JP3709913B2 - Printing system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printing system including an electrophotographic recording apparatus. In particular, the present invention relates to a replacement circuit for replacing resolution and toner supply amount control.
[0002]
[Prior art]
As described in Japanese Patent Application Laid-Open No. 8-310057, a conventional apparatus has a pixel replacement circuit inserted between a printer controller and a printer engine so that a black-and-white binary low-resolution video signal is received from the printer controller. A high-resolution video signal is generated, a laser is driven by the video signal, and recording is performed by electrophotographic recording means. As a result, it was possible to realize high-quality image recording with a simple additional circuit element without changing the printing program.
[0003]
[Problems to be solved by the invention]
In the above prior art, black and white binary low-resolution video signals from the printer controller are stored in a temporary line memory for several lines, and pixel data corresponding to dots recorded by a laser and pixels corresponding to the surrounding dots are recorded. The attribute information of the dots to be recorded is classified from the data, a corresponding high-resolution video signal is generated, and the low-resolution video signal is replaced and output to the printer engine. Attribute information indicates what kind of figure the dots to be recorded are. Usually, about a dozen or so cases are defined, and high-resolution video signals corresponding to each are defined in advance. deep.
[0004]
For the determination of the attribute information of the dots to be recorded, pixel data corresponding to an area having a width of about 7 × 7 dots in the vertical and horizontal directions including the surrounding area is usually used. Since the pixel data is binary, mathematically, the number in the case of 2 to the 49th power is conceivable, but it is impossible to associate an appropriate high-resolution video signal with each of them. Ordinarily, as described above, the attribute information is collected in the case of about a dozen ways. However, for example, when the input low resolution video signal has a relatively easy-to-understand shape such as text, it can be determined appropriately. However, in the case of an image such as a complicated figure or halftone photo, the intention is In some cases, erroneous determination is made as attribute information that is different from the attribute information. This may replace the wrong high-resolution video signal, resulting in poor print quality.
[0005]
If the video signal information necessary for the determination is increased or the number of attribute information is increased, the circuit such as the line memory becomes complicated, and the number of high-resolution video signals corresponding to the attribute information increases, and the processing itself It becomes complicated.
[0006]
Further, the above prior art does not give consideration to the variation in printing density of the electrophotographic recording means. When the print density is high, the details of the printed image are crushed or the line width is increased. Further, when the printing density is low, details of the printed image are rubbed and the line width is thinned.
[0007]
A first object of the present invention is to determine dot attributes without error and to replace an appropriate high-resolution video signal. A second object is to obtain a printed image having an accurate line width without being crushed or rubbed by suppressing fluctuations in the print density of the printer engine.
[0008]
[Means for Solving the Problems]
In order to achieve at least one of the above objects, the present invention detects a pixel data expansion unit that expands print data described in a page description language into pixel data, and attribute information of pixels to be recorded from the print data A detection unit; a pixel replacement unit that replaces a low-resolution video signal with a high-resolution video signal based on the detected attribute information; an electrophotographic recording apparatus that drives and prints a laser with the video signal; and A transmission unit that transmits pixel data to the electrophotographic recording apparatus as the video signal.
[0009]
In addition, the image forming apparatus includes a calculation unit that calculates print rate data of an image to be recorded from pixel data, and a toner replenishment amount control unit that controls a replenishment amount of toner to the developing device based on the print rate data.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIG.
[0011]
FIG. 2 shows a configuration diagram of the electrophotographic recording apparatus. The general-purpose computer system 201 executes a print program to create print data 211 such as characters, graphics, and images, and sends it to the printer controller 202. The controller 202 includes an interface 203, a CPU 204, a font memory 205, a print data memory 206, a pixel data memory 207, a video signal generation circuit 208, and the like. First, the print data 211 is stored in the print data memory 206 through the interface 203. Next, the print data 211 is developed by the CPU 204 using the font data 205 and the like, and is converted into black and white binary pixel data 212 and stored in the pixel data memory 207. Finally, the pixel data 212 is converted into a low-resolution video signal 213 by the video signal generation circuit 208 and output to the pixel replacement circuit 209. The pixel replacement circuit 209 replaces the low-resolution video signal 213 with the high-resolution video signal 214 and outputs it to the printer engine 210. The printer engine 210 drives an internal laser with a high-resolution video signal 214 to form an electrostatic latent image on the electrostatic drum and prints it by electrophotographic recording means.
