Temperature measurement method of micron-sized focus

Abstract

The invention discloses a micron-scale focus temperature measurement method, which comprises the following steps of: exciting a rare earth doped film by using 980nm laser to generate dual-wavelength fluorescence corresponding to a thermal coupling energy level; submicron focusing and collection of fluorescence signals are realized through a microscope objective; a dual-wavelength fluorescence signal is separated by using a narrow-band optical filter group and is converted into an electric signal through a photoelectric detector; the dual-wavelength fluorescence intensity ratio is calculated, and the focus temperature is calculated in real time according to a pre-calibrated temperature-fluorescence intensity ratio curve; two-dimensional temperature distribution scanning is achieved through the three-dimensional displacement platform, a temperature distribution diagram with micron-level spatial resolution is generated, and interference of a traditional contact type temperature measurement method on a micro-scale system is avoided, such as measurement errors caused by heat conduction and damage to the surface of a sample. The method is suitable for temperature measurement in extreme environments such as high temperature, high pressure and strong electromagnetic field, and has wide applicability.

Description

Technical Field

[0001] This invention relates to the field of precision temperature measurement technology, specifically a temperature measurement method with a micron-level focal point. Background Technology

[0002] In today's era of rapid development in microelectronics and nanotechnology, accurate temperature measurement at the micrometer and even nanometer scales has become a critical problem that urgently needs to be solved in many fields. However, existing micrometer-scale temperature measurement technologies have significant limitations and cannot meet the ever-increasing demand for high-precision, high-resolution temperature measurement:

[0003] Infrared thermal imagers: Standard infrared thermal imager lenses are limited by optical diffraction limits and manufacturing processes, typically limiting the minimum detection scale to 100-200 μm. While 30 μm-level detection can be achieved by adding a macro lens, this introduces a series of problems. For example, the depth of field narrows drastically, making focusing difficult, and even slight deviations can lead to inaccurate measurements; the detection distance is limited by lens parameters, such as a 30 μm lens requiring a working distance of ≤30 mm, which significantly restricts practical applications; furthermore, at the microscale, the thermal radiation characteristics of objects change, making the calibration and correction of traditional infrared thermometry more complex and affecting measurement accuracy.

[0004] Fiber optic temperature measurement technology: Traditional fiber optic grating temperature measurement methods are limited in spatial resolution by the grating length, which is typically on the order of millimeters. This makes it difficult to achieve single-point micrometer-level positioning, failing to meet the requirements for precise temperature measurement of tiny areas. While distributed fiber optic temperature measurement systems can measure temperature distribution along the length of the fiber, their spatial resolution is usually on the order of meters, rendering them ineffective for micrometer-scale temperature measurements. Furthermore, fiber optic temperature measurement requires embedding or placing the fiber optic sensor close to the object being measured, which may interfere with the microscale system and affect the accuracy of the measurement results.

[0005] Fluorescence lifetime thermometry: This method measures temperature by measuring the change in fluorescence lifetime of a fluorescent material with temperature. While theoretically offering high temperature resolution, it requires a complex time-correlated single-photon counting system for accurate fluorescence lifetime measurement. Such systems are expensive, complex to operate and maintain, and have stringent environmental requirements. Furthermore, the temporal accuracy of fluorescence lifetime measurement directly affects temperature resolution; in practical applications, factors such as signal noise and detector response time make it difficult to achieve the theoretically high precision.

[0006] To address the aforementioned issues, this invention proposes a non-contact temperature measurement method based on the rare-earth fluorescence thermal coupling effect. This method achieves precise measurement of micron-level focal temperature by using a dual-wavelength fluorescence intensity ratio, providing a novel and efficient solution for microscale temperature measurement. Summary of the Invention

[0007] The purpose of this invention is to provide a temperature measurement method with a micron-level focal spot to solve the problems mentioned in the background art.

