B. Pulse Detection and Heart Rate Calculation
The procedure for detecting a pulse works on the principle[7] that, every heart beat pertains to a rush of blood in the blood vessels, even in the capillaries at the finger-tips. By placing the finger over the camera and turning on the flash through a video recording application, the following observations were made. During a systolic pulse when the capillaries are rich in blood, more light was absorbed by the blood, leading to a low-reflective index and darker frame intensities. Likewise,duringa diastolic pulse, most of the light was reflected leading to bright frames. The change in intensity of light passed through the finger creating an alternative pattern of waves. These changes in intensity with time were used to obtain the pulse of a person. The pixel in formation from the video was split into individual red,blue,and green components.In most of the frames observed, the prominent color was red. We split every frame of the video into four quadrants and considered only the first quadrant for analysis because the fluctuations were more predominant in that region. Then we split the frames on a fixed length window (Wt) to check for the number of peaks(n)occurring at equal intervals of time as shown in Fig.5. We then calculate the Heart rate(HR) given by