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
First Claim
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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Accused Products
Abstract
Disclosed is laser beam scanning apparatus in the form of an electronically-controlled mechanically-damped off-resonant laser beam scanning mechanism. The scanning mechanism comprises an etched scanning element having a small flexible gap region of closely-controlled dimensions disposed between an anchored base portion and a laser beam deflection portion The light beam deflection portion supports a permanent magnet and a light beam deflecting element (e.g., mirror or hologram). A reversible magnetic force field producing device (e.g., an electromagnet) is placed in close proximity with the permanent magnet so that it may be forcibly driven into oscillation in response to electrical current flowing through the electromagnet. The resonant frequency of oscillation of the laser beam deflecting portion relative to the anchored base portion is determined by the closely controlled dimensions of the flexible gap region set during manufacture. The steady-state frequency of oscillation of the laser beam deflecting portion is determined by the frequency of polarity reversal of the electromagnet, which is electronically controlled by the polarity of electrical current supplied thereto. In the illustrative embodiments, the forcing frequency of the electromagnet is selected to be at least ten percent off (i.e. greater or less than) the natural resonant frequency of the laser beam deflecting portion of manufacture to be any one of a very large range of values (e.g., 25-127 Hz) for use in both low-speed and high-speed laser scanning systems.
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Citations
16 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification