JP2007196567A - Image forming method and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration in image quality, even when both a screen processing and an image rotating processing are used in an image forming device using a PWM. <P>SOLUTION: An image forming device has a screen processing part 120 for executing the screen processing relative to image data using a screen threshold matrix at a specified angle, a rotating processing part 130 for executing the image rotating processing of the image data, a control unit 101 for rotating the screen threshold matrix at an angle reverse to the rotating angle in the rotating processing from the specified angle, a PWM processing part 150 for creating an exposure pulse having the pulse width and the pulse position fixed based on the image data which are subjected to the screen processing or the rotating processing, and a printing part 160 for forming an image by executing exposure with a laser light source based on the exposure pulse. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming method and an image forming apparatus that perform exposure according to screen-processed image data to form and output an image on a recording medium, and more particularly to appropriate screen processing and image rotation processing. The present invention relates to an image forming method and an image forming apparatus in consideration of the relationship.

  In the image forming apparatus, two-dimensional image formation is performed by periodically repeating the act of scanning the photosensitive member or the recording paper in the main scanning direction while moving the photosensitive member or the recording paper in the sub-scanning direction. ing. In general, a charged photoreceptor is exposed with a laser beam corresponding to image data. In this case, the scanning direction by the laser beam is the main scanning direction, and the direction along the rotation of the photosensitive member is the sub-scanning direction.

  In addition, there is an image forming apparatus that performs exposure according to screen-processed image data to form and output an image on a recording medium. Further, there is an image forming apparatus that forms an image by performing screen processing using a line screen.

Regarding such an image forming apparatus, the related art is described in Patent Document 1 below.
Japanese Patent Laying-Open No. 2003-519553 (first page, FIG. 1)

  Here, when screen processing is performed by an image forming apparatus that generates a pulse for exposure using a PWM circuit, in addition to a pulse width by PWM, a technique for right-aligning / left-aligning a pulse position is used. ° Line screen can be realized easily.

  By the way, there is a method of reducing two A4 size images by so-called 2 in 1 processing and forming an image in an A4R size. Further, there may be a case where two A4 size images are stored on one A3 recording sheet by 2 in 1 processing to form an image. In the case of the 2-in-1 processing, it is necessary to rotate the screen-processed image data by 90 °.

  However, rotating image data that has undergone screen processing at 45 ° to 90 ° by 90 ° is equivalent to screen processing by a line screen at 135 ° to 180 °, that is, 0 ° to 45 °.

  In this case, it is necessary to move the dots to be exposed in the vertical (sub-scanning) direction. However, in a general image forming apparatus, the dots are horizontally (main-scanned (figure of the main scanning (figure)) by the pulse width and pulse position of the PWM circuit. Can be moved only in the left and right direction)). For this reason, the inventor of the present application has newly found that smooth screen processing cannot actually be performed and moire occurs in the formed image.

  Further, when image data is stored and an image is formed again later, screen processing is performed in the direction (rotation angle) when the input image data is stored. For this reason, if the rotation angle when forming an image later is different from the initial angle, the inventor of the present application newly states that the screen processing is not optimal and moire occurs in the formed image. I found it.

  The present invention has been made to solve the above-described problems, and does not cause image quality degradation even when screen processing and image rotation processing are used together in an image forming apparatus using PWM. An object is to provide an image forming method and an image forming apparatus.

  Further, the present invention has been made to solve the above-described problems, and an image stored in an image forming apparatus using both screen processing and image rotation processing in an image forming apparatus using PWM. An object of the present invention is to provide an image forming method and an image forming apparatus that do not cause image quality deterioration even when data is formed as an image.

The present invention for solving the above problems is as described below.
(1) In the first aspect of the present invention, when image formation is performed without performing rotation processing on image data, screen processing is performed on the image data using a first screen threshold matrix of a predetermined angle, and A drive pulse having a pulse width and a pulse position is generated based on the image data screen-processed by the first screen threshold matrix, an image is formed based on the drive pulse, and the image data is subjected to a rotation process. When image formation is performed, screen processing is performed on the image data using a second screen threshold matrix having an angle different from the predetermined angle, and image data screen-processed using the second screen threshold matrix is processed. Rotation processing at the rotation angle, screen processing using the second screen threshold matrix and the An image forming method comprising generating a drive pulse having a pulse width and a pulse position determined based on the image data subjected to a transfer process, and forming an image based on the drive pulse. .

(2) According to the second aspect of the present invention, screen processing is performed on image data using a first screen threshold matrix having a predetermined angle, and a second screen threshold matrix having an angle different from the predetermined angle is used. The image data subjected to screen processing, the image data subjected to the second screen processing to image rotation processing, and the screen processing using the first screen threshold matrix; Generating a driving pulse having a pulse width and a pulse position determined based on any one of the image data subjected to the screen processing using the two-screen threshold matrix and the rotation processing; An image is formed based on the pulse, and the screen processing is performed using the first screen threshold matrix. Image data and screen processing for storing both of said image data subjected using the second screen threshold matrix, an image forming method, characterized in that.

  (3) The invention according to claim 3 is characterized in that the second screen threshold matrix is generated by rotating the first screen threshold matrix at an angle opposite to the rotation angle at the time of the rotation process. An image forming method according to any one of claims 1 and 2.

  (4) The invention described in claim 4 is a screen processing unit that performs screen processing on image data using a first screen threshold matrix having a predetermined angle or a second screen threshold matrix having an angle different from the predetermined angle. And an image processing unit including a rotation processing unit that performs image rotation processing of the image data, a control unit that controls the image processing unit, and a pulse width based on image data that has been subjected to image processing by the image processing unit And a PWM processing unit that generates a driving pulse in which a pulse position is determined, and a printing unit that forms an image based on the driving pulse, and the control unit performs image rotation processing on the image data. When image formation is performed without using the first screen threshold matrix, the screen processing unit performs screen processing on the image data. When image formation is performed by performing image rotation processing on the image data, the screen processing unit is subjected to screen processing on the image data using the second screen threshold matrix, and the rotation is performed. In the image forming apparatus, the processing unit is configured to rotate the image data screen-processed with the second screen threshold matrix at the rotation angle.

  (5) The invention according to claim 5 is a screen processing unit that performs screen processing on image data using a first screen threshold matrix having a predetermined angle or a second screen threshold matrix having an angle different from the predetermined angle. And an image processing unit including a rotation processing unit that performs image rotation processing on the screen-processed image data, and a pulse width and a pulse position are determined based on the image data subjected to image processing by the image processing unit. A PWM processing unit that generates the generated drive pulse, a print unit that forms an image based on the drive pulse, a storage unit that stores image data, the image processing unit, the PWM processing unit, and the storage unit. A control unit that controls the image processing unit to perform screen processing using the first screen threshold matrix. Image data and image data that has been subjected to screen processing using the second screen threshold matrix and subjected to the rotation processing are generated. One of these image data is output to the PWM processing unit, and both are output. An image forming apparatus, wherein the image forming apparatus is stored in the storage unit.

  (6) In the invention according to claim 6, the control unit generates the second screen threshold matrix by rotating the first screen threshold matrix at an angle opposite to a rotation angle in the rotation process. The image forming apparatus according to claim 5.

  (7) The image forming apparatus according to any one of claims 4 to 6, wherein the screen threshold value matrix used in the screen processing unit is configured by a line screen. is there.

According to the present invention, the following effects can be obtained.
(1) In the first and fourth aspects of the invention, image data is generated using either the first screen threshold matrix or the second screen threshold matrix depending on the presence / absence of rotation processing performed after the screen processing. When screen processing is applied to the screen processed image data and image rotation processing is necessary, the rotation processing is performed to perform image processing. Based on the image data subjected to the image processing, the pulse width and the pulse A drive pulse whose position is determined is generated, and an image is formed based on the drive pulse.

  Note that it is desirable to use at least two types of screen threshold matrixes, one that is rotated at an angle opposite to the rotation angle in the image rotation process and one that is not rotated. The screen threshold matrix used in the screen processing unit is preferably composed of a line screen.

  As a result, when an exposure pulse is generated by adjusting the pulse width and pulse position by PWM processing after image rotation, it becomes the same state as screen processing with a screen threshold matrix of an angle suitable for PWM processing, and PWM is used. Even when screen processing and image rotation processing are used in combination in an image forming apparatus, image formation without causing image quality degradation is possible.

  (2) In the image forming method according to the second and fifth aspects of the present invention, screen processing is performed on the image data using the first screen threshold matrix of a predetermined angle, and the second screen threshold matrix is The image data is subjected to screen processing, and the screen-processed image data is stored.

  As the screen threshold matrix, it is desirable to use at least two kinds of screen threshold matrixes, that is, a screen that is rotated at an angle opposite to the rotation angle in the image rotation process and a screen that is not rotated. The screen threshold matrix used in the screen processing unit is preferably composed of a line screen.

