Non-contact temperature measurement by dual-wavelength shift in brewster's angle

Embodiments disclosed herein relate to a thermal processing chamber having a substrate monitoring system. In one embodiment, a temperature monitoring system is disclosed herein. The temperature monitoring system includes a housing and a window defining an interior volume, one or more light sources, a camera, a polarizer, a collimator, a first mirror, and a second mirror. The one or more light sources are disposed in the interior volume. The camera is configured to capture a plurality of frames of one or more light beams. The polarizer is disposed in an optical path of the one or more light beams. The first mirror is configured to reflect light directed by the collimator towards a bottom surface of a substrate such that the beam creates an angle of incidence equal to a Brewster's angle. The second mirror is configured to direct the one or more light beams to the camera.