CONTACTLESS SYSTEM AND CONTACTLESS DEVICE FOR MEASURING A PERSON'S BODY TEMPERATURE

Description

FIELD OF INVENTION

[0001] The invention relates generally to the measurement of an individual's body temperature, particularly at the entrance to a restricted access area such as a public or private building. STATE OF THE ART

[0002] The current health crisis has highlighted the need for rapid temperature checks of individuals seeking access to specific areas, such as the entrance to a public or private building. In particular, it is desirable to be able to identify individuals with a body temperature above 37.5°C to limit the risk of spreading viruses (such as COVID-19).

[0003] In the medical field, portable contact thermometers are available, offering the advantages of being economical and accurate. However, these thermometers require physical contact with the skin of the individual being measured, resulting in a relatively long measurement time and the need to replace the thermometer's insulation capsule after each measurement to ensure test hygiene.

[0004] There are also handheld infrared temperature monitoring systems of the "gun-like" type. These systems allow an operator to measure an individual's temperature without contact by standing close to the person being checked. The temperature is usually measured on the forehead or wrists, very quickly. However, because the system is gun-shaped, it must be operated by a dedicated technician. Furthermore, the accuracy of the infrared sensor varies over time due to environmental temperature changes and drift in the sensor's characteristics. To improve the system's accuracy, it would need to be calibrated periodically, which is cumbersome for a handheld system of this type. In addition, the distribution of temperature on the face varies depending on exposure to the external environment (e.g., wind or sun) and from individual to individual.However, an operator cannot determine a priori the area of ​​the face with the maximum temperature, so the measured temperature does not necessarily correspond to the individual's actual body temperature.

[0005] There are also fixed infrared monitoring systems, comprising an infrared camera mounted on a stand, with its optical axis parallel to the ground and at the average height of a face. However, these systems suffer from the same limitations as portable systems, although their fixed operation can be more complex in order to improve measurement accuracy. In particular, the behavior of the infrared sensors in these fixed systems is stabilized by thermal control of the temperature measured by the infrared sensor and by the periodic, and sometimes permanent, use of an external blackbody as a reference, with unity emissivity and a known temperature. Nevertheless, the use of an external blackbody often presents installation problems that can complicate the installation of the system's control station.Furthermore, blackbody radiation can be subject to interference (for example, from people passing by). In addition, an operator must manually manage the timing of when the individual whose body temperature is being measured is at an appropriate distance for the measurement and synchronize the temperature reading with the moment the individual passes by. Finally, when measurements are taken at the entrance to a restricted access area, it is difficult to isolate the individual whose temperature is being measured and ignore those passing by, as these individuals also contribute to the heat and are therefore likely to interfere with the measurements.

[0006] US documents 2007 / 153871 A1 and WO 2004 / 097389 A2 disclose examples of prior art. DESCRIPTION OF THE INVENTION

[0007] One aim of the invention is to remedy the aforementioned drawbacks.

[0008] In particular, one aim of the invention is to provide a non-contact measurement system for an individual's body temperature that is reliable, stable over time, and provides an accurate value of the individual's body temperature, regardless of the measurement environment.

[0009] Another objective of the invention is to provide a body temperature measurement system for an individual that can be easily transported by an operator and quickly installed at a given access point and that does not require any handling by the operator during temperature measurement.

[0010] Another objective of the invention is to provide a measurement system that limits environmental disturbances, despite the possible presence of individuals other than the one whose body temperature is being determined.

[0011] For this purpose, according to a first aspect of the invention, a system for measuring the body temperature of an individual is proposed according to claim 1.

[0012] Some preferred but not limiting characteristics of the measurement system according to the first aspect are the following, taken individually or in combination: the first standard, the second standard, the first thermal probe and the second thermal probe are mounted on the gantry; the processing unit is further configured to apply a predetermined compensation coefficient to the temperature value of each infrared image pixel;the measurement system further includes a visible spectrum camera comprising a visible spectrum detection chip comprising a visible pixel array and configured to generate a visible image comprising a plurality of visible image pixels, the visible spectrum camera being fixed to the gantry so that a visual field of the visible spectrum camera covers at least the portion of the passage channel, the processing unit being further configured to identify the visible image pixels corresponding to at least a part of an individual's face, to match the visible image and the electronic image so as to identify the infrared image pixels corresponding to the identified visible image pixels, to determine the maximum temperature value associated with the identified infrared image pixels; the infrared camera and the visible spectrum camera are mounted on an arm fixed to the cross member and extending from an exit of the gantry;the measurement system further includes a presence sensor configured to determine the presence of an individual in the passage channel; the first standard and the second standard are fixed to one of the two side panels and the cross member; the first standard has a first reference temperature and the second standard has a second reference temperature different from the first reference temperature; the first reference temperature and the second reference temperature are between 35°C and 40°C; the measurement system further includes a first heating element and a second heating element configured to maintain the first standard and the second standard at the first reference temperature and the second reference temperature, respectively;The measurement system further includes a signaling unit configured to generate an alert when the maximum temperature value exceeds a predetermined threshold; the processing unit is configured to identify the visible image pixels corresponding to the individual's eyes, preferably an inner corner of at least one of the individual's eyes; and / or the measurement system further includes a light, preferably flashing, fixed near the infrared camera so as to attract the attention of an individual passing through the passage channel.

[0013] According to a second aspect, the invention proposes a method for measuring an individual's body temperature using a measurement system according to the first aspect, according to claim 10.

