JP2014216977A - Image reading apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine that a front end or a rear end of a document sheet reaches a reading position while using image data which are read at the reading position.SOLUTION: In an image reading apparatus 1, when setting a front end detection count criterion value to be used for determining that a front end of a document sheet reaches a reading position and a rear end detection count criterion value to be used for determining that a rear end of the document sheet reaches the reading position, reference data such as the number of edge pixels in read image data are calculated, the read image data being obtained by reading a document pressing member before feeding the document sheet to the reading position. The reference data are compared with criterion data (S54, S56 and S62). In the case where the reference data and the criterion data are not matched within a predetermined range, the front end detection count criterion value and the rear end detection count criterion value are set to multiple values (S60 and S64) and while using the set front end detection count criterion value or rear end detection count criterion value, the front end or the rear end of the document sheet is determined.

Description

  The present invention relates to a technique for conveying an original sheet and reading an image on the original sheet while passing through a reading range of an image reading unit, and particularly to a technique for determining whether or not the end of the original sheet has reached the reading range.

  There is an image reading apparatus of a type that conveys an original sheet and reads an image on the original sheet while passing through a reading range 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 range, and the determination result is used, for example, to determine the reading timing of the image reading unit or 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 the image data read in the predetermined reading range by the image reading unit is the identification image data, so that the leading edge and the trailing edge of the document sheet reach the reading range. 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, for example, it is only determined whether or not the image data read by one reading is identification image data. A problem in that it is not possible to accurately determine whether or not the leading edge or trailing edge of the original sheet has reached the reading position, which is the position of the reading range on the transport path, because it is erroneously determined whether or not it is identification image data. Occurs.

  The present specification discloses a technique for determining that the leading edge or the trailing edge of the document sheet has reached the reading position using image data read at the reading position while suppressing the influence of dust or the like adhering to the facing member. .

  An image reading apparatus disclosed in this specification is configured to face a conveyance unit that conveys a document sheet, an image reading unit that reads an image at a reading position on a conveyance path, and the image reading unit across the conveyance path. An opposing member disposed, a storage unit, and a control unit, wherein the control unit causes the image reading unit to start reading an image before the conveying unit reaches the original sheet at the reading position. A reading process for acquiring read image data sequentially for each main scanning direction group, and before the reading process, the image reading unit reads the counter member, and sets the value of the read image data and the counter member. Whether the difference between the value of the read image data and the reference value is equal to or greater than a certain value by comparing the reference value stored in the storage unit, which is a reference of the read image data when the image reading unit reads Discriminating differences The position of the read image data in which the value of the read image data acquired by the read process has changed by a predetermined value or more when the difference is determined to be greater than or equal to a certain value by the disconnection process and the difference determination process. And a sheet end determination process for determining the end of the original sheet.

  In this image reading apparatus, when setting the number of detections used to determine the edge of the original sheet, the value of the read image data obtained by reading the opposing member before the original sheet is conveyed to the reading position is used as a reference value. In comparison, when the value of the read image data is different from the reference value by a certain amount or more, the number of detections is set to the first consecutive number, that is, a plurality of times. As a result, when the difference between the value of the read image data obtained by reading the facing member and the reference value is relatively large, and there is a possibility that the edge of the original sheet may be erroneously determined if the number of times of detection is single, the number of times of detection is plural. By setting the number of times, erroneous determination can be suppressed, and it can be determined that the leading edge or the trailing edge of the document sheet has reached the reading position using the image data read at the reading position.

  In the image reading apparatus, when the difference is determined not to be more than a constant by the difference determination process in the sheet edge determination process, the control unit performs a second number less than the first continuous number, the specified value or more. The changed position of the read image data may be determined as the end of the original sheet.

  In this image reading apparatus, when the difference between the value of the read image data obtained by reading the facing member and the reference value is relatively small and the edge of the original sheet is difficult to be misjudged, the difference is relatively large. , Reduce the number of detections. Therefore, it is possible to suppress the occurrence of a failure due to a large number of detections, for example, a delay until it is determined to be the end of the original sheet or an error caused by the original sheet being conveyed until it is determined to be the end of the original sheet. it can.

  In the image reading apparatus, the storage unit stores a reference edge pixel number that is the number of edge pixels in a read image when the image reading unit reads the facing member as the reference value. In the difference determination process, the control unit causes the image reading unit to read the counter member, compares the number of edge pixels in the acquired read image with the reference edge pixel number, and determines the number of edge pixels. Is the same as the reference edge pixel number within a predetermined range, it is determined that the difference is not more than a certain value. If the number of the edge pixels does not match the reference edge pixel number within a predetermined range, the difference is more than a certain value. It is good also as a structure judged to exist.

  According to this image reading apparatus, it is possible to set the number of detections used to determine the edge of the document sheet using the number of edge pixels in the acquired read image.

  In the image reading apparatus, the storage unit stores a reference image density that is an image density of a read image when the image reading unit reads the facing member as the reference value, and the control unit In the difference determination process, the image reading unit is caused to read the counter member, the image density of the acquired read image is compared with the reference image density, and the image density is within a predetermined range from the reference image density. It is also possible to determine that the difference is not equal to or greater than a certain value if the difference is within a predetermined range, and to determine that the difference is equal to or greater than a certain value if the image density does not match the reference image density within a predetermined range.

  According to this image reading apparatus, it is possible to set the number of detections used to determine the edge of the original sheet using the image density in the acquired read image.

