Abstract: Optical field scanning pyrometer system having oscillating scan mirror in stationary detector head scans field to measure temperature of moving hot bar or sheet which vibrates in field. Pyrometer scans through the permissible range of product movement to detect the hot product and measures and stores its temperature. The stored temperature signal is continuously fed to an external analytical computer and is updated at the end of each scan. The stored temperature signal is also displayed and recorded, but up-dating is less frequent. Scanning time and width can be varied to suit various process requirements.