JP2014207628A - Optical beacon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both of lengthening life and securing communication in the downlink direction of an optical beacon.SOLUTION: The invention relates to an optical beacon 4 that performs optical communication with an on-vehicle device 2 on a running vehicle 20. The optical beacon 4 comprises a light-emitting unit 13 for transmitting downlink light DO for communication in the downlink direction, and a control unit (beacon control device 7) for increasing the amount of light emitted by the light-emitting unit 13 in a first period T1 mentioned bellow than the amount of light emitted by the light-emitting unit 13 in a second period T2 mentioned bellow. The first period T1: a period with predetermined time length starting triggered by reception of an uplink signal. The second period T2: a period other than the first period T1.

Description

  The present invention relates to an optical beacon that performs optical communication with an in-vehicle device of a traveling vehicle.

As a traffic information service using a road-to-vehicle communication system, so-called VICS (Vehicle Information and Communication System: registered trademark of Road Traffic Information Communication System Center) using optical beacons, radio beacons or FM multiplex broadcasting has already been developed. ing.
Among these, the optical beacon employs optical communication using near infrared rays as a communication medium, and is capable of bidirectional communication with the in-vehicle device. Specifically, uplink information including travel time information between beacons held by the vehicle is transmitted from the in-vehicle device to the infrastructure-side optical beacon.

Conversely, downlink information including traffic jam information, section travel time information, event regulation information, lane notification information, and the like is transmitted from the optical beacon to the in-vehicle device.
For this reason, the optical beacon includes a light projecting / receiving device (also referred to as a “beacon head”) that projects and receives an optical signal with the vehicle-mounted device. A transmission / reception unit for optical communication having a light-emitting element that is transmitted toward a road and a light-receiving element that receives uplink light transmitted from an in-vehicle device is mounted (see Patent Document 1).

JP 2005-268925 A

In the above-described conventional optical beacon, in order to make an in-vehicle device compatible with optical communication sense that it has entered the downlink region, transmission of downlink light is always continued.
However, if the transmission of the downlink light is continued, there is a problem that the lifetime of the light emitting element tends to be reduced due to aging. In particular, when a light-emitting unit in which a plurality of light-receiving elements are closely arranged and arranged vertically and horizontally is employed, the light-emitting unit easily rises in temperature because all the light-emitting elements emit light, and the aging of the light-emitting elements may be accelerated. is there.

Thus, as one of the measures for extending the life of the optical beacon, it is conceivable to adjust the drive currents of all the light emitting elements so that the minimum light emission amount that can be received by the vehicle-mounted device is obtained. However, this measure increases the possibility that the on-vehicle device will miss the necessary downlink signal while passing through the downlink region, and is therefore not a very appropriate measure.
The present invention has been made in view of such a conventional problem, and an object thereof is to achieve both the extension of the lifetime of an optical beacon and the securing of communication in the downlink direction.

(1) An optical beacon of the present invention is an optical beacon that performs optical communication with an in-vehicle device of a traveling vehicle, and a light emitting unit that transmits downlink light for communication in a downlink direction, A control unit that increases the light emission amount of the light-emitting unit in the first period of time than the light emission amount of the light-emitting unit in the following second period.
First period: a period of a predetermined time length that starts when the uplink signal is received Second period: a period other than the first period

Note that the terms defined below are also used in this solution section.
First light emission amount: light emission amount of the light emitting unit in the first period Second light emission amount: light emission amount of the light emitting unit in the second period First element: light emitting element that increases the light emission amount in the first period Second element: second period The light emitting element that has already emitted light and does not increase the light emission amount in the first period (that is, a light emitting element having a constant light emission amount)

In addition, according to the latest interface standard for optical beacons, the amount of light reaching the downlink from the optical beacon to the vehicle-mounted device is a peak value of 4.5 μW / cm ² or more (excluding those that affect the attenuation rate) (Hereinafter referred to as “standard light quantity”).
Therefore, both the first light emission amount and the second light emission amount need to satisfy at least the above-mentioned standard light amount.

According to the optical beacon of the present invention, since the control unit increases the first light emission amount more than the second light emission amount, the downlink light is emitted at a higher first light emission amount in the first period after receiving the uplink signal. Provided to the vehicle-mounted device, the light emitting unit is suppressed to a lower second light emission amount in the other second period.
Therefore, by setting the second light emission amount to the minimum that can be received by the in-vehicle device, it is possible to reliably transmit the downlink light to the in-vehicle device with the increased first light emission amount while suppressing the deterioration of the light emitting element over time. Thus, it is possible to achieve both the extension of the lifetime of the optical beacon and the securing of communication in the downlink direction.

(2) In the optical beacon of the present invention, the start time of the first period may be simultaneously with the detection of reception of the uplink signal, but at the latest, the downlink frame including the lane notification information storing the vehicle ID ( The return frame may be set to a time point before the first continuous transmission after downlink switching.
The reason is that if the first light emission amount is increased before the continuous transmission, the possibility that the in-vehicle device can receive the return frame increases, and the in-vehicle device can easily detect the establishment of communication with the optical beacon.

(3) Moreover, in the optical beacon of the present invention, the start time of the first period is the next to the downlink frame (turnback frame) including the lane notification information storing the vehicle ID, which is transmitted first after downlink switching. May be set to a point in time before transmitting the downstream frame.
The reason is that the lane notification information storing the vehicle ID is usually included in the downstream frame next to the folded frame, so that the first emission amount is increased before transmission of the downstream frame. This is because the possibility that the in-vehicle device can receive the down frame including the lane notification information is increased, and the in-vehicle device can easily detect the establishment of communication with the optical beacon.

(4) In the optical beacon of the present invention, the end point of the first period may be set, for example, at a time point when 350 milliseconds have elapsed since reception of the uplink signal.
The reason for this is that in the optical beacon communication protocol, transmission of the downlink frame after downlink switching is continued for 350 milliseconds after reception of the uplink signal, so the end point of the first period is set to 350 milliseconds This is because it is possible to provide a higher first light emission amount of downlink light to the in-vehicle device that has transmitted the uplink signal at least for a predetermined time length required by the regulations.

(5) The optical beacon of the present invention may further include a sensor unit that senses the vehicle by transmitting incident light to the downstream side of the downlink region and detecting reflected light.
In this case, the end time of the first period may be set to a time when the sensor unit senses the vehicle within a predetermined time (for example, 1 second) from reception of an uplink signal.

  The reason is that when the sensor unit detects the vehicle within a predetermined time from the uplink reception, it can be estimated that the in-vehicle device that has transmitted the uplink signal has passed through the downlink region. This is because, if the detection time is set, while the in-vehicle device that has transmitted the uplink signal passes through the downlink region, it is possible to reliably provide a higher first light emission amount of downlink light to the in-vehicle device.

  (6) In the optical beacon of the present invention, when the light-emitting unit has the first element and the second element individually, the first element is turned off during the second period, and the first period The light emission amount of the light emitting unit may be increased by causing the first element to emit light.

  In this case, since the first element is turned off during the second period, the progress of the aging deterioration of the first element can be suppressed by the reduction of the light emission time. Moreover, since it becomes difficult to raise temperature compared with the case where a 1st and 2nd element always light-emits, progress of aged deterioration accompanying the temperature rise of a 2nd element can be suppressed.

  (7) In the case where the light emitting unit has the first element and the second element individually, the control unit may determine the current value to flow through the first element during the second period. The light emission amount of the light emitting unit may be increased by increasing the value of the current flowing through the first element during the first period.

In this case, since the current value of the first element is set lower in the second period, the progress of the aging deterioration of the first element can be suppressed by the decrease of the current value.
In addition, compared to the case where the first and second elements always emit light at a higher current value, the power consumption of the entire light emitting unit is reduced, the amount of heat generation is reduced, and the temperature is less likely to rise. It is possible to suppress the progress of aging deterioration accompanying the increase.

