JP2014236260A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the arrival of the leading or trailing edge of a document sheet at the reading position, by using the image data read at the reading position.SOLUTION: In an image reader 1, in order to determine whether dust, or the like, is adhering to the opposing surface of a document pressing member, the number of edge pixels of the image data obtained by reading the opposing member, when the document sheet is not conveyed to the reading position, is calculated (S4, S16), and then compared with the reference number of edge pixels (S6, S18). If the number of edge pixels thus calculated does not match the reference number of edge pixels within a specified number (S6:YES, S18:YES), a transition is made to a cleaning mode for cleaning the opposing surface of a document pressing member (S8).

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 area of an image reading unit, and more particularly, to a technique for determining whether or not the end of the original sheet has reached the reading area.

  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, for example, it is erroneously determined whether or not the image data read by the image reading unit is identification image data. Therefore, there arises a problem that it is impossible to accurately determine whether or not the leading edge or the trailing edge of the original sheet has reached the reading position that is the position of the reading range on the conveyance path.

  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. A counter unit disposed, a storage unit, and a control unit, wherein the storage unit stores a reference value serving as a reference of read image data when the image reading unit reads the counter member; The control unit instructs the conveyance unit to convey, and causes the image reading unit to start reading an image before the conveyance unit causes the original sheet to reach the reading position, and sequentially reads the read image data. Processing, sheet edge determination processing for determining 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 as the edge of the original sheet, and the image reading unit A determination process for reading a counter member, comparing the value of the read image data with the reference value, and determining whether a difference between the value of the read image data and the reference value is a predetermined value or more; and the determination When the process determines that the difference is equal to or greater than a specified value, a transition process is executed to shift to a cleaning mode for cleaning the facing member.

  In this image reading apparatus, in order to determine whether dust or the like is attached to the facing member, the value of the read image data read from the facing member is compared with a reference value when the document sheet is not conveyed to the reading position. . If the difference between the value of the read image data and the reference value is equal to or greater than a specified value, the mode is shifted to the cleaning mode. If dust or the like can be removed from the facing member by shifting to the cleaning mode, the value of the read image data read from the facing member can be made equal to the reference value within the specified value, and the facing member is read. Using the read image data, it can be determined that the leading edge or the trailing edge of the document sheet has reached the reading position.

  The image reading apparatus may further include a receiving unit, and the control unit may execute the determination process after the receiving unit receives the reading start command and before executing the reading process. .

  In this image reading apparatus, immediately before the image reading unit reads the document sheet, the image reading unit reads the opposing member, and determines whether or not the difference between the value of the read image data and the reference value is equal to or greater than a specified value. Thereby, it is possible to suppress reading of the document sheet in a state where the difference between the value of the read image data and the reference value is equal to or greater than a predetermined value, that is, in a state where dust or the like is attached to the facing member.

  In the image reading apparatus, the control unit may execute the determination process when the image reading apparatus is activated.

  In this image reading apparatus, when the power of the image reading apparatus is turned on, the image reading unit reads the facing member and determines whether or not the difference between the value of the read image data and the reference value is equal to or greater than a specified value. As a result, when the difference between the value of the read image data and the reference value is equal to or greater than the specified value and dust or the like is attached to the facing member, the power is turned on until a reading start command is input from the user. Using this period, dust and the like can be removed from the opposing member.

  In the above-described image reading apparatus, the control unit may execute the determination process after the conveyance unit stops when the reading process ends.

  When the document sheet passes through the reading position, toner, paper dust, or the like that has adhered to the document sheet may adhere to the opposing member. In this image reading apparatus, the opposing member after the original sheet has passed the reading position is read, and the value of the read image data read is compared with a reference value. Thus, when the difference between the value of the read image data and the reference value is equal to or greater than the specified value, the mode is shifted to the cleaning mode, and dust or the like attached to the facing member is removed when the document sheet passes the reading position. Can do.

  The image reading apparatus further includes a display unit and a receiving unit, and the control unit further displays an instruction or warning for prompting the display unit to clean the counter member in the cleaning mode. Cleaning display processing to be performed, and after the receiving unit receives a cleaning completion command, the image reading unit reads the counter member again, compares the value of the read image data with the reference value, A re-determination process for determining whether or not the difference between the value and the reference value is equal to or greater than a specified value may be performed.

