Laser power control arrangements in electro-optical readers

• US 7,255,275 B2
• Filed: 10/19/2005
• Issued: 08/14/2007
• Est. Priority Date: 09/12/2005
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Barkan, Edward, Gurevich, Vladimir, Vinogradov, Igor
• Primary Examiner(s): LEE, SEUNG H
• Application Number:
  US11/254,090
• Publication Number:
  US 20070057062A1
• Time in Patent Office: 664 Days
• Field of Search: 235/455, 235/436, 235/439, 235/462.25, 372/38.09
• US Class Current: 235/455
• CPC Class Codes: G06K 7/10584 Source control
• 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

Laser power control arrangements interrupt power to a laser used in electro-optical readers upon detection of an over-power condition not conforming to preestablished standards to meet prevalent safety standards.

Claims

1. A laser power control arrangement in a reader for electro-optically reading indicia, comprising:

a) an energizable laser for emitting a laser beam to the indicia for reflection therefrom;

b) a photodetector for detecting light reflected by the indicia during a reading mode, and for generating an electrical signal having a reading amplitude indicative of the light detected by the photodetector;

c) a microcontroller for comparing the reading amplitude with a maximum amplitude, and for generating a control signal when the reading amplitude differs from the maximum amplitude by a predetermined amount; and

d) a circuit for deenergizing the laser upon generation of the control signal.

2. The arrangement of claim 1, wherein the photodetector is operative for detecting light reflected by a light-reflecting source during a calibration mode prior to the reading mode, and for generating an electrical signal having the maximum amplitude.

3. The arrangement of claim 2, wherein the microcontroller has a memory in which the maximum amplitude is stored.

4. The arrangement of claim 2, wherein the light-reflecting source is a white-colored sheet.

5. The arrangement of claim 1, wherein the control signal is generated when the reading amplitude exceeds a predetermined fraction of the maximum amplitude.

6. The arrangement of claim 1, wherein the deenergizing circuit includes a switch having one state in which the switch is connected to the laser, and another state in which the switch is electrically disconnected from the laser.

7. A laser power control method, comprising the steps of:

a) energizing a laser to emit a laser beam to a light-reflecting source for reflection therefrom during a calibration mode;

b) detecting light reflected by the source during the calibration mode, and generating an electrical signal having a maximum amplitude indicative of the light detected during the calibration mode;

c) energizing the laser to emit the laser beam to indicia to be electro-optically read for reflection therefrom during a reading mode;

d) detecting light reflected by the indicia during the reading mode, and generating an electrical signal having a reading amplitude indicative of the light detected during the reading mode;

e) comparing the reading amplitude with the maximum amplitude, and generating a control signal when the reading amplitude differs from the maximum amplitude by a predetermined amount; and

f) deenergizing the laser upon generation of the control signal.

8. The method of claim 7, and the step of storing the maximum amplitude.

9. The method of claim 7, wherein the control signal is generated when the reading amplitude exceeds a predetermined fraction of the maximum amplitude.

10. The method of claim 7, wherein the deenergizing step is performed by opening a switch connected to the laser.

11. The method of claim 7, wherein the calibration mode is performed prior to the reading mode.