JP3654530B2 - Double-sided document reader and image forming apparatus - Google Patents

Description

  The present invention relates to a double-sided document reading device used for, for example, a scanner device, a copying machine, a printer, a facsimile device, and the like, and an image forming apparatus equipped with the double-sided document reading device. In particular, the present invention relates to a measure for appropriately obtaining a read density of read data.

  Conventionally, for example, Patent Document 1 and Patent Document 2 described below disclose a double-sided document reading device having a function of reading images and characters on both sides of a document by reading means arranged on both sides of the document conveyance path.

  Specifically, in Patent Document 1, reading means having a light source for irradiating each surface of a document is disposed on the front side and the back side of the read document, and the light source on the front side and the light source on the back side are turned on. Disclosed is a technical idea for avoiding optical interference by alternately switching off and on the scanning line unit and switching the reading of the front and back sides of the document alternately in conjunction with the turning on and off of the light source. Yes. That is, it is possible to prevent the show-through from occurring in the read data of the original by the other reading unit due to the light source of one reading unit.

On the other hand, in Patent Document 2, each reading unit is shifted to a position that does not face each other so that irradiation emitted from the light source of the reading unit that reads the document surface and irradiation emitted from the light source of the reading unit that reads the document back surface do not interfere with each other A technical idea for avoiding optical interference is disclosed.
JP 9-321947 A Japanese Patent Laid-Open No. 10-98588

  By the way, the technique described in Patent Document 1 controls the turning on and off of both light sources so that only one of the two light sources is turned on for each scanning line. It must be very high. As a result, there is a restriction that a light source with low responsiveness cannot be used. Further, when an attempt is made to increase the document conveyance speed in order to increase the number of originals read per unit time, a light source having a higher response is required, resulting in an increase in cost. Furthermore, since the response of the light source is limited, the document reading speed is limited by the response of the light source, and there is a limit to increasing the document reading speed.

  The technique described in Patent Document 2 can avoid the problem of Patent Document 1 by displacing the positions of the document reading means arranged on both sides of the document transport path in the document transport direction. By the way, in the technique described in Patent Document 2, when the reading of one side of the original is completed, the light source of the original reading means that read the preceding one side is turned off, and the other side is delayed by the amount of displacement. After the reading is completed, the light source of the document reading means that has read the other side is turned off. When the two document reading means are brought close to each other in order to reduce the size of the apparatus (when the displacement is reduced), the light from the light source of one document reading means may be incident on the other document reading means. At this time, the light source on the side where the reading has been completed in advance is turned off even though the reading on the other surface side is not completed, and the density of the other reading data becomes the change of the light quantity. It will be affected. That is, there is a problem that the reading density changes at a position where the amount of light is displaced, and accurate original reading data cannot be obtained.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a double-sided document reading apparatus in which document reading means are provided on both sides of a document transport path to simultaneously read images on both sides of a document. An object of the present invention is to uniformly obtain the reading density of the original reading data over the entire data.

-Summary of invention-
In order to achieve the above object, according to the present invention, the amount of light irradiating each side of the document is kept unchanged and the reading density does not change until the reading operation on both the front and back sides of the document is completely completed. I have to.

