JP2975838B2 - Printer control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer control device used in an apparatus for forming an image by an electrophotographic method, having a line head in an exposure section.

[0002]

2. Description of the Related Art Conventionally, in a facsimile apparatus for transmitting text, drawings, and the like, a received image is recorded on a thermal recording paper using a thermal head. A plain paper facsimile apparatus for recording on plain paper using a photographic method has attracted attention. On the other hand, as a printer using an electrophotographic method, a printer used for a personal computer or the like has been put to practical use in advance. Therefore, it is conceivable to divert such a printer device to a facsimile information printing device to provide a facsimile function and a printer function at the same time, and to provide a composite recording device having an analog exposure system.

However, in this case, the printing resolution of the printer is 240 dpi (dot per in).
ch), 300 dpi, etc., which are generally used in a facsimile apparatus, with a main scanning of 8 pixels / mm and a sub-scanning of 7.7.
Since the resolution does not coincide with the resolution of pixels / mm or the sub-scanning of 3.85 pixels / mm, a resolution conversion process is required to make them coincide.

In a plain paper facsimile apparatus, printing is usually performed using cut sheets. In this case, even if the size of the original document on the transmitting side and the size of the cut sheet on the receiving side are the same, the transmission side uses communication history information called a header added by the transmitting side. In some cases, the length of one page becomes longer and printing on one page cannot be performed.
In such a case, printing is performed over two pages, and the second page uses only a portion of about a few centimeters at the beginning, thus not only increasing waste, but also causing the content of the document to be cut off in the middle. Hard to read. For this reason, the plain paper facsimile apparatus performs a process of reducing a received image so as to fit on one page.

[0005]

However, since the above-mentioned reduction processing is performed by a simple thinning method, there are disadvantages that thin lines are lost or legibility is reduced. In addition, resolution conversion is performed by the nearest neighbor method, and there is a problem that image quality is degraded due to occurrence of moire in a halftone image.

When a line head is used as the exposure means, pixels become thin or thick due to blurring of an image due to optical characteristics, blurring of an image in a sub-scanning direction due to rotation of a photosensitive drum, and the like. In general, in the method of exposing the background (white part) and not exposing the image part (black part), the pixel becomes thinner, and in the method of exposing the image part (black part) and exposing the background part (white part), the pixel becomes thicker. Further, the degree is different between the main scanning direction and the sub-scanning direction. As described above, when a composite recording apparatus is provided with an analog exposure system, the background (white part) is exposed and the image part (black part) is not exposed, so that the facsimile function or the printer function is used. At times, the pixels become thinner.

The present invention has been made in view of the above circumstances, and when an image forming apparatus functions as a printer, performs data correction on image data supplied to the image forming apparatus so that the image forming apparatus does not cause thinning or fattening of pixels. It is an object of the present invention to provide a printer control device capable of performing data correction of image data so as to prevent the disappearance of thin lines and the occurrence of moire when functioning as a facsimile.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a printer control device according to the present invention includes a line buffer for storing and holding input image data, and a single print line image formed of a plurality of sub-line images. Exposure means formed by a plurality of exposures based on data; resolution conversion means for generating a plurality of sub-line image data by sampling corresponding to a resolution conversion rate or an enlargement / reduction conversion rate; Image processing means for generating sub-line image data serving as correction image data; selecting means for appropriately selecting generation of thinning / thickness correction data and resolution conversion or generation of enlargement / reduction correction data depending on whether the mode is a printer mode or a facsimile printing mode; It is characterized by having.

[0009]

According to the above arrangement, one print line is composed of, for example, four sub-lines. In resolution conversion and enlargement / reduction in the main scanning direction, one pixel is formed by a plurality of sub-line image data. Therefore, in the conventional resolution conversion or the like, one pixel after resolution conversion becomes, for example, a black pixel, but, for example, only two sublines out of four sublines in one pixel after resolution conversion become black, for example. , The occurrence of moire in the halftone image can be suppressed.

On the other hand, in thickening / thinning correction, for example, two of the four sub-lines of a pixel that is originally white are set to black, so that in a printer device of a type in which the pixel is thin, the pixel is thinned on the photosensitive drum. Pixels of an appropriate size can be formed. Conversely,
By making two of the four sub-lines white for pixels that would otherwise be black, the pixels are thinned, and in a printer device of a type where the pixels are fat, pixels of an appropriate size are placed on the photosensitive drum. Can be formed.

The selection means for appropriately selecting the generation of thinning / thickening correction data and the resolution conversion or the generation of enlargement / reduction correction data depending on whether the mode is the printer mode or the facsimile printing mode. The image data supplied to the device is corrected so as not to cause thinning or fattening of pixels in the image formation by the apparatus, and when functioning as a facsimile, the data of the image data is controlled so as not to cause the disappearance of thin lines or the occurrence of moire. It is possible to select correction or the like, so that printing in both functions can be performed with high quality.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing the embodiments.

