JP2020096260A - Tilt correction device, reading device, image forming apparatus, and tilt correction method - Google Patents

Abstract

To improve the accuracy of skew amount detection.SOLUTION: A tilt correction device comprises: a conveying unit that conveys a detection object to an imaging position; an imaging unit that picks up an image of the detection object at the imaging position to generate image information on the imaging position; a passage position information acquisition unit that is provided on the upstream side of the imaging position in a conveyance direction and acquires information on a passage position of the detection object; and a tilt correction unit that corrects a tilt of the detection object in the image information, according to the passage position information and the amount of tilt of the detection object obtained in the image information generated by the imaging unit.SELECTED DRAWING: Figure 9

Description

The present invention relates to a tilt correction device, a reading device, an image forming apparatus, and a tilt correction method.

Conventionally, a skew for correcting the inclination (skew) of read image data when reading an image of a detection target by image processing based on information of the skew amount (skew angle) and the registration position detected from the read image data. Correction techniques are known.

Patent Document 1 discloses a technique for detecting the width and skew amount of a document by using the detection time difference between the existing document width detection sensors for the purpose of detecting the skew amount according to the document width. ..

However, according to the conventional skew correction, in order to improve the detection accuracy, it is necessary to detect the contour of the document from the read image by edge detection or the like, and detect the skew amount in the region using the document boundary or the shadow. For this reason, it is necessary to add image processing for detecting the document width and change the parameters for skew amount detection according to the document width. Deterioration of the data and bloat of the amount of memory for data storage will occur.

Further, according to the technique disclosed in Patent Document 1, there is a problem in that the detection accuracy deteriorates or cannot be detected due to the following points, and the detection accuracy of the skew amount cannot be secured.
・Points are small because sampling is performed only with the number of document width detection sensors. ・Detection error between sensors causes skew amount detection error from the actual image. ・Transmissive sensor detects OHP and other transparent documents. What you can't do

The present invention has been made in view of the above, and an object thereof is to improve the accuracy of skew amount detection.

In order to solve the above-mentioned problems and to achieve the object, the present invention provides a conveyance unit that conveys a detection target to an image capturing position, an image of the detection target at the image capturing position, and image information of the image capturing position. An imaging unit that generates, a passage position information acquisition unit that is provided on the upstream side in the transport direction with respect to the imaging position and that acquires passage position information of the detection target, the passage position information, and the passage unit generated by the imaging unit. And a tilt correction unit that corrects the tilt of the detection target in the image information according to the tilt amount of the detection target obtained from the image information.

According to the present invention, it is possible to improve the accuracy of skew amount detection.

FIG. 1 is a sectional view schematically showing a schematic configuration of the image forming apparatus according to the first embodiment. FIG. 2 is a sectional view schematically showing a schematic configuration of the scanner. FIG. 3 is a sectional view schematically showing the schematic configuration of the ADF. FIG. 4 is a diagram schematically showing a schematic configuration of the document width sensor. FIG. 5 is a block diagram showing the hardware configuration of the image forming apparatus. FIG. 6 is a block diagram showing the functions of the image processing apparatus. FIG. 7 is a flowchart schematically showing the flow of the image reading process. FIG. 8A is a diagram illustrating an example of the relationship between the document width detection result and the tilt amount detection region (downstream side edge in the transport direction). FIG. 8-2 is a diagram showing an example of the relationship between the document width detection result and the tilt amount detection region (downstream side edge in the transport direction). FIG. 9 is a diagram showing timings of various kinds of image processing in comparison with the conventional case. FIG. 10A is a diagram illustrating an example of the relationship between the document width detection result and the edge search area of the image forming apparatus according to the second embodiment. FIG. 10B is a diagram illustrating an example of the relationship between the document width detection result and the edge search area of the image forming apparatus according to the second embodiment. FIG. 11 is a diagram illustrating an example of the relationship between the document width detection result and the tilt amount detection region of the image forming apparatus according to the third embodiment. FIG. 12 is a diagram illustrating an example of the relationship between the document width detection result and the tilt amount detection region of the image forming apparatus according to the fourth embodiment. FIG. 13 is a diagram showing a comparison between a document width detection result and a skew straight line of the image forming apparatus according to the fifth embodiment.

Embodiments of a tilt correction device, a reading device, an image forming apparatus, and a tilt correction method will be described in detail below with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a sectional view schematically showing a schematic configuration of an image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 is a multifunction machine having at least two functions of a copy function, a printer function, a scanner function, and a facsimile function.

As shown in FIG. 1, the image forming apparatus 100 includes a paper feeding unit 103, a device body 104, a scanner 101, and an automatic document feeder (ADF: Auto Document Feeder) 102.

The image forming apparatus 100 includes a plotter 120, which is an image forming unit, in the apparatus body 104. The plotter 120 includes a tandem type image forming unit 105, a registration roller 108 that supplies the image forming unit 105 with recording paper from the paper feeding unit 103 through a conveyance path 107, an optical writing device 109, and a fixing unit 110. And a double-sided tray 111.

