JP2014049947A - Image reader - Google Patents

Abstract

An object of the present invention is to achieve both high-speed image processing and low power consumption.
A multifunction device includes a reading unit, a reading unit, a CPU, an image processing unit, a voltage supply unit that supplies the image processing unit with an operating voltage having a first voltage value, and an image processing unit. And a clock signal supply unit 25 that supplies a clock signal having a first driving frequency to the unit 23. The CPU 20 performs a soft compression process on the image read by the reading unit 30 arranged on the upstream side. The image processing unit 23 performs hard compression processing on the image read by the reading unit 60 disposed on the downstream side. The CPU 20 instructs the voltage supply unit 22 to supply an operation voltage having a second voltage value lower than the first voltage value, and instructs the clock signal supply unit 25 to be lower than the first operation frequency. It is instructed to supply a clock signal of a second operating frequency that corresponds to the second voltage value and that completes the soft compression process in conjunction with the soft compression process.
[Selection] Figure 2

Description

  The invention disclosed in this specification relates to an image reading apparatus that reads images on both sides of a document.

  2. Description of the Related Art Conventionally, an image reading apparatus that reads images on both sides of a document and compresses each image obtained by reading each side of the document separately is known (for example, Patent Document 1). In this image reading apparatus, an image obtained by reading one side of a document is compressed by hardware, and an image obtained by reading the other side of a document is compressed by software. In general, compression by hardware requires a longer compression time than compression by software. Therefore, conventionally, the image read earlier is compressed by software, and the image read later is compressed by hardware, thereby reducing the difference in compression time between hardware and software, and image processing. The technology for speeding up is used.

Japanese Patent Laid-Open No. 9-23340

  The image reading apparatus is required to reduce power consumption. Although the prior art discloses a technique for speeding up image processing, no effective technique has been proposed for a technique for suppressing power consumption.

  The present specification discloses a technique for achieving both high-speed image processing and low power consumption in an image reading apparatus that reads images on both sides of a document.

  An image reading device disclosed in the present specification includes a transport unit that transports a document along a transport path, a first reading unit that is located on the transport path and reads an image on one side of the document, A second reading unit positioned on the downstream side of the transport path from the first reading unit and reading an image on the other side of the document; and a compression process for compressing the image read by the first reading unit by software. A control unit to execute, an image processing unit that performs image processing on an image read by the second reading unit by hardware, a voltage supply unit that supplies an operating voltage of a first voltage value to the image processing unit, and the image A clock signal supply unit that supplies a clock signal having a first operating frequency to the processing unit, and the control unit supplies the voltage so as to supply the operating voltage having a second voltage value lower than the first voltage value. Instruct the department, and A clock signal having a second operating frequency lower than the first operating frequency and having the second operating frequency corresponding to the second voltage value that completes the compression by the image compression unit upon completion of the compression processing by the software Further, an instruction process for instructing the clock signal supply unit to supply the signal is further executed.

  In this image reading apparatus, the image read by the first reading unit that reads the document first is compressed by software in the control unit, and is positioned downstream on the conveyance path. The image read by the second reading unit that reads the image data later is compressed by hardware in the image processing unit. In general, compression by software requires a longer compression time than compression by hardware. Therefore, by compressing the image read by the first reading unit that reads the document first by the control unit that requires a relatively long compression time, the difference in compression time between the control unit and the image processing unit is reduced, and the image Processing can be speeded up. On the other hand, even when configured as described above, the compression completion time of the control unit is later than the compression completion time of the image processing unit, and a time difference occurs in the compression completion time.

  In this image reading apparatus, the power consumption of the image reading apparatus is suppressed based on this time difference. In other words, in this image reading apparatus, the operation frequency of the image processing unit is lowered so that the compression in the image processing unit is completed as the compression in the control unit is completed, and the image processing unit is supplied to the image processing unit accordingly. By reducing the voltage, power consumption in the image processing unit is suppressed. According to this image reading apparatus, power consumption can be suppressed.

  In the image reading apparatus, the second operating frequency may be an operating frequency that completes compression by the image compression unit prior to completion of compression processing by the software.

  According to this image reading device, it is avoided that the compression completion time of the image processing unit is later than the compression completion time of the control unit, and the power consumption of the image reading device is maintained while maintaining a state where the image processing is accelerated. Can be suppressed.

