JP5192167B2 - Image reading device - Google Patents

Description

The present invention is a scanner for reading an image of a document to transport the document placed on the original manuscript platform to the image reading position, fax, relates to an image reading apparatus such as a digital copier.

  In an image reading apparatus that reads a document image by transporting a document placed on a document table to an image reading position, generally, in order to obtain image data having no margin, a document size is designated in advance and then the document image is read. read. In addition, by installing a restriction plate for restricting both side edges in the width direction of the document on the document table, the document is prevented from being tilted when the document is conveyed.

  However, when a non-uniform size document is placed on the platen, or when the document is not placed straight along the transport direction on the platen, the image data of the read document is blank. There are many or tilted.

  For these reasons, conventionally, a black background member is placed opposite to a line sensor that reads an image of a document, and a change in density at the boundary between the background member and the document edge is detected from the read image data. The edge of the document is detected to determine the size and inclination of the document, and the image is cut out and the inclination is corrected.

Also, a method has been proposed in which the line sensor detects the edge of the document by irradiating the document with light and transmitting the light transmitted through the document, and the size and inclination of the document are obtained based on the detection result. (Patent Document 1).
JP-A-6-339007

  However, as in the above prior art, in the method of detecting the edge of the document by detecting the density change at the boundary between the background member and the document edge from the read image data, and obtaining the size and inclination of the document, Even if the background member is black, it may not be possible to accurately detect changes in the density at the boundary between the background member and the edge of the document on dark-colored documents such as black backgrounds or documents with solid black prints. There is. In addition, a pattern printed on a document may be erroneously detected as a document edge.

  On the other hand, in Patent Document 1, since the right end and the left end of the original are detected by scanning the transmitted light of the original in a single direction, a change in brightness due to a binder hole or the like on the original may be erroneously detected as the end of the original. There is sex.

  Also, in the case of a very thin document, the amount of light transmitted from the document is large, and the difference in brightness between the part where the document is blocking light and the part where it is not light becomes small. It is necessary to set a threshold value so that it is judged as an end. In this case, if the transmitted light of the document is scanned in a single direction to detect the edge of the document, the amount of transmitted light changes depending on the printed content of the document. there's a possibility that.

  Also, thin and thick originals differ in the degree of light and dark changes at the edges of the original due to differences in the amount of light transmission. There is a possibility of being detected in a different size.

The present invention aims at providing a picture image read Ru can accurately detect with the size or the inclination of the document leading edge of the document conveyed on the conveying path.

To achieve the above object, an image reading apparatus of the present invention is an image reading apparatus comprising: a sheet over preparative conveying device, an image reading sensor reads the image of the sheet conveyed on the conveying path, wherein the sheet The conveying device is disposed to face one surface of the sheet conveyed through the conveying path, and receives a light source that irradiates the sheet with light and an irradiation light of the light source on the opposite side of the light source across the conveying path. Two line sensors that are arranged side by side in the sheet width direction substantially perpendicular to the sheet conveyance direction and scan in the direction from the outside to the inside in the sheet width direction, and the scanning of the two line sensors. in, Bei and a detection means with a plurality of lines detected, detects the inclination or the size of the sheet with the leading edge of the sheet in the width direction of the end of the sheet based on the sheet edge output signal output of the two line sensors , The image reading sensor, said detecting means even after detecting the leading edge of the sheet, and characterized that you start a document reading operation before the leading end of the sheet is conveyed to the image reading position To do.

In order to achieve the above object, an image reading apparatus according to the present invention includes a first line sensor for reading an image of a document conveyed on a conveyance path and an original in the image reading device for acquiring read image data of the document. A light source for irradiating the document with light, and a position for receiving the light emitted from the light source on the opposite side of the light source across the transport path, in the document transport direction. A second line sensor that scans in a direction from the outside to the inside in the width direction of the document that is substantially orthogonal to the document, and a document end output signal that is output from the second line sensor in the scanning of the second line sensor. And detecting means for detecting a plurality of lines at both ends in the width direction of the document and detecting the inclination or size of the document together with the leading edge of the document. The first line sensor includes a detecting means for detecting the leading edge of the document. After detection There are, along with the leading end of the document starts document reading operation before being conveyed to the image reading position, the detecting means, the other for position detection in the width direction of the end of the document and the width direction of the document The second line sensor is scanned starting from a different light receiving portion of the second line sensor at the time of detecting the end position.

In order to achieve the above object, an image reading apparatus according to the present invention includes a first line sensor for reading an image of a document conveyed on a conveyance path and an original in the image reading device for acquiring read image data of the document. A light source that is disposed opposite to one surface of the light source and irradiates light on the document, and is disposed at a position that receives light emitted from the light source on the opposite side of the light source across the transport path, and is directed to the transport direction of the document. A second line sensor that scans in a direction from the outer side to the inner side in the width direction of the document that is substantially orthogonal, and based on a document end output signal that is output by the second line sensor in the scanning of the second line sensor. Read out the output information of a plurality of lines stored in the storage means for storing the output information, and detect one end in the width direction and the other end in the width direction based on the read output information, Document tilt or Comprising a detection means for detecting a size with the front end of the document, wherein the first line sensor, said detecting means even after detecting the leading edge of the document, the leading end of the original is conveyed to the image reading position The reading operation of the original is started before the detection means detects the output order of the output information of the second line sensor from the storage means when detecting one end in the width direction of the original. From the output information on one end side in the width direction of the line sensor to the output information on the other end side, when detecting the other end in the width direction of the document, the output information on the other end side in the width direction of the second line sensor is used. It is characterized by the order of the output information on the one end side.

