Self-clocking glyph code for encoding dual bit digital values robustly

• US 5,245,165 A
• Filed: 12/27/1991
• Issued: 09/14/1993
• 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: Zhang, Xiao B.
• Primary Examiner(s): SHEPPERD, JOHN W
• Application Number:
  US07/814,841
• Time in Patent Office: 627 Days
• Field of Search: 235/454, 235/487, 235/494
• US Class Current: 235/454
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/143 Glyph-codes

Abstract

A self-clocking glyph code is provided for encoding dual bit digital values in the cardinal rotations (0°, 90°, 180° and 270°) of a logically ordered sequence of wedge-shaped glyphs that are written, printed, or otherwise recorded on a hardcopy recording medium in accordance with a predetermined spatial formatting rule. For example, these wedge-shaped glyphs suitably are essentially identical right triangles. The widths of such glyphs vary unidirectionally as a function of their height, so they can be decoded reliably, even when they are degraded by scan errors, dropped scan lines and/or random noise patterns. The decoding can be carried out in a variety of different ways, including by means of a bounding box analysis of the glyphs to determine whether the center of mass of each glyph is in the upper right, upper left, lower right or lower left quadrant of its bounding box; or by means of a bounding box analysis of the glyphs to determine whether the inclined surface of each wedge is on its right-hand side or its left-hand side and tilted to the right or left; or by means of a comparative run length analysis of each of the glyphs to determine whether its shortest run of adjacent ON pixels is spatially located above or below, and to the right or left of center of, its longest run of adjacent ON pixels.

Claims

1. A self-clocking glyph code for transferring dual bit digital values from a hardcopy recording to an electronic document processing system, said code comprising a logically ordered sequence of wedge-shaped glyphs written on said recording medium in accordance with a predetermined spatial formatting rule at relative angular orientations that encode respective ones of said values in said glyphs;

said glyphs having permissible angular orientations oft approximately 0°

, 90°

, 180° and

270°

with respect to a predetermined reference axis for encoding quantitatively different ones of said dual bit digital values.

2. The self-clocking glyph code of claim 1 wherein said reference axis extends laterally with respect to said recording medium.

3. The self-clocking glyph code of either of claims 1 or 2 wherein said glyphs have essentially identical right triangular shapes, each of which is bounded by two shorter sides and a longer side;

the two shorter sides of each of said glyphs being substantially aligned laterally and longitudinally, respectively with respect to said recording medium.

4. The self-clocking glyph code of claim 3 wherein said glyphs have isosceles shapes.

5. A method for decoding a self-clocking glyph code having wedge-shaped glyphs that are oriented at angles of 0°

, 90°

, 180° and

270°

for encoding quantitatively distinct dual bit digital values, said method comprising the steps of;

determining a bounding box for each of said glyphs;

each bounding box having an upper right-hand quadrant, an upper left-hand quadrant, a lower right-hand quadrant, and a lower left-hand quadrant; and

determining, for each of said glyphs, which of the quadrants of its bounding box contains its center of mass.

8. The method of any of claims 5-7 wherein said glyphs have essentially identical right triangular shapes that are oriented so that their shorter sides extend in generally horizontal and vertical directions, respectively.

9. The method of claim 8 wherein said triangular shapes are isosceles shapes.

6. A method for decoding a self-clocking glyph code having wedge-shaped glyphs that are oriented at angles of 0°

, 90°

, 180° and

270°

for encoding quantitatively distinct dual bit digital values, said method comprising the steps of;

finding the longest side of each glyph;

determining, for each glyph, whether its longest side is titled to the right or left and whether its longest side is to the right-hand or left-hand side of the glyph.

7. A method for decoding a self-clocking glyph code having wedge-shaped glyphs that are oriented at angles of 0°

, 90°

, 180° and

270°

for encoding quantitatively distinct bit digital dual values, said method comprising the steps of;

finding a shortest run and longest run of ON pixels for each of said glyphs;

determining, for each glyph, whether its shortest run of ON pixels is spatially located above or below of its longest run of ON pixels and to the left or right of center of said longest run.