JP5482198B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads an image of a document, and more specifically, can read images on the front and back surfaces of a document individually via a front surface reading unit and a back surface reading unit, and the front surface reading unit. The present invention relates to an image reading apparatus in which a back surface reading unit is individually controlled by a front surface control signal and a back surface control signal.

  In recent years, in an image reading apparatus such as a scanner for reading an image of a document (which may be integrated with an image forming apparatus as a copying machine or the like), there is an increasing demand for reading images on both sides of the document. Therefore, the front surface reading unit that reads the image on the front surface of the document and outputs a read signal corresponding to the read image, and the image on the back surface of the document are read, and the read signal corresponding to the read image is output. It has been proposed to include a back surface reading unit and individually control each reading unit with a control signal output from the control unit (see, for example, Patent Document 1).

JP 2000-151907 A

  However, in Patent Document 1, a front surface control signal for controlling the front surface reading unit and a back surface control signal for controlling the back surface reading unit are output from separate terminals of the control unit. . For this reason, it is necessary to provide a large number of terminals in the control unit, and the package size of the ASIC or the like that constitutes the control unit is naturally increased.

  Therefore, the present invention can individually read the images of the front and back surfaces of the document via the front side reading unit and the back side reading unit, and the front side reading unit and the back side reading unit receive the front surface control signal, In the image reading apparatus individually controlled by the control signal for the back surface, the object is to reduce the number of terminals of the control unit required for outputting the control signals.

  In order to achieve the above object, an image reading apparatus of the present invention reads an image on the front side of a document and outputs a read signal corresponding to the read image, and an image on the back side of the document. A back side reading unit that reads and outputs a read signal corresponding to the read image, a front side control signal for controlling the front side reading unit, and a back side control for controlling the back side reading unit And a control unit that sequentially outputs signals from one terminal at a timing that does not overlap each other, and a switching timing between the front surface control signal and the back surface control signal in the signal that the control unit outputs from the terminal. By switching the signal input destination, the control signal switching for inputting the front surface control signal to the front surface reading unit and the back surface control signal to the back surface reading unit, respectively. It is characterized by having a and.

  In the image reading apparatus of the present invention configured as described above, the front side reading unit reads an image on the front side of the document and outputs a read signal corresponding to the read image, and the back side reading unit is configured to output the back side of the document. Are read and a read signal corresponding to the read image is output.

The control unit sequentially outputs a front surface control signal for controlling the front surface reading unit and a back surface control signal for controlling the rear surface reading unit from one terminal at a timing that does not overlap each other. To do. Then, the control signal switching unit switches the input destination of the signal at the switching timing of the front surface control signal and the back surface control signal in the signal output from the terminal by the control unit. By this switching, the front surface control signal is input to the front surface reading unit, and the back surface control signal is input to the back surface reading unit.

  Thus, in the image reading apparatus of the present invention, the front surface control signal for controlling the front surface reading unit and the back surface control signal for controlling the back surface reading unit are not overlapped with each other. The signals are sequentially output from one terminal, and the input destination of the signal is switched at the above timing. For this reason, it is possible to satisfactorily reduce the number of terminals of the control unit required for outputting control signals to the front surface reading unit and the back surface reading unit. Therefore, for example, when the control unit and the terminal are integrally provided in an ASIC or the like, the package size can be reduced favorably. The control unit only has to sequentially output the front surface control signal and the back surface control signal, and does not necessarily have to alternately output front, back, front, back,. For example, it may be output as front, front, back, back, front, front,.

  Further, the present invention is not limited to the following configuration, but the control unit may be either a read signal output from the front surface read unit or a read signal output from the back surface read unit. An image processing unit that outputs a selection signal, further performs image processing on a read signal output from either the front side reading unit or the back side reading unit, and the front side A reading signal switching unit that switches which one of the reading signal output from the reading unit and the reading signal output from the reading unit for the back surface is input to the image processing unit according to the selection signal. The switching timing of the signal output from the terminal by the control unit is synchronized with the change of the selection signal, and the control signal switching unit may switch the input destination based on the selection signal. There.

