JP6658667B2 - Image reading device and image forming device - Google Patents

Description

  The present invention relates to an image reading device that reads image data of a document and an image forming device.

  There is known an image reading apparatus in which a luminous substance is applied to a document cover and a fixed platen portion, and the size of the document is detected based on afterglow emitted from the luminous substance in a state where a light source is turned off (for example, Patent Document 1).

JP 2006-319736 A

  However, in the image reading apparatus, it is necessary to perform processing for turning off the light source and detecting the size of the document before, during, or after the start of the image reading operation. Therefore, the processing time is lengthened by the amount of the processing.

  Further, in the case where the light source is repeatedly turned on and off while scanning the document at a constant speed in the sub-scanning direction to alternately perform image reading and size detection, the image reading resolution is reduced.

  An object of the present invention is to provide an image reading apparatus and an image forming apparatus capable of detecting an edge of a document without turning off a light source.

  An image reading device according to one aspect of the present invention includes a light source for three colors, a light emission control unit, a scanning unit, a background plate, an imaging unit, and a detection processing unit. The light sources of the three colors emit light of different colors to a region along the main scanning direction on the document. The light emission control unit sequentially lights the three color light sources one by one at a preset cycle. The scanning unit scans the original in a sub-scanning direction orthogonal to the main scanning direction with light from the three-color light source by moving one of the original and the three-color light source. The background plate is located on the back side of the original as viewed from the three color light sources, and is coated with a luminous substance. The imaging unit reads image data including an image of the document based on reflected light of light emitted from the three color light sources. The detection processing unit detects an edge of the document in the image data based on a pixel value of a specific color component in the image data.

  An image forming apparatus according to one aspect of the present invention includes the image reading device and an image forming unit. The image forming unit forms an image on a sheet based on image data of a document read by the image reading device.

  According to the present invention, there is provided an image reading apparatus and an image forming apparatus capable of detecting an edge of a document without turning off a light source.

FIG. 1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a system configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing a part of the configuration of the ADF and the image reading unit in the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a view showing an example of document data read by the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a diagram illustrating the amount of reflected light when the blue light source is turned on in the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a diagram illustrating the amount of reflected light when the green light source is turned on in the image forming apparatus according to the embodiment of the present invention. FIG. 7 is a diagram illustrating the amount of reflected light when the red light source is turned on in the image forming apparatus according to the embodiment of the present invention. FIG. 8 is a flowchart illustrating an example of a procedure of an adjustment process performed by the image forming apparatus according to the embodiment of the present disclosure.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments are examples embodying the present invention and do not limit the technical scope of the present invention.

[Configuration of Image Forming Apparatus 10]
First, the configuration of an image forming apparatus 10 according to an embodiment of the present invention will be described with reference to FIGS. Here, FIG. 1 is a schematic sectional view showing the configuration of the image forming apparatus 10. FIG. 3 is a schematic sectional view showing a part of the configuration of the ADF 1 and the image reading unit 2.

  The image forming apparatus 10 is a multifunction peripheral having a plurality of functions such as a facsimile function and a copy function, as well as a scan function of reading image data from a document and a print function of forming an image based on the image data.

  As shown in FIGS. 1 and 2, the image forming apparatus 10 includes an ADF (automatic document feeder) 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, a control unit 5, and an operation display unit 6. Is provided.

  The image forming section 3 can form an image by an electrophotographic method based on image data. Specifically, the image forming unit 3 includes a photosensitive drum, a charging device, an optical scanning device, a developing device, a transfer device, a cleaning device, a fixing device, and a paper discharge tray. The paper feed unit 4 includes a paper feed cassette, a sheet transport path, and a plurality of transport rollers, and supplies a sheet to the image forming unit 3. The image forming unit 3 can form an image on a sheet supplied from the paper feeding unit 4 based on image data of a document read by the image reading unit 2. The sheet on which the image is formed by the image forming unit 3 is discharged to the discharge tray. Note that the image forming section 3 may form an image by another image forming method such as an ink jet method.

