Abstract: A method of correcting a temperature probe reading in a thermal processing chamber for heating a substrate, including the steps of heating the substrate to a process temperature and using a first, a second and a third probe to measure the temperature of the substrate. The first probe has a first effective reflectivity and the second probe has a second effective reflectivity. The first probe produces a first temperature indication, the second probe produces a second temperature indication and the third probe produces a third temperature indication. The first and second effective reflectivities may be different. From the first and second temperature indications, a corrected temperature reading for the first probe may be derived, wherein the corrected temperature reading is a more accurate indicator of an actual temperature of the substrate than an uncorrected readings produced by both the first and second probes.