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Photoplethysmography signals are universally accounted for in healthcare units due to their non-invasive nature and effectiveness. They are used to calculate heart rate, heart rate variability, and other parameters. The PPG field is moving from the traditional setup to acquire the data with the help of LED and photodetector to image-based data acquisition with the help of cameras called i-PPG signals. This study aims to compare PPG with i-PPG signals captured using a smartphone's front camera, especially in calculating heart rate and its variability. Five healthy volunteers participated for this purpose. The reference value of the volunteers’ heart rate was obtained using a commercially available standard pulse-oximeter and Omron BP monitor. PPG signals were collected using a red LED with a wavelength of 660nm in the circuit built with the MAX30102 sensor. Finally, i-PPG signals were recorded as the videos of the right index finger were captured for the duration of 2 minutes for the analysis. Data was recorded in a calm and quiet environment otherwise interference will be observed in the signals. Videos were converted into i-PPG signals, and then both signals (i-PPG and PPG) were pre-processed to remove baseline drift. The heart rate series of both signals was obtained by calculating the time interval between adjacent peaks and multiplying its inverse by 60. The heart rate variability series was also calculated by taking the difference between two adjacent beats per minute values in the heart rate series. The heart rate obtained from the sensor circuit built has a positive correlation of 0.98, 0.99 and i-PPG signals have a positive correlation of 0.91 and 0.98 with reference methods on par with the values obtained from the pulse oximeter. It is significant to note that there were fluctuations while obtaining reference heart rate values.
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