JP7434798B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art Conventionally, a method called "additional printing" has been used in which an image is later added to a sheet of paper on which an image has been printed in advance. Hereinafter, an image printed in advance will be referred to as a "printed image", and an image that will be printed later will be referred to as a "reprint image".

In reprint printing, the image forming apparatus prints the reprint image on the paper in accordance with a reference mark called an "eye mark" printed on the paper in advance, thereby setting the reprint image to a predetermined value relative to the already printed image. I'm trying to adjust it to the position. FIG. 14 is an explanatory diagram showing an example of a conventional overprint image. In the example shown in FIG. 14, the image forming apparatus transports the paper in the direction of arrow A1 (from the right side to the left side in the drawing), and prints the printed image PR formed a predetermined distance downstream from the eye mark MK. An additional printing image IM is formed so as to overlap therewith.

However, in the image forming apparatus, the position of the eye mark detection means may differ from the design value due to production errors of the image forming apparatus. Further, especially in electrophotographic image forming apparatuses, the rollers that convey paper may thermally expand due to the influence of internally generated heat, causing a change in conveyance speed. Therefore, in reprint printing, test printing is usually performed to detect the amount of positional deviation of the reprint image with respect to the already printed image, and to correct the image forming position on the paper.

By the way, the amount of positional deviation of an image can be detected by photographing the printed image with a camera and performing image recognition. However, cameras that can accurately recognize images printed at high speed are expensive. Therefore, if such a camera is introduced into an image forming apparatus, manufacturing costs will increase. Therefore, it has been very difficult to introduce such a camera into an image forming apparatus.

On the other hand, as a technique for correcting the image forming position on paper by detecting the amount of positional deviation of an image, there are techniques such as those disclosed in Patent Document 1 and Patent Document 2, for example. Patent Document 1 describes a technique in which a printed mark is detected after gravure printing and the deviation is adjusted by a path adjustment means. However, Patent Document 1 does not describe a specific means for detecting the amount of stock. Furthermore, Patent Document 2 describes a technique that detects the amount of deviation of the register mark and, if it is greater than a predetermined value, performs register adjustment using a different means from the normal method. However, Patent Document 2 does not describe a specific means for detecting the size of the equivalent amount.

JP2016-13681A Japanese Patent Application Publication No. 2004-262072

The prior art disclosed in Patent Documents 1 and 2 proposes a configuration that detects the positional shift of the reprint image and adjusts the distance from the eye mark to the formation position of the reprint image. However, the conventional techniques disclosed in Patent Documents 1 and 2 have large-scale mechanisms, and do not have a mechanism that accurately detects the amount of positional deviation of a reprinted image with an inexpensive configuration. Therefore, the manufacturing costs of the conventional techniques disclosed in Patent Documents 1 and 2 are high.

The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide an image forming apparatus that obtains the amount of positional deviation of a reprinted image with a simple configuration.

The above-mentioned problems of the present invention are solved by the following means.

(1) An image forming apparatus that includes a first detection section that detects a mark formed in advance on a sheet of paper; and a rectangular shape formed on the sheet of paper based on the square mark detected by the first detection section. an image forming unit that forms an additional printing image; and a second detection unit that detects the mark formed on the paper and the additional printing image and outputs a binary detection signal of high and low representing a detection position. and a calculation unit that calculates the amount of positional deviation of the additional printing image based on the detection signal representing the detected position of the additional printing image and the mark detected and output by the second detection unit. , the image forming unit is configured to form the additional printing image in a rectangular shape, which is long in the direction perpendicular to the conveyance and short in the conveyance direction, and whose length in the conveyance direction is shorter than the length of the mark in the conveyance direction. An image forming apparatus that forms an image on the mark in a conveyance direction .

(2) The image forming apparatus according to (1), wherein the image forming unit forms an overprint image at a position in the conveyance direction of the paper with respect to the mark.

(3) The image forming apparatus according to (1) or (2) above, including a position correction section that corrects the image forming position on the paper based on the positional shift amount.

(4) The image forming apparatus according to any one of (1) to (3) above, including a display unit that displays the amount of positional deviation.

(5) The operation display unit that accepts operation input from the user and displays the status of the image forming apparatus has a reception unit that accepts correction of the image forming position on the paper. The image forming apparatus according to any one of the items.

(6) The image forming unit according to any one of (1) to (5) above, wherein the image forming unit forms the additional printing image on both the upstream side and the downstream side of the conveyance direction with respect to the mark. Device.

(7) Any one of (1) to (6) above, wherein the image forming unit forms the additional printing image at a position corresponding to the length of the mark detected by the first detection unit in the conveyance direction. The image forming apparatus described in .

(8) The length in the conveyance direction of the mark detected by the first detection unit before the formation of the overprint image, and the length in the conveyance direction of the mark detected by the second detection unit after the formation of the overprint image. The image forming apparatus according to any one of (1) to (7) above, further comprising a comparison section that detects a detection failure by comparing the .

(9) The image forming apparatus according to any one of (1) to (8), wherein the image forming unit forms the additional printing image in the same phase in the conveyance direction with respect to the mark.

(10) The image according to any one of (1) to (9) above, wherein one or both of the first detection unit and the second detection unit uses a sensor that detects the presence or absence of an image. Forming device.

(11) When detecting the mark and the reprint image, the calculation unit calculates a combination of rising and falling edges of the detection signal output from the second detection unit before and after the mark. The image forming apparatus according to any one of (1) to (10) above, which compares the periods of (1) to (10).

(12) In any one of (1) to (11) above, the image forming unit forms a plurality of overprint images on both the upstream side and the downstream side in the conveyance direction with respect to one mark. The image forming apparatus described above.

According to the present invention, it is possible to obtain the amount of positional deviation of a reprint image with a simple configuration.

1 is a schematic diagram showing the overall configuration of an image forming system including an image forming apparatus according to an embodiment. 1 is a block diagram showing the internal configuration of an entire image forming system including an image forming apparatus according to an embodiment. 3 is a flowchart showing the operation of the image forming system. FIG. 3 is an explanatory diagram of an eye mark used in the embodiment. FIG. 3 is an explanatory diagram of a reprint image according to the embodiment. FIG. 2 is an explanatory diagram (1) of defect detection. FIG. 2 is an explanatory diagram (2) of defect detection. FIG. 7 is an explanatory diagram (1) of an additional printing image of a first modification. FIG. 7 is an explanatory diagram (2) of the reprint image of the first modification. FIG. 3 is an explanatory diagram of a state in which an eye mark and a reprint image overlap. FIG. 7 is an explanatory diagram (1) of a reprint image of a second modification. FIG. 7 is an explanatory diagram (2) of an additional printing image of a second modification. FIG. 7 is an explanatory diagram (3) of an additional printing image of a second modification. FIG. 6 is an explanatory diagram (1) in which the additional printing images are formed at positions with different phases in the conveying direction with respect to the eye mark. FIG. 6 is an explanatory diagram (2) in which the additional printing image is formed at a position with a different phase in the conveyance direction with respect to the eye mark. FIG. 7 is an explanatory diagram of a reprint image of a third modification. FIG. 2 is an explanatory diagram (1) showing an example of a period suitable for detection. FIG. 3 is an explanatory diagram (2) showing an example of a period suitable for detection. FIG. 3 is an explanatory diagram (3) showing an example of a period suitable for detection. FIG. 7 is an explanatory diagram of a reprint image of a fourth modification. FIG. 7 is an explanatory diagram of a reprint image of a fifth modification. FIG. 7 is an explanatory diagram of a reprint image of a sixth modification. FIG. 2 is an explanatory diagram showing an example of a conventional overprint image.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each figure is merely shown schematically to the extent that the present invention can be fully understood. Therefore, the present invention is not limited to the illustrated example. Further, in each figure, common or similar components are denoted by the same reference numerals, and redundant explanation thereof will be omitted.

