【作者】 乔培玉；

【导师】 何昕；

【作者基本信息】 中国科学院研究生院（长春光学精密机械与物理研究所） ， 机械电子工程， 2012， 博士

【摘要】 枪弹头痕迹比对检验学在公安实践中可以判断发射枪支以证实犯罪，而传统利用显微镜比对效率很低，迫切需要一种高效精确的比对方法。目前基于计算机图像处理学的弹痕比对方法研究较多，但都是基于二维的灰度图像。由于灰度图像在获取的过程中受周围环境光照影响较大，同时不能够获取深度信息，因此比对结果可靠性不高，在最终判别两颗子弹的相似度时还需进行大量的人工比对，效率没有实质性的提升。为了提高枪弹头痕迹比对的效率，通过研究发现，在枪弹头比对过程中，弹痕的深度纹理信息是重点比对对象，因此如何精确的获取弹痕的深度纹理信息是研究工作的重点。本文在枪弹头痕迹测量现状的基础上，根据弹痕比对系统的要求，在获取足够高的测量精度且不会对子弹的纹理信息遭到破坏的前提下，提出了采用光学非接触测量的方法。通过分析发现，基于结构光的投影光栅相移测量技术是通过直接分析变形光栅得到物体的高度信息，此方法具有测量精度高，速度快，对物体的纹理无破坏等优点~[17]，非常符合弹痕三维纹理信息测量的要求。本文以结构光数字投影光栅相移测量技术为主要研究方向，主要研究工作定位在用数字投影光栅相移技术来测量弹痕的三维纹理数据，同时对获取的弹痕数据进行相似度分析。在结构光投影光栅相移测量领域，所测量的对象大都是相对较大的物体，在如对弹痕纹理等微观领域的测量研究相对较少。在详细分析数字投影光栅相移测量技术原理的基础上，从弹痕三维纹理测量的整个系统出发，提出了弹痕测量系统的平台构成。投影光栅相移测量技术中最重要的环节是位相提取和位相展开方法，为了滤除噪声及投影仪畸变，CCD相机畸变等各种影响，对采集的条纹图像采用了自适应维纳滤波和小波多阈值方法进行预处理，提出了十六级平均技术进行位相主值的计算，提高了计算的精度；在位相展开方面，针对位相中存在不能够识别的间断点或是跃变点，提出了基于多频的梯度导向相位展开算法，实验验证其有效地克服了位相中间断点和跃变点对位相展开的影响，提高测量精度。在弹痕三维纹理测量系统参数标定方面，给出了三维弹痕纹理测量系统参数标定的过程，对系统的光学畸变等进行了标定，标定过程中选择高精度的徕卡经纬仪作为辅助设备，采用了分区拟合的算法进行整体的畸变标定；利用标定系数对位相值进行修正，最后进行位相-高度的映射。针对弹痕提取和弹痕比对，首先利用OpenGL编写了重建的软件，添加了伪彩色功能进行辅助分析；讲述了基于椭圆拟合法提取弹痕的原理，给出了坐标转换的具体公式，针对此方法不能处理发生形变的子弹的情况，提出了利用高斯滤波中线法进行弹痕的有效提取，详细的介绍了滤波器的设计过程，给出了滤波器的逼近性能分析，减少了数据冗余，提高了提取的精度和效率，研究了不同的截止波长对提取结果的影响。在基于上述弹痕提取的基础上，运用互相关算法来表征两颗子弹的相似程度，选用比对结果最优的截止波长，同时为了增加比对结果的可靠性，又提出了利用2D+3D的数据融合方法进行人工的辅助分析。为了解决子弹变形严重时弹痕信息遭到破坏问题，又对弹壳的撞针信息进行了分析，利用基于体素的互相关测度法进行相似度计算，为了克服两颗弹壳在数据采集时坐标不一致的问题，提出了基于自适应变系数的迭代算法进行最优相似度的计算，给出了算法的实验流程，结果表明此方法能够提高比对的可靠性。实验结果表明，系统所设计的硬件结构和相关算法能够满足弹痕比对的要求，达到了预期目的。更多还原

