Patent Application
20220051386
This application claims priority to Japanese Patent Application No. 2020-136779, filed on Aug. 13, 2020, the entire disclosure of which being incorporated herein by reference in its entirety.
The present disclosure relates to an image inspecting apparatus, an image inspecting method, and a computer-readable recording medium storing an image inspecting program.
In printed matters on which images are formed by an electrophotographic system, there may be a case where image abnormalities occur. As an example of the image abnormalities of the printed matters, there is a spot-shaped (dot-shaped) abnormality.
On the other hand, at the time of forming an image by the electrophotographic system, there may be a case where spot-shaped abnormalities being not in original image data occur. This spot-shaped abnormality is referred to as a firefly. On image printed matters, fireflies appear as pale undulations. In particular, in halftone image printed matters, fireflies are easy to detect by people's eyes, resulting in that the quality of the printed matters is lowered.
Conventionally, as techniques for detecting the abnormalities of images on printed matters, for example, there is a technique disclosed by Patent Literature 1 (JP 1995-186375A). In Patent Literature 1, a normal image is subjected to filter processing by using a minimum value filter and/or maximum value filter, thereby forming a standard image. Successively, an inspection image is compared with this standard image, thereby acquiring differential values. Successively, these differential values are compared with an allowable value (threshold), thereby detecting abnormalities of an image.
In the conventional technique, the gradation values of pixels of an inspection image are compared with the gradation values of pixels after the filter processing. For this reason, with the conventional technique, in the case where there are large abnormalities, the difference values with the reverse sign may appear in close proximity to that abnormal pixel. In the case where such the difference values with the reverse sign appear, in the conventional technique, even in the case where they are not abnormal, they might have been falsely detected as abnormalities.
Then, an object of the present disclosure may be to provide an image inspecting apparatus, image inspecting method, and image inspecting program that improves inspection accuracy of an image.
The above-described object of the present disclosure can be attained by the following configurations. In order to realize the above-described object, an image inspecting apparatus that reflects one aspect of the present disclosure, includes a calculator that calculates difference data of each image data obtained by performing smoothing processing for image data with multiple smoothing filters different in range; an extractor that extracts multiple abnormal candidate on a basis of the difference data; and a detector that makes a range in which the extracted multiple abnormal candidates are collected, into a target region and detects one abnormal candidate as an abnormality from the multiple abnormal candidates included in the target region on a basis of the difference data.
In order to realize the above-described object, an image inspecting method that may reflect one aspect of the present disclosure, includes (a) calculating difference data of each image data obtained by performing smoothing processing for image data with multiple smoothing filters different in range; (b) extracting multiple abnormal candidates on a basis of the difference data; and (c) making a range in which the extracted multiple abnormal candidates are collected, into a target region and detecting one abnormal candidate as an abnormality from the multiple abnormal candidates included in the target region on a basis of the difference data.
The advantages and features provided by one or more embodiments of the disclosure will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present disclosure.
Hereinafter, with reference to the drawings, embodiments of the present disclosure will be described in detail. However, the scope of the disclosure is not limited to the disclosed embodiments. In this connection, in the description for the drawings, the same constitutional element is provided with the same reference symbol, and the overlapping description is omitted. Moreover, dimensional ratios in the drawings are exaggerated on account of description and may be different from the actual ratios.
As shown in
The image forming apparatus 10 forms images on sheets 90 (recording material) on the basis of original image data (also, referred to as print data).
The image inspecting apparatus 20 includes a reader 23, reads an image on a sheet 90 printed by the image forming apparatus 10, and generates read image data. Moreover, the image inspecting apparatus 20 performs inspection for an image density, color, and an image formation position on the basis of the generated read image data, thereby detecting abnormalities and performing various kinds of image adjustments, such as density adjustment, color adjustment, and position deviation adjustment.
The post processing apparatus 30 performs various kinds of post-processing for sheets printed by the image forming apparatus 10.
In this connection, in the following embodiment, as shown in
As shown in
The processor 11 is a CPU (Central Processing Unit) and performs control for each unit of an apparatus and various kinds of arithmetic processing in accordance with a program. The memory 12 includes a ROM (Read Only Memory) that stores various programs and the various kinds of data beforehand, a RAM that memorizes a program and data temporarily as a work area, a hard disk that stores various programs and various kinds of data, and so on. Such the configurations of the processor 11 and the memory 12 are similar to those of a computer.