<Configuration of image forming system>
The configuration of an image forming system SYS including an image forming apparatus 100 according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing the overall configuration of the image forming system SYS. FIG. 2 is a block diagram showing the internal configuration of the entire image forming system SYS. Here, the description will be made assuming that the image forming apparatus 100 is a printer that forms images by an electrophotographic process. In the following description, "upstream side" and "downstream side" are based on the paper conveyance direction.

As shown in FIGS. 1 and 2, the image forming system SYS includes a paper feeding device 50, an image forming apparatus 100, and a paper discharging device 200. The paper feeding device 50, the image forming device 100, and the paper discharging device 200 are respectively arranged in order from the upstream side (right side in the drawing) to the downstream side (left side in the drawing). Note that the configuration of the image forming system SYS shown in FIG. 1 is only an example, and the configuration may include other devices (for example, a post-processing device for cutting paper, etc.) that are not shown.

The paper feeding device 50 includes a control section 51, a communication section 52, a paper feeding section 55, a paper feeding adjustment section 56, a conveying section 58, and a sensor 59. The control unit 51 controls each unit within the paper feeding device 50 based on instructions from the control unit 101 of the image forming apparatus 100. The communication unit 52 communicates with other devices such as the image forming device 100. The paper feed unit 55 supplies a long sheet of paper (hereinafter sometimes simply referred to as “paper”) from a paper roll toward the image forming apparatus 100 . The paper feed adjustment section 56 adjusts the tension and slackness of the paper supplied from the paper feed section 55 and absorbs fluctuations in the conveyance speed. The conveying unit 58 conveys paper within the paper feeding device 50. The sensor 59 detects various states regarding paper conveyance.

A plurality of eye marks MK (see FIG. 4A) are formed (printed) in advance at predetermined intervals on the edge of the long sheet of paper supplied from the paper feeder 50 to the image forming apparatus 100. The eye mark MK is an image that functions as a reference mark (a mark indicating a reference position relative to a target position) for registration processing. In the image forming apparatus 100, the image forming unit 150 forms (prints) an additional printing image IM (see FIG. 4B) at a predetermined position on the long sheet of paper using the eye mark MK as a reference. The additional printing image IM is an image that functions as a register mark (a mark indicating a target position).

The image forming apparatus 100 includes a control section 101, a communication section 102, a print controller 103, a storage section 104, an operation display section 105, a transport section 107, a first detection section 109, a document reading section 110, It includes a RIP processing section 120, a data storage section 130, an image processing section 140, an image forming section 150, a fixing section 160, and a second detection section 190.

Control unit 101 controls the overall operation of image forming apparatus 100 . The control unit 101 includes a calculation unit 101a, a position correction unit 101b, and a comparison unit 101c.
The calculation unit 101a calculates the positional shift amount of the additional printing image IM based on the eye mark MK (see FIG. 4B) detected by the second detection unit 190 and the additional printing image IM (see FIG. 4B).
The position correction unit 101b corrects the image forming position on the paper based on the positional shift amount of the reprint image IM (see FIG. 4B) calculated by the calculation unit 101a.
The comparison unit 101c compares arbitrary pieces of information. For example, the comparison unit 101c compares the length of the eye mark MK in the transport direction detected by the first detection unit 109 before forming the additional printing image IM (before printing), and the length of the eye mark MK detected by the first detection unit 109 before forming the additional printing image IM (after printing), and The length of the eye mark MK detected by the second detection unit 190 in the transport direction is compared. Thereby, the comparison unit 101c detects a detection failure in the first detection unit 109 or the second detection unit 190.

The communication unit 102 communicates with other devices (external devices, paper feed device 50, paper discharge device 200, etc.).
The print controller 103 receives job data written in a page description language from an external device and stores it as necessary.
The storage unit 104 stores various settings.

The operation display unit 105 receives operation inputs from the user and displays the status of the image forming apparatus 100. The operation display section 105 includes a display section 105a that displays various information and a reception section 105b that receives operations from an operator. The display unit 105a can display, for example, the positional deviation amount ΔL11 (see FIG. 4B) of the reprint image IM (see FIG. 4B). The accepting unit 105b can accept corrections to the image forming position on the paper. Therefore, the operator of the image forming apparatus 100 can check the amount of positional deviation on the display unit 105a and manually correct the image forming position on the paper from the reception unit 105b.
The transport unit 107 transports paper within the image forming apparatus 100 .

The first detection section 109 is a detection means provided upstream of the image forming section 150. The first detection unit 109 detects an eye mark MK (see FIG. 4A) that is previously formed on the paper. Further, the first detection unit 109 detects various states of paper related to image formation and paper transport. In the example shown in FIG. 1, the first detection section 109 is arranged inside the intake section 108 provided on the side surface of the main body of the image forming apparatus 100. The take-in unit 108 guides the paper supplied to the image forming apparatus 100 from the paper feeder 50 to approximately the same height as the secondary transfer roller 158 and takes it into the image forming apparatus 100 .

The document reading unit 110 reads an image of a document using an image sensor and generates document image data.
The RIP processing unit 120 executes RIP processing on job data before RIP (Raster Image Processor) processing, which is written in a page description language received by the print controller 103, to create image-formable data called raster image data. Convert to bitmap format image data.

The data storage unit 130 stores image data and various data when forming an image. Note that the data storage unit 130 includes a reading image memory that receives image data, and a printing image memory that outputs the received image data for image formation.

The image processing unit 140 performs various image processing necessary for image formation.
The image forming unit 150 forms an image on paper using toner (developer) based on the image forming command and image data stored in the print image memory in the data storage unit 130. Image forming section 150 is arranged upstream of fixing section 160 (see FIG. 1).
The fixing unit 160 heats and presses the image (toner image) formed on the paper to fix it on the paper.

The second detection section 190 is a detection means provided downstream of the image forming section 150. The second detection unit 190 detects both the eye mark MK (see FIG. 4B) and the additional printing image IM (see FIG. 4B) that are previously formed on the paper. Although a relatively expensive camera can be used as the second detection unit 190, it is preferable to use a relatively inexpensive sensor that detects the presence or absence of an image. The presence or absence of an image may be detected by detecting the background color of the paper and other colors, or by detecting the color density of the image. Examples of the sensor that detects the presence or absence of an image include a binary sensor and an optical sensor such as a CCD sensor. Among them, binary sensors are particularly inexpensive sensors that detect only the presence or absence of an image. Therefore, the image forming apparatus 100 can particularly reduce manufacturing costs when a binary sensor is used as the second detection section 190.

The paper discharge device 200 includes a control section 201, a communication section 202, a cutting section 203, a paper discharge adjustment section 205, a transport section 206, a paper discharge section 208, and a sensor 209. The control unit 201 controls each unit in the paper ejecting device 200 based on the control of the control unit 101. The communication unit 202 communicates with other devices such as the image forming apparatus 100. The cutting unit 203 cuts the long sheet of paper at a predetermined position. The paper discharge adjustment unit 205 adjusts the tension of the paper discharged from the image forming apparatus 100 and absorbs fluctuations in the conveyance speed. The transport unit 206 transports the paper within the paper ejecting device 200. The paper discharge unit 208 winds up the long sheet of paper conveyed from the image forming apparatus 100 to the paper discharge device 200 into a roll shape and discharges the paper as a paper roll. A sensor 209 detects various states regarding paper conveyance.

<Configuration of image forming section>
For example, as shown in FIG. 1, the image forming section 150 of the image forming apparatus 100 includes a photosensitive drum 151, a charging device 152, an exposure device 153, a developing device 154, and a drum cleaner 155. , an intermediate transfer belt 156 , a primary transfer roller 157 , and a secondary transfer roller 158 .

The photosensitive drum 151 is an image carrier that temporarily carries an image (toner image) formed with toner. The photosensitive drum 151 rotates counterclockwise in the configuration shown in FIG. 1 . The charging device 152 is a device that uniformly charges the surface of the photoreceptor drum 151. The exposure device 153 is a device that exposes the surface of the photoreceptor drum 151 based on image data to form an electrostatic latent image on the surface of the photoreceptor drum 151. The exposure device 153 is configured by, for example, a laser irradiation device. The developing device 154 is a member that attaches toner to the surface of the photoreceptor drum 151 by frictional charging and visualizes (develops) the electrostatic latent image formed on the surface of the photoreceptor drum 151 as a toner image. The developing device 154 includes a hopper 154a that stores toner used in the developing device 154, and a replenishment section 154b that replenishes the toner to the hopper 154a. The drum cleaner 155 is a mechanism that cleans the surface of the photoreceptor drum 151. The intermediate transfer belt 156 is an endless belt to which the toner image formed on the surface of the photoreceptor drum 151 is transferred. Intermediate transfer belt 156 runs clockwise in the configuration shown in FIG. 1 . The primary transfer roller 157 is a member that transfers the toner image formed on the surface of the photoreceptor drum 151 to the outer peripheral surface of the intermediate transfer belt 156. The primary transfer roller 157 is arranged at a position facing the photosensitive drum 151 on the inner peripheral side of the intermediate transfer belt 156 . The primary transfer roller 157 attracts the toner image formed on the surface of the photoreceptor drum 151 and transfers it onto the intermediate transfer belt 156 by applying a voltage from a voltage supply means (not shown). The secondary transfer roller 158 is a member that transfers the toner image transferred onto the outer circumferential surface of the intermediate transfer belt 156 onto a sheet of paper. The secondary transfer roller 158 is disposed on the outer peripheral side of the intermediate transfer belt 156 at a position downstream of the photosensitive drum 151 corresponding to black (K). The secondary transfer roller 158 has the same configuration as the primary transfer roller 157, and by applying a voltage from a voltage supply means (not shown), transfers the toner image transferred to the outer peripheral surface of the intermediate transfer belt 156. Transfer to paper.

In this embodiment, the image forming apparatus 100 includes a photosensitive drum 151 and a charging device as components corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K). 152, an exposure device 153, a developing device 154, a drum cleaner 155, and a primary transfer roller 157. These components have the same configuration except that the color of toner contained in the developing device 154 is different.

The image forming apparatus 100 forms a color image by forming an image using toner of each color on the surface of a photoreceptor drum 151 corresponding to each color, and superimposing and transferring the image of each color onto the outer peripheral surface of an intermediate transfer belt 156. be able to.

Note that the present embodiment will be described assuming that the image forming section 150 is configured to form a color image using toner of a plurality of colors. However, the image forming unit 150 is not limited to this, and may be configured to form a single color image using toner of any one of YMCK colors. Note that FIGS. 1 and 2 merely show an example of the configuration of the image forming apparatus 100, and the configuration of the image forming apparatus 100 is not limited to the configuration shown in FIGS. 1 and 2.

<Operation of image forming system>
The operation of the image forming apparatus 100 will be described below with reference to FIG. 3. FIG. 3 is a flowchart showing the operation of the image forming system SYS. Here, a case will be described assuming that a reprint image IM (see FIG. 4B) is test printed using the eye mark MK (see FIGS. 4A and 4B) as a reference.

As shown in FIG. 3, the image forming system SYS supplies paper on which the eye mark MK (see FIGS. 4A and 4B) is formed (printed) from the paper feeding device 50 to the image forming apparatus 100 (step S105).

The image forming apparatus 100 takes in the paper supplied from the paper feeding device 50 and conveys it toward the paper discharging device 200 . At this time, the image forming apparatus 100 detects the eye mark MK (see FIGS. 4A and 4B) with the first detection section 109 provided upstream of the image forming section 150 (step S110).

Next, while the image forming apparatus 100 is transporting the paper using the transport unit 107, the image forming unit 150 moves the paper to a position that satisfies the following conditions based on the position of the eye mark MK detected by the first detection unit 109. A reprint image IM (see FIG. 4B) is formed (printed) (step S115).
(Condition) The condition is that the position is in the same phase in the transport direction with respect to the eye mark MK, and the position is a predetermined distance from the eye mark MK.
Here, "a position at the same phase in the transport direction with respect to the eye mark MK" means a position in which the eye mark MK overlaps in the transport direction and is not shifted in the transport orthogonal direction with respect to the eye mark MK.

In the example shown in FIG. 4B, the image forming apparatus 100 forms the reprint image IM at a position downstream of the eye mark MK by a predetermined distance L01. Hereinafter, the additional printing image IM formed on the downstream side of the eye mark MK may be referred to as the "overprinting image IMb."

Next, the image forming apparatus 100 detects the eye mark MK and the additional printing image IM with the second detection unit 190 (step S120), and outputs the detection signal SG (see FIG. 4B) to the control unit 101.

Next, in the image forming apparatus 100, based on the detection signal SG (see FIG. 4B) outputted from the second detection section 190 to the control section 101, the calculation section 101a calculates the difference between the eye mark MK and the reprint image IM. A separation distance L11 (see FIG. 4B) is calculated (measured). Furthermore, the calculation unit 101a calculates the positional deviation amount ΔL11 (see FIG. 4B) of the separation distance L11 with respect to the predetermined distance L01 (step S125).

