JP5381656B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus capable of reading both sides of a document.

2. Description of the Related Art Conventionally, in an image reading apparatus such as a copying machine or a facsimile provided with an automatic document feeder (ADF), as disclosed in Patent Document 1, a paper feed tray on which a document before reading is placed, and a reading There is a paper discharge tray on which a subsequent document is placed, and reading devices for reading the front side and the back side of the document are provided at different positions on the transport path in the transport path where the document is transported from the paper feed tray. A technique for reading both sides of a document almost simultaneously with a single document transport is widely known.

  In this ADF, sensors for detecting the leading edge of the document are arranged in front of the reading positions of both reading devices. The time required for the document to be conveyed from the position of each sensor to the reading position of each reading device is determined in advance, and from the time when the time has elapsed since each sensor detected the leading edge of the document. Each reading device uses the read signal read as image data.

JP 2009-88692 A

  However, as in the image reading apparatus of Patent Document 1, it is necessary to provide document sensors for detecting the leading edge of a document during conveyance of the document for both the front side and the back side. There was a problem of cost.

For example, in order to solve the above problem, a case where one sensor is provided on the upstream side of the conveyance path from the position of each reading device may be considered. In this case, the time required for the document to be conveyed from the position of the sensor to the reading position of the reading device on the front side and the time required for the document to be conveyed from the position of the sensor to the reading position of the reading device on the back side calculated in advance, respectively and. Then, it can be considered that whether or not the reading position of the reading device has been reached is determined from the time required for the document to be conveyed to the reading position of each reading device, and reading is started when the reading position is reached.

However, as in the image reading apparatus of Patent Document 1, when the reading device provided for reading each of the front side and the back side is arranged along the conveyance path, between the reading devices The distance along the conveyance path is inevitably increased. Then, there is a possibility that the document is bent in the conveyance path between the both reading devices. Therefore, Ri if predetermined document from had sensor to the reading position of the reading device is different from the time period required to be conveyed is determined in advance is Oh, can not correct the image reading.

  The present invention has been completed based on the above-described circumstances, and the document has arrived at each reading device that reads the front side and the back side of the document provided at different positions on the conveyance path. An object of the present invention is to provide an image reading apparatus capable of reducing the cost without providing a sensor for detecting the above.

  In order to achieve the above object, an image reading apparatus according to a first aspect of the present invention is an image reading apparatus that reads both sides of a document, and transports a transport path for transporting the document and a document on the transport path. A driving unit that drives a conveyance roller, a first image reading unit that reads an image from one side facing the conveyance path, and a conveyance direction of the original more than a position where the first image reading unit is provided A second image reading unit that is provided at a position downstream of the first image reading unit and reads an image from the other side facing the conveyance path, and is located upstream of the first image reading unit in the document conveyance direction, A sensor for detecting the original, and the first image reading unit starts reading when a time required for moving the original to the reading position of the first image reading unit elapses after the sensor detects the original. A first control unit for controlling A first storage unit that stores a reading value of the first image reading unit controlled by the first control unit as image data on the one side of the document, and after the sensor detects the document, A second control unit that controls the second image reading unit to start reading before the time required to move to the reading position of the second image reading unit; and the second image reading unit reads Each time the document is conveyed by the minimum unit by the drive unit, an intermediate storage unit that stores a reading value for a predetermined distance that the second image reading unit reads, and the intermediate storage unit that stores the reading value A determination unit that determines whether or not a reading value corresponds to image data corresponding to the predetermined distance from the leading edge of the document stored in the first storage unit, and a point at which the determination unit determines that the reading value corresponds to the second value. The reading value of the image reading unit It is characterized by comprising a second storage unit for storing as image data of the square side, a.

  An image reading apparatus according to a second aspect of the present invention is the image reading apparatus according to the first aspect, wherein the first image reading unit irradiates the object from the one side. A plurality of light receiving elements that receive reflected light from one side of the object; the second image reading unit: a second light source that irradiates the object from the other side; A plurality of light receiving elements for receiving reflected light from the other side of the object, and corresponding to image data for a predetermined distance from the front end of the document among the image data stored in the first storage unit A first average processing unit that averages values for each of the light receiving elements, a tip image data storage unit that stores image data averaged by the first average processing unit, and the light reception read by the second image reading unit. A second average processing unit that averages the read values for the predetermined distance for each element; The intermediate storage unit stores the read value averaged by the second average processing unit, and the determination unit stores the read value stored in the intermediate storage unit in the tip image data storage unit. It is characterized in that it is determined whether or not the image data corresponds.

