Algorithms for on-line monitoring of micro spheres in an optical tweezers-based assembly cell

Optical tweezers have emerged as a powerful tool for microand nanomanipulation. Using optical tweezers to perform auto-
mated assembly requires on-line monitoring of components in the
assembly workspace. This paper presents algorithms for estimat-
ing positions and orientations of microscale and nanoscale com-
ponents in the 3-Dimensional assembly workspace. Algorithms
presented in this paper use images obtained by optical section
microscopy. The images are first segmented to locate areas of in-
terest and then image gradient information from the areas of in-
terest is used to generate probable locations and orientations of
components in the XY-plane. Finally, signature curves are com-
puted and utilized to obtain component locations and orienta-
tions in 3-D space. We have tested these algorithms with silica
micro-spheres as well as metallic nanowires. We believe that the
algorithms described in this paper will provide the foundation
for realizing automated assembly operations in optical tweezers-
based assembly cells.