WO2015137313A1 - 可視光受信方法 - Google Patents
可視光受信方法 Download PDFInfo
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- WO2015137313A1 WO2015137313A1 PCT/JP2015/056946 JP2015056946W WO2015137313A1 WO 2015137313 A1 WO2015137313 A1 WO 2015137313A1 JP 2015056946 W JP2015056946 W JP 2015056946W WO 2015137313 A1 WO2015137313 A1 WO 2015137313A1
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- visible light
- signal
- pixel
- row
- transmitted
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
- H04B10/114—Indoor or close-range type systems
- H04B10/116—Visible light communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/71—Circuitry for evaluating the brightness variation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/745—Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/76—Circuitry for compensating brightness variation in the scene by influencing the image signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/50—Control of the SSIS exposure
- H04N25/57—Control of the dynamic range
Definitions
- the present invention relates to a visible light receiving method and apparatus for use in visible light communication, and in particular, can be suitably used for a portable terminal equipped with a camera (digital camera or video camera) such as a portable information terminal and a cellular phone.
- the present invention relates to a visible light receiving method.
- a visible light transmitter that superimposes a transmission signal on visible light and transmits the information signal (pulse signal) to be transmitted is modulated (pulse position modulation) by a quaternary PPM method. It operates to generate a transmission signal, apply the transmission signal to a light source using the LED to drive the LED, and transmit the transmission signal superimposed on the visible light emitted by the LED.
- this visible light communication device in order to effectively use the illumination light source that is normally used as the light source of the visible light transmission device, a relatively long digital value is applied when the PPM signal is applied to the LED light source for illumination. During the period of “0”, the LED is continuously lit, and during the period of the short digital value “1”, the LED is caused to blink at a shorter frequency by the carrier signal of the subcarrier. The illuminance required for lighting is ensured.
- visible light emitted from a light source for illumination serving as a light source of a visible light transmitter that performs visible light communication that is, illumination light for visible light communication on which a transmitted information signal is superimposed
- a camera such as a portable terminal.
- a visible light communication apparatus proposed in Japanese Patent Application Laid-Open Publication No. 2004-228561 that analyzes the captured image data, extracts a data bit string included in the image data, and demodulates information signal data transmitted from the data bit string. Has been.
- the visible light communication device for example, the visible light communication device using the illumination light source as a visible light source is photographed with a digital camera or a video camera, and bright visible light (light from the light source) emitted from the illumination light source is used.
- the camera exposure is automatically adjusted over the entire screen. For this reason, the light source image on the photographed image is completely white and is photographed in a whiteout state.
- the contour line of the image is included as noise of the visible light transmission data. It is difficult to extract.
- Patent Document 3 a digital camera equipped with a pixel amplifier sequential output type image sensor such as a CMOS image sensor is used as an image sensor of a digital camera, and charges are accumulated in the pixels in the row at the timing of each pixel row. Then, a signal based on the charge accumulated in each pixel is sequentially output from the pixel amplifier of each pixel at the timing of each pixel, and a striped pattern based on the transmitted signal is added to the pixel row in the captured image.
- a visible light communication device that generates a transmission signal in a direction and extracts and demodulates a transmission signal based on a state of occurrence of a striped pattern.
- the digital modulation / demodulation method of this conventional visible light communication apparatus is roughly one of the pulse width modulation / demodulation methods, and the visible light transmission signal irradiated and transmitted as visible light is irradiated in the form of pulses.
- the irradiation pulse width of the visible light signal the transmitted visible light is superimposed on the visible light, and the irradiated visible light is photographed with a digital camera.
- a stripe pattern (light and dark bands) is generated in the image signal output from each pixel of the image sensor of the digital camera, and the output signal of each pixel corresponding to the stripe pattern of the image sensor is shown in FIG. As described above, the output is shifted by a predetermined time t1.
- a PWM-modulated transmission signal is transmitted by being superimposed on visible light, and the digital camera as a receiving device has a striped pattern (light and dark bands) generated in the captured image. Is measured, and the transmitted visible light transmission signal is demodulated based on the width of the stripe pattern.
- the width of the stripe pattern generated in the captured image is a value that is substantially proportional to the exposure period tx of the digital camera and proportional to the pulse width of the visible light transmission signal.
- the exposure time tx is usually longer than the signal width t2 of the visible light transmission signal, and the received signal acquired as the exposure amount is integrated as the sum of the brightness during the exposure time. .
- the exposure amount of the reception signal is inclined, and the accurate pulse signal information of the signal width t2 of the visible light transmission signal is lost, and the reception signal is accurately Cannot be demodulated.
- the captured image is captured.
- the width of the stripe pattern is 5 milliseconds. Therefore, the shutter speed of the digital camera is very high as the camera shutter speed, for example, 1/5000 seconds, the exposure time tx is 5 milliseconds, and the pulse width t2 of the visible light transmission signal is 0.5 m, for example. If one second (time of one symbol of the transmission signal modulated by four-valued PPM) is used and only one visible light transmission pulse signal is captured in one striped pattern as shown in FIG. The length of the image signal indicating the length corresponds to the length of the transmission pulse signal, and based on the width of the stripe pattern (exposure time tx), there is a possibility that the transmission pulse signal transmitted by visible light can be demodulated. is there.
