Infrared camera and outer window assembly for vehicle glazing

Abstract

To provide an assembly comprising an infrared camera behind an outer window transparent to infrared radiation.SOLUTION: An infrared camera module is provided, comprising: an infrared image sensor (420); an outer window (402) inclined with respect to an optical axis (401) of the infrared image sensor and held in a window mount (410), the outer window (402) having a shape adapted to cooperate, in a removable manner, with a receiving part surrounding a hole passing through a glazing; and an interface part (450) providing a mechanical link between the window mount (410) and the infrared image sensor (420).SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present disclosure relates generally to the field of infrared cameras.

[0002] The present disclosure particularly relates to an assembly that includes an infrared camera behind an exterior window that is transparent to infrared radiation. [Background technology]

[0003] In the field of infrared imaging, infrared cameras ("IR cameras") may be used that are configured to capture thermal images of a scene. IR cameras generally include an arrangement of infrared-sensitive detectors that form an array of pixels. Each pixel in the pixel array converts the temperature measured at the pixel into a corresponding voltage signal, which is converted to a digital output signal by a digital-to-analog converter (ADC). A microbolometer is an example of a pixel used in an uncooled infrared pixel array camera that is adapted to capture a thermal image of an image scene.

[0004] In certain applications, the infrared camera is positioned behind vehicle glazing, such as glass, such as a car windshield. Generally, glass is not transparent to infrared radiation. Therefore, a specific vehicle glazing is generally required that has a hole drilled through its entire depth, is fitted with a receiver, such as a mount, and has attached thereto an element that is transparent to infrared radiation. In the following disclosure, the transparent element may be referred to as an outer window. The outer window is positioned so that the IR camera can receive infrared radiation through the outer window.

[0005] The vehicle glazing, and therefore the exterior window, can be tilted at a non-zero angle relative to the vertical.

[0006] Figure 1 is a cross-sectional view of an example of an infrared camera positioned behind a sloped glass. Figure 1 is a diagram from WO 2021 / 112144 and illustrates a camera unit 100 comprising a vehicle glass 1, an infrared-transparent member 20 provided in an opening in the vehicle glass 1, and an infrared camera CA1 attached to the rear of the transparent member 20. The infrared camera CA1 is attached to a mounting bracket 30 that rests against the inner surface of the vehicle glass 1.

[0007] The solution described in WO 2021 / 112144 has several drawbacks, including the drawback of maintenance and the costs associated with it: indeed, if the vehicle glass has to be replaced, the infrared-transparent element also has to be replaced, and vice versa.

[0008] Furthermore, prior art solutions have other technical drawbacks. For example, the presence of a tilted outer window or a tilted infrared-transparent member can cause undesirable vignetting in the images captured by the infrared camera, i.e., a decrease in brightness at the edges of the image, or in other words, an increase in opacity at the edges of the image. This vignetting worsens as the distance between the outer window and the infrared camera increases. Summary of the Invention

[0009] What is needed is an assembly that includes an infrared camera behind an exterior window that is transparent to infrared radiation.

[0010] One embodiment addresses all or some of the above-mentioned shortcomings.

[0011] One embodiment provides an infrared camera module comprising an infrared imaging sensor, an exterior window tilted relative to the optical axis of the infrared imaging sensor and held in a window mount, the window mount having a shape adapted to removably cooperate with a receiver surrounding a hole through the glazing, and a joint providing a mechanical connection between the window mount and the infrared imaging sensor.

[0012] In one embodiment, the infrared camera module further comprises at least one focusing optical element, such as one or more lenses, positioned inside the joint and centered about the optical axis.

[0013] In one embodiment, the at least one focusing optical element includes at least one lens held in at least one lens mount, the at least one lens mount being coupled to or part of the interface.

[0014] In one embodiment, at least one lens is formed from germanium crystal, zinc sulfide, or zinc selenide, or from an amorphous infrared chalcogenide glass or alloy.

[0015] In one embodiment, at least one lens is coated with an anti-reflective coating adapted to optimize light transmission in the spectral sensitivity range of the infrared image sensor.

[0016] In one embodiment, the thermal imaging sensor comprises an array of vacuum microbolometers, sensitive to all or part of the wavelength range, for example, from 2.5 to 20 μm, preferably from 7.5 to 14 μm.

[0017] In one embodiment, the exterior window has a substantially planar exterior surface.

[0018] In one embodiment, the exterior surface of the exterior window is coated with an anti-reflective coating.

[0019] In one embodiment, the outer window comprises a material that is transparent in the spectral sensitivity range of the infrared image sensor.

[0020] In one embodiment, the outer window has an inner surface that is substantially planar and parallel to its outer surface.

[0021] In one embodiment, the inside surface of the outer window is coated with an anti-reflective coating that is preferably different from the anti-reflective coating on the outer surface.

[0022] In one embodiment, the window mount comprises first means for interfacing with the interface and second means for interfacing with the receiver of the glazing.

