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为了检验该装置的光谱检测特性及成像功能,进行了单个点的光谱探测和二维光谱成像两个实验。
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对聚甲基丙烯酸甲酯(PMMA)、聚乙烯和二氧化硅玻璃样品分别进行了单点的布里渊光谱测试。图7分别为PMMA、聚乙烯和二氧化硅玻璃样品的典型光谱仪输出图。
使用洛伦兹峰值拟合方法,获得了PMMA、聚乙烯和二氧化硅玻璃的布里渊光谱频移,分别为15.4 GHz、16 GHz和33.8 GHz,如图8所示,然后根据公式(2)及公式(3)计算得出上述各材料的纵向弹性模量M,如表1所示,实验结果与参考文献[12]测试结果一致。
Sample Density/
g·cm−3Refractive
indexFrequency
shift/GHzElastic
modulus/GPaPMMA 1.18 1.49 15.4 8.92 Polyethylene 0.19 1.51 16 7.23 Silica glass 2.23 1.47 33.8 83.4 Table 1. Typical parameters of PMMA, polyethylene and silica glass[12]
该系统布里渊光谱的分辨率计算式为[24]:
式中:
$\Delta {{f}}$ 为光谱分辨率;$c$ 为光速(3×108 m/s);$N$ 为通道数(4096);$\Delta \lambda $ 是同步测量范围(4 nm);${\lambda _0}$ 为激光中心波长(532 nm)。代入测量参数,可以得到该实验装置的光谱分辨率为0.25 GHz。 -
由于容易获得PMMA的布里渊信号,因此在该实验中选择了PMMA来验证成像性能。图9是PMMA的二维布里渊光谱图像。图9(a)是在没有激光和反向散射光抑制模块的情况下测得的PMMA的布里渊光谱图像。图9(b)是添加了激光和反向散射光抑制模块后测得的PMMA的布里渊光谱图像,图中两个白色亮点即为PMMA的布里渊光谱图像。通过实验可知,加入激光和背向散色光抑制模块,可以更清楚更有效地获得物质的布里渊光谱图像信息。
Elastic modulus measurement based on virtual image phase array confocal Brillouin spectroscopy technology
doi: 10.3788/IRLA20200265
- Received Date: 2020-03-10
- Rev Recd Date: 2020-04-25
- Available Online: 2021-05-12
- Publish Date: 2021-04-30
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Key words:
- elastic modulus /
- virtual image phase array /
- confocal Brillouin /
- spectral frequency shift
Abstract: The elastic modulus of biological tissues and materials is the key factor to determine their mechanical properties, which is very important for biomedicine and material monitoring. A method for measuring elastic modulus based on virtual image phase array was proposed. Combining virtual image phase array with confocal microscopy system, the Brillouin spectrum frequency shift of biological tissues and materials could be obtained quickly, and then the elastic modulus could be calculated. Firstly, the relationship between the elastic modulus and Brillouin spectrum frequency shift was analyzed theoretically; Then, the principle of the virtual image phase array and the components of the system were introduced; Finally, the spectrum test of the sample material was performed, and the spectra of polyethylene, silica glass, and polymethyl methacrylate (PMMA) were measured, the longitudinal elastic modulus M was calculated to be 7.23 GPa, 83.4 GPa and 8.92 GPa, respectively, and the Brillouin spectral image of PMMA was measured. The results show that the cascade use of the virtual image phase array and the diffraction grating can improve the order overlap phenomenon of the etalon, and increase the resolution and acquisition rate of the Brillouin spectrum. The laser and backscattering light suppression module designed by this system can significantly improve the contrast of the Brillouin signal which is of great significance in material properties, structure monitoring and biomedicine.