WO2024089221A1

WO2024089221A1 - Integrated optical sensor for diffuse reflectance spectroscopy

Info

Publication number: WO2024089221A1
Application number: PCT/EP2023/080019
Authority: WO
Inventors: Angélique Rascle; Luc Andre
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2022-10-27
Filing date: 2023-10-26
Publication date: 2024-05-02
Also published as: FR3141525A1

Abstract

The invention relates to a multilayer device (25) for diffuse reflectance spectroscopy of a scattering and/or absorbing body (1), the optical device comprising: a substrate (30), a layered optical emitter (35) and a layered optical detector (40) which are supported by a face (31) of the substrate and are not placed one on top of the other, the optical emitter comprising at least one light source (501-5010) for emitting light radiation (201-204) having a wavelength of between 400 nm and 1700 nm towards the scattering and/or absorbing body; the optical detector comprising at least one optical sensor (751-7512) for measuring the light radiation scattered and reflected by the scattering and/or absorbing body, the device having a contact face (71, 111) intended to be in contact with the scattering and/or absorbing body, the optical emitter and the optical detector being entirely sandwiched between the contact face and the substrate.

Description

Title: Integrated optical sensor for diffuse reflectance spectroscopy

Technical area

The present invention relates to the field of optical sensors for diffuse reflectance spectroscopy, also known by the abbreviation “DRS”.

Prior art

Diffuse reflectance spectroscopy (DRS) is a non-invasive measurement technique allowing the study of the structure and/or composition of a diffusing body. It is used in particular to measure the concentration of chromophores in biological tissue, for example to measure the oxygenation rate and/or the hydration and/or blood sugar level of skin tissues.

Figure 1 illustrates an example of implementation of DRS according to the prior art for the study of a skin tissue 1. The skin tissue 1 comprises an epidermis 2 and a dermis 3. The epidermis 2 covers the dermis 3. The epidermis 2 comprises epidermis cells 4 and the dermis 3 comprises dermis cells 5 and blood vessels 6. The skin tissue 1 also comprises a stratum corneum 7 composed of dead cells covering the epidermis 2.

A device for implementing DRS generally uses a light source 10 emitting light radiation of wavelength between 400 nm and 1700 nm in the skin tissue 1. It further comprises optical sensors 15i, 152 to detect a backscattered part 20i, or 202, of the light radiation which has interacted with the skin tissue 1.

During their journey within the skin tissue 1, the photons of light radiation are absorbed, deflected and/or diffused by the absorbing or diffusing constituents 4-6 of the skin tissue 1. The absorbing constituents 4-6 are in particular the chromophores, for example water, certain lipids, melanin, hemoglobin or glucose. Diffusing constituents 4-6 include melanosomes, blood cells, collagen, keratin and certain lipids. Only part 20i, 202 of the photons is backscattered, that is to say it emerges by diffuse reflection from the side of the skin tissue 1 through which the light radiation has been introduced, and can thus be detected by one of the sensors optics 15i, 152.

The optical sensor 15i measures the backscattered part 20i of the light radiation in order to study the structure and/or composition of the epidermis 2. The optical sensor 152 measures the backscattered part 2O2 of the light radiation in order to study the structure and/or the composition of the dermis 3. As illustrated in Figure 1, the distance between the sensors 151, 152 and the light source 10 is chosen as a function of the depth in the skin tissue 1 of the study area considered. Likewise, the properties of the light radiation, in particular its wavelength and its angle of incidence on the skin tissue 1, are chosen according to the constituents 4-6 of the skin tissue 1 to be studied.

US 2020/0315473 Al describes an optical system for diffuse reflectance spectroscopy, the optical system comprising a light source and an optical sensor spaced from one another, the optical sensor measuring the backscattered portion of the radiation emitted by the light source in a diffusing body as a function of the angle of incidence at the optical sensor.

EP 6 598 943 A1 describes an optical device for diffuse reflectance spectroscopy, which comprises a light source arranged on a photodetector. However, the optical device described by EP 6 598 943 Al has poor optical contact with a diffusing body to be studied, that is to say that there are significant losses of photons backscattered by the diffusing body at the interface. between the optical device and the diffusing body.

There is no device for carrying out a DRS measurement which is simple to implement and which in particular ensures good optical contact with the body to be studied.

There is therefore a need for an optical device overcoming the aforementioned drawbacks.

Presentation of the invention

The invention relates to a multilayer device for diffuse reflectance spectroscopy of a diffusing and/or absorbing body, the optical device comprising: a substrate, a layered optical emitter and a layered optical detector carried by a face of the substrate and not superimposed on each other, the optical emitter comprising at least one light source for emitting light radiation of wavelength between 400 nm and 1700 nm towards the diffusing and/or absorbing body ; the optical detector comprising at least one optical sensor for measuring the light radiation scattered and reflected by the diffusing and/or absorbing body, the device having a contact face intended to be in contact with the diffusing and/or absorbing body, the transmitter optical and the optical detector being entirely sandwiched between the contact face and the substrate.

