Dual-zone bispectral imaging device
The imaging device uses distinct detection zones and a dichroic filter to simultaneously detect two spectral bands, addressing the limitations of existing technologies and achieving efficient and compact spectral acquisition.
Patent Information
- Application Number
- FR2022012153
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-11-22
- Publication Date
- 2025-11-07
- Estimated Expiration
- 2042-11-22
AI Technical Summary
Existing imaging devices struggle to simultaneously detect spectral information in multiple spectral bands due to the wavelength dependence of optical components, leading to costly and physically large solutions with separate detectors or sequential filtering methods.
An imaging device with distinct detection zones for different spectral bands, utilizing a dioptric and catadioptric channels with a dichroic filter to spatially separate and direct electromagnetic radiation into separate detection zones, allowing simultaneous detection of two spectral bands.
Enables reliable and cost-effective simultaneous acquisition of spectral information in multiple bands, with improved detection efficiency and reduced physical size and mass, while being robust to variability in observed objects and atmospheres.
Smart Images
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Abstract
Description
Title of the invention: Two-zone bi-spectral imaging device technical field
[0001] The invention relates technically to imaging devices, in particular infrared imaging devices.
[0002] In particular, the present invention relates to an imaging device capable of simultaneously imaging an observed scene in two spectral bands. Prior techniques
[0003] The spectral content of an object present in an observed scene can be used to characterize the nature of that object. There are optical scene detection and / or monitoring applications that require detecting spectral information within two spectral bands to characterize the object, for example, to generate an alert signal or to prevent the generation of a false alarm.
[0004] An imaging device capable of recognizing two spectral bands is therefore necessary. However, the wavelength dependence of the optical index of the optical components makes it difficult to observe the scene in an extended spectral band or in several separate spectral bands.
[0005] A commonly used solution consists of placing a wheel equipped with optical filters in front of a broadband detector in order to observe the scene successively through the different optical filters. However, such a solution does not allow for the simultaneous acquisition of spectral information in several spectral bands.
[0006] Another solution involves using two separate detectors, each comprising a sensor and an optical system to image an electromagnetic field from the scene onto the sensor. The first detector is sensitive to a first spectral band, and the second detector is sensitive to a second spectral band. Such a solution allows for the simultaneous acquisition of spectral information in several spectral bands but is financially expensive. Integrating these two detectors is also costly in terms of physical size and mass. Description of the invention
[0007] The present invention therefore aims to overcome all or part of the aforementioned drawbacks and to provide an imaging device configured to simultaneously detect two spectral bands from a scene in a reliable and inexpensive manner.
[0008] The present invention relates to an imaging device comprising a means for detecting electromagnetic radiation emitted from an observed scene, the detection means comprising a first and a second distinct detection zone and respectively sensitive to a first and a second spectral bands of electromagnetic radiation, the imaging device comprising an optical system defining a dioptric channel configured to direct the electromagnetic radiation included in the first spectral band towards the first detection zone, and defining a catadioptric channel configured to direct the electromagnetic radiation included in the second spectral band towards the second detection zone, the optical system comprising a dichroic filter disposed both on the dioptric channel and on the catadioptric channel and configured to transmit the electromagnetic radiation included in the first spectral band and reflect the electromagnetic radiation included in the second spectral band.
[0009] Thus, the present invention makes it possible to spatially separate the spectral information from the scene contained in the first spectral band from the spectral information from the scene contained in the second spectral band. The present invention is robust to the variability of observed objects, scenes, and atmospheres.
[0010] Advantageously, the optical system comprises a concave mirror perforated in its center disposed on the catadioptric path, and a lens radially centered on the concave mirror disposed on the dioptric path and axially between the observed scene and the concave mirror.
[0011] In one embodiment, the dichroic filter includes an optical treatment carried out on a surface of the lens.
[0012] Advantageously, the optical system includes a prism disposed on the dioptric path opposite the observed scene.
[0013] In one embodiment, the optical system comprises an assembly of at least one lens disposed both on the dioptric path and on the catadioptric path, the assembly of at least one lens being disposed opposite the detection means.
[0014] Advantageously, the set of at least one lens comprises at least three lenses.
[0015] In one embodiment, the surface area of the second detection zone is at least twice as large as the surface area of the first detection zone.
[0016] Advantageously, the first spectral band comprises the MWIR spectral band, the second spectral band comprises the LWIR spectral band.
[0017] In one embodiment, the detection means includes an electromagnetic radiation sensor configured to detect electromagnetic radiation included in at least the first and second spectral bands, a lower part of the sensor defining the first detection zone, an upper part of the sensor defining the second detection zone.
