Method and system for characterising at least one optical aberration in an optical lens with a view to correcting it by means of digital processing

Abstract

The invention relates to a method (100) for characterising an optical lens (OO) used for imaging, the method (100) comprising: - a step (104) of measuring, with an image sensor, a lateral chromatic aberration function, LCAF, of the optical lens (OO); and / or - a step (108) of measuring, with an image sensor, a geometric aberration function, GAF, of the optical lens (OO); with a view to at least partially correcting at least one, and in particular each, of the aberrations in an image acquired with the optical lens (OO), after the image has been acquired, by means of digitally processing the image. The invention also relates to a system implementing such a method. The invention further relates to a method and a facility for manufacturing optical lenses implementing such a characterisation method and system. The invention further relates to a method for acquiring an image with a lens characterised by such a characterisation method and system.

Description

DESCRIPTION Title: Method and system for characterizing at least one optical aberration of an optical lens with a view to correcting it by digital processing

[0001] The present invention relates to a method for characterizing at least one optical aberration of an optical lens, with a view to correcting it by digital processing. It also relates to a system implementing such a method. It further relates to a method and an installation for manufacturing optical lenses implementing such a method and characterization system. It further relates to a method for acquiring an image with a lens characterized by such a method and characterization system.

[0002] The field of the invention is generally the field of characterizing an optical lens, in particular an optical lens used for imaging, with a view to correcting at least one optical aberration. State of the art

[0003] An optical lens, or lens in the following, consists of several optical elements, such as lenses, spacers, etc., stacked in a barrel in a stacking direction. Once manufactured, the optical lens undergoes a performance test to determine whether the imaging quality of the lens is satisfactory or not. If the quality of the lens is not satisfactory, the lens is simply discarded, which decreases manufacturing efficiency, causing a waste of time and cost.

[0004] Currently, the quality of an optical lens is tested by measuring the modulation transfer function, MTF (for "Modulation Transfer Function"), said function being dependent on all the optical aberrations of the optical lens.

[0005] However, the MTF does not allow to give the values ​​of optical aberrations. Therefore, it is very difficult, sometimes impossible, to carry out a correction of optical aberration(s) introduced into an image taken with an optical lens, by digital processing of said image.

[0006] An aim of the present invention is to remedy at least one of the aforementioned drawbacks.

[0007] Another aim of the invention is to propose a solution for characterizing an optical objective making it possible to determine at least one optical aberration which can be corrected by digital processing.

[0008] Another aim of the invention is to propose a solution for characterizing an optical objective making it possible to facilitate the correction, by digital processing, of at least one optical aberration.

[0009] Another aim of the invention is to propose a solution for characterizing an optical objective making it possible to increase the quality of images taken with said optical objective, by digital processing. Statement of the invention

[0010] The invention proposes to achieve at least one of the aforementioned aims by a method of characterizing an optical objective used for imaging, said method comprising: - a step of measuring, with an image sensor, at least one lateral chromatic aberration function, FACL, of said optical lens, and / or - a step of measuring, with an image sensor, at least one geometric aberration function, FAG, of said optical lens; with a view to correcting, at least partially, at least one, and in particular each, of said aberrations in an image acquired with said optical lens, by digital processing of said image.

[0011] Thus, the invention proposes to individually measure the lateral chromatic aberration and / or the geometric aberration of the optical lens so as to know these aberrations individually, that is to say without them being mixed with other aberrations. By knowing each of these aberrations individually, it is possible to correct them by digital processing of an image acquired with the optical lens. It is also possible, during the manufacture of the optical lens, to deduce, for each of these aberrations, a correction function allowing the aberration to be corrected. This or these correction functions can be used to correct these aberrations in each of the images taken with the optical lens by digital image processing.

[0012] Indeed, the inventors have noticed that certain optical aberrations, called displacement aberration, or "displacement aberration" in the following, can be corrected very effectively by digital processing of an image. The correction of these aberrations makes it possible to improve the quality of an image acquired with the optical objective.

[0013] By "optical aberration" we mean the notion that the image of a point in the scene becomes a more or less large luminous spot in the place (generally plane) where the image is formed. Aberration results in different types of effects: there are aberration effects whose characteristic is to move the average position of the optical spot produced by a point in the scene, in relation to a place where we would ideally have wanted it to occur. We will call them displacement aberrations. There are other effects which are that the optical spot has a spatially spread energy distribution, instead of being punctual, in the image place. We will call them spreading aberration.

[0014] Aberrations due to an optical lens are commonly referred to as chromatic aberration, geometric aberration and 3D aberration. ème order.

[0015] By "aberrations of 3 èmeorder”, we mean the set of aberrations introduced by an optical lens in an image acquired with said optical lens, except chromatic aberration and geometric aberration. These aberrations of the 3 ème order (and higher order) include for example spherical aberration, Coma, astigmatism, field curvature, distortion (of shape and energy distribution of the optical spot), etc. These aberrations of the 3 ème order (and following order) are of spreading type. In the following, for brevity, the expression "aberrations of the 3 ème order" designates the aberrations of the 3 ème order and following order.

