A new program has been written that utilizes advanced numerical methods to perform high-precision, sub-pixel volume measurements of samples that are processed containerlessly. The volume measurements are essential for the measurement of density and thermal expansion.

Containerless processing provides the ability to study the thermophysical properties of highly reactive materials that would otherwise be contaminated through additional processing or measuring techniques. Levitation is typically used to isolate a sample from its environment in containerless processing. As a result of the isolation, thermophysical property measurements must be performed optically. Modern optical measurements typically consist of capturing grayscale video in a digital format, and then subsequent image analysis is performed by software to measure specific thermophysical properties. Density measurements are of particular importance as they impact other thermophysical property measurements that are measured optically, as well as being commercially important for manufacturing.

For density measurements, volume is measured from 2D silhouettes of the samples. Accurate and repeatable edge detection of the samples in the image is crucial for density measurements. The video process replaces edge discontinuities that can be seen by the eye with steep, but continuous, changes in pixel intensities, effectively smearing the edge of a sample. However, through the use of advanced numerical methods, sub-pixel edge determination is possible by examining the intensity values of pixels surrounding the edge of a sample. Sub-pixel edge detection is essential in reducing measurement errors that can accumulate to as much as several percent.

This work was done by Jan Rogers of Marshall Space Flight Center, and Robert Hyers, Richard Bradshaw, and David Schmidt of the University of Massachusetts – Amherst. For more information, contact Ronald C. Darty, Licensing Executive in the MSFC Technology Transfer Office at This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to MFS-33121-1.


NASA Tech Briefs Magazine

This article first appeared in the November, 2014 issue of NASA Tech Briefs Magazine.

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