Infrared multispectral imaging device and method based on transmission-type correction

Abstract

The invention belongs to the thermal imaging technology, and particularly relates to an infrared multispectral imaging device and method based on transmission-type correction, and the device comprises an objective lens group, an optical filter group, and a detector. The transmission surface of the correction sheet is roughened, and the correction sheet and the optical filter group are arranged on the rotating wheel; when the rotating wheel rotates, the optical filter group and the correction sheet are selectively located on an optical path between the objective lens group and the detector; a standard blackbody radiation source; the optical switching unit is used for enabling heat radiation emitted by the radiation source and light of a measured view field to selectively penetrate through the optical filter set or the correction sheet on the rotating wheel, and the detector receives the light penetrating through the heat radiation and the measured view field. The method has the advantages of easy operation and the like, and is used in infrared spectral imaging.

Description

Technical Field

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

[0002] Multi-spectral imaging combines the characteristics of traditional spectrometers and optoelectronic detection technologies, can provide two-dimensional image information and spectral information simultaneously, and has the quasi-real-time characteristics of a new generation of optoelectronic telemetry.

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

[0004] There are the following two conventional radiation correction methods: 1. Uniformity correction based on a shutter, that is, an oxidized and blackened metal baffle is cut in online, and the uniformity of the inherent pattern is corrected by means of the image of the area array detector, which can reflect the uniformity at the working temperature of the environment where the infrared system is located, and this has been widely used in uncooled thermal imaging systems. However, the uniformity in different radiation temperature scenarios cannot be obtained, and the influence of temperature drift cannot be solved; at the same time, the correction will cause the image to be interrupted for several seconds.

[0005] 2. Correction based on a radiation source. Due to the particularity of infrared technology, for different scene radiations and environmental working temperatures, the optoelectronic responses of infrared detectors are different. Calibration is carried out using a surface source blackbody radiation source at different temperatures in the laboratory to make the responsivity calibration of the radiation temperature. The disadvantage is that the calibration time is long, and periodic calibration is also required. Summary of the Invention

[0006] To solve the deficiencies in the above-mentioned prior art solutions, the present invention provides an infrared multi-spectral imaging device based on transmissive correction.

[0007] The purpose of the present invention is achieved through the following technical solutions: An infrared multi-spectral imaging device based on transmissive correction, comprising an objective lens group, a filter group, and a detector; the imaging device further includes: A correction film and a rotating wheel, the transmissive surface of the correction film is roughened, and the correction film and the filter group are arranged on the rotating wheel; when the rotating wheel rotates, the filter group and the correction film are selectively located on the optical path between the objective lens group and the detector; A standard blackbody radiation source; An optical switching unit is used to selectively make the thermal radiation emitted by the radiation source and the light of the measured field of view pass through the filter group or the correction film on the rotating wheel, and the detector receives the thermal radiation and the light of the measured field of view.

[0008] The object of the present invention is also to provide a working method of an imaging device, and this object of the invention is achieved by the following technical solutions: Based on the working method of the imaging device of the present invention, the working method includes: The optical switching unit works, and the thermal radiation emitted by the radiation source at different ambient temperatures passes through the correction film and is received by the detector. The detector outputs responses X1 and X2 corresponding to different ambient temperatures. Perform two-point temperature response calibration, obtain the calibration result and store it. The calibration result includes gain and offset.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Utilize a transmissive correction film to form a diffuse scattering effect, with real-time scene radiation characteristics, enabling the mid- and short-wave infrared band system to achieve non-clear imaging in the entire temperature range from -40°C to 70°C and from the proximal end (such as 2m) to the distal end (such as 2000m), generating a uniform radiation background and replacing the baffle. Achieve fast uniformity correction under the average radiation brightness temperature of the infrared scene online and in real-time. The result is close to the detector response of the real scene brightness temperature, and the calibration time is short. In the same set of devices, temperature response calibration is achieved in the wide wavelength band range of 1.5μm to 5.4μm (short wave, medium wave).

