FR3071788A1 - DRIVER OBSERVATION SYSTEM AND METHOD OF SEIZING IT BY THE SYSTEM AND METHOD FOR MANUFACTURING THE SYSTEM - Google Patents

Abstract

A driver viewing system (102) for viewing the driver (104) in a vehicle (100), comprising: - a lighting unit (106) for illuminating the driver (104) with electromagnetic radiation (108) of a certain wavelength of illumination; - a wavelength displacement unit (112) for shifting the wavelength of the fraction (111) of the electromagnetic radiation (108) reflected by the conductor (104) to a detection wavelength less than the illumination wavelength; and a detection unit (110) for detecting the radiation transmitted by the wavelength shifting unit (112).

Description

Field of the invention

The present invention relates to a driver observation system as well as to a method of capturing a driver using such an observation system and to a method of producing a displacement unit for wavelength for a conductor observation system.

State of the art

Applications for observing the movements of a driver’s head and eyes are nowadays the backbone of any driver’s observation system, also known as a DMC (Driver Control Camera). Such systems are essential for partially or fully automatic driving, to analyze the driver's reaction capacity, or the driver's reaction capacity.

Monochrome CMOS image sensors, usable for DMC imagers, commercially available, and having the resolution necessary for applications in DMC mode have low quantum efficiency in the near infrared domain used for lighting and this due to technical conversion because it uses semiconductors based on silicon. Their light sensitivity and photosensitivity can result in a non-optimal conversion of the infrared light received by pixels into electrical signals and a signal-to-noise ratio which can be greater in this wavelength range.

Presentation and advantages of the invention

The object of the present invention is to remedy these drawbacks and relates to a driver observation system for observing the driver in a vehicle, this system being characterized in that it comprises a lighting unit for lighting the driver with electromagnetic radiation of a certain illumination wavelength, a wavelength displacement unit for displacing the wavelength of the fraction of the electromagnetic radiation reflected by the conductor towards a detection wavelength, less than the illumination wavelength and a detection unit for detecting the radiation transmitted by the wavelength displacement unit.

A lighting unit is, for example, a unit installed in the dashboard or in the passenger compartment of the vehicle in front of the driver and comprising one or more sources of radiation such as photodiodes. The lighting unit can thus emit infrared radiation.

The wavelength displacement unit is, for example, an array of microlenses, a lens or an optical filter having a particular doping or coating formed of UC particles. The abbreviation UC represents upward photon conversion (UC). The particles UC are, for example, a material of the detection unit, and can be part of the material of the detector unit by doping or in the form of a coating. The detection unit is an optical sensor such as a CMOS sensor or other photosensitive semiconductor component. The wavelength displacement unit is placed upstream of the detection unit as a separate element or else integrated into an active surface of the detection unit. Moving the wavelengths towards the detection wavelengths results in a better quantum efficiency of the detection unit.

The invention is based on the consideration that the upward conversion of photons or anti-Stokes displacement by a non-linear wavelength displacement device makes it possible to increase the quantum efficiency of a monochrome or color image sensor. a DMC imager. For this, a particular material is applied, for example, in the form of thin layers on the lenses or the image sensors, even on the entire surface or even by doping, the microlens array of the DMC imager. Commercial sensors which have a good quantum efficiency for visible light in the wavelength range between 380 and 780 nm but it can be significantly improved by a treatment to increase their quantum efficiency or photosensitivity vis-à-vis infrared light. This makes it possible to significantly simplify the processing of the image signal in applications in DMC mode since the input image data offer better contrast and less noise, that is to say that a better signal-to-noise ratio. The design of the imager's optical path in DMC mode can be optimized by increasing the sensitivity of the image sensor, which also translates into savings.

The detection unit using such a detection wavelength offers better quantum efficiency than for the wavelength of the fraction of electromagnetic radiation reflected by the conductor. The displacement of the wavelength is advantageous under these conditions.

