White-light displacement sensor incorporating signal analysis of channeled spectra

We have developed a technique for distance measurement in which the spectrum from a sensing interferometer is monitored directly with the aid of a diffraction grating and a linear charge-coupled device (CCD) array. The method described is a form of white light interferometry whereby a diffraction grating disperses the composite frequencies which are then examined by a CCD array. This paper presents the experimental results obtained for a fiber Fabry-Perot version of the sensing interferometer, using a powerful pigtailed super luminescent diode. Presented also are the processing techniques used to recover the displacement. The techniques are based upon a software package designed to derive the signal frequency of the channeled spectra. The results are compared with those obtained using previously described signal processing methods. Methods of calibration are explored using reference cavities of sub-micron accuracy to allow absolute measurement.