FR3028741B1 - DEVICE FOR MEASURING THE HEART RATE OF THE DRIVER OF A VEHICLE - Google Patents

Abstract

The invention relates to a device for measuring the cardiac rhythm of the driver of a vehicle, comprising: at least one camera (10), illumination means (11) for the driver's face (3), at least one camera (10) and said illumination means (11) being placed facing the driver. Said illumination means (11) illuminate the face (3) of the conductor with infrared light, and said at least one camera (10) captures images of the face through an infrared filter (12), so that Images obtained are characteristic of the presence of hemoglobin under the surface of the skin. The device according to the invention furthermore comprises means for determining the blood flow under the skin of the driver's face (2) from said image, as well as means for determining the cardiac rhythm of the driver (2) according to the evolution in time of the blood flow.

Description

DEVICE FOR MEASURING THE HEART RATE OF THE DRIVER OF A VEHICLE

[001] The invention relates generally to man-machine interfaces, in particular dedicated to motor vehicles, driving assistance systems and the monitoring of the state, in particular physiological, of the driver of a vehicle. vehicle.

[002] The invention also aims to improve the comfort and well-being on board motor vehicles.

[003] The invention relates more particularly to a device for monitoring the physiological state of the driver of a motor vehicle, by means of original means configured to measure certain physiological parameters, such as heart rate or breathing rate .

[004] The general problem to which the present invention proposes to provide a solution therefore relates to the monitoring of the state, in particular physiological, of the driver of a vehicle, in order to determine his level of vigilance, or detect a health problem such as a heart attack, or a drowsiness.

[005] The monitoring of physiological parameters, including the driver of a vehicle, has already been the subject of studies and development.

[006] It is known, for example, to measure the following physiological parameters of a person: - the heart rate, by electrocardiogram, - the level of sweating, by the measurement of cutaneous conductance - SCL for Skin Conductance Level in English or Galvanic Skin Response technique - body temperature, - heart rate and blood oxygenation, by photoplethysmography or pulse oximetry.

[007] The major disadvantage of conventional techniques for measuring these physiological parameters lies in the fact that they require contact with the body, as well as continuity and high measurement quality to provide reliable measurements. This naturally causes many difficulties in a passenger environment of a motor vehicle, especially since it is not seriously conceivable to equip the driver of a vehicle with sensors arranged on his body.

[008] To answer this general problem, current technologies propose a device installed on the steering wheel, in order to perform measurements of physiological parameters by contact, electrocardiogram, measurement of cutaneous conductance, measurement of the galvanic cutaneous reflex, measurement of the body temperature or pulse oximetry. It is notably in this sense that the device described in WO2014128273 has been proposed. However, the contact between the driver's skin and such devices arranged on the steering wheel is not permanent. In addition, the movements of the hands on the steering wheel produce many artifacts in the measurements whose reliability is therefore uncertain.

[009] There is therefore a need for a more efficient device, allowing precise and non-contact measurement of physiological parameters of the driver of a motor vehicle.

To this end, the device according to the invention comprises one or more camera (s) directed (s) towards the driver's face, and means for illuminating said face by infrared light, invisible to the eye human. The device according to the invention further comprises means for measuring the heart rate, and possibly other physiological parameters, from the images captured by said camera (s). The device according to the invention further comprises means for analyzing the measurements made as a function of time.

In this context, the invention proposes a device for measuring the cardiac rhythm of the driver of a vehicle, comprising: - at least one camera, - illumination means of the driver's face, said at least one camera and said illumination means being placed facing the conductor, such that the illumination means illuminate the driver's face and the camera captures images of said face.

The device according to the invention is remarkable in that the said illumination means illuminate the driver's face with infrared light, in that the said at least one camera captures images of the face through an infrared filter, so that the images obtained are characteristic of the presence of hemoglobin under the surface of the skin, and in that the device for measuring the cardiac rhythm furthermore comprises means for determining the blood flow under the skin of the face of the driver of the vehicle from said image, as well as means for determining the heart rate of the driver as a function of the evolution over time of said blood flow.

According to a preferred embodiment, said infrared light has a wavelength of about 940 nanometers.

Advantageously, the device according to the invention further comprises: - means for detecting the driver's face on each captured image, - means for detecting a set of highly vascularized areas of said face, - means for detecting the captured image a zone of interest, representative of said highly vascularized zones, means for measuring the average intensity of the pixels of each captured image corresponding to said zone of interest, and means for measuring the variations of said intensity. means as a function of time, the means for determining the blood flow under the skin of the driver's face determining said blood flow from said variations in the average intensity of the pixels of the area of interest as a function of time.

[0014] Said highly vascularized areas may especially correspond to the areas where the facial arteries, lower labial, upper labial, and nasal arteries pass.

Advantageously, said means for determining the blood flow under the skin of the driver's face, from the variations of the average intensity of the pixels of the zone of interest as a function of time, comprise means of spectral decomposition. .

According to one embodiment, the device according to the invention further comprises means for determining the respiratory rate as a function of the evolution over time of said determination of the blood flow under the skin of the driver's face.

