JPH1175058A - Picture forming device and picture processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the part of a character or a line from blurring by operating a featured value calculated from the concentration difference of picture data to an interpolation coefficient in a linear interpolation system used for the enlargement of read picture data as weighting, forming enlarged picture data, and forming a picture based on the picture data. SOLUTION: Picture information read by a scanner part 1 or the like is processed by noise removal or moire removal, and range correction by a range correcting part 52, and added to a value obtained by multiplying a result obtained by MTF correction by an HPF 53 in parallel by a K parameter by a multiplier 54 by an adder 55, and the power varying processing of the processed picture is operated by an enlarging/ reducing part 56. For example, the power varying processing of the picture is operated in a main scanning direction by using a linear interpolation method for enlargement. When the picture is enlarged in the linear interpolation system, a part with intermediate concentration is generated, and a blurring picture is generated. Then, the blur can be prevented by operating weight αto an interpolation coefficient (r). The parameters of picture elements P1 and P2 are calculated by α=(|P2-P1/255|)×β, and the value is made larger according as the concentration difference of an edge or the like is larger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a digital copying machine for reading an image of a document and processing the read image with an image processing apparatus to form an image.

[0002]

2. Description of the Related Art In recent years, image forming apparatuses such as a digital copying machine and a facsimile have rapidly spread. Such digital copiers and facsimile magnification / reduction processing (hereinafter referred to as enlargement /
The reduction process is generally realized by image processing in the main scanning direction and by changing the reading speed of the scanner without a line memory in the sub-scanning direction.

In the enlargement / reduction processing by image processing, basically, a sampling position is calculated in accordance with a magnification, an input image (100% image) is resampled, and an output image (magnified image) is calculated. , And a linear interpolation method is often used because the calculation is easy at the time of enlargement.

However, in the prior art, when an image is enlarged by linear interpolation, there is a problem that characters and lines of an output image are blurred. For example, even if a high-pass filter (HPF) process or the like is performed before the enlarging process and the edge portion of the image is emphasized as shown in FIG. Therefore, the image after enlargement is an image with blurred edges as shown in FIGS. 11B and 11C.

[0005]

As described above, in the enlargement / reduction processing by image processing, a linear interpolation method is often used at the time of enlargement because the calculation is simple, but when an image is enlarged by linear interpolation, Since a pixel value between pixels is obtained by a simple interpolation process called linear interpolation, there is a problem that characters and lines of an output image are blurred.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus and an image processing apparatus capable of preventing a character or a line portion of an output image from being blurred when an image is enlarged by linear interpolation. .

[0007]

An image forming apparatus according to the present invention weights an interpolation coefficient of image data read by a reading means for reading an image of a document when the image data read by the reading means is enlarged. Processing means for forming enlarged image data, and image forming means for forming an image based on the image data enlarged by the processing means.

An image forming apparatus according to the present invention includes a reading means for reading an image of a document, and a method for enlarging image data read by the reading means by a linear interpolation method, wherein an interpolation coefficient of the image data includes a density of the image data. The processing unit includes weighted feature amounts calculated from the difference to form enlarged image data, and image forming means for forming an image based on the image data enlarged by the processing unit.

An image forming apparatus according to the present invention performs a reading unit for reading an image of a document, and a control for adjusting a parameter according to a magnification for enlarging image data read by the reading unit by a linear interpolation method. Control means, calculate weights using the parameters adjusted and controlled by the control means,
It is composed of processing means for forming enlarged image data by weighting the interpolation coefficient of the image data, and image forming means for forming an image based on the image data enlarged by the processing means. .

The image processing apparatus of the present invention includes processing means for weighting an interpolation coefficient of the input image data to form enlarged image data when the input image data to be processed is expanded.

The image processing apparatus according to the present invention includes processing means for weighting an interpolation coefficient of the image data to form enlarged image data when the input image data to be processed is enlarged by a linear interpolation method. doing.

