JP6244669B2 - Image reading apparatus and read image correction program - Google Patents

Description

  The present invention relates to a technique for correcting original reading data obtained by reading an original sheet using white reference data obtained by reading a white reference member.

  Conventionally, in an image reading apparatus, as a part of measures against EMI (electromagnetic wave interference), it has been proposed to use a spread spectrum clock whose frequency fluctuates with a constant modulation period. However, when the lighting period of the light source and the reading period of the reading unit in the image reading apparatus are set based on the fluctuation period of the spread spectrum clock, the lighting period and the reading period vary due to the fluctuation of the frequency of the spread spectrum clock. . In contrast, since the original sheet moves relative to the reading unit at a constant speed, the original sheet image cannot be read accurately if the lighting period or the reading period fluctuates.

  Therefore, by setting the lighting period and the reading period to an integral multiple of the modulation period of the spread spectrum clock, the lighting period and the reading period are made constant regardless of the fluctuation of the frequency of the spread spectrum clock. (For example, refer to Patent Document 1 and Patent Document 2).

  However, in order to make the lighting period and reading period of the light source constant regardless of the fluctuation of the frequency of the spread spectrum clock, it is necessary to set it to an integral multiple of the modulation period of the spread spectrum clock. A desired period length cannot be set freely.

JP 2006-332924 A JP 2002-281252 A

  By the way, in the image reading apparatus, the white reference member is read in advance by the reading unit to obtain correction data such as shading correction data, and the original reading data obtained by reading the original sheet by the reading unit is used as the correction data. To correct. When the image reading apparatus is configured to use the above-described spread spectrum clock, the lighting period of the light source and the reading unit are changed depending on the frequency of the spread spectrum clock when the white reference member is read and when the original sheet is read. The reading cycle such as the reading period may be different. Then, even if the correction data is used as it is, the original read data cannot be corrected normally, and the image quality of the read image may be deteriorated. Note that the difference in reading cycle between reading of the white reference member and reading of the original sheet is not limited to the change in the frequency of the spread spectrum clock, and various factors such as a change in ambient temperature can be considered.

  The present specification discloses a technique for suppressing deterioration in image quality of a read image corrected using correction data due to a difference in reading cycle between reading of a white reference member and reading of an original sheet. To do.

  The image reading apparatus disclosed in the present specification reads an image in a reading area along the main scanning direction, and the reading area includes a document reading area and a side area located beside the document reading area. , A moving unit that moves at least one of the original sheet and the reading unit to pass the original sheet into the original reading area, a white reference member, and a control unit, and the control A white section that causes the reading unit to read the white reference member, obtain white reference data that is read data of the original reading area, and obtain first side data that is read data of the side area; In a reference reading process, the reading unit is caused to read the original sheet, and original reading data that is reading data of the original reading area is acquired, and second side data that is reading data of the side area is acquired. original A white correction data generation process for generating white correction data using a reading process, a relative ratio between a value indicated by the first side data and a value indicated by the second side data, and the white reference data; And a white correction process for correcting the original reading data using the white correction data.

  The reading cycle may be different between reading the white reference member and reading the original sheet. However, this difference has a correlation with the relative ratio between the value indicated by the first side data acquired when reading the white reference member and the value indicated by the second side data acquired when reading the original sheet. Therefore, according to this image reading apparatus, white correction data is generated using the relative ratio in addition to the white reference data, and the original image data is corrected using the correction data. As a result, it is possible to suppress deterioration in the image quality of the read image corrected using the correction data, because the reading cycle is different between reading the white reference member and reading the original sheet.

  In the image reading apparatus, the control unit includes a clock generation unit that generates a spread spectrum clock whose frequency fluctuates at a constant modulation period. In the white reference reading process, the read unit includes the spread spectrum clock. The white reference member may be read at a reading cycle according to the document, and in the document reading process, the reading unit may be caused to read the document sheet at a reading cycle according to the spread spectrum clock.

  Due to fluctuations in the frequency of the spread spectrum clock, the reading cycle may differ between when reading the white reference member and when reading the original sheet. However, this difference has a correlation with the relative ratio between the value indicated by the first side data acquired when reading the white reference member and the value indicated by the second side data acquired when reading the original sheet. Therefore, according to this image reading apparatus, white correction data is generated using the relative ratio in addition to the white reference data, and the original image data is corrected using the correction data. Accordingly, it is possible to suppress the image quality of the read image corrected using the correction data from being deteriorated due to the variation of the frequency of the spread spectrum clock while suppressing the setting of the reading cycle.

  In the image reading apparatus, in the document reading process, the control unit reads the document sheet line by line, acquires the document reading data and the second side data for each line, and performs the white correction. In the data generation process, white correction data is generated for each line using the relative ratio and the white reference data, and in the white correction process, the document read data is converted for each line. You may correct | amend using white correction data.

According to this image reading apparatus, by performing the document reading process, the white correction data generation process, and the white correction process for each line, the reading cycle differs between when reading the white reference member and when reading the document sheet. As a result, it is possible to more reliably suppress the deterioration of the image quality of the read image corrected using the correction data.
Do

  The image reading apparatus includes a document table, and the moving unit includes a configuration in which the reading unit is moved with respect to the document sheet disposed on the document table by moving the reading unit. The light reflection characteristic of the part corresponding to the side region of the table may be the same as that of the white reference member.

  According to this image reading apparatus, more accurate white correction data can be generated as compared with a configuration in which the light reflection characteristic of the portion corresponding to the side region is different from that of the white reference member. For this reason, it is possible to more reliably suppress the deterioration in the image quality of the read image corrected using the correction data, because the reading cycle is different between reading the white reference member and reading the original sheet. It is.

