María S. Millán

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Retinal images are essential clinical resources for the diagnosis of retinopathy and many other ocular diseases. Because of improper acquisition conditions or inherent optical aberrations in the eye, the images are often degraded with blur. In many common cases, the blur varies across the field of view. Most image deblurring algorithms assume a(More)
This paper presents a comparative study on the use of no-reference quality metrics for eye fundus imaging. We center on auto-focusing and quality assessment as key applications for the correct operation of a fundus imaging system. Four state-of-the-art no-reference metrics were selected for the study. From these, a metric based of Rényi anisotropy yielded(More)
Retinal images are widely used for diagnostic purposes by ophthalmolo-gists. Therefore, these images are suitable for digital image analysis for their visual enhancement and pathological risk or damage detection. Here, we implement a lu-minosity and contrast enhancement technique based on domain knowledge. We also review and analyze a previous approach in(More)
Recently, a novel nonlinear encryption system based on joint transform correlator (JTC) in the Gyrator domain (GD) was proposed. The encryption system uses a fully nonlinear nonzero order JTC and Gyrator transform (GT). The decryption system is based on two successive GTs. The proposed system preserves the good quality of the decrypted image while increases(More)
First-order and multi-order diffractive lenses are implemented using a LCoS modulator with 8π-phase modulation range for a 514nm operation wavelength. Their performance is compared in terms of energy efficiency in the first and zero order diffractive planes. The influence of the display calibration is evaluated for each phase modulation range.
Joint-transform correlator (JTC) architecture presents some advantages, such as no requirement of interferometric recording of the phase distribution or complex conjugation of the key phase mask, in order to optically implement the well-known double random phase encryption (DRPE) method. In addition, a practical optical realization was proposed in a way(More)
In this work, we present the integration of the photon counting technique (PhCT) with an encryption system in the Gyrator domain (GD) for secure image authentication. The encryption system uses two random phase masks (RPMs), one RPM is defined at the spatial domain and the other RPM is defined at the GD, in order to encode the image to encrypt (original(More)
Retinal photography is important for the assessment of eye diseases. The task of fine focusing the image is demanding and lack of focus is often the cause of suboptimal photographs. The advent of digital cameras has provided the opportunity to automate the focusing process. In this work, we propose an auto-focus system for non-mydriatic retinal imaging. The(More)
The integration of photon-counting imaging techniques to optical encryption systems permits to increase information authentication robustness against intruder attacks. Photon-counting imaging generates distributions with only few photons and provides substantial bandwidth reduction by requiring only a sparse encrypted data. We show that photon-limited(More)