Next, the image forming apparatus 100 uses the position correction unit 101b to adjust (correct) the image forming position on the paper based on the calculated positional deviation amount ΔL11 (step S130). Thereby, the image forming apparatus 100 can eliminate the positional shift of the image. As a result, the image forming apparatus 100 can suppress the occurrence of image misalignment in subsequent image formation.

Note that the paper conveyed from the image forming apparatus 100 to the paper discharge device 200 is taken into the paper discharge device 200. The paper discharge device 200 winds up paper into a roll shape and discharges the paper as a paper roll.

In such a configuration, the image forming apparatus 100 forms a reprint image IM of an arbitrary shape in the vicinity of the eye mark MK in order to detect the amount of positional deviation (registration deviation amount) of the formed image. Then, the image forming apparatus 100 efficiently detects the positional deviation (register deviation) of the image by calculating the positional deviation amount of the reprint image IM with respect to the eye mark MK. Thereafter, the image forming apparatus 100 adjusts (corrects) the image forming position on the paper based on the amount of positional deviation of the reprint image IM.

Such an image forming apparatus 100 can automatically correct (register) the image forming position on the paper at low cost. Further, the image forming apparatus 100 can use an inexpensive binary sensor that detects only the presence or absence of an image as the second detection unit 190. Therefore, the image forming apparatus 100 can reduce manufacturing costs.

<Composition of eye mark and reprint image>
The configurations of the eye mark MK and the reprint image IM will be described below with reference to FIGS. 4A and 4B. FIG. 4A is an explanatory diagram of the eye mark MK. FIG. 4B is an explanatory diagram of the reprint image IM.

FIG. 4A shows the waveform of the detection signal SG when the second detection unit 190 reads the eye mark MK that is previously formed on the paper. In the example shown in FIG. 4A, the second detection unit 190 detects an eye mark MK having a length LMK in the transport direction in the detection signal SG. In this embodiment, the direction of the arrow A1 (from the right side to the left side in the drawing) is the paper conveyance direction, and the left side with respect to the eye mark MK is the upstream side, and the right side is the downstream side. In the example shown in FIG. 4A, the eye mark MK is formed in a square shape. However, the eye mark MK is not limited to a square shape, but can be formed in any shape.

FIG. 4B shows the waveform of the detection signal SG when the second detection unit 190 reads the eye mark MK and the additional printing image IMb after forming the additional printing image IMb as the additional printing image IM. The additional printing image IMb is an image formed at a position downstream of the eye mark MK by a predetermined distance L01. The shape of the additional printing image IMb can be set arbitrarily. In the example shown in FIG. 4B, the reprint image IMb has a rectangular shape that is long in the transport direction (direction perpendicular to arrow A1 shown in FIG. 4A) and short in the transport direction (direction of arrow A1 shown in FIG. 4A). is formed. The additional printing image IMb is formed with a length LIMb in the transport direction. However, the additional printing image IMb is not limited to this shape, and can be formed in any shape.

In the example shown in FIG. 4B, in the detection signal SG, the second detection unit 190 detects an eye mark MK having a length LMK in the transport direction and an additional printing image IMb having a length LIMb in the transport direction. In the example shown in FIG. 4B, a positional deviation corresponding to the positional deviation amount ΔL11 has occurred in the additional printing image IMb. As a result, the additional printing image IMb is formed at a position downstream of the eye mark MK by a distance L11.

In such a state, the calculation unit 101a calculates the positional deviation amount ΔL11 of the reprint image IMb based on the separation distance L11 and the predetermined distance L01. Thereafter, the position correction unit 101b adjusts (corrects) the image forming position on the paper based on the positional deviation amount ΔL11 of the reprint image IMb calculated by the calculation unit 101a.

Note that in the example shown in FIG. 4B, the image forming apparatus 100 forms the additional printing image IM on the downstream side of the eye mark MK, but conversely, it forms the additional printing image IM on the upstream side of the eye mark MK. You can do it like this.

When a positional shift occurs in the additional printing image IMb and a problem occurs in which the additional printing image IMb overlaps the eye mark MK, the image forming apparatus 100 performs a process as shown in FIGS. 5A and 5B, for example. Malfunctions can be detected. 5A and 5B are explanatory diagrams of defect detection, respectively.

FIG. 5A shows the state before the additional printing image IMb is formed (before printing), and FIG. 5B shows the state after the additional printing image IMb is formed (after printing). The comparison unit 101c of the image forming apparatus 100 compares the length LMK1 (see FIG. 5A) of the eye mark MK in the transport direction before forming the additional printing image IM (before printing) and the length LMK1 (see FIG. 5A) of the eye mark MK before forming the additional printing image IM (after printing). The length of the eye mark MK in the transport direction LMK2 (see FIG. 5B) is compared. When the length in the transport direction LMK2 is larger than the sum of the length in the transport direction LMK1 and the allowable error α, the comparison unit 101c determines that a problem has occurred, and rejects the paper on which the image is formed as a defective product (NG). paper).

<Modified example of reprint image>
The reprint image IM can be transformed into any shape. Modifications of the reprint image IM will be described below with reference to FIGS. 6 to 13.

(Reprint image of the first modification)
First, the reprint image IM of the first modification will be described with reference to FIGS. 6A and 6B. FIGS. 6A and 6B are explanatory diagrams of the reprint image IM of the first modification, respectively.

In the example shown in FIG. 6A, the eye mark MK has a rectangular shape and the length LMKa of the eye mark MK in the transport direction is relatively long, so a problem occurs in which the reprint image IMb overlaps the eye mark MK. ing. Therefore, as shown in FIG. 6B, the image forming apparatus 100 determines the formation position of the additional printing image IMb based on the length LMKa of the eye mark MK in the conveyance direction to prevent such an overlapping problem from occurring. , an additional printing image IMb is formed at that position. Thereby, the image forming apparatus 100 can form the reprint image IMb without overlapping the eye mark MK even if the length LMKa of the eye mark MK in the transport direction is relatively long.

(Reprint image of second modified example)
Next, with reference to FIG. 7 and FIGS. 8A to 8C, the additional printing image IM of the second modification will be described. FIG. 7 is an explanatory diagram of a state in which the eye mark MK and the reprint image IM overlap. FIGS. 8A to 8C are explanatory diagrams of the additional printing image IM of the second modification.

In the example shown in FIG. 7, a positional shift occurs in the additional printing image IM, causing a problem that the additional printing image IM overlaps the eye mark MK. Then, in the detection signal SG, the second detection unit 190 detects an overlapping portion between the eye mark MK and the additional printing image IM corresponding to the length LMKx in the transport direction. In the example shown in FIG. 7, the additional printing image IMb overlaps the rear end portion of the eye mark MK. However, for example, even when the reprint image IM overlaps the front end portion of the eye mark MK, the waveform of the detection signal SG has a similar waveform. Therefore, in the case of the example shown in FIG. 7, it is difficult for the image forming apparatus 100 to detect how much positional deviation has occurred in the additional printing image IM. Therefore, it is difficult for the calculation unit 101a to calculate the positional deviation amount ΔL11 of the reprint image IMb.

