Monocular common-target-surface high-speed multispectral imaging system and application

Abstract

The invention provides a monocular common-target-surface high-speed multispectral imaging system and application. The system comprises a lens assembly, a prism filtering assembly and a camera assembly which are arranged in the front light direction with an observed object as a light source. Wherein the prism filtering assembly comprises a light splitting filtering assembly and a supporting assembly, and the supporting assembly is used for mechanical switching between the camera assembly and the lens assembly and supporting and protecting the light splitting filtering assembly; the light splitting and filtering assembly is used for carrying out four-channel equal-optical-path light splitting on incident light and generating four sub-images in mirror symmetry in pairs in the camera assembly after chromatic aberration correction. The system is suitable for high-temporal-spatial-resolution multispectral observation of a macroscopic small-scale high-temperature process, and can also be used for high-speed temperature and deformation process monitoring.

Description

Technical Field

[0001] The present application relates to the technical field of high dynamic optical imaging, and in particular to a monocular common target surface high-speed multi-spectral imaging system and its application. Background Art

[0002] Although snapshot spectral imaging technology still faces many limitations when applied to high-dynamic scenes such as macroscopic and small-scale high-temperature processes (such as additive manufacturing melt pool monitoring, combustion state monitoring, laser processing, etc.). For example, it is difficult to eliminate crosstalk in spatial multiplexing multispectral schemes based on slice lenses, microlens arrays or mosaic filters; multispectral schemes based on multi-aperture imaging are prone to parallax due to optical path separation, resulting in differences in viewing angles between images of different spectral channels, causing errors in photometric emission angles and difficulty in accurate registration, affecting subsequent fusion analysis, which is particularly obvious for targets with three-dimensional structures or fast movements. Multi-channel spectroscopic schemes based on component groups such as dichroic mirror arrays have complex structures and considerable volumes, which bring additional difficulties to assembly and calibration in extreme manufacturing environments. From the perspective of encoding and decoding multispectral imaging methods, the reconstruction algorithm developed for ill-conditioned inverse problems requires a lot of computing time, which is difficult to meet the real-time or quasi-real-time observation requirements of high-dynamic processes; the reconstruction artifacts that may be introduced make it difficult for such methods to be directly applied in high-speed and high-temperature processes involving quantitative spatial analysis.

[0003] In addition, the high price of high-speed sampling sensors with microsecond time resolution makes the non-common target spatial spectrometry solution face huge cost pressure. At such a high time resolution, the time-space registration and calibration differences of multiple target surfaces make it difficult to apply it to actual high-speed process observation.

[0004] In summary, when the existing snapshot spectral imaging technology is applied to the observation of high-dynamic, high-temperature, and small-scale processes, there are generally problems such as limited temporal and spatial resolution, difficulty in eliminating parallax crosstalk between multi-spectral channels, imaging quality (distortion, vignetting, chromatic aberration) needs to be improved, the system is complex / large, the calculation is highly dependent and the real-time performance is insufficient, the reliability of the results is difficult to guarantee, and the cost is high. These problems limit its application in combustion diagnosis, laser processing process monitoring, plasma characteristics analysis, and other scenarios that require high-precision, high-speed, and high-fidelity synchronous multi-spectral information acquisition. Summary of the invention

[0005] This application aims to solve at least one of the technical problems in the related art to some extent. This application provides a monocular co-target-plane high-speed multi-spectral imaging system and its application. By means of a prism filtering component and a single high-speed target plane, monocular co-target-plane integrated four-channel spectral imaging is realized. Combining optical path and chromatic aberration compensation design, synchronous capture of multi-spectral information with high speed, no parallax, no crosstalk, low distortion, low vignetting, and no or low registration error is achieved. The system of this application is applicable to high spatio-temporal resolution multi-spectral observation of macroscopic small-scale high-temperature processes (such as additive manufacturing molten pool monitoring, combustion state monitoring, laser processing, etc.), and this system can also be used for high-speed temperature and deformation process monitoring.

[0006] To achieve the above object, a first aspect of this application proposes a monocular co-target-plane high-speed multi-spectral imaging system, including a lens assembly, a prism filtering component, and a camera assembly arranged along the forward light direction with the observed object as the light source; Wherein the prism filtering component includes a spectral splitting and filtering component and a support component. The support component is used for mechanical transfer between the camera component and the lens component, and supports and protects the spectral splitting and filtering component; the spectral splitting and filtering component is used for four-channel equal optical path spectral splitting of the incident light, and after chromatic aberration correction, four sub-images that are mirror-symmetric in pairs are generated in the camera component respectively.

