JP2002185721A - Device and method for reading image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for reading images in which dust is highly accurately detected with less memory capacity. SOLUTION: This device is provided with a carrying means 1 for successively carrying a plurality of originals, a read means 2 for reading the original carried to an original platen in a carrying state, a resolution conversion means 6 for converting the resolution of the output data of the read means 2, a storage means 8 having a capacity corresponding to the number of the pixels of one line of resolution-converted original images, a comparison means 7 for comparing the output of the resolution conversion means 6 with the corresponding data of the storage means 8 and a control means 9 for controlling the respective pieces of means. After plurality of lines are read, the control means controls the comparison means 7 so as to store the maximum value of a plurality of read pixel data inside the storage means 8 and then detects the presence/absence and position of the dust of the original platen by referring to data inside the storage means 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a copying machine and a facsimile apparatus, and more particularly to detection of dust in an image flow reading apparatus.

[0002]

2. Description of the Related Art Conventionally, when dust is detected in this type of apparatus, the density of a white conveyor belt is partially sampled, and an average density is obtained to determine a threshold value. Then, dust detection is performed by comparing with the read data. Detection is performed a plurality of times, and dust is determined by counting the number of times of detection for each pixel position.

[0003]

However, a memory for storing sampling data is required to obtain the average density of the conveyor belt, and a line memory is also required to count dust for each pixel. It is limited to the number of samplings within the range of numbers.
That is, in order to detect dust with higher accuracy, it is necessary to increase the memory capacity.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an image reading apparatus and an image reading method capable of detecting dust with high accuracy with a smaller memory capacity.

[0005]

According to the present invention, there is provided an image reading apparatus comprising: conveying means for sequentially conveying a plurality of documents; reading means for reading a document conveyed to a document table in a conveying state; and output of the reading means. Resolution conversion means for converting the resolution of the data, storage means having a capacity corresponding to the number of pixels of one line of the original image subjected to the resolution conversion, and comparing the output of the resolution conversion means with the corresponding data of the storage means An image reading apparatus comprising: a comparing unit that performs a reading operation; and a control unit that controls each of the units. The controlling unit stores a maximum value of a plurality of pieces of read pixel data in the storage unit after reading a plurality of lines. After controlling the comparison means as described above, the presence / absence and position of dust on the document table are detected by referring to data in the storage means.

Further, in the image reading apparatus of the present invention, dust is erased by replacing a pixel corresponding to the detected position of dust with pixel data adjacent thereto.

Further, in the image reading apparatus of the present invention, the dust is erased by replacing a pixel corresponding to the detected position of the dust with pixel data inputted one pixel earlier than the pixel. I do.

The image reading method according to the present invention further comprises a conveying step of sequentially conveying a plurality of originals, a reading step of reading the originals conveyed to the original platen in a conveying state, and a resolution of output data in the reading step. A resolution conversion step of converting, a storage step of storing the number of pixels of one line of the resolution-converted original image, a comparison step of comparing an output in the resolution conversion step with corresponding data in the storage step, And a control step of controlling the step, after reading a plurality of lines, after comparing in the comparison step so that the maximum value of the plurality of pixel data read in the storage step is stored, the It is characterized in that the presence / absence and position of dust on the platen are detected by referring to data in the storage step.

Further, in the image reading method of the present invention, dust is erased by replacing a pixel corresponding to a detected dust position with pixel data adjacent thereto.

Further, in the image reading method of the present invention, the dust is erased by replacing a pixel corresponding to the detected position of the dust with pixel data inputted one pixel before the pixel. I do.

According to another aspect of the present invention, there is provided an image reading apparatus comprising: conveying means for sequentially conveying a plurality of originals; reading means for reading an original conveyed to an original table in a conveying state; and requantization of output data of the reading means. Requantization means for performing quantization, storage means having a capacity corresponding to the number of pixels of one line of a requantized original image, and comparing the output of the requantization means with the corresponding data of the storage means An image reading apparatus comprising: a comparing unit that performs control and a control unit that controls each of the units, wherein the control unit performs requantization of a plurality of pixel data read in the storage unit after reading a plurality of lines. After controlling the comparing means so that the maximum value is stored, the presence or absence and the position of dust on the document table are detected by referring to the data in the storing means.