  In the image reading apparatus, the control unit instructs the image processing unit to supply the operating voltage having the first voltage value, and supplies the clock signal having the first operating frequency. A first operation mode instructing the image processing unit; instructing the image processing unit to supply an operating voltage of the second voltage value; and supplying a clock signal of the second operating frequency. A selection process for selecting the second operation mode instructed to the image processing unit may be further executed, and the instruction process may be executed when the second operation mode is selected in the selection process.

  According to this image reading apparatus, the power consumption of the image reading apparatus is suppressed by selecting the second operation mode.

  In the image reading apparatus, the first operation mode is an operation mode in which compression by the image compression unit is completed earlier than compression processing by the control unit, and the second operation mode is the image compression unit. It is good also as a structure which is the operation mode which completes the compression by a part together with the compression process by the said control part.

  According to this image reading apparatus, power consumption of the image reading apparatus is suppressed in the second operation mode in which the compression by the image compression unit is completed together with the compression processing by the control unit.

  The image reading apparatus further includes a communication unit that communicates with an external device. In the second operation mode, the first reading unit and the second reading unit read the image according to an instruction from the external device. The operation mode may be such that the compressed image and the compressed image are transferred to the external device via the communication unit.

  In the so-called PC scanner mode, in which the compressed image is transferred to the external device and the subsequent processing is performed by the external device, the compression of the image read by the first reading unit and the second reading unit is almost completed. However, the processing in the image reading apparatus is not complicated. According to this image reading apparatus, in the PC scanner mode, the operating frequency of the image processing unit is reduced, and the voltage supplied to the image processing unit is reduced correspondingly, thereby suppressing the power consumption of the image reading apparatus. be able to.

  In the image reading apparatus, the second operation mode may be an operation mode that operates while suppressing power consumption. According to this image reading apparatus, in the energy saving mode, the power consumption of the image reading apparatus is suppressed by reducing the operating frequency of the image processing unit and correspondingly reducing the voltage supplied to the image processing unit. Can do.

  The image reading apparatus disclosed in this specification can achieve both high-speed image processing and low power consumption.

Schematic cross-sectional view of a multifunction machine Block diagram schematically showing the electrical configuration of the MFP Diagram explaining the operation mode Flow chart showing the reading process Flow chart showing duplex reading process Flow chart showing soft compression processing

<Embodiment>
One embodiment will be described with reference to FIGS.

1. 1 is a cross-sectional view of a multifunction machine 1 that is an example of an image reading apparatus according to the present embodiment. The multifunction device 1 is a multi-function peripheral device having a printer function, a scanner function, a copy function, a facsimile function, and the like.

  As shown in FIG. 1, the multifunction device 1 includes a reading unit 30 on a main body unit 2, a first platen glass 52 and a second platen glass 53 made of a transparent glass plate, and an image forming unit that prints an image on a sheet material ( (Not shown, see FIG. 2) and the like, and a reading mechanism 3 for reading a document is provided above the main body 2. The reading mechanism 3 includes an automatic document feeder (hereinafter referred to as ADF) 40, a reading unit 60, and the like. The reading unit 30 is an example of a second reading unit, and the reading unit 60 is an example of a first reading unit.

  The ADF 40 is provided in a document cover 48, and includes an ADF cover 41, a document tray 42, pressing members 43 and 44, various rollers 46, a paper discharge tray 47, a front sensor (hereinafter referred to as F sensor) 11, and a first rear sensor ( Hereinafter, an R1 sensor 12, a second rear sensor (hereinafter R2 sensor) 13, a third platen glass 55 made of a transparent glass plate, and the like are included.

  The ADF 40 is provided with a transport path 45 for transporting documents from the document tray 42 to the paper discharge tray 47. Hereinafter, a direction along the transport path 45 is referred to as a transport direction, and a direction orthogonal to the direction is referred to as an orthogonal direction. In FIG. 1, the conveyance direction is indicated by an arrow 81. Further, the side of the transport path 45 near the original tray 42 is called an upstream side, and the side of the transport path 45 near the paper discharge tray 47 is called a downstream side.

  The roller 46 transports the document placed on the document tray 42 along the transport path 45 and discharges it to the discharge tray 47. That is, the document placed on the document tray 42 is conveyed to the paper discharge tray 47 by the roller 46 and the motor M (see FIG. 2) that rotationally drives the roller 46. The roller 46 and the motor M are an example of a transport unit.

