Kouwenhoven E, Mast F, van Rijk-Zwikker G L
Department of Thoracic Surgery, University Hospital Leiden, The Netherlands.
Phys Med Biol. 1993 Jan;38(1):13-24. doi: 10.1088/0031-9155/38/1/002.
We use an electronic video endoscope (Fujinon EG7-HR2) to image the mitral valve in situ in an isolated pig heart preparation. From video recordings, images are digitized and analysed with a computer. A complication encountered during the study concerned the geometric wide angle distortion caused by the device. The present paper describes a method developed to reconstruct the image, and to correct for this distortion. In order to quantify the relation between object and image, model equations were formulated based on mild assumptions. Points in object space are transformed through a non-linear relation to corresponding points in image space. Furthermore, an oblique camera view, and an aspect ratio correction factor, are accounted for. As a test object, a regular grid of points was recorded at several distances from the camera. The images of the grid points were digitized, and the model equations were fitted to these data. From test measurements, carried out in air as well as in water, it was concluded that the distortion could be quantified by three parameters. Application of the straightforward correction procedure enables us to obtain quantitative information from endoscopic images.
我们使用电子视频内窥镜（富士能EG7-HR2）对离体猪心标本中的二尖瓣进行原位成像。从视频记录中，图像被数字化并通过计算机进行分析。研究过程中遇到的一个问题是该设备引起的几何广角畸变。本文描述了一种为重建图像并校正这种畸变而开发的方法。为了量化物体与图像之间的关系，基于适度假设制定了模型方程。物体空间中的点通过非线性关系变换为图像空间中的对应点。此外，还考虑了倾斜的相机视角和长宽比校正因子。作为测试对象，在距相机不同距离处记录了规则的点网格。网格点的图像被数字化，并且将模型方程拟合到这些数据。通过在空气和水中进行的测试测量得出结论，畸变可以由三个参数量化。应用直接校正程序使我们能够从内窥镜图像中获得定量信息。
