JP2002252758A - Image reader and method for discriminating front side/ rear side of original - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for discriminating a front side/a rear side of the original used for an image reader that reads an image of both sides of the original and can independently output image data of each side, automatically discriminates the front side/rear side of the original even when the front side/rear side of the original is wrongly read, replaces the front side data with the rear side data, outputs the respective data under a proper arrangement and output only data collected from a required side in the case of one-side reading. SOLUTION: After applying binary processing to image data of each side of an original, data are compressed, and the front side/rear side is discriminated on the basis of a compression rate of the compressed data. The image reading method includes a method where image data of each side of the original obtained by reading the front side/rear side of the original are arranged within one image pattern and outputted and a method where only images on the front side or rear side of many originals are collected and outputted, and also a method where they are stored in a hard disk unit or the like and the front side or the rear side is independently outputted by discriminating the front side from the rear side.

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 capable of reading images on both sides of a document, discriminating between front and back sides, and outputting these image data independently, and a front / back discrimination of the document used here Method and.

[0002]

2. Description of the Related Art There is known an image reading apparatus which continuously transports many originals of the same type such as checks and bills, and reads front and rear images of the originals by a slit exposure method during the transportation.
In this case, the front and back of the document are illuminated by different light sources, and the front and back images are read separately by a pair of line sensors.

[0003] The signal output from the line sensor is image data that continuously changes in accordance with the brightness of the image. This data is multi-valued to a predetermined density gradation (for example, 256 gradations) by a multi-value conversion circuit. Then, image processing such as shading correction and edge enhancement is performed, and the image is binarized by a binarization circuit.

[0004]

The data subjected to the image processing in this manner is recorded in a memory, transferred to another computer or the like, or printed out. Here, the document is not always read with the front and back aligned correctly,
Some originals may be read with the front and back reversed. In this case, there is a problem that the data is recorded, transferred, and printed out with the front and back reversed.

When the front and back sides of a document are output side by side or up and down, the output position of the front and back images changes left and right or up and down depending on the loading condition of the document, and the operator visually recognizes the image. It becomes difficult, and the operator needs to perform operations such as exchanging the front and back images.

When only one of the front and back sides of a document is read (single-sided reading), it is necessary to perform the reading operation again later for a document whose front and back sides have been read in reverse. For this reason, the work efficiency was poor and troublesome.

The present invention has been made in view of such circumstances, and even if a document is read with the front and back wrong, the front and back are automatically discriminated and the front and back data are exchanged, and each data is replaced. It is a first object of the present invention to provide a method of discriminating the front and back of a document which can be output in an appropriate arrangement and collect and output only necessary surfaces in the case of single-sided reading.
It is a second object of the present invention to provide an image reading apparatus using this method.

[0008]

A first object of the present invention is to provide a method of reading an image on both sides of a document and independently determining the front and back sides of the document for use in an image reading apparatus capable of independently outputting image data of each side. , After binarizing the image data of each side of the original,
This is achieved by a method of discriminating the front and back of a document, which discriminates front and back based on a compression ratio of the data compression while performing data compression.

In this image reading method, image data of each side obtained by reading the front and back of a document is arranged and output in one screen, and only the front or back of many documents is collected and output. Including things. In addition, those which are stored in a hard disk device or the like and which can be output independently by distinguishing the front and back sides are also included. When the image data is stored in the storage device, the front and back image data may be stored as separate files.

The same purpose is to read images on both sides of a document,
This is a method for discriminating the front and back of a document used in an image reading apparatus capable of independently outputting the image data of each of the surfaces. The image data of each of these surfaces is multi-valued, and the density frequency distribution of the multi-valued image data And a method for determining the front and back of a document based on the above.

In this case, the ratio of the appearance frequency of the certain intermediate density gradation range to the appearance frequency of the separately set density gradation range is defined as a multi-value frequency ratio, and is determined for at least one surface. A surface where the multi-value frequency ratio is larger than a predetermined set value can be set as the front (or back). Instead of comparing the multi-value frequency ratio obtained for one surface with the set value, the magnitude of the multi-value frequency ratio obtained for both surfaces is compared, and the surface with the larger multi-value frequency ratio is compared. May be the front (or back).

