The Heart of Harvard's Time Machine

The Project:   When Harvard University associate Dr. Robert Simcoe, was designing a groundbreaking photographic plate scanner, he contacted GrayGlass looking for an unusual white glass platen incorporating Anti-Newton Ring glass. That is a simple requirement, but GrayGlass project manager Bart Fried identified an underlying issue – a requirement for extremely uniform diffusion of the backlight source. The light source is an array of LED's directly under the platen. The LED’s give a reasonably uniform 'wall' of light for general purposes, but it was not nearly uniform enough for this demanding application. One of the critical functions of the scanner is to accurately scan the density of the entire photo plate including its seemingly “empty” space, without imparting any artificial density changes or artifacts created by the scanner itself.

 
The Solution:   GrayGlass laminated three layers of Schott™ 'flashed opal' to accomplished the goal with excellent photometric uniformity and light transmission. Clear PVB film was selected for the interlayers. Secondary processing was required to remove a few very fine sleeks in the raw material which are normally irrelevant for architectural use, but are painfully obvious in this demanding application. These were flat-polished out on Grayglass' large Blanchard polisher and then added a very fine ball-mill ground finish to prevent the Newton rings that would normally occur when the flat photographic plates lay on the flat platen supporting them. Additonal precision milling was required to remove the perimeter of the top layer, creating a step around the platen that allowed for mounting from below the work surface.


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