According to the present invention, it is possible to accurately detect the size or inclination of a document regardless of the background color of the document at the time of image reading, the thickness of the document, the document description, the document color, and the presence or absence of a binder hole.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic cross-sectional view for explaining the image reading apparatus according to the first embodiment of the present invention, and FIG. 3 is a diagram schematically showing a main part of the image reading apparatus shown in FIG.

  As shown in FIG. 2, the image reading apparatus 200 of this embodiment includes a document table 1 on which a plurality of documents are stacked and driven up and down by a document table drive motor 2. The document detection sensor 3 detects the document on the document table 1. The paper feed roller 4 sends out the document on the document table 1 from the document table 1. The paper feed motor 5 rotates the paper feed roller 4.

  The feed roller 6 is rotationally driven by a feed motor 8 in a direction in which the document is conveyed downstream. The separation roller 7 always receives a rotational force for conveying the document upstream from the separation motor 9 via a slip clutch (not shown). However, when the number of documents is one, the separation roller 7 receives the document conveyance force and receives the document by the slip clutch. The feed roller 6 is allowed to follow and rotate and follow. Then, when there are a plurality of documents, the separation roller 7 rotates in a direction in which the document is conveyed upstream, and pushes the document back upstream.

  Due to the action of feeding the original on the feeding roller 6 to the downstream side and the action of returning the original on the separation roller 7 to the upstream side, the originals are overlapped and fed to the nip portion between the feeding roller 6 and the separation roller 7. Then, the upper sheet of the overlapped original is conveyed downstream, and the lower original is pushed back upstream, and the overlapped original is separated and conveyed. A pair of separation belt rollers (not shown) may be used instead of the pair of rollers of the feeding roller 6 and the separation roller 7.

  The transport motor 10 drives the document transport rollers 20, 21, 22, 23 for transporting the separated and fed document from the document reading position to the discharge position. The nip gap adjusting motor 11 adjusts the gap between the feeding roller 6 and the separation roller 7 or the pressure contact pressure of the feeding roller 6 against the separation roller 7 so that the document is fed with a gap suitable for the thickness of the document or the pressure contact pressure. Separate and transport.

  The document reading unit 43 includes reading units 14 and 15. The reading units 14 and 15 are provided with a line sensor that reads an image of the conveyed document and a light source for image reading. Light emitted from the light source is reflected by the reading surface of the document, and the reflected light is reflected by the line sensor. By receiving the light, the image of the original is read.

  The document discharge sensor 16 detects that the document passes through the document reading unit 43 and is discharged to the document discharge unit 44. The registration rollers 17 and 18 temporarily stop and restrict the document from being conveyed downstream to correct the skew of the document. The registration clutch 19 transmits the rotation of the conveyance motor 10 to the registration roller 18 or turns it off.

  The document transport rollers 20, 21, 22, and 23 transport the document F to the document discharge unit 44. The two guide plates of the upper guide plate 40 and the lower guide plate 41 guide the document F conveyed between the roller pairs 6 and 7, the registration rollers 17 and 18, and the document conveyance rollers 20, 21, 22 and 23. To do.

  The pre-feed document sensor S1 detects the front end (downstream end) of the fed document. The transmitted light amount detection sensor S2 is installed at a position for receiving the light of the infrared light source L2 installed on the opposite side across the conveyance path, and when the fed document blocks the light from the infrared light source L2. The thickness of the original is detected from the difference in the amount of transmitted light.

  The pre-registration sensor S3 detects a document that is disposed upstream of the registration rollers 17 and 18 and is fed. The post-registration sensor S4 detects a document that is disposed downstream of the registration rollers 17 and 18 and is fed.

  The image size detection unit 51 includes a line sensor having a width wider than the width of the conveyance path, and detects the right edge and the left edge of the document by blocking the document conveyed with the light from the light source L1.

  FIG. 1 is a block diagram for explaining a control system of the image reading apparatus 200.

  As shown in FIG. 1, the image reading apparatus 200 includes line sensors 101 and 102 that constitute the reading units 14 and 15 of the image reading unit 43, and the line sensors 101 and 102 are images on the front and back sides of a document, respectively. Is output and an image signal is output. The image processing unit 103 performs level correction processing, A / D conversion processing, shading correction processing, and the like on the image signals output from the line sensors 101 and 102, and generates and outputs image data. The memory unit 104 temporarily stores the image data output from the image processing unit 103.

The line sensor 105 is a sensor for detecting the image size and inclination of the document, and constitutes an image size detection unit 51. As the line sensor 105, a line sensor capable of switching the scanning direction is used. The image processing unit 106 performs A / D conversion processing or the like on the document edge output signal output from the line sensor 105 to generate and output document edge image data. Also, the image processing unit 106 can generate more accurate document edge image data by performing level correction processing and shading correction processing.

The document size / tilt detection unit 108 outputs an image end output signal which is output from the line sensor 105 receiving and outputting the light emitted from the light source L1 and passing through a portion where the document does not exist and the light transmitted through the document. Based on the document edge image data generated by processing in 106, the size and inclination of the document are detected. Here, the image processing unit 106 and the document size / tilt detection unit 108 constitute detection means of the present invention.

  The paper thickness detector 111 detects the thickness of the document based on the intensity of the output signal of the transmitted light amount detection sensor S2. The conveyance stop instruction unit 112 instructs a document conveyance control unit (not shown) to perform control for stopping conveyance.

  The operation of the image reading apparatus 200 having the above configuration will be described.

  When the document is conveyed and reaches the transmitted light amount detection sensor S2, the output signal of the transmitted light amount detection sensor S2 changes. The transmitted light amount detection sensor S2 uses a phototransistor or a photodiode, and as shown in FIG. 7, can receive light from the light source L2 installed on the opposite side across the conveyance path 703. In the present embodiment, the light source L2 uses an infrared light emitting element such as an infrared LED.