A second object of the present invention is to provide an image reading apparatus which reads images on both sides of a document by a slit exposure method and can output image data on each of these surfaces independently. A pair of document reading means for reading the images separately, a binarizing circuit for binarizing the output of each document reading means and outputting a binary signal, and data for compressing the binary signal for each side of the document A compression circuit, a compression ratio detection unit that determines a compression ratio of compressed data for at least one surface of the document, and a comparison unit that determines the front and back of each surface by comparing the compression ratio with a predetermined set value. The image reading apparatus is characterized in that the image data of each surface is sorted into front and back sides based on the determination result of the comparison unit.

In this case, the compression ratio detecting section obtains the compression ratio for each side of the document, and the comparing section compares the compression ratios of the respective sides to determine the side having the lower compression ratio as the front or the back. You may do so.

The same object is to provide an image reading apparatus in which images on both sides of a document are read by a slit exposure system and image data on each side can be output independently, and a pair of images for reading images on both sides of the document separately. Document reading means, a multi-valued circuit for multi-valued output of each document reading means and outputting a multi-valued signal, and a density level for which the appearance frequency of a certain intermediate density gradation range is set separately from the multi-valued signal. A multi-value frequency ratio detection unit for obtaining a multi-value frequency ratio, which is a ratio occupying the tonal range, for at least one surface of the document, and comparing the obtained multi-value frequency ratio with a predetermined set value for each surface. A comparison unit that determines the front and back of the
And an image reading apparatus characterized in that the image data of each surface is sorted into front or back based on the determination result of the comparison unit.

The multi-value frequency ratio detection section calculates the multi-value frequency ratios for both sides of the document, and compares these to determine the surface with the larger multi-value frequency ratio as the front (or back). it can. The image reading means used in these apparatuses can be formed by a one-dimensional imaging device such as a CCD line sensor.

The data obtained by reading the front and back images may be alternately switched for every predetermined number of main scanning lines and serially inputted to a binarizing circuit or a multi-level circuit. With this configuration, one set of the binarization circuit and the multi-level circuit is sufficient, and an increase in the number of components can be suppressed. Further, the operation rate of the binarization circuit or the multi-level circuit can be improved.

[0017]

FIG. 1 is a view showing an image of an entire system according to an embodiment of the present invention, FIG. 2 is an external view of an image reading apparatus, FIG. 3 is a left side view showing an internal structure thereof, and FIG. FIG. 5 is a diagram illustrating an arrangement of each part of the unit, FIG. 5 is a diagram illustrating an optical system,
6 is a block diagram of a control system, FIG. 7 is a diagram showing an outline of a processing unit for image data, FIG. 8 is a diagram showing output signals of each unit,
FIG. 9 is a conceptual diagram of image output.

The manuscript to be read here is assumed to be, for example, a check or a bill handled by a bank, a seal stamp report, a transfer request form, a payment request form for taxes and public charges, and the like.

In FIGS. 1 to 3, reference numeral 10 denotes an image reading device, which is mounted on a base box 14 that houses a printer 12. The image reading device 10 has a document input port 16
And a document discharge port 18 is provided near the center of the upper surface. The upper surface is formed in a mountain shape in a side view, and a liquid crystal display panel 20 as a rectangular display means is mounted on a slope on the front side thereof. The document insertion port 16 is located below the display board 20 and is long in the horizontal direction. The document outlet 18 is provided on the display panel 20.
And is horizontal with the upper side of the display panel 20.

A document 22 is input from the document input port 16,
The sheet is separated for each sheet by the double feed prevention unit 24 and enters the conveyance unit 26. The double feed prevention unit 24 includes a feed roller 30 driven by a belt by a paper feed motor 28 and a reverse roller 32 driven to rotate in a reverse direction. The document 22 enters between the feed roller 30 and the reverse roller 32 and is prevented from double feeding, so that only one document 22 is separated.