  The image reading apparatus includes a pressing member that presses a document sheet disposed on the document table and has a width in the main scanning direction wider than the document sheet, and the width of the white reference member in the main scanning direction is: It is equal to or larger than the width of the reading region in the main scanning direction, and the light reflection characteristic of at least the portion corresponding to the side region of the pressing member is the same as that of the white reference member.

  According to this image reading apparatus, the second side data based on the same light reflection characteristics as the white reference member can be acquired by reading the pressing member.

  In the image reading apparatus, a non-arrangement portion is provided at a side position of the document table, and the width of the white reference member in the main scanning direction is equal to or larger than the width of the reading region in the main scanning direction. The light reflection characteristic of at least the portion corresponding to the side region in the arrangement portion may be the same as that of the white reference member.

  According to this image reading apparatus, the second side data based on the same light reflection characteristics as the white reference member can be acquired by reading the non-arranged portion.

  In the image reading apparatus, the moving unit includes a configuration that conveys the document sheet toward the reading position, and the white reference member is opposed to the reading unit in the reading region. The width of the opposing member in the main scanning direction may be equal to or greater than the width of the reading region in the main scanning direction.

  According to this image reading apparatus, white reference data, first side data, and second measurement data can be acquired by reading a common white reference member.

  The present invention can be realized in various modes such as an image processing apparatus, a read image correction method, a computer program for realizing the functions of these methods or apparatuses, and a recording medium on which the computer program is recorded.

  According to the invention disclosed in this specification, the image quality of the read image corrected using the correction data is deteriorated because the reading cycle is different between reading the white reference member and reading the original sheet. Can be suppressed.

The perspective view which shows the external appearance structure of the multifunctional device which concerns on one Embodiment. Sectional drawing which shows internal structure of a cover part and a part of apparatus main body Block diagram showing the electrical configuration of the MFP The schematic diagram which looked at the 1st reading part and the counter member for 1st ADF from the front A top view of the apparatus main body, and a schematic view of the first reading unit and the FB pressing member viewed from the front. Graph showing the relationship between white reference data and spectrum frequency Flow chart showing reading control processing (at the time of ADF reading) Flow chart showing reading control processing (when reading FB)

<One Embodiment>
An embodiment will be described with reference to FIGS. The MFP 1 according to the present embodiment is an example of an image processing apparatus, and can execute a plurality of modes such as a copy mode and a print mode in addition to a scan mode. In the following description, the lower right side of FIG. 1 is the front side (F) of the multifunction machine 1, the lower left side of the page is the left side (L) of the multifunction machine 1, and the upper side of the page is the upper side (U) of the multifunction machine 1. .

(Mechanical structure of the MFP)
As shown in FIG. 1, the multifunction machine 1 includes a cover unit 2 and an apparatus body 3. A support member (not shown) is provided on the rear end side of the upper surface of the apparatus body 3, and the rear end side of the cover portion 2 is connected to the support member so as to be rotatable about a rotation axis along the left-right direction. ing. As a result, the cover unit 2 can be displaced between a closed posture that covers the upper surface of the device body 3 and an open posture (see FIG. 1) that opens the upper surface of the device body 3.

  FIG. 2 shows a simplified internal structure of a part of the cover unit 2 and the apparatus main body 3. In the figure, the upper part from the dotted line D is the cover part 2. The cover unit 2 includes a supply tray 11, a front sensor 12, a discharge tray 13, an automatic document feeder (hereinafter referred to as “ADF”) 14, a first ADF facing member 15, an FB pressing member 16, 2 includes a reading unit 17, a rear sensor 18, and the like. In the cover portion 2, a transport path R is formed for returning a document sheet (not shown) from the supply tray 11 into a U shape and transporting it to the discharge tray 13. The document sheet is an example of a sheet, and is not limited to paper but may be plastic.

  A plurality of original sheets before image reading can be arranged on the supply tray 11. The front sensor 12 is a document presence / absence sensor that detects the presence / absence of a document sheet on the supply tray 11 at a detection position RF on the leading end side (left end side) of the supply tray 11, and transmits the detection result to the control unit 30. . The rear sensor 18 is a document presence / absence sensor that detects the presence / absence of a document sheet at a detection position RR downstream of the detection position RF in the transport path R, and transmits the detection result to the control unit 30. The discharge tray 13 is provided above the supply tray 11 and discharges an original sheet after image reading. The position on the most downstream side of the transport path R is called a discharge position RE.

  The ADF 14 is an example of a moving unit, and performs a transport operation in which a plurality of document sheets on the supply tray 11 are separated one by one, transported along the transport path R, and sequentially discharged to the discharge tray 13. Specifically, the ADF 14 includes a supply roller 14A, a separation roller 14B, a separation pad 14C, a plurality of conveyance rollers 14D, a plurality of driven rollers 14E driven in pressure contact with the respective conveyance rollers 14D, and a plurality of guides for guiding the document sheet. It has member 14F etc.

  The supply roller 14A, the separation roller 14B, and the conveyance roller 14D are rotationally driven by a stepping motor 14G described later. As a result, the supply roller 14A conveys the plurality of document sheets stacked on the supply tray 11 to the conveyance path R side, and the separation roller 14B and the separation pad 14C feed the plurality of document sheets one by one. Separated and sent out in the transport path R. The conveyance roller 14 </ b> D conveys the separated document sheet along the conveyance path R and discharges it onto the discharge tray 13.

