JP2015026974A - Image reader and rear end decision program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the number of excessive lines being read during a time from read start timing to rear end decision timing, with the decision of a rear end.SOLUTION: After starting read processing, a scanner 1 executes delay processing for delaying the carriage speed of an ADF 5 before the rear end of a manuscript sheet M reaches a read position X2 to elongate a line period, so that the number of lines read per unit time is decreased as compared to a state before the delay processing is executed. This enables a suppressed number of excessive lines read during the time from the read start timing to the rear end decision timing, with the decision of the rear end, as compared to the prior configuration having a constant carriage speed and line period during the time from the read start timing to the rear end decision timing of the image of the manuscript sheet.

Description

  The present invention relates to a technique for conveying an original sheet toward a predetermined reading position and reading an image on the original sheet at a reading position by a reading unit.

  There is an image reading apparatus of a type that conveys an original sheet and reads an image on the original sheet at a reading position on a conveyance path by a reading unit. An image reading apparatus as an example includes a document pressing plate disposed opposite to a 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 is provided on the document pressing plate. It is drawn. Then, the image reading apparatus sequentially reads images in predetermined line units at the reading position by the reading unit, and determines whether or not the data of each read line matches the data of the identification image. The position where the determination result is changed is determined to be the rear end of the original sheet on the read image, in other words, the rear end of the original sheet has reached the reading position (see Patent Document 1). The determination result of the trailing edge is used, for example, for determining the image size of the document in the read image.

JP 2004-120425 A

  By the way, in the image reading apparatus, for example, due to the processing speed, the read image is actually read from the trailing edge of the document sheet with respect to the trailing edge reading timing when the reading unit reads the trailing edge of the document sheet at the reading position. The rear end determination timing determined to be is delayed. For this reason, during this delay time, an extra line after the original sheet passes the reading position is read. In addition, the conventional image reading apparatus is configured to always read an image at a constant conveyance speed and line cycle from the reading start timing of the original sheet image to the trailing edge determination timing. For this reason, there is a possibility that a relatively large number of extra lines may be read.

  The present specification discloses a technique capable of suppressing the number of extra lines read between the read start timing and the rear end determination timing while performing the rear end determination.

  An image reading apparatus disclosed in this specification includes a transport unit that performs a transport operation for transporting a document sheet toward a predetermined reading position, and an image for each line along the main scanning direction at the reading position. A reading unit that performs a reading operation; a counter member that is disposed to face the reading unit at the reading position; and a control unit, wherein the control unit performs a transport operation on the transport unit, and reads the read unit. A reading process that sequentially acquires a read image for each line, and after the start of the reading process, before the trailing edge of the document sheet in the conveyance direction of the conveyance unit reaches the reading position. Between the delay process that slows down the transport speed of the transport operation in the process and lengthens the reading cycle of the read operation, and the read image for each line acquired after the execution of the delay process, the value of the image is the opposite Element A rear end that determines that the position on the changed image is the rear end of the original sheet on the read image by the reading unit when the reference value is changed from outside the reference range including the image value to the reference range. And a determination process.

  According to this image reading apparatus, after the reading process is started and before the trailing edge of the original sheet reaches the reading position, a delay process is performed to slow down the conveying speed of the conveying unit and increase the reading cycle. The number of lines read per unit time is smaller than that before execution of the delay process. Therefore, compared with the conventional configuration in which the conveyance speed and the line cycle are constant from the reading start timing of the original sheet image to the trailing edge determination timing, the trailing edge determination is performed from the reading start timing while performing the trailing edge determination. It is possible to suppress the number of extra lines read until the timing.

  In the image reading apparatus, in the reading process, the control unit causes the reading unit to perform a reading operation before the conveyance unit reaches the reading position, and before the delay process is performed. When the value of the image changes between the acquired read images for each line from the reference range to the outside of the reference range, the changed position on the image is determined on the original sheet on the read image. You may have the structure which performs the front-end | tip determination process determined to be a front-end | tip.

  According to this image reading apparatus, the leading edge of the original sheet on the read image can be determined from the read image for each line acquired from the reading unit.

  In the image reading apparatus, the control unit further obtains the dimension in the main scanning direction of the original sheet from the read image for each line acquired in the reading process, and calculates one side of the dimension in the main scanning direction. And having a determination process of determining the shortest dimension as the dimension in the transport direction among the other sides of the fixed size having, and in the delay process, the leading edge of the original sheet is determined by the leading edge determination process. From the determined time point, when the original sheet is transported by a distance corresponding to the dimension in the transport direction determined in the determination process, the transport speed of the transport operation in the reading process is decreased, and the reading cycle of the read operation May be lengthened.

  According to this image reading apparatus, the delay process is executed when the document sheet is conveyed by a distance corresponding to the dimension in the conveyance direction of the document sheet from the time when it is determined that the leading edge is the document sheet. For this reason, it is possible to start the delay process for the document sheet from an appropriate position corresponding to the dimension in the conveyance direction.

  In the image reading apparatus, the transport unit, the control unit, in the delay process, the document sheet of the document sheet that can be transported by the transport unit from the time when the leading edge determination process determines that it is the leading edge of the document sheet. When the original sheet is conveyed by a distance corresponding to the minimum dimension in the conveyance direction, the conveyance speed of the conveyance operation in the reading process may be slowed down and the reading cycle of the reading operation may be lengthened.

