JP2009262425A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform a highly fine printing by increasing the resolution in the subscanning direction as compared with the main scanning direction without generating lateral stripes and vertical stripes when an image is formed by an optical printing head. <P>SOLUTION: In an image forming apparatus wherein a photo-conductor 22 is exposed along the main scanning direction by an optical print head 20 with a free gradation print, paper feeding 24 is performed to the photo-conductor along the subscanning direction, and the resolution in the subscanning direction is improved higher than the resolution in the main scanning direction, to the print data 8 stored as binary data, regularly changing gradations are given respectively to the main scanning direction and the subscanning direction. Based on the print data to which the gradations are given, the photo-conductor drum or the like is exposed by the optical print head. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using a photosensitive drum or the like, and more particularly to an image forming apparatus in which the resolution in the sub-scanning direction is higher than that in the main scanning direction.

  In JP2002-330282A, in an image forming apparatus using an optical print head such as an LED print head or a laser beam print head, the resolution in the sub-scanning direction is set to 4 times or 8 times the main scanning direction. The size of each dot is changed according to the line number in the sub-scanning direction. For example, when the resolution in the sub-scanning direction is four times that in the main scanning direction, four lines A, B, C, and D are arranged along the sub-scanning direction, and these four lines are repeated. Then, the dot size on line A is maximized, line C is in the middle, and dot sizes on lines B and D are minimized.

However, when the line A and the line C are compared here, for example, the dot sizes are different. For this reason, the line thickness differs between the case where all the dots of the line A are printed and the other lines are blank, and the case where all the dots of the line C are printed and the other lines are blank. In addition, horizontal stripes may occur in the images printed on line A and line C. If the gradation of all dots is maximized instead of changing the gradation for each line, the dots overlap in the sub-scanning direction, and the print density (recording density) becomes too high.
JP2002-330282A

  An object of the present invention is to perform high-definition printing by increasing the resolution in the sub-scanning direction relative to the main-scanning direction without generating horizontal stripes or vertical stripes when forming an image with an optical print head.

The present invention exposes a photoconductor along the main scanning direction with an optical print head capable of gradation printing, and feeds the photoconductor along the sub-scanning direction, and the resolution in the sub-scanning direction. In the image forming apparatus in which the resolution is higher than the resolution in the main scanning direction,
A storage unit for storing print data as binary data;
A gradation degree imparting section that imparts a gradation degree that regularly changes in each of the main scanning direction and the sub-scanning direction with respect to the print data read from the storage section,
According to the present invention, printing is performed by the optical print head based on print data to which a gradation is given. The gradation providing unit may be realized by, for example, firmware in the optical print head, but preferably, the gradation is provided before the optical print head so that a general-purpose optical print head can be used.

In the present invention, printing is performed by controlling the gradation so that the print density does not become unnecessarily high even if dots overlap in the sub-scanning direction. Further, since the gradation changes regularly both in the main scanning direction and in the sub-scanning direction, unlike the case where the gradation is changed for each line, no vertical stripe or horizontal stripe is generated. In this invention,
・ High resolution printing is performed by increasing the resolution in the sub-scanning direction.
・ By controlling the gradation, the print density is prevented from becoming too high,
-By regularly changing the gradation in both the main scanning direction and the sub-scanning direction, vertical and horizontal stripes can be prevented.

Here, when the first gradation and the second gradation lower than the first gradation are alternately applied in the main scanning direction and the sub-scanning direction, the gradation can be easily provided and the sub-gradation can be easily provided. The resolution in the scanning direction can be doubled. For example, if the first gradation is a and the second gradation is b (a> b),
The gradation changes regularly so that (a, b) appears alternately in the main scanning direction and in the sub-scanning direction. For this reason, there are no vertical or horizontal streaks, and it is easy to provide gradation, and the overlap of dots along the sub-scanning direction is the overlap of high and low b, so the print density becomes too high. Absent.

  In addition, in an optical print head, gradation printing can be easily performed by performing gradation printing by modulation of exposure time or light emission current. In this specification, printing, printing, and recording all refer to transferring an image onto recording paper using toner.

