JP3305756B2 - Image processing device - Google Patents

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, and more particularly, to correcting shading distortion based on reference white information and performing predetermined image processing based on a peak value of the corrected image processing apparatus signal. For example, the present invention relates to an image processing device such as a facsimile, a digital copier or an image scanner.

[0002]

2. Description of the Related Art Conventionally, like a facsimile machine,
In a reading unit of a device that reads a document image and performs predetermined image processing, shading distortion caused by illuminance deviation of a light source, aberration of a lens, variation in sensitivity of an image sensor, and the like, may cause even reading of uniform density information. However, the output level of the image sensor was not uniform. Therefore, in order to correct this distortion, the standard white information is read prior to the reading of the normal document, and the output of the image sensor at that time is used as sensitivity variation information in a RAM or RO.
It is stored in storage means such as M. When reading the original, the variation information is read, and a predetermined correction operation is performed on the output of the image sensor to correct the distortion.

In order to enhance the reproducibility of an image, a conventional image processing unit detects a peak value (maximum level value) of an image signal after the shading correction is performed, and determines the peak value as a reference level (maximum level value). Various types of image processing are performed as the background level of the original.

A conventional facsimile apparatus of this type is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-154768 or Japanese Patent Application Laid-Open No. 2-203671.

[0005]

According to the above-mentioned conventional facsimile apparatus, the distortion data is collected in a state where foreign matter such as dust and paper dust adheres to the optical path for reading the white reference surface, and the original is read. Sometimes, when the foreign matter is removed by the conveyance of the original document, there is a problem that the pixel to which the foreign matter has adhered cannot be accurately corrected. That is, if a foreign substance is attached in the optical path, the optical information is blocked at that portion, and the output level of the image sensor decreases. Therefore, if this is stored as sensitivity variation information, a correction calculation of the image sensor output is performed based on the sensitivity variation information when reading the original. For this reason, a pixel whose level has been reduced by foreign matter is corrected so as to increase the level of the pixel. However, if the foreign matter deviates from the optical path due to the conveyance of a document or the like, the level of the image signal does not decrease. Has a problem that the level of the pixel is excessively increased due to overcorrection.

Further, when the peak value of the image signal is detected after the above correction and the image processing is performed while maintaining this value, an excessive rise of the peak value is caused, so that the image is significantly deteriorated. There was a problem of letting them do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and when a peak value serving as a reference for image processing is updated and followed in a predetermined level unit, shading overcorrection is performed. An object of the present invention is to provide an image processing apparatus capable of preventing a peak value of an image signal from excessively increasing even when a pixel is generated, and performing stable image processing.

[0008]

According to the first aspect of the present invention,
Based on the scan data of the white member of the reference read during the prescanning, the image signal correction means for correcting the shading distortion of read image signal, by the image signal correction means
Detecting a peak value of the corrected image signal, and the detection pin
A peak value holding means for holding over click value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the peak and peak value of the corrected image signal by the image signal correction means and image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding the picture
As a result of the comparison by the signal level comparing means, the image signal correction
The peak value of the image signal corrected by the means is the peak value
Peak value adjusting means for increasing and updating the peak value held by the peak value holding means by a predetermined level when the peak value is higher than the peak value held by the holding means ;
The peak value held by the value holding means is the background level of the document.
Image processing means for performing various types of image processing as a criterion, and the peak value adjustment means does not detect the peak value for a predetermined period for a pixel whose peak value has been updated.

[0009] The invention according to claim 2 is characterized in that at the time of pre-scan,
Based on the scan data of the reference white member read, peak and image signal correction means for correcting the shading distortion of read image signal, detects the peak value of the corrected image signal by the image signal correcting means, that the detection a peak value holding means for holding a value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the image signal complement
Said peak and peak value of the corrected image signal by positive means
And image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding said image signal level comparator hand
As a result of the comparison by the step, the image signal is corrected by the image signal correcting means.
The peak value of the obtained image signal is held by the peak value holding means.
The peak value held by the peak value holding means is increased by a predetermined level to update the peak value held by the peak value holding means;
The peak value of the
An image processing means for performing image processing, the image signal les
As a result of the comparison by the bell comparing means, the image signal correcting means
The peak value of the image signal corrected by the
First, the peak value holding means when higher than the peak value stage is held continuously occurs a predetermined number in the main scanning direction
It is characterized in that the peak value held in the step is raised by a predetermined level.

According to the third aspect of the present invention, the pre-scan
Based on the scan data of the reference white member read, peak and image signal correction means for correcting the shading distortion of read image signal, detects the peak value of the corrected image signal by the image signal correcting means, that the detection a peak value holding means for holding a value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the image signal complement
Said peak and peak value of the corrected image signal by positive means
And image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding said image signal level comparator hand
As a result of the comparison by the step, the image signal is corrected by the image signal correcting means.
The peak value of the obtained image signal is held by the peak value holding means.
The peak value held by the peak value holding means is increased by a predetermined level to update the peak value held by the peak value holding means;
The peak value of the
Image processing means for performing image processing , wherein the peak value
For a predetermined number of pixels before and / or after the pixel whose peak value has been updated by the level adjusting means, the peak value is not detected for a predetermined period.

