EP3867688A1 - Dispositif micro-fluidique adapté pour modifier la phase d'un front d'onde et système optique comprenant un tel dispositif - Google Patents
Dispositif micro-fluidique adapté pour modifier la phase d'un front d'onde et système optique comprenant un tel dispositifInfo
- Publication number
- EP3867688A1 EP3867688A1 EP19786983.7A EP19786983A EP3867688A1 EP 3867688 A1 EP3867688 A1 EP 3867688A1 EP 19786983 A EP19786983 A EP 19786983A EP 3867688 A1 EP3867688 A1 EP 3867688A1
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- EP
- European Patent Office
- Prior art keywords
- chambers
- membrane
- chamber
- fluid
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/06—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the phase of light
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/004—Optical devices or arrangements for the control of light using movable or deformable optical elements based on a displacement or a deformation of a fluid
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/06—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of fluids in transparent cells
Definitions
- Microfluidic device adapted to modify the phase of a wavefront and optical system comprising such a device
- the invention relates to the field of microfluidic devices and more particularly those applied to optics.
- the invention also relates to optical systems based on these devices making it possible to effect an active modification of the phase of a light wave, for example for adaptive optics or active optics applications.
- optics adaptive There are a number of devices for modifying the phase of a light wave to adapt to changing environmental conditions (compared to an external measurement), this concept being generally designated by the term optics adaptive.
- Adaptive optics are used in multiple applications such as beam shaping of power lasers, correction of images of astronomical observations crossing the atmosphere or for display systems such as video projectors.
- the concept of adaptive optics is illustrated in Figure 1.
- the phase profile is applied for example via a deformable mirror 6 and the beam reflected by it is a corrected wavefront 7.
- An alternative in adaptive optics is to implement a measurement by phase diversity, which does not require external means of measurement but requires having significant computing power, which can limit the speed of the correction.
- the wavefront to be corrected is measured once and for all and the corrective phase law is memorized and applied to the mirror 6.
- a feedback loop 4 determines, from the measurement of the incident wavefront, the phase law to be applied to the mirror 6 to correct the incident wavefront.
- FIG. 2 illustrates two examples of optimal arrangement of zones 20 to which a predetermined phase will be applied for a correction using Zernicke polynomials.
- Figure 2a shows an arrangement of 31 areas
- Figure 2b shows an arrangement of 61 areas.
- the arrangement of the zones is concentric, and typically the zones have a disc segment or polygon shape.
- FIG. 3 Another solution for producing an active lens working in transmission is an electrically controlled lens from the company Optotune, the focal length of which is controlled electrically or mechanically, as illustrated in FIG. 3.
- the lens is composed of a membrane 40 which constitutes an interface between 2 chambers, each of them being filled with a material with a refractive index different from the other (for example one filled with a liquid and the other with air).
- the pressure 41 between the 2 chambers determines the shape of the membrane and therefore the radius of curvature of the lens.
- Figure 3a illustrates a position of the membrane and Figure 3b another position.
- the pressure for varying the shape of the membrane can be applied mechanically, electro-mechanically or pneumatically.
- This lens is its response time from a few ms to 50 ms. However, it is currently only used on small opening diameters ( ⁇ 16mm), which is limiting in terms of application. In addition, its shape cannot be free, only the curvature of the lens changes. It is not possible with this system to synthesize an active freeform, that is to say a component capable of applying any predetermined phase law (polynomial of order> 3) and reprogrammable.
- an active lens is the lens from the company Varioptic based on an electrowetting control.
- the deformation, under the effect of an electrical voltage, of the surface between the two fluids ensures the variation of the optical focal length.
- An object of the present invention is to remedy the aforementioned drawbacks by proposing an innovative device based on microfluidic technology suitable for producing an active "free-form" optic, and a system of adaptive optics or optics. active using this device.
