JP2001036742A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a peak hold reading position from getting out of a white reference plate by reading the image data on the white reference plate covering a line decided as its front end through a line decided as its rear end respectively and then storing and calculating the image data as the white reference data. SOLUTION: An original 13 is set on an original reading base 3 and a light source 4a is turned on. Then the image of a white reference plate 15 is read by a photoelectric transducer CCD 7, undergo the analog-digital conversion and stored as the reference data to be used for the shading correction of image data. The head line of the plate 15 is detected in the vertical scanning direction for detecting the gain value setting peak data. The head position of the plate 15 is separated from the plate 15 since the installing member of the plate 15 is black. The peak hold processing is carried out via the detection of the tip line of the plate 15 for setting the gain value to the reading of the image data after the white reference data are read.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image reading apparatus having a one-dimensional line sensor for reading an image, such as an image scanner, a facsimile, and a copying machine.

[0002]

2. Description of the Related Art In recent years, in image reading apparatuses such as facsimile machines and copiers, CCD (Charge Coupled Device) line sensors have been widely used as image sensors for reading original images.

[0003] White reference data for shading correction is created by reading image data of a white reference plate before reading image data. When a stepping motor is used, the required number of stepping pulses up to the position of the white reference plate are generated in accordance with the reading position of the white reference plate, and after the number of pulses is generated, the gain control value of the video is read and the white reference data is read. Was reading.

In order to obtain reference data for shading correction, a method has been reported in which several lines of an image on a white reference plate are read and an averaging process is performed between the lines to obtain white reference data regardless of the presence or absence of defective pixels. ing. Alternatively, a method has been reported in which a defective pixel is determined and a measure is taken not to take in the data of the defective pixel.

[0005]

However, the above-described method is based on the premise that image data not deviating from the white reference plate has been read, and if the image data is read off the white reference plate, accurate data will be obtained. The problem that white reference data cannot be collected cannot be solved.

Further, there is a problem of accuracy in moving to the white reference plate position, and a margin of the white reference plate width is provided in the sub-scanning direction in order to absorb a variation in the movement accuracy. However, it is difficult to increase the size of the white reference plate without limit, and there is a demand for downsizing of the device itself. Therefore, it is necessary to surely read the white reference data with the white reference plate having a limited size. . Also, even within the limited sampling range, pixels outside the white reference plate should not be included in the white reference data.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and specifies a reading start position of a white reference plate in the sub-scanning direction, and sets a peak hold reading position for gain control of a video amplifier from the white reference plate. An object of the present invention is to keep the length of the sub-scanning end portion of the white reference plate from being deviated and to minimize the length margin.

It is another object of the present invention to maintain the accuracy of the shading correction calculation by reading the white reference data again when the portion deviating from the white reference plate is read and stored and processed as white reference data.

Further, if it is determined that a position deviating from the white reference plate has been read before the accumulation operation of the white reference data is performed, data outside the white reference plate is excluded from the calculation target of the white reference accumulation operation. An object of the present invention is to perform a storage operation of high-quality white reference data.

[0010]

In order to achieve the above object, according to the present invention, there is provided an image reading means for reading image data using a line sensor including a plurality of one-dimensionally arranged photoelectric conversion elements. First detecting means for detecting the leading edge of the white reference plate, second detecting means for detecting the trailing edge of the white reference plate, and white reference by the first and second detecting means by the image reading means. Storage operation means for reading the image data of the white reference plate from the line determined to be the front end of the plate to the line determined to be the rear end of the white reference plate, and storing and calculating the image data as white reference data; It is characterized in that shading correction of original image data read by the image reading means is performed based on the white reference data accumulated and computed by the accumulation computing means.

According to a second aspect of the present invention, there is provided an image reading means for reading image data using a line sensor including a plurality of one-dimensionally arranged photoelectric conversion elements, and a first detection for detecting a leading edge of a white reference plate. Means and image reading means,
Accumulating means for reading the image data of the white reference plate from the line determined to be the white reference plate by the first detecting means and accumulating and calculating the image data as white reference data; and detecting the trailing edge of the white reference plate A second detection unit configured to reduce the number of lines to be read when the image data read by the image reading unit is not white reference data; The image data read by the image reading means is subjected to accumulation calculation by the accumulation operation means, and shading correction of the original image data read by the image reading means is performed based on the white reference data accumulated and operated by the accumulation operation means. .

