Image forming apparatus

Abstract

To ensure visibility of an identification pattern.SOLUTION: An image forming apparatus comprises: an image carrier that carries an image and an identification pattern; an image forming unit that forms the image on the image carrier; a pattern forming unit that forms the identification pattern on the image carrier; a transfer unit that transfers the image and the identification pattern on the image carrier directly or indirectly to a recording medium; and a pattern discrimination unit that discriminates whether the identification pattern is an image part pattern 41 arranged at a position overlapping with the image or a position adjacent to the image, or a non-image part pattern 42 not arranged at both the position overlapping with the image and the position adjacent to the image. The non-image part pattern 42 is formed larger than the image part pattern 41.SELECTED DRAWING: Figure 8

Description

Technical Field

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

Background Art

[0002] As an image forming apparatus such as a copying machine or a printer, there is one that forms an identification pattern to which identification information is added in addition to the originally formed image.

[0003] The identification pattern includes, for example, a tracking pattern that enables tracking of information such as which device formed the image, and information such as the serial number of the image forming apparatus that formed the image is expressed by a predetermined dot pattern.

[0004] Although such a tracking pattern needs to be formed reliably, the visibility of the tracking pattern may vary due to various factors.

[0005] For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2017-151135), a change in the film thickness of the photoreceptor that supports the image is cited as one of the factors that cause the visibility of the tracking pattern to vary. Therefore, in Patent Document 1, a technique has been proposed in which the area of the image region constituting the tracking pattern is changed according to the thickness of the film thickness of the photoreceptor, so that a tracking pattern having a certain visibility can be formed.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, identification patterns such as tracking patterns may be formed in a region separate from the image that is originally formed, or they may be formed overlapping with the image. In such cases, it has been found that identification patterns formed at a location far from the image are less likely to be transferred compared to identification patterns formed at a location overlapping with or adjacent to the image, and parts of the tracking pattern are more likely to be lost. Such findings have not been shown in any prior art documents other than the above-mentioned Patent Document 1, and no measures have been proposed to ensure the visibility of identification patterns formed at a location far from the image region. [Means for solving the problem]

[0007] To solve the above problems, the image forming apparatus according to the present invention comprises an image carrier that carries an image and an identification pattern; an image forming unit that forms the image on the image carrier; a pattern forming unit that forms the identification pattern on the image carrier; a transfer unit that directly or indirectly transfers the image and the identification pattern on the image carrier to a recording medium; and a pattern determination unit that determines whether the identification pattern is an image part pattern that is positioned at a position overlapping with or adjacent to the image, or a non-image part pattern that is not positioned at either a position overlapping with or adjacent to the image, wherein the non-image part pattern is formed to be larger than the image part pattern. [Effects of the Invention]

[0008] According to the present invention, the visibility of the identification pattern can be ensured. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. [Figure 2] This figure shows an example of a tracking pattern. [Figure 3] This figure shows an example where the tracking pattern is formed using a photosensitive material for yellow images. [Figure 4]This figure shows an example of the arrangement of the image and tracking pattern that are originally formed. [Figure 5] This figure shows how a tracking pattern, formed at a location separate from the image, is transferred to an intermediate transfer belt. [Figure 6] This figure shows how a tracking pattern, formed at a position overlapping or adjacent to the image, is transferred to an intermediate transfer belt. [Figure 7] This is a block diagram showing the configuration of the image forming apparatus according to this embodiment. [Figure 8] This figure shows an example of an image area pattern and a non-image area pattern. [Figure 9] This figure shows other examples of image area patterns and non-image area patterns. [Figure 10] This figure shows an example of changing the size of the image pattern according to the image density. [Figure 11] This figure shows an example of changing the size of the image pattern depending on which photoreceptor the image pattern is formed on. [Figure 12] This is a block diagram showing the hardware configuration of the image forming apparatus according to this embodiment. [Figure 13] This is a functional block diagram showing the image processing flow in the image forming apparatus according to this embodiment. [Figure 14] This figure shows a simplified representation of the image information used in the pattern discrimination unit according to this embodiment. [Figure 15] This is a flowchart of the pattern discrimination process in the pattern discrimination unit according to this embodiment. [Figure 16] This diagram shows the configuration of a direct transfer type image forming apparatus equipped with only one photoreceptor. [Figure 17] This diagram shows the configuration of a direct transfer type image forming apparatus equipped with multiple photoreceptors. [Modes for carrying out the invention]

[0010] Hereinafter, the present invention will be described based on the attached drawings. In each of the drawings for explaining the present invention, for components such as members and components having the same function or shape, the same reference numerals are given as much as possible to avoid redundant explanations after the first explanation.

