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# Scan Angle Multiplication on a Holographic Scanner

IP.com Disclosure Number: IPCOM000051625D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 33K

IBM

## Related People

Dickson, LD: AUTHOR

## Abstract

In an optical scanner having a rotating holographic disc, scan angle multiplication is achieved by directing a collimated reconstructing beam along a path intersecting with the axis of rotation of the disc.

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Scan Angle Multiplication on a Holographic Scanner

In an optical scanner having a rotating holographic disc, scan angle multiplication is achieved by directing a collimated reconstructing beam along a path intersecting with the axis of rotation of the disc.

Figs. 1 and 2 are side and top views of a beam-deflecting disc 10. The disc 10 may have a glass substrate 12 which supports a track 14 of holographic sectors 16A, 16B, 16C, etc. A collimated reconstruction beam 18 (the size of which is greatly exaggerated for purposes of illustration) is directed along a path intersecting with the axis of rotation 20 of disc 10. As the disc 10 rotates, each of the facets traverses the point of incidence of the reconstruction beam. The relative movement between the beam 18 and the facets produces a deflected image beam 22 which is preferably a converging or focussed beam having a focal length f. As each facet moves across the point of incidence of the beam 18, an angle theta(t) is subtended. The deflected beam 22 subtends a scan angle theta The relationship between theta(t) and theta(s) is approximated by the following equation. theta(s) = theta(t) [r over f2 cos (alpha-beta over 2) cos (alpha beta over 2)]. where the distances r, f and the angles alpha, beta are defined in Figs. 1 and 2.

The primary advantage of achieving scan angle multiplication is that the length of scan lines can be increased without increasing the distance between disc 10 and the region in which the scan...