[0016] By "chromatic aberration", which results from the decomposition of light into several bands of colors, we mean an optical aberration that produces different positions in space of the focal point depending on the wavelength. For a so-called "lateral" chromatic aberration, this is a displacement of the focal point in the image location, depending on the wavelength. We then observe an image with iridescent contours, or colored fringes around objects of uniform color, for example white. For a so-called "axial" chromatic aberration, this is a focusing outside the image location because the focal points are shifted along an axis perpendicular to the image location (or the axis corresponding to the central optical ray arriving at the image point, which may be oblique to the image location). We then observe an image in which certain colors are blurred.Lateral chromatic aberration can be corrected by digital processing of the image captured by a lens as long as it is quantified, i.e. measured during the design / manufacture of the optical lens. It is similar to displacement-type aberrations. Axial chromatic aberration, on the other hand, is similar to spreading-type aberrations, because if, for example, the green color is focused on the image plane sensor, the red color can focus before, and the red optical beam becomes widened when it meets the sensor further than the focal point.

[0017] Geometric aberration means a deviation between a paraxial ray defined in the Gaussian approximation and the corresponding real ray. Geometric aberration can also be characterized by a deviation between the paraxial wave surface and the real wave surface. For example, geometric aberrations produce a distortion of the shape of the resulting image. For example, a square can become a shape equal to the outline of a barrel (turned corners), or a dressmaker's cousin (growths on the corners). Thus, the straight and vertical edges of a building can become curved, not vertical. This aberration can be corrected by digital processing of the captured image as soon as it is quantized, i.e. measured during the design / manufacturing of the optical lens. Geometric aberrations are of the displacement type.

[0018] By "displacement aberration" or "displacement aberration" we mean lateral chromatic aberration and geometric aberration.

[0019] By "spreading-type aberration" or "spreading aberration" is meant axial chromatic aberration and aberrations of the 3 ème order.

[0020] The measured FACL can be in any form.

[0021] According to embodiments, the FACL may be in the form of a field of values ​​comprising, for each of several positions (x,y) of the image sensor, at least one displacement vector. According to an exemplary embodiment, for at least one position (x,y), the field of values ​​may comprise: - a displacement vector measured for the color red, - a displacement vector measured for the green color, and - a displacement vector measured for the color blue; relative to a reference position. The reference position can be any previously chosen position. For example, the reference position can be a barycenter of the positions of the three colors.

[0022] According to an exemplary embodiment, the position of one of the three colors can be chosen as a reference. In this case, for at least one position (x,y), the value field can include a displacement vector for each of the other two colors. For example, the position of the color green can be chosen as a reference: in this case, for at least one position (x,y), the value field can include a displacement vector for the color red and a displacement vector for the color blue.

[0023] Alternatively, the FACL can be a mathematical function taking as input a position (x,y) of the sensor and providing one or more displacement vectors, such as those indicated above.

[0024] FACL measurement can be performed in different ways.

[0025] According to embodiments, a target formed of patterns, such as dots, lines, etc., may be positioned in front of the optical lens, to a measuring plane. The target is illuminated by white radiation, or successively by green, red and blue radiation. A pattern corresponding to a position (x,y) of the image sensor, generates on said image sensor a spot for each of the colors. The position of each color spot can be detected by the image sensor. The detected positions of the three color spots are then used to calculate a displacement vector, relative to a reference position, which can be the position of one of said three spots, or another position.

[0026] By performing, simultaneously or in turn, the measurement for several positions (x,y) in the sensor plane, also called the image plane, it is then possible to determine the FACL.

[0027] According to embodiments, the FACL may be measured for all positions of the image sensor. Alternatively, the FACL may be measured for only certain positions of the image sensor.

[0028] The measured FAG can be in any form.

[0029] According to embodiments, the FAG can be presented in the form of a field of values ​​comprising, for several angles (0i,yi) relative to the axis of the optical lens at least one displacement distance (with 0i the angle relative to the axis of the optical lens and yi the angle of rotation around said optical axis). According to an exemplary embodiment, for at least one angle (0i,yi), the field of values ​​can comprise: - a travel distance measured for the color red, - a travel distance measured for the green color, and - a displacement distance measured for the blue color; relative to the center of the image sensor.

[0030] According to an exemplary embodiment, for at least one angle (0i,yi), the field of values ​​may comprise a single displacement distance, obtained from the displacement distances for the three colors, for example an average of said displacement distances.

[0031] Alternatively, the FAG can be a mathematical function taking as input an angle (0i,yi) and providing a single travel distance for all three colors, or a travel distance individually for each color.

[0032] FAG measurement can be performed in different ways.

[0033] According to embodiments, a target formed of patterns, such as points, lines, etc., can be positioned in front of the optical lens, at a measurement plane. The target is illuminated by white radiation, or successively by green, red and blue radiation. A pattern located at an angle (0i,yi) relative to the axis of the optical lens, generates on said image sensor a spot for each of the colors red, green and blue. The position of each color spot can be detected by the image sensor. The detected positions of the three spots are then used to calculate a displacement distance for each color, relative to the center of the optical lens. Optionally, the displacement distance can be divided by the focal length, so as to obtain an angular magnitude as a function of the angle 0i of the optical beam entering the optical lens relative to the axis of the optical lens.

[0034] By performing, simultaneously or in turn, the measurement for several angles 0i with respect to the optical axis of the optical objective, it is possible to determine the FAG.

[0035] According to embodiments, the FAG may be measured for all positions of the image sensor. Alternatively, the FAG may be measured for only certain positions of the image sensor.

[0036] According to embodiments, the method according to the invention may comprise a step of providing at least one lateral chromatic aberration correction function, FCACL, as a function of the measured lateral chromatic aberration.