[0011] FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. Here, the "image forming apparatus" in this specification includes a printer, a copier, a facsimile machine, a printing machine, or a multifunction machine combining two or more of these. First, referring to FIG. 1, the overall configuration and basic operation of the image forming apparatus according to this embodiment will be described.

[0012] As shown in FIG. 1, the image forming apparatus 100 according to this embodiment includes a plurality of image forming units 1Y, 1M, 1C, 1Bk, an exposure device 6, a transfer device 8, a paper feeding device 7, a fixing device 20, and a paper discharging device 9.

[0013] Each of the image forming units 1Y, 1M, 1C, 1Bk has basically the same configuration except that it contains different color toners (developers) of yellow, magenta, cyan, and black corresponding to the color separation components of a color image. Specifically, each of the image forming units 1Y, 1M, 1C, 1Bk includes a photoreceptor 2 as an image carrier that carries an image on its surface, a charging member 3 that charges the surface of the photoreceptor 2, a developing device 4 that supplies toner as a developer to the surface of the photoreceptor 2 to form a toner image, and a cleaning member 5 that cleans the surface of the photoreceptor 2.

[0014] The transfer device 8 includes an intermediate transfer belt 11, a primary transfer roller 12, and a secondary transfer roller 13. The intermediate transfer belt 11 is an intermediate transfer member composed of an endless belt member and is stretched by a plurality of support rollers. Four primary transfer rollers 12 are provided inside the intermediate transfer belt 11. When each primary transfer roller 12 contacts each photoreceptor 2 via the intermediate transfer belt 11, a primary transfer portion (primary transfer nip) is formed between the intermediate transfer belt 11 and each photoreceptor 2. The secondary transfer roller 13 contacts the outer peripheral surface of the intermediate transfer belt 11 and forms a secondary transfer portion (secondary transfer nip).

[0015] The paper feeding device 7 includes a paper feeding cassette 14 that houses the paper P as a recording medium, and a paper feeding roller 15 that feeds out the paper P from the paper feeding cassette 14. Hereinafter, the "recording medium" will be described as "paper", but the "recording medium" is not limited to paper (paper). The "recording medium" includes not only paper (paper) but also OHP sheets, fabrics, metal sheets, plastic films, or prepreg sheets in which carbon fibers are impregnated with resin in advance. Also, the "paper" includes, in addition to plain paper, cardboard, postcards, envelopes, tissue paper, coated paper (such as coated paper and art paper), tracing paper, and the like.

[0016] The fixing device 20 includes a fixing rotating body 21 heated by a heat source such as a heater, and a pressing rotating body 22 that presses against the outer peripheral surface of the fixing rotating body 21 to form a fixing nip.

[0017] The paper discharging device 9 includes a pair of paper discharging rollers 17.

[0018] Subsequently, while referring to FIG. 1, the basic operation of the image forming apparatus 100 according to the present embodiment will be described.

[0019] When an image forming command is given in the image forming apparatus 100, the photoreceptors 2 of each image forming unit 1Y, 1M, 1C, 1Bk and the intermediate transfer belt 11 of the transfer apparatus 8 begin to rotate. At the same time, the paper feed roller 15 begins to rotate, and paper P is fed out from the paper feed cassette 14. The fed paper P comes to rest upon contact with a pair of timing rollers 16, and the transport of paper P is temporarily stopped until the image to be transferred to paper P is formed.

[0020] In each image unit 1Y, 1M, 1C, and 1Bk, first, the surface of the photoreceptor 2 is charged to a uniform high potential by the charging member 3. Next, based on the image information of the original document read by the document reader or the print image information instructed to print from the terminal, the exposure unit 6 exposes the surface (charged surface) of each photoreceptor 2. As a result, the potential of the exposed area decreases, and an electrostatic latent image is formed on the surface of each photoreceptor 2. Then, the developing unit 4 supplies toner to this electrostatic latent image, and a toner image is formed on each photoreceptor 2. When the toner image formed on each photoreceptor 2 reaches the primary transfer section (position of the primary transfer roller 12) as each photoreceptor 2 rotates, it is transferred sequentially onto the rotating intermediate transfer belt 11. Thus, a full-color toner image is formed on the intermediate transfer belt 11. Note that a monochrome image can be formed using any one of the image units 1Y, 1M, 1C, and 1Bk, or a two-color or three-color image can be formed using any two or three of them. Furthermore, after the toner image has been transferred from the photoreceptor 2 to the intermediate transfer belt 11, the cleaning member 5 removes any remaining toner from each photoreceptor 2.

