JP6111897B2 - Image reading device - Google Patents

Description

  The present invention relates to a technique for conveying an original sheet and reading an image on the original sheet while passing a reading position of an image reading unit.

  There is a type of image reading apparatus that conveys an original sheet and reads an image on the original sheet while passing through a reading area of an image reading unit. In this type of image reading apparatus, it is determined whether or not the leading edge or the trailing edge of the document sheet in the transport direction has reached the reading area, and the determination result is used to determine, for example, the reading timing of the image reading unit or the read image. Some of them are used to determine the image size of the original document.

  An image reading apparatus as an example includes a document pressing plate disposed opposite to an image reading unit, and an identification image such as a pattern whose color is switched along the main scanning direction, a barcode, or a specific pattern on the document pressing plate. Is drawn. Then, the image reading apparatus determines whether or not the image data read in the predetermined reading area by the image reading section is the identification image data, so that the leading edge or the trailing edge of the document sheet reaches the reading area. It is determined whether or not (Patent Document 1).

JP 2004-120425 A

  By the way, in the conventional image reading apparatus, when dust or the like adheres to a facing member such as a document pressing plate, it is erroneously determined whether or not the image data read by the image reading unit is identification image data. It cannot be accurately determined whether or not the leading edge or trailing edge of the document sheet has reached the reading position, which is the position of the reading area on the conveyance path.

  For example, let us consider a case where dust such as paper dust adheres to the opposing member and the trailing edge of the original sheet is determined based on identification image data including the paper dust. In this case, if the amount of paper dust or the like adhering to the opposing member fluctuates during conveyance of the document sheet, the image data read after the trailing edge of the document sheet reaches the reading position does not match the identification image data, and the document It cannot be determined that the trailing edge of the sheet has reached the reading position. As a result, the reading of the image reading unit cannot be completed when the trailing edge of the document sheet reaches the reading position, and the image data is output even though the document sheet has actually been read. There was a problem that could not be done.

  The present specification discloses a technique for outputting an image of a document sheet while suppressing the influence of dust or the like attached to a facing member.

  An image reading device disclosed in this specification includes a conveyance unit that conveys a document sheet along a conveyance path, an image reading unit that reads an image at a reading position on the conveyance path, a storage unit, a control unit, The controller is configured to cause the image reading unit to start reading an image before the conveyance unit reaches the reading position of the original sheet, and sequentially acquires read image data; and Edge detection processing for detecting edge pixels from each read image data acquired in the image acquisition processing, and edge pixel number storage processing for sequentially storing the number of edge pixels detected in the edge detection processing in the storage unit A density acquisition process for acquiring an image density from each of the read image data acquired by the image acquisition process, and before the density acquisition process between the read image data. When the image density changes, there is no change in the image density in the sheet edge determination process for determining the position on the read image of the read image data that has changed as the edge of the original sheet, and the sheet edge determination process. The area on the read image based on the position on the read image of the read image data in which the number of edge pixels stored in the edge pixel number storage process exceeds the threshold among the read image data And a trimming process for extracting and outputting.

  In this image reading apparatus, the edge of the original sheet is determined using the image density, and if the end of the original sheet cannot be determined, the area on the read image is determined using the number of edge pixels stored in the storage unit. Extract and output. For this reason, even when the edge of the original sheet cannot be determined using the image density, and the region on the read image obtained by reading the original sheet cannot be extracted, the number of edge pixels corresponding to the end position of the original sheet has a threshold value. By extracting the area on the read image based on the position exceeding the position, the area including the read image data obtained by reading the original sheet can be extracted and output.

  The above-described image reading apparatus further includes a facing member disposed to face the image reading unit with the conveyance path interposed therebetween, and the storage unit reads the facing member when the image reading unit reads the facing member. A reference value serving as a reference for the read image data is stored, and the control unit is a case where the image density acquired by causing the image reading unit to read the counter member is different from the reference value, and the sheet The trimming process may be executed when there is no change in the image density in the edge determination process.

  In this image reading apparatus, in order to determine whether dust or the like is attached to the opposing member, the value of the read image data obtained by reading the opposing member is compared with a reference value. When the value of the read image data is different from the reference value, there is a high probability that dust or the like is attached to the facing member, and therefore the trimming process is executed when the image density satisfies a predetermined condition. As a result, even if the edge of the original sheet cannot be determined using the image density due to the movement of dust attached to the facing member and the area on the read image cannot be extracted, the number of edge pixels on the read image is used. An area can be extracted and output.

  In the image reading apparatus, in the trimming process, among the read image data in which the number of edge pixels exceeds the threshold value, the read image data first acquired in the image reading process is on the read image. A position may be detected as the leading edge position of the document sheet, and the region may be extracted from the read image data acquired after the leading edge position and output.

  According to this image reading apparatus, when extracting the area of the read image data in the trimming process, the area of the read image data acquired after the leading edge position is extracted. Easy to include original sheet images.

  In the image reading apparatus, of the read image data acquired next to the tip edge position in the image reading process among the read image data in which the number of edge pixels exceeds the threshold value in the trimming process. The position on the read image may be detected as the trailing edge position of the document sheet, and the read image data acquired from the leading edge position to the trailing edge position may be extracted and output as the area. good.

  According to this image reading apparatus, when extracting the area of the read image data in the trimming process, only the area of the read image data obtained by reading the original sheet can be extracted.

  In the image reading apparatus, the conveying unit continuously conveys a plurality of document sheets, and a leading edge threshold for detecting the leading edge position and a trailing edge for detecting the trailing edge position. The threshold may be set to a different value.

  When a document sheet is continuously conveyed, the leading edge position of the next document sheet may exist in the vicinity of the trailing edge position of the target document sheet, and the read image in which the number of edge pixels exceeds the threshold value Even when the position of the data is detected, it may be impossible to distinguish whether it is the trailing edge position of the target document sheet or the leading edge position of the document sheet next to the target document sheet. In this image reading apparatus, since the leading edge threshold value and the trailing edge threshold value are set to different values, the leading edge edge position and the trailing edge edge position can be distinguished and detected based on the threshold value used.

