JP6069883B2 - Image reading apparatus and image reading method - Google Patents

Description

  The invention disclosed in this specification relates to a technique for specifying a document area.

  Conventionally, a reading device that acquires an original image as electronic data by reading an original is used (for example, Patent Document 1). This apparatus detects a boundary position between a document image and a background by reading the document in a wider range than the document and analyzing the read data. The detected boundary position is used when obtaining electronic data of a document image such as document size detection or document skew correction. In the prior art, when detecting the boundary position between the document image and the background from the read data, the peripheral area of the document is acquired using a certain threshold value.

JP 2008-124828 A

  However, in the reading device, there are individual differences in the reading device such as an assembly error when configuring the reading device and individual differences in the reading unit included in the reading device. Therefore, even when the same document is read using different reading devices, the acquired read data may be different. In the prior art, the boundary position between the document image and the background is detected using a certain threshold, and the document area that is the area within the boundary position is specified. However, there has been a problem that the document area cannot be properly specified, for example, the document area cannot be correctly specified by another reading apparatus.

  The invention disclosed in this specification discloses a technique for specifying a document area.

An image reading device disclosed in the specification includes a reading unit that reads a document in a main scanning direction and relatively moves in a sub-scanning direction orthogonal to the main scanning direction with respect to the document .
A control unit;
With
The controller is
And reading preparative process by the reading unit Ru to read the area preparative including reading said original,
An acquisition process for acquiring a plurality of bright degree of each pixel included in the pre Ki読 preparative process read preparative result from the reading results above, in the sub-scanning direction, the sub-scan direction towards read earlier by the reading unit and forward, as the sub-scanning direction backwards towards read later by the reading section, of the prior Ki読 preparative result, a secondary scanning direction in front of the region of the reading area, the sub-scanning direction in front of the document The front reading result obtained by reading the front area including the edge of the document, and the rear reading of the area behind the reading area in the sub-scanning direction and including the rear edge of the original in the sub-scanning direction. results of brightness difference for each pixel adjacent to the sub-scanning direction in each of the calculation processing of calculating using the luminance of each pixel acquired by the acquisition process, the sub-scanning direction in front of the document A maximum threshold value of the luminance difference calculated by the calculation process is set for the front reading result as a front threshold value for specifying an edge in the document, and the edge of the original document in the sub-scanning direction is specified. A setting process for setting a maximum value of the absolute value of the luminance difference calculated by the calculation process with respect to the backward reading result .

In this image reading apparatus, the front reading result in the front in the sub-scanning direction of the original read by the reading unit that reads the original in the main scanning direction and that moves relative to the original in the sub- scanning direction orthogonal to the main scanning direction and A front threshold value and a rear threshold value are set using the backward reading results in the rear in the sub-scanning direction. According to this image reading apparatus, it is possible to set a threshold value corresponding to the reading unit for the front side in the sub-scanning direction and the back side in the sub-scanning direction of the document, compared to the conventional technique in which the threshold value is set to a constant value. Thus, it is possible to set a threshold value that can appropriately specify the document area by appropriately specifying the edges of the document in the front and rear in the sub-scanning direction .

In this image reading apparatus, adjacent pixels in the sub-scanning direction that are equal to or higher than the front threshold with respect to the front reading result are extracted, and adjacent to the sub-scanning direction that is equal to or higher than the rear threshold with respect to the rear reading result. An edge in the sub-scanning direction of the document is identified from pixels extracted as pixels that are equal to or higher than the front threshold value by the extraction process, and the threshold value is equal to or higher than the rear threshold value by the extraction process. It is also possible to perform a specifying process for specifying the edge of the original in the sub-scanning direction from the pixel extracted as a pixel .

According to this image reading apparatus, it is possible to appropriately specify the document area by appropriately specifying the front edge of the document in the front and rear of the sub-scanning direction .

In the image reading apparatus, before Kihara draft is a plain reference document, wherein, before performing the reading of the read target document image has been formed, the reading process with reference to the reference document, The acquisition process, the calculation process, and the setting process may be executed . In the image reading apparatus, since the threshold value is set using a plain reference original, the forward and the backward reading result, in the pixel corresponding to the edge of the document, the absolute value of the Brightness difference is the maximum value . According to this image reading apparatus, since the set forward and the rear threshold value using the read result of reading the edge of the document, in the sub-scanning forward and backward to be read of the document on which the image is formed It is possible to set a threshold value that can specify the edge .

