Optical wireless communication system, receiving device, optical wireless communication method, and program

Abstract

To provide a high-speed optical wireless communication system.SOLUTION: An optical wireless communication system (1000) includes a transmission device (100) and a reception device (200). The transmission device includes: a signal conversion unit (101) that converts communication data to an optical signal; and a light source (102) that emits near infrared light corresponding to the optical signal. The reception device includes an optical detection unit (300) that receives the near infrared light. The optical detection unit includes: an imaging optical system (301); an imaging element (303) including a plurality of two-dimensionally arranged opto-electric conversion units; and a filter (302) that limits a wavelength range of light incident upon the imaging element. The plurality of opto-electric conversion units each are an avalanche diode.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an optical wireless communication system, a receiving device, an optical wireless communication method, and a program.

Background Art

[0002] In recent years, with the increase in communication volume, the development of optical wireless communication systems has been carried out. An optical wireless communication system performs communication by receiving a pattern displayed on a light source such as an LD (Laser Diode) or an LED (Light-Emitting Diode) with a light receiving element such as an avalanche diode.

[0003] Patent Document 1 discloses an optical wireless communication system capable of performing data communication using a two-dimensional pattern of an LED. Patent Document 2 discloses an optical wireless communication system using an avalanche diode as a light receiving element for visible light communication using an LED.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the optical wireless communication system disclosed in Patent Document 1, the communication speed depends on the frame rate of the imaging device. In the optical wireless communication system disclosed in Patent Document 2, in order to suppress the influence on the human body, it is necessary to limit the output of visible light. Therefore, the optical wireless communication systems of Patent Document 1 and Patent Document 2 cannot perform high-speed optical wireless communication.

[0006] Therefore, an object of the present invention is to provide a high-speed optical wireless communication system. [Means for solving the problem]

[0007] One aspect of the present invention is an optical wireless communication system having a transmitting device and a receiving device, wherein the transmitting device transmits communication data 2D A signal conversion unit that converts to an optical signal, and the 2D It emits near-infrared light corresponding to the optical signal. array The receiving device has a light source and a photodetector that receives the near-infrared light, the photodetector has an imaging optical system, an image sensor including a plurality of photoelectric conversion units arranged in two dimensions, and a filter that limits the wavelength band of the light incident on the image sensor, and each of the plurality of photoelectric conversion units is an avalanche diode.

[0008] Other objects and features of the present invention are described in the following embodiments. [Effects of the Invention]

[0009] According to the present invention, a high-speed optical wireless communication system can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] This is a configuration diagram of the optical wireless communication system in each embodiment. [Figure 2] This is a block diagram of the optical wireless communication system in the first embodiment. [Figure 3] This is a diagram showing the configuration of the pixel region of the light detection unit in the first embodiment. [Figure 4] This is a flowchart showing the operation of the optical wireless communication system in the first embodiment. [Figure 5] This is a flowchart showing the operation of the optical wireless communication system in the first embodiment. [Figure 6] This is a flowchart showing the operation of the optical wireless communication system in the first embodiment. [Figure 7] This block diagram shows the operation of the optical wireless communication system in the second embodiment. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0012] First, with reference to Figure 1, an overview of the optical wireless communication system 1000 in this embodiment will be described. Figure 1 is a configuration diagram of the optical wireless communication system 1000. The optical wireless communication system 1000 includes a transmitter 100 and a receiver 200. The transmitter 100 emits near-infrared light corresponding to an optical signal. The receiver 200 receives the near-infrared light emitted by the transmitter 100. The following describes each embodiment in detail. (First Embodiment) First, the optical wireless communication system 1000 in the first embodiment will be described with reference to Figure 2. Figure 2 is a block diagram of the optical wireless communication system 1000 in this embodiment. The optical wireless communication system 1000 includes a transmitter 100 and a receiver 200. The transmitter 100 includes a signal conversion processing unit (signal conversion unit) 101 and a light source 102. The light source 102 may be a single light source or multiple light sources. The light source 102 may be an LD (Laser Diode) or an LED (Light-Emitting Diode), but is not limited to these.

