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Athermal Objective Lens Cell

Athermal Objective Lens Cell

Cartoon illustrating the design concept (credit: mechanical engineer Robert Weber) for a large aperture refractive lens cell in which the large coefficient of thermal expansion (CTE) of Delrin (100E-06 per deg C) is used to compensate for the CTE mismatch between the aluminum lens cell (CTE 24E-06 per deg C) and the glass (just a few x 1E-06 per deg C). The diameters of the Delrin plugs are chosen so that as the temperature drops and the I.D. of the aluminum lens cell shrinks faster than the O.D. of the glass lens, the distances across each of the Delrin plugs will also shrink *very* significantly. But decreasing the Delrin plug dimensions indicated by the dashed yellow lines actually works to increase the I.D. of the assembly, and thus by appropriately choosing the Delrin plug diameters, the lens cell assembly is designed to be self-compensating over temperature changes so that the lens is held in place without being squeezed (when temperature falls) or becoming loose (when temperature rises).

Appears in my CN post here: https://www.cloudyni...let/?p=11030065

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