JPH09116753A - Image reading device - Google Patents

Abstract

The present invention relates to an image reading apparatus, and an object of the present invention is to obtain an image which is not affected by stains on the backing and which has no back reflection even on a thin paper document. An image reading apparatus of the present invention is configured as follows by reading image data corresponding to a surface area of a backing before reading a document image. (1) Subtract the backing image data from the original image data. (2) The light transmittance of the document medium is obtained from the reference mark, and the image data of the document is converted into the background level based on the image data of the backing. (3) The backing image data is multiplied by the transmittance and subtracted from the original image data. (4) Convert the original image data below the threshold to the background level. (5) The image data after the processes of (1) to (4) is developed into a matrix and the central pixel is determined to correct it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input technique, and more particularly to an image reading device using a backing.

[0002]

2. Description of the Related Art With the progress of paperless offices in recent years, as a means for inputting a large amount of documents into an optical disk device or the like, there is an increasing demand for a document feeding type image reading device capable of inputting all documents at once. ing. Further, it is troublesome to input the originals one by one even for a small amount for personal use, and there is a demand for an image reading apparatus capable of inputting the originals collectively and having excellent read image quality.

In a document feeding type image reading apparatus, a rotating member called a backing for pushing a document from the back to the image sensor side is used also as a sheet pressing for document feeding. In the original stationary image reading apparatus, a flat plate member is used for the backing. In both cases, the backing becomes dirty as it is repeatedly used, but this dirt may be seen through on a document of thin paper thickness.

Conventionally, a technique for removing the back slip has been devised because the back slip that is visible on the back side of the original printed on both sides makes the image quality worse. A technique of pre-scanning the background of an original to obtain color correction data like a color copying machine and removing the background fog and back fog (for example, the background fog removal and background removal method of the image forming apparatus of JP-A-5-207280), , A technique for maintaining the image quality by detecting a change in the light amount by reading the white reference on the backing surface or the home position between document readings (for example, Japanese Patent Laid-Open No. 3-0429).
62 white reference reading method in an image reading apparatus) is known.

[0005]

In a conventional image reading apparatus such as an image scanner or a facsimile, when reading a thin paper document or a document having a high transmittance, the dirt on the backing and the back-shifting of the double-sided document are removed. There was a problem of reading it as it was.

In view of the above points, the present invention provides an image reading apparatus which is free from the influence of stains on the backing even for an original having a high transmittance and is capable of obtaining a clear image without back-back even on an original made of thin paper. The purpose is to provide.

[0007]

The above-mentioned problems can be solved by an image reading apparatus configured as follows. (1) The image reading device of the present invention stores the backing image data of the backing of the document provided facing the image reading element in the storage means.

By subtracting the backing image data from the image data read from the original at the time of reading the original,
The effect of dirt on the surface of the backing is removed from the image data of the original.

(2) As another means, the image reading apparatus of the present invention forms a reference mark in the main scanning direction of the backing of the document provided facing the image reading element, and the backing is performed as in (1). The backing image data for the surface area and the mark portion image data of the reference mark portion are read and stored in the storage means.

The light transmittance of the manuscript medium is calculated from the image data of the transmissive mark portion which has permeated the manuscript at the time of reading the manuscript and the image data of the mark portion. By converting the image data of the original corresponding to the portion that does not exceed the background level of the original, the influence of dirt on the surface of the rotating body is removed from the image data of the original.

(3) As still another means, the image reading apparatus of the present invention forms a reference mark in the main scanning direction on the backing as in (2), and a rotary member image corresponding to the surface area of the backing is read before reading an original. The data and the mark portion image data of the reference mark portion are read and stored in the storage means.

Similarly to (2), the light transmittance of the original medium is calculated at the time of reading the original, but the rotary image data is multiplied by the transmittance, and the multiplication result is obtained from the image data read from the original. By subtracting, the influence of dirt on the surface of the rotating body is removed from the image data of the document with higher accuracy than in (2).

(4) As another means, the image reading apparatus of the present invention is
Similar to (3), a reference mark is formed on the backing in the main scanning direction, and the image data of the mark portion of the reference mark portion is read before reading the original and stored in the storage means.