- the shutter speed is 1/500 seconds
- the exposure time tx is 50 milliseconds
- the pulse width t2 of the visible light transmission signal is 0.5 milliseconds
- the visible light transmission signal is digital camera.
- the signal is received at 2
- two or more transmission pulse signals are input within the exposure time tx based on the shutter speed, and the demodulation based on the stripe pattern width results in the loss of the transmitted pulse signal information.
- the transmission signal cannot be demodulated.
- the frequency of the visible light transmission signal that is, the transmission speed of the visible light transmission data is limited by the shutter speed (exposure time) of the digital camera, and there is a problem that the increase in the transmission speed of the visible light communication is hindered.
- the present invention solves the above-described problems, and uses a mobile terminal equipped with a general-purpose camera to capture visible light for visible light communication and receive visible light communication transmission signals.
- An object of the receiving method is to provide a visible light receiving method capable of stably and reliably receiving a transmission signal and increasing the visible light communication speed.
- the visible light receiving method of the present invention that solves the above-described problem is based on the image data of the image sensor imaged by the camera, in which the visible light irradiated for visible light communication is imaged by a camera having the image sensor.
- a visible light receiving method for receiving a visible light transmission signal transmitted by being superimposed on the visible light The visible light transmission signal is modulated based on the information signal to be transmitted and superimposed on the visible light
- the camera shoots using a pixel amplifier sequential output type imaging device, and the pixel amplifier sequential output type imaging device amplifies the charge generated in each pixel by each pixel amplifier and sequentially picks up an imaging signal from each pixel amplifier.
- the image data of the striped pattern obtained from the imaging signal is captured in units of frames, and the differential value is calculated based on the difference in the exposure amount of each row or each pixel output in order, and each row or The signal is demodulated based on the differential value of the imaging signal of a plurality of samples with each pixel as one sample.
- each row of image data of one frame is taken as one sample, a plurality of samples of the information signal are captured in one process, and the exposure amount of each row of pixels corresponding to the stripe pattern in the image data of each sample
- the differential value is calculated from the displacement of. This differential value represents a visible light transmission pulse signal.
- the pulse information of the transmission pulse signal transmitted by visible light transmission can be accurately demodulated based on the differential value of the exposure amount generated for each row of pixels corresponding to the stripe pattern. Further, the differential value of the exposure amount of the pixels in each row is calculated, and the transmission pulse signal is extracted from the waveform of the differential value.
- a visible light transmission signal transmitted at a much higher speed than in the past can be received only by photographing with a general-purpose digital camera, and the transmission signal can be demodulated at a high speed.
- the visible light transmission signal is on-off modulated based on the information signal to be transmitted and superimposed on the visible light, and the differential value is calculated by differentiating the exposure amount indicating the stripe pattern,
- a predetermined threshold value can be set for the differential value, and the differential value data can be binarized by the threshold value to demodulate the visible light transmission signal.
- the pulse width of the visible light transmission signal is shorter than the exposure period of each row of pixels, and the pulse interval of the visible light transmission signal is different from the exposure period.
- the exposure period is a period in which charges are accumulated based on the light received by each pixel of the image sensor at the time of imaging by the camera, and the length (width) of the striped pattern that appears in the captured image is the exposure period.
- the time is approximately proportional to time and proportional to the transmitted visible light transmission signal.
- the image data of the striped pattern (the luminance component of the pixel), that is, the exposure amount indicating the striped pattern is differentiated to calculate the differential value, and when a negative differential value occurs in the waveform of the differential value, the negative value A phenomenon in which the differential value occurs at the same timing as the positive differential value in the pulse of the next transmission signal and cancels out does not occur, and the transmission signal can be stably received and the received data can be demodulated.
- the exposure period is set longer than the pulse interval of the visible light transmission signal. According to this, even if the exposure period is determined by the performance of the camera, the transmission interval of the transmission pulse signal can be increased by shortening the pulse interval of the visible light transmission signal, and based on the calculated differential value.
- the visible light transmission pulse signal can be accurately demodulated.
- a visible light for visible light communication is photographed using a general-purpose camera, and a visible light transmission signal transmitted for visible light communication is received and demodulated at high speed. be able to.
- FIG. 1 is a configuration block diagram of a visible light receiving apparatus as an embodiment that implements the visible light receiving method of the present invention.
- FIG. It is a block diagram of a schematic configuration of a pixel amplifier sequential output type image sensor. It is circuit diagram explanatory drawing of a pixel. It is a flowchart of the reception process of a visible light receiver. It is explanatory drawing which shows the accumulation
- FIG. 1 shows a schematic block diagram of a portable terminal 1, which has a visible light receiving device that implements a visible light receiving method, shoots visible light irradiated for visible light communication, and displays visible light. Receive transmission signal.
