Many people are familiar with facial recognition systems that unlock smartphones and gaming systems or allow us to access our online bank accounts. But modern technology may need square projectors and lenses. Now researchers report Nano Letters About an advanced 3D surface imaging system with flatter and simplified optics. In proof-of-concept demonstrations, the new system recognized the face of Michelangelo’s David as well as the existing smartphone system.

3D surface imaging is a common tool used for smartphone facial recognition as well as computer vision and autonomous driving. These systems usually consist of a point projector with several components: a laser, lenses, a light guide, and a diffractive optical element (DOE).

DOE is a special type of lens that splits the laser beam into an array of approximately 32,000 infrared dots. So when a person looks at the lock screen, the facial recognition system projects a series of dots over a large part of their face, and the device’s camera reads the created pattern to verify identity. However, dot projector systems are relatively large for small devices such as smartphones. So Yu-Heng Hong, Hao-Chung Kuo, Yao-Wei Huang and their colleagues set out to design a more compact facial recognition system that would be nearly flat and require less power to operate.

To do this, the researchers replaced the traditional dot projector with a low-power laser and a flat surface made of gallium arsenide; This significantly reduced the size and power consumption of the image processing device. They etched the top of this thin metal surface with a nanosurface pattern that creates a metasurface that scatters light as it passes through the material.

In this prototype, a low-power laser light scatters 45,700 infrared dots that are projected onto an object or face in front of the light source. Like the dot projector system, the new system includes a camera that will read the patterns created by infrared dots.

During prototype testing, the system accurately identified a 3D replica of Michelangelo’s David by comparing infrared dot patterns with online photos of the famous statue. Remarkably, this was achieved using five to ten times less energy than a conventional dot projector system and on a platform with a surface area approximately 230 times smaller. The researchers say their prototype demonstrates the utility of metasurfaces for efficient low-power image processing solutions for facial recognition, robotics and augmented reality.