-Solution-
Specifically, the one surface of the document is irradiated with light from the first light source and the other surface of the document is irradiated with light from the second light source, whereby the one surface and the other surface of the document are irradiated. A double-sided document reading device that reads images on both sides of this side is assumed. With respect to the double-sided document reading device, a first reading unit that is disposed in a region for reading the one side of the document and that includes the first light source and reads an image of the one side of the document, A second reading unit that is arranged in a region for reading the other surface and includes the second light source and reads an image on the other surface of the document. In addition, the first light source and the second light source are separate light sources, and the first light source has a light amount larger than that of the second light source. After the light source of the reading unit located on the downstream side in the document conveyance direction and the light source of the reading unit located on the upstream side in the document conveyance direction among the first reading unit and the second reading unit are driven to light And is lit before the reading of the document image by the reading unit located upstream in the document conveyance direction, and is further downstream in the document conveyance direction among the first reading unit and the second reading unit. The first light source and the second light source are turned off after reading of the conveyed document by the reading unit located is completed.
Other solutions are listed below. By irradiating light from the first light source to one surface of the document being conveyed and irradiating light from the second light source to the other surface of the document, both surfaces of the one surface and the other surface of the document are A double-sided document reading device that reads an image is assumed. A first reading unit that is disposed in an area for reading the one side of the original and reads the image of the one side of the original with the first light source, and A second reading unit that is arranged in a region for reading the other surface and includes the second light source and reads an image on the other surface of the document. In addition, a document detection sensor is provided for detecting the document to be conveyed further upstream of the reading unit located upstream of the document conveyance direction in the first reading unit and the second reading unit. Further, the first light source and the second light source are formed as separate light sources, and the first light source has a light amount larger than that of the second light source. Then, after the original is detected by the original detection sensor, the light source of the reading unit located on the upstream side in the original conveying direction among the first reading unit and the second reading unit is turned on, and then the original conveying direction Before starting the reading of the document image by the reading unit positioned on the upstream side, the light source of the reading unit positioned on the downstream side in the document transport direction is driven to the lighting state, and the first reading unit and the second reading unit Of these, the first light source and the second light source are turned off after the reading of the conveyed document by the reading unit located downstream in the document conveying direction is completed.

  Due to this specific matter, light is emitted from each light source toward the front and back surfaces of the document traveling on the document conveyance path, and for example, by reading the reflected light, the images on the front and back surfaces of the document are read by each document reading unit. In the present invention, the first light source and the second light source are turned off after the reading of the document is completed by the reading unit located on the downstream side in the document transport direction. For this reason, there is no change in the amount of received light in the downstream document reading section during the reading operation, and it is avoided that the reading density changes.

  The following configuration is listed as an addition to the above solution. First, the first reading unit is configured to read an image of the one side of the traveling document to be conveyed and an image of one side of the placed stationary document. Further, the second light source is a light emitting diode.

  In addition, an image forming apparatus equipped with any one of the above-described solving means and a double-sided document reading apparatus is also within the scope of the technical idea of the present invention.

  As described above, according to the present invention, both reading operations on both the front and back sides of a document are completely completed with respect to a double-sided document reading apparatus that reads a document image while irradiating light from a light source on the front and back sides of the document. Until then, the lighting state of the light applied to each side of the document is maintained. For this reason, the amount of received light does not change during the reading operation of the original image in each original reading unit, and the reading density does not change, and the reading density of the original reading data is made uniform over the entire read data. Thus, accurate image data can be acquired, and the reliability of the apparatus can be improved. In addition, this makes it possible to bring the positions of the light sources close to each other without causing deterioration of the image data, so that the entire apparatus can be reduced in size.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a case where the present invention is applied as a scanner device will be described.

  First, a schematic configuration of the scanner device 1 will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing an internal configuration of a scanner device 1 according to this embodiment. FIG. 2 is a control block diagram of the scanner apparatus 1.

  As shown in FIG. 1, the scanner device 1 includes a stationary document reading unit 2, a first traveling document reading unit 3, and a second traveling document reading unit 4. The stationary document reading unit 2 reads an image of a document (stationary document) that is not subject to automatic feeding, such as a book document or a pasted document manually placed on the first contact glass 21 made of transparent glass by the user. This is the reading area. The first traveling document reading unit 3 and the second traveling document reading unit 4 are reading areas for reading an image of a document in a traveling state that is automatically fed onto the second contact glass 31 made of transparent glass. is there. The first running document reading unit 3 reads an image on the front side of the document (the surface facing downward in FIG. 1), and the second running document reading unit 4 reads the image on the back side (the side facing upward in FIG. 1). It is supposed to be. The document image data read by the reading units 2, 3, and 4 is sent to a first image processing unit 56 and a second image processing unit 57, respectively, which will be described later (see FIG. 2), where various processes are performed. After that, the image data is stored in the image memory 55 via the image processing relay unit 54. The image data transmission / reception operation will be described later.

  Hereinafter, the configuration of the scanner apparatus 1 will be described in detail with reference to FIGS. FIG. 3 is a cross-sectional view showing the main part of the scanner device 1.

