JP2001121738A - Image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image-forming apparatus which can meet a resolution enhancement of a laser printer of a multibeam scanning type and can particularly print uniform images without variations. SOLUTION: The apparatus has a line memory group for developing image data corresponding to a plurality of laser beams to image data of a plurality of lines, a template matching group for detecting coincidence with a preliminarily prepared template pattern from the image data of the plurality of lines and outputting matching data, a modulation circuit for outputting modulation image data to set a printing size and a position of a target pixel at the center of a template from the matching data, and a delay adjustment circuit for adjusting a delay time of the modulation image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for printing image data by simultaneously scanning a plurality of laser beams.

[0002]

2. Description of the Related Art In recent years, a laser printer using electrophotography has been used for an output device of a computer, an output unit of a facsimile, or a so-called digital copying machine for printing image data read from an image scanner.

[0003] Laser printers are of the digital type,
The print quality greatly depends on the resolution. When the resolution is low, image defects such as jagged oblique lines become noticeable. In order to obtain a high-quality image, 300 to 600 dpi (dot / inch) is considered as one standard as a necessary resolution. Since an increase in the resolution of the input image directly leads to an increase in the load at the time of image processing, the resolution cannot be unnecessarily increased. Therefore, there is resolution enhancement as a technique for improving the resolution by estimating (without increasing the resolution of the image) from an image having a small amount of information. The most typical method among the resolution enhancement methods is a method using template matching. The template matching method scans a pattern of a target pixel (pixel at the center position of the template) and its surrounding pixels, compares the pattern with a prepared pattern (template pattern), and sets the target pixel according to the result. This is a method of determining the print size and position of the image.

[0004] As conventional techniques for performing such resolution enhancement, there are Japanese Patent No. 2797224 and Japanese Patent No. 2886192.

In order to increase the speed of a laser printer, it is necessary to scan a laser beam at high speed in a main scanning direction and a sub-scanning direction. Specifically, the rotating polygon mirror is rotated at a high speed in the main scanning direction, and the photoconductor is rotated at a high speed in the sub-scanning direction.

However, a laser beam (laser light)
The rotation speed of the rotating polygon mirror that deflects the light is close to the limit. For this reason, instead of increasing the rotation speed of the rotary polygon mirror, a multi-beam method of simultaneously scanning a plurality of laser beams is employed. As described above, the laser printer often employs the multi-beam scanning method in order to perform high-speed printing.

[0007]

In order to enhance resolution with the above-described high-speed laser printer, it is necessary to cope with a multi-beam scanning system, but there is a problem that the above-mentioned prior art cannot cope with the problem.

An object of the present invention is to provide an image forming apparatus capable of coping with the enhancement of the resolution of a multi-beam scanning type laser printer, and in particular, to provide an image forming apparatus capable of printing a uniform image without any variation. It is.

[0009]

According to the present invention, there is provided an image forming apparatus for recording input image data by scanning a plurality of laser beams. A line memory group that expands the image data into a plurality of lines of image data, a template matching group that compares the plurality of lines of image data with a plurality of predetermined template patterns, and outputs matched matching data; and A modulation circuit for outputting modulated image data for setting a print size and a position of a pixel of interest at the center of the template and a delay adjusting circuit for adjusting a delay time of the modulated image data are provided.

[0010] With this configuration, a uniform printed image without variation can be obtained.

[0011]

FIG. 2 shows an embodiment of the present invention.

In FIG. 2, image data D1 created by a host computer (personal computer) 1 is input to a printer controller 2. Image data D1
Is created by a user using input means (not shown) of the host computer 1. The image data D1 will be described as page description data indicating the content of the page to be recorded.

The image data D1 output from the host computer 1 is transmitted to the printer controller 2 via a network (not shown).

The printer controller 2 expands the image data D1 which is page description data transmitted from the host computer 1 for each page, and converts the image data D1 into raster image data D2 which is an array of two-dimensional image data.
Output to

The image correction device 3 has a function of raster image data D2.
And outputs the modulated image data D6 for setting the print size and position of the pixel of interest at the center of the template according to the comparison result with a pattern (template pattern) prepared in advance by template matching.

Here, the laser printer 4 adopts a multi-beam scanning system for simultaneously scanning two laser beams.

