JP4924416B2 - Image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an adverse influence of wrong detection of a document edge on postprocessing using a detection result with respect to an image reader. <P>SOLUTION: A multifunction machine pre-scans a partial area on a document table to read a lower area of a document placed on the document table, converts image data as a read result into edge image data, and extracts an edge point group corresponding to document edges from the edge image data. Further, the extracted edge point group is linearly approximated to estimate a document area of the edge image data. Then the occupation rate of edge points in an area other than the document area of the edge image data is calculated (S610) and when the calculated occupation rate is less than a threshold, it is evaluated that the accuracy of the estimated document area is high (S630), but when the occupation rate exceeds the threshold, it is evaluated that the accuracy is low (S660). Then when it is evaluated that the accuracy is low, it is estimated that the size of the document placed on the document table is a predetermined basic size (S670). <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image reading apparatus that generates image data representing a read image of a document placed on a document table by conveying the reading unit and causing the reading unit to read an image on a document table.

  2. Description of the Related Art Conventionally, an image reading apparatus includes a reading unit below a reading glass, and conveys the reading unit under the reading glass, and causes the reading unit to perform a reading operation when the reading unit is transported, whereby the document placed on the reading glass. An image reading apparatus that generates image data representing a read image of a document is known.

  When the image reading apparatus has a copy function, the generated image data is used for, for example, a printing process. That is, the image data representing the read image is subjected to a printing process, whereby a copy image of the read original is printed on the recording paper. As such an image reading apparatus having a copy function, a digital multifunction peripheral having a printer function, a fax (FAX) function, and the like in addition to a copy function is known.

  In addition, the image reading device grasps the area where the document is placed on the reading glass by pre-scanning, and at the time of the main scanning, the reading area is not the entire area under the reading glass but the area where the document is placed. In this reading area, a reading unit that conveys a reading unit and reads a document is known.

  In addition, an image reading apparatus that detects the size of a document based on the result of reading the document by a reading unit is known. Specifically, there is known a technique for detecting an edge of a document from a reading result and detecting a document size from the detection result (see Patent Documents 1 to 4).

The document size detection result obtained in this way is used, for example, for an automatic setting operation of a reading area at the time of a main scan and an automatic setting operation of a scaling factor at the time of copying. For example, from the detected document size and recording paper size, set the scaling ratio according to the ratio of the document size to the recording paper size, enlarge / reduce the scanned image according to the set scaling ratio, and copy the document For example, an image is printed on a recording paper at a magnification according to the paper size.
JP 2004-201240 A JP 2005-285010 A Japanese Patent Application Laid-Open No. 7-245681 JP 2001-036696 A

  However, the method of detecting the document size based on the result of reading the document by the reading unit has a problem that a ruled line in the document may be erroneously detected as the document edge.

  As a method for detecting a document edge, read image data read by a reading unit is passed through an image filter (so-called differential filter), and the read image data is converted into edge image data representing an edge image. A method for detecting the document edge, which is the outer edge of the document, is known. However, when the scanned image data is passed through an image filter, a continuous pattern of edge points is detected at the outer edge of the document. Even at the point where there is a ruled line, a pattern of continuous edge points similar to the outer edge of the document is detected.

  On the other hand, the document to be read does not necessarily have to be entirely within the readable area of the document table. For example, when the user places the document in a complicated manner, the edge of the document is out of the readable area, or the document to be read is too large, such as a newspaper, and the edge of the document is readable. May not fit in.

  Therefore, if the document edge is detected from the edge image data as a result of reading even though the edge of the document is not read, the document size is erroneously detected. If such an erroneous detection of the document size occurs, for example, a variable magnification setting error occurs and the copy function does not work well.

  The present invention has been made in view of these problems, and an object of the present invention is to suppress an adverse effect on subsequent processing (such as a copying operation) using a detection result due to erroneous detection of an original edge in an image reading apparatus. And

Is made the inventions in order to achieve the above object, carries the reading unit in a transparent document his honor the original to be read is placed, an image caught on the document table, by reading the reading unit, document An image reading apparatus that generates image data representing a read image of a document placed on a table, and includes an extraction unit, an outer edge recognition unit, and an accuracy evaluation unit.

Extraction means, read image data is a result of reading unit and converted into an edge image data representing an edge image, from among the edge image data, the edge points corresponding to the edges of the document placed on the original manuscript platform The edge point group estimated as a group is extracted.

  On the other hand, the outer edge recognizing means recognizes the outer edge of the original by linearly approximating the edge point group corresponding to each side of the original extracted by the extracting means, and the accuracy evaluating means determines the accuracy of the original recognized by the outer edge recognizing means. Based on the distribution of edge points in the edge side area of the document table with respect to the outer edge, the accuracy of the outer edge recognized by the outer edge recognition means is evaluated.

  The configuration of the image reading apparatus is based on information on the outer edge of the original recognized by the outer edge recognition means, estimating the original size, the inclination of the original, and the area on which the original is placed on the original table. In the image reading apparatus having such a configuration, the outer edge recognition unit erroneously recognizes the outer edge of the document. Regardless, if the subsequent process is executed, an error also occurs in the subsequent process, and the process result desired by the user cannot be obtained.

  Therefore, when it is presumed that the outer edge recognition means is misrecognizing, it is preferable to switch the contents of subsequent processing or notify the user that there is a possibility of misrecognition. Since there is no way to determine misrecognition, the subsequent processing is adversely affected.

  Therefore, in the present invention, the accuracy evaluation means is provided, and the accuracy of the outer edge recognized by the outer edge recognition means is determined based on the distribution of the edge points in the edge side area of the document table from the outer edge of the original recognized by the outer edge recognition means. I tried to evaluate.

  In the outer area of the document placed on the document table, there is usually nothing except dust, and if the outer edge of the document is recognized correctly, it will be outside the recognized outer edge. , There should be no edge points. Therefore, if accuracy evaluation is performed as in the present invention, it is possible to evaluate with high accuracy whether or not the outer edge recognized by the outer edge recognition means is accurate.

  As a result, according to the present invention, the content of the subsequent processing can be switched according to the accuracy of the recognition result, the adverse effect of erroneous recognition on the subsequent processing can be suppressed, and an image reading apparatus that is less likely to be dissatisfied by erroneous recognition can be used by the user. Can be provided.

The accuracy evaluation unit described above calculates the amount of edge points distributed in the edge side region of the document table from the outer edge of the document recognized by the outer edge recognition unit, and the calculated amount of edge points exceeds the threshold value. If evaluates the been accuracy of the outer edge is less recognized by the outer margin recognition unit, when the amount of edge points calculated above is equal to or smaller than the threshold, Ru can be configured to evaluate the probable.

The image reading equipment described above can be constructed as follows.
In other words, the image reading apparatus transports the reading unit in a part of the readable area that is an area of the document table that can be read by the reading unit, and causes the reading unit to perform a reading operation in this part of the area. comprising means, extracting means, the image data is a result of reading obtained reading unit by the operation of the pre-scanning means, is converted into an edge image data, from among the edge image data is placed on the original manuscript platform and Ru can be configured to extract the edge point group estimated as edge points corresponding to edges of the document.

  As an image reading apparatus, a configuration in which only a partial area of a document is read and the size of the document is estimated from the read result can be considered, but the outer edge of the document is determined based on image data in which the entire image of the document is not captured. In the case of recognition, the accuracy is inferior to the method of reading the entire original and recognizing the outer edge of the original from the read result.

  Therefore, if the concept of the present invention is applied to such an image reading apparatus, the problem due to misrecognition can be alleviated by switching processing, and a highly convenient image reading apparatus can be provided to the user. it can.

  Also, if the outer edge of the document is recognized by pre-scanning a part of the area, the document size and the like can be estimated more efficiently than the method of pre-scanning the entire readable area and recognizing the outer edge of the document. Therefore, if the present invention is applied to such an image reading apparatus, it is possible to provide the user with an image reading apparatus having a high processing speed and less adverse effects due to malfunction.

In addition, when the image reading apparatus is configured to recognize the outer edge of the document by pre-scanning of a partial area, specifically, the image reading apparatus may be configured as follows.
That is, it is preferable that the document table has a quadrangular shape, and one of the four corners is defined as a position where the corners of the document should be aligned. The part corresponding to the readable area, which is an area from the edge of the document table constituting one side of the document table extending from a specific corner to a position a predetermined distance away from the inside of the document table, is defined as the partial region. in the region, it carries the reading unit, has good when it is in the configuration to execute the reading operation to the reading unit.

  If the image reading apparatus is configured in this manner, the image of the document placed on the document table can be easily captured in the image data as the prescan result, and the outer edge of the document can be accurately grasped from the image data. .

The image reading apparatus estimates the size of the document placed on the document table from the outer edge of the document recognized by the outer edge recognition unit when the accuracy evaluation unit evaluates that the accuracy is high. When accuracy is evaluated as low by the evaluation unit, the size of the document placed on the document table is not good when providing the document size estimation means for estimating that the predetermined size. In particular, it is more preferable that the manuscript size estimation unit is configured to switch the manuscript size estimated to be evaluated as having low accuracy by the accuracy evaluation unit in accordance with a user instruction.

  If the image reading apparatus is configured so that the document size estimation method is switched in this way depending on the level of accuracy evaluated by the accuracy evaluation unit, it is possible to suppress adverse effects on subsequent processing caused by erroneous recognition of the outer edge recognition unit. it can.

  For example, even when the accuracy of the recognition result by the outer edge recognition unit is low, when the document size is estimated based on the recognition result, how the document size estimation unit estimates the document size with respect to the true document size. However, if the accuracy of the recognition result by the outer edge recognition means is low, the document size is not estimated based on the recognition result. Is estimated to be a specific document size, the influence of the estimation result on the subsequent processing can be controlled regardless of whether or not the estimation result matches the true document size.