- the mobile terminal 1 is a terminal device equipped with a camera (digital camera) 10 such as a mobile phone, and in the camera mode of the mobile terminal 1, a function switch or the like is operated to capture a still image or a moving image. When this still image or moving image is captured, a visible light information signal transmitted for visible light communication is received.
- a camera digital camera
- a function switch or the like is operated to capture a still image or a moving image.
- an imaging lens 13 is disposed in the light incident portion of the camera 10
- an iris 14 having a diaphragm function is disposed inside the lens 13, and an inside of the iris (iris diaphragm mechanism) 14.
- the image pickup device 11 is disposed on the lens 13 and allows visible light of an image taken through the lens 13 and the iris 14 to enter.
- the iris 14 can be a diaphragm mechanism in place of the ND filter (a neutral density filter).
- a light diffusion filter 12 is disposed in front of the lens 13 in order to receive a visible light signal transmitted for visible light communication.
- an ordinary digital camera can be used without providing the light diffusion filter 12. It is also possible to take a normal image and generate a striped pattern in the image to receive a visible light signal.
- the light diffusing filter 12 When the light diffusing filter 12 is disposed in front of the lens 13, the diffused light of the subject enters the camera 10, and the projector of the visible light transmitter that projects visible light for visible light communication is an illumination like a spotlight. Even if it is an instrument, the light source image of the projector will not be blown out. Further, since the light from the subject is diffused by the light diffusing filter 12 and made incident on the camera 10 and visible light can be photographed as being blurred with the diffused light, the light and darkness and contour lines of the subject are extracted from the striped pattern. When photographing visible light for visible light communication without adversely affecting (noise), a striped pattern in the image can be easily captured.
- the light diffusion filter 12 is composed of a sheet glass or a film sheet having a light diffusion layer such as a ground glass or a light diffusion film, and is attached to the outer surface of the lens 13 exposed to the outside of the portable terminal 1 when receiving visible light. Can be used.
- the light diffusing filter 12 is movably disposed in the portable terminal 1, and when receiving visible light, the light diffusing filter 12 is moved so as to enter the incident light path by a switch operation or the like, and the camera is operated in a normal manner. When used for photography, the light diffusion filter 12 may be moved so as to be removed from the optical path.
- the light diffusion filter 12 can be composed of a film liquid crystal that switches between light diffusion and light transmission according to the applied voltage.
- a film liquid crystal is a thin and light weight liquid crystal filter in which, for example, a TN liquid crystal is filled in an overlapped film. In a normal state, the liquid crystal is in a light-transmitting state, and can be used as a normal camera. The liquid crystal is put into a light diffusing state such as milky white according to the applied voltage.
- a film liquid crystal can be easily used as the light diffusion filter 12 capable of switching between light diffusion and light transmission.
- a pixel amplifier sequential output type image pickup device 11 that amplifies charges generated in each pixel 21 by each pixel amplifier 22 and sequentially outputs an image pickup signal from each pixel amplifier 22 is provided in the mobile terminal 1.
- a CMOS image sensor is an image pickup device that amplifies charges generated in pixels by each pixel amplifier and outputs an image pickup signal in order from each pixel amplifier. Can do.
- the pixel amplifier sequential output type image pickup device 11 is configured as shown in FIG. 2, and the scanning device includes a row scanning device 16 that scans in the row direction and a column scanning device 17 that scans in the column direction.
- the pixel amplifier sequential output type imaging device 11 composed of a CMOS image sensor has a large number of pixels 21 arranged in a matrix.
- each pixel 21 has a light receiving element and a capacitor unit that accumulates the charge generated in the light receiving element, and according to the switching operation of the changeover switch 28, It is configured to switch the output of the pixel signal based on the charged charges.
- each pixel 21 that is, the charge accumulation operation
- the shutter signal line for each row of pixels 21 so that the pixels 21 in the same row accumulate charges at the same accumulation timing.
- the pixels 21 in each row accumulate charges at the same timing in each row.
- a row selection switch 32 is connected to the shutter signal line 30 disposed along each row, and as shown in FIG. 5, each row of the pixels 21 performs charge accumulation, that is, exposure operation at a timing shifted in sequence for each row.
- the signal based on the charge is outputted in order from the pixel 21 in the row in which the charge is accumulated, and the pixel signal is outputted in order from all the pixels 21.
- a pixel amplifier 22 is provided on the output side of each pixel 21, and the output side of the pixel amplifier 22 is connected to a vertical signal line 25 via a pixel selection switch 23.
- the row scanning device 16 amplifies the electric charge of each pixel 21 arranged in a matrix by a pixel amplifier 22 and sends it through the pixel selection switch 23 to each vertical signal line 25 in the column direction connected to the output side.
- the signals based on the charges of the pixels 21 in each row are connected so as to be sequentially output through the vertical signal lines 25.