  In this image reading apparatus, in the cleaning mode, a cleaning instruction or a warning is displayed on the display unit to urge the opposing member to be cleaned. Then, when the user is cleaned in accordance with this, and a cleaning completion command is received from the user via the receiving unit, the opposite member is read again, and the read image data value and the reference value obtained again It is determined whether or not the difference is greater than the specified value. This makes it possible to determine whether dust or the like has been removed from the opposing member.

  In the above-described image reading apparatus, the control unit further includes an exchange display process for displaying an instruction to replace the facing member on the display unit when the difference is determined to be greater than or equal to a predetermined value by the redetermination process. It may be configured to execute.

  In this image reading apparatus, when it is determined that the difference between the value of the read image data and the reference value is equal to or greater than the specified value even when the mode is changed to the cleaning mode and dust or the like is not removed from the opposing member. Then, a replacement instruction is displayed on the display unit to prompt replacement of the opposing member. If the facing member is replaced by the user in accordance with this, it is possible to determine that the leading edge or the trailing edge of the document sheet has reached the reading position using the read image data obtained by reading the replaced facing member. it can.

  In the image reading apparatus, the control unit further displays a completion display process for displaying the cleaning completion of the facing member on the display unit when it is determined that the difference is smaller than a predetermined value by the re-determination process. It is good also as composition which performs.

  In this image reading apparatus, as a result of shifting to the cleaning mode, when the value of the read image data becomes equal to the reference value within the specified value, and it is determined that no dust or the like is attached to the opposing member, the display unit displays Displays cleaning completion. Thus, the user can recognize that the original sheet can be read again using the image reading apparatus.

  In the image reading apparatus, the control unit performs the cleaning display process and the redetermination process again when the difference is determined to be greater than or equal to a predetermined value by the redetermination process, and the redetermination is performed. The cleaning display process and the re-determination process may be repeated until it is determined that the difference is smaller than a specified value.

  In this image reading apparatus, when it is determined that the difference between the value of the read image data and the reference value is equal to or greater than the specified value even when the mode is changed to the cleaning mode and dust or the like is not removed from the opposing member. Then, the cleaning display process and the redetermination process are repeated to make the value of the read image data equal to the reference value within the specified value. Thus, it can be determined that the leading edge or the trailing edge of the document sheet has reached the reading position using the read image data obtained by reading the facing member.

  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 image reading process 7 is a flowchart showing processing in the cleaning mode of the first embodiment. Flow chart showing the reading process Flow chart showing rear end detection processing Graph showing the number of edge pixels in scanned image data 10 is a flowchart showing processing in the cleaning mode of the second embodiment.

<Embodiment 1>
The first 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. 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. In the paper feed roller 40 and the transport roller 44, a so-called one-way clutch mechanism is configured using the difference in the transport speed. That is, even if a central processing unit (hereinafter referred to as CPU) 20 to be described later does not recognize the original size of the original sheet G, the distance between originals of the original sheet G that is continuously conveyed according to the original size of the original sheet G. Is configured.

  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 32 (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 each LED 32 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 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.

  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. . The image reading apparatus 1 includes a power switch 16 and various setting buttons, and includes an operation unit 11 that receives various commands 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. 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. The operation unit 11 is an example of a receiving unit.

2. As shown in FIG. 2, the image reading apparatus 1 includes an ASIC (Application Specific Integrated Circuit) 29, a ROM 26, a RAM 27, an NVRAM 28, a low-voltage power supply unit 24, a power supply unit 25, and the like. The image reading unit 30, the operation unit 11 and the like are connected to these. As indicated by a one-dot chain line 17 in FIG. 2, the ASIC 29, the ROM 26, the RAM 27, the NVRAM 28, and the power supply unit 25 are provided on the same substrate. 2 includes an ASIC 29, a ROM 26, a RAM 27, and an NVRAM 28 as an example of a 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 a power switch detection circuit 22 and an 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 nonvolatile memory, stores reference values such as a reference edge pixel number, a reference maximum pixel number, and a reference peak luminance. These reference values are reference values used for image reading processing, and details thereof will be described later.

  The low-voltage power supply unit 24 is connected to the AC100V power supply by the user, converts the power supplied from the power supply by the AC100V to the DC100V, for example, based on an instruction from the power switch detection circuit 22, and outputs it to the power supply unit 25 and the like. To do. The power supply unit 25 converts DC6V power supplied from the low-voltage power supply unit 24 into, for example, DC3.3V power, and outputs the power to the ASIC 29, the image reading unit 30, and the like.

