JP2006340232A - Color image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image reader, capable of easily and reliably preventing a color drift from occurring. <P>SOLUTION: The color image reader receives spectral light obtained by making spectral color image light into a plurality of frequency bands by a plurality of light receiving elements. The color image reader comprises: reference plates 23, 51 in which n pieces of narrow lines are depicted between a main scanning read start position and a main scanning read end position in a sub-scanning direction, respectively; and correction means 43, 50 for, of the number of pixels of each of red (R), green (G) and blue (B) in the light receiving element obtained from read image data from central narrow lines in a main scanning direction to each narrow line in the reference planes read by each of the light receiving elements, detecting the number of drift pixels of R and B when the number of G pixels is set as the number of reference pixels, to carry out a color drift correction in the main scanning direction in response to the number of drift pixels. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color image reading apparatus that can be applied to a digital color copying machine, a color facsimile apparatus, and the like.

FIG. 8 is a schematic configuration diagram of a conventional color image reading apparatus. The document 1 is illuminated by the light source 2, and the image light reflected by the document 1 is focused by the lens 4 by the mirror 3 and enters the dichroic mirror body 5. The dichroic mirror body 5 splits the image light into a plurality of frequency bands. For example, spectroscopic light divided into three frequency bands of red (R), green (G), and blue (B) is incident on three light receiving elements 6, 7, and 8, respectively, and each of the light receiving elements 6-8. Then, the spectral light is converted into an electrical signal and output as image data.
In the above color image reading apparatus, if the position adjustment of each of the light receiving elements 6 to 8 is not performed with high accuracy, color misregistration during reproduction occurs. The position adjustment is performed in both the main scanning direction and the sub-scanning direction, and the adjustment in the sub-scanning direction is performed using a jig when the apparatus is assembled. Further, the adjustment in the main scanning direction uses a document 10 or the like on which a thin line 9 is drawn on the surface as shown in FIG. 9, and the light receiving elements 6 to 8 that read the document 10 as shown in FIG. The waveforms of the read signals 11, 12, and 13 are respectively displayed on a measuring instrument, the timing of a shift (SH) pulse that is one type of light receiving element driving pulse is changed, and the peak P11 of the waveform of each of the read signals 11 to 13 is changed. This is done by matching the positions of P12 and P13.
Patent Document 1 discloses an image reading apparatus that can output high-quality image data regardless of the presence or absence of uneven scanning speed or a resonance phenomenon by detecting scanning position deviation and correcting image data based on the detected position deviation. The following techniques have been proposed for the purpose of providing.
In a color image reading apparatus that receives spectral light obtained by splitting color image light into a plurality of frequency bands with a plurality of light receiving elements, thin lines are drawn in the sub-scanning direction at the main scanning reading start position and the main scanning reading end position, respectively. Detecting the number of pixels shifted by the reference plate and the number of pixels and the reference pixel number in the light receiving element obtained from the read image data from one thin line to the other thin line in the reference plate read by each light receiving element, Color shift correction in the main scanning direction is performed according to the number of shifted pixels.
Japanese Patent Laid-Open No. 4-172063