  As a result, even if image data is saved and image formation is performed again later, image formation is performed later regardless of the orientation (rotation angle) when the input image data is stored and the processed screen processing. It is possible to select image data by suitable screen processing as the rotation angle at the time.

  In other words, even in the case where an image forming apparatus using PWM uses both screen processing and image rotation processing to form an image of stored image data later, image formation that does not cause image quality degradation is achieved. It becomes possible.

  The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the drawings. Hereinafter, the configuration and operation of the image forming apparatus will be described. However, the operation of the image forming apparatus is an image forming method.

<Electrical configuration of image forming apparatus>
FIG. 1 is a circuit configuration diagram showing an electrical configuration of a copying machine as an image forming apparatus according to a first embodiment of the present invention.

  In FIG. 1, each part of the image forming apparatus 100 is connected to a bus 100b. The control unit 101 is connected to the bus 100b and controls the entire image forming apparatus 100. The control unit 101 performs control to rotate a screen threshold matrix having a predetermined angle for screen processing from a predetermined angle at an angle opposite to the rotation angle in the rotation processing.

  The control unit 101 stores the screen-processed image data in the storage unit, and the screen processing unit screen-processes the screen threshold matrix at an angle different from the screen threshold matrix used in the screen processing. Control to store data in the storage unit.

  The operation input unit 102 is connected to the bus 100b, receives an operation input from the user or key operator for setting operation of the image forming apparatus 100, and sends a signal corresponding to the operation input to the control unit 101 via the bus 100b. introduce.

  The display unit 103 is connected to the bus 100b, and displays various states of the image forming apparatus 100 to the user under the control of the control unit 101. Here, although the operation input unit 102 and the display unit 103 that individually perform input and display of operations are shown, the configuration of an operation display unit that includes a touch panel that performs both may be used.

The print controller 105 is connected to the bus 100b and performs control when exchanging data with an external device (not shown).
The image reading unit 110 is connected to the bus 100b and optically scans and reads image information of a document to generate image data. In the image reading unit 110, a user places a document on the platen glass one by one when the document placed on the document placing unit is automatically fed and scanned to generate image data. Two types of scanning are possible, as in the case where image data is generated by placing and scanning. As the image reading unit 110, various known scanners using an image sensor using a CCD, a CIS, or the like can be used.

  Here, when the document is placed on the platen glass with the reading surface facing downward, the reading optical system scans along the platen glass and performs reading. When the document is automatically fed, reading is performed with the reading optical system fixed.

  The screen processing unit 120 is connected to the bus 100b and performs screen processing on the image data using a screen threshold matrix of a predetermined angle. Note that it is desirable to use a line screen as the screen threshold mask used here.

  The rotation processing unit 130 is connected to the bus 100b and performs image rotation processing of screen-processed image data. This rotation processing unit 130 is based on an instruction from the control unit 101 when forming an image of an A4 original on A4R recording paper, or when forming an image of two pages of A4 original on an A4R recording paper by 2in1 processing. A rotation process for rotating the data by 90 ° is executed.

  Note that the screen processing unit 120 that performs screen processing as one of the image processing and the rotation processing unit 130 that performs image rotation processing as one of the image processing constitute an image processing unit in the claims.

  The storage unit 140 is connected to the bus 100b. Based on instructions from the control unit 101, the storage unit 140 stores image data input from the print controller 105 or the image reading unit 110 or image data subjected to screen processing and image rotation processing. Read.

  The PWM processing unit 150 is connected to the bus 100b, and generates an exposure pulse suitable for screen processing in which the pulse width and pulse position are determined based on the image data subjected to screen processing or image rotation processing.

  The printing unit 160 is connected to the bus 100b, and performs exposure with a laser light source based on the exposure pulse generated by the PWM 150 to form and output a visible image on recording paper. The print unit 160 corresponds to various electrophotographic print engines using a photosensitive drum or a photosensitive belt. That is, the print unit 160 corresponds to an electrophotographic type using a laser beam from a laser light source.

The image forming apparatus 100 described above corresponds to various image forming apparatuses such as a copying machine, a facsimile apparatus, an all-in-one printer, and a light printing apparatus.
In the above case, for example, as shown in FIG. 2, when signals with pixel values of 50%, 100%, and 50% exist, 50%, 100%, and 50 according to the clock (FIG. 2A). % PWM waveform (FIG. 2 (b)) is right-justified, centered, and left-justified (FIG. 2 (b) → (c)), and is an aggregate of multiple exposure dots that become “lines” for screen processing. Is generated (FIG. 2C).

