JP6369371B2 - 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.

  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 light emitting unit, an image scanning unit, a light emission control unit, a scanning control unit, a state selection unit, a region sorting unit, and a background replacement unit. The light emitting unit emits light 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 light emission control unit alternately switches the state of the light emitting unit between a first state in which light is emitted with a predetermined reference light amount and a second state different from the first state. The scanning control unit causes the image scanning unit to execute the image reading process in parallel with the alternate switching of the state of the light emitting unit. The state selection unit includes a first image data sequence that is the image data sequence corresponding to the first state of the light emitting unit when the state switching of the light emitting unit is alternately performed and the image reading process is performed. Each time it is obtained, the second state next to the light emitting unit emits light with a light quantity larger than that in the unlit state and the first state, depending on whether or not the first image data string satisfies a predetermined condition. Select one of the brightening states. The region dividing unit compares a pair of the image data sequences obtained for each switching period of the state of the light emitting unit, and second image data corresponding to the first image data sequence and the second state of the light emitting unit. Each pixel is divided into a document area pixel and a document outside area pixel according to a difference in data of the pixels corresponding to each other in a column. The background replacement unit replaces each of the data of the pixels divided into the non-document area pixels in each of the first image data strings with one background data.

  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 alternately switching the state of the light emitting unit between a first state in which light is emitted with a predetermined reference light amount and a second state different from the first state. The second step is a step of causing the image scanning unit to execute the image reading process in parallel with the alternate switching of the state of the light emitting unit. The third step obtains a first image data string that is the image data string corresponding to the first state of the light emitting unit when the switching of the state of the light emitting unit and the image reading process are performed. Each time the first image data string is lighted, the second state next to the light-emitting unit emits light with a light quantity larger than that of the light-off state and the first state, depending on whether or not a predetermined condition is satisfied. This is a step of selecting which state to use. The fourth step compares a pair of the image data sequences obtained for each switching period of the state of the light emitting unit, and a second image data sequence corresponding to the first image data sequence and the second state of the light emitting unit. In this step, each pixel is divided into a document area pixel and a document outside area pixel according to a difference in data of the pixels corresponding to each other. The fifth step is a step of replacing each of the pixel data divided into the outside-document region pixels in each of the first image data strings with one background 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 block diagram of an image processing related device provided in the image reading apparatus according to the first embodiment. FIG. 3 is a flowchart illustrating an example of a procedure of image reading processing 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 second embodiment. FIG. 5 is a diagram illustrating an example of a document. FIG. 6 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. 7 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. 8 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. 9 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 document whose background is light. FIG. 10 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, a first embodiment which is a reference example of the present invention and a second embodiment which is an example of the present invention will be described with reference to the accompanying drawings. In addition, the following embodiment 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. An ADF (Auto Document Feeder) 120 is incorporated in the document table cover 12.

  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 a light emitting unit 112, a scanning mechanism 111, an optical system 113 such as a mirror and a lens, an image sensor 114, 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.

  The light emitting unit 112 is a light source that irradiates light toward the document 90 placed on the transparent document table 13. The light emitting unit 112 irradiates the document 90 with the strip-shaped light along the main scanning direction R <b> 1 through 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. It is also conceivable that the light emitting unit 112 is a straight tubular fluorescent lamp along the main scanning direction R1.

  The optical system 113 includes a mirror and a lens for guiding emitted light from a linear region on the document table 13 along the main scanning direction R1 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 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. It is a sensor that outputs. For example, the image sensor 114 may be a CCD (Charge Coupled Device) 114.

  The image sensor 114 outputs an image data string corresponding to the detected light amount for each pixel in the linear region. The image data string includes data of a plurality of pixels that are partitioned regions in the main scanning direction R1 in the linear region.

  The scanning mechanism 111 is a mechanism that supports a part of the light emitting unit 112 and the optical system 113 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 a part of the optical system 113 that guides light from the light emitting unit 112 and the linear region to the image sensor 114 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.

  Note that a contact image sensor (CIS) in which the light emitting unit 112, the image sensor 114, and the lens are integrated may be employed in the image scanning unit 11. In this case, the contact image sensor is supported by the scanning mechanism 111 so as to be movable along the sub-scanning direction R2.

  The ADF 120 conveys the document 90 set on the document tray 121 to the document discharge tray 123 via the image reading position by a plurality of rotating conveyance rollers 122. At that time, the image scanning unit 11 reads the image of the document 90 in a state where the scanning mechanism 111 is stopped at the image reading position.

  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.

  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 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. 2, 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 the MPU 81 executing various programs Pr1 to Pr4 stored in the storage unit 82 in advance.