Further, in the image reading apparatus according to the present invention, dust is erased by replacing a pixel corresponding to the position of the detected dust with pixel data adjacent thereto.

In the image reading apparatus of the present invention, the dust is erased by replacing a pixel corresponding to the detected position of the dust with pixel data inputted one pixel before the pixel. I do.

Further, the image reading method of the present invention includes a transporting step of sequentially transporting a plurality of originals, a reading step of reading the originals transported to a document table in a transported state, and a requantization of output data in the reading step. Requantization step for performing quantization, a storage step for storing the number of pixels of one line of the requantized original image, and a comparison step for comparing an output in the requantization step with corresponding data in the storage step And a control step of controlling each of the steps, wherein after reading a plurality of lines, the requantized maximum value of the plurality of pixel data read in the storage step is stored. After the comparison in the comparing step, the presence or absence and the position of dust on the platen are detected by referring to the data in the storing step.

Further, in the image reading method of the present invention, the dust is erased by replacing a pixel corresponding to the detected position of the dust with pixel data adjacent thereto.

Further, in the image reading method according to the present invention, dust is erased by replacing a pixel corresponding to the position of the detected dust with pixel data inputted one pixel before the pixel. I do.

The storage medium of the present invention is a computer-readable storage medium storing a program for causing a computer to function as any one of the above means. Further, a storage medium of the present invention is a computer-readable storage medium storing a program for executing any of the above-described processing procedures.

According to the present invention, since a plurality of white data in the non-image area are sampled and only the maximum value is held, the white data is not read in the dust area. Therefore, it is necessary to determine the threshold from the average density. The processing can be simplified and the memory can be deleted. Further, the number of samplings is not limited by the bit width of the memory, and more samplings can be performed. This makes it possible to achieve both high-precision dust detection by reducing the memory capacity and making the number of sampling times unlimited.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration related to processing according to the first embodiment of the present invention.
The document transport unit 1 transports a plurality of documents by a white transport belt.
The sheets are sequentially conveyed one by one. And the CCD of the image reading unit 2
600 DPI in the main scanning direction and 600 DPI in the sub-scanning direction
Read at DPI density. The pre-processing unit 3 converts the output signal of the CCD into a digital signal by an A / D converter and performs shading correction. The digital data after the shading correction is 8 bits of 0 to 255 and is luminance data.

Thereafter, the image data is divided into those for dust detection and those for image data. The image data is input to the image processing unit 4 and then printed out by the print output unit 5.
The image processing unit 4 enlarges / reduces the image as necessary.
Spatial filter processing, luminance-density conversion, multi-valued-binary conversion,
Smoothing processing and the like are performed.

On the other hand, dust detection data is input to the dust detection unit 10 by emphasizing dust data using a one-dimensional edge enhancement filter. In the dust detection unit 10, a small value (black) from two adjacent pixels in the resolution conversion unit 6
Of data from 600 DPI to 30
Converted to 0DPI. The line memory 8 is 300D
The capacity of one line is represented by PI, and 8 bits are provided for one pixel. The data in the line memory 8 corresponding to each pixel position after the resolution conversion is read out, compared with the image data after the resolution conversion by the comparator 7, and larger data (data close to white) is selected and stored in the line memory 8 again. Write. This operation is performed on the data in which the input data is read by the image reading unit 2 at the position corresponding to the white data (conveying belt) between the papers.

The control unit 9 sets 0 (black) as an initial value in the line memory 8 in advance. According to the above procedure, a plurality of lines of the data between the sheets are read in accordance with the designation of the control unit 9. Thereafter, the data in the line memory 8 should be substantially white data (255). While the data corresponding to each pixel of the line memory 8 is replaced with white data without dust during the reading of a plurality of lines, dust on the platen is continuously read at the fixed position. The garbage data remains at the address 8.
By extracting this at a certain threshold or less, the position of dust data can be recognized.

FIG. 2 shows a state in which there is no dust on the document table and the transport belt is extremely dirty (objects transported by 60,000 sheets or more).
Then, the above operation is performed on 128 lines (FIG. 2A) and 25 lines.
This shows the data in the line memory after performing six lines (FIG. 2B). When reading 128 lines, the data value is 2
There are a plurality of pixels of 00 or less, but there are no pixels of 200 or less in reading 256 lines.

