Invisible light communication system and signal processing device

Abstract

To provide a non-visible light communication system and signal processing device that enable accurate information collection while suppressing an increase in processing load on the receiving side of optical communication, i.e., the side that reads the signal. [Solution] The invisible light communication system 100 includes a transmitting unit TT that modulates and blinks invisible light wavelength band optical EL as invisible light and transmits a signal, a receiving unit RR that receives invisible light wavelength band optical EL, a first reading unit RU1 that reads the signal at a predetermined frame rate for a first range of the image acquired by receiving light at the receiving unit RR, and a second reading unit RU2 that reads the signal at a higher frame rate than the first reading unit RU1 for a second range that is narrower than the first range.

Description

Technical Field

[0006] ,

[0001] The present invention relates to a non-visible light communication system and a signal processing device that transmit and receive signal information including non-visible light communication and perform signal identification.

Background Art

[0002] For example, there is a communication using light in a wavelength band outside the visible light range, that is, non-visible light. On the signal generation side, there is known a device that generates a plurality of types of signal information having different blinking periods (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1 above, it is premised that, for example, the blinking period on the transmission side is adjusted in consideration of the frame rate on the reception side (imaging side) so that the identification of a plurality of types of signal information is maintained on the reception side (imaging side).

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a non-visible light communication system and a signal processing device that enable accurate information collection while suppressing an increase in processing load for processing on the side that receives optical communication, that is, the side that reads signals.

Means for Solving the Problems

[0006] A non-visible light communication system for achieving the above objective comprises a transmitting unit that transmits signals by modulating and flashing non-visible light, a receiving unit that receives non-visible light, a first reading unit that reads signals at a predetermined frame rate for a first range of an image acquired by receiving light at the receiving unit, and a second reading unit that reads signals at a higher frame rate than the first reading unit for a second range that is narrower than the first range.

[0007] In the above invisible light communication system, signal reading is possible in two stages: reading by the first reading unit and reading by the second reading unit. Furthermore, by narrowing (more restricting) the image range during reading by the second reading unit, it is possible to perform reading at a higher frame rate than reading by the first reading unit while suppressing an increase in processing load.

[0008] In a specific aspect of the present invention, the first reading unit reads the identification information of the transmitting unit, and the second range in the second reading unit is narrowed to include the image of the transmitting unit to be processed based on the reading result of the first reading unit. In this case, by using a higher frame rate for an appropriately limited range, detailed signal reading from the image of the transmitting unit becomes possible.

[0009] In another aspect of the present invention, the exposure time in one frame in the second reading unit is shorter than the exposure time in one frame in the first reading unit. In this case, the difference in exposure time allows for more detailed signal reading.

[0010] In yet another aspect of the present invention, a switching unit is provided to switch from the frame rate and exposure time for reading in the first reading unit to the frame rate and exposure time for reading in the second reading unit. In this case, the frame rate and exposure time can be changed in conjunction with the switching operation in the switching unit.

[0011] In yet another aspect of the present invention, the transmitting unit emits infrared light in a specific frequency band as invisible light, and the receiving unit has a bandpass filter that transmits infrared light in a specific frequency band. In this case, the effects of ambient light and other factors can be suppressed, and the necessary invisible light components can be accurately captured.

[0012] In yet another aspect of the present invention, the transmitting unit has an invisible light emitting unit that emits invisible light and a visible light emitting unit that emits colored light, and the invisible light emitting unit and the visible light emitting unit share a power supply for each color of light. In this case, by sharing a power supply between the invisible light emitting unit and the visible light emitting unit for each color of light, it is possible to reliably transmit a signal with the desired modulation and blinking with a simple configuration.

[0013] A signal processing device for achieving the above objective includes a first reading unit that reads a signal at a predetermined frame rate for a first range of an image acquired by receiving modulated flashing invisible light, and a second reading unit that reads a signal at a higher frame rate than the first reading unit for a second range that is narrower than the first range.