  According to this image reading apparatus, as long as a document sheet of any size can be conveyed as long as it can be conveyed by the image reading apparatus, the trailing edge determination is performed and the period between the reading start timing and the trailing edge determination timing is determined. It is possible to suppress the number of extra lines to be read.

  In the image reading apparatus, the transport unit sequentially transports a plurality of document sheets one by one, and the control unit determines from the determination results of the leading edge determination process and the trailing edge determination process for one document sheet, A transport direction dimension determining process for determining a dimension of the one document sheet in the transport direction; and in the delay process, for the other document sheet transported after the one document sheet, the leading edge When the document sheet is transported by a distance corresponding to the dimension in the transport direction from the time when it is determined in the determination process that the leading edge of the document sheet, the transport speed of the transport operation in the reading process is slowed down, The reading cycle of the reading operation may be lengthened.

  According to this image reading apparatus, by using the measured value of the dimension in the conveyance direction of one original sheet, the other original sheet thereafter is appropriately determined from the time when it is determined as the front end of the original sheet by the front end determination process. The conveyance speed can be reduced at a proper timing.

  The present invention can be realized in various modes such as an image reading apparatus, an image reading method, a computer program for realizing the functions of these methods or apparatuses, and a recording medium on which the computer program is recorded.

  According to the invention disclosed in this specification, it is possible to suppress the number of extra lines read between the read start timing and the rear end determination timing while performing the rear end determination.

1 is a schematic configuration diagram of a scanner according to an embodiment. Enlarged view showing the reading section and document holding member in a simplified manner Block diagram showing the electrical configuration of the scanner Flow chart showing reading control processing Flow chart showing tip determination processing Flow chart showing intermediate reading process Flow chart showing rear end determination / reading process

<One Embodiment>
A scanner 1 according to an embodiment will be described with reference to FIGS. The scanner 1 is an example of an image reading device. In the following description, the left side of FIG. 1 is the front side (F) of the scanner 1, the front side of the paper is the right side (R) of the scanner 1, and the upper side of the paper is the upper side (U) of the scanner 1.

(Mechanical structure of the scanner)
As shown in FIG. 1, a scanner 1 includes a case 2, a document tray 3, a discharge tray 4, an automatic document feeder (hereinafter referred to as "ADF") 5, a reading unit 6, a document pressing member 7, a front sensor 8, and the like. Prepare.

  Specifically, the document tray 3 is provided in the opening on the rear surface of the case 2, and one or a plurality of document sheets M can be arranged on the document tray 3. The document sheet M is not limited to paper, but may be made of plastic such as an OHP sheet. A front sensor 8 is provided on the front end side of the document tray 3. The front sensor 8 is a document presence / absence sensor that detects the presence / absence of the document sheet M on the document tray 3 at the detection position X1 set on the front end side of the document tray 3, and transmits the detection result to the control unit 21. . A discharge tray 4 is provided on the upper surface side of the case 2, and one or a plurality of document sheets M are discharged to the discharge tray 4.

  The ADF 5 is an example of a transport unit, and performs a transport operation for transporting the document sheet M on the document tray 3 toward a predetermined reading position X2. Specifically, the ADF 5 includes a separation roller 5A, a separation pad 5B, a plurality of conveyance rollers 5C, a plurality of driven rollers 5D that are driven in pressure contact with the respective conveyance rollers 5C, and a guide unit (not shown) for guiding the document sheet M. Etc.

  The separation roller 5A and the conveyance roller 5C are rotationally driven by a stepping motor 5E described later. Thus, the separation roller 5A and the separation pad 5B separate the plurality of document sheets M on the document tray 3 one by one and send them out into the transport path R. The conveyance roller 5 </ b> C conveys the separated document sheet M in a U-shape along the conveyance path R and discharges it onto the discharge tray 4. Hereinafter, the direction in which the ADF 5 transports the original sheet M along the transport path R is simply referred to as a transport direction.

  The ADF 5 continuously executes the continuous transfer operation from the reception of the transfer start command from the control unit 21 until the transfer stop command is received. In this continuous conveyance operation, a plurality of document sheets M on the document tray 3 are separated one by one, the document sheets M are continuously conveyed along the conveyance path R, and sequentially discharged to the discharge tray 4. It is.

  The reading unit 6 is a reading device having a CIS (Contact Image Sensor). The reading unit 6 sequentially reads a line-like image (an example of a read image for each line) along the main scanning direction (left-right direction) orthogonal to the conveyance direction at the reading position X2 on the conveyance path R. Data of the pixel column of the line is transmitted to the control unit 21. Hereinafter, the pixel column data of each line is referred to as line data. Further, an image density value (image value) indicated by each pixel constituting the pixel column is referred to as a pixel value, and the pixel value is, for example, a value in a range of 0 to 255. ) Is high.

  Each transmitted line data is AD converted by an AD converter (not shown) included in the controller 21. The specific configuration of the reading unit 6 and the arrangement relationship with the document pressing member 7 will be described later. In addition, the reading unit 6 is not limited to the CIS, and may be configured to have, for example, a CCD (Charge Coupled Drive Image Sensor).

  The document pressing member 7 is an example of a facing member, and is disposed to face the reading unit 6 via the transport path R at the reading position X2. Of the document pressing member 7, the facing surface 7A facing the reading unit 6 is, for example, white, and the document pressing member 7 functions as a white reference member. Note that the facing surface 7A is not necessarily white, and may be another color such as gray.

