Design of a signal processing algorithm for error-minimized optical triangulation displacement sensors

Optical triangulation displacement sensors are widely used for their non-co ntact measurement characteristic, sub-micrometre order resolution, simple s tructure and long operation range. However. errors originating from surface inclination, speckle effect, light source fluctuation and detector noise r estrict the wider use. In order to minimize these errors. a structure for a n optical triangulation displacement sensor, which is composed of an incohe rent source and a linear CCD (charge coupled device), has been proposed. Ho wever. using a linear CCD causes several problems in signal processing. Bec ause CCDs consist of spatially discrete pixels, it is impossible to detect the peak position movement within a pixel. This is an inherently severe pro blem of CCDs. Therefore, a new approach is needed. In this paper, we propos e an adequate signal processing algorithm to overcome the limited resolutio n problem of a CCD for the proposed sensor structure. The signal processing algorithm is composed of a pre-processing algorithm and a modified cross c orrelation algorithm. With the help of the proposed algorithm, the limited resolution problem of the CCD can be solved.