Researchers are presently working on drives with track widths in the 5 to 1 micron region. For these small widths, tape wander, properly called Lateral Tape Movement (LTM), must be less than 1 micron. This is because the track following head always lags the moving target and produces a position error signal. If the position error signal gets to be larger than about 1/10 the track width, the track cannot be read. However, it follows that the smaller the LTM, the smaller the error is. This allows more tracks can be placed on the tape. Measuring small in the computer hardware field is just part of challenge. The advent of nanotechnology and microscopic machines in other fields makes the capability to do this even more necessary. Measurement of this sort may be possible now on a limited basis.
The challenge is to do it cheaply, conveniently, routinely, and accurately. This instrument by MTII of Albany NY gives tape edge displacement by measuring the amount of light blocked by the tape. The fiber optic probe directs a curtain of light past the measurement target edge to a receiving bundle. The intensity of light received changes with the edge position. This translated directly into microns of tape edge motion via the appropriate calibration setup.