Image forming apparatus

Abstract

To obtain an image forming apparatus in which a simulation condition is accurately adjusted.SOLUTION: A simulation processing unit 42 derives a light quantity of an exposure device and a developing bias of a developing device on the basis of a simulation condition. A calibration processing unit 43 adjusts the simulation condition on the basis of a density measurement value of a test pattern measured by a density sensor. The test pattern includes a solid first patch image, a half-tone second patch image, and a third patch image consisting of a plurality of isolated dots.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] An image forming apparatus includes an image simulation unit, which changes the development bias, one of the simulation conditions, based on a comparison result between a density measurement value of a patch image formed on an intermediate transfer drum and a density prediction value of the patch image by simulation, so that the two match (see, for example, Patent Document 1). In this image forming apparatus, the patch image is a solid image with a dot area ratio of 100% or a halftone image with a dot area ratio of 50%. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-163883 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned image forming apparatus, since little information can be obtained from the measurement results of the patch images, there is a possibility that the simulation conditions cannot be accurately adjusted.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide an image forming apparatus in which simulation conditions are accurately adjusted. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention includes a photoconductor drum, an exposure device for irradiating the photoconductor drum with light at a predetermined light amount to form an electrostatic latent image on the photoconductor drum, a development device for forming a toner image by attaching toner to the electrostatic latent image at a predetermined development bias, an intermediate transfer body to which the toner image is primarily transferred, a density sensor for measuring the density of a test pattern as the toner image on the intermediate transfer body, a simulation processing unit for deriving the light amount and the development bias based on simulation conditions, and a calibration processing unit for adjusting the simulation conditions based on the density measurement value of the test pattern by the density sensor. The test pattern includes a first patch image that is a solid color, a second patch image that is a halftone color, and a third patch image that is composed of a plurality of isolated dots. Effect of the Invention

[0007] According to the present invention, an image forming apparatus in which the simulation conditions are accurately adjusted can be obtained.

[0008] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view showing the mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a part of the electrical configuration of the image forming apparatus shown in FIG. [Diagram 3] FIG. 3 is a diagram showing an example of a test pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] Fig. 1 is a side view showing the internal mechanical configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in Fig. 1 is a device having an electrophotographic printing function, such as a printer, a facsimile machine, a copier, or a multifunction machine.

[0012] The image forming apparatus of this embodiment has a tandem type color developing device. This color developing device has photoconductor drums 1a to 1d, an exposure device 2, and developing devices 3a to 3d. The photoconductor drums 1a to 1d are photoconductors of four colors, cyan, magenta, yellow, and black, and electrostatic latent images are formed on the photoconductor drums 1a to 1d.

[0013] The exposure device 2 is a device that irradiates the photoconductor drums 1a-1d with light (here, laser light) at a predetermined light amount to form electrostatic latent images on the photoconductor drums 1a-1d. The exposure device 2 has a laser diode that is a light source of the laser light, and optical elements (lenses, mirrors, polygon mirrors, etc.) that guide the laser light to the photoconductor drums 1a-1d. The photoconductor drums 1a-1d may be made of amorphous silicon or organic photoconductors (OPC).

[0014] Developing devices 3a-3d develop the electrostatic latent images on photoconductor drums 1a-1d by applying toner from a toner cartridge to the electrostatic latent images on the photoconductor drums 1a-1d with a developing roller 4 using a predetermined developing bias, forming a toner image. Magenta development is performed by photoconductor drum 1a and developing device 3a, cyan development is performed by photoconductor drum 1b and developing device 3b, yellow development is performed by photoconductor drum 1c and developing device 3c, and black development is performed by photoconductor drum 1d and developing device 3d.

[0015] The intermediate transfer belt 5 is a circular intermediate transfer body that contacts the photoconductor drums 1a to 1d and carries the toner images on the photoconductor drums 1a to 1d after primary transfer. The intermediate transfer belt 5 is stretched around a drive roller 6a and a tension roller 6b, and rotates from the contact position with the photoconductor drum 1a to the contact position with the photoconductor drum 1d by the driving force of the drive roller 6a.