[0037] According to embodiments, the FCACL may be in the form of a field of values ​​comprising, for each of several positions (x,y) of the image sensor, at least one displacement vector to be applied to correct said lateral chromatic aberration at said position. For at least one position (x,y) of the sensor, the FCALC may comprise: - a single displacement vector for each of the colors red, green and blue; or - for at least one of said colors, a displacement vector dedicated to said color.

[0038] Alternatively, the FCACL may be a mathematical function taking as input the position (x,y) of the image sensor and providing one or more displacement vectors to be applied to correct said aberration at said position (x,y).

[0039] According to yet another alternative, the FCACL can be presented in the form of a correspondence table indicating, for each of several pixels of the image sensor, a corrected position of said pixel and this individually: - for each color, or - for the red color and for the blue color in the case where the green color is taken as a reference.

[0040] According to embodiments, the method according to the invention may comprise a step of providing at least one geometric aberration correction function, FCAG, as a function of the measured geometric aberration.

[0041] According to embodiments, the FCAG may be presented in the form of a field of values ​​comprising, for each of several angles (0i,yi), at least one distance vector to be applied to correct said geometric aberration. For at least one angle (Oi,yi), the FCAG may comprise: - a single distance correction value to be applied for each of the red, green and blue colors; or - for at least one of said colors, a distance correction value dedicated to said color.

[0042] Alternatively, the FCAG can be a mathematical function taking as input an angle (0i,yi) relative to the axis of the optical objection and providing one or more distance correction values.

[0043] Following yet another alternative, the FCAG can be presented in the form of a correspondence table indicating, for each of several pixels of the image sensor, a corrected position of said pixel and this individually for each color.

[0044] According to embodiments, the step of providing at least one correction function can provide: - an individual correction function for lateral chromatic aberration, and / or - an individual correction function for geometric aberration.

[0045] Thus, these aberrations can be corrected individually in a desired order. For example, it may be useful to correct lateral chromatic aberration first, before correcting geomatic aberration, or vice versa.

[0046] According to embodiments, the step of providing at least one correction function may provide a common correction function for lateral chromatic aberration and / or for geometric aberration.

[0047] In this case, applying this single correction function will correct both ACL and GA. In this case, applying this single correction function will correct both ACL and GA. A common correction function allows correction to be performed on all colors, without having to define what is chromatic and what is geometric.

[0048] Furthermore, with this common correction function, it is possible to achieve better correction and avoid over-correction. Indeed, according to an example of implementation, the application of a lateral chromatic aberration correction at a point (x,y) can partially or completely correct the geometric aberration at this point. In this case, applying the geometric correction individually can ultimately lead to over-correction, which is not desirable. The use of a common correction function makes it possible to avoid this.

[0049] According to non-limiting embodiments, at least one, and in particular each, correction function may be, or may be presented in the form of a field of values, or a correspondence table, indicating for at least one color component (red, green, blue) of at least one pixel of the image sensor, a corrected position of said component in an image acquired with the optical lens.

[0050] According to embodiments, the method according to the invention may comprise a step of identifying a plane, called the measurement plane, corresponding to the greatest focusing, or to a satisfactory focusing, obtained by said optical objective, the measurement of at least one aberration being carried out for said measurement plane.

[0051] Such a measuring plane is preferably perpendicular to the axis of the optical objective.

[0052] The same measurement plane can be used for both lateral chromatic aberration function measurement and geometric aberration function measurement. Different measurement planes can be used for both lateral chromatic aberration function measurement and geometric aberration function measurement.

[0053] Identifying a, or the, measuring plane can be achieved in various ways. For example, a target can be placed in front of the optical lens. The relative position of the target to the lens can be changed along the axis of the optical lens and the focus value can be monitored to identify the measuring plane.

[0054] Alternatively, it is also possible to identify the measuring plane as follows. Place the plane at a specific distance from the optical lens, and adjust the focus of the camera module formed by the optical lens and the image sensor for the best sharpness at that distance.

[0055] Of course, other embodiments are possible and these non-limiting examples are given for illustration purposes only.

[0056] As indicated above, for at least one aberration, the step of measuring said aberration can be carried out with at least one target comprising one or more patterns.

[0057] According to another aspect of the present invention, there is provided a system for characterizing an optical objective used for imaging, said system comprising at least one measuring apparatus configured to measure, with an image sensor: - a lateral chromatic aberration function, FACL, of said optical lens, and / or - a geometric aberration function, FAG, of said optical objective; with a view to correcting at least one, and in particular each, of said aberrations in an image acquired with said optical objective, after acquisition of said image, by digital processing of said image.

[0058] The system according to the invention may comprise, in terms of means and / or configuration, any combination of the optional characteristics described above in relation to the characterization method according to the invention and which are not repeated here for the sake of brevity.

[0059] According to embodiments, the system according to the invention may comprise a single measuring apparatus for measuring the lateral chromatic aberration function and measuring the geometric aberration.

[0060] According to embodiments, the system may include a first measuring apparatus for measuring the lateral chromatic aberration function, and a second measuring apparatus for measuring the geometric aberration function.

[0061] At least one measuring device may include a source associated with at least one target, or a grid or any other means for illuminating the optical objective with patterns.

[0062] The light source may emit red radiation and / or green radiation and / or blue radiation. Alternatively, the light source may emit white radiation.

[0063] At least one test pattern may include transparent patterns.

[0064] At least one test pattern may include patterns of a given color, chosen from red, green, and blue.

[0065] At least one measuring device may comprise a calculation module for determining the aberration, for a point (x,y) and / or for an angle Oi, depending on the measurements taken.

