JP2005123703A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity in preliminary reading and main reading. <P>SOLUTION: This apparatus is provided with a first conveying path 31 for conveying fed originals, a CIS 50 for reading the image of one side of an original from one side of the path 31, a CCD image sensor 78 for reading the image of one side of the original from the other side opposing the one side via the conveying path, a third conveying path 33 performing reversely conveyance to invert the front side and rear side of the original whose image has been read and convey it again to the conveying path, a fourth conveying path 34, and a fifth conveying path 35. The CIS 50 preliminarily reads (pre-scans) one side image of the original, the original is reversely conveyed, and the CCD image sensor 78 mainly reads (mainly scans) the one side image of the original. Also, when the CCD image sensor 78 mainly scans the one side image of the original, the CIS 50 preliminary scans the other one side image of the original. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus that reads an image on a document, and more particularly, to an image reading apparatus that performs preliminary reading (pre-scan) and main reading (main scan) to read an image.

  Conventionally, an image reading device (automatic double-sided reading device) that automatically reads image information on both sides of a document without user intervention is used as a reading device such as a copying machine or a facsimile, or a scanner for computer input. . As these automatic double-sided reading devices, a method of reading a document by reversing the front and back with a document reversing unit is most widely adopted. When inputting image information with the front and back reversed, after reading the image on the front side with a specific original reading unit, the original is turned over and conveyed to the specific original reading unit again, and the image on the back side is read. .

  Further, in the image reading apparatus, not only a normal white document but also a document having various background densities, such as newspapers and colored paper, is targeted for reading. Since such a document other than a white background has a high background density, if the image data read by the document reading unit is reproduced as it is, the background appears and the image quality deteriorates. Therefore, there is a technique for preliminarily reading (pre-scanning) an image of an original to detect the background of the original, and then removing the background from the image data obtained by reading the original (main scanning) (Patent Document). 1).

Japanese Patent No. 2861410 (page 2-3, FIG. 1)

  However, if the background is to be removed using the automatic double-side reading apparatus described above by the method described in Patent Document 1, for example, in the case of a double-sided document in which images are formed on both sides, Since it is necessary to pass through the front surface and the back surface twice, the time required to complete the reading becomes long. Also, for example, in the case of a single-sided document with an image formed on only one side, when the document is reversed and conveyed after prescanning of the surface of the document, the back side of the document, that is, the side without an image Therefore, it is necessary to perform the main scan after the document is reversed and conveyed again, and the time required to complete the reading is also increased. In addition, since the document has to be reversed and conveyed many times, there is a problem that the document is greatly damaged during reading.

The present invention has been made to solve such a technical problem, and an object of the present invention is to improve productivity during execution of preliminary reading and main reading.
Another object is to reduce the damage that the document receives during the preliminary reading and the main reading.

  For this purpose, an image reading apparatus to which the present invention is applied includes a paper feed unit that feeds a document, a transport path that transports a document fed by the paper feed unit, and one side of the transport path. A first sensor that reads an image on one side of a document, a second sensor that reads an image on one side of a document from the other side facing the one side via a conveyance path, and a first sensor or a second sensor A reversing conveyance path that reverses the front and back of the document whose image has been read by the sensor and conveys it again to the conveyance path. The first sensor pre-reads a single-sided image of the document and reverses the document through the reversing conveyance path. This is characterized in that the image is conveyed and a single-sided image of the original is read by the second sensor.

  The image reading apparatus may further include an image processing unit that performs image processing by pre-reading using the first sensor on the single-sided image of the original that has been read by the second sensor. . The second sensor may be characterized in that when the original is transported to read the single-sided image of the original by the second sensor, the other single-sided image of the original is preliminarily read by the first sensor. In this case, the image processing apparatus further includes an image processing unit that performs image processing on the single-sided image of the original read by the first sensor based on the single-sided image of the original that has been pre-read by the second sensor. Can be characterized. The second sensor can be characterized by having higher resolution characteristics than the first sensor.

From another point of view, the image reading apparatus according to the present invention includes a sheet feeding unit that feeds a document, a conveyance path that conveys a document fed by the sheet feeding unit, and one side of the conveyance path. A first sensor that reads an image on one side of a document, a second sensor that reads an image on one side of a document from the other side facing the one side via a conveyance path, and a first sensor or a second sensor A reverse conveyance path that reverses the front and back of the document whose image has been read by the sensor and conveys the original again to the conveyance path. The first sensor pre-reads a single-sided image of the document and the second sensor A single-side image is preliminarily read, the original is reversely conveyed through a reverse conveyance path, and a single-side image of the original is read by a second sensor, and another single-side image of the original is read by a first sensor. It is said.
Here, based on the single-sided image of the original document preliminarily read by the first sensor, the single-sided image of the original image read by the second sensor is subjected to image processing, and the original document preliminarily read by the second sensor. The image processing unit may further include an image processing unit that performs image processing on the single-sided image of the original that has been read by the first sensor based on the single-sided image.

  Further, from another point of view, the image reading apparatus according to the present invention includes a paper feed unit that feeds a document, a transport path that transports a document fed by the paper feed unit, and one side of the transport path. A first sensor that reads an image on one side of a document, a second sensor that reads an image on one side of a document from the other side facing the one side via a conveyance path, and a first sensor or a second sensor Based on the reverse conveyance path for reversing the front and back of the document whose image has been read by the sensor and conveying it again to the conveyance path, the analysis unit for analyzing the image data read by the second sensor, and the analysis result by the analysis unit And a correction unit that corrects image data read by the first sensor.

  Here, the analysis unit detects the contrast or background of the image based on the image data read by the second sensor, and the correction unit corrects the contrast or background of the image data read by the first sensor. Can be characterized. Further, the image data analyzed by the analyzing unit and the image data corrected by the correcting unit may be obtained by reading images of the same document and the same surface. And an analysis unit that analyzes the image data read by the first sensor, and a correction unit that corrects the image data read by the second sensor based on an analysis result by the analysis unit. can do.

