Imaging device having high geometric distortion

Abstract

The invention relates to an imaging device (1), comprising: - an image sensor (2); - an optical system (3) which comprises an optical axis (4) and is arranged to receive light beams and to direct them towards the sensor, the optical system having a variable magnification on the sensor that depends on the orientation and / or the position of each optical beam incident on the optical system with respect to the optical axis, characterised in that the magnification of the optical system comprises a minimum value on the sensor and a maximum value on the sensor, the ratio of the maximum magnification of the optical system to the minimum magnification of the optical system being equal to at least 1.2.

Description

[0001] DESCRIPTION

[0002] TITLE: High Geometric Distortion Imaging Device

[0003] Technical field

[0004] The present invention relates to an imaging device. It also relates to a corresponding method.

[0005] State of the prior art

[0006] Smartphone camera modules are often multiple within a single smartphone. In fact, several camera modules with different focal lengths are often combined to create a very wide-angle module, a wide-angle module, and a narrower-angle module within the same smartphone. The images from the three modules can be digitally merged. This has the disadvantage of multiplying the number of camera modules, which is more expensive.

[0007] Similarly, a periscope-type module can be used, which allows a large displacement of a lens group in order to ensure a fairly significant optical zoom function in amplification. These modules cost more than a camera module simply equipped, if necessary, with an adjustment of the lens focusing distance.

[0008] In another field, anamorphic lenses are known, which are devices that do not project the image with the same compression ratio along two perpendicular axes. These lenses are used in cinema, in particular to convert a width / length ratio of the image taken according to the ratio of another support (for example 24x36 to 9x16). These devices have an inhomogeneous magnification ratio along the two axes X and Y, but homogeneous along one of these axes. The present invention cannot use this type of lens to achieve the intended objective, because it aims to obtain a different magnification in at least one or some areas of the image, in order to associate a zoom function with it.

[0009] The aim of the present invention is to propose an imaging device or method allowing a zoom function while obtaining all or part of the technical advantages below:

[0010] - reduction in manufacturing cost, and / or

[0011] - better compactness, and / or - mechanical simplification, compared to the state of the art.

[0012] Statement of the invention

[0013] This objective is achieved with an imaging device, comprising:

[0014] - An image sensor,

[0015] - An optical system comprising an optical axis and arranged to receive light beams and direct them, preferably at least partly parallel to the optical axis, towards the sensor, the optical system having a variable magnification on the sensor and which depends on the orientation and / or the position of each optical beam incident on the optical system preferably relative to the optical axis and / or to the optical system, characterized in that the magnification of the optical system comprises a minimum value on the sensor and a maximum value on the sensor, the ratio of the maximum of the magnification of the optical system to the minimum of the magnification of the optical system being equal to at least 1.2.

[0016] Different light beams corresponding to a decrease in the magnification of the optical system can be imaged at different parts of the sensor moving away from a point or segment or surface on the sensor.

[0017] The magnification of the optical system may decrease when the angle of the light beam incident on the optical system increases preferably relative to the optical axis.

[0018] The optical system can include two lenses including:

[0019] - A first lens or a first face of a single lens (which ensures a first spatial concentration of an incident beam), preferably with constant or substantially constant magnification, and

[0020] - A second lens, or a second face of the single lens, located respectively between the first lens or the first face of the single lens and the sensor, responsible at least in part for the variability of the magnification of the optical system. The second lens may be located at a distance from the first lens equal to the focal length of the first lens plus or minus 20% of the value of this focal length of the first lens.

[0021] The magnification of the second lens may decrease as the angle of the light beam incident on the second lens increases preferably relative to the optical axis.

[0022] The magnification of the second lens may include a minimum value and a maximum value, the ratio of the maximum of the magnification of the second lens to the minimum of the magnification of the second lens being at least 2.

[0023] The optical system can be symmetrical around the optical axis.

[0024] The magnification of the optical system can be maximum on a central or substantially central part of the sensor.

[0025] The magnification of the optical system may be minimal on a peripheral part of the sensor.

[0026] The magnification of the optical system can be minimal on a part of the sensor elongated in one direction.

[0027] The device according to the invention may comprise longitudinal displacement means arranged to move the position of the sensor relative to the optical system so as to modify the distance between the optical system and the sensor and thus modify the focusing distance of the optical system and / or the magnification values ​​of the optical system on the sensor.

[0028] The device according to the invention may comprise lateral displacement means arranged to move the position of the sensor relative to the optical system so as to shift the sensor preferably relative to the optical axis and thus modify the part of the sensor having the maximum value of the magnification of the optical system.

[0029] The lateral displacement means can be position-controlled to restore a stable image.

[0030] The image sensor may comprise an array of pixels, said pixels all having the same dimension.

[0031] The image sensor may include a Bayer array:

[0032] - whose patterns all have the same dimension, or - the Bayer matrix being more resolved in lateral or peripheral parts arranged around a central part to increase a saturation threshold in these lateral or peripheral parts.

[0033] The device according to the invention may comprise means arranged and / or programmed to modulate the gain of an analog-digital converter at the output of the sensor.

[0034] The device according to the invention may further comprise correction means arranged and / or programmed to correct an image captured by the image sensor, comprising in particular:

[0035] - means of correcting or compensating for geometric distortion of the image, and / or

[0036] - means of correcting or compensating for vignetting or inhomogeneity in image brightness, and / or

[0037] - means of correcting or compensating for chromatic distortion of the image, and / or

[0038] - means of correcting or compensating for image sharpness.

[0039] The device according to the invention may further comprise zoom means arranged and / or programmed to zoom on an image from the image sensor by selecting a sub-part of the image sensor preferably so that an increase in the zoom on the image from the image sensor corresponds to an increase in the average value of the magnification of the optical system on the selected sub-part of the sensor.

[0040] According to yet another aspect of the invention, there is provided a smartphone comprising a device according to the invention.

[0041] According to yet another aspect of the invention, there is provided a vehicle comprising a device according to the invention, preferably integrated into a driving assistance system and / or for providing images for the automatic piloting of said vehicle.

[0042] The vehicle can be an automobile, a drone, or an airplane.

[0043] According to yet another aspect of the invention, there is provided an alarm and / or video surveillance system, comprising a device according to the invention.

[0044] According to yet another aspect of the invention, there is provided a medical imaging device, comprising a device according to the invention. The medical imaging device may comprise a diagnostic system or a surgical operation system.

[0045] According to yet another aspect of the invention, there is provided an imaging method implemented by a device according to the invention, comprising:

[0046] - a reception, by the optical system, of light beams so as to direct them preferably at least partly parallel to the optical axis towards the sensor, including different light beams having between them different orientations and / or positions of incidence on the optical system preferably with respect to the optical axis the optical system having a variable magnification on the sensor and which depends on this orientation and / or position of each optical beam incident on the optical system preferably with respect to the optical axis and / or to the optical system, so that the different beams are imaged on the sensor with different magnifications of the optical system on the sensor, characterized in that the magnification of the optical system comprises a minimum value on the sensor and a maximum value on the sensor, the ratio of the maximum of the magnification of the optical system to the minimum of the magnification of the optical system,preferably for the different beams imaged on the sensor, being equal to at least 1.2.,

[0047] Different light beams corresponding to a decrease in the magnification of the optical system can be imaged at different parts of the sensor moving away from a point or segment or surface on the sensor.

