JPH10224615A - Picture reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the density of a black strip part equal to that of the place near a part where it occurs and to improve the appearance of a read original picture by substituting the density of the black stripe part detected by a black stripe detection means only in a set center area for peripheral density. SOLUTION: Input picture data density is compared with a threshold stored in a density register 32 by a comparator 31. When picture data is higher, the output of the comparator 31 is made active. At that time, an address in a main scanning direction is kept in a start address register 34 and an address in the main scanning direction when it returns to inactive in an end address register 35. A density conversion signal generation circuit 38 extracts the black stripe place with the two addresses and outputs a signal. When the output and an erasing signal are turned on, the signal is outputted to a density conversion block 40 through an AND circuit 51. Data by picture density data average value density immediately before the black stripe is detected is outputted from the density conversion block 40 and black stripe part density is converted into peripheral picture element density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus for reading a book document.

[0002]

2. Description of the Related Art An image reading apparatus for reading a book document is:
Both pages are read at a time with the book (book) open. The scanned image is a copier or printer,
Alternatively, it is output as image data to a computer, and an image is formed on paper by these copying machines.
It is also used for processing various images by a computer. In such an image forming apparatus, a dark portion may occur at a binding portion (center portion) of a book document, and a black streak may occur at a central portion of a read image. And
Such black streaks have been shunned by users because they make the appearance of the image poor.

In a conventional book document reading apparatus, as a countermeasure against black streaks, for example, as shown in Japanese Patent Application Laid-Open No. 6-46214 or Japanese Patent Application Laid-Open No. 7-234555, a shadow is formed at the center of a book. A method is disclosed in which a black streak region is masked and a certain region near the occurrence of a black streak is erased white.

[0004]

However, in the above-described conventional method, all images in the main scanning direction are erased (masked to white) in a fixed area in the scanning sub-scanning direction.
A blank line occurs in the center of the image.

In the case where the image of the book document to be read is composed of only characters, there is almost no character in the binding portion in a normal book. . However, in the case of a photo original, there is also an image that covers both the left and right pages across the binding line.In such a case, if the binding portion is erased with a white mask, the color of the background is different from the background color, On the contrary, there is a problem that an image looks bad.

Accordingly, an object of the present invention is to eliminate black streaks caused by shadows at the binding portions of a book without completely whitening the streaks around the black streaks around the black streaks. It is an object of the present invention to provide an image reading apparatus for improving the appearance of a document image read so as to be substantially equal to the density.

[0007]

According to the first aspect of the present invention, there is provided a center area setting means for setting a center area near a binding of a book document.
Black streak detecting means for detecting black streaks caused by the shadow of the binding portion of the book document, black streak density adjusting means for replacing the density of the black streak portion detected by the black streak detecting means with the density around the black streak, Only the center area set by the center area setting means, a control means for controlling the black streak density adjusting means so that the black streak detecting means functions and replaces the density of the detected black streak portion with the peripheral density. An image reading apparatus comprising:

According to a second aspect of the present invention, in the configuration of the first aspect, the black streak detecting means stores in advance the densities of a plurality of pixels arranged in the book binding direction of the read original image. The image reading apparatus is characterized in that the image reading apparatus compares the density threshold value and a plurality of pixels equal to or greater than the threshold value and determines that the pixel is a black streak when a plurality of pixels continue.

According to a third aspect of the present invention, there is provided the image reading apparatus according to the second aspect, wherein the density threshold value is set to be different between a document to be read and a text to be read. Device.

According to a fourth aspect of the present invention, there is provided the image reading apparatus according to the second aspect, wherein the value of the density threshold value is sequentially changed as approaching the center of the book original. .

According to a fifth aspect of the present invention, in the configuration of the second aspect, the density threshold value is obtained by sequentially calculating an average value of the density of the read image, and based on the average value, a book document is obtained. An image reading apparatus characterized in that the image reading apparatus sequentially changes as it approaches a center.

According to a sixth aspect of the present invention, the above object is achieved.
According to the present invention, there is provided a center area setting means for setting a center area near a binding portion of a book document, and a density of a read image is gradually changed to a peripheral area only in the center area set by the center area setting means. And an image density adjusting means for replacing the image.