FIG. 1 is a block diagram schematically showing a printer control device. In the figure, 1 is an image input unit, 2 is a line buffer, 3 is an exposure control unit, 4a is a resolution conversion unit,
b is an image processing unit, and 5 is a line head. The line head 5 and the exposure control means 3 constitute an exposure means.

An image input unit 1 takes in a raster-scanned image input from the outside and writes one line of image data into a line buffer 2. Alternatively, one line of image data in the received image data is written into the line buffer 2.

The line buffer 2 has a storage capacity for three lines. These three lines are composed of a print line and one line before and after the print line. The line after the printing line (hereinafter, referred to as a rear line) is the image input unit 1 described above.
The print line and the line immediately before (hereinafter, referred to as a previous line) are read lines supplied to the image processing unit 4b.

First, the conversion components such as the resolution will be described.

The resolution conversion unit 4 a generates an address at which the print line image data is stored, and supplies the generated address to the line buffer 2. As a result, the print line image data is read from the line buffer 2. The reading of the image data is repeated the same number of times as the number of line divisions (4 in this embodiment) within the time for writing the image data of the subsequent line. The read image data of the print line is supplied to the line head 5 as sub-line image data. At this time, resolution conversion and enlargement / reduction processing are performed.

Specifically, the resolution conversion and the like are as follows: a) In the case of resolution conversion in the main scanning direction The input image data is sampled at a frequency corresponding to the resolution conversion rate. The sample positions are different from each other depending on the number of the subline).

(B) In the case of enlargement / reduction in the main scanning direction Similarly, input image data is sampled at a frequency corresponding to the enlargement ratio or the reduction ratio. The sample positions differ from each other.

Note that the above processing is an example and the present invention is not limited to this.

Exposure control means 3 sets the number of exposures equal to the number of repetitions of image data reading (the number of line divisions) to one.
This is performed for a print line. At each exposure, information indicating the number of times is output to the resolution conversion unit 4 so that subline image data corresponding to the number of times is generated, and the subline image is output. The line head 5 is driven (lighting control) based on the data.

The line head 5 includes a shift register 6, a line buffer 7, and a light emitting section 8. The sub-line image data subjected to the resolution conversion and the like is stored in the shift register 6. When one sub-line image data is stored in the shift register 6, the image data is simultaneously transferred to the line buffer 7. Then, the light emitting section 8 of the line head 5 is turned on based on the image data of the line buffer 7. This lighting is the original one
This is 1/4 of the lighting time for the line. That is, while one line of image is input, four sub-line image data are sequentially supplied to the line head 5, and the light emitting section 8 of the line head 5 generates four lighting patterns.

The size of the light-emitting elements constituting the light-emitting section 8 does not necessarily have to be reduced in the sub-scanning direction in accordance with the number of sub-line divisions. I just need. That is, the size of the light emitting element may be a normal size, and the light emitting element may be configured to emit light four times while the photosensitive member rotates by one line.

Next, the operation of the printer control device will be described with reference to FIG. FIG. 2 shows the resolution conversion in the main scanning direction. FIG. 2A is a conceptual diagram showing the lighting state of the light emitting unit 8 in the line head 5 for each subline after resolution conversion for facsimile image data. .
FIG. 2B is a time chart showing facsimile image data, and FIGS. 2C to 2F are time charts showing sample timing signals of each subline.

In FIG. 2, one line is formed by a plurality of sub-lines. The sub-line is obtained by dividing one line in the sub-scanning direction by the number of repetitions. In this embodiment, the number of sub-lines is four as described above. Here, as shown in this figure, the II-th pixel and the III-th pixel in the image data after the resolution conversion for the facsimile image data in the same figure (b), all of the four sub-lines are white or black pixels. Instead, variations occur. This is because the sample timing signals in the first to fourth sub-line image data generation correspond to (c) to (f) in FIG.
This is because the sample positions are different from each other as shown in FIG. FIG. 3 simply shows sample positions of the first to fourth sublines.

The four sub-line image data of one line generated as described above are
Supplied to Since the light emission of the light emitting unit 8 of the line head 5 is controlled in accordance with the sub-line image data, for example, in the case of the second pixel, the minute light-emitting units corresponding to the first, second, and third sub-lines are turned off, and The minute light emitting section corresponding to the sub line is turned on.

As described above, one printing line is set to, for example, 4 lines.
In the resolution conversion in the main scanning direction based on the image data of the print line, the sample positions at the time of generating each sub-line image data are made different from each other. FIG. 2 shows that all the one pixel (the II-th pixel and the III-th pixel) after resolution conversion becomes a black pixel (the sample position is the center), as shown in FIG. For example, it is possible to suppress the occurrence of moiré in a halftone image by causing variations in subline units, for example, only two sublines become black.

