CN111103579A - Visible light indoor positioning system and method based on mobile phone camera - Google Patents
Visible light indoor positioning system and method based on mobile phone camera Download PDFInfo
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Abstract
A visible light indoor positioning system and a positioning method based on a mobile phone camera comprise a sending end subsystem and a receiving end subsystem, wherein the sending end subsystem comprises a microcontroller, a serial port module, a cache circuit, an LED driving circuit and an LED light source which are sequentially connected, and the receiving end subsystem comprises a mobile phone with a camera and an indoor positioning module. The method comprises the steps of firstly coding position coordinate information to be transmitted through a microcontroller, caching a coded data stream, inputting the coded data stream into an input port of an LED driving circuit, controlling high-speed flicker of an LED light source, then photographing light emitted by the LED light source through a mobile phone to obtain a stripe image with light and shade change, generating a dynamic threshold through curve fitting after picture clustering to judge whether the information represented by the current brightness is '0' or '1', and decoding to obtain coordinate information. The invention has high reliability and stronger anti-interference capability.
Description
Technical Field
The invention belongs to the field of optical communication, and relates to a visible light indoor positioning system and a visible light indoor positioning method based on a mobile phone camera.
Background
Currently, the Global Positioning System (GPS) is the most widely used positioning system. However, because the GPS signal is blocked by the roof and walls of a building and the indoor multipath phenomenon is severe, the GPS signal is very weak or even disappears indoors, which causes the positioning accuracy of the GPS to be greatly reduced, usually the error reaches tens of meters, and it is difficult to meet the indoor positioning requirement of the user. In modern society, people mostly live indoors, such as large indoor spaces of large shopping malls, underground parking lots, libraries, museums and the like, so that a more effective and higher-precision indoor positioning system is more urgently needed.
In recent years, a new semiconductor lighting technology, typified by a Light Emitting Diode (LED), enjoying the designation "green lighting" has been developed very rapidly. The white light LED has the advantages of low power consumption, long service life, small size, environmental friendliness, better LED modulation performance and higher response sensitivity compared with the traditional illumination light source. The visible light communication technology utilizes the characteristics of the LED, and not only meets the illumination requirement, but also modulates the signal on the LED for data transmission. Visible light communication technology has also been developed to transmit identification information for positioning, which transmits identification information using a change in visible light (color, intensity, or position). This communication technique for transmitting identification information is based on a high frequency flashing light signal. Specifically, identification information to be transmitted is first encoded into a digital signal; the digital signal is then used to modulate the duration or frequency of the drive current or drive voltage of the light source, causing the light source to blink at a high frequency. The high frequency flicker signal may be detected by a photosensitive device, e.g. an image sensor. The image sensor may be exposed at different times based on a "rolling shutter" mechanism, i.e. different parts of the sensor, each row or column being exposed at different times. Based on this feature, when an image of a light source whose luminance changes rapidly is captured, an image sensor with a rolling shutter can acquire an image containing light or dark stripes. By measuring the width of the stripes, the frequency of the light source drive current and drive voltage can be calculated, and thus the transmitted identification information can be recovered. In the conventional visible light communication, a receiving end performs a receiving optical signal by using a Photo Detector (PD) of the receiving end, converts the received optical signal into an electrical signal, and performs information processing. Therefore, the visible light communication receiving device must have optical signal receiving and photoelectric conversion functions. Research shows that the mobile phone with the camera in the current market can just replace the receiving end containing the PD. Nowadays, smart phones stably occupy the mainstream market of mobile phones, 4G is completely popularized, the 5G era is coming, and the smart phones are about to completely unify the mobile phone market. And based on the characteristics that the smart phone has an open operating system, the running speed is high, the functions are complete, the design is humanized and the like, convenience is provided for the normal work of the camera.