  In the image reading apparatus, the image reading unit includes a light source that emits light obliquely downstream along the conveyance path, and a light receiving unit, and the leading edge threshold is larger than the trailing edge threshold. It is good also as a structure set to the value.

  When the light source emits light obliquely downstream, shadows are less likely to occur at the trailing edge of the document sheet than the leading edge of the document sheet, and the number of detected edge pixels is small. In this image reading apparatus, the trailing edge threshold value for detecting the trailing edge position of the document sheet is set to a value smaller than the leading edge threshold value for detecting the leading edge position of the document sheet. It can be detected with high accuracy.

  In the image reading apparatus, in the trimming process, the leading edge threshold is used to detect the leading edge position, and then the position of the read image data in which the number of edge pixels exceeds the leading edge threshold is set as a boundary position. The trailing edge position may be detected using the trailing edge threshold between the leading edge position and the boundary position.

  In this image reading apparatus, the leading edge threshold is used to detect the leading edge position from the first conveyed document sheet, the boundary position is detected from the next conveyed document sheet, and the trailing edge position is determined as the leading edge edge. Detect between the position and the boundary position. Therefore, the time required to detect the trailing edge position compared to the case where the trailing edge position is detected using all of the read image data acquired after the leading edge position without determining the boundary position. Can be shortened.

  In the image reading apparatus, the control unit may further perform a jam determination process for determining that the original sheet is jammed when the boundary position is not detected in the trimming process.

  According to this image reading apparatus, when a document sheet is continuously conveyed, it is possible to determine whether the document sheet is jammed when the next conveyed document sheet cannot be detected.

  In the image reading apparatus disclosed in this specification, it is possible to output an image of an original sheet while suppressing the influence of dust or the like adhering to the facing member.

Schematic sectional view of an image reading device Block diagram schematically showing the electrical configuration of the image reading apparatus Flow chart showing image reading process Flow chart showing image reading process Flow chart showing image reading process Flow chart showing trimming process Flow chart showing trimming process A graph showing the time change of the number of edge pixels of the read image data Graph showing the histogram of scanned image data

<Embodiment>
One embodiment will be described with reference to FIGS.

1. As shown in FIG. 1, the image reading apparatus 1 transports a plurality of document sheets G placed on a paper feed tray 2 to a paper discharge tray 4 by a user, This is a sheet feed scanner that reads an original sheet G using an image reading unit 30 included in the main body unit 3.

  The main body 3 of the image reading apparatus 1 is provided with a conveyance path 48 that connects the paper feed tray 2 and the paper discharge tray 4. A paper feed roller 40, a separation pad 42, and the periphery of the conveyance path 48 are provided. , A conveyance roller 44, a document pressing member 46, an image reading unit 30, a paper discharge roller 50, and a front sensor (hereinafter referred to as F sensor) 13.

  The paper feed roller 40 is rotationally driven by a drive motor M (see FIG. 2). The paper feed roller 40 abuts on the original sheet G placed on the paper feed tray 2 and draws the original sheet G placed on the paper feed tray 2 into the main body 3 by a frictional force. At this time, the document sheet G is separated for each document sheet G by the frictional force of the separation pad 42 and sent out to the conveyance path 48.

  The conveyance roller 44 is driven to rotate by the drive motor M, and continuously conveys the plurality of document sheets G drawn into the main body 3 by the paper feed roller 40 along the conveyance path 48.

  The image reading unit 30 is arranged at the reading position P1 on the conveyance path 48 and reads one surface of the original sheet G conveyed in the conveyance direction D2 along the conveyance path 48 at the reading position P1. A document pressing member 46 that presses the document sheet G on the conveyance path 48 toward the image reading unit 30 is disposed at a position facing the image reading unit 30 across the conveyance path 48 at the reading position P1. The document pressing member 46 has a facing surface 46 </ b> A facing the image reading unit 30 that is, for example, white, and its reflectance is higher than the reflectance of the white document sheet G. The image reading unit 30 also reads the facing surface 46A of the document pressing member 46 at the reading position P1. The document pressing member 46 is an example of a facing member.

  As shown in FIG. 1, the image reading unit 30 includes a light source 32 and a light receiving unit 34. The light source 32 includes a plurality of light emitting diodes (hereinafter referred to as LEDs) arranged in the main scanning direction D1 orthogonal to the transport direction D2. In the light source 32, a blue LED 32B that emits blue light, a green LED 32G that emits green light, and a red LED 32R that emits red light are arranged at positions shifted from each other from the upstream side in the transport direction D2. The light source 32 emits light emitted from the LEDs 32B, 32G, and 32R obliquely from the upstream side to the downstream side of the transport path 48.

  The light receiving unit 34 includes a plurality of light receiving elements arranged linearly in the main scanning direction D1. The light receiving unit 34 receives the light emitted from the light source 32 and reflected by one surface of the document sheet G passing through the reading position P1 using each light receiving element. Further, the image reading unit 30 receives the light emitted from the light source 32 and reflected by the facing surface 46A of the document pressing member 46 using each light receiving element.

  The paper discharge roller 50 is disposed on the downstream side of the reading position P1 in the transport path 48. The paper discharge roller 50 is rotationally driven by the drive motor M in the same manner as the paper supply roller 40 and the conveyance roller 44, and sends the document sheet G conveyed on the conveyance path 48 to the paper discharge tray 4. In other words, the conveyance unit 15 conveys a plurality of document sheets G placed on the sheet feed tray 2 along the conveyance path 48 by the sheet feed roller 40, the conveyance roller 44, the sheet discharge roller 50, and the drive motor M (see FIG. 2) is formed.

  A protruding portion 52 that protrudes upward is provided on the conveyance path 48 side of the paper discharge tray 4, and the document sheet G sent to the paper discharge tray 4 warps upward on the conveyance path 48 side according to the protrusion 52. Go up. Therefore, when the document sheet G transported later along the transport path 48 is sent out to the paper discharge tray 4, the document sheet G transported first and the projecting portion 52, that is, the document transported first. It is sent out so as to sink into the lower side of the sheet G. As a result, a plurality of original sheets G placed in order from the bottom side with one side facing down in the paper feed tray 2 are in a state where one side faces up in the paper discharge tray 4. A so-called submerged paper discharge mechanism that is placed in order from the upper side is configured.