An image processing apparatus according to the present invention includes a first processing unit for performing a filtering process on input image data to be processed and an image data processed by the first processing unit which is enlarged by a linear interpolation method. At this time, second processing means for weighting the interpolation coefficient of the image data to form enlarged image data, and γ-correction, density adjustment, and scale adjustment are performed on the image data enlarged by the second processing means. And a third processing means for performing tone adjustment processing.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a cross-sectional view illustrating the internal structure of a digital copying machine as an image forming apparatus according to one embodiment of the present invention.

That is, the digital copying machine includes a scanner unit 1 as reading means for optically reading image information of an original O, and an image read through the scanner unit 1 is converted into a recording material, that is, a copy sheet. And a printer unit 2 as an image forming means for outputting the image on P.

In the scanner section 1, a document to be copied is placed on a document table 3, and a document O placed on the document table 3 is exposed to light as a light source extending in the sub-scanning direction. The reflected light from the original O illuminated by the lamp 4 and illuminated by the exposure lamp 4 is photoelectrically converted by the CCD sensor 5 as a photoelectric conversion element, and the image information is converted into an image signal into the reflected light.

A reflector 6 for efficiently converging the illumination light from the exposure lamp 4 onto the original O is disposed beside the exposure lamp 4. Between the original O and the C
A plurality of mirrors 7 for bending an optical path through which a light beam directed to the CD sensor 5, that is, a reflected light beam from the original O is passed;
8, 9 and a lens 10 for converging the reflected light on the light condensing surface of the CCD sensor 5 are arranged.

The optical system for guiding the light reflected from the exposure lamp 4 and the original O to the CCD sensor 5 includes carriages 11 and 12.
And transported in the main scanning direction by a pulse motor (not shown). The exposure lamp 4 illuminates the area of the original O in the sub-scanning direction, and the carriages 11 and 12 are moved in the main scanning direction to illuminate the area of the original O in the sub-scanning direction one after another. It will be illuminated by the exposure lamp 4.

A document cover 13 for placing the document O in close contact with the document placing table 3 is disposed above the document placing table 3.
The document O can be replaced with, for example, an SDF, that is, a semi-automatic document feeder, or an ADF, that is, an automatic document feeder, depending on the size of the digital copying machine or the copying ability.

The image forming section as the printer section 2 is provided with a photosensitive drum 14 which is cylindrical and is rotated in a desired direction by a motor or the like (not shown) and charged to a desired potential. I have. When the laser beam is applied to the photosensitive drum 14, the potential of the area irradiated with the laser beam is changed, and an electrostatic latent image is formed on the photosensitive drum 14.

Around the photosensitive drum 14, a charging device 15 for applying a desired potential to the photosensitive drum 14 and a laser unit 16 for outputting a laser beam modulated on the photosensitive drum 14 in accordance with image information. And the laser beam from the laser unit 16
Developing device 17 for supplying a visualizing agent, that is, toner, to the electrostatic latent image formed in
A transfer device 18 for transferring the visualized toner image developed on the photosensitive drum 14 onto a recording material fed from a recording material feeding unit described later, that is, a copy sheet P; Device 19 for peeling copy paper P from paper
And are arranged.

The laser unit 16 includes a semiconductor laser oscillator 24 for generating a laser beam, and a polygon mirror for changing the laser beam supplied from the semiconductor laser oscillator 24 via a collimator lens (not shown) to a beam for each line. 25 and fθ for changing the laser beam from the polygon mirror 25 for each scanning line to parallel light
The mirror 26 includes a lens 26, a mirror 27 that reflects parallel light from the lens 26 and guides the parallel light to the photosensitive drum 14, and a mirror motor 28 that rotates the polygon mirror 25.

On the downstream side of the peeling device 19 in the direction of rotation of the photosensitive drum 14, toner remaining on the surface of the photosensitive drum 14 of the photosensitive drum 14 is removed, and the photosensitive drum 14 is irradiated with a laser beam. A cleaner unit 20 for erasing a change in the potential generated thereon for the next image formation
Is arranged.

Between a developing device 17 and the transfer device 18, a recording material feed for feeding a copy sheet P on which a toner image formed on the photosensitive drum 14 is transferred toward the transfer device 18. The part 21 is arranged.

