Laser scanning code symbol reading system employing multi-channel scan data signal processing with synchronized digital gain control (SDGC) for full range scanning

• US 8,789,759 B2
• Filed: 05/16/2013
• Issued: 07/29/2014
• Est. Priority Date: 05/18/2012
• Status: Active Grant

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Xian, Tao, Wang, Ynjiun P., Liu, Yong, Feng, Chen
• Primary Examiner(s): TRAIL, ALLYSON NEEL
• Application Number:
  US13/895,616
• Publication Number:
  US 20130306734A1
• Time in Patent Office: 439 Days
• Field of Search: 235/462.33, 235/462.06, 235/462.42
• US Class Current: 235/462.33
• CPC Class Codes: G06K 2007/10524 Hand-held scanners
• CPC Class Codes: G06K 7/10564 Light sources
• CPC Class Codes: G06K 7/10821 further details of bar or optical code scanning devices
• 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 7/1408 the method being specifically adapted for the type of code
• CPC Class Codes: G06K 7/1413 1D bar codes

Abstract

A laser scanning code symbol reading system includes an analog scan data signal processor for producing digital data signals, wherein during each scanning cycle, a light collection and photo-detection module generates an analog scan data signal corresponding to a laser scanned code symbol, a multi-channel parallel scan data signal processor/digitizer processes the analog scan data signal along multiple cascaded multi-stage signal processing channels, to generate digital data signals corresponding thereto, while a synchronized digital gain control module automatically processes the digital data signals in response to start of scan (SOS) signals generated by a SOS detector. Each signal processing channel supports different stages of amplification and filtering using a different set of band-pass filtering and gain parameters in each channel, to produce multiple digital first derivative data signals, and/or multiple digital scan data intensity data signals, having different signal amplitudes and dynamic range characteristics for use in decode processing.

Claims

1. A code symbol reading system, comprising:

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

a scan line detector for detecting a start of each scanning cycle performed by the 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 scanning field and generating a first signal corresponding to the detected light intensity;

a signal processor, comprising;

a first processing channel for generating a first data signal and a first derivative data signal, the first processing channel having;

a first differentiation stage for processing the first signal and generating a first derivative signal; and

a first amplification stage for amplifying the first signal and the first derivative signal using a gain; and

a second processing channel for generating a second data signal and a second derivative data signal and having a second amplification stage for amplifying the amplified first signal and the amplified first derivative signal generated by the first amplification stage using a fixed gain;

a gain control module for, during each scanning cycle, controlling the gain of the first processing channel'"'"'s first amplification stage within the signal processor using the SOS signal generated by the scan line detector, the first data signal and the first derivative data signal generated by the first processing channel, and the second data signal and the second derivative data signal generated by the second processing channel; and

a decode processor for processing the first data signal, the first derivative data signal, the second data signal, and the second derivative data signal and generating data representative of a code symbol in the scanning field.

2. The code symbol reading system of claim 1, wherein the scanning module comprises a rotating polygon or an oscillating mechanism for scanning the light beam across the scanning field.

3. The code symbol reading system of claim 1, wherein the scanning module comprises:

a laser source;

a laser drive module for driving the laser source to produce the light beam; and

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

4. The code symbol reading system of claim 1, wherein the gain control module comprises a programmed microprocessor.

5. The code symbol reading system of claim 1, the signal processor'"'"'s first processing channel having:

a first filtering stage for filtering the amplified first signal and the amplified first derivative signal from the first amplification stage and generating a filtered amplified first signal and a filtered amplified first derivative signal; and

a first conversion stage for converting the filtered amplified first signal into the first data signal and the filtered amplified first derivative signal into the first derivative data signal.

6. A code symbol reading system, comprising:

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

a scan line detector for detecting a start of each scanning cycle performed by the 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 scanning field and generating a first signal corresponding to the detected light intensity;

a signal processor, comprising;

a first processing channel for generating a first derivative data signal, the first processing channel having;

a first differentiation stage for processing the first signal and generating a first derivative signal; and

a first amplification stage for amplifying the first derivative signal using a gain; and

a second processing channel for generating a second derivative data signal and having a second amplification stage for amplifying the amplified first derivative signal generated by the first amplification stage using a fixed gain;

a gain control module for, during each scanning cycle, controlling the gain of the first processing channel'"'"'s first amplification stage within the signal processor using the SOS signal generated by the scan line detector, the first derivative data signal generated by the first processing channel, and the second derivative data signal generated by the second processing channel; and

a decode processor for processing the first derivative data signal and second derivative data signal and generating data representative of a code symbol in the scanning field.

7. The code symbol reading system of claim 6, comprising a hand-supportable housing or a fixed-mounted housing.

8. The code symbol 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.

9. The code symbol reading system of claim 6, wherein:

in response to the SOS signal during each scanning cycle, the gain control module processes the first derivative data signal generated by the first processing channel and the second derivative data signal generated by the second processing channel, generates a gain signal, and transmits the gain signal to the signal processor; and

the first processing channel'"'"'s amplification stage uses the gain signal to control the gain of the first derivative signal during each scanning cycle.

10. The code symbol reading system of claim 6, wherein the first derivative data signal generated by the first processing channel comprises absolute value derivative data of the first signal.

11. A code symbol reading system, comprising:

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

a scan line detector for detecting a start of each scanning cycle performed by the 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 scanning field and generating a first signal corresponding to the detected light intensity;

a signal processor, comprising;

a first processing channel for generating a first data signal and having a first amplification stage for amplifying the first signal using a gain; and

a second processing channel for generating a second data signal and having a second amplification stage for amplifying the amplified first signal generated by the first amplification stage using a fixed gain;

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

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

12. The code symbol reading system of claim 11, the signal processor'"'"'s first processing channel having:

a first filtering stage for filtering the amplified first signal from the first amplification stage and generating a filtered amplified first signal; and

a first conversion stage for converting the filtered amplified first signal into the first data signal.

13. The code symbol reading system of claim 11, the signal processor'"'"'s second processing channel having:

a second filtering stage for filtering the amplified first signal from the second amplification stage and generating a filtered amplified second signal; and

a first conversion stage for converting the filtered amplified second signal into the second data signal.

14. The code symbol reading system of claim 11, comprising a communication interface for transmitting and receiving signals from a host system.

15. The code symbol reading system of claim 11, wherein:

in response to the SOS signal during each scanning cycle, the gain control module processes the first data signal generated by the first processing channel and the second data signal generated by the second processing channel, generates a gain signal, and transmits the gain signal to the signal processor; and

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

16. The code symbol reading system of claim 11, wherein:

in response to the SOS signal during each scanning cycle, the gain control module processes the first data signal generated by the first processing channel and the second data signal generated by the second processing channel, calculates a first histogram from the first data signal and a second histogram from the second data signal, calculates a cumulative histogram from the first histogram and the second 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 a gain signal to the signal processor; and

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

17. The code symbol reading system of claim 16, wherein the first histogram and the second histogram are calculated using sub-sampling.

18. The code symbol reading system of claim 11, wherein the scanning module comprises a rotating polygon or an oscillating mechanism for scanning the light beam across the scanning field.

19. The code symbol reading system of claim 11, wherein the scanning module comprises:

a laser source;

a laser drive module for driving the laser source to produce the light beam; and

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

20. The code symbol reading system of claim 11, wherein the gain control module comprises a programmed microprocessor.