METHOD FOR DETECTING AN OBJECT USING A TIME-OF-FLIGHT SENSOR

Abstract

According to one aspect, a method for detecting at least one object (OBJ) within a detection zone (DET) is proposed, comprising: - emission of optical radiation by emission means (EM) of a time-of-flight (CTV) sensor, - reception by reception means (MR) of the time-of-flight (CTV) sensor of a quantity of optical radiation photons reflected by said at least one object (OBJ), - measurement by measurement means (MM) of the time-of-flight (CTV) sensor of a quantity of photons (SIGN) and a distance (DIST) between said time-of-flight (CTV) sensor and said at least one object (OBJ), and - analysis of the quantity of detected photons (SIGN) and the associated distance (DIST) so as to determine the presence of at least one object (OBJ) within a detection zone (DET) of the time-of-flight (CTV) sensor. Figure for the abstract: Fig 1

Description

Title of the invention: METHOD FOR DETECTING AN OBJECT BY A TIME-OF-FLIGHT SENSOR

[0001] Embodiments and implementations relate to object detection devices, in particular the detection of an object in a detection zone by a time-of-flight sensor.

[0002] A time of flight sensor is a sensor using the propagation of light to measure a distance between an object and the sensor. In particular, the time of flight sensor is configured to emit optical radiation, for example of the infrared or laser type, towards an object and to measure a time of flight, that is to say the time that elapses between the emission of this radiation and its reception by the sensor after the reflection of the radiation on the object. The measurement of the time of flight makes it possible to determine the distance between the object and the sensor, knowing the speed of the radiation.

[0003] Other known devices make it possible to detect an object from optical radiation, such as for example devices using an optical barrier (known by the English term "optical barrier"). The optical barrier typically has a group of LEDs (an acronym for "Light-Emitting Diode" in French) and a matrix of photodiodes each continuously receiving the optical radiation emitted by an LED. The matrix of photodiodes makes it possible to return a Boolean data item depending on whether an object has been detected, i.e. when a photodiode no longer receives radiation, or not, in the opposite case.

[0004] However, these devices are often more expensive and complex since the optical barrier is an application that may require the use of an integrated circuit dedicated to the application, usually referred to by the acronym "ASIC" for "Application-Specific Integrated Circuit", and a high computing power linked to the quantity of data to be processed from a high number of photodiodes that may result in excess energy consumption. In addition, the detection rate of these devices is often limited, and rarely exceeds 90%.

[0005] Furthermore, it is known that the algorithms implemented in the time-of-flight sensor are likely to generate erroneous results commonly called “false positives” when these indicate the presence of an object by mistake. Other erroneous results may come from a lack of detection of objects which are confused with the environment of the sensor, such as for example with walls, located in the detection zone of the sensor. These algorithms do not make it possible to obtain a sufficient detection rate to avoid these erroneous results and to make it possible to detect objects in any environment, especially objects near walls.

[0006] Furthermore, the sensor's detection is limited when these algorithms are used since they do not allow the sensor to detect small objects such as coins or dust particles. Dust particles, once accumulated in the detection area, can be as problematic as other larger objects in certain applications such as the display of data on a screen where certain parts may be masked by these objects.

[0007] Thus, there is a need to propose object detection solutions that make it possible to improve object detection.

[0008] According to one aspect, there is provided a method for detecting at least one object in a detection zone of a time-of-flight sensor, comprising:

[0009] - an emission of optical radiation by emission means of the sensor flight time,

[0010] - a reception by reception means of the time-of-flight sensor of a quantity of photons of optical radiation reflected by said at least one object,

[0011] - a measurement by measuring means of the time-of-flight sensor of a quantity of photons and a distance between the time-of-flight sensor and said at least one object,

[0012] - an analysis of the quantity of photons detected and the associated distance so as to determine the presence of at least one object in the detection zone of the time-of-flight sensor.

[0013] A time-of-flight sensor is therefore proposed using an object detection algorithm based on an analysis of two distinct types of measurement data: a quantity of photons detected by the sensor upon reception of the reflected optical radiation and a distance calculated from the time elapsed between the emission and reception of the optical radiation. The analysis relates the two types of data so that the values ​​of these data coincide upon the appearance of an object in the detection zone.

