A system and method are used to detect parameters regarding an exposure portion or an exposure beam. The system comprising a substrate stage and a metrology stage. The substrate stage is configured to position a substrate to receive an exposure beam from an exposure portion of a lithography system. The metrology stage has a sensor system thereon that is configured to detected parameters of the exposure system or the exposure beam. In one example, the system is within a lithography system, which further comprises an illumination system, a patterning device, and a projection system. The patterning device patterns a beam of radiation from the illumination system. The projection system, which is located within the exposure portion, projects that pattered beam onto the substrate or the sensor system.