Pixels are one of the building blocks of modern technology.
They create the images we see on television screens, smartphones, and computer monitors. They also allow digital cameras to capture photos by detecting incoming light.
Until now, however, a pixel could only perform one of these jobs—it could either produce light for a display or detect light for a camera.
Researchers at ETH Zurich have now developed a completely new type of pixel that can do both.
The breakthrough could one day lead to devices that work as both a camera and a display at the same time.
Instead of having separate screens and camera sensors, future smartphones, tablets, or wearable devices might combine both functions into a single layer.
The researchers recently published their findings in the journal Nature.
The new technology is based on a natural property of light called interference. Light travels in waves, and when different light waves meet, they interact with each other. If the waves line up perfectly, they become stronger.
If they are out of step, they cancel each other out. This principle is responsible for many colorful patterns seen in nature, such as soap bubbles and oil floating on water.
The ETH Zurich team learned how to control this effect with incredible precision. They created tiny wave-shaped patterns on the surface of each pixel that are accurate to within just a few nanometers, or billionths of a meter.
When light enters one of these specially designed pixels, it is first converted into a special type of wave that travels across the surface of the material. Later, the wave is converted back into ordinary light. Because the researchers carefully designed the surface pattern, they can control exactly how the outgoing light behaves.
Unlike ordinary pixels, these new “Fourier pixels” can control not only the brightness of light but also several other important properties.
One of these is polarization, which describes the direction in which a light wave vibrates. Polarization is already widely used in technologies such as sunglasses, camera filters, and advanced communication systems. The new pixels can both create and measure different polarization states.
The researchers can also control the phase of light. Phase describes where a light wave is in its repeating cycle and plays an important role in many scientific instruments and optical technologies. By carefully adjusting the phase, the team can even create unusual doughnut-shaped beams of light that contain a dark hole in the center.
The pixels also work with different colors of light, allowing them to generate full-color images.
Perhaps even more impressive is that the same pixel can work in reverse. Instead of shaping light, it can analyze incoming light by measuring its brightness, phase, and polarization. To do this, the pixel compares incoming light with a reference light wave and uses the resulting interference pattern to calculate the light’s properties.
Because the system uses a mathematical method called Fourier analysis, these calculations can be performed directly by the pixel itself without requiring complicated computer processing.
The researchers believe this technology could eventually be useful in many fields, including displays, digital cameras, fiber-optic communications, medical imaging, and scientific instruments.
Their next goal is to build large arrays containing many of these smart pixels. If successful, future devices could combine image capture and image display into a single compact system, creating entirely new possibilities for consumer electronics and advanced optical technologies.
