JP2008261941A - Positional deviation detecting device, image forming apparatus, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect positional deviation of a position on a second face corresponding to a position on the first face of a sheet type object without forming an exclusive positioning mark or the like. <P>SOLUTION: When receiving a read signal, characteristic information on random change distributed in a paper fingerprint area is read by a reading part (100 and 102). Paper fingerprint information on the paper fingerprint area of paper is stored in a RAM as a reference for detecting positional deviation (104). When receiving the read signal, characteristic information on random change distributed in a reading area is read by the reading part (106 and 108) so as to perform comparing processing (110), arithmetically calculate the deviation amount of the position in the area having coincident characteristic from the position of the center of the reading area (114), and perform correcting processing in accordance with the deviation amount of the position so that an image on the second face can be formed at the position corresponding to an image formed on the first face (116). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a misregistration detection apparatus, an image forming apparatus, and a program.

  In an image forming apparatus such as a copying machine or a printer, when an image is formed on both the first surface and the second surface of a sheet, the image is formed on the first surface and the second surface. It is necessary to prevent the position of the image from shifting.

For example, in Patent Document 1, dedicated positioning marks # 1 to # 4 are formed in the margin of a fixed paper, and the marks # 1 to # 4 are read by a first CCD line sensor provided in a refeed path. , The magnifications in the main scanning direction and the sub-scanning direction of the second surface are corrected, and the marks # 1 to # 4 are read by the second CCD line sensor arranged upstream of the conveyor belt, and the main scanning direction of the second surface, Techniques for correcting image positions in the sub-scanning direction and the rotation direction have been proposed.
JP 2000-305324 A

  The present invention has been made based on the above-described background art, and does not form a dedicated positioning mark or the like, but on a second surface corresponding to a position on the first surface of a sheet-like object such as paper. It is an object of the present invention to provide a misalignment detection apparatus, an image forming apparatus, and a program that can accurately detect misalignment of a position.

  In order to achieve the above object, the invention of claim 1 is obtained by reading a predetermined region of the first surface of the sheet-like object in which unique features having randomness are distributed from the first surface side. Storage means for storing the feature information as reference feature information, reading means for reading the feature of the sheet-like object, the reference feature information, and the first surface of the inverted sheet-like object. Comparing means for comparing read information obtained by reading the area corresponding to the predetermined area on the second surface on the opposite side by the reading means, and based on the comparison result of the comparing means, the first Misalignment detecting means for detecting misalignment of the position on the second surface corresponding to the position on the surface.

  According to the invention of claim 2, a predetermined region of the first surface of the sheet-like object in which unique characteristics having randomness are distributed is transmitted through the sheet-like object and emitted from the first surface. Storage means for storing feature information obtained by reading from the first surface side using transmitted light as reference feature information, and transmitted light that transmits the feature of the sheet-like object through the sheet-like object. Reading means for reading using, the reference feature information, and an area corresponding to the predetermined area on the second surface opposite to the first surface of the inverted sheet-like object, One piece of read information obtained by reading by the reading means using transmitted light that passes through the object and exits from the second surface, the reference feature information, and the other information of the read information The ratio of the inverted information And a positional deviation detecting means for detecting a positional deviation of the position on the second surface corresponding to the position on the first surface based on the comparison result of the comparing means. .

  According to a third aspect of the present invention, information obtained by reading by the reading means is used as the reference feature information.

  The invention according to claim 4 reads a predetermined region of the sheet-like object in which unique features having randomness are distributed from the first surface side using reflected light reflected from the sheet-like object. Storage means for storing the feature information obtained by the above as reference feature information, reading means for reading the feature of the sheet-like object using reflected light reflected from the sheet-like object, and the reference feature information And comparison means for comparing the predetermined area of the inverted sheet-like object with the reading means using the reflected light by the reading means, and based on the comparison result of the comparison means Misalignment detecting means for detecting misalignment of the position on the second surface corresponding to the position on the first surface.

  According to a fifth aspect of the present invention, the reading means is an area sensor or a line sensor.

  According to a sixth aspect of the present invention, another reading unit is provided in correspondence with the reading unit, and information obtained by reading by the other reading unit is used as the reference feature information.

  According to a seventh aspect of the present invention, the reading means and the other reading means are area sensors or line sensors.

According to an eighth aspect of the present invention, there is provided the positional deviation detection device according to any one of the first to seventh aspects, and the first surface and the second surface of the sheet-like object at an image forming position. Image forming means for forming an image, reversing means for reversing the sheet-like object having an image formed on one side thereof, and conveying the sheet-like object reversed by the reversing means to the image forming position A conveying unit; and a control unit that controls at least one of image formation by the image forming unit and conveyance by the conveying unit so that the positional deviation detected by the positional deviation detecting unit is eliminated. The invention according to claim 9 is a computer on a side opposite to the first surface corresponding to a predetermined region of the first surface of the sheet-like object in which unique characteristics having randomness are distributed. In the area of the second side A reading step for causing the reading means to read reading information indicating characteristics from the inverted sheet-like object, and reading the predetermined region of the first surface of the sheet-like object from the first surface side. And comparing the reference characteristic information stored in advance in the storage means with the read information read by the reading step, and based on the comparison result of the comparing step, the first step And a misregistration detection step of detecting a misregistration of a position on the second surface corresponding to a position on the surface.

