Method for locating an item of equipment in a closed environment

Abstract

The present invention relates to a method and system for locating a first item of equipment in a closed environment. The method emits a first light signal modulated according to at least one pair of frequencies, each pair of frequencies representing a symbol and the at least one represented symbol identifying a location in the closed environment of a second item of equipment close to the first item of equipment. The location of the first item of equipment is that of the second item of equipment when the first and second items of equipment are close to each other.

Description

Method for locating equipment in a closed environment

[0001] The present invention relates to the localization of equipment in a closed environment. Technological background

[0002] Geolocation allows us to obtain a geographical position of a piece of equipment. A geolocation system corresponds for example to a system of type GPS (from the English "Global Positioning System" or in French "Système de emplacement global"), to a Galileo satellite positioning system set up by the European Union or even GLONASS (in English "Global Navigation Satellite System", in French system of satellite navigation (Russian).

[0003] While extremely accurate outdoors, a geolocation system has significant drawbacks in enclosed environments such as road structures (bridges, tunnels, etc.) or buildings (shops, warehouses, etc.) because physical obstacles like thick walls, building materials, and multiple stories can weaken and reflect satellite signals, leading to location errors. Therefore, applications requiring precise location in enclosed environments, such as urban navigation or locating objects within buildings, can face major challenges when relying solely on satellite signals. This is especially problematic inside buildings, where satellite signals may be completely absent or severely weakened.

[0004] Equipment location systems exist that are suitable for enclosed environments, such as Wi-Fi® network location, often called "XiFi," ultrasonic or infrared location systems, or simultaneous localization and mapping (SLAM) systems. While these alternative solutions address some of the shortcomings of geolocation systems used for indoor equipment location, they also present their own technical and operational challenges.

[0005] First, Wi-Fi® location can be subject to variations in accuracy due to the density and arrangement of Wi-Fi® access points in an enclosed environment. Electromagnetic interference, physical obstacles, and signal fluctuations can lead to significant location errors, especially in large complexes or highly dynamic environments.

[0006] Regarding simultaneous mapping and localization (SLAM) systems, while these solutions offer the ability to create maps and locate oneself simultaneously in unfamiliar environments, they can face challenges in terms of accuracy and reliability. Real-time mapping and localization require sophisticated algorithms and precise sensors, and even small errors in position or map estimation can accumulate and lead to significant deviations in the final location.

[0007] Furthermore, simultaneous mapping and localization (SLAM) systems can be limited in their ability to handle complex environments with changing characteristics, such as crowds of moving people, rapid changes in lighting, or the arrangement of objects. In such situations, the reliability and robustness of SLAM systems can be tested, compromising localization accuracy.

[0008] Ultrasonic and infrared location systems have some drawbacks that can limit their effectiveness in certain situations. For example, both ultrasonic and infrared signals have limited range. In particular, ultrasound can be absorbed by obstacles, often limiting its range to a few meters, while infrared can be blocked by solid objects. Both ultrasonic and infrared signals can be affected by physical barriers such as walls, furniture, and other objects. This can lead to location errors or a loss of accuracy, especially in cluttered environments. Ultrasonic and infrared signals can also be disrupted by other sources of noise or similar signals. For example, infrared lights in home environments can interfere with infrared location systems.Environmental conditions such as temperature, humidity, and the presence of reflective surfaces can affect the propagation of ultrasonic and infrared signals, which can impair location accuracy. Implementing ultrasonic or infrared-based location systems may require the installation of transmitters and receivers in the relevant environment, which can be costly and require careful planning. Due to the nature of ultrasonic and infrared signals, location accuracy can be low, particularly in environments with significant signal reflection.

[0009] In summary, although ultrasonic and infrared localization systems can be useful in certain contexts, they have limitations in terms of range, sensitivity to obstacles, interference, dependence on environmental conditions, installation complexity, and accuracy. Summary of the present invention

[0010] One object of the present invention is to solve at least one of the problems of the technological background described above.

[0011] Another object of the present invention is to determine a system for locating equipment in a closed environment.

[0012] According to a first aspect, the present invention relates to a method for locating a first piece of equipment in a closed environment characterized in that it comprises the following steps: - emission, by a second piece of equipment, of a first light signal modulated according to at least one pair of frequencies, each pair of frequencies representing a symbol and said at least one symbol represented identifying a location in the closed environment of the second piece of equipment; - the frequencies of said at least one pair of frequencies being determined such that during a replacement, during the modulation of the first light signal, of a first frequency by a second frequency of said at least one pair of frequencies, the highest frequency, among said first and second frequencies, is at most equal to twice the lowest frequency, among said first and second frequencies;- reception, by the first piece of equipment, of the first light signal and obtaining said at least one symbol by demodulating the first light signal received; - emission of a second signal carrying said at least one symbol; - reception, by a third piece of equipment, of the second signal carrying said at least one symbol; and - obtaining, by the third piece of equipment, the location of the first piece of equipment from said at least one symbol carried by the second signal received.

[0013] According to one variant, the second signal carrying said at least one symbol is emitted, by the first piece of equipment, to the third piece of equipment.

[0014] According to one variant, the transmission of the second signal bearing said at least one symbol comprises the following steps: - transmission, by the first equipment, of a third signal to the second equipment; - reception, by the second equipment, of the third signal and obtaining said at least one symbol; - transmission, by the second equipment, of the second signal bearing said at least one symbol to the third equipment.

[0015] According to one variant, the second signal is a second light signal modulated according to said at least one pair of frequencies representing said at least one symbol and for which obtaining said at least one symbol includes demodulation of the second light signal received.

[0016] According to one variant, the third signal is a third light signal modulated according to said at least one pair of frequencies representing said at least one symbol and for which obtaining said at least one symbol includes demodulation of the third light signal received.

[0017] According to one variant, the first, second or third light signal bearing said at least one symbol is a signal modulated by a control signal comprising a succession of time cycles, each time cycle being defined by an alternation of a high level corresponding to a high level of light intensity of the modulated light signal maintained for a first duration and a low level corresponding to a low level of light intensity of the light signal maintained for a second duration, a total duration of each time cycle being defined from a frequency.

[0018] According to one variant, the emission of the first, second or third light signal modulated by the control signal comprises the following steps:- determination of said at least one pair of frequencies;- generation of the succession of time cycles, the total duration of at least one time cycle being defined from each frequency of each pair of frequencies determined;- modulation of the light signal by the generated control signal; and- emission of the modulated light signal.

[0019] According to one variant, the highest frequency among the frequencies of said at least one determined pair of frequencies is at most equal to twice the lowest frequency among the frequencies of said at least one determined pair of frequencies.

[0020] According to one variant, at least one of the time cycles in the succession of time cycles has a total duration defined from a starting frequency of the emission of said at least one symbol, the starting frequency of the emission of said at least one symbol being determined so that when, during the modulation of the first, second or third light signal, the starting frequency of the emission of said at least one symbol is replaced by a frequency of one of said at least one determined pair of frequencies, the highest frequency, among the starting frequency of the emission of said at least one symbol and said frequency of said pair of frequencies, is at most equal to twice the lowest frequency, among the starting frequency of the emission of said at least one symbol and said frequency of said pair of frequencies.

[0021] According to one variant, at least one of the time cycles in the succession of time cycles has a total duration defined from an end-of-emission frequency of said at least one symbol, the end-of-emission frequency of said at least one symbol being determined so that when a frequency of one of said at least one pair of frequencies determined by the end-of-emission frequency of said at least one symbol is replaced during the modulation of the first, second or third light signal, the higher frequency of said at least one symbol and said frequency of said pair of frequencies is at most equal to twice the lower frequency of said at least one symbol and said frequency of said pair of frequencies.

[0022] According to one variant, the highest frequency among the frequencies of said at least one determined pair of frequencies, the start frequency of transmission of said at least one symbol and the end frequency of transmission of said at least one symbol is at most equal to twice the lowest frequency among the frequencies of said at least one determined pair, the start frequency of transmission of said at least one symbol and the end frequency of transmission of said at least one symbol.

[0023] According to one variant, at least one of the time cycles in the succession of time cycles has a defined duration starting from a determined cutoff frequency such that, during the modulation of the first, second, or third light signal, the cutoff frequency is replaced by a frequency of said at least one determined pair of frequencies or by the emission termination frequency of said at least one symbol, or during the replacement of a frequency of said at least one determined pair of frequencies or the emission start frequency of said at least one symbol by the cutoff frequency, the highest frequency among said frequency of said pair of frequencies, the emission start frequency of said at least one symbol, the emission termination frequency of said at least one symbol, and the cutoff frequency, is at most equal to twice the lowest frequency among said frequency of said pair of frequencies.the transmission start frequency of said at least one symbol, the transmission end frequency of said at least one symbol, and the cutoff frequency.

[0024] According to one variant, if the frequencies of said at least one determined pair of frequencies, the start frequency of transmission of said at least one symbol and the end frequency of transmission of said at least one symbol belong to a set of frequencies whose highest frequency is less than or equal to four times the lowest frequency, the cutoff frequency is defined as a median value between the highest and lowest frequencies of the set of frequencies.

[0025] According to one variant, the control signal being a gate signal comprising a rising edge and a falling edge per time cycle, a replacement of one determined frequency by another determined frequency is triggered on the rising or falling edges of the time cycles.

[0026] According to one variant, each time cycle whose total duration is defined by a frequency is repeated a defined number of times from a frequency of frequency change.

[0027] According to one variant, the frequency of frequency change is at most equal to 100Hz.