  Therefore, according to the present invention, regardless of whether or not the document size estimation result is correct, it is possible to suppress the influence of the erroneous recognition of the outer edge recognition means on the subsequent processing. Specifically, when the accuracy of the recognition result of the document outer edge obtained by the pre-scan is low, if the size of the document placed on the document table is estimated to be the maximum size, the image reading that automatically sets the reading area is performed. In the apparatus, it is possible to prevent the reading area at the time of the main scan from becoming narrower than the correct reading area due to erroneous recognition by the outer edge recognition unit. As a result, the entire image of the original desired by the user can be read correctly during the main scan.

  Further, if the image reading apparatus is configured so that the document size estimated by the document size estimation unit can be switched according to the user's instruction when the accuracy evaluation unit evaluates that the accuracy is low, the user is adversely affected by the erroneous recognition. Therefore, the adverse effect on the subsequent processing caused by the erroneous recognition of the outer edge recognition means can be effectively suppressed.

In addition, when recognizing the outer edge of the document by pre-scanning of a partial area, it is preferable to configure the image reading apparatus and estimate the document size as follows.
That is, the extraction means is configured to extract an edge point group estimated as an edge point group corresponding to this side from the edge image data for each of the three sides of the document placed on the document table. The recognizing unit recognizes two intersection points where three straight lines obtained by linear approximation of the edge point group corresponding to each side extracted by the extracting unit are corners of the document placed on the document table. It is good to be configured to do.

Further, when the accuracy evaluation unit evaluates that the accuracy is high, the manuscript size estimation unit assumes that the manuscript placed on the manuscript table is a standard sheet, and the outer edge recognition unit uses the corner of the manuscript. The size of the document placed on the platen is estimated based on the distance between the two intersections recognized as being present, and if the accuracy is evaluated to be low, the accuracy of the document placed on the platen is estimated. size, has good that is in the configuration of estimating that the predetermined size.

  If the image reading apparatus is configured in this manner, both the vertical and horizontal widths of the document can be derived as the document size even from the pre-scan result of the partial area, and the original can be derived from the pre-scan result of the partial area. The outline of the entire document placed on the table can be grasped almost accurately.

  Further, in an image reading apparatus in which a specific corner of the document table is determined as a position where the corner of the document should be aligned and provided with the above-described pre-scanning means, the extraction means and the accuracy evaluation means are specifically described below. It is good to be configured as follows.

In other words, the extracting means calculates an edge point group estimated as an edge point group corresponding to the “side of the document placed on the document table” opposite to the “side of the document table extending from the specific corner on the document table”. being in the configuration to be extracted from the edge image data is good, accuracy evaluating unit mounting "the platen facing the extracted by the extraction means" platen sides extending from said specific angular in platen " The amount of the edge point group in the area of the edge image data corresponding to the area surrounded by the approximate straight line of the edge point group corresponding to “the side of the placed document” and the outer edge of the document table is determined by the outer edge recognition unit. It has good Once the structure is calculated as the amount of the recognized edge points distributed on the document table of the edge region of the outer edge of the document.

  In an image reading apparatus that is set to align a document with a specific corner, the position of the document placed by the user is generally determined on the document table. However, in this case, it is difficult to read the side of the document extending from the corner of the document that matches the specific corner by prescanning.

  That is, the side of the document extending from the corner of the document that is aligned with the specific corner is likely to protrude from the readable area of the document table, and the side cannot be read by pre-scanning. There is a high possibility that edge points other than the sides of the document, such as ruled lines drawn in the document, will be extracted as edge point groups corresponding to the sides of the document.

  Therefore, if the above-described accuracy evaluation means is provided in such an image reading apparatus, “the side of the document placed on the document table” opposite to “the side of the document table extending from the specific corner of the document table”. It is possible to evaluate whether or not the edge point corresponding to is correctly extracted, and as a result, it is possible to correctly evaluate the accuracy of the recognition result of the outer edge recognition means, and minimize the adverse effect on the subsequent processing due to erroneous recognition. It can be done.

  The invention relating to the document size estimation means described above is determined by the reading area determination means for determining the reading area by the reading unit and the reading target area determination means based on the document size information estimated by the document size estimation means. An image reading apparatus comprising: a main scanning unit configured to generate image data representing a read image of a document placed on a document table by conveying the reading unit in the reading region and causing the reading unit to perform a reading operation. Can be applied.

  In the image reading apparatus that performs the main scan in this way, erroneous recognition by the outer edge recognition unit may ultimately have an adverse effect on the setting of the reading area. However, in the present invention, the accuracy of the recognition result of the outer edge recognition unit Is low, the document size is estimated to be a fixed size, so that it is possible to suppress the erroneous recognition of the outer edge recognition means from adversely affecting the setting of the reading area.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1A is a block diagram illustrating the configuration of the digital multifunction peripheral 1 according to the present embodiment. As shown in FIG. 1A, the digital multifunction peripheral 1 of this embodiment includes an image reading unit 10, a reading control unit 20, a printing unit 30, a printing control unit 40, a display operation unit 50, a communication unit 60, a CPU 70, A RAM 80 and a flash memory 90 are provided, and various processes are executed by the CPU 70 based on a program recorded in the flash memory 90 to control the entire apparatus.

  Specifically, the image reading unit 10 is configured as shown in FIGS. FIGS. 1B and 1C are explanatory diagrams showing the configuration of the image reading unit 10. The image reading unit 10 is configured such that a transparent plate-shaped reading glass 11 on which a document P to be read is placed is supported by a housing 13, and the reading is performed below the reading glass 11 in the housing 13. A reading unit 15 that optically reads an image reflected on the glass 11 in the main scanning direction, a conveying mechanism 16 that conveys the reading unit 15 in the sub-scanning direction, and a motor 17 that drives the conveying mechanism 16 are provided.

  The image reading unit 10 drives the transport mechanism 16 by the rotational force of the motor 17 in accordance with a control signal input from the reading control unit 20, thereby causing the reading unit 15 to move under the reading glass 11 in the sub-scanning direction (FIG. 1 ( b) While being conveyed in the direction of the dotted arrow shown in (c), the reading unit 15 is caused to perform a reading operation during conveyance.

  Note that the reading unit 15 is controlled by the reading control unit 20 and, as it moves in the sub-scanning direction, reads an image shown on the reading glass 11 line by line and outputs a line image signal representing the read image. (CIS). The line image signal output from the reading unit 15 is converted into digital data (line image data) by an A / D converter (not shown) and input to the reading control unit 20.

  The image reading unit 10 is provided with a lid (not shown) that can cover the reading glass 11 so as to be openable and closable similarly to a known scanner. When the reading operation by the reading unit 15 is performed, a manual operation by the user is performed. By the operation, the lid is closed so as to be placed on the document placed on the reading glass 11. The inner side of the lid facing the reading glass 11 is made of a white member so that the image of the lid does not appear in the read image of the document.

  On the other hand, the reading control unit 20 executes a reading control process in accordance with an instruction from the CPU 70, and controls the movement of the reading unit 15 in the sub-scanning direction and controls the reading operation of the reading unit 15 in the reading control process. To do.

  With this control, the reading control unit 20 causes the reading unit 15 to read an image reflected in the reading area of the reading glass 11 designated by the CPU 70 while conveying the reading unit 15 under the reading glass 11 in the sub-scanning direction. Image data representing an image shown in the reading area of the reading glass is recorded in the RAM 80. By such an operation, image data representing a read image of the document P placed in the reading area of the reading glass 11 is recorded in the RAM 80.

  The reading control unit 20 temporarily stores each line image data input from the image reading unit 10 in a built-in buffer, performs image processing such as shading correction on each line image data, and then executes each line image data. Image data is recorded in the RAM 80.

  In addition, the printing unit 30 conveys a recording sheet placed on a tray (not shown) to a recording position in accordance with a control signal input from the printing control unit 40, and is well-known such as an ink jet method or a laser printer method. In this recording method, an image corresponding to the control signal is formed on the recording paper.

  The print control unit 40 controls the printing unit 30 to form an image on recording paper. In accordance with a command from the CPU 70, an image based on the print target data designated by the CPU 70 is transmitted through the printing unit 30. Print on recording paper.

  The communication unit 60 includes a group of interfaces for communicating with an external device, and includes a USB interface, a LAN interface, a FAX modem, and the like. That is, the multi-function device 1 is configured to be capable of performing FAX communication with an external FAX device through a FAX modem provided in the communication unit 60, and configured to be capable of communicating with an external personal computer through a USB interface or a LAN interface.

  In addition, the display operation unit 50 includes a liquid crystal display (not shown) for displaying information and various operation keys, and is controlled by the CPU 70 to display information for the user on the liquid crystal display. The command from the user input through is input to the CPU 70.

  Further, the CPU 70 realizes a copy function, a FAX function, a scanner function, a printer function, and the like according to a command input through an operation key or a command input from an external personal computer or the like through the communication unit 60 by executing a program. To do.

  For example, when a copy command is input from the user through an operation key provided on the display operation unit 50, the CPU 70 executes a copy control process (see FIG. 3) to control each unit in the apparatus, and on the reading glass 11. The read image of the placed document P is printed on a recording sheet. More specifically, the size of the document P placed on the reading glass 11 is estimated based on the reading result by the reading unit 15, and the scaling ratio is set from the estimated document size and the recording paper size, and the document P The read image is enlarged or reduced to a size suitable for the recording paper size, and this is printed on the recording paper through the printing unit 30 (automatic scaling copying process).

The contents of the copy control process will be specifically described below. Prior to that, the characteristics of the image reading unit 10 of this embodiment will be described with reference to FIG.
FIG. 2 is an explanatory view showing the readable region R0 of the reading glass 11. As shown in FIG. In the multifunction device 1, a reading glass 11 that is a rectangular glass plate is provided so as to close the opening portion in the opening portion of the rectangular housing 13 whose one surface is opened. The periphery of the reading glass 11 is supported by a housing 13.

