JP4354443B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads an image of an original, and more particularly, to a technique for detecting the size of an original to be read.

Conventionally, the detection of the document size in an image reading apparatus such as a copying machine, a scanner, or a facsimile is performed when a document is placed on the platen glass. This is done using a sensor that detects the presence or absence of a document at a predetermined position above. When the placed document is pulled in by the sheet feeder, the document size in the main scanning direction is detected by detecting the position of the document guide plate, and the document size in the sub scanning direction is detected at the head in the sub scanning direction. And it was done using a sensor that detects when the tail passes.
JP-A-10-010651 JP-A-10-090807 Japanese Patent Application Laid-Open No. 08-083033

  However, in the prior art, it is necessary to provide the image reading apparatus with special hardware for detecting the document size in order to detect the document size, such as a sensor, which increases the cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image reading apparatus that can detect the document size without providing hardware such as a sensor for detecting the document size.

The invention according to claim 1 comprises reading means for reading an image from the document for each main scanning line;
A pattern image provided with a predetermined image provided on the back side of the document at the document reading position of the reading unit;
Comparison data storage means for storing image data of the pattern image as comparison data;
Each pixel of the comparison data stored in the comparison data storage means, and the pixels of the image data for each main scanning line read by the reading means at the position in the main scanning direction that coincides with the pixels, and positions before and after the pixels A difference calculation unit for calculating each difference from a predetermined number of pixels and a difference between the corresponding pixels calculated by the difference calculation unit for each main scanning line is determined in advance. A first coincidence determination unit that determines whether or not the corresponding pixels match when the difference is within a predetermined value, and the predetermined match determination unit A predetermined number of determination results for each main scanning line by the first coincidence determination unit for each pixel of the comparison data for which the difference is calculated by the difference calculation unit with respect to pixels having a predetermined number of pixels. Only match The image data at the position in the main scanning direction where the pixels of the comparison data coincide with the pixels of the comparison data when it is determined that the predetermined number matches. A second coincidence determining unit that determines that the pixel of the comparison data matches the pixel of the original data, and the number of pixels determined by the second match determination unit that the pixel of the comparison data matches the pixel of the document data has reached a predetermined number If the image data of the main scanning line matches the comparison data, the boundary between the matching main scanning line and the non-matching main scanning line is determined in the sub-scanning direction of the image data of the document. A sub-scanning direction end position determination unit having an end position determination unit that determines the end position;
The image reading apparatus includes: a size calculating unit that obtains the size of the document based on the end position in the sub-scanning direction determined by the sub-scanning direction end position determining unit.

According to this configuration, the image data is read for each main scanning line from the document and the background by the reading unit, and the image data of the read main scanning line and the image data of the pattern image stored in the comparison data storage unit Are compared by the sub-scanning direction end position determining means, and the boundary between the main scanning line having a high coincidence and the main scanning line having a low coincidence is sub-scanning the image data of the document to be read. It is determined as the end position in the direction.

Further , according to this configuration, the difference calculation unit calculates a difference between one pixel of the comparison data and a plurality of pixels in the image data for each main scanning line of the document, and the first match determination unit includes: Among the plurality of differences, when the predetermined number is within a predetermined value, it is determined that the two pixels match, so the pixel position of the pattern image or the image data of the document is slightly inaccurate. Even when the document is read, the accurate document size can be detected.

The invention according to claim 2 is the image reading apparatus according to claim 1 , wherein the difference calculation unit calculates a difference only for pixels every predetermined number of pixels in the main scanning direction of the comparison data. This is the target pixel.

  According to this configuration, since the number of pixels that are subjected to difference calculation by the difference calculation unit is small, the document size can be detected more quickly.

The invention according to claim 3 is the image reading apparatus according to claim 1 or 2 , wherein a lattice pattern is used as the pattern image.

  In this configuration, by using a lattice pattern as a pattern image, it is easy to determine the boundary between the image formed on the original and the image formed on the back surface.

A fourth aspect of the present invention is the image reading apparatus according to any one of the first to third aspects, wherein a low-density image is used as the pattern image formed on the back surface.

  In this configuration, by using a low-density image as the pattern image, the pattern image is prevented from being seen through the original, and the occurrence of show-through during reading of the image from the original is reduced.