  As shown in FIGS. 1 to 3, the scanner device 1 includes a main body portion 11 and an opening portion 12, and can perform two-mode document reading operations of a single-sided reading mode and a double-sided reading mode. On the upper surface of the main body 11, a first contact glass 21, a document reference plate 13, and a second contact glass 31 are disposed in order from the right side of FIGS. 1 and 3.

  The original reference plate 13 is printed with an index (not shown) indicating the size and placement direction of the original so that the original can be easily placed on the stationary original reading portion on the first contact glass 21 according to the index. It has become. Further, on the side of the document reference plate 13 facing the first contact glass 21, the first photoelectric conversion element 68 of the first reading scanning system 6, which will be described later, is used for shading (determining the white level). A one-reference white plate 14 is provided.

  Inside the main body 11, a first scanning unit 63, a second mirror 64, and a third mirror 65 that integrally support a first light source 61 and a first mirror 62 for irradiating a document with light are integrated. A first reading scanning system 6 comprising a second scanning unit 66, a first imaging lens 67, and a first photoelectric conversion element (CCD) 68, which are supported in a general manner, is arranged. The first scanning unit 63 and the second scanning unit 66 are wound with a wire (not shown) and are driven by a first reading scanning system driving motor 69 (see FIG. 2) which is a stepping motor. Each scanning unit 63, 66 moves to the right in FIG. 1 when the first reading scanning system drive motor 69 rotates forward, and when the first reading scanning system drive motor 69 rotates in reverse in FIG. Move to the left. Specifically, the second scanning unit 66 moves in the same direction as the first scanning unit 63 at a half speed with respect to the first scanning unit 63.

  The first reading scanning system 6 as document reading means is used both when reading a stationary document and when reading a traveling document. At the time of reading a stationary document, the first scanning unit 63 of the first scanning system 6 moves from the position pos1 in FIG. 1 to the position pos2, and performs scanning for scanning on the document stationary on the first contact glass 21. At the time of reading the traveling document, the first scanning unit 63 of the first reading scanning system 6 is stopped at the position pos1 in FIG.

  The first scanning unit 63 irradiates light from the first light source 61 toward the document (toward the irradiation area in the present invention) while performing scanning scanning, and reflects the reflected light from the document to the first. The light is reflected toward the second mirror 64 of the second scanning unit 66 through the first mirror 62. The second scanning unit 66 reflects the reflected light from the first mirror 62 toward the first imaging lens 67 via the second mirror 64 and the third mirror 65. The first imaging lens 67 images the reflected light from the third mirror 65 on the light receiving surface of the first photoelectric conversion element 68. The first photoelectric conversion element 68 converts it into an electrical image signal according to the intensity of the received light and outputs it.

  As shown in FIG. 2, the control system of the scanner device 1 includes a system controller 51, a communication control unit 52, a reading control unit 53 that receives a signal from the operation unit 1A of the device 1, and the image processing relay unit. 54, an image memory 55, a first image processing unit 56, and a second image processing unit 57 are provided.

  The system controller 51 controls the reading control unit 53 via the communication control unit 52, and further controls the image processing relay unit 54 and the image memory 55 via the system bus B so that a series of document reading operations can be appropriately performed. The entire image reading system is controlled so as to be performed.

  As shown in FIG. 2, the first light source substrate 71 turns on or off the first light source 61 of the first reading scanning system 6 based on a signal from the reading control unit 53.

  The first reading scanning system driving motor control board 72 controls the first reading scanning system driving motor 69 on the basis of the signal from the reading control unit 53, and displays the first scanning unit 63 and the second scanning unit 66. 1 Move to the middle right or left.

  The first reading scanning system position sensor group 73 is disposed in the vicinity of the position where the first scanning unit 63 faces the first traveling document reading unit 3 and the position where the first reference white plate 14 can be read. When 63 comes to this position, a reference position signal is output to the reading control unit 53.

  The reading control unit 53 calculates the position of the first scanning unit 63 based on the reference position signal of the first reading scanning system position sensor group 73 and the number of steps of the first reading scanning system drive motor 69, and performs the first reading. The first scanning unit 63 and the second scanning unit 66 are reciprocated by forward / reversely controlling the scanning system drive motor 69.

