Method and system for efficiently characterizing a lens

Abstract

The invention relates to a method (300) for characterizing a lens, comprising the following steps: - measuring, with an image sensor, an optical transfer function, OTF, of the lens (OO) for at least one colour, and - comparing the measured OTF with at least one threshold OTF, the method further comprising at least one step of measuring, with an image sensor, at least one lateral chromatic aberration function, LCAF, and / or at least one geometric aberration function, GAF, of the 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 lens (OO), via digital processing of the image. The invention also relates to a system for characterizing a lens implementing such a characterizing method.

Description

DESCRIPTION Title: Method and system for high-performance characterization of an optical objective

[0001] The present invention relates to a method and system for characterizing an optical lens. It further relates to a method and system for manufacturing an optical lens implementing such a characterization method and system, a camera module implementing an optical lens characterized by such a characterization method and system, and an image acquisition method using such a camera module. The invention further relates to an apparatus and a vehicle implementing such a camera module.

[0002] The field of the invention is generally the field of characterization of optical objectives, in particular optical objectives used for imaging. State of the art

[0003] An optical lens 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, and causes a waste of time and cost.

[0004] Currently, the quality of an optical lens is tested by measuring the Modulation Transfer Function (MTF) of the optical lens. The measured MTF value is compared to a predefined threshold to determine whether the lens quality is satisfied.

[0005] The inventors discovered that optical aberrations due to a lens include on the one hand aberrations, such as lateral chromatic aberration and geometric aberration, which can be effectively corrected by calculation, and other aberrations, such as axial chromatic aberration and 3-axis aberrations. ème order and higher order (called "3rd order aberrations") ème order" in the following for the sake of brevity) which is very difficult, if not impossible, to correct by calculation.

[0006] However, the MTF measurement as currently performed gives a quantity representative of all the optical aberrations of the lens, including aberrations that can be corrected by calculation. Therefore, the MTF does not provide a relevant characterization of the optical quality of the optical lens. Furthermore, the MTF measurement does not provide any information on aberrations that can be corrected by calculation.

[0007] An aim of the present invention is to remedy at least one of the aforementioned drawbacks.

[0008] Another aim of the invention is to propose a more relevant solution for characterizing an optical objective.

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

[0010] The invention proposes to achieve at least one of the aforementioned aims by a method for characterizing an optical objective, said method comprising a qualification phase comprising the following steps: - measuring, with an image sensor, an optical transfer function, OTF, of said optical objective (00), individually for at least one of the following radiations: green radiation, blue radiation, red radiation, and - for at least one of said radiations: comparison of the measured FTO with at least one predetermined threshold FTO, to determine whether the optical quality of said objective is satisfactory; said method further comprising a quantification phase, carried out at least when the optical quality of said optical objective is satisfactory, and comprising the following steps: - measuring, with an image sensor, at least one lateral chromatic aberration function, FACL, of said optical lens (00), and / or - measurement, with an image sensor, of 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.

[0011] The inventors have noticed that optical aberrations of the displacement type, also called "displacement aberrations" in the following, due to an optical objective can be corrected very effectively by calculation, i.e. by digital processing of the acquired images, whereas aberrations of the spreading type, also called "spreading aberrations" in the following, are very difficult to correct, or sometimes even impossible to correct depending on the imaged scene. Based on this observation, the present invention proposes to measure the optical quality of an optical objective by using not a measured MTF of said optical objective with white light as is currently the case, but an FTO measured individually for at least one, and in particular for each, of the red, green and blue components.Indeed, the characterization of the optical objective for each color individually allows to obtain a more relevant characterization of the contrast quality than in white light. Indeed, in white light, it is possible to obtain a poor contrast, despite a high contrast on each detected color, in particular as soon as the lateral chromatic aberration becomes of the same order as the pitch of the pattern which is used to evaluate this contrast ratio, therefore the MTF.

[0012] Thus, the invention proposes a new solution for characterizing an optical objective that is more efficient and allows said optical objective to be better characterized.

[0013] Furthermore, the invention proposes to individually measure the lateral chromatic aberration and / or the geometric aberration of the lens. optical 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 correction of said aberration. This or these correction functions can be used to correct these aberrations in each of the images taken with the optical lens by digital processing of the image. The correction of these aberrations makes it possible to improve the quality of an image acquired with the optical lens.

[0014] 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, relative 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.

[0015] Aberrations due to an optical lens are commonly referred to as chromatic aberration, geometric aberration and 3D aberration. ème order.

[0016] 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 the spreading type. In the following, for greater conciseness, the expression "aberrations of the 3 ème order" designates the aberrations of the 3 ème order and following order.

[0017] 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.

[0018] 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 long as it is quantified, i.e. measured during the design / manufacture of the optical lens. Geometric aberrations are of the displacement type.

[0019] By "displacement aberration" or "displacement aberration" we mean lateral chromatic aberration and geometric aberration.

[0020] By "spreading-type aberration" or "spreading aberration" is meant axial chromatic aberration and aberrations of the 3 ème order.

[0021] According to embodiments, the qualification and quantification phases can be carried out at least partially simultaneously.

[0022] Thus, the method according to the invention can be carried out more quickly, which can be used when the invention is integrated into a manufacturing chain.

[0023] For example, the qualification phase can be carried out at the same time as the quantification phase.

[0024] As another example, the quantification phase can be started before the qualification phase is completed, or vice versa.

[0025] Depending on the embodiments, the qualification and quantification phases can be carried out one after the other.

[0026] In particular the qualification phase can be carried out before the quantification phase so that the qualification phase is completed before starting the quantification phase.

[0027] Thus, it is possible to know the optical quality of the optical objective before carrying out the quantification phase.

[0028] According to embodiments, the quantification phase can be carried out, whether the quality of the optical objective is satisfactory or not.

[0029] Alternatively, the quantization phase is only performed when the optical quality of the optical objective is satisfactory.

[0030] According to embodiments, the method according to the invention may comprise a step of preserving or not preserving the optical objective depending on the result of the comparison step.

[0031] If the comparison step shows that the optical quality of the lens is not satisfactory, then the optical lens can be discarded. Otherwise, the optical lens can be kept.

[0032] The step of retaining or not retaining the optical objective can be carried out after the qualification phase and before the quantification phase. Alternatively, the step of retaining or not retaining the optical objective can be carried out after the qualification phase and after the quantification phase.

[0033] When the FTO is measured for a single color radiation, namely red radiation or green radiation or blue radiation, then the optical objective can be retained if, for said radiation, the measured FTO satisfies the at least one predetermined threshold FTO.

[0034] When the FTO is measured for several color radiations, namely red radiation and / or green radiation and / or blue radiation, the optical objective can be retained if, for each measured radiation, the measured FTO satisfies the at least one respective predetermined threshold FTO for said radiation.