[0016] The secondary transfer roller 7 brings the conveyed print sheet (such as print paper) into contact with the intermediate transfer belt 5, and performs secondary transfer of the toner image on the intermediate transfer belt 5 onto the print sheet. The print sheet onto which the toner image has been secondarily transferred is conveyed to the fixing device 10. The fixing device 10 includes a heater, and uses the heater to fix the toner image onto the print sheet by a heating and pressurizing method.

[0017] The density sensor 8 is a reflective optical sensor that irradiates the intermediate transfer belt 5 with light, receives the reflected light (for example, specularly reflected light and diffusely reflected light), and outputs an electrical signal corresponding to the amount of reflected light received. After a calibration toner image (test pattern) is primarily transferred to the intermediate transfer belt 5, the density sensor 8 optically detects the density of the toner image on the intermediate transfer belt 5.

[0018] For example, during calibration, the density sensor 8 measures the density of a test pattern (each patch image) that passes through the arrangement position of the density sensor 8. Specifically, the density sensor 8 irradiates light onto a predetermined measurement area and receives the reflected light, thereby measuring the density of the test pattern that passes through the measurement area.

[0019] The primary transfer rollers 9a to 9d are disposed opposite the photoconductor drums 1a to 1d with the intermediate transfer belt 5 interposed therebetween, and perform primary transfer of the toner images on the photoconductor drums 1a to 1d from the photoconductor drums 1a to 1d to the intermediate transfer belt 5, respectively.

[0020] Fig. 2 is a block diagram showing a part of the electrical configuration of the image forming apparatus shown in Fig. 1. As shown in Fig. 2, the image forming apparatus shown in Fig. 1 further includes a controller 31. The controller 31 electrically controls each part in the image forming apparatus. The controller 31 includes an ASIC (Application Specific Integrated Circuit), a microcomputer, etc., and operates as various processing parts that perform either or both of hardware processing and software processing.

[0021] The controller 31 operates as a control unit 41, a simulation processing unit 42, and a calibration processing unit 43.

[0022] The control unit 41 performs predetermined image processing (such as gradation adjustment using a gamma curve and half-toning) on ​​a target image specified by a user, and controls the mechanical configuration shown in FIG. 1 (such as photosensitive drums 1a to 1d, exposure device 2, and developing devices 3a to 3d) to print the target image after image processing.

[0023] The simulation processing unit 42 derives the light amount of the exposure device 2 and the development biases of the development devices 3a to 3d described above based on the simulation conditions. Specifically, the simulation processing unit 42 simulates the development process to derive process setting values ​​such as the setting value of the exposure light amount of the exposure device 2 and the setting value of the development biases of the development devices 3a to 3d described above, and sets these process setting values ​​in the exposure device 2 and the development devices 3a to 3d.

[0024] The calibration processing unit 43 performs calibration at a predetermined timing, and in the calibration, forms a test pattern using the exposure device 2 and the developing devices 3a to 3d under predetermined conditions, measures the density of the test pattern using the density sensor 8 (optical sensor), and adjusts the above-mentioned simulation conditions based on the density measurement value of the test pattern measured by the density sensor 8.

[0025] Fig. 3 is a diagram showing an example of a test pattern. For example, as shown in Fig. 3, the test pattern 21 includes a first patch image 21s that is solid (100% dot area ratio) and second patch images 21-1 to 21-5 that are halftone (dot area ratio less than 100%). The second patch images 21-1 to 21-5 are multiple patch images corresponding to multiple gradations (multiple dot area ratios). The test pattern 21 includes patch images for at least eight gradations.

[0026] Here, at least one of the second patch images 21-1 to 21-5 is a patch image (third patch image) consisting of a plurality of isolated dots (isolated dots at the print resolution). The third patch image may be provided separately from the second patch images 21-1 to 21-5. The third patch image includes a plurality of isolated dots and does not include continuous dots.