  According to the first aspect of the present invention, the document has passed through each of the first image reading unit that reads an image on one side of the document and the second image reading unit that reads an image on the other side of the document. Since it is only necessary to provide the sensor only in the first image reading unit without providing the sensor to detect, the cost can be reduced.

  According to the second aspect of the present invention, the determination unit corresponds to image data for the predetermined distance from the front end of the original surface of one surface read by the first image reading unit stored in the front end image data storage unit. Since the average value for each light receiving element to be read is compared with the average value of the read values for a predetermined distance read by the second image reading unit stored in the intermediate storage unit, the first image reading unit and the second image reading unit It is possible to prevent erroneous detection due to noise or the like when the unit reads dust.

It is explanatory drawing which shows the cross section of an image reading apparatus typically. 2 is a configuration diagram of a reading device 230. FIG. 2 is a circuit block diagram showing an electrical configuration of the image reading apparatus 10. FIG. 6 is a flowchart (first half) when reading both sides of a document of the image reading apparatus 10 according to the first embodiment. 6 is a flowchart (second half) when reading both sides of a document of the image reading apparatus 10 according to the first embodiment. 9 is a flowchart (first half) when reading both sides of a document of the image reading apparatus 10 according to the second embodiment. 9 is a flowchart (second half) when reading both sides of a document of the image reading apparatus 10 according to the second embodiment. 14 is a flowchart (first half) when reading both sides of a document of the image reading apparatus 10 according to the third embodiment. 9 is a flowchart (intermediate) when reading both sides of a document of the image reading apparatus 10 according to the third embodiment. 10 is a flowchart relating to front document leading edge detection data storage processing. 14 is a flowchart (second half) when reading both sides of a document of the image reading apparatus 10 according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments of the present invention are not limited to the following embodiments, and various forms can be adopted as long as they belong to the technical scope of the present invention.

(Configuration of image reading apparatus)
FIG. 1 is an explanatory diagram schematically showing a cross section of the image reading apparatus 10.
The image processing apparatus 10 includes an apparatus main body 20 and an automatic document feeder (ADF: Auto Document Feeder) 30 disposed on the upper part of the apparatus main body 20. The ADF 30 is provided so as to be rotatable with respect to the apparatus main body 20. The upper surface of the apparatus main body 20 is covered with an ADF 30 as shown in FIG.

  The ADF 30 transfers a paper feed tray 110 on which a document is placed, a paper discharge tray 130 on which the document is ejected, and a document placed on the paper feed tray 110 to a U-turn conveyance path 111 (an example of a conveyance path). It has the conveyance rollers 121-127 conveyed along. In addition, the ADF 30 includes paper discharge rollers 128 and 129 for transporting the document transported by the transport rollers 121 to 127 to the paper discharge tray 130.

  In the following description, when an original is placed on the paper feed tray 110, the upper side of the original in FIG. 1 is used as the front side of the original, and the lower side of the original in FIG. And

  The U-turn conveyance path 111 is provided with one sensor 320 as a document sensor for detecting the presence or absence of a document being conveyed to a corresponding position.

  The U-turn conveyance path 111 is provided with an upstream reading position 215 and a downstream reading position 235. A reading device 210 for reading an image on the back side of the document is provided corresponding to the upstream side reading position 215. Further, a document presser 220 that presses the document passing through the upstream reading position 215 against the reading surface of the reading device 210 is provided. The reading device 210 typically employs a contact image sensor (CIS) or a charge coupled device (CCD).

Further, the reading device 230 provided in the apparatus main body 20 is configured to be movable to a position corresponding to the downstream reading position 235 in order to read the image on the surface of the document. A front-side document presser 240 that presses a document passing through the downstream side reading position against the reading surface of the front-side CIS 230 is provided. The reading device 230 typically employs a CIS (Contact Image Sensor) or a CCD (Charge Coupled Device).

  As described above, the back side of the document is read by the reading device 210 from one side facing the U-turn conveyance path 111 at the upstream reading position 215. Then, the document presser 240 or the surface of the document is read by the reading device 230 from the other side facing the U-turn conveyance path 111. The document holders 220 and 240 are white plates having a predetermined reflectance.

  The image reading apparatus 10 may have any configuration as long as the ADF 30 is applicable. Although the present embodiment exemplifies the case where the present invention is implemented as the apparatus main body 20 and the ADF 30 applicable to the apparatus main body 20, the present invention attaches an image recording material such as toner or ink to a recording sheet and performs image processing. May be implemented as an image recording apparatus that records a recording sheet, or a sheet conveying apparatus that conveys a recording sheet to an image recording position in the image recording apparatus.