[0035] We will now describe each of the qualification and quantification phases in turn. The order in which these phases are described does not mean that they are carried out in the same order. As indicated above, these phases can be carried out in different orders, or at least partially simultaneously.

[0036] In addition, some steps in these phases can be combined or shared, as will be described later. For example, the step of identifying a measurement plan can be carried out only once, and the chosen measurement plan can be used both in the qualification phase and in the quantification phase.

[0037] According to embodiments, the optical transfer function, OTF, may be the modulation transfer function, MTF (or MTF for “Modulation Transfer Function”).

[0038] According to embodiments, the optical transfer function, OTF, may be the point spread function, PSF (or FEP for “Point Spread Function”).

[0039] Regardless of the FTO, namely MTF or PSF, the FTO is measured and the FTO threshold are of the same nature, either MTF or PSF.

[0040] According to embodiments, at least one, and in particular each, measured FTO may be represented by FTO values ​​measured at several points, for example at the center of the lens on the edge of the lens, etc. Preferably, the measured FTO may be represented by a field of values ​​comprising several measured FTO values, each for a position (x,y), and in particular at a pixel of position (x,y), of an image sensor used to carry out said measurement.

[0041] Alternatively, it is possible, from the measured values, to deduce a mathematical relationship taking as input a position (x,y) of the image sensor and giving as output a measured FTO value.

[0042] Of course, at least one measured FTO can be in other forms, such as a matrix, a vector, etc.

[0043] According to embodiments, at least one, and in particular each threshold FTO, can be represented by a set of values, also called a field of values, for several positions (x,y), or for several pixels of position (x,y), of an image sensor: for example at the center of the sensor, on the edge, etc. According to an exemplary embodiment, for at least one position (x,y), the field of values ​​can comprise a minimum FTO value to be reached. Alternatively, or in addition, for at least one position (x,y), the field of values ​​can comprise a pair of values ​​formed of a minimum FTO value and a maximum FTO value.

[0044] Alternatively, at least one threshold FTO can be presented in the form of at least one mathematical relationship taking as input a position (x,y) of the image sensor and giving as output: - a threshold value of FTO, and in particular a minimum value of FTO, or - a pair comprising a minimum FTO value and a maximum FTO value.

[0045] Of course, at least one threshold FTO can come in other forms, such as a matrix, a vector, etc.

[0046] At least one threshold FTO may be determined by an experimental design or test plan. Alternatively, or in addition, at least one threshold FTO may be determined during the design of the optical lens. Of course, these examples are not limiting and at least one threshold FTO may be determined in another way.

[0047] According to embodiments, the measuring step can perform the FTO measurement only for a single radiation.

[0048] In this case, the FTO measured for this single radiation is compared to the predetermined threshold FTO for this single radiation. If the measured FTO satisfies the threshold FTO, then the optical objective is considered to have satisfactory optical quality.

[0049] According to embodiments, the only radiation for which the FTO is measured may be green radiation.

[0050] In fact, the inventors discovered that the green color is the most representative of the three colors in terms of image perception.

[0051] According to embodiments, during the qualification phase, the measurement step can carry out the FTO measurement individually for at least two, in particular for each, of the red, green and blue radiations.

[0052] In other words, the FTO measurement step performs the measurement of one FTO individually for several of the red, green and blue radiations.

[0053] In this case, for each measured radiation, a measured FTO is obtained. For example, if a measurement is made for red radiation, a measured FTO is obtained for red radiation. For example, if a measurement is made for green radiation, a measured FTO is obtained for green radiation. For example, if a measurement is performed for blue radiation, a measured FTO is obtained for blue radiation.

[0054] Preferably, the FTO measuring step performs the measurement of an FTO individually for each of the red, green and blue radiation. In this case, a measured FTO is obtained for the red radiation, a measured FTO is obtained for the green radiation, and a measured FTO is obtained for the blue radiation.

[0055] When the FTO measurement step performs the measurement of an FTO individually for several, or even each, of the red, green and blue radiations, during the qualification phase, the comparison step can perform a comparison of each measured FTO to at least one predetermined threshold FTO.

[0056] In this case, the optical quality of the optical objective can be judged satisfactory if and only if each measured FTO satisfies the threshold FTO to which it is compared.

[0057] According to embodiments, the same threshold FTO can be used for at least two, and in particular all, radiations.

[0058] According to embodiments, different threshold FTOs may be used for at least two, and in particular all, of the radiations.

[0059] In other words: - a threshold FTO is associated with the red radiation and the FTO measured for said red radiation is compared to said threshold FTO; - a threshold FTO is associated with the green radiation and the FTO measured for said green radiation is compared to said threshold FTO; and - a threshold FTO is associated with the blue radiation and the FTO measured for said blue radiation is compared to said threshold FTO.

[0060] According to embodiments, for at least one radiation, the FTO measurement can be carried out for a measurement plane corresponding to the greatest focusing, or for a plane for which a satisfied focusing is obtained.

[0061] Such a measuring plane is preferably perpendicular to the axis of the optical objective.

[0062] To do this, the method according to the invention may comprise a step of identifying said measurement plane by measuring the focus for several planes and identifying the plane for which the greatest focus, a satisfactory focus is obtained. For example, a target may be arranged in front of the objective. The relative position of the target with respect to the objective may be modified along the axis of the optical objective and the value of the focus may be monitored to identify the measurement plane.

[0063] When the measurement step performs an FTO measurement for several radiations, the same measurement plan can be used for several, in particular all, radiations.

[0064] Alternatively, it is also possible to identify the measuring plane as follows. A measuring plane is placed at a specific distance from the optical lens, and the focus of the camera module formed by the optical lens and the image sensor is adjusted for the best sharpness at that distance.

[0065] Of course, other embodiments are possible and these non-limiting examples are given for illustration purposes only.

[0066] This measurement plan can be used for the qualification phase, but also for the quantification phase.

[0067] According to embodiments, for at least one radiation, the measurement step of the qualification phase can carry out a measurement of a value of the FTO at several points. The FTO measured, for this radiation, is represented by, or obtained from, the values ​​measured for these several points.

[0068] As indicated above, for at least one radiation, the measured FTO may be represented by a field of several values, this field of values ​​comprising said measured values, and possibly other estimated values, for example by interpolation. Alternatively, the measured FTO may be represented by a mathematical relationship deduced from the measured values.

[0069] According to embodiments, for at least one radiation, the measurement step of the qualification phase can be carried out with a target, comprising one or more patterns, positioned in front of the optical objective.

[0070] For at least one radiation, the test pattern may directly include patterns whose color corresponds to the color of the radiation, namely red, green or blue. Alternatively, the test pattern may include transparent patterns illuminated by red, green or blue radiation.

