JP6658016B2 - Image processing apparatus, image processing method, and image processing system - Google Patents

Description

  The present invention relates to an image processing device, an image processing method, and an image processing system.

  In an electrophotographic image forming apparatus, a predetermined gradation correction pattern (IBACC pattern) is generated on an image carrier such as an intermediate transfer belt, and the density is measured by an optical sensor, so that dither processing is performed. An image density correction method for calculating density correction data and correcting the formation of a dithering pattern to properly control the image density has already been known (for example, see Patent Document 1).

  In addition, when writing an electrostatic latent image on a photoconductor drum by an optical writing device, a TC exposure (Time Concentration Exposure) for exposing a fine image whose beam size is not negligible and intensively exposing it to a narrow area with strong light. Exposure method. Such TC exposure makes it possible to form a deep and sharp latent image and increase the latent image resolution.

  By the way, in order to perform such TC exposure, it is necessary to perform TC exposure processing on the dithering pattern. However, in the conventional image density correction method, the tone correction pattern simply represents the density level formed by the dithering pattern using a binary staggered pattern or a binary line pattern. No consideration is given to the characteristics of the latent image after performing the TC exposure process.

  Therefore, in the conventional image density correction method, a difference in density occurs between the toner image based on the gradation correction pattern and the toner image based on the dithering pattern of the actual image, and accurate density positive data for dither processing can be calculated. There is a problem that can not be.

  Further, the characteristics of the latent image after performing the TC exposure processing on the dither pattern are different between the case where the low-resolution dither pattern is used and the case where the high-resolution dither pattern is used. For this reason, the conventional image density correction method still has a problem in that accurate density positive data for dither processing cannot be calculated.

  The present invention has been made in view of the above circumstances, and has as its object to calculate highly accurate density correction data for dither processing.

In order to solve the above problem, one embodiment of the present invention provides a dithering processing unit that generates dithered image data obtained by performing dithering processing on image data, and each pixel in the generated dithered image data. A tone correction pattern generating unit that sets tone information of multi-valued data and generates a tone correction pattern simulating dithering processing according to each resolution from low resolution to high resolution according to each resolution , for each gradation correction pattern generated, performs pattern matching using a plurality of reference matrices the number of pixels is different, including the pixel of interest, according to the result of the pattern matching, the generated correct the gradation correction pattern And a tone correction pattern correction unit.

  According to the present invention, highly accurate density correction data for dither processing can be calculated.

FIG. 1 is a block diagram schematically illustrating a hardware configuration of an image processing system according to an embodiment of the present invention. FIG. 7 is a diagram for explaining a resolution conversion process (in the case of low resolution input) performed by a resolution conversion unit according to the embodiment of the present invention. FIG. 7 is a diagram for explaining a resolution conversion process (in the case of low resolution input) performed by a resolution conversion unit according to the embodiment of the present invention. FIG. 7 is a diagram for explaining a resolution conversion process (in the case of low resolution input) performed by a resolution conversion unit according to the embodiment of the present invention. FIG. 7 is a diagram for explaining a resolution conversion process (in the case of low resolution input) performed by a resolution conversion unit according to the embodiment of the present invention. FIG. 7 is a diagram for explaining a resolution conversion process (in the case of high resolution input) performed by a resolution conversion unit according to the embodiment of the present invention. FIG. 4 is a diagram for explaining a TC exposure process performed by an image processing unit according to the embodiment of the present invention. FIG. 5 is a diagram for describing diagonal pixel strong exposure processing performed by the image processing unit according to the embodiment of the present invention. FIG. 5 is a diagram for describing diagonal pixel strong exposure processing performed by the image processing unit according to the embodiment of the present invention. FIG. 5 is a diagram for explaining a left-right folding process performed by the image processing unit according to the embodiment of the present invention. FIG. 5 is a diagram for explaining a left-right folding process performed by the image processing unit according to the embodiment of the present invention. FIG. 4 is a diagram for explaining up / down folding processing performed by the image processing unit according to the embodiment of the present invention. FIG. 4 is a diagram for explaining up / down folding processing performed by the image processing unit according to the embodiment of the present invention. FIG. 9 is a diagram for explaining the effect of the TC exposure processing according to the embodiment of the present invention. FIG. 9 is a diagram for explaining the effect of the TC exposure processing according to the embodiment of the present invention. FIG. 9 is a diagram for explaining the effect of the TC exposure processing according to the embodiment of the present invention. FIG. 4 is a diagram for explaining an IBACC pattern generated by an image processing unit according to the embodiment of the present invention. FIG. 5 is a diagram for explaining TC exposure processing timing for an IBACC pattern in the image processing unit according to the embodiment of the present invention. FIG. 9 is a diagram for explaining a halftone IBACC pattern corresponding to the TC exposure processing according to the embodiment of the present invention. FIG. 9 is a diagram for explaining a halftone IBACC pattern corresponding to the TC exposure processing according to the embodiment of the present invention.

  First, a transfer flow of image data in the image processing system according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram schematically illustrating a hardware configuration of the image processing system according to the present embodiment.

  1, in the image processing system according to the present embodiment, the plotter control units 1, 2, and 3 convert the image data of the electrophotograph into a VCSEL (Black) 10, a VCSEL (Cyan) 11, a VCSEL (Magenta) 12, and a VCSEL (Magenta) 12. (Yellow) 13 is assumed. Hereinafter, the VCSEL (Black) 10, the VCSEL (Cyan) 11, the VCSEL (Magenta) 12, and the VCSEL (Yellow) 13 are referred to as VCSEL 10, VCSEL 11, VCSEL 12, and VCSEL 13, respectively.

  These plotter control units (serializer transmission) 1 and plotter control units (serializer reception) 2 and 3 store parameters for controlling various functional units, and transmit parameter control units 100 and 200 to each functional unit. , 300. Hereinafter, the plotter control unit (serializer transmission) 1 is referred to as a plotter control unit 1, and the plotter control units (serializer reception) 2, 3 are referred to as plotter control units 2, 3, respectively. Each of the parameter controllers 100, 200, and 300 can rewrite stored parameters by being connected to the external CPU 4.

  Normally, the parameters are stored using a flip-flop (FF) inside the parameter control unit, but a memory such as an SRAM (Static Random Access Memory) or a FIIFO (First In First Out) may be used. In addition, an external memory 5 connected to the CPU 4 is provided, and the storage area can be expanded or optimized for each model.