[0012]
Here, the print data 211 is a collection of commands and data generally called a page description language. In this embodiment, a typical page description language PostScript (manufactured by AdobeSystems) will be described as an example. Here, it is assumed that the pixel data 212 and the low-resolution video signal 213 are white (0) black (1) binary data having a resolution of 600 dpi (dot / inch). Here, it is assumed that the high-resolution video signal 214 is a signal of 2400 dpi (main scanning) × 600 dpi (sub-scanning) that has been increased in resolution four times in the main scanning direction.
[0013]
FIG. 1 is a diagram for explaining the operation of the present invention. First, the command scan program 101 of the present invention inspects one page of print (PostScript) data 211 stored in the print data memory 206, and picks up command information related to characters, graphics, and images. For example, PostScript commands include “show” for drawing characters, “stroke” and “fill” for drawing figures, and “image” for drawing images. Since these are simple text data in the print data 211, the command scan program 101 can easily find the print data 211 by scanning (searching) the print data 211.
[0014]
FIG. 3 shows an example of the “image” command therein. For details on commands, etc.
Since it is described in “PostScript Langage Reference Manual Second Edition”, Adobe Systems Incorporated, the outline is explained here.
[0015]
Line (1) indicates the position in the page at the lower left corner of the rectangular image area to be drawn in the x and y coordinates.
[0016]
Line (2) indicates the size of the rectangular image area to be drawn in x and y coordinates. Line (3) indicates the size of the rectangular image area to be drawn, the number of dots in the x and y directions, and the number of bits of the information (binary data).
[0017]
Line (4) shows the coefficients of the transformation matrix for transforming the rectangular image area to be drawn.
[0018]
Line (5) indicates that image data is read from the print data 211.
[0019]
Line (6) shows the image command.
[0020]
Line (7) indicates the image data as hexadecimal data.
[0021]
Line (8) is a command for printing the drawn pixel data 212.
[0022]
When the command scan program finds the command “image” on line (6), it picks up the command information and creates the attribute information table 102.
[0023]
FIG. 10 shows the attribute information table 102. Data corresponding to “show”, “stroke”, “fill”, “image”, etc. is included in the command section, data indicating the area position of each image is required in the area position section, and other information is necessary for other information. If there is, halftone dot information such as the number of halftone lines and halftone dot angle is stored. In the case of FIG. 3, “image” is stored in the command item, the lower left coordinates and upper right coordinates of the rectangular area are stored in the position, and other information is blank.
[0024]
Returning to FIG. 1, the print (PostScript) data 211 is expanded by the PostScript data expansion program 103 and stored in the image data memory 207 as image data 212 for one page. In this embodiment, the image data memory 207 is provided for several pages, and the image data 212 can be output with a delay of at least three pages.
[0025]
Next, the pixel data scanning program 104 of the present invention inspects the pixel data 212 for one page stored in the pixel data memory 207 and picks up the printing rate data 105 per page. In this embodiment, since it is monochrome information of 1 bit per pixel, the printing rate data 105 per page is obtained by simply counting the number of black dots per page and dividing by the total number of pixels. Further, in the case of monochrome halftone information of a plurality of bits per pixel, the print rate data 105 per page is obtained by adding the information and dividing by the value obtained by adding all the pixels as solid black (maximum density). The obtained printing rate data 105 per page is temporarily stored in the printing rate data 105.
[0026]
Next, the video signal generation circuit 208 generates and outputs a video signal 213 from the pixel data 212 in accordance with the synchronization signals PAGE and LINE from the printer engine 210.
[0027]
FIG. 4 shows a timing chart of the video signal 213. A page synchronization signal PAGE from the printer engine is a signal indicating a print area of each page. Accordingly, the synchronization signal PAGE is turned on, that is, the video signal 213 is output within the print area.
In the present invention, the contents of the command table 102 and the printing rate data 105 are converted into serial data and sent to the pixel replacement circuit 209 and the printer engine 210 when the synchronization signal PAGE is off, that is, outside the printing area. Since it is combined with the conventional video signal 213, it is not necessary to newly install a new signal line.
[0028]
In the present embodiment, as shown in the figure, the print rate data 105 is sent corresponding to a page to be printed three pages after the page to be printed. For example, the print rate data 105 of the (n + 3) th page is sent immediately before the video signal 213 of the nth page. As described above, since the apparatus of this embodiment has the image data memory 207 for at least three pages as described above, the video signal 213 can be delayed by three pages with respect to the printing rate data 205.
