Method for detecting tracking error in magnetic tapes with using an X-Y stage calibration means

A method for obtaining a corrected distance between two points on the recording surface of a magnetic tape, said recording surface being in generally parallel relationship with a generally planar measuring surface, said measuring surface having a first measuring scale in the X direction and a second measuring scale in the Y direction, said first and second measuring scales being collinear with X and Y lines, respectively, said X and Y lines intersecting at a point of origin, said measuring scales adapted to provide an X - Y coordinate reading for any of a plurality of points on said recording surface, comprising the steps of:

• (1) providing measuring means for determining a measured distance between a first point on said recording surface corresponding to said point of origin and a second point on said recording surface, said measured distance determined by reference to said measuring scales;
• (2) providing calibration means for determining a standard distance between said first point and said second point;
• (3) determining an error parameter for said second point by determining the difference between said measured distance and said standard distance;
• (4) determining error parameters for said plurality of points on said recording surface by repeating steps (1) through (3) for said plurality of points;
• and
• (5) measuring the distance between two points on said magnetic tape by using said measuring means to determine a measured distance between each of said two points and said point of origin, and applying respective ones of said error parameters to each of said two points to obtain a corrected distance between said two points.