Remote High Speed Measurement of Small Diameters by Optical Diffractometry and Interferometry
Abstract
The characteristics of pulsed diode lasers and linear CCD array optical detectors are explored in the context of high speed precision dimension and location measurements by optical diffraction and interference. It is suggested that pixel based metrology may, with appropriate signal extraction and processing methods, be made more accurate by making edges less well defined: if the mechanism of definition loss is well understood, e.g., diffraction, the intensity distribution over many pixels can be matched to a template to within a small fraction of a pixel, obviating the need to make sub-pixel interpolations based on local intensities. The specific example of making remote flash measurements of the diameter and location of an opaque cylindrical object, e.g., a fast-moving textile strand, is examined. A model is developed for calculating the diffraction pattern given the target and instrument parameters. The results are examined and compared with experimental data. Algorithms for finding the diameter and location given the diffraction and interference pattern and for finding the diameter and location given the diffraction and interference pattern and the instrument parameters are described.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1988
- Accession Number
- ADA204401
Entities
People
- M. W. Siegel
Organizations
- Carnegie Mellon University