Mid-infrared nonlinear pinhole imaging
Abstract
Pinhole imaging is the most primitive and simplest lensless imaging paradigm, capable of transcending the physical limitations of conventional lens optics. This modality is particularly attractive for accessing a virtually infinite depth of focus or operating at extreme wavelengths. Here, we devise and implement a mid-infrared (MIR) pinhole imaging system at 3.07 m based on nonlinear spatial filtering. Instead of using a physical aperture, the involved pinhole is optically formed by a near-infrared pump at 1.03 m within a nonlinear crystal, which allows flexible and precise control over the effective aperture size to optimize imaging performance. Meanwhile, the MIR rays passing through the nonlinear pinhole are spectrally upconverted to facilitate sensitive imaging via a silicon camera. Consequently, the implemented upconversion pinhole imaging enables a large depth of field over 35 cm, beyond the reach of typical lens-based upconversion imagers. Furthermore, depth-resolving imaging across a large depth range is demonstrated in both the reflection and transmission modes based on time-of-flight and trigonometric techniques, respectively. The achieved capabilities -- featuring large operation depth, wide field of view, and flexible adaptability to various illumination conditions -- highlight the potential of the presented MIR imaging architecture for expansive scene detection and motion-aware applications in industrial inspection and night vision.
Cite
@article{arxiv.2605.23154,
title = {Mid-infrared nonlinear pinhole imaging},
author = {Yanan Li and Kun Huang and Jianan Fang and Zhuohang Wei and Heping Zeng},
journal= {arXiv preprint arXiv:2605.23154},
year = {2026}
}