  Next, FIG. 2 is a perspective view of a main part showing the configuration of the reading device 230 in more detail. The configuration of the reading device 210 is basically the same as the configuration of the reading device 230. The reading device 230 includes a lens 237, a substrate 238, a light receiving element 232 that detects light collected by the lens 237 formed on the substrate 238, and a pair of lenses disposed on both sides along the lens 237. The cylindrical light guide members 236a and 236b and the LED lamps 231a and 231b disposed on the light guide members 236a and 236b, respectively, are configured.

  When the LED lamps 231a and 231b are turned on, the light that has been turned on is applied to the document retainer 240 or the surface of the document through the light guide members 236a and 236b. The irradiated light is reflected by the document presser 240 or the surface of the document. A plurality of lenses 237 and light receiving elements 232 are arranged in one row along the main scanning direction, and a plurality of reflected lights reflected by the document presser 240 or the surface of the document are received in the one row. Element 232 detects. A plurality of light receiving elements arranged in a line along the main scanning direction respectively output an analog voltage corresponding to the amount of accumulated reflected light as read data.

  FIG. 3 is a circuit block diagram showing an electrical configuration of the image reading apparatus 10. The image reading apparatus 10 includes a CPU 100, a ROM 101, a RAM 102, an NVRAM (nonvolatile memory) 103, a drive circuit 105, an ASIC 104 connecting them, reading devices 210 and 230, AFE circuits 214 and 234, The LED circuits 213 and 233 and a document sensor 320 that detects that a document has arrived constitute the main part.

  The ROM 101 stores various control programs, various settings, initial values, and the like for controlling the image reading apparatus 10. The RAM 102 is used as a work area from which various control programs are read or as a storage area for temporarily storing image data.

  The CPU 100 controls the function of the ASIC 104 described below while storing the processing result in the RAM 102 or the NVRAM 103 according to the control program read from the ROM 101.

  The RAM 102 is provided with a storage area for each function, such as a first storage unit, a second storage unit, an intermediate storage unit, and a tip image data storage unit, which will be described below. Stored in the area.

The ASIC 104 includes a reference clock (CLK) for operating the image reading apparatus 10;
Based on the reference clock, a pulse signal (SP) of one line period is supplied to the reading devices 210 and 230, respectively. Similarly, the ASIC 104 inputs a reference clock to the drive circuit 105. Then, the driving circuit 105 outputs a pulse signal synchronized with a pulse signal (SP) having a period corresponding to the reading time for one line by the reading devices 210 and 230 as a driving signal for the motor 106.

  The motor 106 (an example of a drive unit) is a stepping motor, and is driven to rotate by one rotation angle by one pulse of a drive signal. When the motor 106 is driven by one step, the respective transport rollers 121-127 are driven, and the original is transported on the U-turn transport path 111 by a predetermined distance.

  Further, the ASIC 104 generates a PWM (Pulse Width Modulation) signal, and uses the respective drive current values of the light source 211 of the reading device 210 and the light source 231 of the reading device 230 as the PWM signals. To enter.

  Further, the ASIC 104 inputs a TRIG (trigger) signal to the LED circuit 213 and the LED circuit 233, respectively, during the light emission time required for the light source 211 and the light source 231 within one line period. The LED circuit 213 controls light emission of the light source 211 and the LED circuit 233 controls light emission of the light source 231 based on the input PWM signal and TRIG signal.

  The reading device 210 irradiates light from the light source 211 to the back side of the document passing through the upstream side reading position 215, and the light reflected by the back side of the document is accumulated in the light receiving element 212, as analog back side read data. Output. The analog back side read data output from the reading device 210 is input to the AFE circuit 214. The read data is converted into digital back side read data (an example of a read value of the first image reading unit) by an A / D conversion circuit included in the AFE circuit 214.

  Similarly, the reading device 230 irradiates light from the light source 231 to the surface of the document or the document presser 240 that passes through the downstream reading position 235, and the light reflected by the surface of the document or the document presser 240 is received by the light receiving element 232. And output as analog read data. The analog read data output from the reading device 230 is input to the AFE circuit 234, and converted into digital read data (an example of a read value of the second image reading unit) by the A / D conversion circuit included in the AFE circuit 234. Converted.

