Light measure apps
How apps like "Cardiography" and "Heart Rate" are using camera and flash to measure the heart rate?
The link to the app is- https://play.google.com/store/apps/details?id=com.macropinch.hydra.android&feature=search_result#?t=W251bGwsMSwxLDEsImNvbS5tYWNyb3BpbmNoLmh5ZHJhLmFuZHJvaWQiXQ..

Any code, sample or explanation will be helpfull.
Light measure apps
===

How apps like "Cardiography" and "Heart Rate" are using camera and flash to measure the heart rate?
The link to the app is- https://play.google.com/store/apps/details?id=com.macropinch.hydra.android&feature=search_result#?t=W251bGwsMSwxLDEsImNvbS5tYWNyb3BpbmNoLmh5ZHJhLmFuZHJvaWQiXQ..

Any code, sample or explanation will be helpfull.