JPH11298683A - Image processor and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain image data for forming correct images without distortion of the images or inclination of the images by correcting the distortion of the images generated because the main scanning direction of a read means and an original carrying direction deviate from the right angle and correcting the inclination of the images generated when an original is inclined and carried. SOLUTION: An original feeder DDF is inclined to a copying machine main body A as much as an angle α and an original OR is inclined to the original feeder DDF as much as an angle θ. The relation of the original OR placed with such double inclinations to the copying machine main body A becomes an image provided with the inclination of α-θ to recording paper set inside a device main body. The information of the angle α is measured by the test of image formation performed prior to copying and the information of the inclination angle θ of the original OR carried in the original feeder DDF is measured for every copying. Correction to the deviation angle α of the original feeder DDF and the inclination angle θ of the original OR at the time of carrying the original is composed of variable power correction and shift processing correction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing apparatus for processing image data obtained by reading a document image and an image reading apparatus having the image processing apparatus. Such an image processing device or image reading device can be used for a digital copying machine, a scanner, or the like.

[0002]

2. Description of the Related Art As a method of reading an image of a document, a method of reading an image of a document stopped at a reading position after stopping the front end of the document conveyed by a document conveying device by abutting against a stopper (hereinafter referred to as a document). And a method in which a document is read by a stationary reading unit while the document is moved by a document feeder (hereinafter referred to as a document moving method).

[0003]

In the document stationary system, when the document is transported to the exposure position, the leading edge of the document is brought into contact with a stopper provided at the exposure position.
The document is stopped at the exposure position. Therefore, in the original stationary method, even if the installation angle of the original transport device is incorrect with respect to the main body of the reading device provided with the reading means, as long as the original is transported normally, the original can be accurately moved by the stopper. It is set at the reading position and no distortion occurs in the read image.

On the other hand, in the original moving system,
If there is a deviation in the installation angle of the document feeder with respect to the document reading device main body provided with the reading means, the image data obtained by the reading becomes a mixture of the elements of the angle deviation and is reproduced from the data. The image is distorted.

[0005] Such image distortion is not only unsatisfactory in appearance, but also a problem that cannot be ignored in copying a drawing or the like.

[0006] Further, the original is not always conveyed normally in the original conveying device, and depends on the paper quality of the original or
Depending on the state of the document conveying device, the document may be conveyed at an angle. In this case, an image reproduced from the image data obtained by reading is formed as an inclined image on a recording sheet.

Conventionally, as for such correction of the inclination of the original, the inclination is detected by pre-scanning, and the read image data is corrected based on information obtained from the pre-scanning. However, this correction can be applied to the original stationary system, but cannot be applied to the original moving system.

An object of the present invention is to provide an apparatus capable of producing image data for forming a correct image without such image distortion and image inclination. The present invention described in (7) and (7) is to provide an image processing device or an image reading device that corrects the above-described image distortion and inclination in one image processing device.

[0009]

The object of the present invention is as follows.
(1) An image reading apparatus including a document feeder that feeds a document in a fixed document feed direction at a reading position where an image of the document is read, and a reading unit that scans and reads an image of the document being fed by the document feeder. In the apparatus, correction of image distortion caused by deviation of the main scanning direction of the reading unit from the document conveyance direction of the document conveyance device from a right angle and conveyance of the document in the document conveyance device at an angle An image processing apparatus having a correction unit for correcting a generated image inclination; and (2) a document feeder for feeding a document in a fixed direction at a reading position where an image of the document is read, and the document feeder Inclination detecting means for detecting the inclination of the document conveyed in the apparatus, reading the image of the document being conveyed by the document conveying device,
Reading means for outputting image data, and correcting the inclination of an image caused by the inclined conveyance of the document in the document conveying apparatus based on the output of the inclination detecting means, and performing main scanning of the reading means. This is achieved by an image reading device having correction means for processing image data so as to correct distortion of an image caused by deviation of a direction of a document and a document conveyance direction of the document conveyance device from a right angle. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Image Reading Apparatus Hereinafter, a digital copier incorporating an image reading apparatus according to an embodiment of the present invention will be described with reference to the drawings.
In this digital copying machine, the reading means of the image reading device, that is, the image sensor is provided in the body of the copying machine constituting the image forming section of the copying machine, and the document conveying device of the image reading device is provided separately from the body of the copying machine. It is formed as a unit and attached to the copier body.