  The first ADF facing member 15 is an example of a facing member and a white reference member, and faces the first reading unit 25 through the ADF glass 21A when the cover unit 2 is in the closed posture. Hereinafter, the facing position between the first ADF facing member 15 and the first reading unit 25 is referred to as a first reading position R1. Of the first ADF facing member 15, the facing surface 15 </ b> A facing the first reading unit 25 is white with substantially uniform light reflectance, and the first ADF facing member 15 is used for acquiring white reference data to be described later. Used as a white reference member.

  The FB pressing member 16 is an example of a pressing member, and is provided on the lower surface side of the cover portion 2. When the cover portion 2 is in the closed posture, the FB glass 21 </ b> B described later is almost entirely covered. The light reflection characteristics of the facing surface 16A of the FB pressing member 16 facing the FB glass 21B are the same as those of the white reference plate 22A described later. The second reading unit 17 is provided on the downstream side of the transport path R with respect to the first ADF facing member 15. The specific configuration of the second reading unit 17 is the same as that of the first reading unit 25 described later, and detailed description thereof is omitted.

  As shown in FIG. 1, the apparatus main body 3 is formed in a box shape that is long in the left-right direction as a whole, and a platen glass 21 is disposed on the upper surface portion of, for example, an opening of a resin frame 3A. It is configured. A partition member 22 is provided on the upper surface of the platen glass 21 at a position on the left side. The platen glass 21 is divided into two parts by the partition member 22. Hereinafter, the left part is referred to as ADF glass 21A, and the right part is referred to as FB (Flat Bed) glass 21B. The FB glass 21B is an example of a document table.

  A white reference plate 22A is provided on the lower surface of the partition member 22 (see FIG. 2). The white reference plate 22A is an example of a white reference member, and is opposed to the first reading unit 25. It is a white member having a substantially uniform reflectance. Further, the portion of the lower surface of the partition member 22 adjacent to the white reference plate 22A is black.

  The apparatus body 3 is provided with an operation unit 23, a display unit 24, and the like. As shown in FIG. 2, a first reading unit 25, a device moving mechanism 26 (see FIG. 3), a second ADF facing member 27, and the like are provided in the apparatus main body 3.

  The first reading unit 25 faces the first ADF facing member 15 via the first reading position R1 when the cover unit 2 is in the closed posture. The first reading unit 25 is a reading device having a CIS (Contact Image Sensor), and includes, for example, a light emitting unit 25A and a light receiving unit 25B. The light emitting unit 25A is composed of light emitting elements (light emitting diodes, etc.) of three colors of red, green, and blue.

  The light receiving unit 25B includes a light receiving lens 25C and a light receiving substrate 25D (see FIG. 4). The light receiving lens 25C is an optical member that guides light from the first reading position X1 side to the light receiving substrate 25D. The light receiving substrate 25D has a configuration in which a plurality of light receiving elements 25E are arranged side by side in the left-right direction, in other words, in the main scanning direction. Note that the first reading unit 25 is not limited to the CIS, and may be configured to have, for example, a CCD (Charge Coupled Drive Image Sensor).

  The device moving mechanism 26 is an example of a moving unit, and the first reading unit 25 is moved in the left-right direction, in other words, in the sub-scanning direction on the lower side of the ADF glass 21A, the partition member 22 and the FB glass 21B. It is possible to move. Hereinafter, the position where the first reading unit 25 faces the ADF glass 21A is referred to as an ADF position XA. The position where the first reading unit 25 faces the partition member 22 is an example of a reference position, and is hereinafter referred to as a home position X0. The position where the first reading unit 25 faces the FB glass 21B is an example of a second facing position, and is hereinafter referred to as an FB position XF. Furthermore, a control unit 30 and a printing unit 28, which will be described later, are provided in the apparatus main body 3 (see FIG. 3).

(Electric configuration of the multifunction device)
As shown in FIG. 3, the multifunction machine 1 includes a control unit 30, and the control unit 30 includes a first reading unit 25, a second reading unit 17, an ADF 14, a device moving mechanism 26, a front sensor 12, and a rear sensor 18. The operation unit 23, the display unit 24, and the printing unit 28 are connected so that data communication is possible.

  The control unit 30 includes a central processing unit (hereinafter referred to as CPU) 31, a ROM 32, a RAM 33, an image processing circuit 34, and a clock generation unit 35. The ROM 32 stores a program (an example of a read image correction program) for executing a reading control process, which will be described later, and a program for executing various operations of the multifunction device 1. The CPU 31 controls each unit of the multifunction machine 1 according to the program read from the ROM 32. In addition to the ROM 32 and the RAM 33, the storage medium storing the various programs may be a non-volatile memory such as a CD-ROM, a hard disk device, or a flash memory.

  The image processing circuit 34 is a hardware circuit dedicated to image processing. The clock generator 35 generates and outputs a control signal corresponding to a spread spectrum clock whose frequency varies with a constant modulation period. Specifically, the clock generation unit 35 includes a reference clock generation circuit 35A, a spread spectrum clock generation unit 35B, and a clock generation circuit 35C. The reference clock generation circuit 35A outputs a reference clock SCLK having a constant frequency.

  The spread spectrum clock generator 35B modulates the frequency of the reference clock SCLK to generate and output the spread spectrum clock SSCG_CLK. The clock generation circuit 35C uses the spread spectrum clock SSCG_CLK as a reference, and controls the first reading unit 25 and the second reading unit with control signals that determine the lighting periods and reading periods of the light sources of the first reading unit 25 and the second reading unit 17. 17 As a result, the first reading unit 25 and the second reading unit 17 execute an image reading operation line by line at a reading cycle corresponding to the modulation frequency of the spread spectrum clock SSCSSCG_CLK (hereinafter simply referred to as spectrum frequency). Read data of pixel rows corresponding to each read image is sequentially output. The read data is AD converted by an AD converter (not shown) and stored in the RAM 33.