The invention disclosed in this specification is also embodied in an image reading method realized by using the image reading apparatus. An image reading method disclosed in the present specification is an image reading method for reading an image of a document, and a reading step of reading the document in a reading region including the document, and a reading result read in the reading step, Of the reading results, the acquisition step of acquiring the luminance for each of the plurality of pixels constituting the reading region and the one read earlier by the reading step as the front and the one read later by the reading step as the rear A front reading result obtained by reading the front area including the front edge of the original and the rear area of the original, and the rear edge of the original. In each of the rear reading results obtained by reading the rear area including the luminance difference for each pixel adjacent in the front-rear direction of the reading area is acquired by the acquisition step. A calculation step of calculating using the luminance for each pixel to be set, and a maximum value of the absolute value of the luminance difference calculated by the calculation step with respect to the front reading result is set as a front threshold, and the rear reading result A setting step of setting a maximum value of the absolute value of the luminance difference calculated by the calculation step as a rear threshold value, and extracting pixels adjacent in the front-rear direction that are equal to or greater than the front threshold value with respect to the front reading result. An extraction step of extracting pixels adjacent in the front-rear direction that are equal to or greater than the rear threshold value with respect to the rear reading result, and specifying the front edge of the document from the pixels extracted using the front threshold value And a specifying step of specifying the rear edge of the document from the pixels extracted using the rear threshold value .

In the image reading method, respectively set the front and rear threshold based on forward reading results and rear reading result of reading preparative process, by using the threshold, the edge side in the sub-scanning forward and the sub scanning direction behind the original properly identified, because identifying the original area, as compared with the prior art threshold is set to a constant value, it is possible to appropriately identify the document region.

  By using the image reading apparatus and the image reading method disclosed in this specification, it is possible to appropriately specify the document area.

Schematic cross-sectional view of a multifunction machine Schematic block diagram of multifunction device Schematic block diagram of the image processing unit 24 Flow chart showing correction processing 6 is a flowchart illustrating document reading processing according to the first embodiment. The figure which shows a 1st reading area | region and a calculation area | region The figure explaining irradiation of the light to a manuscript from a reading part 10 is a flowchart illustrating document reading processing according to the second embodiment. The figure which shows a 2nd reading image

<Embodiment 1>
The first embodiment will be described with reference to FIGS.

1. FIG. 1 is a cross-sectional view of a multifunction machine 1 that is an example of an image reading apparatus according to the present invention. The multifunction device 1 is a multi-function peripheral device having a printer function, a scanner function, a copy function, a facsimile function, and the like.

  As shown in FIG. 1, the multifunction machine 1 includes an image reading unit 3 for reading a document above a main body unit 2. The image reading unit 3 includes a reading unit 30, an automatic document feeder (hereinafter referred to as ADF) 40, a document placing unit 50, and the like.

  The document placing unit 50 includes a frame 51, a first platen glass 52 made of a transparent glass plate, a second platen glass 53, and an intermediate frame 54 disposed between these glasses 52 and 53. The document placement unit 50 is covered with a document cover 48 including the ADF 40 so as to be opened and closed.

  The ADF 40 is provided in a document cover 48, and includes an ADF cover 41, a document tray 42, a pressing member 44, various rollers 46, a paper discharge tray 47, a front sensor (hereinafter referred to as F sensor) 13, a rear sensor (hereinafter referred to as R sensor). ) 14 etc.

  The ADF 40 is provided with a conveyance path 45 that conveys the document from the document tray 42 to the paper discharge tray 47. Hereinafter, a direction along the transport path 45 is referred to as a transport direction, and a direction orthogonal to the direction is referred to as an orthogonal direction. In FIG. 1, the conveyance direction is indicated by an arrow 81. Further, the side of the transport path 45 near the original tray 42 is called an upstream side, and the side of the transport path 45 near the paper discharge tray 47 is called a downstream side.

  The roller 46 transports the document placed on the document tray 42 onto the transport path 45 and discharges it to the discharge tray 47. That is, the reading drive unit 25 (see FIG. 2) that transports the document placed on the document tray 42 to the discharge tray 47 is formed by the roller 46 and the motor M (see FIG. 2) that rotationally drives the roller 46. ing.

  An F sensor 13 is disposed on the document tray 42. The F sensor 13 detects whether or not a document is placed on the document tray 42. An R sensor 14 is disposed on the transport path 45. The R sensor 14 detects whether or not a document is present at the position where the sensor is arranged on the conveyance path 45.

  Further, the reading unit 30 is disposed on the transport path 45 downstream of the R sensor 14. The reading unit 30 is disposed in the main body unit 2 and is formed so as to expand in the orthogonal direction perpendicular to the transport direction, and is supported so as to be movable in the movement direction indicated by an arrow 82 in FIG. That is, the orthogonal direction is equal to the main scanning direction of the reading unit 30.

