JP3260883B2 - Information recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording apparatus for forming an image by sequentially superimposing images of respective color components on a recording medium.

[0002]

2. Description of the Related Art Conventionally, information recording apparatuses using an electrophotographic method, such as a laser beam printer, have been widely used as output apparatuses for computers. These information recording devices have many advantages such as quietness, high-quality printing, and high-speed printing, and have been a factor for rapidly expanding the field of desktop publishing (DTP).

Further, in recent years, electrophotographic color printers have been developed, and so-called monochrome printers have been developed due to the development of high memory capacity, high-speed processing, low price, etc. of a host computer and a controller for controlling the printer as described above. The handling and printing of not only printing but also color images has been put to practical use and is becoming widespread. In this color printing, as a method of printing a color image having gradation, that is, a method of printing a full-color image, there is a method of expressing gradation by the density of dots to be printed. This is a method of printing a full-color image by changing the print dot density per unit area in a printer.
A dither method, a density pattern method, an error diffusion method, and the like are used. Further, since a laser beam printer can relatively easily increase the dot density in the main scanning direction, a full-color image is printed using pulse width modulation of a recording pixel.

[0004]

However, in the above-described conventional printers, particularly, in the information recording apparatus for performing monochrome printing, characters and the like represented only in black are changed to gray and various characters in the information recording apparatus for performing color printing. For example, colors expressed as 0% yellow, 0% magenta, 0% cyan, and 80% black, or 82% yellow, 0% magenta, 70% cyan, and 0% black are used. When printing image information that ideally has a smooth curve using such a color, 300d
When printing at a resolution of about 500 dpi or 600 dpi, there is a problem that the image does not have a smooth curve.

That is, at a resolution of 300 dpi, the dot arrangement interval is about 85 microns, and at a resolution of 600 dpi, it is approximately 42 microns, which is wider than the interval of about 20 microns which is generally said to be visually recognizable to humans.
At a resolution of 300 dpi or 600 dpi, the outline of a character or graphic formed by dots looks jagged, and it cannot always be said that high-quality printing is performed.

The present invention eliminates the above-mentioned disadvantages of the prior art.
To the input multi-valued image information value of multiple pixels.
Based on a plurality of pixels including the pixel of interest.
Turns are formed, and the formed pattern is the same
An image containing multiple pixels with multi-level image information values
If the pattern is part of a pattern,
By changing the multi-value image information value of the pixel of interest,
Edges are detected from image information,
-To provide an information recording device that can obtain images
I do. Also, the present invention has a relatively smoothing effect.
In low-density parts of the image,
To obtain a good color image because the conversion process is not performed
It is an object of the present invention to provide an information recording device capable of performing the above .

[0007]

In order to achieve the above object, an information recording apparatus according to the present invention scans an image carrier with a light beam modulated according to a multi-valued image information value , and scans the image carrier on the image carrier. In an information recording apparatus that develops the formed latent image with a recording material of a plurality of colors and transfers the developed image to the same transfer material according to the plurality of colors to obtain a visible image, an image composed of a plurality of pixels is used.
An input unit for inputting a multi-valued image information value of each pixel of an image, and a pattern formed by a plurality of pixels including a pixel of interest based on the multi-valued image information value of a plurality of pixels input by the input unit. The forming means for forming and the pattern formed by the forming means form multi-level image information values of the same level other than 0.
Pattern that constitutes the edge of the image including multiple pixels
If you are over emissions, characterized in that it comprises an image information changing means for changing the multi-value image information value of the pixel of interest in the pattern. Here, the image information changing means, the for each color to be developed by the recording material, changing the multi-value image information value of the target pixel with reference to the pattern formed by a plurality of pixels around the pixel of interest. Further, the image carrier is scanned with a light beam modulated in accordance with the multi-valued image information value , and the latent image formed on the carrier is developed with a recording material of a plurality of colors. In an information recording device that obtains a visible image by transferring to the same transfer material according to the
Input means for inputting a multi-valued image information value of each pixel, forming means for forming a pattern formed by a plurality of pixels including a pixel of interest based on the multi-valued image information values of a plurality of pixels input by the input means; based on the pattern formed by said forming means, and an image information changing means for changing the multi-value image information value of the pixel of interest in the pattern, the image
The information changing means does not change the multi-valued image information value of the target pixel when the density of the image is low.