[0028] According to one variant, the frequency of frequency change varies depending on the lighting conditions of an environment in which the light signal is emitted.

[0029] According to one variant, a duty cycle of each time cycle of the control signal is equal to the same value within a deviation around that value.

[0030] According to one variant, the reception of the first, second or third light signal modulated by the control signal comprises the following steps: - reception and sampling of the light signal; and - demodulation of the light signal to obtain said at least one symbol, each symbol being represented by a pair of frequencies detected from a spectral analysis of samples of the received light signal; - the detected frequencies of said at least one pair of frequencies being such that when a first detected frequency is replaced by a second detected frequency during the demodulation of the light signal, the highest frequency, among said first and second detected frequencies, is at most equal to twice the lowest frequency, among said first and second detected frequencies.

[0031] According to one variant, the highest frequency among the detected frequencies of said at least one pair of frequencies is at most equal to twice the lowest frequency among the detected frequencies of said at least one pair of frequencies.

[0032] According to one variant, the method further comprises a step of detecting a reception start frequency of said at least symbol from a frequency spectrum of the light signal determined from a first set of samples of the received light signal, the detection of the reception start frequency of said at least one symbol preceding the detection of a first frequency of a first pair of frequencies representing a first symbol to be received.

[0033] According to one variant, the method further comprises a step of detecting an end-of-reception frequency of said at least one symbol from a frequency spectrum of the light signal determined from a second set of samples of the received light signal, the detection of the end-of-reception frequency of said at least one symbol following the detection of a second frequency of a pair of frequencies representing a last symbol to be received.

[0034] According to one variant, the detected frequencies of said at least one pair of frequencies, the reception start frequency of said at least one detected symbol and the reception end frequency of said at least one detected symbol belong to a set of frequencies whose highest frequency is at most equal to twice the lowest frequency of the set of frequencies.

[0035] According to one variant, the method further comprises a step of detecting a cutoff frequency from a frequency spectrum determined from a fifth set of samples of the received light signal, the cutoff frequency being defined as a median value between the highest and lowest frequencies of the set of frequencies, the highest frequency of the set of frequencies being at most equal to four times the lowest frequency of the set of frequencies, the cutoff frequency being detected following the detection of each frequency of each pair of frequencies, the detection of the start frequency of reception of said at least one symbol and the detection of the end frequency of reception of said at least one symbol.

[0036] According to one variant, the frequencies of the entire frequency set are less than 5kHz.

[0037] According to one variant, said at least one symbol is determined from a table defining an association between each symbol and a pair of frequencies.

[0038] According to a second aspect, the present invention relates to a system for locating equipment comprising means for implementing the steps of the process according to the first aspect of the present invention. Brief description of the figures

[0039] Other features and advantages of the present invention will become apparent from the description of the specific embodiments of the present invention below, with reference to the attached Figures 1 to 26, in which:

[0040] schematically illustrates a system for locating a first piece of equipment in a closed environment, according to a particular embodiment of the present invention.

[0041] schematically illustrates a variant of the localization system for a first piece of equipment in a closed environment.

[0042] illustrates a flowchart of the different stages of a process for locating the first piece of equipment implemented by the location system, according to a particular embodiment of the present invention.

[0043] schematically illustrates a variant of a step in the localization process, according to a particular embodiment of the present invention.

[0044] illustrates a flowchart of the different stages of a process for emitting at least one symbol carried by a light signal modulated by a control signal, according to a particular embodiment of the present invention.

[0045] schematically illustrates an example of the time evolution of the control signal used to control the modulation of a light signal according to a particular embodiment of the present invention.

[0046] schematically illustrates an example of the time evolution of the control signal used to control the modulation of a light signal when a first frequency, replaced by a second frequency during the modulation of the light signal, is equal to twice the second frequency according to a particular embodiment of the present invention.

[0047] schematically illustrates an example of the time evolution of the control signal used to control the modulation of a light signal when a first frequency, replaced by a second frequency during the modulation of the light signal, is greater than a second frequency according to a particular embodiment of the present invention.

[0048] schematically illustrates an example of the time evolution of a control signal used to control the modulation of a light signal when the first frequency, replaced by a second frequency during the modulation of the light signal, is lower than the second frequency according to a particular embodiment of the present invention.

[0049] schematically illustrates step 520 of control signal generation according to a particular embodiment of the present invention.

[0050] schematically illustrates an example of the time evolution of the control signal used to control the modulation of the light signal according to a particular embodiment of the present invention.

[0051] illustrates a schematic example of the time evolution of the control signal used to control the modulation of a light signal according to a particular embodiment of the present invention.

[0052] illustrates a schematic example of the time evolution of the control signal used to control the modulation of a light signal according to a particular embodiment of the present invention.

[0053] illustrates a schematic example of the time evolution of the control signal used to control the modulation of a light signal according to a particular embodiment of the present invention.

[0054] illustrates a schematic example of the time evolution of the control signal used to control the modulation of a light signal according to a particular embodiment of the present invention.

[0055] illustrates examples of PWM signals with duty cycles ranging from 0% (zero light intensity level) to 100% (maximum light intensity level).

[0056] illustrates an example of a PWM signal with a constant duty cycle of 50%.

[0057] illustrates a flowchart of the different stages of a process for receiving at least one symbol carried by a light signal modulated by a control signal, according to a particular embodiment of the present invention.

[0058] illustrates a flowchart of the sub-steps of the 220 demodulation step of the light signal for the reception of at least one symbol, according to a particular embodiment of the present invention.

[0059] illustrates an example of steps 6210, 6220, 6240, 6250 and 6260 of step 620 of light signal demodulation, according to a particular embodiment of the present invention.

[0060] illustrates an example of a frequency spectrum obtained from a discrete Fourier transform spectral analysis of a set of samples.

[0061] illustrates an example of updating the scores associated with the frequencies of the frequency set from three spectra determined from three consecutive sets of samples, according to a particular embodiment of the present invention.

[0062] illustrates an example of a base 64 table that groups 64 associations between symbols and pairs of frequencies, according to a particular embodiment of the present invention.

[0063] schematically illustrates a device 1 configured to emit and / or receive at least one symbol carried by a light signal modulated by a control signal, according to a particular embodiment of the present invention.

[0064] schematically illustrates an implementation of the device 2 for emitting light signals configured to emit at least one symbol carried by a light signal modulated by the control signal according to a particular example of the present invention.

[0065] schematically illustrates an implementation of the light signal reception device 3 configured to receive at least one symbol carried by a light signal modulated by the control signal 100 according to a particular example of the present invention. Description of examples of achievements

[0066] A method and device for locating equipment in a closed environment will now be described in what follows with joint reference to Figures 1 to 26. The same elements are identified with the same reference signs throughout the description that follows.

[0067] The terms "first," "second" (or "firsts," "seconds"), etc., are used in this document by arbitrary convention to identify and distinguish different elements (such as operations, means, etc.) implemented in the embodiments described below. Such elements may be distinct or correspond to a single element, depending on the embodiment.

[0068] Subsequently, a light signal is a signal that can belong to the visible spectrum or the infrared spectrum.

[0069] Infrared light (infrared spectrum) is classified into 3 groups:

[0070] -Near Infrared (NIR): This band covers wavelengths from 0.75 to 1.4 micrometers (750 to 1400 nanometers). Typical applications include remote sensing, fiber optic communication, and certain forms of medical imaging;

[0071] -Mid-infrared (MIR): Wavelengths in this band range from 1.4 to 3 micrometers (1400 to 3000 nanometers). MIR is used in various applications such as spectroscopy for chemical analysis and gas detection, as well as in certain heating technologies.

[0072] -Far Infrared (FIR): This band extends from 3 micrometers to approximately 1000 micrometers (3000 nanometers to 1 millimeter), although the precise classification may vary. FIR is primarily used for heating applications and certain types of remote sensing and thermal imaging.

[0073] For example, light signals may belong to the near-infrared frequency band, in the 750-950 nm range, with a peak at 850 nm.

[0074] According to a particular embodiment of the present invention, locating a first piece of equipment in an enclosed environment is achieved by a second piece of equipment emitting a first light signal modulated according to at least one pair of frequencies. Each pair of frequencies represents a symbol, and said at least one symbol represents a location of the second piece of equipment. The frequencies of said at least one pair of frequencies are determined such that, during the modulation of the first light signal, when a first frequency is replaced by a second frequency of said at least one pair of frequencies, the higher of said first and second frequencies is at most twice the lower of said first and second frequencies. The first light signal is received by the first piece of equipment, which obtains said at least one symbol by demodulating the first received light signal.The first device then emits a second signal carrying at least one symbol. This second signal is received by a third device, which determines the location of the first device based on the at least one symbol carried by the second received signal.

[0075] The present invention is advantageous because the first piece of equipment is located when it is in the beam of the first light signal, that is to say in the vicinity of the second piece of equipment.

[0076] The accuracy of the location of the first device then depends on the range of the first signal and the number of second devices distributed in the closed environment.

[0077] The modulation (and demodulation) according to the present invention makes it possible to transmit a first light signal between a light signal emitting device and a light signal receiving device without generating visible flickering (when these light signals belong to the visible spectrum) for a user and without prematurely aging the emitting and receiving devices.

[0078] The modulation and demodulation of the first light signal according to the present invention makes it possible to optimize the energy efficiency and the lifespan of the light signal emitting and receiving devices.

