JP6772616B2 - Image forming device, image correction method - Google Patents

Description

The present invention relates to an image forming apparatus in a copier, a printer, a facsimile, or a multifunction device thereof that corrects an image by using an image measurement reference means. The present invention also relates to an image correction method.

In an image forming apparatus in a copier, a printer, a facsimile, or a multifunction device thereof, an image formed on a recording medium may be misaligned with respect to a desired image, and image correction is required. As such deviations with respect to the desired image, for example, there are deviations in the position of the formed image, deviations in size, deviations in density, and the like.

In order to correct the above image and obtain a desired image, an image for correction and a recording medium on which the image is formed are used by using an image measurement reference means as a reference for measuring an image formed on a recording medium. The invention for measuring the above has already been made.

For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-349892) discloses a correction jig for correcting an image formation position or the like. A center line and a reference image whose dimensions have been measured in advance are formed on the correction jig. By arranging the center line formed on the correction jig so as to overlap the center of the paper on which the correction image is formed in the main scanning direction and measuring the respective distances, the position correction in the main scanning direction, etc. Can be done. Further, by comparing the position and length of the reference image with the position and length of the image for correction formed on the paper, it is possible to correct the position and size of the image.

It is possible to correct an image formed on a recording medium by using a correction jig as in Patent Document 1. However, if information such as the date and time when the image for correction is formed, the state of the image forming device, and the setting conditions is unknown, it may not be possible to perform correction with the optimum set value with high accuracy. The recording medium cannot be used for correction. Therefore, it is necessary to record the information at the time of forming the correction image on the recording medium and manage it separately, but it is troublesome and burdensome for the operator.

Under these circumstances, the present invention provides an image forming apparatus that enables easy management of information such as set values at the time of image formation and realizes accurate correction of an image formed on a recording medium. It is an issue.

In order to solve the above problems, the present invention includes an image forming means for forming an image on a recording medium, an image reading means for reading an image, and a correction means for correcting an image formed on the recording medium. The correction recording medium on which the image for correction is formed is provided so as to be superimposed on the image measurement reference means that serves as a reference for measuring the image, and the image measurement reference means is formed on the recording medium. The image reading has an image hole provided at a position corresponding to the image and a reading hole provided at a position corresponding to a one-dimensional code or a two-dimensional code formed in the recording medium. The means reads the image for correction and the code information recorded on the recording medium for correction through the image hole and the reading hole provided in the image measurement reference means, and the read correction. It is characterized by an image forming apparatus that corrects an image formed by the correction means on a subsequent recording medium based on the image and code information .

In the present invention, the reading information recorded on the recording medium can be read through the reading holes provided in the image measurement reference means. Therefore, it is not necessary to separately manage various information necessary for image correction and the like, and the operator can easily perform the correction under more appropriate conditions.

It is a schematic block diagram of an image forming apparatus. It is the schematic explaining the deviation of the image formed on the paper. It is a top view of the image measurement reference means which concerns on 1st Embodiment of this invention. It is a top view of the paper on which the reading information was printed. It is a top view of the state which the paper is sandwiched in the image measurement reference means. It is a top view of the image measurement reference means which concerns on 2nd Embodiment of this invention. It is a figure which shows the change of the size of the paper immediately after image formation. It is a figure which shows the flow of determination whether or not to correct an image. It is a block diagram of the image forming apparatus which concerns on embodiment. It is a schematic diagram explaining the image position measurement method by reading an image. It is a schematic diagram explaining the image position measurement method by reading an image. It is a schematic diagram explaining the image position measurement method by reading an image. It is a schematic diagram explaining the image position measurement method by reading an image. It is a schematic diagram explaining the image position measurement method by reading an image. It is a schematic diagram explaining the image position measurement method by reading an image.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted.

In the center of the color image forming apparatus 1 shown in FIG. 1, an image forming unit 2 to which four process units 9Y, 9M, 9C, and 9Bk are detachably provided is arranged. Each process unit 9Y, 9M, 9C, 9Bk accommodates developers of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. It has the same configuration except that it is.

Specific process units 9 include a photoconductor drum 10 which is a drum-shaped rotating body capable of carrying toner as a developer on the surface, and a charging roller 11 which uniformly charges the surface of the photoconductor drum 10. A developing device 12 or the like having a developing roller 13 for supplying toner to the surface of the photoconductor drum 10 is provided.

An exposure unit 3 is arranged above the process unit 9. The exposure unit 3 is configured to emit laser light based on the image data.

