Receiving device, transmitting device, and optical wireless communication system

Abstract

The present application relates to a receiving device, a transmitting device, and an optical wireless communication system, and proposes a new protocol applied in optical wireless communication using an event camera. The receiving device is provided with an event camera that detects rising and falling of luminance as events, and a controller configured to receive an optical wireless communication signal transmitted from the transmitting device by the event camera. In the optical wireless communication signal, data 0 is represented by a 0th event set including one or more events. Data 1 is represented by a 1st event set including one or more events and different from the 0th event set. The controller is configured to recognize data represented by the optical wireless communication signal without referring to time between events.

Description

Technical Field

[0001] This disclosure relates to optical wireless communication technology utilizing an event camera. Background Technology

[0002] Patent Document 1 discloses a visible light communication device for use in vehicles. The visible light communication device acquires images captured by an onboard camera. Images (frames) are acquired every 1 / 60th of a second. Each bit (data) is represented by the brightness change of pixels between two consecutive frames. More specifically, a brightness increase between two consecutive frames corresponds to a bit "1", and a brightness decrease corresponds to a bit "0". The brightness change between a given bit and the next bit is not used for visible light communication.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2017-085230 Summary of the Invention

[0004] In optical wireless communication, consider a method where the receiving side receives optical wireless communication signals via an event camera. The event camera can detect increases and decreases in brightness as events. One object of this disclosure is to propose a novel protocol for application in optical wireless communication utilizing an event camera.

[0005] The first point concerns the receiving device.

[0006] The receiving device includes: an event camera that detects increases and decreases in brightness as events; and a controller configured to receive optical wireless communication signals transmitted from the transmitting device via the event camera.

[0007] In optical wireless communication signals, data 0 is represented by a set of events 0 containing more than one event. Data 1 is represented by a set of events 1 containing more than one event and different from the set of events 0.

[0008] The controller is configured to identify data represented by optical wireless communication signals without referring to the time intervals between events.

[0009] The second point concerns the transmitting device.

[0010] The transmitting device has a controller for transmitting optical wireless communication signals.

[0011] The receiving device for receiving optical wireless communication signals is configured to include an event camera that detects increases and decreases in brightness as events, and receives optical wireless communication signals through the event camera.

[0012] The controller represents data 0 in the optical wireless communication signal through a set of events 0 containing one or more events. Additionally, the controller represents data 1 in the optical wireless communication signal through a set of events 1 containing one or more events, which is different from the set of events 0.

[0013] The receiving device identifies the data represented by the optical wireless communication signal without referring to the time interval between events.

[0014] The third point concerns optical wireless communication systems.

[0015] An optical wireless communication system includes: a transmitting device for transmitting optical wireless communication signals; and a receiving device for receiving optical wireless communication signals transmitted from the transmitting device.

[0016] The receiving device is configured to have an event camera that detects increases and decreases in brightness as events, and receives optical wireless communication signals through the event camera.

[0017] The transmitting device represents data 0 in the optical wireless communication signal through a set of events 0 containing one or more events. Alternatively, the transmitting device represents data 1 in the optical wireless communication signal through a set of events 1 containing one or more events, which is different from the set of events 0.

[0018] The receiving device is configured to identify data represented by optical wireless communication signals without referring to the time between events.

[0019] According to this disclosure, a novel protocol is proposed for application in optical wireless communication utilizing an event camera. More specifically, data in the optical wireless communication signal is represented by a set of events independent of the time intervals between events. Therefore, the receiving device can identify the data represented by the optical wireless communication signal even without referring to the time intervals between events. Since the step of measuring the time intervals between events can be eliminated, the processing load in the receiving device can be reduced. Attached Figure Description

[0020] Figure 1 It is a block diagram used to illustrate the general outline of an optical wireless communication system.

[0021] Figure 2 This is a conceptual diagram illustrating the contrast between optical wireless communication signals and noise.

[0022] Figure 3 This is a conceptual diagram used to illustrate an example of a protocol applied in optical wireless communication utilizing an event camera.

