CN107831470B - Visible light positioning method based on polarization and hardware system thereof - Google Patents
Visible light positioning method based on polarization and hardware system thereof Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/16—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using electromagnetic waves other than radio waves
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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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The invention discloses a visible light positioning method based on polarization and a hardware system thereof. The first polaroid at the transmitting end converts unpolarized light emitted by the lamp into polarized light, binary Color Shift Keying (BCSK) modulation is carried out on the polarized light through the liquid crystal layer, and the polarized light emitted by the liquid crystal layer is dispersed into polarized light with different colors through the chromatic dispersion device. At the receiving end, the light beam passes through the second polaroid and only passes through one beam of polarized light, and polarized light in the other directions is filtered, so that the polarization change of the light beam is converted into brightness change to be accurately captured by the image equipment; and a camera-based receiving angle (AOA) positioning algorithm is combined to realize higher-precision positioning. The invention can reduce the system calculation difficulty, improve the accuracy of visible light positioning, and is suitable for electronic mobile terminal equipment such as smart phones, tablet computers, *** glasses and the like.
Description
Technical Field
The invention relates to the technical field of visible light communication, in particular to a visible light positioning method based on polarization and a hardware system thereof.
Background
The visible light communication is a technology which can build a wireless communication network by adding a data transmission function on basic public lighting facilities, and compared with the traditional wireless communication technology, the visible light communication technology has the advantages of rich bandwidth resources, no electromagnetic interference, lighting and positioning and the like.
Due to the influence of multipath effect and path loss, the conventional GPS navigation positioning can not meet the requirements of people on positioning accuracy. Therefore, a series of indoor positioning systems based on bluetooth, WIFI, ultrasound and infrared are presented, but none of these positioning systems has been widely used due to problems of positioning accuracy and installation cost. The visible light communication positioning is a technology for improving indoor positioning precision, an indoor lighting lamp attaches a beacon node to a light source to be sent out, a receiving end receives an identification light signal to analyze identity identification information sent by the lamp, and positioning is completed by utilizing a corresponding positioning algorithm. The technology can finish indoor accurate positioning under the condition of not affecting indoor normal illumination, and meanwhile, a large amount of application of lamp illumination reduces the technical cost and facilitates the technical popularization.
In the existing visible light positioning system based on intensity modulation, the transmitting end needs to provide high-rate pulses to avoid adverse effects caused by strong flickering of light in consideration of the light intensity flickering effect caused by atmospheric turbulence, so that a receiving end of the system needs to be quite complex equipment to meet the detection and receiving of the high-rate pulses, the construction cost of the system is increased, and serious burden is brought to the realization of the system. Therefore, how to avoid the light intensity flicker effect, and to more accurately and inexpensively perform the visible light positioning is a technical problem to be solved in the present invention.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provide a visible light positioning method based on polarization and a hardware system thereof.
According to a disclosed embodiment, a first aspect of the present invention discloses a polarization-based visible light positioning method, which includes the following steps:
s1, an external light source generates polarized light beams with different colors and different polarization directions through a VLC transmitting end, wherein the VLC transmitting end comprises a first polaroid, a liquid crystal layer and a chromatic dispersion device, an ID of a positioning beacon is carried in the light beam, and the polarization state of the light beam is reserved in the light channel propagation process;
s2, detecting polarized light in a certain direction by a second polaroid, capturing an image by an image sensor, extracting information source data according to pixel intensity, demodulating a detected beacon through binary decoding to obtain a positioning beacon ID, and obtaining indoor position coordinates of a beacon node by inquiring a beacon database;
s3, combining the indoor position coordinates of the obtained beacon node with a receiving angle positioning algorithm to obtain the position [ Tx, ty, tz ] of the receiving end, thereby realizing the positioning of the receiving end.
Further, the step S1 includes the following steps:
s101, converting unpolarized light beams emitted by a light source into polarized light by the first polaroid;
s102, applying control voltage to the liquid crystal layer to carry out binary coded modulation of polarized light, inputting data to be transmitted into an FPGA (field programmable gate array) to be converted into the control voltage, directly connecting an output end of the FPGA with an electrode of the liquid crystal layer, and applying the control voltage to the liquid crystal layer to carry out polarized light modulation, wherein the polarized light modulation is represented by dark and bright state codes of 0 and 1;
s103, dispersing the passed polarized light into multiple polarized light beams by the disperser, wherein each polarized light beam has unique color and polarization direction, and the colors received by different coded information in any directions are obviously different.
