A new lens-free and compact system for facial recognition scans a bust of Michelangelo’s David and reconstructs the image using less power than existing 3D surface imaging systems. Credit: Adapted from Nano Letters, 2024, DOI: 10.1021/acs.nanolett.3c05002
Key points:
- Researchers seek to improve current facial recognition systems by making them more compact.
- Their new system replaces a traditional dot projector with a low-power laser and a flat gallium arsenide surface.
- A nearly-flat prototype successfully identified a 3D replica of Michelangelo’s David by comparing the infrared dot patterns to online photos of the famous statue.
Facial recognition systems are quickly becoming ubiquitous in today’s society. With that in mind, scientists from Taiwan are seeking to improve and replace the current system with a “sleeker” 3D surface imaging system that features flatter, simplified optics.
According to their study published in ACS’ Nano Letters, in proof-of-concept demonstrations, the new system recognized the face of Michelangelo’s David just as well as an existing smartphone system.
Typical facial recognition systems—like the ones in our smartphones—rely on a dot projector that contains multiple components: a laser, lenses, a light guide and a diffractive optical element (DOE). The DOE is a special kind of lens that breaks the laser beam into an array of about 32,000 infrared dots. So, when a person looks at a locked screen, the facial recognition system projects an array of dots onto most of their face, and the device’s camera reads the pattern created to confirm the identity.
However, dot projector systems are relatively large for small devices. Thus, scientists at National Yang Ming Chiao Tung University focused on developing a more compact system—one that would be nearly flat.
To do this, they replaced a traditional dot projector with a low-power laser and a flat gallium arsenide surface, reducing the imaging device’s size and power consumption. They etched the top of this thin metallic surface with a nanopillar pattern, which creates a metasurface that scatters light as it passes through the material.
In prototype tests, the low-powered laser scattered light into 45,700 infrared dots that were projected onto an object or face positioned in front of the light source. The device accurately identified a 3D replica of Michelangelo’s David by comparing the infrared dot patterns to online photos of the famous statue. Notably, it accomplished this using five to 10 times less power and on a platform with a surface area about 230 times smaller than a common dot-projector system.
The researchers say their prototype demonstrates the usefulness of metasurfaces for effective small-scale low-power imaging solutions for facial recognition, robotics and extended reality.