JP2012019521A - Image reading device and image reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device capable of reducing deterioration in the quality of a read image due to color shift.SOLUTION: An image reading device comprises: registration means; document feeder means; reading means; and image processing means. The registration means registers an influenced range which is influenced by the speed variation of document feeding in read image data. The document feeder means feeds the document to a document reading position. The reading means reads the image of the document at the document reading position. The image processing means applies first image processing to a non-influenced range other than the influenced range in the read image data obtained by reading the image by the reading means and applies second image processing to the influenced range in the read image data.

Description

  Embodiments described herein relate generally to an image reading apparatus and an image reading method.

  An image reading apparatus provided with an automatic document feeder is known. The automatic document feeder takes out the set original, conveys the taken out original to the reading surface of the image reading apparatus, and discharges the original after reading the image. In recent years, the speed of document feeding performance of an automatic document feeder has been remarkably increased, and the automatic document feeder can convey and discharge many set documents in a short time.

JP 2007-73046 A

  The conveyance speed of one document conveyed by the automatic document feeder may not be constant. That is, the conveyance speed of one original document conveyed by the automatic document feeder may change midway. For example, when the conveyed document collides with the reading surface and a load is applied to the document, the document conveyance speed changes. Further, when the document passes through the conveyance roller, the clamping pressure on the document changes, and thereby the document conveyance speed changes.

  If the conveyance speed of one original changes midway, color misregistration may occur in the original reading result. There is a desire to reduce the deterioration of the read image quality due to the color misregistration.

  The problem to be solved by the present invention is to provide an image reading apparatus and an image reading method capable of reducing deterioration of read image quality due to color misregistration.

  The image reading apparatus according to the embodiment includes a registration unit, a document conveying unit, a reading unit, and an image processing unit. The registering unit registers an influence range that is affected by a change in the document conveyance speed in the read image data. The document conveying means conveys the document to the document reading position. The reading unit reads an image of a document at the document reading position. The image processing means applies first image processing to a non-influence range other than the influence range in the read image data obtained by reading the image of the reading means, and the influence range in the read image data The second image processing is applied to.

1 is a cross-sectional view illustrating an example of a schematic configuration of an image reading apparatus of a digital copying machine according to an embodiment. 1 is a block diagram illustrating an example of an internal configuration of a digital copying machine according to an embodiment. It is a figure which shows an example of the image reading apparatus at the time of reading a white reference signal. FIG. 3 is a diagram illustrating an example of an image reading apparatus during reading of an image of a document conveyed by an ADF. 1 is a diagram illustrating an example of an image reading apparatus after reading a document image. FIG. 6 is a flowchart illustrating an example of color misregistration correction processing when a low-resolution RGB signal and a high-resolution BK signal are simultaneously read using a 4-line sensor. 6 is a flowchart illustrating an example of color misregistration correction processing when an RGB signal is read using a three-line sensor. It is an example of an image showing a BK signal of a read image using a 4-line sensor. It is an example of the image which shows the RGB signal of the read image using a 4 line sensor. It is an example of the image which shows the signal used as a reference | standard among the RGB signals of the read image using a 3 line sensor. It is a figure which shows an example of the image which shows two remaining signals other than the signal used as a reference | standard among the RGB signals of the read image using a 3 line sensor.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating an example of a schematic configuration of an image reading apparatus 1 of a digital copying machine according to an embodiment. FIG. 2 is a block diagram showing an example of the internal configuration of the digital copying machine according to the embodiment.

  As shown in FIGS. 1 and 2, the digital copying machine 41 includes an image reading unit 1 a, a CPU 51, an image processing unit 64, an image processing unit 54, an image forming unit 47, which constitute an image reading apparatus (image processing apparatus) 1. A communication interface unit (I / F unit) 57 and the like are provided.

  The CPU 51 can control the image data in the page memory 55 to be processed by the image processing unit 54. The communication interface unit (I / F unit) 57 receives image data transmitted from an external device such as a PC, and the CPU 51 can control to write the received image data into the page memory 55. it can. The CPU 51 can also control to transmit the data in the page memory 55 to an external device such as a PC via the I / F unit 57. For example, the CPU 61, the image processing unit 64, and the like execute resolution conversion processing, abnormality detection processing, and image correction processing described later.

