JP2003304380A - Image reader and control program thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader which can avoid misdetecting a defective area due to discoloration of fouling of a conveyor belt for automatic document feeding, when detecting defective area of dirt, etc., on an original platen. <P>SOLUTION: The image reader, which detects whether there is a defective area on the original platen, is equipped with a first cumulative addition means for cumulative addition processing of a specified number of lines in a vertical scanning direction for a read image of a non-document area, a setting means for setting a binarization slice level according to the cumulative addition result, a binarizing means of generating binarized image data by binarizing the read image of the non-document area according to the binarization level, a second cumulative addition means for cumulative addition processing of the specified number of lines by pixels in the vertical scanning direction for the binarized image data, and a defect deciding means for comparing the addition result of the second cumulative addition means with a predetermined defect decision level and deciding whether there is a defective area on the original platen according to the comparison result. <P>COPYRIGHT: (C)2004,JPO

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 having a function of detecting a defective area such as dust or dirt adhering to a document table.

[0002]

2. Description of the Related Art Conventionally, as an image reading apparatus using a linear image sensor, there is one having a structure shown in FIG.

In FIG. 5, 101 is a document illumination lamp,
Reference numerals 102 to 104 are first to third mirrors, 105 is a lens, 106 is a linear image sensor, 107 is a platen glass, 108 is an original, and 109 is a white plate serving as a reference for shading correction.

In this image reading apparatus, the first to third mirrors and the illumination lamp move in the directions shown by arrows S in FIG. 5 to perform optical scanning (sub-scanning), and the original 108 is two-dimensionally scanned. Can be read.

FIG. 6 shows a configuration example in which an automatic document feeder is attached to such an image reading apparatus. The automatic document feeder is a device that conveys the documents 108 one by one to the platen glass 107 of the image reading device, and the drive rollers 203 rotate the automatic document conveyance belt 202 to convey the documents.

In an image reading mode using such an image reading apparatus and automatic document feeder, the original is fixed on the original table glass 107 by rotating the automatic original feeding conveyance belt 202 without moving the optical system. There is a mode in which the image on the original is read by moving at a speed (commonly called "flow-reading mode"). The "scanning reading mode" is an optical system (lamp 101 and mirror groups 102 to 10) for reading a predetermined position on the platen glass 107 on the image reading device side.
In this mode, the image on the document is read while moving the document at a constant speed on the automatic document feeder side without moving 4). At this time, the position on the platen glass 107 that is being read by the image reading device side is called a “flow reading position” and is a predetermined position as shown by a broken line 200 in FIG. 7A. On the other hand, the original is fed by the automatic original feeder to
It moves in the direction shown by the arrow in (a).

In this flow-reading mode, it is sufficient to simply move the original document in a fixed direction. Therefore, when a large number of original documents are continuously read, the time between the original documents is shorter than the scanning operation. is there.

However, in this flow-reading mode, if there is dust or dirt (201) at the flow-reading position of the original platen glass 107 as shown in FIG. 7 (a), it will be read as shown in FIG. 7 (b). Black streaks 3 appear at the corresponding main scanning position of the image 302.
There is a problem that 03 will occur.

As a method for solving this problem, conventionally, the following method has been proposed. It has a means to detect dust on the platen glass, and rotates the conveyor belt for automatic document feeding during the non-document reading period at the flow reading position on the platen glass to detect dust from the read image in the non-document area. If dust is present, there is a method of displaying a message prompting to clean the platen glass or changing the flow reading position to a dust-free position (Japanese Patent Laid-Open No. 2001-14490).
No. 1). According to this method, it is possible to reduce the occurrence of black streaks during flow reading.

Next, an image reading apparatus having such a conventional dust detection function will be described.

FIG. 8 is a block diagram showing a main part of an image reading apparatus having a conventional dust detecting means.

In the figure, 401 is a linear image sensor, 402 is an amplifier, 403 is an A / D converter, and 404.
Is a shading correction circuit, and 400 is a dust detection circuit unit.

