Near-infrared 3D imaging with upconversion detection

Abstract

We demonstrate a photon-sensitive, three-dimensional (3D) camera by active near-infrared illumination and fast time-of-flight gating. It uses picosecond pump pulses to selectively upconvert the backscattered photons according to their spatiotemporal modes via sum-frequency generation in a χ 2 nonlinear crystal, which are then detected by an electron-multiplying CCD with photon sensitive detection. As such, it achieves sub-millimeter depth resolution, exceptional noise suppression, and high detection sensitivity. Our results show that it can accurately reconstruct the surface profiles of occluded targets placed behind highly scattering and lossy obscurants of 14 optical depth (round trip), using only milliwatt illumination power. This technique may find applications in biomedical imaging, environmental monitoring, and wide-field light detection and ranging.

Mid-infrared single-photon 3D imaging

“…The pulsed pumping favors to increase the conversion efficiency due to intensive peak power, and meanwhile to suppress the background noise with the narrow time window 43 – 45 . In addition to improving the SNR ratio for MIR upconversion detection, the pump pulse serves as an ultrafast optical gate for the upconversion imager, thus allowing to identify incoming photons with different time delays 40 , 46 . Second, the temporal resolution of the imaging system is determined by the peak width of the intensity cross-correlation trace between the pump and probe pulses, instead of being restricted to the response time of the detector itself.…”

“…Second, the temporal resolution of the imaging system is determined by the peak width of the intensity cross-correlation trace between the pump and probe pulses, instead of being restricted to the response time of the detector itself. Here, the pulse duration of the pump pulse is optimized at the femtosecond regime, which significantly improves the depth resolution in comparison to previous demonstrations with picosecond pulses 40 , 41 , 46 . On the other hand, the walk-off effect within the nonlinear crystal becomes more prominent for shorter pulses 44 , 45 , which may reduce the conversion efficiency as a trade-off.…”

“…Third, the wide-field upconversion is implemented to achieve a full imaging capability, which simplifies the data acquisition and reduces the acquisition time in comparison to the raster-scanning performance 46 . Moreover, the use of spinning diffuser allows us to implement an incoherent imaging based on the pseudo-thermal source 39 , thus resulting in an enhanced the spatial resolution than that in the coherent imaging regime 40 , 41 . Fourth, the self-synchronization preparation for the dual-color light sources with disparate wavelengths eliminates the relative timing jitter between the signal and pump pulses.…”

“…Despite tremendous efforts, the presented imaging modality based on the OCT architecture faces the challenges that the total acquisition time is rather long due to the lateral raster scanning fashion. In this regard, wide-field operation based on a silicon camera is developed in the framework of parametric upconversion imaging, which favors high-pixel density mapping with fast data acquisition and quick processing speed 39 , 40 . The snapshot capability allows one to capture the spatial information with an exposure time down to the microsecond level 41 .…”

Monitoring Soft Shape Surface Deformation via Optical Images for the Distinction of Contact State

“…[ 36 ] The optical sensing method based on image acquisition has the advantages of a large amount of information and high spatial resolution, [ 37 ] which can capture small deformations by directly observing the deformation of elastomers. [ 38–40 ] For example, the optical sensing strategy of the planar optical waveguide structure could detect the real contact area with high accuracy, which has great potential in the study of interface friction. [ 41 ] However, limited by the planar optical waveguide structure.…”