Method for calibrating a batch of lenses, associated image correction method and imaging system

Abstract

The invention relates to a method for calibrating a batch of lenses each comprising a plurality of phase objects (16) arranged in tiers, the method comprising: - obtaining, for each tier: * geometric data indicative of a shape of the corresponding phase object (16); * optical data relating to a refractive index depending on a position in said phase object (16); - calculating, from the geometric data of each phase object, position data representative of an effective position of each phase object in an element (14) for assembling a lens (8) of the batch of lenses; - simulating, from the calculated position data and the obtained optical data, at least one optical response associated with the batch of lenses; and - storing each simulated optical response in a memory, in association with an identifier of the batch of lenses.

Description

Method for calibrating a batch of lenses, associated image correction method and imaging system DESCRIPTION Technical field

[0001] The present invention relates to a method for calibrating a batch of lenses.

[0002] The invention also relates to a computer program, an image correction method and an imaging system implementing such a method.

[0003] The invention applies to the field of optics, and in particular to lenses for camera modules. State of the art

[0004] It is known to integrate one or more camera modules into an electronic device, such as a smartphone. Each camera module typically includes a lens associated with a sensor.

[0005] Typically, the lens consists of a set of phase objects, particularly lenses, stacked according to a predetermined stack. Such a stack is usually calculated by simulation during a design stage prior to manufacturing the phase objects and assembling them into a lens.

[0006] However, a real lens usually has deviations, similar to defects, from the nominal configuration.

[0007] Such deviations are, for example, partly attributable to imperfections in the shape of the phase objects compared to the expected theoretical shape. These imperfections are due, for example, to the shrinkage of the plastic material from which the phase objects (especially lenses) are made, to the machining precision of the molds, to the functional clearances of the mold parts guidance, etc. This results in a potential misalignment of the phase objects (tilt and / or decentering) compared to the corresponding expected theoretical position.

[0008] Furthermore, the quality of the plastic material used for molding phase objects (lenses, in particular), as well as the way in which it is injected (temperature, pressure, cooling cycle time) are likely to lead to deviations in refractive index from an expected refractive index.

[0009] Furthermore, the deposition of anti-reflective layers on the lenses is a potential source of deviations in the actual thickness of each lens compared to an expected thickness.

[0010] These structural defects result in optical defects, i.e. an optical response of the lens that is different from that expected (generally worse), and which includes point spread defects, chromatic aberration defects and / or geometric aberration defects (notably distortion).

[0011] Usually, to compensate for these defects, manufacturers integrate an image correction module into the electronic device equipped with the camera module, implementing a predetermined correction, for example, a contrast enhancement.

[0012] Another way to compensate for these defects is to image a predetermined reference pattern (e.g., a grid) through each lens, and compare the resulting image with the reference pattern to deduce the optical aberrations introduced by the lens to be corrected.

[0013] However, such a correction does not give complete satisfaction.

[0014] Indeed, the nature and extent of defects attributable to manufacturing processes vary over time, resulting in an optical response that also varies over time. In other words, lenses manufactured according to the same predetermined stack, but at different dates, have a different optical response. Using the same correction for all lenses produced therefore does not lead to satisfactory results.

[0015] Furthermore, the optical aberrations determined by imaging the reference pattern are only a composition of the spatial impulse response of the lens with said reference pattern. However, effective correction requires knowledge of the spatial impulse response itself, and not the result of its composition with the reference pattern.

[0016] An aim of the present invention is to remedy at least one of the drawbacks of the state of the art.

[0017] Another object of the invention is to provide a calibration method which makes it possible to obtain a reliable and precise optical response associated with an objective, without requiring the characteristics of each objective to be measured individually. Statement of the invention

[0018] To this end, the invention relates to a calibration method of the aforementioned type, in which each objective of the batch comprises an assembly element and a plurality of phase objects staged according to a predetermined stack and mounted in the assembly element, the batch of objectives being such that, for two objectives of said batch, the respective phase objects of the same stage of the stack have been manufactured according to the same manufacturing process, the calibration process being implemented by computer and comprising the steps: - for each level of the stack, obtaining: • geometric data indicative of a shape: o of at least one diopter of a phase object positioned at said stage; o of a first bearing surface of said phase object on an internal face of the assembly element; and / or o of a second bearing surface of said phase object on a neighboring phase object; • optical data relating to a refractive index as a function of a position in said phase object; - calculation, from the geometric data of each phase object, of position data representative of an effective position of each phase object in the assembly element of a lens of the batch of lenses; - simulation, from the calculated position data and the obtained optical data, of at least one optical response associated with the batch of objectives; and - storage of each simulated optical response in a memory, in association with an identifier of the batch of objectives.

