A pulse oxymeter uses light as a modality which we explore here. The oxygene level is detected by comparing the absorption of visible light against infrared. Here, we use it to detect the pulse rate because at every heart beat blood flows into the finger and increases the absorption.
The software used for the pulse oxymeter CMS-50D+ is based on "glexox" by Greg Courville. The version used in this clip can be downloaded here.
next: measuring the body temperature while smoking a cigarette