Nowadays, a smart phone in the electronic product market is generally a CMOS camera, and the CMOS camera performs exposure in a rolling shutter mode, which is different from a global shutter mode (performing exposure on a whole frame at a time), but performs exposure on each row of pixels in sequence. Therefore, when receiving a high-frequency white light signal (the frequency is much higher than the frame rate of the CMOS image sensor) emitted by the LED lamp, the CMOS camera shoots a rolling curtain effect pattern with light and dark stripes distributed in a staggered manner. In the rolling curtain effect pattern, the gray value of the pixels in the middle column is selected for data reading, the pixels in the rows of the bright stripes are recorded as logic bytes '1', the pixels in the rows of the dark stripes are recorded as logic bytes '0', and the transmission of a plurality of logic bytes can be carried out in one frame, so that the short-distance visible light communication is realized.
Disclosure of Invention
The invention aims to solve the problem of inconvenient implementation of visible light communication in the prior art, and provides a visible light indoor positioning system and a visible light indoor positioning method based on a mobile phone camera.
In order to achieve the purpose, the invention has the following technical scheme:
a visible light indoor positioning system based on a mobile phone camera comprises a sending end subsystem and a receiving end subsystem, wherein the sending end subsystem comprises a microcontroller, a serial port module, a cache circuit, an LED driving circuit and an LED light source which are sequentially connected, and the receiving end subsystem comprises a mobile phone with a camera and an indoor positioning module; the transmitting end subsystem encodes the position information of the LED light source, modulates the position information on the light intensity of the light source and transmits a positioning signal to the indoor space; the receiving terminal subsystem obtains an image of an object under illumination through a camera of the mobile phone, decodes the image to obtain coordinate values, and obtains accurate position information by combining map data; the LED light source sends out a light positioning image containing a light positioning signal, the camera is a CMOS camera, the flickering light signal is imaged by utilizing the rolling shutter exposure characteristic of the CMOS camera to generate a stripe image with light and shade change, and then the stripe image is processed to detect the flickering frequency of the light source to realize the acquisition of information.
Preferably, in one embodiment of the visible light indoor positioning system based on the mobile phone camera, the LED light source is a white LED, the white LED modulates a signal into irradiation energy of light, and the LED driving circuit is a current driving circuit.
Preferably, in one embodiment of the visible light indoor positioning system based on the mobile phone camera, the indoor positioning module in the mobile phone comprises a map database importing module, an indoor object photographing processing module and a positioning result outputting module; the indoor object photographing processing module collects light positioning image information which is sent by an LED light source and contains light positioning signals, processes the collected image information, and determines distance information and position information by searching identification information in a predefined map database; and specific position information is obtained through a positioning result output module, and the ID number of the specific position information is marked on a map which is imported in advance.
Preferably, in an embodiment of the visible light indoor positioning system based on the mobile phone camera, the map database importing module determines the area of the location through an image processing algorithm before searching for the identification information, and searches for the identification information in a predefined map database by using data of the area to determine the distance information and the location information.
Preferably, in one embodiment of the visible light indoor positioning system based on the mobile phone camera, the LED driving circuit is built by using an NPN triode, and the LED driving circuit can make the forward voltage drop of the LED light source higher than the input direct current voltage drop, control the LED driving circuit, and make the current of the LED light source and the luminous flux keep a linear relationship.
Preferably, in an embodiment of the visible light indoor positioning system based on the mobile phone camera, the format of the image shot by the CMOS camera is YUV format, and the shooting mode is preview mode;
at a location, one or more images are acquired at one or more points in time from visible light signals emitted by the LED light sources, the level of which varies between high and low levels at varying frequencies at different points in time.
Preferably, in an embodiment of the visible light indoor positioning system based on the mobile phone camera, the identification information of the number of the light stripes or the number of the dark stripes obtained by the shooting by the CMOS camera includes data bits, the data bits include data corresponding to frequency changes, and each data bit corresponds to one of the number of the light stripes or the number of the dark stripes;
the identification information corresponding to the number of the variations of the light stripes or the dark stripes further includes one or more start bits for identifying the start positions of a group of data bits and one or more error correction bits for checking errors in the data bits.
