Canon was yesterday granted US patent 6,388,709 (filed in 1996) which is titled "Image sensing apparatus with optical modulation elements having transmission characteristics controllable by pixel". This patent goes on to describe an image sensor which can control the colour of the filter in front of each pixel. From looking through the diagrams it appears the idea is to capture two images, each with a shifted RRGGBGG pattern and then combine these two images to produce a full colour image output. This design also allows the control of the amount of light to each pixel, extending dynamic range. - Our thanks to Wilfried Bittner for spotting this.