  According to the first and ninth aspects of the present invention, on the first surface, a dedicated positioning mark or the like is not formed on a sheet-like object in which unique characteristics having randomness are distributed, such as paper. There is an effect that the positional deviation of the position on the second surface corresponding to the position can be detected with high accuracy.

  According to the invention of claim 2, since reading is performed using transmitted light, even a sheet-like object whose surface is subjected to a coating process such as art paper can read unique features. The effect of being able to be obtained is obtained.

  According to the invention of claim 3, since the reference feature information and the read information are read by the same reading means, an effect that the number of constituent members can be reduced is obtained.

  According to the fourth aspect of the present invention, since reading is performed using reflected light, an effect that a unique feature can be read is obtained even for a sheet-like object that does not transmit light.

  According to the fifth and seventh aspects of the present invention, by using an area sensor or a line sensor as the reading means, the positional deviation of the position on the second surface corresponding to the position on the first surface can be accurately performed. The effect that it can detect is acquired.

  According to the eighth aspect of the present invention, the second surface can be displaced so that the positional deviation on the second surface corresponding to the position on the first surface can be eliminated without forming a dedicated positioning mark or the like. The effect that the formation of the image and the conveyance of the sheet-like object can be controlled is obtained.

The best mode for carrying out the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 shows an embodiment of an image forming apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, below the image forming apparatus 10, sheets as sheet-like objects are stacked and stored in the sheet feed tray 12, and the stored sheets are sequentially taken out from the top layer. Then, it is conveyed to the image forming unit 14 by the conveying means (not shown) as indicated by arrows A1 and A2.

  The image forming unit 14 has a general configuration in which an image is formed by an electrophotographic process using a laser beam, and includes Y, M, C, and K including a photoconductor, a developing device, and a scanning optical system. Each color developing unit 16Y, 16M, 16C, 16K (collectively, developing unit 16) is provided.

  The image forming unit 14 scans and exposes the photosensitive members provided in the developing units 16Y, 16M, 16C, and 16K based on the raster data of each color of Y, M, C, and K to form an electrostatic latent image. Each of the developing units 16 develops a toner image corresponding to raster data by developing the electrostatic latent image electrostatically formed on the photosensitive member using toner of each color.

  In the image forming unit 14, the toner images of the respective colors formed on the respective developing units 16 are transferred while being superimposed on the paper.

  In the image forming unit 14, when the toner image is transferred onto the paper, the toner image is fixed by heating the paper on which the toner image has been transferred using the fixing module 18 while applying pressure, and the image is formed on the first surface of the paper. Form. When an image is formed on only one side of the sheet, the sheet that has passed through the fixing module 18 is discharged to the discharge tray 20 as indicated by an arrow A3.

  The image forming apparatus 10 of the present embodiment can form images on both sides of a sheet. When image formation on both sides of the paper is instructed, the paper on which the image is formed on the first side that has passed through the fixing module 18 passes through the conveyance path for double-sided processing as indicated by arrows A4 and A5. Then, as shown by arrow A6, it is sent to the reverse path (not shown). The sheet conveyed from the reverse path as indicated by the arrow A7 is reversed by being conveyed along the conveyance path as indicated by the arrows A8, A9, and A2, and is conveyed again to the image forming unit. From the position indicated by the arrow A10, the second surface on which the image is not formed becomes the upper surface of the sheet conveyed to the image forming unit 14.

  The image forming unit 14 forms an image on the second surface of the sheet conveyed from the reverse path. The sheet on which images are formed on both the first surface and the second surface is discharged to the discharge tray 20 as indicated by an arrow A3.

  The sheet is temporarily stopped on the downstream side of the position indicated by the arrow A10. In this temporary stop period, it is confirmed whether the paper feeding from the paper feed tray 12 is normal, and the paper conveyed from the reverse path to form an image on the second surface is normally conveyed to the image forming unit 14. Confirmation is made.

  Reads a predetermined area in the image forming blank portion of the temporarily stopped paper on the downstream side of the position indicated by the arrow A10 on the transport path, that is, on the transport path where the paper upstream from the image forming unit 14 is transported. A reading unit 22 is provided as a means. When the image formation on both sides of the paper is instructed, the reading unit 22 is instructed to read, and before the image formation on the first side of the paper is performed, and on the second side of the paper Before the formation is performed, reading of a predetermined area of the sheet and an area corresponding to the predetermined area is instructed.

  FIG. 2 shows a schematic configuration of the reading unit 22.

  The reading unit 22 according to the first embodiment includes an area sensor that reads a two-dimensional area of a sheet conveyed in the direction of an arrow with transmitted light, and an illumination unit 24 that irradiates the sheet with light. And a light receiving unit 26 that receives the transmitted light that has been irradiated by the illumination unit 24 and transmitted through the paper. Further, a window portion 28 is provided in the conveyance path corresponding to the position where the reading unit 22 is provided. The reading unit 22 irradiates light from the illumination unit 24, and receives light transmitted through the window 28 and the paper by the light receiving unit 26, thereby reading characteristic information indicating the unique characteristics of the paper. .