According to the present invention, it is possible to improve the productivity at the time of executing the preliminary reading and the main reading.
Further, according to the present invention, it is possible to reduce the damage received on the original when performing the preliminary reading and the main reading.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing an image reading apparatus to which the present embodiment is applied. This image reading apparatus is roughly divided into a document feeding device 10 that sequentially conveys documents from a stacked document bundle, a scanner device 70 that reads an image by scanning, and a processing device 80 that processes a read image signal.

  The document feeder 10 includes a document tray 11 on which a bundle of documents composed of a plurality of documents is stacked, and a tray lifter 12 that raises and lowers the document tray 11 as an example of components of a paper feed unit. Also, a nudger roll 13 that conveys the document on the document tray 11 raised by the tray lifter 12, a feed roll 14 that conveys the document on the document tray 11 raised by the nudger roll 13 further downstream, and a nudger roll 13. A retard roll 15 is provided for feeding supplied documents one by one. In a first conveyance path 31 serving as a conveyance path through which the original is first conveyed, a takeaway roll 16 that conveys the originals that are being fed one by one to the downstream roll, and further conveys the original to the downstream roll. A pre-registration roll 17 for forming a loop, a registration roll 18 for supplying a document while adjusting the registration to the document reading unit after resuming rotation after stopping once, and a platen for assisting document conveyance during reading A roll 19 and an out-roll 20 for conveying the read document further downstream are provided. The first transport path 31 includes a baffle 41 that rotates about a fulcrum according to the loop state of the document being transported. Further, a CIS (Contact Image Sensor) 50 is provided between the platen roll 19 and the out-roll 20.

  A second transport path 32 and a third transport path 33 are provided on the downstream side of the out-roll 20, a transport path switching gate 42 for switching between these transport paths, a discharge tray 40 for stacking documents that have been read, and a discharge tray A first discharge roll 21 that discharges the original document 40 is provided. Further, an inverter roll 22 and an inverter pinch roll 23 that are provided in the fourth transport path 34 and the fourth transport path 34 for switching back the document that has passed through the third transport path 33 and actually switch back the document, and the fourth transport. A fifth switch path 35 that guides the document switched back by the path 34 to the first transport path 31 having the pre-registration roll 17 and the like again, and discharges the document switched back by the fourth transport path 34 to the discharge tray 40. An exit provided in the transport path 36 and the sixth transport path 36 for switching the transport paths of the second discharge roll 24, the fifth transport path 35, and the sixth transport path 36 that transports the reversely discharged document to the first discharge roll 21. A switching gate 43 is provided. These third conveyance path 33, fourth conveyance path 34, and fifth conveyance path 35 constitute a reverse conveyance path.

  The nudger roll 13 is lifted up and held at the retracted position during standby, and descends to the nip position (original transport position) during transport of the document to transport the uppermost document on the document tray 11. The nudger roll 13 and the feed roll 14 convey a document by connecting a feed clutch (not shown). The pre-registration roll 17 forms a loop by abutting the leading end of the document against the stopped registration roll 18. In the registration roll 18, the front end of the document bitten by the registration roll 18 is returned to the nip position when forming a loop. When this loop is formed, the baffle 41 opens around the fulcrum and functions so as not to interfere with the loop formed on the document. In addition, the takeaway roll 16 and the pre-registration roll 17 hold a loop of the original being read. By this loop formation, the read timing can be adjusted, and the skew associated with the document conveyance at the time of reading can be suppressed, and the alignment adjustment function can be enhanced. In synchronization with the reading start timing, the stopped registration roll 18 starts rotating, the original is pressed against the second platen glass 72B (described later) by the platen roll 19, and the image is viewed from the lower surface direction by the CCD image sensor 78 described later. Data is read.

  The conveyance path switching gate 42, for example, at the end of reading a single-sided document that does not perform preliminary reading (pre-scanning, which will be described later) and at the end of simultaneous double-sided reading of a double-sided document, passes the document via the out-roll 20 to the second conveyance path 32. Then, it is switched to discharge to the discharge tray 40. On the other hand, the conveyance path switching gate 42 is switched to guide the original to the third conveyance path 33 in order to invert the original when sequentially reading the single-sided original and the double-sided original for executing the prescan. The inverter pinch roll 23 is retracted in a state where a feed clutch (not shown) is turned off and the nip is opened when sequentially reading double-sided originals, and guides the originals to the fourth conveyance path (inverter path) 34. Thereafter, the inverter pinch roll 23 is nipped, the original to be inverted by the inverter roll 22 is guided to the pre-registration roll 17, and the original to be reversed and discharged is conveyed to the second discharge roll 24 of the sixth conveyance path 36.

  The scanner device 70 is configured to be capable of placing the document feeder 10 described above, supports the document feeder 10 by an apparatus frame 71, and reads an image of the document conveyed by the document feeder 10. Yes. The scanner device 70 includes a first platen glass 72A for placing a document to be read in a stationary state on a device frame 71 forming a casing, and a light for reading a document being conveyed by the document feeder 10. The second platen glass 72B having the opening is provided.

  Further, the scanner device 70 is stationary under the second platen glass 72B, and scans the entire first platen glass 72A to read an image, and the light obtained from the full rate carriage 73 is input to the image coupling unit. A half-rate carriage 75 is provided. The full-rate carriage 73 includes an illumination lamp 74 that irradiates light on the original and a first mirror 76A that receives reflected light obtained from the original. Further, the half-rate carriage 75 is provided with a second mirror 76B and a third mirror 76C that provide the light obtained from the first mirror 76A to the imaging unit. Furthermore, the scanner device 70 includes an imaging lens 77 that optically reduces the optical image obtained from the third mirror 76C, and a second sensor that photoelectrically converts the optical image formed by the imaging lens 77. A CCD (Charge Coupled Device) image sensor 78 and a drive substrate 79 to which the CCD image sensor 78 is attached are provided, and an image signal obtained by the CCD image sensor 78 is sent to the processing device 80 via the drive substrate 79. That is, in the scanner device 70, an image is formed on the CCD image sensor 78 as an image sensor using a so-called reduction optical system.