[0023] In one embodiment, the window mount has a first outer surface designed to slide into the through hole and a second outer surface designed to rest on a shoulder portion of the receiver, the shoulder portion being dimensioned so that the outer surface of the exterior window is substantially aligned with the outer surface of the glazing as an extension of the glazing.

[0024] In one embodiment, the outer surface of the outer window is inclined with respect to the optical axis of the infrared image sensor by a tilt angle comprised between 20° and 70°, for example between 15° and 45° or between 45° and 65°.

[0025] In one embodiment, the infrared camera module further comprises a mechanical shutter positioned along the optical axis adapted to cut off the light path coming from the outer window to the infrared image sensor.

[0026] In one embodiment, the junction includes a temperature sensor.

[0027] In one embodiment, the junction includes a mirror designed to deflect the optical axis.

[0028] In one embodiment, the joint includes an internal structure designed to protect the infrared imaging sensor from stray light.

[0029] In one embodiment, the joint is covered with an absorptive coating in the spectral sensitivity range of the infrared image sensor, for example black paint or black anodized aluminum.

[0030] In one embodiment, the junction is thermally conductive at least in the area of ​​the junction that is exposed to stray light.

[0031] In one embodiment, the junction is thermally coupled to the first heat dissipation system.

[0032] In one embodiment, the thermal imaging sensor is thermally coupled to the second heat dissipation system.

[0033] One embodiment provides a method for assembling an infrared camera module, the method including assembling an infrared imaging sensor to an exterior window tilted relative to an optical axis of the infrared imaging sensor by a joint, the exterior window being held in a window mount, the window mount having a shape adapted to removably cooperate with a receiver surrounding a hole through the glazing, the joint providing a mechanical connection between the window mount of the exterior window and the infrared imaging sensor.

[0034] The foregoing and other features and advantages will be explained in detail in the following description of particular embodiments, given by way of example and not limitation with reference to the accompanying drawings, in which: FIG. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a cross-sectional view of an example of an infrared camera positioned behind a sloped glass window. [Figure 2] FIG. 10 is a cross-sectional view of another example of an infrared camera positioned behind a tilting glass window. [Figure 3A] FIG. 1 is a front view illustrating glazing adapted to receive an infrared camera module, according to one embodiment. [Figure 3B] FIG. 1 is a front view illustrating glazing adapted to receive an infrared camera module, according to one embodiment. [Figure 3C] 1 is a cross-sectional view illustrating glazing adapted to receive an infrared camera module, according to one embodiment. [Figure 3D] 3A-3C, according to one embodiment. [Figure 4A] FIG. 2 is a cross-sectional view illustrating details of an infrared camera module, according to one embodiment. [Figure 4B] FIG. 2 is a cross-sectional view illustrating details of an infrared camera module, according to one embodiment. [Figure 4C] FIG. 2 illustrates an example of a lens in an infrared camera module according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0036] Similar features are designated by similar reference numerals in the various figures, and in particular, structural and / or functional features that are common among the various embodiments may have the same reference numerals and may be provided with the same structural, dimensional, and material properties.

[0037] For clarity, only those operations and elements useful for understanding the embodiments described herein have been shown and described in detail. In particular, the optical system, e.g., lenses and their mount(s), and the infrared detector, e.g., in the form of an array of microbolometers or photodiodes, have not been described in detail and are known to those skilled in the art of the invention.

[0038] Unless otherwise specified, when referring to two elements connected to each other, this means a direct connection without any intermediate elements other than connectors or conductors, and when referring to two elements coupled to each other, this means that these two elements may be connected or coupled via one or more other elements.

[0039] In the following disclosure, unless otherwise specified, references to absolute position modifiers such as terms like "front," "back," "top," "bottom," "left," "right," etc., or relative position modifiers such as terms like "above," "below," "higher," "lower," etc., or orientation modifiers like "horizontal," "vertical," etc., refer to the infrared camera module as oriented in the orientation shown in the figures or during normal use.

[0040] When reference is made to the terms "forward of" or "upstream of", it refers to the direction of propagation of the light ray / radiation, i.e., from the outer window to the infrared detector. When reference is made to the terms "backward of" or "downstream", it refers to the direction opposite to the direction of propagation of the light ray / radiation, i.e., from the infrared detector to the outer window.

[0041] Unless otherwise specified, the terms "about," "approximately," "substantially," and "about" mean within 10% or 10°, preferably within 5% or 5°.

[0042] FIG. 2 is a cross-sectional view of another example of an infrared camera positioned behind a tilting glass.