In the above prior art, the positional deviation amount (color misregistration amount) is obtained by using a jig or the like for the light receiving elements 6 to 8 subjected to mechanical adjustment at the time of assembly, and the value is set to an internal fixed switch or the like. The above-mentioned position adjustment (color misregistration correction) is performed, however, it is necessary to set an internal fixing switch or the like at the time of assembling, and after the assembling, the light receiving elements 6 to 8 are misaligned, which is electrically Even if it can be corrected, a new adjustment is required. Furthermore, there is a problem that no means for detecting the occurrence of color misregistration is provided, and errors during reproduction cannot be prevented.
Further, according to the above-described prior art, the position adjustment of the light receiving elements 6 to 8 in both the main scanning direction and the sub-scanning direction can be performed, but there are elements that are impossible only by these adjustments. It is the distance from each light receiving element 6 to 8 to the lens 4. According to FIG. 8, it is the direction of the arrow A. The adjustment in the direction A is impossible with high accuracy only by focusing the lens 4 and the light receiving elements 6 to 8.
If this adjustment is not performed, the reduction ratios of the three light receiving elements 6 to 8 will be different. If the reduction ratio is different, a color shift in the main scanning direction occurs. Specifically, when color misregistration correction is performed at a certain point on the main scan by the above-described conventional method, even if there is no color misregistration at that point, the color misregistration occurs as the distance from the point is increased. Happens.
For example, the color deviation adjustment in the main scanning direction is performed on the document 10 as shown in FIG. 9, the adjustment in the sub scanning direction is performed as in the prior art, and then several fine lines 9 are arranged in the sub scanning direction as shown in FIG. Read the manuscript 10 on which “is drawn”. If the reduction ratios of the three light receiving elements 6 to 8 are different, for example, the image data of the three light receiving elements 6 to 8 are as shown in FIG. Here, 14, 15 and 16 are image data of the three light receiving elements 6-8.
In order to perform color misregistration adjustment in the main scanning direction on the document 10 as shown in FIG. 9, the position of the thin line 9 'is aligned with each of the image data 14 to 16 near the main scanning reading start position a. The position of the thin line 9 ′ gradually shifts for each of the image data 14 to 16 as it goes to the end position b. For this reason, color misregistration occurs.
Further, the lens 4 has a characteristic called chromatic aberration, which is a phenomenon in which the image forming position shifts for each color. The amount of image forming position shift for each color is slightly different depending on the image height. In the color image reading apparatus of Japanese Patent Application No. 2-299040 that corrects color misregistration at vertical fine lines, the color misregistration is corrected in the vicinity of the vertical thin line portion (image height), but at other positions (image height). Color shift is caused by the influence of chromatic aberration.
Furthermore, in the color image reading apparatus described in Patent Document 1, color misregistration correction is performed when the power is turned on. However, since the light receiving elements 6 to 8 have a high temperature due to their configuration, the positions of the lens 4 and the light receiving elements 6 to 8 are caused by thermal expansion. There may be a slight shift.
An object of the present invention is to provide a color image reading apparatus that can easily and reliably prevent the occurrence of color misregistration.

In order to achieve the above object, according to a first aspect of the present invention, there is provided a color image reading apparatus that receives spectral light obtained by separating color image light into a plurality of frequency bands by a plurality of light receiving elements, and a main scanning reading start position and a main scanning reading position. A reference plate in which several thin lines are drawn in the sub-scanning direction between the scanning and reading end position, and reading from the center thin line in the main scanning direction to each thin line on the reference plate read by each light receiving element Of the number of RGB pixels in the light receiving element obtained from the image data, the number of shifted pixels of the R pixel number and the B pixel number when the G pixel number is set as the reference pixel number is detected, and according to the shifted pixel number And correction means for correcting color misregistration in the main scanning direction.
The invention according to claim 2 is characterized in that the correction means performs color misregistration correction at the time of the shading operation.
According to a third aspect of the present invention, a memory for storing a pixel shift measurement result of the correction unit is provided, and the correction unit compares the previous value every time the pixel shift is measured, and uses the previous value when greatly different. The color image reading apparatus according to Item 2 is characterized.
According to a fourth aspect of the present invention, there is provided a color image reading apparatus according to the third aspect, further comprising an operation unit for setting a pixel shift measurement value of the correcting unit.

