In order to avoid small field-of-view and limited depth-of-field of micro-vision, image definition based on gradient field and wavelet transformation was used. Microscope was set on the macro-micro dual-drive table in order to ensure the positioning precision. A selective focusing technique was developed to auto focus on the objects in different depth. Closed-loop feedback control was carried out. Experimental results showed that dynamic performance and stability of the system was satisfied, the response velocity of system increased from 0.3s-1 to 3s-1, meanwhile, collision-avoidance was executed according to vertical position relations computed by image definition.