Indicia reading system employing digital gain control

• US 8,752,766 B2
• Filed: 05/07/2013
• Issued: 06/17/2014
• Est. Priority Date: 05/07/2012
• Status: Active Grant

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Xian, Tao, Germaine, Gennady, Zhu, Xiaoxun, Wang, Ynjiun Paul
• Primary Examiner(s): Labaze, Edwyn
• Application Number:
  US13/888,884
• Publication Number:
  US 20130292474A1
• Time in Patent Office: 406 Days
• Field of Search: 235/462.26, 235/462.45, 235/472.45, 235/472.01, 235/375, 235/462.25
• US Class Current: 235/462.26
• CPC Class Codes: G06K 2007/10524 Hand-held scanners
• CPC Class Codes: G06K 7/10 by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
• CPC Class Codes: G06K 7/10554 Moving beam scanning
• CPC Class Codes: G06K 7/10613 by rotation, e.g. polygon
• CPC Class Codes: G06K 7/10633 by oscillation
• 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 7/146 the method including quality enhancement steps

Abstract

A laser scanning code symbol reading system includes an analog scan data signal processor for producing digitized data signals, wherein during each laser beam scanning cycle, a light collection and photo-detection module generates an analog scan data signal corresponding to a laser scanned code symbol, an analog scan data signal processor/digitizer processes the analog scan data signal to generate digital data signals corresponding thereto, and a synchronized digital gain control module automatically processes the digitized data signals in response to start of scan (SOS) signals generated by a SOS detector. The synchronized digital gain control module generates digital control data which is transmitted to the analog scan data signal processor for use in controlling the gain of at least one signal processing stage in the light collection and photo-detection module and/or analog scan data signal processor, during the corresponding laser beam scanning cycle.

Claims

1. An indicia reading system, comprising:

a laser scanning module for scanning a laser beam across a laser scanning field in a scanning cycle;

a scan line detector for detecting a start of each scanning cycle performed by the laser scanning module and generating a start of scan (SOS) signal in response to the detection of the start of each scanning cycle;

a photo-detector for detecting the intensity of light reflected from the laser scanning field and generating a first signal corresponding to the detected light intensity;

a signal processor having an amplification stage for amplifying the first signal followed by a processing stage for processing the first signal and converting the processed first signal into a second signal;

a gain control module for, during each scanning cycle, controlling the gain of the processing stage within the signal processor using the SOS signal generated by the scan line detector and the second signal generated by the signal processor; and

a decode processor for processing the second signal and generating data representative of indicia in the scanning field;

wherein, in response to the SOS signal during each scanning cycle, the gain control module processes the second signal, calculates a histogram from the second signal, calculates a cumulative histogram from the calculated histogram, calculates a discrete gain for the scanning cycle from the cumulative histogram, calculates a discrete gain change from the discrete gain, and transmits the discrete gain change as the digital control signal for the scanning cycle to the signal processor.

2. The indicia reading system of claim 1, wherein:

in response to the SOS signal during each scanning cycle, the gain control module processes the second signal, generates a digital control signal, and transmits the digital control signal to the signal processor; and

the signal processor'"'"'s processing stage uses the digital control signal to control the gain of the first signal during each scanning cycle.

3. The indicia reading system of claim 1, comprising at least one light collection optic element for collecting light reflected from the laser scanning field.

4. The indicia reading system of claim 1, wherein the histogram is calculated using sub-sampling.

5. The indicia reading system of claim 1, wherein the laser scanning module comprises a rotating polygon or an oscillating mechanism for scanning the laser beam across the laser scanning field.

6. An indicia reading system, comprising:

a laser scanning module for scanning a laser beam across a laser scanning field in a scanning cycle;

a scan line detector for detecting a start of each scanning cycle performed by the laser scanning module and generating a start of scan (SOS) signal in response to the detection of the start of each scanning cycle;

a photo-detector for detecting the intensity of light reflected from the laser scanning field and generating a first signal corresponding to the detected light intensity;

a signal processor having a processing stage for amplifying the first signal, processing the first signal, and converting the processed first signal into a second signal;

a gain control module for, during each scanning cycle, controlling the gain of the processing stage within the signal processor using the SOS signal generated by the scan line detector and the second signal generated by the signal processor; and

a decode processor for processing the second signal and generating data representative of indicia in the scanning field;

wherein, in response to the SOS signal during each scanning cycle, the gain control module processes the second signal, calculates a histogram from the second signal, calculates a cumulative histogram from the calculated histogram, calculates a discrete gain for the scanning cycle from the cumulative histogram, calculates a discrete gain change from the discrete gain, and transmits the discrete gain change as the digital control signal for the scanning cycle to the signal processor.

