JPH11261816A - Shading correction processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of shading correction processing defects such as the generation of vertical stripes in output images due to dust and stains stuck to a mirror and a lens, the dust and the stains stuck to a white reference whiteboard and image abnormality by the detect of an image sensor further. SOLUTION: This processor is provided with plural white reference white boards for stripulating white data at the time of reading original images, a white data generation part 101 for reading the respective white reference whiteboards and generating the plural reference values of the white data, a vertical stripe detection part 103 for comparing the object picture element of the white data and the peripheral picture elements and extracting singular point where the values of the object picture element and the peripheral picture element are largely different, a storage part 113 for storing the position in the case that the positions of the singular points both coincide in the reference values of the plural white data and a vertical stripe correction part 104 for referring to the peripheral picture element at the position of the singular point and replacing with the value of the peripheral picture element to the read original image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
The present invention relates to a shading correction processing device of an image reading device mounted on a scanner, a facsimile, or the like.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine or a facsimile reads an image of a sheet-like original set on an original platen in an analog or digital manner by an original reading means such as a one-dimensional image sensor. An image reading device is provided. The document image reading device includes a document moving type in which the document reading means is fixed and the document is moved,
There is a document fixed type in which a document on a platen is fixed and a reading position is moved. When a document is set on the platen, the fixed document image scanning device scans a mirror that illuminates the document and a mirror that transmits the image of the document that has received light from the illuminated lamp to a fixed image sensor. And scan the original. Also, in the case of a document moving type document image reading apparatus, a lamp for illuminating the document and a mirror for transmitting an image of the document received by the illuminated lamp to a fixed image sensor are fixed, and the document is placed on the mirror. The image is read by moving. In either case of the above two types of document image reading apparatuses, a white plate (white reference white plate) set as a white reference immediately before reading a document image is used as a white color as a reference of image density when reading a document. The density of the read original is determined with reference to the reading and the value. In other words, the white reference white plate defines white in document image reading and determines the dynamic range.Therefore, it is required to read a white plate as much as possible, and also make sure that no foreign matter such as dust gets on after installation. is necessary. In addition, the mirror for transmitting the image of the document which has received the light of the lamp to the fixed image sensor also changes the amount of light due to foreign matter such as dust, so that the image density does not differ from the original due to the foreign matter. You need to be very careful. In particular, in the case of an original reading type image reading apparatus, if dust adheres to the original reading position on the original platen, the original changes because the original moves and the density change due to the dust is also read during the scanning period. It is important to take care that no debris adheres to the table. In view of such a problem, the document image reading apparatus described in Japanese Patent Application Laid-Open No. 9-27910 has a plurality of document reading elements in order to suppress the generation of vertical streaks due to dust on the document table in the document moving type document image reading apparatus. The original is read at a plurality of focal points at the same time.

[0003]

When the white reference white plate is contaminated with dirt or dirt as described above, the data serving as the white reference of the original is shifted to the black side only at the position where the dirt is present. Then, when the original image is read by using the reference shifted to the black side, the image after the shading correction processing shifts to the white side from the original image density, and as a result, white streaks appear on the output sheet such as transfer paper. Appears. In addition, when dust gets on the mirror, both the data serving as the white reference and the density of the read document image change, so that correct shading correction processing cannot be expected. Also, Japanese Patent Application Laid-Open No. 9-2
The invention described in JP 7910 is effective when dirt adheres to the document table, but is not suitable for removing the influence of dirt or dirt on a white reference white plate or a mirror. Therefore, the problem to be solved by the present invention is that dirt and dirt attached to a mirror and a lens, dirt and dirt attached to a white reference white plate, and furthermore, an image abnormality due to a defective image sensor causes vertical streaks in an output image. It is an object of the present invention to provide a shading correction processing device capable of preventing the occurrence of the shading correction processing failure.

