JP2016039416A - Shading compensation device, and image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow for execution of accurate shading correction.SOLUTION: When replacing dirty document reading time shading data acquired immediately before reading a document with a dirt-free initial shading data, the lens pitch unevenness of initial data is corrected to match the phase of the lens pitch unevenness of current data. Consequently, vertical streak due to deviation of lens pitch unevenness with time can also be suppressed, and accurate shading correction can be carried out.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a shading correction apparatus and an image processing apparatus.

  In the image reading apparatus, shading correction is performed in order to correct the variation in the light amount distribution for each main scanning position of the reading optical system and the variation in the sensitivity for each sensor chip pixel. Specifically, shading correction of input data is performed using, for example, a reading result (shading data) of a white density reference member.

  Japanese Patent Application Laid-Open No. 2010-011297 discloses an image in which the initial shading data and the shading data acquired immediately before reading a document are different in light quantity, thereby reducing the change in the amplitude of rod lens cycle unevenness. A processing device is disclosed. This image processing apparatus corrects the light amount ratio (the ratio of the initial shading data to the entire main scanning area of the shading data acquired immediately before reading the document or the average value of the specific area of the main scanning) to the initial shading data without any dirt. To replace and interpolate. Thereby, the change of the amplitude of the rod lens period nonuniformity resulting from the above-mentioned difference in the amount of light can be reduced.

  However, in the conventional technique including the image processing apparatus disclosed in Patent Document 1, there is a problem in that vertical stripes are generated at a place where dirt is detected and replaced with initial shading data. That is, an amplitude difference due to ripple unevenness occurs between the rod lenses between the shading data acquired immediately before reading the original and the initial shading data. As a result, vertical stripes are generated. For this reason, there has conventionally been a problem that it cannot be said that accurate shading correction is performed.

  SUMMARY An advantage of some aspects of the invention is that it provides a shading correction apparatus and an image processing apparatus capable of performing accurate shading correction.

  In order to solve the above-described problems and achieve the object, the present invention smoothes initial data, which is shading data serving as a reference read from a density reference member, and generates first smoothed data. The first high-frequency component generation unit that generates the first high-frequency component that is the difference between the initial data and the first smoothed data, and the density reference member that is later in time than the initial data. A second smoothing unit that smoothes current data that is shading data to generate second smoothed data; and a second smoothing unit that generates a second high-frequency component that is a difference between the current data and the second smoothed data. And a phase shift block that generates a plurality of first high-frequency components having different phases by shifting the phases of the two high-frequency component generating units and the first high-frequency components by different shift amounts. The first high-frequency component having a small phase difference with respect to the phase of the second high-frequency component is detected by comparing the phase of each first high-frequency component whose phase is shifted with the phase of the second high-frequency component. The difference comparison unit, the selection unit that selects the first high-frequency component with a small phase difference detected by the difference comparison unit among the first high-frequency components whose phases are shifted, and the selected phase difference The first high-frequency component with a small value and the first smoothed data are added, and a correction data generation unit that generates shading data in which the phase of the high-frequency component is corrected, and the corrected shading data are used as input data. A shading correction unit that performs shading correction processing and outputs the result.

  According to the present invention, there is an effect that accurate shading correction can be performed.

FIG. 1 is a schematic diagram of a reading module (CIS). FIG. 2 is a diagram for explaining the shift of the main scanning distribution due to heat generation. FIG. 3 is a cross-sectional view of the MFP (MFP) according to the first embodiment of this invention. FIG. 4 is a cross-sectional view of an automatic document conveyance mechanism provided in the MFP according to the first embodiment. FIG. 5 is a block diagram of a controller that controls the automatic document conveyance mechanism provided in the MFP according to the first embodiment and peripheral circuits of the controller. FIG. 6 is a block diagram of a second reading unit provided in the MFP according to the first embodiment. FIG. 7 is a functional block diagram of the white correction unit of the MFP according to the first embodiment. FIG. 8 is a diagram for explaining an operation of extracting a high-frequency component of initial data in the white correction unit of the MFP according to the first embodiment. FIG. 9 is a diagram for explaining the shift amount of each phase shift unit of the white correction unit of the MFP according to the first embodiment. FIG. 10 is a diagram for explaining the phase shift operation of the initial data in each phase shift unit of the white correction unit of the MFP according to the first embodiment. FIG. 11 is a diagram for explaining the difference comparison output of the difference comparison unit provided in the white correction unit of the MFP according to the first embodiment. FIG. 12 is a diagram for explaining an operation of generating shading data in which the phase is corrected so that the ripple unevenness and the amplitude of the current data match in the white correction unit of the MFP according to the first embodiment. FIG. 13 is a diagram for explaining an operation of suppressing vertical stripes due to dirt and scratches on the density reference member by shading correction in the white correction unit of the MFP according to the first embodiment. FIG. 14 is a functional block diagram of the white correction unit of the MFP according to the second embodiment. FIG. 15 is a diagram for explaining the stain detection operation of the stain detection unit provided in the white correction unit of the MFP according to the second embodiment. FIG. 16 is a diagram illustrating an example of the detection output of the dirt detection unit provided in the white correction unit of the MFP according to the second embodiment. FIG. 17 is a diagram for explaining the rewriting operation of the phase shift unit number at the position where the stain is detected by the phase shift amount determination unit provided in the white correction unit of the MFP according to the second embodiment. FIG. 18 is a diagram for explaining the timing at which the phase shift amount determination unit provided in the white correction unit of the MFP according to the second embodiment writes the phase shift unit number in the shift amount memory. FIG. 19 is a diagram for explaining a plurality of types of shift amounts set in the phase shift block of the white correction unit of the MFP according to the third embodiment. FIG. 20 is a functional block diagram of the white correction unit of the MFP according to the fourth embodiment. FIG. 21 is a diagram for explaining an operation in which the output ratio calculation unit of the white correction unit of the MFP according to the fourth embodiment calculates the ratio between the smoothed initial data and the smoothed current data for each pixel. It is. FIG. 22 is a diagram for explaining an operation of generating shading data in which the white correction unit of the MFP according to the fourth embodiment corrects the offset component as well as the high frequency component.

  Hereinafter, as an example, an MFP (Multifunction Peripheral) according to an embodiment to which the present invention is applied will be described in detail with reference to the drawings. Note that the MFP is an electronic device having one or more of a printing function, a copying function, a scanner function, and a facsimile function, for example.

(Overview)
In an electronic apparatus such as an MFP that reads an image, shading correction is performed to correct variation in light amount distribution for each main scanning position of the reading optical system and variation in sensitivity for each sensor chip pixel. Specifically, the reading result (shading data) of the density reference member having a predetermined white color is set to “SD”, the input data is set to “Din”, and the calculation of the following equation (1) is performed on the input data. “Dout”, which is the result of the shading correction, is obtained.

  Dout = Din / SD (Expression 1)

  Here, when the shading data used for the shading correction is generated, if dirt is attached to the density reference member, the value of the shading data at the place where the dirt is attached becomes a value for which accurate shading correction is difficult. This is because, for example, pixels corresponding to locations where dirt attached to the density reference member is attached along the main scanning direction (direction in which the pixels are arranged) of a reading optical system such as a line-shaped image sensor. This means that the pixel data is not accurately subjected to shading correction. For this reason, it corresponds to a location where the density reference member is contaminated on one image generated by scanning the reading optical system in the sub-scanning direction orthogonal to the two-dimensional direction with respect to the main scanning direction. This causes inconvenience in which streaky noise appears.