The light transmittance of the original medium is calculated from the image data of the transparent mark portion which has passed through the original at the time of reading the original and the image data of the mark portion, and the transmittance is used as a threshold value to correspond to a portion which does not exceed the threshold value. By converting the image data of the original document to the background level of the original document, the backside of the original document is removed from the image data of the original document along with the influence of dirt on the surface of the rotating body.

(5) In the image reading apparatus described in (1) to (4), the influence of dirt on the surface of the rotating body and the backside portion of the original are removed, but the original image data exists in that portion. If so, this image data may also be removed.

Therefore, the image reading apparatus of the present invention includes (1) to (4)
The image reading device described above, further comprising: a binarization circuit that binarizes the corrected multivalued image data, and a register that develops the binarized image data into a matrix.
By determining the center pixel from the matrix,
Correct the image data that is missing in the image data processing described in (1) to (4) and restore it.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiments of the present invention, an image reading apparatus with a document feeding mechanism will be described. FIG. 1 is a diagram of a rotating body that is an auxiliary unit for conveying a document in an example of an embodiment of the present invention. This rotator also serves as a backing for the original document, and functions to hold down the sheet when the original document is conveyed. In FIG. 1, 1 is a reference mark and 2 is a rotating body. The reference mark 1 serves as a reference for recognizing that the rotating body 2 makes one rotation. In the embodiment of the present invention, the starting point is set when the image of the rotating body is read. The reference mark 1 has a line length (line width) of 5 mm in the width direction of the rotating body 2, that is, the main scanning direction.
A line length (line thickness) of about 1 millimeter in the sub-scanning direction is sufficient.

The rotator 2 rotates during document transportation, and the document passes over it. Further, an image sensor is located on it, and for example, an A4 portrait original can be read if the rotary body 2 rotates several times.

As described above, the rotating body 2 presses the sheet against the image sensor side as an auxiliary means for conveying the original, and presses the original from the back side, so that it serves as a so-called backing for preventing back slip. There is. Therefore, the surface of the rotating body 2 is generally white or gray.

In the embodiment of the present invention, the rotary member 2 is rotated at least once before the document is read, and the image data on the surface of the rotary member 2 is stored in the storage means, that is, the memory. However, when reading originals of the same size continuously, it is not always necessary to execute every page.

FIG. 2 is a block diagram of the image reading apparatus according to the first embodiment of the present invention. Reference numerals 2, 3, 4, 5 and 60 in FIG. 2 denote a rotating body, an image sensor, an amplifier, an AD converter, and an original in this order. Reference numeral 10 in FIG. 2 is a data processing unit, which includes a reference mark detection unit 6, a memory address generation unit 7, and a memory 8. Reference numeral 9 in the data processing unit 10 is a subtraction unit that subtracts the image data of the surface of the rotating body 2 stored in the memory 8 from the image data read from the document.

The processing when the monochrome scanner is taken as an example in the embodiment of the present invention will be described with reference to FIG. In FIG. 3, the horizontal axis represents the data position. That is, the horizontal axes x and y represent the positions using both the main scanning direction x and the sub scanning direction y.
In the vertical axis of FIG. 3, the upper two represent the potential v, and the lower two represent the white level and the lower black level after binarization. In a monochrome scanner, the slice level is a threshold value for binarizing white or black, and can be set variably in general.

In FIG. 3, A shows image data obtained by reading a document, and B shows image data on the surface of the rotating body 2 stored in the memory. The data B has stains such that a black level is created in one place each time the rotating body makes one revolution.
There is 1 dot of original data in this 1 round. A black level of 1 dot appears periodically in both the data A and the data B due to the dirt on the rotor 2. In the upper left part of FIG. 3, the mark □ shows the original black level of the original without the influence of the backing, and the mark ○ shows the influence of the stain on the backing.

The upper right diagram of FIG. 3 shows that as a result of the subtraction of AB, stains can be removed and only original data can be obtained. The lower right diagram after binarization shows that the stain can be removed.

Next, the reference mark detector 6 will be described. The reference mark detection unit 6 detects the reference mark and notifies the address generation unit of the memory of the reference mark detection signal.
FIG. 4 shows a circuit diagram of the reference mark detector, and FIG. 5 shows a timing chart thereof.

C, D, E, and F in FIGS. 4 and 5 are the reference mark start address, the reference mark end address, the reference mark width, and the reference mark length in the sub-scanning direction (line thickness).
And their values are preset.