According to one development, the lighting unit illuminates the conductor with electromagnetic radiation, and the wavelength displacement unit displaces the wavelength of the reflected fraction towards a detection wavelength located in the wavelength range of visible light.

The near infrared corresponds to the region of the electromagnetic spectrum adjacent to the longest wavelength close to the visible light range towards the long wavelengths.

The driver observation system can thus operate directly with infrared lighting, for example the lighting is pulsed. The infrared light emitter is normally located in the dashboard or in the passenger compartment, directed towards the driver.

For lighting, infrared light is used having a wavelength in the near infrared around 940 nm to arrive at a situation of ambient light of homogeneous lighting as independent as possible, not visible to the driver and not risking dazzle. To reduce ambient light, an optical bandpass filter can be used, placed in the optical path of the conductor observation system. This lighting of the region of interest with infrared light sources must optimally illuminate the face or the bust of the driver taking into account the instantaneous distance from the head, the reflections generated by glasses or the ambient lighting situation. outside. The main function is to illuminate the characteristic area, that is to say the driver's head so that it detaches well from the background, that is to say is segmented from the background and that all the characteristics of the face to be examined offer, thanks to image processing, an appropriate contrast.

According to another development, the wavelength displacement unit comprises a fluorescent material to produce an anti-Stokes displacement. The fluorescent material is, for example, constituted by ions of the Rare Earths, the Lantanoids and the Actinoids.

The anti-Stokes displacement is a wavelength displacement according to which the energetic excitation based on matter and physical relationships is suppressed by the emission of photons, the wavelengths of the emitted photons being shorter than those incident photons.

For example, the wavelength displacement unit includes fluorescent material of ytterbium and / or Erbium ions. This results in an effective displacement of the wavelength.

According to one development, the wavelength displacement unit is an array of microlenses and / or a lens and / or an optical filter, this array of microlenses and / or this lens and / or this optical filter being doped and / or coated with the fluorescent material and / or the wavelength shifting unit is formed by doping and / or coating the detection unit with the fluorescent material.

It is advantageous for the microlens array and / or the lens and / or the optical filter to be doped and / or coated with fluorescent material on the side facing the detection unit. This makes it possible to preserve the optical properties of the microlens arrays, of the lens or of the optical filter, despite doping or coating with the fluorescent material, for example, the diffraction on the particles thus placed.

The invention also relates to a vehicle equipped with such a driver observation system. The vehicle is, for example, a partially autonomous or fully automated vehicle. The driver observation system is, for example, integrated in the dashboard or in the passenger compartment of the vehicle.

The subject of the invention is also a method of inputting the conductor using an observation system comprising a lighting unit, a detection unit and a wavelength displacement unit consisting in illuminating the conductor with electromagnetic radiation of a certain lighting wavelength using the lighting unit, shift the wavelength of the fraction of electromagnetic radiation reflected by the conductor to a wavelength of detecting less than the lighting wavelength using the wavelength shift unit and detecting the radiation transmitted by the wavelength shift unit using the wavelength unit detection.

Advantageously, the displacement of the wavelength gives a better quantum efficiency to the imager for detection.

The invention also relates to a method for producing a wavelength displacement unit for a conductor observation system consisting in doping and / or coating the array of microlenses and / or the lens and / or the optical filter and / or the fluorescent material detection unit to form the wavelength displacement unit.

drawings

The present invention will be described below, in more detail with the aid of exemplary embodiments of the conductor observation method as well as a conductor observation system, its manufacturing method and that of the realization of such a system: FIG. 1 is a schematic representation of an exemplary embodiment of a vehicle, FIG. 2 shows a diagram presenting the quantum efficiency as a function of the wavelength in a CMOS sensor, FIG. 3 shows different views of a wavelength displacement unit according to FIG. 1, FIG. 4 schematically represents a CMOS pixel of a detection unit corresponding to an exemplary embodiment, FIG. 5 is a schematic representation of a CMOS pixel according to FIG. 4 in combination with a microlens of an array of microlenses according to FIG. 3, FIG. 6 is a diagram in exploded view of a CM pixel OS according to FIGS. 4 and 5, FIG. 7 is a very schematic representation of a particle of fluorescent material for coating or doping a wavelength displacement unit corresponding to an exemplary embodiment, FIG. 8 is a schematic representation of a CMOS pixel according to FIG. 5 with a doped microlens, FIG. 9 is a schematic representation of an imager of a conductor observation system corresponding to an exemplary embodiment, FIG. 10 is a schematic representation of another embodiment of a driver observation system imager, FIG. 11 shows a simplified flowchart of a conductor input method according to an exemplary embodiment, and FIG. 12 shows a simplified flowchart of the production method a wavelength displacement unit according to an exemplary embodiment.

