Direct hyperspectral dual-comb imaging

Even though dual-comb-based systems are employed almost routinely nowadays in an ever-increasing number of applica-tions, an efficient combination of this effective technique withan imaging arrangement, which would undoubtedly revolu-tionize hyperspectral imaging, had not yet been demonstrated. Here we present, to our knowledge, the first hyperspectral dual-comb imaging system in which interferograms are directly detected by a video camera. The system, based on a dual-comb scheme capable of consistently generating interfer-ograms at a rate of 1 Hz and below, combines fast hyperspectral imaging with unprecedented optical resolution and fully multiplex operation. Various proof-of-principle experiments demonstrating hyperspectral imaging of molecular resonances have proved that the direct hyperspectral dual-comb imaging method presented here is capable of characterizing a scene with super-fine resolution in a narrow optical span within 1 s.European Commission (ATTRACT project Grant Agreement 777222

Programmable Spectrometry -- Per-pixel Classification of Materials using Learned Spectral Filters

Many materials have distinct spectral profiles. This facilitates estimation of the material composition of a scene at each pixel by first acquiring its hyperspectral image, and subsequently filtering it using a bank of spectral profiles. This process is inherently wasteful since only a set of linear projections of the acquired measurements contribute to the classification task. We propose a novel programmable camera that is capable of producing images of a scene with an arbitrary spectral filter. We use this camera to optically implement the spectral filtering of the scene's hyperspectral image with the bank of spectral profiles needed to perform per-pixel material classification. This provides gains both in terms of acquisition speed --- since only the relevant measurements are acquired --- and in signal-to-noise ratio --- since we invariably avoid narrowband filters that are light inefficient. Given training data, we use a range of classical and modern techniques including SVMs and neural networks to identify the bank of spectral profiles that facilitate material classification. We verify the method in simulations on standard datasets as well as real data using a lab prototype of the camera

Seeing the Big Picture: System Architecture Trends in Endoscopy and LED-Based hyperspectral Subsystem Intergration

Early-stage colorectal lesions remain difficult to detect. Early development of neoplasia tends to be small (less than 10 mm) and flat and difficult to distinguish from surrounding mucosa. Additionally, optical diagnosis of neoplasia as benign or malignant is problematic. Low rates of detection of these lesions allow for continued growth in the colorectum and increased risk of cancer formation. Therefore, it is crucial to detect neoplasia and other non-neoplastic lesions to determine risk and guide future treatment. Technology for detection needs to enhance contrast of subtle tissue differences in the colorectum and track multiple biomarkers simultaneously. This work implements one such technology with the potential to achieve the desired multi-contrast outcome for endoscopic screenings: hyperspectral imaging. Traditional endoscopic imaging uses a white light source and a RGB detector to visualize the colorectum using reflected light. Hyperspectral imaging (HSI) acquires an image over a range of individual wavelength bands to create an image hypercube with a wavelength dimension much deeper and more sensitive than that of an RGB image. A hypercube can consist of reflectance or fluorescence (or both) spectra depending on the filtering optics involved. Prior studies using HSI in endoscopy have normally involved ex vivo tissues or xiv optics that created a trade-off between spatial resolution, spectral discrimination and temporal sampling. This dissertation describes the systems design of an alternative HSI endoscopic imaging technology that can provide high spatial resolution, high spectral distinction and video-rate acquisition in vivo. The hyperspectral endoscopic system consists of a novel spectral illumination source for image acquisition dependent on the fluorescence excitation (instead of emission). Therefore, this work represents a novel contribution to the field of endoscopy in combining excitation-scanning hyperspectral imaging and endoscopy. This dissertation describes: 1) systems architecture of the endoscopic system in review of previous iterations and theoretical next-generation options, 2) feasibility testing of a LED-based hyperspectral endoscope system and 3) another LED-based spectral illuminator on a microscope platform to test multi-spectral contrast imaging. The results of the architecture point towards an endoscopic system with more complex imaging and increased computational capabilities. The hyperspectral endoscope platform proved feasibility of a LED-based spectral light source with a multi-furcated solid light guide. Another LED-based design was tested successfully on a microscope platform with a dual mirror array similar to telescope designs. Both feasibility tests emphasized optimization of coupling optics and combining multiple diffuse light sources to a common output. These results should lead to enhanced imagery for endoscopic tissue discrimination and future optical diagnosis for routine colonoscopy

Direct hyperspectral dual-comb gas imaging in the mid-infrared

In this Letter, we present and experimentally validate the first direct hyperspectral dual-comb gas imaging system operating in the mid-infrared region. This method provides an unmatched combination of super-fine spectral characterization and high temporal resolution without the need for thermal contrast between the target molecules and the background. In a proof-of-concept experiment, the system has allowed us to perform precision hyperspectral imaging of butane in the 3.4 µm band with a time resolution of 1 s.Ministerio de Economía y Competitividad (TEC2017-86271-R); H2020 European Research Council (777222)

Sub-GHz optical resolution mid-infrared hyperspectral imaging with dual-comb

High-performance hyperspectral imaging is becoming one of the most sought-after tools in the world today by providing a wide range of capabilities and applications. However, traditional systems have significant performance limitations, mainly related to the ability to resolve narrow spectral features and to detection sensitivity. With the aim of addressing these weaknesses, we present here the first hyperspectral dual-comb imaging system capable of providing sub-GHz (<0.033 cm−1) optical resolutions and fast acquisition rates in the mid-infrared region. The system has been experimentally demonstrated by analyzing methane at 2968 cm−1 with optical resolutions of down to 300 MHz (0.01 cm−1) and time resolutions well into the sub-second range.This research was supported in part by the Ministry of Science and Innovation, State Investigation Agency, through the project PID2020–116439GB-I00

A review of snapshot multidimensional optical imaging: Measuring photon tags in parallel

Multidimensional optical imaging has seen remarkable growth in the past decade. Rather than measuring only the two-dimensional spatial distribution of light, as in conventional photography, multidimensional optical imaging captures light in up to nine dimensions, providing unprecedented information about incident photons’ spatial coordinates, emittance angles, wavelength, time, and polarization. Multidimensional optical imaging can be accomplished either by scanning or parallel acquisition. Compared with scanning-based imagers, parallel acquisition–also dubbed snapshot imaging–has a prominent advantage in maximizing optical throughput, particularly when measuring a datacube of high dimensions. Here, we first categorize snapshot multidimensional imagers based on their acquisition and image reconstruction strategies, then highlight the snapshot advantage in the context of optical throughput, and finally we discuss their state-of-the-art implementations and applications