JP2002127503A - Printing device and image generation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variety of dither matrices in a limited capacity of a component memory element of a dither matrix table forming a gradation conversion circuit of a printing device. SOLUTION: Dither matrix threshold data can be written to a dither matrix table storage section 11. When tonal value conversion is executed for Y toner print data, a dither X address 105 as a counter output value is fed back to a comparator 4, and resets a counter 5 when it becomes equal to an X size specification value 101. Similarly, it functions as an L-adic counter, resetting the counter when it becomes equal to a Y size specification value 106. By inputting the x address signal 105, a y address signal 110, an X size signal 101, and the Y size signal 106 to an address synthesis section 20, and combining data bits of all address signals in accordance with a dither matrix size, a dither matrix address 111 is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a printing apparatus and an image generating method thereof, and more particularly, to a printing apparatus such as a laser beam printer connected to a host computer via a bidirectional interface and an image generating method thereof. .

[0002]

2. Description of the Related Art As a method of converting a gradation value of print data transmitted from a host computer into a gradation value printable by a printing apparatus, there are a dither matrix method, an error diffusion method, and the like. In particular, it is a dry-type printing apparatus with less bleeding and scattering. Laser beam printers and LED printers often employ a dither matrix method as a data gradation conversion method.

[0003] The dither matrix method is a method of expressing a gradation by the degree of dispersion of dots per unit area. A matrix table in which threshold values arranged in an m × n matrix are defined in advance is prepared and the original gradation data is prepared. By comparing the threshold value at the same address as the above, whether the specific dot in the unit area is ON / OFF (whether to apply toner or ink) or whether the shape of the specific dot is increased or decreased (multi-valued) Is determined).
Depending on the size of the matrix table and the manner of defining the threshold value, the screen ruling, the screen angle, and the gradation value of the print image can be freely changed.

In the multi-value dither matrix method, multi-value data is obtained as an output value by preparing a plurality of threshold data on one address. Output gradation value is 2bi
In the case of t, three threshold data, and in the case of 4 bits, 15
Threshold data is required. In a color laser beam printer capable of multi-value printing and high resolution,
In many cases, a multi-valued dither matrix is employed.

[0005]

Generally, when the size of the dither matrix is equal, the screen angle is also equal. In the case of color printing, if all the screen angles of the three primary colors are equal, a moire phenomenon, which is an interference fringe, occurs, and image quality may be degraded. In order to prevent this, it is necessary to prepare dither matrices having different sizes for each printing color and change the screen angle.

Further, the type of print data (text / C
G, photograph), the required resolution and gradation value are different, and the image generating unit of the color printer must prepare various kinds of matrix dither tables in order to realize high image quality. .

However, if dither matrix tables of different sizes are prepared for each color, a large memory capacity is required for the dither matrix table. Along with this, when the dither matrix is realized by the ASIC, there is a problem that the layout is difficult due to an increase in die size, and when the dither matrix is realized by an external existing memory element, high-speed processing becomes difficult. Is becoming apparent.

The present invention has been made in view of such a problem, and an object of the present invention is to solve the problem of the limited capacity of the memory elements constituting a dither matrix table constituting a gradation conversion circuit of a printing apparatus. Accordingly, an object of the present invention is to provide a printing apparatus having a function of providing a variety of dither matrices by maximally changing a dither matrix size, and an image generating method thereof.

[0009]

According to the present invention, in order to achieve the above object, according to the first aspect of the present invention, there is provided an image processing apparatus comprising: a gradation information which is density information per pixel of print data from a host computer; Is a printing apparatus having a tone value converting means for converting a dither matrix method into a reproducible information amount, employing a dither matrix method as the tone value converting means, and registering a plurality of dither matrix tables before the printing process. And a dither matrix storage means capable of storing a matrix having an arbitrary matrix size for each color printing of yellow (Y), magenta (M), cyan (C), and black (K) during printing of one page. A matrix table is registered in the dither matrix storage means, and tone value conversion of a different matrix size for each printing color is performed based on threshold data of the dither matrix table. It is characterized in that it has a dither address generating means capable of implementing the management.

[0010] The invention described in claim 2 is the same as the claim 1.
In the invention described in the above item, the dither address generation means may include a dither matrix X size setting means and a dither matrix Y for designating a size in order to arbitrarily change a matrix shape of the dither matrix table under a condition of a fixed maximum matrix area. Size setting means, X axis, Y
An address counter capable of generating dither address data of the maximum size of each side of the axis, comparing the dither matrix size setting value with the dither address data, and clearing the address data counter if they match; Comparing means, dither start address setting means for setting a start address of a dither matrix table capable of positioning the dither matrix table in an arbitrary area of a printed document, and an X address and a Y address according to the dither matrix size And dither address combining means for combining the valid data bits to generate dither address data.

