JP4840252B2 - Document reader - Google Patents

Description

  The present invention relates to a document reading apparatus that detects a skew amount when a document is conveyed based on image data acquired by reading the document, and corrects the inclination of the image data based on the detected skew amount. Is.

  An apparatus such as a copying machine or a facsimile machine is an image formed by an optical system having a CCD (Charge Coupled Device) line sensor or the like in which a large number of photoelectric conversion elements are arranged in the main scanning direction (direction orthogonal to the document transport direction), for example. A reading device is provided. In addition, an ADF (Automatic Document Feeder) mechanism is provided, and the originals are separated one by one from the original bundle set on a predetermined mounting table, taken into the apparatus main body, and the taken originals are sequentially read to acquire image data. Configured document reading apparatuses are in widespread use.

  Such a reading apparatus is configured to perform shading correction that removes non-uniformity in the amount of light from the light source irradiated on the document, variation in sensitivity among the elements constituting the CCD line sensor, and the like. Specifically, the reading device has a shading plate having a white surface at a predetermined position, for example, acquires data based on reflected light from the shading plate as shading data, and reads image data read from a document. Correct based on shading data.

  The reading device is configured to detect the skew amount of the document with respect to the reference position based on the image data read from the document, and to correct the inclination of the read image data based on the detected skew amount. Yes. The reading device has a back plate at a predetermined position for pressing the document against the contact glass when the document is read so that no gap is generated between the document and the contact glass in order to read the document with high accuracy. Therefore, when a back plate having a black pressing surface for pressing an original is used, if the original is a white background, the edge of the original becomes clear and the skew amount of the original can be calculated more accurately.

In Patent Document 1, two black triangle marks are provided on a white reference plate, a skew amount or a resist amount is calculated based on an output width of the triangular black mark when the white reference plate is read, and skew adjustment or registration is performed. An apparatus for performing the adjustment is disclosed. According to the reading apparatus of Patent Document 1, for example, after being attached to a copying machine or a multi-function machine, skew adjustment and registration adjustment can be performed only by its own apparatus.
JP 2006-186429 A

  In a reading apparatus, a back plate for pressing a document against a contact glass may be used as a shading plate for acquiring shading data. However, since many originals are white, shading data used for shading correction is preferably acquired by a white background shading plate. However, as described above, the skew amount of the original is more accurate for white backgrounds. In order to calculate well, it is preferable to use a black plate for the back plate. Therefore, conventionally, for example, a serviceman manually replaces different plates when data used for shading correction is acquired and when skew correction is performed based on image data read from a document. It has the problem of being necessary.

  The reading device disclosed in Patent Document 1 can adjust the skew amount or the resist amount variation generated when the reading device is attached to a copying machine, a multifunction device, or the like. However, when a document to be read is conveyed. It is not considered to correct the generated skew.

  The present invention has been made in view of such circumstances, and an object of the present invention is to use a reference member used when acquiring reference data used for shading correction as a skew amount when a document is conveyed. It is an object of the present invention to provide a document reading apparatus that can be used even when detecting the above.

  Another object of the present invention is a document reading that can be used to correct the skew of the image data read from both sides of the document, based on the skew amount detected when reading one side of the document. To provide an apparatus.

  Another object of the present invention is to provide a document reading apparatus that can use a reference member used when acquiring reference data used for shading correction also when detecting a document width.

  Another object of the present invention is to more accurately detect the skew amount when a document is conveyed based on the skew amount at the leading edge of the document and the skew amount at the trailing edge of the document. Is to provide a simple original reading apparatus.

Document reading apparatus according to the present invention, a reading section that acquires image data by reading an original conveyed, is provided inside the said read unit, the longitudinal direction intersecting the conveying direction of the document, for shading correction have a light reflectance of the reference, the reference member wider reading surface than the width of the width of the image data is arranged in a position opposed to the original, acquiring the reading unit reads the reading surface of the reference member based on the shading data generated from the reference data, the document reading apparatus and a shading correction unit that corrects the shading of the image data to which the reading unit has acquired, the reading surface of the reference member, the conveying direction of the document has a low reflection region of a predetermined width at a lower reflectivity than the light reflectance of each of the reference to the three or more locations in the direction orthogonal to the, conveyed on the reading surface of the reference member The document a per acquired read data when the reading unit has read with the reading surface, the data corresponding to the low reflection region in different positions in the direction intersecting the transport direction of the document to be, respectively, of the document depending on the length of the conveying direction of a detector for detecting a skew amount of the original, on the basis of the skew amount detection unit detects and corrects the inclination of the image data included in the read data And a correction unit.

  According to the present invention, the document reading device skews a document based on data at a boundary portion with image data included in data acquired by reading the document conveyed on the reading surface of the reference member together with the reading surface. Detect the amount. Further, the document reading device corrects the inclination of the image data included in the acquired data, that is, the image data read from the document, based on the detected skew amount.

A document reading apparatus according to the present invention includes a first reading unit that reads one side of a document to be conveyed to acquire image data, and is provided in the first reading unit , the longitudinal direction intersecting the document conveying direction. the reference of the light reflectance possess, the reference member is wider reading surface than the width of the image data is arranged in a position opposed to the document, the first reading unit to the reference member for shading correction A shading correction unit that corrects shading of image data acquired by the first reading unit based on shading data generated from reference data acquired by reading the reading surface, and an image obtained by reading the other side of the document in the document reading apparatus and a second reading unit for obtaining the data, the reading surface of the reference member, the light anti of each of the reference to the plurality of positions in the direction orthogonal to the conveying direction of the document Has a low reflection region of a predetermined width at a lower reflectance than the rate, is obtained when the first reading unit with said reading surface one surface of the document conveyed on the reading surface of the reference member is read per read data, the data corresponding to the low reflection region in different positions in the direction intersecting the transport direction of the document, depending on the length of the conveying direction of each of the document, it detects the skew amount of the original a detection unit for, based on the skew amount detection unit detects and corrects the inclination of the image data included in the read data, to correct the inclination of the image data to which the second reading section obtains the correction unit It is characterized by providing.