The layered conformation on the substrate of the optical emitter and the optical detector facilitates the implementation of a DRS measurement by simply bringing the device into contact with the diffusing and/or absorbing body, for example by manual application of the device on the diffusing and/or absorbing body. The invention thus makes it possible for the user, after having positioned the optical transmitter on the diffusing and/or absorbing body, to avoid the tedious step of positioning the optical detector relative to the optical transmitter, or vice versa. .

The device is advantageously portable. The wearer of the device is for example an animal or a human being. It then makes it possible to measure by diffuse reflectance spectroscopically the concentration of chromophores in a biological tissue, for example the wearer's skin. It is thus possible, for example, to determine the rate of oxygenation and/or hydration and/or blood sugar levels of the wearer's skin tissue.

Preferably, the distance, measured according to the thickness of the substrate, between the face of the optical emitter opposite the substrate and the face of the optical detector opposite the substrate is less than or equal to 100 pm, preferably less than or equal to 10 pm .

Preferably, the contact face of the device, when observed in a direction normal to the substrate, extends over a surface area less than or equal to 100 mm ² , preferably between 1 mm ² and 100 mm ² . Preferably said contact face has a length and a width less than or equal to 10 mm and greater than or equal to 1 mm. So, the optical contact between the device and the diffusing and/or absorbing body is optimal, particularly when the diffusing and/or absorbing body is more flexible than the device.

Preferably, in order to ensure optimal optical contact, the portion of the contact face facing the optical emitter and the optical detector has a flatness difference less than or equal to 100 pm, preferably less than or equal to 10 pm. The flatness difference corresponds to the distance between the two closest parallel planes between which the portion of the contact face is entirely included.

The optical transmitter and the optical sensor are preferably spaced at a distance of less than 50 mm, preferably between 1 pm and 50 mm. Preferably, the optical transmitter comprises several light sources and/or the optical detector comprises several optical sensors, the light source and the optical sensor furthest from each other are preferably 8 mm apart.

The device may include an electric current generator, for example an autonomous battery, to electrically power the optical transmitter and the optical detector.

Preferably, the optical transmitter comprises a plurality of light sources arranged regularly, for example periodically, on the substrate. Preferably, at least one of the light sources is configured to emit light radiation of a wavelength different from the light radiation emitted by at least one other of the light sources, in particular by each of the other light sources.

Preferably, the optical detector comprises at least two optical sensors arranged regularly, for example periodically, on the substrate. Preferably, the optical detector comprises at least two groups of optical sensors configured to detect light radiation scattered and reflected by the diffusing and/or absorbing body of wavelength ranges different from each other. Preferably, the optical detector comprises a first group of optical sensors configured to detect light radiation of wavelength between 450 nm and 650 nm, a second group of optical sensors configured to detect light radiation of wavelength included between 650 nm and 900 nm and a third group of optical sensors configured to detect light radiation of wavelength between 850 nm and 1600 nm. In this way, several types of diffusing and/or absorbing elements, sensitive over various wavelength ranges, can be studied by DRS. For example, during a diffuse reflectance spectroscopy analysis of a skin tissue, it is thus possible to detect and quantify the interfering chromophores which disrupt the study of the target chromophores, and thus reduce the measurement noise due to these chromophores.

Preferably, the device comprises a barrier opaque to at least one light radiation of wavelength between 400 nm and 1700 nm, the opaque barrier being carried by the substrate and arranged between the optical emitter and the optical detector in order to prevent the radiation emitted by the light source from directly reaching the optical sensor. Such an opaque barrier reduces measurement noise during a DRS measurement. Radiation emitted by a light source reaching “directly” a sensor has not undergone reflection and/or refraction between its emission and its reception. In particular, it was not reflected by the diffusing and/or absorbing body and/or did not penetrate and then be refracted by the diffusing and/or absorbing body. The barrier can be a metallic, polymeric material, for example a resin, or semiconductor.

Preferably, each light source comprises at least one light-emitting layer, an anode and a cathode sandwiching the light-emitting layer and each being electrically connected with the light-emitting layer. Preferably, the anode is interposed between the photoemitting layer and the substrate. The anode and/or the cathode may be in contact with the photoemitting layer. In particular, the photo-emitting layer can be deposited on the anode and/or the cathode can be deposited on the photo-emitting layer. A “photo-emitting layer” converts a signal, in particular an electrical current, into light radiation. At least one of the light sources may comprise a plurality of photo-emitting layers stacked on top of each other with the anode and the cathode arranged on either side of the stack.

Preferably, the photoemitting layer is chosen from a light-emitting diode, a quantum dot and a laser diode. The light-emitting diode can be organic or inorganic. For example it is made of GaN, or AlInGaP, or InP, or Alqa. or in DCM, or in Ir(ppy)3, or in FIrPic, or in DABNA. A quantum dot is a nanocrystalline semiconductor material, for example germanium (Ge) or indium gallium arsenide (InGaAs), behaving like a potential well confining the electric charges in the three dimensions of space. The laser diode may be a vertical cavity surface emitting laser diode (VCSEL).