FIG. 3 shows 128 lines (FIG. 3) in a state where dust is attached to the document table by a conveyance belt with little dirt.
(A)) and data in the line memory when 256 lines (FIG. 3 (b)) are performed. Since the transport belt is less contaminated, data on the contaminated belt is not visible. On the other hand, data of data values 0, 50, and 200 can be confirmed in the pixel corresponding to dust. This value is the same for 256 lines and 512 lines, and is not affected by the number of read lines. Therefore, by determining the threshold value in consideration of the degree of dirt on the transport belt and the number of read lines, it is possible to determine the dirt and dust on the transport belt with high accuracy.

If it is determined by the above operation that dust is present on the document table, the position of the CCD of the image reading unit 2 is moved with respect to the document table, and the same dust detection is performed again.
Scan the document in a dust-free position.

In the above embodiment, when dust is detected, the position of the CCD of the image reading unit 2 is moved to avoid reading the dust. In the example shown in FIG. 4, however, it is possible to erase the dust from the image data. it can.

That is, first, a dust detection result is prepared in the line memory 8 in the same procedure as in the above embodiment. Next, the control unit 9 sets a threshold for judging dust in the comparison unit 7. This set value is determined by the state of the conveyor belt and the number of reference lines in dust detection. The image reading unit 2 reads the effective data area of the original image, reads the corresponding data in the line memory 8 with respect to the input data from the preprocessing unit 3 corresponding to the data, Decide whether or not there is trash.

If it is determined that there is dust, the pixel data input from the preprocessing unit 3 is replaced with the data replacement unit 11.
, The data is replaced with the data input one pixel before.
As a result, dust is erased and input to the image processing unit 4.

Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram illustrating a configuration related to a process according to the first embodiment of the present invention. The document transport unit 1 sequentially transports a plurality of documents one by one using a white transport belt. Then, the CCD of the image reading unit 2 moves 60
Reading is performed at 0 DPI and a density of 600 DPI in the sub-scanning direction. The pre-processing unit 3 converts the output signal of the CCD into a digital signal by an A / D converter and performs shading correction. The digital data after the shading correction is 8 bits of 0 to 255 and is luminance data.

Thereafter, the image data is divided into those for dust detection and those for image data. The image data is input to the image processing unit 4 and then printed out by the print output unit 5.
The image processing unit 4 enlarges / reduces the image as necessary.
Spatial filter processing, luminance-density conversion, multi-valued-binary conversion,
Smoothing processing and the like are performed.

In the second embodiment, dust detection data is subjected to dust processing using a one-dimensional edge emphasis filter, and is input to the dust detection unit 10. In the dust detection section 10, the gradation conversion section 6 'requantizes the data into 32-bit data of 5 bits by bit shifting. The line memory 8 has a capacity for one line and has 5 bits for one pixel. The data in the line memory 8 corresponding to each pixel position after the gradation conversion is read out, compared with the image data after the gradation conversion by the comparator 7, and larger data (data close to white) is selected, and the line memory is again read. Write 8 This operation is performed on the data in which the input data is read by the image reading unit 2 at the position corresponding to the white data (conveying belt) between the papers.

The control unit 9 sets 0 (black) as an initial value in the line memory in advance. According to the above procedure, a plurality of lines of the data between the sheets are read in accordance with the designation of the control unit 9. After that, the data in the line memory 8 is almost white data (255). The data corresponding to each pixel in the line memory 8 is replaced with white data without dust during reading of a plurality of lines. However, dust on the platen continues to read dust data at a fixed position. The garbage data remains at the address 8. By extracting this at a certain threshold or less, the position of dust data can be recognized.

FIG. 6 shows a state in which there is no dust on the document table and the transport belt is extremely dirty (objects transported over 60,000 sheets).
Then, the above operation is performed for 128 lines (FIG. 6A) and 25 lines.
6 shows the data in the line memory after performing six lines (FIG. 6B). When reading 128 lines, the data value is 2
Although there are a plurality of pixels of 5 or less, there are no pixels of 25 or less in reading 256 lines.

