JP5593882B2 - Image reading apparatus, image forming apparatus, and image reading method - Google Patents

Description

  The present invention relates to an image reading apparatus, an image forming apparatus, and an image reading method for reading an original at a predetermined reading position while conveying the original.

  2. Description of the Related Art Conventionally, as an image reading method in an image reading apparatus such as an image scanner, a method of reading an original using a contact type line sensor or the like disposed at a predetermined reading position while conveying the original at a predetermined speed is known.

  Some image reading apparatuses include an image memory for temporarily storing read image data in order to absorb a difference between a document reading speed and a data transfer speed to an image data transfer destination. . Since the capacity of the image memory is limited, when the processing capacity of the image data transfer destination is low, it is also assumed that the document reading speed greatly exceeds the data transfer speed and the image memory becomes full. . Therefore, when the remaining amount of memory in the image memory is low, the conveyance of the original is interrupted to stop reading, and during that time, data transfer from the image memory to the image data transfer destination is advanced, so that there is room in the remaining amount of memory in the image memory. After that, it is known to perform a so-called intermittent reading operation in which the conveyance of the document is restarted and the reading is restarted (see, for example, Patent Document 1, Patent Document 2, etc.).

  However, when an intermittent reading operation is performed, through-down processing for gradually reducing the document conveyance speed and conversely through-up processing for gradually increasing the document conveyance speed are performed, thereby performing reading in that section. The obtained image data has a problem that the expansion and contraction of the image in the sub-scanning direction occurs and the quality is deteriorated. In addition, there is a process of reading the document once by retreating it in the sub-scanning direction in order to transport the document again at a constant speed from the stopped position after stopping the document transport. There has been a problem that image data becomes conspicuous due to a shift.

  In addition, there is a process of reading the image data by extending or contracting the line cycle of the reading sensor at the time of through-down and through-up and gaining a moving time to a desired sub-scanning position during that time. In this case, the light amount per line is As a result, there is a problem that the level of the image data fluctuates as compared to the case of constant speed conveyance during through-down and through-up.

  Japanese Patent Application Laid-Open No. 2004-151561 discloses that when performing an intermittent reading operation, image deterioration is prevented by conveying a document with a slow through-up and through-down speed curve different from that at the start and end of document transportation. ing. However, in the technique disclosed in Patent Document 1, in order to reduce the influence of vibration caused by inertial force generated by acceleration and deceleration generated during through-up and through-down, line data used for driving by adjusting timing. In order to obtain the optimal speed curve and line data acquisition, it is necessary to perform cut-and-try in order to obtain the optimal curve at the design stage.

  Further, in the technique disclosed in Patent Document 1, the response to through-up and through-down when changing the moving speed of the sub-scan to change the image in the sub-scanning direction depends on each magnification. Each adjustment must be performed, and it is possible to cope with the situation by conveying according to the assumed speed curve, and there is a problem that the capture of the line data deviates from the actual movement of the original conveyance.

  Further, in the technique disclosed in Patent Document 1, if the switching of the timing control for capturing the line data is not smooth with respect to the switching from the through-up timing to the target constant speed, the data is lost or unnecessary. There is a problem that data acquisition occurs.

  The present invention has been made in view of the above, and when reading a document at a predetermined reading position while transporting a document, the present invention is suitable even during through-up and through-down caused by intermittent reading operation. An object of the present invention is to provide an image reading apparatus, an image forming apparatus, and an image reading method capable of capturing line data and obtaining high-quality image data.

In order to solve the above-described problems and achieve the object, an image reading apparatus according to the present invention uses a rotating body that rotates as a document is conveyed and a position that faces the peripheral surface of the rotating body as a reading position. A reading unit that reads image data of a document that passes through the reading position, and a pattern that is provided on the peripheral surface of the rotating body and that is read by the reading unit together with the document that passes through the reading position. Is a document conveyance amount detection pattern that changes according to the document conveyance amount at the reading position, an image memory that temporarily stores image data of the document read by the reading unit, and a remaining memory capacity of the image memory. When the first reference value or less is reached, the conveyance of the document is interrupted, and when the remaining amount of memory in the image memory becomes equal to or greater than the second reference value that is larger than the first reference value, the conveyance of the document is performed. Based on the image data of the conveyance control means to be resumed and the original conveyance amount detection pattern read by the reading means, it is determined whether or not the line data of the sub-scan line in the image data of the original read by the reading means is necessary. Corresponding to determination means for determining , sub-scanning scaling means for changing the original image data read by the reading means by changing the document conveying speed in the sub-scanning direction, and a target scaling factor in the sub-scanning direction Storage means for storing image data of the original conveyance amount detection pattern read by the reading means when the original is conveyed at the conveyance speed as a matching pattern image, and the sub-scanning scaling means is the reading means So that the image data of the document carry amount detection pattern read by the image data matches the matching pattern image. Characterized Rukoto varying the transport speed of the manuscript.

  An image forming apparatus according to the present invention includes: the image reading apparatus according to the present invention; and an image forming unit that forms an image based on image data of a document output from the image reading apparatus. To do.

