Fixing lenses in place

Lenses in optical devices are kept in place by adhesives but this can cause problems when the microscopes and cameras are used in a vacuum, as the adhesives may release gases that contaminate the lenses.

At high temperatures, too, or when using lasers in the UV range, the adhesives also cause problems: they become soft or brittle, and the optical components can slip by several micrometres.

One alternative is to solder them instead. And, working in conjection with engineers from Pac Tech, that's exactly what engineers at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena have developed a new system to do.

'We solder the optical components instead of gluing them,' said IOF group manager Dr-Ing. Erik Beckert. 'This has a definite advantage: the solder material is resistant to extreme temperatures and radiation, and also conducts heat and electricity.'

To enable them to apply the solder to the lenses just as flexibly as an adhesive, the researchers adapted the ‘solder bumping’ technique normally used in electronics manufacture. Small balls of solder contained in a dosing head slip one by one into a capillary, where a laser beam heats them until they become liquid.