[0014] Some preferred but not limiting characteristics of the measurement method according to the second aspect are the following, taken individually or in combination: The method further comprises the following steps: S2: producing a visible image of all or part of the portion of the passage channel, the visible image comprising a plurality of visible image pixels; S3: identifying the visible image pixels corresponding to at least a part of an individual's face, preferably at least one inner corner of the eyes; S4: matching the visible image and the electronic image so as to identify the infrared image pixels corresponding to the visible image pixels identified in step S3; step S9 being carried out on the infrared image pixels identified in step S3; steps S1 and S2 are simultaneous; the method further comprises applying a predetermined compensation coefficient to the temperature value of each image pixel or to the maximum temperature value determined in step S9;The method further includes, prior to step S1, a step S0 for determining the presence of an individual in the portal, with steps S1 to S9 being implemented only when an individual is present in the passage channel; the method further includes a step for generating an alert when the maximum temperature value exceeds a predetermined threshold; and / or during step S3, the visible image pixels corresponding to the individual's eyes are identified, preferably the visible image pixels corresponding to at least one inner corner of the individual's eyes. DESCRIPTION OF THE FIGURES

[0015] Other features, purposes and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which: There figure 1illustrates schematically an example of an implementation of a measurement system conforming to an embodiment of the invention; The figure 2 is a partial front view of the measurement system of the figure 1 ; There figure 3 is a partial rear view of the measurement system of the figure 1 ; There figure 4 is a top view of the measurement system of the figure 1 , on which the light beams from four photoelectric barriers have been represented in dashed lines; The figure 5 is a side view of the measurement system of the figure 1 , on which examples of the visual fields of view of the infrared camera and the visible spectrum camera were shown; The figure 6 is an exploded view of an example of a calibration module implementation; The figure 7 is an exploded view of an example embodiment of a housing comprising the infrared camera and the visible spectrum camera of a measurement system according to the invention. figure 8 illustrates an example of an electronic image that can be obtained by the infrared camera of the measuring device. figure 1 , on which a detailed and schematic example of a calibration module was illustrated; The figures 9 And 10 These are flowcharts of the steps in a measurement process according to one embodiment of the invention. figure 11 is a synoptic diagram of an example of an embodiment of a measurement system according to the invention.

[0016] Across all figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to perform reliable, stable and non-contact measurements of an individual's temperature, the invention proposes a system for measuring an individual's body temperature comprising: a portal 11; an infrared camera 12; a visible spectrum camera 6; optionally, a presence sensor 13 and / or a light 30, preferably flashing; and a processing unit 15 configured to determine an individual's body temperature. Portico 11

[0018] The gantry 11 comprises two side panels 1 connected by a crossbar 2, together defining a passageway 9 for one person. The side panels 1 and the crossbar 2 are mechanically connected to form a single unit.

[0019] Optionally, the gantry 11 may include an additional cross member 2, substantially parallel to the cross member 2 and also connecting the two side panels 1.

[0020] Each side panel 1 has an inner face oriented towards the passage channel 9. More precisely, the inner face of the first panel faces the inner face of the second panel so as to laterally delimit the channel. The side panels 1 also each have a first end, or entrance end, which together define an entrance 9a into the channel for an individual, and a second end, or exit end, which is opposite the entrance end and defines the exit 9b of the channel 9. The passage channel 9 is therefore delimited by the entrance 9a and the exit 9b of the gantry 11, the entrance 9a and the exit 9b being defined by the direction of movement of an individual in the gantry 11.

[0021] The gantry 11 further includes a support, mounted on one of the side panels 1 and the cross member 2 and configured to receive the infrared camera 12 and the visible spectrum camera 6. In one embodiment, the support includes an arm 7, comprising a first end mounted on the gantry 11, preferably at the exit 9b of the gantry 11, and a second free end, opposite the first end and extending in line with the gantry 11. The infrared camera 12 and the visible spectrum camera 6 can, for example, be mounted on the second end of the arm 7 so as to be oriented towards the inside of the passage channel 9.

[0022] The arm 7 allows for easy mounting and orientation of the cameras 6 and 12 towards the inside of the passageway. Furthermore, this configuration allows the infrared 12 and visible spectrum 6 cameras to be positioned downstream of the gantry 11, thus ensuring that the images captured include images of the individual when they are inside the passageway. The field of view 31 and 32 of the cameras 6 and 12 can indeed cover more of the passage channel 9 than if they were mounted directly on the crossbar 2 or the side panels 1.

[0023] Preferably, arm 7 is mounted on crossbeam 2 at exit 9b of gantry 11 and extends perpendicularly to crossbeam 2, downstream of passage channel 9.

[0024] The implementation of a gantry 11 delimiting a passage channel 9 for the individual advantageously ensures that only one individual at a time is in the field of vision 31, 32 of the infrared camera 12 and the visible spectrum camera 6, and thus improves the accuracy of the measurements taken. 12 Infrared Camera

[0025] The infrared camera 12 is configured to produce an electronic image of the individual. For this purpose, it includes an infrared detection chip 25 comprising a processor (or microprocessor) and a pixel array (hereinafter, "infrared" pixels), and an optical system 26, 27 configured to focus infrared energy onto the infrared pixel array. Each infrared pixel in the array is configured to generate an electrical signal based on the infrared energy entering through the optical system during the electronic image acquisition. This electrical signal is transmitted to the processor of the infrared detection chip 25, which converts it into a corresponding temperature value. The processor generates an electronic image comprising a plurality of infrared image pixels, each infrared image pixel representing the temperature value received by a corresponding infrared pixel in the array.This electronic image can, if necessary, be transmitted and displayed on a screen in the form of a color map representing the individual's apparent temperature.

[0026] The infrared pixels of the infrared detection chip 25 are configured to detect infrared energy with a wavelength greater than or equal to eight micrometers and less than or equal to fourteen micrometers. Each infrared pixel can have a maximum width greater than or equal to five micrometers and less than or equal to one hundred micrometers, depending on the desired overall resolution of the infrared camera 12. This resolution range allows for accurate temperature measurement of areas of the body with a small surface area, such as the inner corner of the eye.

[0027] The infrared detection chip 25 may be a MEMS micro-electromechanical system (English acronym for microelectromechanical system).

[0028] The infrared detection chip 25 is fixed to a printed circuit board 24. In one embodiment, the printed circuit board 24 includes a pad in which a through-hole cavity is formed. The infrared detection chip 25 is then mounted in the cavity.

[0029] The optical system comprises one or more lenses 26 positioned on the optical axis of the infrared camera 12 and configured to focus infrared energy onto the infrared sensing chip 25. For example, the optical system may include a lens 26 mounted in the cavity in front of the infrared sensing chip 25. The optical system further comprises a diaphragm 27 positioned on the optical axis of the lens 26 and configured to delimit an area from the passage of an infrared beam. If necessary, the diaphragm 27 may be mounted on or in front of the pad so as to close the cavity housing the infrared sensing chip 25 and isolate it from the external environment.