- the column scanning device 17 is configured by connecting a column selection switch 24 connected to the output side of each vertical signal line 25 to one horizontal signal line 26, and in the column direction by ON / OFF control of each column selection switch 24.
- the vertical signal line 25 is selected, and a signal based on the load is output from the pixel 21 of each vertical signal line 25 through one horizontal signal line 26.
- each vertical signal line 25 is arranged along the column direction, and the output side of the pixel 21 of each row line arranged in each row direction is connected to the vertical signal line 25 via the pixel amplifier 22 and the pixel selection switch 23.
- the vertical signal lines 25 extend in the column direction and are arranged in parallel with the columns along the large number of pixels 21 arranged on each column in the matrix form.
- a second amplifier 27 is connected to the lower end of each vertical signal line 25, and an output side of the second amplifier 27 is connected to one horizontal signal line 26 via a column selection switch 24.
- the row scanning device 16 is provided with the shutter signal lines 30 along the rows of the pixels 21 as described above, and the pixels 21 in the same row are separated from the shutter signal lines when the camera is operated by the shutter. Charges are accumulated simultaneously at the exposure timing based on the signal.
- the output signal from the pixel 21 is connected so as to be output based on the switching operation of the changeover switch 28 and the operation of the pixel selection switch 23 after the charge is accumulated. As shown in FIG. Pixel signals are sequentially output from the pixels 21.
- the pixel amplifier sequential output type image pickup device 11 stores charges at the same timing in each pixel 21 in each row. After the charge is accumulated, the signals based on the accumulated charges are sequentially output from all the pixels 21 and amplified by the pixel amplifier 22, and then the switching operation of the pixel selection switch 23 and the switching operation of the column selection switch 24 are performed. Is sent to the vertical signal line 25 and output through the horizontal signal line 26.
- the row selection switch 32 of the uppermost shutter signal line 30 is turned on, and charge accumulation is simultaneously performed in the uppermost pixel 21.
- the row selection switch 32 of the shutter signal line 30 in the second row is turned on, and charges are accumulated in the pixels 21 in the second row.
- charges are sequentially accumulated up to the pixel 21 in the last row in the third and fourth stages, and the charges are accumulated at the exposure timing in which the exposure for each row (charge accumulation) is shifted in order for each row. Done.
- the pixel 21 in each row sequentially outputs pixel signals based on charges from the uppermost pixel 21.
- the uppermost pixel selection switch 23 connected to the leftmost vertical signal line 25 is turned on, and the leftmost column selection switch 24 connected to the horizontal signal line 26. Is turned on, whereby a signal is output from the pixel 21 at the left end of the uppermost row, and then the pixel selection switch 23 of the second pixel 21 from the left end of the same row is turned on, and the second vertical signal line 25 is turned on.
- the connected column selection switch 24 is turned on, whereby a signal is output from the second pixel 21 in the same row.
- the row selection switch 32 is turned on in order from the uppermost shutter signal line 30, and charges are simultaneously accumulated in the uppermost pixel 21.
- the row selection switch 32 of the shutter signal line 30 in the second row is turned on, and an exposure operation is performed so that charges are accumulated in the pixels 21 in the second row.
- pixel signals based on charges are sequentially output from the uppermost pixel 21.
- a signal is finally output from the pixel 21 in the lowermost row through the vertical signal line 25 at the right end, and an image signal of one frame is captured.
- the charge accumulation operation in each row of the pixels 21, that is, the exposure timing is sequentially shifted, and the exposure timings in the pixels in the second and third rows from the top are shifted in sequence. Therefore, for example, the time for capturing one frame of image signal is set to the frame rate of the camera (for example, 1/30 seconds to 1/60 seconds).
- the frame rate of the camera for example, 1/30 seconds to 1/60 seconds.
- transmission data that has been subjected to OOK modulation (on-off keying modulation) is superimposed as a transmission pulse signal, and temporal brightness is produced according to the transmission pulse signal, so that output is performed from the pixels of each matrix in one frame.
- transmission data superimposed on visible light is included as a transmission pulse signal at the time when pixels in one frame are exposed.
- the transmission pulse signal that is OOK-modulated and superimposed on the visible light has a time of one sample, for example, about 0.5 milliseconds, and the imaging element 11 captures the change in brightness of the visible light including the transmission pulse signal as a stripe pattern. Occurs in the image.
- a stripe pattern including an information signal is captured in one frame, and the image signal is sent to the image processing apparatus through the scanning device.
- a camera 10 incorporated in a general-purpose mobile phone normally includes a pixel amplifier sequential output type image pickup device (CMOS image sensor) 11 and has, for example, 12 million pixels, for example, 3000 rows ⁇ 4000 columns. The pixels are arranged, which constitutes one frame. Since the time for capturing a signal from each pixel of one frame of the image sensor 11 is the frame rate of the camera 10, for example, when shooting at a frame rate of 1/30 seconds, the time of one frame is about 33 milliseconds, Since the 1 bps time of the information signal for visible light communication based on the visible light communication standard is about 0.25 msec, by processing each row as one sample, the information signal of a plurality of samples is captured by one frame. This is possible in a visible light receiving apparatus using 10.
