Browse Prior Art Database

Dual-Purpose Holographic Optical Element for a Scanner

IP.com Disclosure Number: IPCOM000062541D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Fortenberry, RS: AUTHOR

Abstract

This article describes a dual-purpose holographic optical element for redirecting an outgoing scanning beam while collecting/redirecting incoming or reflected light. Fig. 1 shows part of a rotating, holographic disk 10. Such a disk has a plurality of facets which are used to redirect an incoming scanning beam 12 along different scan lines to create a scanning pattern suitable for reading bar codes. The scanning beam 12 is generated by a laser 14. Light 16, reflected from an object, is transmitted through the facets on the holographic disk 10 to eventually impinge on a photodetector 18. A dual-purpose holographic optical element (HOE) 20 is mounted between the disk 10 and laser 14 or detector 18. The scanning beam produced by laser 14 is directed at a small hologram 22 at the center of HOE 20.

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Dual-Purpose Holographic Optical Element for a Scanner

This article describes a dual-purpose holographic optical element for redirecting an outgoing scanning beam while collecting/redirecting incoming or reflected light. Fig. 1 shows part of a rotating, holographic disk 10. Such a disk has a plurality of facets which are used to redirect an incoming scanning beam 12 along different scan lines to create a scanning pattern suitable for reading bar codes. The scanning beam 12 is generated by a laser 14. Light 16, reflected from an object, is transmitted through the facets on the holographic disk 10 to eventually impinge on a photodetector 18. A dual-purpose holographic optical element (HOE) 20 is mounted between the disk 10 and laser 14 or detector 18. The scanning beam produced by laser 14 is directed at a small hologram 22 at the center of HOE 20. The hologram 22 redirects the laser beam toward the rotating holographic disk 10 along the indicated path. The HOE 20 includes a much larger hologram 24 surrounding hologram 22. The function of the larger hologram 24 is to redirect reflected light toward photodetector 18. Figs. 2 and 3 show the two-step process required to produce HOE 20. Referring first to Fig. 2, an opaque mask 26 is positioned over the central region of a sheet 28 of unexposed, photosensitive material mounted on a glass substrate 30. The photosensitive material is then exposed to a collimated reference beam 31 and a diverging object beam 32. An interf...