[0011] The invention according to claim 3 is based on claim 1.
In the invention described in (1), when the dither address generating means arbitrarily specifies the dither matrix size, if the total number of cells is equal to or less than a predetermined total number of cells, one pixel;
The feature is that the dither matrix size of all combinations in one line unit can be designated.

The invention described in claim 4 is the first invention.
In the invention described in the above, the dither address generating means has means for adding a specified offset value to a start address of a dither X address in a specified dither Y size unit, and by intentionally shifting a dither matrix,
It is characterized by having a function of realizing an arbitrary screen angle in drawing data after gradation conversion.

According to a fifth aspect of the present invention, there is provided a printing method having a tone value converting step of converting tone information which is density information per pixel of print data from a host computer into a reproducible information amount. An image generation method for an apparatus, comprising:
A dither matrix method is adopted as the gradation value conversion step, and a dither matrix storage step in which a plurality of dither matrix tables can be registered at a stage prior to the printing process, and a yellow (Y) during the printing process of one page. , Magenta (M), cyan (C), and black (K), a dither matrix table of an arbitrary matrix size is registered in the dither matrix storage step, and each dither matrix table is registered based on the threshold data of the dither matrix table. A dither address generation step capable of executing a gradation value conversion process of a different matrix size for each print color.

The invention described in claim 6 is the same as the invention described in claim 5.
In the invention described in (1), the dither address generation step includes a dither matrix X size setting step of specifying a size and a dither matrix Y in order to arbitrarily change a matrix shape of the dither matrix table under a condition of a fixed maximum matrix area. A size setting step, and an address counter capable of generating dither address data of the maximum size of each side of the X-axis and Y-axis. The dither matrix size set value is compared with the dither address data. An X address comparison step and a Y address comparison step, and a dither start address setting step of setting a start address of a dither matrix table capable of positioning the dither matrix table in an arbitrary area of a print document. Depending on the dither matrix size, X address, is characterized in that it has a dither address binding step of combining the valid data bit of the Y address generating dither address data.

[0015] Further, the invention according to claim 7 is based on claim 5.
In the invention described in the above, in the dither address generation step, when the dither matrix size is arbitrarily specified, if the total number of cells is equal to or less than a predetermined total number of cells, the dither matrix size of all combinations of one pixel and one line unit is changed. It can be specified.

The invention described in claim 8 is the same as the claim 5.
In the invention described in the above, the dither address generating step has a step of adding a specified offset value to a start address of a dither X address in a specified dither Y size unit, and intentionally shifting a dither matrix, It is characterized by having a function of realizing an arbitrary screen angle in drawing data after gradation conversion.

With such a configuration, dither matrices of various sizes can be realized from the dither matrix table storage means with a minimum memory capacity and a simple logic circuit, and the number of screen lines, screen angles, and gradation values can be flexibly adjusted. Thus, provision of a higher quality color print image can be realized.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. Before describing the configuration of the present embodiment, a configuration of a color laser beam printer suitable for applying the present embodiment will be described with reference to FIGS. The printer to which the present embodiment is applied is not limited to a color laser beam printer, and it goes without saying that a printer of another printing method such as a sublimation printer may be used.

FIG. 7 is a sectional view showing the structure of a first output device to which the present invention can be applied, and is a diagram showing a case of a color laser beam printer (CLP). Reference numeral 160 in the figure
Reference numeral 0 denotes the CLP main unit,
The printer control unit 100 receives code data and image data described in a printer language sent from the printer unit 0 and generates multi-valued image data of magenta, cyan, yellow, and black for one page based on the data.
0 (hereinafter, referred to as a controller) and a series of electronic devices that form a latent image by scanning a laser beam modulated in accordance with input multi-valued image data on a photosensitive drum, transfer the latent image to recording paper, and then fix it. It is composed of a printer engine 1500 (hereinafter, referred to as engine) for performing recording by a photographic process.

Reference numeral 1530 denotes an operation panel on which switches for operation, an LCD display, and the like are arranged.
The controller 1000 and the engine 1500 are connected by an interface signal line 1200. The main interface signals are / RDY, / PRNT,
/ TOP, / LSYNC, VDO7 to VDO0, VCL
K, which will be briefly described below.

