JP2003125177A - Image reader and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader capable of reading an image with high quality by maintaining density uniformity of white shading data. SOLUTION: An averaging circuit 44 calculates a moving average of image data resulting from reading a white reference board by obtaining a simple average of L lines in each block as to m-blocks by the L lines as a result of movement of one line each. A register 47 stores the moving average. A peak hold circuit 45 obtains a peak of the moving average of each pixel to be obtained by each block. That is, the circuit 45 obtains a peak of the simple average of each pixel in the main scanning direction. Then a peak hold circuit 46 obtains a peak among peaks obtained by the peak hold circuit 45 for every block. Finally the register 47 outputs the simple average obtained by the averaging circuit 44 as to the block in which the peak exists to a shading arithmetic circuit 43 as shading data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus and an image forming apparatus equipped with this image reading apparatus.

[0002]

2. Description of the Related Art In a conventional image reading apparatus of a moving image reading unit represented by a flat bed type, the density of a reference white plate arranged while the carriage moves while accelerating to an effective reading range is read. Thus, the white shading data is generated. Further, in a fixed-type image reading device such as a sheet-through type image reading device, white shading data is generated by reading the density of a reference white plate or a white roller arranged on the opposite surface of the fixed reading unit. is doing.

However, in the conventional white shading data generation technique, dirt adheres to the surface of the reference white plate or the white roller over time, and the density to be used as a reference varies depending on the reading position of the reference white plate or the white roller. The density uniformity required to generate white shading data cannot be maintained. Particularly, in the case of the sheet-through type, since the document is conveyed on the surface of the reference white plate or the white roller, the reference white plate or the white roller becomes significantly soiled as the frequency of use increases.

On the other hand, Japanese Patent Laid-Open No. 2000-270159 discloses that
The white reference area is read in block units by dividing the white reference area into multiple blocks that are divided in the sub-scanning direction, and the average output value of the individual read pixels is calculated for each block. A technique for eliminating the influence of dust adhering to the optical path in the device by comparing and collating the calculated average output values of individual read pixels is disclosed. In this case, there is also disclosed a technique in which the white reference is configured with the maximum value of the average output values of the individual read pixels calculated for each block.

[0005]

[Problems to be Solved by the Invention] However, JP-A-2000-270
The technique disclosed in Japanese Patent Publication No. 159 is to divide into a plurality of blocks in the sub-scanning direction and calculate the average output value of the individual read pixels for each block. If the block contains dirt, the effect of dirt adhering to the white reference cannot be effectively eliminated, and there is a problem that sufficient white shading correction cannot be performed.

An object of the present invention is to enable white shading data to be created by effectively eliminating the influence of dirt adhering to the white reference, and to perform sufficient white shading correction, as compared with the prior art. That is.

[0007]

According to a first aspect of the present invention, there is provided a photoelectric conversion element for reading an image of an original, a white reference for white shading correction of image data, and the white reference for reading the white reference by the photoelectric conversion element. A white shading data creation device that creates and outputs the white shading data from the image data, and a shading calculation device that corrects the white shading of the image data of the original read by the photoelectric conversion element using the white shading data. The shading data creation device moves by taking the average value of each pixel value for each of the plurality of lines obtained by moving the image data obtained by reading the white reference by a predetermined number of lines in the sub-scanning direction. Averaging means for obtaining an average and each moving average value stored in a storage device Storage means, first to determine the peak value of the main scanning direction of each of the moving average value for each said block
Peak value calculation means, second peak value calculation means for calculating a peak value among the calculated peak values, and the block to which the calculated peak value belongs, which is stored by the storage means. And an deciding unit that sets the moving average value as white shading data.

Therefore, it is possible to take the average value of each pixel value for a plurality of lines in each block where the positions are shifted by a predetermined line and overlap each other.

According to a second aspect of the present invention, in the white shading data creating apparatus according to the first aspect, the averaging means sets the predetermined number of lines to one line.