  Further, the F sensor 11 is disposed on the document tray 42. The F sensor 11 detects whether or not a document is placed on the document tray 42. Further, the R1 sensor 12 is disposed on the transport path 45. The R1 sensor 12 detects the presence or absence of a document conveyed to the reading unit 60 by the ADF 40. Further, an R2 sensor 13 is disposed on the downstream side of the R1 sensor 12 on the transport path 45. The R2 sensor 13 detects the presence / absence of a document conveyed to the reading unit 30 by the ADF 40.

  The reading unit 60 is disposed on the transport path 45 downstream of the R1 sensor 12 and upstream of the R2 sensor 13. The reading unit 60 is disposed in the document cover 48, is formed so as to spread in the orthogonal direction, and is supported so as not to move with respect to the ADF 40. That is, the orthogonal direction is equal to the main scanning direction of the reading unit 60. The reading unit 60 reads the back surface of the document when the document transported through the transport path 45 passes over the third platen glass 55. The back side of the document is an example of one side of the document.

  The pressing member 43 is disposed to face the reading unit 60 with the third platen glass 55 interposed therebetween. The pressing member 43 presses the document against the third platen glass 55 so that the document passing over the third platen glass 55 does not float from the third platen glass 55.

  On the downstream side of the R2 sensor 13 in the conveyance path 45, the reading unit 30 is arranged. That is, the reading unit 30 is disposed on the downstream side of the reading unit 60 on the conveyance path 45. The reading unit 30 is disposed in the main body unit 2 and is formed so as to spread in the orthogonal direction. That is, the orthogonal direction is equal to the main scanning direction of the reading unit 60. The reading unit 30 is supported so as to be movable in the sub-scanning direction as indicated by an arrow 82 in FIG. When reading the original, the reading unit 30 reads the original placed stationary on the first platen glass 52 while moving in the sub-scanning direction as indicated by a dotted line in FIG. Further, as indicated by a solid line in FIG. 2, the document moves to the reading position L below the second platen glass 53 and reads the surface of the document conveyed along the conveyance path 45. The surface of the document is an example of the other surface of the document.

  A pressing member 44 is disposed so as to face the second platen glass 53. The pressing member 44 presses the document against the second platen glass 53 so that the document passing over the second platen glass 53 does not float from the second platen glass 53. In the following description, unless otherwise specified, as indicated by a solid line in FIG. 1, the state of the reading unit 30 that reads the image of the document that is stationary on the reading position L and conveyed on the conveyance path 45, and It is assumed that the operation is described.

  Next, the structure of the reading unit 60 will be described. The reading unit 60 reads a document placed on the third platen glass 55 by a so-called CIS method using a CIS (Contact Image Sensor). The reading unit 60 includes a linear image sensor 63 in which a plurality of light receiving elements are linearly arranged in the main scanning direction, a light source 61 including a light emitting diode, and the like. It includes a light guide 66 that guides the arranged document or the like, a rod lens array 62 that forms an image of reflected light reflected by the document or the like on each light receiving element of the linear image sensor 63, and a carriage 64 on which these are mounted.

  The configuration of the reading unit 30 is basically the same as the configuration of the reading unit 60, and a duplicate description is omitted. However, the structures of the reading units 30 and 60 do not necessarily have the same structure. For example, one of the reading unit 30 and the reading unit 60 may be a CIS and the other may be a CCD.

  The multifunction device 1 is further provided with a display / input unit 71 that includes various buttons and a touch panel, accepts an operation input from the user, and displays the state of the multifunction device 1.

2. As shown in FIG. 2, the multifunction device 1 includes a central processing unit (hereinafter referred to as CPU) 20, a ROM 26, a RAM 27, a voltage supply unit 22, an image processing unit 23, a clock signal supply unit 25, and device control. Unit 14, analog front end (hereinafter referred to as AFE) 15 and 16, direct memory controller 28, communication unit 17, panel control unit 18, and drive circuit 19, and F sensor 11 and R sensor 12 via bus 29. , 13, etc. are connected. As shown by a dotted line 21 in FIG. 2, the one including the CPU 20, the ROM 26, and the RAM 27 is an example of the control unit.

  Various programs for controlling the operation of the multifunction device 1 are stored in the ROM 26. The CPU 20 controls each unit in accordance with the program read from the ROM 26, and the image data read by the reading unit 30 is stored in the ROM 26. A software compression process is performed to compress the software using a program.

