CN114189813A - Target positioning method and system based on visible light communication - Google Patents

Target positioning method and system based on visible light communication Download PDF

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Publication number
CN114189813A
CN114189813A CN202111444056.2A CN202111444056A CN114189813A CN 114189813 A CN114189813 A CN 114189813A CN 202111444056 A CN202111444056 A CN 202111444056A CN 114189813 A CN114189813 A CN 114189813A
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target
led
positioning
information
stripe
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Chinese (zh)
Inventor
杜笑笑
汪涛
朱义君
薛婧姝
王小景
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Information Engineering University of PLA Strategic Support Force
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Information Engineering University of PLA Strategic Support Force
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/02—Services making use of location information
    • H04W4/029—Location-based management or tracking services
    • 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
    • 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
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/502—LED transmitters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/70—SSIS architectures; Circuits associated therewith
    • H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H04W4/33—Services specially adapted for particular environments, situations or purposes for indoor environments, e.g. buildings

Abstract

The invention belongs to the technical field of visible light communication, and discloses a target positioning method and a target positioning system based on visible light communication, wherein the method comprises the following steps: arranging LEDs with coded information on the ceiling of a room, wherein a moving object carries a CMOS camera and moves perpendicular to the ceiling; acquiring a light and dark stripe image under a target motion state according to a rolling shutter exposure mode of a CMOS camera; decoding the information of the LED by using the stripe information of the stripe image to obtain the position of the LED; positioning a target by utilizing the relation between the gray value of the fringe image and the received light power; the positioning information of the target assists the light and dark stripe communication, and the error rate of stripe image decoding is reduced. The invention considers the target positioning conditions of different positions in the light spot of the same LED, fully utilizes the stripe information and the received light power information of the stripe image, and can realize the integration of communication and positioning without additional auxiliary equipment.