[0013] In order to achieve the above object, a seventh aspect of the present invention is provided.
The invention described above is characterized in that a center area setting means for setting a center area near a binding of a book document, a black streak detecting means for detecting a black streak caused by a shadow of a binding portion of the book document, and the black streak detection A black streak density adjusting unit that replaces the density of the black streak portion detected by the unit with a density obtained by averaging the density of the black streak portion and the density of the black streak periphery. .

According to a still further aspect of the present invention, in the configuration according to the seventh aspect, the averaged density is a weighted average of the density of the black streak portion and the density of the black streak periphery. An image reading apparatus characterized in that:

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

Embodiment 1 First, an outline of a book original reading apparatus, which is an image reading apparatus to which the present invention is applied, will be described, and then, black streak erasure to which the present invention is applied will be described in detail.

FIG. 1 is an external view showing the overall configuration of a book document reading apparatus to which the present invention is applied. The book document reading device (hereinafter simply referred to as a device) 10 mounts a book document on document tables 1a and 1b which can be individually moved up and down on the left and right sides, with the document surfaces of the left and right pages thereof kept substantially horizontal. The image is read by the CCD line sensor of the imaging camera unit 2. At the time of image reading, the side surface shape of the book document reflected on the mirror 5 is read by a CCD line sensor via an optical system in the imaging camera unit 2, and the height of the document surface is detected. Further, the CCD line sensor photographs white and black density patterns provided on the side surfaces of the document tables 1a and 1b reflected on the mirror 5, and detects the height of the document tables 1a and 1b. A more accurate document surface height is determined based on both the document height and the platen height, and using this, focus adjustment in the imaging camera unit 2 and distortion of the read image are corrected,
This is to obtain a book document image without distortion.

CC provided inside the imaging camera unit 2
The D-line sensor is arranged so that the photosensors are lined up from the front of the apparatus to the back (in the direction of arrow A in the figure, the main scanning direction), and in the left-right direction (the direction of arrow B in the figure, sub-scanning direction) by a motor. Be moved. As a result, the reflected light from the document surface illuminated by the light source 3 is received, and the image is read. In the image reading operation, first, the CCD line sensor moves as a preliminary scan from either the left or right direction to read the original surface to determine the density of the original surface, and to determine the height of the original surface from the image projected on the mirror 5. The height of the original platen is determined by recognizing the height of the original platen. Then, the CCD line sensor moves as a main scan, and appropriate focusing is performed on the height of the document surface at each scanning position during the main scan based on the accurate document surface height obtained by the preliminary scan. A reading is made. The book document reading device is known (for example, Japanese Patent Application Laid-Open No. 8-242347), and a detailed description of its operation and structure will be omitted.

FIG. 2 is a diagram showing a state in which a book document to be read is placed on the above-described apparatus. In this apparatus, as shown in the figure, the book is placed so that the center portion of the book document, that is, the binding portion of the book matches the center mark shown on the device. As a result, the apparatus itself can recognize the binding position of the book document on which the document is placed.

However, when aligning the binding position of the book with the position of the center mark, an accurate alignment may not always be performed due to a manual error. Therefore, in this apparatus, even if the actual book binding position is slightly deviated from the center mark position, it is determined that the book binding position is located within a certain range near the center mark. I do.

When the book original placed in this manner is read as it is, that is, when no processing such as erasing black streaks on the center line is performed (the image distortion for reading the book original is corrected. Is)
3 is shown in FIG. As shown in the figure, a black streak appears at the center of the image corresponding to the binding of the book.

In the present invention, in order to prevent the appearance from being impaired by such black streaks, the black streaks are detected and replaced with the density of the peripheral image.

Hereinafter, an image processing system for implementing the present invention will be described.

FIG. 4 is a block diagram of an image processing system built in the above device.

First, the CC built in the photographing head 2
When the D line sensor 21 reads the reflected light from the original,
An analog signal is converted to a digital signal by an A / D (digital / analog) converter 11. Here, the image data is converted into 8-bit image data per pixel. The converted digital signal is subjected to MTF conversion processing such as density correction and edge enhancement by the first image processing circuit 12.

