JP6285734B2 - Image adjustment method and image forming apparatus using the method - Google Patents

Description

  The present invention relates to an image adjustment method for improving image quality defects and an image forming apparatus using the method.

  An electrophotographic image forming apparatus includes a charger that charges the surface of a photoreceptor, an exposure unit that exposes the surface of the photoreceptor to form an electrostatic latent image, and a developing bias applied to the surface of the photoreceptor. An engine unit including a developing unit that visualizes an electrostatic latent image into a toner image and a reading unit that reads an image from a document are formed, and an image is formed on a sheet based on image data.

  When an image is formed on a sheet, the image data is converted into a digital signal in CMYK format, and then subjected to various image processing and output to the engine unit. Various image processing includes halftone processing that faithfully reproduces gradation (changes in image brightness and color).

  In the halftone processing, image processing is performed on the image data using the correction value of the correction table for correcting the input density level of the image data. In order to reproduce the gradation more faithfully, it is necessary to set the correction value in the correction table with higher accuracy. Therefore, there is a technique that adjusts the correction value of the correction table using a patch pattern formed by a plurality of dithers (see, for example, Patent Document 1). In the correction value adjustment method of the correction table, a plurality of image patterns formed by a plurality of dithers are printed on a sheet, and the plurality of image patterns are read from the printed sheet by a reading unit. Then, the density characteristics for the input density level of each dither are calculated based on the measurement results of the density levels of the plurality of read image patterns, and the correction values in the correction table are adjusted so that the calculated density characteristics become the specified density characteristics. To do.

JP 2002-374415 A

  However, image quality defects caused by the engine unit cannot be improved only by performing halftone processing using the correction table described in Patent Document 1.

  An object of the present invention is to provide an image adjustment method and an image forming apparatus using the method, which can automatically improve image quality defects caused by an engine unit.

  The image adjustment method of the present invention includes a charger for charging the surface of the photoconductor, an exposure unit for forming an electrostatic latent image on the surface of the photoconductor, and a developer for developing the electrostatic latent image into a toner image. For the image forming apparatus including the engine unit, the control unit executes the first step and the second step. In the first step, the first image pattern is read from the sheet on which the first image pattern, which is a combination of one or more image patterns having a constant density, is printed by the image forming apparatus. The second step executes a second step of adjusting a parameter for setting the operation of the engine unit based on the first image pattern read in the first step.

  In this configuration, the image forming apparatus prints a first image pattern that is a combination of one or more image patterns having a constant density. The image forming apparatus reads the first image pattern from the sheet on which the first image pattern is printed by the reading unit, and adjusts parameters for setting the operation of the engine unit based on the read first image pattern. Parameters for setting the operation of the engine unit include, for example, a parameter for setting the charging amount of the charger, a parameter for setting the exposure amount of the exposure unit, a parameter for setting the exposure time of the exposure unit, or a developing bias value of the developing unit. One of the parameters to be set.

  In this configuration, when the second image pattern is read from the paper on which the second image pattern whose density is not constant is read by the image forming apparatus in the first step, the second step is the second image read in the first step. It is preferable to further adjust the correction value of the correction table for halftone processing based on the pattern.

  In this configuration, the image forming apparatus prints the first image pattern and the second image pattern whose density is not constant on the sheet. The image forming apparatus reads the first image pattern and the second image pattern from a sheet on which the first image pattern and the second image pattern are printed. The image forming apparatus adjusts a correction value of a correction table used for halftone processing based on the read second image pattern, and adjusts parameters for setting the operation of the engine unit based on the read first image pattern. As a result, the image forming apparatus can also adjust the parameters for setting the operation of the engine unit when adjusting the correction table used for halftone processing.

  In addition, when the first image pattern includes vertical and horizontal line drawings, the second step is a parameter for setting the operation of the engine unit according to the comparison result between the vertical and horizontal lines of the line drawing read in the first step. It is preferable to perform the adjustment.

  In this configuration, for example, if the vertical and horizontal line widths are too narrow, the exposure amount of the exposure unit or the developing bias of the developing device is increased. If the line width is different between the vertical line and the horizontal line, the exposure amount or developing bias of the exposure unit is increased or the exposure time of the exposure unit is increased for the narrower line width. Thereby, an image can be formed on a sheet with an appropriate line width.

  In addition, when the first image pattern includes a test image that surrounds the solid image with a halftone image, the second step depends on whether or not the test image read in the first step has an outline. It is preferable to adjust parameters for setting the operation of the engine unit.

  In this configuration, for example, when white spots exist, the developing bias of the developing device is increased. As a result, it is possible to reduce white spots that occur at the boundary between solid coating and halftone and white spots that occur at the edge of the halftone.