Preferably, the optical transmitter comprises at least one electrically insulating wall arranged between two adjacent light sources so as to electrically isolate the anode of one of the two light sources from the anode of the other of the two light sources. Preferably, the insulating wall is made of insulating resin, or an oxide, or a semiconductor, or a metal. Preferably, the insulating wall is opaque at at least one, preferably at all wavelengths between 400 nm and 1700 nm.

Preferably, each optical sensor comprises at least one photosensitive layer, an anode and a cathode sandwiching the photosensitive layer and each being electrically connected with the photosensitive layer. Preferably, the anode is interposed between the photosensitive layer and the substrate. The anode and/or the cathode may be in contact with the photosensitive layer. In particular, the photosensitive layer can be deposited on the anode and/or the cathode can be deposited on the photosensitive layer. A “photosensitive layer” converts light radiation into an electrical signal, in particular a current. At least one of the optical sensors may comprise a stack of photosensitive layers superimposed on one another with the anode and the cathode arranged on either side of the stack.

Preferably, the photosensitive layer is chosen from a silicon and/or germanium photodetector, an organic photodetector, for example based on ZnPc preferably doped with CÔO, and a quantum dot.

The cathode of the light source and/or the cathode of the optical sensor may be made of a material transparent to at least one, preferably all, wavelengths between 400 nm and 1700 nm. Said transparent material can be chosen from a metal or an alloy, in transparent conductive oxide (TCO), for example chosen from indium-tin oxide (ITO), tin dioxide (SnO2), a titanium/titanium bilayer. titanium nitride (Ti/TiN), aluminum (Al), and silver (Ag). The cathode of the light source and/or the cathode of the optical sensor may each have a thickness of between 10 nm and 30 nm.

At least two of the light sources can share the same cathode. At least two of the optical sensors can share the same cathode.

The anode of the light source and/or the anode of the optical sensor may be a material chosen from a metal or an alloy, a conductive oxide, for example indium-tin oxide (ITO), a titanium/bilayer. titanium nitride (Ti/TiN), silver (Ag), aluminum (Al), germanium (Ge), nickel (Ni), and gold (Au). Preferably, the anode of the light source and/or the anode of the optical sensor is made of a reflective material. The anode of the light source and/or the anode of the optical sensor may each have a thickness of between 5 nm and 50 nm, preferably between 5 nm and 30 nm.

Preferably, the optical detector comprises at least one electrically insulating wall arranged between two adjacent optical sensors so as to electrically isolate the photosensitive layer and the anode of one of the two optical sensors of the photosensitive layer and the anode of the other of the two optical sensors. Preferably the electrically insulating wall of the optical detector is made of an electrically insulating resin, or an oxide, or a semiconductor, or a metal. Preferably, it is opaque at at least one, preferably at all wavelengths between 400 nm and 1700 nm.

Preferably, along an observation axis normal to the substrate, the area of the substrate is greater than or equal to the sum of the area of the optical emitter and the area of the optical detector and, where appropriate, the area of the opaque barrier. Preferably, the substrate extends over a surface area less than or equal to 100 mm ² , preferably less than or equal to 50 mm ² , preferably less than or equal to 25 mm ² .

Preferably, the device comprises an electrically conductive via in electrical contact with the anode and passing through the substrate right through depending on the thickness of the substrate. Preferably, the via is made of an N or P doped semiconductor, or of a metal or metal alloy, for example tungsten (W), or copper (Cu), or aluminum (Al), or a bilayer of titanium. /titanium nitride (Ti/TiN). It thus makes it possible to establish an electrical connection with the anode from the side of the substrate opposite the contact face. It notably allows the control of the anode by a CMOS type integrated circuit. In the variant where several anodes are arranged on the substrate, the device comprises several vias which each connect one of the anodes and pass through the substrate right through. Alternatively, the device may comprise one or more electrically conductive tracks in electrical contact with the anode and extending beyond the portion of the substrate carrying the optical emitter and the optical detector. The electrically conductive track(s) can be arranged in the thickness of the substrate.

The substrate can be rigid or flexible. Unlike a rigid substrate, a flexible substrate deforms elastically under the effect of its own weight. A flexible substrate advantageously makes it possible to conform the device to the diffusing and/or absorbing body, to improve optical contact.

The substrate may be made of a material chosen from silicon, a polymer, and a glass. It may include a silicon portion carried by an electrically insulating support.

Preferably, the substrate can carry an electrical contact pad electrically connected to the cathode(s) and arranged at a distance from the portion of the substrate carrying the optical emitter and the optical detector.

Preferably, the device comprises a transparent coating at at least one, preferably at all wavelengths between 400 nm and 1700 nm, covering the face of the optical emitter and the face of the optical detector opposite the substrate. Preferably, the transparent coating is made of alumina (AI2O3), or of silicon monoxide (SiO), or of organic resin, or of a multilayer formed of the aforementioned materials. Preferably, the transparent coating has a thickness less than or equal to 10 μm.

Preferably, the device comprises an optical absorber arranged between the optical emitter and the optical detector, the optical absorber comprising a face merging with the contact face. The optical absorber prevents reflections of light radiation at the interface between the diffusing and/or absorbing body and the optical absorber. Preferably, the optical absorber has a refractive index greater than 1.3, or even greater than 1.4. The optical absorber may include, or even consist of, the opaque barrier.

