Remote temperature measurement system

Abstract

Remote temperature measurement system The present invention relates to a remote temperature measurement system (100), arranged to measure a temperature on a person, in particular on at least one area of the person's face, this system comprising: a first temperature sensor (1) operating in the infrared and arranged to measure at least one skin temperature of the person, in particular on at least one area of the person's face, this first sensor being in particular an infrared camera, the skin temperature measured by this first sensor being called (Tir), a second temperature sensor (2) arranged to measure an ambient temperature, a processing unit (3). Figure for the abstract: Fig. 1

Description

Title of the invention: Remote temperature measurement system

[0001] The present invention relates to a remote temperature measurement system.

[0002] The detection of potential COVID 19 patients is currently carried out by taking temperature, additional clinical examinations, then by a COVID 19 test which still has a relatively low level of confidence.

[0003] There is a significant need to be able to rapidly detect, in particular using mobile means, potential patients with contagious diseases, for example the disease linked to COVID 19.

[0004] Temperature measurements that are as reliable as possible are crucial for such disease detections.

[0005] The invention thus relates to a remote temperature measurement system, arranged to measure a temperature on a person, in particular on at least one area of the person's face, this system comprising:

[0006] - a first temperature sensor operating in the infrared and arranged to measure at least one skin temperature of the person, in particular on at least one area of the person's face, this first sensor being in particular an infrared camera, the skin temperature measured by this first sensor being called (Shot),

[0007] - a second temperature sensor arranged to measure a temperature ambient,

[0008] - a processing unit arranged for:

[0009] - determine an intermediate skin temperature (Tbb) as a function of at least the temperature measured (Tir) by the first temperature sensor, of a distance value representative of the distance between the first sensor and the person, and the ambient temperature measured by the second sensor, and

[0010] - determine a corrected skin temperature value (Ts) as a function of at least the intermediate skin temperature (Tbb) and a correction linked to the emissivity of the person's skin.

[0011] The invention makes it possible in particular to obtain the most precise skin temperature possible, which is not or only slightly affected by the parameters of distance and ambient temperature. Other parameters in addition to distance and ambient temperature can be taken into account, as will be seen later.

[0012] The intermediate skin temperature value (Tbb) is not calculated with consideration of the emissivity of the skin. The emissivity is taken into account in determining the final corrected temperature (Ts), as will be seen later.

[0013] According to one aspect of the invention, the system comprises a distance measuring apparatus for providing the distance value.

[0014] Alternatively, this distance value may be a predetermined value. For example, this distance value is set in advance based on the location of the chair where the person who is subject to the temperature measurement sits, this value being for example set at 1 meter.

[0015] According to one aspect of the invention, the processing unit is arranged to determine the corrected skin temperature value (Ts) from a single intermediate skin temperature value (Tbb).

[0016] According to one aspect of the invention, this system comprises a distance measuring device arranged to measure the distance between the person's face and the first temperature sensor.

[0017] According to one aspect of the invention, this distance measurement is based for example on an area of the person's face, for example on the area of the face where the first temperature sensor measures the skin temperature (Tir).

[0018] According to one aspect of the invention, this device is chosen from a stereoscopic measuring device, a radar, a Time of Flight (TOF) Sensor type device, an inertial balance which in particular makes it possible to position the person's body on a virtual reference checkerboard.

[0019] According to one aspect of the invention, the distance measurement can also be carried out by image processing by measuring a gap between the eyes on the image and then determining, from this estimated gap, the distance between the face on which the temperature is measured and the first temperature sensor.

[0020] According to one aspect of the invention, the processing unit is arranged to determine the corrected skin temperature value (Ts) from a plurality of intermediate skin temperature values (Tbb).

[0021] According to one aspect of the invention, the processing unit is arranged to use the same distance value to determine all intermediate skin temperature values (Tbb).

[0022] This may prove sufficient, namely to use the same distance value, when the distance between the person and the first sensor is sufficiently large, for example at least 1 meter.

[0023] Alternatively, the processing unit is arranged to use several distance values to determine the intermediate skin temperature values (Tbb).

[0024] In particular, each calculation of the intermediate skin temperature value (Tbb) uses an associated distance value.

[0025] Each distance value corresponds to a point on the person's face. This point is a point where the temperature measurement by the first sensor is made.

[0026] According to one aspect of the invention, the first temperature sensor is arranged to measure the temperatures at a plurality of points on the person's face.

[0027] This plurality of points notably forms a mask of measurement points placed on the person's face.

[0028] The distance measurement at each temperature measurement point allows for better accuracy of the intermediate skin temperature (Tbb) values.