[0008]

[Action] In the above configuration, based on the multivalued image data values of a plurality of pixels input, to form a pattern composed of a plurality of pixels including the target pixel, the formed pattern is 0
Other pixels with the same level of multi-level image information value
If the pattern constitutes the edge of the image ,
By changing the multivalued image information value of the target pixel in the pattern, an edge can be detected from the multivalued image information, and a color image with smooth edges can be obtained. Also, the appear unlikely low concentration portion of the image of relatively smoothing effect, a conversion process multivalued image data value than not adversely rows, it is possible to obtain an excellent color image.

[0009]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of a color page printer which is an information recording apparatus according to an embodiment of the present invention. In FIG.
0 is a color page printer, 104 is a host computer, 101 is a printer controller, 102 is a printer engine, and 103 is a multi-value image conversion circuit.

In the color page printer having the above configuration, the host computer 104 issues a print command to the printer 100. The content of this print command is interpreted by the controller 101 inside the printer,
The raster image is expanded inside the controller. The developed raster image is sent to the multi-level image conversion circuit 103 for each of the colors yellow, magenta, cyan, and black.

The multi-valued image conversion circuit 103 changes the pixel values of the input multi-valued image so that when the image is printed, it looks smooth without jaggies. Then, the image changed by the multi-level image conversion circuit 103 is sent to the printer engine 102 and printed. <Description of printer engine> As a method of obtaining a color image in a color page printer, charging on an image carrier,
There is a method in which a process of transferring a recording image formed by exposure and development onto recording paper is repeated a plurality of times to form a multi-color superimposed image on the recording paper. A color page printer of this type is disclosed in, for example, Japanese Patent Application Laid-Open No. 50-509.
It is described in detail in, for example, Japanese Patent Publication No. 35, and has been put to practical use in a configuration according to these descriptions.

FIG. 2 is a vertical sectional view of the color page printer according to the embodiment. As shown in FIG. 1, the photosensitive drum 1, corona charger 2, roller charger 3, and a plurality of developing devices 4a,
A support rotating shaft 9 supporting the rotatable supports 4b, 4c and 4d is provided. Also, as shown in FIG.
On the same cylinder of the support rotating shaft 9, the developing units 4a, 4
b, 4c, 4d developing opening surfaces 5a, 5b, 5c, 5d
Is set.

As shown in FIG. 3, yellow toner, magenta toner, cyan toner, and black toner are accommodated in the developing units 4a, 4b, 4c, and 4d, respectively. , 6d and toner regulating members 7a, 7b, 7c, 7d are provided.
a, 8b, 8c, and 8d, the developing rollers 8a, 8b, and 8d on the toner application rollers 6a, 6b, 6c, and 6d.
8c and 8d, the toner is applied to the toner regulating members 7a and 8d.
The necessary tribo is given to the toner by 7b, 7c, and 7d.

The material of the regulating member is preferably a material which is charged in the opposite direction to the polarity of the toner. For example, when the toner has a negative polarity, nylon or the like is preferable, and when the toner is positively charged, silicon rubber or the like is used. Is good. It is preferable to select the peripheral speed of the developing roller in a range of 1.0 to 2.0 times the peripheral speed of the photosensitive drum 1 (the speed of the drum surface). Developing devices 4a, 4b, 4c, 4d attached to support rotating shaft 9
As shown in FIG. 3, the developing units 4a, 4b, 4c, and 4d are driven such that the developing opening surfaces 5a, 5b, 5c, and 5d always face the photosensitive drum surface. This driving method is described in detail in, for example, Japanese Patent Application Laid-Open No. 50-93437. A transfer roller 1 having a function of holding a transfer sheet (not shown) on the left side of the photosensitive drum 1 and transferring an image on the photosensitive drum 1 onto the transfer sheet (not shown).
0 is arranged.

