Dual-Purpose Holographic Optical Element for a Scanner
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
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.