Development of InGaAs radiation thermometers

In 1996 an InGaAs radiation thermometer was developed for the temperature range from 150degC to 1100degC. The quality was good except for the size of source effect (SSE). NMIJ and Chino jointly developed a technique for reducing the SSE by using a ray trace method in the design of the objective lens of 0.65 mum and 0.9 mum radiation thermometers. We applied this technique to develop new InGaAs radiation thermometers with the measuring wavelength of 1.6 mum and 2 mum and their SSEs were much improved. The detector temperature of the 2 mum thermometer should be cooled down to -15degC to obtain a good signal to noise ratio at the indium point. These thermometers can be used as standard thermometers from 150degC to 1100degC for 1.6 mum and from 100degC to 660degC for 2 mum, respectively.