  The reading glass 11 is provided slightly below the upper surface of the housing 13 from the upper surface of the housing 13, and an area 11 a of the reading glass 11 exposed from the housing 13 (hereinafter, referred to as “original table”). A step is formed at the boundary BD between the casing 13 and the casing 13 so that the original P can be abutted (hereinafter referred to as a portion 13a above the reading glass 11 of the casing 13 (the portion forming the step)). Expressed as “frame”.)

  Further, in the image reading unit 10, due to the relationship between the line width of the reading unit 15 and the size of the document table 11 a, a rectangular region R 0 that is slightly narrower than the entire region of the rectangular document table 11 a is the reading unit 15. Is defined as a readable area R0 where the original can be read. Specifically, the readable area R0 is an area having an outer periphery at a position away from the boundary BD between the frame 13a and the reading glass 11 by a minute amount (3 mm in this embodiment), as indicated by a dotted line in FIG. ing.

  In the image reading unit 10, a mark MK is instructed in the lower left part of the frame 13a to instruct the corner of the document P to abut. In this embodiment, the corner of the document table 11a to which the mark MK is attached is defined as “lower left corner”, and the corner of the document table 11a located at a point farther in the main scanning direction than the lower left corner is defined. The “lower right corner” is defined, and the corner of the document table 11a located at a point away from the lower left corner in the sub-scanning direction is defined as “upper left corner”.

  That is, in the multi-function device 1, the lower left corner of the document table 11a (in other words, the lower left corner inside the frame 13a) is determined as a position where the corner of the document P should be aligned. Under the assumption that the document P is placed in accordance with the mark MK, the document size is estimated and the document copy operation is realized.

  In addition, in the multifunction machine 1 of this embodiment, the lower left corner of the readable area R0 corresponding to the inner lower left corner of the frame 13a with the mark MK is the origin, the main scanning direction is the X axis, and the sub scanning direction is An XY coordinate system (see FIG. 2B) with the Y axis is introduced, and the CPU 70 executes the copy control process shown in FIG. 3 using this XY coordinate system.

  Next, a copy control process executed by the CPU 70 will be described. FIG. 3 is a flowchart showing a copy control process executed by the CPU 70 when a copy command is input through the operation keys.

  When the copy control process is started, the CPU 70 determines whether or not the copy command input through the operation key is an “automatic scaling / tilt correction” copy command (S110), and copies the “automatic scaling / tilt correction”. If it is determined that it is a command (Yes in S110), the automatic zoom copying process shown in FIG. 4 is executed in S120. Thereafter, the copy control process ends.

  On the other hand, if it is determined that the copy command input through the operation key is a copy command other than the “automatic scaling / tilt correction” copy command (for example, a normal copy command without an automatic scaling or tilt correction instruction). In step S130, the CPU 70 executes processing corresponding to the input copy command, and then ends the copy control processing.

Next, the automatic scaling copying process executed by the CPU 70 in S120 will be described. FIG. 4 is a flowchart showing the automatic scaling copying process executed by the CPU 70.
When the CPU 70 starts the automatic scaling copying process in S120, first, the document reading start position is set to the lower end (Y = 0) of the readable area R0, and the document reading end position is predetermined in the design stage. By setting a position (Y = YPRE) that is a predetermined distance away from the lower end of the readable area R0, a part of the readable area R0 corresponding to the area from the original reading start position to the original reading end position is read. The area is set, and the image reading unit 10 is caused to execute a pre-scan operation for the reading area through the reading control unit 20 (S210: tip portion pre-scanning process).

  That is, in S210, the pre-scanning operation is not performed on the entire readable area R0 by the image reading unit 10, but from the lower end of the readable area R0 to a point a predetermined distance away from the readable area R0 (this embodiment). In the example, the image reading unit 10 is caused to perform a pre-scan operation for a point 30 mm away from the lower end of the readable region R0. As a result, the CPU 70 acquires, as a pre-scan result, image data representing the read result of a partial area of the readable area R0 from the image reading unit 10.

  As a pre-scan operation, the image reading unit 10 conveys the reading unit 15 in the sub-scanning direction at a speed corresponding to the pre-scan resolution from the end of the set reading area to the end of the reading area. The image is read by the reading unit 15 and, as a prescan result, low resolution image data (hereinafter referred to as “prescan image data”) is recorded in the RAM 80 through the read control unit 20.

  When the processing in S210 is completed in this way, the CPU 70 performs edge detection processing on the pre-scan image data recorded in the RAM 80, and generates edge image data corresponding to this image data (S215). That is, the prescan image data recorded in the RAM 80 is passed through an image filter for edge detection (a well-known differential filter), and edge image data representing an edge image corresponding to the image data is generated.

  When the process in S215 is completed, the CPU 70 sets the generated edge image data as inspection target data, and executes the document estimation process shown in FIG. 5 (S220). Although details will be described later, in this document estimation process, the inspection object data (edge image data obtained in S215) is analyzed, and the size (vertical width and horizontal width) of the document placed on the document table 11a, and The document inclination angle θ and the document placement area on the document table 11a are estimated.

  Specifically, under the assumption that the document placed on the document table 11a has a square shape, the edge of the document placed on the document table 11a is detected in the inspection target data, and the detection result is used. The document area in the inspection target data is estimated by estimating the lower left corner position and the lower right corner position of the document, and the accuracy of the estimated document area is evaluated from the distribution of edge points in the area outside the document area of the inspection target data.

  When the accuracy of the document area is high, the document is placed on the document table 11a under the assumption that the document placed on the document table 11a is a standard sheet based on the estimated angular position information. The size of the original, the inclination angle θ of the original, and the original placement area on the original table 11a are estimated. However, here, the angle formed by the lower side of the document with respect to the X-axis is the document inclination angle θ (see FIG. 8).

  On the other hand, when the accuracy of the document area is low, or when the document edge cannot be detected normally, it is estimated that the document placed on the document table 11a is a document of a predetermined fixed size. In S220, processing with such contents is executed.

  When the processing in S220 is completed, the CPU 70 causes the printing unit 30 to perform a paper feeding operation through the print control unit 40 (S230), and detects the size of the recording paper that is the target of the paper feeding operation (S230). S235). The size of the recording paper can be detected by a well-known method using, for example, a sensor provided in the recording paper conveyance path.

  When this process is finished, the CPU 70 has made a “failure” determination in S431 (see FIG. 5) or S471 due to the failure of the document edge detection in the immediately preceding document estimation process (S220). It is determined whether or not (S240). If it is determined that the “failure” determination has been made (Yes in S240), the process proceeds to S261. On the other hand, if it is determined that the “failure” determination has not been made in the immediately preceding document estimation process (S220) (No in S240), the process proceeds to S245.

  In S245, it is determined whether or not the “high accuracy” determination is made in the immediately preceding document estimation process (S245). In the document estimation process, as described above, the document size estimation method is switched according to the estimated accuracy of the document area. Here, whether or not the accuracy of the document area is low and the document size is estimated to be a fixed size is determined based on whether or not the “high accuracy” determination is made in the immediately preceding document estimation process.

  When it is determined that the “low accuracy” determination is made (No in S245), the process proceeds to S261. When it is determined that the “high accuracy” determination is made (Yes in S245), the process proceeds to S251.

  In step S251, the CPU 70 sets a scaling ratio according to a predetermined calculation formula based on the document size estimated in step S220 and the recording paper size detected in step S235. Specifically, the scaling factor is set to a magnification corresponding to the ratio between the document size and the recording paper size (for example, recording paper short side length ÷ original short side length), and the copy of the original is performed in the subsequent processing. The image is enlarged (or reduced if the magnification is less than 1) at a magnification corresponding to the ratio of the recording paper size to the document size and printed on the recording paper.

  When this processing is completed, the CPU 70 sets the inclination correction amount of the image data from the original inclination angle θ estimated in S220 (S253). Specifically, the tilt correction amount is set so that the copy image of the document is printed straight on the recording paper without tilting. However, when the estimated document inclination angle θ is a minute amount (in the present embodiment, −0.5 degrees ≦ θ ≦ 0.5 degrees), the inclination correction amount is set to zero in consideration of errors. To do.

  When the processing in S253 is completed, the CPU 70 sets the document reading start position and the document reading end position based on the document placement area information estimated in S220, and sets the document reading start position and the document reading end position. The determined reading area is made to correspond to the document placement area on the document table 11a (S255).

  Specifically, the document reading start position is set to a position corresponding to the end point of the document located on the lowermost side in the sub-scanning direction so that the reading unit 15 can read the entire document placement area. The document reading end position is set to a position corresponding to the end point of the document located on the uppermost side in the sub-scanning direction, and the reading area is made to correspond to the document placement area on the document table 11a. When this process is finished, the process proceeds to S270.

  On the other hand, when proceeding to S261, the CPU 70 sets the scaling ratio to 1 and sets the tilt correction amount to zero so that the copy image of the document is printed on the recording paper at the same magnification (S263). Further, based on the document size information estimated in the immediately preceding document estimation process, the document reading start position and the document reading end position are set, and the reading area defined by the document reading start position and the document reading end position is set on the document table. It is made to correspond to the document placement area in 11a (S265).

  Specifically, in S265, it is assumed that the lower left corner of the document is aligned with the lower left corner of the document table 11a (the lower left corner inside the frame), and the document is correctly placed on the document table 11a. The lower end (Y = 0) of the readable region R0 is set, and the document reading end position is set to a position separated from the estimated lower side of the document from the lower edge of the document table 11a (in other words, the lower side of the frame 13a). Set. In this manner, in S265, the reading area is made to correspond to the document placement area on the document table 11a.

  However, in S265, the reading area does not need to be set larger than the recording paper size in order to realize a copying operation with a scaling factor of 1 in the subsequent processing, so that the recording paper size is smaller than the document size. The reading area may correspond to the recording paper size. In this way, when the processing in S265 is completed, the CPU 70 proceeds to S270.

  In step S <b> 270, the CPU 70 controls the image reading unit 10 through the reading control unit 20 to convey the reading unit 15 to the image reading unit 10 from the document reading start position to the document reading end position in the sub-scanning direction. In addition, during the conveyance, the reading unit 15 performs a reading operation for each line, causes the reading unit 15 to read the image of the set reading area, and image data representing a reading result of the reading area is It is recorded in the RAM 80 (S270).