  In this case, the reading signal output from the front surface reading unit and the reading signal output from the back surface reading unit are switched by the reading signal switching unit according to the selection signal output from the control unit. The images are sequentially input to the image processing unit. Then, the image processing unit performs image processing on the read signal corresponding to the selection signal. Therefore, in this case, the number of terminals related to the image processing unit can also be reduced.

  The switching timing of the signal output from the terminal by the control unit is synchronized with the change of the selection signal. Therefore, the control signal switching unit switches the input destination based on the selection signal, so that the front surface control signal is transferred to the front surface reading unit and the back surface control signal is transferred to the back surface as described above. Can be input to each reading unit. That is, in this case, since the input signal is switched by the control signal switching unit using the selection signal for selecting the read signal, the switching timing of the input signal is indicated by a separately generated signal. In comparison, the number of terminals of the control unit can be further reduced.

It is explanatory drawing which represents typically the principal part cross section of the image reading apparatus to which this invention is applied. It is a block diagram showing the structure of the image sensor control system of the image reading apparatus. It is a block diagram showing the structure of the LED light source control circuit of the control system in detail. It is a time chart showing the process in the control system.

[Outline of Image Reading Device]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view schematically showing a cross section of a main part of an image reading apparatus 10 to which the present invention is applied. As shown in FIG. 1, an image reading apparatus 10 includes a document placing table 20 that functions as a flat bed scanner, and a document that includes an ADF (Auto Document Feeder) attached to the document placing table 20 by a hinge. And a cover 30. In other words, the document cover 30 includes a mechanism for automatically conveying a document (not shown) placed on the document feeding unit 110. First, the configuration of the document cover 30 will be described in detail.

  As shown in FIG. 1, the document cover 30 conveys a document placed on the document feeding unit 110 to the document discharge unit 130 along a conveyance path (shown by a thick dotted line in FIG. 1). 129. In addition, the following upstream reading position and downstream reading position are set in this transport path. A back side image sensor 210 (an example of a back side reading unit) for reading an image on the back side of a document is provided corresponding to the upstream side reading position, and passes through the upstream side reading position at the opposite position. A back side document pressing unit 220 that presses a document to be pressed against the reading surface of the back side image sensor 210 is provided. Further, the front surface image sensor 230 (an example of the front surface reading unit) provided on the document placing table 20 is configured to be movable to a position corresponding to the downstream side reading position. A front document pressing unit 240 that presses the document passing through the reading position against the reading surface of the front image sensor 230 is provided.

  In addition, an F sensor 310, an RB sensor 320, and an R sensor 330 for detecting the presence or absence of a document being conveyed at a corresponding position are provided on the conveyance path. In addition, since the structure and operation | movement of these various sensors 310-330 are well-known and are not directly related to this invention, detailed description is abbreviate | omitted here.

[Configuration of control system of image reading apparatus]
Next, the configuration of the control system of the back surface image sensor 210 and the front surface image sensor 230 will be described with reference to the block diagram of FIG. The back side image sensor 210 is configured as a CIS (Contact Image Sensor), reads an image on the back side of the document passing through the upstream side reading position, and is an analog as an example of a read signal corresponding to the read image. The output signal AO_BS is sequentially output from the AOUT terminal 211 in units of lines along the main scanning direction. The front-side image sensor 230 is similarly configured as a CIS, reads an image on the surface of the document passing through the downstream reading position, and outputs an analog output signal AO_FS corresponding to the read image along the main scanning direction. Output sequentially from the AOUT terminal 231 in line units. The subscripts FS and BS of the analog output signals AO_FS and AO_BS respectively represent the front surface and the back surface (the same applies to other signals described later).

  Analog output signals AO_BS and AO_FS output from the image sensors 210 and 230 are input to one AO terminal 401 of an ASIC 400 as an example of a control unit via an analog switch 500 as an example of a reading signal switching unit. . In other words, the analog switch 500 receives the selection signal CIS_SEL output from the SEL terminal 402 of the ASIC 400 and periodically and alternately changing between the H level and the L level. The analog switch 500 inputs the analog output signal AO_FS or AO_BS to the AO terminal 401 of the ASIC 400 depending on whether the selection signal CIS_SEL is at the H level or the L level. The ASIC 400 performs an AD converter 410 that converts the analog output signal AO_BS or AO_FS input to the AO terminal 401 into a digital signal, and performs image processing such as various corrections, enlargement, reduction, and color conversion on the digital signal. A digital signal processing unit 420 is provided. Note that the AD converter 410 and the digital signal processing unit 420 correspond to an example of an image processing unit, and may be provided outside the ASIC 400.