[0071] In the case where the FTO is the MTF, the measurement of the MTF of a point corresponds to the contrast measured for said point.

[0072] According to an exemplary embodiment, a target is placed at a certain distance, called the scene distance, chosen from the sensor and the lens. This distance can also be achieved by means of an optic inserted between the target and the lens, in order to change the apparent distance of the target from the sensor, beyond the physical distance between the target and the lens. This apparent distance can even be made infinite to obtain a scene distance called infinity. The lens is possibly moved relative to the sensor to select the best sharpness of the target for this apparent scene distance. (The best sharpness can be obtained on an area of ​​the sensor, on a color component, but not necessarily on all 3 color components at once, nor the entire sensor at once...). This target includes an alternation: - patterns, called dark, which do not let the radiation pass through, and - patterns, called light, which correspond to the color of the radiation. Dark patterns are assumed to result in radiation-free patterns on the sensor since they do not allow radiation to pass through. Light patterns are assumed to result in patterns of the same color as the radiation since they allow radiation to pass through.

[0073] In this configuration, the MTF of a point (x,y) of the sensor is calculated in the following manner. For an area centered on the point (x,y), and comprising several alternating patterns, several contrast values ​​are calculated based on the values ​​received by the pixels of said area, each contrast value corresponding to an alternating pattern in said area. The MTF value for point (x,y) is calculated based on said measured values, for example by an average of said values.

[0074] In the case where the FTO is the PSF, the measurement of the PSF of a corresponding point is carried out in a conventional manner.

[0075] According to an exemplary embodiment, a target is arranged in front of the sensor and the lens, for example at a plane corresponding to maximum focusing, directly or via a distance adaptation optic. This target comprises a plurality of points allowing the radiation to pass through. The rest of the target is opaque and does not allow the radiation to pass through.

[0076] Each point located at a position (x,y) is captured on the sensor in the form of a more or less large task and of a more or less different shape.

[0077] When the task is a perfect circle, then the value of the PSF of the point (x,y) corresponds to the radius of the task captured on the sensor.

[0078] When the spot has another shape, the PSF can, for example, be calculated as the mean radius of the spot. The mean radius can be calculated as follows. First, the center of the spot is extracted, for example, by determining the barycenter of the positions of the points forming the spot, weighted by the intensity detected at each position. Then, the sum of the detected amplitude multiplied by the square of the distance to the barycenter is calculated. This sum is divided by the sum of the detected amplitudes. This gives a square of the mean radius of the spot. The square root is taken. This gives an effective mean radius of the spot.

[0079] The measured lateral chromatic aberration function, FACL, can be of any form.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] FACL measurement can be performed in different ways.

[0084] According to embodiments, a target formed of patterns, such as points, lines, etc. can be positioned in front of the optical objective, at a measurement 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.

[0085] By carrying out, 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.

[0086] 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.

[0087] The measured geometric aberration function, GAF, can be in any form.

[0088] According to embodiments, the FAG may be in the form of a field of values ​​comprising, for several angles 0i relative to the axis of the optical lens, and for several angles of rotation yi around the axis of the optical lens, at least one displacement distance. According to an exemplary embodiment, for at least one angle (0i,yi), the field of values ​​may 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.

[0089] 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.

[0090] Alternatively, the FAG can be a mathematical function taking as input an angle (0i,yi) and providing a single displacement distance for all three colors, or a displacement distance individually for each color.

[0091] FAG measurement can be performed in different ways.

[0092] According to embodiments, a target formed of patterns, such as dots, lines, etc., can be positioned in front of the optical lens, at a measuring 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,yi) of the optical beam entering the optical lens relative to the axis of the optical lens.

[0093] 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.

[0094] 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.

[0095] According to embodiments, the quantification phase may comprise a step of providing at least one lateral chromatic aberration correction function, FCACL, as a function of the measured lateral chromatic aberration.

[0096] 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.

[0097] 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).

[0098] 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.

[0099] According to embodiments, the quantification phase may comprise a step of providing at least one geometric aberration correction function, FCAG, as a function of the measured geometric aberration.

[0100] 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.

[0101] Alternatively, the FCAG can be a mathematical function taking as input an angle (0i,yi) relative to the optical lens axis (and a second angle yi to fully localize the incident ray relative to the sensor) and providing one or more distance correction values.

[0102] According to 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] According to non-limiting embodiments, at least one, and in particular each, correction function may be, or may be 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 objective.

[0109] 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.

[0110] Such a measuring plane is preferably perpendicular to the axis of the optical objective. [YES] 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 the measurement of lateral chromatic aberration function, and the measurement of geometric aberration function.

[0112] 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.

[0113] 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.

[0114] Of course, other embodiments are possible and these non-limiting examples are given for illustration purposes only.

[0115] Furthermore, this measurement plan identification step is optional and may not be carried out, or may be shared with the qualification phase. More precisely, when a measurement plan is identified / chosen during the qualification phase, said measurement plan can also be used during the quantification phase.

[0116] 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.

[0117] According to another aspect of the same invention, there is provided a system for characterizing an optical objective, said system comprising: - at least one measuring device; and - a computing unit; configured to implement the method according to the invention.

[0118] The characterization 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 method of characterization according to the invention and which are not repeated here for the sake of brevity.

[0119] 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 characterization method according to the invention,

[0120] According to embodiments, each manufactured optical lens can be characterized.

[0121] Alternatively, only some manufactured optical lenses may be characterized. For example, within the same batch of optical lenses, only one, or a few, optical lenses may be characterized. The FTO(s) measured for said lens(es) of said batch may be used for all lenses of the same batch.

[0122] A batch of optical lenses may correspond to lenses with the same design.

[0123] Alternatively, a batch of optical lenses may correspond to lenses having the same design and assembled according to the same assembly recipe.

[0124] According to another aspect of the present invention, there is provided an installation for manufacturing optical lenses comprising: - an optical lens manufacturing line, and - a characterization system according to the invention for characterizing at least one optical objective.

[0125] The manufacturing 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. manufacturing according to the invention and which are not repeated here for the sake of brevity.

[0126] 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.

[0127] According to embodiments, the optical lens can be used for 2D or 3D imaging.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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

[0132] The user device according to the invention may in particular comprise at least one camera module according to the invention.

[0133] In particular, the user device may be a user device such as a smartphone, tablet, etc.

[0134] The user device may optionally include a display screen, in particular a touch screen, etc.

[0135] In particular, the user device may be a virtual reality headset or an augmented reality headset, intended to be worn by a user.

[0136] The helmet may optionally include a display screen, in particular a touch screen, etc.

[0137] In particular, the user device may be a camera or photo device, etc.

