JPH11289455A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that reads originals where no 'defocus' nor 'deformed black pixel' takes place even when a floated part like a file margin of a thick book is in existence in an original in the original reader adopting a contact image scanner CIS system. SOLUTION: In the case of reading a spread book original on an original platen, when a white level read output within a prescribed range is being decreased, it is judged that a file margin of the book original is being read, a reading storage time is extended, the mobile speed of a scanning body is decreased and an edge emphasis processing MTF correction coefficient is emphasized. Furthermore, in the case that a white level read output within a prescribed range increases, it is judged that the file margin of the book original is no longer read, the read storage time and the mobile speed of the scanning body are restored and the MTF correction coefficient is restored to an original weak coefficient by means of a control means 12a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an original reading apparatus such as a facsimile apparatus, a scanner, a digital copying machine, etc., and more particularly, to a contact image sensor (CIS) as shown in FIGS. 5 (a) and 5 (b). In a flat-bed type scanner-type reading system using the scanner 10, even if there is a floating portion A such as a binding margin (binding margin) of a Book document such as a thick book 11, a "defocusing" or " The present invention relates to a document reading apparatus that does not generate “underexposure”.

[0002]

2. Description of the Related Art A method used for a document reading system includes C
Two methods, a "reduced optical reading" method using a CD and an imaging lens, and a "1: 1 image reading" method (hereinafter referred to as "CIS method") using a contact type color image sensor that forms images at 1: 1. There is. FIGS. 1A and 1B show a schematic configuration of a reading system of the above two systems. A reading system of the reduction type optical reading system shown in FIG. 1A includes a document 1a illuminated by a light source (not shown), and an image of the document 1a.
2 is composed of a reduction lens 3 which forms an image. In the figure,
L1 indicates the optical path length of this optical system. FIG.
The reading system of the CIS system shown in FIG. 1B includes a document 1b illuminated by a light source (not shown), and a rod lens 4 for forming an image of the document 1b on a light receiving unit 2 such as a CCD. L2 is the optical path length of this optical system.

In the former reduced optical reading system, the original 1
Since the image of a is formed on the light receiving element surface of the CCD 2 by the reduction lens 3, the optical path length is long, the focal depth is deep, and the reading fluctuation in the height direction is small. On the other hand, in the latter CIS method, the entire unit is thin and can be reduced in size, but on the other hand, because of the structure that forms an image at the same magnification, the optical path length is very short and the depth of focus is extremely shallow,
When the focus position is shifted, the height direction is immediately darkened, and there is a characteristic that reading variation is large.

FIGS. 2A and 2B show a comparison of the depth of focus between the above two methods. 3 (a) and 3 (b) are diagrams comparing the variation characteristics of the read output when the white reference document is raised from the reference position in the height direction, based on changes in the MTF characteristics. The former reduced optical reading method is shown in FIGS.
As shown in (a), since each characteristic such as the depth of focus and the change characteristic of the MTF characteristic is excellent, even a three-dimensional object such as a three-dimensional object or a thick book can be read to some extent, and the character portion can be read. The resolution and the shade of shadow can be reproduced.

However, in the latter CIS system, FIG.
As shown in (b) and FIG. 3 (b), if the target object slightly deviates from the best position, the resolving power is reduced and the reading ability is reduced. Therefore, when reading a floating document such as a binding margin of a thick book, "out of focus" and "blackout" occur, resulting in an image that is very hard to see.
FIG. 4 shows this specific example. In FIG. 4, 5 is “defocus”.
In addition, reference numeral 6 denotes a "blackout" portion. The "blackened portion" wastefully consumes printing toner and the like, which may cause a user's complaint.

As a conventionally used CIS document reading apparatus, for example, an apparatus disclosed in Japanese Patent Application Laid-Open No. 2-109460 is known. This device reads an image information signal in real time, and corrects the rising characteristic of the light source and the output fluctuation by changing the accumulation time and the transport speed of the motor so that the output has a certain appropriate value. .