The device may comprise an additional optical absorber arranged between two adjacent optical sensors, the additional optical absorber comprising a face merging with the contact face and having a refractive index greater than 1.3, or even greater than 1.4. Said additional optical absorber can be formed from one of the insulating walls. The invention also relates to a method of manufacturing a device according to the invention, the method comprising depositing layers on the substrate to form the optical emitter and the optical detector.

Furthermore, the invention relates to the use of at least one device according to the invention for diffuse reflectance spectroscopy of a diffusing and/or absorbing body, preferably the diffusing and/or absorbing body being organic, for example a food of animal, plant or fungal origin, or biological tissue, in particular human or animal.

Use may include:

- the irradiation of the diffusing and/or absorbing body by light radiation emitted by the optical transmitter of the device,

- the detection, by the optical detector of the same device as the optical transmitter having irradiated the diffusing and/or absorbing body, of a part backscattered by the diffusing and/or absorbing body of the light radiation, and/or, of a part of the light radiation reflected by the surface of the diffusing and/or absorbing body.

The use may include the calibration of the optical detector and/or the optical transmitter based on the detection of the part of the light radiation reflected by the surface of the diffusing and/or absorbing body so as to limit the measurement noise during Diffuse reflectance spectroscopy. The part of the light radiation reflected by the surface of the diffusing and/or absorbing body, also called specular reflection, depends on the diffusing and/or absorbing body. For example, for skin tissue, the specular reflection depends on the skin tone of said tissue.

Use may include:

- the irradiation of the diffusing and/or absorbing body with at least two light rays of different wavelength emitted by the optical transmitter,

- for each of the light rays emitted, the detection, by the optical detector of the same device as the optical emitter having irradiated the diffusing body, of a part backscattered by the body diffusing and/or absorbing the corresponding light radiation,

- the determination, from the detections of said backscattered parts, of the wavelength adapted to the study of the constituent of the diffusing and/or absorbing body considered. A plurality of devices according to the invention can be used for the implementation of diffuse reflectance spectroscopy. The measurement can be done in an impulse and/or frequency manner.

Other advantages and characteristics will become clearer on reading the detailed description, given for illustrative and non-limiting purposes, with reference to the following figures.

Brief description of the drawings

[Fig 1] Figure 1 is a schematic cross-sectional representation of an example of implementing a diffuse reflectance spectroscopic measurement known from the prior art.

[Fig 2] [Fig 3] [Fig 4] [Fig 5] Figures 2 to 5 are schematic cross-sectional views of different examples of the multilayer device according to the invention.

[Fig 6] Figure 6 is a schematic top view of an example of the multilayer device according to the invention.

[Fig 7], [Fig 8], [Fig 9] and [Fig 10] Figures 7 to 10 are schematic representations in cross section illustrating different examples of use of the device according to the invention for diffuse reflectance spectroscopy. 'a diffusing and/or absorbing body.

[Fig 11], [Fig 12], [Fig 13], [Fig 14], [Fig 15], [Fig 16], [Fig 17], [Fig 18], and [Fig 19] Figures 11 to 19 are schematic cross-sectional views of the different stages of an example of implementation of the method of manufacturing the device according to the invention.

detailed description

In the figures, the different elements constituting the device according to the invention as well as the diffusing and/or absorbing medium are not represented to scale, for the sake of clarity of the drawing.

Figure 1 was described above.

Figure 2 illustrates a first embodiment of a multilayer device according to the invention. The device 25 comprises a substrate 30, having a face 31, a optical emitter 35 and an optical detector 40 in contact with the face 31. The device 25 further comprises an opaque barrier 45 carried by the substrate 30 and arranged between the optical emitter 35 and the optical detector 40. The opaque barrier forms a wall preventing the direct transmission of light radiation emitted by the optical transmitter 35 to the optical detector 40.

The optical transmitter 35 comprises two light sources 50i and 502 to emit light radiation of wavelength between 400 nm and 1700 nm. It further comprises an electrically insulating wall 55 arranged between the light sources 50i and 502.

Each of the light sources 50i, respectively 502, comprises an anode 60i, respectively 6O2, a photo-emitting layer 65i, respectively 652, and a cathode 70 common to the two light sources 50i and 502. The photo-emitting layer 65i, respectively 652, is sandwiched between the cathode 70 and the anode 6O1, respectively 6O2. Thus, by applying an electric current between the cathode 70 and the anode 6O1 or 6O2, the photoemitting layer 651 or 652 emits light radiation. The photoemitting layers 651 and 652 emit light radiation of wavelength(s) different from each other.

Furthermore, the optical detector 40 comprises two optical sensors 751 and 752. It further comprises an electrically insulating wall 80 arranged between the optical sensors 751 and 752.