[0048] The magnification of the optical system may decrease when the angle of the light beam incident on the optical system increases preferably relative to the optical axis.

[0049] The optical system can include two lenses including:

[0050] - A first lens or a first face of a single lens (which ensures a first spatial concentration of an incident beam), preferably with constant or substantially constant magnification, and

[0051] - A second lens, or a second face of the single lens, located respectively between the first lens or the first face of the single lens and the sensor, responsible at least in part for the variability of the magnification of the optical system.

[0052] The second lens may be located at a distance from the first lens equal to the focal length of the first lens plus or minus 20% of the value of that focal length of the first lens.

[0053] Preferably, the magnification of the second lens may decrease as the angle of the incident light beam relative to the optical axis, on the second lens, increases.

[0054] The magnification of the second lens may comprise a minimum value and a maximum value, the ratio of the maximum of the magnification of the second lens to the minimum of the magnification of the second lens being equal, preferably for the different beams imaged on the sensor, to at least 2.

[0055] The optical system can be symmetrical around the optical axis.

[0056] The magnification of the optical system can be maximum on a central or substantially central part of the sensor.

[0057] The magnification of the optical system may be minimal on a peripheral part of the sensor.

[0058] The magnification of the optical system can be minimal on a part of the sensor elongated in one direction.

[0059] The method according to the invention may comprise a displacement, by the longitudinal displacement means, of the position of the sensor relative to the optical system so as to modify the distance between the optical system and the sensor and thus modify the focusing distance of the optical system and / or the different values ​​of the magnification of the optical system on the sensor.

[0060] Preferably, the method according to the invention may comprise a displacement, by the lateral displacement means, of the position of the sensor relative to the optical system so as to shift the sensor relative to the optical axis and thus modify the part of the sensor having the maximum value of the magnification of the optical system.

[0061] The lateral displacement means can be position-controlled to restore a stable image.

[0062] The image sensor may comprise an array of pixels, said pixels all having the same dimension.

[0063] The image sensor may include a Bayer matrix: - whose patterns all have the same dimension, or

[0064] - the Bayer matrix being more resolved in lateral or peripheral parts arranged around a central part to increase a saturation threshold in these lateral or peripheral parts.

[0065] The method according to the invention may comprise a modulation of the gain of an analog-digital converter at the output of the sensor.

[0066] The method according to the invention may further comprise a correction, by the correction means, of an image captured by the image sensor, comprising in particular:

[0067] - correction or compensation of geometric distortion of the image, and / or

[0068] - correction or compensation for vignetting or inhomogeneity of image brightness, and / or

[0069] - correction or compensation of chromatic distortion of the image, and / or

[0070] - a correction or compensation of image sharpness.

[0071] The method according to the invention may further comprise a zoom, by the zoom means, on an image from the image sensor by selecting a sub-part of the image sensor preferably such that an increase in the zoom on the image from the image sensor corresponds to an increase in the average value of the magnification of the optical system on the selected sub-part of the sensor.

[0072] The method according to the invention can be implemented:

[0073] - within a smartphone; and / or

[0074] - within a vehicle, preferably within an integrated driver assistance system and / or for the provision of images for the automatic piloting of said vehicle. The vehicle may be an automobile, a drone, or an airplane; and / or

[0075] - within an alarm and / or video surveillance system; and / or

[0076] - within a medical imaging device. The medical imaging device may include a diagnostic system or a surgical operating system.

[0077] Description of the figures and embodiments Other advantages and particularities of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, and the following appended drawings:

[0078] [Fig. 1] Figure 1 is a schematic side view of a first embodiment of imaging device 1 according to the invention, which is the preferred embodiment of the invention,

[0079] [Fig. 2a] Figure 2a is a schematic side view of an optical system illustrating the concept of focal length,

[0080] [Fig. 2b] Figure 2b is a schematic side view of the first embodiment of imaging device 1 according to the invention,

[0081] [Fig. 3] Figure 3 illustrates the variation in focal length of the optical system 3 of the first embodiment of the imaging device according to the invention, [Fig. 4] Figure 4 illustrates the distance to equivalent optical center, for the optical system 3 of the first embodiment of the imaging device 1 according to the invention, for a sharpness at 2m,

[0082] [Fig. 5] Figure 5 is a schematic side view of the first embodiment of imaging device 1 according to the invention,

[0083] [Fig. 6] Figure 6 is a schematic side view of the first embodiment of imaging device 1 according to the invention,

[0084] [Fig. 7] Figure 7 illustrates, in the plane of the sensor 2, different areas or parts of different magnifications of the optical system 3 on the sensor 2 in the first embodiment of the imaging device 1 according to the invention, [Fig. 8] Figure 8 illustrates, in the plane of the sensor 2, different areas or parts of different magnifications of the optical system 3 on the sensor 2 in a second embodiment of the imaging device according to the invention,

[0085] [Fig. 9] Figure 9 illustrates, in the plane of the sensor 2, different areas or parts of different magnifications of the optical system 3 on the sensor 2 in a third embodiment of the imaging device according to the invention, [Fig. 10] Figure 10 illustrates, in the plane of the sensor 2, different areas or parts of different magnifications of the optical system 3 on the sensor 2 in a fourth embodiment of the imaging device according to the invention, and

[0086] [Fig. 11] Figure 11 illustrates, in the plane of the sensor 2, different areas or parts of different magnifications of the optical system 3 on the sensor 2 in a fifth embodiment of the imaging device according to the invention.

[0087] These embodiments being in no way limiting, it will be possible in particular to consider variants of the invention comprising only a selection of characteristics described or illustrated subsequently isolated from the other characteristics described or illustrated (even if this selection is isolated within a sentence comprising these other characteristics), 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 comprises at least one preferably functional characteristic without structural details, and / or with only a part of the structural details if this part only is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0088] We will first describe, with reference to Figures 1 to 7, a first embodiment of imaging device 1 according to the invention.

[0089] The first embodiment of imaging device 1 (also called camera 1) comprises:

[0090] - A 2 image sensor,

[0091] - An optical system 3 (also called lens 3) comprising an optical axis 4 also called Z axis (said system 3 being preferably centered on this axis 4) and arranged to receive light beams and direct them at least partly parallel to the optical axis (in order to use the lens preferentially in a configuration of good light capture because its projected surface is generally larger when the beams enter around an axis of optical symmetry of a lens, and this also minimizes certain possible optical aberrations) towards the sensor 2, more precisely to focus them on the sensor 2.

[0092] The light beams of the present description are light beams that can range from X-rays to infrared, and have a wavelength between 10 nm and 3000 nm, preferably between 400 nm and 700 nm. The optical system 3 has (preferably considering a constant wavelength between 10 nm and 3000 nm, preferably between 400 nm and 700 nm) a magnification as well as a focal length:

[0093] - variable depending on the regions on sensor 2, and

[0094] - which depends on the orientation (or angle a) and / or the position of each optical beam incident on the optical system 3 relative to the optical axis 4.

[0095] A magnification (which is a dimensionless quantity) of the system 3 on the sensor 2 is defined for a given incident beam coming from a point of an object as the ratio between the angle , relative to the axis 4, under which the image of this point formed by the optical system 3 is seen (i.e. at the output of the system 3, preferably for the image formed on the sensor 2) and the angle a , relative to the axis 4, under which this point of the object is seen "with the naked eye" i.e. at the input of the optical system 3. These angles are oriented angles. If the image is inverted, the magnification is negative.