The image former 13 forms an image, for example, by an electrophotographic system and includes writers 131 and image creators corresponding to respective basic colors (YMCK). Each image creator includes a photoconductor drum 132, a charging electrode (not shown), a development unit 133 that stores a two-component developer composed of toner and carrier, and a cleaner (not shown). Toner images formed by the respective image creators corresponding to the basic colors (YMCK) are superimposed on each other on an intermediate transfer belt 134 and are transferred onto a conveyed sheet 90 in a secondary transferor 135. The toner images (of full color) on the sheet 90 are fixed on the sheet 90 by being heated and pressurized in a fixer 136 on the downstream side.
The sheet feeding conveyor 14 includes a plurality of sheet feeding trays 141, conveyance paths 142 and 143, a plurality of conveyance rollers disposed on these conveyance paths 142 and 143, and a drive motor (not shown) that drives these conveyance rollers. A sheet 90 fed out from the sheet feeding tray 141 is conveyed on the conveyance path 142, subjected to image formation in the image former 13, and, thereafter, sent to the image inspecting apparatus 20 on the downstream side.
Moreover, in the case where the printing setting of a print job is the setting of double-side printing, a sheet 90 that has been subjected to image formation on its one side surface (first surface), is conveyed to an ADU conveyance path 143 disposed at a lower part of the image forming apparatus 10 by the sheet feeding conveyor 14. The sheet 90 conveyed to this ADU conveyance path 143 is turned upside down on a switchback path, thereafter, joins the conveyance path 142, and is subjected again to image formation on the other side (second side) of the sheet 90 in the image former 13.
The operation display 15 includes a touch panel, a ten key, a start button, a stop button, and the like, displays a state of the image forming system 1, and is used for various kinds of settings and the input of an instruction by a user. Moreover, the operation display 15 receives the execution instruction of below-mentioned color adjustment and image position adjustment by a user. Moreover, in the case where abnormalities have been determined in inspection by the image inspecting apparatus 20, the operation display 15 displays an analysis result.
The communicator 19 is an interface through which the image forming apparatus 10 communicates with the image inspecting apparatus 20, the post processing apparatus 30, and external devices, such as a PC. The communicator 19 transmits and receives various setting values, various kinds of information required for an operation timing control, and the like between itself and the image inspecting apparatuses 20. Furthermore, the communicator 19 receives a print job from an external device.
In the communicator 19, various local connecting interfaces, such as network interfaces based on standards, such as SATA, PCI, USB, Ethernet (registered trademark), and IEEE1394 and wireless communication interfaces, such as a such as Bluetooth (registered trademark) and IEEE802.11, are used.
As shown in
The processor 21 and the memory 22 include the respective similar configurations of the above-mentioned processor 11 and memory 12. This processor 21 performs image adjustment, image inspection, and the like of the image forming system 1 by cooperating with the processor 11 of the image forming apparatus 10.
The processor 21 functions as an image analyzer 210. The processor 21 is a CPU and performs control for each unit of the apparatus and various kinds of arithmetic processing. In particular, the processor 21 executes the functions of the image analyzer by executing an image inspecting program. The memory 22 includes a ROM that stores an image inspecting program and various kinds of data beforehand, a RAM that memorizes a program and data temporarily as a work area, a hard disk that stores various kinds of programs and various kinds of data, and so on. In particular, the memory 22 memorizes original image data, read image data, and so on. Such the configurations of the processor 21 and the memory 22 are similar to those of the computer.
The reader 23 is disposed on the conveyance path 241 and reads an image on a sheet 90 that has been subjected to image formation in the image forming apparatus 10 and then conveyed. In this connection, so as to be able to read both surfaces simultaneously (one pass), the same reader may be disposed also below the conveyance path 241. Alternatively, a conveyance path similar to the ADU conveyance path 143 of the image forming apparatus 10 is disposed such that both surfaces are read by one reader 23.
