WO2022200102A1 - Système de surveillance d'un occupant d'un véhicule automobile - Google Patents
Système de surveillance d'un occupant d'un véhicule automobile Download PDFInfo
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- WO2022200102A1 WO2022200102A1 PCT/EP2022/056533 EP2022056533W WO2022200102A1 WO 2022200102 A1 WO2022200102 A1 WO 2022200102A1 EP 2022056533 W EP2022056533 W EP 2022056533W WO 2022200102 A1 WO2022200102 A1 WO 2022200102A1
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 41
- 238000013186 photoplethysmography Methods 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims description 21
- 230000035790 physiological processes and functions Effects 0.000 claims description 17
- 238000005286 illumination Methods 0.000 claims description 9
- 230000001960 triggered effect Effects 0.000 claims description 6
- 230000012447 hatching Effects 0.000 description 8
- 239000008280 blood Substances 0.000 description 5
- 210000004369 blood Anatomy 0.000 description 5
- 230000008859 change Effects 0.000 description 5
- 210000003128 head Anatomy 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 238000002310 reflectometry Methods 0.000 description 2
- 230000005236 sound signal Effects 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000002526 effect on cardiovascular system Effects 0.000 description 1
- 210000001061 forehead Anatomy 0.000 description 1
- 230000004886 head movement Effects 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 210000000056 organ Anatomy 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000029058 respiratory gaseous exchange Effects 0.000 description 1
- 230000036387 respiratory rate Effects 0.000 description 1
- 230000002123 temporal effect Effects 0.000 description 1
Images
Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/024—Detecting, measuring or recording pulse rate or heart rate
- A61B5/02416—Detecting, measuring or recording pulse rate or heart rate using photoplethysmograph signals, e.g. generated by infrared radiation
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6887—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient mounted on external non-worn devices, e.g. non-medical devices
- A61B5/6893—Cars
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
- A61B5/0062—Arrangements for scanning
- A61B5/0064—Body surface scanning
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/024—Detecting, measuring or recording pulse rate or heart rate
- A61B5/02416—Detecting, measuring or recording pulse rate or heart rate using photoplethysmograph signals, e.g. generated by infrared radiation
- A61B5/02427—Details of sensor
- A61B5/02433—Details of sensor for infrared radiation
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/0816—Measuring devices for examining respiratory frequency
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/86—Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
- G01S17/894—3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
Definitions
- the field of the present invention relates to a system for monitoring an occupant of a motor vehicle. More specifically, this monitoring system aims to determine one or possibly several physiological parameters of an occupant of a motor vehicle by remote photoplethysmography. This monitoring system also aims to define, from said parameter, the physiological state of said occupant. The invention also relates to a method for determining the physiological state of the occupant by photoplethysmography, this method using said monitoring system.
- Plethysmography is a method of measuring changes in the volume of a part of the body (for example an organ) which allows these vital signs to be extracted. Plethysmography is used in particular to detect changes in volume due to a cardiovascular pulse wave which passes through the body of a subject with each heartbeat.
- Known plethysmography methods include photoplethysmography, an optical measurement technique to assess a time-varying change in the reflectance or transmission of light in an area or region of interest.
- Photoplethysmography is based on the fact that the blood absorbs more light than the surrounding tissues, the variations in blood volume generated with each heartbeat consequently affect the transmittance and reflectivity. By evaluating transmittance and/or reflectivity at different wavelengths (typically red and infrared), blood oxygen saturation or other parameters related to the vital signs of the subject being studied can be determined. Photoplethysmography can be performed "remotely" in a non-intrusive manner, i.e. without contact with said subject. For this, light sources (in particular infrared illumination sources) and one or more image acquisition devices, such as a camera or a video camera, are for example used. This equipment is thus placed at a distance from the subject during the shots.
- light sources in particular infrared illumination sources
- image acquisition devices such as a camera or a video camera
- Remote photoplethysmography can prove useful in the context of an automotive application to enhance road safety, in particular to monitor the physiological state of the driver of said motor vehicle.
- changes in the lighting in the passenger compartment of a motor vehicle and more particularly drastic changes in the lighting on the face or the hands of the occupant lead to difficulties in the acquisition and use of data. by the image acquisition device or devices.
- the lighting in the passenger compartment is variable over time, it depends in particular on the environment outside the vehicle (weather, presence of buildings or trees or any other object likely to generate shade, time at time of shooting, etc.).
- the light reflected by the driver comprises a component due to the lighting coming from the infrared light sources and another component due to the ambient lighting
- the variations of the component due to the ambient lighting in the light received by the sensor(s) of the image acquisition device(s) have a significant impact.
- the change in lighting on the driver's face is likely to alter the images, thus limiting the reliability of the data used when determining one or possibly several physiological parameters by photoplethysmography. Real-time monitoring of the motor vehicle occupant's vital signs can be difficult under these conditions.