  When a printing operation is instructed from a PC (Personal Computer) 6, image data is transferred to a CTL (Controller) 7 via a printer driver on the PC 6. The CTL 7 converts the image data into bitmap data and transfers the image data to the image developing unit 8 as image data to be actually printed. The CTL 7 performs dithering processing on the image data to generate dithered image data. That is, in the present embodiment, the CTL 7 functions as a dithering processing unit. The image developing unit 8 exchanges signals with the video input unit 101 and transfers image data to the plotter control unit 1.

  An MFSYNC signal (pulse-type synchronization signal indicating the top of the page) and an MLSYNC signal (pulse-type synchronization signal indicating the top of the line) are output from the video input unit 101 to the image development unit 8. The image developing unit 8 transfers data to the plotter control unit 1 in accordance with the output timing of the MLSYNC signal. The plotter control unit 1 transmits and receives image data and signals of all four colors.

  After the print instruction from the PC 6, it is confirmed that the entire image forming apparatus is ready for printing, and a start trigger is activated in the plotter controllers 1, 2, and 3. As a start trigger, the CPU 4 supplies a start trigger signal (STTRIG) to the plotter controllers 2 and 3 using the parameter controllers 200 and 300 or an external signal. The start trigger signal generates a start trigger (STOUT) in the video input units 207 and 307 of the plotter control units 2 and 3, and serves as a starting point of the FSYNC_N signal and the LSYNC_N signal of the plotter control units 2 and 3.

  The FSYNC_N signal and the LSYNC_N signal of the plotter control units 2 and 3 are transmitted to the noise removal unit 102 of the plotter control unit 1 to remove noise due to an external environment such as an electrostatic pulse. The FSYNC_N signal is transferred to the video input unit 101 of the plotter control unit 1 as an FSYNC signal, and becomes a starting point of the MFSYNC signal.

  The LSYNC_N signal starts the thinning process starting from the FSYNC signal, generates an LCLR signal once for every four LSYNC_N signals, and becomes a line cycle signal of each functional unit including the video input unit 101. The video input unit 101 generates four MLSYNC signals starting from the LCLR signal, and transmits the generated MLSYNC signals to the image developing unit 8.

  The video input unit 101 of the plotter control unit 1 operates with the same operation clock as the image developing unit 8. The image development unit 8 writes the data transmitted for each MLSYNC signal line by line to the page memory 9, writes data for four lines corresponding to four MLSYNC signals, and then converts the data to the LCLR signal. Based on this, data read operations for four lines are simultaneously performed.

  After that, the video input unit 101 adds an internal pattern or performs image processing that requires a line memory such as jaggy correction using the line memory 107. Note that, in order to perform jaggy correction, a corresponding number of memories is required. Therefore, when performing jaggy correction, it is necessary to increase the number of line memories 107.

  The image processing unit 103 can generate a test pattern to be superimposed on the image transfer from the CTL 7, a forgery prevention pattern, and each adjustment pattern generated by the plotter control unit 1, which are different from the internal pattern of the video input unit 101. it can. Further, the image processing unit 103 performs image processing such as trimming processing. There are three types of adjustment patterns: a density adjustment pattern, a color misregistration correction pattern, and a blade turn-avoidance pattern (a photoconductor full exposure pattern).

  The skew correction unit 104 performs skew correction processing by storing the image-processed data in a plurality of skew correction line memories 105 and switching the line memory to be read according to the image position. Frequency conversion can also be performed by writing and reading the line memory 105 for skew correction.

  Further, the pixel counting unit 106 measures the data amount of the image-processed data. Here, the pixels of the test pattern to be superimposed on the image transfer, the forgery prevention pattern, and the respective adjustment patterns generated by the plotter control unit 1 alone can also be counted, so that pixel information closest to toner consumption can be obtained. it can. However, in the case of LD writing, since the toner consumption per pixel further changes by gradation conversion, pseudo gradation conversion can be performed on data input to the pixel counting unit 106.

  As described above, the plotter control unit 1 has a multi-data path in which four lines from the video input unit 101 to the write operation of the skew correction unit 104 are simultaneously performed. By employing a multi-data path, resolution conversion, area gradation correction, and double-density conversion of main scanning and sub-scanning can be easily performed. In addition, two-dimensional data can be simultaneously referred to several pixels at a time in main scanning and sub-scanning, thereby improving the accuracy of image processing such as edge processing and jaggy correction.

  In addition, since the image transfer rate is improved, there are various merits such as high-speed printing, transfer of a high-resolution image such as 2400 dpi / 4800 dpi, and superposition of a high-resolution pattern. When performing the double-density processing in the sub-scanning, the number of transmissions of the MLSYNC signal is reduced, and data written once is read a plurality of times. For example, when the density is doubled in the sub-scanning, two MLSYNC signals are transmitted to the image developing unit 8 in response to four LSYNC_N signals.

  When skew correction is performed, the line cycle after reading is set to 1 / N (N is a natural number) at the time of writing, and data is read N times from one line memory so that the data after skew correction is sub-scanned from the time of writing. It becomes high-density data whose resolution in the direction is N times (hereinafter, referred to as “double density processing”).

  The data subjected to the skew correction and the double density processing is transferred to the plotter control units 2 and 3. Since the transfer rate is very high, after the data is converted by the 8B10B conversion function unit 108, parallel / serial conversion is performed by the SER function unit 109, and the data is transmitted to the plotter control units 2 and 3 by LVDS.

  The plotter control units 2 and 3 receive the LVDS signal at the DES function units 201 and 301 and inversely convert the received data to 8B data. The data that has been inversely converted to 8B data is first subjected to data format conversion in accordance with the light emission resolution of the light source in the resolution converters 202 and 302 in the plotter controllers 2 and 3. In the present embodiment, a VCSEL (Vertical Cavity Surface Emitting LASER) is assumed as an optical system that forms an electrostatic latent image on an image carrier by emitting light. That is, in the present embodiment, the VCSELs 10, 11, 12, and 13 function as light emitting units. The light emission resolution of the VCSELs 10, 11, 12, and 13 is a very high resolution of 2400 dpi in main scanning and 4800 dpi in sub-scanning.

  If the input data is low-resolution multi-value data such as 4 bits of 600 dpi × 600 dpi, simply executing the double-density processing results in a coarse image. For this reason, the resolution conversion units 202 and 302 use a LUT (Look Up Table) to expand the pixels to a preset value. LUTs are available for 600 dpi input and 1200 dpi input. In the case of high-resolution input data such as 2400 dpi, LUT conversion is not performed, and simple double-density processing is performed.

