JP2002314769A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that can completely separate position shift in the subscanning direction from a position shift in the main scanning direction, so as to quickly correct only the dispersion in the read position in the subscanning direction with high accuracy. SOLUTION: The image reader is provided with a measurement means, that measures a position error by an image signal acquired by the image reader from an original, where patterns expressing the contrast of image and comprising parallel lines that have density which is uniform in the main scanning direction and density which is ununiform in the subscanning direction perpendicular to the main scanning direction and patterns with a uniform density in a direction which is neither horizontal or vertical with respect to the main scanning direction are adjacent to each other, and with a correction means that corrects the image of the image reader, by using the position error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus for correcting an error in a pixel position of image data in accordance with an uneven scanning speed in a main scanning direction or a deviation of a scanning position.

[0002]

2. Description of the Related Art Conventionally, as this type of apparatus, for example, there is an "image reading apparatus" (hereinafter referred to as Conventional Example 1) of Japanese Patent Application Laid-Open No. 9-163105. This prior art 1 is an apparatus that measures some positional deviation generated when the image reading apparatus is installed in a diagonal line pattern for measuring a positional error, and corrects the positional error by subtracting the positional deviation from the result. is there. Japanese Patent Application Laid-Open No. 9-98255 (hereinafter referred to as Conventional Example 2) discloses a “pixel position error measuring device”. In the second conventional example, a window is set in the read image data to determine the existence of a diagonal pattern in which a large number of black diagonal patterns forming an angle of 45 ° on a white background are formed at an equal pitch in the sub-scanning direction. This device sequentially shifts windows in the direction of oblique lines and measures the position error of pixels in the sub-scanning direction based on a change in the position of oblique lines in each window.

[0003]

However, according to the above-mentioned prior arts, since the center of gravity is basically determined, even a small amount of dust has a strong influence on the position of the center of gravity, and is weak against noise. However, there was a problem that was reduced.
In addition, the oblique line patterns used in these measurement methods include misalignment components in the main scanning direction, for example, deflection of a return mirror mounted inside the scanner, vibration of an image sensor, and the like, so that sub-scanning is performed with high accuracy. There is a problem that it is difficult to measure the displacement of the pixel in the direction.

The present invention has been made to solve these problems, and completely separates the positional deviation in the sub-scanning direction and the positional deviation in the main scanning direction to quickly reduce only the variation in the reading position in the sub-scanning direction. It is another object of the present invention to provide an image reading apparatus capable of performing highly accurate correction.

[0005]

In order to solve the above-mentioned problems, according to the image reading apparatus of the present invention, the position error measuring means in the main scanning direction and the sub-scanning direction of the pixel is used to measure the position error in the main scanning direction due to the vibration of a mirror or the like. Since the position error in the sub-scanning direction from which the position error component has been removed can be calculated, the variation in the reading position due to the fluctuation of the pixel only in the sub-scanning direction can be corrected with high accuracy. In addition, since the position error component of the pixel in the main scanning direction in the main scanning direction can be calculated by the position error measuring unit in the main scanning direction, the variation of the reading position due to only the fluctuation of the pixel in the main scanning direction can be corrected with high accuracy. be able to.

Further, by making the pattern larger than the resolution of the image pickup device, moiré can be eliminated, and the positional deviation measurement accuracy can be improved.

Furthermore, since the density patterns are not at equal pitch, the minimum value of the positional deviation can be guaranteed to one, and the measurement accuracy can be improved. Further, since the widths of the black patterns are not equal, the minimum value of the positional deviation can be guaranteed to be one, and the measurement accuracy can be improved.

Further, by obtaining the minimum value of the accumulated difference between the pixel rows, the position error of the pixel in the sub-scanning direction can be measured with high accuracy.

Further, by using the interpolation method, it is possible to measure the pixel position deviation with high accuracy.

[0010] Further, by storing the previous minimum value of the accumulated position deviation and estimating the next minimum value position, the comparison area can be reduced, so that the position deviation can be calculated at high speed.

Further, by reducing the number of times of calculation of the difference in the difference area, the position shift can be calculated at high speed without lowering the calculation resolution.

Further, by using the interpolation method for calculating the minimum value, the position deviation can be calculated at high speed without lowering the calculation resolution.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to the present invention comprises a line pattern having a uniform density in the main scanning direction and a non-uniform density in the sub-scanning direction perpendicular to the main scanning direction; Measuring means for measuring a position error from an image signal obtained by an image reading apparatus on a document in which a diagonal pattern having a uniform density in a non-horizontal and non-vertical direction is arranged adjacently, and an image based on the value of the position error Correction means for correcting the image of the reading device.

[0014]

FIG. 1 is a perspective view showing the configuration of an image reading apparatus to be inspected by an image misalignment inspection apparatus according to the present invention. FIG. 2 is a schematic diagram showing the configuration of the image reading device of FIG. FIG. 3 is a block diagram showing the configuration of the image reading apparatus according to the present invention.