[0043] 2 is a diagram from French Patent Application Publication No. 3127633 illustrating an infrared imaging device 200 comprising an infrared (IR) camera 210. The IR camera 210 comprises a housing 212 containing an image sensor 214 and a window 216 arranged in front of the image sensor 214, and a number of lenses 218 held in a lens barrel 219 assembled to the housing 212, the window 216 being positioned between the lens barrel 219 and the image sensor 214. The image sensor 214 and the lenses 218 define an optical axis A of the camera, indicated in the horizontal direction X. The infrared imaging device 200 comprises a wall 130 having an opening into which a porthole 132 is inserted together with a porthole mount 134. The wall 130 and the porthole 132 are inclined at an angle α relative to the optical axis A or at an angle θ relative to the vertical direction Z. The IR imaging device 200 further comprises a mating element 230 positioned between the infrared camera 210 and the porthole mount 134, which allows for accurate positioning of the infrared camera 210 relative to the porthole 132. The mating element 230 allows for control of the distance of the infrared camera 210 relative to the porthole 132, and therefore the phenomenon of vignetting.

[0044] The interface element 230 includes a first end 232 shaped to engage with the porthole mount 134, a second end 234 shaped to engage with the infrared camera 210, and a body 236 between the first and second ends.

[0045] The interface element 230 is a separate element from the wall 130 and the infrared camera 210. This therefore makes it possible to easily replace different elements of the wall and / or the infrared imaging device, for example in case of maintenance or when the interface element has to be replaced, or when the wall has to be replaced, for example if it has been damaged during its use.

[0046] However, if the porthole 132 must be replaced, the wall 130 must also be replaced, and conversely, if the wall 130 must be replaced, the porthole 132 must also be replaced, resulting in high maintenance costs.

[0047] There is therefore a need for an infrared camera module that can overcome the above-mentioned drawbacks, in particular an infrared camera module that can be easily separated from the glazing, for example when the glazing needs to be replaced, and that ensures good positioning of the optical elements of the infrared camera module.

[0048] The present inventors provide an infrared camera module, also called a thermal camera module or camera module, that can address this need.

[0049] The infrared camera module according to each embodiment comprises an assembly of an infrared image sensor, an infrared outer window and a joint, the assembly being intended to be removably attached to a receptacle in the glazing.

[0050] The term "infrared" window refers to a window that is transparent to infrared radiation within the spectral range of operation of an infrared camera module. The term "exterior" window refers to a window positioned in a portion of the infrared camera module that interfaces with the exterior of the module. Generally, this portion corresponds to one end of the module, the end that faces the scene to be imaged.

[0051] The infrared camera module is designed to be joined to, or in other words to work with, the glazing, which is preferably a vehicle glazing, such as the glazing of an automobile, train, ship, aircraft or spacecraft, for example the glazing of a driver's cab, or more specifically the windshield.

[0052] The glazing has a through hole and a receptacle surrounding the through hole that provides a removable attachment joint for the infrared camera module.

[0053] The glazing has a tilt angle relative to the horizontal, and the infrared exterior window is designed to fill the glazing opening and act as an extension of the glazing at the opening, following the slope of the glazing.

[0054] The infrared camera module includes at least the following elements: an infrared imaging sensor, which may comprise an infrared detector based on an array of vacuum microbolometers and an optical window in front of the infrared detector or a vacuum-sealed optical window; an infrared outer window held in a window mount, the material of the outer window being adapted to the application and the infrared outer window may be provided with a suitable outer coating; - A joint that provides a mechanical connection between the window mount and the thermal imaging sensor.

[0055] The infrared detector may be sensitive in the thermal infrared range, typically in a spectral range comprised between 2.5 and 20 μm, for example in the LWIR range, i.e. between 7.5 μm and 14 μm. The infrared detector may also be adapted to operate in another spectral range in the infrared range, typically in a spectral range comprised between 1 μm and 20 μm.

[0056] The infrared camera module preferably includes at least one focusing optical element positioned between the infrared detector and the infrared outer window and configured to form an image. The at least one focusing optical element may be part of a focusing optical system that may be part of the infrared image sensor.

[0057] The infrared camera module may further comprise one or more of the following elements: a mechanical shutter adapted to block scene radiation and provide a black reference image; -temperature sensor, - A structure designed to protect an infrared imaging sensor, e.g. an infrared detector, from stray light, in particular sunlight.

[0058] A first advantage of such an infrared camera module in conjunction with the glazing is that maintenance costs are reduced in case one or all elements of the infrared camera module need to be replaced, recalibrated or requalified without the need to replace the entire glazing, which also applies if the glazing needs to be replaced, without affecting the camera module.

[0059] A second advantage of such an infrared camera module interfacing with glazing is that the manufacturing line or chain of the infrared camera module and the glazing is separated until final assembly with the glazing, which generally constitutes the standards to which the camera module must conform.

[0060] The infrared camera module comprises the entire optical chain up to the infrared outer window, which facilitates the manufacture, assembly, calibration and quality check of the camera module, since the entire chain can be completed before final assembly with the glazing. In particular: -The conditions for assembling the different elements of the camera module, e.g. temperature, pressure, particles, can be controlled. -The seal between the infrared outer window and the joint can be controlled. The alignment tolerance of the optical system with the outer window can be improved, for example allowing for smaller outer window dimensions. The optical system can be focused without glazing, using only the outer window, e.g., a heat source, a test pattern and a collimator. Intrinsic calibration of the camera module can be performed using only the exterior windows, i.e., without glazing, for example in a climate chamber, by placing the camera module in front of a radiative reference surface such as a blackbody.