[0027] It is also preferable that the third patch image has a dot area ratio of 30% or less, which makes it easier to measure the isolated dot size accurately.

[0028] Calibration processing unit 43 adjusts the simulation conditions (exposure light quantity characteristics, density characteristics, gamma characteristics, etc.) so that the density measurement value of first patch image 21s matches the maximum density obtained by simulation, and so that the halftone density measurement values ​​of second patch images 21-1 to 21-5 match the halftone densities obtained by simulation, identifies the isolated dot size (dot width, area of ​​one dot, etc.) of the third patch image, and adjusts the simulation conditions (area of ​​one dot corresponding to one exposure pulse, etc.) based on the isolated dot size.

[0029] Next, the operation of the image forming apparatus will be described.

[0030] The control unit 41 performs predetermined image processing on the target image in accordance with user operations, etc., and controls the photoconductor drums 1a-1d, the exposure device 2, the developing devices 3a-3d, etc. to print the target image after the image processing. At that time, the exposure device 2, the developing devices 3a-3d, etc. operate according to process setting values ​​specified by the simulation processing unit 42.

[0031] Then, when the time to perform calibration arrives, the calibration processing unit 43 adjusts the simulation conditions of the simulation processing unit 42 for each toner color (cyan, magenta, yellow, and black) in the manner described above.

[0032] At this time, test pattern 21 including a third patch image of an isolated dot is formed, and calibration processing unit 43 adjusts the simulation conditions based on the density measurement results of test pattern 21 as described above.

[0033] Thereafter, the exposure apparatus 2, the developing apparatuses 3a to 3d, etc. operate according to the process set values ​​derived under the adjusted simulation conditions.

[0034] As described above, according to the embodiment, the simulation processing unit 42 derives the amount of light of the exposure device 2 and the development biases of the developing devices 3a-3d based on the simulation conditions. The calibration processing unit 43 adjusts the simulation conditions based on the density measurement values ​​of the test pattern 21 obtained by the density sensor 8. Here, the test pattern 21 includes a solid first patch image 21s, halftone second patch images 21-1-21-5, and a third patch image made up of a plurality of isolated dots.

[0035] In this way, by measuring the density of one test pattern 21, the maximum density, gradation characteristics, and dot size are measured and the simulation conditions are adjusted based on these, so that the simulation conditions can be accurately adjusted and printing can be performed with appropriate process setting values.

[0036] It should be noted that various changes and modifications to the above-described embodiments 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. In other words, such changes and modifications are intended to be included within the scope of the claims. [Industrial Applicability]

[0037] The present invention is applicable to image forming apparatuses such as printers and multifunction peripherals. [Explanation of symbols]

[0038] 1a~1d Photoconductor drum 2. Exposure equipment 3a~3d developing device 5 Intermediate transfer belt (an example of an intermediate transfer body) 8 Concentration Sensor 42 Simulation processing section 43 Calibration processing section

Claims

1. A photoconductor drum; an exposure device that irradiates the photosensitive drum with light at a predetermined light amount to form an electrostatic latent image on the photosensitive drum; a developing device that applies a toner to the electrostatic latent image with a predetermined developing bias to form a toner image; an intermediate transfer body onto which the toner image is primarily transferred; a density sensor for measuring the density of a test pattern as the toner image on the intermediate transfer body; a simulation processing unit that derives the light amount and the developing bias based on a simulation condition; a calibration processing unit that adjusts the simulation conditions based on density measurements of the test pattern by the density sensor; the test pattern includes a first patch image of a solid color, a second patch image of a halftone color, and a third patch image consisting of a plurality of isolated dots; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the third patch image is one of the second patch images.

3. 3. The image forming apparatus according to claim 1, wherein the third patch image has an area ratio of 30% or less.

4. 3. The image forming apparatus according to claim 1, wherein the second patch image is a plurality of patch images corresponding to a plurality of gradations.

Images