(Configuration of reading unit and document holding member)
FIG. 2 schematically shows the configuration of the reading unit 6 and the document pressing member 7. In the drawing, the light paths of the light beams LR, LG, and LB of each color are schematically illustrated so that they can be distinguished, and the range of the reading position X2, which is an irradiation range thereof, is also illustrated. Further, FIG. 6 shows a state in which the light beams LR, LG, LB of each color are reflected by the facing surface 7 A of the document pressing member 7.

  As shown in the figure, the reading unit 6 includes a light emitting unit 11 and a light receiving unit 12. The light emitting unit 11 includes an LED substrate 11A and a light guide 11B. The LED board 11A includes an R color LED (an example of a light emitting diode light emitting element) 13R that emits red (R) light LR, a G color LED 13G that emits green (G) light LG, and a blue (B) light LB. B-color LED 13B that emits light is disposed at a position shifted from each other along the transport direction, the front-rear direction in FIG. The light guide 11B is an optical member that guides the light beams LR, LG, and LB from the LEDs 13R, 13G, and 13B to the reading position X2.

  The light receiving unit 12 includes a light receiving lens 12A and a light receiving substrate 12B. The light receiving lens 12A is an optical member that guides light from the reading position X2 side to the light receiving substrate 12B. The light receiving substrate 12B has a configuration in which a plurality of light receiving elements (not shown) are arranged side by side along the main scanning direction, that is, the left and right direction in FIG. The emission directions of the light beams LR, LG, and LB of each color are inclined with respect to the facing direction (vertical direction) between the light receiving unit 12 and the facing surface 7A of the document pressing member 7.

  With the above configuration, the reading unit 6 performs a reading operation of reading an image at the reading position X2 and sequentially outputting each line data corresponding to the read image. The reading unit 6 can perform a reading operation with a plurality of different line periods under the control of the control unit 21. The line period is a time corresponding to the time for the reading unit 6 to output the read value from each light receiving element when reading the image for one line. The image for one line is an image for one color line in a monochrome reading operation, and is an image for three color lines in a color reading operation.

  The reading unit 6 can selectively execute a color reading operation and a monochrome reading operation. In the color reading operation, the LEDs 13R, 13G, and 13B of the light emitting unit 11 are caused to emit light in a time division manner, and the light beams LR, LG, and LB reflected at the reading position X2 are received by the light receiving unit 12, and RGB color line data is This is a reading operation for sequentially outputting a set of line data. In the monochrome reading operation, one of the LEDs 13R, 13G, and 13B (for example, LED 13G) of the light emitting unit 11 is caused to emit light, and the light of each color reflected at the reading position X2 is received by the light receiving unit 12, and one line data Are sequentially output.

(Electrical configuration of the scanner)
As shown in FIG. 3, the scanner 1 includes a control unit 21, and the ADF 5, the reading unit 6, the front sensor 8, the operation unit 22, and the display unit 23 are connected to the control unit 21 so that data communication is possible. ing.

  The control unit 21 includes a central processing unit (hereinafter referred to as CPU) 31, a ROM 32, a RAM 33, and an image processing unit 34. The ROM 32 stores a program for executing a reading control process to be described later (an example of a rear end determination program) and a program for executing various operations of the scanner 1. The CPU 31 controls each unit of the scanner 1 according to a program read from the ROM 32. The ROM 32 and the RAM 33 are examples of a storage unit. In addition to the ROM 32 and the RAM 33, the storage medium for storing the various programs may be a non-volatile memory such as a CD-ROM, a hard disk device, or a flash memory.

  The image processing unit 34 is a hardware circuit dedicated to image processing, and performs processing such as shading correction and gamma correction on the AD-converted line data, and then stores it in the RAM 33.

  The ADF 5 includes a stepping motor 5E and a motor driver 5F, and rotationally drives the rollers 5A and 5C described above. The motor driver 5F is a circuit that drives the stepping motor 5E. When a clock signal is input from the CPU 31, for example, the motor driver 5F rotates the stepping motor 5E by one step (predetermined angle) for each pulse of the clock signal.

  The operation unit 22 has a plurality of buttons, and various input operations can be performed by the user such as selection of a color mode or a monochrome mode. The color mode is a mode in which an image on the original sheet M is read as a color image by the color reading operation, and the monochrome mode is a mode in which the image on the original sheet M is read as a monochrome image by the monochrome reading operation. is there. The display unit 23 includes a liquid crystal display, a lamp, and the like, and can display various setting screens and operation states of the apparatus.

(Reading control processing)
When the user selects a color mode as a reading mode and gives a reading instruction on the operation unit 22, the control unit 21 determines that there is a document sheet on the document tray 3 based on the detection result of the front sensor 8. The reading control process shown in FIGS. 4 to 7 is executed under the conditions. The scanner 1 slows the transport speed of the ADF 5 after starting the reading of the document sheet M by this reading control process and before the trailing end of the document sheet M in the transport direction reaches the reading position X2, and sets the line cycle. After that, the trailing edge of the original sheet M on the read image is determined. This determination is a determination as to whether or not the trailing edge of the document sheet M has reached the reading position X2, in other words, whether or not the trailing edge of the document sheet M has reached the reading position X2.

  First, the control unit 21 generates shading data (S1). Specifically, the CPU 31 sets the document reading cycle T2 as the line cycle of the reading operation. The document reading cycle T2 is set to a longer time as the preset reading resolution is higher, for example. Next, the CPU 31 causes the reading unit 6 to output line data at the original reading cycle T2 without causing the light emitting unit 11 to emit light, and the image processing unit 34 uses the line data as the original reading black reference data in the RAM 33. To remember.