  As shown in FIG. 2, the illuminating unit 24 includes a light source 24B that outputs light and an optical waveguide optical system 24A that guides light emitted from the light source 24B in the paper direction. For example, an LED, a halogen lamp, a fluorescent lamp, or a xenon discharge tube can be used as the light source 24B. Further, instead of the optical waveguide optical system 24A, a condensing lens that condenses light in the paper direction can also be used.

  The light receiving unit 26 is an image sensor 26B, which is an area sensor composed of a CCD or the like in which a number of light receiving elements that output a signal corresponding to the amount of received light are arranged, and transmitted light that is irradiated by the illumination unit 24 and transmitted through the paper Is formed on the light receiving surface of the image sensor 26B, and a signal processing circuit (not shown) that converts the signal output from the image sensor 26B into digital data and outputs the digital data.

  The sheet is formed of a fibrous material, and the entanglement of the fibrous material is random as shown in FIG. The reading unit 22 reads the shade information indicating the random change in the entanglement of the fibrous material as the feature information indicating the unique feature.

  In the present embodiment, the reading resolution by the image sensor 26B is 400 dpi, for example, and the reading gradation by the reading unit 22 is an 8-bit gray scale. The reading resolution and the reading gradation are not limited to such values.

  As shown in FIG. 4, the reading unit 22 is connected to a control unit 30 that controls the operation of each unit of the image forming apparatus 10.

  As shown in FIG. 4, the control unit 30 includes a bus, an external interface 32, a user interface 34 including a display device including a touch panel, a ROM 36, a RAM 38, an HDD 40, a CPU 42, and an I / O. And at least a port 44.

  The bus is used when information is exchanged between the components. The external interface 32 is for connecting to a network, and is composed of a NIC (Network Interface Card) and its driver. The user interface 34 displays information related to the control unit 30 and is used when an operator inputs operations and information of the control unit 30.

  The ROM 36 is a non-volatile storage device that stores a boot program that operates when the control unit 30 is activated.

  The RAM 38 stores various types of log data acquired during the operation of the image forming apparatus 10, and position information for determining an image forming position when image forming processing is performed by the image forming unit 14, and image information such as image density. It is a storage device that temporarily stores set values of various information (parameters) such as image quality information that determines quality.

  The HDD 40 is a non-volatile storage in which an OS (operating system), a program for executing a processing routine to be described later, and an image forming job captured from an upper device (not shown) such as a host system via the external interface 32 are stored. Storage device.

  The CPU 42 governs the overall operation of the control unit 30 and executes a processing routine described later. The CPU 42 is connected to the reading unit 22 via the I / O port 44 so that information can be transmitted and received, and the unique characteristics of the paper read by the reading unit 22 are recorded in the RAM 38 as a storage unit. .

  Further, when the CPU 42 determines that an error has occurred in the sheet conveyance by executing a processing routine described later, the CPU 42 displays, for example, on the user interface 34 that the error has occurred in the sheet conveyance. , Notify the operator.

  Next, referring to the flowchart of FIG. 5, the image on the first surface and the second image when the image is formed on both the first surface and the second surface, which is executed by the control unit 30. The flow of processing for correcting misalignment with a surface image will be described.

  In step 100, it is determined whether or not a read signal serving as a trigger for causing the reading unit 22 to read is received. In the present embodiment, a conveyance stop signal for confirming the conveyance state of the paper is used as a reading signal.

  If the determination in step 100 is affirmative, the process proceeds to step 102, and the reading unit 22 is caused to read the characteristic information of the random change in the light transmittance distributed on the paper, and is shown in FIG. Then, feature information of a random change in light transmittance distributed in a predetermined area (paper fingerprint area) 6A having a predetermined size is cut out.

  As shown in FIG. 6A, the paper fingerprint area 6A is defined as an area of a predetermined size at the center position of the non-image forming area along the paper conveyance direction indicated by the arrow. .

  As shown in FIG. 3, the random change in the entanglement of the fibrous material in a 1 mm square region shows a unique feature. From this it can be seen that the unique features of the 1-2 mm square area can be used as paper fingerprints. In the present embodiment, the size of the paper fingerprint area is, for example, 32 × 32 pixels (about 2 mm × 2 mm).

  By the processing in step 102, feature information indicating the unique features of the paper fingerprint area 6A of the paper is read.

  An example of a feature image obtained by visualizing an image (feature image) represented by the feature information (contrast correction for easy viewing) based on the feature information obtained by reading the paper fingerprint area 6A of the paper in step 102. 7 (A).

  In step 104, information representing an inverted image (hereinafter referred to as a paper fingerprint image) obtained by inverting the feature image of the paper fingerprint area 6A of the paper is stored in the RAM 38 as paper fingerprint information. As in the first embodiment, when reading is performed using transmitted light, an image represented by feature information of a random change in light transmittance read from the first surface using the reading unit 22 is displayed on the reading unit 22. Since it is an image obtained by inverting the image represented by the feature information of the random change in the light transmittance read using the second surface, in step 104, the paper fingerprint information is stored after inverting the feature image. . Note that the paper fingerprint information may be stored in the RAM 38 without being inverted, and the feature information of the random change in the light transmittance of the region 6B read in step 108 described later may be inverted. The paper fingerprint information stored in step 104 is reference feature information that serves as a reference for detecting displacement.

