US Patent 7413280 Detection method of interval of recorded positions

A method for detecting an interval of recorded positions, including the steps of recording a first pattern group in such a way that the recording heads scan a recording medium so that recording elements record a pattern having repeatedly dark density area and light density area perpendicular to a scanning direction of the recording head, recording a second pattern group in such a way that the recording heads scan the recording medium so that recording elements record a pattern having repeatedly dark density area and light density area perpendicular to a scanning direction of the recording head and further the second pattern group is overlapped on and angled to the first pattern group, detecting interference fringes generated by overlap of the first pattern group and the second pattern group, and detecting a change of the interval of the recorded positions via a positional deviation of the interference fringes.