[0014] The above signal processing device enables two-stage signal reading, consisting of reading by the first reading unit and reading by the second reading unit. Furthermore, by narrowing (more restricting) the image range during reading by the second reading unit, it is possible to perform reading at a higher frame rate than reading by the first reading unit while suppressing an increase in processing load. [Brief explanation of the drawing]

[0015] [Figure 1] This is a conceptual side view showing how a non-visible light communication system of one embodiment is employed in a train signaling system. [Figure 2] This figure illustrates the configuration of a non-visible light communication system that includes a signal processing device on the vehicle side in one embodiment. [Figure 3] (A) to (C) are circuit diagrams of the signal lights that make up the transmitting section. [Figure 4] This is a block diagram illustrating an example configuration of a non-visible light communication system including a signal processing device. [Figure 5] Figures (A) through (D) are diagrams illustrating the overview of image processing in a signal processing device. [Figure 6] (A) and (B) are waveform diagrams showing the operating status on the transmitting side. [Figure 7] (A) to (E) are waveform diagrams showing the operating conditions on the transmission side and the reception (light reception) side. [Figure 8] It is a conceptual diagram showing an example of a signal reading method at a high frame rate. [Figure 9] (A) is a conceptual diagram for explaining one aspect of the end and start of signal reading at a high frame rate, and (B) and (C) are conceptual diagrams showing a modified example of the signal reading method at a high frame rate. [Figure 10] It is a flowchart for explaining a series of operation processes related to signal reading on the reception side of a non-visible light communication system. [Figure 11] It is a conceptual diagram for explaining the outline of a non-visible light communication system.

Mode for Carrying Out the Invention

[0016] Hereinafter, an example of a signal processing apparatus according to an embodiment and a non-visible light communication system including the same will be described with reference to FIG. 1 and the like. FIG. 1 is a conceptual side view showing how the non-visible light communication system 100 of the present embodiment is adopted in a train signal system. FIG. 2 is a diagram for explaining a configuration including the signal processing apparatus SD on the vehicle side in the non-visible light communication system 100. FIG. 3 is a block diagram for explaining an example of a configuration of the non-visible light communication system 100 including the signal processing apparatus SD. In an example here, as shown in each figure, on the vehicle side, the signal processing apparatus SD is assumed to be built in a receiving apparatus 10 that performs reception (light reception) for non-visible light.

[0017] First, in FIG. 1, an example of a non-visible light communication system 100 applied to signal communication processing between the on-train side and the ground side during the operation of train TR (including automatic operation) is illustrated. That is, an example is shown where the non-visible light communication system 100 is introduced as a system for railway signals to transmit and receive multiple types of signal information that becomes the signal indication at the railway signal machine RS for signal identification. Regarding the case where the train TR is in automatic operation, various modes are assumed, and it is to widely include those from full unmanned automatic operation without a driver or the like to those where a driver performs driving operations and part of them is assisted by automatic operation.

[0018] As shown in the figure, the non-visible light communication system 100 is composed of a receiving device 10 and a transmitting device 20. The receiving device 10 is mounted on the train TR to function as an on-train device that receives signals from the ground side. On the other hand, the transmitting device 20 is incorporated into the railway signal machine RS installed around the track RL or functions as part of the railway signal machine RS to function as a ground side device.

[0019] The receiving device 10 is composed of a camera (image sensor) or the like to function as a light receiving unit RR for receiving light as signal information transmitted from the transmitting device 20. Here, further, the receiving device 10 incorporates a signal processing device SD, and in the signal processing device SD, it is possible to identify the signal indication at the railway signal machine RS by reading the signal generated by the modulated flashing non-visible light from the transmitting device 20.

[0020] The transmitter 20 is a ground-side device that functions as a transmitter TT that transmits information regarding the progress of the train TR, and outputs various commands to the train TR. In other words, the transmitter 20 functions as a railway signal RS or a part thereof. In the illustrated example, the transmitter 20 has a plurality (four) of signal lights 20α to 20δ. Each signal light 20α to 20δ emits visible light (visible light) in the visible light wavelength band, for example, yellow, blue, and red, and also emits light in the invisible light wavelength band (invisible light: light in the light wavelength band other than visible light) by modulating and flashing. As for light in the light wavelength band other than visible light, it is conceivable to use an infrared emitter that emits infrared light (IR light) in the infrared wavelength band or an ultraviolet emitter that emits ultraviolet light (UV light). In this example, the transmitter 20 as the transmitter TT is assumed to emit IR light (infrared light) in a specific frequency band as invisible light. A more detailed configuration of each signal light 20α to 20δ will be described later with reference to Figure 2.

[0021] Furthermore, in the following, light in the visible light wavelength band will be referred to as visible light wavelength band light VL, and light in the non-visible light wavelength band will be referred to as non-visible light wavelength band light EL. In this example, when the transmitter 20 is lit, the visible light wavelength band light VL is lit normally, while the non-visible light wavelength band light EL (e.g., IR light) is blinked to transmit a signal.

[0022] In particular, in this embodiment, by inserting a sufficiently long period of light extinction between modulated flashing by the transmitting device 20, the receiving device 10 can read the modulated flashing of the transmitting device 20 not only by reading each on / off cycle with a short exposure time, but also by detecting light extinction with a long exposure time.