  As indicated by a dotted line in FIG. 1, the reading unit 30 reads a document placed stationary on the first platen glass 52 while moving in the moving direction in the main scanning direction. At this time, the direction opposite to the moving direction is equal to the sub-scanning direction of the reading unit 30. Further, as indicated by a solid line in FIG. 1, the document moves to a reading position L that is a fixed position on the conveyance path 45 below the second platen glass 53, and reads the document conveyed by the reading drive unit 25 in the main scanning direction. In this case, the document transport direction is the sub-scanning direction of the reading unit. At this time, the reading unit 30 reads the original when the original conveyed by the reading drive unit 25 passes over the second platen glass 53, and the conveyance direction becomes equal to the sub-scanning direction of the reading unit 30.

  A pressing member 44 is disposed so as to face the second platen glass 53. The pressing member 44 presses the document against the second platen glass 53 so that the document passing over the second platen glass 53 does not float from the second platen glass 53. In the following description, it is assumed that the state and operation of the reading unit 30 that reads a document conveyed along the conveyance path 45 at the reading position L unless otherwise specified.

  Next, the structure of the reading unit 30 will be described. The reading unit 30 reads a document placed on the second platen glass 53 by a so-called CIS method using a CIS (Contact Image Sensor). The reading unit 30 includes a linear image sensor 33 in which a plurality of light receiving elements are linearly arranged in the main scanning direction, a light source 31 including a light emitting diode, and the like. It includes a light guide 36 that leads to a placed document or the like, a rod lens array 32 that forms an image of reflected light reflected by the document or the like on each light receiving element of the linear image sensor 33, and a carriage 34 on which these are mounted. The linear image sensor 33 is an example of a light receiving unit.

  The light source 31 irradiates light to the lower surface of the second platen glass 53 from obliquely behind the reading unit 30 in the sub-scanning direction. As a result, the document placed on the second platen glass 53 is irradiated with light from obliquely behind in the transport direction. The linear image sensor 33 receives the reflected light that is irradiated by the light source 31 and reflected by the document or the like. Accordingly, the document that moves relative to the reading unit 30 is read by the reading unit 30.

  Furthermore, the multifunction device 1 includes various buttons and an operation unit 11 (see FIG. 2) that receives an operation input from a user, and a display unit 12 (see FIG. 2) that includes a liquid crystal display that displays the state of the multifunction device 1. Is provided.

2. As shown in FIG. 2, the multifunction machine 1 includes a CPU 21, a ROM 22, a RAM 23, and an image processing unit 24 as main parts, which are connected via a bus 26. . A combination of the CPU 21, the ROM 22, the RAM 23, and the image processing unit 24 is an example of a control unit.

  The ROM 22 stores various programs for controlling the operation of the multifunction device 1, and the CPU 21 controls each unit according to the program read from the ROM 22.

  For example, the CPU 21 transmits a pulse signal to the motor M and controls the reading drive unit 25. The motor M is driven to rotate by one rotation angle with one pulse of the pulse signal. When the motor M is driven by one step, the roller 46 is driven and the document is conveyed on the conveyance path 45 by a specified distance. When conveying the document, the CPU 21 transmits a predetermined number of pulse signals to the motor M, and accordingly, the roller 46 conveys the document by a distance obtained by multiplying the number of pulses of the pulse signal by a specified distance. Hereinafter, the number of pulses of the pulse signal transmitted from the CPU 2 to the motor M is referred to as a step number.

  Further, the CPU 21 controls the reading unit 30 by transmitting a signal for controlling the lighting period and the amount of light of the light source 31 to the reading unit 30. The light source 31 emits light according to a signal from the CPU 21, and the linear image sensor 33 reads reflected light from a document or the like. The CPU 21 controls the reading drive unit 25 and the reading unit 30 at the same time, thereby causing the reading unit 30 to read a reading area YR that includes an original and is set to be wider than the original, and reads the reading area YR. YG is transmitted to the RAM 23. The read image YG is an example of a read result.

  When reading the read image YG, the reading unit 30 performs reading for each light receiving element of the linear image sensor 33 arranged in the main scanning direction, and repeats reading over the reading region YR in the sub scanning direction. Therefore, the read image YG is a data group in which a plurality of pixel data GD, which are RGB signals read by each light receiving element, are arranged in the main scanning direction and the sub-scanning direction.

