JP4367073B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads an image on an original, and more particularly, to an image reading apparatus that can read images on both sides of the original by conveying the original once.

  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. . However, this automatic double-sided scanning by reversing the front and back requires that the original is once discharged and then reversed and transported to the original scanning unit again. End up. Therefore, a so-called double-sided simultaneous reading technique in which two image reading units are provided on both the front and back sides of a document path for conveying a document and the front and back surfaces of the document are automatically read by one document conveyance is being studied.

  As a conventional technique adopting such double-sided simultaneous reading, for example, a surface image reading unit that reads one side (front surface) of a document is arranged opposite to a document path through which the document is conveyed, and the surface image reading device In view of this, there is a technique of disposing a back surface image reading unit that reads the other side (back surface) of the document facing the document path on the downstream side in the document transport direction (see, for example, Patent Document 1). Here, as the front side reading unit and the back side reading unit, a unit provided with a light source extending in a direction orthogonal to the document conveyance direction and an optical sensor arranged in parallel adjacent to the light source is used. It has been. Each reading unit uses a light source to irradiate light on the front surface or back surface of the document, and the reflected light reflected from the irradiated document is received by an optical sensor to read an image on the front surface or back surface of the document. ing.

Patent No. 2622039 (page 1-2, FIG. 5)

  By the way, in the automatic double-sided reading device described in Patent Document 1, when the trailing edge of the document passes through the portion facing the surface image reading unit, there is nothing that blocks the light emitted from the light source of the surface image reading unit. At this time, the optical sensor provided in the back surface image reading unit receives not only the reflected light emitted from the light source of the back surface image reading unit but reflected from the document, but also the light that has come from the light source of the front surface image reading unit. It will be. As a result, the amount of received light changes on the rear end side of the back image of the document, which affects the image data. As one of the techniques for solving such a problem, for example, it is conceivable to dispose the front surface image reading unit and the back surface image reading unit sufficiently apart in the document conveying direction. There is a problem that becomes larger.

  The present invention has been made to solve such a technical problem, and an object of the present invention is to eliminate image unevenness in double-sided automatic reading in which images on both front and back sides of a document are read with a single conveyance of the document. It is to reduce.

  For this purpose, an image reading apparatus to which the present invention is applied includes a paper feed unit that feeds originals from a bundle of originals, a transport path through which a document fed by the paper feed unit is transported, A first light source that irradiates the first surface of the document from one side and a first sensor that receives reflected light from the first surface of the document, and that reads image data on the first surface of the document. A reading unit; a second light source that irradiates the second surface of the document from the other side of the conveyance path; and a second sensor that receives reflected light from the second surface of the document. The second reading unit that reads the image data of the second surface of the document on the downstream side in the document transport direction, and the image data of the second surface of the document read by the second reading unit is the leading edge in the document transport direction. Image correction that corrects image data using different correction values for the side and the trailing end in the transport direction. And a part.

  Here, the image correction unit changes the correction value based on the distance between the rear end position in the document conveyance direction and the reading position by the first sensor and the reading position by the second sensor. be able to. The image correction unit corrects the image data of the first surface of the document read by the first reading unit using different correction values at the leading end side in the document transport direction and the downstream side in the transport direction. Can be characterized. Further, the image correction unit may change the correction value based on the leading end position of the document in the conveyance direction and the distance between the reading position by the first sensor and the reading position by the second sensor. it can.

  From another point of view, the image reading apparatus according to the present invention includes a paper feeding unit that feeds a document from a document bundle, a conveyance path through which a document fed by the paper feeding unit is conveyed, and a conveyance path. A first light source that irradiates the first surface of the document from one side and a first sensor that receives reflected light from the first surface of the document, and that reads image data on the first surface of the document. A reading unit; a second light source that irradiates the second surface of the document from the other side of the conveyance path; and a second sensor that receives reflected light from the second surface of the document. Are also read by the first sensor and / or the second sensor based on the second reading unit that reads the image data of the second surface of the document on the downstream side in the document transport direction and the position in the document transport direction. And an image correction unit for correcting the image data.

