Infrared imaging device

Abstract

Infrared imaging device The present description relates to an infrared imaging device (200) comprising an infrared camera (210) having an optical axis (A) and intended to detect infrared radiation in a spectral range through an element (132) transparent to said infrared radiation, said transparent element being surrounded by a mount (134), the transparent element with the mount being adapted to be inserted into an opening of a wall (130), the transparent element and the wall being inclined by an inclination angle (α) greater than 0° and less than 90° or less than 0° and greater than -90° with respect to the optical axis (A) of the infrared camera; the device further comprising:- an interface element (230) adapted to provide an interface between the infrared camera (210) and the mount (134). Figure for abstract: Fig. 2A

Description

Title of the invention: Infrared imaging device Technical field

[0001] The present description relates generally to the field of infrared imaging and relates in particular to an infrared camera in which an image is detected by said infrared camera through a window transparent to infrared radiation. Prior art

[0002] In the field of infrared imaging, an infrared camera ("IR camera") may be used, adapted to capture thermal images of a scene. An IR camera generally comprises an arrangement of infrared-sensitive detectors forming a pixel array. Each pixel in the pixel array converts a temperature measured at the pixel into a corresponding voltage signal, which is converted by a digital-to-analog converter (ADC) into a digital output signal. A micro-bolometer is an example of a pixel used for an uncooled pixel-array infrared camera, adapted to capture thermal images of an image scene.

[0003] In certain applications, an IR camera may be positioned in an enclosure, or at least be arranged behind a wall so that the radiation is detected by the IR camera through the wall. This wall may be inclined at a non-zero angle relative to the vertical. When the material of the wall is not transparent to IR radiation, the wall is provided with an element transparent to IR radiation, for example a porthole, this porthole being positioned so that the IR camera can receive the IR radiation through said porthole. Generally, such a porthole has the smallest possible lateral dimensions.

[0004] However, when the wall is inclined, the porthole is also inclined. The presence of an inclined porthole whose lateral dimensions are reduced can generate an undesired vignetting phenomenon on the image captured by the IR camera, that is to say a reduction in brightness on the edges of the image (in other words, an increase in opacity on the edges of the image). The phenomenon can worsen when the distance between the porthole and the IR camera increases. Summary of the invention

[0005] There is a need to control the vignetting phenomenon of an infrared camera intended to be positioned behind a wall.

[0006] One embodiment overcomes all or part of the aforementioned drawbacks.

[0007] One embodiment provides an infrared imaging device comprising a An infrared camera having an optical axis and intended to detect infrared radiation in a spectral range through an element transparent to said infrared radiation, said transparent element being surrounded by a mount, the transparent element with the mount being adapted to be inserted into an opening in a wall, the transparent element and the wall being inclined at an angle of inclination greater than 0° and less than 90° or less than 0° and greater than -90° relative to the optical axis of the infrared camera; the device further comprising: - an interface element suitable for providing an interface between the infrared camera and the mount.

[0008] According to one embodiment, at least one interior surface of the interface element is shaped so as to reduce the emission of infrared radiation by said interface element towards the camera.

[0009] According to one embodiment, at least one interior surface of the interface element is made of a material suitable for reducing the emission of infrared radiation by said interface element towards the camera.

[0010] According to one embodiment, at least one interior surface of the interface element is covered with a coating adapted to reduce the emission of infrared radiation by said interface element towards the camera.

[0011] According to one embodiment, the interface element comprises a first end adapted to attach to the frame of the transparent element, for example by shape complementarity with said frame.

[0012] According to one embodiment, the interface element comprises a second end adapted to attach to the infrared camera, for example by shape complementarity with at least one part of said infrared camera.

[0013] According to one embodiment, the infrared camera comprises at least one lens and a lens mount, said at least one lens being held by said lens mount, the second end of the interface element being adapted to hook onto the lens mount, for example by form fit with said lens mount. According to one example, the lens mount at least partially surrounds the at least one lens.

[0014] According to another embodiment, the infrared camera comprises at least one lens and a lens mount, said at least one lens being held by said lens mount, the interface element and the lens mount being integral. According to one example, the lens mount at least partially surrounds the at least one lens.

[0015] According to another embodiment, the infrared camera comprises at least one lens and a lens mount, said at least one lens being held by said lens mount, at least one lens and / or the lens mount comprising a truncated face adapted to be positioned opposite the wall. According to one example, the lens mount at least partially surrounds the at least one lens.

[0016] According to one example, the truncation angle of the truncated face relative to the optical axis of the infrared camera is substantially equal to the angle of inclination of the wall and the transparent element.

[0017] According to one example, the interface element comprises at least one part adapted to cover the truncated face, said part forming for example a thermal protection of the truncated face and / or a protection of said truncated face against infrared radiation.