  Further, when the first image pattern includes a dot image, the second step adjusts a parameter for setting the operation of the engine unit according to whether or not a dot is present in the dot image read in the first step. It is preferable.

  In this configuration, for example, when dots are not printed, the exposure amount of the exposure unit or the developing bias of the developing device is increased, or the charging amount by the charger is decreased. Thereby, a dot image can be appropriately formed on a sheet.

  The image forming apparatus of the present invention includes a reading unit, a first storage unit, an engine unit, a second storage unit, and a control unit. The reading unit reads an image from a sheet. The first storage unit stores image data for printing a first image pattern that is a combination of one or more image patterns having a constant density. The engine unit includes a charger that charges the surface of the photosensitive member, an exposure unit that forms an electrostatic latent image on the surface of the photosensitive member, and a developing unit that visualizes the electrostatic latent image into a toner image. The second storage unit stores parameters for setting the operation of the engine unit. A control part controls an engine part and performs the 1st process and the 2nd process. In the first step, the first image pattern is read from the paper on which the first image pattern is printed by the engine unit. In the second step, a parameter for setting the operation of the engine unit is adjusted based on the first image pattern read by the reading unit.

  In this configuration, the image forming apparatus prints a first image pattern, which is a combination of one or more image patterns having a constant density, on a sheet with reference to the storage content of the first storage unit. The image forming apparatus reads the first image pattern from the sheet on which the first image pattern is printed, and adjusts parameters for setting the operation of the engine unit based on the first image pattern included in the read image. .

  In this configuration, when the first storage unit further stores a second image pattern with a non-constant density, and the second storage unit further stores a correction table used for halftone processing, the control unit performs the first step in the first step. It is preferable that the second image pattern is read from the sheet on which the two-image pattern is printed by the engine unit, and the correction value of the correction table is further adjusted based on the second image pattern read by the reading unit in the second step.

  In this configuration, the image forming apparatus prints the first image pattern and the second image pattern whose density is not constant on a sheet with reference to the storage content of the first storage unit. The image forming apparatus reads the first image pattern and the second image pattern from a sheet on which the first image pattern and the second image pattern are printed. The image forming apparatus adjusts parameters for setting the operation of the engine unit stored in the second storage unit based on the read first image pattern, and stores the parameter in the second storage unit based on the read second image pattern. Adjust the correction value in the correction table. As a result, the image forming apparatus can also adjust the parameters for setting the operation of the engine unit when adjusting the correction table used for halftone processing.

  According to the present invention, it is possible to improve image quality defects caused by the engine unit.

1 is a schematic view of an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating a functional configuration of a control unit included in the image forming apparatus. FIG. 3 is an example of an image pattern stored in the image forming apparatus. It is a flowchart which shows the calibration process by the control part.

  An image forming apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the image forming apparatus 100 includes a reading unit 90, an engine unit 110, and a paper feeding unit 80. Based on an instruction from the control unit 200, image data read from a document by the reading unit 90 or external Using the image data input from the apparatus, multi-color or single-color image forming processing is performed on the paper by an electrophotographic method.

  The reading unit 90 receives image data from a document that passes over the document table 93 by conveyance of the automatic document conveyance device 120 or a document that is manually placed on the document table 92 with an opening / closing operation of the automatic document conveyance device 120 by an operator. Read.

  The engine unit 110 includes an exposure unit 1, developing devices 2 </ b> A to 2 </ b> D, photosensitive drums 3 </ b> A to 3 </ b> D, charging devices 5 </ b> A to 5 </ b> D, an intermediate transfer unit 60, a secondary transfer unit 30, and a fixing unit 70. The chargers 5A to 5D uniformly charge the surfaces of the photosensitive drums 3A to 3D to a predetermined potential. The exposure unit 1 exposes the surfaces of the photosensitive drums 3A to 3D with laser light modulated with Bk, C, M, and Y image data to form electrostatic latent images. The developing units 2A to 2D supply Bk, C, M, and Y toners and apply a developing bias to convert the electrostatic latent images formed on the photosensitive drums 3A to 3D into Bk, C, M, and Y. The toner image is visualized.

  The intermediate transfer unit 60 includes an intermediate transfer belt 61 and primarily transfers the toner images formed on the peripheral surfaces of the photosensitive drums 3 </ b> A to 3 </ b> D onto the surface of the intermediate transfer belt 61. The secondary transfer unit 30 secondarily transfers the toner image on the surface of the intermediate transfer belt 61 onto the paper fed from the paper feed unit 80. The fixing unit 70 heats and presses the paper on which the toner image is transferred, and firmly fixes the toner image on the surface of the paper. The sheet on which the toner image is fixed is discharged to the paper discharge tray 91.