[0014] Measuring the quantity of photons of the reflected radiation and associating this quantity with the measured distance makes it possible to improve the accuracy of the detection of the object in the detection zone. Indeed, the quantity of photons of the reflected radiation also gives information on the position of the object, namely whether it is more or less close to the sensor, and also varies according to the nature of the object, in particular due to the material of the object which can influence its optical reflection properties. When the radiation is reflected by an object close to the sensor for example, the quantity of photons coming from the radiation reflected by the object is relatively high since the photons are almost all detected by the sensor. In other words, the ratio between the number of photons received and the number of emitted photons is close to 1 over short distances between the sensor and the object and decreases over longer distances.

[0015] When an object is located close to a wall, the analysis of the quantity of photons detected and the measured distance makes it possible to differentiate the object from the wall.

[0016] Furthermore, the use of a time-of-flight sensor has advantages in terms of integration which is less complex than with other photonic sensors, temperature compensation, energy consumption and detection rate since the time-of-flight sensor can make it possible to detect objects of reduced size. The time-of-flight sensor can for example detect objects of small dimensions, such as a coin when the edge of the coin is located opposite the sensor, the coin being able to have a width of approximately 11 mm and a thickness of approximately 1.5 mm. The time-of-flight sensor can also detect objects smaller than a coin, such as dust particles.

[0017] The detection method therefore uses a sensor recognized for its extended field of vision and its capacity to measure several parameters of optical radiation to improve the reliability of detection.

[0018] According to one embodiment, the analysis of the quantity of photons associated with the measured distance comprises a successive storage of N values ​​of quantities of photons and associated distances, a calculation of a central tendency indicator of quantity of photons from the N quantities of photons, and a calculation of a central tendency indicator of distance so that said at least one object is detected according to said calculated central tendency indicators.

[0019] The central tendency indicator, such as the mean or the median, corresponds to a statistical value making it possible to make a relatively precise estimate of the position of the object to be detected according to a series of values ​​of quantities of photons and distances measured. The central tendency indicators can be calculated on a number N of quantities of photons and distances measured successively over a time window, that is to say a given time interval, which can be sliding. The time interval can be more or less long depending on the number N of values ​​of quantity of photons and distance measured that one wishes to store and take into account in the calculation of the central tendency indicators. A high number N makes it possible to limit aberrant values ​​of certain measurement data generated in the same time interval and therefore not to produce an erroneous result on the detection of objects in the detection zone.

[0020] According to one embodiment, said at least one object is detected when the central tendency indicator of distance is included in the distance interval and when the central tendency indicator of photon quantities is included in an interval of photon quantities

[0021] The distance interval includes distance values ​​when no object is present in the detection zone. These values ​​generally correspond to objects that are of no interest to be detected. The distance interval therefore makes it possible to exclude these objects from detection by the time-of-flight sensor.

[0022] The sensor can be configured to define intervals of distances and quantities of photons for which it is assumed that an object is detected or not in the detection zone.

[0023] According to one embodiment, said at least one object being detected when the central distance tendency indicator is less than a first distance.

[0024] An object relatively close to the time-of-flight sensor can be reliably detected from the measured distance, regardless of the quantity of photons with which this distance is associated.

[0025] According to one embodiment, the central tendency indicator of photon quantities is a median of the N photon quantities and the central tendency indicator of distance is a median of the N associated distances.

[0026] Calculating the median value of photon quantities and distances can be advantageous in terms of reliability, since it allows reducing the influence of outliers on the detection result.

[0027] According to one embodiment, the central tendency indicator of photon quantities is an average of the N photon quantities and the central tendency indicator of distance is an average of the N associated distances.

[0028] Calculating the average is an alternative to calculating the median of photon quantities and associated distances.

[0029] According to another aspect, there is provided a method for detecting at least one object in a cavity comprising an opening through which said at least one object can enter and a bottom, a time-of-flight sensor being mounted on a wall of the cavity, the time-of-flight sensor having a detection zone extending between the time-of-flight sensor and a wall of the cavity opposite the time-of-flight sensor to the bottom of the cavity.

[0030] The method comprises an implementation of the method mentioned above by the time-of-flight sensor so as to detect the presence of said at least one object when it rests on the bottom of the cavity.