First, the configuration of an image reading apparatus according to the present invention will be described with reference to FIG. 1. An image reading apparatus 10 according to the present invention includes a document setting place 11 which is a document table on which an image document is set, and A traveling body 12 that scans the place 11 in the sub-scanning direction, and forms a line in a direction perpendicular to the traveling body 12;
For example, a one-dimensional image sensor 13 such as a line CCD, a lens 14 that couples the image of the document setting place 11 onto the one-dimensional image sensor 13, and a scan in the sub-scanning direction following the traveling body 12 and reflection from the document The traveling body 15 for appropriately forming an image on the one-dimensional image sensor 13 through the lens 14 and the traveling body 12 scans the original installation location 11 in the sub-scanning direction, thereby setting the original installation location 11. The obtained image is taken in line-sequentially and read as a two-dimensional image by scanning,
An image signal output port 16 for outputting the image signal to an image displacement inspection apparatus (not shown);
And a driving means 17 for driving the.
Note that the image reading apparatus 10 in FIG. 1 is a scanning unit scanning type flat type scanner, but is not limited thereto, and may be a platen scanning type or relative scanning type scanner. Further, an image forming apparatus such as a digital camera may be used.

The operation of the image reading apparatus according to the present invention will be described with reference to FIG.
A reference chart document 19 is set on the top, and a lamp 20 serving as a light source for illuminating the chart document 19 is moved to an imaging area 21.
Is irradiated with light. The traveling body 15 and the traveling body 12 following the traveling body 15 scan from the top to the end of the chart document 19, so that the reflected light passes through the return mirrors 12-1 and 15-1 and the lens 14, and the one-dimensional image sensor At 13, the signal is photoelectrically converted and captured as an image signal.

Next, the operation of the image reading apparatus of the present invention shown in FIG. 3 will be described with reference to FIG. 4 showing an operation flow.
The image of the original of the image reading device is illuminated, and the reflected light of the image is line-sequentially captured by a one-dimensional image sensor that arrives via an optical system such as a folding mirror and a lens. The captured original reflected light is photoelectrically converted by the photoelectric conversion unit 32 and is converted into an electric signal (step S101). This is converted from analog data to digital data by A / D conversion by the A / D converter 33 (step S102). The shading correction unit 34
(Step S10)
3), the corrected image signal is output from the image signal output port. The image data is output line by line by the control unit 31 for all images. The control section 31 cuts out the predetermined oblique line and line pattern area designation data for each pattern area, and stores the image data in the image storage memory 38.
(Step S104). Image storage memory 3
The image data stored in 8 is sequentially extracted by the control unit 31 every two columns, and shift and difference operations are performed. The maximum shift amount is given in advance. Image position shift measuring unit 3
In step 5, the cumulative shift amount is calculated from the two columns of interest, and the minimum value of the positional shift amount is stored in the image storage memory 38 (step S105). The image position deviation measuring unit 35 measures the position error, outputs the measurement result as an error signal, and inputs the error signal as the position error data output from the image position deviation measuring unit 35 to the position error correction unit 36. Then, image data in which a position error has been corrected is generated from the image data read by the position error correction unit 36 and the input error signal, and the image processing unit 37 performs correction of the image data, document recognition, and the like (step S106). . For example, in the case of a digital copying machine, image data processed by the image processing unit 37 is input to an image recording unit (image forming unit) to form an image. The image processing unit 37 includes, for example, a document recognition unit, a scaling unit, a filter unit, a γ correction unit, and a gradation processing unit. The document recognizing unit determines a character area or a picture area according to the image data. The scaling unit performs enlargement, reduction, or equal magnification processing in the main scanning direction, and the filter unit uses an M × N spatial filter based on the frequency characteristics of the image recording unit and the determination result of the document recognition unit to perform smoothing. And sharpening processing. The γ correction unit changes the γ curve based on the frequency characteristics of the image recording unit and the determination result of the document recognition unit,
Execute the correction process. The gradation processing unit performs quantization such as dither processing based on the gradation characteristics of the image recording unit and the determination result of the document recognition unit.

In the image reading apparatus, as shown in FIG. 5, the pattern is arranged in a pattern area 52 outside the subject area 51. For example, as shown in FIG. 6, a black-and-white line pattern in the horizontal direction in the sub-scanning direction and a black-and-white diagonal line pattern having a uniform density in the horizontal and non-vertical directions in the sub-scanning direction are alternately arranged in the sub-scanning direction. A black-and-white diagonal pattern having a horizontal density in the sub-scanning direction and a black-and-white diagonal pattern having a uniform density in the non-perpendicular direction as shown in FIG. 4 is a chart pattern laid out in the vertical direction in the sub-scanning direction. In these cases, the image reading apparatus is an image reading apparatus that corrects the image in real time while the user takes in the image. Also,
As shown in FIG. 8, a black-and-white mixed line and oblique line pattern mixed chart document in the subject area may be treated as a pattern. In this case, for example, in the assembly inspection process, the operator causes the image reading device to read the chart and stores the correction amount. A service person may perform the same operation at the user's site.

