Laser scanner having analog digitizer with increased noise immunity

a scanner and analog technology, applied in the field of scanners, can solve problems such as distortion of photodiode analog signals, disastrous consequences for scanner decoders, and problems such as high noise conditions, and achieve the effect of reducing errors in decoding bar codes and high noise conditions

US20060192012A1Inactive Publication Date: 2006-08-31SYMBOL TECH INC
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
Publication Date
2006-08-31
Estimated Expiration
Not applicable · inactive patent

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Abstract

A laser scanner for reading a bar code having a plurality of bar code elements. The laser scanner includes a digitizer which receives as an input an analog signal from photodetector circuitry and digitizes the analog signal to produce a digital bar code pattern (DBP) signal representative of the bar code. The DBP signal is input to a decoder which reads and decodes the DBP signal thereby decoding the bar code. The digitizer imposes a short duration correction impulse on the DBP signal whenever successive edges of the same polarity are sensed wherein both of the edges are above a threshold level and further wherein the second edge is of greater magnitude than the first edge. When a correction impulse is received on the DBP signal by the decoder, the decoder corrects the DBP signal by removing the first edge and toggling on the second edge.
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Description

FIELD OF THE INVENTION

[0001] The present invention relates to a laser scanner for reading bar codes and, more particularly, to a laser scanner having an analog digitizer with increased noise immunity. BACKGROUND OF THE INVENTION

[0002] Laser scanners are widely used for reading bar codes, including one dimensional and two dimensional bar codes. In a laser scanner, a laser generates a beam, the beam is scanned or rapidly moved across a bar code or a portion of a bar code. Typically, the laser beam is focused by a lens and repetitively scanned by means of an oscillating or rotating mirror. Essentially, the beam generates a beam spot that moves across a target bar code.

[0003] The space elements of the bar code reflect the laser beam illumination and the dark or black bar elements of the bar code absorb the laser beam. The reflected light from the bar code is focused by scanner light-receiving optics through a bandpass filter and onto a photodetector circuitry, such as a photodiode. T...

Examples

Embodiment Construction

[0029] A laser scanner is shown schematically at 10 in FIG. 2. The bar code reader 10, in addition to reading (that is, scanning and decoding) both 1D and 2D bar codes and postal codes, is also capable of capturing images and signatures. In one preferred embodiment of the present invention, the laser scanner 10 is a hand held portable reader supported in a housing 11 that can be carried and used by a user walking or riding through a store, warehouse or plant for reading bar codes for stocking and inventory control purposes.

[0030] However, it should be recognized that digitizing and decoding system of the present invention, to be explained below, may be advantageously used in connection with any type of laser scanner, be it portable or stationary. It is the intent of the present invention to encompass all such laser scanners.

[0031] The bar code reader 10 includes a trigger 12 coupled to the bar code reader circuitry 13 operating under the control of a microprocessor 14 for reading ...