  Specifically, when black stains are attached to the density reference member, the reading light is absorbed by the black stains, and the reflected light is diffusely reflected, so that incident light to the pixel corresponding to the black stain attachment portion is not detected. This causes a drop in the value of the generated shading data. When shading data having such a drop is used for shading correction, the value of the denominator of the above equation 1 becomes small, resulting in a large shading correction result and white streaks (insufficient shading correction). Similarly, when white dirt adheres to the density reference member, the amount of reflection of the reading light increases due to the white dirt. For this reason, the incident light with respect to the pixel corresponding to the spot where the white dirt is attached becomes larger than the other spots, and the value of the generated shading data becomes a large value. When this large value of shading data is used for shading correction, the value of the denominator of the above equation 1 becomes large, resulting in a small shading correction result and black streaks (excessive shading correction).

  In order to prevent the generation of such streaky noise, the density reference member is changed by changing the relative position of the image sensor of the image reading unit and the density reference member with a movable mechanism when generating shading data. It is conceivable to reduce the influence of dirt, scratches, and the like. That is, reading of a plurality of locations on the density reference member is performed while moving the image sensor in the sub-scanning direction. Then, each shading data corresponding to a plurality of locations where reading is performed is averaged. As a result, it is possible to generate shading data in which the influence of dirt and scratches is reduced. Alternatively, a plurality of locations are read while rotating the density reference member formed by the rotating roller. As a result, it is possible to generate shading data in which the influence of dirt and scratches is reduced.

  However, a reading module such as a contact image sensor (CIS: Contact Image Sensor) for reading the back side of a document is often fixed in a small space in an ADF (Auto Document Feeder) apparatus. For this reason, when the concentration reference member and the movable mechanism are provided in the ADF apparatus, the ADF apparatus becomes complicated, large, and expensive.

  Here, the following method can reduce the influence of dirt and scratches on the density reference member without providing a movable mechanism. That is, the initial shading data acquired with a clean density reference member in advance is stored in the nonvolatile memory. The initial shading data is compared with the shading data acquired immediately before reading the document. Data at pixel positions whose comparison results are greater than or equal to a predetermined value is determined as data affected by dirt or scratches. Then, the data affected by the contamination is interpolated by replacing the initial shading data without the contamination with the light amount ratio corrected. The light amount ratio is the ratio of the entire area of the main scan or the average value of the specific area of the main scan between the initial shading data and the shading data acquired immediately before reading the document. Thereby, it is possible to reduce the influence of dirt and scratches on the density reference member without providing a movable mechanism.

  However, even in such a method, at the place where the dirt is detected and replaced with the initial shading data, the amplitude difference of the ripple unevenness that occurs at the rod lens interval between the shading data acquired immediately before reading the original and the initial shading data is detected. The resulting vertical streak occurs.

  In general, there is a possibility that the lens interval may be shifted due to the influence of heat between the initial shading data acquired in advance in a non-volatile memory with a clean density reference member and the shading data acquired immediately before reading a document. This deviation in the lens interval occurs due to a difference in temperature environment depending on the location where shading data is stored in the nonvolatile memory or the location where the product is used. Further, the lens interval shift occurs due to heat generated by a light source unit such as an LED and an integrated circuit such as an ASIC when a large number of documents are continuously read (continuous scanning). LED is an abbreviation for “Light Emitting Diode”. ASIC is an abbreviation for “Application Specific Integrated Circuit”. Hereinafter, a mechanism in which streaks are generated in the original due to ripple unevenness of the lot lens interval due to the influence of heat rise during continuous scanning will be described.

  FIG. 1 shows a schematic diagram of a reading module (CIS). The figure which attached | subjected the code | symbol of (a) of FIG. 1 is an exploded perspective view of the principal part of a reading module. The figure which attached | subjected the code | symbol of (b) of FIG. 1 is an enlarged view of the principal part of a reading module. The figure which attached | subjected the code | symbol of (c) of FIG. 1 is a figure which shows the output waveform corresponding to each rod lens of a reading module.

  The reading module irradiates the original or the density reference member with the light emitted from the light source unit 2 via the light guide 1, and applies a plurality of rod lenses 4a shown in the drawing with the reference numeral (b) in FIG. The reflected light is condensed on the pixels 3 a of the image sensor 3 through the rod lens array 4 formed in a row. Since the reflected light is collected by using the rod lens 4a, the reflected light is easily collected near the center of the rod lens 4a as shown in the figure labeled (c) in FIG. Is expensive. However, the output decreases at the end of the rod lens 4a. For this reason, the position where the output is high and the position where the output is low are periodically generated in the period depending on the arrangement of the rod lens 4a.

  2A and 2B, the main scanning distribution (solid line graph) at 0 minutes (immediately after the LED is turned on) and the main scanning distribution (dotted line graph) after X minutes are shown. As shown in the figure with the symbol (a) in FIG. 2, the amount of light is reduced due to heat generated by the continuous lighting of the LED, and the position where the output is high and the position where the output is low are shifted over time. Such a shift in the main scanning distribution occurs when the rod lens 4a is thermally expanded, the diameter is changed, and the positional relationship between the rod lens 4a and the image sensor 3 is shifted with time. The shift of the main scanning distribution is caused by the substrate extending in the main scanning direction (the direction in which the pixels 3a are arranged) due to thermal expansion of the sensor substrate, and the positional relationship between the rod lens 4a and the image sensor 3 is shifted with time. Occur. If the thermal expansion coefficients of the rod lens 4a and the substrate of the image sensor 3 are equal, the shift of the main scanning distribution does not occur. However, generally, the thermal expansion coefficient of the substrate of the image sensor 3 is higher than the thermal expansion coefficient of the rod lens 4a. For this reason, a shift of the main scanning distribution occurs.

  The figure attached with the reference numeral (b) in FIG. 2 shows the output change rate after X minutes and at 0 minutes. The output change rate in the figure is calculated by the following equation (2).

  Output change rate = Output after X minutes / Output at 0 minutes ... (Formula 2)

  In FIG. 2B, the peak position of the output after X minutes has a high change rate because the difference from the output at 0 minutes is small. Further, the bottom position of the output after X minutes has a large difference from the output at 0 minutes, so the rate of change is low. Also, the output peak position at 0 minutes has a low rate of change because of a large difference from the output after X minutes. And since the difference between the output bottom position at 0 minutes and the output after X minutes is small, the rate of change is high. At positions other than these four positions, the amount of decrease in output is substantially equal from 0 minutes to X minutes later, so the rate of change is uniformly reduced.

  Even if the ripple unevenness of the data at the time of document reading (at 0 minutes) and the data stored in the non-volatile memory match, the ripple unevenness shifts during continuous scanning. For this reason, when the data stored in the non-volatile memory is used as shading data and shading correction is performed on the original data when the original is read after X minutes, as shown in FIG. The ripple unevenness is deviated (the lens condensing rate is deviated), so that streaks are generated in the original. That is, bright and dark streaks are generated in the image data after shading correction at a position where the output change rate is high and a position where the output change rate is low. Such a phenomenon is a phenomenon that occurs in the same manner even in a difference in environment between the location where shading data is stored in the nonvolatile memory and the location where the MFP is used.

(First embodiment)
As described below, the MFP according to the embodiment replaces the shading data with dirt acquired immediately before reading the document with the initial shading data without dirt, and converts the initial shading data before reading the document. Correction is made so that the phase and the ripple irregularity of the shading data acquired in step 1 are matched. As a result, when stains and scratches are detected on the density reference member, the position where the stains and scratches are detected is interpolated using the initial shading data corrected to match the ripple unevenness of the shading data acquired immediately before reading the document. To do. For this reason, it is possible to prevent inconvenience that a bright streak or a dark streak occurs in the output document or output data, and to enable accurate shading correction.