[0013] The receiving device 200 includes a photodetector 300, a control unit 400, an arithmetic processing unit 500, and an image processing unit 600. The photodetector 300 includes an imaging optical system 301, a wavelength cut filter 302, and an image sensor (pixel area) 303. The wavelength cut filter 302 is a filter that limits the wavelength band of light incident on the image sensor 303. Preferably, the image sensor 303 has a SPAD (Single-Photon Avalanche Diode). Since SPADs have high temporal resolution, high-speed communication is possible. In this embodiment, an APD (Avalanche Photodiode) may be used instead of a SPAD. The photodetector 300 is connected to the control unit 400 and detects (measures) near-infrared light emitted from the light source 102 of the transmitting device 100 according to the control of the control unit 400. The photodetector 300 outputs the measurement result to the control unit 400 and the arithmetic processing unit 500. In this embodiment, the image sensor 303 receives near-infrared light emitted from the light source 102, so the wavelength cut filter 302 transmits light with a wavelength of 780 nm or longer.

[0014] The control unit 400 includes a light detection control unit 401 and a pixel count control unit 402. The light detection control unit 401 controls the operation of the light detection unit 300 based on the calculation processing results of the calculation processing unit 500. The pixel count control unit 402 controls the operation of the light detection unit 300 based on the number of pixels of the image sensor 303 set by the user.

[0015] The arithmetic processing unit 500 includes a pixel information calculation unit 501, a correction value calculation unit 502, and an fps value calculation unit 503. The method for calculating pixel information by the pixel information calculation unit 501 will be described later. The correction value calculation unit 502 calculates a correction value for the offset light acquired by the light detection unit 300. The offset light is the light acquired by the image sensor 303 in a state where there is no communication signal information (a state where the light source 102 of the transmission device 100 does not emit near-infrared light corresponding to the optical signal). The correction value calculation unit 502 outputs the calculation result to the image processing unit 600. The fps value calculation unit 503 calculates the number of blinking times per second (fps value) of the near-infrared light detected by the light detection unit 300. The fps value calculation unit 503 outputs the calculation result to the control unit 400 and the image processing unit 600.

[0016] The image processing unit 600 includes a trimming processing unit 601 and a signal processing unit 602. The trimming processing unit 601 performs trimming processing on the pixel information calculated by the arithmetic processing unit 500. The signal processing unit 602 performs signal demodulation processing on the pixel information calculated by the arithmetic processing unit 500. The arithmetic processing unit 500 and the image processing unit 600 constitute processing units that perform processing on the output signal from the light detection unit 300.

[0017] Next, referring to FIG. 3, the pixel region of the image sensor 303 in the light detection unit 300 will be described. FIG. 3 is a configuration diagram of the pixel region of the image sensor 303. In the pixel region, a plurality of SPAD pixels 304 are two-dimensionally arranged along the XY directions. One SPAD pixel 304 includes a photoelectric conversion unit (avalanche diode) 311, a quenching element 312, a control unit 320, a counter / memory 321, and a reading unit 322.

[0018] A potential based on a higher potential VH than the voltage VL supplied to the anode is supplied to the cathode of the photoelectric conversion unit 311. The anode and cathode of the photoelectric conversion unit 311 are supplied with potentials such that a reverse bias is applied to cause the photons incident on the photoelectric conversion unit 311 to undergo avalanche multiplication. By performing photoelectric conversion in a state where such a reverse bias potential is supplied, the charges generated by the incident light cause avalanche multiplication and an avalanche current is generated. When the reverse bias potential is supplied, if the potential difference between the anode and the cathode is greater than the breakdown voltage, the avalanche diode operates in Geiger mode. The photoelectric conversion unit 311 uses Geiger mode operation to detect weak signals at the single photon level at high speed.

[0019] The control unit 320 determines whether to count the output signal from the photoelectric conversion unit 311 (controls the start of light detection by the photoelectric conversion unit 311). The control unit 320 is, for example, a switch (gate circuit) provided between the photoelectric conversion unit 311 and the counter / memory 321. The gate of the switch is connected to the pulse line 332, and the on and off states of the control unit 320 are switched according to the signal input to the pulse line 332. A signal based on the control signal from the light detection control unit 401 in FIG. 3 is input to the pulse line 332. The gates of the switches are controlled all at once. As a result, the start and end of light detection are controlled all at once for all the SPAD pixels 304.

[0020] Note that the control unit 320 may be composed of a logic circuit instead of a switch. For example, as a logic circuit, an AND circuit is provided, and by setting the first input of the AND circuit as the output from the photoelectric conversion unit 311 and the second input as the signal of the pulse line 332, it becomes possible to switch whether to count the output signal from the photoelectric conversion unit 311. Also, the control unit 320 does not necessarily need to be provided between the photoelectric conversion unit 311 and the counter / memory 321, and it may be a circuit that inputs a signal for switching the operation and non-operation of the counter in the counter / memory 321.