  Next, as shown in FIG. 1, the opening portion 12 of the scanner device 1 rotates a hinge (not shown) provided between the scanner device 1 and the main body portion 11 on the back side (right side in FIG. 1). It is configured to rotate upward as a moving fulcrum and to open the front side (left side in FIG. 1) of the scanner device 1. An OC mat 15 having a first contact glass 21 side formed in white is provided below the opening 12 of the scanner device 1 so as to come into contact with the first contact glass 21 when the opening 12 is closed. A sheet-like document placed on the stationary document reading unit 2 is configured to be pressed against the first contact glass 21 by the OC mat 15 to be in close contact therewith.

  As shown in FIGS. 1 and 3, the document is transported and discharged from the document set tray 16 on which the document is set to the first traveling document reading unit 3 and the second traveling document reading unit 4 in the opening portion 12. An automatic document feeder 9 for discharging documents on the tray 17 is arranged. Further, a second reading scanning system 8 as a document reading means is provided on the left side in the opening portion 12 so that a document traveling on the second traveling document reading unit 4 can be read and scanned.

  As shown in FIG. 3, the automatic document feeder 9 includes a carry-in path pas1 between the paper feed unit 91 and the separation feed unit 92, a carry-in path pas2 between the separation feed unit 92 and the alignment roller pair 93, A document reading conveyance path pas3 provided between the alignment roller pair 93 and the paper discharge roller pair 94 and having the first traveling document reading unit 3 and the second traveling document reading unit 4 disposed therein is provided. These transport paths pas1 to pas3 constitute a document transport path. Hereinafter, the configuration and operation of each part of the automatic document feeder 9 will be described.

  The paper feed unit 91 includes a document presser 91 a and a paper feed roller 91 b, and conveys the document set on the document set tray 16 to the separation feeding unit 92.

  The separation feeding unit 92 includes a separation feeding roller 92a and a separation pad 92b. The original fed from the paper feeding unit 91 is called into the separation feeding unit 92 and separated one by one to align the pair of matching rollers. Transport toward 93. The separation feeding unit 92 includes an electromagnetic clutch (not shown) on the drive shaft of the separation feeding roller 92a, and transmits a driving force from a driving motor (not shown) of the automatic document feeder 9. Can be switched between connection and non-connection.

  The alignment roller pair 93 includes an electromagnetic clutch (not shown) on its drive shaft, and can be switched between connection and non-connection with respect to a drive system that transmits a drive force from a drive motor of the automatic document feeder 9. ing. The alignment roller pair 93 is stopped until the leading edge of the document fed by the separation feeding unit 92 comes into contact with the document detection sensor s2 and outputs a signal to the reading control unit 53. After the output, the conveyance is started toward the downstream side.

  The second contact glass 31 forms an original reading conveyance path pas3 with the alignment roller pair 93, and is positioned at a position facing the second reference white plate 81 arranged on the lower surface of the second contact glass 31. A traveling document reading unit 4 is arranged.

  The discharge roller pair 94 is provided integrally and rotatably on the open side surface of the scanner device 1, and discharges the document that has passed through the document reading conveyance path pas 3 to the discharge tray 17.

  Further, document detection sensors s 1, s 2, and s 3 as position detecting means are respectively arranged immediately before the conveyance direction of the paper feed unit 91, immediately before the conveyance direction of the alignment roller pair 93, and immediately downstream in the conveyance direction of the discharge roller pair 94. Yes. As shown in FIG. 2, these document detection sensor groups s1, s2, and s3 are used to transmit the position of the document to the reading control unit 53 to control the conveyance of the document and the on / off of the light source.

  Next, the operation of each part of the automatic document feeder 9 will be described with reference to the block diagram of FIG.

  As shown in FIG. 2, the drive motor control board 95 of the automatic document feeder 9 controls on / off of a drive motor 96 that is a stepping motor in accordance with a signal from the reading control unit 53, thereby controlling the drive system of the automatic document feeder 9. It is configured to be able to drive and transmit a driving force to the above-described paper feed roller 91b, separation and feeding means 92, alignment roller pair 93, paper discharge roller pair 94, and other transport rollers. The rotation speed of the drive motor 96 is variable by the pulse rate from the drive motor control board 95.