Reference numeral 405 is a filter, 406 is a binarization circuit,
Reference numeral 407 is an addition circuit, 408 is a line memory, 409 is a comparison circuit, 410 is a gate circuit, 411 is a determination result holding circuit, and 412 is a CPU.

Next, the operation of the dust detection circuit section 400 will be described.

The image signal output from the linear image sensor 401 is supplied to the dust detection circuit section 400 via the amplifier 402, the A / D converter 403 and the shading correction circuit 404. In the dust detection circuit section 400,
The image signal after shading correction is input to the binarization circuit 406 through the filter 405, and binarized by comparison with a predetermined binarized slice level. After that, the addition circuit 407 and the line memory 408 perform cumulative addition for a predetermined number of lines for each pixel. By cumulatively adding the binarized image data for each pixel, when dust exists, the cumulative addition value for the corresponding pixel becomes a very large value.

Then, the comparison circuit 409 compares the cumulative addition value for each pixel with the determination level, and determines that the pixels exceeding the determination level have dust. The gate circuit 410 is
Only the section signal portion of the effective area used for reading the original in the reading area is transmitted to the determination result holding circuit 411, and the determination result holding circuit 411 determines that even one pixel in the effective section is a black stripe. The CPU 412 is informed of the occurrence of black streaks.

[0017]

However, in the case of performing the conventional dust detection control as described above, the image of the automatic original feeding conveying belt on the original platen glass is read, but the conveying belt surface is There is a problem that it may be erroneously determined that there is dust on the platen glass due to discoloration or stain due to durability.

In view of the above problems of the prior art, the present invention makes it possible to prevent erroneous detection due to discoloration or dirt of the automatic document feeding conveyance belt when performing dust detection processing for detecting a defective area such as dust on the document table. An object of the present invention is to provide an image reading device and the like that can avoid and perform stable dust detection processing.

[0019]

In order to achieve the above object, in the image reading apparatus of the present invention, an optical reading unit for reading the reflected light emitted from the light source and a light transmissive member arranged in the optical path from the light source. On the original table, the original moving means for moving the original in the sub-scanning direction and the cumulative addition processing of a predetermined number of lines in the sub-scanning direction with respect to the read image of the non-original area read during the non- original reading period First cumulative addition means for performing, setting means for setting the binarized slice level based on the cumulative addition result by the first cumulative addition means, and the read image of the non-original area to the binarized slice level Binarizing means for binarizing based on the generated binarized image data,
Second cumulative addition means for performing cumulative addition processing of a predetermined number of lines for each pixel in the sub-scanning direction on the binarized image data, addition results by the second cumulative addition means, and a predetermined defect determination level And a defect determination means for determining the presence or absence of a defective area on the document table according to the comparison result.

In the image reading apparatus of the present invention, the original is moved in the sub-scanning direction on the optical reading means for reading the reflected light emitted from the light source and the light-transmissive original table arranged in the optical path from the light source. A document moving means, a first cumulative addition means for performing cumulative addition processing of a predetermined number of lines in the sub-scanning direction on a read image of a non-document area read during the non-document reading period, and the first accumulation Setting means for setting a defect determination level based on the cumulative addition result by the addition means, and second accumulation for performing cumulative addition processing of a predetermined number of lines in the sub-scanning direction for each pixel on the read image in the non-original area Adding means,
It is characterized by further comprising: defect determination means for comparing the addition result of the second cumulative addition means with the defect determination level, and determining the presence or absence of a defective area on the platen according to the comparison result. .