  Here, the image correction unit starts correcting the image data of the second surface of the document read by the second sensor from the time when the rear end of the document in the conveyance direction passes the reading position by the first sensor. Can be a feature. The image correction unit starts correcting the image data of the first surface of the document read by the first sensor from the time when the leading end of the document in the transport direction passes the reading position by the first sensor. can do. Further, the image correction unit ends the correction of the image data of the first surface of the document read by the first sensor when the leading end of the document in the conveyance direction reaches the reading position by the second sensor. can do. The image correction unit can correct the density of the image data.

  From another point of view, the image reading apparatus according to the present invention includes a paper feeding unit that feeds originals from a bundle of originals, a conveyance path through which a document fed by the paper feeding unit is conveyed, and one of the conveyance paths. A first light source that irradiates the first surface of the document from the side and a first sensor that receives reflected light from the first surface of the document, and reads first image data of the first surface of the document A second light source that irradiates the second surface of the document from the other side of the conveyance path and a second sensor that receives reflected light from the second surface of the document, and an image on the second surface of the document A second reading unit that reads data, and an image correction unit that corrects image data of the second surface of the document read by the second sensor in anticipation of the amount of light that travels from the first light source to the second sensor Including.

  Here, the first light source and the second light source are arranged such that the rear end in the document transport direction is the second sensor or the second sensor before the leading end in the document transport direction reaches the reading position by the first sensor or the second sensor. It can be characterized in that it is lit until it passes the reading position by one sensor. The first light source constituting the first reading unit is an illumination lamp, the first sensor is an image sensor using a reduction optical system, and the second light source constituting the second reading unit is an LED (Light Emitting Diode), the second sensor may be an image sensor using a contact optical system. Further, the image correction unit corrects the data on the first surface of the document read by the first sensor in anticipation of the amount of light that travels from the second light source to the first sensor. it can.

  According to the present invention, image unevenness can be reduced in double-sided automatic reading in which images on both the front and back sides of a document are read with a single conveyance of the document.

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 the first conveyance path 31 where the original is first conveyed, a take-away roll 16 that conveys the originals that are being fed one by one to the downstream roll, and further conveys the original to the further downstream roll and forms a loop. The pre-registration roll 17 to be performed, the rotation is resumed at the timing after being temporarily stopped, the registration roll 18 for supplying the original while performing registration adjustment to the original reading unit, the platen roll 19 for assisting the conveyance of the original being read, the reading An out-roll 20 is provided to convey the original document further downstream. 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 as a second reading unit in the present embodiment 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.

  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 the loop is formed. 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 to rotate, the original is pressed against the second platen glass 72B (described later) by the platen roll 19, and image data is displayed from the lower surface direction by a CCD image sensor described later. Is read.

  The conveyance path switching gate 42 switches so that the document passing through the out-roll 20 is guided to the second conveyance path 32 and discharged to the discharge tray 40 at the end of reading one-sided document and at the same time when reading both-side documents simultaneously. It is done. On the other hand, the transport path switching gate 42 is switched so as to guide the document to the third transport path 33 in order to invert the document when the double-sided document is sequentially read. 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.

  A scanner device 70 as a first reading unit is configured to be able to place the above-described document feeder 10, and is supported by the device frame 71 and conveyed by the document feeder 10. The original image is being scanned. 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 is provided with an illumination lamp 74 as a first light source for irradiating light on the document, and a first mirror 76A for receiving reflected light obtained from the document. 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 first 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 on which the CCD image sensor 78 is mounted 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. The second side of the document can be read by the CIS 50 serving as the second reading unit when it is not coincident but meaning the same as when the same document is conveyed. That is, by using the CCD image sensor 78 and the CIS 50, it is possible to simultaneously read the images on both the front and back sides of the document by transporting the document to the transport path once.