[0066] The system according to the invention may further comprise a processing unit configured, or programmed, to determine at least one correction function: - lateral chromatic aberration as a function of the measured lateral chromatic aberration, and / or - geometric aberration as a function of the measured geometric aberration.

[0067] Optionally, the processing unit can further be configured, or programmed, to determine: - the lateral chromatic aberration function measured as a function of the measurements made for different points, and / or - the geometric aberration function depending on the measurements made for different points.

[0068] According to another aspect of the present invention, there is provided a method of manufacturing optical lenses comprising the following steps for at least one optical lens: - manufacture of said optical lens, - characterization of said optical objective by the method according to the invention.

[0069] According to embodiments, each manufactured optical lens can be characterized.

[0070] Alternatively, only some manufactured optical lenses may be characterized. For example, within a single batch of optical lenses, only one, or a few, optical lenses may be characterized. The measured aberration function(s), and / or the determined aberration correction function(s), may be used for all lenses in the same batch, to correct lateral chromatic aberration and / or geometric aberration.

[0071] A batch of optical lenses may correspond to lenses with the same design.

[0072] Alternatively, a batch of optical lenses may correspond to lenses having the same design and assembled according to the same assembly recipe.

[0073] According to another aspect of the same invention, there is provided an installation for manufacturing optical lenses comprising: - a production line for optical lens(es), and - a system for characterizing an optical objective according to the invention.

[0074] The installation according to the invention may comprise, in terms of means and / or configuration, any combination of the optional characteristics described above in relation to the manufacturing method according to the invention and which are not repeated here for the sake of brevity.

[0075] According to another aspect of the same invention, there is provided a method of acquiring an image of a scene with an optical objective characterized by the method according to the invention, said image acquisition method comprising the following steps: - acquisition of an image with said optical objective, and - digital processing of said image for at least partial correction of lateral chromatic aberration and / or geometric aberration.

[0076] According to embodiments, the optical lens can be used for 2D or 3D imaging.

[0077] According to embodiments, the optical lens can be used for image acquisition to image a scene at a given time, or for acquiring a stream of images, or a video, of a scene.

[0078] According to another aspect of the invention, there is provided a camera module comprising: - an optical objective characterized with the characterization method according to the invention; and - an image sensor associated with said optical lens.

[0079] The image sensor can be any type of image sensor combined with an optical lens, such as a CMOS or CCD image sensor, but is not limited to these image sensors.

[0080] According to another aspect of the invention, there is provided a user apparatus comprising at least one optical objective characterized with the method according to the invention

[0081] The user device according to the invention may in particular comprise at least one camera module according to the invention.

[0082] In particular, the user device may be a user device such as a smartphone, tablet, etc.

[0083] The user device may optionally include a display screen, in particular a touch screen, etc.

[0084] In particular, the user device may be a virtual reality headset or an augmented reality headset, intended to be worn by a user.

[0085] The helmet may optionally include a display screen, in particular a touch screen, etc.

[0086] In particular, the user device may be a camera or photo device, etc.

[0087] The user device of the camera or photo type may optionally include a display screen, in particular a touch screen, etc.

[0088] In particular, the user device may be a computer-type user device.

[0089] The computer-type user device may optionally include a display screen, in particular a touch screen, etc.

[0090] The computer-type user device may optionally include a keyboard, or any other equipment integrated or associated with said device.

[0091] In particular, the user device may be a television.

[0092] The television may optionally include a display screen, in particular a touch screen, etc.

[0093] In particular, the user device may be a medical imaging device.

[0094] The medical imaging device can be, for example, an endoscope, an ultrasound machine, etc.

[0095] Of course, the user device according to the invention is not limited to the examples which have just been given.

[0096] According to another aspect of the present invention, there is provided a vehicle comprising at least one optical objective characterized with the characterization method according to the invention.

[0097] The vehicle according to the invention may in particular comprise at least one camera module according to the invention.

[0098] According to embodiments, the vehicle may be a land vehicle, such as a car, for example non-autonomous driving, semi-autonomous driving or autonomous driving.

[0099] According to embodiments, the vehicle may be a flying vehicle, such as a drone, an airplane, a helicopter, for example with non-autonomous driving, semi-autonomous driving or autonomous driving.

[0100] According to embodiments, the vehicle may be a marine vehicle, such as a boat or a submarine, for example non-autonomously driven, semi-autonomously driven, or autonomously driven. Description of figures and embodiments

[0101] Other advantages and characteristics will appear on examining the detailed description of non-limiting embodiments, and the attached drawings in which: - FIGURE 1 is a schematic representation of a non-limiting exemplary embodiment of a method according to the invention; - FIGURE 2 is a schematic representation of another non-limiting example of embodiment of a method according to the invention; - FIGURE 3 is a schematic representation of a non-limiting exemplary embodiment of a system according to the invention; - FIGURE 4 is a schematic representation of a non-limiting exemplary embodiment of a method for manufacturing optical objective(s) according to the invention; - FIGURE 5 is a schematic representation of a non-limiting exemplary embodiment of an installation for manufacturing optical lens(es) according to the invention; - FIGURE 6 is a schematic representation of a non-limiting exemplary embodiment of a camera module according to the invention; - FIGURE 7 is a schematic representation of a non-limiting exemplary embodiment of a method for acquiring an image according to the invention; - FIGURES 8a-8c are schematic representations of non-limiting exemplary embodiments of an apparatus according to the invention; and - FIGURE 9 is a schematic representation of a non-limiting exemplary embodiment of a vehicle according to the invention.