  The resolution-converted data is subjected to image processing equivalent to that of the plotter control unit 1 by the image processing units 203 and 303. In particular, the image processing units 203 and 303 execute TC exposure (Time Concentration Exposure) processing as high-resolution image processing, and realize high image quality. That is, in the present embodiment, the image processing units 203 and 303 function as tone correction pattern correction units. The TC exposure processing will be described later with reference to FIGS.

  The image-processed data is subjected to γ-conversion processing by the tone correction units 204 and 304, and light emission data optimized for the VCSELs 10, 11, 12, and 13 is formed. That is, in the present embodiment, the tone correction units 204 and 304 function as light emission data generation units. The light emission data is transferred to the drive drivers 205, 206, 305, and 306 of the optical system, and an electrostatic latent image is formed on an image carrier such as a photosensitive drum.

  In the present embodiment, the plotter control units 1, 2, 3, the CPU 4, the external memory 5, the CTL 7, the image development unit 8, and the page memory 9 function as an image processing device.

  In the image processing system configured as described above, one of the points according to the present embodiment is to use a tone correction pattern (IBACC pattern) in an image forming apparatus that performs a TC exposure process on a dither pattern of an actual image. An image that reproduces the density of a pixel pattern using a dither pattern that expresses a monotonous density distribution, regardless of its shape, using a low-resolution, multi-valued tone correction pattern when performing image density correction An object of the present invention is to combine a density correction method and an image density correction method for reproducing the density of a specific pixel pattern such as a high-line-number line, character, or photograph using a high-resolution binary tone correction pattern. Therefore, the image processing system according to the present embodiment can form and detect latent images simulating a large number of dither patterns, and can calculate highly accurate density correction data for dither processing.

  Specifically, in the image processing system configured as described above, one of the points according to the present embodiment is that in an image forming apparatus that performs a TC exposure process on a dither pattern of a real image, a gradation correction pattern ( When performing image density correction using an IBACC pattern), processing is performed on a 2400 dpi 1 bit high resolution dither image or an image subjected to e-MUSIC processing (position shift correction processing such as skew correction in units of 2400 dpi). An object of the present invention is to form a gradation correction pattern that also reflects the effect of the corner pixel processing.

  That is, in the image processing system configured as described above, one of the points according to the present embodiment is an edge processing in which a plurality of TC exposure processes are performed regardless of the resolution and gradation of an input image. In addition to the gradation correction pattern reflecting the effect, a diagonal pixel to be processed for a 2400 dpi 1 bit high resolution dither image or an e-MUSIC processed image (position shift correction processing such as skew correction in units of 2400 dpi) An object of the present invention is to form a gradation correction pattern that reflects the effect of the processing. Therefore, the image processing system according to the present embodiment can form a toner image close to the actual image forming conditions, and can perform gradation correction.

  Next, a resolution conversion process (in the case of low resolution input) performed by the resolution conversion units 202 and 302 according to the present embodiment will be described with reference to FIGS. 2 to 5 are diagrams for explaining the resolution conversion processing (in the case of low resolution input) performed by the resolution conversion units 202 and 302 according to the present embodiment.

  2 to 5, the images on the left side of the arrows are data output from the DES function units 201 and 301 and input to the resolution conversion units 202 and 302, and the images on the right side of the arrow are the resolution conversion units. The format of data output from the image processing units 203 and 303 is shown. 2 to 5 show the case where the input data has a low resolution.

  The resolution converters 202 and 302 convert the resolution to 2400 dpi in the main scanning and 4800 dpi in the sub-scanning in accordance with the emission resolution of the VCSELs 10, 11, 12, and 13. The plotter control units 2 and 3 according to the present embodiment execute the TC exposure processing without emitting the data subjected to the resolution conversion processing to the VCSELs 10, 11, 12, and 13 as they are.

  In the TC exposure processing, as described later with reference to FIG. 5, image processing is performed at a resolution of 4800 dpi × 4800 dpi. Therefore, the resolution conversion units 202 and 302 convert the input data to a resolution of 4800 dpi × 4800 dpi.

  In the case of low-resolution multi-value data such as 4 bits of 600 dpi × 600 dpi, simply performing the double-density processing results in a coarse image. Therefore, the resolution conversion units 202 and 302 use the LUT to extend the pixels to a preset value. LUTs are available for 600 dpi input and 1200 dpi input. In the case of high-resolution input data such as 2400 dpi, LUT conversion is not performed, and simple double-density processing is performed.

  2 to 5, a description will be given of the resolution conversion in the case where 1200 dpi 2-bit data is input. The 2-bit data has four values of 0 to 3, and the pixels after resolution conversion are enlarged to 16 4 × 4 pixels, so that the halftone data of the inputs 1 and 2 has a plurality of conversion patterns.

  That is, input 0 is converted to all white pixels, and input 3 is converted to all black pixels. In the halftone, there are 14 conversion patterns in the main scanning direction in accordance with the combination of front-adjustment, no front-back-adjustment, back-adjustment, and sub-scanning in the top-adjustment, no vertical-adjustment, and bottom-adjustment. is there.

  In addition, unlike the shift pattern, it also has a pattern reproducing high resolution pixel components of 2400 dpi and 4800 dpi. By performing resolution conversion using this pattern, it becomes possible to form an image having a high resolution component such as a skew correction process at 2400 dpi, a high resolution oblique line, and a high resolution isolated pixel.

  Which of the conversion patterns performs the resolution conversion is determined with reference to the LUT. The LUT may be automatically determined according to the type of the input image, or may be set as a parameter from the CPU 4.

  Next, a resolution conversion process (in the case of high resolution input) performed by the resolution conversion units 202 and 302 according to the present embodiment will be described with reference to FIG. FIG. 6 is a diagram for explaining a resolution conversion process (in the case of high-resolution input) performed by the resolution conversion units 202 and 302 according to the present embodiment.

  6, the image on the left side of the arrow is data output from the DES function units 201 and 301 and input to the resolution conversion units 202 and 302, and the image on the right side of the arrow is the resolution conversion units 202 and 302. 3 shows the format of data output from the image processing units 203 and 303. FIG. 6 shows a case where the input data has a high resolution.

  FIG. 6 illustrates resolution conversion in the case where 2400 dpi 1-bit data and 4800 dpi 1-bit data are input. Since both of these data are binary and the input data has a high resolution, simple double density processing is performed as it is.

  As shown in FIG. 6, in the case of 1-bit data of 2400 dpi, data of two pixels in the main scanning direction and the sub-scanning direction are input to the subsequent image processing units 203 and 303 as data of two pixels. Also, as shown in FIG. 6, in the case of 1800 data of 4800 dpi, the data is passed through as it is and input to the image processing units 203 and 303 at the subsequent stage.