[0031] The method can therefore be implemented in the context of object detection in a partially closed space whose walls can be detected by the time-of-flight sensor. In this application, the method is particularly advantageous since it makes it possible to differentiate the detection of an object which rests at the bottom of the cavity from a detection of a wall of the cavity by the time-of-flight sensor.

[0032] According to one embodiment, the detection method comprises an emission of light beams by a screen located at the bottom of the cavity and an orientation of the light beams towards the outside of the cavity by an inclined mirror placed at the opening.

[0033] Thus, a cavity having such a structure makes it possible to transmit information displayed on the screen in a readable manner outside the cavity while protecting the screen located inside the cavity.

[0034] According to one embodiment, the method comprises a calibration of the time-of-flight sensor so as to determine the distance interval and the photon quantity interval from the detection of the wall of the cavity opposite the time-of-flight sensor.

[0035] Calibration allows, after installation of the sensor in a cavity for example, the recording by the sensor of the position of a wall so as not to confuse an object with this wall during the detection phase and thus facilitates its integration into a detection system comprising a cavity of variable dimensions.

[0036] According to another aspect, there is provided a time-of-flight sensor, comprising:

[0037] - emission means configured to emit optical radiation,

[0038] - receiving means configured to detect a quantity of photons of optical radiation reflected by said at least one object,

[0039] - measuring means configured to measure a quantity of photons and a distance between said time-of-flight sensor and said at least one object, and

[0040] - processing means configured to analyze the quantity of photons and the distance associated so as to determine the presence of at least one object in a detection zone.

[0041] According to one embodiment, the processing means comprise storage means configured to successively store N values ​​of quantities of photons and associated distances and calculation means configured to calculate a central tendency indicator of quantity of photons from the N quantities of photons and a central tendency indicator of distance from the N distances so that said at least one object is detected according to said calculated central tendency indicators.

[0042] According to one embodiment, said at least one object is detected when the central tendency indicator of distances is included in the distance interval and when the central tendency indicator of photon quantities is included in a photon quantity interval.

[0043] According to one embodiment, said at least one object is detected when the central distance tendency indicator is less than a first distance.

[0044] According to one embodiment, the central tendency indicator of photon quantities is a median of the N photon quantities and the central tendency indicator of distance is a median of the N associated distances.

[0045] According to one embodiment, the central tendency indicator of photon quantities is an average of the N photon quantities and the central tendency indicator of distance is an average of the N associated distances.

[0046] According to another aspect, there is provided a detection system comprising:

[0047] - a cavity comprising an opening through which said at least one object can to rush into the cavity and a bottom,

[0048] - a previously mentioned time-of-flight sensor, mounted on a wall of the cavity, the detection zone of the time-of-flight sensor extending between the time-of-flight sensor and a wall of the cavity opposite the time-of-flight sensor to the bottom of the cavity so as to be able to detect the presence of said at least one object when it rests on the bottom of the cavity.

[0049] According to one embodiment, the cavity comprises both a screen located at the bottom of the cavity and an inclined mirror placed at the opening and configured to direct light beams emitted by the screen towards the outside of the cavity.

[0050] According to one embodiment, the time-of-flight sensor comprises calibration means configured to determine the distance interval and the photon quantity interval from the detection of the wall of the cavity opposite the time-of-flight sensor.

[0051] Other advantages and characteristics of the invention will appear on examining the detailed description of embodiments and implementations, which are in no way limiting, and the appended drawings in which:

[0052] [Fig.l];

[0053] [Fig.2] ;

[0054] [Fig.3] ;

[0055] [Fig.4] ; and

[0056] [Fig.5] schematically illustrate modes of implementation and embodiment of the invention.

[0057] [Fig.l] schematically illustrates a CTV time-of-flight sensor according to one embodiment of the invention. The CTV time-of-flight sensor comprises emission means ME configured to emit optical radiation RE, such as an infrared light wave or a laser. The emission means ME may comprise a laser diode capable of generating the optical radiation RE continuously or periodically.

[0058] The emitted optical radiation RE travels a distance, for example a distance DI as described below in relation to [Fig.4], until it encounters an object OBJ located in a detection zone DET of the time-of-flight sensor CTV. The optical radiation RE is then reflected by the object OBJ. The time-of-flight sensor CTV comprises reception means MR configured to receive the reflected optical radiation RR continuously or periodically depending on the emission mode of the reflected radiation RR. The reception means MR comprise a matrix of single photon detectors of the single photon triggered avalanche diode type (known by the acronym “SPAD” for “Single Photon Avalanche Diode” in English) known per se to those skilled in the art.