[0004]

According to a first aspect of the present invention, there is provided a shading correction processing apparatus, comprising: a plurality of white reference white plates for defining white data when reading a document image; And white data generating means for reading each of the white reference white boards to generate a plurality of reference values of white data, and comparing the target pixel of the white data and its peripheral pixels, and the values of the target pixel and the peripheral pixels differ greatly. Singularity extracting means for extracting singularities, position storage means for storing the positions of the singularities when the positions of the singularities coincide with each other in the reference values of the plurality of white data, Reference point at the position of the singular point, and a pixel replacement unit that replaces the value of the peripheral pixel with the value of the peripheral pixel, so that dust or dirt attached to the mirror or lens can be removed.
Further, it is possible to prevent a shading correction processing defect such as a vertical streak from occurring in an output image due to an image abnormality due to a defect in the image sensor. Claim 2
In the shading correction processing device according to the invention described in the above,
A plurality of white reference whiteboards for defining white data when reading a document image, and white data generating means for reading the white reference whiteboards and generating a plurality of white data reference values,
By comparing the plurality of reference values, correcting the reference value of the white data at the position of the mismatch, white data correction means for generating white reference data to be referred to, based on the white reference data,
By providing image data correction means for correcting read original image data, it is possible to prevent shading correction processing defects such as generation of white vertical stripes in an output image due to dust or dirt attached to a white reference white plate. I did it. According to a third aspect of the invention, in the shading correction processing apparatus according to the first or second aspect, instead of reading a plurality of white reference white boards and generating a plurality of white data reference values, one white reference white board is used. Is read and a plurality of reference values of white data are generated.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. 1A to 1C are explanatory views showing an embodiment of the present invention, in which FIG. 1A shows a schematic configuration of a document image reading apparatus, and FIG. 1B shows a configuration of a document, a white reference white plate, and a control signal. FIG. 4C illustrates the relationship between the document reading surface, the white reference white plate, and the control signal, respectively. In this example, the document image reading apparatus is a fixed document type and has two white reference white plates. In FIG. 1A, the light source 205 and the mirror 206 are configured to move integrally in the sub-scanning direction (the horizontal direction in the drawing).
2 is moved to the right side in the figure when document scanning starts, and sequentially scans the white reference white plate (1) 202, the white reference white plate (2) 203, and the document table 204. The reading of the original image is performed by scanning the light source 20 with respect to the original D fixed on an original plate 204 that transmits light such as a contact glass.
5 and irradiates the reflected light from the original D with a mirror 20
The light is reflected by the lens 6 and further formed into an image on a light receiving surface of an image sensor (CCD) 208 by a lens and a relay mirror group 207 and converted into an image signal. FIG. 1 (b)
, SHGATEa has two white reference white plates (1) 2
02 and a signal for forming an active period in accordance with a period for sampling white data as a reference within the range of the white reference white plate (2) 203. SHGATEa is L
The period of ow active is indicated by A and B in FIG.
Period. FGATEb forms an active period in accordance with the range of the document D in the sub-scanning direction on the document reading surface 204a of the document table 204. FGATEb is L
In the case of ow active, a period D in FIG. 1C is formed. LGATEd forms an active period of the document reading surface 204a in the main scanning direction, LSYNCc shows a start signal of the document reading surface 204a in the main scanning direction,
It becomes active for a certain period immediately before the active period of LGATEd. Shading correction processing and other image processing are performed based on the above image control signals.

FIG. 2 is a functional block diagram showing an example of the first embodiment according to the present invention. White reference data generator 1
01 is scanner input data (output signal of CCD 208)
And SHGATE, the white reference white board (1) 202
And white reference data in each case of the white reference white plate (2) 203. The white reference data obtained by reading the white reference white board (1) 202 is stored in the white reference data (1) storage unit 111, and the white reference data obtained by reading the white reference white board (2) 203 is stored in the white reference data (2). ) Storage unit 112
, Respectively. FIG. 3A shows the configuration of the white reference data generation unit 101. The first line processing unit 121 of the white reference data generation unit 101 receives the data Di from the original image reading device, performs the following calculation, and outputs D1 = a × Di (a is an arbitrary constant). The weighted average processing unit 122 receives the image data Di and the white reference data Ds from the document image reading device, performs a weighted average process of Dk = (b × Ds + Di) / c (b is an arbitrary constant), and performs a weighted average. The result Dk is output. At this time, if an image Di having a density (black) significantly lower than Ds is temporarily input, the possibility of dust is high. In such a case, the weighted average processing is not performed and the D
Output k. This substantially eliminates the influence of fluctuations such as dust in the sub-scanning direction (the direction perpendicular to the scanning direction by the CCD).