  Next, TC exposure processing performed by the image processing units 203 and 303 according to the present embodiment will be described with reference to FIG. FIG. 7 is a diagram for explaining the TC exposure processing performed by the image processing units 203 and 303 according to the present embodiment.

  TC exposure is a method of exposing with a strong light by concentrating on a narrow area. For a minute image whose beam size cannot be ignored, a deep and sharp latent image is formed while maintaining the image density. In this method, the image resolution is increased, the weak electrolysis area is reduced, and the image stability is improved. By TC exposure, it is possible to improve the stability of character thin lines and low CPP. Note that the TC exposure processing is performed within the period of the actual image (the image output from the CTL 7), and is otherwise skipped.

  The TC exposure process is performed by a pattern matching process using an image matrix. That is, the TC exposure process is performed at a resolution of 4800 dpi × 4800 dpi using an image matrix of 16 dots in the main scan and 16 dots in the sub-scan.

  Specifically, pattern matching (conversion of gradation data) is performed on the target pixel. Pattern matching is roughly divided into four patterns: strong exposure of isolated small dots, strong exposure of diagonal pixels, left / right folding processing, and up / down folding processing. In FIG. 7, the pixel of interest is a pixel at the 8th main scan and 8dot sub-scan.

  In the isolated small dot strong exposure, the reference matrix is 6 dots × 6 dots including the target pixel, and the exposed pixels within 4 × 4 dots surrounded by non-exposure are strongly exposed. The isolated small dot strong exposure processing will be described later with reference to FIG.

  In the diagonal pixel strong exposure processing, the reference matrix is 3 dots × 3 dots including the target pixel, and the diagonal pixels (upper left, lower left, upper right, lower right) of the target pixel are strongly exposed. The diagonal pixel strong exposure processing will be described later with reference to FIG.

  In the left / right folding process, the reference matrix is 16 dots × 1 dot including the pixel of interest, and left / right pattern matching is performed on 16 dots × 1 dot of the 8 dots in the main scanning. Data that matches the pattern matching is replaced by preset pattern data. The left / right turn processing will be described later with reference to FIGS.

  In the vertical folding process, the reference matrix is 1 dot × 16 dots including the pixel of interest, and upper and lower pattern matching is performed on 1 dot × 16 dots of the 8 dots in the sub-scanning. Data that matches the pattern matching is replaced by preset pattern data. The left / right turn processing will be described later with reference to FIGS.

  As described above, there are four types of TC exposure processing using four pattern matchings. Priority is set for each of them. Priority 1 is an isolated small dot strong exposure, priority 2 is a diagonal pixel strong exposure, priority 3 is a left / right folding process, The degree 4 is a vertical folding process. It should be noted that the TC exposure process is terminated when a plurality of processes are not performed repeatedly and one process with a high priority is performed according to the result of the pattern matching.

  When performing pattern matching by TC exposure, Tag information (character, line, character dither, line dither, line dither, photograph dither, etc.) added to the pixel information to select one from a plurality of methods of TC exposure. There is a method of detecting and referencing data for determining the type of pixel.

  Note that the Tag bit is transferred as an extended bit of normal pixel information. When tag bits are added to 2400 dpi × 2400 dpi 1-bit data, a configuration of data transfer of one pixel and two bits is used, and LSB is a pixel bit and MSB is a tag bit.

  When the data transfer rate is low and Tag bits cannot be transferred, there is also a method in which Tag bits are forcibly assigned by the plotter control units 2 and 3. In this case, since the Tag is fixed over the entire page, the accuracy of the TC exposure processing is reduced for an image in which each dither, character, and line are mixed, but the image data of the photo dither processing is arranged uniformly. In the case of a page that has been set, or a page in which character / line data has been uniformly arranged, the TC exposure process can be performed with high accuracy.

  In the TC exposure process, the Tag data of the target pixel and the value of the pixel are referred to determine whether the target pixel is a white character, a white line, a black character, a black line, or dither, and a different pattern matching process is performed according to each. carry out. In the TC exposure, in order to form an image to be exposed with strong light concentrated in a narrow range, in the case of black characters and black lines, a pattern matching process is performed such that a thick thin line becomes a thin dark line.

  In the case of white characters and white lines, a pattern matching process for thickening thin lines is performed. In the case of dither, the density data is replaced with pattern data so as to become preset density data. When the character / line processing is prioritized, or when there is no Tag information and it cannot be determined that the pattern is a dithering pattern, the processing is skipped without any particular operation. In the TC exposure, it is possible to individually set the intensity for each of black character / black line processing, white character / white line processing, and dither processing with reference to Tag information.

  Next, diagonal pixel strong exposure processing performed by the image processing units 203 and 303 according to the present embodiment will be described with reference to FIG. FIG. 8 is a diagram for explaining the diagonal pixel strong exposure processing performed by the image processing units 203 and 303 according to the present embodiment.

  In the isolated small dot strong exposure, pattern matching is performed in a 6 × 6 matrix size. As shown in FIG. 8, when the pattern matching of 4 × 4 dots surrounded by unlit pixels is matched, all the lit pixels inside the pattern are matched. This is a process for performing strong exposure.

  Pixels for which strong exposure has been set are exposed with more luminous energy than normal pixels, although the pixel size and lighting time do not change. As a result, in the isolated small dot strong exposure process, a deep and sharp latent image is formed, the latent image resolution is increased, and the weak electrolysis region is reduced, so that the image stability can be improved.

  As shown in FIG. 8, the isolated small dot strong exposure is performed on a pattern in units of 4800 dpi and 4 dots. Therefore, the isolated small dot strong exposure is processed if the resolution is 1200 dpi or more. In the case of an input image of 600 dpi, no processing is performed for the isolated small dot strong exposure. Therefore, the isolated small dot strong exposure is a process in which the effect of the TC exposure process differs for each resolution.

  Next, diagonal pixel strong exposure processing performed by the image processing units 203 and 303 according to the present embodiment will be described with reference to FIG. FIG. 9 is a diagram for explaining diagonal pixel strong exposure processing performed by the image processing units 203 and 303 according to the present embodiment.

  As shown in FIG. 9, in the diagonal pixel strong exposure processing, when lighting pixels are continuously arranged in a diagonal direction, the diagonal pixels (upper left, lower left, upper right, lower right) of the target pixel are strongly exposed. Processing.

