JP7176390B2 - Tilt correction device, reading device, image forming device, and tilt correction method - Google Patents

Description

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

Conventionally, when an image of an object to be detected is read, the skew of the read image data is corrected by image processing based on information obtained by detecting the skew amount (skew angle) and registration position from the read image data. Correction techniques are known.

Japanese Patent Application Laid-Open No. 2002-200002 discloses a technique for detecting the width and skew amount of a document by using the detection time difference of each sensor of the existing document width detection sensors for the purpose of detecting the skew amount according to the width of the document. .

However, according to the conventional skew correction, in order to improve detection accuracy, it is necessary to detect the outline of the document from the read image by edge detection or the like, and detect the skew amount using the document boundary and shadow in that area. For this reason, it is necessary to add image processing to detect the document width and change the parameters for skew amount detection according to the document width. performance deterioration and an increase in the amount of memory for data storage.

Further, according to the technique disclosed in Patent Document 1, there is a problem that detection accuracy is deteriorated or detection is impossible due to the following points, and the skew amount detection accuracy cannot be ensured.
・Points are few due to sampling only with the number of document width detection sensors. ・Detection error between sensors becomes skew amount detection error from the actual image. Points that cannot be

SUMMARY OF THE INVENTION It is an object of the present invention to improve the accuracy of skew amount detection.

In order to solve the above-described problems and achieve the object, the present invention provides a transport unit that transports a document to a reading position, and an imaging unit that captures an image of the document at the reading position and generates image information of the reading position. a passage position information acquisition unit that is provided on the upstream side of the reading position in the conveying direction and acquires the passage position information of the document ; a tilt amount detection unit that detects the tilt amount of the document based on the image information generated by the image pickup unit; the passing position information; and the tilt amount of the document obtained from the image information generated by the imaging unit. a tilt correcting unit for correcting the tilt of the document in the image information in accordance with the image information ; The tilt amount detection area is switched according to the result of the detection time difference of the sensor, and the tilt amount detection is performed so as to be excluded from the sampling points in the calculation of the linear formula for detecting the tilt amount of the document in the image information. It is characterized in that the information of the area is transmitted to the tilt correction section .

ADVANTAGE OF THE INVENTION According to this invention, it is effective in the ability to improve the precision of a skew amount detection.

FIG. 1 is a cross-sectional view schematically showing the schematic configuration of the image forming apparatus according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing the schematic configuration of the scanner. FIG. 3 is a cross-sectional view schematically showing the schematic configuration of the ADF. FIG. 4 is a diagram schematically showing the 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 functions of the image processing apparatus. FIG. 7 is a flowchart schematically showing the flow of image reading processing. FIG. 8A is a diagram showing an example of the relationship between the document width detection result and the tilt amount detection area (the downstream edge in the transport direction). FIG. 8B is a diagram showing an example of the relationship between the document width detection result and the tilt amount detection area (the downstream edge in the transport direction). FIG. 9 is a diagram showing the timing of various processes related to image processing in comparison with the conventional one. 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 area 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 area of the image forming apparatus according to the fourth embodiment. 13A and 13B are diagrams illustrating a comparison of a document width detection result and a skew straight line of the image forming apparatus according to the fifth embodiment.

Exemplary 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 cross-sectional view schematically showing the schematic configuration of an image forming apparatus 100 according to the first embodiment. Image forming apparatus 100 is a multi-function device having at least two functions out 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 , an apparatus main body 104 , a scanner 101 and an automatic document feeder (ADF) 102 .

The image forming apparatus 100 includes a plotter 120 as an image forming unit inside the apparatus main body 104 . The plotter 120 includes a tandem-type image forming unit 105, registration rollers 108 that supply recording paper from the paper feed unit 103 to the image forming unit 105 through a transport path 107, an optical writing device 109, a fixing unit 110, A double-sided tray 111 is provided.