  FIG. 3 is a sectional view of the MFP according to the embodiment. As shown in FIG. 3, the MFP according to the embodiment includes an automatic document feeder (ADF) 10, a paper feeding unit 20, and an image forming unit 30. The paper feed unit 20 includes paper feed cassettes 21 and 22 that store recording papers having different paper sizes. In addition, the paper feed unit 20 includes a paper feed mechanism 23 including various rollers that transport the recording paper stored in the paper feed cassettes 21 and 22 to the image forming position of the image forming unit 30.

  The image forming unit 30 includes an exposure device 31, a photosensitive drum 32, a developing device 33, a transfer belt 34, and a fixing device 35. The image forming unit 30 exposes the photosensitive drum 32 by the exposure device 31 based on the image data of the original read by the image reading unit in the ADF 10, and forms a latent image on the photosensitive drum 32. Further, the image forming unit 30 develops the developing device 33 by supplying toner of different colors to the photosensitive drum 32. Then, the image forming unit 30 transfers the image developed on the photosensitive drum 32 to the recording paper supplied from the paper feeding unit 20 by the transfer belt 34 and then the toner image transferred to the recording paper by the fixing device 35. The toner is melted to fix the color image on the recording paper.

  FIG. 4 is an enlarged view of a cross section of the ADF 10. FIG. 5 is a block diagram of the controller 11 that controls the ADF 10 and the peripheral circuits of the controller 11. The ADF 10 conveys the read original to a fixed reading unit, and reads an image while conveying the original at a predetermined speed. The ADF 10 includes a document setting unit A, a separation feeding unit B, a registration unit C, a turn unit D, a first reading conveyance unit E, a second reading conveyance unit F, a paper discharge unit G, and a stack unit H. The document setting unit A sets a read document bundle. The separation feeding unit B separates and feeds the originals one by one from the set original bundle. The registration unit C has a function of primarily abutting and aligning the fed document and a function of pulling out and transporting the aligned document. The turn part D turns the document to be conveyed and conveys the document surface toward the reading side (downward). The first reading conveyance unit E reads the surface image of the document from below the contact glass. The second reading conveyance unit F reads the back image of the original after reading. The paper discharge unit G discharges the original whose front and back have been read out of the apparatus. The stack unit H stacks and holds documents after reading.

  The original bundle 130 to be read is set on the original table 132 including the movable original table 131 with the original surface facing upward. Further, the width direction of the document bundle 130 is positioned in a direction perpendicular to the conveyance direction by a side guide (not shown). The document set is detected by the set filler 133 and the document set sensor 100 and transmitted to the main body control unit 122 by the I / F 114.

  Further, the document length detection sensor 134 or 135 provided on the document table surface (a reflective sensor or an actuator type sensor capable of detecting even one document) is used to approximate the length of the document in the conveyance direction. Determined.

  The movable document table 131 is configured to be movable (movable up and down) in the directions a and b indicated by arrows in FIG. When the set of documents is detected by the set filler 133 and the document set sensor 100, the movable document table 131 moves the bottom plate raising motor 112 in the normal direction so that the uppermost surface of the document bundle 130 contacts the pickup roller 148. 131 is raised. The pickup roller 148 operates in the c and d directions indicated by arrows in FIG. 4 by a cam mechanism using the pickup motor 108 as a drive source. The pick-up roller 148 is raised by the movable original table 131 and is pushed by the upper surface of the original on the movable original table 131 to rise in the c direction.

  When the print key is pressed from the operation unit 121 and a document feed signal is transmitted from the main body control unit 122 to the controller 11 via the I / F 114, the pickup roller 148 is driven to rotate by the normal rotation of the feed motor 109. Then, several (ideally one) documents on the document table 132 are picked up. The rotation direction is a direction in which the uppermost document is conveyed to the sheet feeding port.

  The paper feed belt 136 is driven in the paper feed direction by the normal rotation of the paper feed motor 109. The reverse roller 137 is rotationally driven in the direction opposite to the paper feeding direction by the forward rotation of the paper feeding motor 109, separates the uppermost document and the original document thereunder, and feeds only the uppermost document. It has become. More specifically, the reverse roller 137 contacts the paper feeding belt 136 with a predetermined pressure. When the reverse roller 137 is in direct contact with the paper feed belt 136 or is in contact with the original via one original, the reverse roller 137 rotates counterclockwise as the paper feed belt 136 rotates. The reverse roller 137 is set so that the follower force is lower than the torque of the torque limiter when two or more originals enter between the paper feed belt 136 and the reverse roller 137. In this case, the reverse roller 137 rotates in the clockwise direction, which is the original driving direction, and functions to push back the excess original. Thereby, it is possible to prevent double feeding of documents.

  The document separated into one sheet by the action of the paper feed belt 136 and the reverse roller 137 is further fed by the paper feed belt 136, the leading edge is detected by the abutting sensor 105, and the pull-out roller 138 is further advanced and stopped. I hit it. Thereafter, the original is conveyed by a predetermined distance from the detection of the abutting sensor 105 and pressed against the pull-out roller 138 with a predetermined amount of deflection. In this state, the paper feed motor 109 is stopped and the drive of the paper feed belt 136 is stopped. At this time, the pickup motor 108 is rotated, the pickup roller 148 is retracted from the upper surface of the document, and the document is fed only by the conveying force of the paper feed belt 136. As a result, the leading edge of the document enters the nip between the pair of upper and lower rollers of the pull-out roller 138, and alignment (skew correction) of the leading edge is performed.

  The pull-out roller 138 has a skew correction function. The pull-out roller 138 is a roller for conveying the skew-corrected document after separation to the intermediate roller 139 and is driven by the reverse rotation of the paper feed motor 109. At this time (when the paper feed motor 109 rotates in reverse), the pull-out roller 138 and the intermediate roller 139 are driven, but the pickup roller 148 and the paper feed belt 136 are not driven.

  A plurality of document width sensors 104 are arranged in the depth direction and detect the size in the width direction perpendicular to the transport direction of the document transported by the pull-out roller 138. Further, the length of the document in the conveyance direction is detected by using a motor pulse generated by reading the leading edge and the trailing edge of the document with the butting sensor 105.

  When the document is conveyed from the registration unit C to the turn unit D by driving the pull-out roller 138 and the intermediate roller 139, the conveyance speed at the registration unit C is higher than the conveyance speed at the first reading conveyance unit E. Set to As a result, the processing time for sending the document to the reading unit is shortened. When the leading edge of the document is detected by the reading entrance sensor 103, before the leading edge of the document enters the nip between the upper and lower rollers of the reading entrance roller 140, the document feeding speed is reduced to be the same as the reading feeding speed. Start. At the same time, the reading motor 110 is driven to rotate forward, and the reading inlet roller 140, the reading outlet roller 141, and the CIS outlet roller 142 are driven. When the registration sensor 107 detects the leading edge of the document, the document is decelerated over a predetermined conveyance distance, temporarily stops before the reading position 143, and transmits a registration stop signal to the main body control unit 122 via the I / F 114. To do.

  Subsequently, when a reading start signal is received from the main body control unit 122, the document whose registration has been stopped is transported at an increased speed so as to rise to a predetermined transport speed before the leading end of the document reaches the reading position 143. At the timing when the leading edge of the document detected by the pulse count of the reading motor 110 reaches the reading unit, a gate signal indicating an effective image area in the sub-scanning direction on the first surface is sent to the main body control unit 122, and the first reading unit is moved to the document. Sent until the trailing edge is removed.

  In the case of single-sided document reading, the document that has passed through the first reading conveyance unit E is conveyed to the paper discharge unit G through the second reading unit. At this time, when the leading edge of the document is detected by the paper discharge sensor 106, the paper discharge motor 111 is driven to rotate forward, and the paper discharge roller 144 rotates counterclockwise. Further, the discharge motor drive speed is reduced immediately before the trailing edge of the document comes out of the nip between the upper and lower roller pairs of the discharge roller 144 by the discharge motor pulse count from the detection of the leading edge of the document by the discharge sensor 106. As a result, it is possible to prevent inconvenience that the document discharged onto the discharge tray 145 jumps out of the discharge tray 145.

