arXiv subjects

Jonathan P. Newman

Publications and source records attributed to Jonathan P. Newman.

3 recordsLinked to original sources

arXiv2019

A closed-loop all-electronic pixel-wise adaptive imaging system for high dynamic range video

We demonstrated a CMOS imaging system that adapts each pixel's exposure and sampling rate to capture high dynamic range (HDR) videos. The system consist of a custom designed image sensor with pixel-wise exposure configurability and a real-time pixel exposure controller. These parts operate in a closed-loop to sample, detect and optimize each pixel's exposure and sampling rate to minimize local region's underexposure, overexposure and motion blurring. Exposure control is implemented using all-integrated electronics without external optical modulation. This reduces overall system size and power consumption. The image sensor is implemented using a standard 130nm CMOS process while the exposure controller is implemented on a computer. We performed experiments under complex lighting and motion condition to test performance of the system, and demonstrate the benefit of pixel-wise adaptive imaging on the performance of computer vision tasks such as segmentation, motion estimation and object recognition.

eess.IV↗

arXiv2013

Delivery of time-varying stimuli using ChR2

To understand sensory processing in neuronal populations, it is necessary to deliver stimuli to the sensory organs of animals and record evoked population activity downstream. However, the pathways from sensory input to synaptic currents in cells that are several synapses removed from sensory organs are complex. Intrinsic noise and uncontrolled modulatory input from other brain regions can interfere with the delivery of well-defined stimuli. Here we investigate the ability of channelrhodopsins to deliver precise time-varying currents to neurons at any point along the sensory-motor pathway. To do this, we first deduce the amplitude response function of channelrhodopsin-2 (ChR2) using a three state Markov model of channel kinetics. With biophysically realistic parameters, this function supports a relatively broad signal passband and contains a resonance. We confirm the validity of our predicted amplitude response function using time-varying optical stimulation of excitatory neurons that express either wild type ChR2 or the ChR2(H134R) mutant. Together, our results indicate that ChR2-derived optogenetic tools are useful for delivering repeatable, time-varying currents to genetically-specified populations over a physiologically-relevant frequency band.

q-bio.NC↗

arXiv2008

The Effect of Sensory Blind Zones on Milling Behavior in a Dynamic Self-Propelled Particle Model

Emergent pattern formation in self-propelled particle (SPP) systems is extensively studied because it addresses a range of swarming phenomena which occur without leadership. Here we present a dynamic SPP model in which a sensory blind zone is introduced into each particle's zone of interaction. Using numerical simulations we discovered that the degradation of milling patterns with increasing blind zone ranges undergoes two distinct transitions, including a new, spatially nonhomogeneous transition that involves cessation of particles' motion caused by broken symmetries in their interaction fields. Our results also show the necessity of nearly complete panoramic sensory ability for milling behavior to emerge in dynamic SPP models, suggesting a possible relationship between collective behavior and sensory systems of biological organisms.

q-bio.PE↗