[0010] 2. Simple structure and low cost; There is no need to use diffractive optical elements for achromatic design. Only by matching different materials of the lens, optimizing the surface shape parameters of each surface, and appropriately using aspherical surfaces, high-quality imaging of the system in the wide wavelength band range of 1.5μm to 5.4μm (short wave, medium wave) is achieved, greatly reducing the system aberration and correcting the chromatic aberration of the system in the wide spectral range. 3. Clear imaging; This application uses two reflectors to achieve a secondary imaging configuration of U-shaped folding, and realizes clear imaging of the entire optical system from -40°C to 70°C through the focusing group of a single lens. The driving unit belongs to the mature prior art and is simple and easy to control. 4. Large focusing range; A focusing range of 2m to 2000m is achieved through the focusing group, which can realize close-range calibration in the laboratory and long-distance detection in the field. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Referring to the accompanying drawings, the disclosure of the present invention will become more understandable. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention. In the figures: Figure 1 is a schematic structural diagram of the imaging device of the present invention; Figure 2 is a schematic structural diagram of another state of the imaging device of the present invention; Figure 3 is a schematic partial structural diagram of the imaging device of the present invention; Figure 4 is a schematic structural diagram of the imaging device in Embodiment 3 of the present invention.

[0012] In the drawings, 1 - fourth positive focal length lens, 2 - fourth negative focal length lens, 3 - first negative focal length lens, 4 - first positive focal length lens, 5 - second negative focal length lens, 6 - second positive focal length lens, 7 - first mirror, 9 - third negative focal length lens, 10 - third positive focal length lens, 21 - objective lens group, 22 - zoom group, 23 - relay lens group, 24 - filter group, 25 - secondary imaging group, 26 - detector, 27 - motor, 31 - standard blackbody radiation source, 32 - light reflection device, 33 - transmission correction sheet. Detailed Embodiments

[0013] Figures 1 - 4 The following description and illustration depict alternative specific embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. To teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art should understand that variations or substitutions derived from these specific embodiments will fall within the scope of the present invention. Those skilled in the art should 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 alternative specific embodiments, but is defined only by the claims and their equivalents.

[0014] Embodiment 1.

[0015] An infrared multi - spectral imaging device based on transmission correction, as Figures 1 - 2 shown, the imaging device includes: An objective lens group 21, a filter group 24, and a detector 26 arranged in sequence.

[0016] The transmission surface of the transmission correction sheet 33 is roughened and is arranged on a rotating wheel together with the filter group 24; when the rotating wheel rotates, the filter group 24 and the correction sheet 33 are selectively located on the optical path between the objective lens group 21 and the detector 26.

[0017] A standard blackbody radiation source 31, an optical switching unit for selectively making the thermal radiation emitted by the radiation source 31 and the light of the measured field of view pass through the filter group 24 or the correction sheet 33 on the rotating wheel, and the detector 26 receives the thermal radiation and the light of the measured field of view.

[0018] To achieve the switching function, further, the optical switching unit includes an optical reflection device 32 and a driving unit. Under the drive of the driving unit, the optical reflection device 32 selectively enters and exits the optical path between the objective lens group 21 and the filter group 24 (correction film 33).

[0019] When the optical reflection device 32 is in the optical path, the light of the measured field of view is reflected by the optical reflection device 32, then passes through the filter group 24, and is received by the detector 26. When it exits the optical path, the thermal radiation emitted by the radiation source 31 passes through the correction film 33 and is received by the detector 26, as Figures 1 - 2 shown.

[0020] Or, when the optical reflection device 32 is in the optical path, the thermal radiation emitted by the radiation source 31 is reflected by the optical reflection device 32, then passes through the correction film 33, and is received by the detector 26. When it exits the optical path, the light of the measured field of view passes through the filter group 24 and is received by the detector 26, as Figure 4 shown.