[0079] The modulation and demodulation according to the present invention use low frequencies (well below 1 MHz and close to 2 kHz) which optimize the efficiency of the light signal transmitter and receiver, allowing lighting equipment to operate at its nominal capacity and thus preserving its lifespan. The transmission duration of the light signals modulated by these low frequencies improves the probability of correctly reading each frequency used for modulating the emitted light signals.

[0080] The diagram schematically illustrates a system 100 for locating a first piece of equipment 101 in a closed environment, according to a particular embodiment of the present invention.

[0081] System 100 includes the first piece of equipment 101, a second piece of equipment 102 and a third piece of equipment 103.

[0082] The second device 102 is configured to obtain, for example from a memory location, at least one symbol identifying its geographic location within the closed environment and to modulate a first light signal 1011 according to at least one pair of frequencies representing said symbol. The first light signal 1011 can thus be modulated by a single pair of frequencies if the location of the second device 102 is expressed by a single symbol, by two pairs of frequencies if the location of the second device 102 is expressed by two symbols, and so on. The second device 102 is also configured to emit the first light signal 1011.

[0083] The first device 101 is configured to receive the first light signal 1011 and to obtain said at least one symbol by demodulating the first received light signal 1011. The first device is also configured to transmit a second signal 1012 carrying said at least one symbol to the third device 103.

[0084] The third equipment 103 is configured to receive the second signal 1012 and to obtain the location of the first equipment 101 from said at least one symbol carried by the second received signal 1012.

[0085] Laillustre schematically illustrates a variant of the location system of the first piece of equipment 101 of the.

[0086] According to this variant, the first equipment 101 can be configured to transmit a third signal 1013 to the second equipment 102 and the second equipment 102 can then be configured to receive the third signal 1013 and to transmit the second signal 1012 bearing said at least one symbol to the third equipment 103.

[0087] According to one variant, the third 1013 signal may carry said at least one symbol. The second 102 device can then be configured to obtain said at least one symbol from the received third 1013 signal.

[0088] According to another variant, the third signal 1013 may not carry said at least one symbol but may indicate to the second equipment 102 that it can retrieve said at least one symbol identifying the location of the second equipment 102 from a memory for example and that it can then generate the second signal 1012 carrying said at least one symbol.

[0089] According to one variant, the second 1012 signal can be transmitted via a wired communication network such as Ethernet or the Internet, or via a wireless communication network such as WiFi®. The first device 101, or the second device 102 respectively, can then be configured to generate the second 1012 signal carrying at least one symbol that is compatible with a transmission protocol used to communicate on at least one of these communication networks.

[0090] According to one variant, the third signal 1013 can be transmitted via a wired communication network such as Ethernet or the Internet, or via a wireless communication network such as WiFi®. The first device 101 can then be configured to generate the third signal 1013, possibly bearing at least one symbol of said signal according to one variant, which is compatible with a transmission protocol used to communicate on at least one of these communication networks. The second device 102 can then be configured to receive the third signal 1013. 3et, selon une variante, pour obtenir ledit au moins un symbole à partir du troisième signal 1013reçu.

[0091] According to one variant, the second signal 1012 can be a light signal modulated by at least one pair of frequencies representing said at least one symbol. The first device 101, or the second device 102, can then be configured to modulate the second light signal 1012 according to said at least one pair of frequencies. The third device 103 can then be configured to obtain said at least one symbol by demodulating the second light signal 1012.

[0092] According to one variant, the third signal 1013 can be a light signal modulated by at least one pair of frequencies representing said at least one symbol. The first piece of equipment 101 can then be configured to modulate the third light signal 1013 according to said at least one pair of frequencies. The second piece of equipment 102 can then be configured to obtain said at least one symbol by demodulating the third light signal 1013.

[0093] Laillustre un flowchart des différents étapes d’un process 200 de localisation du premier équipement 101 mise en œuvre par le système de localisation de la, selon une exemple d’incarnation particulier de la présent invention.

[0094] In a step 210, the first light signal 1011 is modulated according to at least one pair of frequencies and is emitted by the second equipment 102. Each pair of frequencies represents a symbol and said at least one symbol represented identifies a location (geographic) in the closed environment of the second equipment 102. Thus, a location identifier of the second equipment 102 can be represented by one or more symbols and the light signal 1011 can be modulated according to one or more pairs of frequencies.

[0095] The frequencies of said at least one pair of frequencies are determined so that when, during the modulation of the first light signal (1011), a first frequency is replaced by a second frequency of said at least one pair of frequencies, the highest frequency, among said first and second frequencies, is at most equal to twice the lowest frequency, among said first and second frequencies.

[0096] In a step 220, the first light signal 1011 is received by the first equipment 101 and said at least one symbol carried by the first light signal 1011 is obtained by demodulation of the first light signal 1011 received.

[0097] In step 230, the second signal 1012 bearing said at least one obtained symbol is emitted.

[0098] In a step 240, the second signal 1012 bearing said at least one symbol is received by the third equipment 103.

[0099] In a step 250, the location of the first equipment 101 is obtained by the third equipment 103 from said at least one symbol carried by the second signal 1012 received.

[0100] For example, the third device 103 includes a memory in which associations between the geographic location identifier of devices in the closed environment and a set of at least one symbol are stored. Thus, the third device can retrieve the stored association that corresponds to the set of at least one symbol carried by the second received signal 1012 and thereby obtain the geographic location of the second device 102 in the closed environment. The third device 103 deduces from this that the first device 101 is also located at this geographic location.

[0101] According to a variant of step 230, the second signal 1012 bearing said at least one symbol is emitted, by the first equipment 101, to the third equipment 103.

[0102] This variant of step 230 can be implemented by the localization system 100 of laou or one of its variants.

[0103] According to another variant of step 230, illustrated in the figure, the emission of the second signal 1012 bearing said at least one symbol comprises steps 233 to 235.

[0104] This variant of step 230 can be implemented by a variant of the location system 100 of the.

[0105] In step 233, the first piece of equipment 101 emits the third signal 1013 to the second piece of equipment 102.

[0106] In step 234, the second equipment 102 receives the third signal 1013 and obtains said at least one symbol.

[0107] According to one variant, the third signal 1013 may carry said at least one symbol and the second equipment 102 obtains said at least one symbol from the third signal 1013 received.

[0108] According to another variant, the third signal 1013 may not carry said at least one symbol but may indicate to the second equipment 102 that it can retrieve said at least one symbol identifying the location of the second equipment 102 from a memory for example and then generate the second signal 1012 carrying said at least one symbol.

[0109] In step 235, the second piece of equipment 102 emits the second signal 1012 carrying said at least one symbol to the third piece of equipment 103.

[0110] According to a variant of the processes in Figures 3 and 4, the second signal 1012 may be a second light signal modulated according to said at least one pair of frequencies representing said at least one symbol, the emission (step 230 or 235) of the second light signal 1012 may then include a modulation of the second light signal 1012 according to said at least one pair of frequencies and the obtaining of said at least one symbol (step 250) includes a demodulation of the second light signal (1012) received.

[0111] According to one variant, the third signal 1013 is a third light signal modulated according to said at least one pair of frequencies representing said at least one symbol, the emission by the first equipment may then include a modulation of the third light signal 1013 according to said at least one pair of frequencies (step 233) and the obtaining of said at least one symbol (step 234) includes a demodulation of the third light signal received.

[0112] According to a variant of the processes in Figures 3 and 4, the first light signal 1011 is modulated by a control signal 300.

[0113] According to a variant of the processes in Figures 3 and 4, the second light signal (1012) is modulated by the control signal 300.

[0114] According to a variant of the processes in Figures 3 and 4, the third light signal (1013) is modulated by the control signal 300.

[0115] According to a variant of steps 210, 230, 233, the emission (210, 230, 233) of said at least one symbol by a light signal (1011, 10121013) modulated by the control signal 300 comprises the steps of the emission process of the.

[0116] Laillustre un flowchart des différents étapes d’un processus d’émission d’at least un symbole porté par un signal lumière modulated par le signal de contrôle 300, selon une exemple d’incarnation particulier de la présent invention.

[0117] In a step 510, a pair of frequencies (F 1,s F 2,s ) is determined for each symbol s y to be emitted. At least one pair of frequencies is determined, as many as there are symbols to be emitted.

[0118] The frequencies of said at least one pair of frequencies are constrained to be determined so that when, during the modulation of the light signal, a first determined frequency is replaced by a second determined frequency, the highest frequency, among said first and second frequencies, is at most equal to twice the lowest frequency, among said first and second frequencies.

[0119] This constraint on the frequencies of at least one determined frequency pair ensures that during a frequency change in the modulation of the light signal, the ratio of the lower of the two frequencies involved in this change to the higher of those two frequencies is at least 50%. For example, if a first frequency F1 is higher than a second frequency F2, then the ratio F2 / F1 is at least 50%. If the second frequency F2 is higher than the first frequency F1, then the ratio F1 / F2 is at least 50%.

[0120] For example, F1 = 2kHz and F2 = 3.5kHz to respect this constraint on frequencies.

[0121] Respecting the constraint on the frequencies of said at least one pair of frequencies avoids the appearance of a visible flickering effect of the modulated light signal (when this light signal belongs to the visible spectrum).

[0122] The first and second frequencies can be frequencies of the same frequency pair, that is, the first frequency can be frequency F 1,sy and the second frequency might be the frequency F 2,s of a frequency cut (F 1,sy F 2,sy But a first frequency can also be the frequency F 2,sy1 of a pair of frequencies (F 1,sy1 F 2,sy1 ) representing a symbol s y1 and the second frequency might be the frequency F 1,sy2 of another pair of frequencies representing a symbol s y2 .

