Method and device for acquiring a stack of images of a scene with adjusted sharpness amplitude

Abstract

The invention relates to a method (200) for imaging a scene with at least one camera module, the method comprising acquiring a plurality of images (IM1-IMn) of the scene at various discrete focusing distances, DFi, each with a respective depth of field, PCi={PCi,min;PCi,max}, comprising the respective focusing distance and extending over a respective sharpness range, NETi =PCi,max-PCi,min, the method furthermore comprising a step (202) of determining: - the smallest focusing distance (DF1) such that the lower limit (PC1,min) of the depth of field (PC1) associated therewith is less than or equal to a predetermined lower distance (Dmin); and / or - the greatest focusing distance (DF1) such that the upper limit (PCn,max) of the depth of field (PCn) associated therewith is greater than a predetermined upper distance (Dmax). The invention also relates to a computer program, an apparatus and a vehicle implementing such a method.

Description

DESCRIPTION Title: Method and device for acquiring a stack of images of a scene with adjusted sharpness amplitude

[0001] The present invention relates to a method for obtaining a stack of images of a scene whose sharpness amplitude is adjusted. It also relates to a computer program and a device implementing such a method. It further relates to an apparatus and a vehicle implementing such a method.

[0002] The field of the invention is the field of obtaining a stack of images of a scene comprising images acquired at different focusing distances. State of the art

[0003] An image of a scene is acquired with a camera module at a focusing distance, DF, with a depth of field, PC={PCmin- PCmax}, defining a sharpness range, NET=PCmax-PCmin, around said focusing distance DF. Thus, the image sharply represents a limited part of the scene, and in particular all the objects in the scene, located at a distance from the camera module included in the depth of field, i.e. between PG™ and PCmax. PG™ corresponds to the distance between the camera module and the closest plane of the scene that is sharp in the image, and PCmax corresponds to the distance between the camera module and the furthest plane of the scene that is sharp in the image.

[0004] We know the technique, called focus bracketing, or focus stacking, which allows capturing a stack of images of a scene, each image being captured at a different focusing distance. The stack of images can be used to obtain a consolidated image clearly representing a larger part of the scene, and therefore presenting a greater depth of field.

[0005] In some focus bracketing techniques, images of the scene are acquired at randomly chosen focusing distances, resulting in a random result when representing the scene from these images. Some objects in the scene may never be represented in focus, or the scene may be imaged for parts that do not include any objects, which is of little interest.

[0006] Other techniques perform image acquisition at focusing distances corresponding to the previously measured distances of the objects in the scene. These techniques aim to align the sharp areas of the scene with the objects in it. However, these techniques are complex because they require detecting all objects in the scene and measuring their distances / depths relative to the camera module. Moreover, these techniques are not efficient because they depend on effective detection of objects in the scene, which is not always possible. In addition, some areas of the scene, which do not contain objects, are not sharp in the acquired images, which is a significant limitation.

[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 solution making it possible to image a scene with an improved range of sharpness.

[0009] Another aim of the invention is to propose a solution making it possible to image a scene with an improved amplitude of sharpness, in a simpler and more efficient manner. Statement of the invention

[0010] The invention proposes to achieve at least one of the aforementioned aims by a method for imaging a scene with at least one camera module, each camera module comprising an optical lens associated with an image sensor; said method comprising an acquisition of several images, denoted IMi-IM n in the following, of said scene at different discrete focusing distances, noted DFi in the following, each with a respective depth of field, denoted PCi={PCi,min; PG,max}, comprising said respective focusing distance, DFi, and extending over a respective sharpness range, N ETi = PCi,max“ PG, min an image acquired at a focusing distance, DFi, clearly representing parts of the scene located at distances included in the depth of field PG associated with said focusing distance, DFi; characterized in that it further comprises a step of determining: - the smallest focusing distance so that the lower limit of the depth of field associated with it is less than or equal to a predetermined lower distance; and / or - a step of determining the greatest focusing distance so that the upper limit of the depth of field associated with it is greater than a predetermined upper distance.

[0011] Thus, like known techniques, the invention makes it possible to image a scene to obtain a stack of several images captured at different focusing distances. Such a stack of images makes it possible to represent the scene with a greater depth of field since each image clearly represents different parts of the scene.

[0012] Furthermore, and unlike known solutions, the invention proposes to choose the smallest focusing distance, respectively the largest focusing distance, as a function of a low distance, respectively a high distance, which is predetermined. Thus, the invention makes it possible to image a scene while ensuring sharpness from a low distance, respectively up to a high distance, chosen and not determined randomly or as a function of a depth map of the scene, the determination of which is a complex operation and potentially a source of error. Thus, the invention makes it possible to image a scene with an improved sharpness amplitude, and this in a simpler and faster manner since it does not require determining a depth map of the scene.

[0013] By image, we mean a digital image, and in particular a matrix image, and more particularly an RGB matrix image for example.