The / RDY signal is a signal sent from the engine 1500 to the controller 1000,
This signal indicates that the printing operation can be started or the printing operation can be continued at any time when the engine 1500 receives the / PRNT signal described later.
The / PRNT signal is a signal sent from the controller 1000 to the engine 1500, and is a signal for instructing the start of the printing operation or the continuation of the printing operation.

The / TOP signal is a synchronization signal in the sub-scanning (vertical scanning) direction, and is sent from the engine 1500 to the controller 1000. / LSYNC signal is
A synchronization signal in the main scanning (horizontal scanning) direction, which is sent from the engine 1500 to the controller 1000. The VDO7 to VDO0 signals are image signals sent from the controller 1000 to the engine 1500 and indicate image density information to be printed by the engine 1500. VDO7 is represented by the most significant bit, and VDO0 is represented by the least significant eight bits. In the engine 1500, VDO7 to VDO
When the 0 signal is FFH, printing is performed at the maximum density of the developing toner color, and when 00H, printing is not performed. These are transfer synchronization signals VCL
It is sent out in synchronization with K.

Next, the operation of the engine will be described with reference to FIGS.

The engine 1500 includes the controller 100
When receiving the / PRNT signal from 0, the photosensitive drum 1506 and the transfer drum 1508 are rotated in the direction of the arrow by the drive unit (not shown). Subsequently, the roller charger 15
09 is started, and the potential on the photosensitive drum 1506 is uniformly charged to a predetermined value. Next, the recording paper 152 is moved from the recording paper cassette 1510 by the paper feed roller 1511.
8 is supplied to the transfer drum 1508. Transfer drum 150
Numeral 8 is a dielectric sheet stretched on a hollow support.
It rotates in the direction of the arrow at the same speed as the photosensitive drum 1506. When the recording paper 1528 is supplied to the transfer drum 1508, a gripper 151 provided on a support of the transfer drum is provided.
2, the recording paper 1528 is held by the suction roller 1
513 and the adsorbing charger 1514
8 is attracted to the transfer drum 1508. At the same time, the support 1515 of the developing device is rotated, and the four developing devices 1516M, 1516C, and 15 supported by the support 1515 are rotated.
Of the 16Y and 1516Bk, the developing device 1516M containing magenta toner as the first toner is made to face the photosensitive drum 1506. Reference numeral 1516C denotes a developing device containing cyan toner, 1516Y denotes a developing device containing yellow toner, and 1516Bk denotes a developing device containing black toner.

On the other hand, the engine 1500 includes the transfer drum 1
Detector 1 detects the leading end of recording paper 1528 sucked by 506
In step 517, a vertical synchronization signal / TOP is generated at a predetermined timing and transmitted to the controller 1000.

When the controller 1000 receives the first / TOP signal for the print page, the controller 1000 receives the first / TOP signal from the image data stored in the page memory in the RAM 19.
Is read at a predetermined timing. The read 8-bit image data D7 to D7
0 is transmitted to the engine 1500 as the image signals VDO7 to VDO0 in synchronization with the VCLK signal.

VD output from controller 1000
As shown in FIG. 8, the O7 to VDO0 signals are input to a pulse width modulation circuit 1501, become a laser drive signal VDO having a pulse width (256 steps) corresponding to the level, and sent to a laser driver. At the time of development, which will be described later, the amount of toner adhesion can be adjusted according to the pulse width of the laser drive signal VDO, thereby reproducing 256 shades of each color.

Next, the laser beam 1 from the laser diode 1503 driven according to the laser drive signal VDO
Numeral 527 is deflected by a rotary polygon mirror 1504 that is driven to rotate in the direction of an arrow by a motor (not shown), scans the photosensitive drum 1506 in the main scanning direction via an imaging lens 1505 arranged on the optical path, and A latent image is formed on 1506. At this time, the beam detector 1507 detects the scanning start point of the laser beam, and generates a / LSYNC signal, which is a horizontal synchronization signal for determining an image writing timing of main scanning, from the detection signal. The main scanning operation described above is repeated, and a magenta latent image for one page is formed on the photosensitive drum 1506.

Referring back to FIG. 7, the latent image formed on the photosensitive drum 1506 is the developing device 1 containing the magenta toner.
516M to develop a magenta toner image. This magenta toner image is transferred to a transfer charger 1519.
As a result, the image is transferred onto the recording paper 1528 that is attracted to the rotating transfer roller 1508. At this time, the toner remaining on the photosensitive drum 1506 without being transferred is removed by the cleaning device 1525. Through the above operation, a magenta toner image for one page is formed on the recording paper 1528.

