Device and method for processing image

Abstract

To solve such the problem that the type of noise generated in a recorded image is unknown.SOLUTION: A method for processing an image includes the steps of: acquiring spatial frequency property from the read data acquired by reading an inspection pattern; calculating a component ratio of amplitude of fundamental component waves and harmonic component waves and the number of harmonic components; and determining whether the type of noise on an image is noise due to unevenness, noise due to streaks, or noise due to both streaks and unevenness.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an image processing device and an image processing method. [Background technology]

[0002] In a recording device that records an image on a recording medium by applying a recording material while a recording means such as a recording head is scanning, if the recording medium is conveyed with low accuracy, the recording position between recording scans will be misaligned. This causes white or black streaks or uneven density in the recorded image, resulting in a problem of reduced quality of the recorded image.

[0003] Patent Document 1 discloses an image evaluation device for evaluating noise in a recorded image, which uses a frequency filter to limit the band of a spatial frequency calculated by a Fourier transform means and calculates an evaluation value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-113093 A Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned Patent Document 1 discloses that it is possible to determine at what frequency a noise component exists based on the amplitude of the spatial frequency, but does not disclose how to determine whether the type of noise is caused by unevenness or streaks. In response to such a problem, the present invention aims to provide an image processing device capable of determining the type of noise based on read data obtained by reading an inspection pattern image. [Means for solving the problem]

[0006] The present invention comprises an acquisition means for acquiring spatial frequency characteristics based on read data of an inspection pattern recorded on a recording medium, a calculation means for calculating a component ratio of a fundamental component wave and a harmonic component wave of the spatial frequency characteristics, and a determination means for determining a type of noise based on the component ratio calculated by the calculation means and the number of harmonic components indicating the number of the harmonic component waves, wherein the determination means determines the type of noise to be streaks if the component ratio is smaller than a first threshold value and the number of harmonic components is equal to or greater than a second threshold value, determines the type of noise to be unevenness if the component ratio is equal to or greater than the first threshold value and the number of harmonic components is smaller than the second threshold value, and determines the type of noise to be both streaks and unevenness if the component ratio is equal to or greater than the first threshold value and the number of harmonic components is equal to or greater than the second threshold value. Effect of the Invention

[0007] With the above-described configuration, it is possible to determine whether the type of noise occurring in a recorded image is noise caused by unevenness, noise caused by streaks, or noise caused by both streaks and unevenness. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of an image forming apparatus; [Diagram 2] FIG. 1 is a block diagram showing a control configuration of an image forming apparatus. [Diagram 3] Schematic diagram of the inspection pattern [Figure 4] A diagram showing an example of spatial frequency using FFT [Diagram 5] A diagram showing the spatial frequency of the results obtained by reading streaks and unevenness [Figure 6] Flowchart of determination process [Figure 7] Analysis of the spatial frequency of the read results into streaks, streaks + unevenness, and unevenness DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described with reference to the drawings. Note that the arrangement of components and the like described in this embodiment do not limit the scope of the present invention unless otherwise specified.

[0010] Fig. 1 is a perspective view showing the configuration of an image forming apparatus 100. Fig. 1(a) is an overall external view, and Fig. 1(b) is a view showing the internal structure with an upper cover 101, a fixing mechanism 102, etc. removed.

[0011] The image forming apparatus 100 of this embodiment is an inkjet recording apparatus that records an image on a recording medium by driving a plurality of recording elements provided in a recording head to eject ink as a recording material from nozzles. Here, an inkjet recording apparatus of a so-called serial type, in which an image is recorded while the recording head is scanning and the recording medium is transported between multiple scans, will be described as an example. Note that the present invention can also be applied to an inkjet recording apparatus that uses a so-called line head in which a plurality of recording elements that eject ink are arranged in a line in a direction intersecting the transport direction of the recording medium, and the form is not limited thereto.

[0012] An operation and display device 106 is provided on the top of the image forming apparatus 100. The operation and display device 106 is an operation panel that displays the remaining ink amount and possible types of recording media on a display. A user can select the type of recording media and configure recording settings by operating the operation panel.

[0013] A print head 104 having nozzles (ejection ports) for ejecting ink supplied from an ink tank (not shown) is attached to the carriage 105. The carriage 105 carrying the print head 104 scans in a scanning direction (X direction in the figure) along a shaft (not shown) via a carriage belt 107 by being driven by a carriage motor (not shown).