[0007]

However, when the apparatus disclosed in Japanese Patent Application Laid-Open No. 2-109460 is applied to the reading of a floating portion of a Book document, the light amount can be controlled, but the defocusing is difficult. Therefore, it is impossible to prevent the resolution of the output image in the floating portion of the document from deteriorating.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a "defocusing" or "defocusing" function even when there is a floating portion such as a binding margin of a thick book in a CIS type document reading apparatus. It is an object of the present invention to provide a document reading apparatus which does not cause "blackout".

[0009]

In order to achieve the above-mentioned object, according to the present invention, in a CIS type document reading apparatus, when reading a two-page spread book on a platen, a predetermined number of sheets are read during the scanning of the document surface. When the white background reading output value in the range of the range has decreased, it is determined that the binding margin of the original has been reached, the offset level of the video output from the CIS is increased, the MTF correction coefficient is increased, and If the read output value of the white background has increased, it is determined that it has deviated from the binding margin of the original, the offset level of the video output is reduced, and the MTF correction coefficient is returned to the original weak coefficient. Is provided.

According to the present invention, in a CIS-type original reading apparatus, when reading a double-page spread original on a platen, a white background reading output value within a predetermined range decreases during the original surface scanning. Is determined to be the binding margin of the document, the output is increased by reducing the DUTY during the reset period of the pixel clock, the MTF correction coefficient is increased, and the white background read output value within a predetermined range is increased. Is characterized in that a control means 12b is provided which determines that the document has deviated from the binding margin of the document, lengthens the DUTY during the reset period of the reset pulse to lower the output, and returns the MTF correction coefficient to the original weak coefficient. I do.

According to the present invention, in a CIS-type original reading apparatus, when reading a double-page spread original on an original platen, a predetermined range of white background reading output value decreases during the scanning of the original surface. Is determined to be the binding margin of the document, the A / D conversion timing is delayed, the video output is captured at a high timing, and M
If the TF correction coefficient is increased, and the white background read output value within a predetermined range has increased, it is determined that the original has deviated from the binding margin, and the A / D conversion timing is advanced,
Control means 12c is provided which captures the video output at a low timing and also returns the MTF correction coefficient to the original weak coefficient.

Further, in the present invention, before reading a spread Book original on an original platen, prescanning is performed in advance at a speed higher than a normal reading speed to roughly store an output distribution. When the white background read output value of the range decreases, it is determined that the binding margin of the document has been exceeded, and when the output value has increased, it is determined that the binding margin has deviated from the document binding margin. Then, when actually reading the original, the offset level of the video output is increased in the portion determined to be the binding margin based on the output distribution stored in advance, the MTF correction coefficient is increased, and the binding margin is increased. A control means 12a is provided in which the offset level of the video output is reduced in the portion determined to be out of the portion, and the MTF correction coefficient is returned to the original weak coefficient.

Further, in the present invention, before reading a spread Book original on the original platen, prescanning is performed at a speed higher than a normal reading speed in advance to roughly store an output distribution. When the white background read output value of the range decreases, it is determined that the binding margin of the document has been exceeded, and when the output value has increased, it is determined that the binding margin has deviated from the document binding margin. Then, when actually reading the original, based on the output distribution stored in advance, in the portion determined to be the binding margin, the output is increased by shortening the DUTY of the reset period of the reset pulse, and increasing the MTF correction coefficient. A control unit 12b is provided in which the DUTY in the reset period of the reset pulse is lengthened to reduce the output and the MTF correction coefficient is returned to the original weak coefficient in a portion determined to be stronger and deviated from the binding margin. .

Further, in the present invention, before reading a spread Book original on the original platen, prescanning is performed at a speed higher than a normal reading speed, and the output distribution is roughly stored. When the white background read output value of the range decreases, it is determined that the binding margin of the document has been exceeded, and when the output value has increased, it is determined that the binding margin has deviated from the document binding margin. Then, when actually reading the original, the A / D conversion timing is delayed in the portion determined to be the binding margin based on the output distribution stored in advance, and the video output is taken in at a high timing.
A control unit 12c is provided to increase the TF correction coefficient, advance the A / D conversion timing in a portion determined to be out of the binding margin, take in the video output at a low timing, and return the MTF correction coefficient to the original weak coefficient. It is characterized by having.