[0061] Examples of infrared camera modules are described below, but these examples are non-limiting and different variations will occur to those skilled in the art based on the teachings of this specification.

[0062] Figures 3A, 3B, 3C, and 3D are front and cross-sectional views illustrating a glazing 300 adapted to receive an infrared camera module, according to one embodiment. Figure 3D is a cross-sectional view illustrating the assembly of the glazing 300 of Figures 3A-3D and an infrared camera module 400, according to one embodiment. Figure 3A shows the exterior surface 300A of the glazing 300. Figure 3B shows the interior surface 300B of the glazing 300.

[0063] The glazing 300 has a thickness that is small compared to its lateral dimensions. For example, the glazing 300 is the windshield of a car. The total thickness of the glazing 300 is, for example, a few millimeters, typically about 5 mm.

[0064] The glazing 300 may be constructed from a stack of layers 301, for example, two glass layers 302A and a polyvinyl butyral (PVB) layer 302B sandwiched between the two glass layers 302A.

[0065] The through holes 304 are drilled through the entire depth of the glazing 300. The holes 304 have a lateral dimension of, for example, a few centimeters. Typically, the holes 304 have the shape of a disk with a diameter of a few centimeters, for example about 5 centimeters.

[0066] If the glazing 300 is a car windshield, the hole 304 may be typically positioned in a sensor area 303, for example behind the rearview mirror, where a front camera and / or rain sensor may typically be positioned.

[0067] 3D, the glazing 300 has a tilt angle α relative to the horizontal direction X that is typically comprised between 20° and 65°. In the case of a car windshield, this tilt angle is considered to be at least in the vicinity of the sensor area 303.

[0068] A receiver 305 is inserted into the hole 304, preferably sealingly engaging the laminate 301 inside the hole 304. The receiver 305 has a through hole 307, and its lateral dimension is smaller than the lateral dimension of the hole 304. The receiver 305 comprises a first portion 305A that engages the laminate 301 inside the hole 304, and a second portion 305B that is connected to the first portion 305A and extends to the laminate 301 at the inner surface 300B of the glazing 300. The second portion 305B can be referred to as a shoulder portion. The receiver 305 is typically a flange with the first portion 305A having a shape complementary to the hole 304. The receiver 305 comprises fastening means 308 configured to attach the receiver 305 to the inner surface 300B of the glazing 300. The receiver 305 may include protrusions 306, such as lugs, from which the fastening means 308 extend. A person skilled in the art can design the receiver 305 to insert into the hole 304 and select the appropriate fastening means 308.

[0069] 3D, an infrared camera module 400, which will be described in more detail below, can be removably and tightly, e.g., watertightly, attached to the glazing 300, and in particular to the receptacle 305 of the glazing 300. The infrared camera module 400 has an outer surface 400A that is substantially flush with the outer surface 300A of the glazing 300.

[0070] As will be explained in more detail below, the infrared camera module 400 comprises on its outer surface 400A an optical element 402 shaped and sized to fit into the through hole 307 of the receiver 305, and a mechanical element 410 configured to support the optical element 402 and assemble the optical element into the receiver 305 of the glazing 300, for assembling the infrared camera module 400 to the glazing 300. In the following disclosure, the optical element 402 may be referred to as an outer window, and the mount 410 may be referred to as a window mount.

[0071] Figures 4A and 4B are cross-sectional views showing details of an infrared camera module 400, according to one embodiment. Figure 4A is a cross-sectional view along line BB, and Figure 4B is a cross-sectional view along line CC. Figures 4A and 4B use the same reference numbers as Figure 3D for the outer window 402 and window mount 410.

[0072] FIG. 4C illustrates an example of a lens in an infrared camera module, such as infrared camera module 400 of FIGS. 4A and 4B, according to one embodiment.

[0073] The infrared camera module 400 comprises an infrared (IR) image sensor 420 with an infrared detector 422 and an optical window 423 in front of the infrared detector 422 that is capable of transmitting IR radiation in the working spectral range of the IR image sensor 420. The infrared image sensor 420 may be referred to as a sensor in the following disclosure.

[0074] The infrared imaging sensor 420 is adapted to capture a thermal image of the scene S through the tilted outer window 402 .

[0075] In one embodiment, infrared detector 422 is a focal plane array (FPA) detector, ie, a detector comprising an array of light-sensitive pixels in the focal plane of a lens.