[0059] The time-of-flight sensor CTV further comprises measuring means MM configured to measure a quantity of SIGN photons detected by the receiving means MR and a distance DIST between the CTV sensor and the object OBJ. The measuring means MM may be an electronic circuit for conditioning the electrical signal transmitted by the receiving means MR. The measurements carried out by the measuring means MM make it possible to generate measurement data MES which associate the quantity of SIGN photons with the measured distance DIST. For each detection of radiation reflected by an object OBJ, the quantity of SIGN photons is measured and a distance DIST of this object is determined relative to the CTV sensor. The quantity of SIGN photons may vary depending on the characteristics of the object OBJ to be detected, such as the size or shape of the object OBJ.

[0060] The CTV time-of-flight sensor also comprises processing means MT configured to analyze the quantity of photons SIGN associated with the measured distance DIST so as to determine the presence of at least one object OBJ in a detection zone DET. The processing means MT may be a processor for example. The detection zone DET refers to the physical area covered by the field of vision of the CTV time-of-flight sensor which generally extends up to a maximum detection distance DMAX. The maximum detection distance may depend on various factors related to the environment of the CTV sensor such as ambient light and also related to the size of the object to be detected. The CTV sensor may in particular be configured to be able to detect a coin at a distance of up to 300 mm for example.

[0061] The joint analysis of the quantity of SIGN photons of the reflected radiation RR and the distance DIST makes it possible to improve the accuracy of the detection of the object OBJ in the detection zone DET. Indeed, the quantity of SIGN photons of the reflected radiation RR, like the distance DIST, gives information on the position of the object OBJ, namely whether it is more or less close to the CTV sensor.

[0062] The processing means MT can also receive several values ​​of quantity of photons SIGN and distance DIST generated by the measuring means MM when several optical radiations are emitted by the emission means ME and received by the reception means MR. Consequently, the analysis can be carried out on the basis of several quantities of SIGN photons and DIST distances measured periodically by the MM measuring means and allowing the presence of an OBJ object to be determined throughout the duration of the emission of optical radiation.

[0063] Furthermore, the processing means MT comprise storage means MS and calculation means MC.

[0064] The storage means MS are configured to successively store N values ​​of quantities of photons and associated distances, where N=15 for example. The storage means MS may be a memory integrated in the time-of-flight sensor CTV such as a volatile memory. The values ​​of quantities of photons SIGN and distance DIST may be generated successively by the measuring means MM over a time window, i.e. over a given time interval, and stored periodically in the storage means MS. The number N may be predefined in the algorithm of the time-of-flight sensor CTV.

[0065] The calculation means MC are configured to calculate a central tendency indicator of photon quantity and a central tendency indicator of distance from the values ​​of photon quantities SIGN and distances DIST measured beforehand.

[0066] More particularly, the central tendency indicator of photon quantity may be an average of the N quantities of SIGN photons stored in the storage means MS and the central tendency indicator of distance may be an average of the N distances associated with the quantities of SIGN photons and also stored in the storage means MS.

[0067] Alternatively, the photon quantity central tendency indicator is a median of the N SIGN photon quantities and the distance central tendency indicator is a median of the N distances associated with the SIGN photon quantities.

[0068] These two central tendency indicators are calculated and then updated as soon as the N measurements of SIGN photon quantities and associated DIST distances are available in the memory of the CTV time-of-flight sensor.

[0069] The central tendency indicators can be calculated from a number N of quantities of photons and distances measured successively over a time window, that is to say a given time interval, which can be sliding. The time interval during which the measurement is carried out can be more or less long depending on the number N of quantities of photons and distances measured that one wishes to store and take into account in the calculation of the central tendency indicators. A high number N of measurement data makes it possible to limit aberrant values ​​of certain quantities of photons and distances measured in the same time interval and therefore not to produce an erroneous result.

[0070] [Fig.2] graphically illustrates the result of the analysis by the processing means MT in case no OBJ object is detected in the DET detection zone.

