We describe an optical beam sensing device that can measure transverse disp
lacements with accuracy of a few microns. An analog readout prototype with
a set of four linear CCD arrays arranged around a square aperture, and illu
minated by a cross-hair laser, was built and tested by the authors. Perform
ance tests results demonstrate a linearity better than 5 mu m throughout an
active transverse range of over 20 mm. The reproducibility of the measurem
ents was better than 2 mu m. Long-term stability is 5 mu m. (C) 1999 Elsevi
er Science B.V. All rights reserved.