JP2010120179A - Image processing apparatus, image processing method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively achieve higher operation speed of image processing, and to prevent banding due to screen-processing of image data. <P>SOLUTION: Disclosed is an image processing apparatus including: a band data generating section 33a to divide the image data and generate band data; a screen offset setting section 33c to set coordinates for the band data; a first screen processing section 35d<SB>1</SB>to perform the screen processing of the coordinate-set band data; and a second image processing section 35d<SB>2</SB>to perform the screen processing of the coordinate-set band data, wherein the screen offset setting unit 33c sets the coordinates for use in the screen processing by the first screen processing section 35d<SB>1</SB>or the second screen processing section sets the coordinates for use in the screen processing by the second screen processing section 35d<SB>2</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that screens input image data, a method for image processing of image data, and image formation in which an electrostatic latent image is formed on a latent image carrier by an exposure head having aligned light emitting elements. It relates to the technical field of equipment.

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a printer, an image forming apparatus that forms an electrostatic latent image on a photosensitive member that is a latent image carrier using a line head having light emitting elements such as aligned organic EL elements is known ( For example, see Patent Document 1). In the image forming apparatus described in Patent Document 2, image data is included in an image formation command and image processing is performed by an image processing controller to form video data. The head controller controls the lighting of the light emitting elements of the line head based on the video data, thereby forming an electrostatic latent image on the latent image carrier.

Conventionally, as an image forming apparatus such as a printer, an image forming apparatus in which image data is improved by performing screen processing such as halftone on the image data when printing the image data (for example, Patent Document 2). In the image forming apparatus described in Patent Document 1, high-quality images can be printed by performing N-value processing (halftone processing) on image data using a dither matrix of screen pattern threshold values. Specifically, it is possible to form dots of multiple types of sizes by associating each threshold value of the screen pattern with the input pixel and comparing the size to determine whether the dot corresponding to the pixel value is on or off. ing.
JP 2008-137237 A. Japanese Patent Application Laid-Open No. 2008-153914.

  By the way, in an image forming apparatus using a line head, in recent years, higher speed and higher resolution are increasingly demanded. For this reason, high-speed processing is also required in image processing. However, the amount of image processing data associated with higher resolution and the like is increasing, which is an impediment to increasing the speed of image processing. In addition, the image forming apparatus is also required to have versatility so as to flexibly cope with various high resolutions.

However, the image forming apparatus described in Patent Document 1 does not have versatility, and it is difficult to flexibly cope with various high resolutions. In addition, since data is communicated on a one-to-one basis between the image processing controller and the head controller, it is difficult to further increase the speed of image processing. Further, when developing an image forming apparatus for speeding up such image processing, when screen processing is performed on an input image as described in Patent Document 2, the divided image data is divided by dividing the image data. It is conceivable to perform screen processing every time. That is, the screen processing is performed for each piece of divided image data by associating the threshold value of the screen pattern with the pixels of the divided image data for each piece of divided image data.
However, when screen processing is simply performed for each divided image data by associating the threshold value of the screen pattern with the pixel of the divided image data, the correspondence between the threshold value of the screen pattern and the pixel of the divided image data at the boundary of the divided image data It is possible that the attachment will be reset. Thus, when the above-described association is reset, banding occurs, and the formed image is disturbed.

The present invention has been made in view of such circumstances, and an object of the present invention is to make it possible to prevent banding due to screen processing of image data while effectively increasing the speed of image processing. A processing apparatus, an image processing method, and an image forming apparatus are provided.

  In order to solve the above-described problems, in the image processing apparatus, the image processing method, and the image forming apparatus according to the present invention, the input image data is divided into divided image data such as band data or line data by the image data dividing unit. The Also, coordinates are set in the image data or the divided image data by the coordinate setting unit. Furthermore, the image processing apparatus includes a first image processing unit and a second image processing unit. Therefore, the parallel and distributed processing of the screen processing can be independently performed on the divided image data by the first image processing unit and the second image processing unit. As a result, it is possible to execute image processing of high-resolution and large-capacity image data even more quickly.

  Also, the coordinates set in the divided image data screen-processed by the second image processing unit are offset coordinates offset from the coordinates set in the divided image data screen-processed by the first image processing unit. It is set. Accordingly, the offset coordinates obtained by offsetting the coordinates based on the threshold value of the screen pattern at the boundary portion of the divided image data are designated for the first image processing unit and the second image processing unit. This can prevent image banding.

  Thus, according to the image processing apparatus, the image processing method, and the image forming apparatus according to the present invention, it is possible to prevent banding due to screen processing of image data while effectively increasing the speed of image processing. It becomes like this.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus according to the present invention.
As shown in FIG. 1, the image forming apparatus 1 of this example includes a housing body 2. In the housing body 2, an image forming unit 3, a transfer unit 4, a transfer material supply unit 5 that accommodates a transfer material such as transfer paper, a fixing unit 6, an engine control unit 7, and a paper discharge tray 8 are disposed. ing.

