Researchers have developed the centuries-old idea of pinhole imaging with a modern twist to create a high-performance system for converting middle-infrared light into visible light, all without lenses.
The new system can capture extremely sharp pictures over a large variety of distances in low light, making it useful for challenging situations that require precise 3D reconstructions.
Conventional lens-based setups have a shallow depth of field and require careful design to minimize optical distortions.
The new approach offers high sensitivity and a much larger depth of field compared to other systems.
Optical Pinhole for Nonlinear Crustal Applications
The researchers unearthed how they use light to form a tiny “optical pinhole” using a nonlinear crystal, which also turns the thermal image into a visible one.
They acquired clear mid-infrared images with a depth of field of over 35cm and a field of view of more than 6cm.
This discovery enabled them proficient to use the system to acquire 3D images.
The research team member, Kun Huang from East China Normal University, said, “This approach can enhance night-time safety, industrial quality control and environmental monitoring.”
Pinhole Photography reimagined for the Digital Age
Pinhole was first introduced by the Chinese philosopher Mozi in the 4th century BC and is one of the traditional image-making methods. The conventional method works by letting light pass through a tiny hole in a lightproof box, projecting an inverted image of the outside onto the opposite side.
Unlike lens-based imaging, pinhole has a pivotal role in avoiding distortion and offers a hyperfocal distance across a wide range of wavelengths.
Revolution in Modern Infrared Imaging System
The modern infrared imaging system used an intense laser to form an optical hole inside a nonlinear crystal, which retained special optical properties that can convert infrared image into visible light so that a standard silicon camera can capture it efficiently.
The researchers were of the view that a customized crystal with a chirped-period structure could accept light from a wide variety of directions and was significant in achieving a large field of view.
The up-conversion luminescence (UCL) sensor method naturally suppresses background noise, allowing it to work even in very low light conditions.
The optical pinhole radius of about 0.20 mm produced well-defined sharp details, allowing this lens opening to image targets that were 11cm, 15cm, and 19com away.
The sharp image at the wavelength of 3.07um showed a large depth range and sharp images of objects placed up to 35cm away, thus exhibiting a large depth of field.
The ultimate breakthrough in 3D imaging without lenses has arrived
Investigators scrutinize two types of 3D imaging and uses coherent pulse streams as an optical gate to image a matte ceramic rabbit, which allowed them to reconstruct the 3D shape with micron-level axial precision.
When the input was lessened to about 1.5 photons per pulse, the method still produced 3D images. The technology offers a more condensed version and is easier to deploy.
Future development will enhance the system’s speed and adaptablility to distinct imaging scenarios.
This breakthrough will eliminate the need for bulky, costly and complex conventional lenses, extending the camera’s operation across a wider mid infrared range, and consequently enabling the creation of extremely compact and affordable 3D sensors.