为了快速准确测量磷酸二氢钾(KDP)晶体坯片的体缺陷, 提出了高速激光聚焦线扫描散射成像方法, 并建立了相应的测量系统。研究了该系统的测量原理和图像采集、图像处理和体缺陷信息提取方法。基于激光散射技术, 结合高速运动装置对晶体坯片内部进行三维扫描, 用线阵CCD探测器接收气泡、包裹物等体缺陷产生的散射光。然后利用折射率匹配液消除粗糙表面带来的不利影响。最后结合数字图像处理技术, 对采集的图像进行实时处理。通过去除背景后与设定阈值比较得到具有体缺陷特征的图像, 再对其进行二值化处理, 提取得到体缺陷的位置和尺寸信息。利用该检测装置对KDP晶体坯片体缺陷进行了测量, 结果显示其检测分辨率优于40 μm, 能够为晶体坯片的精确切割和最大程度的利用提供依据, 从而节省了大量成本。

To detect the bulk defects in crystal billet of a KDP(potassium dihydrogen phosphate)crystal quickly and exactly, a laser focusing scanning scattering imaging method was proposed and a corresponding high speed line scanning measurement setup was constructed. The principle of detection, image acquisition, image processing and the extraction of bulk defects were investigated. Based on laser scattering technique, a focused line laser beam was used to scan all parts of the crystal billet with a high-speed movement device. The scattering light caused by bulk defects such as bubbles and inclusions was collected by a linear array CCD. The adverse effect caused by rough surface was eliminated with the index-matching fluid. Combined with digital image processing technique, the captured image was processed in real time. An averaged background was subtracted from the original image, then the image was compared with a threshold to judge the existence of bulk defects. The image with bulk defects was binarized to exact the positions and sizes of bulk defects. Finally, the setup was used to test the crystal billet of a KDP, results show that the sensitivity by proposed method is superior to 40 μm. It verifies that this method provides supports for accurately cutting and making the most use of crystal billet and also saves a lot of costs.