Deformable mirror

Abstract

The invention relates to an adaptive optics system (100) configured to modify an incident wavefront (210), the adaptive optics system (100) comprising a selective heating device and a multilayer deformable mirror comprising a substrate (10), an active layer (20) arranged on the substrate (10), and a reflective layer (30) arranged on the active layer (20) and configured to reflect the incident wavefront (210); the selective heating device (40) being configured to generate a temperature distribution of the active layer (20), the active layer (20) having a variable thickness distribution, the thickness distribution being dependent on the temperature distribution of the active layer (20), the thickness distribution causing a modification of the incident wavefront (210) reflected by the reflective layer (30).

Description

[0001] "DEFORMABLE MIRROR"

[0002] The present invention relates to the field of deformable mirrors. In particular, the field of deformable mirrors by thermomechanical effect.

[0003] STATE OF THE ART

[0004] Deformable mirrors make it possible to generate a wavefront with a particular geometry or to correct irregularities contained in an incident wavefront.

[0005] There are many types of deformable mirrors.

[0006] One type of deformable mirror is composed of a plurality of reflective cells whose respective positions can be modified. The incident wavefront arriving at all the reflective cells will be reflected in different directions, thus modifying the wavefront. However, these systems are unsatisfactory due to edge effects created at the junctions between the reflective cells. Indeed, part of the incident beam is lost when it arrives between two reflective cells. Furthermore, two portions of the reflected beam can interfere with each other. As a result, the reflected wavefront is difficult to control.

[0007] A second type of deformable mirror is one whose reflective surface is a flexible layer that can be locally deformed. This reduces edge effects because there is no longer an interface between different reflective cells.

[0008] The deformation of the flexible layer can be generated mechanically using actuators that move perpendicularly to the mirror surface to locally apply a force to the flexible layer. However, the spatial accuracy of the deformation depends on the size of the actuators. Therefore, it is not possible to modify the wavefront with very high precision. Furthermore, there is a latency during wavefront modification due to the travel time of each actuator. This prevents rapid wavefront modification.

[0009] The deformation of the flexible layer can be generated thermally using an active layer on which the reflective surface is placed. A light source is positioned in front of the mirror and directed towards the active layer, passing through the reflective surface. The light source heats the active layer via Joule heating, which deforms it. However, the properties of the reflective surface that can be used are limited, as it must be transparent at the wavelength of the light source but reflective at the wavelength of the wavefront. Furthermore, in this system, the light source is positioned on the same side of the mirror as the wavefront, which creates space constraints and therefore limits the size of the wavefront and its direction towards the mirror.Furthermore, the wavefront can interact with the light source, resulting in a modification of its physical characteristics (polarization, transmission, phase, etc.). Finally, in these systems, a heat sink is placed behind the mirror, that is, against the active layer on the opposite side from the reflective surface. The need for the heat sink makes the system more complex, resulting in a larger and more expensive manufacturing process.

[0010] A third type of deformable mirror is a thermo-optical mirror. The mirror includes an active layer through which the wavefront passes, and whose refractive index is modified in order to alter the wavefront.

[0011] A known system applying this principle consists of a reflective surface sandwiched between a resistor and an active layer whose refractive index varies with temperature. The resistor alters the temperature of the active layer. The incident wavefront passes through the active layer before being reflected back onto the reflective surface, then passes through the active layer again. The wavefront is thus modified by these two passes through the active layer. However, this system is unsatisfactory because the incident wavefront passes through the active layer and is therefore subject to imperfections in the active layer material, such as inhomogeneity, achromaticity, and absorption. Since the wavefront passes through the active layer twice, these imperfections have a twice greater effect on the wavefront. Furthermore, the use of a resistor does not allow for homogeneous and precise heating.Indeed, resistors have fixed dimensions. Therefore, the spatial accuracy of the heating will be limited by the resistor dimensions. Furthermore, current variations occur within a single resistor, meaning the resulting surface temperature of a single resistor can be inhomogeneous. Finally, the heat map generated by the resistors is not continuous due to the interface between them.

[0012] A second known system applying the thermo-optical effect comprises an active layer sandwiched between two substrate layers. A light source is placed on one side of the active layer, while the source of the incident wavefront is placed on the other side. The wavefront passes through the active layer to be modified and emerges on the side of the light source. However, in these systems, the wavefront interacts with the light source, resulting in a modification of its physical characteristics. Furthermore, the incident wavefront passes through the active layer and is therefore subject to imperfections in the active layer material, such as inhomogeneity, achromaticity, absorption, etc.