  When there is no document on the conveyance path 703, the transmitted light amount detection sensor S2 directly receives the light emitted from the light source L2, and therefore the output signal has a high value. When the original is conveyed to a position where the light from the light source L2 is blocked, the light incident on the transmitted light amount detection sensor S2 is reduced and the output signal is lowered.

  At this time, when the original is thick, the light emitted from the light source L2 is completely blocked. When the original is thin, the light emitted from the light source L2 passes through the thin original and enters the transmitted light amount detection sensor S2. Although it is minute, when the transmitted light amount detection sensor S2 receives the transmitted light, the output signal of the transmitted light amount detection sensor S2 becomes higher than that of a thick original.

  The paper thickness detection unit 111 determines the thickness of the document from the difference in the signal level, and outputs the document thickness information to the document size / tilt detection unit 108. Instead of the thickness information, the degree of light passing through the document may be detected, and the detected information may be output to the document size / tilt detection unit 108.

  When the original reaches the line sensor 105 of the image size detection unit 51, the irradiation light from the light source L1 is blocked by the original. The light source L1 may be an LED arranged in an array or a light guide that diffuses and irradiates light from the LEDs arranged at both ends or one end of the line sensor 105 in the longitudinal direction. In the present embodiment, the light source L1 arranges an LED as a point light source at a sufficient distance above the line sensor 105, and irradiates the line sensor 105 by passing light from the LED through a slit opened in a line shape. To do.

  Specifically, as shown in FIG. 8, the light source L1 is an LED that is a point light source and has a wide irradiation width so that the entire line sensor 105 is irradiated with light, and is sufficiently above the line sensor 105. They are arranged at a distance. Light from the light source L1 passes through a slit 802 opened in a sheet metal or the like and is irradiated on the entire line sensor 105. The line sensor 105 uses a photoelectric conversion element such as a CIS sensor whose output signal changes depending on the amount of light received.

  As shown in FIG. 4, the line sensor 105 has a length wider than the width of the transport path. Therefore, the width of the conveyed document is narrower than the length of the line sensor 105. For this reason, the line sensor 105 has a portion that is blocked by the document and a portion that is not blocked by the document. Since the light emitted from the light source L1 is directly incident on the portion of the line sensor 105 that is not blocked by the original, the output signal of the line sensor 105 corresponding to this portion becomes high.

Conversely, the portion of the line sensor 105 that the light source L1 by the document is interrupted, because the light from the light source L1 is hardly incident, document No. Tanshin is lowered which is an output signal of the line sensor 105 corresponding to this portion. It is possible to detect the position of the edge of the document by the position in the longitudinal direction of the line sensor 105 where the change of the output signal occurs. The image size / tilt detection unit 108 reads document edge image data obtained by A / D converting the document edge output signal output from the line sensor 105 by the image processing unit 106, and detects the document edge.

  Next, referring to FIG. 9, a method for detecting the edge of the document will be described.

  In FIG. 9, document edge image data 902 which is digital data obtained by A / D converting the output signal of the line sensor 105 starts with pixel data corresponding to the light receiving element at the end of the line sensor 105 when performing line scanning. The images are sequentially input to the image size / tilt detection unit 108. Scanning the line sensor 105 means that the charges accumulated by the light receiving elements of the line sensor 105 are converted into output signals and sequentially read out in this way.

  The image size / tilt detection unit 108 performs binarization processing using the threshold value 903 on the document edge image data 902 based on the output signal of the line sensor 105. In the binarized document edge image data 905 and 906, white represents a pixel having a pixel value of 1, and black represents a pixel having a pixel value of 0. By performing binarization using an appropriate threshold value, a portion where the original 901 is not applied to the line sensor 105 becomes a white pixel, and a portion where the original is applied becomes a black pixel. The A / D conversion process may be omitted, and the binarization process may be performed on the output signal that is an analog signal.

  When detecting the left edge of the document in the width direction, if the line sensor 105 performs line scanning from the left, the line sensor 105 scans from the left edge (tip) of the line sensor 105 in the direction of arrow C, and the pixel corresponding to the left light receiving element. Are sequentially input to the image size / tilt detection unit 108.

  The image size / tilt detection unit 108 monitors the binarized document edge image data 905 in the order in which the leftmost pixel is input as the head, and searches for which pixel the pixel has changed from white to black first. In FIG. 9, the binarized output signal 905 changes from white to black at the m-th pixel counting from the left end of the line sensor 105. When this change point is detected, the process for detecting the left edge of the document in the line is terminated. It should be noted that detection may be continued over several pixels after detection of the change point to prevent erroneous detection due to noise.

  Next, when detecting the right end in the width direction of the document, if the line sensor 105 performs line scanning from the right, the right end (rear end) of the line sensor 105 is moved in the direction of the arrow D contrary to the time of detecting the left end. Scanned data is sequentially input to the image size / tilt detection unit 108 in the direction of arrow D with the binarized data of the pixel corresponding to the rightmost light receiving element as the head.

  The image size / tilt detection unit 108 monitors in order of input with the rightmost pixel as the head, and searches for the pixel at which the pixel first changed from white to black. The binarized document edge image data 906 changes from white to black at the nth pixel counting from the right edge of the line sensor 105. When this change point is detected, the process for detecting the right edge of the document in the line ends.

  It should be noted that detection may be continued over several pixels after detection of the change point to prevent erroneous detection due to noise. As described above, since both the left end and the right end in the document width direction are detected by scanning from the outside in the document width direction, erroneous detection due to the presence or absence of a binder hole is prevented. Further, since the detection process can be stopped when the document edge is detected, the processing time can be shortened.