  (8) In the optical beacon of the present invention, the light emitting unit includes a first element group in which a plurality of the first elements are arranged in a predetermined pattern, and a second element group in which the plurality of the second elements are arranged in a predetermined pattern. It is preferable that the light emission direction of the second element group is directed upstream from the light emission direction of the first element group.

The reason is as follows. That is, in order to more reliably perform road-vehicle communication in a limited communication area, it is desirable that the in-vehicle device detects a downlink signal as upstream as possible in the downlink area.
In this case, if the light emission direction of the first element group that is turned off or the light emission amount decreases in the second period is set to the upstream side, the upstream end of the downlink region cannot be determined at a predetermined position, whereas the light emission amount is throughout the period. This is because the upstream end of the downlink region can be determined at a predetermined position by setting the light emitting direction of the constant second element group to the upstream side.

  (9) In the optical beacon of the present invention, the light emitting unit includes a first element group in which a plurality of the first elements are arranged in a predetermined pattern, and a second element group in which the plurality of the second elements are arranged in a predetermined pattern. The first element group and the second element group are alternately arranged in a mixed state on the same circuit board surface so that the downlink light can be transmitted to almost the entire downlink region. May be.

  In this case, since both the first element group and the second element group can transmit downlink light to almost the entire downlink region, the light emission amount of the light emitting unit is small in the second period and in the first period. In order to be large, almost the entire range of the downlink area will be dimmed.

  As described above, according to the present invention, in an optical beacon that performs optical communication with an in-vehicle device of a traveling vehicle, it is possible to achieve both a long life of the optical beacon and ensuring communication in the downlink direction. it can.

It is a block diagram which shows the whole structure of a road-vehicle communication system. It is the top view of the road which looked at the installation part of an optical beacon from the top. It is a side view of the road which shows the communication area | region and incident area of an optical beacon. It is a functional block diagram which shows an example of the circuit structure of an optical beacon. It is a sequence diagram which shows an example of the communication procedure of road-to-vehicle communication. (A) is a perspective view at the time of seeing the beacon head of an installation state from diagonally downward, (b) is a side view of the beacon head of an installation state. It is a perspective view which shows the internal structure of a beacon head. It is a side view of the road which shows the irradiation range of downlink light. It is a flowchart which shows an example of the light control which a beacon controller performs. It is explanatory drawing which shows an example of the arrangement pattern of a 1st element group and a 2nd element group. It is explanatory drawing which shows the other example of the arrangement pattern of a 1st element group and a 2nd element group.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overall system configuration]
FIG. 1 is a block diagram showing an overall configuration of a road-vehicle communication system according to an embodiment of the present invention. FIG. 2 is a plan view of the road R when the installation portion of the optical beacon 4 of this embodiment is viewed from above.
As shown in FIG. 1, the road-to-vehicle communication system of this embodiment includes an infrastructure-side traffic control system 1 and an in-vehicle device 2 mounted on a vehicle 20 (see FIG. 3) traveling on a road R. .

The traffic control system 1 includes a central device 3 provided in a traffic control room and the like, and a large number of optical beacons (optical vehicle detectors) 4 installed in various places on the road R. The optical beacon 4 transmits near infrared rays. Wireless communication can be performed with the in-vehicle device 2 by optical communication as a communication medium.
The optical beacon 4 includes a beacon controller 7 that performs communication control and the like, and a plurality of (four in the example of FIG. 1) beacon heads (projector / receiver) 8 connected to the sensor interface of the beacon controller 7. have.

The beacon controller 7 is connected to a communication unit 6 on the infrastructure side, and the communication unit 6 is connected to the central apparatus 3 by a communication line 5 such as a telephone line.
The communication unit 6 can be configured by, for example, a traffic signal controller that controls the color of a signal lamp, an information relay device that performs a relay process of traffic information on the infrastructure side, and the like.

The optical beacon 4 of this embodiment employs a full-duplex communication method. That is, the beacon controller 7 described later simultaneously performs transmission control in the downlink direction for the light emitting unit 13 for optical communication and reception control in the uplink direction for the light receiving unit 14 for communication.
On the other hand, the in-vehicle device 2 of the present embodiment employs a half-duplex communication method. That is, the below-described vehicle-mounted controller 21 does not simultaneously perform uplink direction transmission control for the optical transmission unit 23 and downlink direction reception control for the optical reception unit 24.

[Overall configuration of optical beacon]
The beacon head 8 of the optical beacon 4 includes a transmission / reception unit 11 for optical communication and a sensor unit 12 for vehicle detection inside a housing 31 (see FIG. 3).
As described above, in this embodiment, each unit 11, 12 for optical communication and vehicle detection is incorporated in the casing 31 of one beacon head 8, so that the optical communication function and the vehicle detection function are combined. A beacon 4 is configured.

The transmission / reception unit 11 is an optical transceiver that transmits and receives optical signals to and from the in-vehicle device 2 wirelessly.
As shown in FIG. 1, the transmission / reception unit 11 includes a light-emitting unit 13 for optical communication that transmits downlink light DO, and a light-receiving unit 14 for optical communication that receives uplink light UO and converts it into an electrical signal. Have.

A light emitting unit 13 for optical communication (hereinafter also referred to as “communication light emitting unit 13”) includes a transmission circuit that converts a downstream frame transmitted from the beacon controller 7 into a serial transmission signal having a predetermined transmission rate; A light emitting element made of a light emitting diode (LED) that converts the output transmission signal into an optical signal in a downlink direction.
The light emitting element of the communication light emitting unit 13 sends the downlink light DO (see FIG. 3), which is a near infrared light signal, obliquely downward toward the upstream side.

The light receiving unit 14 for optical communication (hereinafter also referred to as “communication light receiving unit 14”) amplifies a light receiving element such as a photodiode (PD) and an electric signal output from the light receiving element. And a receiving circuit for generating a digital signal.
The light receiving element of the communication light receiving unit 14 receives the uplink light UO (see FIG. 3) which is a near-infrared light signal transmitted from the vehicle-mounted device 2, and the receiving circuit of the communication light receiving unit 14 receives the received uplink. The optical UO is converted into an electric signal and sent to the beacon controller 7.

The sensor unit 12 is a light detection sensor for detecting the presence of the vehicle 20 passing almost directly below the beacon head 8 without contact.
As shown in FIG. 1, the sensor unit 12 includes a vehicle sensing light emitting unit 15 that transmits incident light IO, and a vehicle sensing light receiving unit 16 that receives reflected light RO and converts it into an electrical signal.

The vehicle-sensing light-emitting unit 15 (hereinafter also referred to as “sensing light-emitting unit 15”) transmits incident light IO (see FIG. 3), which is a light pulse signal having a predetermined period, downward.
The vehicle sensing light receiving unit 16 (hereinafter also referred to as the “sensing sensing light receiving unit 16”) receives and receives the reflected light RO (see FIG. 3) of the incident light IO on the road R and the vehicle 20. The reflected light RO is converted into an electric signal and sent to the beacon controller 7.

The beacon controller 7 includes a computer device having a signal processing unit, a CPU, a memory, and the like. And a function as a sensing control unit of the vehicle 20.
The beacon controller 7 stores a computer program for communication control and sensing control in a storage device, and the CPU reads out and executes the program so that the CPU controls the communication control unit and the sensing control unit. Function as.

For example, the beacon controller 7 transmits a downlink signal including lane communication information without a vehicle ID to the communication light emitting unit 13 at a predetermined period, and the vehicle that the in-vehicle device 2 transmits when receiving the downlink signal is triggered. Wait for the uplink signal containing the ID.
When the beacon controller 7 receives the uplink signal at the communication light receiving unit 14, the beacon controller 7 includes another lane notification information storing the vehicle ID extracted from the uplink signal and provision information for the vehicle ID. A downlink signal is generated to perform downlink switching, and the generated downlink signal is transmitted to the communication light emitting unit 13 at a predetermined period.