[0030] Lens 26 and diaphragm 27 can, for example, be made of germanium in order to allow infrared radiation to pass through.

[0031] The infrared camera 12 is fixed to the gantry 11 so that its field of view 32 covers at least a portion of the passage channel 9, preferably at least the upper portion of the passage channel 9 which is intended to include the face and possibly the torso of the individual (see for example figure 5The upper portion here refers to the portion of the passage channel 9 located on the side of the cross member 2 of the gantry 11. The field of view 32 of the infrared camera 12 is defined by a vertical angle (φ) and a horizontal angle (θ) (vertical and horizontal being defined with respect to the orientation of the gantry 11 during its operation, i.e., when the gantry 11 is installed on the ground or a support and is taking temperature measurements). In order to optimize the temperature measurement, the vertical angle (φ) and the horizontal angle (θ) are greater than or equal to 30° and less than or equal to 120° to limit the risk of the field of view 32 of the infrared camera 12 covering the surroundings and to ensure that an individual's face is within the field of view 32 of the infrared camera 12 when they pass through the passage channel 9, regardless of their size. 6-inch Visible Spectrum Camera

[0032] The visible spectrum camera 6 is configured to produce a visible image of the individual. To this end, it includes a visible spectrum detection chip 29 comprising a pixel array (hereinafter, "visible pixels") and an optical system configured to focus visible electromagnetic radiation onto the visible pixel array. Each visible pixel in the array is configured to generate an electrical signal based on visible radiation entering through the optical system during the acquisition of the visible image. This electrical signal is transmitted to a processor (or microprocessor) in the visible spectrum detection chip 29, which converts it into a corresponding color. The processor generates a visible image comprising a plurality of visible image pixels, each visible image pixel being representative of the visible radiation received by a corresponding visible pixel in the array.

[0033] The visible pixels of the visible spectrum detection chip 29 are configured to detect visible radiation with a wavelength greater than or equal to 0.4 micrometers and less than or equal to 0.7 micrometers. Each visible pixel can have a maximum width greater than or equal to one micrometer and less than or equal to thirty micrometers, depending on the desired total resolution of the visible spectrum camera 6. This resolution range makes it possible to obtain an image in which areas of the individual with a small surface area, such as the inner corner of the eye, are accurately identifiable.

[0034] The visible spectrum detection chip 29 can be a MEMS microelectromechanical system (English acronym for microelectromechanical system).

[0035] The visible spectrum detection chip 29 is fixed to a printed circuit board 28, as illustrated in figure 7If necessary, the visible spectrum detection chip 29 can be fixed on the same printed circuit board 24 as the infrared detection chip 25.

[0036] The optical system of the visible spectrum camera 6 is conventional and comprises, in a manner known per se, one or more lenses positioned on the optical axis of the visible spectrum camera 6 and configured to focus visible radiation onto the visible spectrum detection chip 29.

[0037] The visible spectrum camera 6 is fixed on the gantry 11 so that its field of view 31 covers at least the portion of the passage channel 9 which is covered by the field of view 32 of the infrared camera 12. Where appropriate, the field of view 31 of the visible spectrum camera 6 may be larger than the field of view 32 of the infrared camera 12.

[0038] The printed circuit board(s) on which the infrared camera(s) 12 and visible spectrum camera(s) 6 are mounted are housed in a casing 8 comprising a base, on which the printed circuit board(s) 28, 24, and a cover 23 attached to the base are mounted. The cover 23 has a first opening, positioned facing the infrared camera 12, and a second opening positioned facing the visible spectrum camera 6. Alternatively, a single opening positioned facing both cameras 6 and 12 may be made in the cover 23.

[0039] The diaphragm 27 can notably be mounted between the infrared camera 12 and the cover 23.

[0040] In one embodiment, the measurement system 10 comprises only one infrared camera 12, 6 (or two infrared cameras 12, 6), the infrared camera 6 further implementing the functions carried out by the visible spectrum camera 6. Processing Unit 15

[0041] The processing unit 15 may include a processor, microprocessor, microcontroller, etc. type computer configured to execute instructions and control the processor of the infrared detection chip 25, the visible spectrum camera 6 and, optionally, a presence sensor 13 and / or at least one signaling unit 33 (detailed later).

[0042] In one embodiment, the processing unit 15 is mounted on the same printed circuit board as the infrared detection chip 25. The processing unit 15 may, in particular, integrate the processor of the infrared detection chip 25. Alternatively, the processing unit 15 and the processor of the infrared camera 12 may be separate, in which case the processing unit 15 may be housed in the gantry 11, or remotely in a control panel separate from the gantry 11 (see, for example, figure 1 ) or networked.

[0043] The processing unit 15 is configured to determine the body temperature of an individual passing through the passage channel 9 from the electronic image obtained by the infrared camera 12 and, where appropriate, from the visible image obtained by the visible spectrum camera 6.

[0044] In the case where the system 10 includes a visible spectrum camera 6, the processing unit 15 is connected to the visible spectrum camera 6 and configured to receive the visible image and identifies within this visible image the visible image pixels that are representative of at least a part of an individual's face. In one embodiment, the processing unit 15 preferably identifies only a part of the face, typically the eyes or even an inner corner of the eyes. Indeed, the area with the highest temperature on a face generally corresponds to the inner corner of the eye.

[0045] The processing unit 15 is further connected to the infrared camera 12 and configured to receive the electronic image and correlate it with the electronic image so as to identify in the electronic image the infrared image pixels that correspond to the visible image pixels representing the face, or, where applicable, the eyes and / or the inner corner of one or both eyes. This correlation ensures, in particular, that the temperature values ​​calculated from the electronic image correspond to the individual's temperature, and not to that of their environment. The specific choice of the eyes, and more particularly the inner corner of the eyes, further limits environmental interference by ensuring that the measured temperature value is close to the individual's core body temperature.

[0046] Finally, regardless of the configuration (with or without a visible spectrum camera 6), the processing unit 15 is configured to determine a maximum temperature value Tmax associated with the infrared image pixels corresponding to the face, eyes and / or inner corner of the eyes, and to deduce the individual's body temperature.