The laser printer 4 outputs modulated image data D6.
Is formed on a recording sheet as a print image.

FIG. 1 is a block diagram of the image correction device 3 shown in FIG.

The line memory group 5 stores raster image data D
2 is developed into a plurality of lines of image data D3.

The template matching group 6 compares a plurality of lines of image data D3 with a pattern (template pattern) prepared in advance by template matching, and outputs matching data D4.

The modulation circuit 7 outputs, from the matching data D4, modulated image data D5 for setting the print size and position of the target pixel at the center of the template.

The delay adjusting circuit 8 adjusts the delay time of the modulated image data D5 and outputs image data D6.

FIG. 3 is an example of the laser printer 4 shown in FIG.

When the laser printer 4 receives the image data D6, it generates a laser beam 10 by the laser beam generating circuit 9. The laser printer 4 includes a charger 12, a developing device 13, and a transfer device 14 around a photoconductor 11,
The surface of the photoreceptor 11 is uniformly charged by the charger 12, exposed by the laser beam 10, toner is adhered by the developing device 13, the toner is transferred to the recording paper 15 by the transfer device 14, and the recording paper is The printed image is obtained on the recording paper 15 by fusing the toner to the recording paper 15.

FIG. 4 shows an example of the line memory group 5 shown in FIG.

The line memory group 5 includes line memories 17 to 2
0, and the raster image data D2, that is, the multi-beam scanning method in which the laser printer 4 scans two laser beams simultaneously, converts the two raster image data D2-1 and D2-2 into six lines. The image data is developed into image data D3, that is, D3-1 to D3-6. Here, the image data D3-1 to D3-6 of six lines are developed by setting the template size of the template matching 6 to 5 × 5.
Is assumed.

FIG. 5 shows an example of the template matching group 6 shown in FIG.

The template matching group 6 includes first to fourth template matchings 21 to 24. The five lines of image data input to the first template matching 21 and the second template matching 22 are D
3-1 to D3-5, and five lines of image data input to the third template matching 23 and the fourth template matching 24 are D3-2 to D3-6.
The first to fourth template matchings 21 to 24 are 6
The line image data D3 is converted into first to fourth matching data D4-1 to D4-4.

FIG. 6 shows an example of the modulation circuit 7 shown in FIG.

The modulation circuit 7 comprises first to fourth PWM (pulse width modulation) circuits 25 to 28. 1st to 4th P
WM (pulse width modulation) circuits 25 to 28 convert the first to fourth matching data D4-1 to D4-4 into first to fourth modulated image data D5-1 to D5-4.

FIG. 7 shows an example of the delay adjusting circuit 8 shown in FIG.

The delay adjusting circuit 8 comprises first to fourth delay circuits 29 to 32. First to fourth delay circuits 29 to 3
2 is the first to fourth modulated image data D5-1 to D5-4
To the first to fourth image data D6-1 to D6-
4 is output.

FIG. 8 shows an example of the laser beam generating circuit 9 shown in FIG. The laser beam generation circuit 9 includes first to fourth LD (laser diode) drivers 33 to 36 and first and second LDs 37 to 38. The output current I1 of the first LD driver 33 and the output current I2 of the second LD driver 34 are added and supplied to the first LD 37. The output current I3 of the third LD driver 35 and the fourth LD driver 36 Are added and supplied to the second LD 38. That is, the first and second image data D6-
1 to D6-2, the first LD 37 emits light, and the third LD 37 emits light.
To the fourth image data D6-3 to D6-4.
LD emits light.

FIG. 9 shows the operation of the image correction device 3 of FIG.

The 6-line image data D3-1 to D3-6 output from the line memory group 5 shown in FIG. 4 are as shown in FIGS. 9A to 9F, and are shown in FIG. It is assumed that both the template matching 21 and the template matching 23 match a preset template pattern. Then, the matching data D4-1 of the first template matching 21 matching the template pattern and the matching data D4-3 of the third template matching 23 become "2" as shown in (g) and (i). Since other template patterns are set in the second template matching 22 and the fourth template matching 24, the image pattern in FIG. 9 does not match with each template pattern, and the matching data D4
-2 and D4-4 are "0" or "1" as in (h) and (j).
Is output. First PWM 25 and third PWM shown in FIG.
M27 indicates that matching data D4-1 and D4-3 are "2"
, The modulated image data D5-1 and D5 having a pulse width of t9.
Since -3 is output, (k) and (m) are obtained. Since the matching data D4-2 and D4-4 are "1", the second PWM 26 and the fourth PWM 28 are the same as the image data (c) and (d) as in (l) and (n). The modulated image data is output.

