The present document discloses a solution for optical biometric measurements. According to an aspect, a sensor device comprises: a sensor head configured to face a skin of a human body, the sensor head comprising at least one optical emitter configured to emit light towards a direction of the skin and at least one photodetector configured to sense the emitted light from the direction of the skin; and an array of parallel light guide elements arranged to form a plurality of parallel light paths directing light from the at least optical emitter to the at least one photodetector, each light guide element comprising, between a first end and a second end of said light guide element, an optically transparent core and an optical barrier surrounding the core, the core together with the optical barrier focusing light along the core between the ends.