- DESCRIPTION OF THE INVENTION The subject of the present invention is a microfluidic device comprising: a substrate on which walls are arranged delimiting a plurality of contiguous chambers,
- each chamber said channel being connected to only one chamber, a channel being intended to activate the associated chamber by applying a determined pressure to the fluid of said chamber, so as to create locally an elastic deformation of said membrane, a chamber therefore being intended to be activated by the associated channel independently of the other chambers.
- the chambers and the channels are filled with fluid.
- the channel associated with a room is unique.
- the material constituting the walls is identical to the material of the substrate and the channels are arranged in an upper part of said walls.
- the material constituting the walls is identical to the material of the membrane and the channels are arranged in a lower part of said walls in contact with the substrate.
- the flexible membrane further comprises a plurality of pillars distributed over an internal wall of the membrane and configured so that they are in abutment on the substrate or very close to it when said membrane is at rest.
- the substrate further comprises a plurality of pillars configured so that they are in contact with the flexible membrane or very close to it when it is at rest.
- an additional membrane is arranged above the flexible membrane.
- the chambers of the device comprise a structure configured to be porous to the fluid capable of being injected.
- the device according to the invention further comprises an index adaptation structure deposited on the substrate and / or an anti-reflective layer deposited on an outer wall of the membrane.
- the device according to the invention further comprises a reflective layer deposited on the substrate, so that said device operates in reflection.
- the invention relates to an optical system intended to operate a modification of a phase of a wavefront of a light wave having at least one wavelength and comprising:
- At least one microfluidic device according to the invention said fluid being transparent to said wavelength
- the optical system according to further comprises a processing unit connected to the injection device and configured to determine said pressures to be applied from said predetermined phase shifts.
- the injection device comprises at least one pump and a plurality of microvalves connected to said pump and to said channels and configured to apply said pressures to said channels.
- the channel associated with each chamber is unique and the injection device comprises:
- a source cavity being connected to a channel and closed by said flexible membrane, a chamber, its channel and its associated source cavity forming a system closed filled with said fluid, a plurality of actuators associated respectively with the plurality of source cavities, an actuator being configured to locally deform the flexible membrane closing the associated source cavity, so as to generate pressure to activate the associated chamber.
- the invention relates to a method for modifying a phase of a wavefront of a light wave having at least one wavelength and comprising the steps consisting in:
- FIG. 1 already cited illustrates the concept of adaptive optics.
- FIG. 2 already cited illustrates an arrangement of zones of an adaptive optic to which a predetermined phase shift is applied according to the state of the art, the arrangement of FIG. 2a comprising 31 electrodes, and that of FIG. 2b 61 electrodes.
- FIG. 3 already cited, describes the operation of an active lens working in electrically controlled transmission according to the state of the art.
- Figure 3a illustrates a position of the membrane and Figure 3b another position.
- FIG. 4a describes a device based on microfluidics according to the state of the art producing a matrix of microlens.
- FIG. 4b illustrates the device at rest, when the membrane is flat and not deformed, and
- FIG. 4c illustrates the device “activated”, that is to say when sufficient pressure is applied so as to cause deformation of the membrane.
- FIG. 5 illustrates the operating principle of the microfluidic device according to the invention.
- FIG. 6 illustrates an embodiment of a microfluidic device according to the invention in top view, with chambers having a concentric arrangement.
- FIG. 7 illustrates another embodiment of a microfluidic device according to the invention in top view, with chambers having a matrix arrangement.
- FIG. 8 illustrates a first variant in which the material constituting the walls is identical to the material of the membrane
- FIG. 9 illustrates a second variant in which the material constituting the walls is identical to the material of the substrate.
- FIG. 10 illustrates a variant in which the chambers of the device comprise support pillars, and the sub-variant for which the pillars are distributed over the internal wall of the flexible membrane.
- FIG. 11 illustrates this same variant in which the chambers of the device comprise support pillars, and the sub-variant for which the pillars are distributed on the substrate.