  For example, the image reading apparatus 1 uses a CCD sensor 19 (hybrid 4-line sensor) to simultaneously read a low-resolution color signal and a high-resolution monochrome signal. That is, the image reading apparatus 1 outputs a color signal for each line in units of pixels corresponding to the resolution (low resolution) and a monochrome signal for each line in units of pixels corresponding to the resolution (high resolution).

  FIG. 1 is a cross-sectional view illustrating a configuration of the image reading apparatus 1. An image reading apparatus 1 shown in FIG. 1 includes an image reading apparatus main body (image reading unit) 1 a and an automatic document feeder (ADF) 2.

  First, the configuration of the image reading apparatus main body (image reading unit) 1a will be described.

  As shown in FIG. 1, the image reading apparatus main body 1a includes a light source 11, a reflector 12, a first mirror 13, a second mirror 14, a third mirror 15, a first carriage 16, a second carriage 17, and a condenser lens 18. , A CCD sensor (hybrid 4-line sensor) 19, a CCD substrate 20, a scanner control substrate 21, a platen glass 22, a white reference plate 23, and the like. The CCD sensor 19 simultaneously reads a low resolution color signal and a high resolution monochrome signal. That is, the image reading apparatus 1 outputs a color signal for each line in units of pixels corresponding to the resolution (low resolution) and a color signal for each line in units of pixels corresponding to the resolution (high resolution).

  The light source 11 emits light for irradiating the document Org. The reflector 12 uniformly irradiates the original Org with light emitted from the light source 11. That is, the reflector 12 adjusts the light distribution characteristic at the reading position of the original Org. The first mirror 13 receives reflected light from the document Org. The first mirror 13 is installed so as to guide the reflected light from the document Org to the second mirror 14.

  The second mirror 14 receives the reflected light from the first mirror 13. The second mirror 14 is installed so as to guide the reflected light from the first mirror 13 to the third mirror. The third mirror 15 receives the reflected light from the second mirror 14. The third mirror 15 is installed so as to guide the reflected light from the second mirror 14 to the condenser lens 18. The condensing lens 18 condenses the reflected light from the third mirror. The condensing lens 18 is installed so as to condense the reflected light from the third mirror and form an image on the imaging surface (reading surface) of the CCD sensor 19.

  The CCD sensor 19 is mounted on the CCD substrate 20. The CCD sensor 19 performs photoelectric conversion that converts light energy imaged by the condenser lens 18 into electric charges. Thereby, the CCD sensor 19 converts the image formed by the condenser lens 18 into an electrical signal. The CCD substrate 20 outputs an electrical signal photoelectrically converted by the CCD sensor 19 to the scanner control substrate 21.

  The document table glass 22 is a document table on which the document Org is placed. The white reference plate 23 is composed of a white member. The white reference plate 23 serves as a white reference for correcting (shading correction) the read image of the document.

  The light source 11, the reflector 12, and the first mirror 13 are mounted on the first carriage 16. The second mirror 14 and the third mirror 15 are mounted on the second carriage 17. The first carriage 16 is configured to move in the left-right direction by driving means (not shown). The second carriage 17 is configured to follow in the same direction as the first carriage 16 at a half speed. As a result, even if the first carriage 16 moves, the optical path length of the light guided from the document surface to the imaging surface of the CCD sensor 19 does not change.

  That is, the optical system constituted by the first mirror 13 mounted on the first carriage 16, the second mirror 14 mounted on the second carriage 17, and the third mirror 15 mounted on the second carriage is as follows. The optical path length from the document surface to the imaging surface of the CCD sensor 19 is always constant.