  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, front side) of the document 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, back side) is read from the other side facing through the conveyance path for conveying the document. The CIS 50 includes a glass 51 opposed to the conveyance path, an LED (Light Emitting Diode) 52 as a second light source that transmits the light to the second surface of the document through the glass 51, A SELFOC lens 53 that is a lens array for collecting the reflected light and a line sensor 54 as a second sensor for reading the 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 the present embodiment is applied is large and includes a signal processing unit 81 that processes image information obtained from sensors (CCD image sensor 78 and line sensor 54), a document feeder 10 and a scanner device 70. And a control unit 90 for controlling. The signal processing unit 81 performs image correction on the respective outputs from the CCD image sensor 78 that reads the front surface (first surface) of the document and the line sensor 54 of the CIS 50 that reads the back surface (second surface). It has a function as a part. 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 two systems of image processing circuits that perform various processing such as shading correction and offset correction on the digital signal, and performs image processing on the image data on the front surface (first surface). A first image processing circuit 100 for performing image processing and a second image processing circuit 200 for performing image processing on image data on the back surface (second surface) are provided. 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 an image reading control 91 that controls the entire document feeding device 10 and the scanner device 70, including various double-sided scanning control and single-sided scanning control, a CCD / image sensor 78 and a CCD / CIS 50 that controls the CIS 50. The CIS 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, 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, etc. A scanning control 94 that controls the motor, a motor control in the document feeder 10, a transport mechanism control 95 that controls various roll operations, feed clutch operations, gate switching operations, and the like. There. 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. As this reading mode, the double-sided simultaneous reading mode by 1 pass (without reversal), the reversing double-sided reading mode by reversing pass, the single-sided reading mode by 1 pass, etc. can be considered.

Next, the function and operation of each image processing circuit (first image processing circuit 100 and second image processing circuit 200) will be described.
FIG. 4 is a block diagram illustrating the configuration of the signal processing unit 81 in further detail. The first image processing circuit 100 includes a first CPU 101 that performs overall control, an AFE 102 that performs sample hold, offset adjustment, A / D conversion, and the like on the surface image data output from the CCD image sensor 78, and front and back images. A selector (SEL) 103 for selecting and outputting data is provided. Furthermore, an A integrated circuit (ASIC-A) 110 that performs shading correction, line interpolation (RGB misregistration interpolation), and the like, and an B integrated circuit (ASIC-B) that performs MTF filter, reduction / enlargement processing, binarization processing, etc. ) 130.

  On the other hand, the second image processing circuit 200 is obtained from a second CPU 201 that performs overall control, for example, white reference shading data at the time of factory shipment, a flash ROM (FROM) 202 that stores (stores) LED light amount correction values, and a CIS 50. C integrated circuit (ASIC-C) 210 that performs various image processing on the backside image data, and temporarily holds the backside image data that has undergone image processing, and outputs it to the selector (SEL) 103 in accordance with a predetermined output timing A memory 203 is provided. In the present embodiment, white reference shading data obtained in advance at the time of factory shipment is stored in a flash ROM (FROM) 202 by the CIS 50 which is a contact image sensor for reading the back surface.

  FIG. 5 is a block diagram showing the configuration of the A integrated circuit (ASIC-A) 110. The A integrated circuit 110 includes a shading correction unit 111 for correcting shading data in the CCD image sensor 78, a GAP correction unit 112 for correcting the positions of RGB line sensors, a black line correction unit 113 for correcting black lines, and an input. An ENL 115 that performs gradation correction and a color space conversion unit 116 that converts BGR → L *, a *, b * are provided. In addition, a timing generation unit 119 that generates drive clocks for the CCD image sensor 78 and the AFE 102 and a CPU interface 120 that communicates with the first CPU 101 are provided.

  FIG. 6 is a block diagram showing the configuration of the B integrated circuit (ASIC-B) 130. The B integrated circuit 130 includes a digital filter unit 131 that performs MTF correction and smoothing, a sub-scanning reduction unit 132 that performs a reduction process with respect to the sub-scanning direction that is the document transport direction, and a CCD that is in a direction orthogonal to the document transport direction. A main scanning enlargement / reduction unit 133 that performs enlargement / reduction processing in the main scanning direction that is the scanning direction of the image sensor 78, a background removal unit 135 that removes the background of the read document, L *, a *, b * → Y, M, C , K is provided with a look-up table (LUT) 136 for color space conversion. Further, a background detection unit 139 that detects the background of the read document and a CPU interface 140 that communicates with the first CPU 101 are provided.

  FIG. 7 is a block diagram showing the configuration of the C integrated circuit (ASIC-C) 210. The C integrated circuit 210 includes a multiplex (MPX O / E synthesis) circuit 211 that synthesizes output signals of two channels composed of Odd / Evn, and a shading correction unit that performs shading correction based on data stored in the shading memory 221. 212, an L * conversion unit (LUT) 213 that performs input tone correction, a sub-scanning / reducing unit 214 that performs reduction processing in the sub-scanning direction, and a main-scanning / enlarging unit that performs enlargement / reduction processing in the main-scanning direction 215, a filter unit 216 that performs MTF correction and smoothing, a background removal unit 217 that performs background removal based on a background detection result by the background detection unit 222, a look-up table (LUT) 218 that performs output tone correction, and binarization A Packing error diffusion processing unit 219 is provided. In addition, a CPU interface 223 that performs communication with the second CPU 201 is provided.

  Here, in the present embodiment, when an image is read by conveying the document by the document feeder 10, the scanner device 70 (CCD image sensor 78) is used for the document conveyed to the platen roll 19 through the second platen glass 72B. And can be read using the CIS 50 provided in the document feeder 10. However, as described above, the depth of focus differs between the reading by the CCD image sensor 78 using the mechanism of the scanner device 70 and the reading using the line sensor 54 of the CIS 50, and the resolution characteristics are different. There will be a difference. In particular, when a color image such as a photograph is read, color matching becomes difficult when both are read, and the image quality obtained by reading both is different. Therefore, in this embodiment, a plurality of reading modes are prepared, and an optimum mode can be selected based on the setting state of the apparatus, the type of document, the user's selection, and the like.

  FIG. 8 is a flowchart showing an example of processing executed by the image reading control 91 shown in FIG. In the image reading control 91, first, it is determined whether or not the conveyed document is a single-sided document (step 101). This determination is made by, for example, selection from a user using a control panel (not shown) provided on the scanner device 70, or, for example, when the automatic selection reading function is working, the first conveyance before image reading. It can be recognized by sensors (not shown) provided on both sides of the conveyance path on the path 31. In addition, a request from the host system or a selection from the user via a network or the like can be considered. If it is determined in step 101 that the document is a single-sided original, single-sided reading is performed by one pass (one-time original conveyance pass without using a reverse pass) (step 102). In this one-pass single-sided reading, either the reading by the CCD image sensor 78 or the reading by the CIS 50 may be selected, but when the image reading with higher image quality is realized, the reading by the CCD image sensor 78 is selected. It is preferable. In such a case, the document is placed on the document tray 11 so that the document surface faces upward and the first page of the document comes, and the document is transported from the first page and sequentially read.

  Here, if it is not a single-sided original in step 101, that is, if it is a double-sided original, it is determined whether or not the original is a monochrome original (step 103). The determination in step 103 is determined by the selection from the user or the automatic selection reading function as in step 101. There are cases where the user desires black-and-white reading even for a color original. When monochrome reading is not performed, that is, when color reading is performed, it is determined whether or not image quality is important (step 104). For example, in the case of a color image such as a color photograph or a pamphlet, the image quality is generally more important than the productivity for increasing the reading speed. Such a determination is also made based on user settings. If it is determined in this step 104 that the image quality is important, double-sided reading by the reverse pass, which is the first double-sided reading mode, is executed (step 105). That is, without reading by the CIS 50, the first surface of the document and the second surface of the document are read by the CCD image sensor 78 as the first sensor. As a result, both the first surface of the document and the second surface of the document can be read on both sides with high image quality using a reading means having a deep focal depth.