  The A / D conversion circuit included in the AFE circuits 214 and 234 has a resolution that decomposes the read data of analog signals output from the light receiving elements 212 and 232 into 8-bit (0 to 255) read data as digital signals. It is.

  In addition, reading is completed for one line in which the reading device 210 is all the light receiving elements 212 while the document is conveyed by a distance of one step. The same applies to the reading device 230.

  In the present embodiment, the CPU 100 is provided outside the ASIC 104, but the ASIC 104 may include the CPU 100.

(Description of operation)
[First Embodiment]
FIG. 4 and FIG. 5 are flowcharts of the first embodiment of the operation procedure of the image reading apparatus 10 when receiving a reading command for reading both the front and back surfaces of a document whose front and back ground colors are the same. This will be described with reference to FIG. Note that at least one document is placed on the sheet feed tray 110. This operation is executed when a reading command for reading both the front surface and the back surface of the document is received from the user via an operation unit (not shown).

  First, the CPU 100 instructs to drive the transport rollers 121 to 127 (S101). Specifically, the CPU 100 inputs a reference clock (CLK) to the drive circuit 105. Then, the drive circuit 105 outputs a drive signal that is a pulse signal at regular intervals based on the reference clock. Then, the motor 106 is driven, and the respective transport rollers 121-127 are driven. As a result, the document is taken into the ADF 30 one by one by the transport roller 121, and the document moves on the transport path 111 via the transport rollers 122-127.

  As described above, every time the motor 106 rotationally drives one step with one pulse of the drive signal, the transport rollers 122-127 move the document by a distance corresponding to the one step.

  Next, the sensor 320 detects whether or not the leading edge of the document has reached the position of the sensor 320 (S102). When the sensor 320 reaches the leading edge of the document (S102: YES), the CPU 100 starts counting the number of pulses of the output drive signal, that is, the number of steps after the sensor 320 detects the leading edge of the document. (S103).

  In the ROM 101, the number of steps necessary for moving the document from the position of the sensor 320 to the upstream reading position 215 of the reading device 210 is stored in advance as the first step number. Then, the CPU 100 compares the first step number stored in the ROM 101 with the count value that started counting in S103, and determines whether or not the count value has reached the first step number (S104).

  If the count value has not reached the first step number (S104: NO), the leading edge of the document has not yet reached the upstream side reading position 215, so that the document corresponds to one step by the transport rollers 122-127. The distance is conveyed (S105).

  When the count value reaches the first step number (S104: YES), it is assumed that the leading edge of the document has reached the reading position 215, and the CPU 100 controls the reading device 210 to read the back side of the document. Accordingly, the reading device 210 reads an image on the back side of the document located at one line and the reading position 215 (S106).

  The read data, which is an analog signal output from the reading device 210 for each light receiving element in S106, is A / D converted by an AFE circuit having an A / D conversion circuit. The A / D converted read data is stored in the RAM 102 for each light receiving element 212 as document leading edge detection data (S107).

  Further, the CPU 100 stores the same A / D converted read data as the document leading edge detection data as image data on the back side of the document in a region of the RAM 102 different from the region where the document leading edge detection data is stored. (S108).

  The data for detecting the leading edge of the document is read data in which the reading device 210 reads the back surface of the document while the document moves a distance of one step, and the back surface is scanned by a distance of one step from the leading edge of the document. This is image data (an example of image data for a predetermined distance from the leading edge of the document. In this embodiment, the predetermined distance is a distance for one step).

Next, the CPU 100 compares the second step number stored in the ROM 101 with the count value counted from S103, and determines whether or not the count value has reached the second step number (S109). The second step number means the number of steps necessary for moving the document from the position of the sensor 320 to the vicinity of the downstream reading position 235 of the reading device 230 and is stored in the ROM 101 in advance.

  If the count value has not reached the second step number (S109: NO), the leading edge of the document has not reached the reading position 235 of the front surface reading device 230. Therefore, the document is conveyed by a distance corresponding to one step (S110). The CPU 100 functioning as the first control unit controls the reading device 210 to read the back side of the document, and the reading device 210 reads the image on the back side of the document located at one line and the reading position 215 (S111). Then, the read data read by the reading device 210 is A / D converted as described above, and is stored in the RAM 102 as image data of the back side of the document of the next line (S108).

  Next, when the count value reaches the second step number (S109: YES), the leading edge of the document is located in the vicinity of the reading position 235 before the reading device 230 for the front side. Therefore, the CPU 100 functioning as the second control unit controls the reading device 230 to read the surface of the document. Therefore, the reading device 230 reads one line. The read data read is stored in a predetermined area of the RAM 102 (S112, RAM 102: an example of an intermediate storage unit).