- CMOS image sensor pixel amplifier sequential output type image pickup device
- the color image signal that is captured and output by the camera 10 is subjected to grayscale conversion, converted into a monochrome image signal, and a luminance component is extracted.
- a luminance component can be extracted for each color signal from a color image signal that is captured and output.
- each of the plurality of visible light transmitters is unique.
- ID information is assigned and set, and the ID information can be sufficiently included in one frame of image data.
- the camera 10 is used to capture a single still image, and transmit or transmit visible light signals based on image data including a stripe pattern to reproduce or display the transmitted data signals. It is also possible to take a moving image by using a projector (lighting fixture) of a visible light transmitting apparatus as a subject, take in a plurality of frames of image data, and take out a transmission data signal from a striped pattern included therein.
- a projector light fixture
- the shutter signal lines 30 are arranged along the row direction of the pixels 21 (horizontal horizontal direction in FIG. 2), and the pixels 21 in each row are shifted simultaneously at the same time and for each row.
- the shutter signal lines are arranged along the column direction of the pixels 21 (vertical direction in FIG. 2), and the pixels 21 in each column are simultaneously and column by column.
- the charge can be accumulated at timings shifted in order.
- a striped pattern including an information signal captured and transmitted in one frame of the captured image is generated in the column direction of the pixels 21. That is, as described above, when charge accumulation is performed at the same time for the pixels 21 in each row and sequentially shifted from row to row, a striped pattern (horizontal striped pattern) along the row direction is generated in the captured image. When charge accumulation is performed for the pixels 21 in the column at the same time and sequentially shifted from column to column, a striped pattern (vertical striped pattern) along the column direction is generated in the captured image, but is transmitted to the striped pattern. Since transmission data is included, data transmitted based on the striped pattern can be extracted.
- the image processing apparatus that processes a captured image signal includes an AD converter 18 and an image processing LSI 19, converts the image signal into a digital signal through the AD converter 18, and takes the digital signal into the image processing LSI 19. , Configured to perform image processing.
- the image processing LSI 19 takes in an image digital signal including color information and luminance information
- the image processing LSI 19 extracts only the luminance information and converts it into, for example, grayscale data of 0 to 255 gradations, and extracts the luminance component of the signal, that is, the striped pattern component
- the extracted data is sent to the microprocessor 48 as shown in FIG.
- FIG. 6 such a striped pattern of a captured image of one frame is generated in the captured image as a horizontal striped pattern, and an information signal for visible light communication is generated in each horizontal striped state. Will be included.
- the mobile terminal 1 includes the camera 10 as described above, and is composed of a PDA that can be connected to a wireless LAN, a tablet terminal, or a mobile phone communication network or a mobile phone that can be connected to a wireless LAN. Connected to the network.
- the portable terminal 1 includes a microprocessor 48 as a main part, and includes a storage unit 50 including a RAM, a ROM, etc., and a peripheral interface 53 including an input / output circuit.
- the mobile terminal 1 includes a touch-sensitive display 57 that can perform touch input for various function switch inputs, displays moving images, still images, text, and the like, a display controller 56 that controls the touch-sensitive display 57, and the like.
- the mobile terminal 1 includes an RF circuit 54 for connecting to a wireless LAN or a mobile phone communication network, and can be connected to the wireless LAN or the mobile phone communication network through the peripheral interface 53 and the RF circuit 54.
- the storage unit 50 of the mobile terminal 1 stores in advance browser software, audio reproduction software, visible light reception processing software, and the like.
- the microprocessor 48 of the portable terminal 1 takes in the transmission data signal (image data) for visible light communication photographed by the camera 10 having the above configuration, calculates the average value of the luminance component in the row direction, and further averages it. A differential value is calculated based on the displacement of the average value of the luminance data of each row.
- the average value of the brightness data indicates the exposure amount of the stripe pattern generated in each row of each pixel of the image sensor 11, and the differential value is calculated based on the displacement of the exposure amount.
- the microprocessor 48 sets a predetermined threshold value for the differential value of the exposure amount, binarizes the differential value of the exposure amount based on the threshold value, extracts a transmission signal received from the binarized data, and transmits it.
- the signal is demodulated in accordance with the OOK system, and transmission information such as audio data or image data transmitted from the visible light transmitter is acquired and reproduced or displayed.
- transmission information such as audio data or image data transmitted from the visible light transmitter is acquired and reproduced or displayed.
- the information signal transmitted by visible light is unique ID information of the visible light transmitter, the content information corresponding to the ID information is reproduced or displayed.
- the portable terminal 1 is provided with an audio circuit 46 for reproducing an audio signal and the display 57 for displaying images and characters.
- a speaker 52 is connected to the output side of the audio circuit 46.