[0014] Focusing distance refers to the distance at which an optical lens is focused, with reference to the position of the lens. The focusing distance for capturing an image is generally adjusted by changing the distance between the image sensor and the optical lens. Thus, a first image of a scene acquired at a first focusing distance will clearly represent a first part of the scene, and a second image of a scene acquired at a second focusing distance will clearly represent a second part of the scene.

[0015] Depth of field refers to the extent of the area of ​​sharpness that appears in an image, that is, the area between the sharp foreground and the sharpest plane of the image.

[0016] The term "sharpness range" refers to the distance over which the sharp part of the image extends, or the depth of field, that is, the distance from the sharp foreground to the sharpest last plane of the image.

[0017] According to a non-limiting example of embodiment, given as an illustration of the definitions indicated above, the focusing distance can be 15 meters. The sharpness range can be 1.50 meters and the depth of field can be 14.50 meters - 16 meters. In this case, the image will clearly represent all the objects, or parts of the scene, located at a distance of between 14.5m and 16m from the optical objective.

[0018] According to embodiments, the predetermined low distance can be selected by the user.

[0019] This allows the user to set a lower sharpness limit for imaging the scene, independently of the imaging device, or at least one camera module, used to image the scene. Thus, the invention allows the scene to be imaged in a customizable manner according to the wishes and / or intentions of each user.

[0020] Alternatively, the predetermined low distance may correspond to the distance of the nearest object in the scene, in particular the distance between the imaging module and the nearest object in the scene.

[0021] This embodiment makes it possible to adapt the smallest focusing distance used to image the scene, to the composition of the scene and in particular to the objects located in the scene. Thus, the scene is imaged by ensuring that the objects / parts of the scene which are closest to the camera module will be imaged in a sharp manner, at least one of the images in the image stack. In addition, this embodiment makes it possible to avoid taking images with depths of field which do not correspond to any object in the scene, in particular below the most distant object in the scene.

[0022] Alternatively, the predetermined low distance may correspond to the smallest sharpness distance permitted by the at least one camera module, and in particular to the lower limit of the smallest focusing distance permitted by the at least one camera module.

[0023] Such an embodiment provides the possibility of making the most of the capacity of the at least one camera module used to image the scene, in particular for the objects / areas closest to the scene.

[0024] When the predetermined low distance corresponds to the distance of the closest object to the scene, the method according to the invention may further comprise a step of determining the distance of the closest object to the scene.

[0025] The distance to the nearest object can be measured / estimated.

[0026] Measuring / estimating the distance to the nearest object can be done in different ways: - using a sensor, for example a LIDAR or time-of-flight camera type sensor; - from the signal received by the at least one camera module whose focus is gradually increased starting from the smallest focusing distance permitted by said at least one camera module; - from one or more images taken by said at least one camera module. Indeed, the distance of an object in a scene can be measured using for example a triangulation distance measurement technique; - from an image taken by a camera module and optical transfer functions, and in particular PSF functions (for “Point Spread Function”), from said camera module; or - from an image taken by a camera module entered into a previously trained artificial intelligence model to provide said distance. Of course, other examples of embodiment are possible and the invention is not limited to these examples which are given for information purposes only.

[0027] According to embodiments, the predetermined high distance can be selected by the user.

[0028] This allows the user to set a high sharpness limit for imaging the scene, independently of the imaging device, or at least one camera module, used to image the scene. Thus, the invention allows the scene to be imaged in a customizable manner according to the wishes and / or intentions of each user.

[0029] Alternatively, the predetermined high distance can correspond to the distance of the farthest object in the scene.

[0030] This embodiment allows the largest focusing distance used to image the scene to be adapted to the composition of the scene and in particular to the objects in the scene. Thus, the scene is imaged ensuring that the objects / parts of the scene that are furthest from the camera module will be imaged sharply. In addition, this embodiment avoids taking images with depths of field that do not correspond to any object in the scene, in particular beyond the furthest object in the scene.

[0031] Alternatively, the predetermined upper distance may correspond to the greatest sharpness distance permitted by the at least one camera module, and in particular to the upper limit of the greatest focusing distance permitted by the at least one camera module.

[0032] Such an embodiment provides the possibility of making the most of the capacity of the at least one camera module used to image the scene, in particular for the objects / areas furthest from the scene.

[0033] When the predetermined low distance corresponds to the distance of the object furthest from the scene, the method according to the invention may further comprise a step of determining the distance of the object furthest from the scene.

[0034] The distance to the farthest object can be measured / estimated.

[0035] Measuring / estimating the distance to the farthest object can be done in different ways: - using a sensor, for example a LIDAR or time-of-flight camera type sensor; - from the signal received by the at least one camera module whose focus is progressively reduced starting from the greatest focusing distance permitted by said at least one camera module; - from one or more images taken by said at least one camera module. Indeed, the distance of an object in a scene can be measured using, for example, a triangulation distance measurement technique; - from an image taken by a camera module and optical transfer functions, and in particular PSF functions (for “Point Spread Function”), from said camera module; or - from an image taken by a camera module entered into a previously trained artificial intelligence model to provide said distance. Of course, other examples of embodiment are possible and the invention is not limited to these examples which are given for information purposes only.

