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Register a new userReal-time High-Resolution Mid-infrared Optical Coherence Tomography
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The potential for improving the penetration depth of optical coherence tomography systems by using increasingly longer wavelength light sources has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at 4 micron central wavelength with an axial resolution of 8.6 microns is demonstrated. The system produces 2D cross-sectional images in real-time enabled by a high-brightness 0.9-4.7 micron mid-infrared supercontinuum source with 1 MHz pulse repetition rate for illumination and broadband upconversion of more than 1 micron bandwidth from 3.58-4.63 microns to 820-865 nm, where a standard 800 nm spectrometer can be used for fast detection. Images produced by the mid-infrared system are compared with those delivered by a state-of-the-art ultra-high-resolution near-infrared optical coherence tomography system operating at 1.3 {mu}m, and the potential applications and samples suited for this technology are discussed. In doing so, the first practical mid-infrared optical coherence tomography system is demonstrated, with immediate applications in real-time non-destructive testing for the inspection of defects and thickness measurements in samples that are too highly scattering at shorter wavelengths.
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We report on Mid-infrared (MIR) OCT at 4 $mu$m based on collinear sum-frequency upconversion and promote the A-scan scan rate to 3 kHz. We demonstrate the increased imaging speed for two spectral realizations, one providing an axial resolution of 8.6 $mu$m, and one providing a record axial resolution of 5.8 $mu$m. Image performance is evaluated by sub-surface micro-mapping of a plastic glove and real-time monitoring of CO$_2$ in parallel with OCT imaging.
We report on a technically simple approach to achieve high-resolution and high-sensitivity Fourier-domain OCT imaging in the mid-infrared range. The proposed OCT system employs an InF3 supercontinuum source. A specially designed dispersive scanning spectrometer based on a single InAsSb point detector is employed for detection. The spectrometer enables structural OCT imaging in the spectral range from 3140 nm to 4190 nm with a characteristic sensitivity of over 80 dB and an axial resolution below 8 um. The capabilities of the system are demonstrated for imaging of porous ceramic samples and transition-stage green parts fabricated using an emerging method of lithography-based ceramic manufacturing. Additionally, we demonstrate the performance and flexibility of the system by OCT imaging using an inexpensive low-power (average power of 16 mW above 3 um wavelength) mid-IR supercontinuum source.
Mid-infrared light scatters much less than shorter wavelengths, allowing greatly enhanced penetration depths for optical imaging techniques such as optical coherence tomography (OCT). However, both detection and broadband sources in the mid-IR are technologically challenging. Interfering entangled photons in a nonlinear interferometer enables sensing with undetected photons making mid-IR sources and detectors obsolete. Here we implement mid-infrared frequency-domain OCT based on ultra-broadband entangled photon pairs. We demonstrate 10 ${mu}$m axial and 20 ${mu}$m lateral resolution 2D and 3D imaging of strongly scattering ceramic and paint samples. Together with $10^6$ times less noise scaled for the same amount of probe light and also vastly reduced footprint and technical complexity this technique can outperform conventional approaches with classical mid-IR light.
Optical coherence tomography (OCT) is a high-resolution three-dimensional imaging technique that enables non-destructive measurements of surface and subsurface microstructures. Recent developments of OCT operating in the mid-infrared (MIR) range (around 4 {mu}m) lifted fundamental scattering limitations and initiated applied material research in formerly inaccessible fields. The MIR spectral region, however, is also of great interest for spectroscopy and hyperspectral imaging, which allow highly selective and sensitive chemical studies of materials. In this contribution, we introduce an OCT system (dual-band, central wavelengths of 2 {mu}m m and 4 {mu}m) combined with MIR spectroscopy that is implemented as a raster scanning chemical imaging modality. The fully-integrated and cost-effective optical instrument is based on a single supercontinuum laser source (emission spectrum spanning from 1.1 {mu}m to 4.4 {mu}m). Capabilities of the in-situ correlative measurements are experimentally demonstrated by obtaining complex multidimensional material data, comprising morphological and chemical information, from a multi-layered composite ceramic-polymer specimen.
We present a benchmark pilot study in which high-resolution Full-Field Optical Coherence Tomography (FF-OCT) is used to image human breast tissue and is evaluated to assess its ability to aid the pathologists management of intra-operative diagnoses. Our aim included evaluating the safety of FF-OCT on human tissue and determining the concordance between the images obtained with routinely prepared histopathological material. The compact device used for this study provides a 2 {mu}m-lateral and a 1 {mu}m-axial resolution, and is able to scan a 1.5cm^2 specimen in about 7 minutes. 75 breast specimens obtained from 22 patients have been imaged. Because the contrast in the images is generated by endogenous tissue components, no biological, contrast agents or specimen preparation is required. We characterized the major architectural features and tissue structures of benign breast tissue, including adipocytes, fibrous stroma, lobules and ducts. We subsequently characterized features resulting from their pathological modification and developed a decision tree for diagnosis. Two breast pathologists applied these criteria, resulting in a demonstrable ability to distinguish between normal or benign tissue, in situ and invasive carcinomas using FF-OCT images, with a sensitivity of 97% and 90%, respectively, and specificity of 74% and 77% respectfully. FF-OCT shows great potential for the evaluation of human tissue and its characterization as normal/benign vs. lesional, for numerous ex-vivo clinical use-cases. Its high imaging accuracy for in-situ and invasive carcinoma paves the way for applications where a fast architectural assessment could improve the core needle biopsy workflow, tumor margin assessments, and provides quality assurance for tissue acquired for clinical care and research.
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