  The paper from which the paper fingerprint area 6A has been read is conveyed to the image forming unit 14, an image is formed on the first surface, passes through the reverse path, and is conveyed to the position where the reading unit 22 is provided. .

  In step 106, it is determined whether a read signal has been received.

  If the determination in step 106 is affirmative, the process proceeds to step 108, and the reading unit 22 is caused to read the characteristic information of the random change in the light transmittance distributed on the paper, as shown in FIG. Then, the characteristic information of the random change of the light transmittance distributed in the reading area 6B of a predetermined size of the paper is cut out.

  As shown in FIG. 6B, this reading area 6B is an area of a size larger than the paper fingerprint area 6A shown in FIG. 6A, which is set at the center position along the paper conveyance direction. .

  For example, when an area of 32 × 32 pixels (about 2 mm × 2 mm) is defined as the paper fingerprint area 6A, as shown in FIG. 6B, the paper fingerprint area 6A is larger than the paper fingerprint area 6A. Is read as a reading area (for example, 64 × 64 pixels (about 4 mm × 4 mm)) 6B.

  FIG. 7B shows an example of a read image obtained by visualizing an image represented by the read information (hereinafter referred to as a read image) based on the read information obtained by reading the read area 6B in step 108.

  In step 110 as a comparison means, a comparison process is performed. Hereinafter, the comparison process will be described with reference to the flowchart of FIG.

  In step 150, the information extraction position (calculation target area position) in the reading area 6B is initialized to the position of the center area of the reading area 6B (that is, the area corresponding to the paper fingerprint area 6A).

  In the comparison processing according to the present embodiment, although details will be described later, feature information corresponding to a region (calculation target region) having the same size as the paper fingerprint region 6A is extracted from the feature information of the reading region 6B. The calculation of the correlation value with the paper fingerprint information stored in is repeated while moving the position of the calculation target area. For this reason, in step 150, the information extraction position (the position of the calculation target area) in the reading area is initialized.

  In step 152, feature information of an area having the same size as the paper fingerprint information located at the set information extraction position (hereinafter referred to as calculation target information) from the read information obtained by reading the read area 6B in step 108. To extract.

  In the next step 154, a correlation value between the paper fingerprint information stored in the RAM 38 and the calculation target information extracted in step 152 is calculated.

  In step 156, it is determined whether or not the correlation value calculated in step 154 exceeds a predetermined value stored in advance in the ROM 36 or the like. If the area from which the calculation target information is extracted matches the paper fingerprint area, the correlation value exceeds a predetermined value, so it is determined whether the area from which the calculation target information is extracted matches the paper fingerprint area. can do. If the determination in step 156 is affirmed, the comparison process is terminated, and if the determination is negative, the process proceeds to step 158.

  In step 158, it is determined whether the calculation target area has scanned the entire surface of the reading area 6B. If the result is negative, the process proceeds to step 160, the information extraction position is moved by one pixel in the vertical direction or the horizontal direction, and the process returns to step 152. Note that when reading the gist by the reading unit 22 in step 108, an area wider than the area indicated by the reading area 6B was read, and the paper fingerprint area was not included in the area indicated by the reading area 6B. In this case, feature information of a region wider than the region indicated by the reading region 6B may be cut out, and the processing from step 152 to step 160 may be repeated.

  The processing from step 152 to step 160 is repeated until the determination in step 156 is affirmed.

  If the determination in step 158 is affirmative, the correlation value is less than or equal to a predetermined value for the entire surface of the reading area, so the position of the sheet when the reading unit 22 reads the first surface side, and the reading unit 22 The positional deviation from the position of the sheet when the second surface side is read is out of an allowable range, and it is determined in step 162 that the conveyance of the sheet is an error.

  In step 112, it is determined whether or not an error is determined in the comparison process in step 110. When the result is negative, the process proceeds to step 114, and when the result is positive, the process proceeds to step 118.

  In step 114 as the position deviation detection means, a deviation amount between the center position of the area where the correlation value exceeds a predetermined value and the center position of the reading area 6B is calculated.

  In step 116, according to the amount of positional deviation calculated in step 114, for example, image formation timing control by the image forming unit 14, transport speed control by the transport means, and the like are performed. Is corrected at a position corresponding to the image formed on the first surface.

  In step 118, the operator is notified by displaying, for example, on the user interface 34 that an error has occurred in the conveyance of the sheet.

  In this way, by reading the unique features of the predetermined area of the paper, the amount of positional deviation of the position on the second surface corresponding to the position on the first surface without forming an image such as a dedicated positioning mark. Can be detected in units of pixel pitch. Furthermore, an image can be formed at a corresponding position between the first surface and the second surface of the paper in accordance with the detected positional deviation amount in pixel pitch units.

