Patent ID: 6236471
Filing Date: 2001-05-22
Classification: B41J,H04N

Abstract:
An alignment correction apparatus for a bidirectional scanner device, comprising:an optical reading unit reading image data from a surface of an original document when said optical reading unit is being transported along a first path of conveyance in a first direction from a first scan start point in a first scan area across the surface of the original document to a second scan area, and reading image data from the original document when said optical unit is being transported along a second path of conveyance in a second direction from a second scan start point in said second scan area across the surface of the original document to said first scan area, the second direction being opposite to the first direction, said optical reading unit detecting a reference line at said first scan area;a carriage return motor performing a first plurality of rotation steps to transport said optical reading unit in the first direction from said first scan start point in said first scan area to said second scan area, and performing a second plurality of rotation steps to transport said optical reading unit in the second direction from said second scan start point in said second scan area to said first scan area;a control unit reading an alignment correction routine, detecting said first and second pluralities of rotation steps of said carriage return motor;when said first and second pluralities of rotation steps are not equal, said control unit outputting an alignment correction signal corresponding to a difference among said first and second pluralities of rotation steps and in accordance with the alignment correction routine; anda motor controller receiving said alignment correction signal from said control unit, and controlling said second scan start point in said second scan area according to said alignment correction signal to equalize said first and second pluralities of rotation steps, said first and second pluralities of rotation steps being equalized prior to said optical reading unit reading the image data from the surface of the original document;said controlling of said second scan start point comprising:determining when said first reference value is equal to said second reference value;when said first reference value is not equal to said second reference value, determining a third reference value by subtracting said second reference value from said first reference value; andwhen said third reference value is within a first set of parameters, modifying said second scan start point by offsetting said second scan start point to a first side of said second scan area by an amount corresponding to said third reference value.