Calibration Services

Spectral radiant flux is the total power of light source at a given wavelength without considering the human perception factor. The unit of spectral radiant flux is watt per nano-meter (W/nm). At SCL, the calibration is performed inside a 1.65-m diameter integrating sphere with high diffuse and spectral flat reflective coating. The integrated light signal is coupled to a high precision double monochromator by an optical fiber for spectral measurement at the wavelength range from 365 nm to 850 nm. The calibration and measurement capability (CMC) for spectral radiant flux measurements is 2.2%.

 

Spectral radiance is the ratio of the amount of electromagnetic radiant flux per unit solid angle, to the projected area of the source element at a particular wavelength and a particular direction. The unit of spectral radiance is Wm^-2sr^-1nm^-1 where steradian (sr) is the unit of the solid angle.

At SCL, source-based method is used to calibrate the spectral radiance of light source (radiance gauge). Calibration is usually performed at the perpendicular direction to the output port of the light source. The spectral distribution of the optical radiation emitted from the light source is compared with the laboratory references via a high precision double monochromator with CMC of 2.4%. Wavelength range covers from 300 nm to 1800 nm.

 

Spectral irradiance is a fundamental radiometric unit and is defined as the amount of electromagnetic radiation incident on a surface area with the unit of Wm⁻² at a specific frequency, Hz (or for a particular wavelength, nm). Hence, spectral irradiance can be understood as the spectral distribution of optical radiation and a function of photon wavelength, with the unit of Wm⁻²nm⁻¹. At SCL, spectral irradiance is calibrated by comparing optical radiation from a light source under test with the laboratory references via a high precision double monochromator with CMC of 1.5%. The wavelength range covers from 250 nm to 1800 nm.