The image forming unit 3 includes a first image forming station 9Y that is a yellow (Y) image forming station, a second image forming station 9M that is a magenta (M) image forming station, and a cyan (C) image forming station. And a fourth image forming station 9K which is a black (K) image forming station. The first to fourth image forming stations 9Y, 9M, 9C, 9K are arranged in tandem in this order. The arrangement order of the first to fourth image forming stations 9Y, 9M, 9C, 9K is arbitrary. Hereinafter, the first to fourth image forming stations 9Y, 9M, 9C, and 9K shown in FIG.

The first to fourth image forming stations 9Y, 9M, 9C, 9K are all configured identically. Therefore, the first image forming station 9Y of yellow (Y) will be described, and detailed descriptions of the second to fourth image forming stations 9M, 9C, 9K of other colors will be omitted. Note that the constituent elements of the second to fourth image forming stations 9M, 9C, and 9K have the same reference numerals and subscripts of M, C, and K as the corresponding constituent elements of the yellow (Y) image forming station 4Y. Attached is shown.

The first image forming station 9Y has a first photoconductor 10Y which is a latent image carrier. The first image forming station 9Y includes a first charging unit 11Y, a first line head 12Y that is an exposure head of an image writing unit, a first developing unit 13Y, around the first photoconductor 10Y.
And a first photoconductor cleaner 14Y.
The first charging unit 11Y includes a conventionally known first charging roller 15Y. The first charging roller 15Y charges the surface of the first photoconductor 10Y to a preset surface potential.

  As shown in FIG. 2, the first line head 12Y includes a first base substrate 16Y, a first LED array 17Y, a first driver IC 18Y, and a first rod lens array 19Y. The first LED array 17Y includes LED elements that are light emitting elements. In this case, the LED elements are arranged on the first base substrate 16Y along a first direction α (so-called main scanning direction) that is orthogonal or substantially orthogonal to the transfer material conveyance direction (movement direction).

  The first driver IC 18Y is adjacent to the first base substrate 16Y adjacent to the LED element along a second direction β (so-called sub-scanning direction) β that is the same or substantially the same direction as the transfer material conveyance direction. And arranged along the first direction α. At this time, a preset number of LED elements are connected to one first driver IC 18Y. Accordingly, one first driver IC 18Y drives the connected LED element. In that case, when a video signal is given from the head controller 36 described later, the LED element emits light by driving the first driver IC 18Y based on the video signal.

  Furthermore, the first rod lens array 19Y has a first gradient index rod lens 20Y. The first gradient index rod lenses 20Y are arranged in a zigzag pattern in two rows along the first direction α, and are arranged facing the LED elements. The first gradient index rod lens 20Y optically forms an image of the light from the LED element to expose the first photoconductor 10Y, and a yellow (Y) static light is applied to the first photoconductor 10Y. An electrostatic latent image is formed. The first gradient index rod lens 20Y is not limited to two rows, and can be arbitrarily arranged in three or more rows.

The first developing unit 13Y has a first developing roller 21Y. The first developing roller 21Y supplies yellow (Y) toner to the first photoconductor 10Y. With this toner, the electrostatic latent image on the first photoconductor 10Y is developed, and a yellow (Y) toner image is formed on the first photoconductor 10Y.
The first photoconductor cleaner 14Y cleans the first photoconductor 10Y to which the toner image is transferred.

  As shown in FIG. 1, the transfer unit 4 includes a yellow (Y) first transfer unit 22Y, a magenta (M) second transfer unit 22M, a cyan (C) third transfer unit 22C, and a black ( B) a fourth transfer portion 22K, an endless transfer belt 23 as a transfer medium, a fifth transfer portion 24, and a transfer belt cleaner 25.

The first transfer portion 22Y has a first transfer roller 26Y. The second transfer portion 22M has a second transfer roller 26M. Further, the third transfer portion 22C has a third transfer roller 26C. Further, the fourth transfer portion 22K has a fourth transfer roller 26K. The first transfer roller to the fourth transfer rollers 26Y, 26M, 26C, and 26K press the transfer belt 23 to the corresponding first to fourth photoconductors 10Y, 10M, 10C, and 10K and The toner images of the first to fourth photoreceptors 10Y, 10M, 10C, and 10K are transferred to the transfer belt 23 by the transfer bias or the fourth transfer bias.

The transfer belt 23 is stretched between a driving roller 27 and a driven roller 28 and is rotated by the driving roller 27 in the arrow γ direction.
The fifth transfer unit 24 has a fifth transfer roller 29. The fifth transfer roller 29 brings the transfer material into pressure contact with the transfer belt 23 and transfers the toner image on the transfer belt 23 to the transfer material with a fifth transfer bias.
The transfer belt cleaner 25 cleans the transfer belt to which the toner image is transferred.