  As in the case of S108, the read data, which is an analog signal output for each light receiving element of the reading device 230, is read into the read data, which is a digital signal A / D converted by the AFE circuit 234, for each light receiving element. Converted.

  Next, the CPU 100 functioning as a determination unit uses the document leading edge detection data stored in the RAM 102 and the read data stored in the RAM 102 functioning as the intermediate storage unit obtained in S112 to each light receiving element (pixel). Each time it is checked whether it is within a predetermined threshold range. Then, the CPU 100 determines whether or not all the light receiving elements are within a predetermined threshold range (S113).

  It is assumed that the image reading apparatus 10 according to the present embodiment reads both sides of a document having the same ground color on the front and back sides of the document. Then, since the ground color of the front surface and the back surface of the document is the same color (for example, white) at the leading edge portion of the document, the reading device 210 for the back surface and the reading device 230 for the front surface read the leading edge of the document. The data should be the same value. However, there is a case where there is a reading error between the reading device 210 for the back surface and the reading device 230 for the front surface, which may not exactly match.

  Therefore, if the threshold value is within ± 5 of 8 bits (0 to 255) (example of the predetermined threshold), it is included in the reading error. In this case, the CPU 100 determines that the read data read by the reading device 210 and the reading device 230 for each light receiving element correspond to each other. Then, the CPU 100 determines that the leading edge of the document has reached the downstream reading position 235 if all the light receiving elements are within the range of the threshold value of ± 5 (S113: YES).

  However, since the second step number is defined as the number of steps necessary to move the document to the vicinity of the downstream reading position 235, the reading device 230 reads when the count value reaches the second step number. Is a document presser 240. Therefore, in this embodiment, when the process proceeds to YES in S109, the determination in S113 of the CPU 100 proceeds to NO.

In the present embodiment, the document presser 240 is a white plate having a predetermined reflectance. The amount of light received by the light receiving element 232 that accumulates the reflected light of the white plate having a predetermined reflectance is clearly different from the amount of light received by the light receiving element 232 that reflects the reflected light reflected by the white background document. ing. Therefore, even if the document presser 240 is white and the background color of the document is white, the process of S113 is appropriately performed and the process proceeds to NO.

  If the process proceeds to NO in S113, the document is conveyed by a distance of one step (S114). Then, the reading device 210 reads one line of the back side of the document. Similarly to S108, the read data read by the reading device 210 is stored in the RAM 102 as image data of the back side of the document on the next line (S116). Then, the reading device 230 reads one line again (S112).

  When the CPU 100 determines in S113 that the leading edge of the document has reached the downstream reading position 235, the read data stored in the RAM 102 functioning as an intermediate storage unit is used as image data of the document surface, and the surface of the document surface of the RAM 102 is read. It is stored in an area for storing image data (S117: an example of a second storage unit).

  Next, the document is conveyed by a distance of one step (S118). Then, if the number of lines of image data on the back side of the document stored in the RAM 102 functioning as the first storage unit is equal to the size of the document, the CPU 100 completes reading the back side of the document (YES in S119). If the size of the original is not stored in the RAM 102, the CPU 100 determines that reading of the back side of the original has not been completed, and the process proceeds to S120.

  In S120 to S123, the reading device 210 reads the back side of the original and the reading device 230 reads the front side of the original while the original is transported by one step in S118 (S120, S122). The read data read by the reading device 210 is stored in the RAM 102 functioning as the first storage unit (S121), and the read data read by the reading device 230 is stored in the RAM 102 functioning as the second storage unit (S123). , Respectively. The processes of S118 to S123 are repeated until the reading of the back side of the document is completed.

  If the reading of the back side of the document is completed (S119: YES), the process proceeds to S124. The reading device 230 reads the surface of the document (S124). The read data read by the reading device 230 is stored in the RAM 102 that functions as the second storage unit (S125). In S126, if the number of lines of the image data on the back side of the document stored in the RAM 102 functioning as the second storage unit is equal to the size of the document, the CPU 100 completes reading the back side of the document (S126, YES). Further, the CPU 100 determines that the reading of the document surface has not been completed if the RAM 102 does not have the size of the document (S126: NO). Then, the document is conveyed by a distance of one step (S127). Then, the process returns to S124 again, and the processes of S124 to S127 are repeated until the reading of the back side of the document is completed.

  Then, the document is discharged to the discharge tray 130 by the discharge rollers 128 and 129 (S128). Here, the double-sided reading process of the document is completed.