  The ADF 14 includes a stepping motor 14G and a motor drive circuit 14H, and rotates the above-described rollers 14A, 14B, and 14D by rotating the stepping motor 14G.

  The motor drive circuit 14H receives a clock signal from the CPU 31. Then, the motor drive circuit 14H updates the signal for each pulse of the clock signal, and supplies a current to the coil based on the signal, thereby rotating the stepping motor 14G by one step (predetermined angle).

  With the above-described configuration, the multi-function device 1 can execute ADF reading and FB reading. ADF reading is an operation in which the first reading unit 25 is stopped at the ADF position XA and an image on a document sheet conveyed by the ADF 14 is read. Furthermore, in ADF reading, single-sided reading for reading only one side of a document sheet using only the first reading unit 25, and double-sided reading for reading both sides of a document sheet using the first reading unit and the second reading unit 17 Can be executed. The FB reading is an operation of reading an image of an original sheet placed on the FB glass 21B while moving the first reading unit 25 along the FB glass 21B by the device moving mechanism 26.

  The operation unit 23 has a plurality of buttons, and various input operations can be performed by the user, such as designation of each mode described above. The display unit 24 includes a liquid crystal display, a lamp, and the like, and can display various setting screens and operation states of the apparatus. The printing unit 28 prints an image based on the image data such as the read data on a printing sheet (not shown) by, for example, an electrophotographic method or an inkjet method.

(About the reading area of the reading unit)
(1) Side area when the first reading unit is located at the ADF position XA FIG. 4 is a schematic view of the first reading unit 25 and the first ADF facing member 15 located at the ADF position XA as viewed from the front. It is shown. The reading area EA of the first reading unit 25 at this time extends in the left-right direction at the first reading position X1, and the width in the left-right direction is the total length of all the light receiving elements 25E arranged on the light receiving substrate 25D. And substantially the same. Note that the width in the left-right direction of the reading area EA may be substantially the same as the total length of the effective light receiving element row corresponding to the effective pixels used for image reading among all the light receiving elements 25E.

  The reading area EA includes a passing area E1A and a side area E2A arranged in the left-right direction. The passage area E1A is an example of an original reading area, and is an area that is located in the conveyance path R and through which an original sheet passes. That is, the passage area E1A is an original readable area in which an image on the original sheet can be read. The side area E2A is located in the side of the passage area E1A when viewed from the front-rear direction, and the original sheet does not pass through. That is, the side region E2A is a document unreadable region where a document sheet image cannot be read.

  On the other hand, the first ADF facing member 15 has a facing surface 15A, and the facing surface 15A faces the first reading unit 25 when the cover unit 2 is in the closed position (see FIG. 1). The opposing surface 15A has substantially the same reflection characteristics as the white reference plate 22A. Further, the width in the left-right direction of the facing surface 15A is equal to or greater than the width of the reading area EA, and the facing surface 15A faces the first reading unit 25 over the entire length of the reading area EA. For this reason, the 1st reading part 25 can read not only the image in passage area E1A but the image in side field E2A.

  That is, the first reading unit 25 images the opposing surface 15A of the first ADF opposing member 15 in the side region E2A not only when there is no original sheet at the first reading position X1 but also when there is an original sheet. Can be read. Hereinafter, the reading data for the entire one line read by the first reading unit 25 in the reading area EA is referred to as the entire reading data, and the reading data of the portion read in the passage area E1A among the entire reading data. The read data of the portion read in the side area E2A is referred to as side data.

(2) Reading area when the first reading unit is located at the FB position XF The upper part of FIG. 5 shows the upper surface portion of the apparatus body 3, and the lower part shows the first reading part located at the FB position XF. The schematic diagram which looked at the holding member 16 for 25 and FB from the front is shown. The reading area EF of the first reading unit 25 at this time has a width in the left-right direction that is substantially the same as the entire length of all the light receiving elements 25E arranged on the light receiving substrate 25D. Note that the width in the left-right direction of the reading area EF may be substantially the same as the total length of the effective light receiving element row corresponding to the effective pixels used for image reading among all the light receiving elements 25E.

  The reading area EF includes an arrangement area E1F and side areas E2F and E3F arranged in the left-right direction. The arrangement area E1F is an example of an original reading area, and is an area corresponding to a portion of the FB glass 21B where an original sheet is arranged, as shown in the upper part of FIG. Hereinafter, the portion where the original sheet is arranged is referred to as an original arrangement portion. The width in the left-right direction of the document placement portion is slightly larger than the width of the maximum size of the document sheet that can be read by the multifunction machine 1, for example. In the multi-function device 1, the original sheet is placed on the FB glass 21B so that the corner of the original sheet is aligned with one vertex W (the upper right vertex in FIG. 5) of the FB glass 21B.

  As shown in the lower part of the figure, the side area E2F is located on the right side of the arrangement area E1F when viewed from the front-rear direction, corresponds to the frame 3A, and is an area where no document sheet is arranged. The frame body 3A is an example of a non-arranged part. The lower surface of the frame body 3A is white, and a sticker 3B is attached to the frame body 3A on the right side of the document placement portion over substantially the entire length in the left-right direction of the document placement portion. The lower surface of the seal 3B has the same light reflection characteristics such as light reflectance as the white reference plate 22A. Accordingly, the first reading unit 25 reads an image on the lower surface of the seal 3B in the side area E2A not only when the original sheet is not arranged in the arrangement area E1F but also when the original sheet is arranged. be able to.