[0102] It is understood that the embodiments which will be described below are in no way limiting. In particular, it will be 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 characteristic of functional preference without structural details, or with only part of the structural details if it is only this part which is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art.

[0103] In particular, all the variants and embodiments described can be combined with each other if there is no technical obstacle to this combination.

[0104] In the figures and in the rest of the description, the elements common to several figures retain the same reference.

[0105] FIGURE 1 is a schematic representation of a non-limiting exemplary embodiment of a method according to the present invention.

[0106] The method 100 of FIGURE 1 can be used to characterize an optical lens 00 used for imaging, i.e., for acquiring an image or a video (stream of images), with an image sensor. The lens 00 is associated with the image sensor within an imaging module, or a camera module, and can be integrated into different devices. A non-limiting example of an imaging module will be given later.

[0107] An optical lens is usually composed of several optical elements, such as lenses, spacers, etc. The different elements of the optical lens are stacked, in a barrel, following a stacking direction which also corresponds to the axis of the optical lens.

[0108] The method 100 of FIGURE 1 comprises a step 102 of identifying a measurement plane, perpendicular to the optical axis of the optical objective 00, for the aberration measurement.

[0109] To do this, for example, a target may be arranged in front of the optical objective 00. The relative position of the target with respect to the optical objective 00 may be varied along the axis of the optical objective 00 and the focus value may be monitored to identify the measurement plane providing the greatest focus, or a satisfactory focus value with respect to a predetermined focus threshold.

[0110] The method 100 then comprises a step 104 of measuring a lateral chromatic aberration function, FACL, of the optical objective. [YES] FACL measurement can be performed in different ways.

[0112] According to an exemplary embodiment, a target formed of patterns, such as points, lines, etc. is positioned in front of the optical objective 00, at the measurement plane identified during step 102. The target is illuminated by white radiation, or successively by green, red and blue radiation. A pattern corresponding to a position (x,y) of the sensor, generates on said image sensor a spot for each of the colors: a red spot, a green spot and a blue spot. The position of each spot can be detected by the image sensor. The detected positions of the three spots are then used to calculate a displacement vector, relative to a reference position, which can be the position of one of said three spots, or another position.

[0113] By performing, simultaneously or in turn, the measurement for several points (x,y) in the sensor plane, also called the image plane, it is then possible to determine the FACL.

[0114] The measured FACL can be presented in any form, as described above. In the example described, the FACL can be presented in the form of a field of values ​​including, for each of several points (x,y) of the image sensor: - a displacement vector measured for the position of the red color spot, with reference to the position of the green color spot, - a displacement vector measured for the position of the blue color task, with reference to the position of the green color task. Thus, step 104 provides a FACL indicating for several positions (x,y) on the sensor, i.e. for several pixels of the sensor, the measured chromatic aberration.

[0115] The method 100 then comprises a step 106 of calculating a lateral chromatic aberration correction function, FCACL, from the FACL.

[0116] FCALC can be determined in different ways.

[0117] In the example described, the FCACL may be in the form of a field of values ​​comprising, for each of several positions (x,y) of the image sensor, at least one displacement vector to be applied to correct said aberration at said point. For at least one position (x,y), the FCALC may comprise: - a displacement vector for the red color, and - a displacement vector for the blue color; when the green color is taken as a reference.

[0118] Alternatively, the FCACL can be presented in the form of a correspondence table indicating, for each of several pixels of the image sensor, a corrected position of said pixel and this individually: - for each color, or - for the red color and for the blue color in the case where the green color is taken as a reference.

[0119] The method 100 then comprises a step 108 of measuring a geometric aberration function, FAG of the optical lens.

[0120] FAG measurement can be performed in different ways.

[0121] In the example of FIGURE 1, a target formed of patterns, such as dots, lines, etc. is positioned in front of the optical lens 00, at the measurement plane identified during step 102. The target is illuminated by white radiation, or successively by green, red and blue radiation. A pattern located at an angle (0i,yi) relative to the axis of the optical lens 00, generates on the image sensor a spot for each of the colors: a red spot, a green spot and a blue spot. The position of each color spot is detected by the image sensor. The detected positions of the three spots are then used to calculate a displacement distance for each color, relative to the center of the optical lens 00.Optionally, the displacement distance can be divided by the focal length, so as to obtain a quantity as a function of the angle (0i,yi) of the optical beam entering the optical lens, relative to the axis of the optical lens.

[0122] By performing, simultaneously or in turn, the measurement for several angles (0i,yi) relative to the optical axis of the optical objective, it is possible to determine the FAG.

[0123] The measured FAG can be in any form, as described above. In the example described, the FAG is presented in the form of a field of values ​​including, for several angles (0i,yi) relative to the axis of the optical objective: - a travel distance measured for the color red, - a travel distance measured for the green color, and - a displacement distance measured for the blue color; relative to the center of the sensor.

[0124] The method 100 then comprises a step 106 of calculating a geometric aberration correction function, FCAG, from the FAG.

[0125] FCAG can be determined in different ways.

[0126] In the example described, the FCAG can be presented in the form of a field of values ​​comprising, for each of several angles Oi: - a distance correction value to apply for the red color, - a distance correction value to be applied for the green color, and - a distance correction to be applied for the red color.

[0127] Alternatively, the FCAG can be presented in the form of a field of values ​​comprising, for each of several angles Oi, a single distance correction value to be applied to each of the red, green and blue colors.

