Methods and means for reducing bit error rates in reading self-clocking glyph codes

• US 5,221,833 A
• Filed: 12/27/1991
• Issued: 06/22/1993
• Est. Priority Date: 12/27/1991
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Hecht, David L.
• Primary Examiner(s): SHEPPERD, JOHN W
• Application Number:
  US07/815,005
• Time in Patent Office: 543 Days
• Field of Search: 235/454, 235/487, 235/494
• US Class Current: 235/494
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• CPC Class Codes: G06K 7/143 Glyph-codes

Abstract

The glyphs of a self-clocking glyph code for encoding n-bit long multi-bit digital values are preordered in a cyclical sequence, based on their analytically or empirically determined probabilities of being confused with each other, such that each glyph is adjacent in that sequence to the two glyphs with which it is more likely to be confused during decoding. Binary encoding values then are assigned to these ordered glyphs in accordance with an n-bit long Gray code sequence, so that the value assigned to any given glyph differs in just one bit position from the values assigned to the glyphs with which it is most likely to be confused.

Claims

1. A method for reducing bit errors in reading self-clocking glyph codes that encode n-bit long multi-bit digital values in a set of 2ⁿ graphically discriminable glyphs, said method comprising the steps of

identifying a cyclical serial ordering of said glyphs wherein each glyph is an adjacent neighbor of the glyphs with which it is most likely to be confused during said reading, and

assigning successive n-bit long Gray code values to said glyphs in accordance with said ordering, whereby the value encoded by each of said glyphs differs from the values encoded by the glyphs with which it is most likely to be confused by just one bit position.

2. The method of claim 1 wherein

said glyphs have different rotational orientations, and

said digital values are encoded in the rotational orientations of said glyphs.

3. The method of claim 2 wherein said glyphs are elongated symbols.

4. The method of claim 3 wherein the rotational orientations of said glyphs are angularly displaced from each other by substantially equal angular increments.

5. The method of any one of claims 1-4 wherein said cyclical ordering of said glyphs is determined analytically.

6. The method of any one of claims 1-4 wherein said cyclical ordering of said glyphs is determined empirically.