Patent ID: 8388088

Claim:
A dot position measurement method, comprising: a line pattern forming step of forming a measurement line pattern including a plurality of lines formed by dot sequences corresponding to respective recording elements on a recording medium, by continuously recording dots by the recording elements while causing a recording head having the recording elements and the recording medium to move relatively to each other in a relative movement direction, the measurement line pattern including: a plurality of line blocks each constituted of a group of lines to be recorded using the recording elements spaced a prescribed interval apart in an effective direction of alignment of the recording elements which is perpendicular to the relative movement direction, the line blocks being formed at mutually different positions in a lengthwise direction of the lines on the recording medium; and a reference line block containing lines to be recorded by the recording elements which are common respectively with the recording elements forming the line blocks; a reading step of reading the measurement line pattern formed on the recording medium in the line pattern forming step by an image reading device, and acquiring electronic image data representing a read image of the measurement line pattern; a position-in-line-block identifying step of identifying line positions in each of the line blocks and the reference line block, from the read image acquired in the reading step; and a position correcting step of correcting the line positions of the line blocks determined in the position-in-line-block identifying step in accordance with the reference line block, by employing a correction function using a piecewise polynomial expression, wherein the polynomial expression is a low-order polynomial of an order not greater than five.