Image reading apparatus
地域：
Nagoya
摘要
An image reading apparatus, having a conveyer, a sheet tray, an obtaining device, a memory, a determining device, and a controller, is provided. The controller determines whether information concerning pixels in the memory indicates edge positions or edge absence in in read-image data concerning a sheet, detects an upstream leading-end position and a downstream leading-end position, detects upstream continuing pixels and downstream continuing pixels, detects an upstream lateral-end position and a downstream lateral-end position, calculates a line representing an upper end of the sheet based on the upstream leading-end position and the downstream leading-end position, calculates an upstream corner position and a downstream corner position based on the upstream and downstream lateral-end positions and the line representing the upper end of the sheet, and calculates a width of the sheet based on the upstream corner position and the downstream corner position.
說(shuō)明書(shū)
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This application claims priority from Japanese Patent Application No. 2017-189935, filed on Sep. 29, 2017, the entire subject matter of which is incorporated herein by reference.
An aspect of the present disclosure is related to an image reading apparatus.
權(quán)利要求
What is claimed is:1. An image reading apparatus, comprising:a conveyer configured to convey a sheet to be read downstream along a sub-scanning direction; a sheet tray configured to support the sheet at a position on a supporting surface with reference to a central position located at a center of the supporting surface in a main-scanning direction, the main-scanning direction intersecting orthogonally with the sub-scanning direction; an obtaining device including a line sensor, the line sensor comprising a plurality of sensor components aligning in line along the main-scanning direction, the plurality of sensor components including a foremost sensor component located at a most upstream position in the line along the main-scanning direction and a rearmost sensor component located at a most downstream position in the line along the main-scanning direction, each sensor component being configured to read an image element corresponding to a pixel on the sheet, the line sensor being configured to read a plurality of lines of images extending along the main-scanning direction on the sheet being conveyed from the sheet tray downstream in the sub-scanning direction, the obtaining device being configured to obtain read-image data including image data of the plurality of lines of images read by the line sensor, a memory; a determining device configured to:determine edge positions contained in a predetermined area defined by a main-scanning range and a sub-scanning range in the read-image data and store information concerning pixels in the predetermined area indicating the edge positions in a storage area in the memory, the main-scanning range being a range of pixels in the read-image data aligning along the main-scanning direction between a foremost pixel position, which is a position of pixels read by the foremost sensor component, and a rearmost pixel position, which is a position of pixels read by the rearmost sensor component, the sub-scanning range being a range of pixels in the read-image data aligning along the sub-scanning direction between an upstream pixel position, which is a position of pixels in a most upstream line among the plurality of lines of images, and a pixel position of another line of pixels, which are apart downstream in the sub-scanning direction from the upstream pixel position for a first predetermined distance, the determining device being configured to search for edges of the sheet through the pixels in the predetermined area in the read-image data from the upstream pixel position downstream along the sub-scanning direction at each pixel position in the main-scanning direction, and the determining device being configured to save the pixel position in the main-scanning direction in the storage area in the memory as the information indicating the edge position if colors in the pixels within the sub-scanning range in the read-image data shifted from white to black along the sub-scanning direction for a first time at the pixel position in the main-scanning direction, and the determining device being configured to save information indicating edge absence in the storage area in the memory if the colors in the pixels within the sub-scanning range in the read-image data do not shift from white to black at the pixel position in the main-scanning direction; and a controller configured to:examine the information concerning the pixels stored in the storage area in the memory along the main-scanning direction consecutively upstream from a central pixel position, which is a position of pixels read by a central sensor component among the plurality of sensor components located at the central position, to the foremost pixel position and determine whether the information concerning each of the examined pixels indicates the edge position or edge absence; detect a pixel position, which is farthest upstream from the central pixel position along the main-scanning direction and of which information concerning the pixel in the storage area in the memory is determined to indicate the edge position, as an upstream leading-end position, among the pixel positions within a range along the main-scanning direction between the central pixel position and an upstream no-edge pixel position, which is upstream from the central pixel position in the main-scanning direction and of which information concerning the pixel in the storage area in the memory is determined to indicate edge absence; examine the information concerning the pixels stored in the storage area in the memory along the main-scanning direction consecutively downstream from the central pixel position to the rearmost pixel position and determine whether the information concerning each of the examined pixels indicates the edge position or edge absence; detect a pixel position, which is farthest downstream from the central pixel position along the main-scanning direction and of which information concerning the pixel in the storage area in the memory is determined to indicate the edge position, as a downstream leading-end position, among the pixel positions within a range along the main-scanning direction between the central pixel position and a downstream no-edge pixel position, which is downstream from the central pixel position in the main-scanning direction and of which information concerning the pixel in the storage area in the memory is determined to indicate edge absence; detect pixel positions, of which information concerning the pixels in the storage area in the memory is determined to indicate the edge positions sequentially, as upstream continuing pixel positions, among the pixel positions within a range along the main-scanning direction between the upstream no-edge pixel position and the foremost pixel position; detect a pixel position, which is farthest from the central pixel position along the main-scanning direction, among the upstream continuing pixel positions as an upstream lateral-end position; detect pixel positions, of which information concerning the pixels in the storage area in the memory is determined to indicate the edge positions sequentially, as downstream continuing pixel positions, among the pixel positions within a range along the main-scanning direction between the downstream no-edge pixel position and the rearmost pixel position; detect a pixel position, which is farthest from the central pixel position along the main-scanning direction, among the downstream continuing pixel positions as a downstream lateral-end position; calculate a line representing an upper end of the sheet based on the upstream leading-end position and the downstream leading-end position; calculate an upstream corner position based on the upstream lateral-end position and the line representing the upper end of the sheet; calculate a downstream corner position based on the downstream lateral-end position and the line representing the upper end of the sheet; and calculate a width of the sheet in the main-scanning direction based on the upstream corner position and the downstream corner position. 