BARCODE READER WITH EDGE DETECTION ENHANCEMENT

• US 20120118974A1
• Filed: 11/17/2010
• Published: 05/17/2012
• Est. Priority Date: 11/17/2010
• Status: Active Grant

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.), Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.), Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Germaine, Gennady, Xian, Tao, Feng, Chen, Wang, Ynjiun, Zhu, Xiaoxun, Blake, Robert, Colavito, Stephen
• Granted Patent: US 8,950,678 B2
• Time in Patent Office: Days
• US Class Current: 235/462.27
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/1452 detecting bar code edges

Abstract

An optical reader for decoding an encoded symbol character of a symbology includes a scan data signal processor having as an input a scan data signal encoding information representative of the encoded symbol character. The scan data signal processor includes a first time delay stage adapted to provide a primary phase waveform from the scan data signal, a second time delay stage adapted to provide an early phase waveform from the scan data signal, and a third time delay stage adapted to provide a delayed phase waveform from the scan data signal. The early phase waveform has a propagation delay less than the primary phase waveform, and the delayed phase waveform has a propagation delay greater than the primary phase waveform. The scan data signal processor further includes a peak window detection stage for generating a peak window timeframe when an amplitude of the primary phase waveform is greater than, less than, or equal to both an amplitude of the early phase waveform and the delayed phase waveform. The optical reader further includes a digitizer circuit adapted to accept, within the peak window timeframe, the scan data signal processor output.

Claims

1. An optical reader for decoding an encoded symbol character of a symbology, the optical reader comprising:

a laser source for generating a laser beam along an optical path;

a lens assembly for focusing the laser beam on the encoded symbol character at a plane of focus;

a scanning mechanism for oscillating the laser beam at a pre-determined frequency to sweep over the encoded symbol character according to a pre-described scan pattern;

a photodetector having as an input detected light intensity corresponding to the laser beam scattered off the scanned encoded symbol character, and having as an output a scan data signal encoding information representative of the encoded symbol character; and

a scan data signal processor having an input and an output, the scan data signal processor comprising a first time delay stage adapted to provide a primary phase waveform from the scan data signal, a second time delay stage adapted to provide an early phase waveform from the scan data signal, the early phase waveform having a propagation delay less than the primary phase waveform, and a third time delay stage adapted to provide a delayed phase waveform from the scan data signal, the delayed phase waveform having a propagation delay greater than the primary phase waveform, the scan data signal processor further comprising a peak window detection stage for generating a peak window timeframe when an amplitude of the primary phase waveform is greater than or equal to, less than, or equal to both an amplitude of the early phase waveform and the delayed phase waveform; and

a digitizer circuit adapted to accept, within the peak window timeframe, the scan data signal processor output.

2. The optical reader of claim 1, wherein the input to the scan data signal processor is an electrical analog scan data signal, and the output is a digital scan data signal.

3. The optical reader of claim 2, wherein the analog scan data signal is preamplified.

4. The optical reader of claim 2, wherein the analog scan data signal is a first derivative output signal.

5. The optical reader of claim 1, further comprising an envelope detection stage defining a criterion timeframe inside which the scan data signal processor output is passed to the digitizer.

6. The optical reader of claim 5, wherein the criterion timeframe is that period of time that the amplitude of a waveform exceeds a threshold signal amplitude.

7. The optical reader of claim 6, wherein the threshold signal amplitude is approximately half the value of the expected peak amplitude.

8. The optical reader of claim 6, wherein the threshold signal amplitude is greater than the amplitude of the expected noise associated with the operation of the optical reader.

9. The optical reader of claim 1, wherein at least one of the first time delay stage, the second time delay stage, and the third time delay stage is a Bessel filter.

10. The optical reader of claim 1, wherein the early phase waveform propagation delay is approximately 0.002 milliseconds less than that of the primary phase waveform propagation delay.

11. The optical reader of claim 1, wherein the delayed phase waveform propagation delay is approximately 0.002 milliseconds greater than that of the primary phase waveform propagation delay.

12. The optical reader of claim 1, further including a second derivative stage for providing a zero crossing indicator to the digitizer circuit.

13. The optical reader of claim 1, wherein the scan data signal processor is realized with digital circuits.

14. A method for processing scan data in an optical reader, comprising the steps of:

providing a laser source within a housing for generating a laser beam along an optical path, a lens assembly for focusing the laser beam on an encoded symbol character, and a photodetector for detecting light intensity corresponding to the laser beam scattered off the scanned encoded symbol character and generating a scan data signal encoding information representative of the encoded symbol character;

generating a primary phase waveform from the scan data signal having a nominal propagation delay;

generating an early phase waveform from the scan data signal having a waveform propagation delay less than the nominal propagation delay of the primary phase waveform;

generating a delayed phase waveform from the scan data signal having a waveform propagation delay greater than the nominal propagation delay of the primary phase waveform;

comparing an amplitude of the primary phase waveform with an amplitude of the early phase waveform and an amplitude of the delayed phase waveform;

generating a peak window timeframe if the amplitude of the primary phase waveform is greater than, less than, or equal to both the amplitude of the early phase waveform and the delayed phase waveform; and

attempting to decode the encoded symbol character during the peak window timeframe.

15. The method of claim 14, further comprising the step of providing a first derivative signal generation stage for generating a first derivative output signal from the scan data signal, and generating the primary phase waveform, the early phase waveform, and the delayed phase waveform from the first derivative output signal.

16. The method of claim 14, wherein the step of attempting to decode the scan data signal occurs only during the peak window timeframe.

17. The method of claim 14, further comprising the step of comparing the amplitude of the primary phase waveform with a peak threshold and, if the amplitude exceeds the peak threshold, generating an envelope window timeframe.

18. The method of claim 17, wherein the peak threshold is an upper limit.

19. The method of claim 18, further including the step of generating a positive envelope input signal from the amplitude of the primary phase waveform, and generating the envelope window timeframe if an amplitude of the positive envelope input signal exceeds the upper limit peak threshold.

20. The method of claim 17, wherein the peak threshold is a lower limit.

21. The method of claim 20, further including the step of generating a negative envelope input signal from the amplitude of the primary phase waveform, and generating the envelope window timeframe if an amplitude of the negative envelope input signal is less than the upper limit peak threshold.

22. The method of claim 17, wherein the step of attempting to decode the scan data signal occurs during the peak window timeframe and the envelope window timeframe.