  The transfer material supply unit 5 includes a transfer material storage unit 5 a that stores a transfer material such as transfer paper, and a transfer material supply unit 5 b that supplies the transfer material from the transfer material storage unit 5 a to the fifth transfer unit 24. is doing. The transfer material supply unit 5 supplies transfer materials one by one from the transfer material storage unit 5a to the fifth transfer unit 24 during image formation.

  The fixing unit 6 includes a heating roller 30 and a pressure belt 31. The pressure belt 31 presses the transfer material on which the toner image is transferred by the fifth transfer unit 24 to the heating roller 30. The heating roller 30 heats the toner image transfer surface of the transfer material. As a result, the toner image is fixed on the transfer material, and an image is formed on the transfer material.

The image forming unit 3, the transfer unit 4, the transfer material supply unit 5, and the fixing unit 6 constitute an engine unit 32 of the image forming apparatus 1.
The engine control unit 7 controls the engine unit 32. As shown in FIG. 3, the engine control unit 7 includes a power circuit board (not shown), a main controller 33, an engine controller 34, an image processing controller 35, and a head controller 36. The main controller 33 and the image processing controller 35 constitute an image processing apparatus.

When an image formation command is given from an external device (not shown) such as a host computer, the main controller 33 sends a control signal for starting the engine unit 32 to the engine controller 34 via a UART (general purpose asynchronous transmission / reception) communication line. Send.
When the engine controller 34 receives a control signal from the main controller 33, the engine controller 34 starts initialization and warm-up of the engine unit 32. When initialization and warm-up are completed and the image forming operation is ready, the engine controller 34 outputs a synchronization signal that triggers the start of the image forming operation to the head controller 36 via the UART communication line. To do. Further, in the communication between the engine controller 34 and the head controller 36, in addition to the transmission of the synchronization signal, the line heads 11Y, 11M, 11C, 11K
(Transmission and reception of signals of these control parameters is the same as that of the image forming apparatus described in Patent Document 1 described above, and therefore, details thereof will be described.) Will be omitted).

Further, as shown in FIG. 4, the main controller 33 includes a band data generation unit 33a that is an image data division unit, a screen offset calculation unit 33b, a screen offset setting unit 33c that is a coordinate setting unit, and a data transfer unit 33d. ing. As shown in FIG. 5, the band data generation unit 33a screen-processes the image data included in the image formation command, so that a screen table (look-up table: LUT) that associates a screen pattern threshold value with the image data is displayed. Generate. In the example shown in FIG. 5, a relatively small 4 × 3 screen having a screen table width (LutWidth) of 4 (four threshold values) and a screen table height (LutHeigh) of 3 (3 threshold values). It is a table (LUT). Thus, by reducing the screen table (LUT), the design becomes easy and the memory capacity can be reduced. Further, the same screen table (LUT) is repeatedly used in the first direction and the second direction as the screen table (LUT). Therefore, the same threshold is used because the same screen table (LUT) is used. In that case, the screen table (LUT) shifts the threshold value in the first direction or the second direction so that the unevenness in the first direction or the unevenness in the second direction is not visible at the band data boundary. Yes. Note that the threshold value of the screen table (LUT) can be shifted in the first direction and the second direction. Then, band data is generated by dividing the image data associated with the screen pattern into an arbitrary number of divided data. Details of generation of band data by dividing the image data will be described later.

  When the screen offset calculation unit 33b shifts from one band data to the next band data in the screen processing, the coordinates offset from each threshold value associated with the first pixel of each band data (first direction that is the main scanning direction) Offset value / second direction offset value in the sub-scanning direction) is calculated. When the next band data shifts, the screen offset setting unit 33c sets an offset to the offset value calculated from the threshold value associated with the first pixel of the next band data. The data transfer unit 33d transfers the band data to the image processing controller 35. When transferring the band data, the data transfer unit 33d notifies the coordinates of the set offset together. As a result, every time the next band data is transferred from a certain band data, it is transferred after being offset based on the coordinates.

The image processing controller 35 includes n (n ≧ 2) first image processing controllers 35a _1.
To have an image processing controller 35a _n of the n. The first image processing controller 35a ₁ includes a first image processing unit 35b ₁ and a first image processing side communication module 35c ₁ . Furthermore, the first image processing unit 35b ₁ includes a first screen processing unit 35d ₁ and a first screen data storage unit 35e ₁ which are _first image processing units. Other image processing controller is also similar, for example, the image processing controller 35a _n of the n is an image processing section of the n-th image processing side communication module 35c _n of the image processing unit 35b _n and the n of the n
have. Furthermore, the image processing unit 35b _n of the n has a screen processing unit 35d _n and the screen data storing unit 35e _n of the n of the n. In that case, the image processing controller 35a _n of the first image processing controller 35a ₁ to the n are driven independently.

