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The main objective of this research is to present a wavelet network based optical lateral position sensor for vibration monitoring using a 2×2 photodetector array. In our approach, the power distribution of the light spot is measured taking into consideration the radial symmetry of the spot and its Gaussian intensity profile. The proposed system uses a He-Ne laser source whose Gaussian beam impinges on the photodetector array. The normalized optical power for each photocell is obtained theoretically by deriving the optical power equations as the beam scans the plane of photodetectors. The position detection is based on finding a relationship between the power distribution of the photodetector array and the position of the beam center. An experimental setup of the system is developed to validate the theoretical results. Furthermore, a wavelet network function approximation technique is used to estimate the x-y position of the beam center corresponding to the measured optical powers.iii

A novel optical vibration sensing method using Gaussian beam analysis is presented. In the proposed system, a Gaussian beam is emitted from a laser source with wavelength λ = 633nm, and incident on to a fixed quad-cell photodetector array, which captures the light intensity distribution. A methodology will be developed to estimate the position of the beam on the plane of photodetectors, by finding a relationship between the optical power distribution of the quadcell and the x-y spatial axis of the centroid of the beam. This will enable us to identify certain characteristics of the vibration applied, such as direction, frequency and strength. The normalized power distribution for each cell has been obtained through simulation, as the beam scans the whole plane of photodetectors, and as the beam follows the trajectory y = x while moving with a speed of 1 cm/s.

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