CN116539162A - Near-field thermal radiation measurement system and measurement method based on all-optical method - Google Patents
Near-field thermal radiation measurement system and measurement method based on all-optical method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/06—Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity
- G01J5/061—Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/48—Thermography; Techniques using wholly visual means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/90—Testing, inspecting or checking operation of radiation pyrometers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/06—Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity
- G01J5/061—Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
- G01J2005/063—Heating; Thermostating
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Abstract
The invention discloses a near-field thermal radiation measurement system and a measurement method based on an all-optical method, wherein the near-field thermal radiation measurement system comprises the following steps: the device comprises a radiator, a receiver, a heat sink substrate, a spacer, a vacuum chamber, a laser and a thermal imaging module. The radiator and the receiver are samples to be measured, the size and the material of the radiator and the receiver are determined according to the requirements, the distance requirement is measured by forming a spacer through a nano structure, the radiator is heated by a laser light source through the combination of laser heating and an infrared thermal imaging technology, the temperature monitoring of the transient state and the high resolution of the measured object is realized by utilizing a thermal imaging module, and the heat dissipation process of the radiator is analyzed, so that the real-time near-field thermal radiation value is obtained. The invention has no any electric elements such as electrodes, leads and the like, avoids the Joule heating effect and heat dissipation by additional heat conduction, simplifies the measuring method of near-field heat radiation, and solves the practical problems of overlong measuring time, low repeatability of measuring results, inadvisable to small measuring samples and the like in the traditional mode.
Description
Technical Field
The invention belongs to the field of near-field optics and heat radiation heat transfer, and particularly relates to a near-field heat radiation measurement system and a measurement method based on an all-optical method.
Background
All objects in nature above absolute zero inevitably generate spontaneous radiation electromagnetic waves to the periphery, and the upper limit of far-field radiation intensity is generally determined by the Spanish-Boltzmann law of a blackbody, which is called blackbody radiation limit. Near field thermal radiation (Near-field radiative heat transfer, NFRHT for short) is a radiation phenomenon that occurs when the distance between a radiator and a receiver is smaller than the characteristic wavelength of radiation (at room temperature, the wavelength is about 10 microns), and the radiation intensity of the Near field thermal radiation can break through the blackbody radiation limit by several orders of magnitude, so that the classical radiation theory using the transmission wave as the dominant is not applicable any more. In near-field thermal radiation, tunneling effect of evanescent waves at extremely small intervals gradually takes the dominant role of thermal radiation, and local state density of photons is very high in the near field, so that a large amount of heat energy is transferred from a radiator to a receiver through radiation of thermal photons.
Therefore, compared with far-field radiation, the near-field radiation has important potential and significance in aspects of micro-nano system thermal management systems, thermal photovoltaic systems, thermal logic elements and the like. Experimental measurements for near field thermal radiation are even more indispensable. However, the conventional near-field thermal radiation measurement method is generally based on electrical measurement, and because the electrical components inevitably bring about joule heating effect of current and heat dissipation of additional heat conduction, the reliability and repeatability of the measurement are both somewhat disjointed from the requirements of the physical exploration of the preamble, and the cost is high, and the key components still depend on import, so that a low-cost transient and accurate near-field thermal radiation measurement method is very needed.
Disclosure of Invention
The laser heating and the infrared thermal imaging technology are combined, the laser light source is used for heating the radiator, the control of the initial temperature of the radiator can be realized, and the infrared thermal imager and the infrared lens are used for realizing the transient state and high-resolution temperature monitoring of the measured object, so that a real-time temperature change curve is obtained. Through the fitting analysis of the temperature drop curve, the near-field heat radiation heat flow value between flat objects can be obtained with higher precision, and meanwhile, the method has the advantages of high robustness, simple structure, low cost, high precision and the like, and is insensitive to sample materials, structures and radiation intervals. Therefore, the design of a near-field thermal radiation measurement system based on the all-optical method provides a very effective solution to the current problems.