  In the case of double-sided original reading, the second reading unit 113 is detected when the leading end of the original reaches the second reading unit 113 by the pulse count of the reading motor 110 after the paper discharge sensor 106 detects the leading end of the original. A gate signal indicating an effective image area in the sub-scanning direction is transmitted from the controller 11 through the second reading unit 113 until the trailing edge of the document is removed. The second reading roller 146 suppresses the floating of the document in the second reading unit 113. The second reading roller 146 also serves as a reference white portion (density reference member) for acquiring shading data by the second reading unit 113.

  FIG. 6 is a block diagram of the main part of the electric circuit of the second reading unit 113. As shown in FIG. 6, the second reading unit 113 includes the light source unit 2 including an LED, a fluorescent lamp, a cold cathode tube, or the like. The light source unit 2 constitutes an irradiation unit that irradiates light in the main scanning direction together with a light guide (not shown).

  The second reading unit 113 includes a plurality of pixels (photoelectric conversion elements) 3a arranged in the main scanning direction (a direction corresponding to the document width direction), a plurality of amplifier circuits 202 connected to each pixel 3a, and each amplifier circuit. A plurality of A / D converters 203 connected to 202 are also provided. The output signal of the A / D conversion unit 203 includes a black level offset component in addition to the signal component. The second reading unit 113 includes a black correction unit 204 that removes a black level offset component.

  The white correction unit 205 performs white correction processing on the output signal of the black correction unit 204, thereby removing adverse effects on the image data due to unevenness of the light source unit 2 and uneven sensitivity of each pixel 3a. As will be described in detail later, the white correction unit 205 replaces the dirty original reading shading data acquired by reading the density reference member immediately before reading the original with the original initial shading data without dirt. The phase of the initial shading data is corrected so that the ripple unevenness and the amplitude of the shading data at the time of document reading match. This prevents the inconvenience that bright or dark streaks occur in the output document or output data.

  The second reading unit 113 also includes an image processing unit 206, a frame memory 207, an output control circuit 208, an I / F circuit 209, and the like.

  Prior to the conveyance of the document to the reading position where reading is performed by the second reading unit 113, a lighting signal for ON control of lighting is supplied from the controller 11 to the light source unit 2. As a result, the light source unit 2 is turned on, light is irradiated onto a document (not shown), and reflected light is generated. The reflected light from the original is condensed and received by each pixel 3a by the rod lens 4a. Each pixel 3a generates a read signal that is an electrical signal corresponding to the received reflected light. The read signal is amplified by the amplifier circuit 202 and then digitized into read data by the A / D converter 203. For example, when the read data is 8 bits, the black level is “0” and the white level is “255”.

  The read data is subjected to offset component removal processing by the black correction unit 204, and shading correction described later is performed by the white correction unit 205. Further, the read data is temporarily stored in the frame memory 207 after being subjected to an inter-line correction process or the like by the image processing unit 206. Thereafter, the read data is converted into a data format that can be processed by the main body control unit 122 by the output control circuit 208 and then supplied to the main body control unit 122 via the I / F circuit 209. In addition to the lighting signal of the light source unit 2 described above, the controller 11 sends the second reading unit 113 a timing at which the leading edge of the document reaches the reading position by the second reading unit 113 (image data after that timing is stored). A timing signal for notifying that the data is treated as valid data, a power source, and the like are supplied.

  Next, the shading correction operation in the white correction unit 205 will be described. FIG. 7 is a functional block diagram of the white correction unit 205. As illustrated in FIG. 7, the white correction unit 205 includes a storage unit 251, a high frequency component extraction unit 252, a high frequency component phase correction unit 253, a data correction unit 254, and a shading correction unit 312.

  As an example, the high-frequency component extraction unit 252, the high-frequency component phase correction unit 253, the data correction unit 254, and the shading correction unit 312, as shown in FIG. By executing a shading correction program stored in the storage unit 101, etc., a function realized by software is provided. ROM is an abbreviation for “Read Only Memory”. RAM is an abbreviation for “Random Access Memory”.

  In this example, the high frequency component extraction unit 252, the high frequency component phase correction unit 253, the data correction unit 254, and the shading correction unit 312 of the white correction unit 205 will be described as being realized by software. However, some or all of the high-frequency component extraction unit 252, the high-frequency component phase correction unit 253, the data correction unit 254, and the shading correction unit 312 may be realized by hardware.

  Further, the shading correction program may be provided as a file in an installable format or an executable format recorded on a recording medium readable by a computer device such as a CD-ROM or a flexible disk (FD). Further, the program may be provided by being recorded on a computer-readable recording medium such as a CD-R, a DVD, a Blu-ray disc (registered trademark), or a semiconductor memory. DVD is an abbreviation for “Digital Versatile Disk”. Further, the shading correction program may be provided by being installed via a network such as the Internet. The shading correction program may be provided by being incorporated in advance in a ROM or the like in the device.

  The storage unit 251 stores the input data obtained by reading the uncontaminated density reference member (in this example, the above-described second reading roller 146) at the initial stage such as when the MFP of the embodiment is shipped from the factory. Stored in 301. In addition, the data stored in the first storage unit 301 is stored in the second storage unit 302 configured by a nonvolatile memory or the like. Hereinafter, the data stored in the second storage unit 302 is referred to as initial shading data or initial data. Further, input data obtained by reading the density reference member immediately before reading the document at the time of reading the document is stored in the first storage unit 301. Hereinafter, the data stored in the first storage unit 301 is referred to as original reading shading data or current data.

  In the smoothing unit 303, which is an example of the first smoothing unit, the high-frequency component extracting unit 252 is a second AC waveform having a predetermined frequency as shown in the diagram with the symbol (a) in FIG. Periodic fluctuation components corresponding to the lens pitch of the rod lens array 4 of the reading module are removed from the initial shading data (initial data) stored in the storage unit 302. As a result, the AC waveform of the predetermined frequency of the initial data is shaped into a smoothed waveform as shown in the diagram with the symbol (b) in FIG. In addition, the high frequency component extraction unit 252 includes initial data obtained by removing periodic fluctuation components and the like by the smoothing unit 303 and the second storage unit 302 in the high frequency component extraction unit 305 that is an example of the first high frequency component extraction unit. The difference from the initial data stored in is detected. Thereby, the high frequency component extraction part 305 extracts only the high frequency component of initial data as shown in the figure which attached | subjected the code | symbol of (c) of FIG.

  Similarly, in the smoothing unit 304, which is an example of the second smoothing unit, the high-frequency component extracting unit 252 has an AC waveform with a predetermined frequency as shown in the diagram with the reference numeral (a) in FIG. The periodic fluctuation component corresponding to the lens pitch of the rod lens array 4 of the reading module is removed from the original reading shading data (current data) stored in the first storage unit 301. Thereby, the alternating current waveform of the predetermined frequency of the current data is shaped into a smoothed waveform as shown in the diagram with the symbol (b) in FIG. Further, the high frequency component extraction unit 252 includes initial data obtained by removing the periodic fluctuation component and the like by the smoothing unit 304 in the high frequency component extraction unit 306 that is an example of the second high frequency component extraction unit, and the second storage unit 302. The difference from the initial data stored in is detected. As a result, the high frequency component extraction unit 306 extracts only the high frequency component of the initial data as shown in the diagram with the reference numeral (c) in FIG.

  Next, the high-frequency component phase correction unit 253 includes a phase shift block 307 including first to n-th phase shift units, a difference calculation block 308 including first to n-th difference calculation units, and a difference. A degree comparison unit 309 is provided. “N” is a natural number of 2 or more.

