JPH06169377A - Image reader - Google Patents

Abstract

PURPOSE:To prevent an image after printing from being deformed by eliminating a characteristic difference in linearity between odd bits and even bits of a CCD. CONSTITUTION:The image reader is equipped with a gray scale which linearly varies in density with the position, an odd-bit memory 107 wherein odd-numbered output density is stored corresponding to a read position on the gray scale when the gray scale is read, an even bit memory 108 wherein even-numbered output density is stored corresponding to a read position on the gray scale when the gray scale is read, a CPU 110 which reads respective output density values corresponding to read positions on the gray scale stored in the odd-bit memory 107 and even-bit memory 108 and generates specific correction data on the odd-bit memory 107 and even-bit memory 108, and a parity correcting circuit 109 which determines print density at the time of a read of a document on the basis of the correction data generated by the CPU 110.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device such as an image scanner, a copying machine, a facsimile device and an electronic blackboard, and more particularly to an image reading device using a dual channel shift register.

[0002]

2. Description of the Related Art A conventional image reading apparatus will be described in detail below with reference to the drawings. CCDs include a single-channel CCD and a dual-channel CCD. 4A and 4B are explanatory views showing CCDs of a single channel system and a dual channel system. FIG. 4A shows a single channel system and FIG. 4B shows a dual channel system. In addition, 401 shows a light receiving part and 402-404 has shown the shift register. As shown in FIG. 6A, in the single-channel CCD, the data read by the light receiving unit 401 is
It is transferred and output by a pair of shift registers 402. Further, as shown in FIG. 2B, in the dual channel CCD, the data read by the light receiving unit 401 is divided into two odd number bits and even number bits by the two sets of shift registers 403 and 404 and is output respectively. is doing. It should be noted that the dual-channel CCD is more frequently used than the single-channel CCD because the dual-channel CCD has a higher degree of integration and less transfer loss.

FIG. 5 is a graph showing the output voltages of odd-numbered bits and even-numbered bits when a gray scale is read by a dual-channel CCD, and FIG. 5 (a) shows the difference between the output voltages of odd-numbered bits and even-numbered bits. Showing the graph,
FIG. 11B is a graph showing the characteristic difference between the linearity of odd bits and that of even bits. In addition, 501 represents an even-bit waveform, 502 represents an odd-bit waveform, and 503
Shows an odd-bit waveform, and 504 shows an even-bit waveform. The output voltage of odd bits is
It is the output 1 of (b), and the output voltage of even bits is as shown in FIG.
It is the output 2 of (b). Dual channel CCD
In the above, although the degree of integration is high and the transfer loss is small,
There is an inconvenience that there is a difference in output voltage between the odd-numbered bit and the even-numbered bit as shown in FIG. 5A and a characteristic difference in linearity as shown in FIG. 5B.

For this reason, in the conventional image reading apparatus, as shown in FIG.
With the configuration as shown in (1), the difference between the output voltages of the odd bit and the even bit of the CCD is improved. Here, FIG. 6 is an explanatory diagram showing a part of the configuration of the image reading device, and a graph showing the output voltage of this device. FIG. 1A is an explanatory diagram showing a part of the configuration, in which the reflected light of the light emitted from the light source (not shown) to the document is converted into an electric signal (analog signal).
A CCD 601 for converting into an analog electric signal, an amplifier 602a for amplifying an analog electric signal corresponding to an odd-bit pixel of the analog electric signal output from the CCD 601, and a volume resistor 602b for adjusting an amplification factor of the amplifier 602a.
And an amplifier 603a for amplifying an analog electric signal corresponding to an even-bit pixel among the analog electric signals output from the CCD 601 and a volume resistor 603b for adjusting the amplification factor of the amplifier 603a.
Further, FIG. 6B is a graph showing an output voltage when a gray scale is read by the image reading apparatus having the above configuration, 604 shows a waveform of odd bits, and 605 shows a waveform of even bits. Further, 606 is a waveform 605
The waveform after correction is shown. In the conventional image reading apparatus, as shown in FIG. 6A, since the volume resistor 602b and the volume resistor 603b are added to the amplifier 602a and the amplifier 603a for amplifying the output of the CCD 601, for example, the amplification factor of the amplifier 603a is increased. By adjusting, as shown in FIG. 6B, the output of the even bits is adjusted, and the difference between the output voltages of the odd bits and the even bits can be eliminated.