According to one embodiment, said at least one camera is attached to a vehicle cockpit dashboard or to an interior rearview mirror of a vehicle passenger compartment.

According to one embodiment, said illumination means are attached to a vehicle cockpit dashboard or to an interior rearview mirror of a vehicle passenger compartment.

Other features and advantages of the invention will appear on reading the detailed description of the embodiments of the invention, given by way of example only, and with reference to the drawings which show: FIG. a diagram of a device according to the invention installed in a vehicle cabin; • Figure 2, a diagram showing the processing of an image of a driver's face captured by the camera of the device according to the invention.

In what follows, the described embodiments focus more particularly on an implementation of the device according to the invention within a motor vehicle. However, any implementation in a different context, in particular in any type of vehicle, is also covered by the present invention.

Figure 1 schematically shows the principle of operation of the device for measuring the heart rate of the driver of a vehicle, according to the invention.

Said conductor 2 is shown in a vehicle interior 1. The device for measuring heart rate according to the invention comprises, in the embodiment of FIG. 1, a camera 10 and an infrared illuminator 11. The illuminator infrared 11 constitutes illumination means of the face 3 of the conductor 2 by infrared light. According to a preferred embodiment of the present invention, said infrared light has a wavelength of about 940 nanometers. The camera 10 captures images of the face 3 of the conductor 2 through an infrared filter 12.

The device for measuring the cardiac rhythm of the driver of a vehicle also comprises means, not shown, for processing the images captured by the camera 10. These processing means make it possible to measure, in real time and without contact, the driver's heart rate 2, as well as possibly his breathing rate. These measurements can be analyzed to determine the general physiological state of the conductor 2.

The camera 10 can be integrated in the dashboard, as shown in Figure 1, but also, alternatively or additionally and additionally, in the combined, in the upper half-sheath of the steering column , or in the rearview mirror of the vehicle cabin 1. The - or -illuminators 11 can share the same location as the camera 10, or be positioned (s) close to the camera, or be arranged in the one of the other locations mentioned above, distinct from the one where the camera 10 is located.

The illumination means 11 and the camera 10 are placed facing the conductor 2, so as to, respectively, illuminate his face 3 and capture images.

Preferably, the illuminator 11 illuminates the face 3 of a light having a wavelength of about 940 nanometers. This wavelength of 940 nanometers is preferred because it is, in the near infrared, that for which the absorption by hemoglobin present in the blood, in its oxygenated form HbO2, is the strongest.

The camera 10 captures the image of the face 3 and therefore achieves the acquisition of an image of the reflection of infrared light on the skin of the face 3 at the wavelength of about 940 nanometers. This image is characteristic of the presence of hemoglobin under the surface of the skin.

Over time, the camera 10 thus acquires the image sequence of the face 3 of the driver, infrared light at a desired frequency, which can be, for example, 30 frames per second.

Optionally, the camera 10 can record a background image, in this case that corresponding to the reflection of ambient light on the skin of the face 3. This background image can then be subtracted from the image of the face captured in infrared to eliminate the corresponding noise. However, if the infrared optical filter 12 placed in front of the camera 10 is sufficiently effective, the level of intensity of the background image is very low and the implementation of this subtraction of the background image to the captured image in infrared is useless.

Referring to Figure 2, the device according to the invention further comprises detection means in each captured image of the driver's face 2, among other elements of the cabin surrounding it.

[0031] The algorithms for detecting a face in an image are known. As an illustration, it is possible to use for example a detector operating according to the known method of Viola and Jones.

Referring to Figure 2, a portion 30 of each image, corresponding to the driver's face, is then considered for subsequent processing. Therefore, when the driver moves in front of the camera 10, his head is constantly followed, as well as the area corresponding to the portion 30 of the image in which the face was detected, following his movements.

Still with reference to Figure 2, from this part 30 of each image, the device according to the invention implements means for detecting areas 31 where the skin is highly vascularized. These highly vascularized areas 31 generally correspond to the cheeks and the upper and lower parts of the mouth, where are the facial arteries, the lower and upper labia and lateral nasal arteries.

For this purpose, the use of a facial feature location algorithm, based on a statistical model, such as the active appearance model algorithm, or AAM for the Active Appearance Model according to the acronym, allows, in successive convergence stages, to find characteristic points on the face, such as the corners of the lips, eyes, nostrils, eyebrows, corresponding to highly vascularized areas 31 of Figure 2.

Still with reference to Figure 2, from these characteristic points 31 detected on the part 30 of the face, the device according to the invention comprises means for extracting an area of interest 32 representative of the areas strongly vascularized 31 of the face.

According to the preferred embodiment of the present invention, the device according to the invention comprises means for calculating the average intensity of the pixels corresponding to this area of interest 32 in each captured image.

The evolution of this average intensity of the pixels forming the area of interest 32 on each image captured by the camera 10 is thus analyzed as a function of time, the camera capturing image sequences of the face 3 at a predetermined frequency. , between 25 Hertz and 60 Hertz, and may for example be equal to about 30 Hertz.