  In this embodiment, the line memory is not required, which is effective for cost reduction. However, the document edge image data generated from the output signal of the line sensor 105 or the binarized document edge image data is once stored in the line memory. You may make it make it. In this way, it is not necessary to use a line sensor that can be read from the left end and the right end in the width direction of the document as in this embodiment.

  In the case of using a line memory, if the address of the memory to be read first is changed and the reading direction from the line sensor is changed by changing the increment and decrement of the address, it can be equivalent to the case of performing the line scan.

  That is, when the left end of the document is detected, the reading start point is read out from the binarized document end image data 905 where the binarized data of the pixel corresponding to the left end (first) light receiving element is stored. And When the right end of the document is detected, the binarized document end image data 905 is read out from the address storing the binarized data of the pixel corresponding to the right end (rear end) light receiving element. Read while decrementing the address as the starting point. By configuring in this way, the same effect as changing the scanning direction of the line sensor can be obtained.

  As described above, the line sensor 105 is installed so that its reading range is wider than the conveyance path. Therefore, the vicinity of the right end (start) and the left end (rear end) of the line sensor 105 is always outside the document. For this reason, the vicinity of both ends of the binarized document edge image data generated from the output signal of the line sensor 105 is always a white pixel signal.

  The portion of the black pixel whose binarized pixel value is 0 is the portion where the document is applied to the line sensor 105. Therefore, the portion first changed from the white pixel to the black pixel from the leftmost pixel is the portion of the document. Hit the left edge. Further, the portion where the white pixel first changes from the right end pixel to the black pixel corresponds to the right end of the document. That is, the mth pixel from the left is the left end of the document 901, and the nth pixel from the right is the right end of the document 901.

  By scanning in this way, the edge of the document can be detected under the same left and right conditions. In other words, when scanning from the left or right, the edge of the document can be searched from the position where there is no document on the line sensor 105, and the white pixel is first changed to the black pixel from the leftmost pixel as described above. The point at which the changed point first changes from the white pixel to the black pixel from the left and right end pixels of the document becomes the right end of the document.

  By doing so, for example, even if the document has a binder hole, the pixel at the edge of the document is scanned before the pixel at the position where the binder hole exists, and the edge of the binder hole is correspondingly scanned. A pixel that changes from white to black at the edge of the original can be detected earlier than a pixel that changes from white to black, and erroneous detection of the original width in an original having a binder hole can be prevented.

  Also, even if the document has a solid black print that changes the amount of light transmitted, the document must be scanned before scanning the pixels corresponding to the document part, as in the case of a document with a binder hole. Since the pixels corresponding to the edge of the document are scanned, it is possible to reliably detect the document edge regardless of the print contents.

  Detection of changes from white pixels to black pixels. When small dust or the like is attached to the line sensor, it is detected only when a predetermined number or more of white pixels or black pixels continue before and after the change point. By controlling it, it is possible to ignore small garbage.

  Next, with reference to FIG. 10, document length detection will be described.

  FIG. 10 is a diagram illustrating a position where the line sensor 105 scans the conveyed document. A dotted line 1002 indicates a position scanned by the line sensor 105 at time t (0). Similarly, the dotted line 1003 is the time t (1), the dotted line 1004 is the time t (2), the dotted line 1005 is the time t (3), and the dotted line 1006 is the time t (n-2). 1007 is the scanning position at time t (n−1), and the dotted line 1008 is the scanning position at time t (n).

  At time t (0), since the document has not yet reached the line sensor 105, all the image signals output from the line sensor 105 are white pixel signals.

  That is, since the right edge and the left edge of the document cannot be found, it can be determined that the document has not yet reached the line sensor 105. At time t (1), since the document reaches the line sensor 105, the right and left ends of the document can be detected.

  Therefore, it is considered that the leading edge of the document has reached the line sensor 105 while the time elapses from t (0) to t (1).

  Similarly, for the trailing edge of the document, the right and left edges of the document can be detected at time t (n−1), and the right and left edges of the document cannot be detected at time t (n). It can be considered that the trailing edge of the document has passed through the line sensor 105 during the elapse of time t (n) from (n-1).

  Here, since the line sensor 105 is scanned at regular intervals, the length of the document can be detected from the number of scans and the conveyance speed from when the leading edge of the document is detected until the trailing edge is removed.

  Further, since the scanning time of the line sensor 105 is very short with respect to the document conveyance speed, the amount by which the document advances from time t (0) to time t (1), from time t (n−1). The amount by which the document has advanced during time t (n) is a value that can be ignored.

  The threshold used for binarization is changed according to information from the paper thickness detection unit 111. For example, as shown in FIG. 5, when the original is thick and thin, there is a difference in the change in the output signal of the line sensor 105 at the edge of the original because the light wraps around the original and the transmission amount differs. As a result, an appropriate document size cannot be detected when a fixed threshold is used.

  If binarization is performed using the threshold A shown in FIG. 5, when the document is thick, the color is switched from white to black at the edge of the document almost accurately. The change in the output signal from the line sensor 105 at the edge becomes gentle, and the edge of the document is detected inside the actual document. In the case of a thin document, binarization is performed using the threshold B, so that the edge of the document can be detected accurately.

  In the present embodiment, the paper thickness detection unit 111 detects the thickness of the document based on the output signal of the transmitted light amount detection sensor S2, and controls to increase the threshold when a thin document comes, so that it is thin even when the document is thick. Sometimes an appropriate threshold can be set, and the edge of the document can be detected accurately.