Next, the support 1515 of the developing device is rotated so that the developing device 1516C containing the cyan toner as the second toner is opposed to the photosensitive drum 1506. Subsequently, as in the case of magenta, the leading end of the recording paper 1528 that rotates while being attracted to the transfer roller 1508 is detected by the detector 1517, and a vertical synchronization signal / TOP is generated and sent to the controller 1000. In response, the controller 1000 reads cyan data from the page memory 19. Hereinafter, by the same operation, the recording paper 152
The cyan toner image is transferred onto the magenta image 8 so as to overlap the magenta toner image. Further, similarly, a yellow toner image as the third toner and a black toner image as the fourth toner are transferred onto the recording paper 1528 in a superimposed manner, and become a full-color toner image.

The recording paper 1528 on which all the four color toner images have been transferred passes through a separation charger 1520 and is separated from the transfer drum 1508 by a separation claw 1521.
The sheet is supplied to the fixing device 1523 by the conveyance unit 1522. At this time, the transfer drum cleaner 1526 cleans the surface of the transfer drum. The toner image on the recording paper is melted and fixed by being heated and pressed by the fixing device 1523, and becomes a final color output image. Then, the recording paper on which the recording has been completed is output to the discharge tray 152.
4 is discharged.

In FIG. 9, 3000 is a host computer, and 2000 is a host computer control unit. In the host computer control unit 2000,
C for executing document processing in which graphics, images, characters, tables (including spreadsheets, etc.) are mixed based on a document processing program or the like stored in the program ROM of the ROM 2003
The CPU 2001 is provided with a PU 2001, and the CPU 2001 controls each device connected to the system bus 2004.

The program ROM of the ROM 2003 stores a control program of the CPU 2001 and the like. The font ROM of the ROM 2003 stores font data and the like used in the above document processing.
The data ROM 003 stores various data (for example, overlay form data, background image data, and external characters) used when performing the document processing and the like. 2002
Denotes a RAM, which functions as a main memory, a work area, and the like of the CPU 2001. A keyboard controller (KBC) 2005 controls key input from a keyboard 3001 or a pointing device (not shown).

Reference numeral 2006 denotes a CRT controller (CRT)
C) controls the display on the CRT display (CRT) 3002. 2007 is a disk controller (DK
C), boot program, various applications,
It controls access to an external memory 3003 such as a hard disk (HD) for storing font data, user files, and edited files, and a floppy (registered trademark) disk (FD). 2008 is a printer controller (P
RTC), is connected to the printer 1500 via a predetermined bidirectional interface (interface) 2009, and executes communication control processing with the printer 1500.

The CPU 2001 is, for example, a RAM
The outline font is expanded (rasterized) to the display information RAM set on the 2002 and the CR is executed.
WYSIWYG on T3002 is enabled. Further, the CPU 2001 opens various registered windows based on a command specified by a mouse cursor or the like (not shown) on the CRT 3002, and executes various data processing.

FIG. 10 is a block diagram illustrating the configuration of a printer control system 1000 according to an embodiment of the present invention. Note that, as long as the functions of the present invention are executed, the present invention is applicable to a single device, a system including a plurality of devices, and a system in which processing is performed via a network such as a LAN. It goes without saying that the invention can be applied.

In the printer 1500, reference numeral 1001 denotes a printer CPU, which is a program ROM of the ROM 1003.
Access to various devices connected to the system bus 1005 based on a control program or the like stored in the system ROM 1004 or a control program or the like stored in the extension ROM module 1004. An image signal as output information is output to a connected printing unit (printer engine) 1007.
The program ROM of the ROM 1003 includes C
The control program of the PU 1001 is stored. ROM1
The font ROM 003 stores font data and the like used when generating the output information.
The data ROM 3 stores an overlay form, external character information, and the like used on the host controller.

The CPU 1001 can perform communication processing with the host computer via the input unit 1008, and transmits information in the printer to the host computer 2000.
Is configured to be notified. 1002 is a CPU 100
A RAM functioning as a main memory, a work area, a page memory, and the like. The memory capacity can be expanded by an expansion RAM module connected to an expansion port (not shown). Note that the RAM 1002
Are used for an output information development area, an environment data storage area, and the like.