  The device control unit 14 is connected to each of the reading units 30 and 60, and transmits a reading control signal for controlling reading of a document in the reading units 30 and 60 to the reading units 30 and 60 based on an instruction from the CPU 20. . When the reading units 30 and 60 receive the reading control signal from the device control unit 14, the light sources 31 and 41 are turned on, and the reflected light reflected from the document conveyed on the conveyance path 45 is transmitted to the linear image sensors 33 and 63. To receive light. The reading unit 30 (60) outputs image data, which is an analog signal corresponding to the amount of light received by the linear image sensor 33 (63), to the AFE 15 (16) for each line of the linear image sensor 33 (63).

  The AFE 15 (16) is connected to the reading unit 30 (60), and converts analog signal image data output from the reading unit 30 (60) into digital signal image data based on an instruction from the CPU 20. To do. The image data A / D converted by the AFE 15 (16) is stored in the RAM 27 via the bus 29. In the software compression process, the CPU 20 compresses the image data read by the reading unit 30 and A / D converted by the AFE 15.

  The voltage supply unit 22 generates an operating voltage having a first voltage value or a second voltage value lower than the first voltage value from an external voltage supplied from the outside of the device in accordance with an instruction from the CPU 20 and supplies the operation voltage to the image processing unit 23. To do. Further, the clock signal supply unit 25 generates a clock signal having a first operation frequency or a second operation frequency lower than the first operation frequency in accordance with an instruction from the CPU 20 and supplies the clock signal to the image processing unit 23.

  The image processing unit 23 operates based on the operating voltage supplied from the voltage supply unit 22 and the clock signal supplied from the clock signal supply unit 25, and performs various image processing on the image data read by the reading units 30 and 60. Execute. The image processing unit 23 has a Jpeg compressor 24 configured by hardware, and the Jpeg compressor 24 compresses image data read by the reading unit 60 and A / D converted by the AFE 16. Perform compression processing. In other words, in the multifunction device 1, the image data on the back side of the document read by the reading unit 30 is compressed by software by the CPU 20, and the image data on the front side of the document read by the reading unit 60 is converted by hardware in the image processing unit 23. Compressed.

  The direct memory controller 28 controls writing and reading of image data to the RAM 27. The communication unit 17 is connected to an external computer (hereinafter referred to as an external PC) through a communication line such as a USB cable, and enables mutual data communication with the external PC or the like. The panel control unit 18 is connected to the display / input unit 71, receives an input instruction input from the user via the display / input unit 71, and displays predetermined contents on the display / input unit 71 according to the instruction from the CPU 20. To do.

  The drive circuit 19 is connected to the motor M and rotationally drives the motor M based on the pulse signal input from the CPU 20. The motor M is driven to rotate by one rotation angle with one pulse of the pulse signal. When the motor M is driven by one step, the roller 46 rotates by a predetermined angle, and the document is conveyed on the conveyance path 45 by a predetermined distance. When conveying the document, the CPU 20 transmits a pulse signal to the drive circuit 19, and the roller 46 conveys the document by a distance obtained by multiplying the number of pulses of the pulse signal by a specified distance. Hereinafter, the number of pulses of the pulse signal that the CPU 20 transmits to the drive circuit 19 is referred to as a step number.

3. Operation Mode With reference to FIG. 3, two operation modes when the CPU 20 controls the image processing unit 23 will be described. When controlling the image processing unit 23, the CPU 20 controls the voltage supply unit 22 and the clock signal supply unit 25 to switch to one of the first operation mode and the second operation mode.

  In the first operation mode, the CPU 20 instructs the voltage supply unit 22 to supply the operation voltage having the first voltage value, and instructs the clock signal supply unit 25 to perform the first operation frequency corresponding to the first voltage value. Instruct to supply the clock signal. Further, in the second operation mode, the voltage supply unit 22 is instructed to supply the operation voltage having the second voltage value, and the clock signal supply unit 25 has the second operation frequency corresponding to the second voltage value. Instructs to supply a clock signal.

  In the first operation mode, since the operation frequency is higher than that in the second operation mode, the speed of the compression process in the Jpeg compressor 24 of the image processing unit 23 is faster than that in the second operation mode, and the document in the image processing unit 23 is scanned. The back surface compression time TU necessary for the back surface image compression processing is shorter than the front surface compression time TO necessary for the CPU 20 to compress the front surface image of the document. Therefore, in the first operation mode, as shown in the upper part of FIG. 3, the surface image is taken into consideration even when the transport time difference HT necessary for transporting the document from the reading unit 60 to the reading unit 30 along the transport path 45 is taken into consideration. This compression processing can be completed earlier than the back surface image compression processing by a reference time KT or more.

