Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-04-29
2001-06-19
Le, Thien M. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462010
Reexamination Certificate
active
06247648
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to bar code reader devices, and more particularly to apparatus for generating a scanned light beam for use in reading bar code symbols.
Bar code readers are disclosed in U.S. Pat. Nos. 4,387,297, 4,409,470, 4,251,798, and 4,760,248, all assigned to Symbol Technologies, Inc. The bar code readers described in these patents, as well as other devices of this type that are commercially available, usually employ oscillating mirrors or similar mechanical means to generate a scanning pattern. While such devices are widely used in retail and other business establishments today and have been quite successful in accomplishing their objectives, there is nevertheless a continuing requirement to improve reliability, reduce power consumption, reduce size and weight, lower the parts cost and manufacturing cost, and increase the speed and accuracy of operation. One of the elements of the prior bar code scanners most susceptible to improvement along these lines is the mechanical scanner device. The scanner devices may consist of a mirror mounted on a stepper motor; the mirror includes a flat portion to direct the outgoing laser beam and also a concave portion to collect reflected light and focus it upon a photodetector.
Bar code readers employ decoding circuitry to interpret the signals produced by a photodetector receiving the reflected light from the bar code symbol. Conventional decoding schemes rely upon data collected by a single scanning spot moved linearly across the field where the bar code symbol is located. The bar code data is embedded in background noise, and the decoding circuitry is more effective if the signal can be enhanced. To this end, faster scanning rates would permit the implementation of multiple scans to increase reliability of the data collected, but the mechanical scan generators previously used constrict the speed and thus place limitations on the multiple scan approach.
It is the principal object of the invention to provide a bar code reader or the like that does not require mechanical devices such as oscillating mirrors to cause a light beam to scan a symbol to be read. Another object is to provide a bar code reader that is capable of faster scan, as by implementing the scan with no moving parts. A further object is to take advantage of fast scanning techniques to provide multiple scans to thereby increase the signal recovery ability, i.e., increase the likelihood of recovering a valid decode of the bar code signal. In addition, the capability of providing multiple scans using a fast scan method permits improved facility for reading two dimensional bar code symbols of the type having multiple rows of bar code patterns. Other objects include reducing the size, weight and power consumption of a laser scan type of bar code reader, as well as reducing the manufacturing cost and increasing the reliability and operating lifetime of such devices.
SUMMARY OF THE INVENTION
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, a bar code scanner includes a light source for generating a light beam, a liquid crystal device for splitting light beams, a mirror system for directing the split light beams toward a bar code symbol, and a photodetector for summing the light reflected by the bar code symbol from each of the split light beams and generating an electrical signal for processing to decode the bar code symbol. A microprocessor signals the liquid crystal device to alter the splitting of the light beam when the bar code symbol is not successfully decoded, in an attempt to obtain a successful reading of the bar code symbol.
In accordance with another embodiment of the present invention, a method is provided for reading a bar code symbol, comprising the steps of generating and splitting a light beam, directing the light split beams toward a bar code symbol and detecting and summing the light reflected by the bar code symbol from each of the split light beams. An electrical signal, indicative of the summed light, is processed to decode the bar code symbol. If this decoding is not successful, the split light beams are modified for subsequent reading of the bar code symbol.
REFERENCES:
patent: 5256864 (1993-10-01), Rando et al.
patent: 5258605 (1993-11-01), Metlitsky et al.
patent: 5545886 (1996-08-01), Metlitsky et al.
patent: 5565668 (1996-10-01), Reddersen et al.
patent: 5869827 (1999-02-01), Rando
patent: 5912450 (1999-06-01), Katz et al.
patent: 5945670 (1999-08-01), Rudeen
patent: 5945676 (1999-08-01), Khalil et al.
Katz Joseph
Marom Emanuel
Metlitsky Boris
Kirschstein et al.
Le Thien M.
Symbol Technologies Inc.
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