The transport section 26 includes a drive roller group 36 driven by a transport motor 34 and a transport belt 38.
And a plurality of driven rollers 40 arranged sequentially in opposition to the drive roller group 36, and a detachable pressing roller mounted on the transport belt 38 from above to hold the driven rollers arranged in a substantially L-shape. And a support 42 (FIG. 3).

The transport belt 38 and the pressing roller support 42 transport the original 22 sent from the double feed prevention unit 24 substantially horizontally while sandwiching the original 22 from above and below, and further drive the drive roller group 36 and the driven roller 36 upward. It is made to enter between the group 40. The document 22 is sandwiched between the driving roller group 36 and the driven roller group 40 and is sent almost vertically upward, is discharged to the document discharge port 18 and is collected. By opening the case of the image reading apparatus 10, that is, the main body case 10 </ b> A, the pressing roller support 42 can be put in and out by hand from above, and the document 22 jammed in the transport unit 26 can be removed.

A pair of photographing glasses 44 sandwiching the document 22 from both sides in the vertical conveying path of the driving roller group 36.
(44a, 44b) are provided. Shooting glass 4
4, a horizontal and long light source lamp 46 (46 a, 46
b) is provided (see FIGS. 3 and 5). Here, the lamps 46a and 46b have different heights. That is, the lamp 46a for illuminating the front surface of the document 22 is the lamp 4 for illuminating the back surface.
6b, so the front image reading position 60a is lower than the back image reading position 48b (FIG. 5).

Further, a black light-shielding film 50 (50a, 50b) is formed on each of the glasses 44a, 44b in order to prevent the transmitted light of the opposite lamps 46b, 46a from being incident. Each of the lamps 46a and 46b is provided with a light shielding plate 52 (52
a, 52b) to block unnecessary light. 54
Is a reflection plate, which reflects a part of the light of the lamp 46 a illuminating the front side and guides it to the surface of the document 22 before entering the space between the glasses 44.

The illuminance on the surface of the document 22 illuminated with the light reflected by the reflection plate 54 is detected by a phototransistor 56 serving as an AE sensor.
, The illuminance of the lamp 46 is automatically controlled. That is, automatic exposure control is performed. The incident angle theta ₂ with respect to the document 22 in reflected light of the reflector 54 here, by equalizing the incident theta ₁ with respect to the image reading position 48a of the lamp 46a, align the illumination condition of the image reading position 48a and the illuminance detection position I have.

The image on both sides of the original 22 is
When the image passes between a and 44b, the image is read by the slit exposure method at the respective image reading positions 48a and 48b. That is, the images on the front and back sides are the slits 5 shown in FIG.
8 (58a, 58b), and further guided to the optical unit 60 (60a, 60b) shown in FIG. The optical unit 60 has a plurality of mirrors 62, an imaging lens 64, and a CCD line sensor 66 as image reading means. The light passing through the slit 58 is reflected by the mirror 62, guided to the imaging lens 64, and forms an image on the line sensor 66.

A dropout filter 68 (68a, 68b, FIGS. 1 and 3) can be mounted on the optical unit 60. This dropout filter 68
Reference numeral denotes a color filter that can move forward and backward on the optical axis near the imaging lens 64 so that a specific color of the document 22 can be read out. For example, when a red ruled line, a frame, or a character is written on the document 22, an image in which the red ruled line or the like is made invisible by passing through a red filter is sent to the line sensor 66.
To selectively read only numbers and characters written in other than red (for example, black).

When the line sensor 66 reads the entire front and back images of the document 22, the data is sent to an image processing unit 102, which will be described later. Is cut out from the area where is recorded, and a number or the like is read. That is, the image processing unit 102 binarizes the entire image and has a function as an OCR (optical character reading device). In this embodiment, when data compression is performed after binarizing the image data of the front and back sides, the front and back sides are discriminated according to the magnitude of the data compression ratio. This discrimination method will be described later. Note that a specific area may be subjected to image processing as a multi-valued image. For example, the seal imprint of a seal may be processed in multi-level gradation, and the entire image including this area may be processed in binary gradation.

