Browse Prior Art Database

Method for Eccentricity Compensation for Holographic Scanners

IP.com Disclosure Number: IPCOM000050897D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Ih, CC: AUTHOR [+2]

Abstract

An improved holographic scanner is described which provides correction for eccentricity errors due to changes in radial location of the individual hologram facets.

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Method for Eccentricity Compensation for Holographic Scanners

An improved holographic scanner is described which provides correction for eccentricity errors due to changes in radial location of the individual hologram facets.

A particularly useful holographic scanner is shown in the upper figure which utilizes an auxiliary reflector 12 to convert the normally curved scan line to a straight scan line. However, this scanner is sensitive to eccentricity errors in the placement of individual hologram facets on hologram disk 10. A playback beam 14 is collimated and normally incident on disk 10 to produce reconstruction beam
16. Should the hologram at point "a" be displaced toward the center 0, the reconstruction will follow a different path shown by dotted line 20 and end up displaced in the scan plane. Likewise, a radial shift of point "b" will cause a similar displacement in the opposite direction, as shown by dotted line 22.

The improved holographic scanner is shown in the lower figure. This scanner utilizes a reference recording source R which originates on the axis of rotation of the disk 10 at a point approximately symmetric to the virtual image point of the object wave reflected from the spherical surface of auxiliary reflector 12. Under conjugate readout conditions, a demagnification of the radial error occurs so that a greatly increased radial error can be accommodated. The compensation occurs because the previously described radial shift in the hologram loca...