In the control program of the present invention, the original is moved in the sub-scanning direction on the optical reading means for reading the reflected light emitted from the light source and the light-transmissive original table arranged in the optical path from the light source. A control program for controlling an image reading apparatus having a moving means by a computer, the first cumulative addition for performing a cumulative addition process of a predetermined number of lines in a sub-scanning direction on a read image of the non-original area. Step, a setting step of setting the binarized slice level based on the cumulative addition result of the first cumulative addition step, and the read image of the non-original area is binarized based on the binarized slice level. And a binarization step of generating binarized image data, and a second accumulation process for performing a cumulative addition process of a predetermined number of lines in the sub-scanning direction for each pixel on the binarized image data. An addition step and a defect determination step of comparing the addition result of the second cumulative addition step with a predetermined defect determination level and determining the presence or absence of a defective area on the platen according to the comparison result. It is characterized by

In the control program of the present invention, the original is moved in the sub-scanning direction on the optical reading means for reading the reflected light emitted from the light source and the light-transmissive original table arranged in the optical path from the light source. A control program for controlling an image reading apparatus having a moving means by a computer, the first cumulative addition for performing a cumulative addition process of a predetermined number of lines in a sub-scanning direction on a read image of the non-original area. Step, setting step of setting a defect determination level based on the cumulative addition result of the first cumulative addition step, and accumulation of a predetermined number of lines in the sub-scanning direction for each pixel for the read image of the non-original area. A second cumulative addition step of performing an addition process, the addition result of the second cumulative addition step and the defect determination level are compared, and the original table is determined according to the comparison result. Characterized in that a defect determination step of determining the presence or absence of defective areas.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing the electrical construction of the essential parts of an image reading apparatus according to the first embodiment of the present invention. The mechanical structure of the image reading apparatus of this embodiment is the same as that shown in FIG.

In FIG. 1, 501 is a linear image sensor, 502 is an amplifier, 503 is an A / D converter, and 504.
Is a shading correction circuit, and the image data after the shading correction of 504 is output as a read image signal.

Reference numeral 500 denotes a dust detection circuit section, 505 a filter, 506 a binarization circuit for binarizing image data by comparing it with a predetermined slice level, 507 an addition circuit, 508 a line memory, 509 is a comparison circuit, 51
Reference numeral 0 is a gate circuit and 511 is a determination result holding circuit. 5
Reference numeral 13 is an image addition memory, and 514 is an addition circuit. 51
A CPU 2 controls a series of reading operations of the image reading apparatus including dust detection control.

The dust detection circuit section 5 of this embodiment shown in FIG.
The basic operation of 00 is almost the same as the operation of FIG. 8 described above, except that the binarization slice level SR used in the binarization circuit 506 is determined by the value of the image addition memory 513.

The dust detection process according to this embodiment will be described below in detail with reference to the flowchart of FIG.

First, the automatic document feeding conveyance belt 202 is rotated during the non-document reading period (step S11), and the non-document area, that is, the automatic document feeding conveyance belt 202 is read at the flow reading position on the document table glass 107 ( Step S12). That is, the linear image sensor 501
The read image signal output from the conveyor belt 202 is amplified by the amplifier 502 by a predetermined gain, converted into a digital signal by the A / D converter 503, and then shading correction is performed by the shading correction circuit 504. And is supplied to the dust detection circuit unit 500.

The reading level of the conveyor belt 202 subjected to the shading correction processing is cumulatively added to the image addition memory 513 via the adder 514 in the dust detection circuit section 500 (step S13).

The CPU 512 reads the value of the image addition memory 513 and calculates the image average level for each predetermined area. Specifically, the average value in the sub-scanning direction is calculated by dividing by the number of added lines in the sub-scanning direction (step S14), and then the average value in the main scanning direction in the predetermined area is calculated. Then, a predetermined value is subtracted from the smallest value in those areas to determine the binarized slice level SR (step S1
5), and output to the binarization circuit 506.

On the other hand, in the dust detection circuit section 500, the image signal after shading correction is supplied to the binarization circuit 506 via the filter 505. The binarization circuit 506 compares the image signal after shading correction with the binarized slice level SR determined by the CPU 512,
It is binarized (step S16). At this time, if it is smaller than the binarized slice level, it is binarized as "1", and if it is larger than it, it is binarized as "0".

