INJECTION MOULDING OF OPTICAL COMPONENTS

A method for injection moulding an optical component (20), e.g. a cover for a luminaire, with an incorporated optical function, the component (20) comprising an injection moulded body (18) and at least one optically functional relief structure (4) applied thereto, the relief structure (4) forming or contributing to the optical function of the component (20) to be moulded, wherein the method comprises: (i) providing an insert (2) comprising the said optical structure (4) in the form of an open-face relief structure (4) provided on a face, surface or portion of the insert (2), (ii) mounting the insert (2) inside a mould cavity (11) in which the component (20) is to be moulded, with the open-face relief structure (4) facing and at least partially abutting a surface portion of the mould cavity (11), and (iii) rear-injection moulding a body (18) of the component (20) within the mould cavity (11) so as to incorporate the insert (2) in the component body (18), wherein the said method is carried out with parameters selected and/or controlled such that during the injection moulding step (iii) the temperature at or on the face, surface or portion of the insert (2) provided with the relief structure (4) remains below the lowest of the glass transition temperature, melting temperature and temperature of onset of thermal decomposition of the material of that face, surface or portion of the insert (2).