The invention also provides a visible light indoor positioning method based on the mobile phone camera, which comprises the following steps:
the method comprises the steps of firstly encoding position coordinate information to be transmitted through a microcontroller, outputting the position coordinate information to the input end of a cache circuit through a serial port module, caching a coded data stream, then inputting the data stream into the input port of an LED driving circuit, controlling high-speed flicker of an LED light source, then photographing light emitted by the LED light source through a mobile phone with a camera and an indoor positioning module to obtain a light and shade change stripe image, clustering the images through a k-means algorithm, then judging whether the information represented by the current brightness is '0' or '1' by adopting curve fitting to generate a dynamic threshold, and finally decoding to obtain coordinate information.
Preferably, in an embodiment of the visible light indoor positioning method based on the mobile phone camera, the microcontroller converts the position coordinate information to be transmitted into binary information, and then converts the binary information into a segment of code through manchester coding, the coded information output by the microcontroller through the serial port module is TTL level, 0V voltage represents binary "0", 3.3V voltage represents binary "1", and the LED light source is used as a carrier to code the segment of position coordinate information to the mobile phone at the receiving end.
Preferably, in an embodiment of the visible light indoor positioning method based on the mobile phone camera, the LED flickering picture is obtained by the mobile phone camera, a light stripe in the LED flickering picture represents a binary "1", a dark stripe represents a binary "0", the coded information is identified by image processing, and coordinate information carried by the LED flickering picture is obtained after decoding; and sending the decoded coordinate information to a database, and obtaining a position map of the LED light source at the moment through comparison and query.
Compared with the prior art, the invention has the following beneficial effects: the circuit is used for driving the LED light source to enable the LED light source to carry certain position information, and the CMOS camera of the mobile phone is used as a terminal for receiving the information to receive the position information carried by the LED light source. The position information of the LED light source is converted into binary information, then the binary information is converted into a section of code through Manchester coding, the high-speed flicker of the LED light source is controlled, and the LED flicker picture is used as a carrier to transmit the section of position information code to a receiving terminal subsystem. The receiving terminal subsystem mainly depends on a mobile phone with a camera and an indoor positioning module to photograph the LED light source to obtain a light and dark stripe picture, the receiving terminal subsystem analyzes position information carried by the LED flickering picture through an image processing technology, and generally, human eyes are insensitive to flickering above 60Hz, so that in order to ensure the illumination quality of the LED light source, the flickering frequency is 1000Hz, and the flickering of the LED can not cause discomfort to the human eyes. When the subsystem with the receiving end is close to the LED illumination area, the coding information of the LED can be analyzed by using a portable mobile phone, and the corresponding position information is determined in the map database by using the obtained coding information, so that the positioning purpose is achieved. The LED driving circuit can enhance the definition of the light and shade stripe picture of the LED light source, and the image processing result is more accurate. The invention can acquire coordinate information by identifying the light reflected by the LED light source on the object without aligning the camera to the LED light source, and has stronger convenience and anti-interference performance.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the positioning system of the present invention;
FIG. 2 is a block diagram of a transmitting end subsystem according to the present invention;
FIG. 3 is a schematic diagram of a circuit configuration of an LED driving circuit according to the present invention;
FIG. 4 shows a light and dark stripe picture obtained by the receiving end subsystem of the present invention;
FIG. 5 is a block diagram of the receiving subsystem according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The visible light indoor positioning system based on the mobile phone camera comprises a sending end subsystem and a receiving end subsystem, wherein the sending end subsystem comprises a microcontroller, a serial port module, a cache circuit, an LED driving circuit and an LED light source which are sequentially connected, and the receiving end subsystem comprises a mobile phone with a camera and an indoor positioning APP. The sending end subsystem encodes the position information of the LED light source, modulates the position information on the light intensity of the light source and sends a positioning signal to the indoor space; the receiving end subsystem obtains an image of an object under illumination through a camera of the mobile phone, decodes the image to obtain coordinate values, and obtains accurate position information by combining map data. The LED light source emits a light positioning image containing a light positioning signal, the camera is a CMOS camera of the mobile phone, the flickering light signal is imaged by utilizing the exposure characteristic of a rolling shutter of the CMOS camera to generate a stripe image with light and shade change, and the stripe image is processed to detect the flickering frequency of the light source to realize the acquisition of information.
As shown in fig. 1, the microcontroller encodes the position coordinate information to be transmitted, the position coordinate information is output to the input end of the cache circuit through the serial port module, the encoded data stream is input to the input port of the LED driving circuit after being cached, so as to control the high-speed flash of the LED light source, then the light emitted by the LED light source is photographed through the mobile phone with the camera and the indoor positioning APP, light and dark stripe pictures are obtained, the light and dark stripe pictures are clustered through the k-means algorithm, then the information carried by the LED light source can be obtained by adopting curve fitting, and the positioning result can be obtained and displayed after decoding.
The key point of the invention is that the LED light source is driven by the circuit to carry certain position information, and the position information carried by the LED light source is received by using the mobile phone camera as a terminal for receiving information. The main principle is that the position information is converted into binary information, then the binary information is converted into a section of code through Manchester coding, the high-speed flicker of the LED light source is controlled, and the LED light source is used as a carrier to transmit the section of position information code to a receiving end. Referring to fig. 5, a receiving end subsystem mainly depends on a mobile phone with a camera and an indoor positioning APP to photograph light emitted by an LED light source to obtain a light and dark stripe picture, the receiving end analyzes position information carried by the LED light source through a certain image processing technology, and generally, human eyes are insensitive to flicker above 60Hz, so that in order to ensure the illumination quality of the LED, the flicker frequency is 1000Hz, and the flicker of the LED light source is ensured not to cause discomfort to human eyes. When a person carrying the receiving terminal subsystem approaches the LED illumination area, the coded information of the LED light source can be analyzed by using a mobile phone, and the corresponding position information is determined in the map database by using the obtained coded information, so that the positioning purpose is achieved.
The invention relates to a visible light indoor positioning method based on a mobile phone camera, which comprises the following specific steps:
the system working scene is an indoor space such as a supermarket, a museum and the like;
the LED light source of the indoor space carries specific position coordinate information;
the mobile phone with the camera can normally shoot indoor objects and can decode to obtain position information carried by the LED light source;
opening an indoor positioning App of the mobile phone, checking whether map data of a scene where the shooting is performed exist in map data existing in a map database importing module in the App, and if not, importing map information; after the map data is established, the mobile phone camera is aligned to an object to be shot or an LED light source by using the shooting function of the App indoor object shooting processing module, after a plurality of seconds, the mobile phone positioning result output module can display the specific position coordinate information and marks and displays the information on a corresponding map, and meanwhile, the positioning result can be exported and stored.
Firstly, the LED light source is driven to illuminate, the coordinates of the LED light source in a map are recorded, and the LED light source sends coordinate information at the frequency of 1000 Hz. In order to ensure the integrity of information transmission, the coordinate information is manchester encoded before being transmitted, and then the encoded information is transmitted to the input section of the LED driving port through the serial port, as shown in fig. 2.
The microcontroller is in a TTL level (voltage 0V represents binary '0', voltage 3.3V represents binary '1') through a serial port output coding information mode, in order to ensure that an LED can effectively bear the coding information, an NMOS tube is used for converting a voltage signal of the microcontroller into a current signal to control high-speed flicker of the LED, meanwhile, the driving current of the LED can be amplified, and the brightness of the LED meets requirements.
As shown in figure 3, a voltage signal coded by a microcontroller is input to an input end Ui of a buffer circuit through a serial port, an output Uo of the buffer circuit is connected to an input end of an LED drive circuit after being isolated, high-speed flicker of an LED is controlled, and because the input impedance of a common-collector-class amplification circuit is extremely high, when the serial port of the microcontroller is input to Ui1, almost all the voltage signal is added to Ui1, the output impedance of the common-collector-class amplification circuit is extremely low, and when the Uo is input to the input end Ui2 of the drive circuit of the LED, almost all the voltage signal is added to the input end Ui2 of the drive circuit, so that a buffer isolation effect is well played. Therefore, a coded signal output by the microcontroller is buffered and then is added to the LED driving circuit, an NMOS in the LED driving circuit converts a voltage signal into a current signal so as to drive an LED, and because the output frequency of the microcontroller is high, in order to accelerate the switching speed of an NMOS tube and improve the brightness of the LED, a fixed bias of about 0.9V is added to a grid electrode of the NMOS through resistors R4 and R6 in the circuit. The capacitor C1 plays a role in filtering a direct-current signal of the microcontroller, the capacitor C2 plays a role in filtering direct-current bias of the buffer circuit, the LED light source can twinkle in light and shade instead of twinkle in a very bright condition, and therefore the result obtained by image processing is more accurate. Secondly, the coordinate information carried by the LED light source is identified through a camera of the mobile phone. Adjusting the shutter time of the mobile phone camera to obtain the LED flashing picture, as shown in fig. 3, the light stripe in the LED flashing picture represents a binary "1", the dark stripe represents a binary "0", image processing is performed on fig. 3 to identify the encoded information carried in the picture, and the coordinate information carried by the LED can be obtained after decoding. The receiving end subsystem sends the decoded coordinate information to a database, and a position map of the LED light source at the moment can be obtained through comparison and query.