  The image processing unit 24 performs necessary correction processing such as acquisition processing and extraction processing on the read image YG stored in the RAM 23. As shown in FIG. 3, the image processing unit 24 includes an edge extraction unit 60 and a color adjustment unit 61 as main parts, and the edge extraction unit 60 includes a conversion unit 62 and an extraction unit 63. The converter 62 performs YIQ conversion on the read image YG, and executes acquisition processing for acquiring the luminance component Y for each pixel data GD. Using the threshold value K stored in the RAM 23, the extraction unit 63 executes an extraction process for extracting edge pixel data ED that is pixel data GD obtained by reading the edge of the document from the read image YG. The color adjustment unit 61 executes color adjustment processing for adjusting the hue of the read image YG in accordance with a medium on which the read image YG is displayed, such as a print sheet or a display.

3. Scan Processing Next, scan processing for reading a document will be described with reference to FIGS. 4 to 7. The scanning process includes a document reading process that actually reads a document and a correction process that is executed prior to the reading process and acquires a luminance difference Δ for setting a threshold value K used in the reading process.

(Correction process)
The CPU 20 starts the correction process when the multifunction device 1 is initially used or when a correction instruction is input via the operation unit 11. The correction process is performed using a predetermined reference document. Here, the reference original (an example of the first original) is a plain (blank) original and means a standard-size original such as A4.

  As shown in FIG. 4, when the correction process is started, the CPU 21 notifies the user or the like that the reference document is placed on the document tray 42 using the display unit 12 (S2). The CPU 21 confirms that the reference document is placed on the document tray 42 using the F sensor 13 (S4: NO). Then, when the CPU 21 confirms that the reference document is placed on the document tray 42 (S4: YES), the CPU 21 executes a first reading process for reading the first reading region YR1 including the reference document by the reading unit 30, The first read image YG1 read from the first reading area YR1 is stored in the RAM 23 (S6).

  At this time, the CPU 21 acquires the position information Z in the main scanning direction and the sub-scanning direction for each pixel data GD included in the first read image YG1 by the reading drive unit 25, and associates it with the first read image YG1. And stored in the RAM 23.

Next, the CPU 21 executes an acquisition process using the image processing unit 24 on the first read image YG1 read from the first reading area YR1, and the luminance for each pixel data GD included in the first read image YG1. The component Y is acquired (S8). The CPU 21 executes a calculation process for calculating the luminance difference Δ between the pixel data GD adjacent in the sub-scanning direction using the acquired luminance component Y of the first read image YG1 (S10 to S1 6 ).

  In the calculation process, the CPU 21 first sets the first calculation region SR1 in the first read image YG1, and calculates the luminance difference Δ of the pixel data GD adjacent in the sub-scanning direction in the first calculation region SR1 (S10). . The first calculation area SR1 shown in an enlarged manner in FIG. 6 is a read image obtained by reading the first front area ZR1 of the first reading area YR1, and as shown in FIG. 6, the first front area ZR1 is the first reading area. The region YR1 is a central region in the main scanning direction, and is set to a region on the sub scanning direction side.

  The first front area ZR1 is set so as to include the edge of the reference document on the sub-scanning direction side. Therefore, the edge of the reference document on the side of the sub-scanning direction is read in the first calculation area SR1. Pixel data GD. The first calculation area SR1 is an example of a first front reading result.

  FIG. 6 shows the distribution of the luminance component Y in the sub-scanning direction of the first calculation region SR1. When calculating the luminance difference Δ in the sub-scanning direction, the CPU 21 calculates the difference ΔY between the luminance components Y of the adjacent pixel data GD and the difference ΔZ between the position information Z, and the luminance component Y obtained by dividing the difference ΔY by the difference ΔZ. Is calculated as a luminance difference Δ. That is, the gradient of the luminance component Y in FIG. 6 corresponds to the luminance difference Δ.

  The CPU 21 stores the maximum absolute value of the luminance difference Δ calculated in the first calculation area SR1 in the RAM 23 as the first maximum luminance difference ΔM1 (S10). Here, the absolute maximum value does not necessarily need to be the absolute maximum value, and is a value equal to or smaller than the absolute maximum value, and the difference from the absolute maximum value is within a predetermined range (for example, 5 %). As shown in FIG. 7, the reading unit 30 irradiates the original with light from obliquely behind in the sub-scanning direction, and reads the reflected light from the original. Therefore, when reading the edge of the original in the sub-scanning direction, light is not irradiated on the side surface of the original in the sub-scanning direction and light is not reflected due to the predetermined thickness of the original. The first maximum luminance difference ΔM1 is an example of a maximum value on the front side.

  Therefore, as shown in FIG. 6, in the pixel data GD obtained by reading the edge of the reference document on the sub-scanning direction side, the luminance component Y is lower than the surrounding pixel data GD, and the luminance difference Δ having a large absolute value. Is acquired. As a result, the luminance difference Δ calculated using the pixel data GD obtained by reading the edge on the sub-scanning direction side of the reference document is stored in the RAM 23 as the first maximum luminance difference ΔM1.

