Typically, a CMOS image sensor is positioned at the integrating sphere uniform plane of irradiance. Illumination is provided indirectly by multiple diffuse reflections so the device is exposed to uniform irradiance across its active area.
The sensor is located at the exit port of the uniform source or at a specified distance from the exit port defined by the f/# of the device under test (DUT). An illuminance or irradiance monitor, which is mounted on the sphere wall, is calibrated to monitor the power per unit area at the DUT. This provides the amount of power density on the surface of the semiconductor, which is then used to determine the electro-optical response of the device.
Different types of light sources may be used in this approach. The sphere may be illuminated with current regulated incandescent lamps or with more sophisticated sources to simulate a specified spectral distribution, such as that of average daylight. The integrating sphere may also be coupled to a monochromator for the purpose of spectral characterization.
Labsphere’s Uniform Source Systems are used to uniformly irradiate semiconductor wafers and devices to test their quantum efficiency.