Then, the image data subjected to the MTF conversion processing is sent to the center line density adjusting circuit 13, where the black streak of the center portion is corrected as described later in detail. The correction processing of the center portion is performed by the CPU 16.
This is executed by the erase signal from.

The image data on which the center line correction processing has been performed is sent to the second image processing circuit 14, where the image data is subjected to scaling processing and binarization processing and output I / F (interface).
15 to the outside. The output image data is printed out on paper by a copier, a printer, or a computer, and is used for image processing.

The CPU 16 determines a scan start position based on a signal from the scan home position detection sensor 17 and outputs the first image processing circuit 12 for each line in the main scanning direction during the scanning operation based on the scan start position. In response to the interrupt signal (H-SYNC), the position where the CCD line sensor is currently scanning is constantly monitored, and when the scan position reaches the center area area (erase area) where the book document is bound, the erase signal is output. The output is performed (erase signal ON), and black streak correction processing is executed. Note that the scan home position detection sensor 17 outputs a signal when it is confirmed that the CCD line sensor 21 is at a predetermined home position. The CPU 16 drives the scan motor 18 according to the interrupt signal, and controls the CCD line sensor 21 to move in the sub-scanning direction.

As shown in FIG. 5, the center area area (erase area) for turning on the erase signal is such that the CCD line sensor moves in the direction of an arrow shown as the CCD sub-scanning direction in the figure during the main scan. , Near the binding of the book document, between B and C shown in the figure.

The center line density adjusting circuit 13 is shown in FIG.
As shown in the figure, a black streak detection block 3 for detecting a black streak
0 and a density conversion block 40 for replacing the detected density of black streaks with the density of peripheral pixels.

The image data (8-bit digital data) sent from the first image processing circuit 12 is branched, and one of them is input to the density detection block 30. The image data input to the density detection block 30 is
Is compared with a threshold value stored in the density register 32 in advance. As a result of the comparison, when the value of the image data is higher than the threshold of the density register (the density of the image data is higher than the density according to the threshold of the density register), the comparator 31 activates its output. The signal from the comparator 31 is N
It is input to the pixel counter 33.

The N-pixel counter 33 determines whether or not the active state of the output of the comparator 31 continues for N pixels or more in the main scanning direction. The N-pixel counter 33 counts the active state of the signal from the comparator 31 and determines it in advance. If it does not continue for N pixels or more, a reset signal is output.

The signal from the comparator 31 is also input to a start address register 34 and an end address register 35. The start address register 34 outputs the address in the main scanning direction when the output of the comparator 31 becomes active. And the end address register 35 holds the address in the main scanning direction when the output of the comparator 31 returns to inactive. Each register 3
4 and 35 are reset by a reset signal output from the N pixel counter 33. Further, each of the registers 34 and 35
Are held in the start address latch 3 by the input of the line synchronization signal TG.
6. The address value stored in the end address latch 37 and simultaneously held in the registers 34 and 35 is reset.

As a result, the density conversion signal generating circuit 38 extracts the location of the black streak from the two addresses (start address and end address), and indicates that there is a black streak between them (between the start address and the end address). Output a signal. The density conversion signal generation circuit 38
From CPU and erase from CPU16 (ERASE)
A signal is output to the density conversion block 40 through the AND circuit 51 only when both signals are ON.

The main scanning address referred to by each of the above registers is generated by a main scanning address counter 39, and the main scanning address counter 39 outputs a pixel clock signal (SYNC, each photo lined up on a CCD line sensor). A timing signal for reading out the charge of the sensor pixel by pixel is counted to generate an address in the main scanning direction.

Next, the operation of the density conversion block 40 will be described.

In the density conversion block 40, an average value of the density of a certain pixel in the main scanning direction is obtained by the averaging block 41 from the input image data. This is obtained by sequentially adding the input image data by the adder 42 and dividing the total value by the total number of pixels by the divider 43.

The obtained average value of the density of the image data enters the first selector 44, and when the signal from the black streak detection block 30 is inactive, the image data of this average value is one line FIFO (first in first out).
The data is input to the memory 45 and is sequentially updated.