[0007] In some embodiments, the lens assembly includes a double telecentric lens or a DED coaxial imaging interface.

[0008] In some embodiments, the spectral splitting and filtering component includes a prism component and a filter plate component; wherein the prism component includes a first prism group and a second prism group. The incident light is split into two channels of light by the first prism group; each of the split lights enters the second prism group and is split into two channels of light again, realizing four-channel equal optical path spectral splitting of the incident light.

[0009] In some embodiments, the first prism group and the second prism group are respectively glued by two and four single prisms with the included angles of the inner optical surfaces being 30°, -60°, and -90°, and spectral splitting coating is performed on the glued surfaces so that the reflectivity and transmittance are 50:50; the filter plate component includes an achromatic flat plate with thickness partitions and coated with filter films. Different split lights pass through different thickness partitions of the achromatic flat plate respectively, which is used for spectral channel separation and correction of axial chromatic aberration.

[0010] In some embodiments, the spectral splitting coating is a metal-dielectric film with a reflection-transmission ratio of 1:1 for 30° incidence so as to achieve nearly equal spectral splitting in a wide band; in the achromatic flat plate coated with filter films, the filter film is a narrow-band filter film.

[0011] In some embodiments, the first prism group and the second prism group are respectively formed by gluing two and four single prisms with the included angles of the inner optical surfaces being 30°, -60°, and -90°, and dichroic films are arranged on the gluing surfaces; the filter plate assembly includes an achromatic plate with thickness zoning and transparency, and different re-spectra respectively pass through different thickness zones of the achromatic plate for spectral channel separation and correction of axial chromatic aberration.

[0012] In some embodiments, both the first prism group and the second prism group include a light incident surface, a light exit surface, a total reflection surface, and a non-reflection / transmission surface; antireflection films are deposited on the light incident surface and the light exit surface; an extinction layer is arranged on the non-reflection / transmission surface.

[0013] In some embodiments, the single prism is a K9 material prism or a fused silica glass prism.

[0014] In some embodiments, the support assembly includes an adapter and a support fixing frame; the adapter is connected to the camera assembly and mechanically transfers with the lens assembly; the spectral splitting and filtering assembly is arranged in the adapter through the support fixing frame.

[0015] In some embodiments, the support fixing frame includes a prism slot surrounded by a support frame, wherein the prism assembly is arranged in the prism slot and a parallel air gap is formed in the prism assembly; the filter plate assembly is fixed on the support frame through a magnetic fixing member.

[0016] According to a second aspect of the present application, there is provided an application in multi-channel colorimetric temperature measurement on a single target surface or an application in spectral dynamic monitoring based on the system described in any of the above embodiments.

[0017] The present application has the following advantages compared with the prior art: The present application effectively solves the problems faced by the prior art such as parallax, crosstalk, distortion, vignetting, chromatic aberration, and the difficulty in balancing spatio-temporal resolution and data quality during the observation of macroscopic small-scale high-temperature processes, and provides a technical solution capable of performing high-speed, high-fidelity, and high-precision synchronous multi-spectral observations on a single expensive target surface, which is particularly suitable for the diagnosis and analysis of high-temperature processes with demanding requirements for dynamic change details and spectral characteristics.

[0018] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description of the embodiments in conjunction with the drawings, wherein: Figure 1It is a schematic structural diagram of a monocular co-target-plane high-speed multispectral imaging system in an embodiment of the present application; Figure 2 is Figure 1 the enlarged view of part A in Figure 3 It is a cross-sectional view of an achromatic beam-splitting and filtering component in an embodiment of the present application; Figure 4 It is a typical optical path diagram of a single Bauernfeind prism in an embodiment of the present application; Figure 5 It is a schematic structural diagram of a prism component in an embodiment of the present application; Figure 6 It is another schematic structural diagram of a prism component in an embodiment of the present application; Figure 7 It is a simulated optical path diagram when the prism component in an embodiment of the present application forms an image at the center point of the field of view; Figure 8 It is a simulated design optical path diagram of the system when using an ideal double telecentric lens for imaging in an embodiment of the present application; Figure 9 It is the spot diagram of each channel on the image plane when using an achromatic flat plate in an embodiment of the present application; Figure 10 It is the spot diagram of each channel on the image plane when not using an achromatic flat plate in an embodiment of the present application; Figure 11 It is the object plane reference and the corresponding image plane imaging result of the simulated imaging in an embodiment of the present application; Figure 12 It is the image plane vignetting diagram when the image-side NA takes different values in an embodiment of the present application; Figure 13 In an embodiment of the present application, when the image-side NA is 0.03, it is the vignetting diagram of uniform bright field imaging (without filtering).