Of the divided band data, r (r ≧ 1) band data are transferred from the data transfer unit 33d to the first image processing unit 35b ₁ . Also, among the divided band data, other s (s ≧ 1) pieces of band data is transferred from the data transfer unit 33d to the second image processing section 35b _2. Similarly, the band data is transferred to other image processing units, but n
The n-th image processing unit 35b _n includes other t (t ≧ 0) out of the divided band data.
) Pieces of band data are transferred from the data transfer unit 33d (when t = 0, the band data is not transmitted to the n-th image processing unit 35b _n , that is, the image data is divided into two pieces of minimum band data. etc. If it is, the number of the divided band data is sometimes band data is not transmitted to the image processing unit 35b _n of the third image processing unit 35b _3, second n.).

  By the way, in the image forming apparatus 1 of this example, the band data is transmitted to the image processing unit in this way. Therefore, when the data of the input image is divided into band data, as shown in FIG. 6, the first band data to the third band data in which the screen pattern is associated with the input image independently for each band data. It is conceivable to generate band data. In addition, when dividing the data of the input image per page into band data, it is not limited to dividing into the three band data shown in FIG. 6, and it is not limited to two or more pieces of band data. Can be divided. Further, the band data shown in FIG. 6 has four lines.

However, generated the band data as shown in FIG. 6, the image processing controller 35a _n of the first image processing controller 35a ₁ through n-th are independently driven, an input pixel and screen pattern threshold It is conceivable that the association is reset at the band boundary between the first band data and the second band data, for example. As described above, if the association between the input pixel and the threshold value of the screen pattern is reset at the band boundary, banding may occur and the print image may be disturbed. If the screen pattern can be created in accordance with the band size, banding can be avoided. However, since the screen design is restricted, it is difficult to improve the image quality.

  Therefore, in the image forming apparatus 1 of this example, when dividing the input image data into band data, as shown in FIG. 7, the association of the screen pattern with the input image is offset based on the coordinates for each band data. By assigning screens, first band data to third band data are generated. In this case, in the band data shown in FIG. 7, the first band data has screen pattern coordinates (threshold values) “15”, “55”, “35”, “40” associated with the first pixel of the line. It is. In the second band data, the coordinates (threshold values) of the screen pattern associated with the first pixel of the line are “125”, “73”, “35”, and “150”. Further, in the third band data, the coordinates (threshold values) of the screen pattern associated with the first pixel of the line are “82”, “22”, “70”, and “34”.

  That is, the second band data is offset from the first band data by the offset value 1 in the first direction, which is the main scanning direction, and by the offset value 1 in the second direction, which is the sub-scanning direction. Thus, the coordinates of the first pixel of the second band data are determined (first direction offset value = 1 / second direction offset value = 1). Therefore, the offset coordinates are designated for the image processing controller that screen-processes the second band data.

  The third band data is offset from the first band data by an offset value 2 in the first direction, which is the main scanning direction, and by an offset value 2 in the second direction, which is the sub-scanning direction. Thus, the coordinates of the first pixel of the third band data are determined (first direction offset value = 2 / second direction offset value = 2). Accordingly, the offset coordinates are designated for the image processing controller that screen-processes the third band data. The third band data is offset from the second band data by the offset value 1 in the first direction, and is offset by the offset value 1 in the second direction which is the sub-scanning direction.

  Further, the fourth band data is not offset with respect to the first band data, and the coordinates of the first pixel of the third band data are determined (first direction offset value = 0 / second direction offset). Value = 0). Therefore, the same coordinates as the coordinates of the first band data are designated for the image processing controller that screen-processes the fourth band data. The fourth band data is offset from the third band data by the offset value 1 in the first direction, and is offset by the offset value 1 in the second direction which is the sub-scanning direction.

In this way, by performing the screen processing by offsetting the band data, even if the image processing controller 35a _n of the first image processing controller 35a ₁ through n-th are driven independently, the input pixel and the threshold screen pattern Is not reset at the band boundary. Therefore, banding at the band boundary can be avoided without restricting the screen design.

Next, a description will be given of a flow in which the leading coordinates of the band data in which the coordinates of the screen pattern are determined for each band data and each line as described above are offset for each band data and transferred to the image processing controller. FIG. 8 is a diagram showing an example of this flow.
As shown in FIG. 8, in the flow of this example, image data is first divided to generate band data, and then offset coordinates are set for the generated band data.