  In the image reading apparatus, the control unit determines that the number of edge pixels in the read image of the read image data is the first for the read image data acquired by the read process in the sheet edge determination process. It is determined whether an edge condition that has changed by more than a specified number and a density condition in which the image density of the read image has changed by a second specified number or more are satisfied, and the difference determination process determines that the difference is greater than or equal to a certain value. If it is determined that at least one of the edge condition and the density condition is satisfied for the first consecutive number of times, the leading edge of the document sheet in the transport direction of the transport unit has reached the reading position. If the determination that both the edge condition and the density condition are satisfied is continued for the first consecutive number of times, the document sheet in the transport direction is End may be configured to determine that has reached the reading position.

  The determination of the trailing edge of the document sheet is more difficult than the determination of the leading edge of the document sheet because it is affected by characters and graphics written on the document sheet. In this image reading apparatus, since the detection conditions for the leading edge and the trailing edge of the document sheet are different, the determination of the leading edge of the document sheet can reduce the burden on the determination. In the determination of the trailing edge of the document sheet, The accuracy can be improved.

  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 control unit is configured to perform the sheet edge detection process. The leading edge continuous number, which is the first consecutive number used to determine the leading edge and trailing edge of the document sheet, and to determine the trailing edge of the document sheet, is used to determine the leading edge of the document sheet. It is good also as a structure larger than the number of times of the tip continuous being the 1st number of times of use used.

  When the light source emits light obliquely downstream, the trailing edge of the document sheet is less likely to be shaded than the leading edge of the document sheet, so the trailing edge of the document sheet is difficult to judge compared to the leading edge of the document sheet. . In this image reading apparatus, since the first continuous number used to determine the trailing edge of the original sheet is made larger than the first continuous number used to determine the leading end of the original sheet, the trailing end of the original sheet is read. It is possible to accurately determine that the position has been reached.

  In the image reading apparatus disclosed in the present specification, the leading edge and the trailing edge of the original sheet have reached the reading position using the image data read at the reading position while suppressing the influence of dust or the like adhering to the facing member. Can be judged.

Schematic sectional view of an image reading device Block diagram schematically showing the electrical configuration of the image reading apparatus Flow chart showing the reading process Flow chart showing the reading process Flow chart showing detection count reference value setting processing Flowchart showing document presence / absence detection processing Flow chart showing rear end detection processing Graph showing the number of edge pixels in scanned image data Graph showing the histogram of scanned image data

<One 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 paper feed tray 2 is an example of a mounting table.

  The main body 3 of the image reading apparatus 1 is provided with a conveyance path 22 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 22 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 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 transport path 22.

  The transport roller 44 is driven to rotate by the motor M, and continuously transports a plurality of document sheets G drawn into the main body 3 by the paper feed roller 40 along the transport path 22. In the paper feed roller 40 and the transport roller 44, the transport speed of the transport roller 44 is set faster than that of the paper feed roller 40. The paper feed roller 40 and the transport roller 44 constitute a so-called one-way clutch mechanism using the difference in transport speed, and a central processing unit (hereinafter referred to as CPU) 20 described later recognizes the document size of the document sheet G. Even if not, a mechanism is set in which the distance between the originals of the original sheet G that is continuously conveyed is set according to the original size of the original sheet G.

  The image reading unit 30 is arranged at the reading position P1 on the conveyance path 22 and reads one surface of the original sheet G conveyed in the conveyance direction D2 along the conveyance path 22 at the reading position P1. A document pressing member 46 that presses the document sheet G on the conveyance path 22 toward the image reading unit 30 is disposed at a position facing the image reading unit 30 across the conveyance path 22 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 31 and a light receiving unit 34. The light source 31 includes a plurality of light emitting diodes 32 (hereinafter referred to as LEDs) arranged in the main scanning direction D1 orthogonal to the transport direction D2. In the light source 31, 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 31 emits light emitted from each LED 32 obliquely from the upstream side to the downstream side of the transport path 22.

  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 each LED 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 each LED 32 and reflected by the facing surface 46 </ b> A of the document pressing member 46 using each light receiving element.

  A paper discharge roller 50 is disposed on the downstream side of the reading position P <b> 1 on the conveyance path 22. The paper discharge roller 50 is rotationally driven by the motor M similarly to the paper feed roller 40 and the transport roller 44, and sends the document sheet G transported on the transport path 22 to the paper discharge tray 4. In other words, the transport unit 15 (see FIG. 2) transports a plurality of document sheets G placed on the paper feed tray 2 along the transport path 22 by the paper feed roller 40, the transport roller 44, and the paper discharge roller 50. Is formed.

  A protruding portion 52 that protrudes upward is provided on the conveyance path 22 side of the discharge tray 4, and the conveyance path 22 side of the document sheet G sent to the discharge tray 4 warps upward in accordance with the protrusion 52. Go up. Therefore, the original sheet G conveyed later along the conveyance path 22 is the original sheet G conveyed first, and the original whose sheet is conveyed upward as a result of being sent to the paper discharge tray 4. The sheet G is sent out between the sheet G and the protruding portion 52, that is, below the original sheet G conveyed earlier. 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. . The image reading apparatus 1 includes a power switch and various setting buttons, and includes an operation unit 11 that receives an operation command and the like from a user, and a display unit 12 that includes an LED and a liquid crystal display and displays the status of the image reading apparatus 1. Is provided.

2. Electrical Configuration of Image Reading Device As shown in FIG. 2, the image reading device 1 includes a CPU 20, a ROM 26, a RAM 27, an ASIC 29, a device control unit 23, an analog front end (hereinafter referred to as AFE) 24, a motor. A driver 25 and an image processing unit 28 are provided, to which an image reading unit 30, a transport unit 15, an operation unit 11, a display unit 12, an F sensor 13, and the like are connected. As shown by a solid line 21 in FIG. 3, the CPU 20, the ROM 26, the RAM 27, and the ASIC (Application Specific Integrated Circuit) 29 are examples of the control unit, and the ROM 26 and the RAM 27 are included. Is an example of a storage unit.