  On the other hand, when black and white reading is performed in step 103 or when a color image output is required in step 104, for example, when subtle hues such as business colors are not emphasized, or in the case of plus one color (black In the case where the image quality is not so important and other factors such as productivity are important, such as red and blue), the reverse pass is the second duplex scanning mode. Simultaneous reading on both sides by one pass is performed without using (step 106). That is, the first image of the original is read by the CCD image sensor 78 as the first sensor, and the second side of the original is read by the CIS 50 in the same conveyance path during the reading conveyance path. This eliminates the need to transport the document twice to the same reading unit, improves the document reading speed, and simplifies the transport path, thereby avoiding document transport troubles such as document jamming (JAM). Can be suppressed. Note that, as described above, “simultaneous reading” does not necessarily mean a case where they are positioned temporally, but means that both sides are read almost at the same time in one transport pass.

  The flow shown in FIG. 8 is simplified, and when reading a double-sided original, double-sided simultaneous reading in Step 106 is executed when reading a black and white original, and in the case of a color original, the reverse pass of Step 105 is sequentially performed. It can also be configured to read a document. It is also possible to mix and use these modes according to the type of document surface.

Next, a document transport method in each document reading mode will be described with reference to FIGS.
FIGS. 9A and 9B show the document path in the single-sided reading mode by one pass shown in step 102 of FIG. 8 and the second double-sided reading mode in which double-sided simultaneous reading by one pass shown in step 106 is performed. It is a figure. As shown in FIG. 9A, 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 As shown in FIG. 9B, the supplied document is moved to the second conveyance path 32 by the conveyance path switching gate 42 via the reading section of the platen roll 19 and the reading section of the CIS 50, and the discharge tray 40. Are sequentially discharged. In the case of single-sided reading, reading is performed using the CCD image sensor 78 of the scanner device 70 shown in FIG. However, as described above, single-sided reading using the CIS 50 is also possible. In the case of simultaneous reading on both sides by one pass, the first surface is read using the CCD image sensor 78 of the scanner device 70, and the second surface is read using the CIS 50 during the same conveyance. As a result, it is possible to read both sides of the document by one document pass.

  FIGS. 10A to 10D are diagrams for explaining the double-sided reading by the reverse path shown in step 105 of FIG. 8, that is, the first double-sided reading mode. As shown in FIG. 10A, the originals placed on the original tray 11 are sequentially supplied to the first transport path 31, and the platen roll is used by using the CCD image sensor 78 of the scanner device 70 shown in FIG. Reading is performed from below at 19 locations. Then, the transfer path switching gate 42 moves to the fourth transfer path 34 via the third transfer path 33. As shown in FIG. 10B, 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 by the exit switching gate 43. .

  The document supplied to the fifth conveyance path 35 is again supplied to the first conveyance path 31. Then, as shown in FIG. 10 (c), the document is read from below by the CCD image sensor 78 of the scanner device 70. At this time, the document is in an inverted state from the case shown in FIG. 10A, and the second side that is different from the first side is read. The original on which the second side has been read is in an inverted state. If the original 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, as shown in FIG. 10C, the document whose second surface has been read is moved to the fourth transport path 34 via the third transport path 33 using the transport path switching gate 42. The document supplied to the fourth conveyance path 34 and completely passing through the exit switching gate 43 is discharged to the discharge tray 40 by the outlet switching gate 43 via the sixth conveyance path 36 as shown in FIG. Is done. This makes it possible to align the page order of the original after reading in the first double-sided reading mode in which images on both sides of the original are sequentially read.

  As described above, in the present embodiment, after reading one side (first side) of the original using the CCD image sensor 78 as the first sensor, the original is reversed and the other side (second side) is read. The first double-sided reading mode in which the first sensor sequentially reads, and the CIS50, which is a second sensor provided on the other side of the first sensor that faces the first sensor together with the first sensor. Was used to prepare a second double-sided reading mode for reading both the front and back sides (first side and second side) with a single conveyance of the document. These modes are configured to be selectable automatically or based on a user designation or the like as necessary. This makes it possible to select the duplex scanning mode appropriately and use these modes depending on the application, for example, whether output is monochrome or color, whether speed (productivity) is important, or whether image quality is important. can do.