  The side area E3F is located on the left side of the arrangement area E1F when viewed from the front-rear direction, and corresponds to a non-arrangement portion of the FB glass 21B where no document sheet is arranged. On the other hand, as described above, the FB pressing member 16 almost entirely covers the FB glass 21B. Therefore, the first reading unit 25 has a lower surface 16A of the FB pressing member 16 in the side area E3A not only when the original sheet is not arranged in the arrangement area E1F but also when the original sheet is arranged. Images can be read. Hereinafter, the read data for one whole line read by the first reading unit 25 in the reading area EF is referred to as whole reading data, and the reading data of the portion read in the arrangement area E1F among the whole reading data. The read data of the portion read in the side area E2F or the side area E3F, which is referred to as the arrangement read data, is referred to as side data.

(Relationship between white reference data and spectrum frequency)
For example, a difference in density may occur in the image based on the read data due to differences in the light receiving characteristics of the plurality of light receiving elements 25E. The shading correction data is an example of white correction data, and is correction data for suppressing the density difference. The shading correction data includes a plurality of white correction values F. The plurality of white correction values F are correction coefficients for correcting the pixel value of each pixel included in the passage reading data to a pixel value indicating white.

  Here, as will be described later, the shading correction data is generated using the white reference data, and the white reference data is acquired by the reading operation with respect to the white reference member such as the first ADF facing member 15. In order to perform white correction of the document read data with accuracy using the white reference data, the spectrum is different between the reading operation for acquiring the white reference data and the reading operation for acquiring the document read data. It is preferable that the frequencies match.

  However, as described above, the control unit 30 causes the first reading unit 25 to execute an image reading operation line by line at a reading cycle corresponding to the spectrum frequency. Therefore, as shown in FIG. 6, the white reference data varies according to the spectrum frequency during the reading operation for the white reference member. Further, as will be described later, the reading operation for acquiring the white reference data and the reading operation for acquiring the document reading data are different in timing. For this reason, the spectrum frequency may differ between the reading operation for acquiring the white reference data and the reading operation for acquiring the document reading data. In such a case, there is a possibility that the document read data cannot be corrected with accuracy using the white reference data.

  Specifically, in the figure, white reference data WD0 indicated by a solid line is white reference data when the spectrum frequency is FG0, and white reference data WDN indicated by a dotted line is white reference data when the spectrum frequency is FGN. Suppose that It is assumed that a reading operation for acquiring white reference data is executed when the spectrum frequency is FG0, and a reading operation for acquiring document reading data is executed when the spectrum frequency is FGN. In this case, the document reading data and the white reference data WD0 are data obtained by reading operations executed at times when the spectrum frequencies are different from each other. For this reason, when white correction is performed on the original read data based on the white reference data WD0, the accuracy of white correction is lower than when white correction is performed based on the white reference data WDN.

(Reading control processing)
For example, when the user performs an operation for instructing execution of any one of the scan mode, the copy mode, and the facsimile mode on the operation unit 23, the control unit 30 executes the reading control process shown in FIGS. When the control unit 30 determines that there is a document sheet on the supply tray 24 based on the detection result of the front sensor 12, the control unit 30 performs ADF reading, and determines that there is no document sheet on the supply tray 24. FB reading is executed.

  In this reading control process, it is suppressed that the image quality of the read image corrected using the shading correction data is deteriorated due to the difference in reading cycle between reading of the white reference plate 22A and reading of the original sheet. Is done. At the start of the reading control process, the first reading unit 25 stands by at the home position X0 directly below the white reference plate 22A. Hereinafter, a description will be given separately for the time of executing ADF reading and single-sided reading and the time of executing FB reading.

(1) During ADF Reading As shown in FIG. 7, the CPU 31 first moves the first reading unit 25 from the home position X0 to the ADF position XA by the device moving mechanism 26 (S1), and starts the transport operation to the ADF 14 (S2). As a result, the original sheets are conveyed one by one from the supply tray 11 along the conveyance path R.

  The CPU 31 causes the first reading unit 25 to perform the reading operation for the entire one line with respect to the first ADF facing member 15 before the document sheet reaches the first reading position X1 after the start of the conveying operation ( S3), the entire reading data is acquired. Further, the CPU 31 initializes the line number N to 0 (S3). The CPU 31 acquires passage reading data out of the entire reading data acquired in S3 as white reference data and stores it in the RAM 33 (S4).

  Further, the CPU 31 acquires the pixel value of the image based on the side data from the side data among the entire read data acquired in S3 (S5). Hereinafter, the side data at this time is referred to as first side data, and the pixel value is hereinafter referred to as a first pixel value G (0). The pixel value of the image based on the side data may be a pixel value of one pixel included in the side data, or an average value of pixel values of a plurality of pixels or a maximum value among pixel values of a plurality of pixels. Or the center value of the minimum value. The processing of S3 to S5 is an example of white reference reading processing. Note that the order of the process of S4 and the process of S5 may be reversed.

Next, the CPU 31 generates the shading correction data from the white reference data acquired in S4 (S6). Hereinafter, the shading correction data at this time is particularly referred to as basic shading correction data, and the white correction value F included in the basic shading correction data is referred to as basic white correction value F (0). Note that the basic white correction value F (0) is represented by the following equation, for example.
F (0) = pixel value indicating white / pixel value of each pixel of white reference data When the value indicated by the pixel value is 0 to 255, the pixel value indicating white is, for example, 255.

