System for reading a symbol by activitating a liquid crystal device to control a scanning path
First Claim
1. A method of reading a bar code symbol comprising the steps of:
- generating a scanning light beam;
detecting said light beam;
changing the light beam in accordance with said detected light beam;
directing said light beam upon a field where said bar code symbol may be present;
varying a light path of said scanning beam by changing an electrical signal applied to a liquid crystal device in said path to thereby create a scan line to traverse said field as the electrical signal changes;
detecting light reflected by said field; and
decoding said detected reflected light while ignoring segments of the reflected light corresponding to areas indicated as defective based on the detected scanning light beam.
3 Assignments
0 Petitions
Accused Products
Abstract
A bar code scanner employs an electronic means for causing the light beam to scan a bar code symbol, rather than using a mechanical device to generate the scan. A linear array of light sources, activated one at a time in a regular sequence, may be imaged upon the bar code symbol to simulate a scanned beam. Instead of a single linear array of light sources, a multiple-line array may be employed, producing multiple scan lines. The multiple scan lines may be activated in sequence, or activated simultaneously (time-division or frequency-division multiplexed. The multiple scan lines can provide signal enhancement, noise reduction or fault correction if directed to the same bar code pattern. Multiple scan lines may be generated using a single light source and a beam splitter, with mechanical scanning, as well as by the sequentially-activated light sources. Multiple simultaneous scan lines may be employed to generate a raster scan at lower mechanical scan frequency. In another embodiment, a tunable laser may be employed to provide a scan without moving parts; a laser beam from the tunable laser is reflected from a diffraction grating that produces an angular deviation dependent upon the wavelength of the laser output. As the frequency of the tunable laser is varied in some selected pattern, the laser beam will scan accordingly.
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Citations
22 Claims
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1. A method of reading a bar code symbol comprising the steps of:
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generating a scanning light beam; detecting said light beam; changing the light beam in accordance with said detected light beam; directing said light beam upon a field where said bar code symbol may be present; varying a light path of said scanning beam by changing an electrical signal applied to a liquid crystal device in said path to thereby create a scan line to traverse said field as the electrical signal changes; detecting light reflected by said field; and decoding said detected reflected light while ignoring segments of the reflected light corresponding to areas indicated as defective based on the detected scanning light beam. - View Dependent Claims (2, 3, 4, 5)
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6. A method of reading a bar code symbol comprising the steps of:
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generating a light beam scan line by sequentially activating an array of cells in a liquid crystal device; detecting the generated light beam scan line; changing an electrical signal applied to the liquid crystal device in accordance with the detected light beam scan line to thereby adjust the light beam; directing the light beam scan line to a field where said bar code symbol may be present; detecting light reflected from said field to produce an electrical signal corresponding to said scan line; and decoding said electrical signal while ignoring segments of the reflected light corresponding to areas indicated as defective based on the detected generated light beam. - View Dependent Claims (7, 8, 9, 10)
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11. A bar code symbol reader comprising:
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a light source for generating a scanning light beam; a first photodetector for detecting the generated scanning light beam; means for adjusting the light beam in accordance with the detected light beam; a lens for directing the light beam upon a field where said bar code symbol may be present; means for varying a light path of said scanning beam by changing an electrical signal applied to a liquid crystal device in said path to thereby create a scan line to traverse said field as the electrical signal changes; means for detecting light reflected by said field; and means for decoding said detected reflected light while ignoring segments of the reflected light corresponding to areas indicated as defective based on the detected scanning light beam. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A bar code symbol reader comprising:
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a light source for generating a light beam; an electrical source for generating a scan line by sequentially activating a plurality of cells in a liquid crystal device; a first photodetector for detecting the generated scan line; means for changing an electrical signal applied to the liquid crystal device based upon the detected scan line; a lens for directing the light beam scan line to a field where said bar code symbol may be present; a second photodetector for detecting light reflected from said field to produce an electrical signal corresponding to said scan line; and means for decoding said detected reflected light ignoring segments of the reflected light corresponding to areas indicated as defective based on the detected generated scan line. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification