Image scanning device and calibration method thereof

An image scanning device comprising:

• a scanning device arranged to scan an original;
• an acquiring device arranged to acquire scanned tone values of a plurality of patches each having a different tone with respect to each of a plurality of color components when an original for use in calibration including the plurality of patches is scanned by the scanning device;
• a curve acquiring device arranged to acquire a curve function with respect to each of the plurality of color components based on target tone values of the patches predetermined with respect to each of the plurality of color components and based on the scanned tone values, each curve function approximating a relationship between an input defined as the scanned tone value and an output defined as the target tone value, and then to determine the curve function of each of the plurality of color components such that input value intercepts, each being defined as an upper limit of a range of the input value in which range the output value is maintained at zero, are equal among the plurality of color components;
• and
• a correcting device arranged to use the determined curve functions to correct the tone value of each of the plurality of color components of an image acquired by scanning the original.

A calibration method of an image scanning device, the method comprising the steps of:

• scanning an original used in calibration including a plurality of patches each having a different tone;
• acquiring scanned tone values of the patches of the original used in calibration with respect to each of a plurality of color components;
• acquiring a curve function with respect to each of the plurality of color components based on the scanned tone values and target tone values of the patches predetermined with respect to each of the plurality of color components, each curve function approximating a relationship between an input defined as the scanned tone value and an output defined as the target tone value;
• and
• determining the curve function of each of the plurality of color components such that input value intercepts, each being defined as an upper limit of a range of the input value in which range the output value is maintained at zero, are equal among the plurality of color components.