  When this process is completed, the CPU 70 enlarges or reduces the image data representing the read result recorded in the RAM 80 at a preset magnification, and performs a rotation process for a preset inclination correction amount. Then, the image data representing the read result is converted into image data for printing, and the converted image data is set as print target data (S280). However, if the tilt correction amount is set to zero, the rotation process is not executed in S280.

  When the process in S280 is completed, the CPU 70 executes a print process for the print target data (S290). That is, the printing unit 30 causes the printing unit 30 to print an image based on the print target data on the fed recording paper. Thereafter, the copy control process ends.

  In this way, in the automatic scaling copying process, the document size and the like are estimated based on the prescan result of the partial area in the readable area R0, and the read area at the time of the main scan (when executing S270) is determined based on the result. At the same time, a scaling factor and an inclination correction amount are determined. In particular, when the detection of the document edge fails, or when the accuracy of the document area estimated based on the detected document edge is low, the automatic scaling function is turned off and the copying operation is realized with a scaling factor of 1. In other cases, the automatic scaling function is activated to enlarge or reduce the copy image of the original to a size corresponding to the ratio between the original size and the recording paper size and print it on the recording paper.

Subsequently, the document estimation process executed by the CPU 70 in S220 will be described with reference to FIG. FIG. 5 is a flowchart showing document estimation processing executed by the CPU 70.
When the document estimation process is started, the CPU 70 first sets the variable S to YPRE which is the Y coordinate of the upper end of the pre-scan area (S = YPRE), thereby setting the inspection range in the Y-axis direction to Y = 0. To Y = S = YPRE (S410). When this process ends, the process proceeds to S420, and a right edge detection process is executed. FIG. 6 is a flowchart showing the right edge detection process executed by the CPU 70.

  When the right edge detection process is started, the CPU 70 first sets the sub-scanning direction inspection position Ye to the lower end Y coordinate of the readable area R0 (Ye = 0) in S510, and the main scanning direction inspection position in S515. Xe is set to the right end X coordinate of the readable region R0 (Xe = XMAX). In S515, the variable C is initialized to zero (C = 0). Thereafter, it is determined whether or not the sub-scanning direction inspection position Ye exceeds the inspection range (S520). Specifically, it is determined whether or not Ye> S.

  When determining that the sub-scanning direction inspection position Ye does not exceed the inspection range (No in S520), the CPU 70 determines the inspection position (X, Y) = determined by the main scanning direction inspection position Xe and the sub-scanning direction inspection position Ye = It is determined whether or not the inspection position (Xe, Ye) is an edge point by referring to the pixel value of the inspection target data corresponding to (Xe, Ye) (S525). FIG. 7 is an explanatory diagram showing the configuration of the edge image data, and further showing the locus of the edge point tracked by the right edge detection process. In the example illustrated in FIG. 7, a point with a pixel value “1” corresponds to an edge point.

  If the CPU 70 determines that the inspection position (Xe, Ye) is not an edge point (No in S525), the CPU 70 proceeds to S540 and moves the main scanning direction inspection position Xe by one pixel in the X-axis minus direction. (Xe ← Xe−1), and it is determined whether or not the updated main scanning direction inspection position Xe protrudes from the left end of the readable area R0. Specifically, it is determined whether or not Xe <0 (S543).

  If the CPU 70 determines that the main scanning direction inspection position Xe does not protrude from the left end of the readable region R0 (No in S543), the CPU 70 proceeds to S520, and the sub scanning direction inspection position Ye exceeds the inspection range. If it is determined whether or not (Ye> S) and the sub-scanning direction inspection position Ye does not exceed the inspection range (No in S520), the process proceeds to S525 and the sub-scanning direction inspection position Ye is determined. If it is determined that the value exceeds the inspection range (Yes in S520), the process proceeds to S590.

  On the other hand, in S543, when it is determined that the main scanning direction inspection position Xe protrudes from the left end of the readable area R0 (when it is determined that Xe <0), the CPU 70 proceeds to S547, and the main scanning direction inspection position Xe. Is set to the right end (XMAX) of the readable region R0 (Xe = XMAX), and the sub-scanning direction inspection position Ye is updated to a value obtained by adding 8 to the current value Ye (Ye ← Ye + 8). That is, the sub-scanning direction inspection position Ye is set to a position advanced by 8 pixels in the Y-axis direction. Thereafter, the process proceeds to S520 and the above-described processing is executed.

  If the CPU 70 determines that the inspection position (Xe, Ye) is an edge point (Yes in S525), the CPU 70 proceeds to S530, and the coordinates of the current inspection position (Xe, Ye) are set in the variable (X0, Y0). The value is set (X0 ← Xe, Y0 ← Ye). Further, the variable Y1 is updated to a coordinate value Y1 (= Y0 + 8) advanced by 8 pixels from the coordinate Y = Y0 in the Y-axis direction (S533).

  Thereafter, it is determined whether at least one of the point of coordinates (X0-1, Y1), the point of coordinates (X0, Y1), and the point of coordinates (X0 + 1, Y1) is an edge point (S537). If none of the point of (X0-1, Y1), the point of coordinates (X0, Y1), and the point of coordinates (X0 + 1, Y1) is an edge point (No in S537), the process proceeds to S540. The scanning direction inspection position Xe is updated to a position moved by one pixel in the X axis minus direction (Xe ← Xe−1).

  On the other hand, when it is determined that at least one of the point of coordinates (X0-1, Y1), the point of coordinates (X0, Y1), and the point of coordinates (X0 + 1, Y1) is an edge point (Yes in S537), The process proceeds to S550, where it is determined that the point of coordinates (X0, Y0) is a continuous edge point, and this coordinate (X0, Y0) is temporarily stored as coordinate data of the continuous edge point. .

  When this processing is finished, the CPU 70 proceeds to S560, and at the point of the coordinates (X0-1, Y1), the coordinates (X0, Y1), and the coordinates (X0 + 1, Y1) at the edge point. One of the points is selected according to a predetermined priority.

  Specifically, in the right edge detection process, higher priority is set for coordinates closer to the right end side of the readable area R0. That is, the point of the coordinate (X0 + 1, Y1) close to the right end side of the readable area R0 is set to the priority “high”, the point of the coordinate (X0, Y1) is set to the priority “medium”, and the coordinate (X0− 1, Y1) is set to the priority “small”.

  The priority is set in this way because nothing exists on the platen 11a on the right side from the right end of the document, and there should be no edge point, and an edge point close to the right end side of the readable area R0. This is because there is a higher possibility that the edge point corresponds to the right edge of the document.

  That is, in S560, according to the above priority, the point of the coordinate (X0-1, Y1), the point of the coordinate (X0, Y1), and the point of the coordinate (X0 + 1, Y1) are points that are edge points. To select the point with the highest priority. Then, the variable X0 is updated to the X coordinate of the selected point, and the variable Y0 is updated to the Y coordinate of the selected point. Thereafter, the variable C is updated to a value obtained by adding 1 (S563).

  When this process is finished, the CPU 70 determines whether or not the value of the updated variable C is C = 8. If the CPU 70 determines that C = 8 is not satisfied (No in S567), the process proceeds to S533. The variable Y1 is updated to the Y coordinate of the point advanced by 8 pixels in the Y-axis direction from the coordinate Y = Y0 (Y1 = Y0 + 8). Thereafter, the processing after S537 is executed.

  By executing such processing, the CPU 70 checks whether the edge points are continuous in the Y-axis direction every 8 pixels in the Y-axis direction, as shown in FIG. If it is determined that C = 8 (Yes in S567), the coordinate data of a total of eight points determined as the continuous edge points in the process of S550 that has been repeated eight times is stored in the RAM 80 as the original right edge data. (S570).

  When this process is finished, the CPU 70 proceeds to S580, determines whether or not the sub-scanning direction inspection position Ye exceeds the inspection range (whether or not Ye> S), and performs the sub-scanning direction inspection. If it is determined that the position Ye does not exceed the inspection range (No in S580), the sub-scanning direction inspection position Ye is updated to a position advanced by 64 pixels (S585), and the process proceeds to S515.

  In this way, the CPU 70 repeatedly detects eight consecutive edge points as one set. When the sub-scanning direction detection position Ye exceeds the inspection range (Yes in S520 or Yes in S580), the process proceeds to S590, and the right edge (original document) is selected from the coordinate data group stored as the original right edge data in S570. The edge data representing the right edge of the document) is deleted as a low-accuracy coordinate data group, and the document right edge data is determined.

  Specifically, as shown in FIG. 8, the coordinate data group stored as the document right edge data is clearly continuously located at a position greatly shifted to the document inner area with respect to the coordinate data group having continuity. The inconsistent coordinate data group is removed from the document right edge data to determine the document right edge data. Thereafter, the right edge detection process ends. However, since the process of S590 is a process for improving the document edge detection accuracy, the right edge detection process may be configured not to execute the process of S590.

  In this way, when the right edge detection process is completed, the CPU 70 proceeds to S430, and determines whether or not the right edge detection has failed in the immediately preceding right edge detection process. Specifically, when there is no coordinate data registered as document right edge data in the immediately preceding right edge detection process, it is determined that detection of the right edge has failed, and there is coordinate data registered as document right edge data It is determined that the right edge has been successfully detected.

  However, exceptionally, when the coordinate data registered as the document right edge data is in the vicinity of the left end (Y = 0) of the readable region R0, the coordinate data of the left edge (the edge point representing the left end of the document) is It may be determined that the detection of the right edge has failed even when there is coordinate data registered as the right edge data of the document, assuming that it is erroneously registered as the right edge data of the document.

  Examples of cases where the detection of the right edge fails include a case where the document size is larger than the size of the document table 11a and the right edge of the document protrudes from the document table 11a.