According to a fourth aspect of the present invention, at the time of pre-scan,
Based on the scan data of the reference white member read, peak and image signal correction means for correcting the shading distortion of read image signal, detects the peak value of the corrected image signal by the image signal correcting means, that the detection a peak value holding means for holding a value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the image signal complement
Said peak and peak value of the corrected image signal by positive means
And image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding said image signal level comparator hand
As a result of the comparison by the step, the image signal is corrected by the image signal correcting means.
The peak value of the obtained image signal is held by the peak value holding means.
The peak value held by the peak value holding means is increased by a predetermined level to update the peak value held by the peak value holding means;
The peak value of the
Image processing means for performing image processing , wherein the peak value
When the level adjustment means updates the peak value continuously for a predetermined number of lines in the same pixel, the peak value is not detected for a predetermined period.

According to a fifth aspect of the present invention, at the time of pre-scan,
Based on the scan data of the reference white member read, peak and image signal correction means for correcting the shading distortion of read image signal, detects the peak value of the corrected image signal by the image signal correcting means, that the detection a peak value holding means for holding a value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the image signal complement
Said peak and peak value of the corrected image signal by positive means
And image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding said image signal level comparator hand
As a result of the comparison by the step, the image signal is corrected by the image signal correcting means.
The peak value of the obtained image signal is held by the peak value holding means.
The peak value held by the peak value holding means is increased by a predetermined level to update the peak value held by the peak value holding means;
The peak value of the
Image processing means for performing image processing , wherein the peak value
When the peak value is not updated for a predetermined period by the level adjusting means , the peak value is lowered by a predetermined level during a blanking interval of the image signal, and the lowering of the peak value level is performed during the simple binarization processing of the image. It is characterized by performing only

[0013] The invention according to claim 6 is characterized in that at the time of pre-scan,
Based on the scan data of the reference white member read, peak and image signal correction means for correcting the shading distortion of read image signal, detects the peak value of the corrected image signal by the image signal correcting means, that the detection a peak value holding means for holding a value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the image signal complement
Said peak and peak value of the corrected image signal by positive means
And image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding said image signal level comparator hand
As a result of the comparison by the step, the image signal is corrected by the image signal correcting means.
The peak value of the obtained image signal is held by the peak value holding means.
The peak value held by the peak value holding means is increased by a predetermined level to update the peak value held by the peak value holding means;
The peak value of the
Image processing means for performing image processing , wherein the peak value
The peak value detection by the holding means is performed discretely for each predetermined pixel in the main scanning and / or for each predetermined number of lines in the sub-scanning.

According to a seventh aspect of the present invention, at the time of pre-scan,
Based on the scan data of the reference white member read, peak and image signal correction means for correcting the shading distortion of read image signal, detects the peak value of the corrected image signal by the image signal correcting means, that the detection a peak value holding means for holding a value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the image signal complement
Said peak and peak value of the corrected image signal by positive means
And image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding said image signal level comparator hand
As a result of the comparison by the step, the image signal is corrected by the image signal correcting means.
The peak value of the obtained image signal is held by the peak value holding means.
The peak value held by the peak value holding means is increased by a predetermined level to update the peak value held by the peak value holding means;
The peak value of the
Image processing means for performing image processing , wherein the amount of increase in the peak value by the peak value level adjusting means is reduced when reading the leading edge of the document.

The invention according to claim 8 is characterized in that at the time of prescan,
Based on the scan data of the reference white member read, peak and image signal correction means for correcting the shading distortion of read image signal, detects the peak value of the corrected image signal by the image signal correcting means, that the detection a peak value holding means for holding a value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the image signal complement
Said peak and peak value of the corrected image signal by positive means
And image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding said image signal level comparator hand
As a result of the comparison by the step, the image signal is corrected by the image signal correcting means.
The peak value of the obtained image signal is held by the peak value holding means.
The peak value held by the peak value holding means is increased by a predetermined level to update the peak value held by the peak value holding means;
The peak value of the
An image processing unit for performing image processing is provided, and when the peak value is updated continuously for a plurality of lines by the same pixel, the amount of increase in the peak value is reduced as the pixel becomes later.

According to a ninth aspect of the present invention , the method of
Based on the scan data of the reference white member read, peak and image signal correction means for correcting the shading distortion of read image signal, detects the peak value of the corrected image signal by the image signal correcting means, that the detection a peak value holding means for holding a value as a base level of the reference document when performing the image processing, for each pixel in the main scanning, the image signal complement
Said peak and peak value of the corrected image signal by positive means
And image signal level comparing means for sequentially comparing the level difference between the peak value of the value holding means for holding said image signal level comparator hand
As a result of the comparison by the step, the image signal is corrected by the image signal correcting means.
The peak value of the obtained image signal is held by the peak value holding means.
The peak value held by the peak value holding means is increased by a predetermined level to update the peak value held by the peak value holding means;
The peak value of the
Image processing means for performing image processing, the peak value holding means
When the peak value held in the step exceeds a predetermined set value,
A warning means for issuing a warning to the operator is provided.