The ASIC 400 is further provided with a timing generation circuit 430 that outputs various control signals as follows. That is, the timing generation circuit 430 generates the selection signal CIS_SEL described above and outputs it from the SEL terminal 402 of the ASIC 400. Further, the timing generation circuit 430 generates the clock signal CIS_CLK and outputs it from the CLK terminal 403 of the ASIC 400. The output clock signal CIS_CLK is input to the CLK terminals 212 and 232 of the back surface image sensor 210 and the front surface image sensor 230, and is used as a clock for reading processing by the image sensors 210 and 230.

  Further, the timing generation circuit 430 generates a trigger signal TG, a mode signal CIS_MODE, and LED control signals LED_R, LED_G, and LED_B, and outputs them from the TG terminal 404, the MODE terminal 405, and the LED terminal 406, respectively. These signals are input to a double-sided control signal generation unit 600 as an example of a control signal switching unit. Note that the LED control signal is output from the R_red LED_R, the G_green control LED_G, and the B_blue control LED_B from separate terminals. In FIG. 2, it is illustrated as one LED terminal 406 for convenience.

  The double-sided control signal generation unit 600 includes six AND circuits 611 to 633 as follows. That is, the AND circuit 611 outputs the logical product of the trigger signal TG output from the TG terminal 404 and the inverted signal of the selection signal CIS_SEL output from the SEL terminal 402 as the trigger signal TG_BS to the TG terminal 213 of the back surface image sensor 210. input. The AND circuit 612 inputs the logical product of the mode signal CIS_MODE output from the MODE terminal 405 and the inversion of the selection signal CIS_SEL output from the SEL terminal 402 to the MODE terminal 214 of the back surface image sensor 210 as the mode signal CIS_MODE_BS. To do. The AND circuit 613 inputs the logical product of the LED control signals LED_R, LED_G, LED_B output from the LED terminal 406 and the inversion of the selection signal CIS_SEL to the LED light source control circuit 710 as the LED control signals LED_R_BS, LED_G_BS, LED_B_BS.

  The AND circuit 631 inputs the logical product of the trigger signal TG output from the TG terminal 404 and the selection signal CIS_SEL output from the SEL terminal 402 to the TG terminal 233 of the front surface image sensor 230 as the trigger signal TG_FS. . The AND circuit 632 inputs the logical product of the mode signal CIS_MODE output from the MODE terminal 405 and the selection signal CIS_SEL output from the SEL terminal 402 to the MODE terminal 234 of the surface image sensor 230 as the mode signal CIS_MODE_FS. The AND circuit 633 inputs the logical product of the LED control signals LED_R, LED_G, LED_B and the selection signal CIS_SEL output from the LED terminal 406 to the LED light source control circuit 730 as LED control signals LED_R_FS, LED_G_FS, LED_B_FS.

  Note that three AND circuits 613 and 633 are also provided for each of the above-described LED_R, LED_G, and LED_B, but FIG. 2 shows one AND circuit 613 and 633 for convenience. When the selection signal CIS_SEL is at the L level by the double-sided control signal generation unit 600 configured as described above, the trigger signal TG, the mode signal CIS_MODE, the LED control signals LED_R, LED_G, and LED_B output from the ASIC 400 are converted into the trigger signal TG_BS. , The mode signal CIS_MODE_BS, the LED control signals LED_R_BS, LED_G_BS, and LED_B_BS (respectively, examples of the back surface control signals) are input to the back surface image sensor 210 and the LED light source control circuit 710 connected to the back surface image sensor 210. At this time, the analog switch 500 inputs the analog output signal AO_BS from the back surface image sensor 210 to the AO terminal 401 of the ASIC 400.