[0123] In step 520, the control signal 300 is generated. The generated control signal 300 comprises a succession of time cycles. The total duration of at least one time cycle is defined based on each frequency of each determined frequency pair.

[0124] In step 530, the light signal is modulated by the generated control signal 300.

[0125] In step 540, the modulated light signal is emitted.

[0126] Laillustre schematically an example of time evolution of the control signal 300 used to control the modulation of the light signal according to a particular embodiment of the present invention.

[0127] The control signal 300 is of the PWM type. A PWM signal is a gate signal consisting of a succession of time cycles. Each time cycle is defined by an alternation of a high level, corresponding to a high level of light intensity of the light signal (light signal "on") maintained for a first duration 301, and a low level, corresponding to a low level of light intensity of the light signal (light signal "off") maintained for a second duration 302. A total duration 303 of each time cycle is defined from a frequency F iThe total duration of a time cycle is equal to the inverse of a frequency.

[0128] The light signal is modulated by the control signal 300 (step 530). For this purpose, the light signal is at a high level of light intensity ("on") when the control signal 300 is at a high level and at a low level of light intensity ("off") when the control signal 300 is at a low level.

[0129] According to a particular embodiment of the present invention, the time cycle of duration 303 can be repeated several times. The number of repetitions is defined by the inverse of a frequency change rate.

[0130] For example, the frequency change frequency is at least equal to 100Hz to ensure a frequency change speed of less than 10 ms and thus avoid the appearance of visible flickering of the light signal (when this light signal belongs to the visible spectrum).

[0131] The repetition of the time cycle increases the reliability of demodulation of the modulated light signal.

[0132] Furthermore, excessively slow frequency changes can impact the lighting level. Additionally, a change frequency below 100 Hz induces visible flickering of the modulated light signal (when this light signal belongs to the visible spectrum).

[0133] According to a particular embodiment of the present invention, the frequency of frequency change can vary depending on the lighting conditions of an environment in which the light signal is emitted.

[0134] For example, the lower the lighting conditions, e.g., the lighting conditions in the immediate environment of the light signal emitting device indicate low brightness, and the higher the number of repetitions, i.e., the lower the frequency of frequency changes.

[0135] For example, the frequency of frequency changes varies proportionally to the ambient brightness of the light signal emitting device.

[0136] For example, if the frequency change is 1 / 3, then the time cycle, with a total duration of 303, is repeated three times. The light signal modulated by the control signal 300 flashes according to the frequency F. i for a duration of 304. Another frequency F j can then replace the frequency F i so that the light signal flashes according to the frequency F j The frequencies F i and F j can be equal or different.

[0137] Laillustrate schematically an example of time evolution of the control signal 300 used to control the modulation of a light signal when a first frequency F1, replaced by a second frequency F2 during the modulation of the light signal, is equal to twice the second frequency F2 according to a particular embodiment of the present invention.

[0138] The control signal 300 is described here with a frequency change frequency of 1 / 3, that is to say that a first time cycle of duration 3031 defined from the first frequency F1 is repeated three times (total duration 3041) and a second time cycle of duration 3032 defined from the second frequency F2 is repeated three times (duration 3042).

[0139] According to this example, the first frequency F1 is equal to twice the second frequency F2, i.e. F1=2*F2, and the duration 3032 is equal to twice the duration 1031. The duration 3042 is equal to twice the duration 3041. The ratio F2 / F1 = 50%, which verifies the constraint on the frequencies F1 and F2 that prevents visible flickering of the light signal (when this light signal belongs to the visible spectrum).

[0140] Laillustrate schematically an example of time evolution of the control signal 300 used to control the modulation of a light signal when a first frequency F1, replaced by a second frequency F2 during the modulation of the light signal, is greater than a second frequency F2 according to a particular embodiment of the present invention.

[0141] The control signal 300 is described here with a frequency change frequency of 1 / 3, i.e. a first time cycle of duration 3031 defined from the first frequency F1 is repeated three times (total duration 3041) and a second time cycle of duration 3032 defined from the second frequency F2 is repeated three times (duration 3042).

[0142] According to this example, for the constraint on frequencies F1 and F2 to be verified, the first frequency F1 must be less than twice the second frequency F2, i.e., F1 < 2 * F2, and the duration 3032 is then less than twice the duration 3031. The duration 3042 is less than twice the duration 3041. The ratio F2 / F1 > 50%, which verifies the constraint on frequencies F1 and F2, preventing visible flickering of the light signal (when this light signal belongs to the visible spectrum).

[0143] The illustration schematically shows an example of the time evolution of a control signal used to control the modulation of a light signal when the first frequency F1, replaced by a second frequency F2 during the modulation of the light signal, is lower than the second frequency F2 according to a particular embodiment of the present invention.

[0144] The control signal 300 is described here with a frequency change frequency of 1 / 3, that is to say that a first time cycle of duration 3031 defined from the first frequency F1 is repeated three times (total duration 3041) and a second time cycle of duration 3032 defined from the second frequency F2 is repeated three times (duration 3042).

[0145] According to this example, for the constraint on frequencies F1 and F2 to be verified, the second frequency F2 of the frequency pair must be less than twice the first frequency F1, i.e., F2 < 2 * F1, and the duration 3031 is then less than twice the duration 3032. The duration 3041 is less than twice the duration 3042. The ratio F1 / F2 > 50%, which verifies the constraint on frequencies F1 and F2, preventing visible flickering of the light signal (when this light signal belongs to the visible spectrum).

[0146] The diagram schematically illustrates step 520 of the generation of the control signal 300 according to a particular embodiment of the present invention.

[0147] The 300 control signal comprises a succession of time cycles.

[0148] Step 520 is an iterative step that includes substeps 5210-5230.

[0149] In substep 5210, one of said at least one pair of frequencies (F 1sy , F2sy ) determined in step 510 is considered.

[0150] In substep 5220, at least one first time cycle s1 followed by at least one second time cycle s2 are added to the sequence of time cycles of the control signal 300. Each first time cycle s1 has a total duration (3031) defined from the first frequency F 1sy of the frequency pair (F 1sy , F 2sy ) considered. Each second time cycle s2 has a total duration of 3032 defined from the second frequency F 2sy of the frequency pair (F 1sy , F 2sy ) considered. Step 5220 ends when each frequency pair (F 1sy , F 2sy ) determined was considered (substep 5230).

[0151] The number of first time cycles s1 is defined from the frequency of frequency change and the number of second time cycles s2 is defined from the frequency of frequency change.

[0152] Laillustre schematically an example of time evolution of the control signal 300 used to control the modulation of the light signal according to a particular embodiment of the present invention.

[0153] According to this example, a pair of frequencies is determined to emit a symbol with a frequency change frequency equal to 1 / 3. The succession of time cycles of the control signal 300 then comprises three first time cycles s1 followed by three second time cycles s2.

[0154] According to a particular embodiment of substep 5220, illustrated in the figure, at least one third time cycle s3 may be added to the succession of time cycles of the control signal 100. Said at least one third time cycle s3 precedes said at least one first time cycle s1 of the succession of time cycles of the control signal 300.

[0155] According to the example above, if a symbol s y is emitted with a change frequency equal to 1 / 3, the succession of time cycles of the control signal 300 comprises 3 third time cycles s3 followed by 3 first time cycles s1 whose total duration (3031) is determined from the frequency F 1sy of the frequency couple (F 1sy , F 2sy ) representing the symbol s y to be transmitted (or the first symbol if several symbols are to be transmitted), followed by 3 second time cycles s2 whose total duration (3032) is determined from the frequency F2sy of the frequency couple (F 1sy , F 2sy ).

[0156] Each third time cycle s3a has a total duration 3033 defined from a starting frequency F s emission of at least one symbol. The starting frequency F s is determined so that during a replacement, during the modulation of the light signal (step 530), of the starting frequency F s by a frequency of a determined pair of frequencies, the highest frequency, among said frequency of said pair of frequencies and the starting frequency F s , is at most equal to twice the lowest frequency, among said frequency of said determined frequency pair and the starting frequency F s The number of the third time cycle s3 is defined from the frequency of frequency change.

[0157] According to this last particular embodiment of substep 5220, at least one of the time cycles in the succession of time cycles can have a total duration defined from the starting frequency F s .

[0158] The time sequence of frequencies used for modulating the light signal is then given by [F s ][F 1sy ][F 2sy ].

[0159] According to a particular embodiment of substep 5220, illustrated in Figure 1, at least one fourth time cycle s4 may be added to the sequence of time cycles of the control signal 300. This at least fourth time cycle s4 follows the last of this at least second time cycle s2 of the sequence of time cycles of the control signal 300, the total duration of which is a function of the second frequency F. 2s of the frequency couple (F 1s , F 2s ) representing the last symbol issued.

[0160] According to the example above, if a symbol s y is emitted with a change frequency equal to 1 / 3, the succession of time cycles of the control signal 300 comprises the first 3 time cycles s1 whose total duration (3031) is determined from the frequency F 1sy of the frequency pair (F 1sy , F 2sy ) representing the symbol s y to be emitted, followed by 3 second time cycles s2 whose total duration (3032) is determined from the frequency F 2s1 of the frequency couple (F 1s1 , F 2s1 ) followed by 3 temporal cycles s4.