[0036] According to embodiments, for at least one focusing distance, the depth of field associated with said focusing distance may be contiguous, or overlap, with the depth of field associated with the next focusing distance, in ascending or descending order of focusing distances.

[0037] In this case, continuity of sharpness is obtained at least between two images of the scene acquired at two focusing distances which follow one another in increasing or decreasing order. In other words, the sharpness of the scene is continuous on these two images captured at different focusing distances so that there is no area of ​​the scene which is blurred, or which is not sharp, between said two focusing distances.

[0038] According to embodiments, for each focusing distance, the depth of field associated with said focusing distance may be contiguous, or overlap, with the depth of field associated with the next focusing distance, in the ascending or descending order of the focusing distances.

[0039] In this case, continuity of sharpness is obtained for all images of the scene acquired at different focusing distances. In other words, the sharpness of the scene is continuous across all images captured at different focusing distances. Thus, there is no area of ​​the scene that is blurred, or not sharp, between the focusing distances used for image acquisition, and in particular between the lower limit of the small focusing distance and the upper limit of the largest focusing distance.

[0040] This embodiment makes it possible to maximize the amplitude of sharpness with which the scene is represented on the images since by using all the IMi-IM images n acquired, it is possible to represent the scene clearly over all distances ranging from PCi,min to PCn.max, having a total sharpness amplitude equal to N ETtotaie= PCn,max- PCi,min.

[0041] According to embodiments, for at least one, in particular each, focusing distance, the depth of field associated with said focusing distance can be contiguous with the depth of field associated with the following focusing distance.

[0042] In this case, there is no overlap between the respective depths of field. This allows the focusing distances to be chosen from so as to minimize the total number of images to be acquired while allowing continuity of sharpness between images of the scene.

[0043] For example, the focusing distances DFi and DFi+i, with DFi <DFi+i, peuvent être choisies de sorte que, PCi,max= PCi + l,min . Ainsi, les images IMi et IMi+i acquises respectivement aux distances de focalisation DFi et DFi+i représentent la scène de manière nette sur toute la profondeur allant de PCi,min a PCi + l,max, et ce de manière continue.

[0044] According to embodiments, for at least one, in particular each, focusing distance, the depth of field associated with said focusing distance overlaps with the depth of field associated with the following focusing distance.

[0045] In this case, there is an overlap between the respective depths of field. This allows the focusing distances to be chosen so as to ensure continuity of sharpness between the images of the scene.

[0046] For example, the focusing distances DFi and DFi+i, with DFi < DFi+i, can be chosen so that, PCi,max> PCi + l,min . Thus, the images IMi and IMi+i acquired respectively at the focusing distances DFi and DFi+i represent the scene in a clear manner over the entire depth going from PCi,min to PCi + l,max, and this in a continuous manner, with in addition an overlap of sharpness on the two images IMi and IMi+i. Indeed, the parts of the scene located at the depths included in the interval [ PCi + l,min PCi,max] are represented in a clear manner both on the image I Mi and on the image IMi+i.

[0047] According to embodiments, at least two, in particular all, images may be acquired with the same camera module.

[0048] In this case, even if the imaging device used to image the scene includes several camera modules, only one of these modules is used to acquire said images.

[0049] In this case, the said images are acquired in turn.

[0050] According to embodiments, at least two, in particular all, images may be acquired with different camera modules.

[0051] In this case, at least two camera modules are used to acquire said images. In this case, the images acquired by several camera modules can be acquired simultaneously or in turn.

[0052] For a given number of images, using multiple camera modules allows the scene to be imaged more quickly, compared to a situation where a single camera module is used.

[0053] In addition, using multiple camera modules allows the scene to be imaged over a greater total depth of field. Indeed, the camera modules fitted to a device, for example a smartphone, allow a scene to be imaged with different focusing distances. For example, a smartphone can be equipped, among other things, with a wide-angle camera module and a telephoto camera module that allow the scene to be imaged with different focusing distances.

[0054] According to embodiments, for at least one focusing distance, DFi, the depth of field, PG = {PG, min; PG, max} associated with it is known and given by the imaging module. Indeed, the depth of field is determined by the hardware making up the camera module, and depends on the physical properties of said camera module.

[0055] According to embodiments, for at least one focusing distance, DFi, the depth of field, PG = {PG, min; PG, max} associated therewith may be measured and stored in association with said focusing distance.

[0056] Such a measurement can be carried out in different ways.

[0057] For example, the depth of field PG={PG,min; PG,max} associated with a focusing distance DFi can be measured as follows: - the camera module is configured to acquire an image of a reference scene at said focusing distance, - an image of the reference scene is taken at said focusing distance, - the first clear object on the image taken is identified and its distance is measured: this distance corresponds to PG, min; - the last sharp object on the image taken is identified and its distance is measured: this distance corresponds to PG, max; Thus, the depth of field PG associated with the focusing distance is determined. It is also possible to determine the sharpness range NE = PG, max- PG, min associated with the said focusing distance.

