The present disclosure relates to thin-film devices for generating a radiation spectrum and, in particular, to a method and apparatus for measuring a temperature corresponding to the radiation spectrum at the thin-film device.
In various optical systems, an optical signal is received from an object at an optical sensor and measurements of the optical signal are obtained at the optical sensor to determine a property of the object. In order to obtain accurate measurements, it is often necessary to calibrate the optical sensor using a known photon flux at one or more standard wavelengths. One method for providing a photon flux at a standard wavelength includes heating one or more blackbody radiators to selected temperatures and using an optical filter to select a calibration wavelength. However, the use of traditional blackbody sources to calibrate an optical sensor introduces size, weight, and power (SWaP) challenges. Thin film devices have been used to create blackbody radiation spectra while overcoming these challenges. These thin-film devices tend to have extended radiative surfaces, such as 10 centimeters (cm) by 10 cm. Effective calibration requires a temperature profile along the radiative surface that is uniform to within about 0.5 degrees kelvin. Therefore, it is desirable to measure temperature at the radiative surface. However, temperature sensors tend to alter local temperatures due to their thermal mass and conductivity, thereby affecting temperature uniformity across the radiative surface. The present disclosure provides a method and apparatus for measuring temperature of a thin-film blackbody source without substantially affecting the uniformity of the temperature at the radiative surface.