  If the CPU 70 determines that detection of the right edge has failed (Yes in S430), the CPU 70 proceeds to S431 to make a “failure” determination, and also determines the size (length and width) of the document placed on the document table 11a. It is estimated that (width) is the maximum size (size corresponding to the readable area R0) that can be placed on the document table 11a (S433). Then, when this process is finished, the document estimation process is finished. If “failure” determination is made in S431, “Yes” is determined in S240 described above.

  On the other hand, if it is determined in S430 that the right edge has been successfully detected (No in S430), the CPU 70 proceeds to S437 and linearly approximates each point indicated by the document right edge data determined in the right edge detection process. An approximate straight line of the point group indicated by the original right edge data (hereinafter referred to as “right edge approximate straight line”) is calculated.

  When this process is finished, the CPU 70 proceeds to S440 and determines whether or not the right edge approximate straight line is inclined more than a predetermined angle with respect to the Y axis. In this embodiment, specifically, it is determined whether or not the right edge approximate straight line is inclined more than 0.5 degrees with respect to the Y axis.

  If it is determined that the slope of the right edge approximate straight line is equal to or smaller than the predetermined angle (No in S440), the CPU 70 is placed on the document table 11a by being abutted against the inner left lower corner of the frame 13a. 5 and the intersection of the right edge approximate straight line and the lower edge of the document table 11a (in other words, the inner side of the lower side of the frame 13a (hereinafter referred to as “lower frame”)), as shown in the right diagram of FIG. The position of the lower right corner of the document is estimated (S441).

  When this processing is finished, the CPU 70 estimates that the lower left corner position of the document is the point of the lower left corner of the document table 11a (in other words, the inner lower left corner of the frame 13a) (S443), and in the inspection target data An area representing the image of the original (hereinafter referred to as “original area”) is estimated (S445).

  Specifically, in S445, the document area in the inspection target data is estimated from the estimated lower left corner position and lower right corner position on the assumption that the document placed on the document table 11a is square. That is, the area of the inspection target data surrounded by the line segment connecting the lower left corner position and the lower right corner position, the line segment extending from the lower right corner position in the Y axis direction, and the line segment extending from the lower left corner position in the Y axis direction is defined as the document area. Estimate (see FIG. 9B).

  When the process in S445 is completed, the CPU 70 proceeds to S447 and executes the document estimation sub-process shown in FIG. FIG. 9A is a flowchart showing the document estimation sub-process executed by the CPU 70.

  When the document estimation sub-process is started in S447, the CPU 70 first calculates the occupancy rate of the edge points in the area outside the document area of the inspection target data based on the document area information estimated in advance (S610). That is, the occupancy ratio of the edge points in the area outside the document area of the inspection target data is calculated according to the following calculation formula “occupancy ratio = number of edge points outside the document area ÷ total number of pixels outside the document area” (S610). ).

Note that FIG. 9B is a diagram illustrating a specific example of the area of the inspection target data that is handled as being outside the original area in the original estimation sub-process executed in S447.
However, here, as an exception, if an edge point registered as document right edge data is outside the document area, it is not counted as the number of edge points outside the document area. That is, in the document estimation sub-process executed in S447, the “number of edge points outside the document area” includes the number of edge points registered as document right edge data and outside the document area. Make it not exist.

  When this process is finished, the CPU 70 determines whether or not the occupation rate calculated in S610 is equal to or less than a predetermined threshold (for example, 0.05 or less) (S620), and calculates the calculated occupation rate. Is determined to be less than or equal to the threshold value (Yes in S620), it is evaluated that the accuracy of the document area estimated in advance is high, and “high accuracy” is determined (S630). If it is determined in S630 that the “accuracy is high”, the CPU 70 determines Yes in the subsequent S245 described later.

  When this process is completed, the CPU 70 proceeds to S640, where the line segment connecting the pre-estimated lower left corner position and lower right corner position of the original document is the original short side, and the original document placed on the original document table 11a is detected. Assuming that it is a standard sheet, the size of the document placed on the document table 11a and the document placement area on the document table 11a are estimated.

  That is, the estimated length from the lower left corner position to the lower right corner position of the original is estimated as the short side length (horizontal width) of the original, and √2 times the short side length is set to the long side length of the original. Assuming that the document size is estimated based on (vertical width), and the document of the document size is placed on the document table 11a with the estimated lower left corner position and lower right corner position as the base points, the upper left corner of the document The coordinates where the corners and the upper right corner are located are derived, and an area within the quadrilateral formed by connecting these four corners is estimated as the document placement area (S640). Here, the reason why √2 times the original short side length is estimated as the long side length of the original is that the ratio of the short side length to the long side length of the standard paper is 1: √2. This is because.

  When this process is completed, the CPU 70 estimates the inclination angle of the document placed on the document table 11a (S650). Note that in the document estimation sub-process executed in S447, it is assumed that the document is placed on the document table 11a by being exactly abutted against the lower left corner of the document table 11a in the immediately preceding processing (S441, S443). Therefore, in S650, it is estimated that the inclination angle of the document is zero (no inclination) in S650. Thereafter, the document estimation sub-process is terminated.

  On the other hand, if it is determined that the occupation rate calculated in S610 exceeds the threshold (No in S620), the CPU 70 evaluates that the accuracy of the document area estimated in advance is low, and determines that “the accuracy is low” ( S660). If it is determined that the “accuracy is low” in S660, the CPU 70 determines No in the above-described S245, which is a subsequent process.

  By the way, in S660, it is evaluated that the accuracy of the document area is low, as long as the estimated document area is correct, an edge point detected by dust or the like exists outside the document area. This is because there should be no edge points outside.

  In other words, when there are many edge points outside the document area, it is estimated that the erroneous area is confused by the ruled lines drawn on the document placed on the document table 11a. The possibility is high, and there is a high possibility that there is a true original area beyond the estimated original area. Therefore, when the occupation ratio is high, it is evaluated that the accuracy of the document area estimated in advance is low, and “accuracy is low” is determined.

  If the CPU 70 determines that the “accuracy is low” in S660, the process proceeds to S670, and the size of the document placed on the document table 11a is set in advance without using the information of the estimated lower left corner position and lower right corner position. Estimated base size. Thereafter, the document estimation sub-process is terminated.

  The multi-function device 1 according to the present embodiment is configured so that basic size information can be obtained from the user through operation keys in advance as setting information. That is, in S670, it is estimated that the size of the document placed on the document table 11a is a basic size document specified in advance by the user. However, in a situation where it is determined that “the accuracy is low” in S660, the size of the document placed on the document table 11a is likely to be larger than the size of the readable area R0. The set value of the size is preferably set to the maximum size of the document that can be placed on the document table 11a.

  In this way, when the document estimation sub-process in S447 is completed, the CPU 70 ends the document estimation process in S220, proceeds to S230, and executes subsequent processes. In other words, the reading area is set based on the document size information estimated in the document estimation process, and the copy operation is realized.

  When the story is returned to S440 (see FIG. 5) of the document estimation process, the CPU 70 determines that the right edge approximate straight line is inclined more than a predetermined angle with respect to the Y axis (Yes in S440), the process proceeds to S450. Then, the left edge detection process shown in FIG. 10 is executed. FIG. 10 is a flowchart showing the left edge detection process executed by the CPU 70.

  When the left edge detection process is started, the CPU 70 sets the sub-scanning direction inspection position Ye = 0 in S710, and sets the main scanning direction inspection position Xe to the left end X coordinate of the readable area R0 in S715. (Xe = 0). In S715, the variable C is initialized to zero (C = 0).

  Thereafter, the CPU 70 determines whether or not the sub-scanning direction inspection position Ye exceeds the inspection range (that is, whether or not Ye> S) (S720), and the sub-scanning direction inspection position Ye exceeds the inspection range. If it is determined that it is not (No in S720), the inspection position (Xe, Ye) is an edge point with reference to the pixel value of the inspection target data corresponding to the inspection position (X, Y) = (Xe, Ye). Whether or not (S725).

  If it is determined that the inspection position (Xe, Ye) is not an edge point (No in S725), the process proceeds to S740, and the main scanning direction inspection position Xe is updated to a point moved by one pixel in the X axis plus direction ( Xe ← Xe + 1), it is determined whether or not the updated main scanning direction inspection position Xe protrudes from the right end of the readable area R0 (S743). Specifically, it is determined whether Xe> XMAX (S743). If it is determined that the main scanning direction inspection position Xe does not protrude from the right end of the readable area R0 (No in S743), the process proceeds to S720.

  On the other hand, when it is determined in S743 that the main scanning direction inspection position Xe protrudes from the right end of the readable region R0 (when it is determined that Xe> XMAX), the CPU 70 proceeds to S747 and sets the main scanning direction inspection position Xe. The sub scanning direction inspection position Ye is set to a position advanced by 8 pixels in the Y-axis direction (Y ← Ye + 8) while being set to the left end of the readable region R0 (Xe = 0). Thereafter, the process proceeds to S720.

  If the CPU 70 determines that the inspection position (Xe, Ye) is an edge point (Yes in S725), the CPU 70 proceeds to S730 and sets the variable (X0, Y0) to the current inspection position (Xe, Ye). The coordinate value is set (X0 ← Xe, Y0 ← Ye), and the variable Y1 is updated to the value Y1 = Y0 + 8 (S733).

  Thereafter, it is determined whether at least one of the point of coordinates (X0-1, Y1), the point of coordinates (X0, Y1), and the point of coordinates (X0 + 1, Y1) is an edge point (S737). If none of the point of (X0-1, Y1), the point of coordinates (X0, Y1), and the point of coordinates (X0 + 1, Y1) is an edge point (No in S737), the process proceeds to S740.

  On the other hand, when it is determined that at least one of the point of coordinates (X0-1, Y1), the point of coordinates (X0, Y1), and the point of coordinates (X0 + 1, Y1) is an edge point (Yes in S737), Moving to S750, it is determined that the point of coordinates (X0, Y0) is a continuous edge point, and the coordinates (X0, Y0) are temporarily stored as coordinate data of the continuous edge point. .