According to a third aspect of the present invention, there is provided an image reading means for reading image data using a line sensor including a plurality of photoelectric conversion elements arranged one-dimensionally, and a first detection for detecting a leading edge of a white reference plate. Means and image reading means,
Accumulating means for reading the image data of the white reference plate from the line determined to be the white reference plate by the first detecting means and accumulating and calculating the image data as white reference data; and detecting the trailing edge of the white reference plate A second detection unit configured to determine whether the image data read by the image reading unit is not white reference data by the second detection unit; It is characterized in that shading correction of original image data read by image reading means is performed based only on data.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the white reference data and the original image data read by the image reading means are amplified by a gain control value. It is characterized by having amplification means.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the gain control value is obtained by adding a peak value of a pixel in the first line data of the white reference plate detected by the first detecting means to a new gain value. As the control value, the gain control value and a preset fixed gain control value are changed.

According to a sixth aspect of the present invention, in the second aspect, the first detecting means detects the leading edge of the white reference plate, the image reading means reads the image data of the white reference plate, and the accumulation calculating means. , The detection of the trailing edge of the white reference plate by the second detection means, and the reduction of the number of read lines are the result of the detection by the second detection means. Is repeatedly performed until the image data becomes the white reference plate image data.

According to a seventh aspect of the present invention, in the first aspect of the invention, the image reading means comprises:
It is characterized by having a shading adjustment plate for adjusting the difference in the amount of reflected light between the center and the end of the line sensor.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

First, an image scanner will be described with reference to FIG. An automatic paper feeder 2 (AD
F) is provided, and an original reading table 3 is provided on the upper surface of the main body, thereby constituting the entire image scanner.

In this case, the light source 4 is provided inside the apparatus body 1.
a traveling body 4 having a mirror 4a and a mirror 5b;
a second traveling body 5 having a and 5b, a lens 6 and a one-dimensional photoelectric conversion element (in this example, a CCD is used) 7,
An exposure scanning optical system 9 including a stepping motor 8 for driving the traveling bodies 4 and 5 is provided. The configuration of the lower stage of the exposure scanning optical system 9 will not be described here.

The automatic paper feeder 2 is provided with an ADF unit 10 and a document table 11. A stepping motor 12 is provided in the ADF unit 10. Further, a document holding plate 14 is provided on the document reading table 3.
The document 13 is set under the document pressing plate 14. A white reference plate 15 for shading correction is arranged at an end of the document reading table 3.

FIG. 2 shows the configuration of a control circuit for processing image data read by the exposure scanning optical system 9 in such an image scanner.
The document reading mode includes a book mode in which image data is read using a document reading table 3 as shown in FIG. 3, and a reading mode in which image data is read using an automatic paper feeder 2 as shown in FIG. There is an ADF mode to perform.

First, the basic operation of reading image data in the book mode as shown in FIG. 3 will be described. After setting the document 13 on the document reading table 3 below the document holding plate 14, the CPU 16
(Light source lighting device) is operated to turn on the light source 4a.
Next, the image of the white reference plate 15 is read by the CCD 7 driven by the CCD driving unit 18, and the A /
The analog-to-digital conversion is performed by a D converter (not shown), and a line buffer (not shown) in the image processing unit 19 is used as reference data for shading correction of image data.
To memorize.

The CPU 16 drives the motor driver 20 (drive device) to operate the stepping motor 8, whereby the traveling body 4 moves in a certain direction of the document 13. When the traveling body 4 scans the document surface at a constant speed, the image data of the document 13 is photoelectrically converted by the CCD 7.

FIG. 5 is a diagram showing the most basic internal configuration of the image processing unit 19. In the image processing unit 19, the analog video signal a, which has been photoelectrically converted, is subjected to digital conversion processing by the analog video processing unit 21. After that, the shading correction processing unit 22 and the image data processing unit 23 respectively perform shading correction and various types of image data processing, and then the binarization processing unit 24 performs binarization processing. Create data b.

Thereafter, the binarized data b is sequentially stored in the scan buffer 25. I / F controller 2
Reference numeral 6 controls output of data in the scan buffer 25 to an external device such as a host computer (not shown). The buffer controller 27 includes the scan buffer 2
5 for input / output of image data.

Next, the basic operation of reading image data in the ADF mode as shown in FIG. 4 will be described. Also in this case, first, after the image on the white reference plate 15 is read, the CPU 16 drives the stepping motor 12 by the motor driver 28 (drive device), so that the original 13 set on the original 29, the sheet is transported by the transport roller 30, and is transported to a predetermined reading position of the traveling body 4.