[0058] According to embodiments, at least one image of the scene may be a 2D image.

[0059] According to embodiments, at least one image of the scene may be a 3D image.

[0060] According to another aspect of the same invention, there is provided a computer program comprising executable instructions which, when executed by a computing device, implement all the steps of the method according to the invention.

[0061] The computer program can be in any computer language, such as machine language, C, C++, JAVA, Python, etc.

[0062] Such a computer program may be presented as a standalone application. Alternatively, such a computer program may be integrated into a photo or video acquisition application.

[0063] According to another aspect of the invention, there is provided an apparatus comprising: - at least one camera module, - at least one computing unit; configured to implement all the steps of the method according to the invention.

[0064] In particular, the device may be a user device such as a smartphone, tablet, etc. comprising a display screen.

[0065] In this case, the user device may further comprise a display screen, a capacitive sensing surface, etc.

[0066] In particular, the device may be a computer-type user device.

[0067] In this case, the computer-type user device may comprise a display screen, a touch surface, in particular integrated into, or associated with, the display screen of said computer, etc.

[0068] In particular, the device may be a television.

[0069] In particular, the device may be a virtual reality headset or an augmented reality headset.

[0070] In this case, the headset may include a display screen, one or more sensors, particularly optical ones, etc.

[0071] In particular, the device may be a medical imaging device.

[0072] In particular, the medical imaging device may be an endoscope, an ultrasound device, etc.

[0073] Of course, the apparatus according to the invention is not limited to the examples which have just been given.

[0074] According to another aspect of the present invention, there is provided a vehicle comprising: - at least one camera module, and - at least one computing unit; configured to implement all the steps of the method according to the invention.

[0075] According to embodiments, the vehicle may be a ground vehicle, such as a car, which is autonomous, semi-autonomous or non-autonomous.

[0076] According to embodiments, the vehicle may be a flying vehicle, such as a drone, an airplane, a helicopter, autonomous, semi-autonomous or non-autonomous.

[0077] According to embodiments, the vehicle may be a maritime vehicle, such as a boat or a submarine, which is autonomous, semi-autonomous or non-autonomous. Description of figures and embodiments

[0078] 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 example of different quantities used in the present invention; - FIGURE 2-5 are schematic representations of non-limiting exemplary embodiments of a method according to the invention; - FIGURE 6 is a schematic representation of a non-limiting exemplary embodiment of an apparatus according to the invention; - FIGURES 7-9 are schematic representations of non-limiting exemplary embodiments of apparatuses according to the invention; and - FIGURE 10 is a schematic representation of a non-limiting exemplary embodiment of a vehicle according to the invention.

[0079] 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 a part of the structural details if it is this part which is only sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0080] In particular, all the variants and embodiments described can be combined with each other if there is no technical obstacle to this combination.

[0081] In the figures and in the rest of the description, the elements common to several figures retain the same reference.

[0082] FIGURE 1 is a schematic representation of a non-limiting example of various quantities used in the present invention.

[0083] FIGURE 1 shows a camera module 102. The camera module 102 includes an optical lens 104, also called an optical system, comprising one or more optical elements such as lenses. The camera module 102 further includes an image sensor 106, such as a CCD or CMOS sensor, disposed opposite the optical lens 104. The optical lens 104 serves to direct light from different parts of a scene to be imaged toward the image sensor 106.

[0084] The distance between the optical lens 104 and the image sensor 106, denoted DOC, can be adjusted to change the area of ​​the scene that will be clearly perceived on the image sensor 106. This DOC distance can be adjusted in different ways, for example by a mechanism (not shown) which varies said DOC distance by moving the image sensor 106, or the optical lens 104 or even both.

[0085] In particular, changing the distance DOC makes it possible to modify the focus point 110 of the camera module 102. The distance between the camera module 102 and the focus point 110 is called the focus distance, and denoted DF, in the following.

[0086] When the camera module 102 is adjusted to a given focusing distance DF, the focusing point 110 at the focusing distance DF appears sharply on the image sensor 106. In addition, the image sensor 106 also sharply receives, to some extent, some points after the focusing point 110 and other points before the focusing point 110. Thus, the image sensor sharply receives an area including the focusing point 110. The distance interval including the focusing point 110 and received clearly on the image sensor 102 is called depth of field, noted PC, with PC= {PCmin ; PCmax}, with - PCmin: the distance between the camera module 102 and the closest scene plane clearly received on the image sensor 106; and - PCmax: the distance between the camera module 102 and the most distant scene plane clearly received on the image sensor 106. In addition, the width of the depth of field PCmax-PCmin is noted as the sharpness range and noted NET= PCmax- PCmin

[0087] When multiple IMi-IM images n are acquired at different focusing distances, respectively DFrDFn, each image IMi taken at the focusing distance DFi represents the scene in a sharp manner with respect to the objects / areas of said scene located at distances (relative to the image sensor) included in the depth of field PCi = { PCi,min ; PCi,max} associated with said focusing distance DFi . The image I Mi has a sharpness range NETi = PG, max- PG, min .