[0161] Each fourth time cycle s4a has a total duration of 1034 defined from an end frequency F e of emission of at least one symbol. The end frequency F eThe emission frequency of at least one symbol is determined so that, during the modulation of the light signal (step 530), a frequency of a pair of frequencies is replaced by the end frequency F e , the highest frequency, among said frequency of said frequency pair and the end frequency F e , is at most equal to twice the lowest frequency, among said frequency of said frequency pair and the end frequency F e The fourth time cycle number s4 is defined from the frequency of frequency change.

[0162] According to this last particular embodiment of substep 5220, at least one of the time cycles in the succession of time cycles can have a total duration defined from the end frequency F e .

[0163] The time sequence of frequencies used for modulating the light signal is then given by [F 1sy ][F2sy ] [F e ].

[0164] Laillustre un example de schematicement un example de temps évolution du signal de contrôle 300 utile pour contrôle de modulation du signal lumière selon un example d’incarnation particulier de la présent invention.

[0165] According to this example, the succession of time cycles of the control signal 100 comprises the first, second, third, and fourth time cycles described above. The control signal 300 is described here with a frequency change frequency of 1 / 3, i.e., each time cycle is repeated three times. The time sequence of frequencies used for modulating the light signal is then given by [F s ] [F 1sy ][F 2sy ] [F e ].

[0166] According to a particular embodiment of the present invention, the highest frequency among the frequencies of said at least one determined pair of frequencies is at most equal to twice the lowest frequency among the frequencies of said at least one determined pair of frequencies.

[0167] This example of implementation ensures that the constraint on frequencies is verified regardless of changes between the frequencies of said at least one determined frequency pair during the modulation of the light signal.

[0168] According to a particular embodiment of the present invention, the highest frequency among the frequencies of said at least one determined frequency pair and the starting frequency F s is at most equal to twice the lowest frequency among the frequencies of said at least one determined pair of frequencies and the starting frequency F s .

[0169] This example implementation ensures that the frequency constraint is satisfied regardless of changes between the frequencies of at least one determined frequency pair and between the frequencies of at least one determined frequency pair and the starting frequency F s .

[0170] According to a particular embodiment of the present invention, the highest frequency among the frequencies of said at least one determined couple and the end frequency F e is at most equal to twice the lowest frequency among the frequencies of said at least one determined pair and the end frequency F e .

[0171] This example implementation ensures that the frequency constraint is satisfied regardless of changes between the frequencies of said at least one determined frequency pair and between said at least one determined frequency pair and the end frequency F eduring the modulation of the light signal.

[0172] According to a particular embodiment of the present invention, the highest frequency among the frequencies of said at least one determined couple, the starting frequency F s and the end frequency F e is at most equal to twice the lowest frequency among the frequencies of said at least one determined pair, the starting frequency F s and the end frequency F e .

[0173] This example implementation ensures that the frequency constraint is satisfied regardless of changes between the frequencies of at least one determined frequency pair and between the frequencies of at least one determined frequency pair, the starting frequency F s and the end frequency F e during the modulation of the light signal.

[0174] According to a particular embodiment of substep 1220, at least one fifth time cycle s5 is added to the sequence of time cycles of the control signal 300 following the last of each series of at least one time cycle in the sequence of time cycles whose duration is determined from a specified frequency. The number of fifth time cycles s5 is defined from the frequency of frequency change.

[0175] If the succession of time cycles of the control signal 300 also includes at least a third time cycle s 3, the succession of time cycles of the control signal 300 may further include at least a fifth time cycle s5, said at least a fifth time cycle s5 being following the last of said at least a third time cycle s3.

[0176] If the succession of time cycles of the control signal 300 also includes at least a fourth time cycle s4, the control signal 300 may further include at least one fifth time cycle s5, said at least one fifth time cycle s5 being following the last of said at least one fourth time cycle s4.

[0177] Laillust schematically illustrates an example of the time evolution of the control signal 300 used to control the modulation of a light signal according to a particular embodiment of the present invention.

[0178] According to the example above, a symbol s yemitted with a change frequency of 1, the succession of time cycles of the control signal 300 includes a third time cycle s3 (last time cycle of a series of 1 third time cycle s3) followed by a fifth time cycle s5 followed by a first time cycle s1 (last time cycle of a series of 1 first time cycle s1) followed by a fifth time cycle s5 followed by a second time cycle s2 (last time cycle of a series of 1 second time cycle s2) followed by a fifth time cycle s5 followed by a fourth time cycle s4 (last time cycle of a series of 1 fourth time cycle s4) followed by a fifth time cycle s5.

[0179] Each fifth time cycle s5a has a total duration 3035 defined from a cutoff frequency F c The cutoff frequency F c is determined so that during a replacement, during the modulation of the light signal (step 530), of the cutoff frequency Fc by a frequency of a determined pair of frequencies or by the end frequency F e or during a replacement of a frequency of a determined pair of frequencies or the starting frequency F s by the cutoff frequency F c , the highest frequency, among said frequency of said pair of frequencies, the starting frequency F s , the end frequency F e and the cutoff frequency F c , is at most equal to twice the lowest frequency, among said frequency of said frequency pair, the starting frequency F s , the end frequency F e and the cutoff frequency F c .

[0180] According to this last particular embodiment of substep 5220, at least one of the time cycles in the succession of time cycles can have a total duration defined from the cutoff frequency F c .

[0181] According to the example above, the time sequence of frequencies used for modulating the light signal is then given by [F s ] [F c ] [F 1sy ] [F c ] [F 2sy ] [F c ][F e ][F c ].

[0182] According to a particular embodiment and limiting my statement of the present invention, if the frequencies of said at least a determined pair of frequencies, the starting frequency F s and the end frequency F e belong to a set F of frequencies whose highest frequency is less than or equal to four times the lowest frequency, the cutoff frequency is defined as a median value between the highest and lowest frequencies of the set F of frequencies.

[0183] The use of the cutoff frequency F cis advantageous because it allows increasing the difference between the lowest and highest frequencies among the frequencies of said at least one determined range of frequencies, the starting frequency F s and the end frequency F e .

[0184] Indeed, to prevent a visible flicker from appearing (when the light signal belongs to the visible spectrum) during a frequency replacement during the modulation of the light signal, at least a fifth time cycle s5 is added in the succession of time cycles of the control signal 300 between each series of time cycles s1, s2, s3, s4.

[0185] Thus, the replacement of a first frequency of a determined frequency pair during the modulation of the light signal by the cutoff frequency F c then the replacement of the cutoff frequency F cBy using a second frequency within the frequency pair, the frequency constraint is checked and a visible flicker of the light signal (when this light signal belongs to the visible spectrum) is avoided, which would occur if the first frequency were replaced by the second frequency without passing through the cutoff frequency. The same applies to any other frequency change, particularly that of the start frequency F. s of emission of said at least one symbol by a frequency of a pair of frequencies or that of a frequency of a pair of frequencies by the end frequency F e .

[0186] The light intensity of a PWM-modulated light signal varies according to a duty cycle defined by the ratio of the duration of a high level of the PWM signal to the duration of a low level of the PWM signal.

[0187] The illustration shows examples of PWM signals with a period of pPWM and duty cycles (DC) ranging from 0% (light intensity level read) to 100% (maximum light intensity level). The dotted line on the illustration represents a resulting light intensity level.

[0188] According to a particular embodiment of the present invention, the duty cycle can be at most equal to 85%.

[0189] This particular embodiment prevents the equipment from being subjected to excessive stress and the risk of overheating. For example, if the highest frequency in the set F of frequencies is 5 kHz, the duration of each time cycle will not exceed 30 ms, thus preventing the light signal emitter and receiver devices implementing the present invention from overheating.

[0190] According to a particular embodiment of the present invention, the duty cycle can be at least equal to 15%.

[0191] This example is advantageous because it guarantees that the light signal receiving device receives enough light to demodulate that light signal.

[0192] According to a particular embodiment of the present invention, the duty cycle of each time cycle of the control signal 300 can be equal to the same value within a deviation around this value, i.e. that this duty cycle is quasi-constant.

[0193] Figure 1 illustrates an example of a PWM signal with a constant duty cycle of 50% for frequencies of 3 kHz and 4 kHz. The PWM signal is a gate signal comprising rising and falling edges. In Figure 1, the rising edges are marked by dots.

[0194] Maintaining a constant duty cycle avoids effects of variation in light intensity, and therefore visible flickering (when the light signal belongs to the visible spectrum).

[0195] According to a particular embodiment of the present invention, the frequency change can be triggered synchronously with a rising or falling edge of the control signal 300.

[0196] This example makes it possible to keep the duty cycle constant and to avoid the appearance of visible flickering of the modulated light signal (when this light signal belongs to the visible spectrum).

[0197] Laillustre un flowchart des différents étapes d’un processus de recevoir d’at least un symbole porté par un signal lumière modulated par le signal de contrôle 300, selon une exemple d’incarnation particulier de la présent invention.

[0198] The light intensity of the light signal is modulated by a control signal 300 consisting of a succession of time cycles. Each time cycle is defined by an alternation between a high level, corresponding to a high level of light intensity of the light signal (the "on" signal), maintained for a first duration, and a low level, corresponding to a low level of light intensity of the light signal (the "off" signal), maintained for a second duration. The total duration of each time cycle is defined from a frequency within a set F of frequencies. For example, the modulation of the light signal is controlled by the control signal 300 generated by the process of...

[0199] In step 610, the light signal is received and sampled according to a sampling frequency.

[0200] For example, the received light signal is sampled at a frequency of 44kHz.