In the image forming unit 105, four photosensitive drums 112 are arranged in parallel corresponding to four colors of Y (yellow), M (magenta), C (cyan), and K (key plate (black)). .. An image forming element including a charging device, a developing device 106, a transfer device, a cleaner and a charge eliminator is arranged around each photoconductor drum 112. Further, an intermediate transfer belt 113, which is stretched between a driving roller and a driven roller while being sandwiched between the nip of the transfer device and the photoconductor drum 112, is arranged.

The tandem-type image forming apparatus 100 configured as described above uses the optical writing device 109 on the photoconductor drum 112 corresponding to each color of YMCK based on the original image obtained by reading the original sent from the ADF 102 with the scanner 101. Optical writing is performed from the above, the developing device 106 develops each color toner, and the primary transfer is performed on the intermediate transfer belt 113 in the order of Y, M, C, and K, for example. Then, the image forming apparatus 100 secondarily transfers the full-color image in which the four colors are superimposed by the primary transfer onto the recording sheet supplied from the sheet feeding unit 103, and then the fixing unit 110 fixes and discharges the sheet. A full-color image is formed on the recording paper.

Next, the scanner 101 will be described.

FIG. 2 is a sectional view schematically showing a schematic configuration of the scanner 101. As shown in FIG. 2, the scanner 101 includes a first carriage 25, a second carriage 26, an imaging lens 27, and an image pickup unit 28. Each of these components is a main body frame 101a of the scanner 101. It is arranged inside each.

Inside the main body frame 101a of the scanner 101, first rails and second rails (not shown) are provided so as to extend in the sub-scanning direction (the horizontal direction in FIG. 2). The first rail is composed of two rails arranged at a predetermined interval in the main scanning direction orthogonal to the sub scanning direction. The second rail has the same configuration as the first rail.

The first carriage 25 is slidably attached to the first rail, and is moved in the sub-scanning direction by a drive motor (not shown) through a first carriage drive wire (not shown) to a position indicated by a solid line and a position indicated by a broken line in FIG. It is configured to be able to reciprocate between and. The first carriage 25 is provided with a light source 24 and a first mirror member 25a.

The second carriage 26 is slidably attached to the second rail, and is driven by a drive motor (not shown) via a second carriage drive wire (not shown) in the sub-scanning direction in a position indicated by a solid line and a broken line in FIG. It is configured to be able to reciprocate between the position shown. The second carriage 26 is provided with a second mirror member 26a and a third mirror member 26b.

Here, the first carriage 25 and the second carriage 26 move in the sub-scanning direction at a speed ratio of 2:1. Due to such a relationship of the moving speed, even if the first carriage 25 and the second carriage 26 move, the optical path length of the light from the document surface to the imaging lens 27 does not change.

The imaging lens 27 focuses the reflected light from the document, which is incident via each mirror member, onto the imaging unit 28. The image pickup unit 28 is composed of an image pickup device such as a CCD, and photoelectrically converts the reflected light image of the original image formed through the image forming lens 27 to output an analog image signal which is a read image.

Next, the ADF 102 mounted on the scanner 101 will be described.

FIG. 3 is a sectional view schematically showing a schematic configuration of the ADF 102. As shown in FIG. 3, the ADF 102 includes a document tray 11 on which a document is placed. The document tray 11 has a movable document table 41 that rotates in the directions a and b in the drawing with the base end as a fulcrum, and a pair of side guide plates 42 that position the document in the left-right direction with respect to the document feeding direction. .. By rotating the movable document table 41, the front end of the document in the feeding direction is adjusted to an appropriate height.

Further, the document tray 11 is provided with document length detection sensors 89 and 90 which detect whether the document is oriented vertically or horizontally, and are separated from each other in the feeding direction. As the document length detection sensors 89 and 90, a reflection type sensor which detects without contact by an optical means or a contact type actuator type sensor may be used.

One side of the pair of side guide plates 42 is slidable in the left-right direction with respect to the sheet feeding direction, and is configured so that documents of different sizes can be placed.

On the fixed side of the pair of side guide plates 42, a set filler 46 which is rotated by placing a document is provided. Further, a document set sensor 82 for detecting that a document is placed on the document tray 11 is provided at the lowermost portion on the movement locus of the tip of the set filler 46. That is, the document set sensor 82 detects the presence/absence of a document set in the ADF 102 depending on whether or not the set filler 46 is rotated and is disengaged from the document set sensor 82.

The ADF 102 includes a transport unit 50 including a separation/feed unit 51, a pull-out unit 52, a turn unit 53, a first reading transport unit 54, a second reading transport unit 55, and a paper discharge unit 56. ing. Each of the transport rollers of the transport unit 50 is rotationally driven by one or more transport motors.

The separating/feeding unit 51 has a pickup roller 61 arranged in the vicinity of a paper feed port 60 for feeding a document, and a paper feed belt 62 and a reverse roller 63 arranged so as to face each other across a conveyance path. doing.

The pickup roller 61 is supported by a support arm member 64 attached to the paper feed belt 62, and is illustrated between a contact position where it contacts a document stack and a separation position where it separates from the document stack via a cam mechanism (not shown). It moves up and down in the middle c and d directions. The pickup roller 61 picks up several (ideally one) documents among the documents stacked on the document tray 11 at the contact position.

