The car headlamp is made from an optical fibre (1) leading to a lens unit (3,4). The optical fibre has a specified refractive index. The fibre goes from a round cross-section to a polyhedral cross-section near where it joins the lens unit, the circular cross-section completely covering the polyhedral cross-section. The polyhedral section generates the desired light distribution pattern. The entry surface of the lens unit covers the whole of the polyhedral cross-section and transmits the light distribution pattern forwards. The polyhedral exit surface from the fibre lies at a focus of the lens unit and is at right angles to its optical axis.