The transfer unit 4 is arranged directly below the image forming unit 2. The transfer unit 4 is attached to the drive roller 14, the driven roller 15, the endless intermediate transfer belt 16 stretched around the secondary transfer opposed roller 35 so as to be able to travel around, and the photoconductor drum 10 of each process unit 9. It is composed of primary transfer rollers 17 and the like arranged at opposite positions with the intermediate transfer belt 16 interposed therebetween. Each primary transfer roller 17 presses the inner peripheral surface of the intermediate transfer belt 16 at each position, and a primary transfer nip is formed at a position where the pressed portion of the intermediate transfer belt 16 and each photoconductor drum 10 come into contact with each other. Has been done.

Further, the secondary transfer roller 18 is arranged at a position facing the secondary transfer opposed roller 35 with the intermediate transfer belt 16 interposed therebetween. The secondary transfer roller 18 presses the outer peripheral surface of the intermediate transfer belt 16, and a secondary transfer nip is formed at a position where the secondary transfer roller 18 and the intermediate transfer belt 16 come into contact with each other.

The paper feed unit 5 is located at the lower part of the image forming apparatus 1, and includes a paper feed cassette 19 containing the paper P as a recording medium, a paper feed roller 20 for carrying out the paper P from the paper feed cassette 19, and the like. ing.

The image forming apparatus 1 is provided with a manual paper feeding unit 50 separately from the paper feeding unit 5. The manual paper feed unit 50 includes a manual paper feed tray 36 on which the paper P is placed, a manual paper feed roller 37 that feeds the paper P into the apparatus, a manual feed separation roller 38 that separates the paper P one by one, and a manual feed. A paper feed path 39 and the like are provided.

The transport path 6 is a transport path for transporting the paper P carried out from the paper feed section 5 or the manual feed feed section 50, and is a pair of transport rollers up to the paper ejection section 8 described later in addition to the pair of resist rollers 21. Is appropriately arranged in the middle of the transport path 6.

The fixing portion 7 has a fixing roller 22 that is heated by a heating source, a pressure roller 23 that can pressurize the fixing roller 22, and the like.

The paper ejection unit 8 is provided at the most downstream side of the transport path 6 of the image forming apparatus 1. The paper ejection section 8 is provided with a pair of paper ejection rollers 24 for ejecting the paper P to the outside and a paper ejection tray 25 for stocking the ejected paper P. Further, a branch claw 31 for changing the transport direction of the paper P and feeding the paper P to the reverse transport path 6a is provided. A plurality of double-sided roller pairs for transporting the paper P are provided in the reversing transport path 6a.

The scanner unit 40 as an image reading unit is arranged above the image forming apparatus 1, and is an imaging lens that forms an image of the incident light with the first traveling body 41 and the second traveling body 42 traveling in the scanner unit 40. It has a 43, a reading sensor 44 as an image reading means for reading the image contents, and a reading glass 45 having an image reading surface and placing paper P on the image reading surface.

The ADF (automatic document feeder) 46 is arranged above the scanner unit 40. The ADF 46 automatically conveys the paper P placed on the paper base 47, and the scanner unit 40 reads the image contents.

The image forming unit 2, the exposure unit 3, the transfer unit 4, and the like are image forming means for forming an image on the paper P.

Hereinafter, with reference to FIG. 1, the basic operation of the image forming apparatus 1 will be described with reference to a case where the image on the paper P is read and copied by the scanner unit 40.

First, the paper P placed on the paper base 47 is automatically conveyed to the reading glass 45 by the ADF 46, and the scanner unit 40 reads the image information of the paper P. Alternatively, with the ADF 46 open, the scanner unit 40 reads the image information of the paper P placed on the reading glass 45.

Specifically, in the scanner unit 40, the first traveling body 41 and the second traveling body 42 travel along the surface of the paper P. Then, the light source of the first traveling body 41 irradiates the paper P with light, and the first traveling body 41 receives the reflected light from the image plane of the paper P. This reflected light is reflected toward the second traveling body 42, the irradiated reflected light is further reflected by the mirror of the second traveling body 42, and is incident on the reading sensor 44 through the imaging lens 43. Then, the image information is read by the reading sensor 44.

When the image forming operation is started, an electrostatic latent image based on the read image information is formed on the surface of the photoconductor drum 10 of each process unit 9Y, 9C, 9M, 9Bk. The image information exposed by the exposure unit 3 on each photoconductor drum 10 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information. An electrostatic latent image is formed on each photoconductor drum 10, and the toner stored in each developing device 12 is supplied to the photoconductor drum 10 by a drum-shaped developing roller 13, so that the electrostatic latent image is formed. It is visualized as a visible toner image (developer image).