[0071] In the analysis illustrated in [Fig. 2], several measurements MES1 were carried out by the measurement means MM in the absence of objects OBJ in the detection zone DET and projected onto an ordinate axis corresponding to the quantities of photons and onto an abscissa axis corresponding to the distances. Furthermore, the quantities of photons SIGN come from radiation reflected by a wall of a cavity located in the detection zone DET at a distance included in a distance interval, for example between a first distance DI and a second distance D2 greater than the first distance D1.

[0072] The sensor may allow some distance deviations. In particular, the DIST distances measured by the CTV time-of-flight sensor may be slightly below or slightly above the actual distance between the CTV time-of-flight sensor and the wall depending on the conditions in which the radiation is emitted or received, for example.

[0073] The measured photon quantities are for example included in a photon quantity interval, for example between a first photon quantity SI and a second photon quantity S2 greater than the first photon quantity SL. The photon quantity interval and the distance interval are illustrated in [Fig.2] by a zone ZNE. The detection result can therefore be erroneous if the time-of-flight sensor CTV confuses the PAR wall with an object OBJ to be detected.

[0074] The processing means MT can be calibrated so as to define a distance interval and a photon quantity interval which are associated with a detection of the PAR wall located opposite the CTV time-of-flight sensor.

[0075] The first distance D1, the second distance D2, the first value SI and the second value S2 depend on the position of the wall PAR and, more generally, on the structure in which the time-of-flight sensor CTV is placed such as the cavity CAV which is described below in relation to [Fig.4].

[0076] The central tendency indicator of photon quantities SMIL1 and the central tendency indicator of distances DMIL1 are calculated from the different measurements MES1 of photon quantity and distance. The result of the analysis can be graphically represented by a value MIL1 corresponding to the value of the central tendency indicator of distance DMIL1 associated with the value of the central tendency indicator of photon quantity SMIL1.

[0077] The distance central tendency indicator DMIL1 is included in the distance interval, i.e. between the first distance D1 and the second distance D2, and the photon quantity central tendency indicator SMIL1 is included in the interval of quantity of photons, between the first value SI and the second value S2 and makes it possible to conclude that there is an absence of object OBJ in the detection zone DET.

[0078] [Fig.3] graphically illustrates the result of the analysis by the processing means MT in the case where an object OBJ is detected in the detection zone DET.

[0079] In the analysis illustrated in [Fig.3], several MES2 measurements were carried out by the MM measurement means during the presence of at least one object OBJ in the detection zone DET and represented on the graph described previously in relation to [Fig.2].

[0080] Furthermore, the quantities of photons SIGN come from radiation reflected by an object OBJ located in the detection zone DET at a distance less than the first distance Dl.

[0081] The measured photon quantities SIGN may for example be greater than the second photon quantity S2 and the distances associated with the photon quantities may be less than the first distance DL. The central tendency indicator of the photon quantities SMIL2 and the central tendency indicator of distance DMIL2 are calculated from the different measurements MES2 of photon quantities and distances. The result of the analysis may be represented graphically by a value MIL2 corresponding to the value of the central tendency indicator of distance DMIL2 associated with the value of the central tendency indicator of photon quantity SMIL2.

[0082] The object OBJ is detected in the detection zone DET when the distance central tendency indicator DMIL2 is less than the first distance D1, regardless of the value of the photon quantity central tendency indicator SMIL2. On the other hand, for an object OBJ located near the wall PAR, for example at a distance DIST included in the distance interval, the measurement of the photon quantity SIGN can be advantageous for distinguishing the object OBJ from the wall PAR. When the value of the photon quantity central tendency indicator SMIL2 calculated from the measurement data MES2 is included in another photon quantity interval, i.e. is less than the first value SI or is greater than the second value S2, the central tendency indicators make it possible to conclude that at least one object OBJ is present in the detection zone DET.

[0083] [Fig.4] illustrates a sectional view of a SYS detection system. The SYS system comprises the CTV time-of-flight sensor described previously in relation to Figures 1 to 3 and a CAV cavity. The CAV cavity comprises an opening OUV and a bottom FND. Without limitation, the CAV cavity may be a space delimited by side walls PAR.