  When this process is finished, the CPU 70 proceeds to S760, where the coordinates (X0-1, Y1), the coordinates (X0, Y1), and the coordinates (X0 + 1, Y1) are the edge points. One of the points is selected according to a predetermined priority.

  Specifically, in the left edge detection process, higher priority is set for coordinates closer to the left end side of the readable area R0. That is, the point of the coordinates (X0-1, Y1) close to the left end side of the readable area R0 is set to the priority “large”, the point of the coordinates (X0, Y1) is set to the priority “medium”, and the coordinates ( The point of X0 + 1, Y1) is set to the priority “small”. The priority is set in this way because there is nothing on the document table 11a on the left side of the left edge of the document, and there should be no edge point, and the edge point close to the left edge side of the readable area R0. This is because there is a high possibility that the edge point is an edge point corresponding to the left end of the document.

  Therefore, in S760, according to the priority, the point of the coordinate (X0-1, Y1), the point of the coordinate (X0, Y1), and the point of the coordinate (X0 + 1, Y1) are points that are edge points. To select the point with the highest priority. Then, the variable X0 is updated to the X coordinate of the selected point, and the variable Y0 is updated to the Y coordinate of the selected point. Thereafter, the variable C is updated to a value obtained by adding 1 (S763).

  When this process is finished, the CPU 70 determines whether or not the value of the updated variable C is C = 8. If the CPU 70 determines that C = 8 is not satisfied (No in S767), the process proceeds to S733. The variable Y1 is updated to Y1 = Y0 + 8. Thereafter, the processing after S737 is executed.

  By such a processing procedure, the CPU 70 checks whether the edge points are continuous in the Y-axis direction every 8 pixels in the Y-axis direction, as in the right edge detection process (see FIG. 7). If it is determined that C = 8 (Yes in S767), the coordinate data of a total of eight points determined as continuous edge points in S750 are stored in the RAM 80 as document left edge data (S770).

  When this process is finished, the CPU 70 proceeds to S780, determines whether or not the sub-scanning direction inspection position Ye exceeds the inspection range (whether or not Ye> S), and performs the sub-scanning direction inspection. If it is determined that the position Ye does not exceed the inspection range (No in S780), the sub-scanning direction inspection position Ye is updated to a point advanced by 64 pixels (S785), and the process proceeds to S715.

  In this way, the CPU 70 repeatedly detects eight consecutive edge points. When the sub-scanning direction detection position Ye exceeds the inspection range (Yes in S720 or Yes in S780), the process proceeds to S790, and the left edge (original document) is selected from the coordinate data group stored as the original left edge data in S770. The edge data representing the left edge of the document) is deleted as a low-accuracy coordinate data group, and the document left edge data is determined.

  Specifically, in the same manner as the processing in S590, the coordinate data group stored as the document left edge data is clearly continuously located at a position greatly shifted to the document inner area with respect to the coordinate data group having continuity. The inconsistent coordinate data group is removed from the document left edge data to determine the document left edge data. Thereafter, the left edge detection process ends. However, the left edge detection process may be configured not to execute the process of S790.

  In addition, when the left edge detection process is completed in this way, the CPU 70 proceeds to S455, linearly approximates each point indicated by the document left edge data determined by the left edge detection process, and the document left edge data is obtained. An approximate straight line (hereinafter referred to as “left edge approximate straight line”) of the point group shown is calculated. Thereafter, the process proceeds to S460.

  However, if there is no coordinate data registered as document left edge data in the immediately preceding left edge detection process, it is determined that detection of the left edge has failed, and the process proceeds to S460 without calculating the left edge approximate straight line. It shall be. In addition, when all or part of the coordinate data registered as the document left edge data is also registered in the document right edge data, the coordinate data of the right edge (the edge point representing the right edge of the document) is incorrect. Even if there is coordinate data registered as document left edge data, it is determined that detection of the left edge has failed, and without calculating the left edge approximate straight line, You may make it transfer to S460.

In S460, the CPU 70 executes the lower edge detection process shown in FIG. FIG. 11 is a flowchart showing the lower edge detection process executed by the CPU 70.
When the lower edge detection process is started, the CPU 70 sets the main scanning direction inspection position Xe to the left end X coordinate of the readable area R0 (Xe = 0) in S810, and the sub scanning direction inspection position Ye in S815. Is set to the lower end Y coordinate of the readable area R0 (Ye = 0). In S815, the variable C is initialized to zero (C = 0).

  When this process is finished, the CPU 70 determines whether or not the main scanning direction inspection position Xe exceeds the right end of the readable area R0 (that is, whether Xe> XMAX) (S820). If it is determined that the scanning direction inspection position Xe does not exceed the right end of the readable region R0 (No in S820), the pixel value of the inspection target data corresponding to the inspection position (X, Y) = (Xe, Ye) is referred to. Then, it is determined whether or not the inspection position (Xe, Ye) is an edge point (S825).

  If it is determined that the inspection position (Xe, Ye) is not an edge point (No in S825), the process proceeds to S840, and the sub-scanning inspection position Ye is updated to a position moved by one pixel in the Y-axis plus direction. (Ye ← Ye + 1), it is determined whether or not the updated sub-scanning direction inspection position Ye exceeds the inspection range (whether or not Ye> S) (S843).

If it is determined that the sub-scanning direction inspection position Ye does not exceed the inspection range (No in S843), the process proceeds to S820.
On the other hand, when it is determined in S843 that the sub-scanning direction inspection position Ye exceeds the inspection range (when it is determined that Ye> S), the CPU 70 proceeds to S847, and the sub-scanning direction inspection position Ye is set in the readable area. While setting at the lower end of R0 (Ye = 0), the main scanning direction inspection position Xe is set to a position advanced by 8 pixels in the X-axis direction (Xe ← Xe + 8). Thereafter, the process proceeds to S820.

  In addition, when the CPU 70 determines in S825 that the inspection position (Xe, Ye) is an edge point (Yes in S825), the CPU 70 proceeds to S830 and sets the current inspection position (Xe, Y0) in the variable (X0, Y0). The coordinate value of (Ye) is set (X0 ← Xe, Y0 ← Ye). Also, the variable X1 is updated to the value X1 = X0 + 8 (S833).

  Thereafter, the CPU 70 determines whether or not at least one of the coordinates (X1, Y0-1), the coordinates (X1, Y0), and the coordinates (X1, Y0 + 1) is an edge point (S837). ), If any of the point of coordinates (X1, Y0-1), the point of coordinates (X1, Y0), and the point of coordinates (X1, Y0 + 1) is not an edge point (No in S837), the process proceeds to S840. .

  On the other hand, if it is determined that at least one of the coordinates (X1, Y0-1), the coordinates (X1, Y0), and the coordinates (X1, Y0 + 1) is an edge point (Yes in S837), the CPU 70 Moving to S850, it is determined that the point of coordinates (X0, Y0) is a continuous edge point, and this coordinate (X0, Y0) is temporarily stored as coordinate data of a continuous edge point. .

  When this process is finished, the CPU 70 proceeds to S860, where the coordinates (X1, Y0-1), the coordinates (X1, Y0), and the coordinates (X1, Y0 + 1) are the edge points. One of the points is selected according to a predetermined priority.

  Specifically, in the lower edge detection process, a higher priority is set for coordinates closer to the lower end side of the readable area R0. That is, the point of the coordinates (X1, Y0-1) close to the lower end side of the readable area R0 is set to the priority “large”, the point of the coordinates (X1, Y0) is set to the priority “medium”, and the coordinates ( The point of (X1, Y0 + 1) is set to the priority “small”. The priority is set in this way because there is nothing on the document table 11a below the lower end of the original, there should be no edge point, and the edge close to the lower end of the readable area R0. This is because the point is more likely to be the edge point corresponding to the lower end of the document.

  Therefore, in S860, according to this priority, the point that is the edge point among the point of the coordinate (X1, Y0-1), the point of the coordinate (X1, Y0), and the point of the coordinate (X1, Y0 + 1) is preferred. Select the point with the highest degree. Then, the variable X0 is updated to the X coordinate of the selected point, and the variable Y0 is updated to the Y coordinate of the selected point. Thereafter, the variable C is updated to a value obtained by adding 1 (S863).

  When this process is finished, the CPU 70 determines whether or not the value of the updated variable C is C = 8 (S867). If it is determined that C = 8 is not satisfied (No in S867), the process proceeds to S833. Then, the variable X1 is updated to X1 = X0 + 8. Thereafter, the processing after S837 is executed.

  By executing such processing, the CPU 70 checks whether the edge points are continuous in the X-axis direction every 8 pixels in the X-axis direction. If it is determined that C = 8 (Yes in S867), the coordinate data of a total of eight points determined as continuous edge points in S850 are stored in the RAM 80 as document lower edge data (S870).

  When this process is finished, the CPU 70 proceeds to S880 to determine whether the main scanning direction inspection position Xe exceeds the right end of the readable area R0 (whether Xe> XMAX). If it is determined that the scanning direction inspection position Xe does not exceed the right end of the readable region R0 (No in S880), the main scanning direction inspection position Xe is updated to a point advanced by 64 pixels (S885), and the process proceeds to S815.

  In this way, the CPU 70 repeatedly detects eight consecutive edge points. When the main scanning direction detection position Xe exceeds the right end of the readable area R0 (Yes in S820 or Yes in S880), the process proceeds to S890, and the coordinate data group stored as the document lower edge data in S870 is The coordinate data group with low accuracy is deleted as an edge (edge point representing the lower end of the document), and the document lower edge data is determined.

  Specifically, as in the process at S590, the coordinate data group stored as the document lower edge data is clearly continuously located at a position greatly shifted to the inner area of the document with respect to the coordinate data group having continuity. The inferior coordinate data group is removed from the document lower edge data to determine the document lower edge data. Thereafter, the lower edge detection process ends. However, the lower edge detection process may be configured not to execute the process of S890.

