Normal reconstruction from specularity in the endoscopic setting
This work addresses surface normal reconstruction for anatomical surfaces in endoscopic settings, which is incremental as it builds on known specularity analysis but applies it to a specific medical imaging domain.
The paper tackled the problem of reconstructing surface normals from specular reflections in endoscopic images by showing that specular isophotes form concentric circles on planes, which appear as nested ellipses in images, enabling normal estimation validated on simulated data and applied to laparoscopic and colonoscopic images.
We show that for a plane imaged by an endoscope the specular isophotes are concentric circles on the scene plane, which appear as nested ellipses in the image. We show that these ellipses can be detected and used to estimate the plane's normal direction, forming a normal reconstruction method, which we validate on simulated data. In practice, the anatomical surfaces visible in endoscopic images are locally planar. We use our method to show that the surface normal can thus be reconstructed for each of the numerous specularities typically visible on moist tissues. We show results on laparoscopic and colonoscopic images.