  Here, first, when reading an image of a document placed on the first platen glass 72A, the full rate carriage 73 and the half rate carriage 75 move in the scanning direction (arrow direction) at a ratio of 2: 1. . At this time, the light of the illumination lamp 74 of the full rate carriage 73 is irradiated on the surface to be read of the document, and the reflected light from the document is reflected in the order of the first mirror 76A, the second mirror 76B, and the third mirror 76C. Then, it is guided to the imaging lens 77. The light guided to the imaging lens 77 forms an image on the light receiving surface of the CCD image sensor 78. The CCD image sensor 78 is a one-dimensional sensor and processes one line at the same time. The full rate carriage 73 is moved in this line direction (scanning main scanning direction) to read the next line of the document. By executing this over the entire original, reading of one page of the original is completed.

  On the other hand, the second platen glass 72B is constituted by a transparent glass plate having a long plate-like structure, for example. A document conveyed by the document feeder 10 passes over the second platen glass 72B. At this time, the full-rate carriage 73 and the half-rate carriage 75 are stopped at the solid line positions shown in FIG. First, the reflected light of the first line of the document that has passed through the platen roll 19 of the document feeder 10 is imaged by the imaging lens 77 via the first mirror 76A, the second mirror 76B, and the third mirror 76C. An image is read by the CCD image sensor 78 which is the first sensor in the present embodiment. That is, after one line in the main scanning direction is simultaneously processed by the CCD image sensor 78 which is a one-dimensional sensor, the next line in the main scanning direction of the document conveyed by the document feeder 10 is read. After the leading edge of the original reaches the reading position of the second platen glass 72B, the original passes through the reading position of the second platen glass 72B, thereby completing one page of original reading in the sub-scanning direction.

  In the present embodiment, the full-rate carriage 73 and the half-rate carriage 75 are stopped, and the first platen glass 72B is used to read the first surface of the document by the CCD image sensor 78. It is possible to read the second side of the original by the CIS 50 (meaning that it is not coincident but the same as when the same original is conveyed).

  FIG. 2 is a diagram for explaining a reading structure using the CIS 50. As shown in FIG. 2, the CIS 50 is provided between the platen roll 19 and the out roll 20. One side (first side) of the original is pressed against the second platen glass 72B, and the image on the first side is read by the CCD image sensor 78. On the other hand, in the CIS 50, an image on the other side (second side) is read from the other side facing through the conveyance path for conveying the document. The CIS 50 condenses the reflected light from the glass 51 that is disposed opposite the conveyance path, an LED (Light Emitting Diode) 52 that irradiates the second surface of the original through the glass 51, and light. A selfoc lens 53 and a line sensor 54 as a second sensor for reading light collected by the selfoc lens 53 are provided. As the line sensor 54, a CCD, a CMOS (Complementary Metal Oxide Semiconductor) sensor, a contact type sensor, or the like can be used, and an image with an actual width (for example, A4 longitudinal width 297 mm) can be read. In the CIS 50, an image is captured using a close-contact optical system composed of the SELFOC lens 53 and the line sensor 54 without using a reduction optical system, so that the structure can be simplified and the housing can be made compact. Power consumption can be reduced. In addition, when reading a color image, if the LED 52 is combined with LED light sources of three colors of R (red), G (green), and B (blue), and a set of three columns for RGB three colors is used as the line sensor 54, Good. Similarly to the reading of the image on the first surface, one line in the main scanning direction is simultaneously processed by the one-dimensional line sensor 54, and then one line in the next main scanning direction in the conveyed document is read. In this way, one page of original is read in the sub-scanning direction on the back side of the conveyed original.

  Further, when the image is read by the CIS 50, a control member 55 extending from the housing of the CIS 50 and an abutting member 60 against which the document pressed by the control member 55 is abutted are provided in the conveyance path constituting the reading unit. A guide member 61 is provided on the downstream side of the abutting member 60. The control member 55 and the abutting member 60 correspond to the positions of the conveyance path from the front surface to the rear surface of the document feeder 10 in the direction orthogonal to the document conveyance path (that is, from the front surface to the rear surface of the document feeder 10). Is provided.

  Furthermore, since the CIS 50 employs the SELFOC lens 53 as an optical imaging lens, the depth of focus (field of view) is as shallow as about ± 0.3 mm, which is about 1 compared with the case where the scanner device 70 is used. The depth is less than / 13. For this reason, when reading by the CIS 50, it is required to set the reading position of the document within a predetermined narrow range. Therefore, in the present embodiment, the control member 55 is provided facing the conveyance path, the original is pressed against the abutting member 60 by the control member 55 and conveyed, and the original between the platen roll 19 and the out roll 20 is conveyed. It was configured to be able to stably control the attitude of the. The two-dot chain line arrow in FIG. 2 shows the movement of the document when the control member 55 is provided. It can be understood that the document is conveyed while being pressed against the abutting member 60 by the control member 55. That is, by reading the document conveyed by the control member 55 while being pressed against the abutting member 60, the sweetness of the focus when the CIS 50 having a deep depth of field is used is improved.

Next, the processing device 80 shown in FIG. 1 will be described.
FIG. 3 is a block diagram for explaining the processing device 80. The processing device 80 to which this embodiment is applied is large, and includes a signal processing unit 81 as an image processing unit that processes image information obtained from sensors (CCD image sensor 78 and line sensor 54), and the document feeder 10. And a control unit 90 for controlling the scanner device 70. The signal processing unit 81 performs predetermined image processing on each output from the CCD image sensor 78 that reads one side (first side) of the document and the line sensor 54 of the CIS 50 that reads the other side (second side). It has a function. The signal processing unit 81 includes an AFE (Analog Front End) 82 that performs analog signal processing on the output from the line sensor 54, and an ADC (Analog Digital Converter) 83 that converts the analog signal to a digital signal. . However, these functions can also be configured to be processed inside the CIS 50. The signal processing unit 81 includes an AFE 84 that performs analog signal processing on the output from the CCD image sensor 78 and an ADC 85 that converts the analog signal into a digital signal.