[0019] Indeed, the manufacturing processes of phase objects of the same batch of lenses are assumed to vary negligibly over short periods of time. In this way, by measuring the characteristics of a single lens of the batch, the method according to the invention makes an optical response accessible for all the lenses of the batch. As a result, a reliable correction is likely to be achieved for all of these lenses.

[0020] The calibration method according to the invention is therefore less tedious, less expensive and more precise than known methods.

[0021] Advantageously, the calibration method according to the invention has one or more of the following characteristics, taken in isolation or in any technically possible combination:

[0022] for each stage of the stack, the geometric data relating to the phase object positioned on said stage are, in addition, indicative of an angular position of said phase object;

[0023] at least one phase object is a lens, the batch of lenses being such that, for two lenses of said batch, the respective lenses of the same stage of the stack come from the same cavity of the same mold;

[0024] the stack comprises at least one shim, each shim being arranged between two respective predetermined stages of the stack, the method further comprising, for each shim, obtaining respective geometric data indicative of a thickness of the shim, of a shape of each bearing surface of the shim on an internal face of the assembly element and / or of a shape of each auxiliary bearing surface of the shim on a neighboring phase object, the position data also depending on the geometric data relating to each shim;

[0025] the at least one simulated optical response associated with the batch of objectives comprises at least: - a distortion map induced by a lens of said batch in a predetermined reference plane, the reference plane being orthogonal to a target optical axis of the lens and located at a predetermined distance from said lens; and / or - an optical transfer function of an objective of said batch between at least one point in space and the reference plane;

[0026] each simulated optical response is associated with a respective range of wavelengths;

[0027] the simulation step includes providing position data and optical data as input to an artificial intelligence model, forming an optical response model, the optical response model being associated with the stack and being configured to produce, as output, a simulated optical response associated with said position data and optical data, the optical response model having been previously trained on the basis of a training dataset comprising a plurality of input datasets, each associated with a corresponding optical response, each input dataset comprising position data and optical data of phase objects arranged according to said stack within an objective, the corresponding optical response forming an expected output for said input dataset;

[0028] the phase objects of the same stage of the objectives of the batch of objectives were previously manufactured in the same predetermined time window.

[0029] According to another aspect of the invention, there is provided a computer program comprising executable instructions which, when executed by a computer, implement the steps of the method as defined above.

[0030] The computer program can be in any computer language, such as machine language, C, C++, JAVA, Python, etc.

[0031] According to another aspect of the invention, there is provided a calculation unit for calibrating at least one batch of lenses, each lens of the batch comprising an assembly element and a plurality of phase objects staged according to a predetermined stack and mounted in the assembly element, the batch of lenses being such that, for two lenses of said batch, the respective phase objects of the same stage of the stack have been manufactured according to the same manufacturing process, the calculation unit being configured to: - calculate position data representative of an effective position of each phase object in the assembly element of a objective of the set of objectives, from geometric data of each phase object, the geometric data of each phase object being indicative of a shape: • at least one diopter of a phase object positioned on said stage; • a first support surface for said phase object on an internal face of the assembly element; and / or • a second support surface of said phase object on a neighboring phase object; - simulating at least one optical response associated with the batch of objectives, from the calculated position data and optical data of each phase object, the optical data of each phase object relating to a refractive index as a function of a position in said phase object; and - store each simulated optical response in a memory, in association with an identifier of the batch of objectives.

[0032] According to another aspect of the invention, there is provided a method for correcting an image acquired by means of a camera module comprising a lens and a sensor, the sensor being arranged to acquire an image of a scene observed through the lens, the lens belonging to a predetermined batch associated with an optical response simulated by the implementation of the calibration method as defined above, the correction method comprising a generation of a corrected image from the acquired image and the simulated optical response associated with the batch to which the lens of the camera module belongs.

[0033] Advantageously, the correction method according to the invention has the following characteristic:

[0034] the generation of the corrected image includes a deconvolution of the image acquired by the optical response.

