Single lens logarithmic confocal distance measurement array

This article presents a method and results based on confocal microscopy for non-contact axial distance measurement from a lens to a partially reflective surface using an array of photodetectors. The ratio of the photodetector signals is independent of the surface reflectivity and light source variations over a range of distance. By using logarithmic photodetector signals the object distance is proportional to the difference between the signals. This technique potentially allows measurement of sound produced by single living cells, or the high velocity surface shape changes in the hohlraum in laser fusion experiments.