Bar code symbol reading system employing electronically-controlled raster-type laser scanner for reading bar code symbols during hands-on and hands-free modes of operation

• US 6,742,709 B2
• Filed: 11/28/2001
• Issued: 06/01/2004
• Est. Priority Date: 09/11/1990
• Status: Expired due to Fees

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Knowles, C. Harry, Amundsen, Thomas C., Carullo, Thomas, Naylor, Charles, Zhu, Xiaoxun, Blake, Robert E., Colavito, Stephen J.
• Primary Examiner(s): Lee, Michael G.
• Assistant Examiner(s): Kim, Ahshik
• Application Number:
  US09/996,079
• Publication Number:
  US 20020170968A1
• Time in Patent Office: 916 Days
• Field of Search: 235/462.01, 235/462.11
• US Class Current: 235/462.11
• CPC Class Codes: G06K 7/10584 Source control
• CPC Class Codes: G06K 7/10683 Arrangement of fixed elements

Abstract

A bar code symbol reading system is disclosed comprising a hand-supportable bar code symbol reading device which embodies an electronically-controlled bar code symbol reading engine for producing a raster-type laser scanning pattern in either a hands-free or hands-on mode of operation for scanning 1-D and 2D bar code symbols. The electronically-controlled bar code symbol reading engine has (i) a high-speed/high-resolution raster scanning mode of operation, during which a high-speed, high-resolution raster-type scanning pattern is precisely generated under electronic control, and (ii) a high-speed/low-resolution raster scanning mode of operation during which a high-speed, low-resolution raster-type scanning pattern is precisely generated under electronic control. The electronically-controlled bar code symbol reading engine is induced into its high-speed/high-resolution raster scanning mode of operation when the hand-supportable bar code symbol reading device is removed from its support stand, and into its high-speed/low-resolution raster scanning mode when the hand-supportable bar code symbol reading device is placed into its support stand. The bar code symbol reading engine comprises a pair of mechanically-damped off-resonant laser beam scanning mechanisms that are arranged on a miniature optical bench and electronically-controlled by either a synchronously or asynchronously driven drive circuit. When asynchronously driven, the raster laser scanning pattern floats slightly along the y-scanning direction to facilitate reading of 2-D bar code symbols during the hands-on mode of operation.

Claims

1. A system for producing a raster-type scanning pattern for scanning 2-D bar code symbols, said system comprising:

a housing;

a light source disposed in said housing, for producing a light beam having cross-sectional characteristics suitable for scanning a 2-D bar code symbol;

a first light beam scanning mechanism, disposed in said housing and responsive to a first electrical control voltage signal, for scanning said light beam along a first reference direction;

said first light beam scanning mechanism further including

a first scanning element of unitary construction having a first base portion, a first light beam deflecting portion, and a first flexible photo-etched gap region disposed therebetween,

said first base portion being anchored with respect to a first optical bench so as to permit said first light beam deflecting portion to pivot about a first fixed pivot point defined between said first base portion and said first flexible photo-etched gap region,

said first light beam deflecting portion having a first front surface and a first rear surface and being flexibly connected to said first base portion by said first photo-etched gap region,

said first light beam deflecting portion having a first natural resonant frequency of oscillation about said first fixed pivot point determined in part by the physical dimensions of said first flexible photo-etched gap region,

a first permanent magnet mounted on said first light beam deflecting portion,

a first light beam deflecting element mounted on said first light beam deflecting portion, for deflecting said light beam falling incident upon said first light beam deflecting element,

a first magnetic-field producing coil having a first pair of input terminals, and disposed adjacent said first permanent magnet, for producing a first magnetic force field of reversible polarity in the vicinity of said first permanent magnet in response to a first electrical current signal flowing through said first magnetic-field producing coil, at an amplitude which varies at a first controlled frequency,

a first electrical circuit operably connected to said first pair of input terminals, and producing said first electrical control voltage signal which causes said first electrical current signal to flow through said first magnetic-field producing coil and produce in the vicinity of said first permanent magnet, said first magnetic force field having a polarity which varies in accordance with the amplitude and frequency of said first electrical current signal flowing through said first magnetic-field producing coil, and

said first magnetic force field interacting with said first permanent magnetic and forcing said first light beam deflecting portion to oscillate about said first fixed pivot point at a first forced frequency of oscillation that is substantially equal to said first controlled frequency of said first electrical current signal and substantially different in frequency from said first natural resonant frequency of oscillation of said first light beam deflecting portion, and when said light beam is incident upon said first light beam deflecting element, said light beam being periodically deflected as said first light beam deflecting portion oscillates about said first fixed pivot point at said first forced frequency of oscillation;

a second light beam scanning mechanism, disposed in said housing and responsive to a second electrical control voltage signal, for scanning said light beam along a second reference direction orthogonal to said first reference direction, so as to produce a raster-type scanning pattern for scanning said 2-D bar code symbol;

wherein said second light beam scanning mechanism further includes

a second scanning element of unitary construction having a second base portion, a second light beam deflecting portion, and a second flexible photo-etched gap region disposed therebetween,

said second base portion being anchored with respect to a second optical bench so as to permit said second light beam deflecting portion to pivot about a second fixed pivot point defined between said second base portion and said second flexible photo-etched gap region,

said second light beam deflecting portion having a second front surface and a second rear surface and being flexibly connected to said second base portion by said second photo-etched gap region,

said second light beam deflecting portion having a second natural resonant frequency of oscillation about said second fixed pivot point determined in part by the physical dimensions of said second flexible photo-etched gap region,

a second permanent magnet mounted on said second light beam deflecting portion,

a second light beam deflecting element mounted on said second light beam deflecting portion, for deflecting said light beam falling incident upon said second light beam deflecting element,