4 and FIG. 5 correspond to each other. When FIG. 4 and FIG. 5 are turned on, the reference mark start address is detected, and when is turned off, the reference mark end address is detected. Indicates that Is the logical product of and. That is, the reference mark width E between C and D is shown in the upper diagram of FIG.

During this period, if the reference mark is present, is turned on and is turned on. In FIG. 5, -2 shows the case where the reference mark exists, and -1 shows the case where the reference mark does not exist. HGATE and VGATE in FIG. 5 are signals that are turned on during the reading operation in the main scanning direction and the sub-scanning direction, respectively. (N) and (N + 1) indicate the Nth line and the N + 1th line, respectively. The upper diagram of FIG. 5 shows a mode of reference mark detection for one line, and the lower diagram of FIG. 5 shows a mode of reference mark detection for a plurality of lines.

4 and 5 show the state after the detection of the reference mark in each line. Figures 4 and 5 show the count values of.
In this example, it is assumed that the reference mark is 2 lines and the value of F is 2. Is turned on by counting twice, and FIG. 5 shows the image data area of the rotating body 2. The reference mark detection signal is obtained from and. The reference mark detection signal is supplied to the memory address generator 7.

The memory address generation unit 7 generates addresses for reading and writing the rotating body image data in the memory and for reading the original image data and reading the rotating body image data from the memory. FIG. 6 shows a circuit diagram of the memory address generator 7, and FIG. 7 shows a timing chart thereof. The V clock and the 1/4 V clock in FIGS. 6 and 7 are signals while the VGATE signal in FIG. 5 is valid. The address of the image data of the rotator is reset by the reference mark detection signal of FIGS. 4 and 5, and is advanced by the V clock while the H gate signal is valid.

The read signal (OE) and the write signal (WE) corresponding to the address of the image data of the rotating body are obtained from the signals -1 and -2 obtained from the V clock and the 1/4 V clock. The address of the image data of the rotating body and the read signal (OE) and the write signal (WE) corresponding thereto are supplied to the memory 8. A write signal (WE) is sent when reading the image data of the rotating body 2, and a read signal (OE) is sent when reading the image data of the document.

In this way, the rotary member 2 is read before the document is read.
The image data of the rotating body can be stored in the memory 8 at the time of reading the original, and the image data of the rotating body can be read from the memory 8 from the image data being read at the time of reading the original by the address of the portion corresponding to the image data. Subtract the image data of the rotating body.

FIG. 8 shows another embodiment of the rotating body according to the present invention. The reference mark 1 added to the rotating body 2 is linearly formed. The reference mark 1 serves as a reference for recognizing that the rotating body 2 makes one rotation, and also serves as data for calculating the light transmittance of the original medium. The line length of the reference mark 1 is long enough to cover the width of the original medium in the main scanning direction and the reference position can be recognized, and the line width is about 1 mm.

The rotating body 2 of FIG. 8 is the same as the rotating body 2 of FIG. 1 except that the reference mark is formed in a straight line. FIG.
The density of the color of the reference mark 1 of the rotating body 2 is data for calculating the light transmittance. When the color of the reference mark 1 is seen through the original medium, the color is removed as stains on the rotating body 2 and as back-side printing of the double-sided printed original.

FIG. 9 is a diagram for explaining the light transmittance of the embodiment of the present invention. In FIG. 9, the horizontal axis represents the main scanning direction x, the vertical axis represents the potential v, and the upper side represents the white level and the lower side represents the black level. 9A shows the reference mark position data at the time of reading the original, and B shows the reference mark data read when the original is not read or before the original is read.

In the embodiment of the present invention, the maximum value of A (Ama
x) and the value of B at the maximum value of A (Ba), the light transmittance (T) is obtained. (T = Ba / Amax) Here,
Since the original image data may exist on the position of the reference mark, the denominator is set to the maximum value of A.

Three embodiments of image processing using the light transmittance (T), that is, data conversion (1) and (2) and using a multiplication circuit will be described with reference to the drawings.
FIG. 10 is a diagram for explaining the data conversion (1) for converting the image data of the original so as to remove the influence of the backing. The upper diagram of FIG. 10 shows the data before conversion, and the lower diagram shows the data after conversion. The table in the middle shows the process of data conversion (1). In FIG. 10, the horizontal axes x and y are the main scanning direction x and the sub scanning direction y.
Data positions using both are shown. The vertical axis represents the potential v, the upper side represents the white level, and the lower side represents the black level. The slice level is a threshold for binarizing white or black in a monochrome scanner.