  Next, the CPU 21 sets the second calculation region SR2 in the first read image YG1, and calculates the luminance difference Δ between the pixel data GD adjacent in the sub-scanning direction in the second calculation region SR2 (S14). The second calculation area SR2 shown in an enlarged manner in FIG. 6 is a read image obtained by reading the first rear area KR1 of the first reading area YR1, and as shown in FIG. 6, one rear area KR1 is the first reading area. This is the central area of YR1 in the main scanning direction, and is set in the area opposite to the sub-scanning direction.

  The first rear region KR1 is set so as to include an end opposite to the sub-scanning direction of the reference document. Therefore, the second calculation region SR2 has a side opposite to the sub-scanning direction of the reference document. Pixel data GD obtained by reading the end side is included. The second calculation area SR2 is an example of the first backward reading result.

  FIG. 6 shows the distribution of the luminance component Y in the sub-scanning direction of the second calculation region SR2. The CPU 21 stores the maximum absolute value of the luminance difference Δ calculated in the second calculation area SR2 in the RAM 23 as the second maximum luminance difference ΔM2 (S16). Also in this case, the maximum absolute value does not necessarily need to be the maximum absolute value, and is a value equal to or less than the maximum absolute value, and the difference from the maximum absolute value is within a predetermined range (for example, 5%). As shown in FIG. 7, the reading unit 30 irradiates the original with light from obliquely behind in the sub-scanning direction, and reads the reflected light from the original. For this reason, when reading the edge of the document opposite to the sub-scanning direction, the side surface of the document on the side of the sub-scanning direction is irradiated with light due to the predetermined thickness of the document, and the reflected light increases. The second maximum luminance difference ΔM2 is an example of a rear maximum value.

  Therefore, as shown in FIG. 6, in the pixel data GD obtained by reading the edge on the opposite side to the sub-scanning direction of the reference document, the luminance component Y increases compared to the surrounding pixel data GD, and the luminance having a large absolute value is obtained. A difference Δ is obtained. As a result, the luminance difference Δ calculated using the pixel data GD obtained by reading the edge on the side opposite to the sub-scanning direction of the reference document is stored in the RAM 23 as the second maximum luminance difference ΔM2.

(Original reading process)
Next, the document reading process will be described. As shown in FIG. 5, the CPU 20 confirms that the target document (an example of the second document) is placed on the document tray 42 using the F sensor 13, and instructs the reading of the target document via the operation unit 11. Is input, the document reading process is started.

  When starting the document reading process, the CPU 21 controls the reading drive unit 25 and the reading unit 30 to start conveying and reading the target document (S22). The CPU 21 executes a second reading process for reading the second reading area YR2 including the target document by the reading unit 30 (S24: NO).

  Then, when it is confirmed that the reading of the target document has been completed using the R sensor 14 (S24: YES), the CPU 21 calculates the first maximum luminance difference ΔM1 and the second maximum luminance difference ΔM2 acquired by the correction process. A setting process for setting the threshold value K is executed (S26). In the setting process, the CPU 21 selects the smaller maximum luminance difference ΔM among the first maximum luminance difference ΔM1 and the second maximum luminance difference ΔM2, sets the maximum luminance difference ΔM as the threshold value K, and stores it in the RAM 23. .

  Next, the CPU 21 performs an acquisition process using the image processing unit 24 on the second read image YG2 read from the second read area YR2, and performs luminance for each pixel data GD included in the second read image YG2. The component Y is acquired. Then, the CPU 21 performs an extraction process using the image processing unit 24 on the acquired luminance component Y of the second read image YG2 (S28).

  In the extraction process, the CPU 21 performs a process using the threshold value K set in the setting process. The CPU 21 calculates the luminance difference Δ of the pixel data GD adjacent in the sub-scanning direction in the second read image YG2, and among the pixel data GD whose luminance difference Δ is equal to or greater than the threshold value K, pixel data on the sub-operation direction side. GD is extracted as edge pixel data ED.

  The CPU 21 executes a specifying process for specifying the document area GR from the extracted edge pixel data ED (S30). The document area GR is a read image obtained by reading the target document in the second read image YG2, and the pixel data GD on the edge of the document area GR is the pixel data GD obtained by reading the corresponding edge of the document. . The CPU 21 specifies the extracted edge pixel data ED as the pixel data GD of the edge on the sub-operation direction side and the opposite side to the sub-operation direction of the document region GR, and specifies the document region GR. The CPU 21 stores and stores the read image of the specified document area GR in the RAM 23, and ends the scanning process (S32).