- FIG. 12 illustrates a chamber of the device according to the sub-variant of FIG. 10 with a membrane at rest (FIG. 12a) and with an activated membrane (FIG. 12b).
- FIG. 13 illustrates an embodiment of the device according to the invention comprising an additional membrane.
- Figure 13a illustrates the activated device, Figure 13b the device at rest.
- FIG. 14 illustrates an embodiment of the device according to the invention in which the chambers comprise a structure porous to the injected fluid.
- FIG. 15 illustrates the use of an anti-reflective layer as an index adaptation structure between the substrate and the liquid and an anti-reflective index adaptation layer between the membrane and the external medium.
- FIG. 16 illustrates the use as an index adaptation structure of a layer of structured flexible material deposited / bonded on the support substrate producing an index gradient between the index of the substrate and that of the liquid.
- FIG. 17 illustrates an optical system intended to operate a modification of a phase of a wavefront of a light wave according to another aspect of the invention.
- FIG. 18 illustrates another embodiment of the system according to the invention in which the phase shifts are calculated directly by the processing unit.
- FIG. 19 illustrates another embodiment of the system according to the invention in which the phase shifts are calculated by the processing unit from a real-time measurement of the wavefront to be corrected by a wavefront analyzer.
- FIG. 20 illustrates an embodiment in which the injection device comprises additional chambers called source cavities CSi arranged on the substrate at the periphery of the adjoining chambers.
- FIG. 21 illustrates the modification of the height of the source cavity and finally the modification of the volume of the optical cavity by the application of a positive or negative potential across the terminals of the piezoelectric activator.
- FIG. 22 illustrates an optical system intended to effect a modification of the phase of a wavefront of a light wave according to the invention having an injection device as described in FIGS. 20 and 21.
- One aspect of the invention consists of a device based on microfluidics specially adapted for the production of an active "free-form" optic, and intended to be integrated into an adaptive optics or active optics system.
- the device according to the invention is thus adapted to modify the phase of a wavefront.
- microfluidic-based devices performing optical functions are arrays of microlenses developed in the framework of "labs on a chip", as illustrated in FIG. 4a.
- These matrices are produced from a PDMS type elastomer deposited on a Sub substrate, typically glass, and structured so as to form chambers 40 hollowed out of the elastomeric material 42 and closed by a membrane 43 also made of elastomer.
- the lenses of a line are interconnected by channels 41, 41 'hollowed out in the elastomer 42.
- the lenses and channels are filled with liquid, typically an oil whose index is suitable.
- a pressure 44 is applied to the inlet of the channels, and is transmitted into the chambers 40. Under the effect of the pressure, the membrane 43 deforms elastically.
- FIG. 4b illustrates the device at rest, when the membrane is flat and not deformed, and FIG.
- FIG. 4c illustrates the device “activated”, that is to say when sufficient pressure is applied so as to cause deformation of the membrane.
- the deformed membrane defines the curved surface of a lens made of liquid, which focuses a light beam passing through it.
- the results show that the order of magnitude of the deformation obtained on a 200pm diameter lens is of the order of ten micrometers.
- the microlenses of the matrix have a diameter of 200 ⁇ m for a height of 100 ⁇ m at rest, and occupy a small part of the surface of the substrate.
- the measured transmission of these oil-filled lenses is 95%.
- the lens located at the edge of the substrate is supplied by a channel 41 connected to the outside of the device, and the lenses located on a line are interconnected with each other, the liquid flowing from one to the other via connection channels 41 '(see dotted lines 41' illustrating a connecting channel located in another section plane than the channel 41).
- microlens arrays all having the same dynamic focal length controlled by the internal pressure of the fluid. These devices make it possible, for example, to observe the optical response in the thickness of the volume located under the lens under a microscope, for localized and micrometric imaging.
- the microfluidic device according to the invention uses this same principle of activation of a membrane and has specific characteristics to be adapted to the realization of a “free-form” optic, in which all the active cells are contiguous, so as to constitute the complete surface of an optic.
