Optical components

A moulding apparatus for moulding a substantially transparent optical component which comprises polymer, the optical component having substantially matching grating imprints on opposing portions of its surface, wherein the grating imprints have a substantially zero relative orientation angle, the apparatus comprising:

• a moulding component having two surfaces, the surfaces having surface modulations which form two substantially matching gratings, wherein the moulding component is configurable to change the relative orientation angle of the gratings;
• a drive mechanism coupled to the moulding component controllable to configure the moulding component;
• wherein at least an alignment portion of the moulding component is substantially transparent, the alignment portion located so that light which has interacted with both gratings is observable from the alignment portion when the substantially transparent polymer is between the surfaces, whereby an observable fringe pattern is formed as the relative orientation angle of the gratings is changed towards zero, the fringe pattern exhibiting a fringe spacing which increases as the relative orientation angle decreases, the apparatus further comprising:
• a light sensor configured to receive at least some of the light which has interacted with both gratings;
• and
• a controller configured, whilst the polymer is still liquid, to control the drive mechanism based on sensed data received from the image sensor to reconfigure the moulding component from a current configuration to a new configuration in which the fringe spacing of the fringe pattern is substantially maximal, thus aligning the gratings to have a substantially zero relative orientation angle, wherein the new configuration is maintained whilst the polymer sets.