The paper feed belt 62 rotates in the feeding direction, and the reverse roller 63 rotates in the opposite direction to the feeding direction. Further, the reverse roller 63 rotates in the opposite direction to the paper feed belt 62 when the documents are double-fed, but when the reverse roller 63 is in contact with the paper feed belt 62 or only one document is fed. When it is being conveyed, it is rotated along with the sheet feeding belt 62 by the action of a torque limiter (not shown). This prevents the document from being double-fed.

The pullout section 52 has a pullout roller 65 composed of a pair of rollers arranged so as to sandwich the transport path 52a. The pull-out section 52 performs primary abutting alignment (so-called skew correction) of the fed document by the drive timing of the pull-out roller 65 and the pickup roller 61, and pulls out and transports the aligned document.

The turn portion 53 has an intermediate roller 66 and a reading inlet roller 67, which are a pair of rollers and are arranged so as to sandwich the curved conveyance path 53a from the upper side to the lower side. The turn portion 53 turns the original drawn and conveyed by the intermediate roller 66 by conveying the curved conveying path, and turns the original by the reading entrance roller 67 so that the surface of the original faces downward and the original reading position (imaging position). It is conveyed to the vicinity of the slit glass 7.

Here, the conveyance speed of the document from the pullout section 52 to the turn section 53 is set to be higher than the conveyance speed of the first reading conveyance section 54. As a result, the transport time of the document transported to the first reading transport unit 54 is shortened.

The first reading/conveying unit 54 has a first reading roller 68 arranged so as to face the slit glass 7, and a first reading outlet roller 69 arranged on the conveying path 55a after completion of reading. The first reading/conveying unit 54 conveys the surface of the document conveyed to the vicinity of the slit glass 7 while contacting the slit glass 7 with the first reading roller 68. At this time, the original is read by the scanner 101 through the slit glass 7. At this time, the first carriage 25 and the second carriage 26 of the scanner 101 are stopped at the home position. The first reading/conveying unit 54 further conveys the document after the reading by the first reading outlet roller 69.

The second reading/conveying unit 55 reads the back side of the document, the second reading unit 70, the second reading roller 70 disposed so as to face the second reading unit 91 with the conveyance path 55a interposed therebetween, and the second reading unit 91. The second reading outlet roller 71 is disposed downstream in the transport direction of the.

In the second reading/conveying unit 55, the second reading unit 91 reads the back side of the original after the front side reading. The document whose back side has been read is conveyed toward the paper exit by the second reading exit roller 71. The second reading roller 70 serves to suppress the floating of the document in the second reading unit 91 and also serves as a reference white portion for acquiring the shading data in the second reading unit 91. When the double-sided reading is not performed, the original document passes through the second reading unit 91.

The paper discharge unit 56 is provided with a pair of paper discharge rollers 72 near the paper discharge port, and discharges the document conveyed by the second reading outlet roller 71 to the paper discharge tray 12.

Further, the ADF 102 is provided with various sensors such as an abutting sensor 84, a registration sensor 81, and a paper discharge sensor 83 along the transport path, and is used for transport control of a document transport distance, a transport speed, and the like.

Further, a document width sensor 85 that functions as a passage position information acquisition unit is provided between the pullout roller 65 and the intermediate roller 66. The length of the document in the conveying direction is detected from the motor pulse by reading the leading edge and the trailing edge of the document with the abutment sensor 84 and the registration sensor 81.

Next, the document width sensor 85 will be described.

FIG. 4 is a diagram schematically showing a schematic configuration of the document width sensor 85. As shown in FIG. 4, the document width sensor 85 measures the width size of a general fixed-form document from a reference position (for example, the fixed side of the side guide plate 42) when the document is fed from the paper feed port 60 of the ADF 102. Five width detection sensors SN1 to SN5 are arranged side by side at a distinguishable interval.

Types of the width detection sensors SN1 to SN5 include a transmissive/reflective sensor that reacts when a document passes and a sensor that detects that a filler accommodates the document. The width detection sensors SN1 to SN5 of the present embodiment are provided with light receiving elements, and detect the document width based on the light reception result from the irradiation light provided at the facing position with the conveyance path sandwiched therebetween.

As described above, the document passes through the document width sensor 85 provided between the pullout roller 65 and the intermediate roller 66 immediately after being fed. The image processing apparatus 200 (see FIG. 5), which will be described later, detects the width information, which is the passage position information of the document, based on the light receiving results of the width detection sensors SN1 to SN5 in the document width sensor 85. Specifically, depending on which width detection sensor SN1 to SN5 of the document width sensor 85 receives light, the image processing apparatus 200 can detect the width of the document in the interval unit. For example, when all of the five width detection sensors SN1 to SN5 have received light, it can be seen that a document having a width of E or more is being conveyed. Further, when the three width detection sensors SN1 to SN3 receive the light, it is understood that the document having the width C or more and less than D is being conveyed.

Next, the hardware configuration of the image forming apparatus 100 will be described.