The reader 23 includes a sensor array, a lens optical system, an LED (Light Emitting Diode) light source, and a housing that store these components. The sensor array is a color line sensor (for example, a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and so on) in which a plurality of optical elements is arranged in a line shape along a main scanning direction, and its reading region in a width direction corresponds to the full width of a sheet 90. An optical system includes a plurality of mirrors and lenses. Light from the LED light source penetrates an original document glass and irradiates the surface of a sheet 90 that passes a reading position on the conveyance path 241. Image light by surface-reflected light on this reading position is led by an optical system and is formed as an image on a sensor array. The resolution of the reader 23 is 100 to hundreds dpi.
The conveyor 24 includes a conveyance path 241, a plurality of conveyance rollers disposed on this conveyance path 241, and a drive motor (not shown) that drives these conveyance rollers. The conveyance path 241 is connected with the conveyance path 142 disposed on the upstream side, receives a sheet 90 on which an image has been formed in the image forming apparatus 10, and sends the sheet 90 to the post processing apparatus 30 disposed on the downstream side.
The communicator 29 functions as an original image data input/output unit 290. The communicator 29 performs transmitting and receiving various kinds of setting values and various kinds of information necessary for operation timing control between itself and the communicator 19 of the image forming apparatus 10. Then, the communicator 29 receives original image data included in a print job from the communicator 19 of the image forming apparatus 10 by the control of the processor 21. The communicator 29 memorizes the received original image data in the memory 22. The communicator 29 includes a local connection interface necessary for communicating with the communicator 19.
The post processing apparatus 30 includes a post processor 31 and a conveyor 34 as shown in
The conveyance path 341 is connected to the conveyance path 241 disposed on the upstream side and receives a sheet 90 conveyed from the image inspecting apparatus 20. Then, the post processing apparatus 30 performs the post processing according to printing setting for the sheet 90, and thereafter, discharges it to the sheet delivery tray 342. Moreover, the post processing apparatus 30 discharges the conveyed sheet 90 in accordance with the printing setting to the sheet delivery tray 344 via the conveyance path 343. Moreover, the post processing apparatus 30 may discharge a sheet 90 determined as normal in the later-mentioned inspection to an ordinary sheet delivery tray 342 and discharge a sheet 90 determined as abnormal to another sheet delivery tray 344.
The post processor 31 performs various kinds of post-processing, such as staple processing, punch processing, and booklet formation processing. For example, the post processor 31 includes a stacker that stacks sheets and a stapler, superimposes a plurality of sheets 90 in the stacker, and, thereafter, performs flat stitching processing by using staples in the stapler.
Image inspecting processing is processing that detects abnormalities of an image printed on a sheet 90 by the image forming apparatus 10. The processor 21 of the image inspecting apparatus 20 performs the image inspecting processing as a function of the image analyzer 210.
The image analyzer 210 functions as a calculator that calculates difference data of each of image data that have been subjected to smoothing processing with smoothing filters with respective ranges differ for image data. Moreover, the image analyzer 210 functions as an extractor that extracts an abnormal candidate on the basis of the difference data. Moreover, the image analyzer 210 functions as a detector that collects a plurality of extracted abnormal candidates in a range, makes the range a target region, and detects one abnormal candidate as abnormalities, on the basis of the difference data, from the plurality of abnormal candidates included in the target region.
In the image inspecting processing, first, the processor 11 of the image forming apparatus 10 becomes a main member and performs printing an image onto a sheet and conveying the printed sheet to the image inspecting apparatus 20. Successively, the processor 21 of the image inspecting apparatus 20 makes the reader 23 read an image from the printed sheet conveyed to the reader 23.
In the present embodiment, the image inspecting processing is described on a basis of an example of a case where a firefly (also, referred to as a white void and a white spot) being one of abnormalities within an image is made a detection target. The term “firefly” used in here is a phenomenon that a part of an image after transfer turns to white (an image density becomes thin) in a circular shape due to the following reasons. That is, for example, carrier particles in a development unit 133 adhere to an intermediate transfer belt 134 via a photoconductor drum 132, and the carrier particles become foreign substances at the time of secondary transfer. Then, the carrier particles make the adhesion between a sheet 90 and the intermediate transfer belt 134 insufficient in their periphery, resulting in the part of an image after transfer turns to white. For this reason, in many cases, fireflies appear as white-spot-shaped pixels in a color image. A color image means, for example, an image colored with colors other than the ground color of a sheet and includes an image of a single color of black. In particular, fireflies tend to become more noticeable in so-called halftone image with uniform intermediate image densities.