- any light detected by the sensor of the acquisition device generates noise ("shot noise" in English) so that a high value of the component due to ambient illumination decreases the signal-to-noise ratio and makes the more complex useful signal detection. It is therefore essential to overcome the component due to ambient illumination in the light received by the sensor of the image acquisition device to promote the reliability of the method for determining a physiological parameter of the occupant of the motor vehicle by photoplethysmography.
- the object of the invention is to at least partially overcome these disadvantages of the prior art by proposing a simple, effective and economical solution.
- the subject of the invention is a system for monitoring an occupant of a motor vehicle, the monitoring system comprising a pulsed light source configured to emit a train of light pulses in the direction of the occupant, a device image acquisition device, such as a time-of-flight camera, said image acquisition device comprising an image sensor and a shutter configured to pass light to the image sensor during a first period of acquisition during which the pulsed light source emits a light pulse and during a second acquisition period during which the pulsed light source is inactive, the second acquisition period being triggered outside the first acquisition period , the respective duration of the first and of the second acquisition periods being at least equal to the duration of a light pulse emitted by the pulsed light source, the light received by the image sensor during the first acquisition period and the second acquisition period comprising a component due to the ambient lighting and a component due to the light pulse emitted by the pulsed light source, the monitoring system comprising also a processing unit configured to determine from the images acquired a physiological parameter of the occupant by photoplethy
- Such a monitoring system therefore makes it possible to overcome the variations introduced by the component due to the ambient lighting on the images acquired by the image acquisition device or devices, thus making it possible to apply the photoplethysmography methods therein in order to to determine one or possibly several physiological parameters of the occupant with the aim of evaluating his physiological state.
- a time-of-flight camera therefore also makes it possible to reconstruct the filmed scene (in the present case in particular the face of the driver) in three dimensions in real time.
- Such a surveillance system can thus allow real-time monitoring of the movements of the occupant, in particular of his head, and to select the images presenting a profile (in particular from the front) to be processed during the process for developing the physiological state of the occupant while removing in particular the images deemed unusable in terms of photoplethysmography.
- the invention may further comprise one or more of the following aspects taken alone or in combination:
- the respective duration of the first , of the second and of the third acquisition period is less than 50 ns and more particularly equal to 20 ns;
- the durations of the first, second and third vesting periods are identical to each other;
- the duration of a pulse of the train of light pulses emitted by the pulsed light source is equal to the duration of the first acquisition period
- the monitoring system comprises a control unit configured to synchronize the start of the train of light pulses emitted by the pulsed light source with the opening of the shutter at the start of the first acquisition period;
- control unit is configured to control the opening and closing of the shutter
- the monitoring system is configured to select a region of interest on the occupant's face to allow determination of the physiological parameter
- the image sensor is configured to establish a depth map of the occupant's face from the images acquired by the image acquisition device;
- the image acquisition device has three separate shutters: a first shutter configured to pass light to the image sensor during the first acquisition period, a second shutter configured to pass light to the image sensor during the second acquisition period and a third shutter configured to pass light to the image sensor during the third acquisition period.
- the invention also relates to a method for determining the physiological state of the occupant by photoplethysmography.
- the method may further comprise the following steps: – the pulsed light source emits a train of light pulses in the direction of the occupant, this corresponds to a first step; – simultaneously, the shutter is opened in order to let the light pass towards the image sensor, this light includes a component due to the ambient lighting and a component due to the light pulse emitted by the pulsed light source, this corresponds at a second stage; – at the end of the first acquisition period, the pulsed light source is deactivated, this corresponds to a third step; – the shutter is open in order to let the light pass towards the image sensor during a second acquisition period, this light includes a component due to the ambient lighting and possibly a component due to the light pulse emitted previously by the pulsed light source, this corresponds to a fourth step; – in the case where the image acquisition device comprises several shutters, the method comprises a fifth step during which the second shutter is closed and the third shutter is opened; – the shutter is open in order to let the light pass towards the image sensor during a third acquisition
- The is a figure similar to and schematically represents the state of the monitoring system during a first acquisition period
- The is a figure similar to and schematically represents the state of the monitoring system during a second acquisition period
- The is a figure similar to the previous figure and schematically represents the state of the monitoring system of the during a second vesting period
- The is a figure similar to the two previous figures and schematically represents the state of the monitoring system of Figures 6a and 6b during a third acquisition period, and
- certain elements can be indexed, such as the first element or the second element, for example.
- it is a simple indexing to differentiate and name elements that are close but not identical. This indexing does not imply a priority of one element over another and it is easy to interchange such denominations without departing from the scope of the present description. Nor does this indexing imply an order in time.
- the surveillance system 1 more particularly comprises a pulsed light source 3, an image acquisition device 5, such as a time-of-flight camera, and a processing unit 7.
- the pulsed light source 3 is configured to emit a train of light pulses, in particular in the infrared and therefore invisible to humans, in the direction of the occupant 2.