A fixing device 22 for fixing the toner image on the copy paper is provided in the direction in which the copy paper P on which the toner image has been transferred by the transfer device 18 is separated from the photosensitive drum 14. ing. This fixing device 2
A transport device 23 for transporting the copy sheet P toward the fixing device 22 is disposed between the transfer device 2 and the transfer device 18.

FIG. 3 is a block diagram illustrating a control system of the copying machine of FIG. In FIG. 3, a main control unit 31 for controlling the digital copier is connected to a calculation unit 44 for performing various calculations and four sub-control units 32 to 34 for controlling each unit. ing.

The main control unit 31 includes an operation panel 35 for instructing various types of image processing, an area management unit 36 for managing image processing areas, image quality improvement of captured image information, editing of image information, Image processing unit 3 for processing information
7 are connected and control these.

The sub-control unit 32 includes a light source control unit 40 for controlling the light source light intensity of the exposure lamp 4 and a mechanism driving unit 4 for controlling a mechanical input unit mechanism 41 such as a paper feed mechanism shown in FIG.
2, and an A / D conversion unit 43 that converts analog image information converted by the CCD sensor 5 that detects reflected light into image information and converts the analog image information into a digital data signal, and controls them.

The sub-control unit 33 expands the edited or processed image information for image formation and stores the image information, and the image information from the image expansion unit 45 (the scanner unit 1). An image output unit 46 that outputs a pulse signal (image information for the printer unit 2) as a laser modulation signal using the image information from the
A mechanism driving section 49 for driving an output section mechanism 48 such as a driving system such as a solenoid is connected and controls these.

A data transmission / reception unit 50 is connected to the sub-control unit 34, and controls data transmission / reception with an external device.
In the above-described digital copying machine, the original O is illuminated by the exposure lamp 4, and the reflected light reflected from the original O is C
An image is formed on the CD sensor 5 and converted into an analog electric signal. The analog image signal is converted into a digital signal by the A / D converter 43 and output to the image processor 37.

The image processing section 37 performs filtering processing of image information from the scanner section 1, enlargement / reduction processing in the main scanning direction, gradation processing, and the like. FIG. 1 shows the internal configuration of an image processing unit 37 as an image processing device (image processing means).

The image processing unit 37 is a line buffer (L) for temporarily taking in image information input from the scanner unit 1.
DI) 59, a line buffer (LD2) 60, and a low-pass filter (hereinafter, LPF) for suppressing moire and the like of image information.
51), a range corrector 52 for correcting the contrast of the image, and a high-pass filter (hereinafter, referred to as HPF) connected in parallel with the LPF 51 to enhance the edges and the like of the characters of the image read by the scanner unit 1. ) 53, H
A multiplier 54 for multiplying the image information from the PF 53 by the K parameter;
Adder 55 for adding image information from the imager, an enlargement / reduction unit 56 for performing enlargement or reduction processing on the image information from the adder 55, γ correction and density adjustment for performing various γ corrections and density adjustments on the image information Unit 57, γ correction / density adjustment unit 57
And a gradation processing unit 58 that performs gradation processing on the image information from.

The present invention relates to the enlargement / reduction unit 56 shown in FIG.
This is related to the enlargement / reduction processing. Image processing unit 37
Is for inputting image information read and input by a reading device such as the scanner unit 1 as digital data of, for example, 8 bits per pixel and performing N-value processing (N ≧ 2). The line buffers 59 and 60 temporarily store such image information and provide the image processing described below.

In the low-pass filter processing by the LPF 51, image information output from the line buffers 59 and 60 in synchronization with a predetermined clock is input, and for example, a target pixel is included from the image information (3 × 3). By performing low-pass filter processing in the pixel area, noise removal of an input image and moire removal of a halftone dot document or the like are performed.

In parallel with this, in the high-pass filter processing of the HPF 53, for example, a target pixel is included from the image information output from the line buffers 59 and 60 (3 × 3).
MTF of image after high-pass filter processing in pixel area
Make corrections.

