Rotating Scanning Mirror for Fast FTIR Spectroscopy

The patent replaces the conventional linearly moving movable mirror with a rotating scanning mirror. This substitution transforms the mechanical motion from linear translation to rotation, enabling much higher speeds. The rotating scanning mirror can achieve frequencies of several kHz to MHz, dramatically improving the acquisition speed of molecular vibration spectra compared to the limited linear motion speed of traditional movable mirrors.

The patent employs periodic rotation of the scanning mirror to generate the interferogram. Instead of continuous linear movement requiring acceleration and deceleration, the rotating mirror uses periodic rotational motion where the light path length difference varies sinusoidally with the rotation angle. This periodic action eliminates the need for repeated acceleration and stopping, enabling high-speed continuous measurement.

The rotating scanning mirror operates in continuous periodic rotation, eliminating the need for acceleration and deceleration cycles required by linear movable mirrors. The interferogram is generated during each rotation cycle, and multiple cycles can be averaged to improve signal-to-noise ratio without requiring the mirror to stop, thus eliminating the time loss associated with repeated start-stop operations.

The rotating scanning mirror maintains continuous rotational motion during measurement, ensuring the useful action of generating interferograms continues without interruption. Unlike linear movable mirrors that must stop at the end of each scan range, the rotating mirror can continuously rotate and generate interferograms throughout its rotation, maximizing the utilization of motion for data acquisition.