- the surveillance system 1 is arranged in the passenger compartment of the motor vehicle such that the pulsed light source 3 makes it possible to illuminate more particularly the face of the occupant 2 and such that the images acquired by the image acquisition device 5 comprise part or all of of the face of the occupant 2.
- the monitoring system 1 is for example arranged within the dashboard. Other locations are possible, such as the structure of the interior mirror or the roof of the passenger compartment more generally.
- the pulsed light source 3 is located outside the enclosure of the structure of the image acquisition device 5. According to another embodiment of the monitoring system, the pulsed light source 3 can be included within the structure of the image acquisition device 5.
- the pulsed light source 3 is for example an infrared radiation source. It may in particular be in the form of a light-emitting diode (LED) or a laser diode.
- the wavelength of the train of light pulses emitted by such a light source is for example included in an interval delimited in particular between 850 nm and 940 nm.
- such infrared radiation is invisible to the human eye. The risk of diverting the attention of the occupant 2 during the emission of the train of light pulses is therefore relatively low.
- the image acquisition device 5 comprises an image sensor 9, such as for example a photographic sensor, such as a CMOS or CCD sensor.
- the image acquisition device 5 also comprises a shutter 11 configured to allow light to pass towards the image sensor 9, this shutter 11 can be mechanical or electronic. According to a non-illustrated embodiment of the image acquisition device 5, the latter may comprise several image sensors 9.
- the images acquired by the image acquisition device 5 are intended to be processed by the processing unit 7 which is configured to determine one or more physiological parameters of the occupant 2 from said images.
- the determination of the physiological parameter(s) is done by remote photoplethysmography. Remote photoplethysmography methods are known and will not be detailed in this description.
- the physiological parameter can be heart rate, respiratory rate or arterial blood oxygen saturation.
- the monitoring system 1 can be configured to select one or more regions of interest 12 on the face of the occupant 2 with the aim of allowing the determination of the physiological parameter by remote photoplethysmography in a non-intrusive manner.
- a region of interest 12 can in particular designate a part or even the whole of the forehead, the cheeks or the chin of the occupant 2, as indicated for example on the .
- the image acquisition device 5 is a time-of-flight (ToF) camera.
- This type of camera makes it possible to simultaneously acquire information on the light intensity and information on the distance separating the occupant 2 from the sensor 9 of the image acquisition device 5 of the surveillance system 1. vol is thus able to reconstruct the filmed scene in three dimensions in a minimum of time, which promotes real-time monitoring of the movements of the occupant 2.
- the image sensor 9 is configured to establish a depth map of the face of the occupant 2 from the images acquired by the image acquisition device 5.
- This depth map makes it possible more particularly to evaluate the position of the head of the occupant 2 and to locate the displacement of the region(s) of interest 12 on the face of the occupant 2 when he is required to move, such as when he turns his head to perform a reverse, for example.
- the head movements of the occupant 2 can complicate the identification of the region(s) of interest 12 on the images of the face of the occupant 2 intended to be processed by the processing unit 7.
- This monitoring system 1 also makes it possible to circumvent another difficulty identified in the introduction: the change in ambient lighting within the passenger compartment of the motor vehicle. Due to the almost uninterrupted evolution of light inside and around the motor vehicle, the ambient lighting may change frequently, which may affect the intensity on the images acquired by the acquisition device. image 5 from surveillance system 1. That is, the face of occupant 2 is not uniformly illuminated over time; a Ca component due to ambient illumination on the images is variable over time. It is therefore necessary to overcome this component Ca due to the ambient lighting which interferes with said images and which can disturb the determination of the physiological parameter by remote photoplethysmography carried out by the processing unit 7.
- first acquisition period P1 the acquisition of said images occurs cyclically and each cycle comprises three times which will be referred to as "first acquisition period P1", “second acquisition period P2” and “third acquisition period P3" in following this description.
- the second acquisition period P2 is triggered outside the first acquisition period P1.
- the third acquisition period P3 is triggered outside of the first P1 and the second P2 acquisition periods.
- These three acquisition periods P1, P2, P3 may in particular follow one another, in this case the second acquisition period P2 begins when the first acquisition period P1 ends and the third acquisition P3 begins when the second acquisition period P2 ends.
- FIGS. 3a, 3b and 3c diagram respectively the actions of the surveillance system 1 during the first acquisition period P1, the second acquisition period P2 and the third acquisition period P3.
- the first acquisition period P1 is marked by two events taking place at the same time: the surveillance system 1 is configured such that the pulsed light source 3 emits a light pulse in the direction of the occupant 2, this is in particular represented by the hatched area between the two dotted arrows pointing towards the occupant 2.
- the light emitted by the pulsed light source 3 is represented by horizontal hatching.
- the shutter 11 is opened to allow light to pass from the occupant 2 to the image sensor 9 of the acquisition device 5 of the surveillance system 1 during the first acquisition period P1, this is more particularly represented by the hatched area between the two arrows pointing towards the rectangle representing the shutter 11.