Further, the step S2 includes the following steps:
s201, filtering polarized light in other directions by a second polaroid through one beam of polarized light in a certain direction, so as to obtain effective coding information;
s202, capturing a color image by an image sensor, directly detecting a related positioning beacon from the image, obtaining a positioning beacon ID through a binary decoding and demodulation process, and obtaining the space position coordinates of the positioning beacon by a positioning beacon ID index ID database.
Further, the positioning algorithm in the step S3 is a camera-based angle-of-arrival positioning algorithm, and the optimal scale factor K is searched by extracting the mutual distance relation of the beacons in the image i Matching the true mutual distances to obtain the true positions [ Tx, ty, tz ] of the receiving ends]The gradient of the optimization function is utilized in the calculation process to guide the search so as to reduce the search domain.
Further, the binary coded modulation adopts binary color shift keying modulation.
Further, the binary decoding demodulation adopts binary color shift keying demodulation.
According to a disclosed embodiment, a second aspect of the present invention discloses a hardware system of a polarization-based visible light positioning method, the hardware system comprising: a VLC transmitting end and a VLC receiving end,
the VLC transmitting end comprises a first polaroid, a liquid crystal layer and a chromatic dispersion device which are sequentially arranged in parallel, wherein the liquid crystal layer is connected with the FPGA output end; the first polaroid converts unpolarized light emitted by an external light source into polarized light; the liquid crystal layer carries out binary color shift keying modulation on polarized light through control voltage applied by the FPGA; the said disperser disperses the polarized light emitted by the liquid crystal layer into polarized light with different colors;
the VLC receiving end comprises a second polaroid, an image collector, an electronic signal processor and a liquid crystal display screen, wherein the second polaroid is arranged right in front of the image collector, the electronic signal processor and the liquid crystal display screen are sequentially connected, and the second polaroid only allows one beam of polarized light to pass through according to the polarization direction and filters out other beams of light and projects an optical image passing through the second polaroid to the surface of the image sensor; the image sensor is used for detecting the brightness change of the light beam, and generating an electric signal containing pixel data in the image in the irradiation pixel unit after the photoelectric effect occurs; the electronic signal processor is converted into a digital image signal through A/D conversion, then an imaging link is completed through digital signal processing, and the processed digital image signal is displayed through the liquid crystal display.
Further, the control end of the liquid crystal layer is controlled by the FPGA, data to be transmitted is input into the FPGA to be converted into control voltage, polarization light modulation is performed by applying the control voltage to the liquid crystal layer, and dark and bright state codes are represented by 0 and 1.
Further, the FPGA comprises a configurable logic module CLB and a programmable output-input module IOB, and is communicated through an internal bus.
Compared with the prior art, the invention has the following advantages and effects:
1. the invention avoids the complex equipment at the receiving end in the traditional visible light positioning method based on intensity modulation, avoids the problem of strong flickering of the lamplight, allows lower pulse rate, reduces the burden on the system hardware composition, and is suitable for small wearable equipment.
2. The invention provides that a chromatic dispersion device is added at the VLC (Visible Light Communication) transmitting end and Binary Color Shift Keying (BCSK) modulation is adopted, so that the change of signal-to-noise ratio (SNR) caused by continuous movement of the receiving end is effectively solved, and the communication reliability is stronger.
3. The invention adopts the self-adaptive sampling reduction algorithm and the clock of the operating system to process the problem of unbalanced sampling of the low-cost camera, obtains more accurate video frame time, reduces pixel sampling, and is suitable for the low-cost camera.
4. The invention adopts the receiving angle (AOA) positioning optimization algorithm based on the camera to convert the parameter optimization problem into the nonlinear least square problem, has high positioning precision and strong capability of processing data in real time, and is convenient for the system to be applied to small-sized equipment such as smart phones, wearable equipment and the like.
