JPH05301374A - Printing method and its device - Google Patents

Abstract

PURPOSE:To provide a printing method which can print an image by raising printing quality apparently without improving resolution and its device. CONSTITUTION:In a printer which prints an image on a medium to be recorded by scanning each line, a beam detector which outputs a synchronizing signal per scan of each line, a shifting circuit 5 which inputs the synchronizing signal 12 from the beam detector and varies timing from the synchronizing signal 12 to start of outputting an image signal 15 per scan, and a printing part which prints the image on the medium to be recorded based on the image signal, are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing method and apparatus for scanning each line to print an image on a recording medium.

[0002]

2. Description of the Related Art A laser beam is modulated in accordance with an image signal, the laser beam is scanned on a photosensitive drum to generate an electrostatic latent image, a toner image is formed thereon, and the toner image is recorded on a recording paper. There is known a laser printer that transfers an image to a printer to print an image. In such a laser beam printer, a beam detector (BD) for detecting the laser beam is provided immediately before the photosensitive drum on which the laser beam scans in order to synchronize the scanning timing of the laser beam with the image signal. The beam detect signal (B
D signal) is used as a horizontal synchronizing signal. Then, the image signal is output after a certain time elapses after the input of the horizontal synchronizing signal.

[0003]

As described above, in the conventional art, the timing from the input of the horizontal synchronizing signal to the output of the image signal is always constant. Therefore, for example, as shown in FIGS. Dot positions are always printed in the sub-scanning direction for each scanning line. If the dot positions are printed in this manner, there is a problem that jaggedness on the stairs is conspicuous in the shaded portion of the image. Therefore, in order to eliminate such jaggedness and to print, it is necessary to increase the resolution and decrease the dot diameter. However, increasing the resolution increases the image data capacity, and the image data for one page (pattern data ) Increases the memory capacity for storing. Further, since a large amount of image data has to be processed, the CPU of the control unit and the like are required to have a higher speed, which increases the cost of the entire apparatus.

The present invention has been made in view of the above conventional example, and an object of the present invention is to provide a printing method and apparatus capable of printing an image with apparently improved printing quality without increasing resolution.

[0005]

In order to achieve the above object, the printing apparatus of the present invention has the following configuration. That is,
A printing apparatus for scanning an image on a recording medium by scanning each line, wherein a synchronization signal generating means for outputting a synchronization signal for each scanning of the line and the synchronization signal from the synchronization signal generating means are inputted. A timing changing unit that changes the timing from the synchronization signal until the output of the image signal is started for each scan, and a printing unit that prints an image on a recording medium based on the image signal.

In order to achieve the above object, the printing method of the present invention comprises the following steps. That is, a printing method of scanning each line to print an image on a recording medium, the step of outputting a synchronization signal at the start of scanning each line, and inputting the synchronization signal at the start of scanning each line. And a step of changing the timing from the output of the image signal to a step of printing the image on the recording medium based on the image signal.

[0007]

In the above structure, the timing from the input of the synchronizing signal from the synchronizing signal generating means for outputting the synchronizing signal for each scanning of each line and the start of outputting the image signal from the synchronizing signal is changed for each scanning. Then, an image is printed on the recording medium based on the image signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a sectional view showing the internal structure of the laser beam printer (LBP) 100 of this embodiment.
P100 is a data source (not shown) (host computer, etc.)
Character pattern registration and fixed form (form data)
It is configured to be able to register etc.

In FIG. 2, reference numeral 100 denotes an LBP main body, which inputs and stores character information (character code) supplied from an externally connected host computer or the like, form information, macro commands, and the like. A corresponding character pattern, form pattern, or the like is created according to the information, and an image is formed on a recording paper, which is a recording medium. Three
Reference numeral 00 is an operation panel on which various switches for operation and LED displays are arranged, and 101 is a printer control unit for controlling the entire LBP 100 and analyzing character information supplied from the host computer. The printer control unit 101 mainly converts character information into a video signal of a corresponding character pattern and outputs it to the laser driver 102.

The laser driver 102 is a semiconductor laser 10.
3 is a circuit for driving the semiconductor laser 3 and switches the semiconductor laser on and off according to the input video signal. The laser beam 104 is swung in the left-right direction by the rotary polygon mirror and scans the electrostatic drum 106. As a result, the electrostatic drum 106
An electrostatic latent image of a character pattern is formed on the surface. This latent image is developed by the developing unit 107 around the electrostatic drum 106 and then transferred to the recording paper. A cut sheet is used as the recording paper, and the cassette recording paper is stored in a paper cassette mounted on the LBP 100, taken into the apparatus by the paper feed roller 109 and the conveyance rollers 110 and 111, and supplied to the electrostatic drum 106. It A beam detector (BD) 112 detects the laser beam immediately before the laser beam scans the photosensitive drum 106 and outputs it to the printer control unit 101.