The invention according to claim 10 is the first or third invention.
5. The image processing apparatus according to claim 4, wherein the peak value is detected.
During the non-printing period, the adjustment is performed according to the image reading mode.
It is characterized by the fact that it is knotted .

The invention according to claim 11 is the invention according to claim 6.
In the image processing device, specify the pixel for detecting the peak value
It is characterized in that it is determined randomly for each line .

The invention according to claim 12 is the invention according to claim 9
In the image processing apparatus, the setting value is an image reading value.
It is characterized by being variable according to the mode .

The invention according to claim 13 is the invention according to claims 1 to 12
In the image processing apparatus according to any one of the above, the peak value
The detection area of the peak value detected by the holding means is one main scanning line.
It is a predetermined section shorter than in.

[0021]

According to the first aspect of the present invention, when a pixel exceeding the peak level occurs, the peak value is increased by a predetermined level regardless of the level of the pixel. , There is no immediate response to this, and overcorrection can be prevented. Ma
Also, the peak value of the updated pixel is
By not detecting the value, the peak value
It does not follow overcorrected pixels, and can read good images.
You can take out. Also, for the pixel whose peak value has been updated,
Not to detect peak values for a specified period of time
Prevents the peak value from following the overcorrected pixel.
As a result, a good image can be read .

According to the second aspect of the present invention, the peak level is
When the number of pixels exceeds, regardless of the level of the pixel
Since the peak value is increased by a predetermined level,
Instant response to sudden noise
Overcorrection can be prevented.
In addition, the number of pixels exceeding the peak level is a predetermined number in the main scanning direction.
The peak value is set to the specified level for the first time when it occurs continuously.
Only over-corrected pixels and sudden
Prevents direct influence of noise, etc.
Do not follow them, and good image reading
I can do it .

According to the third aspect of the present invention, the peak level is
When the number of pixels exceeds, regardless of the level of the pixel
Since the peak value is increased by a predetermined level,
Instant response to sudden noise
Overcorrection can be prevented.
Also, before and / or after the pixel whose peak value has been updated.
Do not detect the peak value for a predetermined number of pixels for a predetermined period.
Following over-corrected pixels over several pixels
, And good image reading can be performed .

According to the fourth aspect of the present invention, the peak level is
When the number of pixels exceeds, regardless of the level of the pixel
Since the peak value is increased by a predetermined level,
Instant response to sudden noise
Overcorrection can be prevented.
In addition, the update of the peak value is continued for a predetermined number of lines in the same pixel.
The peak value is detected only for a predetermined period of time.
To avoid shading due to dust
Peak value overcorrection pixels like the grayed distortion without the follow child
And good image reading can be performed .

According to the fifth aspect of the present invention, the peak level is
When the number of pixels exceeds, regardless of the level of the pixel
Since the peak value is increased by a predetermined level,
Instant response to sudden noise
Overcorrection can be prevented.
If the peak value is not updated for a predetermined period,
The peak value is reduced by a predetermined level during the image signal retrace interval.
The density difference will not appear in the image.
Therefore, it is possible to favorably follow the background level of the document. Also,
Updating of peak value during binary processing of signal for a predetermined period
If not, the peak value will be lowered by a predetermined level.
Therefore, no density difference appears in the image at the time of the binary processing,
The base level of the document can be tracked satisfactorily .

According to the sixth aspect of the present invention, the peak level is
When the number of pixels exceeds, regardless of the level of the pixel
Since the peak value is increased by a predetermined level,
Instant response to sudden noise
Overcorrection can be prevented.
Further, the detection of the peak value is performed at every predetermined pixel in the main scanning and / or
Or by performing discretely for each predetermined line of sub-scan,
Low probability that peak value continuously follows for each overcorrected pixel
And good image reading can be performed .

According to the seventh aspect of the present invention, the peak level is
When the number of pixels exceeds, regardless of the level of the pixel
Since the peak value is increased by a predetermined level,
Instant response to sudden noise
Overcorrection can be prevented.
When reading the leading edge of a document, the peak value
Specularly reflected light due to curling of the original, etc.
Prevents the peak value from rising,
You can take out .

According to the eighth aspect of the present invention, the peak level is
When the number of pixels exceeds, regardless of the level of the pixel
Since the peak value is increased by a predetermined level,
Instant response to sudden noise
Overcorrection can be prevented.
When updating the peak value for multiple lines in succession for the same pixel
Means that the later the pixel, the smaller the peak value
The peak value due to overcorrected pixels, etc.
As a result, good image reading can be performed .

According to the ninth aspect of the present invention, the peak level is
When the number of pixels exceeds, regardless of the level of the pixel
Since the peak value is increased by a predetermined level,
Instant response to sudden noise
Overcorrection can be prevented.
Alerts the operator when the peak value exceeds the specified value.
By issuing a notification, it is possible to encourage the confirmation of image quality.
I can .

According to the tenth aspect, the peak value is detected.
The period during which scanning is not performed corresponds to the image reading mode.
Because it is variable, it is possible to read images suitable for various modes
I can do it .