Drawings
FIG. 1 is a schematic diagram of a light source, VLC transmitting end and VLC receiving end provided by the invention;
FIG. 2 is a schematic diagram of a hardware system for implementing a polarization-based visible light localization method of the present invention;
FIG. 3 is a schematic diagram of a polarizer for generating and detecting polarized light in accordance with the present invention;
FIG. 4 is a schematic diagram of binary coded modulation of a liquid crystal layer according to the present invention;
FIG. 5 is a schematic diagram of the internal structure of an FPGA according to the present invention;
fig. 6 is a schematic diagram of Binary Color Shift Keying (BCSK) demodulation in accordance with the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Examples
Referring to fig. 1, the present invention is based on polarization modulation technology, and the light source generates polarized light beams with different colors and different polarization directions through the VLC transmitting end. The VLC transmitting end comprises three parts: a first polarizer (linear polarizer), a liquid crystal layer, and a disperser. The first polaroid at the transmitting end converts the unpolarized light emitted by the lamp into polarized light, the polarized light is subjected to Binary Color Shift Keying (BCSK) modulation through the liquid crystal layer, and the polarized light emitted by the liquid crystal layer is dispersed into polarized light with different colors through the chromatic dispersion device. At the receiving end, the polarization change of the light cannot be directly captured by the camera, the light beam passes through the second polaroid at first, and the rest light beams are filtered by only one beam of polarized light, and the polarization change of the light is converted into brightness change, so that the brightness change can be accurately captured by the image acquisition equipment.
Referring to fig. 2, the polarization-based visible light localization system PIXEL includes a VLC transmitting end, a VLC receiving end, and is based on an angle of reception (AOA) localization algorithm. The light source periodically sends a beacon ID to the VLC channel through the VLC transmitting end, the VLC receiving end captures images through the image sensor, information source data are extracted according to pixel intensity, the detected beacon obtains a positioning beacon ID through the BCSK demodulation module, and indoor position coordinates of the beacon node are obtained through inquiring the beacon database. And combining with a receiving angle (AOA) positioning algorithm to obtain the azimuth information of the receiving end, thereby realizing the positioning of the receiving end.
As shown in fig. 3, the first polarizer at the VLC transmitting end converts the unpolarized light beam emitted from the light source into polarized light, the polarization characteristics are maintained during the light propagation process, and the polarization of the light is not recognized by human eyes, which is visually identical to that of the normal light beam; the second polarizer at the receiving end is different from the first polarizer at the transmitting end in polarization direction, and the second polarizer at the receiving end can detect polarized light and filter the characteristics of interference polarized light beams by using the polarizers.
Wherein the intensity of the detected polarized light is based on Malus's law, and the intensity of the polarized light before passing through the polaroid is defined as I 0 The light intensity after passing through the polaroid is I θ There is the following relationship:
I θ ＝I 0 cos 2 θ (1)
wherein: θ is the azimuth angle in the polarization direction of the polarized light and the polarizer. If the polarized light is parallel to the polarization direction of the polaroid, namely θ=0°, the light beam passing through the polaroid is not weakened; if the polarized light is perpendicular to the polarization direction of the polarizer, i.e., θ=90°, the light beam will be completely blocked by the polarizer.
As shown in fig. 4, binary coded modulation of polarized light is performed by applying a control voltage to the liquid crystal layer. Specifically, when the applied voltage is zero, the polarized light passes through the liquid crystal layer to generate 90-degree azimuth twist, and the receiving-end polaroid can not detect the polarized light completely; as the applied voltage increases, the azimuthal distortion of the polarized light gradually decreases until the specific voltage no longer causes the directional distortion, at which time the second polarizer at the receiving end detects light of high brightness. The control end is controlled by the FPGA, data to be transmitted are input into the FPGA and converted into control voltage, the output end of the FPGA is directly connected with the electrode of the liquid crystal layer, polarization light modulation is carried out by applying the control voltage to the liquid crystal layer, and the dark and bright states are used for coding 0 and 1.
As shown in fig. 5, the FPGA includes three parts, namely a configurable logic module CLB, a programmable output-input module IOB and an internal bus, the logic of the FPGA is implemented by loading programming data into an internal static memory unit, then the encoded information is input into the FPGA, the value stored in the memory unit determines the logic function of the logic module, and the input-output module is used to apply control voltage to the liquid crystal layer to complete the two-level encoding of polarized light.
The disperser disperses one beam of polarized light passing through the disperser into a plurality of beams of polarized light, each beam of light has unique color and polarization direction, and the colors received by different coded information in any directions are obviously different.
The second polaroid at the receiving end only passes through one beam of light according to the polarization direction and filters polarized light in other directions, and the receiving camera only captures polarized light of one color, so that coding information is obtained. When the coding state changes, the color captured by the receiving end changes at the same time, and the image sensor is utilized to capture a color image.