[0015]

FIG. 6 is a schematic block diagram of an image reading apparatus according to an embodiment of the present invention, FIG. 7 is a detailed block diagram of an image processing unit 13 thereof, and FIG. An example of a circuit configuration of the adjustment unit 18 will be described.
In FIG. 6, 12a is a CPU having a built-in ROM storing a program for controlling the entire image reading apparatus according to the present embodiment, 13 is an image processing unit having a RAM 14 for forming a working area, Reference numeral 10 denotes the aforementioned CIS, 15 denotes an A / D converter for digitizing the analog voltage output AVout output from the CIS 10, 1
Reference numeral 6 denotes a CIS control unit for controlling the CIS 10;
Denotes an offset control unit that controls an offset adjustment unit 18 that adjusts an offset when amplifying the analog output of the CIS 10.

In FIG. 7, reference numerals 21 and 22 denote correction units for performing corrections of dark output and shading, respectively.
Denotes a peak level detection unit for detecting a peak level, 24 denotes a γ conversion unit for performing γ correction described later, and 25 denotes an MTF correction unit for performing MTF correction represented by edge enhancement. Note that V1i to V4i indicate voltage output signals from the above-described units. In an offset adjusting section (offset level adjusting circuit) 18 whose details are shown in FIG.
p1 is an operational amplifier, SW01 to SW03 are switches for opening and closing lines including resistors R01 to R03 arranged in parallel, Rg0 and Rg are reference resistors, and Vcc is a power supply. The switches SW01 to SW03 are controlled by a control signal from the offset control unit 17 as described later.

The offset adjuster 18 amplifies the raw analog video output AVin of the CIS 10 and outputs the amplified output AVout.
Get. The A / D converter 15 performs A / D conversion on the analog video output AVout, and then converts the analog video output AVout into a subsequent image processing unit 13.
Hand over to In the image processing unit 13, as shown in FIG.
The digital image raw data V1i is corrected for variations in each pixel by a dark output correction unit 21 and a shading correction unit 22 (V2i), and then passed to a peak level detection unit 23, where the peak level detection unit 23 outputs a certain range in the main scanning direction. Is detected and sent to the CPU 12a.

In accordance with the detected peak value, the CPU 12a operates the offset adjusting section 18 to control the aforementioned CIS1.
In order to adjust the offset level when amplifying the analog output of “0”, a command is sent to the offset control unit 17, and based on this, the offset control unit 17 uses the offset level adjustment switches SW 01 to SW in the offset adjustment unit 18.
Change the 03 on / off control signal. This control is performed, for example, with reference to a conversion table stored in a ROM built in the CPU 12a. Further, after gamma conversion (V3i), edge enhancement processing (MTF correction) and the like are performed to obtain an image information signal V4i.

Since the peak value does not fluctuate when the background portion of the document is being read, the offset level of the raw video signal AVin output from the CIS 10 is equal to the offset level of SW01 to SW03 in the circuit configuration shown in FIG. Turn on. On the other hand, when reading a three-dimensional object having unevenness such as a Book original, the peak value fluctuates. Therefore, the switches SW01 to SW03 are selectively turned on / off according to the fluctuation, and the offset level is gradually changed. . When the reading of the floating document begins, the peak level detector detects that the output V2i has dropped. Therefore, the switches SW01 to SW03 are switched so as to increase the offset level, thereby preventing the level from dropping.
At the same time, an output V4i in which edges such as a character portion are emphasized is obtained by applying a stronger MTF correction than usual.

The operation will be described below with reference to the flowchart shown in FIG. If the output V2i of the shading correction unit 22 is not different from the read output of the previous line during reading (steps 31 to 33), it is determined that the document is in close contact with the contact glass. All are turned on, the offset level is kept constant, and only normal MTF correction is performed (steps 34 and 35), and the process continues to the next line. If the output V2i of the shading correction unit 22 is smaller than the previous line (steps 31 and 32), it is determined that the document is floating. Therefore, the offset level is increased according to the decrease of V2i, and the MTF correction parameter is further increased. The correction is performed intensified (steps 37 to 38).