With the above configuration, the photosensitive drum 1 is driven in a direction indicated by an arrow at a peripheral speed of 100 mm / sec by driving means (not shown). The photosensitive drum 1 has an organic photosensitive member (O 2) on the outer peripheral surface of an aluminum cylinder having a diameter of 40 mm.
The OPC may be made of A-Si, CdS, Se, or the like. A laser diode 11, which constitutes an exposure device, a polygon mirror 13, a lens 14, and a folding mirror 15, which are driven to rotate by a high-speed motor 12, are disposed above the printer main body. 700 V DC voltage, -1500 V _pp (peak to peak) at 700 Hz AC frequency
peak) AC voltage is superimposed and uniformly charged to about -700V.

When a signal according to a yellow image pattern is input to the laser diode 11, the signal is applied to the photosensitive drum 1 through the optical path 16, and the light-irradiated portion of the photosensitive drum 1 is approximately -100V. become. When the photosensitive drum 1 advances in the direction of the arrow, the developing devices 4a, 4b, 4c, 4
visualized by d. Here, the transfer process will be described in detail.

Transfer paper is fed from a transfer paper cassette 17 by a pickup roller 18 in synchronization with an image on the photosensitive drum 1, and the transfer roller 10 is made of metal having a diameter of 156 mm so that the transfer paper is attracted to the transfer roller 10. Cylinder 1
An elastic layer 20 having a thickness of 2 mm is wrapped around 9 and the upper layer is
It is configured by winding a PVDF 21 having a thickness of 100 mm.
The elastic layer 20 rotating in the direction of the arrow at the same speed as the photosensitive drum 1 was made of urethane foam made by Inoac.

When transfer paper (not shown) is supplied to the transfer roller 10, the transfer paper is held by the gripper 22.
The toner image on the photosensitive drum is transferred onto transfer paper by a voltage between the photosensitive drum 1 and the transfer roller 10 by a power supply (not shown). At the same time, the toner is attracted to the transfer roller 10 by charge injection into the transfer paper. In addition, if necessary, a voltage may be applied between the suction rollers 23 to perform suction in advance.

By performing the above steps for magenta, cyan, and black, toner images of a plurality of colors are formed on transfer paper. Then, the transfer paper is peeled off from the transfer roller 10 by the separation claw 24, and the transfer paper is melted and fixed by a known fixing device 25 that performs heating and pressure, thereby obtaining a desired color image. The transfer residual toner on the photosensitive drum 1 is a known fur brush,
It is cleaned by a cleaning device 26 such as a blade. Further, the toner on the transfer roller 10 is also cleaned by a transfer roller cleaning device 27 such as a fur brush or a web as needed. <Description of Image Processing Unit> FIG. 4 is a block diagram for explaining the relationship between the controller 101 and the printer engine 102 for the multivalued image conversion circuit 103 functioning as an image processing unit in the color page printer according to the present embodiment. It is.

In FIG. 4, a color processing unit 51 stores R, R, and R in an image storage unit (not shown) in the printer controller.
A 24-bit G / B image signal is received and converted to an 8-bit VDO signal of Y signal, M signal, C signal, or K signal. In addition, FIG.
5 shows a timing chart when converting R, G, and B image signals into VDO signals.

The Y, M, C, and K VDO signals are represented by γ
The correction unit 52 converts the signal into an 8-bit signal that has been γ-corrected. The signal is input to a pulse width modulation unit 53 (hereinafter, referred to as a PWM unit) via a multi-level image conversion unit 59 at the next stage. The 8-bit image signal input to the PWM unit 53 is latched by the latch 54 in synchronization with the rising edge of the image clock VCLK, and is converted into an analog voltage by the D / A converter 55 at the next stage. 56 is input.

On the other hand, the image clock VCLK is converted into a triangular wave by the triangular wave generator 58, and then input to the analog comparator 56. Then, the analog comparator 56 compares these two signals and outputs a signal that has been pulse-width modulated in accordance with the triangular wave. This signal is inverted by the inverter 57 and output to the laser driver as a PWM signal.

FIG. 6 is a timing chart when the analog comparator 56 performs pulse width modulation on the output signal of the D / A converter 55 based on the triangular wave. As can be seen from the figure, when the input 8-bit image data is FF [H] (H indicates hexadecimal), the PWM unit outputs the widest PWM signal, and the image data becomes 0.
When 0 [H], the narrowest PWM signal is output.