  According to the present invention, the document reading device is configured to read a document on the basis of data at a boundary portion with image data included in data acquired by reading one surface of the document conveyed on the reading surface of the reference member together with the reading surface. Detect the skew amount. The document reading device corrects the inclination of the image data included in the acquired data, that is, the image data read from one side of the document, based on the detected skew amount, and the image data read from the other side of the document. Correct the tilt of the.

In the document reading apparatus according to the present invention, the correction unit may determine whether the correction data of the previous document is based on the presence or absence of data corresponding to low reflection areas at different positions in the direction intersecting the document transport direction. It characterized that you detect the standard size in a direction intersecting the transport direction.

  According to the present invention, the document reading apparatus has a length in a direction intersecting the document transport direction based on reference data included in data acquired by reading a document transported on the reading surface of the reference member together with the reading surface. Detect.

Document reading apparatus according to the present invention, a reading section that acquires image data by reading an original conveyed, is internally provided in said read unit, the longitudinal direction intersecting the conveying direction of the document, for shading correction have a light reflectance of the reference, the reference member wider reading surface than the width of the width of the image data is arranged in a position opposed to the original, acquiring the reading unit reads the reading surface of the reference member based on the shading data generated from the reference data, the document reading apparatus and a shading correction unit that corrects the shading of the image data to which the reading unit has acquired, the reading surface of the reference member, the conveying direction of the document transport of intersection has a low reflection region of a predetermined width at a lower reflectance than the respective plurality of locations in the direction the light reflectance of the reference that, on the reading surface of the reference member and That the per acquired read data when the reading unit with the reading surface of the leading edge of the document read, the data corresponding to the low reflection region in different positions in the direction intersecting the transport direction of the document, respectively depending on the length of the conveying direction of the document, a first detector for detecting a skew amount at the tip of the document, the reading surface of the rear end of the document conveyed to the reading surface above said reference member the reading unit is attached to the acquired read data if read together, the data corresponding to the low reflection region in different positions in the direction intersecting the transport direction of the document, the length of the conveying direction of each of the original by, the second detection unit and the skew amount and the second detection unit is an average value of the skew amounts detected by the first detection unit has detected that detects a skew amount of the trailing end of the document, or Either skew amount is not within the specified range By the other skew amount of engagement, a specifying unit for specifying a skew amount of the original, on the basis of the skew amount specified, the inclination of the image data included in the read data to which the reading unit has acquired And a correction unit for correcting.

  According to the present invention, the document reading apparatus reads the document based on the data of the boundary portion with the image data included in the data acquired by reading the leading edge of the document conveyed on the reading surface of the reference member together with the reading surface. The amount of skew at the tip is detected. Further, the document reading device detects the trailing edge of the document conveyed on the reading surface of the reference member together with the reading surface at the trailing edge of the document based on data at the boundary with the image data included in the acquired data. Detect the amount of skew. Then, the document reading device identifies the skew amount of the document based on the detected skew amount at the leading edge and the skew amount at the trailing edge of the document, and based on the identified skew amount, The inclination of the image data read from is corrected.

  In the present invention, since the reference member used when acquiring the reference data used for shading correction can also be used for detecting the skew amount when the document is conveyed, the data used for the shading correction Thus, there is no need to manually replace different plates between the case of acquiring the image and the case of detecting the skew amount of the document.

  In the present invention, since the reference member used when acquiring the reference data used for shading correction can also be used for detecting the skew amount when the document is conveyed, the data used for the shading correction Thus, there is no need to manually replace different plates between the case of acquiring the image and the case of detecting the skew amount of the document. Further, when both sides of the document are read by different reading units in one transport operation, the skew amount when reading one surface is the same as the skew amount when reading the other surface. The skew amount of the document based on the reference data included in the data obtained by reading the reading surface of the reference member together with one surface can be used when correcting the inclination of the image data read from both sides of the document. .

  In the present invention, the reference member used when acquiring reference data used for shading correction can also be used when detecting the width in the direction intersecting the document conveyance direction. It is not necessary to provide a separate device, and the cost can be reduced.

  In the present invention, for example, even when the skew amount detection fails at the leading edge of the document, the inclination of the image data can be corrected based on the skew amount at the trailing edge of the document. Further, not only the amount of skew of the original but also the case where the original is excessive in the transport direction with respect to the reference position is based on the reference data included in the data acquired by reading the trailing edge of the original together with the reference member. The amount of excess in the transport direction can also be detected, and correction for the transport direction can be performed based on the detected amount.

  Hereinafter, the document reading apparatus according to the present invention will be described in detail based on an embodiment applied to an image scanner (hereinafter referred to as a scanner). FIG. 1 is a schematic perspective view showing the appearance of the scanner according to the present embodiment. In the scanner 1 of the present embodiment, a document tray 3 for stacking document bundles composed of a plurality of documents is attached to one side surface of the apparatus body 2 so as to be movable in the vertical direction. A discharge tray (not shown) for discharging the document processed by the apparatus body 2 is attached to the opposite side surface.

  An operation panel 4 is provided on the upper surface of the apparatus main body 2. On the side surface of the apparatus main body 2 to which the document tray 3 is attached, a feeding port 2 a for feeding the documents stacked on the document tray 3 into the apparatus main body 2 is opened. In the upper center of the feeding port 2a, a pickup roller 5 is provided for taking the documents stacked on the document tray 3 one by one from the uppermost layer. On the upper surface of the document tray 3, document regulation plates 3a and 3a for regulating the position of the stacked document bundle in the width direction are attached so as to be movable in a direction intersecting the document transport direction, in the present embodiment, an orthogonal direction. ing. The document regulating plates 3 a and 3 a regulate the position of the document so that the document is stacked in the center of the document tray 3.

  FIG. 2 is a block diagram illustrating a configuration example of the scanner 1 of the present embodiment. The scanner 1 includes a control unit 10, a ROM 11, a RAM 12, a document reading unit 13, a page memory 16, an image processing unit 17, a CODEC 18, an image memory 19, an operation unit 20, a display unit 21, a communication unit 22, and the like. Are connected to each other via a bus 1a.