7. The indicia reading system of claim 6, wherein the gain control module comprises a programmed microprocessor.

8. The indicia reading system of claim 6, comprising a hand-supportable housing or a fixed-mounted housing.

9. The indicia reading system of claim 6, wherein the second signal generated by the signal processor comprises the first signal'"'"'s raw intensity data, first derivative data, and the absolute value of the first derivative data.

10. The indicia reading system of claim 6, wherein the scan line detector detects an end of each scanning cycle performed by the laser scanning module and generates an end of scan signal in response to the detection of the end of each scanning cycle.

11. An indicia reading system, comprising:

a laser scanning module for scanning a laser beam across a laser scanning field in a scanning cycle;

a scan line detector for detecting a start of each scanning cycle performed by the laser scanning module and generating a start of scan (SOS) signal in response to the detection of the start of each scanning cycle;

a photo-detector for detecting the intensity of light reflected from the laser scanning field and generating a first signal corresponding to the detected light intensity;

a signal processor having a processing stage for processing the first signal and converting the processed first signal into a second signal;

a gain control module for, during each scanning cycle, controlling the gain of the processing stage within the signal processor using the SOS signal generated by the scan line detector and the second signal generated by the signal processor; and

a decode processor for processing the second signal and generating data representative of indicia in the scanning field;

wherein, in response to the SOS signal during each scanning cycle, the gain control module processes the second signal, calculates a histogram from the second signal, calculates a cumulative histogram from the calculated histogram, calculates a discrete gain for the scanning cycle from the cumulative histogram, calculates a discrete gain change from the discrete gain, and transmits the discrete gain change as the digital control signal for the scanning cycle to the signal processor.

12. The indicia reading system of claim 11, wherein:

in response to the SOS signal during each scanning cycle, the gain control module processes the second signal, generates a digital control signal, and transmits the digital control signal to the signal processor; and

the signal processor'"'"'s processing stage uses the digital control signal to control the gain of the first signal during each scanning cycle.

13. The indicia reading system of claim 11, wherein the histogram is calculated using sub-sampling.

14. The indicia reading system of claim 11, wherein the laser scanning module comprises a rotating polygon or an oscillating mechanism for scanning the laser beam across the laser scanning field.

15. The indicia reading system of claim 11, wherein the laser scanning module comprises:

a laser source;

a laser drive module for driving the laser source;

a laser scanning mechanism for scanning the laser beam across the laser scanning field.

16. The indicia reading system of claim 11, wherein the gain control module comprises a programmed microprocessor.

17. The indicia reading system of claim 11, comprising a hand-supportable housing or a fixed-mounted housing.

18. The indicia reading system of claim 11, wherein the second signal generated by the signal processor comprises the first signal'"'"'s raw intensity data, first derivative data, and the absolute value of the first derivative data.

19. The indicia reading system of claim 11, wherein the scan line detector detects an end of each scanning cycle performed by the laser scanning module and generates an end of scan signal in response to the detection of the end of each scanning cycle.

20. An indicia reading system, comprising:

a laser scanning module for scanning a laser beam across a laser scanning field in a scanning cycle;

a scan line detector for detecting a start of each scanning cycle performed by the laser scanning module and generating a start of scan (SOS) signal in response to the detection of the start of each scanning cycle;

a photo-detector for detecting the intensity of light reflected from the laser scanning field and generating a first signal corresponding to the detected light intensity;

a signal processor having a processing stage for processing the first signal and converting the processed first signal into a second signal comprising the first signal'"'"'s raw intensity data, first derivative data, and the absolute value of the first derivative data;

a gain control module for, during each scanning cycle, controlling the gain of the processing stage within the signal processor using the SOS signal generated by the scan line detector and the second signal generated by the signal processor; and

a decode processor for processing the second signal and generating data representative of indicia in the scanning field.