摘要
飞秒激光在微加工过程中衍生的等离子体亮度特征可作为实时反馈的测量信号,因此,研究光斑亮度特征并构造细节信息丰富的高质量亮度变化曲线具有重要意义。首先,针对光斑图像信噪比低、目标区域边缘模糊的情况,采用改进的小波阈值去噪法对光斑图像进行滤波处理,在不改变光斑亮度水平的情况下得到边缘对比度较高的平滑光斑。然后,采用K均值聚类方法分割光斑图像,将表现为噪声的光晕部分分割出去,只保留亮度有效的区域。最后,提取光斑序列图像的亮度变化曲线,用分形与多尺度软阈值滤波相结合的方法对曲线进行处理,得到含有丰富细节信息的高质量亮度变化曲线。用不同功率的光斑图像计算亮度与分形维数,结果表明,光斑亮度和光斑变换的复杂性均随激光加工功率的增大而增大。
The plasma brightness characteristics derived from the femtosecond laser in the micromachining process can be used as real-time feedback measurement signals. Therefore, it is of great significance to study the brightness characteristics of the spot and construct a high-quality brightness change curve with rich details. In this paper, first, in view of the low signal-to-noise ratio of the spot image and the blurred edge of the target area, the improved wavelet threshold denoising method is used to filter the spot image, and a smooth spot with higher edge contrast can be obtained without changing the brightness level of the spot. Then, the K-means clustering method is used to segment the light spot image, and the halo part that appears as noise is segmented out, and only the area with effective brightness is retained. Finally, the brightness change curve of the light spot sequence image is extracted, and the curve is processed by the method of combining fractal and multi-scale soft threshold filtering, and a high-quality brightness change curve with richly detailed information is obtained. The brightness and fractal dimension are calculated using spot images with different powers. The results show that the brightness of the spot and the complexity of the spot transformation both increase with the increase of the laser processing power.
作者
王福斌
孙志林
Wang Fubin;Sun Zhilin(School of Electrical Engineering,North China University of Science and Technology,Tangzhan.Hebei 063210,China)
出处
《激光与光电子学进展》
CSCD
北大核心
2021年第24期519-530,共12页
Laser & Optoelectronics Progress
关键词
超快光学
飞秒激光
等离子体光斑
小波处理
光斑亮度
ultrafast optics
femtosecond laser
plasma spot
wavelet processing
spot brightness
