Infrared multispectral imaging device and method based on transmission correction

Abstract

The present invention belongs to the field of thermal imaging technology, specifically to an infrared multispectral imaging device and method based on transmission correction. The device comprises an objective lens assembly, a filter assembly, and a detector. The transmissive surface of the correction plate is roughened and disposed on a rotating wheel with the filter assembly. When the rotating wheel rotates, the filter assembly and the correction plate are selectively positioned in the optical path between the objective lens assembly and the detector. The device also comprises a standard blackbody radiation source. An optical switching unit is configured to selectively allow thermal radiation emitted by the radiation source and light from a measured field of view to pass through the filter assembly or the correction plate on the rotating wheel, with the detector receiving the light that has passed through the thermal radiation and the measured field of view. The device has advantages such as ease of operation and is suitable for use in infrared spectral imaging.

Description

Technical Field

[0001] The present invention relates to thermal imaging technology, and in particular to an infrared multi-spectral imaging device and method based on transmission correction. Background Art

[0002] Multispectral imaging combines the characteristics of traditional spectrometers and photoelectric detection technology, can provide two-dimensional image information and spectral information at the same time, and has the quasi-real-time characteristics of the new generation of photoelectric telemetry.

[0003] In order to obtain the multispectral radiation image characteristics of the target background, a general multispectral imaging system mainly consists of a filter wheel assembly with multiple filters, a wide-spectrum infrared imaging device, and a radiation correction plate. Multiple filters are used to achieve spectral splitting.

[0004] There are two conventional radiation correction methods:

[0005] 1. Baffle-based uniformity correction involves inserting a blackened, oxidized metal baffle into the image plane and performing uniformity correction on the inherent pattern of the area array detector. This method can reflect the uniformity of the infrared system at the ambient operating temperature and is widely used in uncooled thermal imaging systems. However, it cannot measure uniformity in scenes with varying radiation temperatures, nor can it address the effects of temperature drift. Furthermore, the correction can cause image interruption for several seconds.

[0006] 2. Radiation source-based calibration. Due to the unique characteristics of infrared technology, the photoelectric response of infrared detectors varies with different scene radiation and ambient operating temperatures. Calibration is performed in the laboratory using surface-source blackbody radiation sources of varying temperatures to determine the responsivity to radiation temperature. However, the calibration process is time-consuming and requires periodic recalibration. Summary of the Invention

[0007] In order to solve the deficiencies in the above-mentioned prior art solutions, the present invention provides an infrared multi-spectral imaging device based on transmission correction.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] An infrared multispectral imaging device based on transmission correction includes an objective lens group, a filter group and a detector; the imaging device also includes:

[0010] A correction plate and a rotating wheel, wherein the transmission surface of the correction plate is roughened and the correction plate and the filter group are arranged on the rotating wheel; when the rotating wheel rotates, the filter group and the correction plate are selectively located in the optical path between the objective lens group and the detector;

[0011] Standard blackbody radiation source;

[0012] The optical switching unit is used to allow the thermal radiation emitted by the radiation source and the light of the measured field to selectively pass through the filter group or the correction plate on the rotating wheel, and the detector receives the thermal radiation and the light of the measured field.

[0013] The present invention also aims to provide a working method of an imaging device, which is achieved through the following technical solutions:

[0014] Based on the working method of the imaging device of the present invention, the working method includes:

[0015] When the optical switching unit is in operation, the thermal radiation emitted by the radiation source at different ambient temperatures passes through the calibration plate and is received by the detector, which then outputs responses X1 and X2 corresponding to the different ambient temperatures.

[0016] Perform two-point temperature response calibration, obtain and store calibration results, and the calibration results include gain and offset.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Using a transmissive correction sheet to create a diffuse scattering effect with real-time scene radiation characteristics, it can achieve non-sharp imaging in the short and medium infrared bands over the entire temperature range of -40°C to 70°C and from near end (such as 2m) to far end (such as 2000m), producing a uniform radiation background and replacing the baffle;

[0019] It achieves online, real-time rapid uniformity correction under the average radiation brightness temperature of infrared scenes. The result is close to the detector response of the actual scene brightness temperature, and the calibration time is short.

[0020] In the same set of equipment, temperature response calibration was achieved within a wide band (shortwave and mediumwave) of 1.5μm to 5.4μm.

