Whats so special about Foveons new X3 sensor?
Foveon recently introduced a new sensor technology which they call X3. This is a fundamentally different approach to producing a color sensors. Typical approaches place a Bayer pattern mosaic of color filters over the sensor and use interpolation. The Foveon sensor detects distinct red, green, and blue signals for each pixel. How can it do this? It turns out that in the materials used to make CMOS semiconductors (doped silicon), different wavelengths of light are absorbed at different depths. Foveon layers three photodiodes on top of each other on the surface of their chip. No color filters are used. Instead, the light automatically activates the right sensor based upon its depth of penetration. Since no interpolation is required in the spatial domain, Foveon images can capture sharper images than Bayer pattern sensors with the same number of pixels in the X-Y plane. (Note that Foveon likes to count all of their photodiodes as pixels, so a 4.5MP X3 image samples 3 colors at 1.5 million
