Simultaneous five-wavelength interferometry for head/tape spacing measurement

An improved five-wavelength interferometer with high-speed shutters in the light path was designed and implemented. The interferometer allows switching between two sets of three wavelengths, keeping one wavelength in each measurement in common. The set-up allows nearly simultaneous acquisition of fringe intensities and can be used to measure the head/tape spacing in a moving linear tape drive. The precision of the new five-wavelength interferometer was investigated and was found to be superior to the precision obtained with a three-wavelength interferometer.