[0020] In the figure, 1. lens assembly; 2. beam-splitting and filtering component; 201. prism component; 202. filtering flat plate component; 3. support component; 301. support fixing frame; 302. adapter; 4. high-speed camera; 401. high-speed sensor. Detailed Description of the Embodiment

[0021] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as a limitation of the present application. On the contrary, the embodiments of the present application include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0022] This application is improved based on the following defects in the related art. Snapshot spectral imaging technology aims to capture the complete spatial and spectral information of a scene through a single exposure, which is of great significance for real-time observation of dynamic processes. Existing snapshot multi-spectral imaging schemes can be roughly divided into two categories: one relies on the design of optical elements to directly map the spectral information to the detector; the other uses specially designed optical components to achieve encoding and decodes the spectral information through corresponding post-processing processes.

[0023] Although snapshot spectral imaging technology has made significant progress, existing technologies still face many challenges and limitations when applied to high-dynamic scenes such as macroscopic and small-scale high-temperature processes (such as additive manufacturing melt pool monitoring, combustion state monitoring, laser processing, etc.). For example, it is difficult to eliminate crosstalk in spatial multiplexing multispectral solutions based on slice lenses, microlens arrays or mosaic filters; multispectral solutions based on multi-aperture imaging are prone to parallax due to optical path separation, resulting in perspective differences between images of different spectral channels, causing photometric emission angle errors and difficulty in accurate registration, affecting subsequent fusion analysis, which is particularly obvious for targets with three-dimensional structures or fast movements. Multi-channel spectroscopic solutions based on component groups such as dichroic mirror arrays have complex structures and considerable volumes, which bring additional difficulties to assembly and calibration in extreme manufacturing environments. From the perspective of encoding and decoding multispectral imaging methods, the reconstruction algorithm developed for ill-conditioned inverse problems requires a lot of computing time, which is difficult to meet the real-time or quasi-real-time observation requirements of high-dynamic processes; the reconstruction artifacts that may be introduced make it difficult for such methods to be directly applied in high-speed and high-temperature processes involving quantitative spatial analysis.

[0024] In addition, the high price of high-speed sampling sensors with microsecond time resolution makes the non-common target spatial spectrometry solution face huge cost pressure. At such a high time resolution, the time-space registration and calibration differences of multiple target surfaces make it difficult to apply it to actual high-speed process observation.

[0025] In summary, when the existing snapshot spectral imaging technology is applied to the observation of high-dynamic, high-temperature, and small-scale processes, there are generally problems such as limited temporal and spatial resolution, difficulty in eliminating parallax crosstalk between multi-spectral channels, imaging quality (distortion, vignetting, chromatic aberration) needs to be improved, the system is complex / large, the calculation is highly dependent and the real-time performance is insufficient, the reliability of the results is difficult to guarantee, and the cost is high. These problems limit its application in combustion diagnosis, laser processing process monitoring, plasma characteristics analysis, and other scenarios that require high-precision, high-speed, and high-fidelity synchronous multi-spectral information acquisition.

[0026] To achieve the above objectives, the present application proposes a monocular common target surface high-speed multi-spectral imaging system. Figures 1 - 2As shown in the figure, it includes a lens assembly 1, a prism filtering assembly, and a camera assembly arranged in the direction of the incident light with the observed object as the light source. The prism filtering assembly includes a beam splitting and filtering assembly 2 and a support assembly 3. The support assembly 3 is used for the mechanical connection between the camera assembly and the lens assembly 1, and supports and protects the beam splitting and filtering assembly 2. The beam splitting and filtering assembly 2 is used to perform four-channel equal optical path splitting on the incident light, and after chromatic aberration correction, four sub-images that are mirror-symmetric in pairs are generated in the camera assembly respectively.

[0027] Among them, in the monocular co-target plane high-speed multi-spectral imaging system, with the observed object as the light source, the monocular co-target plane high-speed multi-spectral imaging system includes a lens assembly 1, a prism filtering assembly, and a camera assembly arranged in sequence along the direction of the incident light. Among them, the observed object can be regarded as a blackbody radiation light source, and the monocular co-target plane high-speed multi-spectral imaging system of the present application can be used for non-contact temperature measurement of points on the light source surface of the observed object.