A is image data of the original at the time of reading the original, and B is image data of the rotary body 2 read when the rotary body 2 is rotated once before reading the original. In the area P, there is the original black level data of A, and the base level (Bs) of the rotating body 2 without the B reference mark 1 and dirt is shown.
A in the area Q is the image data of the reference mark 1 read through the original, and there is Amax in this, and the image data of the original is shifted to black due to the influence of the density of the reference mark. The area B in the area Q is the image data of the reference mark 1 read in advance. The region R is contaminated by the rotating body 2 and is affected by the contamination and is shifted to black. It can be assumed that the dirt on the rotating body 2 generally does not exceed the density of the reference mark.

The light transmittance T is obtained from Ba read from the memory 8 at the positions corresponding to Amax and Amax in the document image data at the position corresponding to the reference mark. In the image data B of the rotating body 2, the reference mark 1
Since it is assumed that the density of the portion is the highest, the image data A of the rotating body 2 on the document does not exceed the light transmittance T. Therefore, with the light transmittance T as a threshold value, the image data A of the document corresponding to the portion that does not exceed the threshold value is converted into the background level (As) of the document.

In the data conversion (1), the area to be image-processed is specified from the image data of the rotating body 2 and the light transmittance T stored in advance in the memory, and the original data A is set as the original background level (As) of the original. Replace with. The thick arrows pointing upward in the areas Q and R in the upper part of FIG. 10 both indicate that the image data A of the original document is converted to the background level (As) of the original document by the data conversion (1). The lower part of FIG. 10 shows the result of the data conversion (1).

In the data conversion (1), the rotator image data B read from the memory 8 is higher than the background level (Bs) of the rotator image data and is at the position corresponding to the Amax. In the following, when the original image data A corresponding to the position of B exceeds the transmittance (T), the original image data A is converted to the background level (As) of the original.

In order to convert to the background level of the original, it is made the same as the pixel on the left side of the pixel of interest in the main scanning direction of the original. If the pixel on the left also has the same black level, it is adjusted to the pixel on the left further. In the embodiment of the present invention, the data conversion unit 23 is provided with four stages of registers so that the determination can be performed retroactively up to the third stage.

FIG. 11 shows the configuration of an image reading apparatus for calculating the light transmittance of the original medium and performing the image processing of the data conversion (1) shown in FIG. 10 based on the image data of the rotating body 2. Similar to FIG. 2, reference numerals 2, 3, 4, 5, and 60 in FIG. 11 denote a rotating body, an image sensor, an amplifier, an AD converter, and an original in this order.

Reference numeral 20 in FIG. 11 is similar to the data processing unit 10 in FIG.
It is a data processing unit including a memory 8. Data processing unit 2
21 of 0 is the light transmittance (T = Ba / A) of the original medium from the image data of the surface of the reference mark stored in the memory 8 and the image data of the reference mark obtained through the original medium.
It is a division unit for calculating (max).

Reference numeral 22 in FIG. 11 indicates whether the read manuscript data is converted into the background level based on the transmittance obtained by the divider 21 and the image data of the rotating body 2 which is stored in the memory in advance, or is not changed. Is a transmissivity determining unit that determines a slice level. Reference numeral 23 in FIG. 11 is a data conversion unit that performs data conversion (1) based on the slice level, and converts the read original data to the background level (As). The output is multivalued image data.

The light transmittance of the original medium is calculated in FIG.
The figure for demonstrating the image processing which added the multiplication circuit which multiplies the transmittance to the image data of the rotating body 2 which has already been read and is stored in the memory 8 is shown. In FIG. 12, the horizontal axis x, y
Indicates a data position using both the main scanning direction x and the sub scanning direction y. The vertical axis represents the potential v, and the upper side represents the white level and the lower side represents the black level. The slice level is a threshold value for binarizing white or black in a monochrome scanner.