[0096] The magnification of the optical system 3 comprises a minimum magnification value on the sensor 2 and a maximum magnification value on the sensor 2, the ratio of the maximum magnification of the optical system 3 to the minimum magnification of the optical system 3 being equal (typically for an angle o varying from 0° to 45°) to at least 1.2 in absolute value, preferably at least 1.5 in absolute value, preferably at least 2 in absolute value, preferably at least 4 in absolute value, preferably at least 5 in absolute value, preferably at least 6 in absolute value.

[0097] Different light beams corresponding to a decrease in the magnification of the optical system are imaged in different parts 51, 52, 53 (illustrated in Figure 7) of the sensor 2 moving away from a point 6 or a segment 7 or a surface on the sensor 2.

[0098] In the case of Figure 7, the system 3 has a symmetry around the axis 4, and different light beams corresponding to a decrease in the magnification of the optical system 3 are imaged in different parts 51, 52, 53 of the sensor 2 moving away from a point 6 on the sensor 2, so that there is, on the sensor 2, a central zone 51 (circular or substantially circular) of high magnification (which decreases progressively moving away from the point 6), a first peripheral zone 52 (circular or substantially circular) of lower magnification (which decreases progressively moving away from the point 6) and located around the central zone 51, and a second peripheral zone 53 of even lower magnification (which decreases progressively moving away from the point 6) and located around the first peripheral zone 52.

[0099] The magnification of the optical system 3 decreases when the angle α of the light beam incident on the optical system 3 increases relative to the optical axis 4.

[0100] The optical system 3 includes two lenses including:

[0101] - A first lens 31 (also noted Ll), which ensures a first spatial concentration of an incident beam, and at constant or substantially constant magnification and focal length depending on the angle a, and

[0102] - A second lens 32 (also noted L2), located between the first lens 31 and the sensor 2, and responsible at least in part (and even totally in the first embodiment) for the variability of the magnification and the focal length of the optical system 3.

[0103] The second lens 32 is for example located at a distance from the first lens 31 equal to the focal length of the first lens 31 at plus or minus 20% of the value of this focal length of the first lens 31.

[0104] The magnification of the second lens 32 decreases when the angle α of the light beam incident on the second lens 32 increases relative to the optical axis 4.

[0105] The magnification of the second lens 32 comprises a minimum value and a maximum value, the ratio of the maximum of the magnification of the second lens to the minimum of the magnification of the second lens being equal (typically for an angle a varying from 0° to 45°) to at least 2 in absolute value, preferably at least 6 in absolute value, preferably at least 8 in absolute value, preferably at least 10 in absolute value.

[0106] The optical system 3 is centrosymmetric, that is to say symmetrical around the optical axis 4.

[0107] The magnification of the optical system 3 is maximum on a central or substantially central part 51 of the sensor 2. The magnification of the optical system is minimum on a peripheral part 53 of the sensor 2.

[0108] In the present description, the variability of magnification of the system 3 and of the lens 32 (or its constant character for the lens 31) corresponds to a variability of focal length of the system 3 and of the lens 32 (or its constant character for the lens 31), and vice versa, and the terms magnification and focal length can therefore be exchanged in the present description of the device 1 and of its implemented method while remaining within the scope of the invention.

[0109] Thus, according to the invention, the local curvature of the 2 èmelens varies greatly in the peripheral region, to modulate the equivalent focal length of the optical beam arriving on the lateral zones of the sensor 2.

[0110] According to the state of the art, the focal length of an optical system (lens or a stack of lenses in the format of an objective) is defined as the distance CF between:

[0111] - the optical center C of the optical system and

[0112] - the average point F where the cone of light leaving the system focuses.

[0113] With reference to figure 2a, for the invention, we will call focal length the distance between the projection on axis called ZZ' (which corresponds to axis Z or 4), of respectively points C and F at two points called Cz and Fz (also noted C' and F' in the rest of this description), ZZ' being an axis perpendicular to the image plane considered, this image plane corresponding in figure 2a to the plane of the sensor (whose plane contains F and Fz, for an image coming from infinity at the input of the optical system).

[0114] This definition allows us to directly compare the focal lengths f for the different possible angles formed by the incident beams for different points on the sensor, in particular if it is flat. Thus, equality of magnification between two different parts of the image means that the distances f are also equal.

[0115] According to the state of the art also, for two different angles of incidence a, the focal points have the same projection F on the optical axis, because we are trying to obtain an image appearing in the same plane perpendicular to the optical axis. This defines the focal length of the optical system, which is the one at which to place the image plane, for a set of optical beams coming from a point "at infinity", or very far from the lens, to obtain a sharp image of a plane of the scene at infinity.

[0116] According to the invention, for the optical system 3, this definition is retained but considering as illustrated in figures 2b and 3 that the focal length C'F' of the system 3 depends on the angle a of incidence of all the light beams incident on the optical system 3. Thus, this makes it possible to design an optical system 3 such that the focal length C'F'(o) becomes a non-constant function according to a.

[0117] As illustrated in figures 2b and 3, it is possible to have a ratio for example of at least 1.2 in absolute value or at least 1.5 in absolute value or at least 2 in absolute value or at least 4 in absolute value or at least 5 in absolute value or at least 6 in absolute value between the equivalent focal length C'Fa' at the center of the optical system 3 for o = 0 and the equivalent focal length C'Fb' on the edges of the optical system 3 for example for o = 45°.

[0118] For example, referring to Figure 2b, C'Fa'= 120 mm in the center and C'Fb'=20 mm on the edges.

[0119] When designing the system 3 or each lens 31, 32, the distance (Z) between the plane of the sensor 2 and the equivalent optical center C or Cl or C2 respectively of the system 3 or of the lens 31 or of the lens 32 can also be taken into account.

[0120] In fact, a lens has an equivalent point called the center through which all the rays would appear to pass if the light arrived as a single light ray, this center possibly being physically outside the lens.

[0121] Here, each angle a corresponds to a focal length, therefore to an equivalent pseudo lens. Each of these lenses has a particular position of its pseudo center. When this pseudo center is placed at the focal length of the sensor, the image is sharp at infinity (and the rays entering the focusing device considered 3, 31 or 32 are all parallel).

[0122] We have the conjugation relation: 1 / f = 1 / dl + l / d2 where f is the focal length, dl is the distance from the pseudo center C or Cl or C2 to sensor 2, and d2 the distance from the pseudo center C to the point of the scene.

[0123] Given the chosen definition of focal length as a projection onto the 7.7' axis, it is appropriate to define the conjugation relation with dl, d2, f, as also being the three distances projected onto the 77' axis. Of course, this amounts to factoring out the projection factor and making it disappear with respect to the usual conjugation relation, which therefore continues to be true (to a certain approximation).

[0124] It is appropriate to modulate the distance between the optical center C and sensor 2, for a given angle a. This optical center of variable position as a function of a will be noted C(o). For example, it is a question of simultaneously obtaining all the zones of sensor 2 in focus for all the points of a particular plane of the scene, located at a distance ZO along the Z axis. This scene plane - sensor plane relationship is not obligatory. We can also choose that the surface of sensor 2 corresponds to a surface shape other than a plane.

