CN111835419B - Data secret transmission method for visible light communication of CMOS camera - Google Patents
Data secret transmission method for visible light communication of CMOS camera Download PDFInfo
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- CN111835419B CN111835419B CN202010677055.1A CN202010677055A CN111835419B CN 111835419 B CN111835419 B CN 111835419B CN 202010677055 A CN202010677055 A CN 202010677055A CN 111835419 B CN111835419 B CN 111835419B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
- H04B10/114—Indoor or close-range type systems
- H04B10/116—Visible light communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K1/00—Secret communication
- H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/73—Circuitry for compensating brightness variation in the scene by influencing the exposure time
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Abstract
A data security transmission method for visible light communication of a CMOS camera comprises the following steps: when data is sent, the original data code and the error code are coded at intervals; when receiving data, adjusting the shutter time of the CMOS camera according to the interval error code length, so that the CMOS camera performs light integration of corresponding time length during imaging, shooting to obtain a light and dark stripe image, and extracting original data information from the light and dark stripes of the image through an image processing technology; if the shutter time is incorrect during shooting, the light and dark stripes in the obtained image are different from the original data, and the original data cannot be obtained under the condition that the interval error code characteristic information is unknown. By the method, correct original data can be received only under the condition of the known encryption rule, otherwise, the original data cannot be obtained. The method is simple and effective, and the safety and the integrity of data transmission are ensured.
Description
Technical Field
The invention belongs to the field of visible light communication, and relates to a data secret transmission method for visible light communication of a CMOS camera.
Background
Visible light communication is a short-distance high-speed wireless optical communication technology developed on the basis of LED technology. The basic principle of visible light communication is that by utilizing the characteristic that a Light Emitting Diode (LED) is faster than the switching speed of a fluorescent lamp and an incandescent lamp, communication is carried out through high-frequency flicker of an LED light source, a light represents 1, a non-light represents 0, a high-speed light signal is sent out, and information is obtained through photoelectric conversion. Compared with the traditional infrared and radio communication, the visible light communication system has the advantages of high transmitting power, no electromagnetic interference, no need of applying for spectrum resources and the like, and can be used for manufacturing an information transmission system. In the prior art, although it has been proposed that visible light communication can be applied to various information transmission systems, especially in a system in which a CMOS camera is used for receiving optical signals, all people can read signals through a mobile phone camera, how to encode the optical signals into a code that can be read only by people who know the rules of the coded optical signals becomes a problem that needs to be solved urgently.
Disclosure of Invention
The invention aims to solve the problem that the data transmission security and integrity of visible light communication in the prior art cannot be guaranteed, and provides a data security transmission method of CMOS camera visible light communication, which can receive correct original data information only under the condition of a known encryption rule, and otherwise can not extract effective data from the received information.
In order to achieve the purpose, the invention has the following technical scheme:
a data security transmission method for visible light communication of a CMOS camera comprises the following steps:
when data is sent, the original data code and the error code are coded at intervals;
when receiving data, adjusting the shutter time of the CMOS camera according to the interval error code length, so that the CMOS camera performs light integration of corresponding time length during imaging, shooting to obtain a light and dark stripe image, and extracting original data information from the light and dark stripes of the image through an image processing technology; if the shutter time is incorrect during shooting, the light and dark stripes in the obtained image are different from the original data, and the original data cannot be obtained under the condition that the interval error code characteristic information is unknown.
The interval coding is used for inserting error codes after or before each bit of level data in the level data coded by the original data;
the length of the error code is several bits.
When the data is sent, the coded data is modulated on the light intensity of the LED light source;
and when receiving data, shooting by adopting a CMOS camera with a rolling shutter to obtain a light and dark stripe image.
The CMOS camera shoots the LED light source or an object irradiated by the LED light source.
The shutter time of the CMOS camera is adjusted according to the interval error code length, after the interval length of the error code is known, the shutter time is adjusted to be (interval error code length +1) × original data clock period), the CMOS camera performs light integration in the adjusted shutter time, and light and dark stripes in the obtained image correspond to the high and low levels of the original data sequence one by one.