At this time, the document 13 is conveyed at a constant speed, and the image data on the document surface is read by the CCD 7 while the traveling body 4 is stopped. Hereinafter, the same processing as in the book mode is performed, and the binarized image data is stored in the scan buffer 2.
5, and sent to a host computer (not shown) or the like via the I / F controller 26.

The first embodiment will be described with reference to the drawings. FIG. 6 is a fragmented and extracted portion related to the present embodiment in FIG. 6, each light source 4a illuminates the original 13 on the contact glass, the reflected light is condensed by a lens through a shading adjustment plate, and a line sensor (CCD 7)
Is formed.

In FIG. 6, a mirror for turning back the reflected light is omitted for simplification of the description. The shading adjustment plate plays a role of adjusting the amount of light for eliminating the difference in the amount of reflected light between the center and the end of the line sensor (CCD 7). This is because if there is too much difference in the amount of reflected light between the center and the end of the line sensor (CCD 7) in the shading calculation process, only a calculation result containing a large amount of distortion can be obtained. After that, shading calculation processing is performed.

As an example showing the function of the shading adjustment plate, FIG. 7A is an example of a reproduction level distribution when image data of the white reference plate 15 is read without the adjustment plate. Thus, the level at the center is high and the level drops at the ends.

FIG. 7B shows an example of a level distribution when a shading adjustment plate is used. Line sensor (CCD7)
After performing the photoelectric conversion in (1), the level is adjusted as analog image data, and the A / D converter performs digital conversion. Before performing the sampling processing of the image data of the white reference plate 15, the image data for gain setting must be read in order to determine the gain value of the amplification processing on the image data of the white reference plate 15.

In the processing, image data of the white reference plate 15 is read at a fixed gain value set in advance, and peak detection processing of pixels in the read line data is performed. This is a gain value of the amplification process for the data. Therefore, the image data is read with the calculated gain value from the time of the sampling processing of the image data of the white reference plate 15 for the shading calculation processing.

The peak data for setting the gain value is detected by detecting the first line of the white reference plate 15 in the sub-scanning direction.
The head position of the white reference plate 15 requires that the color of the member on which the white reference plate 15 is installed be a black member. The black member can be separated from the white reference plate 15 (see FIG. 8).

An example of processing for detecting the leading line of the white reference plate 15 will be described. FIG. 9A is a diagram illustrating an example of a level distribution of image data for one line outside the white reference plate 15. When the color is black, the image data has almost no level. The detection positions in this level data, that is, both ends of the white reference plate 15 are the positions of A and B.

The positions A and B indicate the positions of the main scanning width required as the white reference data. Binarization processing is performed on the input image data, and when the detected level is higher than a certain white reference plate 15 detection threshold, it is determined that the data is obtained by reading the white reference plate 15. The determination as to whether or not the read data is at the first line of the white reference plate 15 is performed when the read data is higher than the threshold for detecting the white reference plate 15 and the level thereof is in the main scanning direction.
Is determined to be the head line position of the white reference plate 15 when the line data continues beyond the range of A and B where the width setting is performed.

In the example of FIG. 9, the threshold is indicated as Th. In FIG. 9B, it is determined that the level has sufficiently reached the white reference data level at both the positions A and B, and is set as the first line of the white reference plate 15. However, in the edge portion of the white reference plate 15, the reflection state may be significantly changed. Therefore, when the image data of the white reference plate 15 is advanced by several lines after detecting the front end line, a peak is not obtained. It is desirable to perform hold processing (FIG. 1
0). In this process, the front end line of the white reference plate 15 is detected, and the peak hold process is performed from the detection of the front end line, thereby setting the gain value for reading the white reference data and reading the image data thereafter.

By setting the gain value, the white reference data is read, and the shading correction calculation processing is performed using the data as white reference data. At the same time as reading the white reference data, a detection process of the trailing edge of the white reference plate 15 is performed. The detection process is performed in the same manner as the tip detection.

This will be described with reference to FIG. FIG. 11A shows the relationship between the video level and the threshold value Th when the area inside the white reference plate 15 is read. In this line, it is determined that the levels have sufficiently reached the white reference data level at A and B, which are the determination positions of the white reference plate 15, and it is determined that the white reference plate 15 is being read.

