Abstract: A athermalized optical head is disclosed which comprises a light source such as a laser diode and an optical element, for example, a collimating lens. The collimating lens and the laser diode are mounted along a common optical axis. A thermoelectric cooling element is provided in the head to control the temperature of the laser diode. In order to maintain a spot produced by the head in focus during changes in ambient temperature, the laser diode and the lens are mounted such that the distance between the diode and the lens is maintained constant over a predetermined temperature range.