[0088] FIGURE 2 is a schematic representation of a non-limiting exemplary embodiment of a method according to the present invention.

[0089] The method 200 of FIGURE 2 can be used to obtain, with at least one camera module, a stack of images of the scene, comprising images acquired at different focusing distances, and therefore different depths of field.

[0090] At least one camera module may include an image sensor associated with an optical lens, such as, for example, the camera module 202 of FIGURE 2. The imaging apparatus used to image the scene may include a single camera module. Alternatively, the imaging apparatus may include multiple camera modules.

[0091] The method 200 comprises a step 202 of determining focusing distance(s) for acquiring images of the scene as a function of a predetermined minimum distance Dmin and / or a predetermined maximum distance Dmax.

[0092] According to an example of realization, the focusing distances can be chosen as follows: - a first focusing distance DFi, with a first depth of field PCi= { PCi,min ; PCi,max}, is chosen so that the lower limit PCi,min of the depth of field PCi is equal to or slightly less than said minimum distance Dmin; - a final focusing distance DF n , with a last depth of field PCn= { PCn,min PCn,max} , is chosen so that the upper limit PCn,miax of the depth of field PCn is equal to or slightly greater than said maximum distance Dmax; - and optionally, one or more focusing distances DFi can be chosen between the focusing distances DFi and DF n This method does not necessarily ensure continuity of sharpness between the images that will be acquired.

[0093] According to another example of realization, the focusing distances can be chosen starting from the minimum distance Dmin: - a first focusing distance DFi, with a first depth of field PCi= { PCi,min ; PCi,max}, is chosen so that the lower limit PCi,min of the depth of field PCi is equal to or slightly less than said minimum distance Dmin; - then, the second following focusing distance DF2, with a second depth of field PC2= { PC2,min ; PC2,max} , is chosen so that the lower limit PC2,min of the depth of field PC2 is equal to or slightly lower than the upper limit PCi,max of the depth of field PCi associated with the focusing distance DFi; - and so on up to a distance of DF n , with a depth of field PCn = { PCn,min PCn, max} whose upper limit PCn, max is equal to, or slightly greater than, the maximum distance Dmax.

[0094] Alternatively to what has just been described, the focusing distances can be chosen by starting with the maximum distance Dmax, instead of starting with the minimum distance Dmin. As yet another alternative, it is possible to start with an average distance, Dmoy, located at an equal distance from the minimum distance Dmin and the maximum distance Dmax. Of course, these examples are in no way limiting.

[0095] This embodiment makes it possible to ensure continuity of sharpness between the images that will be acquired: in particular, two images acquired at two focusing distances that follow one another in ascending order, or in descending order, will make it possible to represent the scene over two depths of field that are contiguous or overlap. In the example given, and without loss of generality, step 202 determines focusing distances to obtain continuity of sharpness for all the acquired images.

[0096] In any case, step 202 provides the focusing distances DFi-DFn at which images of the scene are to be acquired.

[0097] Then, the method 200 comprises a step 204 of acquiring IMi-IM images n at said focusing distances DFi-DF n . Some of the IMi-IM images n can be acquired by the same camera module, one after the other. Alternatively, or in addition, some of the IMi-IM images n can be acquired by at least two camera modules, simultaneously or one after the other.

[0098] The focusing distance DF of a camera module can be changed in several ways. According to an exemplary embodiment, the focusing distance DF of a camera module can be changed by changing the distance DOC between the image sensor and the optical lens of the camera module.

[0099] The depth of field associated with a focusing distance is an optical quantity dependent on the architecture of the camera module, and in particular on the optical lens. Generally, the depth of field associated with a focusing distance is provided by the manufacturer or previously measured, and stored in association with the camera module, for example in the imaging device integrating the camera module.

[0100] FIGURE 3 is a schematic representation of another non-limiting exemplary embodiment of a method according to the present invention.

[0101] The method 300 of FIGURE 3 can be used to obtain, with at least one camera module, a stack of images of the scene, comprising images acquired at different focusing distances, and therefore different depths of field.

[0102] Method 300 includes all of the steps of method 200 of FIGURE 2.

[0103] In addition, the method 300 comprises, before steps 202-204, a step 302 for determining, for at least, and in particular each, focusing distance DFi of a camera module, the depth of field PCi associated with said focusing distance DFi.

[0104] Such a measurement can be carried out in different ways.

[0105] According to a non-limiting example of implementation, and without loss of generality, the measurement of the depth of field for a focusing distance is carried out in the following manner: - the camera module is adjusted to obtain the DFi focusing distance, for example by changing the distance between the image sensor and the optical lens of the camera module; - a reference scene, within which the distances are known, is imaged with said camera module at said focusing distance to obtain a calibration image; - the first sharp plane, that is to say the plane of the scene closest to the camera module which is sharp, in said calibration image is identified: the known distance of this first sharp plane corresponds to the lower limit PFi,min of the depth of field PFi; - the last sharp plane, that is to say the plane of the scene furthest from the camera module which is sharp, in said calibration image is identified: the known distance of this second sharp plane corresponds to the upper limit PFi, max of the depth of field PFi.