[0018] According to one embodiment, the infrared camera comprises: - at least one lens and a lens mount, said at least one lens being held by said lens mount; and - an image sensor sensitive to infrared radiation in the spectral range; the sensor and the at least one lens defining the optical axis of the infrared camera, the sensor being disposed substantially in the image focal plane of said at least one lens. According to one example, the lens mount at least partially surrounds the at least one lens.

[0019] According to one embodiment, the interface element is adapted to produce a fluid-tight assembly between the wall and the infrared camera.

[0020] According to one embodiment, the interface element is made of a material with low thermal conduction, for example with thermal conduction less than 10 Wm *.K '.

[0021] According to one embodiment, the interface element is provided with at least one temperature probe, at least one temperature probe being for example connected to a module for processing parasitic light flux, for example a parasitic light flux emitted by the device.

[0022] According to one embodiment, the device comprises a removable shutter element adapted to shutter the infrared camera. According to one example, the shutter element is covered with an emissive coating on a face of said shutter element located opposite the infrared camera.

[0023] According to one embodiment, the interface element comprises an inner emitting surface oriented opposite the infrared camera and adapted to be positioned close to the transparent element, for example against the mount of the transparent element. According to one example, said inner emitting surface is covered with an emissive coating.

[0024] According to one embodiment, the interface element comprises a portion adapted to be positioned opposite a region of the transparent element, for example an edge of said transparent element, so as to form a screen between said region of the transparent element and the infrared camera, said portion comprising a face emitter oriented towards the infrared camera. According to one example, said emitting face is covered with an emissive coating.

[0025] According to one embodiment, the infrared camera comprises a pixel matrix image sensor comprising an angular pixel adapted to capture a light flux coming from an interior zone of the interface element oriented opposite the image sensor and the field of view of the angular pixel, for example an interior zone intended to be positioned around the transparent element. According to one example, said interior zone is covered with an emissive coating.

[0026] One embodiment provides an infrared imaging system comprising: - an infrared imaging device according to one embodiment, and - a wall having an opening into which an element transparent to infrared radiation of a spectral range, surrounded by a mount, is inserted; the infrared camera of the device being adapted to detect infrared radiation of the spectral range through the transparent element; the transparent element and the wall being inclined at an angle of inclination greater than 0° and less than 90° or less than 0° and greater than -90° relative to the optical axis of the camera. Brief description of the drawings

[0027] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0028] [Fig. 1 A], and

[0029] [Fig.1B] are sectional views of an example of an infrared camera arranged behind an inclined wall;

[0030] [Fig.2A] is a sectional view of an exemplary infrared imaging device according to one embodiment;

[0031] [Fig.2B] is a sectional view of a variation of the exemplary infrared imaging device of [Fig.2A];

[0032] [Fig.2C] is a sectional view of another variation of the exemplary infrared imaging device of [Fig.2A];

[0033] [Fig.2D] is a sectional view of another variation of the exemplary infrared imaging device of [Fig.2A];

[0034] [Fig.3A] is a sectional view of a variant of an infrared camera;

[0035] [Fig.3B] is a sectional view of another variant of infrared camera;

[0036] [Fig.4] is a sectional view of another example of an infrared imaging device according to one embodiment. Description of the embodiments

[0037] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0038] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the optics, for example the lenses and their mount, and the image sensor, for example the matrix image sensor in the form of a matrix of micro-bolometers or a matrix of photodiodes, are not detailed, being known to the person skilled in the art in the field of the invention.

[0039] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0040] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures or to an IR imaging device in a normal position of use.

[0041] When referring to the terms, "in front / behind", or "front / rear", reference is made to the direction of propagation of the light rays / radiation, i.e. from the transparent element towards the infrared camera.

[0042] When referring to angle values, it should be understood that these values ​​are given in the trigonometric direction, represented by the quarter-circle arrow with the "+" sign in the figures. A negative angle value thus corresponds to an angle oriented in a clockwise direction.

[0043] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0044] An example of an infrared (IR) camera is shown in Figures 1A and 1B. The infrared camera 110 comprises a housing 112 containing an image sensor 114 sensitive to radiation in the infrared, as well as a window 116 located opposite the image sensor 114 and capable of transmitting IR radiation in the spectral range of use of the IR camera. The image sensor is advantageously a matrix image sensor consisting of a matrix of micro-bolometers. Alternatively, the image sensor is a matrix image sensor consisting of a matrix of photodiodes based on semiconductor materials.

[0045] The IR camera further comprises a plurality of lenses 118 (only one has been shown but there are generally several) capable of operating in the spectral range of use of the camera so as to form an image on the image sensor (the camera is in the image focal plane of the lenses), the lenses being held in a lens mount 119 assembled to the housing 112. The lens mount 119 is positioned so that the window 116 is disposed between said mount and the image sensor 114. The sensor and the lenses define the optical axis A of the camera. In the example shown, the optical axis is in the horizontal direction X.