  The F sensor 13 is arranged on the paper feed tray 2 and is turned on when the document sheet G is placed on the paper feed tray 2, and is turned off when the document sheet G is not placed on the paper feed tray 2. . In addition, the image reading apparatus 1 includes an operation unit 11 that includes various setting buttons and receives various commands from a user, and a display unit 12 that includes an LED or a liquid crystal display and displays the status of the image reading apparatus 1. Yes. As shown in FIG. 1, the operation unit 11 and the display unit 12 may have different configurations, or may have a single configuration such as a touch panel.

2. Electrical Configuration of Image Reading Device As shown in FIG. 2, the image reading device 1 includes an ASIC (Application Specific Integrated Circuit) 29, a ROM 26, a RAM 27, and an NVRAM 28. The part 11 etc. are connected. As indicated by a solid line 21 in FIG. 2, an example including the ASIC 29, the ROM 26, the RAM 27, and the NVRAM 28 is an example of the control unit. Of these, the ROM 26, the RAM 27, and the NVRAM 28 are examples of the storage unit.

  The ASIC 29 includes a CPU 20 and dedicated hardware circuits such as the image processing circuit 23. Various programs for controlling the operation of the image reading apparatus 1 are stored in the ROM 26, and the CPU 20 controls each part in accordance with the program read from the ROM 26 and uses a hardware circuit as necessary later. A process such as an image reading process is executed. The NVRAM 28, which is a non-volatile memory, stores reference values such as the reference maximum number of pixels and reference peak luminance, threshold values such as a leading edge threshold and a trailing edge threshold, and a reference transport time. These values are values used in the image reading process, and details thereof will be described later.

  Based on a command from the CPU 20, the image reading unit 30 turns on the light sources 32 of the respective colors and reads the facing surface 46 </ b> A of the document pressing member 46 and the document sheet G. The image reading unit 30 reads one line in the main scanning direction D1 by one reading, and acquires read image data that is a collection of pixel data acquired by each light receiving element arranged in the main scanning direction D1. The read image data acquired by the image reading unit 30 is converted into read image data of a digital signal and stored in the RAM 27.

  The image processing circuit 23 performs edge detection processing such as binarization processing and enhancement processing on the read image data stored in the RAM 27, and extracts the number of edge pixels. In addition, the image processing circuit 23 performs density acquisition processing for generating a histogram that is a luminance distribution of each pixel data included in the read image data stored in the RAM 27, and the maximum number of pixels in the histogram and the maximum number of pixels are determined. Extract peak luminance. The maximum number of pixels and the peak luminance of the read image data are examples of image density.

3. Image Reading Process Next, the reading process of the original sheet G will be described with reference to FIGS. In the present embodiment, an example will be described in which a plurality of document sheets G are placed on the sheet feed tray 2 and the plurality of document sheets G are continuously conveyed and read. When an instruction for reading an image of the original sheet G is input from the user via the operation unit 11, the CPU 20 starts the following processing.

  As shown in FIG. 3, when the image reading process is started, the CPU 20 first changes the trimming mode for determining whether or not to perform a trimming process (S72) described later to an off mode indicating that the trimming process is not performed. Set (S2). Next, the CPU 20 instructs the image reading unit 30 to turn on the light sources 32 of the respective colors and instructs reading of one line (S4). Thus, the image reading unit 30 reads the facing surface 46A of the document pressing member 46 once during the lighting period of the light source 32 of each color, and the read image data corresponding to each color is stored in the RAM 27. In the following description, reading one line when the color type of the light source 32 is not designated means reading with the light source 32 of each color turned on.

  The CPU 20 performs edge detection processing on the read image data of each color stored in the RAM 27 in S4 using the image processing circuit 23, and calculates the number of edge pixels of each read image data (S6). Further, the CPU 20 performs density acquisition processing on the read image data of each color stored in the RAM 27 in S4 using the image processing circuit 23, and calculates the maximum number of pixels and peak luminance of each read image data (S8). ).

  The CPU 20 stores the number of edge pixels, the maximum number of pixels, and the peak luminance calculated in S6 and S8 in the RAM 27 as the number of reference edge pixels, the maximum number of reference pixels, and the reference peak luminance (S10). Further, the CPU 20 compares the maximum pixel number calculated in S8 with the reference maximum pixel number stored in the NVRAM 28, and compares the peak luminance calculated in S8 with the reference peak luminance stored in the NVRAM 28 (S12).

  Here, the reference maximum number of pixels and the reference peak luminance are the maximum number of pixels in the read image data acquired by reading the facing surface 46A of the document pressing member 46 at the time of shipment of the image reading apparatus 1 or at the start of use. Peak brightness. That is, the reference maximum number of pixels and the reference peak luminance are the maximum number of pixels acquired in the initial stage of use of the image reading apparatus 1 and in a state in which dust or the like is relatively little attached to the facing surface 46A of the document pressing member 46, Peak brightness.

  The CPU 20 matches the maximum number of pixels of all colors calculated in S8 and the reference maximum pixel number in the specified range, and the peak luminance of all colors calculated in S8 matches the reference peak luminance in the specified range. In the case (S12: YES), it is determined that the maximum number of pixels and the peak luminance calculated in S8 are not different from the reference maximum number of pixels and the reference peak luminance. In this case, since it is determined that a state in which dust or the like is attached to the facing surface 46A of the document pressing member 46 is relatively small, the CPU 20 maintains the trimming mode in the off mode.

  On the other hand, the CPU 20 determines that the maximum number of pixels of at least one color (for example, green) calculated in S8 and the reference maximum number of pixels do not match within the specified range, or at least one color (for example, green) calculated in S8. When the peak luminance and the reference peak luminance do not match within the specified range (S12: NO), it is determined that the maximum pixel number and the peak luminance calculated in S8 are different from the reference maximum pixel number and the reference peak luminance. In this case, since it is determined that the adhesion of dust or the like to the facing surface 46A of the document pressing member 46 has increased, the CPU 20 switches the trimming mode to an on mode indicating that the trimming process is executed (S14).