  The document detection sensor groups s1, s2, and s3 transmit a document detection signal to the reading control unit 53 when the document reaches the sensor position. On the other hand, the reading control unit 53 calculates whether or not the document is conveyed at an appropriate timing based on the document detection signals from the document detection sensor groups s1, s2, and s3 and a timer, and the conveyance failure. In this case, a signal indicating the occurrence of a jam is transmitted to the system controller 51 via the system bus B.

  The electromagnetic clutch group 97 is turned on / off in response to a signal from the reading control unit 53, and is switched between connected and disconnected with respect to each drive system of the automatic document feeder 9, and the drive system is stopped or rotated. To do.

  Next, the second reading scanning system 8 will be described. As shown in FIG. 3, the second reading scanning system 8 is disposed inside the opening portion 12 of the scanner device 1, and reads for reading a document traveling on the second traveling document reading unit 4 in a traveling state. Scanning system. The second reading scanning system 8 converts a second light source (LED) 82 for irradiating the upper surface of the document traveling on the second traveling document reading unit 4 and an electrical image signal according to the intensity of the received light. When the second photoelectric conversion element (CIS) 83 to be converted and output and the electrical image signal output from the second photoelectric conversion element 83 is shaded (determination of the white portion level), the white portion And a second reference white plate 81 for reading as a level. The second reference white plate 81 is provided in the main body 11 of the scanner device 1. The second traveling document reading unit 4, which is a region where the second light source 82 emits light toward the document, is a first traveling document reading unit, which is a region where the first light source 61 emits light toward the document. 3 is set on the downstream side in the document transport direction with respect to 3. In this way, by shifting the irradiation area of the light from each of the light sources 61 and 82 in the document transport direction, so-called show-through in which the image data of the non-facing surface enters as document image data acquired by each of the scanning scanning systems 6 and 8. It is possible to prevent.

  As shown in FIG. 2, the second light source substrate 74 turns on or off the second light source 82 of the second reading scanning system 8 based on a signal from the reading control unit 53.

  The reading control unit 53 performs shading on the electrical image signal output from the second photoelectric conversion element 83 in the double-sided reading mode.

  Next, processing of an electrical image signal obtained by reading scanning in the single-sided reading mode and the double-sided reading mode will be described with reference to FIGS.

  As shown in FIG. 2, an electrical image signal (hereinafter referred to as an image signal) obtained by reading scanning by the first photoelectric conversion element 68 of the first reading scanning system 6 and the second photoelectric conversion element 83 of the second reading scanning system 8. Is sent to the image processing units 56 and 57, subjected to predetermined image processing, then sent to the image processing relay unit 54, and further subjected to predetermined image processing, and then the system bus B Are stored in the image memory 55 by being distinguished for each page. The image processing units 56 and 57 include analog signal processing units 56a and 57a, A / D conversion units 56b and 57b, shading correction units 56c and 57c, filter processing units 56d and 57d, and density conversion units 56e and 57e. . These elements of the image processing units 56 and 57 operate under the control of the reading control unit 53.

  The analog signal processing units 56a and 57a perform level conversion processing, sample hold processing, and signal amplification processing on the image signal input from the first photoelectric conversion element 68 and the image signal input from the second photoelectric conversion element 83, respectively. And output to the A / D converters 56b and 57b. Since the first reading scanning system 6 and the second reading scanning system 8 are different in light source light amount, photoelectric conversion efficiency, output signal level, etc., dedicated analog signals for the first photoelectric conversion element and the second photoelectric conversion element, respectively. Processing units 56a and 57a are provided.

  The A / D conversion units 56b and 57b digitally convert the analog image signals input from the analog signal processing units 56a and 57a, and output the quantized image signals to the shading correction units 56c and 57c.