Further, since the reading unit 22 is configured to read the unique characteristics of the paper using transmitted light, for example, even when the paper is a paper whose surface is coated such as art paper, the position can be accurately determined. The amount of deviation can be detected.
(Second Embodiment)
The second embodiment of the present invention will be described below. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description of the configuration is omitted.

  A feature of the second embodiment is that a unique characteristic of a sheet is read using reflected light.

  FIG. 9 shows an image forming apparatus according to the second embodiment of the present invention.

  As shown in FIG. 9, the image forming apparatus 210 includes a first reading unit 212 provided on the upstream side of the image forming unit 14 so as to face a surface on which an image of a sheet to be conveyed is formed, and a conveyance unit. And a second reading unit 214 provided to face the first reading unit 212 across the path. The first reading unit 212 and the second reading unit 218 are instructed to read when image formation on both sides of the sheet is instructed. The first reading unit 212 is instructed to read a predetermined area of the sheet before image formation is performed on the first side and the second side of the sheet, and the second reading unit 218 After image formation on one surface and before image formation on the second surface, an instruction to read an area corresponding to a predetermined area on the sheet is issued.

  FIG. 10 shows a schematic configuration of the first reading unit 212 and the second reading unit 218.

  The first reading unit 212 and the second reading unit 218 include an area sensor that reads a two-dimensional area of the paper, and an illumination unit 214 that irradiates light onto the paper conveyed in the direction of the arrow. 220, and light receiving portions 216 and 222 that receive the reflected light irradiated from the illumination portions 214 and 220 and reflected from the paper. In addition, a window 224 is provided in the conveyance path corresponding to the position where the first reading unit 212 and the second reading unit 218 are provided. The first reading unit 212 irradiates light from the illumination unit 214 and receives reflected light reflected from the sheet by the light receiving unit 216, thereby reading feature information indicating unique characteristics of the sheet. The second reading unit 218 reads feature information indicating unique features of the paper by irradiating light from the illumination unit 220 and receiving reflected light reflected from the paper by the light receiving unit 222. is there.

  As shown in FIG. 10, the illumination units 214 and 220 include light sources 214B and 220B that output light, and optical waveguide optical systems 214A and 220A that guide light output from the light sources 214B and 220B in the paper direction. , Including. For the light sources 214B and 220B, for example, an LED, a halogen lamp, a fluorescent lamp, a xenon discharge tube, or the like can be used. Further, instead of the optical waveguide optical systems 214A and 220A, a condensing lens that collects light in the paper direction can also be used.

  The light receiving units 216 and 222 are imaging light elements 216B and 222B configured by a CCD or the like in which a large number of light receiving elements that output signals according to the amount of received light are arranged, and a sheet of illumination light irradiated by the illumination units 214 and 220. Lens units 216A and 222A that form an image of the reflected light reflected on the light receiving surfaces of the image sensors 216B and 222B, and a signal processing circuit that converts the signals output from the image sensors 216B and 222B into digital data and outputs the digital data (not shown) ). The characteristic feature of the paper is acquired as light and shade information indicating a random change in the degree of entanglement of the fibrous material forming the paper.

  Next, a flow of misalignment correction processing executed by the control unit 30 in the second embodiment will be described with reference to the flowchart of FIG.

  In step 100, it is determined whether a read signal has been received.

  If the determination in step 100 is affirmative, the process proceeds to step 102 ′, and the reading unit 212 is caused to read the characteristic information of the random change in the light reflectance distributed on the paper, and is shown in FIG. Then, the characteristic information of the random change of the light reflectance distributed in the paper fingerprint area 6A of the paper is cut out to obtain the paper fingerprint information indicating the unique characteristic of the paper fingerprint area 6A of the paper.

  In step 104 ', the paper fingerprint information obtained in step 102' is stored in the RAM 38 as reference feature information.

  In step 106, it is determined whether a read signal has been received.

  If the determination in step 106 is affirmative, the process proceeds to step 108 ′, and the reading unit 218 is caused to read characteristic information of a random change in the light reflectance distributed on the paper, and is shown in FIG. The characteristic information of the random change of the light reflectance distributed in the sheet reading area 6B is cut out.

  In step 110 as a comparison means, the comparison process described in the flowchart of FIG. 8 is performed.

  In step 112, it is determined whether or not an error is determined in the comparison process in step 110. When the result is negative, the process proceeds to step 114, and when the result is positive, the process proceeds to step 118.

  In step 114 as the position deviation detection means, a deviation amount between the center position of the area where the correlation value exceeds a predetermined value and the center position of the reading area 6B is calculated.

  In step 116, according to the amount of positional deviation calculated in step 114, for example, image formation timing control by the image forming unit 14, transport speed control by the transport means, and the like are performed. Is corrected at a position corresponding to the image formed on the first surface.

  In step 118, the operator is notified by displaying, for example, on the user interface 34 that an error has occurred in the conveyance of the sheet.

  As described above, the reading units 212 and 218 are configured to read the characteristic features of the paper using the reflected light, so that even the paper that does not transmit light corresponds to the position on the first surface. 2 can be detected in units of pixel pitch.