  Pixels for which strong exposure has been set are exposed with more luminous energy than normal pixels, although the pixel size and lighting time do not change. As a result, in the diagonal pixel strong exposure processing, a deep and sharp latent image is formed for oblique lines, the latent image resolving power is increased, the weak electrolysis area is reduced, and the image stability can be improved.

  As shown in FIG. 9, the diagonal pixel strong exposure is performed on a pattern in units of 4800 dpi and 1 dot. Therefore, the diagonal pixel strong exposure is uniformly processed at a resolution of 4800 dpi, but at a resolution of 2400 dpi or less, the processing is performed only at a boundary where pixels are connected diagonally. Further, in the case of 1200 dpi and 600 dpi halftones, depending on the combination of resolution conversions, pixels are not connected diagonally. Therefore, the diagonal pixel strong exposure is a process in which the effect of the TC exposure process is significantly different for each resolution, in particular, for each of a low-resolution halftone image and a high-resolution binary image.

  Next, the left / right folding process performed by the image processing units 203 and 303 according to the present embodiment will be described with reference to FIGS. FIG. 10 and FIG. 11 are diagrams for explaining the left-right folding process performed by the image processing units 203 and 303 according to the present embodiment. Although FIGS. 10 and 11 show up to 6 dots, the same applies to 7 dots and thereafter.

  As shown in FIG. 10, the left / right folding process is a process of converting (turning) an end portion into a strongly exposed pixel when lighting pixels are continuously arranged in the main scanning direction. Pixels for which strong exposure has been set are exposed with more luminous energy than normal pixels, although the pixel size and lighting time do not change. In the left-right folding process, as shown in FIG. 11, such a process is repeatedly performed in the sub-scanning direction, whereby a deep and sharp latent image is formed on a straight line in the sub-scanning direction, and the latent image resolution is increased. The image stability is improved by reducing the weak electrolysis area.

  For example, as shown in FIG. 11, when the pattern coincides with the pattern of two columns of 4800 dpi, the right pixel is set to a strong exposure pixel and the left pixel is set to a non-lighting pixel, thereby converting to a pattern of one column of strong exposure.

  As described above, when an edge in the main scanning direction is detected as a result of the pattern matching, a deep pixel sharp image is formed by converting a target pixel into a strongly exposed pixel and converting a pixel adjacent to the target pixel into a non-lighted pixel. Is done.

  As shown in FIGS. 10 and 11, the left and right fold processing is performed on an edge of an image in the main scanning direction. Therefore, the left / right folding process is performed almost uniformly regardless of the resolution of the input image.

  Next, a vertical folding process performed by the image processing units 203 and 303 according to the present embodiment will be described with reference to FIGS. FIG. 12 and FIG. 13 are diagrams for explaining the vertical folding process performed by the image processing units 203 and 303 according to the present embodiment. Although FIGS. 12 and 13 show up to 6 dots, the same applies to 7 dots and thereafter.

  As shown in FIG. 12, the vertical folding process is a process of converting (folding) an end portion into a strongly exposed pixel when lighting pixels are continuously arranged in the sub-scanning direction. Pixels for which strong exposure has been set are exposed with more luminous energy than normal pixels, although the pixel size and lighting time do not change. In the vertical folding process, as shown in FIG. 13, such a process is repeatedly performed in the main scanning direction, whereby a deep and sharp latent image is formed on a straight line in the main scanning direction, and the latent image resolution is increased. The image stability is improved by reducing the weak electrolysis area.

  For example, as shown in FIG. 13, when the pattern coincides with a pattern of two rows of 4800 dpi, the lower pixel is set to a strong exposure pixel and the upper pixel is set to a non-lighting pixel, thereby converting to a pattern of one column of strong exposure.

  As described above, when an edge in the sub-scanning direction is detected as a result of the pattern matching, a deep pixel sharp latent image is formed by converting a target pixel into a strongly exposed pixel and converting a pixel adjacent to the target pixel into a non-lighted pixel. Is done.

  As shown in FIGS. 12 and 13, the vertical folding process is performed on an edge of an image in the sub-scanning direction. Therefore, the vertical folding process is performed almost uniformly regardless of the resolution of the input image.

  Next, the effect of the TC exposure processing according to the present embodiment will be described with reference to FIGS. 14 to 16 are diagrams for explaining the effect of the TC exposure processing according to the present embodiment.

  In FIG. 14, the effect of the TC exposure process will be described by taking, as an example, a pattern in which the main scanning direction is shifted forward and the sub-scanning direction is not shifted vertically, among the 14 conversion patterns in the input data of 1200 dpi 2 bits. . 15 and 16, the effect of the TC exposure process will be described by taking as an example a case where a halftone is formed with respect to input data of 2400 dpi 1 bit and 4800 dpi 1 bit.

  14 to 16, the density (the ratio of the lit pixels) will be described with reference to one pixel of 1200 dpi. In the case of 1200 dpi 2 bits, the lighting pixel ratio: 1/4 = the gradation data: 1/3. In the case of 2400 dpi 1 bit, among the four pixels, the lighting pixel ratio: 1/4 = 3, the pixel ratio is 0/1, and the pixel ratio is 1/1. In the case of 4800 dpi 1 bit, the lighting pixel ratio: 1/4 = 4 pixels, 3 pixels are 0/1, and 1 pixel is 1/1.

  When the density is 0 (light-off pixel), the TC exposure process is not performed irrespective of the resolution and gradation of the input image, and all the output images are light-off pixels.

  When the density is low (the ratio of the lit pixels is 1/4), it is divided into 1200 dpi 2 bits, 2400 dpi 1 bit, and 4800 dpi 1 bit.

  In the case of 1200 dpi 2 bits, since a 2 × 2 square is formed, the pixel changes to a 2 × 1 strongly exposed pixel. The processing in this case is a left / right wrapping processing, and since it is an isolated pixel, it is not affected by adjacent pixels.

  In the case of 2400 dpi 1 bit, a 2 × 2 square is also formed, so that it changes to a 2 × 1 strong exposure pixel. The processing in this case is a left / right wrapping processing, and since it is an isolated pixel, it is not affected by adjacent pixels.

  In the case of 4800 dpi 1 bit, the pattern matching does not match, and no strong exposure pixel is generated.

  Also in the case of the intermediate density (the ratio of the lighting pixels is 2/4), it is divided into 1200 dpi 2 bits, 2400 dpi 1 bit, and 4800 dpi 1 bit.