[0047] By way of comparison, conventional measurement systems, and in particular portable systems (contact or non-contact), do not allow for temperature measurement in the corner of the eye, either because they are designed to be placed in contact with the individual's forehead or the inside of their ear, or because it would be impractical for an operator to check an individual's temperature at the entrance to a restricted access area by taking a temperature at eye level. In contrast, since the invention produces an electronic image of the individual, it is possible to determine the point with the highest temperature in the image, which generally corresponds to the inner corner of the eye, without contact and without requiring operator intervention.

[0048] When the system 10 includes only one infrared camera 12, 6, the processing unit is configured to determine directly in the electronic image the infrared image pixels that correspond to the visible image pixels representative of the face, or where appropriate, the eyes and / or the inner corner of an eye or eyes.

[0049] Thus, only the facial area, and preferably only the area including the eyes and / or the inner corners of the eyes, is measured, and the maximum temperature Tmax in this limited area is compared to the predetermined threshold Tseuil. The use of measurement system 10 thus ensures that the temperature value obtained is very close to, or even equal to, the individual's core body temperature. Presence sensor 13

[0050] In order to limit external disturbances when measuring the temperature of an individual, the measurement system 10 may further include a presence sensor 13 configured to determine the presence of an individual within the passage channel 9 of the gantry 11. The processing unit 15 is then configured to generate an electronic image and a visible image only when the presence sensor 13 detects an object (a priori an individual) within the passage channel 9.

[0051] The Applicant has observed that the environment in which the system is positioned generates infrared energy that can interfere with temperature measurements. For example, LED (light-emitting diode) or fluorescent tube lighting emits a temperature of approximately 40°C, which corresponds to a fever and is therefore likely to interfere with the system's temperature measurement. By generating the electronic image only when the individual is within the passage channel 9, it is possible to ensure that the individual occupies the field of view 31, 32 of the infrared camera 12 and the visible-spectrum camera 6 during the acquisition of the electronic and visible images, and that the temperature measurement is thus not affected by external factors.

[0052] The presence sensor 13 can be fixed to the gantry 11, for example on one of the panels or the cross member 2. For example, the presence sensor 13 can include one or more photoelectric barriers fixed to the inner faces opposite the panels. Preferably, the system includes at least one photoelectric barrier positioned at the entrance 9a of the gantry 11 and one photoelectric barrier positioned at the exit 9b of the gantry 11 (and optionally one or more photoelectric barriers distributed between the two), the processing unit 15 then being configured to generate an electronic image and a visible image between the time when the photoelectric barrier at the entrance 9a and the photoelectric barrier at the exit 9b each detect the presence of an individual.

[0053] As is known, photoelectric barriers each comprise a light beam emitter, mounted on one of the inner faces of the side panels 1, and a light beam receiver, mounted on the other inner face. Alternatively, the emitter and receiver can be fixed to the same side panel 1, the photoelectric barrier then comprising a reflector fixed to the opposite inner face and configured to reflect the light signal emitted by the emitter onto the reflector. When a person passes through, the reception of the light beam by the receiver is interrupted: an evaluation electronic (of the microprocessor type) then sends a defined electrical signal to the processing unit 15 indicating the passage of a person. When the photoelectric barrier is placed at the entrance 9a of the portal 11, the central unit infers that a person is present in the passage channel 9.When the photoelectric barrier is placed at exit 9b of gantry 11, the central unit deduces that the individual has exited passage channel 9. Light 30

[0054] Optionally, the measurement system 10 may also include a light 30, preferably flashing, positioned near the infrared camera 12 to attract the individual's attention during the acquisition of electronic and visible images. For example, the light 30 may be mounted on the housing 8, near the infrared camera 12.

[0055] In one embodiment, the light 30 may include a light-emitting diode (LED).

[0056] The light 30 can be switched on, and optionally flash, continuously. Alternatively, the processing unit 15 can be connected to the light 30 so as to switch it on, and optionally make it flash, only when the electronic and visible images need to be acquired. Typically, when the measuring system 10 includes a presence sensor 13, the processing unit 15 can switch on the light 30, and optionally make it flash, when a person is detected by the presence sensor 13. Signaling Unit 33

[0057] In one embodiment, the measurement system 10 may further include at least one signaling unit 33 configured to generate an optical (light signal) and / or audible (acoustic signal) alert when the maximum temperature value Tmax exceeds a predetermined threshold.

[0058] Optionally, the signaling unit 33 can also be configured to generate a signal when the maximum temperature value Tmax is less than or equal to the predetermined threshold Tthreshold, in order to indicate to an operator that a measurement has been taken but that the individual's body temperature is below the threshold. For example, the signaling unit 33 can include a green light and a red light. The processing unit 15 can then send instructions to activate the red light when the maximum temperature Tmax is above the predetermined threshold Tthreshold and the green light when it is less than or equal to this predetermined threshold. Measurement method

[0059] An individual's body temperature can be measured using the measuring system 10 in accordance with the following steps.

[0060] During an initial step S0, the presence of an individual in the gantry 11 and an individual is determined by the presence sensor 13. For this, the processing unit 15 queries the presence sensor 13, such as a photoelectric barrier.

[0061] In the case of a presence sensor comprising photoelectric barriers, when the barrier located at the entrance 9a (respectively at the exit) of the gantry 11 sends a presence signal to the processing unit 15, the latter deduces that an individual enters (respectively exits) the passage channel 9. The processing unit 15 therefore triggers the measurement of the individual's body temperature between the reception of the presence signal from the barrier located at the entrance 9a and the reception of the presence signal from the barrier located at the exit 9b.

[0062] InConversely, when the photoelectric barriers, and in particular the barrier at the entrance 9a, do not send a presence signal, the processing unit 15 deduces that no individual is in the passage channel 9 and therefore does not trigger the temperature measurement.

[0063] During step S1, the processing unit 15 sends instructions to the infrared camera 12 to produce an electronic image. As mentioned above, the infrared camera 12 is oriented, if necessary by means of the arm 7, so that its field of view 32 covers all or part of the passage channel 9, including at least an upper portion.