  The high frequency components of the initial data extracted by the high frequency component extraction unit 305 are supplied to the first to nth phase shift units of the phase shift block 307, respectively. The phase shift amounts of the respective phase shift units of the phase shift block 307 are set to different shift amounts as shown in FIG. The example of FIG. 9 is an example in which the phase shift block 307 includes a total of 31 phase shift units, that is, first to 31st phase shift units. In the case of this example, the phase shift amounts of the first to n-th phase shift units are set so that the resolution shift amount is 1/32 pixels as an example.

  That is, for the first to fifteenth phase shift units, “−15/32, −14/32, −13/32... −2/32, −1/32”, etc. Thus, different shift amounts are set for each pixel on the minus side. In the case of this example, a shift amount of 0/32 is set in the sixteenth phase shift unit. In the case of this example, for the 17th to 31st phase shift units, “+1/32, +2/32, +3/32... +14/32, +15/32”, etc. In this way, different shift amounts are set for each pixel on the plus side. In this example, the phase is shifted to ± 15/32 pixels around the 16th phase shift unit. Note that the shift amount of the sixteenth phase shift unit is zero. For this reason, the phase of the initial data is not shifted.

  The phase shift block 307 performs so-called cubic interpolation processing in each phase shift unit to shift the phase of the high frequency component of the initial data with a resolution of less than one pixel, and the first to nth of the difference calculation block 308. The difference is calculated and supplied to the output selection unit 310 of the data correction unit 254.

  The high frequency components extracted from the current data are also supplied from the high frequency extraction unit 306 to the first to nth difference calculation units of the difference calculation block 308. The difference calculation block 308 is a block obtained by dividing the difference between the absolute values of the phase shift corrected data and the high-frequency component of the current data in each difference calculation unit by the number of pixels in the main scanning direction of the reading module. Add every time (sum of absolute difference (SAD)). The dissimilarity comparison unit 309 indicates the dissimilarity indicating the phase shift unit number (phase shift unit number) corresponding to the lowest difference absolute value sum among the sum of absolute differences from the first to nth dissimilarity calculation units. The comparison output is supplied to the output selection unit 310.

  More specifically, in each of the drawings with the reference numerals (a) to (c) in FIG. 10, the solid line waveform is the waveform of the initial data. Further, in each of the drawings with the reference numerals (a) to (c) in FIG. 10, the dotted waveform indicates the output of the first phase shift unit, the 25th phase shift unit, or the 31st phase shift unit. It is a waveform. As can be seen from FIGS. 10A to 10C, the initial data input to the first phase shift unit is the -15/32 shift described with reference to FIG. The phase is shifted by the amount and supplied to the first difference calculator. The initial data input to the 25th phase shift unit is shifted in phase by the shift amount of +9/32 described with reference to FIG. 9, and is supplied to the 25th difference degree calculation unit. The initial data input to the 31st phase shift unit is shifted in phase by the shift amount of +15/32 described with reference to FIG. 9, and is supplied to the 31st difference calculation unit.

  FIGS. 10 (d) to 10 (f) are attached to the first difference degree calculation unit, the 25th difference calculation unit, and the 31st difference calculation unit. The phase difference between the data (dotted waveform) and the current data (solid waveform) is shown. In the case of the first dissimilarity calculation unit shown in FIG. 10D, the large difference between the phase-shifted initial data (dotted line waveform) and the current data (solid line waveform). There is a phase difference. Further, in the case of the thirty-first dissimilarity calculator shown in FIG. 10 (f), the phase-shifted initial data (dotted line waveform) and the current data (solid line waveform) are inserted. There is a small phase difference. On the other hand, in the case of the twenty-fifth dissimilarity calculator shown in FIG. 10E, the phase-shifted initial data (dotted line waveform), current data (solid line waveform), The phase difference between is substantially zero.

  FIG. 11 is a diagram for explaining the difference comparison output supplied from the difference comparison unit 309 to the output selection unit 310. In the case of the example in FIG. 11, pixels corresponding to the effective pixel region between the line reference signals of the reading module are the first to ten blocks (first block) that are blocks for each predetermined number of pixels. To 10th block). In the case of this example, as shown in FIG. 11 and FIG. 11 in which the first dissimilarity calculation unit adds the reference numeral (d) in FIG. 10, between the initial data and the current data that are phase-shifted for each block. Are calculated, and sums of absolute differences “sad — 1 — 1”, “sad — 1 — 2”... “Sad — 1 — 10” are generated for each block. Similarly, as shown in FIG. 11 and FIG. 11, the twenty-fifth dissimilarity calculator calculates the level between the phase-shifted initial data and the current data for each block. The phase difference is calculated, and the sum of absolute differences “sad — 25 — 1”, “sad — 25 — 2”... “Sad — 25 — 10” is generated for each block. Similarly, the thirty-first dissimilarity calculation unit, as shown in FIG. 11 with the symbol (f) in FIG. 10 and FIG. The phase difference is calculated, and the sum of absolute differences “sad — 31 — 1”, “sad — 31 — 2”... “Sad — 31 — 10” is generated for each block.

  Specifically, the dissimilarity calculation block 308 calculates, for each block in the main scanning direction, the sum of absolute value differences between each phase-shift-corrected data and the high-frequency component of the current data, and The calculation is performed by performing the calculation of Equation 4.

  αm_n (x) = ABS (Dpre (x) −Dinit_m (x)) (Expression 3)

  sad_m_n = Σαm (Expression 4)

  In Equations 3 and 4, “m” is the number (1 to 31) of each phase shift unit. “N” is a block number (1 to 10) in the main scanning direction. “Dpre (x)” is the value of the current data of the xth pixel. “Dinit_m (x)” is a data output value of the phase shift unit m of the x-th pixel. “Αm (x)” is an absolute difference between Dpre (x) and Dinit_m (x) of the x-th pixel. “Sad_m_n” is an addition value (sum of absolute differences) of all αm of the nth block.

  The dissimilarity comparison unit 309 indicates the dissimilarity indicating the phase shift unit number (phase shift unit number) corresponding to the lowest difference absolute value sum among the difference absolute value sums from the first to 31st dissimilarity calculation units. The comparison output is supplied to the output selection unit 310. In the case of the example of FIG. 11, the first block indicates that the sum of absolute difference values corresponding to the seventeenth phase shift unit is the lowest value. Similarly, in the case of the example of FIG. 11, in the eighth block, the sum of absolute difference values corresponding to the sixteenth phase shift unit is the lowest value. Similarly, in the case of the example of FIG. 11, in the tenth block, the value of the sum of absolute differences corresponding to the seventeenth phase shift unit is the lowest value. The output selection unit 310 is supplied with a difference comparison output indicating the phase shift unit number such as “17”, “16”, etc., of the phase shift unit corresponding to the lowest sum of absolute differences.

  Next, the output selection unit 310 of the data correction unit 254 is an example of a selection unit, and selects the phase-shifted initial data of the phase shift unit number indicated by the difference comparison output supplied from the difference comparison unit 309. And supplied to the correction data generation unit 311. Specifically, the output selection unit 310 uses the phase shift unit number to select, for example, phase-shifted initial data as shown in FIG. To the unit 311.

  The correction data generation unit 311 includes the initial data smoothed by the smoothing unit 303 and the phase-shifted initial data selected by the output selection unit 310 shown in the diagram with the reference numeral (b) in FIG. Are added. As a result, the correction data generation unit 311 can generate shading data whose phase is corrected so that the ripple unevenness and the amplitude of the current data match, as shown in the diagram with the reference numeral (c) in FIG. The shading correction unit 312 performs shading correction of input data using the shading data whose phase is corrected so that the ripple unevenness and amplitude of the current data match.