  After generating the basic shading correction data, the CPU 31 determines whether or not the leading edge in the document sheet conveyance direction has reached the first reading position R1 (S7). The CPU 31 waits while determining that the leading edge of the document sheet has not reached the first reading position R1 (S7: NO), and determines that the leading edge of the document sheet has reached the first reading position R1. (S7: YES), go to S8. Specifically, the CPU 31 determines whether or not the original sheet is detected at the detection position RR based on the detection result of the rear sensor 18, and waits while determining that the original sheet is not detected. On the other hand, if the CPU 31 determines that the document sheet has been detected, it is assumed that the leading edge of the document sheet has reached the detection position RR, and whether or not the document sheet has been conveyed by the first distance from the time when it is determined that the document sheet has been detected. Judging.

  The first distance is a distance from the detection position RR to the first reading position R1. The CPU 31 measures the transport distance by counting the number of steps of a drive motor (stepping motor) that drives the ADF 4 to rotate. Note that the CPU 31 may measure the transport distance of the document sheet from the time counted from the time when it is determined that the document sheet is detected by the built-in timer and the transport speed V2.

  The CPU 31 stands by while determining that the original sheet is not conveyed by the first distance, and when determining that the original sheet has been conveyed by the first distance, the leading edge of the original sheet reaches the first reading position R1. (S7: YES). Then, the CPU 31 causes the first reading unit 25 to execute a reading operation for the entire line, and acquires the entire reading data (S8). Further, the CPU 31 adds 1 to the line number N (S8).

  When the reading operation in S8 is executed, the document sheet passes through the passage area E1A. Accordingly, the CPU 31 acquires passage reading data among the entire reading data acquired in S8 as document reading data, and stores it in the RAM 33 (S9). Moreover, CPU31 acquires the pixel value of the image based on the said side data from side data among the whole reading data acquired by S8 (S10). Hereinafter, the side data at this time is referred to as second side data, and the pixel value is hereinafter referred to as second pixel value G (N). The processes in S8 to S10 are an example of a document reading process.

Next, the CPU 31 generates shading correction data using the relative ratio between the first pixel value G (0) and the second pixel value G (N) and the basic shading correction data generated in S6 ( S11). The processing of S6 and S11 is an example of white correction data generation processing. Specifically, the CPU 31 corrects each basic white correction value F (0) included in the basic shading correction data by the following formula to calculate each white correction value F (N).
F (N) = F (0) × (G (0) / G (N))

  Next, the CPU 31 corrects the original reading data using the shading correction data generated in S11 (S12). The process of S12 is an example of a white correction process. Specifically, the CPU 31 multiplies the pixel value of each pixel included in the document read data by the corresponding white correction value F (N). As a result, even when the spectrum frequency is different between the reading operation for acquiring the white reference data and the reading operation for acquiring the document reading data, the document reading data is substantially changed to the document reading data. And the white reference data acquired at the same time of the spectrum frequency can be corrected.

  In the example of FIG. 6 described above, when the spectrum frequency is FG0, the reading operation for obtaining the white reference data in S3 is executed, and when the spectrum frequency is FGN, the reading operation for obtaining the document reading data in S8 is performed. Assume that a reading operation has been executed. In this case, the white reference data acquired in S4 is WD0, and the white reference data acquired at the same time as the original read data and the spectrum frequency is WDN. The ratio of the pixel values of the white reference data WD0 and WDN due to the difference in spectrum frequency is the relative ratio (= G (N) / G (0)) based on the first side data and the second side data. Can be grasped as. Therefore, by using the relative ratio in addition to the white reference data, it is possible to perform a white correction process substantially equivalent to correcting the original read data using the WDN for the white reference data.

  After executing the white correction process, the CPU 31 determines whether or not the trailing edge in the document sheet conveyance direction has passed the first reading position R1 (S13). If the CPU 31 determines that the trailing edge of the document sheet has not passed through the first reading position R1 (S13: NO), the CPU 31 returns to S8 and executes the processes of S8 to S12 for the next ranking line. On the other hand, when the CPU 31 determines that the trailing edge of the document sheet has passed the first reading position R1 (S13: YES), the CPU 31 stops the reading operation of the first reading unit 25 and discharges the document sheet to the discharge tray 13. Thereafter, the ADF 14 stops the conveying operation, and the reading control process is terminated.

  Specifically, the CPU 31 determines whether or not the document sheet is detected at the detection position RR based on the detection result of the rear sensor 18, and waits while determining that the document sheet is detected. On the other hand, if the CPU 31 determines that the document sheet is no longer detected, the CPU 31 determines that the trailing edge of the document sheet has passed the detection position RR, and conveys the document sheet by the second distance from the time when it is determined that the document sheet is no longer detected. Determine if you did. The second distance is a distance from the first reading position R1 to the discharge position RE. The CPU 31 measures the transport distance by counting the number of steps of the drive motor that rotationally drives the ADF 4.

(2) At the time of FB reading As shown in FIG. 8, the CPU 31 first causes the first reading unit 25 to perform a reading operation for one whole line with respect to the white reference plate 22A at the home position X0 (S21). To obtain the entire reading data. Further, the CPU 31 initializes the line number N to 0 (S21). CPU31 acquires arrangement | positioning reading data as white reference data among the whole reading data acquired by S21 similarly to said S4, and memorize | stores it in RAM33 (S22).

  Similarly to S5, the CPU 31 acquires the first pixel value G (0) based on the first side data from the first side data among the entire read data acquired in S21 (S23). The processing of S21 to S23 is an example of white reference reading processing. Note that the order of the process of S22 and the process of S23 may be reversed. Next, as in S46, the CPU 31 generates basic shading correction data from the white reference data acquired in S22 (S24).