FIG. 11B shows the relationship between the level of the white reference data and the threshold Th when the line advances m lines from that line. After moving m lines, white reference plate 15
The video level does not reach the threshold Th because the reading position is out of the range and the background member of the white reference plate 15 is read. If it does not reach Th, it is determined that it has deviated from the position of the white reference plate 15.

The processing performed when it is determined that a portion other than the white reference plate 15 has been read during the reading of the white reference data by the image reading apparatus of the present embodiment will be described. If it is detected that the position deviates from the white reference plate 15 during the parallel or sequential processing for accumulating the white reference data at the same time as reading the data as the white reference data, the white reference Line data obtained by reading a part other than the white reference plate 15 is present in the data read as data.

Therefore, it can be determined that the read data of the white reference plate 15 is not correct, and the reading process of the white reference plate 15 is performed again. When reading the white reference plate 15, the reading process is performed with the number of read lines smaller than the number of read lines when the previous white reference plate 15 was removed in order to read the white reference plate 15 so as not to deviate from the position of the white reference plate 15. In addition, the detection processing of the rear end is also operated. Although the processing is aimed at preventing reading from the white reference plate 15 by reducing the number of lines, if the reading still occurs, the reading processing of the white reference plate 15 is performed with the number of reading lines further reduced. Correct white reference data is obtained by repeating the processing.

A second embodiment will be described with reference to the drawings. In the image reading apparatus according to the first embodiment, the white reference data is read again when a portion other than the position of the white reference plate 15 is read as the white reference data. In the device,
A process for removing the data read outside the white reference plate 15 from the captured white reference data will be described. For this processing, it is necessary to prepare a plurality of line buffers for storing the white reference data. FIG. 12 shows a configuration example of a white reference data generation block having a line buffer of a plurality of lines. Here, for simplicity of description, the number of line buffers is four, but the same processing is performed regardless of whether the number of line buffers is large or small.

As an example of processing, a case where four lines of white reference data are read and the white reference data of the four lines are averaged will be described. The four white reference data are accumulated, and if the reading position does not deviate from the white reference plate 15 during the accumulation processing, the white reference data for four lines is averaged as it is to generate white reference data. If it is detected that the white reference data 15 has deviated from the white reference plate 15 during accumulation of the white reference data, the white reference data after the white reference data of the line where the deviation has been detected is excluded from the target of the averaging process, and the white reference data before that is removed. Perform averaging processing only.

If it is detected that the white reference data deviates from the white reference plate 15 during the accumulation of the white reference data of the fourth line, the white reference data of the fourth line is excluded from the target of the averaging calculation, and An averaging operation is performed on the white reference data up to the line to obtain white reference data for shading calculation.

The third embodiment will be described. When white reference data is generated while performing weighted averaging processing, data resulting from the weighted averaging processing is accumulated in the line buffer 1, and three lines of image data are held as line data before the weighted averaging processing. As long as the reading position does not deviate from the reference plate 15, the white reference data accumulated in the line buffer 2 is subjected to the weighted averaging process. At the same time as the reference data is weighted and averaged, the data is shifted from the line buffer 3 to the line buffer 2 to the line buffer 4 to the line buffer 3, and the line buffer 4 stores the newly read white reference data.

Therefore, in the generation of the white reference data by the weighted average processing, a processing result is generated in the line buffer 1, and the white reference data stored in the line buffer 1 is used as the white reference data in the shading calculation processing.

[0047]

As is apparent from the above description, according to the first aspect of the present invention, the reading start position of the white reference plate in the sub-scanning direction is specified, and the peak hold reading position for gain control of the video amplifier is determined. Can be read without deviating from the white reference plate, and the trailing edge can be detected by the sub-scanning trailing edge detection processing of the white reference plate, generating high-quality white reference data as shading correction data. can do.

According to the second aspect of the present invention, even if data outside the white reference plate is read based on the detection result of the rear end of the white reference plate, the white reference data is read again, and high-quality data for shading correction is obtained. White reference data can be generated.

According to the third aspect of the present invention, even if data outside the white reference plate is read based on the detection result of the rear end of the white reference plate, the data is excluded from the processing for generating white reference data for shading correction. High-quality white reference data can be generated.

According to the fourth aspect of the invention, by amplifying the read image data by the gain control value, the image data can be polarized and the A / D conversion can be facilitated.

According to the fifth aspect of the invention, by changing the gain control value to a new value, image data can be amplified with an appropriate gain control value.

According to the sixth aspect of the present invention, the white reference data is sampled until the rear end detection result becomes data in the white reference plate, so that only the image data in the white reference plate is used. Can be generated.

According to the seventh aspect of the present invention, by providing the line sensor with the shading adjusting plate, the difference in the amount of reflected light between the center and the end of the line sensor can be eliminated, and the amount of light can be adjusted.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an image reading device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a control circuit according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining image reading in a book mode according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining image reading in an ADF mode according to the embodiment of the present invention.

FIG. 5 is a block diagram illustrating an internal configuration of an image processing unit according to the embodiment of the present invention.

FIG. 6 is a block diagram for describing an internal configuration of an image processing unit according to the embodiment of the present invention.

FIG. 7 is a reproduction level distribution diagram of image data according to the presence or absence of a shading adjustment plate according to the embodiment of the present invention.

FIG. 8 is a sectional view of a white reference plate according to the embodiment of the present invention.

FIG. 9 is a reproduction level distribution diagram of image data when detecting the leading end line of the white reference plate according to the embodiment of the present invention.

FIG. 10 is a timing chart when detecting the leading end line of the white reference plate according to the embodiment of the present invention.

FIG. 11 is a reproduction level distribution diagram of image data when detecting the rear end line of the white reference plate according to the embodiment of the present invention.

FIG. 12 is a block diagram for explaining a second and a third embodiment.

[Explanation of symbols]

 4a light source 4b, 5a, 5b mirror 6 lens 7 photoelectric conversion element (CCD) 8,12 stepping motor 15 white reference plate 16 CPU 17 light source lighting device (light source driver) 25 scan buffer

Claims (7)

[Claims] An image reading unit that reads image data using a line sensor including a plurality of one-dimensionally arranged photoelectric conversion elements; a first detection unit that detects a leading edge of a white reference plate; A second detection unit for detecting a rear end edge of the plate; and a rear end of the white reference plate from a line determined by the image reading unit to be a front end of the white reference plate by the first and second detection units. Storage means for reading the image data of the white reference plate up to the line determined to be, and accumulating and calculating the image data as white reference data. An image reading apparatus for performing shading correction on document image data read by the image reading means based on the image reading means. 2. An image reading means for reading image data using a line sensor including a plurality of one-dimensionally arranged photoelectric conversion elements, a first detecting means for detecting a leading edge of a white reference plate, and the image reading Means for reading image data of the white reference plate from a line determined to be the white reference plate by the first detection means, and accumulating and calculating the image data as white reference data; A second detecting means for detecting a trailing edge, and when the second detecting means determines that the image data read by the image reading means is not the white reference data, the number of lines to be read is reduced. The image data of the white reference plate is read again by the image reading means, and the accumulation operation is performed by the accumulation operation means. Image reading apparatus characterized by performing shading correction of the original image data read by the image reading means on the basis of quasi-data. 3. An image reading means for reading image data using a line sensor including a plurality of one-dimensionally arranged photoelectric conversion elements; a first detecting means for detecting a leading edge of a white reference plate; Means for reading image data of the white reference plate from a line determined to be the white reference plate by the first detection means, and accumulating and calculating the image data as white reference data; A second detecting means for detecting a trailing edge of the image data, when the second detecting means determines that the image data read by the image reading means is not the white reference data, The shading correction of the document image data read by the image reading unit is performed based only on the white reference data read at the white reference plate position. Image reading apparatus. 4. An amplifying means for amplifying the white reference data and the document image data read by the image reading means with a gain control value. The image reading device according to claim 1. 5. The gain control value according to claim 1, wherein
Wherein the peak value of the pixel in the first line data of the white reference plate detected by the detecting means is set as a new gain control value, and the gain control value and a preset fixed gain control value are changed. The image reading device according to claim 4, wherein 6. A detection of a leading edge of the white reference plate by the first detection means, a reading of image data of the white reference plate by the image reading means, an accumulation operation of the white reference data by the accumulation operation means, The detection of the trailing edge of the white reference plate by the second detection unit and the reduction of the number of read lines are performed as follows. As a result of the detection by the second detection unit, the image data read by the image reading unit is 3. The image reading apparatus according to claim 2, wherein the processing is repeated until image data of a white reference plate is obtained. 7. The image reading device according to claim 1, wherein the image reading unit includes a shading adjustment plate that adjusts a difference in the amount of reflected light between a center portion and an end portion of the line sensor. The image reading device according to claim 1.