Further, if information useful for traffic signal control such as probe information is included in the uplink signal, the beacon controller 7 transfers the information to the central device 3.
Further, the beacon controller 7 transmits the incident light IO having a predetermined wavelength to the sensing light emitting unit 15 at a constant intensity and a pulse period, and whether the received light intensity of the reflected light RO received by the sensing light receiving unit 16 is equal to or greater than a threshold value. Thus, the presence of the vehicle 20 is detected. This threshold value is not limited to a fixed value, and may vary depending on, for example, a follow-up process according to the received light intensity of the reflected light RO.

That is, the beacon controller 7 generates a sensing signal of the vehicle 20 and transmits the sensing signal to the central device 3 when the light receiving intensity of the reflected light RO that is equal to or greater than the threshold value is detected in the sensing light receiving unit 16.
The wavelength of the incident light IO transmitted from the sensing light emitting unit 15 is the same as the wavelength of the downlink light DO transmitted from the communication light emitting unit 13 or close enough to cause interference with the downlink light DO. Wavelength (for example, 850 nm).

[Optical beacon installation status]
As shown in FIG. 2, the optical beacon 4 of the present embodiment is installed on a road R having a plurality (four in the illustrated example) of lanes R1 to R4 in the same direction.
The optical beacon 4 includes a plurality of the beacon heads 8 provided respectively corresponding to the lanes R1 to R4, and one beacon controller 7 which is a control unit that collectively controls the beacon heads 8. ing.

The beacon controller 7 is installed on a support column 17 standing on the side of the road. Each beacon head 8 is attached to an erection bar (beam member) 18 that is horizontally installed from the support column 17 to the road R side, and is disposed immediately above each lane R1 to R4 of the road R.
The communication light emitting unit 13 of each beacon head 8 emits the downlink light DO toward the upstream side in the vehicle traveling direction from directly below the own device, and thereby, road-to-vehicle communication with the in-vehicle device 2. The communication area A for performing the above is set on the upstream side of the beacon head 8.

  Further, the sensing light emitting unit 15 of each beacon head 8 emits the incident light IO directly below the own aircraft, and thereby the sensing area of the vehicle 20 that passes through the predetermined lanes R1 to R4 of the road R. The incident region B is set almost directly below the beacon head 8.

[Communication area and incident area of optical beacons]
FIG. 3 is a side view of the road R showing the communication area A and the incident area B of the optical beacon 4.
As shown in FIG. 3, the communication area A of the transmission / reception unit 11 includes a downlink area DA (solid hatched portion) that is a receivable range of the downlink light DO by the in-vehicle device 2 and an uplink light UO by the beacon head 8. And an uplink area UA (dashed hatched portion), which is a light receiving range.

According to the “near-infrared interface standard” of an optical beacon (optical vehicle sensor), the upstream ends c0 of both areas DA and UA coincide with each other.
Further, the standard values (in the case of ordinary roads) of the upstream and downstream end positions of the areas DA and UA in the above standard are exemplified as follows. However, this standard value is a value when the height H from the road surface is 1.0 m and the upstream direction from the position immediately below the light emitter / receiver 8 (origin O) is a positive number.

Downstream area DA downstream end position a0: +1.3 m
Downstream end position b0 of the uplink area UA: a0 + 2.1 m (= 3.4 m)
Upstream end position c0 of both areas DA and UA: b0 + 1.6 m (= 5.0 m)

The incident area B of the sensor unit 12 is an irradiation range of the incident light IO on which the sensing light emitting unit 15 enters the road R.
Here, if the light emission direction E1 of the incident light IO is set strictly below (downward in the vertical direction), for example, when a puddle is formed on the road surface when it rains, the intensity of the reflected light RO from the road surface increases. There is a high possibility that detection will increase and proper vehicle sensing will not be possible. Therefore, normally, the emission direction E1 of the incident light IO is directed upstream (plus side) by a predetermined angle α (for example, 4.5 °) with respect to the vertical direction.

The set values of the upstream and downstream end positions x0 and y0 of the incident area B at the road surface height H = 1.0 m when the light emission direction E1 is oriented as described above are as follows.
Downstream end position x0 of incident area B: -0.15 m
Upstream end position y0 of incident area B: +0.93 m

The light emission direction E1 of the incident light IO may be directed downstream (minus side) by a predetermined angle (for example, 4.5 °) with respect to the vertical direction, contrary to the above.
In this way, it is possible to further reduce the interference of the incident light IO with the downlink light DO, compared to the case where the light emission direction V1 is directed upstream with respect to the vertical direction.
If the light emission direction E1 is directed downstream, the downstream end position a0 of the downlink area DA can be set further downstream, and the length of the downlink area DA in the vehicle traveling direction can be extended. For this reason, there is an advantage that the downlink communication capacity can be expanded in the optical beacon 4 having both the optical communication function and the vehicle sensing function.

[Configuration of in-vehicle device]
As shown in FIG. 3, the in-vehicle device 2 of this embodiment includes an in-vehicle controller 21 and an in-vehicle head 22. An optical transmitter 23 and an optical receiver 24 are accommodated in the in-vehicle head 22.
Among these, the optical transmission unit 23 has a light emitting element that emits uplink light UO (uplink direction optical signal) made of near infrared rays, and the optical reception unit 24 is a near infrared ray transmitted to the downlink area DA. And a light receiving element that receives downlink light UO (an optical signal in the downlink direction).

The optical transmission unit 23 is a light emitting circuit that converts an upstream frame output from the in-vehicle controller 21 into a serial transmission signal having a predetermined transmission rate, and converts the output transmission signal into an optical signal in the uplink direction. And a light emitting element made of a diode or the like.
According to the current standard, the transmission speed of the uplink optical UO transmitted by the optical transmission unit 23 of the in-vehicle device 2 is 64 kbps.

The light receiving unit 24 includes a light receiving element such as a photodiode and a receiving circuit that amplifies an electric signal output from the light receiving element and generates a digital reception signal.
According to the current standard, the transmission speed of the downlink optical DO received by the optical receiver 24 is 1024 kbps.

The in-vehicle controller 21 includes a computer device having a signal processing unit, a CPU, a memory, and the like, and has a function as a communication control unit that performs road-to-vehicle communication with the optical beacon 4.
The in-vehicle controller 21 stores a computer program for communication control in a storage device, and the CPU functions as the communication control unit when the CPU reads and executes the program.

Furthermore, the in-vehicle controller 21 generates traveling data of the host vehicle (for example, probe information that is traveling locus data in which passing positions and passing times are arranged in time series) as uplink data, and the optical transmission unit 23. It also has a function of transmitting to the uplink.
In this case, for example, if the uplink speed is increased, more probe information (such as a longer road section that records the travel locus, or a higher recording density of the passage position and passage time in the same road section) Information) can be transmitted.

In addition, the vehicle-mounted controller 21 of this embodiment may have a circuit configuration in which a simple control unit including an ASIC (Application Specific Integrated Circuit) is provided separately from the main body control unit including the CPU.
For example, when the optical receiving unit 24 receives any downlink frame, the simple control unit includes only one uplink frame (conventional uplink frame having a transmission rate of 64 kbps) including the vehicle ID of the host vehicle, and the optical transmission unit 23. Has the function of transmitting to the uplink.

[Circuit configuration of optical beacon]
FIG. 4 is a functional block diagram showing an example of the circuit configuration of the optical beacon 4.
As shown in FIG. 4, the beacon head 8 includes a light emitting unit 13 and a light receiving unit 14 for optical communication, and a light emitting unit 15 and a light receiving unit 16 for vehicle detection.
The beacon controller 7 includes a communication IC 69 for communication control, a sensing processing unit 71 for sensing control, and a main CPU 70 and a sensing CPU 72 that perform digital signal processing.