The selector (1) 123 receives SHGATE, first selects the processing result D1 of the first line when SHGATE is active and is in the first period of the first line in the main scanning direction, and further counts the active period of SHGATE. The active period is white reference white board (1) 20
2, the white reference data (1) is stored in the storage unit 111, and when the white reference white plate (2) 203 is displayed, the white reference data (2)
When the SHGATE is active and is not the first line in the main scanning direction, the weighted average processing result Dk is selected, the active period of the SHGATE is counted, and the active period is set to the white reference white board (1) 20.
2, the white reference data (1) is stored in the storage unit 111, and when the white reference white plate (2) 203 is displayed, the white reference data (2) is stored.
Transfer to storage section 112. White reference data (1) storage unit 1
The 11 and white reference data (2) storage unit 112 stores the data received from the selector (1) 123 in a storage element such as a FIFO and sequentially outputs the data.

The selector (2) 124 receives the SHGATE, and when the active period of the SHGATE indicates the white reference white board (1) 202, the white reference data (1) storage unit 11
When the data from No. 1 indicates the white reference white board (2) 203, the data from the white reference data (2) storage unit 112 is selected and passed to the weighted average processing unit 122. As a result, FIG.
As shown in (b), the transition of the white reference data in the sub-scanning direction at the position in the main scanning direction xi draws a rising saturation curve according to the weight of the weighted average starting from the result D1 of the first line processing, and The asymptote is drawn against the density of the white plate. As a result, an example of the obtained white reference data is almost constant at the top as shown in FIG.
At both end portions where the light amount of the light source 205 decreases, a drop appears gradually. However, when reading the actual image, the portions near both ends are not used, so that the magnitude of the dynamic range due to the fall of the white reference data is almost uniform in the main scanning direction.

The shading correction section 102 receives the white reference data of any of the white reference data (in this case, the white reference data (1) 111) and performs shading correction. Because the shading correction normalizes the read data of the original image based on the white reference data,
Light amount unevenness of the light source 205 in the main scanning direction can be corrected. The vertical streak detecting unit 103 stores the white reference data (1)
11 and the white reference data (2) The white reference data is received from the accumulation unit 112, and adjacent pixels are compared for each white reference data. Then, a singular point whose image density is significantly different from the vicinity is extracted, and the position of the singular point is determined based on the white reference data (1) white reference data from the storage unit 111 and the white reference data (2) white reference data from the storage unit 112. If they match, the position data of the singular point is stored in the singular point data storage unit 113.

FIG. 4A shows an example of the configuration of the vertical streak detecting section 103. The singular point detection unit 131 of the vertical line detection unit 103 detects a singular point with reference to the white reference data received from the white reference data (1) storage unit 111 and the white reference data (2) storage unit 112, respectively. FIG. 4B shows an example of the abnormal white reference data for the target pixel. When dust such as dust floating in the air adheres, the size is CCD2.
08 pixel size (63.5μm at 400dpl)
Is relatively close to, for example, if the size is exactly two pixels, the density of the white reference data of the portion where the dust adheres greatly drops to the black side, and if that portion is used as it is as the white reference data, The shading correction result of the data is greatly inclined to the white side, and appears on the transfer paper as a white vertical stripe. The singular points detected by the singular point detection unit 131 are temporarily stored as singular point data in the singular point data storage unit (1) 132 and the singular point data storage unit (2) 133, respectively. The singularity determination unit 134 stores these
32, the singularity data is received, the singularity positions are compared, and only when the singularity positions detected in the respective data coincide with each other are determined as singularities and stored in the singularity data storage unit 113. I do. Since there is a low possibility that dust adheres to the same position of a plurality of (two in this example) white reference white plates arranged at different positions, the singular point determined here is determined as an image abnormality due to a defect of the CCD 208 or It is conceivable that the mirror or lens transmitting the image to the CCD 208 is dirty. The period during which the singular point detection is performed is from the end of reading all the white reference white boards to just before the image data effective range, that is, as shown in FIG. 1C, the end of the last active period of SHGATE. To the start of the FGATE active period (range C in the figure).