A fifth aspect of the present invention is the image reading apparatus according to any one of the first to fourth aspects, wherein the main scanning line image data read by the reading unit and the comparison data storage unit store the image data. The comparison data is compared with each other to obtain the degree of coincidence at each position of the main scanning line, and the boundary between the high coincidence area and the low coincidence area is the original in the main scanning direction of the image data of the original. An end position determining means for determining the end position of the main scanning direction,
The size calculating means obtains the size of the document based on the edge positions in the sub-scanning direction and main scanning direction of the document determined by the sub-scanning direction edge position determining means and the main scanning direction edge position determining means. It is.

  According to this configuration, the image data of the document read by the reading unit and the background data of the pattern image stored in advance in the comparison data storage unit are compared by the main scanning direction end position determining unit, and the main scanning is performed. The boundary between the high coincidence area and the low coincidence area at each line position is determined as the end position of the original in the main scanning direction of the image data of the original. Then, based on the edge position of the document in the main scanning direction and the edge position of the document in the sub-scanning direction determined by the sub-scanning direction edge position determination unit, the size of the document is obtained by the size calculating unit.

According to the first aspect of the invention, since the document size in the sub-scanning direction can be detected without providing hardware such as a sensor for detecting the document size, the document size can be detected at a low cost. Further, the size detection is not performed at a single point as in the conventional document size detection using a sensor, but size detection is performed using image data on a line extending in the main scanning direction. Even different documents can be accurately detected in size. Thereby, for example, even when documents of different sizes are mixedly placed on the automatic document feeder, the sizes of the respective documents can be accurately detected.

Furthermore, according to the first aspect of the present invention, the document size in the sub-scanning direction can be accurately detected even when the pixel position of the pattern image or the image data of the document is read slightly inaccurately. .

According to the second aspect of the present invention, since the number of pixels that are subjected to difference calculation by the difference calculation unit is small, the document size can be detected more quickly.

According to the third aspect of the present invention, since the lattice pattern is used as the pattern image, it is easy to determine the boundary between the image formed on the original and the image formed on the back surface.

According to the fourth aspect of the present invention, since a low-density image is used as the pattern image, the pattern image is prevented from being seen through the original, and the occurrence of show-through when the image is read from the original is reduced. Can do.

According to the fifth aspect of the present invention, the end position of the document in the main scanning direction determined by the main scanning direction end position determination unit and the end of the document in the sub scanning direction determined by the sub scanning direction end position determination unit. Based on the position, document size detection in the main scanning direction and the sub-scanning direction can be performed with an inexpensive configuration without providing hardware such as a sensor for detecting the document size.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a mechanical schematic configuration of a sheet feeder portion of an image reading apparatus according to an embodiment of the present invention. The image reading apparatus is applied to, for example, a copying machine, a scanner, a facsimile machine, or a multifunction machine having both functions. The documents 112 are placed with the reading surface facing down, and conveyed one by one in the direction of arrow A by a document drawing mechanism (not shown) of the sheet feeder. A reading sensor 113 that reads an image of the original is provided at a position corresponding to the lower part of the original drawn by the original drawing mechanism. The reading sensor 113 is composed of a CCD (charge coupled device) or the like, and can read, for example, one scanning line in the main scanning direction of the document. The reading sensor 113 reads the entire surface of the document by repeating reading of one scanning line in the main scanning direction with respect to the document 112 to be pulled in all scanning lines. In the sheet feeder, a predetermined pattern image 114 is drawn on a portion 111 on the back side of the document with respect to the reading sensor 113 and read by the reading sensor 113 when the document is not placed. The pattern image 114 is preferably not a show-through on the original and has a clear boundary with the original for all types of original images. For example, the pattern image 114 is a low-density pattern, a lattice pattern, or a low-density lattice pattern. In the present embodiment, the pattern image 114 is assumed to be composed of a low-density lattice pattern. When the document is transported, the reading sensor 113 reads an image on the surface of the document and also reads a pattern image 114 in the outer region of the recording paper in a direction orthogonal to the document transport direction. The reading sensor 113 reads the pattern image 114 before and after the document is conveyed.

