Image reading apparatus, defect detection method, and storage medium

A defect detection method for detecting a defect in an image generated by an image reading apparatus including a reading unit having an image sensor including a plurality of light receiving elements arranged in a predetermined direction and a lens array including a plurality of lenses arranged to guide light to the image sensor, and a background portion serving as a background of a reading area of the reading unit, the defect detection method comprising:

• a first acquisition step of acquiring first background image data having reading values of the background portion read by the reading unit stored in advance for individual pixels;
• a second acquisition step of acquiring second background image data having reading values of the background portion read by the reading unit for individual pixels;
• an interpolation step of generating third background image data by increasing resolution of the first background image data by performing a pixel interpolation calculation on the first background image data and generating fourth background image data by increasing resolution of the second background image data by performing the pixel interpolation calculation on the second background image data;
• a shift amount detection step of detecting a shift amount of the image sensor relative to the lens array in the predetermined direction by performing a comparison process of shifting a specific pixel range including a number of pixels of the fourth background image data relative to the third background image data and comparing the specific pixel range with the third background image data;
• and
• a defect detection step of determining whether each of pixels included in fifth background image data obtained by shifting the fourth background image data in accordance with the shift amount is a defective pixel having an abnormal value by comparing the fifth background image data with the third background image data.

A non-transitory computer-readable storage medium storing a defect detection program for detecting a defect in an image generated by an image reading apparatus including a reading unit having an image sensor including a plurality of light receiving elements arranged in a predetermined direction and a lens array including a plurality of lenses arranged to guide light to the image sensor, and a background portion serving as a background of a reading area of the reading unit, the defect detection program comprising:

• a first acquisition function of acquiring first background image data having reading values of the background portion read by the reading unit stored in advance for individual pixels;
• a second acquisition function of acquiring second background image data having reading values of the background portion read by the reading unit for individual pixels;
• an interpolation function of generating third background image data by increasing resolution of the first background image data by performing a pixel interpolation calculation on the first background image data and generating fourth background image data by increasing resolution of the second background image data by performing the pixel interpolation calculation on the second background image data;
• a shift amount detection function of detecting a shift amount of the image sensor relative to the lens array in the predetermined direction by performing a comparison process of shifting a specific pixel range including a number of pixels of the fourth background image data relative to the third background image data and comparing the specific pixel range with the third background image data;
• and
• a defect detection function of determining whether each of pixels included in fifth background image data obtained by shifting the fourth background image data in accordance with the shift amount is a defective pixel having an abnormal value by comparing the fifth background image data with the third background image data.