  Next, the CPU 20 detects whether or not the document sheet G is placed on the paper feed tray 2 using the F sensor 13 (S16). When it is detected that the original sheet G is placed on the paper feed tray 2 (S16: YES), the CPU 20 instructs the conveying unit 15 to convey the original sheet G, and conveys the original sheet G. In addition to starting (S18), the elapsed time T from the start of conveyance of the original sheet G is counted.

  Subsequently, the CPU 20 instructs the image reading unit 30 to turn on the green light source 32 and instructs one line to be read (S20). That is, the CPU 20 causes the image reading unit 30 to start reading before the leading end (hereinafter referred to as the leading end) of the document sheet G in the transport direction D2 reaches the reading position P1.

  The CPU 20 performs edge detection processing on the read image data stored in the RAM 27 in the immediately preceding S20, and calculates the number of edge pixels (S22). Hereinafter, when the read image data stored in the RAM 27 is described, the read image data means the read image data most recently stored in the RAM 27 in the designated process.

  Next, as shown in FIG. 4, the CPU 20 detects the setting of the trimming mode (S24). When the trimming mode is the on mode (S24: YES), the CPU 27 calculates the number of edge pixels calculated in the immediately preceding S22. (S26). Hereinafter, when the calculated values such as the number of edge pixels, the maximum number of pixels, and the peak luminance are described, the calculated values mean the calculated values calculated most recently in the designated process. On the other hand, when the trimming mode is the off mode (S24: NO), the process proceeds to S28 without storing the calculated number of edge pixels in the RAM 27.

  The CPU 20 compares the number of edge pixels calculated in S22 with the number of reference edge pixels stored in the RAM 27, and detects whether the difference between the number of edge pixels and the number of reference edge pixels is equal to or greater than a specified value (S28). . When the difference is smaller than the specified value (S28: NO), the CPU 20 further performs density acquisition processing on the read image data stored in the RAM 27 in S20, and calculates the maximum number of pixels and peak luminance (S30). ). Then, the CPU 20 compares the maximum number of pixels calculated in S30 with the reference maximum number of pixels stored in the RAM 27, and compares the peak luminance calculated in S30 with the reference peak luminance stored in the RAM 27 (S32).

  When the maximum number of pixels calculated in S30 and the reference maximum number of pixels match in a predetermined range, and the peak luminance calculated in S30 and the reference peak luminance match in a predetermined range (S32: YES) That is, when there is no change with respect to the maximum reference pixel number and the reference peak luminance corresponding to both the maximum pixel number and the peak luminance calculated in S30, the read image data stored in the RAM 27 in S20 is the document pressing unit. It is determined that the read image data is obtained by reading the facing surface 46A of the member 46. That is, the CPU 20 determines that the leading edge of the document sheet G has not reached the reading position P1.

  In this case, the CPU 20 detects an elapsed time T from the start of conveyance of the original sheet G (S34). The NVRAM 28 stores a first reference transport time that is longer than the time until the document sheet G is transported from the paper feed tray 2 to the reading position P1 based on the transport speed of the document sheet G. The time T is compared with the first reference transport time. When the elapsed time T is shorter than the first reference transport time (S34: NO), the CPU 20 repeats the processing from S20.

  On the other hand, when the elapsed time T is equal to or longer than the first reference transport time (S34: YES), it is highly possible that the original sheet G cannot pass through the transport path 48 and a jam has occurred. In this case, the CPU 20 instructs the transport unit 15 to stop transporting the original sheet G (S36), further instructs the display unit 12 to display the occurrence of a jam error (S38), and ends the image reading process. To do.

  On the other hand, when the difference between the number of edge pixels calculated in S22 and the number of reference edge pixels has changed to a predetermined value or more (S28: YES), the CPU 20 reads the read image data stored in the RAM 27 in S20 into the original sheet G It is determined that the read image data has been read. In addition, the maximum number of pixels calculated in S30 has changed beyond a predetermined range with respect to the maximum number of reference pixels, or the peak luminance calculated in S30 has changed beyond a predetermined range with respect to the reference peak luminance. In the case (S32: NO), that is, when at least one of the maximum pixel number and the peak luminance calculated in S30 changes with respect to the corresponding reference maximum pixel number and the reference peak luminance, it is similarly stored in the RAM 27 in S20. It is determined that the read image data thus read is switched to read image data obtained by reading the original sheet G.

  In these cases, the CPU 20 determines that the leading edge of the original sheet G has reached the reading position P1 at the elapsed time T when the read image data is read. The CPU 20 stores the elapsed time T when the read image data is read in the RAM 27 as the leading edge density change position, and instructs the image reading unit 30 to start reading the original sheet G (S40). The tip density change position is an example of a position on the read image of the read image data.

  When starting to read the original sheet G, the CPU 20 instructs the image reading unit 30 to read one line (S42), and calculates the number of edge pixels of the read image data stored in the RAM 27 in S42 (S44). ). The CPU 20 detects the setting of the trimming mode (S46). When the trimming mode is the on mode (S46: YES), the CPU 20 stores the number of edge pixels calculated in S44 in the RAM 27 (S48). On the other hand, when the trimming mode is the off mode (S46: NO), the process proceeds to S50 without storing the calculated number of edge pixels in the RAM 27.

  Next, as shown in FIG. 5, the CPU 20 compares the number of edge pixels calculated in S44 with the number of reference edge pixels stored in the RAM 27 (S50). The CPU 20 determines whether or not the difference between the number of edge pixels calculated in S44 and the number of reference edge pixels is equal to or greater than a specified value. If the difference is smaller than the specified value (S50: NO), the processing from S42 is performed. repeat.

  On the other hand, when the difference between the number of edge pixels calculated in S44 and the number of reference edge pixels has changed to a specified value or more (S50: YES), the CPU 20 further applies the read image data stored in the RAM 27 in S42. A density acquisition process is performed to calculate the maximum number of pixels and the peak luminance (S52). Then, the CPU 20 compares the maximum pixel number calculated in S52 with the reference maximum pixel number stored in the RAM 27, and compares the peak luminance calculated in S52 with the reference peak luminance stored in the RAM 27 (S54).