  Specifically, the control unit 10 is configured by a CPU (Central Processing Unit), an MPU (Micro Processor Unit), or the like, and controls each of the above-described hardware units connected via the bus 1a, as well as the ROM 11 Various software functions are realized in accordance with the control program stored in. The ROM 11 stores in advance various control programs necessary for operating the scanner 1 as the document reading apparatus of the present invention. The RAM 12 is configured by SRAM, flash memory, or the like, and temporarily stores data generated when the control unit 10 executes the control program.

  The document reading unit 13 separates documents one by one from a bundle of documents stacked on the document tray 3 and conveys them to a predetermined reading position, and an upper surface of the document conveyed by the document conveying unit 13a. And a lower surface reading unit 15 for reading the lower surface of the document, and operates as a reading unit that reads the document and acquires image data. The document reading unit 13 outputs image data read from the document to the page memory 16.

  The page memory 16 is a memory for temporarily storing image data read from the original by the original reading unit 13 in units of pages. The image data stored in the page memory 16 is output to the image processing unit 17 in accordance with an instruction from the control unit 10. The image processing unit 17 removes various distortions generated in the illumination system, the imaging system, and the imaging system included in the image reading unit 13 from the image data output from the page memory 16, various color adjustments, and skewing. Line correction is performed, and the processed image data is output to the CODEC 18.

  The CODEC 18 performs a predetermined encoding process such as JPEG on the image data output from the image processing unit 17, and stores the obtained image data in the image memory 19. The image memory 19 includes a DRAM or a flash memory, and stores image data read from the original by the original reading unit 13 and subjected to predetermined processing by the image processing unit 17 and the CODEC 18.

  The operation unit 20 includes various keys necessary for the user to operate the scanner 1. When each key is operated by the user, the operation unit 20 sends a control signal corresponding to the operated key to the control unit 10, and the control unit 10 executes processing corresponding to the control signal acquired from the operation unit 20. . The display unit 21 is configured by, for example, a liquid crystal display (LCD), and displays the operation status of the scanner 1, information to be notified to the user, information input from the operation unit 20, and the like. In addition, it is also possible to substitute a part or all of the various keys of the operation unit 20 by using the display unit 21 of a touch panel type.

  The communication unit 22 is an interface for connecting to a network (not shown) such as a LAN, and transmits the image data stored in the image memory 19 to an external device connected to the network. Thus, the scanner 1 functions as a network scanner that transmits image data read from a document to an external device via a network.

  Hereinafter, the configuration of the document reading unit 13 of the present embodiment will be described. FIG. 3 is a block diagram illustrating a configuration example of the document reading unit 13. 3A is a longitudinal sectional view of the inside of the apparatus main body 2 in FIG. 1 as viewed from the direction indicated by the arrow A, and FIG. 3B is a schematic plan view showing a configuration example of the shading plate 15a. The apparatus main body 2 has a rectangular parallelepiped casing, and a platen glass 9 is disposed at a predetermined position inside. Further, inside the apparatus main body 2, a separate document that is separated from the bundle of documents by the pickup roller 5 one by one is conveyed to the upper surface of the platen glass 9 in the conveyance direction indicated by an arrow B in FIG. A roller 6, a retard roller 7, and transport rollers 8 and 8 are provided at appropriate positions. Accordingly, the document conveying portion 13a is constituted by the pickup roller 5, the separating roller 6, the retard roller 7, the conveying rollers 8, 8 and the like.

  The separate roller 6, the retard roller 7, and the transport rollers 8 and 8 are each driven to rotate by a drive circuit that operates according to instructions from the control unit 10. A belt 5a is stretched between the pickup roller 5 and the separation roller 6, and the rotation of the separation roller 6 controlled by the drive circuit is transmitted to the pickup roller 5 through the belt 5a, and the pickup roller 5 is sent to the document. While pressing the bundle, the pickup roller 5 is rotated to feed the uppermost document toward the separation roller 6.

  The pickup roller 5, the separation roller 6, and the transport rollers 8 and 8 are controlled to rotate in the direction in which the document is transported in the transport direction B, while the retard roller 7 is controlled to rotate in the reverse direction. As a result, the document in the double feed state can be separated and conveyed one by one by the rotation of the separation roller 6 and the retard roller 7. The document transport unit 13a further includes a sensor (not shown) for detecting the position of the pickup roller 5 that presses the document bundle, a drive circuit for raising the document tray 3, and the like. When it is detected that the lowering is lower than the predetermined position, the driving circuit is operated to raise the document tray 3. As a result, the pickup roller 5 can reliably take even the lowermost document in the document bundle into the apparatus main body 2.

  The transport rollers 8 and 8 are controlled to rotate at a speed faster than the rotational speed of the separate roller 6. When the document is transported to the transport rollers 8, 8, the transport speed of the document transported by the transport rollers 8, 8 is higher than the transport speed transported by the separation roller 6. A support arm (not shown) is provided between the pickup roller 5 and the separation roller 6. Thus, in a state where the document is conveyed at a speed higher than the rotation speed of the separation roller 6 by the drive circuit, the separation roller 6 is idled and the pickup roller 5 is lifted to a position not in contact with the document via the support arm. Accordingly, the original conveyed to the conveying rollers 8 and 8 is conveyed onto the platen glass 9 only by the rotation of the conveying rollers 8 and 8.

  When the document passes through the separation roller 6 and the retard roller 7, idling of the separation roller 6 by the document conveyed by the conveyance rollers 8 and 8 is finished, and the pickup roller 5 lifted by the support arm is placed on the document bundle. Since the document is returned, the conveyance of the next document is started. Thus, every time a document passes through the separation roller 6 and the retard roller 7, the transport of the next document is started, so that each document is transported at a predetermined interval.

  On the upper part of the platen glass 9, a shading plate 15a as shown in FIG. 3B is arranged at a position close to the conveyance roller 8 so that the longitudinal direction intersects the document conveyance direction B, and in the present embodiment, is orthogonal. Has been. A lower part of the platen glass 9 is composed of a white fluorescent lamp, a cold cathode tube, or the like, and is conveyed onto the platen glass 9 and a light source lamp 15b that irradiates light to a lower surface of a part of the platen glass 9 facing the shading plate 15a. The mirror 15c for guiding the reflected light from the lower surface of the original document to the imaging lens 15d is arranged at a predetermined position and the longitudinal direction is perpendicular to the document conveyance direction B. Below the platen glass 9, an imaging lens 15d that collects the reflected light from the lower surface of the document whose optical path has been changed by the mirror 15c, and a CCD ( Charge Coupled Device) is provided with an image sensor 15e composed of a line sensor or the like.