[0028] What is special about the monocular co-target plane high-speed multi-spectral imaging system of the present application is the prism filtering assembly. It is arranged in front of the camera assembly and behind the lens assembly 1, realizing the non-parallax spatial multiplexing of the image field. In addition, the prism filtering assembly realizes the non-crosstalk wavelength separation of different image fields and the correction of axial chromatic aberration between different image fields. Through the collaborative design of the lens assembly 1 and the prism filtering assembly, the vignetting and distortion are ensured to be controlled at an extremely low level. Therefore, the present application can control the cost of observing high-speed dynamic processes at a reasonable level, and support the convenient replacement of different observation bands to achieve multi-spectral applications covering different application ranges, such as monitoring the temperature and morphology of the molten pool.

[0029] The present application realizes the non-crosstalk wavelength separation of different image fields through a filter or dichroic film; realizes the correction of axial chromatic aberration between different image fields through an aberration correction film. In addition, through the collaborative design of the double telecentric lens and the prism group, the vignetting and distortion are ensured to be controlled at an extremely low level. Therefore, the present application can control the cost of observing high-speed dynamic processes at a reasonable level, and support the convenient replacement of different observation bands to achieve multi-spectral applications covering different application ranges, such as monitoring the temperature and morphology of the molten pool.

[0030] In some embodiments, the lens assembly 1 includes a double telecentric lens or a DED coaxial imaging interface.

[0031] The lens assembly 1 is located on the side of the prism filtering assembly away from the camera assembly and is mechanically connected to the prism filtering assembly. In other words, the lens assembly 1 and the prism filtering assembly can be mechanically movably connected. For example, it is connected to the prism filtering assembly through a mechanical bayonet, which is convenient for the replacement and maintenance of the prism filtering assembly.

[0032] Among them, the lens assembly 1 includes a double telecentric lens or a DED coaxial imaging interface; for example, the double telecentric lens has a magnification ratio of -0.2, a working distance of 319 mm, an image-side NA of 0.04 - 0.13 variable aperture, corresponding to an object-side NA of 0.0092 - 0.03, an image field diameter of 11 mm, corresponding to a 2 / 3-inch sensor (single image field). The telecentric lens used has a back intercept of 29 mm at the working distance, an image-side chief ray angle < 0.3°, and an object-side chief ray angle < 0.06°, showing good bilateral telecentric performance. When the object-side NA = 0.02 and the corresponding image-side NA ≈ 0.085, it has the best resolution, with the vignetting at the image edge less than 5% and the distortion less than 0.3%. When the lens assembly 1 is a DED coaxial imaging interface, it realizes the multi-spectral dynamic monitoring of the normal reflected light of the molten pool.

[0033] In some embodiments, the beam splitting and filtering assembly 2 includes a prism assembly 201 and a filter plate assembly 202; among them, the prism assembly 201 includes a first prism group and a second prism group, and the incident light is split into two channels of light propagation after passing through the first prism group; each split light enters the second prism group and is split into two channels of light propagation again, realizing the four-channel equal optical path splitting of the incident light.

[0034] Among them, the prism assembly 201 includes a first prism group and a second prism group as Figure 5 shown, among which, the first prism group is glued by two single prisms with inner optical surface angles of 30°, -60°, and -90°. For example, the single prism glue can be ultraviolet-glued by two single Bauernfeind prisms, and the typical optical path diagram of a single Bauernfeind prism is as Figure 4 shown. A beam splitting coating is applied to the glued surface formed by the two single prisms in the first prism group so that the reflectivity and transmittance are 50:50. For example, the beam splitting coating is a metal-dielectric film with a reflection-transmission ratio of 1:1 for 30° incidence.

[0035] As Figure 5 shown, the first prism group is ultraviolet-glued by two single Bauernfeind prisms A1 and A2 with inner optical surface angles of 30°, -60°, and -90°. A metal-dielectric film is provided on the spacer surface between A1 and A2, and the metal-dielectric film has a reflection-transmission ratio of 1:1 for 30° incidence. Therefore, when the light enters the first prism group from the incident surface, it is split into two channels of light propagation and enters the second prism group.

[0036] The second prism group is formed by gluing four single prisms with the included angles of the inner optical surfaces being 30°, -60°, and -90°. For example, a single prism can be glued by ultraviolet gluing of two single Bauernfeind prisms. On the glued surfaces formed by the four single prisms in the second prism group, beam splitting coatings are applied to make the reflectivity and transmittance 50:50. For example, the beam splitting coating is a metal-dielectric film with a reflection-transmission ratio of 1:1 for 30° incidence.