Although a processing procedure will be mentioned later, in image inspecting processing, first, original image data to be used for printing is acquired from a print job, and further, read image data is generated by reading a sheet 90 after printing.
Successively, in the image inspecting processing, for each of the original image data and the read image data, smoothing processing is performed with smoothing filters different in processing range. The smoothing filters includes a first smoothing filter and a second smoothing filter.
A range for which the first smoothing filter 201 performs the smoothing processing is a first region. A range for which the second smoothing filter 202 performs the smoothing processing is a second region. The first smoothing filter 201 shown in
The first smoothing filter 201 is a small-area smoothing filter for eliminating high frequency components (noise). For example, it calculates average gradation. The second smoothing filter 202 is a large-area smoothing filter for calculating average gradation of a background.
As shown in
Successively, in the image inspecting processing, difference data are calculated from image data after the smoothing processing by the two kinds of smoothing filters. The difference data are values acquired by subtracting the gradation value of each pixel after the smoothing processing by the second smoothing filter 202 from the gradation value of each pixel after the smoothing processing by the first smoothing filter 201. The difference data are acquired for both the read image data and the original image data.
In the image inspecting processing, an abnormal candidate is extracted by comparing the difference data after the smoothing processing to the read image data with the difference data after the smoothing processing to the original image data.
As shown in
On the other hand, in the original image data, there is no abnormality like a firefly. Although not shown in the drawings, for this reason, the graph of the difference data of the original image data does not become a mountain shape. Therefore, as a result of comparing the difference data of the original image data with the difference data of the read image data as shown in
In an image evaluating method that does not apply the present embodiment, there is a method of determining that a pixel having a different gradation value has an abnormality, by comparing the gradation value of each pixel in the difference data of original image data with the gradation value of each pixel in the difference data of read image data. In such the image evaluating method that does not apply the present embodiment, a portion of a firefly in
Then, in the present embodiment, in order to suppress or prevent the erroneous detection of a fake firefly, fake firefly eliminating processing is being performed.
Successively, in the fake firefly eliminating processing, the regions containing a plurality of abnormal candidates are extended. In the extending processing, each of the pixels in each of the abnormal candidates is applied with the extending filter 203 and extended to a range of pixels contained in the extending filter 203. With this, the multiple abnormal candidates are collected and are made to a target region. The extending filter 203 is a circular filter that makes a plurality of pixels a range, as shown in
Then, in the fake firefly eliminating processing, only one abnormal candidate having a pixel with the highest gradation value in the target region is selected, and it is determined that there is a firefly (being abnormal).
In
Next, the procedures of the image inspecting processing by the image inspecting apparatus 20 is described.
The processor 21 acquires original image data through the communicator 29 and, in addition, generates read image data by making the reader 23 read a sheet 90 (S101). The original image data and the read image data are linked as a pair of image data and memorized in the memory 22.
Successively, the processor 21 performs the smoothing processing with the first smoothing filter 201 and the second smoothing filter 202 for each of the original image data and the read image data (S102).
Then, the processor 21 calculates difference data of each of the original image data and the read image data after the smoothing processing (S103).
Successively, the processor 21 makes the difference data (difference value) into the absolute value (S104). In this connection, the processing of making into the absolute value may be performed at any stage in conformity with processing content as long as before performing the next maximum gradation value search (S108).
Then, the processor 21 acquires the gradation value of each pixel of the difference data (S105).
Successively, the processor 21 compares the difference data of the read image data with the difference data of the original image data and extracts pixels with gradation values different more than a threshold for as an abnormal candidate of a lump each same sign (S106).
Then, the processor 21 extends a range including an abnormal candidate by the extending filter 203 and sets a target region (S107).
Then, the processor 21 searches a pixel of the maximum gradation value from the target region (S108).
Subsequently, the processor 21 detects one abnormal candidate containing the pixel of the maximum gradation value as a firefly (S109). With the above description, the image inspecting processing is ended.
As explained in the above, in the present embodiment, from a target region including an abnormal candidate with a true firefly and an abnormal candidate with a fake firefly, one abnormal candidate containing a pixel with the highest gradation value is determined as having a firefly, whereby it is possible to prevent detecting a fake firefly as abnormalities. Therefore, according to the present embodiment, the inspection or detection accuracy of an image abnormality can be improved.
