The End of Bayer Sensors Is Nigh, But What’s Next?

In the coming two years, major changes in sensor technology lie ahead. With the exception of Fujifilm cameras based around EXR and X-Trans image sensors and the Foveon-based camera lineup from Sigma, almost every digital camera on the market today has a Bayer color filter array, named after inventor and Kodak scientist Bryce Bayer. Bayer filters have a significant drawback: they work by absorbing — and thereby: blocking — incoming light at each photodiode, allowing only certain ranges of wavelengths to pass. In the process, a very significant portion of the incoming light is blocked before it can reach the sensor. New sensor technologies are about to be introduced that waste less of the incoming light.

Researchers from Technische Universität München (TUM) have developed a new generation of image sensors that are more sensitive to light than the conventional silicon versions, with the added bonus of being simple and cheap to produce. They consist of electrically conductive plastics, which are sprayed on to the sensor surface in an ultra-thin layer. Even works on glass or flexible plastic films! The chemical composition of the polymer spray coating can be altered so that even the invisible range of the light spectrum can be captured. | TUM
Researchers from Technische Universität München (TUM) have developed a new generation of image sensors that are more sensitive to light than the conventional silicon versions, with the added bonus of being simple and cheap to produce. They consist of electrically conductive plastics, which are sprayed on to the sensor surface in an ultra-thin layer. Even works on glass or flexible plastic films! The chemical composition of the polymer spray coating can be altered so that even the invisible range of the light spectrum can be captured. | TUM
The new sensor technologies basically boil down to a race between Sony and a Panasonic-Fujifilm joint venture. The latter two announced in June 2013 they’re working on an organic sensor that will be ready for commercial markets in late 2014 or early 2015.

What’s an organic sensor? It increases the sensor’s saturation level while at the same time reducing noise by dumping silicon and using an organic layer instead.

The new technology results in a nearly 10% better signal-to-noise (s/n) ratio than conventional silicon sensors. A 12dB s/n increase is expected to mean that the new sensor design is capable of gathering four times the light of a traditional design — or about 2 f-stops more dynamic range.

Typical camera sensors rely on silicon to trap photons and turn them into electrons. Fujifilm has pioneered the use of organic (carbon-based) compounds to do the same job. It was first granted a patent on the process in 2011, but a partnership with Panasonic is designed to bring the technology to life in a complete sensor implementation.

By placing the photosensitive layer on top of the electronics, the organic sensor design is expected to reach a nearly 100% fill factor — the percentage of the surface area sensitive to light — resulting in increased low-light sensitivity.

The new technology offers increased incident angle, 1.2 times higher sensitivity and industry's highest dynamic range. | Fujifilm
The new technology offers increased incident angle, 1.2 times higher sensitivity and industry’s highest dynamic range. | Fujifilm

The increased absorption capability of the organic compounds also results in thinner sensors. The light-sensing layer can shrink from around 3 microns to 0.5 micron. This allows the sensor to capture light from a larger angle of incidence, as shown by the illustration above, providing yet more light sensitivity. The thinner photosites will also make it easier to design lenses, as the need to send light directly down into the photosites of current sensors is one factor driving up the cost of lenses for digital cameras.

The new sensor also has the potential reducing noise, as seen in the image below. Its designers are claiming reset noise as low as 3 electrons, well below the typical level for current designs. The combination of higher saturation and lower noise could make organic sensors a clear winner over current silicon-based versions.

The new imaging technology promises to prevent highlight clipping in bright scenes and capture a dark subject with vivid colors and rich textures. | Fujifilm
The new imaging technology promises to prevent highlight clipping in bright scenes and capture a dark subject with vivid colors and rich textures. | Fujifilm

Not much is yet know about Sony’s future sensor approach. Andrea of Sony Alpha Rumors tells me Sony is working on the same organic technology, according to a Sony patent. Their new sensor, says Andrea, will “not necessarily be Foveon-like, but certainly not Bayer. Coming at the earliest in 2015.”

Expect a major leap forward in sensor imaging technology within the next two years. Of course the competitors will observe each other and launch their new groundbreaking technologies accordingly.

Stay tuned, it will all be on THEME.




  • Bengt Nyman

    You mention a 10% improvement in signal-to-noise. I hope that is a typo. I would expect at least another zero.
    Otherwise I agree; the Bayer filter has to go, or has to be reduced to cover only a small portion of each pixel compound, enough to determine color while providing significantly improved transmission of light to the dynamic portion of the pixel.

    • I was referring to the new organic CMOS image sensor offering the industry’s highest dynamic range of 88dB, that’s about 10% more relating to dB levels. Real world improvements are proportionally higher.

      • Bengt Nyman

        That’s a different story, more informative and impressive.

        • Joe

          Sony’s patent: RGB multi layer image sensor type BSI so it’s foveon like?

          • Bengt Nyman

            Conventional Silicon image sensors place necessary electrical conductors on top of the light sensing material partially reflecting and obscuring incoming light.

            The BSI technology places necessary electrical conductors below the light sensing material improving the capture of incoming light.

            https://en.wikipedia.org/wiki/Back-illuminated_sensor

            So far both methods have relied on Bayer filters to selectively and separately determine the amount of red, green and blue light, absorbing and discarding all other frequencies.

            The Foveon technology utilizes the fact that a shorter wavelength light (like blue) carries a higher energy and consequently penetrates deeper into the sensor material.
            A Foveon sensor captures unfiltered light (no Bayer filter) and determines color (penetration depth) and amount of light at each pixel location.

            A new technology capturing a greater portion of incoming light and possibly recognizing a larger number of colors (compare high quality printers using additional colors) would be very welcome.

  • tom rose

    Well, two years have passed and the Bayer array is still going strong, and producing ever more accurate images. This could easily have been predicted, but facing reality rarely leads to sensational headlines does it?