[0037] As Figure 5 and Figure 6 shown, the second prism group is formed by ultraviolet gluing of four single Bauernfeind prisms B1, B2, B3, and B4 with the included angles of the inner optical surfaces being 30°, -60°, and -90°. Metal-dielectric films are provided on the spacer surfaces between B1 and B2, between B1 and B3, between B2 and B4, and between B3 and B4. The metal-dielectric film has a reflection-transmission ratio of 1:1 for 30° incidence. Therefore, after the beam splitting light propagating along two channels emitted from the first prism group enters the second prism group, each beam splitting light is divided into re-beam splitting light propagating along two channels, and after forming four-channel equal optical path beam splitting, it is emitted from the second prism group to the filter flat plate assembly 202.

[0038] In addition, the single prism is a K9 material prism or a fused silica glass prism. That is, to control the overall cost, a K9 material prism can be used in multi-spectral observations that do not involve the ultraviolet band; while for applications with a wider spectral bandwidth, fused silica glass can be used.

[0039] Since the first prism group and the second prism group include multiple Bauernfeind prisms, in order to reduce stray light, environmental interference, and stray reflections on the light incident surface and the light exit surface, the first prism group and the second prism group are respectively divided into a light incident surface, a light exit surface, a total reflection surface, and a non-reflection / transmission surface; anti-reflection films are coated on the light incident surface and the light exit surface of the first prism group and the second prism group. The anti-reflection film can be an AR coating with a light transmittance of 99.5% to reduce stray reflections on the incident and exit surfaces; and an extinction layer is provided on the non-reflection / transmission surface of the first prism group and the second prism group to reduce stray light and environmental interference, where the extinction layer can be set by coating an extinction paint. In some embodiments, an extinction paint can also be coated on the surface of the support component 3 to achieve the effect of reducing stray light and environmental interference, as Figure 6 shown.

[0040] In this embodiment, the bonding surface between individual Bauernfeind prisms in the first prism group and the second prism group does not participate in filtering. To control the overall cost and ensure spectral allocatability, a metal-dielectric film with a reflection-transmission ratio of 1:1 at a 30° incidence is used in combination with the filter flat assembly 202 to achieve broadband near-equal-ratio spectral splitting. The filter flat assembly 202 includes an achromatic flat with thickness partitions and coated with a filter film. Different re-spectral splittings pass through different thickness partitions of the achromatic flat respectively, which is used for spectral channel separation and correction of axial chromatic aberration.

[0041] In other words, the filter flat assembly 202 includes an achromatic flat coated with a filter film, and the filter film is a narrow-band filter film. Exemplarily, the achromatic flat includes four partitions with different thicknesses. For example, the thicknesses of the four partitions with different thicknesses are 0.50 mm, 0.72 mm, 0.91 mm, and 1.06 mm; correspondingly, narrow-band filter films for narrow-band pass OD6 filtering at 450, 532, 650, and 808 nm ± 10 nm are respectively configured on the four partitions with different thicknesses.

[0042] It should be explained that all the element surface types in this embodiment are flat surfaces, and the surface type accuracy is λ / 10 @632.8 nm; the angular accuracy of the first prism group and the second prism group is 30 arc seconds. In this application, the re-spectral splittings emitted from the second prism group pass through different thickness partitions on the achromatic flat respectively, and after chromatic aberration correction, they are respectively imaged on the image plane of the camera assembly, generating four 2×2 sub-images that are mirror-symmetric in pairs. After the sub-images are subjected to translation and rotation transformations, registration can be achieved for multi-channel colorimetric temperature measurement applications.

[0043] In some embodiments, the first prism group is glued together by two individual prisms with included angles of 30°, -60°, and -90° between their inner optical surfaces. For example, a single prism glue can be formed by ultraviolet gluing of two individual Bauernfeind prisms. A dichroic film is provided on the bonding surface formed by the two individual prisms in the first prism group. For example. As Figure 5 and Figure 6 shown, the first prism group is formed by ultraviolet gluing of two individual Bauernfeind prisms A1 and A2 with included angles of 30°, -60°, and -90° between their inner optical surfaces. A dichroic film is provided on the spacer surface between A1 and A2. Therefore, when light enters the first prism group from the incident surface, it is divided into spectral splits propagating along two channels and enters the second prism group.

[0044] Meanwhile, the second prism group is formed by ultraviolet gluing of four individual Bauernfeind prisms B1, B2, B3, and B4 with inner optical surface angles of 30°, -60°, and -90°. Dichroic films are provided on the spacer surfaces between B1 and B2, between B1 and B3, between B2 and B4, and between B3 and B4. Therefore, after the spectral light traveling along two channels emitted from the first prism group enters the second prism group, each spectral light is divided into re-spectral light traveling along two channels, forming four-channel equal optical path spectral splitting and then being emitted from the second prism group to the filter flat plate assembly 202. The simulated optical path diagram when the prism assembly 201 forms an image at the center point of the field of view is as Figure 7 shown.