  In the case of 1200 dpi 2 bits, since a 4 × 2 rectangle is formed, the pixel changes to a 4 × 1 strongly exposed pixel. The processing in this case is a left / right wrapping processing, and since it is an isolated pixel, it is not affected by adjacent pixels.

  In the case of 2400 dpi 1 bit, a 2 × 2 square is also formed and connected diagonally. Therefore, in this case, diagonal pixel strong exposure and left / right folding processing are performed, and the image is changed to a mixed image of lighting pixels and strong exposure pixels.

  In the case of 4800 dpi 1 bit, an image in which 1 × 1 isolated pixels are consecutively formed, all of which match the pattern matching of the diagonal pixel strong exposure. Therefore, all pixels are strongly exposed pixels.

  In the case of high density (the ratio of the lit pixels is 4/4), regardless of the resolution and gradation of the input image, it is recognized as a horizontal 4-dot line, and a vertical fold process is performed to change to a strongly exposed pixel of a horizontal 2-dot line. . Note that this conversion varies depending on the adjacent pixels. The edges of the three input pixels that are in contact with the white pixels change to the high exposure pixels.

  As described above, when the TC exposure processing is performed on data having different resolutions and gradations, the effect of the TC exposure processing is significantly different between a low-resolution halftone image and a high-resolution halftone image. If it is desired to measure this effect using a tone correction pattern, the effect cannot be measured simply by simply expressing the density level formed by the dithering pattern using a binary staggered pattern or a binary line pattern. Therefore, when expressing a halftone using a dithering pattern, it is necessary to design the resolution and gradation of the image in consideration of matching with the TC exposure processing.

  Next, an IBACC pattern generated by the image processing unit 103 according to the present embodiment will be described with reference to FIG. FIG. 17 is a diagram illustrating an IBACC pattern generated by the image processing unit 103 according to the present embodiment. The image obtained by developing the electrostatic latent image formed on the photosensitive drum based on the IBACC pattern and transferring the developed IBACC pattern to the intermediate transfer belt is a gradation correction pattern image.

  The IBACC pattern is generated by the image processing unit 103 of the plotter control unit 1. That is, in the present embodiment, it functions as a gradation correction pattern generation unit. Since the IBACC pattern needs to reproduce the dithering process generated by the CTL 7, it is desirable that the IBACC pattern can be formed as large as possible.

  Further, in order to reproduce a pattern corresponding to the pattern matching of the TC exposure process, a size larger than the image matrix of the TC exposure (4800 dpi 16 dots × 16 dots) is required. In the present embodiment, a 32 dot × 32 dot matrix is formed, and mask processing is performed on the data input to the image processing unit 103 at a matrix cycle. When reproducing the pattern matching of the TC exposure, it is more preferable that the size is an integral multiple of the image matrix of the TC exposure.

  In the mask processing, mask data is individually set for each pixel in a matrix of 32 dots × 32 dots, that is, for all 1024 pixels (hereinafter, “mask setting”). The pixel for which the mask data is set ignores the content of the data input to the image processing unit 103 and outputs the mask data.

  The data for generating the IBACC pattern input to the image processing unit 103 uses a density adjustment pattern. The density adjustment pattern originally has a small-size mask processing function (8 dots × 8 dots pixels) for adjusting the light amount of the light source. For this reason, unlike the color matching adjustment pattern and the charge removal pattern, it is assumed that a square pattern of about 10 mm × 10 mm is formed, and thus has high affinity with the IBACC pattern.

  ON / OFF of the setting of the mask data is determined by the IBACC execution flag. When the IBACC execution flag is ON, all pixels in the matrix are set to mask data. The mask data has a 4-bit configuration, and a value can be set in a range of 0 to 15 for each pixel. This makes it possible to handle multi-valued images of 600 dpi × 600 dpi 4 bits and high resolution images of 1200 dpi × 1200 dpi 1/2 bits.

  Also, the 4-bit configuration can be set to 2 bits for image data and 2 bits for Tag data. Accordingly, it is possible to cope with a high-quality image such as 2400 dpi × 2400 dpi 1 bit + Tag 1 bit.

  Also, the gradation data can be set to 0 or 1, and a high-resolution binary mask pattern such as 2400 dpi 1 bit and 4800 dpi 1 bit can be generated. In this case, since the repetition period is constant (32 × 32), the specific pattern size in the pattern is reduced, and the shape that can be expressed by the pattern is reduced.

  The IBACC execution flag is configured to be set by the CPU 4 in each of the parameter control units 100, 200, and 300 of the plotter control units 1, 2, and 3. Note that the execution flag is not limited to this, and may be configured to be passed as a signal from the plotter control unit 1 to the plotter control units 2 and 3 or may be replaced with an FGATE signal of a density adjustment pattern.

  Next, TC exposure processing timing for the IBACC pattern in the image processing units 203 and 303 according to the present embodiment will be described with reference to FIG. FIG. 18 is a diagram for describing the timing of the TC exposure processing on the IBACC pattern in the image processing units 203 and 303 according to the present embodiment.

  In FIG. 18, it is assumed that the plotter control unit 1 forms an actual image, a color matching pattern, a density correction pattern, and an IBACC pattern in this order, and transmits them to the plotter control units 2 and 3. The plotter control units 2 and 3 form a real image FGATE and a non-image FGATE in accordance with the operation timing of the plotter control unit 1.

  The IBACC flag is used to determine whether the density correction pattern of the plotter control unit 1 is ON or OFF. The CPU 4 sets the IBACC flag in the parameter control units 200 and 300 of the plotter control units 2 and 3 in accordance with the density correction pattern forming timing.

  A period surrounded by a dotted line is a period during which the plotter control units 2 and 3 actually form an IBACC pattern. The IBACC flag needs to be set in a range wider than the dotted line. The TC exposure flag for executing the TC exposure processing is an OR of the actual image FGATE of the plotter control units 2 and 3 and the IBACC flag. This makes it possible to achieve both the TC exposure processing on the actual image and the TC exposure processing on the IBACC pattern.

  Next, a halftone IBACC pattern corresponding to the TC exposure processing according to the present embodiment will be described with reference to FIGS. FIGS. 19 and 20 are diagrams for explaining a halftone IBACC pattern corresponding to the TC exposure processing according to the present embodiment. 19 and 20, an IBACC pattern specialized for a low-resolution halftone image and a high-resolution halftone image will be described.

  In a normal IBACC pattern, gradation information of each pixel is set as multi-value data using mask data, and a dense image simulating a dither pattern is formed in a matrix. A plurality of patterns are formed on the intermediate transfer belt, and this is detected by an optical sensor. The density level is constant in each pattern, and by detecting this with an optical sensor, correction data under one condition is generated for each pattern.