  Next, the CPU 31 sets the leading edge determination cycle T1 as the line cycle of the reading operation. The leading edge determination cycle T1 may be the same cycle as the document reading cycle T2 or a different cycle. However, if the leading edge determination cycle T1 is shorter than the document reading cycle T2, the document sheet M is conveyed at high speed during the leading edge determination process (S5 in FIG. 4) described later, and the leading edge of the document sheet M is at the reading position X2. It can be determined at an early stage whether or not it has been reached. On the other hand, if the leading edge determination cycle T1 is longer than the document reading cycle T2, the document sheet M is conveyed at a low speed during the leading edge determination process, and it is accurately determined whether the leading edge of the document sheet M has reached the reading position X2. Can be determined.

  Thereafter, the CPU 31 causes the reading unit 6 to output line data at the leading end determination period T1 without causing the light emitting unit 11 to emit light, and the image processing unit 34 stores the line data in the RAM 33 as black reference data for leading end determination. Remember.

  Further, the CPU 31 sets a rear end determination period T3 as the line period of the reading operation. The trailing edge determination cycle T3 is a cycle longer than at least the document reading cycle T2. Thereafter, the CPU 31 causes the reading unit 6 to output line data at the rear end determination period T3 without causing the light emitting unit 11 to emit light, and the image processing unit 34 uses the line data as rear end determination black reference data. Store in the RAM 33.

  Next, the CPU 31 causes the reading unit 6 to perform color reading operation on the facing surface 7A of the document pressing member 7 at the document reading cycle T2 and output color line data, and the image processing unit 34 outputs the color line data. The line data is stored in the RAM 33 as white reference data for document reading. Thereafter, the CPU 31 causes the image processing unit 34 to generate document reading shading data based on the document reading black reference data and the document reading white reference data, and store the generated data in the RAM 33.

  The original reading shading data is correction data for correcting original reading line data output from the reading unit 6 during an execution period of an intermediate reading process (S9 in FIG. 4) described later. In this way, the original reading shading data is generated based on the original reading white reference data acquired at the same original reading period T2 as the execution period of the intermediate reading process, so that the original reading line data described later can be appropriately set. It can be corrected.

  Further, the CPU 31 causes the reading unit 6 to execute monochrome reading operation on the facing surface 7A of the document pressing member 7 at the leading edge determination period T1 and output monochrome line data, and the image processing unit 34 outputs the monochrome line. The data is stored in the RAM 33 as leading edge determination white reference data. Thereafter, the CPU 31 causes the image processing unit 34 to generate tip determination shading data based on the tip determination black reference data and the tip determination white reference data, and store the shading data in the RAM 33.

  The tip determination shading data is correction data for correcting the tip determination line data output from the reading unit 6 in the execution period of the tip determination process. In this way, by generating the tip determination shading data based on the tip determination white reference data acquired at the same tip determination cycle T1 as the execution period of the tip determination process, the tip determination line data described later is appropriately set. It can be corrected.

  Further, the CPU 31 causes the reading unit 6 to perform color reading operation on the opposed surface 7A of the document pressing member 7 at the trailing edge determination period T3 and output color line data, and the image processing unit 34 outputs the color line data. The line data is stored in the RAM 33 as white reference data for rear end determination. Thereafter, the CPU 31 causes the image processing unit 34 to generate rear end determination shading data based on the rear end determination black reference data and the rear end determination white reference data, and store the generated rear end determination shading data in the RAM 33.

  The trailing edge determination shading data is correction data for correcting the trailing edge determination line data output from the reading unit 6 during the execution period of the trailing edge determination / document reading process (S10 in FIG. 4). Thus, the trailing edge determination shading data is generated based on the trailing edge determination white reference data acquired at the trailing edge determination period T3 that is the same as the execution period of the trailing edge determination / document reading process, thereby determining the trailing edge determination. The time line data can be corrected appropriately.

  Next, the CPU 31 acquires leading edge determination reference data by the reading operation at the leading edge determination period T1 (S2). Specifically, the CPU 31 causes the reading unit 6 to execute a monochrome reading operation on the facing surface 7A of the document pressing member 7 at the leading edge determination period T1. Further, the CPU 31 corrects the monochrome data output from the reading unit 6 in the image processing unit 34 using the shading data for leading edge determination, and stores the corrected monochrome data in the RAM 33 as leading edge determination reference data. Let

  Next, the CPU 31 acquires document reading reference data by a reading operation at the document reading cycle T2 (S3). Specifically, the CPU 31 causes the reading unit 6 to perform a color reading operation on the facing surface 7A of the document pressing member 7 at the document reading cycle T2. In addition, the CPU 31 corrects the color data output from the reading unit 6 in the image processing unit 34 using the document reading shading data, and stores the corrected color data in the RAM 33 as document reading reference data. Let

  Further, the CPU 31 acquires rear end determination reference data by the reading operation in the rear end determination cycle T3 (S4). Specifically, the CPU 31 causes the reading unit 6 to perform a color reading operation on the facing surface 7A of the document pressing member 7 at the trailing edge determination period T3. Further, the CPU 31 corrects the color data output from the reading unit 6 to the image processing unit 34 using the shading data for rear end determination, and uses the corrected color data as the rear end determination reference data in the RAM 33. Remember me. The control unit 21 may execute the processes of S2 to S4 in an order different from that in FIG.