[0045] In addition, in order to reduce stray light and environmental interference, as well as stray reflections on the light incident surface and exit surface, and the settings for reducing stray light and environmental interference in the first prism group and the second prism group, reference can be made to the above content and will not be elaborated here. However, in this embodiment, the filter flat plate assembly 202 includes a transparent achromatic flat plate. By way of example, the achromatic flat plate includes four partitions with different thicknesses. For example, the thicknesses of the four partitions with different thicknesses are 0.50 mm, 0.72 mm, 0.91 mm, and 1.06 mm.

[0046] It should be explained that in this embodiment, the surface types of all components are flat, and the surface type accuracy is λ / 10 @632.8 nm; the angular accuracy of the first prism group and the second prism group is 30 arc seconds. Although the four-channel wavelength separation of light can also be achieved in this application, it should be pointed out that although such a method has a low total spectral energy loss rate, it is limited by the coating process and crosstalk may occur when observing strong light sources. During application, after two-stage prism spectral splitting by the first prism group and the second prism group, the spectral splitting filter assembly 2 generates a region with a total size of 18.69 * 14.9 mm, arranged in an equal-sized 2 * 2 pattern.

[0047] In some embodiments, the support assembly 3 includes an adapter 302 and a support fixing frame 301; the adapter 302 is connected to the camera assembly and is mechanically adapted to the lens assembly 1; the spectral splitting filter assembly 2 is disposed in the adapter 302 through the support fixing frame 301.

[0048] Among them, the support assembly 3 includes an adapter 302 and a support fixing frame 301 as Figure 3 shown. For example, the adapter 302 is an adapter barrel adapted to the bayonet of the lens assembly 1, and the spectral splitting filter assembly 2 is disposed in the adapter barrel through the support fixing frame 301. For example, the support fixing frame 301 includes a prism slot surrounded by a support frame, where the prism assembly 201 is disposed in the prism slot and a parallel air gap is formed in the prism assembly 201; the filter flat plate assembly 202 can be fixed to the support frame through a magnetic fixing member.

[0049] Exemplarily, in the installation of the prism filter assembly, the prism slots surrounded by the support frame are used to paste the first prism group and the second prism group into the prism slots surrounded by the support frame using optical glue, and the support frame is connected with screws, so that a parallel air gap is formed in the prism assembly 201 as Figure 6 shown, and the filter flat plate assembly 202 is fixed on the support frame by magnetic fixing parts.

[0050] In some embodiments, in this embodiment, the camera assembly is located on one side of the prism filter assembly and has a monochromatic or multi-color CMOS for high-speed optoelectronic conversion. The camera assembly includes a high-speed camera 4, where the high-speed camera 4 is a single-target high-speed camera equipped with a high-speed sensor 401. The size of the monochromatic high-speed target pixel used is 14.6um, the resolution is 1280*1024, the image plane size is 18.688*14.950mm, the full-frame frame rate is 20000fps, the minimum single-frame exposure time is 100ns, and it has 160GB of flash memory. The imaging dynamic range of the high-speed camera 4 is 60dB, the bit depth is 10bit, and the standard gain is 67000. Through the monochromatic high-speed target surface, this application can continuously obtain the complete data cube of 4 spectral channels at a rate of 20,000 fps, achieving an ultra-high time resolution at the ten-thousand-frame level, which helps to reveal the key physical mechanisms in the processes of high-temperature and high-speed machining and precision manufacturing.

[0051] According to a second aspect of the present application, there is provided an application of the system in any of the above embodiments in multi-spectral observation or high-speed temperature and deformation process monitoring on a single target surface.

[0052] Exemplarily, a monocular co-target surface high-speed multi-spectral imaging system includes a lens assembly 1, a prism filter assembly, and a camera assembly arranged along the front-light direction with the observed object as the light source. The lens assembly 1 is a double telecentric lens for multi-spectral observation or high-speed temperature and deformation process monitoring simulation experiments.