[0013] There is therefore a need for a simple, compact deformable mirror system that can rapidly generate significant deformations of the reflective layer, ensuring high spatial resolution and / or avoiding interaction between the light source activating the active layer and the wavefront.

[0014] The object of the invention is to provide an adaptive optics system comprising a deformable mirror with an active layer disposed on a substrate and a reflective layer disposed on the active layer. The active layer is deformed by a selective heating device through the substrate in order to locally modify its thickness. The incident wavefront is reflected by the reflective layer, the deformation of which is defined by the thickness distribution of the active layer.

[0015] SUMMARY

[0016] The invention relates, according to a first aspect, to an adaptive optics system configured to modify an incident wavefront, the adaptive optics system comprising:

[0017] a multi-layered deformable mirror comprising:

[0018] o a substrate;

[0019] an active layer deposited on the substrate; and

[0020] o a reflective layer placed on the active layer and configured to reflect the incident wavefront;

[0021] a selective heating device.

[0022] The selective heating device is configured to generate a temperature distribution of the active layer, and the active layer has a variable thickness distribution, the thickness distribution being a function of the temperature distribution of the active layer, the thickness distribution implying a modification of the incident wavefront reflected by the reflective layer.

[0023] Indeed, variations in the thickness of the active layer cause deformation of the reflective layer placed on top of it. The wavefront arriving at the reflective layer is therefore reflected in different directions depending on the layer's deformation. Thus, by altering the temperature distribution within the active layer, the shape of the reflected wavefront changes relative to the incident wavefront.

[0024] Since the wavefront is reflected by the reflective layer, it does not pass through the active layer. Therefore, the wavefront is not subject to imperfections in the active layer material, such as inhomogeneity, achromaticity, and absorption.

[0025] Furthermore, since the selective heating device is positioned on the opposite side of the substrate from the active layer, there is no interaction between the wavefront and the selective heating device, and there are no obstruction issues on the wavefront source side. Finally, unlike a thermo-optical system, there are no limitations on the choice of materials for the reflective layer. Therefore, any reflective coating can be used.

[0026] As an example, the heating device can be integrated into the substrate, or located at the interface between the substrate and the active layer.

[0027] As an example, the selective heating device can be configured to generate the active layer temperature distribution across the substrate. This active layer temperature distribution may not be generated across the substrate, particularly when the heating device is located at the interface between the substrate and the active layer.

[0028] According to one embodiment, the active layer has a thermal conductivity less than or equal to 1 W / m / K, preferably less than or equal to 0.5 W / m / K.

[0029] Low thermal conductivity prevents heat diffusion, meaning the temperature doesn't homogenize too quickly. This ensures highly localized heating and therefore high spatial resolution of the reflective layer's deformation.

[0030] In one embodiment, the active layer has a linear thermal expansion coefficient greater than or equal to 100 pm / m / K, preferably greater than or equal to 200 pm / m / K. A high thermal expansion coefficient allows for a significant variation in the thickness of the active layer for small temperature gradients in the temperature distribution. Consequently, less energy is required to achieve a greater variation in thickness.

[0031] According to one embodiment, the substrate has a thermal conductivity greater than or equal to 1 W / m / K, preferably greater than or equal to 10 W / m / K.

[0032] High thermal conductivity allows for faster dissipation of accumulated heat. This enables quicker cooling in one or more areas of the active layer when the heating element is no longer applied to those areas. As a result, the active layer can quickly return to its original thickness. This ensures greater modularity because the active layer does not retain its deformation. Furthermore, this allows the heat flux to drain vertically, thus limiting its lateral diffusion and guaranteeing high spatial resolution of the reflective layer's deformation.

[0033] To increase the heat dissipation effect, the adaptive optics system may include a heat sink preferably positioned at the periphery of the substrate. The heat sink may be active or passive.

[0034] According to one embodiment, the selective heating device comprises at least one light source having an emission wavelength, the substrate having a transmittance greater than or equal to 80%, preferably greater than or equal to 95%, at the emission wavelength, the active layer having an absorbance greater than or equal to 80%, preferably greater than or equal to 90%, at the emission wavelength.