  With such a configuration, the originals separated and conveyed one by one are pressed against the upper surface of the platen glass 9 by the shading plate 15a, and one line of reflected light from the original is irradiated by the light source lamp 15b. The image sensor 15e takes in each. Until one original passes through the shading plate 15a, the image sensor 15e continues to acquire reflected light from the original, thereby reading the lower surface image of one original. The light source lamp 15b, the mirror 15c, the imaging lens 15d, and the image sensor 15e constitute a lower surface reading unit 15 (see FIG. 2) that reads an image on the lower surface of the conveyed document.

  On the lower surface of the platen glass 9, a shading plate 14 a with a white application surface on the platen glass 9 is pasted at a position far from the conveyance roller 8, with the longitudinal direction intersecting the document conveyance direction B, and in the present embodiment orthogonal. Has been. An upper part of the platen glass 9 is composed of a white fluorescent lamp, a cold cathode tube, or the like, and is conveyed onto the platen glass 9 and a light source lamp 14b that irradiates light on the upper surface of the part of the platen glass 9 facing the shading plate 14a. The mirror 14c for guiding the reflected light from the upper surface of the original to the imaging lens 14d is arranged at a predetermined position, and the longitudinal direction is orthogonal to the conveyance direction B of the original. On the upper part of the platen glass 9, there are further formed an imaging lens 14d for collecting the reflected light from the upper surface of the document whose optical path has been changed by the mirror 14c, and an image sensor for acquiring the reflected light incident through the imaging lens 14d. 14e.

  With such a configuration, an original document that is separated and conveyed one by one and whose lower surface is read by the lower surface reading unit 15 is irradiated with light by the light source lamp 14b at the position where the shading plate 14a is disposed. The image sensor 14e captures the reflected light from each line. The image sensor 14e continues to acquire the reflected light from the original until one original passes the arrangement position of the shading plate 14a, thereby reading the upper surface image of one original. The light source lamp 14b, the mirror 14c, the imaging lens 14d, and the image sensor 14e constitute an upper surface reading unit 14 (see FIG. 2) that reads an image on the upper surface of the conveyed document.

  The document whose image has been read by the lower surface reading unit 15 and the upper surface reading unit 14 is conveyed by a conveyance roller (not shown) provided at an appropriate place, and is discharged onto a predetermined discharge tray. With the above-described configuration, the scanner 1 can read images on both the upper surface and the lower surface of the document in one transport operation in which the document separated one by one by the pickup roller 5 is transported to the discharge tray.

  Here, in the present embodiment, the upper surface reading unit 14 is used as a shading plate for acquiring shading data used in the shading correction performed by the image processing unit (shading correction unit) 17 on the image data read from the document. A shading plate 14a made of a white plate having a width of about 5 mm and a length of about 30 cm is used. On the other hand, as shown in FIG. 3 (b), the lower surface reading unit 15 has a width of about 5 mm and a length of about 30 cm on a white background plate, and is approximately 5 mm in three positions at a distance of about 7 cm in the longitudinal direction. A shading plate (reference member) 15a provided with a band-like black region having a width, specifically, black stripes 15aa, 15aa, 15aa is used. The shading plate 15a is arranged with the surfaces provided with the black stripes 15aa, 15aa, and 15aa facing downward so that the surfaces provided with the black stripes 15aa, 15aa, and 15aa become the reading surfaces of the lower surface reading unit 15. .

  Here, an example in which the shading plate 14a is formed of a white plate will be described. However, the reading surface of the upper surface reading unit 14 has a light reflectance necessary for shading correction (hereinafter referred to as a reference light reflectance). If there is, it is not limited to white. Similarly, a description will be given of a configuration in which the shading plate 15a is provided with black stripes 15aa, 15aa, and 15aa on a white plate. However, the reading surface of the lower surface reading unit 15 has a color base having a reference light reflectance for shading correction. In addition, any color stripe having a lower reflectance than the reference light reflectance may be provided. However, since many originals to be read are white, the shading plate 14a is preferably configured with a white background, and the shading plate 15a is preferably configured with a black stripe on a white background.

  In the scanner 1 having the above-described configuration, for example, when a serviceman who performs maintenance and inspection of the scanner 1 instructs the shading data acquisition process via the operation unit 20, the lower surface reading unit 15 performs the shading according to the instruction from the control unit 10. The reflected light from the plate 15a is read to obtain shading data (reference data) for the lower surface of the document, and the upper surface reading unit 14 reads the reflected light from the shading plate 14a in accordance with an instruction from the control unit 10 to read the document. Get shading data for the top surface of. The shading data acquired by the upper surface reading unit 14 and the lower surface reading unit 15 is stored in a memory (not shown) of the image processing unit 17.

  Thus, the image processing unit 17 performs shading correction based on the shading data for the upper surface for the image data acquired by the upper surface reading unit 14, and applies to the lower surface for the image data acquired by the lower surface reading unit 15. It becomes possible to perform shading correction based on shading data.

  Since the shading plate 15a is provided with three black stripes 15aa, 15aa, 15aa on a white background, when the lower surface reading unit 15 reads the shading plate 15a and acquires shading data, the black stripes 15aa, 15aa, The data value changes at the position 15aa. Therefore, when the lower surface reading unit 15 reads the shading data from the shading plate 15a, the control unit 10 executes the control program stored in the ROM 11 in advance, so that the black stripes 15aa, 15aa, 15aa in the shading data are obtained. The read data is interpolated based on the data before and after that to generate original shading data. The control unit 10 stores the generated shading data in the memory of the image processing unit 17.

  In the scanner 1, for example, when a user instructs a document reading process via the operation unit 20, the lower surface reading unit (first reading unit) 15 is arranged according to an instruction from the control unit 10. The image data is obtained by reading the reflected light from the lower surface (one surface) of the original that has been conveyed to the upper surface reading unit (second reading unit) 14 according to the instruction from the control unit 10. The image data is acquired by reading the reflected light from the upper surface (other surface) of the document that has been conveyed to the front.