Therefore, as shown in FIGS. 8A to 8C, the image forming apparatus 100 preferably forms additional printing images IMf and IMb on both the upstream and downstream sides of the eye mark MK. The reprint images IMf and IMb are formed at the same distance from the eye mark MK when they are formed at ideal positions. In the example shown in FIGS. 8A to 8C, the additional printing image IMf is formed with a length LIMf in the transport direction.

In the case shown in FIG. 8A, the control unit 101 of the image forming apparatus 100 first detects the eye mark MK and the additional printing image IMf formed upstream of the eye mark MK using the second detection unit 190. Then, the calculation unit 101a of the image forming apparatus 100 calculates the positional deviation amount ΔL11 of the reprint images IMf and IMb based on the distance Lf from the front end portion of the reprint image IMf to the front end portion of the eye mark MK in the detection signal SG. calculate.

Thereafter, as shown in FIG. 8B, the position correction unit 101b of the image forming apparatus 100 adjusts the registration based on the calculated positional deviation amount ΔL11 so that both the additional printing images IMf and IMb are formed on the paper. The position (approximate directional position to aim for) is determined, the formation position of the additional printing images IMf, IMb is moved to the target position, and in this state, the additional printing images IMf, IMb are formed on the long sheet of paper. As a result, the control unit 101 of the image forming apparatus 100 detects both the eye mark MK and the reprint images IMf and IMb using the second detection unit 190.

Thereafter, the position correction unit 101b of the image forming apparatus 100 determines the register position based on the distance Lf and the distance Lb in the detection signal SG so as to eliminate the positional deviation of the image, and the reprint images IMf, IMb is moved to the target position, and in that state, additional printing images IMf and IMb are formed on the long sheet of paper. The distance Lf is the distance from the front end of the reprint image IMf to the front end of the eye mark MK. The distance Lb is the distance from the rear end of the eye mark MK to the rear end of the reprint image IMb. As a result, as shown in FIG. 8C, the image forming apparatus 100 forms reprint images IMf and IMb at positions where distance Lf and distance Lb are evenly allocated. Similarly, the image forming apparatus 100 can register the image forming position on the paper.

(Reprint image of third modification)
Next, with reference to FIGS. 9A to 9C, the reprint image IM of the third modification will be described. FIGS. 9A and 9B are explanatory diagrams in the case where the additional printing image IM is formed at different phase positions in the transport direction with respect to the eye mark MK. FIG. 9C is an explanatory diagram of the additional printing image IM of the third modification. Here, "a position at a different phase in the transport direction with respect to the eye mark MK" means a position shifted in the transport orthogonal direction with respect to the eye mark MK.

In the example shown in FIGS. 9A and 9B, the additional printing image IM is formed at a position at a different phase in the transport direction with respect to the eye mark MK. Therefore, the reprint images IMf and IMb are separated from the eye mark MK in the sub-scanning direction (vertical direction of the drawing). In such a case, the image forming apparatus 100 needs to detect the eye mark MK and the reprint images IMf and IMb using the relatively expensive second detection unit 190, which increases the manufacturing cost. .

For example, in the example shown in FIG. 9A, the second detection unit 190 is configured to have two spot sensors SN1 and SN2, and the two spot sensors SN1 and SN2 detect the eye mark MK and the overprint images IMf and IMb. It is configured to detect. Since the second detection unit 190 with this configuration includes two spot sensors SN1 and SN2, it becomes expensive accordingly. As a result, the manufacturing cost of the image forming apparatus 100 increases.

Further, for example, in the example shown in FIG. 9B, the second detection unit 190 has a configuration including one line sensor SN3, and a configuration in which the line sensor SN3 detects the eye mark MK and the reprint images IMf and IMb. It has become. The second detection unit 190 with this configuration includes the line sensor SN3, which is more expensive than the spot sensor, and therefore becomes more expensive. As a result, the manufacturing cost of the image forming apparatus 100 increases.

Therefore, in the example shown in FIG. 9C, the image forming apparatus 100 forms the reprint image IM of the third modification. The additional printing image IM of the third modification is an image formed at a position having the same phase in the transport direction (an overlapping position in the transport direction) with respect to the eye mark MK. In the example shown in FIG. 9C, the image forming apparatus 100 forms the reprint images IMf and IMb at positions with the same phase in the transport direction (overlapping positions in the transport direction) with respect to the eye mark MK. Thereby, the image forming apparatus 100 can detect the additional printing images IMf, IMb and the eye mark MK with one spot sensor SN1. Therefore, in the example shown in FIG. 9C, the second detection unit 190 is configured to have one spot sensor SN1, and the spot sensor SN1 is configured to detect the eye mark MK and the reprint images IMf and IMb. ing. Since the second detection unit 190 with this configuration has only one spot sensor SN1, it is cheaper than the second detection unit 190 with the configuration shown in FIGS. 9A and 9B. Therefore, the image forming apparatus 100 can reduce manufacturing costs.

Note that the detection operation of the second detection unit 190 in the case of forming additional printing images IMf and IMb on both the upstream side and the downstream side with respect to the eye mark MK is preferably as shown in FIG. 10C. FIG. 10A shows the ideal waveform of the detection signal SG1 and the waveform of the actual detection signal SG2 when the second detection unit 190 detects the eye mark MK. 10B and 10C show the ideal waveform of the detection signal SG1 and the waveform of the actual detection signal SG2 when the second detection unit 190 detects the eye mark MK and the reprint images IMf, IMb.

As shown in FIG. 10A, the falling point of the actual detection signal SG2 may be slightly delayed from the falling point of the ideal detection signal SG1. Therefore, there is a possibility that the period PE2 in the detection signal SG shown in FIG. 10B is not the same. The period PE1 is a period between the rising point (ON point) of the reprint image IMf and the rising point (ON point) of the eye mark MK. The period PE2 is a period between the falling point (OFF point) of the reprint image IMf and the falling point (OFF point) of the eye mark MK.

Therefore, as shown in FIG. 10C, the calculation unit 101a of the image forming apparatus 100 calculates the period of the combination of the rising point (ON point) and the falling point (OFF point) of the detection signal SG (in the example shown in FIG. 10C, , period PE3 and period PE4). The period PE3 is a period between the falling point (OFF point) of the reprint image IMf and the rising point (ON point) of the eye mark MK in the detection signal SG. The period PE4 is a period between the falling point (OFF point) of the eye mark MK in the detection signal SG and the rising point (ON point) of the reprint image IMf. Thereby, the calculation unit 101a of the image forming apparatus 100 can efficiently detect the positional deviation of the additional printing images IMf and IMb.

(Reprint image of the fourth modification)
Next, with reference to FIG. 11, the reprint image IM of the fourth modification will be described. FIG. 11 is an explanatory diagram of the additional printing image IM of the fourth modification. The reprint images IM of the fourth modification are images formed in plural numbers on both the upstream side and the downstream side with respect to the eye mark MK. In the example shown in FIG. 11, the additional printing image IM of the fourth modification is formed as two additional printing images IMf1, IMf2 on the upstream side and two additional printing images IMb1, IMb2 on the downstream side with respect to the eye mark MK. ing.