In the transfer unit 4, the intermediate transfer belt 16 is driven to travel in the direction of arrow A in the figure by the rotational drive of the drive roller 14. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 17. As a result, a transfer electric field is formed at the primary transfer nip, and the toner images formed on each photoconductor drum 10 are sequentially superimposed and transferred on the intermediate transfer belt 16 at the primary transfer nip.

On the other hand, when the image forming operation is started, the paper feed unit 5 conveys the paper P having a size corresponding to the read image information from the paper feed cassette 19 by rotating the corresponding paper feed roller 20. It is sent out to the road 6. The paper P sent out to the transport path 6 is timed by the resist roller 21 and sent to the secondary transfer nip between the secondary transfer roller 18 and the drive roller 14. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 16 is applied, and a transfer electric field is formed in the secondary transfer nip. The toner image on the intermediate transfer belt 16 is collectively transferred onto the paper P by the transfer electric field formed in the secondary transfer nip.

When paper is fed from the manual paper feed unit 50, the paper P placed on the manual paper feed tray 36 is fed into the device by the manual paper feed roller 37, and is fed one by one by the manual feed separation roller 38. It is separated and sent out to the manual paper feed path 39. The manual feed feed path 39 joins the transport path 6 at the end thereof, and the paper P conveyed from the manual feed feed path 39 to the transport path 6 is timed by the resist roller 21 to become a secondary transfer nip. Sent.

The paper P to which the toner image is transferred is conveyed to the fixing portion 7, and the paper P is heated and pressed by the fixing roller 22 and the pressure roller 23 to fix the toner image on the paper P. Then, the paper P on which the toner image is fixed is separated from the fixing roller 22, is conveyed by the transport roller pair, and is discharged to the paper discharge tray 25 by the paper discharge roller 24 at the paper discharge unit 8.

When an image is formed on both sides of the paper P, the branch claw 31 is rotated by a driving means such as a solenoid while the paper P is conveyed from the fixing portion 7 to the paper ejection portion 8, and the paper P is formed. The transport route is changed and the paper is sent to the reverse transport path 6a.

Then, the paper P is carried on the reverse transport path 6a by the double-sided roller pair on the reverse transport path 6a, and is returned to the transport path 6 again with the front and back sides of the paper P inverted. After that, an image is formed on the back surface as in the front surface, and after the image is fixed, the image is discharged to the paper ejection tray 25.

The above description is an image forming operation when forming a full-color image on paper P, but a single-color image can be formed by using any one of four process units 9Y, 9C, 9M, and 9Bk. It is also possible to use two or three process units 9 to form a two-color or three-color image.

An image is formed on the paper P by the image forming apparatus 1 as described above, but the image may be displaced from the desired image. For example, as shown in FIG. 2, the image B formed on the paper P is displaced from the desired image position B'. This is caused by misalignment or inclination of the paper P when the paper P is conveyed in each of the paper transport paths, distortion of the paper P itself, or the like.

Therefore, in the image forming apparatus according to the first embodiment of the present invention, in order to eliminate the above-mentioned misalignment of the image, the image of the paper P is imaged by the image reading method using the image measurement reference means of the present embodiment described later. Is read, and the position shift of the image is corrected. Specifically, in the image reading method according to the embodiment of the present invention, the position of the image B formed on the paper P is measured by reading the paper P by the reading sensor 44 via the image measurement reference means. The misalignment is corrected. Hereinafter, the image measurement reference means and the image reading method according to the present embodiment will be described.

As shown in FIG. 3, the measurement reference sheet 26 as the image measurement reference means according to the first embodiment of the present invention has a paper hole 27a as a recording medium hole (or hole) for detecting the position of the edge portion of the paper P. , 27b, 27c and image holes 28a, 28b, 28c, 28d as holes for detecting the image position formed on the paper P. The paper holes 27 (paper holes 27a, 27b, 27c) and the image holes 28 (image holes 28a, 28b, 28c, 28d) are formed in a circular shape. The relative positions of the holes in the measurement reference sheet 26 are accurately calculated, and are used for calculating the position of the paper P and the image position formed on the paper P, which will be described later. Further, the measurement reference sheet 26 is provided with a reading hole 60, which is a rectangular window portion for reading the reading information of the paper P described later.

The measurement reference sheet 26 is made of a member having a small coefficient of linear expansion in order to minimize the positional deviation of each hole due to a temperature change, and is made of, for example, a resin plate such as a PET film having a thickness of 0.1 to 0.25 mm. It is composed. A plurality of measurement reference sheets 26 made of different materials depending on the usage environment may be prepared.