[0035] Optical addressing, unlike the use of resistors, provides homogeneous, precise, and continuous heating. In one embodiment, the reflective layer has a transmittance less than or equal to 10%, preferably less than or equal to 5%, at the emission wavelength. This prevents the light emitted by the light source from passing through the reflective layer and disturbing the incident wavefront.

[0036] According to one embodiment, the light source comprises at least one laser configured to emit radiation towards the active layer through the substrate and an optical scanning system configured to move the radiation from at least one laser.

[0037] Using a laser allows for homogeneous and precise heating. Indeed, the laser generates a spatially and temporally coherent beam of light. Furthermore, this enables the achievement of high power levels and therefore rapid, significant temperature variations.

[0038] In one embodiment, the light source is configured to emit a light beam covering at least a portion of the active layer through the substrate. The light source includes a spatial modulation system configured to spatially modulate the intensity of the light beam. Large coverage by the light beam improves the continuity of heating of the active layer due to the absence of interfaces between the heating elements.

[0039] In one embodiment, the active layer is a polymer comprising pigments. The pigments increase the opacity of the active layer and thus increase its coefficient of thermal expansion.

[0040] According to one embodiment, the selective heating device includes an electrode device, at least one current generator configured to generate a current in the electrode device, and at least one resistance in contact with the active layer configured to be traversed by the current generated by the current generator.

[0041] The use of heating elements allows for a high heating speed.

[0042] The invention also relates to a method of using the adaptive optics system according to the first aspect to modify an incident wavefront into a target reflected wavefront, the method comprising:

[0043] a generation, by the selective heating device, of a temperature distribution of the active layer as a function of the incident wavefront and the target reflected wavefront to be reached so as to generate a thickness distribution of the active layer, and

[0044] Illumination of the reflective layer by the incident wavefront, the incident wavefront being reflected by the reflective layer deformed by the thickness distribution of the active layer so as to form the target reflected wavefront.

[0045] DEFINITIONS

[0046] In the present invention, the terms below are defined as follows:

[0047] "Variable thickness" refers to the variation over time of the thickness of the active layer at a given position. It is therefore a temporal variation.

[0048] "Thickness distribution" refers to the thickness of the active layer at a set of positions at a given point in time. It is therefore a spatial distribution. DESCRIPTION OF THE FIGURES

[0049] Figure 1 represents an adaptive optics system 100 according to an embodiment of the invention in which the selective heating device 40 comprises two light sources 41.

[0050] Figure 2 is a diagram representing the use of the adaptive optical system 100 according to the embodiment of Figure 1, the plane incident wavefront 210 being modified by reflection on the deformed reflective layer 10.

[0051] Figure 3 represents an adaptive optics system 100 according to an embodiment of the invention in which the selective heating device 40 comprises two resistors placed in the substrate.

[0052] Figure 4 represents a selective heating device 40 according to an embodiment of the invention comprising a matrix of point electrodes 42 and linear electrodes 43.

[0053] Figure 5 represents an adaptive optics system 100 according to an embodiment of the invention in which the selective heating device 40 comprises the electrode matrix of Figure 4 forming the substrate of the multilayer deformable mirror.

[0054] DETAILED DESCRIPTION

[0055] The present invention relates to an adaptive optics system 100 configured to modify an incident wavefront 210. Such an adaptive optics system 100 is for example shown in figures 1, 2, 3 and 5.

[0056] The incident wavefront describes the shape of the surface defined by a set of photons of the same phase emitted by an incident source. In other words, the incident wavefront is formed by all the photons that have traveled the same distance from the incident source. The incident source is therefore configured to emit light comprising at least one wavelength. The light emitted by the incident source may consist of a single wavelength, called the principal wavelength. The light emitted by the incident source may also consist of a range of wavelengths. The distribution of light within this wavelength range may be centered on a principal wavelength.

[0057] The adaptive optics system 100 includes a deformable mirror comprising at least one reflective layer.

[0058] When the deformable mirror is flat, an incident wavefront 210 arriving on the flat deformable mirror will be reflected to form a reflected wavefront 220 which has the same shape as the incident wavefront 210. For example, the reflected wavefront 220 created by the reflection of a flat incident wavefront 210 on the flat deformable mirror will be flat.