[0125] Furthermore, when system 3 is moved longitudinally (parallel to axis 4) above sensor 2 to change its focusing distance, it is likely that the new selected sharpness surface will no longer be a plane.

[0126] Thus, in use, the distance between the sensor 2 and the lens 3 can be modified (by the movement means 8, 81 described below) to move this zone of sharpness on the scene, which will then be deformed.

[0127] Figure 4 illustrates the equivalent optical center distance, for sharpness at 2m, obtained from the same lens 3 as in Figure 3 having a distance of 120mm at the center and 20mm at the edge, set for a sharp image at infinity, whose lens is moved to tune it at a distance of 2m. If sharpness is desired over the entire image, at 2m, it would then be necessary to modify by 7.45mm the projected distance on the Z axis, between the optical centers for the central part at high magnification Cl and for the lateral part C2.

[0128] We notice in fact a difference of (127.65-20.20) - (120 -20) = 7.45 mm between the equivalent optical centers, between the 2 settings at infinity and at 2m.

[0129] In practice, as the beam is more parallel (to the optical axis) in the center, we can concentrate on the sharpness at the edge, that in the center will be relatively little degraded. But the image to be observed does not necessarily need sharpness everywhere, we can also maintain sharpness in the center.

[0130] Typically, a longer focal length means less focused beam. Therefore, it is appropriate to modulate the low angle areas a by giving the lens 32 little curvature near the 4 axis.

[0131] Thus, according to the invention, the device comprises for the system 3 and / or for the lens 32 a focal distance (the highest) in its central zone (i.e. for its parts closest to the axis 4), a lower focal distance for each lateral zone (i.e. for its parts furthest from the axis 4), and a continuous variation of the focal distance between the central zone and each lateral zone.

[0132] This allows for a fairly magnified image in the central area, and a much less magnified image in the lateral areas.

[0133] Thus, the device 1 according to the invention consists of a camera module 1 capable of having a high resolution in a central part 51, medium resolution around 52, and low resolution on the edges 53. Other arrangements are possible, but the latter is more natural because physiologically, we generally focus our attention in the center of the field of view where human vision is also more resolved.

[0134] Along with this higher resolution, the magnification power is modulated strongly depending on the angle: more magnification in the center 51 where the resolution is higher.

[0135] The magnification of a lens is linked to its so-called focal length. The greater the latter, the more the image produced downstream of the lens (here constituted by system 3, that is to say by lenses 31 and 32) will be dilated by simple geometric effect.

[0136] Thus, in an equivalent manner, the focal length of each angular sector of the objective 3 produced for the invention is made strongly dependent on the angle a: we ensure that there is less focal length when the angle a of the incident beam increases relative to the optical axis 4 of the objective 3.

[0137] This gives an image capture system 1, also called camera module 1, using an optic 3 with high geometric distortion. This high geometric distortion is designed to increase the density of points preferentially in the central part of the field of the sensor 2. This allows the demand to obtain more resolution such as:

[0138] - an optical zoom, or

[0139] - switching to another camera module with a narrower angle, or in a lower resolution mode to provide a wider angle image.

[0140] So from the same device 1, the device 1 makes it possible to create the equivalent of a mechanically more complex device with optical zoom or multiple camera modules. With reference to Figure 1, in a concrete case of the first, non-limiting embodiment of the device 1 according to the invention:

[0141] - the first lens 31 ensures a focal length substantially equal to 240 mm in all its directions (i.e. according to all angles o of the beams)

[0142] - for the 2 ème lens 32: o in the center: the 2 èmeLens 32 contains a moderate curvature at its center (i.e. for its parts closest to axis 4), which also gives it a focal length of 240mm at its center. The 2 lenses 31, 32 add their focusing power (1 / f), which leads to a total focal length of system 3 of 120mm at the center of system 3 (i.e. for its parts closest to axis 4). o At the edges: On the extreme o angles around lens 32 (i.e. for its parts furthest from axis 4), the 2 ème lens 32 is very curved to locally reach at its ends an equivalent focal length of 22mm. The sum of the two focal lengths of the two lenses 31, 32 then makes a total focal length of the system 3 of 20mm for the highest values ​​of o.

[0143] We therefore have a magnification or focal length ratio, between its maximum value and its minimum value:

[0144] - From 240 / 22 = 10.9 for the 32 lens

[0145] - From 120 / 20 = 6 for system 3

[0146] The optical center Cl for the central part (i.e. closest to axis 4 or corresponding to the smallest angles a) of system 3 can be located quite far from the 2 lenses 31, 32 on the left, to be approximately 120 mm from sensor 2.

[0147] The optical center C2 of the extreme parts (i.e. the furthest from the axis 4 or corresponding to the highest angles a) of the system 3 can be located substantially inside the end of the 2nd lens 32 to be approximately 20 mm from the sensor 2.

[0148] Typically, each lens 31, 32 is made of plastic, for example polycarbonate, and has a diameter, perpendicular to the axis 4, of approximately 10 mm for example. The device 1 comprises means 8, 81 for longitudinal movement (typically comprising one or more micrometric motors along 1 axis, or along 2 or 3 distinct axes preferably perpendicular to each other, preferably a single axis parallel to the axis 4) arranged to move the relative position of the sensor 2 (parallel to the optical axis 4) relative to the optical system 3 so as to modify the distance between the optical system 3 and the sensor 2 and thus modify the values ​​of the magnification of the optical system 3 on the sensor 2.

[0149] The device 1 comprises means 8, 82 for lateral movement (typically comprising one or more micrometric motors along 1 axis, or along 2 or 3 distinct axes preferably perpendicular to each other, preferably 2 axes perpendicular to each other and to the axis 4) arranged to move the relative position of the sensor 2 (perpendicular to the optical axis 4) with respect to the optical system 3 so as to shift the sensor 2 with respect to the optical axis 4 and thus modify the part of the sensor 2 on which the beam having the maximum value of the magnification of the optical system is imaged.

[0150] The lateral displacement means 8, 82 are positionally controlled to the restitution of a stable image by a processing unit 9 despite the movements of the device 1.

[0151] Ideally, two moving groups are required to modulate both the focal length and the distance to the equivalent optical center if one wants to keep the image sharp when zooming, and / or work with a large depth of field. For example, the distance of lens 31 and that of lens 32 can be modulated separately. This can provide the degree of freedom to change both focus and magnification.

[0152] At least one so-called liquid lens can also be used to modify at least one curvature, which can modulate the focusing distance and / or the magnifications of the objective.

[0153] The processing unit 9 comprises at least one computer, a central or computing unit, an analog electronic circuit (preferably dedicated), a digital electronic circuit (preferably dedicated), and / or a microprocessor (preferably dedicated), and / or software means.

[0154] The image sensor 2 comprises a matrix of pixels, said pixels all having the same dimension. The image sensor 2 comprises a Bayer matrix (i.e. a matrix of light detection patterns), the patterns of which all have the same dimension and are optionally interspersed with so-called dual pixel patterns (for adjusting the focusing distance).

[0155] This strong modulation of the equivalent focal length of system 3 and / or lens 32 (located between lens 31 of system 3 and sensor 2) is accompanied by several effects:

[0156] (a) The projection of a grid occupying the major part of the field of camera 1 (square mesh grid) of the scene is no longer a grid (square mesh): there is a strong geometric dispersion, called cousin, because the corners of the grid appear strongly inside the expected grid design, due to the compression of the distances which pushes the projected points towards the center of sensor 2, for the points located angularly far from a = 0.