A is the image data of the original at the time of reading the original, and B is the image data of the rotary body 2 when the original is not read or when the rotary body 2 is rotated once before the original is read and read. Is. The rotating body image data B is stored in the memory 8. In the area P, there is the original black level data of A, and there is no reference mark 1 of B or the rotating body 2 without stains.
The base level (Bs) of the above is shown. A in the area Q is image data of the reference mark 1 read through the document, and there is Amax in this. B in the area Q is image data of the reference mark 1 read in advance. The region R has dirt on the rotating body 2. It can be assumed that the dirt on the rotating body 2 generally does not exceed the density of the reference mark.

The light transmittance (T) is obtained from Ba and Amax. Since it is assumed that the density of the reference mark 1 is the highest in the image data B of the rotator 2, the image data A of the rotator 2 in the original document does not exceed the light transmittance (T).

The product of the transmittance T and the image data B of the rotating body is BT in the upper diagram of FIG. The lower part of FIG. 12 shows the result (A-BT) obtained by subtracting the multiplication result BT from the original read data A.

Thus, the image data of the rotating body 1 is simply subtracted from the read data of the original by multiplying the image data of the rotating body 2 by the light transmittance of the original medium and subtracting the multiplication result from the read data of the original. More accurate image data can be obtained than that.

The structure of the image reading apparatus for performing the image processing described in FIG. 13 with reference to FIG. 12, in which a multiplication circuit for calculating the light transmittance of the original medium and multiplying the image data of the rotator 1 by the transmittance is added. Indicates. Reference numerals 2, 3, 4, 5, and 60 in FIG. 13 are a rotating body, an image sensor, an amplifier, an AD converter, and an original document in this order, as in FIGS.

Reference numeral 30 in FIG. 13 is the data processing unit 20 in FIG.
The data processing unit includes a reference mark detection unit 6, a memory address generation unit 7, a memory 8 and a division unit 21 similarly to the above. The multiplication unit 31 in the data processing unit 30 is a multiplication unit for multiplying the image data of the surface of the rotating body 1 stored in the memory 8 and the transmittance obtained by the division unit 21, and the output is a multi-valued one. It is image data.

Reference numeral 39 in FIG. 13 denotes a subtraction unit for subtracting the multiplication result of the multiplication unit 31 from the multivalued image data read from the original, and the output is multivalued image data. FIG.
FIG. 4 is a diagram for explaining a data conversion (2) for converting the image data of the original so as to remove the influence of the backing and the back slip. The upper diagram of FIG. 14 shows the state before the data conversion.
The lower diagram shows the result after conversion, and the table in the middle of FIG. 14 shows the process of data conversion. In FIG. 14, the horizontal axes x and y indicate data positions using both the main scanning direction x and the sub scanning direction y. The vertical axis represents the potential v, the upper side represents the white level, and the lower side represents the black level. The slice level is a threshold value for binarizing white or black in a monochrome scanner.

A is the image data of the original at the time of reading the original, and B is the image data of the reference mark 1 when the original is not read or before the original is read by rotating the rotator 2 once. Is. In the area P, there is the original black level data of A, and the base level (Bs) of the rotating body 2 without the B reference mark 1 and dirt is shown. Area Q
A is the image data of the reference mark 1 read through the document, and there is Amax in this. B in the area Q is image data of the reference mark 1 read in advance. The region R has dirt on the rotating body 2. It can be assumed that the dirt on the rotating body 2 generally does not exceed the density of the reference mark.

The light transmittance (T) is obtained from Ba and Amax. (T = Ba / Amax) Since it is assumed that the density of the portion of the reference mark 1 is the highest, the image data A of the rotating body 2 on the document does not exceed the light transmittance (T). Therefore, with the light transmittance (T) as a threshold value, the image data A of the document corresponding to the portion that does not exceed the threshold value is converted into the background level (As) of the document.

In the data conversion (1), the area to be subjected to the image processing is specified based on the image data of the rotating body 2 and the light transmittance T which are stored in the memory in advance. When the original data A exceeds the transmissivity (T) of A, that is, the original data A is Amax or more, the original data A is replaced with the background level As of the original. Areas Q, R, and S in the upper part of FIG. 14 indicate that thick upward arrows indicate that the image data A of the document is converted to the background level (As) of the document by the data conversion (2). The lower part of FIG. 14 shows the result of the data conversion (2).