Description

Target positioning method and system based on visible light communication
Technical Field
The invention belongs to the technical field of visible light communication, and particularly relates to a target positioning method and system based on visible light communication.
Background
The target positioning technology based on visible light is divided into two types of imaging and non-imaging according to different receiving ends. The imaging positioning receiving end adopts an image sensor, such as a mobile phone camera, a camera and the like. The non-imaging positioning receiving end adopts PD, namely a photoelectric detector. The CMOS camera uses a rolling shutter exposure mode, and line-by-line scanning exposure is adopted when a sensor is exposed. The rolling shutter records the on/off state of the LEDs as light and dark stripes in the image. Positioning a target by a CMOS image sensor: for each row of pixels in the image, finding a first position and a last position of which the pixel values are not 0, and calculating the average value of the pixels in the middle of the two positions; setting a threshold value, judging that a representative signal of each line is 0 or 1 according to the relation between the calculated pixel average value and the threshold value, and converting an image into a string of digital sequences only containing 0 and 1; and finally, comparing the decoded digital sequence with a pre-coded LED to find the position of the target. However, this method can only determine that the target is located in the spot of a certain lamp, and the specific position in the spot cannot be determined. In addition, relying on streak decoding alone, the bit error rate is high.
The receiving end adopts visible light non-imaging positioning, the position of the receiver is estimated by measuring the intensity of a visible light signal sent by an LED through a PD, and the positioning method is a positioning algorithm based on a channel model, namely an RSS method. Commonly in the RSS method, the PD needs to capture the signal of at least 3 LEDs. For example, 2D positioning, 3 LEDs are used as beacons, and the coordinates of the LEDs are known. When the PD cannot capture enough LED signals due to the LED being blocked, the RSS method cannot be applied, which brings a huge test for the reliability of indoor positioning.
However, the current indoor target positioning technology based on visible light has many limitations in practical application. The method has the advantages that the visible light communication and the visible light positioning exist independently, and the current stripe decoding communication method based on the CMOS image sensor is high in error rate and cannot decode the specific position of a target in a light spot. Second, visible non-imaging positioning relies on the PD being able to receive enough LED signals for positioning.
Disclosure of Invention
Aiming at the problems that the existing indoor target positioning technology based on visible light has a plurality of limitations in practical application: the method comprises the following steps that firstly, visible light communication and visible light positioning exist independently, and in the conventional stripe decoding communication method based on the CMOS image sensor, the error rate is high, and the specific position of a target in a light spot cannot be decoded; secondly, visible light non-imaging positioning depends on that enough LED signals for positioning can be received by the PD; a target positioning method based on visible light communication is provided.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a target positioning method based on visible light communication on one hand, which comprises the following steps:
step 1: arranging LEDs with coded information on the ceiling of a room, wherein a moving object carries a CMOS camera and moves perpendicular to the ceiling;
step 2: acquiring a light and dark stripe image under a target motion state according to a rolling shutter exposure mode of a CMOS camera;
and step 3: decoding the information of the LED by using the stripe information of the stripe image to obtain the position of the LED;
and 4, step 4: positioning a target by utilizing the relation between the gray value of the fringe image and the received light power;
and 5: the positioning information of the target assists the light and dark stripe communication, and the error rate of stripe image decoding is reduced.
Further, the step 4 comprises:
under the condition of a single LED, the target is positioned according to the fringe images of the frames before and after the target is collected in a mobile manner and the received light power at two continuous moments.
Further, the received optical power is derived from a lambertian radiation model of the LED light source.
In another aspect, the present invention provides a target positioning system based on visible light communication, including:
the device arrangement module is used for arranging the LED with the coded information on the indoor ceiling, and the moving object carries the CMOS camera and moves vertical to the ceiling;
the acquisition module is used for acquiring a light and dark stripe image under a target motion state according to a rolling shutter exposure mode of the CMOS camera;
the LED position obtaining module is used for decoding the information of the LED by utilizing the stripe information of the stripe image to obtain the position of the LED;
the positioning module is used for positioning the target by utilizing the relation between the gray value of the fringe image and the received light power;
and the auxiliary communication module is used for assisting the light and dark stripe communication by the positioning information of the target and reducing the error rate of stripe image decoding.
Compared with the prior art, the invention has the following beneficial effects:
the invention utilizes the rolling shutter exposure mode of the CMOS camera to collect and decode the rolling shutter image of the target under the LED, locates the range of the target and records the gray value of the stripe image. And then, positioning the specific position of the target in the radiation range according to the relation between the gray value of the fringe image and the received light power by using a Lambert radiation model of the LED light source. And finally, reversely assisting to decode the stripe image by using the specific position of the target, and reducing the error rate of visible light communication.
The invention considers the target positioning conditions of different positions in the light spot of the same LED, fully utilizes the stripe information and the received light power information of the stripe image, and can realize the integration of communication and positioning without additional auxiliary equipment.
Drawings
Fig. 1 is a flowchart of a target positioning method based on visible light communication according to an embodiment of the present invention;
fig. 2 is a diagram illustrating the received optical power of the target under the lambertian model.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
as shown in fig. 1, a target positioning method based on visible light communication includes:
step 1: arranging an LED (light emitting diode) with coded information on a ceiling in a room, wherein a moving object carries a CMOS camera and moves vertical to the ceiling; specifically, the coded information refers to the beacon of the LED; the CMOS camera comprises a CMOS image sensor; the CMOS image sensor consists of a PD array;
step 2: acquiring a light and dark stripe image (namely a rolling shutter image) under a target motion state according to a rolling shutter exposure mode of a CMOS camera (particularly a CMOS image sensor);
and step 3: decoding the information of the LED by using the stripe information of the stripe image to obtain the position of the LED;
and 4, step 4: locating the object using a relationship between a gray value of the fringe image and a received optical power (of the PD); specifically, the gray value of the image formed by each pixel on the CMOS camera is converted according to the exposure amount of the corresponding PD, that is, the gray value and the exposure amount are in a numerical direct relationship, wherein the exposure amount is in direct proportion to the received optical power, so that the target can be positioned by using the relationship between the gray value of the fringe image and the received optical power;
and 5: the positioning information of the target assists the light and dark stripe communication, and the error rate of stripe image decoding is reduced.
Specifically, the CMOS image sensor maps temporally varying intensity signals from the beaconing LED at the transmitting end to spatially varying light and dark stripes of the captured image. The LED light source is used as a beacon sending end, and the on state (1) and the off state (0) are switched according to the value of the code word. The width of the bright and dark stripes corresponds to the duration of the bright and dark states of the LEDs and carries data information sent by the system. And decoding the beacon of the LED by using the width of the bright and dark stripes and the pixel resolution, simultaneously acquiring gray level images of the target at different positions, and calculating the gray level value of the image.
The radiation model according to the LED light source, i.e. the lambertian model, is shown in fig. 2.The optical power P received by the receiving end (PD)rCan be expressed as:
Figure BDA0003383485520000041
wherein, PtDenotes the emission power of the LED, phi is the light emission angle,
Figure BDA0003383485520000043
is the angle of incidence, m ═ ln2/ln (cos (Φ)1/2) Is the luminous order of the Lambert model, ΨcDenotes the maximum value of the incident angle of the PD receiving the visible light signal, phi is the angle of view of the PD1/2At the LED half-power angle, μ is the responsivity of the PD, d is the distance from the LED to the PD, ArIs the effective receiving area, T, of the PDs(psi) is the gain of the optical filter, gs(ψ) represents the condenser gain.
The CMOS image sensor is composed of an image sensing unit array, namely a PD array, wherein the distance between the arrays is small, the received optical power of each PD is basically equal, and the received optical power of the arrays can be regarded as the total number of the PDs multiplied by the received optical power of a single PD. In calculating the optical power here, the CMOS camera is regarded as a PD having a large receiving surface. Therefore, when there is only one LED and one CMOS camera, the received light power at two consecutive times is collected, and the position of the target is calculated according to the received light power ratio:
Figure BDA0003383485520000042
wherein, Pr,iRepresenting the received optical power, P, at the ith instant PDr,jRepresents the received optical power, phi, of the j-th instant PDiIndicates the light-emitting angle, phi, at the ith timejIndicating the light emission angle at the j-th time, diIndicates the distance, d, between the LED and the PD at the ith timejIndicating the distance from the LED to the PD at the jth instant.
The width of the fringes and the received optical power vary during the movement of the object. Therefore, the position of the LED can be decoded according to the stripe image, and the relation between the gray value of the stripe image and the received light power can be calculated. Therefore, visible light communication and positioning without knowledge of the LED position can be achieved only by rolling shutter images of the CMOS image sensor. Specifically, stripe images at continuous moments are collected, the beacon of the LED is decoded according to the width of the stripe, the position of the LED is determined, and the decoding error rate is high at the moment. And then, the specific position of the target in the light source radiation range is calculated by utilizing the relation between the image gray value and the received light power, and meanwhile, the decoding is assisted in a reverse mode, so that the error rate of communication is reduced. The two are in feedback relationship with each other.
On the basis of the above embodiment, the present invention further provides a target positioning system based on visible light communication, including:
the device arrangement module is used for arranging the LED with the coded information on the indoor ceiling, and the moving object carries the CMOS camera and moves vertical to the ceiling;
the acquisition module is used for acquiring a light and dark stripe image under a target motion state according to a rolling shutter exposure mode of the CMOS camera;
the LED position obtaining module is used for decoding the information of the LED by utilizing the stripe information of the stripe image to obtain the position of the LED;
the positioning module is used for positioning the target by utilizing the relation between the gray value of the fringe image and the received light power;
and the auxiliary communication module is used for assisting the light and dark stripe communication by the positioning information of the target and reducing the error rate of stripe image decoding.
In summary, the present invention utilizes the rolling shutter exposure mode of the CMOS camera to collect and decode the rolling shutter image of the target under the LED, locate the range of the target, and record the gray value of the stripe image. And then, positioning the specific position of the target in the radiation range according to the relation between the gray value of the fringe image and the received light power by using a Lambert radiation model of the LED light source. And finally, reversely assisting to decode the stripe image by using the specific position of the target, and reducing the error rate of visible light communication.
The invention considers the target positioning conditions of different positions in the light spot of the same LED, fully utilizes the stripe information and the received light power information of the stripe image, and can realize the integration of communication and positioning without additional auxiliary equipment.
The above shows only the preferred embodiments of the present invention, and it should be noted that it is obvious to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and these modifications and improvements should also be considered as the protection scope of the present invention.

