Method for generating multiple scan lines in a thin scanner

Details Method for generating multiple scan lines in a thin scanner Method for generating multiple scan lines in a thin scanner

1999-03-26

2001-02-13

Schuberg, Darren (Department: 2872)

Optical: systems and elements

Deflection using a moving element

C359S204200, C359S205100, C235S462320, C235S462400

Reexamination Certificate

active

06188500

ABSTRACT:

BACKGROUND OF THE INVENTION
The field of the present invention relates to scan line generation for scanners. In particular, a method and apparatus is described herein for generating multiple scan lines in a thin scanner such as used for barcode scanning.
Traditional fixed scanners generate parallel scan lines by use of a spinning facet wheel, also called a polygon mirror, having a plurality of facet mirrors arranged at different tilt angles.
FIG. 1
illustrates such a configuration
10
having a polygon mirror
12
having multiple mirror facets. A reading beam generated from for example a laser diode (not shown) is directed onto the polygon mirror
12
which as it rotates creates a scan line via each facet mirror. The scan lines
14
and
16
are reflected by facets onto a fold mirror
18
thereby projecting parallel scan lines into the scan volume. This configuration requires downstream pattern mirror(s) to have a larger height to intercept these lines and fold them into a scan pattern of parallel lines.
Another method commonly employed for rapidly and repetitively scanning the illumination beam across a scanned region is mirror dithering. Dithering, i.e. rapid oscillation, of an illumination beam steering mirror about an axis substantially parallel to the mirror face causes the illumination beam to move rapidly back and forth thereby forming a scan line. Generally a dithering mirror can only produce a single scan line. In either method, when a scan line illuminates a barcode, the resulting time dependent signal due to detected light scattered and/or reflected from the bars and spaces of the barcode is decoded to extract the information encoded therein.
SUMMARY OF THE INVENTION
The present invention is directed to a method of generating multiple scan lines, particularly parallel scan lines. In its preferred embodiment, the method comprises generating a reading beam, using a suitable scanning mechanism to scan or dither the reading beam, directing the scanned beam onto an optical element, controlling the system such that the beam is alternately transmitted or reflected by the optical element, and directing multiple scan lines into the scan volume. When the optical element is reflective, a scan line is produced directly off the optical element; when the optical element is transmissive, a scan line passes through the optical element and is reflected by a fold mirror and into the scan volume.


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