Further, for example, only the black and white line pattern portion shown in FIG.
By calculating the center of gravity of the black pattern, the positional deviation in the main scanning direction is measured. The window for finding the center of gravity is
Determined by the size of the black and white pattern. For example, if the background is a white pattern in the main scanning direction and the black pattern is 10 pixels, the window size is set to 20 × 1 pixel (main scanning direction × sub-scanning direction) in consideration of the reading position shift in the main scanning direction. , 30 × 1 pixel or the like can be applied. In a window of 20 × 1 pixels, if the arrangement is ideal, the arrangement is such that there are 5 pixels in the white pattern, 10 pixels in the black pattern and 5 pixels in the white pattern in the main scanning direction. Window is 1 in the sub-scanning direction
It moves by pixels and calculates the center of gravity within the window.
The first center of gravity calculation result is stored in the storage memory.
The first barycenter calculation result data is read from the storage memory, and the difference from the barycenter calculation result in the current window is obtained as a position shift in the main scanning direction. This displacement data is stored in the storage memory. Further, the center of gravity is calculated in the same manner using only the black-and-white diagonal line pattern portion shown in FIG. 9 to obtain a position shift in the sub-scanning direction.

Alternatively, as shown in FIGS. 10 and 11, for example, as shown in FIGS. 10 and 11, the image misalignment measuring section 35 uses the monochrome line pattern shown in FIG. The first and second columns of data are read out, and if the pattern is a diagonal line pattern, tan θ (θ is the angle between the diagonal line and the sub-scan), for example, θ
Is divided by 45 degrees to correct the movement of the original pattern. The pixel data of the first column and the second column for each pixel obtained as described above, for example, monochrome gradation of a pixel, 0 to 255 in 8 bits
The difference between the values up to is taken, and if the sign is negative, the sign is inverted. This is calculated as a cumulative value in the range of a preset column. When the calculation of the cumulative value is completed, the image data in the second column is shifted to the right by, for example, one pixel, and the cumulative value of the difference between the pixels in the first and second columns is obtained. Assuming that the accumulated value calculation is, for example, a preset maximum shift 8,-
The acquisition of the accumulated value is repeated from the four pixel position to the +4 pixel position. The minimum value is calculated from the accumulated values for these eight maximum shifts. These operations are sequentially performed up to the last column of the image, and the minimum value for each column is calculated. These operations are the same as, for example, sequentially shifting the array that takes the difference from the first column if the pixel data of the second column is included in the array. For example,
If there are 2048 pixels in one column, to calculate the cumulative value eight times, if the evaluation range is 2040 pixels from the comparison center, the second column is shifted eight times from -4 to +4, and the cumulative value is calculated. And find their minimum values. This operation is sequentially performed up to the last column of the image, and the minimum value for each column is obtained.
Note that the minimum value is determined by the pixel shift position.

Then, the minimum positional deviation data of the line pattern calculated by the pixel positional deviation measuring unit 35 in FIG. 3 is stored. For example, the minimum line position deviation data is read from the minimum line position deviation amount storage, and the minimum line position deviation amount of the oblique line pattern adjacent to the line line pattern is set to tanθ.
And subtract the data. By further dividing tan θ by the result, the minimum positional deviation amount in the sub-scanning direction from which the positional deviation component in the main scanning direction has been removed is calculated. The result is stored in the image storage memory 38 of FIG.

The position error correction unit 36 in FIG. 3 removes a position error in the main scanning direction by using a line pattern and a position error in the sub-scanning direction by using a diagonal line pattern. There is something.

Next, the means for correcting the position error in the main scanning direction will be described. The position error amount to be obtained is a value obtained by cumulatively adding the minimum values up to the (first column-1) column in the column of interest. For example, the amount of positional deviation in the main scanning direction with respect to the first column is calculated. Therefore, if there is a +0.1 shift between the first column and the second column of the image, this is a position error of the second column. If there is a -0.2 shift between the second and third columns of the image, the position error in the third column is -0.1. It is assumed that the correction amount is, for example, uniformly moved in parallel in the main scanning direction. In the plan view of FIG. 5, since there are patterns on both sides, data obtained by adding the measured values of the position error amounts and dividing by 2 may be used. Therefore, in order to make a correction, a shift process is performed by the amount of displacement. For example, as a method of correcting the position error, as shown in FIG. 12, an image is shifted in the main scanning direction using a smoothing filter (step S401). Image restoration for image smoothing is performed using an enhancement filter (step S40).
2). When the correction amount is an integer value, only the smoothing filtering for performing the shift processing is performed. For example, if the position error is +
In the case of one pixel, since the correction is performed by shifting by one pixel,
The (1, 0, 0) smoothing filter is read and applied to the image data sequence. When the correction amount includes a decimal value, after the shift processing, enhancement processing filtering is performed to correct a smoothing filter accompanying the shift processing. For example, when the position error is −0.1 pixel, the correction is performed by shifting by +0.1 pixel, so that a (0, 0.9, 0.1) smoothing filter is applied to the read image data sequence. Further, in order to correct the smoothing filter, (−0.05, 1.1, −0.0
The emphasis processing filtering of 5) is performed.