  Various programs for controlling the operation of the image reading apparatus 1 are stored in the ROM 26. The CPU 20 controls each unit in accordance with the program read from the ROM 26, and will be described later using an ASIC 29 as necessary. Processing such as reading processing is executed. The ROM 26 stores a reference edge pixel number, a reference maximum pixel number, a reference peak luminance, and the like, which will be described later.

  The device control unit 23 is connected to the image reading unit 30 and transmits a reading control signal to the image reading unit 30 based on a command from the CPU 20. Based on the reading control signal from the device control unit 23, the image reading unit 30 turns on the LEDs 32 of each color, and reads the facing surface 46A of the document pressing member 46 and the document sheet G.

  The image reading unit 30 repeats reading at the reading position P1 of the conveyance path 22 when reading the facing surface 46A of the document pressing member 46 and the document sheet G. The image reading unit 30 acquires read image data that is a collection of pixel data acquired by each light receiving element arranged in the main scanning direction D1 by one reading. The image reading unit 30 outputs the acquired read image data to the AFE 23.

  The AFE 24 is connected to the image reading unit 30, and converts analog read image data output from the image reading unit 30 into digital signals, that is, read image data of gradation data. The AFE 24 stores the converted read image data in the RAM 27.

  The image processing unit 28 performs edge extraction processing such as binarization processing and enhancement processing on the read image data stored in the RAM 27 to extract the number of edge pixels. In addition, a distribution generation process for generating a histogram that is a luminance distribution of each pixel data included in the read image data stored in the RAM 27 is performed, and the maximum number of pixels of the histogram and the peak luminance at the maximum number of pixels are extracted.

The motor driver 25 is connected to the motor M and rotationally drives the motor M based on the pulse signal. By the rotation drive of the motor M, the paper feed roller 40, the transport roller 44, and the paper discharge roller 50, which are the transport unit 15, are rotated, and the original sheet G is transported.

3. Reading Process Next, the reading process of the original sheet G will be described with reference to FIGS. FIG. 3 shows a flowchart of a reading process executed by the CPU 20 according to a predetermined program.

  When the CPU 20 confirms that the original sheet G is placed on the paper feed tray 2 using the F sensor 13 and receives an instruction for reading the original sheet G from the user via the operation unit 11, Start processing.

  When starting the reading process, the CPU 20 instructs the image reading unit 30 to turn on the green LED 32G and instructs one line to be read (S2). Accordingly, the image reading unit 30 reads the facing surface 46A of the document pressing member 46 once before reading the document sheet G (S26 to S34), and the read image data is stored in the RAM 27.

  Next, the CPU 20 performs distribution generation processing on the read image data stored in the RAM 27 using the image processing unit 28, and calculates the maximum number of pixels and peak luminance of the read image in the read image data (S4). ). The CPU 20 stores the calculated maximum pixel number and peak luminance in the RAM 27 as the reference maximum pixel number and reference peak luminance (S6).

  Further, the CPU 20 performs edge extraction processing on the read image data stored in the RAM 27 using the image processing unit 28, and calculates the number of edge pixels of the read image in the read image data (S8). The CPU 20 stores the calculated edge pixel number in the RAM 27 as the reference edge pixel number (S10). When the reference data such as the maximum reference pixel number, the reference peak luminance, the reference edge pixel number and the like are stored in the RAM 27, the CPU 20 executes a detection count reference value setting process (S12). The reference data is an example of the value of the read image data.

(Detection count reference value setting process)
In the detection count reference value setting process, the CPU 20 compares the reference data stored in the RAM 27 with the reference data stored in the ROM 26, and detects the leading edge (hereinafter referred to as the leading edge of the original sheet G) in the conveyance direction D2 of the original sheet G. And a trailing edge detection count reference value used for detecting a trailing edge (hereinafter, trailing edge of the document sheet G) in the conveyance direction D2 of the document sheet G.

  Here, the reference data means a reference maximum pixel number, a reference peak luminance, a reference edge pixel number, and the like. The reference maximum pixel number, the reference peak luminance, and the reference edge pixel number are the read image in the read image data obtained 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. The maximum number of pixels, peak luminance, and number of edge pixels calculated from the above. That is, these reference data are values obtained in the initial stage of use of the image reading apparatus 1 and in a state in which dust or the like is not attached to the facing surface 46A of the document pressing member 46. The reference data is an example of a reference value.

  As shown in FIG. 5, in the detection count reference value setting process, the CPU 20 first reads the reference data from the ROM 26 (S52), and compares the reference maximum pixel number stored in the RAM 27 with the reference maximum pixel number (S54). ). Further, the reference peak luminance stored in the RAM 27 is compared with the standard peak luminance (S56).

  In the above comparison, the CPU 20 confirms whether the values to be compared match within a predetermined range. Here, the predetermined range means an error range. When the values match within the predetermined range, the difference between the values to be compared is about the error. When the values do not match within the predetermined range, the difference between the values to be compared is equal to or greater than the error. It means that. When the reference peak luminance and the standard peak luminance coincide with each other within a predetermined range, and the reference maximum pixel number and the standard maximum pixel number coincide with each other within the predetermined range (S54: YES, S56: YES), the CPU 20 detects the tip detection count. The reference value and the rear end detection count reference value are set to a small value ("small" in FIG. 5) (S58). The small value is a natural number of 1 or more. For example, the small value of the leading end detection count reference value is “2”, and the small value of the trailing end detection count reference value is “4”. The small value is an example of the second number of times.