When the CIS 10 deviates from the floating portion and reaches the portion in close contact with the contact glass, the output V2i of the shading correction section 22 rises from the peak value of the previous line (steps 31 to 33). The offset level is lowered and the MTF correction coefficient is also weakened to return to a normal value (steps 39 to 40). Note that the γ conversion shown in the figure is a process of converting image information that changes linearly with respect to reflectance into a level that is linear with respect to density. According to the above-described embodiment, it is possible to obtain a document reading apparatus that does not generate “defocus” or “blackout” even when there is a floating portion such as a binding margin of a thick book.

FIG. 10 is a schematic block diagram of an image reading apparatus according to another embodiment of the present invention, FIG. 11 is an operation timing chart of the clock waveform adjusting unit 19 in FIG. 10, and FIG. FIG. 13 is an enlarged explanatory diagram of the video waveform and the CLK waveform, and FIG. 13 is an operation flowchart thereof. 10, symbols 10 and 13 to 16 denote the same components as those shown in FIG. 6, and 12b denotes a ROM storing a program for controlling the entire image reading apparatus according to the present embodiment. Built-in CPU,
Reference numeral 19 denotes a clock waveform adjusting unit 19 for controlling the output of the CIS 10. In the clock waveform adjusting unit 19 of the image reading apparatus according to the present embodiment, a CPU
The reset period is controlled based on the pixel clock (reset pulse) sent from the 12b via the CIS control unit 16 to adjust the video output AVin.

That is, in the A / D converter 15, the CIS
After the A / D conversion of the 10 raw analog video outputs AVin, the data is transferred to the image processing unit 13 to obtain digital image raw data V1i. The image processing unit 13 corrects the variation of each pixel of the obtained digital image raw data V1i by the dark output correction unit 21 and the shading correction unit 22 (V2i), and then passes the corrected data to the peak level detection unit 23. At 23, a peak value within a certain range in the main scanning direction is detected. The CPU 12b varies the reset period via the clock waveform adjusting unit 19 according to the detected peak value, and changes the video output. Further, after gamma conversion (V3i), edge enhancement processing (MTF correction) is performed to obtain an image information signal V4i.

More specifically, when the background portion of the document is being read, there is no change in the peak value, so that the reset (H level) period of the pixel clock is set to normal (maximum). On the other hand, when reading a three-dimensional object having irregularities such as a Book original, the peak value fluctuates. Therefore, the reset (H level) period is narrowed according to the fluctuation, and the video output is changed. When the reading of the floating document begins, the peak level detector 23 detects a drop in the output V2i, so that the reset period is narrowed to prevent the level from dropping. At the same time, an output V4i in which edges such as a character portion are emphasized is obtained by performing MTF correction stronger than usual.

The operation will be described below with reference to the flowchart shown in FIG. If the output V2i of the shading correction unit 22 is not different from the read output of the previous line during reading (steps 31 to 33), it is determined that the document is in close contact with the contact glass, so that the reset period is maximized. Video output is obtained.
Only correction is performed (steps 34 and 35), and the process continues to the next line. If the output V2i of the shading correction unit 22 is smaller than the previous line (steps 31 and 32), it is determined that the document is floating. Therefore, the reset period is narrowed according to the decrease of V2i, and the MTF correction parameter is further reduced. A stronger correction is performed (steps 41, 34, 38) to obtain an output V4i in which edges are emphasized.

Eventually, when the CIS 10 deviates from the floating portion and reaches the portion in contact with the contact glass, the output V2i of the shading correction unit 22 rises above the peak value of the previous line (steps 31 to 33). Accordingly, the reset period is extended, and the MTF correction coefficient is also weakened to return to the normal value (steps 42, 34, 40). According to the present embodiment as well, it is possible to realize a document reading apparatus that does not generate “defocus” or “blackout” even if there is a floating portion such as a binding margin of a thick book.

FIG. 14 is a schematic block diagram of an image reading apparatus according to another embodiment of the present invention. FIG. 15 is an operation timing chart of the A / D timing adjustment section 20 in FIG. 2 shows an operation flowchart thereof. In FIG. 14, symbols 10 and 13-1
6 shows the same components as shown in FIG.
Is a C containing a ROM storing a program for controlling the entire image reading apparatus according to the present embodiment.
Reference numeral 20 denotes a PU and an A / D timing adjustment unit for controlling the output of the A / D conversion unit 15. The A / D timing adjustment section 20 of the image reading apparatus according to the present embodiment controls the A / D conversion timing based on the A / D conversion timing control signal sent from the CPU 12c, and obtains the video output AVin.

