CN106568720A - Metal test piece surface laser reflectivity measuring device and method - Google Patents

Abstract

The invention belongs to the technical field of laser effect testing, and relates to a device and a method for measuring the surface reflectance of a metal test piece. The device provided by the invention comprises a measuring integrating sphere and a background integrating sphere, and a through test piece installation hole is arranged at the joint of the measuring integrating sphere and the background integrating sphere; a measuring photodetector is installed on the measuring integrating sphere, and a The background photodetector; the measuring integrating sphere is also provided with a laser entrance hole, and the laser entrance hole is located on the other side of the ball wall opposite to the installation hole of the test piece. The present invention sets up a series of integrating sphere groups, uses measuring integrating spheres and background integrating spheres to obtain measurement signals and background thermal radiation signals respectively, obtains real reflectivity coefficients through data processing, and overcomes thermal radiation on the surface of metal specimens at high temperatures The effect of the signal on the reflectance measurement.

Description

Device and method for measuring laser reflectivity on the surface of a metal test piece

technical field

The invention belongs to the technical field of laser effect testing, and relates to a device and a method for measuring the surface reflectance of a metal test piece.

Background technique

When studying the coupling law between laser and metal materials, it is usually necessary to measure the relationship between the surface reflectance coefficient of the effect test piece and the laser power and the light emitting time. The more commonly used method is the integrating sphere measurement scheme shown in Figure 1: the first step is to place the standard test board inside the integrating sphere 4, and measure the response signal of the photodetector 5 loaded on the standard test board by the laser 1. In the second step, the effect test piece 3 is placed inside the integrating sphere 4, and the response signal of the photodetector 5 loaded by the laser 1 on the effect test piece 3 is measured, and the comparison between the two is the surface reflectance coefficient of the effect test piece 3. In practical application, due to the effect, the temperature of the specimen rises during the laser loading process, and the external thermal radiation is strengthened, and this part of the thermal radiation signal will be mixed in the effective signal and measured by the photodetector on the integrating sphere, which will affect the accuracy of the measurement results. Accuracy, especially when the specimen is laser loaded to high temperature, the error of the reflectance measurement becomes very large.

The document "Influence of Thermal Radiation in Reflectance Measurement and Its Elimination Method, Intense Laser and Particle Beam, 2011, Vol.23(7), p1767-1770" discloses a dual-detector integrating sphere measurement method to eliminate metallic materials The method for thermal radiation to interfere with the reflectivity measurement, the laser beam emitted by the 1064nm laser is used to irradiate the surface of the metal material, the reflected light and thermal radiation on the surface of the metal material are collected and homogenized by the integrating sphere, the first photodetector and the second photoelectric The detectors are used to measure the light intensity after homogenization, wherein a 1064nm narrow-band filter is installed in front of the first photodetector, and a 1319nm narrow-band filter is installed in front of the second photodetector. When measuring the reflectivity of metal materials, collect the signals of the first photodetector and the second photodetector during the heating period of the metal material during laser loading and the cooling period after laser loading, and use the first photodetector during the cooling period of the metal material after laser loading. The data of the photodetector and the second photodetector are calibrated to obtain a calibration relationship curve. The measurement data of the second photodetector in the laser loading section is then used to obtain the thermal radiation component in the first photodetector, and then the reflectance component in the first photodetector in the laser loading section is obtained. The method described in the literature ignores the change in emissivity caused by surface oxidation of metal materials during the heating and cooling process, and the thermal radiation calibration curve in the cooling section cannot strictly describe the thermal radiation signal in the heating section in theory, which brings large measurement uncertainties Spend.

Contents of the invention

In order to solve the technical problem of inaccurate measurement results of existing effect test piece surface reflectance measurement methods, the present invention provides a metal test piece surface laser reflectance measurement device and method that overcomes thermal radiation signal interference.

The technical solution of the present invention is: a metal test piece surface laser reflectance measuring device, which is special in that it includes a measuring integrating sphere and a background integrating sphere, and the connection between the measuring integrating sphere and the background integrating sphere is provided with a through-hole The mounting hole of the test piece; the measuring integrating sphere is equipped with a measuring photodetector, and the background integrating sphere is equipped with a background photodetector; the measuring integrating sphere is also provided with a laser inlet, and the laser inlet It is located on the other side of the ball wall opposite to the mounting hole of the test piece.

The above-mentioned measuring integrating sphere and the background integrating sphere have an integrated structure, and a test piece mounting groove is arranged on the wall of the ball at the test piece mounting hole.

The above-mentioned measurement integrating sphere and the background integrating sphere have the same structure size and inner surface treatment process.

