|Smoke and Mirrors: Ultra-Rapid-Scan FT-IR
Rotating cube corner reflectors - Another approach to the symmetry
problem is the use of rotating corner cube retroreflectors. By spinning them off axis, the
shear can be made to vary as a function of angle. Each shear value produces a different
path length. A series of patent disclosures by Tank et al describe many variations
on this theme (see for example, US patent 5,341,207 and 5,148,235). The advantages of this
approach are intrinsic tilt- and shear-compensation, as well as fairly rapid scan rates.
The disadvantages are the inherent imbalance of spinning corner cubes off axis, and above
6000 rpm distortion of the corner cube reflectors becomes significant. Large cube corner
retroreflectors are somewhat expensive.