Then, the binarized image data is cumulatively added for each pixel by the addition circuit 507 and the line memory 508 (step S17). The cumulative addition is performed for a predetermined number of lines, but it is conceivable that the lines to be cumulatively added are continuous lines or intermittent lines with N line intervals.

By cumulatively adding the binarized image data for each pixel, when dust exists, the cumulative addition value for the corresponding pixel becomes a very large value.

Next, the comparison circuit 509 compares the cumulative addition value for each pixel with the dust determination level ZR (step S
18), it is determined that there is dust in the pixels exceeding the dust determination level ZR (steps S19 and S20), and it is determined that there is no dust in the other pixels (step S2).
1).

After that, the gate circuit 510 informs the determination result holding circuit 511 of only the section signal portion of the effective area used for reading the original in the reading area, and the determination result holding circuit 51.
If 1 pixel is determined to be a black streak in the effective section, 1 notifies the CPU 512 of the black streak occurrence information.

The CPU 512 can check the contents stored in the line memory 508, and by comparing the stored data with the dust determination level ZR, can also obtain the main scanning address at which dust is detected. This makes it possible to know the dust position for dust correction.

According to the present embodiment, it is possible to set the binarized slice level SR that reflects the discoloration or the stain on the automatic document feeding conveyance belt 202, and the color change or the stain on the automatic document feeding conveyance belt 202 can be set. It is possible to avoid a problem that dirt is erroneously determined as dust (dirt) on the platen glass 107.

In the present embodiment, the CPU 512 reads and calculates the reading level of the automatic document feeding conveyance belt 202 to determine the binarized slice level SR, but the image average or minimum value is used. It is also possible to adopt a configuration in which processing such as detection and subtraction up to the determination of the binarized slice level is performed by hardware.

[Second Embodiment] In the dust detection circuit of the first embodiment described above, the binarization slice level SR can be changed in a configuration having a binarization circuit 506 that binarizes image data after shading correction. However, in the second embodiment, the binarization circuit 506 is not provided, and the dust determination level Z
Adopt a configuration in which R can be changed.

FIG. 3 is a block diagram showing the electrical configuration of an image reading apparatus according to the second embodiment of the present invention.
The mechanical configuration of the image reading apparatus of this embodiment is as shown in FIG.
It is assumed to be the same as that shown in.

The dust detection circuit 600 according to the present embodiment has a configuration in which the binarization circuit 506 is removed in the configuration of FIG.
The dust determination level ZR is supplied from the PU 512 to the comparison circuit 509.

The dust detection process according to this embodiment will be described below in detail with reference to the flowchart of FIG.

First, the processing from step S31 to step S34 is performed by the steps S11 to S14 in FIG.
The process is performed in the same manner as in step S35, and the dust determination level ZR is determined in step S35.

Then, the read image data is added to the adding circuit 507.
And the line memory 508 performs cumulative addition for each pixel (step S36). The cumulative addition is performed for a predetermined number of lines, but it is conceivable that the lines to be cumulatively added are continuous lines or intermittent lines with N line intervals.

By cumulatively adding the read image data for each pixel in this way, when dust is present, the cumulative addition value for the corresponding pixel becomes a very large value.

Next, the comparison circuit 509 compares the cumulative addition value for each pixel with the dust determination level ZR (step S
37), it is determined that there is dust in the pixels exceeding the dust determination level ZR (steps S38 and S39), and it is determined that there is no dust in the other pixels (step S4).
0).

After that, the gate circuit 510 informs the determination result holding circuit 511 of only the section signal portion of the effective area used for reading the original in the reading area, and the determination result holding circuit 51.
If 1 pixel is determined to be a black streak in the effective section, 1 notifies the CPU 512 of the black streak occurrence information.