  Further, the signal processing unit 81 is provided with two systems of image processing circuits for performing various processes such as shading correction and offset correction on the digital signal, and for the single-sided image data read by the CCD image sensor 78. A first image processing circuit 100 that performs image processing, and a second image processing circuit 200 that performs image processing on the other one-sided image data read by the CIS 50. The output from these image processing circuits is output to an IOT (Image Output Terminal) such as a printer or a host system such as a personal computer (PC).

  On the other hand, the control unit 90 includes a CCD / CIS for controlling the image reading control 91, the CCD image sensor 78, and the CIS 50 for controlling the entire document feeder 10 and the scanner device 70, including double-sided scanning control and single-sided scanning control. The control 92, the lamp control 93 for controlling the LED 52 of the CIS 50 and the illumination lamp 74 of the full-rate carriage 73 in accordance with the reading timing, and the scanning operation by the full-rate carriage 73 and the half-rate carriage 75 by turning on / off the motor in the scanner device 70. A scan control 94 for controlling, a motor control in the document feeder 10, a transport mechanism control 95 for controlling various roll operations, feed clutch operations, gate switching operations, and the like are provided. . From these various controls, control signals are output to the document feeder 10 and the scanner device 70, and these operations can be controlled based on the control signals. The image reading control 91 sets a reading mode based on a control signal from the host system, a sensor output detected in the automatic selection reading function, a selection from the user, and the like, and controls the document feeder 10 and the scanner device 70. I have control.

FIG. 4 shows a functional block diagram of the first image processing circuit 100 and the second image processing circuit 200 in the present embodiment.
The first image processing circuit 100 includes a shading correction unit 101 for correcting shading data in the CCD image sensor 78, a GAP correction unit 102 for correcting the position of the RGB three-color image sensor, and γ / gray for correcting γ / gray balance. Balance correction unit 103, color space conversion unit 104 that converts BGR → L *, a *, b *, enlargement / reduction unit 105 that performs enlargement / reduction processing in the main scanning direction and sub-scanning direction, MTF correction and smoothing A filter unit 106 that performs a contrast adjustment, a contrast adjustment unit 107 that performs contrast adjustment of the read document, and a background removal unit 108 that performs background removal of the read document. Further, the first image processing circuit 100 includes a contrast amount detection unit 109 serving as an analysis unit that detects the contrast amount of the read document based on L *, a *, and b * converted by the color space conversion unit 104, and reading. A background detection unit 110 is provided as an analysis unit for detecting the background value of the document.

  On the other hand, the second image processing circuit 200, like the first image processing circuit 100, has a shading correction unit 201 for correcting shading data in the CIS 50, a GAP correction unit 202 for correcting the position of the RGB three-color line sensor 54, γ / Gamma / gray balance correction unit 203 for correcting gray balance, color space conversion unit 204 for converting BGR → L *, a *, b *, enlargement for performing enlargement / reduction processing in the main scanning direction and the sub-scanning direction A reduction unit 205, a filter unit 206 that performs MTF correction and smoothing, a contrast adjustment unit 207 that adjusts the contrast of the read document, and a background removal unit 208 that removes the background of the read document. Further, the second image processing circuit 200 includes a contrast amount detection unit 209 serving as an analysis unit that detects the contrast amount of the read document based on L *, a *, and b * converted by the color space conversion unit 204 and the reading. It has a background detection unit 210 as an analysis unit for detecting the background value of the document.

  In the present embodiment, the contrast amount of the read document read by the CIS 50 and detected by the contrast amount detection unit 209 of the second image processing circuit 200 is the contrast adjustment unit 107 (correction unit) of the first image processing circuit 100. Is output. Further, the background value of the read document read by the CIS 50 and detected by the background detection unit 210 of the second image processing circuit 200 is output to the background removal unit 108 (correction unit) of the first image processing circuit 100. It has become. On the other hand, the contrast amount of the read document read by the CCD image sensor 78 and detected by the contrast amount detection unit 109 of the first image processing circuit 100 is sent to the contrast adjustment unit 207 (correction unit) of the second image processing circuit 200. It is output. Further, the background value of the read document read by the CCD image sensor 78 and detected by the background detection unit 110 of the first image processing circuit 100 is output to the background removal unit 208 (correction unit) of the second image processing circuit 200. It has come to be.

  Further, in the present embodiment, before acquiring an actual original image (main scan) for the purpose of obtaining a high-quality image by acquiring the background value and contrast amount of the original to be read in advance. In addition, a pre-scan for preliminarily capturing the same document image is performed. Here, in the document reading apparatus according to the present embodiment, when an image is read by document transport by the document feeder 10, the document transported to the platen roll 19 through the second platen glass 72B is scanned by the scanner device 70 (CCD image). It is possible to read using the sensor 78) and to read using the CIS 50 provided in the document feeder 10. In addition, it is possible to reverse the front and back of the original that has passed the reading position by the CCD image sensor 78 or the CIS 50 in the third conveying path 33, the fourth conveying path 34, and the fifth conveying path 35, and to convey it again to the reading position. It has become. Therefore, in this document reading apparatus, when images are read by pre-scanning and main scanning, both sides of the document are pre-scanned using the CCD image sensor 78 and the CIS 50, and then the document is reversed and conveyed, and the CCD image sensor 78 and The CIS 50 is used to perform main scanning on both sides of the document.