[0021] 2. Simple structure and low cost;

[0022] Without the need to use diffractive optical elements for achromatic design, high-quality imaging in a wide wavelength range of 1.5μm to 5.4μm (shortwave and mediumwave) is achieved simply by matching different lens materials, optimizing the surface parameters of each surface, and appropriately using aspheric surfaces. This greatly reduces system aberrations and corrects chromatic aberration across a wide spectral range.

[0023] 3. Clear imaging;

[0024] This application uses two reflectors to achieve a U-shaped secondary imaging configuration, and a single lens focusing group is used to achieve clear imaging from -40°C to 70°C for the entire optical system. The drive unit is a mature existing technology that is simple and easy to control.

[0025] 4. Large focusing range;

[0026] The focusing group achieves a focusing range of 2m to 2000m, which can be used for short-range calibration in the laboratory and long-range detection in the field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. Those skilled in the art will readily appreciate that these drawings are merely used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0028] Figure 1 It is a schematic structural diagram of the imaging device of the present invention;

[0029] Figure 2 is a schematic structural diagram of another state of the imaging device of the present invention;

[0030] Figure 3 It is a schematic diagram of the partial structure of the imaging device of the present invention;

[0031] Figure 4 It is a schematic structural diagram of the imaging device in embodiment 3 of the present invention.

[0032] In the accompanying drawings, 1-the fourth positive power lens, 2-the fourth negative power lens, 3-the first negative power lens, 4-the first positive power lens, 5-the second negative power lens, 6-the second positive power lens, 7-the first reflecting mirror, 9-the third negative power lens, 10-the third positive power lens, 21-the objective lens group, 22-the zoom group, 23-the relay lens group, 24-the filter group, 25-the secondary imaging group, 26-the detector, 27-the motor, 31-the standard black body radiation source, 32-the light reflecting device, and 33-the transmission correction plate. DETAILED DESCRIPTION

[0033] Figures 1-4 The following description describes optional embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand that variations or substitutions derived from these embodiments will be within the scope of the present invention. Those skilled in the art will understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following optional embodiments, but is limited only by the claims and their equivalents.

[0034] Example 1.

[0035] An infrared multispectral imaging device based on transmission correction, such as Figure 1-Figure 2 As shown, the imaging device includes:

[0036] The objective lens group 21, the filter group 24 and the detector 26 are arranged in sequence.

[0037] The transmission surface of the transmission correction plate 33 is roughened, and the correction plate 33 and the filter group 24 are arranged on a rotating wheel; when the rotating wheel rotates, the filter group 24 and the correction plate 33 are selectively located in the optical path between the objective lens group 21 and the detector 26.

[0038] The standard blackbody radiation source 31 and the optical switching unit are used to allow the thermal radiation emitted by the radiation source 31 and the light of the measured field to selectively pass through the filter group 24 or the correction plate 33 on the rotating wheel, and the detector 26 receives the thermal radiation and the light of the measured field.

[0039] In order to realize the switching function, the optical switching unit further includes a light reflecting device 32 and a driving unit. Under the drive of the driving unit, the light reflecting device 32 selectively enters and exits the optical path between the objective lens group 21 and the filter group 24 (correction plate 33).

[0040] When the light reflecting device 32 is in the optical path, the light of the measured field of view is reflected by the light reflecting device 32, then passes through the filter group 24, and is received by the detector 26. When exiting the optical path, the thermal radiation emitted by the radiation source 31 passes through the correction plate 33 and is received by the detector 26. Figure 1-Figure 2 shown.

[0041] Alternatively, when the light reflecting device 32 is in the optical path, the thermal radiation emitted by the radiation source 31 is reflected by the light reflecting device 32, then passes through the correction plate 33 and is received by the detector 26. When the light exits the optical path, the light of the measured field of view passes through the filter set 24 and is received by the detector 26. Figure 4 shown.

[0042] In order to obtain a better diffuse scattering effect, the roughness η of the correction plate 33 satisfies:

[0043] η≥[5794(L2-L1)·δT·λ / (L2·T0 2 )] 1 / 2 , L2 is the far end distance, L1 is the near end distance, δT is the temperature difference between the temperature zones, λ is the response cutoff wavelength of the detector 26, and T0 is the ambient temperature.

[0044] The correction plate is made of sapphire, or zinc sulfide, zinc selenide and barium fluoride wafers, or germanium, silicon and chalcogenide glass.