The receiving end positioning firstly obtains the space position coordinates of the positioning beacon. The related positioning beacons can be directly detected from the image shot by the camera, and the VLC receiving end decodes the identification of the positioning beacons through a Binary Color Shift Keying (BCSK) demodulation process to obtain the ID of the positioning beacons; and obtaining the space position coordinates of the positioning beacons through an identification database indexed by the positioning beacon IDs. And combining an angle of arrival (AOA) positioning algorithm to obtain the azimuth of the receiving equipment.
As shown in fig. 6, 3-dimensional sampling points in Binary Color Shift Keying (BCSK) demodulation are projected into a 1-dimensional differential vector by a dimension reduction module, and the dimension reduction process requires that the sample distances of different coding states are kept unchanged. The video is downsampled by using the clock of the operating system to reduce pixel points so as to cope with uneven sampling of the camera, thereby reducing the calculation difficulty of the system and outputting a series of corresponding symbols. The demapping module determines '0' and '1' from the symbols through bit decisions, outputs a series of binary bit codes, and completes a Binary Color Shift Keying (BCSK) demodulation process.
Wherein, the implementation principle of the camera-based angle of arrival (AOA) positioning algorithm is as follows: firstly, the algorithm extracts the mutual distance relation of beacons in the image and searches the optimal proportion factor K i Matching the true mutual distance. Wherein K is i Indicating the magnification of beacon i in the image. Then according to the optimal scale factor K i And the true position of each beacon is obtained as the true position [ Tx, ty, tz ] of the receiving end]. Optimizing positioning accuracy requires enough search space, and PIXEL directs the search through the gradient of the optimization function to reduce the search domain. The optimization problem based on the AOA positioning algorithm can be regarded as a nonlinear least square problem. The algorithm avoids measuring the distance between the transmitting end and the receiving end, ensures simple system calculation and high running speed.
Based on the above principle introduction, the present embodiment discloses a visible light positioning method based on polarization, which specifically includes the following steps:
s1, an external light source generates polarized light beams with different colors and different polarization directions through a VLC transmitting end, and the VLC transmitting end comprises three parts: a first polarizer, a liquid crystal layer, and a disperser. The beam carries the ID of the locating beacon, and the polarization state of the beam is preserved during the propagation of the optical channel.
The light source is used as a carrier for information transmission, and the light beam is subjected to a series of operations to enable the light beam to bear required data information, so that the LED lamp, the fluorescent lamp and sunlight can meet the requirements.
The step S1 includes the steps of:
in step S101, the first polarizer at the VLC transmitting end converts the unpolarized light beam emitted by the light source into polarized light, and the polarized state of the light is not recognized by human eyes, which is visually identical to the normal light beam, so that the problem of flickering of light intensity is avoided.
And step S102, applying control voltage to the liquid crystal layer at the VLC transmitting end to carry out binary coded modulation of polarized light. The data to be transmitted is input into an FPGA and converted into control voltage, the output end of the FPGA is directly connected with the electrode of the liquid crystal layer, polarization light modulation is carried out by applying the control voltage to the liquid crystal layer, and the '0' and the '1' are coded by using dark and bright states.
Wherein binary coded modulation employs Binary Color Shift Keying (BCSK) modulation.
Step S103, a disperser at the VLC transmitting end disperses one beam of polarized light passing through the disperser into a plurality of beams of polarized light, each beam of light has unique color and polarization direction, and the colors received by different coded information in any directions are obviously different.
S2, detecting polarized light in a certain direction by a second polaroid at the VLC receiving end, capturing an image by an image sensor, extracting information source data according to pixel intensity, obtaining a positioning beacon ID by the detected beacon through a BCSK demodulation module, and obtaining indoor position coordinates of the beacon node by inquiring a beacon database.
The step S2 specifically includes the following steps:
s201, the second polaroid at the VLC receiving end only filters polarized light in other directions by one beam of polarized light in a certain direction, and the receiving end only receives useful coding information.
S202, the image sensor captures a color image, related positioning beacons can be directly detected from the image, IDs of the positioning beacons are obtained through a Binary Color Shift Keying (BCSK) demodulation process, and spatial position coordinates of the positioning beacons are obtained through a positioning beacon ID index ID database.
