JP6364861B2 - Correction control device, image reading device, correction control program - Google Patents

Description

  The present invention relates to a correction control apparatus, an image reading apparatus, and a correction control program.

  In Patent Document 1, a non-linear filter is used as a filtering correction process depending on a document mode (text document, photo document, print document, mixed document), and image information read from an image by an image reader is used. It is described that noise and halftone components are removed without impairing the image quality.

Japanese Patent Laid-Open No. 03-088478

  It is an object of the present invention to provide a correction control device, an image reading device, and a correction control program that can suppress deterioration in image quality due to a shift in focal length when a document image is read.

The invention according to claim 1 includes a sensor unit including a light receiving element, and a plurality of reading units that read images recorded on the document at different reading positions while relatively moving the sensor unit and the document. A correction unit that performs edge enhancement correction on the information of the image read by the reading unit, and a filter process that is applied by the correction unit according to a distance difference between the sensor unit and the document includes a plurality of the readings. Setting means for setting each reading position by the means, and the setting means calculates the resolving power based on the storage means for storing the correlation characteristic between the resolving power and the distance and the pattern for measuring the resolving power read at each reading position. And calculating means for estimating the distance from the resolving power calculated by the calculating means based on the correlation characteristic between the resolving power and the distance stored in the storage means.

The invention according to claim 2 includes a sensor unit including a light receiving element, and a plurality of reading units that read images recorded on the document at different reading positions while relatively moving the sensor unit and the document, A correction unit that performs edge enhancement correction on the information of the image read by the reading unit, and a filter process that is applied by the correction unit according to a distance difference between the sensor unit and the document includes a plurality of the readings. Setting means for setting each reading position by the means, wherein the setting means calculates the resolving power based on the density pattern read at each reading position and the storage means for storing the correlation characteristic between the density and the distance. And an estimation means for estimating a distance from the concentration calculated by the calculation means based on a correlation characteristic between the concentration and the distance stored in the storage means.

According to a third aspect of the present invention, there is provided a sensor unit in which a plurality of light receiving elements are arranged in one direction, the sensor unit arranged in a first position, and a document in which an image is recorded intersects the one direction. First reading means for reading the image while moving to the second position, and second reading means for reading the image while moving the sensor unit in a direction crossing the one direction, with the document placed at the second position. And correction means for performing edge enhancement correction on the image information read by the first reading means and the second reading means, the first reading means, and the second reading means, Based on the distance difference between the sensor unit and the reading position of the image, the filter processing applied by the correction unit differs between the image read by the first reading unit and the image read by the second reading unit. Setting means for setting the processing The setting means stores a correlation characteristic between the resolution and the distance, a calculation means for calculating the resolution based on the resolution measurement pattern read at each reading position, and the resolution and the distance stored in the storage means. And estimating means for estimating the distance from the resolving power calculated by the calculating means based on the correlation characteristics with

According to a fourth aspect of the present invention, there is provided a sensor unit in which a plurality of light receiving elements are arranged in one direction, the sensor unit arranged in a first position, and a document in which an image is recorded intersects the one direction. First reading means for reading the image while moving to the second position, and second reading means for reading the image while moving the sensor unit in a direction crossing the one direction, with the document placed at the second position. And correction means for performing edge enhancement correction on the image information read by the first reading means and the second reading means, the first reading means, and the second reading means, Based on the distance difference between the sensor unit and the reading position of the image, the filter processing applied by the correction unit differs between the image read by the first reading unit and the image read by the second reading unit. and a setting means for setting the processing The setting means includes a storage means for storing a correlation characteristic between density and distance, a calculation means for calculating a resolving power based on a density pattern read at each reading position, and a density and a distance stored in the storage means. Estimation means for estimating the distance from the concentration calculated by the calculation means based on the correlation characteristic .

According to a fifth aspect of the present invention, an image recorded on an original is read in advance by a computer with respect to information of an image read by a plurality of reading means while relatively moving a sensor unit having a light receiving element and the original. When performing edge enhancement correction based on the set filter processing, the correlation characteristic between the resolution and the distance is stored, the resolution is calculated based on the resolution measurement pattern read at each reading position, and the stored resolution and Based on the correlation characteristics with the distance, the distance is estimated from the calculated resolving power, and the edge according to the distance between the sensor unit and the image reading position at each of the reading positions by the plurality of reading units It is a correction control program for executing the setting of the filter processing applied in the enhancement correction independently for each of the plurality of reading positions.

According to the sixth aspect of the present invention, an image recorded on an original is read in advance by a computer with respect to image information read by a plurality of reading means while relatively moving a sensor unit having a light receiving element and the original. When performing edge emphasis correction based on the set filter processing, the correlation characteristics between the density and the distance are stored, the resolving power is calculated based on the density pattern read at each reading position, and the stored density and distance are stored. Based on the correlation characteristics, the distance is estimated from the calculated density, and the edge enhancement correction is performed according to the distance between the sensor unit and the image reading position at each of the reading positions of the plurality of reading units. This is a correction control program that executes the setting of the filter processing applied in step S5 independently for each of the plurality of reading positions.

According to the first, third, and fifth aspects of the present invention, when the focal length of the sensor is small, the image quality is lower than when the same enhancement processing is performed even though the distance between the sensor and the document is different. The decrease can be suppressed. Further, the distance can be estimated from the change in resolution.