- the microfluidic device according to the invention is intended to operate according to the principle illustrated in FIG. 5.
- a chamber Ch filled with liquid Liq is disposed between a transparent substrate Sub and a flexible membrane Memb and is supplied by a channel CA.
- the chamber has, when the membrane is at rest, an optical thickness eO as illustrated in FIG. 5a.
- the membrane deforms and the chamber Ch then has an average optical thickness e1 as illustrated in FIG. 5b.
- FIG. 5c illustrates the aforementioned substrate / liquid / membrane assembly in perspective and crossed by a light wave OL which thus undergoes a phase variation depending on the thickness ep of the liquid crossed. This modifies the phase of the OL wave locally. With a deformation e of about ten microns in amplitude, phase shift excursions greater than several times 2p in the visible are obtained.
- FIG. 6 An embodiment of a microfluidic device 10 according to the invention in top view is illustrated in FIG. 6.
- the device comprises a Sub substrate on which walls W are arranged, preferably of the same height, delimiting a plurality of Chi chambers contiguous, and a flexible membrane Memb (not shown in this figure) deposited over the chambers and fixed to the walls so as to form closed chambers, the chambers being intended to be filled with liquid.
- the device 10 also includes at least one channel CAi connected to each chamber Chi, the channel CAi being connected to only one chamber Chi.
- a channel is intended to activate the associated chamber by applying a determined pressure to the liquid in the chamber, so as to locally create an elastic deformation of the Memb membrane.
- An index i is used when it is necessary to distinguish several chambers and associated channels.
- the contiguous aspect of the chambers is important because the device according to the invention is intended to be inserted into an optical system to constitute one of the surfaces therein, and we therefore seek to minimize the space between the chambers.
- the chambers have a concentric arrangement.
- This radial configuration of the same type as that of FIG. 2a has the advantage of minimizing the number of cells (chambers).
- the shape of the cells adapts locally to the aberrations of an optical system (increasing with its opening).
- this arrangement comprises a circular central chamber, and chambers corresponding to the same circle having the shape of a sector of a circle. We keep here an axial symmetry.
- the chambers corresponding to the same circle or crown have a shape of polygons (see FIG. 2b).
- This type of concentric arrangement is suitable for the decomposition of a phase law with Zernicke polynomials.
- FIG. 7 illustrates another embodiment of a microfluidic device 10 according to the invention in top view, with chambers having a matrix arrangement.
- each chamber is intended to correspond to an area of adaptive optics.
- the channel CAi connected to the corresponding chamber Chi is connected only to one chamber Chi and to no other.
- Each of the different chambers is therefore intended to be activated by its associated channel independently of the other chambers.
- the channel associated with an interior chamber is arranged at least partially in at least one wall delimiting two adjacent chambers. The location of the channel in the wall (s) makes it possible to supply the interior chamber without reducing the useful surface constituted by the chambers. This is the case for example of the channels supplying the 8 interior quarters and the central disk of FIG. 6 and of the four central rectangular pixels of the 4x4 matrix of FIG. 7.
- the Sub substrate is typically glass or any other material transparent to the wavelength of interest (IR, visible or UV). According to one embodiment the substrate is planar, according to another embodiment the substrate is not planar, typically curved, which avoids having to manage the aberrations introduced by the planar surfaces.
- the membrane is typically made of an elastomeric material, for example COC or PDMS.
- COC ethylene glycol dimethacrylate
- PDMS polymethyl methacrylate
- crosslinking takes place at low temperature (70 ° C)
- the chambers and the channels are filled with a Liq fluid, the fluid being able to be a liquid, a gas or a gel.
- the fluid is chosen preferably so as to have an optical index adapted to that of the substrate to limit the interface phenomena (diffusion and Fresnel losses). Typically this is possible by diluting oils with a different optical index.
- the channel CAi associated with a chamber Chi is unique.
- the inlet and outlet of the fluid during pressure variations takes place via this channel, there is no circulation of the fluid which would enter through one channel and exit through another.