Here, the color processing section 51 converts the RGB signals in an image storage section (not shown) inside the controller 101 into Y signals.
The process of generating the MCK signal will be described. FIG.
FIG. 3 is a block diagram illustrating a configuration of a color processing unit 51. Referring to FIG. 1, reference numeral 201 denotes a raster image storage memory for storing a raster image developed by the controller 101; and 202, an image for reading a color image stored in the raster image storage memory 201 in a necessary order. The readout circuit 203 is a YMC from the RGB color system.
A color correction circuit 204 for converting into a color system extracts a black component from the YMC color system to create a black image plane, and converts each of the yellow, magenta, and cyan components into black. A black extraction / under color removal circuit having a function of removing the color component, and a selector circuit 205 for selecting an image signal of one color from yellow, magenta, cyan, and black.

The controller 101 develops a color image as a raster image in the raster image storage memory 201 in accordance with a command generated by the host computer 104. The color image developed here is an RGB color system,
The red image is developed as an image plane (R), the green image is developed as an image plane (G), and the blue image is developed as an image plane (B) as 600 dpi data.

An image readout circuit 202 controlled by a control circuit (not shown) reads out the image from the image planes of the respective colors one by one from the color image developed in the raster image storage memory 201, and outputs red, green, Create a blue parallel signal. FIG. 8 (a)
3 is a diagram showing R, G, B parallel signals created by the image reading circuit 202. As shown in the figure, the image reading circuit 202 includes red, green,
The blue image is read four times, each representing a single color image.

Next, the R, G, B parallel signals are converted into Y, M, C parallel signals by the color correction circuit 203.
FIG. 8B shows the state of the converted Y, M, and C parallel signals. As described above, since the same image is read four times by the image reading circuit 202, the Y, M, and C parallel signals are also output four times. Further, the Y, M, C parallel signals are converted into Y,
Create M, C, K parallel signals. In the case of a color laser beam printer, in principle, yellow, magenta,
Although black can be created using cyan toner, it is necessary to use black toner in order to improve print quality.

Therefore, a black component is extracted from the Y, M, and C parallel signals to create a black raster image. Further, the components used to create the black component are subtracted from the yellow, magenta, and cyan components. FIG. 8C shows the Y, M, C, and K parallel signals generated by the black extraction / under color removal circuit 204 from the Y, M, and C parallel signals. Here, the same image is read four times by the image reading circuit 202 as in the case of the Y, M, and C parallel signals, so that the same data is output four times for the Y, M, C, and K parallel signals.

Finally, only one color is selected from the Y, M, C, and K parallel signals by a selector circuit 205 controlled by a control circuit (not shown). The same data is output four times as the Y, M, C, and K parallel signals by the selector circuit 20.
5, the colors yellow, magenta, cyan, and black are sequentially selected. Note that the selector circuit 2
FIG. 8 (d) shows the signal output from 05.

As described above, from the color processing section 51, yellow image data, magenta image data, cyan image data, and black image data are sequentially output as multi-valued image signals. Next, how a laser beam printer forms an electrostatic image on a photosensitive drum from an electric signal will be described.

FIG. 9 is a diagram showing a configuration of an optical system in a laser beam printer. In the figure, 300 is
A laser driver for driving the semiconductor laser 301,
301 is a semiconductor laser that converts an electric signal into an optical signal,
302 is a rotating polygon mirror for scanning the laser beam on the photosensitive drum, 303 is an f-θ lens for focusing the laser beam on the photosensitive drum, 304 is
A beam detector for detecting the start of scanning of the main scanning line, and 306 is a photosensitive drum for forming an electrostatic image.

The semiconductor laser 301 shown in FIG. 9 is driven by the laser driver 300 according to the PWM signal generated by the PWM unit 53 shown in FIG. Semiconductor laser 301
Is scanned in the main scanning direction by the rotary polygon mirror 302, and further, an f-θ lens 303 disposed between the rotary polygon mirror 302 and the photosensitive drum 306.
Through the photosensitive drum 305. The laser beam forms an image on the photosensitive drum and forms a latent image on the main scanning line by scanning in the main scanning direction.