[0064] Since the electronic image is captured between the detections made by the barrier at the entrance 9a and the barrier at the exit 9b of the gantry 11, it necessarily includes the individual. Furthermore, as the infrared camera 12 is mounted on the gantry 11 so that its field of view 32 covers at least the upper portion of the passage channel 9, the individual's face and possibly torso are within the field of view 32 of the infrared camera 12.

[0065] During an S2 step, the processing unit 15 sends instructions to the visible spectrum camera 6 to produce a visible image of all or part of the portion of the passage channel 9.

[0066] In one embodiment, the visual field 31 of the visible spectrum camera 6 and the visual field 32 of the infrared camera 12 cover substantially the same portion of the passage channel 9, and in any case the upper portion thereof so that the visible image and the electronic image both cover the face and torso of the individual.

[0067] Optionally, the field of view 32 of the infrared camera 12 and / or the field of view 31 of the visible spectrum camera 6 can cover the entire height of the passage channel 9.

[0068] Preferably, steps S1 and S2 are simultaneous to facilitate the matching of visible and infrared images. Furthermore, in one embodiment, the light 30 can be switched on by the processing unit 15 (or kept on continuously), optionally flashing, to attract the individual's attention during the acquisition of the electronic and visible images in steps S1 and S2.

[0069] During step S3, the processing unit 15 identifies in the visible image the visible image pixels that correspond to the individual's face, the individual's eyes, and / or the inner corners of the eyes. Preferably, the processing unit 15 identifies the visible image pixels corresponding to at least one inner corner of the eyes.

[0070] To achieve this, the processing unit 15 detects the face (or, respectively, the eyes and / or at least one inner corner of the eyes) using the Viola-Jones method (or integral image), which is a supervised learning process employing a Haar feature cascade classifier. For further details on this method, see the article by Paul Viola and Michael Jones, "Rapid Object Detection using a Boosted Cascade of Simple Features," presented at the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition.

[0071] Other methods can be used to perform step S3, such as deep learning methods using a semantic segmentation classifier. For more details on the use of semantic segmentation classifiers, see the article by Alex Krizhevsky, Ilya Stuskever, and Geoffroy E. Hinton, "ImageNet Classification with Deep Convolutional Neural Networks," or the article by Vijay Badrinarayanan, Alex Kendall, and Roberto Cipolla, "SegNet: A Deep Convolutional Encoder-Decoder Architecture for Image Segmentation." These methods can be used and combined as needed to increase the detection speed and accuracy of the desired features.

[0072] During a step S4, the processing unit 15 matches the visible image and the electronic image so as to identify the infrared image pixels corresponding to the visible image pixels identified in step S3.

[0073] The mapping of visible and infrared image pixels can be achieved by transposing the coordinates of the image pixels from the visible image to the electronic image, taking into account the positions and orientations of the visible spectrum camera 6 and the infrared camera 12, in a manner known to those skilled in the art. For example, this can be done by automatically learning the characteristics of the cameras 6 and 12 (intrinsic parameters of the cameras 6 and 12 such as focal length and distortion, and extrinsic parameters such as position and orientation). This learning is performed once and for all, typically during the installation and calibration of the measurement system 10. For example, the transposition can be done by implementing an affine transformation of the visible image into the electronic image. For this purpose, the coefficients of the affine transformation are determined during the calibration of the measurement system 10.For this purpose, visual references can be positioned in space at known positions relative to the cameras, and then visible and infrared images of these visual references are made with cameras 6, 12. Knowing the three-dimensional position of the visual references relative to the two cameras 6, 12, it is then possible to determine the coefficients of the affine application of the visible image in the electronic image.

[0074] During a step S9, the processing unit 15 determines the maximum temperature value Tmax associated with the infrared image pixels identified in step S4 and deduces the body temperature of the individual. Calibration of infrared measurements

[0075] According to the invention, to correct the electronic image obtained by the infrared camera 12 and ensure the reliability of the body temperature measurement, the measurement system 10 further comprises: a support 16; a first standard 4 and a second standard 5 positioned in the field of view 32 of the infrared camera 12; and a first thermal probe 20 and a second thermal probe 22 configured to measure an instantaneous temperature of the first standard 4 and the second standard 5.

[0076] Furthermore, the processing unit 15 is also configured to determine a gain coefficient and a shift coefficient of the infrared camera 12 and thus correct the electronic image obtained by the infrared camera 12, in order to determine at step S9 the maximum temperature value Tmax associated with the infrared image pixels identified at step S4.

[0077] In what follows, the invention will be described generally in the case where the processing unit 15 performs the calibration of the infrared measurements. This is not, however, limiting; this calibration can be performed by any processor or microprocessor, such as a dedicated microcontroller chip controlled by the processing unit 15 or by an external computer, either local or remotely networked. First stallion 4 and second stallion 5

[0078] The first standard 4 has a first reference temperature and the second standard 5 has a second reference temperature; their function is to allow the calibration of the infrared camera 12 during the acquisition of each electronic image. The first and second reference temperatures are preferably different. For example, the first standard 4 and the second standard 5 can each comprise a surface heated to the corresponding reference temperature. Alternatively, the first standard 4 and the second standard 5 can each comprise a surface, which may be substantially flat, heated to the corresponding reference temperature.

[0079] To ensure optimal correction of the electronic image produced by the infrared camera 12, the first and second temperatures are close to the body temperature at which an individual is usually considered to have symptoms of fever, typically 37.5°C. The first and second reference temperatures can, for example, be between 35°C and 40°C. In one embodiment, the first reference temperature is 36°C and the second reference temperature is 39°C.

[0080] The first standard 4 and the second standard 5 are each positioned within the field of view 32 of the infrared camera 12 such that the electronic image comprises image pixels representative of their respective temperature values. Preferably, the first standard 4 and the second standard 5 are fixed relative to the infrared camera 12 and are positioned within the field of view 32 of the infrared camera 12.