[0021] The counter / memory 321 counts the number of photons entering the photoelectric conversion unit 311 and stores it as digital data. The counter / memory 321 initializes the counter circuit and performs other operations in response to control signals input via the control line 323. The readout unit 322 is connected to the counter / memory 321 and the readout signal line 331. The readout unit 322 controls the electrical connection and disconnection between the counter / memory 321 and the readout signal line 331 based on control signals supplied via the control line 324.

[0022] Next, with reference to Figure 4, the operation of the optical wireless communication system 1000 (optical wireless communication method for offset correction) will be described. Figure 4 is a flowchart showing the operation of the optical wireless communication system 1000.

[0023] First, in step S101, the light detection unit 300 acquires offset light (light received by the image sensor 303 when the light source 102 is not emitting near-infrared light). Next, in step S102, the arithmetic processing unit 500 calculates an offset value based on the offset light. Next, in step S103, the arithmetic processing unit 500 calculates the fps value (the number of times the light detected by the light detection unit 300 flashes per second) for the light detected by the light detection unit 300. Next, in step S104, the arithmetic processing unit 500 determines whether the fps value is above or below a threshold. If it is determined that the fps value is below the threshold, the process returns to step S101. On the other hand, if it is determined that the fps value is above or below the threshold, the process proceeds to step S105.

[0024] In step S105, the image processing unit 600 acquires a signal from the arithmetic processing unit 500 and performs signal demodulation processing by correcting the offset value of the acquired signal. In this embodiment, the threshold value of the fps value may be either a threshold value set in advance in the optical wireless communication system 1000 or a threshold value set by the user. This makes it possible to suppress unwanted signal processing caused by light other than near-infrared light emitted from the light source 102 of the transmitting device 100.

[0025] Next, with reference to Figure 5, the operation of the optical wireless communication system 1000 (optical wireless communication method related to trimming) will be described. Figure 5 is a flowchart showing the operation of the optical wireless communication system 1000.

[0026] First, in step S201, the light detection unit 300 detects near-infrared light emitted by the light source 102 of the transmitting device 100, and the arithmetic processing unit 500 acquires pixel information corresponding to the near-infrared light detected by the light detection unit 300. Next, in step S202, the arithmetic processing unit 500 determines whether or not to apply a trimming process to the pixel information acquired by the arithmetic processing unit 500. If it is determined that a trimming process should not be applied, the process proceeds to step S205. On the other hand, if it is determined that a trimming process should be applied, the process proceeds to step S203.

[0027] In step S203, the arithmetic processing unit 500 obtains trimming range information from the pixel information and outputs it to the image processing unit 600. Subsequently, in step S204, the image processing unit 600 performs trimming on the pixel information based on the trimming range information. Subsequently, in step S205, the image processing unit 600 performs signal demodulation using the trimmed pixel information. This further improves the processing speed of the optical wireless communication system 1000.

[0028] Next, with reference to Figure 6, the operation of the optical wireless communication system 1000 (optical wireless communication method related to setting the number of image pixels) will be described. Figure 6 is a flowchart showing the operation of the optical wireless communication system 1000.

[0029] First, in step S301, the control unit 400 acquires the number of imaging pixels of the image sensor 303 set by the user as the number of imaging pixels to be controlled (set number of pixels). Next, in step S302, the light detection unit 300 detects the near-infrared light emitted by the light source 102 of the transmitting device 100. Next, in step S303, the control unit 400 controls the operating area of ​​the image sensor 303 based on the set number of pixels. Next, in step S304, the image processing unit 600 performs signal demodulation processing on the acquired pixel information. This makes it possible to further reduce the power consumption in the optical wireless communication system 1000. (Second embodiment) Next, with reference to Figure 7, the optical wireless communication system 1000a in the second embodiment will be described. Figure 7 is a block diagram of the optical wireless communication system 1000a in this embodiment. The optical wireless communication system 1000a differs from the optical wireless communication system 1000 in that it has a transmitter 100a equipped with a light source 102a instead of a transmitter 100 equipped with a light source 102. Note that the other components of the optical wireless communication system 1000a are the same as those of the optical wireless communication system 1000, so their description will be omitted.

[0030] In this embodiment, the light source 102a is an array light source (a two-dimensional array light source). Therefore, the signal conversion processing unit 101 converts the communication data into a two-dimensional optical signal (an optical signal of a two-dimensional pattern corresponding to the light source 102a), and the light source 102a emits near-infrared light corresponding to the two-dimensional optical signal. This makes it possible to increase the amount of data transmitted per second in the optical wireless communication system 1000a.