The additional printing images IMf1, IMf2 and the additional printing images IMb1, IMb2 are formed in order from the eye mark MK. The additional printing images IMf1, IMf2 and the additional printing images IMb1, IMb2 are formed line-symmetrically about their midpoints. The reprint images IMf1, IMf2 and the reprint images IMb1, IMb2 are formed at the same distance from the eye mark MK when they are formed at ideal positions.

The control unit 101 of the image forming apparatus 100 detects the eye mark MK and the additional printing images IMf1, IMf2, IMb1, and IMb2 using the second detection unit 190. The calculation unit 101a of the image forming apparatus 100 calculates the amount of positional deviation of the additional printing images IMf1, IMf2, IMb1, IMb2 based on the distances Lf1, Lf2, Lb1, Lb2 in the detection signal SG. Thereby, the calculation unit 101a of the image forming apparatus 100 can efficiently detect the positional deviation of the reprint images IMf and IMb. Note that the distance Lf1 is the distance from the rear end of the reprint image IMf1 to the front end of the eye mark MK. The distance Lf2 is the distance from the rear end of the reprint image IMf2 to the front end of the eye mark MK. The distance Lb1 is the distance from the rear end of the eye mark MK to the front end of the reprint image IMb1. The distance Lb2 is the distance from the rear end of the eye mark MK to the front end of the reprint image IMb2.

In the image forming apparatus 100, the second detection unit 190 detects the paper on which one additional printing image IM is printed for one eye mark MK multiple times, and the calculation unit 101a detects the paper on which one additional printing image IM is printed for the plurality of times using the calculation unit 101a. The amount of positional deviation may be calculated and the results of multiple calculations may be averaged. Then, the image forming apparatus 100 may correct the image forming position on the paper based on the calculated result of the averaged positional deviation amount of the additional printing image IM. Thereby, the calculation unit 101a of the image forming apparatus 100 can efficiently detect the positional shift of the additional printing image IM.

(Reprint image of the fifth modification)
Next, with reference to FIG. 12, the additional printing image IM of the fifth modification will be described. FIG. 12 is an explanatory diagram of the additional printing image IM of the fifth modification. The additional printing image IM of the fifth modification is an image formed in the transport direction and the transport orthogonal direction with respect to the eye mark MK. In the example shown in FIG. 12, the additional printing image IM of the fifth modification is formed as a rectangular additional printing image IMs surrounding the eye mark MK.

Here, supplementary explanation will be given regarding the additional printing image IM of the fifth modification. For example, paper expands and contracts under the influence of humidity. At this time, the paper expands and contracts not only in the transport direction but also in a direction perpendicular to the transport direction. Therefore, it is preferable that the image forming apparatus 100 is capable of correcting the image forming position not only in the transport direction but also in the direction orthogonal to transport. Therefore, the image forming apparatus 100 may form an image at a position in the paper conveyance direction and a position perpendicular to the conveyance direction with respect to the eye mark MK, like the reprint image IM of the fifth modification.

For example, in the example shown in FIG. 12, the image forming apparatus 100 forms a rectangular additional printing image IMs surrounding the eye mark MK as the additional printing image IM of the fifth modification. Note that the second detection unit 190 preferably uses a line sensor so that it can detect images in a direction perpendicular to the conveyance direction.

In the image forming apparatus 100, the line sensor SN3 of the second detection unit 190 detects the eye mark MK and the additional printing image IMs in the sheet conveyance direction, and generates a detection signal SGa. Furthermore, the image forming apparatus 100 detects the eye mark MK and the additional printing image IMs in the direction orthogonal to the conveyance of the paper using the line sensor SN3 of the second detection unit 190, and generates the detection signal SGb.

In the detection signal SGa, the distance Lf represents the distance from the front end of the reprint image IMs (left end in the drawing) to the front end of the eye mark MK, and the distance Lb represents the distance from the rear end of the eye mark MK (right end in the drawing). It represents the distance to the rear end of the additional printing image IMs.

In the detection signal SGb, the distance Lr represents the distance from the right end of the reprint image IMs (upper end in the drawing) to the right end of the eye mark MK, and the distance Ll represents the distance from the left end of the eye mark MK (lower end in the drawing) to the reprint image IMs. It represents the distance to the left edge of the printed image IMs.

The calculation unit 101a of the image forming apparatus 100 detects the offset direction of the reprint image IMs in the direction perpendicular to the conveyance based on the eye mark MK detected by the second detection unit 190 and the reprint image IMs, and The amount of positional shift of the additional printing image IMs in the offset direction is calculated. Thereby, the calculation unit 101a of the image forming apparatus 100 can efficiently detect the positional shift of the additional printing image IMs. Thereafter, the image forming unit 150 forms an additional printing image IMs so as to eliminate the amount of positional deviation in the offset direction with respect to the eye mark MK of the long paper. Then, the image forming apparatus 100 detects again whether there is a positional shift in the additional printing image IMs.

(Reprint image of the 6th modification)
Next, with reference to FIG. 13, the additional printing image IM of the sixth modification will be described. FIG. 13 is an explanatory diagram of the additional printing image IM of the sixth modification. Similar to the additional printing image IM of the fifth modification, the additional printing image IM of the sixth modification is an image formed in the transport direction and the transport orthogonal direction with respect to the eye mark MK. In the example shown in FIG. 13, the additional printing image IM of the sixth modification is formed as four bar-shaped additional printing images IMsf, IMsb, IMsr, and IMsl surrounding the eye mark MK.

For example, in the example shown in FIG. 13, the image forming apparatus 100 generates four bar-shaped additional printing images IMsf, IMsb, IMsr, and IMsl surrounding the eye mark MK as the additional printing images IM of the sixth modification. is forming. The additional printing image IMsf is formed on the front side (on the left side in the drawing) of the eye mark MK. The additional printing image IMsb is formed on the rear side (on the right side in the drawing) of the eye mark MK. The additional printing image IMsr is formed on the right side (upper side in the drawing) of the eye mark MK. The additional printing image IMsl is formed on the left side (lower side in the drawing) of the eye mark MK. Note that the second detection unit 190 preferably uses a line sensor so that it can detect images in a direction perpendicular to the conveyance direction.

The image forming apparatus 100 detects the eye mark MK and the reprint images IMsf, IMsb, IMsr, and IMsl in the sheet conveyance direction with the line sensor SN3 of the second detection unit 190, and generates a detection signal SGa. Further, the image forming apparatus 100 detects the eye mark MK and the reprint images IMsf, IMsb, IMsr, and IMsl in the direction orthogonal to the sheet conveyance using the line sensor SN3 of the second detection unit 190, and generates a detection signal SGb.

In the detection signal SGa, the distance Lf represents the distance from the front end of the reprint image IMsf (left end in the drawing) to the front end of the eye mark MK, and the distance Lb represents the distance from the rear end of the eye mark MK (right end in the drawing). It represents the distance to the rear end of the additional printing image IMsb.