[0106] This operation can be performed for all the focusing distances of the camera module during step 302. If the imaging device comprises several camera modules, step 302 can be repeated for each camera module in turn or at the same time. Thus, at the end of step 302, we obtain, for each focusing distance DFi of each camera module the depth of field PG associated with said focusing distance DFi.

[0107] Step 302 can be performed just before steps 202-204.

[0108] Alternatively, step 302 can be performed well before steps 202-204, for example during the manufacture of the camera module, or during the integration of the camera module into the imaging device, or during a calibration operation of the camera module and / or the imaging device, or during a calibration operation of an imaging application installed in the imaging device.

[0109] FIGURE 4 is a schematic representation of another non-limiting exemplary embodiment of a method according to the present invention.

[0110] The method 400 of FIGURE 4 can be used to obtain, with at least one camera module, a stack of images of the scene, comprising images acquired at different focusing distances, and therefore different depths of field. [YES] Method 400 includes all of the steps of method 200 of FIGURE 2. Alternatively, method 400 could include all of the steps of method 300 of FIGURE 3.

[0112] The method 400 further comprises a step 402 of measuring the distance, denoted DSmin, between the camera module and the object / area of ​​the scene which is closest to said camera module. Such a measurement can be carried out in different ways. For example, a lidar sensor can be used to carry out said measurement. The distance DSmin thus measured is used as the minimum distance Dmin during step 202, so that Dmin = DSmin . Thus, the smallest focusing distance DFi can be chosen so as to clearly image the object (area) closest to the scene in the corresponding image acquired at said focusing distance.

[0113] The method 400 further comprises a step 404 of measuring the distance, denoted DSmax, between the camera module and the object / area of ​​the scene which is the furthest from said camera module. Such a measurement can be carried out in different ways. For example, a lidar sensor can be used to carry out said measurement. The distance DSmax thus measured is used as the maximum distance Dmax in step 202, so that Dmax= DSmax. Thus, the largest focusing distance DF n is chosen so as to clearly image the object (area) furthest from the scene in the corresponding image acquired at said focusing distance DF n .

[0114] Of course, the method 400 may comprise only one of the steps 402 and 404.

[0115] Furthermore, the method 400 may optionally comprise the step 302 of determining a depth of field for at least one focusing distance.

[0116] FIGURE 5 is a schematic representation of another non-limiting exemplary embodiment of a method according to the present invention.

[0117] The method 500 of FIGURE 5 can be used to obtain, with at least one camera module, a stack of images of the scene, comprising images acquired at different focusing distances, and therefore different depths of field.

[0118] Method 500 includes all of the steps of method 200 of FIGURE 2. Alternatively, method 400 could include all of the steps of method 300 of FIGURE 3.

[0119] The method 500 further comprises a step 502 of choosing the minimum distance Dmin. This minimum distance can be chosen by the user or by a manufacturer or even by an imaging application used. This minimum distance can be a function of the scene or not. This minimum distance can be a function of an imaging mode chosen from several imaging modes, such as for example landscape mode, portrait mode, etc. In the example given, and without loss of generality, the choice of the minimum distance Dmin is made manually. The minimum distance Dmin can be indicated through a numeric keypad or using a cursor, or any other user interface.

[0120] The method 500 further comprises a step 504 of choosing the maximum distance Dmax. This maximum distance can be chosen by the user or by a manufacturer or even by an imaging application. used. This maximum distance may or may not be a function of the scene. This maximum distance may be a function of an imaging mode chosen from several imaging modes, such as landscape mode, portrait mode, etc. In the example given, and without loss of generality, the choice of the maximum distance Dmax is made manually. The maximum distance Dmax can be indicated through a numeric keypad or using a cursor, or any other user interface.

[0121] Of course, the method 500 may comprise only one of the steps 502 and 504.

[0122] Further, method 500 may optionally include step 302 of FIGURE 3 to determine at least one depth of field for at least one focus distance.

[0123] In all the examples described, step 202 takes into account a predetermined minimum distance Dmin to determine the focusing distances. Alternatively, step 202 may determine the focusing distances by taking into account, not a minimum distance Dmin, but by taking into account the smallest focusing distance technically achievable with the at least one camera module. In this case, the choice of the focusing distances may begin, or end, with said smallest focusing distance and the depth of field associated therewith. In this case, the minimum distance Dmin is chosen as the lower bound of the smallest focusing distance technically achievable with the at least one camera module.

[0124] In all the examples described, step 202 takes into account a predetermined maximum distance Dmax to determine the focusing distances. Alternatively to what is described with reference to FIGURE 2, step 202 may determine the focusing distances by taking into account, not a maximum distance Dmax, but by taking into account the greatest focusing distance technically achievable with the at least one camera module. In this case, the choice of the focusing distances may begin, or end, with said greatest focusing distance and the depth of field associated therewith. In this case, the maximum distance Dmax is chosen as the upper bound of the greatest large focusing distance technically achievable with at least one camera module.