On the other hand, when the signal from the black streak detection block 30 is active, the output of the one-line FIFO memory 45 input to the first selector 44 is selected and input again to the one-line FIFO memory 45 as it is. . Therefore, when the signal from the black streak detection block 30 is active, the image data at the time of the black streak detection is not stored, and the previous data is maintained.

The output of the one-line FIFO memory 45 is input to the second selector 46. In the second selector 46, the image data itself is also input in addition to the output of the one-line FIFO memory 45. When the signal from the black streak detection block 30 is inactive, the input image data itself is output. And the output from the one-line FIFO memory 45 is output when the signal from the black streak detection block 30 is active.
Therefore, during the period when the detection block 30 detects a black streak, that is, between the start address and the end address of the black streak in the main scanning direction, the density conversion block 40
From the image data immediately before the black streak is detected. That is, the density of the black streak portion is converted to the density of the peripheral pixels.

Here, the threshold value stored in the density register 32 will be described.

As can be seen from the above description, the threshold value stored in the density register 32 determines how much density near the binding of the book document should be determined as a black streak. Things.

In a book document, the illuminance of the document surface gradually decreases at the binding portion of the book, and black streaks occur at the binding portion itself because the illuminance is low. Therefore, the area detected as a black streak can be adjusted by changing the threshold value stored in the density register 32. By adjusting the threshold value, more effective black streak erasure can be performed when the original image is a photograph and when it is a text.

Specifically, for example, when the original to be read is only characters (referred to as a character mode), the threshold value of the density register 32 is set low, and the detection of black streaks is performed quickly. In this character mode, the erasing process can be performed slightly before black streaks occur by setting the detected density lower than the binarized threshold density at which black streaks occur. On the other hand, in the case of a photo original (referred to as a photo mode), the threshold value to be set is larger than that in the case of the text mode. As a result, the original image is left as close to the book binding as possible without erasing the black streaks to the last minute.

As described above, the reason why the black streak erasing area is changed by changing the density threshold between the character mode and the photograph mode is that, in a book original read in the character mode, as shown in FIG. Since there are almost no characters, there is no problem even if the area to be erased is enlarged, and the background is often white near the binding, and if there is a black streak remaining, the unerased portion will be more conspicuous. For,
In order to increase the erasure area, the threshold value is reduced. On the other hand, in the case of a photo original, as shown in FIG. 3 described above, there is a case where there is an image so as to sandwich a stitch, and in such a case, if the area to be erased as a black streak becomes large, the original image will be lost. Therefore, the density threshold is increased to reduce the erase area as much as possible. In the case of a photographic original, the density of the background is often high, so that even if there are some remaining black streaks, the remaining streaks are not noticeable.

As shown in FIG. 8, in the case of a document in which both a character and a photograph are present, at least two values of the character mode and the photograph mode are set in the density register 32 as thresholds. The character area and the photograph area may be distinguished during the preliminary scan, and the main area may be compared with the character mode threshold in the character area and the photograph mode threshold may be compared in the photograph area.

Next, the value of N set in the N-pixel counter 33 sets how far black streaks that enter the book document are detected when the book document is displaced obliquely with respect to the center mark of the mounting table. It is for doing. That is,
When the value of N is increased, only relatively long black streaks are detected. On the other hand, when the value of N is decreased, short streaks, that is, diagonal black streaks are gradually and gradually detected in the sub-scanning direction. As can be detected.

However, when the value of N is set to a small value, a black portion of the image (for example, FIG.
(The black portion in the image of FIG. 1, the lens portion of the binoculars) will be detected as black streaks. However, if it is too large, oblique black streaks cannot be detected.

Therefore, in the present invention, the value of N itself is set to an appropriate value (an appropriate value is set in advance so as to sufficiently detect oblique black streaks), and the value of the density register 32 is changed for one line. By successively changing according to the average value of the concentration of
Perform appropriate black streak detection.

To do this, first, the average density of all the pixels for one line in the main scanning direction that has been read is obtained, and the obtained average density is subtracted from the maximum density (here, 255 for 8 bits). Determine the value of the register. If this is expressed by an equation, Y = 255-X (where Y is a threshold value set in the density register, X
Is the average density for one line).

