Real-time Heart Activity Monitoring with Optical Illusion using a Smartphone- Raw data

In this study, we obtained a pulsatile photoplethysmogram signal from a fingertip using the built-in camera of an iPhone 6s and displayed a real-time heart activity images with holographic projection on a smartphone screen. Our proposed heart activity hologram is simple and can be easily realized with only a smartphone and overhead projector (OHP) film. A square pyramid-shaped OHP film was positioned on a smartphone screen. The actual cardiac cycle on the smartphone screen was projected onto the film while measuring the pulsatile signal from a fingertip placed on the smartphone’s camera. The heart’s beat-to-beat time interval was then recorded. This approach enables observation of one’s own virtual heart activity in real time, rather than seeing a pulsatile signal graphically on a smartphone. To investigate the feasibility of this heart activity monitoring based on holographic projection, we tested it under different conditions in terms of environmental light, smartphone screen light intensity, and film color, and quantified the contrast-to-noise ratio for comparison

本研究中，我们借助iPhone 6s的内置摄像头采集指尖的搏动式光电容积描记图（photoplethysmogram）信号，并在智能手机屏幕上通过全息投影呈现实时心脏活动图像。本研究提出的心脏活动全息投影方案结构简便，仅需智能手机与投影仪（overhead projector, OHP）胶片即可轻松实现。将方形金字塔结构的OHP胶片置于智能手机屏幕之上。当对放置在智能手机摄像头处的指尖进行搏动信号采集时，将智能手机屏幕上的实际心动周期图像投影至该胶片上。随后记录心脏的逐搏间期。该方案可使用户实时观测自身的虚拟心脏活动，而非仅在智能手机上以图形化方式查看搏动信号。为探究该基于全息投影的心脏活动监测方案的可行性，我们分别在环境光照、智能手机屏幕光强以及胶片颜色等不同条件下开展测试，并通过量化对比度噪声比（contrast-to-noise ratio）进行对比分析。