Infrared detector and infrared imager based on carbon nanotube structure

Abstract

An infrared detector comprises: an infrared light absorber for absorbing infrared light and converting the infrared light into heat; a thermoelectric element, on which the infrared light absorber is arranged; an electrical signal detector for detecting changes in the electrical properties of the thermoelectric element; the infrared light absorber comprises a carbon nanotube structure, which comprises a first layer of carbon nanotube film, a second layer of carbon nanotube film and a third layer of carbon nanotube film, wherein the first layer of carbon nanotube film, the second layer of carbon nanotube film and the third layer of carbon nanotube film are stacked, and the first layer of carbon nanotube film, the second layer of carbon nanotube film and the third layer of carbon nanotube film comprise a plurality of carbon nanotubes connected end to end in the extension direction of the carbon nanotubes and extending in the same direction, and the extension directions of the carbon nanotubes in the first layer of carbon nanotube film and the second layer of carbon nanotube film form an angle of 42 to 48 degrees.

Description

Technical Field

[0001] The invention relates to an infrared detector and an infrared imager, and in particular to an infrared detector and an infrared imager based on a carbon nanotube structure. Background Art

[0002] Infrared radiation is an electromagnetic wave with a wavelength between visible light and microwaves, which is imperceptible to the human eye. To detect the existence of this radiation and measure its strength, it must be converted into other physical quantities that can be detected and measured. Infrared detectors are devices that convert infrared signals into electrical signal outputs. They can be used to detect the existence of infrared rays or the size of infrared energy. They are widely used in medical, prospecting, military and daily life fields. Because of their low price and stable technical performance, they have become a hot topic for more and more people to study.

[0003] Infrared detectors can be divided into active infrared detectors and passive infrared detectors. Active infrared detectors are composed of infrared transmitters, infrared receivers and alarm systems. When a person or object comes into contact with the infrared rays emitted by the infrared transmitter, the infrared receiver generates a signal change, which causes the alarm to sound. Passive infrared detectors do not include infrared emission sources. When an external infrared signal is generated and received by it, a certain signal will be generated to detect the existence and energy of infrared rays. An infrared detector, whether it is an active infrared detector or a passive infrared detector, should include at least one object that is sensitive to infrared radiation, which can be called a detection element or an infrared absorber. However, the absorption rate of existing infrared absorbers is low. Summary of the invention

[0004] In view of this, it is indeed necessary to provide an infrared detector and an infrared imager, in which the infrared light absorber has a higher absorption rate.

[0005] An infrared detector comprises: an infrared light absorber for absorbing infrared light and converting the infrared light into heat; a thermoelectric element, on which the infrared light absorber is arranged; and an electrical signal detector for detecting changes in the electrical properties of the thermoelectric element; the infrared light absorber comprises a carbon nanotube structure, which comprises a first layer of carbon nanotube film, a second layer of carbon nanotube film and a third layer of carbon nanotube film, wherein the first layer of carbon nanotube film, the second layer of carbon nanotube film and the third layer of carbon nanotube film are stacked, wherein the first layer of carbon nanotube film, the second layer of carbon nanotube film and the third layer of carbon nanotube film comprise a plurality of carbon nanotubes connected end to end in the extension direction of the carbon nanotubes and extending in the same direction, wherein the extension directions of the carbon nanotubes in the first layer of carbon nanotube film and the second layer of carbon nanotube film form an angle of 42 to 48 degrees, and the extension directions of the carbon nanotubes in the first layer of carbon nanotube film and the third layer of carbon nanotube film form an angle of 84 to 96 degrees.

[0006] An infrared imager comprises: an infrared detector assembly for converting infrared light into electrical signals; a signal processor for processing and calculating the electrical signals to obtain thermal field distribution data; an infrared image display for displaying an infrared thermal image according to the thermal field distribution data; the infrared detector assembly comprises a plurality of infrared detectors distributed in an array.

[0007] Compared with the prior art, the present invention utilizes three-layer stacked carbon nanotube drawn film as an infrared light absorber. Since the length extension directions of the carbon nanotubes in the two layers of carbon nanotube drawn film are vertically crossed, the length extension direction of the carbon nanotubes in the third layer of carbon nanotube drawn film forms an angle of 42 to 48 degrees with the two layers of carbon nanotube drawn film. Therefore, the infrared light absorber not only has a higher absorption rate, almost as high as 99%, but also has omnidirectional absorption performance, and its absorption rate is independent of the polarization of the infrared light. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a scanning electron microscope photograph of the carbon nanotube film provided in the first embodiment of the present invention.

[0009] Figure 2 A schematic diagram of the length extension direction of carbon nanotubes in two vertically crossed carbon nanotube drawn films (sample 1) provided in the first embodiment of the present invention.

[0010] Figure 3 is a scanning electron microscope photograph of the sample 1.

[0011] Figure 4 A schematic diagram of the length extension direction of the carbon nanotubes in the stacked three-layer carbon nanotube drawn film (sample 2) provided in the first embodiment of the present invention.