[0128] Alternatively, the FCAG can be presented in the form of a look-up table indicating, for each of several pixels of the image sensor, a corrected position of said pixel and this individually for each color.

[0129] In an optional step, at least one of the aberration functions measured in steps 104 and 108, and / or at least one of the aberration correction functions determined in steps 106 and 112, may be stored, for later use of said function. In particular, at least one of these functions can be used to correct an image acquired with the optical objective 00, by digital processing of said image.

[0130] FIGURE 2 is a schematic representation of another non-limiting exemplary embodiment of a method according to the present invention.

[0131] The method 200 of FIGURE 2 comprises the step 102 of identifying the measurement plane, then the step of measuring the FACL and the step 108 of measuring the FAG.

[0132] Unlike method 100 of FIGURE 1, method 200 of FIGURE 2 does not include steps 106 and 110. These optional steps are replaced by an optional step 202 determining, as a function of the measured FACL and the measured FAG, a single aberration correction function FCA, to correct both: - lateral chromatic aberration, and - geometric aberration.

[0133] In an optional step 204, the single aberration correction function, determined in step 202, can be stored, for later use of said function. In particular, this single function can be used to correct an image acquired with the optical objective 00, by digital processing of said image.

[0134] FIGURE 3 is a schematic representation of a non-limiting exemplary embodiment of a system for characterizing an optical objective according to the present invention.

[0135] The system 300 of FIGURE 3 can be used to implement a method according to the invention, and in particular any one of the methods 100 or 200.

[0136] The system 300 includes a first measuring device 302 for measuring lateral chromatic aberration, ACL.

[0137] The measuring device 302 may comprise a source emitting a white light beam illuminating a target with transparent patterns such that each pattern creates on the image sensor a red spot, a green spot and a blue spot.

[0138] Alternatively, the measuring apparatus 302 may comprise a source emitting, in turn, red-colored radiation, green-colored radiation and blue-colored radiation, and a target of transparent patterns.

[0139] According to yet another alternative, the measuring device 302 may comprise a source emitting white radiation illuminating in turn three patterns, one comprising red patterns, another comprising green patterns and the last comprising blue patterns.

[0140] The measuring apparatus 302 may comprise an image sensor. Alternatively, the measuring apparatus 302 may not comprise a sensor if the optical lens to be characterized is already assembled with an image sensor.

[0141] The system 300 includes a second measuring device 304 for measuring geometric aberration, AG.

[0142] The measuring device 304 may comprise a source emitting a white light beam illuminating a target with transparent patterns such that each pattern creates on the image sensor a red spot, a green spot and a blue spot.

[0143] Alternatively, the measuring apparatus 304 may comprise a source emitting in turn a red beam, a green beam and a blue beam, and a target of transparent patterns.

[0144] According to yet another alternative, the measuring device 304 may comprise a source emitting white radiation illuminating in turn three patterns, one comprising red patterns, another comprising green patterns and the last comprising blue patterns.

[0145] The measuring apparatus 304 may include an image sensor. Alternatively, the measuring apparatus 304 may not include a sensor if the optical lens to be characterized is already assembled with an image sensor.

[0146] The system 300 further comprises a computing unit 308.

[0147] The computing unit 308 comprises a computing module 310. The computing module 310 can be configured, or programmed, to determine: - the ACL for a point (x,y) of the sensor, and the FACL from the measurements made for several points, and / - the AG for an angle Oi at the entrance of the optical objective, and the FAG from the measurements made for several angles.

[0148] The calculation module 310 can optionally be configured, or programmed, to calculate: - a lateral chromatic aberration correction function, FCACL, from the measured lateral chromatic aberration function; and / or - a geometric aberration correction function, FCAG, from the measured geometric aberration function

[0149] The computing unit 308 may optionally comprise a control module 312 for at least one, and in particular each, of the measuring devices 302-304 for carrying out the measurement of lateral chromatic aberration, and / or the measurement of geometric aberration. Alternatively, each measuring device may comprise its own control module.

[0150] At least one of the modules 310-312 may be a hardware unit such as a processor, a microchip, a computer, a server, etc. Alternatively, at least one of the modules 310-312 may be a software unit, such as an application or a computer program. Alternatively, at least one of the modules 310-312 may be a combination of at least one hardware unit and at least one software unit.

[0151] At least one of the modules 310-312 may be independent of the other of the modules 310-312. Both modules 310-312 may be integrated within a single module.

[0152] According to an alternative not shown of the characterization system, the two measuring devices 302-304 can be integrated within a single measuring device.

[0153] FIGURE 4 is a schematic representation of a non-limiting exemplary embodiment of a method of manufacturing an optical lens according to the present invention.

[0154] The method 400 of FIGURE 4 can be used to manufacture optical lenses used for imaging, i.e., for acquiring an image or video.

[0155] The method 400 comprises a step 402 of manufacturing an optical lens. The manufacturing of the optical lens is carried out in a conventional and known manner and will therefore not be described in detail here.

[0156] The method 400 comprises a step 404 of characterizing an optical objective manufactured during step 402, by the method according to the invention and in particular by the method 100 or by the method 200.

[0157] In method 400, each manufactured objective can be characterized.

[0158] Alternatively, only some manufactured lenses may be characterized. For example, when manufacturing the same batch of optical lenses, only one (or a few) optical lenses may be characterized. The measured aberration function(s), and / or the determined aberration correction function(s), may be used for all lenses in the same batch, to correct, at least partially, lateral chromatic aberration and / or geometric aberration.