[0046] The IR camera 110 may be positioned in an enclosure, or at least be arranged behind a wall 130, so that the radiation is detected by the IR camera through the wall. Such an enclosure or wall may fulfill a mechanical and / or thermal protection function for the camera, and / or protection of the camera from the environment, and / or an aerodynamic function, and / or a user protection function (for example a shield, in particular a windshield), or even an aesthetic function (for example to mask the camera).

[0047] The wall 130 may be a planar wall, as shown. Alternatively, it may locally comprise, in the vicinity of the camera, at least a portion of planar wall.

[0048] The wall may be non-transparent to IR radiation, be incapable of transmitting an image, for example be rough or diffusing, or may not transmit IR radiation with sufficient quality in the spectral range of use of the IR camera, which is for example between 1 and 20 pm, preferably between 8 and 14 pm, or even between 8 and 12 pm. In this case, a porthole 132 transparent to IR radiation in the spectral range of use of the IR camera may be inserted into an opening in the wall. The porthole 132 may for example be inserted into the wall using a porthole mount 134.

[0049] The porthole 132 is adapted to transmit IR radiation to the IR camera 110. For example, the porthole can be formed from a plate of zinc sulfide (ZnS), zinc selenide (ZnSe), silicon (Si), germanium (Ge), barium fluoride (BaF2), calcium fluoride (CaF2), sapphire, chalcogenide glass or any other material transparent to IR radiation in the spectral range of use of the IR camera.

[0050] The porthole 132 is characterized by two substantially parallel faces of a given occupation surface (called "pupil"), the two faces being separated by a distance (thickness). The dimensions of the two faces (dimensions of the pupil) are for example of the order of a centimeter, or of ten centimeters, with a thickness of the order of a few millimeters.

[0051] In some applications, the wall 130 and the porthole 132 may be inclined by a tilt angle 0 relative to the focal plane of the lenses (in the example shown, the focal plane is parallel to the vertical plane YZ whose vertical direction Z has been shown in the sectional views), strictly between 0 and 90°, and more specifically between 30° and 70°, for example around 60°. In other words, the wall 130 and the porthole 132 can be inclined at an angle α relative to the optical axis A which is shown in the horizontal direction X. The angle α is complementary to the angle α, therefore strictly between 0 and 90°, and more specifically between 20° and 60°, for example around 30°.

[0052] Furthermore, it is sometimes sought that the pupil of the porthole be as small as possible. Indeed, given that the surface occupied by the wall is subtracted from the surface occupied by the porthole and possibly by the porthole frame, this reduces the capacity of the wall to fulfill its function, for example its protective or aesthetic function. In addition, increasing the pupil of the porthole can alter the mechanical integrity of the wall. Furthermore, the material used to form the pupil of the porthole has a significant cost, which is sought to be reduced by reducing the pupil and, to a lesser extent, its thickness.

[0053] However, the reduction of the pupil of the porthole, when the latter is inclined, has the consequence and disadvantage of limiting the field of view of the IR camera (called "FOV" for "Field Of View" in English), by causing a vignetting phenomenon, since the rays at the ends of the field of view are cut by the edge of the porthole. In particular, the vertical field of view ("VFOV" for "Vertical Field Of View" in English) can be degraded compared to the horizontal field of view ("HFOV" for "Horizontal Field Of View" in English) due to the inclination of the porthole.

[0054] The vignetting phenomenon worsens when the distance between the porthole and the IR camera increases. Thus, it is advantageous to position the IR camera as close as possible to the porthole, within the limit of the spacing between the IR camera 110 and the wall 130 (this limit is indicated by the dotted circles in FIGS. 1A and 1B). This spacing is all the more reduced as the angle of inclination 0 relative to the vertical direction is large.

[0055] Furthermore, if the optical axis A of the IR camera 110 is centered on the refracted optical axis B of the porthole 132, i.e., the optical axis after deflection by the effect of refraction in said porthole, as illustrated in [Fig.lA], then the IR camera may exhibit asymmetric vertical vignetting, for example, vignetting favoring the upper part of the vertical field of view. Symmetric vignetting may be achieved by vertically decentering the optical axis A of the IR camera 110 by a distance D relative to the refracted optical axis B of the porthole 132, as shown in [Fig.lB] (even if this has the effect of further reducing the spacing between the IR camera and the wall, as can be seen by comparing FIGS. 1A and 1B).

[0056] There is therefore a need to precisely position an infrared camera with respect to an inclined window in order to control the vignetting phenomenon. In addition, in certain applications, for example when the IR camera may be subject to accelerations and / or shocks, it would be advantageous if the positioning could be maintained and controlled reliably even in the event of acceleration and / or shock. In other words, there is a need to precisely position, and preferably robustly, an IR camera with respect to an inclined window.

[0057] The inventors propose an infrared imaging device capable of meeting these needs.

[0058] Examples of infrared imaging devices will be described below. These examples are non-limiting and various variations will become apparent to those skilled in the art from the indications of the present description.