Assuming that the surface placed on the reading glass 45 and read by the reading sensor 44 is the front surface of the paper P and the measurement reference sheet 26, the backing member 29 is provided on the back surface side of the measurement reference sheet 26.

As shown in FIG. 4, the reading information 61 is printed on the correction paper P at the same time that the correction image B is printed (the image is formed). As the reading information 61, a one-dimensional code such as a barcode or a two-dimensional code such as a QR code (registered trademark) is printed, and information necessary for image position correction such as the printing date and time of the image described later is recorded.

By using a barcode, QR code (registered trademark), or the like for the reading information 61, analysis with commonly used software is possible, and the recorded information is read by reading the reading information 61 with the reading sensor 44. It is possible to pull out.

As shown in FIG. 5, when reading an image using the measurement reference sheet 26 of the present embodiment, a worker such as a serviceman or a user performs a paper between the measurement reference sheet 26 and the backing member 29. Insert P (the measurement reference sheet 26 and the paper P are overlapped). At this time, the operator arranges the paper P so that the corresponding portions of the paper P (edges such as sides and corners of the paper described later) are located in the respective holes of the measurement reference sheet 26. The side on which the measurement reference sheet 26 in the figure is arranged is the side of the reading glass 45 of the image forming apparatus 1, the side of the backing member 29 is the side of the ADF 46 (see FIG. 1), and the paper P is sandwiched as described above. The measurement reference sheet 26 is interposed between the reading sensor 44 and the paper P.

When the operator sandwiches the paper P between the measurement reference sheet 26 and the backing member 29, the respective paper holes 27 are formed in a part of two sides of the paper P and one corner formed by the two sides. They are arranged at corresponding positions, and each image hole 28 is arranged at a position corresponding to the four corners of the image B. In this way, the respective paper holes 27 and 28 are provided at appropriate positions on the measurement reference sheet 26 according to the sizes of the paper P and the image B. The reading sensor 44 can read the edges of the paper P (each side or corner of the paper P) and the respective corners of the image B through the paper holes and the image holes.

Further, in a state where the measurement reference sheet 26 is arranged so that the paper holes 27 and the image holes 28 are aligned with the edges of the paper P and the corners of the image as described above, the reading holes 60 are provided at positions corresponding to the reading information 61. .. The reading sensor 44 can read the reading information 61 printed on the paper P through the reading hole 60. By reading the reading information 61, the image forming apparatus can automatically acquire the necessary information, so that it is not necessary to separately manage various information such as settings at the time of image forming, which saves the labor and burden of the operator. Can be reduced. Further, as compared with the case where the information is managed manually by the operator, it is possible to prevent erroneous information from being recorded due to an input error. The information recorded as the read information 61 is the following information regarding the image formation conditions at the time of image formation.

The reading information 61 records the date and time when the image B and the reading information 61 were printed on the paper P. As a result, even if the date and time when the image B was printed becomes unknown, the date and time of printing can be confirmed by reading the paper P. If a long time has passed since the image was printed, conditions such as the state of the image forming apparatus 1 and the environmental temperature may change, and accurate image correction may not be possible. However, by reading the read information 61, the date and time can be easily managed, and accurate image correction can be performed.

In the reading information 61, the identification information of the image forming apparatus 1 on which the image B and the reading information 61 are printed is recorded. As a result, even if a plurality of sheets P are confused and it is not clear which image forming apparatus 1 prints the image B on the sheet P, the image B printed by reading the identification information is displayed. The device can automatically identify the forming device 1.

Information on the paper P such as the brand and size of the paper P is recorded in the reading information 61. As a result, even if the brand or size of the paper P becomes unknown, it can be confirmed. Further, the position correction can be automatically performed under the optimum conditions according to the brand of the paper P.

In the reading information 61, information on the temperature and humidity around the image forming apparatus 1 when the image B and the reading information 61 are printed is recorded. As a result, it is possible to automatically perform position correction under the optimum conditions in consideration of the temperature and humidity environment.

The reading information 61 includes information on set values relating to the position where the image is formed. As a result, the image position to be formed can be automatically corrected in the apparatus based on the read image.

Next, the measurement reference sheet 26 of the second embodiment shown in FIG. 6 is an image measurement reference means that serves as a reference when measuring the density of an image. By performing image measurement using the image-side hand reference means, it is possible to correct the image formed on the paper P to a desired image density. The configuration similar to that of the first embodiment will be omitted as appropriate.

The measurement reference sheet 26 has a reference patch 62 and a density hole 63 as an image hole for reading the density pattern 64 formed on the paper P by the reading sensor 44.