When the subject area itself is a pattern using the line chart of FIG. 8, for example, it can be considered that the main scanning has a position error due to the image area cut out into the main and sub areas.
For example, in A3, 256 × 2048 pixels are cut out, and correction data in the main scanning direction is held in 27 × 20 divisions. The correction data may be stored in advance, or may be retaken by a service person to correct the actual image of the subject area.

Next, a description will be given of a means for correcting a position error in the main and sub scanning directions using a cubic function convolution. FIG. 13 is a model diagram of the correction using the cubic function convolution, and FIG. 15 is a flowchart showing the processing procedure of the correction. As can be seen from FIG. 13, pixel positions in the main (sub) scanning direction when there is no positional deviation (speed fluctuation) are equally spaced as shown by the pixel column P. However, when there is a positional deviation (speed fluctuation), the interval varies as shown by the pixel column Q and deviates from a correct position. In practice there must be a pixel in the original position of P _n in Figure 13 shows that in the position of the pixel Q _n. here,
An example will be described in which image data (density data) of data _{Pn in} a certain scanning direction on the nth line is created from the image data of the pixel column Q and the position data using a cubic function convolution as a weighting function. When using the cubic function convolution, data within two pixels (r0) from the ideal position of the nth line ( _Pn ) is detected from the position error data (step S501). In this _{case, Q n, Q n + 1} , Q n + 2, Q n + 3, Q n + 4 of the data are of interest. Here, the reason why the number of pixels is within two pixels is that data of r0 or more is treated as having a correction coefficient of 0, so that no more data is required. And
An interpolation function h (r) for each data Q is obtained from the distance r of each data from _Pn . This is the correction coefficient. Here, the interpolation function h (r) is a piecewise cubic polynomial approximation of sinx / x, and the following equation, depending on the distance r from the center:

H (r) = 1-2 | r | 2+ | r | 3 (1) where 0 ≦ | r | <1 h (r) = 4-8 | r | +5 | r | 2 − | R | 3 (2) where 1 ≦ | r | <2 h (r) = 0 (3) where 2 ≦ | r |

## EQU2 ## And this interpolation function h
Under (r), the correction coefficient is multiplied by the corresponding Q data to obtain _Pn . Further, in order to correct the density unevenness, the sum of the correction coefficients is set to the denominator so that the sum of the correction coefficients becomes 1. That is,

[0028] _{P n = {Q n · h} (r1) + Q n + 1 · h (r2) + Q n + 2 · h (r3) + Q n + 3 · h (r4) + Q n + 4 · h (r5) {/ {H (r1) + h (r2) + h (r3) + h (r4) + h (r5)} (4)

When this control is completed for the data in the main scanning direction of the n-th line, the control is shifted to the (n + 1) -th line, and is repeated until the last line. At this time, the calculation of the sum of the interpolation coefficient h (r) and the interpolation coefficient of the denominator in the equation (4) and the calculation of the reciprocal thereof may be performed once before the correction of the corresponding image data in the main scanning direction. By performing such control, it is possible to create image data when read at a correct position from the read image data based on the position error data measured as described above, thereby correcting the position error. Becomes possible. In FIGS. 4 and 15, the image misalignment measurement and the position error correction process the entire image, respectively.
In consideration of the efficiency of the memory, the correction may be performed immediately after fetching every two lines and measuring the positional deviation.

FIGS. 16 and 17 show "line pattern" and "diagonal line pattern" in this embodiment, respectively. Here, the “line pattern” means a pattern in which, for example, black and white patterns are arranged at equal pitches in a direction horizontal to the scanning direction of the optical system. The “diagonal pattern” refers to a pattern in which, for example, black and white patterns are arranged at equal intervals in a direction that is not horizontal and not perpendicular to the scanning direction of the optical system. This pattern is a pattern composed of a line pattern and an oblique line pattern in which the pattern interval is larger than the resolution of the image reading apparatus.

The "density pattern" in the present embodiment
Are shown in FIG. 18 and FIG. Here, the “pattern” refers to, for example, a black and white pattern in which the black patterns having the same width are arranged at a non-equidistant pitch in a direction horizontal to the scanning direction of the optical system. The width of the black pattern is a line pattern that is larger than the resolution of an image reading apparatus, for example, a scanner apparatus having a CCD. Alternatively, a `` pattern '' is one in which, for example, black and white patterns are arranged at equal intervals with an angle θ with respect to a direction perpendicular to the scanning direction of the optical system, and black patterns with the same width are not at equal intervals. , Means something in line. The width of the black pattern is a pattern formed by a diagonal pattern larger than the resolution of an image reading device, for example, a scanner device having a CCD.

