Compact device for imaging a wavefront by interferometry

Abstract

Imaging module (Mod) designed to characterize a wavefront by interferometry, comprising: an imaging sensor (Sens) including an array (Mat) of photosensitive pixels formed on a planar substrate (Sub); and an optical phase and / or amplitude grating (Arr) formed of a support (Sprt) one face (StrctFac) of which is structured so as to introduce periodic variations in phase and / or amplitude into an incident light beam; in which the grating (Arr) is fixed to the imaging sensor (Sens) such that at least one optical element (Sprt, OptEl) is interposed between the structured face (StrctFac) of the grating (Arr) and the array (Mat) of photosensitive pixels, the optical element comprising two opposite faces (StrctFac, nStrctFac, F1, F2) each parallel to the array (Mat) of photosensitive pixels and to the structured face (StrctFac) of the grating (Arr), and one of them being in mechanical contact with the imaging sensor (Sens). Figure to be published with the abbreviation: Fig.4.

Description

Title of the invention: Compact device for imaging a wavefront by interferometry. TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a device for analyzing the wavefront of incident light radiation. The light radiation passes through an optical device that introduces periodic variations in phase and / or intensity. Such a device is based on interferometric analysis such as, for example, quadrawave lateral shearing interferometry, or QLSI. TECHNOLOGICAL BACKGROUND

[0002] Imaging of a wavefront

[0003] Quadrulateral shift interferometry, or QLSI, is an imaging technique Quantitative phase detection (QLSI) is based on the use of a diffraction grating placed in front of an imager. This grating creates an image called an interferogram, from which the intensity and phase profiles of an incoming light beam can be derived. Invented in the 1990s, QLSI is used in numerous applications, such as laser beam characterization, optical lens metrology, topographic measurements, adaptive optics, gas jet metrology, and, more recently, the technique has been implemented in optical microscopes to characterize micro- and nano-objects for bioimaging and nanophotonics applications.

[0004] A diffraction grating used for wavefront analysis is designed to induce (i) phase and / or amplitude differences and (ii) a diffraction phenomenon in light radiation passing through the grating. The diffraction grating can thus be defined as an optical device introducing periodic variations in phase and / or intensity.

[0005] The network generates different beams which interfere by forming an image whose distortions are linked to the gradients of the analyzed wave surface.

[0006] A specific case of wavefront analysis techniques, QLSI relies on so-called "four-wave" interference obtained using a diffraction grating comprising (i) opaque lines and columns delimiting transparent apertures and (ii) periodic thickness differences in a checkerboard pattern at these apertures. Such an optical device introduces periodic variations in phase and intensity. Reference may be made, for example, to French patent FR 2795 175B1.

[0007] Other variants of these techniques are called "three-wave" and are based on the use of hexagonal geometry gratings. Such gratings can be designed for introduce only periodic phase variations or only periodic intensity variations. Reference can be made, for example, to patent FR 2712978 Bl.

[0008] Thus, in general, a diffraction grating used for the analysis of a wavefront by interferometry can be defined as an optical device introducing (i) periodic variations in phase, (ii) periodic variations in amplitude, or (iii) periodic variations in phase and periodic variations in amplitude.

[0009] In all cases, it is a characterization of the wavefront of an incident wave by interferometry.

[0010] The sensitivity of the wavefront characterization system, composed of the imager and the diffraction grating, depends on the pixel size p of the imager used and the distance d separating the structured face of the diffraction grating from the image sensor. It is therefore clear that a high-quality wavefront characterization requires a good understanding of these two parameters, the only one potentially accessible to the user being the distance d once the imager has been selected. The periodicity of the diffraction grating is precisely known and fixed from its manufacture. Furthermore, it is adapted to the dimensions of the photosensitive pixels of the image sensor used. However, a precise knowledge of the distance d requires precise positioning and parallelism of the diffraction grating with respect to the image sensor to ensure a uniform distance d across the entire sensor surface for quantitative wavefront analysis.

[0011] Figure 1 illustrates a conventional imaging camera, not equipped for QLSI, comprising, within a camera housing 150, an electronic board 140 mechanically supporting and electronically controlling a conventional ImConv imager. This imager includes a photosensitive element 110, a protective housing 120 containing the photosensitive element 110, and a protective window 130. The photosensitive element 110 may be formed of a two-dimensional array of photosensitive pixels. The protective housing 120 is hermetically sealed by the window 130, located in front of the photosensitive element 110. The internal volume of the housing 120 may have a controlled atmosphere or be under vacuum. During operation, incident radiation Inc passes through the window 130 and strikes the photosensitive element 110.