[0012] Figure 5 A schematic diagram of the length extension direction of carbon nanotubes in a stacked four-layer carbon nanotube drawn film (sample three) provided in the first embodiment of the present invention.

[0013] Figure 6 is a scanning electron microscope photograph of the sample three.

[0014] Figure 7 A schematic diagram of the length extension direction of the carbon nanotubes in the three-layer carbon nanotube drawn film (sample four) provided in the first embodiment of the present invention.

[0015] Figure 8 Schematic diagram of the structure of sample four.

[0016] Fig. 9 is a scanning electron microscope photograph of the sample 4.

[0017] Fig.10 It is a transmission spectrum diagram of the sample 1 in the ultraviolet (UV)-near infrared (NIR) wavelength range.

[0018] Fig.11 It is the reflection spectrum diagram of the sample three in the ultraviolet (UV)-near infrared (NIR) wavelength range.

[0019] Fig.12 It is the transmission spectrum of the sample 4 in the ultraviolet (UV)-near infrared (NIR) wavelength range.

[0020] Fig.13 It is the reflection spectrum diagram of the sample 4 in the ultraviolet (UV)-near infrared (NIR) wavelength range.

[0021] Fig.14 This is the absorption spectrum of the sample four in the ultraviolet (UV)-near infrared (NIR) wavelength range.

[0022] Fig.15 This is the transmission spectrum of sample 4 in the mid-infrared (MIR) wavelength range.

[0023] Fig.16 This is the reflection spectrum of sample 4 in the mid-infrared (MIR) wavelength range.

[0024] Fig.17 This is the absorption spectrum of sample 4 in the mid-infrared (MIR) wavelength range.

[0025] Fig.18 This is a spectrum of the sample 4 in the visible to near-infrared wavelength range measured when the incident angle is 0° to 60°.

[0026] Fig.19This is a spectrum diagram of the sample 4 measured in the mid-infrared wavelength range when the incident angle is 0° to 60°.

[0027] Fig. 20 This is a spectrum diagram of the sample 4 measured in the visible light-infrared wavelength range when the incident polarization degree is 0° to 90°.

[0028] Fig.21 This is a spectrum diagram of the sample 4 measured in the mid-infrared wavelength range when the incident polarization degree is 0° to 90°.

[0029] Fig. 22 This is a schematic structural diagram of an infrared detector provided in the second embodiment of the present invention.

[0030] Fig.23 Optical photographs of an infrared light absorber provided with a resist layer provided in the second embodiment of the present invention being scratched by a cloth, a knife and sandpaper respectively.

[0031] Fig.24 A schematic structural diagram of an infrared imager provided in the third embodiment of the present invention.

[0032] Fig.25 This is a schematic structural diagram of an infrared stealth fabric provided in a fourth embodiment of the present invention.

[0033] Fig.26 An optical photograph of a hand covered by an infrared invisible cloth provided by the fourth embodiment of the present invention.

[0034] Fig. 27 This is a thermal image of a hand covered with infrared invisible cloth provided by the fourth embodiment of the present invention.

[0035] Fig.28 This is a schematic structural diagram of the infrared invisible clothing provided in the fifth embodiment of the present invention.

[0036] Main component symbols

[0037] Sample 10

[0038] Sample 20

[0039] Sample 330

[0040] Sample 440

[0041] The first layer of carbon nanotube film 12

[0042] The second layer of carbon nanotube film 14

[0043] The third layer of carbon nanotube film 16

[0044] The fourth layer of carbon nanotube film 18

[0045] Infrared detector 100

[0046] Infrared light absorber 110

[0047] Thermoelectric element 112

[0048] Electrical signal detector 114

[0049] Infrared Imager 200

[0050] Infrared receiver 210

[0051] Infrared detector assembly 220

[0052] Signal processor 230

[0053] Infrared image display 240

[0054] Infrared invisible fabric 300

[0055] Fabric backing 310

[0056] Infrared invisible clothing 400

[0057] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0058] The infrared detector and infrared imager provided by the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0059] The first embodiment of the present invention provides an infrared absorber, which is a carbon nanotube structure formed by stacking multiple layers of carbon nanotube films.

[0060] See also Figure 1The carbon nanotube film comprises a plurality of carbon nanotubes connected end to end and extending substantially in the same direction. The carbon nanotubes comprise one or more of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes. The diameter of the single-walled carbon nanotubes is 0.5 nanometers to 50 nanometers, the diameter of the double-walled carbon nanotubes is 1.0 nanometers to 50 nanometers, and the diameter of the multi-walled carbon nanotubes is 1.5 nanometers to 50 nanometers. The carbon nanotubes are evenly distributed and parallel to the surface of the carbon nanotube film. The carbon nanotubes in the carbon nanotube film are connected by van der Waals forces. On the one hand, the carbon nanotubes connected end to end are connected by van der Waals forces, and on the other hand, the parallel carbon nanotubes are also connected by van der Waals forces. Therefore, the carbon nanotube film has a certain flexibility, can be bent and folded into any shape without breaking, and has good self-supporting performance. The carbon nanotube film can be obtained by directly stretching a carbon nanotube array. It can be understood that the carbon nanotubes extending in the same direction in the carbon nanotube film are the majority of the carbon nanotubes extending in the same direction. Of course, there are a few randomly arranged carbon nanotubes in the carbon nanotube film, and these carbon nanotubes will not have a significant impact on the overall orientation arrangement of the majority of carbon nanotubes in the carbon nanotube film. Therefore, "essentially extending in the same direction" can more accurately describe the internal structure of the carbon nanotube film.

