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Techniques for miniaturizing bar code scanners including spiral springs and speckle noise reduction

Imported: 24 Feb '17 | Published: 09 Sep '03

Edward Barkan, Paul Dvorkis, Howard Shepard, Miklos Stern, Chinh Tan

USPTO - Utility Patents

Abstract

Various techniques for reducing the size of bar code scanner modules are disclosed including embodiments having miniature moving mirror elements employing spiral tape springs and micro machined structures. Other embodiments employ VCSELs and relatively small collection areas, while minimizing speckle noise through beam shaping and signal processing techniques.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are, respectively, side and front cross-sectional views of a ring scanner employing a scanning device of an embodiment of the present invention;

FIGS.

3(

a) and

3(

b) are, respectively, side and front cross-sectional views of a spiral spring scanning device of the present invention;

FIG. 4 is a pictorial view of a spiral tape spring;

FIG. 5 illustrates an alternate embodiment of a spiral spring scanning device of the present invention;

FIGS.

6(

a)-(

c) and

7(

a) and (

b) are side and plan cross-sectional views of a spiral spring scanning device illustrating the response of the device to g-forces;

FIGS. 8 and 9 illustrate two dimensional scanning devices and spiral springs and magnets therefor;

FIGS. 10 and 11 are views of leaf spring and spiral spring based scanning devices, respectively, illustrating certain dimensional comparisons;

FIG. 12 is a pictorial view in partial cross section of components of a compact scanning module of a preferred embodiment of the present invention;

FIG. 13 is a schematic circuit diagram of an embodiment of the present invention including amplifiers, a digitizer and automatic gain control;

FIG. 14 is a plan view of a two dimensional bar code laser spot and beam profile of a preferred embodiment of the present invention;

FIGS.

15(

a) and

15(

b) are alternative embodiments of optical systems for producing the laser spot, halo and beam profile of FIG.

14.

Claims

1. In a reader for electro-optically reading a bar code symbol, the symbol comprising bars and spaces of different light reflectivity and having specific relative widths, by sweeping a laser spot across the symbol for reflection therefrom, by detecting laser light reflected from the symbol, and by generating an analog electrical signal indicative of the laser light detected, an arrangement for reducing speckle noise influence in the analog signal, the arrangement comprising:

2. The arrangement of claim 1, wherein the emitter comprises a laser diode for generating the laser beam with a wavelength of 630 nm.

3. The arrangement of claim 1, wherein the emitter comprises a vertical cavity surface emitting laser diode.

4. The arrangement of claim 1, wherein the emitter includes a focusing lens for forming said spot size on the symbol.

5. The arrangement of claim 1, wherein the reader detects the laser light reflected from the symbol over a collection area of less than 10 square millimeters.

6. The arrangement of claim 5, wherein the collection area is on a collection mirror having dimensions of 3 millimeters by 3 millimeters.

7. The arrangement of claim 1, wherein the non-differentiating digitizer produces a digitized signal as a two-level square wave of varying widths.

8. The arrangement of claim 1, wherein the reader is operative for reading the symbol within a working range of less than eight inches.

9. In a method of electro-optically reading a bar code symbol, the symbol comprising bars and spaces of different light reflectivity and having specific relative widths, by sweeping a laser spot across the symbol for reflection therefrom, by detecting laser light reflected from the symbol, and by generating an analog electrical signal indicative of the laser light detected, a method of reducing speckle noise influence in the analog signal, the method comprising the steps of:

10. The method of claim 9, wherein the emitting step is performed by generating the laser beam with a wavelength of 630 nm.

11. The method of claim 9, wherein the emitting step includes focusing the laser beam to form said spot size on the symbol.

12. The method of claim 9, wherein the laser light reflected from the symbol is collected over a collection area of less than 10 square millimeters.

13. The method of claim 9, wherein the collection area has dimensions of 3 millimeters by 3 millimeters.

14. The method of claim 9, wherein the non-differentiating digitizer produces a digitized signal as a two-level square wave of varying widths.