  As is apparent from the above description, the MFP according to the first embodiment, as shown in FIG. 13, for example, has a clean density reference member even when the current data is affected by dirt or scratches on the density reference member. Since the shading correction is performed in place of the initial data acquired from the above, vertical stripes due to dirt and scratches on the density reference member can be suppressed.

  Further, when the current data is replaced with the initial data, the lens pitch unevenness of the initial data is corrected so as to match the phase of the lens pitch unevenness of the current data. For this reason, it is possible to suppress vertical streaks due to deviations in lens pitch unevenness over time. Therefore, the MFP according to the embodiment can perform accurate shading correction.

(Second Embodiment)
Next, an MFP according to the second embodiment of the present invention will be described. In the MFP of the second embodiment, the phase shift unit number of the block corresponding to the position where the contamination of the density reference member is detected is rewritten by linear interpolation from the previous and subsequent blocks where the contamination is not detected. is there. Hereinafter, only the difference between the first embodiment and the second embodiment will be described, and a duplicate description will be omitted.

  FIG. 14 is a functional block diagram of the white correction unit 205 provided in the MFP according to the second embodiment. Of the functional blocks shown in FIG. 14, the functional blocks of the dirt detection unit 351, the shift amount memory 352, the phase shift amount determination unit 353, and the output selection unit 354 are the same as those in the first embodiment. It is a difference.

  In the case of such an MFP according to the second embodiment, current data stored in the first storage unit 301 and initial data stored in the second storage unit 302 are stored in the dirt detection unit 351 shown in FIG. Supplied. The dirt detection unit 351 detects the position where the density reference member is dirty by comparing each data. As such a dirt detection part 351, the technique currently disclosed by Unexamined-Japanese-Patent No. 2010-011297 etc. can be used, for example.

  More specifically, the dirt detection unit 351 calculates a ratio β (initial data / current data) between the initial data and the current data as shown in the diagram with the symbol (a) in FIG. Then, the dirt detection unit 351 compares the preset maximum threshold value and minimum threshold value with the calculated ratio β, as shown in the drawing with the symbol (b) in FIG. As shown in the drawing with the reference numeral (a) in FIG. 15, the value of the ratio β corresponding to the location where the density reference member is contaminated is shown in the drawing with the reference numeral (b) in FIG. As described above, it is equal to or greater than the maximum threshold value or equal to or less than the minimum threshold value. For this reason, the dirt detection unit 351 determines that dirt is attached to the density reference member when the ratio β exceeds the maximum threshold value or when the ratio β falls below the minimum threshold value.

  In addition, by multiplying the ratio β by all pixels of the initial data and the current data, or the ratio γ of the average value of a specific wide area (ratio γ = current data_ave / initial data_ave), the light amount is corrected, It is possible to set the output ratio of the part having no ratio β to 1.0, and the maximum threshold value and the minimum threshold value can be set based on 1.0.

  FIG. 16 shows an example of the detection output of the dirt detection unit 351. The example of FIG. 16 is a block corresponding to a predetermined number of pixels corresponding to the effective pixel area between the line reference signals of the reading module, as shown in the diagrams with the reference numerals (a) and (b). In this example, the first to tenth blocks are divided into a total of ten blocks (first block to tenth block). When the value of the ratio β exceeds the maximum threshold value or falls below the minimum threshold value, the dirt detection unit 351 displays “H (high level)” as shown in FIG. ”Is supplied to the phase shift amount determination unit 353 and the output selection unit 354. In addition, when the value of the ratio β does not exceed the maximum threshold value or exceeds the minimum threshold value, the dirt detection unit 351, as shown in the diagram with the reference numeral (c) in FIG. The detection signal “L (low level)” is supplied to the phase shift amount determination unit 353 and the output selection unit 354.

  On the other hand, as described above, high-frequency components are extracted from the initial data output from the second storage unit 302. Each phase shift unit of the phase shift block 307 shifts the phase of the high frequency component of the initial data with a resolution of less than one pixel. Each phase shift unit has a different shift amount. Each difference calculation unit of the difference calculation block 308 calculates the difference between the high-frequency component of each phase-shifted initial data and the high-frequency component of the current data in the first storage unit 301 in the main scanning direction of the reading module. The total is made for each block divided by an arbitrary number of pixels. The difference comparison unit 309 supplies the shift amount memory 352 with the phase shift unit number corresponding to the difference calculation unit that has calculated the lowest sum of absolute differences.

  The shift amount memory 352 stores the phase shift unit number for each block in the main scanning direction. When the detection signal supplied from the dirt detection unit 351 is “H” (when the density reference member is dirty), the phase shift amount determination unit 353 performs the calculation of Equation 5 below. The phase shift amount determination unit 353 stores the phase shift unit number of the block in the main scanning direction at the position where the contamination is detected, which is stored in the shift amount memory 352, using the block numbers in the main scanning direction before and after the detection of the contamination. Rewrite by linear interpolation.

  As a result, the high-frequency component of the initial data of the abnormal block in which the contamination is detected is interpolated with an approximate value obtained by performing linear interpolation on the high-frequency component of the initial data of the normal block in the vicinity of the abnormal block where the contamination is not detected. be able to. As normal blocks used for linear interpolation processing, for example, normal blocks before and after an abnormal block can be used. Alternatively, the normal block one before and two before the abnormal block may be used, or the normal block one after and two after the abnormal block may be used. Further, not only two adjacent normal blocks but also three or more normal blocks may be used. Further, the abnormal block may be replaced with a normal block immediately before or after the abnormal block.

  dotnum (N) = {1− (N−S) / (E−S)} × dotnum (S) + (N−S) / (E−S) × dotnum (E)... = dotnum (S ) + (Dotnum (E) −dotnum (S)) / (E−S) × (N−S) (Expression 5)

  In equation (5), “dotnum” is a phase shift unit number for each block in the main scanning direction as shown in FIG. 17, for example, stored in the shift amount memory 352. “S” shown in Formula 5 is the correction start block number (the block immediately before the abnormal block that is the head) shown in FIG. “E” is the correction end block number (the block immediately after the abnormal block at the rear end). “N” indicates a target block number.

  The phase shift amount determination unit 353 stores the value of the nearest normal block in the shift amount memory 352 when the leading block includes an abnormal pixel (a pixel that shows an abnormal value due to contamination). If the second block second from the first block is normal, dotnum (1) = dotnum (2). If all of the first block 10 to the last block 10 are abnormal, dotnum (1) = dotnum (2) =... = Dotnum (10) = dotnum (11). When the last block N includes an abnormal pixel, the phase shift amount determination unit 353 stores the value of the nearest normal block in the shift amount memory 352.

  If the block (N-1) is normal, dotnum (N) = dotnum (N-1). If all the blocks N-9 to N are abnormal, dotnum (N-9) = dotnum (N-8) =... = Dotnum (N) = dotnum (N-10).

  Further, the phase shift amount determination unit 353 does nothing when all the blocks include abnormal pixels and when all the blocks are normal.

  Next, the phase shift amount determining operation of the phase shift amount determining unit 353 will be described. The figure which attached | subjected the code | symbol of (a) of FIG. 18 has shown the line reference signal which is a reference signal of 1 line. Further, the diagram with the symbol (b) in FIG. 18 shows a white data acquisition signal indicating a data acquisition period (acquisition of shading data at “L”) from the density reference member.

  The operation timing until the phase shift amount determination unit 353 determines the phase shift amount will be described. After the white data is acquired (after the white data acquisition signal returns to “H”), the phase shift amount determination unit 353 performs the timing of the first line shown in FIG. The phase shift unit number close to the phase of the high frequency component of the current data of each block from the difference degree comparison unit 309 is written in the shift amount memory 352. Note that the phase shift amount determination unit 353 does not write the output from the difference comparison unit 309 to the shift amount memory 352 at the timing after the first line.

