Electronically-controlled mechanically-damped off-resonant light beam scanning mechanism and code symbol readers employing the same

• US 7,255,280 B2
• Filed: 04/04/2005
• Issued: 08/14/2007
• 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, Blake, Robert E., Colavito, Stephen J., Amundsen, Thomas, Naylor, Charles A., Carullo, Thomas
• Primary Examiner(s): Kim; Ahshik
• Application Number:
  US11/098,584
• Publication Number:
  US 20050236486A1
• Time in Patent Office: 862 Days
• Field of Search: 235/462.37, 235/462.36, 235/462.35, 235/462.01
• US Class Current: 235/462.37
• CPC Class Codes: G06F 16/9554 by using bar codes
• CPC Class Codes: G06K 7/10643 Activating means

Abstract

Apparatus for deflecting a light beam, comprising: a scanning element having a base portion, a light beam deflecting portion, and a gap region disposed therebetween. The base portion is anchored with respect to an optical bench to permit the light beam deflecting portion to pivot about a fixed pivot point defined between the base portion and the gap region. The light beam deflecting portion has a natural resonant frequency of oscillation about the fixed pivot point and is mechanically-damped at the gap region. A permanent magnet and right beam deflating portion are mounted on the light beam deflecting portion. A magnetic-field producing coil produces a force field that interacts with the permanent magnet and forces the light beam deflecting portion to oscillate about the fixed pivot point at a controlled frequency of oscillation that is substantially different from the natural resonant frequency of oscillation of the light beam deflecting portion.

Claims

1. Apparatus for deflecting a light beam, comprising:

an optical bench;

a scanning element of unitary construction having a base portion, a light beam deflecting portion, and a gap region disposed therebetween,

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

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

said light beam deflecting portion having a natural resonant frequency of oscillation about said fixed pivot point and being mechanically-damped at said gap region;

a permanent magnet mounted on said light beam deflecting portion;

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

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

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

whereby said magnetic force field interacts with said permanent magnet and forces said light beam deflecting portion to oscillate about said fixed pivot point at a controlled frequency of oscillation that is substantially equal to said controlled frequency and substantially different from said natural resonant frequency of oscillation of said light beam deflecting portion; and

wherein said controlled frequency of oscillation is different in magnitude than said natural resonant frequency of oscillation by at least 10% of said natural resonant frequency.

2. The apparatus of claim 1, wherein a light beam incident upon said light beam deflecting element is periodically deflected as said light beam deflecting portion oscillates about said fixed pivot point at said controlled frequency of oscillation, creating a one-dimensional scanning pattern for scanning bar code symbols.

3. The apparatus of claim 2, which further comprises

a light beam source for producing a light beam for directing incident upon the surface of said light beam deflecting portion.

4. The apparatus of claim 1, wherein said light beam deflecting portion, said gap portion and said base portion each comprise a layer of flexible material, and said light beam deflecting portion, and said base portion each include a pair of metal elements mounted in registration on said layer of flexible material.

5. The apparatus of claim 4, wherein said natural resonant frequency of oscillation of said light beam deflecting portion is related to the thickness of said layer of flexible material and the dimensions of said gap portion.

6. The apparatus of claim 1, wherein said light beam deflecting element comprises a light reflective element mounted onto the front surface of said light beam deflecting portion.

7. The apparatus of claim 1, wherein said light beam deflecting element comprises a light refractive element mounted onto the front surface of said light beam deflecting portion.

8. The apparatus of claim 1, wherein said light beam deflecting element comprises a light diffractive element mounted onto the front surface of said light beam deflecting portion.

9. The apparatus of claim 1, wherein said permanent magnet is mounted on said rear surface of said light beam deflecting portion, and said light beam deflecting element is mounted on said front surface of said light beam deflecting portion.

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

11. The apparatus of claim 10, wherein said module further comprises a pair of stops disposed on opposite sides of said gap portion, to restrict the angular rotation of said scanning element about said fixed pivot point.

12. The apparatus of claim 10, wherein said module comprises a scanning aperture through which said light beam is permitted to be swept as said light beam deflecting portion oscillates about said fixed pivot point at said controlled frequency of oscillation.

13. The apparatus of claim 1, wherein said electrical circuit comprises means for setting said controlled frequency.

14. The apparatus of claim 1, which further comprises

a light source for producing said light beam directed incident on said light beam deflecting element.

15. The apparatus of claim 14, wherein said light source comprises a visible laser diode.

16. A bar code symbol reading system comprising:

said apparatus of claim 1, for producing a one-dimensional scanning pattern for scanning a bar code symbol on an object;

light collecting means for collecting light reflected of said scanned bar code symbol;

light detecting means for detecting said collected light and producing scan data indicative of the intensity of said detected light; and

scan data processing means for decode processing said scan data in order to produce symbol character data representative of said scanned bar code symbol.