According to the second, fourth, and sixth aspects of the present invention, when the focal length of the sensor is small, the image quality is lower than when the same enhancement processing is performed even though the distance between the sensor and the document is different. The decrease can be suppressed. Further, the distance can be estimated from the change in density.

1 is a schematic diagram of an image processing apparatus according to the present embodiment. (A) is a schematic sectional view showing an example of the configuration of the image reading unit according to the present embodiment, and (B) is an enlarged view of a reading region. It is a functional block diagram for image processing control in signal processing of the image reading unit according to the present embodiment. (A) Arrangement pattern diagram of filter coefficient of reference window of edge emphasis filter according to this embodiment, (B) is a chart indicating a variable of filter coefficient, (C) is a pixel of interest to be filtered during image reading (D) is a chart showing an arithmetic expression for filter processing. (A) is a front view of a character image before filtering and a characteristic diagram showing the degree of emphasis, and (B) is a front view of the character image after filtering and a characteristic diagram showing the degree of emphasis. (A) The front view of the distance measurement document of the first example, (B) is a distance-CTF characteristic diagram based on the pattern of FIG. 6 (A). The first example of (A) Front view of distance measurement document of second example, (B) is a distance-density characteristic diagram based on the pattern of FIG. 7 (A). It is a flowchart which shows the filter coefficient setting mode control routine which concerns on this Embodiment. 4 is a flowchart illustrating an image reading control routine according to the present embodiment. (A) is a pattern diagram of a reference window, (B) is a pattern diagram of a DADF window and a platen window showing numerical examples of filter coefficients corrected depending on the focal length depending on the reading mode, FIG. 6C is a pattern diagram of a DADF window and a platen window showing numerical examples in which filter coefficients are changed in the main scanning direction and the sub-scanning direction.

  FIG. 1 shows an image processing apparatus 10 according to the present embodiment.

  The image processing apparatus 10 includes an image forming unit 12 that forms an image on a recording sheet, an image reading unit 14 that reads an original image, and a facsimile communication control circuit 16.

  The image processing apparatus 10 includes a main controller 18. The image processing apparatus 10 controls the image forming unit 12, the image reading unit 14, and the facsimile communication control circuit 16. For example, image data of a document image read by the image reading unit 14 is primary. Or the read image data is sent to the image forming unit 12 or the facsimile communication control circuit 16. The image reading unit 14 is covered with the upper housing 10A, and the image forming unit 12, the facsimile communication control circuit 16, and the main controller 18 are covered with the lower housing 10B. In the lower part of the lower housing 10B, a plurality of tray units 24 for storing recording paper are provided.

  In addition, on the upper surface and the front of the upper casing 10A covering the image reading unit 14, processing operation (service) items including image reading processing, copying processing, image forming processing, and transmission / reception processing are instructed. A user interface 26 (hereinafter also referred to as “UI 26”) for instructing detailed setting of the operation and displaying the state of the image processing apparatus 10 is arranged. The UI 26 is provided with a touch panel unit 28 that can be instructed by bringing an operator's finger or the like into contact with the display screen, and a plurality of hard keys (not shown) that can be instructed by a mechanical operation (for example, pressing operation). A hard key arrangement unit 30 is provided.

  A network communication network 20 such as the Internet is connected to the main controller 18, and a telephone network 22 is connected to the facsimile communication control circuit 16. The main controller 18 is connected to a host computer via, for example, a network communication line network 20 and receives image data or performs facsimile reception and facsimile transmission using the telephone line network 22 via the facsimile communication control circuit 16. Has a role to play.

  In the present embodiment, a service (processing form) including scanning, copying, printing, facsimile transmission, facsimile reception, and printing after reception is performed using the image forming unit 12, the image reading unit 14, and the facsimile communication control circuit 16. It is feasible.

  The image forming unit 12 includes a photoconductor. Around the photoconductor, a charging device that uniformly charges the photoconductor, a scanning exposure unit that scans a light beam based on image data, and the scanning exposure unit. An image developing unit that develops the electrostatic latent image formed by scanning exposure, a transfer unit that transfers the developed image on the photoreceptor to a recording sheet, and a surface of the photoreceptor after the transfer are cleaned. And a cleaning unit. A fixing unit for fixing the image on the recording paper after transfer is provided on the recording paper conveyance path.

  As shown in FIG. 2A, an automatic document feeder 50 is provided on the upper surface of the upper housing 10 </ b> A that accommodates the image reading unit 14.

  A reading glass 70 on which a document for reading an image is placed is provided on the upper surface of the upper housing 10A, that is, the surface facing the automatic document feeder 50.

  The automatic document feeder 50 includes a document table 60 on which a document is placed, and a discharge table 62 from which a document after reading an image is discharged.

  A document conveyance path 61 from the document table 60 to the discharge table 62 has a function of inverting the document M by forming a part of the document conveyance path 61 in an arc shape.

  A paper delivery unit 63 is provided on the most upstream side of the document conveyance path 61. The paper delivery unit 63 picks up the document M placed on the document table 60 (pickup). The document transport path 61 is formed by a plurality of roller pairs (a feed roller pair 64, an alignment roller pair 66, an out roller pair 68, and a discharge roller pair 69). A guide plate 65 for guiding the conveyance of the document M is provided at an appropriate position on the document conveyance path 61.

  The feed roller pair 64 feeds the document at the top of the document sent from the paper feed unit 63 while inverting it.

