Canon has patented a color-sensitive multi-layered sensor design, showing the company is still pursuing the technology. Like Sigma's Foveon chips, the multi-layered design allows each of the sensor's pixels to capture color information without the need for colored filters. The patent, discovered by the Japanese Engineering Accomplishment blog, suggests a system to promote resonance within the sensor, in an attempt to make the lower layers of the sensor more sensitive.

The Canon patent includes a structure (40) designed to induce resonance within the sensor, in an attempt to boost sensitivity to red light.

Canon already uses a two-layer sensor in the iFCL metering system introduced with the EOS 7D, to make it color aware. At present only Sigma, with its Foveon technology, uses a multi-layer design as its main imaging sensor. The principle is that different colors of light have different energies, allowing them to penetrate to different depths within a sensor. Existing designs have not been able to offer the same degree of light sensitivity as more conventional, filtered sensors - at least partly because the red can be lost in the sensor, rather than being recorded.

Canon's iFCL metering sensor (as first used in the EOS 7D), uses a two-layer design to provide an understanding of the color, as well as the brightness, of a scene.

Although the fine detail is not clear (a combination of being written in repetitive 'patentese' and in Japanese means it doesn't lend itself to precise machine translation), it seems Canon's design uses a physical structure that causes light to resonate within the sensor, increasingly the likelihood of the red light being captured.

Canon is not alone in working on layered sensors - Sony has also published several patents in the area, hoping to avoid the risk of color moire and loss of color resolution that exist in the conventional Bayer design. (from Egami blog)