  Therefore, in the first operation mode, using the reference time KT, for example, the image formation using the image forming unit 70 can be performed on the back image in advance of the back image. On the other hand, since the operating voltage is higher in the first operation mode than in the second operation mode, the power consumption is higher than in the second operation mode.

  In the second operation mode, since the operation frequency is lower than that in the first operation mode, the compression processing speed in the JPEG compressor 24 of the image processing unit 23 is slower than that in the first operation mode, and the image processing unit 23 The back surface compression time TU is extended compared to the first operation mode. In the second operation mode, as shown in the lower part of FIG. 3, in consideration of the transport time difference HT, the front surface image compression process is completed together with the back surface image compression process. The second operating frequency is set so that the image compression process is completed at the same time as the back surface image compression process or slightly before the back surface image compression process, and the second voltage value is set correspondingly.

Therefore, in the second operation mode, the compression completion timing for completing the compression processing of both the front image and the back image of the document is maintained at the same timing as in the first operation mode. In the second operation mode, since the operation voltage is lower than that in the first operation mode, power consumption can be suppressed as compared with the first operation mode. The relationship between power consumption and operating voltage is shown below. In the following equations, power consumption is indicated by W and operating voltage is indicated by V. The operating frequency is indicated by F, and the proportionality coefficient is indicated by α.
W = α × V ² × F × TU

  As shown in the above equation, since power consumption is proportional to the square of the operating voltage, power consumption can be suppressed by lowering the voltage value of the operating voltage. Since the product of the operating frequency and the back surface compression time TU is substantially constant regardless of the operating frequency, the influence on the power consumption by reducing the operating frequency can be ignored.

3. Reading Processing Next, processing for reading both sides of the document using the ADF 40 will be described with reference to FIGS. In this process, either side of the document is read, and the read image is transferred to an external PC, or an image is formed using the image forming unit 70, and either process is executed. In this embodiment, a standard document such as A4 or B5 is used as the document. Therefore, the document compression completion timing can be estimated from the document conveyance start timing, and the second drive voltage and the second operating frequency can be set from the compression completion timing.

  FIG. 4 is a flowchart of a reading process executed by the CPU 20 according to a predetermined program. The CPU 20 starts processing when a user places a document on the document tray 42 of the multifunction device 1 and inputs a document reading instruction via the display / input unit 71.

  When the process is started, the CPU 20 first starts selection for selecting in which operation mode the image processing unit 23 is controlled (S2, S4). In the selection process, the CPU 20 confirms whether the PC scanner mode is set in the reading instruction input by the user (S2). Here, the “PC scanner mode” is an operation mode in which the compressed image data is transferred to the external PC via the communication unit 17. When the PC scanner mode is set, the CPU 20 executes processing up to reading of a document and compression of the read image data, and transfers the compressed image data to an external PC. Then, the CPU 20 does not perform subsequent processing such as rotation and rearrangement of the image data, but causes the external PC to execute the processing.

  Further, when the PC scanner mode is not set in the reading instruction input by the user (S2: NO), the CPU 20 further confirms whether the energy saving mode is set in the reading instruction (S4). Here, the “energy saving mode” is an operation mode that operates while suppressing power consumption.

  When the PC scanner mode or the energy saving mode is set in the reading instruction input by the user (S2: YES or S2: NO, S4: YES), the CPU 20 determines that the second operation mode is selected. In this case, in order to control the image processing unit 23 in the second operation mode, the CPU 20 instructs the voltage supply unit 22 to supply the operation voltage having the second voltage value (S6), and the clock signal supply unit. 25 is instructed to supply a clock signal of the second operating frequency (S8). Then, using the image processing unit 23 controlled in the second operation mode, a double-sided document reading process is executed (S14). Steps S6 and S8 are examples of instruction processing.

  On the other hand, when neither the PC scanner mode nor the energy saving mode is set in the reading instruction input by the user (S2: NO, S4: NO), the CPU 20 determines that the first operation mode is selected. In this case, in order to control the image processing unit 23 in the first operation mode, the CPU 20 instructs the voltage supply unit 22 to supply the operation voltage having the first voltage value (S10), and the clock signal supply unit. 25 is instructed to supply a clock signal of the first operating frequency (S12). Then, using the image processing unit 23 controlled in the first operation mode, a double-sided document reading process is executed (S14).

