Mfg. of Schmidt correction plate - uses thin glass plate placed over glass matrix block

摘要

The Schmidt correction plate is made by first forming a matrix (22) on a glass block by grinding and polishing, providing a negative for the required correction plate. A thin glass plate is positioned over the matrix and a vacuum is created between the glass plate and the matrix, so as to establish a glass to glass contact over the whole area of the glass plate. The glass plate and matrix block are rotated and the upper surface of the glass plate is ground flat and polished. The vacuum between the matrix block and the plate is then lifted to allow the latter, which forms the correction plate, to be removed.