  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 switches the light emitting state of the light emitting unit 112 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. 9 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 applied to the original 90 having a light background such as white. FIG. 10 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 a document whose background is a dark color such as black.

  In the graphs shown in FIGS. 9 and 10, 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.

  9 and 10, 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 where the light emitting unit 112 emits light with a reference light amount, and a broken line graph g1 is a state where the light emitting unit 112 is off. 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.

  9 and 10, 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. 9, 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. 10, 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 so that the light emitting unit 112 and a part of the optical system 113 that guides the light from the linear region to the image sensor 114 in the sub-scanning direction R2. Move to the target position in the scanning range. 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.

  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, 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 partial range scanning mode. Subsequently, when the image scanning unit 11 operates in the full range scanning mode, the light emission control unit 84 switches the light emitting unit 112 alternately between the reference state and the comparison state at a predetermined cycle. The comparison state is a state in which the light emission control unit 84 selects between the extinguishing state and the brightening state by executing 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 derivation unit 851, a subtraction unit 852, an area determination 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).

  The representative value deriving unit 851 executes a calculation for deriving a representative value of the sample data 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.

  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.

  Further, the subtracting unit 852, when the state of the light emitting unit 112 is alternately switched between the reference state and the comparison state, the difference ΔB between the pair of image data sequences obtained for each switching period of the state of the light emitting unit 112. Is calculated.

  More specifically, the subtracting unit 852 compares the pair of image data sequences obtained for each state switching cycle of the light emitting unit 112, and compares the first image data sequence and the light emission corresponding to the reference state of the light emitting unit 112. A difference ΔB between pixel data corresponding to each other in the second image data sequence corresponding to the comparison state of the unit 112 is calculated.

  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.

  The area determination unit 853 executes an area division process for dividing each pixel into the original area pixel and the outside-original area pixel based on the difference ΔB calculated by the subtractor 852.

  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.

  Accordingly, the area determination unit 853 determines that a pixel whose difference ΔB is smaller than a threshold light quantity difference, which is a predetermined light quantity difference, is an outside document area pixel, 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.

  The background replacement unit 854 executes background replacement processing for replacing each piece of pixel data divided into the non-document area pixels in each of the first image data strings corresponding to the reference state with one background data.

[Control Method of Image Reading Apparatus]
Next, 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 will be described with reference to the flowchart shown in FIG. In the following description, S101, S102,... 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. 3 when the MPU 81 outputs the operation mode signal Md indicating the open scanning mode.

<Steps S101 and S102>
In the image reading process when the operation mode is the open scanning mode, the first light emission control unit 841 that is a part of the light emission control unit 84 changes the state of the light emitting unit 112 to the reference state in which light is emitted with the reference light amount. (S101).

  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 (S102).

  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 light emitting unit 112 is in the reference state (S102). 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 (S102). The outputted sample data is temporarily stored in a line buffer (not shown) in the image processing unit 85.

  For example, in step S102, 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 S102 may be, for example, a range of one line from the starting point, or a range of several lines or more than a dozen lines from the starting point.

<Step S103>
Next, the representative value deriving unit 851 of the image processing unit 85 derives a representative value of the sample data (S103). 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.

<Step S104>
Further, the MPU 81 selects either the extinguished state or the brightened state as the comparison state of the light emitting unit 112 according to whether or not the sample data satisfies a predetermined condition (S104). 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 S105>
In parallel with steps S103 and S104, the first scanning control unit 831 returns the scanning mechanism 111 to a state of scanning at the starting point (S105).

<Steps S106 and S107>
After the steps S103 to S105, the second light emission control unit 842, which is a part of the light emission control unit 84, alternately switches the state of the light emitting unit 112 between the reference state and the comparison state selected in step S104 ( S106).

  Further, in parallel with the alternate 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 (S107). 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 and the second image data corresponding to the comparison state of the light emitting unit 112. The columns are output alternately (S107).

  Then, every time the state of the light emitting unit 112 is switched, that is, every time one first image data sequence and one second image data sequence are obtained, the image processing unit 85 performs the following steps: The processing of S108 to S111 is executed.

<Step S108>
First, the subtraction 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 state switching cycle of the light emitting unit 112 (S108).

<Step S109>
Next, the area determination unit 853 of the image processing unit 85 executes the area division process of dividing each pixel into the original area pixel and the outside original area pixel based on the difference ΔB calculated by the subtraction part 852. (S109). As described above, the area determination unit 853 classifies pixels that have a difference ΔB smaller than the predetermined threshold light amount difference as the outside-area area pixels, and classifies other pixels as the area area pixels. To do.

