The history of the laws of thermal radiation is briefly reviewed, and the theoretical relations basic to some of the optical methods of temperature measurement are given. Comments on a number of optical methods are presented, as well as a selected reference with each method where more detail is available. In conclusion, several problems, in areas of uncertainty in the field of optical methods of temperature measurement, are suggested in the belief that a solution to these problems will greatly enhance the technical value of this field.
George A. Hornbeck, "Optical Methods of Temperature Measurement," Appl. Opt. 5, 179-186 (1966)