[0012] Conventional ImConv imagers are usually supplied by their manufacturers in protective housings, leaving it to companies providing image analysis solutions to integrate this component into cameras. However, QLSI practice requires the diffraction grating to be located at a distance d between 0.5 and 10 mm from the imaging plane represented by the photosensitive pixels. Such a requirement is not very compatible with conventional ImConv imagers.

[0013] Conventional QLSI approaches

[0014] As mentioned above, the distance d determines the sensitivity of the optical system and must therefore be adjusted according to the intended application. Parallelism between the diffraction grating and the image sensor must also be ensured. There are two approaches to manufacturing wavefront analysis devices according to QLSI.

[0015] A first approach is illustrated by the QLSI system 200 in [Fig. 2]. This approach allows the diffraction grating 220 to be placed at an arbitrary distance from the imaging plane, which is materialized by the photosensitive element 210 integrated into a camera housing 250. Such an arrangement is possible using an optical coupling system consisting here of two lenses 230 and 240 with the same focal length f. The diffraction grating 220 is then placed at a distance 4f+d from the imaging plane, instead of the distance d in the absence of the optical coupling system. Reference may be made to the publication by Guillaume Baffou, “Quantitative phase microscopy using quadriwave lateral shearing interferometry (QLSI): principle, terminology, algorithm and grating shadow description,” J. Phys. D: Appl. Phys. 54 (2021) 294002 (13pp).

[0016] This system has several advantages. In particular, it allows for the assembly of a system capable of performing QLSI using a camera of any specifications without compromising the integrity of the camera's photosensitive sensor housing. The protective housing maintains them in a controlled atmosphere, and therefore protects them from dust, humidity, condensation, and even freezing, the latter being critical when the camera is equipped with a sensor cooling system. Another advantage is the ability to very precisely adjust the distance d separating the diffraction grating from the imaging plane.

[0017] On the other hand, assembling the entire system is complex, requiring the mechanical fastening of several components: diffraction grating, lenses, camera, and, inside the camera, the image sensor itself. Adjusting the parallelism, in particular, can be tricky. Furthermore, the assembly can become bulky and cumbersome to use, and the use of lenses inherently introduces chromatic aberrations that must be taken into account for quantitative measurements.

[0018] A second approach is illustrated by the system 300 of [Fig. 3]. Here, the diffraction grating 320 is mounted near the photosensitive element 310 located in the camera housing 350 by means of a mechanical assembly that allows the distance d separating the diffraction grating 320 from the photosensitive element 310, which constitutes the image sensor of the system, to be modulated. Without going into detail, the mechanical assembly consists of two rings 330A and 330B capable of sliding relative to each other in a controlled manner. Ring 330A is fixed to the camera housing, while ring 330 is fixed to the diffraction grating. The sliding The relative of the two rings therefore allows the distance d to be adjusted. This approach, detailed in patent document FR 2 879 288, has the main advantages of allowing a very fine adjustment of the distance d and a great simplicity of this adjustment.

[0019] On the other hand, adjusting the parallelism appears tricky, and the assembly, integrating the camera and the mechanical sliding control mechanism, is bulky. Furthermore, bringing the diffraction grating close to small distances, such as on the order of a millimeter or less, for example 500 pm, requires removing the glass isolating the image sensor from the camera environment, leading to a high risk of contamination by dust and ambient humidity. This latter problem is exacerbated when the image sensor used requires cooling, with a risk of freezing and damage to the sensor from the resulting ice crystals.

[0020] The technical solutions envisaged so far only lead to wavefront characterization systems which are bulky, require delicate adjustments due to the number of mechanical elements involved, and do not always effectively protect the image sensor, which is nevertheless a central element of these systems. Description of the invention

[0021] An object of the invention is to provide a wavefront imaging device that is easy to use, robust and compact.

[0022] For the purpose of realizing these objects, one aspect of the invention is an imaging module designed to characterize a wavefront by interferometry, comprising: an imaging sensor comprising a matrix of photosensitive pixels formed on a planar substrate, and a phase and / or amplitude optical grating formed of a support having one face structured so as to introduce periodic variations of phase and / or amplitude in an incident light beam, in which the grating is fixed to the imaging sensor in such a way that at least one optical element is interposed between the structured face of the grating and the matrix of photosensitive pixels, the optical element comprising two opposite faces each parallel to the matrix of photosensitive pixels and to the structured face of the grating, and one of them being in mechanical contact with the imaging sensor.