[0029] This is particularly advantageous when the first temperature sensor is placed relatively close to the person's face, for example at a distance of a few tens of centimeters. Over these short distances, the accuracy of the distance value between the temperature measuring point and the first sensor has a significant influence on the accuracy of the intermediate skin temperature value (Tbb).

[0030] For example, the intermediate temperature (Tbb) on the tip of the nose must be corrected with a distance value measured on the tip of the nose. Indeed, when the first sensor is relatively close to the face, a distance measured on the tip of the nose and the distance measured on another point of the face, for example on the cheekbone, can differ greatly, in proportion.

[0031] In the case of measurements of several distance values on the face, the system may comprise a measuring device for determining the distance at a plurality of points on the person's face, this device being chosen for example from a stereoscopic measuring device or a device of the Time of Flight (TOF) Sensor type.

[0032] This camera operates on the principle of time of flight (TOF) which allows a 3-dimensional (3D) scene to be measured in real time. This type of camera is known.

[0033] On the other hand, when the first sensor is placed sufficiently far from the person, for example more than 70 cm, it is possible to use the same distance value to correct the values taken by the first sensor, in order to determine the different intermediate temperature values (Tbb). The variations in distance at the different measurement points on the face remain relatively small and do not significantly affect the accuracy of the corrected temperature values.

[0034] According to one aspect of the invention, it comprises a camera, in particular a Red Green Blue camera, or RGB camera, arranged to define on the person's face the remarkable temperature measurement point, or the remarkable temperature measurement points, for the first sensor. In particular, this camera operates in the visible range.

[0035] The first and / or second temperature sensor comprises a component for measuring the temperature in a housing of the sensor and / or a sensitive element of this sensor.

[0036] For example, if the temperature measured by this sensor is outside a predetermined temperature range for which the sensor is calibrated, the system considers the first and / or the second temperature sensor as unreliable, and does not take into account the data resulting therefrom.

[0037] According to one aspect of the invention, the correction linked to the emissivity of the person's skin is chosen to be dependent on the intermediate skin temperature (Tbb).

[0038] According to one aspect of the invention, the corrected skin temperature value is given by a curve with the intermediate skin temperature on the abscissa and the corrected skin temperature on the ordinate, taking into account the emissivity of the skin.

[0039] The dependence of skin emissivity on skin temperature is contained in this curve.

[0040] This curve is obtained for example using real measurements.

[0041] In an exemplary embodiment of the invention, the system does not need to explicitly access a skin emissivity value. The system uses the aforementioned curve which contains the influence of the emissivity on the measurement of the temperature of the region concerned, in particular the face. The correction linked to the emissivity is contained in this curve.

[0042] According to one aspect of the invention, the correction linked to the emissivity of the person's skin is chosen to also depend on the person's perspiration and makeup.

[0043] According to one aspect of the invention, the intermediate skin temperature (Tbb) is equal to a polynomial function, for example of order 2, of the temperature measured (Tir) by the first temperature sensor, of a distance value representative of the distance between the first sensor and the person, and the ambient temperature measured by the second sensor.

[0044] According to one aspect of the invention, it comprises a light intensity sensor, in particular a thermopile type sensor comprising thermocouples and arranged to convert thermal energy into electrical energy.

[0045] According to one aspect of the invention, the processing unit is connected to this light intensity sensor, in particular of the thermopile type, and is arranged to use light intensity data provided by this sensor to correct the temperature (Tbb).

[0046] The correction for ambient brightness can integrate this light intensity data divided by a radiant thermal power value associated with the person's basal metabolism.

[0047] According to one aspect of the invention, the first temperature sensor is a camera operating in the infrared, preferably at a wavelength between 7 and 14 micrometers.

[0048] According to one aspect of the invention, this camera is of the digital type.

[0049] According to one aspect of the invention, the entire system is of the digital type, without analog component.

[0050] According to one aspect of the invention, the second temperature sensor arranged to measure an ambient temperature is a sensor comprising a platinum-based sensitive element, in particular of the PT 100 type.

[0051] The invention also relates to a method for measuring temperature remotely, for measuring a temperature on a person, in particular on at least one area of the person's face, this method comprising the following steps:

[0052] - providing a first temperature sensor operating in the infrared and arranged to measuring at least one skin temperature of the person, in particular on at least one area of the person's face, this first sensor being in particular an infrared camera, the skin temperature measured by this first sensor being called (Tir),

[0053] - providing a second temperature sensor arranged to measure a temperature ambient,

[0054] - determine an intermediate skin temperature (Tbb) as a function of at least the temperature measured (Tir) by the first temperature sensor, of a distance value representative of the distance between the first sensor and the person, and the ambient temperature measured by the second sensor, and

[0055] - determine a corrected skin temperature value (Ts) as a function of at least the intermediate skin temperature (Tbb) and a correction linked to the emissivity of the person's skin.