  For example, when reading an image of a document placed on the platen glass 22, the first carriage 16 moves from the left to the right in FIG. 1 (sub-scanning direction). As the first carriage 16 moves in the sub-scanning direction, the reading position (one line in the main scanning direction) P with respect to the document Org also moves from left to right (sub-scanning direction). By moving the reading position in the sub-scanning direction, an image at the reading position of the original Org (image for one line in the main scanning direction) is sequentially formed on the imaging surface of the CCD sensor 19. As a result, the CCD sensor 19 converts the image of the entire document into image information.

  A plurality of photodiodes are arranged one-dimensionally on the imaging surface of the CCD sensor 19. The CCD sensor 19 reads an image for one line in the main scanning direction by a plurality of photodiodes arranged one-dimensionally.

  Next, the configuration of the automatic document feeder (ADF) 2 will be described.

  The automatic document feeder (ADF) 2 includes a document tray 31, a pickup roller 32, a registration roller pair 33, a conveyance drum 34, a conveyance roller 35, a jump table 36, and a document discharge unit 37.

  The document tray 31 is a tray on which the document Org to be read is stacked. The pickup roller 32 picks up the originals Org stacked on the original tray 31 one by one and supplies them to the registration roller pair 33. The registration roller pair 33 conveys the document Org picked up by the pickup roller 32 toward the conveyance drum 34. The registration roller pair 33 corrects the inclination of the document Org and transports the document Org while preventing the document Org from being double-fed.

  The transport drum 34 and the transport roller 35 transport the original document Org transported from the registration roller pair 33. Further, the transport drum 34 transports the reading surface of the document Org while pressing it against the surface of the document table glass at the reading position P. The jump table 36 is a member that guides the document Org transported by the transport drum 34 and the transport roller 35 to the document discharge unit 37. The document discharge unit 37 stacks the document Org to be discharged.

Next, a configuration example of a digital copying machine 41 including the image reading apparatus as described above and a system including the digital copying machine 41 will be described.
FIG. 2 is a block diagram illustrating a configuration example of a control system in the image reading apparatus main body (image reading unit) 1a, a configuration example in the digital copying machine 41, and a configuration example of a network system including the digital copying machine 41. FIG.

  As shown in FIG. 2, the digital copying machine 41 is connected to an Internet server 43 via a network 42. The digital copying machine 41 includes a system control unit 45, a control panel 46, an image forming unit 47, an image reading unit 1a, an automatic document feeder 2, and the like.

  The digital copying machine 41 is connected to the network 42. The network 42 is, for example, a local area network. The Internet server 43 is a server device for connecting from a device connected to the network 42 to another network such as the Internet. The Internet server 43 is operated, for example, at a center (not shown) that provides maintenance for the digital copying machine 41 or a service related to the digital copying machine 41.

  For example, when a problem occurs in the digital copying machine 41, the Internet server 43 is notified from the digital copying machine 41 that a problem has occurred. When a problem is notified to the Internet server 43, a center that provides a service for the digital copying machine 41 dispatches a person (herein referred to as a serviceman) having specialized knowledge such as maintenance. Thus, the service person implements a service system that performs maintenance of the digital copying machine 41.

  The system control unit 45 controls the entire digital copying machine 41. The system control unit 45 includes a CPU 51, a ROM 52, a RAM 53, an image processing unit 54, a page memory 55, a hard disk drive (HDD) 56, a communication interface unit (I / F unit) 57, and the like.

  The CPU 51 controls the entire system control unit 45. The ROM 52 is a nonvolatile memory. The ROM 52 stores, for example, a control program and control data. The RAM 53 is composed of a volatile memory. The RAM 53 stores, for example, various parameters and work data. The image processing unit 54 performs image processing on the image data. The communication interface 57 is an interface that performs data communication with an external device via the network 42.

  The control panel 46 is a user interface through which various operation instructions are input. The control panel 46 includes, for example, a liquid crystal display device with a built-in touch panel, a hard key such as a numeric keypad, and the like. The image forming unit 47 is a printer that forms an image corresponding to the image data supplied from the system control unit 45 on an image forming medium.

  Next, the operation of the digital copying machine configured as described above will be schematically described.