Subsequently, a range correction is performed by a range correction unit 52 in order to improve the contrast of the image subjected to the low-pass filter processing by the LPF 51. The result of the range correction and the value obtained by multiplying the result of the high pass filter processing of the HPF 53 by the K parameter in the multiplier 54 are added in the adder 55.

When performing scaling processing on the processed image from the adder 55, the enlargement / reduction unit 56 performs scaling processing on the image in the main scanning direction using, for example, a linear interpolation method for enlargement and a projection method for reduction. . Further, the gamma correction / density adjustment unit 57 performs processing such as gamma correction for making the input / output characteristics linear, and density adjustment for converting the density of the image to an appropriate density in accordance with the document mode, and finally the processing. The image is printed by the tone processing unit 58 to the printer unit 2
To perform pseudo gradation processing such as an error diffusion method.

Next, an image enlarging method according to the image forming apparatus of the present invention in such a configuration will be described. Since the enlargement method is performed by applying the conventional linear interpolation method, the conventional linear interpolation will first be briefly described.

For example, from the pixels P1 and P2 of the original image to 40
To calculate a 0% enlarged image, it is obtained by the following equation.
(See FIG. 11) H1 = (1−r) × P1 + r × P2 H2 = (1-2 × r) × P1 + 2 × r × P2 H3 = (1−3 × r) × P1 + 3 × r × P2 where H1 H3 is an interpolated pixel value, r = 1 / magnification =
1/4.

When an image is enlarged by such a linear interpolation method, gradation is maintained in a region where gradation is smoothly changed, such as a photographic image, but an edge portion such as a character or a line is maintained in an edge portion. It will be blurred.

This example will be described with reference to FIG. 11. FIG. 11B shows an image obtained by performing a high-pass filter process to sharpen edges as shown in FIG. As described above, a portion having an intermediate density is generated, and as a result, a blurred image as shown in FIG. 11C is obtained.

Further, there is a problem that the blur of the image is more conspicuous because the larger the enlargement ratio, the more intermediate pixels are generated. On the other hand, the present invention prevents edge blurring by weighting the interpolation coefficient r in the above equation.

More specifically, by the calculation of the following equation, an enlarged image as shown in FIGS. 4B and 4C is obtained from the image of FIG. H1 = (1−r−α) × P1 + (r + α) × P2 H2 = (1-2 × r−α) × P1 + (2 × r + α) × P
2 H3 = (1−3 × r−α) × P1 + (3 × r + α) × P
2 where H1, H2, and H3 are “25” when 255 or more.
If it is 5 or less than 0, it is clipped to 0.

At this time, the parameter α is determined by the following equation (1) so that the value becomes larger as the density difference such as an edge becomes larger. α = (| P2−P1 | / 255) × β (1) where || is an absolute value.

In this way, when the density difference between the pixels used for interpolation is large, that is, in the edge region of a character or a line, α
Is large, the effect is great. On the other hand, in a portion where the density difference is small, such as a photographic region, the value of α is small, so that the image is almost the same as the conventional linear interpolation.

Note that the parameter α at the time of enlargement is 0 <α <
The value is in the range of 1. FIG. 5 shows a value obtained when the edge area is enlarged to 400% by the conventional method, and a value obtained by enlarging the area by 400% according to the present invention.
Shows an example of the value when enlarged. It can be seen that the values of H1 to H3 are larger and the rising of the edge is sharper than in the conventional method. Further, it can be seen that the larger the value of α, the sharper the rise of the edge and the greater the effect.

On the other hand, FIG. 6 shows that the halftone area is
It shows a value when the image is enlarged at 0% and a value when the image is enlarged to 400% using the present invention. H1 in the case of a halftone area
It can be seen that the values up to H3 are not different from those of the conventional method, and the values do not change even if α is changed. Therefore, no adverse effect on the halftone area by this method is observed.