Description of embodiments

Figure 1 schematically shows an exemplary embodiment of a vehicle 100. The figure shows the schematic arrangement of a driver observation system 102 for observing the driver 104 installed in the vehicle 100. The driver observation system 102 includes a lighting unit 106 for lighting the conductor 104 with electromagnetic radiation 108 having a wavelength, for example, in the infrared range as well as a detection unit 110 for detecting the fraction reflected 111 by the conductor 104 of the emitted radiation 108. The detection unit 110 is preceded by a wavelength displacement unit 112 which displaces the wavelength of the reflected fraction 111 towards a detection wavelength before this reflected fraction

111 does not arrive on the detection unit 110. The detection wavelength is less than the lighting wavelength. This wavelength shift makes it possible to increase the quantum efficiency and the photosensitivity of the detection unit 110. This corresponds to an important advantage of the invention.

Figure 2 shows the diagram representing the quantum efficiency as a function of the wavelength for a CMOS image sensor. The curve 200 shown shows that the quantum efficiency is relatively low in the near infrared range between 900 and 950 nm.

FIG. 3 shows different schematic views of a wavelength displacement unit 112 in FIG. 1. According to this exemplary embodiment, the wavelength displacement unit 112 is produced in the form of an array microlenses with doping by a special coating to ensure the wavelength displacement and which is congruent with respect to the pixels of the detection unit which is, for example, a CMOS image sensor. The main function of the microlens array is to enlarge the photosensitive surface by pixels, that is to say the photosensitivity and thus the signal / noise ratio per pixel. This makes it possible to reduce the photosensitive surface of the pixel of a CMOS sensor for the same yield or the same light sensitivity, which results in that for the same CMOS chip surface there will be a greater pixel density and thus a resolution. larger image. Figures 4 and 5 graphically represent this situation.

FIG. 4 is a schematic representation of a CMOS pixel 400 of a detection unit 110 corresponding to an exemplary embodiment like the detection unit described above with the aid of FIG. 1. The detection unit 110 is composed of a set of analog CMOS 400 pixels.

FIG. 5 schematically represents a CMOS pixel 400 according to FIG. 4 in combination with a microlens 500 of a network of microlenses produced as a wavelength displacement unit according to FIG. 3. The microlens 500 is located facing the surface of the CMOC image sensor pixel.

The surfaces 502 at the edge of the CMOS pixel 400 represent the conductive paths not sensitive to light used for wiring the various active surfaces of pixel 504. The microlens 500 conducts the incident light into the photosensitive zone of the pixel 400 and thus focuses this light. This increases the photosensitivity per pixel depending on the ratio of the active surface to the non-active surface of the pixel. Depending on the distance between the pixel and the image sensor, the microlens 500 has, for example, a diameter of 5 to 3000 µm. The microlens 500 is, for example, of spherical cylindrical or elliptical shape with a height of up to 100 μm. The microlens 500 is produced by lithography or screening in glass or quartz.

FIG. 6 shows the diagram of the structure of a CMOS pixel 400 according to FIGS. 4 and 5. The CMOS pixel 400 comprises a microlens 500, a color filter 600, a combination of layers 602 with conductive paths and, where appropriate, transistors, an anode 604, a layer of silicon oxide 606, a layer of silicon-p 608 and a cathode 610. Next to the microlens 500 and the color filter 600, the conductive paths with the pilot transistors and the active surface of pixels produced as photodiode with the anode 604, the silicon oxide blocking layer 606, the p-doped silicon 608 and the cathode 610 are shown superimposed. According to the exemplary embodiment, an anti-aliasing filter or infrared blocking filter has also been integrated.

