Micro-objects measurement system based on structured light fringe projection

In order to measure micro-objects by the method of structured light projection, a set of three-dimensional topography measurement system for micro-objects was built, and the field rangecould reach 1.8 cm×1.6 cm.This measurement system took advantage of the high-speed projection feature of Light Crafter 4 500 digital projection module, low distortion scaling feature of stereoscopic microscope, extended depth of field and low distortion imaging feature of telecentric lenses. First the phase shift fringes projected by Light Crafter 4 500 were scaled down with low distortion by stereoscopic microscope, then projected it to the surface of the measured object, and the camera equipped with telecentric lens synchronously recorded deformable fringes that were modulated by the object surface topography. The corresponding truncation phase diagram was calculated by using three-step phase shift method, and then the continuous phase distribution by phase-unwrapping algorithm based on reliable path tracking was also sought for. The three-dimensional surface topography of the measured object was reconstructed. The experiment successfully reconstructs the three-dimensional topography of micro-objects surface such as BGA chips, and the results show that the system measurement accuracy reaches 11 μm, as well as the effective depth measurement range of the system is 700 μm.