In the image forming unit 105, four photosensitive drums 112 are arranged in parallel corresponding to the four colors of Y (yellow), M (magenta), C (cyan), and K (key plate (black)). . Arranged around each photoreceptor drum 112 are imaging elements including a charger, a developer 106, a transfer device, a cleaner and a discharger. Further, an intermediate transfer belt 113 is arranged between the transfer device and the photosensitive drum 112 and stretched between the drive roller and the driven roller while being nipped between the two.

The tandem-type image forming apparatus 100 configured in this manner writes by the optical writing device 109 to the photosensitive drum 112 corresponding to each color of YMCK based on the document image read by the scanner 101 from the document sent from the ADF 102 . Then, the developing device 106 develops each color toner, and primary transfer is performed on the intermediate transfer belt 113 in the order of Y, M, C, and K, for example. Image forming apparatus 100 secondarily transfers the four-color superimposed full-color image by primary transfer onto recording paper supplied from paper feeding unit 103, fixes the image by fixing unit 110, and discharges the paper. A full-color image is formed on the recording paper.

Next, the scanner 101 is described.

FIG. 2 is a cross-sectional view schematically showing the schematic configuration of the scanner 101. As shown in FIG. As shown in FIG. 2, the scanner 101 includes a first carriage 25, a second carriage 26, an image forming lens 27, and an imaging section 28. Each of these constituent members is a body frame 101a of the scanner 101. are placed inside each.

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

The first carriage 25 is slidably mounted on a first rail, and is driven by a drive motor (not shown) through a drive wire for the first carriage (not shown) in the sub-scanning direction at the position indicated by the solid line and the position indicated by the broken line in FIG. It is configured to be reciprocable 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 mounted on a second rail, and is driven by a drive motor (not shown) through a second carriage drive wire (not shown) in the sub-scanning direction at positions indicated by solid lines and dashed lines in FIG. It is configured to be able to reciprocate between the positions 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 this moving speed relationship, even if the first carriage 25 and the second carriage 26 move, the optical path length of light from the document surface to the imaging lens 27 does not change.

The imaging lens 27 converges and forms an image on the imaging unit 28 of the reflected light from the document incident through each mirror member. The image pickup unit 28 is composed of an image pickup device such as a CCD, and photoelectrically converts a reflected light image of the document imaged through the imaging lens 27 to output an analog image signal as a read image.

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

FIG. 3 is a cross-sectional view schematically showing the schematic configuration of the ADF 102. As shown in FIG. As shown in FIG. 3, the ADF 102 has a document tray 11 on which documents are placed. The document tray 11 has a movable document table 41 that rotates in directions a and b in the drawing with its base end as a fulcrum, and a pair of side guide plates 42 that position the documents in the horizontal direction with respect to the document feeding direction. . By rotating the movable document table 41, the front end portion 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 spaced apart in the feeding direction for detecting whether the document is oriented vertically or horizontally. As the document length detection sensors 89 and 90, a reflection type sensor that detects the document length without contact by 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 paper feeding direction, and documents of different sizes can be placed.

A set filler 46 is provided on the fixed side of the pair of side guide plates 42 so as to rotate when a document is placed. A document setting sensor 82 for detecting that a document is placed on the document tray 11 is provided at the lowest part of the moving locus of the leading end of the set filler 46 . In other words, the document set sensor 82 detects the presence or absence of the document set on the ADF 102 based on whether or not the set filler 46 rotates and is removed from the document set sensor 82 .

The ADF 102 includes a conveying section 50 composed of a separation feeding section 51 , a pullout section 52 , a turn section 53 , a first reading and conveying section 54 , a second reading and conveying section 55 , and a sheet discharging section 56 . ing. Each transport roller of transport unit 50 is rotationally driven by one or more transport motors.

The separating and feeding unit 51 has a pickup roller 61 arranged near a paper feed port 60 for feeding documents, and a paper feed belt 62 and a reverse roller 63 which are arranged to face each other across the transport path. is doing.