Each optical sensor 751, respectively 752, comprises an anode 851, respectively 852, a first photosensitive layer 90i, respectively 902, a second photosensitive layer 95i, respectively 952, and a cathode 72. The first and second photosensitive layers 90i and 951, respectively 902 and 952, are sandwiched between the cathode 72 and the anode 85i, respectively 852. Thus, when light radiation reaches at least one of the first and second photosensitive layers 90i and 951 or 902 and 952, the latter converts this radiation into electric current. The first photosensitive layer 90i or 902 can be configured to convert light radiation of wavelength included in a first range, for example from 400 nm to 900 nm, and the second photosensitive layer 951 or 952 can be configured to convert the light radiation of wavelength included in a second range different from the first range, for example from 850 nm to 1700 nm. Furthermore, the electrically insulating wall 80 insulates electrically the anodes 85i and 852 from each other and the first and second photosensitive layers 90i, 9 (, 95i and 952 from one optical sensor 751 or 752 to the other 751 or 752.

As illustrated in Figure 2, the cathode 70 is common to each of the light sources 50i and 502 and the cathode 72 is common to each of the optical sensors 75i and 752. During a spectroscopic by diffuse reflectance of a diffusing body and/or absorbent, the device 25 is brought into contact with said diffusing and/or absorbing body by applying the contact face 71 of the device 25 opposite the substrate 30 against the diffusing and/or absorbing body. In the example of Figure 2, the contact face 71 consists of the faces of the cathode 70 and the cathode 72 opposite, respectively, the photosensitive layers 85i, 852 and the photoemitting layers 651, 652. Furthermore, the radiation light emitted by the photoemitting layer 65i or 652 is transmitted through the transparent cathode 70, to the diffusing and/or absorbing body, then part of this light radiation is backscattered by the diffusing and/or absorbing body and transmitted through the cathode 72 to photosensitive layers 90i, 902, 95i and 952.

On the other hand, the substrate 30 comprises vias 100 passing right through the substrate 30 so as to establish electrical contact of each of the anodes 60i, 6O2, 85i and 852 through the substrate 30. In this way, the electrical power supply of the optical transmitter 35 and the optical detector 40 can be carried out opposite the contact face 71. This prevents the quality of the optical contact from being hampered by electrical power supply circuitry of the device 25.

We have illustrated in Figure 3 a second example of device 25 which differs from the example illustrated in Figure 2 in that each of the light sources 50i, respectively 502, comprises a first photoemitting layer 651, respectively 652, and a second light-emitting layer 661, respectively 662. The first and second light-emitting layers 65i and 661, respectively 652 and 662, are stacked one on top of the other. They are sandwiched between cathode 70 and anode 6O1, respectively 6O2.

The third example of device 25 illustrated in Figure 4 differs from the example illustrated in Figure 2 in that the substrate 30 carries an electrical contact pad 105 on the periphery of the substrate 30. The electrical contact pad 105 is electrically connected to the cathode 70. It facilitates the electrical supply of the cathode 70 to apply an electric current between the cathode 70 and the anode 60i or 6O2. In addition, it facilitates the measurement of the electrical signal produced by one of the photosensitive layers 90i, 902, 95i and 952. In particular, during a DRS measurement, the cathode 70 is brought into contact with the diffusing and/or absorbing body or sandwiched between the diffusing and/or absorbing body and the substrate 30. The electrical contact pad 105 makes electrical contact with the cathode 70 more accessible for an electrical signal power supply and/or measuring device.

As is also shown in Figure 4, the optical emitter 35 and the optical detector 40 do not have the same heights hi and I12 measured from the substrate along an axis parallel to the thickness of the substrate. This results in a distance di between the face 36 of the optical emitter 35 and the face 41 of the optical detector 40 which are each opposite the substrate 30. Preferably, the distance di is less than 100 pm, in order to ensure good optical contact. Furthermore, in the embodiment shown in Figure 4, the flatness difference of the contact face 71 is at most equal to the distance di. A reduction in the distance advantageously leads to a reduction in the flatness difference.

We have illustrated in Figure 5 a fourth example of device 25 which differs from that illustrated in Figure 4 in that it comprises a transparent coating 110 for wavelengths between 400 nm and 1700 nm. The coating 110 is placed in contact with the cathode 70 and the cathode 72. It covers the optical emitter 35 and the optical detector 40. The optical emitter 35 and the optical detector 40 are sandwiched between the substrate 30 and the coating 110. The coating 110 protects the optical emitter 35 and the optical detector 40, which is particularly advantageous if the latter are composed at least in part of organic materials. During a DRS measurement, the device 25 is placed on the diffusing and/or absorbing body with the coating 110 in contact with the diffusing and/or absorbing body. Thus, the contact face of the device is the face 111 of the coating 110 opposite the substrate 30.

As is also shown in Figure 5, the coating 110 comprises a step 112 caused by the distance di between the face 36 of the optical emitter 35 and the face 41 of the optical detector 40. In the embodiment illustrated in the figure 5, the step 112 has a height d2 equal to the distance di. However, it may be advantageous to reduce the height d2 of the step 112 by producing a coating 110 of non-uniform thickness, in order to reduce the difference in flatness of the contact face 111 of the device 25. It is in particular it is possible that the height d2 of the step 112 and the flatness difference of the contact face 111 are substantially equal to 0 pm.