  Here, the shading plates 14a and 15a are designed to be longer than the width of the document that can be read by the upper surface reading unit 14 and the lower surface reading unit 15, and the upper surface reading unit 14 and the lower surface reading unit 15 are conveyed. The entire area of the shading plates 14a and 15a can be read regardless of the size of the document. Accordingly, when the original reading unit 13 reads the conveyed original, the original reading unit 13 also reads a part of the shading plates 14a and 15a that is not covered with the original together with the conveyed original. The document reading unit 13 is provided with a sensor (not shown) at a predetermined position in the document transport path, and starts reading the document when the passage of the document is detected by this sensor. An area longer than the document size is also read in the conveyance direction B.

  FIG. 4 is a schematic diagram showing a state of the entire image data (hereinafter referred to as read data) read by the lower surface reading unit 15. In the scanner 1, for example, when an A4 size original is conveyed with the short side at the top, the lower surface reading unit 15 acquires read data as shown in FIG. In FIG. 4A, an area indicated by a one-dot chain line indicates read data 101, and an area indicated by a solid line with hatching indicates image data (hereinafter also referred to as original image data) 100 read from the original. . Therefore, the read data 101 includes shading data read from the shading plate 15 a as an area other than the original image data 100. Note that the shading data here is simply data based on the reflected light from the shading plate 15a and is not used for shading correction, and is referred to as surplus data for the sake of simplicity. Further, of the surplus data, data read from the black stripes 15aa, 15aa, 15aa provided on the shading plate 15a is referred to as black data.

  4B shows the state of the read data when the document is conveyed obliquely, and FIG. 4C shows the leading end portion of the read data shown in FIG. 4B (FIG. 4B). The enlarged view of the upper part in FIG. As shown in FIG. 4B, when the original is conveyed obliquely, the black data in the surplus data is compared with the read data in the case where the original is not inclined as shown in FIG. Data shape, area and length in the transport direction are different. Specifically, as shown in FIG. 4C, the lengths d1, d2, and d3 of the three black data are different in the surplus data from the leading edge of the read data to the leading edge of the document image data. As shown in FIG. 4C, when the document is skewed to the right, the length of the three black data is d1 <d2 <d3, and the document is skewed to the right. In this case, the length of the three black data is d1> d2> d3.

  Therefore, the image processing unit 17 detects the length of the three black data from the leading end of the reading data to the leading end of the document image data based on the reading data acquired by the lower surface reading unit 15, and detects each detected The skew angle θ (skew amount) of the document can be calculated based on the length. Therefore, the image processing unit 17 is based on the surplus data included in the read data acquired when the original conveyed on the reading surface of the shading plate 15a is read together with the shading plate 15a and the data of the boundary portion of the image data. Thus, it operates as a detection unit that detects the skew angle θ of the document.

  The image processing unit (correction unit) 17 stores the detected skew angle θ in the memory, and corrects the inclination of the document image data read from the lower surface of the document by the lower surface reading unit 15 based on the skew angle θ. To do. The image processing unit 17 performs the process of calculating the skew amount of the document and the process of correcting the inclination of the document image data based on the detected skew amount from the lower surface of the document by the lower surface reading unit 15 as described above. This is executed after the acquired read data is stored in the page memory 16. Here, since the scanner 1 of the present embodiment can read both sides of the document by one transport operation, the skew angle θ calculated based on the read data acquired by the lower surface reading unit 15 as described above. Can also be used when correcting the inclination of the document image data read by the upper surface reading unit 14 from the upper surface of the document.

  FIG. 5 is a schematic diagram illustrating a state of read data read by the document reading unit 13. FIG. 5A shows the state of the read data read by the upper surface reading unit 14, and FIG. 5B shows the state of the read data read by the lower surface reading unit 15. As shown in FIG. 5A, when the document image data 100 read from the upper surface of the document is inclined downwardly with respect to the read data 101, it is read from the lower surface of the document as shown in FIG. The document image data 100 is inclined to the upper right with respect to the read data 101, and the skew angles (absolute values) of both coincide. Therefore, when the image processing unit 17 calculates the skew angle θ based on the read data acquired by the lower surface reading unit 15, the image processing unit 17 tilts the document image data read from the lower surface of the document based on the skew angle θ. And the inclination of the document image data read from the upper surface of the document is corrected based on the skew angle -θ.

  As described above, the skew amount calculated based on the read data read from one side of the document can be used in common for the skew correction for the image data read from both sides of the document. Compared with the case where the skew angle is calculated for each surface, the burden of the skew angle calculation processing by the image processing unit 17 can be reduced.

  Here, as described above, the image processing unit 17 of the present embodiment calculates the skew angle of the document based on the length of the black data in the surplus data from the leading edge of the read data to the leading edge of the document image data. In addition, the skew angle of the document is also calculated based on the length of the black data in the surplus data from the trailing edge of the document image data to the trailing edge of the read data. FIG. 6 is a schematic diagram illustrating a state of read data read by the lower surface reading unit 15. FIG. 6A shows the state of read data when the original is conveyed while being skewed, and FIG. 6B shows the state of read data when the original slides in the conveyance direction.

  In the present embodiment, the image processing unit (first detection unit, second detection unit) 17 has a skew angle θ1 at the leading end of the document based on black data from the leading end of the read data to the leading end of the document image data. , And the skew angle θ2 at the trailing edge of the document is detected based on black data from the trailing edge of the document image data to the trailing edge of the read data. Then, the image processing unit (specification unit) 17 specifies the skew angle of the document based on the skew angle θ1 at the leading end of the document and the skew angle θ2 at the trailing end of the document, and specifies the specified skew angle. Is stored in the memory. The image processing unit 17 corrects the inclination of the document image data read from the lower surface of the document by the lower surface reading unit 15 based on the skew angle stored in the memory, and the upper surface reading unit 14 reads from the upper surface of the document. Corrects the inclination of the original image data.