(1) Tip determination processing When acquiring each reference data, the CPU 31 executes tip determination processing shown in FIG. 5 (S5). The leading edge determination process is a process for determining whether or not the leading edge of the document sheet M in the transport direction has reached the reading position X2. First, the CPU 31 gives a conveyance start command to the ADF 5 and starts the conveyance operation of the document sheet M at the leading edge determination speed V1 corresponding to the leading edge determination period T1 (S21). Next, the CPU 31 causes the reading unit 6 to start a monochrome reading operation at the leading edge determination cycle T1 (S22). As a result, the reading unit 6 sequentially outputs monochrome line data for each line.

  The CPU 31 causes the image processing unit 34 to correct each monochrome line data sequentially output from the reading unit 6 using the shading data for tip end determination (S23). Hereinafter, the corrected monochrome line data is referred to as leading edge determination line data.

  The CPU 31 determines whether or not the value (for example, the number of edge pixels, the average value of the pixel values of each pixel, the most frequently used pixel value, etc.) indicated by the tip determination line data is within the tip determination range (S24). . Note that the number of edge pixels is the number of pixels having a pixel value equal to or greater than a threshold among the pixels included in the line data. The tip determination range is a range including the value of the tip determination reference data, and for example, a range centered on the value of the tip determination reference data is preferable. If the value of the tip judgment line data is within the tip judgment range, it can be regarded as substantially matching the value of the tip judgment reference data, and if it is outside the tip judgment range, It can be assumed that the values do not substantially match.

  Since the leading edge of the document sheet M has not yet reached the reading position X2 at the beginning of the execution of the leading edge determination process, the reading unit 6 performs a reading operation on the facing surface 7A of the document pressing member 7. Become. Therefore, the CPU 31 determines that the value of the tip determination line data is within the tip determination range (S24: YES), and returns to S23.

  On the other hand, when the leading edge of the document sheet M reaches the reading position X2, the reading unit 6 reads the document sheet M from the facing surface 7A of the document pressing member 7, and the value of the line data at the leading edge determination is the leading edge determination reference. The value changes from the data value. Therefore, the CPU 31 determines that the value of the tip determination line data is out of the tip determination range (S24: NO). In short, the CPU 31 can determine that the leading edge of the original sheet M has reached the reading position X2 by determining that the value of the line data at the leading edge determination has changed from within the leading edge determination range to outside the leading edge determination range.

  When the CPU 31 determines that the leading edge of the document sheet M has reached the reading position X2 (S24: NO), the reading operation is stopped by the reading unit 6 and a conveyance stop command is given to the ADF 5 to stop the conveying operation ( S25), the leading end determination process is terminated, and the process proceeds to S6 in FIG. Note that the control unit 21 controls the control unit 21 with respect to the leading edge reading timing at which the reading unit 6 actually reads the leading edge of the document sheet M at the reading position X2 due to the processing speed and the processing times of S23 and S24. The leading edge determination timing for determining that the leading edge of the original sheet M has reached the reading position X2 from the read line data may be delayed.

  Therefore, the control unit 21 causes the reading unit 6 to continue the reading operation for each line with respect to the document sheet M even during the leading edge delay period from the leading edge reading timing to the leading edge determination timing. Even after the leading edge passes through the reading position X2, the line data at the time of leading edge determination is stored in the RAM 33. Therefore, it is preferable that the leading edge determination speed V1 is slower than a document reading speed V2 described later, and the leading edge determination period T1 is longer than the document reading period T2. Thereby, it is possible to suppress the number of extra lines read during the leading edge delay time.

(2) Determination of reference distance when document sheet is first sheet In S6, the CPU 31 determines that the document sheet M currently being read, in other words, the leading edge has reached the reading position X2 in S5. It is determined whether the original sheet M is the first original sheet after receiving the reading command. If the CPU 31 determines that the document sheet is the first document sheet (S6: YES), the CPU 31 determines the reference distance from the dimension of the document sheet M in the main scanning direction (S7). The process of S7 is an example of a determination process.

  Specifically, the CPU 31 causes the image processing unit 34 to perform edge detection processing on, for example, monochrome line data read during the leading edge delay period. In the edge detection process, the image processing unit 34 detects the edge intensity of each pixel from the monochrome line data, and determines the edge pixel if the edge intensity is equal to or greater than a predetermined threshold value. The CPU 31 specifies the distance between the two edge pixels located at both ends on one line as the size of the document sheet M in the main scanning direction.

  Here, for example, A4, letter size, legal size, B4, and other predetermined standard sizes of commercially available paper, the dimensions of one side coincide with each other, and the other side orthogonal to the one side. Some have different dimensions. For this reason, even if the dimension of one side is obtained as the dimension in the main scanning direction, the dimension in the sub-scanning direction (conveyance direction) cannot be determined uniformly, and it is difficult to determine the reference distance appropriately. On the other hand, the CPU 31 determines the distance corresponding to the dimension of the other side of the standard size having one side of the specified dimension in the main scanning direction as the reference distance. That is, the longer the dimension of the other side, the longer the reference distance. In addition, when there are a plurality of standard sizes having one side of the specified dimension in the main scanning direction, the CPU 31 determines the distance corresponding to the shortest dimension among the other sides of the standard size as the reference distance. . That is, the longer the shortest dimension, the longer the reference distance. The reference distance is preferably a distance obtained by subtracting a predetermined margin distance from the dimension of the other side of the standard size.