Therefore, it is possible to obtain the moving average of each block obtained by moving the white reference read image data line by line in the sub-scanning direction.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the image reading device described in the paragraph, the photoelectric conversion element is
The white reference is a roller-shaped member that is arranged on the original conveyance path to which the original is conveyed and reads an image of the original. The white reference is a roller-shaped member that is arranged on the original conveyance path so as to face the photoelectric conversion element. Then, the distance between the image surface of the original and the photoelectric conversion element is kept constant, the surface serves as a white reference for white shading correction, and has a center of curvature on a straight line orthogonal to its axis, and The reading roller has a reference white reading surface formed of a curved surface positioned inside the maximum outer peripheral locus on the surface.

Therefore, the white shading data can be created by using the reference white reading surface which is less likely to be contaminated due to changes over time.

According to a fourth aspect of the present invention, in the image reading apparatus according to the third aspect, the width of each block in the sub-scanning direction is smaller than the width of the reference white reading surface in the sub-scanning direction.

Therefore, the reference white reading surface is always required to be 1
The calculation in the block can be performed.

According to a fifth aspect of the present invention, in the image reading apparatus according to any one of the first to fourth aspects, the averaging means includes pixel values for every one or a plurality of lines in each block. The average value of is calculated.

Therefore, even if the white reference has a small flaw or stain, its influence on the calculation of the white shading data can be reduced.

According to a sixth aspect of the invention, an image is formed on a sheet based on the image reading apparatus according to any one of the first to fifth aspects and the image data of the original read by the photoelectric conversion element. An image forming apparatus including a printer engine for performing the above.

Therefore, the same operation as the invention according to any one of claims 1 to 5 is achieved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described.

FIG. 1 is a vertical sectional front view showing a schematic structure of a copying machine according to an embodiment of the present invention. This copier is
As shown in FIG. 1, the image forming apparatus of the present invention is embodied. An image is formed on a sheet by an electrophotographic method based on an image scanner 1 which is an image reading apparatus and image data read by the image scanner 1. And a printer 2 that realizes a printer engine.

The image scanner 1 includes a first image reading unit 3, a second image reading unit 4, a document setting unit 5, a document discharge unit 6, a document transport path 7, a number of transport rollers 8, a first contact glass 9, The second contact glass 10, the first reading roller 11, the second reading roller 12 and the like are included.

A document D to be read (see FIG. 3) is set in the document setting unit 5, and the document D from which an image has been read is discharged to the document discharge unit 6. The document conveyance path 7 is a path provided between the document setting section 5 and the document discharge section 6, and the documents D from which images are read are conveyed one by one. When the document D is read, the first mode is selected when the document D is a single-sided document by switching the mode.
The image is read only by the image reading unit 3, and when the document D is a double-sided document, the first image reading unit 3 and the second image reading unit 4 read the image.

The first image reading section 3 can read the image of the document D placed on the first contact glass 9 at a fixed position by the CCD 3a which is a photoelectric conversion element, and the second contact glass 10 and the second contact glass 10. The image (front surface image) of the document D conveyed between the first reading roller 11 (that is, on the document conveyance path 7) can be read. Document transport path 7
When the document D conveyed above is read, the first reading roller 11 is rotationally driven at the same speed as the conveyance roller 8 by a stepping motor (not shown) for driving, and the document D conveyed to the second position is rotated. It acts so as to be pressed against the contact glass 10.

The second image reading section 4 can read the image (back side image) of the document D conveyed on the document conveyance path 7 by the CCD 25 (see FIG. 4) which is a photoelectric conversion element.
The second reading roller 12 is arranged to face the second image reading unit 4 with the document feeding path 7 interposed therebetween. When the document D is read by the second image reading unit 4, the second reading roller 12 is a stepping motor (see FIG. It is driven to rotate at the same speed as the conveying roller 8 by a not shown), and acts so as to maintain a constant distance between the image surface of the document D and the second image reading unit 4.