- the chambers preferably have an adapted lateral dimension, and much greater than the height eO (typically a hundred ⁇ m).
- the typical dimensions of the chambers / cells are of the order of a few mm 2 to a few cm 2 .
- the sizes of the CA channels are typically micrometric, as are the W walls.
- the ratio between a lateral dimension and a height of a room, or of all rooms, is greater than 5, preferably greater than 10.
- the thickness of the layers of materials is a few millimeters or less depending on the excursion of the membrane, its rigidity or the size of the cell, this quantity not constituting a constraint for the adaptive optical application.
- the occupancy rate of the rooms on the substrate surface is greater than 85%, that is to say that the walls W occupy a small part of the surface of the substrate.
- the chambers of the device 10 are contiguous, as close to each other as the manufacturing technology. allows it, so as to constitute one of the surfaces of an optical system.
- the overall efficiency of the optics is all the more important as the dimensions of the walls are negligible compared to the deformable zones.
- Figures 8 and 9 illustrate a profile view of the device 10 according to the invention according to section AA of Figure 6 according to a first and a second variant respectively.
- the Mat material constituting the walls W is identical to the material of the Memb membrane, and the channels are then preferably arranged in a lower part of the walls in contact with the substrate Sub, that is to say between the walls and the substrate.
- the manufacturing of a device according to this variant takes place by structuring the material intended to produce the membrane and the walls.
- the material constituting the walls W is identical to the material of the substrate Sub, and the channels are then preferably arranged in an upper part of the walls, preferably between the walls and the membrane.
- the manufacturing of a device according to this variant takes place by structuring the substrate.
- the chambers to be produced require relatively large surfaces with respect to microfluidic applications, typically having dimensions of a few millimeters to a centimeter while their thickness is millimeter or even submillimeter.
- the membrane sags at center in the absence of sufficient pressure in the fluid.
- the chambers of the device 10 include supporting pillars.
- the flexible membrane Memb further comprises a plurality of pillars 80 distributed over the internal wall 81 of the membrane and configured so that they are in abutment on the Sub substrate or very close to it when the membrane is at rest. Preferably their height is calculated to be flush / very close to the substrate at rest.
- the Sub substrate which comprises a plurality of pillars 90 configured so that they are in abutment on the internal wall of the flexible membrane or very close to it when it is at rest. Preferably their height is calculated to be flush / very close to the membrane at rest.
- Figure 12 illustrates a chamber Ch of the device according to the sub-variant of Figure 10, with a membrane at rest ( Figure 12a) and with an activated membrane ( Figure 12b). During activation, the pillars, which are not fixed, rise with the deformation of the membrane.
- the pillars and the walls are made of the same material as illustrated in FIGS. 10 and 11.
- the membrane For proper functioning of the membrane as an optical surface of the system in which it is inserted, it is sought to obtain a deformation as continuous as possible of the Memb membrane and to avoid / minimize the high frequencies induced at the interfaces of the different cavities.
- the device according to the invention comprises an additional membrane 13 disposed above the flexible membrane.
- the membrane 13 is continuous and fixed to the periphery of the device, which it completely covers. Its role is to smooth the variations in curvature present at the interfaces between the chambers during the application of pressures.
- Figure 13a illustrates the activated device
- Figure 13b the device at rest.
- the additional membrane 13 is also flexible but preferably its mechanical rigidity is greater than that of the Memb membrane.
- These two membranes are independent of each other and separated by a space constituting an uncontrolled fine cavity, preferably filled with the same fluid as that injected into the chambers.
- a thin layer of fluid 14 is located between the two membranes, each being at rest.
- each chamber pushes the flexible membrane Memb which is then in contact with the additional membrane. The fluid expelled from this contact zone will go into the transition zones between the chambers, typically the zones in which the mechanical support walls are located.
- the chambers of the device comprise a structure 14 configured to be porous to the injected fluid.
