JP6369373B2 - Image reading apparatus, image processing apparatus, and image reading apparatus control method - Google Patents

Description

  The present invention relates to an image reading apparatus, an image processing apparatus including the image reading apparatus, and a method for controlling the image reading apparatus.

  In general, an image reading apparatus includes an image scanning unit that scans a document while detecting the amount of light emitted from the document placed on a transparent document table. The image scanning unit includes a light emitting unit that irradiates light on a document and an image sensor that receives reflected light from a linear region along the main scanning direction of the document, and scans the document along the sub-scanning direction. The image sensor outputs a data string corresponding to the detected light amount for each pixel of the linear region in the document. The sub-scanning direction is a direction orthogonal to the main scanning direction.

  In the image reading apparatus, it is known that a CIS (Contact Image Sensor) unit having a structure in which the light emitting unit and the image sensor are integrated is employed. The CIS includes a plurality of the light emitting units each having a different emission color.

  The image data of the two-dimensional image of the document is obtained by synthesizing along the sub-scanning direction a data string of the image density of the linear region obtained through the image scanning unit. An image processing apparatus such as a copying machine includes an image reading apparatus and an image forming apparatus. An image forming apparatus of a copying machine forms a secondary image on a recording sheet by sequentially forming on the recording sheet a linear image corresponding to an image density data string of the linear region obtained through the image scanning unit. .

  Further, normal image density data obtained when the light quantity of the light emitting unit is set to a normal light quantity, and comparison image density data obtained when the light quantity of the light emitting part is set to another comparative light quantity, It is known that a pixel region having a large density difference is specified as a document region (see, for example, Patent Document 1).

JP 2013-110506 A

  By the way, in the image reading apparatus, the document scanning may be performed by the image scanning unit in a state where the cover of the document table is opened. In this case, a noise image caused by external light such as room lighting entering the image sensor tends to appear in the document outside area.

  In order to remove the noise image in the area outside the original, it is conceivable to specify the original area from the image data. For example, it is conceivable to detect the boundary position between the document area and the document outside area by edge detection processing. It is also conceivable to specify a pixel area having a large density difference between the normal image data obtained with the normal light quantity and the comparison image data obtained with the comparative light quantity as the document area.

  However, in the above-described processing for specifying the document area, there may occur a situation in which the document area cannot be correctly specified without a significant difference in density when the background state of the document is various. For example, there may occur a situation in which the document area cannot be correctly specified in one of the case where the background of the document is a light color close to white and the color close to black.

  Therefore, it is desired that a noise image appear in the area outside the document due to the influence of external light regardless of the difference in the background state of the document.

  An object of the present invention is to prevent a noise image from appearing in an area outside a document due to the influence of external light, regardless of the state of the background of the document, when the document is scanned with the document table cover open. An image reading apparatus, an image processing apparatus, and a method for controlling the image reading apparatus are provided.

  An image reading apparatus according to one aspect of the present invention includes a plurality of light emitting units, an image scanning unit, a first light emission control unit, a first scanning control unit, a state selection unit, a second light emission control unit, A second scanning control unit, a temporary region dividing unit, and a main region dividing unit are provided. Each of the light emitting units irradiates light of different colors toward a document placed on a transparent document table. The image scanning unit can execute an image reading process. The image reading process is performed on the document table along the sub-scanning direction orthogonal to the main scanning direction while detecting the amount of light emitted from the linear region along the main scanning direction on the document table for each pixel. This is a process of sequentially outputting an image data sequence corresponding to the detected light amount for each pixel in the linear region by scanning. The first light emission control unit sets each light emitting unit to a first state in which light is emitted with a predetermined reference light amount for each color. The first scanning control unit causes the image scanning unit to scan a part of the scanning range in the sub-scanning direction when the light-emitting unit is in the first state, so that the at least one linear region is scanned. Sample data including an image data string is output to the image scanning unit. According to whether the sample data satisfies a predetermined condition, the state selection unit selects either the extinguishing state or the brightening state in which the light emission unit emits light with a larger amount of light than the first state, depending on whether or not a predetermined condition is satisfied. Select either one. The second light emission control unit causes each of the light emission units to emit light sequentially with the reference light amount one color at a time, and the state of each of the light emission units for each reference period in which light emission with the reference light amount makes a round for all emission colors. Are switched between the first state and the second state selected based on the sample data. The second scanning control unit causes the image scanning unit to execute the image reading process in parallel with switching of the states of the light emitting units. The temporary area dividing unit compares a pair of the image data sequences obtained for each emission color for each reference period. Further, the temporary area dividing unit executes a process of dividing each of the pixels into a document area pixel and a document outside area pixel for each light emission color. The temporary area dividing unit includes data of the pixels corresponding to each other in a first image data sequence corresponding to the first state of the light emitting unit and a second image data sequence corresponding to the second state of the light emitting unit. Each of the pixels is divided into a document area pixel and a document outside area pixel according to the difference. The main area dividing section classifies the pixels divided into the original area pixels with respect to at least one of the emission colors by the temporary area dividing section into the original area pixels, and other pixels as the outside original area pixels. Break down.

  An image processing apparatus according to another aspect of the present invention includes the image reading apparatus according to one aspect of the present invention and an image forming apparatus. The image forming apparatus forms an image corresponding to the plurality of first image data strings obtained by the image reading apparatus on a recording sheet.

  An image reading apparatus control method according to another aspect of the present invention includes the following steps. The first step is a step of executing a first light emission control in which each of the light emitting units is set to a first state in which each color is emitted with a predetermined reference light amount. The second step is a step of executing the first scanning control. In the first scanning control, when the light emitting unit is in the first state, the image scanning unit scans a part of the scanning range in the sub-scanning direction, so that the image of at least one linear region is scanned. In this control, sample data including a data string is output to the image scanning unit. The third step is a step of executing state selection processing. In the state selection process, depending on whether or not the sample data satisfies a predetermined condition, the second state of the light emitting unit is either a light-off state or a light-intensifying state in which light is emitted with a larger light amount than the first state. This is a process for selecting one of them. The fourth step is a step of executing the second light emission control. In the second light emission control, each of the light emitting units is caused to emit light one color at a time with the reference light amount, and the state of each light emitting unit is changed for each reference period in which light emission with the reference light amount makes a round for all light emission colors. Control for switching between the first state and the second state selected based on the sample data.

  According to the present invention, when a document is scanned with the cover of the document table opened, a phenomenon in which a noise image appears in an area outside the document due to the influence of external light regardless of the state of the background of the document is avoided. It is possible to provide an image reading apparatus, an image processing apparatus, and a control method for the image reading apparatus.

FIG. 1 is a configuration diagram of an image processing apparatus including the image reading apparatus according to the first embodiment. FIG. 2 is a configuration diagram of a portion of the image sensor unit in the image reading apparatus according to the first embodiment. FIG. 3 is a block diagram of an image processing related device provided in the image reading apparatus according to the first embodiment. FIG. 4 is a flowchart illustrating an example of a procedure of image reading processing in the image reading apparatus according to the first embodiment. FIG. 5 is a flowchart illustrating an example of the procedure of the comparison state selection process in the image reading apparatus according to the first embodiment. FIG. 6 is a time chart illustrating a state change of the light emitting unit and a data state change of the image processing unit in the image processing apparatus according to the first embodiment. FIG. 7 is a flowchart illustrating an example of a procedure of image reading processing in the image reading apparatus according to the second embodiment. FIG. 8 is a diagram illustrating an example of a document. FIG. 9 is a diagram illustrating an example of a two-dimensional image synthesized from an image data sequence obtained when the light emitting unit is turned on in the image reading apparatus according to each embodiment. FIG. 10 is a diagram illustrating an example of a two-dimensional image synthesized from an image data sequence obtained when the light emitting unit is turned off in the image reading apparatus according to each embodiment. FIG. 11 is a diagram illustrating an example of a two-dimensional image synthesized from an image data sequence output by the image reading apparatus according to each embodiment. FIG. 12 is a graph showing the distribution of the values of the image data sequence obtained by the image scanning unit when different amounts of light are irradiated onto the original whose background is light. FIG. 13 is a graph showing the distribution of the values of the image data sequence obtained by the image scanning unit when different amounts of light are irradiated on the document whose background is dark.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the following embodiment is an example which actualized this invention, Comprising: It does not have the character which limits the technical scope of this invention.

[First Embodiment]
First, the configuration of the image processing apparatus 10 including the image reading apparatus 1 according to the first embodiment will be described with reference to FIGS. The image processing apparatus 10 includes an image reading apparatus 1 and an image forming apparatus 2. Further, the image processing apparatus 10 also includes a control unit 8 and an operation display unit 80 that are common to the image reading apparatus 1 and the image forming apparatus 2.

  For example, the image processing apparatus 10 is a copying machine, a printer or a facsimile machine having a copying machine function, or a multifunction machine having a plurality of image processing functions including an image reading function.

  As shown in FIG. 1, the image reading apparatus 1 includes a transparent document table 13, an image scanning unit 11, and a document table cover 12. The document table cover 12 incorporates an ADF (Auto Document Feeder) 14.