In the present embodiment, each density pattern 64 formed on the paper P is read through the density holes 63. Then, the density of each patch of the reference patch 62 provided on the measurement reference sheet 26 and whose density is measured in advance is compared with the density of the density pattern 64. As a result, it is possible to calculate the amount of deviation of each density of the density pattern 64 with respect to the target density, and it is possible to correct each density.

The reading information 61 includes information on set values related to the density at the time of image formation. As a result, each set value can be automatically changed when the image density is corrected.

By the way, when the image is corrected by using the image measurement reference means of each of the above embodiments, the variation in the size of the paper P may become a problem. That is, since the size of the paper P changes according to the change in the amount of water contained in the paper P, the size of the paper P tends to fluctuate immediately after printing the image on the paper P, which affects the accuracy of image correction. It ends up. Therefore, it is desirable to correct the image of the paper P after a certain period of time has passed after printing the image and the water content of the paper P has stabilized.

FIG. 7 is a line graph showing the rate of change in the size of the paper per hour (vertical axis) for each of the three different brands A to C over time (horizontal axis). The basis weight of each paper was 80 gsm for brand A, 180 gsm for brand B, and 350 gsm for brand C.

Immediately after printing the image for each brand, the rate of change in the size of the paper is large, and it can be seen that the paper is shrinking. Further, it can be seen that the larger the basis weight of the paper, the smaller the rate of change in the size of the paper, and the more stable the size of the paper is in a short time.

Based on the above results, the time required for the paper size to stabilize (hereinafter, also referred to as the stabilization time) is 10 hours for brand A, 8 hours for brand B, and 6 hours for brand C, after printing the image. , It was decided to correct the image after the stabilization time had elapsed.

Further, if a long time has passed since the image was printed, the conditions such as the state of the image forming apparatus 1 and the environmental temperature may change significantly, and accurate image correction may not be possible. Therefore, in the present embodiment, the paper P within 24 hours after printing the image can be used for image correction.

The time lapse management of the paper P after printing the image as described above can be performed by reading the information recorded in the above-mentioned reading information 61. In this way, the necessity of image correction is determined based on the information recorded in the reading information 61. FIG. 8 shows a flow chart of the procedure of the image correction method of the present embodiment including the determination of the presence or absence of the above correction.

First, the paper P on which the image B and the reading information 61 are printed is prepared (step S0). Then, the reading sensor 44 (see FIG. 1) reads the edge of the paper P, the image B printed on the paper P, and the reading information 61, and obtains information such as the date and time when the image B was printed and the brand of the paper P. Acquire (steps S1 and S2).

According to the read information, if the date and time at the time of reading is 24 hours after the date and time when the image B was printed, an error notification is sent (step S3). It is determined that the paper P to which the error notification has been given cannot be used for image correction, and the determination flow is terminated by determining that the apparatus does not automatically perform the correction operation.

Then, if the date and time at the time of reading is within 24 hours from the date and time when the image B was printed, the process proceeds to the next step, and it is determined whether the stable time has elapsed since the image B was printed (step S4). ). Since the stabilization time (judgment standard) differs depending on the type of paper such as the brand of paper P and the presence or absence of a coating agent, the stabilization time is determined by reading information such as the brand from the reading information 61.

The paper P for which the stable time has passed is automatically determined to be a paper that can be used for image correction, and each setting is made based on the information read by the reading information 61 and the measured image information. The value is calculated and preparations are made for image correction (step S5).

On the other hand, if the paper P has not passed the stable time (when it is determined that the position correction is not automatically performed), a warning notification is given to the operator, and the image is corrected using the paper (forced). A confirmation display is made to the operator as to whether or not to execute (step S41). When the worker inputs that the forced execution is to be performed, each set value is calculated and preparations for image correction are made (step S5).

By the above steps, it is determined whether or not the paper P within a predetermined time after the image is printed is used for image correction based on the information of the print date and time recorded in the reading information 61. Then, when it is determined that the image is corrected, the position and density of the image formed on the subsequent paper are taken into consideration by taking into account the information such as the temperature and humidity at the time of forming the image B obtained from the reading information 61. Can be corrected.

As described above, in the configuration of the present embodiment, only the paper P at an appropriate timing can be used for image correction by obtaining information such as the printing date and time of the image and the brand of the paper. Further, when correcting an image, the influence of temperature and humidity at the time of image formation can be taken into consideration. From these things, it becomes possible to correct an image with higher accuracy.