  On the other hand, the CPU 20 determines at least one of the case where the reference peak luminance and the standard peak luminance do not match within the predetermined range (S54: NO), or the case where the reference maximum pixel number does not match the standard maximum pixel number within the predetermined range. If it is determined (S54: YES, S56: NO), the leading end detection count reference value and the trailing end detection count reference value are set to a large value ("large" in FIG. 5) (S60). For example, the large value of the leading end detection count reference value is “5”, and the large value of the trailing end detection count reference value is “8”. The large value is an example of the first consecutive number.

  Next, the CPU 20 compares the reference edge pixel number stored in the RAM 27 with the standard edge pixel number (S62). When the reference edge pixel count and the reference edge pixel count match within a predetermined range (S62: YES), the CPU 20 maintains the leading end detection count reference value and the trailing end detection count reference value at a small value, and sets the detection count reference value. The process ends. On the other hand, if the number of reference edge pixels and the number of reference edge pixels do not match within a predetermined range (S62: NO), the leading edge detection count reference value and the trailing edge detection count reference value are reset to large values, or the large value (S64), and the detection count reference value setting process ends.

  That is, the CPU 20 determines that the reference peak luminance and the standard peak luminance match within a predetermined range, and determines that the reference maximum pixel number and the standard maximum pixel number match within the predetermined range, and the reference edge pixel number When it is determined that the reference edge pixel number matches within a predetermined range, the leading edge detection count reference value and the trailing edge detection count reference value are set to a small value smaller than the large value. On the other hand, if it is determined that at least one of the three determinations does not match within a predetermined range, the value is set to a large value that is larger than the small value. Therefore, the large value is a natural number of 2 or more, that is, a plurality.

  In both the small value and the large value, the rear end detection count reference value is set to a value larger than the front end detection count reference value. This corresponds to the structure in which the light source 31 of the image reading unit 30 emits light from the upstream side to the downstream side of the conveyance path 22, and a shadow is caused by the thickness of the document sheet G at the rear end of the document sheet. This is because it is less likely to occur than the leading edge of the original sheet.

  When the leading edge detection count reference value and the trailing edge detection count reference value are set in the detection count reference value setting process, the CPU 20 sets the operation mode to the conveyance mode and instructs the conveyance unit 15 to convey the document sheet G. Then, the conveyance of the original sheet G is started (S14), and the elapsed time from the start of the conveyance of the original sheet G is counted. Next, the CPU 20 executes document presence / absence detection processing (S16).

  The conveyance of the original sheet G in the conveyance mode is different from the conveyance of the original sheet G in the reading mode described later. In transporting the document sheet G in the transport mode, the document sheet G is transported at a transport speed suitable for detecting the leading edge of the document sheet G executed in the document presence / absence detection process.

(Document presence detection processing)
In the document presence / absence detection process, the CPU 20 detects that the leading edge of the document sheet G has reached the reading position P1 using the leading edge detection count reference value. Therefore, the document presence / absence detection process can also be referred to as a leading edge detection process.

  As shown in FIG. 6, in the document presence / absence detection process, the CPU 20 first resets the leading edge detection count used for comparison with the leading edge detection count reference value to “0” (S 72). Instruct to turn on the green LED 32G and instruct to read one line (S74). That is, the CPU 20 causes the image reading unit 30 to start reading before the leading edge of the document sheet G reaches the reading position P1.

  The CPU 20 performs distribution generation processing on the read image data stored in the RAM 27 in the immediately preceding S74 using the image processing unit 28, and calculates the maximum number of pixels and peak luminance of the read image in the read image data ( S76). 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.

  Further, the CPU 20 performs edge extraction processing on the read image data stored in the RAM 27 in the immediately preceding S74 using the image processing unit 28, and calculates the number of edge pixels of the read image in the read image data (S78). ). The maximum number of pixels, the peak luminance, and the number of edge pixels calculated in S76 and 78 are examples of values of the read image data acquired by the reading process.

  Next, the CPU 20 compares the calculated number of edge pixels with the reference edge pixel number stored in the RAM 27 (S80), and determines whether the calculated edge pixel number is greater than the reference edge pixel number stored in the RAM 27 by a threshold value or more. Check. The threshold value is an example of a first specified value. When the difference between the calculated edge pixel number and the reference edge pixel number is smaller than the threshold (S80: NO), the CPU 20 further compares the calculated maximum pixel number with the reference maximum pixel number stored in the RAM 27, The calculated peak luminance is compared with the reference peak luminance stored in the RAM 27 (S82).

  When the calculated maximum pixel count and the reference maximum pixel count calculation match within a predetermined range, and the calculated peak luminance matches the reference peak luminance within the specified range (S82: YES), the CPU 20 again sets the tip detection count. It is reset to “0” (S86). The specified range is an example of a second specified value. That is, the CPU 20 maintains all the calculated data such as the calculated number of edge pixels, maximum number of pixels, and peak luminance as values that do not differ by more than a predetermined specified value such as a threshold value or a specified range with respect to the reference data. If it is determined that the tip is detected, the tip detection count is reset.

  On the other hand, when the difference between the calculated edge pixel number and the reference edge pixel number is equal to or greater than the threshold value (S80: YES), or the calculated maximum pixel number and the reference maximum pixel number calculation are within a predetermined range. If not, or if the calculated peak brightness does not match the reference peak brightness within the specified range (S80: NO, S82: NO), the tip detection count is increased by “1” (S84). That is, when the CPU 20 determines that at least one calculation data has changed to a value different from the corresponding reference data by a predetermined value or more, the CPU 20 increases the tip detection count. The difference between the calculated edge pixel number and the reference edge pixel number changes to a threshold value or more is an example of an edge condition, and the calculated maximum pixel number and the reference maximum pixel number calculation do not match within a predetermined range. It is an example of the density condition, and another example of the density condition is that the calculated peak luminance and the reference peak luminance do not match within the specified range.