  The power switch detection circuit 22 is connected to the power switch 16 of the operation unit 11, and a start command for turning on the power of the image reading device 1 from the user via the power switch 16 or the power switch detection circuit 22 of the image reading device 1. It is detected whether or not a stop command for turning off the power is input. The power switch detection circuit 22 is also connected to the low-voltage power supply unit 24, and outputs a signal permitting the power supply to the power supply unit 25 to the low-voltage power supply unit 24 when a start command is input from the user. To do. When a stop command is input from the user, the low-voltage power supply unit 24 outputs a signal that causes the low-voltage power supply unit 24 to stop supplying power to the power supply unit 25.

  Based on a command from the CPU 20, the image reading unit 30 turns on the LEDs 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 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. Further, the image processing circuit 23 performs a distribution generation process for generating a histogram which is a luminance distribution of each pixel data included in the read image data stored in the RAM 27, and the maximum pixel number of the histogram and the maximum pixel number Extract peak luminance.

3. Image Reading Process Next, the reading process of the original sheet G will be described with reference to FIGS. When the CPU 20 detects that the activation command is input from the user using the power switch detection circuit 22, the CPU 20 outputs a signal permitting the power supply to the power supply unit 25 to the low-voltage power supply unit 24 and the image reading apparatus. 1 is turned on and the image reading process is started.

  As shown in FIG. 3, when the image reading process is started, the CPU 20 first executes a determination process (S2 to S6) for determining whether dust or the like is attached to the facing surface 46A of the document pressing member 46. . In the determination 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). As a result, the image reading unit 30 reads the facing surface 46 </ b> A of the document pressing member 46 once, and the read image data is stored in the RAM 27.

  Next, the CPU 20 performs edge extraction processing on the read image data stored in the RAM 27 in S2 by using the image processing circuit 23, and calculates the number of edge pixels of the read image in the read image data (S4). . The CPU 20 compares the calculated number of edge pixels with the reference number of edge pixels stored in the NVRAM 28 (S6). The number of edge pixels calculated in S4 is an example of the value of the read image data.

  Here, the reference edge pixel number is the number of edge pixels 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. That is, the reference edge pixel number is the number of edge pixels acquired in the initial stage of use of the image reading apparatus 1 and with little dust or the like adhering to the facing surface 46A of the document pressing member 46. Therefore, the reference edge pixel number can be used as a reference for determining whether dust or the like is attached to the facing surface 46A of the document pressing member 46. The reference edge pixel number is an example of a reference value.

  The CPU 20 confirms whether or not the calculated number of edge pixels is greater than a specified number than the reference edge pixel number stored in the NVRAM 28. The specified number (see the lower diagram in FIG. 7) is an example of a specified value, and means an allowable range of dust or the like adhering to the facing surface 46A of the document pressing member 46. The prescribed number is determined based on, for example, the difference between the reflectance of the facing surface 46A of the document pressing member 46 and the reflectance of the white document sheet G. When the difference between the calculated number of edge pixels and the reference edge pixel number is equal to or greater than the specified number (S6: YES), the CPU 20 attaches an excessive amount of dust or the like to the facing surface 46A of the document pressing member 46. Therefore, the process proceeds to the cleaning mode for cleaning the facing surface 46A of the document pressing member 46 (S8).

(Cleaning mode)
As shown in FIG. 4, in the cleaning mode, the CPU 20 first instructs the display unit 12 to display “Please clean the document pressing member because it is dirty”, and the user presses the document pressing member 46. The cleaning of the facing surface 46A is urged (S32). After the display, the CPU 20 waits for the user to clean the facing surface 46A of the document pressing member 46 and to input a cleaning completion report from the user via the operation unit 11 (S34). The cleaning completion report is an example of a cleaning completion instruction.

  CPU20 continues said display until the report of cleaning completion is input from the user (S34: NO). When a cleaning completion report is input from the user (S34: YES), the CPU 20 executes redetermination processing (S36 to S40). The re-determination process (S36 to S40) is substantially the same process as the above-described determination process (S2 to S6). In the re-determination process (S36 to S40), the CPU 20 reads the facing surface 46A of the document pressing member 46 again (S36), recalculates the number of edge pixels (S38), and uses the recalculated number of edge pixels as the reference edge. The number of pixels is compared (S40).