That is, in the A / D converter 15, the CIS
After the A / D conversion of the 10 raw analog video outputs AVin, the data is transferred to the image processing unit 13 to obtain digital image raw data V1i. The image processing unit 13 corrects the variation of each pixel of the obtained digital image raw data V1i by the dark output correction unit 21 and the shading correction unit 22 (V2i), and then passes the corrected data to the peak level detection unit 23. At 23, a peak value within a certain range in the main scanning direction is detected. The CPU 12c generates an A / D conversion timing control signal according to the detected peak value, and controls the signal capture time. Furthermore, after γ conversion (V3i),
The image information signal V4i is subjected to edge enhancement processing (MTF correction).
Get.

More specifically, when the background portion of the document is read, there is no fluctuation in the peak value, so that the image information is fetched at the position where the A / D conversion timing is the earliest (short wave line portion). . On the other hand, when reading a three-dimensional object having irregularities such as a Book original, the peak value fluctuates, so that the timing of A / D conversion is delayed according to the fluctuation. When the reading of the floating document is started, the output V2i is detected by the peak level detection unit.
Is detected, the timing of A / D conversion is delayed to prevent a level drop. At the same time, an output V4i in which edges such as a character portion are emphasized is obtained by applying a stronger MTF correction than usual.

The operation will be described below with reference to the flowchart shown in FIG. During reading, if the output V2i of the shading correction unit 22 is not different from the reading output of the previous line (steps 31 to 33), it is determined that the document is in close contact with the contact glass, and the normal A / D At the timing of conversion, a sufficient digital video output is obtained, and only normal MTF correction is performed (step 3).
4, 35) and continues to the next line. Shading correction unit 2
2 is smaller than the previous line (steps 31 and 32), it is determined that the document is floating.
The timing of the A / D conversion is delayed in accordance with the fall of V2i, and the MTF correction parameter is further strengthened for correction (steps 51, 34, 38), and the edge-enhanced output V4i.
Get.

Eventually, when the CIS 10 deviates from the floating portion and reaches the portion in close contact with the contact glass, the output V2i of the shading correction section 22 rises above the peak value of the previous line (steps 31 to 33). Accordingly, the timing of A / D conversion is advanced, and the MTF correction coefficient is also weakened and returned to a normal value (steps 52, 34 and 40). According to the present embodiment as well, it is possible to realize a document reading apparatus that does not generate “defocus” or “blackout” even if there is a floating portion such as a binding margin of a thick book.

FIGS. 17A and 17B show an operation flowchart of an image reading apparatus according to still another embodiment of the present invention. The schematic configuration of the device is the same as that of the first embodiment, and only the content of control by the CPU 12a is different. In the image reading apparatus according to the present embodiment, a rough output distribution of a reading target is stored in the memory (RAM 14) by performing a pre-scan as shown in FIG. . At this time, since detailed image information is not required, the line density may be coarse and there is no problem, and reading may be performed at a speed several times higher than a normal scanning speed (steps 61 and 62). From the collected output distribution information,
The line having a low output value is determined to be a floating portion of the document, and the setting of each parameter during the actual reading of the document, which is the next step, is changed (step 63).

Since the peak value of the output distribution does not fluctuate when the background portion of the document is read, the offset level of the video signal is fixed in a minimum state (SW01 to SW03 are all on). On the other hand, when reading a three-dimensional object having irregularities such as a Bock original, the peak value fluctuates. Therefore, the offset level is increased according to the fluctuation estimated from the distribution information, and the A / D output is compared with the output AVout. After a series of processing such as conversion, an MTF correction stronger than usual is performed to obtain an output V4i in which edges such as character portions are emphasized. Actual operation,
Hereinafter, description will be given according to the flowchart of FIG.
From the document output distribution information captured during prescan, V
If 2i is not different from the reading output of the previous line, it is determined that the document is in close contact with the contact glass (steps 71 to 72), and after γ conversion, only normal MTF correction is performed (step 34, 35) Continue to the next line.