  The CPU 20 has changed so that the maximum pixel number calculated in S52 matches the reference maximum pixel number in a predetermined range, and the peak luminance calculated in S52 matches the reference peak luminance in a predetermined range. In the case (S54: YES), that is, when at least one of the maximum pixel number and peak luminance calculated in S52 changes with respect to the corresponding reference maximum pixel number and reference peak luminance, the read image stored in the RAM 27 in S42 It is determined that the data has been switched to read image data obtained by reading the original sheet G.

  In this case, the CPU 20 determines that the trailing edge (hereinafter, trailing edge) in the conveyance direction D2 of the document sheet G has reached the reading position P1 at the elapsed time T when the read image data is read. The CPU 20 stores the elapsed time T when the read image data is read in the RAM 27 as the trailing edge density change position, and instructs the image reading unit 30 to stop reading the document sheet G (S56). The rear end density change position is another example of the position of the read image data on the read image.

  When the reading of the original sheet G is stopped, the CPU 20 again determines whether or not the original sheet G is placed on the paper feed tray 2 using the F sensor 13 (S16). When the CPU 20 determines that the document sheet G is placed on the paper feed tray 2 (S16: YES), the processing from S18 is repeated.

  On the other hand, when the CPU 20 determines that the document sheet G is not placed on the paper feed tray 2 (S16: NO), the CPU 20 transports the last read document sheet G to the paper discharge tray 4 and then the transport unit 15. Is instructed to stop conveying the original sheet G, and the conveyance of the original sheet G is terminated (S58). The CPU 20 extracts the read image of the read image data read from the leading edge density change position to the trailing edge density change position from the read image data read so far. The CPU 20 stores the read image data corresponding to the extracted read image in the RAM 27 as read image data for output (S60), and ends the image reading process.

  On the other hand, the CPU 20 maintains a state in which the maximum number of pixels calculated in S52 has changed beyond a predetermined range with respect to the reference maximum number of pixels, or the peak luminance calculated in S52 becomes the reference peak luminance. On the other hand, when the state changed beyond the predetermined range is maintained (S54: NO), that is, the maximum number of pixels and the peak luminance calculated in S52 both correspond to the reference maximum pixel number and the reference peak luminance. If there is no change, it is determined that the read image data stored in the RAM 27 in S42 is read image data obtained by reading the document sheet G. That is, the CPU 20 determines that the trailing edge of the document sheet G has not reached the reading position P1.

  In this case, the CPU 20 detects an elapsed time T from the start of conveyance of the original sheet G (S62). The NVRAM 28 stores a second reference transport time until the document sheet G is transported from the paper feed tray 2 to the paper discharge tray 4 based on the transport speed of the document sheet G. The CPU 20 stores the elapsed time T Is compared with the second reference transport time. When the elapsed time T is shorter than the second reference transport time (S62: NO), the CPU 20 repeats the processing from S20.

  On the other hand, when the elapsed time T from the start of conveyance of the document sheet G is equal to or longer than the second reference conveyance time (S62: YES), there is a possibility that the document sheet G cannot pass through the conveyance path 48 and a jam has occurred. high. In this case, the CPU 20 instructs the image reading unit 30 to stop reading the original sheet G (S64) and instructs the conveying unit 15 to stop conveying the original sheet G (S66).

  Then, the CPU 20 detects the setting of the trimming mode (S68). When the trimming mode is the off mode (S68: NO), the CPU 20 instructs the display unit 12 to display the occurrence of a jam error (S70), and ends the image reading process. On the other hand, when the trimming mode is the on mode (S68: YES), the CPU 20 executes a trimming process (S72).

(Trimming process)
In the trimming process, the CPU 20 extracts an area on the read image stored in the RAM 27, that is, a range of the read image data stored in the RAM 27, from the read image data stored in the RAM 27 until the reading of the original sheet G is stopped.

  In the trimming process, the CPU 20 compares the plurality of edge pixel numbers stored in the RAM 27 in S26 and S48 with the threshold value stored in the NVRAM 28. The RAM 27 stores the number of edge pixels in association with the elapsed time T when the read image data used to calculate the number of edge pixels is read, and the change in the number of edge pixels with respect to the elapsed time T is shown in FIG. It is expressed as 8.

  In the trimming process, the CPU 20 selects one of the number of edge pixels stored in the RAM 27, compares the selected number of edge pixels with a threshold value, and sub-scans the selected number of edge pixels along the elapsed time T. The direction is switched, and the comparison between the selected number of edge pixels and the threshold value is repeated. Hereinafter, the position in the sub-scanning direction of the selected number of edge pixels, that is, the elapsed time T corresponding to the selected number of edge pixels is referred to as an edge scanning position.

  As shown in FIG. 6, in the trimming process, the CPU 20 first sets an image output mode indicating whether or not the range of the read image data is extracted in the trimming process, and indicates that the range of the read image data is not extracted. The off mode shown is set (S80).

  Next, the CPU 20 initializes the edge scanning position, and selects the number of edge pixels having the minimum elapsed time T corresponding to the number of edge pixels stored in the RAM 27 (S82: initialization position in FIG. 8). (See L0). The CPU 20 compares the selected number of edge pixels with the tip threshold value SS stored in the NVRAM 28 (S84). The leading edge threshold SS is a threshold for detecting the leading edge of the document sheet G.

  When the selected edge pixel number is equal to or less than the tip threshold SS (S84: NO), the CPU 20 further stores in the RAM 27 whether the edge scanning position is the final position LL, that is, the selected edge pixel number. It is determined whether the number of edge pixels corresponding to the elapsed time T is the maximum among the plurality of edge pixels (S86).

  If the edge scanning position is not the final position LL (S86: NO), the CPU 20 moves the edge scanning position in the sub-scanning direction (S88), and repeats the processing from S84. On the other hand, when the edge scanning position is the final position LL (S86: YES), the CPU 20 determines that the leading edge position where the number of edge pixels exceeds the leading edge threshold SS could not be detected. In this case, since the range in which the original sheet G is read from the read image data cannot be specified even using the number of edge pixels, the CPU 20 ends the trimming process while maintaining the image output mode in the off mode. .