The singular point data storage unit 113 is provided with the vertical streak detector 1
For each data in the main scanning direction corresponding to the data from each pixel of the CCD 208 received from the CCD 03, the result of the singularity determination is accumulated. The vertical stripe correction unit 104 receives the image data after the shading correction and the singularity determination result from the singularity data storage unit 113. And the singularity determination result,
If it is determined that the image is a normal image (an image that is not a singular point), the image data after shading correction is output as it is. Replace with nearby image data,
Output as a shading correction processing result. FIG. 4C shows an example of the white reference data after the correction processing.

FIG. 5A shows an example of an embodiment according to the second aspect. In this case, a white reference data correction unit 105 is provided, and the white reference data correction unit 105 includes a white reference data (1) storage unit 111 and a white reference data (2) storage unit 11
2 and white reference data (1) and (2)
If necessary, the white reference data is corrected, and the corrected white reference data is passed to the white reference data storage unit 114. FIG. 5B shows the configuration of the white reference data correction unit 105. As illustrated, the configuration of the white reference data correction unit 105 is the same as that of FIG.
It has two singularity detecting units 131 like the vertical streak detecting unit 103 shown in FIG. Singularity data obtained by both singularity detection units 131 in the same manner as the vertical streak detection unit 103 is
First, the data is sent to the comparing unit 135, and is compared for each pixel with a predetermined threshold value Dt. Here, although each white reference data refers to a different white reference white plate, the density (degree of white) of the white reference white plate itself should not basically change, and the value of the generated white reference data The main reasons for the difference are that the difference in the exposure time due to a slight change in the reading speed and the error in the asymptotic value due to the difference in the number of weighted averaging times can only be considered. Therefore, the above threshold value Dt
Need only take account of those slight fluctuation factors and need not be so large. However, since processing is possible if there is one final white reference data, the density of the remaining white reference white plate can be changed. In that case, two white reference values need to be normalized and compared. When pixels having different densities of the white reference data appear as a result of the comparison, it is considered that any one of the white reference white plates forms a singular point of the image density due to the influence of dust or dirt. To determine this, the white reference data correction unit 136 refers to two pieces of singular point data at a position where a mismatch is found in the comparison result of each pixel, and determines which data has a singular point. If a singular point exists on one side, it is determined that the singular point is caused by dust or dirt on the white reference white board, and correction is performed by replacing the singular point with white reference data closest to the singular point. In addition, a case where there is no singular point in any of the white reference data at the mismatching point can be considered depending on how to take Dt. In such a case, both are treated as white reference data without correction. A plurality of each of the finally corrected white reference data is completed, but what to do with the final white reference data is a process of selecting any of the corrected white reference data or an average of all the white reference data. One of the processes to be performed can be selected, the type of correction has a range, and the processing result is passed to the white reference data storage unit 114. The white reference data storage unit 114 receives the corrected white reference data from the white reference data correction unit 105, stores the corrected white reference data corresponding to the pixel array of the CCD 208, and passes the corrected white reference data to the shading correction unit 104. This performs shading correction. Here, similarly to the vertical streak detection, the correction processing of the white reference data is performed from the end of reading all the white reference white boards to before the image data effective range, and from the end of the last active period of SHGATE to the activation of FGATE. Until the start of the period, that is, the range of C in FIG. Therefore, the storage unit used for the white reference data storage unit 114 can be shared with a temporary data storage unit such as the white reference data (1) storage unit 111, so that the configuration can be simplified and the cost can be reduced. As described above, the white color, which is to be the reference of the image density when reading the original, that is, the white reference data is specified in the range of SHGATE.
It can be specified by activating E. Therefore,
As shown in FIGS. 6A and 6B, the white reference white plate 209
By combining SHGATE in a plurality of times as shown in FIG. 6C in the reading range of the white reference white plate 209, a plurality of temporary white reference data can be generated. (Corresponding to claim 3).

As shown in FIG. 7, the configuration of FIG.
By combining the configuration of (a), the function of the embodiment corresponding to claim 1 and the function of the embodiment corresponding to claim 2 can be simultaneously realized. In this case, the vertical line detection unit 103 and the white reference data correction unit 105
As shown in FIGS. 4 (a) and 5 (b), it has components common to each other, that is, a singularity detection unit 131, a singularity data storage unit (1) 132, and a singularity data storage unit (2) 133. These can be shared.