[0045] In order to obtain clear imaging, further, Figure 1-Figure 2 As shown, the imaging device further includes:

[0046] The focusing group 22 and the relay lens group 23 are sequentially arranged on the optical path between the objective lens group 21 and the rotating wheel. Figure 3 As shown, the focusing group 22 includes a first negative optical focal length lens 3 and a driving unit thereof with the convex surface facing the relay lens group 23, and the relay lens group 23 includes a first positive optical focal length lens 4 with the convex surface facing away from the focusing group 22, a biconcave second negative optical focal length lens 5 and a second positive optical focal length lens 6 with the convex surface facing the focusing group 22, which are arranged in sequence.

[0047] The secondary imaging group 25 is arranged on the optical path between the relay lens group 23 and the rotating wheel. The secondary imaging group 25 includes a biconcave third negative power lens 9 and a biconvex third positive power lens 10 arranged in sequence.

[0048] In order to achieve optical path folding, the imaging device further includes:

[0049] The light emitted from the relay lens assembly 23 is reflected by the reflector 7 and the light reflecting device 32 in sequence and enters the secondary imaging assembly 25 ; the angle between the reflector 7 and the light reflecting device 32 is 90 degrees.

[0050] In order to improve the optical performance, further, the fourth negative power lens 2, the first negative power lens 3, the first positive power lens 4 and the second positive power lens 6 are meniscus lenses.

[0051] In order to achieve high-quality imaging (reduce aberrations and correct chromatic aberrations), the fourth positive power lens 1, the first positive power lens 4 and the third positive power lens 10 are made of zinc selenide material, and the second negative power lens 5 and the third negative power lens 9 are made of barium fluoride material.

[0052] In order to eliminate chromatic aberration, except for the second negative power lens 5 and the third negative power lens 9, single surfaces of other lenses are aspherical.

[0053] A working method of an imaging device according to an embodiment of the present invention includes:

[0054] like Figure 1 As shown, the optical switching unit works, the thermal radiation emitted by the radiation source 31 at different ambient temperatures passes through the calibration plate 33 and is received by the detector 26, and the detector 26 outputs responses X1 and X2 corresponding to the different ambient temperatures;

[0055] Perform two-point temperature response calibration, obtain and store calibration results, and the calibration results include gain and offset.

[0056] The working method further comprises:

[0057] like Figure 2 As shown, the optical switching unit is working, the light path is aligned with the field of view to be measured, and the all-pass filter in the filter group 24 is used to focus from the near end to the far end, and the position F of the clear image is recorded;

[0058] The image data of the detector 26 corresponding to the calibration plate 33 is extracted, uniformity correction is performed, and the correction data is stored.

[0059] Example 2.

[0060] An application example of the infrared multi-spectral imaging device and method based on transmission correction in embodiment 1 of the present invention.

[0061] In this application example, if Figure 1-Figure 2 As shown, the objective lens group 21, the focusing group 22, the relay lens group 23, the reflector 7, the light reflecting device 32, the secondary imaging group 25, the rotating wheel and the detector 26 are arranged in sequence.

[0062] The optical switching unit adopts a combination of a light reflecting device 32 and a translation unit. Under the drive of the translation unit, the light reflecting device 32 enters or exits the optical path between the reflector 7 and the secondary imaging group 25, so that when exiting the optical path, the thermal radiation emitted by the radiation source 31 is reflected by the light reflecting device 32, passes through the secondary imaging group 25 and the correction plate 33, and is received by the detector 26; when entering the optical path, the light of the field to be measured passes through the objective lens group 21, the focusing group 22 and the relay lens group 23 in sequence, and then enters the second imaging group 25 after being reflected by the reflector 7 and the light reflecting device 32, and then passes through the filter group 24 and is received by the detector 26.

[0063] The motor 27 drives the rotating wheel, and the filter set (including the all-pass filter) 24 and the transmissive correction plate 33 are arranged on the rotating wheel.

[0064] To achieve uniform radiation background for mid- and short-infrared systems, including non-sharp imaging over the entire -40°C to 70°C temperature range and from near-end (L1 = 2m) to far-end (L2 = 2000m), the calibration plate 33 utilizes a 1.2mm thick zinc sulfide (ZnS) flat wafer with both transmission surfaces roughened.

[0065] The parameters of this embodiment are: δT=70+40=110K, ambient temperature T0=300K, L1=2m, L2=2000m, λ=5μm, and η is about 6μm.

[0066] like Figure 3 As shown, the angle between the first reflector 7 and the light reflecting element 32 (using a reflector) is 90 degrees. The aperture is located on the cold aperture of the refrigerated detector 26, meeting the 100% cold aperture efficiency of the system.

