JPH1132224A - Image-processing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain proper effects for correcting longitudinal stripes without side effects, even when read resolution is changed by automatically revising number of pixels of a maximum longitudinal stripe width through the read resolution. SOLUTION: A shading correction circuit 1 corrects shading by using light level data, and a dirt detection processing circuit 2 detects a position of dirt in the main scanning direction by using the light level data used by the shading correction circuit 1. A dirt correction processing circuit 3 corrects longitudinal stripes of actual image data by using the result of the dirt detection processing circuit 2. The dirt detection processing circuit 2 detects the start position of a defective pixel, due to the dirt according to a prescribed start condition and discriminates the end of the defective pixel, when a prescribed end condition is satisfied. The information of the position of the defective pixels is stored for succeeding correction processing. The dirt correction processing circuit 3 corrects the pixels at the detected position having dirt, by referencing adjacent pixel data and revises a maximum width of longitudinal stripes to be corrected corresponding to the resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus used for a facsimile, a copying machine, a multifunction peripheral, a printer, and the like, and more particularly to an image processing apparatus capable of removing the influence of dust attached on an optical path of a document reading optical system. .

[0002]

2. Description of the Related Art Conventionally, an original image is read at a predetermined resolution, an analog image signal obtained thereby is converted into a digital signal having a predetermined number of bits, and the converted digital image signal is converted into an image having a lower number of bits. 2. Description of the Related Art An image processing apparatus that converts a signal into a signal, outputs the signal, stores the signal, and performs communication is known. If dust adheres to the optical path of the original reading optical system of such an image processing apparatus, there is a problem that the original cannot be read correctly. In particular, when dirt adheres to a mirror of a traveling body of a scanner, a reading sensor, or a reflecting mirror, vertical streaks are generated in an output image.

The inventor has already proposed a method for suppressing a vertical streak of an output image caused by dust on an optical path when a document is read by an image processing apparatus such as a facsimile. At this time, as for the width of the vertical streak generated in the output image due to dust, if the dust has the same size, the number of pixels increases as the reading resolution increases. For example, 200 dpi
Garbage causing vertical streaks with a width of 2 pixels at 400 dpi
In this case, a vertical streak having a width of 4 pixels is formed.

Conventionally, the pixel width to be corrected has been determined in advance and the correction has been performed. This is because if you correct a vertical streak that is too wide, characters often disappear,
This is because side effects are greater than effects. When the maximum number of pixels to be corrected is fixed as in this conventional technique, in an optical system with a variable reading resolution, when the reading resolution is increased, the width of the maximum vertical stripe that is actually corrected becomes smaller, There is a disadvantage that the effect of streak correction is reduced.

In the prior art, pixel data of a defective pixel is supplemented by using normal pixel data adjacent to the defective pixel in the main scanning direction in the vertical scanning direction or by using a second pixel having one pixel. Was like that. For example, in a case where defective pixels are interpolated using pixel data separated from the vertical stripe by a certain pixel, if the reading resolution is increased, the defective pixels cannot be compensated appropriately.

For example, in the case of a resolution of 200 dpi, if the distance from a vertical streak, which is considered to be free from the influence of dust, is one pixel or more, at 400 dpi, the effect of the dust is reduced to three pixels or more. That is, since the size of one pixel varies depending on the resolution, it is impossible to obtain a distance at which the influence of dust assumed in advance is reduced. Further, in the conventional example, the pixel width is automatically limited even in a region where there is no need to limit the pixel width for correction in an area where there is no character or picture around or a solid area.

[0007]

As described above, since the pixel width to be corrected is determined in advance and the correction is performed, when the resolution changes, the width of the vertical stripe actually corrected by the change varies. There is a problem that the effect of vertical streak correction is reduced and side effects are increased.
Further, if a defective pixel is corrected using pixel data separated from the vertical streak by a certain pixel, there is a problem that the defective pixel cannot be properly compensated for depending on the reading resolution.