FIG. 1 is a diagram showing a mechanical configuration of a digital copying machine incorporating an image reading apparatus according to the present embodiment.

An original conveying device DD is connected to the copying machine main body A.
F is formed and attached as a separate unit from the main body. Reference numeral 11 denotes a document table, which forms a document path and a document illumination position when a moving document is read. Light from the light source 12 is reflected by the original and is reflected by the mirror 13.
Then, the light is incident on a line sensor 15 composed of a CCD via an imaging lens 14.

The document feeder DDF is fed by a feed tray 21 on which a document is placed, a feed roller 22 for feeding the documents placed on the feed tray 21 one by one, and a feed roller 22. Rollers 23 for transporting the originals to the reading position and transporting the originals in a fixed direction at the reading position D, a discharge roller 24 for discharging the originals conveyed by the rollers 23, and a discharge tray 25 for placing the discharged originals. The originals on the paper feed tray 21 are separated one by one by a paper feed roller 22, passed through a roller 23 and a paper discharge roller 24, and discharged to a paper discharge tray 25.

A document passing through a reading position formed by the document placing table 11 and the rollers 23 is scanned, and an image is read by a document moving method.

In this embodiment, it is also possible to perform image reading by a document stationary system.

That is, an image can be read from a document placed on the document table 11 while moving the light source 12 and the mirror 13.

The document feeder DDF includes a paper feed roller 22.
The sensors S ₁ and S ₂ , which consist of a light emitter and a light receiver, which detect the passage of the document immediately after the document, are provided at right angles to the document transport direction with the document transport path interposed therebetween. The sensors S ₁ and S ₂ are sensors for detecting the angle of the leading edge of the document conveyed in the document conveying path, that is, the inclination of the document during traveling of the document in the document conveying device DDF.

FIG. 2 shows an electrical configuration of the image reading apparatus according to the present embodiment. In FIG. 2, the line sensor 15
A scanner 40 having an amplifier 41 and an A / D converter 4
The image processing apparatus 50 that processes the image signal from the scanner 40 includes a scaling correction section 51, a shift processing section 52, and an image processing apparatus CPU 53. Document feeder DDF
Is an amplifier 71 that amplifies the outputs of the sensors S ₁ , S ₂ and the sensors
a, 71b, comparators 72a, 72b and comparators 72a, 7b that compare the outputs of the amplifiers 71a, 71b with thresholds and output signals corresponding to the passage time of the leading edge of the document.
It has a time difference measuring unit 73 for calculating the time difference between the outputs of 2b.

An image signal obtained by reading by the line sensor 15 is amplified by an amplifier 41, converted into digital data by an A / D converter 42, and input to an image processing device 50. In the image processing device 50, the MTF
After performing correction, scaling correction, various editing processes, and multi-value processing, the image data is output to the printer 60, and the printer 60 reproduces an image.

(2) Image Tilt Correction and Image Distortion Correction Before describing the image tilt correction and the image distortion correction, the image tilt and the image distortion appearing in the reproduced image will be described.

A document feeder DDF is provided for the copying machine main body A.
However, the copying machine main unit A and the document feeder DDF are mounted in such a manner that they are mounted at an angle from a regular mounting angle at which the main scanning direction and the document conveying direction are perpendicular to each other, and the document OR is not conveyed correctly and conveyed at an angle. FIG. 3 shows the relationship between the angle and the document OR.

The document feeder DDF is tilted by an angle α with respect to the copying machine main body A, and the document OR is tilted by an angle θ with respect to the document feeder DDF. The relationship of the original OR placed with such a double inclination with respect to the copying machine main body A is such that the inclination of α-θ is relative to the apparatus main body, in other words, the line sensor 15 and the recording paper set in the apparatus main body. It becomes an image with.

The outline of the image processing in this embodiment is as follows.
Such double inclination is a correction for removing image distortion and inclination occurring in a reproduced image.