The image reading method according to the present invention reads the image data of the document passing through the reading position, with the rotating body rotating as the document is conveyed and the position facing the peripheral surface of the rotating body as the reading position. A pattern provided on a peripheral surface of the reading unit and the rotating body and read by the reading unit together with the document passing through the reading position, and the read image data is in accordance with the conveyance amount of the document at the reading position. A document conveyance amount detection pattern that changes, an image memory that temporarily stores image data of a document read by the reading unit, and document conveyance when the remaining amount of memory in the image memory falls below a first reference value And a conveyance control means for resuming the conveyance of the document when the remaining amount of memory in the image memory becomes equal to or greater than a second reference value greater than the first reference value. An image reading method executed by a reading device, wherein the reading unit reads image data of a document passing through the reading position together with image data of the document conveyance amount detection pattern, and is read by the reading unit. Determining whether or not it is necessary to take in the line data of the sub-scanning line in the image data of the document read by the reading unit based on the image data of the document conveyance amount detection pattern; and the document read by the reading unit Based on the image data of the carry amount detection pattern, the step of changing the carry speed of the document so as to obtain the target variable magnification in the sub-scanning direction, and the line data captured according to the variable magnification, And interpolating using non-captured data .

  According to the present invention, since it is determined whether or not the line data needs to be captured based on the image data of the document conveyance amount detection pattern read together with the image data of the document passing through the reading position, the through-up caused by the intermittent reading operation is determined. Even during the through-down, line data can be appropriately taken in, and high-quality image data can be obtained.

FIG. 1 is a diagram illustrating a schematic configuration of an image scanner. FIG. 2 is a block diagram showing an outline of a control mechanism for processing image data of the image scanner. FIG. 3 is a front view of the transport drum. FIG. 4 is a diagram illustrating an example of an image input to the data receiving unit in the ADF mode. FIG. 5 is a diagram for explaining an example when the document conveyance amount detection pattern is read at the pixel level. FIG. 6 is a block diagram illustrating a functional configuration of an image data receiving unit that performs sub-scanning reference verification processing. FIG. 7 is a diagram for explaining a through-up operation at the time of starting document conveyance and a through-down operation at the time of document conveyance stop accompanying the start / stop of document conveyance. FIG. 8 is a diagram for explaining an example of processing for determining whether or not line data needs to be captured based on an image of a document conveyance amount detection pattern read at the time of through-down. FIG. 9 is a diagram for explaining an example of processing for determining whether or not line data needs to be captured based on an image of a document conveyance amount detection pattern read during through-up. FIG. 10 shows a read image of the document conveyance amount detection pattern when the document is conveyed from the constant speed conveyance through the through-down to the conveyance stop state and then from the conveyance stop state through the through-down to the constant speed state. FIG. FIG. 11 is a diagram illustrating an example of a suitable pattern shape of the document conveyance amount detection pattern. FIG. 12 is a diagram illustrating an example of the sub-scanning matching pattern used when the sub-scan scaling process is performed based on the image of the document conveyance amount detection pattern. FIG. 13 is a diagram schematically illustrating a data interpolation processing unit that performs interpolation processing.

  Exemplary embodiments of an image reading apparatus, an image forming apparatus, and an image reading method according to the present invention are explained in detail below with reference to the accompanying drawings. Hereinafter, an example in which the present invention is applied to an image scanner having a book mode that is a document fixing mode and an ADF mode that is a document conveyance mode as modes of a document reading operation will be described.

  FIG. 1 is a diagram illustrating a schematic configuration of an image scanner 10 according to the present embodiment. As shown in FIG. 1, the image scanner 10 has a contact glass 1 on which a document is placed. A first traveling body 4 on which the reflection mirror 2 and the illumination lamp 3 are mounted is disposed at a position facing the contact glass 1 from below so as to be movable in the sub-scanning direction. In the reflected light path of the first traveling body 4, a second traveling body 5 that turns back the optical path by the two reflecting mirrors 2 is disposed so as to be movable in the sub-scanning direction. An imaging lens 6 and a CCD (Charge Coupled Device) 8 mounted in a line on an SBU (Sensor Board Unit) 7 are disposed in the reflected light path of the second traveling body 5.

  A traveling body motor 9 composed of a stepping motor is connected to the first traveling body 4 and the second traveling body 5 by a pulley, a wire, or the like. The first traveling body 4 and the second traveling body 5 are movable in the same sub-scanning direction at a 2: 1 speed by driving the traveling body motor 9. In the image scanner 10, the two traveling bodies 4 and 5 move in this manner, whereby the image of the document placed on the contact glass 1 is read and scanned by the CCD 8 in the sub-scanning direction.

  The reading and scanning of the original as described above is executed under the setting of the book mode that is the original fixing mode. The image scanner 10 according to the present embodiment is in the original conveyance mode in addition to the book mode. An ADF mode is also prepared as a switchable operation mode. Under the setting of the ADF mode, the document is transported in the sub-scanning direction by the ADF 11 serving as a document transport device in a state where the two traveling bodies 4 and 5 are disposed at the home position as illustrated by a broken line at the right end in the drawing. While reading the document.