  For example, if the upper part of the document is a black image, the boundary with the black data becomes unclear at the leading edge of the image data read from the document, so it is difficult to accurately calculate the skew angle at the leading edge of the document. It becomes. However, in the present invention, when the skew angle at the trailing edge of the document can be calculated, the skew of the document image data can be corrected based on the skew angle at the trailing edge, so that the skew correction can be reliably performed. Can be performed. Further, as shown in FIG. 6B, when the document slides forward in the transport direction, it can be detected that the document slips forward based on the skew amount at the rear end of the document. . In this case, although it is not possible to interpolate the area that could not be read from the document, it is possible to perform correction of moving the image data downward in the transport direction together with the skew correction for the image data that can be read from the document.

  Note that the method for specifying the skew angle of the document based on the skew angle θ1 at the leading edge of the document and the skew angle θ2 at the trailing edge of the document is, for example, the skew angle θ1 at the leading edge and the trailing angle at the trailing edge. A method of adopting an average value of the skew angle θ2, and when the skew angle θ1 at the front end (or the skew angle θ2 at the rear end) is not within a predetermined range, the skew angle θ2 at the rear end (or A method of adopting the skew angle θ1) at the tip can be considered. As a result, the skew angle of the original can be calculated more accurately, and the inclination of the image data read from the original can be accurately corrected.

  A document image reading process by the scanner 1 having the above-described configuration will be described below. FIG. 7 is a flowchart showing a procedure of document image reading processing by the scanner 1. The following processing is executed by the control unit 10 in accordance with a control program stored in the ROM 11. In the following, when the skew angle at the leading edge of the document can be detected, the skew of the document image data is corrected based on the skew angle at the leading edge, and the skew angle at the leading edge cannot be detected. First, the inclination of the document image data is corrected based on the skew angle at the trailing edge of the document.

  For example, when the user instructs a document image reading process via the operation unit 20, the control unit 10 operates the document reading unit 13 and starts conveying the document by the document conveying unit 13a (S1). The control unit 10 starts reading the images on both sides of the conveyed document by the document reading unit 13 (S2), and accumulates the read data read in the page memory 16 (S3). The control unit 10 determines whether or not reading of both sides of one document is completed (S4). If the reading is not completed (S4: NO), the page memory 16 of the read data read by the document reading unit 13 is determined. The accumulation is continued (S3).

When reading of both sides of one document is completed (S4: YES), the control unit 10 analyzes the leading end portion of the read data acquired by the lower surface reading unit 15 by the image processing unit 17 (S5), and the black data and It is determined whether the boundary with the document image data is clear (S6). It should be noted that the analysis of the leading end portion of the read data acquired by the lower surface reading unit 15 can be performed after the reading of the lower surface of the document is completed, even after the reading of both sides of the document is completed.

When it is determined that the boundary between the black data and the document image data is clear (S6: YES), the control unit 10 detects the length of each detected black data by the image processing unit 17 (S7) and detects it. Based on each length, the skew angle at the leading edge of the document is calculated and stored in the memory of the image processing unit 17 (S8). The control unit 10 corrects the inclination of the document image data read from the lower surface of the document and stored in the page memory 16 based on the skew angle at the leading edge of the document stored in the memory by the image processing unit 17. Then, the inclination of the document image data read from the upper surface of the document and stored in the page memory 16 is corrected (S9). The document image data whose inclination is corrected by the image processing unit 17 is output to the CODEC 18.

When it is determined that the boundary between the black data and the document image data is not clear (S6: NO), the control unit 10 analyzes the rear end portion of the read data acquired by the lower surface reading unit 15 by the image processing unit 17 (S10). ), It is determined whether or not the boundary between the black data and the document image data is clear (S11). When it is determined that the boundary between the black data and the document image data is clear (S11: YES), the control unit 10 detects the length of each detected black data by the image processing unit 17 (S12) and detects it. Based on each length, the skew angle at the trailing edge of the document is calculated and stored in the memory of the image processing unit 17 (S13). If it is determined that the boundary between the black data and the original image data is not clear even at the rear end portion of the read data (S11: NO), the control unit 10 ends the above-described processing. In this case, the document image data stored in the page memory 16 is not corrected for inclination and is output to the CODEC 18 after predetermined image processing is performed by the image processing unit 17.

  The control unit 10 determines the inclination of the document image data read from the lower surface of the document and stored in the page memory 16 based on the skew angle at the trailing edge of the document stored in the memory by the image processing unit 17. Then, the inclination of the document image data read from the upper surface of the document and stored in the page memory 16 is corrected (S9). The document image data whose inclination is corrected by the image processing unit 17 is output to the CODEC 18.

  As described above, by providing the black stripes 15aa, 15aa, and 15aa at predetermined positions of the shading plate 15a, the skew feeding used for the skew correction using the shading plate 15a for obtaining the shading data used for the shading correction. The amount can be detected. Accordingly, it is not necessary to perform operations such as changing different plates when acquiring shading data and when detecting the amount of skew.

  In the scanner 1 having the above-described configuration, when the shading data is acquired or before the reading of the document is started, only the shading plate 15a is read, and the malfunction of the light source lamp 15b is detected based on the acquired shading data. Is also configured. As shown in FIG. 3B, the shading plate 15a is provided with black stripes 15aa, 15aa, and 15aa at predetermined three locations. Therefore, the shading data obtained by reading the shading plate 15a is the black stripe 15aa, The value of data becomes small at 15aa and 15aa. Accordingly, in the shading data, data based on the reflected light from the white background (white data) and black data based on the reflected light from the black stripes 15aa, 15aa, 15aa are generated.

When the lighting state of the light source lamp 15b is not good, the difference between the white data and the black data becomes small. Therefore, when this difference becomes a predetermined value or less, it can be determined that a problem has occurred in the light source lamp 15b. . Note that a predetermined value for determining whether or not a failure has occurred in the light source lamp 15b is stored in the ROM 11 in advance.
In a scanner using a white back plate, it is usually possible to determine that a problem such as a light source lamp not being lit has occurred when the amount of reflected light from the back plate is small. However, with this method, it may not be possible to accurately determine the occurrence of a defect with respect to a light source lamp having a variation in light quantity. However, according to the shading data acquired from the shading plate 15a as in the present embodiment, it is possible to accurately detect a defect in the light source lamp even if the light source lamp has a variation in the amount of light.