To make these corrections, (1) information on the deviation angle α of the document feeder DDF and (2) information on the inclination angle θ of the document OR are required.

First, the deviation angle α of the document feeder DDF is the angle in the document transfer direction when the document is normally fed in the document feeder DDF, and is a line sensor installed in the copying machine main unit A. Can be said to be the angle in the document conveyance direction with respect to the direction perpendicular to the main scanning direction. The information of the angle α is stored in the image processing device 5 as follows.
0 is introduced.

An image having an angle α is obtained by reading an image of a document performed in a state where the document conveying device OR is installed and by performing test copying for reproducing image data obtained by the reading into an image. The inclination angle of the obtained image is measured to obtain α, and this information is input to the operation unit 30 of the copying machine. The input information is input to the image processing device CPU 53 through the main body control CPU 31 and stored.

As described above, the information on the angle α is measured by an image forming test performed prior to copying, and is introduced in advance into a copying machine. θ information is measured for each copy and introduced. In other words, in document transport during copying,
The passage of the leading edge of the document at both ends is detected by sensors S ₁ and S ₂ provided in the document transport device DDF. Time difference measurement unit 7
At 3, the time difference s is calculated. If the distance between the sensors S ₁ and S ₂ is d and the conveying speed of the document is v, the inclination angle θ
Is represented by θ = tan ⁻¹ {s / (v · d)}.

The relationship between the time difference s and the inclination angle θ is stored in the ROM 8
0, and by inputting the time difference s calculated by the time difference measuring unit 73, the angle θ is read from the ROM 80.
Is output.

The correction for the deviation angle α of the document feeder DDF and the inclination angle θ of the document OR at the time of the document feed include magnification change correction and shift processing correction. Hereinafter, these corrections will be described.

(A) Magnification Correction Before explaining the magnification correction, the original conveying device D
DF is attached with a shift angle α, and the document OR is θ
A description will be given of a reproduced image in the case where the image is read while being conveyed only at an angle and is created without correcting the image data described later.

In the following description, the vertical axis V indicates the main scanning direction of the line sensor 15, and the horizontal axis H indicates the sub-scanning direction of the line sensor 15.

When the document feeder DDF is mounted with a shift angle α, the reproduced image has a distortion as described below. That is, as shown in FIG. 4A, the rectangle Z ₁ on the document is reproduced as a parallelogram Z ₂ having a side inclined at an angle α with respect to the vertical axis V and a side parallel to the horizontal axis H. You. Note that this parallelogram is enlarged by 1 / cos α in the vertical axis V direction.

On the other hand, a rectangular Y ₁ on the original OR conveyed inclined, as shown in FIG. 4 (b), is reproduced as a rectangular Y ₂ having an inclination angle theta.

The deviation angle α of the document feeder DDF and the document OR
When the image is reproduced without correction when the inclination θ of the image overlaps, a reproduced image of a rectangle (Z ₁ or Y ₁ ) on the original is represented by a horizontal axis H and a vertical axis V as shown in FIG. is reproduced as a parallelogram W ₁ having a θ _1, θ ₂ of the angles against. The relationship between the angles θ ₁ and θ ₂ formed by the long side L ₁ and the horizontal axis H and the short side S ₁ and the vertical axis V and the angles α and θ in the parallelogram W ₁ is expressed by the following equation. You.

Tan θ ₁ = 1 / (1 / tan θ + tan α) tan θ ₂ = tan θ + tan α Correction for transforming an image having a deviation angle from such a rectangle into a rectangle is performed. The original image is not reproduced. In the directions of the vertical axis V and the horizontal axis H, it is necessary to perform zooming correction processing.

First, the deviation angle α of the document feeder DDF
Requires a magnification correction. This variable magnification correction ratio is expressed as follows.

H direction: same magnification V direction: cos α times Second, magnification correction for the inclination θ of the original in the original conveyance device is necessary, and this magnification correction rate is expressed as follows.

H direction: 1 / cos θ times V direction: cos θ times In order to perform these scaling corrections in one operation, the following formula may be used. This is the magnification change processing of the magnification indicated by.

H direction: 1 / cos θ times V direction: cos α · cos θ times Such scaling processing is performed by scaling processing in the sub-scanning direction and scaling processing in the main scanning direction described below.