  In addition, when the lower edge detection process is completed in this way, the CPU 70 proceeds to S465, linearly approximates each point indicated by the document lower edge data determined by the lower edge detection process, and the document lower edge data is obtained. An approximate straight line (hereinafter referred to as a “lower edge approximate straight line”) of the indicated point group is calculated. Thereafter, the process proceeds to S470. However, if there is no coordinate data registered as the document lower edge data in the immediately preceding lower edge detection process, it is determined that the lower edge detection has failed, and the process proceeds to S470 without calculating the lower edge approximate straight line. It shall be.

  In step S470, the CPU 70 determines the right edge detection process (S420), the left edge detection process (S450), and the lower edge detection process from the mutual relationship between the right edge approximate line, the left edge approximate line, and the lower edge approximate line. In (S460), it is determined whether or not the document edge is correctly detected. That is, it is determined whether all of the right edge, the left edge, and the lower edge have been detected normally.

  Specifically, the right edge approximate line and the left edge approximate line are parallel, the right edge approximate line and the lower edge approximate line are orthogonal, and the left edge approximate line and the lower edge approximate line are orthogonal If there is a relationship, it is determined that the document edge is correctly detected, and the determination in S470 is Yes.

  On the other hand, if detection of any one of the right edge, the left edge, and the lower edge fails, or if the relationship between the right edge, the left edge, and the lower edge is not correct, it is determined No in S470. . That is, the right edge approximate line and the left edge approximate line are parallel, the right edge approximate line and the lower edge approximate line are orthogonal, and the left edge approximate line and the lower edge approximate line are orthogonal. Except in the case of No., it is determined that the document edge is not correctly detected, and No is determined in S470. However, the determination of the mutual relationship here should be executed in consideration of an error.

  If it is determined that the document edge is not correctly detected (No in S470), the CPU 70 proceeds to S471 to make a “failure” determination and place it on the document table 11a as in the process in S670. It is estimated that the size of the original is a preset basic size (S473). Thereafter, the document estimation process is terminated, and the processes after S230 are executed to set a reading area and the like based on the document size information estimated in S473 (S265), with a scaling factor of 1 and an inclination correction amount of zero. The copy operation is realized.

  On the other hand, if it is determined in S470 that the document edge is correctly detected (Yes in S470), the CPU 70 proceeds to S481 and sets the lower left corner position of the document between the left edge approximate line and the lower edge approximate line. It is estimated that the point is an intersection, and its coordinate value is calculated. Further, the lower right corner position of the document is estimated to be the intersection of the right edge approximate line and the lower edge approximate line, and the coordinate value is calculated ( S483). FIG. 12 is an explanatory diagram showing a method for estimating the document lower left corner position Ka and the document lower right corner position Kb in S481 and S483. In the figure, white circles represent edge points, and black circles represent the corner positions Ka and Kb.

  When the process in S483 is completed, the CPU 70 estimates the document area in the inspection target data from the estimated relationship between the lower left corner position and the lower right corner position of the document, similarly to the process in S445 (S485).

  Specifically, in S485, the line segment of the lower edge approximate straight line, the line segment from the point corresponding to the lower left corner position of the document to the point corresponding to the lower right corner position of the document, the line segment of the right edge approximate straight line and the original document The line segment from the point corresponding to the lower right corner position to the edge of the inspection target data in the Y axis plus direction, the line segment of the left edge approximate straight line, and the inspection object in the Y axis plus direction from the point corresponding to the lower left corner position of the document An area in the inspection target data surrounded by the line segment to the edge of the data is estimated as a document area (see FIG. 9C).

When the process in S485 is completed, the CPU 70 proceeds to S490 and executes the document estimation sub-process shown in FIG. 9A as in the process in S447.
That is, in S610, the CPU 70 calculates the occupancy rate of the edge points in the area outside the document area of the inspection target data based on the document area information estimated in S485. However, in S610 of the document estimation sub-process executed in S490, when the occupation ratio is calculated according to the above calculation formula, the “right edge data outside the document area”, the document left edge data, and the document bottom It is assumed that the number of edge points registered in one of the edge data and outside the document area is not included. That is, in S610, as an exception, even if the edge point registered in any of the document right edge data, document left edge data, and document bottom edge data is outside the document area, It is not counted as the number of outside edge points.

FIG. 9C is an explanatory diagram showing a specific example of the area of the inspection target data that is handled as being outside the original area in the original estimation sub-process executed in S490.
When the processing in S610 is completed, the CPU 70 determines whether or not the occupation rate calculated in S610 is equal to or less than the threshold (S620). If the calculated occupation rate is equal to or less than the threshold (Yes in S620). ), It is evaluated that the accuracy of the document area estimated in S485 is high, and it is determined that the accuracy is high (S630). If the CPU 70 determines “high accuracy” in S630, the CPU 70 determines Yes in S245.

  When this processing is completed, the CPU 70 proceeds to S640, and the line segment connecting the lower left corner position and the lower right corner position of the document estimated in S481 and S483 is the document short side and is placed on the document table 11a. Assuming that the original is a standard paper, the size of the original placed on the original platen 11a and the placement area of the original on the original platen 11a are estimated, and the inclination of the original placed on the original platen 11a is estimated. The angle θ is estimated based on the right edge approximate straight line (S650). That is, in S650, the angle formed by the right edge approximate line with respect to the Y axis is estimated as the document inclination angle θ. Thereafter, the document estimation sub-process is terminated.

  On the other hand, if it is determined that the occupation rate calculated in S610 exceeds the threshold (No in S620), the CPU 70 evaluates that the accuracy of the document area estimated in advance is low, and determines that “the accuracy is low” ( S660), without using the information of the lower left corner position and the lower right corner position estimated in S481 and S483, it is estimated that the size of the document placed on the document table 11a is a preset basic size (S670). . Thereafter, the document estimation sub-process is terminated. If it is determined that the accuracy is low in S660, the CPU 70 determines No in S245.

When the document estimation sub-process is terminated in this way at S490, the CPU 70 terminates the document estimation process at S220, proceeds to S230, and executes subsequent processes.
With such an operation, the CPU 70 assumes that the original is a standard paper when the accuracy of the original area estimated from the edge image data (inspection target data) obtained by the prescan is high. Based on the information of the lower left corner position and the lower right corner position estimated from the data, the size of the document placed on the document table 11a is estimated and the inclination angle θ of the document is estimated. Based on this, the scaling factor and the inclination correction are performed. An amount is set (S251, S253), and a reading area is further set (S255). Thereafter, the process proceeds to the main scan (S270).

  In the main scan (S270), the reading unit 15 is transported under the set reading area, and the reading unit 15 is caused to read an image shown in the area. Then, the read result is enlarged / reduced in accordance with the set variable magnification, and rotated in accordance with the set inclination correction amount to generate image data for printing. Also, by printing this as print target data, a copy image of the original, which has been automatically scaled and further tilt-corrected, is printed on recording paper through the printing unit 30.

  On the other hand, when the accuracy of the document area estimated from the edge image data obtained by the prescan is low, the CPU 70 estimates that the document is a basic size document (S670), and the lower left corner of the document is the document table. Assuming that the document is placed in a straight line with the lower left corner of 11a, the tilt correction amount is set to zero (S263), and the automatic scaling function is disabled. The magnification is set to 1 (S261).

  Further, a reading area is set according to the estimated document size (S265), and the process proceeds to the main scan (S270). Then, a copy image of the document is printed on the recording paper through the printing unit 30 at a scaling factor of 1.

  The configuration of the digital multi-function peripheral 1 according to the present embodiment has been described above. However, in the multi-function peripheral 1 according to the present embodiment, a partial area of the readable area R0 is pre-scanned, and the document state ( The document size, document tilt, and document placement area are estimated. Therefore, according to the present embodiment, the prescan operation can be completed faster than the conventional method of prescanning the entire readable region R0, and the state of the document can be estimated efficiently. it can.

  However, if a method of pre-scanning a partial area instead of the entire readable area R0 is adopted, the entire image of the original can be read by pre-scanning, and the estimation accuracy of the original state may be deteriorated. is there.

  Therefore, in this embodiment, as described above, the accuracy of the document area estimated from the edge image data obtained by the pre-scan is evaluated, and when the accuracy is high, the document area is derived. The document size (vertical width / horizontal width) is estimated from the position coordinate information of the lower left corner and the lower right corner of the document. If the accuracy is low, the document size is estimated to be a size predetermined by the user. I did it.

  Therefore, according to the present embodiment, in the process of estimating the document area from the edge image data, when an error occurs in the estimation of the document area due to being confused by a figure such as a ruled line drawn on the document, It is possible to execute processing in accordance with the user's desire (size specified by the user) by switching the mode. Therefore, according to the present embodiment, it is possible to prevent an erroneous scaling ratio or reading area from being set due to erroneous estimation and a copy operation unnecessary for the user from being executed. Therefore, according to the present embodiment, it is possible to provide the multifunction device 1 that is highly convenient for the user.

  In the above embodiment, when it is determined that the “accuracy is low” in S660, the process is shifted to S670 without notifying the user, but in S660, the display of the display operation unit 50 is displayed. It is also possible to notify that it is determined that “the accuracy is low”.

  In addition, in S660, while notifying that the “accuracy is low” is displayed through the display of the display operation unit 50, the user is inquired as to whether or not to continue the subsequent processing, and an answer to continue using the operation key is input. If YES, the process proceeds to S670, but if an answer indicating that the operation is not continued is input through the operation key, the process does not proceed to S670 and the copy control corresponding to the copy command that has led to the process of S660 is performed. The processing may be terminated and the copy command may be invalidated.

Further, the document estimation sub-process executed in S490 may be changed to the content shown in FIG.
[Modification]
FIG. 13A is a flowchart showing the document estimation sub-process of the modification executed by CPU 70 in S490. When the document estimation sub-process shown in FIG. 13A is started, the CPU 70 sets the area outside the document area, which is the area to be inspected separated by the left edge approximate straight line estimated in S450, as the occupation rate calculation area. Then, the occupancy rate of the edge points in the occupancy rate calculation area is calculated (S1010). FIG. 13B is an explanatory diagram showing a specific example of the occupation rate calculation area set in S1010. In the figure, the bold line represents the estimated outer edge of the document area, and the hatched line represents the occupation rate calculation area.