[0035] According to another aspect of the invention, there is provided an imaging system comprising a processing unit and at least one camera module, each camera module comprising a lens and a sensor, the sensor being arranged to acquire an image of a scene observed through the lens, the processing unit being configured to store, for each camera module, a simulated optical response corresponding to the batch of lenses to which the lens of said camera module belongs, the processing unit also being configured to generate, for each image acquired by a camera module of the imaging system, a corrected image from the acquired image and the simulated optical response associated with the batch to which the lens of the camera module belongs.

[0036] Preferably, the imaging system is a smart mobile phone (or "smartphone" in English), also called a ordiphone or multifunction mobile phone).

[0037] In this case, the invention also relates to a use of a correction method according to the invention, within the smart mobile telephone, to correct an image acquired by means of a camera module included in the smart mobile telephone.

[0038] Alternatively, the imaging system is a touchscreen tablet.

[0039] In this case, the invention also relates to a use of a correction method according to the invention, within a touchscreen tablet, to correct an image acquired by means of a camera module included in the touchscreen tablet.

[0040] Alternatively, the imaging system is a computer.

[0041] In this case, the invention also relates to a use of a correction method according to the invention, within the computer, to correct an image acquired by means of a camera module included in the computer.

[0042] Alternatively, the imaging system is a television or display terminal.

[0043] In this case, the invention also relates to a use of a correction method according to the invention, within the television or the display terminal, to correct an image acquired by means of a camera module included in the television or the display terminal.

[0044] Alternatively, the imaging system is a virtual reality headset or an augmented reality headset.

[0045] In this case, the invention also relates to a use of a correction method according to the invention, within the virtual reality headset or the augmented reality headset, to correct an image acquired by means of a camera module included in the virtual reality headset or the augmented reality headset.

[0046] Alternatively, the imaging system is a medical imaging system, for example an endoscope.

[0047] In this case, the invention also relates to a use of a correction method according to the invention, within the medical imaging system, to correct an image acquired by means of a camera module included in the medical imaging system.

[0048] Alternatively, the imaging system is included in a vehicle, autonomous or not, such as a land vehicle (e.g., a car), an aircraft (e.g., a drone, an airplane, a helicopter, etc.) or a maritime vehicle (e.g., a boat, a submarine, etc.).

[0049] In this case, the invention also relates to a use of a correction method according to the invention, within the vehicle, to correct an image acquired by means of a camera module included in the vehicle. Brief description of the figures

[0050] The invention will be better understood on reading the description which follows, given solely as a non-limiting example and made with reference to the appended drawings in which:

[0051] Figure 1 is a schematic representation of an imaging system according to the invention;

[0052] Figure 2 is a sectional representation of a lens of the imaging system of Figure 1, along a longitudinal plane of the lens; and

[0053] Figure 3 is a flowchart of a calibration method according to the invention.

[0054] It is understood that the embodiments which will be described below are in no way limiting. In particular, it is possible to imagine variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection includes at least one preferably functional characteristic without structural details, or with only part of the structural details if it is this part which is only sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0055] In particular, all the variants and embodiments described can be combined with each other if there is no technical obstacle to this combination.

[0056] In the figures and in the rest of the description, the elements common to several figures retain the same reference. Detailed description

[0057] An imaging system 2 according to the invention is illustrated in Figure 1.

[0058] The imaging system 2 is intended to acquire at least one image. For example, the imaging system 2 is a digital camera, a video camera, a smartphone, a tablet, a computer, a medical imaging system, etc.

[0059] The imaging system 2 comprises at least one camera module 4 for acquiring images. In addition, the imaging system 2 comprises a processing unit 6 intended, in particular, to correct all or part of the images acquired by means of the camera module 4.

[0060] Each camera module 4 comprises a lens 8 associated with a sensor 10. More precisely, the sensor 10 is arranged to acquire an image of a scene observed through the lens 8.

[0061] Typically, the sensor 10 comprises a matrix of photodetectors (also called “photosites”).

[0062] Preferably, the sensor 10 is a so-called “color filter array” sensor. In this case, the sensor 10 comprises, in addition to the photosite matrix, a mosaic of colored filters arranged on the photosite matrix, each colored filter being placed opposite a respective photosite so that the light rays coming from the lens first pass through the mosaic of colored filters before reaching the photosite matrix.