  Furthermore, it is extremely easy to read out the print data from the storage unit for each line and assign the first gradation and the second gradation depending on whether the dot number in the line is even or odd and whether the line number is even or odd. Can be provided with a gradation.

  In the following, an optimum embodiment for carrying out the present invention will be shown.

  1 to 4 show a multifunction machine 2 according to an embodiment. In each figure, reference numeral 4 denotes a scanner, which may be a monochrome scanner or a color scanner, and generates print data composed of binary data. The print data may be supplied from the personal computer 5 or the received facsimile data 6 may be used as the print data. The print data is stored in the image memory 8. For example, the resolution in the main scanning direction is 600 dpi, the resolution in the sub scanning direction is 1200 dpi, and the resolution in the sub scanning direction is higher than the resolution in the main scanning direction. It is an integral multiple of the resolution in the scanning direction, twice in the embodiment.

  The address control 10 reads the print data in the range to be printed from the image memory 8, and the least significant bit of the line number of the line to be read is transferred to the binary counter C1, and the least significant bit of the dot number in the line is transferred to the binary counter C2. Supply. Every time the row to be read changes, the output of the binary counter C1 changes, and the initial value of the counter C2 is changed between 0 and 1 at the output edge of the counter C1. The output of the counter C2 is input to the logic circuit 14. The binary data from the image memory 8 is input to the logic circuit 14, and the gradation is output by a combination of the output of the counter C2 and the binary data.

  For example, the gradation is determined as shown on the right side of FIG. 1, and the data from the image memory 8 means that 1 is printed and 0 is not printed. When the data is 1 and the output of the counter C2 is 1, the gradation is, for example, 12, and when the data is 1 and the output of the counter C2 is 0, the gradation is, for example, 8. When the print data is 0, the output of the logic circuit 14 is 0. The output of the logic circuit 14 is written in the line memory 18 as the gradation. Note that a table may be used in place of the logic circuit 14, and the gradation may be given by referring to the table by 2-bit data of the output of the counter C2 and the data from the image memory 8. The configuration of the counters C1 and C2 and the logic circuit 14 is arbitrary. Further, when the least significant bit of the line number and the least significant bit of the dot number in the line are input to the EX-OR element, the counters C1 and C2 are substituted.

  The line memory 18 supplies print data to an optical print head 20 such as an LED print head or a laser beam print head, and the optical print head 20 exposes the photosensitive drum 22 to the paper fed from the paper feed mechanism 24. Print. In order to change the gradation, the light output may be controlled by controlling the light emission current to the LED or laser diode in multiple stages. Alternatively, the duty ratio of the light emission time may be controlled by controlling the light emission time of the LED or laser diode in multiple stages. In addition to this, the paper feed mechanism 24 is provided with a paper feed roller from a cassette or the like, and a fixing roller for fixing the toner adhered on the photosensitive drum 22. Further, instead of the photoconductive drum 22, a belt-shaped photoconductor may be used.

  The printing result is schematically shown in FIG. Here, it is assumed that the print data in the image memory 8 for each dot is 1, 12 and 8 in the figure represent the gradation, and an optical print head having a gradation of 0 to 15 is assumed. The gradation changes alternately between 12 and 8 in both the main scanning direction and the sub-scanning direction.

  In this way, since the gradation is reduced below the maximum of 15, even if dots overlap in the sub-scanning direction, the print density does not become too high. In addition, since the gradation changes regularly in a two-dot cycle in both the main scanning direction and the sub-scanning direction, no vertical stripe or horizontal stripe occurs. Since the resolution in the sub-scanning direction is twice that in the main scanning direction, high-definition printing can be performed.