  If the difference between the recalculated number of edge pixels and the reference edge pixel number is greater than or equal to the specified number (S40: YES), it can be seen that the number of edge pixels has not decreased even after cleaning. That is, it can be seen that dust or the like was not removed from the facing surface 46A of the document pressing member 46 even by cleaning. In this case, the CPU 20 instructs the display unit 12 to display “Please replace the document pressing member”, and prompts the user to replace the document pressing member 46 (S42). Exit.

  In addition, when the difference between the recalculated number of edge pixels and the reference edge pixel number is smaller than the specified number (S40: NO), it can be seen that the number of edge pixels has decreased due to cleaning. That is, it can be seen that dust or the like has been removed from the facing surface 46A of the document pressing member 46 by cleaning. In this case, the CPU 20 instructs the display unit 12 to display “cleaning completed” to notify the user that the cleaning of the document pressing member 46 has been completed (S44), and ends the cleaning mode.

  On the other hand, in the image reading process shown in FIG. 3, the CPU 20 determines that the difference between the number of edge pixels calculated in S4 and the reference edge pixel number is smaller than the specified number (S6: NO), or the document pressing member in the cleaning mode. When dust or the like is removed from the facing surface 46A of 46, it waits for an input of a reading start instruction for the original sheet G from the user via the operation unit 11 (S10: NO). When it is confirmed that the original sheet G is placed on the paper feed tray 2 using the F sensor 13 and an image reading command for the original sheet G is input from the user via the operation unit 11, the CPU 20 Then, the reading process is executed (S12).

(Reading process)
As shown in FIG. 5, in the reading process, the CPU 20 first executes a determination process (S52 to S56). The determination processing (S52 to S56) is substantially the same processing as the above-described determination processing (S2 to S6). The CPU 20 executes the determination process (S52 to S56) before executing the conveyance reading process (S62 to S82) in which the document sheet G is conveyed to the conveyance unit 15 and the image reading unit 30 reads the document sheet G. The conveyance reading process is an example of a reading process.

  In the determination process (S52 to S56), the CPU 20 causes the facing surface 46A of the document pressing member 46 to be read again (S52), calculates the number of edge pixels again (S54), and calculates the calculated number of edge pixels as the reference edge pixel number. (S56). When the difference between the calculated edge pixel number and the reference edge pixel number is equal to or larger than the specified number (S56: YES), the CPU 20 shifts to the cleaning mode (S58). On the other hand, when the difference is smaller than the specified number (S56: NO), or when dust or the like is removed from the facing surface 46A of the document pressing member 46 in the cleaning mode, the CPU 20 calculates the number of edge pixels calculated immediately before. The number of reference edge pixels is stored in the RAM 27 (S60).

  That is, when the difference between the calculated edge pixel number and the reference edge pixel number is smaller than the specified number (S56: NO), the CPU 20 stores the edge pixel number calculated in S54 in the RAM 27 (S60). Further, when dust or the like can be removed from the facing surface 46A of the document pressing member 46 in the cleaning mode, the CPU 20 stores the number of edge pixels calculated in S38 of the cleaning mode in the RAM 27. When the CPU 20 stores the reference edge pixel number in the RAM 27, the CPU 20 executes a conveyance reading process (S62 to S82).

  In the conveyance reading process (S62 to S82), the CPU 20 instructs the conveyance unit 15 to convey the original sheet G, and starts conveying the original sheet G (S62). Next, the CPU 20 executes document presence / absence detection processing (S64 to S68) for detecting the presence / absence of the document sheet G from the read image data acquired by the image reading unit 30. In the document presence / absence detection process, the presence or absence of the document sheet G is detected by detecting the leading edge of the conveyed document sheet G in the transport direction D2 using the read image data acquired by the image reading unit 30. It can be called detection processing. The document presence / absence detection process is an example of a sheet edge determination process.

  In the document presence / absence detection process, the CPU 20 instructs the image reading unit 30 to turn on the green LED 32G and instructs one line to be read (S64). As a result, the image reading unit 30 starts reading before the leading edge of the document sheet G in the transport direction D2 reaches the reading position P1, and acquires the read image data of the facing surface 46A of the document pressing member 46.

  Next, the CPU 20 performs edge extraction processing on the read image data stored in the RAM 27 in the immediately preceding S64 using the image processing circuit 23, and calculates the number of edge pixels of the read image in the read image data ( S66). 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.