Figure 6 shows a top view of another example of a device 25 according to the invention. The optical transmitter 35 comprises ten 50i-50w light sources arranged periodically on the substrate 30 in five rows and two columns. The optical detector 40 comprises twelve optical sensors 751-7512 arranged periodically on the substrate 30 in four rows and three columns. The numbers and arrangements of light sources and optical sensors are not limiting. Other arrangements may be considered.

Each of the 5Oi-5Oio light sources is configured to emit light radiation of different wavelength from the other 5Oi-5Oio light sources.

The distance e between the light sources 502, 504, 50Ô, 50S and 5Oio and the optical sensors 75i, 754, 75? and the nearest 75io is less than or equal to 8 pm. The distance e is equal to the thickness of the optical barrier 45, but in another example not shown, the thickness of the optical barrier 45 is less than the distance e.

The advantages of the device 25 will appear from the different modes of use which are described below.

Figure 7 illustrates an example of use of a device 25 according to the invention. It differs from that illustrated in Figure 1 by the presence, instead of the light source 10, of the device 25. The optical transmitter 35 emits light radiation into the skin tissue 1. Part of the radiation 20i is measured, after backscattering in the epidermis 2 of the skin tissue 1, by the optical sensor 151 and thus allows the study of the chromophores 4 of the epidermis 2. Another part of the radiation 202 is measured, after backscattering in the dermis 3 of the skin tissue 1 , by the optical sensor 152, and thus allows the study of the chromophores 5 and 6 of the dermis 3. A part 2O3 of the radiation is reflected by the surface of the skin tissue 1, this specular reflection is measured by the optical detector 40 of the device 25

Measuring the specularly reflected part 2O3 of the radiation makes it possible to calibrate the optical transmitter 35 so that the specular reflection influences as little as possible the measurements of the chromophores 4-6 of the dermis and/or the epidermis. In other words, the measures backscattered parts 201 and 2Û2 of the radiation are corrected by taking into account the measurement of the specular reflection 2O3 of the radiation.

Another example of use of the device 25 according to the invention is illustrated in Figure 8. The device is in optical contact with a diffusing and/or absorbing body 1. The diffusing and/or absorbing body 1 comprises a first layer 2 and a second layer 3. In the use of the device 25 shown in Figure 8, first 50i and second 5Ch light sources emit first and second light radiation in the diffusing and/or absorbing body 1. The first light radiation has a different wavelength from the second light radiation.

A part of the first light radiation 201 and a part of the second light radiation 2O2 are then diffused in and then reflected by the first layer 2 of the diffusing and/or absorbing body 1 to optical sensors 751, respectively 752. The optical sensors 751 and 752 measure the backscattered parts 20i and 2O2 of the first and second light radiations. It is thus possible to determine the most suitable wavelength for the study of an element of the first layer 2.

9 illustrates an example of use of a plurality of devices 25i-25s according to the invention for diffuse reflectance spectroscopy of a diffusing and/or absorbing body 1. The diffusing and/or absorbing body 1 comprises first, second and third layers respectively 2, 3 and 8 superimposed on each other. Five 25i-25s devices according to the invention are placed in optical contact with the diffusing body 1 and spaced from each other. The devices 252-254 are spaced from the first device 25i as a function of the target depth in the diffusing and/or absorbing body 1 that they are intended to measure.

The optical transmitter 35i of the first device 251 emits light radiation into the diffusing and/or absorbing body 1.

A part 20i of the light radiation circulates in the first layer 2 then is backscattered by it. The backscattered part 20i of the light radiation is then measured by the optical detector 402 of the second device 252. A part 202 of the light radiation sinks until then circulates in the second layer 3 then is backscattered by it. The backscattered part 2O2 of the light radiation is then measured by the optical detector 40a of the third device 25a.

A part 204 of the light radiation sinks until then circulates in the third layer 8 then is backscattered by it. The backscattered part 204 of the light radiation is then measured by the optical detector 404 of the fourth device 254.

A part 20a of the light radiation is reflected by the surface of the diffusing and/or absorbing body 1 then measured by the optical detector 40i of the first device 251. Similar to the example illustrated in Figure 7, the measurement of this specular reflection 2O3 makes it possible to best calibrate the optical transmitter 35i in order to best limit the effects of specular reflection for the other parts 201, 2O2 and 204 backscattered from the light radiation.

The backscattered parts 20i, 2O2 and 204 of the light radiation make it possible to study by diffuse reflectance spectroscopically the different layers 2, 3 and 8 of the diffusing and/or absorbing body 1.

10 illustrates an example of a device 25 comprising an optical absorber 46 disposed between the optical transmitter 35 and the optical detector 40. The device 25 further comprises additional optical absorbers 47 between each of the optical sensors 751, 752 and 753. The device 25 is placed in optical contact with a first layer 2 of a diffusing and/or absorbing body 1. The optical absorbers 46 and 47 have a refractive index greater than the refractive index of the first layer 2.

