US Patent 7199814 Direct write holographic printer

A direct write holographic printer for producing RGB color reflection holograms is disclosed. A Nd:YLF crystal (1) in a laser cavity is excited to produce an emission at 1313 nm which is frequency converted by doubling to 656.5 nm and by tripling to 437.7 nm. In a separate cavity a similar Nd:YLF crystal (1a) is synchronously or asynchronously excited to produce an emission at 1047.1 nm (or at the related line of 1053 nm) which is frequency converted by doubling to 523.6 nm (or 526.5 nm). The emissions at 437.7 nm and 656.5 nm are combined co-linearly with the emission at 523.6 nm (or 526.5 nm) to produce a single RGB pulsed laser beam.