- the surveillance system 1 can comprise a control unit 13 (represented schematically in FIGS. 1, 3a, 3b and 3c) which is configured to synchronize the start of the train of light pulses emitted by the pulsed light source 3 with the opening of the shutter 11 at the start of the first acquisition period P1. Furthermore, this control unit 13 can also be configured to control the opening and closing of the shutter 11.
- the light pulse emitted by the pulsed light source 3 makes a journey of variable duration depending on the distance between the object it illuminates and the image sensor 9 of the image acquisition device 5 of the system surveillance 1.
- the travel time of a light pulse reflected on an object placed near the image sensor 9 and the pulsed light source 3 will be shorter than that of a light pulse reflected on an object placed more far.
- this travel time makes it possible to calculate the distance which separates in particular the regions of interest 12 of the face of the occupant 2 and the image sensor 9 of the image acquisition device 5 of the monitoring system 1.
- the light emitted by the pulsed light source 3 and reflected by the occupant 2 does not necessarily have time to cross the shutter 11 of the image acquisition device 5 before the end of the first acquisition period P1, which is why there is the second acquisition period P2 which follows it.
- the sensor 11 is open during the second acquisition period P2 to let the light pass to the sensor 9 of the image acquisition device 5.
- part of the light pulse emitted by the pulsed light source 3 and reflected by the occupant 2 may therefore have to pass through the shutter 11 during this second acquisition period P2 to avoid a potential loss of data.
- This "late" part of the light received by the image sensor 9 of the image acquisition device 5 corresponds in particular to the rays of light which are reflected on objects placed at a greater distance from the pulsed light source 3.
- the pulsed light source 3 is inactive: it no longer emits a light pulse in the direction of the occupant 2.
- the light passing through the shutter 11 towards the sensor 9 during the first acquisition period P1 also comprises a component Ca due to the ambient lighting and a component Ci due to the light pulse.
- the component Ci due to the light pulse in the light reflected by the region or regions of interest 12 of the face of the occupant 2 in the direction of the shutter 11 is represented by a zone with horizontal hatching and the component Ca due to the ambient lighting in the light reflected by the region(s) of interest 12 of the face of the occupant 2 towards the shutter 11 is represented by oblique hatching in this same zone.
- the pulsed light source 3 emits a light pulse in the infrared range
- the light perceived by the image sensor 9 during the first and the second acquisition period P1, P2 therefore comprises a light component visible and an infrared light component.
- the respective duration of the first acquisition period P1 and of the second acquisition period P2 is at least equal to the duration of a light pulse emitted by the pulsed light source 3.
- the duration of a pulse of the train of light pulses emitted by the pulsed light source 3 is equal to the duration of the first acquisition period P1.
- the pulsed light source 3 is deactivated at the end of the first acquisition period P1 and remains inactive during the second and third acquisition periods P2 and P3.
- the shutter 11, for its part, allows light to pass towards the image sensor 9 during each of the three acquisition periods P1, P2 and P3.
- the durations of the first, of the second and of the third acquisition period P1, P2, P3 can be identical to each other.
- the duration of the light pulse, the duration of the first, second and third acquisition periods P1, P2 and P3 and the distance separating the occupant 2 from the surveillance system 1 are such that the light received by the image sensor 9 during the third acquisition period P3 does not include any component Ci due to the light pulse emitted by the pulsed light source 3.
- only ambient light is received by the image sensor 9 during the third period of acquisition P3.
- the component Ca due to the ambient lighting is represented by oblique hatching in the zone representing the light reflected by the region(s) of interest 12 of the face of the occupant 2 towards the shutter 11. There is no no horizontal hatching in this zone, since this light is devoid of a component Ci due to the light pulse emitted by the pulsed light source 3.
- the respective durations of the three acquisition periods P1, P2, P3 are very short, they are for example less than 50 ns and more particularly equal to 20 ns. They are so short that the change in the ambient illumination on the face of the occupant 2 is negligible over this period of time, i.e. the Ca component due to the ambient illumination in the light received by the image sensor 9 is considered to be identical on all the images acquired by the image acquisition device 5 during these three acquisition periods P1, P2, P3 belonging to the same cycle.
- the processing unit 7 is configured to subtract this component Ca from part or all of said images in order to isolate the component Ci due to the light pulse emitted by the pulsed light source 3.
- This operation is shown schematically in the .
- This figure shows several timelines with a time axis t whose start is marked by the origin O.
- the time axis t is divided into three segments of the same length highlighted by double arrows.
- Each double-arrow represents an acquisition period P1, P2, P3.
- the rectangular blocks surmounting these double arrows represent the light received by the image sensor 9 during these three acquisition periods P1, P2 and P3.
- this component Ca is here represented by a first rectangular block comprising oblique hatching.
- the total length of this first block corresponds to the sum of the lengths of the three double arrows.
- a second block of a length equal to a single double-arrow surmounts the first block.
- the horizontal hatching inside the second block represents the component Ci due to the light pulse emitted by the pulsed light source 3.