  After generating the basic shading correction data, the CPU 31 causes the device moving mechanism 26 to start moving the first reading unit 25 from the home position X0 to the FB position XF (S25). And CPU31 judges whether the 1st reading part 25 reached the reading start position of the left end of FB glass 21B, for example from the amount of movement of the 1st reading part 25 by device movement mechanism 26, for example (S26). ). The CPU 31 stands by while determining that the first reading unit 25 has not reached the reading start position (S26: NO), and when determining that the first reading unit 25 has reached the reading start position (S26). : YES), the first reading unit 25 performs the reading operation for the entire line, and acquires the entire read data (S27). Further, the CPU 31 adds 1 to the line number N (S27).

  When the reading operation of S27 is executed, the document sheet passes through the arrangement area E1F. Therefore, the CPU 31 acquires the arrangement reading data among the entire reading data acquired in S27 as document reading data, and stores it in the RAM 33 (S28). Similarly to S10, the CPU 31 acquires the second pixel value G (N) based on the second side data from the second side data among the entire read data acquired in S27 (S29). The processes in S27 to S29 are an example of a document reading process.

  Next, the CPU 31 performs shading correction using the relative ratio between the first pixel value G (0) and the second pixel value G (N) and the basic shading correction data generated in S24, as in S11. Data is generated (S30). The processing of S24 and S30 is an example of white correction data generation processing. Next, the CPU 31 corrects the document read data using the shading correction data generated in S30, similarly to S22 (S31). The process of S31 is an example of a white correction process.

  After executing the white correction process, the CPU 31 determines whether the first reading unit 25 has reached the reading end position near the right end of the FB glass 21B, for example, based on the amount of movement of the first reading unit 25 by the device moving mechanism 26. Is determined (S32). When the CPU 31 determines that the first reading unit 25 has not reached the reading end position (S32: NO), the CPU 31 returns to S27 and executes the processes of S27 to S31 for the next ranking line. On the other hand, when the CPU 31 determines that the first reading unit 25 has reached the reading end position (S32: YES), the CPU 31 causes the device moving mechanism 26 to stop the moving operation of the first reading unit 25 and ends the reading control process. To do.

(Effect of this embodiment)
The reading cycle may be different between reading the white reference member and reading the original sheet. However, this difference has a correlation with the relative ratio between the value indicated by the first side data acquired when reading the white reference member and the value indicated by the second side data acquired when reading the original sheet. Therefore, according to the present embodiment, white correction data is generated using the relative ratio in addition to the white reference data, and the original image data is corrected using the correction data. As a result, it is possible to suppress deterioration in the image quality of the read image corrected using the correction data, because the reading cycle is different between reading the white reference member and reading the original sheet.

  Further, according to the multi-function device 1, by performing the document reading process, the white correction data generation process, and the white correction process for each line, the reading cycle is different between the reading of the white reference member and the reading of the document sheet. By making the difference, it is possible to more reliably suppress the deterioration of the image quality of the read image corrected using the correction data.

  In the ADF reading, the first ADF facing member 15 is used as a white reference member, and the first side data and the second side data are acquired by the reading operation with respect to the common first ADF facing member 15. For this reason, it is possible to calculate a white correction value with higher accuracy than in a configuration in which the first side data and the second side data are acquired by reading operations on different members.

  The light reflection characteristics of the facing surface 16A of the FB pressing member 16 are the same as those of the white reference plate 22A. Therefore, more accurate white correction data can be generated in the FB reading compared to a configuration in which the light reflection characteristics of the two are different from each other. For this reason, it is possible to more reliably suppress the image quality of the read image subjected to the white correction from being deteriorated due to the fluctuation of the frequency of the spread spectrum clock.

<Other embodiments>
The technology disclosed in the present specification is not limited to the embodiments described with reference to the above description and drawings, and includes, for example, the following various aspects.

  The “image processing apparatus” is not limited to the multifunction machine 1 but may be a single scanner apparatus having only a scanner function, a printing apparatus having only a printing function, a facsimile apparatus, a copying apparatus, or the like. Further, the “image processing apparatus” may be configured to execute only one of ADF scanning and FB scanning, or may be configured to perform only single-sided scanning.

  In the above embodiment, the control unit 30 is configured to execute the reading control process by one CPU 31. However, the present invention is not limited to this, and the control unit 30 has a configuration in which the CPU and a hardware circuit such as the image processing circuit 34 execute the reading control processing, a configuration in which the reading control processing is executed only by one or a plurality of CPUs, and an ASIC ( A configuration in which the reading control process is executed only by a hardware circuit such as Application Specific Integrated Circuit) may be used. For example, the control unit 30 may be configured to cause the image processing circuit 34 to execute part or all of the document reading process, the white correction data generation process, and the white correction process.

  The clock generation unit 35 may not have the spread spectrum clock generation unit 35B and may output the reference clock SCLK having a constant frequency as it is. That is, the control unit 30 may be configured to control the lighting period, the reading period, and the like of the light sources of the first reading unit 25 and the second reading unit 17 on the basis of a constant frequency of the reference clock SCLK. Even in such a configuration, for example, due to a change in the frequency of the reference clock SCLK due to a temperature change or the like, the image quality may be affected by a difference in timing between reading the white reference member and reading the original sheet. On the other hand, the control unit 30 can suppress the influence on the image quality by executing the reading control process of FIG.

  The “facing member” is not limited to the first ADF facing member 15, and may be any configuration having a facing surface that faces the first reading unit 25 at least in the side region E <b> 2 </ b> A.

  The light reflection characteristics of the facing surface 16A of the FB pressing member 16 may be different from that of the white reference plate 22A. In this case, it is preferable to further correct the basic shading correction data using, for example, the ratio of the light reflectance between the facing surface 16A and the white reference plate 22A.