  In the present embodiment, one sensor 320 is provided without a sensor for detecting that the document has passed through each of the reading device 210 that reads the image on the back side of the document and the reading device 230 that reads the image on the front side of the document. Only good. Therefore, even if the original is bent or the position of the original cannot be detected accurately due to the motor 106 stepping out, the image reading apparatus 10 of the present embodiment allows the reading device 230 to accurately detect the front end of the original and The reading of the surface image can be started accurately.

[Second Embodiment]
Next, a second embodiment of the operation procedure of the image reading apparatus 10 will be described with reference to the flowcharts of FIGS. Note that the basic operation processing is the same as that already described with reference to FIGS. 4 and 5, and thus common items are given the same numbers. In the following description of the second embodiment, only differences from the first embodiment will be described.

  S101 to S106 are the same processes as in the first embodiment. The CPU 100 functioning as the first average processing unit averages the read data for each light receiving element 212 read by the reading device 210 by the number of the light receiving elements 212 (S201). In S107, the read data averaged in S201 is stored as document leading edge detection data in the RAM 102 functioning as a leading edge image data storage unit.

  S118 to S112 are the same processing as in the first embodiment. The CPU 100 functioning as the second average processing unit averages the read data for each light receiving element 232 read by the reading device 230 by the number of the light receiving elements 232, and the averaged read data is stored in the RAM 102 functioning as an intermediate storage unit. Stored (S202).

  The CPU 100 functioning as a determination unit compares the averaged read data of the reading device 230 stored in the intermediate storage unit with the document front end detection data stored in the RAM 101 functioning as the front end image data storage unit. If the threshold value is within the range of ± 5 of the bits (0 to 255), it is determined that the leading edge of the document has reached the downstream reading position 235 (S203: YES).

  The processes after S203 are the same as those in the first embodiment. In the second embodiment, the CPU 100 functioning as the determination unit stores the average value of the read data read by the reading device 210 stored in the RAM 102 functioning as the tip image data storage unit and the intermediate storage unit. The average value of the read data read by the reading device 230 is compared. Therefore, from the process of S113 in the first embodiment, it is possible to prevent erroneous detection due to noise or the like when the first image reading unit and the second image reading unit read dust.

  Note that the processing of S113 or S203 of the CPU 100 functioning as the determination unit is not limited to the present embodiment. For example, in S113, the read data of all the light receiving elements are compared, but the CPU 100 has a threshold value of ± 5 out of 8 bits (0 to 255) between the read data obtained by thinning out the light receiving elements every three light receiving elements. It may be determined whether it is within the range. If it does so, there exists an effect that CPU100 can reduce the process of S113.

  In the first and second embodiments, the second step number is the number of steps necessary for moving the document from the position of the sensor 320 to the vicinity of the downstream reading position 235 of the reading device 230. Instead, the number of steps may be used to move the document from the position of the sensor 320 to the downstream reading position 235 of the reading device 230. Then, as long as an error such as step-out of the motor 106 does not occur, the read data read by the reading device 230 can be processed as image data on the surface of the document.

In the first embodiment, the document leading edge detection data is image data obtained by reading the back surface by a distance corresponding to one step from the leading edge of the document while the document moves a distance corresponding to one step. Further, while the original moves a distance of one step, the CPU 100 compares the read data read by the reading device 230 and the image data to determine whether the leading edge of the original has reached the downstream reading position 235. Yes.
[Third Embodiment]
Therefore, the CPU 100 compares the image data corresponding to the distance of three steps and the read data read by the reading device 230 while the document is moved by the distance of three steps, and the leading edge of the document reaches the downstream reading position 235. The case where it is determined whether or not has been performed will be described with reference to the flowcharts of FIGS. 8, 9, 10, and 11 in the third embodiment.

  The processing of S301 to S305 is the same as the processing of S101 to S105 of the first embodiment. When the count value reaches the first step number (S104: YES), it is assumed that the leading edge of the document has reached the upstream reading position 215, and the CPU 100 controls the reading device 210 to read the back side of the document. Therefore, while the original is transported a distance corresponding to one step, the reading device 210 reads an image on the back side of the original positioned on one line and the reading position 215 (S306).

  The read data, which is an analog signal output from the reading device 210 for each light receiving element in S306, is A / D converted by an AFE circuit having an A / D conversion circuit. The A / D-converted read data is stored in the RAM 102 for each light receiving element 212 as document leading edge detection data for one step (S307).