[0061] When at least two layers of carbon nanotube films are overlapped, adjacent carbon nanotube films are tightly bound by van der Waals forces. Further, the extension directions of the carbon nanotubes in the two adjacent layers of carbon nanotube films form an angle α, 0≤α≤90 degrees.

[0062] The self-supporting property means that the carbon nanotube film does not need a large area of ​​carrier support, but can be suspended in the air as a whole and maintain its own film state as long as the two sides provide support force, that is, when the carbon nanotube film is placed on (or fixed on) two supports set at a fixed distance, the carbon nanotube film between the two supports can maintain its own layered state. It can be understood that the infrared absorber also has a self-supporting property.

[0063] In order to study the absorption performance of the infrared absorber, the present invention prepared four different samples for testing and comparison. The four samples are respectively as follows: Figures 2 to 8 In order to clearly show the position and arrangement relationship of carbon nanotubes in sample 1, sample 2, sample 3 and sample 4, Figure 2 , Figure 4 , Figure 5 and Figure 7 In the drawings, each layer of the carbon nanotube drawn film only draws one carbon nanotube (in fact, each layer of the carbon nanotube drawn film includes a plurality of substantially parallel carbon nanotubes), which cannot be a limitation to the present invention.

[0064] Sample 10

[0065] Two layers of carbon nanotube films are arranged vertically and crosswise to form a sample 10. Specifically, Figure 2 and Figure 3 As shown, sample 10 is composed of two layers of carbon nanotube films arranged vertically and crossed, the carbon nanotubes in each layer of carbon nanotube films are connected end to end and extend in the same direction, and the length extension directions of the carbon nanotubes in the two layers of carbon nanotube films form an angle of about 90 degrees. That is, in sample 10, the two layers of carbon nanotube films are stacked and formed in the shape of a "cross".

[0066] Sample 20

[0067] Three layers of carbon nanotube films are stacked, and the length extension directions of the carbon nanotubes in adjacent carbon nanotube films form an angle of about 60 degrees. Figure 4 As shown, the sample 20 is composed of a first layer of carbon nanotube film 12, a second layer of carbon nanotube film 14 and a third layer of carbon nanotube film 16 stacked in sequence ( Figure 4 In the figure, only one carbon nanotube is drawn in each of the first layer of carbon nanotube film 12, the second layer of carbon nanotube film 14 and the third layer of carbon nanotube film 16, so as to clearly show the positional relationship of the carbon nanotubes in the first layer of carbon nanotube film 12, the second layer of carbon nanotube film 14 and the third layer of carbon nanotube film 16). The second layer of carbon nanotube film 14 is located between the first layer of carbon nanotube film 12 and the third layer of carbon nanotube film 16. The length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14 form an angle of about 60 degrees. The length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of about 60 degrees.

[0068] Sample 330

[0069] Four layers of carbon nanotube film are stacked. Specifically, Figure 5 and Figure 6 As shown, sample three 30 is composed of a first layer of carbon nanotube drawn film 12 , a second layer of carbon nanotube drawn film 14 , a third layer of carbon nanotube drawn film 16 and a fourth layer of carbon nanotube drawn film 18 stacked in sequence. Figure 5In the figure, only one carbon nanotube is drawn in each of the first carbon nanotube film 12, the second carbon nanotube film 14, the third carbon nanotube film 16 and the fourth carbon nanotube film 18, so as to clearly show the positional relationship of the carbon nanotubes in the first carbon nanotube film 12, the second carbon nanotube film 14, the third carbon nanotube film 16 and the fourth carbon nanotube film 18. The length extension direction of the carbon nanotubes in the first carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the second carbon nanotube film 14 form an angle of 45 degrees, and the length extension direction of the carbon nanotubes in the second carbon nanotube film 14 and the length extension direction of the carbon nanotubes in the third carbon nanotube film 16 form an angle of 45 degrees. The length extension direction of the carbon nanotubes in the fourth layer of carbon nanotube film 18 forms an angle of 45 degrees with the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16, and forms an angle of 90 degrees with the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12. That is, in sample three 30, four layers of carbon nanotube film are stacked and formed in the shape of a "R" character.

[0070] Sample 440

[0071] Three layers of carbon nanotube film are stacked. Specifically, Figure 7 and Figure 8 As shown, sample 40 is stacked in sequence by a first layer of carbon nanotube film 12, a second layer of carbon nanotube film 14 and a third layer of carbon nanotube film 16, the second layer of carbon nanotube film 14 is located between the first layer of carbon nanotube film 12 and the third layer of carbon nanotube film 16, the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14 form an angle of 45 degrees, the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of 45 degrees. The length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of 90 degrees.