(Double-sided scanning)
FIG. 5 shows a flowchart of the double-sided reading process.
When starting the double-sided reading process, the CPU 20 controls the drive circuit 19 and starts conveying the document along the conveyance path 45 in units of steps (S22). The CPU 20 confirms the position of the document conveyed on the conveyance path 45 using the R1 sensor 12 (S24: NO). When the CPU 20 detects that the R1 sensor 12 is turned on and the document has reached a position corresponding to the R1 sensor 12 in the transport path 45 (S24: YES), the R1 sensor 12 in the transport direction after the R1 sensor 12 is turned on. The document is further conveyed by the first number of steps corresponding to the distance between and the reading unit 60, and reading of the back side image of the document is started using the reading unit 60 (S26). Thereby, the image data of the back surface image read by the linear image sensor 63 of the reading unit 60 and variously corrected by the image processing unit 23 is sequentially stored in the RAM 27 for each line of the linear image sensor 63. When starting the reading of the back image, the CPU 20 starts a soft compression process for the read back image (S28).

(Soft compression processing)
FIG. 6 shows a flowchart of the soft compression process.
When starting the software compression process, the CPU 20 determines whether or not 16 lines of image data of the back image are stored in the RAM 27 (S62). Specifically, the CPU 20 determines by counting how many lines of image data of the back image are stored in the RAM 27.

  When the image data of the back side image for 16 lines is not stored in the RAM 27 (S62: NO), the CPU 20 checks whether the back side image has been read using, for example, the R1 sensor 12 (S64). If the image reading has not been completed (S64: NO), the processing from S62 is repeated.

  On the other hand, when the back surface image data for 16 lines is stored in the RAM 27 (S62: YES), the CPU 20 reads the image data for 16 lines from the RAM 27 (S66) and compresses it by software (S68). . Then, the CPU 20 outputs the compressed image data for 16 lines to the RAM 27 (S70).

  Next, the CPU 20 confirms whether the PC scanner mode is set (S72). If the PC scanner mode is set (S72: YES), the compressed image data output to the RAM 27 is transferred to the communication unit 17. (S74). On the other hand, when the PC scanner mode is not set (S72: NO), the CPU 20 executes processing such as rotation and rearrangement on the compressed image data output to the RAM 27, and outputs a plurality of data to the RAM 27. A back side image compressed by the image data is formed.

  The CPU 20 monitors the occurrence of both of the event that the reading of the back image has ended and the fact that the image data of the back image does not remain in the RAM 27 (S76), and if at least one of the events has not occurred (S76). S76: NO), the processing from S62 is repeated. In this case, there may occur a situation in which the reading of the back surface image ends when the image data of the back surface image is not stored for 16 lines in the RAM 27 (S62: NO, S64: YES).

  In this case, the CPU 20 reads out image data of less than 16 lines from the RAM 27, generates dummy image data, and generates image data of 16 lines in which the image data of the back surface image and the dummy image data are mixed. (S78). Then, the CPU 20 executes the processing of S68 to S72 for the image data for 16 lines.

  On the other hand, the CPU 20 ends the soft compression process when both of the reading of the back image and the image data of the back image remain in the RAM 27 have occurred (S76: YES). .

  Next, in the double-sided reading process, the CPU 20 confirms the position of the document conveyed along the conveyance path 45 using the R2 sensor 13 (S30: NO). When the CPU 20 detects that the R2 sensor 13 is turned on and the document has reached a position corresponding to the R2 sensor 13 in the transport path 45 (S30: YES), the R2 sensor 13 in the transport direction after the R2 sensor 13 is turned on. The document is further conveyed by the number of second steps corresponding to the distance between and the reading unit 30, and reading of the surface image of the document is started using the reading unit 30 (S32). Reading of the surface image of the document is started using the reading unit 30. Thereby, the image data of the surface image read by the linear image sensor 33 of the reading unit 30 and variously corrected by the image processing unit 23 is sequentially stored in the RAM 27 for each line of the linear image sensor 33. When starting the reading of the surface image, the CPU 20 controls the direct memory controller 28 and the image processing unit 23 to execute a hard compression process on the read surface image (S34).