If the adopted shutter time is less than (interval error code length +1) multiplied by original data clock period', the light and dark stripes in the obtained image contain error code information, and original data cannot be directly obtained; if the adopted shutter time is longer than "(interval error code length +1) × original data clock period", the bright and dark stripes in the obtained image are the result of exposure after multi-bit interval error codes and multi-bit original data sequences are mixed together, and the original data cannot be obtained; thus, if the shutter time at the time of shooting is incorrect, the original data cannot be obtained.
Compared with the prior art, the invention has the following beneficial effects: when data is sent, the original data codes and error codes are subjected to interval coding, a method of inserting interval error codes is adopted to code data which needs to be transmitted through a CMOS camera visible light communication system, the shutter time of the CMOS camera is adjusted according to the length of the interval error codes, so that the CMOS camera performs light integration of corresponding time length during imaging, light and dark stripe images are obtained through shooting, original data information is extracted from the light and dark stripes of the images through an image processing technology, correct original data can be received only under the condition of a known encryption rule, and otherwise, the original data cannot be obtained. The method is simple and effective, and the safety and the integrity of data transmission are ensured.
Drawings
FIG. 1 illustrates an embodiment of the present invention of raw data level waveforms;
FIG. 2 is a schematic diagram of a stripe image captured before encryption according to an embodiment of the present invention;
FIG. 3 illustrates a data level waveform after adding an alternate error code according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a fringe image captured with correct shutter time after encryption according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a fringe image captured with an incorrect shutter time after encryption according to an embodiment of the present invention;
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The principle of the invention for carrying out visible light communication based on the CMOS camera is as follows: the existing camera modules of the smart phone use CMOS photosensitive modules, and adopt rolling electronic shutters, the highest synchronous speed of most cameras (i.e. the time required by a mechanical shutter curtain to cross an imaging element) does not exceed 1/250s, and the shutters with the speed higher than this time are not actually fully opened, at this time, if the time difference of the movement of the front and rear curtains is equal to the shutter time to be photographed, it can be ensured that the photosensitive element area swept by the gap left between the front and rear curtains is the desired exposure time, and the gap is scanned from top to bottom until the scanning of a frame of image is completed, therefore, if the LED status is bright when the first line is scanned, the line senses bright light and displays bright stripes in the image, and if the LED status is off when the second line is scanned, the line senses no light and displays dark stripes in the image, and so on until a whole image is scanned. When the blinking state of the LED is determined by the level of the data level, the bright and dark stripes in the captured image contain data information, and the data can be obtained by image processing.
The data security transmission method comprises the following steps: in a visible light communication system based on a CMOS camera, when data is sent, original data codes and error codes are subjected to interval coding, and simultaneously, at a receiving end, the shutter time of the CMOS camera is adjusted according to the length of the interval error codes, so that the CMOS camera performs light integration of corresponding time length during imaging, light and dark stripe images are obtained through shooting, and original data information is extracted from the light and dark stripes of the images through an image processing technology. If an image is taken with an incorrect shutter time, the correct data sequence cannot be obtained from the bright and dark stripes in the image.
The data transmission method of the present invention is further described below by specific embodiments: if the original data level clock frequency is 1ms and the sequence is 10110101, as shown in fig. 1, a picture of the stripes can be obtained by taking a picture with a CMOS camera, as shown in fig. 2. If a 1ms high error code is inserted after each bit of data, the sequence becomes 1101111101110111, as shown in fig. 3, 1 in the original data sequence corresponds to 11 in the error-coded data sequence, and 0 in the original data sequence corresponds to 01 in the error-coded data sequence. Setting the shutter time of the CMOS image sensor as follows: the (alternate error code length +1) × original data clock period is 1/500s, and light integration is performed within 1/500s to obtain a light and dark stripe image as shown in fig. 4. The bright stripes correspond to the sequence 11, the dark stripes correspond to 01, the bright stripes originally corresponding to the data 1 are changed into wider bright stripes due to being converted into the sequence 11, the black stripes originally corresponding to the data 0 are changed into the sequence 01 and are shown into gray stripes (dark stripes), and the original data information can be obtained by setting a reasonable threshold value through an image processing technology.
If an incorrect shutter time is adopted, for example, the shutter time is 1/1000s and is less than 1/500s, an image obtained after exposure is as shown in fig. 5, at this time, the stripe sequence obtained by the image processing is the same as the stripe sequence after the error code is inserted, and the information containing the error code sequence is obtained as 1101111101110111. At this time, if the receiving end does not know the specific characteristics (information such as the number of bits and the level of high or low) of the error code, the original data information cannot be restored from the information including the error code sequence.
