The present invention relates to a device, system and method for determining vital signs of a subject. To balance accuracy and reliability with unobtrusiveness, the device comprises an interface (30) for receiving input signals from a detection unit (18) that is configured for contactless detection of radiation reflected from a subject (14) in response to illumination by an illumination source (22), a processing unit (32) for deriving photoplethysmography, PPG, signals from the received input signals, an analysis unit (34) for deriving a desired vital sign from the PPG signals, and a control unit (36) for controlling one or more parameters of the illumination source (22), the detection unit (18) and/or the analysis unit (34) in dependence on the physical state of the subject, the quality of the input signals or the derived vital sign and/or the value of the vital sign.