The pickup roller 61 is supported by a support arm member 64 attached to the paper feed belt 62, and moves between a contact position at which the pickup roller 61 comes into contact with the document bundle and a separated position away from the document bundle 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) of 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 direction opposite to the feeding direction. Also, the reverse roller 63 rotates in the opposite direction to the paper feed belt 62 when multiple documents are fed. When the sheet is being conveyed, it rotates together with the sheet feeding belt 62 due to the action of a torque limiter (not shown). This prevents double feeding of documents.

The pull-out section 52 has pull-out rollers 65 which are a pair of rollers arranged to sandwich the transport path 52a. The pull-out unit 52 performs primary abutment alignment (so-called skew correction) on the fed document according to the driving timing of the pull-out roller 65 and the pickup roller 61, and pulls out and conveys the aligned document.

The turn section 53 has an intermediate roller 66 and a reading entrance roller 67 which are a pair of rollers arranged to sandwich the conveying path 53a curved from top to bottom. The turning section 53 turns the document pulled out and conveyed by the intermediate rollers 66 by conveying it along a curved conveying path, and directs the surface of the document downward by the reading entrance roller 67 to the reading position (imaging position) of the document. is conveyed to the vicinity of the slit glass 7 .

Here, the transport speed of the document from the pull-out portion 52 to the turn portion 53 is set higher than the transport speed in the first reading/transporting portion 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 to face the slit glass 7, and a first reading exit roller 69 arranged on the conveying path 55a after completion of reading. The first reading/conveying unit 54 conveys the document conveyed to the vicinity of the slit glass 7 while bringing the surface of the document into contact with the slit glass 7 with the first reading roller 68 . At this time, the document 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 reading is completed by the first reading/exit rollers 69 .

The second reading/conveying unit 55 includes a second reading unit 91 that reads the back surface of the document, a second reading roller 70 arranged to face the second reading unit 91 across the conveying path 55a, and the second reading unit 91. and a second reading exit roller 71 disposed downstream in the conveying direction of the second reading exit roller 71 .

In the second reading/conveying section 55 , the second reading section 91 reads the back side of the document after reading the front side. The document whose back surface has been read is conveyed toward the paper exit by the second reading exit roller 71 . The second reading roller 70 suppresses floating of the document in the second reading section 91 and also serves as a reference white portion for obtaining shading data in the second reading section 91 . The document passes through the second reading section 91 without double-sided reading.

The paper ejection section 56 has a pair of paper ejection rollers 72 provided near the paper ejection port, and ejects the document conveyed by the second reading exit rollers 71 to the paper ejection tray 12 .

In addition, the ADF 102 is provided with various sensors such as a contact sensor 84, a registration sensor 81, and a discharge sensor 83 along the transport path, which are used for transport control such as document transport distance and transport speed.

Further, between the pullout roller 65 and the intermediate roller 66, a document width sensor 85 that functions as a passage position information acquisition unit is provided. 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 the schematic configuration of the document width sensor 85. As shown in FIG. As shown in FIG. 4, the document width sensor 85 detects the width size of a general standard document from the 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 discriminable intervals.

Width detection sensors SN1 to SN5 may be of a transmission/reflection type sensor that reacts when a document passes through or a sensor that detects that a filler has been accommodated by the document. The width detection sensors SN1 to SN5 of this embodiment are provided with light receiving elements, and detect the width of the document based on the results of light received from the illuminating light provided at opposite positions across the transport path.

As described above, the document passes 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 document passing position information, based on the light reception results of the width detection sensors SN1 to SN5 in the document width sensor 85 . Specifically, depending on which width detection sensors SN1 to SN5 of the document width sensor 85 receive light, the image processing apparatus 200 can detect the width of the document in units of intervals. For example, when all of the five width detection sensors SN1 to SN5 receive light, it can be understood that a document of width E or more is being conveyed. Further, when the three width detection sensors SN1 to SN3 receive the light, it can be understood that a document having a width of 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 the hardware configuration of the image forming apparatus 100. As shown in FIG. As shown in FIG. 5, the image forming apparatus 100 is provided with an image processing apparatus 200 that performs predetermined processing on a document image read by a scanner 101 and outputs the processed image data to a plotter 120 . The scanner 101, the ADF 102, and the image processing device 200 constitute 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 chipset 206 , an image processing ASIC 207 , a controller ASIC 208 , a main memory 209 and an I/O ASIC 210 . ASIC is an abbreviation for application specific integrated circuit.