Note that various known mechanical configurations of the image forming apparatus 100 used in the present embodiment can be used, and thus description of the mechanical configuration is omitted.
<Operation of Image Forming Apparatus (1)>
The operation of the image forming apparatus according to the first embodiment will be described below with reference to the flowchart of FIG.

  First, image data is input to the image forming apparatus 100 via the print controller 105 or read by the image reading unit 110 (S1 in FIG. 3). As the image data is input, an instruction for image processing including image quality, density, presence / absence of image rotation, and the like is input from the operation input unit 102 or the print controller 105. Further, this image data is stored in the storage unit 140 in accordance with an instruction from the control unit 101.

Here, the control unit 101 analyzes the presence / absence of an instruction to rotate the image data as an instruction for the input image processing (S2 in FIG. 3).
Here, two images (FIGS. 4A and 4B) are rotated by a so-called 2-in-1 process (FIG. 4C) and are stored on one sheet of recording paper (FIG. 4D). )). In this case, after the image data is rotated 90 ° by the rotation processing unit 130 in the image forming apparatus 100, image formation is executed by the printing unit 160. In this case, there is no direct instruction from the operator for 90 ° rotation, but the 2 in 1 process is considered to be a process including 90 ° rotation (Y in FIG. 3 S2). Similarly, when forming an image of an A4 original on A4R transfer paper, there is no direct instruction from the operator to rotate the image, but it is considered that the A4 original → A4R recording paper includes 90 ° rotation (Y in FIG. 3). ).

  Here, as a screen threshold mask of a predetermined angle used in the screen processing unit 120, for example, a linear one in the direction of 60 ° shown in FIGS. 5A and 6A is planned to be used. .

  As shown in FIG. 2, when screen processing is performed by an image forming apparatus that generates a pulse for exposure using PWM, in addition to the pulse width by PWM, a technique for right-aligning / left-aligning the pulse position is used. Thus, a line screen of 45 ° to 90 ° can be easily realized. That is, in this embodiment, it is desirable to use a 45 ° to 90 ° line screen as the screen threshold mask of a predetermined angle.

  In this case, the control unit 101 gives a rotation of −90 ° to the screen threshold mask as an angle in the reverse direction of 90 ° specified in the image rotation processing (FIGS. 5B and 5C). 6 (b) (c)). It should be noted that the reverse angle is desirably the same numerical value excluding the sign, but there may be some difference in numerical values.

  Then, based on an instruction from the control unit 101, the image data stored in the storage unit 140 is read out and the screen threshold mask in the state rotated by −90 ° as described above (FIGS. 5C and 6C). ), The screen processing unit 120 performs screen processing (FIG. 3S4, FIGS. 6E and 6F).

  Further, based on an instruction from the control unit 101, the image data subjected to screen processing is subjected to image rotation processing at a rotation angle of 90 ° by the rotation processing unit 130 to generate image data for printing (S5 in FIG. 3). FIG. 6 (g) (h)). The printing image data in this state has a screen having the same angle as that of the initial screen threshold mask in the state shown in FIG. 5A or FIG. 6A.

  On the other hand, when there is no instruction to rotate the image (N in FIG. 3 S2), the screen processing unit 120 uses the original screen threshold mask (FIG. 5A) according to the instruction from the control unit 101. Screen processing is executed (S6 in FIG. 3).

In the image rotation process and the screen process described above, image data is stored in the storage unit 140 and read out as needed in a timely manner.
In response to an instruction from the control unit 101, the PWM processing unit 150 determines the pulse width and the pulse position for the screen-processed print image data or the print image data subjected to the screen process and the image rotation process. The exposure pulse in the state is generated (S7 in FIG. 3). Further, based on the instruction from the control unit 101, the printing unit 160 forms a visible image on the recording paper using this exposure pulse and outputs it (S8 in FIG. 3).

  As described above, screen processing is performed on image data in a state where the screen threshold matrix of a predetermined angle is rotated to an angle opposite to the rotation angle required at the time of image rotation processing. An image rotation process is performed on the obtained image data, and an exposure pulse having a pulse width and a pulse position determined based on the image data subjected to the screen process and the image rotation process is generated. Based on the exposure pulse By performing exposure with a laser light source and forming an image, it becomes the same state as screen processing with a screen threshold matrix having an angle suitable for PWM processing, and screen processing and image rotation processing are performed in an image forming apparatus using PWM. Even in the case of using together, it becomes possible to form an image without causing image quality deterioration.