  In the hard compression processing, when the image data of the surface image is stored for 16 lines in the RAM 27, the direct memory controller 28 transmits the image data for 16 lines to the Jpeg compressor 24. The image processing unit 23 uses the drive voltage supplied from the voltage supply unit 22 and the clock signal supplied from the clock signal supply unit 25 to compress the image data for the 16 lines by the Jpeg compressor 24. The direct memory controller 28 outputs the image data for 16 lines compressed by the Jpeg compressor 24 to the RAM 27. When the PC scanner mode is set, the CPU 20 transfers the compressed image data output to the RAM 27 to the external PC via the communication unit 17. On the other hand, when the PC scanner mode is not set, the CPU 20 performs processing such as rotation and rearrangement on the compressed image data output to the RAM 27 and compresses the compressed image data using the plurality of image data output to the RAM 27. Forming a finished surface image.

  When the reading of the document is started, the CPU 20 waits for the reading of the back side image of the document to be completed using the R1 sensor 12 (S36: NO). When the CPU 20 detects that the R1 sensor 12 is turned off and the document has passed the position corresponding to the R1 sensor 12 on the transport path 45 (S36: YES), the document is the first number of steps after the R1 sensor 12 is turned off. Are further conveyed, and reading of the back side image of the document is terminated (S38).

  Further, the CPU 20 waits for the reading of the surface image of the document to be completed using the R2 sensor 13 (S40: NO). When the CPU 20 detects that the R2 sensor 13 is turned off and the document has passed a position corresponding to the R2 sensor 13 in the transport path 45 (S40: YES), the document is the second number of steps after the R2 sensor 13 is turned off. Are further conveyed, and the reading of the surface image of the document is terminated (S42).

  After completing the reading of the document, the CPU 20 monitors whether the hard compression process and the soft compression process are completed. As shown in FIG. 3, in the MFP 1 of the present embodiment, the hard compression process in the image processing unit 23 is more than the soft compression process in the CPU 20 in both the first operation mode and the second operation mode. It is set to complete quickly.

  Therefore, the CPU 20 first monitors the completion of the hard compression process (S44: NO). When the hard compression process is completed (S44: YES), the CPU 20 checks whether the PC scanner mode is set (S46). When the PC scanner mode is not set (S46: NO), the CPU 20 outputs the compressed front image to the image forming unit 70. When the compressed surface image is input, the image forming unit 70 forms the surface image on the sheet material (S48). When the PC scanner mode is set (S46: YES), or when the output of the compressed front image to the image forming unit 70 is completed, the CPU 20 proceeds to the following processing.

  Next, the CPU 20 monitors the completion of the software compression process (S50: NO). When the hard compression process is completed (S50: YES), it is confirmed whether the PC scanner mode is set (S52). When the PC scanner mode is not set (S52: NO), the CPU 20 outputs the compressed back side image to the image forming unit 70. When the compressed back side image is input, the image forming unit 70 forms the back side image on the sheet material (S54). When the PC scanner mode is set (S52: YES) or when the output of the compressed back side image to the image forming unit 70 is completed, the CPU 20 ends the double-sided reading process and the reading process.

4). Advantages of the present embodiment (1) In the multifunction device 1 of the present embodiment, the CPU 20 performs a soft compression process on the back image read by the reading unit 60 that is located upstream on the conveyance path 45 and reads the document first. Then, the image processing unit 23 performs hard compression processing on the surface image that is located on the downstream side of the conveyance path 45 and is read by the reading unit 30 that reads the original later. In general, the soft compression process requires a longer compression time than the hard compression process. Therefore, as shown in the timing chart in the first operation mode of FIG. 3, the soft compression processing and the hard compression are performed by performing the soft compression processing by the CPU 20 that requires a relatively long compression time for the back-side image read first. The difference in the compression time in the processing can be reduced, and the compression processing of the front image and the back image can be speeded up.

  The MFP 1 of the present embodiment further includes a second operation mode, and image processing is performed so as to relieve the difference in compression time still occurring even when the CPU 20 performs soft compression processing on the back-side image read first. The drive frequency supplied to the unit 23 is lowered, and the drive voltage value supplied to the image processing unit 23 is lowered correspondingly. In general, the power consumption in the image processing unit 23 is proportional to the square of the drive voltage value. Therefore, the power consumed by the image processing unit 23 can be suppressed by selecting the second operation mode.

(2) In the MFP 1 of the present embodiment, the driving frequency in the second operation mode is set so that the compression of the front surface image in the hard compression process is completed prior to the completion of the compression of the back surface image in the soft compression process. . Therefore, as a result of lowering the drive frequency supplied to the image processing unit 23 in order to reduce the power consumption in the image processing unit 23, the completion of the compression of the front surface image in the hard compression processing is the result of the compression of the back surface image in the soft compression processing. It can be avoided that the compression processing of the front surface image and the back surface image is delayed after the completion.