[0059] The deformable mirror is multi-layered. In fact, it comprises:

[0060] a substrate 10;

[0061] an active layer 20 disposed on the substrate 10; and

[0062] a reflective layer 30 disposed on the active layer 20 and configured to reflect the incident wavefront 210.

[0063] The individual layers (10, 20, 30) extend perpendicularly to a stacking axis A and are stacked along this axis as shown in Figure 1. These layers (10, 20, 30) can be reversibly joined together. This allows for a modular system in which the layers can be selected and stacked as needed. Similarly, if one of the layers is defective, it can be replaced instead of the entire deformable mirror.

[0064] Each layer (10, 20, 30) therefore has longitudinal dimensions comprising a length and a width measured perpendicular to the stacking axis A. Each layer (10, 20, 30) also has a thickness measured parallel to the stacking axis A. The active layer 20 has a first surface in contact with the substrate 10 and a second surface in contact with the reflective layer 30. The thickness is therefore measured between the first surface and the second surface.

[0065] The active layer 20 has a variable thickness. That is to say, at each longitudinal position, the thickness can vary over time.

[0066] Furthermore, the active layer 20 can exhibit a thickness distribution. That is, the thickness at a given time can differ between at least two different longitudinal positions. Therefore, the active layer 20 exhibits a variable thickness distribution.

[0067] The substrate 10 preferentially has low or zero flexibility so that the variation in thickness mainly involves a deformation of the second surface of the active layer 20.

[0068] Since the reflective layer 30 is located on the second surface, the thickness distribution of the active layer 20 implies a local deformation of the reflective layer 30. In other words, at each longitudinal position, the distance between the reflective layer 30 and the substrate 10 corresponds to the thickness of the active layer 20 at that longitudinal position. The thickness distribution of the active layer 20 is a function of the temperature distribution of the active layer 20. Thus, when the entire active layer 20 is at room temperature, it exhibits a standard thickness distribution E0. The second surface therefore has a standard curvature. The first surface is preferably flat to facilitate the construction of the deformable mirror. The second surface can be flat (zero curvature).If the first and second surfaces of the active layer 20 are flat and parallel to each other, the standard thickness E0 of the active layer is the same in any longitudinal position. The second surface may have a non-zero standard curvature (spherical, parabolic, or hyperbolic), thus making the mirror convex or concave in the direction of the incident wavefront. If the first surface is flat and the second surface is spherical, parabolic, or hyperbolic, the standard thickness distribution E0 will be spherical, parabolic, or hyperbolic, respectively. The second surface may also have a predefined shape.

[0069] If the temperature of the active layer 20 at one or more longitudinal positions differs from the ambient temperature, the thicknesses (E1, E2) of the active layer 20 at these positions will differ from the standard thickness E0. Furthermore, a temperature variation over time at a longitudinal position implies a variation in the thickness at that position. This variation can correspond to more than 5% of the standard thickness E0, preferably more than 10% of the standard thickness E0, and even more preferably more than 15% of the standard thickness E0.

[0070] In order to modify the incident wavefront 210, the adaptive optics system 100 includes a selective heating device 40 working in combination with the active layer 20.

[0071] The selective heating device 40 is configured to deform the deformable mirror under the effect of the heat generated by the selective heating device 40. The selective heating device 40 is configured to generate, through the substrate 10, a temperature distribution of the active layer 20. When the active layer 20 has different temperatures at different longitudinal positions, the reflective layer 30 exhibits a local deformation relative to standard curvature. As explained previously, the deformation of the reflective layer 30, and therefore the thickness distribution of the active layer 20, implies a modification of the incident wavefront 210 reflected by the reflective layer 30, as schematically shown in Figure 2. The selective heating device 40 is also preferentially configured to modify the temperature distribution of the active layer 20.The variation generated by the selective heating device 40 is therefore local, that is, extending over less than 5% of the total surface area of ​​the deformable mirror, preferably less than 1% of the total surface area of ​​the deformable mirror. This allows the thickness distribution of the active layer 20 to be varied temporally. Thus, the reflected wavefront 220 can be modified over time.Thus, a method of using the adaptive optics system 100 described here includes, firstly, the generation, by the selective heating device 40, of a temperature distribution of the active layer 20 as a function of the incident wavefront 210 and the target reflected wavefront 220 to be reached so as to generate a thickness distribution of the active layer 20, and, secondly, the illumination of the reflective layer 30 by the incident wavefront 210, the incident wavefront 210 being reflected by the reflective layer 30 deformed by the thickness distribution of the active layer 20 so as to form the target reflected wavefront 220.