The present invention solves this problem, and in a relatively simple manner, even if the resolution changes, the correction pixel width is optimally selected according to the change, and the pixel is supplemented from an appropriate position to always optimize the correction pixel width. It is an object of the present invention to realize an image processing apparatus capable of correcting a defective pixel and expanding the pixel width of correction in an area where there is no character or picture around or a solid area.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an image reading means for optically reading an original image as an image signal at a predetermined reading resolution and converting it into an analog image electric signal; Analog / digital conversion means for converting an analog image electrical signal output by the means into a digital image signal having a predetermined number of bits;
A dust detection means for detecting a vertical streak image due to dust located on an optical path of the image reading means based on a digital image signal output from the analog / digital conversion means; and a dust detection means for detecting the dust on the digital image signal. In an image processing apparatus provided with a dust component correcting means for correcting a detected vertical streak image using normal pixel data, a reading resolution at which the image reading means reads a maximum vertical streak width to be corrected by the dust component correcting means. And a correction vertical streak width selection means for automatically changing the width in accordance with the above.

[0010] The image forming apparatus further comprises a correction pixel position selection means for automatically changing a pixel position of normal pixel data used for vertical streak correction by the dust component correction means in accordance with a reading resolution read by the image reading means. I do.

Further, the present invention is characterized in that the dust component correcting means has a corrected vertical streak width setting means for externally setting a maximum vertical streak width to be corrected.

The solid area detecting means further comprises a solid area detecting means for judging from the density distribution around the vertical streaks corrected by the dust component correcting means that the area around the vertical streaks is a solid area of solid black or ground. When the means determines that the area around the vertical streak is a solid area, there is no limitation on the maximum vertical streak width to be corrected by the dust component correcting means.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of a facsimile terminal as an example of a system to which the present invention is applied. This terminal has a full duplex configuration. The reading unit of the facsimile terminal includes a reading scanning unit 11, a reading processing unit 12, a line memory 15, and a line memory control unit 16. The recording unit includes a recording scanning unit 13, a recording processing unit 14, a line memory 15, and a line memory. The control unit 16 is configured.

The image information read by the reading scanning unit 11 is temporarily stored in the line memory 15 via the reading processing unit 12. The line memory control unit 16 removes redundancy while reading image information from the line memory 15 according to the mode of the information compression unit 17, and stores the image information in the RAM 24 again via the data bus 29. And this RAM2
4 is used as a transmission buffer and transmitted to the modem 18 via the communication control unit 19. The signal modulated by the modem 18 is sent out to the line via the network control unit 28.

Conversely, the image information received from the line is demodulated by the modem 18 via the network control unit 28, and the communication control unit 1
9 and is output to the data bus 29 and stored in the RAM 24. Here, the RAM 24 is used as a reception buffer, and the stored data is sequentially input to the information restoring unit 17 again via the data bus 29, and after the information restoring unit 17 has added redundancy, the line memory control unit 16 Are stored in the line memory 15. Then, the line memory 15
The image information read from is read by the recording scanning unit 13 via the recording processing unit 14.

As described above, the image information simply passes through the network control unit 28 and the communication control unit 19,
The communication control information is read and understood in the communication control unit 19, and execution processing such as transmission control and error control is performed in accordance therewith. When journal information is required, a nonvolatile function is provided. It is stored in the RAM 24.

A call signal for network control, etc.
It is controlled by the network control unit 28. Further, image information that does not require information compression and decompression can be directly extracted from the reading processing unit 12 and the line memory 15 to the outside via the data bus 29 and used for image processing and image communication. Further, it is also possible to directly input image-processed information or image-synthesized information, store the information in the line memory 15 while superimposing it on the read image information, and store and reproduce the information. In such a case, the line memory 15 can be used separately from the information compression / decompression unit 17, and the compressed information is decompressed irrespective of the reading scanning unit 11 and the recording scanning unit 13. A use form in which hot water is output is also conceivable.

The overall control of system control and information flow management, communication control, and network control is performed by the MPU.
25. The main measures of the system control performed by the MPU 25 are control related to the man-machine interface performed by the panel unit 20 and control related to the reading unit and the recording unit by the mechanism control unit 22.

