Classifications

• • 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
  • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
  • H04B10/114—Indoor or close-range type systems
  • H04B10/1149—Arrangements for indoor wireless networking of information

Definitions

• the invention relates to the field of communication systems using modulated light signals of the Li-Fi signal type.
• Li-Fi technology for "Light Fidelity”
• Light Fidelity for "Light Fidelity”
• the Li-Fi technology is perfectly adapted to transmit and receive music, videos, internet data, measurement data (temperature, humidity, brightness, etc.), alarms (fire, presence of toxic vapors, intrusion). , etc.), to connect sensors or other types of devices in a network.5
• Designers of Li-Fi signal communication systems are of course seeking to reduce the cost of developing and integrating communication systems.
• the object of the invention is to reduce the cost of a communication system using modulated light signals of the Li-Fi signal type.
• a reception device for receiving a modulated light signal of the Li-Fi signal type, comprising a photodetector adapted to detect the modulated light signal and to transform it into an electrical signal, and a processing module connected to the photodetector and for acquiring the electrical signal to extract transmitted data.
• the photodetector has a semiconductor sensing surface and a converging lens for focusing the modulated light signal on the sensing surface.
• the use of the convergent lens makes it possible, for a given position of the receiving device with respect to a modulated light signal transmitter (such as a light-emitting diode lamp), to improve the ability of the reception device to detect radii. light emitted by the transmitter and thus to receive the modulated light signal. This improves the efficiency of communication within a modulated light signal communication system without multiplying the number of transmitters or receiving devices. This reduces the cost of the communication system.
• a modulated light signal transmitter such as a light-emitting diode lamp
• a receiving device similar to that just described having a plurality of lenses positioned side by side and each inclined with respect to the detection surface of a different inclination angle.
• angles of inclination differ two by two from one angle. between 10 ° and 15 °.
• a reception device similar to the one just described comprising a plurality of lenses positioned side by side in the same plane and substantially aligned, each lens having a slight offset of position in the plane with the one or more adjacent lenses.
• a display device comprising a reception device similar to those described above, and a display for displaying the received data.
• the display being a liquid crystal display, an electrophoretic display or an electrochromic display.
• the invention also relates to a communication system comprising a light-emitting diode lamp and a receiving device such as those just described, the light-emitting diode lamp being intended to emit a modulated light signal and the device receiving means being adapted to be positioned with respect to the LED lamp so as to receive said signal.
• FIG. 1 represents a part of a magazine in which an LED lamp, a first display apparatus and a second display apparatus are installed, the first display apparatus and the second display apparatus each comprising a receiving device of the invention;
• Figure 2a is a side view of the first display apparatus attached to an upper radius of a shelf
• FIG. 2b is a side view of the second display apparatus attached to a lower radius of the shelf;
• FIG. 3 is a simplified diagram of the receiving device of the invention.
• FIG. 4 shows four lenses and four semiconductor detection surfaces of the receiving device of the invention
• FIG. 5 is a detailed view of one of the lenses and the associated detection surface
• FIG. 6 shows the four lenses each inclined at a different angle with respect to the associated detection surface, as well as incident light rays coming from the LED lamp;
• FIG. 7 is a figure similar to FIG. 6, in which the angles of incidence of the incident light rays are different.
• the invention is here implementation in a price display application of products offered for sale in a store.
• An LED lamp 1 comprising a plurality of light-emitting diodes 2, is attached to the ceiling of a room of the store.
• the LED lamp 1 is of course used to illuminate the store room, but also to transmit, using the Li-Fi technology, display data to a first display device 3a and a second display device 3b.
• the display data enables the first display apparatus 3a and the second display apparatus 3b to display the price of a first product associated with the first display apparatus 3a and a second product associated with the second display apparatus. 3b display.
• the first display apparatus 3a is attached to an upper radius 4a of a shelf 5 of the magazine and the second display apparatus 3b is attached to a lower radius 4b of the shelf 5.
• the display data contains data on the price of the product, data relating to certain other characteristics of the product (eg size or weight or product name or brand), data identification and data on the position of the LED lamp 1.