  First, it is assumed that the user inputs a copy instruction on the control panel 46. When receiving a copy instruction from the control panel 46, the CPU 51 of the system control unit 45 outputs a document image reading instruction to the image reading apparatus 1. In the image reading apparatus 1, a document image reading process is performed in response to a document image reading instruction from the system control unit 45. The document image data read by the document image reading process is supplied from the image reading apparatus 1 to the system control unit 45.

  In the system control unit 45, the image processing unit 54 converts the format of the image data supplied from the image reading apparatus 1 into a format (image forming format) for the image forming unit 47 to perform image forming processing. Convert. When the format of the image data of the document read by the image reading apparatus 1 is converted into the format for image formation, the system control unit 45 outputs the image data to the image forming unit 47 at a predetermined timing. The image forming unit 47 forms an image corresponding to the image data supplied from the system control unit 45 on the image forming medium. For example, the image forming unit 47 forms an image on a sheet by electrophotography.

  It is assumed that the user inputs an instruction to scan the original image and transfer the original image data on the control panel 46. In this case, the CPU 51 of the system control unit 45 outputs a document image reading instruction to the image reading apparatus 1. In the image reading apparatus 1, a document image reading process is performed in response to a document image reading instruction from the system control unit 45. The document image data read by the document image reading process is supplied from the image reading apparatus 1 to the system control unit 45.

  The CPU 51 of the system control unit 45 receives the image data read by the image reading device 1 and temporarily stores it in the HDD or the like. At this time, the CPU 51 converts the image data into a desired format by the image processing unit 54. When the image data read by the image reading device 1 is stored in the HDD, the CPU 51 transfers the image data to a desired client PC (not shown) via the network 42 by the communication interface 57.

  The digital copying machine 41 has a function (network printer function) for printing image data from a client PC (not shown) connected to the network 42. For example, it is assumed that the system control unit 45 receives a print output signal (print request and print output image data) from a client PC (not shown) connected to the network 42 via the communication interface 57. . In this case, the system control unit 45 temporarily stores the print output image data received from the client PC in the HDD or the like. At this time, the system control unit 45 converts the format of the received image data into a format for the image forming unit 47 to perform image forming processing (format for image formation). Further, the system control unit 45 outputs the image data converted into the image forming format to the image forming unit 47 at a predetermined timing. The image forming unit 47 forms an image corresponding to the image data supplied from the system control unit 45 on the image forming medium.

  The system control unit 45 also has a function of performing data communication with an external device via the network 42 and the Internet as an external network. For example, the system control unit 45 has a function of transmitting image data to the external device via the network 42 and the Internet. The system control unit 45 also has a function of transmitting information indicating the current state of the digital copying machine 41 to an external device on the Internet.

Next, the configuration of the control system of the image reading unit 1a will be described.
The control system of the image reading device is provided, for example, on the control board 21 of the image reading device main body (image reading unit) 1a. As shown in FIG. 2, a CPU 61, a RAM 62, a ROM 63, an image processing unit 64, a drive control unit 66, an exposure control unit 67, and the like are provided on the control board 21 of the image reading unit 1a.

  The CPU 61 controls the entire image reading unit 1a. The RAM 62 includes a volatile memory. The ROM 63 is composed of a nonvolatile memory. The ROM 63 stores control programs executed by the CPU 61, control data, and the like. For example, the ROM 63 stores coordinate values indicating the position of the first carriage 16 corresponding to the black reference reading position, the white reference reading position, the reading position of the document conveyed by the ADF 2, and the like.

  The image processing unit 64 processes an output signal (image data) from the CCD sensor 19. The image processing unit 64 performs processing such as analog / digital conversion processing, shading correction processing, and image correction processing, for example. The configuration within the image processing unit 64 will be described in detail later. The drive control unit 66 performs drive control of a drive motor 68 that drives the first carriage 16 in the image reading apparatus main body 1a. The exposure control unit 67 performs lighting control of the light source 11.