The expansion ROM module 1004 such as an IC card described above includes a memory controller (MC) 100
9 controls the access. The extension ROM module 1004 is connected as an option and stores font data, an emulation program, form data, and the like. Reference numeral 1010 denotes an image generation unit that assists the CPU 1001 in generating print data by calculation. It has a function to perform high-speed processing of print data with logic circuits such as enlargement / reduction, rotation, color conversion, and superposition. Reference numeral 1530 denotes the above-described operation unit in which switches for operation, an LCD display, and the like are arranged.

The above-mentioned extension module is not limited to one, but is provided with at least one or more, and includes an optional font card, an external memory storing a program for interpreting a printer control language of a different language system in addition to a built-in font. It may be configured so that a plurality of connections can be made. Further, an NVRAM (not shown) is provided.
May be stored.

According to the present invention, in a print system composed of these units, a dither matrix method is adopted for an image generation unit of a printer, and various kinds of dither matrix tables corresponding to print data are supplied, thereby achieving gradation. This realizes a print result that is rich in expression.

Hereinafter, each embodiment will be described. First Embodiment FIG. 1 shows a first embodiment of the present invention in which a dither matrix size flexible switchable (however, the number of cells M
FIG. 3 is a block diagram of a printer gradation value conversion unit. In the figure, the same numbers are added to the blocks already described in the conventional example, and the description is omitted.

The tone value converter 1 includes a dither X-axis start address setting register 3, a Y-axis start address setting register 7, a dither X size setting register 2, a Y size setting register 6, dither comparators 4, 8, It comprises M-ary counters 5 and 9 with a preload / clear function, an address synthesizing unit 10, a dither matrix table storing unit 11 composed of a rewritable memory such as an SRAM, and a data comparing unit 12.

Hereinafter, a specific data flow will be described with reference to FIGS. 1, 2, 3 and 10. In the dither matrix table storage unit of the present embodiment, square dither matrix threshold data for a total of M cells can be written. In this case, the memory capacity required for the dither matrix table storage unit is M × (threshold data bit length). For example, if an 8 × 8 matrix is used to perform gradation conversion from 8 bits to 4 bits, an SR of 8 * 8 * 8 bits * 15 = 7680 bits
AM is required.

CPU 1001 analyzing print data from host computer by program ROM 1003
Represents a plurality of b per pixel as original tone data 113
It generates image data having the tone information of it. At the same time C
The PU 1001 selects a dither matrix suitable for the Y toner print data, and writes the matrix size (dither X size 101, dither Y size 106) into predetermined registers (X size register 2, Y size register 6) (here, x Size = K, y size = L.
* L = <M).

Next, the CPU 1001
3 is stored. The K * L dither matrix table data for Y toner printing is copied to the K * L area of the dither matrix table storage unit 11. Further, a value (OFFSETX, OFFSETX) indicating to which address of the dither matrix table the original tone data 113 is to be referred.
Y) is determined and set in the start address registers 3 and 7.

When the gradation value conversion of the Y toner print data is executed, the OFFSETX value 103 is preloaded as an initial value to the M-ary counter 5, and the M-ary counter 5 is set to 1 pi.
xel image data (pixel signal 10
In 4), the counter value is incremented by one. The dither X address 105, which is the counter output value, is fed back to the comparator 4, and resets the counter 5 when it becomes equal to the X size designation value 101 (= K). This gives M
The binary counter 5 functions as a K-ary counter.

Similarly, OFFSETY is set in the M-ary counter 9.
Each time the drawing line is switched (Line signal 109), the counter value is incremented by 1 and the dither Y address 110 is output. When the value 107 becomes equal to the specified Y size value 106 (= L), the counter is reset. Functions as an L-base counter to reset.

X address signal 105, y address signal 1
10, the X-size signal 101 and the Y-size signal 106 are input to the address synthesizing unit 20, where the data bits of each address signal are combined according to the dither matrix size to generate a dither matrix address 111.

The above operation will be described with reference to the flowchart of the image processing based on FIG. 2. First, when print data is input from the host computer (S1), the input print data is analyzed (S2). , Y print processing (S3). This Y printing process includes the following steps.

First, the Y print dither matrix size is set (S31), the Y dither matrix threshold data is set (S32), and the dither start address is set (S33). A dither address is synthesized according to the set size (S34), and image generation processing (gradation value conversion) is performed (S35). Drawing and composition are performed on the bitmap memory (S36), and printing is performed (S37).

When such a series of Y printing processing is completed (S3), the M printing processing (S31 to S37) is repeated (S4), and further the C printing processing (S31 to S37).
Is repeated (S5), and finally the K printing process (S31 to S3)
7) is repeated (S6).