  For example, A4, letter size, and legal size have the same short side dimensions. When the specified dimension in the main scanning direction matches the dimension of the short side such as A4 size, the CPU 31 sets the distance according to the dimension of the long side of the shortest letter size as the reference distance. That is, the longer the long side dimension, the longer the reference distance. As a result, it is possible to suppress delay processing described later from being executed after the trailing edge of the original sheet M has passed the reading position X2. Further, it is preferable to read the original sheet M quickly. For this purpose, it is preferable to start the delay process at the timing when the trailing edge of the original sheet M is as close as possible to the reading position X2. In this respect, according to the present embodiment, the original sheet can be read as quickly as possible by setting the reference distance to a distance obtained by subtracting a predetermined margin distance from the dimension of the other side of the standard size. It is possible to reliably determine that the rear end has reached the reading position X2.

(3) Intermediate Reading Process After determining the reference distance, the CPU 31 executes the intermediate reading process shown in FIG. 6 (S9). The intermediate reading process is a process for executing a reading operation on the document sheet M after the leading edge of the document sheet M reaches the reading position X2 and before the trailing edge of the document sheet M in the transport direction reaches the reading position X2. It is. First, the CPU 31 causes the ADF 5 to start the conveyance operation of the original sheet M at the original reading speed V2 corresponding to the original reading period T2 (S31).

  Next, the CPU 31 causes the reading unit 6 to read an image for one line by the color reading operation at the document reading cycle T2 (S32), and causes the image processing unit 34 to output the color line data output from the reading unit 6 as follows. Correction is performed using the document reading shading data (S33). Hereinafter, the corrected color line data is referred to as original reading line data. Note that the process of S32 is an example of a reading process.

  After correcting the line data, the CPU 31 determines whether or not the distance that the document sheet M has been conveyed has reached the reference distance from the time when it is determined in S24 that the leading edge of the document sheet M has reached the reading position X2 ( S34). Note that the CPU 31 determines whether the distance that the document sheet M has been transported from the start of the transport operation in S31 and the distance that the document sheet M has been transported from the start of the read operation in S32 has reached a distance corresponding to the reference distance. The determination of S34 may be made indirectly by determining whether or not. Further, the CPU 31 can make the determination in S34 using, for example, the elapsed time from the time when it is determined that the leading edge of the document sheet M has reached the reading position X2 and the number of steps of the stepping motor 5E.

  When the CPU 31 determines that the reference distance has not been reached (S34: NO), the CPU 31 returns to S32 and executes the processes of S32 and S33 for the next line. On the other hand, if the CPU 31 determines that the reference distance has been reached (S34: YES), the CPU 31 stops the transport operation of the ADF 5 (S35), ends the intermediate reading process, and proceeds to S10 in FIG. Here, when the reference distance is reached, the portion between the leading edge and the trailing edge of the document sheet M has reached the reading position X2, and the trailing edge of the document sheet M has still reached the reading position X2. Absent. The part is preferably a position near the rear end of the document sheet M, and more preferably a position in front of the rear end in the transport direction.

(4) Rear end determination / reading process After executing the intermediate reading process, the CPU 31 executes the rear end determination / reading process shown in FIG. 6 (S10). The trailing edge determination / reading process is a process for determining whether the trailing edge of the document sheet M in the transport direction has reached the reading position X2 while executing a reading operation on the document sheet M. First, the CPU 31 causes the ADF 5 to start conveying the original sheet M at the trailing edge determination speed V3 corresponding to the trailing edge determination cycle T3 (S41). Next, the CPU 31 causes the reading unit 6 to start a color reading operation at the trailing edge determination cycle T3 (S42). Thereby, the reading unit 6 sequentially outputs color line data for each line. Note that the process of S42 is an example of a reading process.

  The CPU 31 causes the image processing unit 34 to correct each color line data sequentially output from the reading unit 6 by using the rear end edge determination shading data (S43). Hereinafter, the corrected color line data is referred to as rear end determination line data.

  The CPU 31 determines whether the value of the line data at the time of rear end determination (for example, the number of edge pixels, the average value of each pixel value, the most frequently used pixel value, etc.) is within the rear end determination range (S44). The rear end determination range is a range including the value of the rear end determination reference data, and for example, a range centered on the value of the rear end determination reference data is preferable. When the trailing edge judgment line data value is within the trailing edge judgment range, it can be regarded as substantially matching the trailing edge judgment reference data value. It can be considered that the value of the edge determination reference data does not substantially match.

  Since the trailing edge of the original sheet M has not yet reached the reading position X2 at the beginning of execution of the trailing edge determination process, the reading unit 6 performs a reading operation on the original sheet M. Therefore, the CPU 31 determines that the value of the rear end determination line data is outside the rear end determination range (S44: NO), and returns to S43.

  On the other hand, when the trailing edge of the document sheet M reaches the reading position X2, the reading unit 6 reads the facing surface 7A of the document pressing member 7 from the document sheet M, and the value of the line data at the time of trailing edge determination is It changes to a value close to the value of the edge judgment reference data. Therefore, the CPU 31 determines that the value of the rear end determination line data is within the rear end determination range (S44: NO). In short, the CPU 31 determines that the trailing edge of the original sheet M has reached the reading position X2 by determining that the value of the trailing edge determination line data has changed from outside the trailing edge determination range to within the trailing edge determination range. be able to.