Further, the main control section 31 calculates β in the above equation (1).
It is also possible to change the degree of emphasis by adjusting the value of. That is, when the value of β is increased, the value of α is increased, and the effect of edge enhancement is increased as α is increased. Therefore, the value of β can be set according to the magnification.
In this case, in the conventional linear interpolation, the larger the magnification, the larger the blur of the edge. Therefore, if the value of β is set to be larger as the magnification is higher, the effect of improvement is large.

FIG. 7 shows an example in which the edge area is scaled up to 200 by the conventional method.
2 shows an example of a value when the image is enlarged to% and a value when the image is enlarged to 200% according to the present invention. H1 compared to the conventional method
And the rise of the edge becomes sharp. Further, the larger the value of α, the sharper the rise of the edge and the greater the effect.
This is the same as the case of 00%.

On the other hand, FIG. 8 shows that the halftone region is
It shows a value when enlarged at 0% and a value when enlarged to 200% using the present invention. In the case of the halftone region, H
The value of 1 is the same as that of the conventional method, and the value does not change even when α is changed, as in the case of the magnification of 400%.

FIG. 9 shows that the edge area is scaled up to 300 by the conventional method.
5 shows an example of a value when the image is enlarged to% and a value when the image is enlarged to 300% according to the present invention. H compared to the conventional method
1, the value of H2 increases, and the rise of the edge is also sharp. Further, as the value of α is increased, the rising of the edge is sharpened and the effect is increased, as in the case of the magnification of 400%.

On the other hand, FIG. 10 shows that the halftone area is 3
It shows a value when enlarged by 00% and a value when enlarged to 300% using the present invention. In the case of the halftone area,
The values of H1 and H2 are the same as those in the conventional method, and the values do not change even when α is changed, as in the case of the above-mentioned magnification of 400%.

Here, the weight α to be applied to the interpolation coefficient is obtained from the density difference between the two pixels, but this calculation is not limited to the density difference. Any value can be used as long as it represents the characteristics of the character area and the photograph area. Using the result of image area separation in advance, the weight α is considered only for the character area, and the photograph area can be calculated by conventional linear interpolation. .

As described above, according to the embodiment of the present invention, when an image is enlarged by a digital copying machine, if a conventional linear interpolation method is used to enlarge the image, the edges of characters and lines are blurred. Points can be improved. Also,
By appropriately adjusting the parameters of this method, it is possible to set so that the degree of edge enhancement increases as the magnification increases.

[0054]

As described in detail above, according to the present invention,
When an image is enlarged by linear interpolation, it is possible to provide an image forming apparatus and an image processing apparatus capable of preventing characters and lines of an output image from blurring.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an image processing unit in a digital copying machine according to the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a digital copying machine according to the image processing apparatus of the present invention.

FIG. 3 is a diagram showing a schematic configuration of a control system of the digital copying machine of FIG. 2;

FIG. 4 is a diagram illustrating an enlarged image according to the present invention.

FIG. 5 is a diagram showing values when the edge region is enlarged by 400% by the conventional method and the present invention.

FIG. 6 is a diagram showing values when a halftone region is enlarged by 400% by a conventional method and the present invention.

FIG. 7 is a diagram showing values when the edge region is enlarged by 200% by the conventional method and the present invention.

FIG. 8 is a diagram showing values when a halftone region is enlarged by 200% by the conventional method and the present invention.

FIG. 9 is a diagram showing values when the edge region is enlarged by 300% between the conventional method and the present invention.

FIG. 10 is a diagram showing values when a halftone region is enlarged by 300% by the conventional method and the present invention.

FIG. 11 is a view for explaining a conventional enlarged image.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Scanner part 2 ... Printer part 31 ... Main control part (control means) 37 ... Image processing part 51 ... LPF (low-pass filter) 52 ... Range correction part 53 ... HPF (high-pass filter) 54 ... Multiplier 55 ... Adder 56 ... Enlarging / reducing unit (processing means) 57 .gamma. Correction / density adjusting unit (third processing means) 58.