On the other hand, when the selection signal CIS_SEL is at the H level, the trigger signal TG, the mode signal CIS_MODE, the LED control signals LED_R, LED_G, and LED_B output from the ASIC 400 are the trigger signal TG_FS, the mode signal CIS_MODE_FS, the LED control signals LED_R_FS, LED_G_FS, LED_B_FS (each of which is an example of the front surface control signal) is input to the front surface image sensor 230 and the LED light source control circuit 730 connected to the front surface image sensor 230. At this time, the analog switch 500 inputs the analog output signal AO_FS from the surface image sensor 230 to the AO terminal 401 of the ASIC 400.

  Next, the configuration of the LED light source control circuits 710 and 730 will be described with reference to the block diagram of FIG. As shown in FIG. 3, the LED light source control circuit 710 is energized from a 12 V DC power supply based on a known current value control signal (not shown in FIG. 2) output from the ASIC 400 separately from the above signals. A constant current control unit 711 that performs constant current control of the current is provided. The current subjected to constant current control by the constant current control unit 711 is supplied to a red LED 713, a blue LED 714, and a green LED 715 provided as a light source in the back surface image sensor 210. An ON / OFF circuit 716 that switches between energization / non-energization of the LEDs 713, 714, and 715 according to the LED control signals LED_R_BS, LED_B_BS, and LED_G_BS between the LEDs 713, 714, and 715 and the ground (GND). , 717, 718.

  Further, the LED light source control circuit 730 is similarly configured as shown in FIG. 3 with the reference numerals enclosed in parentheses, and controls the LEDs 733, 734, and 735 provided as light sources in the surface image sensor 230. A constant current control unit 731 and ON / OFF circuits 736, 737, 738 are provided.

[Processing in the above control system and its effect]
Next, FIG. 4 is a time chart showing processing in the control system by presenting specific examples of the signals. 4A is a signal output from the ASIC 400, FIG. 4B is a signal input / output to the front-side image sensor 230, and FIG. 4C is input / output to the back-side image sensor 210. Represents the respective signals.

  As shown in FIG. 4A, the selection signal CIS_SEL is set to an equal period between the H level period and the L level period, and one set of the H level period and the L level period is one cycle. It becomes a cycle. A period in which one cycle period is sequentially arranged for the three colors R, G, and B is one line period. Then, the ASIC 400 synchronizes with the timing when the selection signal CIS_SEL changes to the H level or the L level, and various signals (front surface control signal) for controlling the front surface image sensor 230 and the back surface image sensor as follows. Various signals (control signal for back surface) for controlling 210 are switched and output.

  That is, the timing generation circuit 430 of the ASIC 400 uses the above-described trigger signal TG, mode signal CIS_MODE, and LED control as the front surface control signal for controlling the front surface image sensor 230 during the period in which the selection signal CIS_SEL is at the H level. The signal LED_R or LED_G or LED_B is output. Then, as described above, these signals are input only to the surface image sensor 230 and the LED light source control circuit 730 connected thereto as the trigger signal TG_FS, the mode signal CIS_MODE_FS, the LED control signal LED_R_FS, or the LED_G_FS or LED_B_FS. The During this period, the analog output signal AO_FS output from the front surface image sensor 230 is input to the ASIC 400 via the analog switch 500.

Similarly, the timing generation circuit 430 generates a trigger signal TG, a mode signal CIS_MODE, and an LED control signal LED_R as a back surface control signal for controlling the back surface image sensor 210 during a period in which the selection signal CIS_SEL is at the L level. LED_G or LED_B is output. Then, as described above, these signals are converted into the trigger signal TG_B.
S, the mode signal CIS_MODE_BS, the LED control signal LED_R_BS, LED_G_BS, or LED_B_BS are input only to the back surface image sensor 210 and the LED light source control circuit 710 connected thereto. During this period, the analog output signal AO_BS output from the back surface image sensor 210 is input to the ASIC 400 via the analog switch 500.

  However, for example, in the first one cycle period in FIG. 4, the analog output signals AO_BS and AO_FS corresponding to blue (B) are output by the image sensor 210 during the period in which the LED control signal LED_R for lighting the red LED 713 is output. , 230. This is because charge is accumulated in the light receiving element of the image sensor 210 or 230 while the LED 713 to 735 of R, G, or B is shining in response to the LED control signal LED_R, LED_G, or LED_B, and the charge is This is because the signal TG is output as a trigger. Although not shown, when the document is transported, the leading edge of the document passes in the order of the position facing the back surface image sensor 210 and the position facing the front surface image sensor 230, so at the beginning of control start. Only outputs various signals for controlling the image sensor 210 for the back surface.