Further, FIGS. 20 and 21 show a "line pattern" and a "diagonal line pattern" in this embodiment. Here, the “line pattern” is, for example, a black-and-white density pattern in which patterns having different black pattern widths are arranged at equal pitches in a direction horizontal to the scanning direction of the optical system. The width of the black pattern is a line pattern that is larger than the resolution of an image reading apparatus, for example, a scanner apparatus having a CCD. "Diagonal pattern"
Is an angle θ with respect to a direction perpendicular to the scanning direction of the optical system, for example, black and white density patterns are arranged at equal pitches, and patterns with different black pattern widths are arranged at equal pitches. Say. The width of the black pattern is a pattern formed by a diagonal pattern larger than the resolution of an image reading device, for example, a scanner device having a CCD.

Next, the cumulative value calculating means in this embodiment,
The minimum value calculating unit, the position calculating unit, the line minimum position shift amount storing unit, the optical system scanning direction position shift calculating unit, and the position error calculating unit will be described with reference to FIGS.

The first and second columns of the line data or the oblique line pattern image data are read from the storage memory. If the oblique line pattern is used, tan θ (θ is the oblique line and the sub-scan is formed in the second data line) Angle), for example, θ is 45 degrees, to correct the movement of the document pattern. The difference between the pixel data of the first and second columns, for example, the monochrome gradation of the pixel, the value of 8 bits from 0 to 255 is obtained for each pixel, and the sign is inverted if the sign is negative. Let it. This is added within a preset range of columns to calculate an accumulated value. When the calculation of the cumulative value is completed, the image data in the second column is shifted, for example, by one pixel to the right, and the cumulative value of the difference between the pixels in the first and second columns is obtained (cumulative value calculating means). The calculation of the accumulated value is performed, for example, by using a preset maximum shift 8
Then, the acquisition of the accumulated value is repeated from the −4 pixel position to the +4 pixel position. The minimum value is calculated from the accumulated values of these eight maximum shifts (minimum value calculating means). These operations are sequentially performed up to the last column of the image, and the minimum value for each column is calculated (position shift calculating unit). These operations are the same as, for example, sequentially shifting the array that takes the difference from the first column if the pixel data of the second column is included in the array. For example, when there are 2048 pixels in one column, to calculate the cumulative value eight times, if the evaluation range is 2040 pixels from the comparison center, then 2
The column is shifted eight times from -4 to +4, and the accumulated value is calculated, and the minimum value is calculated. This operation is sequentially performed up to the last column of the image, and the minimum value for each column is obtained. In addition,
The minimum value is determined by the pixel shift position.

The minimum displacement data of the line pattern calculated by the position displacement calculating means is stored (minimum line displacement amount storage means). For example, the parallel line minimum position shift data is read from the parallel line minimum position shift amount storage, and the minimum position shift amount of the oblique line pattern adjacent to the parallel line pattern is multiplied by tan θ to subtract the data. By further dividing the result by tan θ, the minimum positional deviation amount in the sub-scanning direction from which the positional deviation component in the main scanning direction has been removed is calculated (optical system scanning direction positional deviation calculating means). The result is stored in the data storage memory. The position error amount to be obtained is a value obtained by cumulatively adding the minimum values up to the (first column-1) column in the column of interest. The minimum value for each column is calculated as the amount of positional deviation in the main scanning direction with respect to the first column. Therefore, if there is a +0.1 shift between the first column and the second column of the image, this is a position error of the second column. If there is a -0.2 shift between the second and third columns of the image, the position error in the third column is -0.1.

Position error: Sn = a1 + a2 +... + An
-1 (n = 1, 2, 3,..., An-1 is the minimum positional deviation amount of the column)

The data interpolation means and the accumulated value acquisition means in this embodiment will be described with reference to FIGS. For example, in the case of an image reading apparatus having a resolution of 600 dpi, one pixel is about 42.3 μm. The pixel pitch is also 42.3 μm. In order to achieve higher accuracy, interpolation is performed between pixel pitches (between pixel centers) using, for example, a spline interpolation technique (data interpolation means). For example, if a section is divided into eight, 5.2 μm
Can be calculated with an accuracy of. 2 using the interpolation pitch
By shifting the image data in the column in a direction perpendicular to the direction in which the optical system scans, highly accurate positional deviation can be measured (accumulated value acquisition means).