According to the eleventh aspect of the present invention, the detection of the peak value is determined at random for each predetermined line, so that the probability that the peak value continuously follows overcorrected pixels and the like is further reduced, and a good image quality can be obtained. Can read.

According to the twelfth aspect of the present invention, there is provided the ninth aspect.
In the invention of the above, when the operator is warned, the peak value is
The set value to be compared changes depending on the image reading mode.
The image quality according to the reading mode.
You can check .

According to the thirteenth aspect, the peak value is detected.
The output area is a predetermined area shorter than one scan line, for example, both areas.
By setting it in the middle area excluding the edge,
Good image quality without being affected by irregular reflection
Can read .

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

First, the configuration will be described.

FIG. 1 is a block diagram showing the configuration of an image reading unit in an image processing apparatus according to one embodiment of the present invention. In the figure, reference numeral 1 denotes a document for reading an image, and 2 denotes a document 1
3 is a contact glass constituting a reading surface for reading a document image while guiding the document 1, 4 is a white reference member extending in the main scanning direction having a reflectance close to that of a white document, and 5 is a document. A mirror group that folds the reflected light from 1 or the white reference member 4 by a predetermined optical path length, 6 is a lens that forms a reflected light image of the original 1 at a predetermined reduction ratio, and 7 is CCD (Charg
e, an image sensor such as an e-coupled device, 8 an operational amplifier (op-amp) that amplifies the analog image signal from the image sensor 7 at a predetermined magnification, and 9 an A / D converter that converts the amplified analog image signal into a digital value. , 10 generates a reference signal of the A / D converter 9 as an analog signal corresponding to digital control data.
An A converter 11 is a distortion correction unit that controls digital input data to the D / A converter 10 based on white reference data.
Reference numeral 2 denotes a digital image processing unit that performs various image processing on the digital image signal from the A / D converter 9, and 13 denotes a RAM that stores shading distortion data and data for image processing.
(Random Access Memory) or FIFO (First-
in First-out). These series of operations are controlled by a system control unit (not shown).

Therefore, as shown in FIG. 1, prior to reading the document 1, the system control unit turns on the light source 2 and
The white reference member 4 arranged just above the scan line is illuminated. The reflected light from the white reference member 4 is image-formed and projected on the image sensor 7, and is output as an analog waveform including shading distortion. The white waveform is quantized by the A / D converter 9 into a predetermined number of bits and stored in the line buffer 13.

At this time, the D / A converter 10 outputs, for example, the peak value of the white waveform to the A / D converter 9 as a quantization reference (ref) level (see FIG. 2A). Then, when shading distortion is removed by a digital method, when quantization is performed by the A / D converter 9,
Correction is performed so that the quantization level becomes uniform (FIG. 2B)
reference). When shading distortion is removed by the variable gain method, as shown in FIG. 2C, the gain is changed for each pixel so that the white waveform after amplification becomes uniform with respect to the reference white waveform. to correct.

However, when dust or the like is attached to the optical path when the distortion data is collected, as shown in FIG. 3A, a partially lowered waveform is stored as distortion data. When the original is read, the distortion data is read out and shading correction is performed. If the foreign matter deviates from the optical path due to conveyance of the original at this time, the level does not decrease due to the foreign matter, and therefore, as shown in FIG. The pixel is overcorrected, and the level of the image signal partially protrudes.

In general, when image processing is performed, the peak value of the image signal after the shading correction is detected in order to enhance the reproducibility of the image, and this peak value is recognized as the background level of the document, and various processes are performed. It has been implemented.

However, when various types of image processing are performed using the peak value after the shading correction described above as a reference level,
Image degradation occurs due to excessive rise of the peak value.

FIG. 4 is a block diagram showing a configuration example of the peak value detecting section according to one embodiment of the present invention. In FIG. 4, reference numeral 14 denotes an up / down counter having a load function, and 15 denotes a comparator for comparing the output of the up / down counter 14 with the output of the A / D converter 9. , 16 is up / down
A correction operation unit 17 for performing a predetermined correction operation based on the output of the counter 14 and the distortion data from the line buffer 13;
6 is a multiplexer that selects one of the output 6 and the full scale data and outputs it to the D / A converter 10.

As described above, the light source 2 is turned on and the white reference member 3 is scanned by the image sensor 7 before reading the original. The multiplexer 17 first selects the full scale data and outputs it to the D / A converter 10. D / A
The converter 10 converts the full-scale data into an analog signal,
The signal is output to the D converter 9 as a quantized reference signal (ref). The up / down counter 14 is reset to “0” or an offset level close to “0”, and the comparator 15 sequentially compares the output of this counter with the output of the A / D converter 9.

When the output level of the A / D converter 9 is higher, the comparator 15 is turned on and off.
A load signal (load) is generated for the counter 14, and the quantized data at that time is taken in and updated. By performing such an operation at least one line, the up-down counter 14 holds the peak value of the white waveform.

Next, the multiplexer 17 selects a peak value from the output of the counter 14, and the D / A converter 10
Outputs an analog level corresponding to this to the A / D converter 9. Then, the quantized data from the A / D converter 9 is
It is normalized by the peak value of the white waveform, and is sequentially stored in the line buffer 13 as distortion data. When reading the original, the distortion data is read to reproduce a white waveform, and the distortion is removed by performing a quantization reference. At this time, the reference level fluctuates following the peak level so as to be suitable for the (background) density of the document.

