作者：王福斌, 潘兴辰, 孙志林

作者单位：华北理工大学电气工程学院, 河北 唐山 063210

关键词：飞秒激光;光斑图像分割;Freeman链码;Huffman编码

摘要：

利用飞秒激光对单晶硅材料烧蚀加工时，在烧蚀过程中会出现等离子体发光现象，为得到其中有价值的加工工艺信息，需要对其进行光斑轮廓信息的提取。该文使用Freeman链码描述光斑轮廓，并使用Huffman编码对图像链码进行压缩，减少图像特征处理计算量。首先，对光斑图像进行增强处理，采用多尺度Retinex增强法突出光斑核心区域的边界特征，使得光斑核心区域的形貌特征便于观察。其次，采用最大类间方差（Ostu）阈值分割方法对光斑核心区域目标的分割提取。最后，采用Canny+Gasussian方法分割光斑图像核心区域的轮廓，提取光斑轮廓的Freeman链码，并用Huffman编码对图像链码进行压缩。使用Huffman编码压缩后的链码串在进行计算时，速度快于直接采用Freeman链码计算时的速度。并且使用Huffman编码压缩后的链码串对图像进行描述时，可有效地减少计算量，节省大量时间。

Research on the contour extraction of spot ablated by femtosecond laser and its chain code description
WANG Fubin, PAN Xingchen, SUN Zhilin
College of Electrical Engineering, North China University of Science and Technology, Tangshan 063210, China
Abstract: When the single-crystal silicon material is ablated by femtosecond laser, plasma luminescence phenomenon occurs during the ablation process. In order to obtain valuable processing information, it is necessary to extract the spot contour information. In this paper, the Freeman chain code is used to describe the spot contour, and the image chain code is compressed by Huffman coding to reduce the amount of calculation at the image feature. Firstly, the spot image is enhanced, and the multi-scale Retinex enhancement method is used to highlight the boundary features of the core area of the spot, so that the topographical features of the spot core area are easy to observe. Secondly, the maximum inter-class variance (Ostu) threshold segmentation method is used to segment and extract the target of the spot core region. Finally, the Canny+Gasussian method is used to segment the contour of the core region of the spot image, extract the Freeman chain code of the spot contour, and compress the image chain code with Huffman coding. The chain code string compressed with Huffman coding is faster than the speed of the Freeman chain code calculation. And when the Huffman coded compressed chain code string is used to describe the image, the calculation amount is effectively reduced, and a large amount of time can be saved.
Keywords: femtosecond laser;image segmentation of spot;Freeman chain code;Huffman coding
2020, 46(4):116-122  收稿日期: 2019-10-04;收到修改稿日期: 2019-11-14
基金项目:
作者简介: 王福斌(1968-),男,山东菏泽市人,副教授,博士,研究方向为数字图像处理、机器视觉、飞秒激光微纳加工
参考文献
[1] 彭元钦, 杨丽, 卢博文, 等. 钛铝合金表面飞秒激光烧蚀特性研究[J]. 激光杂志, 2018, 39(11):51-54
[2] 戴激光, 张力, 李晋威, 等. 一种链码跟踪与相位验证相结合的直线提取方法[J]. 测绘学报, 2017, 46(2):218-227
[3] 邓仕超, 李伟明, 龙芋宏, 等. 一种改进的二值图像边界跟踪与边界链码获取算法[J]. 激光与光电子学进展, 2018, 55(6):147-153
[4] 王竞雪, 宋伟东, 赵丽科, 等. 改进的Freeman链码在边缘跟踪及直线提取中的应用研究[J]. 信号处理, 2014, 30(4):422-430
[5] BERA S, SABBALL A J, DURFEE C G, et al. Development of a femtosecond micromachining workstation by use of spectral interferometry[J]. Optics Letters, 2005, 30:373
[6] WANG F B, ZHAO L H, TU P, et al. Image feature analysis of plasma spot produced from femtosecond laser ablation for silicon wafer[J]. Journal of Micro/Nanolithography Mems & Moems, 2017, 16(2):025003
[7] 曹远佳, 尉广军, 李先龙. 激光光斑的图像处理及边缘检测的改进[J]. 激光与红外, 2016, 46(9):1160-1164
[8] PARK S, MOON B, KO S, et al. Low-light image restoration using bright channel prior-based variational Retinex model[J]. Eurasip Journal on Image & Video Processing, 2017, 2017(1):44
[9] KIM S W, JUNG J Y, YOO C H, et al. Retinex-based illumination normalization using class-based illumination subspace for robust face recognition[J]. Signal Processing, 2016, 120:348-358
[10] 黄允浒, 吐尔洪江·阿布都克力木, 刘芳园, 等. 多尺度Retinex算法与其它图像增强方法比较[J]. 新疆师范大学学报(自然科学版), 2017, 36(2):69-77
[11] MA J, FAN X, NI J, et al. Multi-scale retinex with color restoration image enhancement based on Gaussian filtering and guided filtering[J]. International Journal of Modern Physics B, 2017, 31(16/19):1744077
[12] MATIN F, JEONG Y, KIM K, et al. Color image enhancement using multiscale retinex based on particle swarm optimization method[C]//Journal of Physics Conference Series. Journal of Physics Conference Series, 2018.
[13] 李晓明, 沈学举, 刘恂, 等. 基于OTSU算法的激光光斑图像提取研究[J]. 激光杂志, 2015, 36(7):72-73
[14] CANNY J. A computational approach to edge detection[J].IEEE Trans. Pattern Analysis and Machine Intelligence, 1986(8):679-714.
[15] FREEMAN H. On the encoding of arbitrary geometric configurations[J]. Ire Transactions on Electronic Computers, 1961, 10(2):260-268
[16] B ŽALIK, D MONGUS, K R ŽALIK, et al. Chain code compression using string transformation techniques[J]. Digital Signal Processing, 2016, 53(C):1-10
[17] HUFFMAN D A. A method for the construction of minimum-redundancy codes[J]. Resonance, 2006, 11(2):91-99
[18] 吴轶. 基于边界追踪的图像信息编码方法[D]. 南昌:南昌大学, 2015.