[0157] (b) The central part of the image is less exposed, in terms of brightness received per unit area, than the peripheral parts. Indeed, the high magnification in the center selects for each pixel a narrower cone of light, therefore less light. For a factor of 6 like the example in figure 1, the ratio in area, therefore in brightness, is 6 2 = 36 so quite strong between the high angle parts and in the center.

[0158] (c) Finally, the chromatic dispersion can also be accentuated, with a fixed number of lenses 31, 32 making up the system 3. By increasing the number of lenses 31, 32, etc. of the system 3, the chromatic distortion can be reduced.

[0159] (d) When the nominal focusing distance of camera module 1 is changed, there is a modulation of the shape of the surface of the sharpness locus. From flat, it can become curved.

[0160] The device 1 further comprises correction means (forming part of the processing unit 9) arranged and / or programmed to correct an image captured by the image sensor, comprising in particular:

[0161] - (a) means for correcting or compensating for geometric distortion of the image; the correction means are arranged and / or programmed to process the images produced by the sensor 2 with the aim of displaying them without distortion, with high compensation for geometric distortion, according to known state-of-the-art methods. This amounts to moving parts of the image outwards, therefore translating and / or interpolating pixels in the high angle areas a. Symmetrically, pixels can also be decimated in the centre according to the current representation of the image, if this allows not needing the full resolution of the sensor 2. It is also possible to advantageously use sampling that is too high compared to the current one of the display, for a particular representation of the contours of the imaged objects. As a general rule, this geometric distortion can depend on the distance between the point of the object in the scene and the camera module 1.This effect is generally accentuated for objects close to camera 1. In this case, the compensation may benefit from receiving an estimate of this distance as input, in order to be more precise; and / or.

[0162] - (b) means of correcting or compensating for vignetting or inhomogeneity of brightness of the image. This phenomenon compensates and even overcompensates for the vignetting effect. This effect is as follows: when the light arrives at an angle a, the captured angular surface decreases because the lens 31 at the entrance is seen at an oblique angle which reduces its apparent section and therefore its light collection.The correction means use for this a Bayer Matrix (part of the sensor 2) with a higher exposure time in the center of the sensor 2 to compensate for the loss of brightness, and a lower exposure time around to avoid saturation; It is also possible to use a first lens 31 with a fairly concave shape, to increase vignetting: as such a shape is contradictory with the expected convergence effect of the beam, it is then necessary to produce more convex curvature on the second face of the lens 31, or on at least one other lens 32 located between the input lens 31 and the sensor 2. It is possible, if the pixel pitch is not already at the minimum possible for the technology, to use a more resolved Bayer matrix in the lateral parts to increase the saturation threshold.It is also possible to modulate the gain of an analog-to-digital converter at the output of sensor 2, for example by dividing the photocurrent received from sensor 2 before sampling it, for example by a capacitive divider at the input of a blocking sampler, to limit the charge to be taken into account in the Analog / Digital conversion. It is also possible to use a technology with 'active' sampling time individualized according to the region of sensor 2: this makes it possible to limit the time elapsed between the resetting (RAZ) of the capacitors accumulating the charge generated by the photodiodes of sensor 2, and the action of the blocking sampler, where less electrical gain is desired; and / or.

[0163] - (c) means for correcting or compensating for chromatic distortion of the image. The correction means are arranged and / or programmed to compensate for chromatic distortion by processing the pixel displacements of the 3 colors differently; and / or

[0164] - (d) means for correcting or compensating for image sharpness. The correction means are arranged and / or programmed to correct the effects of loss of sharpness, in particular to enhance sharpness, by taking into account the PSF transfer function (Point spread function), or an estimate of its effects.

[0165] The device 1 further comprises zoom means forming part of the processing unit 9) arranged and / or programmed to zoom in on an image, coming from the image sensor 2, by selecting a sub-part of the image sensor 2 so that an increase in the zoom on the image coming from the image sensor 2 corresponds to an increase in the average value of the magnification of the optical system 3 on the selected sub-part of the sensor 2. For example, by default the device 1 can record and / or display a zoomed-out image corresponding to the assembly of the zones 51, 52, and 53, and a user can zoom in progressively by removing at least a part of the zone 53, then all of the zone 53 and at least a part of the zone 52, then all of the zone 53 and all of the zone 52 and at least a part of the zone 51, so as to increase the average value of the magnification on the recorded and / or displayed image as and when increasing the zoom.

[0166] In the preceding description, the variable magnification or focal length must be understood as at least one variable magnification or focal length, because as will be seen later (with reference to figures 5 and 6) the system 3 or the lens 32 can comprise, in variants described in a more detailed or complex manner, several magnifications or focal lengths which vary (typically two magnifications or focal lengths, along two different axes for example U and V, which preferably vary continuously as a function of a).

[0167] The focal length of a lens is a distance, which would be the distance at which a parallel beam entering the said lens is supposed to focus on a single point at the exit of the lens (if it is converging), or at the entrance (virtual point) if the lens is diverging, relative to the "optical center" of the said lens.

[0168] This focal length therefore characterizes the bending power of the light entering the lens.

[0169] From the previous focal point, on the axis connecting the point from which the input light appears to come (point A) to the point where the output light appears to converge (point B), by subtracting the focal length on this axis, we arrive at a point which appears to be the one by which the light does not appear to be deflected. This point is called the optical center of the lens.

[0170] Applying these two notions to the concept of multi-magnification in an objective, we obtain:

[0171] - For each point of origin of the light entering the optical system (lens or objective stack of lenses), there is a cone of light, defined by a source point (virtual or real) (A) from which the light seems to come, a point possibly at infinity.

[0172] At the exit of the lens, this cone of light is supposed to focus in a fairly punctual zone at the exit (B), possibly located at infinity if the wavefront is very flat, or if the light rays are very parallel.

[0173] When one of the points is at infinity, point A or point B, we can continue to define the optical center by considering the point at a finite distance, and the optical direction defined on the side of the point at infinity (because the beam is then parallel).

[0174] Referring to Figures 5 and 6, consider for example the two stacked centrosymmetric lenses 31, 32.

[0175] - The first lens 31 is assumed to be convex and relatively close to a “classical ideal” lens, in the sense that over a wide angular aperture, the image of a point at infinity is formed in a plane without significant geometric distortion.

[0176] - The second lens 32 has 2 concave faces, its second face on the sensor 2 side being very curved on the edges. So:

[0177] On an axis inclined relative to the central axis 4, we observe in this second face of this second lens 32 a very different radius of curvature according to the local radial axis, also called sagittal (let us call it the U), and the so-called tangential axis (let us call it the V). Along U, the curvature is significant. Along V, the curvature is very small, or even zero.

[0178] Thus, let us assume that the incident beam is still spherically symmetrical when exiting lens 31. When it exits lens 32, it undergoes a much greater curvature along the U axis. This causes this component to converge at a shorter distance than the curvature along the other axis. Thus, we can define 2 different focusing distances along the U axis and the V axis.

[0179] The proper axes are defined according to the combination of the effects of the different lenses 31, 32 of the system 3.

[0180] Generally, one of the two U and V axes is the sagittal axis, the other is the tangential axis, in a centrosymmetric optical system.