  Below, the process which detects that the malfunction occurred in the light source lamp 15b in the scanner 1 of this embodiment is demonstrated. FIG. 8 is a flowchart showing the procedure of the defect detection process of the light source lamp 15b by the scanner 1. The following processing is executed by the control unit 10 in accordance with a control program stored in the ROM 11. In the following, a configuration for detecting a failure of the light source lamp 15b when acquiring shading data based on the reflected light from the shading plate 15a will be described. However, the light source lamp 15b before reading a document in normal document reading. It is also possible to detect defects.

  For example, when a service person who performs maintenance and inspection of the scanner 1 instructs shading data acquisition processing via the operation unit 20, the control unit 10 operates the lower surface reading unit 15 of the document reading unit 13 to turn on the light source lamp 15 b. (S21), and obtain shading data based on the reflected light from the shading plate 15a (S22). The control unit 10 temporarily stores the shading data acquired from the shading plate 15a in the page memory 16, and calculates the difference between the white data and the black data in this shading data (S23).

  The control unit 10 determines whether or not the calculated difference is greater than a predetermined value stored in advance in the ROM 11 (S24). If it is determined that the value is larger than the predetermined value (S24: YES), the control unit 10 determines that there is no malfunction in the light source lamp 15b, and the black data in the shading data stored in the page memory 16 Interpolation is performed based on the preceding and following white data, and the generated shading data is stored in the memory of the image processing unit 17 (S25). Thus, the image processing unit 17 can perform shading correction on the document image data read from the lower surface of the document, based on the shading data stored in the memory.

  Next, the control unit 10 operates the upper surface reading unit 14 of the document reading unit 13 to turn on the light source lamp 14b (S26), acquires shading data based on the reflected light from the shading plate 14a, and acquires the acquired shading data. It is stored in the memory of the image processing unit 17 (S27). As a result, the image processing unit 17 can perform shading correction on the document image data read from the upper surface of the document, based on the shading data stored in the memory.

  If it is determined in step S24 that the calculated difference is equal to or smaller than the predetermined value (S24: NO), the control unit 10 detects that a problem has occurred in the light source lamp 15b (S28). The control unit 10 notifies that a defect has occurred in the light source lamp 15b (S29), and ends the shading data acquisition process as described above. As a method of notifying the occurrence of a malfunction in the light source lamp 15b, a method of displaying a predetermined message on the display unit 21, a method of separately providing an error lamp and lighting the error lamp, or a separate audio output unit is provided. A method of outputting a voice message can be used.

  As described above, it is possible to determine whether or not the light source lamp 15b is normally lit using the shading plate 15a for acquiring shading data used for shading correction. Further, by detecting the malfunction of the light source lamp 15b using such a shading plate 15a, it is possible to determine whether or not the light source lamp 15b is normally lit even when the light amount of the light source lamp 15b varies. It can be detected with high accuracy.

The image processing unit 17 of the present embodiment is also configured to detect a standard size in a direction that intersects the document transport direction, specifically, a direction that is orthogonal (width direction) when reading the document. FIG. 9 is a schematic diagram illustrating a state of read data read by the lower surface reading unit 15. FIG. 9 shows the state of the read data when an A4 size document is conveyed starting from the long side. FIG. 4A shows the state of read data when an A4 size original is conveyed with the short side at the top, and the shading plate 15a is placed outside the original image data in the width direction read from the original. There is black data based on the reflected light from the black stripes 15aa, 15aa, 15aa. On the other hand, when an A4 size document is conveyed starting from the long side, there is no black data outside the document image data in the width direction, as shown in FIG.

Therefore, the image processing unit ( standard size detection unit) 17 can detect the standard size in the width direction of the document based on the black data in the read data read by the lower surface reading unit 15. Further, by providing a black stripe at a position corresponding to each standard size of the document, the document in the width direction of the document is determined based on whether or not the conveyed document is conveyed on each black stripe of the shading plate 15a. The standard size can be detected more accurately. Therefore, the shading plate 15a of the present embodiment has a configuration in which black stripes 15aa, 15aa, and 15aa are provided at appropriate three locations as shown in FIG. 3B, but is limited to such a configuration. Absent. For example, in the shading plate 15a shown in FIG. 3 (b), when black stripes having a width of about 5 mm are provided at two locations separated from each of both ends by a distance of about 5 cm, an A4 size document is a short side. This can be detected when it is conveyed from the side.

As described above, in the present embodiment, the standard size in the width direction of the document can be accurately detected using the shading plate 15a for acquiring the shading data used for the shading correction, so that the document width is detected. There is no need to provide a separate mechanism.

  In the above-described embodiment, the example in which the document reading apparatus of the present invention is applied to the scanner 1 has been described. However, the scanner is not limited to the scanner as long as it includes a document reading apparatus that reads an image from a document. For example, the document reading apparatus of the present invention can be used in a copying machine, a facsimile machine, a multifunction machine, and the like.

  In the above-described embodiment, the scanner 1 configured to read both sides of the document in one transport operation has been described as an example. However, the scanner 1 includes a single reading unit and an ADF mechanism that reverses the document. The present invention can also be applied to a reading apparatus configured to invert the front and back sides of the document after reading and read the back side of the document. In this case, since the skew amount of the image data read from the front surface of the document is different from the skew amount of the image data read from the back surface of the document, it is necessary to perform the skew amount detection processing.

  The present invention can also be applied to an FBS (Flat Bed Scanner) type reading apparatus that reads an image while a document is stationary on a platen glass. In this case, a black stripe may be provided at a predetermined position on the white surface of the back plate that presses the document placed on the platen glass. Furthermore, the widths of the black stripes 15aa, 15aa, 15aa provided on the shading plate 15a are not necessarily the same, and may be configured to be different from each other. In this case, it is determined at which position of the shading plate 15a the black data in the read data read by the lower surface reading unit 15 is the black data based on the reflected light from the black stripes 15aa, 15aa, 15aa. I can grasp it.