- the offset between the start of this second block and the origin O is due to the travel time of the light pulse emitted by the pulsed light source 3.
- the subtraction operation performed by the processing unit 7 takes place as follows: the processing unit 7 identifies the component Ca due to the ambient lighting on the images acquired by the image acquisition device 5 during the third acquisition period P3, this is symbolized by the bold dotted lines on the first timeline.
- the value of this component Ca is subtracted from the quantity of light received by the image sensor 9 during which said image sensor 9 also receives the component Ci due to the light pulse reflected by the region(s) of interest 12 of the face of the occupant 2, this is represented on the second timeline located below the first timeline.
- the processing unit 7 therefore focuses on the images which no longer include the component Ci to apply thereto a photoplethysmograhie method in order to determine a physiological parameter of the occupant 2. This last step is symbolized by the frame with thick lines on the third frieze of the .
- the component Ca due to the ambient lighting is specific to each cycle, this is represented by the different sizes of the blocks Ca1, Ca2 and Ca3 with the oblique hatching. The thus illustrates the repetition of the subtraction operation carried out by the processing unit 7 cycle after cycle.
- the processing unit 7 is therefore configured to subtract the component Ca due to the ambient illumination from the light received by the sensor 9 of the image acquisition device 5 for the images acquired during the first and the second period of acquisition P1 and P2.
- the images acquired by the image acquisition device 5 during the first and the second acquisition periods P1 and P2 are no longer interfered with by the component Ca due to the ambient lighting, which increases the efficiency of the processing image performed by the processing unit 7 in the context of determining the physiological parameter by remote photoplethysmography.
- the processing unit 7 is also configured to define, from the physiological parameter, the physiological state of the occupant 2.
- the processing unit 7 can for example compare the value of the physiological parameter(s) to one or more thresholds predetermined.
- the physiological parameter is heart rate. If this is greater than a predetermined maximum threshold or less than a predetermined minimum threshold within the processing unit 7, it is possible that the physiological state of the occupant 2 does not allow him to drive.
- the monitoring system 1 can in particular be configured to emit, for example, a sound signal or any other form of alert when the physiological parameter(s) do not correspond to the predetermined criteria within the processing unit 7.
- a sound signal can alert the occupant of a potential danger, such as driving while fatigued.
- the surveillance system 1 can comprise several shutters 111, 112 and 113.
- the image acquisition device 5 can comprise a first shutter 111 configured to pass light to image sensor 9 during the first acquisition period P1, a second shutter 112 configured to pass light to image sensor 9 during the second acquisition period P2 and a third shutter 113 configured to allow light to pass towards the image sensor 9 during the third acquisition period P3, as illustrated respectively in images 5a, 5b and 5c.
- the first shutter 111 is open at the start of the first acquisition period P1 and closed again at the end of the first acquisition period P1
- the second shutter 112 is open at the start of the second acquisition period P2 and closed at the end of the second acquisition period P2 and the same principle applies for the third shutter 113 and the third acquisition period P3.
- the operation of this second embodiment of the monitoring system 1 is very similar to that of the first embodiment, hence the similarity between Figures 6a, 6b and 6c with Figures 3a, 3b and 3c respectively.
- control unit 13 can be configured to control the opening and the closing in cascade of the first, second and third shutters 111, 112 and 113.
- the closing of the first shutter 111 coincides with the opening of the second shutter 112 and the closing of the second shutter 112 coincides with the opening of the third shutter 113. result in an increased lifespan of the monitoring system 1.
- a method for determining the physiological state of the occupant 2 by photoplethysmography is detailed in the following description.
- This method makes use of a monitoring system 1 such as that described previously.
- the method comprises several steps E1, E2, E3, E4, E5, E6, E7, E8, E9 and E10.
- Steps E1 and E2 take place at the same time during the first acquisition period P1.
- the pulsed light source 3 emits a train of light pulses in the direction of the occupant 2 while for step E2, which takes place simultaneously, the shutter 11 or the first shutter 111 is opened in order to to let the light pass towards the image sensor 9.
- This light comprises a component Ca due to the ambient lighting and a component Ci due to the light pulse emitted by the pulsed light source 3.
- Step E3 also marks the end of the first acquisition period P1 and the start of the second acquisition period P2.
- this step E3 is also marked by the closing of the first shutter 111 and the opening of the second shutter 112.
- step E4 the shutter 11 or the second shutter 112 is opened in order to let the light pass towards the image sensor 9 during the second acquisition period P2, this light comprises a component Ca due to the ambient lighting and possibly a component Ci due to the light pulse previously emitted by the pulsed light source 3.
- Step E5 marks the end of the second acquisition period P2 and the start of the third acquisition period P3.
- step E5 also corresponds to the moment when the second shutter 112 is closed and the third shutter 113 is open.
- step E6 the shutter 11 or 113 is opened in order to let the light pass towards the image sensor 9 during the third acquisition period P3, this light comprises a component Ca due to the ambient lighting , but no more component Ci due to the light pulse previously emitted by the pulsed light source 3.