FIG. 7 also shows 128 lines (FIG. 7
(A)) and data in the line memory when 256 lines (FIG. 7 (b)) are performed. Since the transport belt is less contaminated, data on the contaminated belt is not visible. On the other hand, in the pixel corresponding to dust, data values 0 and 50 and data before and after can be confirmed. This value is the same for 256 lines and 512 lines, and is not affected by the number of read lines. Therefore, by determining the threshold value in consideration of the degree of dirt on the transport belt and the number of read lines, it is possible to determine the dirt and dust on the transport belt with high accuracy.

If it is determined by the above operation that dust is present on the document table, the position of the CCD of the image reading unit 2 is moved with respect to the document table, and the same dust detection is performed again.
Scan the document in a dust-free position.

In the second embodiment, when dust is detected,
Although dust is not read by moving the position of the CCD of the image reading unit 2, dust can be eliminated from the image data in the example shown in FIG.

That is, first, a dust detection result is prepared in the line memory 8 in the same procedure as in the above embodiment. Next, the control unit 9 sets a threshold for judging dust in the comparison unit 7. This set value is determined by the state of the conveyor belt and the number of reference lines in dust detection. The image reading unit 2 reads the effective data area of the original image, reads the corresponding data in the line memory 8 with respect to the input data from the preprocessing unit 3 corresponding to the data, Decide whether or not there is trash.

Here, when it is determined that there is dust, the pixel data input from the preprocessing unit 3 is replaced with the data replacement unit 11.
, The data is replaced with the data input one pixel before.
As a result, dust is erased and input to the image processing unit 4.

Here, each functional block and processing procedure shown in the above various embodiments may be constituted by hardware, or may be constituted by a CPU or MPU, ROM and R
It may be constituted by a microcomputer system composed of an AM or the like, and its operation may be realized according to a work program stored in a ROM or a RAM. The present invention also includes a software program for realizing the functions described above, which is provided to a RAM so as to realize the functions of the respective functional blocks, and which is executed by operating the functional blocks according to the programs. include.

In this case, the software program itself implements the functions of the above-described embodiments, and the program itself and means for supplying the program to a computer, for example, a recording medium storing the program Constitute the present invention. As a storage medium for storing such a program, the above-described ROM or RAM
Besides, for example, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-RO
M, CD-I, CD-R, CD-RW, DVD, zi
p, a magnetic tape, a nonvolatile memory card, or the like can be used.

When the computer executes the supplied program, not only the functions of the above-described embodiment are realized, but also the OS (operating system) or other application software running on the computer. Needless to say, such a program is also included in the embodiment of the present invention when the functions of the above-described embodiment are realized in cooperation with the above.

Further, after the supplied program is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the program is provided in the function expansion board or the function expansion unit based on the instruction of the program. It is needless to say that the present invention also includes a case where the CPU or the like performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0043]

As described above, according to the present invention, it is not necessary to obtain the average density of the white data area (conveying belt) as in the prior art, so that the memory for sampling addition can be eliminated. Further, by converting the image data for dust detection to a low resolution, it is possible to reduce the capacity of the line memory and reduce the circuit size.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration related to processing according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating data in a line memory when detection is performed on 128 lines and 256 lines when there is no dust on a document table according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating data in a line memory when detection is performed on 128 lines and 256 lines when dust is present on a document table according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration related to processing in a modification of the present invention.

FIG. 5 is a block diagram illustrating a configuration related to processing according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating data in a line memory when detection is performed on 128 lines and 256 lines when there is no dust on a document table according to the second embodiment of the present invention.

FIG. 7 is a diagram illustrating data in a line memory when detection is performed on 128 lines and 256 lines when dust is present on a document table according to the second embodiment of the present invention.