[0021] To obtain a better diffuse scattering effect, the roughness η of the correction film 33 satisfies: η≥[5794(L2-L1)·δT·λ / (L2·T0 2 )] 1 / 2 , where L2 is the distal distance, L1 is the proximal distance, δT is the temperature difference of the temperature range, λ is the response cut-off wavelength of the detector 26, and T0 is the ambient temperature.

[0022] The correction film is made of sapphire, or zinc sulfide, zinc selenide and barium fluoride wafers, or germanium, silicon and chalcogenide glasses.

[0023] To obtain clear imaging, further, as Figures 1 - 2 shown, the imaging device further includes: A focusing group 22 and a relay lens group 23. 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. As Figure 3 shown, the focusing group 22 includes a first negative power lens 3 with its convex surface facing the relay lens group 23 and its driving unit. The relay lens group 23 includes a first positive power lens 4 with its convex surface facing away from the focusing group 22, a double-concave second negative power lens 5, and a second positive power lens 6 with its convex surface facing the focusing group 22 arranged in sequence.

[0024] A secondary imaging group 25. 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 double-concave third negative power lens 9 and a double-convex third positive power lens 10 arranged in sequence.

[0025] In order to achieve optical path folding, further, the imaging device further includes: The light emitted from the relay mirror group 23 is sequentially reflected by the mirror 7 and the light reflecting device 32 and enters the secondary imaging group 25; the included angle between the mirror 7 and the light reflecting device 32 is 90 degrees.

[0026] In order to improve the optical performance, further, the fourth negative focal length lens 2, the first negative focal length lens 3, the first positive focal length lens 4, and the second positive focal length lens 6 are meniscus lenses.

[0027] In order to achieve high-quality imaging (reduce aberration and correct chromatic aberration), further, the fourth positive focal length lens 1, the first positive focal length lens 4, and the third positive focal length lens 10 are made of zinc selenide material, and the second negative focal length lens 5 and the third negative focal length lens 9 are made of barium fluoride material.

[0028] In order to correct chromatic aberration, further, except for the second negative focal length lens 5 and the third negative focal length lens 9, the single surface of other lenses is aspherical.

[0029] The working method of the imaging device according to the embodiment of the present invention, the working method includes: As Figure 1 shown, the optical switching unit works, and the thermal radiation emitted by the radiation source 31 at different ambient temperatures passes through the correction film 33 and is received by the detector 26, and the detector 26 outputs responses X1, X2 corresponding to different ambient temperatures; Perform two-point temperature response calibration, obtain the calibration result and store it, and the calibration result includes gain and offset.

[0030] The working method further includes: As Figure 2 shown, the optical switching unit works, the optical path is aligned with the measured field of view, the all-pass filter in the filter group 24 is used, and focusing is performed from the proximal end to the distal end, and the position F of clear imaging is recorded; Extract the image data of the detector 26 corresponding to the correction film 33, perform uniformity correction, and store the correction data.

[0031] Embodiment 2.

[0032] An application example of the infrared multi-spectral imaging device and method based on transmissive correction according to Embodiment 1 of the present invention.

[0033] In this application example, as Figures 1 - 2 shown, the objective lens group 21, the focusing group 22, the relay mirror group 23, the mirror 7, the light reflecting device 32, the secondary imaging group 25, the rotating wheel, and the detector 26 are sequentially arranged.

[0034] The optical switching unit adopts a combination of an optical reflection device 32 and a translation unit. Driven by the translation unit, the optical reflection device 32 enters or exits the optical path between the reflecting mirror 7 and the secondary imaging group 25. When exiting the optical path, the thermal radiation emitted by the radiation source 31 is reflected by the optical reflection device 32, passes through the secondary imaging group 25 and the correction film 33, and is received by the detector 26. When entering the optical path, the light of the field of view to be measured sequentially passes through the objective lens group 21, the focusing group 22 and the relay lens group 23, is reflected by the reflecting mirror 7 and the optical reflection device 32, enters the second imaging group 25, and then passes through the filter group 24 and is received by the detector 26.