That is, in step S1, the coordinates of the screen pattern are associated (coordinate setting step), and the input image is divided by the band data generation unit 33a to generate band data (image data division step). In that case, the coordinate setting step and the image data dividing step can be performed simultaneously, or the coordinate setting step can be performed first, and then the image data dividing step can be performed. Next, in order to offset the coordinates of the screen pattern at the first pixel of the generated band data, the offset coordinates are calculated in the screen offset calculation unit 33b. That is, in step S2, a first direction offset value is calculated to offset the coordinates of the first pixel of the band data in the first direction (main scanning direction). In step S3, a second direction offset value is calculated in order to offset the coordinates of the first pixel of the band data in the second direction (sub-scanning direction).

As a calculation method of the offset coordinates of the screen pattern in the band data, a method of determining the offset coordinates of the screen pattern for each band and a method of determining the offset coordinates of the screen pattern for each line of the band data can be considered.
FIG. 9 shows the flow of the method for determining the offset coordinates of the screen pattern for each band, (a) shows the flow of calculation of the first direction offset, and (b) shows the calculation of the second direction offset. It is a figure which shows a flow.

The following flow will be described based on the LUT and band data shown in FIG. The LUT width (LutWidth) is 4, the LUT height (LutHeigh) is 3, and the LUT shift amount (LutShift) is 1. LutShift is 1 in the first stage LUT and the second stage LUT shown in FIG. 7 with respect to the reference coordinate where the threshold value of the first pixel of the first stage LUT is “15”. The threshold value of the first pixel of the first LUT is “40” (indicated by circles), and the shift amount of the second-stage LUT is “1” with respect to the first-stage LUT .

As shown in FIG. 9A, in the calculation of the first direction (main scanning direction) offset, the absolute line number (LineNo) of the first line of the band data is acquired in step S11. The absolute line number (LineNo) of the first line of the band data is the number of stages of the first pixel of the LUT line in the band data. The number of stages is set so that the head of the first line of the first LUT starts from 0. In the example of the LUT shown in FIG. 7, the absolute line number of the first line of the second band data is 4. More specifically, the absolute line number of the first line of the first band data (the line indicated by the first threshold being “15”) is 0, and the next line (the first line of the first band data) The absolute line number of the line whose threshold is “55” is 1. Therefore, the absolute line number of the first line of the second band data (the line whose first threshold is indicated by “125”) is 4.

Next, in step S12, the lookup table number (LutNo) to which the first line of the band data belongs is calculated. This LutNo is given by LineNo / LutHeight (LutNo = LineNo / LutHeight). Therefore, for example, since the first line's LutNo of the second band data is 4/3, it is determined as “1”. Next, in step S13, the total table shift amount (TotalShift) at the head line of the band data is calculated. This TotalShift is given by LutNo × Lutshift (TotalShift = LutNo × Lutshift). Therefore, for example, since the No. of the first line of the second band data is “1” and the Lutshift is “1”, TotalShift at the first line of the second band data is determined as “1”. The Next, in step S14, an offset (OffsetMain) in the first direction (main scanning direction) of the first pixel of the band data is acquired. This OffsetMain is given by TotalShift% LutWidth (% is a remainder) (OffsetMain = TotalShift% LutWidth). Therefore, for example, OffsetMain in the first direction of the first pixel of the second band data is determined to be 1 (1% 4). Thus, the first directional offset is calculated.

As shown in FIG. 9B, next, in the calculation of the second direction (sub-scanning direction) offset, the absolute line number (LineNo) of the first line of the band data is acquired in step S21. Since this is the same as the case of the calculation of the first direction offset described above, the absolute line number of the first line of the second band data is 4. Next, in step S22, the offset (OffsetSub) in the second direction of the first pixel of the band data is acquired. This OffsetSub is given by LineNo% LutHeight (% is remainder) (OffsetSub = LineNo% LutHeight:% is remainder)
. Therefore, for example, OffsetSub in the second direction of the first pixel of the second band data is 1 (
4% 3). Thus, a second directional offset is calculated.

FIG. 10 shows a flow of a method for determining an offset coordinate of a screen pattern for each line of band data, (a) is a diagram showing a flow of calculation of a first direction offset, and (b) is a second direction offset. It is a figure which shows the flow of calculation of.
Determining the offset coordinates of the screen pattern for each line is the same as obtaining the offset coordinates for each band data as described above for the band data having one line. Therefore, the flow for determining the offset coordinates of the screen pattern for each line is substantially the same as the flow for obtaining the offset coordinates for each band data described above.

  That is, as shown in FIG. 10A, in the calculation of the first direction (main scanning direction) offset, the absolute line number (LineNo) of the corresponding line is acquired in step S31. This LineNo is the same as in the case of obtaining coordinates for each band data described above, and is 4.

Next, in step S32, the LUT number (LutNo) to which the corresponding line belongs is calculated. Since the LutNo of this corresponding line is 4/3 as described above, it is determined as “1”. Next, in step S33, the table total shift amount (TotalShift) of the corresponding line is calculated. TotalShift on this line is determined to be “1” as described above. Next, in step S34, an offset (OffsetMain) in the first direction (main scanning direction) of the first pixel of the corresponding line is acquired. OffsetMain of the first pixel of the corresponding line is determined to be 1 (1% 4) as described above. Thus, the first directional offset is calculated.

