Abstract
A multiwavelength radiation thermometer having a hybrid detector of a 64-element silicon-germanium linear array and an infrared detector of a 48-element InSb linear array was developed for measurements of temperature and emissivity. A wide wavelength range detection by one fixed grating from 0.55μm to 1.6μm were realized by the hybrid detector. The InSb detector and a LiF prism were used for the long wavelength range from 1.3μm to 5.3μm.
The two-detector optical system without mechanical wavelength scanning and light chopping improved the stability and the response time as short as 256μs to scan a total of 112 wavelengths. In a continuous 6-month operation without optical adjustment, no wavelength drift and 5% reduction in responsivity were observed.
A reference radiation source of a plane blackbody furnace was used for the compensation of the responsivity reduction and the atmospheric absorption of the optical pass of the multiwavelength radiation thermometer.
The temperature scale and the wavelength of each detector element were calculated from calibration data. Two blackbody furnaces and 24 narrow-band-pass filters were used in the calibration. The noise equivalent. temperature differences were estimated from the temperature scales and noise data of the analog signals when the time constant of the amplifiers was 100ms and the target was a blackbody operated at 1052°C; they were 0.16°C, 0.08°C, 0.24°C, and 0.54°C at the wavelengths of 0.55μm, 0.66μm, 2.0μm, and 5.0μm, respectively.
