Acceptance of vision systems has been slow because hard-nosed assembly operators have found it difficult to credit the claims made for vision systems. However, these claims are proving to be true. Vision systems can provide operator control of the assembly process. Mistakes can be caught immediately and misalignments corrected before the multiplying process of a costly error begins. Vision systems offer the assembly operation the ability to see what is going on at every stage. This can generally be achieved with very little or no slowdown in the assembly operation. Vision systems offer additional benefits, such as reliability, accuracy, repeatability, and flexibility. Vision systems can perform many types of inspection before, during, and after each assembly operation, and they can frequently guide the assembly operation. Vision systems currently available can be divided into 2 types: edge finders and correlators. While both types are pattern recognition systems, significant differences exist and a clear distinction of these is useful