Multiple source/dense pattern optical scanner

Details Multiple source/dense pattern optical scanner Multiple source/dense pattern optical scanner

1999-07-23

2001-09-18

Pitts, Harold I. (Department: 2876)

Registers

Coded record sensors

Particular sensor structure

C235S462120, C235S462380

Reexamination Certificate

active

06290135

ABSTRACT:

BACKGROUND OF THE INVENTION
The field of the present invention relates to data reading systems. In particular, an optical scanning and method for optical scanning are described herein for creating for creating a dense scan pattern with potentially a wide range of reading distances.
Longer range scanners have been proposed of a variety configurations. In U.S. Pat. No. 5,869,827 (Rando), multiple beam sources and distance sensing mechanisms are employed to provide an extended focus range. U.S. Pat. No. 5,641,958 (Rudeen et al.) discloses a system as employed in the PSC SP400LR scanner in which an LCD diffractive control module changes the waist location of the scanning beam. In U.S. Pat. No. 4,560,862 (Eastman et al.) the facets of a polygon mirror are provided with different curvatures such that the scan lines produced by the different facets are focused at varying distances. U.S. Pat. No. 5,475,207 (Bobba, Acosta et al.) discloses a variety of single and multiple source laser scanners, and single and multiple scan mechanisms for creating relatively dense scan patterns through multiple scan housing windows.
Typical scanners rely on the number of facets in the polygon mirror and the number of pattern mirrors to generate a certain number of scanning segments or scan lines. The number of pattern mirrors is limited by the size of the scanner housing.
Bar code scanners have also been proposed wherein the outgoing laser beam is focused by different areas of the focusing lens such as described in U.S. Pat. No. 5,565,668 (Reddersen et al.). This design permits the beam to be focused to more than one waist location and, in theory, to provide increased depth of field. Because the light from the out-of-focus beam is still present when the other beam is in focus there is the potential for reduced resolution for each zone.
SUMMARY OF THE INVENTION
The present invention is directed to a system for and a method of efficiently generating a dense pattern of scan lines. In a preferred configuration, multiple laser beams are formed and directed along offset paths onto a scanning mechanism such as a polygon mirror which scans the beams across pattern mirrors to generate simultaneous scan patterns out into the scan volume. Return light from both scan patterns are retrodirectively collected and redirected by a common collection element such as a collection lens. The collection lens focuses return light from the first beam onto a first detector and light from the second beam onto a second detector.
These multiple laser beams may be focused at different waist locations/distances. By arranging the outgoing beams in an offset condition, the collected light may focused to different locations because of the angular and/or axial offset condition.


REFERENCES:
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patent: 4694182 (1987-09-01), Howard
patent: 4786798 (1988-11-01), Lonsdale
patent: 5007691 (1991-04-01), Bobba et al.
patent: 5457308 (1995-10-01), Spitz et al.
patent: 5841121 (1998-11-01), Koenck
patent: 5921421 (1999-07-01), Cherry et al.

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