Further, the preceding stage minimum position storage means and difference area calculation means in this embodiment will be described with reference to FIGS. First row and second row of image data from storage memory
The column is read out, and in the case of the oblique line pattern, the movement of the document pattern is adjusted by multiplying 1 / tan θ by the data column of the second column. For example, one pixel is divided into 100 by spline interpolation, and shifted from the −50 interpolation pitch by a +50 interpolation pitch. For each interpolation pitch, the difference between the pixel data calculated from the interpolation formulas of the first and second columns, for example, the monochrome gradation of the pixel, a value of 0 to 255 in 8 bits, is calculated. Turn it over. This is calculated as a cumulative value in a comparison range of a preset column. When the calculation of all the accumulated values is completed, the image data in the second column is, for example,
After shifting by the interpolation pitch, the cumulative value of the difference between the first and second columns is obtained. A predetermined maximum shift amount, for example, 10
The acquisition of the cumulative value is repeated until the 0 shift. The minimum value is acquired from among the accumulated values that are the relative positions for the maximum 100 shifts. The position at the minimum value is stored (previous stage minimum position storage means). If this minimum position is the center position of the shift from the next time, for example, if the comparison range is 40, the position -20 from the minimum position is set as the initial position of the second column (difference area calculation means). These operations are sequentially performed up to the last column of the image, and the minimum value for each column is calculated. To divide one pixel into 100 is, for example, the same operation as calculating a gradation for each interpolation pitch from one pixel data and converting one array to 100 arrays. First shift is maximum shift 1
00 times are performed, but the minimum value is driven by a maximum of 40 shifts from -20 to +20 around the previous minimum position, such as the first minimum position from the second time and the second time from the third time. For example, when one column of image data is 2048 pixels and the interpolation pitch is 1/100 of one pixel, 10
To calculate the cumulative value 0 times, set the comparison range to 2 from the comparison center.
Assuming 047 pixels, the first time is 10 from -50 to +50.
The shift is performed 0 times, the cumulative value is calculated, and the minimum value is calculated. If the position where the minimum value becomes +1 is, the second column to be compared next time is shifted from -19 to +21,
Calculate the cumulative value. The minimum value of the accumulated value is extracted and stored. This operation is sequentially performed up to the last column of the image, and the minimum value for each column is obtained.

Further, the data interpolation means and the difference area calculation means in this embodiment will be described with reference to FIGS. The second column adjacent to the first column of the image data is read from the storage memory, and in the case of a diagonal pattern, the data column of the second column is multiplied by 1 / tan θ to adjust the movement of the original pattern. For example, one pixel in the second column is divided by 100 by spline interpolation, and shifted by -50 interpolation pitch to +50 interpolation pitch to shift (data interpolation means). For each pixel pitch, adjacent to the first column and the pixel pitch, for example,
The difference from the pixel data in the second column is obtained for each left-end interpolation pitch, and if the sign is negative, the sign is inverted (difference area calculation means). This is calculated as a cumulative value in a comparison range of a preset column. When the calculation of all the accumulated values is completed, the image data in the second column is shifted to the right by, for example, one interpolation pitch,
The cumulative value of the difference between the 1st pixel pitch in the 1st column and the 2nd column is acquired. The acquisition of the accumulated value is repeated up to a preset maximum shift, for example, 100 shifts. The minimum value is obtained from among the accumulated values for these 100 maximum shifts. These operations are sequentially performed up to the last column of the image, and the minimum value for each column is calculated.

Further, the cumulative value interpolation means in this embodiment,
FIG. 35 shows the interpolation data calculating means and the minimum value obtaining means.
And FIG. By the cumulative value calculation means,
When the first and second columns of interest, which are in a relative positional relationship, are sequentially shifted and all the accumulated values are calculated, the accumulated values are interpolated using an interpolation method, for example, a spline interpolation method ( Cumulative value interpolation means). The cumulative value interpolation means calculates cumulative value interpolation data corresponding to a preset number of divisions of the interpolation section (interpolation data calculation means). The minimum value is obtained from the interpolated values including the accumulated values (minimum value obtaining means). For example, it is assumed that the interpolation pitch is divided into 20 pixels. The data interpolation means according to claim 4, wherein when interpolating the accumulated value, the interpolation pitch is divided into five.
This is equivalent to a pixel divided into 100 parts.

The present invention is not limited to the above embodiment, and needless to say, various modifications and substitutions can be made within the scope of the claims.

[0042]

As described above, according to the image reading apparatus of the present invention, the position error component in the main scanning direction due to the vibration of the mirror or the like is removed by the position error measuring means for the pixels in the main and sub scanning directions. Since the position error in the sub-scanning direction can be calculated, it is possible to accurately correct the variation in the reading position due to the fluctuation of the pixel only in the sub-scanning direction. In addition, since the position error component of the pixel in the main scanning direction in the main scanning direction can be calculated by the position error measuring unit in the main scanning direction, the variation of the reading position due to only the fluctuation of the pixel in the main scanning direction can be corrected with high accuracy. be able to.

Further, by making the pattern larger than the resolution of the image sensor, moiré can be eliminated, and the positional deviation measurement accuracy can be improved.

Further, since the density patterns are not at the same pitch, the minimum value of the positional deviation can be guaranteed to be one, and the measurement accuracy can be improved. Further, since the widths of the black patterns are not equal, the minimum value of the positional deviation can be guaranteed to be one, and the measurement accuracy can be improved.

