Patent ID: 9743838
Date: 2017-08-29
CPC Classifications: A61B

Claim:
1. A method for removing a component of a signal corresponding to ambient light in a photoplethysmographic sensor device, the method comprising: capturing, using a switch in a first position, a first detected light signal and holding the first detected light signal as voltage across a capacitor, the first detected light signal representing ambient light; causing a light emitter to generate a source light signal driven at a first level; capturing a second detected light signal, the second detected light signal representing the source light signal after interacting with a user's tissue; generating, using the switch in a second position, a first output signal based on the second detected light signal adjusted by the first detected light signal held in the capacitor; changing the light emitter to generate a source light signal driven at a second level that is different than the first level; capturing a third detected light signal, the third detected light signal representing the source light signal driven at the second level after interacting with the user's tissue; generating, using the switch in the second position, a second output signal based on the third detected light signal adjusted by the first detected light signal held in the capacitor; and changing the light emitter again to generate the source light signal driven at the first level and capturing a fourth detected light signal representing the source light signal driven at the first level interacting with the user's tissue; generating a third output signal based on the fourth detected light signal adjusted by the first detected light signal held in the capacitor; and generating a photoplethysmographic signal based on a weighted combination of the first, second, and third output signals, wherein initially detected ambient light is removed during the generating of the first, second, and third output signals, and dynamic changing ambient light is removed as a result of the weighted combination of the first, second, and third output signals.