• the price data and the data relating to certain other characteristics are intended to be displayed by the first display apparatus 3a and by the second display apparatus 3b.
• the identification data makes it possible to identify, from the first display apparatus 3a and the second display apparatus 3b, the display apparatus 3 of destination display data.
• the data relating to the position of the LED lamp 1 enable the first display apparatus 3a and the second display apparatus 3b to determine their position by geolocation (the geolocation method does not form part of the invention and will not be not described here).
• the first display apparatus 3a and the second display apparatus 3b each have a generally planar general shape.
• the first display apparatus 3a extends in a plane PI and the second display apparatus 3b extends in a plane P2.
• Each display apparatus 3 comprises an electrical card 7 on which are mounted an electrorectric display 8 and a reception device according to the invention 9.
• the receiving device 9 of each display apparatus 3 comprises a photodetector 11 and a processing module 12 comprising an amplification module 13, a first microcontroller 14, a second microcontroller 15 and a memory module 16.
• the LED lamp 1 transmits to the first display apparatus 3a and the second display apparatus 3b Li-Fi signals containing the display data.
• the Li-Fi signals here are light signals modulated according to a so-called PPM modulation (for "pulse-position modulation in English, or” modulation in position of pulses "in French).
• the photodetector 11 of the receiving device 9 of each display apparatus 3 receives the Li-Fi signals and transforms the Li-Fi signals into an analog electrical signal also modulated in PPM.
• the module amplifier 13 amplifies the analog electrical signal.
• the first microcontroller 14 acquires the analog electrical signal and digitizes it to obtain a digital signal.
• the first microcontroller 14 deletes from the digital signal the information related to the communication protocol used (for example, header data or cryptographic hash data) and generates a useful signal containing the display data.
• the first microcontroller 14 transmits the useful signal to the second microcontroller 15 via a UART output interface (for "Universal Asynchronous Receiver Transmitter" in English or "universal asynchronous transceiver” in French).
• the second microcontroller 15 decodes the wanted signal, extracts the display data from the useful signal, converts the price data and the data relating to certain other characteristics of the display data into a graphic signal compatible with the display 8 and transmits the display 8 the graphical signal via a serial interface type SPI (for "Serial Peripheral Interface" in English). If the display 8 is in a low power consumption operation mode, it sends a return signal to the first microcontroller 14 which goes to sleep.
• SPI Serial Peripheral Interface
• the memory module 16 makes it possible to store certain data among the display data as well as data specific to the operation of the display apparatus 3.
• the quality of the reception of the display data by the first display apparatus 3a and the second display apparatus 3b depends in particular on the position of the first display apparatus 3a and the second apparatus. display 3b with respect to the LED lamp 1.
• the quality of reception of the display data can be defined, for each display apparatus 3, by an error rate of reception of the Li-Fi signals emitted by the LED lamp 1 and which are intended for it, the receiving error must be less than a maximum receive error rate.
• the reception rate depends on the capacity of each LED device. 3 to receive the light rays emitted by the LED lamp 1. This capacity itself depends on the relative position of the display apparatus 3 with respect to the LED lamp 1, and in particular the orientation of the luminaires. display 3 with respect to the LED lamp 1.
• the first display apparatus 3a is fixed to the upper radius 4a of the shelf 5 while being oriented by a first orientation angle 9o formed between the plane PI of the first display apparatus 3a and an orthogonal plane P3 at the upper radius. 4a.
• the relative positions of the first display apparatus 3a and the ends of the LED lamp 1 define a first relative position angle 9ra.
• the second display apparatus 3b is attached to the lower radius 4b by being oriented by a second orientation angle 9ob formed between the plane P2 of the second display apparatus 3b and the plane P'3.
• the relative positions of the second display apparatus 3b and the ends of the LED lamp 1 define a second angle of relative position 9rb.
• the reception quality of the display data therefore depends in particular on the orientation angle ⁇ and the relative position angle ⁇ r of the display apparatus 3.
• the reception device 9 makes it possible to improve the reception quality of each display apparatus 3 by improving, for a given relative position of the display apparatus 3 with respect to the LED lamp 1, and therefore for an angle of orientation ⁇ given and a relative position angle 9r given, the ability of the display apparatus 3 to receive the light rays emitted by the LED lamp 1.
• the photodetector 11 of the reception device 9 comprises four convergent circular lenses 20a, 20b, 20c, 20d each associated with a semiconductor detection surface 21a, 21b, 21c, 21d (here it is noted that only a lens 20 and a semiconductor sensing surface 21 are shown in Figures 2a and 2b to improve the clarity of these Figures 2a and 2b).