[0023] The configuration of the receiving device 10 and the transmitting device 20, as well as the emission (light emission) and reception (light reception) of light, will be explained below with reference to Figure 2. Further details of the signal lights 20α to 20δ that constitute the transmitting device 20 will be explained here. Note that the figure shows the configuration of one of the signal lights 20α of the transmitting device 20, and although the colors emitted differ, the mechanical configuration of the other signal lights 20β to 20δ is the same, so their illustration and explanation are omitted.

[0024] First, the receiving device 10 comprises an imaging device 11, which is composed of, for example, a camera (image sensor) CA, a bandpass filter 12 that transmits light in a specific wavelength band, and a control / processing device 13. Of these, the control / processing device 13 incorporates a signal processing device SD.

[0025] Of the receiving device 10, various types of cameras (image sensors) CA can be used as the imaging device 11, but for example, depending on the invisible light wavelength band EL to be captured, an image sensor for IR light can be used. In this example, a bandpass filter 12 is further attached to the front of the camera CA, which is the imaging device 11. The bandpass filter 12 efficiently transmits light in the wavelength band of the component of the invisible light wavelength band EL incident from the transmitting device 20. In other words, the receiving device 10 as the light receiving unit RR has a bandpass filter 12 that transmits IR light (infrared light) in a specific frequency band. By matching the bandpass filter 12 to the invisible light wavelength band EL, the receiving device 10 (light receiving unit RR) is configured to efficiently capture the component of the invisible light wavelength band EL in the imaging device 11. On the other hand, it is also possible to configure the system to transmit the invisible light wavelength band EL as light in a single wavelength band. By focusing on a single wavelength band, the effects of ambient light can be further suppressed (resistance to ambient light is improved).

[0026] The control / processing device 13 performs processing to read the signal from the transmitter 20 by analyzing the image data acquired by the imaging device 11. In this case, the signal processing device SD analyzes the results of continuous image acquisition to read the content of the signal from the blinking pattern of the modulated blinking non-visible light wavelength band EL. In particular, in this embodiment, there is a first stage of reading in which the signal is read from the entire image at a predetermined frame rate, and a second stage of reading in which the image range is narrowed and the signal is read from that range at a frame rate higher than the predetermined frame rate.

[0027] On the other hand, the signal lamp 20α, which constitutes the transmitting device 20 that is the source of the light signal transmission, is constructed by arranging a large number of LED elements EE,EE,... planarly, as shown in the figure. In particular, in this embodiment, as shown by the difference in hatching patterns in the figure, the signal lamp 20α is constructed by mixing visible light LED elements EEv,EEv,... and invisible light LED elements EEi,EEi,... to form the LED elements EE,EE,... In other words, the signal lamp 20α is formed by a visible light emitting section VP composed of a large number of visible light LED elements EEv,EEv,... and an invisible light emitting section IP composed of a large number of invisible light LED elements EEi,EEi,...

[0028] As previously described, the visible light wavelength band light VL emitted from the visible light emission unit VP, which is composed of visible light LED elements EEv, EEv, ..., is normally lit (lit without intended flashing modulation) when illuminated, and each signal lamp 20α to 20δ, as a railway signal RS, transmits information about the train TR's progress to people or sensors that can detect the color of the visible light emitted at each placement location. On the other hand, the invisible light wavelength band light EL emitted from the invisible light emission unit IP, which is composed of invisible light LED elements EEi, EEi, ..., transmits signals by flashing in a modulated manner when illuminated. In other words, each signal lamp 20α to 20δ transmits information about the train TR's progress to sensors that can detect the difference in how it flashes in a modulated manner.

[0029] Figure 3(A) shows a circuit diagram of one of the signal lights 20α to 20δ that make up the transmitting device 20 (for example, signal light 20α). In the above configuration, the timing of power supply for normal illumination on the visible light side and modulated flashing on the invisible light side can be the same. Therefore, the invisible light light emitting unit IP and the visible light light emitting unit VP can be configured to share a power supply PW for each color of light, i.e., for each signal light 20α to 20δ. In the illustrated example, power is supplied from a single power supply PW to the visible light side, i.e., the visible light light emitting unit VP side, which is enclosed by a dashed line in Figure 3(B), and to the invisible light side, i.e., the invisible light light emitting unit IP side, which is enclosed by a dashed line in Figure 3(C). As shown in the illustration, the visible light light emitting unit VP side has a circuit for normal illumination operation for each color of signal light 20α to 20δ. On the other hand, the non-visible light emitting section IP is equipped with a modulation circuit and the like to perform a desired modulated flashing operation for each signal lamp 20α to 20δ. In particular, in this embodiment, it is possible to include various information such as the ID information of the transmitting device 20 in addition to the indication information in the information transmitted by modulated flashing.