  As described above, in the image reading apparatus 10 of the present embodiment, various signals for controlling the front surface image sensor 230 (front surface control signal) and various signals for controlling the back surface image sensor 210 (back surface control). Signal) are sequentially output from terminals 403 to 406 provided one by one according to the type of signal, and the input destination of the signal is switched by the double-sided control signal generation unit 600 based on the selection signal CIS_SEL. For this reason, the number of terminals of the ASIC 400 required for outputting the above various signals to the front surface image sensor 230 and the back surface image sensor 210 can be reduced favorably. As a result, the package size can be reduced and the cost can be reduced. Can be reduced.

  In addition, in the present embodiment, different types of front surface control signals and back surface control signals are sequentially output from each of the plurality of terminals 403 to 406 at timings that do not overlap each other. Appears more prominently. In addition, the front control signal and the back control signal are individually output from the same terminals 403 to 406 at different timings, so that the resolution is different between the front and back, or only the front or back is read. Control is also easy.

  In this embodiment, an analog output signal AO_FS or AO_BS corresponding to the selection signal CIS_SEL is input to the ASIC 400 via the analog switch 500. For this reason, it is only necessary to provide one AO terminal 401, and the number of terminals of the ASIC 400 can be further reduced. Furthermore, in the present embodiment, the input destination is switched by the double-sided control signal generation unit 600 using the selection signal CIS_SEL for controlling the analog switch 500 as described above. The number of terminals of the ASIC 400 can be further reduced as compared with the case where an instruction is generated using a separately generated signal.

  In addition, this invention is not limited to the said embodiment at all, It can implement with a various form in the range which does not deviate from the summary of this invention. For example, the analog output signals AO_FS and AO_BS described above are not necessarily combined into one, and the AD converter 410 and the digital signal processing unit 420 may be provided in the ASIC 400, respectively. Furthermore, the present invention can be similarly applied to various image reading apparatuses such as an image reading apparatus using a CCD and a copying machine integrated with the image forming apparatus.

DESCRIPTION OF SYMBOLS 10 ... Image reading device 20 ... Original mounting stand 30 ... Original cover 210 ... Image sensor 211, 231 ... AOUT terminal 212,232,403 ... CLK terminal 213,233,404 ... TG terminal 214,234,405 ... MODE terminal 230 ... Image sensor for surface 401 ... AO terminal 402 ... SEL terminal 406 ... LED terminal 410 ... AD converter 420 ... Digital signal processing unit 430 ... Timing generation circuit 500 ... Analog switch 600 ... Double-sided control signal generation unit 611, 612, 613 , 631, 632, 633 ... AND circuit 710, 730 ... LED light source control circuit

Claims (2)

A front surface reading unit that reads an image on the surface of the document and outputs a read signal corresponding to the read image;
A back side reading unit that reads an image on the back side of the original and outputs a read signal corresponding to the read image;
A control unit that sequentially outputs a front surface control signal for controlling the front surface reading unit and a back surface control signal for controlling the rear surface reading unit from a single terminal at a timing that does not overlap each other;
By switching the input destination of the signal at the switching timing of the front surface control signal and the back surface control signal in the signal output from the terminal by the control unit, the front surface control signal is transferred to the front surface reading unit. And a control signal switching unit for inputting the back side control signal to the back side reading unit,
An image reading apparatus comprising: The control unit outputs a selection signal for selecting either the reading signal output from the front surface reading unit or the reading signal output from the back surface reading unit,
Furthermore,
An image processing unit that performs image processing on a read signal output from either the front surface reading unit or the back surface reading unit;
A read signal switching unit for switching which one of the read signal output from the front surface reading unit or the read signal output from the back surface reading unit is input to the image processing unit according to the selection signal; ,
With
The switching timing of the signal output from the terminal by the control unit is synchronized with the change of the selection signal,
The image reading apparatus according to claim 1, wherein the control signal switching unit switches the input destination based on the selection signal.

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