  The alignment roller pair 66 adjusts the reading timing of the document M sent from the upstream side, and passes the facing area (reading area) of the reading glass 74.

  FIG. 2B shows the details of the document conveyance path 61 in this reading area.

  As shown in FIG. 2B, a thin-film elastic film 109 for guiding the document M to the reading glass side is arranged on the upstream side of the document M on the conveyance side with respect to the reading glass 74. A pad 111 is supported on the upper surface of the left end of the reading glass 74 below the elastic film 109. The pad 111 is made of, for example, a low-friction material so as to guide the original M guided downward by the elastic film 109 to the right in FIG. The document M guided by the pad 111 passes above the reading glass 74 with a predetermined gap G, is guided by the jump guide plate 115 of the document M, and is conveyed by the downstream side out roller pair 68.

  Below the reading glass 74, a CIS unit 88, which is an example of a contact type sensor in this embodiment described later, stands by, and an image of the original M is read by the CIS unit 88.

  The out roller pair 68 and the discharge roller pair 69 discharge the read document M to the discharge table 62.

  As shown in FIG. 2A, the image reading unit 14 accommodated in the upper housing 10A includes a CIS (Contact Image Sensor) unit 88 and signal processing for processing an image information signal read by the CIS unit 88. And a scanning control unit 92 that controls scanning of the CIS unit 88.

  As shown in FIG. 2B, the CIS unit 88 is accommodated in a casing 89 whose longitudinal direction is the depth direction of FIG. 2B, and the reading glass 74 is moved along a rail mechanism (not shown). It can move below and below the reading glass 70.

  At this time, the CIS unit 88 is fixedly disposed at a predetermined position below the reading glass 74 (see the solid line position in FIG. 2B), and the document conveyed along the document conveyance path 61. The M image planes are sequentially confronted. That is, sub-scanning is performed on the document M sent from the automatic document feeder 50 (hereinafter referred to as “DADF sub-scanning”).

  On the other hand, the CIS unit 88 reciprocates within a predetermined range below the reading glass 70. The CIS unit 88 indicated by the chain line in FIG. 2B is a home position in this reciprocating movement.

  Here, when the document M is positioned on the upper surface of the reading glass 70, one of the reciprocating movements (forward path or return path) is sub-scanning for reading an image from the document M (hereinafter referred to as “platen sub-scanning”). Called).

  The scanning control unit 92 executes control for positioning the CIS unit 88 at a predetermined position below the reading glass 74 during DADF sub-scanning, and determines the lower side of the reading glass 70 during platen sub-scanning. Control to reciprocate at a certain speed.

  The CIS unit 88 is provided with a sensor substrate 104 to which a light source 100, a rod lens array 102, and a photoelectric conversion element 104A are attached.

  The light source 100 is for illuminating the original M. For example, the light source 100 includes light emitting elements having emission wavelengths of red (R), green (G), and blue (B), and sequentially or selectively or lights up simultaneously. To be controlled. Note that the light emitted from the light source 100 is read above the reading glass 74 by an elongated light guide (not shown) arranged in the width direction of the document M (the depth direction in FIG. 2B). The document M that passes through is irradiated.

  The rod lens array 102 includes a plurality of erecting equal-magnification imaging elements arranged in the same direction as the longitudinal direction of the light guide, and the reflected light from the document M is converted into photoelectric conversion elements on the sensor substrate 104. The image is formed on 104A.

  A plurality of photoelectric conversion elements 104A are arranged along the longitudinal direction of the rod lens array 102, and reflected light from the original M is sequentially imaged through the rod lens array 102 from one side to the other side of the longitudinal direction (DADF sub-array). Common main scan in scanning and platen sub-scanning).

  The photoelectric conversion element 104A converts the imaged reflected light into an electrical signal. Also, the main scanning of the color image is executed by changing all the reflected light of each color of red (R), green (G), and blue (B) into electric signals, and the electric signals are sent to the signal processing unit 90. Sent out.

  By the way, as shown in FIG. 2B, in the image reading unit 14, the document M is conveyed from the automatic document feeder 50 along the document conveyance path 61 and passes over the reading glass 74 (DADF sub-scanning). A distance L1 from the original M to the upper end surface of the CIS unit 88 when reading an image (hereinafter referred to as “DADF reading”) and a position below the reading glass 70 (platen sub-scanning) are positioned on the reading glass 70. There is a difference Δ between the distance L2 from the original M to the upper end surface of the CIS unit 88 when an image is read from the original M (hereinafter referred to as “platen reading”).

  Although the reading glass 70 and the reading glass 74 are on the same plane, the difference Δ is read on the reading glass 70 while the original M is brought into close contact with the original. One factor is that M is transported with a gap G to avoid moving (sliding) while contacting the reading glass 74. If there is a step between the upper surfaces of the reading glasses 70 and 74, this step may be one of the factors.

  The CIS unit 88 has a shallower depth of focus than, for example, a CCD (individual imaging device). For this reason, when one focus is in focus due to the difference Δ, the other focus may be shifted, and a difference may occur in the image quality of images read by both.

  Or, due to the difference in the device including the CIS unit 88 and the error including the error at the time of assembly (hereinafter collectively referred to as “device-dependent error”) with respect to the focal depth as a design standard. , DADF reading and platen reading may not be in focus.