[0138] The user device of the camera or photo type may optionally include a display screen, in particular a touch screen, etc.

[0139] In particular, the user device may be a computer-type user device.

[0140] The computer-type user device may optionally include a display screen, in particular a touch screen, etc.

[0141] The computer-type user device may optionally include a keyboard, or any other equipment integrated or associated with said device.

[0142] In particular, the user device may be a television.

[0143] The television may optionally include a display screen, in particular a touch screen, etc.

[0144] In particular, the user device may be a medical imaging device.

[0145] The medical imaging device can be, for example, an endoscope, an ultrasound machine, etc.

[0146] Of course, the user device according to the invention is not limited to the examples which have just been given.

[0147] 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.

[0148] The vehicle according to the invention may in particular comprise at least one camera module according to the invention.

[0149] 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.

[0150] 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.

[0151] 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

[0152] Other advantages and characteristics will appear on examining the detailed description of non-limiting embodiments, and the attached drawings in which: - FIGURES 1a-1b are schematic representations of a non-limiting exemplary embodiment of a qualification phase of an optical objective which can be implemented in the present invention according to the invention; - FIGURES 2a-2b are schematic representations of a non-limiting example of a quantization phase of a optical objective that can be implemented in the present invention according to the invention; - FIGURES 3a-3c are schematic representations of a non-limiting exemplary embodiment of a method according to the invention for characterizing an optical objective; - FIGURE 4 is a schematic representation of a non-limiting exemplary embodiment of a system according to the invention for characterizing an optical objective; - FIGURE 5 is a schematic representation of a non-limiting exemplary embodiment of a method for manufacturing optical objective(s) according to the invention; - FIGURE 6 is a schematic representation of a non-limiting exemplary embodiment of an installation for manufacturing optical lens(es) according to the invention; - FIGURE 7 is a schematic representation of a non-limiting exemplary embodiment of a camera module according to the invention; - FIGURE 8 is a schematic representation of a non-limiting exemplary embodiment of a method for acquiring an image according to the invention; - FIGURES 9a-9c are schematic representations of non-limiting exemplary embodiments of an apparatus according to the invention; and - FIGURE 10 is a schematic representation of a non-limiting exemplary embodiment of a vehicle according to the invention.

[0153] 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 from the prior art.

[0154] In particular, all the variants and embodiments described can be combined with each other if there is no technical obstacle to this combination.

[0155] In the figures and in the rest of the description, the elements common to several figures retain the same reference.

[0156] The invention, and in particular the following examples, can be implemented to characterize an optical lens 00 used for imaging, i.e. for acquiring an image, a stream of images or a video. Such a lens 00 can be associated with an image sensor to form an imaging module, or a camera module, and be integrated into different devices or vehicles.

[0157] An optical lens is usually composed of several optical elements, such as lenses, spacers, etc. The different elements of the optical lens are stacked according to a stacking direction, which also corresponds to the axis of the optical lens.

[0158] The optical lens 00 may be associated with an image sensor (not shown in FIGURES 1a-1b, 2a-2b and 3a-3c). In this case, this image sensor is used for the characterization of said optical lens 00. Alternatively, the optical lens may not be associated with an image sensor. In this case, an image sensor of a measuring device is used for the characterization of said optical lens 00.

[0159] FIGURE 1a is a schematic representation of a non-limiting exemplary embodiment of a qualification phase that can be implemented in the present invention, and in particular in a method for characterizing an optical objective according to the present invention.

[0160] Qualification phase 110 is carried out, for example, to characterize an optical objective 00.

[0161] Prior to the qualification phase, the method according to the invention may comprise a step 102 of identifying a measurement plane, perpendicular to the optical axis of the optical objective 00, for the measurement of at least one optical transfer function, OTF.

[0162] Identifying a measurement plan can be done in different ways.

[0163] According to an exemplary embodiment, 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 modified along the axis of the optical objective (possibly by means of an adaptive optic) and the value of the focus may be monitored to identify the measurement plane providing the greatest focus, or a satisfactory focus value with respect to a predetermined focus threshold.

[0164] According to another embodiment, it is also possible to identify the measuring plane in the following way. A measuring plane is placed at a determined distance from the optical lens, and the focus of the camera module formed by the optical lens 00 and the image sensor is adjusted for the best sharpness at this distance.

[0165] Of course, other examples of implementation are possible and the examples given are not limiting.

[0166] The measurement plan identified during step 102 can be used for the qualification phase, but also for the quantification phase. In other words, step 102 of identifying a measurement plan can be carried out only once in the method according to the invention. Alternatively, a measurement plan can be identified for the qualification phase, and another measurement plan can be identified for the quantification phase.

[0167] In the non-limiting example shown in FIGURE 1a, the qualification phase 100 comprises a step 104 of measuring the MTF of the optical objective 00, for green radiation.

[0168] In the non-limiting example of FIGURE 1a, the green radiation may be green radiation whose wavelength is between 500 nm and 570 nm, and in particular equal to 535 nm.

[0169] The measurement of the MTF can be carried out according to the technique described above. In particular, a target is positioned in the measurement plane identified during step 102. This target, associated with a light source, emits an image according to green color patterns towards the lens. The image of these patterns passes through the optical lens and is captured by the image sensor. For a point of the sensor, the MTF can be measured as the average contrast obtained on several patterns, or several lines of the pattern located around said point.

[0170] Step 104 performs a plurality of measurements of MTF values ​​for multiple points of the image sensor and provides a measured MTF represented by a field of measured MTF values, each for an (x,y) position of the sensor.

[0171] Then, a step 106 performs a comparison of the measured MTF for the green radiation with at least one predetermined threshold MTF for said green radiation.

[0172] According to an exemplary embodiment, the measured MTF is compared to a threshold MTF giving minimum MTF values. If the measured MTF is greater than the threshold MTF then the qualification phase 100 continues. Otherwise, the qualification phase is stopped and the optical objective is considered to be of insufficient quality.

[0173] According to an exemplary embodiment, the measured MTF is compared to a first threshold MTF giving minimum MTF values ​​and to a second threshold MTF giving maximum MTF values. If the measured MTF is between the first threshold MTF and the second threshold MTF, the qualification phase 100 continues. Otherwise, the qualification phase 100 is stopped and the optical quality of the optical objective is deemed unsatisfactory.

[0174] The comparison of the measured MTF to one, in particular each, threshold MTF can be performed value by value. In other words, for a position (x,y) of the sensor, the measured value of the MTF for said position (x,y) is compared to the threshold value of the MTF for said position. The measured MTF satisfies the threshold MTF, if and only if, for each of the positions measurement value (x,y), the measured value of MTF satisfies the threshold value of MTF. Finally, the threshold MTF can also depend on (x,y).