  The control unit 5 includes control devices such as a CPU, a ROM, a RAM, and an EEPROM (registered trademark) not shown. The CPU is a processor that executes various arithmetic processing. The ROM is a non-volatile storage medium in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile storage medium, and the EEPROM is a nonvolatile storage medium. The RAM and the EEPROM are used as a temporary storage memory (work area) for various processes executed by the CPU. In the control unit 5, various control programs stored in the ROM in advance are executed by the CPU. Thus, the control unit 5 controls the image forming apparatus 10 as a whole. The control unit 5 may be configured by an electronic circuit such as an integrated circuit (ASIC), and is a control unit provided separately from the main control unit that controls the image forming apparatus 10 in an integrated manner. You may.

  The operation display unit 6 includes a display unit such as a liquid crystal display that displays various information according to a control instruction from the control unit 5, and an operation key or a touch panel that inputs various information to the control unit 5 according to a user operation. And the like.

  The ADF 1 conveys a document to be read (ie, a document from which image data is read by the image reading unit 2). Specifically, as shown in FIGS. 1 and 3, the ADF 1 includes a document conveyance path 1 </ b> A, a document placement unit 11, a plurality of conveyance rollers 12, a conveyance guide 13, and a paper discharge unit 14. The ADF 1 is supported so as to be openable and closable with respect to a document table 21 described later, and also functions as a document cover for a document placed on the first contact glass 211 of the document table 21.

  In the ADF 1, each of the transport rollers 12 is driven by a motor (not shown). As a result, the document placed on the document placing section 11 is transported along the document transport path 1A formed inside the ADF 1. The document conveyed along the document conveyance path 1A is guided to the reading position P1 (see FIG. 3) on the second contact glass 212 of the document table 21 by the conveyance guide 13, and then is discharged to the paper discharge unit 14. . Here, the ADF 1 is an example of the document transport unit in the present invention. The document conveying path 1A is an example of the conveying path in the present invention.

  The image reading section 2 can read image data from a document. Specifically, the image reading section 2 includes a document table 21, a reading unit 22, a mirror 23, a mirror 24, an optical lens 25, and a CCD 26, as shown in FIGS.

  The document table 21 is provided on an upper surface of a housing of the image forming apparatus 10. The document table 21 includes a first contact glass 211, a second contact glass 212, and a white reference plate 213, as shown in FIGS. The first contact glass 211 and the second contact glass 212 are transparent glasses. An original is placed on the first contact glass 211. The second contact glass 212 is provided at a position facing the conveyance guide 13 of the ADF 1 in a state where the second contact glass 212 is closed with respect to the document table 21. As shown in FIG. 3, the white reference plate 213 is provided on the upper surface of the end of the first contact glass 211 on the second contact glass 212 side. The surface of the white reference plate 213 facing the first contact glass 211 is white.

  The image reading unit 2 can read image data from a document by two different reading methods. Specifically, the image reading unit 2 can read image data from a document placed on the first contact glass 211. Further, when the document is conveyed by the ADF 1 through the reading position P1 on the second contact glass 212, the image reading unit 2 can also read image data from the document.

  The reading unit 22 is provided below the document table 21. The reading unit 22 is configured to be movable in the sub-scanning direction (the left-right direction in FIG. 1) by a moving mechanism (not shown) having a driving unit such as a stepping motor. The reading unit 22 includes a light source 221 of three colors and a mirror 222 as shown in FIG. The three-color light sources 221 emit light of different colors to a region along a main scanning direction (a direction perpendicular to the paper surface in FIG. 1) of the document. Specifically, as shown in FIG. 3, the three color light sources 221 are a red light source 221R, a green light source 221G, and a blue light source 221B. The red light source 221R is a plurality of red LEDs arranged along the main scanning direction. The green light source 221G is a plurality of green LEDs arranged along the main scanning direction. The blue light source 221B is a plurality of blue LEDs arranged along the main scanning direction. The red light source 221R, the green light source 221G, and the blue light source 221B are sequentially turned on one by one in a preset cycle by a light emission control unit 50 described later. Hereinafter, when it is not necessary to particularly distinguish the red light source 221R, the green light source 221G, and the blue light source 221B, these are collectively referred to as a light source 221. The light emitted from the light source 221 is transmitted through the first contact glass 211 or the second contact glass 212 and is applied to a document placed on the first contact glass 211 or a document conveyed by the ADF 1. The mirror 222 reflects the light emitted from the light source 221 and reflected on the original to the mirror 23.

