arXiv subjects

Nimrod Kruger

Publications and source records attributed to Nimrod Kruger.

5 recordsLinked to original sources

arXiv2026

Optical Linear Systems Framework for Event Sensing and Computational Neuromorphic Imaging

Event vision sensors (neuromorphic cameras) output sparse, asynchronous ON/OFF events triggered by log-intensity threshold crossings, enabling microsecond-scale sensing with high dynamic range and low data bandwidth. As a nonlinear system, this event representation does not readily integrate with the linear forward models that underpin most computational imaging and optical system design. We present a physics-grounded processing pipeline that maps event streams to estimates of per-pixel log-intensity and intensity derivatives, and embeds these measurements in a dynamic linear systems model with a time-varying point spread function. This enables inverse filtering directly from event data, using frequency-domain Wiener deconvolution with a known (or parameterised) dynamic transfer function. We validate the approach in simulation for single and overlapping point sources under modulated defocus, and on real event data from a tunable-focus telescope imaging a star field, demonstrating source localisation and separability. The proposed framework provides a practical bridge between event sensing and model-based computational imaging for dynamic optical systems.

cs.CV↗

arXiv2025

Seeing like a Cephalopod: Colour Vision with a Monochrome Event Camera

Cephalopods exhibit unique colour discrimination capabilities despite having one type of photoreceptor, relying instead on chromatic aberration induced by their ocular optics and pupil shapes to perceive spectral information. We took inspiration from this biological mechanism to design a spectral imaging system that combines a ball lens with an event-based camera. Our approach relies on a motorised system that shifts the focal position, mirroring the adaptive lens motion in cephalopods. This approach has enabled us to achieve wavelength-dependent focusing across the visible light and near-infrared spectrum, making the event a spectral sensor. We characterise chromatic aberration effects, using both event-based and conventional frame-based sensors, validating the effectiveness of bio-inspired spectral discrimination both in simulation and in a real setup as well as assessing the spectral discrimination performance. Our proposed approach provides a robust spectral sensing capability without conventional colour filters or computational demosaicing. This approach opens new pathways toward new spectral sensing systems inspired by nature's evolutionary solutions. Code and analysis are available at: https://samiarja.github.io/neuromorphic_octopus_eye/

cs.CV↗

arXiv2020

Luminescent solar power: PV/thermal hybrid electricity generation for cost effective dispatchable solar energy

The challenge in solar energy today is not the cost of photovoltaic (PV) electricity generation, already competing with fossil fuel prices, but rather utility-scale energy storage and flexibility in supply. Low-cost thermal energy storage (TES) exists but relies on expensive heat engines. Here, we introduce the concept of luminescent solar power (LSP), where sunlight is absorbed in a photoluminescent (PL) absorber, followed by red-shifted PL emission matched to an adjacent PV cell's band-edge. This way the PV cell operates nearly as efficiently as under direct illumination, but with minimal excessive heat. The PL-absorber temperature rises due to thermalization, allowing it to store the excessive heat, which can later be converted into electricity. Tailored luminescent materials that support an additional 1.5kWh PV-electricity for every 1 kWh of (virtual) heat engine-electricity, with a dynamic shift between the two sources are experimentally demonstrated. Such an ideal hybrid system may lead to a potential reduction in the cost of electricity for a base-load solution.

physics.app-ph↗

arXiv2018

Efficient tenfold up-conversion through steady-state non-thermal-equilibrium excitation

Frequency up-conversion of a few low-energy photons into a single high-energy photon contributes to imaging, light sources, and detection. However, the up-converting of many photons exhibits negligible efficiency. Up-conversion through laser heating is an efficient means to generate energetic photons, yet the spectrally broad thermal-emission and the challenge of operating at high temperatures limit its practicality. Heating specific modes can potentially generate narrow up-converted emission; however, so far such "hot-carriers" have been observed only in down-conversion processes and as having a negligible lifetime, due to fast thermalization. Here we experimentally demonstrate up-conversion by excitation of a steady-state non-thermal-equilibrium population, which induces steady, narrow emission at a practical bulk temperature. Specifically, we used a 10.6um laser to generate 980nm narrow emission with 4% total efficiency and up-converted radiance that far exceeds the device s possible black-body radiation. This opens the way for the development of new light sources with record efficiencies.

physics.optics↗

arXiv2013

Entropy driven multi-photon frequency up-conversion

Frequency up-conversion of few low-energy photons into a single high-energy photon, greatly contributes to imaging, light sources, detection and other fields of research. However, it offers negligible efficiency when up-converting many photons. This is because coherent process are fundamentally limited due to momentum conservation requirements, while in incoherent up-conversion the finite intermediate states lifetime requires huge intensities. Thermodynamically, conventional incoherent up-conversion is driven by the internal energy of the incoming photons. However, a system can also drive work through change in its collective properties such as entropy. Here we experimentally demonstrate entropy driven ten-fold up-conversion from 10.6μ to 1μm at internal efficiency above 27% and total efficiency above 10%. In addition, the emitted radiance at 1μm exceeds the maximal possible Black-Body radiance of our device, indicating emitter's effective-temperature that is considerably above the bulk-temperature. This work opens the way for up-conversion of thermal-radiation, and high-temperature chemistry done at room-temperature.

physics.optics↗