[0059] The infrared domain is characterized by a spectral range comprising wavelengths from 1 pm to 20 pm.

[0060] Advantageously, the infrared camera and the imaging device according to one embodiment are adapted to operate in a spectral range included in the far infrared domain ("LWIR" for "Long-Wave Infrared" in English) which is a spectral domain extending between 8 pm and 12 pm.

[0061] According to another example, the infrared camera and the imaging device according to one embodiment are adapted to operate in a spectral range included in the short-wave infrared domain ("SWIR" for "Short-Wave Infrared" in English) which is a spectral domain extending between 1 pm and 2.5 pm.

[0062] According to another example, the infrared camera and the imaging device according to one embodiment are adapted to operate in a spectral range included in the mid-infrared domain ("MWIR" for "Medium-Wave Infrared" in English) which is a spectral domain extending between 3 pm and 5 pm.

[0063] According to another example, the infrared camera and the imaging device according to one embodiment are adapted to operate in a spectral range included in the very far infrared domain ("VLWIR" for "Very Long-Wave Infrared" in English) which is a spectral domain extending between 12 pm and 22 pm.

[0064] Obviously, the infrared camera and the device can be adapted to operate in a spectral range extending into several of the aforementioned ranges.

[0065] [Fig.2A] is a cross-sectional view of an exemplary IR imaging device according to one embodiment, comprising an infrared camera 210 shown behind a wall 130 (the wall not being part of the device).

[0066] Similar to the infrared camera 110 described in relation to FIGS. 1A and 1B, the infrared camera 210 comprises a housing 212 containing an image sensor 214 sensitive to radiation in the infrared, as well as a window 216 located in view of the image sensor 214 and capable of transmitting IR radiation in the spectral range of use of the IR camera. The image sensor is advantageously a matrix image sensor comprising a matrix of micro-bolometers. Alternatively, the image sensor is a matrix image sensor comprising a matrix of photodiodes based on semiconductor materials.

[0067] The IR camera further comprises a plurality of lenses 218 adapted to operate in the spectral range of use of the camera so as to form an image on the image sensor, the camera being in the image focal plane of the lenses. The lenses are held in a lens mount 219 assembled to the housing 212, the lens mount 219 being positioned so that the window 216 is disposed between said mount and the sensor 214. The sensor and the lenses define the optical axis A of the camera, represented in the horizontal direction X.

[0068] The wall 130 is similar to the wall shown in Figures 1A and 1B. Thus, it includes a porthole 132 (also referred to as a "transparent element"), the porthole being transparent to infrared radiation in the spectral range of use of the IR camera. The porthole 132 is inserted with a porthole mount 134 into an opening in the wall 130. The wall may be a shield, for example a windshield. The wall may be a wall of an enclosure, for example a closed enclosure, in particular a closed enclosure capable of being thermally regulated.

[0069] For example, the porthole may be formed from a plate of zinc sulfide (ZnS), zinc selenide (ZnSe), silicon (Si), germanium (Ge), barium fluoride (BaF2), calcium fluoride (CaF2), sapphire, chalcogenide glass or any other material transparent to IR radiation in the spectral range of use of the IR camera.

[0070] The wall 130 and the porthole 132 are inclined at an angle α relative to the optical axis A which is represented in the horizontal direction X. The angle of inclination α is strictly between 0 and 90°, and more specifically between 20° and 60°, for example around 30°.

[0071] The infrared camera is adapted to capture a thermal image of an image scene through the inclined window.

[0072] The IR imaging device further comprises an interface element 230 positioned between the infrared camera 210 and the window mount 134. The interface element 230 is adapted to provide an interface between the IR camera and the window mount, in order to allow relative positioning of the device with respect to the transparent element.

[0073] The interface element 230 shown is a rigid, single-piece element having a substantially oblique and hollow truncated cone shape, suitable for connecting the IR camera 210 and the mount 134. The interface element 230 shown comprises: - a first end 232 shaped to attach to the porthole frame 134 by complementary shape with said frame, thus assembling to the wall all around the porthole; - a second end 234 shaped to attach to the lens mount 219 by complementary shape with said lens mount; - a body 236 between the first and second ends.

[0074] The body 236 forms an envelope preferably opaque to light radiation in a spectral range. Said envelope is thus preferably adapted to block all or part of the stray light rays coming from the rear of the wall 132, likely to penetrate into the space between the wall and the IR camera, for example in the optical path between the porthole and the IR camera, the stray light rays being able to generate a stray image on the image sensor 214.

[0075] According to an alternative example, the second end may be shaped to hook onto the housing 212 of the IR camera, or onto both the lens mount 219 and the housing 212.

