Edge enhanced imaging via the spiral phase contrast enables to reveal the phase or amplitude gradients of a target, which has been proved useful in feature recognition, machine vision, and object identification. A long quest is to extend the operation wavelength into the mid-infrared (MIR) region, as highly demanded in various fields including infrared sensing, astronomic observation, and biomedical diagnosis. Here, ultra-sensitive MIR imaging at the single-photon level based on nonlinear frequency upconversion is demonstrated, where the spectrally converted replica of the MIR object image at 3070 nm is captured by a silicon electron multiplying charged coupled device. The imaging sensitivity is significantly improved by the coincidence pulsed pumping with a spectro-temporal optimization. Furthermore, the edge enhancement is realized by imprinting the spiral phase pattern of the pump onto the upconverted field at the Fourier plane within the nonlinear crystal. Such a nonlinear spatial filter not only provides an effective way to implement the required high-fidelity vortex screening in the edge enhanced detection, but also renders the MIR illumination into a visible image in an efficient and low-noise fashion. The presented system for MIR edge enhanced imaging might facilitate immediate applications in label-free histopathological diagnosis and non-destructive defect inspection.

中文翻译：

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基于非线性涡流滤波的中红外单光子边缘增强成像

通过螺旋相位对比的边缘增强成像能够揭示目标的相位或幅度梯度，这已被证明在特征识别、机器视觉和物体识别中非常有用。一个长期的任务是将工作波长扩展到中红外 (MIR) 区域，这在包括红外传感、天文观测和生物医学诊断在内的各个领域都有很高的需求。在这里，展示了基于非线性频率上转换的单光子级超灵敏 MIR 成像，其中 3070 nm 的 MIR 物体图像的光谱转换副本由硅电子倍增电荷耦合器件捕获。通过具有光谱时间优化的重合脉冲泵浦显着提高了成像灵敏度。此外，边缘增强是通过将泵浦的螺旋相位图案压印到非线性晶体内傅立叶平面的上变频场上来实现的。这种非线性空间滤波器不仅提供了一种在边缘增强检测中实现所需的高保真涡流筛选的有效方法，而且还以高效、低噪声的方式将 MIR 照明渲染为可见图像。所提出的 MIR 边缘增强成像系统可能有助于直接应用于无标记组织病理学诊断和无损缺陷检查。而且还以高效且低噪声的方式将 MIR 照明渲染为可见图像。所提出的 MIR 边缘增强成像系统可能有助于直接应用于无标记组织病理学诊断和无损缺陷检查。而且还以高效且低噪声的方式将 MIR 照明渲染为可见图像。所提出的 MIR 边缘增强成像系统可能有助于直接应用于无标记组织病理学诊断和无损缺陷检查。