[0021] The toner image transferred onto the intermediate transfer belt 11 is transported to the secondary transfer section (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and is transferred onto the paper P that has been transported by the timing roller 16. The paper P is then transported to the fuser 20. In the fuser 20, the toner image on the paper P is heated and pressurized by the fuser rotating body 21 and the pressurizing rotating body 22, and the toner image is fixed to the paper P. After that, the paper P is transported by the paper discharge roller 17 and discharged into the paper discharge tray 18 provided in the main body of the image forming apparatus. This completes the series of image forming operations.

[0022] Incidentally, the image forming apparatus according to this embodiment is configured to form a tracking pattern for identifying which apparatus formed the image, in addition to the image based on the image information obtained from the document reading device or terminal as described above. The tracking pattern consists of, for example, a dot pattern to which information such as the manufacturing number, model name, serial number, and copying date and time for each image forming apparatus is added. Furthermore, as shown in Figure 2, since the tracking pattern A is printed on the paper P together with the image B that is originally formed, the tracking pattern A is generally formed using a toner of an inconspicuous color such as yellow so as not to impair the quality of image B.

[0023] Figure 3 shows an example of forming a tracking pattern using a photosensitive material for yellow images.

[0024] In this case, when the image information of the original document is read by the document reader, or when image information is sent from a terminal to the image forming apparatus, the pattern information of the tracking pattern is added to the image information, and the tracking pattern A is formed on the photoreceptor 2Y together with the yellow image. Then, the tracking pattern A is transferred to the intermediate transfer belt 11 in the primary transfer section N1a of the photoreceptor 2Y for the yellow image, and then transported to the secondary transfer section N2 as the intermediate transfer belt 11 rotates, and is transferred to the paper P in the secondary transfer section N2.

[0025] Here, the tracking pattern A formed on the photoreceptor 2Y for the yellow image passes through the primary transfer section N1a of the photoreceptor 2Y, as well as the primary transfer sections N1b, N1c, and N1d of the other photoreceptors 2M, 2C, and 2Bk, before being transferred to the paper P via the intermediate transfer belt 11. At this time, in each primary transfer section N1a, N1b, N1c, and N1d, due to the influence of the friction coefficient between each photoreceptor 2Y, 2M, 2C, and 2Bk and the intermediate transfer belt 11, some of the toner on the photoreceptor 2Y may not be completely transferred to the intermediate transfer belt 11 and may remain on the photoreceptor 2Y, or some of the toner on the intermediate transfer belt 11 may be reverse-transferred to the photoreceptors 2M, 2C, and 2Bk. As a result, there is a risk that the toner that is ultimately transferred to the paper P will be incomplete, and the visibility of the tracking pattern A may decrease.

[0026] Thus, the toner constituting the tracking pattern may be lost due to remaining on the photoreceptor or being reverse-transferred as it passes through the primary transfer section. It has been found that such toner loss in the tracking pattern is particularly likely to occur in tracking patterns formed at positions far from the image that is originally formed. Specifically, as shown in Figure 4, the tracking pattern includes tracking pattern A1, which is positioned to overlap with image B, tracking pattern A2, which is positioned adjacent to image B, and tracking pattern A3, which is positioned away from image B. In particular, tracking pattern A3, which is positioned away from image B, is more prone to toner loss than tracking pattern A1, which is positioned to overlap with image B, and tracking pattern A2, which is positioned adjacent to image B. Note that the position adjacent to image B means an area within 1 mm outside the edge of image B.

[0027] In tracking patterns formed at locations separate from the image, toner defects are more likely to occur for the following reasons:

[0028] As shown in Figure 5(a), the tracking pattern A3, which is formed at a location separate from the image, is surrounded by toner that makes up the image. Therefore, when it is transferred from the photoreceptor 2 to the intermediate transfer belt 11, or when it passes through the primary transfer section, local stress is applied to the toner Ta that makes up the tracking pattern A3, causing the toner Ta to aggregate. As a result, as shown in Figure 5(b), some of the toner Ta adheres to the surface of the photoreceptor 2, so that the toner Ta is not completely transferred from the photoreceptor 2 to the intermediate transfer belt 11, or conversely, the toner Ta is reverse-transferred from the intermediate transfer belt 11 to the photoreceptor 2, resulting in a loss of toner Ta in the tracking pattern A3. In addition, if the coefficient of friction of the photoreceptor 2 is greater than the coefficient of friction of the intermediate transfer belt 11, the toner Ta in the tracking pattern A3 is more likely to be lost.