  Therefore, in this embodiment, the defocus due to the device-dependent error is recognized, and the image quality deterioration is suppressed by the image processing of the image data read from the document M.

  In the present embodiment, the “recognition” is an analysis based on a measurement document for measuring the distance from the CIS unit to the document M. More specifically, the “image processing” is more specifically described in this embodiment. This is edge enhancement filter processing for filtering with a filter coefficient based on the distance obtained by the analysis, which is an example of the filtering processing in FIG.

  FIG. 3 is a block diagram functionally showing the signal processing unit 90 in the image reading unit 14. Note that this block diagram does not limit the hardware configuration of the signal processing unit 90.

  The photoelectric conversion element 104 </ b> A of the CIS unit 88 is connected to the reception unit 150, and sends out a photoelectric conversion signal (analog electric signal) to the reception unit 150.

  The receiving unit 150 converts at least the received RGB electrical signals (analog) into digital signals (A / D conversion), and sends the converted digital signals to the shading processing unit 152 in the normal mode.

  On the other hand, in the distance dependent filter coefficient setting mode, the digitally converted electrical signal (image information) is sent to the window setting unit 154. The distance dependent window setting mode will be described later.

  The shading processing unit 152 stores a correction table for correcting variations in output signals of the photoelectric conversion elements 104A arranged in the main scanning direction in the CIS unit 88 in advance. That is, for example, a difference in output when a document having a constant density is read in the main scanning direction is corrected to a constant value.

  The shading processing unit 152 is connected to the first filter processing unit 156. The first filter processing unit 156 has a function of correcting a deterioration in image quality (“blur” or “smear”) caused by a difference between a designed focal position and a focal position when actually reading. .

  This deterioration in image quality due to the difference in focal position is corrected by edge enhancement filter processing.

(Principle of edge enhancement filter processing)
FIG. 4 explains the principle of the edge enhancement filter processing as a reference.

  FIG. 4A shows a reference filter coefficient table 110 (hereinafter also referred to as “reference window 110”) arranged in a matrix of a total of 25 frames of vertical 5 frames × horizontal 5 frames. Each frame is photoelectrically converted. This corresponds to a pixel read by the element 104A. The pixel to be filtered is the center of the reference window 110 (reference numeral A in FIG. 4A).

  Nine codes A to I are assigned to each frame of the reference window 110, and each code becomes a different filter coefficient.

  In the reference window 110 in FIG. 4A, the symbols are symmetrically arranged on the left and right and up and down, and as a result, even if there are 25 frames of pixels, they are processed with 9 types of codes (9 types of filter coefficients). Means.

  FIG. 4B is a chart showing the filter coefficients of the respective codes. Coef (symbol) is a predetermined numerical value and is a filter coefficient for the symbol of the reference window 110. For example, CoefA is a predetermined numerical value and is a filter coefficient for the symbol A of the reference window 110. Hereinafter, CoefB to CoefI are filter coefficients for symbols B to I.

  FillVal is a pixel value used when the photoelectric conversion element 104A is located outside the image reading area of the document M.

  4C shows the corresponding arrangement state of the reference window 110 immediately after the image reading of the document M is started, that is, when scanning (main scanning and sub-scanning) is started from the upper left corner of the document M. Is shown. In the arrangement state of the reference window 110, the photoelectric conversion element 104A reads the read information P as shown in the left diagram of FIG. In the two-digit numerical value after the symbol P, the first digit indicates the main scanning direction and the tenth digit indicates the sub-scanning direction. P00 to P04, P10 to P14, P20 to P24, P30 to P34, P40. The reading information P of a total of 25 frames is distinguished by -P44.

  Here, when the filter processing is performed on the target pixel (P22 in FIG. 4C), it is obtained by the calculation shown in FIG. 4D.

  That is, the output of the target pixel P22 is calculated by the following calculation formula (1).

P22
＝ P00 × Coef I + P01 × Coef H + P02 × Coef F + P03 × Coef H + P04 × Coef I
+ P10 × Coef G + P11 × Coef E + P12 × Coef C + P13 × Coef E + P14 × Coef G
+ P20 × Coef D + P21 × Coef B + P22 × Coef A + P23 × Coef B + P24 × Coef D
+ P30 × Coef G + P31 × Coef E + P32 × Coef C + P33 × Coef E + P34 × Coef G
+ P40 × Coef I + P41 × Coef H + P42 × Coef F + P43 × Coef H + P44 × Coef I
... (1)
In the above example, since P00 to P04, P10 to P14, P20, P21, P30, P31, P40, and P41 are outside the image reading area, “FillVal” is applied as the pixel value. The filter coefficient is the same as that used when the outside of the image reading area is not included.

  FIG. 5 is a characteristic diagram showing the relative difference between the density of the pixel of interest and the density of its surrounding pixels by edge enhancement processing.

  5A shows the image information received by the receiving unit 150 (see FIG. 3), and FIG. 5B shows the image information on which the edge enhancement processing has been executed.

  As shown in FIG. 5, the edge enhancement process increases the density difference between the target pixel and surrounding pixels. For example, image quality degradation such as blurring and blurring due to a shift in focal length is corrected by a filter process (edge enhancement process). It turns out that it is possible.

(Filter processing based on distance difference between DADF reading and platen reading)
Here, in the first filter processing unit 156 (see FIG. 3) of the present embodiment, the difference in focal position between the DADF reading and the platen reading (FIG. 2B) using the principle of the filter processing. The image quality deterioration (blur and blur) depending on Δ (= L1−L2) shown in FIG.