  In order to obtain density correction data of a dithering pattern based on normal IBACC, it is only necessary that the density can be expressed with the resolution of the detection range (0.5 to 2 mm) of the optical sensor. Therefore, the density is expressed by a simple rule. . Further, in order to form an image in a short time, a pattern in which the density level formed by the dithering pattern is simply expressed using a binary staggered pattern or a binary line pattern is used.

  However, in order to form different types of dithering according to characters, lines, and photographs, a plurality of types of complex patterns are formed using halftones. Therefore, even when the macroscopic density levels are the same at the time of the pixel data, the latent images formed by the binary data and the halftone data after performing the resolution conversion and the TC exposure processing are significantly different.

  In order to calculate density correction data of the same quality as when a toner image is formed using a dithering pattern of an actual image using a toner image of an IBACC pattern that has been subjected to resolution conversion and TC exposure processing, a halftone is also used. It is necessary to form an IBACC pattern, perform resolution conversion and TC exposure processing to form a latent image, and detect a toner image with an optical sensor.

  However, as described with reference to FIGS. 14 to 16, when the normal resolution conversion is performed and the TC exposure processing is performed, the influence of the diagonal pixel strong exposure causes a low-resolution halftone image and a high-resolution halftone image. It differs greatly from the image.

  Therefore, in order to accurately measure the gradation correction data that accurately considers the effect of the diagonal pixel strong exposure from the IBACC pattern detection result, the low-resolution halftone image and the high-resolution halftone image must be separately measured. It is necessary to form an IBACC pattern using the EBACC pattern and perform the TC exposure processing under various conditions different in the influence of the TC exposure processing including the diagonal pixel strong exposure.

  First, a pattern is formed with an IBACC matrix size larger than the TC exposure image matrix (4800 dpi 16 dots × 16 dots), preferably an integral multiple of the size. The matrix size of the IBACC pattern is 32 dots × 32 dots (1200 dpi), which is sufficiently larger than the image matrix size of the TC exposure.

  Further, in order to observe the influence of the TC exposure processing without omission, the IBACC pattern covers a halftone other than 0. In this embodiment, since it is 1200 dpi 2 bits, an IBACC pattern of halftone data of 1/3 density is formed and detected.

  First, the case of 1200 dpi 2 bits will be described. When a 1200 dpi 2-bit, halftone IBACC pattern of isolated pixels is formed, the left and right fold processing is performed on all illuminated pixels under the influence of resolution conversion, thereby forming two strongly exposed pixels. By forming this toner image and detecting it with an optical sensor, it is possible to observe the effect of the TC exposure on the dither pattern when the image is output at 1200 dpi 2 bits and a halftone of an isolated pixel.

  Next, the case of 2400 dpi 1 bit will be described. When forming a halftone IBACC pattern of 2400 dpi 1 bit, isolated pixels, a strong exposure pixel subjected to diagonal pixel strong exposure, a strong exposure pixel subjected to left / right folding processing, and a normal lighting pixel are formed. By forming this toner image and detecting it with an optical sensor, it is possible to observe the effect of TC exposure on the dither pattern when outputting at 2400 dpi 1 bit, halftone of an isolated pixel.

  Next, the case of 4800 dpi 1 bit will be described. When forming a halftone IBACC pattern of 4800 dpi 1 bit, isolated pixels, all pixels are strongly exposed pixels subjected to diagonal pixel strong exposure. By forming this toner image and detecting it with an optical sensor, it is possible to observe the effect of the TC exposure on the dither pattern when outputting at 4800 dpi 1 bit, halftone of an isolated pixel.

  Further, the shape of the IBACC pattern forms the same number of types as the function of the dithering pattern. In the present embodiment, an example of a staggered shape is shown. Other types include “character dither”, “line dither”, and “photo dither”. "Character dither" and "line dither" form a line of one or two lines by changing the ratio of black pixels and the density of each pixel. This is because it is TC-exposed and converted to thinner, darker lines to form a sharp latent image.

  In order to perform the TC exposure on the “black character / black line”, it is necessary to make the TC exposure unit recognize the “black character / black line” based on the tag bit information and the density information. The “black character / black line” is recognized by Tag bit = 1 and pixel density> 0. The data of Tag bit = 1 is transferred from the plotter control unit 1 to 2 as a part of the pixel bit of the IBACC pattern or the data of the extension bit. Incidentally, in order to reduce the data transfer amount, there is also a method in which 1 is forcibly added at the time of reception by the plotter control units 2 and 3 without transferring Tag bits.

  In the case of “white characters / white lines”, one line or two lines of white outline are formed while changing the ratio of black pixels and the density of each pixel. This is to prevent the line from being crushed when it is subjected to the TC exposure and converted into a thicker white line.

  In order to perform the TC exposure on the “white character / white line”, it is necessary to make the TC exposed portion recognize the “white character / white line” based on the tag bit information and the density information. The “white character / white line” is recognized by Tag bit = 0 and pixel density = 0. The data of Tag bit = 1 is transferred from the plotter control unit 1 to the data 2, 3 as part of the pixel bit of the IBACC pattern or data of the extended bit. In order to reduce the amount of data transfer, there is also a method in which Tag bits are not transferred, and 1 is forcibly added when the plotter controllers 2 and 3 receive the data.

  In the "photo dither", a pattern such as a square, a rectangle, a rhombus, and an oblique line is formed while changing the ratio of black pixels and the density of each pixel. This is because when TC exposure is performed, a latent image is formed in which the edges are coordinated. In order to perform TC exposure on “photo dither”, it is necessary to make the TC exposure unit recognize “dither” by tag bit information and pattern matching.

  “Dither (edge)” is recognized by Tag bit = 0 and pattern matching. The data of Tag bit = 0 is transferred from the plotter control unit 1 to 2, 3 as a part of the pixel bit of the IBACC pattern or the data of the extended bit. In order to reduce the amount of data transfer, there is also a method in which Tag bits are not transferred, and 0 is forcibly added when the plotter controllers 2 and 3 receive the data.

  As described above, the image processing system according to the present embodiment can form an IBACC pattern specialized for a low-resolution halftone image and a high-resolution halftone image. The image processing system according to the present embodiment detects this with an optical sensor, generates tone correction data for dithering processing, feeds it back to CTL 7, calculates density correction data for dither processing in CTL 7, A dithering correction process is performed based on the calculated dither processing density correction data. Therefore, the image processing system according to the present embodiment can obtain high-precision gradation correction data of the same quality as the actual image. That is, in the present embodiment, the CTL 7 functions as a correction value calculation unit.