  When increasing the tip detection count, the CPU 20 compares the increased tip detection count with the tip detection count reference value (S88). When the increased tip detection count is smaller than the tip detection count reference value (S88: NO), or when the tip detection count is reset (S86), the CPU 20 reads the read image data stored in the RAM 27 in S74. Is determined to be read image data obtained by reading the facing surface 46 </ b> A of the document pressing 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 confirms the elapsed time from the start of conveyance of the original sheet G (S90). The ROM 26 stores a first reference transport time during which the leading edge of the document sheet G is transported to the reading position P1 based on the transport speed of the document sheet G. The CPU 20 has elapsed since the start of transport of the document sheet G. The time is compared with the first reference transport time. When the elapsed time from the start of conveyance of the original sheet G is shorter than the first reference conveyance time (S90: NO), the CPU 20 repeats the processing from S74.

  On the other hand, when the elapsed time from the start of conveyance of the original sheet G is equal to or longer than the first reference conveyance time (S90: YES), it is highly likely that the original sheet G cannot pass through the conveyance path 22 and a jam has occurred. . In this case, the CPU 20 instructs the display unit 12 to display the occurrence of a jam error (S94), ends the document presence / absence detection process, and further, in the reading process shown in FIG. An instruction to stop the conveyance of G is given (S38), and the reading process is terminated.

  Further, when the increased tip detection count is greater than or equal to the tip detection count reference value (S88: YES), that is, when the change in calculation data that increases the tip detection count continues for more than the tip detection count reference value, the CPU 20 In S74, it is determined that the read image data stored in the RAM 27 has been switched to read image data obtained by reading the original sheet G. In this case, the CPU 20 determines that the leading edge of the document sheet G has reached the reading position P1 at the timing when the scanned image data is scanned. That is, the scanned image data is read by scanning the leading edge of the document sheet G. The image data is determined (S92), and the document presence / absence detection process is terminated.

  In FIG. 3, when detecting the leading edge of the document sheet G in the document presence / absence detection process, the CPU 20 instructs the transport unit 15 to stop transporting the document sheet G and stops transporting the document sheet G (S18). Next, in FIG. 4, the CPU 20 changes the operation mode from the conveyance mode to the reading mode (S20), and resets the manuscript detection count used for comparison with the trailing edge detection count reference value to “0” (S22). ).

  Then, the CPU 20 instructs the conveyance unit 15 to convey the original sheet G, starts conveyance of the original sheet G in the reading mode (S24), and instructs the image reading unit 30 to start reading the original sheet G. Instruct (S26). When reading of the original sheet G is started, the CPU 20 instructs reading of one line every predetermined time (S28). Thus, the image reading unit 30 individually turns on the LEDs 32 of each color in one reading of one line, reads each time during the lighting period of each LED 32, and stores the read image data corresponding to each color in the RAM 27. . Next, the CPU 20 executes rear end detection processing (S30).

(Rear edge detection process)
In the trailing edge detection process, the CPU 20 detects that the trailing edge of the document sheet G has reached the reading position P1 using the read image data and the trailing edge detection count reference value stored in the RAM 27 in S28.

  As shown in FIG. 7, in the rear end detection process, the CPU 20 first performs distribution generation processing on the read image data of each color stored in the RAM 27 using the image processing unit 28, and reads the read image data of each color. The maximum number of pixels and the peak luminance of the read image are calculated (S102). Further, the CPU 20 performs edge extraction processing on the read image data of each color stored in the RAM 27 using the image processing unit 28, and calculates the number of edge pixels of the read image in the read image data of each color (S104). . The maximum number of pixels, the peak luminance, and the number of edge pixels calculated in S102 and S104 are other examples of the values of the read image data acquired by the reading process.

  Next, the CPU 20 compares the calculated edge pixel number of each color with the reference edge pixel number stored in the RAM 27 (S106), and the calculated edge pixel number of each color is a threshold value than the reference edge pixel number stored in the RAM 27. Check if it is larger. When the difference between the calculated number of edge pixels of all colors and the number of reference edge pixels is smaller than the threshold value (S106: NO), the CPU 20 further calculates the calculated maximum number of pixels of each color and the reference maximum pixel stored in the RAM 27. The calculated peak luminance of each color is compared with the reference peak luminance stored in the RAM 27 (S108).

  When the difference between the calculated edge pixel number of at least one color and the reference edge pixel number is equal to or greater than the threshold (S106: YES), the CPU 20 calculates the maximum pixel number of at least one color and the reference maximum pixel number calculation. If they do not match within the predetermined range, or if the calculated peak luminance of at least one color and the reference peak luminance do not match within the specified range (S106: NO, S108: NO), the rear end detection count is set to “0” again. Reset (S112). That is, the CPU 20 resets the rear end detection count when it is determined that at least one calculation data is maintained at a value different from the corresponding reference data by a predetermined value or more.

  On the other hand, when the calculated maximum number of pixels of all colors and the reference maximum pixel number calculation match within a predetermined range, and the calculated peak luminance of all colors matches the reference peak luminance within a predetermined range (S108). : YES), the rear end detection count is increased by “1” (S110). That is, if the CPU 20 determines that all the calculated data has changed to a value that does not differ by more than a specified value, the CPU 20 increases the rear end detection count.

  When increasing the rear end detection count, the CPU 20 compares the increased rear end detection count with the rear end detection count reference value (S114). When the trailing edge detection count after the increase is smaller than the trailing edge detection count reference value (S114: NO), or when the leading edge detection count is reset (S112), the CPU 20 reads the reading stored in the RAM 27 in S28. The image data is determined to be 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 and has not detected the trailing edge of the document sheet G (S118), and ends the trailing edge detection processing.