4). Advantages of the present embodiment (1) In the MFP 1 of the present embodiment, the threshold K is set using the first read image YG1 obtained by reading the reference document using the reading unit 30, and the target document is used using the threshold K. The document area GR is specified from the second read image YG2 obtained by reading. According to the multifunction device 1, the threshold value K corresponding to the reading unit 30 can be set, and the document region GR can be appropriately specified as compared with the conventional technique in which the threshold value K is set to a constant value. it can.

(2) When the threshold value K is set, the multifunction device 1 of the present embodiment calculates the luminance difference Δ of the pixel data GD adjacent in the sub-scanning direction in the first read image YG1, and uses the luminance difference Δ to determine the threshold value. Set K. Therefore, it is possible to appropriately specify the edge of the document region GR in the sub-scanning direction, which is the direction in which the reading unit 30 moves relative to the document.

(3) More specifically, when setting the threshold value K, the first maximum luminance difference ΔM1 calculated in the first calculation region SR1, the second maximum luminance difference ΔM2 calculated in the second calculation region SR2, The threshold value K is set using one of the above. Therefore, the pixel data GD having the luminance difference Δ greater than or equal to the maximum luminance difference ΔM in the second read image YG2 can be extracted as the edge pixel data ED, and the edge of the document region GR in the sub-scanning direction is appropriately specified. can do.

(4) When calculating the luminance difference Δ, the MFP 1 of the present embodiment calculates the difference ΔY of the luminance component Y and the difference ΔZ of the position information Z of the pixel data GD adjacent in the sub-scanning direction, and the difference ΔY Is calculated as the luminance difference Δ. Therefore, the luminance difference Δ can be calculated from the inclination of the luminance component Y in consideration of the position information, and the edge of the document area GR can be specified appropriately.

(5) In the multifunction device 1 of the present embodiment, the correction process is executed using a predetermined plain reference document. Since a plain reference document is used, the threshold value K can be set from the pixel data GD obtained by reading the edge of the reference document in the sub-scanning direction. The threshold value K is used to appropriately set the edge of the document region GR. Can be identified.

<Embodiment 2>
The second embodiment will be described with reference to FIGS. The multi-function device 1 of this embodiment sets the first maximum luminance difference ΔM1 and the second maximum luminance difference ΔM2 as the threshold value K, and executes the extraction process, among the first maximum luminance difference ΔM1 and the first maximum luminance difference ΔM1. This is different from the first embodiment in which only one of the two maximum luminance differences ΔM2 is set as the threshold value K. In the following description, the same description as that of the first embodiment will not be repeated.

1. Document Reading Process The scanning process of this embodiment will be described with reference to FIGS. Among the scanning processes of the present embodiment, the correction process is the same as that of the first embodiment, and thus the description thereof will be omitted.

  As shown in FIG. 8, when reading the second reading area YR2 by the reading unit 30 in the document reading process (S24: YES), the CPU 21 first sets the first maximum luminance difference ΔM1 as the front threshold value ZK (S42). ) And stored in the RAM 23.

  The CUP 21 sets the first extraction region TR1 in the second read image YG2, and executes the extraction process using the image processing unit 24 on the luminance component Y of the first extraction region TR1 (S44). A first extraction region TR1 surrounded by a dotted line in FIG. 9 is a read image obtained by reading the second front region ZR2 of the second reading region YR2, and the second front region ZR2 is a sub-scanning direction of the second reading region YR2. This is an area on the side, and is set so as to include all the edges on the side of the target document in the sub-scanning direction. The first extraction region TR1 is an example of a second front reading result.

  In the extraction process, the CPU 21 performs a process using the front threshold value ZK. In the first extraction region TR1, the CPU 21 calculates the luminance difference Δ between the pixel data GD adjacent in the sub-scanning direction, and among the pixel data GD whose luminance difference Δ is equal to or greater than the front threshold value ZK, the pixel on the sub-operation direction side Data GD is extracted as edge pixel data ED. The CPU 21 specifies the edge pixel data ED extracted using the front threshold value ZK as the pixel data GD of the edge on the sub operation direction side of the document area GR (S46).

Next, the CPU 21 sets the second maximum luminance difference ΔM2 as the rear threshold value KK (S48) and stores it in the RAM 23. C PU 21, in the second read image YG2 set the second extraction region TR2, executes the extraction process using the image processing unit 24 the luminance component Y of the second extraction region TR2 (S50). A second extraction region TR2 surrounded by a dotted line in FIG. 9 is a read image obtained by reading the second rear region KR2 of the second reading region YR2, and the second rear region KR2 is the sub-scanning direction of the second reading region YR2. And is set so as to include all edges on the opposite side to the sub-scanning direction of the target document. The second extraction region TR2 is an example of a second backward reading result.