[0072] In sample four 40, the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 respectively form an angle of 42 to 48 degrees with the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14, and the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of 84 to 96 degrees. Preferably, the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 respectively form an angle of 45 degrees with the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14, and the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of 90 degrees.

[0073] The following is a comparative analysis of the absorption properties of the above four samples from the perspective of the range of the absorbed spectrum, the absorption spectra at different incident angles, and the absorption spectra at different polarization angles.

[0074] Fig. 9 is the transmission spectrum of the sample 10 in the ultraviolet (UV)-near infrared (NIR) wavelength range. Fig. 9 It can be seen that the transmittance of sample 10 is very high, which leads to its low absorptivity. The reason is that the structure of sample 10 is too sparse, the number and size of pores are large, and more light passes through the pores of sample 10, resulting in sample 10 having a strong light transmittance of up to 2.6%, but the light absorptivity is very low.

[0075] Fig.10 is the reflection spectrum of the sample 30 in the ultraviolet (UV)-near infrared (NIR) wavelength range. Fig.10 It can be seen that the reflectivity of sample 3 30 is very high, up to 3.3%, which leads to a low absorption rate. The reason is that the structure of sample 3 30 is too compact and dense. When light irradiates sample 3 30, more light is reflected by sample 3 30, resulting in sample 3 30 having a strong light reflectivity, but a low light absorption rate. In addition, the absorption rate of sample 2 20 is also very low.

[0076] Furthermore, the light transmittance and reflectance of the sample 40 were measured using two independent optical measurement systems. Fig.11 and Fig.12 They are respectively the transmission spectrum and reflection spectrum of sample 40 in the ultraviolet (UV) to near infrared (NIR) wavelength range, that is, in the wavelength range of 250 nanometers (nm) to 2 micrometers (μm). Fig.13This is a spectrum measured in the UV to NIR wavelength range using a spectrophotometer equipped with an integrating sphere. The inset is an enlarged view of the high absorption region. Figures 11 to 13 It can be seen that the absorptivity of sample 40 in the UV to NIR wavelength range (250 nm to 2 μm) is greater than or equal to 98.85%.

[0077] Fig.14 and Fig.15 They are respectively the transmission spectrum and reflection spectrum of sample 40 measured in the mid-infrared (MIR) wavelength range (2μm~20μm). Fig.16 The figure is a spectrum measured by Fourier transform infrared (FTIR) spectrometer in the MIR wavelength range, and the inset is a magnified view of the high absorption region. Figures 14 to 16 It can be seen that the absorption rate of sample 40 in the MIR wavelength range (2μm~20μm) is greater than or equal to 98.975%.

[0078] Fig.17 is a spectrum of the sample 440 measured in the visible to NIR wavelength range when the incident angle is 0° to 60°, where the incident angle refers to the angle between the light and the normal line, and the normal line is perpendicular to the surface of the sample 440. That is, in the sample 440, the length extension direction of the carbon nanotubes is parallel to the surface of the sample 440, and the angle between the light and the normal line when the light irradiates the surface of the sample 440 is the incident angle. Fig.17 It can be seen that within the wavelength range of 250nm to 2μm, the absorptivity of sample 440 remains stable and has nothing to do with the incident angle of light, and the lowest absorptivity among all incident angles is greater than 98%. Therefore, sample 440 can achieve omnidirectional absorption within the wavelength range of 250nm to 2μm from visible light to NIR. The "omnidirectional absorption" means that sample 440 has a high absorptivity at all incident angles.

[0079] Fig.18 4 is a spectrum of the sample 40 measured in the mid-infrared wavelength range when the incident angle is 0° to 60°. Fig.18 It can be seen that within the wavelength range of 2μm to 20μm, the absorptivity of sample 40 remains stable, regardless of the incident angle of light, and the lowest absorptivity among all incident angles is greater than 98.5%. Therefore, sample 40 can also achieve omnidirectional absorption within the mid-infrared wavelength range of 2μm to 20μm.

[0080] Fig.19 4 is a spectrum of the sample 40 measured in the visible light-infrared wavelength range when the incident polarization degree is 0° to 90°. Fig.19It can be seen that the absorption spectrum is almost the same regardless of the polarization of the incident light. Therefore, the absorption of sample 40 in the visible to NIR wavelength range of 250nm to 2μm is independent of the polarization of light.

[0081] Fig. 20 4 is a spectrum of the sample 40 measured in the mid-infrared wavelength range when the incident polarization degree is 0° to 90°. Fig. 20 It can be seen that the absorption spectrum is almost the same regardless of the polarization of the incident light. Therefore, the absorption of sample 40 in the mid-infrared wavelength range of 2μm to 20μm is also independent of the polarization of light.

[0082] Depend on Figure 11-Figure 20 The test results show that the absorption of sample 440 in the ultraviolet to mid-infrared wavelength range (250nm to 20μm) is independent of the incident angle and polarization of light. Therefore, for the absorption of light in the ultraviolet to mid-infrared wavelength range (250nm to 20μm), sample 440 has omnidirectional performance and is independent of polarization.