To convert the background level of the document, the same pixel as the pixel on the left side of the pixel of interest in the main scanning direction of the document is used. If the pixel on the left also has the same black level, it is adjusted to the pixel on the left further. In the embodiment of the present invention, the data conversion unit 23 is provided with four stages of registers so that the determination can be performed up to the third stage.

The area S in FIG. 14 is the image data B of the rotating body 2.
Is the background level Bs, and the read data A of the document has a lower value than the background level As. This indicates that there is a back reflection of the manuscript. As a result of the data conversion (2), it is possible to remove this backsiding.

FIG. 15 shows the configuration of an image reading apparatus which performs image processing of data conversion (2) using the light transmittance of the original medium as a threshold. 2, 3, 4, 5, and 60 in FIG. 15 are shown in FIG.
1, a rotating body, an image sensor, an amplifier, an AD converter, and an original in the same manner as in FIG.

Reference numeral 40 in FIG. 15 is the data processing unit 20 in FIG.
Similarly to the above, the data processing unit includes a reference mark detection unit 6, a memory address generation unit 7, a memory 8 and a division unit 21. Reference numeral 21 in the data processing unit 40 is a division for calculating the light transmittance of the document medium from the image data of the surface of the reference mark stored in the memory 8 and the image data of the reference mark obtained through the document medium. It is a department.

Reference numeral 43 in FIG. 15 is a slice level generating section 42.
Is a data conversion unit that performs data conversion (2) based on the data from the
s). The output is multivalued image data.

By realizing the above, it is possible to remove the influence of dirt on the backing and the back slip of the original of thin paper.
However, if the position of the dirt or backsiding matches the position of the original document data, it may be removed during the above-described image processing. Therefore, in the embodiment of the present invention, the data correction processing is performed as follows to restore the image data.

FIG. 16 shows a 3 × 3 matrix register. A technique of expanding a 3 × 3 pattern in a ROM (read-only memory) and determining the value of the central pixel (for example, Japanese Patent Laid-Open No. 6-
164931 image signal processing device) is well known. In the embodiment of the present invention, the center pixel is determined from the surrounding pixels in the image data after the binarization process. M rows, N
The pixel P of the digit is M-1 row, from the N-1 digit, M + 1 row,
It is a function determined by vertical, horizontal, and diagonal surrounding pixels up to N + 1 digits. As shown in the examples (1) to (4) of FIG. 16, the value of the central pixel P is determined by presetting the output pattern for the input pattern.

FIG. 17 shows the arrangement of an image reading apparatus for correcting and restoring image data that is missing in the image processing for removing the influence of stains on the backing and the back slip of double-sided originals. FIG.
2, 3, 4, 5, and 60 are shown in FIG. 2, FIG. 11, FIG. 13, and FIG.
Similar to 5, rotating body, image sensor, amplifier, AD
The converter and the manuscript are shown.

Reference numeral 50 in FIG. 17 indicates the data processing unit 10 in FIG.
The data processing unit 20 of FIG. 11 and the data processing unit 30 of FIG.
Alternatively, it is a data processing unit equivalent to the data processing unit 40 of FIG. 15, and includes a reference mark detection unit 6, a memory address generation unit 7, and a memory 8. The calculation unit 59 in the data processing unit 50 is the subtraction unit 9 in FIG. 2 or the data conversion unit 2 in FIG.
3, which is equivalent to the subtraction unit 39 in FIG. 13 or the data conversion unit 43 in FIG. 15, and the output is multivalued image data.

Reference numeral 51 in FIG. 17 is an image processing unit for performing multivalued image processing such as image enhancement, enlargement and reduction. 17 of FIG.
Reference numeral 2 is a binarization unit that binarizes multivalued data in the image processing unit. Reference numeral 53 in FIG. 17 is a buffer memory for holding binary data for three lines. Reference numeral 54 in FIG. 17 denotes a masking unit that performs a process of obtaining a central pixel from surrounding pixels. The masking unit 54 restores the data described with reference to FIG.

It should be noted that in the embodiment of the present invention, it takes 3 to restore the data.
A matrix register of × 3 was used, but generally N × N
Needless to say, it can be realized by using the matrix.
Further, in the embodiment of the present invention, a black and white scanner is mainly described for convenience of description, but it is also possible to replace the black and white level with the level of each color and apply it to a color scanner.