Upon detecting the laser beam, the beam detector 304 disposed at the laser beam scanning start position outputs a BD signal as a synchronization signal for determining an image writing timing in the main scanning direction. <Description of Multi-Valued Image Conversion> Next, a multi-valued image conversion circuit constituting the color page printer according to the present embodiment will be described.

In the present embodiment, the multi-value image conversion circuit 103 has a function of changing the value of the pixel of interest with reference to the pixels surrounding the pixel of interest so that the printed image becomes a high-quality image. Have. FIG. 10 is a diagram illustrating a target pixel and surrounding pixels to be referred to. In the figure, the pixel corresponding to the mark marked at the position of the coordinate F5 is the target pixel. In this embodiment, 11 pixels in the main scanning direction × 9 pixels in the sub-scanning direction are set as the reference area around the pixel of interest. However, the size of the reference area is not limited to this, and may be any size.

More specifically, for example, the letter "a" in the alphabet as shown in FIG.
Among the magenta, cyan, and black, this is 8-bit multi-valued image data composed of only black.
(White) and black circles indicate a region S (11 pixels in main scanning × 9 pixels in sub-scanning = 99 pixels) surrounding the pixel of interest A when printing the pixel of interest A in image data having a value of 255 (black). ) Is stored in a line memory as temporary storage means. FIG. 12 is a diagram illustrating a state of image data stored in the line memory.

Then, the multivalued image conversion circuit 103 checks the characteristics of the image data in the reference area S, and changes the data of the target pixel A to be printed according to the characteristics and prints the data.
At this time, the data is changed so that the outline of the graphic composed of pixels is smooth when printed by the printer engine. FIG. 13 is a block diagram showing the internal configuration of the multi-level image conversion circuit. As shown in the figure, the multi-level image conversion circuit 103 is roughly composed of two parts. One is a storage unit 401 that stores the surrounding pixels to be referred to, and the other is a pixel conversion unit 402 that changes the pixel of interest with reference to the surrounding pixels.

The storage unit 401 for storing the surrounding pixels includes:
Further, a line memory 403 for storing data for several main scanning lines and a window memory 404 for storing only pixels in a reference area to be actually referred to. FIG.
5 is a block diagram illustrating a configuration example of a line memory 403. FIG. As shown in the figure, the line memories 1 to 8 store the input multi-valued image data while sequentially shifting it in synchronization with the image clock VCLK. Each line memory is
Line memory 1 → Line memory 2 → Line memory 3 → ...
→ It is connected in the order of the line memory 8 and stores dot information corresponding to (for 8 lines in the sub-scanning direction) × (the number of dots of the main scanning length).

The line memory shown in FIG. 14 is used when the controller develops an image in a multi-level color of 300 dpi and outputs it with a multi-level color engine of 300 dpi.
3 is a configuration example of a line memory used when the resolution of an image developed by a controller is the same as the resolution printed by an engine. On the other hand, the line memory shown in FIG. 15 is used when the controller develops an image in 300 dpi multi-valued color and outputs it with a 600 dpi multi-valued color engine.
This is a configuration example used when the resolution printed by the engine is twice the resolution of the image developed by the controller.

In FIG. 15, line memories 1 to 9
This is a line memory for storing 8-bit multivalued image data for one main scanning line. As described above, when the controller expands image data at 300 dpi and the printer engine prints at 600 dpi, the 600 dpi horizontal synchronization signal EB output from the printer engine is output.
From D (not shown), a 300 dpi horizontal synchronization signal BD created by a horizontal oscillator (not shown) and a synchronization clock generation circuit is created.

FIG. 16 is a timing chart when the multivalued image data VDO is input to the line memory shown in FIG. 15 in synchronization with the horizontal synchronizing signal BD. here,
The multi-valued image data VDO for one main scanning line is 600d
pi is input to the line memory during one cycle of the horizontal synchronizing signal EBD. Then, the multi-level image data VDO input to the line memory is first input to the multi-level selector 501. The multi-value selector 501 receives an 8-bit input at its terminals A and B, and outputs one of the inputs to an output terminal Y according to a selector signal (not shown).