[0175] When the measured MTF for green radiation is satisfactory in step 106, the qualification phase 100 comprises a step 108 of measuring the MTF for red radiation, in a similar manner to the measurement of the MTF for green radiation in step 104.

[0176] In the non-limiting example of FIGURE 1, the red radiation may be red radiation whose wavelength is between 570 and 730 nm, and in particular equal to 650 nm.

[0177] In a step 110, the measured MTF for the red radiation is compared to at least one predetermined threshold MTF for the red radiation. If the comparison shows that the measured MTF for the red radiation does not satisfy the at least one threshold MTF, then the optical quality of the optical objective 00 is deemed unsatisfactory and the qualification phase is stopped. Otherwise, the optical objective 00 is retained and the qualification phase 100 continues.

[0178] When the measured MTF for red radiation is satisfactory in step 110, the method 100 comprises a step 112 of measuring the MTF for blue radiation, similarly to the measurement of the MTF for green radiation in step 104.

[0179] In the non-limiting example of FIGURE 1, the blue radiation may be blue radiation whose wavelength is between 400 and 500 nm, and in particular equal to 450 nm.

[0180] In a step 114, the measured MTF for the blue radiation is compared to at least one predetermined threshold MTF for the blue radiation. If the comparison shows that the measured MTF for the blue radiation does not satisfy the at least one threshold MTF, then the quality of the optical objective 00 is deemed unsatisfactory. Otherwise, the quality of the optical objective 00 is deemed satisfactory.

[0181] In the example of FIGURE 1, the measured MTF for one color is compared to at least one threshold MTF before measuring the MTF for another color. This avoids measuring the MTF for said other color when the measured MTF for the current color is not satisfactory.

[0182] According to an alternative not shown, steps 104, 108 and 112 can be carried out before carrying out comparison steps 106, 110 and 114.

[0183] FIGURE 1b is a schematic representation of another non-limiting exemplary embodiment of a qualification phase that can be implemented in the present invention, and in particular in a method for characterizing an optical objective according to the present invention.

[0184] Unlike qualification phase 100 of FIGURE 1 which tests the optical quality of optical lens 00 based on each color (green, red and blue), qualification phase 150 of FIGURE 1b tests the quality of optical lens 00, based on an individually measured MTF for a single color.

[0185] In the example in FIGURE 2, the only color used to characterize the optical lens is green. Of course, alternatively, it is possible to use red or blue.

[0186] Qualification phase 150 includes steps 102-106 described with reference to FIGURE 1, and does not include steps 110 and following.

[0187] When in step 106, the measured MTF for the green radiation satisfies the at least one threshold MTF, the quality of the optical objective 00 is judged satisfactory and the qualification phase 150 is terminated. Otherwise, the optical quality of the optical objective 00 is judged unsatisfactory and the qualification phase 150 is terminated.

[0188] According to another alternative not shown in the FIGURES, the optical objective 00 can be characterized on the basis of two colors chosen from the colors green, red and blue.

[0189] In the examples in FIGURES 1a and 1b, the measured FTO is the MTF. Alternatively, instead of using the MTF as the FTO, it is possible to use the PSF.

[0190] FIGURE 2a is a schematic representation of a non-limiting exemplary embodiment of a quantification phase that can be implemented in the present invention, and in particular in a characterization method according to the present invention.

[0191] Prior to the quantification phase, the method according to the invention may comprise a step 102 of identifying a measurement plane, perpendicular to the optical axis of the optical objective 00, for the measurement of at least one optical transfer function, FTO.

[0192] Identifying a measurement plan can be done in different ways, as described above.

[0193] This step 102 is optional if it has already been carried out in the method according to the invention, for example for the test step. In other words, this measurement step can be carried out only once for the qualification phase and the quantification phase.

[0194] The quantification phase 200 comprises a step 204 of measuring a lateral chromatic aberration function, FACL, of the optical objective.

[0195] FACL measurement can be performed in different ways.

[0196] 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 vector of displacement, relative to a reference position, which may be the position of one of said three tasks, or another position.

[0197] 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.

[0198] 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 204 provides a FACL indicating for several positions (x,y) on the sensor, i.e. for several pixels of the sensor, the measured chromatic aberration.

[0199] The quantization phase 200 then comprises an optional step 206 of calculating a lateral chromatic aberration correction function, FCACL, from the FACL.

[0200] FCALC can be determined in different ways.

[0201] 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.

[0202] 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.

[0203] The quantification phase 200 then comprises a step 208 of measuring a geometric aberration function, FAG of the optical objective.

[0204] FAG measurement can be performed in different ways.

[0205] According to an exemplary embodiment, a target formed of patterns, such as points, 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.

[0206] By performing, simultaneously or in turn, the measurement for several angles (0i,yi) relative to the optical axis of the optical lens 00, and several angles yi in rotation around the center of the lens, it is possible to determine the FAG.

[0207] The measured FAG can be presented in any form, as described above. For example, the FAG can be presented as 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.

[0208] The quantification phase 200 then comprises a step 210 of calculating a geometric aberration correction function, FCAG, from the FAG.

[0209] FCAG can be determined in different ways.

[0210] In the example described, the FCAG can be presented in the form of a field of values ​​including, for each of several angles (0i,yi): - 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.

[0211] Alternatively, the FCAG can be presented as a field of values ​​comprising, for each of several angles (0i,yi), a single distance correction value to be applied to each of the red, green and blue colors.

[0212] 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.

[0213] In an optional step, at least one of the aberration functions measured in steps 204 and 208, and / or at least one of the aberration correction functions determined in steps 206 and 210, may be stored, for later use of said function. In particular, at least one of these functions may be used to correct an image acquired with the optical objective 00, by digital processing of said image.

[0214] FIGURE 2b is a schematic representation of another non-limiting exemplary embodiment of a quantification phase that can be implemented in the present invention, and in particular in a characterization method according to the present invention.

[0215] Unlike the quantization phase of FIGURE 2a, the quantization phase 250 of FIGURE 2b does not include steps 206 and 210. These optional steps are replaced by an optional step 252 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.

[0216] In an optional step 254, the single aberration correction function, determined in step 252, 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.

[0217] FIGURE 3a is a schematic representation of a non-limiting exemplary embodiment of a method for characterizing an optical objective according to the present invention.

[0218] The method 300 of FIGURE 3a can be used to characterize an optical lens, and in particular the optical lens 00.

[0219] The method 300 comprises the step 102 of identifying a measurement plan, as described above with reference to FIGURE 1a. This step 102 is carried out only once and the identified measurement plan is used both for the qualification phase and for the quantification phase. In other words, the qualification phase, respectively the quantification phase, does not include a step of identifying a measurement plan and uses the measurement plan identified during step 102 for the different measurements to be carried out during said phase.