  In other words, independent filter coefficient tables (DADF window 110D, platen window 110P) are set for DADF reading and platen reading, and windows (DADF window 110D, platen window 110D) are set according to the respective reading modes. 110P) is selected and applied.

  That is, as shown in FIG. 3, a window temporary storage unit 158 is connected to the first filter processing unit 156. The window temporary storage unit 158 stores a window (DADF window 110D or platen window 110P) in which filter coefficients corresponding to a reading form (DADF reading or platen reading) are arranged in a matrix.

  The window temporary storage unit 158 is connected to the window reading unit 160. The window reading unit 160 is connected to the reading mode information reading unit 162 and the window storage unit 164.

  Here, the reading mode information reading unit 162 reads reading mode information (DADF reading or platen reading) from the scanning control unit 92 and sends it to the window reading unit 160. Based on the reading mode information, the window reading unit 160 selects either the DADF window 110D in which the DADF filter coefficient is set from the window storage unit 164 or the platen window 110P in which the platen filter coefficient is set. Is stored in the window temporary storage unit 158. That is, the window (DADF window 110D or platen window 110P) that is sequentially stored is changed in the window temporary storage unit 158 in accordance with the reading mode at the time of image reading to be executed by the image reading unit 14 from now on. It is like that.

  Note that the DADF window 110D and the platen window 110P stored in the window storage unit 164 are the distance measurement document M1 (see FIG. 6A) or the distance measurement document M2 (see FIG. 7A). ), And the generation procedure will be described later.

  The first filter processing unit 156 uses the filter coefficient of the window (DADF window 110D or platen window 110P) stored in the window temporary storage unit 158 to calculate each pixel based on the above-described arithmetic expression (1). Calculate the concentration.

  The image information filtered by the first filter processing unit 156 is sent to the color conversion processing unit 166. The color conversion processing unit 166 converts the input image information into RGB, for example, CMYK, which is image information for image formation in the image forming unit 12. In this color conversion, for example, color conversion to CMYK may be performed via the L * a * b * color space (RGB → L * a * b * → CMYK). The color conversion is not limited to CMYK, and may be converted to a designated color space.

  The color conversion processing unit 166 is connected to the second filter processing unit 168. The second filter processing unit 168 is a filter process executed depending on the image mode. For example, the document image is classified into a character mode, a photo mode, a print mode, and a mixed mode, and filter processing suitable for each image is executed. In the second filter processing unit 168, for example, a non-linear filter is used, and noise and halftone components are removed without damaging the edge portion. More specifically, a nonlinear smoothing filter and a nonlinear edge enhancement filter are applied. The nonlinear smoothing filter removes noise and halftone components while preserving the edge portion. Further, the nonlinear edge enhancement filter emphasizes only the edge portion without enhancing noise.

  The color conversion processing unit 166 is connected to the density adjustment unit 170. In the density adjusting unit 170, for example, all image information that has been subjected to filter processing and color conversion processing is finally subjected to a gray scale (for example, an intermediate value) so that the integrated average density of all pixels finally becomes a predetermined gray scale. Correct the pixels uniformly. The adjustment of the density adjustment unit 170 is not limited to the above example.

  The image information whose density has been adjusted by the density adjusting unit 170 is sent to the image forming unit 12 via the output unit 172, for example. Alternatively, the image data may be transferred to a PC or server that has instructed image reading.

(Generate a window with filter coefficients arranged in matrix)
In the present embodiment, filter coefficients for executing optimum edge enhancement processing are set for DADF reading and platen reading with different focal lengths.

  This filter coefficient setting is executed in the distance-dependent filter coefficient setting mode, unlike the normal mode described above. In the filter coefficient setting mode, the image information received by the receiving unit 150 and A / D converted is sent to the window setting unit 154.

  In the filter coefficient setting mode, the distance measurement original M1 (see FIG. 6A) dedicated to the filter coefficient setting or the distance measurement original M2 (see FIG. 7A) is applied.

(First example "applying distance measurement document M1")
As shown in FIG. 6, a CTF (resolution) measurement pattern 113 is printed on the distance measurement document M1 of the first example. The CTF measurement pattern 113 is a pattern (5LP (LinePair) / mm) in which there are five pairs in which black lines and white lines alternately exist within 1 mm, and the distance measurement document M1 in FIG. Therefore, it is used for measuring the resolution in the main scanning direction.

  In the distance-dependent filter count setting mode, an image reading process is executed using the distance measuring document M1, and the window setting unit 154 (see FIG. 3) uses the following equation (2) based on the read image information. Calculate the resolution.

CTF = (density of black line-density of white line) / (density of black reference-density of white reference) x 100 [%] (2)
For example, assuming that the density of the black line is 160, the density of the white line is 70, the density of the black reference is 200, and the density of the white reference is 50, according to the calculation formula (2), the CTF value is 60%.

  FIG. 6B is a characteristic diagram showing the relationship between the CTF value and the distance. In the characteristic diagram of FIG. 6B, the relationship between the CTF value and the distance indicates a quadratic curve relationship, and thus the distance can be estimated from the CTF value. The CTF value 60% of the calculation result is the starting point of the characteristic diagram of FIG. 6B and indicates that the focus is achieved. For example, the characteristic diagram of FIG. 6B is stored in a storage medium that can be read by the window setting unit 154 shown in FIG.

