The Antikythera Mechanism is an ancient astronomical device built by the Greeks around 80BC and found on a shipwreck off the Greek island of Antikythera by sponge divers in 1901. It is believed to have been created to track lunar and solar cycles for agricultural and religious purposes, but its precise function and how it works has eluded scholars for more than a century.

In September 2005, members of the Antikythera Research Project invited HP Labs research scientists, Tom Malzbender and Dan Gelb, to Athens to apply their patented reflectance imaging techniques to the front and rear surfaces of the more than 70 fragments that comprise the mechanism, including metal plates and gears, some of which are inscribed with faded Greek characters.

The technique involves taking photos of an artefact from a fixed point and 50 different light sources arrayed in a hemisphere over the object. The HP researchers computer program then ties the images together, enabling an archaeologist to change the angle of light or texture of the surface of the object to make faint markings appear more vivid.

One of the advantages of reflectance imaging is that you can change the quality of the surface of an object, by, for example, making dull surfaces shiny, like obsidian, says Gelb, senior research scientist at HP Labs. That way, the faint markings on these ancient artefacts become more visible and that helps scholars to determine their meaning.

By capturing the images digitally, the technique also enables scholars around the world to study the rare, delicate objects without having to travel to where they are stored or to handle them.

Some of the reflectance images, technically described as polynomial texture maps, are available at www.hpl.hp.com/research/ptm/antikythera_mechanism/index.html.

The results of Malzbender and Gelbs work, in collaboration with researchers from the UK and Greece, appear in the latest British science journal, Nature (Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism). The other researchers used an X-ray technique, called computer tomography, to probe the depths of the device.

The new research explains how the gears work and identifies twice as many markings on the device as previously detected.

The Antikythera Mechanism is the only technological device from the ancient world and the oldest computer or calculator known to man, says Malzbender, distinguished technologist, HP Labs. Nothing like it appears until the Renaissance, when clocks first appeared.

This is not the first time that the HP Labs researchers work has been used for archaeological purposes. In 2000, Malzbender volunteered the resources of the technology to capture faded Sumerian tablets for researchers at Yale and the University of Southern California. It was this work that caught the attention of the Antikythera project.

The technology was originally developed not for archaeology, but as a method for improving photorealism and rendering efficiency in 3D graphics. It also could be used in criminal forensics, detecting distinctive characteristics in footprints or tyre marks, for example.

The technology also still has potential commercial uses for HP, but many of the techniques have been made available to the scientific world for academic purposes.