[0053] The monocular co-target surface high-speed multi-spectral imaging system in this embodiment can be fixed on the processing robotic arm of direct energy deposition (DED). The double telecentric lens is used to align the laser focus area. After the light enters the first prism group from the incident surface, it is split into two channels for propagation. The split light enters the second prism group respectively and is split again into two channels for propagation, realizing four-channel equal optical path splitting as Figure 7 shown. After chromatic aberration correction by the filter flat plate assembly 202, the images are respectively formed on the image plane of the camera assembly, generating four 2*2 sub-images that are mirror-symmetrical in pairs as Figure 8As shown. The sub-images can be aligned after translation and rotation transformation, and are used in multi-channel colorimetric temperature measurement applications. Therefore, the present application uses a prism filter assembly and a single high-speed target surface to simultaneously image multiple spectral channel information from the same field of view onto the photosensitive surface of a single high-speed sensor without parallax and crosstalk (or extremely low crosstalk). This fundamentally eliminates the parallax problem and complex spatiotemporal alignment requirements of the multi-optical path system, ensures accurate spatial correspondence of different spectral images at the pixel level in high-speed sampling, and truly realizes monocular common target surface imaging.

[0054] When the image side NA = 0.08, the spot diagrams of each channel with and without the achromatic plate are as follows Figure 9 and Figure 10 As shown, Figure 9 and Figure 10 In the legend, the plane is the image plane, the unit is μm, and the radius of the Airy disk is 6.181μm. It can be seen that the achromatic plate uniformly compresses the focal size of each channel to the diffraction limit range, improving the axial chromatic aberration. In addition, when using an ideal telecentric imaging system in which the main light is completely parallel to the optical axis, the prism element does not introduce other chromatic aberrations except spherical aberration; even if the image telecentricity is poor, when the angle between the main light and the optical axis reaches 1.5°, the slight coma presented by the focus does not exceed the diffraction limit. Figure 11 The simulation results of the object plane reference and the corresponding image plane imaging when the image plane NA=0.08; Figure 11 As shown, the sub-images are arranged in a 2*2 array of equal size, and are mirror-symmetrical with each other. However, it is worth noting that Figure 10 When the achromatic plate is not used, the point diagram of each channel on the image plane shows that the focus at the edge of the image field has vignetting. Therefore, the present application is different from the technology in the related art that sacrifices spatial resolution in exchange for spectral information. The present application can ensure that each spectral channel has a spatial resolution close to the diffraction limit and excellent imaging quality while achieving multi-spectral separation, and realizes high-speed, parallax-free, crosstalk-free, low distortion, low vignetting, and no or low registration error multi-spectral information synchronous capture.

[0055] Figure 12 The image plane vignetting diagram when the image side NA takes different values, such as Figure 12 As shown in the figure, the degree of vignetting is controlled by the image-side NA. For high-temperature and high-speed processes, a small NA is generally used to ensure exposure and depth of field: when the image-side NA = 0.03, the vignetting area around the sub-image only accounts for 5% of the sub-image height, and it can be considered that the vignetting is well controlled. Figure 13 This is the vignetting diagram of uniform bright field imaging (without filtering) when the image side NA is 0.03, as shown in Figure 13 As shown, the vignetting is also symmetrically distributed at the edge of each sub-field of view, which makes it possible to avoid the vignetting correction process when performing colorimetric calculations in this embodiment.

[0056] In this embodiment, an aberration-free double telecentric lens is simulated using an ideal paraxial surface, with a magnification ratio of -1.0, a working distance of 100 mm, the image field setting being the same as that of the actual lens, the image-side NA being adjustable corresponding to the NA range of the actual lens, and the existence of other aberrations being ignored to fully consider the optical performance of the aberration-corrected beam-splitting and filtering element. The achromatic beam-splitting and filtering assembly 2 is modeled as described above, and film scattering is not considered for the time being.

[0057] Exemplarily, in another application of the system of the present application, a monocular co-axial-plane high-speed multi-spectral imaging system includes a lens assembly 1, a prism filtering assembly, and a camera assembly arranged in the direction of incident light with the observed object as the light source. Among them, the system does not have a double telecentric lens, and the system is fixed to the DED coaxial imaging interface to realize multi-spectral dynamic monitoring of the normal reflected light of the molten pool.

[0058] Therefore, the highly integrated optical design adopted in the present application is more compact than other high-speed multi-spectral solutions, and is easier to deploy and calibrate in environments such as industrial sites and experimental platforms, with simplicity and real-time performance. The present application provides unprecedented high spatio-temporal-spectral resolution observation means for fields such as combustion chemical kinetics research, such as the simultaneous evolution of transient component concentrations and temperature fields, laser-matter interactions, such as the rapid expansion and spectral characteristic changes of plasma plumes, material dynamic responses, such as phase changes and failure processes under shock loading, hypersonic flows, such as gas component and temperature changes in the shock layer, etc., which helps to understand complex dynamic processes under extreme conditions.

