Image scanning apparatus, and method and computer-readable medium therefor

A method implementable on a processor coupled with an image scanning apparatus, the image scanning apparatus comprising:

• a document tray;
• an image scanner configured to scan an image of a document sheet being conveyed from the document tray, along a main scanning direction;
• a conveyor configured to convey the document sheet placed on the document tray, in a conveyance direction perpendicular to the main scanning direction;
• a distance detector disposed downstream of the document tray in the conveyance direction and in a particular position in the main scanning direction, the distance detector being configured to output a detection signal having a value corresponding to a distance between the distance detector and a side end of the document sheet being conveyed by the conveyor, the side end being a side of the document sheet that is substantially along the conveyance direction;
• and
• a storage, the method comprising:
• a first determining process of determining whether the value of the detection signal from the distance detector is equal to or more than a first value corresponding to a first particular distance in response to the side end of the document sheet being brought within the first particular distance from the distance detector;
• a first storing process of, when determining that the value of the detection signal from the distance detector is equal to or more than the first value, storing into the storage a first position of the document sheet in the conveyance direction relative to an initial position of the document sheet placed on the document tray, the first position being a position of the document sheet at a point of time when the side end of the document sheet is brought within the first particular distance from the distance detector;
• a second determining process of determining whether the value of the detection signal from the distance detector is equal to or more than a second value corresponding to a second particular distance in response to the side end of the document sheet being brought within the second particular distance from the distance detector, the second particular distance being shorter than the first particular distance;
• a second storing process of, when determining that the value of the detection signal from the distance detector is equal to or more than the second value, storing into the storage a second position of the document sheet in the conveyance direction relative to the initial position, the second position being a position of the document sheet at a point of time when the side end of the document sheet is brought within the second particular distance from the distance detector;
• and
• a skew angle calculating process of calculating a skew angle of the document sheet based on the first position and the second position, the skew angle being an angle, relative to the conveyance direction, of the side end of the document sheet being conveyed by the conveyor.

A non-transitory computer-readable medium storing computer-readable instructions that are executable by a processor coupled with an image scanning apparatus, the image scanning apparatus comprising:

• a document tray;
• an image scanner configured to scan an image of a document sheet being conveyed from the document tray, along a main scanning direction;
• a conveyor configured to convey the document sheet placed on the document tray, in a conveyance direction perpendicular to the main scanning direction;
• at least one distance detector disposed downstream of the document tray in the conveyance direction and in a particular position in the main scanning direction, the at least one distance detector being configured to output a detection signal having a value corresponding to a distance between the at least one distance detector and a side end of the document sheet being conveyed by the conveyor, the side end being a side of the document sheet that is substantially along the conveyance direction;
• and
• a storage, the instructions being configured to, when executed by the processor, cause the processor to perform:
• a first determining process to determine whether the value of the detection signal from the at least one distance detector is equal to or more than a first value corresponding to a first particular distance in response to the side end of the document sheet being brought within the first particular distance from the at least one distance detector;
• a first storing process to, when determining that the value of the detection signal from the at least one distance detector is equal to or more than the first value, store into the storage a first position of the document sheet in the conveyance direction relative to an initial position of the document sheet placed on the document tray, the first position being a position of the document sheet at a point of time when the side end of the document sheet is brought within the first particular distance from the at least one distance detector;
• a second determining process to determine whether the value of the detection signal from the at least one distance detector is equal to or more than a second value corresponding to a second particular distance in response to the side end of the document sheet being brought within the second particular distance from the at least one distance detector, the second particular distance being shorter than the first particular distance;
• a second storing process to, when determining that the value of the detection signal from the at least one distance detector is equal to or more than the second value, store into the storage a second position of the document sheet in the conveyance direction relative to the initial position, the second position being a position of the document sheet at a point of time when the side end of the document sheet is brought within the second particular distance from the at least one distance detector;
• and
• a skew angle calculating process to calculate a skew angle of the document sheet based on the first position and the second position, the skew angle being an angle, relative to the conveyance direction, of the side end of the document sheet being conveyed by the conveyor.