The printer 2 comprises a photoconductor 14, a laser unit 15, a developing unit 16, a transfer unit 17, a fixing unit 18, and the like. The surface of the photoconductor 14 is uniformly charged by a charger (not shown), and the image read by the first image reading unit 3 or the second image reading unit 4 is formed on the surface of the photoconductor 14 by the laser unit 15. Written to form an electrostatic latent image. This electrostatic latent image is visualized as a toner image by supplying toner from the developing device 16,
The visualized toner image is transferred to the paper 20 fed from the paper feed cassette 19 by the function of the transfer device 17. The sheet 20 on which the toner image has been transferred is subjected to a fixing process by the fixing unit 18, and then discharged onto the sheet discharge tray 21.

FIG. 2 is a vertical sectional front view of the second reading roller 12 used in this copying machine and the document conveying path before and after it. FIG. 3 is an enlarged front view of the second reading roller 12. As shown in FIGS. 2 and 3, the second reading roller 12 is
It is arranged so as to face the CCD 25 of the second image reading unit 4, and is formed in a shape having a substantially circular cross section, and is formed in white with rubber or resin as a material. A reference white reading surface 13 extending along the axial direction of the second reading roller 12 is formed on a part of the outer peripheral portion of the second reading roller 12. The reference white reading surface 13 has a center of curvature B on a straight line a that is orthogonal to the axis A of the second reading roller 12, and has a maximum outer peripheral surface locus of the second reading roller 12 (the reference white surface 13 in the state where the reference white surface 13 is not provided 2 is a substantially circular outer peripheral surface of the reading roller 12, and is formed by a convex curved surface located inside a portion C indicated by a solid line and a broken line.

FIG. 4 is a block diagram showing the electrical connection of the control system of this copying machine. As shown in FIG. 4, the main body control unit 22 includes a CPU (not shown) and controls the entire copying machine. Further, the controller 23 is provided with a CPU, and various actuators and sensors of the image scanner 1 such as a motor for driving the conveying roller 8 are connected thereto, and the controller 23 controls these. The operation unit 32 includes
Various keys and LCD for various operations of this copying machine
A display is provided.

The second image reading unit 4 collects the original image on the CCD 25 through a lens (not shown) by the light emitted from the light source 24 to the original D in response to the lighting control signal from the controller 23, and the controller 23 outputs the image. The original D is read by the second image reading unit 4 by the gate signal XSFGATE (described later).
The image of the document D is read at the timing when the read image data reaches the frame, and the read image data is temporarily stored in the frame memory 29 via the AMP circuit 26, the A / D conversion circuit 27, and the image processing circuit 28. After that, the image data is transferred to the main body control unit 22 via the output control circuit 30 and the I / F circuit 31, and the image data obtained by reading the back surface of the document D is transferred to the image processing circuit 33.

With this structure, in this copying machine, when the double-sided copy mode is selected, the documents D set in the document setting section 5 with the front side facing up are transported one by one through the document transport path 7. Then, the image on the front side is read by the first image reading unit 3, and the image on the back side is read by the second image reading unit 4. Then, the images read by the first and second image reading units 3 and 4 are copied on the front surface and the back surface of the same sheet 20, and double-sided copying is performed.

In this copying machine, the image processing circuit 33 performs image processing such as black shading correction, white shading correction and γ correction on the image data of the document D. In this case, the white shading data used for the white shading correction is generated by the second image reading unit 4 by the CCD.
The reading is performed by reading the surface of the second reading roller 12 that is arranged opposite to 25. The creation of white shading data will be described below.

As shown in the timing chart of FIG.
The period in which the gate signal XSFGATE indicating the reading period of the document D is not active (document region), that is, the document D is the second
While not being applied to the image reading unit 4, the gate signal XSHGATE indicating the generation period of the white shading data is active in a constant range in the circumferential direction of the second reading roller 12, for example, a range of one round (white shading area). And obtain white shading data.

FIG. 6 shows a white shading correction circuit 41 for performing white shading correction in the image processing circuit 33.
3 is a block diagram showing an example of the circuit configuration of FIG. As shown in FIG. 6, the white shading correction circuit 41 includes a white shading data creation circuit 42 which is a white shading data creation device and a white shading calculation circuit 43 which is a white shading calculation device. The white shading data creation circuit 42 includes an average value circuit 44, peak hold circuits 45 and 46, and a register 47, and creates white shading data.

