Overcoming Scattering in Near-Infrared Imaging
Near-infrared light is a workhorse in modern imaging, from medical diagnostics to autonomous vehicle sensors. Unlike visible light, it can penetrate certain materials, but it still suffers from scattering when traversing complex media like biological tissue or fog. This scattering causes photons to deviate from their path, resulting in blurred or unusable images. Traditional solutions rely on expensive, specialized detectors, limiting accessibility.
Researchers at the University of Rochester have introduced a novel imaging system that addresses both cost and clarity. By using inexpensive silicon-based detectors and a technique called time-gating, the system converts near-infrared light to visible light in real time, producing sharper images through scattering environments. The work, published in Nature Communications, represents a significant step toward affordable, high-performance imaging.
The Time-Gating Principle
Time-gating acts like a camera shutter, but instead of a mechanical mechanism, it uses ultrafast pulses of light to control the passage of photons. Lead author Yang Xu explains, "In a traditional camera, the shutter is mechanical—when it opens, light comes in, and when it closes, light is rejected. In this case, we use light to control light."
The gate is a thin film made of indium tin oxide (ITO). When a near-infrared photon hits the film while the gate is open, it is converted to visible light, which can be captured by standard silicon detectors. The gate opens for only about a picosecond—the time it takes light to travel the length of a period at the end of a sentence. This ultrafast gating effectively filters out scattered photons that arrive later, preserving the ballistic (non-scattered) light that carries the clear image.
Advantages Over Existing Systems
Current near-infrared imaging systems often rely on detectors made from exotic materials like indium gallium arsenide, which are costly and not widely available. The Rochester system leverages silicon, the same material used in everyday electronics, dramatically reducing cost. Additionally, the time-gating approach improves image quality in scattering media, a challenge that has plagued conventional near-infrared systems.
The technique has been refined over more than a decade in the laboratory of Robert Boyd, the William F. Krupke Distinguished Professor in Optics. The team's persistence has led to a practical implementation that can be adapted for various applications.
Potential Applications
The ability to see clearly through deep tissue could enhance medical imaging, aiding in the detection of tumors or other abnormalities without invasive procedures. In autonomous driving, the system could help vehicles navigate through fog, improving safety. Other potential uses include environmental monitoring, security screening, and industrial inspection, where seeing through obscurants is critical.
Future Directions
The researchers are now exploring ways to further optimize the system, such as increasing the field of view and improving the conversion efficiency. They also aim to test the technology in real-world scenarios, moving from laboratory demonstrations to practical deployment. With its low cost and high performance, this time-gating technique could soon become a standard tool in imaging applications where scattering is a challenge.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