Claims (4)

1. A target positioning method based on visible light communication is characterized by comprising the following steps:
step 1: arranging LEDs with coded information on the ceiling of a room, wherein a moving object carries a CMOS camera and moves perpendicular to the ceiling;
step 2: acquiring a light and dark stripe image under a target motion state according to a rolling shutter exposure mode of a CMOS camera;
and step 3: decoding the information of the LED by using the stripe information of the stripe image to obtain the position of the LED;
and 4, step 4: positioning a target by utilizing the relation between the gray value of the fringe image and the received light power;
and 5: the positioning information of the target assists the light and dark stripe communication, and the error rate of stripe image decoding is reduced.
2. The visible light communication-based target positioning method according to claim 1, wherein the step 4 comprises:
under the condition of a single LED, the target is positioned according to the fringe images of the frames before and after the target is collected in a mobile manner and the received light power at two continuous moments.
3. Target positioning method based on visible light communication according to claim 1 or 2, characterized in that the received light power is derived from a lambertian radiation model of the LED light source.
4. A target location system based on visible light communication, comprising:
the device arrangement module is used for arranging the LED with the coded information on the indoor ceiling, and the moving object carries the CMOS camera and moves vertical to the ceiling;
the acquisition module is used for acquiring a light and dark stripe image under a target motion state according to a rolling shutter exposure mode of the CMOS camera;
the LED position obtaining module is used for decoding the information of the LED by utilizing the stripe information of the stripe image to obtain the position of the LED;
the positioning module is used for positioning the target by utilizing the relation between the gray value of the fringe image and the received light power;
and the auxiliary communication module is used for assisting the light and dark stripe communication by the positioning information of the target and reducing the error rate of stripe image decoding.
CN202111444056.2A 2021-11-30 2021-11-30 Target positioning method and system based on visible light communication Pending CN114189813A (en)

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