  As shown in FIG. 2, the control unit 200 includes a CPU 201, a ROM (corresponding to the second storage unit of the present invention) 202, and a RAM 203, and a storage unit (corresponding to the first storage unit of the present invention). 210, the operation unit 220, the reading unit 90, the image processing unit 130, and the engine unit 110.

  The CPU 201 reads the control program recorded in the ROM 202, and executes the control program using the RAM 203 as a working area. Further, the CPU 201 sets the correction value of the correction table stored in the ROM 202 in the image processing unit 130 at the start of the image forming process or the calibration process, and the various parameters stored in the ROM 202 are stored in the engine unit 110. Set. The calibration process is a process for adjusting the color output characteristics of the image forming apparatus.

  The correction table stores correction values used for halftone processing. The various parameters are parameters for setting the operation of the engine unit 110. Specifically, the parameters for setting the charge amounts of the chargers 5A to 5D, the parameters for setting the exposure amount of the exposure unit 1, and the exposure unit 1 exposure. This is either a parameter for setting the time or a parameter for setting the developing bias value of the developing devices 2A to 2D.

  The image processing unit 130 performs various image processing on the input image data. For example, the image processing unit 130 performs halftone processing on the image data using the correction value of the set correction table.

  The engine unit 110 operates based on various set parameters. Specifically, the chargers 5A to 5D charge the photosensitive drums 3A to 3D with the set charge amount of the parameter. The exposure unit 1 exposes the photosensitive drums 3A to 3D with the exposure amount of the set parameter during the exposure time of the set parameter. The developing devices 2A to 2D apply a developing bias with a developing bias value of a set parameter.

  The storage unit 210 stores the image data 300. As an example, as shown in FIG. 3, the image data 300 includes an image pattern (corresponding to the second image pattern of the present invention) 301 used for adjustment of the correction table, and an image pattern used for adjustment of various parameters (of the present invention). Corresponding to the first image pattern) 302.

  The image pattern 301 is an image pattern whose density is not constant. For example, an image pattern of a gray scale or a color scale whose density continuously changes at a constant rate.

  The image pattern 302 is a combination of one or more image patterns having a constant density. For example, an image pattern of a line drawing including vertical lines and horizontal lines, an image pattern of a test image surrounding a solid image with a halftone image, an image pattern of a dot image, or an image pattern of a combination thereof.

  The operation unit 220 receives operation inputs such as an instruction to start an image forming process and an instruction to start a calibration process. The image adjustment method of the present invention is included in the calibration process.

  When a signal indicating that the image forming process start instruction has been received is input from the operation unit 220, the control unit 200 sets the correction value of the correction table in the image processing unit 130 and sets various parameters in the engine unit 110. To do. The control unit 200 performs image processing on the image data read by the reading unit 90 or image data input from an external device by the image processing unit 130, and outputs the image data after the image processing to the engine unit 110 to be printed on paper. Form an image.

  As shown in FIG. 3, when a signal indicating that a calibration processing start instruction has been received is input from the operation unit 220 (S11), the control unit 200 displays the image data stored in the storage unit 210. The image forming process is performed on the sheet (S12). The control unit 200 sets correction values in the correction table in the image processing unit 130 and sets various parameters in the engine unit 110. The control unit 200 performs image processing on the image data by the image processing unit 130, outputs the image data after the image processing to the engine unit 110, and forms an image on a sheet. Image patterns 301 and 302 are printed on the paper.

  When the reading unit 90 reads the image patterns 301 and 302 from the sheet on which the image patterns 301 and 302 are printed (S13), the control unit 200 adjusts the correction value of the correction table based on the read image pattern 301 (S14). ).

  If there is a problem with the read image pattern 302 (S15: YES), the control unit 200 adjusts parameters for setting the operation of the engine unit 110 (S16).

  The control unit 200 increases the exposure amount of the exposure unit 1 when the line width of the image pattern of the line drawing including the vertical line and the horizontal line cannot be confirmed (when the line is erased or when the line width is thin), or The parameter is set so that at least one of the increase in the developing bias value of the developing devices 2A to 2D is realized.

  When the line width of the image pattern of the line drawing including the vertical line and the horizontal line is different between the vertical line and the horizontal line, the control unit 200 increases the number of dots of the thin line or the dot density in order to increase the exposure unit 1. The parameter is set so that at least one of the increase in the exposure amount, the increase in the exposure time, or the increase in the developing bias value of the developing devices 2A to 2D is realized.