[0030] Hereinafter, with reference to the block diagram shown as Figure 4, an example configuration of the invisible light communication system 100 including the signal processing device SD of this embodiment will be described.

[0031] First, the transmitting device 20 (transmitter TT) of the non-visible light communication system 100, which is the signal transmitting side, comprises a control board 21 and an LED board 22, which constitute each signal lamp (LED signal lamp) 20α to 20δ. The control board 21 consists of a visible light illumination control unit 21v and a non-visible light modulation control unit 21i, and the LED board 22 consists of a visible light light emitting unit VP and a non-visible light light emitting unit IP. The visible light illumination control unit 21v of the control board 21 corresponds to the circuit section on the visible light side as explained with reference to Figure 3, and receives power supplied from a shared power supply PW to illuminate (normal illumination) the visible light light emitting unit VP of the LED board 22. The non-visible light modulation control unit 21i of the control board 21 corresponds to the circuit section on the non-visible light side as explained with reference to Figure 3, and receives power supplied from a shared power supply PW to illuminate (modulated blinking) the non-visible light light emitting unit IP of the LED board 22. The visible light emitting unit VP emits visible light wavelength band light VL according to the operation control by the visible light lighting control unit 21v, and the non-visible light emitting unit IP emits non-visible light wavelength band light EL according to the operation control by the non-visible light modulation control unit 21i.

[0032] On the other hand, the receiving device 10 of the non-visible light communication system 100, which is the signal receiving side, comprises an imaging device 11, a bandpass filter (BPF) 12, and a control / processing device 13, as described above. Of these, the control / processing device 13 functions as a signal processing device SD and comprises an image acquisition unit GR, an imaging device control unit CC, an image analysis unit GA, and an output unit OT.

[0033] In the control / processing device 13, the image acquisition unit GR, part of the signal processing device SD, acquires image data by receiving invisible light wavelength band light EL emitted by the invisible light emission unit IP and passed through the bandpass filter 12 at the imaging device 11. The image acquisition unit GR outputs the acquired image data to the image analysis unit GA.

[0034] The imaging device control unit CC controls the operation of the imaging device 11 according to the commands and instructions from the image analysis unit GA. As a result, the desired image data is acquired by the image acquisition unit GR.

[0035] The image analysis unit GA performs the above-described operational control to acquire image data and also performs analysis processing on the acquired image data. For this purpose, as partially enlarged in the figure, it is equipped with a first reading unit RU1 and a second reading unit RU2 for signal reading, and further equipped with a switching unit SW that switches between signal reading by the first reading unit RU1 and signal reading by the second reading unit RU2.

[0036] The first reading unit RU1 reads the signal at a predetermined frame rate for a first range of the image acquired by the image acquisition unit GR, which is responsible for receiving light in the receiving device 10, which acts as a light receiving unit RR. For example, the first reading unit RU1 sets the first range to the range of the entire image acquired by the image acquisition unit GR and processes a continuous image with the predetermined frame rate set to 60fps. The first reading unit RU1 also reads the identification information of the transmitting device 20, which acts as a transmitting unit TT, from the result of demodulating the modulated blinking based on the 60fps frame rate.

[0037] The second reading unit RU2 reads signals from a second range, which is a narrower range than the first range, i.e., the range of the entire image, at a higher frame rate than the first reading unit RU1. As an example, the second reading unit RU2 defines the second range as a rectangular region extracted from the entire image, surrounding one target transmitter 20, and processes this region as a continuous image at a higher frame rate than the first range, namely 600fps. In other words, in the second reading unit RU2, the second range is narrowed to include the image of one transmitter 20 to be processed, based on the reading result of the first reading unit RU1, i.e., based on the identification information of the transmitter 20 that was read. By limiting the processing to this narrowed range and performing processing at a faster rate of 600fps than 60fps, it is possible to obtain more detailed information while suppressing an increase in processing load.

[0038] Hereinafter, reading at a relatively low frame rate by the first reading unit RU1 will be referred to as low-fps reading, and reading at a relatively high frame rate by the second reading unit RU2 will be referred to as high-fps reading.

[0039] Furthermore, in the above embodiment, the exposure time in one frame in the second reading unit RU2 is consequently shorter than the exposure time in one frame in the first reading unit RU1. In other words, the shutter speed in the second reading unit RU2 is faster.

[0040] The switching unit SW switches between reading by the first reading unit RU1 and reading by the second reading unit RU2. In a typical operation, when the reading result from the first reading unit RU1 narrows down the number of transmitters 20 to be processed, the switching unit SW performs a process to switch from the frame rate and exposure time for reading by the first reading unit RU1 to the frame rate and exposure time for reading by the second reading unit RU2.

[0041] Furthermore, the series of processes performed by the first reading unit RU1, the second reading unit RU2, and the switching unit SW in the image analysis unit GA described above can be composed of various programs that perform a series of data processing operations.

[0042] The output unit OT outputs various signal information, such as the display information resulting from the analysis in the image analysis unit GA, to a display device (DP) or a sounding device (voice notification device) VD.

[0043] The following describes the image processing in the signal processing unit SD, which constitutes the main part of the receiving device 10, with reference to the image diagrams shown in Figures 5(A) to 5(D). Here, if an image sensor for IR light is used as the camera CA that constitutes the imaging device 11 of the receiving device 10, the images shown in Figure 5(A), etc., will be grayscale images for IR light. Furthermore, depending on the properties of the bandpass filter 12 used on the front of the imaging device 11, it is conceivable that almost nothing but the light-emitting part of the signal light that emits IR light in a specific wavelength band will be captured. However, for the sake of clarity of explanation, the image here shows the entire signal light and even its surroundings captured.

[0044] First, Figure 5(A) is an image diagram showing the overall image G0 acquired by the image acquisition unit GR. In the example shown, the image includes multiple transmitters 20, 20, ... One of these is transmitter 20 containing the signal light to be read. Note that the multiple transmitters 20, 20, ... in the image can be extracted and enclosed in a rectangular region RA by performing appropriate image processing, as shown in Figure 5(B).

[0045] The invisible light-emitting units IP (see Figure 4, etc.) emitted from each extracted transmitter 20, 20, ... have different modulated blinking patterns. The first reading unit RU1 reads the overall image G0 as the first range RE1, narrowing down the image GG to include the target transmitter 20, as shown in Figure 5(C). In particular, it is assumed that adjustments have been made in advance to the signal generation so that differences between neighboring transmitters 20, 20, ... can be identified even when reading at low fps by the first reading unit RU1. In the figure, the differences in the generated signal waveforms that appear as differences in the results of reading at low fps are shown in callouts, and each signal waveform is further numbered.

[0046] Here, since the number of transmitters 20 that can be included in a single overall image G0 is not assumed to be very large, identification is possible even if the amount of information that can be obtained by reading at low fps is limited. In other words, from the multiple transmitters 20, 20, ... extracted as shown in Figure 5(B), it is possible to narrow down the image GG containing the rectangular region that should be processed based on the reading results for the first range RE1 (overall image G0) by the first reading unit RU1, as shown in Figure 5(C).

[0047] As described above, once the target is narrowed down to one transmitter 20, or identified, and the range of the image GG in the rectangular region including one transmitter 20, as shown in Figure 5(D), is limited to the second range RE2, the switching unit SW performs a process to switch from reading by the first reading unit RU1 to reading by the second reading unit RU2. In other words, high-fps reading is performed on the range of the image GG.

[0048] The following example illustrates the operational status of signal transmission and reception between the transmitting and receiving (optical) sides, with reference to Figure 6 and other figures.

[0049] First, let's explain the operation of the transmitting side by referring to Figure 6. Figure 6(A) is a waveform diagram showing the operation of the transmitting side, and Figure 6(B) is a waveform diagram that corresponds to an enlarged view of a part of Figure 6(A).

[0050] As previously described, the modulated flashing in the transmitter 20 includes periods of complete blackout that are sufficiently longer than the exposure time. More specifically, it includes periods of complete blackout that are sufficiently longer than the exposure time at low fps (for example, a period of about 60 fps) as measured by the first reading unit RU1 of the receiver 10. Here, as shown in Figure 6(A), the time during which the light is blacked out for such a long period (the time during which the off state is maintained) is defined as unit time t_Lo, and the on / off switching for low fps on the receiver (light receiving) side is configured with unit time t_Lo as the period. However, as shown in Figure 6(B), which is a magnified view of part of Figure 6(A), during the on period in one unit time t_Lo, more finely modulated flashing of on / off is performed. This modulated flashing corresponds to the reading at high fps on the receiver (light receiving) side. Here, as shown in Figure 6(B), the time for one short flash for high fps is defined as unit time t_Hi. In other words, the on / off switch for high fps on the receiving (light-receiving) side is configured with a period of unit time t_Hi. The period for switching between on and off, i.e., unit time t_Hi, is set to a frequency of, for example, 100Hz or 120Hz. Conversely, unit time t_Lo can be set to be long enough so that unit time t_Hi can be switched a sufficiently large number of times within one unit time t_Lo to contain information.