[0220] In the example of FIGURE 3a, the method 300 firstly comprises a qualification phase 302. The qualification phase 302 may for example be any one of the qualification phases 100 or 150 of FIGURES 1a and 1b. This qualification phase 302 determines whether or not the optical objective has sufficient / satisfactory optical quality.

[0221] During a step 304, and depending on the result of the qualification phase 302, it is determined whether the optical objective is retained or not.

[0222] If step 304 results in the preservation of the optical lens because the optical quality of the optical lens 00 is deemed satisfactory at the end of the qualification phase 302, then the method 300 comprises a quantization phase 306. The quantization phase 304 may for example be any one of the quantization phases 200 or 250 of FIGURES 2a and 2b. This quantization phase 304 determines the lateral chromatic aberration and / or the geometric aberration, and optionally, but preferably, at least one function for correcting the lateral chromatic aberration and / or the geometric aberration.

[0223] If step 304 results in the rejection of the optical objective 00 because the optical quality of the optical objective 00 is deemed unsatisfactory, then it is put to process 300 and the quantification phase is not carried out.

[0224] FIGURE 3b is a schematic representation of another non-limiting exemplary embodiment of a method for characterizing an optical objective according to the present invention.

[0225] The method 310 of FIGURE 3b can be used to characterize an optical lens, and in particular the optical lens 00.

[0226] The method 310 comprises all the steps of the method 300 of FIGURE 3a. In the method 310 of FIGURE 3b, unlike the method 300 of FIGURE 3a, the step 304 of retaining or not the optical objective is carried out after the qualification phase 302 and after the quantification phase 306. In other words, the quantification phase 306 is carried out before determining whether the optical objective 00 is retained or not.

[0227] FIGURE 3c is a schematic representation of another non-limiting exemplary embodiment of a method for characterizing an optical objective according to the present invention.

[0228] The method 320 of FIGURE 3c can be used to characterize an optical lens, and in particular the optical lens 00.

[0229] The method 320 comprises all the steps of the method 300 of FIGURE 3a. In the method 320 of FIGURE 3c, unlike the method 300 of FIGURE 3a, the step 304 of preserving or not the optical objective 00 is carried out after the qualification phase 302 and after the phase of quantization 306, like the method 310 of FIGURE 3b. In other words, the quantization phase 306 is carried out before determining whether the optical objective OO is preserved or not.

[0230] Furthermore, in the method 320 of FIGURE 3c, unlike the method 300 of FIGURE 3a and the method 310 of FIGURE 3b, the quantification phase 306 is carried out at least partially simultaneously with the qualification phase 302.

[0231] According to embodiments, the qualification phase 302 and the quantification phase 304 can be carried out simultaneously in parallel.

[0232] According to embodiments, the qualification phase 302 and the quantification phase 304 can be carried out in an interleaved manner so that the steps of said phases can be mixed. In particular, the measurements carried out during these phases 302 and 306, concerning radiation of a given color, can be grouped together. For example, when the FTO is measured for a color radiation (green, red or blue), it is possible at the same time, just after, to measure the FACL and / or the FAG for this radiation.

[0233] Of course, other embodiments are possible.

[0234] FIGURE 4 is a schematic representation of a non-limiting exemplary embodiment of a system for characterizing an optical objective according to the present invention.

[0235] The system 400 of FIGURE 4 can be used to implement a method according to the invention, and in particular any of the methods 300, 310 or 320 of FIGURES 3a-3c.

[0236] The system 400 includes a first measuring apparatus 402 for measuring an FTO with green-colored radiation. The measuring apparatus 302 may include a green-colored radiation source illuminating a target with transparent patterns, such that the optical objective receives green-colored patterns. Alternatively, the measuring apparatus 402 may include a white-colored radiation source illuminating a target with green color patterns, so that the optical lens receives green color patterns.

[0237] The system 300 includes a second measuring apparatus 404 for measuring an FTO with red color radiation. The measuring apparatus 404 may include a red color radiation source illuminating a target with transparent patterns, such that the optical lens receives red color patterns. Alternatively, the measuring apparatus 404 may include a white color radiation source illuminating a target with red color patterns, such that the optical lens receives red color patterns.

[0238] The system 400 includes a third measuring apparatus 406 for measuring an FTO with blue-colored radiation. The measuring apparatus 406 may include a blue-colored radiation source illuminating a target with transparent patterns, such that the optical lens receives blue-colored patterns. Alternatively, the measuring apparatus 406 may include a white-colored radiation source illuminating a target with blue-colored patterns, such that the optical lens receives blue-colored patterns.

[0239] It is recalled that the FTO can be the MTF or the PSF.

[0240] The system 400 includes a fourth measuring device 408 for measuring lateral chromatic aberration, ACL.

[0241] The measuring device 408 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.

[0242] Alternatively, the measuring apparatus 408 may comprise a source emitting, in turn, red-colored radiation, green-colored radiation and blue-colored radiation, and a target of transparent patterns.

[0243] According to yet another alternative, the measuring device 408 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.

[0244] The measuring apparatus 408 may include an image sensor. Alternatively, the measuring apparatus 408 may not include a sensor if the optical lens to be characterized is already assembled with an image sensor.

[0245] The system 400 includes a fifth measuring device 410 for measuring geometric aberration, AG.

[0246] The measuring device 410 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.

[0247] Alternatively, the measuring apparatus 410 may comprise a source emitting in turn a red beam, a green beam and a blue beam, and a target of transparent patterns.

[0248] According to yet another alternative, the measuring device 410 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.

[0249] 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.

[0250] According to an alternative not shown of the system 400, at least two of the measuring devices 402-410 can be integrated within a single measuring device.

[0251] According to an exemplary embodiment, the measuring devices 402 and 404 can be integrated within the same device.

[0252] According to an exemplary embodiment, the measuring devices 406-410 can be integrated within a single device.

[0253] According to an example of implementation, all measuring devices 402-410 can be integrated within a single device.

[0254] The system 400 further comprises at least one computing unit 412.

[0255] The calculation unit 412 comprises a calculation module 414. The calculation module 414 can be configured / programmed, for, for a given color: - calculate a measured FTO value based on the measurements taken, - compare the measured FTO to one or more predetermined threshold FTOs, - calculate the ACL for a point (x,y) of the sensor, and the FACL from the measurements taken for several points, - calculate the ACL for a point (x,y) of the sensor, and the FACL from the measurements taken for several points, - calculate at least one FCACL from the FACL, - calculate the AG for an angle (0i,yi) at the input of the optical objective, and the FAG from the measurements made for several angles, and / or - calculate at least one FCAG from the FAG.

[0256] Alternatively, at least one of these operations can be performed in a calculation module integrated into one of the measuring devices 402-410.