In a region where the output distribution is low, it is determined that the document is floating (steps 71 to 72), so that the offset level is increased in accordance with the decrease of V2i (step 3).
7) Further, the MTF correction parameter is further enhanced to perform the correction (step 38), and an output V4i in which the edge is emphasized is obtained.
Thereafter, in the region where the power distribution is high, it is determined that the CIS 10 has deviated from the floating portion and has reached the portion in close contact with the contact glass. Therefore, the offset level is reduced according to the rise, and the MTF correction coefficient is also weakened. (Steps 71 to 72, 34, 35). According to the above-described embodiment, it is possible to realize a document reading apparatus that does not generate “defocus” or “blackout” even when there is a floating portion such as a binding margin of a thick book.

FIGS. 18A and 18B show an operation flowchart of an image reading apparatus according to still another embodiment of the present invention. The schematic configuration of the device is the same as that of the second embodiment, and only the content of the control by the CPU 12b is different. In the image reading apparatus according to the present embodiment, a rough output distribution to be read is stored in a memory (RAM 14) by performing a pre-scan as shown in FIG. . At this time, since detailed image information is not required, the line density may be coarse and there is no problem, and reading may be performed at a speed several times higher than a normal scanning speed (steps 61 and 62). From the collected output distribution information,
The line having a low output value is determined to be a floating portion of the document, and the setting of each parameter during the actual reading of the document, which is the next step, is changed (step 63).

Since the peak value of the output distribution does not fluctuate when the background portion of the document is read, the reset (H level) period of the pixel clock is set to a normal (maximum) period and the video output is kept constant. On the other hand, when reading a three-dimensional object having irregularities such as a Book original, the peak value fluctuates. Therefore, the reset (H level) period is narrowed according to the fluctuation estimated from the distribution information, and the video output is changed. That is,
When the reading of the floating document begins, the peak level detector detects a drop in the output V2i.
By increasing the output, an analog video signal AVin is obtained.
After a series of processing such as A / D conversion, the output V4i in which edges such as a character portion are emphasized is obtained by applying MTF correction stronger than usual.

The actual operation will be described below with reference to the flowchart of FIG. If V2i is not different from the read output of the previous line from the document output distribution information captured during the prescan, it is determined that the document is in close contact with the contact glass (steps 71 to 72).
After the γ conversion, only normal MTF correction is performed (step 3).
4, 35) and continues to the next line. In the region where the output distribution is low, it is determined that the document is floating. Therefore, the reset period is narrowed according to the decrease of V2i (step 41), and M
The correction is performed by strengthening the TF correction parameter (step 3
8) Obtain an output V4i in which edges are emphasized.

Thereafter, in a region where the output distribution is high, CI
Since it is determined that S10 has deviated from the floating portion and has reached the portion in close contact with the contact glass, the reset period is extended according to the rise, and the MTF correction coefficient is also weakened to return to a normal value (step 71). ~ 72, 34, 35).
According to the above-described embodiment, it is possible to realize a document reading apparatus that does not generate “defocus” or “blackout” even when there is a floating portion such as a binding margin of a thick book.

FIGS. 19A and 19B show an operation flowchart of an image reading apparatus according to still another embodiment of the present invention. The schematic configuration of the device is the same as that of the third embodiment, and only the content of control by the CPU 12c is different. In the image reading apparatus according to the present embodiment, a rough output distribution of a reading target is stored in a memory (RAM 14) by performing a pre-scan as shown in FIG. . At this time, since detailed image information is not required, the line density may be coarse and there is no problem, and reading may be performed at a speed several times higher than a normal scanning speed (steps 61 and 62). From the collected output distribution information,
The line having a low output value is determined to be a floating portion of the document, and the setting of each parameter during the actual reading of the document, which is the next step, is changed (step 63).

When the background portion of the document is being read, there is no change in the peak value of the output distribution.
The digital image information output after D conversion is obtained. Meanwhile, Book
When reading a three-dimensional object having irregularities such as a manuscript, the peak value fluctuates. Therefore, the timing of A / D conversion is delayed according to the fluctuation estimated from the distribution information to obtain image information AVin having a high output. . After A / D conversion and a series of processing of the obtained image information AVin, an MTF correction stronger than usual is performed to obtain an output V4i in which edges of a character portion and the like are emphasized.