[0076] Thus, the interface element 230 makes it possible to precisely position the infrared camera relative to the porthole, i.e. to fix the distance between the camera and the porthole in the direction of the optical axis A (the horizontal direction X in the example shown), but also the distance between the optical axis A of the infrared camera and the refracted optical axis B of the porthole in a direction perpendicular to the optical axis A (the vertical direction Z in the example shown). In the example of [Fig. 2A], the optical axis A of the camera 210 coincides with the refracted optical axis B of the porthole 132. In the examples of FIGS. 2B and 2C, described later, the optical axis A of the camera is offset by a distance D relative to the refracted optical axis B of the porthole 132 in the vertical direction Z.

[0077] In the example shown, the interface element 230 is a separate element from the wall 130 and the infrared camera 210. This makes it easier to replace the different elements of the wall and / or the IR imaging device, for example in the event of maintenance, or when the interface element must be changed in order to be able to place the infrared camera behind a different wall or behind an identical wall with a different angle of inclination, or when the wall must be replaced, for example if it is damaged during use.

[0078] According to an advantageous example, the interface element 230 is adapted to provide a fluid-tight seal between the porthole mount 134 and the IR camera 210. This makes it possible to reduce variations in the composition of the gas, for example air, in the space between the porthole and the IR camera and contained in said interface element. For example, this can make it possible to reduce humidity, particles and / or dust in said space, so as to provide the highest image quality. constant as possible or at least to limit variations in image quality. For example, the space between the porthole and the IR camera can be saturated with nitrogen, with a low concentration of particles and / or dust before being enclosed in the interface element.

[0079] According to one example, at least a first interior surface of the interface element is formed from a material that is absorbent in the spectral range of use of the IR camera or is covered with a coating that is absorbent in said spectral range.

[0080] According to one example, at least a second interior surface of the interface element is formed from a reflective material in the spectral range of use of the IR camera, for example metallic, or is covered with a reflective coating in said spectral range, for example a metallic coating.

[0081] According to one example, the interface element comprises at least a first interior surface formed from an absorbent material in the spectral range of use of the IR camera or covered with an absorbent coating in said spectral range, and at least a second interior surface formed from a reflective material in said spectral range, for example metallic, or covered with a reflective coating in said spectral range, for example a metallic coating.

[0082] The first and second surfaces are for example defined as a function of exposure to parasitic light radiation and / or as a function of a temperature gradient likely to impact them.

[0083] According to one example, all or part of the interior surfaces 238 of the interface element 230 is shaped to limit the emission of parasitic light radiation by said interface element towards the camera, for example the interior surfaces inclined opposite the camera are reduced, or even excluded.

[0084] According to one example, the interface element comprises, inside said element, at least one structure adapted to limit the emission of parasitic light radiation by said interface element towards the camera, for example a structure of the screen, cover and / or light trap type. This may be one (or more) structure(s) arranged regularly around the optical axis in the interface element, or structures arranged irregularly around the optical axis in the interface element.

[0085] According to one example, the interface element is made of a material with low thermal conduction, for example with a thermal conduction of less than 10 Wm *.K '. This makes it possible to promote thermal insulation between the porthole and the IR camera. Indeed, the environment around the porthole can undergo temperature variations, in particular depending on the conditions outside the wall, but the temperature variations can degrade the performance of the infrared camera, in particular by generating a parasitic thermal flux. For example, when the wall is a wall of an enclosure capable of being thermally regulated, the combination of thermal regulation in the enclosure and Thermal insulation by the interface element allows for better performance of the infrared camera.

[0086] According to one example, the interface element 230 is provided with at least one temperature probe 240. A temperature probe may preferably be arranged inside said interface element, but may also be arranged outside said interface element. For example, several temperature probes may be positioned at different locations of the interface element in order to be able to determine a temperature gradient.For example, one or more temperature probes may be positioned in the vicinity of the window 132 so as to estimate a temperature of the window, and / or one or more temperature probes may be positioned in the vicinity of the lens mount so as to estimate a lens temperature, and / or one or more temperature probes may be positioned on one or more interior surfaces of the interface element so as to estimate a value of emission of stray light radiation (stray light flux) by said surface(s).

[0087] According to one example, at least one temperature probe is connected to a module for processing the stray light flux, i.e. the light flux captured by the infrared camera but originating from at least one source other than the image scene, for example a stray light flux emitted by the imaging device and / or the porthole. The module for processing the stray light flux may be included in or connected to an image processing module in order to determine the light flux originating essentially from the image scene, for example by correcting it for the stray light flux.

[0088] Alternatively, all or part of the parasitic luminous flux can be determined without a temperature probe, and thus simplify the IR imaging device. Examples of means suitable for determining a parasitic luminous flux without a temperature probe are described in the following description, in relation to FIGS. 2B and 2C.