  In step S109, the threshold light amount difference when the comparison state is the extinguishing state is different from the threshold light amount difference when the comparison state is the brightening state. In general, the threshold light amount difference corresponding to the extinguishing state is larger than the threshold light amount difference corresponding to the brightening state.

<Step S110>
Further, the MPU 81 obtains the result of segmentation of the document area pixel from the area determination unit 853, and outputs the image from the length from one end to the other end of the area segmented in the document area pixel in the main scanning direction R1. A suitable size of the recording sheet 9 is specified (S110). Step S110 is executed only once at the first stage of scanning in the sub-scanning direction R2.

  For example, step S110 is executed only once for the pair of image data strings obtained first by scanning from the starting point in the sub-scanning direction R2. It is also conceivable that step S110 is executed only once based on the result of the region segmentation processing a plurality of times. In this case, a data buffer for temporarily storing a plurality of the image data strings before outputting them to the laser controller 86 is necessary.

  The MPU 81 executes the process of step S110 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.

<Step S111>
Further, the background replacement unit 854 of the image processing unit 85 replaces each piece of pixel data divided into the outside-document area pixels in each of the first image data strings obtained in step S107 with one background data (S111). ).

  The background data may be data corresponding to a predetermined 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 S112>
In addition, for each switching period of the state of the light emitting unit 112, the second scanning control unit 832 of the scanning control unit 83 determines whether scanning of the entire scanning range in the sub-scanning direction R2 is completed (S112). Then, the second light emission control unit 842, the second scanning control unit 832, and the image processing unit 85 repeat the processes of steps S106 to S109 and S111 until the scanning of the entire scanning range is completed.

  When the second scanning control unit 832 determines that the scanning of the entire scanning range in the sub-scanning direction R2 is finished, the image reading process by the control unit 8 is finished.

  When the image reading apparatus 1 is an apparatus capable of reading a color image, the image scanning unit 11 includes a plurality of image sensors 114 that detect different colors of light. In this case, it is conceivable that the image processing unit 85 performs the processes of steps S103 and S108 to S110 on the image data sequence obtained by the image sensor 114 having a predetermined color.

  It is also conceivable that the image processing unit 85 performs the processes of steps S103 and S108 to S110 on data obtained by averaging a plurality of the image data sequences obtained by the plurality of image sensors 114. However, the background replacement process is executed for each image data sequence corresponding to each of the plurality of image sensors 114.

  Further, when the image reading apparatus 1 is an apparatus capable of reading a color image, it is conceivable that the image forming apparatus 2 includes 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 to alternately switch the state of the light emitting unit 112 between the reference state and the comparison state (S106). Further, the second scanning control unit 832 causes the image scanning unit 11 to execute the image reading process in parallel with the alternate switching of the state of the light emitting unit 112 (S107).

  Further, the subtraction unit 852 compares a pair of the image data sequences obtained for each state switching period of the light emitting unit 112, and the first image data sequence corresponding to the reference state and the first corresponding to the comparison state. A difference ΔB between the pixel data corresponding to each other in the two image data sequences is calculated. Then, the area determination unit 853 classifies each of the pixels into the document area pixel and the outside document area pixel according to the magnitude of the difference ΔB. Note that the subtraction unit 852 and the region determination unit 853 are examples of the region sorting unit.

  More specifically, the region determination unit 853 corresponds to the difference ΔB that satisfies the difference condition when a predetermined difference condition including a condition that the difference ΔB is larger than a preset threshold value is satisfied. A pixel is divided into the original area pixels, and if not, a pixel corresponding to the difference ΔB is divided into the original area pixels.

  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 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. 9, 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. 9, 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. 4 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, 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 S201>
In the image reading process when the operation mode is the open scanning mode, first, the MPU 81 selects the initial state of the comparison state of the light emitting unit 112 (S201). For example, the MPU 81 selects a predetermined one of the extinguishing state and the brightening state as the initial state of the comparison state.

  Further, in step S201, the MPU 81 may select the initial state of the comparison state based on the first image data sequence as in step S104. In this case, the MPU 81 determines whether the representative value of the first image data sequence obtained at the starting point in the sub-scanning direction R2 satisfies a predetermined condition when the light emitting unit 112 is in the reference state. To select an initial state of the comparison state.

  When the MPU 81 selects the initial state of the comparison state based on the first image data string, in step S201, the first light emission control unit 841 sets the light emission unit 112 to the reference state, and the first scan control unit 831 performs image processing. The scanning unit 11 is caused to scan the linear region for one row of the starting point in the scanning range in the sub-scanning direction R2. The first image data string obtained in this way is an example of the sample data.