[0014]

As described above, according to the present invention, the following excellent effects can be exhibited. According to the first and third aspects of the present invention, a shading correction processing defect such as a vertical streak in an output image occurs due to dust or dirt attached to a mirror or a lens, or an image abnormality due to a defective image sensor. Can be prevented. According to the second and third aspects of the present invention, it is possible to prevent shading correction processing defects such as white vertical stripes from being generated in an output image due to dust or dirt attached to a white reference white plate. According to the third aspect of the present invention, it is not always necessary to provide a plurality of white reference white plates, and even one of them can exhibit the effects of the first and second aspects.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention;
(A) illustrates a schematic configuration of a document image reading device, (b) illustrates a relationship between a document and a white reference white plate and a control signal, and (c) illustrates a timing of a control signal in a sub-scanning direction. .

FIG. 2 is a functional block diagram showing an example of an embodiment corresponding to claim 1;

3A is a functional block diagram illustrating a configuration example of a white reference data generation unit illustrated in FIG. 2, FIG. 3B is an explanatory diagram illustrating that white reference data changes in the sub-scanning direction, and FIG. It is explanatory drawing of white reference data.

4A is a functional block diagram illustrating a configuration example of a vertical stripe detection unit illustrated in FIG. 2, FIG. 4B is an explanatory diagram illustrating an example of abnormal white reference data, and FIG. FIG. 4 is an explanatory diagram showing an example of data.

FIG. 5A is a functional block diagram illustrating an example of an embodiment according to claim 2, and FIG. 5B is a functional block diagram illustrating a configuration example of a white reference data correction unit.

FIG. 6A is a schematic configuration diagram of a document image reading apparatus showing an example of an embodiment according to claim 3, and FIG. 6B is an explanatory diagram illustrating the relationship between a document, a white reference white plate, and a control signal; (C) is an explanatory diagram illustrating the timing of a control signal in the sub-scanning direction.

FIG. 7 is a functional block diagram showing another embodiment of the present invention.

[Explanation of symbols]

101 white reference data generation unit, 102 shading correction unit, 103 vertical streak detection unit (singular point detection means), 10
4 Vertical streak correction section (pixel replacement means), 105 white reference data correction section, 111 white reference data storage section, 112 white reference data storage section, 113 singular point data storage section (position storage means), 114 white reference data storage section , 121 1st line processing unit, 122 weighted average processing unit, 123 selector, 124 selector, 131 singularity detection unit, 13
2 singularity data storage unit, 133 singularity data storage unit,
134 singularity determination unit, 135 comparison unit, 136 white reference value data correction unit, 202 white reference white plate, 203 white reference white plate, 204 platen, 204a document reading surface,
205 light source, 206 mirror, 207 lens and relay mirror group, 208 CCD (image sensor), 20
9 White reference white board, D original.

Claims (3)

[Claims] A plurality of white reference white plates for defining white data when reading a document image; a white data generating unit for reading the white reference white plates and generating a plurality of white data reference values; A singularity extracting means for comparing the target pixel of the data with its surrounding pixels and extracting a singularity whose values of the target pixel and the surrounding pixels are significantly different, and wherein, in the reference values of the plurality of white data, the position of the singularity is A position storing unit that stores the position when both coincide with each other; and a pixel replacing unit that refers to a peripheral pixel at the position of the singular point and replaces the read original image data with a value of the peripheral pixel. A shading correction processor. 2. A plurality of white reference white plates for defining white data when reading a document image; a white data generating means for reading each of the white reference white plates and generating a plurality of white data reference values; White data correction means for correcting the reference value of the white data at the position of the mismatch by comparing the reference values of the white data, and generating white reference data to be referred to; a document image read based on the white reference data A shading correction processing device comprising: image data correction means for correcting data. 3. Instead of reading a plurality of white reference white boards and generating a plurality of white data reference values, a configuration is adopted in which one white reference white board is read and a plurality of white data reference values are generated. The shading correction processing device according to claim 1 or 2, wherein