<Operation of Image Forming Apparatus (2)>
The operation of the image forming apparatus according to the second embodiment will be described below with reference to the flowchart of FIG.

  First, image data is input to the image forming apparatus 100 via the print controller 105 or read by the image reading unit 110 (S1 in FIG. 7). As the image data is input, an instruction for image processing including image quality, density, presence / absence of image rotation, and the like is input from the operation input unit 102 or the print controller 105. The image data is stored in the storage unit 140 in accordance with an instruction from the control unit 101 (S2 in FIG. 7).

  Here, the control unit 101 analyzes whether or not there is an instruction to rotate the image data as an instruction for the input image processing. Here, in the case where processing including 90 ° rotation is instructed, such as so-called 2 in 1 processing or when an A4 original is imaged on A4R transfer paper, the control unit is the same as in the first embodiment described above. 101 gives a rotation of −90 ° to the screen threshold mask as an angle in the reverse direction of 90 ° designated in the image rotation processing. Then, based on an instruction from the control unit 101, the screen processing unit 120 reads out the image data stored in the storage unit 140 and uses the screen threshold mask in the state rotated by −90 ° as described above to perform screen processing. (S3 in FIG. 7).

At this stage, the image data subjected to the above screen processing is stored in the storage unit 140 based on an instruction from the control unit 101 (S4 in FIG. 7).
Further, based on the instruction of the control unit 101, the image data subjected to screen processing is subjected to image rotation processing at a rotation angle of 90 ° by the rotation processing unit 130 to generate image data for printing (S5 in FIG. 7). . The image data for printing in this state has a screen having the same angle as the initial screen threshold mask, as in the first embodiment.

  Then, in response to an instruction from the control unit 101, an exposure pulse having a pulse width and a pulse position determined by the PWM processing unit 150 is generated for the printing image data subjected to the screen processing and the image rotation processing (S6 in FIG. 7). ). Further, based on an instruction from the control unit 101, the printing unit 160 forms a visible image on the recording paper using the exposure pulse and outputs the visible image (S7 in FIG. 7).

  In the second embodiment, a screen threshold mask having an angle different from the screen threshold mask used in the above screen processing is prepared in accordance with an instruction from the control unit 101, and image data stored in the storage unit 140 is stored. The data is read and screen processing # 2 is performed by the screen processing unit 120 (S8 in FIG. 7).

  In the second embodiment, it is desirable to use at least two types of screen threshold matrixes, one that is rotated at an angle opposite to the rotation angle in the image rotation process and one that is not rotated.

  At this stage, the image data that has been subjected to the above-described screen processing # 2 is stored in the storage unit 140 based on an instruction from the control unit 101 (S9 in FIG. 7). Further, the original image data stored in the storage unit 140 is deleted (S10 in FIG. 7).

  In the second embodiment described above, when the rotation angle of the image rotation processing is 90 °, the screen threshold mask used in the first screen processing is rotated by −90 ° as in the first embodiment described above. It is desirable to use a screen threshold mask used in the subsequent screen processing without using rotation.

  As described above, screen processing is performed on image data using a screen threshold matrix at a predetermined angle, the screen-processed image data is stored, and image rotation processing is performed on the screen-processed image data. And generating an exposure pulse having a pulse width and a pulse position determined based on the image data subjected to the image rotation processing, forming an image by performing exposure with a laser light source based on the exposure pulse, By storing image data screen-processed with a screen threshold matrix having an angle different from that of the screen threshold matrix used in this screen processing, the image data can be stored and later imaged again. , Orientation (rotation angle) when saving the input image data and processed screen processing Regardless, as the rotation angle when an image is formed later, it is possible to select the image data with a suitable screen processing. In other words, even in the case where an image forming apparatus using PWM uses both screen processing and image rotation processing to form an image of stored image data later, image formation that does not cause image quality degradation is achieved. It becomes possible.

  In addition, when the input original image data is 8 bits for each pixel, the gradation can be sufficiently expressed by 4 bits as the screen-processed image data. Since the data size is the same for one piece of image data and two pieces of screen-processed image data, the problem of the capacity of the storage unit 140 does not occur.

  Further, by holding the image data screen-processed with the two types of screen threshold masks as described above, the processing time can be shortened when an image is formed later. In other words, it becomes possible to select an optimal image according to the rotation angle of the image when the image is re-edited and the image is formed and output at a later date.