[0089] [Fig.2B] is a sectional view of a variant of the exemplary IR imaging device of [Fig.2A]. The device 201 of [Fig.2B] differs from the device 200 of [Fig.2A] primarily in that: - the optical axis A of the camera is offset by a distance D from the refracted optical axis B of the porthole in the vertical direction Z; and - the first end 232 of the interface element 230 comprises an inner surface 231 oriented opposite the infrared camera 210 and positioned against an edge of the porthole frame 134. The inner surface 231 is emitting, for example it is covered with an emissive coating 233; the emissive coating allows the surface thus covered to be captured more efficiently by the infrared camera.

[0090] The inner emitting surface 231 is shown in a lower portion of the first end 232, but this is a non-limiting example. Alternatively, the The emitting interior surface may be in another portion of the first end 232 and / or be another interior surface of the interface element 230, for example another interior surface near the porthole when determining a stray light flux emitted by the porthole and / or another interior surface of the interface element when determining a stray light flux emitted by the imaging device. Several emitting interior surfaces may be provided.

[0091] This is an example of a configuration for deliberately degrading vignetting in a region of the field of view of the infrared camera, preferably a region that is not critical for the intended application, and for producing an image of the inner surface of the interface element opposite said degraded region of the field of view. The temperature determined by the image sensor in this degraded region of the field of view can then be used in a stray light flux processing module.

[0092] [Fig.2C] is a sectional view of another variation of the exemplary IR imaging device of [Fig.2A]. The device 202 of [Fig.2C] differs from the device 200 of [Fig.2A] in that: - the optical axis A of the camera is offset by a distance D from the refracted optical axis B of the porthole in the vertical direction Z; and - the first end 232 of the interface element 230 comprises a portion 235 forming a screen of a region 133 of the transparent element 132 with respect to the infrared camera 210; the portion 235 comprises an emitting face oriented opposite the infrared camera 210, for example covered with an emissive coating 237.

[0093] The portion 235 is shown as being an inward extension of the first end 232, in an upper part of said first end, but this is a non-limiting example. Alternatively, the screen-forming portion may be an extension of another part of the first end 232 and / or be positioned elsewhere in the interface element 230, for example near the porthole when determining a stray light flux emitted by the porthole, or even not necessarily near the porthole when determining a stray light flux emitted by the imaging device. Several screen-forming portions may be provided.

[0094] This is another example of a configuration making it possible to voluntarily degrade the vignetting on a region of the field of view of the infrared camera, preferably a region not critical for the intended application, and to produce an image of the inner surface of the portion of the interface element opposite said degraded region of the field of view. The temperature determined by the image sensor in this degraded region of the field of view can then be used in a stray light flux processing module.

[0095] In another example, the infrared camera 214 may include a pixel array image sensor including image pixels and at least one angular pixel.

[0096] By angular pixel is meant a pixel for detecting stray light flux, or stray thermal flux, which is a pixel having a field of view modified relative to that of the image pixels of the pixel matrix, in order to promote the capture of stray thermal flux. For example, each stray thermal flux detection pixel is arranged to capture a larger portion of stray thermal flux than each image pixel of the pixel matrix.

[0097] The angular pixel is adapted to capture a parasitic light flux coming from an interior zone of the interface element oriented opposite the image sensor and in the field of view of said angular pixel, for example an interior zone positioned around the transparent element, the zone being for example covered with an emissive coating.

[0098] Examples of an infrared camera with a parasitic thermal flux detection pixel, a method of calibrating such an infrared camera, and a method of correcting an image captured by such an infrared camera are described in international patent applications WO2019234215A1 and WO2019234216A1.

[0099] Compared to the solutions described in relation to figures 2B and 2C, this makes it possible not to have to degrade the field of view of the camera, and in particular not to have to degrade the vignetting.

[0100] [Fig.2D] is a sectional view of another variant of the exemplary IR imaging device of [Fig.2A]. The device 203 of [Fig.2C] differs from the device 200 of [Fig.2A] mainly in that it comprises a removable shutter 242 adapted to close the infrared camera 210. The shutter 242 may be in the form of a shutter flap. The shutter 242 may be assembled to the interface element 230. Preferably, the shutter 242 is located close to the IR camera, i.e. at a distance less than the hyperfocal distance of the IR camera. This makes it possible to blur possible inhomogeneities of the shutter, in terms of infrared emission.

[0101] A uniform shutter allows for example to calibrate the camera, the shutter forming a uniform calibration image in front of the camera when it is closed.

[0102] The shutter may for example be covered with an emissive coating on a face of the shutter located opposite the infrared camera.

[0103] According to one example, the shutter 242 is in thermal contact with the interface element 230: in this case, the calibration image makes it possible to quantify the quantity of parasitic flux emitted by the interface element 230 in use.

[0104] The variants of Figures 2B to 2D may be combined with each other, as well as with one or more of the examples given in relation to [Fig.2A].

[0105] As described in the description in relation to Figures 1A and 1B, the vignetting phenomenon worsens when the distance between the porthole and the IR camera increases, and it is therefore advantageous to position the IR camera as close as possible to the porthole, within the limit of the spacing between the IR camera and the wall. As can be understood from Figures 1A and 1B, in the example where the wall is inclined at an angle strictly between 0 and 90° relative to the horizontal, when the upper part of the lens mount comes into contact with the inclined wall, it is no longer possible to reduce the distance between the IR camera and the porthole.