  The ADF 11 that transports the document includes a paper feed tray 12, a pickup roller 13, a pair of registration rollers 14, a transport drum 15, and a plurality of transport rollers 16. 17 is discharged. The paper discharge tray 17 is formed on the upper surface of the original pressure plate 18, and the original pressure plate 18 is provided on the contact glass 1 so as to be freely opened and closed. A paper feed motor 19 including a stepping motor is connected to the pickup roller 13 and the registration roller 14 of the ADF 11 by a gear train or the like. Further, a transport motor 20 including a stepping motor is connected to the transport drum 15 and the transport roller 16 by a gear train or the like. In the ADF mode, the first traveling body 4 on which the reflecting mirror 2 and the illumination lamp 3 are mounted is disposed at the home position, and between the first traveling body 4 and the peripheral surface of the transport drum 15 facing the first traveling body 4. This is the original reading position.

  FIG. 2 is a block diagram showing an outline of a control mechanism for processing image data of the image scanner 10 of the present embodiment. The image scanner 10 has an analog video processing unit 50, an image data receiving unit 51, an image processing unit 52, an image memory control unit 53, an image memory 54, and an I / F controller as control mechanisms for processing image data. A unit 55, a drive control unit 56, a CPU 57, a ROM 58, and a RAM 59 are provided.

  The reflected light of the read original that has entered the CCD 8 on the SBU 7 is converted into analog image data having a voltage value corresponding to the light intensity in the CCD 8, and is divided into odd bits and even bits, and an analog video processing unit. 50 are sequentially output. The analog video processing unit 50 removes the dark potential portion from the input image data, combines the odd bits and the even bits, adjusts the gain to a predetermined amplitude, and then performs A / D (Analog / Digital) conversion. Digitize.

  The image data digitized by the analog video processing unit 50 is subjected to shading correction in the image data receiving unit 51, where sub-scanning reference verification processing is executed. The sub-scanning reference verification process is a process for outputting a gate enable signal LGATE_EN indicating whether or not line data is necessary for image data output to the next-stage image processing unit 52 in units of lines in the sub-scanning direction. is there. Details of this sub-scanning reference verification process will be described later.

  The image processing unit 52 captures line data, which is required to be captured by the gate enable signal LGATE_EN, as necessary line data with respect to the input image data, but does not need to be captured by the gate enable signal LGATE_EN. The data is discarded, and image data that reproduces the original image is generated. The generated image data is subjected to various required image processing.

  The image data subjected to various image processing by the image processing unit 52 is input to the image memory control unit 53 and temporarily stored in the image memory 54. The image data stored in the image memory 54 is read from the image memory 54 in response to a transfer request from an image data transfer destination such as the host computer 105, and the image data such as the host computer 105 is transmitted via the I / F controller unit 55. Transferred to the destination.

  Here, when the transfer request from the image data transfer destination such as the host computer 105 is delayed, the image data is stored in the image memory 54 until the transfer request is received from the image data transfer destination by the function of the image memory control unit 53. Is done. When the remaining amount of memory in the image memory 54 falls below a certain reference value (first reference value), the drive control unit 56 stops driving the paper feed motor 19 and the carry motor 20 in accordance with a command from the CPU 57, and the original document. By stopping the conveyance, the reading of the document is stopped.

  If there is a request from the image data transfer destination such as the host computer 105 while the reading of the original is stopped, the image data stored in the image memory 54 is read and transferred to the image data transfer destination. As a result, the remaining memory capacity of the image memory 54 increases, and the remaining memory capacity of the image memory 54 becomes greater than or equal to a certain reference value (a second reference value that is larger than the first reference value). Then, the drive control unit 56 drives the paper feed motor 19 and the carry motor 20 in accordance with a command from the CPU 57 to start the document feed, whereby the document reading is resumed.

  The CPU 57 comprehensively controls the above processing in the image scanner 10. A program for realizing control by the CPU 57 is stored in the ROM 58. The RAM 59 is used as a work area when the CPU 57 executes a program.

  The drive control unit 56 performs information communication with the CPU 57, and controls the document conveyance timing in the ADF 11 by driving and controlling the paper feed motor 19 and the conveyance motor 20 according to a command from the CPU 57, and also according to a command from the CPU 57. The driving timing of the first traveling body 4 and the second traveling body 5 is controlled by controlling the traveling body motor 9.

  FIG. 3 is a front view of the conveyance drum 15 serving as a document background at the reading position when the document is read while being conveyed in the ADF mode (viewed from the front direction with respect to the circumferential surface of the conveyance drum 15). It is. The transport drum 15 is a rotating body that rotates as the document is transported, and a document transport amount detection pattern P is provided on the peripheral surface thereof. In the example shown in FIG. 3, a document conveyance amount detection pattern P is provided at the end position of the circumferential surface of the conveyance drum 15 on the left side in the drawing. The position of the document conveyance amount detection pattern P on the circumferential surface of the conveyance drum 15 is a position where the document does not pass during document conveyance, and is read by a reading unit including the reflection mirror 2, the illumination lamp 3, the imaging lens 6, and the CCD 8. This is the position where the image can be read.

  In the present embodiment, the document conveyance amount detection pattern P provided on the peripheral surface of the conveyance drum 15 is read together with the document passing through the reading position. The conveyance drum 15 serves to convey a document by rotating according to the control of the drive control unit 56, and a document conveyance amount detection pattern P provided on the peripheral surface of the conveyance drum 15 is a document conveyance amount at a reading position. Can be shown. That is, when the original passes through the reading position, the original conveyance amount detection pattern P is read for each line together with the original, thereby detecting the movement amount of the original in line units.