[0031] In each embodiment, preferably, when the illuminance of near-infrared light from light source 102 or light source 102a is L[lux], the following condition (1) is satisfied.

[0032] L < 10000 …(1) Condition (1) defines a preferred range for near-infrared illuminance. Exceeding the upper limit of condition (1) is undesirable because it increases the power consumption of the photoelectric conversion unit 311.

[0033] In each embodiment, more preferably, the numerical range of condition expression (1) is set as shown in condition expression (1a) below.

[0034] L < 5000 …(1a) In each embodiment, more preferably, the numerical range of condition expression (1) is set as shown in condition expression (1b) below.

[0035] L < 3000 …(1b) Furthermore, in each embodiment, preferably, when the peak wavelength of near-infrared light from light source 102 or light source 102a is λ [nm], the following condition (2) is satisfied.

[0036] 700 < λ < 1100 …(2) Conditional equation (2) defines a preferred range of wavelengths for near-infrared light from light source 102 or light source 102a. Exceeding the lower limit of conditional equation (2) is undesirable because it increases luminous sensitivity and has a greater impact on the human body. On the other hand, exceeding the upper limit of conditional equation (2) is undesirable because it reduces the sensitivity of the photoelectric conversion unit 311.

[0037] In each embodiment, more preferably, the numerical range of condition expression (2) is set as shown in condition expression (2a) below.

[0038] 750 < 1050 …(2a) In each embodiment, more preferably, the numerical range of condition expression (2) is set as shown in condition expression (2b) below.

[0039] 780 < λ < 1000 …(2b) (Other embodiments) The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0040] Each embodiment can provide a high-speed optical wireless communication system, a receiving device, an optical wireless communication method, and a program.

[0041] Each embodiment of the disclosure includes the following configuration and method.

[0042] (Composition 1) An optical wireless communication system having a transmitting device and a receiving device, The transmitting device is A signal conversion unit that converts communication data into optical signals, The system includes a light source that emits near-infrared light corresponding to the aforementioned optical signal, The receiving device has a light detection unit that receives the near-infrared light, The light detection unit comprises an imaging optical system, an image sensor including a plurality of photoelectric conversion units arranged in two dimensions, and a filter that limits the wavelength band of light incident on the image sensor. The optical wireless communication system is characterized in that each of the plurality of photoelectric conversion units is an avalanche diode. (Configuration 2) The receiving device further includes a processing unit that processes the output signal from the light detection unit, The optical wireless communication system according to configuration 1, characterized in that the processing unit performs the processing only on a portion of the output signals corresponding to the light-receiving region of the near-infrared light. (Composition 3) The optical wireless communication system according to configuration 1 or 2, characterized in that the light detection unit receives near-infrared light within a range of pixel areas set by the user in the image sensor. (Composition 4) The aforementioned processing unit, The light detection unit determines whether the number of flashes per second of light detected is equal to or greater than a threshold. If it is determined that the number of flashes is less than the threshold, the processing is not performed on the light. The optical wireless communication system according to configuration 2, characterized in that if the number of flashes is determined to be greater than the threshold, the process is performed on the light. (Composition 5) The signal conversion unit converts the communication data into a two-dimensional optical signal. The optical wireless communication system according to any one of configurations 1 to 4, characterized in that the light source is an array light source that emits near-infrared light corresponding to the two-dimensional optical signal. (Composition 6) When the illuminance of the near-infrared light from the light source is L[lux], L<10000 An optical wireless communication system according to any one of configurations 1 to 5, characterized in that it satisfies the following conditional expression. (Composition 7) When the peak wavelength of the near-infrared light from the light source is λ [nm], 700 < λ < 1100 An optical wireless communication system according to any one of configurations 1 to 6, characterized in that it satisfies the following conditional expression. (Composition 8) A receiving device that receives an optical signal transmitted from a transmitting device in optical wireless communication, The device has a light detection unit that receives near-infrared light corresponding to the optical signal from the transmitting device, The light detection unit comprises an imaging optical system, an image sensor including a plurality of photoelectric conversion units arranged in two dimensions, and a filter that limits the wavelength band of light incident on the image sensor. The receiving device is characterized in that each of the plurality of photoelectric conversion units is an avalanche diode. (Method 1) The steps include: converting communication data into an optical signal using a transmitting device and emitting near-infrared light corresponding to the optical signal; The process includes the step of receiving the near-infrared light using a receiving device, The receiving device comprises an imaging optical system, an image sensor including a plurality of photoelectric conversion units arranged in two dimensions, and a filter that limits the wavelength band of light incident on the image sensor. The optical wireless communication method is characterized in that each of the plurality of photoelectric conversion units is an avalanche diode. (Composition 9) A program characterized by causing a computer to execute the optical wireless communication method described in Method 1.