The same applies to the case of enlargement / reduction in the main scanning direction. Sampling is performed at a frequency corresponding to the enlargement ratio or reduction ratio, and the sampling position for each subline at this time is made different from each other for facsimile. The image quality is improved by sampling the image data.

In the resolution conversion and enlargement / reduction in the sub-scanning direction, the lighting time of each light emitting element in the light emitting section 8 and the rotation speed of the photosensitive member may be adjusted.

In this embodiment, the number of repetitions (the number of sub-lines) is set to 4. However, by increasing the number of repetitions, the performance of reducing moire can be improved. However, since reading from the line buffer 2 and storing data in the line head 5 are frequently performed, the number of sub-lines is determined in consideration of the balance between them.

Next, components related to thickening / thinning correction will be described.

The generated address is supplied to the line buffer 2 using the address generation function of the resolution conversion unit 4a, and the image data of the print line and the previous line is read from the line buffer 2. The reading of the image data is repeated the same number of times as the number of line divisions (4 in this embodiment) within the time for writing the image data of the subsequent line. The read image data of both lines is supplied to the image processing unit 4b. Further, the exposure control unit 3 supplies data indicating the number of repetitions to the image processing unit 4b.

The image processing section 4b considers the image data of the previous line supplied from the line buffer 2 and, based on the image data of the print line, converts a plurality of sub-line image data to be thinned or thickened image data based on the image data of the print line. These are sequentially generated and supplied to the line head 5. That is, the pixel is made thinner or thicker in the lighting state of the light emitting unit 8 of the line head 5.

Specifically, a) In the case where the pixel is thickened in the sub-scanning line direction For a certain pixel A on the print line, this is a white pixel, and the corresponding pixel A 'on the previous line is a black pixel. In some cases, for the white pixel A, the sub-line image data is generated such that, for example, two of the four repetitions are black pixels.

B) In the case where a pixel is narrowed in the sub-scanning line direction For a certain pixel A on the print line, if this is a black pixel and the corresponding pixel A 'on the previous line is a white pixel, For the black pixel A, the sub-line image data is generated such that, for example, two of the four repetitions are white pixels.

C) When the pixel is thickened in the main scanning line direction For a certain pixel A on the print line, if this is a white pixel and the pixel B on the right is a black pixel, the white pixel A Is, for example, 2 out of 4 repetitions
The sub-line image data is generated so that the batch becomes black pixels.

D) In the case of narrowing the pixels in the exposure in the main scanning line direction For a certain pixel A on the print line, if this is a black pixel and the pixel B to the right of this is a white pixel, For pixel A, for example, 2 out of 4 repetitions
The sub-line image data is generated so that the batch becomes white pixels.

Note that the above processing is an example, and the present invention is not limited to this.

The sub-line image data generated by the image processing section 3 is stored in the shift register 6. When one sub-line image data is stored in the shift register 6, the image data is simultaneously transferred to the line buffer 7. Then, the light emitting section 8 of the line head 5 is turned on based on the sub-line image data of the line buffer 7.
This lighting is １ ／ of the original lighting time for one line. That is, as described above, while the image input for one line is performed, the four sub-line image data are sequentially supplied to the line head 5, and the light emitting unit 8 of the line head 5
In this case, four lighting patterns are generated.

FIG. 3 is a conceptual diagram showing a lighting state of a line head for thickening pixels in the sub-scanning line direction. FIG. 4 is a conceptual diagram showing a lighting state of a line head for thickening pixels in the main scanning line direction. FIG. Note that the portion represented by “1” in the drawing is essentially a black pixel portion (non-lighting region), and the portion represented by “2” in the drawing is a portion that becomes black by correction (non-lighting region). Area).

In FIG. 3, lines a, b, c, and d correspond to the width of one line of an image, and each line is formed by a plurality of sub-lines. The sub-line is obtained by dividing one line in the sub-scanning direction by the number of repetitions. In this embodiment, the number of sub-lines is four as described above. Here, as shown in this figure, a black portion represented by “2” is added to the I-th and II-th pixels in the first and second sub-lines in the c-line. In addition, a black portion represented by “2” is added to the II-th and IV-th pixels in the first and second sub-lines in the d-line.

This processing is based on the above-described processing of thickening in the sub-scanning line direction. Here, the c line will be described more specifically. When the c-line is a print line,
The previous line is the b line, and the correction of the c line is performed in consideration of the b line. And the first of the repetition (division)
The processing of the first time (first subline) is performed, and the number of times of processing is notified from the exposure control means 3. In the first and second processes, since the pixel on the corresponding b-line is a black pixel, the first and second sub-lines of the corresponding pixel on the c-line are set to black. On the other hand, in the third and fourth processes, the third and fourth sub-lines of the corresponding pixel on the c-line remain white even if the corresponding pixel on the b-line is a black pixel. By such processing, sub-line image data of the c-line is obtained.