[0063] For example, the mosaic of colored filters is a regular mosaic whose elementary pattern forms a Bayer matrix. Such a Bayer matrix consists of four filters, arranged in two rows of two filters. In this case, two green filters (i.e., rejecting photons outside the green range) form the diagonal of the matrix, while the other two locations are respectively occupied by a blue filter (rejecting photons outside the blue range) and a red filter (rejecting photons outside the red range).

[0064] Such a sensor 10 has the advantage of detecting several color bands through a single lens 8 which projects the observed scene onto the plane of said sensor 10.

[0065] As illustrated in Figure 2, the lens 8 comprises an assembly element 14 and a plurality of phase objects 16. Preferably, the lens 8 further comprises at least one shim 17, in particular at least one annular shim.

[0066] The objective 8 belongs to a corresponding batch of objectives, which is associated with a predetermined stack of the phase objects 16 (and, possibly, of the or each shim 17), conforming to a target geometry. Such a target geometry depends, in particular, on desired performances and / or behavior for each objective 8 belonging to said batch of objectives.

[0067] Furthermore, the batch of lenses is such that, for two lenses belonging to said batch, the respective phase 16 objects of the same stage of the stack were manufactured using the same manufacturing process.

[0068] Advantageously, the phase 16 objects of the same stage of the objectives of the same batch of objectives have been previously manufactured during the same predetermined time window. Such a characteristic is advantageous, insofar as it leads to grouping, in the same batch, a plurality of objectives for which the manufacturing processes are assumed to have changed little during the predetermined time window. In this way, the objectives of the same batch are assumed to have the same optical response, and a single calibration is required for all the objectives of the same batch.

[0069] As a result, a given lot is likely to include a single objective, or several.

[0070] As shown in the figure, the assembly element 14 comprises a wall 18 radially delimiting a cavity 20. The cavity 20 opens onto the outside via the two ends of the assembly element 14, so as to allow the propagation of light rays coming from the scene to the sensor 10. For example, the assembly element 14 is monobloc, i.e. made from a single piece. Alternatively, the assembly element 14 comprises several parts assembled together (for example, by screwing or interlocking) to form the assembly element 14. In this case, said parts advantageously have shapes allowing them to be centered relative to each other during their assembly.

[0071] Preferably, the wall 18 comprises, on its internal face 22 oriented towards the cavity 20, a plurality of reliefs 24, such as shoulders, intended to cooperate with the phase objects 16 and / or the wedges 17 of the objective 8.

[0072] As shown in the figure, the assembly element 14 is likely to be in the form of a barrel having the general shape of a cylinder extending along an axis D.

[0073] The phase objects 16 are staggered according to the predetermined stacking associated with the respective batch of objectives, and mounted in the assembly element 14 (more precisely, in its cavity 20).

[0074] Preferably, the predetermined stacking is such that the optical axes of the phase objects 16 are coincident, and aligned with a longitudinal axis of the assembly element 14.

[0075] Each phase 16 object has characteristics that give it the ability to locally modify the phase of the light passing through it.

[0076] Preferably, at least one phase object 16 is a lens.

[0077] In particular, at least one lens is produced by molding. In this case, for two lenses of the same batch, the respective lenses of the same stage of the stack come from the same cavity of the same mold.

[0078] Alternatively, or in addition, at least one phase object 16 is an element structured so as to have predetermined optical properties. Such a structured element has surface or volume patterns, the dimensions of which are typically of the same order of magnitude as the wavelength of the light with which the structured element is intended to interact. Such patterns are, for example, produced by etching, pressing, masking and deposition, or any other suitable technique known to those skilled in the art. Such patterns give the structured element its optical properties, in particular the ability to locally modify the phase of the light passing through it. In this way, the structured element forms a phase object, capable of behaving, for example, like a conventional lens. For example, the structured element has a general disc shape.

[0079] As shown in the figure, each phase object 16 bears against the internal face 22 of the assembly element 14, against a neighboring phase object 16 and / or against a wedge 17, for its positioning in the cavity 18.

[0080] Preferably, at least one phase object 16 comprises a first bearing surface 30 of said phase object 16 on the internal face 22 of the assembly element 14.