  Next, the functional configuration of the scanner 1 as an embodiment of the image reading apparatus according to the present invention will be described. FIG. 2 is a block diagram illustrating a functional configuration of the scanner 1. The scanner 1 includes an image reading unit 11, a comparison data storage unit 13, a document edge position determination unit 14, and a size calculation unit 15 as functional units. Here, the description about the output of the image data of the scanner 1 is omitted.

  The image reading unit 11 reads an image from a document. The mechanical configuration of the image reading unit 11 corresponds to the sheet feeder portion of the image reading apparatus shown in FIG.

  The comparison data storage unit 13 stores in advance the back pattern image read by the reading sensor 113 when no document is placed. The comparison data storage unit 13 is composed of, for example, a RAM. In the comparison data storage unit 13, the pattern image on the back side is read and stored immediately before the image reading unit 11 reads the document data. The pattern image reading time is an arbitrary time before reading the original data, for example, when the original reading start button (not shown) of the scanner 1 is pressed. The pattern image stored in the comparison data storage unit 13 is image data when the image of the document is read (this image data includes the image of the document and the background pattern image around it). Is used to detect the outer edge position of the document in the main scanning direction and the sub-scanning direction.

  For example, (1) from which scanning line of a plurality of main scanning lines arranged in the sub-scanning direction to which scanning line of the document edge position determination unit 14 in the document. (2) By determining whether or not each pixel in one scanning line in a predetermined main scanning direction is in the document, the position of the edge of the document in the sub-scanning direction and the main scanning direction is determined. . Details of the configuration and processing of the document edge position determination unit 14 will be described later.

The size calculation unit 15 obtains the size of the document in the sub-scanning direction and the main scanning direction based on the document end position determined by the document end position determination unit 14. The size calculation unit 15 subtracts the number of pixels outside the both end positions in the main scanning direction determined by the document end position determination unit 14 from the total number of read pixels in the main scanning direction read by the reading sensor 113 (that is, The length obtained by multiplying the number of pixels in the main scanning direction of the document by the length in the main scanning direction occupied by one pixel is calculated as the document size x in the main scanning direction. Further, the size calculation unit 15 subtracts the number of pixels outside the both end positions in the sub-scanning direction determined by the document end position determination unit 14 from the total number of read pixels in the sub-scanning direction read by the reading sensor 113. A length obtained by multiplying (that is, the number of pixels in the sub-scanning direction of the document) by the length in the sub-scanning direction occupied by one pixel is calculated as a document size y in the sub-scanning direction.

  Next, the configuration and processing details of the document edge position determination unit 14 will be described. Based on FIG. 2, the document end position determining unit 14 includes a difference calculating unit 141, a first match determining unit 142, a second match determining unit 143, and an end position determining unit 144.

  The difference calculation unit 141 is a pixel value between the pixels constituting the comparison source data stored in the comparison data storage unit 13 and the pixels of each main scanning line data read by the image reading unit 11 corresponding to the pixels. Is calculated. The difference calculation unit 141 calculates a difference from a plurality of comparison target pixels for one comparison source pixel. Hereinafter, a group of comparison target pixels that are differences calculation targets for one comparison source pixel is referred to as a block.

  The first match determination unit 142 determines whether or not each difference obtained by the difference calculation unit 141 is equal to or less than a threshold (for example, if the pixel value is expressed by a value in the range of monochrome data 0 to 255). , 9 or less), and if the difference is less than or equal to the threshold value, it is determined that the comparison source pixel and the comparison destination pixel match, and if the difference is greater than the threshold value, It is determined that there is a mismatch with the comparison target pixel.

  The second match determination unit 143 determines a match with the comparison target data for each comparison source pixel. The second match determination unit 143 determines that the comparison source pixel and the comparison destination data match if there is at least one match in the match determination result by the first match determination unit 142 for all the pixels in the block. . In addition, when there is no match in the block, the second match determination unit 143 determines that the comparison source pixel and the comparison destination data do not match.