Next, a document image reading operation using the automatic document feeder 2 will be described.
FIG. 3 is a diagram illustrating an example of an image reading apparatus when reading a white reference signal. FIG. 4 is a diagram illustrating an example of an image reading apparatus during reading of an image of a document conveyed by the ADF 2. FIG. 5 is a diagram illustrating an example of an image reading apparatus after reading a document image.

  First, when a document image reading process is performed using the ADF 2, the image reading apparatus sequentially performs a black reference signal reading process, a white reference signal reading process, and a document image reading process. In the black reference signal reading process (black reference reading process), the light source 11 is turned off to read an image as a black reference. In the white reference signal reading process, the light source 11 is turned on to read an image of the white reference plate 23. In the document image reading process, the document image conveyed by the ADF 2 is read at a predetermined reading position P1.

That is, the CPU 61 sequentially performs a black reference signal reading process (black reference reading process), a white reference signal reading process (white reference reading process), and an original image reading process (original reading process).
First, as a black reference signal reading process, the CPU 61 turns off the light source 11 by the exposure control unit 67 and drives the drive motor 68 by the drive control unit 66 to show the first carriage 16 in FIG. Move to the left end (left side of the white reference plate 23).

  When the first carriage 16 is moved to the left end, the CPU 61 causes the drive controller 66 to move the first carriage 16 from the left end to the right side (sub scanning direction) while the light source 11 is turned off. Move several lines. During this time, the CCD sensor 19 outputs a signal as a black reference. That is, the CCD sensor 19 reads an image for several lines with the light source 11 turned off as a black reference image. In the image processing unit 64, the average value for each pixel in the output signal (black reference image) for several lines from the CCD sensor 19 is used as the black reference signal.

  Next, the CPU 61 performs a white reference signal reading process. As the white reference reading process, the CPU 61 turns on the light source 11 by the exposure control unit 67 and drives the drive motor 68 by the drive control unit 66 to bring the first carriage 16 to the white reference reading start position. Move. The reading position P0 shown in FIG. 3 indicates the reading position of the first carriage 16 with respect to the white reference plate 23.

  When the first carriage 16 is moved to the white reference reading start position, the CPU 61 moves the first carriage 16 to the right (in the sub-scanning direction) by the drive control unit 66 while the light source 11 is in a lighting state. Move several lines. During this time, the CCD sensor 19 outputs a signal as a white reference. That is, the CCD sensor 19 reads an image for several lines of the white reference plate 23 read with the light source 11 turned on as a white reference image. In the image processing unit 64, the average value for each pixel in the output signal (white reference image) for several lines from the CCD sensor 19 is used as the white reference signal.

  Next, the CPU 61 performs a document image reading process. As the document reading process, the CPU 61 drives the drive motor 68 by the drive control unit 66 while the light source 11 is turned on by the exposure control unit 67 to move the first carriage 16 to the document reading position P1. Move. The reading position P1 shown in FIGS. 4 and 5 indicates the reading position for the document conveyed by the ADF2.

  On the other hand, the CPU 61 instructs the ADF 2 to start document conveyance. The ADF 2 starts conveying the document Org on the document tray 31 in response to an instruction from the CPU 61. The originals Org on the original tray 31 are picked up one by one by the pickup roller 32. The leading edge of the document Org picked up by the pickup roller 32 is conveyed to the registration roller pair 33. In front of the registration roller pair 33, a sensor (not shown) for detecting that the document has reached the registration roller pair 33 is installed.

  The document Org detected by this sensor to arrive before the registration roller pair 33 is conveyed to the subsequent stage by the registration roller pair 33 in accordance with the timing instructed by the CPU 61. In the subsequent stage of the registration roller pair 33, the document Org is conveyed by the conveyance drum 34 and the conveyance roller 35. The document Org transported by the transport drum 34 and the transport roller 35 passes through the document reading position P1 and is transported to the document discharge section 37 as shown in FIG. Further, the document Org that has passed the document reading position P1 is guided to the document discharge section 37 by the jump table 36, as shown in FIG.