[0081] For example, the first bearing surface 30 comprises a peripheral portion of the phase object 16 extending in a plane orthogonal to a theoretical optical axis of the phase object 16. Alternatively, or additionally, the first bearing surface 30 comprises a peripheral edge of the phase object 16.

[0082] Furthermore, at least one phase object 16 comprises a second bearing surface 32 of said phase object 16 against a neighboring phase object 16.

[0083] Preferably, such a second bearing surface 32 has a frustoconical shape, the axis of which is, preferably, the theoretical optical axis of the phase object 16.

[0084] Advantageously, each first bearing surface 30 and / or second bearing surface 32 allows, due to its design, mechanical centering of the corresponding phase object 16 in the assembly element 14.

[0085] In addition, each phase object 16 includes diopters 34 for the entry and exit of light rays.

[0086] Each diopter 34 is positioned in a central part of the phase object 16. In the case of a lens, each corresponding diopter 34 generally has an axisymmetric profile of the aspherical type.

[0087] As indicated previously, the objective 8 is likely to comprise at least one wedge 17. In this case, each wedge 17 is arranged between two respective predetermined stages of the stack associated with the objective 8.

[0088] In particular, each wedge 17 is arranged between two corresponding phase objects 16 to space said phase objects 16 by a predetermined distance.

[0089] In this case, each shim 17 has a predetermined thickness, defined, for example, as the gap, in a direction parallel to the axis of the assembly element 14, that the shim 17 imposes between the two phase objects 16 which are adjacent to it.

[0090] Furthermore, each wedge 17 comprises, for each adjacent phase object 16, an auxiliary support surface 36 at the level of which said phase object 16 bears against the wedge 17, by a corresponding surface.

[0091] For example, each auxiliary bearing surface 36 also has a frustoconical shape (with an axis formed by an axis of revolution of the wedge) to contribute to the mechanical centering of each adjacent phase object 16 in the assembly element 14.

[0092] For example, each shim 17 further comprises a bearing surface against the internal face 22 of the assembly element.

[0093] According to another example, at least one shim 17 has the shape of a flat washer having the function of ensuring a predetermined spacing between two successive phase objects 16 of the stack, without constraining their centering. In this case, preferably, the shim does not have a frustoconical shape. In addition, the shim 17 is likely to have no contact surface with the assembly element 14.

[0094] Each objective 8 is associated with an optical response of the respective batch of objectives, said optical response having been previously simulated using a calibration method 40 according to the invention, illustrated by figure 3.

[0095] Such a calibration method 40 is implemented by a calculation unit (not shown) and comprises, as appears in the figure, a step 42 of obtaining data (called “loading step”), a step 44 of calculating position (called “calculation step”), a step 46 of simulating optical response (called “simulation step”) and a storage step 48. Loading step 42

[0096] More precisely, the calculation unit is configured to obtain, during the loading step 42, for at least one objective 8 of any given batch of objectives, and for each stage of the respective stack: - geometric data relating to the phase 16 object positioned on said floor; and - optical data relating to a refractive index as a function of a position in said phase object 16.

[0097] In particular, the refractive index is the refractive index along an optical axis of the phase 16 object, i.e. in a central part of the phase 16 object.

[0098] Such geometric and optical data have, for example, been measured beforehand by an operator, preferably for the same objective of the batch, and recorded in a memory accessible to the calculation unit. Alternatively, the geometric and optical data have been measured beforehand for a plurality of objectives of the batch. In this case, the geometric and optical data used in the remainder of the calibration method 40 are, for example, an average of the geometric and optical data measured for each objective of the plurality of objectives.

[0099] For each phase object 16, such geometric data are indicative of a shape of at least one respective diopter 34, of a shape of the respective first bearing surface 30, and / or of a shape of the respective second bearing surface 32.

[0100] Preferably, such geometric data are further indicative of an angular position of the phase object 16 in the assembly element 14.

[0101] By "angular position" of a phase object, it is understood, for the purposes of the present invention, three angles between two predetermined radii of the assembly element 14 and two predetermined radii of said phase object 16.

[0102] By "radius of the assembly element" is meant an axis or a segment perpendicular to the longitudinal axis of said assembly element.

[0103] Furthermore, by "radius of the assembly element" is meant an axis perpendicular to the assembly axis of a phase object.