  When the calculated maximum pixel number and the reference maximum pixel number calculation match within a predetermined range, and the calculated peak luminance and the reference peak luminance match within the predetermined range (S78: YES), the CPU 20 stores them in the RAM 27 in S10. It is determined that the read image data is switched to read image data obtained by reading the facing surface 46A of the document pressing member 46. In this case, the CPU 20 determines that the trailing edge of the document sheet G has reached the reading position P1 at the timing when the scanned image data is scanned, that is, the scanned image data reads the trailing edge of the document sheet G. The read image data is determined (S80), and the trailing edge detection process is terminated.

  On the other hand, when the rear end detection count after the increase is greater than or equal to the rear end detection count reference value (S114: YES), the CPU 20 changes the calculated data that increases the rear end detection count greater than or equal to the rear end detection count reference value. If it is continuous, it is determined that the read image data stored in the RAM 27 in S28 is switched to the read image data obtained by reading the document sheet G. In this case, the CPU 20 determines that the trailing edge of the document sheet G has reached the reading position P1 at the timing when the scanned image data is scanned, that is, the scanned image data reads the trailing edge of the document sheet G. The read image data is determined (S116), and the trailing edge detection process is terminated.

  After completion of the trailing edge detection process, the CPU 20 checks whether or not the trailing edge has been detected in the trailing edge detection process in the reading process shown in FIG. 4 (S32). When the trailing edge is not detected (S32: NO), the CPU 20 checks the elapsed time from the start of conveyance of the original sheet G (S40). The ROM 26 stores a second reference transport time during which the trailing edge of the document sheet G is transported to the reading position P1 based on the transport speed of the document sheet G. The CPU 20 starts from the start of transport of the document sheet G. The elapsed time is compared with the second reference transport time. When the elapsed time from the start of conveyance of the original sheet G is shorter than the second reference conveyance time (S40: NO), the CPU 20 repeats the processing from S28.

  If the elapsed time from the start of conveyance of the document sheet G is equal to or longer than the second reference conveyance time (S40: YES), it is highly likely that the document sheet G cannot pass through the conveyance path 22 and a jam has occurred. . In this case, the CPU 20 instructs the display unit 12 to display the occurrence of a jam error (S42). Then, the CPU 20 instructs the image reading unit 30 to stop reading the original sheet G (S44), and instructs the conveying unit 15 to stop conveying the original sheet G (S38), and ends the reading process. .

  On the other hand, when the trailing edge is detected (S32: YES), the CPU 20 instructs the image reading unit 30 to stop reading the document sheet G (S34). Next, the CPU 70 checks the state of the F sensor 13 (S36), and if the F sensor 13 is on (S36: YES), that is, if the original sheet G remains in the paper feed tray 2. , The process from S16 is repeated. On the other hand, when the F sensor 13 is off (S18: NO), the conveyance unit 15 is instructed to stop conveyance of the document sheet G (S38), and the reading process is terminated.

4). Advantages of the present embodiment (1) In the image reading apparatus 1 of the present embodiment, the leading edge detection count reference value used to determine the leading edge of the document sheet G and the trailing edge of the document sheet G are used. When the rear end detection count reference value to be set is set, reference data calculated from read image data obtained by reading the facing surface 46A of the document pressing member 46 before the document sheet G is conveyed to the reading position P1 is stored in the ROM 26. The leading edge detection count reference value and the trailing edge detection count reference value are set based on the comparison result.

  In the initial stage of use of the image reading apparatus 1, since there is relatively little dust, dirt, or the like adhering to the facing surface 46 </ b> A of the document pressing member 46, the reference data and the reference data substantially match. Therefore, as shown in FIG. 8 using the number of edge pixels, in the upper diagram in the initial stage of use, even if an upper limit value larger than the reference edge pixel number by a threshold is set based on the reference edge pixel number, the original sheet G There is a sufficient difference between the number of edge pixels calculated from the read image data obtained by reading and the upper limit value.

  Therefore, as shown by a mark 54 in FIG. 8, even when the number of edge pixels calculated from the read image data obtained by reading the original sheet G is changed by the pattern described on the original sheet G, the value is the upper limit. It did not happen to fall below. Further, since dust, dirt, and the like attached to the facing surface 46A of the document pressing member 46 are relatively small, the number of edge pixels calculated from the read image data obtained by reading the facing surface 46A of the document pressing member 46 is the upper limit value. Never exceeded.

  However, as indicated by the arrow 62, when the use period of the image reading apparatus 1 is increased, dust, dirt, and the like adhering to the facing surface 46A of the document pressing member 46 increase, and as shown in the lower diagram of FIG. The reference data and the reference data (see the two-dot chain line in FIG. 8) do not match within a predetermined range. As a result, the difference between the number of edge pixels calculated from the read image data obtained by reading the original sheet G and the upper limit value is reduced, and as shown by a mark 56 in FIG. In this case, the number of edge pixels calculated from the read image data obtained by reading the document sheet G exceeds the upper limit value. Further, as indicated by a mark 58 in FIG. 8, the edge calculated from the read image data obtained by reading the facing surface 46A of the document pressing member 46 due to irregular reflection due to dust or the like adhering to the facing surface 46A of the document pressing member 46. It has occurred that the number of pixels exceeds the upper limit.

  Therefore, when the number of reference edge pixels and the number of reference edge pixels do not match within a predetermined range, the number of edge pixels calculated from the read image data obtained by reading the facing surface 46A of the document pressing member 46 exceeds the upper limit value. If it is determined that the leading edge of the document sheet G has reached the reading position P <b> 1 after only one abnormal event has occurred, the leading edge of the document sheet G is erroneously determined. Further, it is determined that the trailing edge of the original sheet G has reached the reading position P1 only when an abnormal event occurs in which the number of edge pixels calculated from the read image data obtained by reading the original sheet G falls below the upper limit. Then, there is a problem that the rear end of the original sheet G is erroneously determined.

