JP2017044826A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of toner to be consumed in gradation expression in half toning.SOLUTION: A storage device 16 stores toner consumption characteristic data 31 indicating the toner consumption characteristics for the gray scale in each of a plurality of half toning methods. A half toning processing part 23 selects, from the plurality of half toning methods, a half toning method consuming the least amount of toner for the density of an object image on the basis of the toner consumption characteristic data 31, and performs half toning of the object image with the selected half toning method. A controller 24 prints a quantized image obtained through the half toning with a printer 13.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus.

  Some image forming apparatuses perform halfning using a dither matrix, and reduce the toner consumption by adjusting the dot arrangement pattern of halfning (see, for example, Patent Document 1).

JP 2012-20435 A

  In an electrophotographic image forming apparatus, when a dot is formed at a certain pixel position, the toner amount distribution of the toner adhering to the photosensitive drum during development is as shown in FIG. More toner is required than the amount of toner required.

  The present invention has been made in view of the above problems, and an object of the present invention is to obtain an image forming apparatus that reduces the amount of toner consumed in gradation expression by halftoning.

  The image forming apparatus according to the present invention includes a storage device that stores toner consumption characteristic data indicating characteristics of toner consumption with respect to density gradation for each of a plurality of halftoning methods, and the plurality of the plurality of halftoning methods based on the toner consumption characteristic data. A halftoning method that selects the halftoning method that consumes the least amount of toner with respect to the density of the target image, and a halftoning processing unit that performs halftoning of the target image using the selected halftoning method; A controller that prints the obtained quantized image with a printing apparatus.

  According to the present invention, the amount of toner consumed in gradation expression by halftoning is reduced.

  These and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram showing an example of the toner consumption characteristic data 31 in FIG. FIG. 4 is a diagram for explaining a change in unnecessary toner consumption due to a difference in the number of screen lines. FIG. 5 is a diagram for explaining the toner amount distribution in one dot to be printed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 is an apparatus having an electrophotographic printing function, such as a printer, a facsimile machine, a copying machine, or a multifunction machine.

  The image forming apparatus of this embodiment has a tandem color developing device. The color developing device includes photosensitive drums 1a to 1d, an exposure device 2, and developing units 3a to 3d. The photoconductor drums 1a to 1d are four-color photoconductors of cyan, magenta, yellow, and black. The photosensitive drums 1a to 1d are made of amorphous silicon, for example.

  The exposure devices 2a to 2d are devices that form electrostatic latent images by irradiating the photosensitive drums 1a to 1d with laser light while scanning. The laser beam is scanned in a direction (main scanning direction) perpendicular to the rotation direction (sub-scanning direction) of the photosensitive drums 1a to 1d. The exposure apparatuses 2a to 2d have a laser scanning unit including a laser diode that is a light source of laser light and an optical element (lens, mirror, polygon mirror, etc.) that guides the laser light to the photosensitive drums 1a to 1d.

  Further, around the photosensitive drums 1a to 1d, a charger such as a scorotron, a cleaning device, a static eliminator and the like are arranged. The cleaning device removes residual toner on the photosensitive drums 1a to 1d after the primary transfer, and the static eliminator neutralizes the photosensitive drums 1a to 1d after the primary transfer.

  The developing units 3a to 3d attach the toner cartridge filled with toners of four colors of cyan, magenta, yellow and black, and the toner conveyed from the toner hopper in the toner cartridge to the photosensitive drums 1a to 1d. A developing unit, and the toner is attached to the electrostatic latent images on the photosensitive drums 1a to 1d to form a toner image. The toner is transported from the toner hopper to the developing device by a toner transport unit that is operated by a driving device such as a motor (not shown).

  The photosensitive drum 1a, the exposure device 2a, and the developing unit 3a develop magenta, and the photosensitive drum 1b, the exposure device 2b, and the developing unit 3b develop cyan, the photosensitive drum 1c, and exposure. Yellow development is performed by the apparatus 2c and the development unit 3c, and black development is performed by the photosensitive drum 1d, the exposure apparatus 2d, and the development unit 3d.

  The intermediate transfer belt 4 is an annular image carrier (intermediate transfer member) that comes into contact with the photosensitive drums 1a to 1d and primarily transfers the toner images on the photosensitive drums 1a to 1d. The intermediate transfer belt 4 is stretched around the driving roller 5 and circulates in the direction from the contact position with the photosensitive drum 1d to the contact position with the photosensitive drum 1a by the driving force from the driving roller 5.

  The transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4 and secondarily transfers the toner image on the intermediate transfer belt 4 to the paper. The sheet on which the toner image has been transferred is conveyed to the fixing device 9 and the toner image is fixed on the sheet.

  The roller 7 has a cleaning brush, and the cleaning brush is brought into contact with the intermediate transfer belt 4 to remove the toner remaining on the intermediate transfer belt 4 after the transfer of the toner image onto the paper.

  FIG. 2 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. As shown in FIG. 2, the image forming apparatus includes a communication device 11, an image reading device 12, a printing device 13, an operation panel 14, an arithmetic processing device 15, and a storage device 16.