In order to solve the technical problems, the invention firstly provides a near-field thermal radiation measurement system based on an all-optical method, which comprises a heat sink substrate, a receiver processed by a material to be measured, a radiator processed by the material to be measured, a spacer, a laser, a thermal imaging module and a vacuum chamber;
the vacuum chamber is used for providing a vacuum environment, the top of the vacuum chamber is provided with a window, the radiator, the receiver, the heat sink substrate and the spacer are placed in the vacuum chamber, and the heat sink substrate is adhered to the upper surface of the bottom of the vacuum chamber through heat conducting glue; the lower surface of the receiver is adhered to the upper surface of the heat sink substrate, and the heat sink substrate and the vacuum chamber are made of heat conducting materials, so that the receiver and the external environment temperature of the vacuum chamber are in common temperature; the spacer is of a columnar structure and is arranged on the upper surface of the receiving body; placing the radiator on a spacer; the radiator is parallel to the surface of the receiver, and the size of the radiator is smaller than that of the receiver; the laser and the thermal imaging module are arranged outside the vacuum chamber; the laser is used for heating the radiator; the thermal imaging module is used for recording the temperature change of the radiator.
As a preferred embodiment of the invention, the surface of the radiator and the surface of the receiver are polished in nanometer order to ensure that the radiator is parallel to the surface of the receiver, and the radiator is smaller than the receiver in size.
As a preferable scheme of the invention, the vacuum chamber provides vacuum degree smaller than 10 -4 Vacuum environment of Pa.
As a preferable scheme of the invention, the thermal imaging module comprises a thermal imager and an infrared micro-distance lens.
The invention also provides a near-field thermal radiation measurement method based on the measurement system, which comprises the following steps:
1) The method comprises the steps of processing a to-be-detected material to obtain a receiver and a radiator, and carrying out nanoscale polishing on the surfaces of the radiator and the receiver to ensure that the radiator is parallel to the surface of the receiver, wherein the size of the radiator is smaller than that of the receiver;
2) Adhering a heat sink substrate to the upper surface of the bottom of the vacuum chamber through heat-conducting glue, and adhering the lower surface of the receiver to the upper surface of the heat sink substrate;
3) Manufacturing a spacer on the upper surface of the receiver by adopting a photoetching process, wherein the spacer is used for supporting the radiator;
4) Spraying black body paint on the upper surface of the radiator, and placing the radiator on the spacer;
5) Starting a laser, and transmitting laser to the radiator through a window of the vacuum chamber by the laser to stably heat the radiator until the radiator reaches a thermal steady state; closing the laser, recording the temperature and time change of the radiator in the cooling process by using the thermal imaging module, and importing data into a computer to obtain a cooling curve;
6) And analyzing the cooling curve by using an energy conservation theorem to obtain near-field thermal radiation measurement results of the material to be measured under different temperature differences.
In the step 2), spacers having a thickness of 50-500 nm are formed on the upper surface of the receiving body, and the spacers are epoxy resin.
As a preferable scheme of the invention, in the step 4), the radiator is placed on the spacer, and the contact area of the radiator and the spacer is the heat conduction area, which is marked as A C Let the radiator temperature be T 1 The temperature of the receiver is T 2 Then the heat of conduction Q through the spacer support structure C The method comprises the following steps:
Q C ＝A C ×k(T 1 -T 2 )/d
where k is the spacer equivalent thermal conductivity, as determined by the spacer material parameters.
In the step 4), the laser emitted by the laser is normally incident to the upper surface of the radiator through the vacuum chamber window, and the radiator can be heated for 3-5 minutes to reach a thermal steady state; the laser is limited to beam expansion, collimation and focusing processes, and a light spot with proper size is obtained on the radiator, so that only the radiator is directly heated.
In the step 5), the heat power lost by the radiator is equal to the heat conduction Q through the spacer at the same time according to the law of conservation of energy C Far field radiation Q of radiator F And near field radiation Q of the radiator and the receiver N The sum of the energy powers; in the cooling process, the heat quantity of the radiator changes Q along with the time t T (t) writing:
Q T (t)＝cm dT 1 /dt
wherein c and m are the specific heat capacity and mass of the radiator, dT 1 The dt is the instantaneous temperature change of the radiator, and is recorded by a thermal imager;
a far-field radiation channel is arranged between the radiator and the surrounding environment cavity, and the far-field radiation energy Q of the far-field radiation channel F Writing:
wherein A is F Is the far field radiating area, e is the equivalent emissivity, determined by the emissivity of the cavity environment and the emissivity of the radiator, σ is the spandex-boltzmann constant;
the measurement of the near field thermal radiation between the radiator and the receiver is obtained by analyzing the real-time energy conservation process of the radiator, i.e. the near field thermal radiation measurement is obtained by:
Q N ＝Q T -Q C -Q F 。
compared with the prior art, the invention has the following beneficial effects:
the device disclosed by the invention has no any electrical components such as electrodes and leads, a complex system is converted into a simple system on the premise of ensuring the accuracy of experimental results, and the heat dissipation process of the radiator is analyzed, so that the purpose of near-field thermal radiation measurement is achieved, and the practical problems that the measurement time is too long, the repeatability of the measurement results is not high, the measurement sample is not suitable to be too small and the like are solved.