  As described above, the image processing system according to the present embodiment performs image density correction using a gradation correction pattern (IBACC pattern) in an image forming apparatus that performs a TC exposure process on a dither pattern of an actual image. When performing, using a low-resolution multi-value gradation correction pattern, regardless of its shape, an image density correction method that widely reproduces the density of a pixel pattern using a dither pattern expressing a monotonous density distribution, An object of the present invention is to combine an image density correction method for reproducing the density of a specific pixel pattern, such as a line with a high number of lines, characters, and photographs, using a high-resolution binary tone correction pattern. Therefore, the image processing system according to the present embodiment can form and detect latent images simulating a large number of dither patterns, and can calculate highly accurate density correction data for dither processing.

  Specifically, in the image processing system configured as described above, one of the points according to the present embodiment is that in an image forming apparatus that performs a TC exposure process on a dither pattern of a real image, a gradation correction pattern ( When performing image density correction using an IBACC pattern), processing is performed on a 2400 dpi 1 bit high resolution dither image or an image subjected to e-MUSIC processing (position shift correction processing such as skew correction in units of 2400 dpi). An object of the present invention is to form a gradation correction pattern that also reflects the effect of the corner pixel processing.

  That is, in the image processing system configured as described above, one of the points according to the present embodiment is an edge processing in which a plurality of TC exposure processes are performed regardless of the resolution and gradation of an input image. In addition to the gradation correction pattern reflecting the effect, a diagonal pixel to be processed for a 2400 dpi 1 bit high resolution dither image or an e-MUSIC processed image (position shift correction processing such as skew correction in units of 2400 dpi) An object of the present invention is to form a gradation correction pattern that reflects the effect of the processing. Therefore, the image processing system according to the present embodiment can form a toner image close to the actual image forming conditions, and can perform gradation correction.

1 Plotter control unit 2 Plotter control unit 3 Plotter control unit 4 CPU
5 External memory 6 PC
7 CTL
Reference Signs List 8 Image expansion unit 9 Page memory 100 Parameter control unit 101 Video input unit 102 Noise removal unit 103 Image processing unit 104 Skew correction unit 105 Line memory 106 Pixel count unit 107 Line memory 108 8B10B conversion unit 109 SER function unit 200 Parameter control unit 201 DES function unit 202 resolution conversion unit 203 image processing unit 204 gradation correction unit 205 drive driver 206 drive driver 200 parameter control unit 301 DES function unit 302 resolution conversion unit 303 image processing unit 304 gradation correction unit 305 drive driver 306 drive driver

JP 2015-18170 A

Claims (10)

A dithering processing unit that generates dither processing image data obtained by performing dithering processing on the image data,
The gradation information of each pixel in the generated dither processing image data is set as multi-value data, and a gradation correction pattern simulating dithering processing according to each resolution from low resolution to high resolution is set according to each resolution. and gradation correction pattern generating unit for generating Te,
For each gradation correction pattern generated, performs pattern matching using a plurality of reference matrices the number of pixels is different, including the pixel of interest, according to the result of the pattern matching, the generated correct the gradation correction pattern A tone correction pattern correction unit that performs
An image processing apparatus comprising: A light emission data generation unit that generates light emission data for controlling light emission of a light emission unit that forms an electrostatic latent image on an image carrier by emitting light, based on the corrected tone correction pattern,
Calculating a correction value for the dithering process based on a detection result of a gradation correction pattern image formed by developing the electrostatic latent image formed on the image carrier based on the generated light emission data; And a correction value calculation unit that performs
The image processing apparatus according to claim 1, wherein the dithering processing unit performs a dithering correction process for correcting the dithering process based on the calculated correction value. The tone correction pattern generation unit generates a first tone correction pattern simulating a dithering process according to a high resolution and a second tone correction pattern simulating a dithering process according to a low resolution. And
The correction value calculation unit calculates a first correction value that is a correction value of the dithering process based on a detection result of the gradation correction pattern image based on the generated first gradation correction pattern, and generates the correction value. Based on the detection result of the tone correction pattern image by the second tone correction pattern is calculated a second correction value that is a correction value of the dithering process,
The image processing apparatus according to claim 2, wherein the dithering processing unit performs the dithering correction process based on the calculated first correction value and the calculated second correction value. A resolution conversion unit that performs resolution conversion on the generated tone correction pattern,
The tone correction pattern correction unit performs the pattern matching on the resolution-converted tone correction pattern, and corrects the resolution-converted tone correction pattern according to the result of the pattern matching. The image processing apparatus according to claim 1, wherein:   The apparatus according to claim 1, wherein the tone correction pattern correction unit performs the pattern matching centering on a pixel of interest, and converts the pixel of interest into a strongly exposed pixel when detecting a preset pattern. 4. The image processing apparatus according to claim 1.   6. The gradation correction pattern correction unit according to claim 5, wherein as a result of the pattern matching, when a diagonal pixel is detected as the preset pattern, the target pixel is converted into a strongly exposed pixel. 7. Image processing device.   The tone correction pattern correction unit converts the target pixel into a strong exposure pixel when the pattern matching detects an isolated pixel group surrounded by a white pixel frame as the preset pattern. The image processing apparatus according to claim 5 or 6, wherein   The image processing apparatus according to claim 1, wherein the gradation correction pattern generation unit generates the gradation correction pattern by setting a mask for each pixel of the density adjustment pattern. . Generate dithered image data obtained by performing dithering processing on the image data,
The gradation information of each pixel in the generated dither processing image data is set as multi-value data, and a gradation correction pattern simulating dithering processing according to each resolution from low resolution to high resolution is set according to each resolution. It generates Te,
For each gradation correction pattern generated, performs pattern matching using a plurality of reference matrices the number of pixels is different, including the pixel of interest, according to the result of the pattern matching, the generated correct the gradation correction pattern An image processing method comprising: A dithering processing unit that generates dither processing image data obtained by performing dithering processing on the image data,
The gradation information of each pixel in the generated dither processing image data is set as multi-value data, and a gradation correction pattern simulating dithering processing according to each resolution from low resolution to high resolution is set according to each resolution. and gradation correction pattern generating unit for generating Te,
For each gradation correction pattern generated, performs pattern matching using a plurality of reference matrices the number of pixels is different, including the pixel of interest, according to the result of the pattern matching, the generated correct the gradation correction pattern An image processing system comprising: