Patent ID: 8192077

Claim:
A method of measuring the in situ differential emissivity between two sites on a surface of an object, comprising: detecting infrared radiation arising at a first wavelength from a first site on a surface of a body when not irradiated by external infrared radiation; detecting infrared radiation arising at said first wavelength from said first site while said first site is irradiated by external infrared radiation at said first wavelength; detecting infrared radiation arising at said first wavelength from a second site on the surface of said body when not irradiated by external infrared radiation; detecting infrared radiation arising at said first wavelength from said second site while said second site is irradiated by external infrared radiation at said first wavelength; and determining an in situ differential emissivity value based on the detection of infrared radiation arising from said first site and said second site without irradiation by external infrared radiation and with irradiation by external infrared radiation.