  In the image reading section 2, when image data is read from a document placed on the first contact glass 211, the reading unit 22 is moved to a position below the first contact glass 211 by the moving mechanism. As a result, light emitted from the light source 221 is transmitted through the first contact glass 211 and irradiated on the original placed on the first contact glass 211. The reading unit 22 is moved in the sub-scanning direction by the moving mechanism. Thus, the light from the light source 221 is scanned in the sub-scanning direction on the original placed on the first contact glass 211. Here, the moving mechanism is an example of the scanning unit in the present invention.

  In the image reading section 2, when image data is read from a document conveyed by the ADF 1, the reading unit 22 is moved to a position below the second contact glass 212 by the moving mechanism. Specifically, the reading unit 22 is moved to a position where the light emitted from the light source 221 passes through the reading position P1 (see FIG. 3) by the moving mechanism. As a result, the light emitted from the light source 221 is transmitted through the second contact glass 212 and is radiated by the ADF 1 onto the document conveyed through the reading position P1. Thus, the light from the light source 221 is scanned in the sub-scanning direction on the document conveyed through the reading position P1. Here, the ADF 1 is an example of the scanning unit in the present invention.

  In the image reading section 2, when image data is read from the white reference plate 213, the reading unit 22 is moved to a position below the white reference plate 213. As a result, light emitted from the light source 221 passes through the first contact glass 211 and irradiates the white reference plate 213 provided on the first contact glass 211.

  The mirror 23 reflects the light reflected by the mirror 222 of the reading unit 22 to the mirror 24. The mirror 24 reflects the light reflected by the mirror 23 to the optical lens 25. The optical lens 25 condenses the light reflected by the mirror 24 and makes the light enter the CCD 26.

  The CCD 26 is an image sensor having a plurality of photoelectric conversion elements arranged along the main scanning direction. The CCD 26 outputs an electric signal corresponding to the amount of received light. In the image reading unit 2, reflected light emitted from the light source 221 and reflected by the original is incident on the CCD 26 via the mirror 222, the mirror 23, the mirror 24, and the optical lens 25. The CCD 26 outputs an electric signal according to the amount of reflected light. Specifically, when the red light source 221R is turned on, an electric signal corresponding to the amount of reflected light of the light emitted from the red light source 221R is output from the CCD 26. When the green light source 221G is turned on, the CCD 26 outputs an electric signal corresponding to the amount of reflected light of the light emitted from the green light source 221G. When the blue light source 221B is turned on, the CCD 26 outputs an electric signal corresponding to the amount of reflected light of the light emitted from the blue light source 221B. Thus, the CCD 26 sequentially outputs analog electric signals of each color component corresponding to the image of the document. The analog electric signal of each color component output from the CCD 26 is converted into a digital electric signal (image data) of each color component by an analog front-end circuit (not shown) and input to the control unit 5. Here, the CCD 26 and the analog front-end circuit are examples of the imaging unit of the present invention. In the image data, each color of each pixel is represented by a pixel value of 256 gradations from 0 (lower limit value) to 255 (upper limit value).

  By the way, a luminous substance is applied to the document cover (ADF1) and the fixed platen portion (second contact glass 212), and the document is based on the afterglow emitted from the luminous substance with the light source (light source 221) turned off. There is known an image reading apparatus for detecting the size of an image. However, in the image reading apparatus, it is necessary to perform processing for turning off the light source and detecting the size of the document before, during, or after the start of the image reading operation. Therefore, the processing time is lengthened by the amount of the processing. Further, if the light source is repeatedly turned on and off while scanning the original at a constant speed in the sub-scanning direction to alternately perform image reading and size detection, the image reading resolution is reduced. On the other hand, according to the image forming apparatus 10 of the present embodiment, as described below, it is possible to detect the edge of the document without turning off the three color light sources 221 at the same time.

