3D-printed light steerers could one day fix grainy phone photos at night

A research team has 3D-printed microscopic structures that guide light to a camera sensor instead of blocking it. In a lab, they sent about 70% of incoming light to the right spots. That could one day help with grainy night photos, but it is not close to showing up in a phone.

Why night photos look grainy

Almost every camera sensor sits behind a Bayer filter. It is a grid of red, green and blue filters. Each pixel lets one color through and blocks the others. As a result, only about 30% of the incoming light gets through. The rest is wasted. That is one reason dim shots can look grainy, blur easily or need longer exposures.

What the team built

Researchers at Singapore University of Technology and Design, with partners in China and Japan, made tiny units called color routers. Each one has four pillars made of resin. Together the pillars steer red, green and blue light toward the matching areas of a sensor. The work was reported in Nature Communications.

The pillars are printed with a method called two-photon polymerization. A focused laser hardens liquid resin into extremely small shapes. Earlier routers used materials such as titanium dioxide, which bends light strongly but was hard to make with high precision. This team used ordinary resin, which bends light less, and made up for it with carefully designed pillar shapes and sizes.

What the tests showed

• On a patch one millimeter wide, about 70% of light reached the intended sensing areas.
• That is 40% more than a typical color filter.
• A router-based setup matched the brightness with an exposure of about 4 milliseconds instead of 10.
• Colors came out closer to reality.

A shorter exposure matters because it can reduce motion blur in dark scenes.

What is still missing

This is still a lab experiment. The test used a monochrome sensor, not a complete smartphone camera. There is also some color leakage: about 25% of blue light reached the red channel.

What happens next

Lead researcher Joel Yang says the design must be adapted to materials and factory processes that chipmakers already use. The next step is to build a color router directly onto a real image sensor and see how it performs. Moving from a lab result to a phone feature can take years, so there is no reason to delay an upgrade for this.