  3 and 4 show a modification. In the modified example, as shown in FIG. 3, three kinds of gradations of 12, 10, and 8 are used, and the gradation is changed at a period of 3 dots in both the main scanning direction and the sub-scanning direction. The resolution in the sub scanning direction is, for example, three times the resolution in the main scanning direction, but the resolution in the sub scanning direction may be 1.5 times the resolution in the main scanning direction. Here, if the resolution in the sub-scanning direction is three times that in the main scanning direction using dots having an aspect ratio of approximately 1 and a nearly circular shape, the overlapping of dots in the sub-scanning direction is too strong, and the actual resolution is 3 Do not double. On the other hand, if the resolution in the sub-scanning direction is 1.5 times that in the main scanning direction, the resolution cannot be increased. For these reasons, it is preferable to set the resolution in the sub-scanning direction to be twice that in the main scanning direction so that two types of gradation appear alternately in a two-dot cycle in both the main scanning direction and the sub-scanning direction.

  A gradation generation circuit in the modification of FIG. 3 is shown in FIG. 4, and the same reference numerals as those in FIG. The counters C3 and C4 are ternary counters, and the counter C3 obtains a remainder obtained by dividing the line number by 3, and this remainder changes the initial value of the output of the counter C4 to 0, 1, and 2. The initial value to be set is, for example, 0 when the output of the counter C3 is 0, 1 when 1, 2 and 2. The counter C4 receives the dot number in the line and outputs a value obtained by adding the initial value input from the counter C3 to the remainder obtained by dividing this by 3. As a result, the output of the counter C4 is either 0, 1, or 2, and the output changes depending on the dot number and changes at a 3-dot cycle.

  The logic circuit 16 generates four types of outputs based on the three types of data input from the counter C4 and the binary data input from the image memory 8. When the print data is 0, the output of the logic circuit 16 is 0, the print data is 1 and the output of the counter C4 is 0, the output of the logic circuit 16 is 12, the print data is 1 and the output of the counter C4 is 1 When the output is 10, the print data is 1, and the output of the counter C4 is 2, the output is 8. When the output of the logic circuit 16 is written in the line memory 18, printing can be performed as in the embodiment. The gradation is the pattern shown in FIG. 3, and the gradation changes regularly in a period of 3 dots both in the main scanning direction and in the sub-scanning direction.

  In the embodiment, an example in which the gradation is changed to 12/15 and 8/15 is shown, but this is merely an example, the range of gradation data that can be handled by the optical print head 20, the characteristics of the photosensitive drum 22, and the like. The gradation level may be determined according to the above. The type of print is not limited to monochrome, and may be color. Furthermore, the use of the image forming apparatus is not limited to a multifunction machine, and may be a copier, a facsimile machine, a printer, or the like.

In the embodiment, the following effects can be obtained.
(1) High-definition printing is possible.
(2) The print density does not become too high even though adjacent dots overlap in the sub-scanning direction.
(3) No horizontal or vertical stripes.
(4) Conversion from binary data to gradation data is easy.

Example block diagram of complex values The figure which shows the printing density of each dot in an Example The figure which shows the printing density for every dot in the modification The figure which shows the gradation data generation circuit used for the modification of FIG.

Explanation of symbols

2 MFP 4 Scanner 5 Personal computer 6 Facsimile data 8 Image memory 10 Address control 14, 16 Logic circuit 18 Line memory 20 Optical print head 22 Photosensitive drum 24 Paper feed mechanism C1-C4 Counter

Claims (4)

The photosensitive printhead is exposed along the main scanning direction with an optical print head capable of gradation printing, and the paper is fed to the photosensitive body along the subscanning direction, and the resolution in the subscanning direction is set to the main scanning direction. In an image forming apparatus with higher resolution than
A storage unit for storing print data as binary data;
A gradation degree imparting unit that imparts a gradation degree that regularly changes in each of the main scanning direction and the sub-scanning direction with respect to the print data read from the storage unit,
An image forming apparatus, wherein printing is performed by the optical print head based on print data to which a gradation is given. The gradation providing unit alternately applies a first gradation and a second gradation lower than the first gradation in both the main scanning direction and the sub-scanning direction. Item 2. The image forming apparatus according to Item 1. 3. The image forming apparatus according to claim 2, wherein the optical print head performs gradation printing by modulating exposure time or light emission current. The gradation assigning unit reads the print data from the storage unit for each row, and determines whether the first gradation and the second step are based on whether the dot number in the row is even or odd and whether the line number is even or odd. The image forming apparatus according to claim 2, wherein furniture is provided.

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