  Specifically, the document conveyance amount detection pattern P is, for example, an oblique line that is oblique to the document conveyance direction at the reading position along the circumferential direction of the conveyance drum 15 corresponding to the document conveyance direction at the reading position. A plurality of patterns are provided.

  FIG. 4 is a diagram illustrating an example of an image input to the data receiving unit 51 in the ADF mode. As shown in FIG. 4, the image input to the image data receiving unit 51 includes a document conveyance amount detection pattern area that is an image area of the document conveyance amount detection pattern P in addition to the document image area that is the image area of the document. Contains. That is, this input image has an area corresponding to the reading width (reading sensor reading area) by the reading means in the main scanning direction, and the original is conveyed to a position outside of the original reading area (left side in the example of FIG. 4). There is an amount detection pattern region, and in this document conveyance amount detection pattern region, a document conveyance amount detection pattern P provided on the peripheral surface of the conveyance drum 15 is reproduced as an image. In the example of FIG. 4, the image of the document conveyance amount detection pattern P is reproduced as a continuous line segment of 45 degrees oblique to the sub-scanning direction.

  A document conveyance amount detection pattern P in which a plurality of oblique lines of 45 degrees obliquely arranged along the circumferential direction of the conveyance drum 15 can be read as line data of 45 degrees if the main scanning and the sub scanning have the same reading density. . That is, the read image data of the document conveyance amount detection pattern P is accompanied by movement of one pixel in the main scanning direction with respect to movement of one document conveyance line in the sub-scanning direction.

  Here, an example when the document conveyance amount detection pattern P is read at the pixel level will be described with reference to FIG. In the example of FIG. 5, each hatched image of the document conveyance amount detection pattern P is a black line in which data for five pixels are arranged in the sub-scanning direction at an inclination of 45 degrees in the main scanning direction. When this data is read together with the main and sub pixel densities, pixel movement occurs for each pixel in the main scanning direction. That is, when attention is paid to the reading current line, there is a movement of one pixel in the main scanning direction from the previous line data, and the rear line further moves in the main scanning direction by one pixel. Using the relationship that one pixel movement in the main scanning direction occurs with respect to the movement of one line in the sub-scanning direction, the movement of one line in the sub-scanning direction is detected, and the sub-data in the document image data is detected. The scanning line data can be captured.

  FIG. 6 is a block diagram illustrating a functional configuration of the image data receiving unit 51 that performs the sub-scanning reference verification process. As shown in FIG. 6, the image data receiving unit 51 includes a shading correction unit 511, a data separation unit 512, a pattern verification unit 513, and a gate enable signal generation unit 514.

  The input image data input from the analog video processing unit 50 is input to the shading correction unit 511 and subjected to shading correction, and then input to the data separation unit 512. The data separation unit 512 separates the input data after the shading correction into the document image area data and the document carry amount detection pattern area data shown in FIG. The data (line data) of the document image area separated by the data separation unit 512 is sent to the image processing unit 52, and the data of the document conveyance amount detection pattern region is input to the pattern verification unit 513.

  The pattern verification unit 513 verifies the data of the document conveyance amount detection pattern area, that is, the data of the read image of the document conveyance amount detection pattern P, and uses the characteristics of the image of the document conveyance amount detection pattern P described with reference to FIG. Then, the movement of one line of the input image data in the sub-scanning direction is detected. Then, it is determined whether or not line data is taken in / out in units of lines in the sub-scanning direction, and the determination result is output to the gate enable signal generator 514 (determination means). The gate enable signal generation unit 514 generates a gate enable signal LGATE_EN indicating whether or not line data fetching is necessary according to the determination result by the pattern verification unit 513. The gate enable signal LGATE_EN is input to the image processing unit 52. The image processing unit 52 takes in only necessary line data in accordance with the gate enable signal LGATE_EN, and discards unnecessary line data.

  Next, referring to FIG. 7, a through-up operation at the start of document conveyance accompanying the start / stop (intermittent reading operation) of document conveyance by controlling the operation of a conveyance motor 20 (stepping motor) that drives document conveyance, and A through-down operation when the document conveyance is stopped will be described. The operation described below is realized by the drive control unit 56 controlling the drive of the carry motor 20 in accordance with an instruction from the CPU 57 (conveyance control means).

  First, a case where document conveyance is started from a state where document conveyance is stopped will be described. The document conveyance acceleration process is performed at the document conveyance start T1. In this case, the operation of the carry motor 20 is accelerated at a pulse interval having a frequency obtained by thinning the pulse interval from the pulse interval at a constant speed. In the example of FIG. 7, the operation is performed at a frequency in which the number of pulses of the carry motor 20 is thinned out during the through-up section.

  When the conveyance speed reaches the target speed in the through-up section, conveyance at a constant speed is performed as the frequency of pulse intervals for conveying the document at a constant speed with the number of pulses of the conveyance motor 20. The fact that the remaining amount of image memory is low in the constant speed section indicates that the remaining amount of memory in the image memory 54 is less than or equal to the first reference value. That is, before the image data can be stored in the image memory 54 when it is transported at a constant speed, the transport speed is lowered to reduce the frequency of generating effective line data. In this case, the pulse interval of the conveyance motor 20 is thinned out from the frequency of a constant speed, and a through-down operation is performed, so that deceleration is performed slowly. Finally, the document conveyance is stopped at a speed of 0. At that time, the pulse generation of the transport motor 20 is stopped.