The radiator and the receiver in the device are arranged in a vacuum cavity, and the laser and the thermal imager are arranged outside the cavity and record the ambient temperature and the cavity temperature. The radiator and the receiver in the vacuum cavity avoid any unnecessary contact so as to reduce the influence of heat conduction. The thermal imager can detect the temperature change of the radiator with the size of tens of micrometers to several centimeters through the infrared window of the vacuum cavity and the micro-distance lens with proper focal length. Because the test time is much faster than the traditional electrical measurement, the measurement can be repeated for many times within a certain time, and the influence of environmental temperature drift and background noise can be avoided.
The device can obtain the near-field heat radiation value between the radiator and the receiver by measuring the temperature reduction process or the temperature rising process of the radiator or the heat steady-state process under the condition of laser heating.
Drawings
FIG. 1 is a schematic top view of a design of a near-field heat radiation apparatus based on a plenoptic method; the relative size of the spacers 4 is subjected to an enlargement process.
FIG. 2 is a schematic diagram of a design cross-section of a near-field thermal radiation device and a schematic diagram of a laser and a thermal imager based on an all-optical measurement; the schematic here only shows that the laser and the thermal imaging module are outside the vacuum chamber, and the relative positions of the laser and the radiator are required to be set according to measurement requirements; the relative size of the spacers is amplified.
FIG. 3 is an equivalent thermal flow diagram of a system, Q T 、Q F 、Q N 、Q C The heat flows are respectively heat flows dissipated by the radiator, far-field radiation heat flows, near-field radiation heat flows and heat conduction heat flows; t (T) 1 、T 2 Is the temperature of the radiator and the receiver; the heat sink is the end point of heat dissipation.
Reference numerals illustrate: 1. a heat sink; 2. a receiver 3 and a radiator; 4. a spacer; 5. a laser; 6. a thermal imaging module; 7. a vacuum chamber.
Detailed Description
The invention is further illustrated and described below in connection with specific embodiments. The described embodiments are merely exemplary of the present disclosure and do not limit the scope. The technical features of the embodiments of the invention can be combined correspondingly on the premise of no mutual conflict.
The invention aims to provide a design method of a near-field thermal radiation measurement system based on an all-optical method. According to the design of the near-field thermal radiation measurement system to be realized, the radiator and the receiver are samples to be measured, the size and the material of the radiator and the receiver are determined according to the requirements, the distance measurement requirement is realized by forming a spacer through a nano structure, and then the radiation heat flow transient accurate measurement is realized by combining a laser heating technology and an infrared thermal imaging technology.
As shown in fig. 1 and 2, a near-field thermal radiation measurement system based on an all-optical method of the present invention includes: a radiator 3, a receiver 2, a heatsink substrate 1, a spacer 4, a laser 5, a thermal imaging module 6, and a vacuum chamber 7.
In this embodiment, the sample to be measured is placed in the vacuum chamber 7, and the vacuum chamber 7 provides a vacuum degree of less than 10 -4 The vacuum environment of Pa makes the influence of air heat transfer negligible.
In this embodiment, the heat sink substrate 1 may be a copper block with a larger volume, the upper surface of the heat sink substrate 1 is fully contacted and fixed with the receiving body through the heat-conducting glue, and the lower surface is fully contacted and fixed with the vacuum chamber body. The heat transferred by the radiator 3 can be rapidly and uniformly dissipated in the heatsink substrate 1 and the temperature variation of the receiver is made negligible.
The spacers 4 are formed on the upper surface of the receiving body. The spacer with the thickness d can be formed by using a photoresist structure after development and curing, wherein the main component is epoxy resin or a structure formed by a vapor deposition method and dry/wet etching. The spacers 4 are arranged to provide a stable support, for example in a centrally symmetrical pattern. Since the near field thermal radiation intermediate distance plays a critical role, the thickness of the spacer 4 can be controlled within tens of nanometers by the specific formulation.