  The document table 13 is a portion on which a document 90 that is an image reading object is placed. Generally, the document table 13 is called platen glass. The document table cover 12 is supported by the casing 100 of the image processing apparatus 10 so as to be rotatable between a closed position that covers the document table 13 and an open position that releases the document table 13.

  The image scanning unit 11 includes an image sensor unit 110, a scanning mechanism 111, and the like. In the following description, one direction in the horizontal plane and a direction perpendicular thereto are referred to as a main scanning direction R1 and a sub-scanning direction R2, respectively.

  As shown in FIG. 2, the image sensor unit 110 includes a light emitting unit 112, a lens 113, an image sensor 114, and the like. The image sensor unit 110 in this embodiment is a CIS unit. The light emitting unit 112, the lens 113, and the image sensor 114 are formed in a rod shape along the main scanning direction R1.

  The light emitting unit 112 includes a red light emitting unit 112R, a green light emitting unit 112G, and a blue light emitting unit 112B. The light emitting unit 112 and the lens 113 are formed in a rod shape along the main scanning direction R1.

  The light emitting unit 112 emits sheet-shaped light toward the document 90 on the document table 13. For example, it is conceivable that the light emitting unit 112 is an LED array including a plurality of light emitting diodes arranged along the main scanning direction R1. Further, it is conceivable that the light emitting unit 112 includes one or a plurality of light sources and an optical system such as a cylindrical lens that converts the light emitted from the light sources into sheet-like light.

  The red light emitting unit 112 </ b> R, the green light emitting unit 112 </ b> G, and the blue light emitting unit 112 </ b> B are light sources that emit light of different colors toward the original 90 placed on the transparent original table 13. The red light emitting unit 112 </ b> R, the green light emitting unit 112 </ b> G, and the blue light emitting unit 112 </ b> B irradiate the document 90 through the document table 13 with strip-shaped light along the main scanning direction R <b> 1. For example, each of the red light emitting unit 112R, the green light emitting unit 112G, and the blue light emitting unit 112B may be an LED array including a plurality of light emitting diodes arranged along the main scanning direction R1.

  The lens 113 condenses the emitted light from the linear region on the document table 13 along the main scanning direction R <b> 1 to the light receiving unit of the image sensor 114. When the document 90 is placed on the document table 13, the emitted light from the linear area on the document table 13 includes the emitted light from the document 90 and the emitted light from the region outside the document. When the light emitting unit 112 is turned on, the light emitted from the original 90 is reflected light of the light emitted from the light emitting unit 112 irradiated on the original 90.

  When the document table cover 12 is closed, the emitted light from the outside region of the document is emitted light from the inner surface of the document table cover 12. In the state where the document table cover 12 is closed, the inner surface of the document table cover 12 is along the surface of the document table 13.

  In a state where the document table cover 12 is opened, the emitted light from the outside region of the document is external light that enters the document table 13 from above the document table 13. This external light causes a noise image in the area outside the document in the image read by the image reading apparatus 1.

  The image sensor 114 is a photoelectric conversion element array including a plurality of photoelectric conversion elements arranged along the main scanning direction R1. Generally, the photoelectric conversion element is a CMOS image sensor. The image sensor 114 detects the amount of light emitted from the linear region along the main scanning direction R1 on the document table 13 for each pixel, and uses the detected light amount data of each pixel as an image data string of the linear region. Output.

  The image sensor 114 sequentially detects the amount of light emitted from the linear region while moving in the sub-scanning direction R2 along the document table 13, thereby allowing the image of the document 90 to be line by line along the main scanning direction R1. Read.

  The amount of light detected by the image sensor 114 is an index value of the image density of the document 90. The smaller the amount of light detected by the image sensor 114, the higher the image density of the document 90.

  In the step of reading the image of the document 90, each of the red light emitting unit 112R, the green light emitting unit 112G, and the blue light emitting unit 112B is turned on in order, and red light, green light, and blue light are sequentially irradiated onto the document 90. As a result, the image sensor 114 sequentially outputs three sets of image data sequences representing the densities of the red image, the green image, and the blue image on the document 90. As a result, the image of the original 90 can be read as a color image.

  When the image of the original 90 is read as a monochrome image, each of the red light emitting unit 112R, the green light emitting unit 112G, and the blue light emitting unit 112B is turned on simultaneously. Thereby, white light is irradiated to the linear region, and a data string of the detected light amount of the reflected light from the linear region is output as a monochrome image data string.

  The scanning mechanism 111 is a mechanism that supports the image sensor unit 110 and moves it along the sub-scanning direction R2. Thereby, the position in the sub-scanning direction R <b> 2 of the linear region that is the light irradiation target of the light emitting unit 112 is changed. The linear region irradiated with light from the light emitting unit 112 is also a target for detecting the amount of emitted light by the image sensor 114. The scanning mechanism 111 also includes a driving unit (not shown) such as a stepping motor.

  The scanning mechanism 111 moves the image sensor unit 110 including the light emitting unit 112 along the sub-scanning direction R2. As a result, the image scanning unit 11 scans the document table 13 along the sub-scanning direction R2 while detecting the amount of light emitted from the linear region along the main scanning direction R1 on the document table 13 for each pixel. . In a state where the document 90 is placed on the document table 13, a part or all of the scanning target of the image scanning unit 11 is the document 90.

  As described above, the image scanning unit 11 scans the document table 13 along the sub-scanning direction R2 while detecting the amount of light emitted from the linear region on the document table 13 for each pixel. Thereby, the image scanning unit 11 can execute an image reading process for sequentially outputting the image data sequence corresponding to the detected light amount for each pixel in the linear region.

  The scanning mechanism 111 can stop the image sensor unit 110 at a predetermined first position P <b> 1 in the document conveyance path 140 of the ADF 14. In a state where the image sensor unit 110 is located at the first position P1, the light emitting unit 112 irradiates the first surface of the document 90 being transported by the ADF 14 through the transparent contact unit 13a. Further, the image sensor 114 sequentially outputs the image data string on the first surface of the original 90 being conveyed by the ADF 14.

  The ADF 14 transports the document 90 set on the document tray 121 to the document discharge tray 123 along the document transport path 140 by a plurality of rotating transport rollers 122. At that time, the image sensor unit 110 supported at the first position P1 by the scanning mechanism 111 reads the image of the first surface of the document 90.

  In the example shown in FIG. 1, the image reading apparatus 1 includes another image sensor unit 120 attached to a second position P <b> 2 in the document conveyance path 140 of the ADF 14. The image sensor unit 120 is a CIS unit having the same structure as the image sensor unit 110.

  The image sensor unit 120 reads an image on the second side of the original 90 being transported by the ADF 14 and sequentially outputs an image data string corresponding to the image on the second side.

  When the image reading process in the duplex reading mode is designated through the operation display unit 80, the ADF 14 transports the document 90 along the document transport path 140, and the two image sensor units 110 and 120 move along the document transport path 140. The images on both sides of the original document 90 are read in parallel.

  In the example illustrated in FIG. 1, the image reading apparatus 1 also includes a document sensor 801 and a cover sensor 802. The document sensor 801 is a sensor that detects whether or not the document 90 is set on the document tray 121. The cover sensor 802 is a sensor that detects whether or not the document table cover 12 is closed.

  The image forming apparatus 2 is an apparatus that forms an image on the recording sheet 9 according to the image data string output from the image reading apparatus 1. The recording sheet 9 is a sheet-like image forming medium such as paper, coated paper, postcard, envelope, and OHP sheet.

  For example, the image forming apparatus 2 includes a sheet conveying unit 3, an image forming unit 4, an optical scanning unit 5, a fixing unit 6, and the like. An image forming apparatus 2 shown in FIG. 1 is an electrophotographic image forming apparatus. It is also conceivable that the image forming apparatus 2 is an image forming apparatus of another method such as an ink jet method.

  In the sheet conveying unit 3, the sheet delivery unit roller 31 sends the recording sheet 9 from the sheet storage unit 30 to the sheet conveying path 300. Further, the sheet conveyance roller 32 conveys the recording sheet 9 along the sheet conveyance path 300. Further, the discharge roller 33 discharges the recording sheet 9 on which the image has been formed from the exit of the sheet conveyance path 300 onto the recording sheet discharge tray 101.

  The image forming unit 4 forms an image on the surface of the recording sheet 9 moving on the sheet conveyance path 300. The image forming unit 4 includes a drum-shaped photoreceptor 41, a charging unit 42, a developing unit 43, a transfer unit 45, a cleaning unit 47, and the like. The photoconductor 41 is an example of an image carrier.

  The photoconductor 41 rotates, and the charging unit 42 uniformly charges the surface of the photoconductor 41. Further, an electrostatic latent image is written on the surface of the photoreceptor 41 charged by the optical scanning unit 5 scanning the laser beam. Further, the developing unit 43 supplies the developer to the photosensitive member 41 to develop the electrostatic latent image into the image of the developer. The developer is supplied to the developing unit 43 from a developer supply unit (not shown).

  Further, the transfer unit 45 transfers the image of the developer on the surface of the photosensitive member 41 to the recording sheet 9 moving on the sheet conveyance path 300. Finally, the cleaning unit 47 removes the developer remaining on the surface of the photoreceptor 41.

