Recent Works on Direct-Write Digital Holography

Direct-write digital holographic (DWDH) printing is a highly flexible technique for the generation of photoresist masters, which are required to produce the metallic shims used for the mass production of holograms in the security and packaging industries. Here we describe a new type of holographic feature, which can be combined with any other feature printable using DWDH: full-parallax, full-colour transmission masters containing limited animation. We will also describe a technique to print the fringe pattern of each hogel without using a reference beam. By programming the required fringe calculation algorithm on a graphics card using CUDA, we obtain acceptable calculation times. The advantage of using such direct fringe writing is that once again DWDH allows extra features to be written onto a master and combined with other features to produce a stronger security solution. Finally, we present results concerning the use of hogel image dithering to improve the grey-scale performance of DWDH printers.