  As shown in FIG. 10B, in the calculation of the second direction (sub-scanning direction) offset, the absolute line number (LineNo) of the corresponding line is acquired in step S41. Since this is the same as the calculation of the first direction offset described above, the absolute line number of the corresponding line is 4. Next, in step S42, the offset (OffsetSub) in the second direction of the first pixel of the corresponding line is acquired. OffsetSub in the second direction of the first pixel of the corresponding line is determined to be 1 (4% 3). Thus, a second directional offset is calculated.

  The flow returns to the flow of offsetting every band data shown in FIG. 8 and transferring it to the image processing controller. In step S4, offset coordinates are set based on the offset value in the first direction and the offset value in the second direction calculated by the screen offset setting unit 33c (offset coordinate setting step). Next, in step S5, the band data together with the set offset coordinates is transferred to an image processing controller that screen-processes the band data. Thereby, in the image processing controller to which the band data has been transferred, the screen processing is performed on the band data based on the offset coordinates (first screen processing step and second screen processing step). Next, in step S6, it is determined whether or not the transfer of all band data from the main controller 33 to the image processing controller 35 has been completed. If it is determined that the transfer of all band data has not been completed, the process returns to step S1, and the processes of steps S1 to S6 are repeated. If it is determined in step S6 that the transfer of all band data has been completed, the transfer of the offset band data to the image processing controller 35 is completed.

4, the band data transferred to the first image processing section 35b ₁ are generated video data (Video Data) of the toner colors in the first image processing section 35b _1. And
The video data is screen-processed by the first screen processing unit 35d ₁ and
The screen data subjected to the screen processing is stored in the first screen data storage unit 35e ₁ . Similarly, the band data transferred to the image processing unit 35b _n of the n, the first n
The image processing unit 35b _n generates video data for each toner color. Then, the video data with the screen processing by the screen processing unit 35d _n of the n, the screened screen data is stored in the screen data storage section 35e _n of the n.

Thus, in the image forming apparatus 1 of this embodiment, the image processing controller 35 to the n (n ≧ 2) pieces first image processing section to the image processing unit 35b ₁ of the first n, ......, 35b _n is distribution Established. Since n image processing units are arranged, the image data to be printed is divided into a number equal to or greater than the number of image processing units, and these divided image data are distributed in parallel in each image processing unit. Image processing is performed.

  The divided image data used in the image forming apparatus 1 of this example is image data in an interleave format. For example, if the image data is YMCK image data of yellow (Y), magenta (M), cyan (C), and black (K) as shown in FIG. This is image data in which YMCK image data is color-expanded into four YMCK toner colors for each pixel. The divided image data is composed of several pixels of data per line. Furthermore, one page of image data is divided into several lines in the second direction (sub-scanning direction) and configured as band data, or several pages of image data are divided into one page as page data. Composed. Therefore, the divided image data is not data in a format divided for each color of yellow (Y), magenta (M), cyan (C), and black (K).

As shown in FIG. 3, the head controller 36 includes a first head side communication module 36a ₁ , a second head side communication module 36a ₂ ,..., And an nth head side communication module c36a. The head controller 36 includes a head control module 36b and a page memory 36c.

The first image processing side communication module 35c ₁ and the first head side communication module 36a ₁ can communicate bidirectionally. Then, a page request signal Preq indicating the head of image data of one page and the first band data of the image data are sent from the first head side communication module 36a ₁ to the first image processing side communication module 35c _1. A line request signal Lreq for requesting video data for one line among the constituent lines is transmitted.

Further, the first image processing side communication module 35c ₁ is a first head side communication module 36.
Upon receiving the page request signal Preq and line request signals Lreq from a _1, the first
The corresponding first band data is output from the screen data storage unit 35e ₁ to the first head side communication module 36a ₁ . That is, the first image processing communication module c _1, after receiving a page request signal Preq from the first head-side communication module 36a _1, receives a line request signal Lreq from the first head-side communication module 36a ₁ Each time, the video data is sequentially output to the _first head side communication module 36a ₁ by one line from the head portion of the first band data.

Similarly, the image processing side communication module 35c _n of the n and the head-side communication module 36a _n of the n is capable of communicating bidirectionally. Then, from the head-side communication module 36a _n of the n to the image processing side communication module 35c _n of the n, the page request signal Preq and band data of the n of the image data indicating the top of the image data of one page A line request signal Lreq for requesting video data for one line among the constituent lines is transmitted.