  Further, at the original reading position P1, as shown in FIG. 4, the original is irradiated with light from the light source 11 through the original table glass 22, and the reflected light is incident on the first mirror 13. Light incident on the first mirror 13 (reflected light from the document) is incident on the CCD sensor 19 through the optical system such as the second mirror, the third mirror, and the condenser lens. That is, the original Org conveyed by the ADF 2 is sequentially read in the main scanning direction at the original reading position P1. The image information (output signal from the CCD sensor 19) photoelectrically converted by the CCD sensor 19 is corrected by the image processing unit 64 using the black reference signal and the white reference signal.

  Next, an outline of resolution conversion processing by the digital copying machine 41 (image reading apparatus 1) will be described.

  The digital copying machine 41 (image reading apparatus 1) can perform resolution conversion processing using a low resolution color signal (RGB signal) and a high resolution monochrome signal (K signal) to obtain a high resolution color signal. it can. That is, the image reading apparatus 1 (image processing unit 64 or the like) has a resolution based on the low resolution color signal (RGB signal) and the high resolution monochrome signal (K signal) acquired by the image reading unit 1a (CCD sensor 19). Conversion processing can be executed to obtain a high-resolution color signal. For example, the image processing unit 64 or the like calculates a color difference signal using a color signal, executes various processes such as calculating color information by RGB → YIQ conversion, and replaces the luminance signal with a monochrome signal to perform the resolution conversion process. Execute.

  Next, an example of color misregistration correction processing by the digital copying machine 41 (image reading apparatus 1) will be described.

  The conveyance speed of one document conveyed by the automatic document feeder 2 of the image reading apparatus 1 may not be constant. That is, the conveyance speed of one original document conveyed by the automatic document feeder may change midway. For example, when the document to be conveyed collides with the jump table 36, the document table glass 22 or the like and the document is loaded, the document conveyance speed changes. Further, when the document passes through the pickup roller 32, the registration roller pair 33, the conveyance drum 34, and the conveyance roller 35, the nipping pressure with respect to the document changes, thereby changing the document conveyance speed.

  If the conveyance speed of one original changes midway, color misregistration occurs in the original reading result. The digital copying machine 41 (image reading apparatus 1) can reduce deterioration of the read image quality due to the color misregistration by the color misregistration correction processing described below.

  The speed change described above does not occur irregularly but occurs regularly. That is, the speed change occurs in the same range for each document. As a result, the influence of the speed change occurs in the same range in the read image data corresponding to the original.

  From the characteristics of the image reading apparatus 1, it is possible to detect (calculate) a range (speed change influence range) in which the influence of the speed change in the read image data occurs. For example, the speed change influence range is stored (registered) in the ROM 63 when the digital copying machine 41 (image reading apparatus 1) is shipped. After the digital copier 41 (image reading apparatus 1) is shipped, when the image reading apparatus 1 reads an image, the image processing unit 64 performs a first resolution conversion process (first averaging) on an unregistered range. The second resolution conversion processing (second averaging processing method) is applied to the registered speed change influence range. That is, the image processing unit 64 changes the resolution conversion process for the unregistered range and the resolution conversion process for the registered speed change influence range. Thereby, the deterioration of the image quality due to the color shift is reduced.

  That is, the image processing unit 64 can increase the effect of correcting color misregistration by changing the average processing range of the read image data. As described above, the CCD sensor 19 (4-line sensor) of the image reading apparatus 1 reads a low resolution RGB signal and a high resolution BK signal simultaneously. The image processing unit 64 performs resolution conversion processing using the RGB signal and the BK signal. By changing the resolution conversion processing method (averaging processing method) between the designated range and the non-designated range, the image processing unit 64 causes color misregistration. Reduce image quality degradation.

  In the above description, the case of a four-line sensor has been described. However, in the case of an image reading apparatus that obtains an RGB signal using a three-line sensor, color misregistration correction processing is performed within a specified range.

  FIG. 6 is a flowchart illustrating an example of color misregistration correction processing when a low-resolution RGB signal and a high-resolution BK signal are simultaneously read using a 4-line sensor.