[0081] The first standard 4 and the second standard 5 can, for example, be fixed to the gantry 11. In one embodiment, the first standard 4 and the second standard 5 are fixed to the cross member 2 of the gantry 11, within the field of view 32 of the infrared camera 12. This configuration is particularly feasible when the infrared camera 12 is mounted on an arm 7 so as to extend downstream of the passage channel 9. Advantageously, fixing the first and second standards 4, 5 to the cross member 2 ensures that the standards 4, 5 are fixed relative to the infrared camera 12 and are not at risk of being obscured by the individual as they pass through the channel.

[0082] If necessary, the first standard 4 and the second standard 5 can be housed in the same case 3.

[0083] The position and surface area of ​​the first standard 4 and the second standard 5 relative to the infrared camera 12 are chosen such that the first standard 4 and the second standard 5 each extend within the field of view 32 by at least one pixel of the infrared detection chip 25, for example, a sub-matrix comprising 3x3 pixels. For this purpose, the first and second standards 4, 5 can be placed at a distance between 20 cm and 1.5 meters from the infrared detection chip 25 and have a surface area between 25 mm² and 400 cm².

[0084] In one embodiment, the first standard 4 and the second standard 5 can be fixed on the inner face of one and / or the other of the side panels 1 of the gantry 11, preferably near the cross member 2.

[0085] Optionally, to protect the first and second standards 4, 5, the system may further include a diaphragm 17, 18 positioned in front of each standard 4, 5 to shield them from the environment and prevent potential disturbances (such as the presence of a draft or anything that could alter the temperature of the standards 4, 5). If necessary, the diaphragm(s) 17, 18 may be mounted between the first standard 4 and the second standard 5, respectively, and a cover of the housing 3.

[0086] The measuring system 10 further includes a first heating element 21 and a second heating element 23 configured to maintain the first standard 4 and the second standard 5 at the first reference temperature and the second reference temperature, respectively. The first and second heating elements 21, 23 may, for example, each include a resistor connected to the first and second standards 4, 5, respectively. In one embodiment, the first and second heating elements 21, 23 are mounted on the face opposite the infrared camera 12 (which corresponds to the face opposite the first and second standards 4, 5) so as not to be seen by the infrared camera 12 (see figure 6 ).

[0087] If necessary, the first and second heating elements 21, 23 can be housed in the same casing 3 as the first and second standards 4, 5. First and second thermal probes 20, 22

[0088] The first and second thermal probes 20, 22 are configured to measure the instantaneous temperature of the first standard 4 and the second standard 5, respectively. According to the invention, the first and second thermal probes 20, 22 are in contact (direct or indirect) with the first or second standard 4, 5, respectively. The first and second thermal probes 20, 22 are preferably monolithic with the first and second standards 4, 5, respectively. It should be noted, however, that preferably, the first and second thermal probes 20, 22 are positioned so as not to form an obstacle between the individual and the infrared camera 12.

[0089] Preferably, the first and second thermal probes 20, 18 have a measurement accuracy of less than or equal to 0.1°C in order to provide a very precise value of the instantaneous temperature of each standard 4, 5. As we will see later, it is this value of the instantaneous temperature of the first and second standard 4, 5 which is then used by the processing unit 15, and not the value of the first and second programmed reference temperatures, to correct the electronic image generated by the infrared camera 12.

[0090] According to the invention, the thermal probe 20, 22 is connected to the corresponding standard 4, 5 via a conductive track. The Applicant, however, observed that, during operation, the temperature of this conductive track was substantially equal (within 0.1 °C) to the temperature of the heated surface of the corresponding standard 4, 5. Consequently, in one embodiment, the conductive track connecting the first thermal probe 20 to the heated surface of the first standard 4 and the second thermal probe to the heated surface of the second standard 5 can be considered as forming part of the standards 4, 5 respectively by means of a processing unit 15. In this embodiment, the first and second thermal probes 20, 22 can therefore be mounted in the immediate vicinity of the first standard 4 and the second standard 5.According to the invention, the first thermal probe 20 can be fixed to the center of the heated surface of the first standard 4 and the second thermal probe 22 is fixed to the center of the heated surface of the second standard 5 (see for example . figure 8 ). The first and second thermal probes 20, 22 may, for example, include a semiconductor chip. The standard 4, 5 is then framed by the upper part of the semiconductor chip, at the edge of the reading area.

[0091] When the 16 support includes an additional printed circuit board, the thermal probes can be mounted on this additional printed circuit board.

[0092] If necessary, the first and second heating elements 21, 23 can be controlled by the processing unit 15 as a function of the instantaneous value of the temperature of the first and second standard 4, 5 which is measured by the first and second thermal probe 20, 22.

[0093] In order to correct the electronic image of the infrared camera 12, the processing unit 15 is further configured to determine the gain coefficient and the shift coefficient from the respective instantaneous temperatures of the first standard 4 and the second standard 5 and the temperature values ​​of the first standard 4 and the second standard 5 in the electronic image and to apply the gain coefficient and the shift coefficient thus determined to the temperature value associated with each image pixel so as to obtain the corrected electronic image.

[0094] Thus, unlike conventional measuring devices, the measurement system 10, which creates an electronic image of the individual and determines the temperature value at each image pixel, does not simply take measurements at a random point on the individual's face and thus limits the risks of measurement interference from the environment.

[0095] The processing unit 15 is therefore configured to execute instructions and control the first and second thermal probes 20, 22 and the first and second heating elements 21 and 23. Infrared measurement calibration method

[0096] The temperature values ​​associated with the infrared image pixels identified in step S4 can then be calibrated using the measurement system 10 in accordance with the following steps.

[0097] During a step S5, the instantaneous temperature of the first standard 4 and the second standard 5 is determined by the first thermal probe 20 and the second thermal probe 22, respectively.

[0098] Preferably, steps S1 and S5 are simultaneous. By simultaneous, we understand here that steps S1 and S5 are carried out at the same time, or with a time difference at most equal to the time required for the temperature of the first standard 4 and the second standard 5 to change by 0.1 °.

[0099] During a step S6, the processing unit 15 determines in the electronic image obtained in step S1 the temperature value of each infrared image pixel corresponding to the first standard 4 and the second standard 5. The infrared image pixels corresponding to standards 4, 5 can be identified in the electronic image insofar as the spatial position of the first and second standards 4, 5 relative to the infrared camera 12 is known and fixed.