If an incorrect shutter time is adopted, for example, the shutter time is 1/250s, which is more than 1/500s, at this time, the CMOS image sensor exposes every 4-bit data in the sequence after the error code is inserted in each light integration time, and a stripe is formed by exposing in the duration of 4-bit data, which cannot extract valid information, for example, the stripes formed after exposure of 0111, 1110, 1101, and 1011 have the same brightness and darkness, and are indistinguishable from an image, and the original data information cannot be obtained from the image.
In summary, if an image is captured with an incorrect shutter time, the correct original data sequence cannot be obtained from the light and dark stripes in the image.
The above-mentioned objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only specific examples of the present invention, and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A data security transmission method for visible light communication of a CMOS camera is characterized by comprising the following steps:
when data is sent, the original data code and the error code are coded at intervals;
when receiving data, adjusting the shutter time of the CMOS camera according to the interval error code length, so that the CMOS camera performs light integration of corresponding time length during imaging, shooting to obtain a light and dark stripe image, and extracting original data information from the light and dark stripes of the image through an image processing technology; if the shutter time is incorrect during shooting, the light and shade stripes in the obtained image are different from the original data, and the original data cannot be obtained under the condition that the interval error code characteristic information is unknown; the adjustment of the shutter time of the CMOS camera according to the interval error code length is that after the interval length of the error code is known, the adjustment of (interval error code length +1) × original data clock period) is carried out on the shutter time, the CMOS camera carries out light integration in the adjusted shutter time, and light and dark stripes in an obtained image correspond to high and low levels of an original data sequence one by one.
2. The data security transmission method for visible light communication of the CMOS camera according to claim 1, wherein: interval coding is carried out on the level data after the original data coding, and error codes are inserted after or before each bit of level data;
the length of the error code is several bits.
3. The data security transmission method for visible light communication of the CMOS camera according to claim 1, wherein:
when data is sent, the coded data is modulated on the light intensity of the LED light source;
and when receiving data, shooting by adopting a CMOS camera with a rolling shutter to obtain a light and dark stripe image.
4. The data security transmission method for visible light communication of the CMOS camera according to claim 1 or 3, wherein: the CMOS camera shoots the LED light source or an object irradiated by the LED light source.
5. The data security transmission method for visible light communication of the CMOS camera according to claim 1, wherein: if the adopted shutter time is less than (interval error code length +1) multiplied by original data clock period', the light and dark stripes in the obtained image contain error code information, and original data cannot be directly obtained; if the adopted shutter time is longer than "(interval error code length +1) × original data clock period", the bright and dark stripes in the obtained image are the result of exposure after multi-bit interval error codes and multi-bit original data sequences are mixed together, and the original data cannot be obtained; thus, if the shutter time at the time of shooting is incorrect, the original data cannot be obtained.
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| CN105846898A (en) * | 2016-05-20 | 2016-08-10 | 中国人民解放军信息工程大学 | Visible light communication method, sending device, receiving device and system |
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| CN106972887A (en) * | 2012-05-24 | 2017-07-21 | 松下电器（美国）知识产权公司 | Information communicating method, information-communication device, program and recording medium |
| CN109586791A (en) * | 2018-12-21 | 2019-04-05 | 西北工业大学 | A kind of visible light communication method and device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107612617A (en) * | 2017-09-13 | 2018-01-19 | 华南理工大学 | A kind of visible light communication method and device based on universal CMOS camera |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106972887A (en) * | 2012-05-24 | 2017-07-21 | 松下电器（美国）知识产权公司 | Information communicating method, information-communication device, program and recording medium |
| CN104346544A (en) * | 2013-07-30 | 2015-02-11 | 联想(北京)有限公司 | Data processing method, data embedding device and data separating device |
| CN106471795A (en) * | 2014-05-12 | 2017-03-01 | 飞利浦灯具控股公司 | Checking using the image of the timestamp capture always being decoded from the illumination of modulated light source |
| CN105846898A (en) * | 2016-05-20 | 2016-08-10 | 中国人民解放军信息工程大学 | Visible light communication method, sending device, receiving device and system |
| CN109586791A (en) * | 2018-12-21 | 2019-04-05 | 西北工业大学 | A kind of visible light communication method and device |
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