For beam focusing applications in environments subject to wide temperature variation, Optical Surfaces is able to produce athermalised beam expanders that deliver stable high performance.
The company's athermalised beam expanders are based upon a Dall-Kirkham off-axis mirror design that incorporates INVAR elements to provide thermal stabilisation. In addition, to better control thermal behaviour, the off-axis mirrors in the athermalised beam expanders have a short focal length resulting in a very robust assembly that is less sensitive to temperature changes. As a result, high optical performance is maintained over a wide range of temperature (-40°C to +50°C).
Benefiting from an off-axis design, the athermalised beam expanders provide an unobstructed output and highly efficient transmission. The reflective design of these beam expanders is achromatic and with aluminium coatings can operate from UV to far IR without adjustment or internal realignment. Each athermalised beam expander is housed in an aluminium housing with provision for fixing to an optical table. Alignment aids are provided to ensure correct beam pointing. Standard beam expanders have fixed magnification. Variable magnification beam expanders can be supplied with interchangeable primary mirrors. An interferogram and OPD map is supplied with every athermalised beam expander manufactured by Optical Surfaces.