In the above-mentioned present embodiment, one abnormal candidate is detected as an abnormality (firefly) on the basis of the gradation value of each pixel in each abnormal candidate included in a target region. However, a method for detecting one abnormal candidate as an abnormality (firefly) by removing a fake firefly from a plurality of abnormal candidates included in a target region, is not limited to this. Hereinafter, other methods for detecting one abnormal candidate as an abnormality (firefly) are described as modified examples. In this connection, even in other methods, the procedures up to the setting of a target region are the same as the image inspecting processing in the above-mentioned embodiment.
In the modified example 1, one abnormal candidate is detected as an abnormality on a basis of the sign of the gradation value of each pixel in each abnormal candidate included in a target region. As can be understood from the already-explained
The modified example 2 detects one abnormal candidate as an abnormality on the basis of the number of pixels in each of abnormal candidates included in a target region. As can be seen from the already-explained
The modified example 3 detects one abnormal candidate as an abnormality on the basis of an integrated value of a gradation value of each pixel and the number of pixels in each abnormal candidate included in a target region. As can be seen from the already-explained
The modified example 4 detects one abnormal candidate as an abnormality on the basis of a position of each abnormal candidate included in the above-mentioned target region. As can be seen from the already-explained
Furthermore, as the image inspecting processing, the above-mentioned embodiment and the modified examples may be combined appropriately.
As mentioned in the above, although the embodiments of the present disclosure have been described, various modified examples are possible. In the above-mentioned embodiment and modified examples, although an abnormality to be detected has been described on the basis of an example of a firefly, abnormalities capable of being detected by the present disclosure are not limited to the firefly. As the abnormalities capable of being detected by the present disclosure, for example, streaky scratches and the like that appear as lines with high gradation values relative to peripheral pixels, can be detected. In the case where difference data by two kinds of smoothing filters are taken from streaky scratches similarly to fireflies, there may be a case where false streaky scratches appear around a true streaky scratch. By applying the present disclosure, it is possible to remove such false streaky scratches and to improve the detection accuracy of streaky scratches.
Moreover, as the embodiment and modified example of the present disclosure, it is possible to improve detection accuracies for spot-shaped abnormalities and streaky scratches that do not exist in original image data and become high density than peripheral pixels. In the spot-shaped abnormalities and streaky scratches that become high density than peripheral pixels, their gradation values become lower than the peripheral pixels. In the case of such abnormalities, within the read image data, the gradation value becomes lower in the abnormal portions. Therefore, in the case of such abnormalities, similarly to the embodiment and the modified example, in a graph where peripheral pixels (background) are set to 0, the gradation value becomes a shape (a valley shape) that protrudes in the direction of the sign of −(minus). Moreover, even in such abnormalities, in a graph of difference data after the smoothing processing, small mountain shapes (a sign is +) becoming a fake abnormality appear in the vicinity of a large valley shape being a true abnormality. In such a graphical shape, the respective signs of the portions of an abnormality and a fake abnormality are merely reversed relative to the white-void abnormalities described in the embodiment. For this reason, for the abnormalities in which the gradation values is lower than peripheral pixels, with the processing similar to the processing in the above-mentioned embodiment and modified example, it is possible to detect only a true abnormality. Moreover, in the embodiment, since the value of difference data is made into the absolute value in the middle of processing, it is possible to perform processing without considering differences in sign in abnormal portions.
In addition, conditions, numerical values, etc. used in the description of the embodiment are prepared only for description. Accordingly, the present disclosure is not limited to these conditions and numerical values.
Moreover, on the basis of the configuration described in the scope of claims, various modifications are possible for the present disclosure. However, such the various modifications are included in the scope of the present disclosure.
Although embodiments of the present disclosure have been described and illustrated in detail, the disclosed embodiments are made for purpose of illustration and example only and not limitation. The scope of the present disclosure should be interpreted by terms of the appended claims.
As used herein, the words “can” and “may” are used in a permissive (i.e., meaning having the potential to), rather than mandatory sense (i.e., meaning must). The words “include,” “includes,” “including,” and the like mean including, but not limited to. Similarly, the singular form of “a” and “the” include plural references unless the context clearly dictates otherwise. And the term “number” shall mean one or an integer greater than one (i.e., a plurality).
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-136779 | Aug 2020 | JP | national |