[0023] A first advantage of the device according to the invention is its ease of use, parallelism being ensured in a simple and definitive way by the use of the optical element which, with its parallel faces, allows the structured face of the diffraction grating to be rigorously oriented parallel to the imaging plane materialized by the matrix of photosensitive pixels.

[0024] A second advantage of the device is that the distance d separating the active face of the diffraction grating from the imaging plane can be perfectly defined (i) by the thickness of the optical element, which can be made up of the diffraction grating itself. (ü) by the thickness of an additional optical element mounted on the imaging sensor, or (iii) by the thickness of a combination of the diffraction grating and this additional optical element. Thus, the sensitivity of the device is also very precisely known, allowing optimal use of the images acquired during the analysis of incident radiation. It should be noted that the sensitivity is not simply dependent on the geometric distance separating the grating from the array of photosensitive pixels, but is also a function of the refractive index of each of the media traversed by the incident radiation after its diffraction by the grating. It is therefore necessary to take into account the optical index of the material(s) forming these elements when determining the distance d.

[0025] A third advantage of the device is its compact size, allowing it to be integrated into conventional imaging camera housings, and therefore into any type of camera, while retaining all their functionalities. Thanks to its compactness, the device can be effectively protected from its environment, preventing the harmful effects of dust, humidity, and freezing, particularly in situations where the image sensor requires cooling.

[0026] According to additional, non-limiting features of the invention, considered individually or in any technically feasible combination:

[0027] - the optical network may comprise a structured face having (i) lines and opaque orthogonal columns delimiting transparent openings and (ii) half of the transparent openings, distributed according to a checkerboard pattern, having an engraving of a given depth so as to form a phase checkerboard;

[0028] - at least one optical element can be in direct contact with the sensor imaging;

[0029] - the imaging sensor may include a microlens array covering the photosensitive pixel matrix;

[0030] - at least one optical element can be attached to the imaging sensor by gluing to using an adhesive;

[0031] - the adhesive can be formed continuously around a periphery of the network and in direct contact with the imaging sensor and the network;

[0032] - at least one optical element may be made up of the grating, a distance of separation between the structured face of the grating and the matrix of photosensitive pixels being fixed by means of a thickness of the grating;

[0033] - the imaging module may further include an additional optical element, the network being interposed between this additional optical element and the imaging sensor;

[0034] - at least one optical element may consist of an additional optical element Interposed between the imaging sensor and the grating, a separation distance between the structured face of the grating and the photosensitive pixel matrix can be fixed: (i) by means of a sum of a grating thickness and a thickness of the additional optical element if the grating support is interposed between the imaging sensor and the structured face of the grating, or (ii) by means of the thickness of the optical element if the structured face of the grating is interposed between the optical element and the grating support;

[0035] - the additional optical element can be chosen from a spectral filtering element, a spatial filtering element, and a polarization filtering element;

[0036] - the optical element can be structured at the scale of a group of pixels photosensitive matrix, or at a scale of one pixel of the matrix;

[0037] - the optical element may comprise a face structured so as to constitute a Fabry-Pérot filter array, the optical element being oriented in such a way that this structured face is immediately adjacent to the sensor.

[0038] Another aspect of the invention relates to an imager comprising a housing in which the imaging module according to the invention is placed.

[0039] The imager may include a protective glass closing the housing.

[0040] The invention extends to a camera comprising a camera housing containing the imaging module according to the invention or the imager according to the invention. BRIEF DESCRIPTION OF THE FIGURES

[0041] Other features and advantages of the invention will become apparent from the detailed description of the invention which follows with reference to the accompanying figures in which:

[0042] [Fig.1] Fig.1 illustrates a conventional camera;

[0043] [Fig.2] The [Fig.2] illustrates a first conventional approach for a QLSI optical system;

[0044] [Fig.3] The [Fig.3] illustrates a second conventional approach for a QLSI optical system;

[0045] [Fig.4] The [Fig.4] illustrates an imaging module for characterizing a wavefront by interferometry;

[0046] [Fig.5] The [Fig.5] illustrates a first variant for the module of the [Fig.4];

[0047] [Fig.6] The [Fig.6] illustrates a second variant for the module of the [Fig.4];