Here, FIG. 5 is a block diagram showing a hardware configuration of the image forming apparatus 100. As shown in FIG. 5, the image forming apparatus 100 is provided with an image processing apparatus 200 that performs a predetermined process on a document image read by the scanner 101 and outputs it as image data to the plotter 120. The scanner 101, the ADF 102, and the image processing apparatus 200 form a tilt correction device and a reading device.

The image processing apparatus 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a main memory 205, a chip set 206, an image processing ASIC 207, a controller ASIC 208, a main memory 209, and an I/O ASIC 210. Note that ASIC is an abbreviation for application specific integrated circuit.

The CPU 201 is for controlling the image forming apparatus 100. The main memory 205 is a memory (image memory) in which a program for the CPU 201 to control the image forming apparatus 100 is developed and used as a work area for the program, or image data to be handled is temporarily stored. The chip set 206 is used together with the CPU 201 and controls access to the main memory 205 by the controller ASIC 208 and the I/O ASIC 210.

A program executed by the image forming apparatus 100 according to the present embodiment is a file in an installable format or an executable format, such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disk). It may be configured to be provided by being recorded in a computer-readable recording medium.

Further, the program executed by the image forming apparatus 100 according to the present embodiment may be stored in a computer connected to a network such as the Internet and provided by being downloaded via the network. Further, the program executed by the image forming apparatus 100 according to the present embodiment may be provided or distributed via a network such as the Internet.

The scanner 101 has a function of reading image data to be copied and image data to be output to an external interface. The plotter 120 has a function of printing the image data placed in the main memory 209.

The image processing ASIC 207 performs image processing on the image data read by the scanner 101 and outputs the image data to the controller ASIC 208. The image processing ASIC 207 performs image processing so that the image data from the controller ASIC 208 can be printed by the plotter 120, and sends the image data in accordance with the printing timing of the plotter 120.

The controller ASIC 208 uses the main memory 205 over the chipset 206 to rotate and edit the image data handled by the image forming apparatus 100, stores the image data in the HDD 211, and transmits/receives the image data to/from the image processing ASIC 207. The main memory 209 is used as an image memory in which the controller ASIC 208 performs image processing. A HDD (Hard Disk Drive) 211 is used to temporarily store image data that has undergone image processing.

The I/O ASIC 210 is an external interface for giving an additional function to the image forming apparatus 100. For example, the I/O ASIC 210 is an interface such as a network interface, USB, SD card, operation unit, SPI, I2C, document width sensor 85 (width detection sensors SN1 to SN5), or a hardware accelerator for accelerating image processing. , An encryption processing circuit, and the like.

Next, the function exerted by the image processing apparatus 200 will be described.

Here, FIG. 6 is a block diagram showing the functions of the image processing apparatus 200. In addition, here, of the functions exhibited by the image processing apparatus 200, characteristic functions in the present embodiment will be described.

As shown in FIG. 6, the image processing apparatus 200 includes a document width information control unit 300, a tilt amount detection unit 310, and a tilt correction unit 320. In the present embodiment, the chip set 206 has the document width information control unit 300, and the controller ASIC 208 has the tilt amount detection unit 310 and the tilt correction unit 320. Note that the document width information control unit 300, the tilt amount detection unit 310, and the tilt correction unit 320 may be realized by executing the program by the CPU 201, without being limited thereto.

The document width information control unit 300 is a document width information of a document (setting of an inclination amount detection area and the like) which is a detection result by the document width sensor 85 (width detection sensors SN1 to SN5) before the document is read by the imaging unit 28 of the scanner 101. Information) is transmitted to the tilt amount detection unit 310 for each document. As the transmission means, for example, a signal transmission method may be used, or the CPU 201 goes to read the document width information stored in the main memory 205 and tilts the document width information (setting information such as a tilt amount detection area) corresponding thereto. A method applied to the controller ASIC 208 having the amount detection unit 310 and the tilt correction unit 320 may be used.

The tilt amount detection unit 310 presets a tilt amount detection region based on the document width information, and detects the tilt amount (skew amount) of the image data read by the scanner 101.

When detecting the skew amount of a document using image information, generally, the edge of the document front end on the downstream side in the transport direction is detected, and the skew angle (skew amount) can be detected by calculating the linear expression. Many. As for the front end of the original, there is a method of detecting the boundary between the background of the reading position of the ADF 102 and the read original at the front of the original, and a method of detecting the edge using the shadow of the original.

However, in the former method, there is a possibility that the linear type may be erroneously detected when there is a portion of the same color as the background due to the pattern near the leading edge of the document. On the other hand, the latter method does not have the problem of the former method because the skew is detected by the shadow regardless of the pattern and color of the document, but it may be different in the width direction depending on how the ADF 102 reading position is mechanically assembled. There is a case in which the width of the shadow changes along with it, and the skew angle of the document and the skew angle of the shadow locally differ. Further, even when the document is curled, the behavior of the front end of the document is not linear, and there is a possibility of false detection. Therefore, in both methods, it is necessary to widen the detection area to the width of the document to improve the linear accuracy, and in the prior art, the contour of the document was extracted using the image information when reading the image.