  In the image forming apparatus 10 according to the present embodiment, the transport guide 13 is coated with a luminous substance. The transport guide 13 is located on the far side of the document passing through the reading position P1 when viewed from the light sources 221 of three colors. Here, the transport guide 13 is an example of a background plate in the present invention. The phosphorescent substance is a substance that continuously emits light (afterglow) of a wavelength (emission wavelength) longer than the specific wavelength after absorbing light of a specific wavelength (excitation wavelength) to be in an excited state. . In the present embodiment, as an example of the phosphorescent material, a phosphorescent material that is excited by blue light and emits afterglow is applied to the transport guide 13.

  The control unit 5 includes a light emission control unit 50, a detection processing unit 51, an adjustment processing unit 52, a replacement processing unit 53, and a correction processing unit 54, as shown in FIG. The control unit 5 functions as each of these processing units by executing various processes according to the control program. Further, the control unit 5 may include an electronic circuit that realizes a part or a plurality of processing functions of each of these processing units. Here, the device including the ADF 1, the image reading unit 2, and the control unit 5 is an example of the image reading device according to the present invention. Note that the present invention is applicable to an image reading device or an image forming device such as a scanner device, a facsimile device, and a copy machine.

  The light emission control unit 50 sequentially turns on the three color light sources 221 one by one at a preset cycle. For example, the light emission control unit 50 turns on the light sources 221 of three colors in the order of blue light source 221B → green light source 221G → red light source 221R → blue light source 221B →. Note that the order in which the light emission control unit 50 turns on the three color light sources 221 is not limited to the above order.

  The detection processing unit 51 detects an edge of a document in the image data based on a pixel value of a specific color component in the image data read by the image reading unit 2. Specifically, the specific color component is a color component different from a color component corresponding to an excitation wavelength of the light storage material (that is, a wavelength absorbed by the light storage material). In the present embodiment, a phosphorescent material that is excited by blue light and emits afterglow is applied to the transport guide 13. In this case, the detection processing unit 51 detects the edge of the document in the image data based on the pixel value of the green component or the red component in the image data read by the image reading unit 2.

  Hereinafter, an edge detection method by the detection processing unit 51 will be specifically described with reference to FIGS.

  FIG. 4 shows an example of the image data D1 read by the image reading unit 2. The horizontal direction of the image data D1 corresponds to a direction orthogonal to the document conveyance direction (the main scanning direction), and the vertical direction of the image data D1 corresponds to the document conveyance direction (the sub-scanning direction). The image data D1 includes an image of the document conveyed by the ADF1. An area A1 shown in FIG. 4 is an area showing an image of the original (that is, an area inside the original), and an area A2 is an area showing an image of the transport guide 13 (that is, an area outside the original). The boundary between the area A1 and the area A2 is the edge E1 to E4 of the document.

  In the present embodiment, light of different colors is sequentially emitted from the light source 221 of three colors toward the document. 5 shows a state when the blue light source 221B is turned on, FIG. 6 shows a state when the green light source 221G is turned on, and FIG. 7 shows a state when the red light source 221R is turned on. .

  As shown in FIG. 5, when the blue light source 221B is turned on, the blue irradiation light B1 emitted from the blue light source 221B is reflected by the original or the conveyance guide 13, and the blue reflected light B2 is incident on the CCD. Here, when the blue irradiation light B1 is reflected by the original, the amount of the blue reflected light B2 changes according to the color (blue component) of the original. As shown in the left part of FIG. 5, when the blue irradiation light B1 is reflected by a white document, the amount of the blue reflected light B2 becomes maximum. The length of the arrow corresponding to the blue reflected light B2 in FIG. 5 schematically represents the amount of the blue reflected light B2. On the other hand, when the blue reflected light B <b> 2 is reflected by the transport guide 13, the amount of the blue reflected light B <b> 2 changes due to the action of the luminous substance applied to the transport guide 13. In the present embodiment, a luminous substance that absorbs blue light is applied to the transport guide 13. Therefore, when the blue irradiation light B1 is reflected by the transport guide 13, the light amount of the blue reflected light B2 is smaller than that when the blue irradiation light B1 is reflected by a white original as shown in the right part of FIG.

