投影式幻影成像中局域几何畸变的校正方法研究

Study on Correction Method of Local Geometric Distortion in Projection Phantom Imaging

在幻影成像系统中,投影式成像装置具有制造成本低、成像系统操作便捷的优点,但由于投影光线发散和光源处光束偏轴角的存在,投影图像照射到四棱锥斜面时会发生几何畸变,导致三维模型失真。针对该问题,提出一种投影图像局域几何畸变的校正方法。通过提取投影图片,分析并建立投影图像形状和三维模型失真程度的映射关系,利用透视变换,构建投影图像局部几何畸变的矫正模型,实现三维模型的失真补偿。实验结果证明,校正后图像边长误差从34.4%降低到3.3%,角度误差从18.3%降低到3.3%,验证了该方法的有效性和可行性。

In the phantom imaging system,the traditional imaging light source device uses four display screens to display the front,rear,left,right,and four sides of the object,respectively,and the light vertical display screen is mapped on each surface of the quadrangular pyramid,thereby forming a threedimensional model inside it.Compared with the traditional imaging device,the projection imaging device has the advantages of low manufacturing cost and convenient operation of the imaging system.However,because the projector’s light projection method is based on the divergent projection of the midpoint of the light source,and when the light passes through the projector lens,the central axis light can be refracted to generate an off-axis angle,so that the image projection illuminates the area of each surface area of the quadrangular pyramid.Geometric distortion,resulting in distortion of the 3D model.Aiming at this problem,a correction method for local geometric distortion of projection images is proposed.By changing the position of pixel points in the distorted image,it is in the same position as the pixel corresponding to the reference image,the effect of correcting image distortion is achieved.The image projected onto the outer surface of the tetrahedron is a parametrizable projection surface.According to the inverse deformation method,the perspective transformation method is used for point-by-point mapping for geometric correction to ensure the accuracy of the image.First,extract the projection image,select the original image and the regular shape image corresponding to the distorted image for analysis,establish the mapping relationship between the shape of the projected image and the degree of distortion of the 3D model,and construct a correction model for the local geometric distortion of the projected image,so that the original image is compared with the original image.Inversely transform the distorted image to an equal proportion;then through the inverse transformation matrix to reverse the pre-distortion of the original image as a whole,and then artificially deform the original image into the required pre-distorted image;finally,as the projected image cached by the projector,it is used to offset the axial angle and different degrees of image distortion caused by the non-perpendicular mapping of the beam and the projection plane to achieve the distortion compensation of the three-dimensional model to achieve the effect of distortion correction.After that,through the regular graph cube experiment test,the results show that:after correction,the error of the image side length in millimeters is reduced from 34.4%to 3.3%,and the angle error is reduced from 18.3%to 3.3%,which verifies the effectiveness and feasibility of the method.