[0056] According to one aspect of the invention, the remarkable temperature measurement point(s) are defined geometrically by means of an image area called a Building box, which surrounds it, for example by means of the geometric mean of the sides of the image area. This image area is a surface delimited by a series of points which is constructed by an object identification algorithm.

[0057] The system can be packaged in a transportable box and can be placed in a building, for example an airport, a hospital or any other location.

[0058] The invention can serve as an aid for providing diagnostic information, in particular for the detection of a disease in a person, in particular a contagious disease such as COVID 19.

[0059] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures:

[0060] [Fig.l] schematically illustrates a system according to a non-limiting embodiment of the invention.

[0061] [Fig.2] schematically illustrates a system according to another non-limiting embodiment of the invention,

[0062] [Fig.3] illustrates notable measurement points on a person's face, using the system according to the invention,

[0063] [Fig.4] shows a curve illustrating the influence of emissivity on temperature measurements.

[0064] [Fig.l] shows a remote temperature measurement system 100, arranged to measure a temperature on a person, here on the person's face.

[0065] This system 100 comprises a first temperature sensor 1 operating in the infrared and arranged to measure a skin temperature of the person, on areas or points of the person's face.

[0066] The first temperature sensor 1 is a camera operating in the infrared, for example between 7 and 14 micrometers.

[0067] The skin temperature measured by this first sensor 1 is called Tir,

[0068] This system 100 further comprises a second temperature sensor 2 arranged to measure an ambient temperature Tamb.

[0069] The second temperature sensor 2 arranged to measure an ambient temperature is a sensor comprising a platinum-based sensitive element, in particular of the PT 100 type.

[0070] This system 100 comprises a processing unit 3 arranged for:

[0071] - determine an intermediate skin temperature Tbb as a function of at least the temperature measured by the first temperature sensor 1, of a distance value Dist representative of the distance between the first sensor 1 and the person, and the ambient temperature Tamb measured by the second sensor 2, and

[0072] - determine a corrected skin temperature value Ts as a function of at least the intermediate skin temperature Tbb and a correction linked to the emissivity of the person's skin.

[0073] The system 100 comprises a distance measuring apparatus 5 for providing the distance value Dist.

[0074] Alternatively, this distance value Dist may be a predetermined value. For example, this distance value is set in advance based on the location of the chair where the person who is subject to the temperature measurement sits, this value being for example set at 1 meter.

[0075] In the exemplary embodiment of [Fig.l], the processing unit 3 is arranged to determine the corrected skin temperature value Ts from a single intermediate skin temperature value Tbb.

[0076] The distance measuring apparatus 5 is arranged to measure the distance between the person's face and the first temperature sensor 1.

[0077] This distance measurement is based for example on an area of the person's face, for example on the area of the face where the first temperature sensor 1 measures the skin temperature Tir.

[0078] This distance measuring device 5 is chosen from a stereoscopic measuring device, a radar, a Time of Flight (TOF) Sensor type device, an inertial balance.

[0079] The distance measurement can also be carried out by image processing by measuring a distance between the eyes on the image and then determining, from this estimated difference, the distance between the face on which the temperature is measured and the first temperature sensor.

[0080] In the exemplary embodiment of [Fig.2], the processing unit 100 is arranged to determine the corrected skin temperature value Ts from a plurality of intermediate skin temperature values Tbb.

[0081] In a first embodiment, the processing unit 3 is arranged to use the same distance value Dist to determine all the intermediate skin temperature values Tbb.

[0082] This may prove sufficient, namely to use the same distance value, when the distance between the person and the first sensor 1 is sufficiently large, for example at least 1 meter.

[0083] When the first sensor is placed sufficiently far from the person, it is possible to use the same distance value to correct the values taken by the first sensor, in order to determine the different intermediate temperature values (Tbb). The variations in distance at the different measurement points on the face remain relatively small and do not significantly affect the accuracy of the corrected temperature values.

[0084] In another embodiment, the processing unit 3 is arranged to use several distance values Dist to determine the intermediate skin temperature values Tbb.

[0085] In particular, each calculation of the intermediate skin temperature value Tbb uses an associated distance value Dist.

[0086] Each distance value Dist corresponds to a point on the person's face. This point is a point where the temperature measurement by the first sensor 1 is made.

