Large optics manufacturing in the Loxham lab
The Loxham Laboratory, located in Cranfield University, is and accurately temperature and humidity controlled large optics aspherisation facility. It employs state of art ultra precision machines a number of which are unique to Cranfield University. Through advanced thermal control of the laboratory and its machine s systems a combination of surface accuracy and speed is offered second to none. The facility is an established supplier of optics and systems to ESO, ESA and NASA.
The facility has capability for freeform grinding on the Cranfield BoX machine, diamond turning, large scale tactile metrology using a Leitz pmmf and final figure correction using reactive atomic plasma technology, across a range of materials and component sizes.
Grinding
The Cranfield BoX grinding machine offers high dynamic stiffness coupled with high accuracy axis motions. With a capacity to produce spheres, aspheres and free forms. Materials processed include Zerodur, ULE, Silicon Carbide, Fused Silica and Sapphire. Accuracy typically < 1 micron RMS per metre with sub surface damage < 5 micron.
BoX in action 3m x 2m CMM
Metrology
Metrology for large surfaces up to 3 metres by 2 metres is provided. All measurments are issued with traceable measuring certificates having a 1 micron level of measurement uncertainty. Surface roughness measurements are provided by a range of white light scanning interferometers, contacting profilometers and scanning electron microscope using replica imprint techniques.
Final figure correction
Based on an inductively coupled pasma using fluorinated gas, the Reactive Atom Plasma (RAP) process offers figuring capability better than 30 nm RMS, with material removal rates in the range 0.5 - 2 cubic mm/min for fused silica. Other possible materials include ULE, silicon, BK7 and silicon carbide.
RAP machine RAP plasma torch