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Proceedings Paper

Effects Of Substrate Scattering On Bar-Code Scanning Signals
Author(s): Eric Barkan; David Sklar
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Paper Abstract

When a beam of light strikes a piece of paper or similar substrate, a portion of its energy penetrates into the bulk and, due to multiple scattering, may re-emerge at some distance from the point of entry. We refer to this phenomenon as substrate scattering. In this paper we describe a general model for scattering substrates and, using linear systems theory, we investigate its implications for bar-code scanning. We show that the effects of substrate scattering can be represented as a modified reflectance distribution associated with the original printed reflectance pattern. This effective distribution is shown to be independent of the details of scanning system configuration. We show that under a broad range of conditions substrate scattering will decrease modulation and will cause scanners to overestimate barwidths. A specific diffusion model of the scattering process is developed, providing a family of functions which can be used in empirical studies. We conclude that the scattering distributions will not even be approximately Gaussian. Experimental results are presented which are consistent with this conclusion and inconsistent with a Gaussian model. Further experimental results are presented which show that, for typical substrates, depth of modulation may be decreased by 20 percent or more and perceived bar-width increases will be on the order of one mil.

Paper Details

Date Published: 5 April 1983
PDF: 17 pages
Proc. SPIE 0362, Scattering in Optical Materials II, (5 April 1983); doi: 10.1117/12.934152
Show Author Affiliations
Eric Barkan, Symbol Technologies, Inc. (United States)
David Sklar, Symbol Technologies, Inc. (United States)

Published in SPIE Proceedings Vol. 0362:
Scattering in Optical Materials II
Solomon Musikant, Editor(s)

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