In the color image reading apparatus according to claim 1, the reading is performed by the reference plates each having n thin lines drawn in the sub-scanning direction between the main scanning reading start position and the main scanning reading end position, and the light receiving elements. Of the number of pixels of red (R), green (G), and blue (B) in the light receiving element obtained from the read image data from the thin line at the center in the main scanning direction to the thin line in the reference plate, Since there is a correction means for detecting the number of shifted pixels of the R pixel number and the B pixel number when the number of pixels is the reference pixel number, and correcting the color shift in the main scanning direction according to the shifted pixel number. In addition, it is possible to eliminate the influence of color misregistration due to the difference between the ideal value and the actual measurement value between the thin lines, and it is possible to perform color misregistration correction with higher accuracy.
In the color image reading apparatus according to claim 2, since the correction unit is configured so that it can be performed together with the shading operation, even if the CCD surface fluctuates and the CCD position slightly shifts with time, the image is captured. Since shading is performed every time and color misregistration correction is performed, a high-quality image with small color misregistration can always be maintained.
In the color image reading apparatus according to claim 3, the pixel deviation measurement result of the correction unit can be stored in a memory, and the pixel value measurement result is compared with the previous value every time the pixel deviation is measured. Therefore, even when a measurement error occurs due to the influence of noise or the like, a high-quality image with a small color shift can be maintained without erroneous correction.
In the color image reading apparatus according to the fourth aspect, since the pixel shift measurement value of the correction unit can be set from the operation unit, setting using a jig is possible in the manufacturing process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a basic configuration diagram of a color image reading apparatus of the present invention. The apparatus main body 20 includes a contact glass 21 on which an original 22 is placed, an index (reference plate) 23 described later provided outside the original reading range of the contact glass 21, a light source 24 that irradiates the original 22, a reflection mirror 25, and an original 22. The optical unit 26 which injects the image light reflected by 1 through the reflection mirror 25 is provided.
FIG. 2 is a plan view showing the index of FIG. 1, and n vertical thin lines 27 are arranged on the surface of the index 23 at substantially equal intervals.
FIG. 3 is a control block diagram of the color image reading apparatus according to the embodiment of the present invention. The lens 29, the dichroic mirror body 30, and the dichroic mirror body 30 provided in the optical unit 26 are used to generate a plurality of frequency bands (for example, three types of red (R), green (G), and blue (B)) from the image light. ) Analog processing units 34, 35 for analog processing of outputs from a plurality (three in this embodiment) of light receiving elements (CCD) 31, 32, 33 and CCDs 31-33 that receive the spectral light split into 36. A / D converters 37, 38, 39, line buffer unit 40, interface (I / F) provided for analog processing units 34 to 36, respectively, for performing analog / digital (A / D) processing of output signals. ) Unit 41, a CCD control unit 42 as correction means, a line buffer control unit 43 as correction means, and a CPU (central processing unit) 44 as calculation means.
In FIG. 3, the read signals output from the three CCDs 31 to 33 are digitized via the analog processing units 34 to 36 and the A / D converters 37 to 39 and stored in the line buffer unit 40. The data stored in the line buffer unit 40 is sent to the I / F unit 41 at a timing controlled by the CPU 44. The CPU 44 can read a part or all of the line buffer unit 40 via the line buffer control unit 43, and can set the reading start position of the CCDs 31 to 33 via the CCD control unit 42. .
Furthermore, in this embodiment, correction address point setting which is correction means for inputting data from the A / D conversion units 37 to 39 and outputting correction address point data to be described later to the line buffer control unit 43 under the control of the CPU 44. Part 50 is provided. The memory 60 stores the correction address point setting value of the correction address point setting unit 50, and can control the value stored in the memory 60 from the operation unit 61.

FIG. 4 is a control flow diagram of the color image reading apparatus of the present invention. When the power of the apparatus is turned on (S1) and document reading is started (S2), shading (S3) is performed to correct illuminance distribution unevenness in the main scanning direction, and then each CCD 31 of the optical unit 26 is scanned. ˜33 reads n thin lines 27 of the index 23 (S4), and as shown in FIG. 5, the position shifts of the peaks PB, PR, PG of the read signals DB, DR, DG caused by the position shifts of the CCDs 31-33, as shown in FIG. Are analyzed and calculated by the CPU 44, and the amount of color misregistration in the main scanning direction with respect to the center line is calculated (S5). If the CCD control unit 42 can control the CCDs 31 to 33 using this color misregistration amount as a main scanning correction value (YES in S6), CCD control is performed (S7).
Therefore, in the above control example, when the color misregistration after mechanical adjustment is electrically corrected, it is not necessary to perform the correction work at the time of assembly, and the assembly process can be reduced. In addition, by performing color misregistration correction every time an image is read, even if there is a mechanical or atmospheric temperature misalignment after assembly, it is automatically corrected if electrical correction is possible, so readjustment is necessary. Disappear.
Further, since the color misregistration amount is calculated by the CPU 44, an error display process (S8) is performed when an uncorrectable color misregistration occurs. In this case, the precorrection value held in the memory 60 is used ( S9) The image can be read as it is (S10), or the reading operation of the document 22 can be stopped.
FIG. 6 is a plan view of a reference plate used in place of the index 23 shown in FIG. 2. The surface of the reference plate 51 has a main scanning reading start position and a main scanning reading end position in the sub-scanning direction. N fine lines 52 are formed.