  Further, when the threshold is set according to a thin original document from the beginning, even a minute dust adhering to the line sensor may be detected as an edge of the original document because it becomes a black pixel after binarization. In order to prevent this, it is desirable to increase the threshold only when a thin original comes (when it is detected that the amount of transmitted light is large). If the output signal of the line sensor 105 is configured to decrease as the amount of light received increases, control is performed to lower the threshold when a thin original comes (when a large amount of transmitted light is detected).

  Next, processing when the conveyed document is tilted will be described.

  Since the line sensor 105 scans the document at regular intervals, the pixel position of the document edge pixel, which is a change point from the white pixel to the black pixel, can be detected every time one line is scanned. The detected pixel position of the document edge pixel is stored in a memory (not shown) for each line. FIG. 6 shows the pixel positions of the stored document edge pixels that are simplified and arranged on the XY coordinates for each distance the document travels at regular intervals.

  In the figure, (x11, y1), (x13, y3), (x15, y5), (x17, y7), (x19, y9) are the coordinates of the leftmost pixel of the document, and (x22, y2), (x24, y4), (x26, y6), and (x28, y8) are the coordinates of the rightmost pixel of the document. As shown in the figure, the coordinates of the left end pixel and the right end pixel are detected every two lines. The coordinates of the document edge pixels that are not detected for each line can be obtained by interpolation or the like.

  The distance that the document is transported in the predetermined time can be determined from the transport speed of the document. The image size / tilt detection unit 108 can detect the tilt of the document from the distance that the document is conveyed in the predetermined time and the average deviation amount per line of the document edge pixel position.

  Further, the four corners of the document can be calculated from the detected document inclination, and the document size can be detected even when the document is inclined.

  After the post-registration sensor S4 detects the top of the document, scanning is started using the line sensors 101 and 102 for image reading after a predetermined time. After a certain period of time is the time required for conveyance from when the leading edge of the document reaches the post-registration sensor S4 until the document reaches the image reading position of the line sensors 101 and 102 for image reading. Considering that the document is skewed, the scanning may be started slightly before the time required for the conveyance elapses.

  The image signals output from the line sensors 101 and 102 are output as image data after undergoing processing such as level correction, A / D conversion, and shading correction in the image processing unit 103, and are temporarily stored in the memory 104. . The memory 104 is a page memory and can store image data for one page.

  The document image cutout / tilt correction unit 109 performs a rotation process on the image data stored in the memory 104 according to the amount of tilt detected by the document size / tilt detection unit 108, and converts the detected image size to the detected image size. In addition, the image data is cut out and sent to an image processing unit (not shown) in the subsequent stage.

  By using the above configuration, it is possible to detect the size and inclination of the document, cut out image data, and correct the inclination.

  Further, if it is predicted from the value detected by the document size / tilt detection unit 108 that the document being transported is out of the transport path, the document transport control (not shown) is stopped so as to stop the transport of the document. By configuring so as to instruct the unit, it is possible to prevent the document from being damaged due to contact with the gear or the like.

  If the document is transported with a large inclination, the vicinity of the leading edge of the document will fit within the transport path, but as the document approaches the trailing edge, the document gradually passes the end of the transport path, and the document is eventually transported. There is a possibility of going out of the road and coming into contact with a gear or the like, or hitting a wall or the like provided at the end of the conveyance path and being damaged. The document size / tilt detection unit 108 predicts that the document will go out of the conveyance path based on the document width and tilt amount information near the leading edge of the document. Alternatively, it is possible to determine whether or not the document edge is likely to exit the conveyance path by looking at the coordinates of the document edge pixel. As described above, when the document is likely to go out of the conveyance path, the document is prevented from being damaged by controlling the conveyance to be stopped.

  In addition, as shown in FIG. 10, the output signal of the line sensor 105 when scanning a place where there is no document does not have a change point from a white pixel to a black pixel. Since a change point to the pixel should appear, when the change point from the white pixel to the black pixel first appears, it can be determined that the leading edge of the document has reached the image reading position of the line sensor 105.

  In this embodiment, the post-registration sensor S4 detects the leading edge of the document, and the line sensors 101 and 102 start reading the image of the document after a predetermined time after the post-registration sensor S4 detects the leading edge of the document. However, it is also possible to detect the leading edge of the document as described above using the line sensor 105 without providing the post-registration sensor S4.

  One post-registration sensor S4 is usually installed near the center in the width direction of the conveyance path and detects the leading edge and the trailing edge of the conveyed document. However, the document is skewed. In some cases, the leading edge of the document may be off the center of the conveyance path. For this reason, when the post-registration sensor S4 detects the document, the leading edge of the document already exists downstream of the post-registration sensor S4 in the transport direction. Since the line sensors 101 and 102 start the image reading operation after a predetermined time from the registration sensor S4 detecting the document, there is a possibility that the image at the leading edge of the document is missed when the document is skewed.

  On the other hand, the line sensor 105 can see the entire width direction of the conveyance path, so that the front end of the original can be reliably detected regardless of the position where the original is skewed and the front end of the original is located. . Since the time for the document to advance the distance in the conveyance direction from the line sensor 105 to the image reading position of each of the line sensors 101 and 102 can be determined from the conveyance speed, wait for this time after the line sensor 105 detects the leading edge of the document. By starting the image reading operation of the line sensors 101 and 102, the image at the leading edge of the document is not missed, and the entire document can be reliably read.

  In this embodiment, the output signal of the line sensor 105 is binarized using a threshold value determined based on the output signal of the transmitted light amount detection sensor S2, and a change point from a white pixel to a black pixel is detected. Although the left and right edges of the document are detected, the present invention is not limited to this.

