通过偏振光增强激光散斑血流成像对比度

When coherent light is used to irradiate biological tissue, the differential optical path length leads to a variegated intensity image, which is characterized by fluctuations in brightness. This phenomenon is known as laser speckle. Laser light has polarization characteristics, and linear polarizers can be leveraged to eliminate surface reflections, increase penetration depth, and enhance the contrast value of speckle, which can be used to improve the contrast value and detection depth of speckle imaging. In this study, an experimental investigation was carried out to enhance the contrast of laser speckle imaging using polarization effects, which is based on a mouse spinal window model. Two adjustable linear polarizers are added to the laser speckle imaging system, and the original speckle images are processed and compared by using the temporal laser speckle contrast analysis (tLASCA). Under the conditions of a laser wavelength of 632.8 nm and an exposure time of 20 ms, imaging details were more abundant under S and P polarization than under polarization at a 45^◦ angle. Through comparison of the contrast value of each image before and after the addition of polarizer, it is found that all three polarization methods have improved speckle contrast. Notably, the S-polarization at a polarization angle of 120^◦ and the P-polarization at an angle of 30^◦ exhibited the most significant enhancements.