The present invention relates to the removal of the influence of the dust on the image signal in the optical system of the reading and scanning section 11. The reading / scanning unit 11 converts the multivalued image into a CCD scanner (CI
When reading with an S sensor or the like, shading correction is usually performed on the read image data in order to correct the image distortion due to the variation in the sensitivity of each sensor of the CCD and the variation in the light amount of the light source.

The shading correction requires light level data obtained by reading a reference white board. Since the light level data is obtained by reading a reference white board, if dust adheres on the optical path, the level of the pixel in that portion is significantly reduced (darkens). By using this data, garbage can be detected with high accuracy. In addition, since the detection result needs only one line in the main scanning direction, it is possible to suppress an increase in cost.

FIG. 2 is a block diagram showing one embodiment of the configuration of the vertical streak correction circuit used for such a purpose. The shading correction circuit 1 performs correction using the light level data. The dust detection processing circuit 2 detects the position of dust in the main scanning direction using the light level data used in the shading correction circuit 1. The dust correction processing circuit 3 corrects the vertical streak portion of the actual image data using the result of the dust detection processing circuit 2.

FIG. 3 shows an example of a dust detection method used in the dust detection processing circuit 2. Under the start condition shown in FIG. 3, first, the start of a defective pixel due to dust is detected. This condition is that the luminance of a certain pixel is lower than the adjacent pixel by 20% or more of the peak value of the light level data, and the luminance is 50% or less of the peak value of the light level data. When dust is detected, it is immediately checked whether or not the end condition shown in FIG. 3 is satisfied. The termination condition is that the luminance of a certain pixel is increased by 20% or more of the peak value of the light level data with respect to the adjacent pixel, and the luminance is 50% or more of the peak value of the light level data.

Until the termination condition is satisfied, the pixel is a defective pixel. When this end condition is satisfied, it is determined that the end of the defective pixel is reached. That is, all pixels between the start and the end of this detection are defective pixels due to dust. Such a processing method is performed because the number of defective pixels that cause vertical streaks may range from one area to several pixels. The detection result shows only the position in the main scanning direction, and the position of the defective pixel is held in a buffer for the next correction processing.

Next, the dust correction processing circuit 3 corrects the pixel at the position of the detected dust with reference to adjacent pixel data, as shown in an example in FIG. Vertical streak correction has two aspects: effects such as erasure of vertical streaks and restoration of horizontal lines, and a reduction in the readability of characters caused when correction is not properly performed. The effect can be obtained as the width of the vertical stripe that can be corrected is increased. However, if the width is too large, the character may become unreadable due to the correction.

According to the first aspect of the present invention, corresponding to the resolution,
The maximum width of the vertical stripe to be corrected is changed. For example, it is assumed that vertical streaks are generated by dust having a size as shown in FIG. The maximum vertical streak width at which the side effects are suppressed to some extent and the effect is obtained is checked in advance. Here, the maximum vertical streak correction width in the case of 200 dpi is 2
Let it be the pixel width. 4 resolutions for the same size of garbage
In the case of 00 dpi, the vertical stripe having the same width as 200 dpi cannot be corrected unless the maximum width of the vertical stripe is 4 pixels.

FIG. 6 is a block diagram showing an embodiment of a vertical streak correction circuit in the case where a correction is selected based on resolution. When the reading resolution changes from 200 dpi to 400 dpi, the correction processing 4 changes the maximum correction width of the vertical streak from 2 pixels to 4 pixels based on the resolution information sent from the resolution instruction section 4 shown in FIG.

Further, according to the invention of claim 2, the position of a pixel used for correction is changed according to the resolution. In the related art, pixels used for correction are pixels at a fixed position from both ends of the vertical streak.

As shown in FIG. 5, the reading resolution is 200
In the case of dpi, the data of the defective pixel is interpolated using the data of the second pixel from both ends of the vertical streak. According to the second aspect of the present invention, when it is instructed that the reading resolution has become 400 dpi, the pixel in which the influence of dust is reduced becomes the third pixel data, and accordingly, the correction processing 4 is used for the correction. Is changed from the second pixel to the third pixel.