  When the CPU 31 determines that the trailing edge of the document sheet M has reached the reading position X2 (S44: YES), the reading section 6 stops the reading operation, the ADF 5 stops the conveying operation (S45), and the trailing edge. The determination / reading process ends, and the process proceeds to S11 in FIG. Here, the control unit 21 controls the trailing edge reading timing at which the reading unit 6 actually reads the trailing edge of the document sheet M at the reading position X2 due to the processing speed and the processing times of S43 and S44. The trailing edge determination timing at which the section 21 determines that the trailing edge of the document sheet M has reached the reading position X2 from the read line data may be delayed. For this reason, the control unit 21 causes the reading unit 6 to continue the reading operation with respect to the document sheet M even in the trailing edge delay period from the trailing edge reading timing to the trailing edge determination timing. Even after the trailing edge passes the reading position X2, the trailing edge determination line data is stored in the RAM 33, and an extra image is added to the rear side (lower side) of the trailing edge of the document sheet M on the read image. .

  However, the control unit 21 slows the transport speed of the ADF 5 and lengthens the line cycle of the reading unit 6 before the trailing end of the document sheet M reaches the reading position X2 in the process of reading the document sheet M. Delay processing (S31 and S32 in FIG. 6, S41 and S42 in FIG. 7) is executed. As a result, the rear end delay time is the same as that of the present embodiment, and in the process of reading the original sheet M, the transport speed of the ADF 5 is not delayed and the line period of the reading unit 6 is not lengthened. While performing the rear end determination, it is possible to suppress the number of extra lines read between the reading start timing and the rear end determination timing.

  In S11, if the CPU 31 determines that there is a document sheet M in the document tray 3 (S11: YES), it returns to S5, and if it determines that there is no document sheet M in the document tray 3 (S11: NO), finally. After the read document sheet M is discharged onto the discharge tray 4, the ADF 5 stops the conveying operation (S12), and the reading control process is terminated. When the user selects the monochrome mode on the operation unit 22 and gives a reading instruction, the control unit 21 executes a monochrome reading operation in S1, S3, S4, S32, and S42.

(5) Determination of the reference distance when the document sheet is the second and subsequent sheets When the CPU 31 determines that the document sheet is the first or subsequent document sheet at S6 (S6: NO), A distance corresponding to the dimension in the sub-scanning direction is determined as a reference distance (S8), and the process proceeds to S9. The CPU 31 calculates the dimension from the leading edge to the trailing edge of the document sheet M on the read image using the determination result (S24, S44) of the leading edge and the trailing edge with respect to the first document sheet M. The dimension is in the sub-scanning direction. The dimension in the sub-scanning direction substantially matches the actual dimension of the document sheet M.

  The CPU 31 determines a distance obtained by subtracting a predetermined margin distance from the dimension in the sub-scanning direction as a reference distance. Thus, by using the measured value of the dimension of the first document sheet M in the sub-scanning direction, the reference distance is determined as an appropriate distance according to the measured value for the second and subsequent document sheets M. can do. Further, even when the timing at which the trailing edge of the original sheet M reaches the reading position X2 varies due to a surrounding environment of temperature, a change in speed of the transport mechanism, or the like, the influence can be suppressed.

(Effect of this embodiment)
According to the present embodiment, after the reading process is started and before the trailing edge of the original sheet M reaches the reading position X2, a delay process is executed to slow the ADF 5 conveyance speed and lengthen the line cycle. The number of lines read per unit time is smaller than that before execution of the delay process. Therefore, compared with the conventional configuration in which the conveyance speed and the line cycle are constant from the reading start timing of the original sheet image to the trailing edge determination timing, the trailing edge determination is performed from the reading start timing while performing the trailing edge determination. It is possible to suppress the number of extra lines read until the timing.

<Other embodiments>
The technology disclosed in the present specification is not limited to the embodiments described with reference to the above description and drawings, and includes, for example, the following various aspects.

  In the embodiment described above, the scanner 1 having only the scanner function is given as an example of the image reading apparatus. However, the present invention is not limited to this, and the image reading apparatus may be a multifunction machine capable of executing a plurality of functions such as a copy function, a facsimile machine, or the like in addition to the scan function. Further, the image reading apparatus may be configured such that the document tray is disposed above the discharge tray.

  In the above embodiment, the control unit 21 is configured to execute the reading control process by the CPU 31 and the hardware circuit such as the image processing unit 34. However, the present invention is not limited to this, and the control unit 21 is configured to execute read control processing or the like by only one or a plurality of CPUs, or to execute read control processing or the like only by a hardware circuit such as an ASIC (Application Specific Integrated Circuit). But you can. For example, the control unit 21 may be configured to execute at least a part of each process executed by the image processing unit 34 in FIGS. 4 to 7 using a CPU and a memory.

  The control unit 21 is configured to execute a reading operation or the like for each line, but is not limited thereto, and may be configured to execute a reading operation or the like in units of a plurality of lines.

  The control unit 21 may cause the reading unit 6 to perform a color reading operation in S1, S2, and S22.

  The control unit 21 may determine a distance corresponding to the shortest dimension in the conveyance direction of the sheet that can be conveyed by the ADF 5 as a reference distance in S7 of FIG. That is, the longer the shortest dimension in the transport direction, the longer the reference distance. As shown in FIG. 1, in the scanner 1, the transport distance DL between the pair of transport rollers 5C and 5C located at the most upstream among the transport distances between the plurality of transport rollers 5C is the shortest. The shortest transport distance DL means the shortest dimension in the transport direction of the document sheet M that can be transported by the ADF 5.