That is, the controller 23 outputs the gate signal XSHGATE to read the predetermined range of the second reading roller 12 by the CCD 25.

As shown in FIG. 7, the read image data is input to the average value circuit 44. Average value circuit 44
Then, the L lines are set as one block, and the calculation is performed for each block (blocks 1 to m) by a moving average calculation method that shifts for each line, for example. L in each block
The simple average of the lines is found. That is, a simple average value between lines is obtained for the value of each pixel in each line in each block. This implements the averaging means. The obtained simple average value is stored in the register 47 which is a storage device. This implements the storage means. Then, the peak value of the obtained simple average value of each pixel is obtained by the peak hold circuit 45 for each block.
That is, the peak value in the main scanning direction of the simple average value of each pixel is taken. This implements the first peak value calculation means. Then, by the peak hold circuit 46,
The peak value among the peak values calculated by the peak hold circuit 45 is calculated for each block. This implements the second peak value calculation means. Then, the simple average value obtained by the average value circuit 44 for the block in which the peak value exists is output from the register 47 to the shading calculation circuit 43 as white shading data. This implements the determining means.

The processing performed by the white shading data generation circuit 42 is expressed by the following equations: Simple average calculation in each block (average value circuit 44)
Dm (n) = INT [ΣD (n) / L] Dm (n): Calculation data of the nth pixel of the mth block The line in the m block is from m * L to (m + 1) * L-1 D (n): Read data ΣD (n) for the nth pixel: Addition value of 1 to L lines of D (n) L: Number of lines in one block INT []: Round off the decimal point ・ Peak in each block Value detection (executed by peak hold circuit 45) Dmmax = Dm (n) Dmmax: Peak value of m-th block / peak value detection in gate signal XSHGATE (executed by peak hold circuit 46) Dpmax = Dmmax Dpmax when Dpmax <Dmmax In the case of ≧ Dmmax, Dpmax = Dpmax Dpmax: The peak value in the first m block is Dpmax = Dmmax. Therefore, the shading data is the mth block data having Dmmax.

The shading correction calculation performed by the shading calculation circuit 43 is Dsh = (D (n) / Dp (n)) × 255 Dp (n): shading data.

As described above, in the average value circuit 44, the moving average calculation method for obtaining the average value of the pixel values of L lines is performed for each of the blocks 1 to m that are displaced by one line and overlap. Even if the range of stains on the white reference is wide, it is possible to effectively eliminate the influence of stains attached to the white reference and perform stable white shading correction as compared with the conventional case.

The moving average calculation may be performed such that the positions are shifted by a plurality of lines, but if the positions are shifted by one line, the moving average value can be finely obtained, and more stable white shading can be achieved. Can be corrected.

As shown in FIG. 8, the width of each block in the sub-scanning direction (the number of lines L) is smaller than the width of the reference white reading surface 13 in the sub-scanning direction (that is, the reference white reading surface 1).
The number of lines L is smaller than the number of read lines of 3).

As a result, when the block is divided into m blocks, the calculation within one block can be performed only by the part of the second reading roller 12 that does not hit the original, so that the accurate peak value (white shading data) can be calculated. ) Can be generated.

Further, since the data for one round of the second reading roller 12 is read and the data is divided into m blocks for calculation, even if the second reading roller 12 is soiled, it is stable on the surface that does not come into contact with the original. White shading data can be generated (because the second reading roller 12 is clean at the beginning,
The white shading data may be created in any part (block), but the second reading roller 12 may be used due to rubbing of the document or the like.
When the image becomes dirty, the peak value (white shading data) finally obtained by the above calculation is obtained from the data of the surface not touching the document).

Further, the number of lines L when the assertion period of the gate signal XSHGATE is divided into the number of blocks m is set to a value that cannot be divided by the number of lines L during the assertion period of the gate signal XSHGATE (a surplus line appears. ). By doing so, the second reading roller 12
It is possible to detect the peak value more accurately by reading for several cycles.

Further, when the average value circuit 44 calculates the average value using the data of L lines in one block, the calculation may be performed using the data of every other line or every plural lines. . By doing this, the second
Even if there are small scratches or stains on the reading roller 12, it is possible to reduce the influence on the calculation of the white shading data.