  The lower surface of the seal 3B may be different from the white reference plate 22A in light reflection characteristics such as light reflectance. In this case, it is preferable to further correct the basic shading correction data using, for example, the ratio of the light reflectance between the lower surface of the seal 3B and the white reference plate 22A.

  The control unit 30 may be configured to perform document reading processing, white correction data generation processing, and white correction processing in units of a plurality of lines. For example, white correction data is generated from side data of one line of a plurality of lines, and the read data for a plurality of lines is corrected using the white correction data. Even with such a configuration, it is possible to more reliably suppress the deterioration of the image quality of the read image corrected using the correction data because the reading cycle is different between reading the white reference member and reading the original sheet. It is possible.

  In the reading control processing of FIGS. 7 and 8, the control unit 30 does not generate basic shading correction data when acquiring white reference data, but performs shading using the white reference data and the above relative ratio when acquiring document reading data. Correction data may be generated. Specifically, the CPU 31 proceeds to S7 without calculating the basic white correction value F (0) of S6 after executing the process of S5 in FIG. 7, and in S11, the pixel value of each pixel of the white reference data Alternatively, the correction may be performed by multiplying the relative ratio, and shading correction data may be generated from the corrected white reference data. Further, after executing the process of S23 of FIG. 8, the CPU 31 proceeds to S25 without calculating the basic white correction value F (0) of S24, and in S30, sets the pixel value of each pixel of the white reference data to Correction may be performed by multiplying the relative ratio, and shading correction data may be generated from the corrected white reference data.

In S11 and S30 of the reading control processing of FIGS. 7 and 8, the control unit 30 sets the white correction value F (N), the basic correction value G (0), the first pixel value G (0), and the Nth line. Calculated from the second pixel value GN). However, the present invention is not limited to this, and the control unit 30 sets the white correction value F (N) as the white correction value F (N) of the immediately preceding N−1 number line, as shown in the following equation. May be calculated from the second pixel value G (N-1) of the second line and the second pixel value GN of the Nth line).
F (N) = F (N−1) × (G (N−1) / G (N))

  The controller 30 may be configured to acquire the first side data and the second side data by reading operations on different members in ADF reading. For example, the control unit 30 may acquire the first side data by a reading operation with respect to the white reference plate 22 </ b> A and may acquire the second side data by a reading operation with respect to the first ADF facing member 15. At this time, the light reflection characteristic of the facing surface 15A of the first ADF facing member 15 is preferably the same as that of the white reference plate 22A, but may be different. When the light reflection characteristics are different, it is preferable to further correct the basic shading correction data using, for example, the ratio of the light reflectance between the first ADF facing member 15 and the white reference plate 22A.

  The control unit 30 may execute the reading control process shown in FIG. 7 for the reading of the second reading unit 17 at the time of duplex printing. In this case, the second ADF facing member 27 is preferably used as a white reference member.

  1: MFP 14: ADF 15: First ADF facing member 16: FB holding member 22A: White reference plate 17: First reading unit 25: Second reading unit 26: Device moving mechanism E1: Passing area E2: Side region

Claims (5)

An image is read in a reading area along the main scanning direction, and the reading area includes a document reading area and a side area located to the side of the document reading area;
A moving unit that moves at least one of the original sheet and the reading unit to pass the original sheet into the original reading region;
A white reference member;
A control unit having a clock generation unit that generates a spread spectrum clock whose frequency fluctuates at a constant modulation period; and
The controller is
The reading unit is caused to read the white reference member at a reading cycle according to the spread spectrum clock, and obtains white reference data that is read data of the document reading region in which the output of the reading unit is AD-converted, A white reference reading process for obtaining first side data which is read data of the side region obtained by AD conversion of the output of the reading unit;
A basic shading correction data calculation process for calculating basic shading correction data that is a value obtained by dividing a value indicating white by the white reference data;
Read data of the original reading area obtained by causing the reading unit to read the original sheet line by line at a reading cycle according to the spread spectrum clock and AD-converting the output of the reading part for each line. Document reading processing for acquiring document reading data and second side data which is reading data of the side area obtained by AD conversion of the output of the reading unit ;
By dividing the value indicated by the first side data by the second side data acquired for each line by the document reading process, and multiplying the divided value by the basic shading correction data, for each line. Shading correction data acquisition processing for acquiring shading correction data in
A shading correction process for correcting the original reading data acquired for each line using the shading correction data of the line;
An image reading apparatus having a configuration for executing The image reading apparatus according to claim 1,
Equipped with a platen,
The moving unit includes a configuration in which the reading position is moved with respect to a document sheet disposed on the document table by moving the reading unit;
The image reading apparatus, wherein a light reflection characteristic of a portion corresponding to the side region of the document table is the same as that of the white reference member. The image reading apparatus according to claim 2,
Holding down a document sheet placed on the platen, and a pressing member having a width in the main scanning direction wider than that of the document sheet,
The width of the white reference member in the main scanning direction is equal to or greater than the width of the reading region in the main scanning direction.
The image reading device, wherein the light reflection characteristic of at least a portion corresponding to the side region of the pressing member is the same as that of the white reference member. The image reading apparatus according to claim 2, wherein
A non-arrangement portion is provided at a side position of the document table,
The width of the white reference member in the main scanning direction is equal to or greater than the width of the reading region in the main scanning direction.
The image reading device in which the light reflection characteristic of at least a portion corresponding to the side region in the non-arranged portion is the same as that of the white reference member. The image reading apparatus according to any one of claims 1 to 4,
The moving unit includes a configuration for conveying the document sheet toward the reading position;
The white reference member is a facing member disposed to face the reading unit in the reading region,
The width of the opposing member in the main scanning direction is equal to or greater than the width of the reading region in the main scanning direction.

Images