  The fixing unit 6 sandwiches the recording sheet 9 on which an image is formed between a fixing roller 61 including a heater such as a halogen heater and a pressure roller 62, and sends the recording sheet 9 to a subsequent process. As a result, the fixing unit 6 heats the image that is the image of the developer on the recording sheet 9 and fixes the image on the recording sheet 9.

The control unit 8 controls various electric devices included in the image processing apparatus 10 based on input information input through the operation display unit 80 and detection results of various sensors including the document sensor 801 and the cover sensor 802.
The control unit 8 displays an operation menu or the like on the operation display unit 80. Further, the control unit 8 performs image processing on an image input through the image reading device 1. further,

  For example, as shown in FIG. 3, the control unit 8 includes an MPU (Micro Processor Unit) 81, a storage unit 82, a scanning control unit 83, a light emission control unit 84, an image processing unit 85, a laser control unit 86, a signal interface 87, and the like. Is provided.

  The MPU 81 is a processor that executes various arithmetic processes. The storage unit 82 is a nonvolatile information storage medium in which information such as programs Pr1 to Pr4 for causing the MPU 81 to execute various processes is stored in advance. Furthermore, the storage unit 82 is also an information storage medium in which various information can be read and written by the MPU 81.

  The control unit 8 comprehensively controls the image processing apparatus 10 by causing the MPU 81 to execute various programs stored in advance in the storage unit 82.

  The signal interface 87 is an interface circuit that relays signal exchange between the MPU 81 and the sensor, control target device, and the like. The MPU 81 inputs detection signals (measurement signals) from various sensors such as the document sensor 801 and the cover sensor 802 via the signal interface 87. Further, the MPU 81 outputs a control signal to the control target device via the signal interface 87.

  The scanning control unit 83 controls the scanning mechanism 111 of the image scanning unit 11 so that the scanning position in the sub-scanning direction R2 by the image scanning unit 11, that is, the position of the linear region that the image scanning unit 11 scans. To control.

  The light emission control unit 84 controls the light emitting unit 112 of the image scanning unit 11 and individually switches the light emitting states of the red light emitting unit 112R, the green light emitting unit 112G, and the blue light emitting unit 112B according to the situation. The image processing unit 85 inputs image data obtained through the image scanning unit 11 and executes image processing.

  The laser control unit 86 inputs the recording image data sequence output from the image processing unit 85, and adjusts the amount of laser light output from the optical scanning unit 5 in accordance with the density of each pixel indicated by the recording image data sequence. To do.

  In the following description, an area where the original 90 is present in all the scanning areas of the image scanning unit 11 on the original table 13 is referred to as an original area, and the remaining area is referred to as an area outside the original.

  By the way, in the image reading apparatus 1, the document 90 may be scanned by the image scanning unit 11 with the document table cover 12 opened. In this case, a noise image caused by external light such as room lighting entering the image sensor 114 tends to appear in the outside area of the document.

  In order to remove the noise image in the area outside the original, it is conceivable to specify the original area from image data. For example, it is conceivable to detect a boundary position between the document area and the document outside area by edge detection processing. It is also conceivable to specify a pixel area having a large density difference between the normal image data obtained with the normal light quantity and the comparison image data obtained with the comparative light quantity as the document area.

  However, in the above-described processing for specifying the document area, when the background state of the document 90 is various, there may occur a situation in which the document area cannot be specified correctly without the density difference being noticeable. For example, there may occur a situation in which the document area cannot be correctly specified in one of a case where the background of the document 90 is a light color close to white and a color close to black.

  FIG. 12 is a graph showing the distribution of values of the image data sequence obtained by the image scanning unit 11 when different amounts of light are irradiated on the original 90 having a light background such as white. FIG. 13 is a graph showing the distribution of the values of the image data sequence obtained by the image scanning unit when different amounts of light are irradiated on a dark original such as a black background.

  In the graphs shown in FIGS. 12 and 13, the horizontal axis is the position in the main scanning direction R1, and the vertical axis is the data value of each pixel in the image data sequence. The data value of each pixel corresponds to the amount of light detected by the image sensor 114.

  12 and 13, a solid line graph g0 is a value of an image data string obtained when the light emitting unit 112 is in a reference state in which the light emitting unit 112 emits light with a reference light amount, and a broken line graph g1 indicates that the light emitting unit 112 is in an extinguished state. The values of the image data sequence obtained at times and the broken line graph g2 indicate the values of the image data sequence obtained when the light emitting unit 112 is in a light-intensifying state in which light is emitted with a light amount larger than the reference light amount. The reference light amount is a light amount of the light emitting unit 112 that is set in a normal image reading process for reading an image of the document 90.

  12 and 13, ΔB1 is the pixel value of the background portion of the document 90 in the image data sequence in the reference state and the pixel value of the background portion of the document 90 in the image data sequence in the unlit state. It is a difference. ΔB2 is the difference between the pixel value of the background portion of the document 90 in the image data sequence in the reference state and the pixel value of the background portion of the document 90 in the image data sequence in the bright state. Hereinafter, the former is referred to as a first difference ΔB1, and the latter is referred to as a second difference ΔB2.

  As shown in FIG. 12, when the background color of the original 90 is light, the second difference ΔB2 is smaller than the first difference ΔB1. Therefore, when the background color of the original 90 is light, if the second difference ΔB2 is used for specifying the original area, a situation may occur in which the original area cannot be specified correctly.

  On the other hand, as shown in FIG. 13, when the background color of the original 90 is dark, the first difference ΔB1 is smaller than the second difference ΔB2. For this reason, when the first difference ΔB1 is used for specifying the document area, it may occur that the document area cannot be specified correctly.

  The image reading apparatus 1 according to the present embodiment has a function for avoiding a phenomenon in which a noise image appears in the area outside the original document due to the influence of external light regardless of the difference in the state of the background of the original document 90. The function will be described below.

[Scanning Control Unit 83]
The scanning control unit 83 controls the scanning mechanism 111 and the image sensor 114 to cause the image scanning unit 11 to execute the image reading process. More specifically, the scanning control unit 83 controls the scanning mechanism 111 to move the image sensor unit 110 to a target position in the scanning range in the sub-scanning direction R2. Further, the scanning control unit 83 controls the image sensor 114 to cause the image sensor 114 to output the image data string.

  The scanning control unit 83 in the present embodiment operates the image scanning unit 11 in two types of scanning modes, the full range scanning mode and the partial range scanning mode. The full range scanning mode is a mode in which the image scanning unit 11 scans the entire scanning range from the start point to the end point in the sub-scanning direction R2. The partial range scanning mode is a mode in which the image scanning unit 11 scans only a part of the scanning range in the sub-scanning direction R2.

  For example, each of the starting point and the end point in the scanning range may be a preset position. In this case, it is conceivable that the positions of the starting point and the ending point are positions at both ends of the scannable range in the sub-scanning direction R2 of the image scanning unit 11.

  It is also conceivable that the position of one or both of the start point and the end point is set within the scannable range by an operation on the operation display unit 80. For example, when information on the size and orientation of the document 90 is input to the operation display unit 80, one end of the scannable range is set as the position of the starting point, and the position corresponding to the size and orientation of the document 90 Is set as the position of the end point.

  It is also conceivable that the image processing unit 85 automatically sets one or both of the start point and the end point. In this case, the image processing unit 85 performs document edge detection processing for detecting one or both of the leading edge position and trailing edge position in the sub-scanning direction R2 of the document 90 on the document table 13, and the detection result is set as the starting point or the Set as end point. Various known algorithms can be employed as the document edge detection processing algorithm.

  In the present embodiment, the MPU 81 outputs an operation mode signal Md described later. The operation mode signal Md is a signal indicating one of the open scanning mode and the closed scanning mode as well as the start signal of the image reading process.

  When the MPU 81 detects that a predetermined reading start operation has been performed on the operation display unit 80, the MPU 81 outputs an operation mode signal Md to the scanning control unit 83, the light emission control unit 84, and the image processing unit 85. . The scanning control unit 83, the light emission control unit 84, and the image processing unit 85 execute the image reading process when the operation mode signal Md is input.

  The open scanning mode is an operation mode in which the document 90 on the document table 13 is scanned assuming that the document table cover 12 is opened. The closed scanning mode is an operation mode in which the document 90 on the document table 13 is scanned assuming that the document table cover 12 is closed.

  When the operation mode signal Md output from the MPU 81 is a signal indicating the open scanning mode, the scanning control unit 83 causes the image scanning unit 11 to operate in the full range scanning mode after operating the image scanning unit 11 in the partial range scanning mode. . Details thereof will be described later.

  On the other hand, when the operation mode signal Md is a signal indicating the closed scanning mode, the scanning control unit 83 operates the image scanning unit 11 in the full range scanning mode. Thereby, the general image reading process is executed.

[Light emission control unit 84]
The light emission control unit 84 controls the light emission state of the light emitting unit 112. More specifically, the light emission control unit 84 has three states of the light emitting unit 112: a light-off state, the reference state that emits light with the reference light amount, and the light-intensifying state that emits light with a light amount larger than the reference light amount. Can be set to one of two states. The amount of light emitted from the light emitting unit 112 in each of the reference state and the brightening state is determined in advance. The reference state corresponds to the first state, and the comparison state corresponds to the second state.

