project, which is funded by the German Federal Ministry of Education and Research, attempts to improve the accessibility of diagnostic instruments for glaucoma screening. The presented approach aims to realize real-time nearinfrared video fundus imaging that enables the use of targeted fixation stimuli to ensure continuous imaging. The integration of near-infrared illumination with a wavelength of 780 nm not only avoids pupil constriction, but also enables mesopic imaging in darkened ambient light, ensuring optimal visualization of the retinal structure. This innovative system achieves nearly reflection-free imaging through polarized illumination with polarization-dependent beam paths. Its primary aim is to capture extensive fundus areas to facilitate correlations with linear optical coherence tomography (LOCT) measurements. In the future, the fundus setup will be integrated into the LOCT setup. In this research project, the primary aim is to generate images of the optic nerve, but it is also possible to carry out examinations of the macula. Unlike from traditional fundus cameras, this system has a controllable screen for generating individual fixation stimuli, which creates continuous eye movements and enables controlled imaging. The main objective is to capture large fundus areas and track eye positions to combine this information with the LOCT measurements A-scan positions, which enables the creation of B-scans with irregular geometries. This approach replaces the need for complex scanning systems by leveraging natural eye movements. The approach can thus be used to detect retinal pathologies in a different way and could therefore be used for more comprehensive diagnostic and scientific applications.
This work focuses on enhancing the quality of A- and B-scans of a novel linear optical coherence tomography system (LOCT), addressing the image degradation caused by noise and the blurring characteristics of the system’s three-dimensional point spread function. The enhancement procedure includes an initial spatial and frequencybased pre-filtering that is applied to the measured interference pattern. Subsequently, a more robust envelope detection technique based on the Hilbert transform is employed. Lastly, image structures are reconstructed using a deconvolution algorithm based on maximum likelihood estimation, tailored to meet our unique requirements by adapting it to Rician distributed intensity values and employing a sparseness regularization term. For the deconvolution, both the lateral and axial blur of the system are considered. Emphasis is placed on the optimization of signal detection in high-noise regions, while simultaneously preventing image boundary artifacts. The efficacy of this approach is demonstrated across multiple types of measurement objects, including both artificial and biological samples. All results show a significant reduction in noise as well as enhanced resolution. Structure distinguishability is also increased, which plays a crucial role in tomography applications. In summary, the proposed enhancement method substantially improves image quality. This is achieved by still using the same initial measurement data, but incorporating prior knowledge and maximizing the amount of extracted information. Although initially designed for LOCT systems, the processing steps have potential for broader application in other types of optical coherence tomography and imaging systems.
This publication introduces a prototype of a fiber-based linear optical coherence tomography system (LOCT) that can be used for economical retinal screening in ophthalmology. The system uses standard off-the-shelf components to reduce production costs, complexity, and adjustment efforts while providing high-quality imaging of artificial retinal structures. We present the results of A- and B-scans of technical samples and an artificial eye model that was conducted to assess the system’s performance regarding axial resolution, imaging depth, and dispersion compensation. The study’s findings suggest that LOCT is a cost-effective solution for ophthalmology and shows great potential for monitoring the progression of retina-related diseases such as glaucoma or age-related macular degeneration.
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