[0029] In contrast, as shown in Figure 6(a), tracking patterns A1 and A2, which are formed in positions overlapping with or adjacent to image B, are surrounded by toner Tb that constitutes image B. Therefore, even if local stress is applied to the toner Ta constituting each tracking pattern A1 and A2, that stress is distributed to the toner Tb of image B. As a result, the toner Ta of each tracking pattern A1 and A2 is less likely to aggregate. Consequently, as shown in Figure 6(b), the adhesion (residue) of toner Ta to the photoreceptor 2 is suppressed, and each tracking pattern A1 and A2 is transferred to the intermediate transfer belt 11 relatively well.

[0030] In this example, tracking pattern A is formed on the yellow image photoreceptor 2Y, which is located at the uppermost position in the movement direction (rotation direction) of the intermediate transfer belt 11 starting from the secondary transfer section 2N, among the multiple photoreceptors 2Y, M, 2C, and 2Bk. However, the toner defect phenomenon described above is not limited to this example. Therefore, even when tracking pattern A is formed on a photoreceptor other than the uppermost position, tracking pattern A3, which is formed at a position away from the image, tends to be more prone to toner defect than tracking patterns A1 and A2, which are formed at positions overlapping with or adjacent to image B, due to the same mechanism as described above.

[0031] As described above, the degree of toner loss in the tracking pattern differs depending on whether the location where the tracking pattern is formed overlaps with or is adjacent to the image, or is located away from the image. Taking these circumstances into consideration, the image forming apparatus according to this embodiment is controlled as follows. The control method for forming the tracking pattern in this embodiment will be described below.

[0032] Figure 7 is a block diagram showing the configuration of the image forming apparatus according to this embodiment.

[0033] As shown in Figure 7, the image forming apparatus 100 according to this embodiment includes a printer interface 53 as an image information acquisition unit, a pattern generation unit 31, a plotter unit 54 as an image forming unit, a pattern forming unit 33, and a pattern discrimination unit 34.

[0034] The printer interface 53 acquires image information from the document reader or terminal. The acquired image information is sent from the printer interface 53 to the plotter unit 54 and the pattern discrimination unit 34.

[0035] The pattern generation unit 31 generates a pattern that is pre-associated with identification information, such as a serial number, used to identify the image forming apparatus. The generated pattern information is sent from the pattern generation unit 31 to the pattern forming unit 33 and the pattern discrimination unit 34.

[0036] The plotter unit 54 forms an image on the paper using the image formation units 1Y, 1M, 1C, 1Bk and the exposure device 6, based on the input image information obtained from the printer interface 53. The plotter unit 54 also forms an image in which the input image and the tracking pattern are superimposed.

[0037] The pattern forming unit 33 forms a tracking pattern based on the pattern information obtained from the pattern generation unit 31 and the discrimination result of the pattern discrimination unit 34. In this embodiment, since the tracking pattern is formed using yellow toner, the tracking pattern is superimposed on the yellow input image and sent to the plotter unit 54 as new image information. The superimposed image is then formed on the paper by the image creation unit 1Y which generates the yellow image and the exposure device 6.

[0038] The pattern discrimination unit 34 determines the position of the tracking pattern relative to the image based on the input image information obtained from the printer interface 53 and the pattern information obtained from the pattern generation unit 31. Specifically, the pattern discrimination unit 34 determines whether the tracking pattern is tracking pattern A1 located in a position overlapping with image B shown in Figure 4, tracking pattern A2 located adjacent to image B, or tracking pattern A3 located away from image B. Hereinafter, tracking pattern A1 located in a position overlapping with image B and tracking pattern A2 located adjacent to image B will be collectively referred to as "image pattern," while tracking pattern A3 located away from image B will be referred to as "non-image pattern."