FIG. 8 is a block diagram illustrating a configuration related to processing according to a modified example of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 document feeder 2 image reader 3 preprocessor 4 image processor 5 print output unit 6 resolution converter 6 ′ gradation converter 7 comparator 8 line memory 9 controller 10 dust detector 11 data replacement unit

Continued on the front page F term (reference) 5B047 AA01 BA02 BB02 BC14 CA07 CB06 CB10 CB23 5C051 AA01 DA03 DB01 DE09 DE13 5C072 AA01 BA17 EA05 NA01 NA08 TA05 5C076 AA21 AA22 BA03 BA06 BA08 BB04 BB06 CB01

Claims (14)

[Claims] A transport unit for sequentially transporting a plurality of originals;
Reading means for reading a document conveyed to the document table in a conveyed state; resolution converting means for converting the resolution of output data of the reading means; and a capacity corresponding to the number of pixels of one line of the resolution-converted document image. Having storage means,
An image reading apparatus comprising: a comparison unit that compares an output of the resolution conversion unit with corresponding data of the storage unit; and a control unit that controls each of the units. After controlling the comparison means so that the maximum value of the plurality of pixel data read in the storage means is stored, the presence / absence and position of dust on the document table are detected by referring to the data in the storage means. An image reading device characterized by the above-mentioned. 2. An apparatus according to claim 1, wherein the dust is erased by replacing a pixel corresponding to the detected dust position with pixel data adjacent thereto. 3. The apparatus according to claim 1, wherein a pixel corresponding to the position of the detected dust is set to one pixel.
An image reading apparatus, wherein dust is erased by replacing pixel data with pixel data input before a pixel. A transporting step of sequentially transporting a plurality of originals;
A reading step of reading a document conveyed to a platen in a conveyed state, a resolution conversion step of converting the resolution of output data in the reading step, and a storage step of storing the number of pixels of one line of the resolution-converted document image An image reading method comprising: a comparison step of comparing an output in the resolution conversion step with corresponding data in the storage step; and a control step of controlling each of the steps. After comparing in the comparing step so that the maximum value of the plurality of pixel data read in is stored, the presence or absence and position of dust on the document table are detected by referring to the data in the storing step. Image reading method. 5. The image reading method according to claim 4, wherein a pixel corresponding to the detected position of the dust is replaced with pixel data adjacent to the detected dust to delete the dust. 6. The method according to claim 4, wherein a pixel corresponding to the position of the detected dust is set to one pixel.
An image reading method, wherein dust is erased by replacing pixel data with pixel data input before a pixel. 7. A conveying means for sequentially conveying a plurality of originals,
Reading means for reading a document conveyed to a platen in a conveyed state; requantizing means for requantizing output data of the reading means;
Image reading comprising storage means having a capacity corresponding to the number of pixels in a line, comparison means for comparing the output of the requantization means with corresponding data in the storage means, and control means for controlling each of the means The apparatus, wherein after the plurality of lines are read, the control unit controls the comparing unit so that a requantized maximum value of the plurality of read pixel data is stored in the storage unit. An image reading apparatus for detecting presence and position of dust on a document table by referring to data in the means. 8. The image reading apparatus according to claim 7, wherein the dust corresponding to the detected position of the dust is replaced with pixel data adjacent thereto, thereby eliminating the dust. 9. The apparatus according to claim 7, wherein a pixel corresponding to the position of the detected dust is set to one pixel.
An image reading apparatus, wherein dust is erased by replacing pixel data with pixel data input before a pixel. 10. A transporting step of sequentially transporting a plurality of documents, a reading step of reading a document transported to a document table in a transported state, and a requantization step of requantizing output data in the reading step. A storage step of storing the number of pixels of one line of the requantized original image, a comparison step of comparing an output in the requantization step with corresponding data in the storage step, and controlling each of the steps. An image reading method having a control step, after reading a plurality of lines, after comparing in the comparing step such that the requantized maximum value of the plurality of pixel data read in the storing step is stored, An image reading method, wherein the presence / absence and position of dust on a platen are detected by referring to data in the storage step. 11. The image reading method according to claim 10, wherein the dust corresponding to the position of the detected dust is replaced with pixel data adjacent thereto so as to erase the dust. 12. The method according to claim 10, wherein a pixel corresponding to the position of the detected dust is set to one pixel.
An image reading method, wherein dust is erased by replacing pixel data with pixel data input before a pixel. 13. A computer-readable storage medium storing a program for causing a computer to function as each means according to claim 1. Description: 14. The method according to claim 4, wherein
A computer-readable storage medium storing a program for executing a processing procedure of the method according to any one of the above.