In search of silver linings

A commercial recording material for holograms that can produce more life-like holographic displays has been developed by a group of European researchers.

Under the

, researchers from the

(NEWI) have optimised the qualities of silver halide crystals to produce emulsion-coated plates capable of rendering high-resolution, full-colour holograms.

in Belgium and The Holographic Image Studio are also involved.

Prof Hans Bjelkhagen at NEWI said: 'The [silver halide] emulsion has a grain size of around 10nm, and these are like photographic materials, but the unusual thing is the size of the grains we have been able to make, which is an absolute necessity to be able to produce full-colour holograms.'

Normal photographic materials (light-sensitive film that captures and plays back light wave interference patterns) have a grain size of about 100nm, and Bjelkhagen said companies such as Kodak have made holographic materials with a grain size of 50nm in the past.

The researchers achieved a much smaller grain size, using a freezing and thawing technique. 'It's a special technique where you concentrate it by freezing it, then it will melt and you extract the water to increase the concentration to make them light sensitive,' said Bjelkhagen.

He said images can be recorded to look identical to a real object, but admitted they do not yet have 100 per cent accurate colour reproduction because of the number of laser wavelengths to which they have access. 'You need more than three wavelengths to get an error difference that's not possible to see with the human eye. If you put them side by side you can see the colours are slightly different, but they are still extremely good because of the reflections, shadows and everything moves,' he said.