  Next, a method of conveying a document when executing pre-scan and main scan in the present embodiment will be described with reference to FIGS. 1 to 4 and FIG. Here, FIG. 5 is a chart for explaining the relationship between the document conveyance state and the operations of the CCD image sensor 78 and the CIS 50. Here, an example of a double-sided document in which images are formed on both sides is shown. . In this description, it is assumed that the user has set a document on the document tray 11 with the front side facing downward.

  The documents placed on the document tray 11 are sequentially supplied to the first conveyance path 31 by the nudger roll 13, the feed roll 14, the retard roll 15, and the takeaway roll 16. The supplied document passes through a reading unit by the CCD image sensor 78 and a reading unit of the CIS 50. At this time, an image on the front side of the document is read by the CIS 50 (front side prescan), and an image on the back side of the document is read by the CCD image sensor 78 (back side prescan). Then, the document moves to the fourth conveyance path 34 via the third conveyance path 33 by the conveyance path switching gate 42. The document completely passing through the third conveyance path 33 is switched back by the inverter roll 22 and the inverter pinch roll 23 and supplied to the fifth conveyance path 35 (reversed).

  The document supplied to the fifth conveyance path 35 is again supplied to the first conveyance path 31. Then, the image on the back side of the original is read by the CIS 50 (back side main scan), and the image on the front side of the original is read by the CCD image sensor 78 (front main scan). At this time, the document is in a state in which the front and back sides are reversed from those at the time of the previous reading, and the CIS 50 and the CCD image sensor 78 read the front and back surfaces different from those at the time of the previous reading. The document for which the main scan has been completed is in an inverted state, and if it is discharged as it is to the discharge tray 40, the page order of the stacked originals after reading will be out of order. Therefore, the document on which the main scan has been completed is moved to the fourth conveyance path 34 via the third conveyance path 33 using the conveyance path switching gate 42. The document supplied to the fourth transport path 34 and completely passing through the exit switching gate 43 is discharged by the exit switching gate 43 to the discharge tray 40 via the sixth transport path 36 (reversal / discharge). This makes it possible to align the page order of the original after the main scan.

  On the other hand, in the signal processing unit 81, the document surface reading data (surface prescan data) output from the CIS 50 during the prescan (front surface prescan) of the document surface is input to the second image processing circuit 200 and the shading correction unit. After the shading correction by 201, the GAP correction by the GAP correction unit 202, and the γ / gray balance correction by the γ / gray balance correction unit 203, the color space is converted by the color space conversion unit 204, and the contrast is detected by the contrast amount detection unit 209. The background value is obtained for each amount by the background detection unit 210. The obtained contrast amount is output to the contrast adjusting unit 107 of the first image processing circuit 100, and the obtained background value is output to the background removing unit 108 of the first image processing circuit 100.

  In addition, during the pre-scanning of the back side of the document (back side pre-scanning) that is performed in parallel with the front side pre-scan, the reading data (back side pre-scan data) of the back side of the document output from the CCD image sensor 78 is sent to the first image processing circuit 100. After being input and subjected to shading correction by the shading correction unit 101, GAP correction by the GAP correction unit 102, and γ / grey balance correction by the γ / gray balance correction unit 103, the color space conversion unit 104 performs color space conversion, and contrast A contrast amount is obtained by the amount detection unit 109, and a background value is obtained by the background detection unit 110. The obtained contrast amount is output to the contrast adjusting unit 207 of the second image processing circuit 200, and the obtained background value is output to the background removing unit 208 of the second image processing circuit 200.

  Thereafter, at the time of main scanning of the back side of the document (back side main scan), the reading data (back side main scan data) of the back side of the document output from the CIS 50 is input to the second image processing circuit 200, and shading correction by the shading correction unit 201, GAP After GAP correction by the correction unit 202 and γ / grey balance correction by the γ / gray balance correction unit 203, color space conversion is performed by the color space conversion unit 204, and further, enlargement / reduction processing by the enlargement / reduction unit 205, filter unit 206 Is processed. In this embodiment, the contrast adjustment processing is performed by the contrast adjustment unit 207. In this embodiment, contrast adjustment is performed using the contrast amount obtained based on the back-side prescan data by the CCD image sensor 78 as a correction reference. Yes. Further, after the contrast adjustment processing by the contrast adjustment unit 207 is performed, the background removal processing by the background removal unit 208 is performed. In this embodiment, the background adjustment processing is performed based on the backside prescan data by the CCD image sensor 78. The background is removed using the corrected background value as a correction standard.

  In the main scan of the original surface (front main scan) that is performed in parallel with the back main scan, the original surface read data (front main scan data) output from the CCD image sensor 78 is sent to the first image processing circuit 100. After being input and subjected to shading correction by the shading correction unit 101, GAP correction by the GAP correction unit 102, and γ / gray balance correction by the γ / gray balance correction unit 103, the color space conversion unit 104 performs color space conversion. Enlargement / reduction processing by the enlargement / reduction unit 105 and processing by the filter unit 106 are performed. Contrast adjustment processing is performed by the contrast adjustment unit 107. In this embodiment, contrast adjustment is performed using the contrast amount obtained based on the surface prescan data by the CIS 50 as a correction reference. Further, after the contrast adjustment processing by the contrast adjustment unit 107 is performed, the background removal processing by the background removal unit 108 is performed. In this embodiment, the background value obtained based on the backside prescan data by the CIS 50 is used. The background is removed using the correction standard.

  Incidentally, in a conventional image reading apparatus in which only one reading sensor (here, the CCD image sensor 78) is provided, as shown in FIG. It is necessary to reverse the document 4 times including the last reversal / discharge operation. As a result, it is understood that it takes a long time to read an image, and damage to the manuscript increases with the reversing operation. This example shows a case where the user sets a document on the document tray 11 with the front side facing upward.

