JP2005110172A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus for reducing unevenness of a read image in double side automatic reading of an original to read images on both front and rear sides of the original by one time carrying of the original. <P>SOLUTION: The image reading apparatus uses an illumination lamp 74 to emit light to the original from one side of an original carrying path on which the original is carried, uses a CCD image sensor to receive a reflected light from the front side of the original, uses an LED 52 to emit light onto the original from the other side of the original carrying path, and uses a line sensor 54 to receive the reflected light from the rear side of the original. Then the illumination lamp 74 is turned off just after the tail end of the original passes through the read position by the CCD image sensor to prevent the light from the illumination lamp 74 from sneaking into the line sensor 54. Further, the LED 52 is turned on just before the tip of the original reaches the read position by the line sensor 54 to prevent the light from the LED 52 from sneaking into the CCD image sensor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 reflected from the first surface of the document, and that reads image data on 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 the reflected light reflected from the second surface of the document. The first light source and / or the second light source is turned on based on the second reading unit that reads the image data of the second surface of the document on the downstream side of the document transport direction and the position in the document transport direction. And a lighting control unit to be controlled.

  Here, the lighting control unit can be characterized in that the first light source is turned off after the rear end in the document transport direction passes the reading position by the first sensor. Further, the lighting control unit can turn on the second light source after the leading end of the document in the conveyance direction passes the reading position by the first sensor.

  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. The lighting of the first light source is controlled in anticipation of 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 amount of light that travels from the first light source to the second sensor. And a lighting control unit.

  Here, when the thickness of the document is equal to or greater than the predetermined thickness, the lighting control unit is configured such that the rear end in the document transport direction is from the first position before the leading end of the document transport direction reaches the reading position by the first sensor. The first light source is turned on until the sensor passes the reading position. In addition, when the thickness of the document is thinner than the predetermined thickness, the lighting control unit is configured so that the trailing end of the document in the transport direction is the second sensor before the leading end of the document in the transport direction reaches the reading position by the first sensor. The first light source can be turned on until it passes through the reading position.

Further, from another point of view, the image reading apparatus according to the present invention includes a paper feeding unit that feeds documents from a bundle of documents, a conveyance path through which a document fed by the sheet 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. A second reading unit that reads image data of the second surface of the document on the downstream side in the document transport direction;
A lighting control unit that controls lighting of the second light source in consideration of the amount of light that travels from the second light source to the first sensor is included.

  Here, when the thickness of the document is equal to or greater than the predetermined thickness, the lighting control unit is configured so that the rear end in the document transport direction is the second before the leading end of the document transport direction reaches the reading position by the second sensor. The second light source is turned on until it passes the reading position by the sensor. In addition, when the thickness of the document is thinner than the predetermined thickness, the lighting control unit is configured so that the trailing end of the document in the transport direction is the second sensor before the leading end of the document in the transport direction reaches the reading position by the first sensor. The second light source is turned on until it passes through the reading position.

  Furthermore, the image reading apparatus of the present invention includes a paper feeding unit that feeds documents from a bundle of documents, a conveyance path that conveys the documents fed by the sheet feeding unit, and a document that is fed from one side of the conveyance path. A first reading unit that includes a first light source that irradiates the first surface and a first sensor that receives reflected light reflected from the first surface of the document; A second light source that irradiates the second surface of the document from the other side of the path, and a second sensor that receives reflected light reflected from the second surface of the document, and transports the document more than the first reading unit. A second reading unit that reads image data of the second surface of the document on the downstream side in the direction, and reading of the image of the first surface of the document by the first reading unit is completed, and the second surface of the document by the second reading unit Lighting controller that turns off the first light source when the image is read It contains.

  Here, the lighting control unit performs the second operation when the first reading unit performs image reading on the first side of the document and the second reading unit does not perform image reading on the second side of the document. The light source can be turned off. 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.

  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 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 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 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. 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 has a function of performing predetermined image processing on 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). Have. 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. The CIS control 92, the lamp control 93 as a lighting control unit for controlling the LED 52 of the CIS 50 and the illumination lamp 74 of the full rate carriage 73 in accordance with the read timing, the motor in the scanner device 70 is turned on / off, and the like. A scanning control 94 that controls the scanning operation by the carriage 75, a motor control in the document feeder 10, a transport mechanism controller that controls various roll operations, feed clutch operations, gate switching operations, and the like. It is equipped with a roll 95. 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.