【Abstract】 The comparison and verifying of the bullets trail could identify the fired guns toprove the criminal, the efficiency of comparison using microscope is vefy low, so it’sneed for an more efficient and more accurate method. At present there are manymethods based on computer image processing, but they are based on two-dimensionalgray image, due to the influence of ambient light, and not include the information ofdepth, the reliability of the results of compared grayscale image is not high enough, soit’s also need lots of manual matching to distinguish the similarity of the two bullets,the efficiency of comoparison is rarely improved.In order to improve the efficiency of bullet trail comparison, the recent scientificstudies indicate that the depth topography of the bullet trail is very importantinfromation when we compared the bullets, so how to accurately obtain the depthtexture is emphases in research. On the basis of the measuring status in the traces ofthe bullets, according to the requirements of the system, at the same time to obtain asufficiently high measurement accuracy, nor will be destroyed the bullet textureinformation, we present optical non-contact measurement method. The analysis showsthat the grating projected method based on struct optical can get the objects highinformation by analyzing the change grating and there are several advantages, such asaccuracy of data is very high, the measurement speed is quick, gets the texture of theobject without damage et al..., all of these fit the requirements of bulletthree-dimensional texture information measurement. So we choose the gratingprojected phase method, then the importent thing is to measure the three dimensionalinformation of bullets, and analyzed the similarity of the bullets simultaneously.In the field of the structed light projection grating phase shift measurement, themeasured object are relatively large objects, the study is relatively less in themeasurement of microscopic field, analyzing the grating projected phase methodparticularly and considering the system of bullets, the paper presents the structure ofall measurement system. The most importent aspects of the projection grating phaseshift measurement is phase calculating and unwrapping, in the first place, we selectedadaptive Wiener filter and layered soft-threshold wavelet to denoising, proposed thesixteen phase shift based on average method to calculated the phase, and the accuracy is improved, in terms of phase unwrapping, introduted the details of the gray code,and describes its principle, analyzed its drawbacks. We proposed the gradient-orientedphase unwrapping algorithm based on multi-frequency, experimental results showsthat this algorithm could overcome the discontinuity point and the transition point ofphase unwrapping, the measurement accuracy is improved effctively.In the calibration of the measurement system, all calibration parameters of systemare described particularly, and calibrated the optical distortion of the system, weselected the high-precision Leica theodolite as auxiliary equipment, used partionedfitting algorithm to calibrated the overall distortion, utilized the calibration coefficientto corrected the phase, then carried out the calculation of phase-height mapping.Aim to bullet extraction and bullet comparison, first we wrote the software usedOpenGL, added the pseudo-color function; talked about the principle based on ellipsefitting to extract the bullet trace, and given the specific methods and formulas of thecoordinate transformation. For this method can’t handle the case of deformation of thebullet, proposed the Gaussian filter midline to extracted the bullet trace, descriped thedesin process of the filter in detailed, given the analysis of the filter approximationperformance, reduced data redundancy, improved accuracy and efficiency of theextraction, discussed the extracted results in the different cut-off wavelength. Basedon the above extracted results, we used the cross-correlation algorithm to characterizethe degree of similarity of the two bullets. In order to increase the reliability of theresults, we proposed the data fusion of2D+3D for artifical assisted analysis.In order to solve the bullet topography information destructed while the bulletwas deformated seriously, we analyzed the cartridge case, using voxel-basedcross-correlation measure method to calculate the similarity. In order to overcome theincosistency of coordinates, proposed the iterative algorithm based on adaptivevariable coefficient for the calculation of the optimal similarity, given theexperimental procedure, the result shows that this method can improve the reliabilityof matching.Experimental results show that the algorithm and hardware design of this systemmeet the bullet comparison needs and it achieves the desired purpose.更多还原