  From the through-down operation to the stop state, the image data stored in the image memory 54 is transferred from the I / F controller unit 55 to the image data transfer destination such as the host computer 105, and the remaining amount of the image memory 54 is increased. Go.

  When it is determined that the remaining amount of memory in the image memory 54 has reached the remaining amount necessary for reading the document (second reference value or more), document conveyance is started. This is the timing of the document conveyance start T2 shown in FIG. Thereafter, by the same processing, the conveyance motor 20 is controlled according to the remaining memory capacity of the image memory 54 to create through-up, through-down, constant speed, and stop states, and control of document conveyance and document reading is performed.

  Next, an example of processing for determining whether or not it is necessary to take in line data based on the image of the document conveyance amount detection pattern P read at the time of through-down will be described with reference to FIG. As described above, the control of the transport motor 20 by the drive control unit 56 generates through-up, through-down, constant speed, and stop states for document transport. The image shown in FIG. A document conveyance amount detection pattern P read at the time of down is shown.

  The read image of the document conveyance amount detection pattern P shown in FIG. 5 is the one when the document is conveyed at a constant speed, and the pattern image in that case moves one pixel in the main scanning direction for each line. Met. On the other hand, the image shown in FIG. 8 moves one pixel in the main scanning direction with respect to one line data in the constant speed section, but it can be seen that the input line data is not accompanied by one pixel movement when through-down. . That is, since the amount of movement in the sub-scanning direction per unit time is insufficient, one pixel does not move in the main scanning direction with respect to one line data.

  In the example of FIG. 8, since the original is conveyed at a constant speed from the first line to the fourth line in the order from the top (moving one pixel in the main scanning direction for each line), these lines are used. Import data as valid line data. In the fifth line, since the amount of movement of one line in the sub-scanning direction is insufficient, there is no movement of one pixel in the main scanning direction. Therefore, the line data of the fifth line is not taken as invalid line data.

  In the next sixth line, since the amount of movement in the sub-scanning direction is secured, one pixel movement is seen in the main scanning direction. Therefore, the line data of the sixth line is taken as valid line data. Similarly, the 7th and 8th lines are invalid line data because the amount of movement in the sub-scanning direction is insufficient and one pixel does not move in the main scanning direction, and the 9th line is in the main scanning direction. Since one pixel movement is seen, it is captured as effective line data.

  From the 10th line onwards, the document conveyance is stopped, and there is no movement in the sub-scanning direction, so there is no movement of one pixel in the main scanning direction. Therefore, the 10th and subsequent lines are invalid line data, and line data is not taken in.

  As described above, it is possible to determine valid line data and invalid line data at the time of through-down by verifying the read image of the document conveyance amount detection pattern P from document conveyance at a constant speed to stoppage. It is possible to realize control for taking only valid line data into the image processing unit 52. Whether or not line data needs to be captured for each sub-scanning line (whether it is valid line data or invalid line data) is transmitted to the image processing unit 52 by a gate enable signal LGATE_EN that matches the line synchronization signal LSYNC. In the example of FIG. 8, a gate enable signal LGATE_EN that is at a low level at the timing of valid line data to be captured and at a high level at the timing of invalid line data is input to the image processing unit 52. The image processing unit 52 captures line data at a timing when the gate enable signal LGATE_EN is at a low level.

  Next, an example of a process for determining whether or not line data needs to be captured based on an image of the document conveyance amount detection pattern P read at the time of through-up will be described with reference to FIG. As described above, the control of the conveyance motor 20 by the drive control unit 56 generates through-up, through-down, constant speed, and stopped states for document conveyance. The image shown in FIG. The document conveyance amount detection pattern P read at the time of up is shown.

  In the example of FIG. 9, the conveyance is stopped from the first line to the fourth line in order from the top of the figure, and there is no movement of one pixel in the main scanning direction. Therefore, the line data from the first line to the fourth line are not taken as invalid line data. On the fifth line, since there is a movement of one pixel in the main scanning direction, it is determined that there is a movement in the sub scanning direction. For this reason, the line data of the fifth line is captured as valid data.

  The next 6th and 7th lines are invalid line data because the amount of movement in the sub-scanning direction is insufficient and there is no movement of 1 pixel in the main scanning direction, and the 8th line is 1 pixel in the main scanning direction. Since movement is seen, it is captured as effective line data. Similarly, the ninth line and the tenth line are invalid line data because the amount of movement in the sub-scanning direction is insufficient and one pixel does not move in the main scanning direction, and the eleventh line is in the main scanning direction. Since one pixel movement is seen, it is taken in as valid line data, and the 12th line becomes invalid line data.

  The 13th and subsequent lines are transported at a constant speed, and one pixel is moved in the main scanning direction for each line. Therefore, the line data after the 13th line is captured as effective line data.