  The MPU 81 executes the process of step S201 by executing the state selection program Pr2.

<Steps S202 to S205>
After step S201 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 (S202, S204).

  Further, in parallel with the alternate 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 (S203, S205). That is, the second scanning control unit 832 sequentially advances the scanning position in the sub-scanning direction R2. Furthermore, the second scanning control unit 832 alternately performs the image scanning in the reference state (S203) and the image scanning in the comparison state (S205) to the image scanning unit 11 in synchronization with the switching of the state of the light emitting unit 112. Let it run.

  Under the control of steps S <b> 203 and 205, 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 alternately.

<Steps S206 and S207>
In addition, when the switching of the state of the light emitting unit 112 (S202, S204) and the image reading process (S203, S205) are performed, the representative value deriving unit 851 is obtained every time the first image data string is obtained. Then, the MPU 81 performs processing for selecting the next comparison state of the light emitting unit 112 (S206, S207). 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 S103 and S104.

  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 S203 (S206). The first image data string obtained in step S203 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.

  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 first image data string obtained in step S203 satisfies a predetermined condition. Is selected (S207). 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 S203 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 unit 112 is switched, that is, every time one first image data sequence and one second image data sequence are obtained, the image processing unit 85 performs steps S108 to S108 described above. Similarly to S111, the processes of steps S208 to S211 shown below are executed.

<Step S208>
First, the subtraction 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 state switching cycle of the light emitting unit 112 (S208). This step S208 is the same as step S108 described above.

<Step S209>
Next, the area determination unit 853 of the image processing unit 85 executes the area division process of dividing each pixel into the original area pixel and the outside original area pixel based on the difference ΔB calculated by the subtraction part 852. (S209). This step S209 is the same as the above-described step S109.

  That is, in step S208, the subtraction unit 852 compares the pair of image data sequences obtained for each state switching cycle of the light emitting unit 112. Further, in step S209, the region determination unit 853 classifies each of the pixels into the document region pixel and the document outside region pixel according to the magnitude of the difference ΔB. Note that the subtraction unit 852 and the region determination unit 853 are examples of the region sorting unit.

<Step S210>
Further, the area determination unit 853 of the image processing unit 85 specifies the size of the recording sheet 9 suitable for image output from the length from one end to the other end of the area divided into the document area pixels in the main scanning direction R1. (S210). Step S210 is executed only once in the first stage of scanning in the sub-scanning direction R2. This step S210 is the same as the above-described step S210.

<Step S211>
Further, the background replacement unit 854 of the image processing unit 85 replaces each of the pixel data divided into the outside-document region pixels in each of the first image data strings obtained in step S203 with one background data ( S211).

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

<Step S212>
In addition, for each switching period of the state of the light emitting unit 112, the second scanning control unit 832 of the scanning control unit 83 determines whether scanning of the entire scanning range in the sub-scanning direction R2 is completed (S212). Then, the second light emission control unit 842, the second scanning control unit 832, and the image processing unit 85 repeat the processes of steps S202 to S209 and S211 until the scanning of the entire scanning range is completed.

When the second scanning control unit 832 determines that the scanning of the entire scanning range in the sub-scanning direction R2 is finished, the image reading process by the control unit 8 is finished.
In the second embodiment described above, the second light emission control unit 842 alternately switches the state of the light emitting unit 112 between the reference state in which light is emitted with the reference light amount and the comparison state different from the reference state (SS202, S204). . Further, the second scanning control unit 832 causes the image scanning unit 11 to execute the image reading process in parallel with the alternate switching of the state of the light emitting unit 112 (S203 and 205).

  Further, the MPU 81 that executes the state selection program Pr2 when the state switching of the light emitting unit 112 and the image reading process are being performed, the first image data is obtained each time the first image data string is obtained. Depending on whether or not the column satisfies a predetermined condition, the next comparison state of the light emitting unit 112 is selected to be either the extinguishing state or the brightening state (S207).

  Further, the subtracting unit 852 compares the pair of image data sequences obtained for each switching period of the state of the light emitting unit 112, and corresponds to each other in the first image data sequence and the second image data sequence corresponding thereto. A difference ΔB between the pixel data is calculated (S208). Further, the area determination unit 853 classifies each pixel into the original area pixel and the non-original area pixel according to the calculated difference ΔB (S209). Note that the subtraction unit 852 and the region determination unit 853 are examples of the region sorting unit.