Each time one line in the main scanning direction is read, the value of Y is set as a threshold value in the density register 32 sequentially. As a result, when the black streak has not yet been reached, the average density of one line is low (there is a certain level of illuminance), so that the threshold value set in the density register 32 becomes large, making it difficult to detect black streaks. , The average density of one line increases (illuminance on the document surface decreases), the threshold value decreases, and black streaks are easily detected. Therefore, even if the value of N is small, it is possible to determine the black portion and the black streak of the document image as shown in FIG.

Alternatively, simply, the threshold value of the density register 32 may be gradually increased as approaching the center of the book document. In this case as well, as described above, the black streak becomes easier to detect as it approaches the center of the book, and on the other hand, it becomes more difficult to detect the black streak as the distance from the center increases. However, in this case, since the center of the book is the center mark portion shown on the apparatus, appropriate processing may not be performed if the book is largely displaced on the apparatus.

Next, the operation procedure of the above-described image processing system will be described. FIG. 9 is a flowchart showing the operation procedure. First, when the main scan is started (S1), CC
The D sensor moves in the sub-scanning direction and reads one line in the main scanning direction (S2), and the CPU 16 receives an interrupt signal from the first image processing apparatus 12, counts the number of interrupts, and thereby determines the number of read lines. It counts up (S3). The CPU 16 determines from the number of lines in the main scanning direction whether or not the CCD line sensor has reached an area for erasing black streaks (erase area) (S16).
4) If the erase area is reached, turn on the erase signal
(S5). Thus, the processing for replacing the previously described black streak portion with the peripheral density is executed.

Thereafter, counting of the number of read lines is continued (S6), and when it is detected that the erased area has been left (S7), the erase signal is turned off (S8). Then, the main scan operation ends (S9).

A description will be given of the result of image reading by the present apparatus configured as described above.

FIG. 10 is a drawing showing the density near the binding. FIG. 10 (a1) schematically shows data for each line near the binding, and FIG. 10 (a2) shows the data. 5 is a diagram illustrating a density distribution of an AA line portion of an image. As can be seen from the figure, the density increases toward the center of the image. From the density data, when the density portion equal to or higher than the threshold value stored in the density register 32 described above is replaced with the density immediately before it, FIGS. 10 (b1) and 10 (b2)
As shown in (2), the density exceeding the threshold value in the central part with the binding is replaced with the density immediately before.

FIG. 11 shows an example in which a photographic original is actually read by the present apparatus, and FIG. 12 shows an enlarged view of a black streak portion of this image. For comparison, FIG. 13 shows an example in which black streaks are completely erased using a white mask, as in the conventional method. As shown in the figure, in the image shown in FIG. 11 to which the present invention is applied, black streaks in the central portion of the image are more clearly erased compared to the case where no processing shown in FIG. 3 is performed. It can be seen that the image is not outlined as shown in FIG. 13 and a good-looking image is obtained. In addition, the black portion in the image is not erased by mistake, and the original image remains. Also, as can be seen from FIG. 12, the black streak portion is replaced by the image data immediately before the black streak. Note that when the image is enlarged in this manner, a slight image shift is observed, but this is not particularly noticeable in a normal image (the image shown in FIG. 11).

Embodiment 2 Embodiment 2 is for dealing with an image in which the appearance of the image cannot be sufficiently improved only by replacing the black streak area with the density before the black streak.

This occurs, for example, when the density immediately before the black streak area is different from the density immediately after it, as in the image shown in FIG. 12, or when a sharp density step occurs immediately after the black streak. Therefore, in the second embodiment, in such a case,
In order to prevent a sharp density step from occurring, the density immediately before the black streak area and the density immediately after the black streak area are replaced with a gradation to further improve the appearance of the image. Note that the external configuration of the book document reading apparatus and the basic image reading operation are the same as those in the first embodiment, and thus description thereof will be omitted.

FIG. 14 is a block diagram showing a circuit configuration for replacing black streak areas with gradation.

This circuit joins black streaks of 64 lines with gradation.

The input image data is branched into two, one of which is accumulated by a 64-line delay circuit 201 for 64 lines.
It is output with a delay of 64 lines. The 64-line delay circuit 201 is configured using 64 1-line FIFOs. The other one of the branched image data is input to the latch 204 as described later.