Further, the information necessary for determining the necessity of correction and the information necessary for correcting the image can be read from the correction paper P used for correcting the image. Therefore, the worker does not need to manage the information separately, the labor of the worker can be eliminated, and the erroneous correction due to the input error or the recording error of the worker's information can be prevented.

A block diagram of the image forming apparatus 1 that processes the above information is shown in FIG.
The image forming unit can form an image on the paper P based on the input image information. The image forming unit prints the image B for correction and the reading information 61 on the paper P, and can create the paper P used for correcting the position and density of the image.

The image B for correction and the paper P on which the reading information 61 is printed are read by the scanner unit 40 (see FIG. 1) when the image is corrected. Then, each process such as noise removal and correction for increasing the image resolution is performed by the IPU (image processing unit) on the scanner unit side, and the analysis application analyzes the image B and the information printed on the read information 61. The reading is done.

Then, based on the read information, a condition setting value for image correction is calculated, the condition setting value is input to the controller of the image forming unit, and the correction means on the image forming unit side is based on the set value. IPU performs correction control such as correcting the light emission power and the light emission timing of the exposed portion, and the corrected image is printed on the paper P.

For the above information processing, an optimum condition setting value can be calculated by a device having an arithmetic processing function such as a personal computer, and the set value can be input to an image forming device such as a printer. Further, in a digital multifunction device such as the image forming apparatus 1 of the present embodiment having a scanner unit, it is possible to automatically perform from image measurement to completion of setting of optimum condition setting values in the apparatus.

Next, the position of the paper P on which the image B is formed is measured using the respective paper holes 27 and image holes 28 provided in the measurement reference sheet 26 (see FIG. 3 and the like) of the first embodiment. , The method of correcting the position of the image will be described below.

As shown in FIG. 5, when the paper P is sandwiched between the measurement reference sheet 26 and the backing member 29 by the operator, each paper hole 27 is a part of two sides of the paper P and the two. It is arranged at a position corresponding to one corner formed by the sides, and each image hole 28 is arranged at a position corresponding to the four corners of the image B. The measurement reference sheet 26, the paper P, and the backing member 29 have different surface densities so that their boundaries can be read. For example, if the paper P to be passed is a white background, the measurement reference sheet 26 body is gray, the backing member 29 is black, and so on.

For example, in the paper hole 27a of FIG. 10, the density measurement in the direction of the arrow C5 (x-axis direction) is repeated while shifting the position in the y-axis direction by reading the image by the scanner unit. As a result, as shown in FIG. 11, the density E1 of the measurement reference sheet 26, the density E2 of the background portion of the paper hole 27a (the density of the backing member 29 in this embodiment), and the density E3 of the paper P are discriminated from each other. Can be done.

Then, by repeating the density measurement in the direction of the arrow C5, as shown in FIG. 12, the range of the paper P portion (the gray scale portion in the figure) included in the paper hole 27a can be known. However, at this point, although the range of the paper P occupying the paper hole 27a shown by the gray scale in the figure can be known, it is unknown at which position this gray scale portion is with respect to the paper hole 27a. Therefore, it is not possible to know the position of the paper P with respect to the paper hole 27a.

Therefore, the position of the grayscale portion with respect to the center of the circle D1 (the point whose position is predetermined) is calculated. That is, assuming that the coordinates of one corner Pa of the paper P are the origin (0,0), arbitrary points at the end of the paper hole 27a where the paper P is arranged are (x1, y1), (x2, y2). ), The radius of the paper hole 27a determined in advance is R, and the coordinates of the circle center D1 of the paper hole 27a are (−k, −m). Then, since arbitrary points (x1, y1) and (x2, y2) are points on the circumference whose center D1 and radius are R, the equation (x + k) ^ 2 + (y + m) ^ 2 = R ^ 2 The values of k and m can be obtained by solving two simultaneous equations obtained by substituting x1 and x2 for x and y1 and y2 for y. As described above, the coordinates of the center of the circle of the paper hole 27a can be obtained, and the position of one corner Pa of the paper P with respect to the paper hole 27a can be calculated only by measuring the density in one scanning direction.

Further, as shown in FIG. 13, for the paper hole 27b, the density measurement by scanning in the x-axis direction of the figure is repeated while shifting the position in the y-axis direction, so that the end portion P1 (of the paper P) from the center D2 of the circle is repeated. The vertical distance n up to one side P1) can be obtained. Then, the inclination of the paper P in the vertical direction with respect to the measurement reference sheet 26 can be obtained from the horizontal distance Lab of the circular center D1 of the paper hole 27a and the circular center D2 of the paper hole 27b and the vertical distance n described above. Then, by the same method, the inclination of the paper P in the vertical direction with respect to the measurement reference sheet 26 can be obtained in relation to the paper hole 27c, and the position of the paper P with respect to the measurement reference sheet 26 can be measured.