[0076] The light-sensitive pixels are, for example, vacuum microbolometers adapted to capture a thermal image of the scene S. For example, each microbolometer of the array comprises an absorber on a suspended thermo-resistive plate, typically based on amorphous silicon or doped vanadium oxide. The temperature of each microbolometer can be altered by radiative communication with scene elements, and the temperature is then read by thermo-resistive measurement to extract a thermal radiation image of the scene via an electronic readout circuit and an image processing unit (not shown).

[0077] The array may have, for example, a video graphics array (VGA) 4:3 format, which is 640 x 480 pixels, or a Quart-VGA 16:9 format, which is 320 x 180 pixels, although the array may have other formats with more or fewer pixels. The pixel pitch may be, for example, about 12 μm or about 8.5 μm, although other pixel pitches may also be used.

[0078] The optical window 423 is configured to seal the vacuum chamber 424 so that the infrared detector 422 can be placed in a vacuum. The optical window 423 may be referred to as a vacuum-sealed window.

[0079] The optical window 423 is made of, for example, float zone silicon (FZ silicon) or germanium. The optical window 423 preferably has an anti-reflection optical coating and advantageously has wavelength filtering capabilities.

[0080] The thermal imaging sensor 420 may be designed to be sensitive in the thermal infrared range, a spectral range typically comprised between 2.5 and 20 μm, for example in the LWIR range, ie between 7.5 μm and 14 μm.

[0081] The infrared detector 422 and optical window 423 may be contained in a housing 421 having an opening 421A in front of an optical system 440, described below. For example, the opening 421A may have substantially the dimensions of the optical window 423, or may be larger or smaller. Preferably, the opening 421A is large enough to avoid vignetting.

[0082] Advantageously, the infrared imaging sensor 420 may be thermally coupled to a heat dissipation system 431. For example, the heat dissipation system 431 is a radiator with a plurality of fins 432. The function of the heat dissipation system 431 is to remove heat generated by at least the electronic readout circuit and the image processing unit. The heat dissipation system 431 is, for example, positioned against a side 421B of the housing 421 facing the opening 421A.

[0083] The infrared detector 422 is located in the focal plane of an optical system 440 that includes at least one lens capable of operating in the used spectral range of the infrared image sensor 420. The optical system 440 may be referred to as a focal optical system.

[0084] The optical system 440 may be part of the infrared imaging sensor 420 .

[0085] The infrared detector 422 and the at least one lens define an optical axis 401 (or optical path) of the infrared camera module 400, indicated in the horizontal direction X.

[0086] Infrared detector 422 and optical window 423 are positioned along optical axis 401 between heat dissipation system 431 and focusing optical system 440 .

[0087] The optical system 440 is positioned along the optical axis 401 between the optical window 423 and the outer window 402 , ie, upstream of the outer window 402 .

[0088] The optical system 440 is configured to form an image of the scene in the spectral sensitivity range of the sensor.

[0089] 4A and 4B, optical system 440 comprises three lenses 441, 442, and 443. Lens 441 is positioned along optical axis 401 between optical window 423 and lens 442. Lens 442 is positioned along optical axis 401 between lens 441 and lens 443. Lens 443 is positioned along optical axis 401 between lens 442 and outer window 402, upstream of outer window 402. Those skilled in the art will be able to apply other configurations and numbers of lenses, or other optical elements, or more generally other focusing optical systems.

[0090] Each lens may be formed, for example by machining, molding, or lithography / engraving, starting from a material that is transparent in the spectral sensitivity range of the sensor, and then polished.

[0091] For example, each lens may be formed from a germanium crystal, or from zinc sulfide (ZnS), or from zinc selenide (ZnSe).

[0092] In a preferred embodiment, each lens is formed from an amorphous infrared chalcogenide glass / alloy such as: -Ge 33 As 12 Se 55 -Ge 30 As 13 Se 32 Te 25 -Ge 10 As 40 Se 50 -Ge 28 Sb 12 Se 60 -As 40 Se 60

[0093] Each lens may be advantageously coated with an anti-reflection coating adapted to optimize light transmission in the spectral sensitivity range of the sensor.

[0094] In a multi-lens optical system, the lenses are preferably assembled using conventional opto-mechanical assembly techniques, such as threaded compartments or mounts provided with spacers and locking rings.

[0095] For example, in the illustrated example, lenses 441 and 442 are held in a lens mount 444, i.e., a lens barrel. Lens mount 444 has a first end 444A designed to cooperate with an end of housing 421; for example, first end 444A of lens mount 444 extends into housing 421 through opening 421A. Lens 443 is held in another lens mount 445, i.e., a lens barrel, having an end designed to cooperate with second end 444B of lens mount 444. For example, second end 444B of lens mount 444 extends into lens mount 445.

[0096] In the advantageous embodiment shown in FIG. 4C , the lens 443 closest to the outer window 402 has a truncated portion 443T. The truncated portion 443T is formed in the portion of the lens 443 closest to the sloped outer window 402, here the upper portion of the lens 443. The lens mount 445, which has the shape of the lens 443, also has a truncated portion 445T, here the upper portion of the lens mount 445. These truncations allow the sloped outer window 402 to be closer to the lens 443, and therefore the optical system 440 and the infrared image sensor 420, thereby limiting vignetting. The truncated portion 443T of the lens 443 is covered by the mount truncated portion 445T, thus protecting the lens truncation.