[0072] The wavefront is therefore reflected before it penetrates the active layer 20. For this purpose, a deformable mirror is positioned relative to the incident source so as to direct the incident wavefront 210 towards the reflective layer 30 on the side opposite the active layer 20. Consequently, the incident wavefront 210 is not modified by a change in the refractive index of the active layer but rather by a local change in the thickness of the active layer 20.

[0073] Since the selective heating device 40 is configured to generate the temperature distribution of the active layer 20 through the substrate 10, the selective heating device 40 can be positioned on the side of the substrate 10 opposite the active layer 20. This reduces the footprint on the wavefront side.

[0074] In one embodiment, an increase in the temperature of the active layer 20 at a longitudinal position implies an increase in the thickness of the active layer 20 at that position. Similarly, a decrease in the temperature of the active layer 20 at a longitudinal position implies a decrease in the thickness of the active layer 20 at that position.

[0075] Alternatively, an increase in the temperature of the active layer 20 at a longitudinal position results in a decrease in the thickness of the active layer 20 at that position. Similarly, a decrease in the temperature of the active layer 20 at a longitudinal position results in an increase in the thickness of the active layer 20 at that position. The selective heating device 40 can be configured to locally heat and / or cool the active layer 20.

[0076] In a particular embodiment, the adaptive optics system 100 may include a plurality of deformable mirrors and a selective heating device 40.

[0077] The active layer 20

[0078] The active layer 20 can be characterized by its coefficient of thermal expansion. The coefficient of thermal expansion of the active layer 20 is preferably high to allow for a large variation in thickness for a small variation in temperature. For example, active layer 20 has a linear coefficient of thermal expansion greater than or equal to 100 pm / m / K, preferably greater than or equal to 200 pm / m / K.

[0079] The active layer 20 can also be characterized by its thermal conductivity. The thermal conductivity of the active layer 20 is preferably low to avoid longitudinal temperature propagation. This ensures high spatial resolution of the temperature and therefore high spatial accuracy of the deformation of the reflective layer 30. For example, the active layer 20 has a thermal conductivity less than or equal to 1 W / m / K, preferably less than or equal to 0.5 W / m / K.

[0080] The standard thickness of the active layer 20 can range from a few microns to a few hundred microns. The thickness is determined primarily by the thermal conductivity of the material used. For example, the standard thickness of the active layer 20 is between 5 µm and 500 µm, preferably between 10 µm and 100 µm.

[0081] The active layer 20 can comprise a matrix, for example, at least one polymer such as polydimethylsiloxane (PDMS) or an elastomer, for example, silicone. Polymers and elastomers have a high coefficient of thermal expansion and low thermal conductivity. For example, polydimethylsiloxane (PDMS) has a thermal conductivity of 0.25 W / m / K and a coefficient of thermal expansion of 300 pm / m / K. The active layer 20 can, for example, be a resin such as those commonly used in microelectronics. Resins can advantageously be deposited as thin films.

[0082] The active layer 20 can be deposited by spin coating onto the substrate 10. This creates a thin active layer 20. The active layer 20 can be deposited onto the substrate 10 before polymerization. A thin layer of polymer with adhesive properties, such as polydimethylsiloxane (PDMS), can be deposited onto the substrate 10 before depositing the active layer 20.

[0083] Substrate 10

[0084] The substrate 10 primarily serves as mechanical support for the deformable mirror. The substrate 10 is preferably configured to dissipate heat rapidly. Indeed, to ensure a rapid change in the shape of the reflected wavefront 220, when the selective heating device 40 no longer heats or cools the active layer 20, the active layer 20 should quickly return to ambient temperature and thus to a standard thickness. For example, if the selective heating device 40 is configured to locally heat the active layer 20, the temperature should dissipate rapidly. To achieve this, the substrate 10 can be characterized by a preferably high thermal conductivity. For example, the thermal conductivity of the substrate 10 greater than or equal to 1 W / m / K, preferably greater than or equal to 10 W / m / K.The rapid heat dissipation of the substrate 20 eliminates the need for an external heat sink. Furthermore, the compact design of the adaptive optics system 100 further enhances heat dissipation. The thickness of the substrate 10 can range from a few hundred microns to a few tens of millimeters. This thickness is primarily determined by the thermal conductivity of the material used. For example, the thickness of the substrate 10 is typically between 200 µm and 50 mm, preferably between 500 µm and 10 mm.