[0048] [Fig.7] The [Fig.7] illustrates a third variant for the module of the [Fig.4];

[0049] [Fig.8] The [Fig.8] illustrates a fourth variant for the module of the [Fig.4];

[0050] [Fig.9] The [Fig.9] illustrates a fifth variant for the module of the [Fig.4];

[0051] [Fig. 10] The [Fig. 10] illustrates a first imager integrating an imaging module for characterizing a wavefront by interferometry;

[0052] [Fig. 11] The [Fig. 11] illustrates a second imager integrating an imaging module for characterizing a wavefront by interferometry;

[0053] [Fig. 12] The [Fig. 12] illustrates the attachment of a diffraction grating for characterizing a wavefront by interferometry to an imaging sensor;

[0054] [Fig. 13] Fig. 13 illustrates a camera incorporating an imager such as that shown in Figures 10 and 11; and

[0055] [Fig. 14] The [Fig. 14] illustrates a diffraction grating used in QLSI. DETAILED DESCRIPTION OF THE INVENTION Method of embodying the invention

[0056] One embodiment of the invention is detailed with reference to Figures 4 to 13.

[0057] Figures 4 to 6 illustrate three variants of an imaging Mod module in in which a diffraction grating (Arr) is in direct contact with an imaging direction sensor. Figures 7 to 9 illustrate three variants of the imaging module, in which an OptEl optical element is interposed between the imaging direction sensor and the Arr grating. This optical element is chosen to have an optical function useful for analyzing incident radiation: it may be a spectral filtering, spatial filtering, or polarizing element, for example.

[0058] Figure 4 is a cross-sectional view of a first variant of an imaging module designed to characterize a wavefront, with an imaging module comprising an imaging direction sensor and the diffraction grating Arr. The Arr grating can be more specifically described as a phase and / or amplitude optical grating, due to its function of modulating the phase and / or amplitude of radiation passing through it.

[0059] The imaging Sense sensor comprises a Mat matrix of photosensitive pixels formed on a planar substrate Sub. The Mat matrix can be formed according to known principles, for example by employing CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) type sensors or other detection technologies in the infrared domains such as InGaAs technology for example.

[0060] The diffraction grating Arr is formed of an optically transparent Sprt support, one face of which StrcFac is structured to introduce periodic variations in phase and / or amplitude (and therefore intensity) into an incident light beam. In the case of QLSI, this can be a Sprt support on which a pattern of periodic horizontal Str (H-Str) and vertical Str (V-Str) bands of zero transmission are formed, delimiting transparent areas. The transparent areas are etched to form an achromatic phase shifter in a checkerboard pattern: for every other aperture in a checkerboard geometry, the surface of the support is etched to a certain depth e, such that this thickness consists of the support material for every other aperture and air for the other apertures, which generates phase shifts in the incident radiation.Periodic bands and structured transparent areas are responsible for amplitude and phase modulation. of radiation passing through the network. See patent document FR 2 795 175.

[0061] The face of the Arr lattice opposite the structured face is designated by nStrctFac. The two faces StrctFac and nStrctFac are parallel to each other.

[0062] In this variant, the Arr grating is in direct mechanical contact with the surface of the imaging sensor housing the Mat matrix. Thus, parallelism between the active face of the Arr grating and the imaging plane, materialized by the Mat matrix, is ensured.

[0063] The structured face StrctFac of the Arr network is located on the opposite side to the Mat matrix, that is to say that the support Sprt is interposed between the Mat matrix and the structured face StrctFac of the Arr network.

[0064] The distance d separating the structured face StrctFac of the Arr grating and the Mat matrix of photosensitive pixels is naturally determined and fixed by the thickness t^ of the Arr grating. In this configuration, the distance d is even equal to the thickness. It is therefore necessary to choose the thickness of the Sprt support on which the structured face StrctFac is formed according to the intended use for the imaging Mod module.

[0065] In determining the distance d, it is necessary to take into account the refractive index of the material forming the support Sprt. In the situation of [Fig.4], where the space separating the structured face StructFac from the photosensitive pixels is essentially filled with the material forming the support Sprt, the distance d is d0 / n, where n represents the refractive index of the material forming the support Sprt and d0 represents the geometric positioning distance of the grating with respect to the photosensitive pixels in a conventional situation where the propagation medium of the radiation emerging from the structured face StructFac of the grating is air.