[0083] In addition, the inventors found that in the sample 410, the second layer of carbon nanotube film 14 is exchanged with the first layer of carbon nanotube film 12, or with the third layer of carbon nanotube film 16, and the absorption performance of the sample 410 is not affected. That is, in the sample 410, the second layer of carbon nanotube film 14, the first layer of carbon nanotube film 12 and the third layer of carbon nanotube film 16 are stacked in sequence; the first layer of carbon nanotube film 12 is located between the second layer of carbon nanotube film 14 and the third layer of carbon nanotube film 16; the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14 form an angle of 42 degrees to 48 degrees, and the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of 42 degrees to 48 degrees. The length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of 84 to 96 degrees. Preferably, the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14 form an angle of 45 degrees, the length extension direction of the carbon nanotubes in the second layer of carbon nanotube film 14 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of 45 degrees, and the length extension direction of the carbon nanotubes in the first layer of carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third layer of carbon nanotube film 16 form an angle of 90 degrees.

[0084] The absorption rate of sample 10 is relatively low, which may be because the two layers of carbon nanotube films in sample 10 are cross-stacked, the carbon nanotubes are sparse, and most of the light passes through the gaps between the sparse carbon nanotubes in sample 10. Therefore, the transmittance of sample 10 is relatively high, while the absorption rate is relatively low.

[0085] In the sample three 30, four layers of carbon nanotube film are stacked in a "M" shape. As the number of carbon nanotube film layers increases, the gaps between the carbon nanotubes gradually decrease, and the transmittance decreases. However, since the carbon nanotubes are relatively dense, more reflections will be caused at the interface between the air and the carbon nanotubes, and most of the light will be reflected. Therefore, the reflectivity of the sample three 30 is higher, while the absorptivity is also lower.

[0086] Therefore, as an infrared absorber, compared with the stacked two-layer carbon nanotube film (the sample 10) and the four-layer carbon nanotube film (the sample 3 30), the stacked three-layer carbon nanotube film has a higher absorption rate. Further, the inventors found that when the two layers of carbon nanotube film are almost vertically crossed, and the remaining layer of carbon nanotube film is almost at a 45-degree angle with the two layers of carbon nanotube film (the sample 4 40), it has a higher absorption rate, almost up to 99%, and has omnidirectional absorption performance, and its absorption rate is independent of the polarization of infrared light. However, when the length extension direction of the carbon nanotubes in the adjacent carbon nanotube films forms an angle of about 60 degrees (the sample 2 20), there is no such effect.

[0087] See also Fig. 22 The second embodiment of the present invention provides an infrared detector 100, which includes an infrared light absorber 110, a pyroelectric element 112 and an electrical signal detector 114. The infrared light absorber 110 is disposed on the pyroelectric element 112 and is disposed in direct contact with the pyroelectric element 112. When the pyroelectric element 112 and the infrared light absorber 110 are stacked, the length extension direction of the carbon nanotubes in the infrared light absorber 110 is parallel to the contact surface between the pyroelectric element 112 and the infrared light absorber 110. The electrical signal detector 114 is electrically connected to the pyroelectric element 112 through a wire, and the electrical signal detector 114 and the pyroelectric element 112 are connected in series to form a loop for detecting changes in electrical signals of the pyroelectric element 112.

[0088] The infrared light absorber 110 is a carbon nanotube structure having the same structure as the sample 40, that is, the infrared light absorber 110 is formed by stacking a first layer of carbon nanotube film 12, a second layer of carbon nanotube film 14, and a third layer of carbon nanotube film 16 in sequence. The first layer of carbon nanotube film 12, the second layer of carbon nanotube film 14, and the third layer of carbon nanotube film 16 each include a plurality of carbon nanotubes connected end to end in the extension direction of the carbon nanotubes and extending in the same direction. The second layer of carbon nanotube film 14 is located between the first layer of carbon nanotube film 12 and the third layer of carbon nanotube film 16, and the first layer of carbon nanotube film 12 and the third layer of carbon nanotube film 16 are in direct contact with the second layer of carbon nanotube film 14. The length extension direction of the carbon nanotubes in the first carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the second carbon nanotube film 14 form an angle of 42 to 48 degrees, and the length extension direction of the carbon nanotubes in the second carbon nanotube film 14 and the length extension direction of the carbon nanotubes in the third carbon nanotube film 16 form an angle of 42 to 48 degrees. The length extension direction of the carbon nanotubes in the first carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third carbon nanotube film 16 form an angle of 84 to 96 degrees. Preferably, the length extension direction of the carbon nanotubes in the first carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the second carbon nanotube film 14 form an angle of 45 degrees, the length extension direction of the carbon nanotubes in the second carbon nanotube film 14 and the length extension direction of the carbon nanotubes in the third carbon nanotube film 16 form an angle of 45 degrees, and the length extension direction of the carbon nanotubes in the first carbon nanotube film 12 and the length extension direction of the carbon nanotubes in the third carbon nanotube film 16 form an angle of 90 degrees. The first carbon nanotube film 12, the second carbon nanotube film 14 and the third carbon nanotube film 16 are all self-supporting structures, so the infrared light absorber 110 is also a self-supporting structure. The multiple carbon nanotubes in the infrared light absorber 110 are parallel to the surface of the thermoelectric element 112.