[0097] For example, optical system 440 is typically designed to have a horizontal field of view comprised between about 20° and 50°, with the vertical field of view being approximately equal to the horizontal field of view divided by the aspect ratio of the sensor.

[0098] The infrared camera module 400 further comprises a joint 450. The joint 450 is used to position the optical system 440, and therefore the infrared image sensor 420, relative to the mount 410 of the outer window 402.

[0099] It should be noted that the tilt angle α and / or the size of the hole 304 may vary depending on the type of glazing 300. The interface 450 may be available in several variations so that the same type of detector and optics of the thermal imaging sensor 420 can be adapted to different types of glazing 300.

[0100] The joint 450 is assembled to, for example, the lens mount 445 through, for example, a threaded hole 446 in the mount 445, a threaded hole 453 in the joint 450, and a screw 447 or the like that can cooperate with the threaded hole.

[0101] It is contemplated that lens mount 445 , and possibly lens mount 444 , may be part of interface 450 .

[0102] In one advantageous embodiment, junction 450 is covered, at least on its inner surface, with an absorptive coating in the spectral sensitivity range of the sensor, such as black paint or black anodized aluminum.

[0103] In an advantageous embodiment, all or part of the inner surface of the joint 450 is structured to protect the sensor 420, e.g., the detector 422, from stray light, in particular sunlight. For example, the structure 452 of the joint 450 has the form of a step.

[0104] In an advantageous embodiment, junction 450 is thermally conductive, at least in the area exposed to stray light, so as not to store heat absorbed from the stray light, and in fact, the exposed area, when heated, becomes a secondary source of stray radiation via heat emission from junction 450.

[0105] In an advantageous embodiment, the joint 450 is coupled to a separate heat dissipation system 433, for example an inner portion 451 of the joint 450 that is exposed to stray light, particularly sunlight, is coupled to the heat dissipation system 433. For example, the heat dissipation system 433 is a radiator designed to remove heat generated by the stray light absorbed by the joint 450. For example, the heat dissipation system 433 comprises a plurality of fins 434 aligned in the longitudinal direction of the heat dissipation system 433. Advantageously, the heat dissipation system 433 can particularly contribute to the rigidity of the joint 450.

[0106] In one embodiment, junction 450 includes a temperature sensor 454, which can transmit its measurements to an image processing unit. In particular, the temperature measurements can be used to evaluate an image of the thermal stray flux emitted by junction 450 so that it can be subtracted from the scene image. For example, the image processing unit can determine the flux inherently resulting from the scene image and correct for the stray flux.

[0107] Optionally, junction 450 may include additional optical elements, for example, junction 450 may include a mirror designed to deflect optical axis 401 as required, for example, to limit the dimensions of optical system 440 and / or camera module 400.

[0108] The camera module 400 can include a mechanical shutter 425 positioned anywhere along the optical axis 401 between the vacuum-sealed window 423 and the inner surface 402A of the infrared outer window 402. The mechanical shutter 425 can cut off the light path, for example, to provide a black reference to the image processing unit for differential processing, for example, to calibrate the image sensor 420. The mechanical shutter 425 can also protect the image sensor 420, for example, when a strong light source, such as the sun, appears in the scene S or when the vehicle is parked.

[0109] The mechanical shutter 425 is preferably positioned near the pupil 448 of the optical system 440 to provide a good reference image regardless of the spatial non-uniformity of the shutter, or at a location where the light field is small to reduce the size of the shutter 425 and therefore make it brighter.

[0110] The shutter 425 may, for example, have the shape of a disk and be coated with an emissive coating on the sensor side and a reflective coating on the scene side.

[0111] The shutter 425 can be tilted from an open position to a closed position by a motor 426. The motor 426 may advantageously be connected to the control and power electronics of the image sensor 420.

[0112] Other types of shutters may be used by those skilled in the art, for example shutters made of multiple blades or irises.

[0113] The outer window 402 includes two surfaces: an inner surface 402A and an outer surface 402B.

[0114] The outer surface 402B is preferably substantially planar, for example, to be flush with the glazing 300 and to match the tilt angle α of the glazing 300. The outer window 402 has its outer surface 402B, which is therefore inclined by a tilt angle θ. The tilt angle θ of the outer window 402 corresponds substantially to the tilt angle α of the glazing 300. The tilt angle θ is typically comprised between 20° and 65°, for example between 15° and 45°, or between 45° and 65°.

[0115] The outer window 402 is preferably contained within the volume opened up by the hole 307 in the receiver 305 of the glazing 300. For example, the outer window 402 does not protrude laterally on either side of the hole 307.