  The end position determination unit 144 determines the end position of the document in the sub-scanning direction and the main scanning direction. When determining the document end position in the sub-scanning direction, the end position determination unit 144 counts the number of consecutive comparison source pixels determined to be inconsistent by the determination of the second match determination unit 143, and compares the comparison source pixels that do not match. If the continuous number does not reach a predetermined number set in advance (= appropriately set threshold: for example, a value indicating, for example, 25 to 30% of the total number of pixels in the main scanning line of the image reading unit 11) It is determined that the main scanning line matches the pattern image. Also, the end position determination unit 144 determines that the main scanning line does not match the pattern image when the number of consecutive comparison source pixels that do not match has reached the predetermined number. Based on the determination result, the end position determination unit 144 determines the boundary between the mismatched main scan line and the matched main scan line as the end position in the sub-scanning direction of the document image data.

  When determining the document end position in the main scanning direction, the end position determination unit 144 determines that the mismatch in the block match determination result of the second match determination unit 143 continues in the direction from the outside of the scan line to the inside of the document. When the predetermined number (= threshold value set as appropriate: for example, a value indicating, for example, 25 to 30% of the total number of pixels in the main scanning line of the image reading unit 11) is reached, the continuous start pixel is set in the main scanning direction. Is determined to be a pixel at the original start position in the image, and a predetermined number of coincidence in the direction from the inside of the original of the scanning line to the outside of the original (= threshold value set as appropriate: for example, data acquired by reading by the image reading unit 11 And the comparison data stored in the comparison data storage unit 13, a value indicating the number of pixels having the minimum width (main scanning direction) that can be properly verified (details will be described later). 1 of The previous pixel is determined as the pixel at the document end position in the main scanning direction.

  An outline of image reading processing by the scanner 1 will be described. FIG. 3 is a flowchart showing an outline of image reading processing by the scanner 1. When the image reading unit 11 reads the document and its peripheral image for each main scanning line (S1), the image processing unit (not shown) inputs input data such as scanner correction and shading correction for the read image data. The normalization process is performed (S2).

  Then, based on the image data that has undergone this normalization processing, the document end position determination unit 14 starts detecting the document start position and end position in the sub-scanning direction and the main scanning direction, and generates an effective section (S3). ). The image data read by the image reading unit 11 from the time when the document end position determination unit 14 detects the effective section start position in the sub-scanning direction and the main scanning direction in S3 is stored in the memory as image data in the effective section. It starts (S4). While the image data is stored in the memory, the document end position determination unit 14 continues the document end position detection process in the sub-scanning direction and the main scanning direction.

  When the effective section end position in the main scanning direction is detected, the data up to the detected effective section end position is stored in the memory for the data in the main scanning direction. When the document end position determination unit 14 detects the end position of the effective section in the sub-scanning direction, data up to the main scanning line that is the effective section end position in the sub-scanning direction is stored in the memory. Up to this point, the image data has been taken into the memory. The size calculator 15 calculates the document size from the detected effective section.

  As described above, since the reading of the original image data, the reading of the original image data into the memory, and the detection of the effective original section have been completed when the acquisition of the image data into the memory is completed, the control unit of the scanner 1 (Not shown) reads out data from the memory, the image processing unit (not shown) performs image processing according to the detected effective section information, and then outputs the data as scanner data to a personal computer or the like. If it is applied to the image forming apparatus, it is output to the image forming unit as print target data (S5).

  The flow of the edge position determination process in the sub-scanning direction and main scanning direction of the document will be described. 4 to 6 are flowcharts showing the flow of edge position determination processing in the sub-scanning direction and main-scanning direction of the document.

  When the image reading start button of the scanner 1 is depressed by the operator (S11), the image reading unit 11 reads the pattern image 114 and acquires comparison data (S12), and the acquired comparison data is stored in the comparison data storage unit 13. Remembered. The document transport mechanism of the copying machine starts transporting the document to the document reading position of the image reading unit 11 (position where the reading sensor 113 is disposed) (S13).

  From here, the process of detecting the leading edge position of the document in the sub-scanning direction is started. The reading sensor 113 of the image reading unit 11 starts reading data of an image for one scanning line in the main scanning direction (S14). The image reading by the image reading unit 11 starts from a time before the time when the document is assumed to reach the reading position of the reading sensor 113. At this time, the end position determination unit 144 initializes the counter value N of the counter that counts the number of consecutive non-matching pixels when the comparison data (pattern image) and the read data by the image reading unit 11 are compared. .

