Embodiments of the present disclosure provide a substrate measuring device in a lithography projection apparatus that provides multiple light sources having different wavelengths. In some embodiments, a lithography projection apparatus includes a substrate measuring system disposed proximate to a substrate stage, the substrate measuring system further including an emitter including multiple light sources configured to provide multiple beams of light, each of at least some of the multiple beams of light having a different wavelength, at least one optical fiber, wherein each of respective portions of the at least one optical fiber is configured to pass a respective one of the multiple beams of light, and a receiver positioned to collected light emitted from the emitter and reflected off of a substrate disposed on the substrate stage.