  The communication device 11 can be connected to a host device via a network or a peripheral device interface, and performs data communication using a predetermined communication protocol.

  The image reading device 12 optically reads a document image from a document and generates image data of the document image.

  The printing apparatus 13 is an internal device that prints a document image with a mechanical configuration as shown in FIG.

  The operation panel 14 is installed in the image forming casing and includes a display device such as a liquid crystal display that displays an operation screen to the user, and an input device such as a touch panel and a hard key that receives a user operation.

  The arithmetic processing unit 15 includes a computer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an application specific integrated circuit (ASIC), a storage device 16, a ROM, and the like. The various processing units are realized by loading a program from RAM to RAM and executing the program by the CPU. The storage device 16 is a rewritable nonvolatile storage device such as a flash memory, and stores toner consumption characteristic data 31 and pseudo contour condition data 32.

  In this embodiment, the processing unit 15 implements processing units such as an operating system (not shown), a print image acquisition unit 21, an image processing unit 22, a halftoning processing unit 23, and a controller 24.

  The print image acquisition unit 21 acquires image data of an image to be printed (hereinafter referred to as a print image). For example, the print image acquisition unit 21 controls the communication device 11 to receive a print request (such as PDL (Page Description Language) data) from a host device or the like, and generates image data of the print image from the received print request. For example, the print image acquisition unit 21 acquires image data generated by the image reading device 12 as image data of a print image.

  Further, the image processing unit 22 performs predetermined image processing (color conversion, gamma correction, etc.) on the acquired image data of the print image, and a print image having a predetermined number of bits for each toner color Generate data.

  In addition, the halftoning processing unit 23 is, for each toner color, a halftoning target image (for example, a gradation image such as a photograph or a figure in the print image after the image processing by the image processing unit 22, and a part of the print image or A halftoning process is executed on all of them to generate a quantized image.

  The halftoning processing unit 23 reads the toner consumption characteristic data 31 from the storage device 16, and based on the toner consumption characteristic data 31, from the plurality of halftoning methods, the most toner consumption with respect to the density of the target image in the print image. A halftoning method with a small amount is selected, and the target image is halftoned with the selected halftoning method.

  The toner consumption characteristic data 31 is data indicating the characteristic of toner consumption with respect to density gradation for each of a plurality of halftoning methods.

  FIG. 3 is a diagram showing an example of the toner consumption characteristic data 31 in FIG. In FIG. 3, the toner consumption with an output density of 100% is 100%. The output density is the density of the target image in the print image after gamma correction.

  FIG. 4 is a diagram for explaining a change in unnecessary toner consumption due to a difference in the number of screen lines. As shown in FIG. 4, the amount of unnecessary toner consumption, which is the amount exceeding the amount of toner required for the dot density specified by the data, tends to decrease as the number of screen lines increases. However, since the shape of the toner consumption distribution in the dots as shown in FIG. 4 changes depending on the specifications and states of the development system described above, the toner consumption when the number of screen lines is large may increase.

  Therefore, when gradation calibration is performed at a predetermined timing such as when the photosensitive drums 1a to 1d are replaced, the toner consumption amount is measured for each halftoning method, and toner consumption characteristic data is based on the measurement result. 31 is updated.

  In this embodiment, in the toner consumption characteristic data 31, the plurality of halftoning methods include a halftone method, a line method, and an error diffusion method.

  In the toner consumption characteristic data 31, the plurality of halftoning methods include one or both of a plurality of screen line number halftone methods and a plurality of screen line number halftone methods (here, both).

  In the toner consumption characteristic data 31 shown in FIG. 3, for example, an error diffusion method is selected for an output density of 10%, a 100-line halftone method is selected for an output density of 20%, and an output density of 70%. The 150 LPI line halftone dot method is selected. In the toner consumption characteristic data 31, the halftoning method for the output density closest to the density of the target image is selected.

  In this embodiment, when there are a plurality of halftoning methods in which the toner consumption amount is the smallest with respect to the density of the target image in the toner consumption characteristic data 31, the halftoning processing unit 23 has the least toner consumption amount. Among the halftoning methods, in the toner consumption characteristic data 31, the halftoning method having the smallest toner consumption amount with respect to the adjacent density is selected.

  For example, in the toner consumption characteristic data 31 shown in FIG. 3, the halftoning method that consumes the least amount of toner with respect to an output density of 50% is a 200-line halftone method and a 200 LPI (Line per Inch). There are two types of toner consumption of the line system. In the toner consumption characteristic data 31 shown in FIG. 3, since the toner consumption amount of the 200 LPI line system is the minimum with respect to the output density of 60%, as the halftoning system for the output density of 50%, the 200 LPI line system is used. The toner consumption amount is selected.

  In this embodiment, the halftoning processing unit 23 determines that the density of the target image and the selected halftoning method match the selected halftoning method when the density and the halftoning method indicated by the pseudo contour condition data 32 match. Selects another halftoning method, and halftones the target image using the selected other halftoning method.