The diffusing and/or absorbing body 1 also comprises a second layer 3 comprising the elements whose study is desired. Figure 10 represents the measurement of these elements by DRS. For this, the optical emitter 35 emits light radiation at different depths in the diffusing and/or absorbing body 1. A portion 20i of the light radiation circulates in the first layer 2 at an intermediate depth then is backscattered by it. The backscattered part 20i of the light radiation is then measured by the optical sensor 751. A part 2O2 of the light radiation circulates in the first layer 2 up to the limit of the second layer 3, then is backscattered by the first layer 2. The backscattered part 2(h of the light radiation is then measured by the optical sensor 752. A part 2O3 of the light radiation sinks until then circulates in the second layer 3 then is backscattered by it The backscattered part 2O3 of the light radiation is then measured by the optical sensor 753.

Advantageously, the presence of optical absorbers 46 and 47 eliminates the unwanted reflections of light radiation emitted by the optical emitter 35 at the interface between the first layer 2 and the device 25, and therefore, thereby, limits the measurement of radiation parasites which would not have circulated in the second layer 3 and would have reached the optical sensor 753.

Furthermore, for the DRS measurement of the elements of the second layer 3 illustrated in Figure 10, it is interesting to subtract from the information collected by the optical sensor 753 the information collected by the sensors 751 and 752. Thus, the DRS measurement is localized on the elements of the second layer 3 and is less disturbed by the influence of the first layer 2 crossed by the light radiation 2O3.

Subsequently, a method of manufacturing a device 25 is described. The method first comprises a step a) of supplying a substrate 30. The substrate 30 may include recesses in which the vias 100 are formed. It can also be coated with the electrical contact pad 105. The method then comprises a step b) of manufacturing the optical emitter 35 and the optical detector 40 by deposition of layers on the substrate 30 as is illustrated in Figures 11 to 19.

The manufacturing in step b) may comprise the following successive sub-steps: bi) manufacturing by deposition of at least one layer on the substrate 30 of the anodes 6O1, 6O2, 85i and 852 of the light source(s) 50i, 502 , and the optical sensor(s) 751, 752, b2) manufacturing the photosensitive layer(s) 90i, 902, 95i and 952 of the optical sensor(s) 751, 752, by depositing a layer on the anodes 851, 852, intended to form the anodes 85i, 852, of the optical sensor(s) 751, 752, b,) manufacturing of the photoemitting layer(s) 651, 652, of the optical source(s) 50i, 502, by layer deposition on the anodes 6O1, 6O2, intended to form the anodes 6O1, 6O2, of the optical source(s) 50i, 502,

64) manufacturing the cathode 70 of the light source(s) 50i, 502, and the light source(s) optical sensors 75i, 752, by deposition of an electrically conductive material on the photosensitive layers 951, 952, and the photoemitting layers 651, 652.

Substep bi) may include the deposition, illustrated in Figure 11, on the substrate 30 of an electrically conductive material to form a primary layer 115 followed by etching, illustrated in Figure 12, preferably by photolithography, of the primary layer 115 so as to form the different anodes 60i, 6O2, 85i and 852.

The method may include an intermediate sub-step between sub-steps bi) and 62) during which an electrically insulating resin 117 is applied between the anodes 6O1, 6O2, 85i and 852, for example by layer deposition and localized etching. This intermediate sub-step is illustrated in Figure 13. The electrically insulating resin 117 then defines at least part of the insulating walls 55 and 80 and part of the opaque barrier 45.

Substep b2) may include the deposition, illustrated by Figure 14, preferably by transfer, of one or more secondary layers 120 and 125 made of the materials constituting the photosensitive layer(s) 90i, 902, 951 and 952 on the anodes 6O1, 6O2, 851 and 852. Said deposition is then followed by an etching, illustrated in Figure 15, preferably by ion bombardment, of the secondary layer(s) 120 and 125 so as to form the photosensitive layer(s). 90i, 902, 951 and 952 optical sensors 751, 752.

The method may include an intermediate sub-step between sub-steps b2) and ba) during which the opaque barrier 45 is manufactured by layer deposition and localized etching. This intermediate sub-step is illustrated by Figures 17 and 18, Figure 16 illustrating the deposition of a layer 130 of the material constituting the opaque barrier 45 and Figure 17 illustrating the result of the localized etching of the layer 130 thus forming the opaque barrier 45 between the zone of the substrate 30 intended to carry the optical emitter 35 and the zone of the substrate 30 intended to carry the optical detector 40.

The manufacture of the photoemitting layer(s) 651, 652, during sub-step ba) can be done by localized deposition using stencil masks, as illustrated in Figure 18.

Alternatively, sub-step ba) may comprise the deposition, preferably by transfer, to form one or more tertiary layers of materials constituting the photo-emitting layer(s) 651, 652, on the anodes 6O1, 6O2, followed by etching, preferably by ion bombardment, of the tertiary layer(s) so as to form the photo-emitting layer(s) 651, 652, light sources 50i, 50 ₂ .

19 illustrates substep 64) during which a layer of an electrically conductive material is deposited on the photosensitive layers 951, 952, the photoemitting layers 65i, 652 and the opaque barrier 45, said layer thus forming the cathode 70 of the light source(s) 50i, 502, and the optical sensor(s) 751, 752.

