Abstract: A system and a method are disclosed for identifying and characterizing a stress state of a user based on features of blood flow identified from optical signals. One embodiment of a disclosed system (and method) includes an optical sensing system to detect features of blood flow and identify and characterize a stress state of a user based on those blood flow features. Light transmitted or reflected from tissue of the user is measured by an optical sensor. A processor analyzes the received optical signal to identify features of the blood flow. The stress state of the user is determined based on the identified features. The stress state is characterized according to a type of stress, a level of stress or both. Additionally stress events are identified.

Abstract: A biometric device configured to be attached to a portion of a body of a user measures biometric data of the user. The device includes an optical emitter, a wavelength filter, an optical sensor and a processor, for sending a light to the body of a user, receiving light received from the user, filtering and processing it to measure biometric data of the user, including for example, heart rate and blood flow rate. In addition, the biometric device may include other sensors, such as a galvanic skin response sensor, an ambient temperature sensor, skin temperature, motion sensor, etc., to enable the biometric device to measure arousal or conductivity changing events, ambient temperature, user temperature and motion associated with the user. Additionally, information from each sensor may be used to further filter noise in one or more signals received by the sensors to provide biometric data to the user.