  Here, the pseudo contour condition data 32 is simulated at the boundary between two regions when two regions each having an adjacent density in the density gradation of the toner consumption characteristic data 31 are halftoned by different halftoning methods. It is the data which shows the density | concentration and halftoning system in case an outline generate | occur | produces. The pseudo contour condition data 32 is specified in advance by experiments or the like.

  For example, in the toner consumption characteristic data 31, the halftoning method with an output density of 20% is a 150-line halftone method, the halftoning method with an output density of 30% is a 175-line halftone method, and the output density is 40%. When the halftoning method is a 150-line halftone method, a region having a density of 20% halftoned by the 150-line halftone method and a region having a density of 30% halftoned by the 175-line halftone method are used. When a pseudo contour is generated at the boundary or the boundary between the 40% density region halftoned by the 150-line halftone method and the 30% density region halftoned by the 175-line halftone method, the output density 30 A pair of halftone dots of% and 175 lines is registered in the pseudo contour condition data 32.

  In this case, when the 175-line halftone method is selected for the output density of 30% based on the toner consumption characteristic data 31, the half-toning method for the output density of 30% is the 150-line halftone method (that is, adjacent). The same method as the halftoning method for density).

  When the halftoning mode setting data is stored in the storage device 16 and the value of the halftoning mode setting data is prior to toner reduction, the halftoning method is changed based on the pseudo contour condition data 32 as described above. If the value of the halftoning mode setting data is prioritized in image quality, the halftoning method may be changed based on the pseudo contour condition data 32 as described above.

  The controller 24 is a processing unit that monitors and controls an internal device such as the printing apparatus 13. Here, the controller 24 prints the quantized image obtained by the halftoning of the halftoning processing unit 23 with the printing device 13.

  The controller 24 sets process conditions in the electrophotographic system to a drive source (not shown) that drives the above-described roller, a bias application circuit that applies a development bias and a primary transfer bias, and exposure apparatuses 2a to 2d. A processing circuit that sets and executes development, transfer, and fixing of a toner image, and paper feeding, printing, and paper ejection. The developing bias is applied between the photosensitive drums 1a to 1d and the developing units 3a to 3d, respectively, and the primary transfer bias is applied between the photosensitive drums 1a to 1d and the intermediate transfer belt 4, respectively.

  Next, the operation of the image forming apparatus will be described.

  The print image acquisition unit 21 acquires image data (for example, RGB data) of the print image, and the image processing unit 22 performs predetermined image processing on the image data.

  Then, as described above, the halftoning processing unit 23 selects the halftoning method to be applied to the print image, performs halftoning of the target image region in the print image by the selected halftoning method, and performs quantization. Generate an image.

  For the target image area in the print image, the controller 24 controls the printing apparatus 13 to print the generated quantized image, and causes the printing apparatus 13 to print the print image.

  As described above, according to the embodiment, the toner consumption characteristic data 31 indicating the characteristic of the toner consumption amount with respect to the density gradation for each of the plurality of halftoning methods is stored in the storage device 16, and the halftoning is performed. Based on the toner consumption characteristic data 31, the processing unit 23 selects a halftoning method that consumes the least amount of toner with respect to the density of the target image from a plurality of halftoning methods, and uses the selected halftoning method for the target image. Halftoning is performed. Then, the controller 24 prints the quantized image obtained by the halftoning with the printing device 13.

  As a result, unnecessary toner consumption is suppressed for each dot, so that the amount of toner consumed in gradation expression by halftoning is reduced.

  Various changes and modifications to the above-described embodiment will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. That is, such changes and modifications are intended to be included within the scope of the claims.

  The present invention is applicable to, for example, an electrophotographic image forming apparatus.

16 Storage device 23 Halftoning processing unit 24 Controller

Claims (5)

A storage device for storing toner consumption characteristic data indicating characteristics of toner consumption with respect to density gradation for each of a plurality of halftoning methods;
Based on the toner consumption characteristic data, a halftoning method that consumes the least amount of toner with respect to the density of the target image is selected from the plurality of halftoning methods, and halftoning of the target image is performed using the selected halftoning method. A halftoning processing unit to perform,
A controller that prints the quantized image obtained by the halftoning with a printing device;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the plurality of halftoning methods include a dot method, a line method, and an error diffusion method.   3. The image forming apparatus according to claim 1, wherein the plurality of halftoning methods include a halftone method with a plurality of screen lines or a halftone method with a plurality of screen lines.   When there are a plurality of halftoning methods that consume the least amount of toner with respect to the density of the target image, the halftoning processing unit includes the toner consumption characteristic data in the plurality of halftoning methods that consume the least amount of toner. The image forming apparatus according to claim 1, wherein a halftoning method that consumes the least amount of toner with respect to adjacent densities is selected. The storage device includes the density when the pseudo contour is generated at the boundary between the two areas when two areas having adjacent densities in the density gradation are halftoned by different halftoning methods. Stores pseudo contour condition data indicating the halftoning method,
The halftoning processing unit is different from the selected halftoning method when the density of the target image and the selected halftoning method match the density and the halftoning method indicated by the pseudo contour condition data. Selecting a halftoning method and halftoning the target image with the selected other halftoning method;
The image forming apparatus according to claim 1, wherein:

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