Originally posted by falconeye IMHO, it is because the silicon part of things wouldn't change (except that it needs a pixel pitch of 2.9µm when Bayer needs 5.0µm). You only need to replace the microlens/filter layer by something else (the trichroic microlens layer) which is pure optics/micro mechanics.
The Foveon approach however, requires a complete reimplementation of the photo-electric effect in CMOS.
yes, but still it is wrong to call it close ("spiritually") to the solution which was by its core nature based on filtering out the light... it is actually close to the original Foveon which started w/ prism based cameras (their first product was
prism-based, three-sensor, one-shot studio camera) and by nature based on separating the light spectrum to absorb all parts (instead of filtering).
So "bayer" approach is to filter out and absorb only what was left, "foveon" approach is split and absorb everything after all... technically if you are talking about replacing CFA layer w/ prism layer it is close to how we make "bayer" sensors, yes... but idea is totally "foveon".