Wang Shuang, Han Xie, Li Kewu
School of Data Science and Technology, North University of China, Taiyuan 030051, China.
Engineering and Technology Research Center of Shanxi Province for Opto-Electric Information and Instrument, North University of China, Taiyuan 030051, China.
Sensors (Basel). 2024 Aug 10;24(16):5174. doi: 10.3390/s24165174.
A snapshot multi-wavelength birefringence imaging measurement method was proposed in this study. The RGB-LEDs at wavelengths 463 nm, 533 nm, and 629 nm were illuminated with circularly polarized light after passing through a circular polarizer. The transmitted light through the birefringent sample was captured by a color polarization camera. A single imaging process captured light intensity in four polarization directions (0°, 45°, 90°, and 135°) for each of the three RGB spectral wavelength channels, and subsequently measured the first three elements of Stokes vectors (, , and ) after the sample. The birefringence retardance and fast-axis azimuthal angle were determined simultaneously. An experimental setup was constructed, and polarization response matrices were calibrated for each spectral wavelength channel to ensure the accurate detection of Stokes vectors. A polymer true zero-order quarter-wave plate was employed to validate measurement accuracy and repeatability. Additionally, stress-induced birefringence in a PMMA arch-shaped workpiece was measured both before and after the application of force. Experimental results revealed that the repeatability of birefringence retardance and fast-axis azimuthal angle was better than 0.67 nm and 0.08°, respectively. This approach enables multispectral wavelength, high-speed, high-precision, and high-repeatability birefringence imaging measurements through a single imaging session.
本研究提出了一种快照多波长双折射成像测量方法。波长为463nm、533nm和629nm的RGB发光二极管在通过圆偏振器后用圆偏振光照射。通过双折射样品的透射光由彩色偏振相机捕获。单个成像过程在三个RGB光谱波长通道中的每一个通道中捕获四个偏振方向（0°、45°、90°和135°）的光强度，随后测量样品后斯托克斯矢量的前三个元素（、和）。同时确定双折射延迟和快轴方位角。构建了实验装置，并对每个光谱波长通道的偏振响应矩阵进行了校准，以确保斯托克斯矢量的准确检测。采用聚合物真零级四分之一波片来验证测量精度和重复性。此外，在施加力之前和之后测量了PMMA拱形工件中的应力诱导双折射。实验结果表明，双折射延迟和快轴方位角的重复性分别优于0.67nm和0.08°。这种方法能够通过单次成像实现多光谱波长、高速、高精度和高重复性的双折射成像测量。
