A method and apparatus for calibration non-contact temperature sensors within a process chamber are described herein. The calibration of the non-contact temperature sensors includes the utilization of a band edge detector to determine the band edge absorption wavelength of a substrate. The band edge detector is configured to measure the intensity of a range of wavelengths and determines the actual temperature of a substrate based off the band edge absorption wavelength and the material of the substrate. The calibration method is automated and does not require human intervention or disassembly of a process chamber for each calibration.