  In the present embodiment, when the operation mode signal Md is a signal representing the open scanning mode, the light emission control unit 84 sets the light emitting unit 112 and the reference state in a predetermined cycle after setting the light emitting unit 112 to the reference state. Switch alternately to other comparison states.

  More specifically, when the image scanning unit 11 operates in the partial range scanning mode, the first light emission control unit 841 that is a part of the light emission control unit 84 includes the red light emission unit 112R, the green light emission unit 112G, and the blue light emission unit 112G. Each of the light emitting units 112B is brought into the reference state by one color. Further, when the image scanning unit 11 operates in the full range scanning mode, the second light emission control unit 842, which is a part of the light emission control unit 84, has the red light emission unit 112R, the green light emission unit 112G, and the blue light emission unit 112B. Each one is made to emit light one by one with the reference light amount.

  In the following description, a period in which the light emission with the reference light amount makes a round for all emission colors when the image scanning unit 11 operates in the full range scanning mode is referred to as a reference period T0. That is, the reference period T0 is a period corresponding to a period in which all of the red light emitting unit 112R, the green light emitting unit 112G, and the blue light emitting unit 112B are once in the reference state in the full range scanning mode.

  Further, in the full range scanning mode, the light emission control unit 84 switches the state of each of the light emitting units 112R, 112G, and 112B between the reference state and the comparison state every reference period T0.

  The comparison state is a state selected from the extinguishing state and the brightening state when the light emission control unit 84 executes a state selection process described later. Details thereof will be described later.

  In the following description, one or more image data sequences obtained when the image scanning unit 11 operates in the partial range scanning mode is referred to as sample data.

  When the operation mode signal Md is a signal representing the closed scanning mode, the light emission control unit 84 sets the light emitting unit 112 to the reference state when the image scanning unit 11 operates in the full range scanning mode. Thereby, the general image reading process is executed.

  For example, it is conceivable that the MPU 81 sets the operation mode signal Md according to an operation on the operation display unit 80 by the user by executing the operation mode setting program Pr1.

  It is also conceivable that the MPU 81 automatically sets the operation mode signal Md according to whether the detection results of the document sensor 801 and the cover sensor 802 satisfy a predetermined open scanning mode condition. In this case, the MPU 81 automatically sets the operation mode signal Md by executing the operation mode setting program Pr1.

  For example, in the open scanning mode condition, the document sensor 801 detects a state where the document 90 is not set on the document tray 121, and the cover sensor 802 indicates a state where the document table cover 12 is not closed. It is detecting. When the MPU 81 detects that a copy execution operation has been performed on the operation display unit 80 in a state where the open scan mode condition is satisfied, the MPU 81 sets the operation mode signal Md to the open scan mode state. In other cases, the operation mode signal Md is set to the closed scanning mode.

[Image processing unit 85]
The image processing unit 85 includes a representative value deriving unit 851, a temporary region segmenting unit 852, a main region segmenting unit 853, and a background replacement unit 854. For example, the image processing unit 85 may be configured by an ASIC (Application Specific Integrated Circuit) or a DSP (Digital Signal Pocessor).

  When the operation mode signal Md indicates the open scanning mode, the control unit 8 changes the state selection process for selecting the comparison state, the state of the light emitting unit 112 for each emission color, the standard state, and the comparison state. The process of acquiring the image data sequence is executed while switching to At that time, the image processing unit 85 executes a part of the state selection process and a process of classifying each pixel into the document area pixel and the outside document area pixel based on the image data string. The details will be described below.

[Control Method of Image Reading Apparatus]
Hereinafter, with reference to the flowcharts shown in FIGS. 4 and 5 and the time chart shown in FIG. 6, an example of the procedure of the image reading process of the image reading apparatus 1 when the operation mode signal Md indicates the open scanning mode. explain. In the following description, S101, S102,..., S201, S202,... Represent identification codes of respective steps executed by the MPU 81, the scanning control unit 83, the light emission control unit 84, and the image processing unit 85 in the control unit 8.

  The control unit 8 starts the processing shown in FIG. 4 when the MPU 81 outputs the operation mode signal Md indicating the open scanning mode.

<Step S101>
In the image reading process when the operation mode is the open scanning mode, first, the control unit 8 executes the state selection process. FIG. 5 is a flowchart showing an example of the procedure of the state selection process.

<Step S201>
In the state selection process, first, the first light emission control unit 841 which is a part of the light emission control unit 84 selects one predetermined emission color. That is, one of the three color light emitting units 112R, 112G, and 112B is selected. Thereafter, the first light emission control unit 841 performs processing steps S202 to S205 described below and returns to the step S201, so that the light emission units 112R, 112G, and 112B of the three colors are arranged in a predetermined order. Are sequentially selected.

<Steps S202 and S203>
Further, the first light emission control unit 841 sets the state of the light emitting unit 112 of the selected color to the reference state in which light is emitted with the reference light amount (S202).

  Further, when the light emitting unit 112 is in the reference state, the first scanning control unit 831 which is a part of the scanning control unit 83 operates the image scanning unit 11 in the partial range scanning mode (S203).

  That is, the first scanning control unit 831 causes the image scanning unit 11 to scan a part of the scanning range in the sub-scanning direction R2 when the selected color light emitting unit 112 is in the reference state (S203). Accordingly, the first scanning control unit 831 causes the image scanning unit 11 to output the sample data including the image data string of at least one of the linear regions (S203). The outputted sample data is temporarily stored in a line buffer (not shown) in the image processing unit 85.

  For example, in step S203, the first scanning control unit 831 causes the image scanning unit 11 to scan a part on the starting point side in the scanning range in the sub-scanning direction R2. The scanning range of the image scanning unit 11 in step S203 may be, for example, a range of one line from the starting point, or a range of several lines or a dozen lines from the starting point.

<Step S204>
Next, the first light emission control unit 841 determines whether or not all light emission colors have been selected in a step in step S201. If not all the emission colors have been selected, the process returns to step S201, and the processes of steps S201 to S203 are repeated for the remaining emission colors. When all the emission colors are selected in a round, the next step S205 is executed.

<Step S205>
Each time Steps S202 and S203 are executed for all emission colors, the first scanning control unit 831 determines whether or not scanning of a predetermined partial range in the entire scanning range in the sub-scanning direction R2 is completed. judge. If scanning of a predetermined range is not completed, the process is returned to step S201, and the processes of steps S201 to S204 are repeated for the remaining scanning range. When scanning of a predetermined range is completed, the next step S206 is executed.

  That is, in the state selection process, the first light emission control unit 841 causes the light emission unit 112 to emit light in the standard state for each emission color (S201, S202, S204), and the scan control unit 83 is in the partial range scanning mode. The image scanning unit 11 is operated (S203, S205).

<Step S206>
Next, the representative value deriving unit 851 of the image processing unit 85 derives a representative value of the sample data for each emission color. That is, the representative value deriving unit 851 performs a calculation for deriving a representative value of the sample data of each color obtained when the image scanning unit 11 operates in the partial range scanning mode. The representative value is a value that serves as a measure of the amount of reflected light or the density of pixels corresponding to the background area of the original 90 in the sample data.

  The representative value deriving unit 851 includes the representative value of the sample data corresponding to the standard state of the red light emitting unit 112R, the representative value of the sample data corresponding to the standard state of the green light emitting unit 112G, and a blue light emitting unit. The representative values of the sample data corresponding to the standard state of 112B are respectively derived.

  For example, it is conceivable that the representative value is the value of the class having the highest frequency in the frequency distribution of the sample data. In general, most of the area in the original 90 is a background area where no image is formed, and the remaining area with a relatively small occupation ratio is often an image area. For this reason, the class value having the highest frequency in the frequency distribution of the sample data is suitable as the representative value that is a measure of the amount of reflected light from the background area of the document 90 or the density of the background area. The class value having the largest frequency is, for example, the minimum value, maximum value, median value, or average value of the range of the class.

  As will be described later, the representative value is an index value for selecting whether the comparison state of the light emitting unit 112 is the extinguishing state or the brightening state. Therefore, the representative value may be a relatively coarse resolution that can determine whether or not the color of the background area of the document 90 is a particularly dark color. Therefore, when the representative value is derived based on the frequency distribution of the sample data, the number of the plurality of classes divided in the frequency distribution may not be large. Thereby, the calculation load of the representative value deriving unit 851 is reduced.

<Step S207>
Furthermore, the MPU 81 selects one of the extinguishing state and the brightening state as the comparison state of the light emitting unit 112 depending on whether or not the sample data satisfies a predetermined condition. For example, the MPU 81 selects the comparison state for each emission color. The comparison state of each of the light emitting units 112R, 112G, and 112B for each light emission color selected in the present embodiment is a common state in the entire scanning range in the sub-scanning direction R2.

  The MPU 81 executes the process of this step by executing the state selection program Pr2. The MPU 81 that executes the state selection program Pr2 is an example of the state selection unit.

  More specifically, the MPU 81 selects the brightening state as the comparison state when the representative value of the sample data is a value indicating a light amount smaller than a predetermined threshold light amount, and when not, The off state is selected as the comparison state.