  The CPU 20 compares the calculated number of edge pixels with the reference edge pixel number stored in the RAM 27 (S68), and checks 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. To do. The threshold (see FIG. 7) is an example of a predetermined value, and is set separately from the specified number. When the difference between the calculated edge pixel number and the reference edge pixel number is smaller than the threshold value (S68: NO), the CPU 20 reads the read image data stored in the RAM 27 in S64 on the facing surface 46A of the document pressing member 46. It is determined that the read image data is obtained by reading. That is, the CPU 20 determines that the leading edge of the document sheet G has not reached the reading position P1 and has not detected the leading edge of the document sheet G, and repeats the processing from S64.

  On the other hand, when the difference between the calculated number of edge pixels and the number of reference edge pixels is larger than the threshold value (S68: YES), the CPU 20 reads the read image data stored in the RAM 27 in S64 as the facing surface 46A of the document pressing member 46. It is determined that the read image data obtained by reading the original sheet G is switched to the 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 and has detected the leading edge of the document sheet G at the timing when the read image data is read, and the document is read from the image reading unit 30. The start of reading of the sheet G is instructed (S70).

  When the CPU 20 starts reading the original sheet G, it instructs to read one line every predetermined time (S72). 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 (S74). The trailing edge detection process is another example of the sheet edge determination process.

(Rear edge detection process)
As shown in FIG. 6, in the trailing edge detection process, the CPU 20 first performs edge extraction processing on the read image data of each color stored in the RAM 27 in S72 using the image processing circuit 23, and reads each color. The number of edge pixels of the read image in the image data is calculated (S92).

  Next, the CPU 20 compares the calculated number of edge pixels of each color with the number of reference edge pixels stored in the RAM 27 (S94), and whether the calculated number of edge pixels of each color is greater than the reference edge pixel number by a threshold value or more. Confirm. When the difference between the calculated number of edge pixels of all colors and the number of reference edge pixels is equal to or larger than the threshold value (S94: YES), the CPU 20 reads the original sheet G as the read image data stored in the RAM 27 in S72. It is determined that the image data is read image data. 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 (S96), and ends the trailing edge detection process.

  On the other hand, if the difference between the calculated number of edge pixels of at least one color and the number of reference edge pixels is smaller than the threshold value (S94: NO), the read image data stored in the RAM 27 in S72 reads the original sheet G. 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, at the timing when the read image data is read, the CPU 20 determines that the trailing edge of the document sheet G has reached the reading position P1 and has detected the trailing edge of the document sheet G (S98), and detects the trailing edge. The process ends.

  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 (S76). CPU20 repeats the process from S72, when a rear end is not detected (S76: NO).

  On the other hand, when the trailing edge is detected (S76: YES), the CPU 20 instructs the image reading unit 30 to stop reading the document sheet G (S78). Next, the CPU 20 checks the state of the F sensor 13 (S80), and if the F sensor 13 is on (S80: YES), that is, if the original sheet G remains in the paper feed tray 2. , The process from S64 is repeated. On the other hand, when the F sensor 13 is off (S80: NO), the conveyance unit 15 is instructed to stop conveyance of the original sheet G (S82), and the reading process is terminated.

  After completion of the reading process, the CPU 20 executes a determination process (S14 to S18) in the image reading process shown in FIG. The determination processing (S14 to S18) is substantially the same processing as the above-described determination processing (S2 to S6). In the determination process (S14 to S18), the CPU 20 reads the facing surface 46A of the document pressing member 46 after the document sheet G is conveyed (S14), calculates the number of edge pixels (S16), and calculates the calculated edge. The number of pixels is compared with the number of reference edge pixels (S18). When the difference between the calculated edge pixel number and the reference edge pixel number is equal to or larger than the specified number (S18: YES), the CPU 20 shifts to the cleaning mode (S8).

  On the other hand, when the difference between the calculated edge pixel number and the reference edge pixel number is smaller than the prescribed number (S18: YES), the CPU 20 determines whether or not a stop command is input from the user using the power switch detection circuit 22. Is confirmed (S20). CPU20 repeats the process from S10, when the stop command is not input (S20: NO).

  On the other hand, when a stop command is input (S20: YES), the CPU 20 outputs a signal for stopping the supply of power to the power supply unit 25 to the low-voltage power supply unit 24 to turn off the power of the image reading apparatus 1. Then, the image reading process ends.

4). Advantages of the present embodiment (1) In the image reading apparatus 1 of the present embodiment, the original sheet G is conveyed to the reading position in order to determine whether or not the facing surface 46A of the original pressing member 46 needs to be cleaned. If not, the facing surface 46A of the document pressing member 46 is read. Then, the number of edge pixels calculated from the acquired read image data is compared with the reference number of edge pixels stored in the NVRAM 28.