Further, by determining the minimum value of the accumulated difference between the pixel rows, the position error of the pixel in the sub-scanning direction can be measured with high accuracy.

Further, by using the interpolation method, it is possible to measure the pixel position deviation with high accuracy.

Further, the comparison area can be reduced by storing the last accumulated position deviation minimum value position and estimating the next minimum value position, so that the position deviation can be calculated at high speed.

Further, by reducing the number of times of calculation of the difference in the difference area, it is possible to perform the position shift calculation at a high speed without lowering the calculation resolution.

Further, by using the interpolation method for calculating the minimum value, the position shift can be calculated at high speed without lowering the calculation resolution.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an image reading apparatus according to the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of the image reading apparatus of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of an image reading apparatus according to the present invention.

FIG. 4 is a flowchart showing a series of operations of the image reading apparatus according to the present invention.

FIG. 5 is a plan view showing a scanning surface in the image reading device of FIG. 1;

FIG. 6 is a diagram showing an example of a line pattern used in the present invention.

FIG. 7 is a diagram showing another example of a line pattern used in the present invention.

FIG. 8 is a diagram showing another example of a line pattern used in the present invention.

FIG. 9 is a diagram showing another example of a line pattern used in the present invention.

FIG. 10 is a flowchart illustrating a main scanning position deviation measuring operation in the first embodiment.

FIG. 11 is a flowchart illustrating a sub-scanning position displacement measuring operation in the first embodiment.

FIG. 12 is a flowchart illustrating a main scanning position error correction operation in the first embodiment.

FIG. 13 is a diagram illustrating a correction model based on a cubic function convolution.

FIG. 14 is a flowchart illustrating a sub-scanning position error correction operation in the first embodiment.

FIG. 15 is a flowchart showing an image position shift measuring operation in the first embodiment.

FIG. 16 is a diagram illustrating an example of a diagonal line pattern according to the present invention.

FIG. 17 is a diagram illustrating an example of a line pattern according to the present invention.

FIG. 18 is a diagram showing another example of the oblique line pattern in the present invention.

FIG. 19 is a diagram showing another example of a line pattern in the present invention.

FIG. 20 is a diagram showing another example of the oblique line pattern in the present invention.

FIG. 21 is a diagram showing another example of a line pattern in the present invention.

FIG. 22 is a flowchart illustrating an image position shift measuring operation in the second embodiment.

FIG. 23 is a flowchart illustrating a main scanning position deviation measuring operation in the second embodiment.

FIG. 24 is a flowchart illustrating a sub-scanning position shift measuring operation in the second embodiment.

FIG. 25 is a diagram illustrating a spline interpolation method.

FIG. 26 is a flowchart showing an image position shift measuring operation in the third embodiment.

FIG. 27 is a flowchart illustrating a main scanning position deviation measuring operation in the third embodiment.

FIG. 28 is a flowchart showing a sub-scanning position shift measuring operation in the third embodiment.

FIG. 29 is a diagram showing a state of shifting image data and obtaining a minimum value.

FIG. 30 is a flowchart showing an image position shift measuring operation in the fourth embodiment.

FIG. 31 is a flowchart illustrating a main scanning position deviation measuring operation in the fourth embodiment.

FIG. 32 is a flowchart showing a sub-scanning position shift measuring operation in the fourth embodiment.

FIG. 33 is a flowchart showing a main-scanning-position deviation measuring operation in the fifth embodiment.

FIG. 34 is a flowchart showing a sub-scanning position displacement measuring operation in the fifth embodiment.

FIG. 35 is a flowchart showing a main scanning position deviation measuring operation in the sixth embodiment.

FIG. 36 is a flowchart showing a sub-scanning position shift measuring operation in the sixth embodiment.

[Explanation of symbols]

10: Image reading device, 11: Document installation location, 12, 1
5; running body, 12-1, 15-1; mirror, 13; one-dimensional image sensor, 14; lens, 16; image signal output port, 17; driving means, 18; contact glass, 19;
Chart original, 20; lamp, 21; imaging area, 31;
Control section 32; photoelectric conversion section 33; A / D conversion section 3
4; shading correction unit, 35; image position deviation measurement unit, 36; position error correction unit, 37; image processing unit, 38;
Image storage memory.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Tada 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Yunami 1-3-6 Nakamagome, Ota-ku, Tokyo Share F term in Ricoh Company (reference) 5B047 AA01 BB02 CA05 CA07 5C072 AA01 BA17 BA18 EA05 5C077 LL03 MM12 PP55

Claims (11)

