The Imaging of the Archimedes Palimpsest

LED Imaging

As we saw the initial experimental images of the Archimedes Palimpsest were dramatic, but not very helpful to the scholars. They combined individual wavelengths of light to bring out the Archimedes text in particular. There were several problems with them. Among these were that:

1) They were of insufficient resolution

2) Because different wavebands of light needed to be filtered differently, the images did not register very well, making them appear somewhat fuzzy.

As a result, in production imaging, we only used two broadbands of light: The red channel from visible light, and the blue channel from UV fluorescent light. Nonetheless, the imagers realized that there was potential for enhanced performance by using narrower bands of light, if the registration issue could be solved, and if images were captured at a higher resolution.

The team decided to do this by using light emitting diodes. LEDs as they are called, are inexpensive,and produce light at specific wavelengths. The idea was not to put filters in front of the lens to get different wavelengths, then, but rather to illuminate the Archimedes leaves with very specific bands of light, and take images of them.

William Christens-Barry and Keith Knox, setting up the LED apparatus
for imaging the Archimedes Palimpsest.

The LEDs can be used in different combinations.
Here, all the LED’s in the array are shown.

The LEDs can also be used singly. Here a green one is used.

By using the LEDs as luminants in this way, very specific combinations
of wavelengths can be applied to the Archimedes Palimpsest.

In this image, you can see how the Archimedes text appears at different wavelengths.
At the top left you see it imaged at 625nm, at the top right at 530nm, and at the bottom left at 365nm.

By combining images of different wavelengths, one can apply the algorithms that were used in the production imaging to produce the same colour effects. They are some improvement over the production images. Here for example, you see a processed LED images (above), compared to standard production image (below).

The imaging team may take further LED images in the future on particularly difficult areas of text. If you would like to know about LED imaging in more detail, please click here.

Continue to "Production Imaging"

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