- step E7 at the end of the third acquisition period P3, the shutter 11 or the third shutter 113 is closed.
- step E8 the processing unit 7 subtracts the component Ca due to the ambient lighting contained in the light received by the image sensor 9 during the third acquisition period P3 from the light received by the image sensor 9 during the first and second acquisition periods P1, P2 with the aim of isolating the component Ci due to the light pulse emitted by the pulsed light source 3 on the images acquired by the acquisition device image 5 during the first and second acquisition periods P1, P2.
- step E9 the processing unit 7 determines from said images a physiological parameter of the occupant 2 by photoplethysmography.
- step E10 the processing unit 7 defines, from the physiological parameter, the physiological state of the occupant 2 by photoplethysmography. It is not necessarily necessary to repeat steps E9 and E10 for each cycle. In other words, it is possible to repeat steps E1 to E8 several times in a row before starting steps E9 and E10.
- the processing unit 7 of the surveillance system 1 can be configured to select the images worthy of being processed during the process for developing the physiological state of the occupant 2 by removing, for example, the images on which the occupant 2 is not oriented facing the surveillance system 1, as in the case where the occupant is a driver and the latter turns his head to carry out a reverse gear with his vehicle, because these images do not allow reliably determining a physiological parameter of the occupant 2 by photoplethysmography.
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Abstract
Description
– la source lumineuse pulsée émet un train d’impulsions lumineuses en direction de l’occupant, ceci correspond à une première étape ;
– simultanément, l’obturateur est ouvert afin de laisser passer la lumière vers le capteur d’image, cette lumière comprend une composante due à l’éclairage ambiant et une composante due à l’impulsion lumineuse émise par la source lumineuse pulsée, ceci correspond à une deuxième étape ;
– à la fin de la première période d’acquisition, la source lumineuse pulsée est désactivée, ceci correspond à une troisième étape ;
– l’obturateur est ouvert afin de laisser passer la lumière vers le capteur d’image pendant une deuxième période d’acquisition, cette lumière comprend une composante due à l’éclairage ambiant et éventuellement une composante due à l’impulsion lumineuse émise précédemment par la source lumineuse pulsée, ceci correspond à une quatrième étape ;
– dans le cas où le dispositif d’acquisition d’image comporte plusieurs obturateurs, le procédé comporte une cinquième étape au cours de laquelle le deuxième obturateur est refermé et le troisième obturateur est ouvert ;
– l’obturateur est ouvert afin de laisser passer la lumière vers le capteur d’image pendant une troisième période d’acquisition, cette lumière comprend une composante due à l’éclairage ambiant, mais plus de composante due à l’impulsion lumineuse émise précédemment par la source lumineuse pulsée, ceci correspond à une sixième étape ;
– à la fin de la troisième période d’acquisition, l’obturateur est refermé ; ceci correspond à une septième étape ;
– l’unité de traitement soustrait la composante due à l’éclairage ambiant contenue dans la lumière reçue par le capteur d’image pendant la troisième période d’acquisition à la lumière reçue par le capteur d’image pendant la première et la deuxième périodes d’acquisition dans le but d’isoler la composante due à l’impulsion lumineuse émise par la source lumineuse pulsée sur les images acquises par le dispositif d’acquisition d’image pendant la première et la deuxième périodes d’acquisition, ceci correspond à une huitième étape ;
– l’unité de traitement détermine à partir desdites images un ou plusieurs paramètres physiologiques de l’occupant par photopléthysmographie, ceci correspond à une neuvième étape ;
– l’unité de traitement définit, à partir du paramètre physiologique, l’état physiologique de l’occupant par photopléthysmographie, ceci correspond à une dixième étape.