  As shown in FIG. 3, the window setting unit 154 uses the filter coefficients of the reference window 110 fetched from the reference window storage unit 155 as a reference, based on the distance estimated in the DADF reading (see FIG. 4 ( A Coef value corresponding to codes A to I of A) is set, and the set DADF window 110D is sent to the window writing unit 174. That is, the window setting unit 154 has functions of storing characteristic diagrams, calculating resolving power, and estimating distance.

  The window writing unit 174 stores the received DADF window 110D in the window storage unit 164.

  On the other hand, the window setting unit 154 uses the reference window filter coefficient fetched from the reference window storage unit 155 as a reference, and based on the estimated distance in the platen reading, each frame of the window (reference A in FIG. 4A). (Coef value corresponding to .about.I) is set, and the set platen window 110P is sent to the window writing unit 174.

  The window writing unit 174 stores the received platen window 110P in the window storage unit 164.

  The reference window 110 stored in the reference window storage unit 155 is set with design filter coefficients.

(Second example "applying distance measurement document M2")
As shown in FIG. 7, the density measurement pattern 114 is printed on the distance measurement document M2 of the second example. The density measurement pattern 114 is a rectangular white reference pattern, and is formed as, for example, a 20 mm × 20 mm square pattern that is not affected by the resolving power of the CIS unit 88 (see FIG. 2).

  In the filter coefficient setting mode, image reading processing is executed using the distance measuring document M2, and the density of the read image information is obtained in the window setting unit 154 (see FIG. 3).

  FIG. 7B is a characteristic diagram showing the relationship between density and distance. In the characteristic diagram of FIG. 7B, the relationship between the density and the distance of the density measurement pattern 114 is a linear (proportional) relationship with a quadratic curve. Can be estimated. For example, the characteristic diagram of FIG. 7B is stored in a storage medium that can be read by the window setting unit 154 shown in FIG.

  As shown in FIG. 3, the window setting unit 154 uses each frame of the window (FIG. 4 (A) based on the distance estimated in the DADF reading with reference to the filter coefficient of the reference window fetched from the reference window storage unit 155. ) Are set, and the set DADF window 110D is sent to the window writing unit 174. That is, the window setting unit 154 has functions of storing characteristic diagrams, calculating resolving power, and estimating distance.

  The window writing unit 174 stores the received DADF window 110D in the window storage unit 164.

  On the other hand, the window setting unit 154 uses each frame of the window (reference symbols A to A in FIG. 4A) based on the distance estimated in the platen reading using the filter coefficient of the reference window fetched from the reference window storage unit 155 as a reference. (Coef value corresponding to I) is set, and the set platen window 110P is sent to the window writing unit 174.

  The window writing unit 174 stores the received platen window 110P in the window storage unit 164.

  The reference window 110 stored in the reference window storage unit 155 is set with design filter coefficients.

  The operation of this embodiment will be described below.

(Filter coefficient setting mode control routine)
The filter coefficient setting for setting the windows (DADF window 110D and platen window 110P) to which the filter coefficients for DADF and platen are assigned will be described with reference to the flowchart of FIG. In FIG. 8, the distance measurement document M1 according to the first example (see FIG. 6) is employed.

  In step 200, the automatic document feeder 50 is instructed to load the distance measurement document M1. For example, a message for prompting loading may be displayed on the UI 26.

  In the next step 202, it is determined whether or not there has been an instruction to start reading. If an affirmative determination is made, the process proceeds to step 204, where the CIS unit 88 performs document image reading control. Here, in the reading control, the CIS unit 88 is fixedly arranged below the reading glass 74 and the conveyed distance measurement document M1 is read.

  In the next step 206, image information read from the document M1 (CTF measurement pattern 113 shown in FIG. 6A) is received, and then in step 208, initial processing including A / D conversion is executed, and the image information is received. (Digital) is sent to the window setting unit 154.

  In the next step 210, the image information is analyzed, the CTF value is calculated based on the calculation formula (2), and then the process proceeds to step 212, where the CTF value is calculated based on the characteristic diagram of FIG. Estimate distance.

  In the next step 214, the reference window 110 is corrected based on the estimated distance, a DADF window 110 </ b> D is generated, the process proceeds to step 216, and is stored in the window storage unit 164. Thus, the generation of the DADF window 110D is completed, and then the generation of the platen window 110P is executed.

  In the next step 218, the reading glass 70 is instructed to load the distance measuring document M 1. For example, a message for prompting loading may be displayed on the UI 26.

  In the next step 220, it is determined whether or not a reading start instruction has been issued. If an affirmative determination is made, the process proceeds to step 222, where document image reading control by the CIS unit 88 is executed. Here, in the reading control, the CIS unit 88 is moved to the home position below the reading glass 70 and moved back and forth from the home position, thereby reading the distance measuring document M1 fixedly arranged on the upper surface of the reading glass 70. .

  In the next step 224, the read image information is received. Next, in step 226, initial processing including A / D conversion is executed, and the image information (digital) is sent to the window setting unit 154.

  In the next step 228, the image information is analyzed, the CTF value is calculated based on the calculation formula (2), and then the process proceeds to step 230, where the CTF value is calculated based on the characteristic diagram of FIG. Estimate distance.