Further, the image processing side communication module 35c _n n-th head side communication module 36 of the n
Upon receiving the page request signal Preq and line request signals Lreq from a _n, a n
The n-th band data corresponding the screen data storing unit 35e _n toward the head-side communication module 36a _n of the n output. That is, the image processing side communication module c _n of the n, after receiving a page request signal Preq from the head-side communication module 36a _n of the n, receives a line request signal Lreq from the head-side communication module 36a _n of the n Each time, video data is sequentially output to the _nth head side communication module 36an by one line from the head portion of the nth band data.

In the head control module 36b, the interleaved divided image data transmitted to the _first head-side communication module 36a ₁ is stored in a first FIFO buffer in the head control module 36b (not shown). The divided image data stored in the first FIFO buffer is color-coded as shown in FIG. 11B, and sequentially, a yellow Y line buffer (not shown), a magenta M line buffer, a cyan color in the head control module 36b. The data are sorted and stored in the C line buffer and the black K line buffer. Similarly, the interleaved divided image data transmitted to the _nth head side communication module 36an is stored in a first FIFO buffer in the head control module 36b (not shown). The divided image data stored in the nth FIFO buffer is color-coded as shown in FIG. 11B, and sequentially, a yellow line buffer, a magenta line buffer, a cyan line buffer (not shown) in the head control module 36b, And sorted and stored in the black line buffer.

  When one line of yellow (Y) data is accumulated in the yellow line buffer, the line data is transferred to and stored in a yellow page data memory unit (not shown) of the page memory 36c. Similarly, when magenta (M) data, cyan (C) data, and black (K) data for one line are accumulated in the magenta line buffer, cyan line buffer, and black line buffer, these line data are stored. Are transferred to and stored in a magenta page data memory unit, a cyan page data memory unit, and a black page data memory unit (not shown) of the page memory 36c.

At this time, when the line data is transferred from the line buffer to the page data memory unit, the data necessary for the line head is rearranged into the line data of each color. The line data of each color after the rearrangement is transferred to the corresponding memory address of each page data memory unit and stored. Then, the head control module 36b takes out the line data of each color from the page memory 36c as required, and outputs it to the first line heads 12Y, 12M, 12C, 12K of the corresponding colors. As a result, the first to fourth line heads 12Y, 12M, 12C, 12
K writes the image of each color on the first to fourth photoreceptors 10Y, 10M, 10C, and 10K according to the supplied line data.

As described above, the image processing apparatus of this embodiment, an image processing method, and according to the image forming apparatus 1, beamed image processing controller 35, the image processing controller 35a _n of the first image processing controller 35a ₁ to the n is doing. Thus, possible parallel distributed processing of independently image processing by the image processing controller 35a _n of the first image processing controller 35a ₁ through n-th relative a divided image data obtained by dividing the input image data band data or line data It becomes. As a result, it is possible to execute image processing of high-resolution and large-capacity image data even more quickly.

Further, the image processing controller 35a _n of the first image processing controller 35a ₁ through the n, specifies the offset coordinates offset coordinates based on the threshold screen pattern at the boundary of the divided image data. This can prevent image banding. Therefore, it is possible to prevent banding due to screen processing of image data while effectively achieving higher speed image processing.

FIG. 12 is a diagram similar to FIG. 8 for explaining another example of the flow in which the leading coordinates of the band data are offset for each band data and transferred to the image processing controller.
In the flow of the example shown in FIG. 8, the image data is first divided to generate band data, and then the offset coordinates are set for the generated band data. On the other hand, as shown in FIG. 12, in the flow of this example, first, offset coordinates are set for image data, and then the image data set with the offset coordinates are divided to generate band data. ing.

  That is, as shown in FIG. 12, in step S51, a first direction offset value is calculated in order to offset the coordinates of the first pixel of the image data in the first direction (main scanning direction). In step S52, a second direction offset value is calculated to offset the coordinates of the first pixel of the image data in the second direction (sub-scanning direction). The calculation of the first direction offset value and the second direction offset value is substantially the same as the example shown in FIGS. 9A and 9B. In this case, image data is used instead of band data.

  In step S53, offset coordinates are set based on the offset value in the first direction and the offset value in the second direction. Next, the image data for which the offset coordinates are set in step S54 is divided to generate band data. In step S55, the band data is transferred to an image processing controller that processes the band data. As a result, the image processing controller to which the band data has been transferred performs screen processing on the band data based on the offset coordinates. Next, in step S56, it is determined whether or not the transfer of all band data from the main controller 33 to the image processing controller 35 has been completed. If it is determined that the transfer of all band data has not been completed, the process returns to step S51, and the processes of steps S51 to S56 are repeated. If it is determined in step S56 that the transfer of all band data has been completed, the transfer of the offset band data to the image processing controller 35 is completed.

Note that other configurations and other image operations in the image forming apparatus 1 of this example are substantially the same as those of the image forming apparatus described in Patent Document 1, and thus the description thereof is omitted.
The present invention is not limited to the above-described examples, and various design changes can be made within the scope of the matters described in the claims.