The technical scheme of the invention has the following outstanding characteristics:
1) and (4) coding mode of LED coordinate information.
2) The LED driving circuit is used for inserting the coded information of the coordinates into an LED technology, human eyes cannot sense the flicker of the LED, the voltage signal output by the serial port of the microprocessor is converted into current information by the NMOS tube to drive the LED to flicker, the common-collector circuit is used for buffering, light rays emitted by the LED light source can effectively carry the coded coordinate information, and the reliability is high. And the light and shade stripe picture obtained by driving the last receiving end of the LED light source by the NMOS tube is more obvious than the light and shade stripe picture obtained by driving the LED receiving end by the triode, and the image processing result is more accurate.
3) The invention relates to a technology for identifying coordinate information carried by an LED by utilizing a mobile phone camera, which utilizes a CMOS image sensor to receive an LED light signal, can obtain light and dark stripe pictures by adjusting shutter time of a rolling screen, adopts a k-means algorithm to cluster the pictures, then adopts curve fitting to generate a dynamic threshold to judge whether the information represented by the current brightness is '0' or '1', and finally decodes to obtain the coordinate information. The invention can acquire coordinate information by identifying the light reflected by the LED light source on the object without aligning the camera to the LED light source, and has better convenience and anti-interference performance.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical solution of the present invention, and it should be understood by those skilled in the art that the technical solution can be modified and replaced by a plurality of simple modifications and replacements without departing from the spirit and principle of the present invention, and the modifications and replacements also belong to the protection scope of the claims.
Claims (10)
1. The utility model provides a visible light indoor positioning system based on cell-phone camera which characterized in that: the system comprises a sending end subsystem and a receiving end subsystem, wherein the sending end subsystem comprises a microcontroller, a serial port module, a cache circuit, an LED driving circuit and an LED light source which are sequentially connected, and the receiving end subsystem comprises a mobile phone with a camera and an indoor positioning module; the transmitting end subsystem encodes the position information of the LED light source, modulates the position information on the light intensity of the light source and transmits a positioning signal to the indoor space; the receiving terminal subsystem obtains an image of an object under illumination through a camera of the mobile phone, decodes the image to obtain coordinate values, and obtains accurate position information by combining map data; the LED light source sends out a light positioning image containing a light positioning signal, the camera is a CMOS camera, the flickering light signal is imaged by utilizing the rolling shutter exposure characteristic of the CMOS camera to generate a stripe image with light and shade change, and then the stripe image is processed to detect the flickering frequency of the light source to realize the acquisition of information.
2. The visible light indoor positioning system based on the mobile phone camera of claim 1, wherein: the LED light source adopts a white light LED, the white light LED modulates a signal into irradiation energy of light, and the LED driving circuit is a current driving circuit.
3. The visible light indoor positioning system based on the mobile phone camera of claim 1, wherein: the indoor positioning module in the mobile phone comprises a map database import module, an indoor object photographing processing module and a positioning result output module; the indoor object photographing processing module collects light positioning image information which is sent by an LED light source and contains light positioning signals, processes the collected image information, and determines distance information and position information by searching identification information in a predefined map database; and specific position information is obtained through a positioning result output module, and the ID number of the specific position information is marked on a map which is imported in advance.