  On the other hand, in the present embodiment, the images formed on both sides of the conveyed document are pre-scanned at the same time, and the document formed on both sides is reverse-conveyed and the images formed on both sides are simultaneously main-scanned. To pre-scan and main-scan double-sided images, it is only necessary to reverse the document once (two times including the last reversing / discharging operation). As a result, the image reading operation can be speeded up. Can do. Further, in the present embodiment, since the number of inversions of the original can be reduced, the probability of the original being damaged or jammed can be reduced.

-Embodiment 2-
This embodiment is substantially the same as the first embodiment, but differs from the first embodiment in that the pre-scan is always performed by the CIS 50 and the main scan is always performed by the CCD image sensor 78. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

FIG. 6 shows a functional block diagram of the first image processing circuit 100 and the second image processing circuit 200 in the present embodiment.
The basic configuration of the first image processing circuit 100 is substantially the same as that of the first embodiment, but since the main scan by the CIS 50 is not required, the contrast amount detection unit 109 and the background detection unit 110 are provided. Absent. On the other hand, the basic configuration of the second image processing circuit 200 is substantially the same as that of the first embodiment, but since it is not necessary to perform main scanning by the CIS 50, the enlargement / reduction unit 205, the filter unit 206, the contrast adjustment unit 207, The background removing unit 208 is not provided.

  Next, a method for conveying a document during execution of pre-scan and main scan in the present embodiment will be described with reference to FIGS. 1 to 3, 6 and 7. Here, FIG. 7 is a chart for explaining the relationship between the document conveyance state and the operation of the CCD image sensor 78 and the CIS 50. FIG. 7A is an example of a double-sided document in which images are formed on both sides. FIG. 7B shows an example of a single-sided document in which an image is formed only on one side. In this description, it is assumed that the user has set a document on the document tray 11 with the front side facing downward.

First, the case of the double-sided document shown in FIG.
The documents placed on the document tray 11 are sequentially supplied to the first transport path 31 by the nudger roll 13, the feed roll 14, the retard roll 15, and the takeaway roll 16. The supplied document passes through a reading unit by the CCD image sensor 78 and a reading unit of the CIS 50. At this time, an image on the surface of the original is read by the CIS 50 (front surface prescan). Further, the CCD image sensor 78 does not perform a reading operation (indicated by “−”). Then, the document moves to the fourth conveyance path 34 via the third conveyance path 33 by the conveyance path switching gate 42. The document completely passing through the third conveyance path 33 is switched back by the inverter roll 22 and the inverter pinch roll 23 and supplied to the fifth conveyance path 35 (reversed).

  The document supplied to the fifth conveyance path 35 is again supplied to the first conveyance path 31. Then, the image on the back side of the document is read by the CIS 50 (back side prescan), and the image on the surface of the document is read by the CCD image sensor 78 (front surface main scan). At this time, the document is in a state in which the front and back sides are reversed from those at the time of the previous reading, and the CIS 50 and the CCD image sensor 78 read the front and back surfaces different from those at the time of the previous reading. Further, the document moves to the fourth transport path 34 via the third transport path 33 by the transport path switching gate 42. The document completely passing through the third conveyance path 33 is switched back by the inverter roll 22 and the inverter pinch roll 23 and supplied to the fifth conveyance path 35 (reversed).

  The document supplied to the fifth conveyance path 35 is supplied again to the first conveyance path 31. Then, the image on the back side of the document is read by the CCD image sensor 78 (back side main scan). At this time, the CCD image sensor 78 does not perform a reading operation (indicated by “−”). At this time, the document is in a state where the front and back sides are reversed from those at the time of the previous reading, and the CCD image sensor 78 reads the surface different from that at the time of the previous reading. The document that has been subjected to the double-sided main scan is in an inverted state. If the document is discharged to the discharge tray 40 as it is, the page order of the loaded document after reading will be out of order. Therefore, the document on which the main scan has been completed is moved to the fourth conveyance path 34 via the third conveyance path 33 using the conveyance path switching gate 42. The document supplied to the fourth transport path 34 and completely passing through the exit switching gate 43 is discharged by the exit switching gate 43 to the discharge tray 40 via the sixth transport path 36 (reversal / discharge). This makes it possible to align the page order of the original after the main scan.

  On the other hand, in the signal processing unit 81, the document surface reading data (surface prescan data) output from the CIS 50 during the prescan (front surface prescan) of the document surface is input to the second image processing circuit 200 and the shading correction unit. After the shading correction by 201, the GAP correction by the GAP correction unit 202, and the γ / gray balance correction by the γ / gray balance correction unit 203, the color space is converted by the color space conversion unit 204, and the contrast is detected by the contrast amount detection unit 209. The background value is obtained for each amount by the background detection unit 210. The obtained contrast amount is output to the contrast adjusting unit 107 of the first image processing circuit 100, and the obtained background value is output to the background removing unit 108 of the first image processing circuit 100.

  Next, at the time of the main scan of the original surface (front main scan), read data (front main scan data) of the original surface output from the CCD image sensor 78 is input to the first image processing circuit 100 and is processed by the shading correction unit 101. After shading correction, GAP correction by the GAP correction unit 102, and γ / gray balance correction by the γ / gray balance correction unit 103, color space conversion is performed by the color space conversion unit 104, and further enlargement / reduction processing by the enlargement / reduction unit 105 The process by the filter unit 106 is performed. The contrast adjustment unit 107 performs contrast adjustment using the contrast amount input from the contrast amount detection unit 209 as a correction reference. After the contrast adjustment processing by the contrast adjustment unit 107 is performed, the background removal unit 108 performs background removal using the background value input from the background detection unit 210 as a correction reference.

  In addition, at the time of prescanning of the back side of the document (backside prescan) performed in parallel with the front side main scan, reading data (back side prescan data) of the back side of the document output from the CIS 50 is input to the second image processing circuit 200. After the shading correction by the shading correction unit 201, the GAP correction by the GAP correction unit 202, and the γ / gray balance correction by the γ / gray balance correction unit 203, the color space is converted by the color space conversion unit 204, and the contrast amount detection unit The contrast amount is obtained by 209, and the background value is obtained by the background detection unit 210. The obtained contrast amount is output to the contrast adjusting unit 107 of the first image processing circuit 100, and the obtained background value is output to the background removing unit 108 of the first image processing circuit 100.