As described above, the CPU 512 can also obtain the main scanning address at which dust is detected by comparing the data stored in the line memory 508 with the dust determination level ZR.

According to the present embodiment, it is possible to set the dust determination level ZR that reflects the discoloration or dirt on the automatic document feeding conveyance belt 202, and to prevent the discoloration or dirt on the automatic document feeding conveyance belt 202. It is possible to avoid a problem that the document table glass 107 is erroneously determined to be dust (dirt).

In the first and second embodiments described above, the configuration by the automatic document feeding of the belt transport system is described, but the same effect can be obtained by the configuration by the automatic document transport of the roller transport system. Further, the cumulative addition line number, the cumulative addition line interval, and the effective section area are all set in the CPU 512.
Can be changed by

The above control method can be realized by storing the program according to the flowcharts of FIGS. 2 and 4 in the storage device in the image reading apparatus and operating the program.

The present invention is not limited to the apparatus of the above-described embodiment, but may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. A storage medium storing a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. Needless to say, it can be completed by doing.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk,
A magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory card, and a ROM can be used. In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the OS or the like running on the computer executes actual processing based on the instruction of the program code. It goes without saying that a case where some or all is performed and the functions of the above-described embodiments are realized by the processing is also included.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion board inserted into the computer or the function expansion unit connected to the computer, based on the instruction of the next program code. Needless to say, this also includes the case where the CPU or the like provided in the expansion board or the expansion unit performs the expansion function to perform a part or all of the actual processing, and the processing realizes the function of the above-described embodiment. Yes.

[0056]

As described above in detail, according to the present invention, when the detection process for detecting a defective area such as dust on the platen is executed, it is possible to prevent erroneous detection due to discoloration or dirt of the document moving means. This can be avoided, and stable detection processing can be performed. As a result, it is possible to significantly reduce the occurrence of black stripes in the flow reading mode, for example.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical main configuration of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart of dust detection processing according to the first embodiment.

FIG. 3 is a block diagram showing an electrical main configuration of an image reading apparatus according to a second embodiment.

FIG. 4 is a flowchart of dust detection processing according to the second embodiment.

FIG. 5 is a conceptual diagram showing a main configuration of a conventional image reading apparatus.

FIG. 6 is a conceptual diagram showing a configuration when an automatic document feeder is attached to a conventional image reading apparatus.

FIG. 7 is a conceptual diagram for explaining a black stripe occurrence state.

FIG. 8 is a block diagram showing a main part of an image reading apparatus having a conventional dust detection unit.

[Explanation of symbols]

501 linear image sensor 502 amplifier 503 AD converter 504 Shading correction circuit 500 Dust detection circuit 505 Filter 506 binarization circuit 507 Adder circuit 508 line memory 509 comparison circuit 510 gate circuit 511 Judgment result holding circuit 512 CPU 513 image addition memory 514 Adder circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/107 H04N 1/40 103A 1/403 F term (reference) 2H109 CA21 5B047 AA01 BA01 BA02 BB02 BC05 DB01 DB03 DB10 DC09 5C072 AA01 BA20 DA02 DA04 EA04 LA18 NA10 UA12 UA13 5C077 LL02 PP02 PP48 PQ12 PQ20 PQ24 RR02 RR15 SS01 TT06

Claims (12)