Preferably, the method may comprise a subsequent step c) of manufacturing a transparent coating 110 for wavelengths between 400 nm and 1700 nm, the manufacturing being carried out by layer deposition, on the face of the emitter optical detector 35 opposite the substrate 30 and the face of the optical detector 40 opposite the substrate 30.

Other variants and improvements can be considered without departing from the scope of the invention as defined by the claims below.

Claims

1. Multilayer device (25) for diffuse reflectance spectroscopy of a diffusing and/or absorbing body (1), the optical device comprising: a substrate (30), an optical emitter (35) in layer and an optical detector ( 40) in layer carried by one face (31) of the substrate and not superimposed on each other, the optical emitter comprising at least one light source (5Oi-5Oio) for emitting light radiation (201 -204 of wavelength between 400 nm and 1700 nm towards the diffusing and/or absorbing body; the optical detector comprising at least two optical sensors (751-7512), arranged regularly on the substrate, to measure the light radiation scattered and reflected by the diffusing and/or absorbing body, the device having a contact face (71, 111) intended to be in contact with the diffusing and/or absorbing body, the optical emitter and the optical detector being entirely sandwiched between the face contact and the substrate, the optical detector comprising at least two groups of optical sensors configured to detect light radiation scattered and reflected by the diffusing and/or absorbing body of wavelength ranges different from each other.

2. Device according to the preceding claim, the contact face when observed in a direction normal to the substrate, extending over a surface area less than or equal to 100 mm ² , preferably between 1 mm ² and 100 mm ² , preferably said contact face having a length and a width less than or equal to 10 mm and greater than or equal to 1 mm.

3. Device according to one of the preceding claims, the device comprising an optical absorber (45, 46) arranged between the optical transmitter and the optical detector, the optical absorber comprising a face merging with the contact face, preferably the optical absorber having a refractive index greater than 1.3, or even greater than 1.4.

4. Device according to one of the preceding claims, the portion of the contact face facing the optical transmitter and the optical detector has a flatness difference less than or equal to 100 pm, preferably less than 10 p.m.

5. Device according to one of the preceding claims, the optical transmitter comprising a plurality of light sources (5Oi-5Oio) arranged regularly, for example periodically, on the substrate, preferably at least one of the light sources being configured to emit a light radiation of wavelength different from the light radiation emitted by at least one other light source, in particular by each of the other light sources.

6. Device according to one of the preceding claims, comprising a barrier (45) opaque to at least one light radiation of wavelength between 400 nm and 1700 nm, the opaque barrier being carried by the substrate and arranged between the optical transmitter and the optical detector in order to prevent the radiation emitted by the light source from directly reaching the optical sensor.

7. Device according to one of the preceding claims, each light source comprising at least one photo-emitting layer (65i, 652, 66i, 662), an anode (6O1, 6O2) and a cathode (70) sandwiching the photo-emitting layer and each being electrically connected with the photoemitting layer.

8. Device according to the preceding claim, the photoemitting layer being chosen from a light-emitting diode, a quantum dot and a laser diode.

9. Device according to one of claims 7 and 8, the optical transmitter comprising at least one electrically insulating wall (55) arranged between two adjacent light sources so as to electrically isolate the anode of one of the two light sources of the the anode of the other of the two light sources.

10. Device according to one of claims 7 to 9, the substrate carrying an electrical contact pad (105) electrically connected to the cathode(s) of the light sources and arranged at a distance from the portion of the substrate carrying the optical emitter and the optical detector.

11. Device according to one of the preceding claims, each optical sensor comprising at least one photosensitive layer (90i, 902, 95i, 952), an anode (85i, 862) and a cathode (72) sandwiching the photosensitive layer and each being electrically connected with the photosensitive layer.

12. Device according to the preceding claim, the photosensitive layer being chosen from a silicon and/or germanium photodetector, an organic photodetector, for example based on ZnPc preferentially doped with CÔO, and a quantum dot.

13. Device according to one of claims 11 and 12, the optical detector comprising at least one electrically insulating wall (80) arranged between two adjacent optical sensors so as to electrically isolate the photosensitive layer and the anode of one of the two sensors optical sensors of the photosensitive layer and the anode of the other of the two optical sensors.

14. Device according to one of claims 7 to 13, comprising an electrically conductive via (100) in electrical contact with the anode of the light source or with the anode of the optical detector and passing through the substrate right through according to the the thickness of the substrate, preferably the via being made of N or P doped semiconductor, or of metal or of a metal alloy, for example tungsten (W), or copper (Cu), or aluminum (Al), or a titanium/titanium nitride (Ti/TiN) bilayer.

15. A method of manufacturing a device (25) according to any one of the preceding claims, the method comprising the deposition of layers on the substrate to form the optical emitter and the optical detector.

16. Use of at least one device (25) according to one of claims 1 to 14 for diffuse reflectance spectroscopy of a diffusing and/or absorbing body (1), preferably the diffusing and/or absorbing body being organic, for example a food of animal, plant or fungal origin, or biological tissue, in particular human or animal.