[54] LINEARIZATION OF RASTER PATTERNS IN 2D OPTICAL SCANNERS
[75] Inventors: Raj Bridgelall, Mount Sinai; Duanfeng He, Farmingville; Eugene Joseph, Port Jefferson; William John Sakoda, East Setauket, all of N.Y.
[73] Assignee: Symbol Technologies, Inc., Holtsville, N.Y.
[21] Appl. No.: 789,660
[22] Filed: Jan. 27, 1997
[51] Int. CI. G06K 7/10
[52] U.S. CI 235/462; 235/454; 235/470
[58] Field of Search 235/462, 454,
235/456, 467, 470, 472, 463, 466
[56] References Cited
U.S. PATENT DOCUMENTS
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FOREIGN PATENT DOCUMENTS
0-384-955-A2 9/1990 European Pat. Off. .
Primary Examiner—Michael G. Lee
Attorney, Agent, or Firm—Kirschstlen, et al.
[57] ABSTRACT
An optical scanner for reading two-dimensional indicia such as bar code symbols and the like includes a scan element arranged to create a two-dimensional raster pattern which may be scanned across the indicia to be read. In order to improve linearity of response in the vertical direction, perpendicular to the direction of the scan lines, the scan element is driven in that direction by a modified triangle waveform in which the amplitude and/or the phase of at least one of the harmonics has been altered. A scanning synchronization signal is provided by a long thin photodetector which is swept by the scanning beam at the left hand end of each scan path. This enables reading of vertically-modulated bar code symbologies such as POSTNET and PostBar.
25 Claims, 5 Drawing Sheets