A CPU 201 is for controlling the image forming apparatus 100 . A main memory 205 is used as a work area for developing a program for the CPU 201 to control the image forming apparatus 100, and temporarily stores image data to be handled (image memory). Chipset 206 is used in conjunction with CPU 201 to control access to main memory 205 by controller ASIC 208 and I/O ASIC 210 .

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

Further, the program executed by image forming apparatus 100 of the present embodiment may be stored on a computer connected to a network such as the Internet, and provided by being downloaded via the network. Also, the program executed by the image forming apparatus 100 of 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. Plotter 120 has a function for printing image data placed in 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. FIG.

A controller ASIC 208 rotates and edits image data handled by the image forming apparatus 100 using the main memory 205 through the chipset 206 , stores the image data in the HDD 211 , and transmits/receives the image data to/from the image processing ASIC 207 . A 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 providing additional functions to the image forming apparatus 100 . For example, the I/O ASIC 210 includes interfaces such as a network interface, USB, SD card, operation unit, SPI, I2C, document width sensor 85 (width detection sensors SN1 to SN5), and a hardware accelerator for speeding up image processing. , an encryption processing circuit, and the like.

Next, functions exhibited by the image processing apparatus 200 will be described.

Here, FIG. 6 is a block diagram showing functions of the image processing apparatus 200. As shown in FIG. Note that here, among functions exhibited by the image processing apparatus 200, a characteristic function in the present embodiment will be described.

As shown in FIG. 6 , the image processing apparatus 200 has a document width information control section 300 , a tilt amount detection section 310 and a tilt correction section 320 . In this embodiment, the chipset 206 has a document width information control section 300 , and the controller ASIC 208 has a tilt amount detection section 310 and a tilt correction section 320 . The document width information control unit 300, the tilt amount detection unit 310, and the tilt correction unit 320 may be realized by the CPU 201 executing a program.

The document width information control unit 300 controls the document width information of the document, which is the result of detection 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 (setting of the inclination amount detection area, etc.). 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. A method applied to the controller ASIC 208 having the amount detection unit 310 and the tilt correction unit 320 may also be used.

The tilt amount detection unit 310 presets a tilt amount detection area 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 amount of skew in a document using image information, it is generally possible to detect the angle of skew (amount of skew) by detecting the edge of the leading edge of the document on the downstream side in the transport direction and calculating its linear equation. many. For the leading end of the document, there is a method of detecting the border between the background of the reading position of the ADF 102 and the document to be read from the leading end of the document itself, and there is also a method of detecting the edge using the shadow of the document.

However, the former method may erroneously detect the linear type 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 same problem as the former method because the skew is detected by the shadow regardless of the pattern or color of the document. The width of the shadow changes along the line, and there are cases where the skew angle of the document and the skew angle of the shadow are locally different. Also, when the document is curled, the behavior of the leading edge of the document is not linear, and there is a possibility of erroneous detection. Therefore, in both methods, it is necessary to expand the detection area to the width of the document to improve the accuracy of the linear method.

Therefore, the tilt amount detection unit 310 of the present embodiment detects the tilt amount detection area based on the document width information acquired 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. is set in advance to detect the amount of skew.

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, image reading processing in the image forming apparatus 100 of this embodiment will be described.

Here, FIG. 7 is a flow chart schematically showing the flow of image reading processing. As shown in FIG. 7, when the ADF 102 starts conveying the document, the image processing apparatus 200 (document width information control unit 300) controls the document width sensor 85 (width detection sensor) before the document is read by the imaging unit 28 of the scanner 101. SN1 to SN5), the document width information of the document (setting information of the skew amount detection area, etc.) is transmitted to the skew amount detection unit 310 for each document (step S1).

Next, the image processing apparatus 200 obtains image data obtained by reading the original document conveyed to the slit glass 7, which is the reading position, by the ADF 102 (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 tilt amount detection area (the downstream edge in the transport direction). In FIGS. 8-1 and 8-2, (a) shows the document width detection result, and (b) shows the tilt amount detection area. FIG. 8-1 shows the case of documents with width E or more, and FIG. 8-2 shows the case of documents with widths C to D. FIG.

The black circles in FIGS. 8-1 and 8-2 indicate sampling points in the image, and as an example, linear equations for skew amount detection in a shadow detection method. Using the document width sensor 85 shown in FIG. 4 as an example, when all of the width detection sensors SN1 to SN5 receive light, a document (maximum size) of width E or more is being conveyed. A width E is a tilt amount detection region of a linear calculation point for skew amount detection.

As a matter of course, the linear calculation point area for skew amount detection is substantially the same for the document width automatically for the image information acquired at the reading position.

On the other hand, when the width detection sensors SN1 to SN3 receive the light, the document having the width C or more and less than D is conveyed. Let the width of the region be C.

Of course, in this case as well, the linear calculation point area for skew amount detection is substantially the same for the document width automatically with respect to the image information acquired at the reading position.

8-1 and 8-2, the reference position is the back side of the ADF 102, so the left edge of the document is the same position regardless of the document size. However, in the case of the center-position-based ADF, where the reference position of the left edge of the document differs depending on the document size, the area of the left edge of the document shifts according to the document size, so the left edge of the calculation point area also shifts. .

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

The processes of steps S1 to S4 described above are executed for all documents conveyed by the ADF 102. FIG.

As a result, since the tilt amount detection area setting based on the document width information has already been set in the tilt amount detection unit 310 before the document image is read by the imaging unit 28 of the scanner 101, processing to change processing parameters during image reading, Image processing for detection can be omitted.

Here, FIG. 9 is a diagram showing the timing of various processes related to image processing in comparison with the conventional one. As shown in FIG. 9A, conventionally, when an image is acquired, several lines of image data are accumulated for edge detection, the edge of the document is detected, the width of the document is detected, parameters are switched, and the amount of skew is detected. / Skew correction processing was being performed.

On the other hand, as shown in FIG. 9B, in the present embodiment, information on the tilt amount detection area based on the document width information is obtained for each document before the image pickup unit 28 of the scanner 101 reads the document image. Since the skew amount detection unit 310 has already been set, it is possible to omit processing for changing parameters for image data accumulation, document width detection, and skew amount detection during image reading.

As a result, by using the existing width detection sensors SN1 to SN5 to obtain a good document width with rough accuracy in advance and accurately detecting the skew amount in the image, it is possible to optimize the document width and the skew amount detection accuracy. Since it is possible to omit the process of changing the parameter for skew amount detection and the image processing for width detection, the image output (after skew correction) is not delayed, and the skew correction accuracy is maintained while maintaining the skew correction accuracy. It is possible to prevent the deterioration of productivity and the bloat of the memory capacity for data storage due to the delay of the image data after the amount detection/skew correction.

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

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

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

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

10-1 and 10-2 are diagrams showing an example of the relationship between the document width detection result and the edge search area of the image forming apparatus 100 according to the second embodiment. FIG. 10-1 shows the case of documents with width E or more, and FIG. 10-2 shows the case of documents with widths C to D. FIG.

In this embodiment, it is assumed that the ADF 102 is based on the center position, in which the reference position of the left edge of the document varies depending on the size of the document. That is, the ADF 102 of this embodiment conveys the document with the center as a reference regardless of the document size. In this case, since the area of the left edge of the document is shifted according to the size of the document, the left edge of the calculation point area is also shifted. Along with this, 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 toward the left end in the main scanning direction.

By the way, depending on the method of detecting the amount of skew, it may be necessary to specify the left and right edges in order to extract the upper left origin of the original for rotational correction during the processing of detecting the amount of skew. In this case, the position is specified by the change in the level of the image, etc. However, if the search area is to be detected from the left end of the background area, the detection process will take a long time.

On the other hand, since the tilt amount detection unit 310 has the document width information, it is possible to search in a state in which the edge search area is limited to the intervals of the width detection sensors SN1 to SN3, thereby shortening the edge detection time. can be done.

As shown in FIG. 10-1, in the case of document width E (light is received by all of width detection sensors SN1 to SN3), the left edge search area is the area outside width detection sensor SN1, and the search width is width detection. It becomes the interval of sensor SN. 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 E, and the search width is the interval of the width detection sensors SN.

As shown in FIG. 10B, in the case of document width C (light received by width detection sensors SN2 and SN3), the left edge search area is the area outside width detection sensor SN2, and the search width is the width detection sensor SN. interval. 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 of the width detection sensors SN.

As described above, according to the present embodiment, the left end and right end, which are regions from which external factors (noise stains) are removed based on the document passage position information acquired by the width detection sensors SN1 to SN3 before the document is read by the ADF 102, are detected. This edge detection configuration reduces the number of sampling points and intervals for edge detection during image reading, and reduces the effects of external factors (noise stains) that can cause false detection during detection and reduces the impact of external factors (noise stains) that cause false detection. Optimal edge detection can be performed. As a result, it is possible to improve the detection accuracy of the skew amount.

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

The third embodiment differs from the first embodiment in that execution/non-execution of skew correction is switched according to the detected document width (document passage position information). Hereinafter, in the description of the third embodiment, the description of the same portions as those of the first embodiment will be omitted, and the portions different from those of the first embodiment will be described.

FIG. 11 is a diagram showing an example of the relationship between the document width detection result and the tilt amount detection area 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 responds for a certain period of time (original document with width A or more and less than B). In FIG. 11, (a) shows the document width detection result, and (b) shows the inclination amount detection area. Note that FIG. 11 shows a linear equation for skew amount detection in the shadow detection method.

As shown in FIG. 11, the linear calculation point area for skew amount detection has a width A. As shown in FIG. However, even if the skew amount is detected in the calculation area according to the width of the document, the error factors (local distribution of patterns and shadow widths at the leading edge of the document, dust, noise, etc.) ) occurs in the entire calculation area, the linear equation for skew amount detection is erroneously detected. That is, when skew amount detection/skew correction is performed on a small size document, the skew of the document edge differs from the skew of the detected approximate straight line as shown in FIG. 11, resulting in insufficient correction or erroneous correction. there is a possibility. The influence of such errors increases as the document size decreases.

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

Even if such control is used, it is possible to determine whether or not to implement skew correction at the upstream stage of document transport. Image processing can be omitted.

As described above, according to the present embodiment, when a small-sized original is easily affected by curling or original shadow depending on the transport path, there are cases where it is better not to perform skew correction. At times, it is possible to automatically switch whether or not correction is performed.

In recent years, an auxiliary tray for reading small-sized originals may be installed in order to continuously read business cards or the like with the ADF 102 . In this case, when the auxiliary tray is attached to the ADF 102, it is known that the small size document will be read. Therefore, when the attachment of the auxiliary tray is detected, the skew amount detection/skew correction is automatically turned OFF. A similar effect can be obtained with the configuration.

In addition, there is a use case where the user of the scanner 101 wants to intentionally skew the document. In this case, the user arbitrarily selects execution/non-execution of the skew correction using the operation unit or the like, and sends the information to the tilt amount detection unit 310 and the tilt correction unit 320, thereby reducing the skew amount. It is possible to plan In this manner, regardless of the detected document width, the user can arbitrarily switch between execution and non-execution of skew correction.

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

The fourth embodiment differs 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 passage position information). . Hereinafter, in the description of the fourth embodiment, the description of the same portions as those of the first embodiment will be omitted, and the portions different from those of 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 area 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 inclination amount detection area. FIG. 12 shows a case where all the width detection sensors SN1 to SN5 in FIG. 4 cannot receive light (original of width E).

As shown in FIG. 12, in the calculation of the linear equation for skew amount detection, if the conveyed document has an edge fold or missing portion, the skew will change locally. Therefore, there is a problem that the amount of skew is erroneously detected if the edge folds and missing portions of the document are included in the linear calculation.

Therefore, in order to prevent such a problem, the tilt amount detection unit 310 detects the edge folds and missing parts of the document based on the difference in the response time (the time it takes for the document to pass) of the width detection sensors SN1 to SN5. to detect. FIG. 12 shows a case where the document is placed on the ADF 102 and the edges are bent or chipped on the side of the reference position. In this case, the width detection sensors SN2 to SN5 respond almost simultaneously, but the response of the width detection sensor SN1 is delayed due to the edge breakage or chipping, resulting in a time lag.

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

It should be noted that the time difference to be excluded from the detection area is determined in accordance with the amount of deviation of the sampling points that affects the document conveying speed and linearity.

As described above, according to the present embodiment, there is a difference in the detection time of the plurality of sensors for width detection, and if there is a delay at the edge of the document, the edge of the document is folded or missing. Therefore, the tilt amount detection unit 310 can prevent erroneous detection of skew by excluding the edge portion from the tilt amount detection area.

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

In the fifth embodiment, the amount of skew is estimated from the result of the detection time difference of the width detection sensors SN1 to SN5 for detecting the document width (document passage position information), and then, when detecting the skew amount, This differs from the first embodiment in that a portion of the skew amount due to the time difference that is greater than a preset threshold value is not used for calculating the skew amount. Hereinafter, in the description of the fifth embodiment, the description of the same portions as those of the first embodiment will be omitted, and the portions different from those of the first embodiment will be described.

13A and 13B are diagrams showing a comparison of the document width detection result and the skew straight line of the image forming apparatus 100 according to the fifth embodiment. In FIG. 13, (a) shows the width detection result of the document, and (b) shows the comparison of skew straight lines. FIG. 13 shows the difference in passing time of the width detection sensors SN1 to SN5 when skew occurs in a document of width E or more. As shown in FIG. 13, in this case, the width detection sensors SN1 to SN5 respond in order, and skew occurs in which the width detection sensor SN1 side precedes. That is, the tilt amount detection unit 310 estimates the skew amount from the time difference and the conveying speed, and improves the accuracy of the linear calculation for the skew amount detection as the second skew amount detection result.

However, the number of sampling points is five, which is the number of the width detection sensors SN. information.

After that, the skew 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. During the sampling, the tilt amount detection unit 310 detects partial linear errors due to error factors (linear detection errors due to local distribution of patterns and shadow widths at the leading edge of the document), dust, noise, and the like. A portion where the skew is different from the skew by the width detection sensors SN1 to SN5 by a certain threshold or more (encircled sampling points in FIG. 13) is not used for calculating the linear expression. As a result, error factors, dust, noise, and the like can be excluded, and the calculation accuracy of the linear formula for skew amount detection can be improved.

Note that the threshold for exclusion from the detection area is determined according to the deviation amount of sampling points that affects the linear equation for skew amount detection. Alternatively, a determination method may be used in which only the polarity is simply looked at and the portion having the opposite polarity to the skew by the width detection sensors SN1 to SN5 is excluded.

As described above, according to the present embodiment, if there is a curled document or an error factor (a pattern at the leading edge of the document, a local distribution of shadow widths, dust, or a straight-line misdetection due to noise), that portion is excluded. Since the amount of skew can be detected, erroneous correction of skew can be prevented.

In each of the above-described embodiments, the scanner 101, the ADF 102, and the image processing apparatus 200 are used as tilt correction devices, and tilt detection during transport of an inspection object (original) has been described, but the present invention is not limited to this. For example, the tilt correcting device of each embodiment can also be applied to detecting the tilt of an inspection object of an FA (Factory Automation) inspection device.