FIGS. 11A to 11C are diagrams for explaining a document conveyance state and document reading in the above-described second duplex reading mode (double-pass simultaneous reading mode by one pass). In these drawings, the conveyance path is substantially straight for simplification.
FIG. 11A shows a state where the front surface (first surface) of the conveyed document is read by the CCD image sensor 78 (see FIG. 1) and the back surface (second surface) of the document is read by the line sensor 54. Yes. In the present embodiment, as described above, the surface of the document is irradiated by the illumination lamp 74, and reflected light from the document is input to the CCD image sensor 78 via the first mirror 76A and the like. On the other hand, the back surface of the document is illuminated by the LED 52, and reflected light from the document is input to the line sensor 54 via the Selfoc lens 53 and the like.

  FIG. 11B shows a state in which the reading operation of the front side of the document by the CCD image sensor 78 is completed and the reading operation of the back side of the document by the CIS 50 is continued, that is, the trailing edge of the conveyed document is A state in which the reading position by the CCD image sensor 78 is removed is shown. In the present embodiment, even after the trailing edge of the document leaves the reading position by the CCD image sensor 78, the illumination lamp 74 is lit as shown in the figure, and light is irradiated toward the conveyance path. On the other hand, the back side of the document is continuously irradiated by the LED 52, and the reflected light from the document is input to the line sensor 54 via the SELFOC lens 53 and the like.

  In the present embodiment, the reading position on the front surface of the document by the CCD image sensor 78 and the reading position on the back surface of the document by the CIS 50 are arranged so as to be shifted with respect to the transport direction of the document, and the distance X is about 30 mm. Therefore, in the state shown in FIG. 11B, that is, the state immediately after the trailing edge of the conveyed document passes through the document reading position by the CCD image sensor 78 as the first sensor, the illumination lamp 74 emits light. There is a possibility that the emitted light may wrap around the line sensor 54. When such light wraparound occurs while reading the back side of the document, the amount of light received by the line sensor 54 increases, and as shown in FIG. And the area B from the trailing edge of the document to the distance X has a difference in image data density, and the area B becomes an image having a low density.

  Therefore, in the present embodiment, the image data input to the line sensor 54 is corrected by the signal processing unit 81 (specifically, the second image processing circuit 200) shown in FIG. The influence of the light that circulates from the illumination lamp 74 is removed. Specifically, from the second CPU 201 shown in FIG. 4 before and after the trailing edge of the document passes the reading position by the CCD image sensor 78, that is, at the leading edge side (region A) and the trailing edge side (region B) of the document. Based on the above command, the LUT (correction value) of the L * conversion unit 213 in the C integrated circuit 210 is switched and adjusted so that the density serving as the reference of the image data becomes substantially constant. Here, whether or not the trailing edge of the document has passed the reading position by the CCD image sensor 78 can be determined based on, for example, an elapsed time after the registration roll 18 starts rotating (starts document conveyance). . In order to estimate the timing at which the trailing edge of the document passes through the reading position by the CCD image sensor 78 from the document conveyance start timing by the registration roll 18, the length Y of the document conveyance direction is required. And an output from a size detection sensor (not shown) or the like.

  On the other hand, FIG. 11C shows a state immediately before the leading edge of the document enters the reading position by the CCD image sensor 78. In the present embodiment, before the leading edge of the document enters the reading position by the CCD image sensor 78, the LED 52 is lit as shown in the figure, and light is irradiated toward the conveyance path. For this reason, the light irradiated from the LED 52 may wrap around the CCD image sensor 78. If such light wraparound occurs while reading the surface of the document, the amount of light received by the CCD image sensor 78 increases, and as shown in FIG. A difference in image data density occurs between the area C from the leading edge to the distance X and the area D on the trailing edge side of the document, and the area C becomes an image having a low density.

  Therefore, in the present embodiment, as in the case of the back side of the document, the image data input to the CCD image sensor 78 is converted into the signal processing unit 81 (specifically, the first image) shown in FIG. The correction is made by the processing circuit 100), and the influence of the light coming from the LED 52 is removed. Specifically, before and after the leading edge of the document passes the reading position by the line sensor 54, that is, in the areas C and D, the input in the ENL 115 in the A integrated circuit 110 is performed based on the command from the first CPU 101 shown in FIG. The gradation correction coefficient is switched, and the image data reference density is adjusted to be substantially constant. Here, whether or not the leading edge of the document has passed the reading position by the line sensor 54 can be determined based on, for example, an elapsed time after the registration roll 18 starts rotating (starts document conveyance).