[0008] To address the aforementioned technical problems, this invention provides the following technical solution: a micrometer-level focal point temperature measurement method, comprising the following steps: using a 980nm laser to excite a rare-earth-doped thin film to generate dual-wavelength fluorescence corresponding to a thermally coupled energy level; achieving sub-micrometer-level focusing and collection of the fluorescence signal using a microscope objective; separating the dual-wavelength fluorescence signal using a narrow-band filter group and converting it into an electrical signal via a photodetector; calculating the dual-wavelength fluorescence intensity ratio and calculating the focal point temperature in real time based on a pre-calibrated temperature-fluorescence intensity ratio curve; and achieving two-dimensional temperature distribution scanning using a three-dimensional displacement platform to generate a temperature distribution map with micrometer-level spatial resolution.

[0009] According to the above technical solution, the rare earth-doped thin film is Y2O3:Er 3+ Yb 3+ Materials, of which Er 3+ Ion concentration of 1-5 mol%, Yb 3+ The ion concentration is 3-10 mol%.

[0010] According to the above technical solution, the numerical aperture (NA) of the microscope objective is ≥0.4, the working distance is ≤5mm, and the focused spot diameter is ≤1μm.

[0011] According to the above technical solution, the system for realizing the temperature measurement method includes an excitation source module, an optical coupling system, a rare-earth fluorescent thin film, a fluorescence detection module, a three-dimensional displacement platform, and a data processing unit. The excitation source module includes a 980nm semiconductor laser; the optical coupling system includes an optical fiber collimator group, a microscope objective, and a beam splitter group; the rare-earth fluorescent thin film is coated on the surface of the device under test; the fluorescence detection module includes a narrowband filter group and a photodetector group; the three-dimensional displacement platform is used for micrometer-level positioning and scanning; and the data processing unit is used for fluorescence signal acquisition and temperature calculation.

[0012] According to the above technical solution, the narrowband filter group includes narrowband filters with center wavelengths of 482nm and 443nm, and a bandwidth of ≤10nm.

[0013] According to the above technical solution, the photodetector group adopts an APD detector with a response wavelength range of 400-1100nm and a dark current ≤100pA.

[0014] According to the above technical solution, the positioning accuracy of the three-dimensional displacement platform is ±0.1μm, the repeatability is ±0.05μm, and the stroke range is ≥50mm×50mm×20mm.

[0015] According to the above technical solution, the data processing unit adopts an FPGA+ARM dual-core architecture to realize real-time acquisition of fluorescence signals and temperature calculation, with a single-point measurement time of ≤10ms.

[0016] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: By incorporating an excitation light source module, an optical coupling system, a rare-earth fluorescent thin film, a fluorescence detection module, a three-dimensional displacement platform, and a data processing unit, this invention achieves sub-micron-level spot focusing through a microscope objective, achieving a spatial resolution better than 1 μm. This enables precise measurement of temperature distribution in minute regions, meeting the high-precision temperature measurement needs of fields such as microelectronics and nanotechnology. Furthermore, it avoids the interference of traditional contact temperature measurement methods on microscale systems, such as measurement errors caused by heat conduction and damage to the sample surface. It is suitable for temperature measurement in extreme environments such as high temperature, high pressure, and strong electromagnetic fields, and has broad applicability. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of the overall system structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the system workflow of the present invention; Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1-2 The present invention provides a technical solution: a temperature measurement method with a micrometer-level focal spot, comprising the following steps:

[0022] 1. Optical path calibration:

[0023] The laser output power was adjusted to 10mW, and after collimation by the first fiber optic collimator, it was focused onto the surface of the rare-earth thin film through a microscope objective. Using auxiliary equipment such as a microscope or laser power meter, the focal length and position of the microscope objective were precisely adjusted to ensure that the diameter of the focused spot was ≤1μm, thus ensuring that the spot accurately fell on the area to be measured.

[0024] Adjust the angle of the second beam splitter to evenly distribute the fluorescence signal to the two detection channels. This can be done by placing a power meter in the detection channel or observing the output signal of the photodetector, and then fine-tuning the beam splitter angle to ensure that the fluorescence signal intensities received by the two channels are essentially the same. During the adjustment process, it is necessary to continuously observe the power meter reading or the output signal waveform of the photodetector, and adjust the beam splitter angle according to the changes in signal intensity until the signal intensities of the two channels reach equilibrium.