[0125] FIGURE 6 is a schematic representation of a non-limiting exemplary embodiment of an apparatus according to the present invention.

[0126] The apparatus 600 of FIGURE 6 may be used to obtain a stack of images of the scene, including images acquired at different focusing distances, and thus at different depths of field.

[0127] The device 600 of FIGURE 6 can be used to implement a method according to the invention, and in particular any one of the methods 200, 300, 400 or 500 of FIGURES 2-5.

[0128] The device 600 comprises at least one camera module. In the example described, and in a non-limiting manner, the device 600 comprises K camera modules 602I-602K, with K>1. In the following, the reference 602 designates a camera module.

[0129] Each camera module 602 comprises an optical lens associated with an image sensor, and possibly a mechanism for changing the focusing distance of said camera module.

[0130] At least two camera modules can have identical focusing distances.

[0131] Alternatively, or in addition, at least two camera modules may have different focusing distances: in other words, one of the camera modules may produce an image of a scene at a focusing distance that the other camera module cannot.

[0132] The apparatus 600 further comprises a calculation unit 604 configured to carry out different steps of the method according to the invention.

[0133] The calculation unit 604 comprises an optional module 606 for determining a depth of field for at least one focusing distance, for example from a reference scene. This module 606 can for example be configured / programmed to carry out step 302 of the methods 300, 400 and 500.

[0134] The calculation unit 604 further comprises an optional module 608 for determining the distance of at least one object in the scene, in particular the distance of the closest object and / or the distance of the most distant object. This optional module 608 may for example be configured / programmed to carry out at least one of the steps 402 and 404 of the method 400.

[0135] The calculation unit 604 further comprises an optional module 610 for choosing at least one distance, in particular a minimum distance and / or a maximum distance, in order to determine the focusing distances for imaging the scene. This optional module 610 can for example be configured / programmed to carry out at least one of the steps 502 and 504 of the method 500.

[0136] The calculation unit 604 further comprises a module 612 for choosing / determining focusing distances for imaging the scene. This module 612 can for example be configured / programmed to carry out at least step 202 of any one of the methods 200, 300, 400 and 500.

[0137] The computing unit 604 further comprises a module 614 for controlling at least one camera module for acquiring images of the scene at different focusing distances. This module 614 can for example be configured / programmed to carry out at least step 204 of any one of the methods 200, 300, 400 and 500.

[0138] At least one of the modules 606-614 may be an independent module of the others.

[0139] At least two of the 606-614 modules can be integrated within the same module.

[0140] The computing unit 604, and / or at least one of the modules 606-614, may be a hardware module, such as a processor, an electronic chip, etc.

[0141] The computing unit 604, and / or at least one of the modules 606-614, may be a software module, such as a computer program.

[0142] The computing unit 604, and / or at least one of the modules 606-614, may be a combination of at least one software module and at least one hardware module.

[0143] In particular, the computing unit 604 or at least one of the modules 606-614 can be integrated into an electronic chip, or even into an application installed in a user device.

[0144] The device 600 may further comprise, optionally, an image storage means 616, for storing the acquired images. This module 616 may for example be configured to store at least one of the images acquired during step 204 of the methods 200, 300, 400 and 500.

[0145] FIGURE 7 is a schematic representation of a non-limiting exemplary embodiment of an apparatus according to the present invention.

[0146] The apparatus 700 of FIGURE 7 comprises means configured to implement the invention, and in particular any one of the methods 200, 300, 400 and 500.

[0147] The apparatus 700 of FIGURE 7 may include all of the elements of the apparatus 600 of FIGURE 6.

[0148] In the example shown in FIGURE 7, the device 700 is a smartphone, or a tablet, comprising all the elements of the device 600 of FIGURE 6. In a non-exhaustive manner, the device 700 of FIGURE 7 comprises a camera module 602 and the computing unit 604.

[0149] In addition, the apparatus 700 comprises a display screen 702 equipped with a detection surface 704, for example capacitive.

[0150] Of course, the device 700 may include other components than those indicated above.

[0151] FIGURE 8 is a schematic representation of another non-limiting exemplary embodiment of an apparatus according to the present invention.

[0152] The apparatus 800 of FIGURE 8 comprises means configured to implement the invention, and in particular any one of the methods 200, 300, 400 and 500.

[0153] The apparatus 800 of FIGURE 8 may include all of the elements of the apparatus 600 of FIGURE 6.

[0154] In the example shown in FIGURE 8, the device 800 is a virtual reality, VR, headset, or an augmented reality headset, comprising all the elements of the device 600 of FIGURE 6. The headset 800 of FIGURE 8 comprises in particular a camera module 602 and the computing unit 604.

[0155] Additionally, the helmet 800 includes a display screen 802 in / on a visor of said helmet 800.

[0156] Of course, the 800 helmet may include other components than those indicated above.

[0157] FIGURE 9 is a schematic representation of a non-limiting exemplary embodiment of an apparatus according to the present invention.