The operation of the control system of the color image reading apparatus shown in FIG. 3 will be described. First, the positional deviation adjustment in the main scanning direction is performed using the thin line 52 at the center of the reference plate 51 as a reference. At this time, if the reduction ratios of the CCDs 31 to 33 are different, the image data of the thin line 52 ′ (FIG. 6) on the reading end position side read by the CCDs 31 to 33 is shifted, and as shown in FIG. The image numbers l1, l2, and l3 from the center of the central thin line 52 of the image data 53, 54, and 55 to the thin lines 52 ′ in .about.33 are different from each other.
The correction address point setting unit 50 detects how many other pixel numbers l2 and l3 are deviated from the reference number of pixels (in this embodiment, the number of pixels 11), and then, according to the detected number of displaced pixels. The address point on the main scan to be corrected is set.
More specifically, for example, in FIG. 7, the method of setting the correction address point with respect to the number of pixels 12 is as follows. If the deviation of the number of pixels 12 with respect to the number of pixels 11 is Δnx pixels, the number of correction address points is Δnx. Set.
That is, assuming that the first correction address point is HAx1, HAx1 = l2 / (Δnx + 1), the second correction address point is HAx2, and the following correction address points are sequentially HAx3, HAx4 and symbol HAxn. Then, up to n-th correction address points are set such that HAx2 = 2HAx1, HAx3 = 3HAxl, HAx4 = 4HAxl · · HAxn = nHAxl.
As described above, the correction address point setting unit 50 sets correction address points (HAx1 to HAxn), and the line buffer control unit 43 corrects pixels corresponding to the correction address points of the line buffer unit 40.

As a result of the correction, the number of pixels 12 is expanded in the direction A in FIG. 7 by the amount of Δnx pixels as a whole and becomes equal to the number of pixels 11, and the number of pixels 13 is entirely thinned by Δny pixels. Reduced in the direction to be equal to the number of pixels l1. Accordingly, the number of pixels 11, 12, and 13 can be matched, and a positional shift due to a reduction ratio in the main scanning direction in the CCDs 31 to 33, that is, a color shift can be corrected electrically.
In addition, since independent magnification correction can be performed at (n-1) places obtained by subtracting 1 from the number n of thin lines in the main scanning direction, even when the amount of color shift differs depending on the image height, such as lens chromatic aberration. It can be corrected electrically. Moreover, the accuracy of color misregistration can be improved by increasing the number of correction points. Furthermore, since the color misregistration correction value can be controlled from the operation unit 61, management such as setting an initial value of the color misregistration correction value using a jig or the like in the manufacturing process can be performed.
As described above, according to the present invention, color misregistration in the main scanning direction of a plurality of light receiving elements can be corrected electrically and automatically, and further, correction of the color misregistration is performed every time the power is turned on, It is possible to provide a color image reading apparatus that can reliably prevent the occurrence of color misregistration.

1 is a basic configuration diagram of a color image reading apparatus of the present invention. It is a top view which shows the parameter | index of FIG. It is a control block diagram of a color image reading apparatus according to an embodiment of the present invention. It is a control flowchart of the color image reading apparatus of the present invention. It is a figure which shows the reading signal of a parameter | index. It is a top view of the reference | standard board used instead of the parameter | index 23 shown in FIG. It is a figure which shows the difference in the pixel number of image data. It is a schematic block diagram of the conventional color image reading apparatus. FIG. 3 is a diagram (part 1) illustrating an adjustment document. It is a figure which shows the reading signal of the original for an adjustment. FIG. 6 is a second diagram illustrating an adjustment document. FIG. 12 is a diagram illustrating image data of the adjustment document in FIG. 11.

Explanation of symbols

  23 Index (reference plate), 43 Line buffer control unit (correction unit component), 50 Correction address point setting unit (correction unit component), 51 Reference plate, 60 Memory, 61 Operation unit

Claims (4)

  In a color image reading device that receives spectral light obtained by splitting color image light into a plurality of frequency bands with a plurality of light receiving elements, several fine lines are provided between the main scanning reading start position and the main scanning reading end position in the sub-scanning direction. Out of the number of pixels for each of RGB in the light receiving element obtained from the read image data from the thin line at the center in the main scanning direction to each thin line in the reference plate read by each of the light receiving elements And a correction means for detecting a shift pixel number of the R pixel number and the B pixel number when the G pixel number is set to the reference pixel number, and correcting a color shift in the main scanning direction according to the shift pixel number. A color image reading apparatus.   The color image reading apparatus according to claim 1, wherein the correction unit performs color misregistration correction in conjunction with a shading operation.   3. The memory according to claim 2, further comprising a memory for storing a pixel deviation measurement result of the correction means, wherein the correction means compares the previous value every time the pixel deviation is measured, and uses the previous value if the difference is greatly different. Color image reading apparatus.   The color image reading apparatus according to claim 3, further comprising an operation unit that sets a pixel shift measurement value of the correction unit.

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