  As shown in the upper diagram of FIG. 7, in the initial stage of use of the image reading apparatus 1, the amount of dust and the like adhering to the facing surface 46 </ b> A of the document pressing member 46 is relatively small. The number of edge pixels is almost the same. Therefore, even if the number of edge pixels calculated immediately before reading the document sheet G is set as the reference edge pixel number and an upper limit value larger than the reference edge pixel number by a threshold is set, the read image data read from the document sheet G There is a sufficient difference between the number of edge pixels calculated from the above and the upper limit value.

  Therefore, as shown by a mark 54 in FIG. 7, 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 has an upper limit value. It did not happen to fall below. Further, since the amount of dust or the like adhering to the facing surface 46A of the document pressing member 46 is 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 exceeds the upper limit value. Never exceeded.

  However, as shown by the arrow 62, as the usage period of the image reading apparatus 1 becomes longer, dust or the like adhering to the facing surface 46A of the document pressing member 46 increases and is calculated as shown in the lower diagram of FIG. The number of edge pixels and the number of reference edge pixels (see the two-dot chain line in FIG. 7) do not match within the specified number. As a result, when the reference edge pixel number and the upper limit value are set based on the edge pixel number, the difference between the edge pixel number calculated from the read image data obtained by reading the document sheet G and the upper limit value becomes small.

  Therefore, as indicated by a mark 56 in FIG. 7, depending on the pattern described on the original sheet G, the number of edge pixels calculated from the read image data obtained by reading the original sheet G falls below the upper limit, and the edge pixel At the timing when the read image data whose number is calculated is acquired, there is a problem in that it is erroneously determined that the trailing edge of the original sheet G has reached the reading position P1. Further, as indicated by a mark 58 in FIG. 7, an edge calculated from read image data obtained by reading the facing surface 46 </ b> A of the document pressing member 46 due to irregular reflection due to dust or the like adhering to the facing surface 46 </ b> A of the document pressing member 46. There has been a problem in that it is erroneously determined that the leading edge of the original sheet G has reached the reading position P1 at the timing when the number of pixels exceeds the upper limit and the read image data for which the number of edge pixels is calculated is acquired. .

  In the image reading apparatus 1 of the present embodiment, when the calculated number of edge pixels and the number of reference edge pixels do not match within a specified number, the mode shifts to a cleaning mode for cleaning the facing surface 46A of the document pressing member 46. . If dust or the like can be removed from the facing surface 46A of the document pressing member 46 by shifting to the cleaning mode, the calculated edge pixel number and reference edge pixel number are defined as shown in the upper diagram of FIG. Can be equal in number. That is, a sufficient difference can be ensured between the number of edge pixels calculated from the read image data obtained by reading the document sheet G and the upper limit value, and the leading edge and the trailing edge of the document sheet G are read using the read image data. Can be determined to have reached the reading position.

  (2) The determination as to whether or not the facing surface 46A of the document pressing member 46 needs to be cleaned may be performed before the document sheet G is read or may be performed after the document sheet G is read. The determination is performed before reading the original sheet G, so that it is determined that there is no need for cleaning, that is, the opposed surface 46A of the original pressing member 46 that is determined not to have much dust or the like attached thereto. The original sheet G can be read, and it can be determined by using the read image data that the leading edge or the trailing edge of the original sheet G has reached the reading position.

  In particular, since the determination as to whether or not the facing surface 46A of the document pressing member 46 needs to be cleaned is executed immediately before reading the document sheet G, the document pressing unit 46 can be compared with a case where the elapsed time from the determination is long. It is possible to reliably suppress reading of the document sheet G in a state where dust or the like is attached to the facing surface 46A of the member 46. In addition, since the determination is performed when the image reading apparatus 1 is started, if dust or the like is attached to the facing surface 46A of the document pressing member 46, the image reading apparatus 1 starts the reading from the user. Using the period until the start command is input, dust and the like can be removed from the facing surface 46A of the document pressing member 46.