[0181] The 4-axis (also called the Z-axis) is chosen as the rotational symmetry axis of a centrosymmetric 3-axis system. The X and Y axes define any plane perpendicular to this 4-axis.

[0182] We then have, with reference to figures 5 and 6:

[0183] A: point from which the beams of light appear to originate before reaching system 3.

[0184] Bu: point where the beams of light seem to converge along the proper axis

[0185] U, at the exit of system 3.

[0186] Bv: point where the beams of light seem to converge along the proper axis

[0187] V, at the exit of system 3.

[0188] Cu: Optical center of system 3 for the U axis.

[0189] Cv: Optical center of system 3 for the V axis.

[0190] Fu is the focal distance defined between Cu and Bu when A is at infinity (left) in Figure 1, 2b, 5 or 6.

[0191] Fv is the focal length defined between Cv and Bv when A is at infinity (left) in Figure 1, 2b, 5 or 6.

[0192] But the image obtained may not be sharp whatever the position of the sensor 2, which is not desirable. To remedy this fact, it is then appropriate to move, by designing the shapes of the lenses 31 and 32, the "optical centers" along the U and V axes, by placing the Cv at a z coordinate (along the Z or 4 axis) lower than the z coordinate (along the Z or 4 axis) of Cu, more precisely at the difference between the focal lengths Fu and Fv, which then means that, for a source point at infinity, the focalizations become merged again in a certain plane P (which preferably corresponds to the plane of the sensor 2 thanks to the means 81). It is then ensured that this plane P is also that for the other incident angles of the beam, including in particular the zero angle a at the center. Thus, it is possible to obtain a sharp image everywhere, despite a different magnification ratio depending on the distance from the optical axis R, and a different ratio between the local axes U and V.

[0193] Thus, still for a non-zero angle of incidence a, we ensure that the curvature of the lens 32 along the axis V is negligible, which is naturally the case with a lens that is very curved in the radial axis. We can then consider that the center Cv would be substantially that of the passage of light in the lens 31, for example.

[0194] And we make sure that the focal length Fv is substantially that defined by the lens 31 also, with the offset linked to the refraction in the lens 32 close, to be included in the design. This defines the position of the convergence point in the other axis V.

[0195] On the other axis U, a significant difference in curvature is introduced between the two faces of the lens 3, so that each beam is greatly modified in curvature by the lens 32 in this direction when passing from the first face of the lens 32 (on the side of the lens 31) to the second face of the lens 32 (on the side of the sensor 2). Thus, the distance Fu is much less than Fv, and the center of curvature Cu can be moved to the level of the lens 32, for example, or at least towards the lens 32, compared to Cv which remains towards the lens 31. Thus, by adjusting the curvatures of the faces of the lens 32, it is ensured that the point of convergence is also in the plane P of convergence along the axis V.

[0196] Figures 5 and 6 are not to scale: point A is generally quite far away, its position here is not to scale, for example the distance between A and lens 31 is of the order of a meter, the distance between lens 31 and sensor 2 is of the order of 5 to 10mm.

[0197] In Figure 6, the beam 41 in the center and the beam 42 on the edge do not travel through the same area of ​​the lens 32, which makes it possible to benefit from quite different beam curvature powers between these two areas (here central and peripheral). Of course, there is a continuous modulation, with overlapping areas between the two.

[0198] If the design is to predominantly use a source point located at a finite distance A from the objective, it is appropriate to ensure equality of the convergence points for this distance and not for a source point located at infinity.

[0199] In the previous design reasoning, the local focal length, along each axis, must be replaced by that such as: l / (distance between Cu and A) + l / (distance between Cu and Bu) = 1 / Fu l / (distance between Cv and A) + l / (distance between Cv and Bv) = 1 / Fv

[0200] We then make sure that Bu is close to Bv along the Z axis, in order to arrive at the same result, but in this case, it is the distance between Cu and Bu and the distance between Cv and Bv that should be added to Z(Cu) (the position of Cu along the Z axis, i.e. axis 4) and Z(Cv) (the position of Cv along the Z axis, i.e. axis 4), to obtain a z(Bu) (the position of Bu along the Z axis, i.e. axis 4) and z(Bv) (the position of Bv along the Z axis, i.e. axis 4) that are close.

[0201] Since there is also a risk of obtaining a position difference according to AR = (R(Bu) - R(Bv) ), we can also usefully seek to compensate for this aspect, by keeping AR close to zero. For example, we can also introduce a geometric distortion defect from lens 31 to obtain this result.

[0202] Whatever its variant or embodiment, the imaging device 1 according to the invention can be integrated into numerous forms of system or device, and one can for example have, in a non-limiting manner:

[0203] - A smartphone comprising an imaging device 1, and / or

[0204] - a vehicle comprising an imaging device 1, preferably integrated into a driving assistance system and / or for providing images for the automatic piloting of said vehicle; this vehicle may for example be an automobile, or an aircraft such as a drone or an airplane; and / or

[0205] - an alarm and / or video surveillance system, comprising an imaging device 1; and / or

[0206] - a medical imaging device, comprising an imaging device 1. This medical imaging device may comprise a diagnostic system or a surgical operating system. The device 1 (and its implemented method) offers numerous technical advantages.

[0207] Device 1 allows for improved night vision: the central part of sensor 2 receives less light. It will therefore be possible to expose for longer periods in the center if the technology of sensor 2 allows it; the disadvantage being greater sensitivity to movements, either of device 1, or of the observed scene, or of both.

[0208] Compared to state-of-the-art devices combining several camera modules including a wide-angle module and a moderate-angle module, the device 1 allows the removal of a wider-angle camera module. Thus, two state-of-the-art camera modules can be replaced by the device 1 providing vision at these wider angles, but also fine resolution at smaller angles. The invention makes it possible, for example, to merge several state-of-the-art cameras into a single one, with a more resolved area in the center, the image of which can be selected exclusively if one is interested in magnification in relation to this part of the field.

[0209] In the prior art, it is even common to combine, for example, 3 cameras: one small angle, one medium angle, one large angle (for example, a smartphone having 3 separate camera lenses), with only one of the cameras providing the image to be obtained depending on the area to be viewed. The invention makes it possible to merge these 3 modules into one.

[0210] The invention also allows the optical zoom function to be removed from a state-of-the-art camera module specializing in reduced angles. For example, if a user wishes to have more details in the central part of the image:

[0211] - in the prior art, it requires an optical zoom function, i.e. a modification of the lens-sensor distance, over a relatively large distance. At the same time, it may be necessary to modify the optical center-sensor distance to keep it consistent with the observed part. There may possibly be 2 mobile optical groups, with a second distance modification.

[0212] - the invention makes it possible to eliminate this or these mobile optical groups. It replaces this optical zoom function with a more framed image restitution on an interior zone such as what the optical zoom would have done. As the pixel density is greater, the better resolved information is present in the image at the sensor 2. If necessary, if the sharpness of the optics is not sufficient, a deconvolution taking into account the PSF of the sensor can further improve the sharpness of the image obtained in this zoomed part.

[0213] That being said, a device 1 according to the invention can furthermore, if necessary, integrate another camera module with a wider angle than that corresponding to the optical system 3. This other module can provide the missing information of the image in the peripheral zones, compared to a restitution of straight edges, which causes loss of information in the less dilated lateral zones, compared to those dilated. This other camera module with even wider angles than the system 3 can provide the missing data during these image distortion compensations.

