An analytic-numerical image flicker study to test novel flicker metrics

Abstract

The IEEE P2020 Automotive Image Quality working group is proposing new metrics and test protocols to measure image flicker. A comprehensive validation activity is therefore required. Light source flicker (often LED flicker), as captured in a camera output, is a product of camera exposure time, sensitivity, full well capacity, readout timing, HDR scheme, and the light source frequency, duty cycle, intensity, waveform and spectrum. The proposed LED flicker metrics have to be tested and validated for a sufficient number of combinations of these camera and lighting configurations. The test space of the combinations of camera and lighting parameters is unfeasibly large to test with physical cameras and lighting setups. A numerical simulation study to validate the proposed metrics has therefore been performed. To model flicker, a representative pixel model has been implemented in code. The pixel model incorporates exposure time, sensitivity, full well capacity, and representative readout timings. The implemented light source model comprises an hybrid analyticnumerical approach that allows for efficient generation of complex temporal lighting profiles. It simulates full and half wave rectified sinusoidal waveforms, representative of AC lighting, as well as pulse width modulated lighting with variable frequency, duty cycle, intensity, and complex edge rise/fall time behaviour. In this article, both initial results from the flicker simulation model, and evaluation of proposed IEEE metrics, are presented.