FIG. 3 is a diagram showing examples of various dither matrices which can be realized by a memory for 64 cells. With reference to FIG. 3, the dither matrix size and the dither address generation method will be supplemented. As an example, let M = 64. The x-address 105 and the y-address 110 are 6-bit signals because they are the outputs of the 64-bit counter. (DZXA [5:
0], DZYA [5: 0])

X size signal 101, Y size signal 106
According to the matrix shape defined by the following, the address combining unit 10 performs bit combination as described below to generate a dither address signal 111. Examples are listed below.

Matrix shape Dither address 8 * 8 DZYA [2: 0] & DZXA [2: 0] 16 * 4 DZYA [1: 0] & DZXA [3: 0] 32 * 2 DZYA [0] & DZXA [4: 0] 4 * 16 DZYA [3: 0] & DZXA [1: 0] 14 * 3 DZYA [1: 0] & DZXA [3: 0]

With the dither matrix address 111 generated in this way, the dither matrix table storage 1
1 is selected, and the data comparison unit 12
Enter

The data comparing section 12 compares the threshold data 112 with the original gradation data 113, generates drawing data 114 having changed gradation values in accordance with a predetermined logic, and generates a drawing memory 114 reserved in the RAM 1002. To store. At this time, the gradation width of the drawing data 114 is a gradation width which can be expressed by the printing apparatus main body, and may be multi-value data as well as binary data.

As described above, the drawing data for the Y toner printing which has been subjected to the gradation value conversion of the K × L dither matrix size by using the dither matrix storage for M cells is obtained.
Similarly, in generating the M toner print drawing data,
Dither X size register 2, Dither Y size register 3
Then, by setting the intended size value and changing the dither matrix table data in the dither matrix table storage unit, it is possible to obtain M toner print drawing data that has been subjected to gradation conversion with a dither matrix size different from the Y toner. Can be. The same applies to C toner printing and K toner printing.

As described above, the output value of the dither X address counter and the output value of the dither Y address counter are bit-combined according to the dither matrix size to generate a dither address. It is possible to realize dither matrices having different shapes from the memory elements described above, and thereby, it is possible to improve the color print image quality by delicately changing the dither matrix size for each print color. Also, when it is desired to change the screen ruling according to the type of print data, this can be realized by changing the dither matrix size.

[Second Embodiment] FIG. 4 is a block diagram of a dither matrix size flexible switchable (however, matrix size M cell or less) printer gradation value conversion unit according to a second embodiment of the present invention. In the figure, the same numbers are added to the blocks already described in the conventional example, and the description is omitted.

The gradation value converter 21 is provided with the dither X-axis start address setting register 3 described in the first embodiment,
Axis start address setting register 7, dither X size setting register 2, similarly Y size setting register 6, dither comparators 4, 8, M-ary counters 5, 9 with preload function,
In addition to an address synthesizing unit 10, a dither matrix table storage unit 11 composed of a rewritable memory such as an SRAM, and a data comparing unit 12, a value that linearly changes the start offset value of the dither X address for each dither Y size line number Register 2 for setting "cycle offset X"
2, a selector 23, an adder 24, and a comparator 25 for monitoring that the load value of the dither X address counter does not become larger than the designated X size.

Hereinafter, differences from the first embodiment will be mainly described with reference to FIGS. 4, 5 and 6. As shown in FIG. 4, the initial dither x start address 102 and the cycle offset X value 121 are input to the selector 23. The selector 23 outputs the initial x start address 102 at the start of the conversion process, and thereafter outputs the cycle offset X121 every time the dither Y address counter becomes “0”. Otherwise, "0" is output.

The adder 24 cumulatively adds the value of the offset X122 every time the dither Y address counter becomes "0". The comparator 25 calculates the cumulative offset X
There is a function of correcting when the value of the value 123 exceeds the value of the X size 101, thereby generating a load value 124 of the dither X address counter. Tone value conversion circuit 21
Other functions related to the third embodiment are the same as those of the first embodiment.

Next, FIG. 5 is a diagram showing a dither matrix (16 pixels × 8 lines) using the cycle offset. According to FIG. 5, the total number of cells = 32, the initial offset X = 0, and the cycle offset X = 4. Matrix shape: The effect of the cycle offset will be described using a dither matrix table of 16 pixels × 2 lines as an example.

Reference numerals 00 to 0F and 10 to 1F in the matrix indicate the coordinates and ID of each dither cell. Same ID
No. cells store the same gradation conversion threshold data.