[0051] In the above case, when reading at low fps on the receiving (light receiving) side, the amount of information acquired per unit of time is limited, while when reading at high fps, it becomes possible to acquire detailed information.

[0052] The following describes an example of the operation status of the transmitting side, as well as an example of the operation status for signal transmission and reception between the transmitting side and the receiving (optical receiving) side, with reference to Figure 7.

[0053] Figure 7(A) shows the operation of the reading side at low fps on the receiving (light receiving) side, and Figures 7(B) and 7(C) are waveform diagrams to explain the reading of invisible light by the receiving (light receiving) side at low fps. Furthermore, Figure 7(D) is a waveform diagram corresponding to an enlarged portion of Figure 7(C). In addition, Figure 7(E) is a waveform diagram to explain the reading of invisible light by the receiving (light receiving) side at high fps.

[0054] First, in Figure 7(A), the period PT represents the shutter interval during reading by the first reading unit RU1 of the receiving device 10, i.e., during reading at low fps, and corresponds to the reciprocal of the frame rate. Furthermore, the exposure time in one period PT is denoted as τ_Lo.

[0055] Figure 7(B) shows the reading of the transmitted signal illustrated in Figure 6(A) in the above embodiment. As shown in the figure, here the period PT and its exposure time τ_Lo shown in Figure 7(A) are shorter than the unit time t_Lo, and multiple exposures occur per unit time t_Lo. For this reason, as shown in Figure 7(C), for example, at least one exposure time τ_Lo is received within one unit time t_Lo, and the result is detected as the amount of light received on the receiving side. The magnitude of one amount of light received is determined by the on-off ratio (duty cycle) in which finer flickering occurs within one unit time t_Lo, as shown in Figure 7(D). For example, by setting the on ratio within one unit time t_Lo to half (50%) or more, a sufficient amount of light for detection can be secured. As a result, the receiving (light receiving) side reads (decodes) the signal for low fps based on one unit time t_Lo.

[0056] Next, the reading on the receiving (light-receiving) side at high frame rates will be described. As shown in FIG. 7(D), and as described with reference to FIG. 6(B), in order to cope with the reading at high frame rates, on the transmitting side, multiple fluctuations of on-off blinking, that is, switching between on and off, are performed per unit time t_Lo. Here, it is assumed that the on-off switching is performed with the unit time t_Hi as the period. In this case, t_Hi < t_Lo. On the receiving device 10 side, in order to read the on-off blinking at the unit time t_Hi, reading by the second reading unit RU2, that is, reading at high frame rates (for example, about 600 fps) is performed. Looking at it from another perspective, it means that on the transmitting side, high-speed on-off blinking corresponding to the reading at high frame rates on the receiving (light-receiving) side is being performed.

[0057] In this case, as shown in FIG. 7(E), light reception for at least one or more exposure times τ_Hi is performed within one unit time t_Hi, and as a result, it is detected as the light reception amount on the light-receiving side. As described above, on the receiving (light-receiving) side, signal reading (decoding) for high frame rates based on one unit time t_Hi is performed.

[0058] In order to achieve the above-described mode, in the receiving device 10, the exposure time τ_Hi in one frame in the second reading unit RU2 is shorter than the exposure time τ_Lo in one frame in the first reading unit RU1. Also, summarizing the relationship with the unit time t_Lo and the unit time t_Hi on the transmitting side, τ_Hi < t_Hi < τ_Lo < τ_Hi.

[0059] Hereinafter, an example of the signal reading method at high frame rates will be described with reference to the conceptual diagrams shown in FIG. 8 and the like. Note that FIG. 9(A) is a conceptual diagram for explaining one aspect of the end and start of signal reading at high frame rates, and FIGS. 9(B) and 9(C) are conceptual diagrams showing a modified example of the signal reading method at high frame rates.