  On the other hand, as shown in FIG. 8, when the selected number of edge pixels exceeds the leading edge threshold SS (S84: YES), the CPU 20 stores the edge scanning position corresponding to the edge pixel number in the RAM 27 as the leading edge position. Store (S90). Since the leading edge position stored in S90 is the leading edge position detected first after the trimming process is started, the first conveyed document sheet G among the continuously conveyed document sheets G. This corresponds to the position of the leading edge of the sheet G1. Therefore, hereinafter, the leading edge position stored in S90 is referred to as the leading edge position L1 of the first sheet.

  The CPU 20 further moves the edge scanning position in the sub-scanning direction (S92), and continues to detect the leading edge position using the leading edge threshold SS (S94). When the selected number of edge pixels is equal to or less than the tip threshold SS (S94: NO), the CPU 20 further determines whether the edge scanning position is the final position LL (S96).

  When the edge scanning position is not the final position LL (S96: NO), the CPU 20 repeats the processing from S92. On the other hand, when the edge scanning position is the final position LL (S96: YES), the CPU 20 determines that the position of the leading edge of the document sheet G conveyed to the second sheet cannot be detected.

  In this case, as shown in the middle of FIG. 8, the original sheet G1 conveyed in the first sheet is out of specification, the original sheet G1 extends in the conveying direction D2, and the original sheet conveyed in the first sheet. It is conceivable that the reading of G1 has not ended. That is, since the read image data of the entire area of the original sheet G1 conveyed to the first sheet is not stored in the RAM 27, the range of the read image data is not extracted and the image output mode is maintained in the off mode. Then, the trimming process is finished.

  On the other hand, as shown in the upper or lower part of FIG. 8, when the selected number of edge pixels exceeds the leading edge threshold SS (S94: YES), the CPU 20 determines the edge scanning position corresponding to the edge pixel number as the leading edge position. Is stored in the RAM 27 (S98). The leading edge position stored in S98 corresponds to the leading edge position of the original sheet G2 conveyed to the second sheet, and is hereinafter referred to as a leading edge position L2 of the second sheet. The leading edge position L2 of the second sheet is an example of a boundary position.

  In this case, since the read image data of the entire area of the original sheet G1 conveyed to the first sheet is stored in the RAM 27, the CPU 20 changes the image output mode to the read image data as shown in FIG. The mode is switched to the on mode indicating that the range is extracted (S100).

  The CPU 20 moves the edge scanning position to the leading edge position L1 of the first sheet (S102), and moves the edge scanning position in the sub-scanning direction (S104). Then, the CPU 20 compares the selected number of edge pixels with the rear end threshold value KS stored in the NVRAM 28 (S106). The trailing edge threshold value KS is a threshold value for detecting the trailing edge of the document sheet G. The rear end threshold value KS is set to a value smaller than the front end threshold value SS in correspondence with the structure in which the light source 32 of the image reading unit 30 emits light obliquely downstream.

  When the selected number of edge pixels is equal to or less than the rear end threshold value KS (S106: NO), the CPU 20 further moves the edge scanning position in the sub-scanning direction (S108), and the edge scanning position after the movement is 2 It is determined whether or not it is the leading edge position L2 of the sheet (S110).

  If the edge scanning position is not the leading edge position L2 of the second sheet (S110: NO), the CPU 20 repeats the processes from S106. On the other hand, when the edge scanning position is the leading edge position L2 of the second sheet (S110: YES), the CPU 20 determines that the position of the trailing edge of the original sheet G conveyed to the first sheet cannot be detected. To do.

  In this case, as shown in the lower part of FIG. 8, the RAM 27 stores the read image data of the entire area of the original sheet G1 conveyed to the first sheet, and the leading edge position L1 of the first sheet is detected. However, the position of the trailing edge of the original sheet G conveyed to the first sheet cannot be detected. Therefore, the CPU 20 extracts the read image of the read image data read from the leading edge position L1 to the final position LL of the first sheet (S112), and ends the trimming process.

  On the other hand, as shown in the upper part of FIG. 8, when the selected number of edge pixels exceeds the rear end threshold value KS (S106: YES), the CPU 20 determines the edge scanning position corresponding to the number of edge pixels as the rear end edge. The position is stored in the RAM 27 (S114). The trailing edge position stored in S114 is the trailing edge position detected first after the trimming process is started, and the leading edge position L1 of the first sheet and the leading edge position L2 of the second sheet Therefore, it corresponds to the position of the rear end of the document sheet G2 conveyed second, among the document sheets G continuously conveyed. Therefore, hereinafter, the rear edge position stored in S114 is referred to as the first rear edge position L3.

  In this case, the CPU 20 extracts the read image of the read image data read from the first leading edge position L1 to the first trailing edge position L3 (S116), and ends the trimming process.

  When the trimming process ends, the CPU 20 detects whether or not the image output mode is set to the on mode in the trimming process as shown in FIG. 5 (S74). When the image output mode is set to the off mode in the trimming process (S74: NO), the CPU 20 instructs the display unit 12 to display the occurrence of a jam error (S70), and ends the image reading process.

  On the other hand, when the image output mode is set to the on mode in the trimming process (S74: YES), the CPU 20 stores the read image data corresponding to the read image extracted in the trimming process in the RAM 27 (S76). The process ends.

4). Advantages of the present embodiment (1) In the image reading apparatus 1 of the present embodiment, when extracting a read image corresponding to the read image data stored in the RAM 27, first, the tip is used by using the maximum number of pixels, peak luminance, and the like. A density change position and a rear end density change position are detected and a read image is extracted. If the front end density change position and the rear end density change position are not detected, trimming processing is executed, and the front end edge position L1 or the rear end edge position L3 is detected using the number of edge pixels stored in the RAM 27. A read image is extracted. Therefore, conventionally, even when the leading edge density changing position and the trailing edge density changing position are not detected and the read image cannot be extracted, when the leading edge position L1 or the trailing edge position L3 is detected, these are detected. The read image can be extracted using the edge position L, and the read image data corresponding to the original sheet G can be stored in the RAM 27.

(2) In the image reading apparatus 1 of the present embodiment, as a condition for executing the trimming process, it is determined whether dust or the like is attached to the facing surface 46A of the document pressing member 46. When it is determined that a relatively large amount of dust or the like is attached to the facing surface 46A of the document pressing member 46, the number of edge pixels is stored in the RAM 27, and the leading edge density change position and trailing edge density change are stored. When the position is not detected, the trimming process is executed.