[0116] For example, the outer window 402 is made from a material that is transparent in the spectral sensitivity range of the sensor, such as the example materials given for the lens.

[0117] The outer surface 402B of the infrared outer window 402 can be advantageously coated with a state-of-the-art anti-reflective coating suitable for outdoor environmental conditions.

[0118] By integrating the infrared outer window 402 into the camera module 400, there is considerable freedom to design the outer window 402, especially its geometric shape.

[0119] In one embodiment, the inner surface 402A of the outer window 402 is substantially planar and parallel to the outer surface 402B. The inner surface 402A of the outer window 402 may be provided with a standard anti-reflective coating, such as that used on other optical elements, but preferably is different from the anti-reflective coating on the outer surface 402B. When the inner surface 402A of the outer window 402 is substantially planar and parallel to the outer surface 402B, the quality of the optical system, such as sharpness, is not affected or only slightly affected by the outer window 402.

[0120] The outer window 402 is held by a window mount 410, which may be an opto-mechanical mount. The window mount 410 fits against a side 402C of the outer window 402. In particular, the window mount 410 has an inner surface 411 that is designed to fit against the side 402C of the outer window 402.

[0121] The window mount 410 interfaces with the joint 450 on the one hand and with the receiver 305 of the glazing 300 on the other hand. Preferably, the window mount 410 has an outer surface 412 designed to slide into the through-hole 307 of the receiver 305 and another outer surface 413 designed to rest on the second portion 305B (shoulder portion) of the receiver 305.

[0122] The window mount 410 is preferably dimensioned so that the exterior surface 402 B of the exterior window 402 substantially aligns with the exterior surface 300 A of the glazing 300 , such as an extension of the glazing 300 .

[0123] The window mount 410 comprises fastening means 416 which may complement the fastening means 308 of the receiver 305 .

[0124] The window mount 410 typically has the shape of a flange having a first portion 414 that fits between the side surface 402C of the outer window 402 and the first portion 305A of the receiver 305, and a second portion 415 that is attached to the abutment 450 and the receiver 305. The first portion 414 includes an inner surface 411 and an outer surface 412. The second portion 415 includes an outer surface 413. Those skilled in the art will be able to design the window mount 410 to mate with the abutment 450 and the receiver 305 and select appropriate fastening means.

[0125] The infrared camera module 400 has an entire optical chain up to the infrared outer window 402, which facilitates the manufacturing, assembly, calibration and quality check chain of the infrared camera module 400, as the entire chain can be completed before assembly with the glazing 300.

[0126] The assembly of the infrared camera module 400, i.e., the assembly of its different elements, can be performed under controlled conditions, such as temperature, pressure, or particle conditions. For example, the assembly of the infrared camera module 400 can be performed in a clean room or a gray room, depending on the assembly stage. Also, the sealing between the infrared outer window 402 and the joint 450 can be controlled. Furthermore, in the optical assembly chain, the alignment tolerance of the optics with the outer window 402 can be improved, allowing for a smaller outer window 402. These favorable conditions improve the quality of the infrared camera module 400.

[0127] Focusing of the optical system, particularly sharpness adjustment, can be performed in the presence of the outer window 402, i.e., along the entire optical chain. Focusing can be performed, for example, using a heat source, a test pattern, and a collimator. For example, at least one optical element or a group of optical elements is moved along a certain degree of freedom, such as a longitudinal sliding or spiral motion, until sharpness is optimized on the test pattern image. Once sharpness is achieved, the focus adjustment can be locked, for example, by an ultraviolet (UV) flash on an adhesive that bonds when exposed to UV light. From an industrial perspective, it is easier to adjust the infrared camera module 400 without the entire glazing 300.

[0128] The image processing unit must generally be calibrated, for example, with a so-called "intrinsic" calibration. Typically, the image processing unit first records reference images from a uniform scene under controlled ambient temperature conditions. In particular, these reference images take into account the contribution of stray light flux emitted by all elements of the infrared camera module 400, which may be at different temperatures when thermal equilibrium is established.

[0129] To do this, the entire infrared camera module 400, including the outer window 402, may be placed in a climate chamber positioned to face a blackbody, i.e., radiative reference surface, having a controlled, substantially uniform temperature. A set of climate chamber temperatures representing the ambient temperature range of the mission profile, i.e., the eligible ambient operating temperature range, is recorded, and a set of blackbody temperatures representing the scene temperature range of the mission profile is also recorded. It is also possible to simulate changes in the temperature of the glazing 300, and therefore the temperature of the outer window 402 and its mount 410, by locally altering the temperature of the outer window mount 410 with any external tool in thermal contact with the thermostat.

[0130] The set of reference images can be used by the image processing unit to be able to provide a good quality image correction that can correct for fixed spatial noise related to response non-uniformities in the sensor 420, e.g. of the microbolometer detectors 422, and for thermal stray light flux emitted by all elements of the infrared camera module 400. From an industrial point of view, it is easier to calibrate the infrared camera module 400 without the glazing 300.