The radiator 3 is placed between by gravityOn the spacer 4, the contact area of the radiator 3 and the spacer 4 is the heat conduction area, denoted as A C Let the radiator temperature be T 1 The acceptor temperature is T 2 Then the heat of conduction Q through the spacer support structure C The method comprises the following steps:
Q C ＝A C ×k(T 1 -T 2 )/d ①
where k is the spacer equivalent thermal conductivity, as determined by the spacer material parameters. The thermal conductivity of the spacers should be as small as possible for accuracy of the results.
The radiator 3 and the receptor 2 are wafers with surface polished in nanometer level, and the surface roughness and the platelet warpage within 100 nanometers are used for ensuring that the radiator is parallel to the surface of the receptor. The surface roughness and warpage can be detected using a white light interferometer. The radiator 3 should be smaller in size than the receptor 2 to ensure that the effective area of the near field radiation is accurately determinable.
In one embodiment of the invention, the upper surface of the radiator 3 is coated with black body paint, which on the one hand absorbs the heating light of the laser light source and on the other hand, due to the known emissivity, facilitates the detection of temperature by the thermal imaging module.
In one embodiment of the invention, the radiator 3 and the receiver 2 are placed in a vacuum chamber, and the laser 5 and the thermal imaging module 6 are outside the vacuum chamber 7, recording the ambient temperature and the chamber temperature. The radiator 3 and the receiving body 2 in the vacuum chamber 7 avoid any unnecessary contact to reduce the influence of heat conduction.
In one embodiment of the invention, the laser light from the tunable power laser is normally incident on the upper surface of the radiator through the vacuum chamber window, and the radiator is heated to a thermal steady state in typically 3-5 minutes. The laser may be subjected to, but is not limited to, beam expansion, collimation, focusing, etc. to obtain a spot of a suitable size on the sample such that only the emitter is directly heated. The near-field thermal radiation value between the radiator and the receiver can be obtained by measuring the temperature reduction process or the temperature rise process of the radiator or the thermal steady state process under the condition of laser heating. This embodiment utilizes a videocordable, suitable frame rate, high resolution thermal imager product as a system for monitoring the real-time temperature of the radiator.
In one embodiment of the invention, the thermal imager can detect temperature changes in the size of tens of microns to centimeters of the radiator through the infrared window of the vacuum chamber and the appropriately focused macro lens. The radiator has huge heat capacity difference with the receiving body and the heat sink, and the temperature change of the receiving body and the heat sink is negligible in a certain temperature difference range.
In one embodiment of the invention, the above mentioned heat transfer channels via the spacers are removed during measurement, and there is also a far field radiation channel between the radiator and the surrounding cavity. Its far field radiant energy Q F Writing:
wherein A is F Is the far field radiating area, e is the equivalent emissivity, determined by the emissivity of the cavity environment and the emissivity of the radiator, σ is the spandex-boltzmann constant. The temperature of the cavity is the same as that of the receiving body, so the temperature of the cavity is also T 2 And (3) representing.
The measurement of the near field thermal radiation between the radiator and the receiver is obtained by analyzing the real-time energy conservation process of the radiator. In the embodiment of the cooling process, the heat of the radiator changes Q with time t T (t) can be written as:
Q T (t)＝cm dT 1 /dt ③
wherein c and m are the specific heat capacity and mass of the radiator, dT 1 The value of/dt is the instantaneous temperature change of the radiator, which is recorded by a thermal imager. According to the law of conservation of energy, at the same time, the heat power lost by the radiator is equal to the heat conduction Q through the spacer C Far field radiation Q of radiator F And near field radiation Q of the radiator and the receiver N The sum of the energy and power is shown in figure 3. Thus Q N Writing:
Q N ＝Q T -Q C -Q F ④
in one embodiment of the invention, the comprehensive influence of heat conduction, far-field radiation and near-field radiation is required to be analyzed in real time, the switch and the power of the laser can be controlled by software, the time-dependent temperature change process of the radiator is analyzed, and then the near-field heat radiation value can be obtained by calculating the heat change, the conduction and the far-field radiation change of the radiator. In one complete measurement, different radiator temperatures correspond to different moments, theoretical values of near-field heat radiation can be obtained by a heat fluctuation theory, and the accuracy and the practicability of the invention are further verified under mutual verification of the theory and the experiment.