  As shown in FIG. 9, in the initial stage of use of the image reading apparatus 1, since the dust or the like adhering to the facing surface 46 </ b> A of the document pressing member 46 is relatively small, the facing surface 46 </ b> A of the document pressing member 46 is read. As shown in the upper diagram of FIG. 9, the generated histogram is a peak luminance corresponding to the reflectance of the facing surface 46A of the document pressing member 46, that is, a histogram concentrated on the standard peak luminance. The maximum number of pixels is almost the same. Therefore, when a predetermined range is set based on the maximum number of reference pixels and the like, the maximum pixel number calculated from the read image data obtained by reading the original sheet G (see the broken line in FIG. 9) and the reference maximum pixel number are within the predetermined range. There is no match. Accordingly, the read density can be extracted by detecting the front end density change position and the rear end density change position based on the reference maximum pixel number and the like.

  However, as indicated by an arrow 64, when the usage period of the image reading apparatus 1 is increased, dust or the like adhering to the facing surface 46A of the document pressing member 46 increases, and the reference maximum pixel number is increased due to the influence of dust or the like. As a result, the reference maximum pixel number and the reference maximum pixel number (see the two-dot chain line in FIG. 9) do not match within the specified range. As a result, as indicated by a mark 60 in the lower diagram of FIG. 9, depending on the pattern described on the original sheet G, the maximum number of pixels calculated from the read image data obtained by reading the original sheet G and the maximum number of reference pixels are predetermined. Anomalous events that match within range may occur. In this case, the front end density change position and the rear end density change position are detected based on the maximum number of reference pixels and the read image cannot be extracted.

  In the image reading apparatus 1, as described above, when the reference maximum pixel number and the reference maximum pixel number match within the specified range, that is, dust or the like adhering to the facing surface 46A of the document pressing member 46 increases. If it is determined that the number of edge pixels is stored in the RAM 27, the trimming process can be executed. As a result, even if the leading edge density changing position and the trailing edge density changing position are not detected due to the influence of dust adhering to the facing surface 46A of the document pressing member 46, the number of edge pixels stored in the RAM 27 is set. The leading edge position L1 or the trailing edge position L3 can be detected and the read image can be extracted.

(3) In the image reading apparatus 1 of this embodiment, in the trimming process, the leading edge threshold position SS is used to detect the leading edge position L1 of the first sheet, and then the leading edge position L2 of the second sheet is detected. By detecting the leading edge position L2 of the second sheet, it is determined that the read image data of the entire area of the first document sheet G1 is stored in the RAM 27. Therefore, the read image data including the read image of the entire area of at least the first original sheet G1 can be stored in the RAM 27 based on the leading edge position L1 of the first sheet.

(4) When the leading edge position L2 of the second sheet is detected, the trailing edge position L3 of the first sheet is positioned between the leading edge position L1 of the first sheet and the leading edge position L2 of the second sheet. Is determined to exist. For this reason, when detecting the first trailing edge position L3 after detecting the leading edge position L1 of the first sheet, between the leading edge position L1 of the first sheet and the leading edge position L2 of the second sheet. It is only necessary to detect the trailing edge position L3 of the first sheet, and one sheet is detected between the leading edge position L1 of the first sheet and the final position LL as in the case where the leading edge position L2 of the second sheet is not detected. There is no need to detect the rear edge position L3 of the eye. Accordingly, it is possible to shorten the time required to detect the rear edge position L3 of the first sheet.

(5) If the rear end edge position L3 of the first sheet is detected, a read image of the read image data read between the leading edge position L1 of the first sheet and the rear end edge position L3 of the first sheet. That is, the read image data obtained by reading the first original sheet G1 can be extracted, and the corresponding read image data can be stored in the RAM 27.

(6) On the other hand, if the leading edge position L2 of the second sheet is not detected, even the read image data of the entire area of the first document sheet G1 may not be stored in the RAM 27. In the image reading apparatus 1 of the present embodiment, when the leading edge position L2 of the second sheet is not detected, the occurrence of a jam error is displayed on the display unit 12, so that the user can jam the document sheet G by the display. Alternatively, it can be recognized that the original sheet G is a non-standard original sheet G that cannot be read by the image reading apparatus.

(7) In the image reading apparatus 1 of the present embodiment, in the trimming process, the leading edge threshold SS for detecting the leading edge positions L1 and L2 is different from the trailing edge threshold KS for detecting the trailing edge position L3. Is set to a value.

  When a plurality of document sheets G are continuously conveyed and read as in the present embodiment, for example, a document sheet G2 conveyed to the second sheet in the vicinity of the rear end of the document sheet G1 conveyed to the first sheet. The tip of exists. Therefore, if the leading edge threshold SS and the trailing edge threshold KS are set to a common threshold S, even when the edge position L is detected using the threshold S, the edge position L is the first trailing edge. It may be difficult to identify whether the position is the position L3 or the leading edge position L2 of the second sheet. In particular, if either the first trailing edge position L3 or the second leading edge position L2 cannot be detected, the identification may not be possible.

  In the image reading apparatus 1, since the front end threshold value SS and the rear end threshold value KS are set to different values, the front end edge positions L1 and L2 and the rear end edge position L3 are distinguished and detected by the threshold S used. can do.

(8) In particular, in the image reading apparatus 1 of the present embodiment, the rear end threshold value KS is set to a value smaller than the front end threshold value SS in correspondence with the structure in which the light source 32 of the image reading unit 30 emits light obliquely downstream. Is set. When the light source 32 emits light obliquely downstream, a shadow due to the thickness of the original sheet G is less likely to occur at the rear end of the original sheet G than the front end of the original sheet G, and the number of detected edge pixels is small. In the image reading apparatus 1, the trailing edge threshold value KS is set to a value smaller than the leading edge threshold value SS in accordance with the above-mentioned characteristics of the apparatus, so that the leading edge position L1, L2 and the trailing edge position L3 are set. It can be distinguished and detected. In particular, it is possible to accurately detect the trailing edge position L3 that has a small number of edge pixels and is more difficult to detect than the leading edge positions L1 and L2.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and the drawings, and for example, the following various aspects are also included in the technical scope of the present invention.
(1) In the above embodiment, the image reading apparatus 1 having the scanner function has been described. However, the present invention is not limited to this, and an image reading apparatus having a printer function, a copy function, a facsimile function, and the like is used. There may be.