[0131] During focusing, intrinsic calibration, and additional quality tests, the quality of each infrared camera module, including the entire optical chain, can be verified before integration into the glazing. As a result, defective infrared camera modules can be sorted out before integration into the glazing.

[0132] Various embodiments and variations have been described, and those skilled in the art will understand that certain features of these embodiments can be combined and that other variations will readily occur to those skilled in the art.

[0133] Finally, the actual implementation of the embodiments and variations described herein is within the capabilities of those skilled in the art based on the functional descriptions provided above.

Claims

1. an infrared image sensor (420); an outer window (402) tilted relative to an optical axis (401) of the infrared image sensor and held in a window mount (410), the window mount having a shape adapted to removably cooperate with a receiver (305) surrounding a hole (304) through the glazing (300); a joint (450) providing a mechanical connection between the window mount (410) and the infrared imaging sensor (420); An infrared camera module comprising:

2. 2. The infrared camera module (400) of claim 1, further comprising at least one focusing optical element (441, 442, 443), such as one or more lenses, positioned inside the joint (450) and centered relative to the optical axis (401).

3. 3. The infrared camera module (400) of claim 2, wherein the at least one focusing optical element includes at least one lens (441, 442, 443) held in at least one lens mount (444, 445), the at least one lens mount being coupled to or part of the joint (450).

4. The at least one lens (441, 442, 443) - made from germanium crystals, zinc sulfide or zinc selenide, or from amorphous infrared chalcogenide glasses or alloys; and / or An infrared camera module (400) according to claim 3, coated with an anti-reflection coating adapted to optimize light transmission in the spectral sensitivity range of said infrared image sensor (420).

5. An infrared camera module (400) according to any one of claims 1 to 4, wherein the infrared image sensor (420) comprises an array of vacuum microbolometers, for example sensitive to all or part of the wavelength range of 2.5 to 20 μm, preferably 7.5 to 14 μm.

6. An infrared camera module (400) as described in any one of claims 1 to 5, wherein the outer window (402) has a substantially planar outer surface (402B), and the outer surface of the outer window is coated, for example with an anti-reflective coating.

7. The infrared camera module (400) of any one of claims 1 to 6, wherein the outer window (402) comprises a material that is transparent in the spectral sensitivity range of the infrared image sensor (420).

8. 8. An infrared camera module (400) as described in claim 6 or 7, wherein the outer window (402) has an inner surface (402A) that is substantially planar and parallel to its outer surface (402B), and the inner surface of the outer window is coated, for example, with an anti-reflective coating that is preferably different from the anti-reflective coating of the outer surface.

9. An infrared camera module (400) according to any one of claims 1 to 8, wherein the window mount (410) comprises first means for joining with the joining portion (450) and second means for joining with the receiving portion (305) of the glazing (300).

10. An infrared camera module (400) as described in any one of claims 1 to 9, wherein the window mount (410) has a first outer surface (412) designed to slide into the through hole (304) and a second outer surface (413) designed to stop at a shoulder portion (305B) of the receiver (305), the shoulder portion being dimensioned so that the outer surface (402B) of the outer window (402) is substantially aligned with the outer surface (300A) of the glazing (300) as an extension of the glazing.

11. An infrared camera module (400) according to any one of claims 1 to 10, wherein the outer surface (402B) of the outer window (402) is inclined with respect to the optical axis (401) of the infrared image sensor by a tilt angle (θ) comprised between 20° and 70°, for example between 15° and 45° or between 45° and 65°.

12. An infrared camera module (400) as described in any one of claims 1 to 11, further comprising a mechanical shutter (425) positioned along the optical axis (401) adapted to cut off the light path coming from the outer window (402) to the infrared image sensor (420).

13. The joint (450) a temperature sensor (454); and / or and / or comprising a mirror designed to deflect said optical axis (401); an internal structure (452) designed to protect the thermal imaging sensor (420) from stray light; and / or covered with an absorbing coating in the spectral sensitivity range of the infrared image sensor (420), for example black paint or black anodized aluminum; and / or thermally conductive at least in the area of ​​the junction exposed to stray light; and / or An infrared camera module (400) according to any one of claims 1 to 12, thermally coupled to a first heat dissipation system (433).

14. The infrared camera module (400) of any one of claims 1 to 13, wherein the infrared imaging sensor (420) is thermally coupled to a second heat dissipation system (431).

15. A method of assembling an infrared camera module (400), comprising:

1. A method comprising assembling an infrared imaging sensor (420) to an outer window (402) tilted with respect to an optical axis (401) of the infrared imaging sensor by a joint (450), the outer window being held in a window mount (410), the window mount having a shape adapted to removably cooperate with a receiver (305) surrounding a hole (304) through a glazing (300), the joint (450) providing a mechanical connection between the window mount (410) of the outer window (402) and the infrared imaging sensor (420).

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