  As shown in FIG. 6, the image processing unit 64 executes SHD correction (ACT 11) and inter-line correction (ACT 12) according to the number of image lines (according to the range of image data), and an unregistered range. If it is (speed conversion non-influence range), it is determined that there is no correction (ACT13, NO), and normal resolution conversion processing (first resolution conversion processing) is executed (ACT14). If it is determined that there is correction (ACT13, YES), color misregistration correction processing (second resolution conversion processing) is executed (ACT15), and the process proceeds to subsequent image processing (ACT16).

  FIG. 7 is a flowchart illustrating an example of color misregistration correction processing when an RGB signal is read using a three-line sensor. In the above description, the case where the CCD sensor 19 is a 4-line sensor has been described. Here, a case where the CCD sensor 19 is a 3-line sensor will be described.

  As shown in FIG. 7, the image processing unit 64 performs SHD correction (ACT 21) and inter-line correction (ACT 22) according to the number of image lines (according to the range of the image data), and a non-registered range. If not, it is determined that there is no correction (ACT23, NO), and no special processing is performed, and if it is a registered speed change influence range, it is determined that there is correction (ACT23, YES), and color misregistration correction processing (second) Resolution conversion processing) is executed (ACT25), and the process proceeds to the subsequent image processing (ACT26).

  FIG. 8 is an example of an image showing a BK signal of a read image using a 4-line sensor. FIG. 9 is an example of an image showing RGB signals of a read image using a 4-line sensor. The color misregistration correction processing described with reference to FIG. 6 will be described with reference to FIGS. As shown in FIGS. 8 and 9, the target pixel of the BK signal is A, the target pixel of the color signal indicating the RGB signal is B, and the output color signal is B ′. Further, the image processing unit 64 executes the following calculation, and the following calculation is performed for each of the RGB signals.

<Normal resolution conversion process (first resolution conversion process)>
c_rng1 = (B + C2) / 2
c_rng2 = (B + B) / 2
k_rng1 = (A + K3) / 2
k_rng2 = (A + K4) / 2
B '= ((c_rng1 + (c_rng1 / k_rng1) * (A-k_rng1)) + (c_rng2 + (c_rng2 / k_rng2) * (A-k_rng2))) / 2
<Color misregistration correction process (second resolution conversion process)>
c_rng1 = (B + C2 + C2 + C1) / 4
c_rng2 = (B + B + C3 + C3) / 4
k_rng1 = (A + K3 + K2 + K1) / 4
k_rng2 = (A + K4 + K5 + K6) / 4
B '= ((c_rng1 + (c_rng1 / k_rng1) * (A-k_rng1)) + (c_rng2 + (c_rng2 / k_rng2) * (A-k_rng2))) / 2
The image processing unit 64 corrects the influence of color misregistration by averaging in the color sub-scanning method. Although the resolving power of the color signal is reduced by the averaging process, the image processing unit 64 restores the resolution information by adding the ratio of the difference value from the average value of the BK signal to the color signal. As described above, the image processing unit 64 switches the averaging range between normal processing and color misregistration correction processing. Thereby, the color misregistration correction effect within the range can be obtained.

  The range to be averaged is variable in the normal processing unit and the color misregistration correction process.

  FIG. 10 is an example of an image showing a reference signal among RGB signals of a read image using a three-line sensor. FIG. 11 is a diagram illustrating an example of an image showing the remaining two signals other than a reference signal among RGB signals of a read image using a three-line sensor. The color misregistration correction processing described with reference to FIG. 7 will be described with reference to FIGS. Assume that the pixel of interest of the reference signal is X, the pixel of interest of the other two signals is Y, and the color signal of the output result is Y ′. Further, the following calculation is performed for each of two signals other than the target pixel.

<Color shift correction processing>
x_rng1 = (X + S13) / 2
x_rng2 = (X + S14) / 2
y_rng1 = (Y + C13) / 2
y_rng2 = (Y + C14) / 2
Y '= ((y_rng1 + (y_rng1 / x_rng1) * (X-x_rng1)) + (y_rng2 + (y_rng2 / x_rng2) * (X-x_rng2))) / 2
The image processing unit 64 corrects the influence of color misregistration by averaging in the color sub-scanning method. Although the resolving power of the color signal is reduced by the averaging process, the image processing unit 64 restores the resolution information by adding the ratio of the difference value from the average value of the reference signal to a signal other than the reference signal. The color misregistration correction effect within the range can be obtained by the above arithmetic expression.

