Multiwavelength pyrometer for gray and non-gray surfaces in the presence of interfering radiation

A pyrometer apparatus for detecting a temperature of a gray or non-gray surface which is receiving undesirable extraneous interfering radiation from an interfering radiation source comprising:

• an auxiliary radiation source which directs auxiliary radiation onto said gray or non-gray surfaces;
• a chopper for selectively allowing radiation to pass from the auxiliary radiation source to said surface;
• a spectral radiometer for detecting and measuring a respective radiation spectrum of each of the auxiliary source, the gray or non-gray surfaces and the extraneous radiation source wherein S.sub.0 represents the spectrum of the auxiliary radiation source, S.sub.I represents the spectrum of the interfering radiation source, S.sub.II represents the spectrum of the surfaces in the presence of the extraneous radiation when the chopper is not allowing radiation from the auxiliary source to reach the surface, S.sub.III represents the spectrum of the surfaces in the presence of the extraneous radiation when the chopper is allowing the radiation from the auxiliary source to reach the surface;
• and,
• a computer connected to the radiometer, said computer being programmed to:
• calculate a surface reflectivity of the surface by dividing the S.sub.III spectrum minus the S.sub.II spectrum by the S.sub.O spectrum;
• calculate a surface emissivity by subtracting from 1 the calculated surface reflectivity divided by f;
• and
• solve for T the equation ##EQU11## where .lambda. is a wavelength, z(.lambda.) is the measured reflectivity, C.sub.1 and C.sub.2 are radiation constants, and f and h are constants relating to a geometry of the pyrometry apparatus, using a method of least squares.