[0029]
FIG. 5 shows how the attribute information table 102 and the print rate data 105 are sent when the printer engine 210 does not have a print area outside as in a continuous paper printer. A line synchronization signal LINE from the printer engine is a synchronization signal for matching the printing position of each line. Even if LINE occurs, it does not become a printing area immediately. Therefore, the contents of the attribute information table 102 and the printing rate data 105 in the non-printing area up to that time are converted into serial data, and the pixel replacement circuit 209 and the printer engine. 210 respectively. If it cannot be sent in one line, it can be sent in multiple lines. Also in this case, since it is combined with the conventional video signal 213, it is not necessary to newly install a new signal line.
[0030]
The composite video signal 213 is replaced with a high-resolution video signal 209 in the pixel replacement circuit 209. However, as described above, the pixel replacement circuit 209 is effective for the smoothing of characters, but may deteriorate the image quality in a complicated figure or image. Therefore, according to the information of the attribute information table 102 sent, the high resolution data to be replaced is changed from the case of characters, or the low resolution data is output as it is.
[0031]
FIG. 6 shows a block diagram of means for changing the high-resolution video signal 214 to be replaced to another signal. The counter 601 is reset by the signal PAGE and counted by the signal LINE. Therefore, the position of the currently recorded line, that is, the y-direction coordinate value is output to the attribute memory 602. The contents of the attribute information table 102 included in the composite signal are stored in the temporary attribute memory 602, and an attribute value 603 corresponding to the y-direction coordinate output from the counter 601 is output to the pixel replacement circuit 209. In this embodiment, the y-coordinate between 50 and 388 in which an image exists in the image is switched by the attribute value 603, and the replacement with the high-resolution video signal 214 is not performed, and the low-resolution video signal 213 is changed. It outputs as it is. However, the replacement method in the pixel replacement circuit 209 can be changed according to the attribute value 603.
[0032]
The high-resolution video signal 214 is input to the printer engine 210, drives an internal laser, forms an electrostatic latent image on the electrostatic drum, and is printed by a known electrophotographic process. The printer engine 210 of this embodiment has a two-component developing machine.
[0033]
FIG. 7 shows the configuration of the two-component developing machine of this embodiment. Inside the developing device 701 is a developer 702 in which a carrier and toner are mixed at a certain ratio (toner density of several percent). When printing is performed, only the toner is developed from the developing roll 703 onto the photoconductor 704, so that the toner concentration of the developer 702 is lowered. The developer 702 is always stirred by a stirring roller for charging. A toner concentration sensor 706 is installed in the flow path, and when the toner concentration of the developer 702 falls below a set value, the toner replenishing sponge roller 707 rotates, and the toner contained in the toner hopper 708 is transferred into the developing device 701. To supply. Even when such toner replenishment control is performed, the toner density varies from the target value. When the toner density is higher than the set value, the development amount increases, and details of the printed image are crushed or the line width is increased. When the toner density is lower than the set value, details of the printed image are rubbed and the line width is narrowed.
[0034]
FIG. 8 is an explanatory view of the fluctuation of the toner density when the development amount is abruptly changed, which is one of the fluctuation factors of the toner density. In (1), the horizontal axis represents the page number to be printed, and the vertical axis represents the printing rate data. Since the printing apparatus of this embodiment has a printing speed of 60 pages per minute, the rate is 1 second per page. Pages 1 to 5 are set to print at a printing rate of 10%, pages 5 to 10 are printed at a printing rate of 50%, and pages 11 to 16 are printed at a printing rate of 10% again. (2) is the toner concentration of the developer 702 in the developing unit, and the value indicated by the dotted line is the set value. (3) is a detection value of the toner density sensor 706, and a value indicated by a dotted line is a target setting value for toner supply control. That is, the toner replenishment amount from the toner hopper 708 is manipulated based on the difference between the detected value of the toner density sensor 706 and the target set value for toner replenishment control. (4) is a toner replenishment amount from the toner hopper 708.