Therefore, the tilt amount detection unit 310 of the present embodiment detects the tilt amount based on the document width information acquired by the document width sensor 85 (width detection sensors SN1 to SN5) before the document reading by the imaging unit 28 of the scanner 101. Is preset and the skew amount is detected.

The tilt correction unit 320 corrects the tilt according to the tilt amount (skew amount) of the image data read by the scanner 101. More specifically, the tilt correction unit 320 performs rotation processing based on the skew amount detected by the tilt amount detection unit 310, and outputs a skew-corrected image.

Next, an image reading process in the image forming apparatus 100 according to the present embodiment will be described.

Here, FIG. 7 is a flowchart schematically showing the flow of the image reading process. As shown in FIG. 7, when document feeding is started by the ADF 102, the image processing apparatus 200 (document width information control unit 300) causes the document width sensor 85 (width detection sensor) before the document reading by the imaging unit 28 of the scanner 101. The document width information of the document (setting information such as a tilt amount detection area) which is the detection result in SN1 to SN5) is transmitted to the tilt amount detection unit 310 for each document (step S1).

Next, the image processing apparatus 200 acquires image data obtained by the scanner 101 reading the document conveyed by the ADF 102 to the slit glass 7 which is the reading position (step S2).

Next, the image processing apparatus 200 (tilt amount detection unit 310) detects the skew amount in the tilt amount detection area based on the document width information (setting information such as the tilt amount detection area) of the document transmitted in step S1 ( Step S3).

Here, FIGS. 8A and 8B are diagrams showing an example of the relationship between the document width detection result and the inclination amount detection region (edge on the downstream side in the transport direction). 8A and 8B, (a) shows the result of document width detection, and (b) shows the tilt amount detection area. FIG. 8A shows the case of an original having a width of E or more, and FIG. 8B shows the case of an original having a width of C to D.

Note that black circles in FIGS. 8A and 8B indicate sampling points in the image, and as an example, a straight line type for skew amount detection by a shadow detection method. Explaining with the example of the document width sensor 85 shown in FIG. 4, when all the width detection sensors SN1 to SN5 receive the light, the document (maximum size) having the width E or more is conveyed, and therefore the tilt amount detection unit 310 The width E is the inclination amount detection area of the linear calculation point for detecting the skew amount.

As a matter of course, with respect to the image information acquired at the reading position, the linear calculation point area for detecting the skew amount automatically becomes substantially the same with respect to the document width.

On the other hand, when the width detection sensors SN1 to SN3 receive the light, since the document having the width C or more and less than D is conveyed, the inclination amount detection unit 310 detects the inclination amount of the linear calculation point for detecting the skew amount. The area has a width C.

In this case, of course, the linear calculation point area for detecting the skew amount is automatically the same as the document width for the image information acquired at the reading position.

Note that, in FIGS. 8A and 8B, since the reference position is the back side of the ADF 102, the left end of the document is at the same position regardless of the document size. However, in the case of the center position reference ADF in which the reference position at the left end of the document differs depending on the document size, the region at the left end of the document shifts according to the document size, and the left end portion of the calculation point region also shifts. ..

Next, the image processing apparatus 200 (tilt correction unit 320) performs skew correction that performs rotation processing based on the skew amount detected by the tilt amount detection unit 310, and outputs the skew-corrected image (step S4).

The above steps S1 to S4 are executed for all the originals conveyed by the ADF 102.

As a result, since the tilt amount detection area setting based on the document width information is already set in the tilt amount detection unit 310 before the document image is read by the image pickup unit 28 of the scanner 101, processing for changing the processing parameter at the time of image reading or Image processing for detection can be omitted.

Here, FIG. 9 is a diagram showing timings of various processes related to image processing in comparison with the related art. As shown in FIG. 9A, conventionally, several lines of image data are stored for edge detection at the time of image acquisition, the document edge is detected, the document width is detected, and then the parameter is switched to detect the skew amount. / Skew correction processing was performed.

On the other hand, as shown in FIG. 9B, in the present embodiment, the information of the tilt amount detection area based on the document width information is read for each document before the document image is read by the imaging unit 28 of the scanner 101. Since the inclination amount detection unit 310 has already been set, it is possible to omit the process of changing the image data storage, document width detection, and skew amount detection parameters at the time of image reading.

Thus, a document width that is good with a rough accuracy is acquired in advance by using the existing width detection sensors SN1 to SN5, and the skew amount is detected with high accuracy in the image, so that the document width is optimal and the skew amount detection accuracy is improved. Since it is possible to omit the processing for changing the parameters for skew amount detection and the image processing for width detection while maintaining the same, there is no delay in the completion of the output of the image (after skew correction), and the skew correction accuracy is improved while maintaining the skew. It is possible to prevent productivity deterioration due to delay of the image data after the amount detection/skew correction and enlargement of the data storage memory amount.

As described above, according to the present embodiment, conventionally, the object information (original passage position information) is acquired at the time of image acquisition, and the image processing is performed after the parameter switching. Since the setting information has already been set in the tilt amount detection unit 310 for each object (original) before image acquisition, the processing of changing the image processing parameter at the time of image acquisition and the image processing for object information acquisition are omitted. be able to. As a result, it is possible to prevent a decrease in productivity without delaying the completion of output of the skew amount. That is, the accuracy of skew amount detection can be improved.