[0023] Figure 4 This is a conceptual diagram used to illustrate the third protocol.

[0024] Figure 5 This is a conceptual diagram used to illustrate a variation of the third protocol.

[0025] Figure 6 This is a block diagram illustrating the processes involved in the controller of the receiving device. Detailed Implementation

[0026] 1. Utilizing optical wireless communication from an event camera.

[0027] Figure 1 This is a block diagram illustrating the general outline of the optical wireless communication system 1 according to this embodiment. The optical wireless communication system 1 performs optical wireless communication utilizing light. Here, light includes visible light and infrared light. That is, optical wireless communication includes visible light communication and infrared light communication. The optical wireless communication system 1 includes a transmitting device 100 and a receiving device 200. The transmitting device 100 transmits (outputs) an optical wireless communication signal OSG composed of light flickering. The receiving device 200 receives the optical wireless communication signal OSG transmitted from the transmitting device 100.

[0028] The transmitting device 100 includes a controller 110 and a light source 120. The controller 110 includes one or more processors that perform various processes and one or more storage devices that store various information. Examples of processors include CPUs, ASICs, FPGAs, integrated circuits, etc. The processor can also be referred to as a processing circuitry. Examples of storage devices include volatile memory, non-volatile memory, HDDs, SSDs, etc. Examples of light sources 120 include LEDs (Light Emitting Diodes).

[0029] The controller 110 encodes the transmitted data to generate a blinking pattern of the light source 120 representing the transmitted data. That is, the controller 110 converts the transmitted data into a blinking pattern of the light source 120. Then, the controller 110 generates (outputs) an optical wireless communication signal OSG representing the transmitted data by causing the light source 120 to blink rapidly according to the blinking pattern.

[0030] The receiving device 200 includes an event camera 210 and a controller 220. The controller 220 includes one or more processors that perform various processes and one or more storage devices that store various information. Examples of processors include CPUs, ASICs, FPGAs, integrated circuits, etc. The processor can also be referred to as a processing circuitry. Examples of storage devices include volatile memory, non-volatile memory, HDDs, SSDs, etc.

[0031] The event camera 210 is configured to detect brightness changes as events on a per-pixel basis. More specifically, the event camera 210 incorporates an event-based vision sensor (EVS). The event-based vision sensor detects brightness changes above a threshold as events. Increases in brightness are detected as positive events, and decreases in brightness are detected as negative events. Events are detected per pixel.

[0032] The event camera 210 is also capable of detecting brightness changes associated with the optical wireless communication signal OSG. The optical wireless communication signal OSG includes a rising edge (ER) representing a rise in brightness and a falling edge (EF) representing a fall in brightness. The event camera 210 detects the rising edge ER and the falling edge EF as positive and negative events, respectively.

[0033] Event data EVT represents the event detection results of event camera 210. More specifically, event data EVT represents the temporal / spatial distribution of events detected by event camera 210. Event data EVT includes not only the signal components corresponding to the optical wireless communication signal OSG involved in the flickering of light source 120, but also noise components. For example, noise components may arise from changes in the position and orientation of receiving device 200 (event camera 210). As other examples, noise components may also arise from changes in the position and orientation of transmitting device 100 (light source 120).

[0034] Figure 2 This is a conceptual diagram illustrating the comparison between optical wireless communication signal OSG (signal components) and noise.

[0035] exist Figure 2 In diagram (A), the vertical axis represents the number of pixels observing the event, and the horizontal axis represents the frequency. The frequency of the optical wireless communication signal OSG (signal component) corresponds to the flicker frequency of the light source 120, ranging from several 100 Hz to several 100 kHz. On the other hand, the frequency of noise is at most several Hz to 30 Hz. That is, the frequency bands of the optical wireless communication signal OSG and the noise are significantly different. Therefore, the optical wireless communication signal OSG and the noise can be easily separated. For example, the signal component can be easily extracted from the event data EVT using a high-pass filter.