[0201] In a step 620, the light signal is demodulated to obtain said at least one symbol, each symbol being represented by a pair of frequencies detected from a spectral analysis of samples of the received light signal.

[0202] The detected frequencies of said at least one pair of frequencies comply with the constraint on the frequencies described above, that is to say that when a first detected frequency is replaced by a second detected frequency during the demodulation of the light signal, the highest frequency, among said first and second detected frequencies, is at most equal to twice the lowest frequency, among said first and second detected frequencies.

[0203] According to a particular embodiment of the present invention, the highest frequency among the detected frequencies of said at least one pair of frequencies is at most equal to twice the lowest frequency among the detected frequencies of said at least one pair of frequencies.

[0204] Laillustre un flowchart of the sub-steps of the 620 demodulation step of the light signal for the reception of said at least one symbol, according to a particular embodiment of the present invention.

[0205] Step 620 is an iterative step. At each iteration, a symbol s y is obtained by executing substeps 6210-6260.

[0206] In substep 6210, a first frequency F 1,sy is detected from a frequency spectrum of the light signal determined from a set E1d'samples of the received light signal.

[0207] In substep 6220, a second frequency F2,sy is detected from a frequency spectrum of the light signal determined from a set E2d'samples of the received light signal.

[0208] In substep 6230, the symbol s y is determined from the frequency pair (F 1,sy, F 2,sy ) detected.

[0209] The first frequency F 1,sy and the second frequency F 2,sy detected from the frequency pair (F 1,sy, F 2,sy ) comply with the frequency constraint described above.

[0210] According to a particular embodiment of the present invention, in substep 6240, a starting frequency F s At least one symbol can be detected from a frequency spectrum of the light signal determined from a set E3 of samples of the received light signal, the detection of the starting frequency F spreceding the detection of a first frequency of a first pair of frequencies representing a first symbol to be received.

[0211] Detection of the starting frequency F s indicates the start of the demodulation process of the received light signal for the reception of at least one symbol.

[0212] According to a particular embodiment of the present invention, in a substep 6250, a termination frequency F e The reception of said symbol, at least one symbol, can be detected from a frequency spectrum of the light signal determined from a set E4 of samples of the received light signal, the detection of the end frequency F e following the detection of a second frequency of a pair of frequencies representing a final symbol to be received.

[0213] The detection of the end frequency F e indicates that the last symbol to be received has been received.

[0214] According to a particular embodiment of the present invention, the detected frequencies of said at least one pair of frequencies, the starting frequency F s detected and the end frequency F e detected can belong to a set F of frequencies whose highest frequency is at most equal to twice the lowest frequency of the set F of frequencies.

[0215] For example, the frequency set F includes frequencies ranging from 2kHz to 4kHz.

[0216] According to a particular embodiment of the present invention, in a substep 6260, a cutoff frequency F c can be detected from a frequency spectrum determined from a set E5 of samples of the received light signal, the cutoff frequency F ccan be defined as a median value between the highest and lowest frequencies of the set F of frequencies, the highest frequency of the set F of frequencies being at most equal to four times the lowest frequency of the set F of frequencies, the cutoff frequency F c being detected following the detection of each frequency of each pair of frequencies.

[0217] According to one variant, the cutoff frequency F c can also be detected following the detection of the starting frequency F s .

[0218] According to one variant, the cutoff frequency F c can also be detected following the detection of the end frequency F e .

[0219] The use of the cutoff frequency F cis advantageous because it allows increasing the amplitude of the entire frequency range F compared to the previous implementation example which does not use a cutoff frequency F c .

[0220] For example, the frequency set F includes frequencies that can range from 2kHz to 8kHz.

[0221] Furthermore, the use of the cutoff frequency F c This allows the received light signal to be demodulated without needing to know a parameter of the modulation process, because the cessation of score updates, described later, is determined by the time interval between the detection of two consecutive cutoff frequencies. This time interval can vary depending on, for example, the lighting conditions in the environment of the light signal emitter.

[0222] According to a particular embodiment of the present invention, the frequencies of the set F of frequencies are less than 5kHz.

[0223] For example, the frequency set F includes frequencies ranging from 2kHz to 5kHz and the median frequency F c is equal to 3.5kHz.

[0224] According to a particular embodiment of the present invention, the detection of a frequency (step 6210, 6220, 6240, 6250 and 6260) from a frequency spectrum of the light signal determined from a set of samples may include steps 6270 and 6280.

[0225] Laillustre an example of steps 6210, 6220, 6240, 6250 and 6260 of step 620 of light signal demodulation, according to a particular embodiment of the present invention.

[0226] Steps 6210, 6220, 6240, 6250 and 6260 each detect a frequency F r (first frequency F 1,s , second frequency F 2,s , starting frequency F s , end frequency F e , cutoff frequency F c ) from a set of samples Ei (i=1 to 5).

[0227] In step 6270, SCi scores associated with the frequencies of the frequency set F are evaluated from the amplitudes of the corresponding frequencies of the frequency spectrum determined from the sample set E i .

[0228] According to a particular embodiment of the present invention, step 6270 comprises substeps 6271 to 6273.

[0229] In substep 6271, a frequency spectrum SPi of the light signal is determined from continuously received samples of the light signal. This means that spectral analysis is performed over a sliding time window so that the frequency spectrum is updated as new samples of the light signal become available. Thus, the first set E1(i=1) of available samples is formed (for example, the first 128 samples), and a frequency spectrum of the light signal is determined. At least one new sample becomes available, and the second set of samples E2(i=2) is formed from this at least one new sample and, possibly, from at least one sample from the first set E1. At least one new sample becomes available, and the third set E3(i=3) of samples is formed from this at least one new sample and, possibly, from at least one sample from the second set E2, and so on.

[0230] For example, each sample set comprises 128 samples (N=128).

[0231] According to a particular embodiment of the present invention, a frequency spectrum of the light signal is determined by applying a discrete Fourier transform to samples of a set of samples of the received light signal.

[0232] To do this, N samples x(n) (n=0,…, N-1) of the received light signal are defined on the sliding time window of duration T=N*Te with Fe=1 / Te. N points S(k) of the frequency spectrum are then determined on this time window of duration T by applying the discrete Fourier transform, each of these points S(k) corresponding to a particular frequency and amplitude of a frequency component of the frequency spectrum:

[0233]

[0234] Laillustre an example of a frequency spectrum SPi determined by discrete Fourier transform of a set of samples E i The frequency spectrum is represented in a two-dimensional space where the x-axis represents the frequencies composing this frequency spectrum and the y-axis represents the amplitudes corresponding to these frequencies. In the example, the frequency spectrum SP1 is determined from N=11 samples.

[0235] In substep 6272, the SCi scores associated with the frequencies of the F set of frequencies are initialized, for example to 0.

[0236] In substep 6273, the SCi score of each frequency in the set F of frequencies is updated from the frequency amplitudes of at least one SPi frequency spectrum determined from at least one sample set E i .

[0237] This illustrates an example of updating the SCi scores associated with the frequencies of the set F of frequencies from three SPi spectra determined from three sets E i of consecutive samples according to a particular embodiment of the present invention.

[0238] According to the example, the set F of frequencies comprises three frequencies F1, F C and F2. At a), the SC1 score associated with the frequency F1 is updated from the amplitude a1 of the first of the three frequency spectra, the SC score c of the cutoff frequency F c is updated from the amplitude a c The SC2 score for frequency F2 is updated from the amplitude a2 of the first of the three frequency spectra. In lab), the SC1 score associated with frequency F1 is updated from the amplitude corresponding to frequency F1 of the second of the three frequency spectra. cof the cutoff frequency F c is updated from the amplitude a c corresponding to the cutoff frequency F c The second of the three frequency spectra and the SC2 score of frequency F2 is updated from the amplitude a2 corresponding to frequency F2 of the second of the three frequency spectra. At lac), the SC1 score associated with frequency F1 is updated from the amplitude corresponding to frequency F1 of the third of the three frequency spectra, the SC score c of the cutoff frequency F c is updated from the amplitude a c corresponding to the cutoff frequency F c of the third of the three frequency spectra and the SC2 score of the frequency F2 is updated from the amplitude a2 corresponding to the frequency F2 of the third of the three frequency spectra.

[0239] As an example, an SCi score associated with a frequency from the F set of frequencies is updated from a frequency spectrum by adding the amplitude of that frequency from the frequency spectrum.

[0240] According to a particular example of the present invention, the updating of scores stops when a variation between two frequencies detected from two consecutive frequency spectra is greater than a threshold.

[0241] This example implementation allows the updating of scores to be stopped without the demodulator knowing the modulation parameters of the light signal such as the frequency of frequency change.

[0242] As an example, the threshold value may vary depending on the lighting conditions of an environment in which the light signal is received.

[0243] For example, the lower the lighting conditions, e.g., the lighting conditions in the immediate environment of the light signal demodulator indicate low brightness, and the lower the threshold value will be.

[0244] For example, the threshold value may vary proportionally to the ambient brightness of the light signal receiver.

[0245] In substep 6280, after the scores have been updated, the frequency F r is detected among the frequencies of the set F of frequencies from the SCi scores associated with the frequencies of the set F of frequencies.

[0246] For example, the frequency associated with the highest score is the F frequency. r detected.

[0247] According to a particular embodiment of the present invention, a symbol is represented by a pair of frequencies (F 1,s , F 2,s) and the association between a symbol and a pair of frequencies is stored in a reference frequency table.