[0018] In another embodiment, the detection means comprises a first electromagnetic radiation sensor configured to detect electromagnetic radiation within at least the first spectral band and defining the first detection zone, and a second electromagnetic radiation sensor configured to detect electromagnetic radiation within at least the second spectral band and defining the second detection zone. Brief description of the drawings
[0019] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:
[0020] [Fig-1] schematically illustrates an imaging device according to the invention, the scene observed emitting electromagnetic radiation within the first spectral band;
[0021] [Fig.2] schematically illustrates the imaging device of [Fig.1], the scene observed emitting electromagnetic radiation within the second spectral band;
[0022] [Fig.3] schematically illustrates the imaging device of the [Fig.1], the scene observed emitting electromagnetic radiation included in the first spectral band and in the second spectral band;
[0023] [Fig.4] schematically illustrates a detection means according to a first mode of realization of the invention; and
[0024] [Fig.5] schematically illustrates a detection means according to a second mode of realization of the invention. Detailed description
[0025] Figure 1 schematically represents an imaging device 2 comprising a detection means 4 sensitive to electromagnetic radiation, for example, a bolometer sensitive to infrared electromagnetic radiation. The imaging device 2 is oriented towards a scene emitting electromagnetic radiation in a first spectral band and in a second spectral band distinct from the first spectral band. A spectral band of electromagnetic radiation is understood to be a portion of the spectrum of said electromagnetic radiation. In other words, a spectral band is the set of wavelengths between two predefined wavelengths.
[0026] The detection means 4 comprises a first detection zone 6 sensitive to the first spectral band of electromagnetic radiation. The first detection zone 6 is capable of collecting spectral and spatial information from the observed scene and contained within the first spectral band.
[0027] The detection means 4 comprises a second detection zone 8, distinct from the first detection zone 6 and sensitive to the second spectral band of electromagnetic radiation. The second detection zone 8 is capable of collecting spectral and spatial information from the observed scene and contained within the second spectral band.
[0028] The imaging device 2 comprises an optical system 10 defining a dioptric channel 12 and a catadioptric channel 14 (represented in [Fig.2]), light rays from the scene undergoing refraction and not undergoing reflections on the dioptric channel 12, light rays from the scene undergoing refractions and reflections on the catadioptric channel 14.
[0029] The optical system 10 includes optical components on the dioptric channel 12 capable of directing the electromagnetic radiation emitted by the scene and included in the first spectral band towards the first detection zone 6.
[0030] The optical system 10 includes optical components on the catadioptric path 14 capable of directing the electromagnetic radiation emitted by the scene and included in the second spectral band towards the second detection zone 8.
[0031] The optical system 10 includes a dichroic filter 16 disposed both on the dioptric channel 12 and on the catadioptric channel 14. The dichroic filter 16 is configured to transmit electromagnetic radiation included in the first spectral band and to reflect electromagnetic radiation included in the second spectral band.
[0032] Preferably, the first and second detection zones 6, 8 are spatially separated. Thus, electromagnetic radiation within the first spectral band is detected by the first detection zone 6, while electromagnetic radiation within the second spectral band is not directed towards the first detection zone 6 by the optical system 10. Electromagnetic radiation within the second spectral band is detected by the second detection zone 8, while electromagnetic radiation within the first spectral band is not directed towards the second detection zone 8. Alternatively, the first and second detection zones 6, 8 may partially overlap.
[0033] The detection means 4 is for example connected to computing means (not shown) to process the spectral and spatial information from the scene and collected by the first and second detection zones 6, 8.
[0034] The optical system 10 comprises a concave mirror 18 perforated in its center and arranged on the catadioptric path 14.
[0035] The optical system 10 comprises a lens 20 radially centered on the same optical axis as the concave mirror 18 and disposed on the dioptric channel 12. The lens 20 is disposed axially between the observed scene and the concave mirror 18.
[0036] Preferably, the diameter of the concave mirror 18 is twice the diameter of the lens 20, the latter corresponding approximately to the size of the perforation in the center of the concave mirror 18. The diameter of the concave mirror 18 is for example 65 mm, the distance between the concave mirror 18 and the detection means 4 is for example 40 mm.
[0037] The dichroic filter 16 here includes an optical treatment carried out on a surface of the lens 20, said surface being opposite the detection means 4 and corresponding to the second diopter of the lens 20. The optical treatment includes, for example, a dielectric treatment.
[0038] Preferably, the optical system 10 comprises a prism 22 arranged on the dioptric channel 12 opposite the observed scene. Thus, the lens 20 is arranged axially between the prism 22 and the detection means 4. The prism 22 is able to align the field of view of the dioptric channel 12 with the field of view of the catadioptric channel 14 so that the first and second detection zones 6, 8 observe the same scene.