In FIGS. 1 and 3, reference numeral 70 denotes an imprinter, which prints data for document identification on the document 22 in the middle of the transport section 26. For example, when the document 22 is a bank document, data composed of a store number, a document number, a date, a serial number, and the like is printed. As shown in FIG. 1, the imprinter 70 includes a print head 72, a font memory 74, and a control circuit 76, and is detachable from the image reading apparatus 10. Data is input to the control circuit 76 from an external PC or a keyboard, and predetermined data is printed at a predetermined position for each document 22. The line sensor 66 also reads the print data of the imprinter 70.

In FIGS. 1 and 2, reference numeral 78 denotes a magneto-optical disk drive, which opens to the right as viewed from the front of the image reading apparatus 10. The image data read by the CCD line sensor 66 is processed by an image processing device 102 described later, and data such as numerals and characters are read, and a magneto-optical disk (M
O) Recorded at 80.

In FIG. 4, 82 is a trailing edge sensor for detecting the trailing edge of the document 22 being conveyed, 84 is a skew sensor for detecting the inclination of the document 22, 86 is a start detection sensor for finding a reference position for starting image reading, 88 Is a paper ejection sensor.

Reference numeral 90 denotes a transparent touch panel provided on the surface of the display panel 20 (FIGS. 3 and 6). The touch panel 90 is used for making various settings of the image reading apparatus 10 and controlling the operation thereof. That is, from the touch panel 90, the density of the image to be recorded,
The user sets the resolution, whether to read the front or back or whether to read both sides, a search index, and other conditions for reading and recording an image. From the touch panel 90, the reading start / end, the magneto-optical disk 80
And various operation controls such as enlargement, reduction, rotation, and printing start of the image read from the magneto-optical disk 80.

The magneto-optical disk 80 in which the data read by the image reading device 10 is stored is set in the magneto-optical disk drive of another external computer 92 as shown in FIG. Used for Numeral 94 denotes a magneto-optical disk in which dedicated software for reading and searching the magneto-optical disk 80 is stored.
4 enables a predetermined operation.

The control system of the device 10 is configured as shown in FIG. In this figure, reference numeral 100 denotes a control unit, 102
Denotes an image processing unit, and 104 denotes a mechanical control unit, each of which is constituted by a microcomputer, and transmits and receives signals to and from each other. In the present invention, the device 10 is provided with an interface 106. The interface 106 is, for example, SCSI-2 and enables data transmission and reception with an external computer (PC) 108 as shown in FIG. Reference numeral 110 denotes a magneto-optical disk storing dedicated software for performing the operation of the external computer 108.

The control unit 100 receives an input signal from a touch panel 90 provided on the display panel 20. The control unit 100 operates the printer 12 and the disk drive device 78 based on a command from the touch panel 90, and also commands the external computer 108 to transfer data. Various images are displayed on the display panel 20.
For example, it displays image information processed by the image processing unit 102, a selection display screen for selection on the touch panel 90, and the like.

The image processing section 102 starts reading an image by the line sensor 66 at a predetermined position of the document 22 based on signals from the trailing edge sensor 82, the skew sensor 84, the start detection sensor 86, the paper ejection sensor 88, and the like. Then, the image signal is read and various processes are performed. That is, the output signal of the line sensor 66 is converted into a digital signal, and processing such as shading correction, background processing, edge enhancement, and binarization is performed.

Further, the phase shift between the front and back images is corrected,
Appropriate processing such as enlargement / reduction / rotation of the image is performed. In addition, read numbers and letters. These processes are performed in parallel with the reading of the image, and the results are sequentially sent to the control unit 100, where the data are totaled as necessary and recorded in the disk drive device 78. It is also displayed on the display panel 20.