  As shown in FIG. 6, when the green light source 221G is turned on, the green irradiation light G1 emitted from the green light source 221G is reflected by the document or the transport guide 13, and the green reflected light G2 is incident on the CCD. Here, when the green irradiation light G1 is reflected by the document, the amount of the green reflected light G2 changes according to the color (green component) of the document. As shown in the left part of FIG. 6, when the green irradiation light G1 is reflected by the white document, the amount of the green reflected light G2 becomes maximum. Note that the length of the arrow corresponding to the green reflected light G2 in FIG. 6 schematically represents the amount of the green reflected light G2. On the other hand, when the green irradiation light G1 is reflected by the transport guide 13, as shown in the right part of FIG. The afterglow L is incident on the CCD 26. As described above, when the green irradiation light G1 is reflected by the transport guide 13, the amount of light received by the CCD 26 becomes larger by the amount of the afterglow L than when reflected by a white original.

  As shown in FIG. 7, when the red light source 221R is turned on, the red irradiation light R1 emitted from the red light source 221R is reflected by the original or the transport guide 13, and the red reflected light R2 is incident on the CCD. Here, when the red irradiation light R1 is reflected by the original, the amount of the red reflected light R2 changes according to the color (green component) of the original. As shown in the left part of FIG. 7, when the red irradiation light R1 is reflected by a white document, the amount of the red reflected light R2 becomes maximum. Note that the length of the arrow corresponding to the red reflected light R2 in FIG. 7 schematically represents the amount of the red reflected light R2. On the other hand, when the red irradiation light R1 is reflected by the transport guide 13, as shown in the right part of FIG. 7, in addition to the red reflected light R2, the light emitted from the phosphorescent material excited when the blue light source 221B is turned on. The afterglow L is incident on the CCD 26. As described above, when the red irradiation light R1 is reflected by the transport guide 13, the amount of light received by the CCD 26 becomes larger by the amount of the afterglow L than when it is reflected by a white original.

  As described above, when the green irradiation light G1 or the red irradiation light R1 is reflected by the transport guide 13, the amount of light received by the CCD 26 is larger than when the green irradiation light G1 or the red irradiation light R1 is reflected by a white document. Therefore, the detection processing unit 51 can determine whether each pixel is a pixel inside the document or a pixel outside the document based on the pixel value of the green component or the red component of each pixel in the image data D1. . Therefore, the detection processing unit 51 can detect the edges E1 to E4 of the document in the image data D1. Note that when a light-storing substance that absorbs blue light is used, not only blue light but also green light may be slightly absorbed. In this case, the amount of light received by the CCD 26 may not be sufficiently large when the green light source 221G is turned on. Therefore, the detection processing unit 51 determines the above based on the pixel value of the red component in the image data read by the image reading unit 2. It is preferable to detect the edge of the document in the image data.

  The detection processing unit 51 determines that the pixel is located outside the document when the pixel value of the specific color component (for example, red component) of each pixel in the image data D1 is within a predetermined range. . For example, when the pixel value of the specific color component of each pixel in the image data D1 is equal to or greater than a predetermined specific value, the detection processing unit 51 may determine that the pixel is located outside the document. . The specific value may be any value that is larger than the pixel value of the specific color component in the image data when a white document is read by the image reading unit 2. For example, when the pixel value of the specific color component in the image data when a white original is read is 245, the specific value may be a value of 246 or more. The specific value may be an upper limit value of the pixel value (that is, 255).