[0066] The Arr grating is attached to the Sens sensor using an adhesive Ad. Mechanical attachment is possible, but adhesive attachment offers the advantages of simplicity and compactness. As illustrated in (A) of [Fig. 12], the adhesive Ad can be formed from dots of glue at the Cire periphery of the Arr grating. Alternatively, as illustrated in (B) of [Fig. 12], the adhesive can be formed continuously around the Cire periphery of the Arr grating and in direct contact with the imaging Sens sensor and the Arr grating, forming a dust- and moisture-proof barrier and thus protecting the Mat matrix from environmental damage. In this second case, a glass cover hermetically sealing the Sens sensor housing is not necessary, although it provides valuable additional protection and sealing.

[0067] Figure 5 illustrates a first variant of the Imaging Mod module of Figure 4. In this variant, the Imaging Sensing sensor is equipped with a LensAr array of microlenses covering the Mat matrix of photosensitive pixels. Microlenses can be used to focus the incident radiation onto the photosensitive surface of the pixels constituting the Mat matrix. In this case, the microlens array constitutes the part of the Sens sensor in mechanical contact with the Arr array. The distance d is no longer identical to the thickness t^ of the array, so the integrator of the Arr array on the Sens sensor might have to take into account the height of the microlenses if it is not negligible with regard to the intended uses. That being said, the module continues to benefit from the fixed distance d and the parallelism ensured by the support of the array itself, as in the situation of [Fig. 4].

[0068] Figure 6 is similar to Figure 5, with the imaging module further equipped with an additional OptEl optical element stacked on the Arr array. The Arr array is thus interposed between this additional OptEl optical element and the Imaging Sense sensor.

[0069] The OptEl element can be chosen from a filtering element, optionally a spatial filtering element, and a polarizing element, among other examples.

[0070] Figures 7 to 9 illustrate three variants of the imaging Mod module of [Fig. 4], in which an additional OptEl optical element is interposed between the imaging Sens sensor and the Arr grating, unlike the variants in Figures 4 to 6. The separation distance d between the structured face StrctFac of the Arr grating and the Mat matrix is ​​therefore at least conditioned by the thickness tOptEi of the OptEl optical element. Both the Arr grating and the optical element can be attached to the Sens sensor by bonding with the Ad adhesive as described above and illustrated in Figures 4 to 12.

[0071] Figure 7 illustrates a variant of the imaging Mod module, which includes the OptEl optical element interposed between the imaging Sens sensor and the Arr grating. The OptEl element comprises two opposing faces Fl and F2 parallel to each other, one of these faces being in direct contact with the Sens sensor and the other being in direct contact with the structured face StrctFac of the Arr grating. Thus, parallelism between the active face of the Arr grating and the imaging plane, materialized by the Mat matrix, is ensured.

[0072] The distance d separating the structured face StrctFac of the Arr grating and the Mat matrix of photosensitive pixels is naturally determined and fixed by the thickness tOptEi of the OptEl element. In this configuration, the distance d is even equal to the thickness top®. It is therefore appropriate to choose the thickness toptEi of the OptEl element according to the intended use for the Mod module in the same way as the thickness t^ of the Arr grating in the situation of [Fig. 1].

[0073] The OptEl optical element may comprise a structured face at the scale of a group of photosensitive pixels of the Mat matrix, or at the scale of a pixel of the Mat matrix, which means that the smallest structural element of the OptEl element The structured face can have a lateral extension dimension on the order of a lateral dimension of the matrix, on the order of a lateral dimension of a pixel array such as a two-dimensional matrix of 2x2, 3x3, 4x4, or 5x5 pixels, or on the order of the lateral dimension of a single pixel, respectively. The expression "a dimension on the order of" here means "a dimension between 50% and 150% of." In such a case, the structured face must be as close as possible to the photosensitive pixels; therefore, the additional OptEl optical element must be placed directly against the Sens sensor, interposed between the latter and the Arr grating. Furthermore, the structured face must be on the Sens sensor side, that is, immediately adjacent to the Sens sensor, this structured face (F2 in Figures 7 and 8) being interposed between the Sens sensor and the opposite face of the OptEl optical element (F1 in Figures 7 and 8).Figures 7 and 8 illustrate such a case, in which the structured face is the F2 face of the OptEl optical element. Such a spectral filtering optical element can comprise an array of spectral filters such as Fabry-Pérot filters or resin filters designed to each cover a pixel or group of pixels, with applications in the field of multispectral imaging.