When the modulated image data (k) to (n) are output, delays are generated for the input image data as shown at t1 to t4. The delay adjustment circuit 8 shown in FIG. 7 performs image data D6-1 and D6-2 of (o) and (p).
, And the image data D6-3 and D6-4 of (q) and (r) are in phase with each other, so that delays t5 to t6 are generated.

The image data D6-1 to D6-4 are (o)
When the current is supplied to the first to fourth LD drivers 33 to 36 shown in FIG. 8 as shown in (r) to (r), the current I5 supplied to the first LD 37 is changed to the second LD 38 as shown in (s). Is supplied as shown in (t).

The first LD 37 emits light by the current I5 of (s), and the second LD 38 emits light by the current I6 of (t).

As described above, the first and second template matchings 21 to 22 for the first LD 37, and the delay circuits 29 to 30 for adjusting the delay times of the respective image data D6-1 to D6-2. And a second LD3
8 for the third and fourth template matching 23-2
4 and the delay circuits 31 to 32 for adjusting the delay time of the respective image data D6-3 to D6-4, a uniform printed image without variation can be obtained.

[0040]

As described above, according to the present invention, since there are provided a plurality of template matchings for a plurality of laser beams and a delay adjusting circuit for adjusting a plurality of delay times, variations are provided. A uniform printed image free of defects can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of the image correction device shown in FIG. 2;

FIG. 2 is an embodiment of the present invention.

FIG. 3 is an example of the laser printer 4 shown in FIG.

FIG. 4 is an example of a line memory group 5 shown in FIG. 1;

FIG. 5 is an example of a template matching group 6 shown in FIG.

FIG. 6 is an example of a modulation circuit 7 shown in FIG.

FIG. 7 is an example of a delay adjustment circuit 8 shown in FIG. 1;

8 is an example of the laser beam generation circuit 9 shown in FIG.

FIG. 9 is a time chart for explaining the operation of the image correction device 3 of FIG. 1;

[Explanation of symbols]

5 ... line memory group, 6 ... template matching group,
7 modulation circuit, 8 delay adjustment circuit, 9 laser beam generation circuit, 33 to 36 LD driver, 37 to 38 L
D.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinya Kobayashi 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Masaki Masuchi 2-6-Otemachi, Chiyoda-ku, Tokyo No. 2 Nippon Koki Co., Ltd. (72) Tadashi Kitai 2-6-2, Otemachi, Chiyoda-ku, Tokyo F-Term, Nippon Koki Co., Ltd. (Reference) 2C362 BA56 BA66 CB02 CB04 CB07 CB08 CB43 CB75 CB77 5C072 AA03 BA03 BA16 HA02 HA06 HA13 HB06 HB20 UA12 XA05 5C074 AA02 AA12 BB03 CC22 DD05 DD07 DD14 DD17 EE12 EE20

Claims (4)

[Claims] 1. An image forming apparatus which scans a plurality of laser beams and records input image data, wherein: a line memory group for expanding image data corresponding to the laser beam into image data of a plurality of lines; A template matching group that compares the image data of the line with a plurality of predetermined template patterns and outputs matched matching data; and a modulation that sets the print size and position of a target pixel at the center of the template from the matching data. An image forming apparatus comprising: a modulation circuit that outputs image data; and a delay adjustment circuit that adjusts a delay time of the modulated image data. 2. The image forming apparatus according to claim 1, wherein said template matching group has a plurality of template matchings for each laser beam, and said template patterns are different from each other. 3. The image forming apparatus according to claim 1, wherein the modulation circuit has a plurality of PWM circuits according to a plurality of template matchings. 4. The image forming apparatus according to claim 1, wherein said delay adjustment circuit has a delay adjustment circuit according to a plurality of template matchings.