  For example, a case where the data value and the representative value of each pixel in the image data sequence are values indicating the light intensity in 256 gradations from 0 to 255 can be considered. In this case, the MPU 81 selects the brightening state as the comparison state when the representative value is smaller than a preset threshold value, and selects the extinguishing state as the comparison state otherwise.

  On the other hand, it is conceivable that the data value and the representative value of each pixel in the image data sequence are values indicating image density with 256 gradations from 0 to 255. The magnitude relationship between the values indicating the image density is opposite to the magnitude relationship between the values indicating the light quantity. In this case, the MPU 81 selects the brightening state as the comparison state when the representative value is larger than a preset threshold value, and selects the extinguishing state as the comparison state otherwise.

  When the representative value corresponding to the amount of reflected light from the background area of the document 90 is a value indicating a relatively small amount of light, the background area of the document 90 is considered to be black or a dark color close to black. . In this case, the MPU 81 selects the brightening state as the comparison state.

  On the other hand, when the representative value is a value indicating a relatively large amount of light, the background area of the document 90 is considered to be white or a light color close to white. In this case, the MPU 81 selects the extinguished state as the comparison state.

<Step S208>
In parallel with steps S206 and S207, the first scanning control unit 831 returns the scanning mechanism 111 to a state of scanning at the starting point. The above is an example of the state selection process.

<Step S102>
Further, when the state selection process is completed, the second light emission control unit 842 which is a part of the light emission control unit 84 selects one predetermined emission color. That is, one of the three color light emitting units 112R, 112G, and 112B is selected. Thereafter, the second light emission control unit 842 performs processing steps S103 to S111 described below, and returns to step S102, so that among the three color light emission units 112R, 112G, and 112B in a predetermined order. Are sequentially selected.
<Steps S103 and S104>
Further, the second light emission control unit 842 sequentially switches the state of the light emitting unit 112 of the selected color between the reference state and the comparison state selected in the state selection process (S103).

  Further, in parallel with the switching of the state of the light emitting unit 112, the second scanning control unit 832 which is a part of the scanning control unit 83 operates the image scanning unit 11 in the full range scanning mode (S104). Accordingly, the image scanning unit 11 executes the image reading process, and the first image data sequence corresponding to the reference state of the light emitting unit 112 of the selected color and the second image data sequence corresponding to the comparison state. Are output (S104). The output first image data sequence corresponding to the standard state is temporarily stored in a line buffer (not shown) in the image processing unit 85.

  Then, every time the state of the light emitting unit 112 of one color is switched, that is, every time one first image data sequence and one second image data sequence are obtained, the image processing unit 85 Steps S105 and S106 shown in FIG.

<Step S105>
In step S <b> 105, the temporary area dividing unit 852 of the image processing unit 85 calculates a difference ΔB between the first image data sequence and the second image data sequence obtained for each state switching cycle of the light emitting unit 112 of one color. To do.

  That is, the provisional region sorting unit 852 has a pair of the above-described obtained light emission colors for each reference period T0 in a state where the state of each light emission color of the light emitting unit 112 is alternately switched between the reference state and the comparison state. The image data strings are compared, and a difference ΔB is calculated. The pair of image data strings are the first image data string corresponding to the standard state and the second image data string corresponding to the comparison state. The difference ΔB is a difference between data of pixels corresponding to each other in the first image data sequence and the second image data sequence.

  When the comparison state of the light emitting unit 112 is the extinguished state, the difference ΔB is a difference obtained by subtracting the data of each pixel of the second image data sequence from the data of each pixel of the first image data sequence. is there. This difference corresponds to the first difference ΔB1 in FIG.

  Further, when the comparison state of the light emitting unit 112 is the brightening state, the difference ΔB is obtained by subtracting the data of each pixel of the first image data sequence from the data of each pixel of the second image data sequence. It is a difference. This difference corresponds to the second difference ΔB2 in FIG.

  Further, in step S105, the temporary area dividing unit 852 executes a temporary area dividing process. The temporary area dividing process is a process of dividing each pixel in the linear area into the original area pixel and the outside original area pixel based on the difference ΔB. At that time, the provisional area sorting unit 852 classifies the pixels satisfying the document area condition in which the difference ΔB is predetermined into the document area pixels. The temporary area dividing unit 852 executes the temporary area dividing process for each emission color.

  For example, it is conceivable that the temporary area dividing unit 852 executes the pixel classification according to the first classification rule shown below. The first classification rule determines whether or not the document area condition is satisfied for each of the plurality of pixels continuous in the main scanning direction R1, classifies the pixels in the area satisfying the document area condition into the document area pixels, and others. The above-mentioned pixel is divided into the non-document area pixels.

  The document area condition in the first classification rule is a condition that the difference shows a difference larger than a predetermined light amount difference continuously for a predetermined number or more in the main scanning direction.

  In addition, it is conceivable that the temporary area classification unit 852 executes the pixel classification according to the second classification rule shown below. In the second division rule, all pixels in the range from the pixel closest to the first end of the linear region to the pixel closest to the second end of the linear region in the pixels satisfying the document region condition are satisfied. The rule is to divide the pixels into the document area pixels.

  It is conceivable that the document area condition in the second classification rule is the same as the document area condition in the first classification rule. For example, it is conceivable that the MPU 81 has a function of selecting one of the first classification rule and the second classification rule in accordance with an operation on the operation display unit 80. In this case, the temporary area classification unit 852 executes the pixel classification according to the selected one classification rule.

  It is also conceivable that the temporary area classification unit 852 determines whether or not the document area condition is satisfied for each pixel, and classifies the pixels satisfying the document area condition into the document area pixels. In this case, the document area condition is a condition that the difference shows a difference larger than a predetermined light amount difference.

  In step S105, the first light amount difference when the comparison state is the extinguishing state is different from the second light amount difference when the comparison state is the brightening state. In general, the first light amount difference corresponding to the extinguishing state is larger than the second light amount difference corresponding to the brightening state.

  The classification result of the main area classification process, which will be described later, is the final classification result, whereas the classification result of the temporary area classification process is a classification result in the middle of obtaining the final result.

  In the image data string, the data of each pixel in the document area changes relatively greatly according to the change in the state of the light emitting unit 112. On the other hand, the data of each pixel in the area outside the original hardly changes even if the state of the light emitting unit 112 changes.

  Therefore, the temporary area classification unit 852 determines pixels that have a difference ΔB smaller than a threshold light amount difference, which is a predetermined light amount difference, as non-document area pixels, and determines other pixels as document area pixels. . The document area pixel is a pixel in an area on the document table 13 where the document 90 is present, and the outside-document area pixel is a pixel in the other area.

<Step S106>
Next, the second light emission control unit 842 determines whether or not all the light emission colors have been selected in step S102. If not all the emission colors have been selected, the process returns to step S102, and the processes of steps S102 to S105 are repeated for the remaining emission colors. When all the emission colors are selected in a cycle, the next step S107 is executed.

  In FIG. 6, Lr, Lg, and Lb indicate the light emission states of the red light emitting unit 112R, the green light emitting unit 112G, and the blue light emitting unit 112B, respectively. STN and CMP in each of the light emitting states indicate the standard state and the comparative state, respectively.

  In FIG. 6, X0 indicates the image data sequence that is sequentially output from the image sensor 114. Xr, Xg, and Xb indicate the image data string corresponding to the standard state of each emission color stored in the line buffer among the image data strings sequentially output from the image sensor 114.

  In FIG. 6, Rstn, Rcmp, Gstn, Gcmp, Bstn, and Bcmp are respectively the red standard state, the red comparison state, the green standard state, the green comparison state, the blue standard state, and The image data sequence corresponding to the blue comparison state is shown. That is, Rstn, Gstn, and Bstn indicate the first image data string of each color. Rcmp, Gcmp, and Bcmp indicate the second image data string of each color.

  As shown in FIG. 6, the second light emission control unit 842 causes each of the light emitting units 112R, 112G, and 112B to emit light one by one with the reference light amount in steps S102 and S103. At that time, the second light emission control unit 842 changes the states Lr, Lg, and Lb of the light emitting units 112R, 112G, and 112B to the standard state STN for each reference period T0 in which light emission with the reference light amount completes for all emission colors. And the comparison state CMP selected based on the sample data.

  In addition, among the image data string X0 output from the image sensor 114, the latest first image data strings Rstn, Gstn, Bstn corresponding to the standard state of each emission color are stored in the line buffer.

  Further, during the execution of steps S102 to S106, the temporary area classification unit 852 generates red temporary area classification data Yr, green temporary area classification data Yg, and blue temporary area classification data Yb as a result of the temporary area classification processing. Output. When the temporary area division data Yr, Yg, Yb is 1-bit data for each pixel, it is considered that the original area pixel and the non-original area pixel are represented by “1” and “0”, respectively. It is done.

  The red provisional area division data Yr is obtained each time a pair of the image data strings Rstn, Rcmp corresponding to the standard state and the comparison state of the red light emitting unit 112R is obtained. Is output as a result of the temporary area segmentation processing based on the above.