  In the adjustment processing unit 52, in the image data of the white reference plate 213 read by the image reading unit 2, the pixel value of the specific color component (for example, red component) becomes the upper limit value, and the conveyance read by the image reading unit 2 is performed. In the image data of the guide 13, the light amounts of the three color light sources 221 are adjusted so that the pixel value of the specific color component is less than the upper limit. Accordingly, the detection processing unit 51 determines that the pixel having the pixel value of the specific color component (for example, red component) of 255 in the image data D1 illustrated in FIG. 4 is a pixel outside the document. However, a pixel whose pixel value of the specific color component is less than 255 can be determined to be a pixel in the document. Therefore, the detection processing unit 51 can detect the edges E1 to E4 of the document in the image data D1.

  By the way, as described above, when the blue irradiation light B1 is reflected by the transport guide 13, the amount of light received by the CCD 26 is smaller than when the blue irradiation light B1 is reflected by a white original, and the green irradiation light G1 and the red irradiation light When R1 is reflected by the transport guide 13, the amount of light received by the CCD 26 is larger than when reflected by a white document. Therefore, in the image data D1 shown in FIG. 4, the area A2 outside the document shows a pale yellow (that is, the color of the luminous substance applied to the transport guide 13). When an image is formed on a sheet in the image forming unit 3 based on such image data D1, a light yellow color may be applied to an area outside the document. For example, if the size of the sheet is larger than the size of the document, or if the document is inclined even if the size of the sheet and the document is the same, the area of the sheet outside the document is colored light yellow.

  Therefore, in order to prevent the above coloring, the pixel value of the pixel included in the area A2 may be replaced with, for example, a pixel value indicating white or a pixel value indicating transparency. For example, when the pixel value of the specific color component (for example, red component) is the upper limit value (that is, 255) for each pixel of the image data, the replacement processing unit 53 replaces the remaining color component (that is, 255). , Blue component and green component) may be replaced with the upper limit. As a result, for a pixel whose pixel value of the red component is 255 (that is, a pixel located outside the document), the pixel values of the blue component and the green component are replaced with 255, and thus the pixels of the pixels included in the area A2 The value is a pixel value indicating white. Accordingly, when an image is formed on a sheet in the image forming unit 3 based on the image data, it is possible to prevent a light yellow color from being applied to an area outside the document.

  The correction processing unit 54 performs rotation correction on the image data based on the inclination of the edge of the document detected by the detection processing unit 51. For example, the correction processing unit 54 calculates the coordinates (x1, y1) of the intersection C1 of the edge E1 and the edge E2 and the coordinates (x2, y2) of the intersection C2 of the edge E2 and the edge E3 in the image data D1 shown in FIG. Is calculated. Then, the correction processing unit 54 calculates the inclination of the edge E2 (that is, the inclination of the document) based on the coordinates of the intersection C1 and the intersection C2, and calculates the coordinates of the middle point C3 between the intersection C1 and the intersection C2 ( x3, y3) is calculated. Then, the correction processing unit 54 performs rotation correction on the image data D1 such that the inclination of the edge E2 is horizontal with the center point C3 as the center.

[Adjustment process]
Next, an example of a procedure of an adjustment process executed by the control unit 5 (adjustment processing unit 52) will be described with reference to FIG. Here, steps S1, S2,... Represent the numbers of the processing procedures (steps) executed by the control unit 5. The adjustment process is started, for example, when the power of the image forming apparatus 10 is turned on. Alternatively, the adjustment processing may be started in response to a predetermined adjustment start operation being performed. Alternatively, the adjustment processing may be started when the image reading operation by the image reading unit 2 is started. Note that the adjustment process is executed in a state where the document is not conveyed by the ADF 1.

<Step S1>
First, in step S1, the control unit 5 controls the moving mechanism to move the reading unit 22 to a position below the white reference plate 213.

<Step S2>
In step S2, the control unit 5 sets a gain for amplifying an analog electric signal of each color component output from the CCD 26 to an initial value (for example, 1).

<Step S3>
In step S <b> 3, the control unit 5 supplies a current to the three color light sources 221 to sequentially light the three color light sources 221.

<Step S4>
In step S4, the control unit 5 determines a pixel value of any color component in the image data based on the image data read by the image reading unit 2 (that is, the image data of the white reference plate 213). The supply currents of the three color light sources 221 are adjusted so as to reach the target value. The target value is an arbitrary value larger than 0 and smaller than 255, for example, 200. In this case, the control unit 5 gradually increases the supply currents of the three color light sources 221 until the pixel value of any color component in the image data reaches 200. Then, for example, when the pixel value of the green component reaches 200, the process proceeds to step S5.