  During reading by the image reading unit 11, the document end position determination unit 14 determines whether or not the image data acquired by the reading matches the comparison data stored in the comparison data storage unit 13. Perform (S15).

  Here, the document edge position determination process by the document edge position determination unit 14 will be described. FIG. 7 is a diagram showing a circuit configuration example of the document end position determination unit 14, and FIG. 8 is a diagram schematically showing a state of document end position determination processing by the document end position determination unit 14.

  When one pixel constituting the image data of the main scanning line read by the image reading unit 11 is input from the image reading unit 11 to the document end position determination unit 14 as a comparison destination pixel, the comparison data storage unit 13 Also, the pixel serving as the comparison source data is input to the document edge position determination unit 14 as the comparison source pixel. Then, a difference between the two is calculated by a subtractor (functioning as a difference calculation unit 141) 1411a, and the calculated difference is stored in the threshold value storage memory 16 by a comparison circuit (functioning as the first match determination unit 142) 1421a. It is determined whether it is below a predetermined threshold value (described above).

  Subsequently, the pixel of the next new comparison source data is input from the comparison data storage unit 13 to the document end position determination unit 14, and the pixel as the next new comparison destination data is input from the image reading unit 11 to the document end position determination unit. 14, difference calculation and comparison with the threshold value of the difference are performed, but the previous comparison source pixel is continuously compared with the newly input comparison by the subtractor 1411 b, flip-flop 1412 b, and comparison circuit 1421 b. Difference calculation with the previous pixel and comparison with the threshold value of the difference are performed. That is, once the comparison source pixel is input to the document edge position determination unit 14, the difference between the flip-flops 1412a to 1412e and the new comparison destination pixels input one after another is calculated by the subtracters 1411a to 1411e. And the comparison with the threshold value of the difference is repeated. Thereby, as shown in FIG. 8, one pixel serving as comparison source data is compared with a plurality of pixels (five pixels in the present embodiment) sequentially input as pixels serving as comparison destination data. Difference calculation and comparison with the threshold of the difference are performed.

  In this way, after one comparison source pixel (pattern image data) is determined to match or mismatch with five comparison target pixels (data read by the image reading unit 11), the five comparisons are performed. The result is input to the OR circuit (functioning as the second match determination unit 143) 143a. The OR circuit 143a determines that the pixel of the comparison data matches the pixel of the read data when at least one of the comparison results matches, and if no pixel matches the pixel of the read data, It is determined that the original data does not match.

  If it is determined that the comparison source pixel matches the comparison destination pixel based on the determination result of the document edge position determination processing by the document edge position determination unit 14 (YES in S15), the comparison destination pixel is outside the document. Since there is a high possibility of being an image pixel, the counter value of the counter that counts the number of consecutive mismatched pixels when the comparison data stored in the comparison data storage unit 13 and the read data by the image reading unit 11 are compared. N is cleared (S16). If it is determined that the comparison source pixel does not match the comparison destination pixel (NO in S15), the counter value N is incremented (S17).

  When the comparison between the comparison source pixel and the comparison target pixel is completed for all the pixels constituting the main scanning line data (YES in S18), the end position determination unit 144 determines that the counter value N is a predetermined value (for example, If it is equal to or greater than the total number of pixels of the main scanning line of the image reading unit 11 (for example, a value indicating 25 to 30%) (YES in S19), the data of the main scanning line is image data in the document. It is determined that there is, and the main counter line is stored in the pixel counter 144a as the sub-scanning effective section start position (S20). That is, the end position determination unit 144 determines the boundary between the main scanning line with a high degree of coincidence and the main scanning line with a low degree of coincidence as the leading end position in the sub-scanning direction of the document image data. This completes the detection of the effective section start position in the sub-scanning direction (the document front end position in the sub-scanning direction).