  The provisional green region segment data Yg is obtained each time a pair of the image data sequences Gstn, Gcmp corresponding to the standard state and the comparison state of the green light emitting unit 112G is obtained. Is output as a result of the temporary area segmentation processing based on the above.

  The blue provisional area division data Yb is obtained each time a pair of the image data strings Bstn and Bcmp corresponding to the standard state and the comparison state of the blue light emitting unit 112B is obtained. Is output as a result of the temporary area segmentation processing based on the above.

<Step S107>
Then, every time Yr, Yg, Yb is obtained as a result of the provisional area dividing process for all the emission colors, the main area dividing unit 853 of the image processing unit 85 executes the main area dividing process. In the main area dividing process, the pixels divided into the original area pixels with respect to at least one of the emission colors by the temporary area dividing process are divided into the original area pixels, and the other pixels are set as the non-original area pixels. It is a process to classify.

  In the main area dividing process, the main area dividing unit 853 outputs main area dividing data Y0 corresponding to the contents of the division result of the temporary area dividing unit 852 obtained for each emission color for each reference period T0.

  More specifically, the main area dividing unit 853 divides the pixels divided into the original area pixels for at least one of the emission colors by the processing of the temporary area dividing unit 852 into the original area pixels, and the other The pixels are divided into the original area pixels.

  For example, if the temporary area division data Yr, Yg, Yb for each color is data in which the original area pixel is “1”, that is, “true”, and the non-original area pixel is “0”, that is, “false”. The unit 853 outputs the logical sum data of the latest temporary area division data Yr, Yg, Yb of each color as main area division data Y0.

<Step S108>
Further, the MPU 81 obtains the result of segmentation of the document region pixels by the main region segmentation processing from the main region segmentation unit 853, and from one end to the other end of the region segmented into the document region pixels in the main scanning direction R1. From the length, the size of the recording sheet 9 suitable for image output is specified.

  For example, it is conceivable that step S108 is executed only once at the first stage of scanning in the sub-scanning direction R2. It is also conceivable that step S108 is executed only once based on the result of the main area segmentation process a plurality of times. It is also conceivable that step S108 is executed every time the result of the main area sorting process is obtained, and the specified maximum size is adopted as the size of the recording sheet 9.

  The MPU 81 executes the process of step S108 by executing the sheet size specifying program Pr4. The MPU 81 that executes the sheet size specifying program Pr4 functions as a sheet size specifying unit that specifies the size of the recording sheet 9 as an image forming destination from the result of the document area pixel classification by the main area sorting process.

<Step S109>
Further, the background replacement unit 854 of the image processing unit 85 has the pixel data segmented into the non-document region pixels by the main region segmentation process in each of the first image data strings Rstn, Gstn, and Bstn for each of the emission colors. Each is replaced with preset background data.

  The background data may be data corresponding to a preset color, for example, data corresponding to white or data corresponding to black. It is also conceivable that the MPU 81 sets the background data in advance according to a user operation on the operation display unit 80 by executing the background data setting program Pr3.

  The first image data sequence after the data of the pixel outside the document is replaced is subjected to the final post-processing by the image processing unit 85 and then output to the laser control unit 86 as the recording image data sequence. The As a result, an image corresponding to the first image data string after the background replacement process is performed is formed on the recording sheet 9 by the image forming apparatus 2.

  For example, the post-processing is a density conversion process for converting data of each pixel corresponding to the amount of light emitted from the linear region in the first image data sequence into data representing pixel density. When the data of each pixel is data of 256 gradations from 0 to 255, the pixel density data of 256 gradations is calculated by subtracting the light amount data of each pixel from the maximum gradation value 255. The

<Step S110>
Each time Steps S103 to S109 are executed for all emission colors, the second scanning control unit 832 determines whether or not scanning of the entire scanning range in the sub-scanning direction R2 has been completed. If the scanning of the entire scanning range is not completed, the process is returned to step S102, and the processes of steps S102 to S109 are repeated for the remaining scanning range. When the scanning of the entire scanning range is finished, the image reading process by the control unit 8 is finished.

  When the image reading apparatus 1 operates in a monochrome mode in which an image of the document 90 is read as a monochrome image, the first light emission control unit 841 causes the light emission units 112 of all emission colors to be simultaneously used in the state selection process S202. The light is emitted in the standard state. Further, when the image reading apparatus 1 operates in the monochrome mode, the second light emission control unit 842 alternately changes the states of the light emitting units 112 of all the emission colors to the standard state and the comparison state at the same time in step S103. Switch.

  It is also conceivable that the image forming apparatus 2 is a color image forming apparatus including a plurality of image forming units 4 corresponding to different color developers. In this case, each of the image forming units 4 transfers an image to an intermediate transfer belt (not shown), and the image on the intermediate transfer belt is transferred to the recording sheet 9.

  As described above, the second light emission control unit 842 executes control for alternately switching the state of the light emitting unit 112 between the reference state and the comparison state for each emission color (S102, S103). Further, the second scanning control unit 832 causes the image scanning unit 11 to execute the image reading process in parallel with the switching of the state of the light emitting unit 112 (S104).

  Further, the temporary area classification unit 852 compares the first image data string and the second image data string for each emission color, and determines each of the pixels as the original area pixel and the outside area of the original according to the difference ΔB. Divided into pixels.

  More specifically, the provisional region sorting unit 852 corresponds to the difference ΔB that satisfies the difference condition when the predetermined difference condition including the condition that the difference ΔB is larger than a preset threshold value is satisfied. The pixel corresponding to the difference ΔB is divided into the non-document area pixel.

  For example, the difference condition may include a condition that the difference ΔB indicates a difference larger than a predetermined light amount difference continuously for a predetermined number or more in the main scanning direction R1. In general, the document area often includes a plurality of pixels that are continuous in the main scanning direction R1. Therefore, if the difference condition is that the pixels corresponding to the difference ΔB indicating a relatively large light amount difference are continuous, the pixel to be classified as the outside document area pixel is erroneously classified as the document area pixel. Can be prevented.

  By the way, when the background color of the original 90 is a complementary color of the light emission color of the light emitting unit 112 or a color having a hue close to the complementary color, the pixel to be classified as the original area pixel may be classified as the non-original area pixel. There is.

  However, in the image reading apparatus 1, the main area dividing unit 853 divides the pixels divided into the original area pixels for at least one of the emission colors by the temporary area dividing process into the original area pixels. As a result, if the correct result of the provisional area classification process is obtained for at least one emission color, the correct classification result of the document area pixels can be obtained.

  By performing the above control, according to the image reading apparatus 1, when scanning of the document 90 is performed with the document table cover 12 opened, a noise image is generated in the region outside the document due to the influence of external light. Appearance can be avoided.

  In addition, the first scanning control unit 831 causes the image scanning unit 11 to scan a part of the scanning range in the sub-scanning direction R2 while the first light emission control unit 841 sets the light emitting unit 112 in the reference state. Sample data is obtained.

  Then, the MPU 81 that executes the state selection program Pr2 selects one of the extinguishing state and the brightening state as the comparison state depending on whether or not the sample data satisfies a predetermined condition.

  As can be seen from FIG. 12, when the background color of the original 90 is light, the first difference ΔB1 is larger than the second difference ΔB2. Therefore, if the original area and the non-original area are distinguished by determining the size of the first difference ΔB1, the original area can be easily specified correctly.

  As can be seen from FIG. 13, when the background color of the original 90 is dark, the second difference ΔB2 is larger than the first difference ΔB1. For this reason, if the document area and the document outside area are distinguished by determining the magnitude of the second difference ΔB2, the document area can be easily specified correctly.

  Therefore, according to the image reading apparatus 1, it is possible to avoid the appearance of a noise image in the outside area of the document due to the influence of external light regardless of the background state of the document 90.

[Second Embodiment]
Next, an image reading apparatus according to the second embodiment will be described with reference to the flowchart shown in FIG. FIG. 7 is a flowchart illustrating an example of the procedure of the image reading process when the operation mode signal Md indicates the open scanning mode in the image reading apparatus according to the second embodiment. In the following description, S301, S302,... Represent identification codes of respective steps executed by the MPU 81, the scanning control unit 83, the light emission control unit 84, and the image processing unit 85 in the control unit 8.

  The control unit 8 starts the processing shown in FIG. 7 when the MPU 81 outputs the operation mode signal Md indicating the open scanning mode.

  In the present embodiment, the second light emission control unit 842 that sets the light emission units 112R, 112G, and 112B of each color to the standard state for each reference period T0 also serves as the first light emission control unit 841 in the state selection process.

  Further, in the present embodiment, the second light emission control unit 842 causes the image scanning unit 11 to execute the image reading process in response to the light emission units 112R, 112G, and 112B of the respective colors being set to the standard state. The unit 832 also serves as the first scanning control unit 831 in the state selection process.

  Then, the MPU 81 that executes the state selection program Pr2 is employed in the next reference period T0 depending on whether or not the sample data for each emission color obtained in each reference period T0 satisfies a predetermined condition. The comparison state of each of the light emitting units 112R, 112G, and 112B for each of the emission colors is selected. The details will be described below.

<Step S301>
In the image reading process when the operation mode is the open scanning mode, first, the second light emission control unit 842 selects the initial state of the comparison state of the light emitting units 112R, 112G, and 112B of each color. For example, the MPU 81 selects a predetermined one of the extinguishing state and the brightening state for each emission color as the initial state of the comparison state.