[0014] A recording medium 103 such as roll paper is conveyed on a platen 108 in a conveying direction (Y direction in the figure) by a conveying roller (not shown). The platen 108 is provided corresponding to the scanning area of ​​the recording head 104, and supports the conveyed recording medium 103 from the back side. With the recording medium 103 supported, while the carriage 105 scans in the scanning direction, ink is ejected from the recording head 104 and an image is recorded on the recording medium 103. When the carriage 105 moves to the end of the recording area on the recording medium 103, the conveying roller conveys the recording medium 103 a certain amount and moves the area to be scanned next to a position where the recording head 104 can record. By repeating the above operations, an image is recorded on the recording medium 103.

[0015] Ink tank boxes 109A and 109B are provided at both ends of the moving range of the carriage 105. Each of the ink tank boxes 109A and 109B in this embodiment can detachably mount six ink tanks, and the two ink tank boxes 109A and 109B can mount twelve ink tanks. In this embodiment, the ink tanks are mounted to sub-tanks (not shown) provided in the ink tank boxes 109A and 109B. Ink supplied to the sub-tank by the user is further supplied from the sub-tank to the ink tank box. The twelve ink tanks contain inks such as cyan, light cyan with a lower colorant density than cyan, magenta, light magenta with a lower colorant density than magenta, yellow, black, gray, blue, and red, respectively. A plurality of print heads 104 that eject inks of the respective colors are mounted corresponding to these twelve colors of ink. The number of ink colors and the number of tanks are not limited to the above example. Each of the ink tank boxes 109A and 109B is connected to the carriage 105 by an ink supply tube (not shown), and ink is supplied from each ink tank to the corresponding print head 104.

[0016] A recovery device 110 is provided at a position corresponding to one end of the moving range of the carriage 105. The recovery device 110 performs negative pressure suction with a cap on the nozzle surface on which the nozzles that eject ink are provided. This allows ink to be discharged from within the print head through the nozzles, and further from ink supply paths such as ink supply tubes. The discharged ink is collected in a waste ink tank (not shown).

[0017] In this embodiment, the ink discharged from the recording head 104 is latex ink. When heat is applied to the ink, the water in the ink evaporates, the latex resin melts and mixes with the pigment, and a film is formed on the surface of the recording medium, which then hardens. When using a general water-based ink, an ink-receiving layer is required on the recording medium to catch the ink and prevent bleeding, but when using latex ink, it is possible to record on a recording medium that does not have an ink-receiving layer. In this embodiment, the recording medium 103 after recording is transported to the fixing mechanism 102, where heat is applied to the recording medium 103, and the recording medium 103 is discharged from the fixing mechanism 102 in a state in which the ink is hardened and fixed on the recording medium 103.

[0018] The reading device 111 is a contact image sensor (hereinafter, CIS), and is fixed to the fixing mechanism 102. The reading device 111 is disposed parallel to the transport direction, and reads the recording medium 103 discharged from the fixing mechanism 102. The reading device 111 can also move in accordance with the size of the recording medium 103.

[0019] 2 is a block diagram for explaining the control configuration of the image forming apparatus 100. The image forming apparatus 100 is composed of a load side system 200 and a power supply unit 201. The load side system 200 and the power supply unit 201 are electrically connected to each other using a connector, a cable, or the like (not shown).

[0020] The power supply unit 201 has an AC / DC conversion circuit 202 and is connected to a commercial power supply. A predetermined voltage is output from the input of the commercial power supply via the AC / DC conversion circuit 202, and power is supplied to the load side system 200.

[0021] The DC / DC conversion circuit 203 is composed of a switching regulator and its peripheral circuits, and has a function of converting the DC output voltage output from the AC / DC conversion circuit 202 into a predetermined DC voltage required by each block of the load side system 200, outputting it, and distributing it.

[0022] The controller 204 is a main control unit, and includes, for example, a CPU 205 in the form of a microcomputer, a ROM 206 in which programs, required tables, and other fixed data are stored, and a RAM 207 in which an area for developing image data, a working area, and the like are provided.