[0158] The apparatus 900 of FIGURE 9 comprises means configured to implement the invention, and in particular any one of the methods 200, 300, 400 and 500.

[0159] The apparatus 900 of FIGURE 9 may include all of the elements of the apparatus 600 of FIGURE 6.

[0160] In the example shown in FIGURE 9, the device 900 is a medical imaging device, such as an endoscope, an ultrasound device, etc. In particular, the medical imaging device 900 comprises a camera module 602 and the computing unit 604.

[0161] In addition, the medical imaging device 900 comprises a display screen 902 equipped with a detection surface 904, for example capacitive.

[0162] Of course, the medical imaging device 900 may include other organs than those indicated above.

[0163] FIGURE 10 is a schematic representation of a non-limiting exemplary embodiment of a vehicle according to the present invention.

[0164] The vehicle 1000 of FIGURE 10 comprises means configured to implement the invention, and in particular any one of the methods 200, 300, 400 and 500.

[0165] The vehicle 1000 of FIGURE 10 may include all of the elements of the apparatus 600 of FIGURE 6.

[0166] In the example shown in FIGURE 10, the vehicle 1000 is a land vehicle, in particular a car, comprising all the elements of the apparatus 600 of FIGURE 6. In particular, the vehicle 1000 comprises a camera module 602 and the computing unit 604.

[0167] In addition, the vehicle 1000 comprises a display screen 1002 equipped with a detection surface 1004, for example capacitive, arranged in the passenger compartment of the vehicle 1000.

[0168] Of course, the vehicle 1000 may include other components than those indicated above.

[0169] Of course, the invention is not limited to the examples which have just been described.

Claims

CLAIMS 1. Method (200;300;400;500) for imaging a scene with at least one camera module, each comprising an optical lens associated with an image sensor; said method comprising an acquisition of several images (IMi-IM n) of said scene at different discrete focusing distances, DFi, each with a respective depth of field, PCi = {PCi,min; PG, max}, comprising said respective focusing distance, DFi, and extending over a respective sharpness range, NET = PG, max- PG, min; an image acquired at a focusing distance, DFi, sharply representing parts of the scene located at distances included in the depth of field, PG, associated with said focusing distance, DFi; characterized in that it further comprises a step (202) of determining: - the smallest focusing distance (DFi) such that the lower limit (PCi,min) of the depth of field (PCi) associated therewith is less than or equal to a predetermined lower distance (Dmin); and / or - the greatest focusing distance (DFi) so that the upper limit (PCn,max) of the depth of field (PG.) associated with it is greater than a predetermined upper distance (Dmax).

2. Method (200;300;400;500) according to any one of the preceding claims, characterized in that the predetermined low distance (Dmin): - is chosen by a user; or - corresponds to the distance of the nearest object in the scene; or - corresponds to the smallest sharpness distance allowed by at least one camera module (602I-602K).

3. Method (400) according to the preceding claim, characterized in that it further comprises a step (402) of determining the distance of the closest object to the scene.

4. Method (200;300;400;500) according to any one of the preceding claims, characterized in that the predetermined high distance (D max): - is chosen by a user; or - corresponds to the distance of the most distant object in the scene; - corresponds to the greatest sharpness distance allowed by at least one camera module (602I-602K).

5. Method (200; 300; 400; 500) according to the preceding claim, characterized in that it further comprises a step (404) of determining the distance of the object furthest from the scene.

6. Method (200;300;400;500) according to any one of the preceding claims, characterized in that, for at least one focusing distance, the depth of field associated with said focusing distance is contiguous, or overlaps, with the depth of field associated with the following focusing distance.

7. Method (200; 300; 400; 500) according to the preceding claim, characterized in that, for each focusing distance, the depth of field associated with said focusing distance is contiguous, or overlaps, with the depth of field associated with the following focusing distance.

8. Method (200; 300; 400; 500) according to any one of claims 6 or 7, characterized in that, for at least one focusing distance, the depth of field associated with said focusing distance is contiguous with the depth of field associated with the following focusing distance.

9. Method (200;300;400;500) according to any one of claims 6 to 8, characterized in that, for at least one focusing distance, the depth of field associated with said focusing distance overlaps with the depth of field associated with the following focusing distance.

10. Method (200;300;400;500) according to any one of the preceding claims, characterized in that at least two, in particular all, images are acquired with the same camera module (602).

11. Method according to any one of the preceding claims, characterized in that at least two images are acquired with different camera modules (602I-602K).

12. Computer program comprising executable instructions which, when executed by a computing device, implement all the steps of the method (200; 300; 400; 500) according to any one of the preceding claims.

13. Apparatus (600;700;800;900) comprising: - at least one camera module (602), - at least one calculation unit (604); configured to implement all the steps of the method (200; 300; 400; 500) according to any one of claims 1 to 11.

14. Apparatus (1000) comprising: - at least one camera module (602), - at least one calculation unit (604); configured to implement all the steps of the method (200; 300; 400; 500) according to any one of claims 1 to 11.

Images