The mechanical control unit 104 controls the conveyance of the original when reading the image of the original 22 and the illuminance of the light source lamp 46. That is, the feed motor 28 and the transport motor 34 are controlled in synchronization with the image reading operation by the image processing unit 102. Further, the brightness of the light source lamp 46 is controlled based on the output of the AE sensor 56.

Next, using FIG. 7, FIG.
A description will be given of a binary signal generation unit 102A for converting a value and a front / back determination unit 102B for determining the front / back based on the binary signal.
The binary signal generation unit 102A binarizes the images A and B on each side of the document 22 (one is the front side and the other is the back side, but it is still unknown which side is the front or back). Value Th
Is used. Further, by inputting the image data of the images A and B of the respective surfaces alternately to the common binarization circuit 200, the two line sensors 66a and 66
Process the output data of b.

In FIG. 7, reference numeral 202 denotes a clock generator, and 204 (204a, 204b) drive circuits,
Clock generator 202 includes line sensors 66a and 66
b sends a clock signal at which image data is read out to the drive circuit 204, and the drive circuit 204 drives the line sensor 66. Here, the image A on both sides of the document 22,
The timing for reading B is set by the timing setting circuit 206, and each of the drive circuits 204a and 204b reads data alternately at the set timing. That is, the line sensors 66a and 66b are driven so as to output data by shifting one main scanning line of the images A and B alternately with time. As shown in FIG. 8, the output data P ₁ and P ₂ of the line sensors 66a and 66b are signals that are temporally and alternately shifted for each main scanning line.

These output data P ₁ and P ₂ are supplied to the amplifier 2
08 (208a, 208b) and input to the data switching circuit 210. Data switching circuit 2
Reference numeral 10 outputs the output Q shown in FIG. 8 by alternately switching the output data P ₁ and P ₂ of the line sensors 66a and 66b for each main scanning line and connecting them in series. Here, the switching timing is set by the timing setting circuit 206. 212 is a threshold memory.

The output Q of the data switching circuit 210 and the threshold value Th are input to the binarization circuit 200, and the output data P1 and P2 are binarized by the threshold value Th. As a result, the output of this binarization circuit 200 is the binary signal R shown in FIG.
become that way.

This binary signal R is divided by a data dividing circuit 214 into image data R (A) of one image A and image data R (B) of the other image B, and each is divided into a separate binary memory 216 ( 216a, 216b). The image data R of each surface A and B recorded in these memories 216
Based on (A) and R (B), the front / back determination unit 102B performs front / back determination. That is, it is determined which of the surfaces A and B is the front and which is the back. In this embodiment, the front / back determination unit 102B determines the front / back based on the magnitude of the data compression ratio of the binary data.

In FIG. 7, 218 (218a, 218b)
A data compression circuit 220 for compressing the binary signals R (A) and R (B) of the images A and B, 220 (220a, 220b)
Is an image memory for storing compressed image data. One data of each image memory 220a, 220b,
For example, the data in the memory 220a is
And the data compression ratio α of each binary data R (A) is obtained. The compression ratio α is defined by (data size after compression) with respect to (data size before compression). Here, the data size is width × length of image data 長 8
Defined by dots.

The compression ratio α has the property of increasing as the amount of lines and characters included in an image decreases. Therefore, if the document 22 has more characters and lines on the front side than on the back side, the compression ratio α becomes large on the back side. If the type of the document 22 has a fixed format such as a bill or a check, the compression rate α is smaller than the predetermined set value N1 for the image of the table.

The compression ratio α is compared with the set value N1 by the comparator 224. For example, when α ≦ N1, it is determined that the image A on this surface is a table. Conversely, when α> N1, this image A is determined to be the back. Reference numeral 226 denotes a data switching circuit which outputs data of the memory 220a as front data when the image A is determined to be front, and outputs data of the memory 220a as back data when the image A is determined to be back. Thus, the data output port is switched.

The front and back image data output by the data switching circuit 226 are recorded in the MO 80 and displayed on the external computer 92, displayed on the external computer 108, or displayed on the display panel 20 (FIGS. 1, 2, and 3). Can be displayed.