In the above-described embodiment of the present invention, the image reading apparatus with the original feeding mechanism in which the backing is a rotating body has been described, but the original is formed by forming the reference marks in the main scanning direction on the flat backing. Of course, it can be applied to a stationary image reading device.

[0069]

As is apparent from the above description, according to the present invention, in an image reading apparatus with a backing such as an image scanner or a facsimile, even an original having a high transmittance is not affected by stains on the backing and is thin. There is a remarkable effect that it is possible to obtain a beautiful image without a back reflection even on a paper document.

[Brief description of the drawings]

FIG. 1 is a diagram of a rotating body that is a sheet pressing member that doubles as a backing of a document according to an example of an embodiment of the present invention.

FIG. 2 is a configuration diagram of an image reading apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining a processing result according to the embodiment of the present invention.

FIG. 4 is a circuit diagram of a reference mark detection unit.

FIG. 5 is a timing chart of a reference mark detection unit.

FIG. 6 is a circuit diagram of a memory address generator.

FIG. 7 is a timing chart of a memory address generator.

[Fig. 8] Diagram of a rotating body for calculating transmittance

FIG. 9 is a diagram for explaining the transmittance according to the embodiment of the present invention.

FIG. 10 is a diagram for explaining the data conversion (1).

FIG. 11 is a configuration diagram of an image reading device according to a second embodiment of the present invention.

FIG. 12 is a diagram for explaining image processing in which a multiplication circuit is added.

FIG. 13 is a configuration diagram of an image reading device according to a third embodiment of the present invention.

FIG. 14 is a diagram for explaining the data conversion (2).

FIG. 15 is a configuration diagram of an image reading device according to a fourth embodiment of the present invention.

FIG. 16 is a diagram for explaining image data correction.

FIG. 17 is a configuration diagram of an image reading device according to a fifth embodiment of the present invention.

[Explanation of symbols]

 1 reference mark 2 rotating body 3 image sensor 4 amplifier 5 AD converter 6 reference mark detection unit 7 memory address generation unit 8 memory 9, 39 subtraction unit 10, 20, 30, 40, 50 data processing unit 21 division unit 22 transmission Rate determination unit 23, 43 Data conversion unit 31 Multiplication unit 42 Slice level generation unit 51 Image processing unit 52 Binarization unit 53 Buffer memory 54 Masking unit 59 Calculation unit 60 Original

Claims (5)

[Claims] 1. A storage means for storing backing image data of a backing of a document provided opposite to the image reading element, and a circuit for subtracting the backing image data from the image data of the document. An image reading apparatus, wherein the backing image data is subtracted from the image data of the original at the time of reading the original. 2. A reference mark is formed in a main scanning direction of a backing of an original provided opposite to an image reading element, and the backing image data for the surface area of the backing and the mark portion image of the reference mark portion are formed. The backing image data includes a storage unit for storing data, a transparent mark portion image data transmitted through a document, and a circuit for calculating the light transmittance of the document medium from the mark portion image data. An image reading apparatus for converting image data of the document corresponding to a portion which does not exceed a threshold value obtained from the transmittance to a background level of the document. 3. A reference mark is formed in a main scanning direction of a backing of an original provided opposite to an image reading element, and backing image data for the surface area of the backing and a mark portion image of the reference mark portion are formed. Storage means for storing data, a circuit for calculating the light transmittance of the original medium from the transparent mark image data transmitted through the original and the mark image data, and the transmittance for the backing image data An image reading apparatus, comprising: a circuit for multiplying by and a circuit for subtracting the multiplication result from image data of an original, and subtracting the multiplication result from image data of the original at the time of reading the original. 4. A storage means for forming a reference mark in the main scanning direction of the backing of the document provided facing the image reading element, and storing the mark portion image data of the reference mark portion, and the document. The transparent mark portion image data and a circuit for calculating the light transmittance of the original medium from the mark portion image data are provided, and the portion corresponding to a portion which does not exceed a threshold value obtained from the transmittance at the time of reading an original document is provided. An image reading apparatus for converting image data of a document to a background level of the document. 5. The image reading device according to claim 1, 2, 3 or 4, wherein a binarization circuit for binarizing the corrected multi-valued image data, and the binarized image. A register for expanding data into a matrix is provided, and the central pixel is determined from the matrix to correct the image data after the image data processing according to claim 1, 2, 3 or 4. Image reading device.