[0100] According to the invention, particularly when the thermal probes include a semiconductor chip, the processing unit 15 determines the temperature value of each infrared image pixel corresponding to the conductive track connecting the first standard 4 and the second standard 5 to the first thermal probe 20 and the second thermal probe 22. As mentioned above, these conductive tracks have a temperature substantially equal to that of the corresponding standard 4 and 5 and are therefore considered to be part of the first standard 4 and the second standard 5, respectively. The overlapping area of ​​the thermal probes 20 and 22 and the heated surface of the standards 4 and 5 significantly reduces errors caused by temperature drops. In a variant not corresponding to the invention, the processing unit 15 can determine the temperature value associated with the heated surface of the standards 4 and 5.When several image pixels correspond to the first standard 4 and the second standard 5 in the electronic image, the processing unit 15 can in particular choose the average temperature value from the sub-matrix of image pixels as the instantaneous value of the corresponding standard 4, 5.

[0101] During a step S7, the processing unit 15 deduces from the temperature values ​​determined in step S6 and from the instantaneous temperature of the first and second standards 4 and 5 measured in step S5 a gain coefficient k 1 and a shift coefficient k 2 of the infrared camera 12. The gain coefficient k 1 corresponds to a deviation in amplitude of the infrared camera 12 while the shift coefficient k 2 corresponds to an error having a constant value corresponding to a shift of the measured values ​​on the ordinate axis of the output voltage of the infrared detection chip 25.

[0102] More precisely, the instantaneous temperature T i_1 (respectively, T i_2 ) of the first standard 4 (respectively, of the second standard 5) is equal to the sum of the gain coefficient K 1 multiplied by the temperature value T IR_1 (respectively, T IR_2 ) determined in step S3 for the first standard 4 (respectively, for the second standard 5) and the shift coefficient k 2: T i _ 1 = T IR _ 1 * k 1 + k 2 T i _ 2 = T IR _ 2 * k 1 + k 2

[0103] The instantaneous temperatures Ti_1 and Ti_2 of the first standard 4 and the second standard 5 are independent of the deflection of the infrared camera 12, as they are measured by the first and second thermal probes 20 and 22. Furthermore, the deflection of the infrared camera 12 is the same for the temperature values ​​TIR_1 and TIR_2 determined in step S3. It follows that k1 and k2 are identical in these two equations. Thus, solving these equations, made possible by the presence of the two standards 4 and 5 and the determination of their instantaneous temperatures Ti_1 and Ti_2 by the associated thermal probes 20 and 22, allows us to determine the values ​​of the gain coefficient k1 and the offset coefficient k2 of the infrared camera 12.

[0104] During a step S5, the processing unit 15 applies the gain coefficient k1 and the shift coefficient k2 determined in step S4 to the temperature value associated with each infrared image pixel in order to obtain a corrected electronic image.

[0105] Thus, for each infrared image pixel i of the electronic image generated in step S3, the processing unit 15 applies the gain coefficient k1 and the shift coefficient k2 to the temperature value TIR_i associated with this infrared image pixel i so as to obtain, for each image pixel i, the corrected temperature value Tcorr_i and deduce the corrected electronic image which includes the corrected infrared image pixels: T corr _ i = k 1 * + T IR _ i + k 2

[0106] During step S9, the processing unit 15 determines the maximum temperature value Tmax in the corrected electronic image and compares this maximum temperature value Tmax with a predetermined threshold Tseuil. Since the body temperature at which an individual is usually considered to have fever symptoms is generally 37.5°C, the predetermined threshold Tseuil could, for example, be equal to 37.5°C.

[0107] When the maximum temperature Tmax is greater than or equal to the predetermined threshold Tseuil, the processing unit 15 sends instructions to the signaling unit 33 in order to generate an alert (typically, a visual and / or acoustic alert).

[0108] In one embodiment, the measurement process further includes a step S8 in which the processing unit 15 applies a predetermined compensation coefficient k3 to the temperature value of each infrared image pixel in order to compensate for a difference in emissivity between the first and second standards 4, 5 and human skin and thus obtain a corrected temperature value closer to the actual value of the individual's body temperature: T finale _ i = T corr _ i * k 3

[0109] It is then this corrected and compensated temperature value T final_i that is used during step S9 to determine the maximum temperature value Tmax, and not the corrected value T corr_i.

[0110] In one embodiment, the compensation coefficient may only be applied to the maximum temperature value Tmax determined in step S9. Step S8 then takes place after step S9.

[0111] The compensation coefficient k3 is a fixed, predetermined coefficient that does not depend on any potential thermal deviation or the measurement environment. This coefficient does, however, depend on the emissivity of human skin and the emissivity of the first and second standards 4, 5, and more specifically on the material constituting their heated surface or, where applicable, the conductive track connected to it. Therefore, it may be preferable to make the first and second standards 4, 5 from the same constituent material, differing only in their respective reference temperatures.

[0112] In one embodiment, steps S1 to S9 can be implemented continuously following the same interrogation period (which can be between ten milliseconds and five hundred milliseconds of interrogation), regardless of the detection of an individual in the passage channel 9. In this case, the processing unit 15 sends instructions to generate an alert to the signaling unit 33 only if the presence sensor 13 detects an individual in the passage channel 9.

[0113] Furthermore, steps S1 to S9 are repeated as long as the individual remains in passage channel 9, typically until the photoelectric barrier at exit 9b of passage channel 9 detects the individual's exit. The repetition period of these steps can, in particular, be equal to the polling period of the presence sensor 13 by the processing unit 15.

[0114] Furthermore, it should be noted that at any time during the operation of the system (and therefore during the interrogation of the presence sensor 13 by the processing unit 15), the first and second heating elements 21, 23 maintain the first standard 4 and the second standard 5 at the first reference temperature and the second reference temperature, respectively, so as to guarantee that the instantaneous temperature of said elements is close to their respective reference temperature during steps S1 and S5.

[0115] As is known in itself, the measurement system 10 further includes a kiosk comprising a base and a screen, connected to the system's processing unit, for example via an Ethernet interface.