For this embodiment, the near field thermal radiation formula between semi-infinite plates is used:
wherein A is N ，ω，H(ω，d)，ζ l (ω，k || )，r l ，k || ，k 0 ，k z0 Is near field radiation area, frequency, heat transmission spectrum, transmission coefficient of radiator and receiver, fresnel reflection coefficient, in-plane wave vector, vacuum wave vector and normal vacuum wave vector; im is a mathematical operator taking the imaginary part, e is a natural constant, and i is an imaginary unit. The average energy of the Planck resonator is written as:
k B and T is an reduced Planck constant, a Boltzmann constant, and a temperature. By combining formulas (5) and (6), the theoretical result of the invention can be obtained from known or measured data, and can be well compared with experimental data.
In order to more clearly illustrate the device of the present invention, a detailed description of one measurement of the examples is given below:
first, spacers are fabricated on a receiver substrate. The spacers which are of four cylindrical structures, have the same height and have the height of 50-500 nanometers are manufactured by adopting a photoetching process, and play a role in supporting the space between the radiator and the receiver under the near field;
then, the receiving body substrate is adhered to the copper block heat sink by using the heat conduction adhesive, so that the temperature of the receiving body is the same as the ambient temperature, and the temperature change is ignored in the experimental measurement process; spraying black body paint on the upper surface of the radiator substrate by using a long-focus microscope; placing the radiator substrate on a spacer of the receiver by using a tele microscope, enabling the lower surface to be in contact with the spacer, and fixing the radiator by using gravity; the copper block heat sink, the receiver and the radiator are placed in a vacuum chamber together, and the vacuum chamber is vacuumized by a mechanical pump-molecular pump-ion pump group until the gas pressure reaches 10 -4 Pa and below, so that the vacuum environment reaches the experimental requirement; the laser with adjustable power is connected outside the cavity, and the laser is emitted to the radiator through a window of the vacuum cavity to stably heat the radiator, so that the radiator reaches a thermal steady state; closing the laser, recording the temperature and time change of the radiator in the cooling process by using a thermal imager, and importing data into a computer;
then, analyzing the cooling curve by using the formulas (1) and (4), and obtaining near-field thermal radiation measurement results of the sample to be measured under different temperature differences;
finally, obtaining a near-field heat radiation theoretical result of the sample to be tested based on a heat fluctuation theory by utilizing formulas (5) and (6), comparing the near-field heat radiation theoretical result with an experimental result, and verifying whether the experiment is successfully completed;
in this embodiment, improving the frame rate and temperature sensitivity of the thermal imager can further improve the accuracy of the experiment, for example, using a refrigeration type thermal imager. Meanwhile, as the test time is much faster than that of the traditional electrical measurement, the measurement can be repeated for many times within a certain time, and the influence of environmental temperature drift and background noise can be avoided.
According to the invention, no electrical elements such as electrodes and leads are used, a complex system is converted into a simple system on the premise of ensuring the accuracy of experimental results, and the heat dissipation process of the radiator is analyzed, so that the purpose of near-field thermal radiation measurement is achieved, and the practical problems that the traditional measurement mode is too long in time, the repeatability of the measurement results is not high, the measurement sample is not suitable to be too small and the like are solved.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit of the invention.
Claims (9)
1. The near-field thermal radiation measurement system based on the plenoptic method is characterized by comprising a heat sink substrate (1), a receiver (2) processed by a material to be measured, a radiator (3) processed by the material to be measured, a spacer (4), a laser (5), a thermal imaging module (6) and a vacuum chamber (7);
the vacuum chamber (7) is used for providing a vacuum environment, the top of the vacuum chamber is provided with a window, the radiator (3), the receiver (2), the heat sink substrate (1) and the spacer (4) are placed in the vacuum chamber, and the heat sink substrate (1) is adhered to the upper surface of the bottom of the vacuum chamber through heat conducting glue; the lower surface of the receiving body (2) is adhered to the upper surface of the heat sink substrate (1), and the heat sink substrate (1) and the vacuum chamber are made of heat conducting materials, so that the receiving body (2) and the external environment temperature of the vacuum chamber are in common temperature; the spacer (4) is of a columnar structure, and the spacer (4) is arranged on the upper surface of the receiving body (2); -placing said radiator (3) on a spacer; the radiator is parallel to the surface of the receiver, and the size of the radiator is smaller than that of the receiver; the laser (5) and the thermal imaging module (6) are arranged outside the vacuum chamber (7); the laser (5) is used for heating the radiator (3); the thermal imaging module (6) is used for recording the temperature change of the radiator (3).