Next,When reading a document,up·
Exceeds the peak value held by the down counter 14
When a pixel occurs(Shading of scanned original
The peak value (maximum level value) of the image signal after correction increases.
Exceeds the peak value held by the down counter 14
This is also referred to as overflow.)
Is a carry indicating an overflow from the A / D converter 9.
A signal is output. At this time, the up / down counter 14
Counts up by a predetermined level (for example, several LSBs)
To increase the peak value.Here, up, down,
Stored in counter 14 The peak value held is equal to this peak value.
In the following, it will be updated to the value raised by the predetermined level
Also referred to as updating the peak value.Also prescribedperiodOverflow
-If no signal is generated, generate a down signal and
Count down by a certain level, lower the peak value
You. This down signal is generated by the system controller.
Or you can make it happen in hardware
Is also good.

In this embodiment, by performing the above-described control, it is possible to perform a correction process that follows a change in the density of the document. In the present invention, the peak value is increased by a predetermined amount with respect to the pixel exceeding the peak value regardless of the level of the pixel, so that even if sudden noise or the like enters, the peak value is instantaneously excessively increased. Can be prevented.

This will be described with reference to FIG.
As shown in (a), if a foreign matter is adhered to the optical path only when the white reference data is collected, when the document 1 is read,
There level of the pixel of that portion decreases. As a result, as shown in FIG. 5B, the corrected image signal always overflows in the pixel and generates a carry signal, so that the peak value gradually increases. Will be generated.

For this reason, the present embodiment is characterized in that a configuration is employed in which the peak value does not respond to such overcorrected pixels. The peak value detection area is one primary.
The predetermined section may be shorter than the scanning line.
For example, the area where the peak value is detected is excluded from both ends of the document 1.
By setting it in the middle area, the random
Good image reading
I can take it. The overcorrected pixels shown in FIG. 5B are always at the same position during the reading of the original, so
For a pixel whose peak value has been updated for the same pixel in succession or for a plurality of lines consecutively, the peak value is not detected during a predetermined period or between predetermined lines, thereby causing an abnormal image. It is possible to prevent the peak value from rising excessively. That is,
The peak value of the pixel for which the
I try not to go out. More specifically, the peak value
If the update has been performed continuously for a predetermined number of lines in the same pixel
Does not detect peak values for a predetermined period.
You.

Further, as shown in FIG. 5A, since the level decrease due to the foreign matter has a quadratic function distribution, the probability that the preceding and following pixels are also overcorrected pixels increases. Therefore, by not detecting the peak value for these pixels, the stability of the image can be further improved. That is, before and after the pixel whose peak value has been updated.
And / or a predetermined number of subsequent pixels
Do not detect the lock value.

[0051] Further, when said overflow condition has occurred continuously for a predetermined number in the main scanning direction, which may be as Ru raise the peak value is determined to be background level. That is, pixels larger than the peak value are mainly
Peak occurs only when a predetermined number of consecutive occurrences occur in the scanning direction
The value is increased by a predetermined level.

Further, the peak value is continuously updated by the overcorrection pixel by discretely sampling the pixel for detecting the peak value for each predetermined pixel in the main scanning direction and / or for each predetermined line in the sub-scanning direction. it is that a little. You
That is, the peak value is detected at every predetermined pixel in the main scanning direction.
And / or discretely for each predetermined line in the sub-scanning direction.
So that Furthermore, if sampling is performed at random for each predetermined line, it is less likely to continuously follow overcorrected pixels, and an excessive rise in peak value can be suppressed. That is, the pixel for detecting the peak value is
It is determined randomly for each predetermined line.

In addition to the above-mentioned means, when the peak value is continuously updated over a plurality of lines by the same pixel, an excessive rise of the peak value can be prevented by configuring so that the amount of rise is smaller in the later pixels. It is possible to suppress. Sand
That is, the peak value is updated continuously for a plurality of lines with the same pixel.
In some cases, the later the pixel, the smaller the peak value rise
To do it.

During binary image processing, the density of the background of the document is processed as a white background, so that it is necessary to always follow the peak value of the image signal even during reading of the document. For this reason, when the update of the peak value is not performed for a predetermined period , the peak value is lowered by a predetermined level to balance the peak value with the true peak value. At this time, if the peak value is decreased in the blanking interval (no signal period) of the image signal, it is possible to prevent a density difference from occurring in the image. That is,
If the peak value is not updated for a predetermined period, the peak value
Is lowered by a predetermined level during the image signal retrace interval.
To Also, this decrease in peak value level is
It is performed only during the binarization processing.

On the other hand, when performing halftone processing, it is generally necessary to perform gradation processing on the basis of an absolute white background level, so that the peak value is not normally lowered even when the document density is lowered. If the absolute white background level is high, a decrease in the peak value can be recognized.