The sub-line image data of the c-line generated in this manner is supplied to the line head 5 in order. The light emission of the light emitting section 8 of the line head 5 is controlled in accordance with the sub-line image data.
Are turned off for all the pixels, and in the exposure on the third and fourth sub-lines, the pixels are turned off for the III and IV pixels.

Therefore, if such a printer control device is used in a printer device that causes pixel thinning, even if pixel thinning occurs, the portion thickened by "2" compensates for thinning. Therefore, the pixel is not thinned, and the image quality is improved.

The same applies to the thickening correction in the main scanning line direction in FIG. That is, as shown in the figure, there is a black pixel to the right of the II-th pixel, so in the processing of this II-th pixel, the first and third sub-lines are set to black, and the second and fourth sub-lines are set. The subline remains white. in this way,
By adding a black portion to a white pixel portion in the main scanning direction, fat correction is performed in the main scanning direction.

Although the number of repetitions (the number of sub-lines) is set to 4, the number of repetitions is appropriately determined in consideration of correction accuracy, data processing speed, and the like. Here, if the number of repetitions is increased, finer correction can be performed. However, reading from the line buffer 2 and data supply to the line head 5 are frequently performed. Determine the number of sublines.

Further, since the amount of thinning and thickening of the pixel differs depending on the characteristics of the line head and the mechanism of the printer device, it is desirable to make the thinning correcting amount and the thickening correcting amount variable. The correction amount can be changed depending on how many of the sub-lines constituting the pixel to be corrected are black (or white), and can be changed at the time of shipment or on the user side. Constitute.

In the correction in the main scanning direction, the priority order of the sub-lines (for example, which sub-line is black when two sub-lines are black) is determined by the first sub-line, the third sub-line, and the second sub-line. , The fourth sub-line, but the present invention is not limited to this, and the order may be the first sub-line, the fourth sub-line, the second sub-line, and the third sub-line.

Next, the selection of the driving of the resolution conversion unit 4a and the driving of the image processing unit 4b will be described. This selection is performed by a selection signal from a control unit (not shown).

FIG. 5 is a flowchart showing the selection control. First, a print mode determination process is executed (step 1). In the case of the FAX mode (reception), generation of corrected image data, which is resolution conversion, is performed by the resolution conversion unit 4a or the like described above (step 2). On the other hand, in the case of the printer mode, the image processing section 4b or the like executes generation of corrected image data for thickening / thinning correction (step 3). Then, a printing process is performed based on the correction data (step 4).

As described above, by switching the driving of the resolution conversion unit 4a and the image processing unit 4b depending on whether the mode is the print mode or the facsimile mode, when the image forming apparatus functions as a printer, the pixels are thinned by the image formation by the apparatus. Data correction of image data supplied thereto is performed so as not to cause thickening, and when functioning as a facsimile, data correction of image data is performed so as to prevent the disappearance of thin lines and the occurrence of moire.

It is to be noted that thickening / thinning correction may be performed simultaneously with resolution conversion or the like when the image forming apparatus functions as a facsimile.

[0053]

As described above, according to the present invention, in an electrophotographic image forming apparatus having both a facsimile function and a printer function or an analog exposure system, printing in each function can be performed with high quality. This has the effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a printer control device of the present invention.

FIG. 2 is a conceptual diagram illustrating a lighting state of a line head when performing resolution conversion in a main scanning line direction according to the present invention, and a timing chart illustrating timing signals and the like of each sub line.

FIG. 3 is a conceptual diagram showing a line head lighting state in which pixels are thickened in a sub-scanning line direction according to the present invention.

FIG. 4 is a conceptual diagram illustrating a line head lighting state according to the present invention in which pixels are enlarged in the main scanning line direction.

FIG. 5 is a flowchart illustrating switching control between generation of correction data for a printer and generation of correction data for a facsimile according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image input part 2 Line buffer 3 Exposure control means 4a Resolution etc. conversion means 4b Image processing part 5 Line head 8 Light emitting part

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H04N 1/23 103 G06F 15/66 415

Claims (1)

(57) [Claims] 1. A line buffer for storing and holding input image data, an exposure unit for forming one print line image by a plurality of exposures based on a plurality of sub-line image data, a resolution conversion rate or an enlargement / reduction Resolution conversion means for generating a plurality of sub-line image data by sampling corresponding to the conversion rate, image processing means for generating sub-line image data to be thinned or fattened corrected image data by a plurality, printer mode or facsimile printing Selecting means for appropriately selecting generation of thinning / thickening correction data and resolution conversion or generation of enlargement / reduction correction data depending on a mode.