[0036] exist Figure 2 In (B), the vertical axis represents the number of pixels that observed the event, and the horizontal axis represents the amount of brightness change. The brightness change of the optical wireless communication signal OSG (signal component) is greater than the brightness change of noise.

[0037] As explained above, the event camera 210 detects brightness changes for each pixel as an event. For pixels without brightness changes, no event data (EVT) is specifically generated. On the other hand, a conventional camera needs to generate full-pixel data for each frame. Therefore, compared to a conventional camera, the event camera 210 generates less data, enabling high-speed processing and thus offering the advantage of high temporal resolution. It can be said that the high-speed and high-temporal-resolution event camera 210 has high "compatibility" with the high-speed flickering of the light source 120 represented by the LED.

[0038] The controller 220 of the receiving device 200 receives event data EVT representing the event detection results of the event camera 210. Then, the controller 220 extracts the signal components corresponding to the optical wireless communication signal OSG from the event data EVT. For example, the controller 220 extracts the signal components from the event data EVT using a high-pass filter. Then, the controller 220 decodes the signal components to identify the data represented by the optical wireless communication signal OSG (transmitted data transmitted from the transmitting device 100).

[0039] Thus, the controller 220 of the receiving device 200 is able to receive the high-frequency optical wireless communication signal OSG by utilizing the event camera 210. In other words, the controller 220 is able to receive the high-frequency optical wireless communication signal OSG via the event camera 210. Then, the controller 220 decodes the received optical wireless communication signal OSG to identify the data represented by the optical wireless communication signal OSG (transmission data sent from the transmitting device 100).

[0040] The transmitting device 100 is, for example, installed on a stationary object on the street. Examples of stationary objects on the street include streetlights, traffic lights, and electronic bulletin boards. The receiving device 200 is, for example, mounted on a portable terminal. Examples of portable terminals include smartphones, tablets, and augmented reality terminals. As other examples, the receiving device 200 may also be mounted on a moving object such as a vehicle or robot.

[0041] One example of the application of the optical wireless communication described above is based on the self-position inference of the receiving device 200 (controller 220). More specifically, the transmitted data contained in the optical wireless communication signal OSG transmitted from the transmitting device 100 represents the position (absolute position) of the light source 120 of the transmitting device 100 in the absolute coordinate system. Such optical wireless communication signals OSG are repeatedly transmitted from the transmitting device 100. The receiving device 200 receives multiple optical wireless communication signals OSG from multiple transmitting devices 100 respectively. The receiving device 200 identifies the absolute positions of the multiple light sources 120 by decoding the multiple optical wireless communication signals OSG. On the other hand, the receiving device 200 can also obtain the image coordinates of the multiple light sources 120 in the image plane. By combining the absolute positions of the multiple light sources 120 and their image coordinates, the receiving device 200 can infer the position (absolute position) of the receiving device 200 in the absolute coordinate system.

[0042] 2. Examples of Protocols

[0043] As described above, according to this embodiment, optical wireless communication is performed using an event camera 210. The event camera 210 detects the rising edge ER and falling edge EF of the optical wireless communication signal OSG as events. Therefore, it is necessary to represent each of the data (bit) "0" and data (bit) "1" based on the events.

[0044] The protocol defines how data "0" and data "1" are represented in the optical wireless communication signal OSG. In other words, the protocol defines the rules for representing data "0" and "1" in the optical wireless communication signal OSG. More specifically, the protocol defines the conversion rules between data "0" and "1" and the flickering mode of the light source 120. Various protocols can be used as protocols for optical wireless communication utilizing the event camera 210.

[0045] Figure 3 This is a conceptual diagram illustrating an example of a protocol used in optical wireless communication utilizing the event camera 210. Here, two protocols, Protocol 1 and Protocol 2, are introduced. The reference period T is a defined period that serves as the basis for data communication. Each reference period T may result in a "rising edge ER", a "falling edge EF", or "no brightness change".