  Further, by reading both the paper fingerprint area and the reading area from the first surface side of the paper, the characteristic information of either the paper fingerprint information of the paper fingerprint area 6A or the reading information of the reading area 6B is obtained. The position shift can be detected by performing the comparison process without reversing.

In the above description, the example in which the feature information read by the first reading unit 212 is compared with the read information read by the second reading unit 218 as the reference feature information has been described. The obtained feature information may be compared with the read information read by the first reading unit 212 as reference feature information.
(Third embodiment)
The third embodiment of the present invention will be described below. Note that in the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description of the configuration is omitted.

  A feature of the third embodiment is that a unique characteristic of a one-dimensional area of a sheet is read using a line sensor.

  FIG. 12 shows an image forming apparatus according to the third embodiment.

  As shown in FIG. 12, the image forming apparatus 310 is provided with a reading unit 312 as a reading unit that reads a one-dimensional area in a direction perpendicular to the sheet conveyance direction on the upstream side of the image forming unit 14. Yes. The reading unit 312 is instructed to perform image formation on both sides of the sheet, and before the image is formed on the first side of the sheet and before the image is formed on the second side of the sheet. Before the formation is performed, reading of a predetermined line area of the sheet and an area corresponding to the predetermined line area is instructed.

  The reading unit 312 according to the third embodiment is configured to include a line sensor that reads a one-dimensional area of a sheet using transmitted light. Similarly to the reading unit 22 according to the first embodiment, an optical waveguide optical device is used. The illumination unit 314 is configured to include a system and a light source, and the light receiving unit 316 is configured to include a lens unit, an imaging device, and a signal processing circuit.

  Next, a flow of misalignment correction processing executed by the control unit 30 in the third embodiment will be described with reference to the flowchart of FIG.

  In step 350, it is determined whether or not a first read signal serving as a trigger for causing the reading unit 312 to perform reading is received. In the present embodiment, a signal that causes the optical scanning system that is scanned to form an image on the first surface of the sheet to start scanning is used as the first reading signal.

  If the determination in step 350 is affirmative, the process proceeds to step 352, where the reading unit 312 has a random change in light transmittance distributed in the line area of the paper corresponding to the position where the reading unit 312 is provided. Read feature information.

  The reading unit 312 is provided so as to read the line area at the center position of the non-image forming area along the sheet conveyance direction when the first reading signal is output. In the present embodiment, the line area at the center position along the paper conveyance direction is referred to as a paper fingerprint area.

  By the processing in step 352, feature information indicating the unique features of the paper fingerprint area of the paper is read.

  In step 354, information representing an inverted image (hereinafter referred to as a paper fingerprint image) obtained by inverting the feature image of the paper fingerprint area of the paper is stored in the RAM 38 as paper fingerprint information. As in the first embodiment, when reading is performed using transmitted light, an image represented by feature information of a random change in light transmittance read from the first surface using the reading unit 312 is displayed on the reading unit 312. Since this is an image obtained by inverting the image represented by the feature information of the random change in the light transmittance that is read from the second surface, in step 354, the paper fingerprint information is stored after inverting the feature image. . Note that the feature information of the random change in the light transmittance of the region read in step 358 described later may be reversed. The paper fingerprint information stored in step 354 is reference feature information that serves as a reference for detecting displacement.

  The paper on which the paper fingerprint area has been read is conveyed to the image forming unit 14, an image is formed on the first surface, passes through the reverse path, and is conveyed to the position where the reading unit 312 is provided.

  In step 356, it is determined whether the reading unit 312 has detected a sheet.

  If the determination in step 356 is affirmative, the process proceeds to step 358, and the reading unit 312 has a random change in the light transmittance distributed in the line area of the paper corresponding to the position where the reading unit 312 is provided. Read feature information.

  In step 360 as a comparison means, a correlation value between the paper fingerprint information stored in the RAM 38 and the read information extracted in step 358 is calculated.

  In step 362, it is determined whether or not the correlation value calculated in step 360 exceeds a predetermined value. This predetermined value is stored in the RAM 38 in advance, and the correlation value exceeds the predetermined value only when the area read by the reading unit 312 matches the paper fingerprint area. If the determination in step 362 is affirmed, the comparison process ends. If the determination is negative, the process proceeds to step 368.

  In step 364 as the position deviation detection means, the amount of deviation from the timing at which the second reading signal is received at the timing at which the region where the correlation value exceeds the predetermined value is calculated. In the present embodiment, a signal that causes the optical scanning system that is scanned to form an image on the second surface of the paper to start scanning is used as the second reading signal.

  In step 366, according to the amount of timing deviation calculated in step 364, for example, image formation timing control by the image forming unit 14, transport speed control by the transport unit, and the like are performed. Is corrected at a position corresponding to the image formed on the first surface.

  In step 368, it is determined whether the reading unit 312 has detected a sheet. If the determination is affirmative, the process proceeds to step 358, and if the determination is negative, the process proceeds to step 370.

  Steps 358 and 360 are repeated until the determination in step 362 is affirmed. Since the reading unit 312 in the third embodiment reads the paper being conveyed, the characteristic information of the random change in the light transmittance distributed in the line area read in step 358 is different each time.