<Step S5>
In step S5, while maintaining the supply current adjusted in step S4, the control unit 5 controls each color so that the pixel values of all the color components in the image data become the target values (for example, 200). Adjust the gain of. For example, when the pixel value of the green component reaches 200 in step S4, the red gain and the blue gain are gradually increased until the pixel values of the red component and the blue component reach 200. Then, when the pixel values of the red component and the blue component reach 200, the process proceeds to step S6.

<Step S6>
In step S6, the control unit 5 controls the moving mechanism to move the reading unit 22 to a position below the second contact glass 212.

<Step S7>
In step S7, based on the image data read by the image reading unit 2 (that is, the image data of the transport guide 13), the control unit 5 sets the pixel value of the red component in the image data to the target value (for example, 200). It is determined whether or not it exceeds. When it is determined that the pixel value of the red component exceeds the target value (S7: Yes), the process proceeds to step S8. On the other hand, if it is determined that the pixel value of the red component does not exceed the target value (S7: No), the process returns to step S1.

  In addition, since the luminous substance is applied to the transport guide 13, when the light emitted from the red light source 221 </ b> R is reflected by the transport guide 13, it is compared with the case where the light is reflected by the white reference plate 213 or the white original. As a result, the pixel value of the red component increases. Therefore, as long as the supply currents of the three light sources 221 and the gains of the respective colors are adjusted so that the pixel value of the red component becomes 200 in the processing of the steps S1 to S5, unless there is any abnormality, the step S7 is performed. It is determined that the pixel value of the red component in the image data exceeds 200.

<Step S8>
In step S8, the control unit 5 sets the pixel value of the red component in the image data to the upper limit value (for example, 255) based on the image data read by the image reading unit 2 (that is, the image data of the transport guide 13). The supply currents of the three color light sources 221 are adjusted so that For example, the control unit 5 gradually increases the supply currents of the three color light sources 221 until the pixel value of the red component in the image data reaches 255. Then, when the pixel value of the red component reaches 255, the process proceeds to step S9.

<Step S9>
In step S9, the control unit 5 controls the moving mechanism to move the reading unit 22 to a position below the white reference plate 213.

<Step S10>
In step S10, based on the image data read by the image reading unit 2 (that is, the image data of the white reference plate 213), the control unit 5 sets the pixel value of the red component in the image data to the upper limit value (for example, 255). ) Is determined. When it is determined that the pixel value of the red component is less than the upper limit (S10: Yes), the process proceeds to step S11. On the other hand, if it is determined that the pixel value of the red component is the upper limit (S10: No), the process returns to step S7.

<Step S11>
In step S11, the control unit 5 stops supplying the current to the light sources 221 for three colors and turns off the light sources 221 for three colors.

<Step S12>
In step S12, the control unit 5 saves the adjusted set values (that is, the adjusted gain in step S5 and the adjusted supply current in step S8) in a nonvolatile storage medium such as the EEPROM. I do. Then, the adjustment process ends.

  The set values stored in step S12 are used when the image reading unit 2 reads the image data of the document. By using the set value, the pixel value of the specific color component (for example, red component) of the pixel in the document in the image data read by the image reading unit 2 becomes less than the upper limit value (for example, 255), The pixel value of the specific color component of the pixel outside the document is the upper limit. Therefore, the control unit 5 can detect the edge of the document in the image data based on the pixel value of the specific color component in the image data.

  As described above, in the image forming apparatus 10 according to the present embodiment, the luminous substance is applied to the transport guide 13. Then, based on the pixel value of a specific color component of each pixel in the image data read by the image reading unit 2, it is determined whether the pixel is a pixel in the document or a pixel outside the document. Therefore, according to the image forming apparatus 10 of the present embodiment, it is possible to detect an edge of a document while suppressing an increase in cost and a decrease in productivity.