[0085] In one embodiment, the adaptive optics system includes a heat sink preferably located at the periphery of the substrate to minimize its size. The heat sink may be active or passive. In another embodiment compatible with the previous one, the selective heating device 40 may also be configured to cool the active layer 20 when an increase in the temperature of the active layer 20 results in an increase in the thickness of the active layer 20, or to heat the active layer 20 when an increase in the temperature of the active layer 20 results in a decrease in the thickness of the active layer 20.

[0086] The reflective layer 30

[0087] Preferably, the reflective layer 30 reflects more than 80% of the incident wavefront. The reflective layer 30 can be reflective only for a specific range of wavelengths in order to form a dichroic mirror. In other words, the reflective layer 30 is preferentially reflective at the main wavelength.

[0088] The reflective layer 30 may include a metal such as aluminium, gold, silver or chromium which have high reflectivity.

[0089] The reflective layer 30 is preferably thin in order to be deformable under the effect of the thickness distribution of the active layer 20.

[0090] The reflective layer 30 can be deposited by the well-known methods of evaporation, physical vapor deposition (PVD), chemical vapor deposition (CVD), electrodeposition, spin coating or dip coating.

[0091] The 40 selective heating device

[0092] In a first embodiment, the selective heating device 40 comprises at least one light source 41 as shown in Figures 1 to 2. The light source 41 is configured to emit light comprising at least one wavelength. The light emitted by the light source 41 may comprise one wavelength: the emission wavelength. The light emitted by the light source 41 may comprise a range of wavelengths. The distribution of the light within the wavelength range may be centered on a single emission wavelength. The emission wavelength is, for example, between 300 nm and 15,000 nm. For example, the emission wavelength is in the "UVA-Visible-NIR" range between 315 nm and 1400 nm. For example, the emission wavelength is in the "UV" range between 10 nm and 380 nm. In particular, UVA refers to the sub-range of UV radiation from 315 nm to 380 nm.For example, the emission wavelength falls within the "visible" range, between 380 nm and 780 nm. Similarly, the emission wavelength falls within the "infrared" range, between 780 nm and 1 mm. This range is generally divided into three sub-ranges. Near-infrared (NIR) corresponds to wavelengths between 780 nm and 1400 nm. Short-wavelength infrared (SWIR) corresponds to wavelengths between 1400 nm and 3000 nm. Mid-wavelength infrared (MWIR), also called intermediate infrared, corresponds to wavelengths between 3000 nm and 5000 nm. Preferably, the emission wavelength is between 400 nm and 450 nm, between 500 nm and 11000 nm or between 1000 nm and 1100 nm.

[0093] Illuminating the active layer 20 by the light source 41 allows the generation of a temperature distribution of the active layer 20 in such a way as to generate a thickness distribution of the active layer 20. Indeed, the light emitted by the light source 41 is absorbed by the active layer 20 and is converted into heat by Joule effect.

[0094] The advantage of using a light source 41 is that the light source 41 can be located away from the deformable mirror, with the light being directed towards the active layer 20 through the substrate 10 by a set of mirrors. This reduces the footprint near the deformable mirror.

[0095] The light source 41 may include at least one laser configured to emit radiation towards the active layer 20 through the substrate 10. The laser is advantageous because it allows for the illumination and therefore heating of a spatially restricted area. The laser may have a power output ranging from 1 mW to 100 W per square millimeter. Preferably, the laser has a power output of at least 10 mW / mm². 2 and 1 W / mm 2To heat the entire active layer 20, the light source 41 may comprise a plurality of lasers, the combined radiation of which covers the entire active layer 20. Alternatively, the light source 41 may comprise one or more lasers whose combined radiation does not cover the entire active layer 20. In this latter embodiment, the light source 41 may also include an optical scanning system configured to move the radiation from at least one laser. The optical scanning system includes, for example, at least one movable mirror.