In the image processing apparatus according to the present embodiment, the period during which the peak value is not detected may be varied according to various reading modes. Sand
In other words, during the period when the peak value is not detected,
Variable according to the mode. For example, the reading mode includes processing modes such as binary image processing and halftone image processing, and various modes such as linear density and reading speed. In general, for example, it is desirable to set short during binary image processing or reading with low line density, and long during halftone image processing or reading with high line density.

Next, in a sheet scanner such as a general facsimile apparatus, a pair of rollers is provided on a paper feed side and a paper discharge side with respect to a reading position, and a document is transported. Therefore, when reading the leading edge of the original, the original is not held by the rollers on the paper discharge side, so the conveyance becomes unstable, and when the edge of the original is turned up and curled, the light of the light source 2 on the original surface is reflected. Specular reflection, etc., which is directly incident. For this reason, the output of the image sensor 7 temporarily increases due to such specular reflection, and the peak level also rises excessively following this, resulting in the above-mentioned defective image state. Therefore, it controls to increase the step of peak value in this way the original tip may be smaller than usual
be able to. That is, when reading the leading edge of the original,
Can make the peak value increase smaller than usual
You. Alternatively, the above problem can be improved by not sampling the image signal near the front end.

In another embodiment, when the peak value is excessively increased as described above, an alarm buzzer or a warning lamp is blinked for the operator, or an image is displayed on the display unit. By calling attention, the image quality can be easily confirmed. Sand
That is, when the peak value exceeds a predetermined set value,
To be warned. Also, this setting value
You may make it variable according to the image reading mode.

FIG. 6 is a diagram showing a configuration example of a detection unit for overflow pixels that are continuous in the main scanning direction. In the figure,
Reference numeral 18 denotes a flip-flop group which holds and shifts the carry signal from the A / D converter 9 in units of one pixel, and 19 denotes an AND gate which outputs a logical product of outputs from the flip-flops 18 It is.

Then, the carry signal from the A / D converter 9 is sequentially taken into each flip-flop 18, and when the flip-flop continues for several pixels, the AND gate becomes active "H", and this output becomes high. The up / down counter 14 in FIG. 4 is counted up.

FIG. 7 is a diagram showing an example of the configuration of a peak value update detecting unit for a plurality of consecutive lines of the same pixel.
Is a flip-flop that holds the peak value update history of the same pixel in each line. Therefore, the AND gate 19
When the peak value is continuously updated by the number of lines of the flip-flop 20, the AND gate 19 becomes active "H" and generates a peak detection inhibition signal.

FIG. 8 is a diagram showing an example of the configuration of the control unit during the peak value non-detection period. Reference numeral 21 denotes a flip-flop that holds the peak value non-detection period, and 22 denotes a predetermined amount from the output of the flip-flop 21. , A comparator 23 for determining the sign of the output of the subtractor 22,
Reference numeral 4 denotes a peak value detection period control unit capable of arbitrarily setting a peak value detection period, and 25 denotes a random number generator.

Therefore, as shown in FIG. 8, when a peak value detection inhibition signal (Inhibit) is generated, an arbitrary peak value detection inhibition period (for example, 1
Set 0). Then, the subtractor 22 subtracts the set value for each line or every plural lines, and stores the result in the line buffer 13. In the next line, the stored data is read out, and thereafter, this operation is repeated cyclically. When the output of the subtractor 22 becomes negative, the comparator 23 becomes “H” and activates the carry signal from the A / D converter via the AND gate 19. Then, the time until the set value turns negative is a peak value non-detection period.

Further, the peak value detection period control section 24 can perform various peak value detection controls by the output operation of the random number generator 25. As described above, in the present embodiment, an example in which the control unit is configured by hardware has been described. However, it is needless to say that the control unit may be configured to be controlled by software.

Next, the operation of this embodiment will be briefly described with reference to FIG.

FIG. 9 is a flowchart for explaining an embodiment of the present invention.

First, in step 100, initialization is performed. Here, the peak value rising step (α), the peak value falling cycle (β), and the peak value falling step (γ) are set, and the first pixel number (n) is set to 1, and no peak value is detected at first. It is assumed that the state is (PD = 0) and the number of non-detected lines with no peak value is also present (HLD = 0).

Next, in step 101, the peak value (Vp) of the white reference plate is detected, and it is determined whether or not the pixel is a pixel for which a carry signal has been detected due to overflow (step 102). If the peak value of the overflowed pixel is detected (step 103), it is determined whether or not the period is during the peak value prohibition period (step 104). If not, the peak value is determined at step 105. Is raised by the rising step (α). During the peak value detection prohibition period, the peak value is not increased.

Next, at step 106, the process proceeds to the next pixel, and the above operation is repeated until n = 1728, which is the number of pixels for one line, has been completed.

When the above processing is completed for each pixel of one line, it is determined in step 108 whether or not a peak value has been detected. If a peak value has been detected, the number of non-peak value detected lines is “ 0 "(step 10
9).

In step 110, the number of peak value non-detection lines is added, and it is determined whether or not the number of peak value non-detection lines is greater than the peak value falling period (β) (step 111). When the number of lines is larger than the peak value falling period (β), the peak value is lowered by a predetermined level (γ).

If the reading has not been completed in step 113, the process returns to step 102 and the above operation is repeated until the reading is completed.

