A new approach to the absolute measurement of two-dimensional optical path differences
is presented in this thesis. The method, which incorporates a white light interferometer and
a hyperspectral imaging system, is referred to as Hyperspectral Interferometry. A prototype
of the Hyperspectral Interferometry (HSI) system has been designed, constructed and
tested for two types of measurement: for surface profilometry and for depth-resolved
displacement measurement, both of which have been implemented so as to achieve single
shot data acquisition.
The prototype has been shown to be capable of performing a single-shot 3-D shape
measurement of an optically-flat step-height sample, with less than 5% difference from the
result obtained by a standard optical (microscope) based method. The HSI prototype has
been demonstrated to be able to perform single-shot measurement with an unambiguous
352 (m depth range and a rms measurement error of around 80 nm. The prototype has also
been tested to perform measurements on optically rough surfaces. The rms error of these
measurements was found to increase to around 4× that of the smooth surface.
For the depth-resolved displacement field measurements, an experimental setup was
designed and constructed in which a weakly-scattering sample underwent simple
compression with a PZT actuator. Depth-resolved displacement fields were reconstructed
from pairs of hyperspectral interferograms. However, the experimental results did not
show the expected result of linear phase variation with depth. Analysis of several possible
causes has been carried out with the most plausible reasons being excessive scattering
particle density inside the sample and the possibility of insignificant deformation of the
sample due to insufficient physical contact between the transducer and the sample.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.