Browse Prior Art Database

Holographic Disk Geometry for Multidirectional Scanning

IP.com Disclosure Number: IPCOM000035848D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Dickson, LD: AUTHOR [+2]

Abstract

The disclosed holographic disk facet exposure geometry creates scanning spots whose motion has a significant component perpendicular to the holographic disk. (Image Omitted)

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Holographic Disk Geometry for Multidirectional Scanning

The disclosed holographic disk facet exposure geometry creates scanning spots whose motion has a significant component perpendicular to the holographic disk.

(Image Omitted)

In existing holographic bar code scanners, the focused scanning spot created by a holographic facet moves along a line that is essentially parallel to the plane of the disk. The facet is exposed with the object and reference points coplanar with the center line of the facet, see Fig. 1. As the facet is rotated past a fixed read beam, the spatial frequency of the holographic fringes "seen" by the read beam does not vary significantly. Thus, the angle of the diffracted beam with respect to the plane of the disk remains essentially constant. The motion of the scanning spot is essentially parallel to the disk.

In the disclosed holographic facets, the object beam is skewed out of the plane containing the reference point and the facet center line by approximately 90 degrees (see Fig. 2). The spatial frequency of the resulting holographic fringes changes significantly when measured tan- gentially across the facet. As the facet rotates, the diffraction angle of the scanned beam relative to the plane of the disk changes. The motion of the scanning spot has a significant component perpendicular to the disk. (This exposure geometry produces an aberration of the focused spot, but the characteristics of the focused spot remain suitable for bar-code s...