As described above, in the image processing apparatus according to the present embodiment, the peak value detected by the white reference plate overflows.
The peak value by a predetermined level,
If the peak value non-detection line number continues, the peak value is lowered by a predetermined level, so that even if the background density of the document changes, the appropriate peak value is updated in accordance with the change, It can be automatically adjusted to an appropriate level. For this reason, the image processing apparatus according to the present embodiment can perform stable image processing, and can achieve good image reading.

[0074]

As described above, according to the first aspect of the present invention, when a pixel exceeding the peak level occurs, the peak value is increased by a predetermined level regardless of the level of the pixel. Therefore, even if sudden noise or the like occurs, it does not immediately respond to this,
A good image can be read. Also,
Detect peak value for a predetermined period for pixels with updated update values
Is not performed, the peak value may follow overcorrected pixels, etc.
And good image reading can be performed.
You .

According to the second aspect of the present invention, the peak level
When a pixel exceeding the threshold occurs, the level of the pixel
Instead of raising the peak value by a predetermined level
Therefore, even if sudden noise occurs,
Response to the
I can. Pixels exceeding the peak level are mainly
When a predetermined number of consecutive occurrences occur in the scanning direction, the peak value is
Because it is raised only by a certain level, overcorrected pixels and
The peak value follows even when there is sudden noise, etc.
And good image reading can be performed.
I can .

According to the third aspect of the present invention, the peak level
When a pixel exceeding the threshold occurs, the level of the pixel
Instead of raising the peak value by a predetermined level
Therefore, even if sudden noise occurs,
Response to the
I can. Also, before the pixel whose peak value has been updated,
A predetermined period of time for a predetermined number of pixels after and / or
Since no value is detected, overcorrected pixels over several pixels
No longer follows the image and performs good image reading
Can be .

According to the fourth aspect of the present invention, the peak level
When more than Le pixels occurs, involved in the level of the pixel
Instead of raising the peak value by a predetermined level
Therefore, even if sudden noise occurs,
Response to the
I can. Also, update of the peak value is performed for the same pixel.
If the operation is performed continuously for a fixed number of lines,
Detection is not performed, so that dust
The peak value is added to the overcorrected pixels due to shading distortion
Obtain good image reading
Can be .

According to the fifth aspect of the present invention, the peak level
When a pixel exceeding the threshold occurs, the level of the pixel
Instead of raising the peak value by a predetermined level
Therefore, even if sudden noise occurs,
Response to the
I can. The peak value is updated for a predetermined period.
If it is not possible, only a predetermined level
Lowers the peak value, which may cause density differences in the image.
And can follow the background level of the original satisfactorily.
it can. Also, it is necessary to update the peak value during binary processing.
If not performed for a fixed period, lower the peak value by a predetermined level.
The density difference in the image during binary processing.
Does not appear, and the tracking of the background level of the original is improved.
I can .

According to the sixth aspect of the present invention, the peak level
When a pixel exceeding the threshold occurs, the level of the pixel
Instead of raising the peak value by a predetermined level
Therefore, even if sudden noise occurs,
Response to the
I can. In addition, detection of the peak value is
Discretely for each pixel and / or for each predetermined line of sub-scan
By doing so, the peak value is continuously added for each overcorrected pixel.
The probability that the image will be read
Can be .

According to the seventh aspect of the present invention, the peak level
When a pixel exceeding the threshold occurs, the level of the pixel
Instead of raising the peak value by a predetermined level
Therefore, even if sudden noise occurs,
Response to the
I can. Also, peak at the time of the tip portion reading of the original
The step of raising the peak value
The peak value is prevented from rising due to specular light
Thus, good image reading can be performed .

According to the eighth aspect of the present invention, the peak level
When a pixel exceeding the threshold occurs, the level of the pixel
Instead of raising the peak value by a predetermined level
Therefore, even if sudden noise occurs,
Response to the
I can. In addition, the same pixel is continuously used for multiple lines.
When updating the peak value, the later the pixel, the higher the peak value
Since the steps have been reduced, the peaks
The image reading does not increase and good image reading is performed.
Can be .

According to the ninth aspect of the present invention, the peak level
When a pixel exceeding the threshold occurs, the level of the pixel
Instead of raising the peak value by a predetermined level
Therefore, even if sudden noise occurs,
Response to the
I can. Also, if the peak value exceeds the
Warning to the operator when the
Can be recognized .

According to the tenth aspect, the peak value
The period during which the detection is not performed corresponds to the image reading mode.
Variable, so that it can read images suitable for various modes.
Can be performed .

According to the eleventh aspect of the present invention, the detection of the peak value is randomly determined for each predetermined line, so that the probability that the peak value continuously follows the overcorrected pixel or the like is further reduced, A good image can be read.

According to the twelfth aspect, according to the ninth aspect,
In the described invention, when a warning is issued to an operator,
The set value to be compared with the value depends on the image reading mode.
Because it is changed, the image product according to the reading mode
You can check the quality .

According to the thirteenth aspect, the peak value
Detection area is set to a predetermined area shorter than one scan line
To be affected by specular reflection at the document edge.
And a good image can be read .