(2) In the above embodiment, the image reading apparatus 1 has the CPU 20 and the ASIC 29, and the CPU 20 executes various processes such as an image reading process using a hardware circuit in the ASIC 29 as necessary. Although the description has been given by using the example configured, the present invention is not limited to this. For example, if the CPU exists separately from the ASIC and the processing executed by the control unit may be executed by the CPU, the CPU does not exist in the ASIC, and the control unit is installed by a hardware circuit provided in the ASIC. Processing to be executed may be executed. Furthermore, the process which a control part performs may be performed by one or several CPU and ASIC.

(3) The program executed by the CPU 20 is not necessarily stored in the ROM 26, and may be stored in the ASIC 29 or in another storage device.

(4) In the above embodiment, when the first leading edge position L1 and the second leading edge position L2 are detected, but the first trailing edge position L3 is not detected, Although the description has been given using the example of extracting the read image of the read image data read from the first edge position L1 to the final position LL, the present invention is not limited to this. For example, in the above case, a read image of read image data read from the leading edge position L1 of the first sheet to the leading edge position L2 of the second sheet may be extracted.

(5) In the above embodiment, when the leading edge position L2 of the second sheet is not detected even though the leading edge position L1 of the first sheet is detected, an example in which the read image is not extracted is used. However, the present invention is not limited to this. For example, in the above case, a read image of read image data read from the leading edge position L1 of the first sheet to the final position LL may be extracted.

(6) Although the above embodiment has been described using an example in which the light source 32 of the image reading unit 30 emits light obliquely downstream, the present invention is not limited to this. For example, the light source 32 of the image reading unit 30 may emit light obliquely upstream. In this case, since the number of edge pixels detected at the leading edge of the document sheet G is smaller than that at the trailing edge of the document sheet G, the leading edge threshold SS is preferably set to a value smaller than the trailing edge threshold KS.

(7) In the above embodiment, when the image reading apparatus 1 has the trimming mode for determining whether or not to execute the trimming process and is set to the on mode indicating that the trimming process is performed, Although the description has been given using the example in which the number of edge pixels is stored in the RAM 27 and the trimming process is executed, the present invention is not limited to this. For example, the number of edge pixels may always be stored in the RAM 27 without setting the trimming mode, and the trimming process may be executed.

(8) Although the above embodiment has been described using an example in which read image data for output is stored in the RAM 27, the present invention is not limited to this. For example, when the image reading device 1 is further connected to an external device such as a USB or an external PC, read image data for output may be stored in the storage unit included in the image reading device 1.

30: Image reading unit, 46: Document pressing member, 46A: Opposing surface, G: Document sheet, SS: Leading edge threshold, KS: Trailing edge threshold, L0: Initialization position, L1: First leading edge position, L2 : Leading edge position of the second sheet, L3: trailing edge position of the first sheet, LL: final position, T: elapsed time

Claims (8)

A transport unit that transports a document sheet along a transport path;
An image reading unit that reads an image at a reading position on the conveyance path;
A storage unit;
A control unit;
With
The controller is
An image acquisition process for causing the image reading unit to start reading an image before the transport unit causes the original sheet to reach the reading position, and sequentially acquiring read image data;
Edge detection processing for detecting edge pixels from each read image data acquired in the image acquisition processing;
Edge pixel number storage processing for sequentially storing the number of the edge pixels detected in the edge detection processing in the storage unit;
Density acquisition processing for acquiring image density from each read image data acquired in the image acquisition processing;
A sheet edge determination process for determining, when the image density acquired in the density acquisition process is changed between the respective read image data, a position on the read image of the changed read image data as an edge of the original sheet; ,
When there is no change in the image density in the sheet edge determination process, the read image data of the read image data in which the number of edge pixels stored in the edge pixel number storage process exceeds the threshold among the read image data. Trimming processing for extracting and outputting an area on the read image based on a position on the read image;
An image reading apparatus having a configuration for executing the above. The image reading apparatus according to claim 1,
Furthermore,
A facing member disposed to face the image reading unit across the transport path;
With
The storage unit stores a reference value serving as a reference of read image data when the image reading unit reads the facing member.
The controller is
When the image density acquired by causing the image reading unit to read the facing member is different from the reference value, and when there is no change in the image density in the sheet edge determination process, the trimming process is performed. An image reading apparatus to be executed. The image reading apparatus according to claim 2,
In the trimming process,
Of the read image data in which the number of edge pixels exceeds the threshold, the position of the read image data first acquired in the image acquisition process on the read image is detected as the leading edge position of the document sheet. An image reading apparatus that extracts and outputs the region from the read image data acquired after the tip edge position. The image reading apparatus according to claim 3,
In the trimming process,
Among the read image data in which the number of edge pixels exceeds the threshold value, the position on the read image of the read image data acquired next to the leading edge position in the image acquisition process is determined after the original sheet. An image reading device that detects an end edge position and extracts and outputs the read image data acquired from the leading edge position to the trailing edge position as the region. The image reading apparatus according to claim 4,
The transport unit continuously transports a plurality of document sheets,
An image reading apparatus, wherein a leading edge threshold for detecting the leading edge position and a trailing edge threshold for detecting the trailing edge position are set to different values. The image reading apparatus according to claim 5,
The image reading unit
A light source that emits light obliquely downstream along the transport path;
A light receiver;
Have
The image reading apparatus, wherein the leading edge threshold is set to a value larger than the trailing edge threshold. The image reading apparatus according to claim 6,
In the trimming process,
The leading edge threshold is used to detect the leading edge position, and then the position of the read image data in which the number of edge pixels exceeds the leading threshold is detected as a boundary position, and the leading edge position and the boundary position are detected. An image reading device that detects the trailing edge position using the trailing edge threshold. The image reading apparatus according to claim 7,
The controller is
Furthermore,
A jam determination process for determining that the document sheet is jammed when the boundary position is not detected in the trimming process;
An image reading apparatus that executes

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