[0059] At the same time, the present application realizes high-speed, multi-dimensional, in-situ online monitoring and feedback control of key parameters during additive manufacturing such as molten pool temperature, keyhole behavior, and multi-spectral synchronous monitoring of spatter, laser processing such as real-time analysis of material removal mechanisms and plasma-assisted effects, and plasma spraying, etc., so as to improve product quality and production efficiency. In addition, precise measurement of the synchronous high-speed evolution process of multiple physical quantities in a complex system, such as spectral feature inversion, can be achieved, successfully overcoming the technical obstacles in high-dynamic, high-temperature, and small-scale observation applications of related technologies, and achieving the purpose of monocular co-axial-plane, ultra-high-speed multi-spectral measurement.

[0060] It should be noted that in the description of the present application, terms such as "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0061] Any process or method description depicted in a flowchart or otherwise described herein can be understood to represent a module, segment, or portion of code including one or more executable instructions for implementing a specific logical function or process. The scope of the preferred embodiments of the present application includes additional implementations where functions may be executed in a substantially simultaneous manner or in a reverse order according to the functions involved, rather than in the order shown or discussed, which should be understood by those skilled in the art to which the embodiments of the present application pertain.

[0062] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0063] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A monocular common target surface high-speed multi-spectral imaging system, characterized in that: It includes a lens assembly, a prism filter assembly and a camera assembly arranged along the light direction with the observed object as the light source; The prism filter assembly includes a spectroscopic filter assembly and a support assembly, wherein the support assembly is used for mechanical connection between the camera assembly and the lens assembly, and supports and protects the spectroscopic filter assembly; The spectroscopic filter assembly is used to perform four-channel equal-path spectroscopic separation on the incident light, and after chromatic aberration correction, four sub-images with mirror symmetry between two of them are generated in the camera assembly respectively.

2. The system according to claim 1, characterized in that The lens assembly includes a bi-telecentric lens or a DED coaxial imaging interface.

3. The system according to claim 2, characterized in that The spectroscopic filter assembly includes a prism assembly and a filter plate assembly; wherein the prism assembly includes a first prism group and a second prism group, and the incident light passes through the first prism group and is divided into spectra propagating along two channels; each of the spectra enters the second prism group and is divided into re-splits propagating along two channels, thereby realizing four-channel equal-optical-path spectroscopic analysis of the incident light.

4. The system according to claim 3, characterized in that The first prism group and the second prism group are respectively formed by gluing two and four single prisms with internal optical surface angles of 30°, -60°, and -90°, and the gluing surfaces are subjected to spectral coating so that the reflectivity and transmittance are 50:50; the filtering plate assembly includes an achromatic plate with thickness partitions and a filter film, and the different re-split beams pass through partitions of different thicknesses of the achromatic plate, respectively, for spectral channel separation and correction of axial chromatic aberration.

5. The system according to claim 4, characterized in that The spectroscopic coating is a metal-dielectric film with a reflection-transmittance ratio of 1:1 at 30° incidence, so as to achieve nearly equal distribution of light in a wide band; in the achromatic plate coated with a filter film, the filter film is a narrow-band filter film.

6. The system according to claim 3, characterized in that The first prism group and the second prism group are respectively formed by gluing two and four single prisms with internal optical surface angles of 30°, -60°, and -90°, and dichroic films are arranged on the gluing surfaces; the filtering plate assembly includes a transparent achromatic plate with thickness partitions, and the different re-split beams pass through partitions of different thicknesses of the achromatic plate, respectively, for spectral channel separation and correction of axial chromatic aberration.

7. The system according to any one of claims 4 to 6, characterized in that: The first prism group and the second prism group both include a light incident surface, a light exit surface, a total reflection surface and a non-reflection / transmission surface; wherein the light incident surface and the light exit surface are coated with an anti-reflection film; and an extinction layer is arranged on the non-reflection / transmission surface.

8. The system according to claim 7, characterized in that The single prism is a K9 material prism or a fused silica glass prism.

9. The system according to claim 7, characterized in that The supporting component includes an adapter and a supporting fixing frame; the adapter is connected to the camera component and mechanically connected to the lens component; the spectroscopic filter component is arranged in the adapter through the supporting fixing frame.

10. The system according to claim 9, characterized in that The supporting frame comprises a prism slot surrounded by a supporting frame, wherein the prism assembly is arranged in the prism slot and a parallel air gap is formed in the prism assembly; the filter plate assembly is fixed on the supporting frame by a magnetic fixing member.

11. The system according to any one of claims 1 to 10 is used in multi-channel colorimetric temperature measurement on a single target surface or in spectral dynamic monitoring.

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