- This structure is for example obtained by inhomogeneous crosslinking of a polymer. Obtaining such a state of material is typically obtained by playing on the crosslinking conditions of the material chosen to produce the flexible membranes of the chambers. The concentration of crosslinker determines the density of the material and therefore the porosity of the crosslinked material obtained.
- the device according to the invention comprises an index adaptation structure deposited on the substrate and / or an AR2 anti-reflective layer deposited on an outer wall of the membrane.
- FIG. 15 illustrates a device according to the invention comprising a first AR1 anti-reflective layer as an index adaptation structure between the substrate and the fluid and a second AR2 anti-reflective layer on the membrane.
- FIG. 16 illustrates the use of a layer of flexible structured material SL as an index adaptation structure, deposited / bonded on the substrate of Sub support and producing an index gradient between the index of the substrate and that of the fluid.
- the device according to the invention is designed to operate in reflection.
- the substrate is covered with a reflective layer (for example depositing a thin metallic layer).
- the invention relates to an optical system 15 intended to operate a modification of a phase of a wavefront of a light wave OL having at least one wavelength l, an embodiment of the system 15 being illustrated in FIG. 17.
- light wave is meant a wave having a wavelength or a spectral band between the far infrared and the ultraviolet.
- the system 15 comprises at least one microfluidic device 10 filled with fluid according to the invention, the Liq fluid being transparent at the wavelength l.
- the fluid is incompressible.
- the system 15 also includes an ID device for injecting the fluid into each channel CAi connected to a chamber Chi.
- the injection device is configured to apply the pressures Pi to the chambers Chi via the associated channels CAi.
- the Chi chambers being activated independently of each other, each pressure Pi is specific to the corresponding activated chamber.
- the pressures Pi and therefore the deformations local ei of the membrane are determined so as to apply predetermined phase shifts Df ⁇ to the wave OL.
- the modification of the pressure of the fluid within the chambers makes it possible to modify the curvature of the membrane of each chamber and consequently the average thickness of each chamber.
- the optical phase of the system is checked at the chamber scale. The system 15 therefore makes it possible to apply an arbitrary phase function to the OL wave via the plurality of addressed chambers.
- the fluidic device as described above is thus used for an adaptive optics or active optics application operating in transmission.
- the incident wavefront is modified or controlled according to a desired spatial distribution which is calculated from the individual response of each chamber and the pressure applied to it.
- the optical system also comprises a processing unit UT connected to the injection device ID and configured to determine the pressures Pi to be applied, from predetermined phase shifts Df ⁇ .
- phase shifts Df ⁇ (l) are calculated independently and loaded into the processing unit.
- the phase shifts Df ⁇ (l) are calculated directly by the processing unit as illustrated in FIG. 18.
- the incident wavefront 30 is processed by the system 15 which applies the local phase shifts Df ⁇ (l ), thus transforming it into a wavefront 31.
- This configuration typically corresponds to an application of the active pupil coding type, to perform a zoom function for example. This type of application is for example described in the document FR1102210.
- An initial calibration of the mechanical response of the chambers to the pressure is preferably carried out, in order to know the Pi / e relationships of each. It is thus possible to know directly the pressure map to be applied to each chamber by knowing the phase map.
- the phase shifts Df ⁇ (l) are calculated by the processing unit from a real time measurement of the wavefront to be corrected carried out by a wavefront analyzer 5.
- the injection device ID comprises at least one Pump pump and a plurality of micro-valves pVi connected to the pump and to the channels CAi and configured to apply the pressures Pi to the channels.
- the injection device comprises as many micro-pumps as there are channels to be supplied. This mode is compatible with system 15 having a small number of rooms, for example 21 rooms (see arrangement of FIG. 2a).
- the injection device comprises, as illustrated in FIGS. 20 to 22, additional chambers called source cavities CSi arranged on the substrate at the periphery of the plurality of adjoining chambers . These source cavities are arranged outside the optically active zone formed by the adjoining chambers and called the opening of the optical system.