4. The visible light indoor positioning system based on the mobile phone camera of claim 3, wherein: the map database importing module determines a region of a position through an image processing algorithm before searching for identification information, and searches for the identification information in a predefined map database by using data of the region to determine distance information and position information.
5. The visible light indoor positioning system based on the mobile phone camera of claim 1, wherein: the LED driving circuit is built by adopting an NPN triode, the forward voltage drop of the LED light source can be higher than the input direct current voltage drop, the LED driving circuit can be controlled, and the current and the luminous flux of the LED light source keep a linear relation.
6. The visible light indoor positioning system based on the mobile phone camera of claim 1, wherein:
the format of the shot image of the CMOS camera is YUV format, and the shooting mode is preview mode;
at a location, one or more images are acquired at one or more points in time from visible light signals emitted by the LED light sources, the level of which varies between high and low levels at varying frequencies at different points in time.
7. The visible light indoor positioning system based on the mobile phone camera of claim 1, wherein: the identification information of the number of the light stripes or the dark stripes shot by the CMOS camera comprises data bits, the data bits comprise data corresponding to frequency change, and each data bit corresponds to one of the number of the light stripes or the number of the dark stripes;
the identification information corresponding to the number of the variations of the light stripes or the dark stripes further includes one or more start bits for identifying the start positions of a group of data bits and one or more error correction bits for checking errors in the data bits.
8. A visible light indoor positioning method based on a mobile phone camera is characterized by comprising the following steps:
the method comprises the steps of firstly encoding position coordinate information to be transmitted through a microcontroller, outputting the position coordinate information to the input end of a cache circuit through a serial port module, caching a coded data stream, then inputting the data stream into the input port of an LED driving circuit, controlling high-speed flicker of an LED light source, then photographing light emitted by the LED light source through a mobile phone with a camera and an indoor positioning module to obtain a light and shade change stripe image, clustering the images through a k-means algorithm, then judging whether the information represented by the current brightness is '0' or '1' by adopting curve fitting to generate a dynamic threshold, and finally decoding to obtain coordinate information.
9. The visible light indoor positioning method based on the mobile phone camera of claim 8, wherein: the microcontroller converts the position coordinate information to be transmitted into binary information, then the binary information is converted into a section of code through Manchester coding, the coded information output by the microcontroller through the serial port module is TTL level, 0V voltage represents binary '0', 3.3V voltage represents binary '1', and the LED light source is used as a carrier to transmit the section of position coordinate information code to the mobile phone at the receiving end.
10. The visible light indoor positioning method based on the mobile phone camera of claim 8, wherein: obtaining an LED flashing picture through a camera of the mobile phone, wherein a light stripe in the LED flashing picture represents a binary '1', a dark stripe in the LED flashing picture represents a binary '0', identifying coding information through image processing, and obtaining coordinate information carried by the LED flashing picture after decoding; and sending the decoded coordinate information to a database, and obtaining a position map of the LED light source at the moment through comparison and query.
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| CN111953417A (en) * | 2020-07-24 | 2020-11-17 | 西安理工大学 | Indoor visible light communication automatic alignment system and method |
| CN111953416A (en) * | 2020-07-24 | 2020-11-17 | 西安理工大学 | Automatic indoor visible light communication alignment system based on photoresistor |
| CN112087838A (en) * | 2020-08-17 | 2020-12-15 | 暨南大学 | Visible light dynamic label and implementation method thereof |
| CN112698339A (en) * | 2020-12-31 | 2021-04-23 | 中国人民解放军战略支援部队信息工程大学 | Target detection method, device and system |
| CN112738325A (en) * | 2020-12-25 | 2021-04-30 | 浙江工业大学 | Intelligent LED identification method based on Android mobile phone |
| CN114189813A (en) * | 2021-11-30 | 2022-03-15 | 中国人民解放军战略支援部队信息工程大学 | Target positioning method and system based on visible light communication |
| CN116232458A (en) * | 2022-12-06 | 2023-06-06 | 重庆邮电大学 | Visible light hybrid positioning and communication method and system for ensuring consistent positioning and communication |
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