高功率激光近场空域计算方法

Calculated Methods of High Power Laser Near Field Parameters

为了使目前高功率激光近场空域的对比度和调制度评价更加科学化,在数值计算中采用图像分割灰度门限法,对CCD采集的原始近场图像进行信噪分割.用最大类间方差作为判断噪声阈值的主要依据,由噪声区域最大概率灰度值得到本底灰度,然后根据强度是否大于Iavg(1+5σ)值来判断是否存在奇异点.奇异点位置灰度值经8-邻域图像平滑处理得到.通过应用大量近场测量数据分析对比了调制度的两种计算方法,结果表明两种计算方法处理结果是一致的,并规范地给出了高功率激光近场空域评价计算方法.

In order to scientifically evaluate the near field parameters involving the modulation and contrast ratio in space region for high power solid-state laser facility, the grey threshold of image segmentation in image processing is used to separate the noise and signal for the image of near field picked by CCD. The maximum square difference value is taken as the main criterion for noise threshold. The grey background can be obtained from the grey value of the most probability in the noise region. The oddity spot in laser near field can be judged based on whether the intensity is greater than Iavg （1＋ 5σ） or not. The image smoothness technique of eight neighbor regions is adopted to process the oddity spots of pixel. Two evaluated methods for modulation are analyzed and compared with many experimental data. It is shown that two calculation results of modulation are identical, and present evaluated methods of high power laser near field parameters are much more normative.