[0106] The inventors therefore thought of reducing this distance by truncating the lens mount or even by truncating one or more lenses, as shown in Figures 3A and 3B.

[0107] [Fig.3A] represents a variant of infrared camera 310 comprising an image sensor 314, similar to the image sensor described in relation to [Fig.2A], a plurality of lenses 318 and a lens mount 319 truncated at a truncation angle [3 relative to the optical axis A of the infrared camera. The truncation 317 is formed in a portion of the lens mount intended to be opposite an inclined wall, here in the upper rear part of the lens mount.

[0108] [Fig.3B] represents another variant of infrared camera 320 comprising an image sensor 324, similar to the image sensor described in relation to [Fig.2A], a plurality of lenses of which at least one lens 328 is truncated at a truncation angle [3 relative to the optical axis A of the infrared camera and a lens mount 329 also truncated at the same truncation angle [3 in the continuity of the lens truncation. The truncation 327 is formed in a portion of the lens intended to be opposite an inclined wall, here in the upper rear part of the lens.

[0109] Preferably, the lens truncation is designed not to degrade the optical performance of the lens. According to one example, a truncated lens has at least one irregular optical surface (free-form type). The irregular optical surface is at least non-axisymmetric.

[0110] According to an advantageous example, the truncated lens is covered by a portion of lens mount or by another covering part, adapted to cover the lens truncation. This makes it possible to limit, or even eliminate, a degradation of the optical performance of the truncated lens, for example when the truncated lens undergoes temperature variations and / or this makes it possible to protect the environment close to the lens truncation from a parasitic light flux which may be induced by said truncation. [Fig.4] represents an example of a device in which the lens mount, which is also the interface element, is adapted to cover a lens truncation.

[0111] [Fig.4] shows another example of an IR imaging device 400 according to an embodiment comprising an image sensor 414, similar to the image sensor described in relation to [Fig.2A], a plurality of lenses of which at least one lens 418 is truncated at a truncation angle [3 relative to the optical axis A of the infrared camera. The device 400 further comprises an interface element 430 also forming a lens mount. In other words, the interface element 430 and the lens mount are integral. Furthermore, the interface element 430 comprises a covering portion 434, adapted to cover the lens truncation 417, and also adapted to be inserted between the inclined wall 130 and said truncation.

[0112] According to one example, at least the covering portion 434, or even the entire interface element 430, is made of a material suitable for protecting the lens truncation 417 from an external parasitic light flux, for example a reflective or absorbent material.

[0113] According to one example, at least the covering portion 434, or even the entire interface element 430, is made of a material suitable for dissipating a parasitic thermal flux.

[0114] Thus, the interface element 430 of [Fig.4] differs from that of [Fig.2A] mainly in that it is in one piece with the lens mount and is adapted to a lens truncation. This makes it possible to bring the infrared camera closer to the porthole, and thus to reduce the vignetting phenomenon. This also makes it possible to have a single part, for example compact, thus limiting the play between the parts, and allowing more precise positioning between the infrared camera and the inclined porthole.

[0115] Similar to the interface element 230 of [Fig.2A], the interface element 430 of the device 400 comprises a first end 432 shaped to hook onto the window mount 134 by shape complementarity with said mount, thus assembling to the wall around the window. The second end 434 of the interface element is adapted to assemble with the image sensor 414, generally with a housing integrating the image sensor and the window between the sensor and the lenses. The other examples given in the description of [Fig.2A] concerning the interface element can apply to the interface element 430 of [Fig.4].

[0116] In the example shown, the truncation angle [3 is substantially equal to the inclination angle a of the wall, which makes it possible to bring the infrared camera as close as possible to the porthole.

[0117] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, all embodiments may be made with or without an offset between the optical axis of the infrared camera and the refracted optical axis. Further, in the embodiments, the image sensor housing and the lens mount can be in one piece.

[0118] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. An infrared imaging device (200, 201, 202, 203, 400) comprising an infrared camera (210, 410) having an optical axis (A) and intended to detect infrared radiation in a spectral range through a transparent element (132) to said infrared radiation, said transparent element comprising two substantially parallel faces of a given occupation surface, and being surrounded by a mount (134), the transparent element being adapted to be inserted into an opening of a wall (130), with and with the aid of the mount, so as to be included in the volume of the opening of said wall, the transparent element and the wall being inclined by an inclination angle (a) greater than 0° and less than 90° or less than 0° and greater than -90° relative to the optical axis (A) of the infrared camera;the device further comprising: - an interface element (230, 430) adapted to provide an interface between the infrared camera (210, 410) and the mount (134) in order to allow relative positioning of the device with respect to the transparent element.;

2. Device (200, 201, 202, 203, 400) according to claim 1, at least one inner surface (238, 438) of the interface element (230, 430) being shaped so as to reduce the emission of infrared radiation by said interface element towards the camera, and / or being made of a material adapted to reduce the emission of infrared radiation by said interface element towards the camera and / or being covered with a coating adapted to reduce the emission of infrared radiation by said interface element towards the camera.