[0046] Protocol 1 uses both the rising edge (ER) and the falling edge (EF) to represent data "0" and "1". More specifically, Protocol 1 represents data "0" and "1" based on whether a prescribed pattern of rising edge (ER) and falling edge (EF) combinations exists for each reference period T. For example, in... Figure 3 In the example shown, the pair of rising edge ER and its consecutive falling edge EF corresponds to data "1". The rising edge ER and falling edge EF separate the reference period T. Modes other than those corresponding to data "1" correspond to data "0". For example, the pair of falling edge EF and no brightness change corresponds to data "0". Additionally, the pair of no brightness change and rising edge ER corresponds to data "0". Furthermore, the pair of falling edge EF and its consecutive rising edge ER also corresponds to data "0". The pair of no brightness change and no brightness change also corresponds to data "0".

[0047] On the other hand, the second protocol uses only either the rising edge ER or the falling edge EF to represent the data "0" and "1". More specifically, the second protocol uses either the rising edge ER or the falling edge EF as a start (onset), and represents the data "0" and "1" based on the interval (period) between consecutive start edges. For example, in... Figure 3In the example shown, only the rising edge ER is used as the start, and the falling edge EF is not used. The case where the interval between consecutive rising edges ER is a relatively long first interval corresponds to the data "1". On the other hand, the case where the interval between consecutive rising edges ER is a relatively short second interval corresponds to the data "0". The first interval is longer than the second interval. For example, the first interval is N times the reference period T, and the second interval is M times the reference period T. N and M are both integers, with N being greater than M.

[0048] 3. Agreement No. 3

[0049] according to Figure 3 In the first and second protocols shown, the representation of data in the optical wireless communication signal OSG depends on the time interval between events. In this case, the receiving device 200 needs to identify the received data represented by the optical wireless communication signal OSG based on the time interval between events. Hereinafter, a "third protocol" is proposed as a new protocol that can represent data regardless of the time interval between events.

[0050] Figure 4 This is a conceptual diagram used to illustrate the third protocol. Figure 4 In the example shown, the rising edge ER corresponds to the data "1", and the falling edge EF corresponds to the data "0". Alternatively, the rising edge ER can correspond to the data "0", and the falling edge EF can correspond to the data "1".

[0051] In this way, the data in the optical wireless communication signal OSG is represented in a manner independent of the time interval between events. Therefore, the receiving device 200 can identify the data represented by the optical wireless communication signal OSG even without referring to the time interval between events. Since the step of measuring the time interval between events can be eliminated, the processing load in the receiving device 200 can be reduced.

[0052] According to Protocol 3, three or more brightness levels can be used instead of just two levels: fully on / off. That is, the brightness levels of the optical wireless communication signal (OSG) include: the lowest level, the highest level, and one or more intermediate levels between the lowest and highest levels. Figure 4 In the example shown, there are two intermediate levels, LV2 and LV3, between the lowest level LV1 and the highest level LV4. The brightness varies between these four levels LV1 to LV4.

[0053] The number of brightness levels is limited. Therefore, in Figure 4 In the example shown, it may not be possible to represent a large number of repetitions of the same data (the same bit) such as "111111" and "000000". In such cases, the following explanation of a variation of the third protocol is valid.

[0054] Figure 5 This is a conceptual diagram illustrating a variation of the third protocol. According to the variation, the original data is transformed into an "event set" that is a combination of two or more events. This event set can also be called a "brightness change column." More specifically, the original data "0" is transformed into a "0th event set" that is a combination of two or more events. On the other hand, the original data "1" is transformed into a "1st event set" that is a combination of two or more events. The 0th and 1st event sets are different. Furthermore, neither the 0th nor the 1st event set depends on the "time between events."

[0055] And, as Figure 5 As illustrated, the number of rising edges (ER) and falling edges (EF) in event set 0 are equal. That is, the total brightness variation in event set 0 is zero, and the average brightness is constant. Similarly, the number of rising edges (ER) and falling edges (EF) in event set 1 are equal. That is, the total brightness variation in event set 1 is zero, and the average brightness is constant. Therefore, even with a limited number of brightness levels, it is possible to represent a large number of repetitions of the same data (the same bit) such as "111111" and "000000".