  Therefore, the control unit 21 determines a distance corresponding to the shortest transport distance DL as a reference distance. As a result, as long as the scanner 1 can carry the original sheet, the number of extra lines read from the reading start timing to the trailing edge determination timing is determined while performing the trailing edge determination regardless of the size of the original sheet being conveyed. It is possible to suppress. The control unit 21 may determine the reference distance as a reference distance, not limited to the conveyance distance of the conveyance roller 5C, for example, according to the minimum dimension in the conveyance direction of the document sheet M defined in the specification.

  The control unit 21 may be configured to increase the reference distance as the dimension in the sub-scanning direction of the document sheet M identified from the identified main scanning direction and the determination result of the leading edge and the trailing edge in S7 and S8. The reference distance may be always constant. However, in the former configuration, compared to the latter configuration, the execution time of the intermediate reading process executed at a relatively fast original reading speed V2 is lengthened and executed at a relatively slow trailing edge determination speed V3. Therefore, it is possible to suppress an increase in the execution period of the trailing edge determination / reading process, and it is possible to suppress an increase in the reading period as a whole.

  Instead of S7 and S8, the control unit 21 may be configured to identify the dimension in the main scanning direction of the document sheet M from the line data initially obtained by the reading operation of the intermediate reading process and determine the reference distance.

  In S8, the control unit 21 is not limited to the first sheet, and the actual measurement value of the dimension of the second and subsequent original sheets M in the sub-scanning direction or the dimension of the plurality of original sheets M in the sub-scanning direction. A configuration may be used in which the reference distance is determined for another subsequent document sheet M by using an average value of actually measured values or the like.

  1: Scanner 5: ADF 6: Reading unit 7: Document pressing member 21: Control unit X2: Reading position

Claims (6)

A transport unit that performs a transport operation for transporting a document sheet toward a predetermined reading position;
A reading unit that performs a reading operation of reading an image for each line along the main scanning direction at the reading position;
An opposing member disposed opposite to the reading unit at the reading position;
A control unit;
With
The controller is
A reading process in which the conveying unit performs a conveying operation, the reading unit performs a reading operation, and sequentially acquires a read image for each line;
After the start of the reading process, before the trailing edge of the original sheet in the conveying direction of the conveying unit reaches the reading position, the conveying speed of the conveying operation in the reading process is reduced, and the reading period of the reading operation Delay processing to lengthen
Among the read images for each line acquired after execution of the delay process, the value of the image changes when the value changes from outside the reference range including the image value of the opposing member to the reference range. A trailing edge determination process for determining that the position on the image is the trailing edge of the document sheet on the read image by the reading unit;
An image reading apparatus having a configuration for executing The image reading apparatus according to claim 1,
The controller is
In the reading process, before the transport unit causes the original sheet to reach the reading position, the reading unit performs a reading operation,
When the value of the image is changed from the reference range to the outside of the reference range between the read images for each line acquired before the execution of the delay processing, the changed position on the image is read. Having a configuration for executing a leading edge determination process for determining that the leading edge of the document sheet on the image;
Image reading device. The image reading apparatus according to claim 2,
The controller is
Furthermore,
The dimension in the main scanning direction of the original sheet is obtained from the read image for each line acquired by the reading process, and the shortest dimension among the other sides of the standard size having one side in the main scanning direction. Having a determination process for determining the dimension in the transport direction,
In the delay process, when the document sheet is transported by a distance corresponding to the dimension in the transport direction determined in the determination process from the time when the leading edge determination process determines that the leading edge of the document sheet, the reading process is performed. Slowing the transport speed of the transport operation in the process and lengthening the reading cycle of the reading operation
Image reading device. The image reading apparatus according to claim 2,
The controller is
In the delay process, the document sheet is conveyed by a distance corresponding to the minimum dimension in the conveyance direction of the document sheet that can be conveyed by the conveyance unit from the time when the leading edge determination process determines that the document sheet is the leading edge. At this point, the conveyance speed of the conveyance operation in the reading process is reduced, and the reading cycle of the reading operation is lengthened.
Image reading device. The image reading apparatus according to any one of claims 2 to 4,
The transport unit sequentially transports a plurality of document sheets one by one,
The controller is
From the determination results of the leading edge determination process and the trailing edge determination process for one document sheet, the conveyance direction dimension determination process for determining the dimension of the one document sheet in the conveyance direction is performed,
In the delay process, another document sheet transported after the one document sheet is the distance corresponding to the dimension in the transport direction from the time when the leading edge determination process determines that the document sheet is the leading edge of the document sheet. , When the original sheet is conveyed, the conveyance speed of the conveyance operation in the reading process is slowed down, and the reading cycle of the reading operation is lengthened.
Image reading device. A transport unit that performs a transport operation for transporting a document sheet toward a predetermined reading position;
A reading unit that performs a reading operation of reading an image for each line along the main scanning direction at the reading position;
An image reading apparatus comprising: an opposing member disposed to face the reading unit at the reading position;
A reading process in which the conveying unit performs a conveying operation, the reading unit performs a reading operation, and sequentially acquires a read image for each line;
After the start of the reading process, before the trailing edge of the original sheet in the conveying direction of the conveying unit reaches the reading position, the conveying speed of the conveying operation in the reading process is reduced, and the reading period of the reading operation Delay processing to lengthen
Among the read images for each line acquired after the execution of the delay process, when the value of the image changes from outside the reference range including the image value of the facing member to the reference range, the changed image A rear edge determination process for determining that the upper position is the rear edge of the document sheet on the read image by the reading unit;
Rear end determination program that executes

Images