• the lens 20b is positioned between the lens 20a and the lens 20c.
• the lens 20c is positioned between the lens 20b and the lens 20d.
• Each detection surface 21, substantially flat, is mounted on the electrical board 7.
• the associated lens 20 is itself positioned on the detection surface 21, so that light rays emitted by the LED lamp 1 and arriving in the angle of acceptance ⁇ of each lens 20 are projected onto the surface of de- 21.
• the detection surface 21 then transforms the Li-Fi signal carried by the light rays into an analog electrical signal.
• an orthonormal reference consisting of two perpendicular axes X and Y.
• the four lenses 20 are positioned on the electrical board 7 side by side and substantially aligned on an axis X 'parallel to the axis X, each lens having a slight offset ⁇ in the direction of the axis Y with the one or more adjacent lenses.
• the center of the lens 20a is located on the axis X '
• the center of the lens 20b is located above the axis X' at a distance ⁇ from the axis X 'in the direction of the Y axis
• the center of the lens 20c is located above the axis X 'at a distance 2 ⁇ from the axis X * in the direction of the Y axis
• the center of the lens 20d is located at above the X 'axis at a distance 3 ⁇ from the X' axis in the direction of the Y axis.
• the slight offset ⁇ is between one twentieth and one fifth of the diameter D of the lenses 20.
• Each lens 20 is spaced from the adjacent lens (s) by a length d in the direction of the X axis. More precisely, the distance between projection on the X axis of two points closest to two lenses. Adjacent is equal to the length d.
• the length d is 0.4mm.
• each lens 20 of the photodetector 11 and the LED lamp 1 is defined by a plurality of optical parameters, among which: - the radius of curvature of the lens;
• the distance s between the LED lamp 1 and the main object plane Po (s is typically between 3.5 and 5m);
• the lens 20 is not inclined relative to the associated detection surface 21 (or is inclined at an angle of 0 °).
• the four lenses 20a, 20b, 20c, 20d of the photodetector 11 are each inclined at a different angle of inclination y, yb, yc, yd with respect to the associated detection surface 21a, 21b, 21c, 21d.
• the angle of inclination ⁇ between the lens 20a and the detection surface 21a is 0 ° (it is therefore in the case of the lens of FIG. tilt angle yb between the lens 20b and the detection surface 21b is 15 °, the tilt angle yc between the lens 20c and the detection surface 21c is 32 °, and the tilt angle yd between the lens 20d and the detection surface 21d is 43 °.
• the acceptance p of each lens 20 is calculated using the formula:
• D is the diameter of the lens 20 and f is the image focal length of the lens 20.
• the overall acceptance Pg of the photodetector 11 is increased, the capacity of each receiving apparatus 3 to receive the light rays emitted by the LED lamp 1 is increased, and thus increases the reception quality of each display apparatus 3.
• the angle of incidence Qc of the light rays 23 on the lens 20c is 33 °
• the angle of incidence Qd of the light rays 23 on the lens 20d is 40 °.
• the image 24 of the LED lamp 1 on the detection surface 21 associated with each lens 20 is shifted downwards when the angle of inclination y and the incident angle Q increase (Schempflug condition).
• the focal length image is in turn shortened and progressively increases from 4mm for the lens 20a to 3, 6mm for the lens 20d.
• the angle of incidence Qc 'of the light rays 23 on the lens 20c is 18 °
• the angle of incidence Qd' of the light rays 23 on the lens 20d is 28 ° (the angles of inclination ⁇ lenses 20 are the same as those of FIG. 6).
• the product price display application described here is of course in no way limiting.
• the receiving device of the invention can be used in all types of applications in which communication via Li-Fi is implemented.
• the reception device of the invention can in particular equip interconnected Li-Fi signal receivers in a network of Li-IF signal receivers.
• Such a network may for example be intended to transmit information generated by a computer or a server, transmitted to one or more LED lamps and transmitted via Li-Fi signals to the interconnected Li-Fi signal receivers.
• the architecture of the electrical board and the electrical components used can be very different. For example, it is possible to position the lenses and the detection surfaces on a first electrical card and the other components on a second electrical card, or to replace the microcontroller (s) with processing means comprising an FPGA or an ASCI or a microprocessor. It is also possible to use, in place of the electrophoretic display, a liquid crystal or electrochromic display.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Computing Systems (AREA)
• Optical Communication System (AREA)

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Cited By (1)

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• 2015
  • 2015-10-05 FR FR1559453A patent/FR3042082A1/fr active Pending
• 2016
  • 2016-10-03 WO PCT/EP2016/073576 patent/WO2017060200A1/fr active Application Filing
  • 2016-10-03 EP EP16778766.2A patent/EP3360269A1/de not_active Withdrawn

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