  In the extraction processing, the CPU 21 performs processing using the rear threshold value KK. In the second extraction region TR2, the CPU 21 calculates the luminance difference Δ between the pixel data GD adjacent in the sub-scanning direction, and among the pixel data GD whose luminance difference Δ is equal to or greater than the rear threshold value KK, Pixel data GD is extracted as edge pixel data ED. The CPU 21 specifies the edge pixel data ED extracted using the rear threshold value KK as the pixel data GD of the edge on the side opposite to the sub operation direction of the document area GR (S52).

  The CPU 21 stores and stores in the RAM 23 the sub-operation direction and the read image of the document area GR specified from the edge opposite to the sub-operation direction, and ends the scanning process (S32).

4). Effects of the present embodiment In the multifunction device 1 of the present embodiment, the first maximum luminance difference ΔM1 calculated in the first calculation region SR1 is set as the front threshold value ZK, and the edge pixel data in the sub-scanning direction in the first extraction region TR1. Extract ED. Also, set a second maximum luminance difference ΔM2 calculated by the second calculation region SR2 as rear threshold KK, extracts the sub-scanning direction edge pixel data ED in the second extraction region TR 2.

  In the reading unit 30 of the multifunction device 1, the light source 31 irradiates the document with light from an oblique rear side in the sub-scanning direction. Therefore, as shown in the case of using the reference document in FIG. 6, when reading the edge of the document in the sub-scanning direction, the luminance component Y of the pixel data GD decreases, and the side opposite to the document in the sub-scanning direction. In the case of reading the end side, the luminance component Y of the pixel data GD increases. That is, the behavior of the luminance component Y of the pixel data GD differs between when reading the edge of the original in the sub-scanning direction and when reading the edge opposite to the sub-scanning direction of the original, and the magnitude of the inclination is also different. Different.

  In the multifunction device 1 of the present embodiment, the front threshold value and the rear threshold value are set on the sub-scanning direction side and on the opposite side to the sub-scanning direction, respectively. For this reason, even when the amount of light received by the light source 31 on the document in the sub-scanning direction and on the opposite side of the sub-scanning direction differs from each other due to the light irradiating the document from obliquely behind in the sub-scanning direction. The edges on the sub-scanning direction side and the reverse side of the sub-scanning direction of the region GR can be appropriately specified.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and the drawings, and for example, the following various aspects are also included in the technical scope of the present invention.
(1) In the above embodiment, the description has been made using the multifunction machine 1 having a printer function, a scanner function, a copy function, a facsimile function, etc., but the present invention is not limited to this. For example, the presence or absence of other functions is not particularly limited as long as the apparatus has at least a scanner function.

(2) In the above-described embodiment, the MFP 1 has one CPU 21 and executes various processes by one CPU 21. However, the present invention is not limited to this. For example, various processes may be shared by different CPUs, ASICs, and the like.

(3) In the above-described embodiment, the ADF method of reading the document with respect to the reading unit 30 by the ADF 40 has been described as the method of reading the document. However, the method of reading a document is not limited to this, and can also be applied to a flat bed type reading in which the reading unit 30 moves with respect to a document placed stationary on the first platen glass 52.

(4) In the above-described embodiment, the light source 31 of the reading unit 30 has been described using an example in which light is irradiated to the original from an oblique rear side in the sub-scanning direction. However, the present invention can also be applied to the case where light is irradiated on the original from an obliquely forward direction in the sub-scanning direction.

(5) Although the above embodiment has been described using an example in which the correction process is performed using a plain reference document, it is sufficient that the reference document has at least a plain surface to be read by the reading unit 30. Furthermore, on the surface read by the reading unit 30, the portions corresponding to the first front region ZR1 and the first rear region KR1 of the first reading region YR1 may be plain.

(6) The reference document does not necessarily have to be determined in advance. However, if the reference document is a predetermined document, the document region GR can be specified with a certain accuracy.

(7) In the above embodiment, when the luminance difference Δ is calculated, the inclination of the luminance component Y is calculated, and the inclination is set as the luminance difference Δ. However, the present invention is not limited to this. Absent. For example, when calculating the luminance difference Δ between the pixel data GD adjacent to each other or having the position information Z at equal intervals, the difference ΔY between the luminance components Y of the pixel data GD may be used as the luminance difference Δ.

