Design of the KOSMOS oil-coupled spectrograph camera lenses

TL;DR

This paper details the innovative design of oil-coupled lens groups for the KOSMOS spectrograph camera, emphasizing assembly, sealing, and thermal compensation techniques to ensure optical performance and durability.

Contribution

It introduces a novel use of silicone rubber O-rings for precise lens centering and sealing in oil-coupled systems, along with a design for thermal expansion compensation.

Findings

Robust sealing of oil within lens gaps using O-rings.

Effective thermal expansion compensation with an expansion diaphragm.

Improved assembly and testing procedures for oil-coupled lenses.

Abstract

We present the design details of oil-coupled lens groups used in the KOSMOS spectrograph camera. The oil-coupled groups use silicone rubber O-rings in a unique way to accurately center lens elements with high radial and axial stiffness while also allowing easy assembly. The O-rings robustly seal the oil within the lens gaps to prevent oil migration. The design of an expansion diaphragm to compensate for differential expansion due to temperature changes is described. The issues of lens assembly, lens gap shimming, oil filling and draining, bubble mitigation, material compatibility, mechanical inspection, and optical testing are discussed.