Method of selectively projecting scan lines in a multiple-line barcode scanner

• US 8,371,507 B2
• Filed: 10/08/2007
• Issued: 02/12/2013
• Est. Priority Date: 10/08/2007
• Status: Active Grant

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Haggerty, Thomas, Brady, Robert H.
• Primary Examiner(s): Le, Thien M
• Assistant Examiner(s): KIM, TAE W
• Application Number:
  US11/868,953
• Publication Number:
  US 20090095814A1
• Time in Patent Office: 1,954 Days
• Field of Search: 235/462.32
• US Class Current: 235/462.32
• CPC Class Codes: G02B 26/127 Adaptive control of the scanning light beam, e.g. using the feedback from one or more detectors G02B27/0031 takes precedence
• CPC Class Codes: G02B 26/129 Systems in which the scanning light beam is repeatedly reflected from the polygonal mirror
• CPC Class Codes: G06K 7/10613 by rotation, e.g. polygon
• 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

Abstract

A method of selectively generating one or more scan lines from a multi-scan line scanner involves measuring the pulse widths of the pulses in a signal output of a motor driving the polygon mirror of the scanner wherein the signal relates to the position of the polygon'"'"'s mirror facets. By measuring and distinguishing each of the pulses in the signal, the illumination of the scan beam can be synchronized with the rotation of the polygon mirror to only generate a desired number of scan line patterns that is less than the full complement of the scan line patterns capable of being generated by the multi-scan line scanner.

Claims

1. In a laser scanning system including a laser source producing a laser beam that is scanned across a scanning field by a polygon mirror having mirror facets rotated by a DC multi-pole motor having a rotor with multiple magnet poles, and an internal Hall Effect sensor for sensing each magnet pole passing said internal Hall Effect sensor during each rotation of said rotor and generating a binary signal pulse for each sensed magnet pole, a method of determining an occurrence of a predetermined home transition point in said DC multi-pole motor, comprising the steps of:

(a) rotating, said multi-pole rotor within said motor;

(b) while said rotor is rotating, using said internal Hall effect sensor to generate a signal pulse train comprising sequential sets of two or more binary signal pulses for each revolution of said rotor;

wherein each binary signal pulse has a time duration corresponding to a relative position of one said magnet pole;

wherein, within a given revolution, each of said binary signal pulses has a pulse width that is different from pulse widths of other binary signal pulses generated by the other magnet poles, and these pulse width difference allow the binary signal pulses to be distinguished from each other during the revolution of said rotor; and

wherein only one edge of one of said binary signal pulses is associated with said home transition point of said DC multi-pole motor; and

(c) during each revolution of said multi-pole rotor, measuring the pulse widths of said binary signal pulses with appropriate accuracy to distinguish each said binary signal pulse by its said measured pulse width, tracking a ranking order of measured pulse widths of said binary pulse signals generated during each revolution of said rotor, and determining the occurrence of said predetermined home transition point associated with said DC multi-pole motor.

2. The method of claim 1, wherein during step (c), said measuring of the pulse widths of said binary signal pulses comprises using one or more hysteresis counters to keep track of the ranking order of measured pulse widths.

3. The method of claim 1, further comprising calibrating said DC multi-pole motor to determine said predetermined home transition point as a time offset from one edge of one of one of the previously identified said pulses.

4. The method of claim 1, which further comprises:

(d) determining at least one set of start and stop times for turning on and off, said laser beam in relation to said predetermined home transition point;

wherein said each set of start and stop times is correlated to a selected mirror facet of said rotating polygon mirror and the position of said selected mirror facet; and

(e) driving said laser source during a time interval defined by said at least one set of start and stop times, so that said laser scanning system generates a scan line pattern for each set of start and stop times.

5. The method of claim 4, wherein said start and stop times are correlated to a selected mirror facet of said polygon mirror, and wherein the start and stop times are identified by respective start and stop time intervals and each interval measured from said predetermined home transition point.

6. A laser scanning system comprising:

a DC multi-pole motor having (i) a rotor with multiple magnet poles, (ii) an internal Hall Effect sensor for sensing each magnet pole passing said internal Hall Effect sensor during each rotation of said rotor and generating a binary signal pulse having a pulse width that is different from pulse widths of other binary signal pulses generated by other magnetic poles, and (iii) a predetermined home transition point that is associated with only one of said binary signal pulses;

a polygon mirror having mirror facets rotated by the rotor of said DC multi-pole motor;

a laser source producing a laser beam that is scanned across a scanning field by the mirror facets of said rotating polygon mirror;

a programmed microprocessor having an operating frequency;

a timer circuit having a clock speed;

an oscillator for controlling the operating frequency of said programmed microprocessor and the clock speed of said timer circuit;

wherein while said rotor is rotating, said internal Hall effect sensor generates a signal pulse train comprising sequential sets of two or more binary signal pulses for each revolution of said rotor;

one or more hysteresis counters, controlled by said timer circuit, for tracking a ranking order of measured pulse widths of said binary signal pulses generated during each revolution of said rotor;

wherein each binary signal pulse has a time duration corresponding to a relative position of one said magnet pole;

wherein, within a given revolution, each of said binary signal pulses has a pulse width that is different from the pulse widths of other binary pulse signals generated by the other magnet poles, and these pulse width differences allow the binary signal pulses to be distinguished from each other during the revolution of said rotor;

wherein only one edge of one of said binary signal pulses is associated with said home transition point of said DC multi-pole motor; and

wherein, during each revolution of said rotor, (i) said timer circuit measures the pulse widths of said binary signal pulses with appropriate accuracy so as to distinguish each said binary signal pulse by its said measured pulse width, (ii) said one or more hysteresis counters track the ranking order of measured pulse widths of said binary pulse signals generated during each revolution of said rotor, and (iii) said programmed microprocessor determines the occurrence of said predetermined home transition point associated with said DC multi-pole motor.

7. The laser scanning system of claim 6,

wherein at least one set of start and stop times are determined for turning on and off said laser beam in relation to said predetermined home transition point;

wherein said each set of start and stop times is correlated to a selected mirror facet of said rotating polygon mirror and the position of said selected mirror facet; and

wherein said laser source is driven during a time interval defined by said at least one set of start and stop times, so that said laser scanning system generates a scan line pattern for each set of start and stop times.

8. The laser scanning system of claim 7, wherein said start and stop times are correlated to a selected mirror facet of said polygon mirror, and wherein the start and stop times are identified by respective start and stop time intervals and each interval measured from said predetermined home transition point.