The multi-value selector 501 first performs an operation of outputting an input to the terminal A to a terminal Y in accordance with the above selector signal. The multi-level image data output from the terminal Y of the multi-level selector 501 is input to the window memory WM1 and also to the line memory 1 at the same time. And
Each line memory receives the multi-valued image data for one pixel output from the terminal Y of the multi-value selector, and outputs the multi-valued image data for one pixel to a predetermined window memory.

In the timing chart shown in FIG.
The relationship between the image data input after the generation of the 00 dpi horizontal synchronization signal BD and the reading of the line memory is shown. As shown in the figure, the 300 dpi 8-bit multi-valued image data VDO input to the line memory in synchronization with the horizontal synchronizing signal BD is converted to a 600 dpi horizontal synchronizing signal EBD.
, And nothing is input in one cycle of the next 600 dpi horizontal synchronization signal EBD.

The multi-value selector selects the multi-value image data VD
The data path is switched so that image data flows from the input terminal B to the output terminal Y in one cycle of the 600 dpi horizontal synchronizing signal EBD to which O is not input. Then, in synchronization with the image clock VCLK, multi-valued image data is read from each line memory, input to the input terminal B of the multi-value selector, and then output from the output terminal Y.

The data output from the output terminal Y is sent to the window memory and is also input to the line memory that has output the data. That is, the 600 dpi horizontal synchronization signal E to which the multi-valued image data VDO is not input.
When the period of one BD cycle ends, the same data has been written to the line memory as before. In this manner, the same data is sent to the window memory twice during one cycle of the horizontal synchronization signal BD of 300 dpi.

As a result, an image of 300 dpi in the sub-scan can be printed at 600 dpi in the sub-scan. FIG.
FIG. 4 is a block diagram illustrating a configuration example of a window memory 404. Each shift register shown in the figure can hold 8-bit multi-value data, and the input is 8 bits ×
There are 9 lines, and the output is 8 bits × 9 × 11 lines.

FIGS. 18 to 21 are diagrams showing an algorithm for changing the pixel value of the multi-valued image data so that the printing result in the color page printer according to this embodiment becomes smooth. Note that these figures show, as an example, a pattern to be subjected to smoothing particularly for a figure having a vertical boundary line. In FIG. 18, the vicinity of the target pixel 5F is a pixel pattern (3f, 4f) as shown.
pixel values of e, 4f, 5e, and 6e are 0, and 3g, 4
When the pixel values of g, 5f, and 6f are other than 0 and are all the same value), the value of the target pixel is changed to a value of 50% of ●.

In FIG. 19, the pixel pattern (3g, 4g, 5g, 5f, 6f) shown in FIG.
When the pixel value of f is 0 and the pixel values of 3f, 4f, 5e, and 6e are other than 0 and are all the same value), the value of the target pixel is changed to a value of 25% of ●. Is shown. In FIG. 20, the vicinity of the target pixel 5F is a pixel pattern (2f, 3e, 3f, 4e, 5e, 6e) as shown in the figure.
pixel values of e and 7e are 0, and 2g, 3g, 4f, 5
When the pixel values of f, 6f, and 7f are other than 0 and are all the same value), it indicates that the value of the target pixel is changed to a value of 50% of ●.

Further, FIG. 21 shows that the pixel pattern (2g, 3g, 4f,
The pixel values of 4g, 5f, 6f, 7f are 0, and 2f,
When the pixel values of 3f, 4e, 5e, 6e, and 7e are all other than 0 and are the same value), the value of the target pixel is
It shows that it changes to the value of%. As other patterns, although not shown, the patterns shown in FIGS. 18 to 21 are patterns in which the left and right are switched around the pixel of interest, a pattern in which the top and bottom are switched, and a pattern in which the top and bottom and left and right are switched. Has each set of

The multi-valued image conversion circuit 103 is a circuit for realizing the algorithm for converting the multi-valued image as described above. The multi-valued image data converted by this conversion circuit is converted to the PWM data 53 shown in FIG. After being modulated to the area gradation, the image data is sent to the printer engine 102 and printed. FIGS. 22 and 23 are diagrams showing other examples of smoothing in the present embodiment. Among them, FIG. 22 shows an example of smoothing of a diagonal line close to horizontal and FIG. 23 shows an example of a smoothing of a diagonal line close to vertical. I have.