The operation will be described below with reference to the flowchart shown in FIG. If V2i is not different from the read output of the previous line from the document output distribution information captured at the time of the prescan, it is determined that the document is in close contact with the contact glass (steps 71 to 7).
2) After γ conversion, only normal MTF correction is performed (steps 34 and 35), and the process continues to the next line. In an area where the output distribution is low, it is determined that the document is floating (steps 71 to 71).
72) Therefore, the timing of the A / D conversion is delayed in accordance with the fall of V2i (step 51), and the MTF correction parameter is further enhanced to perform the correction (step 38) to obtain the output V4i with the edge emphasized.

Thereafter, in a region where the output distribution is high, CI
Since it is determined that S10 has deviated from the floating portion and has reached the portion in close contact with the contact glass, the timing of A / D conversion is reduced according to the rise, and the MTF correction coefficient is also weakened to return to a normal value. Go (Steps 71 to 72, 3
4, 35). According to the present embodiment as well, it is possible to realize a document reading apparatus that does not generate “defocus” or “blackout” even if there is a floating portion such as a binding margin of a thick book.

It is to be noted that each of the above embodiments is an embodiment of the present invention, and it is needless to say that the present invention should not be limited to these embodiments. For example, the determination of the floating area based on the pre-scan data shown in FIGS.
That is, the evaluation is not limited to one-stage evaluation, but may be performed in a plurality of stages. In this case, a countermeasure corresponding to each stage is prepared.

[0044]

As described above in detail, according to the present invention, even if there is a floating portion such as a binding margin of a thick book in a CIS type document reading apparatus, "defocusing" can be achieved.
And an image reading apparatus which does not cause blackout or "blackout" and can obtain high image quality can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a comparison between both “reduced optical reading” and “CIS”.

FIG. 2 is a schematic diagram illustrating a comparison between output fluctuations in the height direction of both “reduced optical reading” and “CIS”.

FIG. 3 is a schematic diagram showing a comparison of MTF characteristic fluctuation in the height direction of both the “reduced optical reading” and the “CIS”.

FIG. 4 is a diagram illustrating an example of an output image (enlargement) of a Book document floating portion read by the “CIS” method.

FIG. 5 is a diagram showing a schematic configuration of a CIS-equipped flatbed type scanner type reading system.

FIG. 6 is a block diagram illustrating a schematic configuration of an image reading device according to an embodiment of the present invention.

FIG. 7 is a block diagram showing details of an image processing unit 13 in FIG. 6;

FIG. 8 is a diagram illustrating a circuit configuration example of an offset adjusting unit 18 in FIG. 6;

FIG. 9 is an operation flowchart according to the embodiment shown in FIG. 6;

FIG. 10 is a block diagram illustrating a schematic configuration of an image reading apparatus according to another embodiment of the present invention.

11 is an operation timing chart of the clock waveform adjusting unit 19 in FIG.

FIG. 12 is an enlarged explanatory diagram of a video waveform / CLK waveform.

FIG. 13 is an operation flowchart according to the embodiment shown in FIG. 10;

FIG. 14 is a block diagram illustrating a schematic configuration of an image reading apparatus according to another embodiment of the present invention.

FIG. 15 shows an A / D conversion timing variable section 20 shown in FIG.
3 is an operation timing chart (enlarged view) of FIG.

FIG. 16 is an operation flowchart according to the embodiment shown in FIG. 10;

FIG. 17 is a flowchart illustrating an operation of an image reading apparatus according to another embodiment of the present invention.

FIG. 18 is a flowchart illustrating an operation of an image reading apparatus according to still another embodiment of the present invention.