1 is a circuit configuration diagram showing an electrical configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a waveform diagram showing an operation of the image forming apparatus according to the embodiment of the present invention. 3 is a flowchart illustrating an operation of the image forming apparatus according to the first embodiment of the present invention. It is explanatory drawing which shows the mode of the process in embodiment of this invention. It is explanatory drawing which shows the mode of the process in embodiment of this invention. It is explanatory drawing which shows the mode of the process in embodiment of this invention. 6 is a flowchart illustrating an operation of the image forming apparatus according to the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Control part 102 Operation input part 103 Display part 105 Print controller 110 Image reading part 120 Screen process part 130 Rotation process part 140 Storage part 150 PWM process part 160 Print part

Claims (7)

When image formation is performed without performing rotation processing on image data, the image data is subjected to screen processing using a first screen threshold matrix at a predetermined angle, and the screen processing is performed using the first screen threshold matrix. A drive pulse having a pulse width and a pulse position determined based on the image data is generated, and an image is formed based on the drive pulse.
When image formation is performed by performing rotation processing on the image data, screen processing is performed on the image data using a second screen threshold matrix having an angle different from the predetermined angle, and the second screen threshold matrix is used. Rotation processing is performed on the screen-processed image data at the rotation angle, and a pulse width and a pulse position are determined based on the image data subjected to the screen processing using the second screen threshold matrix and the rotation processing. Generate a drive pulse defined by and form an image based on the drive pulse,
An image forming method. Screen processing the image data using a first screen threshold matrix of a predetermined angle;
Applying screen processing to the image data using a second screen threshold matrix of an angle different from the predetermined angle;
Image rotation processing is performed on the second screen-processed image data;
Either the image data subjected to the screen processing using the first screen threshold matrix, or the image data subjected to the screen processing using the two-screen threshold matrix and the rotation processing. A drive pulse with a pulse width and pulse position determined based on
Forming an image based on the drive pulse;
Storing both the image data screen-processed using the first screen threshold matrix and the image data screen-processed using the second screen threshold matrix;
An image forming method. The second screen threshold matrix is generated by rotating the first screen threshold matrix at an angle opposite to the rotation angle at the time of the rotation process.
The image forming method according to claim 1, wherein the image forming method is an image forming method. A screen processing unit that performs screen processing on image data using a first screen threshold matrix of a predetermined angle or a second screen threshold matrix of an angle different from the predetermined angle, and a rotation that performs image rotation processing of the image data An image processing unit including a processing unit;
A control unit for controlling the image processing unit;
A PWM processing unit that generates a driving pulse in which a pulse width and a pulse position are determined based on the image data subjected to image processing by the image processing unit;
A print unit that forms an image based on the drive pulse;
The control unit includes:
When image formation is performed without performing image rotation processing on image data, the screen processing unit is subjected to screen processing on the image data using the first screen threshold matrix,
When image formation is performed by performing image rotation processing on the image data, the screen processing unit is caused to perform screen processing on the image data using the second screen threshold matrix, and the rotation processing unit To rotate the image data screen-processed with the second screen threshold matrix at the rotation angle.
An image forming apparatus. A screen processing unit that performs screen processing on image data using a first screen threshold matrix of a predetermined angle or a second screen threshold matrix of an angle different from the predetermined angle, and the screen processed image data An image processing unit including a rotation processing unit for performing image rotation processing;
A PWM processing unit that generates a driving pulse in which a pulse width and a pulse position are determined based on image data subjected to image processing by the image processing unit;
A print unit that forms an image based on the drive pulse;
A storage unit for storing image data;
A control unit for controlling the image processing unit, the PWM processing unit, and the storage unit;
And the control unit includes:
Image data that has undergone screen processing using the first screen threshold matrix and image data that has undergone screen processing using the second screen threshold matrix and have undergone the rotation processing are processed by the image processing unit. Generating and outputting one of these image data to the PWM processing unit and storing both in the storage unit,
An image forming apparatus. The control unit generates the second screen threshold matrix by rotating the first screen threshold matrix at an angle opposite to a rotation angle in the rotation process.
6. The image forming apparatus according to claim 4 or 5, wherein the image forming apparatus is an image forming apparatus. The screen threshold matrix used in the screen processing unit is configured by a line screen.
The image forming apparatus according to claim 4, wherein the image forming apparatus is an image forming apparatus.

Images