  In step S301, the MPU 81 may select the initial state of the comparison state based on the first image data sequence, similarly to steps S206 and S207. In this case, the first light emission control unit 841 sequentially causes the light emission units 112R, 112G, and 112B of each color to emit light in the standard state, and the first scanning control unit 831 operates the image scanning unit 11 at the starting point in the sub-scanning direction R2. Let The first image data string corresponding to the starting point thus obtained is an example of the sample data.

  Further, the MPU 81 determines whether or not the representative value of the first image data sequence obtained at the starting point satisfies a predetermined condition when the light emitting units 112R, 112G, and 112B of the respective colors are in the reference state. To select an initial state of the comparison state. The MPU 81 executes the process of step S301 by executing the state selection program Pr2.

<Step S302>
Further, the second light emission control unit 842 selects one predetermined light emission color as in step S102.

<Steps S303 to S306>
After step S302 ends, the second light emission control unit 842 alternately switches the state of the light emitting unit 112 between the reference state and the comparison state selected in advance (S303, S305).

  Further, in parallel with the switching of the state of the light emitting unit 112, the second scanning control unit 832 operates the image scanning unit 11 in the full range scanning mode (S304, S306). That is, the second scanning control unit 832 sequentially advances the scanning position in the sub-scanning direction R2. Further, the second scanning control unit 832 alternately performs the image scanning in the reference state (S304) and the image scanning in the comparison state (S306) in synchronization with the switching of the state of the light emitting unit 112 of each color. 11 is executed.

  Under the control of steps S304 and S306, the image scanning unit 11 executes the image reading process, and corresponds to the first image data string corresponding to the reference state of the light emitting unit 112 and the comparison state of the light emitting unit 112. The second image data sequence is output.

<Steps S307 and S308>
Further, when the switching of the state of the light emitting unit 112 (S303, S305) and the image reading process (S304, S306) are performed, every time the first image data string corresponding to each light emission color is obtained, The representative value deriving unit 851 and the MPU 81 perform processing for selecting the next comparison state of the light emitting unit 112 of the color (S307, S308). The representative value deriving unit 851 and the MPU 81 perform a process of selecting the next comparison state of the light emitting unit 112, similarly to steps S206 and S207.

  More specifically, the representative value deriving unit 851 of the image processing unit 85 derives the representative value of the first image data sequence obtained in step S304 (S307). The first image data string obtained in step S304 is an example of the sample data. As described above, it is conceivable that the representative value is a class value having the highest frequency in the frequency distribution of the sample data.

  Further, the MPU 81 determines whether the first image data sequence obtained in step S304 satisfies the predetermined condition, and the next comparison of the light emitting unit 112 of the color corresponding to the first image data sequence. One of the extinguishing state and the brightening state is selected as a state (S306). The MPU 81 executes the process of this step by executing the state selection program Pr2. The MPU 81 that executes the state selection program Pr2 is an example of the state selection unit.

  In the present embodiment, the first image data sequence obtained in step S304 is an example of the sample data. That is, in the present embodiment, the second scanning control unit 832 also functions as the first scanning control unit 831 that outputs the sample data to the image scanning unit 11.

  Then, every time the state of the light emitting units 112R, 112G, and 112B of each color is switched, that is, every time one first image data string and one second image data string are obtained for each light emitting color, The process part 85 performs the process of process S309-S314 shown below similarly to process S105-S110 mentioned above.

<Step S309>
First, the temporary area sorting unit 852 of the image processing unit 85 calculates the difference ΔB between the first image data sequence and the second image data sequence obtained for each switching period of the state of the light emitting unit 112.

  Further, the temporary area dividing unit 852 of the image processing unit 85 executes the temporary area dividing process of dividing each pixel into the original area pixel and the outside-original area pixel based on the difference ΔB. This step S309 is the same as step S105 described above.

<Step S310>
Furthermore, the second light emission control unit 842 determines whether or not all the light emission colors have been selected in step S302, as in step S106. If all the emission colors are not yet selected, the process returns to step S302, and the processes of steps S302 to S309 are repeated for the remaining emission colors. When all the emission colors are selected in a round, the next step S310 is executed.

<Step S311>
Every time the results Yr, Yg, Yb of the temporary area dividing process for all the emission colors are obtained, the main area dividing unit 853 of the image processing unit 85 executes the main area dividing process in the same manner as in step S107. As a result, the pixels that have been classified into the document area pixels for at least one of the emission colors by the temporary area classification process are classified into the document area pixels, and the other pixels are classified into the outside document area pixels.

<Step S312>
Further, as in step S108, the MPU 81 obtains the result of segmentation of the document area pixels by the main area segmentation process from the main area segmentation unit 853, and extracts the area segmented into the document area pixels in the main scanning direction R1. The size of the recording sheet 9 suitable for image output is specified from the length from one end to the other end.

<Step S313>
Further, the background replacement unit 854 of the image processing unit 85 classifies the pixel area outside the document by the main area segmentation process in each of the first image data strings Rstn, Gstn, and Bstn for each of the emission colors, similarly to step S109. Each of the pixel data is replaced with preset background data.

<Step S314>
Each time Steps S303 to S313 are executed for all emission colors, the second scanning control unit 832 determines whether scanning of the entire scanning range in the sub-scanning direction R2 is completed. When the scanning of the entire scanning range is not completed, the process step is returned to step S302, and the processes of steps S302 to S313 are repeated for the remaining scanning range. When the scanning of the entire scanning range is finished, the image reading process by the control unit 8 is finished.

  Also in the second embodiment, when scanning of the document 90 is performed with the document table cover 12 opened, a noise image is generated in the region outside the document due to the influence of external light regardless of the background state of the document 90. You can avoid appearing.

  Further, according to the second embodiment, the sample data collection and the comparison state selection process of the light emitting unit 112 based on the sample data are executed for each position in the sub-scanning direction R2. That is, the appropriate comparison state of the light emitting unit 112 is selected for each position in the sub-scanning direction R2. As a result, even when the background density of the document 90 is not uniform in the sub-scanning direction R2, the document area and the document outside area are correctly classified.

[Specific examples of image processing results]
Next, an example of a specific two-dimensional image obtained by image processing executed by the image processing apparatus 10 will be described with reference to FIGS. FIG. 8 is a diagram illustrating an example of the document 90. 9 to 11 are synthesized from the first image data string obtained when the document 90 on the document table 13 is scanned in the open scanning mode in the image processing apparatus 10 with the document table cover 12 opened. A two-dimensional image obtained is shown.

  FIG. 9 is a diagram illustrating an example of a two-dimensional image synthesized from the first image data sequence obtained when the light emitting unit 112 is in the reference state. FIG. 10 is a diagram illustrating an example of a two-dimensional image synthesized from the second image data sequence obtained when the light emitting unit 112 is in the extinguished state. FIG. 11 is a diagram illustrating an example of a two-dimensional image synthesized from the first image data sequence after the background replacement process when the background data is data corresponding to black.

  Consider a case where two originals 90 shown in FIG. 8 are scanned in the open scanning mode in the image processing apparatus 10. One of the two documents 90 is a document in which an opening 900 is partially formed.

  When two originals 90 shown in FIG. 8 are scanned in the open scanning mode, a two-dimensional image obtained by synthesizing the first image data sequence corresponding to the reference state of the light emitting unit 112 is, for example, shown in FIG. The image looks like this.

  As shown in FIG. 9, the image when the light emitting unit 112 is in the reference state is an image including two images of the original 90 and an image outside the original. In the example shown in FIG. 9, the image outside the document includes a noise image Ng including an external light image and a shadow image of an object that blocks the external light.

  On the other hand, as shown in FIG. 10, the image when the light emitting unit 112 is in the extinguished state is an image including the shadow image of the two originals 90 and the image outside the original. Further, as shown in FIGS. 9 and 10, the image in the outside area of the document is substantially the same when the light emitting unit 112 is in the reference state and in the extinguishing state.

  Then, the image after the pixels in the area outside the document are replaced with black pixels by the background replacement process is an image as shown in FIG. As shown in FIG. 11, according to the image reading apparatus 1, the document area and the document outside area are correctly divided.

  In addition, when the said brightening state is selected as the said comparison state of the said light emission part 112, the image when the said light emission part 112 is the said comparison state differs from the image shown in FIG.

  The image of the original area when the light emitting unit 112 is in the bright state is a brighter image than the image shown in FIG. On the other hand, the image in the area outside the original when the light emitting unit 112 is in the bright state is equivalent to the image shown in FIGS.

  Then, according to the image reading apparatus 1, as shown in FIG. 11, both in the case where the background of the original 90 is a light color such as white and in the case where the background of the original 90 is a dark color such as black. The document area and the outside-document area are correctly classified.

[Application example]
In the image reading apparatus 1 shown above, when the operation mode signal Md is in the open scanning mode, image scanning in the sub-scanning direction R2 is performed more than when the operation mode signal Md is in the closed scanning mode. It is conceivable that the scanning speed of the section 11, that is, the moving speed of the scanning mechanism 111 is set to a low speed. Thereby, it can be avoided that the image resolution in the sub-scanning direction R2 by the image scanning unit 11 in the open scanning mode is reduced to half of the image resolution in the closed scanning mode.