[0159] In the present application, “a batch of optical lenses” may correspond to lenses having the same design. Alternatively, “a batch of optical lenses” may correspond to lenses having the same design and assembled according to the same assembly recipe.

[0160] FIGURE 5 is a schematic representation of a non-limiting exemplary embodiment of an installation for manufacturing an optical lens according to the present invention.

[0161] The manufacturing facility 500 of FIGURE 5 may be used to manufacture optical lenses used for imaging, i.e., for acquiring an image or video.

[0162] The installation 500 comprises a line 502 for manufacturing optical lens(es). The manufacturing line 502 is in the form of a conventional, known, optical lens manufacturing line and will therefore not be described in detail here.

[0163] The facility 500 further includes a system 504, which may be the system 300 of FIGURE 3, for characterizing one, or each, optical lens manufactured by the manufacturing line 502.

[0164] FIGURE 6 is a schematic representation of a non-limiting exemplary embodiment of a camera module.

[0165] The camera module 600 of FIGURE 6 includes an optical lens 602 characterized in accordance with the present invention, and in particular by the method 100 of FIGURE 1 or by the method 200 of FIGURE 2. The optical lens 602 may be the optical lens 00 of FIGURES 1-5.

[0166] In the non-limiting example shown in FIGURE 6, the optical lens 602 comprises four lenses 604-610, stacked in a barrel 612 in a stacking direction 614, which also corresponds to the axis 614 of the optical lens 602.

[0167] The camera module 600 further comprises an image sensor 616 associated with the optical lens 602. The image sensor 616 may be any type of image sensor such as a CCD or CMOS sensor.

[0168] Of course, the camera module 600 may include other organs / components which are not shown in FIGURE 4, such as for example a mechanism modifying the imaged viewing angle or a mechanism modifying the imaged sharpness zone.

[0169] The camera module 600 may optionally comprise a module 618 for digitally processing the data captured by the image sensor 616. Such a digital processing module 618 may for example be arranged to carry out a correction of the image captured by the image sensor. 616, for example to correct lateral chromatic aberration and / or geometric aberration. This module 618 may for example integrate one or more previously determined aberration correction functions, for example the correction function(s) determined in steps 106, 110 or 202.

[0170] The processing module 618 may be an independent module. Alternatively, the processing module 618 may be integrated into another module or another application, such as for example a photo application used for the acquisition of image(s).

[0171] The module 618 may be a hardware unit such as a processor, a microchip, a computer, a server, etc. Alternatively, the module 618 may be a software unit, such as an application or a computer program. Alternatively, the module 618 may be a combination of at least one hardware unit and at least one software unit. The module 618 may be an individual module. Alternatively, the module 618 may be integrated into an existing module within a device, such as, for example, a photo application of a device equipped with the camera module 600.

[0172] FIGURE 7 is a schematic representation of a non-limiting exemplary embodiment of a method for acquiring an image according to the invention.

[0173] The method 700 comprises a step 702 of acquiring an image with an optical objective characterized by the present invention, or with a camera module according to the invention, and in particular the camera module 600 of FIGURE 6.

[0174] The method 700 further comprises a step 704 of digital processing of the acquired image. Such digital processing may perform a correction of the acquired image in order, for example, to correct, at least in part, the lateral chromatic aberration and / or the geometric aberration, due to the optical objective used for acquiring the image. Such an aberration correction may, for example, be performed with at least one aberration correction function such as that(s) provided to one any of steps 106, 110 of method 100, or step 202 of method 200.

[0175] FIGURE 8a is a schematic representation of a non-limiting exemplary embodiment of an apparatus according to the present invention.

[0176] The apparatus 810 of FIGURE 8a comprises at least one imaging module according to the present invention, and in particular the imaging module 600 of FIGURE 6.

[0177] In the example shown in FIGURE 8a, the device 810 is a smartphone, or a tablet.

[0178] Optionally, the device 810 may further comprise a display screen 812 equipped with a touch surface 814, for example capacitive.

[0179] The imaging apparatus 810 may further comprise an imaging application 816, such as a photo and / or video application, installed on said apparatus 810 and executed by said apparatus 810. The application 816 may for example integrate the processing module 618 of the imaging module. Alternatively, the processing module 618 may be independent of the application 816.

[0180] FIGURE 8b is a schematic representation of another non-limiting exemplary embodiment of an apparatus according to the present invention.

[0181] The apparatus 820 of FIGURE 8b comprises at least one imaging module according to the present invention, and in particular the imaging module 600 of FIGURE 6.

[0182] In the example shown in FIGURE 8b, the apparatus 820 is a virtual reality, VR, headset or an augmented reality, VA, headset.

[0183] Optionally, the headset 820 may further comprise a display screen 822. Optionally, the headset 820 may further comprise a sensor (not shown) for detecting the position aimed by an eye, or eyes, of the user on said display screen 822.

[0184] The headset 820 may further include an imaging application (not shown), such as a photo and / or video application, installed on said device and executed by said device 820. The imaging application may for example, integrate the processing module 618 with the imaging module. Alternatively, the processing module 618 may be independent of the imaging application of the headset 820.

[0185] FIGURE 8c is a schematic representation of another non-limiting exemplary embodiment of an apparatus according to the present invention.

[0186] The apparatus 830 of FIGURE 8c comprises at least one imaging module according to the present invention, and in particular the imaging module 600 of FIGURE 6.

[0187] In the example shown in FIGURE 8c, the apparatus 830 is a medical imaging apparatus, such as an endoscope, an ultrasound apparatus, etc.