First, scaling processing in the H direction, that is, the sub-scanning direction, is performed.

The main body control CPU 31 includes a document feeder DDF
Is set to the normal transport speed, that is, cos θ times the transport speed for reading at the same magnification. The document transport device DDF transports the document at the set transport speed, and reads the document. The image signal generated by reading the original is an image signal that has been scaled by a factor of 1 / cos θ in the H direction.

Next, the scaling correction section 51 performs scaling processing in the V direction, ie, the main scanning direction, on the image signal scaled in the H direction. This processing is called cosα · co
This is a scaling process for multiplying by sθ, and is performed, for example, according to simple linear interpolation.

FIG. 6 shows the concept of the magnification correction described above. Although parallelograms W ₁ shown in FIG. 6 (a) illustrates in Figure 5, the results obtained by performing the variable magnification correction on the parallelogram W _1, shown in Figure 6 (b) Thus, a parallelogram W ₂ is obtained.

The angle θ formed by the long side L ₂ and the vertical axis H and the short side S ₂ and the vertical axis V of the parallelogram W ₂ in FIG.
₃ and θ ₄ are represented by the following equations.

Angle to horizontal axis H: θ ₃ = tan ⁻¹ (t
an θ ₁ · cos ² θ ₁ · cos α) Angle to vertical axis V: θ ₄ = tan ^-1 ｛tan θ ₂ / (c
os ² θ ₂ · cos α)｝ (b) Shift processing correction i) Vertical shift correction In the scaling correction section 51, the following shift processing is performed on the image signal on which the scaling correction has been performed.

[0046] First, a shift processing to match the side AB of the parallelogram W ₂ after the zooming the horizontal axis H will be described with reference to FIG. This shift process is a process of moving pixels in the vertical axis direction for each line of image data and aligning them on the horizontal axis H, as conceptually shown in FIG. 7A.

The movement amount J of an arbitrary coordinate point (x, y) in the image data is obtained by taking one corner of the parallelogram W ₂ on the vertical axis.
If the coordinates of the point as (0, ys), is expressed as J = ys-xtanθ _3. When J is positive (> 0), upward, negative (<
In the case of 0), it moves downward. Since the movement amount J is a function of x and does not depend on y, it is not a pixel but a unit delimited by x, x ₁ , x ₂ , x ₃ ,. . . , _Xn is calculated.

By this processing, the parallelogram W ₂ shown in FIG. 7A is converted into a parallelogram W ₃ having a side parallel to the horizontal axis H as shown in FIG. 7B.

The angle δ ₅ between the vertical axis V and the hypotenuse of the parallelogram W ₃ is represented by the following equation.

Θ ₅ = tan ⁻¹ {1 / (tan θ ₃ + 1 / tan θ ₄ )} ii) Horizontal shift correction The horizontal shift correction is performed on the data on which the vertical shift correction shown in FIG. The horizontal axis of ordinates H and V shown in FIG.
Rectangular W ₄ is obtained having sides parallel to. In this shift correction, an arbitrary point (x, y) in FIG.
Is represented by the following equation.

K = −y · tan θ ₅ K <0 indicates movement to the left, and K> 0 indicates movement to the right. Since the moving amount is a function of y and does not depend on x, it is a unit y ₁ , y ₂ , y separated by y.
₃ ,. . . correction by the calculation of the movement amount for each y _n can be performed.

As described above, since the shift processing correction is performed by moving the memory in units of x or y in the vertical shift correction and the horizontal shift correction collectively, the above-described total movement amounts J and K are calculated. The amount is small compared to the conventional calculation method. In other words, while the conventional affine transformation requires x × y movement amount calculations, the present method requires only x + y calculation times.

[0053] The above-described magnification correction, vertical shift correction and rectangular W ₄ obtained by the horizontal shift correction, the original OR
It has an angle and size equal to the upper rectangle Z ₁ (or Y ₁ ).

When the shift angle α of the document feeder DDF and the tilt angle θ of the fed document are small, the approximations θ ₃ ≒ θ ₁ and θ ₄ ≒ θ ₂ are established, and the correction calculation is relatively difficult. Be simple.