  The shading correction units 56c and 57c perform black reproduction and white reproduction on the quantized image signals input from the A / D conversion units 56b and 57b, and output them to the filter processing units 56d and 57d. Note that black reproduction means sampling the implicit output of the first photoelectric conversion element 68 or the second photoelectric conversion element 83 and storing it, and reading the first photoelectric conversion element 68 or the second photoelectric conversion at the time of reading a document as read data. The effect of the implied output is eliminated by subtracting from the image signal output from the element 83. White reproduction refers to normalizing an image signal at the time of reading a document to each pixel based on an image signal for each pixel when the reference white plates 14 and 81 having a uniform reflectance are read, and the influence of unevenness in light quantity or influence of optical parts. And correcting variations in pixel sensitivity of the first photoelectric conversion element 68 and the second photoelectric conversion element 83.

  The filter processing units 56d and 57d perform predetermined filter processing on the image signals input from the shading correction units 56c and 57c based on a coefficient that determines the filter characteristics set by the reading control unit 53, specifically, By applying a spatial filtering process, high-frequency components of the image are emphasized, and “blurring” of the image is repaired. That is, the image signals output from the first photoelectric conversion element 68 and the second photoelectric conversion element 83 include optical components such as lenses and mirrors, and aperture openings on the light receiving surfaces of the first photoelectric conversion element 68 and the second photoelectric conversion element 83. There is a deterioration in MTF (Modu1ation Transfer Function) due to transfer efficiency and afterimages of the first photoelectric conversion element 68 and the second photoelectric conversion element 83, integration effects due to physical scanning, operation irregularities, and the like, and the filter processing unit 56d. 57d compensates for this MTF degradation. As described above, since the deterioration degree of the MTF varies greatly depending on the first photoelectric conversion element 68 and the second photoelectric conversion element 83, appropriate filter processing is performed. Further, since the degradation of the MTF is more remarkable in the high frequency range, the filter processing units 56d and 57d perform “enhancement processing” on the image signal in the high frequency range to repair “blurring” and improve the image quality. It is improving.

  Therefore, the filter processing units 56d and 57d differ in filter processing depending on whether the input image signal is an image signal from the first photoelectric conversion element 68 or an image signal from the second photoelectric conversion element 83.

  The density conversion units 56e and 57e (density conversion means and binarization means) are for performing density conversion on the image signals filtered by the filter processing units 56d and 57d. For example, the image signals are transmitted by facsimile. If the printing condition is specified or binarization is specified, the image signal is binarized. If the printing condition is multi-valued, such as a photographic image, the density conversion is performed by a predetermined density characteristic. , Improving image quality. The density conversion units 56e and 57e include a RAM control unit (not shown), a RAM, and the like (not shown), and read out a data conversion look-up table set in the RAM as an address of the input image signal. Data conversion is performed to perform density conversion processing. The image signal for which the density conversion process has been completed is stored in the image memory.

  The above is the processing operation of the image signal obtained by the first photoelectric conversion element 68 and the second photoelectric conversion element 83 by the image processing units 56 and 57.

  Next, regarding the operations of the first reading scanning system 6 and the second reading scanning 8, the operation of the automatic document feeder 9, and the operations of the first light source 61 and the second light source 82 in the duplex reading mode, FIGS. Will be described below.

  As shown in FIG. 1, in the double-sided scanning mode, the first scanning unit 63 of the first scanning system 6 moves to the position pos1 in FIG. 1 and stops. The surface on the side of the contact glass (the lower surface in the figure) of the document traveling 3 is irradiated and scanned by the first light source 61. Further, the second reading scanning system 8 performs scanning by irradiating the upper surface of the document traveling on the second traveling document reading unit 4 with the second light source 82.

  FIG. 4 is a flowchart of the double-sided document reading process showing the embodiment of the present invention. As shown in this figure, when the double-sided document reading process is started, first, timers T1 to T7 are set in step ST1, and then, in step ST2, the separation feeding roller 92a and the feeding roller 91b operate. Start and feed paper. Then, after the original detection sensor s2 detects the original (determined as YES in step ST3), timers T1 to T5 are started (step ST4). Here, T1 is the time from the document detection of the document detection sensor s2 (YES determination in step ST5) to the alignment (operation to temporarily stop the document by the alignment roller pair 93 and cancel the oblique feeding state), When the timer T1 expires, the separation feeding roller 92a and the sheet feeding roller 91b are stopped, the sheet feeding operation is terminated, and the process returns to (1) (step ST6). T2 is the time required from the detection of the document by the document detection sensor s2 until the light sources 61 and 82 are turned on. T3 is the time from the original detection of the original detection sensor s2 to the start of the operation of the alignment roller pair 93. Details of these will be described later. T4 and T5 are times from when the original detection sensor s2 detects the original to when the original reaches the first traveling original reading unit 3 and the second traveling original reading unit 4, respectively. First reading of the front surface image of the document in the traveling document reading unit 3 and second scanning (reading of the back image of the document in the second traveling document reading unit 4) are started and the process returns to (1) (steps ST9 and ST10). .