[0056] The brightness levels of the optical wireless communication signal OSG include the lowest level, the highest level, and one or more intermediate levels between the lowest and highest levels. Preferably, both event set 0 and event set 1 start from an intermediate level (e.g., LV3).

[0057] The correspondence between the original data "0" and the 0th event set can be predetermined. Similarly, the correspondence between the original data "1" and the 1st event set can also be predetermined. A transformation map representing these correspondences can be prepared in advance. The controller 110 of the transmitting device 100 maintains the transformation map and uses it to convert the original data into the corresponding event set. The controller 220 of the receiving device 200 maintains the transformation map and uses it to inversely convert the event set back into the original data.

[0058] Converting the original data into an event set is equivalent to "spread spectrum coding". When encoding the transmitted data, the controller 110 of the transmitting device 100 converts the transmitted data into an event set by multiplying the spread spectrum coding rows and columns by the transmitted data. When decoding the received event set, the controller 220 of the receiving device 200 restores the original data by multiplying the reverse rows and columns of the spread spectrum coding by the event set. By utilizing spread spectrum coding, noise-robust (robust) optical wireless communication can be achieved.

[0059] If Figure 4 The examples shown and Figure 5 The generalized variation shown is as follows.

[0060] In optical wireless communication signals (OSG), data "0" is represented by a "set of events 0" containing one or more events. Conversely, data "1" is represented by a "set of events 1" containing one or more events. The set of events 0 and the set of events 1 are different. Furthermore, neither the set of events 0 nor the set of events 1 depends on the "time between events".

[0061] The controller 110 of the transmitting device 100 represents the data "0" in the optical wireless communication signal OSG through the 0th event set and the data "1" in the optical wireless communication signal OSG through the 1st event set. That is, the data in the optical wireless communication signal OSG is represented by event sets that do not depend on the time between events. The controller 220 of the receiving device 200 identifies the data represented by the optical wireless communication signal OSG without referring to the time between events. Since the step of measuring the time between events can be eliminated, the processing load in the receiving device 200 can be reduced.

[0062] exist Figure 4 In the example shown, event set 0 contains only one of the rising edge ER and falling edge EF. Event set 1 contains only the other of the rising edge ER and falling edge EF.

[0063] exist Figure 5 In the example shown, event set 0 is a combination of two or more events. The number of rising edges (ER) and falling edges (EF) in event set 0 is equal. Similarly, event set 1 is a combination of two events. The number of rising edges (ER) and falling edges (EF) in event set 1 is equal. Therefore, even with a limited number of brightness levels, it is possible to represent a large number of repetitions of the same data (the same bit) such as "111111" and "000000".

[0064] The brightness levels of the optical wireless communication signal OSG include a minimum level, a maximum level, and one or more intermediate levels between the minimum and maximum levels. Preferably, event sets 0 and 1 start from an intermediate level.

[0065] 4. Processing Example

[0066] The transmitting device 100 uses a certain protocol to generate and transmit an optical wireless communication signal (OSG). More specifically, the controller 110 of the transmitting device 100 encodes the transmitted data according to a certain protocol to generate a blinking pattern of the light source 120 representing the transmitted data. That is, the controller 110 converts the transmitted data into a blinking pattern of the light source 120 according to a certain protocol. Then, the controller 110 generates (outputs) the optical wireless communication signal (OSG) representing the transmitted data by causing the light source 120 to blink rapidly according to the blinking pattern.

[0067] The controller 220 of the receiving device 200 receives the optical wireless communication signal OSG transmitted from the transmitting device 100 via the event camera 210. At this time, if the controller 220 does not recognize the protocol applied in the received optical wireless communication signal OSG, it cannot accurately identify the data represented by the received optical wireless communication signal OSG.