(8) The above embodiment has been described using an example in which processing is performed between pixel data GD adjacent in the sub-scanning direction when calculating the luminance difference Δ or extracting the edge pixel data ED. However, the present invention is not limited to this. If processing may be performed between pixel data GD adjacent in the main operation direction, processing may be performed between predetermined pixel data GD in the sub-scanning direction or the sub-operation direction.

(9) In the above embodiment, when the edge pixel data ED is extracted, the edge pixel data ED is extracted from the sub-scanning direction side and the opposite side of the document region GR. Although described, the edge pixel data ED may be extracted only at one end. That is, if the first maximum luminance difference ΔM1 is set as the threshold value K and only the edge pixel data ED corresponding to the edge of the document region GR on the sub-scanning direction side may be extracted, the second maximum luminance difference ΔM2 is set as the threshold value. It may be set as K, and only the edge pixel data ED corresponding to the edge of the document region GR opposite to the sub-scanning direction may be extracted.

3: Image reading unit, 24: Image processing unit, 25: Reading drive unit, 30: Reading unit, 50: Document placement unit, 60: Edge extraction unit, 62: Conversion unit, 63: Extraction unit, ED: Edge pixel Data, GD: Pixel data, GR: Document area, K: Threshold, KR: Back area, SR: Calculation area, TR: Extraction area, Y: Luminance component, YG: Scanned image, YR: Scan area, Z: Position information , ZR: front area, Δ: luminance difference, ΔM: maximum luminance difference

Claims (3)

A reading unit that reads a document in a main scanning direction and moves relative to the document in a sub-scanning direction orthogonal to the main scanning direction;
A control unit;
With
The controller is
A reading process for causing the reading unit to read a reading area including the document;
An acquisition process for acquiring the luminance for each of a plurality of pixels included in the reading result of the reading process from the reading result;
In the sub-scanning direction, the one read by the reading unit first is the front in the sub-scanning direction, and the one read later by the reading unit is the rear in the sub-scanning direction,
Among the reading results, a front reading result obtained by reading a front area of the reading area in front of the sub-scanning direction, including a front edge of the document in front of the sub-scanning direction, and the sub area of the reading area. A luminance difference for each pixel adjacent in the sub-scanning direction in each of the rear reading results obtained by reading the rear area including the rear edge in the sub-scanning direction of the original and the rear area in the sub-scanning direction is acquired. A calculation process for calculating using the luminance of each pixel acquired by
A maximum value of the absolute value of the luminance difference calculated by the calculation process is set for the front reading result as a front threshold value for specifying an end edge of the document in the sub-scanning direction, and the sub-scanning direction of the document is set. A setting process for setting a maximum value of the absolute value of the luminance difference calculated by the calculation process with respect to the backward reading result, as a rear threshold value for specifying an edge on the rear side in the scanning direction;
An image reading apparatus that executes The image reading apparatus according to claim 1,
Extraction of pixels adjacent in the sub-scanning direction that are equal to or greater than the front threshold for the front reading result, and extraction of pixels adjacent to the sub-scanning direction that are equal to or greater than the rear threshold for the rear reading result Processing,
From the pixels extracted as pixels that are equal to or higher than the front threshold by the extraction process, the edge in the sub-scanning direction front of the document is specified, and from the pixels extracted as pixels that are equal to or higher than the rear threshold by the extraction process A specifying process for specifying an end edge of the original in the sub-scanning direction;
An image reading apparatus that executes An image reading method for reading an image of a document,
A reading step of reading the document in a reading area including the document;
An acquisition step of acquiring luminance for each of a plurality of pixels constituting the reading region from the reading result read in the reading step;
The one read earlier by the reading step is the front, the one read later by the reading step is the rear,
Out of the reading results, a front reading result of reading the front area including the front edge of the original, and a rear area of the reading area. A luminance difference for each pixel adjacent in the front-rear direction of the reading region in each of the rear reading results obtained by reading the rear region including the rear edge is calculated using the luminance for each pixel acquired by the acquisition step. A calculation process to perform,
A maximum value of the absolute value of the luminance difference calculated by the calculation step with respect to the front reading result is set as a front threshold value, and the absolute value of the luminance difference calculated by the calculation step with respect to the rear reading result A setting step for setting the maximum value of as a rear threshold;
An extraction step of extracting pixels adjacent in the front-rear direction that are equal to or greater than the front threshold with respect to the front reading result, and extracting pixels adjacent to the front-rear direction that are equal to or greater than the rear threshold with respect to the rear reading result; ,
A specifying step of specifying the front edge of the document from the pixels extracted using the front threshold and specifying the rear edge of the document from the pixels extracted using the rear threshold; ,
An image reading method comprising:

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