Video-rate, mid-infrared hyperspectral upconversion imaging

Abstract

In this work we demonstrate, to the best of our knowledge, a novel wide field-of-view upconversion system, supporting upconversion of monochromatic mid-infrared (mid-IR) images, e.g., for hyperspectral imaging (HSI). An optical parametric oscillator delivering 20 ps pulses tunable in the 2.3-4 μm range acts as a monochromatic mid-IR illumination source. A standard CCD camera, in synchronism with the crystal rotation of the upconversion system, acquires in only 2.5 ms the upconverted mid-IR images containing 64 kpixels, thereby eliminating the need for postprocessing. This approach is generic in nature and constitutes a major simplification in realizing video-frame-rate mid-IR monochromatic imaging. A second part of this paper includes a proof-of-principle study on esophageal tissues samples, from a tissue microarray, in the 3-4 μm wavelength range. The use of mid-IR HSI for investigation of esophageal cancers is particularly promising as it allows for a much faster and possibly more observer-independent workflow than state-ofthe-art histology. Comparing histologically stained sections evaluated by a pathologist to images obtained by either Fourier transform IR or upconversion HSI based on machine learning shows great promise for further work pointing towards clinical translation using the presented mid-IR HSI upconversion system.

Parametric upconversion imaging and its applications

“…Although the technique is quite promising, one needs to take care of image distortion associated with the refraction in the crystal surfaces as it is scanned. Very recently Junaid et al [168] used such scheme to demonstrate a full FoV (10 mm object diameter) monochromatic imaging at around 3 µm (OPO source) acquired within 2.5 ms using a bulk LiNbO3 crystal. In 2016, Maestre et al [169], [170] proposed an alternative approach for increasing the monochromatic FoV.…”

“…Together with researchers from the Institute of Photonic Sciences in Barcelona and the University of Exeter, our group has recently demonstrated a novel upconversion imaging system for obtaining wide FoV MIR images (Nres = 64 ´ 10 3 ) with a frame acquisition time of 2.5 ms [168]. The system employs an OPO emitting 20 ps laser pulses with a selectable wavelength in the 2.3 -4 µm range as a monochromatic illumination of an object plane.…”

“…31. Adapted from [168]. Setup for an upconversion-based imaging, where the idler beam from a picosecond OPO is used as an illumination source and a synchronized picosecond 1064 nm laser source is used as the upconversion pump source.…”

Nonlinear crystals for imaging and detection of mid-IR radiation

“…change the angle of the three interacting fields relative to the optical axis of the material. In ref 11 , the object was spatially scanned by rotating the nonlinear crystal, upconverting individual concentric ring shaped sections of the object at a time. The phase matching curve possess close to rotational symmetry around the wavelength axis, see Fig.…”

Perspectives for Applications of Quantum Imaging

“…In particular, efforts toward image‐preserving frequency conversion and amplification are being pursued by numerous nonlinear optics groups around the world. With recent advances in imaging based on structured illumination, the development of suitable frequency converters and mode analyzers could also extend the wavelength range for coherent imaging schemes based on structured wave fronts.…”