- a source cavity CSi is connected to a channel CAi and is closed by the flexible membrane Memb, which is fixed locally on the periphery of each source cavity.
- another membrane different from the flexible membrane Memb closing the chambers, for example by its thickness, closes the source cavities.
- the assembly consisting of two cavities (chamber corresponding to the active optical cavity / source cavity) connected by a channel forms a closed system filled with fluid: there is a flow of fluid from the source cavity towards the chamber and vice versa.
- a variation in volume in one cavity results in the same variation in volume in the other cavity.
- a compressible fluid the variation in volume of the chamber takes into account the compression of the fluid. There is no outward flow of fluid (finite volume of fluid in the system).
- the injection system also comprises a plurality of ACTi actuators respectively associated with the plurality of source cavities.
- An actuator ACTi is mechanically linked at the level of the membrane closing the associated source cavity CSi. It is configured to locally deform the flexible membrane closing the source cavity CSi, so as to generate pressure to activate the associated chamber Chi via the channel CAi.
- a source cavity is thus mechanically coupled to an actuator allowing its volume to be modified by pushing or pulling the membrane which closes it.
- This system is versatile, it can be used to activate any form of optical cavity (chamber) with sections typically ranging from pm 2 to cm 2 .
- actuators can be physically integrated as there are necessary optical cavities and is compatible with a relatively large number of cavities.
- Classic systems have been developed for medical applications and have a precise resolution of pressure (at 0.01 bar) or flow (nL / min). Their price and their size greatly limit the number of cavities that can be controlled simultaneously. From a practical point of view, this number is typically limited to ten. Certain applications of wavefront corrections may require the control of about twenty cavities. From a general point of view, the greater the number of cavities, the better the resolution of the optical system and its versatility.
- the system is produced in a monolithic manner, that is to say that the same material delimits the two types of cavities.
- the same flexible membrane closes the two types of cavities.
- the substrate material which forms the set of cavities and channels, as illustrated in FIG. 9.
- the material delimiting the cavities and forming the membrane is the same Mat material, as illustrated in FIGS. 8 and 20 to 22.
- the actuators are of the piezoelectric type, which allows electrical actuation of the cavities.
- Figures 20 and 21 illustrate the operation of a double cavity Chi / CSi system actuated by a piezoelectric ACTi.
- the actuator is at rest (0V voltage applied to the piezo), and no pressure is applied to the Chi chamber.
- the piezoelectric is energized and causes by variation of its thickness a deformation of the membrane closing the source cavity, leading to a reduction in the height of the source cavity by a value of hp.
- the source cavity CSi (length L C s and width not shown) does not necessarily have the same dimensions as the chamber Chi (length L C o and width not shown), and therefore the increase in the height of the chamber Chi hco result may be different from hp, as illustrated in figure 21.
- a small variation in the thickness of one cavity results in a large variation in the thickness of the other.
- This allows in particular to adjust the resolution of the piezoelectric actuator to the desired optical resolution.
- the application of a positive or negative potential across the terminals of the piezoelectric activator makes it possible to modify the height of the source cavity and finally to modify the volume of the optical cavity as described in FIG. 21.
- the integration of the actuator requires the installation of a mechanical support 50 on either side of the source cavity in order to guarantee the effectiveness of the compression of the latter.
- This holder is added so that it is outside the optical aperture of the system.
- FIG. 22 A complete system 15 presenting an injection device as described above is illustrated in FIG. 22. Each source cavity is thus addressed individually by multiplexing using conventional electronics comprising an electrical driver ED.
- piezoelectric actuators also has the advantage of a short response time.
- a mechanical piston is used which is attached and connected to the cavity via a catheter. It is possible to calculate the response time constant t of such a system when pressure is applied in the hydrodynamic actuator (here a mechanical piston). This characteristic time describes the time required for the pressure imposed by the piston to be transmitted up to the exit of the catheter and therefore into the optical cavity.