[0104] It is advantageous to define two radii perpendicular to each other for each of the assembly elements and phase object, in order to obtain three angular position angles (namely a tip angle, a tilt angle, and a rotation angle) to completely define the angular position of the phase object relative to the assembly element.

[0105] Preferably, in the case where the objective 8 comprises at least one wedge 17, the calculation unit is also configured to obtain geometric data relating to each wedge 17.

[0106] For each shim 17, such geometric data are indicative of a thickness of the shim, of a shape of each bearing surface of the shim on the internal face 22 of the assembly element and / or of a shape of each auxiliary bearing surface 36 of the shim on a neighboring phase object 16. Calculation step 44

[0107] The calculation unit is also configured to calculate, during the calculation step 44, position data for any objective of the batch of objectives, from the geometric data obtained at the end of the loading step 42.

[0108] Such position data is representative of an actual position (i.e., an expected actual position) of each phase object 16 in the assembly element 14 of each lens 8 of the lens set.

[0109] In the case where the objective comprises at least one wedge 17, the calculation unit is configured to take into account the geometric data relating to each wedge to calculate the position data.

[0110] Such position data arise from the mechanical interaction of the different elements of the lens 8 with each other, through their respective support surfaces: - first bearing surface 30 of each phase object 16 with the internal face 22 of the assembly element 14; - second bearing surface 32 of each phase object 16 with the or each adjacent phase object 16; - auxiliary bearing surface 36 of each wedge 17 with the corresponding surface of each adjacent phase object 16; and / or - bearing surface of each wedge 17 with the internal face 22 of the assembly element 14.

[0111] As a result, during the calculation step 14, the calculation unit determines in particular, for each phase object 16: - an error in the position of the center of each of the two corresponding faces relative to the center of support of said phase object 16 on the assembly element 14 (in English, “lens shift”); and / or - an inclination of the two faces of the phase 16 object relative to the common support plane (in English, “lens tilt”).

[0112] Such a position error results in an offset of the optical axis of the phase object 16 from its expected direction (i.e., a translation along a vector orthogonal to the expected direction). Such an expected direction is, in particular, but not necessarily, an axis common to all the phase objects.

[0113] Such a position error between the actual position of the center of each face and the assembly center is also likely to result in one or two rotation angles of the phase object relative to the assembly element.

[0114] Furthermore, such an inclination results in the existence of two angles between the optical axis of the phase object 16 and its expected direction, or two angles between the optical axis of the phase object and its assembly axis. Furthermore, a third rotation angle of the phase object relative to the assembly element is preferentially taken into account during the calculations.

[0115] Advantageously, in order to calculate the position data, the calculation unit is also configured to take into account the mechanical properties of the materials from which the phase objects 16, the shims 17 and / or the assembly element 14 are made so as to, by balancing the mechanical constraints between said members, calculate more precisely the positions of the phase objects 16.

[0116] For example, the computing unit 42 is configured to implement mechanical simulation software to calculate said position data.

[0117] The calculation unit is also configured to simulate, during the simulation step 46, at least one optical response associated with the batch of objectives, from the optical data obtained during the loading step 42 and the position data calculated during the calculation step 44.

[0118] Preferably, the at least one simulated optical response associated with the set of objectives comprises at least: - a distortion map induced by a lens of said batch in a predetermined reference plane; and / or - an optical transfer function of said objective between at least one point in space and the reference plane.

[0119] Preferably, the reference plane is a plane orthogonal to a target optical axis of the lens and is located at a predetermined distance from said lens. In particular, the reference plane is the plane in which the sensor 10 extends.

[0120] Preferably, the optical transfer function is the spatial impulse response (in English, “point spread function”) of the objective 8.

[0121] Advantageously, the calculation unit is configured to calculate each simulated optical response for a respective range of wavelengths. Such a feature is advantageous, insofar as it allows the chromatic aberrations induced by the objective 8 to be taken into account.

[0122] In this case, each wavelength range is preferably a bandwidth of a filter of the color filter array of the sensor 10.

[0123] Preferably, to simulate each optical response, the computing unit is configured to implement optical simulation software.

[0124] Alternatively, or in addition, the computing unit is configured to implement an artificial intelligence model, called an “optical response model”, in order to simulate each optical response. In this case, the computing unit is configured to provide the position data and the optical data as input to the optical response model in order to obtain, as output, each optical response.

