Reducing the cycle time of cementing processes for high quality doublets

Abstract

For the manufacturing of high performance optical systems, centered alignment of the optical surfaces within the assembly is becoming increasingly important. In this contribution, we will present a system for the automated alignment of optical surfaces for the high-throughput manufacturing of cemented doublets (and triplets) with optimized imaging performance. First of all, different concepts for the alignment of doublets etc. are discussed. Standard methods for cementing evaluate mechanical features, such as the outer barrel of one element as reference axis. Using this procedure the optical performance of the assembly that can be achieved is limited by imperfections in the collinearity of the element’s barrel axis and its optical axis. Instead, using the optical axis of the bottom element as target axis opens up perspectives for the production of multiplets with perfect symmetric imaging performance. For this concept, all three center of curvature positions of the optical surfaces are measured. Then, the top surface is aligned to the bottom element's optical axis using high-precision actuators. In order to increase the throughput of this procedure, the system is equipped with a novel measurement head that acquires autocollimation images of all three surfaces of a doublet at the same time. Thus, the positions of all surfaces are measured simultaneously during just a single rotation, avoiding both additional rotations and focus movements. Using this approach, cycle times can significantly be reduced from an average of 1 min to less than 10 seconds (w/o curing time). The system is reconfigurable in order to support a wide range of sample designs and enables cementing of high quality optics with centering errors below 2 μm.