[Claims] 1. An image reading apparatus which relatively scans an arbitrary subject with an optical reading unit to optically read an image of the subject to obtain an image signal, wherein the image reading device has a uniform density in a main scanning direction; A line pattern having a non-uniform density in the sub-scanning direction perpendicular to the main scanning direction and a diagonal pattern having a uniform density in the non-horizontal and non-vertical direction in the main scanning direction are arranged adjacent to each other. An image reading apparatus, comprising: a measuring unit that measures a position error from an image signal obtained from a document by the image reading device; and a correcting unit that corrects an image of the image reading device based on the value of the position error. 2. The image reading apparatus according to claim 1, wherein the line pattern or the oblique line pattern is a pattern that is larger than a resolution of the optical reading unit. 3. The density pattern according to claim 1, wherein the line pattern or the diagonal pattern is a density pattern in which a density pattern having a constant width and a horizontal width in the sub-scanning direction of the optical reading unit of the document is not equal pitch. Image reading device. 4. The line pattern or the oblique line pattern is a density pattern in which a density pattern having a fixed width in a direction that is not horizontal and perpendicular to a main scanning direction of the optical reading unit of the document is not equal pitch. Or the image reading device according to 2. 5. The line pattern according to claim 1, wherein the line pattern horizontally and horizontally adjacent to each other in the sub-scanning direction of the optical reading means of the document has a uniform pitch and a different width. Image reading device. 6. The oblique line pattern according to claim 1, wherein the oblique line pattern is a pattern that is adjacent to the original in a direction that is not horizontal and perpendicular to the scanning direction of the optical reading unit and that has a uniform pitch and a different width. Image reading device. 7. The data line of an image signal first column perpendicular to the main scanning direction of the optical reading unit with respect to an arbitrary area of the line pattern or the oblique line pattern. Calculates the cumulative value of the difference between the data sequence and the adjacent data sequence with respect to the adjacent data sequence of the second image signal adjacent to the image data, and determines the relative position in the direction in which the optical reading unit performs main scanning. A cumulative value calculating means for sequentially shifting in a vertical direction to obtain respective cumulative values; and a minimum value calculating means for comparing respective cumulative values obtained by the cumulative value calculating means and calculating a minimum value thereof. The minimum value calculating means is sequentially performed on the entire area of the image signal;
Position calculating means for calculating a minimum value for each column; position error calculating means for cumulatively adding the minimum value for each column obtained by the position calculating means; a minimum displacement of the diagonal pattern and the diagonal pattern A minimum position deviation amount storage unit for storing a minimum position deviation amount of the line pattern adjacent to the line pattern; and the optical reading using the minimum position deviation amount of the oblique line pattern and the minimum position deviation amount of the line pattern. 2. The image reading apparatus according to claim 1, further comprising: a main scanning direction position shift calculating unit that calculates a minimum position shift amount of only the main scanning direction. 8. A data interpolating means for performing a numerical operation for smoothly combining each data with respect to a data sequence of the image signal and interpolating between data, and a direction in which the optical reading means performs main scanning. Image signal 1 perpendicular to
The data sequence at a relative position in a direction perpendicular to the main scanning direction of the optical reading unit with respect to a data sequence of a column and an adjacent data sequence of a second image signal adjacent to the data sequence. And, in the adjacent data string, calculate the cumulative value of the difference for each interpolation pitch calculated by the data interpolation means, sequentially shift the relative position in a direction perpendicular to the direction of the main scanning by the optical reading means, The image reading apparatus according to claim 1, further comprising: a cumulative value calculating unit that obtains each cumulative value. 9. The minimum value calculating means for comparing the cumulative value obtained by the cumulative value calculating means and calculating the minimum value, the position of the minimum value obtained by the minimum value calculating means. A minimum position storage means for storing the position of the minimum position storage means when the optical reading means, which is an object of the minimum value calculation means, advances one line in the main scanning direction. And a difference area calculating means for obtaining a difference for each interpolation pitch from a predetermined comparison range, and a minimum value calculating means for sequentially executing the minimum value calculating means over the entire area of the image signal to calculate a minimum value for each column. The image reading device according to claim 8, further comprising a calculating unit. 10. The data interpolating means for interpolating between data by performing a numerical operation on the data sequence of the image signal to smoothly combine each data, and the optical reading means. Image signal 1 perpendicular to the scanning direction
The data interpolating means is applied only to the first data line or the second data line adjacent to the first image data column or the second data line adjacent to the second data line and the second data line adjacent to the data sequence. In the pixel data of the data string, and the pixel data generated by the data interpolation means of the leftmost or rightmost adjacent data string adjacent to the pixel, the cumulative value of the difference is calculated, and the relative position is calculated. 9. The image reading apparatus according to claim 8, further comprising: a cumulative value calculating unit that sequentially shifts the optical reading unit in a direction perpendicular to the main scanning direction at every interpolation pitch and obtains each cumulative value. 11. The cumulative value interpolating means for performing a numerical operation for smoothly combining respective cumulative values obtained by the cumulative value calculating means and interpolating between the cumulative values, the cumulative value interpolating means, Means for calculating cumulative value interpolation data corresponding to the number of divisions of the interpolation section set in advance by the means; and comparing the interpolation data of each cumulative value calculated by the interpolation data calculating means with the minimum The image reading apparatus according to claim 8, further comprising an interpolation data minimum value calculating unit that calculates a value.