  In step 370, a positional tolerance between the position of the sheet before image formation on the first side of the sheet and the position of the sheet before image formation on the second side of the sheet is allowed. It is determined that the paper conveyance is an error, and the operator is notified by displaying, for example, on the user interface 34 that the paper conveyance error has occurred.

  In this way, even when reading a unique characteristic of a predetermined area of the sheet using the line sensor, the second surface corresponding to the position on the first surface is formed without forming an image such as a dedicated positioning mark. The image forming apparatus can detect the correspondence between the first surface and the second surface of the paper according to the detected positional displacement amount in pixel pitch units. An image can be formed at the position to be.

  Note that the line sensor may be one that reads using reflected light. In this case, the reading unit is provided at two positions across the conveyance path, as in the second embodiment.

  In the above-described embodiment, the position of the predetermined area is the center position in the paper transport direction, but the position of the predetermined area is not limited to the center position in the paper transport direction. When the position of the predetermined area is different from the center of the sheet, the position along the transport direction of the predetermined area before being reversed and the position along the transport direction of the area corresponding to the predetermined area after being reversed Therefore, the reading is performed so that the area to be read before being inverted corresponds to the area to be read after being inverted.

  Further, in the above-described embodiment, the predetermined area is the area of the image forming blank portion of the paper, but it may be an area where an image of the paper is formed. In this case, the reading unit that reads the paper fingerprint region is provided on the downstream side of the image forming unit, and the reading unit reads a random pattern of the entanglement of the fibers and a fine random pattern of the toner.

  In the first embodiment and the second embodiment, the predetermined area of the sheet is read at the timing when the conveyance of the paper is temporarily stopped. However, the structure may be such that the sheet being conveyed is read.

  In the above embodiment, the image forming apparatus including the tandem image forming unit 14 is described as an example. However, the image forming unit may be an intermediate transfer member such as the image forming apparatus 410 illustrated in FIG. Alternatively, a transfer belt system using a transfer belt 412 may be used.

  In this case, the reading unit 414 is provided at a position upstream of the secondary transfer unit 416 in the conveyance path through which the inverted paper is conveyed.

  Further, the image forming unit may use any method such as a transfer drum method using a transfer drum as an intermediate transfer member, or a direct transfer method using a developing unit in which four colors are integrated.

  In the above embodiment, a sheet is used as the sheet-like object. However, the sheet is not limited to a sheet as long as it is a sheet-like member having a random pattern formed on the surface.

  In addition, the position shift detection function on the second surface corresponding to the position on the first surface described above is not limited to the image forming apparatus, but may be a position on the first surface such as a device for forming a substrate. And a corresponding position on the second surface can be mounted on a device.

  Further, the misregistration detection function according to the above embodiment may be realized by a computer program.

  FIG. 15 is an explanatory diagram of an example of a computer program, a storage medium storing the computer program, and a computer when the function of detecting misregistration according to the embodiment of the present invention is realized by the computer program. In the figure, 400 is a program, 402 is a computer, 404 is a magneto-optical disk, 406 is an optical disk, 408 is a magnetic disk, 410 is a memory, 412 is an internal memory, 416 is a reading device, 420 is a hard disk, 418 is an interface, and 422 is an interface. Communication units 424 are connection ports.

  Part or all of the misregistration detection function according to the embodiment of the present invention described above can be realized by a program 400 that can be executed by a computer. In that case, the program 400, data used by the program, and the like can be stored in a computer-readable storage medium. The storage medium causes a change state of energy such as magnetism, light, electricity, etc. to the computer 402 according to the description content of the program, and transmits the description content of the program to the computer 402 in the form of a corresponding signal. It can be communicated. For example, a magneto-optical disk 404, an optical disk 406 (including a CD and a DVD), a magnetic disk 408, a memory 410 (including a USB memory) and the like. Of course, these storage media are not limited to portable types.

  The program 400 is stored in these storage media, and the program 400 is read from the computer and stored in the internal memory 412 or the hard disk 420, for example, by mounting these storage media on the reader 416 or the connection port 424 of the computer 402. Then, by executing the program 400 by the CPU 414, it is possible to realize the function of detecting misalignment according to the embodiment of the present invention. Alternatively, the program 400 is transferred to the computer 402 via a network or the like, and the computer 402 receives the program 200 by the communication unit 422 and stores it in the internal memory 412 or the hard disk 420, and the program 400 is executed by the CPU 414. You may implement | achieve the function of the position shift detection which concerns on embodiment of invention.

  The computer 402 can be connected to various devices via an interface 418, and is connected to a reading unit as reading means. Further, for example, a display device for displaying information and an input device for inputting information by an operator are also connected via the interface 418.