FIG. 9 shows an example of an image 230 displayed on the external computers 92 and 108.
30a and the back image 230b are output side by side. The main scanning line of the image 230 is formed by the signal R1 (R11, R12,...) Corresponding to the front image of the binary signal R. The main scanning line of the image 220b is a signal R2 (R21, R22,...) Corresponding to the back image of the binary signal R.
Formed by

In this embodiment, the front and back image data are alternately switched every fixed number of main scanning lines and binarized while being output in series. Therefore, one binarization circuit 200 is sufficient. Therefore, an increase in the number of parts can be suppressed. Further, the operation rate of the binarization circuit 200 and the like can be improved.

[0050]

FIG. 10 is a diagram showing an outline of a processing section for image data according to another embodiment. In this embodiment, the front / back discrimination unit 102B shown in FIG. 7 is changed to 102BB. That is, the front / back determination unit 102BB
A pair of data compression ratio detection units 222 (222a, 222b) for obtaining compression ratios α and β for the images A and B are provided.

The comparing section 224 compares the compression rates α and β with each other. When α ≦ β, the image A is determined to be the front and the image B is determined to be the back. Conversely, α>
At the time of β, it is determined that the image B is the front and the image A is the back. In FIG. 10, the other configuration is the same as that of FIG. 7, and therefore, description thereof will not be repeated.

[0052]

FIG. 11 is a diagram showing an outline of a processing section for image data according to another embodiment. FIG. 12 is an explanatory diagram of the multi-value frequency ratio. In this embodiment, the image data is converted into a multi-level signal by a multi-level signal generation unit 102C,
In 2D, the front and back are determined from the density frequency distribution (histogram) of the multi-level signal.

The multi-level signal generation unit 102C is provided in FIG.
In this example, the binarization circuit 200 of the binary signal generation unit 102A in FIG. Here, the image data is multi-valued into, for example, 256 gradations, and then divided by the data dividing circuit 214 into data of images A and B, and each image data is stored in the image memory 234 (234a, 234).
It is stored in b).

The data of the image A is sent from the memory 234a to the multi-value frequency ratio detection unit 236 of the front / back determination unit 102D.
Here, the multi-value frequency ratio γ is obtained. The multi-value frequency ratio γ is a multi-value signal S for an image on one surface (here, image A).
It is obtained as shown in FIG. 12 based on the density frequency distribution (histogram) of (A).

FIG. 12 is a histogram showing the gradation (0-255) on the horizontal axis and the appearance frequency on the vertical axis. Gradation 0-39
Corresponds to the black frame area. Gradation 40-1
The 59 intermediate density gradation range b is a range including main information such as characters, and corresponds to a character area. Gradation 160-255
Corresponds to the background of the original.

The multi-value frequency ratio γ is defined, for example, as a ratio of the sum of the appearance frequencies 中間 b of the intermediate density gradation range b to the appearance frequency Σ (b + c) of the density gradation range (b + c) set separately. be able to. That is, γ = Σb / Σ (b +
c). A large multi-value frequency ratio γ means that the ratio of the appearance frequency of the intermediate density gradation is large, and therefore contains a large amount of information such as characters. That is, since the ratio γ is large, it can be determined that the document is a table of the document 22.

The multi-value frequency ratio γ is compared with a predetermined set value N2 by the comparator 238. For example, when γ ≧ N2, it is determined that the image A of this surface is a table. Conversely, when γ <N2, the image A is determined to be the back. Memory 234
The output ports of the data switching circuits 240a and 234b are determined based on the determination result of the front / back determination unit 102D.
Is switched by

According to this embodiment, the front and back image data are temporally switched and alternately input to the multi-value conversion circuit 232, where the multi-value conversion is performed, and one multi-value conversion circuit 232 is sufficient. As a result, an increase in the number of parts can be suppressed. In addition, the operation rate of the multi-level circuit 232 can be improved.