The present invention also provides a method for measuring laser reflectivity on the surface of a metal test piece, which is special in that it includes the following steps:

1) Aim the laser at the laser entrance hole, set the laser power P and the light output time T;

2) Place the standard test board on the mounting hole of the test piece and load the laser;

3) Record and measure the time-varying signal V _0s (t) of the photodetector and the time-varying signal V _0b (t) of the background photodetector; then, turn off the laser and remove the standard test board;

4) Place the metal specimen to be tested on the mounting hole of the specimen and load the laser;

5) Record and measure the time-varying signal V _1s (t) of the photodetector and the time-varying signal V _1b (t) of the background photodetector; then, turn off the laser and remove the metal specimen to be tested;

6] According to the formula k=(V _1s (t)-V _1b (t))/(V _0s (t)-V _0b (t)) to calculate the surface reflectance coefficient k of the metal specimen under the condition that the laser power is P ;

7) Change the laser loading power P and the light output time T, and repeat steps 1-6] to obtain the surface reflectance coefficient k of the metal specimen under different input conditions;

8] Multiply the surface reflectance coefficient k of the metal test piece by the reflectance of the standard test plate to obtain the surface laser reflectance of the metal test piece to be tested.

The above-mentioned standard test plate is an inert metal plate or an inorganic material plate with known reflectance.

Preferably, the included angle between the laser incident direction of the laser and the normal direction of the standard test plate or the metal specimen to be tested is α, where 0°<α≦8°.

The above-mentioned metal test piece to be tested is a sheet structure with a thickness less than 5mm.

The two surfaces of the metal test piece to be tested are made by the same treatment process.

The beneficial effects of the present invention are:

(1) The present invention prepares the metal test piece into a sheet shape, the front and rear surfaces have the same initial state, and have the same oxidation state under the same temperature history, so that the front and rear surfaces of the metal test piece have the same temperature during the laser irradiation process. Ascension process, so it has the same thermal radiation signal, by setting a series of integrating spheres, using the measuring integrating sphere and the background integrating sphere to obtain the measurement signal and the background thermal radiation signal respectively, and the real reflectance coefficient is obtained through data processing, which overcomes the Effect of thermal radiation signal on reflectivity measurement of metal specimen surface at high temperature.

(2) The measurement device and method are suitable for different laser target spot shapes and light intensity distributions. No filter is used in the measurement. It has the characteristics of simple operation, wide application range, and convenient placement of test pieces. It is especially suitable for Measurement and calibration of large batches of test pieces.

Description of drawings

Fig. 1 is a traditional metal test piece surface laser reflectance measuring device diagram;

Fig. 2 is a diagram of a device for measuring laser reflectance on the surface of a metal test piece according to a preferred embodiment of the present invention.

Wherein, reference signs are as follows: 1-laser, 2-laser beam, 3-metal specimen, 4-integrating sphere, 41-measurement integrating sphere, 42-background integrating sphere, 5-photoelectric detector, 51-measurement photoelectric detection device, 52-background photodetector, 6-test piece installation hole, 7-laser access hole.

detailed description

The invention provides a device and method for measuring laser reflectivity on the surface of a metal test piece. The measurement signal and the background thermal radiation signal are respectively obtained by setting the measuring integrating sphere and the background integrating sphere, and the real reflectivity coefficient is obtained by data processing, which overcomes the problem of metal test pieces. The influence of the thermal radiation signal on the measurement results of the surface of the workpiece at high temperature. The structure of the preferred embodiment of the measuring device of the present invention is as shown in Figure 2, comprising a measurement integrating sphere 41 and a background integrating sphere 42 arranged next to each other, and a through test piece mounting hole 6 is provided at the connection between the two; Place the metal test piece or standard test plate to be measured. A measuring photoelectric detector 51 is installed on the measuring integrating sphere 41, and a background photodetector 52 is installed on the background integrating sphere 42; a laser inlet 7 is also arranged on the measuring integrating sphere 41, and the laser inlet 7 is located in the same position as the test piece mounting hole 6. On the opposite wall of the ball. The laser beam 2 emitted by the laser 1 is incident on the surface of the metal test piece 3 through the laser entrance hole 7 .

The measuring integrating sphere and the background integrating sphere can be a split structure that is spliced after being processed separately. The joint of the two is a common test piece mounting hole that penetrates the inside of the two integrating spheres. During the actual test process, first disassemble the measuring integrating sphere and the background integrating sphere, install (or take out) the metal test piece or standard test plate to be tested, and then put the two integrating spheres together.

More preferably, the measuring integrating sphere and the background integrating sphere can also be processed into an integrated structure, and a test piece mounting groove is arranged on the ball wall at the test piece mounting hole. When testing is required, insert the metal specimen to be tested or the standard test board into the specimen installation slot, completely covering the specimen installation hole. After the test is completed, just pull out the metal test piece or standard test board directly.

In order to eliminate the influence of the thermal radiation signal of the metal test piece 3 on the measurement results at high temperatures, the metal test piece 3 is in the shape of a thin sheet with a thickness of no more than 5 mm. The two surfaces of the metal test piece 3 are made with the same treatment process to ensure that the two The signal of the external heat radiation on the surface is consistent, and the structural size and inner surface treatment process of the measuring integrating sphere 41 and the background integrating sphere 42 are all the same to ensure that the obtained signal amplitudes are basically the same, so that the signal obtained by measuring the integrating sphere 41 is effective The reflection signal and the front surface heat radiation signal of the metal test piece 3, while the signal obtained by the background integrating sphere is the heat radiation signal on the back surface of the metal test piece 3, since the metal piece is very thin and has the same surface treatment process, the integrating sphere 41 and the background heat radiation signal are measured at the same time The amplitudes of the response signals of the integrating sphere 42 are basically the same, so the two can be subtracted to obtain an effective reflection measurement signal.

