IEEE Access (Jan 2020)
Dedicated Exposure Control for Remote Photoplethysmography
Abstract
This paper aims to show that control of exposure time during video capture will improve the accuracy of remote photoplethysmography (rPPG). We propose a purpose specific exposure control algorithm for use in heart rate estimation via rPPG applicable for any controllable camera. Our novel algorithm works by selecting exposure that acheives maximum Signal-to-Noise Ratio (SNR) before distortion will occur. We performed experiments to test the accuracy of non-contact PPG extracted simultaneously from two identical cameras positioned together but with different exposure time controls. Our purpose specific algorithm in camera A controlled exposure time to maximise rPPG SNR ratio while camera B remained set at one of a range of values. Exposure time set by our novel algorithm out-performed camera B with a lower mean absolute error relative to a standard pulse oximeter. A significant improvement to heart rate estimation performance using a research camera can be made with specific control of exposure time. The improvements in performance demonstrated here are an important step in taking rPPG out of a lab environment and into less controlled circumstances such clinical settings and emergency rescue scenarios.
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