[0068] Figure 6 This is a block diagram illustrating the processing performed by the controller 220 of the receiving device 200 according to this embodiment. The controller 220 includes a signal detection unit 221, a protocol identification unit 222, and a decoding unit 223 as functional modules.

[0069] The signal detection unit 221 receives event data EVT, which represents the event detection results related to the event camera 210. The signal detection unit 221 detects the start of reception of the optical wireless communication signal OSG based on the event data EVT.

[0070] For example, the signal detection unit 221 detects the start of reception of the optical wireless communication signal OSG based on the event occurrence frequency per pixel of the event camera 210. Figure 2 As shown in (A), the frequency bands of the optical wireless communication signal OSG (signal component) and noise are significantly different. The frequency band of the optical wireless communication signal OSG is a specific high-frequency band (several 100 Hz to several 100 kHz). Therefore, by monitoring whether there are events in this specific high-frequency band, it is possible to determine whether the reception of the optical wireless communication signal OSG has started. More specifically, the signal detection unit 221 calculates the event occurrence frequency per pixel based on the event data EVT. Then, when an event occurrence frequency belonging to the specific high-frequency band is detected, the signal detection unit 221 determines that the reception of the optical wireless communication signal OSG has started, that is, the reception of the optical wireless communication signal OSG has been detected.

[0071] As another example, the signal detection unit 221 can also detect the start of receiving the optical wireless communication signal OSG based on the change in the total amount of event data EVT observed by the event camera 210 across all pixels. Figure 2 As shown, if reception of the optical wireless communication signal OSG begins, the total amount of event data EVT increases significantly. Therefore, by monitoring the total amount of event data EVT in advance, the start of reception of the optical wireless communication signal OSG can be detected without calculating the frequency of event occurrence. For example, if the increase in event data EVT per unit time exceeds a threshold, the signal detection unit 221 determines that reception of the optical wireless communication signal OSG has begun, that is, detects the start of reception of the optical wireless communication signal OSG.

[0072] If the reception of the optical wireless communication signal OSG is detected to have begun, the signal detection unit 221 separates the received optical wireless communication signal OSG from noise. That is, the signal detection unit 221 extracts the signal component corresponding to the received optical wireless communication signal OSG from the event data EVT. For example, the signal detection unit 221 extracts the high-frequency band signal component from the event data EVT using a high-pass filter.

[0073] In response to the detection of the start of reception of the optical wireless communication signal OSG, the protocol identification unit 222 identifies the protocol applied in the received optical wireless communication signal OSG. Hereinafter, the protocol applied in the optical wireless communication signal OSG will be referred to as the "application protocol". Furthermore, the process of identifying the application protocol applied in the received optical wireless communication signal OSG will be referred to as the "protocol identification process".

[0074] An example of protocol identification processing is as follows. In this example, optical wireless communication signals (OSGs) with the same content are repeatedly transmitted from the same transmitting device 100. In addition to the data section, each OSG includes a "protocol specification mode". The data section represents the transmitted data. On the other hand, the protocol specification mode indicates the application protocol applied in the OSG. For example, the protocol specification mode is embedded in the preamble of the OSG.

[0075] More specifically, the protocol specification mode is a combination of rising edge ER and falling edge EF. When the application protocol is Protocol 1, the protocol specification mode is Protocol 1 specification mode. When the application protocol is Protocol 2, the protocol specification mode is Protocol 2 specification mode. When the application protocol is Protocol 3, the protocol specification mode is Protocol 3 specification mode. Protocol 1 through Protocol 3 specification modes are set differently from each other, but all are given as known modes.

[0076] The controller 110 of the transmitting device 100 stores information about the i-th protocol specification mode (i = 1 to 3) in advance. The information about the i-th protocol specification mode is stored in the storage device of the controller 110. The controller 110 generates the optical wireless communication signal OSG in a manner that includes the protocol specification mode representing the application protocol.