  Specifically, in S1010, the occupancy rate of the edge points in the occupancy rate calculation area is calculated according to the following calculation formula: “occupancy rate = number of edge points in the occupancy rate calculation region ÷ total number of pixels in the occupancy rate calculation region”. . However, here, as an exception, when an edge point registered as document left edge data is in the occupancy rate calculation area, it is not counted as the number of edge points in the occupancy rate calculation area. . That is, in S1010, the “number of edge points in the occupation rate calculation area” does not include the number of edge points registered in the document left edge data and in the occupation rate calculation area.

  When this process is finished, the CPU 70 determines whether or not the occupation rate calculated in S1010 is equal to or less than a predetermined threshold (S1020), and determines that the calculated occupation rate exceeds the threshold. Then (No in S1020), the process proceeds to S1080, and subsequent processes (S1080 to S1090) similar to the processes of S660 to S670 described above are executed. Thereafter, the document estimation sub-process is terminated.

  On the other hand, if it is determined that the calculated occupancy is equal to or less than the threshold (Yes in S1020), the CPU 70 proceeds to S1030 and is an area of the inspection target data separated by the lower edge approximate straight line estimated in S460, and the document The area outside the area is set as an occupancy ratio calculation area, and the occupancy ratio of edge points in the occupancy ratio calculation area is calculated according to the same calculation formula as in S1010 (S1030).

FIG. 13C is an explanatory diagram showing a specific example of the occupation rate calculation area set in S1030. In the figure, the bold line represents the estimated outer edge of the document area, and the hatched line represents the occupation rate calculation area.
However, here, as an exception, if the edge point registered as the document lower edge data is in the occupation rate calculation area, it is not counted as the number of edge points in the occupation rate calculation area. . That is, in S1030, the “number of edge points in the occupation rate calculation area” does not include the number of edge points registered as the document lower edge data and in the occupation rate calculation area.

  When this process is finished, the CPU 70 determines whether or not the occupation rate calculated in S1030 is equal to or less than a predetermined threshold (S1040), and determines that the calculated occupation rate exceeds the threshold. Then (No in S1040), the process proceeds to S1080, the subsequent processes (S1080 to S1090) similar to the processes of S660 to S670 described above are executed, and then the document estimation sub-process is terminated.

  On the other hand, if it is determined that the calculated occupancy is equal to or less than the threshold (Yes in S1040), the CPU 70 proceeds to S1050 and executes subsequent processes (S1050 to S1070) similar to the processes of S630 to S650 described above. Thereafter, the document estimation sub-process is terminated.

  Although the document estimation sub-process of the modification has been described above, even if the document estimation sub-process having such contents is executed in S490, the same effects as the document estimation sub-process shown in FIG. Obtainable.

  Further, although the embodiment of the present invention has been described above, the extraction means of the present invention is realized by the processing of S215, S420, S450, S460 executed by the CPU 70 in the above embodiment, and the outer edge recognition means is S437, S455, S465, S441 to S445, S481 to S485 are realized, and the accuracy evaluation means is realized by S610 to S630, S660, S1010 to S1050, and S1080.

  The pre-scanning means is realized by the processing of S210 executed by the CPU 70 and the operation of the reading control unit 20, the document size estimation means is realized by the processing of S640, S670, S1060, and S1090, and the reading area determining means is This scanning means is realized by the processing of S255 and S265, and is realized by the processing of S270 and the operation of the reading control unit 20.

  Further, the present invention is not limited to the above-described embodiments, and can take various forms. For example, in the above-described embodiment, the example in which the present invention is applied to the digital multifunction peripheral 1 including the contact image sensor as a reading unit has been described. However, the present invention is limited to an image reading apparatus including the contact image sensor as a reading unit. Needless to say, it is not something.

2 is an explanatory diagram illustrating a configuration of a digital multi-function peripheral 1. FIG. It is explanatory drawing which showed readable area | region R0 of the reading glass. 6 is a flowchart illustrating a copy control process executed by a CPU. 6 is a flowchart showing an automatic scaling copying process executed by a CPU. 6 is a flowchart showing document estimation processing executed by CPU. It is a flowchart showing the right edge detection process which CPU70 performs. It is explanatory drawing which showed the structure of edge image data. FIG. 6 is an explanatory diagram illustrating a method for determining original right edge data. FIG. 6 is a flowchart (a) showing a document estimation sub-process executed by a CPU 70 and explanatory diagrams (b) and (c) regarding an occupation rate calculation area. It is a flowchart showing the left edge detection process which CPU70 performs. It is a flowchart showing the lower edge detection process which CPU70 performs. FIG. 5 is an explanatory diagram showing a method for estimating a document lower left corner position and a document lower right corner position. FIG. 6 is a flowchart (a) showing a document estimation sub-process of a modification executed by the CPU 70 and explanatory diagrams (b) and (c) regarding an occupation rate calculation area.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Digital compound machine, 10 ... Image reading part, 11 ... Reading glass, 11a ... Original plate, 13 ... Housing | casing, 13a ... Frame, 15 ... Reading unit, 16 ... Conveyance mechanism, 17 ... Motor, 20 ... Reading control part , 30 ... printing section, 40 ... print control section, 50 ... display operation section, 60 ... communication section, 70 ... CPU, 80 ... RAM, 90 ... flash memory, MK ... mark, P ... original, R0 ... readable area

Claims (7)

A reading unit is conveyed under a transparent document table on which a document to be read is placed, and an image on the document table is read by the reading unit, whereby a read image of the document placed on the document table is read. An image reading device for generating image data representing
Image data which is read result of the reading unit, is converted into an edge image data representing an edge image, from among the edge image data, as edge points corresponding to edges of the front SL document placed on the document table Extracting means for extracting the estimated edge point group ;
Outer edge recognition means for recognizing the outer edge of the original by linearly approximating edge points corresponding to each side of the original extracted by the extraction means;
Means for evaluating the accuracy of the outer edge recognized by the outer edge recognition means based on the distribution of edge points of the edge side region of the document table from the outer edge of the original recognized by the outer edge recognition means , The amount of edge points distributed in the edge side region of the document table is calculated from the outer edge of the document recognized by the outer edge recognition means, and when the calculated amount of edge points exceeds a threshold, the outer edge When the accuracy of the outer edge recognized by the recognition unit is evaluated to be low, and the amount of the calculated edge point is equal to or less than a threshold, the accuracy evaluation unit to evaluate that the accuracy is high ,
An image reading apparatus comprising: Pre-scanning means for conveying the reading unit in a partial area of the readable area that is an area of the original platen that can be read by the reading unit and causing the reading unit to perform a reading operation in the partial area. ,
The extracting means, the image data is a read result of the reading unit obtained by the operation of the pre-scanning unit, is converted into an edge image data representing an edge image, from among the edge image data, before Symbol platen The image reading apparatus according to claim 1, wherein an edge point group estimated as an edge point group corresponding to a side of the document placed on the document is extracted. The document table has a quadrangular shape, and one specific corner among the four corners is defined as a position where the corners of the document should be aligned,
The pre-scanning unit is an area from the edge of the document table that forms one side of the document table extending from the specific corner of the document table to a position that is a predetermined distance away from the document table inside. The image according to claim 2 , wherein a part corresponding to a possible area is defined as the partial area, and the reading unit is transported in the area to cause the reading unit to perform a reading operation. Reader. If the accuracy evaluation unit evaluates that the accuracy is high, the size of the document placed on the document table is estimated from the outer edge of the document recognized by the outer edge recognition unit, but the accuracy is low by the accuracy evaluation unit. When evaluated as the size of the document placed on the platen is any one of claims 1 to 3, characterized in that it comprises a document size estimation means for estimating that the predetermined size The image reading apparatus described in 1. The extraction means is configured to extract an edge point group estimated as an edge point group corresponding to this side from the edge image data for each of the three sides of the document placed on the document table ,
The outer edge recognizing means sets two intersection points at which three straight lines obtained by linearly approximating the edge point group corresponding to each side extracted by the extracting means to the corners of the document placed on the document table. It is configured to recognize that
Furthermore, the image reading apparatus
If the accuracy evaluation unit evaluates that the accuracy is high, the outer edge recognition unit recognizes the corner of the document under the assumption that the document placed on the document table is a standard sheet. Based on the distance between the two intersections, the size of the document placed on the document table is estimated. If the accuracy evaluation means evaluates that the accuracy is low, the size of the document placed on the document table is estimated. The image reading apparatus according to claim 2, further comprising a document size estimation unit configured to estimate that the size is a predetermined size. The extraction means estimates from the edge image data as an edge point group corresponding to a side of the document placed on the document table facing a side of the document table extending from a specific corner of the document table. Is configured to extract the edge point group ,
The accuracy evaluation unit approximates an edge point group corresponding to a side of the document placed on the document table opposite to a side of the document table extending from a specific corner of the document table extracted by the extraction unit. The amount of the edge point group in the area of the edge image data corresponding to the area surrounded by the straight line and the outer edge of the document table is the edge side of the document table from the outer edge of the document recognized by the outer edge recognition means. Calculated as the amount of edge points distributed in the region, and when the calculated amount of edge points exceeds a threshold value, the accuracy of the outer edge recognized by the outer edge recognition means is evaluated to be low, and the calculation The image reading apparatus according to claim 3 , wherein when the amount of edge points is equal to or less than a threshold value, the accuracy is evaluated to be high. A reading area determining means for determining a reading area by the reading unit based on the information of the document size estimated by the document size estimating means;
Image data representing a read image of a document placed on the document table by transporting the reading unit and causing the reading unit to perform a reading operation in the reading region determined by the reading target region determining means. A main scanning means for generating
The image reading apparatus according to claim 4, further comprising:

Images