In addition, the shading plate 15a of the present embodiment has a configuration in which the black stripes 15aa, 15aa, and 15aa are provided on a white background. However, the shading plate 15a may be configured by a roller, for example. FIG. 10 is a schematic view showing a modification of the shading plate. FIG. 10A is a perspective view, and FIG. 10B is a view of the shading roller 30 viewed from the direction indicated by the arrow C in FIG. 10A. The shading roller 30 shown in FIG. 10 is, for example, a white background roller having a diameter of about 5 cm and a length of about 30 cm. 30a and 30a are provided. Such a shading roller 30 is disposed at a position where the shading plate 15a is disposed in FIG. 3A with the axial direction orthogonal to the document conveyance direction B.

In the scanner 1 having such a configuration, when the lower surface reading unit 15 reads an image on the lower surface of the document, the control unit 10 rotates the shading roller 30 in a direction indicated by an arrow D in the drawing, thereby reading the document. The originals separated one by one by the original conveying unit 13 a of the unit 13 and conveyed to the platen glass 9 are pressed against the upper surface of the platen glass 9 by the shading roller 30 and conveyed in the conveying direction B. Therefore, the shading roller 30 also functions as a pressing plate when reading a document, and can acquire image data from the document with high accuracy.

1 is a schematic perspective view showing an external appearance of a scanner according to an embodiment. It is a block diagram which shows the structural example of the scanner of this embodiment. 3 is a block diagram illustrating a configuration example of a document reading unit. FIG. It is a schematic diagram which shows the state of the read data which the lower surface reading part read. 6 is a schematic diagram illustrating a state of read data read by a document reading unit. FIG. It is a schematic diagram which shows the state of the read data which the lower surface reading part read. 6 is a flowchart illustrating a procedure of document image reading processing by a scanner. It is a flowchart which shows the procedure of the malfunction detection process of the light source lamp by a scanner. It is a schematic diagram which shows the state of the read data which the lower surface reading part read. It is a schematic diagram which shows the modification of a shading plate.

Explanation of symbols

1 Scanner (document reading device)
10 Control Unit 13 Document Reading Unit (Reading Unit)
14 Upper surface reading unit (second reading unit)
15 Lower surface reading unit (first reading unit)
15a Shading plate (reference member)
15b Light source lamp 17 Image processing unit (detection unit, first detection unit, second detection unit)

Claims (4)

A reading section that acquires image data by reading an original conveyed, is provided inside the said read unit, the longitudinal direction intersecting the conveying direction of the document, have a reference light reflectance for shading correction, a reference member which is wider reading surface than the width of the image data is arranged in a position opposed to the original, the shading data generated from a reference data to which the reading unit has acquired by reading the reading surface of the reference member A document reading apparatus comprising a shading correction unit that corrects shading of image data acquired by the reading unit,
The reading surface of the reference member has a low reflection region of a predetermined width at a lower reflectivity than the light reflectance of each of the reference to the three or more locations in the direction orthogonal to the conveying direction of the document,
Per read data obtained when the reading unit the document conveyed over the reading surface of the reference member with the reading surface is read, the low reflection region in different positions in the direction intersecting the transport direction of the document corresponding data, depending on the length of the conveying direction of each of the document, a detection unit that detects a skew amount of the original,
An original reading apparatus comprising: a correction unit that corrects an inclination of the image data included in the read data based on a skew amount detected by the detection unit. A first reading section that acquires image data by reading one side of a transported document is internally provided to the first reading section, the longitudinal direction intersecting the conveying direction of the document, the reference for shading correction light the reflectance possess, a reference member that wider reading surface than the width is arranged at a position opposed to the original width of the image data, the first reading unit obtains by reading the reading surface of the reference member A shading correction unit that corrects shading of image data acquired by the first reading unit based on shading data generated from reference data; a second reading unit that acquires image data by reading the other side of the document; A document reading apparatus comprising:
Reading surface of the reference member has a low reflection region of a predetermined width at a lower reflectivity than the light reflectance of each of the reference to the plurality of positions in the direction orthogonal to the conveying direction of the document,
Per has been read data acquired when the first reading unit with said reading surface one surface of the document conveyed on the reading surface of the reference member is read, the different positions in the direction intersecting the transport direction of the document a detection unit of the data corresponding to the low reflection region, depending on the length of the conveying direction of each of the document, detects the skew amount of the original,
Based on the skew amount detection unit detects, further comprising a correcting unit that corrects the inclination of the image data included in the read data, to correct the inclination of the image data to which the second reading unit acquires An original document reading device. The correction unit has a standard size in a direction that intersects the transport direction of the previous document depending on the presence or absence of data corresponding to low reflection regions at different positions in the direction that intersects the transport direction of the document. document reading apparatus according to claim 1 or 2, characterized that you detect. A reading section that acquires image data by reading an original conveyed, is internally provided in said read unit, the longitudinal direction intersecting the conveying direction of the document, have a reference light reflectance for shading correction, a reference member which is wider reading surface than the width of the image data is arranged in a position opposed to the original, the shading data generated from a reference data to which the reading unit has acquired by reading the reading surface of the reference member A document reading apparatus comprising a shading correction unit that corrects shading of image data acquired by the reading unit,
Reading surface of the reference member has a low reflection region of a predetermined width at a lower reflectivity than the light reflectance of each of the reference to the plurality of positions in the direction orthogonal to the conveying direction of the document,
Per read data obtained when the reading unit the front end of the document conveyed over the reading surface of the reference member with the reading surface is read, the low at different positions in the direction intersecting the transport direction of the document data corresponding to the reflective region, depending on the length of the conveying direction of each of the document, a first detector for detecting a skew amount at the tip of the document,
Per read data obtained when the reading unit the rear end of the document conveyed over the reading surface of the reference member with the reading surface is read, the different positions in the direction intersecting the transport direction of the document data corresponding to the low reflection region, depending on the length of the conveying direction of each of the document, and a second detector for detecting a skew amount of the trailing end of the document,
The skew amount detected by the first detector and the average value of the skew amounts detected by the second detector , or the skew amount of the other when the skew amount is not within a predetermined range, A specific part for specifying the skew amount of the document,
An original reading apparatus comprising: a correction unit that corrects the inclination of the image data included in the read data acquired by the reading unit based on the specified skew amount.

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