S3, combining the indoor position coordinates of the obtained beacon node with a receiving angle positioning algorithm to obtain the position [ Tx, ty, tz ] of the receiving end, thereby realizing the positioning of the receiving end.
The step S3 specifically includes the following steps:
the positioning algorithm is based on an angle of arrival (AOA) positioning algorithm of a camera, and the optimal scaling factor K is searched by extracting the mutual distance relation of beacons in the image i Matching the true mutual distances to obtain the true positions [ Tx, ty, tz ] of the receiving ends]. In the calculation process, the gradient of the optimization function is utilized to guide the search, so that the search domain is reduced, and the calculation difficulty is simplified.
Based on the above principle and the introduction of the positioning method, the embodiment also discloses a hardware system of the visible light positioning method based on polarization, which specifically comprises: a VLC transmitting end, a VLC receiving end,
the VLC transmitting end comprises a first polaroid, a liquid crystal layer and a chromatic dispersion device which are sequentially arranged in parallel, wherein the liquid crystal layer is connected with the FPGA output end;
the first polaroid converts unpolarized light emitted by the lamp into polarized light; the liquid crystal layer carries out Binary Color Shift Keying (BCSK) modulation on polarized light through control voltage applied by the FPGA; the disperser disperses polarized light emitted by the liquid crystal layer into polarized light of different colors.
The VLC receiving end comprises a second polaroid, an image collector, an electronic signal processor and a liquid crystal display screen, wherein the second polaroid is arranged in front of the image collector, and the image collector, the electronic signal processor and the liquid crystal display screen are sequentially connected.
The optical image passing through the second polaroid is projected onto the surface of the image sensor, a photoelectric effect is generated, a corresponding electric signal is generated in the irradiation pixel unit, the electric signal is transmitted to the electronic signal processor and converted into a digital image signal through A/D conversion, an imaging link is completed through digital signal processing, and the processed digital image signal is displayed through the liquid crystal display.
At the receiving end, the polarized light beam passes through the second polaroid at the receiving end, and then the rest light beams are filtered by only one beam of polarized light, and the polarization change of the polarized light beam is converted into brightness change; the image collector accurately captures the color image and obtains the information of the positioning beacon. The light source periodically sends a beacon ID to the VLC channel through the transmitting end, the receiving end captures images by using the image sensor, information source data are extracted according to pixel intensity, the detected beacon obtains a positioning beacon ID through the BCSK demodulation module, and indoor position coordinates of the beacon node are obtained by inquiring the beacon database. And then combining a receiving angle (AOA) positioning algorithm based on a camera to obtain the azimuth information of the receiving end, thereby realizing the positioning of the receiving end.
The VLC transmitting end applies control voltage to the liquid crystal layer through the FPGA so as to complete binary coded modulation of polarized light. The FPGA comprises a configurable logic module CLB, a programmable output input module IOB and an internal bus, the logic of the FPGA is realized by loading programming data into an internal static storage unit, then coding information is input into the FPGA, the value stored in the storage unit determines the logic function of the logic module, and the input/output module is used for applying control voltage to a liquid crystal layer so as to complete the two-level coding of polarized light.
In summary, in the positioning of the receiving end in the present invention, an angle of arrival (AOA) positioning algorithm based on a camera is used, and the relationship of the mutual distances between beacons is distorted in the image according to the position of the image collector by using the optical imaging characteristics. Firstly, the positioning method extracts the mutual distance relation of beacons in the image, and searches the optimal proportion factor to match the real mutual distance; and then, positioning the receiving end according to the optimal scale factors and the real position of each beacon. The invention can reduce the system calculation difficulty, improve the accuracy of visible light positioning, and is suitable for electronic mobile terminal equipment such as smart phones, tablet computers, *** glasses and the like.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (8)
1. The visible light positioning method based on polarization is characterized by comprising the following steps of:
s1, an external light source generates polarized light beams with different colors and different polarization directions through a VLC transmitting end, wherein the VLC transmitting end comprises a first polaroid, a liquid crystal layer and a chromatic dispersion device, an ID of a positioning beacon is carried in the light beam, and the polarization state of the light beam is reserved in the light channel propagation process;
step S1 comprises the steps of:
s101, converting unpolarized light beams emitted by a light source into polarized light by the first polaroid;
s102, applying control voltage to the liquid crystal layer to carry out binary coded modulation of polarized light, inputting data to be transmitted into an FPGA (field programmable gate array) to be converted into the control voltage, directly connecting an output end of the FPGA with an electrode of the liquid crystal layer, and applying the control voltage to the liquid crystal layer to carry out polarized light modulation, wherein the polarized light modulation is represented by dark and bright state codes of 0 and 1;
s103, dispersing one beam of polarized light passing through the disperser into a plurality of beams of polarized light, wherein each beam of light has unique color and polarization direction, and the colors received by different coded information in any directions are obviously different;
s2, detecting polarized light in a certain direction by a second polaroid, capturing an image by an image sensor, extracting information source data according to pixel intensity, demodulating a detected beacon through binary decoding to obtain a positioning beacon ID, and obtaining indoor position coordinates of a beacon node by inquiring a beacon database;
s3, combining the indoor position coordinates of the obtained beacon node with a receiving angle positioning algorithm to obtain the position [ Tx, ty, tz ] of the receiving end, thereby realizing the positioning of the receiving end.