In the selector 202, the input is switched by the erase signal, and in the non-black streak normal region, a 64-line delayed image on the a side is output. On the other hand, in the black streak area, as described later, the image data input to the b side is output.

The erase signal goes high during the 64 line period of the black streak area. The race signal is input as a signal delayed by 64 lines.

The latch 203 latches the currently output image data that has passed through the 64-line delay circuit 201 in response to the high rise of the erase signal due to the start of the black streak. At the same time, raw data that does not pass through the 64-line delay circuit 201 is latched in the latch 204. This raw data is data that is 64 lines ahead when viewed from the data that has passed through the 64-line delay circuit 201.

The counter 205 enters the black streak area, and when the erase signal goes high, clearing is canceled and the counter 205 starts counting up. The counter 205 outputs a signal counted up for each line in the black streak area. This counter output is output from the latch 2
03 and 204 are used as distribution ratios to combine the outputs.

The multiplier 207 multiplies the density data immediately before the black streak from the latch 203 by the reciprocal of the output of the counter 205 and outputs a value obtained by dividing by 63. The counter 20
5 is output to the multiplier 207 via the inverter circuit 206.
Is input to

A multiplier 208 multiplies the density data after the black streak from the latch 204 by the output of the counter 205,
The value divided by 63 is output.

The adder 209 adds the outputs of the two multipliers 207 and 208 and sends the result to the selector 209.

At this time, the selector 202 outputs the data from the adder 209 input to the b side in response to the high rise of the erase signal due to the start of the black streak.

The output data from the adder 209 can be expressed by the following equation.

S = k × ((63−1) / 63) + m × (n / 63) where S is the adder output, k is the output of the latch 203 (data of the current line), and m is the output of the latch 204. (Data preceding 64 lines) n is the output of the counter (the number of lines after entering the black streak area (n
= 0 to 63)) As a result, after entering the black streak area, while the erase signal is high, the black streak area is replaced with image data whose density gradually changes as represented by the above equation. Therefore, in the black streak area after the replacement, a sharp change in density does not occur, and an image with a better appearance can be obtained.

<< Embodiment 3 >> In the above-described Embodiment 2, abrupt changes in black streaks do not occur, but the image data to be replaced (the data input to the latch 204 shown in FIG. 14) is black streaks. Since the data is not interpolation data in the area, the final image of the black streak area differs from the original image.

Therefore, in the third embodiment, the image (especially a photographic image) is continuously displayed by averaging the images in the black streak area, and an image with a better appearance is obtained.

FIG. 15 is a block diagram showing a circuit configuration for averaging and replacing black streak areas.

The input image data is branched into three, one of which is input to a 64-line delay circuit 201 as in the second embodiment, is accumulated for 64 lines, and is output with a delay of 64 lines. Another one branched is a one-line delay circuit 21.
1 and the other one is input to a latch 214.

The selector 202 outputs a 64-line delayed image on the a side in the non-black streak normal region. on the other hand,
In the black streak area, as described later, the image data input to the b side is output.

The latch 212 receives a signal indicating that a black streak has been detected from the black streak detection circuit 216, and latches the output from the one-line delay circuit 211. Therefore, the latch 212 latches the image data immediately before the black streak is detected. It should be noted that the black streak detection circuit 216 is provided by the black streak detection block 130 in FIG.
Is the same as

The latch 214 outputs a signal from the black streak detection circuit 216 to the one-line delay circuit 215 and the inverter circuit 2.
The image data immediately after the end of the black streak is latched.

The averaging circuit 213 averages the output from the latch 212 and the output from the latch 214, and
2 to the b input terminal.

The input of the selector 202 is switched by applying a signal from the black streak detecting circuit 216 to the 64-line delay circuit 21.
7 by a signal delayed by 64 lines. Therefore, in the area where the black streak is detected, the image data from the averaging circuit 213 is output from the selector 202. On the other hand, in an area where a black streak is not detected, image data from the 64-line delay circuit 201 is output.

As a result, the portion where the black streak is detected is replaced with a density obtained by averaging the black streak density and the surrounding densities.