[0035] The motor 27 drives the rotating wheel, and the filter group (including the all-pass filter) 24 and the transmissive correction film 33 are arranged on the rotating wheel.

[0036] In order to achieve non-clear imaging of the mid-short infrared band system in the entire temperature range from -40°C to 70°C and from the near end (L1 = 2m) to the far end (L2 = 2000m), and generate a uniform radiation background. The correction film 33 uses a 1.2-mm-thick zinc sulfide (ZnS) flat wafer, and the two transmissive surfaces are roughened.

[0037] The parameters of this embodiment are: δT = 70 + 40 = 110K, the ambient temperature T0 = 300K, L1 = 2m, L2 = 2000m, λ = 5μm, and η is about 6μm.

[0038] As Figure 3 shown, the included angle between the first reflecting mirror 7 and the optical reflection device 32 (using a reflecting mirror) is 90 degrees. The aperture stop is located on the cold aperture stop of the cooled detector 26, meeting the 100% cold aperture stop efficiency of the system.

[0039] The objective lens group 21 includes a fourth positive-power lens 1 with a convex surface facing the object side and a fourth negative-power lens 2 with a convex surface facing the object side. The focusing group 22 includes a first negative-power lens 3 with a convex surface facing the relay lens group 23 and its driving unit. The relay lens group 23 includes a first positive-power lens 4 with a convex surface facing away from the focusing group 22, a double-concave second negative-power lens 5, and a second positive-power lens 6 with a convex surface facing the focusing group 22 arranged in sequence. The secondary imaging group 25 includes a double-concave third negative-power lens 9 and a double-convex third positive-power lens 10 arranged in sequence.

[0040] 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 material, and the second negative-power lens 5 and the third negative-power lens 9 are made of barium fluoride material.

[0041] Except for the second negative power lens 5 and the third negative power lens 9, single surfaces of other lenses are aspherical surfaces.

[0042] The parameters of this embodiment are shown in Table 1 below.

[0043] 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.

[0044] Table 1 shows the parameters of each optical device.

[0045] .

[0046] In Table 1 above, the radius of curvature refers to the radius of curvature of each surface, and the spacing refers to the distance between two surfaces of adjacent lenses. For example, the spacing of surface S1 is the distance between surface S1 and surface S2. Glass material is the material used for manufacturing and processing of the lens.

[0047] 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.

[0048] Table 2 shows the parameters of the lens surface.

[0049] .

[0050] The displacement of the optical axis direction of an aspherical surface based on the vertex is defined as follows: .

[0051] Among them, the meanings of each parameter are: Z—position change 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.

[0052] The working band of the present invention is 1.5 μm to 5.4 μm; the diaphragm is located on the cold diaphragm of the refrigeration detector 26, satisfying the 100% cold diaphragm efficiency of the system.

[0053] The present invention adopts a secondary imaging design, wherein the system entrance pupil is located on the first surface of the fourth positive power lens 1, the primary imaging surface is located between the reflector 7 and the light reflecting device 32, and the secondary imaging surface is located on the focal plane of the detector 26. Experimental results show that the present invention has good imaging quality.

[0054] The working method of the imaging device according to the embodiment of the present invention comprises: like Figure 1As shown, the translation unit drives the optical reflection device 32 out of the optical path. The thermal radiation emitted by the radiation source 31 at different ambient temperatures passes through the correction film 33 and is received by the detector 26. The detector 26 outputs responses X1 and X2 corresponding to different ambient temperatures. Perform two-point temperature response calibration, obtain the calibration results and store them. The calibration results include gain and offset.