(3) The determination as to whether or not the facing surface 46A of the document pressing member 46 needs to be cleaned may be performed after reading the document sheet G. In reading the original sheet G, the original sheet G is conveyed after passing through the reading position P1, so that the toner, paper dust, etc. adhering to the original sheet G become dust or the like on the opposing surface 46A of the original pressing member 46. May adhere. In some cases, dust or the like attached to the facing surface 46A of the document pressing member 46 is easier to remove as the elapsed time from the attachment is shorter. In the image reading apparatus 1 of the present embodiment, the above determination is performed even after reading the document sheet G, so that when dust or the like adheres to the facing surface 46A of the document pressing member 46, the dust or the like is quickly removed. Can be removed.

(4) In the image reading apparatus 1 of the present embodiment, in the cleaning mode, the display unit 12 is displayed to prompt the cleaning of the facing surface 46A of the document pressing member 46, and the user cleans the facing surface 46A of the document pressing member 46. Let However, even if the facing surface 46A of the document pressing member 46 is cleaned by the user, dust or the like is not necessarily removed from the facing surface 46A of the document pressing member 46, and the facing of the document pressing member 46 is not performed. If the surface 46A is scratched, it cannot be removed by cleaning.

  In this image reading apparatus 1, when a cleaning completion report is input from the user, the opposite surface 46 A of the document pressing member 46 is read again, and the number of edge pixels calculated from the read image data acquired again is used as the reference edge. Compare with the number of pixels. That is, it is determined again whether or not the facing surface 46A of the document pressing member 46 needs to be cleaned. Thereby, it is possible to determine whether dust or the like has been removed from the facing surface 46 </ b> A of the document pressing member 46.

(5) When it is determined that dust or the like has been removed from the facing surface 46A of the document pressing member 46, the completion of cleaning of the facing surface 46A of the document pressing member 46 is displayed on the display unit 12. Accordingly, the user can recognize that the original sheet G can be read again by using the image reading apparatus 1.

(6) On the other hand, for example, the facing surface 46A of the document pressing member 46 is scratched, and the number of edge pixels calculated from the read image data acquired again is not reduced. When it is determined that dust or the like has not been removed, the display unit 12 is displayed to prompt the user to replace the document pressing member 46, and the user is allowed to replace the document pressing member 46. If the document pressing member 46 is replaced by the user accordingly, it can be determined that the leading edge or the trailing edge of the document sheet has reached the reading position using the read image data.

<Embodiment 2>
A second embodiment will be described with reference to FIG. In the present embodiment, the processing in the cleaning mode is different from that in the first embodiment. In the following description, the same description as that of the first embodiment will not be repeated.

1. Image reading process (cleaning mode)
In the cleaning mode, the CPU 20 performs a display process (S32) for instructing the display unit 12 to display “Please clean the document pressing member because it is dirty”, a re-determination process (S36 to S40), and the like. Execute. If the difference between the number of edge pixels recalculated in the re-determination process (S36 to S40) and the reference edge pixel number is greater than or equal to the specified number (S40: YES), the process from S32 is repeated, and the display process ( S32) and the re-determination process (S36 to S40) are repeated.

  The CPU 20 repeats the display process (S32), the re-determination process (S36 to S40), etc. until the difference between the recalculated number of edge pixels and the reference edge pixel number is smaller than the specified number, The cleaning of the facing surface 46A of the pressing member 46 is repeated. When the difference between the recalculated number of edge pixels and the number of reference edge pixels is smaller than the specified number (S40: NO), the display unit 12 is instructed to display “cleaning complete”, and the cleaning mode ends.

2. Effects of the Present Embodiment In the image reading apparatus 1 of the present embodiment, in the cleaning mode, when it is determined that dust or the like has not been removed from the facing surface 46A of the document pressing member 46 after cleaning by the user, display processing is performed. And the re-determination process is repeated, and the user is made to clean again. Some dust or the like adhering to the facing surface 46A of the document pressing member 46 cannot be removed by one or two cleanings, but can be removed by repeated cleaning.

  In this image reading apparatus 1, when it is determined that dust or the like has not been removed from the facing surface 46A of the document pressing member 46, the user is caused to repeat cleaning. Accordingly, dust or the like can be reliably removed from the facing surface 46A of the document pressing member 46, and it can be determined that the leading edge or the trailing edge of the document sheet G has reached the reading position using the read image data. .

<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 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, in the cleaning mode, an example of displaying on the display unit 12 a message “Please clean the document pressing member because it is dirty”, that is, an instruction to the user is used. Although described, the present invention is not limited to this. For example, an indication that “the original sheet cannot be read because the original pressing member is dirty”, that is, a warning to the user may be displayed.