[0039] The electromagnetic radiation from the observed scene, containing spectral information included in the first spectral band and in the second spectral band, and being on the dioptric path 12 passes through the prism 22 and the first diopter of the lens 20. The spectral information of the electromagnetic radiation included in the first spectral band is then transmitted by the dichroic filter 16 towards the detection means 4, the spectral information of the electromagnetic radiation included in the second spectral band being reflected by the dichroic filter 16.
[0040] The lens 20 comprises, for example, a material transmitting electromagnetic radiation included in the first spectral band and reflecting electromagnetic radiation included in the second spectral band, for example silicon and / or sapphire.
[0041] Advantageously, the lens 20 includes an anti-reflective coating suitable for reducing the reflection of electromagnetic radiation included in the first spectral band.
[0042] As illustrated in [Fig. 2], the electromagnetic radiation from the observed scene, containing spectral information in the first and second spectral bands, and being on the catadioptric channel 14, is reflected by the concave mirror 18 towards the dichroic filter 16. The spectral information of the electromagnetic radiation in the first spectral band is then transmitted by the dichroic filter 16, and the spectral information of the electromagnetic radiation in the second spectral band is reflected by the dichroic filter 16 towards the detection means 4. The optical configuration of the catadioptric channel 14 is close to the optical configuration of a Cassegrain type telescope.
[0043] Alternatively, the dichroic filter 16 could include a dichroic optical component placed axially between the concave mirror 18 and the lens 20, said dichroic optical component comprising, for example, a plate with flat and parallel faces or any other dichroic optical component simplifying the realization and / or manufacture of the spectral filtering function provided by the dichroic filter 16.
[0044] The optical system 10 comprises an assembly of at least one lens 24 disposed both on the dioptric channel 12 and on the catadioptric channel 14. The assembly of at least one lens 24 is disposed opposite the detection means 4, axially between the lens 20 and the detection means 4.
[0045] Fig. 3 simultaneously illustrates the path of electromagnetic radiation from the scene on the dioptric 12 and catadioptric 14 channels.
[0046] The assembly of at least one lens 24 is capable of directing the electromagnetic radiation of the dioptric channel 12, included in the first spectral band and passing through the dichroic filter 16, towards the first detection zone 6.
[0047] The assembly of at least one lens 24 is capable of directing the electromagnetic radiation from the catadioptric channel 14, included in the second spectral band and reflected by the dichroic filter 16, towards the second detection zone 8.
[0048] Optionally, the assembly of at least one lens 24 includes at least three lenses in order to correct the main optical aberrations.
[0049] In a particular embodiment, the first spectral band comprises the MWIR spectral band (MidWave Infrared), and the second spectral band comprises the LWIR spectral band (LongWave Infrared). The MWIR spectral band includes, for example, electromagnetic radiation with wavelengths between 3 and 5 pm. The LWIR spectral band includes, for example, electromagnetic radiation with wavelengths between 8 and 14 pm.
[0050] Advantageously, the detection means 4 comprises a sealed structure (not shown) equipped with a window 26 and a sensor 28 disposed inside the sealed structure, the interior of the sealed structure being suitable for cooling and evacuation, for example under secondary vacuum. Such a detection means 4 makes it possible to perform high-quality infrared electromagnetic radiation measurements.
[0051] Preferably, the concave mirror 18, the prism 22, the lens 20, and the assembly of at least one lens 24 are dimensioned such that the surface area of the second detection zone 8 is at least twice as large as the surface area of the first detection zone 6. In the illustrated example, the surface area of the second detection zone 8 is four times larger than the surface area of the first detection zone 6. This embodiment is particularly advantageous when the intensity of the electromagnetic radiation The magnetic field strength of the first spectral band is lower than the intensity of the electromagnetic radiation in the second spectral band. Concentrating the electromagnetic radiation of the first spectral band further increases the detection range of the first detection zone 6. The larger area of the second detection zone 8 allows for a higher angular resolution of the scene observed by the second detection zone 8. For example, the first and second detection zones 6 and 8 comprise detection pixels of identical individual dimensions and collect spectral and spatial information from the same area of the observed scene.As a result, the second detection zone 8 can include more detection pixels than the first detection zone 6 and therefore collect more precise spatial information from the same space of the observed scene than the information collected by the first detection zone 6, the second detection zone 8 then being able to observe more details of the observed scene than the first detection zone 6.
[0052] In a particular embodiment illustrated in [Fig. 4], the detection means 4 comprises a single electromagnetic radiation sensor 30 sensitive at least to the first and second spectral bands. The sensor 30 comprises a lower portion 32 defining the first detection zone 6 and an upper portion 34 defining the second detection zone 8, the lower portion 32 and upper portion 34 being at least sensitive to the first and second spectral bands of electromagnetic radiation. Preferably, the lower portion 32 and upper portion 34 are spatially separated and sensitive only to the first and second spectral bands of electromagnetic radiation in order to limit the risk of false detection.