  As described above, by verifying the read image of the document conveyance amount detection pattern P from the conveyance stop state to the constant velocity conveyance state, it is possible to determine valid line data and invalid line data at the time of through-up. Thus, it is possible to realize control for taking in only the effective line data into the image processing unit 52. Whether or not line data needs to be captured for each sub-scanning line (whether it is valid line data or invalid line data) is transmitted to the image processing unit 52 by a gate enable signal LGATE_EN that matches the line synchronization signal LSYNC. In the example of FIG. 9, a gate enable signal LGATE_EN that is at a low level at the timing of valid line data to be captured and at a high level at the timing of invalid line data is input to the image processing unit 52. The image processing unit 52 captures line data at a timing when the gate enable signal LGATE_EN is at a low level.

  FIG. 10 shows a read image of the document conveyance amount detection pattern P when the document is conveyed from the constant speed conveyance through the through-down to the conveyance stop state and then from the conveyance stop state through the through-down to the constant speed state. is there. The image shown in FIG. 10 is an image obtained by connecting the image shown in FIG. 8 and the image shown in FIG. By verifying the read image of the document conveyance amount detection pattern P shown in FIG. 10, the conveyance is stopped from the constant speed conveyance through the through-down state, and then the constant speed state is established from the conveyance stop state through the through-down state. It is possible to determine valid line data and invalid line data when a document is being conveyed, and to realize control for fetching only valid line data into the image processing unit 52.

  FIG. 11 is a diagram illustrating an example of a suitable pattern shape of the document conveyance amount detection pattern P. As described above, the document conveyance amount detection pattern P is provided on the peripheral surface of the conveyance drum 15 as a hatched pattern so that the pixels move in the main scanning direction as the line moves in the sub-scanning direction. Here, since the document conveyance amount detection pattern P is provided in a limited space where the document on the circumferential surface of the conveyance drum 15 does not pass, the region in the main scanning direction is limited, and the entire circumference of the conveyance drum 15 is formed. It cannot be formed as a continuous diagonal pattern. For this reason, the document conveyance amount detection pattern P is a pattern divided into a plurality of diagonal lines, but in order to be able to determine whether or not line data needs to be taken in all sub-scanning lines, the continuity of the plurality of diagonal lines is set. It is necessary to have.

  From the above viewpoint, as shown in FIG. 11, the document conveyance amount detection pattern P has a configuration in which the ends of adjacent oblique lines are positioned on the same sub-scanning line, that is, the circumferential direction of the conveyance drum 15 (sub-scanning). The first diagonal line and the second diagonal line start point are detected on the same sub-scanning line when one of the two diagonal lines adjacent to the direction is the first diagonal line and the other is the second diagonal line. It is desirable to form as described above.

  In the example of FIG. 11, the first oblique line can be detected from the first line to the sixth line in order from the top of the figure. Then, at the sixth line, the end point of the first oblique line appears at the same time, the start point of the second oblique line appears, and after that, the second oblique line can be detected. Further, at the 12th line, the end point of the second oblique line appears at the same time, and the start point of the third oblique line appears. Thereafter, the third oblique line can be detected. Thereafter, the hatched pattern is continuously detected in the same manner. Therefore, while verifying the same hatched image, by detecting the movement of one pixel in the main scanning direction, it is detected that the moving distance in the sub scanning direction is secured, and the end point is reached. By detecting the start point of the next oblique line that appears, the verification target can be moved to the next oblique line image. Then, by sequentially switching the diagonal lines to be verified one after another, whether or not line data needs to be captured using a document conveyance amount detection pattern P composed of a plurality of diagonal lines provided within a limited main scanning range. Can be accurately determined. Further, the sub-scan reading control can be executed without narrowing the main scanning reading range by the control using the document conveyance amount detection pattern P as described above.

  In the above, a specific method for verifying the read image of the document carry amount detection pattern P and determining whether or not the line data needs to be captured has been described. However, the read image of the document carry amount detection pattern P is the line data as described above. This can be used not only for determining whether or not to capture the document but also for performing sub-scanning magnification by switching the document conveyance speed. Hereinafter, a method of simply performing the sub-scanning scaling process using the image of the document conveyance amount detection pattern P will be described.

  The sub-scan scaling process is a process for enlarging or reducing the image data in the sub-scanning direction by taking in the line data at the same line cycle as the normal speed while the original conveyance speed is switched from the normal speed for normal reading. is there. For example, if the document conveyance speed is set to twice the normal speed and line data is taken in at the same line cycle as the normal speed, the image data is reduced to 1/2 in the sub-scanning direction. On the other hand, if the document conveyance speed is set to ½ of the normal speed and line data is taken in at the same line cycle as the normal speed, the image data is doubled in the sub-scanning direction.

  FIG. 12A shows a read image of the document conveyance amount detection pattern P when the document conveyance speed is twice the normal speed. The read image of the document conveyance amount detection pattern P shown in FIG. 12A has a relationship of moving two pixels in the main scanning direction by moving one line. By preparing this pattern as a matching pattern image and controlling the document conveyance speed so that the read image of the document conveyance amount detection pattern P obtained during actual image reading matches this matching pattern image, The sub-scanning scaling process for reducing the image data to ½ can be easily realized. In addition, by preparing a plurality of matching pattern images corresponding to various reduction ratios, and selecting and using matching pattern images according to the target reduction ratio, the sub-scanning change at the target reduction ratio can be performed. Double processing can be realized easily.