In the present embodiment, the positional information of the region that is easily affected by the light source and the region that is difficult to receive are obtained in advance from the positional relationship among the illumination lamp 74, the LED 52, the CCD image sensor 78, and the line sensor 54. Based on this, appropriate image processing is performed on both areas to correct the density difference in the same document (same surface), so there is no density unevenness in the document transport direction. An image can be obtained.
In this embodiment, the LED 52 is lit before the leading edge of the document reaches the reading position by the CCD image sensor 78, and the illumination lamp 74 is turned on until the trailing edge of the document passes the reading position by the line sensor 54. Since it is lit, there is an advantage that the power supply voltage does not fluctuate easily and the light quantity of these light sources is stabilized.

  In this embodiment, the CCD image sensor 78 is used as a reading sensor for the document surface, and the line sensor 54 is used as a reading sensor for the document back surface. However, the present invention is not limited to this. The same type of reading sensor may be used. In this embodiment, the illumination lamp 74 is used as the light source for the document surface, and the LED 52 is used as the light source for the document back surface. However, the present invention is not limited to this, and the same type of light source is used. You may do it. Further, in the present embodiment, the density correction of the image data is performed using the input tone correction, but the present invention is not limited to this, and other correction methods may be employed.

It is the figure which showed the image reading apparatus with which this Embodiment is applied. It is a figure for demonstrating the reading structure using CIS. It is a block diagram for demonstrating a processing apparatus. It is the block diagram which detailed the structure of the signal processing part. It is the block diagram which showed the structure of A integrated circuit (ASIC-A). It is the block diagram which showed the structure of B integrated circuit (ASIC-B). It is the block diagram which showed the structure of C integrated circuit (ASIC-C). It is the flowchart which showed an example of the process performed by image reading control. (a), (b) is a figure for demonstrating the original path | pass of the 2nd double-sided reading mode which is the single-sided reading mode by 1 pass, and the double-sided simultaneous reading by 1 pass. (a)-(d) is a figure for demonstrating the 1st double-sided reading mode which is double-sided reading by an inversion path | pass. (a)-(c) is a figure for demonstrating the problem in 2nd double-sided reading mode. (a) is a diagram for explaining image data on the front side of the document, and (b) is a diagram for explaining image data on the back side of the document.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Document feeder, 11 ... Document tray, 13 ... Nudger roll, 19 ... Platen roll, 31 ... 1st conveyance path, 50 ... CIS (Contact Image Sensor), 52 ... LED, 54 ... Line sensor, 60 ... Thing Abutting member, 70 ... scanner device, 72B ... second platen glass, 78 ... CCD (Charge Coupled Device) image sensor, 80 ... processing device, 81 ... signal processing unit, 90 ... control unit, 100 ... first image processing circuit, DESCRIPTION OF SYMBOLS 101 ... 1st CPU, 110 ... A integrated circuit (ASIC-A), 111 ... Shading correction part, 112 ... GAP correction part, 113 ... Black line correction part, 115 ... ENL, 119 ... Timing generation part, 130 ... B integrated circuit (ASIC-B), 200 ... second image processing circuit, 201 ... second CPU, 202 ... flash ROM (FROM), 210 ... C integrated circuit (ASIC-C), 211 Multiplex (MPXO / E synthesis) circuit, 212 ... shading correction unit, 213 ... L * conversion (LUT) unit, 214 ... sub-scanning reduction unit, 215 ... main scanning enlargement / reduction unit, 216 ... filter unit, 217 ... background removal , 218 ... Look-up table (LUT), 219 ... Packing error diffusion processing part, 221 ... Shading memory, 222 ... Background detection part

Claims (12)

