Northeastern University

We describe an optical beam sensing device that can measure transverse displacements with accuracy of a few microns. An analog readout prototype with a set of four linear CCD arrays arranged around a square aperture, and illuminated by a cross-hair laser, was built and tested by the authors. Performance tests results demonstrate a linearity better than five microns throughout an active transverse range of over 20mm. The reproducibility of the measurements was better than 2 µm. Long term stability is 5 µm