A method for producing a plurality of optical prisms comprises: providing at least one manufacturing intermediate; and dividing the at least one manufacturing intermediate into a plurality of individual triangular prisms. The manufacturing intermediate comprises a main body in the form of a triangular prism having three rectangular surfaces and two triangular surfaces. The main body is formed from a light-transmitting material. A layer of opaque material is provided on two of the three rectangular surfaces of the main body, the layer of opaque material having a plurality of axially spaced apertures on each of the two of the three rectangular surfaces, each one of the apertures on one of the two surfaces being disposed at substantially the same axial position as one of the apertures on the other one of the two surfaces. The at least one manufacturing intermediate is divided into a plurality of individual triangular prisms such that each individual triangular prism has one of the apertures on each of two sides thereof.