[0248] Laillum illustrates an example of a base-64 table that groups 64 associations between symbols and frequency pairs, according to a particular embodiment of the present invention. In this example, the symbols A, B, etc., are represented by frequency pairs expressed in binary form, in which each frequency is identified by three bits. For example, the symbol 'E' is associated with the binary word 000100, where 000 identifies the first frequency of the frequency pair and 100 identifies the second frequency of the frequency pair.

[0249] Laillust schematically illustrates a device 1 configured to emit and / or receive at least one symbol carried by a light signal modulated by a control signal, according to a particular embodiment of the present invention.

[0250] Device 1 is, for example, configured to carry out the operations described opposite the steps of at least one of the processes described opposite Figures 5, 10, and 18-20. Examples of such a device 1 include, but are not limited to, electronic equipment used, for example, for lighting an enclosed environment. The elements of device 1, individually or in combination, can be integrated into a single integrated circuit, into several integrated circuits, and / or into discrete components. Device 1 can be implemented as electronic circuits or software (or computer) modules, or a combination of electronic circuits and software modules.

[0251] Device 1 comprises one (or more) microprocessor(s) 10 configured to execute instructions for carrying out the steps of at least one of the processes described opposite Figures 5, 10, 18-20. The microprocessor 10 may include integrated memory, an input / output interface, and various circuits known to those skilled in the art. Device 1 may further comprise at least one memory 11, for example, volatile and / or non-volatile memory, and / or include a memory storage device that may comprise volatile and / or non-volatile memory, such as EEPROM, ROM, PROM, RAM, DRAM, SRAM, flash, magnetic disk, or optical disk.

[0252] The computer code comprising the instructions corresponding to the steps of at least one of the processes described opposite figures 5, 10, 18-20 which it is necessary to load and execute by the microprocessor 10 is for example stored on memory 11.

[0253] According to various specific embodiment examples, device 1 can be configured to be coupled in communication with other similar devices or systems and / or with external devices such as, for example, remote servers equipped with means of communication.

[0254] According to a particular embodiment, the device 1 may include a block 12 of interface elements for communicating with these external devices. The interface elements of the block 12 may include one or more of the following interfaces: - radio frequency RF interface, for example of the Wi-Fi® type (according to IEEE 802.11), for example in the 2.4 or 5 GHz frequency bands, or of the Bluetooth® type (according to IEEE 802.15).1), in the 2.4 GHz frequency band, or Sigfox type using UBN (Ultra Narrow Band) radio technology, or LoRa in the 868 MHz frequency band, LTE (Long-Term Evolution), LTE-Advanced; USB interface (Universal Serial Bus); HDMI interface (High Definition Multimedia Interface); LIN interface (Local Interconnect Network).

[0255] According to one particular embodiment, device 1 can provide output signals to one or more external devices, such as a display screen 15, touch or non-touch, one or more speakers 16 and / or other peripherals 17 via output interfaces 18, 19, 20 respectively. According to a variant, one or more of the external devices is integrated into device 1.

[0256] The illustration schematically shows an implementation of the device 2 for emitting light signals configured to emit at least one symbol carried by a light signal modulated by the control signal 300 according to a particular example of the present invention.

[0257] Device 2 includes a driver 180 (driver in English) which provides electrical power to the other electrical elements of device 1. For example, driver 180 converts an alternating voltage of 110-220v into a direct voltage of 7-50V.

[0258] Device 2 also includes a pilot signal generator 181 and a light signal generator 182 driven by the pilot signal at the output of generator 181.

[0259] For example, the light signal generator 182 is a light-emitting diode driven by the pilot signal at the output of the generator 181.

[0260] The generator 181 includes a microcontroller 183 configured to generate the control signal 300 according to the process described opposite 1a and 6 and a DC voltage modulation means 184 driven by the control signal 300 to provide the signal which drives the voltage across the terminals of the light signal generator 182. For example the DC voltage modulation means 184 is a MOSFET type transistor.

[0261] For example, the MOSFET transistor is suitable to support frequencies of at least 100KHz.

[0262] According to one variant, the generator 181 may include a voltage converter 185 which adapts the output voltage of the driver 180 to the supply voltage of the microcontroller 183.

[0263] According to this device 2, the DC voltage modulation means 184 is controlled by the control signal 300 generated at the output of the microcontroller 183. The signal at the output of the DC voltage modulation means 184 drives the power supply of the light signal generator 182 to reproduce the variations in light intensity of the control signal 300. A symbol can then be transmitted by the light signal thus modulated which is produced by the light signal generator 182.

[0264] For example, the elements of the light signal generator 182 can be grouped on the same printed circuit board (PCB for Printed Circuit Board).

[0265] The localization methods and systems described above, as well as their variants, can be used to locate different types of equipment in various enclosed environments.

[0266] According to a first example, the location system of the present invention can be deployed to locate a shopping cart in a store or a trolley in an airport, for example. The store can be equipped with a network of light points (second devices 102) distributed across the store ceiling. Each shopping cart is equipped with a first device 101, and the third device 103 can be a computer in a store office. Each time a shopping cart moves, it can then be located under a new light point. A light point can also be located at a checkout counter so that a shopping cart's passage through the checkout is time-stamped with the light point at the checkout. It is then possible to determine the routes of the shopping carts within the store anonymously and to link, for all the shopping carts, the purchases and the routes that triggered those purchases.Purchase statistics can also be calculated based on the number of times shopping carts pass in front of certain light points, for example.

[0267] According to a second example, these processes and systems can be used by audio guides, for instance, in a museum. Light points (second piece of equipment 102) can be installed, for example, directly above exhibited works. Each audio guide can be equipped with a first piece of equipment 101, and the third piece of equipment 103 can be a wirelessly connected server that provides additional information, such as visuals, about a work of art as soon as the audio guide is under a light point illuminating that work or is near it. The visitor can thus receive audio commentary from the audio guide and view this visual information on a screen, for example, on their mobile phone. The visit is then interactive. It is also possible for the museum to obtain real-time statistics on visitor times and the number of visits to a work of art, as well as the associated visual information.

[0268] According to a third example, security badges allowing access to offices can incorporate initial equipment (101), such as an electronic chip. A network of light points (second piece of equipment, 102) can be positioned to divide a building into several zones, access to which is controlled by these security badges. A third piece of equipment could be a server controlling access to IT tools. When a staff member or visitor enters a zone authorized by their badge, the badge is located, and IT tools can then be granted to that staff member or visitor as long as their badge remains in that zone. For example, access to Wi-Fi® or an internal server can thus be granted without identification and with rights specific to each badge.When the staff member or visitor leaves the area, the IT tools are no longer accessible as long as the badge is no longer located in the authorized area.

[0269] According to a fourth example, a first device 101 can be implemented on a battery-free electronic key (dongle). As soon as this electronic key is connected to a computer, for example via a USB connection, a second device 102, located at a light point in the office where the computer is located, can emit a first light signal, which is received by the first device 101 on the key. The computer can then be located in the office, and access to IT tools can be granted to it as long as it is in that office. This application of the present invention makes it possible to limit the use of a Virtual Private Network (VPN) and adds security to a physical network.

[0270] According to a fifth example, the location system can be integrated into personal protective equipment (PPE) for a lone worker, such as a headlamp or helmet. When the PPE is stationary or subjected to an impact, it is configured to send an alert to a computer gateway. If a first device 101 is integrated into the PPE and the location system according to the present invention is deployed in the worker's location—for example, if that location is covered by a network of lights incorporating second devices 102—a controller receives the alert with the latest location provided by the location system and can then contact the worker to verify the situation. In case of no response or an accident, the controller can then provide the worker's location to the emergency services.

[0271] According to a sixth example, the location system of the present invention can be deployed in a building to monitor the movement of devices such as cleaning carts within a specific area of ​​the building. The area is covered by a network of light points equipped with secondary devices 102, and each cleaning cart is equipped with a primary device 101. Thus, as an employee moves their cleaning cart, the areas visited can be validated as having been cleaned. The device can also be worn by a security guard making a rounds in a building, and the areas visited can be validated as having been checked.

[0272] According to a seventh example, the localization system according to the present invention can be deployed to ensure that a product follows a predefined processing protocol. For example, dental prostheses must undergo a set sequence of treatments during their manufacture. A first device 101 can be mounted in or on a box containing a dental prosthesis to be manufactured, and the various locations of the processing units can be covered by light points mounted on second devices. Thus, each time the box containing the dental prosthesis is located at a processing unit location, the box is located, and the treatment applied by the processing unit can then be validated as having been completed. Real-time monitoring of the dental prosthesis manufacturing process can then be obtained, as well as processing time statistics for each processing unit.

[0273] According to an eighth example, the location system according to the present invention can be deployed to access operating instructions or digital exploded views of a machine without having to navigate through menus. For example, a machine associated with a first piece of equipment 101 can be illuminated by a light point equipped with a second piece of equipment. The machine can be located and identified by a third piece of equipment 103, for example, a data server, using an identifier from the second piece of equipment 102. The data server can then instruct the second light point 102 to emit information that triggers the display of an operating instruction manual or an exploded view of the machine on a screen near the machine.

[0274] According to a ninth example, the location system of the present invention can be used to reserve a meeting room using a badge. The badge incorporates a first device 101, and the room includes at least one light fixture incorporating a second device 102. A third device 103, via a data server, is configured to manage room reservations based on the badge's entry and exit from the room. When a person is located in a specific area of ​​a building, they can be directed to the nearest available meeting room. When the badge is located as being in the meeting room, the data server reserves the room. When the badge is located outside the meeting room, the data server releases the room. The use of the location system increases the room reservation rate and prevents overbooking of meeting rooms.