[Modification]
In the present embodiment, the case where image data is read from a document conveyed by the ADF 1 has been described. However, the present invention is also applied to a case where image data is read from a document placed on the first contact glass 211. It is possible. In this case, the phosphorescent material may be applied to the lower surface of the document cover (for example, a document pressing sheet provided on the lower surface of the ADF 1) that covers the first contact glass 211. Here, the document cover or the document pressing sheet is an example of a background plate in the present invention.

  Further, in the present embodiment, the case where the excitation wavelength of the luminous substance is the wavelength of blue light has been described, but the present invention is not limited to this. In another embodiment, the excitation wavelength of the phosphorescent material may be a wavelength of green light. In this case, the detection processing unit 51 can detect the edge of the document in the image data based on the pixel value of the red or green component in the image data read by the image reading unit 2. In still another embodiment, the excitation wavelength of the luminous substance may be the wavelength of red light. In this case, the detection processing unit 51 can detect the edge of the document in the image data based on the pixel value of the blue component or the green component in the image data read by the image reading unit 2.

10 Image forming apparatus 1 ADF
13 transport guide 2 image reading section 21 document table 211 first contact glass 212 second contact glass 213 white reference plate 22 reading unit 221 light source 221R red light source 221G green light source 221B blue light source 26 CCD
3 Image forming unit 5 Control unit 50 Light source control unit 51 Detection processing unit 52 Adjustment processing unit 53 Replacement processing unit 54 Correction processing unit 6 Operation display unit

Claims (12)

A light source of three colors that emits light of different colors to a region along a main scanning direction in a document;
A light emission control unit that sequentially lights the three color light sources one by one at a preset cycle;
A scanning unit configured to move one of the light source of the three colors and the document to scan light from the light sources of the three colors in the sub-scanning direction orthogonal to the main scanning direction on the document;
A background plate, which is located on the back side of the original as viewed from the three color light sources and is coated with a phosphorescent material,
An imaging unit that reads image data including an image of the document based on reflected light of light emitted from the three color light sources;
A detection processing unit that detects an edge of the document in the image data based on a pixel value of a specific color component in the image data;
An image reading device comprising: The specific color component is a color component different from the color component corresponding to the excitation wavelength of the phosphorescent material,
The image reading device according to claim 1. The three color light sources are a red light source, a green light source, and a blue light source,
The phosphorescent substance is a phosphorescent substance that emits afterglow when excited by blue light,
The specific color component is a red component,
The image reading device according to claim 1. The detection processing unit, when the pixel value of the specific color component of each pixel in the image data is within a predetermined specific range, determines that the pixel is located outside the document.
The image reading device according to claim 1. The detection processing unit, when the pixel value of the specific color component of each pixel in the image data is equal to or greater than a predetermined specific value, determines that the pixel is located outside the document.
The image reading device according to claim 4. The specific value is a value larger than a pixel value of the specific color component in the image data when a white document is read by the imaging unit.
The image reading device according to claim 5. The specific value is an upper limit of the pixel value,
The image reading device according to claim 6. A white reference plate,
In the image data of the white reference plate read by the imaging unit, the pixel value of the specific color component becomes the upper limit, and in the image data of the background plate read by the imaging unit, the pixel of the specific color component Further comprising an adjustment processing unit for adjusting the light amount of the light source so that the value is less than the upper limit,
The image reading device according to claim 7. For each pixel of the image data, when the pixel value of the specific color component is the upper limit, further comprising a replacement processing unit that replaces the pixel value of the remaining color component with the upper limit.
The image reading device according to claim 7. The image processing apparatus further includes a correction processing unit that performs rotation correction on the image data based on an inclination of an edge of the document detected by the detection processing unit.
The image reading device according to claim 1. The scanning unit is a document transport unit that transports a document to be read along a transport path,
The background plate is a transport guide provided at a position where the document is read in the transport path.
The image reading device according to claim 1. An image reading device according to any one of claims 1 to 11,
An image forming unit that forms an image on a sheet based on image data of a document read by the image reading device;
An image forming apparatus comprising:

Images