A paper feeder that feeds documents from a bundle of documents;
A conveyance path through which the document fed by the sheet feeding unit is conveyed;
And a first sensor for receiving light reflected from the first surface of the first light source and the document for irradiating a first surface of the document from one side of the conveying path, the first reading position A first reading unit for reading image data of the first side of the document;
A second light source that irradiates the second surface of the document from the other side of the conveyance path; and a second sensor that receives reflected light from the second surface of the document, from the first reading position . A second reading unit that reads image data of the second surface of the document at a second reading position downstream of the document in the conveyance direction;
The first light source and the second light source from before the leading end of the document in the transport direction reaches the first reading position until the trailing end of the document in the transport direction passes through the second reading position. A light source control unit for lighting
The image data of the second surface of the document read by the second reading unit is corrected using different correction values at the leading end side and the trailing end side in the transport direction of the document. An image reading apparatus including an image correction unit. The image correction unit changes the correction value based on a rear end position of the document in a conveyance direction and a distance between the first reading position and the second reading position. The image reading apparatus according to 1.   The image correcting unit corrects the image data of the first surface of the document read by the first reading unit using different correction values at the leading end side in the transport direction and the downstream side in the transport direction of the document. The image reading apparatus according to claim 1, wherein: The image correction unit changes the correction value based on a leading end position of the document in a conveyance direction and a distance between the first reading position and the second reading position. The image reading apparatus described. A paper feeder that feeds documents from a bundle of documents;
A conveyance path through which the document fed by the sheet feeding unit is conveyed;
And a first sensor for receiving light reflected from the first surface of the first light source and the document for irradiating a first surface of the document from one side of the conveying path, the first reading position A first reading unit for reading image data of the first side of the document;
A second light source that irradiates the second surface of the document from the other side of the conveyance path; and a second sensor that receives reflected light from the second surface of the document, from the first reading position . A second reading unit that reads image data of the second surface of the document at a second reading position downstream of the document in the conveyance direction;
The first light source and the second light source from before the leading end of the document in the transport direction reaches the first reading position until the trailing end of the document in the transport direction passes through the second reading position. A light source control unit for lighting
An image reading apparatus including: an image correcting unit that corrects image data read by the first sensor and / or the second sensor based on a position in the transport direction of the document. The image correction unit starts correcting the image data of the second surface of the document read by the second sensor from the time when the rear end in the transport direction of the document passes the first reading position. 6. An image reading apparatus according to claim 5, wherein The image correction unit starts correcting the image data of the first surface of the document read by the first sensor from the time when the leading end in the transport direction of the document passes the first reading position. The image reading apparatus according to claim 5. The image correcting unit ends correction of the image data of the first surface of the document read by the first sensor when the leading end of the document in the transport direction reaches the second reading position. The image reading apparatus according to claim 7.   6. The image reading apparatus according to claim 5, wherein the image correction unit corrects the density of the image data. A paper feeder that feeds documents from a bundle of documents;
A conveyance path through which the document fed by the sheet feeding unit is conveyed;
And a first sensor for receiving light reflected from the first surface of the first light source and the document for irradiating a first surface of the document from one side of the conveying path, the first reading position A first reading unit for reading image data of the first side of the document;
A second light source that irradiates the second surface of the document from the other side of the conveyance path; and a second sensor that receives reflected light from the second surface of the document, from the first reading position. A second reading unit that reads image data of the second surface of the document at a second reading position downstream of the document in the conveyance direction ;
The first light source and the second light source from before the leading end of the document in the transport direction reaches the first reading position until the trailing end of the document in the transport direction passes through the second reading position. A light source control unit for lighting
An image reading device including an image correction unit that corrects image data of the second surface of the document read by the second sensor in anticipation of the amount of light that travels from the first light source to the second sensor. .   The first light source constituting the first reading unit is an illumination lamp, the first sensor is an image sensor using a reduction optical system, and the second light source constituting the second reading unit is The image reading apparatus according to claim 10, wherein the LED (Light Emitting Diode) and the second sensor are image sensors using a contact optical system.   The image correction unit corrects the data of the first surface of the document read by the first sensor in anticipation of the amount of light that travels from the second light source to the first sensor. The image reading apparatus according to claim 10.

Images