In the detection signal SGb, the distance Lr represents the distance from the right end of the reprint image IMsr (upper end in the drawing) to the right end of the eye mark MK, and the distance Ll represents the distance from the left end of the eye mark MK (lower end in the drawing) to the right end of the reprint image IMsr (lower end in the drawing). It represents the distance to the left edge of the printed image IMsl.

The calculation unit 101a of the image forming apparatus 100 calculates the portion of the additional printing images IMsr, IMsl in the direction orthogonal to the transport direction based on the eye mark MK detected by the second detection unit 190 and the additional printing images IMsf, IMsb, IMsr, IMsl. The offset direction is detected, and the amount of positional shift of the additional printing images IMsr and IMsl in the offset direction is calculated. Thereby, the calculation unit 101a of the image forming apparatus 100 can efficiently detect the positional deviation of the reprint images IMsf, IMsb, IMsr, and IMsl. Thereafter, the image forming unit 150 forms additional printing images IMsf, IMsb, IMsr, and IMsl on the long paper. At this time, the image forming unit 150 forms additional printing images IMsf and IMsb at positions in the transport direction with respect to the eye mark MK of the long sheet. Further, the image forming unit 150 forms reprint images IMsr and IMsl so as to eliminate the amount of positional deviation in the offset direction with respect to the eye mark MK of the long paper. Then, the image forming apparatus 100 again detects the presence or absence of positional deviation of the reprint images IMsf, IMsb, IMsr, and IMsl.

<Main features of the image forming device>
The main features of the image forming apparatus 100 will be described below.
(1) As shown in FIG. 1, the image forming apparatus 100 according to the present embodiment includes a first detection section 109, an image formation section 150, a second detection section 190, and a calculation section 101a. The first detection unit 109 detects an eye mark MK that is previously formed on the paper. The image forming section 150 forms an additional printing image IM on the paper based on the eye mark MK detected by the first detection section 109. At this time, it is preferable that the image forming unit 150 forms the additional printing image IM at a position in the sheet conveyance direction with respect to the eye mark MK. The second detection unit 190 detects an eye mark MK and an additional printing image IM that are previously formed on the paper. The calculation unit 101a calculates the positional shift amount ΔL11 (see FIG. 4B) of the additional printing image IM based on the eye mark MK detected by the second detection unit 190 and the additional printing image IM.

The image forming apparatus 100 according to the present embodiment can obtain the positional deviation amount ΔL11 (see FIG. 4B) of the reprint image IM with a simple configuration.

(2) As shown in FIG. 3, the image forming apparatus 100 according to the present embodiment includes a position correction unit 101b that corrects the image forming position on the paper based on the amount of positional deviation.

The image forming apparatus 100 according to this embodiment can automatically correct the image forming position on the paper based on the amount of positional deviation.

(3) As shown in FIG. 1, the image forming apparatus 100 according to the present embodiment preferably includes a display section 105a that displays the amount of positional deviation. Further, the image forming apparatus 100 according to the present embodiment preferably includes a receiving unit 105b that receives correction of the image forming position on the paper. In the example shown in FIG. 1, the display section 105a and the reception section 105b are provided in the operation display section 105, but they may be provided separately near the first detection section 109 and/or the second detection section 190. Good too.

In the image forming apparatus 100 according to the present embodiment, the operator can check the amount of positional deviation on the display unit 105a and manually correct the image forming position on the paper from the reception unit 105b.

(4) As shown in FIGS. 8A to 8C, the image forming unit 150 of the image forming apparatus 100 according to the present embodiment prints an additional printing image IMf on both the upstream side and the downstream side in the conveyance direction with respect to the eye mark MK. , IMb may be formed.

For example, as shown in FIG. 7, if there is only one reprint image IM, the image forming apparatus 100 may not be able to detect whether the reprint image IM has shifted upstream or downstream. In contrast, as shown in FIGS. 8A to 8C, the image forming apparatus 100 forms additional printing images IMf and IMb on both the upstream and downstream sides of the eye mark MK, so that the additional printing image IM is It is possible to efficiently detect in which direction the deviation has occurred, the upstream side or the downstream side.

(5) As shown in FIG. 6B, the image forming unit 150 of the image forming apparatus 100 according to the present embodiment follows the eye mark MK detected by the first detection unit 109 to a position corresponding to the length LMKa in the transport direction. It is preferable to form a printed image IM.

The image forming apparatus 100 according to this embodiment can prevent the eye mark MK and the reprint image IM from overlapping. Thereby, the image forming apparatus 100 can accurately detect both the eye mark MK and the additional printing image IM with the second detection unit 190.

(6) As shown in FIGS. 5A and 5B, the image forming apparatus 100 according to the present embodiment transports the eye mark MK detected by the first detection unit 109 before forming the reprint image IM (before printing). A comparison unit 101c detects a detection failure by comparing the direction length LMK1 and the conveyance direction length LMK2 of the eye mark MK detected by the second detection unit 190 after the reprint image IM is formed (after printing). has.

In the image forming apparatus 100 according to the present embodiment, the comparison unit 101c compares the length LMK1 in the transport direction before the reprint image IM is formed with the length LMK2 in the transport direction after the reprint image IM is formed. If the comparison results are significantly different, there is a possibility that an abnormality has occurred in the detection processing of the second detection unit 190 before or after the formation of the reprint image IM. Therefore, the image forming apparatus 100 according to the present embodiment verifies the accuracy (likelihood) of the detection processing of the second detection unit 190 by comparing the length LMK1 in the transport direction and the length LMK2 in the transport direction. , a detection failure in the second detection unit 190 can be detected.

(7) As shown in FIG. 9C, the image forming unit 150 of the image forming apparatus 100 according to the present embodiment may form the additional printing image IM at the same phase in the transport direction with respect to the eye mark MK.

In the image forming apparatus 100 according to the present embodiment, since the eye mark MK and the additional printing image IM are arranged at the same phase in the conveyance direction, a single spot sensor detects both the eye mark MK and the additional printing image IM. can do. That is, the image forming apparatus 100 can detect both the eye mark MK and the reprint image IM by using a single spot sensor for the second detection section 190. Spot sensors are relatively inexpensive components. The image forming apparatus 100 according to the present embodiment does not need to use a plurality of spot sensors or a line sensor, which is more expensive than a spot sensor, in the second detection unit 190, so that manufacturing costs can be reduced. .

(8) In the image forming apparatus 100 according to the present embodiment, one or both of the first detection unit 109 and the second detection unit 190 may use a sensor that detects the presence or absence of an image.

The sensor that detects the presence or absence of an image is a relatively inexpensive sensor. The image forming apparatus 100 according to the present embodiment uses a relatively inexpensive sensor instead of a relatively expensive camera for one or both of the first detection section 109 and the second detection section 190, thereby reducing manufacturing costs. can be reduced. Further, the image forming apparatus 100 can accurately detect the position of an image even though it uses a relatively inexpensive sensor.

