A stereoscopic imaging model and its calibration of micro stereovision for 3D measurement

Micro stereovision based on a stereo light microscope (SLM) is used in micro-domains such as MEMS, micromanipulation, microassembly et al. SLM is an important device obtaining images of micro objects and play an important role in auto micro-navigation, auto micro-position, micro-measurement et al. Definition of the imaging model for a SLM differs from the imaging model of a normal optical microscope in the following aspects: (1) The vision principle of SLM uses the same principle with binocular stereovision. For obtaining depth information of the object space, the stereoscopic imaging model of SLM needs image data from matching of stereo images. (2) There is correlation between the two optical paths of SLM. This indicates that a stereoscopic imaging model of SLM is nonlinear. (3) A stereoscopic imaging model of SLM has its unique calibration parameters differing from parameters of other optical systems. In this paper, a stereoscopic imaging model of SLM is constructed. The symmetry and the differences between the two optical paths of SLM are used to calibrate the main parameters and the rectification parameters of an imaging model. Through experiments, we analyze the robustness and dependency of parameters under different magnification of the objective lens.