Real-time ultra-sensitive anisotropic edge enhanced imaging based on frequency upconversion

Edge-enhanced imaging is invaluable in feature extraction, fingerprinting analysis, and biomedicine due to its ability to accentuate peripheries. Nevertheless, in systems employing vortex phase plates, the modulation of the phase mask is suppressed, resulting in the inability to characterize the modulation function during image reconstruction. To address this need, we propose a nonlinear reconstruction method that incorporates a superimposed vortex phase filter (SVPF) designed to modulate the spectrum of the target. In this paper real-time ultra-sensitive edge enhanced imaging in the short-wavelength-infrared (SWIR) region is demonstrated using nonlinear frequency upconversion. The SWIR signal at 1550 nm is spectrally converted to 864 nm for detection by a quantitative CMOS (qCMOS) camera. Anisotropic edge enhancement with controlled amplitude can be achieved by the SVPF. The imaging sensitivity at the single-photon level is realized by increasing the conversion efficiency and reducing the background noise of the upconversion system. By rapidly switching a series of specific phase patterns with a spatial light modulator, we also present the ability of the scheme to detect outlines and gradual edges in real time. The implemented SWIR edge-enhanced imaging system is expected to be directly used in non-destructive defect inspection and infrared monitoring of low-light objects.