FIG. 1 shows a laser beam printer 1 of this embodiment.
10 is a block diagram showing the configuration of the main part of the printer control unit 101 of No. 00.

In FIG. 1, reference numeral 1 is a control unit for controlling print data and print processing. 2 is a font memory that stores character pattern data or outline-on and data corresponding to a character code, and 3 is a print image (bitmap data) for one page that is pattern-developed using the font memory 2. It is a bitmap memory. Reference numeral 4 denotes a horizontal synchronizing circuit, which synchronizes horizontal scanning of laser light. Reference numeral 5 is a 1/2 dot shift circuit, which makes variable the timing for inputting the horizontal synchronizing signal (BD) 12 and then outputting the print dot pattern. A video generation circuit 6 outputs print dot data to the video driver 102 of the printer engine in synchronization with the clock signal 14 from the 1/2 shift circuit 5. 7 is an address bus, 8 is a data bus, and 9 is a control unit 1.
A control line 10 for outputting to the font memory 2 is a control line for outputting from the control unit 1 to the bitmap memory 3 as well. A horizontal sync enable signal 11 is output from the control unit 1 to the horizontal sync circuit 4. When the signal 11 goes low, a beam detect signal (BD) 12 from the printer engine is input to the horizontal sync circuit 4. 12 is a horizontal synchronizing signal (BD) from the printer engine, 13 is a horizontal video enable signal, 14 is a shift clock for transferring print data, 15 is a video signal modulated by a print dot pattern and transferred to the printer engine. Is.

FIG. 3 is a block diagram showing the configurations of the horizontal synchronizing circuit 4 and the 1/2 dot shift circuit 5 of FIG. 1, and FIG. 4 is a timing chart thereof. The following is a description in order.

Reference numeral 16 is a flip-flop for horizontal synchronization, which is set at the rising edge of the clock signal 25 when the BD signal 12 is input at a low level while the control line 11 from the control section 1 is at a low level. 17 is to shift the dot position output from the video generation circuit 6 for each scan,
A flip-flop that specifies whether or not to shift the dot position when it is set (when the normal signal 26 is at high level) and does not change the dot position, and when it is reset (when the shift signal 27 is at high level) It is controlled to shift.

Reference numerals 18 and 19 denote frequency dividing circuits for dividing the clock signal 25. The flip-flop 20 is a divider circuit at the final stage of the clock signal 25 when the flip-flop 17 is set, that is, when the dots are not displaced. The flip-flop 21 divides the frequency of the clock signal 25 when shifting by 1/2 dot, and together with the flip-flop 22 constitutes a frequency dividing circuit at the final stage of the clock signal 25.

Reference numeral 23 is a scan reset signal input after the end of each scan of the laser beam, and 24 is a page reset signal input after the end of one page. The scan reset signal 23 and the page reset signal 24 are input from the controller 1. It Reference numeral 25 is a clock signal for generating a shift clock for print data. Reference numeral 26 is a horizontal enable signal when the dots are not shifted, 27 is a horizontal enable signal when the dots are shifted by 1/2 dot, 28 is an enable signal of the final stage frequency dividing circuit when the dots are shifted by 1/2 dot, and 29, 3
0 is the shift clock when the dots are not shifted and when they are shifted by 1/2 dot.

Next, the operation will be described with reference to the timing chart of FIG. 4 and the circuit diagram of FIG.

When the signal level of the control line 11 is low level and the horizontal synchronizing signal (BD) 12 is low level, N
The output of the OR circuit 31 becomes high level. Here, when the clock signal 25 rises, the horizontal enable signal 13 becomes high level (timing T1). The first one on the page
At the scan, the flip-flop 17 is reset by the page reset signal 24, so the flip-flop 17 is set at the rising edge of the horizontal enable signal 13 (timing T1). 1/2
The normal signal 26 that does not shift the dots becomes high level. Thus, in the first scan, the normal clock signal 29 that does not shift the dots is output from the OR circuit 34 as the synchronous clock 14.

In the next scan, the flip-flop 16 is similarly set at timing T1 and when the horizontal enable signal 13 rises, the flip-flop 1 is turned on this time.
7 is inverted, and the shift signal 27 becomes high level (timing T2). As a result, the flip-flop 21 becomes 4
When the divided clock signal 25 is input, the timing T
At 2, the Q output 28 becomes high level. Then, the Q output of the flip-flop 22 of the frequency divider circuit at the final stage becomes high level at the timing T3, and the shift clock 30 is output.

As described above, in the 1/2 dot shift circuit 5 of the present embodiment, the shift clock signal 30 for shifting by 1/2 dot every other scan and the normal synchronizing clock signal 29 are alternately arranged. It outputs to 6.
As is apparent from FIG. 4, the timing of the normal clock signal 29 and the shift clock 30 are deviated by exactly 1/2 dot, so that the dot position is 1/2 dot for each horizontal scanning line. It will be displaced in the horizontal scanning direction.