[0214] The imaging method embodiment implemented by the device 1 typically comprises:

[0215] - a reception, by the optical system 3, of light beams so as to direct them at least partly parallel to the optical axis 4 towards the sensor 2, including different light beams having between them different orientations and / or positions of incidence on the optical system relative to the optical axis, the optical system having a variable magnification on the sensor which depends on this orientation and / or position of each optical beam incident on the optical system relative to the optical axis, so that the different beams are imaged on the sensor with different magnifications of the optical system on the sensor, the magnification of the optical system comprises a minimum value on the sensor and a maximum value on the sensor, the ratio of the maximum of the magnification of the optical system to the minimum of the magnification of the optical system, preferably for the different beams imaged on the sensor, being equal to at least 1.2.

[0216] This embodiment of the method according to the invention may further comprise all or part of the steps below:

[0217] - a displacement, by the longitudinal displacement means 8, 81, of the position of the sensor relative to the optical system so as to modify the distance between the optical system and the sensor and thus modify the different values ​​of the magnification of the optical system on the sensor; and / or

[0218] - a displacement, by the lateral displacement means 8, 82, of the position of the sensor relative to the optical system so as to shift the sensor relative to the optical axis and thus modify the part of the sensor having the maximum value of the magnification of the optical system; and / or

[0219] - a correction, by the correction means 9, of an image captured by the image sensor, comprising in particular: o a correction or compensation of geometric distortion of the image, and / or o a correction or compensation of vignetting or inhomogeneity of brightness of the image, and / or o a correction or compensation of chromatic distortion of the image, and / or o a correction or compensation of sharpness of the image; and / or

[0220] - a zoom, by the zoom means 9, on an image from the image sensor by selecting a sub-part of the image sensor so that an increase in the zoom on the image from the image sensor corresponds to an increase in the average value of the magnification of the optical system on the selected sub-part of the sensor.

[0221] The method embodiment according to the invention can be implemented within a smartphone, within a vehicle, within an alarm and / or video surveillance system, and / or within a medical imaging device.

[0222] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. For example, in one or more variants or alternative embodiments considered solely for their differences with respect to the device 1 previously described:

[0223] - the system 3 can be made up of o more than 2 lenses. In this case, the first lens 31 of the system, i.e. the furthest from the sensor 2, preferably has a constant focal length and magnification as previously described, or o a single lens, with a slightly curved central zone and increasingly curved lateral or peripheral zones, for example on the second face on the sensor side, the first face on the imaged object side then having a fairly uniform curvature over the entire lens, which ensures the concentration of the beam in a reduced space on the second face.However, such a variant is quite disadvantageous compared to the case comprising at least two lenses, because it comprises fewer degrees of freedom, typically the shapes of only two surfaces instead of those of four surfaces, typically also, which is related, the presence of air between the two lenses which modifies the possible deflection of the beams, which makes it more difficult to obtain all of the constraints mentioned during the embodiments; and / or compared to the embodiment of device 1 described with reference to figures 1 to 7, and in particular compared to the zones 51, 52, 53 illustrated in figure 7: o with reference to figure 8, different light beams corresponding to a decrease in the magnification of the optical system are imaged in different parts 51, 52, 53 of the sensor moving away from a point 6 on the sensor 2. The magnification of the optical system is minimum on a part of the sensor elongated in one direction.This can for example be achieved by using lenses 31, 32 and / or a system 3 having a section plane equivalent to that of Figure 1 but (instead of symmetry around axis 4) stretching with a slight curvature perpendicular to the plane of Figure 1; and / or o with reference to Figure 9, different light beams corresponding to a decrease in the magnification of the optical system are imaged in different parts 51, 52, 53 of the sensor moving away from a point 6 on the sensor 2. This can for example be achieved by using lenses 31, 32 and / or a system 3 equivalent to a 90° section around axis 4 of the lenses 31, 32 shown in Figure 1 and then recentering this section on the sensor 2; and / or o with reference to figure 10, different light beams corresponding to a decrease in the magnification of the optical system are imaged in different parts 51, 52, 53 of the sensor moving away from a segment 7 on the sensor 2.The magnification of the optical system is minimum on a part of the sensor elongated in one direction. This can for example be obtained by using lenses 31, 32 and / or a system 3 having a section plane equivalent to half that of Figure 1 (on one side or the other of the axis 4), recentered on the sensor 2, and stretching without any curvature perpendicular to the plane of Figure 1; and / or o with reference to Figure 11, different light beams corresponding to a decrease in the magnification of the optical system are imaged in different parts 51, 52, 53 of the sensor moving away from a segment 7 on the sensor 2. The magnification of the optical system is minimum on a part of the sensor elongated in one direction.This can for example be obtained by using lenses 31, 32 and / or a system 3 having a section plane equivalent to that of figure 1 but (instead of a symmetry around the axis 4) stretching without any curvature or with a very small curvature perpendicular to the plane of figure 1; and / or o the point 6 may in reality not be punctual but have a surface and therefore be replaced in the previous description by a surface on the sensor.

[0224] Of course, the various features, forms, variants and embodiments of the invention may be combined with each other in various combinations provided that they are not incompatible or mutually exclusive. In particular, all the variants and embodiments described above may be combined with each other.

Claims

CLAIMS 1. Imaging device (1), comprising: - An image sensor (2), - An optical system (3) comprising an optical axis (4) and arranged to receive light beams and direct them towards the sensor, the optical system having a variable magnification on the sensor, magnification which depends on the orientation and / or the position of each optical beam incident on the optical system, characterized in that the magnification of the optical system comprises a minimum value on the sensor and a maximum value on the sensor, the ratio of the maximum magnification of the optical system to the minimum magnification of the optical system being equal to at least 1.

2.

2. Device according to claim 1, characterized in that different light beams corresponding to a decrease in the magnification of the optical system are imaged in different parts (51, 52, 53) of the sensor moving away from a point (6) or a segment (7) or a surface on the sensor.

3. Device according to any one of the preceding claims, characterized in that the magnification of the optical system decreases when the angle of the light beam incident on the optical system increases relative to the optical axis.

4. Device according to any one of the preceding claims, characterized in that the optical system comprises two lenses including: - A first lens (31), or a first face of the same single lens, preferably with constant or substantially constant magnification, and - A second lens (32), or a second face of the single lens, located respectively between the first lens or the first face of the single lens and the sensor, responsible at least in part for the variability of the magnification of the optical system.

5. Device according to claim 4, characterized in that the second lens is located at a distance from the first lens equal to the focal length of the first lens plus or minus 20% of the value of this focal length of the first lens.

6. Device according to claim 4 or 5, characterized in that the magnification of the second lens decreases when the angle of the light beam incident on the second lens increases relative to the optical axis.

7. Device according to any one of claims 4 to 6, characterized in that the magnification of the second lens comprises a minimum value and a maximum value, the ratio of the maximum of the magnification of the second lens to the minimum of the magnification of the second lens being equal to at least 2.

8. Device according to any one of the preceding claims, characterized in that the optical system is symmetrical around the optical axis.

9. Device according to any one of the preceding claims, characterized in that the magnification of the optical system is maximum on a central or substantially central part of the sensor.

10. Device according to any one of the preceding claims, characterized in that the magnification of the optical system is minimum on a peripheral part of the sensor.