Claims (10)
- Système de surveillance (1) d’un occupant d’un véhicule automobile, le système de surveillance (1) comportant :
– une source lumineuse pulsée (3) configurée pour émettre un train d’impulsions lumineuses en direction de l’occupant (2),
– un dispositif d’acquisition d’image (5), tel une caméra à temps de vol, ledit dispositif d’acquisition d’image (5) comprenant un capteur d’image (9) et un obturateur (11) configuré pour laisser passer de la lumière vers le capteur d’image (9) pendant une première période d’acquisition (P1) au cours de laquelle la source lumineuse pulsée (3) émet une impulsion lumineuse et pendant une deuxième période d’acquisition (P2) au cours de laquelle la source lumineuse pulsée (3) est inactive, la deuxième période d’acquisition (P2) étant déclenchée en dehors de la première période d’acquisition (P1), la durée respective de la première et de la deuxième périodes d’acquisition (P1, P2) étant au moins égale à la durée d’une impulsion lumineuse émise par la source lumineuse pulsée (3), la lumière reçue par le capteur d’image (9) lors de la première période d’acquisition (P1) et de la deuxième période d’acquisition (P2) comportant une composante (Ca) due à l’éclairage ambiant et une composante (Ci) due à l’impulsion lumineuse émise par la source lumineuse pulsée (3);
– une unité de traitement (7) configurée pour déterminer à partir des images acquises un paramètre physiologique de l’occupant (2) par photopléthysmographie et pour définir, à partir dudit paramètre, l’état physiologique de l’occupant (2),
le système de surveillance (1) étant caractérisé en ce que l’obturateur (11) est également configuré pour laisser passer de la lumière vers le capteur d’image (9) pendant une troisième période d’acquisition (P3) déclenchée en dehors de la première et de la deuxième périodes d’acquisition (P1, P2), la source lumineuse pulsée (3) étant inactive pendant la troisième période d’acquisition (P3), ladite lumière comportant la composante (Ca) due à l’éclairage ambiant et en ce que l’unité de traitement (7) est configurée pour soustraire cette composante (Ca) due à l’éclairage ambiant à la lumière reçue par le capteur d’image (9) pendant la première et la deuxième périodes d’acquisition (P1, P2) dans le but d’isoler la composante (Ci) due à l’impulsion lumineuse émise par la source lumineuse pulsée (3) sur une partie des images acquises par le dispositif d’acquisition d’image (5) pendant la première et la deuxième périodes d’acquisition (P1, P2). - Système de surveillance selon la revendication 1, caractérisé en ce que la durée respective de la première, de la deuxième et de la troisième période d’acquisition (P1, P2, P3) est inférieure à 50 ns et plus particulièrement égale à 20 ns.
- Système de surveillance selon la revendication précédente, caractérisé en ce que les durées de la première, de la deuxième et de la troisième période d’acquisition (P1, P2, P3) sont identiques entre elles.
- Système de surveillance selon l’une quelconque des revendications précédentes, caractérisé en ce que la durée d’une impulsion du train d’impulsion lumineuses émis par la source lumineuse pulsée (3) est égale à la durée de la première période d’acquisition (P1).
- Système de surveillance selon l’une quelconque des revendications précédentes, caractérisé en ce qu’il comporte une unité de pilotage (13) configurée pour synchroniser le départ du train d’impulsions lumineuses émis par la source lumineuse pulsée (3) avec l’ouverture de l’obturateur (11) au début de la première période d’acquisition (P1).
- Système de surveillance selon la revendication précédente, caractérisé en ce que l’unité de pilotage (13) est configurée pour piloter l’ouverture et la fermeture de l’obturateur (11).
- Système de surveillance selon l’une quelconque des revendications précédentes, caractérisé en ce qu’il est configuré pour sélectionner une région d’intérêt (12) sur le visage de l’occupant (2) pour permettre la détermination du paramètre physiologique.
- Système de surveillance selon l’une quelconque des revendications précédentes, caractérisé en ce que le capteur d’image (9) est configuré pour établir une carte de profondeur du visage de l’occupant (2) à partir des images acquises par le dispositif d’acquisition d’image (5).
- Système de surveillance selon l’une quelconque des revendications précédentes, caractérisé en ce que le dispositif d’acquisition d’image (5) comporte trois obturateurs (111, 112, 113) distincts :
– un premier obturateur (111) configuré pour laisser passer de la lumière vers le capteur d’image (9) pendant la première période d’acquisition (P1) ;
– un deuxième obturateur (112) configuré pour laisser passer de la lumière vers le capteur d’image (9) pendant la deuxième période d’acquisition (P2) ;
– un troisième obturateur (113) configuré pour laisser passer de la lumière vers le capteur d’image (9) pendant la troisième période d’acquisition (P3). - Procédé de détermination de l’état physiologique de l’occupant (2) par photopléthysmographie, le procédé ayant recours à un système de surveillance (1) selon l’une quelconque des revendications précédentes, caractérisé en ce que le procédé comprend les étapes (E1, E2, E3, E4, E5, E6, E7, E8, E9 et E10) suivantes :
– la source lumineuse pulsée (3) émet un train d’impulsions lumineuses en direction de l’occupant (2), ceci correspond à une première étape (E1) ;