An example of recording using the 1/2 dot shift circuit 5 of this embodiment is shown in FIGS.

FIG. 5 shows that the recording density in the horizontal direction is 300 dp.
i (dot / inch), vertical recording density is 600d
In the figure showing an example of printing using a pi printer, it can be seen that even-numbered dot positions are displaced by 1/2 dot in the horizontal direction.

FIGS. 6 and 7 are diagrams showing dot positions when a horizontal diagonal line and a vertical diagonal line are printed by shifting the dot positions by 1/2 dot for each scan.

Further, in FIGS. 8 and 9, the recording density is 600d.
It is a figure which shows the dot position at the time of printing with the conventional printer which is pi * 300 dpi.

As can be seen by comparing FIGS. 6 and 7 which are the printing examples of the present embodiment with FIGS. 8 and 9 which are the conventional printing examples, the printing quality in the conventional printer is adversely affected. Diagonal line printing has a horizontal resolution of 300 dp
Despite being i, the recording density is 600 dpi × 600 d
It is possible to expect a print quality that is substantially the same as the print quality of the pi printer.

In the above embodiment, the dot position is digitally shifted, but the present invention is not limited to this, and the analog video signal may be shifted using a delay line or the like.

Further, in this embodiment, it is 1/2 for each scan.
Although the dots are shifted one by one, the present invention is not limited to this, and it goes without saying that the print quality can be further improved by making the shift amount finer.

Further, in the present embodiment, the case of the laser beam printer has been described, but the present invention is not limited to this. For example, in a thermal printer or an ink jet printer having a serial recording head, each scan of the recording head is performed. Needless to say, the present invention can be applied to a case where the print start position is shifted and recorded.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program for implementing the present invention to a system or an apparatus.

As described above, according to the present embodiment, the output timing of the print data with respect to the horizontal synchronizing signal is changed to shift the print dot position for each scan, so that a high-quality printer can be used. The print result of can be obtained.

Further, since the printer engine may have a low resolution, the capacity of the memory for storing the image data can be reduced, so that the circuit cost for processing the print data does not increase.

[0033]

As described above, according to the present invention, it is possible to print an image with an apparently high print quality without increasing the resolution.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a main part of a control unit of a laser beam printer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the internal structure of the laser beam printer of this embodiment.

FIG. 3 is a circuit diagram showing configurations of a horizontal synchronizing circuit and a ½ dot shift circuit according to the present embodiment.

FIG. 4 is a timing chart showing the operation of the horizontal synchronizing circuit and the ½ dot shift circuit of this embodiment.

FIG. 5 is a diagram showing a printing example by the laser beam printer of the present embodiment.

FIG. 6 is a diagram showing an example of printing by the laser beam printer of this embodiment.

FIG. 7 is a diagram showing an example of printing by the laser beam printer of this embodiment.

FIG. 8 is a diagram showing a printing example by a conventional laser beam printer.

FIG. 9 is a diagram showing an example of printing by a conventional laser beam printer.

[Explanation of symbols]

1 Controller 2 Font Memory 3 Bitmap Memory 4 Horizontal Sync Circuit 5 1/2 Dot Shift Circuit 6 Video Generation Circuit 12 Horizontal Sync Signal (BD) 13 Horizontal Enable Signal 16, 17, 18, 19, 20, 21, 21, 22 Flip Float 25 clock signal 29 normal clock signal 30 shifted clock signal 100 laser beam printer 101 printer control unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location G06K 15/00 H04N 1/04 104 A 7251-5C 1/23 103 Z 9186-5C 9211-2C B41J 3/10 101 B

Claims (3)

[Claims] 1. A printing apparatus for scanning an image on a recording medium by scanning each line, comprising: a synchronization signal generating means for outputting a synchronization signal for each scanning of the line; and the synchronization signal generating means for outputting the synchronization signal. A timing changing means for changing the timing of inputting a synchronizing signal and starting the output of the image signal from the synchronizing signal for each scanning; and a printing means for printing an image on a recording medium based on the image signal. A printing apparatus having: 2. A printing method for scanning an image on a recording medium by scanning each line, comprising the step of outputting a synchronization signal at the start of scanning each line, and the step of outputting the synchronization signal at the start of scanning each line. A printing method comprising: a step of changing a timing from inputting to outputting an image signal; and a step of printing an image on a recording medium based on the image signal. 3. A printing apparatus for printing an image on a recording medium by scanning a laser beam for each line, wherein a synchronizing signal generating means for outputting a horizontal synchronizing signal for each scanning of each line, said synchronizing signal. Timing changing means for changing the timing of inputting the horizontal synchronizing signal from the generating means and starting output of the image signal from the horizontal synchronizing signal for each scan in 1/2 pixel units, and based on the image signal A printing apparatus comprising: a printing unit that prints an image on a recording medium.