[0188] Optionally, the medical imaging apparatus 830 may further comprise a display screen 832.

[0189] Optionally, the medical imaging device 830 can further be equipped with a detection surface 834, for example capacitive.

[0190] Optionally, the medical imaging device 830 may further comprise a distal objective 836 for collecting light radiation, which may or may not be part of the imaging module 600.

[0191] The imaging apparatus 830 may further comprise an imaging application (not shown), such as a photo and / or video application, installed on said apparatus 830 and executed by said apparatus 830. The imaging application may for example integrate the processing module 618 of the imaging module. Alternatively, the processing module 618 may be independent of the imaging application of the apparatus 830.

[0192] FIGURE 9 is a schematic representation of a non-limiting exemplary embodiment of a vehicle according to the present invention.

[0193] The vehicle 900 of FIGURE 9 comprises at least one imaging module according to the present invention, and in particular the imaging module 600 of FIGURE 6, for example integrated into a camera 902.

[0194] In the vehicle 900, the camera 902 can for example be arranged on the windshield of the vehicle 900 in the upper part of said windshield, or at the above the front windshield. Of course, this positioning is given as a non-limiting example and the camera 902 can be placed elsewhere.

[0195] In the example shown in FIGURE 9, the vehicle 900 is a land vehicle, in particular a car. The vehicle 900 may further comprise a display screen 904 equipped with a touch surface 906, for example capacitive, arranged in the passenger compartment of the vehicle 900.

[0196] The vehicle 900 may further comprise an imaging application 908, such as a photo and / or video application. The imaging application 906 may, for example, integrate the processing module 618 of the imaging module. Alternatively, the processing module 618 may be independent of the imaging application 908.

[0197] Of course, the invention is not limited to a land vehicle. A vehicle according to the invention may be a flying vehicle, such as a flying drone, an airplane, a helicopter, etc. A vehicle according to the invention may be a maritime vehicle, such as a maritime drone, a boat, a submarine, etc.

[0198] The invention is not limited to the examples of devices and vehicles given with reference to the FIGURES. It can be implemented in any type of devices and vehicles.

[0199] Of course, the invention is not limited to the examples which have just been described.

Claims

CLAIMS 1. Method (100;200) for characterizing an optical objective (00) used for imaging, said method (100;200) comprising: - a step (104) of measuring, with an image sensor, at least one lateral chromatic aberration function, FACL, of said optical objective (00), and / or - a step (108) of measuring, with an image sensor, at least one geometric aberration function, FAG, of said optical objective; with a view to correcting, at least partially, at least one, and in particular each, of said aberrations in an image acquired with said optical objective (00), by digital processing of said image.

2. Method (100; 200) according to the preceding claim, characterized in that it further comprises a step (106, 110; 202) of providing at least one correction function: - lateral chromatic aberration as a function of the measured lateral chromatic aberration, and / or - geometric aberration as a function of the measured geometric aberration.

3. Method (100) according to the preceding claim, characterized in that the step (106, 110) of providing at least one correction function provides: - an individual correction function for lateral chromatic aberration, and / or - an individual correction function for geometric aberration.

4. Method (200) according to claim 2, characterized in that the step (202) of providing at least one correction function provides a common correction function for lateral chromatic aberration and for geometric aberration.

5. Method (100; 200) according to any one of claims 2 to 4, characterized in that at least one correction function is, or comprises, a correspondence table indicating for at least one component of color of at least one pixel of the image sensor, a corrected position of said component in an image acquired with the optical objective.

6. Method (100; 200) according to any one of the preceding claims, characterized in that it comprises, for at least one aberration, before the step of measuring (104, 108) said aberration, a step (102) of identifying a plane corresponding to the greatest focusing, or to a satisfactory focusing, obtained by said optical objective (00), the step of measuring (104, 108) said aberration being carried out for said plane.

7. Method (100; 200) according to any one of the preceding claims, characterized in that, for at least one aberration, the step of measuring (104, 108) said aberration is carried out with at least one target comprising one or more patterns.

8. System (300) for characterizing an optical objective (00) used for imaging, said system (300) comprising at least one measuring device (302,304) configured to measure, with an image sensor: - a lateral chromatic aberration function, FACL, of said optical objective (00), and / or - a geometric aberration function, FAG, of said optical objective (00); with a view to correcting at least one, and in particular each, of said aberrations in an image acquired with said optical objective (00), after acquisition of said image, by digital processing of said image.

9. System (300) according to the preceding claim, characterized in that it further comprises a processing unit (308) configured to determine at least one correction function: - lateral chromatic aberration as a function of the measured lateral chromatic aberration, and / or - geometric aberration as a function of the measured geometric aberration.

10. Method (400) for manufacturing optical lenses comprising the following steps for at least one optical lens (00): - manufacturing of said optical lens (00), - characterization of said optical objective (00), by the method (100; 200) according to any one of claims 1 to 7, 11. Installation (500) for manufacturing optical lenses comprising: - a chain (502) for manufacturing optical objective(s), and - a system (300; 504) for characterizing an optical objective (00) according to any one of claims 8 or 9.

12. Method (700) for acquiring an image of a scene with an optical objective (00) characterized by the method (100; 200) according to any one of claims 1 to 7, said image acquisition method (700) comprising the following steps: - acquisition (702) of an image with said optical objective (00), and - digital processing (704) of said image for the at least partial correction of lateral chromatic aberration and / or geometric aberration.

Images