  Note that in S15 described above, in the coincidence determination between the image data acquired by reading and the comparison data, five comparison target pixels (read by the image reading unit 11) with respect to one comparison source pixel (pattern image data). In place of this, instead of this, an average value of a plurality of comparison source pixels (a section composed of the plurality of comparison source pixels is defined as one block), and this The difference between the comparison target pixel and the average value of the same number of comparison target pixels (the section including the plurality of comparison target pixels is defined as one block) is compared with the threshold value, and the comparison source pixel and the comparison target pixel are compared. Match / mismatch is determined for each block. In S19 and S20, the counter value N indicating the number of mismatched blocks is a predetermined value (for example, 25 to 30% of the total number of blocks in the main scanning line of the image reading unit 11). number Or more), it may be determined that the data of the main scanning line is image data in the document.

Thereafter, the document transport mechanism moves the document to the main scanning direction effective section detection position (S21). The main scanning direction effective section detection position is, for example, a position where the reading position of the image reading unit 11 is about 5 mm from the leading end in the sub scanning direction of the document, and is constant after the sub scanning effective section start position is detected in S19. The passage of time is measured by a timer (not shown), and the document transport mechanism moves the document to a position where it is assumed that the leading end in the sub-scanning direction has entered the reading position of the image reading unit 11 by about 5 mm.

  Next, document start and end position detection processing in the main scanning direction will be described. After the document conveyance in S21, the reading sensor 113 of the image reading unit 11 starts reading the image data for one scanning line in the main scanning direction with respect to the document at this position (S31). The end position determination unit 144 initializes a counter value N of a counter that counts the continuous number of mismatched pixels when the comparison data (pattern image) and the read data by the image reading unit 11 are compared.

  During reading by the image reading unit 11, the document end position determination unit 14 determines whether or not the image data acquired by the reading matches the comparison data stored in the comparison data storage unit 13. (S32), and counting the number of consecutive non-matching pixels based on the determination result is performed in the same manner as S15 to S17 (S33, S34).

  After the above counting, when the disagreement continuous count value N becomes equal to or greater than the predetermined value (YES in S35), the end position determination unit 144 positions the first pixel that starts counting the count value N that is equal to or greater than the predetermined value. Is the original start position in the main scanning direction in the main scanning direction, and the coordinates of the position are stored in the pixel counter 144a as the effective section start position in the main scanning direction (S36). Thus, the detection process of the effective section start position in the main scanning direction is completed.

  When the document start position detection process in the main scanning direction is completed, the main scanning direction and the sub-scanning direction are now within the effective section. Therefore, the control unit (not shown) displays the image after this point. The data read by the reading unit 11 is set to be stored in a memory (not shown) (S37). That is, thereafter, the document end position in the main scanning direction is detected together with the reading of the document image and the storage of the read data in the memory.

  Subsequently, the document end position is detected in the main scanning direction, and the end position determination unit 144 counts the continuous number of matching pixels when the comparison data and the read data by the image reading unit 11 are compared. The counter value M is initialized (S38).

  The document edge position determination unit 14 determines whether or not the data acquired by reading by the image reading unit 11 in S31 matches the comparison data stored in the comparison data storage unit 13 (S39). . In this determination, whether or not the comparison source pixel matches the comparison destination pixel is the same as the process of S15, but the value to be left as the counter value M is the continuous number of matching pixels.

  The end position determination unit 144 determines that the counter value M is a predetermined value (for example, the minimum width in which the data acquired by reading by the image reading unit 11 and the comparison data stored in the comparison data storage unit 13 can be properly verified) A value indicating the number of pixels (in the main scanning direction) If the lattice size of the pattern image 114 is 1 mm pitch, if the coincidence can be confirmed with a width of about 3 mm, the data acquired by reading by the image reading unit 11; Since it may be determined that the comparison data stored in the comparison data storage unit 13 matches, in this case, about 50 pixels corresponding to the 3 mm may be set to a predetermined value.) YES), the pixel position immediately before the first pixel that started counting the count value M that has reached the predetermined value or more is set as the document end position in the main scanning direction (see FIG. 8). The position of the coordinate is stored in the pixel counter 144a as an effective section end position in the main scanning direction (S43). This completes the document end position detection process in the main scanning direction. As a result, since the start position and end position of the effective section in the main scanning direction are detected, the control unit (not shown) reads data for each main scanning line read by the image reading unit 11 thereafter. The pixels in the start position and end position of the effective section in the scanning direction are set to be stored in a memory (not shown) (S44).