[0084] The CTV time-of-flight sensor is mounted on an EXT wall of the cavity, for example a PAR side wall so that the DET detection area of ​​the CTV sensor covers the interior space of the CAV cavity, in particular the FND bottom. The CAV cavity also has another PAR wall which can be located opposite the CTV time-of-flight sensor and which is located in the DET detection zone. The PAR wall is capable of reflecting the RE optical radiation and is therefore detected by the CTV time-of-flight sensor.

[0085] The opening OUV is located opposite the bottom FND of the cavity CAV. The opening OUV may for example be a slot formed in a wall PAR opposite the bottom of the cavity. The opening OUV may be crossed by an object OBJ having dimensions smaller than the dimensions of the opening OUV. Such an object may thus enter the cavity CAV through the opening OUV and fall onto the bottom FND of the cavity. The detection of an object OBJ, such as a coin, a card or a dust particle, may be necessary in certain applications when for example the cavity CAV comprises a screen ECR located at the bottom FND of the cavity CAV and an inclined mirror MIR. The screen ECR is configured to emit light beams onto the inclined mirror MIR which is placed at the opening OUV. The MIR mirror is for example fixed to an EXT wall of the CAV cavity and is configured to direct the light beams emitted by the ECR screen towards the outside of the CAV cavity.

[0086] Thus, a CAV cavity having such a structure makes it possible to transmit information displayed on the ECR screen in a readable manner outside the CAV cavity while protecting the ECR screen located inside the CAV cavity.

[0087] Furthermore, the time-of-flight sensor CTV placed inside the cavity CAV makes it possible, in this structure, to detect objects OBJ located in the detection zone DET and, more particularly between the screen ECR and the inclined mirror MIR, which hinder the passage of the light beams emitted by the screen ECR and therefore the transmission of information to the outside of the cavity CAV by the mirror MIR. The light beams can be directed by the mirror MIR towards a window (not shown) so as to project the information onto the window. The window can in particular serve as a dashboard of a vehicle. Alternatively, the screen ECR can also emit light beams directed directly towards the dashboard so as to project the information onto the dashboard without using a mirror MIR.

[0088] The CTV time-of-flight sensor detects the object OBJ when the latter enters the detection zone DET, in particular when the object OBJ rests on the bottom FND of the CAV cavity. The system SYS may comprise other devices (not shown in the figure) capable of receiving the measurement data MES from the CTV time-of-flight sensor or possibly a detection signal when the CTV time-of-flight sensor detects the presence of an object OBJ in the CAV cavity.

[0089] The SYS system cannot be limited to the embodiment described previously in relation to [Fig.4] and can very well be produced with cavities of aspects different and a CTV time-of-flight sensor positioned differently while allowing the DET detection area to cover enough interior space for detection of the OBJ object at the FND bottom of the CAV cavity.

[0090] Furthermore, the CTV time-of-flight sensor comprises MCAL calibration means configured to determine the distance interval and the photon quantity interval from the detection of the PAR wall of the CAV cavity opposite the CTV time-of-flight sensor.

[0091] The calibration by the MCAL calibration means of the CTV sensor allows, after installation of the CTV sensor in the CAV cavity, the recording by the CTV sensor of the position of the PAR wall so as not to confuse an object OBJ with this PAR wall during the detection phase and thus facilitates its integration into a SYS detection system comprising a cavity of variable dimension.

[0092] [Fig. 5] illustrates an example of a method for detecting at least one object OBJ by the time-of-flight sensor CTV as described previously in relation to FIGS. 1 to 4. The method is for example implemented for a detection system SYS as described in relation to [Fig. 4], i.e. after the installation of the time-of-flight sensor CTV in the cavity CAV.

[0093] The method comprises a calibration 100 of the CTV time-of-flight sensor so as to determine the distance interval and the photon quantity interval from the detection of the PAR wall of the CAV cavity opposite the CTV time-of-flight sensor.

[0094] The method comprises an emission 101 of optical radiation RE by the emission means ME. The optical radiation RE propagates in the cavity CAV until it is reflected by an object OBJ or the wall PAR of the cavity CAV.

[0095] The method also comprises a reception 102 of a quantity of SIGN photons coming from the reflected radiation RR by the reception means MR.

[0096] The method comprises a measurement 103 by the measuring means MM of the quantity of photons SIGN and of the distance DIST between the time-of-flight sensor CTV and the object OBJ or the wall PAR.

