Analysis Of Luminance Characteristics Of Femtosecond Laser Ablation Spot Based On Fractal And Wavelet Transform

Femtosecond lasers lack suitable real-time measurement signals during micro-nano processing,and cannot feed back processing status or information.To study the influence of parameters on the ablation depth,a lot of experiments and model analysis are required.However,in the femtosecond laser ablation process,plasma is generated,which forms a light spot.Some researchers pointed out that the brightness level of the spot can be used as a feedback signal for the femtosecond laser micromachining process.Therefore,the analysis of the brightness characteristics of the plasma spot is of strong engineering significance.In order to explore the brightness characteristics of the spot,it is necessary to extract and process the brightness characteristics of the pre-processed spot image,and then analyze its correlation with the ablation processing technology and geometric characteristics.Based on the characteristics of the plasma spot image,an improved wavelet threshold denoising is proposed,which can effectively filter the high frequency noise of the spot image and preserve the brightness characteristics of the original spot image to a great extent.The K-means clustering segmentation method is used in Lab space to eliminate the halo part of the light spot that appears as noise in the image,and retain the effective area of the light spot brightness.Through different brightness calculation definitions in HSL space or RGB space,the brightness characteristics of the effective area of the light spot can be extracted.Based on the method of combining fractal and multi-scale soft threshold denoising,the light spot brightness characteristic curve is processed,which not only clearly retains the detailed information of the brightness characteristic curve,but also makes the curve smoother.Finally,the corresponding relationship between the brightness characteristics and the ablation processing parameters is analyzed,and it is found that there is a strong correlation between the brightness characteristics of the light spot and the ablation processing power;the correlation between the brightness characteristics and the geometric characteristics of the light spot image is analyzed,and the light spot sequence is found The brightness feature of the image has a strong long-range correlation with the spot texture contrast and spot area;it shows a strong anti-correlation relationship with the texture homogeneity.Figure 43;Table 3;Reference 58...