[0043] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist. [Explanation of Symbols]

[0044] 100, 100a Transmitter 101 Signal Conversion Processing Unit (Signal Conversion Section) 102, 102a light source 200 Receiver 300 Light detection unit 301 Imaging Optical System 302 wavelength cut filter (filter) 303 Image sensor 311 Photoelectric conversion unit 1000, 1000a Optical Wireless Communication System

Claims

1. An optical wireless communication system having a transmitting device and a receiving device, The transmitting device is A signal conversion unit that converts communication data into a two-dimensional optical signal, It has an array light source that emits near-infrared light corresponding to the two-dimensional optical signal, The receiving device has a light detection unit that receives the near-infrared light, The light detection unit comprises an imaging optical system, an image sensor including a plurality of photoelectric conversion units arranged in two dimensions, and a filter that limits the wavelength band of light incident on the image sensor. The optical wireless communication system is characterized in that each of the plurality of photoelectric conversion units is an avalanche diode.

2. The receiving device further includes a processing unit that processes the output signal from the light detection unit, The optical wireless communication system according to claim 1, characterized in that the processing unit performs the processing only on a portion of the output signals that correspond to the light-receiving region of the near-infrared light.

3. The optical wireless communication system according to claim 1, characterized in that the light detection unit receives near-infrared light within a range of pixel areas set by the user in the image sensor.

4. An optical wireless communication system having a transmitting device and a receiving device, The transmitting device is A signal conversion unit that converts communication data into optical signals, The system includes a light source that emits near-infrared light corresponding to the aforementioned optical signal, The receiving device has a light detection unit that receives the near-infrared light, The light detection unit comprises an imaging optical system, an image sensor including a plurality of photoelectric conversion units arranged in two dimensions, and a filter that limits the wavelength band of light incident on the image sensor. Each of the aforementioned photoelectric conversion units is an avalanche diode. The optical wireless communication system is characterized in that the light detection unit receives near-infrared light within a range of pixel areas set by the user in the image sensor.

5. The aforementioned processing unit, The light detection unit determines whether the number of flashes per second of light detected is equal to or greater than a threshold. If it is determined that the number of flashes is less than the threshold, the processing is not performed on the light. The optical wireless communication system according to claim 2, characterized in that if it is determined that the number of flashes is greater than the threshold, the process is performed on the light.

6. An optical wireless communication system having a transmitting device and a receiving device, The transmitting device is A signal conversion unit that converts communication data into optical signals, The system includes a light source that emits near-infrared light corresponding to the aforementioned optical signal, The receiving device is, The photodetector that receives near-infrared light, The system includes a processing unit that processes the output signal from the light detection unit, The light detection unit comprises an imaging optical system, an image sensor including a plurality of photoelectric conversion units arranged in two dimensions, and a filter that limits the wavelength band of light incident on the image sensor. Each of the aforementioned photoelectric conversion units is an avalanche diode. The aforementioned processing unit, The above processing is performed only on a portion of the output signals that correspond to the light-receiving region of the near-infrared light. The light detection unit determines whether the number of flashes per second of light detected is equal to or greater than a threshold. If it is determined that the number of flashes is less than the threshold, the processing is not performed on the light. An optical wireless communication system characterized in that, if it is determined that the number of flashes is greater than the threshold, the process described above is performed on the light.

7. When the illuminance of the near-infrared light from the light source is L [lux], L < 10000 An optical wireless communication system according to any one of claims 1 to 6, characterized in that it satisfies the following conditional expression.

8. When the peak wavelength of the near-infrared light from the light source is λ [nm], 700 < λ < 1100 An optical wireless communication system according to any one of claims 1 to 6, characterized in that it satisfies the following conditional expression.

9. The process involves converting communication data into a two-dimensional optical signal using a transmitting device and emitting near-infrared light corresponding to the two-dimensional optical signal using an array light source, The process includes the step of receiving the near-infrared light using a receiving device, The receiving device comprises an imaging optical system, an image sensor including a plurality of photoelectric conversion units arranged in two dimensions, and a filter that limits the wavelength band of light incident on the image sensor. The optical wireless communication method is characterized in that each of the plurality of photoelectric conversion units is an avalanche diode.

10. A program characterized by causing a computer to execute the optical wireless communication method described in claim 9.

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