When the dither address becomes equal to the Y size (2 = 2 lines), the head X address of the next line is: initial offset X + cycle offset X = 0 +
4 = 4, the threshold data of the cell ID No. “04” is referred to the first pixel of the line, and gradation conversion is executed. Thereafter, threshold data offset to the left by 4 pixels every two lines is used for gradation conversion.

As a result, the head cell ID No. becomes “0” again.
It will take 8 lines to reach 0 ",
A 16 × 8 dither matrix having a two-size sub-matrix can be realized. This means that it has a gradation conversion function that is larger than the memory capacity of the mounted dither matrix table.

FIG. 6 is a diagram showing the cycle offset and the screen angle in the 16 × 2 matrix. The screen angle of the print data after gradation conversion can be freely determined by the value of the cycle offset X as shown in FIG. You can choose.

In FIG. 6, a basic dither matrix having 16 pickles × 2 lines is used. When the cycle offset = 0, if there is no sub-matrix in the 16 × 2 area, the screen angle is usually 90 °,
The centers of the print pixels are lined up in the vertical direction. As the cycle offset value is increased, the center of the print pixel gradually shifts in the horizontal direction, and in the case of this example, it can be reduced to the minimum screen angle of 14 °. That is, in the case of a 16 × 2 matrix, nine types of screen angles can be realized as shown in Table 1 below.

[0070]

[Table 1]

As described above, it is effective to change the screen angle for each print color in order to prevent moiré, which is interference fringe caused by superimposition of print colors on a print image. , The dither matrix storage unit 11 in FIG.
Even if only one type of dither table data is written in each print color, the moire can be prevented by changing the print screen angle only by changing the cycle offset X value for each print color. This contributes to improvement of development efficiency and evaluation efficiency, and is an extremely useful means.

[0072]

As described above, according to the present invention, there is provided a tone value conversion means for converting tone information, which is density information per pixel of print data from a host computer, into a reproducible information amount. A dither matrix storage means capable of registering a plurality of dither matrix tables at a stage prior to the printing processing by employing a dither matrix method as a gradation value converting means; Then, a dither matrix table having an arbitrary matrix size is registered in the dither matrix storage means for each color printing of yellow (Y), magenta (M), cyan (C), and black (K), and the threshold value of the dither matrix table is registered. A dither address generating means capable of executing a gradation value conversion process of a different matrix size for each print color based on the data. Therefore, using a dither matrix table storage unit with the same memory capacity as before, a dither matrix of various sizes is realized by adding logic circuits, and the screen ruling, screen angle, and gradation value can be flexibly changed. By doing so, higher quality color printing can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a tone value conversion unit in a printing apparatus image generation unit according to a first embodiment.

FIG. 2 is an image processing flowchart of the first embodiment.

FIG. 3 is an explanatory diagram of available dither matrix sizes and dither addresses according to the first embodiment.

FIG. 4 is a block diagram of a tone value conversion unit in a printing apparatus image generation unit according to a second embodiment.

FIG. 5 is an explanatory diagram of a dither matrix according to a second embodiment.

FIG. 6 is an explanatory diagram of a screen angle of a print image according to the second embodiment.

FIG. 7 is a sectional view of a color laser beam printer.

FIG. 8 is a block diagram of a color laser beam printer optical unit.

FIG. 9 is a block diagram of a host computer.

FIG. 10 is a block diagram of a laser beam printer control system.

[Explanation of symbols]

 1, 21 Gradation value conversion unit of each embodiment 2, 6 Dither matrix size register 3, 7 Dither start address register 4, 8, 25 Comparator 5, 9 Counter 10 Address synthesis unit 11 Dither matrix table storage unit 12 Data comparison unit 22 Cycle offset register 23 Selector 24 Adder 1000 Printer control unit 1001 Printer CPU 1002 Printer RAM 1003 Printer ROM 1004 External memory 1005 Printer system bus 1006 Printing interface 1007 Printing unit 1008 Host interface 1009 Printer memory controller 1010 Image generation unit 1200 Interface signal Line 1500 printer engine 1501 pulse width modulation circuit 1502 laser driver 1503 The diode 1504 Rotating polygon mirror 1505 Imaging lens 1506 Photosensitive drum 1507 Beam detector 1508 Transfer drum 1509 Roller charger 1510 Paper cassette 1511 Paper feed roller 1512 Gripper 1513 Suction roller 1514 Suction charger 1515 Developing device support 1516 Each color developing device 1517 Recording paper leading edge detector 1518 Optical unit 1519 Transfer charger 1520 Separation charger 1521 Separation claw 1522 Transport unit 1523 Fixing device 1524 Discharge tray 1525 Cleaning device 1526 Transfer drum cleaner 1527 Laser beam 1528 Recording paper 1530 Operation unit 1600 Color printer 2000 Host computer control unit 2001 Host CPU 2002 Host RAM 2003 Host ROM 2004 Host system bus 2005 Keyboard controller 2006 CRT controller 2007 Host memory controller 2008 Printer controller 3000 Host computer 3001 Keyboard 3002 CRT 3003 Host external memory