[0025] 2. Fluorescence signal acquisition:

[0026] The fluorescence emitted by the rare-earth thin film under stimulated emission is collected by a microscope objective and then sequentially passes through a second fiber collimator, a first beam splitter, and a second beam splitter before entering two detection channels. During optical transmission, the cleanliness and accurate alignment of all optical components are ensured to avoid signal loss and interference. Regular cleaning and maintenance of the optical components are performed, and their installation positions are checked for accuracy; any deviations are adjusted promptly.

[0027] After the narrowband filter array filters out stray light, the fluorescence signal is converted into an electrical signal by the APD detector. The APD detector operates under a suitable bias voltage to ensure that its internal gain and sensitivity are optimal. Simultaneously, the detector's output signal is appropriately amplified and filtered to improve signal quality. The dual-wavelength fluorescence intensity ratio is calculated, and the focal temperature is calculated in real time based on a pre-calibrated temperature-fluorescence intensity ratio curve.

[0028] 3. Temperature calculation:

[0029] The data processing unit acquires two-channel fluorescence intensity signals, I1 (482nm) and I2 (443nm), and calculates the fluorescence intensity ratio (FIR) = I1 / I2. During the calculation, the acquired signals are averaged multiple times to reduce the influence of random noise and improve the accuracy of the FIR calculation.

[0030] The focal temperature is calculated in real time based on the pre-calibrated temperature-FIR curve (fitting formula: T = A / (ln(FIR) + B) + C, where A, B, and C are calibration coefficients). The calibration process requires calibrating the system on a standard heat source at a known temperature. By measuring the FIR values ​​at different temperatures, the values ​​of A, B, and C are determined using fitting methods such as the least squares method, thus establishing an accurate temperature-FIR relationship model.

[0031] 4. Two-dimensional temperature distribution scanning:

[0032] A three-dimensional displacement platform is used to control the movement of the rare-earth thin film in the XY plane with a stepping accuracy of 0.1 μm, enabling full-surface temperature distribution scanning. During the scanning process, the sample is moved sequentially according to a predetermined scanning path and step size, and a sufficient time is spent at each measurement point to ensure stable acquisition of fluorescence signals and accurate temperature calculation.

[0033] The data processing unit generates a two-dimensional temperature distribution map with a spatial resolution of 1μm×1μm. By interpolating and visualizing the large amount of temperature data obtained from the scan, an intuitive two-dimensional temperature distribution map is generated, clearly showing the temperature distribution of the area under test.

[0034] Specifically, the rare earth-doped thin film is Y2O3:Er 3+ Yb 3+ Materials, of which Er 3+ Ion concentration of 1-5 mol%, Yb 3+ The ion concentration was 3-10 mol%; Y₂O₃:Er 3+ Yb 3+ Rare earth materials are used to prepare fluorescent thin films with a thickness precisely controlled at 500 nm, which are then uniformly coated onto the surface of the device under test using advanced processes such as magnetron sputtering. Among these, Er... 3+ The ion concentration is 2 mol%, Yb 3+ The ion concentration is 5 mol%. Yb 3+ Ions, acting as sensitizers, can efficiently absorb excitation light energy and transfer it to Er. 3+ Ions, improving fluorescence emission efficiency; Er 3+ Ions act as luminescent centers, generating fluorescence emission corresponding to thermally coupled energy levels.

[0035] Specifically, the microscope objective has a numerical aperture (NA) ≥ 0.4, a working distance ≤ 5 mm, and a focused spot diameter ≤ 1 μm. The larger numerical aperture can collect more fluorescence signals and improve the detection sensitivity of the system. At the same time, the shorter working distance helps to achieve sub-micron-level spot focusing, meeting the requirements of micron-level focus temperature measurement.

[0036] Specifically, the system for implementing the temperature measurement method includes an excitation source module, an optical coupling system, a rare-earth fluorescent thin film, a fluorescence detection module, a three-dimensional displacement platform, and a data processing unit. The excitation source module includes a 980nm semiconductor laser. A highly stable 980nm semiconductor laser is used as the excitation source, exhibiting excellent performance with output power stability better than ±0.5% and a linewidth ≤0.1nm. Its output power can be precisely adjusted through a sophisticated current control and temperature regulation system to meet the needs of different measurement scenarios. Simultaneously, the laser is equipped with an optical isolator to effectively prevent damage to the laser from reflected light, improving the stability and reliability of the system.