[0089] The infrared light absorber 110 increases its temperature after absorbing infrared light, and because the thermal conductivity of carbon nanotubes is high, the infrared light absorber 110 can transfer heat to the thermoelectric element 112. When the thermoelectric element 112 absorbs heat, the temperature of the thermoelectric element 112 increases, causing the electrical properties of the thermoelectric element 112 to change.

[0090] The thermoelectric element 112 may be a pyroelectric element, a thermistor, or a thermocouple element. Specifically, the pyroelectric element is a material with a high thermoelectric coefficient, such as lead zirconate titanate ceramics, lithium tantalate, lithium niobate, triglycan titanium sulfate, etc. The thermistor may be a semiconductor thermistor, a metal thermistor, an alloy thermistor, etc. In this embodiment, the thermoelectric element 112 is a lead zirconate titanate ceramics.

[0091] Since the electric signal detector 114 is used to detect the change of the electric signal of the thermoelectric element 112, the type of the electric signal detector 114 varies according to the thermoelectric element 112. In one embodiment, the thermoelectric element 112 is a pyroelectric element, and the temperature increase of the pyroelectric element causes a voltage to appear at both ends of the pyroelectric element or generates a current. In this case, the electric signal detector 114 can be a current-voltage converter, and the current-voltage converter is connected in series with the pyroelectric element to form a loop, so as to detect the change of the voltage or current of the pyroelectric element. In another embodiment, the thermoelectric element 112 is a thermistor, and the temperature increase of the thermistor changes the resistance. In this case, the electric signal detector 114 includes a power supply and a current detector, and the power supply, the current detector and the thermistor are connected in series to form a loop. The change of the current is measured by the current detector to detect the change of the resistance of the thermistor. In another embodiment, the thermoelectric element 112 is a thermocouple, and the infrared light absorber 110 is set at one end of the thermocouple. A temperature difference occurs at both ends of the thermocouple, that is, a potential difference occurs at both ends of the thermocouple. At this time, the electrical signal detector 114 can be a voltage detector, which is connected in series with the thermocouple to form a loop, and can detect the potential change of the thermocouple.

[0092] The working process of the infrared detector 100 is as follows: infrared light is radiated onto the infrared light absorber 110 (i.e., sample four 40), and the sample four 40 perfectly absorbs the infrared light and converts the absorbed infrared light into heat; the heat is transferred to the thermoelectric element 112; after the thermoelectric element 112 absorbs the heat, the temperature rises, causing the electrical properties of the thermoelectric element 112, such as resistance, current or voltage, to change. When the electrical signal detector 114 is electrically connected to the two ends of the thermoelectric element 112 to form a loop, the electrical signal detector 114 can detect that the electrical signal of the thermoelectric element 112 has changed, thereby detecting the presence of infrared light in the detection area.

[0093] Further, a transparent coating is provided on the infrared light absorber 110. Since the coating is transparent, infrared light can pass through the coating and be absorbed by the infrared absorber 110. Therefore, the coating does not affect the absorptivity of the infrared light absorber 110. The coating can improve the mechanical properties of the infrared light absorber 110 without affecting the absorption effect. The coating is provided on the surface of the carbon nanotube structure. Preferably, the coating is provided on the outer surface of each carbon nanotube. The coating can be a photoresist, a transparent polymer, etc. Preferably, the material of the coating is an ultraviolet photoresist, which can be cured under the irradiation of ultraviolet light. The ultraviolet photoresist can be polyvinyl alcohol cinnamate, a cyclized rubber-based resist, etc. Specifically, the ultraviolet photoresist is deposited on the surface of the carbon nanotube in the infrared light absorber 110, and then the ultraviolet light irradiates the infrared light absorber 110 on which the ultraviolet photoresist is deposited, so that the ultraviolet photoresist layer is closely arranged on the infrared light absorber 110. The effect of the ultraviolet light irradiation is not only to promote the close combination of the infrared light absorber 110 and the ultraviolet photoresist layer, but also to enhance the surface morphology of the carbon nanotube network in the infrared light absorber 110, thereby improving its wear resistance. Fig.23 1 is an optical photograph of an infrared light absorber 110 provided with an ultraviolet photoresist layer being scratched by a cloth, a knife, and sandpaper. Fig.23 It can be seen that no matter it is scratched by a cloth, a knife or sandpaper, the infrared light absorber 110 provided with the ultraviolet photoresist layer has good wear resistance and will not be easily damaged.

[0094] The infrared detector 100 provided in the second embodiment of the present invention has the following advantages: first, the infrared light absorber 110 has a good absorption effect on near-infrared to mid-infrared light with a wavelength of 2μm-20μm, thereby improving the responsiveness and sensitivity of the thermoelectric element 112, so that the infrared detector 100 has higher sensitivity; second, the infrared light absorber 110 not only has omnidirectional absorption performance, but also is independent of polarization, thereby expanding the scope of use of the infrared detector 100.