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AA04 AA05 AA16 AA17 AB07 AB20 BB03 BB06 BB22 BC01 BC17 GA13 GA14 GA15 GA52 GA57 2C362 CA03 CA18 CA30 CB74 5B057 AA11 CA01 CA08 CA12 CA16 CB01 CB07 CB12 CH11 CC01 CE MP08 NN09 PQ22 TT02

Claims (8)

[Claims] 1. A printing apparatus comprising: tone value conversion means for converting tone information as density information per pixel of print data from a host computer into a reproducible information amount; A dither matrix method is adopted as the conversion means, and a dither matrix storage means capable of registering a plurality of dither matrix tables at a stage prior to the printing processing. A yellow (Y), magenta (M) ), Cyan (C), and black (K) for each color printing, a dither matrix table of an arbitrary matrix size is registered in the dither matrix storage means, and based on the threshold data of the dither matrix table, A dither address generating means capable of executing gradation value conversion processing of different matrix sizes. . 2. The dither address generation means, in order to arbitrarily change a matrix shape of the dither matrix table under a condition of a fixed maximum matrix area,
A dither matrix X size setting means and a dither matrix Y size setting means for designating a size; an address counter capable of generating dither address data of the maximum size of each side of the X-axis and Y-axis; X data comparing means and Y address comparing means for comparing the data and clearing the address data counter if they match, a start of a dither matrix table capable of positioning the dither matrix table in an arbitrary area of a printed document A dither start address setting means for setting an address; an X address and a Y address according to the dither matrix size.
2. The printing apparatus according to claim 1, further comprising dither address combining means for combining effective data bits of the address to generate dither address data. 3. The dither address generation means, when arbitrarily specifying the dither matrix size, specifies the dither matrix size for all combinations of one pixel and one line if the total number of cells is equal to or less than a predetermined total number of cells. The printing apparatus according to claim 1, wherein the printing apparatus can perform the printing. 4. The dither address generating means includes means for adding a specified offset value to a start address of a dither X address in a specified dither Y size unit,
2. The printing apparatus according to claim 1, wherein the printing apparatus has a function of realizing an arbitrary screen angle in drawing data after gradation conversion by intentionally shifting a dither matrix. 5. An image generating method for a printing apparatus, comprising a tone value conversion step of converting tone information, which is density information per pixel of print data from a host computer, into a reproducible information amount. A dither matrix method is adopted as the gradation value conversion step, and a dither matrix storing step in which a plurality of dither matrix tables can be registered at a stage prior to the printing process; and a yellow (Y) during the printing process of one page. , Magenta (M), cyan (C), and black (K), a dither matrix table of an arbitrary matrix size is registered in the dither matrix storage step, and based on the threshold data of the dither matrix table, A dither address generation step capable of executing gradation value conversion processing of a different matrix size for each print color Method for generating an image printing apparatus characterized by having and. 6. The dither address generating step includes the steps of: arbitrarily changing a matrix shape of the dither matrix table under a condition of a fixed maximum matrix area;
A dither matrix X size setting step and a dither matrix Y size setting step for specifying a size; an address counter capable of generating dither address data of the maximum size of each side of the X-axis and Y-axis; Comparing the data and clearing the address data counter if they match, a comparing step for an X address and a comparing step for a Y address; and starting a dither matrix table capable of positioning the dither matrix table in an arbitrary area of a printed document. A dither start address setting step of setting an address; and an X address and a Y address according to the dither matrix size.
6. The method according to claim 5, further comprising the step of combining dither address data by combining valid data bits of the address. 7. The dither address generating step includes the step of arbitrarily specifying the dither matrix size.
6. The image generation method according to claim 5, wherein the dither matrix size of all combinations of one pixel and one line can be designated as long as the total number of cells is equal to or less than the predetermined total number of cells. 8. The dither address generating step includes a step of adding a specified offset value to a start address of a dither X address in units of a specified dither Y size. 6. The image generation method according to claim 5, further comprising a function of realizing an arbitrary screen angle in the drawing data after the tone conversion.