  In the next step 232, the reference window 110 is corrected based on the estimated distance, a platen window 110 </ b> P is generated, the process proceeds to step 234, and is stored in the window storage unit 164. This completes the generation of the platen window and the DADF window, and this routine ends.

  In FIG. 8, the generation of the platen window 110P is executed serially after the generation of the DADF window 110D, but the generation order may be reversed. Alternatively, DADF reading and platen reading may be executed first using the document M1, and parallel processing may be performed in a time-sharing manner. Further, the generation of the DADF window 110D and the generation of the platen window 110P may be executed independently in separate flowcharts.

(Image reading control routine)
FIG. 9 is a flowchart showing an image reading control routine in the normal mode.

  In the image reading control in the normal mode, it is assumed that the filter coefficient setting in the flowchart of FIG. 8 has already been completed and the DADF window 110D and the platen window 110P are stored in the window storage unit 164.

  In step 250, it is determined whether or not the document M is loaded. This determination can be made based on, for example, a signal from a paper size sensor or the like to determine whether the automatic document feeder 50 is loaded or the upper surface of the reading glass 70.

  If a negative determination is made in step 250, this routine ends. If a positive determination is made, the routine proceeds to step 252.

  In step 252, the reading mode is determined. If it is determined in step 252 that the document M is loaded in the automatic document feeder 50, it is determined that the DADF reading is performed, the process proceeds to step 254, the DADF window 110D is read from the window storage unit 164, and step 258 is performed. Migrate to

  If it is determined in step 252 that the document M is loaded on the reading glass 70, it is determined that the platen is read, and the process proceeds to step 256, where the platen window is read from the window storage unit 164 and the process proceeds to step 258. Transition.

  In step 258, one of the read windows is stored in the window temporary storage unit 158, and the process proceeds to step 260. In step 260, it is determined whether or not there has been an instruction to start reading. If a negative determination is made, the process proceeds to step 262 to determine whether or not there has been an instruction to cancel. If a negative determination is made in step 262, the process returns to step 260, and step 260 and step 262 are repeated until an affirmative determination is made in either step 260 or step 262.

  Here, if an affirmative determination is made in step 262, document reading is stopped and this routine ends. If the determination in step 260 is affirmative, the process proceeds to step 264 to execute reading control of the document image by the CIS unit 88 based on the reading mode.

  In the reading control in the case of DADF reading, the CIS unit 88 is fixedly arranged below the reading glass 74 and the original M conveyed along the original conveying path 61 is read.

  On the other hand, in the reading control of the platen reading, the CIS unit 88 is moved to the home position below the reading glass 70 and reciprocated from the home position, thereby reading the document M fixedly arranged on the upper surface of the reading glass 70.

  In the next step 266, the read image information (analog) is received, and then the process proceeds to step 268 to execute initial processing including A / D conversion, and the process proceeds to step 270 to execute the shading process.

  In the next step 272, the window stored in the window temporary storage unit 158 is read, and then in step 274, device-dependent filtering is executed. In this case, since the DADF window 110D or the platen window 110P is stored in the window temporary storage unit 158 on the basis of the reading mode, filter processing (edge enhancement processing) corresponding to each focal length is executed. The

  Therefore, the image quality does not change between DADF reading and platen reading, and it is possible to eliminate blurring and blurring in any reading mode.

  In the next step 276, the color conversion process is executed, and then the process proceeds to step 278, where the filter process depending on the image mode (character, photograph, print, mixed) is executed, and the process proceeds to step 280. For example, in the color conversion, if the transmission destination is the image forming unit 12, the color conversion is performed in the order of RGB → L * a * b * → CMYK.

  In step 280, density adjustment is performed, the process proceeds to step 282, and is output to the image forming unit 12, for example.

(Filter coefficient adjustment by scanning direction)
In this embodiment, even if the filter coefficients are corrected based on the difference in focal length between the DADF reading and the platen reading, the arrangement of the filter coefficients is basically the reference window 110 (FIG. 10A). (See FIG. 10B).

  By the way, in image reading by the CIS unit 88, there may be a difference in image quality (the degree of blur and blur) between the main scanning direction and the sub-scanning direction. In particular, blur and blur are more noticeable in main scanning than in sub scanning.

  Therefore, it is possible to deviate from the principle of the reference window 110 (symmetrical in the vertical and horizontal directions), and to make the filter coefficient different in the main scanning direction and the sub scanning direction (see FIG. 10C).

  In this case, it is preferable to reflect both in the DADF window 110D and the platen window 110P set in the present embodiment.

  In addition, the numerical value of the filter coefficient shown in FIG. 10 is an example, and the numerical value of the filter coefficient is not limited.

  Further, as a method for differentiating the filter processing, the size of the filter may be changed. In that case, the filter with the sensor and the original should be enlarged, or the filter far from the focal length of the sensor should be enlarged.