  For example, by using multi-value data generated from the output signal of the line sensor 105, it is possible to detect the edge of the document from the change amount of the multi-value data without performing the binarization process. In this case as well, the document edge can be detected more reliably by determining the amount of change in the multi-value data for detecting the document edge based on the output signal of the transmitted light amount detection sensor S2.

  As described above, in the present embodiment, the size and inclination of the document are accurately detected regardless of the background color of the document at the time of image reading, the thickness of the document, the document description, the document color, and the presence or absence of the binder hole. Therefore, the image data can be cut out and the inclination can be corrected with high accuracy.

  Further, the document edge in the width direction of the document can be detected by changing the scanning direction of the line sensor 105 without temporarily storing the output signal of the line sensor 105 in the memory. Is no longer necessary.

  Furthermore, since the conveyance of the document is stopped when a document size or inclination exceeding a certain value is detected, it is possible to prevent the document from being damaged by a gear or the like outside the conveyance path and to trigger the image reading operation start. It can also serve as a tip detection sensor.

  Next, an image reading apparatus according to the second embodiment of the present invention will be described with reference to FIGS. Note that the basic structure of the image reading apparatus is the same as that already described with reference to FIGS. 2 and 3 of the first embodiment, and a description thereof will be omitted.

  FIG. 11 is a block diagram for explaining a control system of the image reading apparatus according to the second embodiment of the present invention.

  As shown in FIG. 11, the image reading apparatus according to the present embodiment includes line sensors 151 and 152 that read images on the front and back sides of a document. The image signals of the document read by the line sensors 151 and 152 are image data. The data is output to the processing unit 153. The image processing unit 153 performs level correction processing, A / D conversion processing, shading correction processing, and the like on the image signals output from the line sensors 151 and 152 to generate image data. The memory unit 154 temporarily stores the image data output from the image processing unit 153.

Line sensors 155 and 156 are sensors for detecting the size and inclination of the image of the document. The line sensors 155 and 156 are composed of photoelectric conversion elements, and output signals change depending on the amount of light received. The image processing unit 157 performs A / D conversion processing on the document edge output signals output from the line sensors 155 and 156, generates document edge image data, and outputs the document edge image data. Also, the image processing unit 157 can generate more accurate document edge image data by performing level correction processing and shading correction processing.

The document size / tilt detection unit 158 has a line memory 16, and the line memory 161 stores information of document edge image data generated from document edge output signals output from the line sensors 155 and 156 for one line. In this embodiment, one line memory 161 is used to store both the document edge image data corresponding to the line sensor 155 and the document edge image data corresponding to the line sensor 156, but the line sensors 155 and 156 are stored. A line memory may be provided for each of the document edge image data corresponding to.

  The paper thickness detector 163 detects the thickness of the document based on the intensity of the output signal of the transmitted light amount detection sensor S2. The conveyance stop instruction unit 162 instructs a document conveyance control unit (not shown) to perform control for stopping the document conveyance.

  Next, the operation of the image reading apparatus having the above configuration will be described.

  When the document reaches the line sensors 155 and 156, the light from the light source L1 is blocked by the document. In the present embodiment, LEDs that are point light sources are provided for the line sensors 155 and 156 as the light source L1, and the LEDs are arranged at a sufficient distance above the line sensors 155 and 156, and slits are formed in a line shape. The line sensors 155 and 156 are irradiated from the portion.

  Specifically, as shown in FIG. 14, the two LEDs 811 and 812 that are the light sources L1 have wide irradiation widths so that the light reaches the entire line sensors 155 and 156, and above the line sensors 155 and 156. Is located at a sufficient distance. Light from the LEDs 811 and 812 passes through slits 813 and 814 opened in a sheet metal or the like and is irradiated to the entire line sensors 155 and 156.

  As shown in FIG. 12, the line sensors 155 and 156 are arranged so that a range wider than the width of the document transport path can be read. In FIG. 12, line sensors 155 and 156 are installed symmetrically in the width direction of the document, and can scan in the directions of arrows a and b in FIG. Since the conveyed document is narrower than the length of the line sensors 155 and 156, the line sensors 155 and 156 have a portion that is blocked by the document and a portion that is not blocked by the document.

  The output of the portion corresponding to the light receiving element in the portion where the light emitted from the light source L1 is not blocked by the document is high because the light emitted from the light source L1 is directly received by the line sensors 155 and 156. On the contrary, the output of the portion where the light emitted from the light source L1 is blocked by the document is low because the light emitted from the light source L1 is hardly incident on the line sensors 155 and 156. This change in output makes it possible to detect where the edge of the document is.

Document edge image data generated by A / D conversion from the document edge output signals of the line sensors 155 and 156 by the image processing unit 157 is input to the image size / tilt detection unit 158, and document edge detection is performed.

  Next, with reference to FIG. 15, a method for detecting the edge of the document will be described. When the line sensors 155 and 156 are installed as shown in FIG. 12, the line memory 161 need not be used. First, a case where the line memory 161 is not used will be described.

In FIG. 15, the document edge image data 914 generated from the document edge output signal output from the line sensor 155 for detecting the left edge of the document 911, and the line sensor 156 for detecting the right edge of the document 911. The document edge image data 915 generated from the document edge output signal to be output is digital data subjected to A / D conversion.

  In FIG. 15, reference numeral 917 denotes document edge image data read by the line sensor 155 binarized by the threshold value 916, and reference numeral 918 denotes document edge image data read by the line sensor 156 binarized by the threshold value 916. is there.