[0059]

Another Embodiment FIG. 13 is a diagram showing an outline of a processing section for image data according to another embodiment. In this embodiment, the front / back discrimination unit 102D shown in FIG. 11 is changed to 102DD. That is, the front / back discrimination unit 102DD
Is provided with a pair of multi-value frequency ratio detection units 236a and 236b for obtaining a pair of multi-value frequency ratios γ and δ for images A and B.

The comparing section 238 calculates these multi-value frequency ratios γ and δ
Compare the size with. When γ ≧ δ, the image A is determined to be the front and the image B is determined to be the back. Conversely, when γ <δ, it is determined that the image B is the front and the image A is the back. In FIG. 13, the other configuration is the same as that of FIG. 11, and therefore description thereof will not be repeated.

[0061]

According to the first aspect of the present invention, as described above, when the front and back of a document are discriminated and the data can be output separately for the front and back, the data compression ratio of the binarized data is used for the front and back. Therefore, even if the original is read incorrectly, the data can be automatically exchanged and the front and back data can be output correctly. It is also easy to read only the front or back of a large number of documents. For this reason, it is not necessary to align the front and back of the document, which reduces the work of the operator and improves the processing efficiency.

According to the second aspect of the invention, the same effect can be obtained because the image data of each side of the document is multi-valued and the front and back of the document are discriminated using the density frequency distribution. Here, from the density frequency distribution, a multi-value frequency ratio, which is a ratio of the appearance frequency of the intermediate density gradation range to the appearance frequency of another density gradation range, is obtained. (Claim 3). A multi-value frequency ratio is obtained for each surface, and the two values are compared, and the surface with the larger ratio can be set as the front (or back) (claim 4).

According to the fifth and sixth aspects of the present invention, it is possible to obtain an image reading apparatus in which the front and back are determined from the compression ratio of the binarized data. According to the seventh and eighth aspects of the present invention, it is possible to obtain an image reading apparatus in which the front and back are determined from the multi-value frequency ratio of the multi-valued data.

The document reading means used in these apparatuses is C
A one-dimensional imaging device such as a CD line sensor is suitable (claim 9). A large number of documents can be read at high speed if the documents are read on both sides by a slit exposure method.

The image data on the front and the back are alternately connected in series and input to a binarization circuit or a multi-valued circuit, so that the data is binarized or multi-valued. Only one set of multi-valued circuits is required, and an increase in the number of components can be suppressed. In addition, the operating rates of these binarization circuits and multi-level circuits can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing an image of an entire system according to an embodiment of the present invention.

FIG. 2 is an external view of an image reading apparatus.

FIG. 3 is a left side view of the same.

FIG. 4 is a diagram showing an outline of an arrangement of each unit.

FIG. 5 is a perspective view showing an optical system.

FIG. 6 is a block diagram of a control system.

FIG. 7 is a diagram showing an outline of a processing unit for image data.

FIG. 8 is a diagram showing output signals of each unit of an image data processing unit.

FIG. 9 is a conceptual diagram of front and back image output.

FIG. 10 is a diagram showing another embodiment of the image data processing unit.

FIG. 11 is a diagram showing another embodiment of the image data processing unit.

FIG. 12 is a diagram illustrating a multi-value frequency ratio.

FIG. 13 is a diagram showing another embodiment of the processing section for image data.

[Explanation of symbols]

Reference Signs List 10 image reading device 16 document input port 18 document discharge port 22 document 26 transport unit 66 (66a, 66b) line sensor 92, 108 external computer (PC) 102A binary signal generating unit 102B, 102BB, 102D, 102DD Front / back discrimination section 102C Multi-level signal generation section 200 Binarization circuit 206 Timing setting circuit 210 Data switching circuit 222 (222a, 222b) Compression rate detection section 224,238 Comparator 226,240 Data switching circuit 232 Multi-level conversion circuit 236 (236a, 236b) Multi-value frequency ratio detector α, β Compression ratio γ, δ Multi-value frequency ratio N1, N2 Set value