[0257] The computing unit 412 may optionally comprise a control module 416 for at least one, and in particular each, of the measuring devices 402-410 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.

[0258] Alternatively, the calculation unit may be integrated into at least one measuring device. In particular, when all the measuring devices 402-410 are integrated into a single measuring device, the calculation unit 412 may be integrated into said measuring device.

[0259] At least one of the modules 414-416 may be a hardware unit such as a processor, a microchip, a computer, a server, etc. Alternatively, at least one of the modules 414-416 may be a software unit, such as an application or a computer program. Alternatively, at least one of the modules 414-416 may be a combination of at least one hardware unit and at least one software unit.

[0260] At least one of the modules 414-416 may be independent of the other of the modules 414-416. Both modules 414-416 may be integrated within a single module.

[0261] Generally, the computing unit 412 may be a hardware unit such as a processor, a microchip, a computer, a server, etc. Alternatively, the computing unit 412 may be a software unit, such as an application or a computer program. Alternatively, the computing unit 412 may be a combination of at least one hardware unit and at least one software unit.

[0262] FIGURE 5 is a schematic representation of a non-limiting exemplary embodiment of a method of manufacturing an optical lens according to the present invention.

[0263] The method 500 of FIGURE 5 can be used to manufacture optical lenses used for imaging, i.e., for acquiring an image or video.

[0264] The method 500 comprises a step 502 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.

[0265] The method 500 comprises a step 504 of characterizing an optical objective manufactured during step 502, by the method according to the invention and in particular by any one of the methods 310, 320 or 330 of FIGURES 3a-3c.

[0266] In method 500, each manufactured objective can be characterized.

[0267] 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.

[0268] A "lot of optical lenses" means lenses with the same design.

[0269] Alternatively, a "batch of optical lenses" may correspond to lenses having the same design and assembled according to the same assembly recipe.

[0270] FIGURE 6 is a schematic representation of a non-limiting exemplary embodiment of an optical lens manufacturing facility according to the present invention.

[0271] The manufacturing facility 600 of FIGURE 6 may be used to manufacture optical lenses used for imaging, i.e., for acquiring an image or video.

[0272] The installation 600 comprises a line 602 for manufacturing optical lens(es). The manufacturing line 602 is in the form of a conventional, known, manufacturing line for optical lenses and will therefore not be described in detail here.

[0273] The facility 600 further includes a system 604, which may be the system 400 of FIGURE 4, for characterizing one, or each, optical lens manufactured by the manufacturing line 602.

[0274] The installation 600 is configured to implement a manufacturing method according to the invention, and in particular the manufacturing method 500 of FIGURE 5.

[0275] FIGURE 7 is a schematic representation of a non-limiting exemplary embodiment of a camera module according to the invention.

[0276] The camera module 700 of FIGURE 7 includes an optical lens 702 characterized in accordance with the present invention, and in particular by any of the methods 300, 310 and 320 of FIGURES 3a-3c. The optical lens 702 may be the optical lens 00 of FIGURES 1-6.

[0277] In the non-limiting example shown in FIGURE 7, the optical lens 702 comprises four lenses 704-710, stacked in a barrel 712 in a stacking direction 714, which also corresponds to the axis 714 of the optical lens 702. This example is given for illustration purposes only and is in no way limiting.

[0278] The camera module 700 further comprises an image sensor 716 associated with the optical lens 702. The image sensor 716 may be any type of image sensor such as a CCD or CMOS sensor.

[0279] Of course, the camera module 700 may include other organs / components which are not shown in FIGURE 7, such as for example a mechanism modifying the imaged viewing angle or a mechanism modifying the focus or the imaged sharpness zone.

[0280] The camera module 700 may optionally comprise a module 718 for digitally processing the data captured by the image sensor 716. Such a digital processing module 718 may for example be arranged to perform a correction of the image captured by the image sensor 716, for example to correct the lateral chromatic aberration and / or the geometric aberration. This module 718 may for example integrate one or more previously determined aberration correction functions, for example the correction function(s) determined in steps 206, 210 and 252.

[0281] The processing module 718 may be an independent module. Alternatively, the processing module 718 may be integrated into another module or another application, such as for example a photo application used for the acquisition of image(s).

[0282] The module 718 may be a hardware unit such as a processor, a microchip, a computer, a server, etc. Alternatively, the module 718 may be a software unit, such as an application or a computer program. Alternatively, the module 718 may be a combination of at least one hardware unit and at least one software unit. The module 718 may be an individual module. Alternatively, the module 718 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.

[0283] FIGURE 8 is a schematic representation of a non-limiting exemplary embodiment of a method for acquiring an image according to the invention.

[0284] The method 800 comprises a step 802 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 700 of FIGURE 7, or the objective 00 of FIGURES 1-6.

[0285] The method 800 further comprises a step 804 of digitally processing 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(those) provided in any one of the steps 206, 210 and 252.

[0286] FIGURE 9a is a schematic representation of a non-limiting exemplary embodiment of an apparatus according to the present invention.

[0287] The apparatus 910 of FIGURE 9a comprises at least one imaging module according to the present invention, and in particular the imaging module 700 of FIGURE 7.

[0288] In the example shown in FIGURE 9a, the device 910 is a smartphone, or a tablet.

[0289] Optionally, the device 910 may further comprise a display screen 912 equipped with a touch surface 914, for example capacitive.

[0290] The apparatus 910 may further comprise an imaging application 916, such as a photo and / or video application, installed in said apparatus 910 and executed by said apparatus 910. The application 916 may for example integrate the processing module 718 of the imaging module 700. Alternatively, the processing module 718 may be independent of the application 916.

[0291] FIGURE 9b is a schematic representation of another non-limiting exemplary embodiment of an apparatus according to the present invention.

[0292] The apparatus 920 of FIGURE 9b comprises at least one imaging module according to the present invention, and in particular the imaging module 700 of FIGURE 7.

[0293] In the example shown in FIGURE 9b, the apparatus 920 is a virtual reality, VR, headset or an augmented reality, VA, headset.

[0294] Optionally, the headset 920 may further comprise a display screen 922. Optionally, the headset 920 may further comprise a sensor (not shown) for detecting the position aimed by an eye, or eyes, of the user on said display screen 922.

[0295] The headset 920 may further comprise an imaging application (not shown), such as a photo and / or video application, installed on said headset 920 and executed by said headset 920. The imaging application may for example integrate the processing module 718 of the imaging module 700. Alternatively, the processing module 718 may be independent of the imaging application of the headset 920.

[0296] FIGURE 9c is a schematic representation of another non-limiting exemplary embodiment of an apparatus according to the present invention.

[0297] The apparatus 930 of FIGURE 9c comprises at least one imaging module according to the present invention, and in particular the imaging module 700 of FIGURE 7.