  In the second line shown in FIG. 18B, the phase shift amount determination unit 353 uses the above-described linear interpolation to detect the phase of the shift amount memory 352 in the shift amount memory 352. Rewrite the number. Note that the phase shift amount determination unit 353 does not rewrite the phase shift unit number written in the shift amount memory 352 until the next white data acquisition signal is asserted / negated after the second line. By complying with such rewrite timing restrictions on the shift amount memory 352, the inconvenience of rewriting the shift amount memory 352 at an unintended timing is prevented.

  Next, the output selection unit 310 selects the high-frequency component of the initial data whose phase is shifted corresponding to the phase shift unit number read from the shift amount memory 352, and supplies it to the correction data generation unit 311. The correction data generation unit 311 adds the high-frequency component of the initial data whose phase is shifted and the smoothed initial data, and supplies the addition output to the output selection unit 354.

  When the detection output from the dirt detection unit 351 is “H”, the output selection unit 354 determines that the density reference member is dirty, and uses the output from the correction data generation unit 311 as shading data to determine the shading correction unit 312. To supply. Further, when the detection output of the dirt detection unit 351 is “L”, the output selection unit 354 supplies the current data to the shading correction unit 312 as shading data. When the detection output of the dirt detection unit 351 is “L”, the addition output of the correction data generation unit 311 may be supplied to the shading correction unit 312 as shading data.

  As is apparent from the above description, the MFP according to the second embodiment generates the phase shift amount of the area where the contamination is detected by linear interpolation from the front and rear phase shift unit numbers where the contamination is not detected. As a result, the phase shift unit number close to the phase of the current data can be grasped even at the location where the contamination is detected, the current data without the contamination can be reproduced, and the streak generated in the lot lens cycle can be suppressed. In addition, even when large stains occur across blocks, the phase shift unit number close to the phase of the current data can be grasped, current data without stains can be reproduced, and streaks that occur in the lot lens cycle can be suppressed. In addition, the same effects as those of the first embodiment described above can be obtained.

(Third embodiment)
Next, an MFP according to the third embodiment of the present invention will be described. In the MFP according to the third embodiment, the phase shift block 307 can select a shift amount according to the application from a plurality of types of shift amounts. Hereinafter, only the differences from the above-described embodiments will be described, and redundant description will be omitted.

  That is, in the case of the MFP according to the third embodiment, a plurality of types of shift amounts as shown in FIG. 19 are set for the phase shift block 307. The example shown in FIG. 19 is an example in which a total of three types of shift amounts, the first shift amount, the second shift amount, and the third shift amount, are set.

  The first shift amount is a shift amount with a resolution of 1/32 pixel described above. The second shift amount is a shift amount with a resolution of 2/32 pixels. The second shift amount is set to a resolution in which the shift amount of the sixteenth phase shift unit is 0/32. The second shift amount is -2/32 pixels, -4/32 pixels, -6/32 pixels,..., -28/32 on the minus side with reference to the shift amount of the sixteenth phase shift unit. A resolution of -30/32 pixels is set. The second shift amount is +2/32 pixels, +4/32 pixels, +6/32 pixels,... +28/32 pixels, + 30 / on the plus side with reference to the shift amount of the sixteenth phase shift unit. A resolution of 32 pixels is set.

  Similarly, the third shift amount is a shift amount with a resolution of 4/32 pixels. The third shift amount is set to a resolution in which the shift amount of the sixteenth phase shift unit is 0/32. The third shift amount is −4/32 pixels, −8/32 pixels, −12/32 pixels,..., −56/32 on the minus side with reference to the shift amount of the sixteenth phase shift unit. A resolution of -60/32 pixels is set. The third shift amount is +4/32 pixels, +8/32 pixels, +12/32 pixels,... +56/32 pixels, + 60 / on the plus side with reference to the shift amount of the sixteenth phase shift unit. A resolution of 32 pixels is set.

  In the MFP according to the third embodiment, the controller 11 shifts the phase shift between the current data and the initial data used by the phase shift block 307 according to the configuration of the reading module or the usage environment. Change control (selection control). Thereby, the phase shift amount of the initial data can be changed according to the application without increasing the circuit scale, and the same effects as those of the above-described embodiments can be obtained.

(Fourth embodiment)
Next, an MFP according to the fourth embodiment of the present invention will be described. In the MFP according to the fourth embodiment, the correction of the offset component together with the high frequency component can be performed to suppress the shading of the image due to the offset component. Hereinafter, only the differences from the above-described embodiments will be described, and redundant description will be omitted.

  FIG. 20 is a functional block diagram of the white correction unit 205 provided in the MFP according to the fourth embodiment. Of the functional blocks shown in FIG. 20, the functional block of the output ratio calculation unit 362 is different from the above-described embodiments.

  In the MFP according to the fourth embodiment, the output ratio calculation unit 362 performs smoothing with the initial data smoothed to remove periodic fluctuation components corresponding to the lens pitch of the rod lens array 4. The ratio with the current data is calculated for each pixel. In the figure attached with the reference numeral (a) in FIG. 21, the dotted waveform data indicates the smoothed current data, and the solid line waveform data indicates the smoothed initial data. The output ratio calculation unit 362 calculates the ratio between the smoothed current data and the smoothed initial data, thereby indicating the ratio for each pixel as shown in the diagram with the symbol (b) in FIG. Data is generated and supplied to the correction data generation unit 311.

  The output selection unit 310 selects the phase-shifted initial data of the phase shift unit number indicated by the difference comparison output supplied from the difference comparison block 308 and supplies it to the correction data generation unit 311. When the detection signal supplied from the dirt detection unit 351 is “H (concentration reference member is dirty)”, the correction data generation unit 311 detects that the ratio data supplied from the output ratio calculation unit 362 is dirty. Rewrite by linear interpolation from the ratio before and after.

  In order to perform the linear interpolation process, the ratio output from the output ratio calculation unit 362 is once stored in a memory in the correction data generation unit 311. The linear interpolation processing is the same as that at the time of determining the phase shift amount described in the third embodiment. The difference between the third embodiment and the fourth embodiment is that the linear interpolation processing that has been performed in units of blocks in the main scanning direction is performed in units of pixels. The rewriting timing is also performed on the first line described with reference to FIG. The linear interpolation processing of the ratio is not performed after the first line.

  After the linear interpolation processing of the ratio output from the output ratio calculation unit 362, the correction data generation unit 311 is supplied from the second storage unit 302 with the high-frequency component after phase shift input from the output selection unit 310. The data obtained by adding the smoothed data of the initial data to the ratio output from the output ratio calculation unit 362 is supplied to the output selection unit 354.

  That is, the data supplied to the correction data generation unit 311 is the data selected by the output selection unit 310 illustrated in the diagram with the symbol (a) in FIG. 22 and the symbol (b) in FIG. This is the initial data smoothed by the smoothing unit 303 illustrated in the figure. Further, the data supplied to the correction data generation unit 311 is ratio data that has been subjected to linear interpolation processing by the output ratio calculation unit 362, as illustrated in the drawing with the reference numeral (c) in FIG.

  The data selected by the output selection unit 310 is data obtained by shifting the phase of the initial data, and is data that is in phase with the current data by the processing of the high frequency component phase correction unit 253. That is, the data selected by the output selection unit 310 is data equivalent to the high frequency component of the current data. The data smoothed by the smoothing unit 303 is equivalent to the offset component of the initial data (not equivalent to the offset component of the current data). Furthermore, the ratio data from the output ratio calculation unit 362 is the ratio of the offset component between the initial data and the current data.