Claims

1. Measurement system (10) of an individual's body temperature comprising: an archway (11) comprising two side panels (1) connected by a cross member (2) and together delimiting a passageway (9) for an individual; an infrared camera (12) comprising an infrared detection chip (25) comprising an infrared pixel matrix and being configured to convert an infrared radiation received by each infrared pixel into a corresponding temperature value and to generate an electronic image comprising a plurality of infrared image pixels, each infrared image pixel being representative of the temperature value received by a corresponding infrared pixel, the infrared camera (12) being fixed onto the archway (11) so that a field of view (32) of the infrared camera (12) covers all or part of the portion of the passageway (9); a processing unit (15) configured to identify the infrared pixels corresponding to at least a part of an individual's face and to determine a maximum temperature value associated with the identified infrared pixels and to deduce therefrom a body temperature of the individual; and a calibration module (3) comprising a first reference target (4) and a second reference target (5) positioned in the field of view (32) of the infrared camera (12) so that the electronic image comprises the infrared image pixels representative of the temperature value of the first reference target (4) and the second reference target (5); the calibration module further comprises a first thermal sensor (20) fixed at the center of a heated surface of the first reference target (4) and configured to measure an instantaneous temperature of the first reference target (4) and a second thermal sensor (22) fixed at the center of a heated surface of the second reference target (5) and configured to measure an instantaneous temperature of the second reference target (5), the first and the second thermal sensors (20, 22) being connected to the first and second reference targets (4, 5), respectively, by means of the first and a second conductive track, the processing unit being further configured to : determine an instantaneous temperature of the first and the second conductive tracks and deduce therefrom the instantaneous temperature of the first and second reference targets (4, 5) respectively; and determine a gain coefficient (k1) and an offset coefficient (k2) from the respective instantaneous temperatures of the first reference target (4) and the second reference target (5) and temperature values of the first reference target (4) and the second reference target (5) in the electronic image and to apply the gain coefficient (k1) and the offset coefficient (k2) thus determined to the temperature value associated with each infrared image pixel so as to obtain a corrected electronic image, the processing unit (15) being configured to determine the maximum temperature value from the corrected electronic image.

2. Measurement system (10) according to claim 1, further comprising a visible spectrum camera (6) comprising a visible spectrum detection chip (29) comprising a visible pixel matrix and being configured to generate a visible image comprising a plurality of visible image pixels, the visible spectrum camera (6) being fixed onto the archway (11) so that a field of view (31) of the visible spectrum camera (6) covers at least a portion of the passageway (9), the processing unit being configured to match the visible image and the electronic image so as to identify the infrared image pixels corresponding to the visible image pixels identified.

3. Measurement system (10) according to one of claims 1 to 2, wherein the processing unit (15) is also configured to apply a predetermined compensation coefficient (k3) to the temperature value of each infrared image pixel.

4. Measurement system (10) according to one of claims 1 to 3, wherein the first and second thermal sensors (20, 22) each comprise a semiconductor chip connected to the first and second reference targets (4, 5), respectively, by means of the first and second conductive tracks.

5. Measurement system according to one of claims 1 to 4, wherein the first reference target (4) and the second reference target (5) are fixed onto one of the two side panels (1) and the cross member (2).

6. Measurement system (10) according to one of claims 1 to 5, also comprising a presence sensor (13) configured to determine a presence of an individual in the passageway (9), the processing unit (15) being configured to generate the electronic image only when the presence sensor (13) detects an object inside the passageway (9).

7. Measurement system (10) according to claim 2, wherein the infrared camera (12) and the visible spectrum camera (6) are mounted on an arm (7) fixed onto the cross member (2) and extending from an exit (9b) of the archway (11).

8. Measurement system (10) according to one of claims 1 to 7, also comprising a light (30), preferably flashing, fixed near the infrared camera (12) so as to draw the gaze of an individual passing through the passageway (9).

9. Measurement system (10) according to one of claims 1 to 8, wherein the field of view (32) of the infrared camera (12) has a vertical angle (φ) and a horizontal angle (θ) greater than or equal to 30° and less than or equal to 120°.

10. Measurement method for an individual's body temperature using a measurement system (10) according to one of claims 1 to 9, comprising the following steps: S1: producing an electronic image of a portion of the passageway (9) in which an individual is located, the electronic image comprising a plurality of infrared image pixels representative of a temperature value received by a corresponding infrared pixel of a matrix of infrared pixels of an infrared camera (12), a first reference target (4) and a second reference target (5) being positioned in the field of view (32) of the infrared camera (12) so that the electronic image comprises infrared image pixels representative of the temperature value of the first reference target (4) and the second reference target (5); S4: identifying the infrared image pixels corresponding to at least part of an individual's face, preferably at least one inner corner of the eyes; S5: determining an instantaneous temperature of a conductive track fixed at the center of a heated surface of the first reference target (4) and of a conductive track fixed at the center of a heated surface of the second reference target (5); S6: determining in the electronic image the temperature value of the image pixels corresponding to the first reference target (4) and to the second reference target (5); S7: deducing therefrom a gain coefficient (k1) and an offset coefficient (k2) for the infrared camera (12); and S8: applying the gain coefficient (k1) and the offset coefficient (k2) to the temperature value associated with each image pixel so as to obtain a corrected electronic image; and S9: determining a maximum temperature value associated with the identified infrared image pixels and deducing therefrom a body temperature of the individual.

11. Measurement method according to claim 10, also comprising the following steps, prior to step S9: S2: producing a visible image of all or part of the portion of the passageway (9), the visible image comprising a plurality of visible image pixels; S3: identifying the visible image pixels corresponding to at least a part of an individual's face, preferably at least one inner corner of the eyes; and such that step S4 comprises matching the visible image and the electronic image so as to identify the infrared image pixels corresponding to the visible image pixels identified in step S3; steps S1 and S2 being optionally simultaneous.

12. Method according to one of claims 10 or 11, comprising applying a predetermined compensation coefficient (k3) to the temperature value of each image pixel or to the maximum temperature value (Tmax) determined in step S9.

13. Method according to one of claims 10 to 12, further comprising, prior to step S1, a step S0 of determination of a presence of an individual in the archway (11), steps S1 to S9 being implemented only when an individual is present in the passageway (9).