[0035]
From page 1 to page 4, the amount of toner to be developed for 10% printing and the amount of toner to be replenished match and operate stably. When the printing rate suddenly increases from page 5 to 50%, the amount of toner to be developed becomes larger than the amount of toner to be replenished, and the toner density of the developer is further decreased from the set value. The toner density sensor 706 detects this decrease in toner density with a delay of about 0.5 seconds and instructs an increase in the replenishment amount. Even if the replenishment increases, it takes about 2 to 3 seconds for the replenished new toner to move while being agitated and charged by the stirrer 705, reach the developing roll 703, and return the toner density to an appropriate value. In the meantime, the toner density of the developer is significantly lower than the set value, and the image density of about 3 pages until recovery is reduced. Further, when the printing rate suddenly returns to 10% from the page 11, the amount of toner to be developed becomes smaller than the amount of toner to be replenished, and the toner concentration of the developer further increases from the set value. The toner density sensor 706 detects this increase in toner density with a delay of about 0.5 seconds, and instructs to stop the replenishment amount. Even if the replenishment is stopped, the toner replenished before it moves while being charged by stirring and reaches the developing roller 703, so that the toner density of the developing portion continues to increase for about 2 seconds. As a result, the toner density of the developer is significantly higher than the set value, and this time, since the toner consumption is small, the image density during the period until recovery is high.
[0036]
FIG. 9 is an explanatory diagram of a toner replenishment amount correction unit according to the present invention. The print rate data 105 combined with the video signal 214 is transmitted to the printer engine 210. (5) is the printing rate data 105. As described above, the video signal 214 to be actually printed is stored in the pixel data memory 207 and output with a delay of 3 pages (3 seconds). Therefore, the printing rate data 105 is to be printed as shown in the figure. Can be obtained three pages before the print rate. Therefore, as shown in (6), setting correction data is created from the difference from the print rate signal three pages before, and the value is superimposed on the target value for toner supply control. (2) shows the resulting change in toner density. According to the present embodiment, there is an effect that the fluctuation amount can be considerably reduced.
[0037]
【The invention's effect】
According to the present invention, since accurate attribute information extracted from print data is added for determination, image quality deterioration due to erroneous determination can be prevented, and appropriate correction can always be performed, so that a high-quality image can be obtained. Further, by knowing the printing rate data in advance, the toner density fluctuation amount can be reduced, so that a high-quality image free from crushing and rubbing can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the operation of a printing system according to the present invention.
FIG. 2 is a diagram showing an embodiment of a printing system according to the present invention.
FIG. 3 is a diagram illustrating a command program according to the present invention.
FIG. 4 is a diagram illustrating control of a toner replenishment amount according to the present invention.
FIG. 5 is a diagram showing a timing chart of a video signal of the video signal generation circuit of the present invention.
FIG. 6 is a diagram showing another timing chart of the video signal of the video signal generation circuit of the present invention.
FIG. 7 is a diagram illustrating an example of video signal conversion according to the present invention.
FIG. 8 is a diagram showing an embodiment of a two-component developing machine according to the present invention.
FIG. 9 is a diagram illustrating a change in toner density according to the present invention.
FIG. 10 is a diagram showing an example of an attribute table according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Command scan program, 102 ... Attribute information table, 103 ... Data development program, 104 ... Pixel data scan program, 105 ... Print rate data, 201 ... General-purpose computer system, 202 ... Controller, 203 ... Interface, 204 ... CPU, 205 ... Font memory, 206 ... Print data memory, 207 ... Pixel data memory, 208 ... Video signal generation circuit, 209 ... Pixel replacement circuit, 210 ... Printer engine, 211 ... Print data, 212 ... Pixel data, 213 ... Low resolution Video signal 214 ... High-resolution video signal 601 ... Counter 602 ... Attribute memory 603 ... Attribute value 701 ... Developer 702 ... Developer 703 ... Developer roll 704 ... Photoconductor, 705 ... Stirrer 706 ... Toner density sensor, 707 ... sponge roller, 708 ... toner hopper.

Claims (2)

A pixel data expansion unit that expands print data described in a page description language into pixel data, a video signal generation unit that replaces the pixel data with a recording video signal, and an electrophotographic image that drives and prints a laser with the recording video signal In a printing system having a recording unit,
A command scan program for detecting attribute information of pixels to be recorded from the print data and its position to create an attribute information table ;
A pixel data scan program for calculating printing rate data for calculating printing rate data of an image to be recorded from the pixel data;
Means for combining the attribute information table and the printing rate data with the recording video signal and outputting the composite video signal;
A pixel replacement unit that replaces the low-resolution video signal replaced by the video signal generation unit with a high-resolution recording video signal based on the attribute information recorded in the attribute information data table and its position data; A printing system, wherein the high-resolution recording video signal and the printing rate data are output to an electrophotographic recording unit. The printing system according to claim 1,
A printing system comprising a toner replenishment amount control unit for controlling a toner replenishment amount to a developing device based on the printing rate data in the electrophotographic recording unit.

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