Zhongwei Li, Youfu Li. “Microscopic Photometric Stereo: A Dense Microstructure 3D Measurement Method”. IEEE International Conference on Robotics and Automation (ICRA), Shanghai, China, 2011.
We propose a novel Microscopic Photometric Stereo (MPS) method based on optical microscope and uncalibrated photometric stereo (UPS) for dense and refined microstructure 3D measurement. The UPS method, which does not require a priori knowledge of the light-source direction or the light-source intensity, is employed to recover surface normals and albedos from the captured micro-images. For resolving the inherent generalized bas-relief (GBR) ambiguity of the UPS, we present a GBR disambiguation method based on a framework of entropy minimization, and extend it using a graph cuts energy minimization to decrease the influence of noise and further refine the recovered surface normal. The proposed MPS method has been tested on synthetic as well as real images and very encouraging results have been obtained.