Claims (14)

[Claims] A reading means for reading an image of a document; a processing means for, when enlarging image data read by the reading means, weighting an interpolation coefficient of the image data to form enlarged image data; An image forming apparatus, comprising: an image forming unit that forms an image based on the image data that has been enlarged by the processing unit. 2. A reading means for reading an image of a document, and when enlarging image data read by the reading means by a linear interpolation method, weighting an interpolation coefficient of the image data to form enlarged image data. An image forming apparatus comprising: a processing unit; and an image forming unit that forms an image based on the image data enlarged by the processing unit. 3. A reading means for reading an image of a document; and a feature amount calculated from a density difference of the image data in an interpolation coefficient of the image data when the image data read by the reading means is enlarged by a linear interpolation method. Image forming apparatus comprising: a processing unit that forms enlarged image data by weighting the image data; and an image forming unit that forms an image based on the image data enlarged by the processing unit. . 4. A reading means for reading an image of an original, and when enlarging the image data read by the reading means by a linear interpolation method, weighting the interpolation coefficient of the image data only in a character area of the image data. An image forming apparatus comprising: a processing unit that forms enlarged image data by using the image data; and an image forming unit that forms an image based on the image data that has been enlarged by the processing unit. 5. A reading means for reading an image of a document, and a control means for controlling, when enlarging image data read by the reading means by a linear interpolation method, adjusting a parameter according to a magnification for enlarging the image data. Processing means for calculating weights using the parameters adjusted and controlled by the means, performing weighting on the interpolation coefficients of the image data to form enlarged image data, and processing the image data enlarged by the processing means. An image forming apparatus, comprising: an image forming unit that forms an image based on the image. 6. A reading means for reading an image of a document, and a process for forming enlarged image data by weighting an interpolation coefficient of the image data when enlarging the image data read by the reading means by a linear interpolation method. Means, image processing means for performing various image processing on the image data enlarged by the processing means, and image forming means for forming an image based on the image data processed by the image processing means. An image forming apparatus comprising: 7. A reading means for reading an image of an original, a first processing means for performing a filtering process on the image data read by the reading means, and a linear interpolation of the image data processed by the first processing means. A second processing unit for weighting the interpolation coefficient of the image data to form enlarged image data when enlarging the image data by a method; and performing various image processing on the image data enlarged by the second processing unit. An image forming apparatus comprising: an image processing unit that performs an image processing; and an image forming unit that forms an image based on image data processed by the image processing unit. 8. A reading means for reading an image of a document, a first processing means for performing a filtering process on the image data read by the reading means, and a linear interpolation of the image data processed by the first processing means. A second processing unit for weighting the interpolation coefficient of the image data to form enlarged image data when enlarging the image data by using the method; An image forming apparatus, comprising: third processing means for performing adjustment and gradation processing; and image forming means for forming an image based on image data processed by the third processing means. . 9. An image processing apparatus comprising: processing means for weighting an interpolation coefficient of image data to form enlarged image data when expanding input processing target image data. 10. An image processing apparatus comprising: processing means for weighting an interpolation coefficient of image data to form enlarged image data when enlarging input processing target image data by a linear interpolation method. Image processing device. 11. When enlarging input processing target image data by a linear interpolation method, an interpolation coefficient of the image data includes:
An image processing apparatus, comprising: a processing unit that weights a feature amount calculated from the density difference of the image data to form enlarged image data. 12. A processing means for, when enlarging input processing target image data by a linear interpolation method, weighting an interpolation coefficient of the image data only in a character area of the image data to form enlarged image data. An image processing apparatus comprising: 13. A control means for performing control for adjusting a parameter according to a magnification when enlarging input processing target image data by a linear interpolation method, and using the parameter adjusted and controlled by the control means. Processing means for calculating a weight and applying the weight to the interpolation coefficient of the image data to form enlarged image data. 14. A first processing unit for performing a filtering process on input processing target image data, and when enlarging the image data processed by the first processing unit by a linear interpolation method, Second processing means for weighting the interpolation coefficient to form enlarged image data; and third processing for performing gamma correction, density adjustment, and gradation processing on the image data enlarged by the second processing means. An image processing apparatus, comprising: processing means;