4th-century pinhole idea inspires lens-free infrared imaging system

Researchers in China have developed a novel lens-free imaging system inspired by the ancient 4th-century pinhole camera concept, enabling sharp mid-infrared imaging without distortion over long distances and in low light. Instead of a physical pinhole, the team created an “optical pinhole” inside a nonlinear crystal using laser light, which converts incoming mid-infrared images into visible ones detectable by standard silicon cameras. This approach overcomes common issues in mid-infrared imaging, such as noise, expense, cooling requirements, and lens-induced distortion or limited depth of field. The system achieves a wide field of view and a large depth of field (over 35 centimeters) with high sensitivity, producing clear images at a mid-infrared wavelength of 3.07 micrometers. Using ultrashort synchronized laser pulses, the researchers also demonstrated 3D time-of-flight imaging with micron-level precision and effective denoising at extremely low photon counts. The method’s simplicity, reliance on standard