- a microphone 51 is connected to the input side.
- the microprocessor 48 of the mobile terminal 1 extracts and receives the ID information of the visible light transmitter from the image data including the stripe pattern of the light source (luminaire) for visible light communication photographed by the camera 10. Process.
- the microprocessor 48 reads the audio data of the content information stored in advance, converts it into an analog signal, and outputs the audio signal to the audio circuit 46.
- the audio circuit 46 amplifies the audio signal and drives the speaker 52 to reproduce the audio.
- the display unit 56 is configured to display them on the touch-sensitive display 57.
- the RF (Radio ⁇ Frequency) circuit 54 of the mobile terminal 1 shown in FIG. 1 includes an antenna system and a tuner, transmits or receives RF signals, and is a wireless LAN access point connected to the Internet or the base of a mobile phone communication network. It is configured to perform radio wave communication with a station.
- the portable terminal 1 is used for viewing commentary contents (audio guide) of exhibits in, for example, art museums and museums.
- a visible light transmitter for example, a visible light transmitter having a projector that also serves as a lighting fixture
- commentary content voice guide
- Different ID information is assigned and set to each visible light transmitter, and content information corresponding to each ID information is stored in the storage unit 50 of the portable terminal 1.
- the portable terminal 1 When the portable terminal 1 is lent to a user as an explanation device for an exhibit like an art museum or a museum, the portable terminal 1 corresponds to each ID information (ID corresponding to each exhibit) in advance.
- the commentary content information is captured and stored in the storage unit 50.
- the content information is stored in advance together with ID information in a content server on the network, for example.
- the content server By operating the content server via the network, the content information can be downloaded to the portable terminal 1 and used.
- the mobile terminal 1 can be used as it is without being connected to the network.
- each visible light transmitter is also used as a lighting fixture in a facility such as a museum, and the light from the projector illuminates the exhibit, and the ID information indicating the content for explaining the exhibit is OOK modulated. (On-off keying modulation) and superimposed on visible light.
- OOK modulation On-off keying modulation
- transmission data is encoded
- a transmission pulse signal is created based on the encoded transmission encoded data
- the transmission pulse signal is superimposed on visible light and transmitted.
- the transmission pulse signal is created so that the ratio of “0” and “1” is always constant, and visible light transmission is performed so that the illuminance of visible light is always constant regardless of the transmission data, and the exhibition is illuminated. I try not to feel uncomfortable.
- the user operates the camera 10 of the mobile terminal 1 to turn on the shutter and shoots visible light that illuminates the exhibit (step 100).
- the imaging device 11 of the camera 10 receives visible light transmitted by visible light, and the pixels 21 in each row are based on signals from the shutter signal line 30 for each row of pixels 21 as shown in FIG. Charges are accumulated at the same timing.
- the pixels 21 in each row accumulate charges at a timing shifted in order for each row.
- pixel signals based on the charges are sequentially output from the pixels 21 in the row in which the charges are accumulated, and are amplified by the pixel amplifier 22. Pixel signals are sequentially output from the pixels 21.
- the imaging device 11 first passes through the vertical signal line 25 and the horizontal signal line 26 in order from the leftmost pixel 21 in the uppermost row.
- the signal from the pixel 21 is captured.
- signals are taken in from the leftmost pixel 21 to the rightmost pixel 21 in the second row, and similarly, signals are sequentially read from the pixels 21 in the third row and the fourth row.
- a signal is output from the rightmost pixel 21 in the lowermost row.
- the image sensor 11 operates so that signals based on accumulated charges are sequentially output through the pixel amplifier 22 and captured at the exposure timing for each row in each pixel 21.
- the uppermost pixel selection switch 23 connected to the leftmost vertical signal line 25 in FIG. 2 is turned on, and the leftmost column selection switch 24 connected to the horizontal signal line 26 is turned on.
- the signal of the pixel 21 located at the left end of the uppermost stage is output.
- the uppermost pixel selection switch 23 connected to the second vertical signal line 25 from the left end of the same row is turned on, and the second column selection switch 24 connected from the left end connected to the horizontal signal line 26 is turned on.
- the pixel signal of the pixel 21 located in the second row from the left of the uppermost row in FIG. 2 is output.
- the image pickup device 11 controls the pixel selection switch 23 and the column selection switch 24 to be turned on / off, and first, for all the pixels 21 in the uppermost row, signals are sequentially output from all the pixels 21 from the left end to the right end. Thereafter, similarly, for the pixels 21 in the second row from the top, signals based on the accumulated charges are output through the vertical signal line 25 and the horizontal signal line 26, and these signals are sequentially supplied from the left end to the right end pixel. A pixel signal is output. Thereafter, similarly, for the pixels 21 in the third row and the fourth row, the signals of the respective pixels 21 are output and taken in through the vertical signal line 25 and the horizontal signal line 26, and the image pickup device 11 finally has the right end. A signal is output from the pixel 21 in the lowermost row through the vertical signal line 25.