[0125] More specifically, each optical response model is associated with a corresponding stack and is configured to produce, as output, a simulated optical response associated with said position data and optical data. In this case, the optical response model has been previously trained based on a training dataset comprising a plurality of input datasets, each associated with a corresponding optical response. Each input dataset comprises position data and optical data of phase objects arranged according to the predetermined stack associated with the lens bundle. Furthermore, the corresponding optical response forms an expected output for said input dataset. Storage step 48

[0126] The computing unit is also configured to write, during the storage step 48, each simulated optical response in a memory, in association with an identifier of the batch of objectives.

[0127] In particular, each simulated optical response associated with the batch corresponding to each objective 8 of the imaging system 2 is written in the processing unit 6 of said imaging system 2.

[0128] In this case, the processing unit 6 is configured to implement a correction method for correcting at least one image acquired by means of a respective camera module 4 of the imaging system 2, on the basis of at least one simulated optical response associated with the batch from which the lens 8 of said camera module 4 originates.

[0129] More precisely, the processing unit 6 is configured to generate a corrected image from the acquired image and the simulated optical response associated with the batch to which the lens 8 of the camera module 4 having acquired said acquired image belongs.

[0130] Preferably, the processing unit 6 is configured to generate the corrected image by deconvolving the image acquired through an objective 8 by the optical response associated with said objective 8 (more precisely associated with the batch to which the objective 8 belongs). Functioning

[0131] The operation of the computing unit and the imaging system 2 will now be described, with reference to the figures.

[0132] During a preliminary measurement step, and for each batch of lenses, an operator measures the geometric and optical data relating to at least one lens of said batch.

[0133] For each batch, the corresponding measured geometric and optical data are stored in a geometric and optical data memory.

[0134] Then, during the loading step 42, the calculation unit loads, from the memory, for each batch of objectives, the geometric and optical data relating to each phase object 16 of each stage of the respective stack.

[0135] Preferably, in the case where the objective 8 comprises at least one wedge 17, the calculation unit also loads the geometric data relating to each wedge 17.

[0136] Then, during the calculation step 44, for each batch of objectives, the calculation unit calculates, from the geometric data obtained during loading step 42, the position data associated with the objectives of the batch of objectives.

[0137] Then, during the simulation step 46, for each batch of objectives, the calculation unit simulates at least one associated optical response, from the optical data obtained during the loading step 42 and the position data calculated during the calculation step 44.

[0138] Then, during the storage step 48, for each batch of objectives, the calculation unit writes each corresponding simulated optical response into an optical response memory, in association with an identifier of the batch of objectives.

[0139] In particular, each simulated optical response associated with the batch corresponding to each objective 8 of the imaging system 2 is written in the processing unit 6 of said imaging system 2.

[0140] In this case, in response to the acquisition of an image by means of a camera module 4 of the imaging system 2, the processing unit 6 implements the correction method described previously to correct said image from the or each simulated optical response associated with the batch from which the lens 8 of said camera module 4 comes.

[0141] Preferably, the processing unit 6 generates the corrected image by deconvolving the image acquired by the optical response associated with the lens 8 of the camera module which acquired said image.

[0142] Of course, the invention is not limited to the examples which have just been described.

Claims

CLAIMS 1. Method (40) for calibrating a batch of lenses, each lens (8) of the batch comprising an assembly element (14) and a plurality of phase objects (16) arranged in a predetermined stack and mounted in the assembly element (14), the batch of lenses being such that, for two lenses (8) of said batch, the respective phase objects (16) of the same stage of the stack have been manufactured using the same manufacturing process, the calibration method (40) being implemented by computer and comprising the steps: - for each level of the stack, obtaining (42): • geometric data indicative of a shape: o of at least one diopter (34) of a phase object (16) positioned at said stage; o of a first bearing surface (30) of said phase object (16) on an internal face (22) of the assembly element (14); and / or o of a second bearing surface (32) of said phase object (16) on a neighboring phase object (16); • optical data relating to a refractive index as a function of a position in said phase object (16); - calculation (44), from the geometric data of each phase object, of position data representative of an effective position of each phase object in the assembly element of a lens of the batch of lenses; - simulation (46), from the calculated position data and the obtained optical data, of at least one optical response associated with the batch of objectives; and - storage (48) of each simulated optical response in a memory, in association with an identifier of the batch of objectives.

