A head/eye tracking system comprising an image sensor for acquiring images of a user, a narrow band light source for illuminating the eyes, and a band-pass filter arranged between the eyes and the image acquisition device and having a pass-band corresponding to the emission spectrum of the light source at a predefined operating temperature. The system further comprises a heat source arranged in proximity to the light source and configured to preheat the light source to reach the predefined operating temperature. By shortening the period during which large temperature variation takes place, sub-optimal performance of the system can be accepted during this short period, thereby relaxing the requirements on light source and filter design.