The light emitting unit 13 for optical communication includes a light emitting member 42 for optical communication and a drive circuit 61, and the light receiving unit 14 for optical communication includes a light receiving member 43 for optical communication, an amplifier 62, a filter circuit 63, and a comparator 64. Including.
The communication IC 69 converts the downlink data acquired from the main CPU 70 by a predetermined encoding method (for example, Manchester code), generates a pulse signal P1 including a serial electric signal having a predetermined period, and generates the pulse signal P1. Output to the drive circuit 61.

  The drive circuit 61 includes a switching element that generates a drive voltage of the light emitting element based on the pulse signal P1 input from the communication IC 69, and outputs the generated drive voltage to the light emitting member 42 to drive the light emitting element.

The amplifier 62 amplifies the electrical signal photoelectrically converted by the light receiving element of the light receiving member 43, and outputs the amplified electrical signal to the filter circuit 63. The filter circuit 63 extracts a high-speed signal component having at least a transmission rate in the uplink direction (64 kbps in this embodiment), and outputs the extracted high-speed signal to the comparator 64.
The comparator 64 compares the input high-speed signal with a threshold value, and outputs a digital reception signal (bit data) extracted by this comparison to the communication IC 69.

  The communication IC 69 determines the transmission speed of the received signal using the first 5-byte idle pattern and generates a reception clock, samples the bit data with the generated clock, and reproduces the upstream data included in the upstream frame. Then, the communication IC 69 sends the reproduced uplink data to the main CPU 70.

The vehicle sensing light emitting unit 15 includes a vehicle sensing light emitting member 45 and a drive circuit 65, and the vehicle sensing light receiving unit 16 includes a vehicle sensing light receiving member 46, an amplifier 66, a filter circuit 67, and a peak hold circuit. 68.
The sensing processing unit 71 autonomously generates a pulse signal P2 having a predetermined period and outputs the pulse signal P2 to the drive circuit 65.

The driving circuit 65 includes a switching element that generates a driving voltage for the light emitting element based on the pulse signal P2 input from the sensing processing unit 71, and outputs the generated driving voltage to the light emitting member 45 to drive the light emitting element. To do.
The amplifier 66 amplifies the electric signal photoelectrically converted by the light receiving element of the light receiving member 46 and outputs the amplified electric signal to the filter circuit 67. The filter circuit 67 extracts a signal having at least the same frequency component as the incident light IO and outputs the extracted signal to the peak hold circuit 68.

The peak hold circuit 68 detects the envelope of the input electric signal and outputs the detection signal to the sensing processing unit 71.
The sensing processing unit 71 determines whether or not the input detection signal is equal to or greater than a predetermined threshold, and outputs a pulse signal during a period when the detection signal is equal to or greater than the threshold to the sensing CPU 72 as sensing data. Then, the sensing CPU 72 outputs the sensing data acquired from the sensing processing unit 71 to the main CPU 70.

[Contents of road-to-vehicle communication and incident light transmission timing]
FIG. 5 is a sequence diagram illustrating a communication procedure of road-to-vehicle communication performed in the communication area A.
Here, in FIG. 5, a frame with a white circle indicates that the frame does not include a vehicle ID (a frame having “lane notification information” without a vehicle ID), and a frame with a black circle indicates a vehicle ID. This indicates that the frame includes the frame (the frame having the “lane notification information” with the vehicle ID).

  In the following description of road-to-vehicle communication, it is assumed that the operation subject is the optical beacon 4 and the in-vehicle device 2, but the actual communication control is performed by the beacon controller (communication control unit) 7 of the optical beacon 4 and the in-vehicle device. The in-vehicle controller (communication control unit) 21 of the machine 2 executes.

As shown in FIG. 5, the optical beacon 4 continues to transmit the downlink frame DL1 at a predetermined transmission cycle from the beacon head 8 provided for each of the lanes R1 to R4. At this stage, the vehicle ID is not stored in the lane notification information.
When the vehicle 20 enters the downlink area DA, the vehicle-mounted device 2 receives the downlink frame DL1 including the lane notification information (no vehicle ID) or the other downlink frame DL1, and the vehicle 20 enters the communication area A of the optical beacon 4. Sense that it has entered.

At this time, the in-vehicle device 2 generates an uplink frame UL1 (hereinafter also referred to as “ID storage frame U1”) in which the vehicle ID is stored in the lane notification information, and transmits the uplink frame UL1 in the uplink.
When there is information to be provided to the optical beacon 4 such as travel time information, the information is stored in the actual data portion of the ID storage frame U1.

When the ID storage frame U1 is properly received by the optical beacon 4 through the CRC check of the received frame, etc., the optical beacon 4 starts to repeatedly transmit the downlink frame DL2 after switching the downlink within 10 milliseconds at the latest. To do.
In a plurality of downlink frames DL2 repeatedly transmitted in downlink, a downlink frame including a vehicle ID in lane notification information continuously transmitted at the head portion (downlink DL2 with a black circle: hereinafter also referred to as “turn-back frame”). And a normal downlink frame DL2 including predetermined provision information repeatedly transmitted thereafter.

  That is, when receiving the ID storage frame U1 from the vehicle-mounted device 2, the optical beacon 4 generates a return frame including the acquired vehicle ID value in the lane notification information, and repeatedly transmits the generated return frame after downlink switching. By interweaving with a plurality of downstream frames DL2, the other vehicle unit 2 is notified that it has detected the vehicle ID notified by the vehicle unit 2.

  The downlink frame DL2 that is repeatedly transmitted after downlink switching includes, for example, uplink information such as traffic jam information, section travel time information, event regulation information, signal information (lighting time of traffic lights, etc.), and charging station position information. Predetermined information determined to be provided according to the header information and data contents of the frame UL1 is included.

The repeated transmission of the downlink frame DL2 is repeated as much as possible within the predetermined time.
Further, as shown in FIG. 5, the return frame (the downlink frame DL2 with a black circle) is a series of a plurality of downlink frames DL2 (for example, five downlink frames DL2) constituting the downlink information during the transmission period of the provided information. And is repeatedly transmitted (every 5 frames in the example of FIG. 5) included only at the beginning of a series of downlink frames DL2.

Since a series of downlink frames DL2 constituting the downlink information can be stored up to 80, ID storage frames (downlink frames DL2 with black circles) have a ratio of one in 80 frames in the case of the least frequency. Will be stored.
The in-vehicle device 2 receives a plurality of downlink frames DL2 from the optical beacon 4, and determines whether or not any of the plurality of downlink frames DL2 includes lane notification information in which the vehicle ID of the host vehicle is written. To do.

When the determination result is affirmative, the in-vehicle device 2 confirms that the loopback of the vehicle ID of the own vehicle has been successful, and switches the communication of the own device from transmission to reception at this point.
On the contrary, while the determination result is negative, the in-vehicle device 2 determines that the loopback of the vehicle ID of the own vehicle is not successful and keeps the communication of the own device as transmitted. In this case, for example, the in-vehicle device 2 transmits the upper frame UL1 again after a predetermined time (for example, 30 ms) after transmission of the upstream frame U1 transmitted previously. The in-vehicle device 2 repeats this retransmission operation until the vehicle ID loopback is successful.

In FIG. 5, the time axis extending to the right from “optical beacon (vehicle detection)” indicates the transmission timing of the incident light IO transmitted by the sensing light emitting unit 15 by the optical beacon 4 of the present embodiment having a vehicle detection function. Is shown.
As shown in this transmission timing, the incident light IO transmitted to the road R for vehicle detection is always at a predetermined transmission period, separately from the downlink light DO transmitted to the road R for optical communication. Sent to road R.

