Radiometry device

A radiometry device, comprising:

• a vacuum ultralow temperature thermostatic chamber that keeps an inside at an ultralow temperature in vacuo;
• a first optical path that amplifies radiation at a first frequency;
• a blackbody provided in the vacuum ultralow temperature thermostatic chamber;
• a second optical path that amplifies radiation at a second frequency;
• a polarization filter that is provided outside of the vacuum ultralow temperature thermostatic chamber and separates radiation into polarized light beams;
• a third optical path through which radiation from the blackbody enters the polarization filter;
• and
• a spectrum analyzer that analyzes a signal having passed through the first optical path and the second optical path,
• wherein the blackbody in the vacuum ultralow temperature thermostatic chamber is kept in a quasi-thermal equilibrium state at an ultralow temperature of 30 K or lower in vacuo of 10−4 Pa or lower,
• when the polarization filter receives radiation of an object, the radiation of the object is separated by the polarization filter into polarized light beams, and a separated one is allowed to enter the first optical path, and
• another is allowed to enter the second optical path simultaneously,
• and
• when the polarization filter receives the radiation of the blackbody through the third optical path,
• the radiation of the blackbody is separated by the polarization filter into polarized light beams, and a separated one is allowed to enter the first optical path, and
• another is allowed to enter the second optical path simultaneously,
• a first radiance of the radiation of the object at the first frequency is measured according to procedures of the polarization filter→the first optical path→the spectrum analyzer,
• a second radiance of the radiation of the object at the second frequency is measured according to procedures of the polarization filter→the second optical path→the spectrum analyzer,
• a third radiance of the radiation of the blackbody at the first frequency is measured according to procedures of the polarization filter→the first optical path→the spectrum analyzer,
• a fourth radiance of the radiation of the blackbody at the second frequency is measured according to procedures of the polarization filter→the second optical path→the spectrum analyzer,
• a ratio between the first radiance and the second radiance measured by the corresponding procedures is calibrated using a ratio between the third radiance and the fourth radiance to thereby
• obtain a measured value T2 of a temperature of the object to be measured using the blackbody,
• a temperature error ΔT (=T1−T2) between a temperature (a temperature of the blackbody defined by Planck's formula) T1 of the object to be obtained and the measured value T2 measured using the blackbody
• decreases inversely proportional to a temperature ratio t1/t2 between an absolute temperature t1 of the object and an absolute temperature t2 of the blackbody to be used, and
• reduction in the temperature of the blackbody to be used improves an effect of reducing the temperature error, and allows accurate measurement of the temperature of the object to be obtained.