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Browse Prior Art Database

Reducing Specular Reflection Problems in a Holographic Scanner

IP.com Disclosure Number: IPCOM000035794D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Dickson, LD: AUTHOR

Abstract

This article describes a relatively simple method of eliminating the most common specular reflection problem in a holographic bar code scanner by making use of the capability of separating the outgoing portion and the return portion of the holographic facet while retaining the advantageous features of retro-collection scanning.

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Reducing Specular Reflection Problems in a Holographic Scanner

This article describes a relatively simple method of eliminating the most common specular reflection problem in a holographic bar code scanner by making use of the capability of separating the outgoing portion and the return portion of the holographic facet while retaining the advantageous features of retro-collection scanning.

In a holographic bar code scanner, the holographic facets are used to direct and focus the outgoing laser beam and to collect a portion of the diffuse light reflected from the bar code label. The outgoing beam and the return beam are coaxially aligned in this mode of operation. This is referred to as retro-reflective scanning.

(Image Omitted)

When the scanning laser beam is normal to the surface of the bar code label that is being scanned, a problem arises if the label surface has any degree of specular (mirror-like) reflection characteristics. The laser light reflected from the bar code label surface will have two components: diffuse and specular. The diffusely reflected light will be modulated by the bars and spaces in the bar code as the laser beam scans across the label. The specularly reflected light contains relatively little modulation and is, therefore, of little use for decoding the label. However, the specularly reflected light is generally much stronger and may saturate the detector, making it difficult or impossible to read the information contained in the diffusely...