[0097] The method comprises an analysis 104 of the quantity of photons SIGN and the associated distance DIST so as to determine the presence of at least one object OBJ in the detection zone DET.

[0098] The analysis 104 comprises a storage 105 of N values ​​of quantities of photons SIGN and distances DIST measured and a calculation 106 of a central tendency indicator of quantity of photons from the N quantities of photons SIGN and a central tendency indicator of distance from the N distances DIST.

[0099] In particular, the storage 105 is carried out by the storage means MS which can store the measurement data MES periodically.

[0100] The calculation 106 of the central tendency indicators is carried out by the calculation means MC from the N values ​​of quantities of photons and distances stored in the storage means MS. In particular, the central tendency indicator of quantities of photons is an average or a median of the N quantities of photons measured and the central tendency indicator of distance is an average or a median of the N distances associated with the quantities of photons.

[0101] The analysis 104 makes it possible to determine the presence or absence of at least one object OBJ in the detection zone DET according to said calculated central tendency indicators. An object OBJ can be detected when the distance central tendency indicator value DMIL2 of the N measured distances is less than the first distance DI or when the distance central tendency indicator value DMIL2 is included in the distance interval and when the photon quantity central tendency indicator value SMIL2 of the N quantities of photons is included in the photon quantity interval, i.e. is less than the first value SI or is greater than the second value S2.

[0102] Finally, the method comprises a calibration of the CTV time-of-flight sensor so as to determine the distance interval and the photon quantity interval from the detection of the PAR wall of the CAV cavity opposite the CTV time-of-flight sensor.

Claims

Claims

1. Method for detecting at least one object (OBJ) in a detection zone (DET), comprising: - an emission of optical radiation by emission means (ME) of a time-of-flight sensor (CTV), - a reception by reception means (MR) of the time-of-flight sensor (CTV) of a quantity of photons of optical radiation reflected by said at least one object (OBJ), - a measurement by measurement means (MM) of the time-of-flight sensor (CTV) of a quantity of photons (SIGN) and a distance (DIST) between said time-of-flight sensor (CTV) and said at least one object (OBJ), and - an analysis of the quantity of detected photons (SIGN) and the associated distance (DIST) so as to determine the presence of at least one object (OBJ) in the detection zone (DET) of the time-of-flight sensor (CTV).

2. Method according to claim 1, wherein the analysis of the quantity of photons (SIGN) associated with the measured distance (DIST) comprises a successive storage of N values ​​of quantities of photons and distances (DIST) associated, a calculation of a central tendency indicator of the quantities of photons (SMIL) from the N quantities of photons, and a calculation of a central tendency indicator of the distances (DMIL) so that said at least one object (OBJ) is detected according to said calculated central tendency indicators.

3. Method according to claim 2, wherein said at least one object (OBJ) is detected when the distance central tendency indicator (DMIL1, DMIL2) is included in a distance interval (Dl, D2) and when the photon quantity central tendency indicator (SMIL1, SMIL2) is included in a photon quantity interval.

4. The method of claim 2, wherein said at least one object (OBJ) is detected when the distance central tendency indicator (DMIL1, DMIL2) is less than a first distance (Dl).

5. Method according to one of claims 2 to 4, in which the central tendency indicator of photon quantities is a median of the N photon quantities (SMIL1, SMIL2) and the tendency indicator central distance is a median of the N associated distances (DMIL1, DMIL2).

6. Method according to one of claims 2 to 4, in which the indicator of central tendency of photon quantities is an average of the N quantities of photons (SMIL1, SMIL2) and the indicator of central tendency of distance is an average of the N distances (DMIL1, DMIL2) associated.

7. Method for detecting at least one object (OBJ) in a cavity (CAV) comprising an opening (OUV) through which said at least one object (OBJ) can enter and a bottom (FND), a time-of-flight sensor (CTV) being mounted on a wall (EXT) of the cavity, the time-of-flight sensor (CTV) having a detection zone (DET) extending between the time-of-flight sensor (CTV) and a wall (PAR) of the cavity (CAV) opposite the time-of-flight sensor to the bottom (FND) of the cavity, the method comprising an implementation of a method according to one of claims 1 to 6 by the time-of-flight sensor so as to detect the presence of said at least one object (OBJ) when it rests on the bottom (FND) of the cavity.