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C072 AA01 BA05 EA05 FB27 RA05 UA07 UA08 UA11 WA02 5C077 LL16 MM03 MM22 PP06 PP61 PQ08 PQ19 PQ22 RR01 RR02 RR16 TT02 TT06 5L096 AA06 A0537 A0537

Claims (12)

[Claims] 1. A method for discriminating front and back sides of an original used in an image reading apparatus for reading images on both sides of the original and enabling image data on each side to be output independently, wherein the image data on each side of the original is binary. A method of discriminating the front and back of a document, wherein the front and back sides are discriminated based on the compression ratio of the data compression while the data is compressed. 2. A method of reading an image on both sides of a document and discriminating the front and back of the document for use in an image reading apparatus capable of independently outputting image data on each side, wherein the image data on each side is multi-valued. And determining the front and back of the document based on the density frequency distribution of the multi-valued image data. 3. A multivalue frequency ratio is defined as a ratio of the appearance frequency of a certain intermediate density gradation range to the appearance frequency of a separately set density gradation range from the density frequency distribution of image data. 3. The method according to claim 2, wherein a multi-value frequency ratio is determined for the image data of one of the surfaces, and the surface where the determined multi-value frequency ratio is greater than a predetermined set value is set as a front or back surface. 4. A multi-value frequency ratio is defined as a ratio of the appearance frequency of a certain intermediate density gradation range to the appearance frequency of a separately determined density gradation range. 3. The method according to claim 2, wherein the side where the multi-value frequency ratio increases by comparing the obtained multi-value frequency ratios is set as the front or back. 5. An image reading apparatus in which images on both sides of a document are read by a slit exposure method and image data on each side can be output independently, wherein a pair of documents which separately read images on both sides of the document are provided. Reading means, a binarization circuit for binarizing the output of each document reading means and outputting a binary signal, a data compression circuit for compressing the binary signal for each side of the document, A compression ratio detection unit that determines a compression ratio of compressed data for at least one surface, and a comparison unit that compares the compression ratio with a predetermined set value to determine the front and back of each surface, and a determination result of the comparison unit An image reading apparatus for sorting image data of each surface into front or back based on the image data. 6. The compression ratio detecting unit according to claim 5, wherein a compression ratio is determined for each side of the document, and a comparison unit compares the compression ratios of the respective surfaces to determine which side has the lower compression ratio. Image reading device that determines 7. An image reading apparatus for reading images on both sides of a document by a slit exposure method and capable of independently outputting image data on each side, comprising: a pair of documents for separately reading images on both sides of the document Reading means, a multi-valued circuit for multi-valued output of each document reading means to output a multi-valued signal, and a density gradation range in which the appearance frequency of a constant intermediate density gradation range is set separately from the multi-valued signal A multi-valued frequency ratio detector for calculating a multi-valued frequency ratio, which is a ratio of the multi-valued frequency ratio, to at least one side of the document; An image reading device, comprising: a comparing unit that determines the image data of each side, based on a result of the determination by the comparing unit; 8. The multi-value frequency ratio detecting unit according to claim 7, wherein the multi-value frequency ratio is obtained for each side of the document, and the comparing unit compares the multi-value frequency ratios for each side. An image reading device that determines a surface with a large ratio as front or back. 9. The image reading apparatus according to claim 5, wherein the document reading means is formed by a one-dimensional imaging device. 10. The image reading apparatus according to claim 5, wherein an image on both sides of the document is read by a slit exposure method. 11. The method according to claim 5, wherein
A timing setting circuit for setting an image reading timing of each document reading means, and a data switching circuit for switching the image data read by each document reading means alternately for a fixed number of main scanning lines by the timing setting circuit and outputting the data in series An image reading apparatus comprising: a single binarizing circuit for binarizing the output of the data switching circuit. 12. The method according to claim 7, further comprising:
A timing setting circuit for setting an image reading timing of each document reading means, and a data switching circuit for switching the image data read by each document reading means alternately for a fixed number of main scanning lines by the timing setting circuit and outputting the data in series An image reading apparatus comprising: a multi-value conversion circuit that multi-values the output of the data switching circuit;