[0005]

However, according to the conventional image reading apparatus, the volume resistance is added to the amplifier for amplifying the output of the CCD to adjust the output voltage, so that the odd number bit and the even number bit in the CCD are adjusted. Although the difference in the output voltage can be eliminated, the difference in the output voltage with respect to the document density is different, so that it is not possible to eliminate the characteristic difference between the odd number bit and the even number bit in the CCD. For example, when a gray uniform chart is read. , It appears as vertical stripes when printed on paper,
That is, there is a problem that the image after printing is disturbed. Since the amplifier itself also has a characteristic difference in linearity, the tendency for image distortion was stronger.

The present invention has been made in view of the above, and it is an object of the present invention to prevent the disorder of the image after printing by eliminating the characteristic difference of the linearity of odd bits and even bits in the CCD.

[0007]

In order to achieve the above object, the present invention is an image reading apparatus for reading an original using a CCD having a dual channel shift register, and the density changes linearly with respect to the position. The gray scale, the first storage means for storing the odd-numbered output density corresponding to the reading position on the gray scale when the gray scale is read, and the reading position on the gray scale when reading the gray scale Second storage means for storing even-numbered output densities in correspondence with each other, and output densities corresponding to the reading positions on the gray scale stored in the first storage means and the second storage means are read and predetermined corrections are made. Based on the correction data creating means for creating data on the first storage means and the second storage means, and the correction data created by the correction data creating means There is provided an image reading apparatus comprising a correction means for determining a printing density at the time of reading the document.

Further, in order to achieve the above object, the present invention is a CCD having a dual channel shift register.
In an image reading apparatus that reads an original using a document, when reading a grayscale in which the density changes linearly with respect to the position, the odd-numbered output density is stored in correspondence with the reading position on the grayscale, and the power is supplied. A first storage means backed up by the second storage means, and a second storage means which stores the even-numbered output density corresponding to the reading position on the gray scale when the gray scale is read, and which is backed up by the power supply. , First storage means and second
The respective output densities corresponding to the reading positions on the gray scale stored in the storage means are read, and predetermined correction data is set as the first correction data.
An image including a correction data creating unit created on the second storage unit and a correction unit determining a print density when a document is read based on the correction data created by the correction data creating unit. A reading device is provided.

[0009]

The image reading apparatus of the present invention reads the gray scale in which the density changes linearly with respect to the position and stores the output densities of the odd bit and the even bit corresponding to the read position on the gray scale, The output density of the odd and even bits corresponding to the stored reading position on the gray scale is read, the predetermined correction data is created, and the print density when the original is read based on the created correction data To decide.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image reading apparatus of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an image reading apparatus according to the present invention. A CCD 101 for converting reflected light of light emitted from a light source (not shown) onto a document into an electric signal (analog signal) and a CCD.
An amplifier 102 that amplifies an analog electric signal corresponding to an odd-numbered pixel of the analog electric signal output from 101 and an analog electric signal corresponding to an even-bit pixel of the analog electric signal output from the CCD 101 are generated. Amplifier 103 for amplification, amplifier 102 and amplifier 1
03 for synthesizing the output of 03, and 8 for converting an analog signal output from the synthesizing unit 104 into a digital signal
bit A / D converter 105 and 8-bit A / D converter 1
Shading correction circuit 106 for performing shading correction on the output of 05, and an odd bit memory 107 for reading gray scale and storing the gray scale density and the output density value of the odd bits when the density is actually read. An even-bit memory 108 for reading the gray scale and storing the gray-scale density and the output density value of the even-bit when the density is actually read
And odd bit memory 107 and even bit memory 10
8, the even-odd correction circuit 1 which corrects the output of the shading correction circuit 106, converts it into an appropriate density value, and outputs it
09 and a CPU 110 that reads the stored contents of the odd-bit memory 107 and the even-bit memory 108 and creates appropriate correction data on the odd-bit memory 107 and the even-bit memory 108.

The operation of the above arrangement will be described.
First, the reading operation will be described. CCD 101
Reads an original and outputs an analog electric signal corresponding to the density of the read original by dividing it into odd bits and even bits. The analog electric signals output from the CCD 101 are amplified by the amplifier 102 and the amplifier 103, respectively, and after being amplified, are combined by the combining unit 104. The analog electric signal synthesized by the synthesizing unit 104 is an 8-bit A / D converter 1
It is converted into a digital signal by 05. In the present embodiment, the number of gradations is 256 gradations (8 bits), and as shown in FIG. 1, the converted digital signal is 8-bit data (256 gradations). Subsequently, the converted digital signal is subjected to shading correction by the shading correction circuit 106. The even-odd correction circuit 109 receives the output a of the shading correction circuit 106, converts it into appropriate density data b, and outputs the converted appropriate density data b.

