Specialized video measuring system (SVMS) is a kind of instruments diagnosing only one special type of part with high performance. In the design of a SVMS, it is necessary to consider the special requirements during the inspection of the parts. We take the video-based inspecting instrument for watch escapement (VIIWE) as an example of SVMS. A method based on least interferences is proposed to determine an optimized movement layout. The quality of image taken by an imaging lens with a limited depth of field (100 μm) may be degraded by two parameters, i.e., the perpendicularity of optical axis to workbench and the parallelism of probe movement plane to workbench. To optimize the two parameters, we calibrate the perpendicularity with a definition function, measure the parallelism with a dial indicator, and develop a mechanism of adjustment. The scheme about movement layout and adjustment has been successfully applied in the VIIWE.