  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. 5 is a diagram illustrating an example of the document 90. 6 to 8 are synthesized from the first image data sequence obtained when the document 90 on the document table 13 is scanned in the open scanning mode with the document table cover 12 opened in the image processing apparatus 10. A two-dimensional image obtained is shown.

  FIG. 6 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. 7 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 extinguished state. FIG. 8 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 in which two originals 90 shown in FIG. 5 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. 5 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. 6, 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. 6, the image of the outside area of the document includes a noise image Ng including an image of outside light and a shadow image of an object that blocks outside light.

  On the other hand, as shown in FIG. 7, 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. As shown in FIGS. 6 and 7, 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 extinguished 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. 8, 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.

  Even when the brightening state is selected as the comparison state of the light emitting unit 112, as shown in FIG. 8, the document area and the document outside area are correctly divided.

[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 30: Sheet storage unit 31: Sheet delivery unit roller 32: Sheet conveying 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 111: Scan mechanism 112: Light emission unit 113 : Optical system 114: Image sensor 121: Document tray 122: Transport roller 123: Document discharge tray 300: Sheet transport path 801: Document sensor 802: Cover sensor 831: First scan control unit 832: Second scan control unit 841: First 1 light emission control unit 842: second light emission control unit 851: representative value derivation unit 852: subtraction unit 853: area determination unit 854: background replacement unit 900: aperture Md: operation mode signal Ng: noise image Pr1: operation mode setting program Pr2 : Status selection program Pr3: Background data setting program P 4: sheet size specifying program R1: main scanning direction R2: the sub-scanning direction

Claims (6)

A light emitting unit that emits light 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 light emission control unit that alternately switches the state of the light emitting unit between a first state that emits light with a predetermined reference light amount and a second state that is different from the first state;
A scanning control unit for causing the image scanning unit to execute the image reading processing corresponding to the first state and the second state of the light emitting unit in synchronization with the switching of the state of the light emitting unit ;
Each time the first image data sequence that is the image data sequence corresponding to the first state of the light emitting unit is obtained when the state switching of the light emitting unit and the image reading process are being performed, Depending on whether or not the first image data string satisfies a predetermined condition, the second state next to the light-emitting unit is set to either a light-off state or a light-intensifying state in which light is emitted with a larger amount of light than the first state. A state selection section for selecting
In every cycle switching of the state of the light emitting portion, comparing the second image data string corresponding to the second state of the first image data stream and the light emitting portion, wherein the first image data stream and the second image data An area dividing unit that divides each of the pixels into a document area pixel and a document outside area pixel according to a difference in data of the pixels corresponding to each other in a column;
An image reading unit comprising: a background replacement unit that replaces each of the pixel data divided into the outside-document area pixels in each of the first image data strings with one background data for each state switching cycle of the light emitting unit. apparatus. The state selection unit selects the brightening state as the second state when the representative value of the first image data sequence is a value indicating a light amount smaller than a predetermined threshold light amount, and when not, The image reading apparatus according to claim 1, wherein the off state is selected as the second state.   The image reading apparatus according to claim 2, wherein the representative value of the first image data sequence is a class value having the highest frequency in the frequency distribution of the first image data sequence.   In the region segmentation unit, the difference between the pixel data corresponding to each other in the first image data sequence and the second image data sequence is predetermined in advance in the main scanning direction. 4. The method according to claim 1, wherein each of the pixels in a region showing a difference larger than a light amount difference is divided into the document region pixels, and each of the other pixels is divided into the outside document region pixels. 5. The image reading apparatus described. An image reading apparatus according to any one of claims 1 to 4,
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 light emitting unit that emits light 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 region,
A step of alternately switching the state of the light emitting unit between a first state in which light is emitted with a predetermined reference light amount and a second state different from the first state;
Causing the image scanning unit to execute the image reading process in parallel with the alternate switching of the state of the light emitting unit;
Each time the first image data sequence that is the image data sequence corresponding to the first state of the light emitting unit is obtained when the state switching of the light emitting unit and the image reading process are being performed, Depending on whether or not the first image data string satisfies a predetermined condition, the second state next to the light-emitting unit is set to either a light-off state or a light-intensifying state in which light is emitted with a larger amount of light than the first state. A process of selecting
In every cycle switching of the state of the light emitting portion, comparing the second image data string corresponding to the second state of the first image data stream and the light emitting portion, wherein the first image data stream and the second image data Separating each of the pixels into a document area pixel and a document outside area pixel according to a difference in data of the pixels corresponding to each other in a column;
A step of replacing each pixel data segmented into the non-document area pixels in each of the first image data strings with one background data for each switching period of the state of the light emitting unit. Control method.

Images