[0067] The objective lens assembly 21 includes a fourth positive power lens 1 with its convex surface facing the object, and a fourth negative power lens 2 with its convex surface facing the object. The focusing assembly 22 includes a first negative power lens 3 and its drive unit, which are convexly facing the relay lens assembly 23. The relay lens assembly 23 includes a first positive power lens 4 with its convex surface facing away from the focusing assembly 22, a second biconcave negative power lens 5, and a second positive power lens 6 with its convex surface facing the focusing assembly 22, which are arranged in sequence. The secondary imaging assembly 25 includes a third biconcave negative power lens 9 and a third biconvex positive power lens 10, which are arranged in sequence.

[0068] The fourth negative power lens 2, the first negative power lens 3, the first positive power lens 4, and the second positive power lens 6 are meniscus lenses. The fourth positive power lens 1, the first positive power lens 4, and the third positive power lens 10 are made of zinc selenide, while the second negative power lens 5 and the third negative power lens 9 are made of barium fluoride.

[0069] Except for the second negative power lens 5 and the third negative power lens 9, single surfaces of other lenses are aspherical.

[0070] The parameters of this embodiment are shown in Table 1 below.

[0071] For a medium-wave infrared cooled HgCdTe photovoltaic array focal plane detector 12 with an array size of 640×512 and a pixel size of 15μm, a medium- and short-wave infrared dual-field multispectral imaging device with a focal length of 100mm and an F number of 2 is designed.

[0072] Table 1 shows the parameters of each optical device.

[0073] .

[0074] In Table 1 above, the radius of curvature refers to the radius of curvature of each surface, and the pitch refers to the distance between adjacent lens surfaces. For example, the pitch of surface S1 is the distance between surface S1 and surface S2. The glass material is the material used in the manufacturing and processing of the lens.

[0075] Table 2 below lists the aspheric coefficients of S1 of the fourth positive power lens 1, S3 of the fourth negative power lens 2, S6 of the first negative power lens 3, S8 of the first positive power lens 4, S11 of the second positive power lens 6 and S17 of the third positive power lens 10.

[0076] Table 2 shows the parameters of the lens surface.

[0077] .

[0078] The displacement of the optical axis direction of an aspheric surface based on the vertex is defined as follows:

[0079] .

[0080] Among them, the meanings of each parameter are: Z—displacement in the direction of the optical axis, y—height of the optical axis, a—lens curvature, K—quadratic surface coefficient, A, B, C, D—aspheric surface coefficients.

[0081] The working band of the present invention is 1.5 μm to 5.4 μm; the aperture is located on the cold aperture of the refrigeration detector 26, meeting 100% cold aperture efficiency of the system.

[0082] The present invention adopts a secondary imaging design, in which the system entrance pupil is located on the first surface of the fourth positive power lens 1, the primary imaging plane is located between the reflector 7 and the light reflector 32, and the secondary imaging plane is located on the focal plane of the detector 26. Experimental results show that the present invention has good imaging quality.

[0083] A working method of an imaging device according to an embodiment of the present invention includes:

[0084] like Figure 1 As shown, the translation unit drives the light reflecting device 32 to exit the optical path, and the thermal radiation emitted by the radiation source 31 at different ambient temperatures passes through the correction plate 33 and is received by the detector 26, which outputs responses X1 and X2 corresponding to the different ambient temperatures;

[0085] Perform two-point temperature response calibration, obtain and store calibration results, and the calibration results include gain and offset.

[0086] like Figure 2 As shown, the translation unit drives the light reflection device 32 into the optical path, the optical path is aligned with the field of view to be measured, and the all-pass filter in the filter group 24 is used to focus from the near end to the far end, and the position F of the clear image is recorded;

[0087] The image data of the detector 26 corresponding to the calibration plate 33 is extracted, uniformity correction is performed, and the correction data is stored.

[0088] Example 3.

[0089] The application example of the infrared multispectral imaging device and method based on transmission correction in Example 1 of the present invention is different from that in Example 2 in that:

[0090] like Figure 4 As shown, when the light reflecting device 32 is in the optical path, the thermal radiation emitted by the radiation source 31 is reflected by the light reflecting device 32, then passes through the correction plate 33, and is received by the detector 26. When exiting the optical path, the light of the measured field of view passes through the filter group 24 and is received by the detector 26.

