Grainy night photos are the bug that no phone startup ever seems to fix, so a potential solution that starts with a 3D printer got my attention.
Researchers from the Singapore University of Technology and Design, together with partners in China and Japan, have 3D-printed small structures called color routers. Think of them as microscopic traffic lights for light. Instead of filtering the light and throwing much of it away, they direct red, green, and blue light to the right spots on a sensor (via Nature Communications).
How does a color router beat a camera filter?
Almost every camera sensor sits behind a Bayer filter. It consists of a grid of red, green, and blue filters that let one color through at each pixel while blocking the other. In the process, only 30% of the incoming light makes it through, while the rest disappears. This is one of the reasons why photos taken in dark conditions look grainy, fade easily or require longer exposures.
A color router takes a completely different approach. Rather than blocking out unwanted colors, it directs the light in a way so that more of it reaches the sensor. Each small unit contains four precisely molded resin pillars.
Researchers print them using so-called two-photon polymerization, a technique that uses a focused laser to harden liquid resin into incredibly small structures. The four pillars work together to direct red, green and blue light to their respective areas in the sensor.
Early color routers relied on materials such as titanium dioxide. While they could bend light strongly, it was difficult to manufacture them with high precision. To tackle this, however, the team took a rather clever approach. They used ordinary resin (which bends light less effectively) and made it up with carefully designed pillar shapes and dimensions.
How much better is it, and when could my phone get one?
On a patch just one millimeter wide, the printed routers directed about 70% of incoming light to the intended sensing areas in real-world tests (40% more than a typical color filter).
Real-world camera tests are also promising. The router-based camera setup achieves similar brightness with an exposure time of about four milliseconds instead of 10. This could actually help reduce motion blur in dark or poorly lit scenes. The color reproduction was also closer to reality.
However, in the end, this is still a laboratory experiment. It was introduced with a monochrome sensor instead of a full smartphone camera. Furthermore, there is also some color leakage, where about 25% of the blue light reaches the red channel.
Lead researcher Joel Yang says the design must be adapted to materials and manufacturing processes already used by chipmakers. The next step is to integrate a color router directly onto an actual image sensor and test how well it works.
In my experience, going from a promising lab experiment to a feature in your phone can take years. So enjoy the idea, but don’t put off that upgrade just yet.
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