2. The method for positioning visible light based on polarization according to claim 1, wherein said step S2 comprises the steps of:
s201, filtering polarized light in other directions by a second polaroid through one beam of polarized light in a certain direction, so as to obtain effective coding information;
s202, capturing a color image by an image sensor, directly detecting a related positioning beacon from the image, obtaining a positioning beacon ID through a binary decoding and demodulation process, and obtaining the space position coordinates of the positioning beacon by a positioning beacon ID index ID database.
3. The method for positioning visible light based on polarization as claimed in claim 1, wherein the positioning algorithm in step S3 is a camera-based angle-of-arrival positioning algorithm, and the optimal scale factor K is searched by extracting the mutual distance relation of beacons in the image i Matching the true mutual distances to obtain the true positions [ Tx, ty, tz ] of the receiving ends]The gradient of the optimization function is utilized in the calculation process to guide the search so as to reduce the search domain.
4. The polarization-based visible light localization method of claim 1, wherein the binary coded modulation is binary color shift keying modulation.
5. The polarization-based visible light localization method of claim 2, wherein the binary coded demodulation employs binary color shift keying demodulation.
6. A hardware system for a polarization-based visible light localization method according to any one of claims 1 to 5, wherein the hardware system comprises: a VLC transmitting end and a VLC receiving end,
the VLC transmitting end comprises a first polaroid, a liquid crystal layer and a chromatic dispersion device which are sequentially arranged in parallel, wherein the liquid crystal layer is connected with the FPGA output end; the first polaroid converts unpolarized light emitted by an external light source into polarized light; the liquid crystal layer carries out binary color shift keying modulation on polarized light through control voltage applied by the FPGA; the said disperser disperses the polarized light emitted by the liquid crystal layer into polarized light with different colors;
the VLC receiving end comprises a second polaroid, an image collector, an electronic signal processor and a liquid crystal display screen, wherein the second polaroid is arranged right in front of the image collector, the electronic signal processor and the liquid crystal display screen are sequentially connected, and the second polaroid only allows one beam of polarized light to pass through according to the polarization direction and filters out other beams of light and projects an optical image passing through the second polaroid to the surface of the image sensor; the image sensor is used for detecting the brightness change of the light beam, and generating an electric signal containing pixel data in the image in the irradiation pixel unit after the photoelectric effect occurs; the electronic signal processor is converted into a digital image signal through A/D conversion, then an imaging link is completed through digital signal processing, and the processed digital image signal is displayed through the liquid crystal display.
7. The hardware system of the polarization-based visible light positioning method according to claim 6, wherein the control end of the liquid crystal layer is controlled by the FPGA, data to be transmitted is input into the FPGA to be converted into control voltages, polarization light modulation is performed by applying the control voltages to the liquid crystal layer, and the control voltages are represented by dark and bright state codes "0" and "1".
8. The hardware system of the polarization-based visible light localization method of claim 6, wherein the FPGA comprises a configurable logic module CLB and a programmable output input module IOB and is connected via an internal bus.
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| CN108572348A (en) * | 2018-06-06 | 2018-09-25 | 华南理工大学 | A kind of indoor visible light vision positioning method and its hardware system |
| CN109143169B (en) * | 2018-07-27 | 2020-12-01 | 清华大学 | Positioning device based on visible polarized light interference |
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