A method for determining change in temperature of an electromagnetically radiating device between un-energized and energized states without contacting the device is disclosed. The method includes establishing a reference image form the device by illuminating the device with an optical signal having a first optical characteristic and capturing the reference image from the device in an un-energized state, establishing an on image form the device by illuminating the device in an energized state, and establishing a modified on image form the device by illuminating the device in the energized state with a modified optical signal having a third illuminating optical characteristic, and comparing the reference image, the on image, and the modified on image to establish changes in reflection as a result of changes in temperature of the device during energization.