Further, according to the image forming apparatus 100, it is possible to appropriately detect the skew amount and correct the skew for each document without deterioration of productivity and memory enlargement due to copying by image reading using the ADF 102.

(Second embodiment)
Next, a second embodiment will be described.

In the second embodiment, in the tilt amount detection area set according to the detected document width (document passing position information), the left edge or right edge of the document in the document transport direction is detected. However, it is different from the first embodiment. In the following description of the second embodiment, the description of the same parts as those of the first embodiment will be omitted, and only the parts different from those of the first embodiment will be described.

10A and 10B are diagrams illustrating an example of the relationship between the document width detection result of the image forming apparatus 100 according to the second embodiment and the edge search area. 10A shows the case of a document having a width of E or more, and FIG. 10B shows the case of a document having a width of C to D.

In the present embodiment, it is assumed that the reference position at the left end of the document is the central position reference ADF 102 that differs depending on the document size. That is, the ADF 102 of the present embodiment conveys a document with the center as a reference regardless of the document size. In this case, since the left end area of the original is shifted according to the original size, the left end of the calculation point area is also shifted. Accordingly, as shown in FIGS. 10-1 and 10-2, the document width sensor 85 has three width detection sensors SN1 to SN3 arranged from the center to the left end in the main scanning direction.

By the way, depending on the method of detecting the skew amount, it may be necessary to specify the left and right edges in order to extract the document upper left origin for rotation correction during the skew amount detection processing. In that case, the position is specified by a change in the level of the image or the like, but if it is attempted to detect the entire search region from the left end of the background region, the detection process will take time.

On the other hand, since the inclination amount detection unit 310 has the document width information, it is possible to perform the search in a state where the edge search area is limited by the intervals of the width detection sensors SN1 to SN3, and the edge detection time is shortened. You can

As shown in FIG. 10A, in the case of the document width E (light is received by all of the width detection sensors SN1 to SN3), the left end edge search area is an area outside the width detection sensor SN1, and the search width is width detection. It becomes the interval of the sensor SN. On the other hand, the right edge search region is a region outside the position of line symmetry with respect to the center of the document E, and the search width is the interval between the width detection sensors SN.

As shown in FIG. 10B, in the case of the document width C (light reception by the width detection sensors SN2 to SN3), the left edge search area is an area outside the width detection sensor SN2, and the search width is the width detection sensor SN. It becomes the interval of. On the other hand, the right edge search area is an area outside the line-symmetrical position with respect to the center of the document C, and the search width is the interval between the width detection sensors SN.

As described above, according to the present embodiment, the left end and the right end, which are regions from which the external factor (noise stain) is removed based on the document passage position information acquired by the width detection sensors SN1 to SN3 of the ADF 102 before the document is read. The edge detection function reduces the influence of external factors (noise stains) that may cause false detections when changing the number of sampling points or intervals for edge detection during image reading, and during detection. Optimal edge detection can be performed. As a result, the accuracy of detecting the skew amount can be improved.

(Third Embodiment)
Next, a third embodiment will be described.

The third embodiment is different from the first embodiment in that skew correction is performed/not performed depending on the detected document width (document passing position information). In the description of the third embodiment, the description of the same parts as those of the first embodiment will be omitted, and only the parts different from the first embodiment will be described.

FIG. 11 is a diagram illustrating an example of the relationship between the document width detection result and the tilt amount detection region of the image forming apparatus 100 according to the third embodiment. FIG. 11 shows a case where only the width detection sensor SN1 in FIG. 4 reacts for a certain period of time (a document whose width is A or more and less than B). In FIG. 11, (a) shows the document width detection result, and (b) shows the tilt amount detection area. Note that FIG. 11 shows a linear expression for detecting the amount of skew in the method of detecting by a shadow.

As shown in FIG. 11, the linear calculation point region for detecting the skew amount has the width A. However, even when the skew amount is detected in the calculation area according to the document width, there are error factors (local distribution of the pattern at the leading edge of the document or the local distribution of the shadow width, erroneous linear detection due to dust and noise). ) Occurs in the entire calculation area, the linear equation for detecting the skew amount is erroneously detected. That is, if the skew amount detection/skew correction is performed on a small-sized document, as shown in FIG. 11, the skew of the document edge and the skew of the detected approximate straight line are different, resulting in insufficient correction or erroneous correction. there is a possibility. The influence of such an error increases as the size of the original decreases.

Therefore, in the present embodiment, the skew amount detection unit 310 and the skew correction unit 320 have the document width sensor 85 (width detection sensors SN1 to SN5) detect a document width less than a certain value (for example, the width detection sensor SN1). If only the light is received), the skew amount detection/skew correction is not performed.

Even with such control, the presence/absence of the implementation can be determined at the upstream stage of the document conveyance, so that the process of changing the processing parameter at the time of image reading and the presence/absence determination of the skew amount detection/skew correction depending on the document width can be performed. Image processing can be omitted.

As described above, according to the present embodiment, the curl of the original and the shadow of the original are easily affected by the conveyance path when the original is small, and it may be better not to perform skew correction. In some cases, whether to perform correction can be automatically switched.