Further, in FIG. 5, the downlink frame DL1 is indicated by a thin line arrow, and the downlink frame DL2 is indicated by a thick line arrow, which is transmitted in the first period T1 by “light control” (FIG. 9) described later. The downstream frame DL2 means that the light emission amount of the communication light emitting unit 13 is increased compared to the downstream frame DL1 transmitted in the second period T2.
The specific contents of the first period T1 and the second period T2 and the details of the dimming control for switching the light emission amount for each of the periods T1 and T2 will be described later.

[Beacon head exterior configuration]
FIG. 6 shows an external configuration in the installed state of the beacon head 8. 6A is a perspective view when the beacon head 8 in the installed state is viewed obliquely from below, and FIG. 6B is a side view of the beacon head 8 in the installed state.

  As shown in FIG. 6, the beacon head 8 includes a casing 31 having an inclined surface 36 formed at the bottom, and a gate-shaped bracket 32 that supports the left and right side surfaces of the casing 31. The central portion of the bracket 32 in the left-right direction is fixed to the beam member 18 via a clamp 33, whereby the casing 31 is attached in a suspended state below the beam member 18.

The housing 31 includes a casing 34 having a substantially rectangular shape when viewed from above and a ceiling plate 35 joined to a flange portion of the upper opening of the casing 34.
A first bottom surface portion 36 located on the upstream side and a second bottom surface portion 37 located on the downstream side are formed at the bottom of the casing 34. The first bottom surface portion 36 is an inclined surface inclined upward from the upstream edge of the second bottom surface portion 37 toward the upstream side, and the second bottom surface portion 37 is set almost horizontally in the installed state of FIG. Has been.

On the first bottom surface portion 36, a pair of left and right rectangular transmission window portions 36L, 36R are juxtaposed in the left-right direction at intervals.
These transmission window portions 36L and 36R conform to a predetermined wavelength (a “near infrared interface standard” for optical beacons) in which a pair of left and right openings formed in the first bottom surface portion 36 is used for optical communication with the vehicle-mounted device 2. It is configured by closing with a light transmitting sheet that mainly transmits light in the wavelength band.

Of the two transmission window portions 36L and 36R, the left window portion 36L is a light reception window for the uplink light UO and corresponds to the light receiving member 43 (see FIG. 7) for optical communication. Accordingly, the uplink light UO transmitted from the in-vehicle device 2 passes through the left window portion 36L and reaches the light receiving member 43.
On the other hand, the right window portion 36R is a light projection window for the downlink light DO and corresponds to the light emitting member 42 (see FIG. 7) for optical communication. Accordingly, the downlink light DO sent out by the light emitting member 42 is transmitted to the outside of the housing 31 through the right window 36R.

Also on the second bottom surface portion 37, a pair of left and right rectangular transmission window portions 37L and 37R are arranged in parallel in the left-right direction with a space therebetween.
These transmission window portions 37L and 37R are configured by closing a pair of left and right openings formed in the second bottom surface portion 37 with a light transmission sheet that mainly transmits light of a predetermined wavelength used for vehicle sensing.

Of the two transmission window portions 37L and 37R, the left window portion 37L is a light projection window for incident light IO, and corresponds to a light-emitting member 45 (see FIG. 7) for on-vehicle sensing. Therefore, the incident light IO transmitted by the light emitting member 45 is irradiated outside the housing 31 through the left window 37L.
On the other hand, the right window portion 37R is a light receiving window for the reflected light RO, and corresponds to the light receiving member 46 for vehicle detection (see FIG. 7). Accordingly, the reflected light RO of the incident light IO reflected by the road R or the vehicle 20 passes through the right window 37R and reaches the light receiving member 46.

[Internal configuration of beacon head]
FIG. 7 is a perspective view showing the internal structure of the beacon head 8.
Specifically, FIG. 7 is a perspective view showing the internal structure when the casing 31 shown in FIG. 6A is turned upside down and the casing 34 is removed from the casing 31 in the inverted state.
6A and FIG. 7, the upstream / downstream side and left / right direction definitions in FIG. 7 follow the case of the installation state shown in FIG. 6A. .

As shown in FIG. 7, the transmission / reception unit 11 includes a flat circuit board 41, a light emitting member 42 for optical communication arranged on the right side of the circuit board 41, and light arranged on the left side of the circuit board 41. And a light receiving member 43 for communication.
The light-emitting member 42 for optical communication has a light-emitting element group including a plurality of light-emitting elements 42A made of, for example, a DIP (Dual Inline Package) type near-infrared LED. It is configured by arranging vertically and horizontally within a predetermined range.

The light emitting element group of the light emitting member 42 is disposed in a mount portion 40 formed on the right side portion of the circuit board 41. The mount portion 40 has a circuit mounting surface that is bent in a mountain shape at the center in the vehicle traveling direction (upstream / downstream direction in FIG. 7), and upstream of the first portion 40A on the downstream side with the bent line as a boundary. It is divided into a second portion 40B on the side.
The circuit mounting surface of the downstream first portion 40A has a slightly smaller gradient than the circuit board 41, and the circuit mounting surface of the upstream second portion 40B has a slightly larger gradient than the circuit board 41.

The light emitting element group of the light emitting member 42 includes a first element group G1 arranged in the first part 40A of the mount portion 40 and a second element group G2 arranged in the second part 40B.
That is, the first element group G1 has a column in the vehicle traveling direction (upstream / downstream direction in FIG. 7) and a road width direction (left / right direction in FIG. 7) with respect to the circuit mounting surface of the first portion 40A. A plurality of light emitting elements 42A arranged in a two-dimensional array.

In addition, the second element group G1 has columns in the vehicle traveling direction (upstream / downstream direction in FIG. 7) and road width direction (left / right direction in FIG. 7) with respect to the circuit mounting surface of the second portion 40B. A plurality of light emitting elements 42A arranged in a two-dimensional array.
In the example of FIG. 7, the first and second element groups G1 and G2 include a total of 50 light emitting elements 42A arranged in 5 columns × 10 columns. The arrangement pattern of the light emitting elements 42A is as follows. For example, the plurality of light emitting elements 42A may be arranged in a so-called zigzag pattern.

The light receiving member 43 for optical communication includes a light receiving element 43A made of, for example, PD attached to the left side portion of the circuit board 41, and a lens 43B that condenses the uplink light UO on the light receiving surface of the light receiving element 43A. ing.
Similarly to the first bottom surface portion 36 of the casing 34, the circuit board 41 of the transmission / reception unit 11 is inclined so as to be higher on the upstream side in the installed state.

When the casing 31 is assembled by joining the flange portion of the casing 34 to the outer peripheral edge portion of the ceiling plate 35 shown in FIG. 7, all the light emitting elements 42 </ b> A constituting the light emitting member 42 for optical communication are transferred to the first bottom surface portion. The right side window part 36R (see FIG. 6) of the 36 is located close to the light transmitting sheet and is placed within the frame of the right side window part 36R.
Further, in this case, the lens 43B of the light receiving member 43 for optical communication is close to the light transmission sheet of the left window portion 36L (see FIG. 6) of the first bottom surface portion 36, and fits within the frame of the left window portion 36L. Placed in.

On the other hand, the sensor unit 12 includes a pair of left and right flat circuit boards 44L and 44R, a vehicle sensing light emitting member 45 provided on the left circuit board 44L, and a vehicle sensing light provided on the right circuit board 44R. Light receiving member 46.
The vehicle-sensing light-emitting member 45 includes a large number of light-emitting elements 45A made of, for example, DIP-type near-infrared LEDs, and is configured by arranging these light-emitting elements 45A vertically and horizontally in a predetermined range of the circuit board 44L.

