EP3360269A1

EP3360269A1 - Li-fi receiver apparatus

Info

Publication number: EP3360269A1
Application number: EP16778766.2A
Authority: EP
Inventors: Huetzin PEREZ OLIVAS; Suat TOPSU; Jorge GARCIA-MARQUEZ
Original assignee: Oledcomm SAS
Current assignee: Oledcomm SAS
Priority date: 2015-10-05
Filing date: 2016-10-03
Publication date: 2018-08-15
Also published as: WO2017060200A1; FR3042082A1

Abstract

The invention relates to a receiver device intended for receiving a modulated light signal of the Li-Fi signal type, comprising a photodetector (11) suitable for detecting the modulated light signal and for transforming same into an electrical signal, and a processing module connected to the photodetector (11) and intended for acquiring the electrical signal in order to extract transmitted data therefrom, characterised in that the photodetector (11) comprises a semiconducting detection surface (21) and a converging lens (20) intended for concentrating the modulated light signal on the detection surface (21).

Description

LiFi receiving device

The invention relates to the field of communication systems using modulated light signals of the Li-Fi signal type.

BACKGROUND OF THE INVENTION

The use of Li-Fi technology (for "Light Fidelity") to implement wireless communication has many advantages including the availability of optical spectrum and the absence of electromagnetic interference.

In addition, thanks to the development of light emitting diodes (LEDs) with very large switching capabilities and photodiodes with very fast response times, data can be transmitted and received with Li-Fi at a much higher rate than the speed offered for example by WiFi technology (for "Wireless 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.

OBJECT OF THE INVENTION

The object of the invention is to reduce the cost of a communication system using modulated light signals of the Li-Fi signal type. SUMMARY OF THE INVENTION

With a view to achieving this object, a reception device is proposed 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.

There is further provided 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.

In addition, a receiving device similar to that described above is proposed, in which the angles of inclination differ two by two from one angle. between 10 ° and 15 °.

In addition, a reception device similar to the one just described is proposed, 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.

There is also provided a receiving device similar to that just described, in which the slight offset is between one twentieth and one fifth of the diameter of the lenses.

In addition, a display device is proposed comprising a reception device similar to those described above, and a display for displaying the received data.

In addition, a display similar to that described above is proposed, 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.

Other characteristics and advantages of the invention will emerge on reading the following description of a particular, non-limiting embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Reference will be made to the accompanying drawings in which:

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;

- Figure 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.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 to 3, 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.

For each product, 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.

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.

However, since the Li-Fi signals are generated by flashing of the LEDs 2 of the LED lamp 1 and are carried by light rays emitted by the LED lamp 1, 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.

For each display apparatus 3, the reception quality of the display data therefore depends in particular on the orientation angle θο and the relative position angle θr 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 θο 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.

With reference to FIG. 4, 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).

Each lens 20 here has a diameter D = 7.5mm.

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 β 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.

In the plane of the electrical board 7 is defined 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 Δ in the direction of the axis Y with the one or more adjacent lenses.

More specifically, 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 Δ 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 2Δ from the axis X * in the direction of the Y axis, and the center of the lens 20d is located at above the X 'axis at a distance 3Δ from the X' axis in the direction of the Y axis.

The slight offset Δ 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.

Here, the length d is 0.4mm.

With reference to FIG. 5, the arrangement of 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 position of the main plane Po object;

the position of the main object point H on the optical axis Xo;

the position of the main plane Pi image;

the position of the main image point H 'on the optical axis Xo;

the distance s between the LED lamp 1 and the main object plane Po (s is typically between 3.5 and 5m);

the distance s 'between the main image point H' and the position of the image of the LED lamp 1 on the detection surface 21;

the height h1 of the detection surface and the half height h1 / 2;

the height h2 of the LED lamp 1 and the half height h2 / 2;

the acceptance angle β of the lens 20;

the half-angle object a.

the half-angle image a '.

In FIG. 5, the lens 20 is not inclined relative to the associated detection surface 21 (or is inclined at an angle of 0 °).

With reference to FIG. 6, 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 α 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 pa of the lens 20a is pa = 20.93 ^e , the acceptance pb of the lens 20b is pb = 17.54 °, the acceptance pc of the lens 20c is pc = 15 °, and the acceptance pd of the lens 20d is pd = 12 °. The acceptance p of each lens 20 is calculated using the formula:

where 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 is therefore pg = 50.46 °.

By using four lenses 20 positioned as described above, 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 of the light rays 23 on the lens 20a is Qa = 10.46 °, the angle of incidence of the light rays 23 on the lens 20b is C2b = 23 °, the angle of incidence Qc of the light rays 23 on the lens 20c is 33 ° and 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.

In FIG. 7, the angle of incidence of the light rays 23 on the lens 20a is Qa '= -10, 46 °, the angle of incidence of the light rays 23 on the lens 20b is Ωo' = 5.46 ^e , the angle of incidence Qc 'of the light rays 23 on the lens 20c is 18 ° and the angle of incidence Qd' of the light rays 23 on the lens 20d is 28 ° (the angles of inclination γ lenses 20 are the same as those of FIG. 6).

Of course, the invention is not limited to the embodiment described, but encompasses any variant within the scope of the invention as defined by the claims.

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 numerical values of the various parameters (number of lenses, optical parameters, inclinations, etc.) cited here are provided by way of example, and It is of course possible to implement the invention by using different values for these parameters.

Likewise, 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.

Claims

1. Receiving device for receiving a modulated light signal of the Li-Fi signal type, comprising a photodetector (11) adapted to detect the modulated light signal and transform it into an electrical signal, and a processing module (12). ) connected to the photodetector (11) for acquiring the electrical signal for extracting transmitted data, characterized in that the photodetector (11) has a semiconductor detection surface (21) and a converging lens (20). for concentrating the modulated light signal on the detection surface (21).

2. Receiving device according to the claim

1, having a plurality of lenses (20a, 20b, 20c, 20d) positioned side by side and each inclined with respect to the detection surface of a different angle of inclination (ya, yb, yc, yd).

3. Receiving device according to the claim

2, in which the angles of inclination differ two by two by an angle between 10 ° and 15 °.

4. receiving device according to claim 1, comprising a plurality of lenses positioned side by side in the same plane and substantially aligned, each lens (20a, 20b, 20c, 20d) having a slight shift (Δ) of position in the plane with the adjacent lens or lenses.

5. Receiving device according to claim 4, wherein the slight offset (A) is between one twentieth and one fifth of the diameter of the lenses (20).

6. Display apparatus having a device receiver according to one of the preceding claims and a display (8) for displaying the received data.

The display apparatus according to claim 6, wherein the display (8) is a liquid crystal display, an electrophoretic display or an electrochromic display.

8. Communication system comprising a light-emitting diode lamp (1) and a receiving device (9) according to one of claims 1 to 6, the light-emitting diode lamp (1) being intended to emit a modulated light signal and the receiving device (9) being adapted to be positioned with respect to the light-emitting diode lamp (1) so as to receive said signal.