– simultanément, l’obturateur (11, 111) est ouvert afin de laisser passer la lumière vers le capteur d’image (9), cette lumière comprend une composante (Ca) due à l’éclairage ambiant et une composante (Ci) due à l’impulsion lumineuse émise par la source lumineuse pulsée (3), ceci correspond à une deuxième étape (E2) ;
– à la fin de la première période d’acquisition (P1), la source lumineuse pulsée (3) est désactivée, ceci correspond à une troisième étape (E3) ;
– l’obturateur (11, 112) est ouvert afin de laisser passer la lumière vers le capteur d’image (9) pendant une deuxième période d’acquisition (P2), cette lumière comprend une composante (Ca) due à l’éclairage ambiant et éventuellement une composante (Ci) due à l’impulsion lumineuse émise précédemment par la source lumineuse pulsée (3), ceci correspond à une quatrième étape (E4) ;
– dans le cas où le dispositif d’acquisition d’image (5) comporte plusieurs obturateurs (111, 112, 113), le procédé comporte une cinquième étape (E5) au cours de laquelle le deuxième obturateur (112) est refermé et le troisième obturateur (113) est ouvert ;
– l’obturateur (11, 113) est ouvert afin de laisser passer la lumière vers le capteur d’image (9) pendant une troisième période d’acquisition (P3), cette lumière comprend une composante (Ca) due à l’éclairage ambiant, mais plus de composante (Ci) due à l’impulsion lumineuse émise précédemment par la source lumineuse pulsée (3), ceci correspond à une sixième étape (E6) ;
– à la fin de la troisième période d’acquisition (P3), l’obturateur (11, 113) est refermé ; ceci correspond à une septième étape (E7) ;
– l’unité de traitement (7) soustrait la composante (Ca) due à l’éclairage ambiant contenue dans la lumière reçue par le capteur d’image (9) pendant la troisième période d’acquisition (P3) à la lumière reçue par le capteur d’image (9) pendant la première et la deuxième périodes d’acquisition (P1, P2) dans le but d’isoler la composante (Ci) due à l’impulsion lumineuse émise par la source lumineuse pulsée (3) sur une partie des images acquises par le dispositif d’acquisition d’image (5) pendant la première et la deuxième périodes d’acquisition (P1, P2), ceci correspond à une huitième étape (E8) ;
– l’unité de traitement (7) détermine à partir desdites images au moins un paramètre physiologique de l’occupant (2) par photopléthysmographie, ceci correspond à une neuvième étape (E9) ;
– l’unité de traitement (7) définit, à partir du paramètre physiologique, l’état physiologique de l’occupant (2) par photopléthysmographie, ceci correspond à une dixième étape (E10).
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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US18/284,034 US20240164652A1 (en) | 2021-03-25 | 2022-03-14 | System for monitoring an occupant of a motor vehicle |
EP22714804.6A EP4312742A1 (fr) | 2021-03-25 | 2022-03-14 | Système de surveillance d'un occupant d'un véhicule automobile |
CN202280023502.9A CN117042683A (zh) | 2021-03-25 | 2022-03-14 | 用于监测机动车辆的乘员的监测系统 |
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FRFR2103023 | 2021-03-25 | ||
FR2103023A FR3121028A1 (fr) | 2021-03-25 | 2021-03-25 | Système de surveillance d’un occupant d’un véhicule automobile |
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WO2022200102A1 true WO2022200102A1 (fr) | 2022-09-29 |
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PCT/EP2022/056533 WO2022200102A1 (fr) | 2021-03-25 | 2022-03-14 | Système de surveillance d'un occupant d'un véhicule automobile |
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US (1) | US20240164652A1 (fr) |
EP (1) | EP4312742A1 (fr) |
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WO (1) | WO2022200102A1 (fr) |
Citations (2)
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US20180191936A1 (en) * | 2014-12-08 | 2018-07-05 | Samsung Electronics Co., Ltd. | Imaging devices with optical shutters and low-power drivers therefor |
US20200297270A1 (en) * | 2017-12-19 | 2020-09-24 | Panasonic Intellectual Property Management Co., Ltd. | Biometric apparatus, biometric method, and determination apparatus |
-
2021
- 2021-03-25 FR FR2103023A patent/FR3121028A1/fr active Pending
-
2022
- 2022-03-14 WO PCT/EP2022/056533 patent/WO2022200102A1/fr active Application Filing
- 2022-03-14 EP EP22714804.6A patent/EP4312742A1/fr active Pending
- 2022-03-14 US US18/284,034 patent/US20240164652A1/en active Pending
- 2022-03-14 CN CN202280023502.9A patent/CN117042683A/zh active Pending
Patent Citations (2)
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US20180191936A1 (en) * | 2014-12-08 | 2018-07-05 | Samsung Electronics Co., Ltd. | Imaging devices with optical shutters and low-power drivers therefor |
US20200297270A1 (en) * | 2017-12-19 | 2020-09-24 | Panasonic Intellectual Property Management Co., Ltd. | Biometric apparatus, biometric method, and determination apparatus |
Non-Patent Citations (1)
Title |
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GONZALEZ-BANOS H ET AL: "Computing depth under ambient illumination using multi-shuttered light", PROCEEDINGS OF THE 2004 IEEE COMPUTER SOCIETY CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION 27 JUNE-2 JULY 2004 WASHINGTON, DC, USA, IEEE, PROCEEDINGS OF THE 2004 IEEE COMPUTER SOCIETY CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION IEE, vol. 2, 27 June 2004 (2004-06-27), pages 234 - 241, XP010708658, ISBN: 978-0-7695-2158-9, DOI: 10.1109/CVPR.2004.1315169 * |
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US20240164652A1 (en) | 2024-05-23 |
EP4312742A1 (fr) | 2024-02-07 |
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