A method needs to be developed to characterize each pixel's sensitivity in a sensor, and identify any bad pixels to map out. The data needs to be stored in a standardized format for integration into the image processing pipeline.
An even intensity light source is generally used to map the sensitivity of each pixel. One method is to use an integrating sphere to produce a highly uniform light source at a port on the sphere. Standard illuminants combined with diffusers may be used for the light sources. An example integrating sphere may be found here:
https://www.labsphere.com/products/image-sensor-calibration/tunable-camera-calibration-source/