[0023] The host device 208 is a source of print data connected to the outside of the device, and may be in the form of a computer that creates and processes print data, or a reader unit for reading images.

[0024] Image data, other commands, status signals, etc. are transmitted and received between the controller 204 via an interface (I / F) 209. In addition, image data read by the reading device 111 is transmitted to the controller 204 via the interface (I / F) 209 and stored in the RAM 207.

[0025] The operation display device 106 includes a group of switches that accepts instruction input by an operator, and an LCD 212 that provides the operator with internal information about the printer, etc. The group of switches includes a power switch 211 and the like.

[0026] The sensor group 213 is a detection group for detecting the state of the device. The encoder sensor 214 is mounted on the carriage 105 and detects the position of the carriage 105. The edge detection sensor 216 is mounted on the carriage 105 and detects the edge between the print head 104 and the print medium 103. The photointerrupter 215 detects the home position.

[0027] The head driver 217 is a driver that drives a nozzle heater 218 in the print head 104 in accordance with print data and the like, and by driving the nozzle heater 218, it becomes possible to eject ink.

[0028] The motor driver A 219 is a driver that drives a carriage motor 220. The motor driver B 221 is a driver that drives a conveyance motor 222 that is used to convey the recording medium 103.

[0029] 3 is a schematic diagram of a test pattern 301 recorded on an end of the recording medium 103. The test pattern 301 is a pattern consisting of a uniform solid image of halftones, and is recorded on the end of the recording medium 103 by the recording head 104. An image instructed to be recorded by a user is recorded on the center of the recording medium 103 in the X direction. The reading device 111 includes a plurality of reading elements. The reading width of the reading elements is configured to be longer than the width L in the X direction of the test pattern 301 recorded on the end of the recording medium 103. The test pattern 301 is read while the recording medium 103 is being transported.

[0030] Figure 4 is an example showing spatial frequencies obtained by applying FFT (Fourier transform) to data obtained by reading an inspection pattern. From the spatial frequency, the frequency with the highest amplitude is extracted and determined as the fundamental component wave. Then, multiple waves of the fundamental component wave are extracted and the number of multiple waves (harmonic component wave number) is calculated. In addition, the component ratio of the amplitude of the fundamental component wave and the multiple waves (harmonic component waves) is calculated.

[0031] FIG. 5 is a diagram showing spatial frequencies when an inspection pattern includes streaks and unevenness. FIG. 5(a) shows one-dimensional data obtained by averaging data obtained by reading an image including unevenness and streaks in one direction, and FIG. 5(b) shows spatial frequency characteristics obtained by applying FFT (Fourier transform) to the one-dimensional data including unevenness and streaks. Here, the inventors have found the following through their studies. When an image includes unevenness, a large peak appears on the low frequency side in the spatial frequency characteristics, and high amplitude does not appear on the high frequency side. When an image includes streaks, harmonics appear from low to high frequencies in the spatial frequency characteristics.

[0032] Fig. 6 is a flow chart of a process for determining whether a read inspection pattern is an image containing only streaks, an image containing both streaks and unevenness, or an image containing only unevenness. This determination process is performed by reading and executing a program stored in a memory. Fig. 7 is a diagram showing analysis of read data into streaks only, both streaks and unevenness, and unevenness only based on the spatial frequency. Fig. 7(a) is a diagram showing one-dimensional data obtained by averaging a read image in one direction, and Fig. 7(b) is a diagram showing data obtained by applying FFT to the one-dimensional data and converting it into spatial frequency characteristics.

[0033] 6, a recording operation is started to record a user image and a test pattern on a recording medium (step S101). Then, the reading device 111 starts a reading operation of the test pattern (step S102). The reading operation is performed while the recording medium 103 is being transported, and monitors whether noise is occurring in the image from the leading edge to the trailing edge of the recording medium 103.