[0039] In this invention, the image portion pattern (tracking patterns A1 and A2, which are positioned to overlap with or adjacent to image B) includes tracking patterns positioned to overlap with image B or within 1 mm outside the edge of image B (see Figure 4). On the other hand, the non-image portion (tracking pattern A3, which is positioned away from image B) refers to tracking patterns positioned further outside than 1 mm from the edge of image B. Note that image B does not have to be a solid rectangular image as shown in Figure 4.

[0040] As described above, in this embodiment, the pattern discrimination unit 34 determines whether the tracking pattern is an image pattern or a non-image pattern. In other words, it determines whether the tracking pattern is a pattern that is less likely to cause toner loss or a pattern that is more likely to cause toner loss. Based on this result, in this embodiment, the size of the tracking pattern (the area of ​​the tracking pattern) is changed.

[0041] Figure 8 shows examples of cases where the tracking pattern is an image pattern and a non-image pattern.

[0042] In Figure 8, the tracking pattern shown in (a) is the image pattern 41, which in this case is composed of 4 dots. On the other hand, the non-image pattern 42 shown in (b) in Figure 8 is composed of 16 dots with the same dot size as the image pattern 41. Thus, in this embodiment, the number of dots constituting the non-image pattern 42 is made greater than the number of dots constituting the image pattern 41, thereby forming the non-image pattern 42 larger (in a larger area) than the image pattern 41. That is, the non-image pattern 42 is a tracking pattern positioned away from the image, and is more prone to toner loss in the primary transfer area compared to the image pattern 41, so the non-image pattern 42 is formed larger than the image pattern 41. As a result, even if some of the toner constituting the non-image pattern 42 is lost, good visibility of the non-image pattern 42 can be ensured.

[0043] Furthermore, as shown in another example in Figure 9, the image pattern 41 and the non-image pattern 42 may be made to differ in size by changing the size of the dots without changing the number of dots. In this example, the image pattern 41 shown in (a) in Figure 9 is composed of four small dots, while the non-image pattern 42 shown in (b) in Figure 9 is composed of four large dots. The size of the dots can be changed by adjusting the spot diameter of the exposure irradiated from the exposure device onto the photoreceptor. In this way, even in the example shown in Figure 9, the non-image pattern 42 is formed to be larger than the image pattern 41, thus ensuring good visibility of the non-image pattern 42.

[0044] Note that the shape, number of dots, and dot size of the image pattern 41 and the non-image pattern 42 are not limited to the examples shown in Figures 8 and 9, and can be changed as appropriate.

[0045] As described above, the non-image pattern 42, which is prone to toner loss, is formed relatively large, while the image pattern 41, which is less prone to toner loss, can be formed relatively small. However, even in the image pattern 41, which is relatively less prone to toner loss, the lower the density (gradation) of the image that overlaps with or is adjacent to the image pattern 41, the less toner (image) is present around the image pattern 41, making it more likely for toner loss to occur in the image pattern 41.

[0046] Therefore, as shown in Figure 10, the size of the image pattern 41 may be changed according to the density (gradation) of the image that overlaps with or is adjacent to the image pattern 41. In this example, the darker midtone image shown in (ii) of Figure 10 has a lower density than the solid image shown in (i) of the same figure, so the image pattern 41 is made larger, and in the case of the lighter midtone image shown in (iii) of the same figure, it is made larger than the image pattern 41. The size of the image pattern 41 may be changed by changing the number of dots that make up the image pattern 41, or by changing the dot size.

[0047] Thus, the lower the density (gradation) of the image overlapping with or adjacent to the image pattern 41, the larger the image pattern 41 can be formed (in a larger area), thereby ensuring good visibility of the image pattern 41. Conversely, the higher the density (gradation) of the image overlapping with or adjacent to the image pattern 41, the smaller the image pattern 41 can be formed, thereby reducing the consumption of toner that makes up the tracking pattern.

[0048] Furthermore, while toner defects are less likely to occur in the image pattern 41, the possibility of toner defects in the image pattern 41 changes depending on which photoreceptor the overlapping or adjacent image is formed on. This will be explained based on the example shown in Figure 3.