[0055] As Figure 2 As shown, the translation unit drives the optical reflection device 32 into the optical path, aligns the optical path with the measured field of view, uses the all-pass filter in the filter set 24, performs focusing from the near end to the far end, and records the position F of clear imaging. Extract the image data of the detector 26 corresponding to the correction film 33, perform uniformity correction, and store the correction data.

[0056] Embodiment 3.

[0057] According to the application example of the infrared multi-spectral imaging device and method based on transmissive correction in Embodiment 1 of the present invention, different from Embodiment 2: As Figure 4 As shown, when the optical reflection device 32 is in the optical path, the thermal radiation emitted by the radiation source 31 is reflected by the optical reflection device 32, then passes through the correction film 33, and is received by the detector 26. When it 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.

Claims

1. An infrared multi-spectral imaging device based on transmissive correction, comprising an objective lens group, a filter group, and a detector; characterized in that, The imaging device further includes: a correction film and a rotating wheel, the transmission surface of the correction film is roughened, and the correction film and the filter set are arranged on the rotating wheel; when the rotating wheel rotates, the filter set and the correction film are selectively located on the optical path between the objective lens group and the detector; a standard blackbody radiation source; an optical switching unit, which is used to selectively make the thermal radiation emitted by the radiation source and the light of the measured field of view pass through the filter set or the correction film on the rotating wheel, and the detector receives the thermal radiation and the light of the measured field of view.

2. The imaging device according to claim 1, wherein, The optical switching unit includes: a light reflecting device and a driving unit, and under the drive of the driving unit, the light reflecting device selectively enters and exits the optical path; 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 film and is received by the detector. When it exits the optical path, the light of the measured field of view passes through the filter set and is received by the detector; or, 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 set and is received by the detector. When it exits the optical path, the thermal radiation emitted by the radiation source passes through the correction film and is received by the detector.

3. The imaging device according to claim 1, characterized in that, The roughness η of the correction film satisfies: η≥[5794(L2 - L1)·δT·λ / (L2·T0 2 )] 1 / 2 , where L2 is the distal distance, L1 is the proximal distance, δT is the temperature difference of the temperature zone, λ is the response cut-off wavelength of the detector, and T0 is the ambient temperature.

4. The imaging device according to claim 1, characterized in that, The imaging device further includes: a focusing group and a relay lens group, the focusing group and the relay lens group are sequentially arranged on the optical path between the objective lens group and the rotating wheel; a secondary imaging group, the secondary imaging group is arranged on the optical path between the relay lens group and the rotating wheel.

5. The imaging device according to claim 2, characterized in that, The imaging device further includes: a reflecting mirror, the light emitted from the relay lens group is reflected by the reflecting mirror and the light reflecting device in sequence and enters the secondary imaging group.

6. The imaging device according to claim 3, wherein, The correction film is made of sapphire, or zinc sulfide, zinc selenide and barium fluoride wafers, or germanium, silicon and chalcogenide glasses.

7. A working method of the imaging device according to claim 1, the working method includes: The optical switching unit works, and the thermal radiation emitted by the radiation source at different ambient temperatures passes through the correction film and is received by the detector, and the detector outputs responses X1 and X2 corresponding to different ambient temperatures; Two-point temperature response calibration is performed, and the calibration result is obtained and stored, and the calibration result includes gain and offset.

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

9. The working method according to claim 7, characterized in that, The roughness η of the correction film satisfies: η≥[5794(L2 - L1)·δT·λ / (L2·T0 2 )] 1 / 2 , where L2 is the distal distance, L1 is the proximal distance, δT is the temperature difference of the temperature zone, λ is the response cut-off wavelength of the detector, and T0 is the ambient temperature.

10. The working method according to claim 7, characterized in that, The imaging device further includes: a focusing group and a relay lens group, the focusing group and the relay lens group are sequentially arranged on the optical path between the objective lens group and the rotating wheel; a secondary imaging group, the secondary imaging group is arranged on the optical path between the relay lens group and the rotating wheel.

Images