Redesign of ancient 4th-century pinhole camera principle applied in contemporary lens-free infrared camera development
Researchers at Tsinghua University in China have made a significant breakthrough in the field of imaging technology. They have developed a lens-free, nonlinear crystal-based image search system that produces sharp mid-infrared images, even under low light and over long distances.
This innovative system, detailed in a recent publication in Optica, addresses a common challenge in mid-infrared image search: the use of traditional lens-based designs that restrict depth of field and suffer from distortion. The researchers' solution? An "optical pinhole" inside a nonlinear crystal, created with laser light.
The system works by using an optical pinhole radius of 0.20 millimeters, which yields sharp details. The crystal converts incoming infrared images into visible ones that standard silicon cameras can detect. This unique approach allows the system to capture clear mid-infrared images, even at extremely low photon counts, thanks to correlation-based denoising.
One of the key advantages of this new imaging system is its ability to improve night vision, industrial inspection, and environmental monitoring. It can also enhance night-time safety and industrial quality control by providing sharper, more sensitive images in the mid-infrared spectrum.
The system's wide field of view is another significant benefit. The crystal's engineered structure allows light from many angles to pass through, giving the system a wide field of view. This feature, combined with the system's ability to capture images over a depth of field greater than 35 centimeters and a field of view wider than 6 centimeters, makes it a powerful tool for various applications.
The researchers have demonstrated the system's capabilities by imaging targets placed at 11, 15, and 19 centimeters. They even reconstructed a ceramic rabbit with micron-level precision using 3D imaging.
Looking ahead, the researchers aim to streamline the setup by developing new nonlinear materials and compact light sources. This could make the system more accessible and widely used in various industries. With this groundbreaking work, the researchers have demonstrated that lens-free nonlinear pinhole imaging can unlock sharper, broader, and more sensitive mid-infrared vision, paving the way for a new era in imaging technology.
