|Smoke and Mirrors: Ultra-Rapid-Scan FT-IR
The A/D converter produces a continuous stream of matching interferogram
points for both the laser and infrared channels. Some reduction of modulated amplitude can
be seen where the laser frequency is highest. Part of the amplitude reduction is caused by
cable capacitance loading the preamp. There may be some contribution from the mirror
distortion, but these two effects are difficult to separate. These scans are each 3
milliseconds long, corresponding to 10,000 rpm. These scans are then separated, for
further processing, into segments at the points where the optical velocity drops to zero.