[0049] In the example shown in Figure 3, the photoreceptor for the yellow image 2Y, the photoreceptor for the magenta image 2M, the photoreceptor for the cyan image 2C, and the photoreceptor for the black image 2Bk are arranged in order from the upstream side in the direction of movement (rotation direction) of the intermediate transfer belt 11, which starts from the secondary transfer section 2N. In this configuration, if the tracking pattern A and the image that overlaps with or is adjacent to it are both formed on the uppermost yellow image photoreceptor 2Y, the tracking pattern A and the image overlap or are adjacent to each other on the uppermost yellow image photoreceptor 2Y, and in that state, the tracking pattern A and the image pass through the primary transfer sections N1a, N1b, N1c, and N1d of the four photoreceptors 2Y, 2M, 2C, and 2Bk. However, if the image on which tracking pattern A overlaps or is adjacent to is formed on the magenta image photoreceptor 2M, which is one downstream from the yellow image photoreceptor 2Y, then the primary transfer sections through which tracking pattern A and the image overlap or are adjacent to each other are three, from the primary transfer section N1b of the magenta image photoreceptor 2M to the primary transfer section N1d of the black image photoreceptor 2Bk. Similarly, if the image on which tracking pattern A overlaps or is adjacent to is formed on the cyan image photoreceptor 2C, which is further downstream, then the number of primary transfer sections through which tracking pattern A and the image overlap or are adjacent to each other is further reduced to two. Thus, the further downstream the photoreceptor on which the image overlapping or adjacent to the image pattern 41 is formed, the fewer primary transfer sections through which tracking pattern A can overlap or be adjacent to the image. This makes it easier for toner to aggregate and for toner defects in tracking pattern A to occur.

[0050] Therefore, as shown in Figure 11, the size of the tracking pattern (image pattern 41) may be changed depending on which photoreceptor is forming the image that overlaps with or is adjacent to the tracking pattern. That is, as shown in (i) to (iv) in Figure 11, the larger the tracking pattern (image pattern 41) should be, the more the image that overlaps with or is adjacent to the tracking pattern (image pattern 41) is formed on the downstream photoreceptor in the order of yellow, magenta, cyan, and black. In this case as well, the size of the image pattern 41 may be changed by changing the number of dots that make up the image pattern 41, or by changing the dot size.

[0051] Thus, the larger the image pattern 41 can be made, the better the visibility of the image pattern 41 can be ensured, as the image that overlaps with or is adjacent to the image pattern 41 is formed on a photoreceptor located downstream. Conversely, the smaller the image pattern 41 can be made, the less toner is consumed to make up the tracking pattern, as the image that overlaps with or is adjacent to the image pattern 41 is formed on a photoreceptor located upstream.

[0052] Figure 12 is a block diagram showing the hardware configuration of the image forming apparatus 100 according to this embodiment.

[0053] As shown in Figure 12, the image forming apparatus 100 according to this embodiment includes a CPU (Central Processing Unit) 50, a ROM (Read Only Memory) 51, a RAM (Random Access Memory) 52, a printer interface 53, a plotter unit 54, and a bus line 55 that electrically connects these.

[0054] The CPU 50 controls the operation of the entire image forming apparatus 100. The program used to drive the CPU 50 is stored in the ROM 51, which is a memory device. The RAM 52 is a separate memory device from the ROM 51 and has an SVRAM that temporarily stores information being processed by the CPU 50, as well as an NVRAM that non-volatilely stores information such as parameters or tables necessary for various controls. The RAM 52 also temporarily stores input image data for image processing. The printer interface 53 is an interface circuit that receives print data input to the image forming apparatus 100 from an external computer (not shown). The plotter unit 54 is a printing unit that superimposes the tracking pattern processed by the image forming apparatus 100 onto the image data input from the printer interface 53 to form an output image on paper.

[0055] Figure 13 is a functional block diagram showing the image processing flow in the image forming apparatus 100 according to this embodiment. Various image processing operations on image data as described in Figure 13 are performed by the CPU 50 applying image data processing to image data input from the printer interface 53 and stored in the RAM 52, based on various image processing programs and processing parameters read from the ROM 51 and RAM 52.

[0056] The input image information shown in Figure 13 is image data for print output that is input to the image forming apparatus 100 via the printer interface 53. The image data is first sent to the color conversion processing unit 61, where a color conversion process is performed to convert the image information from RGB format to CMY format. Next, the black generation processing unit 62 generates black image information (Bk), and image information for each color C, M, Y, and Bk is formed. Then, the density conversion processing unit 63 performs density conversion processing of the image information based on a pre-stored density correction table for each color, and subsequently, the gradation conversion processing unit 64 performs gradation conversion processing of the image information. The C, M, and Bk image data that has undergone gradation conversion processing is sent to the plotter unit 54 as output image data.

