The present invention generally provides an apparatus and a method for inspecting a substrate in a processing system. More specifically, optical signal routing methods and apparatus provide multiple inspection collection points on a semiconductor processing system. In one aspect, an optical inspection system comprises a light source and an optical receiving device, such as a CCD camera, to illuminate and inspect a substrate for various optical signatures. A plurality of optical inspection systems are connected to a signal switching device, such as a multiplexer, which operates to route a particular signal to a detector.