Shape reconstruction from endoscope image by its shadings

This paper describes a total image processing to reconstruct a shape from endoscope images. We have already developed a shape reconstruction procedure from an endoscope image sequence, and produced a global 3D sketch of object shape from an image sequence taken by a moving endoscope. Here, we propose a method to obtain fine 3D structure from its shading based on the global sketch. We consider the shape from the shading problem in the case where a point light source is at the projection center. This condition well approximates the imaging system of an endoscope. In this case, the image gray level depends on not only the gradient of the object surface but also the distance from the light source to each point on the surface. To deal with this difficulty, we introduce the evolution equation for equal-distance contours on the surface. Propagating this contour by solving the equation, we can reconstruct a shape. Experimental results for real medical endoscope images of a human stomach inner wall show feasibility of this method, and present a promising technique for morphological analysis of tumors on human inner organs.