Fourth Embodiment In the third embodiment, the average value of the data before and after the end of the black streak area is taken as the replacement data and replaced with the image data of the black streak part. In the fourth embodiment, a weighted average of image data before and after a black streak portion is used as data to be replaced.

As the circuit configuration, the above-described averaging circuit 213 in FIG. 15 is modified to a configuration for obtaining a weighted average as described below.

That is, in the fourth embodiment, the averaging circuit 2
A counter for counting the number of lines in the erase area and a counter for counting a line synchronizing signal during generation of a black streak detection signal after 64 lines are provided in 13.
As for the number of lines counted at this time, N1 is the total number of lines counted in the former erase area, and N is the count number during the generation of the black streak detection signal.

Then, assuming that the replacement data is S, an arithmetic circuit for obtaining weighted average data as shown in the following equation is provided.

S = k × (N1−N) / N + m × N / N1, where k is data before the start of black streaks (data from latch 212 in FIG. 23), and m is data after the end of black streaks. (Data from latch 214 in FIG. 23)
It is.

As a result, the image data of the black streak detection portion in the erasure area is replaced with data obtained by weighted averaging of the preceding and following data, and the density gradually shifts from the leading end to the trailing end of the region where the black streak is detected. It becomes a gradation image.

[0089]

According to the present invention described above, the following effects can be obtained for each claim.

According to the first aspect of the present invention, the black streak is detected and the black streak portion is replaced with the surrounding image data. Good image is obtained. In particular, when reading a document having an image across a binding portion of a book document such as a photo document, a good image without black streaks and no white spots can be obtained.

According to the second aspect of the present invention, the first aspect is provided.
In the configuration described above, upon detecting a black streak, a predetermined threshold value is compared with image data, and when a plurality of pixels higher than the threshold value are consecutively determined to be a black streak, the book document is placed diagonally. Thus, even when black streaks appear obliquely, it is possible to detect the case.

According to the third aspect of the present invention, a second aspect is provided.
In the configuration described above, when detecting black streaks, the threshold value to be set is set to a different value between a photo document and a text document, so that in the case of a photo document, the original document is erased as much as possible when deleting black streaks (Replace with surrounding image data)
In the case of a text document, black streaks can be prevented from being erased.

According to the present invention described in claim 4, according to claim 2
In the configuration described, at the time of black streak detection, as the threshold to be set is gradually changed as it approaches the center of the book document, the central portion of the book document, that is, a portion where black streaks are likely to occur, It is possible to make it easy to detect black streaks, while making it difficult to detect black streaks in a portion away from the center. This allows
It is less likely that a black image near the center of the book document is erroneously detected as a black streak.

According to the fifth aspect of the present invention, a second aspect is provided.
In the configuration described above, when detecting black streaks, the threshold value to be set is determined as an average value of the densities of the read images, and the threshold value is sequentially changed based on the average value as it approaches the center of the book document. It is possible to make it easy to detect black streaks in the central portion of the document, that is, in a portion where black streaks are likely to occur, while making it difficult to detect black streaks in portions far from the center. Moreover,
Even when the book is displaced and inclined, the threshold setting gradually changes in accordance with the displacement. It is less likely that a nearby black image is erroneously detected as a black streak.

According to the present invention, since the density data that changes gradually in the center area set in advance near the binding of the book document is replaced with the density data, the black color generated by the binding of the book document is changed. Since the image of the streak gradually changes in density and replaces the surrounding image, no sharp image density change occurs even when the image data in the center area where black streaks occur is replaced with the surrounding image. Thus, it is possible to obtain a better-looking image.

According to the present invention, the black streak portion detected by the black streak detecting means is replaced with a density obtained by averaging the density of the black streak and its surroundings. It can be replaced with a continuous density with other surrounding images, especially black streaks that occur in images where photos are placed across the binding of the book manuscript,
Images can be erased as if they were continuous.

According to the present invention, the black streak portion detected by the black streak detecting means is replaced with a density obtained by weighting and averaging the density of the black streak and its surroundings. Can be replaced by gradually changing the concentration.