  Then, in order to read the document data of the next main scanning line and detect the document end position in the sub-scanning direction, the image reading unit 11 reads the next main scanning line (S51). The end position determination unit 144 initializes the counter value N of the continuous number counter of mismatched pixels when the comparison data (pattern image) and the read data by the image reading unit 11 are compared.

  During reading by the image reading unit 11, the document end position determination unit 14 determines whether or not the image data acquired by the reading matches the comparison data stored in the comparison data storage unit 13. This is performed (S52). Counting the number of consecutive non-matching pixels based on the determination result is performed in the same manner as S15 to S17 (S53, S54).

  When the determination of coincidence / non-coincidence is completed for all the pixels constituting the main scanning line data (YES in S55), the end position determining unit 144 determines that the counter value N is a predetermined value (for example, all the pixels of the main scanning line). If it is equal to or smaller than the number (e.g., a value indicating 30% of the number) (YES in S56), it is determined that the data of the main scanning line is image data outside the document, and the pixel counter 144a receives the main scanning. The first scanning line before the line is stored as the sub-scanning effective section end position (S57). That is, the end position determination unit 144 determines the boundary between the main scanning line having a high degree of coincidence and the main scanning line having a low degree of coincidence as the rear end position in the sub-scanning direction of the document image data. This completes the detection of the effective section end position in the sub-scanning direction (the document trailing edge position in the sub-scanning direction).

  Subsequently, the size calculation unit 15 calculates the size of the document read by the image reading unit 11 based on the valid section information in the sub-scanning direction and the main scanning direction calculated as described above (S58). For example, the size calculation unit 15 holds dimension information of a standard size such as A4 size, B5 size, and B4 size (original size x ′ in the main scanning direction × original size y ′ in the sub-scanning direction). As shown in FIG. 5, the document size x ′ in the main scanning direction × the document size y ′ in the sub-scanning direction is larger than the document size x in the main scanning direction × the document size y in the sub-scanning direction obtained as described above. The standard size is determined as the document size (S101 to S103).

  Finally, the control unit (not shown) of the scanner 1 reads data from the memory, and the image processing unit (not shown) performs image processing according to the detected effective section information (S59).

  In this way, it is possible to detect the document size without providing hardware such as a sensor for detecting the document size in the image reading apparatus, and to determine the size of the recording paper suitable for image formation of the document to be read. can do.

  In addition, this invention is not limited to the thing of the said embodiment, The aspect described below can be employ | adopted. In the above embodiment, a low-density grid pattern is used for the pattern image on the back, but it does not show through to the original (that is, low density), and the boundary with the original is easy to understand (that is, the same pattern and color as the original do not easily occur). ) It only needs to be a pattern image, and does not necessarily need to be a low-density lattice pattern. Further, when using a lattice pattern, it is possible to detect the document edge more accurately by using a pattern having a lattice as small as possible.

  Further, in the above-described embodiment, the case where an image is read while pulling the document with the sheet feeder (the document moves and the reading sensor 113 does not move) has been described as an example. However, the document is placed on the platen glass. Even when an image is read (the reading sensor 113 moves without moving the document), the size of the document can be detected by the same method.

  Further, the document size may be detected by using the comparison source data and the comparison destination data in the above embodiment in reverse (that is, the document data is the comparison source data and the comparison data is the comparison destination data).

  In the processing for determining the effective section in the main scanning direction shown in FIGS. 5 and 6, the effective section is determined from the data for one scanning line in the main scanning direction. The effective section in the main scanning direction may be calculated based on the line data. In this way, a more accurate effective section can be obtained.

  In the process of determining the effective section in the main scanning direction shown in FIGS. 5 and 6, all the comparison source pixels are determined to coincide with the comparison target pixel. Only pixels with a predetermined number of pixels (for example, every 5 pixels) may be set as the difference calculation target pixels. Further, based on the result of coincidence / mismatch judgment between one comparison source pixel and a plurality of (5 in the above embodiment) comparison destination pixels, it is determined whether or not the comparison source pixel matches the comparison destination pixel. However, based on the match / mismatch determination result between one comparison source pixel and one comparison destination pixel at the position corresponding thereto, it is determined whether or not the comparison source pixel matches the comparison destination pixel. It may be.