M Document M1 Distance Measurement Document M2 Distance Measurement Document 10 Image Processing Device 10A Upper Housing 10B Lower Housing 12 Image Forming Unit 14 Image Reading Unit 16 Facsimile Communication Control Circuit 18 Main Controller 24 Tray Unit 26 User Interface (UI)
28 Touch Panel 30 Hard Key Arrangement 50 Automatic Document Feeder 60 Document Stand 61 Document Transport Path 62 Discharge Stand 63 Paper Feeding Section 64 Feed Roller Pair 65 Guide Plate 66 Positioning Roller Pair 68 Out Roller Pair 69 Discharge Roller Pair 70 Reading Glass 74 Reading Glass 88 CIS Unit 90 Signal Processing Unit 92 Scanning Control Unit 100 Light Source 102 Rod Lens Array 104 Sensor Substrate 104A Photoelectric Conversion Element 109 Elastic Film 110 Reference Window 110D DADF Window 110P Platen Window 111 Pad 113 CTF Measurement Pattern 114 Density Measurement pattern 115 Jump guide plate 150 Reception unit 152 Shading processing unit 154 Window setting unit (distance-dependent filter coefficient setting)
156 First filter processing unit 158 Window temporary storage unit 160 Window reading unit 162 Reading mode information reading unit 164 Window storage unit 166 Color conversion processing unit 168 Second filter processing unit 170 Density adjustment unit 172 Output unit 174 Window writing unit

Claims (6)

A plurality of reading units that include a sensor unit including a light receiving element, and that read an image recorded on the document at different reading positions while relatively moving the sensor unit and the document;
Correction means for performing edge enhancement correction on information of the image read by the reading means;
A setting unit configured to set a filter process applied by the correction unit for each reading position by the plurality of reading units according to a difference in distance between the sensor unit and the document;
The setting means is
Storage means for storing correlation characteristics between resolution and distance;
Calculation means for calculating a resolution based on a resolution measurement pattern read at each reading position;
Estimating means for estimating the distance from the resolving power calculated by the calculating means based on the correlation characteristic between the resolving power and the distance stored in the storage means;
An image reading apparatus comprising: A plurality of reading units that include a sensor unit including a light receiving element, and that read an image recorded on the document at different reading positions while relatively moving the sensor unit and the document;
Correction means for performing edge enhancement correction on information of the image read by the reading means;
A setting unit configured to set a filter process applied by the correction unit for each reading position by the plurality of reading units according to a difference in distance between the sensor unit and the document;
The setting means is
Storage means for storing a correlation characteristic between density and distance;
Calculating means for calculating the resolving power based on the density pattern read at each reading position;
Estimating means for estimating the distance from the concentration calculated by the calculating means based on the correlation characteristic between the concentration and the distance stored in the storage means;
An image reading apparatus comprising: A sensor unit in which a plurality of light receiving elements are arranged in one direction;
A first reading unit that arranges the sensor unit at a first position and reads the image while moving a document on which an image is recorded in a direction crossing the one direction;
A second reading unit that positions the document at a second position and reads the image while moving the sensor unit in a direction crossing the one direction;
Correction means for performing edge enhancement correction on the image information read by the first reading means and the second reading means;
The first reading unit performs filtering processing applied by the correction unit based on a difference in distance between the sensor unit and the image reading position between the first reading unit and the second reading unit. Setting means for setting different processing for the read image and the image read by the second reading means;
The setting means is
Storage means for storing correlation characteristics between resolution and distance;
Calculation means for calculating a resolution based on a resolution measurement pattern read at each reading position;
Estimating means for estimating the distance from the resolving power calculated by the calculating means based on the correlation characteristic between the resolving power and the distance stored in the storage means;
An image reading apparatus comprising: A sensor unit in which a plurality of light receiving elements are arranged in one direction;
A first reading unit that arranges the sensor unit at a first position and reads the image while moving a document on which an image is recorded in a direction crossing the one direction;
A second reading unit that positions the document at a second position and reads the image while moving the sensor unit in a direction crossing the one direction;
Correction means for performing edge enhancement correction on the image information read by the first reading means and the second reading means;
The first reading unit performs filtering processing applied by the correction unit based on a difference in distance between the sensor unit and the image reading position between the first reading unit and the second reading unit. Setting means for setting different processing for the read image and the image read by the second reading means;
The setting means is
Storage means for storing a correlation characteristic between density and distance;
Calculating means for calculating the resolving power based on the density pattern read at each reading position;
Estimating means for estimating the distance from the concentration calculated by the calculating means based on the correlation characteristic between the concentration and the distance stored in the storage means;
An image reading apparatus comprising:   On the computer,
  When performing edge enhancement correction based on a predetermined filtering process on image information read by a plurality of reading means while relatively moving the sensor unit having the light receiving element and the document while the image recorded on the document is moved In addition,
  Remember the correlation characteristics between resolution and distance,
  Calculate the resolution based on the resolution measurement pattern read at each reading position,
  Based on the correlation characteristics between the stored resolution and distance, the distance is estimated from the calculated resolution,
  Filter processing to be applied in the edge enhancement correction is independently set for each of the plurality of reading positions according to the distance between the sensor unit and the image reading position at each of the reading positions by the plurality of reading units. To
A correction control program that causes   On the computer,
  When performing edge enhancement correction based on a predetermined filtering process on image information read by a plurality of reading means while relatively moving the sensor unit having the light receiving element and the document while the image recorded on the document is moved In addition,
  Remember the correlation characteristics between concentration and distance,
  Calculate the resolving power based on the density pattern read at each reading position,
  Based on the correlation characteristics between the stored concentration and distance, the distance is estimated from the calculated concentration,
  Filter processing to be applied in the edge enhancement correction is independently set for each of the plurality of reading positions according to the distance between the sensor unit and the image reading position at each of the reading positions by the plurality of reading units. To
A correction control program that causes