According to the third aspect of the present invention, the maximum width of the vertical stripe to be corrected can be directly set by the user from outside.
In this case, the user designates the maximum width of the vertical streak through the operation panel, and the garbage correction processing circuit 3 sets the maximum width of the vertical streak based on this value, and corrects the vertical streak accordingly. FIG. 7 shows a block diagram of an embodiment of the vertical stripe correction circuit in this case.

According to a fourth aspect of the present invention, a process for determining whether or not to perform a correction process on a width equal to or greater than the maximum correction width in accordance with density information around a vertical streak is added. As shown in FIG.

The solid area detection circuit 5 determines whether or not there is a correction process that is equal to or greater than the maximum width. The matrix shown in FIG. 9 is used for the solid area detection processing. When the following condition is satisfied, it is determined that the surroundings are in a solid area and there are few side effects due to the correction, and the dust correction processing circuit 3 is instructed to perform the correction processing even when the width is equal to or more than the maximum width of the vertical stripe.

The judgment conditions are shown below. This condition indicates a case where the densities of all 30 points around the corresponding point are lighter (brighter) than the background threshold or darker (darker) than the solid black threshold. The condition around the vertical streak can be known from this condition. When this condition is satisfied, it can be seen that the area around the vertical streak is solid black or ground. In the case of solid black and the background, even if the correction is made, there is no side effect due to the correction, and vertical streaks can be removed. ((A1 <th1 & a2 <t
h1 & a3 <th1 & a4 <th1 & a5 <th1 & a
6 <th1 & a7 <th1 & a8 <th1 & a9 <th
1 & a10 <th1 & a11 <th1 & a12 <th1
& A13 <th1 & a14 <th1 & a15 <th1 &
a16 <th1 & a17 <th1 & a18 <th1 & a
19 <th1 & a20 <th1 & a21 <th1 & a2
2 <th1 & a23 <th1 & a24 <th1 & a25
<Th1 & a26 <th1 & a27 <th1 & a28 <
th1 & a29 <th1 & a30 <th1) or (a1
> Thh &a2> thh &a3> thh &a4> thh
&A5> thh &a6> thh &a7> thh &a8>
thh &a9> thh &a10> thh &a11> th
h &a12> thh &a13> thh &a14> thh
&A15> thh &a16> thh &a17> thh &
a18> thh &a19> thh &a20> thh & a
21> thh &a22> thh &a23> thh & a2
4> thh &a25> thh &a26> thh & a27
> Thh &a28> thh &a29> thh &a30>
thh)), the correction processing unit is instructed to correct even the maximum width or more.

Where a? ? Is the density of each pixel, th1 is the threshold for the background, thh is the threshold for the solid black, &
Represents “and” and or represents “or”. For example, values such as th1 = 20/256 and thh = 200/256 may be set.

[0034]

As described above, according to the first aspect of the present invention,
In the invention, the number of pixels having the maximum vertical stripe width is automatically changed depending on the reading resolution. As a result, even when the reading resolution changes, an appropriate vertical streak correction effect can be obtained without side effects. Since the maximum vertical stripe width is automatically changed, it is possible to eliminate the disadvantage that the pixel width of the maximum vertical stripe to be corrected changes when the reading resolution changes.

According to the second aspect of the present invention, the selection position of the pixel used for interpolation is changed depending on the reading resolution. As a result, when the reading resolution is increased, it is possible to solve the disadvantage of the related art that the defective pixel cannot be appropriately compensated, and it is possible to always perform the optimal defective pixel correction.

According to the invention of claim 3 of the present invention, the maximum width of the vertical streak to be corrected can be changed by the user. As a result, even when the vertical streak is larger than the set maximum value, there is no character or picture in the vertical streak or in the region adjacent to the vertical streak, and a better image can be obtained by correcting the vertical streak. In the first method, the upper limit of the vertical streak is eliminated, and the vertical streak can be removed to a width larger than that, so that the optimum defective pixel correction can always be performed.

According to the invention of claim 4 of the present invention, it is determined from the density distribution around the vertical streak that the area around the vertical streak is a solid area such as solid black or background. Correction is made without any restrictions on the vertical streak width. As a result, even when the vertical streak is larger than the set maximum value, the adjacent area of the vertical streak is a solid area of solid black or background, and there are no characters or pictures. Can be obtained, the upper limit of the vertical streak is abolished, and the vertical streak can be removed to a width larger than that, so that optimum defective pixel correction can always be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a facsimile terminal as an example of a system to which the present invention is applied.

