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LASER BEAM SCANNING DEVICE EMPLOYING A SCANNING ELEMENT HAVING A FLEXIBLE PHOTO-ETCHED GAP REGION DISPOSED BETWEEN AN ANCHORED BASE PORTION AND A LIGHT BEAM DEFLECTING PORTION HAVING A NATURAL FREQUENCY OF OSCILLATION TUNED BY THE PHYSICAL DIMENSIONS OF SAID FLEXIBLE PHOTO-ETCHED GAP REGION AND FORCIBLY OSCILLATED ABOUT A FIXED PIVOT POINT AT AN ELECTRONICALLY-CONTROLLED FREQUENCY OF OSCILLATION SUBSTANTIALLY DIFFERENT FROM SAID NATURAL RESONANT FREQUENCY OF OSCILLATION

  • US 6,874,689 B2
  • Filed: 03/13/2001
  • Issued: 04/05/2005
  • Est. Priority Date: 09/11/1990
  • Status: Expired due to Fees
First Claim
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1. A light beam scanning device for use in a bar code symbol reading system for producing a scanning pattern for scanning bar code symbol on an object said laser beam scanning device comprising:

  • an optical bench;

    a scanning element of unitary construction having a base portion, a light beam deflecting portion, and a flexible photo-etched 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 flexible photo-etched gap region, said light beam deflecting portion having a front surface and a rear surface and being fexibly connected to said base portion by said photo-etched gap region, said light beam deflecting portion having a natural resonant frequency of oscillation about said fixed pivot point tuned by the physical dimensions of said flexible photo-etched gap region;

    a permanent magnet mounted on said light beam deflecting portion;

    a light beam source for producing a light beam;

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

    a magnetic-field producing coil having a pair of input terminals, and 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 controlled frequency; and

    an electrical circuit operably connected to said pair of input terminals, 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, said magnetic force field interacting with said permanent magnetic and forcing 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 in frequency from said natural resonant frequency of oscillation of said light beam deflecting portion, and when said light beam is incident upon said light beam deflecting element, said light beam being periodically deflected as said light beam deflecting portion oscillates about said fixed pivot point at said forced frequency of oscillation, thereby creating a one-dimensional scanning pattern for scanning bar code symbols.

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