[0034] Next, the spatial frequency characteristic is obtained from the result of reading the inspection pattern. Then, the type of noise component is determined based on the component ratio of the amplitude of the fundamental component wave and the harmonic component wave, and the number of harmonic components indicating the number of harmonic component waves. In step S103, it is determined whether the component ratio is smaller than the first threshold value and the number of harmonic components is equal to or larger than the second threshold value. If Yes, the noise component is determined to be a streak (step S107). If No, it proceeds to the determination of step S104. It is determined whether the component ratio is equal to or larger than the first threshold value and the number of harmonic components is smaller than the second threshold value. If Yes, the noise component is determined to be an unevenness (step S108). If No, it proceeds to the determination of step S105. It is determined whether the component ratio is equal to or larger than the first threshold value and the number of harmonic components is equal to or larger than the second threshold value. If Yes, the noise component is determined to be both a streak and an unevenness (step S109). If none of the conditions in steps S103 to S105 are satisfied, the process proceeds to step S106, where it is determined that there is no noise component and that no streaks or unevenness have occurred, and the process proceeds to step S107. The above determination is repeated until recording is completed. The result of the above determination process is notified to the user using a notifying means (not shown). Based on this result, adjustment processing or recovery processing may be performed within the image forming apparatus.

[0035] The larger the area in which the judgment process of the read inspection pattern is performed, the more likely it is that occurrence of low-frequency noise can be detected. The area in which the judgment process is performed may be configured so that the user can set it using a setting means (not shown). In addition, since the type of noise to be judged varies from user to user, the user may be configured to set the amplitude threshold of the fundamental component wave, the first threshold of the component ratio, and the second threshold of the number of harmonic components, which determine the degree of detection of streaks and unevenness, using a setting means (not shown).

[0036] In this way, the spatial frequency is calculated from the results of reading the inspection pattern, and the type of noise component is determined based on the component ratio of the amplitude of the fundamental wave component and the harmonic wave component and the number of harmonic components, thereby making it possible to determine the noise in the recorded image. [Explanation of symbols]

[0037] 100 Image forming device 103 Recording media 104 Recording head 105 Carriage 108 Platen

Claims

1. an acquisition means for acquiring a spatial frequency characteristic based on read data of a test pattern recorded on a recording medium; A calculation means for calculating a component ratio between a fundamental component wave and a harmonic component wave of the spatial frequency characteristic; a determination means for determining a type of noise based on the component ratio calculated by the calculation means and the number of harmonic components indicating the number of harmonic component waves; Equipped with the determination means determines the type of noise to be streaks when the component ratio is smaller than a first threshold and the number of harmonic components is equal to or greater than a second threshold, determines the type of noise to be unevenness when the component ratio is equal to or greater than the first threshold and the number of harmonic components is smaller than the second threshold, and determines the type of noise to be both streaks and unevenness when the component ratio is equal to or greater than the first threshold and the number of harmonic components is equal to or greater than the second threshold.

2. 2. The image processing device according to claim 1, wherein the acquisition means acquires one-dimensional data obtained by averaging the read data in a predetermined direction, and acquires the spatial frequency characteristics by applying an FFT (Fourier transform) to the one-dimensional data.

3. 2. The image processing apparatus according to claim 1, wherein the inspection pattern is a pattern recorded by moving a recording means in a direction intersecting a conveying direction of the recording medium.

4. 2. The image processing apparatus according to claim 1, further comprising a notification unit for notifying a user of the type of noise determined by the determination unit.

5. 2. The image processing apparatus according to claim 1, wherein the inspection pattern is recorded on the same recording medium as the user image.

6. The image processing apparatus according to claim 1 , wherein the acquiring means includes a sensor for reading the test pattern.

7. 7. The image processing apparatus according to claim 6, wherein the sensor is a contact image sensor (CIS).

8. 2. The image processing apparatus according to claim 1, further comprising a setting unit capable of setting the first threshold value and the second threshold value.

9. acquiring spatial frequency characteristics based on read data of the test pattern recorded on the recording medium; calculating a component ratio between a fundamental component wave and a harmonic component wave of the spatial frequency characteristic; determining a type of noise based on the calculated component ratio and the number of harmonic components indicating the number of harmonic component waves; Equipped with an image processing method comprising: determining, when the component ratio is smaller than a first threshold and the number of harmonic components is equal to or greater than a second threshold, the type of noise is determined to be streaks; determining, when the component ratio is equal to or greater than the first threshold and the number of harmonic components is smaller than the second threshold, the type of noise is determined to be unevenness; and determining, when the component ratio is equal to or greater than the first threshold and the number of harmonic components is equal to or greater than the second threshold, the type of noise is determined to be both streaks and unevenness.

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