More specifically, the vehicle-sensing light emitting member 45 is arranged with respect to the circuit board 44L in columns in the vehicle traveling direction (upstream / downstream direction in FIG. 7) and in the road width direction (left side / right side in FIG. 7). The light emitting elements 45A are two-dimensionally arranged in a row in the (direction) direction.
In the example of FIG. 7, a total of 20 light emitting elements 45A are arranged in 4 columns × 5 rows. However, the arrangement pattern of the light emitting elements 45A is not limited to this. The light emitting elements 45A may be arranged in a so-called zigzag pattern.

The vehicle sensing light receiving member 46 includes a light receiving element 46A made of, for example, PD attached to the circuit board 44R, and a lens 46B that collects the reflected light RO on the light receiving surface of the light receiving element 46A.
In the example of FIG. 7, the circuit boards 44L and 44R of the sensor unit 12 are separated for light emission and light reception, but the boards are not separated according to their use, and the light emitting member 45 and the light receiving member 46 are integrated. It may be mounted on the circuit board.

When the casing 31 is assembled by joining the flange portion of the casing 34 to the outer peripheral edge portion of the ceiling plate 35 shown in FIG. 7, all the light emitting elements 45 </ b> A constituting the light emitting member 45 for vehicle detection are converted into the second bottom surface portion. The left side window portion 37L of 37 (see FIG. 6) is positioned almost directly above the light transmitting sheet and is disposed so as to fit within the frame of the left side window portion 37L.
Further, in this case, the lens 46B of the light receiving member 46 for vehicle detection is close to the light transmitting sheet of the right window 37R (see FIG. 6) of the second bottom surface 37, and is in the frame of the right window 37R. It is arranged to fit in.

6 and 7, “V1” indicates the “light emission direction” of the downlink light DO by the first element group G1, and “V2” indicates the “light emission direction” of the downlink light DO by the second element group G2. ing.
Here, the “light emitting direction” refers to the optical axis direction of the downlink DO transmitted from one light source when the plurality of light emitting elements 42A arranged in a predetermined pattern are regarded as one light source. Say.

Accordingly, the light emitting direction V1 of the first element group G1 passes through the center of the mounting area of the first element group G1 in the first part 40A and passes through the circuit mounting surface of the first part 40A vertically. It almost coincides with the direction of.
The light emitting direction V2 of the second element group G2 passes through the center of the mounting area of the second element group G2 in the second part 40B and passes through the circuit mounting surface of the second part 40B vertically. It almost coincides with the direction of.

[Irradiation range of first element group and second element group]
FIG. 8 is a side view of the road showing the irradiation ranges DA1 and DA2 of the downlink light DO by the first element group G1 and the second element group G2.
As shown in FIG. 8, the light emitting direction V1 of the first element group G1 is directed from the downstream side of the downlink area DA, and the light emitting direction V2 of the second element group G2 is upstream of the downlink area DA. More oriented.

Accordingly, the irradiation range DA1 of the downlink light DO by the first element group G1 constitutes the downstream portion of the downlink area DA, and the irradiation range DA2 of the downlink light DO by the second element group G2 is the downlink. This constitutes the upstream portion of the area DA.
The hatched area in FIG. 8 represents an area where the downstream irradiation range DA1 and the upstream irradiation range DA2 overlap.

In the present embodiment, the downstream end position a0 and the upstream end position c1 of the irradiation area DA1 at the height of H = 1.0 m and the upstream end position c2 of the irradiation area DA2 at the height are respectively the following values. The light emitting directions V1 and V2 of the first and second element groups G1 and G2 are adjusted so that
Downstream end position a0 of irradiation range DA1: +1.3 m
Upstream end position c1: +4.0 m of irradiation range DA1
Upstream end position c2 of irradiation range DA2: +6.0 m

[Problem when all light emitting elements always emit light uniformly]
As described above, in the road-to-vehicle communication between the optical beacon 4 and the in-vehicle device 2, while the in-vehicle device 2 passes through the communication area A, as shown in FIG. 5, the downlink frame DL1 is successfully received → the uplink frame UL1. Frame exchange proceeds in the order of successful reception → downlink switching → successful reception of the downlink frame DL2, and the downlink frame DL1 is the beginning of the communication start.

Therefore, the optical beacon 4 continues to transmit the downlink frame DL1 in preparation for optical communication with the subsequent vehicle 20 even after the transmission of the downlink frame DL2 after downlink switching for the specific vehicle 20 is completed. There is a need to.
That is, the optical beacon 4 transmits the downlink light DO having a predetermined light emission amount so that the vehicle-mounted device 2 that supports optical communication can detect that the vehicle has entered the downlink area DA by receiving the downlink frame DL1. Always continue.

However, in this case, in the conventional optical beacon, since all the light emitting elements 42A constituting the light emitting member 42 for communication are uniformly emitted, there is a problem that the life of the light emitting element 42A is likely to be reduced due to deterioration over time. It was.
In particular, the light-emitting member 42 of the communication light-emitting unit 13 usually has a structure in which a plurality of light-emitting elements 42A are densely arranged on a circuit board in a predetermined pattern (see FIG. 7), so that all the light-emitting elements 42A emit light. Then, the temperature of the entire light emitting unit 13 is likely to rise.

For this reason, in the operation in which all the light emitting elements 42A emit light, there is a concern that the deterioration of the light emitting elements 42A may be accelerated more quickly due to the temperature rise.
Therefore, in this embodiment, the beacon controller 7 of the optical beacon 4 causes the light emitting member 42 to emit light with a larger light emission amount during a predetermined first period T1 (see FIG. 5) after receiving the uplink signal. In the other second period T2 (see FIG. 5), “light control” is performed to cause the light emitting member 42 to emit light with a smaller light emission amount, thereby suppressing the aging of the light emitting element 42A constituting the light emitting member 42. The above-mentioned problems are solved.

[Contents of dimming control]
FIG. 9 is a flowchart illustrating an example of dimming control performed by the beacon controller 7. Hereinafter, the contents of the dimming control will be described with reference to FIG.
As shown in FIG. 9, the beacon controller 7 always determines whether or not there is an uplink signal received from the vehicle-mounted device 2 (step ST1), and if there is no reception, the second element Only group G2 is caused to emit light (step ST4).

  Referring to FIG. 4, the above processing will be described in detail. When the main CPU 70 does not detect reception of “ID storage frame U1” (see FIG. 5) by CRC check of the received frame or the like, light emission is performed. Of the light emitting elements 42A constituting the member 42, the pulse signal P1 is output to the switching elements of the drive circuit 61 corresponding to the second element group G2.

As a result, the downlink frame DL1 (see FIG. 5) before downlink switching storing lane notification information (no vehicle ID) from only the light emitting elements 42A constituting the second element group G2 is transmitted to the outside as the downlink light DO. Sent out.
Further, in the optical beacon 4 of the present embodiment, the second element group G2 corresponds to the irradiation range DA2 (see FIG. 8) in the upstream portion of the downlink area DA, and thus the downlink light DO of the downlink frame DL1. Is sent only to the irradiation range DA2.

On the other hand, when receiving an uplink signal from the vehicle-mounted device 2 (Yes in step ST2), the beacon controller 7 causes both the first element group G1 and the second element group G2 to emit light (step ST2). ).
Specifically, when the main CPU 70 detects reception of the “ID storage frame U1” (see FIG. 5) by CRC check or the like of the received frame, the main CPU 70 performs downlink switching and performs not only the second element group G2 but also the second element group G2. The pulse signal P1 is also output to the switching elements of the drive circuit 61 corresponding to the one element group G1.