11. Device according to any one of the preceding claims, characterized in that the magnification of the optical system is minimum on a part of the sensor elongated in one direction.

12. Device according to any one of the preceding claims, characterized in that it comprises longitudinal displacement means (8) arranged to move the position of the sensor relative to the optical system so as to modify the distance between the optical system and the sensor and thus modify the focusing distance of the optical system and / or the magnification values ​​of the optical system on the sensor.

13. Device according to any one of the preceding claims, characterized in that it comprises lateral displacement means (8) arranged to move the position of the sensor relative to the optical system so as to shift the sensor relative to the optical axis and thus modify the part of the sensor having the maximum value of the magnification of the optical system.

14. Device according to claim 13, characterized in that the lateral displacement means are positionally controlled by the restitution of a stable image.

15. Device according to any one of the preceding claims, characterized in that the image sensor comprises a matrix of pixels, said pixels all having the same dimension.

16. Device according to any one of the preceding claims, characterized in that the image sensor comprises a Bayer matrix: - whose patterns all have the same size, or - the Bayer matrix being more resolved in lateral or peripheral parts arranged around a central part to increase a saturation threshold in these lateral or peripheral parts.

17. Device according to any one of the preceding claims, characterized in that it further comprises correction means (9) arranged and / or programmed to correct an image captured by the image sensor, comprising in particular: - means of correcting or compensating for geometric distortion of the image, and / or - means of correcting or compensating for vignetting or inhomogeneity of image brightness, and / or - means of correcting or compensating for chromatic distortion of the image, and / or - means of correcting or compensating for image sharpness.

18. Device according to any one of the preceding claims, characterized in that it further comprises zoom means (9) arranged and / or programmed to zoom on an image from the image sensor by selecting a sub-part of the image sensor so that an increase in the zoom on the image from the image sensor corresponds to an increase in the average value of the magnification of the optical system on the selected sub-part of the sensor.

19. Smartphone comprising a device according to any one of the preceding claims.

20. Vehicle comprising a device according to any one of the preceding claims, preferably integrated into a driving assistance system and / or for providing images for the automatic piloting of said vehicle.

21. Vehicle according to claim 20, characterized in that the vehicle is an automobile, a drone, or an airplane.

22. Alarm and / or video surveillance system, comprising a device according to any one of the preceding claims.

23. Medical imaging device, comprising a device according to any one of the preceding claims.

24. Medical imaging device according to claim 23, characterized in that it comprises a diagnostic system or a surgical operation system.

25. Imaging method implemented by a device according to any one of the preceding claims, comprising: - a reception, by the optical system (3), of light beams so as to direct them towards the sensor (2), including different light beams having between them different orientations and / or positions of incidence on the optical system, the optical system having a variable magnification on the sensor, magnification which depends on this orientation and / or position of each optical beam incident on the optical system, so that the different beams are imaged on the sensor with different magnifications of the optical system on the sensor, characterized in that the magnification of the optical system comprises a minimum value on the sensor and a maximum value on the sensor, the ratio of the maximum of the magnification of the optical system to the minimum of the magnification of the optical system, preferably for the different beams imaged on the sensor, being equal to at least 1.

2.

26. Method according to claim 25, characterized in that different light beams corresponding to a decrease in the magnification of the optical system are imaged in different parts (51, 52, 53) of the sensor moving away from a point (6) or a segment (7) or a surface on the sensor.

27. Method according to any one of claims 25 to 26, characterized in that the magnification of the optical system decreases when the angle of the light beam incident on the optical system increases relative to the optical axis.

28. Method according to any one of claims 25 to 27, characterized in that the optical system comprises two lenses including: - A first lens (31), or a first face of the same single lens, preferably with constant or substantially constant magnification, and - A second lens (32), or a second face of the single lens, located respectively between the first lens or the first face of the single lens and the sensor, responsible at least in part for the variability of the magnification of the optical system.

29. Method according to claim 28, characterized in that the second lens is located at a distance from the first lens equal to the focal length of the first lens plus or minus 20% of the value of this focal length of the first lens.

30. Method according to claim 28 or 29, characterized in that the magnification of the second lens decreases when the angle of the light beam incident on the second lens increases relative to the optical axis.

31. Method according to any one of claims 28 to 30, characterized in that the magnification of the second lens comprises a minimum value and a maximum value, the ratio of the maximum of the magnification of the second lens to the minimum of the magnification of the second lens being equal, preferably for the different beams imaged on the sensor, at least to 2.

32. Method according to any one of claims 25 to 31, characterized in that the optical system is symmetrical around the optical axis.

33. Method according to any one of claims 25 to 32, characterized in that the magnification of the optical system is maximum on a central or substantially central part of the sensor.

34. Method according to any one of claims 25 to 33, characterized in that the magnification of the optical system is minimum on a peripheral part of the sensor.

35. Method according to any one of claims 25 to 34, characterized in that the magnification of the optical system is minimum on a part of the sensor elongated in one direction.

36. Method according to any one of claims 25 to 35, characterized in that it comprises a displacement, by the longitudinal displacement means (8), of the position of the sensor relative to the optical system so as to modify the distance between the optical system and the sensor and thus modify the focusing distance of the optical system and / or the different values ​​of the magnification of the optical system on the sensor.

37. Method according to any one of claims 25 to 36, characterized in that it comprises a displacement, by the lateral displacement means (8), of the position of the sensor relative to the optical system so as to shift the sensor relative to the optical axis and thus modify the part of the sensor having the maximum value of the magnification of the optical system.

38. Method according to claim 37, characterized in that the lateral displacement means are positionally controlled to the restitution of a stable image.

39. Method according to any one of claims 25 to 38, characterized in that the image sensor comprises a matrix of pixels, said pixels all having the same dimension.

40. Method according to any one of claims 25 to 39, characterized in that the image sensor comprises a Bayer matrix: - whose patterns all have the same size, or - the Bayer matrix being more resolved in lateral or peripheral parts arranged around a central part to increase a saturation threshold in these lateral or peripheral parts.

41. Method according to any one of claims 25 to 40, characterized in that it further comprises a correction, by the means (9) for correcting an image captured by the image sensor, comprising in particular: - correction or compensation of geometric distortion of the image, and / or - correction or compensation for vignetting or inhomogeneity of image brightness, and / or - correction or compensation of chromatic distortion of the image, and / or - a correction or compensation of image sharpness.

42. Method according to any one of claims 25 to 41, characterized in that it further comprises a zoom, by the zoom means (9), on an image from the image sensor by selecting a sub-part of the image sensor so that an increase in the zoom on the image from the image sensor corresponds to an increase in the average value of the magnification of the optical system on the selected sub-part of the sensor.

43. Method according to any one of claims 25 to 42, characterized in that it is implemented within a smartphone.

44. Method according to any one of claims 25 to 42, characterized in that it is implemented within a vehicle, preferably within an integrated driving assistance system and / or for the provision of images for the automatic piloting of said vehicle.

45. Method according to claim 44, characterized in that the vehicle is an automobile, a drone, or an airplane.

46. ​​Method according to any one of claims 25 to 42, characterized in that it is implemented within an alarm and / or video surveillance system.

47. Method according to any one of claims 25 to 42, characterized in that it is implemented within a medical imaging device.

48. Method according to claim 47, characterized in that the medical imaging device comprises a diagnostic system or a surgical operation system.

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