FIG. 2 is a block diagram of an embodiment of a vertical stripe correction circuit according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a dust detection method used in the embodiment shown in FIG. 2;

FIG. 4 is an explanatory diagram showing an example of a dust correction method used in the embodiment shown in FIG. 2;

FIG. 5 is an explanatory diagram showing a width of a vertical streak corresponding to a resolution and a position of a correction pixel.

FIG. 6 is a block diagram of another embodiment of the vertical stripe correction circuit of the present invention.

FIG. 7 is a block diagram of another embodiment of the vertical stripe correction circuit of the present invention.

FIG. 8 is a block diagram of another embodiment of the vertical stripe correction circuit of the present invention.

FIG. 9 is an explanatory diagram showing a matrix around pixels on which a solid area detection process is performed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 shading correction circuit 2 dust detection processing circuit 3 dust correction processing circuit 4 resolution instructing unit 5 solid area detection circuit 11 reading scanning unit 12 reading processing unit 13 recording scanning unit 14 recording processing unit 15 line memory 16 line memory control unit 17 information compression Unit restoration unit 18 Modem 19 Communication control unit 20 Panel unit 21, 23 Interface 22 Mechanism control unit 24 RAM 25 MPU 26 ROM 27 DMA controller 28 Network control unit 29 Data bus, address bus

Claims (4)

[Claims] 1. An image reading means for optically reading a document image as an image signal at a predetermined reading resolution and converting it into an analog image electric signal, and converting the analog image electric signal outputted by the image reading means into a predetermined number of bits. Analog / digital conversion means for converting the digital image signal into a digital image signal;
A dust detection means for detecting a vertical streak image due to dust located on an optical path of the image reading means based on a digital image signal output from the analog / digital conversion means; and a dust detection means for detecting the dust on the digital image signal. An image processing apparatus comprising: a dust component correcting unit that corrects a detected vertical streak image using normal pixel data. A reading resolution by which the image reading unit reads a maximum vertical streak width to be corrected by the dust component correcting unit. An image processing apparatus comprising a correction vertical streak width selection means for automatically changing the width in accordance with the image. 2. An image reading means for optically reading an original image as an image signal at a predetermined reading resolution and converting the image signal into an analog image electric signal, and converting the analog image electric signal output by the image reading means into a predetermined number of bits. Analog / digital conversion means for converting the digital image signal into a digital image signal;
A dust detection means for detecting a vertical streak image due to dust located on an optical path of the image reading means based on a digital image signal output from the analog / digital conversion means; and a dust detection means for detecting the dust on the digital image signal. In an image processing apparatus including a dust component correcting unit that corrects a detected vertical streak image using normal pixel data, the image reading unit reads a pixel position of normal pixel data used by the dust component correcting unit for vertical streak correction. An image processing apparatus comprising: a correction pixel position selection unit that automatically changes according to a reading resolution. 3. An image reading means for optically reading a document image as an image signal at a predetermined reading resolution and converting it into an analog image electric signal, and converting the analog image electric signal outputted by the image reading means into a predetermined number of bits. Analog / digital conversion means for converting the digital image signal into a digital image signal;
A dust detection means for detecting a vertical streak image due to dust located on an optical path of the image reading means based on a digital image signal output from the analog / digital conversion means; and a dust detection means for detecting the dust on the digital image signal. An image processing apparatus comprising a garbage component correcting unit for correcting a detected vertical streak image using normal pixel data, wherein a maximum vertical streak width to be corrected by the garbage component correcting unit is externally set. An image processing apparatus comprising setting means. 4. A solid area detecting means for judging from the density distribution around the vertical streak corrected by the dust component correcting means that the area around the vertical streak is a solid area of solid black or ground, The image according to claim 1 or 3, wherein when the means determines that the area around the vertical streak is a solid area, the restriction on the maximum vertical streak width to be corrected by the dust component correcting means is removed. Processing equipment.