[0037] The optical coupling system includes a fiber optic collimator assembly, a microscope objective, and a beam splitter assembly. The fiber optic collimator assembly comprises a first fiber optic collimator (numerical aperture NA = 0.22) and a second fiber optic collimator (NA = 0.15). The first fiber optic collimator collimates the laser beam, making it a parallel beam, reducing the beam divergence angle, and improving the light transmission efficiency. The second fiber optic collimator collimates the collected fluorescence signal, facilitating subsequent optical path transmission and detection.

[0038] Microscope objectives: A high-performance microscope objective with a numerical aperture (NA) of 0.4 and a working distance of 4 mm was selected. This objective has a large numerical aperture, which can collect more fluorescence signals and improve the detection sensitivity of the system; at the same time, the short working distance helps to achieve sub-micron spot focusing, meeting the requirements of micron-level focus temperature measurement.

[0039] The beam splitter assembly consists of a first beam splitter and a second beam splitter (50:50 splitting ratio). The first beam splitter reflects the excitation light to the microscope objective while allowing the fluorescence signal to pass through; the second beam splitter evenly distributes the fluorescence signal to the two detection channels, enabling simultaneous detection of dual-wavelength fluorescence.

[0040] Rare earth fluorescent thin films are coated on the surface of the device under test;

[0041] The fluorescence detection module comprises a narrowband filter group and a photodetector group. The narrowband filter group includes a first filter (center wavelength 482nm, bandwidth 10nm) and a second filter (center wavelength 443nm, bandwidth 10nm). The narrowband filter effectively filters out stray light, allowing only fluorescence signals of specific wavelengths to pass through, thus improving the signal-to-noise ratio and accuracy of fluorescence detection. The photodetector group uses a high-sensitivity APD (avalanche photodiode) detector with a response wavelength range covering 400-1100nm and a dark current ≤50pA. The APD detector has an internal gain mechanism that amplifies weak fluorescence signals, improving the system's detection sensitivity, and is particularly suitable for temperature measurement under low fluorescence intensity conditions.

[0042] Three-dimensional displacement platforms are used for micron-level positioning and scanning;

[0043] Data processing unit: Used for fluorescence signal acquisition and temperature calculation; employs a dual-core architecture of FPGA (Field-Programmable Gate Array) + ARM (Advanced Reduced Instruction Set Machine). The FPGA is responsible for real-time acquisition of the electrical signals output by the photodetector, performing high-speed analog-to-digital conversion and preliminary data processing, such as signal filtering and amplification; the ARM processor further analyzes and calculates the processed data, calculating the focal temperature in real time based on a pre-calibrated temperature-FIR curve and generating a two-dimensional temperature distribution map. Simultaneously, the data processing unit also has data storage and communication functions, allowing measurement data to be saved to local memory or transmitted to a host computer via wired / wireless means for further analysis and processing.

[0044] Specifically, the narrowband filter group includes narrowband filters with center wavelengths of 482nm and 443nm, and a bandwidth of ≤10nm;

[0045] Specifically, the photodetector group adopts an APD detector with a response wavelength range of 400-1100nm and a dark current ≤100pA;

[0046] Specifically, the three-dimensional displacement platform has a positioning accuracy of ±0.1μm, a repeatability of ±0.05μm, and a stroke range of ≥50mm×50mm×20mm. Through a high-precision stepper motor and a precise transmission mechanism, it achieves accurate movement and positioning of the sample under test in the X, Y, and Z directions, meeting the requirements of two-dimensional temperature distribution scanning.

[0047] Specifically, the data processing unit adopts an FPGA+ARM dual-core architecture to realize real-time acquisition of fluorescence signals and temperature calculation, with a single-point measurement time of ≤10ms;

[0048] This invention utilizes the thermally coupled energy level characteristics of rare-earth-doped materials to achieve temperature measurement. When rare-earth ions (such as Er)... 3+ Tm 3+ When a particle (e.g., a molecule) is irradiated with excitation light of a specific wavelength, its electrons transition from the ground state to an excited state. In the excited state, thermally coupled energy levels exist, meaning the energy difference between the two levels is equivalent to thermal energy (kT, where k is the Boltzmann constant and T is temperature). According to the Boltzmann distribution law, the particle number distribution between these two thermally coupled energy levels is closely related to temperature. Specifically, in the excited state...