[0077] The controller 220 of the receiving device 200 also stores information about the i-th protocol specification mode (i = 1 to 3) in advance. The information about the i-th protocol specification mode is stored in the storage device of the controller 220. The protocol identification unit 222 of the controller 220 performs protocol identification processing based on the received optical wireless communication signal OSG. More specifically, the protocol identification unit 222 identifies the application protocol applied in the received optical wireless communication signal OSG based on the protocol specification mode contained in the received optical wireless communication signal OSG.

[0078] The decoding unit 223 receives the signal components corresponding to the received optical wireless communication signal OSG from the signal detection unit 221. Additionally, the decoding unit 223 receives information about the application protocol applied in the received optical wireless communication signal OSG from the protocol identification unit 222. After protocol identification processing, the decoding unit 223 decodes the signal components according to the application protocol to identify the original data (transmitted data) represented by the optical wireless communication signal OSG. In other words, the decoding unit 223 converts the signal components into original data (transmitted data) according to the application protocol. When the application protocol is a third protocol, the time interval between events is not required.

[0079] The acquired raw data is used for subsequent processing. For example, the acquired raw data is used for self-positioning in the receiving device 200.

[0080] Furthermore, once an application protocol is identified through protocol identification processing, the same application protocol can be used for a certain period. Protocol identification processing can also be performed again after the specified period has elapsed.

[0081] The transmitting device 100 can also randomly change the application protocol at constant intervals. The receiving device 200 is able to follow the changes in the application protocol through the aforementioned protocol identification processing. Security is enhanced by randomly changing the application protocol.

[0082] Explanation of reference numerals in the attached figures

[0083] 1… Optical wireless communication system; 100… Transmitting device; 120… Light source; 200… Receiving device; 210… Event camera; 220… Controller; OSG… Optical wireless communication signal.

Claims

1. A receiving device, wherein, have: An event camera detects increases and decreases in brightness as events; and The controller is configured to receive optical wireless communication signals transmitted from the transmitting device via the event camera. In the optical wireless communication signal, data 0 is represented by a set of events 0 that includes more than one event. In the optical wireless communication signal, data 1 is represented by a first event set that contains more than one event and is different from the 0th event set. The controller is configured to identify data represented by the optical wireless communication signal without referring to the time intervals between events.

2. The receiving device according to claim 1, wherein, The 0th event set is a combination of two or more events. The number of increases and the number of decreases contained in the 0th event set are equal. The first event set is a combination of two or more events. The number of increases and the number of decreases contained in the first event set are equal.

3. The receiving device according to claim 2, wherein, The brightness levels of the optical wireless communication signal include a minimum level, a maximum level, and one or more intermediate levels between the minimum and maximum levels. The 0th event set and the 1st event set begin from the intermediate level.

4. The receiving device according to claim 1, wherein, The 0th event set contains only one of the rising and falling events. The first event set contains only the other side of the rise and the fall.

5. A transmitting device, wherein, It has a controller that transmits optical wireless communication signals. The receiving device for receiving the optical wireless communication signal is configured to include an event camera that detects increases and decreases in brightness as events, and receives the optical wireless communication signal via the event camera. The controller is configured as follows: Data 0 in the optical wireless communication signal is represented by a set of events 0 containing more than one event. Data 1 in the optical wireless communication signal is represented by a first event set that contains more than one event and is different from the 0th event set. The receiving device is configured to identify data represented by the optical wireless communication signal without referring to the time interval between events.

6. An optical wireless communication system, wherein, have: Transmitting device, transmitting optical wireless communication signals; and The receiving device receives the optical wireless communication signal transmitted from the transmitting device. The receiving device is configured as an event camera that detects increases and decreases in brightness as events, and receives the optical wireless communication signal through the event camera. The transmitting device is configured as follows: Data 0 in the optical wireless communication signal is represented by a set of events 0 containing more than one event. Data 1 in the optical wireless communication signal is represented by a first event set that contains more than one event and is different from the 0th event set. The receiving device is configured to identify data represented by the optical wireless communication signal without referring to the time interval between events.

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