[0060] In this example, as shown in Figure 8, two blinks (on / off) in a unit time t_Hi for the smallest unit of modulated blinking at the transmitting side are treated as a pair, and each pair is assumed to be either an on-off (Hi-Lo) or on-on (Hi-Hi) combination, with "0" representing the on-off (Hi-Lo) case and "1" representing the on-on (Hi-Hi) case, and the signal is generated accordingly. In this case, in one unit time t_Lo, the "on" state will account for more than 50% of the total. Furthermore, in this case, as shown enclosed by the dashed line in Figure 9(A), it is conceivable that the detection result of the above-mentioned smallest unit of modulated blinking variation can be used to determine the boundary of variation per unit time t_Lo corresponding to low fps at the transmitting side. In other words, as shown in the figure, if an off-off (Lo-Lo) sequence, which is not present in signal generation, occurs after an on (Hi) sequence, it is determined that there is an end to one unit time t_Lo (the transmission of one signal has finished). On the other hand, if an on (Hi) sequence occurs after an off-off (Lo-Lo) sequence, it is determined that one unit time t_Lo has started. For readings at high fps, a set of information may be incorporated into the modulated blinking during the on state in one unit time t_Lo, but as shown in Figure 9(B), multiple (three in the illustrated example) modulated blinking during the on state in unit time t_Lo may be combined. That is, as in the example in Figure 9(A), as shown in Figure 9(C), the end and start of one unit time t_Lo are determined, and by using this determination result to connect the previous end and the next start immediately after the blackout period, it becomes possible to perform the splicing shown in Figure 9(B). In this case, the signal corresponding to one low-fps read can capture more information during a high-fps read. However, in this case, it is necessary to ensure that the proportion of time t_Lo is on (Hi) is sufficiently large to be adequate for low-fps reads.

[0061] The following describes a series of operations related to signal reading on the receiving side of the invisible light communication system 100, with reference to the flowchart shown in Figure 10.

[0062] First, when the receiving device 10 is started up, settings are made to perform reading at a low fps as the imaging condition (step S101), and the imaging device 11 is operated by the control operation of the imaging device control unit CC (step S102), and an image is acquired by the image acquisition unit GR (step S103).

[0063] Next, based on the image acquired in step S103, the image analysis unit GA performs analysis processing (step S104). In the case of operation from the initial settings (step S101), the first reading unit RU1 performs reading at a low fps.

[0064] Subsequently, it is determined whether or not the imaging conditions will be processed (continued) at a low fps (step S105). If it is determined in step S105 that processing will be performed at a low fps (step S105: Yes), then low-fps decoding processing is performed, that is, the signal is read by the first reading unit RU1 (step S106).

[0065] Next, it is determined whether or not to switch to a high fps (step S107). If it is determined that a switch should be made (step S107: Yes), the switching unit SW switches from the first reading unit RU1 to the second reading unit RU2. However, if it is determined in step S107 that a switch should not be made (step S107: No), reading at a low fps by the first reading unit RU1 is maintained. After that, the result of the signal reading is output as the reception result (step S109), and the operation returns to step S102.

[0066] On the other hand, if it is determined that processing is not performed at low fps in step S105 (step S105: No), then decoding processing for high fps is performed, that is, signal reading is performed by the second reading unit RU2 (step S110). A typical example of this would be when a switch to high fps is made in step S107 (step S107: Yes), and then various subsequent image processing steps are performed (steps S108, S109, S102~S104) before reaching the processing in step S105.

[0067] After step S110, it is determined whether or not to switch to a low fps (step S111). If it is determined that a switch should be made (step S111: Yes), the switching unit SW switches from the second reading unit RU2 to the first reading unit RU1. On the other hand, if it is determined in step S111 that a switch should not be made (step S111: No), reading at high fps by the second reading unit RU2 is maintained. After that, the result of the signal reading is output as the reception result (step S109), and the operation returns to step S102.

[0068] The above operations are repeated until signal reading is no longer necessary (for example, until the train has completed its run).

[0069] The following outline of the invisible light communication system 100 will be explained with reference to the conceptual diagram shown in Figure 11.

[0070] As shown in the figure and as previously described, the invisible light communication system 100 including the signal processing device SD of this embodiment includes a transmitting unit TT that transmits a signal by modulating and blinking invisible light wavelength band optical EL as invisible light, a light receiving unit RR that receives invisible light wavelength band optical EL, a first reading unit RU1 that reads the signal at a predetermined frame rate for a first range RE1 of the image G acquired by receiving light at the light receiving unit RR, and a second reading unit RU2 that reads the signal at a higher frame rate than the first reading unit RU1 for a second range RE2 which is narrower than the first range RE1. In the invisible light communication system 100 described above, it is possible to read the signal in two stages, reading at the first reading unit RE1 and reading at the second reading unit RE2, and by narrowing (more restricting) the range of the image when reading at the second reading unit RE2, it is possible to read at a higher frame rate than reading at the first reading unit RE1 while suppressing an increase in processing load.