  Further, in the image reading apparatus according to the present embodiment, when the above-described second double-sided reading mode (double-sided simultaneous reading mode by one pass) is executed, according to the thickness of the original sent from the original feeding device 10, By controlling lighting of the illumination lamp 74 and the LED 52, fluctuations in the amount of light received by the line sensor 54 and the CCD image sensor 78 are suppressed, and unevenness in the read image is suppressed. This lighting control is performed by the lamp control 93 of the control unit 90 shown in FIG. Note that the thickness of the document is, for example, a selection from a user using a control panel (not shown) provided on the scanner device 70, a request from a host system, a selection from a user via a network, or the like. Set by

Next, specific lighting control will be described. FIG. 11 is a flowchart for explaining lighting control in the case of reading a double-sided image of a document having a predetermined thickness such as plain paper.
When double-sided simultaneous reading is started, first, the illumination lamp 74 is turned on (step 201). Thereafter, the leading edge of the conveyed document reaches the surface reading position (reading position by the CCD image sensor 78), and image reading on the surface of the document is started. Next, it is determined whether or not the leading edge of the document has reached the portion immediately before the back surface reading position (reading position by the line sensor 54) (step 202). If the document has reached this part, the LED 52 is turned on (step 203). If not, the process returns to step 202 to wait for the document to arrive. In addition, the site | part immediately before a back surface reading position is between a front surface reading position and a back surface reading position, Comprising: It can select suitably from the side close | similar to a back surface reading position. Further, whether or not the leading edge of the document has reached the portion immediately before the back surface reading position can be determined based on, for example, an elapsed time after the registration roll 18 starts rotating (starts document conveyance).

  After the LED 52 is turned on in step 203, the leading edge of the conveyed document reaches the back surface reading position (reading position by the line sensor 54), and image reading on the back surface of the document is started. Then, it is determined whether the trailing edge of the document has passed the front surface reading position (step 204). Here, if the document has passed the front surface reading position, the illumination lamp 74 is turned off (step 205). If not, the process returns to step 204 to wait for the document to pass. When the document passes through the front surface reading position, the image reading on the front surface of the document is completed. After the illumination lamp 74 is turned off in step 205, it is determined whether or not the trailing edge of the document has passed the back surface reading position (step 206). Here, if the document has passed the back surface reading position, the LED 52 is turned off (step 207). If not, the process returns to step 206 to wait for the document to pass. Note that when the original passes through the back side reading position, the image reading on the back side of the original ends. Then, it is determined whether or not there is a next original (step 208). If there is a next original, the process returns to step 201 to continue the process, and if there is no next original, a series of processing is terminated.

FIGS. 12A to 12C show a document conveyance state and document reading when a second-sided scanning mode (double-sided simultaneous scanning mode by one pass) is executed using a somewhat thick document such as plain paper. It is a figure for demonstrating. 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. In these drawings, the conveyance path is substantially straight for simplification.
FIG. 12A shows a state (between step 201 and step 202) immediately after the front end of the document reaches the front surface reading position. At this time, the illumination lamp 74 is turned on, while the LED 52 is turned off. The surface of the document is irradiated by an 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. In this case, since the LED 52 is turned off, the situation where the light from the LED 52 wraps around the CCD image sensor 78 does not occur.

  FIG. 12B shows a state (between step 203 and step 204) in which the same document exists across the front side document reading position and the back side document reading position. At this time, the illumination lamp 74 and the LED 52 are turned on. The surface of the document is irradiated by an 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. In this case, since the original having a predetermined thickness such as plain paper exists in the conveyance path as described above, the light from the illumination lamp 74 goes around the line sensor 54 or the light from the LED 52 is converted into the CCD image. There is no situation of going around the sensor 78.

  FIG. 12C shows a state (between step 205 and step 206) immediately before the trailing edge of the document passes through the front surface reading position and reaches the back surface reading position. At this time, the illumination lamp 74 is turned off, while the LED 52 is continuously turned on. In this case, the reflected light from the original irradiated by the LED 52 is input to the line sensor 54. At this time, since the illumination lamp 74 is turned off, the situation that occurs when the light from the illumination lamp 74 goes around the line sensor 54 does not occur.

If the illumination lamp 74 is kept on in the case of a document that is thick to some extent, such as plain paper, the state shown in FIG. 12C, that is, the rear end of the conveyed document is a CCD image sensor as a first sensor. Immediately after exiting the document surface reading position by 78, there is a possibility that the light emitted from the illumination lamp 74 may enter 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, when reading a document that is thick to some extent, the illumination lamp 74 can be turned on and off as described above to eliminate the influence of light that circulates from the illumination lamp 74. A substantially constant image density can be obtained in the document conveyance direction.