FIG. 7 shows a very schematic representation of a particle 700 of a fluorescent material for coating or doping a wavelength displacement unit according to an exemplary embodiment. Particle 700 can also be called UC particle or more simply UCP element. The figure shows three arrows 702 which represent the radiation of the lighting wavelength, for example, 940 nm exciting the particle 700 as well as an arrow 704 representing the radiation emitted by the particle 700 and whose wavelength detection is, for example, 570 nm.

FIG. 8 schematically shows a CMOS pixel 400 according to FIGS. 4 to 6 with a doped microlens 500. The particles

700 integrated by doping in the microlens 500 are shown diagrammatically by a multiplicity of points.

FIG. 9 schematically shows an imager 900 of a driver observation system corresponding to an exemplary embodiment. The detection unit 110 is in the form of a CMOS sensor with a wavelength displacement unit 112 upstream of the detection unit 110. This unit 112 is produced here in the form of a lens as well a bandpass filter 904 upstream of the wavelength displacement unit 112. According to this exemplary embodiment, the wavelength displacement unit 112 has a layer of particles 700 on its turned side to the detection unit 110.

FIG. 10 is a schematic representation of an imager 900 of a driver observation system according to another exemplary embodiment. Unlike FIG. 9, the wavelength displacement unit 112 according to the embodiment of FIG. 10 is in the form of a dedicated wavelength displacement disc formed of a UCP doped silicate glass placed in the optical path of the imager 900. By way of example, the wavelength displacement unit 112 is placed between the detection unit 110 and a lens 1000, separate from imager 900.

The object of the invention is in particular to increase the efficiency for improving the photosensitivity of a CMOS image sensor by using infrared lighting for DMC applications. The lens of the imager optics or of the microlens array on the image sensor has been appropriately changed, for example, by doping, i.e. by implantation of foreign atoms using a silicate glass to apply the physical principle of upward photon conversion to shift the wavelength of light reflected by the conductor in the near infrared range from a wavelength of about 940 nm to a range of wavelength for which the image sensor has better quantum efficiency, for example, a wavelength on the order of 570 nm. The operation of such a doped wavelength displacement microlens array will be described below.

Upward photon conversion, abbreviated as UC conversion, is a process by which the sequential absorption of two or more photons by a certain fluorescent material called above UC 700 particle results in the remission of light with a length emission wave _Em less than the excitation wavelength À _cx , which is also called “antiStokes emission”. An example of such a conversion is that of the conversion of near infrared light into visible light. The materials which allow such an upward conversion contain, for example, ions of block d or block f of the periodic table such as Rare Earths, Lanthanoides or Actinoides. For example, one can use Ytterbium (Yb ³⁺ ) or Erbium (Er ³⁺ ) to boost the silicate glass substrate. An excitation with infrared light of wavelength λ _ex ~ 950 nm gives, by upward conversion, a green light visible for the main emissions and having a wavelength λ _em i ~ 545 nm and a red light of length wave em2 ~ 660 nm. These wavelengths are generated by spontaneous photoemissions by passing the levels of the excited electrons of the Er ³⁺ ions between their induced metastable energy states, the Yb ³⁺ ion being used for energy transfer to excite the Er ³ ions. ⁺ .

Figure 8 shows the upconversion in the microlens array. When two or more photons of wavelength At _cx ~ 940 nm arrive on one or more Lanthanoid ions doping the lens, the upward conversion generates the emission of a photon of shorter wavelength At _cm ~ 570 nm. Not all incident photons are transformed by upward conversion into wavelengths or energy because some pass through the lens without acting with doping ions. This is described by the efficiency of the upconversion which depends directly on the density of the doping in particles UC 700 of the lens 500.