In recent years, an auxiliary tray for reading a small-sized document may be attached in order to continuously read a business card or the like with the ADF 102. In this case, since it is known that a small-sized document is read when the auxiliary tray is attached to the ADF 102, the skew amount detection/skew correction is automatically turned off when the attachment of the auxiliary tray is detected. The structure can also obtain the same effect.

Further, there is a use case in which the user of the scanner 101 wants to intentionally skew and read. In this case, it is possible to reduce the skew amount by the user arbitrarily selecting whether or not to perform the skew correction by the operation unit or the like and sending the information to the tilt amount detection unit 310 and the tilt correction unit 320. It is possible to plan. In this way, the user can arbitrarily switch whether or not to perform skew correction, regardless of the detected document width.

(Fourth Embodiment)
Next, a fourth embodiment will be described.

The fourth embodiment is different from the first embodiment in that the tilt amount detection area is switched according to the result of the detection time difference of each sensor for detecting the document width (document passing position information). .. In the following description of the fourth embodiment, the description of the same parts as those in the first embodiment will be omitted, and the differences from the first embodiment will be described.

FIG. 12 is a diagram showing an example of the relationship between the document width detection result and the tilt amount detection region of the image forming apparatus 100 according to the fourth embodiment. In FIG. 12, (a) shows the document width detection result, and (b) shows the tilt amount detection area. FIG. 12 shows a case where all the width detection sensors SN1 to SN5 in FIG. 4 cannot receive light (a document having a width E).

In the linear calculation for detecting the skew amount, as shown in FIG. 12, when the conveyed document has a bent edge or a missing portion, the skew is locally changed. Therefore, if the folds or nicks in the original are also included in the linear calculation, there is a problem that the skew amount is erroneously detected.

Therefore, in order to prevent such a problem, the tilt amount detection unit 310 has a fold or a missing portion of the document based on the difference in the reaction time (time when the document passes) of the width detection sensors SN1 to SN5. To detect. FIG. 12 shows a case where there is an ear fold or a chipped portion on the reference position side when a document is placed on the ADF 102. In this case, the width detection sensors SN2 to SN5 react almost at the same time, but the reaction of only the width detection sensor SN1 is delayed and a time difference occurs due to ear breakage or chipping.

In such a case, the inclination amount detection unit 310 is configured to perform a skew amount detection/inclination correction unit so as to exclude the document portions corresponding to the width detection sensors SN1 and SN2 from the linear sampling points for detecting the skew amount. The detection area information is transmitted.

It should be noted that the time difference excluded from the detection area is determined according to the document conveyance speed and the deviation amount of the sampling point that affects the linear equation.

As described above, according to the present embodiment, when there is a difference in the detection time of a plurality of sensors for width detection and there is a delay on the edge side of the document, the edge of the document becomes bent or chipped. Therefore, the tilt amount detection unit 310 can prevent erroneous skew detection by excluding the end portion as the tilt amount detection region.

(Fifth Embodiment)
Next, a fifth embodiment will be described.

In the fifth embodiment, the skew amount is estimated from the result of the detection time difference of the width detection sensors SN1 to SN5 for detecting the document width (document passing position information), and then, when the skew amount is detected, This is different from the first embodiment in that a portion having a larger difference than a preset threshold with respect to the skew amount due to a time difference is not used for calculating the skew amount. In the following description of the fifth embodiment, the description of the same parts as those in the first embodiment will be omitted, and the differences from the first embodiment will be described.

FIG. 13 is a diagram showing a comparison between a document width detection result and a skew straight line of the image forming apparatus 100 according to the fifth embodiment. In FIG. 13, (a) shows the result of document width detection, and (b) shows the comparison of skew straight lines. FIG. 13 shows the difference between the passage times of the width detection sensors SN1 to SN5 when a document skew having a width of E or more occurs. As shown in FIG. 13, in this case, the width detection sensors SN1 to SN5 are sequentially reacted, and the skew in which the width detection sensor SN1 side precedes is generated. That is, the inclination amount detection unit 310 estimates the skew amount from the time difference and the conveyance speed, and improves the accuracy of the linear equation calculation for the skew amount detection as the second skew amount detection result.

However, the number of sampling points is five, which is equal to the number of width detection sensors SN, and also includes conveyance unevenness and variations in the reaction speed of the width detection sensors SN, and since it is not information at the reading position, it is only auxiliary. Information.

After that, the tilt amount detection unit 310 acquires the image information at the reading position and detects the skew amount in the area of the document width information from the image. When performing sampling, the tilt amount detection unit 310 partially detects a linear type error due to an error factor (a linear type erroneous detection due to a pattern at the front end of the document or a local distribution of the shadow width), dust, noise, or the like. The portion where the skew differs from the skew due to the width detection sensors SN1 to SN5 by a certain threshold value or more (the sampling points circled in FIG. 13) is not used for the calculation of the linear equation. As a result, it is possible to exclude error factors, dust, noise, and the like, and improve the calculation accuracy of the linear equation for detecting the skew amount.