In each of the above-described embodiments, the object to be detected (document) is conveyed and an image is acquired by the stationary imaging unit 28. A method of moving and detecting the inclination of the object to be detected (original document) may also 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 multifunctional machine having at least two functions out of a copy function, a printer function, a scanner function, and a facsimile function will be described. It can be applied to any image forming apparatus such as a machine, a printer, a scanner, a facsimile, and the like.

Although each embodiment of the present invention has been described above, the specific configuration of each part, the content of processing, the format of data, etc. are not limited to those described in the embodiment. Moreover, it goes without saying that the configurations of the embodiments described above can be arbitrarily combined as long as they do not contradict each other.

28 Imaging Unit 50 Conveying Unit 85 Width Information Acquiring Unit 100 Image Forming Apparatus 101, 102 Tilt Correcting Device, Reading Device 120 Image Forming Unit 310 Tilt Amount Detecting Unit 320 Tilt Correcting Unit

JP 2016-163168 A

Claims (8)

a transport unit that transports the document to a reading position;
an imaging unit that captures an image of the document at the reading position and generates image information of the reading position;
a passing position information acquiring unit provided upstream of the reading position in the conveying direction for acquiring passing position information of the document;
a tilt amount detection unit that sets a tilt amount detection area according to the passing position information and detects the tilt amount of the document based on the image information generated by the imaging unit;
a tilt correction unit that corrects the tilt of the document in the image information according to the passage position information and the tilt amount of the document obtained from the image information generated by the imaging unit;
with
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. transmitting information of the tilt amount detection area to the tilt correction unit so as to exclude from sampling points in the calculation of the linear formula for detecting the tilt amount of the document;
A reading device characterized by: The tilt amount detection unit detects the leading edge of the document on the downstream side in the conveying direction in the tilt amount detection area set according to the document passage position information acquired by the passage position information acquisition unit. detect,
2. The reader according to claim 1 , wherein: The tilt amount detection unit detects the left end side or the right end side of the document in the transport direction in the tilt amount detection area set according to the document passage position information acquired by the passage position information acquisition unit. edge detection,
3. The reader according to claim 1 or 2 , characterized in that: The tilt amount detection unit and the tilt correction unit detect the tilt amount of the document in the image information and correct the tilt according to the document passage position information acquired by the passage position information acquisition unit. Toggle between performing/not performing the
4. The reader according to any one of claims 1 to 3 , characterized in that: The tilt amount detection unit and the tilt correction unit detect the tilt amount of the document in the image information and correct the tilt regardless of the passing position information of the document acquired by the passing position information acquisition unit. Toggle between performing/not performing the
4. The reader according to any one of claims 1 to 3 , characterized in that: The tilt amount detection unit estimates the tilt amount from a detection time difference result of each sensor for detecting the passage position information of the document provided in the passage position information acquisition unit . When detecting the tilt amount, a portion of the tilt amount due to the detection time difference that is larger than a preset threshold value is not used for calculating the tilt amount of the document in the image information .
6. The reader according to any one of claims 1 to 5 , characterized in that: a reader according to any one of claims 1 to 6 ;
an image forming unit that forms an image based on the document image read by the reading device;
An image forming apparatus comprising: a conveying step of conveying the document to a reading position;
an image capturing step of capturing an image of the document at the reading position and generating image information of the reading position;
a passage position information acquiring step, which is provided on the upstream side in the transport direction of the reading position and acquires the passage position information of the document;
a tilt amount detection step of setting a tilt amount detection area according to the passing position information and detecting the tilt amount of the document based on the image information generated in the imaging step;
a tilt correction step of correcting the tilt of the document in the image information according to the passage position information and the tilt amount of the document obtained from the image information generated in the imaging step;
including
In the tilt amount detection step, the tilt amount detection area is switched according to the result of the detection time difference of each sensor for detecting the passage position information of the document obtained in the passage position information acquisition step. transmitting information of the tilt amount detection area to the tilt correction step so as to exclude from sampling points in the calculation of the linear formula for detecting the tilt amount of the document;
A reading method characterized by:

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