[0074] Figure 8 presents a variant of the imaging module Mod, which differs from that of Figure 7 in the following two respects: (i) the imaging Sense sensor is equipped with a LensAr microlens array similar to that of Figure 5, and (ii) one of the two opposing faces Fl and F2 is in direct contact with the Sense sensor and the other of these faces is in direct contact with the unstructured face nStructFac of the Arr array. The microlens array constitutes the part of the Sense sensor in direct mechanical contact with the Sense sensor.

[0075] In such a case, the Sprt support of the Arr grating is interposed between the Sens imaging sensor and the structured face StrctFac of the Arr grating, and the distance d is fixed by the sum tOptEi+tAir of the thickness t^ of the Arr grating and the thickness of the optical element OptEl. The distance d is not exactly equal to the sum tOptEi+tAn-, so the integrator of the Arr grating on the Sens sensor might have to take into account the height of the microlenses if this is not negligible with regard to the intended uses. That being said, the device continues to benefit from the fixed distance d and the parallelism ensured by the thickness and parallelism characteristics of the faces of the Arr grating and the OptEl element. It is therefore necessary to choose the thicknesses toptEi and t^ according to the intended use for the Mod module.

[0076] In a configuration like that of [Fig. 8], the Arr grating and the additional OptEl optical element can be bonded by their respective facing surfaces. The excess optical adhesive is small (usually less than 20 micrometers) and potentially negligible with regard to the intended uses. It can also be measured and compensated for if necessary. Parallelism is ensured by Self-leveling of the adhesive before curing. The facing surfaces of the grating and the optical element are chosen so that the adhesive does not interfere with the optical functionalities of these elements.

[0077] Figure 9 illustrates a combination of the variants shown in Figures 7 and 8. More specifically, (i) the imaging Sens sensor is provided with a LensAr array of microlenses as shown in Figure 8 and (ii) one of the two faces of the Sens sensor is in direct contact with the structured face StrctFac of the Arr array as shown in Figure 7.

[0078] In this case, the microlens array constitutes the part of the Sens sensor in direct mechanical contact with the OptEl element. The distance d is not identical to the thickness tAn- of the array, so the integrator of the Arr array on the Sens sensor might have to take into account the height of the microlenses if this is not negligible with regard to the intended uses. That being said, the device continues to benefit from the fixing of the distance d and the parallelism ensured by the OptEl element, as in the situation of [Fig. 7].

[0079] Of course, other variants than those described in figures 4 to 9 are conceivable, by playing on the parameters such as the presence or absence of a microlens array, the presence or absence of an additional optical element and the positioning of the latter in relation to the diffraction filter, or even the orientation of the diffraction filter.

[0080] Integration of the imaging module

[0081] The imaging module Mod is intended to be integrated into equipment enabling an end user to study and characterize incident radiation wavefronts. For this purpose, for convenience and protection, the Mod module can be placed in a protective Box enclosure, as illustrated in Figures 10 and 11, to form an Im imager. This enclosure can be closed with a Gl window, preferably hermetically sealed, to provide additional protection for the Mod module.

[0082] In practice, a Mod module can be manufactured by adding the Arr network and, where appropriate, an additional OptEl optical element to a commercially available and distributed Sens image sensor integrated into the Box housing.

[0083] When the total height of the elements added to the Sens sensor is sufficiently low compared to the depth of the Box housing, it is enough to remove the window, fix the elements to be added to the sensor onto it and close the window.

[0084] When the total height of the elements added to the Sens sensor is too high to be able to put the window back in place directly, then an H+ riser allowing to increase the height of the edges of the housing can be used, as illustrated by [Fig.11].

[0085] Fig. 13 illustrates a Cam camera incorporating a Mod module of any of the variants illustrated by figures 4 to 9. This can also be integrated into an Im imager such as those illustrated by figures 10 and 11, itself integrated into a camera housing 150.

[0086] The present description takes QLSI as representative of wavefront analysis techniques, with a particular geometry of the diffraction grating, but it is understood that the principles detailed above are not limited to QLSI, and arbitrary geometries of diffraction filters may be employed, insofar as they allow the generation of different emergent beams which interfere by forming an image whose deformations are related to the gradients of the analyzed wavefront.

[0087] In this document, the figures are not necessarily to scale. Certain features and components may be shown exaggerated in relation to other components or in a somewhat schematic form, and certain details of conventional elements may not be shown in the interest of clarity and conciseness.

