The measure of spectral responsiveness is used to characterize photodetectors, while the measure of quantum efficiency is used for solar cells. The two techniques are similar and share the same equipment. A globar (intense thermal light source of infrared radiation) or a halogen lamp generates a beam of radiation that is decomposed in a monochromator, and the monochromatic radiation incides on the device to be analyzed. Reference sensors for Si, InGaAs, PbS, and HgCdTe are used to calibrate the radiation from the source between 300 nm and 20 μm. Quantum efficiency measurements are carried out at room temperature, while photodetector spectral responsiveness measurements require an optical cryostat operating between 77 and 300 K.