap energy corresponding to a wavelength of 1350 nm, with respect to the undoped GalnAsP layer The indoor optical wireless transmission system according to claim 3, further comprising a GalnAsP absorption layer disposed on the opposite side of the lnP layer. The second light receiving element is
an lnP layer, having an band gap energy corresponding to a wavelength of 1400 nm, an undoped GalnAsP layer stacked on the lnP layer, and having a band gap energy corresponding to a wavelength of 1350 nm, to the undoped GalnAsP layer 4. The indoor optical wireless transmission system according to claim 3, further comprising a GalnAsP absorption layer disposed on the opposite side of the lnP layer.

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