- the analytical expression of t as a function of the geometric parameters is:
- Dp, De, Lp and Le represent the diameters and lengths of the piston and catheter respectively, and m and E are the viscosity and Young's modulus of the fluid considered.
- the time constant obtained is, for water ( m / E ⁇ 10 -12 s) as fluid, of the order of 40 ms for a displacement of
- response times of the order of 40-50 ms are not compatible with the needs of display applications where the refresh rates must be at least one decade higher than the eye refresh rate, ie 250Hz, that is to say response times of the order of ms.
- the typical response time calculated with formula (1) is 100ps corresponding to a hydrodynamic cutoff frequency of 10kHz.
- the system 15 is coupled to a mechanical system in order to increase the phase amplitude or in order to combine a modification of the phase and a rotation of the component (for example for an optical beam modulation application).
- the invention relates to a method for modifying a phase of a wavefront of a light wave having at least one wavelength l and comprising the steps consisting in:
- the injection into a chamber Chi takes place by applying a determined pressure Pi to the fluid of the chamber, so as to locally create an elastic deformation ei of the membrane Memb.
- the pressures P applied to the chambers Chi via the associated channels CAi and therefore the local deformations ei of the membrane are determined so as to apply to the light wave OL the phase shifts Df ⁇ determined in the previous step.
- the local phase shifts are determined from a measurement of the wavefront to be corrected, so as to effect a correction of said wavefront.
- the local phase shifts are determined so as to operate an active pupil coding.
- the system 15 presents a simplified manufacturing process.
- a reference mold is created equal to the negative of the cavities and networks of channels to be produced, obtained for example by structuring a silicon substrate (dozens of possible replications) or metal (no replication limit before deterioration of the mold).
- the manufacturing steps are as follows (for the variant of FIG. 22 in which the same flexible material is used for the walls, the membrane and the spaces between the active chambers and the source cavities and the cavities sources):
- the total manufacturing time for such a sample represents a few hours knowing that the mold production step is only to be carried out once for the same design.
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Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR1801098A FR3087430B1 (fr) | 2018-10-18 | 2018-10-18 | Dispositif micro-fluidique adapte pour modifier la phase d'un front d'onde et systeme optique comprenant un tel dispositif |
PCT/EP2019/078254 WO2020079169A1 (fr) | 2018-10-18 | 2019-10-17 | Dispositif micro-fluidique adapté pour modifier la phase d'un front d'onde et système optique comprenant un tel dispositif |
Publications (1)
Publication Number | Publication Date |
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EP3867688A1 true EP3867688A1 (fr) | 2021-08-25 |
Family
ID=65951607
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP19786983.7A Pending EP3867688A1 (fr) | 2018-10-18 | 2019-10-17 | Dispositif micro-fluidique adapté pour modifier la phase d'un front d'onde et système optique comprenant un tel dispositif |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP3867688A1 (fr) |
FR (1) | FR3087430B1 (fr) |
WO (1) | WO2020079169A1 (fr) |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
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FR1102210A (fr) | 1954-04-02 | 1955-10-18 | Palette de peintre | |
DE2434541A1 (de) * | 1974-07-18 | 1976-01-29 | Agfa Gevaert Ag | Verfahren und vorrichtung zur phasenmodulation |
AU2001286511A1 (en) * | 2000-08-15 | 2002-02-25 | Nanostream, Inc. | Optical devices with fluidic systems |
-
2018
- 2018-10-18 FR FR1801098A patent/FR3087430B1/fr active Active
-
2019
- 2019-10-17 EP EP19786983.7A patent/EP3867688A1/fr active Pending
- 2019-10-17 WO PCT/EP2019/078254 patent/WO2020079169A1/fr unknown
Also Published As
Publication number | Publication date |
---|---|
FR3087430B1 (fr) | 2020-12-04 |
FR3087430A1 (fr) | 2020-04-24 |
WO2020079169A1 (fr) | 2020-04-23 |
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