1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus according to the present invention. It is a fragmentary perspective view of the line head of the example shown in FIG. It is a block diagram of the engine control part and engine part of the example shown in FIG. 2 is a block diagram schematically showing a main controller and an image processing controller. FIG. It is a figure which shows an example of the image data by which the coordinate by the threshold value of a screen pattern was set. It is a figure which shows the band data which set the screen pattern independently while dividing the image data to which the coordinate shown in FIG. 5 was set. It is a figure which shows the band data which set the screen pattern by dividing | segmenting the image data in which the coordinate shown in FIG. 5 was set, and putting offset. It is a figure explaining an example of the flow which offsets the head coordinate of band data for every band data, and transfers to an image processing controller. It is a figure explaining an example of the flow of the method of determining the offset coordinate of a screen pattern for every band. It is a figure explaining an example of the flow of the method of determining the offset coordinate of a screen pattern for every line. It is a figure which shows an example of division | segmentation image data. It is explanatory drawing of the other example of the flow which offsets the head coordinate of band data for every band data, and transfers to an image processing controller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 3 ... Image forming unit, 7 ... Engine control part, 10Y ... 1st photoreceptor, 10M ... 2nd photoreceptor, 10C ... 3rd photoreceptor, 10K ... 4th photoreceptor, 12Y: first line head, 12M: second line head, 12C: third line head, 12K: fourth line head, 32: engine unit, 33: main controller, 33a: band data generation unit, 33b ... Screen offset calculation unit 33c Screen offset setting unit 33d Data transfer unit 34 Engine controller 35 Image controller 35a ₁ First image controller 35a ₂ Second image controller 35a _n ... image processing controller, 35b ₁ ... first image processing unit of n, 35b ₂ ... second image processing section, 35b _n ... n-th An image processing unit, 35c ₁ ... first image processing communication module, 35c ₂ ... second image processing side communication module, 35c ... image processing side communication module of the n, 3
5d ₁ ... first screen processing unit, 35d ₂ ... second screen processing unit, 35d _n ... n-th screen processing unit, 36 ... head controller, 35e ₁ ... first screen data storage unit, 35e ₂ ... first 2 of the screen data storage unit, the screen data storage section 35e _n ... n-th, 36 ... head controller, 36a ₁ ... first head-side communication module, 36a ₂ ... second head-side communication module, 36a _n ... n-th Head side communication module, 36b ... head control module, 36c ... page memory

Claims (8)

An image data dividing unit for dividing the image data to generate divided image data;
A coordinate setting unit for setting coordinates in the divided image data;
A first image processing unit that screen-processes the divided image data set with the coordinates;
A second image processing unit that screen-processes the divided image data set with the coordinates,
The image processing apparatus, wherein the coordinate setting unit sets the coordinates for screen processing by the first image processing unit or the coordinates for screen processing by the second image processing unit.   The image processing apparatus according to claim 1, further comprising a screen data storage unit that stores screen data for performing the screen processing.   The image processing apparatus according to claim 1, wherein the coordinate setting unit sets the coordinates to band data of the divided image data, or sets the coordinates to line data of the divided image data.   The coordinate setting unit sets the coordinates set in the divided image data screen-processed by the second image processing unit to the divided image data screen-processed by the first image processing unit. The image processing apparatus according to claim 1, wherein the image processing apparatus sets offset coordinates offset with respect to the coordinates. An image data dividing step of dividing the image data to generate divided image data;
A coordinate setting step for setting coordinates in the divided image data;
A first screen processing step in which the first image processing unit screen-processes the divided image data in which coordinates for screen processing in the first image processing unit are set in the coordinate setting step;
A second screen processing step in which the second image processing unit screen-processes the divided image data in which coordinates for screen processing in the second image processing unit are set in the coordinate setting step. Image processing method.   The coordinates set in the divided image data screened in the second screen processing step are offset with respect to the coordinates set in the divided image data screened in the first screen processing step. The image processing method according to claim 5, further comprising an offset coordinate setting step for setting the offset coordinates.   The image processing method according to claim 5, wherein the image data dividing step and the coordinate setting step are performed simultaneously. A latent image carrier on which a latent image is formed;
An exposure head for forming a latent image based on image data on the latent image carrier;
An image data dividing unit for dividing the image data to generate divided image data;
A coordinate setting unit for setting coordinates in the divided image data;
A first image processing unit that screen-processes the divided image data set with the coordinates;
A second image processing unit that screen-processes the divided image data set with the coordinates,
The coordinate setting unit sets coordinates set in the divided image data screen-processed by the second image processing unit to coordinates set in the divided image data screen-processed by the first image processing unit. Set to the offset coordinates offset with respect to
The image forming apparatus, wherein the second image processing unit screen-processes the divided image data based on the offset coordinates.

Images