8. Detection method according to claim 7, comprising an emission of light beams by a screen (ECR) located at the bottom (FND) of the cavity (CAV) and an orientation of the light beams towards the outside of the cavity (CAV) by an inclined mirror (MIR) placed at the level of the opening (OUV).

9. Detection method according to any one of claims 7 or 8, comprising a calibration of the time-of-flight sensor (CTV) so as to determine a distance interval and a photon quantity interval from the detection of the wall (PAR) of the cavity (CAV) opposite the time-of-flight sensor (CTV), said at least one object (OBJ) then being detected when the distance central tendency indicator (DMIL1, DMIL2) is included in the distance interval (Dl, D2) and when the photon quantity central tendency indicator (SMIL1, SMIL2) is included in the photon quantity interval.

10. Time-of-flight sensor, comprising: - emission means (ME) configured to emit optical radiation, - receiving means (MR) configured to detect a quantity of photons of optical radiation reflected by said at least one object (OBJ), - measuring means (MM) configured to measure a quantity of photons (SIGN) and a distance (DIST) between said time-of-flight sensor (CTV) and said at least one object (OBJ), and - processing means (MT) configured to analyze the quantity of photons (SIGN) and the associated distance (DIST) so as to determine the presence of at least one object (OBJ) in a detection zone (DET) of the time-of-flight sensor (CTV).

11. Sensor according to claim 10, wherein the processing means (MT) comprise storage means (MS) configured to successively store N values ​​of photon quantities (SIGN) and associated distances (DIST) and calculation means (MC) configured to calculate a central tendency indicator of photon quantity (SMIL) from the N photon quantities and calculate a central tendency indicator of distance (DMIL) from the N distances so that said at least one object (OBJ) is detected according to said calculated central tendency indicators.

12. Sensor according to claim 11, wherein said at least one object (OBJ) is detected when the distance central tendency indicator (DMIL1, DMIL2) is included in a distance interval (Dl, D2) and when the photon quantity central tendency indicator (SMIL1, SMIL2) is included in a photon quantity interval.

13. The sensor of claim 11, wherein said at least one object (OBJ) is detected when the distance central tendency indicator (DMIL1, DMIL2) is less than a first distance (Dl).

14. Sensor according to one of claims 11 to 13, in which the indicator of central tendency of quantities of photons is a median of the N quantities of photons (SMIL1, SMIL2) and the indicator of central tendency of distance is a median of the N distances (DMIL1, DMIL2) associated.

15. Sensor according to one of claims 11 to 13, in which the indicator of central tendency of quantities of photons is an average of the N quantities of photons (SMIL1, SMIL2) and the indicator of central tendency of distance is an average of the N distances (DMIL1, DMIL2) associated.

16. Detection system (SYS) comprising: - a cavity (CAV) comprising an opening (OUV) through which said at least one object (OBJ) can enter the cavity (CAV) and a bottom (FND), - a time-of-flight sensor (CTV) according to one of claims 10 to 15, mounted on a wall (EXT) of the cavity (CAV), the detection zone (DET) of the time-of-flight sensor extending between the time-of-flight sensor (CTV) and a wall (PAR) of the cavity opposite the time-of-flight sensor (CTV) to the bottom (FND) of the cavity so as to be able to detect the presence of said at least one object (OBJ) when it rests on the bottom (FND) of the cavity.

17. Detection system according to claim 16, wherein the cavity (CAV) comprises and a screen (ECR) located at the bottom (FND) of the cavity (CAV) and an inclined mirror (MIR) placed at the opening (OUV) and configured to orient light beams emitted by the screen (ECR) towards the outside of the cavity (CAV).

18. Detection system according to any one of claims 16 or 17, wherein the time-of-flight sensor comprises calibration means (MCAL) configured to determine a distance interval and a photon quantity interval from the detection of the wall (PAR) of the cavity (CAV) opposite the time-of-flight sensor (CTV), said at least one object (OBJ) then being detected when the distance central tendency indicator (DMIL1, DMIL2) is included in the distance interval (D1, D2) and when the photon quantity central tendency indicator (SMIL1, SMIL2) is included in the photon quantity interval.

Images