(5) Although the above embodiment has been described using an example in which the user cleans in the cleaning mode, the present invention is not limited to this. For example, when the image reading apparatus 1 is provided with a mechanism for cleaning the facing surface 46A of the document pressing member 46, the mechanism may be used for cleaning.

(6) In the above embodiment, the description will be given using an example in which the determination process is executed in three cases: when the image reading apparatus 1 is activated, when a reading command is input from the user, and after the reading process is completed. Although done, the present invention is not limited to this. The determination process may be executed in at least one of the above three cases. That is, it may be executed only before reading the original sheet G or may be executed only after reading the original sheet G.

(7) In the above embodiment, the number of edge pixels is calculated from the read image data and the reference edge pixel number stored in the NVRAM 28 to determine whether or not the facing surface 46A of the document pressing member 46 needs to be cleaned. However, the present invention is not limited to this. For example, the maximum number of pixels in the histogram and the peak luminance at the maximum number of pixels may be calculated from the read image data using the image processing circuit 23 and compared with the reference maximum number of pixels and the reference peak luminance stored in the NVRAM 28.

  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 and the peak luminance that are acquired in the initial stage of use of the image reading apparatus 1 and in a state where dust or the like is not attached to the facing surface 46A of the document pressing member 46. It is. The reference maximum pixel number and the reference peak luminance are other examples of the reference value.

DESCRIPTION OF SYMBOLS 1: Image reading apparatus, 11: Operation part, 12: Display part, 13: F sensor, 15: Conveyance part, 16: Power switch, 22: Conveyance path, 22: Power switch detection circuit, 23: Image processing circuit, 24 : Low voltage power supply unit, 25: Power supply unit, 30: Image reading unit, 40: Paper feed roller, 44: Transport roller, 46: Document pressing member, 46A: Opposing surface, 48: Transport path, 50: Paper discharge roller, 52: Projection, D1: Main scanning direction, D2: Conveying direction

Claims (8)

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 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
A reading process for instructing conveyance to the conveyance unit, causing the image reading unit to start reading an image before the conveyance unit reaches the reading position of the document sheet, and sequentially acquiring read image data;
Sheet edge determination processing for determining the position of the read image data at which the value of the read image data acquired by the reading process has changed by a predetermined value or more as the edge of the document sheet;
The image reading unit is caused to read the facing member, and the value of the read image data is compared with the reference value to determine whether the difference between the value of the read image data and the reference value is equal to or greater than a specified value. Judgment processing,
When the determination process determines that the difference is equal to or greater than a specified value, a transition process for shifting to a cleaning mode for cleaning the opposing member;
An image reading apparatus that executes The image reading apparatus according to claim 1,
Furthermore,
Receiver,
With
The control unit is an image reading apparatus that executes the determination process after the receiving unit receives a reading start command and before executing the reading process. The image reading apparatus according to claim 1, wherein:
The control unit is an image reading device that executes the determination process when the image reading device is activated. An image reading apparatus according to any one of claims 1 to 3,
The image reading apparatus, wherein the control unit executes the determination process after the conveyance of the conveyance unit is stopped due to the end of the reading process. An image reading apparatus according to any one of claims 1 to 4,
Furthermore,
A display unit;
A receiver,
With
In the cleaning mode, the control unit
Furthermore,
An instruction for prompting cleaning of the facing member on the display unit, or a cleaning display process for displaying a warning,
After the receiving unit receives a cleaning completion command, the image reading unit reads the counter member again, compares the value of the read image data with the reference value, and compares the value of the read image data with the reference value. A re-judgment process to determine whether the difference is greater than or equal to a specified value;
An image reading apparatus that executes The image reading apparatus according to claim 5,
The controller is
Furthermore,
If the re-determination process determines that the difference is greater than or equal to a specified value, an exchange display process for displaying an instruction to replace the opposing member on the display unit;
An image reading apparatus that executes The image reading apparatus according to claim 5,
The controller is
Furthermore,
When it is determined by the redetermination process that the difference is smaller than a specified value, a completion display process for displaying the completion of cleaning of the facing member on the display unit;
An image reading apparatus that executes The image reading apparatus according to claim 5,
The controller is
If the redetermination process determines that the difference is equal to or greater than a specified value, the cleaning display process and the redetermination process are executed again, and the cleaning display is performed until the redetermination process determines that the difference is smaller than the specified value. An image reading apparatus that repeats the process and the re-determination process.

Images