The specific test method based on the laser reflectivity measuring device on the surface of the metal test piece provided by the present invention is as follows:

1] Align the laser 1 with the laser entrance hole 7, set the laser power P and the light output time T.

2] Place the standard test board on the mounting hole 6 of the test piece, and load the laser. The reflectance value of the standard test plate is known and has a strong resistance to laser radiation stability, generally an inert metal plate or an inorganic material plate.

3] Record and measure the time-varying signal V _0s (t) of the photodetector and the time-varying signal V _0b (t) of the background photodetector; then, turn off the laser and remove the standard test board.

4) Place the metal specimen to be tested on the mounting hole of the specimen, and load the laser; the angle between the laser incident direction of the laser and the normal direction of the standard test plate or the metal specimen to be tested is α, where 0°﹤α≦ 8° to minimize light loss.

5) Record and measure the time-varying signal V _1s (t) of the photodetector and the time-varying signal V _1b (t) of the background photodetector; then, turn off the laser and remove the metal specimen to be tested.

6] According to the formula k=(V _1s (t)-V _1b (t))/(V _0s (t)-V _0b (t)) to calculate the surface reflectance coefficient k of the metal specimen under the condition that the laser power is P .

7] Change the laser loading power P and the light output time T, and repeat steps 1-6] to obtain the surface reflectance coefficient k of the metal specimen under different input conditions.

8] Multiply the surface reflectance coefficient k of the metal test piece by the reflectance of the standard test plate to obtain the surface laser reflectance of the metal test piece to be tested.

The invention effectively overcomes the influence of thermal radiation on the reflectivity measurement results in laser loading, has the characteristics of simple operation, wide application range, and convenient arrangement of test pieces, and is especially suitable for measurement and calibration of large batches of test pieces.

Claims (8)

1. a kind of metal specimen surface laser measuring apparatus for reflection index, it is characterised in that：Including measurement integrating sphere and Background Integral The junction of ball, the measurement integrating sphere and background integrating sphere is provided with the test specimen installing hole of insertion；On the measurement integrating sphere Measurement photodetector is installed, background photodetector is installed in the background integrating sphere；On the measurement integrating sphere also It is provided with laser and enters hole, the laser enters hole position on the opposite side ball wall relative with test specimen installing hole.

2. metal specimen surface laser measuring apparatus for reflection index according to claim 1, it is characterised in that：The measurement product Bulb separation and background integrating sphere are integral type structure, are provided with test specimen mounting groove on the ball wall at the test specimen installing hole.

3. metal specimen surface laser measuring apparatus for reflection index according to claim 1 and 2, it is characterised in that：The survey The physical dimension and inner surface treatment process all same of amount integrating sphere and background integrating sphere.

4. a kind of metal specimen surface laser method for measuring reflectance, it is characterised in that：Comprise the following steps：

1】Laser alignment laser is entered into hole, laser power P is set and is gone out light duration T；

2】Standard test panel is positioned on test specimen installing hole, laser is loaded；

3】Record measures photodetector signal V over time_0s(t) and background photodetector signal over time V_0b(t)；Then, laser is closed, removes standard test panel；

4】Metal specimen to be measured is positioned on test specimen installing hole, laser is loaded；

5】Record measures photodetector signal V over time_1s(t) and background photodetector signal over time V_1b(t)；Then, laser is closed, removes metal specimen to be measured；

6】According to formula k=(V_1s(t)-V_1b(t))/(V_0s(t)-V_0b(t)) laser power is calculated for the metal under P-condition Surface of test piece reflectivity factor k；

7】Change Laser shock loading power P and go out light duration T, repeat step 1-6】Obtain the metal examination under different input conditions Part surface reflectivity coefficient k；

8】Metal specimen surface reflectivity coefficient k is multiplied with the reflectance of standard test panel and obtains the surface of metal specimen to be measured Laser reflectivity.

5. metal specimen surface laser method for measuring reflectance according to claim 4, it is characterised in that：The standard is surveyed Test plate (panel) is inert metal plate known to reflectance or inorganic material plate.

6. the metal specimen surface laser method for measuring reflectance according to claim 4 or 5, it is characterised in that：Laser instrument Laser light incident direction and standard test panel or the angle of normal direction of metal specimen to be measured be α, wherein 0 ° of ﹤ α≤8 °.

7. metal specimen surface laser method for measuring reflectance according to claim 6, it is characterised in that：The gold to be measured Category test specimen is flake structure of the thickness less than 5mm.

8. metal specimen surface laser method for measuring reflectance according to claim 7, it is characterised in that：The gold to be measured Made using identical handling process on two surfaces of category test specimen.