CN104880437A - Semi-transparent dielectric material photo-thermal character measuring system and method - Google Patents

Abstract

The invention discloses a system and method for measuring photothermal characteristics of translucent medium materials. Parabolic mirror, power line, laser power supply, HCT thermal detector, BNC data line, preamplifier, laser control line, lock-in amplifier, lock-in amplifier control line, data acquisition signal line, the measurement method is based on photothermal radiation The measurement principle uses a computer-controlled function generator to generate a modulation signal, and the signal controls the laser so that the light intensity changes according to the modulation law. After the modulated and changed laser is irradiated on the sample, due to the photothermal effect, the sample has temperature fluctuations and infrared radiation. The thermal radiation signal is related to the photothermal characteristic parameters of the sample, and the signal is received by the HCT thermal detector, and then the photothermal characteristic parameters of the sample are extracted through mathematical operations. The invention can realize completely non-damage, non-contact and high-efficiency measurement of materials.

Description

System and method for measuring photothermal properties of translucent dielectric materials

technical field

The invention relates to a system and method for measuring the photothermal characteristics of translucent dielectric materials, which are suitable for measuring the photothermal characteristics of translucent dielectric materials in the fields of aerospace, microelectronics, and thin-layer structures.

Background technique

The photothermal physical parameters of the material can quantitatively and objectively evaluate the material performance. Generally, the optical and thermal properties of the material are measured separately by different instruments. The instrument is expensive and the measurement process is cumbersome. , size and other factors limit the scope of use of traditional measurement methods.

Translucent media, such as single crystal diamond, fiber film and other materials, are widely used in various fields of industry due to their good mechanical and thermal properties. However, due to the particularity of the size and material of translucent media, traditional photothermal physical parameter detection methods cannot measure most translucent media.   

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the current technology and provide a system and method for measuring the photothermal characteristics of translucent dielectric materials.

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

A system for measuring photothermal properties of translucent dielectric materials, including a computer, a two-dimensional mobile stage, a bracket, a small off-axis parabolic mirror, a collimating mirror, an optical fiber, a semiconductor laser, a large off-axis parabolic mirror, a power cord, a laser power supply, and HCT Thermal detector, BNC data line, preamplifier, laser control line, lock-in amplifier, lock-in amplifier control line, data acquisition signal line, among which: the computer is connected to the lock-in amplifier through the lock-in amplifier control signal line, and the lock-in amplifier The amplifier reference signal output terminal is connected to the laser power supply through the laser control line, the semiconductor laser is connected to the laser power supply through the laser power control line, the semiconductor laser is connected to the collimating mirror through the optical fiber, and the collimating mirror is fixed in the central hole of the small off-axis parabolic mirror , the small off-axis parabolic mirror is fixed on the bracket by bolt connection, the two-dimensional mobile stage is placed directly below the small off-axis parabolic mirror, the large off-axis parabolic mirror is placed relatively parallel to the small off-axis parabolic mirror, and the HCT thermal detector is placed on the large The focus position of the off-axis parabolic mirror, the preamplifier is connected to the HCT thermal detector through the BNC data line, the preamplifier is connected to the lock-in amplifier through the signal line, and the output signal end of the lock-in amplifier is connected to the computer through the data acquisition signal line .

A method for measuring photothermal properties of translucent media materials, based on the principle of photothermal radiometry (PTR), using a computer-controlled function generator to generate a modulation signal, the signal controls the laser to make the light intensity change according to the modulation law, and the modulation changes After the laser irradiates the sample, due to the photothermal effect, the sample has temperature fluctuations and infrared radiation. The photothermal radiation signal is related to the photothermal characteristic parameters of the sample. The signal is received by the HCT thermal detector, and then the sample light is extracted through mathematical operations. Thermal characteristic parameters. The specific implementation steps are as follows:

Step (1): Determine the translucent medium material to be measured;

Step (2): Start the test system for measuring the photothermal characteristics of translucent media;

Step (3): After the semiconductor laser is turned on, place the reflector on the focal point of the small off-axis parabolic mirror to adjust the HCT thermal detector so that it is on the focal point of the large off-axis parabolic mirror;

Step (4): To turn on the HCT thermal detector, the detector needs to be refrigerated for half an hour before testing to achieve the best detection effect;

Step (5): Place the steel piece with good specular reflection on the two-dimensional mobile platform, and move the two-dimensional mobile platform so that the steel piece is at the focus of the small off-axis parabolic mirror;

Step (6): The computer control software sets the start frequency, stop frequency, and number of scan frequencies of the frequency scan;

Step (7): The computer control software signal is output through the function generator, so that it can control the light intensity of the semiconductor laser to change according to the modulation law, and perform a frequency sweep test;

Step (8): The computer control software automatically records the light and heat radiation signals of steel parts at different frequencies as the subsequent test system correction data;

Step (9): After the test is completed, place the translucent medium test material on the focal point of the small off-axis parabolic mirror, and repeat steps (5), (6), and (7) until the test is completed;

Step (10): The test data obtained in step (9) is corrected by the corrected data in step (8). The correction process is: the corrected data obtained in step (8) is normalized in order to exclude the influence of light intensity The treatment is denoted as Am ₁ , the phase value is denoted as Ph ₁ , and the frequency domain response amplitude and phase of the test sample obtained in step (9) are denoted as Am ₂ and Ph ₂ respectively, then the real frequency response signal of the test sample ( Am,Ph )for

(1);

(2).