[0096] The light source 41 can be configured to emit a light beam covering at least part of the active layer 20. Unlike a laser, the light beam is therefore spatially spread, allowing for more continuous coverage of the active layer. The light source 41 then preferably includes a spatial modulation system configured to spatially modulate the intensity of the light beam in order to create the temperature distribution within the active layer 20. The modulation system includes, for example, an array of micromirrors such as a digital micromirror device (DMD) or a chip containing steerable mirrors (DLP; Digital Light Processing). For example, the light source 41 includes a light-emitting diode (LED) or an array of LEDs configured to emit the light beam.

[0097] When the selective heating device 40 includes at least one light source 41, the substrate 10 preferentially has a transmittance greater than or equal to 80%, preferably greater than or equal to 95%, at the emission wavelength.

[0098] When the selective heating device 40 includes at least one light source 41, the active layer 20 preferably has an absorbance greater than or equal to 80%, and preferably greater than or equal to 90%, at the emission wavelength. Indeed, the greater the absorbance, the more efficient and rapid the temperature change. For example, an active layer 20 comprising a transparent polymer loaded with gold nanoparticles exhibits an absorption peak at 520-530 nm. To increase the absorbance of the active layer 20, it may include pigments, preferably dark-colored. These pigments will increase the absorbance of the active layer 20. In this configuration, the active layer 20 may include black pigments dispersed within its polymer matrix.In one embodiment, the black pigments are chosen from the group of carbon black, ivory black, vine black, lamp black, graphene, Mars black, iron black, manganese dioxide, titanium black, and semiconductor nanoparticles having a band gap of 1.6 eV or less. In particular, the semiconductor nanoparticles having a band gap of 1.6 eV or less may be metal chalcogenides, where the metal is chosen from Hg, Pb, Ag, Bi, Cd, Sn, Sb or a mixture thereof and the chalcogen is chosen from S, Se, Te or a mixture thereof, preferably semiconductor nanoparticles having a band gap of 1 or less.6 eV or less can be chosen from HgS, HgSe, HgTe, HgSeS, HgSeTe, HgxCd1-xTe where x is a real number strictly between 0 and 1, PbS, PbSe, PbTe, Bi2S3, Bi2Se3, Bi2Te3, SnS, SnS2, SnTe, SnSe, Sb2S3, Sb2Se3, Sb2Te3, Ag2S, Ag2Se, Ag2Te and their mixtures.

[0099] When the selective heating device 40 includes at least one light source 41, the reflective layer 30 may have a transmittance less than or equal to 10%, preferably less than or equal to 5%, at the emission wavelength to prevent the light from the light source 41 from passing through the reflective layer 30 and interfering with the incident wavefront 210 or reflected wavefront 220. Preferably, the absorbance of the active layer 20 is such that only a very small portion of the light reaches the reflective layer 30. In fact, preferably, more than 95% of the light is absorbed by the active layer 20. In a second embodiment, the selective heating device 40 includes a resistor matrix configured to heat up when a current passes through the resistors. The resistor matrix may be arranged in the substrate as shown in Figure 3. In another embodiment, the substrate is the resistor matrix.

[0100] In a third embodiment, the selective heating device 40 comprises an electrode array, at least one current generator configured to generate a current 44 in the electrode array, and at least one resistor in contact with the active layer 20 configured to carry the current 44 conducted by the electrode array. Thus, when a current 44 is generated between two electrodes (42, 43) of the electrode array, the current 44 flows through the resistor, whose temperature will increase. The temperature of the longitudinal positions of the active layer 20 in contact with the heated resistor will therefore increase. The development cost of this third embodiment is advantageously lower than that of the second embodiment.

[0101] The resistance may include an ink loaded with carbon particles.

[0102] The electrodes can have a circular cross-section as is the case for conductive wires 42. The electrodes can be linear and have the shape of a conductive sheet 43.

[0103] The electrodes can be arranged on a printed circuit board (PCB). The electrode arrangement can then comprise several superimposed printed circuit boards. Alternatively, the electrode arrangement can comprise at least one conductive sheet 43 on which a set of parallel conductive wires 42 is arranged, as shown in Figures 4 and 5. This increases the electrode density and thus the spatial resolution of the temperature distribution. Each electrode can be connected to an electronic control device, which can address each electrode by multiplexing. In this third embodiment, the substrate 10 is preferably resistive, such that at least one resistance is the substrate 10 itself. The electrode arrangement is then in contact with the substrate 10 opposite the active layer 20.For example, the substrate 10 is a thin resistive layer arranged on the surface formed by the electrode array (42, 43). In another example of this third embodiment, the electrode array and at least one resistor are arranged within the thickness of the substrate. The resistor is preferably located as close as possible to the active layer.