[0057] Furthermore, as shown in Figure 13, the tracking pattern is read out by the pattern generation unit 31 as pattern information to be superimposed on the output image based on information pre-stored in the pattern storage unit 60 provided in the ROM 51, and sent to the pattern discrimination unit 34. In the pattern discrimination unit 34, the position of the tracking pattern relative to the image of each color is determined based on the pattern information and the image information of each color C, M, Y, Bk sent from the gradation processing unit 64. That is, it is determined whether the tracking pattern is an image part pattern placed at a position overlapping with or adjacent to the image, or a non-image part pattern placed at a position away from the image. Then, in the pattern formation unit 33, a tracking pattern corresponding to the image part pattern or non-image part pattern is formed based on the determination result of the pattern discrimination unit 34. In the example of this embodiment, since the tracking pattern is formed using yellow toner, the information of the tracking pattern formed in the pattern formation unit 33 is superimposed with the yellow image information Y generated by the gradation conversion processing unit 64, and sent to the plotter unit 54 as new yellow image information Y. The plotter unit 54 forms an output image based on the C, M, and Bk image information transmitted from the grayscale conversion processing unit 64, and the yellow image information Y, which is obtained by superimposing tracking pattern information onto the yellow image information transmitted from the grayscale conversion processing unit 64.

[0058] Figure 14 is a simplified diagram showing the image information used in the pattern discrimination unit 34 according to this embodiment.

[0059] As shown in Figure 14(a), in this embodiment, tracking pattern A is formed so as to be distributed throughout the entire image forming region. Therefore, in this embodiment, in order to determine whether or not an input image (Bk)(C)(M)(Y) exists at a position that overlaps with or is adjacent to each tracking pattern A, a region 70a containing its vicinity is set for each tracking pattern A, and the pattern discrimination unit 34 determines whether or not an input image (Bk)(C)(M)(Y) of each color is contained within that region 70a. Specifically, as shown in Figures 14(b) to (e), regions 70b to 70e corresponding to the region 70a of each tracking pattern A are set for each input image (Bk)(C)(M)(Y) of each color, and it is determined whether or not an input image (Bk)(C)(M)(Y) of each color exists within each region 70b to 70e.

[0060] Figure 15 is a flowchart of the pattern discrimination process in the pattern discrimination unit 34 according to this embodiment.

[0061] As shown in Figure 15, in this embodiment, after the input image processing is performed by the color conversion processing unit 61, ink generation processing unit 62, density conversion processing unit 63, and gradation conversion processing unit 64, the input images (Bk)(C)(M)(Y) of each color are sequentially compared with the tracking pattern images. That is, for each region 70a containing each tracking pattern A shown in Figure 14, the regions 70b to 70e of the corresponding input images (Bk)(C)(M)(Y) of each color are scanned. Then, it is determined whether or not an input image exists within the regions 70b to 70e of the input images (Bk)(C)(M)(Y) of each color. As a result, if an input image exists, the tracking pattern A corresponding to that region is determined to be an image pattern, and if an input image does not exist, the tracking pattern A corresponding to that region is determined to be a non-image pattern.

[0062] Then, once scanning is complete for the regions 70b to 70e of the input images (Bk)(C)(M)(Y) corresponding to all tracking patterns, the comparison between the input images (Bk)(C)(M)(Y) and the tracking pattern images is terminated. This determines whether each tracking pattern is an image pattern or a non-image pattern. Based on this determination, the pattern forming unit 33 forms a tracking pattern corresponding to whether it is an image pattern or a non-image pattern.

[0063] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention.

[0064] Furthermore, the present invention is not limited to cases where it is applied to a color image forming apparatus that indirectly transfers images on multiple photoreceptors 2 to paper P via an intermediate transfer belt 11, as shown in Figure 1, but is also applicable to a monochrome image forming apparatus that has only one photoreceptor 2 and directly transfers the image on that photoreceptor 2 to paper P without using an intermediate transfer belt, as shown in Figure 16. Moreover, the present invention is also applicable to an image forming apparatus that directly transfers images on multiple photoreceptors 2 to paper P, as shown in Figure 17. In such an image forming apparatus, the visibility of the pattern image (identification pattern) varies depending on whether the pattern image (identification pattern) is an image part pattern placed in a position that overlaps with or is adjacent to the image, or a non-image part pattern that is not placed in either a position that overlaps with or is adjacent to the image. Therefore, by applying the present invention, it is possible to ensure particularly good visibility of the non-image part pattern.

