An aggregation scheduler that determines which frames are to be aggregated in an aggregate at a specific time, and allocates a time and duration for each responder of the aggregate. Meter data is cleaned, validated and estimated by separate applications using the above-described application and retrieval processes via the message bus for flexible and efficient processing. The chip has an active surface and a back surface. A refractive index of the optical lens gradually decreases along a direction from the light incident face to the light emitting face of the optical lens. In a preferred embodiment the video display device comprises a data projector.