  When the document trailing edge passes through the document detection sensor s2 and the document detection sensor s2 is turned off, timers T6 and T7 are started (step ST11). The timer T6 is the time from when the trailing edge of the document passes the document detection sensor s2 until it passes the alignment roller pair 93, and stops the alignment roller pair 93 after the passage (steps ST12 and ST13). T7 is the time from when the trailing edge of the document passes through the document detection sensor s2 to when it passes through the second traveling document reading unit 4, and the reading ends after the passage (steps ST14, 15, 16). When the document detection sensor s1 is turned on after the time T6 is up and the presence of the next document is confirmed, the next document feeding operation is started, and the document detection sensor s2 detects the document, and then the timer T1. -T5 starts (steps ST19-21). Thereafter, when T7 times out, the reading is finished and the process returns to (1) (steps ST22 and 23). If it is determined that the original detection sensor s1 is not turned on and there is no next original, the reading is completed and both light sources 61 and 82 are turned off after the time T7 expires (step ST17), and the discharge of the original is completed. The duplex original reading process is terminated (step ST18). Because of such an operation, the maintaining means 18 is configured in the above-described steps ST15 to ST17.

  In the above description, the case where both the light sources 61 and 82 are turned on after the time T2 after the document detection sensor s2 detects the document has been described, but the lighting timing of the light sources 61 and 82 may be set as follows.

  FIG. 5 is a schematic diagram of a portion related to document conveyance and reading of a traveling document, and FIG. 6 is a graph showing the relationship between the time after the first light source 61 and the second light source 82 are turned on and the amount of light.

  As shown in FIG. 2, the scanner device 1 includes a distance from a document traveling position to a first traveling document reading unit (irradiation region) 3 that is an area for reading an image by the first reading scanning system 6, a document traveling speed, Thus, a lighting means 19 is provided for calculating the time when the document reaches the first traveling document reading unit 3 and setting the lighting timing of the first light source 61 based on the calculation result.

  That is, the document transport distance from the alignment roller pair 93 to the center A of the first traveling document reading unit 3 is L and the document transport speed is V as shown in FIG. When the time until the light quantity is stabilized is t1, the time during which the document is conveyed from the alignment roller pair 93 to the first traveling document reading unit center A is L / V. Here, if t1 <L / V, the lighting means 19 turns on the first light source 61 after the alignment roller pair 93 has been activated (L / V-t1), and t1> If it is L / V, after the original reaches the alignment roller pair 93, the alignment roller pair 93 is activated after the first light source 61 has been activated (t1-L / V) to convey the original. Each part is controlled.

  At this time, the second light source 82 is composed of LEDs, and the time until the light quantity is stabilized is sufficiently short, t2 in the figure, so that the lighting timing of the second light source 82 is the same as that of the first light source 61 with a slow response. . Alternatively, the second light source 82 may be turned on while the document reaches the center A of the first traveling document reading unit 3.

  Note that the lighting timing of the second light source 82 may be set similarly to the lighting timing of the first light source 61 described above.

-Effect of the embodiment-
As described above, in this embodiment, both reading scans are performed until the timer T7, which is the time from when the trailing edge of the document passes the document detection sensor s2 to when it passes the second traveling document reading unit 4, is up. The light sources 61 and 82 of the systems 6 and 8 are maintained at a predetermined light amount. That is, the amount of light applied to each surface is kept constant until both reading operations on the front and back surfaces of the document are completely completed. For this reason, while suppressing the show-through by displacing the positions of the reading scanning systems 6 and 8 arranged on both sides of the document conveying path in the document conveying direction, the other reading scanning due to the change in the light amount of one reading scanning system. It is possible to avoid a change in the reading density of the system, and it is possible to make the reading density of the original reading data uniform over the entire data.