[Claims] 1. An optical reading unit for reading reflected light emitted from a light source, an original moving unit for moving an original in a sub-scanning direction on a light-transmissive original table arranged in an optical path from the light source, First cumulative addition means for performing cumulative addition processing of a predetermined number of lines in the sub-scanning direction on the read image in the non-document area read during the document reading period, and the cumulative addition result by the first cumulative addition means. Setting means for setting a binarized slice level based on, binarizing means for binarizing the read image of the non-original area based on the binarized slice level to generate binarized image data, Second cumulative addition means for performing cumulative addition processing of a predetermined number of lines in the sub-scanning direction for each pixel on the binarized image data; addition result by the second cumulative addition means and a predetermined defect determination level And compare the ratio An image reading apparatus comprising: a defect determining unit that determines the presence or absence of a defective area on the platen according to a comparison result. 2. The image reading apparatus according to claim 1, wherein the first cumulative addition means averages and cumulatively adds the image data for each predetermined area in the main scanning direction. 3. The image reading apparatus according to claim 1, wherein the binarized slice level has a value smaller than an average value of cumulative addition results by the first cumulative addition means. 4. The binarized slice level is set to a value smaller than the average value by performing averaging processing in the main scanning direction and the sub scanning direction on the cumulative addition result by the first cumulative addition means. The image reading apparatus according to claim 1 or 2, characterized in that 5. An optical reading unit for reading reflected light emitted from a light source, an original moving unit for moving an original in a sub-scanning direction on a light-transmissive original table arranged in an optical path from the light source, First cumulative addition means for performing cumulative addition processing of a predetermined number of lines in the sub-scanning direction on the read image in the non-document area read during the document reading period, and the cumulative addition result by the first cumulative addition means. Setting means for setting a defect determination level based on a second cumulative addition means for performing cumulative addition processing of a predetermined number of lines in the sub-scanning direction for each pixel on the read image in the non-original area; An image reading device comprising: a defect determination unit that compares the result of addition by the second cumulative addition unit with the defect determination level, and determines the presence or absence of a defective area on the platen according to the comparison result. apparatus. 6. The defect determination level is set to a value smaller than the average value by performing averaging processing in the main scanning direction and the sub scanning direction on the cumulative addition result by the first cumulative addition means. The image reading device according to claim 5. 7. An optical reading means for reading the reflected light emitted from the light source, and an original moving means for moving the original in the sub-scanning direction on a light-transmissive original table arranged in the optical path from the light source. A control program for controlling an image reading device by a computer, comprising: a first cumulative addition step of performing cumulative addition processing of a predetermined number of lines in a sub-scanning direction on a read image in the non-original area; A setting step of setting the binarized slice level based on the cumulative addition result of one cumulative addition step; and a binarized image obtained by binarizing the read image of the non-original area based on the binarized slice level. A binarization step of generating data; a second cumulative addition step of performing a cumulative addition process of a predetermined number of lines in the sub-scanning direction for each pixel on the binarized image data; And a predetermined defect judgment level, and a defect judgment step for judging the presence or absence of a defective area on the document table according to the comparison result. . 8. The control program according to claim 7, wherein in the first cumulative addition step, image data is averaged and cumulatively added for each predetermined area in the main scanning direction. 9. The control program according to claim 7, wherein the binarized slice level is set to a value smaller than an average value of cumulative addition results obtained in the first cumulative addition step. 10. The binarized slice level is set to a value smaller than the average value by performing averaging processing in the main scanning direction and the sub-scanning direction on the cumulative addition result of the first cumulative addition step. 9. The control program according to claim 7, which is characterized in that. 11. An optical reading means for reading reflected light emitted from a light source, and an original moving means for moving the original in a sub-scanning direction on a light-transmissive original table arranged in an optical path from the light source. A control program for controlling an image reading device by a computer, comprising: a first cumulative addition step of performing cumulative addition processing of a predetermined number of lines in a sub-scanning direction on a read image in the non-original area; A setting step of setting a defect determination level based on a cumulative addition result by one cumulative addition step; and a cumulative addition process of a predetermined number of lines in the sub-scanning direction for each pixel for the read image of the non-original area. The second cumulative addition step and the addition result of the second cumulative addition step are compared with the defect determination level, and the presence or absence of a defective area on the platen is determined according to the comparison result. Control program is characterized in that a defect determination step of constant. 12. The defect determination level is set to a value smaller than the average value by performing averaging processing in the main scanning direction and the sub scanning direction on the cumulative addition result of the first cumulative addition step. The control program according to claim 11.