Claims

1. An infrared multispectral imaging device based on transmission correction, comprising an objective lens set, a filter set and a detector; characterized in that: The imaging device further comprises: A correction plate and a rotating wheel, wherein the transmission surface of the correction plate is roughened and the correction plate and the filter group are arranged on the rotating wheel; when the rotating wheel rotates, the filter group and the correction plate are selectively located in the optical path between the objective lens group and the detector; Standard blackbody radiation source; an optical switching unit, the optical switching unit being disposed between the relay lens group and the secondary imaging group, and being used to selectively allow the thermal radiation emitted by the radiation source and the light of the measured field of view to pass through, and then sequentially pass through the secondary imaging group and the filter group or correction plate on the rotating wheel, so that the detector receives the thermal radiation and the light of the measured field of view; A focusing group and a relay lens group, the focusing group and the relay lens group being sequentially arranged on the optical path between the objective lens group and the rotating wheel; the focusing group comprising a first negative power lens with a convex surface facing the relay lens group and a driving unit thereof; the relay lens group comprising a first positive power lens with a convex surface facing away from the focusing group, a biconcave second negative power lens, and a second positive power lens with a convex surface facing the focusing group, which are sequentially arranged; a secondary imaging group, the secondary imaging group being arranged on the optical path between the relay lens group and the rotating wheel; the secondary imaging group comprising a biconcave third negative power lens and a biconvex third positive power lens arranged in sequence; The objective lens group includes a fourth positive power lens with a convex surface facing the object and a fourth negative power lens with a convex surface facing the object; The fourth positive power lens, the first positive power lens and the third positive power lens are made of zinc selenide, the second negative power lens and the third negative power lens are made of barium fluoride, and the first negative power lens and the second positive power lens are made of single crystal silicon. Except for the second negative power lens and the third negative power lens, a single surface of the other lenses is an aspheric surface; the object-facing surfaces of the fourth positive power lens, the fourth negative power lens, and the second positive power lens are aspheric surfaces; the surfaces of the first negative power lens and the first positive power lens facing away from the object are aspheric surfaces; and the surface of the third positive power lens facing away from the detector is an aspheric surface; The optical components with optical power in the imaging device are only the eight lenses mentioned above.

2. The imaging device according to claim 1, wherein The optical switching unit includes: A light reflecting device and a driving unit, wherein the light reflecting device selectively enters and exits the light path when driven by the driving unit; When the light reflecting device is in the optical path, the thermal radiation emitted by the radiation source is reflected by the light reflecting device, then passes through the correction plate and is received by the detector. When exiting the optical path, the light of the measured field of view passes through the filter group and is received by the detector. Alternatively, when the light reflecting device is in the optical path, the light of the measured field of view is reflected by the light reflecting device, then passes through the filter group and is received by the detector. When exiting the optical path, the thermal radiation emitted by the radiation source passes through the correction plate and is received by the detector.

3. The imaging device according to claim 1, wherein The roughness η of the calibration sheet satisfies: η≥[5794(L2-L1)·δT·λ / (L2·T0 2 )] 1 / 2 , L2 is the far end distance, L1 is the near end distance, δT is the temperature difference between the temperature zones, λ is the response cutoff wavelength of the detector, and T0 is the ambient temperature.

4. The imaging device according to claim 1, wherein The imaging device further comprises: The light emitted from the relay mirror group is reflected by the reflector and the light reflecting device in sequence and enters the secondary imaging group.

5. The imaging device according to claim 1, wherein The correction plate is made of sapphire, or zinc sulfide, zinc selenide and barium fluoride wafers, or germanium, silicon and chalcogenide glass.

6. The operating method of the imaging device according to claim 1, comprising: When the optical switching unit is in operation, the thermal radiation emitted by the radiation source at different ambient temperatures passes through the calibration plate and is received by the detector, which then outputs responses X1 and X2 corresponding to the different ambient temperatures. Perform two-point temperature response calibration, obtain and store calibration results, and the calibration results include gain and offset.

7. The working method according to claim 6, characterized in that: The working method further comprises: The optical switching unit works, the optical path is aligned with the measured field of view, and the all-pass filter in the filter set is used to focus from the near end to the far end, and the position F of the clear image is recorded; The detector image data corresponding to the calibration sheet is extracted, uniformity correction is performed, and the correction data is stored.

8. The working method according to claim 6, characterized in that: The roughness η of the calibration sheet satisfies: η≥[5794(L2-L1)·δT·λ / (L2·T0 2 )] 1 / 2 , L2 is the far end distance, L1 is the near end distance, δT is the temperature difference between the temperature zones, λ is the response cutoff wavelength of the detector, and T0 is the ambient temperature.

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