Step (11): Through the thermal wave mathematical model established according to the material characteristics, the least square method parameter fitting is carried out on the corrected photothermal radiation signal (amplitude frequency-phase frequency) of the semitransparent medium material, so as to obtain the photothermal radiation signal of the semitransparent medium material Feature parameters.

In the present invention, the test material is for the translucent medium material.

In the present invention, the wavelength of the laser is determined according to the absorption characteristics of the material.

In the present invention, the frequency scanning range is determined according to the material, size and thickness of the material.

The advantages of the present invention are:

(1) The invention adopts the measurement method of photothermal characteristics of translucent medium materials, which can realize complete non-damage, non-contact and high-efficiency measurement of materials, and is not limited by the size of translucent materials.

(2) The present invention adopts the photothermal characteristic measurement system of the translucent medium material to realize one-time measurement of the photothermal characteristic of the material.

Description of drawings

FIG. 1 is a schematic structural diagram of a measurement system for photothermal characteristics of translucent dielectric materials involved in the present invention.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered by the present invention. within the scope of protection.

As shown in Figure 1, the system for measuring photothermal properties of translucent dielectric materials provided by the present invention consists of a computer 1, a two-dimensional mobile platform 2, a support 3, a small off-axis parabolic mirror 4, a collimating mirror 5, an optical fiber 6, and a semiconductor laser 7 , Large off-axis parabolic mirror 8, power line 9, laser power supply 10, HCT thermal detector (HgCdTe, response wavelength 2μm~14μm) 11, BNC data line 12, preamplifier (response frequency 10Hz~1MHz) 13, laser control Line 14, signal line 15, lock-in amplifier 16 (built-in function generator), lock-in amplifier control line 17, and data acquisition signal line 18. The computer 1 is connected to the lock-in amplifier 16 through the lock-in amplifier control signal line 17, the reference signal output end of the lock-in amplifier 16 is connected to the laser power supply 10 through the laser control line 14, and the semiconductor laser 7 is connected to the laser power supply 10 through the laser power supply control line , the semiconductor laser 7 is connected with the collimating mirror 5 through the optical fiber 6, and the collimating mirror 5 is fixed in the center hole of the small off-axis parabolic mirror 4, and the small off-axis parabolic mirror 4 is fixed on the support 3 through bolt connection, and the two-dimensional mobile stage 2 is directly below the small off-axis parabolic mirror 4, the axis of the large off-axis parabolic mirror 8 coincides with the axis of the small off-axis parabolic mirror 4, the HCT infrared detector 11 is at the focus position of the large off-axis parabolic mirror 8, and the preamplifier 13 passes through the BNC data line 12 is connected with the HCT thermal detector 11, the preamplifier 13 is connected with the lock-in amplifier 16 through the signal line 15, and the output signal end of the lock-in amplifier 16 is connected with the computer 1 through the data acquisition signal line 18.

In the specific embodiment, the translucent dielectric material is polycrystalline diamond with a thickness of 200 μm and a size of 1 cm×1 cm as an example.

The measurement system adopts 808nm semiconductor laser 7 (laser power 32mW, spot diameter 600μm); infrared detector is HCT detector 11 with built-in preamplifier (Poland Vigo Company, detection band 2μm~14μm, detection area 100μm×100μm); phase-locked The amplifier 16 is SR830 of Stanford Company (response frequency 0.01Hz~102KHz).

To start the test system for measuring photothermal characteristics of translucent media, it is necessary to start the computer 1, lock-in amplifier 16, semiconductor laser 7, HCT thermal detector 11 and other equipment. First, the HCT detector 11 needs to be refrigerated for half an hour before testing, so as to achieve the best detection effect. Place the steel piece with high reflectivity (for system correction) on the two-dimensional mobile platform 2, move the two-dimensional mobile platform 2, so that the steel piece is at the focal point of the small off-axis parabolic mirror 4; the computer control software sets the frequency scan The number of start frequency, stop frequency, and scan frequency, the scan range here is 100Hz~100KHz, and the number of scan points is 30; the computer control software signal is output by the built-in function generator of the lock-in amplifier 16, so that it can control the light intensity of the semiconductor laser 7 According to the change of the modulation law, the semiconductor laser 7 is irradiated on the corrected steel piece through the collimating mirror 5, and the frequency scanning test is carried out; the computer control software automatically records the light and heat radiation signals of the steel piece at different frequencies, as the correction data of the subsequent test system; the test is completed Finally, the polycrystalline diamond test material is placed on the 4 focal points of the small off-axis parabolic mirror, and the above test steps are repeated until the test is completed; the obtained test data is corrected by the correction data obtained from the test steel piece; The thermal wave mathematical model of the modified translucent medium material photothermal radiation signal (amplitude frequency - phase frequency) is fitted with the least square method parameters, so as to obtain the semitransparent medium material photothermal characteristic parameters, as shown in Table 1.