FIG. 3 is a perspective view illustrating a mechanical configuration of a sheet feeder portion of the image reading apparatus according to the embodiment of the present invention. 1 is a block diagram illustrating a functional configuration of an image reading apparatus according to an embodiment of the present invention. It is a flowchart which shows the outline of the image reading process by a scanner. 6 is a flowchart illustrating a flow of edge position determination processing in a sub-scanning direction and a main scanning direction of a document. 6 is a flowchart illustrating a flow of edge position determination processing in a sub-scanning direction and a main scanning direction of a document. 6 is a flowchart illustrating a flow of edge position determination processing in a sub-scanning direction and a main scanning direction of a document. 3 is a diagram illustrating a circuit configuration example of a document edge position determination unit. FIG. FIG. 6 is a diagram schematically illustrating a document edge position determination process performed by a document edge position determination unit. FIG. 10 is a flowchart of recording paper size determination processing.

DESCRIPTION OF SYMBOLS 1 Image reader 11 Image reading part (reading means)
114 Lattice pattern (pattern image)
13 Comparison data storage unit (comparison data storage means)
14 Document edge position determination unit (sub-scanning direction edge position determination means, main scanning direction edge position determination means)
141 Difference calculation unit (difference calculation unit)
142 first match determination unit (first match determination unit)
143 Second match determination unit (second match determination unit)
144 Edge position determination unit (edge position determination unit)
15 Size calculator (size calculator)

Claims (5)

Reading means for reading an image from a document for each main scanning line;
A pattern image provided with a predetermined image provided on the back side of the document at the document reading position of the reading unit;
Comparison data storage means for storing image data of the pattern image as comparison data;
The pixels of the comparison data stored in the comparison data storage means, the pixels of the image data for each main scanning line read by the reading means at the position in the main scanning direction coinciding with the pixels, and the positions before and after the pixels A difference calculation unit for calculating each difference from a predetermined number of pixels and a difference between the corresponding pixels calculated by the difference calculation unit for each main scanning line is determined in advance. A first coincidence determination unit that determines whether or not the corresponding pixels match when the difference is within a predetermined value, and the predetermined match determination unit A predetermined number of determination results for each main scanning line by the first coincidence determination unit for each pixel of the comparison data for which the difference is calculated by the difference calculation unit with respect to pixels having a predetermined number of pixels. Only match The image data at the position in the main scanning direction where the pixels of the comparison data coincide with the pixels of the comparison data when it is determined that the predetermined number matches. A second coincidence determining unit that determines that the pixel of the comparison data matches the pixel of the original data, and the number of pixels determined by the second match determination unit that the pixel of the comparison data matches the pixel of the document data has reached a predetermined number If the image data of the main scanning line matches the comparison data, the boundary between the matching main scanning line and the non-matching main scanning line is determined in the sub-scanning direction of the image data of the document. A sub-scanning direction end position determination unit having an end position determination unit that determines the end position;
An image reading apparatus comprising: a size calculating unit that obtains the size of the document based on the end position in the sub-scanning direction determined by the sub-scanning direction end position determining unit. The image reading apparatus according to claim 1 , wherein the difference calculation unit sets only pixels every predetermined number of pixels in the main scanning direction of the comparison data as pixels for difference calculation. Examples pattern image, the image reading apparatus according to claim 1 or Motomeko 2 using a grid pattern. Examples formed pattern image on the back, the image reading apparatus according to any one of claims 1 to 3 using a low density image. The image data of the main scanning line read by the reading unit and the comparison data stored in the comparison data storage unit are compared to obtain the degree of coincidence at each position of the main scanning line, and the degree of coincidence is high. A main scanning direction end position determining means for determining a boundary of the region having a low coincidence with the region as an end position of the document in the main scanning direction of the image data of the document;
The size calculating means obtains the size of the document based on the position of the document in the sub-scanning direction and the main scanning direction determined by the sub-scanning direction end position determining means and the main scanning direction end position determining means. the image reading apparatus according to any one of claims 1 to 4.

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