[0065] Furthermore, the present invention is not limited to image forming apparatuses that form tracking patterns for identifying which apparatus formed the image, but is also applicable to image forming apparatuses that form identification patterns for other purposes.

[0066] To summarize the embodiments of the present invention described above, the present invention includes an image forming apparatus having at least the following configuration.

[0067] [First Structure] The first configuration is an image forming apparatus comprising: an image carrier that carries an image and an identification pattern; an image forming unit that forms the image on the image carrier; a pattern forming unit that forms the identification pattern on the image carrier; a transfer unit that directly or indirectly transfers the image and the identification pattern on the image carrier to a recording medium; and a pattern determination unit that determines whether the identification pattern is an image part pattern that is positioned at a position overlapping with or adjacent to the image, or a non-image part pattern that is not positioned at either a position overlapping with or adjacent to the image, wherein the non-image part pattern is formed larger than the image part pattern.

[0068] [Second Structure] The second configuration is an image forming apparatus that, in the first configuration, increases the number of dots constituting the identification pattern, thereby forming the non-image pattern larger than the image pattern.

[0069] [The third structure] The third configuration is an image forming apparatus that, in the first configuration, makes the non-image pattern larger than the image pattern by making the dots constituting the identification pattern larger.

[0070] [Fourth component] The fourth configuration is an image forming apparatus in which, in any one of the first to third configurations, the image pattern is formed larger the lower the density of the image that overlaps with or is adjacent to the image pattern.

[0071] [Fifth Structure] The fifth configuration is an image forming apparatus that, in any one of the first to fourth configurations, comprises a plurality of image carriers, wherein images on the plurality of image carriers are sequentially transferred to a recording medium, or sequentially transferred to an intermediate transfer body before being transferred to the recording medium, wherein the identification pattern is formed on the image carrier located upstream in the direction of movement of the recording medium or the intermediate transfer body among the plurality of image carriers, and the image pattern is formed larger the more the image overlaps with or is adjacent to the image carrier located downstream in the direction of movement of the recording medium or the intermediate transfer body. [Explanation of symbols]

[0072] 2. Photoreceptor (image carrier) 11. Intermediate transfer belt (intermediate transfer body) 33 Pattern forming section 34 Pattern discrimination unit 41 Image Pattern 42 Non-image pattern 54 Plotter Unit (Image Forming Section) 100 Image forming apparatus A. Tracking pattern (identification pattern) Image B N1a, N1b, N1c, N1d Primary transfer section N2 Secondary Transfer Section P Paper (recording medium) [Prior art documents] [Patent Documents]

[0073] [Patent Document 1] Japanese Patent Publication No. 2017-151135

Claims

1. An image carrier that carries an image and an identification pattern, An image forming unit that forms the image on the image carrier, A pattern forming unit for forming the identification pattern on the image carrier, A transfer unit that directly or indirectly transfers the image and the identification pattern on the image carrier to a recording medium, The system includes a pattern determination unit that determines whether the identification pattern is an image portion pattern located at a position overlapping with or adjacent to the image, or a non-image portion pattern located at neither a position overlapping with nor adjacent to the image. The image forming apparatus is characterized in that the non-image pattern is formed to be larger than the image pattern.

2. The image forming apparatus according to claim 1, wherein the non-image pattern is formed to be larger than the image pattern by increasing the number of dots that constitute the identification pattern.

3. The image forming apparatus according to claim 1, wherein the non-image portion pattern is formed to be larger than the image portion pattern by making the dots constituting the identification pattern larger.

4. The image forming apparatus according to any one of claims 1 to 3, wherein the lower the density of the image that overlaps with or is adjacent to the image pattern, the larger the image pattern is formed.

5. The image carrier comprises a plurality of the aforementioned images, An image forming apparatus in which images on multiple image carriers are sequentially transferred to a recording medium, or are sequentially transferred to an intermediate transfer medium before being transferred to the recording medium, The identification pattern is formed on the image carrier located at the upstream end of the movement direction of the recording medium or the intermediate transfer body among the plurality of image carriers. The image forming apparatus according to any one of claims 1 to 3, wherein the image that overlaps with or is adjacent to the image portion pattern is an image formed on the image carrier located downstream in the direction of movement of the recording medium or the intermediate transfer body, the larger the image portion pattern is formed.

Images