[0095] See also Fig.24 The third embodiment of the present invention provides an infrared imager 200, which includes an infrared receiver 210, an infrared detector assembly 220, a signal processor 230 and an infrared image display 240. The infrared receiver 210 is used to receive the infrared radiation spectrum and transmit the infrared light to the infrared detector assembly 220; the infrared detector assembly 220 is used to convert the infrared radiation spectrum into an electrical signal and transmit the electrical signal to the signal processor 230; the signal processor 230 is used to process and calculate the electrical signal to obtain thermal field distribution data; the infrared image display 240 displays an infrared thermal image according to the thermal field distribution data.

[0096] The infrared receiver 210 is used to receive the infrared radiation spectrum emitted by the object, that is, the infrared light emitted by the object. Further, the infrared receiver 210 can also converge the infrared radiation spectrum. In this embodiment, the infrared receiver 210 is an infrared lens. Specifically, the infrared radiation spectrum emitted by the object is directly transmitted to the infrared detector assembly 220 after being received and converged by the infrared lens. It can be understood that the infrared receiver 210 can also be omitted.

[0097] The infrared detector assembly 220 includes a plurality of infrared detectors 100 in the second embodiment, which are evenly distributed in a two-dimensional array, and each infrared detector 100 can convert the infrared radiation spectrum into an electrical signal change. It can be understood that each infrared detector 100 is equivalent to a pixel point, and each infrared detector 100 converts the infrared radiation spectrum at its location into an electrical signal, thereby realizing the infrared detector assembly 220 to detect the infrared radiation spectrum emitted by the object. The spacing between any two adjacent infrared detectors 100 can be selected according to the resolution requirements of thermal imaging.

[0098] The signal processor 230 is used to process and calculate the electrical signal of each infrared detector 100, so as to obtain the thermal field distribution of the object. Specifically, the signal processor 230 calculates the temperature data of the corresponding surface position of the object according to the change of the electrical signal of each infrared detector 100. That is, the signal processor 230 can calculate the thermal field distribution data of the object according to the electrical signal.

[0099] The infrared image display 240 is used to display the infrared thermal image of the object under test. The infrared thermal image of the infrared image display 240 is displayed according to the thermal field distribution data of the object, and different temperatures are displayed in different colors. Therefore, the infrared thermal image displayed by the infrared image display 240 corresponds to the temperature distribution of the object and is used to reflect the temperature conditions of various positions of the object. For example, when the infrared imager 200 is used in the medical field, the whole body thermal imaging of the human body can be performed, and professional doctors can judge the nature of the disease and the degree of the lesion in different parts of the human body based on the thermal image, providing a basis for clinical diagnosis.

[0100] When the infrared imager 200 is working, the infrared light emitted by the object is received by the infrared receiver 210; after the infrared receiver 210 receives and converges the infrared light, it transmits the infrared light to the infrared detector assembly 220; the infrared detector assembly 220 converts the infrared light into an electrical signal, and then transmits the electrical signal to the signal processor 230; the signal processor 230 processes and calculates the electrical signal to obtain the temperature data of each position of the object, that is, the thermal field distribution data of the object; the infrared image display 240 then displays the infrared thermal image of the object according to the calculated thermal field distribution data.

[0101] The infrared imager 200 provided in the third embodiment of the present invention has the following advantages: first, the infrared light absorber 110 has a good absorption effect on near-infrared to mid-infrared light with a wavelength of 2μm-20μm, thereby improving the responsiveness and sensitivity of the thermoelectric element 112, so that the infrared imager 200 has higher sensitivity; second, the infrared light absorber 110 not only has omnidirectional absorption performance, but also is independent of polarization, thereby expanding the scope of use of the infrared imager 200.

[0102] See also Fig.25 The fourth embodiment of the present invention provides an infrared stealth fabric 300, which includes a fabric substrate 310 and the infrared light absorber 110 disposed on the fabric substrate 310. The infrared light absorber 110 is the sample 40. The infrared light absorber 110 can also be disposed between two fabric substrates 310 to form a sandwich structure. The plurality of carbon nanotubes are parallel to the infrared light absorber 110 and close to the surface of the fabric substrate 310.

[0103] The infrared light absorber 110 can be directly disposed on the fabric substrate 310, or fixed on the fabric substrate 310 by an adhesive. In this embodiment, after the infrared light absorber 110 is directly disposed on the fabric substrate 310, the infrared light absorber 110 and the fabric substrate 310 are wetted or soaked with an organic solvent, and the surface tension generated by the volatilization of the organic solvent is used to tightly combine the infrared light absorber 110 with the fabric substrate 310. The material of the organic solvent is not limited, as long as it is volatile and does not dissolve the fabric substrate 310. In this embodiment, the organic solvent is ethanol. Preferably, the fabric substrate 310 has a through hole, so that the infrared light absorber 110 is suspended on the fabric substrate 310. The material of the fabric substrate 310 is not limited, and it can be an insulating material, a conductor, a flexible material, or a non-flexible material. In this embodiment, the material of the fabric substrate 310 is not limited, such as cotton, polyester, silk, woolen cloth, linen, leather, etc. In another embodiment, the infrared light absorber 110 is sewn between two layers of cloth.