2. Method according to claim 1, wherein, for each stage of the stack, the geometric data relating to the phase object (16) positioned at said stage are, in addition, indicative of an angular position of said phase object (16).

3. Method according to claim 1 or 2, in which at least one phase object (16) is a lens, the batch of lenses being such that, for two lenses (8) of said batch, the respective lenses of the same stage of the stack come from the same cavity of the same mold.

4. Method according to any one of claims 1 to 3, wherein the stack comprises at least one shim (17), each shim (17) being arranged between two respective predetermined stages of the stack, the method further comprising, for each shim (17), obtaining respective geometric data indicative of a thickness of the shim (17), of a shape of each bearing surface of the shim (17) on the internal face (22) of the assembly element (14) and / or of a shape of each auxiliary bearing surface (36) of the shim (17) on a neighboring phase object (16), the position data also depending on the geometric data relating to each shim (17).

5. Method according to any one of claims 1 to 4, in which the at least one simulated optical response associated with the batch of objectives comprises at least: - a distortion map induced by a lens (8) of said batch in a predetermined reference plane, the reference plane being orthogonal to a target optical axis of the lens (8) and located at a predetermined distance from said lens (8); and / or - an optical transfer function of an objective (8) of said batch between at least one point in space and the reference plane.

6. A method according to any one of claims 1 to 5, wherein each simulated optical response is associated with a respective range of wavelengths.

7. A method according to any one of claims 1 to 6, wherein the simulating step (46) comprises providing the position data and the optical data as input to an artificial intelligence model, forming an optical response model, the optical response model being associated with the stack and being configured to produce, as output, a simulated optical response associated with said position data and optical data, the optical response model having been previously trained on the basis of a training data set comprising a plurality of input data sets, each associated with a corresponding optical response, each input data set comprising position data and optical data of phase objects arranged according to said stack within a lens, the corresponding optical response forming an expected output for said input data set.

8. Method according to any one of claims 1 to 7, in which the phase objects (16) of the same stage of the objectives (8) of the batch of objectives have been previously manufactured in the same predetermined time window.

9. A computer program comprising executable instructions which, when executed by a computer, implement the steps of the method according to any one of claims 1 to 8.

10. Calculation unit for calibrating at least one batch of lenses, each lens (8) of the batch comprising an assembly element and a plurality of phase objects staged in a predetermined stack and mounted in the assembly element, the batch of lenses being such that, for two lenses of said batch, the respective phase objects of the same stage of the stack have been manufactured using the same manufacturing process, the calculation unit being configured to: - calculating position data representative of an effective position of each phase object (16) in the assembly element of a lens of the batch of lenses, from geometric data of each phase object, the geometric data of each phase object being indicative of a shape: • at least one diopter of a phase object (16) positioned at said stage; • a first support surface for said phase object (16) on an internal face of the assembly element; and / or • a second support surface of said phase object (16) on a neighboring phase object (16); - simulating at least one optical response associated with the batch of objectives, from the calculated position data and optical data of each phase object, the optical data of each phase object relating to a refractive index as a function of a position in said phase object; and - store each simulated optical response in a memory, in association with an identifier of the batch of objectives.

11. Method for correcting an image acquired by means of a camera module (4) comprising a lens (8) and a sensor (10), the sensor (10) being arranged to acquire an image of a scene observed through the lens (8), the lens (8) belonging to a predetermined batch associated with an optical response simulated by the implementation of the calibration method according to any one of claims 1 to 8, the correction method comprising a generation of a corrected image from the acquired image and the simulated optical response associated with the batch to which the lens (8) of the camera module (4) belongs.

12. Correction method according to claim 11, wherein the generation of the corrected image comprises a deconvolution of the image acquired by the optical response.

13. Imaging system (2) comprising a processing unit (6) and at least one camera module (4), each camera module (4) comprising a lens (8) and a sensor (10), the sensor (10) being arranged to acquire an image of a scene observed through the lens (8), the processing unit (6) being configured to store, for each camera module (4), a simulated optical response corresponding to the batch of lenses to which the lens (8) of said camera module (4) belongs, the processing unit (6) also being configured to generate, for each image acquired by a camera module (4) of the imaging system (2), a corrected image from the acquired image and the simulated optical response associated with the batch to which the lens (8) of the camera module (4) belongs.

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