FIG. 19 is a flowchart illustrating an operation of an image reading apparatus according to still another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 CIS 11 Book original 12a, 12b, 12c CPU with built-in ROM 13 Image processing unit 14 RAM 15 A / D conversion unit 16 CIS control unit 17 Offset control unit 18 Offset adjustment unit 19 Clock waveform adjustment unit 20 A / D timing adjustment Unit 21 dark output correction unit 22 shading correction unit 23 peak level detection unit 24 γ conversion unit 25 MTF correction unit

Claims (6)

[Claims] In a CIS type document reading apparatus, when reading a spread book on a platen, if a white background reading output value in a predetermined range decreases during the scanning of the document surface, the document is read. Judgment is made for the binding margin, the offset level of the video output from the CIS is increased, the MTF correction coefficient is increased, and if the white background reading output value in a predetermined range is increasing, the binding margin of the original is increased. An image reading apparatus, comprising: a control unit that determines that the video output has deviated from the portion, lowers the offset level of the video output, and returns the MTF correction coefficient to the original weak coefficient. 2. A CIS type document reading apparatus, wherein when reading a double-page spread book document on a document table, if a white background read output value within a predetermined range decreases during the document surface scanning, the document is read. Judgment is made for the binding margin, the duty is reduced during the pixel clock reset period, the output is increased, the MTF correction coefficient is increased, and if the white background reading output value within a predetermined range is increasing, the binding of the original is stopped. An image reading apparatus comprising: control means for judging that the duty has deviated from the margin portion, increasing the DUTY during the reset period of the reset pulse to lower the output, and returning the MTF correction coefficient to the original weak coefficient. 3. In a CIS type document reading apparatus, when reading a double-page spread book on a platen, if a white background reading output value within a predetermined range decreases during the scanning of the document surface, the document is read. Judge as the binding margin, delay the A / D conversion timing, capture at high video output timing, and increase the MTF correction coefficient,
Also, when the white background read output value in the predetermined range has increased, it is determined that the original has deviated from the binding margin, and
An image reading apparatus, comprising: control means for advancing A / D conversion timing, capturing video output at a low timing, and returning an MTF correction coefficient to an original weak coefficient. 4. In a CIS type document reading apparatus, before reading a spread Book document on a platen, prescanning is performed at a speed higher than a normal reading speed to roughly store an output distribution, and a predetermined distribution is stored. When the white background reading output value of the range decreases, it is determined that the binding margin of the document has been exceeded, and when the output value has increased, it is determined that it has deviated from the binding margin of the document, and the document is actually read. At that time, based on the output distribution stored in advance, the offset level of the video output from the CIS is increased in the portion determined to be the binding margin, and the MTF correction coefficient is increased to deviate from the binding margin. In the determined part, the offset level of the video output is lowered, and MT
An image reading apparatus, further comprising control means for returning an F correction coefficient to an original weak coefficient. 5. In a CIS type document reading apparatus, before reading a spread Book document on a platen, prescanning is performed at a speed higher than a normal reading speed to roughly store an output distribution, and a predetermined distribution is stored. When the white background reading output value of the range decreases, it is determined that the binding margin of the document has been exceeded, and when the output value has increased, it is determined that it has deviated from the binding margin of the document, and the document is actually read. In this case, based on the output distribution stored in advance, in a portion determined to be a binding margin, the duty is reduced during the reset period of the reset pulse to increase the output, the MTF correction coefficient is increased, and a predetermined range is set. When the white background read output value of the document has increased, it is determined that the document has deviated from the binding margin of the document, the DUTY during the reset period of the reset pulse is lengthened, and the output is lowered, and An image reading apparatus comprising a control unit for returning an MTF correction coefficient to an original weak coefficient. 6. In a CIS type document reading apparatus, a prescan is performed in advance at a speed higher than a normal reading speed to roughly store an output distribution before reading a spread book document on a document table, and a predetermined distribution is stored. When the white background reading output value of the range decreases, it is determined that the binding margin of the document has been exceeded, and when the output value has increased, it is determined that it has deviated from the binding margin of the document, and the document is actually read. In this case, based on the output distribution stored in advance, the A / D conversion timing is delayed in the portion determined to be the binding margin to capture the video output at a high timing, and the MTF correction coefficient is increased. If the white background reading output value in the predetermined range has increased, it is determined that the document has deviated from the binding margin of the original, the A / D conversion timing is advanced, and the video output is low. Ming and MT
An image reading apparatus, further comprising control means for returning an F correction coefficient to an original weak coefficient.