To make a network of microlenses for wavelength displacement for CMOS sensors, two application methods are envisaged. The microlens array is, for example, enriched with UC materials or UC particles during production, before or during its application to the CMOS image sensor. Alternatively, commercially available CMOS image sensor microlens arrays are modified by doping treatment with UC materials or UC particles.

In the absence of a microlens array, other layers can also be used, such as color filters or anti-aliasing filters which cover the active surfaces of the image sensors and which are doped. It must be precisely checked whether and to what extent the concentration and depth of penetration of foreign atoms by doping in the upper layers is likely to influence the functioning of the semiconductor transitions of the CMOS sensor.

In the case of the two manufacturing methods, due to the wavelength offset to be obtained, which changes the lighting wavelength λ _ex to the detection wavelength λ _em , that is to say -distributing the quantum efficiency distribution depends on the wavelength of the CMOS image sensor used, and which is determined for UC materials by the mass ratio and the association of elements, by a precise determination.

The relationship presented above of upconversion and its use for DMC mode applications can also apply directly to conversion in DMC optics which consists of one or more optical elements such as lenses and filters. Figures 9 and 10 each show a diagram with an optical bandpass filter 904 having a pass range of about 940 nm to eliminate ambient light. The upward conversion must advantageously be done behind the bandpass filter 904 in this optical path. To apply the upconversion, there is shown a normal lens of the imager optics as in Figure 9 which is replaced by a lens whose side facing the CMOS sensor has a UC layer. This layer is, for example, obtained by doping with one of the materials mentioned above.

As a variant, a dedicated wavelength shift disc has been integrated, formed of a silicate glass doped with UC particles in the optical path of the conductor observation system as shown in FIG. 10. To make an optic of wavelength shift we have in summary four application methods.

A lens or an optical filter forming part of the DMC optic is manufactured with several layers, one of which contains the UC material or UC particles.

A lens or an optical filter of the DMC optic is doped during manufacture, on one side with the UC material or UC particles.

A commercially available lens or a commercially available optical filter of the DMC optics is modified by a treatment step by doping with the UC material or UC particles.

A dedicated wavelength displacement disc or plate made of silicate glass doped with UC particles is integrated in the optical path of the DMC imager.

Due to the wavelength shift in these manufacturing processes, it is necessary to determine the precise manner of the UC materials to be used as regards their mass ratio and the arrangement of the elements for the wavelength shift and which depends on the lighting wavelength λ _ex and the detection wavelength λ _em, that is to say the distribution of the quantum efficiency over the wavelengths of the CMOS image sensor used.

FIG. 11 shows a flowchart of a method 1100 for entering a conductor corresponding to an exemplary embodiment. The method 1100 can be applied, for example, using the driver observation system described above with the aid of FIGS. 1 to 10. According to the method, in a first step 1110, the driver is illuminated with the lighting unit under electromagnetic radiation of lighting wavelength. In a second step 1120, the wavelength of the reflected fraction of the electromagnetic radiation emitted by the conductor is displaced using the wavelength displacement unit towards the detection wavelength. In a third step 1130, the detection wavelength provided by the radiation transmitted by the wavelength displacement unit is detected with the detection unit so as to grasp the conductor.

FIG. 12 shows a flowchart of a method 1200 for manufacturing a wavelength displacement unit corresponding to an exemplary embodiment. The method 1200 can, for example, be used for manufacturing the wavelength displacement unit described above using FIGS. 1 to 10. Thus, in an optional step 1210, according to the example one embodiment uses a microlens array, a lens or an optical filter. In the next step 1220, the array of microlenses, the lens or the optical filter is doped or coated with the fluorescent material, that is to say particles UC to effect the displacement of wavelength. Alternatively or in addition, in step 1210, the detection unit is produced and in step 1220, the detection unit is doped with the fluorescent material or coated with this material to have the length offset d 'wave. The wavelength shift unit is thus integrated directly into the detection unit.

