The feasibility of applying commercial digital photogrammetric software to
the measurement of small objects photographed through an optical microscope
has been examined. The objects, about 20 mm across, were photographed usin
g a 35 mm film camera (at the lowest magnification setting of the Olympus m
icroscope) giving photographs at a scale of 2:1. The photographs were then
scanned before processing with the VirtuoZo digital photogrammetric system.
Various problems needed to be overcome, some due to the limited options av
ailable with the highly automated digital system which was not designed for
such measurement tasks. The unusual image scales, the uncommon pixel sizes
and the unconventional and uncertain imaging geometry, all impeded immedia
te photogrammetric implementation. Photographic problems with the microscop
e were also faced, as with all microscope photogrammetry. Creating control
points and independently assessing the accuracy of results at these scales
were also difficult operations, but an analytical plotter was utilized for
both these purposes and to verify the imaging geometry. Once such problems
were overcome, image matching proceeded well and an accurate DTM could be c
reated successfully, provided that a suitably textured object was chosen.