Patent ID: 7199814

Claim:
A direct write holographic printer comprising: a pulsed multiple colour laser system to produce a laser beam, said laser beam being split into an object beam and a reference beam, which is mutually coherent with said object beam; a spatial light modulator wherein, in use, said object beam illuminates said spatial light modulator; and a lens system for writing a holographic pixel of a hologram on to a photosensitive medium, said lens system being arranged downstream of said spatial light modulator; wherein said pulsed multiple colour laser system comprises: a first active laser element provided in a first laser cavity, said first active laser element comprising Nd:YLF and wherein said first active laser element is arranged to generate laser radiation at a first fundamental frequency with a wavelength of 1313 nm; means for arranging the laser mode within said first laser cavity to be single longitudinal mode; means for frequency doubling said laser radiation at said first fundamental frequency to provide laser radiation at a first frequency doubled frequency with a wavelength of 656.5 nm; means for frequency trebling said laser radiation at said first fundamental frequency to provide laser radiation at a first frequency trebled frequency with a wavelength of 437.7 nm; a second active laser element provided in a second laser cavity separate from said first laser cavity, said second active laser element comprising Nd:YLF and wherein said second active laser element is arranged to generate laser radiation at a second fundamental frequency with a wavelength of 1053 nm or 1047.1 nm; means for frequency doubling said laser radiation at said second fundamental frequency to provide laser radiation at a second frequency doubled frequency with a wavelength of 526.5 nm or 523.6 nm; and means for arranging the laser mode within said second laser cavity to be single longitudinal mode.