The device for measuring the heart rate of the driver of a vehicle therefore comprises means for analyzing the evolution of this average intensity of the pixels forming the area of interest 32, as a function of time. This evolution is characteristic of the presence of hemoglobin and thus of the blood flow in the skin of the face, itself characteristic of the heart rate, corresponding to the fluctuations with high frequency, and of the respiratory rate, corresponding to the fluctuations to more low frequency.

Thus, the analysis of the evolution of the average intensity of the pixels forming the area of interest 32 of each image of the face 3 of the driver 2, captured by the camera 10, makes it possible to determine the heart rate of said driver. . Indeed, said evolution of the average intensity of the pixels forming the zone of interest 32 corresponds, for frequencies between 0.7 Hertz and 3 Hertz, to a heart rate of between 42 and 180 beats per minute and, for frequencies below 0.5 Hertz, at a respiration rate, it being understood that a frequency of 0.5 Hertz corresponds to a respiratory rate of approximately 30 inspirations / expirations per minute.

In summary, the device according to the invention allows the measurement of the heart rate and the respiratory rate of the driver of a vehicle, reliably, continuously, and without contact.

In addition, optionally and complementary, it should be noted that the same device, thanks in particular to the camera, and adapted processing means, can simultaneously measure the opening of the eyes of the driver 2 in order to determine his waking level, or capture the movements of the head and eyes of the driver 2 to assess his level of distraction.

The merging of all these data - physiological state, level of arousal, distraction - thus, possibly, that data from the vehicle significant behavior of the driver - swaying, uncoordinated actions on the pedals and / or the steering wheel ... etc. - can provide, without contact, a complete measure of the physiological and emotional state of the driver.

This information on the state of the driver can be exploited to configure on-board driving aid systems, in order to adapt the settings of the comfort organs and more generally of the passenger compartment, or even to make it possible to manage extreme cases where the complete measurement of the physiological and emotional state of the driver shows that the execution of the driving task is no longer possible - falling asleep, malaise, epileptic seizure, heart attack ... etc.

It is specified, moreover, that the present invention is not limited to the examples described above and is capable of numerous variants accessible to those skilled in the art.

Claims (8)

Claims: A device for measuring the driver's heart rate of a vehicle, comprising: at least one camera (10), illumination means (11) of the driver's face, said at least one camera (10) and said illumination means (11) being placed facing the conductor (2), so that the illumination means (11) illuminate the face (3) of the conductor and the camera (10) captures images of said face, characterized said illumination means (11) illuminate the face (3) of the conductor with infrared light, in that said at least one camera (10) captures images of the face through an infrared filter (12), such that the images obtained are characteristic of the presence of hemoglobin under the surface of the skin, a part (30) of each image, corresponding to the driver's face, being considered for subsequent treatments so that when the driver moves in front of the camera (10), its head is t constantly followed, as well as the area corresponding to the portion (30) of the image in which the face has been detected, following its movements, and in that the device for measuring the heart rate further comprises means of determination of the blood flow under the skin of the face (3) of the driver (2) of the vehicle from said image, as well as means for determining the cardiac rhythm of the driver (2) according to the evolution over time said blood flow. 2. A device for measuring the heart rate of the driver of a vehicle according to claim 1, characterized in that said infrared light has a wavelength of about 940 nanometers. 3. Device for measuring the heart rate of the driver of a vehicle according to any one of the preceding claims, characterized in that it further comprises: - means for detecting the face (30) of the driver on each captured image, means for detecting a set of highly vascularized zones (31) of said detected face (30); means for extracting from the captured image a zone of interest (32) representative of said highly vascularized zones (31); means for measuring the average intensity of the pixels of each captured image corresponding to said zone of interest (32), and - means for measuring the variations of said average intensity as a function of time, the means for determining the blood flow under the skin of the face (30) of the conductor (2) determining said blood flow from said variations of the average intensity of the pixels of the area of interest (32) as a function of time. 4. Device for measuring the heart rate of the driver of a vehicle according to claim 3, characterized in that said highly vascularized areas (31) correspond to the areas where the facial arteries pass, labial lower, labial upper, and nasal facial. 5. Device for measuring the heart rate of the driver of a vehicle according to any one of claims 3 to 4, characterized in that said means for determining the blood flow under the skin of the driver's face (2), to from the variations of the average intensity of the pixels of the zone of interest (32) as a function of time, comprise means of spectral decomposition. 6. Device for measuring the heart rate of the driver of a vehicle according to any one of the preceding claims, characterized in that it further comprises means for determining the respiratory rate as a function of the evolution over time of said determination of the blood flow under the skin of the driver's face (2). 7. Device for measuring the heart rate of the driver of a vehicle according to any one of the preceding claims, characterized in that said at least one camera (10) is attached to a cockpit dashboard vehicle (1) or to an interior rearview mirror of a vehicle interior (1). The device for measuring the heart rate of a driver of a vehicle according to any one of the preceding claims, characterized in that said illumination means are attached to a vehicle cockpit scoreboard (1) or to a rear view mirror of a vehicle interior (1).