Determining spectral emission characteristics of incident radiation

A system for determining spectral emission characteristics of incident light, the system comprising:

• an array of light sensitive elements composed at least in part of stacked first and second photosensitive regions whose optical responsivity characteristics differ from one another;
• optical filters disposed over the array of light sensitive elements, wherein the optical filters are configured to allow only respective narrow parts of the optical spectrum to pass to different ones of the light sensitive elements such that different ones of the light sensitive elements or sub-groups of the light sensitive elements are operable to sense light in a part of the optical spectrum that differs from other ones of the light sensitive elements or sub-groups of the light sensitive elements;
• and
• processing circuitry coupled to the light sensitive elements and configured to receive respective photocurrents from the first and second photosensitive regions for each light sensitive element, to calculate respective ratios of the photocurrents from the first and second photosensitive regions for at least some of the light sensitive elements, and to assign respective wavelengths to the incident light based on the calculated ratios.