[0275] According to a tenth example, the location system of the present invention can be deployed in a parking lot to indicate an available space to a vehicle. The vehicle carries a navigation system configured to calculate a route based on the received location information of a parking space. Each parking space can be associated with a light point incorporating a second device 102. A third device 103, for example a data server, is configured to determine the available parking spaces based on the information returned by the first devices 101 carried by the vehicles. As the vehicle moves within the parking lot, it is located by the second device 102 and the first device 101 carried by that vehicle.The third piece of equipment 103 can then send this vehicle location information of an available space in the parking lot and the on-board navigation system recalculates a route to get from its current position to that parking space.

[0276] Of course, the present invention is not limited to the embodiments described above but extends to a method for locating equipment in a closed environment that would include secondary steps without departing from the scope of the present invention. The same would apply to a device configured for implementing such a method.

Claims

Method for locating a first piece of equipment (101) in a closed environment characterized in that it comprises the following steps:- emission (210), by a second piece of equipment, of a first light signal modulated according to at least one pair of frequencies, each pair of frequencies representing a symbol and said at least one symbol represented identifying a location in the closed environment of the second piece of equipment;- the frequencies of said at least one pair of frequencies being determined such that during a replacement, during the modulation of the first light signal, of a first frequency by a second frequency of said at least one pair of frequencies, the highest frequency, among said first and second frequencies, is at most equal to twice the lowest frequency, among said first and second frequencies;- reception (220), by the first piece of equipment, of the first light signal and obtaining said at least one symbol by demodulation of the first light signal received; - transmission (230) of a second signal carrying said at least one symbol; - reception (240), by a third piece of equipment, of the second signal carrying said at least one symbol; and - obtaining (250), by the third piece of equipment, the location of the first piece of equipment from said at least one symbol carried by the second signal received. Method according to claim 1, wherein the second signal bearing said at least one symbol is emitted (230), by the first piece of equipment, to the third piece of equipment. A method according to claim 1, wherein the transmission of the second signal bearing said at least one symbol comprises the following steps: - transmission (233), by the first equipment, of a third signal to the second equipment; - reception (234), by the second equipment, of the third signal and obtaining said at least one symbol; - transmission (235), by the second equipment (102), of the second signal (1012) bearing said at least one symbol to the third equipment (103). A method according to any one of claims 1 to 3, wherein the second signal is a second light signal modulated according to said at least one pair of frequencies representing said at least one symbol and wherein obtaining said at least one symbol (250) includes demodulation of the second light signal received. A method according to claim 3 or 4, wherein the third signal is a third light signal modulated according to said at least one pair of frequencies representing said at least one symbol and wherein obtaining said at least one symbol (250) includes demodulating the third light signal received. A method according to claim 5, wherein the first, second or third light signal bearing said at least one symbol is a signal modulated by a control signal comprising a succession of time cycles, each time cycle being defined by an alternation of a high level corresponding to a high level of light intensity of the modulated light signal maintained for a first duration and a low level corresponding to a low level of light intensity of the light signal maintained for a second duration, a total duration of each time cycle being defined from a frequency. A method according to claim 6, wherein the emission (210, 230, 233) of the first, second or third light signal modulated by the control signal comprises the following steps:- determination (510) of said at least one pair of frequencies;- generation (520) of the succession of time cycles, the total duration of at least one time cycle being defined from each frequency of each determined pair of frequencies;- modulation (530) of the light signal by the generated control signal; and- emission (540) of the modulated light signal. A method according to claim 7, wherein the highest frequency among the frequencies of said at least one determined pair of frequencies is at most equal to twice the lowest frequency among the frequencies of said at least one determined pair of frequencies. A method according to claim 7 or 8, wherein at least one of the time cycles in the succession of time cycles has a total duration defined from a starting frequency of the emission of said at least one symbol, the starting frequency of the emission of said at least one symbol being determined such that, during the modulation of the first, second or third light signal, the starting frequency of the emission of said at least one symbol is replaced by a frequency of one of said at least one determined pair of frequencies, the highest frequency, among the starting frequency of the emission of said at least one symbol and said frequency of said pair of frequencies, is at most equal to twice the lowest frequency, among the starting frequency of the emission of said at least one symbol and said frequency of said pair of frequencies. A method according to any one of claim 9, wherein at least one of the time cycles of the succession of time cycles has a total duration defined from an end-of-emission frequency of said at least one symbol, the end-of-emission frequency of said at least one symbol being determined such that during a replacement, during the modulation of the first, second or third light signal, of a frequency of one of said at least one pair of frequencies determined by the end-of-emission frequency of said at least one symbol, the highest frequency, among the end-of-emission frequency of said at least one symbol and said frequency of said pair of frequencies, is at most equal to twice the lowest frequency, among the end-of-emission frequency of said at least one symbol and said frequency of said pair of frequencies. A method according to claim 10, wherein the highest frequency among the frequencies of said at least one determined pair of frequencies, the emission start frequency of said at least one symbol and the emission end frequency of said at least one symbol is at most equal to twice the lowest frequency among the frequencies of said at least one determined pair, the emission start frequency of said at least one symbol and the emission end frequency of said at least one symbol. A method according to claim 11, wherein at least one of the time cycles in the succession of time cycles has a defined duration starting from a determined cutoff frequency such that, during the modulation of the first, second, or third light signal, the cutoff frequency is replaced by a frequency of said at least one determined pair of frequencies or by the emission termination frequency of said at least one symbol, or during the replacement of a frequency of said at least one determined pair of frequencies or the emission start frequency of said at least one symbol by the cutoff frequency, the highest frequency among said frequency of said pair of frequencies, the emission start frequency of said at least one symbol, the emission termination frequency of said at least one symbol, and the cutoff frequency, is at most equal to twice the lowest frequency among said frequency of said pair of frequencies.the transmission start frequency of said at least one symbol, the transmission end frequency of said at least one symbol, and the cutoff frequency. A method according to claim 12, wherein if the frequencies of said at least one determined pair of frequencies, the start-up frequency of said at least one symbol and the end-up frequency of said at least one symbol belong to a set of frequencies whose highest frequency is less than or equal to four times the lowest frequency, the cutoff frequency is defined as a median value between the highest and lowest frequencies of the set of frequencies. A method according to any one of claims 6 to 13, wherein the control signal being a gate signal comprising a rising edge and a falling edge per time cycle, a replacement of one determined frequency by another determined frequency is triggered on the rising or falling edges of the time cycles. A method according to any one of claims 6 to 14, wherein each time cycle whose total duration is defined by a frequency is repeated a defined number of times from a frequency of frequency change. A method according to claim 15, wherein the frequency of frequency change is at most equal to 100Hz. A method according to claim 15, wherein the frequency of frequency change varies according to lighting conditions of an environment in which the light signal is emitted. A method according to any one of claims 7 to 17, wherein a duty cycle of each time cycle of the control signal is equal to the same value within a deviation around that value. A method according to claim 6, wherein the reception (610, 240, 234) of the first, second or third light signal modulated by the control signal comprises the following steps: - reception and sampling (610) of the light signal; and - demodulation (620) of the light signal to obtain said at least one symbol, each symbol being represented by a pair of frequencies detected from a spectral analysis of samples of the received light signal; - the detected frequencies of said at least one pair of frequencies being such that when a first detected frequency is replaced by a second detected frequency during the demodulation of the light signal, the highest frequency, among said first and second detected frequencies, is at most equal to twice the lowest frequency, among said first and second detected frequencies. A method according to claim 19, wherein the highest frequency among the detected frequencies of said at least one pair of frequencies is at most equal to twice the lowest frequency among the detected frequencies of said at least one pair of frequencies. Method according to claim 19 or 20, further comprising a detection step (6240) of a reception start frequency of said at least symbol from a frequency spectrum of the light signal determined from a first set of samples of the received light signal, the detection of the reception start frequency of said at least one symbol preceding the detection of a first frequency of a first pair of frequencies representing a first symbol to be received. Method according to claim 21, further comprising a step of detecting (6250) a reception end frequency of said at least one symbol from a frequency spectrum of the light signal determined from a second set of samples of the received light signal, the detection of the reception end frequency of said at least one symbol following the detection of a second frequency of a pair of frequencies representing a last symbol to be received. A method according to claim 22, wherein the detected frequencies of said at least one pair of frequencies, the reception start frequency of said at least one detected symbol, and the reception end frequency of said at least one detected symbol belong to a set of frequencies whose highest frequency is at most equal to twice the lowest frequency of the set of frequencies. A method according to claim 23, further comprising a step of detecting (6260) a cutoff frequency from a frequency spectrum determined from a fifth set of samples of the received light signal, the cutoff frequency being defined as a median value between the highest and lowest frequencies of the set of frequencies, the highest frequency of the set of frequencies being at most equal to four times the lowest frequency of the set of frequencies, the cutoff frequency being detected following the detection of each frequency of each pair of frequencies, the detection of the reception start frequency of said at least one symbol and the detection of the reception end frequency of said at least one symbol. A method according to any one of claims 23 or 24, wherein the frequencies of the frequency set are less than 5kHz. A method according to any one of the preceding claims, wherein said at least one symbol is determined from a table defining an association between each symbol and a pair of frequencies. Equipment location system comprising means for implementing the steps of the process according to any one of claims 1 to 26.

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