  The range to be averaged is variable in the color misregistration correction process.

  By the color misregistration correction process described above, it is possible to correct a color change due to color misregistration (RGB signal difference) during image reading.

  In other words, the image processing unit 64 has, for example, a relatively wide speed change influence range detected in advance, for example, a relatively wide range (eg, 6 × 6 pixels) of the image (K signal) shown in FIG. A relatively wide range (any of RGB signals) (the same range (for example, 6 × 6 pixels) at a position corresponding to the relatively wide range in FIG. 8) is compared, and high resolution processing is performed. A blur effect can be obtained by performing high-resolution processing by comparing over a relatively wide range, thereby reducing the influence of image quality degradation due to color misregistration. Further, the image processing unit 64 is a range that does not correspond to the speed change influence range detected in advance, for example, a relatively narrow range (for example, 2 × 2 pixels) of the image (K signal) shown in FIG. 9 is compared with a relatively narrow range of the image (any one of the RGB signals) shown in FIG. 9 (the same range (for example, 2 × 2 pixels) at a position corresponding to the relatively narrow range in FIG. 8), and high-resolution processing is performed. By performing high resolution processing by comparing within a relatively narrow range, a high high resolution processing effect can be obtained.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Image reading apparatus, 1a ... Image reading part, 2 ... Automatic document feeder, 41 ... Digital copying machine, 64 ... Image processing part

Claims (10)

Registration means for registering an influence range affected by a change in speed of document conveyance in the read image data;
A document conveying means for conveying the document to a document reading position;
Reading means for reading an image of the original at the original reading position;
The first image processing is applied to a non-influenced range other than the affected range in the read image data obtained by reading the image of the reading unit, and a second is applied to the affected range in the read image data. Image processing means for applying image processing;
An image reading apparatus comprising:   The image reading apparatus according to claim 1, wherein the image processing unit applies a first resolution conversion process to the non-affected range, and applies a second resolution conversion process to the affected range.   The image reading apparatus according to claim 1, wherein the reading unit reads a color signal having a first resolution and a monochrome signal having a second resolution higher than the first resolution.   The reading means includes first, second, and third colors for reading the color signal having the first resolution, and a fourth color for reading the monochrome signal having the second resolution. 4. The image reading apparatus according to claim 3, comprising a corresponding four-line sensor.   The image processing means applies the first resolution conversion process to the non-affected range in the read image data, and applies the second resolution conversion process to the affected range in the read image data. 5. The image reading apparatus according to claim 3, wherein the color signal having the second resolution is generated based on the color signal having the first resolution and the second monochrome signal having the second resolution. Registration means for registering an influence range affected by a change in speed of document conveyance in the read image data;
Transport the document to the document reading position,
Read an image of the original at the original reading position,
First image processing is applied to a non-influenced range other than the affected range affected by a change in speed of document conveyance in the read image data obtained by reading the image of the reading unit, and the read image data in the read image data An image reading method in which the second image processing is applied to the influence range.   The image reading method according to claim 6, wherein a first resolution conversion process is applied to the non-affected range, and a second resolution conversion process is applied to the affected range.   The image reading method according to claim 6 or 7, wherein a color signal having a first resolution and a monochrome signal having a second resolution higher than the first resolution are read.   4-line sensor corresponding to the first, second, and third colors for reading the color signal of the first resolution and the fourth color for reading the monochrome signal of the second resolution The image reading method according to claim 8, wherein the image is read.   Applying the first resolution conversion process to the non-influenced range in the read image data, applying the second resolution conversion process to the affected range in the read image data, and the first resolution 10. The image reading method according to claim 8, wherein the color signal having the second resolution is generated based on the color signal and the second monochrome signal having the second resolution.

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