  Then, during main scan of the back side of the document (back side main scan), read data (back side main scan data) of the back side of the document output from the CCD image sensor 78 is input to the first image processing circuit 100 and shading by the shading correction unit 101 is performed. Correction, GAP correction by the GAP correction unit 102, γ / gray balance correction by the γ / gray balance correction unit 103, color space conversion by the color space conversion unit 104, and further enlargement / reduction processing by the enlargement / reduction unit 105, Processing by the filter unit 106 is performed. The contrast adjustment unit 107 performs contrast adjustment using the contrast amount input from the contrast amount detection unit 209 as a correction reference. After the contrast adjustment processing by the contrast adjustment unit 107 is performed, the background removal unit 108 performs background removal using the background value input from the background detection unit 210 as a correction reference.

  Note that in the conventional image reading apparatus in which only one reading sensor (here, the CCD image sensor 78) is provided, as shown in FIG. It is necessary to reverse the original three times (four times including the last reversal / discharge operation). As a result, it is understood that it takes a long time to read an image, and damage to the manuscript increases with the reversing operation. This example shows a case where the user sets a document on the document tray 11 with the front side facing upward.

On the other hand, in the present embodiment, the CIS 50 is dedicated to pre-scanning and the CCD image sensor 78 is dedicated to main scanning, and pre-scanning and main scanning are simultaneously performed during the scanning operation. It is only necessary to invert the original twice (three times including the last reversal / discharge operation) for the pre-scan and the main scan. As a result, the image reading operation can be speeded up. Further, in the present embodiment, since the number of inversions of the original can be reduced, the probability of the original being damaged or jammed can be reduced.
In the present embodiment, the CIS 50 is dedicated to pre-scanning and the CCD image sensor 78 is dedicated to main scanning. Therefore, the reading efficiency is slightly reduced as compared with the first embodiment, but the obtained reading is performed. There is an advantage that the image quality is stabilized. Furthermore, since it can be dedicated to pre-scanning, an inexpensive CIS 50 can be used as a reading element, and this cost can be reduced.

Next, the case of a single-sided document shown in FIG.
The documents placed on the document tray 11 are sequentially supplied to the first conveyance path 31 by the nudger roll 13, the feed roll 14, the retard roll 15, and the takeaway roll 16. The supplied document passes through a reading unit by the CCD image sensor 78 and a reading unit of the CIS 50. At this time, an image on the surface of the original is read by the CIS 50 (front surface prescan). Further, since the original is a single-sided original, the CCD image sensor 78 does not perform a reading operation (indicated by “−”). Then, the document moves to the fourth conveyance path 34 via the third conveyance path 33 by the conveyance path switching gate 42. The document completely passing through the third conveyance path 33 is switched back by the inverter roll 22 and the inverter pinch roll 23 and supplied to the fifth conveyance path 35 (reversed).

  The document supplied to the fifth conveyance path 35 is again supplied to the first conveyance path 31. Then, the image on the back side of the document is read by the CCD image sensor 78 (back side main scan). Further, since it is a single-sided original, the CCD image sensor 78 does not perform a reading operation (indicated by “−”). At this time, the document is in a state where the front and back sides are reversed from those at the time of the previous reading, and the CCD image sensor 78 reads the surface different from that at the time of the previous reading. The original after the main scan is in an inverted state, and if it is discharged to the discharge tray 40 as it is, the page order of the loaded original after reading will be out of order. Therefore, the document on which the main scan has been completed is moved to the fourth conveyance path 34 via the third conveyance path 33 using the conveyance path switching gate 42. The document supplied to the fourth transport path 34 and completely passing through the exit switching gate 43 is discharged by the exit switching gate 43 to the discharge tray 40 via the sixth transport path 36 (reversal / discharge). This makes it possible to align the page order of the original after the main scan.

  Here, the operation of the signal processing unit 81 at the time of reading a single-sided document is the same as the processing flow of the surface prescan data and the surface main scan data at the time of reading the above-described double-sided image, and therefore detailed description thereof will be omitted. .

  In a conventional image reading apparatus in which only one reading sensor (here, CCD image sensor 78) is provided, as shown in FIG. 7B, a single-sided image is pre-scanned and main-scanned. It is necessary to reverse the document twice (three times including the last reversal / discharge operation). In particular, in this example, when the document on which the front surface pre-scan is performed is reversed, the surface (image surface) of the document is directed to the opposite side to the CCD image sensor 78, so that reading is not performed (“×”). It will be necessary to reverse again. As a result, it is understood that it takes a long time to read an image, and damage to the manuscript increases with the reversing operation. This example shows a case where the user sets a document on the document tray 11 with the front side facing upward.

  On the other hand, in the present embodiment, it is only necessary to reverse the document once to pre-scan and main-scan the single-sided image (two times including the last reversing / discharging operation). The speed of the image reading operation can be increased. Further, in the present embodiment, since the number of inversions of the original can be reduced, the probability of the original being damaged or jammed can be reduced.

  In the present embodiment, the reading operation by the CCD image sensor 78 is not performed when performing the front surface prescan when reading the double-sided image (see 1 in FIG. 7A). Can also be done. However, in this case, the back side main scan data obtained by the back side main scan is temporarily stored in the memory, and the back side pre-scan data obtained by the next back side pre-scan (see 3 in FIG. 7A). The back side main scan data is corrected based on the above. That is, it is possible to correct the back side main scan data obtained earlier based on the back side prescan data obtained later.