The threshold value to be excluded from the detection area is determined according to the shift amount of the sampling point that affects the linear equation for detecting the skew amount. Alternatively, a determination method may be employed in which only the polarity is simply viewed and a portion having a polarity opposite to the skew of the width detection sensors SN1 to SN5 is excluded.

As described above, according to the present embodiment, when there is a curled document or an error factor (local distribution of the pattern or shadow width at the document leading end, a linear error detection due to dust or noise), that part is excluded. Since the skew amount can be detected, it is possible to prevent erroneous correction of the skew.

In each of the above-described embodiments, the scanner 101, the ADF 102, and the image processing device 200 are used as the tilt correction device, and the tilt detection when the inspection target (original) is conveyed is described, but the invention is not limited to this. For example, the tilt correction device according to each embodiment can be applied to the tilt detection of the inspection target of the FA (Factory Automation) inspection device.

Further, in each of the above-described embodiments, the detection target (original) is conveyed and the image is acquired by the fixed image capturing unit 28. On the contrary, the imaging unit 28 stops the detection target (original). A method of moving and detecting the inclination of the detection target (original) may be used.

In each of the above-described embodiments, an example in which the image forming apparatus of the present invention is applied to a multifunction machine having at least two functions of a copy function, a printer function, a scanner function, and a facsimile function will be described. The present invention can be applied to any image forming apparatus such as a machine, a printer, a scanner device, and a facsimile device.

Although the respective embodiments of the present invention have been described above, the specific configurations, processing contents, data formats, and the like of the respective parts are not limited to those described in the embodiments. Further, it goes without saying that the configurations of the embodiments described above can be implemented in any combination as long as they do not conflict with each other.

28 Image pickup unit 50 Conveying unit 85 Width information acquisition unit 100 Image forming device 101, 102 Tilt correction device, reading device 120 Image forming unit 310 Tilt amount detection unit 320 Tilt correction unit

JP, 2016-163168, A

Claims (11)

A transport unit that transports the detection target to the imaging position,
An image capturing unit that captures the detection target at the image capturing position and generates image information at the image capturing position;
A passage position information acquisition unit that is provided on the upstream side in the transport direction with respect to the imaging position and that obtains passage position information of the detection target,
An inclination correction unit that corrects the inclination of the detection target in the image information according to the passage position information and the amount of inclination of the detection target obtained from the image information generated by the imaging unit,
A tilt correction device comprising: A transport unit that transports documents to the scanning position,
An image capturing unit that captures an image of the document at the reading position and generates image information at the reading position;
A passage position information acquisition unit that is provided upstream of the reading position in the transport direction and that acquires passage position information of the original document;
An inclination correction unit that corrects the inclination of the original in the image information according to the passage position information and the amount of inclination of the original obtained from the image information generated by the imaging unit;
A reading device comprising: A tilt amount detection unit that sets a tilt amount detection region according to the passing position information and detects the tilt amount of the document based on the image information generated by the imaging unit;
The reading device according to claim 2, wherein: The tilt amount detection unit detects the leading edge of the document on the downstream side in the transport direction in the tilt amount detection region set according to the passage position information of the document acquired by the passage position information acquisition unit. Detect,
The reading device according to claim 3, wherein The tilt amount detection unit is located on the left end side or the right end side of the document in the transport direction in the tilt amount detection region set according to the passage position information of the document acquired by the passage position information acquisition unit. Detect edges,
The reader according to claim 3 or 4, characterized in that. The tilt amount detection unit and the tilt correction unit switch between performing/not performing the tilt amount detection and the tilt correction in accordance with the document passing position information acquired by the passing position information acquiring unit.
The reading device according to claim 3, wherein the reading device is a reading device. The tilt amount detection unit and the tilt correction unit switch between performing/not performing the tilt amount detection and the tilt correction regardless of the passing position information of the document acquired by the passing position information acquiring unit.
The reading device according to claim 3, wherein the reading device is a reading device. The tilt amount detection unit switches the tilt amount detection area according to a result of a detection time difference of each sensor for detecting the passage position information of the document provided in the passage position information acquisition unit,
The reading device according to claim 3, wherein the reading device is a reading device. The tilt amount detecting unit estimates the tilt amount from the result of the detection time difference of each sensor for detecting the passing position information of the document provided in the passing position information acquisition unit, and then detects the tilt amount. A portion having a larger difference than a preset threshold value with respect to the tilt amount due to the detection time difference is not used for the calculation of the tilt amount,
9. The reading device according to claim 3, wherein the reading device is a reading device. A reading device according to any one of claims 2 to 9,
An image forming unit that forms an image based on a document image read by the reading device;
An image forming apparatus comprising: A transport unit that transports the detection target to the image capturing position, an image capturing unit that captures the detection target at the image capturing position and generates image information of the image capturing position, and a transport unit provided upstream of the image capturing position in the transport direction. A tilt correction method in a tilt correction device comprising: a pass position information acquisition unit that acquires pass position information of the detection target;
A tilt correction step of correcting the tilt of the document in the image information according to the passing position information and the tilt amount of the detection target obtained from the image information generated by the imaging unit;
A tilt correction method characterized by the above.

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