[0087] The first temperature sensor 1 is thus arranged to measure the temperatures at a plurality of points on the person's face. This plurality of points notably forms a mask 20 of measurement points superimposed on the person's face 21, as can be seen in [Fig.3].

[0088] The distance measurement at each temperature measurement point allows for better accuracy of the intermediate skin temperature values Tbb. This is particularly advantageous when the first temperature sensor 1 is placed relatively close to the person's face 21, for example at a distance of a few tens of centimeters. Over these short distances, the accuracy of the distance value between the temperature measuring point and the first sensor 1 has a significant influence on the accuracy of the intermediate skin temperature value Tbb. For example, the intermediate temperature Tbb on the tip of the nose must be corrected with a distance value measured on the tip of the nose. Indeed, when the first sensor is relatively close to the face, a distance measured on the tip of the nose and the distance measured on another point of the face, for example on the cheekbone, can differ greatly, in proportion.

[0089] The number of points on the 20-point mask may be greater than 100, or even greater than 200.

[0090] This number of points of the mask is, in the example described, equal to 366 points.

[0091] To measure this multitude of distance values Dist, the measuring device distance is chosen from a stereoscopic measuring device or a Time of Flight (TOF) Sensor type device.

[0092] This camera operates on the principle of time of flight (TOF) which allows a 3-dimensional (3D) scene to be measured in real time. This type of camera is known.

[0093] The system 100 comprises a Red Green Blue camera 8, or RGB camera, arranged to define on the face 21 of the person the remarkable temperature measurement point, or the remarkable temperature measurement points, for the first sensor 1. This is step 40 of figures 1 and 2.

[0094] The remarkable temperature measurement points are defined geometrically by means of an image area called Building box, which surrounds it, for example by means of the geometric mean of the sides of the image area. This image area is a surface delimited by a series of points which is constructed by an object identification algorithm.

[0095] This camera 8 operates in the visible range.

[0096] After step 40, the infrared camera 1 carries out the temperature measurements on these points of the mask 20 (step 41) to obtain the different measured temperature values Tir.

[0097] The first and / or the second temperature sensor may comprise a component for measuring the temperature in a housing of the sensor and / or a sensitive element of this sensor.

[0098] For example, if the temperature measured by this sensor is outside a predetermined temperature range for which the sensor is calibrated, the system considers the first and / or second temperature sensor as unreliable, and does not take into account the data from them.

[0099] The correction linked to the emissivity of the person's skin is chosen to be dependent on the intermediate skin temperature Tbb.

[0100] The corrected skin temperature value Ts is given by a curve 30 (see [Fig.4]) with the intermediate skin temperature Tbb on the abscissa and the corrected skin temperature Ts on the ordinate, taking into account the emissivity of the skin.

[0101] The dependence of the skin emissivity on the skin temperature is contained in this curve 30.

[0102] In the example described, it is of polynomial form of order 2.

[0103] This curve is obtained for example using real measurements.

[0104] The system does not need to explicitly access a skin emissivity value. The system uses the aforementioned curve which contains the influence of the emissivity on the measurement of the temperature of the region concerned, in particular the face. The correction linked to the emissivity is contained in this curve 30.

[0105] The correction related to the emissivity of the person's skin can, if desired, be chosen to also depend on the person's perspiration and makeup.

[0106] The intermediate skin temperature Tbb is equal to a polynomial function, here of order 2, of the temperature measured Tir by the first temperature sensor 1, of a distance value Dist representative of the distance between the first sensor 1 and the face 21 of the person, and the ambient temperature Tamb measured by the second sensor 2.

[0107] In the example described, the intermediate skin temperature is given by the following equation:

[0108] Tbb=a0+al.Tir+a2.Dist+a3.Tamb+a4.Tir2+a5.Dist2+a6.Tamb2+a7.Tair.Dist

[0109] +a8.Tir.Tamb+a9.Dist.Tamb

[0110] Where aO, al ... a9 are predetermined coefficients of the polynomial.

[0111] The system 100 comprises a light intensity sensor 9, here a thermopile type sensor comprising thermocouples and arranged to convert thermal energy into electrical energy.

[0112] The processing unit 3 is connected to this light intensity sensor 9, in particular of the thermopile type, and is arranged to use light intensity data provided by this sensor to correct Tbb.

[0113] The correction for ambient brightness can integrate this radiant light intensity data divided by a radiant thermal power value associated with the person's basal metabolism.

[0114] For example, this correction due to ambient brightness is a corrective term proportional to the ratio between the radiant light intensity and a radiant thermal power value associated with the person's basal metabolism.

