The spot array DOEs used to parallelise the write process were all designed using a modified three-stage Iterative Fourier Transform Algorithm (IFTA) . DOEs with different target images containing different numbers of output spots and different spots separations (corresponding to different DOE spatial periods and hence diffraction angles) were calculated and fabricated. Typical inter-spot diffraction angles ranged from 1° to 0.01°. The DOEs were all binary phase elements, etched into a layer (thickness ~ 400 nm) of spin-coated S1805 photoresist (MicroChem) on 1.1 mm thick float glass substrates using a custom-built, massively parallel-write photoplotter . Typical DOE experimental diffraction efficiencies of 70-75% were observed. When appropriate, target output spot patterns with a deliberately weakened central spot were chosen to compensate for increased zeroth order spot power resulting from inevitable DOE fabrication process limitations and hence obtain increased experimental array spot power uniformity. Occasionally, over-correction led to a slight underexposure of the central spot.