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an image reading unit in an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of correcting shading distortion.
(A) is an analog white waveform diagram, (b) is a quantized data diagram,
(C) is an analog waveform diagram before quantization.

FIGS. 3A and 3B are diagrams showing an example of overcorrection due to foreign matter adhesion, wherein FIG. 3A is an analog white waveform diagram, and FIG. 3B is a corrected white waveform diagram.

FIG. 4 is a configuration block diagram of an image reading unit in the image processing apparatus according to one embodiment of the present invention.

5A and 5B are diagrams illustrating a peak value tracking unit of the image processing apparatus according to one embodiment of the present invention, wherein FIG.
(B) is a white waveform diagram after correction.

FIG. 6 is a configuration block diagram of a detection unit that detects a plurality of continuous pixels whose peak values overflow in the main scanning direction.

FIG. 7 is a configuration block diagram of a detection unit that detects the same pixel over a plurality of lines where the peak value overflows in the sub-scanning direction.

FIG. 8 is a configuration block diagram of a control unit that controls a peak value non-detection period.

FIG. 9 is a flowchart illustrating the operation of one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 2 Light source 4 White reference member 7 Image sensor 9 A / D converter 10 D / A converter 11 Distortion correction part 12 Digital image processing part 13 Line buffer 14 Up / down counter 15 Comparator 16 Correction calculation part 17 Multiplexer 18 Flip-flop 19 AND gate 20 Flip-flop 24 Peak value detection period control unit 25 Random number generator

Continuation of the front page (56) References JP-A-62-18972 (JP, A) JP-A-4-144482 (JP, A) JP-A-2-203671 (JP, A) JP-A-2-1311078 (JP) JP-A-2-60372 (JP, A) JP-A-4-21267 (JP, A) JP-A-3-23772 (JP, A) JP-A-62-204664 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 1/40-1/409 H04N 1/46 H04N 1/60

Claims (13)

(57) [Claims] An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by the image signal correcting means detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
Means for detecting a peak value of a pixel whose peak value has been updated by the peak value level adjusting means for a predetermined period. 2. An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by said image signal correcting means. detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
Means, and as a result of the comparison by the image signal level comparing means,
The peak value of the image signal corrected by the
First, the peak when higher than the peak value held by over click value holding means occurs continuously a predetermined number in the main scanning direction
An image processing apparatus for increasing a peak value held by a peak value holding means by a predetermined level. 3. An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by the image signal correcting means. detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
Means for detecting a peak value for a predetermined number of pixels before and / or after a pixel whose peak value has been updated by the peak value level adjusting means for a predetermined period. Processing equipment. 4. An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by said image signal correcting means. detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
And means, if the update of the peak value is performed continuously for a predetermined number of lines in the same pixel by the peak value level adjusting means, the image processing apparatus characterized by not detected for a predetermined period peak value. 5. An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by said image signal correcting means. detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
Means for updating the peak value by a predetermined level during a blanking interval of the image signal when the peak value is not updated by the peak value level adjusting means for a predetermined period. An image processing apparatus characterized in that it is performed only at the time of simple binarization processing of an image. 6. An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by said image signal correcting means. detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
Means for detecting the peak value by the peak value holding means discretely for each predetermined pixel in main scanning and / or every predetermined number of lines in sub-scanning. 7. An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by said image signal correcting means. detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
Means for adjusting the peak value level when reading the leading edge of the document.
An image processing apparatus wherein the amount of increase in peak value by means is reduced. 8. An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by said image signal correcting means. detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
Means for updating the peak value for a plurality of lines continuously for the same pixel, wherein the amount of increase in the peak value is reduced as the pixel becomes later. 9. An image signal correcting means for correcting shading distortion of a read image signal based on scanning data of a reference white member read at the time of pre-scanning, and a peak value of the image signal corrected by said image signal correcting means. detects, the detected peak value and the peak value holding means for holding as a reference background level of the document during image processing, for each pixel in the main scanning, the correction of the said image signal correction means
To hold the peak value and the peak value holding means of the field signal is
Image signal level comparing means for sequentially comparing the level difference with the peak value, and a result of the comparison by the image signal level comparing means.
The peak value of the image signal corrected by the
If over click value holding means is higher than the peak value held, the peak value level adjusting means for updating increasing the peak value held by the peak value hold means by a predetermined level, the peak the peak value holding means for holding Value of the original
Image processing that performs various image processing as a base level reference
And means, when a peak value held by the peak value hold means exceeds a predetermined set value, the image processing apparatus characterized by comprising a warning means for issuing a warning to the operator. 10. The method according to claim 1, wherein the data is read at the time of prescan.
5. The image processing apparatus according to claim 3, wherein a period during which the peak value is not detected is adjusted according to an image reading mode. 11. The image processing apparatus according to claim 6, wherein pixels for detecting a peak value are randomly determined for each predetermined line. 12. The image processing apparatus according to claim 9, wherein said set value is variable according to an image reading mode. 13. The image processing apparatus according to claim 1, wherein a peak value detection area detected by said peak value holding means is a predetermined section shorter than one main scanning line. Image processing device.