3. Device (200, 201, 202, 203, 400) according to claim 1 or 2, the interface element (230, 430) comprising a first end (232, 432) adapted to hook onto the mount (134) of the transparent element (132), for example by shape complementarity with said mount.

4. Device (200, 201, 202, 203) according to any one of claims 1 to 3, the interface element (230) comprising a second end (234) adapted to attach to the infrared camera (210), for example by form complementarity with at least a part of said infrared camera.

5. Device (200, 201, 202, 203) according to claim 4, the infrared camera (210) comprising at least one lens (218) and a lens mount (219), said at least one lens being held by said lens mount, the second end (234) of the interface element (230) being adapted to hook onto the lens mount (219), for example by form fit with said lens mount.

6. The device (400) of claim 4, the infrared camera (410) comprising at least one lens (418) and a lens mount, said at least one lens being held by said lens mount, the interface element (430) and the lens mount being integral.

7. Device (400) according to any one of claims 1 to 6, the infrared camera (410) comprising at least one lens (418) and a lens mount, said at least one lens being held by said lens mount, at least one lens (418) and / or the lens mount comprising a truncated face (417) adapted to be positioned opposite the wall (130).

8. Device (400) according to claim 7, the truncation angle (|3) of the truncated face (417) relative to the optical axis (A) of the infrared camera being substantially equal to the inclination angle (a) of the wall (130) and of the transparent element (132).

9. Device (400) according to claim 7 or 8, the interface element (430) comprising at least one part (434) adapted to cover the truncated face (417), said part forming for example a thermal protection of the truncated face and / or a protection of said truncated face against infrared radiation.

10. Device (200, 201, 202, 203, 400) according to any one of claims 1 to 9, the infrared camera (210, 410) comprising: - at least one lens (218, 418) and a lens mount (219), said at least one lens being held by said lens mount; and - an image sensor (214, 414) sensitive to infrared radiation of the spectral range; the sensor and the at least one lens defining the optical axis (A) of the infrared camera, the sensor being arranged substantially in the image focal plane of said at least one lens.

11. Device according to any one of claims 1 to 10, the interface element being adapted to provide a fluid-tight assembly between the wall and the infrared camera.

12. Device according to any one of claims 1 to 11, the interface element being made of a material of low thermal conduction, for example example of thermal conduction less than 10 Wm *.K

13. Device (200) according to any one of claims 1 to 12, the interface element being provided with at least one temperature probe (240), at least one temperature probe being for example connected to a module for processing parasitic light flux, for example a parasitic light flux emitted by the device.

14. Device (203) according to any one of claims 1 to 13, comprising a removable shutter element (242) assembled to the interface element (230), and adapted to shutter the infrared camera (210), said shutter element being for example covered with an emissive coating on a face of said shutter element located opposite the infrared camera.

15. Device (201) according to any one of claims 1 to 14, the interface element (230) comprising an inner emitting surface (231) oriented opposite the infrared camera (210) and adapted to be positioned close to the transparent element (132), for example against the mount (134) of the transparent element, said inner emitting surface being for example covered with an emissive coating (233).

16. Device (202) according to any one of claims 1 to 15, the interface element (230) comprising a portion (235) adapted to be positioned opposite a region (133) of the transparent element (132), for example an edge of said transparent element, so as to form a screen between said region of the transparent element and the infrared camera (210), said portion comprising an emitting face oriented opposite the infrared camera (210), for example covered with an emissive coating (237).

17. Device (200, 201, 202, 203) according to any one of claims 1 to 16, the infrared camera (210) comprising an image sensor (214) with a pixel matrix comprising an angular pixel adapted to capture a light flux coming from an interior zone of the interface element (230) oriented opposite the image sensor and the field of view of the angular pixel, for example an interior zone intended to be positioned around the transparent element (132), said interior zone being for example covered with an emissive coating.

18. An infrared imaging system comprising: - an infrared imaging device (200, 201, 202, 203, 400) according to any one of claims 1 to 17, and - a wall (130) comprising an opening in which an element (132) transparent to infrared radiation of a spectral range, surrounded by a mount (134), is inserted using said mount; the transparent element comprising two substantially parallel faces of a given occupation surface and being included in the volume of the opening of said wall; the infrared camera (210, 410) of the device being adapted to detect infrared radiation of the spectral range through the transparent element; the transparent element (132) and the wall (130) being inclined at an angle of inclination (a) greater than 0° and less than 90° or less than 0° and greater than -90° relative to the optical axis (A) of the camera.

Images