Thereby, from all the light emitting elements 42A constituting the first element group G1 and the second element group G2, the downlink frame DL2 (see FIG. 5) after downlink switching storing lane notification information (with vehicle ID) is stored. It is sent out as downlink optical DO.
In the optical beacon 4 of the present embodiment, the first element group G1 corresponds to the irradiation range DA1 (see FIG. 8) in the downstream portion of the downlink area DA, and the second element group G2 is upstream of the downlink area DA. Since it corresponds to the irradiation range DA2 (see FIG. 8) of the side portion, the downlink light DO of the downlink frame DL2 is transmitted to the entire range of the downlink area DA.

Next, the beacon controller 7 determines whether or not a predetermined first period T1 has elapsed (step ST3), and when it has elapsed, switches to light emission by only the second element group G2 (step ST4).
Specifically, the main CPU 70 corresponds to the output of the pulse signal P1 to the second element group G2 when the timer value from the reception time point of the ID storage frame U1 has passed the preset first period T1. Only the switching element of the drive circuit 61 is switched.

Accordingly, both the first and second element groups G1 and G2 emit light until the predetermined first period T1 elapses after reception of the ID storage frame U1, and in the other second period T2, the second period T2 Only the element group G2 emits light.
In the dimming control described above, the reception detection of the uplink signal, the switching control for the drive circuit 61, and the determination of the elapse of the first period T1 are not limited to the case where the main CPU 70 performs alone, but the communication IC 69 performs alone. Alternatively, both may be shared.

In the present embodiment, the amount of light reaching the downlink light DO transmitted from the first element group G1 to the downstream irradiation range DA1, and the downlink light DO transmitted from the second element group G2 to the irradiation range DA2 on the upstream side. The current value output from the drive circuit 61 to the light emitting element 42A is adjusted so that the amount of light reaching the above becomes at least the above-mentioned standard light amount (peak value is 4.5 μW / cm ² ) or more.

[Start time and end time of the first period]
In the dimming control described above, the vehicle ID is stored because the start time of the first period T1 is set to the reception time of the uplink signal (time when reception of the ID storage frame U1 is detected: see FIG. 5). A downlink frame DL2 (turned frame) including lane notification information is transmitted from the first and second element groups G1, G2. For this reason, possibility that the vehicle equipment 2 will receive a return | turnback frame increases, and road-to-vehicle communication can be performed reliably.

However, from the viewpoint of ensuring the transmission of the first return frame after downlink switching, the start time of the first period T1 does not necessarily have to be the same as the reception time of the uplink signal. Any time before starting the continuous transmission may be used.
That is, for example, if it takes about 3 milliseconds from the time of detection of uplink signal reception tk to the continuous transmission of the return frame, the first period T1 is started within 3 milliseconds from the time of detection tk and the first period T1 is started. The element group G1 may be made to emit light.

Usually, the lane notification information storing the vehicle ID is also included in the downlink frame (only one frame) following the return frame continuously transmitted after downlink switching. Therefore, the start time of the first period T1 may be set to a time before starting transmission of the downstream frame next to the return frame.
In this case, if it takes about 3 milliseconds to start the continuous transmission of the return frame and 7 milliseconds for the continuous transmission, the first period T1 is started within 10 milliseconds from the uplink signal reception detection time tk. The first element group G1 may be made to emit light.

On the other hand, according to the optical beacon communication protocol, it is necessary to continue the transmission of the downlink frame D12 for 350 milliseconds from the reception of the uplink signal.
Therefore, in the above-described dimming control, the end point of the first period T1 is set to a point when 350 msec has elapsed from the reception point of the uplink signal (when the reception of the ID storage frame U1 is detected: see FIG. 5). Is preferred.

  In this way, at least for the predetermined time length required by the regulations, not only the second element group G2 but also the first element group G1 is caused to emit light and downlink to both irradiation areas DA1 and DA2. Since the optical DO can be transmitted, downlink information can be reliably provided to the in-vehicle device 2 that has transmitted the uplink frame UL1.

Further, in the case of an optical beacon having a vehicle sensing function having the vehicle sensing sensor unit 12 as in the optical beacon 4 of the present embodiment, the vehicle 20 within a predetermined time from the reception of the uplink signal by the sensor unit 12. Is detected, it can be estimated that the in-vehicle device 2 that has transmitted the uplink frame UL1 has passed through the downlink area DA.
Therefore, the end time of the first period T1 may be set to a time when the sensor unit 12 senses the vehicle 20 within a predetermined time (for example, 1 second).

  In this way, while the in-vehicle device 2 that has transmitted the uplink frame UL1 passes through the downlink area DA, the downlink light DO can be transmitted to both irradiation areas DA1 and DA2, and therefore the uplink frame UL1. The downlink information can be surely provided to the in-vehicle device 2 that has transmitted.

[Effect of light beacon]
As described above, according to the optical beacon 4 of the present embodiment, the beacon controller 7 sets both the first and second element groups G1 and G2 in the predetermined first period T1 after receiving the uplink signal. Since the light is emitted (steps ST1 to ST3 in FIG. 9), the downlink light DO can be reliably transmitted to the in-vehicle device 2 for the downlink frame DL2 after downlink switching.
Further, the beacon controller 7 causes only the second element group G2 to emit light in the second period T2 other than the first period T1 (steps ST1 and ST4 in FIG. 2).

For this reason, the light emitting element 42A (hereinafter also referred to as “first element”) of the first element group G1 can have a longer light emission time and a longer life, and is a conventional example in which all the light emitting elements 42A emit light. In comparison, since the temperature of the light emitting unit 13 is less likely to increase, it is possible to suppress deterioration over time for the light emitting element 42A (hereinafter also referred to as “second element”) of the second element group G2.
As described above, according to the optical beacon 4 of the present embodiment, it is possible to reliably transmit the downlink light DO to the in-vehicle device 2 while effectively suppressing the aging deterioration of the light emitting element 42A. It is possible to achieve both securing of communication in the link direction.

Further, according to the optical beacon 4 of the present embodiment, as shown in FIG. 8, the light emission direction V2 of the second element group G2 having a constant light emission amount during the first and second periods T1 and T2 is in the first period T1. Only the light emitting direction V1 of the first element group G1 that emits light and extinguishes in the second period T2 is directed upstream of the second element group G2 in the upstream portion (irradiation area DA2) of the downlink area DA. Sends out downlink optical DO.
Therefore, there is an advantage that the upstream end c2 of the downlink area DA can be determined at a predetermined position by the irradiation area DA2 of the second element group G2 having a constant light emission amount.

[First Modification]
In the above-described embodiment, the light emitting element 42A (first element) of the first element group G1 is turned off in the second period T2. However, the first element also emits light relatively darkly in the second period T2. It may be.
That is, the light emission amount of the entire light emitting member 42 (light emitting unit 13) is increased by increasing the current value flowing through the first element during the first period T1 rather than the current value flowing through the first element during the second period T2. It may be.

  Referring to FIG. 4, the above process will be specifically described. In the second period T2, the current value that the drive circuit 61 supplies to the first element group G1 of the light emitting member 42 becomes low, and the first period In the period T1, the main CPU 70 or the communication IC may control the drive circuit 61 so that the current value that the drive circuit 61 supplies to the first element group G1 of the light emitting member 42 becomes high.

According to the first modification, the current value of the light emitting element 42A (first element) of the first element group G1 is set to be lower in the second period T2, so that the current value is decreased to the first element. This load is reduced, and the progress of aging of the first element can be suppressed.
Further, as compared with the case where all the light emitting elements 42A always emit light at a higher current value, the power consumption of the entire light emitting unit 13 is reduced and the amount of heat generation is reduced, and the temperature of the light emitting unit 13 is hardly increased as a whole. For this reason, also with respect to the light emitting element 42A (second element) of the second element group G2, it is possible to suppress the progress of the aging deterioration due to the temperature rise.