  The image size / tilt detection unit 158 binarizes the output signals 914 and 915 of the line sensors 155 and 156 using a threshold value 916. By performing a binarization process using an appropriate threshold value, a portion where the original 911 is not applied to the line sensors 155 and 156 is a white pixel, and a portion where the original is applied is a black pixel. Similar to the first embodiment, the threshold value is changed by the paper thickness detection unit 163 judging the thickness of the document from the signal level of the transmitted light amount detection sensor S2. The threshold value 916 may be set individually for the line sensors 155 and 156.

  The image size / tilt detection unit 158 monitors the binarized document edge image data 917 and 918 based on the output signals of the line sensors 155 and 156 while scanning the line sensors 155 and 156 from the head of the line. First, look for a change from white to black. In FIG. 15, the binarized document edge image data 917 changes from white to black at the m-th pixel counted from the head of the line sensor. In the binarized document edge image data 918, the color changes from white to black at the nth pixel.

  As shown in FIG. 12, the line sensors 155 and 156 scan from the outside to the inside of the conveyance path, and the vicinity of the head of the line is always outside the document. For this reason, the vicinity of the head of the output signals of the line sensors 155 and 156 is always a white pixel signal. The binarized image data in the black pixel portion is a portion where the original is applied to the line sensors 155 and 156. Therefore, the portion where the white pixel is first changed from the black pixel corresponds to the edge of the original. That is, the mth pixel is the left end of the document 911 and the nth pixel is the right end of the document 911.

  Even when the line memory 161 is used, as shown in FIG. 16, the document edge can be similarly detected by writing and reading data from the memory in the scanning order. In FIG. 16, reference numeral 920 indicates the pixel arrangement order when the binarized document edge image data 917 based on the output signal of the line sensor 155 is stored in the line memory 161, and the arrow e indicates the reading direction. ing. Reference numeral 921 indicates the pixel arrangement order when the binarized document edge image data 918 based on the output signal of the line sensor 156 is stored in the line memory 161, and the arrow f indicates the reading direction. .

  Next, an operation when the line memory 161 is used and the line sensors 155 and 156 are installed so as to scan in the same direction as shown in FIG. 13 will be described. In FIG. 13, arrows g and h indicate the scanning directions of the line sensors 155 and 156.

  Even when the scanning direction of the line sensors 155 and 156 is the same as shown in FIG. 13, the line memory 161 is used and the reading direction is changed in the direction opposite to that shown in FIG. As shown in FIG. 12, the same effect as when the line sensors 155 and 156 are installed symmetrically in the width direction of the document can be obtained.

  In FIG. 17, reference numeral 930 is data obtained by binarizing document edge image data based on the output signal of the line sensor 155 using a threshold 916, and reference numeral 931 indicates document edge image data based on the output signal of the line sensor 156 as a threshold 916. The data is binarized using. Reference numeral 932 indicates the pixel arrangement order when the binarized data 930 is stored in the line memory 161, and the arrow i indicates the reading direction from the line memory 161. Reference numeral 933 indicates a pixel arrangement order when the binarized data 931 is stored in the line memory 161, and an arrow j indicates a reading direction from the line memory 161. In other words, the image size / tilt detection unit 158 reads the data from the line memory 161 from the data corresponding to the rear end of the line sensor 156 toward the head, so that the white pixel is changed to the black pixel from the outer side to the inner side of the conveyance path. You can search for the changing point.

  As described above, even when the line sensors 155 and 156 are installed so that the scanning directions are the same, the binarized data based on the signal of the line sensor 156 is temporarily stored in the line memory 161 and read out from the line memory 161. By reversing the order of writing, the same effect as when the line sensors 155 and 156 are installed symmetrically can be obtained. Other configurations and operational effects are the same as those of the first embodiment.

2 is a block diagram for explaining a control system of the image reading apparatus according to the first embodiment of the present invention. FIG. 1 is a schematic cross-sectional view for explaining a basic structure of an image reading apparatus according to a first embodiment of the present invention. It is a figure which shows typically the principal part of the image reading apparatus shown in FIG. It is the figure which looked at the conveyance path from the upper part. It is a graph for demonstrating the difference of the output value change of a thin original and a thick original. FIG. 6 is a diagram in which pixel positions of document edge pixels stored in a memory are simplified and arranged on XY coordinates for each distance traveled by a document at regular intervals. It is sectional drawing for demonstrating a paper thickness detection sensor. It is a perspective view which shows the slit and light source which are arrange | positioned above a line sensor. It is explanatory drawing for demonstrating the output signal and binarization process data of a line sensor. It is a figure which shows the scanning position of the original document by a line sensor. It is a block diagram for demonstrating the control system of the image reading apparatus which is the 2nd Embodiment of this invention. It is the figure which looked at the conveyance path from the upper part. It is the figure which looked at the conveyance path from the upper part. It is a perspective view which shows the slit and light source which are arrange | positioned above a line sensor. It is explanatory drawing for demonstrating the output signal and binarization process data of a line sensor. It is explanatory drawing for demonstrating the reading order from a line memory. It is explanatory drawing for demonstrating the reading order from a line memory.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Document base 2 Document base drive motor 3 Document detection sensor 4 Paper feed roller 5 Paper feed motor 6 Feed roller 7 Separation roller 8 Feed motor 9 Separation motor 10 Carry motor 11 Nip gap adjustment motors 14 and 15 Reading unit 16 Document discharge Sensors 17 and 18 Registration rollers 19 Registration clutches 20 and 21 Document conveyance rollers 22 and 23 Document conveyance rollers 40 Upper guide plate 41 Lower guide plate 43 Document reading unit 44 Document discharge unit 51 Image size detection unit S1 Pre-feed document sensor S2 Transmission Light sensor S3 Pre-registration sensor S4 Post-registration sensor L1 Light source L2 Light source 101 Image reading line sensor 102 Image reading line sensor 103 Image processing unit 104 Memory unit 105 Line size sensor 106 for detecting image size / tilt Image processing unit 107 line Memory 108 original Size / tilt detection unit 109 Document size cutout / tilt correction unit 111 Paper thickness detection unit 112 Conveyance stop instruction unit 151 Image reading line sensor 152 Image reading line sensor 153 Image processing unit 154 Memory unit 155 Image size / tilt detection Line sensor 156 Line sensor 157 for image size / tilt detection Image processing unit 158 Document size / tilt detection unit 159 Document size cutout / tilt correction unit 162 Conveyance stop instruction unit 163 Paper thickness detection unit 200 Image reading device 703 Conveyance path 802 Slit 811 Point light source 812 Point light source 813 Slit 814 Slit