  Further, as shown in FIG. 9, in the initial stage of use of the image reading apparatus 1, there is relatively little dust or dirt attached to the facing surface 46 </ b> A of the document pressing member 46. The histogram generated by reading 46A is a histogram that concentrates on the peak luminance corresponding to the reflectance of the facing surface 46A of the document pressing member 46, as shown in the upper diagram of FIG. The number almost matches. Therefore, when the predetermined range is set based on the maximum number of reference pixels, the original sheet G is read even if the peak luminance calculated from the read image data obtained by reading the original sheet G matches the reference peak luminance. The maximum pixel number calculated from the read image data (see the broken line in FIG. 9) and the reference maximum pixel number do not match within a predetermined range.

  However, as indicated by the arrow 64, when the usage period of the image reading apparatus 1 is increased, dust or dirt attached to the facing surface 46A of the document pressing member 46 increases, and the reference highest pixel is affected by the dust. The number decreases, and the reference maximum pixel number and the reference maximum pixel number (see the two-dot chain line in FIG. 9) do not match within a predetermined 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 designated. Anomalous events that match within range may occur. Thus, if it is determined that the trailing edge of the document sheet G has reached the reading position P1, the trailing edge of the document sheet G is erroneously determined.

  In the image reading apparatus 1 of the present embodiment, when the reference data and the reference data do not match within a predetermined range, the leading end detection count reference value and the trailing end detection count reference value are set to a large value, that is, a plurality. As a result, the leading edge and the trailing edge of the document sheet G are not erroneously determined only when an abnormal event occurs once. In addition, abnormal events rarely occur multiple times in succession. Therefore, it is possible to accurately determine that the leading edge or the trailing edge of the document sheet G has reached the reading position P1 using the read image data.

(2) On the other hand, when the reference data and the reference data match within a predetermined range, it is not necessary to increase the front end detection count reference value and the rear end detection count reference value. If the leading edge detection count reference value and the trailing edge detection count reference value are increased, for example, when the leading edge of the document sheet G is detected, one line reading is repeated until the leading edge detection count becomes the leading edge detection count reference value. Therefore, the time until the leading edge of the original sheet G is detected is delayed. Further, since the document sheet G continues to be conveyed until the leading edge detection count reaches the leading edge detection count reference value, when the leading edge of the document sheet G is detected, the leading edge of the document sheet G passes the reading position P1. Thereafter, the sheet is conveyed by a distance corresponding to the leading edge detection count reference value, and an error occurs in the position of the leading edge of the document sheet G. This is the same when the trailing edge of the original sheet G is detected.

  In the image reading apparatus 1 of this embodiment, when the reference data and the reference data do not match within a predetermined range, the leading end detection count reference value and the trailing end detection count reference value are set to a small value smaller than the large value. As a result, it is possible to suppress the time delay until the leading edge and the trailing edge of the document sheet G are detected and the occurrence of errors when detecting the leading edge and the trailing edge of the document sheet G.

(3) In the image reading apparatus 1 of the present embodiment, the number of edge pixels, the maximum number of pixels, and the peak luminance are used as reference data when setting the leading edge detection count reference value and the trailing edge detection count reference value. Therefore, the leading edge and the trailing edge of the document sheet G can be detected from the change of these values or the combination of the changes when the leading edge and the trailing edge of the document sheet G reach the reading position P1.

(4) In the image reading apparatus 1 of the present embodiment, the condition for increasing the leading edge detection count is different from the condition for increasing the trailing edge detection count. In the leading edge detection count, the calculated number of edge pixels, maximum number of pixels, When at least one of the calculation data such as peak luminance changes to a value different from the specified value, the tip detection count is increased. On the other hand, in the rear end detection count, the rear end detection count is increased when all of the calculated data changes to a value that does not differ by more than a specified value. That is, the condition for increasing the trailing edge detection count is set more strictly than the condition for increasing the leading edge detection count.

  The determination of the trailing edge of the document sheet G is affected by the pattern described on the document sheet G, and thus is difficult to determine compared to the determination of the leading edge of the document sheet G. For example, if the pattern described on the original sheet is a solid black pattern, the number of edge pixels decreases because there are no edge pixels, and the trailing edge of the original sheet G is determined as the number of edge pixels decreases. As a result, the rear end of the original sheet G is erroneously determined. In this image reading apparatus 1, it is possible to suppress erroneous determination of the trailing edge of the document sheet G by setting the condition for increasing the trailing edge detection count more strictly than the condition for increasing the leading edge detection count. Further, by setting the condition for increasing the leading edge detection count to be looser than the condition for increasing the trailing edge detection count, it is possible to reduce the apparatus burden related to the determination of the leading edge of the document sheet G.

(5) In the image reading apparatus 1 of the present embodiment, the rear end detection count reference value is set to a value larger than the front end detection count reference value. When the light source 31 of the image reading unit 30 emits light from the upstream side to the downstream side of the conveyance path 22 as in the image reading apparatus 1 of the present embodiment, a shadow is caused by the thickness of the original sheet G. It is less likely to occur at the trailing edge of the sheet than at the leading edge of the original sheet G, and it is difficult to detect changes in calculated data. In this image reading apparatus 1, it is possible to accurately determine that the trailing edge of the original sheet G has reached the reading position P1 by setting the trailing edge detection count reference value to a value larger than the leading edge detection count reference value. it can.