Table 1

parameter value Thermal diffusivity α /×10 ^-4 (m ² /s) 9.35±0.004 Thermal conductivity k /×10 ² (W/mK) 7.28±0.34 Optical absorption coefficient β /×10 ² (m ^-1 ) 1.19±0.46 Infrared absorption coefficient α _IR ( λ ) /×10 ³ (m ^-1 ) 9.82±1.40

So far, the measurement of the photothermal characteristics of the translucent dielectric material has been completed.

Claims (8)

1. a translucent medium material Photothermal characterisation measuring system, is characterized in that described measuring system is by computing machine, two-dimensional movement platform, support, little off-axis paraboloidal mirror, collimating mirror, optical fiber, semiconductor laser, large off-axis paraboloidal mirror, power lead, laser power supply, HCT thermal detector, BNC data line, prime amplifier, laser control line, lock-in amplifier, lock-in amplifier control line, data acquisition signal line is formed, wherein: computing machine is connected with lock-in amplifier by lock-in amplifier control signal wire, lock-in amplifier reference signal output terminal is connected with laser power supply by laser control line, laser instrument is connected with laser power supply by laser power supply control line, laser instrument is connected with collimating mirror by optical fiber, collimating mirror is fixed in the center pit of little off-axis paraboloidal mirror, little off-axis paraboloidal mirror is bolted and is fixed on support, two-dimensional movement platform is positioned over immediately below little off-axis paraboloidal mirror, large off-axis paraboloidal mirror and the opposing parallel placement of little off-axis paraboloidal mirror, HCT thermal detector is positioned over large off-axis paraboloidal mirror focal position, prime amplifier is connected with HCT thermal detector by BNC data line, prime amplifier is connected with lock-in amplifier by signal wire, lock-in amplifier output signal end is connected with computing machine by data acquisition signal line.

2. translucent medium material Photothermal characterisation measuring system according to claim 1, is characterized in that the response wave length 2 μm ~ 14 μm of described HCT thermal detector, detection area 100 μm × 100 μm.

3. translucent medium material Photothermal characterisation measuring system according to claim 1, is characterized in that the response frequency 10Hz ~ 1MHz of described prime amplifier.

4. translucent medium material Photothermal characterisation measuring system according to claim 1, is characterized in that described laser power 32mW, spot diameter 600 μm.

5. translucent medium material Photothermal characterisation measuring system according to claim 1, is characterized in that described lock-in amplifier built-in function generator.

6. translucent medium material Photothermal characterisation measuring system according to claim 1 or 5, is characterized in that the response frequency 0.01Hz ~ 102KHz of described lock-in amplifier.

7. utilize translucent medium material Photothermal characterisation measuring system described in claim 1 to carry out a method for translucent medium material Photothermal characterisation measurement, it is characterized in that described method step is as follows:

Step (1): determine the translucent medium material that will measure;

Step (2): open translucent medium Photothermal characterisation and measure pilot system;

Step (3): reflective mirror is positioned in little off-axis paraboloidal mirror focus, regulates HCT thermal detector with this, make it be in large off-axis paraboloidal mirror focus after opening by semiconductor laser;

Step (4): open HCT thermal detector, first needs to make detector to freeze after half an hour and tests, reach best Effect on Detecting to make it;

Step (5): steel part is positioned on two-dimensional movement platform, mobile two-dimensional movement platform, makes steel part be in little off-axis paraboloidal mirror focus;

Step (6): computer control software arranges initial frequency, termination frequency, the sweep frequency number of frequency sweeping;

Step (7): computer control software signal is exported by function generator, makes it control semiconductor laser light intensity by the change of modulation rule, carries out frequency sweeping test;

Step (8): computer control software records the steel part optical heat radiation signal under different frequency automatically, as follow-up test system correction data;

Step (9): after being completed, is positioned over translucent medium test material in little off-axis paraboloidal mirror focus, repeats step (5), (6), (7), until be completed;

Step (10): the test figure that step (9) obtains carries out correcting process by the correction data of step (8);

Step (11): by the heat wave mathematical model set up according to material behavior, least square method parameter fitting is carried out to revised translucent medium material optical heat radiation signal, thus obtain translucent medium material Photothermal characterisation parameter.

8. the method utilizing translucent medium material Photothermal characterisation measuring system described in claim 1 to carry out the measurement of translucent medium material Photothermal characterisation according to claim 7, it is characterized in that described correcting process process is: amplitude, in order to get rid of light intensity impact, is normalized and is designated as by the correction data that step (8) obtains am ₁, phase value is designated as ph ₁, the frequency domain response amplitude of the test specimen that step (9) obtains and phase place are designated as respectively am ₂, ph ₂, then real test specimen frequency response signal ( am, Ph) be:

(1)；

(2)。