(9) As shown in FIG. 10C, when detecting the eye mark MK and the reprint image IM, the calculation unit 101a of the image forming apparatus 100 according to the present embodiment calculates the number before and after the eye mark MK. It is preferable to compare the combination periods PE3 and PE4 of the rising and falling edges of the detection signal SG output from the second detection section 190.

The optical sensor used in the second detection unit 190 may have variations in characteristics and responsiveness between the rising side and the falling side of the signal. By comparing the periods PE3 and PE4, the calculation unit 101a of the image forming apparatus 100 according to the present embodiment can make an eye mark without being affected by variations even if there are variations in the characteristics and responsiveness of the optical sensor. Detection processing for MK and reprint image IM can be performed.

(10) As shown in FIG. 11, the image forming unit 150 of the image forming apparatus 100 according to the present embodiment may form a plurality of overprint images IM for one eye mark MK.

The image forming apparatus 100 according to the present embodiment detects each additional printing image IM with the second detection unit 190, so that when a positional deviation occurs in the additional printing image IM, the image forming apparatus 100 can detect the positional deviation. The direction and amount of positional deviation can be detected efficiently.

(11) As shown in FIGS. 12 and 13, the image forming unit 150 of the image forming apparatus 100 according to the present embodiment tracks the position of the paper in the conveyance direction and the position perpendicular to the conveyance direction with respect to the eye mark MK. It is preferable to form a printed image IM. Then, based on the eye mark MK and the additional printing image IM detected by the second detection unit 190, the calculation unit 101a of the image forming apparatus 100 according to the present embodiment calculates the deviation of the additional printing image IM in the direction orthogonal to the conveyance direction. It is preferable to detect the direction and calculate the amount of positional deviation of the additional printing image IM in the offset direction. Furthermore, it is preferable that the image forming unit 150 of the image forming apparatus 100 according to the present embodiment forms an image so as to eliminate the amount of positional deviation in the offset direction.

The image forming apparatus 100 according to the present embodiment is capable of detecting not only the positional deviation direction (registration direction) of the reprint image IM in the transport direction but also the offset direction of the reprint image IM in the direction perpendicular to the transport direction. Can be done. The image forming apparatus 100 according to the present embodiment can obtain the amount of positional deviation of the additional printing image IM in the offset direction. Furthermore, the image forming apparatus 100 according to the present embodiment can form an image so as to eliminate the amount of positional deviation in the offset direction.

As described above, according to the image forming apparatus 100 according to the embodiment, it is possible to obtain the positional deviation amount ΔL11 (see FIG. 4B) of the reprint image IM with a simple configuration.

Note that the present invention is not limited to the embodiments described above, and various changes and modifications can be made without departing from the gist of the present invention.

For example, the embodiments described above have been described in detail in order to explain the gist of the present invention in an easy-to-understand manner. Therefore, the present invention is not necessarily limited to having all the components described. Further, in the present invention, other components can be added to certain components, or some components can be changed to other components. Further, in the present invention, some components can also be deleted.

50 Paper feeding device 51 Control section 52 Communication section 55 Paper feeding section 56 Paper feeding adjustment section 58 Conveyance section 59 Sensor 100 Image forming device 101 Control section 101a Calculation section 101b Position correction section 101c Comparison section 102 Communication section 103 Print controller 104 Storage section 105 Operation display section 105a Display section 105b Reception section 108 Import section 109 First detection section 110 Original reading section 120 RIP processing section 130 Data storage section 140 Image processing section 150 Image forming section 151 Photosensitive drum 152 Charging device 153 Exposure device 154 Developing device 154a Hopper 154b Replenishment section 155 Drum cleaner 156 Intermediate transfer belt 157 Primary transfer roller 158 Secondary transfer roller 160 Fixing section 190 Second detection section 200 Paper discharge device 201 Control section 202 Communication section 203 Cutting section 205 Paper discharge adjustment section 206 Transport section 208 Paper discharge section 209 Sensor IM, IMb, IMf, IMs, IMsb, IMsf, IMsl, IMsr Reprint image L11 Separation distance ΔL11 Positional deviation amount L01, Lb, Lb1, Lb2, Lf, Lf1, Lf2, Ll, Lr Distance PE1, PE2, PE3, PE4 Period LIMb, LIMf, LMK, LMKa, lMK1, LMK2, LMKx Length in transport direction MK Eye mark (mark)
SG, SG1, SG2, SGa, SGb Detection signal SN1, SN2 Spot sensor SN3 Line sensor SYS Image forming system

Claims (12)

a first detection unit that detects marks formed in advance on the paper;
an image forming unit that forms a rectangular additional printing image on the paper based on the rectangular mark detected by the first detection unit;
a second detection unit that detects the mark formed on the paper and the additional printing image and outputs a binary detection signal of high and low representing the detection position;
a calculation unit that calculates a positional shift amount of the additional printing image based on the detection signal representing the detection position of the mark detected and output by the second detection unit and the additional printing image,
The image forming unit is configured to form the reprint image in a rectangular shape that is long in the direction perpendicular to the transport and short in the transport direction, and the reprint image has a length in the transport direction shorter than the length of the mark in the transport direction. is formed in the transport direction with respect to the mark.
Image forming device. The image forming apparatus according to claim 1, wherein the image forming unit forms an additional printing image at a position in the conveyance direction of the paper with respect to the mark. The image forming apparatus according to claim 1 or 2, further comprising a position correction section that corrects the image forming position on the paper based on the amount of positional deviation. The image forming apparatus according to any one of claims 1 to 3, further comprising a display unit that displays the amount of positional deviation. Any one of claims 1 to 4, wherein the operation display unit that accepts operation input from a user and displays the status of the image forming apparatus includes a reception unit that accepts correction of the image forming position on the paper. The image forming apparatus described in . The image forming apparatus according to any one of claims 1 to 5, wherein the image forming unit forms the additional printing image on both an upstream side and a downstream side of the mark in the conveyance direction. The image according to any one of claims 1 to 6, wherein the image forming unit forms the additional printing image at a position corresponding to the length of the mark detected by the first detection unit in the conveying direction. Forming device. The length of the mark in the transport direction detected by the first detection unit before the formation of the additional printing image, and the length of the mark in the transport direction detected by the second detection unit after the formation of the additional printing image. The image forming apparatus according to any one of claims 1 to 7, further comprising a comparing section that compares and detects a detection failure. The image forming apparatus according to any one of claims 1 to 8, wherein the image forming unit forms the additional printing image in the same phase in the conveyance direction with respect to the mark. 10. The image forming apparatus according to claim 1, wherein one or both of the first detection section and the second detection section uses a sensor that detects the presence or absence of an image. When detecting the mark and the additional printing image, the calculation unit calculates the period of the combination of the rising edge and the falling edge of the detection signal output from the second detection unit before and after the mark. The image forming apparatus according to any one of claims 1 to 10, wherein: The image forming unit according to any one of claims 1 to 11, wherein the image forming unit forms a plurality of the reprint images on both the upstream side and the downstream side in the conveyance direction with respect to one mark. Device.

Images