Next, a method of obtaining the coordinates of the four corners of the image B and calculating the position and size of the image B will be described with reference to FIG. The method of measuring the density of each image hole in one direction and determining the amount of deviation between the center of the circle of each image hole and the positions of the four corners of the image B is the same as the above-mentioned case of determining k and m of the paper holes 27a. Since there is, it is omitted. Further, for convenience, in FIG. 14, the size of the image B is displayed smaller than the actual size.

As shown in FIG. 14, the four corners of the image B are Ba, Bb, Bc, and Bd, and the circle centers of the image holes 28a, 28b, 28c, and 28d are Da, Db, Dc, and Dd, respectively, and the corners from the circle center Da. Let xa and ya be the deviations in the x-direction and y-direction up to Ba. Then, similarly, as shown in FIG. 14, the deviation amount is set to xb, yb, xc, yc, xd, and yd.
Each image hole is provided so that the four points at the center of the circle form a square, that is, the center Da and the center Db of the circle, and the center Dc and the center Dd of the circle are provided at the same positions in the y-axis direction. The center of the circle Da and the center of the circle Dc, and the center of the circle Db and the center of the circle Dd are provided at the same positions in the x-axis direction.
The distance between the two points of the circle center Da and the circle center Db, and the circle center Dc and the circle center Dd is both represented by Lab, and the distance between the two points of the circle center Da and the circle center Dc and the circle center Db and the circle center Dd is Both are represented by Vac.

Here, assuming that the center Da of the circle is the origin (0,0), the coordinates of each corner are the corner Ba (xa, ya), the corner Bb (Lab-xb, yb), and the corner Bc (xc, Vac-yc). ), Corner Bd (Lab-xd, Vac-yd).

However, when the measurement reference sheet 26 is placed at an angle with respect to the reading glass 45 (see FIG. 1), the respective circle centers Da, Db, Dc, and Dd are in the x-axis direction or the y-axis described above. The position will be displaced by this inclination from the same position in the direction. It is also conceivable that the inclination of the measurement reference sheet 26 is so large that it cannot be ignored, which affects the accuracy of calculating the coordinates of the center of the circle and each corner. However, even in this case, by calculating the coordinates of the center of the circle in consideration of the inclination of the measurement reference sheet 26, it is possible to calculate the coordinates of each corner with high accuracy. That is, since at least a part of each side of the measurement reference sheet 26 (for example, sides 261,262 in FIG. 5) is provided within the reading range of the reading sensor 44, the reading density differs from that of the backing member 29. , The inclination (inclination with respect to the x-axis and y-axis) of each side of the measurement reference sheet 26 with respect to the reading glass 45 can be calculated. Therefore, the coordinates of each corner can be obtained with high accuracy by obtaining the coordinates of the center of each circle in consideration of this inclination.

As described above, the positions of the four corners of the image B with respect to the circular center Da of the image hole 28a can be measured, and the positions of the image B with respect to the measurement reference sheet 26 can be measured. Further, the relative position of the image B on the paper P can be measured by combining with the measurement result of the position of the paper P with respect to the measurement reference sheet 26 described above. As a result, the formation position of the image can be corrected. For example, the image can be formed at a desired position on the subsequent paper by taking into consideration the shrinkage of the paper and the misalignment of printing due to the change in temperature and humidity. It will be possible.

Further, in a simple method, the position of the image B with respect to the paper P can be obtained by the following method. In order to simplify the explanation, first, a method of calculating the positions of the four corners in the y-axis direction will be described.

As described with reference to FIG. 13, assuming that the deviations of the paper P from the circle centers D1 and D2 in the y-axis direction are calculated as k and n, respectively, y of the edge P1 of the paper P from the circle centers D1 and D2. The axial deviation can be approximately calculated as (m + n) / 2. Then, as shown in FIG. 15, assuming that the vertical distance from the circle center D1 to the circle center Da and the circle center Db is V1, and the vertical distance from the circle center D2 to the circle center Da and the circle center Db is V2, the paper P The vertical distance from the end P1 to one corner Ba is (distance from D1 to Da)-(distance from D1 to P1) + (distance from Da to Ba) = V1- (m + n) / 2 + ya, and the paper. The vertical distance from the end P1 of P to one corner Bb is V2- (m + n) / 2 + yb. Since the positions of the respective paper holes and image holes are accurately calculated in advance, since V1 and V2 are known values, the edges P1 to one corner Ba and Bb of the above paper P are used. You can find the distance. Similarly, assuming that the vertical distance from the circle center D1 to the circle center Dc and the circle center Dd is V3 and the vertical distance from the circle center D2 to the circle center Dc and the circle center Dd is V4, from the edge P1 of the paper P. The vertical distance to one corner Bc is V3- (m + n) / 2 + yc, and the vertical distance from the end P1 of the paper P to one corner Bd is V4- (m + n) / 2 + yd, and the values of V3 and V4 are known. Therefore, these values can also be obtained.