- the pixel signal based on the exposed and accumulated charge is amplified by the pixel amplifier 22 and passes through the vertical signal line 25 and the horizontal signal line 26 as shown in FIG. Are output in order from all the pixels 21 and in the order of arrangement of each row.
- the pixel signal including the transmission data has a stripe pattern (horizontal stripe pattern as shown in FIG. 6) based on light and dark along the row direction. That is, when the captured visible light includes a pulse signal of the visible light transmission signal, the image captured by the image sensor 11 is arranged along the row direction according to the change in the exposure amount of each pixel 21. Striped pattern appears.
- the pixel signal including such a striped pattern output from each pixel 21 of the image sensor 11 is converted into a digital signal by the AD converter 18 and sent to the image processing LSI 19.
- the image processing LSI 19 takes in an image signal for one frame and performs image processing for extracting luminance information contained therein (step 110).
- the frequency of the transmission pulse signal is 5 KHz, for example, a 5 Kbps transmission pulse signal is superimposed on the visible light and irradiated from the projector of the visible light transmitter.
- the time for one sample of the transmission pulse signal is about 0.5 milliseconds, and the brightness change of the visible light including this transmission pulse signal is generated in the captured image of the image sensor 11 as a striped pattern.
- the striped pattern is generated in the row direction of the image sensor 11 as shown in FIG.
- the image processing LSI 19 When the image processing LSI 19 takes in a digital image signal including color information and luminance information, the image processing LSI 19 extracts only the luminance information and converts it into, for example, grayscale data of 0 to 255 gradations, and converts the luminance component of the signal, that is, the stripe pattern component. The extracted data is sent to the microprocessor 48 (step 120). Note that when the image sensor 11 is not for color photography but for monochrome photography, gray scale conversion is not necessary.
- the microprocessor 48 calculates the average value of the luminance component in each row direction (step 130). As shown in the luminance average value graph of FIG. 7, the average value of the luminance component in each row direction is a portion where a striped pattern is generated, and varies greatly according to the horizontal axis (time axis) in each row direction.
- microprocessor 48 calculates a differential value from the difference between the averaged luminance data of each row, that is, the average value of the exposure amount signal of each row (step 140).
- the exposure period Tx and the transmission pulse signal of the pixels 12 in each row of the image sensor 11 are described in the upper stage, the graph of the exposure amount signal is described in the middle stage, and the waveform of the differential value is displayed in the lower stage. be written.
- visible light transmission signal visible light transmission signal
- the visible light is captured by the imaging element 11
- the exposure amount of the pixels 12 increases as the transmission pulse signal SP is included in the exposure period Tx of each row, and the captured image becomes brighter.
- the exposure period at the rising edge of the transmission pulse signal SP since the transmission pulse signal SP is in contact with the end of T0 and the exposure time in the transmission pulse signal SP gradually increases until the next exposure period T1, the exposure amount graph (exposure amount signal) from time t0 to time t1 is gradually increased. Since the exposure time in the transmission pulse signal SP does not change from the exposure period T1 to the exposure period T2, the exposure amount graph from time t1 to time t2 is constant. Furthermore, since the exposure time in the transmission pulse signal SP gradually decreases from the exposure period T2 to the exposure period T3, the exposure amount graph from the time t2 to the time t3 gradually decreases.
- the transmission pulse signal SP can be extracted from the exposure amount of the pixels 12 in each row of the image sensor 11. Become.
- the luminance data of each row that is, the average value of the exposure amount is differentiated with respect to time to calculate a differential value.
- the differential value of the exposure amount is the difference between the exposure amounts in the preceding and following exposure periods, and the graph of the differential value generates a positive pulse P1 in the period of the pulse width Tp of the transmission pulse signal as shown in the lower part of FIG. After that, a waveform in which a negative pulse P2 is generated is obtained during the exposure amount decrease period.
- the waveform of the differential value of the exposure amount indicates a pulse waveform corresponding to the pulse of the transmission pulse signal
- a threshold value is set at a predetermined level for the differential value, and the differential value data is binarized.
- the information of the transmission pulse signal corresponding to the positive pulse P1 is extracted (step 150).
- the waveform of the differential value of the exposure amount is a positive waveform generated at the timing of the previous transmission pulse.
- the negative pulse P2 corresponding to the first pulse P1 and the positive pulse P3 generated at the timing of the next transmission pulse are generated simultaneously.
- the pulse P3 of the differential waveform is canceled and the transmission pulse signal cannot be accurately detected.
- the pulse width of the visible light transmission signal is shorter than the exposure time at the time of imaging, and the pulse interval Tp and the exposure time Tx of the visible light transmission signal may be set differently.
- the microprocessor 48 extracts the transmitted OOK signal (on-off keying modulation signal) from the binarized data binarized as described above (step 160). Since this OOK signal encodes the original transmission data so as to suppress the flicker of visible light that becomes illumination light at the time of visible light transmission, the original transmission data is extracted according to the encoding, and the OOK signal Is demodulated (step 170).