[0104] Fig.26 This is an optical photo of the stealth effect test of the infrared stealth fabric 300. Fig. 27 This is a thermal image captured by an infrared thermal imager of a hand covered with infrared stealth cloth 300. Fig.26 and Fig. 27 It can be seen that when the infrared stealth cloth 300 covers the hand, the infrared emitted by the hand is absorbed by the infrared stealth cloth 300 and will not pass through the infrared stealth cloth 300 to be detected by other infrared detection systems. Therefore, the infrared stealth cloth 300 has a good stealth effect.

[0105] See also Fig.28 The fifth embodiment of the present invention provides an infrared invisible clothing 400, which is at least partially made of the infrared invisible fabric 300. That is, the infrared invisible clothing 400 can be made entirely of the infrared invisible fabric 300, or partially of the infrared invisible fabric 300. The infrared invisible clothing 400 is not limited to clothing, and can be gloves, masks, etc. These clothes, gloves, and masks can be collectively referred to as infrared invisible clothing. The infrared invisible clothing includes a clothing body, at least part of which is made of the infrared invisible fabric 300.

[0106] The infrared stealth fabric 300 provided in the fourth embodiment of the present invention and the infrared stealth clothing 400 provided in the fifth embodiment have the following advantages: first, the infrared light absorber 110 has a good absorption effect on near-infrared to mid-infrared light with a wavelength of 2μm-20μm, thereby improving the stealth effect of the infrared stealth fabric 300 and the infrared stealth clothing 400; second, the infrared light absorber 110 not only has omnidirectional absorption performance, but is also independent of polarization, thereby expanding the use range of the infrared stealth fabric 300 and the infrared stealth clothing 400 and further improving their stealth effects.

[0107] In addition, those skilled in the art may also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included in the scope of protection required by the present invention.

Claims

1. An infrared detector, comprising: an infrared light absorber for absorbing infrared light and converting the infrared light into heat; a thermoelectric element, on which the infrared light absorber is disposed; an electrical signal detector for detecting changes in electrical properties of the thermoelectric element; It is characterized in that the infrared light absorber includes a carbon nanotube structure, which includes a first layer of carbon nanotube film, a second layer of carbon nanotube film and a third layer of carbon nanotube film. The first layer of carbon nanotube film, the second layer of carbon nanotube film and the third layer of carbon nanotube film are stacked, and each of the first layer of carbon nanotube film, the second layer of carbon nanotube film and the third layer of carbon nanotube film includes a plurality of carbon nanotubes connected end to end in the extension direction of the carbon nanotubes and extending basically in the same direction. The extension directions of the carbon nanotubes in the first layer of carbon nanotube film and the second layer of carbon nanotube film form an angle of 42 degrees to 48 degrees, the extension directions of the carbon nanotubes in the second layer of carbon nanotube film and the third layer of carbon nanotube film form an angle of 42 degrees to 48 degrees, and the extension directions of the carbon nanotubes in the first layer of carbon nanotube film and the third layer of carbon nanotube film form an angle of 84 degrees to 96 degrees.

2. The infrared detector according to claim 1, characterized in that: The thermoelectric element and the infrared light absorber are stacked and contacted with each other, and the extension direction of the carbon nanotubes is parallel to the contact surface between the thermoelectric element and the infrared light absorber.

3. The infrared detector according to claim 1, characterized in that: The extension directions of the carbon nanotubes in the first layer of carbon nanotube drawn film and the second layer of carbon nanotube drawn film form an angle of 45 degrees.

4. The infrared detector according to claim 1, characterized in that: The infrared light absorber further includes a transparent coating layer, which is arranged on the surface of the carbon nanotube structure.

5. The infrared detector according to claim 1, characterized in that: The thermoelectric element is one or more of a pyroelectric element, a thermistor and a thermocouple.

6. The infrared detector according to claim 1, characterized in that: The thermoelectric element is a pyroelectric element, and the electric signal detector is a current-voltage converter.

7. The infrared detector according to claim 1, characterized in that: The thermoelectric element is a thermistor, and the electrical signal detector includes a power supply and a current detector. The electrical signal detector is used to detect the resistance change of the thermoelectric element.

8. The infrared detector according to claim 1, characterized in that: The thermoelectric element is a thermocouple, and the electrical signal detector is a voltage detector, which is used to detect the potential change of the thermoelectric element.

9. The infrared detector according to claim 1, characterized in that: The infrared light absorber has an absorptivity greater than or equal to 98.85% in a wavelength range of 250 nm to 2 μm, and an absorptivity greater than or equal to 98.975% in a wavelength range of 2 μm to 20 μm.

10. An infrared imager, comprising: An infrared detector assembly, used to convert infrared light into electrical signals; A signal processor, used for processing and calculating the electrical signal to obtain thermal field distribution data; An infrared image display, used for displaying an infrared thermal image according to the thermal field distribution data; It is characterized in that the infrared detector assembly includes a plurality of infrared detectors distributed in an array, and each infrared detector is the infrared detector described in any one of claims 1-9.

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