[0298] In the example shown in FIGURE 9c, the apparatus 930 is a medical imaging apparatus, such as an endoscope, an ultrasound apparatus, etc.

[0299] Optionally, the medical imaging apparatus 930 may further comprise a display screen 932.

[0300] Optionally, the medical imaging device 930 can further be equipped with a detection surface 934, for example capacitive.

[0301] Optionally, the medical imaging device 930 may further comprise a distal objective 936 for collecting light radiation, which may or may not be part of the imaging module 700.

[0302] The imaging apparatus 930 may further comprise an imaging application (not shown), such as a photo and / or video application, installed on said apparatus 930 and executed by said apparatus 930. The imaging application may for example integrate the processing module 718 of the imaging module. Alternatively, the processing module 718 may be independent of the imaging application of the apparatus 930.

[0303] FIGURE 10 is a schematic representation of a non-limiting exemplary embodiment of a vehicle according to the present invention.

[0304] The vehicle 1000 of FIGURE 10 comprises at least one imaging module according to the present invention, and in particular the imaging module 700 of FIGURE 7, for example integrated into a camera 1002.

[0305] In the vehicle 1000, the camera 1002 may for example be arranged behind the windshield of the vehicle 1000 in the upper part of said windshield, or above the front windshield. Of course, this positioning is given as a non-limiting example and the camera 1002 may be arranged elsewhere.

[0306] In the example shown in FIGURE 10, the vehicle 1000 is a land vehicle, in particular a car. The vehicle 1000 may further comprise a display screen 1004 equipped with a touch surface 1006, for example capacitive, arranged in the passenger compartment of the vehicle 1000.

[0307] The vehicle 1000 may further comprise an imaging application 1008, such as a photo and / or video application. The imaging application 1006 may, for example, integrate the processing module 718 of the imaging module 700. Alternatively, the processing module 718 may be independent of the imaging application 1008.

[0308] 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.

[0309] 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 comprising a camera module.

[0310] Of course, the invention is not limited to the examples which have just been described.

Claims

CLAIMS 1. Method (300;310;320) for characterizing an optical objective (00), said method (300;310;320) comprising a qualification phase (100;150;302) comprising the following steps: - measuring (104,108,112), with an image sensor, an optical transfer function, OTF, of said optical objective (00), individually for at least one of the following radiations: green radiation, blue radiation, red radiation, and - for at least one of said radiations: comparison (106,110,114) of the measured FTO with at least one predetermined threshold FTO, to determine whether the optical quality of said objective (00) is satisfactory; said method (300;310;320) further comprising a quantification phase (200;250;306), carried out at least when the optical quality of said optical objective (00) is satisfactory, and comprising the following steps: - measurement (204), with an image sensor, of at least one lateral chromatic aberration function, FACL, of said optical objective (00), and / or - measurement (208), with an image sensor, of at least one geometric aberration function, FAG, of said optical objective (00); 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 (300; 310; 320) according to the preceding claim, characterized in that the qualification (100; 150; 302) and quantification (200; 250; 306) phases are carried out: - one after the other, in particular the qualification phase (100; 150; 302) is carried out before the quantification phase (200; 250; 306); or - at least partially simultaneously.

3. Method (300; 310; 320) according to any one of the preceding claims, characterized in that it comprises a step (304) of retention or not of the optical objective depending (00) on the result of the comparison step.

4. Method (100; 150; 302) according to any one of the preceding claims, characterized in that the optical transfer function is: - the modulation transfer function, FMT (or MTF for “Modulation Function Transfer”); or - the point spread function, FEP (or PSF for “Point Spread Function”).

5. Method (300;310;320) according to any one of the preceding claims, characterized in that, during the qualification phase (100;302), the measuring step (104,108,112) carries out the measurement of the FTO individually for at least two, in particular for each, of the red, green and blue radiations.

6. Method (300; 310; 320) according to the preceding claim, characterized in that, during the qualification phase (100; 302), the comparison step carries out, for each radiation for which the FTO has been measured, a comparison of said measured FTO with at least one predetermined threshold FTO.

7. Method (300; 310; 320) according to any one of the preceding claims, characterized in that, for at least one radiation, the measurement of the FTO is carried out for a measurement plane corresponding to the greatest focusing, or for a plane for which a satisfied focusing is obtained.

8. Method (300; 310; 320) according to any one of the preceding claims, characterized in that, for at least one radiation, the measuring step (104, 108, 112) of the qualification phase (100; 150; 302) carries out a measurement of the value of the FTO at several points.

9. Method (300; 310; 320) according to any one of the preceding claims, characterized in that, for at least one radiation, the step measurement (104,108,112) of the qualification phase (100; 150; 302) is carried out with a target, comprising one or more patterns, positioned in front of the optical objective (OO).

10. Method (300; 310; 320) according to any one of the preceding claims, characterized in that the quantization phase (200; 250; 306) further comprises a step (206, 210; 252) 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.

11. Method (300; 310; 320) according to the preceding claim, characterized in that the step of providing (206, 210) at least one correction function provides: - an individual correction function for lateral chromatic aberration, and / or - an individual correction function for geometric aberration.

12. Method (300; 310; 320) according to claim 10, characterized in that the step (250) of providing at least one correction function provides a common correction function for lateral chromatic aberration and for geometric aberration.

13. Method (300; 310; 320) according to any one of the preceding claims, characterized in that it comprises, for at least one aberration, before the step of measuring (204, 208) 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 (204, 208) said aberration being carried out for said plane.

14. Method (300; 310; 320) according to any one of the preceding claims, characterized in that, for at least one aberration, the step of measurement (204,208) of said aberration is carried out with at least one target comprising one or more patterns.

15. System (400) for characterizing an optical objective, said system (400) comprising: - at least one measuring device (402-410), and - at least one calculation unit (412); configured to implement all the steps of the method (300; 310; 320) according to any one of the preceding claims.

16. Method (500) for manufacturing optical lenses comprising the following steps for at least one optical lens (OO): - manufacturing (502) of said optical lens (00), and - characterization (504) of said optical objective (00), by the method (300; 310; 320) according to any one of claims 1 to 14.

17. Installation (600) for manufacturing optical lenses comprising: - a manufacturing line (602) of optical lens(es), and - a system (604; 400) for characterizing an optical objective according to claim 14, for characterizing at least one optical objective (00) manufactured in said manufacturing line (602).

18. Method (800) for acquiring an image of a scene with an optical objective (00) characterized by the method (300; 310; 320) according to any one of claims 1 to 14, said image acquisition method (800) comprising the following steps: - acquisition (802) of an image with said optical objective (00), and - digital processing (804) of said image for the correction of at least lateral chromatic aberration and / or geometric aberration.

Images