Optical Integration Without Compromises
Dr. Janos Palhalmi (PhD) and Jan-Hein Broeders Analog Devices Instruments, Technical Articles
Photoplethysmography (PPG) is a common technology for measuring oxygen saturation (SPO 2 ) levels in blood. Light is sent by a light emitter into the body, and the amount of reflective or unabsorbed light is measured with a photoreceiver. Depending on the ratio between two wavelengths, the amount of oxygenated haemoglobin can be measured. Comparable technologies are also used to measure heart rate with an optical technology or heart rate variability. All these systems require one or more photoemitters, which need to be controlled, and a photodetector to measure the amount of photocurrent as a measure for the received light. This receive signal finally needs to be amplified, conditioned, and digitized. Such an optical system might sound straightforward; however, with a missing dose of optical knowledge, it is very easy to retrieve an optical signal, which doesn’t have anything to do with the signals the user is looking for. To help companies achieve their optical objectives, a new, fully integrated optical module has been introduced. It has been tested and compared to a well-proven discrete optical system with outstanding results. You will read more about the results and methodologies behind this exercise.
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