Next, the operation relating to the even-odd correction circuit 109, which is a characteristic operation of the present invention, will be described in detail with reference to FIGS. 2A and 2B are explanatory views showing the document placing table as seen from the CCD 101 side, 201 indicates a white reference plate, and 202 indicates a density that gradually changes from white to black and the density becomes linear with respect to the position. It shows the gray scale. FIG. 3 is an explanatory diagram showing correction of the characteristic difference between the odd number bit and the even number bit in the CCD. Graph A is converted by the even / odd correction circuit 109 with respect to the output (input of the even / odd correction circuit 109) a of the shading correction circuit 106. 6 is a graph showing the relationship of the generated appropriate density data b, and graph B is a graph showing the relationship of the output a of the shading correction circuit 106 with respect to the position on the gray scale 202. Graph C shows gray scale 20.
It is a graph which shows the relationship of the density with respect to the position on 2. As shown, the density changes linearly with respect to the position.

As for the operation relating to the even-odd correction circuit 109, first, as shown in FIG. 2, the white reference plate 201 attached to the upper part of the original reading area is read, and the shading correction circuit 106 is used to determine the light amount distribution in the main scanning direction. Variation,
It is set so as to be uniform by correcting variations between CCD bits. Next, the gray scale 202 is read and the gray scale 202 is divided into 256 (see FIG. 3)
The written position and the output density value of the odd bit when that position is actually read are written in the odd bit memory 107,
A position where the gray scale 202 is divided into 256 and an even-bit output density value when the position is actually read are written in the even-bit memory 108. Odd bit memory 1
The memory content of 07 (256 gradations) is shown in FIG.
The waveform 301a shown in the graph B of FIG. Similarly, when the stored contents (for 256 gradations) of the even-bit memory 108 are represented by a graph, the waveform 302a shown in graph B of FIG. 3 is obtained. When the writing to the odd-numbered bit memory 107 and the even-numbered bit memory 108 is completed, the CPU 110 reads the stored contents of each memory, and rewrites the 256-divided position of the gray scale 202 to the actual density indicated by the position to obtain the correction data. Are created on the odd-bit memory 107 and the even-bit memory 108. If this correction data is expressed in a graph, the odd bits are the waveform 30 shown in graph A of FIG.
1b (corresponding to the waveform 301a), the even bit is the waveform 302
b (corresponding to the waveform 302a). After the correction data is created, the original in the reading area shown in FIG. 2 is read, and the odd-even and even-bit correction circuits 109 read the memories storing the correction data to determine the print density. Therefore, it is possible to obtain image data in which the output voltage difference between the odd bits and the even bits and the characteristic difference in the linearity are eliminated.

The above-described operation will be described with reference to the graph of FIG. 3 by taking as an example a case where one density (the same density as the 128th density of the gray scale 202) is read.
When the density of the read original is the same as the density center, that is, the 128th density of the gray scale 202,
The position of c is shown on the graph B of FIG. 3, and the output density value of the odd bits at this time is d, and the output density value of the even bits is e. In this way, even if the same density is read, the output density value will be different for odd-numbered bits and even-numbered bits. The even-odd correction circuit 109 is the CPU 1
10 reads the data of the odd-numbered bit memory 107 and the even-numbered bit memory 108, and as shown in the graph A of FIG. 3, for different output density values d and e, both the odd-numbered bit and the even-numbered bit have the same density (position of f). The concentration of) is output. Similarly, the density of the original is 0 to 25 in the 256 gradations.
Even if any density value up to 5 is shown, the even-odd correction circuit 109
Outputs the same density for both odd and even bits.

As described above, according to this embodiment, the gray scale 202 is read in advance, and the CPU 110 based on the stored contents of the odd bit memory 107 and the even bit memory 108, the waveform 301b and the waveform 301b shown in the graph A of FIG. Since correction values having the relationship of 302b are created, in other words, since correction is performed for all densities from 0 to 255 in 256 gradations, odd bits and even numbers of the read original are read. It is possible to obtain image data in which the difference in output voltage between bits and the characteristic difference in linearity are eliminated. Further, since the gray scale 202 is actually read and corrected, it is possible to cope with a change with time of the CCD 101 and the like.

