arXiv subjects

Efstratios Skafidas

Publications and source records attributed to Efstratios Skafidas.

4 recordsLinked to original sources

arXiv2025

Color-Blind Image Sensors: Towards Digital Twin of Human Retina

The human retina contains a complex arrangement of photoreceptors that convert light into visual information. Conventional image sensors mimic the trichromacy of the retina using periodic filter mosaics responsive to three primary colors. However, this is, at best, an approximation, as an actual retina exhibits a quasi-random spatial distribution of light-sensitive rod and cone photoreceptors, where the ratio of rods to cones and their concentrations vary across the retina. Hence, the periodic mosaics are limited to accurately simulate the properties of the eye. Here, we present an image sensor with similar distribution, spacing, ratios and spectral characteristics of an actual foveal mosaic for emulating eye-like sampling and mimicking color blindness. To perform image reconstruction, we use a fully convolutional U-Net neural network adopting the concept of receptive fields in the retinal circuitry. Our research will enable the development of digital twin of a retina to further understand color vision deficiencies.

physics.optics↗

arXiv2020

A Single Sensor Based Multispectral Imaging Camera using a Narrow Spectral Band Colour Mosaic Integrated on the Monochrome CMOS Image Sensor

A multispectral image camera captures image data within specific wavelength ranges in narrow wavelength bands across the electromagnetic spectrum. Images from a multispectral camera can extract additional information that the human eye or a normal camera fails to capture and thus may have important applications in precision agriculture, forestry, medicine and object identification. Conventional multispectral cameras are made up of multiple image sensors each fitted with a narrow passband wavelength filter and optics, which makes them heavy, bulky, power hungry and very expensive. The multiple optics also create image co-registration problem. Here, we demonstrate a single sensor based three band multispectral camera using a narrow spectral band RGB colour mosaic in a Bayer pattern integrated on a monochrome CMOS sensor. The narrow band colour mosaic is made of a hybrid combination of plasmonic colour filters and heterostructured dielectric multilayer. The demonstrated camera technology has reduced cost, weight, size and power by almost n times (where n is the number of bands) compared to a conventional multispectral camera.

physics.optics↗

arXiv2013

Highly Scalable Neuromorphic Hardware with 1-bit Stochastic nano-Synapses

Thermodynamic-driven filament formation in redox-based resistive memory and the impact of thermal fluctuations on switching probability of emerging magnetic switches are probabilistic phenomena in nature, and thus, processes of binary switching in these nonvolatile memories are stochastic and vary from switching cycle-to-switching cycle, in the same device, and from device-to-device, hence, they provide a rich in-situ spatiotemporal stochastic characteristic. This work presents a highly scalable neuromorphic hardware based on crossbar array of 1-bit resistive crosspoints as distributed stochastic synapses. The network shows a robust performance in emulating selectivity of synaptic potentials in neurons of primary visual cortex to the orientation of a visual image. The proposed model could be configured to accept a wide range of nanodevices.

cond-mat.other↗

arXiv2013

CMOS-Compatible Nanowire Biosensors

In this chapter, silicon nanowires that are compatible with CMOS fabrication processes have been described. It has been shown that these nanowires can be functionalized by conjugating monoclonal antibodies to their surface in order to build sensitive biochemical sensors. It has also been shown that by using frequency-based signals, all the necessary components to interrogate these nanowires can be built on low-cost CMOS processes.

cond-mat.mes-hall↗