<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 the present invention is a multifunction device having a printer function, a copy function, a facsimile function, and the like. May be.

(2) In the above-described embodiment, the image reading apparatus 1 includes one CPU 20 and one ASIC 29, and the CPU 20 configures a control unit that executes various processes such as a reading process using the ASIC 29 as necessary. Although the description has been given using an example, the present invention is not limited to this. For example, if the process executed by the control unit may be executed only by the CPU, the process executed by the control unit may be executed only by the ASIC. Furthermore, the process which a control part performs may be performed by one or several CPU and ASIC.

(3) Further, the program executed by the CPU 20 does not necessarily have to be stored in the ROM 26, and may be stored in the CPU 20 itself or in another storage device.

(4) In the above embodiment, the description has been given using the example in which the rear end detection count reference value is set to a value larger than the front end detection count reference value, but the present invention is not limited to this. For example, when the light source 31 of the image reading unit 30 has a structure that emits light from the downstream side to the upstream side of the conveyance path 22, the front end detection count reference value is set to a value larger than the rear end detection count reference value. Also good. Regardless of the structure of the image reading unit 30, the front end detection count reference value and the rear end detection count reference value may be set to the same value.

(5) Although the above embodiment has been described using an example in which the condition for increasing the trailing edge detection count is set more strictly than the condition for increasing the leading edge detection count, the present invention is not limited to this. For example, the condition for increasing the leading edge detection count may be set strictly like the condition for increasing the trailing edge detection count. As a result, erroneous determination of the trailing edge of the document sheet G can be suppressed.

(6) Although the above embodiment has been described using an example in which there are a plurality of small values of the leading end detection count reference value and the trailing end detection count reference value, a single number may be set. By setting the number to one, it is possible to suppress a delay in the time until the leading edge and the trailing edge of the original sheet G are detected and the occurrence of errors when detecting the leading edge and the trailing edge of the original sheet G.

DESCRIPTION OF SYMBOLS 1: Image reading device, 30: Image reading part, 31: Light source, 32: LED, 34: Light receiving part, 35: Light receiving element, 46: Document pressing member, 46A: Opposing surface, 52: Protruding part, D1: Main scanning Direction, D2: transport direction, P1: reading position,

Claims (6)

A transport unit for transporting a document sheet;
An image reading unit that reads an image at a reading position on the conveyance path;
An opposing member disposed opposite to the image reading unit across the transport path;
A storage unit;
A control unit;
With
The controller is
A reading process in which the image reading unit starts reading an image before the conveying unit reaches the reading position of the original sheet, and sequentially acquires read image data for each main scanning direction group;
Before the reading process, the image reading unit is caused to read the counter member, and the value of the read image data and the counter member are stored in the storage unit as a reference of the read image data when the image reading unit reads the counter member. A difference determination process for comparing the determined reference value and determining whether or not the difference between the value of the read image data and the reference value is equal to or greater than a certain value;
When it is determined that the difference is greater than or equal to a certain value by the difference determination process, the position of the read image data where the value of the read image data acquired by the reading process has changed by a predetermined value or more is determined for the first consecutive number of times. Sheet edge determination processing for determining the edge of the sheet,
An image reading apparatus that executes The image reading apparatus according to claim 1,
The controller is
In the sheet edge determination process,
If it is determined by the difference determination process that the difference is not equal to or greater than a certain value, the position of the read image data that has changed by a second number less than the first number of consecutive times and the specified value is determined as an end of the document sheet;
Image reading device. The image reading apparatus according to claim 1, wherein:
The storage unit stores a reference edge pixel number that is the number of edge pixels in the read image when the image reading unit reads the facing member as the reference value,
The controller is
In the difference determination process,
The image reading unit is caused to read the facing member, and the number of the edge pixels in the acquired read image is compared with the reference edge pixel number, and the number of the edge pixels is within a predetermined range with respect to the reference edge pixel number. If they match, it is determined that the difference is not more than a certain value, and if the number of edge pixels does not match the reference edge pixel number within a predetermined range, it is determined that the difference is more than a certain value.
Image reading device. An image reading apparatus according to any one of claims 1 to 3,
The storage unit stores, as the reference value, a reference image density that is an image density of a read image when the image reading unit reads the facing member,
The controller is
In the difference determination process,
When the image reading unit reads the counter member and compares the acquired image density of the read image with the reference image density, and the image density matches the reference image density within a predetermined range, the difference If the image density does not match the reference image density within a predetermined range, it is determined that the difference is greater than a certain value.
Image reading device. An image reading apparatus according to any one of claims 1 to 4,
The controller is
In the sheet edge determination process,
For each read image data acquired by the reading process, an edge condition in which the number of edge pixels in the read image of each read image data has changed by a first specified number or more and an image density of the read image are second. It is judged whether or not the concentration condition changed more than the specified number is satisfied,
If it is determined by the difference determination process that the difference is greater than or equal to a certain level,
When the determination that at least one of the edge condition and the density condition is satisfied is continued for the first continuous number of times, it is determined that the leading edge of the document sheet in the transport direction of the transport unit has reached the reading position;
If the determination that both the edge condition and the density condition are satisfied is continued for the first consecutive times, it is determined that the trailing edge of the document sheet in the transport direction has reached the reading position;
Image reading device. An image reading apparatus according to any one of claims 1 to 5,
The image reading unit
A light source that emits light obliquely downstream along the transport path;
A light receiver;
Have
The controller is
In the sheet edge detection process, each of a leading edge and a trailing edge of the document sheet is determined,
The trailing edge continuous number that is the first consecutive number used to determine the trailing edge of the document sheet is greater than the leading edge continuous number that is the first consecutive number used to determine the leading edge of the document sheet. Many,
Image reading device.

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