What's it about?

This paper will examine options in construction of cemented lens assemblies, and considerations for mechanical mounting and cement selection will be offered.

1. DESIGN OF CEMENTED LENS ASSEMBLIES

When designing an optical system, one design strategy may be to incorporate cemented lens assemblies¹. This involves cementing two or more lenses together to build a lens assembly. Strain in excess may cause delamination or fracture of the assembly elements ². Accordingly, management of strain within the assembly represents the main challenge in employing cemented assembles.

There are some inherent sources of strain in cemented assemblies. To provide achromatic performance, assemblies are made from spherical elements of crown and flint materials. Looking at an example achromat³, the coefficient of mean linear thermal expansion (CTE) for F2 is over 25% larger than SK11⁴. Looking at the ~80 - 100°C temperature range specified in standard thermal cycling^5,6 one can expect to see differential expansion causing stress within the cemented assembly. Additionally, the cement itself shrinks as it cures, leading to...