Image position error detection technique

A method for detecting image position errors, comprising the steps of:

• forming a first pattern having a symbol embedded therein;
• and
• forming a second pattern configured such that superpositioning the second pattern on the first pattern exposes the symbol if misalignment between said first and said second patterns exceeds a position error tolerance;
• wherein the first pattern includes one or more lines each having a first width and being parallel with other of said lines;
• wherein the second pattern has one or more first portions, each including a line disposed parallel to the lines of the first pattern and having a second width which exceeds said first width by a position error tolerance, and one or more second portions each extending from an end of a respective one of the first portions and having a plurality of contiguous stepped segments disposed across the second width, each of said segments having a third width which is substantially less than the first width;
• wherein the superpositioning of the second pattern over the first pattern superimposes each of the first portions of the second pattern over a portion of an associated one of the lines of the first pattern and each of the second portions of the second pattern over another portion of the associated one of the lines of the first pattern;
• wherein the symbol is embedded in the one portion of the first pattern;
• and
• wherein the extent of misalignment between the first and the second patterns is determinable by comparing a position of the second portions of the second pattern with that of the another portion of the associated one of the lines of the first pattern.

A system for detecting image position errors, comprising:

• a print device configured to form images on media;
• and
• a controller operable to drive said print device to form a first pattern configured such that superpositioning of said first pattern on a second pattern exposes a symbol embedded in the second pattern only if misalignment between said first and said second patterns exceeds a position error tolerances;
• wherein the second pattern is formed of multiple parallel lines disposed at a pitch, each having a width equal to a number of pixels, and the controller is further operable to drive the print device to form the first pattern so as to be formed of multiple parallel lines disposed at the pitch, each having a width which is equal to the number of pixels plus a position error tolerance.

A system for detecting image position errors, comprising:

• at least one sensor configured to sense a first pattern having a first spatial frequency and a first duty cycle and to generate a first signal representing the sensed first pattern, and to sense a second pattern, having a second spatial frequency equal to the first spatial frequency and a second duty cycle different than the first duty cycle and to generate a second signal representing the sensed second pattern;
• and
• a processor configured to process the first and the second signals to determine a density of a registration pattern corresponding to the second pattern superpositioned on the first pattern;
• wherein the density varies depending upon a degree of misalignment between said first and said second patterns.

A system for detecting image position errors, comprising:

• a sensor configured to sense a registration pattern formed by superpositioning a first pattern, having a first spatial frequency and a first duty cycle, on a second pattern, having a second spatial frequency equal to the first spatial frequency and a second duty cycle different than the first duty cycle and to generate a signal representing the registration pattern;
• and
• a processor configured to process the signal to determine a density of the registration pattern;
• wherein the density varies dependent upon a degree of misalignment between said first and said second patterns.

A method for detecting image position errors, comprising the steps of:

• forming a first pattern to include a line;
• forming a second pattern including a plurality of stepped segments;
• superpositioning the second pattern over the first pattern to thereby superimpose the stepped segments over the line such that the stepped segments extend diagonally across the line;
• and
• determining an extent of misalignment between the first and the second patterns by comparing a position of the stepped segments of the second pattern with that of the line of the first pattern.