In this way, the vertical distance from the edge of the paper P to the four corners of the image can be obtained. Then, the respective distances in the horizontal direction can be obtained by the same method.
Furthermore, since the positional relationship between the edge of the paper P and the measurement reference sheet 26 is also known as described above, the positional relationship between the measurement reference sheet 26, the paper P, and the image B can be calculated. It is possible to correct the position of the image B formed on the paper P.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.
The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, and may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine thereof.

Further, the paper holes 27 and the image holes 28 provided in the measurement reference sheet 26 are made into circular holes, but the holes are not limited to these, and can be appropriately changed, for example, by making them rectangular holes. In this case, the edges of the paper P and the image B can be measured by measuring the density in the direction of arrow C5 in FIG. 10 and in the vertical direction of the figure, and one corner of the paper P and one corner of the image B can be measured. The position of can be measured.

Further, the backing member 29 may not be provided. In this case, the density of the paper P and the measurement reference sheet 26 needs to be different from the density of the background portion to be read.

As the image measurement reference means, the paper hole 27 and the image hole 28 of the first embodiment (see FIG. 3 and the like), and the reference patch 62 and the density hole 63 of the second embodiment (see FIG. 6) are all provided as an image. It goes without saying that an image measurement reference means can be provided as a reference when measuring the position, size, density, etc.

1 Image forming apparatus 26 Measurement reference sheet (image measurement reference means)
27a, 27b, 27c Paper holes (recording medium holes or holes)
28a, 28b, 28c, 28d Image holes (holes)
29 Backing member 44 Reading sensor (image reading means)
60 Reading hole 61 Reading information 62 Reference patch 63 Concentration hole (image hole or hole)
B Image P Paper (Recording medium)
Edge of P1 paper

Japanese Unexamined Patent Publication No. 2004-349892

Claims (6)

It has an image forming means for forming an image on a recording medium, an image reading means for reading an image, and a correction means for correcting an image formed on the recording medium.
A correction recording medium on which a correction image is formed is provided so as to be superimposed on an image measurement reference means that serves as a reference for measuring the image.
The image measurement reference means is provided at a position corresponding to an image formed on the recording medium and a position corresponding to a one-dimensional code or a two-dimensional code which is code information formed on the recording medium. It has a reading hole provided and
The image reading means reads the image for correction and the code information recorded on the recording medium for correction through the image hole and the reading hole provided in the image measurement reference means. An image forming apparatus that corrects an image formed by the correction means on a subsequent recording medium based on the read image for correction and code information. The code information includes information on the date and time when the image was formed on the recording medium.
The image forming apparatus according to claim 1, wherein it is determined whether or not to perform a correction operation by the correction means based on the date and time information. The image forming apparatus according to claim 2, wherein when it is determined that the correction operation is not performed based on the information on the date and time, a confirmation display of the necessity of the correction operation is performed. The image measurement reference means has a reference patch that serves as a reference for density when compared with the density of an image formed on the recording medium.
Any of claims 1 to 3 for correcting the density of an image formed on the recording medium by the correction means by comparing the density of the reference patch read by the image reading means with the density of the image formed on the recording medium. The image forming apparatus according to item 1. The image measurement reference means is provided at a position corresponding to an image formed on the recording medium and a one-dimensional code or a two-dimensional code which is code information formed on the recording medium. Has a reading hole
An image formed on a recording medium and the code information recorded on the recording medium through the image hole and the reading hole provided in the image measurement reference means as a reference for the image reading means to measure an image. Read,
An image correction method for correcting an image formed on a subsequent recording medium based on the read image and code information.
The code information includes information on the date and time when the image was formed on the recording medium.
An image correction method for correcting an image only when the time elapsed since the image was formed on the recording medium is within a predetermined time. If the stable time for stabilizing the size of the recording medium has elapsed, the image is corrected and the image is corrected.
The image correction method according to claim 5, wherein when the stable time has not passed, a display is displayed to the operator for confirming the necessity of the correction operation.

Images