[0053] In another embodiment illustrated in [Fig.5], the detection means 4 comprises a first electromagnetic radiation sensor 36 and a second electromagnetic radiation sensor 38.
[0054] The first electromagnetic radiation sensor 36 is sensitive at least to the first spectral band and defines the first detection zone 6. Preferably, the first electromagnetic radiation sensor 36 is sensitive only to the first spectral band, in particular to improve the detection efficiency of the first electromagnetic radiation sensor 36 in the first spectral band.
[0055] The second electromagnetic radiation sensor 38 is sensitive at least to the second spectral band and defines the second detection zone 8. Preferably, the second electromagnetic radiation sensor 38 is sensitive only to the second spectral band, in particular to improve the detection efficiency of the second electromagnetic radiation sensor 38 in the second spectral band.
[0056] Advantageously, the computing means are capable of analyzing variations of successive acquisitions of the detection means 4, in particular to avoid detecting electromagnetic radiation included in a third spectral band, the third spectral band not including the first and second spectral bands and / or to improve the detection of an object present in the observed scene.
[0057] Optionally, the computing means are capable of performing the ratio of the light intensity detected in the first detection zone 6 and the light intensity detected in the second detection zone 8 in order in particular to determine whether the object present in the observed scene emits more electromagnetic radiation in the first spectral band or in the second spectral band.
[0058] Advantageously, the imaging device 2 is suitable for assisting in the piloting of a helicopter, in particular suitable for improving the perception of the helicopter pilot in degraded situations such as in fog.
[0059] Optionally, the imaging device 2 may include at least one freeform optical component, in particular to adapt the dimensions of the imaging device 2 and / or the number of optical components of the imaging device 2.
[0060] Optionally, the imaging device 2 may include at least one nanostructured optical component, for example a metasurface such as a meta-lens, in particular to reduce the dimensions of the imaging device 2 and / or the number of optical components of the imaging device 2 and / or to add additional optical functions to the imaging device 2.
Claims
Demands
1. Imaging device (2) comprising a means for detecting electromagnetic radiation from an observed scene, the detection means (4) comprising a first and a second detection zone (6, 8) distinct and respectively sensitive to a first and a second spectral band of electromagnetic radiation, the imaging device (2) comprising an optical system (10) defining a dioptric channel (12) configured to direct the electromagnetic radiation included in the first spectral band towards the first detection zone (6), and defining a catadioptric channel (14) configured to direct the electromagnetic radiation included in the second spectral band towards the second detection zone (8),the optical system (10) comprising a dichroic filter (16) disposed both on the dioptric channel (12) and on the catadioptric channel (14) and configured to transmit the electromagnetic radiation included in the first spectral band and to reflect the electromagnetic radiation included in the second spectral band, the optical system (10) comprising a prism (22) disposed on the dioptric channel (12) opposite the observed scene, characterized in that the prism (22) is able to match the field of observation of the dioptric channel (12) with the field of observation of the catadioptric channel (14) so that the first and second detection zones (6, 8) observe the same scene.
2. Imaging device (2) according to claim 1, wherein the optical system (10) comprises a concave mirror (18) perforated in its center disposed on the catadioptric path (14), and a lens (20) radially centered on the concave mirror (18) disposed on the dioptric path (12) and axially between the observed scene and the concave mirror (18).
3. Imaging device (2) according to claim 2, wherein the dichroic filter (16) comprises an optical treatment carried out on a surface of the lens (20).
4. Imaging device (2) according to any one of claims 1 to 3, wherein the optical system (10) comprises an assembly of at least one lens (24) disposed both on the dioptric path (12) and on the catadioptric path (14), the assembly of at least one lens (24) being disposed opposite the detection means (4).
5. Imaging device (2) according to claim 4, wherein the assembly of at least one lens (24) comprises at least three lenses.
6. Imaging device (2) according to any one of claims 1 to 5, wherein the area of the second detection zone (8) is at least twice as large as the area of the first detection zone (6).
7. Imaging device (2) according to any one of claims 1 to 6, wherein the first spectral band comprises the MWIR spectral band, the second spectral band comprises the LWIR spectral band.
8. Imaging device (2) according to any one of claims 1 to 7, wherein the detection means (4) comprises an electromagnetic radiation sensor (30) configured to detect electromagnetic radiation included in at least the first and second spectral bands, a lower portion (32) of the sensor (30) defining the first detection zone (6), an upper portion (34) of the sensor (30) defining the second detection zone (8).
9. Imaging device (2) according to any one of claims 1 to 7, wherein the detection means (4) comprises a first electromagnetic radiation sensor (36) configured to detect electromagnetic radiation included in at least the first spectral band and defining the first detection zone (6), and a second electromagnetic radiation sensor (38) configured to detect electromagnetic radiation included in at least the second spectral band and defining the second detection zone (8).