Contactless vital sign parameter measurement using compact snapshot multispectral multiaperture camera: design, realization, application, evaluation

Contactless camera-based measurement of vital signs like respiratory rate (RR), heart rate (HR) and oxygen saturation (SpO₂) is a demanding task for future medical applications. This is motivated by considerations of user comfort, hygiene, ease of deployment and additional extraction of contextual information from the scene. However, accurate RR measurement based on remote photoplethysmography (rPPG) remains challenging. We developed a novel real-time multispectral sensor system based on a compact snapshot multi-aperture camera approach combined with LED-illumination and dedicated read-out/control boards. The multispectral camera features a single compact hot embossed glass meniscus micro-lens array achieving a high resolution of approximately 1.25 MP per channel at f/4 and a full-diagonal field-of-view of 40°, together with seven distinct bandpass filters in the visible and near-infrared wavelength range. The overall sensor head has dimensions of 85 x 85 x 160 mm³. We outline an approach for pre-processing of multispectral image data, rPPG signal processing and determination of RR, HR, and SpO₂ from multispectral video data. Promising performance was achieved during recording of 12 individuals under controlled laboratory conditions - mean absolute errors of 1.28 breaths per minute for RR, 2.78 beats per minute for HR, and 3.80% for SpO₂. Finally, certain critical influencing factors as well as software and hardware optimizations are briefly discussed.