[0044]

According to the invention described in claim 1, even if the range of white-based stains is wide, the effect of stains adhered to the white standard is effectively eliminated and stable white shading is achieved, compared to the conventional case. Corrections can be made.

According to a second aspect of the present invention, in the white shading data generating apparatus according to the first aspect, it is possible to finely determine the moving average value, and more stable white shading correction can be performed.

The invention described in claim 3 is the invention according to claim 1 or 2.
In the image reading device described in (1), more stable white shading correction can be performed by using the reference white reading surface.

According to the invention described in claim 4, in the image reading apparatus described in claim 3, accurate white shading data can be generated.

According to the invention described in claim 5, in the image reading apparatus according to any one of claims 1 to 4, accurate white shading data can be generated.

The invention described in claim 6 has the same effect as that of the image reading apparatus described in any one of claims 1 to 5.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing a schematic structure of a copying machine according to an embodiment of the present invention.

FIG. 2 is a vertical sectional front view of a second reading roller used in the copying machine and a document conveying path before and after the second reading roller.

FIG. 3 is an enlarged vertical sectional view of the second reading roller.

FIG. 4 is a block diagram showing electrical connection of a control system of the copying machine.

FIG. 5 is a timing chart for explaining generation of white shading data of the copying machine.

FIG. 6 is a block diagram illustrating a circuit configuration of a white shading correction circuit of the copying machine.

FIG. 7 is an explanatory diagram illustrating generation of the white shading data.

FIG. 8 is a vertical cross-sectional front view of the second reading roller and a document conveying path before and after the second reading roller.

[Explanation of symbols]

1 Image reading device 2 Printer engine 3a photoelectric conversion element 12 White reference, reading roller 25 Photoelectric conversion element

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5B047 AA01 AB02 BA01 BB02 BC05                       BC09 BC11 BC14 CB21 DA04                       DC02 DC06                 5C072 AA01 BA08 CA02 DA02 DA04                       EA05 FB12 RA16 UA02 XA01                 5C077 LL04 PP06 PP44 PP46 PP48                       PP62 PQ12 PQ18 PQ24 SS01                       TT06

Claims (6)

[Claims] 1. A photoelectric conversion element for reading an image of an original, a white reference for white shading correction of image data, and the white shading data created and output from image data obtained by reading the white reference by the photoelectric conversion element. And a shading calculation device for performing white shading correction on the image data of the original read by the photoelectric conversion element using the white shading data, and the shading data creation device reads the white reference. Averaging means for obtaining a moving average by averaging pixel values of a plurality of lines obtained by moving the image data by a predetermined number of lines in the sub-scanning direction, and each moving average value. And a storage means for storing the The first peak value calculating means for obtaining the peak value of each moving average value in the main scanning direction, the second peak value calculating means for obtaining the peak value among the obtained peak values, and the obtained peak value are Determining means for determining the moving average value stored in the storage means as white shading data, which is obtained for the block to which the block belongs;
An image reading device equipped with. 2. The white shading data creation device according to claim 1, wherein the averaging means sets the predetermined number of lines to one line. 3. The photoelectric conversion element is arranged on a document conveyance path through which the document is conveyed to read an image of the document, and the white reference is set to the photoelectric conversion element on the document conveyance path. Roller members arranged facing each other rotate to maintain a constant distance between the image surface of the document and the photoelectric conversion element, and the surface serves as a white reference for white shading correction, and is orthogonal to the axis center. The reading roller having a center of curvature on a straight line and a reference white reading surface formed of a curved surface located inside the maximum outer peripheral surface locus is formed on the surface. The image reading device described. 4. The image reading apparatus according to claim 3, wherein the width of each block in the sub-scanning direction is smaller than the width of the reference white reading surface in the sub-scanning direction. 5. The image reading apparatus according to claim 1, wherein the averaging means obtains an average value of pixel values of every one or a plurality of lines in each block. 6. An image reading apparatus according to claim 1, and a printer engine that forms an image on a sheet based on image data of a document read by the photoelectric conversion element. An image forming apparatus provided.