[0115] This coefficient of proportionality is for example between 0.1 and 10.

[0116] This value of radiant thermal power associated with basal metabolism is for example taken equal to 14 W.m2 (Watt per unit of surface).

[0117] In addition to the proportionality described above, it is possible, if desired, to impose this correction due to the ambient brightness as being equal to zero when the ambient radiant brightness is less than 10% of the radiant thermal power associated with the basal metabolism.

[0118] The entire system 100 is of the digital type, without analog components.

[0119] In the example of [Fig. 1], only one measured temperature value Tir is used to obtain the correction. The Tir value taken into account is the highest Tir temperature on the point mask. This step of selecting the highest Tir value is done in step 42 of [Fig.l].

[0120] The temperature point retained is for example a point close to the eye.

[0121] Step 43 aims to determine an intermediate skin temperature Tbb as a function of the measured temperature Tir retained, of a distance value Dist representative of the distance between the first sensor and the person, and the ambient temperature Tamb measured by the second sensor.

[0122] Step 43 uses the aforementioned polynomial function.

[0123] In step 44, a corrected skin temperature value Ts is determined as a function of the intermediate skin temperature Tbb and a correction linked to the emissivity of the person's skin, as explained above.

[0124] In the example of [Fig.2], all the temperature values Tir measured in step 41 are used to determine as many intermediate temperatures Tbb. It is step 47 of [Fig.2] where 366 intermediate temperature values Tbb are obtained using the aforementioned polynomial equation.

[0125] In step 48, all these Tbb values are corrected with the emissivity correction.

[0126] In step 49, the highest corrected value Ts is retained.

[0127]

Claims

Claims

1. System (100) for remote temperature measurement, arranged to measure a temperature on a person, in particular on at least one area of the person's face, this system comprising: - a first temperature sensor (1) operating in the infrared and arranged to measure at least one skin temperature of the person, the first temperature sensor being arranged to measure the temperatures at a plurality of points on the person's face, this first sensor being in particular an infrared camera, the skin temperature measured by this first sensor being called (Tir), - a second temperature sensor (2) arranged to measure an ambient temperature, - a processing unit (3) arranged to: • determine intermediate skin temperatures (Tbb) as a function of the temperatures measured (Tir) by the first temperature sensor, of several distance values (Dist),each intermediate skin temperature value (Tbb) calculation using an associated distance value, each distance value corresponding to a point on the person's face where the measurement by the first sensor is made, and the ambient temperature measured by the second sensor, and • determining a corrected skin temperature value (Ts) from a plurality of intermediate skin temperature values (Tbb) and a correction linked to the emissivity of the person's skin,

2. System according to the preceding claim, in which the system comprises a distance measuring device (5) for providing the distance value, in particular a stereoscopic measuring device, a radar, a Time of Flight (TOF) Sensor type device, an inertial balance.

3. System according to one of claims 1 to 2, in which the plurality of points of the person's face form a mask (20) of measurement points placed on the person's face (21).

4. System according to one of the preceding claims, in which the correction linked to the emissivity of the person's skin is chosen to be dependent on the intermediate skin temperature (Tbb).

5. System according to the preceding claim, in which the corrected skin temperature value (Ts) is given by a curve with the intermediate skin temperature on the abscissa and the corrected skin temperature on the ordinate, taking into account the emissivity of the skin.

6. System according to one of the preceding claims, according to which it comprises a light intensity sensor, in particular a thermopile type sensor (9) comprising thermocouples and arranged to convert thermal energy into electrical energy.

7. System according to the preceding claim, according to which the processing unit is connected to this light intensity sensor, in particular of the thermopile type (9), and is arranged to use light intensity data provided by this sensor to correct the temperature (Tbb).

8. A method for measuring temperature remotely, for measuring a temperature on a person, in particular on at least one area of the person's face, this method comprising the following steps: - providing a first temperature sensor (1) operating in the infrared and arranged to measure at least one skin temperature of the person at a plurality of points on the person's face, this first sensor being in particular an infrared camera, the skin temperature measured by this first sensor being called (Tir), - providing a second temperature sensor (2) arranged to measure an ambient temperature, - determining intermediate skin temperatures (Tbb) as a function at least of the temperature measured (Tir) by the first temperature sensor, of several distance values (Dist), each calculation of intermediate skin temperature value (Tbb) using an associated distance value,each distance value corresponding to a point on the person's face where the measurement by the first, sensor is made, and the ambient temperature measured by the second sensor, - determining a corrected skin temperature value (Ts) from a plurality of intermediate skin temperature values (Tbb) and a correction linked to the emissivity of the person's skin.

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