If the LED 52 is kept on in the case of a document that is thick to some extent such as plain paper, the state shown in FIG. 12A, that is, the leading edge of the document to be conveyed is a CCD image as a first sensor. Immediately after entering the surface reading position of the document by the sensor 78, there is a possibility that the light emitted from the LED 52 may enter the CCD image sensor 78. If such light wraparound occurs while reading the document surface, 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, when reading a document that is thick to some extent, the above-described control of lighting and extinguishing of the LED 52 can eliminate the influence of light that circulates from the LED 52. As a result, the surface image is moved in the document transport direction. A substantially constant image density can be obtained.

In this way, when using a somewhat thick original such as plain paper, the illumination lamp 74 and the LED 52 are turned on and off according to the original conveying position, thereby reducing the density unevenness in the original conveying direction on both sides. Can be obtained.
Moreover, since the illumination lamp 74 or the LED 52 is turned off when it is not necessary, it is possible to suppress wasteful power consumption by the light source and to save power.

On the other hand, FIG. 14 is a flowchart for explaining lighting control in the case of reading a double-sided image of a thin document such as tracing paper.
When double-sided simultaneous reading is started, the illumination lamp 74 is turned on (step 301), and the LED 52 is also turned on (step 302). Thereafter, the leading edge of the conveyed document reaches the surface reading position, and image reading on the surface of the document is started. Further, the leading edge of the conveyed document reaches the back surface reading position, and image reading on the back surface of the document is started. Next, it is determined whether or not the trailing edge of the document has passed the back surface reading position (step 303). If the original has not passed the back side reading position, the process returns to step 303 to wait for the original to pass, and if the original has passed the back side reading position, it is determined whether there is a next original. (Step 304). If there is a next original, the process returns to step 303 with the illumination lamp 74 and the LED 52 turned on and waits for the next original to pass. If there is no next original, the illumination lamp 74 is turned off (step 305). Then, the LED 52 is turned off (step 306), and the series of processing is terminated.

15 (a) to 15 (c) show how a document is transported and how the document is read when the second duplex scanning mode (simultaneous duplex scanning mode with one pass) is executed using a thin document such as tracing paper. It is a figure for demonstrating. In these drawings as well, the conveyance path is substantially straight for simplification.
FIG. 15A shows a state (between step 302 and step 303) immediately after the leading edge of the document reaches the front surface reading position. At this time, the illumination lamp 74 and the LED 52 are turned on. When the document reaches the front surface reading position, the reflected light from the document irradiated by the illumination lamp 74 is input to the CCD image sensor 78 (see FIG. 1) via the first mirror 76A and the like. At that time, the light from the LED 52 slightly enters the CCD image sensor 78 (see FIG. 1) via the first mirror 76A and the like.

  FIG. 15B shows a state in which the same document exists across the front side document reading position and the back side document reading position (continuation between step 302 and step 303). At this time, the illumination lamp 74 and the LED 52 are continuously turned on. The surface of the document is irradiated by an 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. In this case, as described above, a thin original such as tracing paper is present in the conveyance path, so that part of the light from the illumination lamp 74 passes through the original and goes around the line sensor 54 or from the LED 52. A situation occurs in which part of the light passes through the document and goes around to the CCD image sensor 78.

  FIG. 15C shows a state immediately before the trailing edge of the document passes the front surface reading position and reaches the back surface reading position (continuation between step 302 and step 303). At this time, the illumination lamp 74 and the LED 52 are continuously turned on. In this case, the reflected light from the original irradiated by the LED 52 is input to the line sensor 54. At that time, the light from the illumination lamp 74 slightly goes around the line sensor 54.

In the case of a thin document such as tracing paper, if the illumination lamp 74 and the LED 52 are turned on and off while the document is being read, the amount of light received by the CCD image sensor 78 and the line sensor 54 tends to fluctuate. 13 may occur in the areas A and B shown in FIG. 13A and the areas C and D shown in FIG. 13B on the back side of the document.
Therefore, when reading a document that is thin to some extent, the illumination lamp 74 and the LED 52 are turned on until the trailing edge of the document passes through the back surface reading position as described above, in other words, until the document reading operation is completed. By continuing, it is possible to reduce fluctuations in the amount of light that circulates from the illumination lamp 74 or the LED 52, and as a result, it is possible to obtain a substantially constant image density in the document conveyance direction for the front and back images.

  In this embodiment, the illuminating lamp 74 and the LED 52 are turned off to suppress the wraparound of the light. However, the present invention is not limited to this. For example, the lighting lamp 74 and the LED 52 are always lit and turned on. The light wraparound may be suppressed by reducing the amount of light. In the present embodiment, the lighting control of the illumination lamp 74 and the LED 52 is made different between the plain paper and the tracing paper. However, whether or not the illumination lamp 74 and the LED 52 need to be turned off is determined by the illumination lamp. 74 and the lighting amount of the LED 52 are different. That is, the illumination lamp 74 and the LED 52 are turned off even when a tracing paper document is used, or the illumination lamp 74 and the LED 52 are kept on even when a plain paper document is used. It is possible to do. Further, in the present 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.

