by Manuel J. Marques, Ramona Cernat, Jason Ensher , Adrian Bradu, Adrian Podoleanu, Photonics, 8(5), 141 2021. This paper presents a different approach for processing the signal from interferometers driven by swept sources that exhibit non-linear tuning during stable time intervals. Such sources are, for example, those commercialised by Insight, which are electrically tunable and … Read more
by Ralph-Alexandru Erdelyi, Virgil-Florin Duma, Cosmin Sinescu, George Mihai Dobre, Adrian Bradu, and Adrian Podoleanu, Materials 13(21) 4825 2020; https://doi.org/10.3390/ma13214825 A correct diagnosis in dental medicine is typically provided only after clinical and radiological evaluations. They are also required for treatment assessments. The aim of this study is to establish the boundaries from which a … Read more
In this paper, an angular compounding method to achieve speckle contrast reduction in optical coherence tomography (OCT) imaging is explored in detail. The angular compounding approach involves collecting multiple images at different angles of incidence, registering the images to correct for induced distortions, and then incoherently summing the images to reduce speckle. The method was experimentally demonstrated with a spectrometer-based Master-Slave enhanced OCT instrument capable of directly generating en-face images. We have investigated the impact of the angular range and number of averaged frames on the degree of speckle artefact reduction, as well as the effect on image resolution and sharpness. The minimum angular step necessary to secure a sufficiently small speckle pattern correlation between the images has also been determined, and the method has subsequently been validated on a biological sample (potato cells).
This work evaluates the performance of the Complex Master Slave (CMS) method, that processes the spectra at the interferometer output of a spectral domain interferometry device without involving Fourier transforms (FT) after data acquisition. Reliability and performance of CMS are compared side by side with the conventional method based on FT, phase calibration with dispersion compensation (PCDC). We demonstrate that both methods provide similar results in terms of resolution and sensitivity drop-off. The mathematical operations required to produce CMS results are highly parallelizable, allowing real-time, simultaneous delivery of data from several points of different optical path differences in the interferometer, not possible via PCDC.
The morphology of embryos produced by in vitro fertilization (IVF) is commonly used to estimate their viability. However, imaging by standard microscopy is subjective and unable to assess the embryo on a cellular scale after compaction. Optical coherence tomography is an imaging technique that can produce a depth-resolved profile of a sample and can be coupled with speckle variance (SV) to detect motion on a micron scale. In this study, day 7 post-IVF bovine embryos were observed either short-term (10 minutes) or long-term (over 18 hours) and analysed by swept source OCT and SV to resolve their depth profile and characterize micron-scale movements potentially associated with viability. The percentage of en-face images showing movement at any given time was calculated as a method to detect the vital status of the embryo. This method could be used to measure the levels of damage sustained by an embryo, for example after cryopreservation, in a rapid and non-invasive way.
This paper describes the application of the Gabor filtering protocol to a Master/Slave (MS) swept source optical coherence tomography (SS)-OCT system at 1300 nm. The MS-OCT system delivers information from selected depths, a property that allows operation similar to that of a time domain OCT system, where dynamic focusing is possible.