In this embodiment, the gray scale 202
Although it is configured to be attached to the upper part of the reading area as shown in FIG. 2, it may be attached to the position 203 in the figure. In this case, the gray scale 202 is read while moving the CCD 101 in the sub scanning direction. Further, in the present embodiment, the gray scale 202 is attached to the image reading apparatus, but as another embodiment, the stored contents of the odd-bit memory 107 and the even-bit memory 108 are retained even if the power of the apparatus is turned off. In the case where the configuration is possible, the gray scale 202 may not be attached to the device. In the case of this device, the grayscale 202
Odd-bit memory 1
The correction data is created and stored in the 07 and even bit memory 108. Therefore, one gray scale 202 may be prepared for a plurality of devices,
Also in the manufacturing process, the step of attaching the gray scale 202 can be eliminated.

[0017]

As is apparent from the above, according to the image reading apparatus of the present invention, the density changes linearly with respect to the position in the image reading apparatus which reads an original using a CCD having a dual channel shift register. The gray scale, the first storage means for storing the odd-numbered output density corresponding to the reading position on the gray scale when the gray scale is read, and the reading position on the gray scale when reading the gray scale Second storage means for storing even-numbered output densities in correspondence with each other, and output densities corresponding to the reading positions on the gray scale stored in the first storage means and the second storage means are read and predetermined corrections are made. Correction data creating means for creating data on the first storage means and the second storage means, and based on the correction data created by the correction data creating means Since it and a correction means for determining a printing density at the time of reading a document, by eliminating the characteristic difference of the odd bits and even bits linearity in CCD, it is possible to prevent the disturbance of the image after printing.

Further, according to the image reading apparatus of the present invention, when an image reading apparatus which reads an original using a CCD having a dual channel shift register, when a gray scale whose density changes linearly with respect to a position is read. To store the odd-numbered output density corresponding to the reading position on the gray scale, and to correspond to the reading position on the gray scale when the gray scale is read and the first storage means backed up by the power source. Second storage means for storing even-numbered output densities and backed up by a power supply, and output densities corresponding to the reading positions on the gray scale stored in the first storage means and the second storage means. And a correction data creating means for creating predetermined correction data on the first storage means and the second storage means, Since the correction means for determining the print density when the original is read based on the correction data created by the forming means is provided, the image after printing is eliminated by eliminating the characteristic difference between the linearity of odd bits and even bits in the CCD. Disturbance can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image reading apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a document table viewed from the CCD side.

FIG. 3 is an explanatory diagram showing correction of a characteristic difference in linearity between odd bits and even bits in a CCD according to the present invention.

FIG. 4 is an explanatory diagram showing a single-channel CCD and a dual-channel CCD.

FIG. 5 is a graph showing output voltages of odd bits and even bits when a gray scale is read by a conventional dual channel CCD.

FIG. 6 is an explanatory diagram showing a part of the configuration of a conventional image reading device, and a graph showing an output voltage of this device.

[Explanation of symbols]

 101 CCD 107 Odd Bit Memory 108 Even Bit Memory 109 Even / Odd Correction Circuit 110 CPU

Claims (2)

[Claims] 1. An image reading apparatus for reading an original using a CCD having a dual-channel shift register, and a gray scale in which the density changes linearly with respect to a position, and a reading on the gray scale when the gray scale is read. First storage means for storing the odd-numbered output densities corresponding to the positions, and second storage means for storing the even-numbered output densities corresponding to the reading positions on the gray scale when the gray scale is read And reading the respective output densities corresponding to the reading positions on the gray scale stored in the first storage means and the second storage means, and outputting predetermined correction data on the first storage means and the second storage means. Based on the correction data creating means created in step 1 and the correction data created by the correction data creating means, the print density when the original is read is determined. An image reading apparatus comprising: a correction unit. 2. An image reading apparatus for reading an original using a CCD having a dual-channel shift register, and when reading a gray scale whose density changes linearly with respect to the position, the reading position on the gray scale is made to correspond to the read position. The odd-numbered output densities, and the first storage means backed up by the power source, and the even-numbered output densities corresponding to the reading positions on the grayscale when the grayscale is read, Further, the second storage means backed up by the power source, and the output densities corresponding to the reading positions on the gray scale stored in the first storage means and the second storage means are read, and the predetermined correction data is read out. The correction data creation means created on the first storage means and the second storage means, and the correction data creation means created by the correction data creation means. An image reading apparatus comprising: a correction unit that determines a print density when a document is read based on the data.