Multi-aperture ppg reveals varied light and pulse patterns in tissue
Multi-Aperture PPG with MAPIS: Spatial Optical and Temporal Coherence Fields
Computer Vision and Pattern Recognition
Summary
Measuring heart-related signals using light usually combines all light detectors into one or a few readings. The authors used a new device called MAPIS that takes many different light measurements at once through multiple tiny openings. They found unique patterns in how the light intensity and pulse signal relate depending on which opening is used, and differences between red and infrared light. This helps better understand the complex light paths involved in pulse measurement, which are typically mixed together in standard methods.
What this means in practice
- •For wearable health device engineers: Design multi-aperture sensors that capture spatially distinct pulse signals to improve accuracy of heart and blood flow monitoring.
- •For medical imaging developers: Develop new optical measurement techniques that leverage varied temporal coherence from different light paths for enhanced tissue analysis.
Authors
Shuguang Wang, Yuanjing Wang
Abstract
Conventional reflectance photoplethysmography (PPG) typically reduces tissue optical responses to one or a few detector channels. Matrix Pinhole Image Sensing (MAPIS) instead simultaneously samples multiple aperture-dependent optical signals. We analyzed 44 recordings of 30 seconds each from a single MAPIS device to characterize the spatial relationships among DC intensity, pulsatile AC, perfusion index (PI), and temporal coherence across Red and infrared channels. AC increased sublinearly with DC at both wavelengths, resulting in higher PI toward lower-DC apertures, consistent with a first-order relative path-sensitivity interpretation. A second counterintuitive spatial trend was observed in temporal coherence: lower-DC and lower-AC apertures exhibited higher autocorrelation and greater cardiac-periodic spectral concentration. IR signals also showed consistently higher temporal coherence than corresponding Red signals. These observations demonstrate that multi-aperture PPG resolves reproducible spatial relationships among optical intensity, fractional pulsatile sensitivity, and waveform coherence that are largely averaged together in conventional single-channel PPG. The present study establishes within-device relationships and motivates controlled studies of the underlying photon-path mechanisms.