Claims (9)

An image reading apparatus comprising: a sheet conveying device; and an image reading sensor that reads an image of a sheet conveyed on a conveying path ,
The sheet conveying apparatus is
A light source that is disposed to face one surface of the sheet conveyed through the conveyance path, and irradiates the sheet with light;
It is arranged side by side in the width direction of the sheet substantially perpendicular to the sheet conveyance direction at a position where the light emitted from the light source is received on the opposite side of the light source across the conveyance path, and from the outer side to the inner side in the sheet width direction. Two line sensors that scan in the direction toward
In the scanning of the two line sensors, detection of detecting a plurality of lines in the width direction of the sheet based on the sheet edge output signals output from the two line sensors and detecting the sheet inclination or size together with the sheet leading edge. and means, the,
The image reading sensor, said detecting means even after detecting the leading edge of the sheet, the leading end of the sheet is characterized that you start a document reading operation before being conveyed to the image reading position Image reading device. In an image reading apparatus for acquiring read image data of a document,
A first line sensor for reading an image of a document conveyed on the conveyance path;
A light source disposed opposite one side of the document and irradiating the document with light;
Scanning is performed in a direction from the outer side to the inner side in the width direction of the document, which is arranged at a position on the opposite side of the light source to receive the light emitted from the light source across the transport path and is substantially orthogonal to the transport direction of the document. Two line sensors;
In scanning by the second line sensor, a plurality of lines at both ends in the width direction of the document are detected based on a document edge output signal output from the second line sensor, and the inclination or size of the document is detected together with the document leading edge. Detecting means for
The first line sensor starts the document reading operation after the detection unit detects the leading edge of the document and before the leading edge of the document is conveyed to the image reading position. The means scans the second line sensor when a position of one end of the document in the width direction is detected and when a position of the other end of the document in the width direction is detected, using a different light receiving portion of the second line sensor as a starting point. An image reading apparatus. The second line sensor includes a line sensor for detecting one end of the document in the width direction and a line sensor for detecting the other end of the document in the width direction, which are arranged side by side in the document width direction. The image reading apparatus according to claim 2 . Line sensor for the line sensor and the other end detection for the end detection, the image reading apparatus according to claim 3, characterized in that the scannable arranged in a direction from the outside in the width direction of the document to the inside . In an image reading apparatus for acquiring read image data of a document,
A first line sensor for reading an image of a document conveyed on the conveyance path;
A light source disposed opposite one side of the document and irradiating the document with light;
Scanning is performed in a direction from the outer side to the inner side in the width direction of the document, which is arranged at a position on the opposite side of the light source to receive the light emitted from the light source across the transport path and is substantially orthogonal to the transport direction of the document. Two line sensors;
Storage means for storing output information based on a document end output signal output by the second line sensor in scanning of the second line sensor;
A plurality of lines of output information stored in the storage means are read out, one end in the width direction of the document and the other end in the width direction are detected based on the read out output information, and the inclination or size of the document is determined at the leading edge of the document. And detecting means for detecting together with,
The first line sensor starts the document reading operation after the detection unit detects the leading edge of the document and before the leading edge of the document is conveyed to the image reading position. And a means for reading out the output information of the second line sensor from the storage means when detecting one end in the width direction of the document from the output information on one end side in the width direction of the second line sensor. The output information is in the order from the output information on the other end side in the width direction of the second line sensor to the output information on the one end side when the other end in the width direction of the document is detected. Image reading device. The second line sensor includes a line sensor for detecting one end of the document in the width direction and a line sensor for detecting the other end of the document in the width direction, which are arranged side by side in the width direction of the document.
The detection means detects the output order of the information from the storage means when detecting one end of the document in the width direction, and outputs the output information of the line sensor for detecting the one end from the output information on one end side in the document width direction to the other end side. and the forward toward the output information, when the width direction of the other end detection of the document, the order toward the other end output information output information of the line sensor in the width direction of the other end side of the output information of a document at one end of the detection The image reading apparatus according to claim 5 , wherein: A transmitted light amount detection sensor that is installed upstream of the second line sensor in the document conveyance direction and detects a transmitted light amount that passes through the document;
The detection means detects both end positions of the document in the width direction using binarized output information based on the output signal of the second line sensor,
The image reading according to any one of claims 2 to 6 , wherein a threshold value for generating the binarized output information is changed according to an output signal of the transmitted light amount detection sensor. apparatus. The detection means has a function of detecting the inclination of the document based on the output signal of the second line sensor,
One end position and the other end position in the width direction of the document detection unit detects, and any of claims 2-7, characterized in that it comprises a document transport controller to stop the conveyance of the document in accordance with the inclination of the document 2. An image reading apparatus according to item 1. The first line sensor, in any one of claims 2-8, characterized in that the detection means ends the document reading operation later than the time of detecting the width direction of the end of the document finally The image reading apparatus described.

Images