[0049] The ratio of the number of particles in higher energy levels to the number of particles in lower energy levels follows the Boltzmann distribution formula:

[0050]

[0051] N1 and N2 are the number of particles in the high and low energy levels, respectively, and ΔE is the energy difference between the two energy levels.

[0052] Since transitions between different energy levels emit fluorescence of different wavelengths, variations in the particle number distribution between thermally coupled energy levels lead to corresponding changes in the emission intensity of fluorescence at different wavelengths. By measuring the fluorescence intensity ratio (FIR) between two thermally coupled energy levels, the influence of factors such as excitation light intensity fluctuations and fluorescent material inhomogeneities on the measurement results can be eliminated, establishing a quantitative relationship between temperature and fluorescence intensity, thereby achieving high-precision temperature measurement. The theoretical relationship can be expressed as:

[0053]

[0054] Where I1 and I2 are the fluorescence intensities corresponding to the two thermally coupled energy levels, and C is a constant related to the fluorescent material and the measurement system.

[0055] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0056] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A temperature measurement method with a micrometer-level focal spot, characterized in that, Includes the following steps: A rare-earth-doped thin film was excited by a 980nm laser to generate dual-wavelength fluorescence corresponding to thermally coupled energy levels. Submicron-level focusing and collection of fluorescence signals are achieved using microscope objectives; A narrowband filter array is used to separate dual-wavelength fluorescence signals, which are then converted into electrical signals by a photodetector. Calculate the dual-wavelength fluorescence intensity ratio and calculate the focal temperature in real time based on the pre-calibrated temperature-fluorescence intensity ratio curve; Two-dimensional temperature distribution scanning is achieved through a three-dimensional displacement platform, generating a temperature distribution map with micron-level spatial resolution.

2. The temperature measurement method with a micrometer-level focal spot according to claim 1, characterized in that: The rare earth-doped thin film is Y2O3:Er 3+ Yb 3+ Materials, of which Er 3+ Ion concentration of 1-5 mol%, Yb 3+ The ion concentration is 3-10 mol%.

3. The temperature measurement method with a micrometer-level focal spot according to claim 2, characterized in that: The microscope objective has a numerical aperture (NA) ≥ 0.4, a working distance ≤ 5 mm, and a focused spot diameter ≤ 1 μm.

4. The temperature measurement method with a micrometer-level focal spot according to claim 1, characterized in that: The system for implementing the temperature measurement method includes an excitation source module, an optical coupling system, a rare-earth fluorescent thin film, a fluorescence detection module, a three-dimensional displacement platform, and a data processing unit. The excitation source module includes a 980nm semiconductor laser; the optical coupling system includes an optical fiber collimator group, a microscope objective, and a beam splitter group; the rare-earth fluorescent thin film is coated on the surface of the device under test; the fluorescence detection module includes a narrowband filter group and a photodetector group; the three-dimensional displacement platform is used for micrometer-level positioning and scanning; and the data processing unit is used for fluorescence signal acquisition and temperature calculation.

5. The temperature measurement method with a micrometer-level focal spot according to claim 4, characterized in that: The narrowband filter group includes narrowband filters with center wavelengths of 482nm and 443nm, and a bandwidth of ≤10nm.

6. The temperature measurement method with a micrometer-level focal spot according to claim 5, characterized in that: The photodetector group adopts an APD detector with a response wavelength range of 400-1100nm and a dark current ≤100pA.

7. The temperature measurement method with a micrometer-level focal spot according to claim 6, characterized in that: The three-dimensional displacement platform has a positioning accuracy of ±0.1μm, a repeatability of ±0.05μm, and a stroke range of ≥50mm×50mm×20mm.

8. The temperature measurement method with a micrometer-level focal spot according to claim 7, characterized in that: The data processing unit adopts an FPGA+ARM dual-core architecture to realize real-time acquisition of fluorescence signals and temperature calculation, with a single-point measurement time of ≤10ms.

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