a second magnetic-field producing coil having a second pair of input terminals, and disposed adjacent said second permanent magnet, for producing a second magnetic force field of reversible polarity in the vicinity of said second permanent magnet in response to a second electrical current signal flowing through said second magnetic-field producing coil, at an amplitude which varies at a second controlled frequency;

a second electrical circuit operably connected to said second pair of input terminals, and producing said second electrical control voltage signal which causes said second electrical current signal to flow through said second magnetic-field producing coil and produce in the vicinity of said second permanent magnet, said second magnetic force field having a polarity which varies in accordance with the amplitude and frequency of said second electrical current signal flowing through said second magnetic-field producing coil, and

said second magnetic force field interacting with said second permanent magnetic and forcing said second light beam deflecting portion to oscillate about said second fixed pivot point at a second forced frequency of oscillation that is substantially equal to said second controlled frequency of said second electrical current signal and substantially different in frequency from said second natural resonant frequency of oscillation of said second light beam deflecting portion, and when said light beam is incident upon said second light beam deflecting element, said light beam being periodically deflected as said second light beam deflecting portion oscillates about said second fixed pivot point at said second forced frequency of oscillation;

a light collector disposed in said housing, for collecting light reflected off a 2-D bar code symbol scanned by said raster-type scanning pattern;

a light detector disposed in said housing, for detecting said collected light and producing scan data indicative of the intensity of said detected light; and

a scanning mechanism controller, disposed in said housing, for electrically controlling the operation of said first and second light beam scanning mechanisms so as to produce said raster-type scanning pattern for scanning said 2-D bar code symbol.

2. The system of claim 1, wherein said scanning mechanism controller electrically controls said first and second scanning elements in a synchronous manner so that said raster-type scanning pattern as a whole is substantially free of movement relative to said housing.

3. The system of claims 1, wherein said scanning mechanism controller electrically controls said first and second scanning elements in an asynchronous manner so that said raster-type scanning pattern as a whole moves back and forth along relative to said housing so as to improve the scanning of said 2-D bar code symbol when supporting said housing within the hand of an operator.

4. The system of claim 1, wherein said light beam is a laser beam.

5. The system of claim 1, wherein said housing is hand-supportable.

6. The system of claim 1, wherein said housing is body-wearable.

7. The system of claim 1, wherein said scanning mechanism controller comprises means for generating a plurality of y-axis drive voltage signals, each for driving said second scanning element at a different scan rate.

8. The system of claim 7, wherein said scanning mechanism controller further comprises a push-pull type drive circuit for producing a x-axis drive voltage signal having periodic characteristics, for driving said first scanning element.

9. The system of claim 8, wherein said y-axis drive voltage signal increments in small quantized voltage level steps in response to a control signal generated independently from said x-axis drive voltage signal.

10. The system of claim 1, wherein said housing is a minature enclosure that can be supported on the hand of an operator.

11. The system of claim 1, wherein said first forced frequency of oscillation is different in magnitude than said first natural resonant frequency of oscillation by at least 10% of said first natural resonant frequency, and said second forced frequency of oscillation is different in magnitude than said second natural resonant frequency of oscillation by at least 10% of said second natural resonant frequency.

12. The system of claim 1, wherein said first light beam deflecting portion, said first flexible photo-etched gap portion and said first base portion each comprise a first layer of flexible material, and said first light beam deflecting portion and said first base portion each include a first pair of metal elements mounted in registration on said first layer of flexible material, and wherein said second light beam deflecting portion, said second flexible photo-etched gap portion and said second base portion each comprise a second layer of flexible material, and said second light beam deflecting portion and said second base portion each include a second pair of metal elements mounted in registration on said second layer of flexible material.

13. The system of claim 12, wherein said first natural resonant frequency of oscillation of said first light beam deflecting portion is dependent upon the thickness of said first layer of flexible material and the dimensions of said first flexible photo-etched gap portion, and wherein said second natural resonant frequency of oscillation of said second light beam deflecting portion is dependent upon the thickness of said second layer of flexible material and the dimensions of said second flexible photo-etched gap portion.

14. The system of claim 1, wherein said first light beam deflecting element comprises a first light reflective element mounted onto the first front surface of said first light beam deflecting portion, and said second light beam deflecting element comprises a second light reflective element mounted onto the second front surface of said second light beam deflecting portion.

15. The system of claim 1, wherein said first light beam deflecting element comprises a first light refractive element mounted onto the first front surface of said first light beam deflecting portion, and said second light beam deflecting element comprises a second light refractive element mounted onto the second front surface of said second light beam deflecting portion.

16. The system of claim 1, wherein said first light beam deflecting element comprises a first light diffractive element mounted onto the first front surface of said first light beam deflecting portion, and said second light beam deflecting element comprises a second light diffractive element mounted onto the second front surface of said second light beam deflecting portion.

17. The system of claim 1, wherein said first optical bench comprises a first module having a first wall structure in which said first magnetic-field producing coil is mounted, and a second wall structure to which said first base portion is mounted, and said second optical bench comprises a second module having a second wall structure in which said second magnetic-field producing coil is mounted, and a second wall structure to which said second base portion is mounted.

18. The system of claim 17, wherein said first module further comprises a first pair of stops disposed on opposite sides of said first flexible photo-etched gap portion, to restrict the angular rotation of said first scanning element about said first fixed pivot point, and said second module further comprises a second pair of stops disposed on opposite sides of said second flexible photo-etched gap portion, to restrict the angular rotation of said second scanning element about said second fixed pivot point.

19. The system of claim 1, wherein said first electrical circuit comprises means for setting said first controlled frequency, and said second electrical circuit comprises means for setting said second controlled frequency.