2. The near field thermal radiation measurement system of claim 1, wherein the surface of the radiator and the receiver are polished on a nano scale to ensure that the radiator is parallel to the surface of the receiver, the radiator being smaller in size than the receiver.
3. The near field thermal radiation measurement system of claim 1, wherein the vacuum chamber (7) provides a vacuum level of less than 10 -4 Vacuum environment of Pa.
4. The near field thermal radiation measurement system of claim 1, wherein the thermal imaging module (6) comprises a thermal imager and an infrared macro lens.
5. A near field thermal radiation measurement method based on the measurement system of claim 1, comprising the steps of:
1) processing a to-be-detected material to obtain a receiver (2) and a radiator (3), and carrying out nanoscale polishing on the surfaces of the radiator and the receiver to ensure that the radiator is parallel to the surface of the receiver, wherein the size of the radiator is smaller than that of the receiver;
2) Adhering the heat sink substrate (1) to the upper surface of the bottom of the vacuum chamber (7) through heat-conducting glue, and adhering the lower surface of the receiver (2) to the upper surface of the heat sink substrate (1);
3) Manufacturing a spacer (4) on the upper surface of the receiver by adopting a photoetching process, wherein the spacer (4) is used for supporting the radiator;
4) Spraying black body paint on the upper surface of the radiator, and placing the radiator on the spacer;
5) Starting a laser, and emitting laser to the radiator through a window of the vacuum chamber (7) to stably heat the radiator until the radiator reaches a thermal steady state; closing the laser, recording the temperature and time change of the radiator in the cooling process by using the thermal imaging module, and importing data into a computer to obtain a cooling curve;
6) And analyzing the cooling curve by using an energy conservation theorem to obtain near-field thermal radiation measurement results of the material to be measured under different temperature differences.
6. The near field thermal radiation measurement method according to claim 5, wherein in said step 2), a spacer having a thickness of 50 to 500 nm is formed on an upper surface of the receiver, said spacer being an epoxy resin.
7. The method of near field thermal radiation measurement as defined in claim 5, wherein in said step 4), the radiator is placed on the spacer, and the contact area of the radiator and the spacer is the heat conduction area, denoted by A C Let the radiator temperature be T 1 The temperature of the receiver is T 2 Then the heat of conduction Q through the spacer support structure C The method comprises the following steps:
Q C ＝A C ×k(T 1 -T 2 )/d
where k is the spacer equivalent thermal conductivity, as determined by the spacer material parameters.
8. The near field thermal radiation measurement method of claim 5, wherein in said step 4), the laser emitted from the laser is normally incident on the upper surface of the radiator through the window of the vacuum chamber, and the radiator is heated to reach a thermal steady state within 3-5 minutes; the laser is limited to beam expansion, collimation and focusing processes, and a light spot with proper size is obtained on the radiator, so that only the radiator is directly heated.
9. The near field thermal radiation measurement method according to claim 5, wherein in said step 5), according to the law of conservation of energy, the heat power lost by the radiator at the same time is equal to the heat conduction Q through the spacer C Far field radiation Q of radiator F And near field radiation Q of the radiator and the receiver N The sum of the energy powers; in the cooling process, the heat quantity of the radiator changes Q along with the time t T (t) writing:
Q T (t)＝cm dT 1 /dt
wherein c and m are the specific heat capacity and mass of the radiator, dT 1 The dt is the instantaneous temperature change of the radiator, and is recorded by a thermal imager;
a far-field radiation channel is arranged between the radiator and the surrounding environment cavity, and the far-field radiation energy Q of the far-field radiation channel F Writing:
wherein A is F Is the far field radiating area, e is the equivalent emissivity, determined by the emissivity of the cavity environment and the emissivity of the radiator, σ is the spandex-boltzmann constant;
the measurement of the near field thermal radiation between the radiator and the receiver is obtained by analyzing the real-time energy conservation process of the radiator, i.e. the near field thermal radiation measurement is obtained by:
Q N ＝Q T -Q C -Q F 。
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