[Second Modification]
In the above-described embodiment, the irradiation area DA1 of the first element group G1 and the irradiation area DA2 of the second element group G2 are clearly divided, and both are divided into a downstream part and an upstream part of the unlink area DA and are down. The light emitting directions V1 and V2 of both the element groups G1 and G2 are set so as to transmit the link light DO. However, each of the element groups G1 and G2 has the downlink light DO over almost the entire downlink area DA. The light emitting elements 42A may be arranged so that the light can be sent out.

  In this case, “substantially the entire downlink area DA” means an irradiation area DA1 in which the first element group G1 transmits the downlink light DO and an irradiation area in which the second element group G2 transmits the downlink light DO. DA2 is generally coincident with the desired downlink area DA, and the measured values of the deviation amounts in the vehicle traveling direction of these areas DA1 and DA2 are within a predetermined allowable error (for example, 15 cm). It means that.

FIG. 10 is an explanatory diagram showing an example of an arrangement pattern of the first element group G1 and the second element group G2 when the irradiation areas DA1 and DA2 are substantially matched, and FIG. 11 shows the first element group in that case. It is explanatory drawing which shows the other example of the arrangement pattern of G1 and 2nd element group G2.
10 and 11, each box separated by a lattice indicates the light emitting element 42A, the box without hatching indicates the light emitting element 42A of the first element group G1, and the box with hatching indicates the light emitting element of the second element group. 42A is shown. Moreover, the upstream / downstream side and left / right direction definitions in FIGS. 10 and 11 are similar to those in the installation state shown in FIG.

In the example of FIG. 10A, the light emitting elements 42A of the first element group G1 are arranged from the downstream side, and the light emitting elements 42A of the second element group G2 are arranged from the upstream side. However, the order of the upstream side and the downstream side may be switched.
In the example of FIG. 10B, the light emitting elements 42A of the first element group G1 and the light emitting elements 42A of the second element group G2 are alternately arranged in the vehicle traveling direction. Also in this case, the order of the upstream side and the downstream side may be switched.

In the example of FIG. 11A, the light emitting elements 42A of the first element group G1 and the light emitting elements 42A of the second element group G2 are alternately arranged in both the vehicle traveling direction and the left-right direction (so-called staggered pattern). .
In the example of FIG. 11B, the light emitting elements 42A of the first element group G1 and the light emitting elements 42A of the second element group G2 are alternately arranged from the center of the arrangement region toward the periphery.
As shown in these examples, the first element group G1 and the second element group G2 are alternately arranged in a mixed state on the same circuit board surface, so that the irradiation areas DA1 and DA2 of the element groups G1 and G2 are substantially arranged. Can be matched.

According to the second modification, since the first element group G1 and the second element group G2 send the downlink light DO to almost the entire downlink area DA, the light emission amount of the light emitting unit 13 is set to the second period T2. Then, almost the entire range of the downlink area DA is dimmed so as to be small and large in the first period T1.
Also in the second modification, the first element group G1 may be turned off in the second period T2, or may be caused to emit light darker in the second period T2.

Further, in the second modification, the light emission amount of the light emitting unit 13 in the first period T1 (first light emission amount: the light emission amount when both the element groups G1 and G2 emit light) and the light emitting unit 13 in the second period T2. The second light emission amount (second light emission amount: the light emission amount when only the second element group G2 emits light) must be equal to or more than the above-mentioned standard light amount (peak value is 4.5 μW / cm ² ). .
In this case, for example, the second light emission amount is suppressed to a light amount slightly larger than the standard light amount (light amount without margin), and the first light emission amount is set to a light amount obtained by adding a predetermined margin to the standard light amount. What is necessary is just to make a difference in the amount of light emission of both.

[Other variations]
The embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims for patent, and includes all modifications within the scope of the claims and their equivalents.
For example, in the above-described embodiment, the optical beacon 4 having the vehicle sensing function is illustrated, but the present invention can also be applied to an optical beacon that does not have the function.

In the above-described embodiment, the plurality of light emitting elements 42A constituting the light emitting unit 13 are divided into the first element group G1 for dimming and the second element group G2 having a constant light emission amount. 42A may be dimmed so that the amount of light emission increases in the first period T1.
In this case, dimming that is turned off in the second period T2 is impossible, and dimming control is performed to reduce the light emission amount in the second period T2 to such an extent that the in-vehicle device 2 can receive the downlink signal.

In the above-described embodiment, the DIP type near infrared LED is employed as the light emitting element 42A. However, instead of this, an SMD (Surface Mount Device) type near infrared LED may be employed.
If this SMD type is adopted, wiring work is completed on the surface side of the circuit board, so that the troublesome work of penetrating the lead wire into the through hole of the circuit board and soldering, which is necessary for the DIP type, is unnecessary. Therefore, there is an advantage that it can be mounted easily compared to the DIP type.

2 In-vehicle device 4 Optical beacon 7 Beacon controller (control unit)
8 Beacon head (emitter / receiver)
11 Transmission / Reception Unit 12 Sensor Unit 13 Light Emitting Unit (for Communication)
14 Light receiving unit (for communication)
42 light emitting member 42A light emitting element 43 light receiving member G1 first element group G2 second element group T1 first period T2 second period

Claims (9)

An optical beacon that performs optical communication with an in-vehicle device of a running vehicle,
A light emitting unit for transmitting downlink light for communication in the downlink direction;
The optical beacon provided with the control part which makes the light emission amount of the said light emission unit in the following 1st period increase rather than the light emission amount of the said light emission unit in the following 2nd period.
First period: a period of a predetermined time length that starts when the uplink signal is received Second period: a period other than the first period   2. The optical beacon according to claim 1, wherein the start time of the first period is a time before a downlink frame including lane notification information storing a vehicle ID is first continuously transmitted after downlink switching.   2. The start time of the first period is a time before transmitting a downstream frame next to a downstream frame including a lane notification information storing a vehicle ID, which is continuously transmitted after downlink switching. Light beacon.   The optical beacon according to any one of claims 1 to 3, wherein the end time of the first period is a time when 350 milliseconds have elapsed since reception of an uplink signal. It further comprises a sensor unit that senses the vehicle by transmitting incident light downstream of the downlink region and detecting reflected light.
The optical beacon according to any one of claims 1 to 3, wherein the end time of the first period is a time when the sensor unit senses the vehicle within a predetermined time from reception of an uplink signal. The light emitting unit has the following first element and second element individually,
6. The control unit according to claim 1, wherein the controller turns off the first element during the second period and causes the first element to emit light during the first period, thereby increasing the light emission amount of the light emitting unit. The optical beacon according to item 1.
First element: a light emitting element that increases the amount of light emission in the first period Second element: a light emitting element that has already emitted light in the second period and does not increase the amount of light emission in the first period The light emitting unit has the following first element and second element individually,
The said control part increases the light emission amount of the said light emission unit by increasing the electric current value sent through the said 1st element in the said 1st period rather than the electric current value passed through the said 1st element in the said 2nd period. The optical beacon according to any one of 1 to 5.
First element: a light emitting element that increases the amount of light emission in the first period Second element: a light emitting element that has already emitted light in the second period and does not increase the amount of light emission in the first period The light emitting unit includes a first element group in which a plurality of the first elements are arranged in a predetermined pattern, and a second element group in which the plurality of the second elements are arranged in a predetermined pattern,
The optical beacon according to claim 6 or 7, wherein a light emission direction of the second element group is directed upstream of a light emission direction of the first element group. The light emitting unit includes a first element group in which a plurality of the first elements are arranged in a predetermined pattern, and a second element group in which the plurality of the second elements are arranged in a predetermined pattern,
7. The first element group and the second element group are alternately arranged in a mixed state on the same circuit board surface so that downlink light can be transmitted almost over the entire downlink region. Or 7. The optical beacon according to 7.

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