[0104] In yet another example, the active layer 20 can also be resistive. For instance, the active layer 20 comprises graphite nanoparticles. The active layer 20 is deposited directly onto the electrode array, which then serves as a substrate, as shown in Figure 5. NUMERICAL REFERENCES

[0105] 100 - Adaptive optics system / / 10 - Reflective layer II 20 - Active layer II 30 - Substrate II 40 - Selective heating device II 41 - Light source II 42, 43 - Electrodes II 44 - Current / / 210 - Incident wavefront II 220 - Reflected wavefront / / A - Stacking axis II E - Thickness of the active layer at a particular point of the active layer II E0 - Standard thickness of the active layer at a particular point of the active layer II E1, E2 - Deformation thickness of the active layer at a particular point of the active layer

Claims

DEMANDS 1. An adaptive optics system (100) configured to modify an incident wavefront (210), the adaptive optics system (100) comprising: a multi-layered deformable mirror comprising: ■ a substrate (10); ■ an active layer (20) disposed on the substrate (10); and ■ a reflective layer (30) disposed on the active layer (20) and configured to reflect the incident wavefront (210); a selective heating device (40); the selective heating device (40) being configured to generate a temperature distribution of the active layer (20), the active layer (20) exhibiting a variable thickness distribution, the thickness distribution being a function of the temperature distribution of the active layer (20), the thickness distribution implying a deformation of the reflective layer and a modification of the incident wavefront (210) reflected by the reflective layer (30).

2. The adaptive optics system (100) according to claim 1, wherein the active layer (20) has a thermal conductivity less than or equal to 1 W / m / K, preferably less than or equal to 0.5 W / m / K.

3. The adaptive optics system (100) according to claim 1 or 2, wherein the active layer (20) has a linear thermal expansion coefficient greater than or equal to 100 pm / m / K, preferably greater than or equal to 200 pm / m / K.

4. The adaptive optics system (100) according to any one of claims 1 to 3, wherein the substrate (10) has a thermal conductivity greater than or equal to 1 W / m / K, preferably greater than or equal to 10 W / m / K.

5. The adaptive optics system (100) according to any one of claims 1 to 4, wherein the selective heating device (40) comprises at least one light source (41) having an emission wavelength, the substrate (10) having a transmittance greater than or equal to 80%, preferably greater than or equal to 95%, at the emission wavelength, the active layer (20) having an absorbance greater than or equal to 80%, preferably greater than or equal to 90%, at the emission wavelength.

6. The adaptive optics system (100) according to claim 5, wherein the light source (41) comprises at least one laser configured to emit radiation towards the active layer (20) through the substrate (10) and an optical scanning system configured to move the radiation from at least one laser.

7. The adaptive optics system according to claim 5 or 6, wherein the light source (41) is configured to emit a light beam covering at least a portion of the active layer (20) through the substrate (10), the light source (41) comprising a spatial modulation system configured to spatially modulate the intensity of the light beam.

8. The adaptive optics system (100) according to any one of claims 5 to 7, wherein the active layer (20) is a polymer comprising pigments.

9. The adaptive optics system (100) according to any one of claims 1 to 8, wherein the selective heating device (40) comprises an electrode device, at least one current generator configured to generate a current (44) in the electrode device and at least one resistance in contact with the active layer (20) configured to be traversed by the current (44) generated by the current generator.

10. A method of using the adaptive optics system (100) according to any one of claims 1 to 9 to modify an incident wavefront (210) into a target reflected wavefront (220), the method comprising: a generation, by the selective heating device (40), of a temperature distribution of the active layer (20) as a function of the incident wavefront (210) and the target reflected wavefront (220) to be achieved so as to generate a thickness distribution of the active layer (20), and - illumination of the reflective layer (30) by the incident wavefront (210), the incident wavefront (210) being reflected by the reflective layer (30) deformed by the thickness distribution of the active layer (20) so as to form the target reflected wavefront (220).

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