[Brief description of the drawings]

FIG. 1 is an external view of an image reading apparatus to which the present invention is applied.

FIG. 2 is a view showing a state where a book document is placed on the apparatus.

FIG. 3 is a view for explaining an image which has been read by the above-mentioned apparatus and has not been subjected to black streak erasure processing.

FIG. 4 is a block diagram illustrating a configuration of an image processing system of the apparatus.

FIG. 5 is a drawing for explaining a center area (erase area) in the device.

FIG. 6 is a block diagram for explaining a configuration of a center line density adjusting circuit shown in the image processing system.

FIG. 7 is a diagram showing an example of a book document using only characters.

FIG. 8 is a drawing showing an example of a book document in which characters and photographs are mixed.

FIG. 9 is a flowchart showing an operation procedure of the image processing system.

FIG. 10 is a schematic diagram ((a1) and (b1)) for explaining the result of black streak erasure and its density distribution ((a2)).
And (b2)).

FIG. 11 is a view for explaining an image subjected to black streak erasure according to the present invention.

12 is an enlarged view of a black streak portion of the image shown in FIG.

FIG. 13 is a drawing for explaining an image on which black streak erasure has been performed by a conventional method.

FIG. 14 is a block diagram showing a circuit configuration for replacing a black streak region with a gradation in the second embodiment.

FIG. 15 is a block diagram illustrating a circuit configuration for averaging and replacing black streak regions according to the third embodiment.

[Explanation of symbols]

 11: A / D converter, 12: first image processing circuit, 13: center line density adjustment circuit, 14: second image processing circuit, 16: CPU, 30, 216: black streak detection block, 31: comparator, 32 ... Density register, 33 ... N pixel counter, 34 ... Start address register, 35 ... End address register, 36 ... Start address latch, 37 ... End address latch, 38 ... Density conversion signal generation circuit, 39 ... Main scanning address counter, 40: density conversion block, 41: averaging block, 42: adder, 43: divider, 44: first selector, 45: one-line FIFO, 46: second selector, 51: AND circuit, 201: 64 lines Delay circuit, 202: selector, 203, 204, 212, 214: latch, 206, 218: invar Capacitor circuit, 207, 208 ... multiplier, 209 ... adder, (signal) 211, 214 ... one-line delay circuit, 213 ... averaging circuit, 217 ... 64 line delay circuit.

Claims (8)

[Claims] 1. A center area setting means for setting a center area near a binding of a book document; a black stripe detecting means for detecting a black streak caused by a shadow of a binding portion of the book document; Black streak density adjusting means for replacing the density of the black streak portion detected with the density of the black streak periphery; and operating the black streak detecting means only in the center area set by the center area setting means, and detecting the detected black streak. An image reading apparatus, comprising: a control unit that controls the black streak density adjusting unit so as to change the density of the portion to the peripheral density. 2. The black streak detecting means compares a density of a plurality of pixels arranged in a book binding direction of a read original image with a density threshold stored in advance, and a plurality of pixels having the threshold or more are consecutive. 2. The image reading apparatus according to claim 1, wherein it is determined that a black streak occurs. 3. The image reading apparatus according to claim 2, wherein the value of the density threshold is set to be different between a document to be read and a character to be read. 4. The image reading apparatus according to claim 2, wherein the value of the density threshold value is sequentially changed as approaching the center of the book document. 5. The value of the density threshold value according to claim 2, wherein an average value of the densities of the read images is sequentially obtained, and the density threshold value is sequentially changed based on the average value as approaching the center of the book document. Image reading device. 6. A center area setting means for setting a center area near a binding of a book document, and a peripheral image obtained by gradually changing a density of a read image only in the center area set by the center area setting means. And an image density adjusting unit that replaces the image reading device. 7. A center area setting means for setting a center area near a binding portion of a book document, a black streak detecting device for detecting a black streak caused by a shadow of a binding portion of the book document, and the black streaking detecting device. And a black streak density adjusting unit that replaces the detected density of the black streak portion with the density obtained by averaging the density of the black streak portion and the density around the black streak portion. 8. The image reading apparatus according to claim 7, wherein the averaged density is a weighted average of a density of a black streak portion and a density of a periphery of the black streak.