  The figure attached with the reference numeral (d) in FIG. 22 shows the addition data obtained by adding the data selected by the output selection unit 310 and the data smoothed by the smoothing unit 303. The data selected by the output selection unit 310 is equivalent to the high frequency component of the current data, but the data smoothed by the smoothing unit 303 is the offset component of the initial data. For this reason, since the added data of both is different from the current data in the offset component, there is a possibility that a density difference due to the difference in the offset component occurs. As shown in FIG. 21, when there is a difference between the main scan distributions of the current data and the initial data, the output of the initial data is higher than the current data near the center in the main scan direction. Differences may occur as shading data.

  For this reason, in the case of the MFP of the fourth embodiment, the above-described addition data is multiplied by the ratio data from the output ratio calculation unit 362 that is the ratio of the offset component between the initial data and the current data. The solid line waveform in the figure attached with the reference numeral (e) in FIG. 22 is the waveform of the data obtained by multiplying the above-mentioned addition data by the ratio data. Thereby, it is possible to generate shading data equivalent to the current data, in which the offset component is corrected together with the high frequency component.

  Next, the output selection unit 354 is supplied with current data from the first storage unit 301 and shading data in which the offset component is corrected together with the high frequency component. The output selection unit 354 selects and supplies the above-described corrected shading data to the shading correction unit 312 while the detection signal “H (concentration reference member is dirty)” is supplied from the contamination detection unit 351. To do. The output selection unit 354 selects the current data from the first storage unit 301 as the shading data while the detection signal “L (the density reference member is not dirty)” is supplied from the contamination detection unit 351. To the shading correction unit 312. The shading correction unit 312 performs shading correction using the current data or the above-described corrected shading data.

  As is apparent from the above description, the MFP according to the fourth embodiment generates shading data in which the offset component is corrected together with the high frequency component, and performs the shading correction. As a result, the shading of the image due to the offset component can be suppressed, and the same effects as those of the above-described embodiments can be obtained.

  Each of the above-described embodiments has been described by way of example, and is not intended to limit the scope of the present invention. Each of these novel 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. Each embodiment and modifications of each embodiment are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Light guide 2 Light source part 3 Image sensor 3a Pixel 4 Rod lens array 4a Rod lens 11 Controller 146 2nd reading roller (density reference member)
205 White Correction Unit 251 Storage Unit 252 High Frequency Component Extraction Unit 253 High Frequency Component Phase Correction Unit 254 Data Correction Unit 301 First Storage Unit 302 Second Storage Unit 303 Smoothing Unit 304 Smoothing Unit 305 High Frequency Component Extraction Unit 306 High Frequency Component Extraction Unit 307 Phase shift block 308 Difference calculation block 309 Difference comparison unit 310 Output selection unit 311 Correction data generation unit 312 Shading correction unit 351 Dirt detection unit 352 Shift amount memory 353 Phase shift amount determination unit 354 Output selection unit 362 Output ratio calculation unit

JP 2010-011297 A

Claims (7)

A first smoothing unit that smoothes initial data that is reference shading data read from a density reference member to generate first smoothed data;
A first high-frequency component generation unit that generates a first high-frequency component that is a difference between the initial data and the first smoothed data;
A second smoothing unit that smoothes current data that is shading data read from the density reference member later in time than the initial data to generate second smoothed data;
A second high-frequency component generator that generates a second high-frequency component that is a difference between the current data and the second smoothed data;
A phase shift block that generates a plurality of the first high-frequency components having different phases by shifting the phase of the first high-frequency component by different shift amounts;
The first high-frequency component having a small phase difference with respect to the phase of the second high-frequency component by comparing the phase of each first high-frequency component whose phase is shifted with the phase of the second high-frequency component. A difference comparison unit for detecting
A selection unit that selects the first high-frequency component with a small phase difference detected by the difference comparison unit among the first high-frequency components with the phase shifted;
A correction data generation unit that generates the shading data in which the phase of the high frequency component is corrected by adding the first high frequency component with the selected small phase difference and the first smoothed data;
A shading correction device, comprising: a shading correction unit that performs a shading correction process on input data using the corrected shading data. The phase shift block, the difference comparison unit, the selection unit, and the correction data generation unit are configured to shift the phase in block units corresponding to a predetermined number of pixels of a reading module that reads the density reference member. The shading correction apparatus according to claim 1, wherein the first high-frequency component having a small phase difference is selected and the corrected shading data is generated. A first smoothing unit that smoothes initial data that is reference shading data read from a density reference member to generate first smoothed data;
A first high-frequency component generation unit that generates a first high-frequency component that is a difference between the initial data and the first smoothed data;
A second smoothing unit that smoothes current data that is shading data read from the density reference member later in time than the initial data to generate second smoothed data;
A second high-frequency component generator that generates a second high-frequency component that is a difference between the current data and the second smoothed data;
By shifting the phase of the first high-frequency component by a different shift amount in a block unit corresponding to a predetermined number of pixels of the reading module that reads the density reference member, a plurality of the first high-frequency components having different phases can be obtained. A phase shift block that generates one high-frequency component;
By comparing the phase of each first high frequency component whose phase is shifted and the phase of the second high frequency component for each block, the phase difference with respect to the phase of the second high frequency component is small. A difference comparison unit for detecting a first high frequency component;
A stain detection unit that compares the initial data and the current data and detects an abnormal block that is the block indicating an abnormal value;
When the abnormal block is detected, the first high-frequency component with a small phase difference detected by the dissimilarity comparison unit is the first high-frequency of a normal block that is close to the abnormal block and indicates a normal value. An interpolation processing unit that performs interpolation processing with components;
While the normal block is detected by the dirt detection unit, the first high-frequency component having a small phase difference detected by the difference comparison unit is selected and output, and the abnormal block is detected. A first selection unit that selects and outputs the first high-frequency component interpolated by the interpolation processing unit;
A correction data generating unit that adds the first high-frequency component selected by the first selection unit and the first smoothed data to generate shading data in which the phase of the high-frequency component is corrected;
A shading correction device, comprising: a shading correction unit that performs a shading correction process on input data using the corrected shading data. The phase shift block includes a plurality of phase shift units in which different shift amounts are set,
A block number indicating the phase shift unit subjected to phase shift processing is added to the first high-frequency component for each block,
When the abnormal block is detected, the interpolation processing unit sets the block number of the block of the first high-frequency component with a small phase difference detected by the difference comparison unit close to the abnormal block. Interpolate with the block number of the normal block,
While the abnormal state block is detected by the stain detection unit, the selection unit is subjected to phase shift processing by the phase shift unit corresponding to the block number subjected to interpolation processing by the interpolation processing unit. The shading correction apparatus according to claim 3, wherein the first high-frequency component is selected and output. An output ratio calculation unit that detects an offset component between the initial data and the current data, which is a ratio of the initial data and the current data;
A second selection unit that selects the current data or the corrected shading data from the correction data generation unit and supplies the selected shading data to the shading correction unit;
The correction data generation unit adds the first high-frequency component selected by the first selection unit and the first smoothed data, and multiplies the offset component to thereby generate a high-frequency component. Generating the shading data in which the phase and offset components are corrected and supplying the shading data to the second selection unit,
The second selection unit selects corrected shading data from the correction data generation unit and supplies the corrected shading correction unit to the shading correction unit while the abnormal block is detected by the contamination detection unit, 5. The shading correction apparatus according to claim 3, wherein the current data is selected and supplied to the shading correction unit while the normal block is detected by the detection unit. The shading correction according to any one of claims 1 to 5, wherein the phase shift block performs the phase shift by selectively using shift amounts of a plurality of types of resolutions. apparatus. An image processing apparatus comprising the shading correction apparatus according to any one of claims 1 to 6.

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