  FIG. 12B shows a read image of the document conveyance amount detection pattern P when the document conveyance speed is ½ of the normal speed. The read image of the document conveyance amount detection pattern P shown in FIG. 12B has a relationship of moving one pixel in the main scanning direction by moving two lines. By preparing this pattern as a matching pattern image and controlling the document conveyance speed so that the read image of the document conveyance amount detection pattern P obtained during actual image reading matches this matching pattern image, A sub-scanning scaling process for enlarging the image data by a factor of 2 can be easily realized. In addition, by preparing a plurality of matching pattern images corresponding to various enlargement ratios and selecting and using matching pattern images according to the target enlargement ratio, the sub-scanning change at the target enlargement ratio can be performed. Double processing can be realized easily.

  Note that the sub-scanning scaling process as described above is realized by the image data receiving unit 51, the image processing unit 52, and the drive control unit 56 operating in accordance with the control of the CPU 57 (sub-scanning scaling unit). Further, the matching pattern image as shown in FIGS. 12A and 12B may be stored in a storage unit such as the ROM 58, for example.

  By the way, the method for easily realizing the sub-scanning scaling process using the read image of the document conveyance amount detection pattern P has been described above. However, when this sub-scanning scaling process is executed, the line data capturing cycle is performed. However, since there is no period corresponding to the document conveyance speed, there may be a case where necessary data exists in the data discarded as invalid line data with respect to the line data fetched as valid lines.

  Therefore, when a gate enable signal LGATE_EN indicating the capture of line data is generated, a plurality of line data including valid line data and invalid line data is used to interpolate data missing in valid line data with invalid line data. It is desirable to perform interpolation processing.

  FIG. 13 is a diagram schematically illustrating the data interpolation processing unit 521 that performs the above-described interpolation processing. The data interpolation processing unit 521 holds a plurality of lines of sub-scan line data, and executes interpolation processing using the invalid line data for the valid line data. Specifically, the data interpolation processing unit 521 captures a plurality of line data including not only valid line data but also peripheral invalid line data at the timing when the gate enable signal LGATE_EN indicating the capture of line data is generated. If there is data loss in the valid line data and the missing data is included in the invalid line data, the missing data in the valid line data is interpolated with the data included in the invalid line data. The data interpolation processing unit 521 as described above can be realized as one function of the image processing unit 52, for example.

  As described above in detail with specific examples, according to the image scanner 10 of the present embodiment, a line is formed based on the image data of the document conveyance amount detection pattern P read together with the document passing through the reading position. Since it is determined whether or not data capture is necessary, line data can be captured properly even during through-up and through-down caused by intermittent reading operations, and high-quality image data can be obtained.

  Further, according to the image scanner 10 of the present embodiment, the document conveyance amount detection pattern P is obtained by using one of the two diagonal lines adjacent to the circumferential direction (sub-scanning direction) of the conveyance drum 15 as the first diagonal line and the other as the second diagonal line. By forming so that the end point of the first oblique line and the start point of the second oblique line are detected on the same sub-scanning line, the sub-scanning is performed without narrowing the reading range of the main scanning. Reading control can be executed.

  Further, according to the image scanner 10 of the present embodiment, the document conveyance amount detection pattern P is an end position deviated from the position where the document on the circumferential surface of the conveyance drum 15 passes and is within the reading range by the reading unit. Therefore, it is possible to effectively prevent adverse effects such as show-through on the reading of the document, and to obtain image data with high reproducibility.

  Also, according to the image scanner 10 of the present embodiment, the sub-scanning scaling process is realized by controlling the document conveyance speed by pattern matching with the image of the document conveyance amount detection pattern P read together with the document. The sub-scan scaling process can be easily performed. In addition, a plurality of matching pattern images corresponding to various scaling factors are prepared in advance, and by selecting and using matching pattern images according to the target scaling factor, sub-scanning at the target scaling factor is performed. Scaling processing can be realized easily.

  Further, according to the image scanner 10 of the present embodiment, when the sub-scan scaling process is performed, the missing data in the effective line data is interpolated using the data included in the invalid line data. Image data that is faithful to the image of the original can be obtained by preventing omission.

  As described above, the embodiment in which the present invention is applied to the image scanner 10 has been described in detail. However, the present invention is not limited to the image scanner 10 described above, and various image reading types of reading a document with a reading unit while conveying the document. It can be effectively applied to a device. In addition, the present invention provides not only an image reading apparatus configured independently as one apparatus but also a plotter (image forming means) that forms an image based on image data output from the image reading apparatus together with the image reading apparatus. The present invention can also be effectively applied to image forming apparatuses such as copiers, facsimile machines, and multifunction machines.

  The embodiment described above shows an example of a preferred embodiment of the present invention, and the technical scope of the present invention is not limited to the technical matter disclosed as the embodiment as it is. The technical scope of the present invention includes modifications, alternative means, and the like that are easily derived by adding technical common sense to the technical matters disclosed as the embodiments.