[0071] Furthermore, in the above case, it is sufficient to apply a frame rate of, for example, around 600fps to a portion of the image, thus enabling the exchange of necessary information without requiring ultra-high-speed devices such as EVS (Event-Based Vision Sensor) cameras. In addition, by targeting light in a specific wavelength range of non-visible light (IR light or UV light), problems such as flickering that occur when using modulated flashing of visible light can be avoided.

[0072] 〔others〕 This invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit.

[0073] First, regarding the receiving device 10 mentioned above, if accurate light reception is possible, the light-receiving element can be various types, not limited to an image sensor for IR light. For example, a photodiode could be used. Conversely, if a device specialized for a specific wavelength band is used, a configuration without a bandpass filter 12 could be considered.

[0074] Furthermore, the information acquired at high fps can also be varied. For example, by including identification information of the transmitting device 20 in addition to the display information, it may be possible to confirm the success or failure of the information acquired at low fps.

[0075] Furthermore, in the above configuration, it is also possible to provide a separate device for emitting non-visible light wavelength band EL in the transmitting device 20, in addition to the device for emitting visible light wavelength band VL.

[0076] Furthermore, various types of signal information can be handled. In the case of railways, in addition to the information regarding whether or not to proceed as described above, the invisible light communication system 100 may also be used to exchange signals for, for example, instructions to change direction at a turnout.

[0077] Furthermore, while the above describes the application of the invisible light communication system 100 to railway trains operating on dedicated tracks, it is not limited to this. For example, the invisible light communication system 100 can also be adopted for trams running on dedicated tracks (newly constructed tracks, shared tracks) or buses running on dedicated roads. [Explanation of symbols]

[0078] 10...Receiver, 11...Imaging device, 12...Bandpass filter, 13...Control / processing device, 20...Transmitter, 20α-20δ...Signal lamp, 21...Control board, 21i...Non-visible light modulation control unit, 21v...Visible light illumination control unit, 22...LED board, 100...Non-visible light communication system, CA...Camera, CC...Imaging device control unit, DP...Display device (display), EE...LED element, EEi...Non-visible light LED element, EEv...Visible light LED element, EL...Non-visible light wavelength band G...Image, G0...Overall image, GA...Image analysis unit, GG...Image, GR...Image acquisition unit, IP...Non-visible light emission unit, OT...Output unit, PT...Period, PW...Power supply, RA...Rectangular area, RE1...First range, RE2...Second range, RL...Track, RR...Light receiving unit, RS...Railway signal, RU1...First reading unit, RU2...Second reading unit, SD...Signal processing unit, SW...Switching unit, TR...Train, TT...Transmitter, VD...Sounding device (voice notification device), VL...Visible light wavelength band light, VP...Visible light emission unit

Claims

1. A transmitting unit that transmits signals by modulating and flashing invisible light, The light receiving unit that receives the aforementioned invisible light, A first reading unit reads a signal at a predetermined frame rate from a first range of the image acquired by receiving light at the aforementioned light receiving unit, A second reading unit reads signals at a higher frame rate than the first reading unit for a second range that is narrower than the first range. A non-visible light communication system equipped with this feature.

2. The first reading unit reads the identification information of the transmitting unit, The invisible light communication system according to claim 1, wherein the second range in the second reading unit is narrowed to include the image of the transmitting unit to be processed based on the reading result in the first reading unit.

3. The invisible light communication system according to claim 1, wherein the exposure time in one frame in the second reading unit is shorter than the exposure time in one frame in the first reading unit.

4. The invisible light communication system according to claim 1, further comprising a switching unit for switching from the frame rate and exposure time for reading in the first reading unit to the frame rate and exposure time for reading in the second reading unit.

5. The transmitting unit emits infrared light in a specific frequency band as the invisible light. The invisible light communication system according to claim 1, wherein the light receiving unit has a bandpass filter that transmits infrared light in the specific frequency band.

6. The transmitting unit has an invisible light emitting unit that emits invisible light and a visible light emitting unit that emits colored light. The invisible light communication system according to claim 1, wherein the invisible light emitting unit and the visible light emitting unit share a power supply for each color of light.

7. A first reading unit reads the signal at a predetermined frame rate from a first range of an image acquired by receiving modulated flashing invisible light, A second reading unit reads signals at a higher frame rate than the first reading unit for a second range that is narrower than the first range. A signal processing device equipped with the following features.

Images