Differences and effects of two machine concepts on the manufacturing process of aspherical lenses

Abstract

The production of medium to large lenses (200 - 500 mm) is becoming increasingly important against the background of the semiconductor crisis. The value of a lens increases enormously through the entire value chain. A large number of processes are necessary to achieve the final contour and quality. The grinding and polishing processes must be precisely coordinated in order to achieve all requirements. The polishing process is not always a controllable variable, since various chemical and mechanical influences come together and affect the process result. For this reason, it is important to control the grinding process. The question of how it is possible to improve the surface quality as much as possible without allowing any geometric deviations is central. The effect of different machine concepts and their advantages against the background of specific quality requirements is still unknown. Therefore, a comparison of two machine concepts and their effects on the grinding process, the component quality and the possibilities of polishing the generated surfaces will be analyzed in more detail. The focus is on the MCG500 and UPG500 machine concepts from OptoTech Optikmaschinen GmbH. The results show, that the 5-axis grinding machine MCG500 enables a high-quality grinding process, which allows to reach a PV inbetween 1.5 - 3 μm. Compared to the 4-axis machine UPG500, the MCG500 is used as a pre-grinding machine to achieve a PV of 0.4 - 1.5 μm with the help of the UPG500. In addition the, the sub surface damage is only 3 - 7 μm on the UPG500 compared to 10 - 20 μm on the MCG500. With the achieved tolerances of the UPG500, the subsequent polishing process is shortened by approx. 30% compared to the upstream grinding process by the MCG500 and at the same time the process reliability to achieve the final specifications increases.