2 Reflecting mirror 3 Illumination lamp 6 Imaging lens 8 CCD
DESCRIPTION OF SYMBOLS 10 Image scanner 15 Conveying drum 51 Image data receiving part 52 Image processing part 54 Image memory 56 Drive control part 57 CPU
58 ROM
512 Data separation unit 513 Pattern verification unit 514 Gate enable signal generation unit 521 Data interpolation processing unit P Document conveyance amount detection pattern

JP 2005-130527 A JP 2002-171390 A

Claims (7)

A rotating body that rotates as the document is conveyed;
A reading unit that reads the image data of a document that passes through the reading position, and a position facing the peripheral surface of the rotating body;
A document conveyance pattern that is provided on the peripheral surface of the rotating body and that is read by the reading unit together with the document passing through the reading position, and in which the read image data changes according to the document conveyance amount at the reading position Quantity detection pattern,
An image memory for temporarily storing image data of a document read by the reading unit;
When the remaining memory capacity of the image memory becomes equal to or lower than the first reference value, the conveyance of the original is interrupted, and when the remaining memory capacity of the image memory becomes equal to or higher than the second reference value that is larger than the first reference value. Conveyance control means for resuming conveyance of the document;
A determination unit that determines whether or not it is necessary to capture line data of a sub-scanning line in the image data of the document read by the reading unit, based on the image data of the document conveyance amount detection pattern read by the reading unit;
A sub-scanning scaling unit that changes the image data of the document read by the reading unit in the sub-scanning direction by changing the conveyance speed of the document;
Storage means for storing, as a matching pattern image, image data of the document conveyance amount detection pattern read by the reading unit when the document is conveyed at a conveyance speed corresponding to a target scaling factor in the sub-scanning direction ;
The sub-scanning scaling means, image data of the document conveyance amount detection pattern read by the reading means, the read image and wherein Rukoto changing the conveying speed of the document to match the matching pattern image apparatus.   A rotating body that rotates as the document is conveyed;
  A reading unit that reads the image data of a document that passes through the reading position, and a position facing the peripheral surface of the rotating body;
  A document conveyance pattern that is provided on the peripheral surface of the rotating body and that is read by the reading unit together with the document passing through the reading position, and in which the read image data changes according to the document conveyance amount at the reading position Quantity detection pattern,
  An image memory for temporarily storing image data of a document read by the reading unit;
  When the remaining memory capacity of the image memory becomes equal to or lower than the first reference value, the conveyance of the original is interrupted, and when the remaining memory capacity of the image memory becomes equal to or higher than the second reference value that is larger than the first reference value. Conveyance control means for resuming conveyance of the document;
  A determination unit that determines whether or not it is necessary to capture line data of a sub-scanning line in the image data of the document read by the reading unit, based on the image data of the document conveyance amount detection pattern read by the reading unit;
  A sub-scanning scaling unit that changes the image data of the document read by the reading unit in the sub-scanning direction by changing the conveyance speed of the document;
  Data interpolation processing means for performing interpolation processing using data that is not captured with respect to the line data captured according to the magnification of the sub-scanning scaling means,
  The sub-scan scaling unit changes the document conveyance speed so as to obtain a target magnification in the sub-scanning direction based on the image data of the document conveyance amount detection pattern read by the reading unit. An image reading apparatus. The document conveyance amount detection pattern is a pattern in which a plurality of oblique lines oblique to the document conveyance direction at the reading position are provided along the circumferential direction of the rotating body corresponding to the document conveyance direction at the reading position. Yes,
The determination unit detects a document conveyance amount at the reading position from a change in the image data of the document conveyance amount detection pattern read by the reading unit in the main scanning direction, and the document corresponds to one line in the sub-scanning direction. 3. The image reading apparatus according to claim 1, wherein whether or not the line data needs to be captured is determined so that the line data is captured in accordance with the movement. When one of two oblique lines adjacent to the circumferential direction of the rotating body is a first oblique line and the other is a second oblique line, the end point of the first oblique line and the start point of the second oblique line are the same. The image reading apparatus according to claim 3 , wherein the document conveyance amount detection pattern is formed so as to be detected on a sub-scanning line. The document conveyance amount detection pattern is provided at an end position outside the position where the document passes on the peripheral surface of the rotating body and at a position within a reading range by the reading unit. The image reading apparatus according to any one of claims 1 to 4 . An image reading apparatus according to any one of claims 1 to 5 ,
An image forming apparatus comprising: an image forming unit configured to form an image based on image data of a document output from the image reading apparatus. A rotating body that rotates as the document is conveyed;
A reading unit that reads the image data of a document that passes through the reading position, and a position facing the peripheral surface of the rotating body;
A document conveyance pattern that is provided on the peripheral surface of the rotating body and that is read by the reading unit together with the document passing through the reading position, and in which the read image data changes according to the document conveyance amount at the reading position Quantity detection pattern,
An image memory for temporarily storing image data of a document read by the reading unit;
When the remaining memory capacity of the image memory becomes equal to or lower than the first reference value, the conveyance of the original is interrupted, and when the remaining memory capacity of the image memory becomes equal to or higher than the second reference value that is larger than the first reference value. An image reading method executed by an image reading apparatus comprising: a conveyance control unit that resumes conveyance of an original;
Reading the image data of the document passing through the reading position together with the image data of the document conveyance amount detection pattern by the reading unit;
Determining whether or not it is necessary to take in the line data of the sub-scanning line in the image data of the document read by the reading unit based on the image data of the document conveyance amount detection pattern read by the reading unit;
Changing the document conveyance speed so as to obtain a target variable magnification in the sub-scanning direction based on the image data of the document conveyance amount detection pattern read by the reading unit;
An image reading method comprising: interpolating the line data captured according to the variable magnification using data that is not captured .

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