In the above description, the correction processing of the parallelogram image on the original is performed.
By performing the above-described correction, it is needless to say that the distortion and the inclination of the image are removed.

[0056]

According to the present invention, a normal image can be corrected by correcting the image distortion and the image inclination caused by the deviation of the mounting angle of the original conveying apparatus with respect to the image reading apparatus main body and the inclination of the original being conveyed in the original conveying apparatus. Can be formed.

In mounting the document feeder, it is not necessary to increase the accuracy, and the efficiency of assembling the copying machine and the scanner can be improved.

In addition, the correction for the deviation of the installation angle of the document conveying device and the inclination of the document conveyed by the document conveying device are simultaneously corrected.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a mechanical configuration according to an embodiment of the present invention.

FIG. 2 is a diagram showing an electrical configuration of the embodiment shown in FIG.

FIG. 3 is a diagram illustrating a relationship between an angle of the document transport device with respect to the image reading device main body and a document transport angle in the document transport device.

FIG. 4 is a diagram illustrating a deviation of a mounting angle of a document conveying device with respect to an image reading device main body and a distortion and a tilt of a reproduced image caused by a document being conveyed in an inclined manner.

FIG. 5 is a conceptual diagram of an image before scaling correction.

FIG. 6 is a conceptual diagram of zooming correction.

FIG. 7 is a conceptual diagram of vertical shift correction.

FIG. 8 is a conceptual diagram of lateral shift correction.

[Explanation of symbols]

15 line sensor 30 operating unit 31 main body control CPU 50 the image processing apparatus 51 magnification correcting unit 52 shift processing unit 53 an image processing apparatus CPU 73 hour difference measuring unit A copying machine main body DDF document feeder S _1, S ₂ sensor

Claims (7)

[Claims] A document feeder that feeds the document in a fixed document feed direction at a reading position where the image of the document is read; and a reading unit that scans and reads the image of the document being fed by the document feeder. In an image reading apparatus, correction of image distortion caused by deviation of a main scanning direction of the reading means from a right angle with a document conveying direction of the document conveying apparatus, and a document is conveyed at an angle in the document conveying apparatus. An image processing apparatus, comprising: a correction unit configured to correct a tilt of an image generated as a result. 2. The image processing apparatus according to claim 1, wherein the correction unit stores information regarding an angle between the document conveyance direction and the main scanning direction, which is input from the outside, and corrects the distortion of the image based on the stored information. The image processing apparatus according to claim 1, further comprising a correction processing unit that performs correction. 3. The image processing apparatus according to claim 1, wherein the correction unit is a correction unit that simultaneously corrects distortion of the image and correction of a tilt of the image. . 4. The image forming apparatus according to claim 1, wherein the correction unit includes an input unit configured to input information on a tilt of the document in the document feeder, and relates to the information stored in the storage unit and the tilt of the document input to the input unit. The image processing apparatus according to claim 2, wherein correction of distortion of the image and correction of inclination of the image are performed based on information. 5. A document transport device for transporting a document in a fixed direction at a reading position where an image of the document is read, a tilt detecting unit for detecting a tilt of the document transported in the document transport device, and Reading means for reading an image of the conveyed document and outputting image data; and detecting a tilt of the image caused by the document being conveyed while being tilted in the document conveyance device, based on an output of the tilt detection means. A correcting unit that corrects the image data so as to correct image distortion caused by a deviation between a main scanning direction of the reading unit and a document conveying direction of the document conveying device from a right angle. Image reading device. 6. The storage device according to claim 1, wherein the correction unit stores information regarding an angle between the document conveyance direction and the main scanning direction input from outside, and corrects the image distortion based on the stored information. 6. The image reading apparatus according to claim 5, further comprising a correction processing unit for performing correction. 7. The image forming apparatus according to claim 1, wherein the correcting unit corrects an image distortion caused by a deviation between a main scanning direction of the reading unit and a document conveying direction of the document conveying device from a right angle, and a document in the document conveying device. 7. The image reading device according to claim 5, wherein the image reading device is a correction unit that simultaneously performs correction of an image inclination caused by being conveyed while being inclined.