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. It is a flowchart for demonstrating lighting control of an illumination lamp and LED in the case of reading the double-sided image of the document which has predetermined | prescribed thickness. (a)-(c) is a figure for demonstrating the conveyance state of a document, and the reading of a document in the case of reading the double-sided image of the document which has predetermined | prescribed thickness. (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. 6 is a flowchart for explaining lighting lamp and LED lighting control when reading a double-sided image of a thin original. (a)-(c) is a figure for demonstrating the conveyance state of an original in the case of reading the double-sided image of a thin original, and the reading of an original.

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, 110 ... A integrated circuit (ASIC-A), 130 ... B integrated circuit (ASIC-B), 200 ... second image processing circuit, 210 ... C integrated circuit (ASIC-C)

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;
A first light source that irradiates the first surface of the document from one side of the conveyance path; and a first sensor that receives reflected light reflected from the first surface of the document, the first surface of the document A first reading unit for reading the image data;
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 reflected from the second surface of the document, and the first reading unit. A second reading unit that reads image data of the second surface of the document on the downstream side in the transport direction of the document,
An image reading apparatus including: a lighting control unit that controls lighting of the first light source and / or the second light source based on a position of the document in the conveyance direction.   2. The image reading apparatus according to claim 1, wherein the lighting control unit turns off the first light source after a trailing end of the document in the conveyance direction passes a reading position by the first sensor.   2. The image reading apparatus according to claim 1, wherein the lighting control unit lights the second light source after a leading end of the document in the conveyance direction passes a reading position by the first sensor. 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;
A first light source that irradiates the first surface of the document from one side of the conveyance path and a first sensor that receives reflected light from the first surface of the document; A first reading unit for reading image data;
A second light source that irradiates the second surface of the document from the other side of the transport path and a second sensor that receives reflected light from the second surface of the document; A second reading unit that reads image data of the second surface of the document on the downstream side in the transport direction of the document;
An image reading apparatus including a lighting control unit that controls lighting of the first light source in anticipation of a light amount that travels from the first light source to the second sensor.   When the thickness of the document is equal to or greater than a predetermined thickness, the lighting control unit determines whether the trailing end of the document in the transport direction is from before the leading end of the document in the transport direction reaches the reading position by the first sensor. The image reading apparatus according to claim 4, wherein the first light source is turned on until the first sensor passes through a reading position.   When the thickness of the document is thinner than a predetermined thickness, the lighting control unit is configured such that the trailing end of the document in the transport direction is before the leading end of the document in the transport direction reaches the reading position by the first sensor. 5. The image reading apparatus according to claim 4, wherein the first light source is turned on until the second sensor passes the reading position. 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;
A first light source that irradiates the first surface of the document from one side of the conveyance path and a first sensor that receives reflected light from the first surface of the document; A first reading unit for reading image data;
A second light source that irradiates the second surface of the document from the other side of the transport path and a second sensor that receives reflected light from the second surface of the document; A second reading unit that reads image data of the second surface of the document on the downstream side in the transport direction of the document;
An image reading apparatus including a lighting control unit that controls lighting of the second light source in anticipation of the amount of light that travels from the second light source to the first sensor.   When the thickness of the document is equal to or greater than a predetermined thickness, the lighting control unit detects whether the trailing end of the document in the transport direction is before the leading end of the document in the transport direction reaches the reading position by the second sensor. The image reading apparatus according to claim 7, wherein the second light source is turned on until the second sensor passes a reading position.   When the thickness of the document is thinner than a predetermined thickness, the lighting control unit is configured such that the trailing end of the document in the transport direction is before the leading end of the document in the transport direction reaches the reading position by the first sensor. The image reading apparatus according to claim 7, wherein the second light source is turned on until the second sensor passes the reading position. 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;
A first light source that irradiates the first surface of the document from one side of the conveyance path; and a first sensor that receives reflected light reflected from the first surface of the document, the first surface of the document A first reading unit for reading the image data;
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 reflected from the second surface of the document, and the first reading unit. A second reading unit that reads image data of the second surface of the document on the downstream side in the transport direction of the document,
The first light source is turned on when the image reading of the first surface of the document by the first reading unit is completed and the image of the second surface of the document is read by the second reading unit. An image reading apparatus including a lighting control unit that turns off.   The lighting control unit is configured to read an image of the first side of the document by the first reading unit and not to read an image of the second side of the document by the second reading unit. The image reading apparatus according to claim 10, wherein the second light source is turned off.   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.

Images