  Of course, some functions may be configured by hardware, or all may be configured by hardware. Alternatively, it can be configured as a program including the embodiment of the present invention together with other configurations.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to a first embodiment of the present invention. It is a schematic block diagram which shows an example of the reading part which uses the transmitted light. It is an image which shows an example of the random pattern of the fiber of paper. 1 is a block diagram illustrating an example of a functional configuration of an image forming apparatus according to an embodiment of the present invention. It is a flowchart of the position shift correction process which concerns on 1st Embodiment of this invention. (A) is a schematic diagram showing a paper fingerprint area of a paper according to an embodiment of the present invention, and (B) is a schematic diagram showing a paper reading area. (A) is an image figure which shows an example of a paper fingerprint image, (B) is an image figure which shows an example of a read image. It is a flowchart of the comparison process which concerns on 1st Embodiment of this invention. It is a schematic block diagram which shows an example of the image forming apparatus which concerns on 2nd Embodiment of this invention. It is a schematic block diagram which shows an example of the reading part which uses reflected light. It is a flowchart of position shift amendment processing concerning a 2nd embodiment of the present invention. It is a schematic block diagram which shows an example of the image forming apparatus which concerns on 3rd Embodiment of this invention. It is a flowchart of the position shift correction process which concerns on 3rd Embodiment of this invention. It is a schematic block diagram which shows the modification of an image forming apparatus. FIG. 7 is an explanatory diagram of an example of a computer program, a storage medium storing the computer program, and a computer when the positional deviation detection function of the present invention is realized by a computer program.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Paper feed tray 14 Image forming part 16 Developing unit 18 Fixing module 20 Discharge tray 22 Reading part 24 Illuminating part 26 Light receiving part 28 Window part 30 Control part 32 External interface 34 User interface 36 ROM
38 RAM
40 HDD
42 CPU
44 I / O port 210 Image forming devices 212 and 218 Reading units 214 and 220 Illuminating units 216 and 222 Light receiving unit 224 Window unit 310 Image forming device 312 Reading unit 400 Program

Claims (9)

Storage means for storing, as reference feature information, feature information obtained by reading a predetermined region of the first surface of the sheet-like object on which the unique features having randomness are distributed from the first surface side;
Reading means for reading the characteristics of the sheet-like object;
The reference feature information, and reading information obtained by reading the area corresponding to the predetermined area on the second surface opposite to the first surface of the inverted sheet-like object by the reading unit; A comparison means for comparing
A displacement detection means for detecting a displacement of a position on the second surface corresponding to a position on the first surface based on a comparison result of the comparison means;
A misalignment detection apparatus comprising: The predetermined region of the first surface of the sheet-like object in which unique characteristics having randomness are distributed is transmitted using the transmitted light that passes through the sheet-like object and exits from the first surface. Storage means for storing feature information obtained by reading from one surface side as reference feature information;
Reading means for reading the characteristics of the sheet-like object using transmitted light that passes through the sheet-like object;
The reference feature information and a region corresponding to the predetermined region on the second surface opposite to the first surface of the inverted sheet-like object are transmitted through the sheet-like object and the second Comparison of one piece of read information obtained by reading by the reading means using transmitted light emitted from the surface of the surface, the reference feature information, and information obtained by inverting the other information of the read information Means,
A displacement detection means for detecting a displacement of a position on the second surface corresponding to a position on the first surface based on a comparison result of the comparison means;
A misalignment detection apparatus comprising:   The positional deviation detection apparatus according to claim 1, wherein information obtained by reading by the reading unit is used as the reference feature information. Feature information obtained by reading a predetermined region of a sheet-like object in which unique features having randomness are distributed from the first surface side using reflected light reflected from the sheet-like object. Storage means for storing as reference feature information;
Reading means for reading the characteristics of the sheet-like object using reflected light reflected from the sheet-like object;
Comparing means for comparing the reference feature information with reading information obtained by reading the predetermined area of the inverted sheet-like object by the reading means using the reflected light;
A displacement detection means for detecting a displacement of a position on the second surface corresponding to a position on the first surface based on a comparison result of the comparison means;
A misalignment detection apparatus comprising:   The position deviation detection device according to claim 1, wherein the reading unit is an area sensor or a line sensor.   5. The positional deviation detection apparatus according to claim 4, wherein another reading unit is provided in correspondence with the reading unit, and information obtained by reading by the other reading unit is used as the reference feature information.   The positional deviation detection apparatus according to claim 6, wherein the reading unit and the other reading unit are an area sensor or a line sensor. The positional deviation detection device according to any one of claims 1 to 7,
Image forming means for forming an image on the first surface and the second surface of the sheet-like object at an image forming position;
Reversing means for reversing the sheet-like object having an image formed on one surface;
Conveying means for conveying the sheet-like object reversed by the reversing means to the image forming position;
Control means for controlling at least one of image formation by the image forming means and conveyance by the conveyance means so that the positional deviation detected by the positional deviation detection means is eliminated;
An image forming apparatus. On the computer,
Read information indicating the characteristics of the area of the second surface opposite to the first surface corresponding to the predetermined area of the first surface of the sheet-like object in which unique features having randomness are distributed is inverted. A reading step that causes the reading means to read from the sheet-like object that has been performed;
Reference feature information obtained by reading the predetermined area of the first surface of the sheet-like object from the first surface side and stored in advance in the storage means, and read by the reading step A comparison step for comparing the read information;
A displacement detection step of detecting a displacement of a position on the second surface corresponding to a position on the first surface based on a comparison result of the comparison step;
A program for running