  Next, the CPU 100 reads the read data for one step, which has been subjected to the same A / D conversion as the data for detecting the leading edge of the document, in an area of the RAM 102 different from the area in which the data for detecting the leading edge of the document is stored. The image data is stored (S308).

  Then, after detecting the completion of the first step number conveyance in S104, the CPU 100 determines whether or not the document has been conveyed by a distance of three steps (a predetermined number of steps in the drawing) (S309). If the document is not conveyed by the number of three steps (S309: NO), the process proceeds to S310, and the document is conveyed by a distance of one step.

  And it returns to S306 again. In S309, when the document is not conveyed by the number of steps of 3 steps, the processes of S306 to S310 are repeated. When the document is conveyed by the number of steps of 3 (S309: YES), the document leading edge detection data stored in the RAM 102 in S307 stores the image data of the document for 3 steps in order.

  Next, when the count value counted by the CPU 100 does not reach the same second step number as in the first embodiment (S311: NO), the document is conveyed by a distance corresponding to one step (S312). The reading device 210 reads an image on the back side of the document located at one line and the reading position 215 (S313). Then, the read data read by the reading device 210 is A / D converted as described above, and stored in the RAM 102 as image data of the back side of the original of the next line (S314).

  Next, when the count value reaches the second step number (S311: YES), the leading edge of the document is located in the vicinity of the reading position 235 before the reading device 230 for the front side. Again, in S315, one line is read by the reading device 230.

  Then, the process proceeds to S316, which will be described later, for storing the front document leading edge detection data. FIG. 10 illustrates a flowchart relating to the data storing process for detecting the leading edge of the front document in S316.

  In the third embodiment, a storage area is secured in the RAM 102 that functions as an intermediate storage unit so that read data for a distance of three steps can be stored.

As in the first embodiment, the second step number is defined as the number of steps necessary for moving the document to the vicinity of the downstream reading position 235, so when the count value reaches the second step number. The reading device 230 reads the document presser 240.

  The CPU 100 detects whether or not there is a free storage area in the RAM 102 that functions as an intermediate storage unit (S401). If there is a vacancy (S401: YES), the read data for one step read by the reading device 230 in S315 is stored in a vacant area of the intermediate storage unit.

  In the process of S406, if there is an empty storage area for three steps of the RAM 102 functioning as an intermediate storage unit, the read data for one step is stored in the order read in S315.

Further, when there is no space in the storage area for three steps of the RAM 102 functioning as the intermediate storage unit (S401: NO), the read data is stored in the storage area for three steps.
The read data at this time is read data obtained by reading the document presser 240 or the surface of the document by the reading device 230.

  When S401 is NO, the CPU 100 first erases the storage area at the head of the storage areas for three steps (S402). Next, the CPU 100 copies the read data stored in the second storage area among the storage areas for three steps to the top storage area (S403). Then, the CPU 100 copies the read data stored in the third storage area among the storage areas for three steps to the second storage area (S404). Then, the read data read by the reading device 230 in S315 is stored in the last storage area among the storage areas for three steps (S405).

  In the front document front end detection data storage process of FIG. 10, by performing the processes of S402 to S405, every time the document is transported a distance of one step, the front document that is read data of three steps is circulated. The tip detection data is exchanged.

In S317, the CPU 100 determines whether or not the leading edge of the document has reached the downstream reading position 235 based on the following processing. The process in S317 is the same as the process in S113 as the basic process. However, the image data of the back surface for three steps from the leading edge of the document is stored in the RAM 102 as the document leading edge detection data by the processing of S307. The intermediate storage unit is configured to store read data for three steps.

  In step S317, the CPU 100 functioning as a determination unit stores the read data for one step initially stored in the RAM 102 as document leading edge detection data and the first storage area of the RAM 102 functioning as an intermediate storage unit. The read data for one step is compared for each light receiving element, and it is checked whether all the light receiving elements are within a threshold value range of ± 5 out of 8 bits (0 to 255).

  Similarly, the CPU 100 functioning as a determination unit is stored in the second storage area of the RAM 102 functioning as an intermediate storage unit and the read data for one step stored second in the RAM 102 as document leading edge detection data. Compared with the read data for one step, it is checked whether all the light receiving elements are within the threshold value of ± 5 out of 8 bits (0 to 255).

  Similarly, the CPU 100 functioning as a determination unit stores read data for one step stored last as document leading edge detection data in the RAM 102 and one step stored in the last storage area of the RAM 102 functioning as an intermediate storage unit. Compared with the read data of the minute, it is checked whether all the light receiving elements are within the range of the threshold value of ± 5 out of 8 bits (0 to 255).