  The state in which the operation mode signal Md indicates the open scanning mode is an operation state in which the light emitting unit 112 is alternately switched between the reference state and the comparison state while the image scanning unit 11 is scanning. On the other hand, the state in which the operation mode signal Md indicates the closed scanning mode is an operation state in which the light emitting unit 112 continues to be lit in the reference state while the image scanning unit 11 is scanning.

  Further, in the image reading apparatus 1, when the operation mode signal Md is in the open scanning mode, the image scanning unit 11 in the sub-scanning direction R2 is more than when the operation mode signal Md is in the closed scanning mode. It is also conceivable to shorten the light amount detection cycle of the linear region. Thereby, it can be avoided that the image resolution in the sub-scanning direction R2 by the image scanning unit 11 in the open scanning mode is reduced to half of the image resolution in the closed scanning mode. Furthermore, it can be avoided that the scanning time of the image scanning unit 11 becomes long.

  It is also conceivable that the processing of the image processing unit 85 shown above is realized by a processor that executes a computer program. For example, it is conceivable that the MPU 81 or another MPU for image processing executes a process equivalent to the process of the image processing unit 85 by executing a program stored in advance in the storage unit 82.

  The image reading apparatus, the image processing apparatus, and the control method for the image reading apparatus according to the present invention can be freely combined within the scope of the invention described in each claim, Alternatively, the embodiment and application examples can be appropriately modified or partly omitted.

1: Image reading device 2: Image forming device 3: Sheet conveying unit 4: Image forming unit 5: Optical scanning unit 6: Fixing unit 8: Control unit 9: Recording sheet 10: Image processing device 11: Image scanning unit 12: Document Table cover 13: Document table 13a: Contact unit 30: Sheet storage unit 31: Sheet feeding unit roller 32: Sheet transport roller 33: Discharge roller 41: Photoconductor (image carrier)
42: charging unit 43: developing unit 45: transfer unit 47: cleaning unit 61: fixing roller 62: pressure roller 80: operation display unit 81: MPU
82: Storage unit 83: Scan control unit 84: Light emission control unit 85: Image processing unit 86: Laser control unit 87: Signal interface 90: Document 100: Housing 101: Recording sheet discharge tray 110, 120: Image sensor unit 111: Scanning mechanism 112: light emitting unit 112B: blue light emitting unit 112G: green light emitting unit 112R: red light emitting unit 113: lens 114: image sensor 121: document tray 122: transport roller 123: document discharge tray 140: document transport path 300: sheet transport Path 801: Document sensor 802: Cover sensor 831: First scanning control unit 832: Second scanning control unit 841: First light emission control unit 842: Second light emission control unit 851: Representative value deriving unit 852: Temporary region dividing unit 853 : Main area section 854: Background replacement unit 900: Opening Md: Motion Mode signal Ng: noise image Pr1: operation mode setting program Pr2: state selection program Pr3: background data configuration program Pr4: sheet size specifying program R1: main scanning direction R2: the sub-scanning direction T0: reference period

Claims (10)

A plurality of light emitting units for irradiating light of different colors toward a document placed on a transparent document table;
The line is obtained by scanning the document table along the sub-scanning direction orthogonal to the main scanning direction while detecting the amount of light emitted from the linear region along the main scanning direction on the document table for each pixel. An image scanning unit capable of executing an image reading process for sequentially outputting an image data sequence corresponding to the detected light amount for each pixel in the pixel region;
A first light emission control unit that sets each of the light emitting units to a first state in which each color emits light with a predetermined reference light amount;
By causing the image scanning unit to scan a part of the scanning range in the sub-scanning direction when the light emitting unit is in the first state, sample data including the image data string of at least one linear region is obtained. A first scanning control unit for outputting to the image scanning unit;
Depending on whether or not the sample data satisfies a predetermined condition, the second state of the light emitting unit is selected from either a light-off state or a light-enhanced state that emits light with a larger light quantity than the first state A selection section;
Each of the light emitting units is caused to emit light one by one with the reference light amount in order, and the state of each of the light emitting units is changed between the first state and the sample for each reference period in which light emission with the reference light amount makes a round for all light emission colors. A second light emission control unit for switching to the second state selected based on the data;
The image reading that outputs a first image data sequence corresponding to the first state of the light emitting unit and a second image data sequence corresponding to the second state of the light emitting unit for each state switching cycle of the light emitting unit. A second scanning control unit that causes the image scanning unit to execute processing;
For each of the reference period, is obtained for each emission color by comparing the first image data stream and the second image data sequence, the pixels corresponding to each other in the first image data stream and the second image data train A provisional area dividing unit that executes a process for dividing each pixel into a document area pixel and a document outside area pixel according to a difference in data for each of the emission colors;
For each reference period, the provisional area dividing unit classifies the pixels divided into the document area pixels for at least one of the emission colors into the document area pixels, and classifies the other pixels into the document outside area pixels. An image reading apparatus comprising: The second light-emission control unit that sets each of the light-emitting units to the first state for each reference period, and the second scanning control unit that causes the image scanning unit to execute the image reading process correspondingly, respectively. Also serves as one light emission control unit and the first light emission control unit,
The state selection unit determines whether the sample data for each luminescent color obtained for each reference period satisfies a predetermined condition, for each luminescent color employed in the next reference period. The image reading apparatus according to claim 1, wherein the second state of the light emitting unit is selected. The first scanning control unit causes the image scanning unit to output a part of the starting point side in the scanning range in the sub-scanning direction, thereby causing the image scanning unit to output the sample data,
The image reading apparatus according to claim 1, wherein the state selection unit selects the second state of the light emitting unit for each of the light emission colors common in the entire scanning range in the sub-scanning direction.   The state selecting unit selects the brightening state as the second state when the representative value of the sample data is a value indicating a light amount smaller than a predetermined threshold light amount, and when not, the second state. The image reading apparatus according to claim 1, wherein the unlit state is selected as a state.   The image reading apparatus according to claim 4, wherein the representative value of the sample data is a value of a class having the highest frequency in the frequency distribution of the sample data.   The temporary area dividing unit classifies the pixels in an area where the difference is greater than a predetermined light quantity difference continuously in a predetermined number or more in the main scanning direction into the document area pixels, 6. The image reading apparatus according to claim 1, wherein the pixel can be classified according to a first division rule that divides the pixel into the outside-document area pixel.   The tentative area segmentation unit starts from the pixel closest to the first end of the linear area in the pixel that satisfies the document area condition that requires the difference to be larger than a predetermined light amount difference. 7. The pixel division can be executed according to a second division rule that divides all the pixels within a range up to a pixel closest to the second end of the shape region into the document region pixels. The image reading apparatus according to claim 1.   A background replacement unit that replaces each pixel data segmented into the outside-document region pixels by the main region segmentation unit in each of the first image data strings for each of the emission colors with preset background data. The image reading apparatus according to claim 1. The image reading apparatus according to any one of claims 1 to 8,
An image processing apparatus comprising: an image forming apparatus that forms, on a recording sheet, images corresponding to the plurality of first image data sequences obtained by the image reading apparatus. A plurality of light emitting units for irradiating light of different colors toward a document placed on a transparent document table;
The line is obtained by scanning the document table along the sub-scanning direction orthogonal to the main scanning direction while detecting the amount of light emitted from the linear region along the main scanning direction on the document table for each pixel. An image scanning unit capable of executing an image reading process for sequentially outputting an image data sequence corresponding to a detected light amount for each pixel in a pixel region,
Performing a first light emission control for setting each of the light emitting units to a first state in which light is emitted with a predetermined reference light amount for each color;
By causing the image scanning unit to scan a part of the scanning range in the sub-scanning direction when the light emitting unit is in the first state, sample data including the image data string of at least one linear region is obtained. Executing a first scanning control to be output to the image scanning unit;
Depending on whether or not the sample data satisfies a predetermined condition, the second state of the light emitting unit is selected from either a light-off state or a light-enhanced state that emits light with a larger light quantity than the first state Executing a selection process;
Each of the light emitting units is caused to emit light one by one with the reference light amount in order, and the state of each of the light emitting units is changed between the first state and the sample for each reference period in which light emission with the reference light amount makes a round for all light emission colors. Executing second light emission control to switch to the second state selected based on the data;
The image reading process of outputting a first image data sequence corresponding to the first state of the light emitting unit and a second image data sequence corresponding to the second state of the light emitting unit for each switching cycle of the light emitting unit. Performing a second scanning control to be performed by the image scanning unit ;
For each of the reference period, is obtained for each emission color by comparing the first image data stream and the second image data sequence, the pixels corresponding to each other in the first image data stream and the second image data train Performing a provisional area dividing process for executing, for each of the emission colors, a process of dividing each pixel into a document area pixel and a document outside area pixel according to a difference in data;
For each reference period, the pixels that have been divided into the document area pixels for at least one of the emission colors by the temporary area classification process are classified into the document area pixels, and the other pixels are classified into the outside document area pixels. And a step of executing main area segmentation processing.

Images