[0088] Of course the invention is not limited to the described embodiment and alternative embodiments can be made without departing from the scope of the invention as defined by the claims.

Claims

Demands

1. Imaging module (Mod) designed to characterize a wavefront by interferometry, comprising: - an imaging sensor (Sens) comprising an array (Mat) of photosensitive pixels formed on a planar substrate (Sub); and - an optical phase and amplitude grating (Arr) formed of a support (Sprt) one face (StrctFac) of which is structured so as to introduce periodic variations in phase and / or amplitude into an incident light beam;in which the grating (Arr) is fixed to the imaging sensor (Sens) such that at least one optical element (Sprt, OptEl) is interposed between the structured face (StrctFac) of the grating (Arr) and the array (Mat) of photosensitive pixels, the optical element comprising two opposite faces (StrctFac, nStrctFac, Fl, F2) each parallel to the array (Mat) of photosensitive pixels and to the structured face (StrctFac) of the grating (Arr), and one of them being in mechanical contact with the imaging sensor (Sens), the optical grating (Arr) comprising a structured face (StrctFac) having (i) opaque orthogonal lines (H-Str) and columns (V-Str) delimiting transparent apertures (Ap) and (ii) half of the transparent apertures, distributed in a checkerboard pattern, having an etching of a given depth (e) so as to form a checkerboard of phase.;

2. The imaging module (Mod) according to claim 1, wherein at least one optical element (Sprt, OptEl) is in direct contact with the imaging sensor (Sens).

3. The imaging module (Mod) according to any one of claims 1 to 2, wherein the imaging sensor (Sens) comprises an array (LensAr) of microlenses covering the matrix (Mat) of photosensitive pixels.

4. The imaging module (Mod) according to any one of claims 1 to 3, wherein at least one optical element (Sprt, OptEl) is fixed to the imaging sensor (Sens) by bonding with an adhesive (Ad).

5. The imaging module (Mod) according to claim 4, wherein the adhesive (Ad) is formed continuously around a periphery (Wax) of the network (Arr) and in direct contact with the imaging sensor (Sens) and the network (Arr).

6. The imaging module (Mod) according to any one of claims 1 to 5, wherein at least one optical element is made up of the grating (Arr), a separation distance (d) between the structured face (StrctFac) of the grating (Arr) and the matrix (Mat) of photosensitive pixels being fixed by means of a thickness (1^) of the grating (Arr).

7. The imaging module (Mod) according to claim 6, further comprising an additional optical element (OptEl), the grating (Arr) being interposed between this additional optical element (OptEl) and the imaging sensor (Sens).

8. The imaging module (Mod) according to any one of claims 1 to 5, wherein at least one optical element consists of an additional optical element (OptEl) interposed between the imaging sensor (Sens) and the grating (Arr), a separation distance (d) between the structured face (StrctFac) of the grating (Arr) and the matrix (Mat) of photosensitive pixels being fixed: - (i) by means of a sum (tOptEi+tAn-) of a thickness (^) of the grating (Arr) and a thickness of the additional optical element (OptEl) if the support (Sprt) of the grating (Arr) is interposed between the imaging sensor (Sens) and the structured face (StrctFac) of the grating (Arr), or - (ii) by means of the thickness (tOptEi) of the optical element (OptEl) if the structured face (StrctFac) of the grating (Arr) is interposed between the optical element (OptEl) and the support (Sprt) of the network (Arr).

9. The imaging module (Mod) according to claim 8, wherein the additional optical element (OptEl) is selected from a spectral filtering element, a spatial filtering element, and a polarization filtering element.

10. The imaging module (Mod) according to claim 9, wherein the optical element (OptEl) is structured at the scale of a group of photosensitive pixels of the matrix (Mat), or at the scale of a pixel of the matrix (Mat).

11. The imaging module (Mod) according to claim 9, wherein the optical element (OptEl) comprises a structured face (F2) such as to constitute a Fabry-Pérot filter matrix, the element

12.

13.

14. optics (Sens) being oriented such that this structured face (F2) is immediately adjacent to the sensor (Sens). Imager (Im) comprising a housing (Box) in which the imaging module (Mod) according to any one of claims 1 to 11 is placed. The imager (Im) according to claim 12, comprising a protective glass (Gl) closing the housing (Box). Camera (Cam) comprising a camera housing (150) containing the imaging module (Mod) according to any one of claims 1 to 11 or the imager (Im) according to claim 12 or 13.

Images