  The CPU 100 determines that the leading edge of the document has reached the downstream reading position 235 if the reading data for three steps read by the reading device 210 and the reading device 230 are within the threshold value of ± 5 ( S317: YES).

  If the CPU 100 does not determine that the leading edge of the document has reached the downstream side reading position 235 (S317: NO), the processes of S318 to S320, which are the same as the processes of S114 to S116 of the first embodiment, are executed. The If S317 is YES, the front document front end detection data is stored in the RAM 102 as image data on the front surface of the document (S321). Then, the process of FIG. 11 is executed. Note that the processing in FIG. 11 is the same as the processing after S118 in FIG. 5 of the first embodiment.

  As described above, the image reading apparatus 10 according to the third embodiment can appropriately reproduce a document even when the document leading edge detection data stored in the RAM 102 stores document image data of several steps such as three steps. It is possible to detect whether or not the leading edge of the head reaches the downstream reading position 235.

DESCRIPTION OF SYMBOLS 10 ... Image reading apparatus 100 ... CPU (Example of 1st control part, 2nd control part, judgment part, 1st average process part, 2nd average process part)
102... RAM (an example of a first storage unit, a second storage unit, an intermediate storage unit, and a tip image data storage unit)
104 ... ASIC
106... Motor (an example of a drive unit)
107 ・ ・ ・ Conveying roller (an example of a conveying roller)
111 ... U-turn conveyance path (an example of a conveyance path)
121 ... Conveying roller 122 ... Conveying roller 123 ... Conveying roller 124 ... Conveying roller 125 ... Conveying roller 126 ... Conveying roller 127 ... Conveying roller 210 ... Reading device (first device) Example of one image reading unit)
211... Light source (an example of a first light source)
212... Light receiving element 230... Reading device (example of second image reading unit)
231... Light source (example of second light source)
231a ... Light source a (an example of a second light source)
231b ... Light source b (example of second light source)
320 ... Sensor (an example of a sensor)

Claims (2)

An image reading device for reading both sides of a document,
A transport path for transporting the document;
A drive unit that drives a conveyance roller that conveys the document on the conveyance path;
A first image reading unit that reads an image from one side facing the conveyance path;
A second image reading unit provided at a position downstream of the position in which the first image reading unit is provided in the document conveyance direction and reading an image from the other side facing the conveyance path;
A sensor that is located upstream of the first image reading unit in the document conveyance direction and detects the document;
A first control unit that controls the first image reading unit to start reading from when a time required for the movement of the document has elapsed to the reading position of the first image reading unit when the sensor detects the document; ,
A first storage unit that stores a reading value of the first image reading unit controlled by the first control unit as image data on the one side of the document;
The second image reading unit is controlled to start reading before the time necessary for the document to move to the reading position of the second image reading unit after the sensor detects the document. Two control units;
The second image reading unit starts reading, and each time the document is conveyed by the driving unit by the minimum unit , the reading value for each minimum unit conveyance read by the second image reading unit is stored. /> With the storage unit
When the intermediate storage unit stores a reading value for several units, which is the minimum unit, the reading value is stored in the intermediate storage unit.
An intermediate storage erasure unit for erasing the minimum unit reading in the remembered order;
A determination unit that determines whether or not the read value stored in the intermediate storage unit corresponds to the image data for the predetermined distance from the leading edge of the document stored in the first storage unit;
A second storage unit that stores the reading value of the second image reading unit as image data on the other side of the document from the time when the determination unit determines that it is applicable;
An image reading apparatus comprising: The image reading apparatus according to claim 1,
The first image reading unit includes a first light source that irradiates an object from the one side, a plurality of light receiving elements that receive reflected light from one side of the object,
The second image reading unit includes a second light source that irradiates the object from the other side, and a plurality of light receiving elements that receive reflected light from the other side of the object,
Furthermore,
A first average processing unit that averages values for each of the light receiving elements corresponding to the image data for the predetermined distance from the leading edge of the document among the image data stored in the first storage unit;
A tip image data storage unit for storing image data averaged by the first average processing unit;
A second average processing unit that averages the read values for the predetermined distance for each of the light receiving elements read by the second image reading unit;
With
The intermediate storage unit stores the reading value averaged by the second average processing unit,
The determination unit determines whether or not the read value stored in the intermediate storage unit corresponds to image data stored in the tip image data storage unit;
An image reading apparatus.