NOMENCLATURE OF MAIN ELEMENTS

Vehicle

Driver observation system

Driver

Driver lighting unit

Electromagnetic radiation

Detection unit

Reflected fraction of radiation

Wavelength displacement unit

Quantum efficiency curve

Pixel CMOS

microlens

Pixel area

Pixel active area

Color filter

Combination of layers

Anode

Silicon oxide layer

Layer of p-silicon / p-doped silicon

Cathode

Particle

Arrow representing the lighting wavelength

Arrow representing the radiation emitted by the Imager particle

Bandpass filter

Lens

Driver input process flowchart

Method of manufacturing a wavelength displacement unit

Claims (10)

1 °) Driver observation system (102) for observing the driver (104) in a vehicle (100), system (102) characterized in that it comprises: a lighting unit (106) for lighting the conductor (104) with electromagnetic radiation (108) of a certain lighting wavelength, a wavelength displacement unit (112) for moving the length of the fraction (111) of electromagnetic radiation (108) reflected by the conductor (104) to a detection wavelength shorter than the lighting wavelength, and a detection unit (110) for detecting the radiation transmitted by the wavelength displacement unit (112). 2) conductor observation system (102) according to claim 1, characterized in that the detection unit (110) has better quantum efficiency for the detection wavelength than for the wavelength of the fraction reflected (111) by the conductor (104) of the electromagnetic radiation (108). 3) conductor observation system (102) according to one of the preceding claims, characterized in that - the lighting unit (106) illuminates the conductor (104) with electromagnetic radiation (108), and - the wavelength displacement unit (112) displaces the wavelength of the reflected fraction (111) towards a detection wavelength situated in the range of wavelengths of visible light. 4 °) conductor observation system (102) according to one of the preceding claims, characterized in that the wavelength displacement unit (112) comprises a fluorescent material (700) to produce an anti-Sokes displacement. 5 °) conductor observation system (102) according to claim 4, characterized in that the wavelength displacement unit (112) comprises as fluorescent material (700) ions of ytterbium and / or d 'Erbium. 6 °) conductor observation system (102) according to claim 4 or 5, characterized in that the wavelength displacement unit (112) is an array of microlenses and / or a lens and / or an optical filter, and - the microlens array and / or the lens and / or the optical filter are doped and / or coated with fluorescent material (700) and / or the wavelength displacement unit (112) is formed by doping and / or coating the detection unit (110) with the fluorescent material (700). 7) conductor observation system (102) according to claim 6, characterized in that the microlens array and / or the lens and / or the optical filter are doped and / or coated with fluorescent material (700) on the side facing the detection unit (110). 8 °) Vehicle (100) comprising a driver observation system (102) according to one of the preceding claims comprising: a lighting unit (106) for lighting the conductor (104) with electromagnetic radiation (108) of a certain lighting wavelength, a wavelength displacement unit (112) for moving the length of the fraction (111) of electromagnetic radiation (108) reflected by the conductor (104) to a detection wavelength shorter than the lighting wavelength, and a detection unit (110) for detecting the radiation transmitted by the wavelength displacement unit (112). 9 °) Method (1100) for grasping a conductor (104) using a conductor observation system (102) equipped with a lighting unit (106), a detection unit (110 ) and a wavelength displacement unit (112), method (1100) comprising the following steps consisting in: - lighting (1110) the conductor (104) with electromagnetic radiation (108) of a lighting wavelength with a certain lighting wavelength, using the lighting unit ( 106) - moving (1120) the wavelength of the fraction reflected (111) by the conductor (104) of the electromagnetic radiation (108) towards a detection wavelength less than the illumination wavelength at using the wavelength displacement unit (112), and - Detecting (1130) the radiation transmitted by the wavelength displacement unit (112) using the detection unit (110). 10 °) Method (1200) for producing a wavelength displacement unit (112) for a conductor observation system (102) according to claims 6 or 7, consisting in: - doping and / or coating (1220) the microlens array and / or the lens and / or the optical filter and / or the detection unit (110) with a fluorescent material (700) to form the displacement unit wavelength (112).