  The control unit 200, when the image pattern of the test image includes white lines (when white lines appear at the boundary between the solid image and the halftone image, or the edge part of the front end or the rear end of the halftone occurs) The parameters are set so that the developing bias values of the developing devices 2A to 2D are increased.

  When the dot of the image pattern of the dot image cannot be confirmed (when no dot exists), the control unit 200 increases the exposure amount of the exposure unit 1, increases the development bias value of the developing devices 2A to 2D, or the photosensitive drum. The parameters are set so that at least one of the surface potential decreases of 3A to 3D is realized. In order to reduce the surface potentials of the photosensitive drums 3A to 3D, parameters may be set so that the charging amounts of the chargers 5A to 5D are reduced.

  In addition, when there is no defect in the read image pattern 302 (S15: N), the control unit 200 ends the process. Note that the process of S13 is included in the first step and the first step of the present invention. The processes of S14 and S16 are included in the second step and the second step of the present invention.

  As described above, since the image forming apparatus 100 can automatically adjust the parameters for setting the operation of the engine unit 110, the image quality defect caused by the engine unit 110 can be automatically improved. The image forming apparatus 100 can also adjust parameters for setting the operation of the engine unit 110 when adjusting a correction table used for halftone processing.

  The image forming apparatus 100 according to the second embodiment repeatedly executes the calibration process a predetermined number of times. In the process of FIG. S15, the control unit 200 repeatedly executes the processes of S12 to S16 until no trouble occurs in the read image pattern 302. Even when the processes of S12 to S16 are repeated a predetermined number of times, if the image pattern 302 read in the process of S15 is defective, the control unit 200 notifies an error and ends the process.

  Thereby, the image forming apparatus 100 can reliably improve the image quality defect caused by the engine unit 110 by adjusting the parameter for setting the operation of the engine unit 110 until the read image pattern 302 is not defective.

  Note that the control unit 200 may notify the image pattern 302 in which a failure occurs or the adjustment method of the engine unit 110 when notifying the error. For example, when the image pattern of the test image includes white areas, it may be notified that the position of the developing units 2A to 2D is adjusted and the distance between the photosensitive drums 3A to 3D and the developing units 2A to 2D is adjusted. Thereby, it is possible to inform the maintenance person of the image forming apparatus 100 of the adjustment method of the engine unit 110.

  The image forming apparatus 100 according to the third embodiment repeatedly executes the calibration process until a predetermined condition is reached. The storage unit 210 further stores an upper limit value and a lower limit value of each parameter. In the process of FIG. S15, the control unit 200 repeatedly executes the processes of S12 to S16 until no trouble occurs in the read image pattern 302. Even when the various parameters reach the upper limit value or the lower limit value, the control unit 200 notifies the error and ends the process when a defect occurs in the image pattern 302 read in the process of S15.

  Thereby, the image forming apparatus 100 can reliably improve the image quality defect caused by the engine unit 110 by adjusting the parameter for setting the operation of the engine unit 110 until the read image pattern 302 is not defective.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Exposure unit 2A-2D ... Developing device 3A-3D ... Photoconductor drum 5A ... Charger 90 ... Reading part 100 ... Image forming apparatus 110 ... Engine part 200 ... Control part 210 ... Storage part 300 ... Image data 301, 302 ... Image pattern

Claims (2)

Image formation comprising a charger for charging the surface of the photoreceptor, an exposure unit for forming an electrostatic latent image on the surface of the photoreceptor, and an engine unit that develops the electrostatic latent image into a toner image For the device, the controller
A first step of reading the first image pattern from a sheet on which a first image pattern which is a combination of one or more image patterns having a constant density is printed by the image forming apparatus;
Performing a second step of adjusting a parameter for setting the operation of the engine unit based on the first image pattern read in the first step ;
The first image pattern includes a dot image;
The second step is an image adjustment method in which a parameter for setting an operation of the engine unit is adjusted according to whether or not a dot exists in the dot image read in the first step . A reading unit for reading an image from paper;
A first storage unit that stores image data for printing a first image pattern that is a combination of one or more image patterns having a constant density;
An engine unit including a charger for charging the surface of the photosensitive member, an exposure unit for forming an electrostatic latent image on the surface of the photosensitive member, and a developing unit for developing the electrostatic latent image into a toner image;
A second storage unit for storing parameters for setting the operation of the engine unit;
A control unit for controlling the engine unit,
The control unit includes: a first step of reading the first image pattern from a sheet on which the first image pattern is printed by the engine unit; and the engine unit based on the first image pattern read by the reading unit. Performing a second step of adjusting parameters for setting the operation, and
The first image pattern includes a dot image;
In the image forming apparatus, the second step adjusts a parameter for setting an operation of the engine unit according to whether or not a dot is present in the dot image read in the first step .