The printing example in FIGS. 22 and 23 is
w: 100%, mazenta: 0%, Cyan: 40%, black
: 0%. 22 and 23, (1) is multi-valued image data sent from the controller, and (2) is a laser driver that performs PWM modulation on pixels obtained by converting multi-valued image data by a multi-valued image conversion circuit. (3) schematically shows a state in which the image is printed for each color and the boundary of the image is smoothed by the electrophotographic process.

As described above, according to this embodiment,
By converting a pixel value by applying a conversion algorithm based on a pixel pattern formed by the target pixel and its surrounding pixels to the target pixel among the pixels constituting the multi-valued image,
It is possible to extract an image to be printed with a smooth curve, such as a character, from multi-valued image data, and obtain a smooth color print image with respect to the character and the curve.

Note that the above-described algorithm converts the color multi-valued image developed at 600 dpi by the controller to 60.
The algorithm of the multi-valued image conversion when printing with the 0 dpi engine is used. The algorithm of the multi-valued image conversion when the color multi-valued image developed at 300 dpi by the controller is printed with the engine of 600 dpi is also an even-numbered algorithm. If attention is paid to the case of the scanning line and the case of the odd main scanning line, the same algorithm as described above can be applied.

When the density of the image is low,
Since it is relatively insensitive to human vision and the effect of smoothing by the electrophotographic process is small, it is needless to say that the multi-value image conversion may not be required. <Modification> In the above embodiment, as shown in FIG. 1, the multivalued image conversion is performed by hardware between the controller 101 and the printer engine 102 to perform smoothing. It may be performed by hardware.

More specifically, a raster image is created in the controller by a command from the host computer, and the raster image is scanned immediately before sending the raster image to the printer engine. Then, according to the above embodiment, FIG.
21. Multi-value image conversion is performed by software according to the same algorithm as the multi-value image conversion algorithm shown in FIG.

Alternatively, when an image of a predetermined pattern such as a character or the like is printed, there are naturally limitations in consideration of the type of the character, the size of the character, and the number of the colors of the character. A method may be used in which the multivalued image information is stored and held, and is used when creating a raster image. FIG. 24 is a diagram for describing an example of smoothing by software.

In general, a page printer holds image information of characters and figures as vector information, and converts it into raster information as necessary. The curve shown in FIG. 24A will be described as an example of a curve based on vector information.
In FIG. 24A, the square 1 forming the image
If one pixel is 600 dpi, (1) is 600d
When rasterized by pi, the result is as shown in (4). However, when (1) and (4) are compared, their print densities are different. Therefore, the pixel value of 600 dpi is set to an intermediate density pixel value in the same manner as the density of the pixels divided by the curve of (1). An example is shown in (5). Then, the result of PWM modulation of the multi-valued image data of (5) is (2),
(3) is the print result. The image is smoothed by such an electrophotographic process.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device.

[0058]

As described above, according to the present invention,
Based on the multivalued image data values of a plurality of pixels input, the pixel of interest
Forming a pattern composed of a plurality of pixels including
The formed pattern is a multi-level image information of the same level other than 0
The edge of the image is composed of multiple pixels with
If a pattern that, of the target pixel in the pattern multi
By changing the value image information value, an edge can be detected from the multi-value image information, and a color image with smooth edges can be obtained. Also, the appear unlikely low concentration portion of the image of relatively smoothing effect, a conversion process multivalued image data value than not adversely rows, it is possible to obtain an excellent color image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a color page printer according to an embodiment of the present invention.

FIG. 2 is a vertical sectional configuration diagram of a color page printer according to the embodiment.

FIG. 3 is a diagram illustrating a configuration of a developing device.

FIG. 4 is a block diagram of a multi-level image conversion circuit functioning as an image processing unit.

FIG. 5 is a timing chart when converting R, G, and B image signals into VDO signals.

FIG. 6 shows a timing chart of pulse width modulation in the analog comparator.

FIG. 7 is a block diagram illustrating a configuration of a color processing unit.

FIG. 8 is a timing chart of the color processing unit.

FIG. 9 is a diagram illustrating an optical system of the laser beam printer.

FIG. 10 is a diagram showing coordinates of a reference window.

FIG. 11 is a diagram illustrating a relationship between a character pattern of “a” and a reference window.

FIG. 12 is a diagram illustrating a relationship between a character pattern of “a” and a reference window.

FIG. 13 is an internal block diagram of a multi-level image conversion circuit.

FIG. 14 is a configuration example of a line memory.

FIG. 15 is a configuration example of a line memory.

16 is a timing chart of the line memory shown in FIG.

FIG. 17 is a configuration example of a window memory.

FIG. 18 is a diagram illustrating an example of a dot pattern of a reference area and a change pattern of a pixel of interest.

FIG. 19 is a diagram illustrating an example of a dot pattern of a reference area and a change pattern of a target pixel.

FIG. 20 is a diagram illustrating an example of a dot pattern of a reference area and a change pattern of a target pixel.

FIG. 21 is a diagram illustrating an example of a dot pattern of a reference area and a change pattern of a target pixel.

FIG. 22 is a diagram for explaining printing according to an embodiment.

FIG. 23 is a diagram for explaining printing according to an embodiment.

FIG. 24 is a diagram for explaining printing according to a modification.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 corona charger 3 roller charger 4a, 4b, 4c, 4d developing unit 5a, 5b, 5c, 5d developing opening surface 6a, 6b, 6c, 6d coating roller 7a, 7b, 7c, 7d toner regulating member 8a, 8b, 8c, 8d Developing roller 9 Support rotating shaft 10 Transfer roller 11 Laser diode 12 High-speed motor 13 Polyhedral mirror 14 Lens 15 Folding mirror 16 Optical path 17 Transfer paper cassette 18 Pickup roller 19 Metal cylinder 20 Elastic layer 21 PVDF 22 Gripper Reference Signs List 23 suction roller 24 separation claw 25 fixing device 26 cleaning device 27 transfer roller cleaning device 51 color processing unit 52 γ correction unit 54 latch 53 pulse width modulation unit 55 D / A converter 56 analog comparator 57 inverter 58 triangular wave generation unit 1 1 Printer 102 Controller 103 Printer Engine 104 Host Computer 201 Raster Image Storage Memory 202 Image Readout Circuit 204 Black Extraction / Under Color Removal Circuit 205 Selector Circuit 300 Laser Driver 301 Semiconductor Laser 302 Rotating Polygonal Mirror 303 f-θ Lens 304 Beam Detector 305 Main Scan line 306 Photosensitive drum

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B41J 2/44 B41J 2/485 B41J 2/52-2/525 G03G 15/01 H04N 1/40

Claims (3)

(57) [Claims] An image carrier is scanned with a light beam modulated according to a multi-valued image information value , and a latent image formed on the carrier is developed with a recording material of a plurality of colors. An input unit for inputting a multi-valued image information value of each pixel of an image composed of a plurality of pixels , in an information recording apparatus for obtaining a visible image by transferring the image to the same transfer material according to the plurality of colors; Image information of multiple pixels input by
Based on the values, and forming means for forming a pattern composed of a plurality of pixels including the target pixel, the pattern formed by said forming means, the same non-zero level
The edge of an image including multiple pixels with multi-valued image information values
If a pattern constituting a di-, before the pattern
Information recording apparatus characterized by comprising an image information changing means for changing the multi-value image information value of the serial pixel of interest. Wherein said image information changing means, the for each color to be developed by the recording material, changing the multi-value image information value of the target pixel with reference to the pattern formed by a plurality of pixels around the pixel of interest The information recording apparatus according to claim 1, wherein 3. The image carrier is scanned with a light beam modulated in accordance with a multi-valued image information value , and a latent image formed on the carrier is developed with a recording material of a plurality of colors. Input means for inputting a multi-valued image information value of each pixel of an image composed of a plurality of pixels in an information recording apparatus which obtains a visible image by transferring the image to the same transfer material according to the plurality of colors; Multi-valued image information of a plurality of pixels input by the input means
Based on the values, and forming means for forming a pattern formed by a plurality of pixels including the target pixel, based on the pattern formed by said forming means, variable image information to modify the multi-value image information value of the pixel of interest in the pattern an information recording device, wherein the image information changing unit does not change the multi-valued image information value of the pixel of interest when the image density is low.