2. The image reading apparatus according to claim 1 ,wherein, for determining whether the information concerning the pixels between the central pixel position and the foremost pixel position indicates the edge positions or edge absence, the controller is configured to examine the information concerning the pixels stored in the storage area in the memory consecutively along the main-scanning direction upstream from the central pixel position to the foremost pixel position at an interval of a second predetermined distance; wherein, for detecting the upstream leading-end position, the controller is configured to:examine the information concerning the pixels stored in the storage area in the memory downstream along the main-scanning direction from the upstream no-edge pixel position toward the central pixel position sequentially for each pixel position in the range along the main-scanning direction between the central pixel position and the upstream no-edge pixel position and determine whether the information concerning the examined pixels in the storage area in the memory indicates the edge positions or edge absence; and detect the pixel position, of which information concerning the pixel is in the storage area in the memory is determined to indicate the edge position for a first time in sequential determinations along the main-scanning direction in the range from the upstream no-edge pixel position toward the central position, as the upstream leading-end position; wherein, for determining whether the information concerning the pixels between the central pixel position and the rearmost pixel position indicates the edge positions or edge absence, the controller is configured to examine the information concerning the pixels stored in the storage area in the memory consecutively along the main-scanning direction downstream from the central pixel position to the rearmost pixel position at the interval of the second predetermined distance; wherein, for detecting the downstream leading-end position, the controller is configured to:examine the information concerning the pixels stored in the storage area in the memory upstream along the main-scanning direction from the downstream no-edge pixel position toward the central pixel position sequentially for each pixel position in the range along the main-scanning direction between the central pixel position and the downstream no-edge pixel position and determine whether the information concerning the examined pixels in the storage area in the memory indicates the edge positions or edge absence; and detect the pixel position, of which information concerning the pixel is in the storage area in the memory is determined to indicate the edge position for a first time in sequential determinations along the main-scanning direction in the range from the downstream no-edge pixel position toward the central position, as the downstream leading-end position. 3. The image reading apparatus according to claim 2 ,wherein, for detecting the upstream continuing pixel positions, the controller is configured to:add a value 1 to an upstream continuity count value if the information concerning the examined pixel in the storage area in the memory is determined to indicate the edge position; set a value “0” to the upstream continuity count value if the information concerning the examined pixel in the storage area in the memory is determined to indicate edge absence; and detect the pixel position, of which information concerning the examined pixel in the storage area in the memory caused the upstream continuity count value to be greater than or equal to “3,” as the upstream continuing pixel position; and wherein, for detecting the downstream continuing pixel positions, the controller is configured to:add a value 1 to a downstream continuity count value if the information concerning the examined pixel in the storage area in the memory is determined to indicate the edge position; set a value “0” to the downstream continuity count value if the information concerning the examined pixel in the storage area in the memory is determined to indicate edge absence; and detect the pixel position, of which information concerning the examined pixel in the storage area in the memory caused the downstream continuity count value to be greater than or equal to “3,” as the downstream continuing pixel position. 4. The image reading apparatus according to claim 3 ,wherein the controller is configured to detect the upstream leading-end position as the upstream lateral-end position if, after detecting the upstream leading-end position, the controller failed to detect the upstream continuity pixel position; and wherein the controller is configured to detect the downstream leading-end position as the downstream lateral-end position if, after detecting the downstream leading-end position, the controller failed to detect the downstream continuity pixel position. 5. The image reading apparatus according to claim 1 ,wherein, for calculating the line representing the upper end of the sheet, the controller is configured to:calculate a sample variance value among all of inclinations in lines, each extending through two adjoining pixel positions among a plurality of pixel positions between the upstream leading-end position and the downstream leading-end position, based on which the line representing the upper end of the sheet is calculated, as a variance value; calculate the line representing the upper end of the sheet based on the edge positions at pixel positions between the central pixel position and the downstream leading-end position if the variance value is greater than a predetermined value and if the line representing the upper end of the sheet extends toward downstream along the main-scanning direction and toward downstream along the sub-scanning direction; calculate the line representing the upper end of the sheet based on the edge positions at pixel positions between the central pixel position and the upstream leading-end position if the variance value is greater than the predetermined value and if the line representing the upper end of the sheet extends toward downstream along the main-scanning direction and toward upstream along the sub-scanning direction; and calculate the line representing the upper end of the sheet based on the edge positions at pixel positions between the upstream leading-end position and the downstream leading-end position if the variance value is smaller than or equal to the predetermined value. 6. The image reading apparatus according to claim 1 ,wherein, for calculating the upstream corner position, the controller is configured to calculate an upstream perpendicular line extending orthogonally to the line representing the upper end of the sheet and through the upstream lateral-end position and calculates a position of an intersection between the calculated upstream perpendicular line and the line representing the upper end of the sheet as the upstream corner position; and wherein, for calculating the downstream corner position, the controller is configured to calculate a downstream perpendicular line extending orthogonally to the line representing the upper end of the sheet and through the downstream lateral-end position and calculates a position of an intersection between the calculated downstream perpendicular line and the line representing the upper end of the sheet as the downstream corner position. 7. The image reading apparatus according to claim 1 ,wherein, in order to calculate the width of the sheet in the main-scanning direction, the controller is configured to calculate a distance between the upstream corner position and the downstream corner position as the width of the sheet. 8. The image reading apparatus according to claim 1 ,wherein, for calculating the upper end of the sheet, the controller is configured to calculate the line representing the upper end of the sheet by applying the least square method to the edge positions located between the upstream leading-end position and the downstream leading-end position.
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