  Further, in the present embodiment, by calculating the lighting timing of both the light sources 61 and 82 and the document conveyance timing, the time during which the light sources 61 and 82 are lit can be shortened and energy saving can be improved.

  Furthermore, in the present embodiment, for example, when the apparatus is downsized, it is possible to cope with the above-described change in the document conveyance timing and the lighting timings of the two light sources 61 and 82 even if L is reduced.

-Other embodiments-
In the above embodiment, the case where the present invention is applied as a scanner device has been described. The present invention is not limited to this, and can also be applied to a double-sided document reading unit of an image forming apparatus such as a copying machine, a printer, or a facsimile machine.

  In the above-described embodiment, the first traveling document reading unit 3 is disposed upstream of the second traveling document reading unit 4 in the transport direction. Conversely, the second traveling document reading unit 4 is arranged in the first direction. You may make it arrange | position to the conveyance direction upstream rather than the driving | running | working original reading part 3. FIG.

It is the schematic which shows the internal structure of the scanner apparatus which concerns on embodiment. It is a control block diagram of a scanner device. It is sectional drawing which shows the principal part of a scanner apparatus. FIG. 10 is a flowchart showing a double-sided document reading process operation. It is a figure which shows the outline of each driving | running | working original reading part. It is a figure which shows the light quantity change at the time of the lighting start of each light source.

Explanation of symbols

1 Scanner device (double-sided document reader)
3 First traveling document reading unit (first reading unit)
4 Second traveling document reading unit (second reading unit)
61 First light source 82 Second light source

Claims (5)

By irradiating light from the first light source to one surface of the document being conveyed and irradiating light from the second light source to the other surface of the document, both surfaces of the one surface and the other surface of the document are In a double-sided document reading device that reads an image,
A first reading unit arranged in a region for reading the one side of the original and reading the image of the one side of the original with the first light source;
A second reading unit that is disposed in a region for reading the other side of the document and that includes the second light source and reads an image of the other side of the document;
The first light source and the second light source are separate light sources, and the first light source has a light amount larger than that of the second light source,
Among the first reading unit and the second reading unit, after the light source of the reading unit located on the downstream side in the document conveyance direction is driven to the lighting state, And before being started to read the original image by the reading unit located on the upstream side in the original conveying direction, it is driven to a lighting state,
Of the first reading unit and the second reading unit, after the reading of the conveyed document by the reading unit located downstream in the document conveying direction is completed, the first light source and the second light source are turned off. Characteristic double-sided document reader. By irradiating light from the first light source on one surface of the conveyed document and irradiating light from the second light source on the other surface of the document, both surfaces of the one surface and the other surface of the document are In a double-sided document reading device that reads an image,
A first reading unit arranged in a region for reading the one side of the original and reading the image of the one side of the original with the first light source;
A second reading unit arranged in a region for reading the other side of the document and having the second light source to read an image of the other side of the document;
A document detection sensor for detecting the conveyed document on the upstream side in the document conveyance direction of the reading unit located on the upstream side in the document conveyance direction among the first reading unit and the second reading unit;
The first light source and the second light source are separate light sources, and the first light source has a light amount larger than that of the second light source,
After the document is detected by the document detection sensor, the light source of the reading unit located on the upstream side in the document transport direction among the first reading unit and the second reading unit is turned on, and then the upstream side in the document transport direction Before starting the reading of the original image by the reading unit located in the reading unit, the light source of the reading unit located downstream in the document conveying direction is driven to a lighting state,
Of the first reading unit and the second reading unit, after the reading of the conveyed document by the reading unit located downstream in the document conveying direction is completed, the first light source and the second light source are turned off. Characteristic double-sided document reader. The double-sided document reading device according to claim 1 or 2,
The double-sided document reading apparatus, wherein the first reading unit reads an image of the one side of the transported traveling document and an image of one side of the placed stationary document. In the double-sided document reading device according to claim 1, 2, or 3,
A double-sided document reading apparatus, wherein the second light source is formed of a light emitting diode.   An image forming apparatus comprising the double-sided document reading device according to any one of claims 1 to 4.

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