- the microprocessor 48 performs a process of reproducing or displaying the data.
- the information signal transmitted by visible light is unique ID information of the visible light transmitter
- content information (voice guidance or the like) corresponding to the ID information is read from the storage unit 50 and reproduced through the speaker 52 or the display 57. To display.
- the visible light transmitted by the visible light is photographed by the image sensor 11, the striped pattern image data obtained from the image signal is captured in units of frames, and sequentially output based on the displacement of the exposure amount of each row of pixels. Since the differential value is calculated and the visible light transmission signal is demodulated based on the differential value, the difference between the image data before and after the stripe pattern generated for each pixel is calculated. For this reason, the pulse information of the visible light transmission signal can be accurately demodulated based on the striped pattern image data.
- the transmission speed of the transmission signal (the width of the striped pattern) is not limited by the upper limit of the shutter speed as in the conventional method.
- the visible light transmission signal transmitted at a much higher speed can be received only by photographing with a general-purpose digital camera, and the received visible light transmission signal can be demodulated at a high speed.
- an image is captured by the pixel amplifier sequential output type imaging element 11, and a striped pattern corresponding to the information signal is generated in the row direction or the column direction in the captured image.
- the information signal is captured in the captured image.
- the striped pattern included in the captured image includes an information signal that changes with the time axis (change in brightness of the luminance of visible light transmitted), and the information signal transmitted by visible light communication in the state of occurrence of the striped pattern Is included.
- the information signal of visible light communication can be easily received using the general-purpose portable terminal 1. Furthermore, since the image data of each row of one frame can be extracted as a plurality of samples of the information signal by a single process, transmission data can be received at a higher speed than conventional.
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Abstract
Description
該可視光送信信号は送信する情報信号に基づき変調されて可視光に重畳され、
前記カメラが、画素アンプ順次出力式撮像素子を用いて撮影し、該画素アンプ順次出力式撮像素子が、各画素で発生する電荷を各々の画素アンプで増幅して該各画素アンプから順に撮像信号を出力し、該撮像信号から得られる縞模様の画像データをフレーム単位で取り込み、順に出力された画素の各行または各画素の露光量の差分に基づき微分値を算出し、1フレーム内で各行または各画素を1サンプルとする複数サンプルの撮像信号の微分値に基づき、信号を復調することを特徴とする。
10 カメラ
11 撮像素子
12 光拡散フィルター
13 レンズ
14 アイリス
16 行走査デバイス
17 列走査デバイス
18 ADコンバータ
21 画素
22 画素アンプ
23 画素選択スイッチ
24 列選択スイッチ
25 垂直信号線
26 水平信号線
27 第2アンプ
28 切替スイッチ
30 シャッター信号線
31 画素選択スイッチ
32 行選択スイッチ
46 オーディオ回路
48 マイクロプロセッサ
50 記憶部
51 マイク
52 スピーカー
53 周辺インターフェイス
54 RF回路
56 ディスプレイコントローラ
57 ディスプレイ
Claims (4)
- 可視光通信用に照射される可視光を、撮像素子を有するカメラにより撮影し、該カメラが撮影した該撮像素子の画像データに基づき、該可視光に重畳して送信された可視光送信信号を受信する可視光受信方法において、
該可視光送信信号は送信する情報信号に基づき変調されて可視光に重畳され、
前記カメラが、画素アンプ順次出力式撮像素子を用いて撮影し、該画素アンプ順次出力式撮像素子が、各画素で発生する電荷を各々の画素アンプで増幅して該各画素アンプから順に撮像信号を出力し、該撮像信号から得られる縞模様の画像データをフレーム単位で取り込み、順に出力された画素の各行または各画素の露光量の差分に基づき微分値を算出し、1フレーム内で各行または各画素を1サンプルとする複数サンプルの撮像信号の該微分値に基づき、信号を復調することを特徴とする可視光受信方法。 - 前記可視光送信信号は送信する情報信号に基づきオンオフ変調されて可視光に重畳され、前記微分値は前記縞模様を示す画素の各行の露光量を微分して算出され、該微分値に対し所定の閾値を設定し、該閾値に基づき該微分値データを二値化して可視光送信信号を復調することを特徴とする請求項1記載の可視光受信方法。
- 前記可視光送信信号のパルス幅は、前記画素の各行の露光期間より短く、且つ該可視光送信信号のパルス間隔が該露光期間とは相違して設定されることを特徴とする請求項1の可視光受信方法。
- 前記露光期間は前記可視光送信信号のパルス間隔より長く設定されることを特徴とする請求項3の可視光受信方法。
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US15/119,573 US9929807B2 (en) | 2014-03-14 | 2015-03-10 | Visible light receiving method |
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IT201900021309A1 (it) * | 2019-11-18 | 2021-05-18 | Lantincendio S R L | Dispositivo gateway innovativo biocompatibile e relativo metodo per la trasmissione dati |
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