In the first and second embodiments, the contrast amount and the background value are obtained by pre-scanning. However, the present invention is not limited to this. For example, not only analysis of chroma and lightness of a document image, It can also be used to detect image types such as patterns and halftone dots, detection of banknotes and securities, and detection of hidden information embedded in a document image.
Further, in the first and second embodiments, the front surface prescan data and the back surface prescan data obtained by the prescan are used for contrast adjustment and background removal. However, the present invention is not limited to this. It may be used for switching an image processing method using an image or a monochrome image, selecting a filter according to the type of image, TRC processing (gradation conversion processing), adding a code or pattern, and the like.

  Furthermore, in the first and second embodiments, an example of reading an image of a document by performing a prescan and a main scan in the image reading device has been described. It can also be used as a double-sided simultaneous reading device that reads both-side images of a document with the CIS 50 and the CCD image sensor 78, respectively.

1 is a diagram illustrating an image reading apparatus according to an embodiment. It is a figure for demonstrating the reading structure using CIS. It is a figure for demonstrating a processing apparatus. 4 is a block diagram showing a first image processing circuit and a second image processing circuit in Embodiment 1. FIG. 6 is a table for explaining the relationship between the document conveyance state and the operation of the CCD image sensor and the CIS in the first embodiment. 6 is a block diagram showing a first image processing circuit and a second image processing circuit in Embodiment 2. FIG. 10 is a table for explaining the relationship between the document conveyance state and the operations of the CCD image sensor and the CIS in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Document feeder, 31 ... 1st conveyance path, 32 ... 2nd conveyance path, 33 ... 3rd conveyance path, 34 ... 4th conveyance path, 35 ... 5th conveyance path, 36 ... 6th conveyance path, 40 ... Ejection tray 50 ... CIS 54 ... Line sensor 70 ... Scanner device 78 ... CCD image sensor 79 ... Drive substrate 80 ... Processing device 81 ... Signal processing unit 90 ... Control unit 91 ... Image reading control, 92 ... CCD / CIS control, 93 ... Lamp control, 94 ... Scan control, 95 ... Conveyance mechanism control, 100 ... First image processing circuit, 101 ... Shading correction unit, 102 ... GAP correction unit, 103 ... Gamma / Gray balance correction 104, color space conversion unit, 105 ... enlargement / reduction unit, 106 ... filter unit, 107 ... contrast adjustment unit, 108 ... background removal unit, 109 ... Contrast amount detection unit, 110 ... background detection unit, 200 ... second image processing circuit, 201 ... shading correction unit, 202 ... GAP correction unit, 203 ... gamma / gray balance correction unit, 204 ... color space conversion unit, 205 ... enlargement Reduction unit, 206 ... Filter unit, 207 ... Contrast adjustment unit, 208 ... Background removal unit, 209 ... Contrast amount detection unit, 210 ... Background detection unit

Claims (11)

A paper feeder for feeding the original,
A transport path for transporting a document fed by the paper feed unit;
A first sensor that reads an image on one side of a document from one side of the conveyance path;
A second sensor that reads an image on one side of the document from the other side facing the one side through the conveyance path;
A reverse conveyance path that reverses the front and back of the document whose image has been read by the first sensor or the second sensor and conveys the original again to the conveyance path;
An image, wherein the first sensor pre-reads a single-sided image of the original, reversely conveys the original through the reverse conveyance path, and the second sensor performs full reading of the single-sided image of the original. Reading device.   An image reading apparatus, further comprising: an image processing unit configured to perform image processing by preliminary reading using the first sensor on the single-sided image of the original read by the second sensor.   2. The image reading according to claim 1, wherein the first sensor preliminarily reads the other single-sided image of the original when the original is transported to read the single-sided image of the original by the second sensor. apparatus.   The image processing apparatus further includes an image processing unit configured to perform image processing on the single-sided image of the original document read by the first sensor based on the single-sided image of the original document preliminarily read by the second sensor. The image reading apparatus according to claim 3.   The image reading apparatus according to claim 1, wherein the second sensor has higher resolution characteristics than the first sensor. A paper feeder for feeding the original,
A transport path for transporting a document fed by the paper feed unit;
A first sensor that reads an image on one side of a document from one side of the conveyance path;
A second sensor that reads an image on one side of the document from the other side facing the one side through the conveyance path;
A reverse conveyance path that reverses the front and back of the document whose image has been read by the first sensor or the second sensor and conveys the original again to the conveyance path;
The first sensor preliminarily reads a single-sided image of the original and the second sensor preliminarily reads another single-sided image of the original, and reversely conveys the original via the reverse conveyance path. An image reading apparatus characterized in that the single-sided image of the original is read with a sensor and the other single-sided image of the original is read with the first sensor.   Based on the single-sided image of the original document preliminarily read by the first sensor, the single-sided image of the original document read by the second sensor is subjected to image processing and preliminarily read by the second sensor. 7. The image reading apparatus according to claim 6, further comprising an image processing unit that performs image processing on the single-sided image of the original that has been read by the first sensor based on the single-sided image of the original. A paper feeder for feeding the original,
A transport path for transporting a document fed by the paper feed unit;
A first sensor that reads an image on one side of a document from one side of the conveyance path;
A second sensor that reads an image on one side of the document from the other side facing the one side through the conveyance path;
A reversing conveyance path for reversing the front and back of the document whose image has been read by the first sensor or the second sensor and conveying it again to the conveyance path;
An analysis unit for analyzing image data read by the second sensor;
An image reading apparatus comprising: a correction unit that corrects image data read by the first sensor based on an analysis result by the analysis unit. The analysis unit detects the contrast or background of the image based on the image data read by the second sensor,
The image reading apparatus according to claim 8, wherein the correction unit corrects a contrast or background of image data read by the first sensor.   9. The image reading apparatus according to claim 8, wherein the image data analyzed by the analysis unit and the image data corrected by the correction unit are obtained by reading an image of the same original and the same surface. . An analysis unit for analyzing image data read by the first sensor;
The image reading apparatus according to claim 8, further comprising a correction unit that corrects image data read by the second sensor based on an analysis result by the analysis unit.

Images