(3) In the MFP 1 of the present embodiment, the image processing unit 23 is controlled in the first operation mode, so that the hard compression processing of the front surface image is completed more than the reference time KT than the soft compression processing of the back surface image. Can be made. Therefore, in forming an image using the image forming unit 70, when the front image and the back image are continuously formed, the front image and the back image can be formed smoothly using the reference time KT. it can.

(4) In the multifunction device 1 of the present embodiment, the image processing unit 23 is controlled in the second operation mode when the PC scanner mode or the energy saving mode is set in the reading instruction input by the user. When the PC scanner mode is set, it is not necessary to complete the hard compression processing of the front surface image for a reference time KT or more earlier than the soft compression processing of the back surface image, and it is desired to operate with reduced power consumption. . Further, when the energy saving mode is set, it is desired to operate with reduced power consumption. In the MFP 1 according to the present embodiment, when these modes are set, by controlling in the second operation mode, it is possible to realize suppression of power consumption desired in the mode.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and the drawings, and for example, the following various aspects are also included in the technical scope of the present invention.
(1) Although the above embodiment has been described using the multifunction machine 1, the present invention is not limited to this. For example, the apparatus may be provided with at least one of a printer function, a scanner function, a copy function, and a facsimile function.

(2) In the above embodiment, the MFP 1 has one CPU 20, and the control of each unit such as the voltage supply unit 22 and the clock signal supply unit 25 is executed by the one CPU 20. The present invention is not limited to this. For example, each unit may be configured by a plurality of CPUs. Furthermore, each part may be comprised by one or several CPU and ASIC.

(3) The program executed by the CPU 20 is not necessarily stored in the ROM 26, and may be stored in the CPU 20 itself or in another storage device.

(4) In the above embodiment, the description has been given using the compression processing as the common image processing performed in the CPU 20 and the image processing unit 23. However, the present invention is not limited to this, and is applied to the case where other image processing is performed. Also good.

(5) In the above-described embodiment, the description has been given using the example in which the soft compression process is executed on the back image obtained by reading the back side of the document, and the hard compression process is executed on the front image obtained by reading the front side of the document. However, the present invention is not limited to this. For example, it is applied to a case where a soft compression process is performed on a document image read first, and a hard compression process is performed on a document image read later. May be.

1: MFP, 17: communication unit, 20: CPU, 22: voltage supply unit, 23: image processing unit, 24: Jpeg compressor, 25: clock signal supply unit, 28: direct memory controller, 30: reading unit, 47: discharge tray, 60: reading unit, 70: image forming unit, HT: transport time difference, TO: front surface compression time, TU: back surface compression time

Claims (6)

A transport unit that transports a document along a transport path;
A first reading unit that is located on the transport path and reads an image on one side of the document;
A second reading unit that is located downstream of the first reading unit on the transport path and reads an image on the other side of the document;
A control unit that executes a compression process for compressing an image read by the first reading unit by software;
An image processing unit that performs image processing by hardware on the image read by the second reading unit;
A voltage supply unit for supplying an operating voltage having a first voltage value to the image processing unit;
A clock signal supply unit that supplies a clock signal having a first operating frequency to the image processing unit;
With
The controller is
The voltage supply unit is instructed to supply the operating voltage having a second voltage value lower than the first voltage value, and the second operating frequency is lower than the first operating frequency, and compression processing by the software In addition to executing the instruction processing, the instruction processing is further executed to instruct the clock signal supply unit to supply the clock signal having the second operating frequency corresponding to the second voltage value that completes the compression by the image compression unit. Image reading device. The image reading apparatus according to claim 1,
The image reading apparatus, wherein the second operating frequency is an operating frequency for completing compression by the image compression unit prior to completion of compression processing by the software. The image reading apparatus according to claim 1, wherein:
The controller is
A first operation mode instructing the image processing unit to supply an operating voltage having the first voltage value and instructing the image processing unit to supply a clock signal having the first operating frequency; Selecting a second operation mode instructing the image processing unit to supply an operating voltage having a second voltage value and instructing the image processing unit to supply a clock signal having the second operating frequency; Further execute the selection process to
An image reading apparatus that executes the instruction process when the second operation mode is selected in the selection process. The image reading apparatus according to claim 3,
The first operation mode is an operation mode in which compression by the image compression unit is completed earlier than compression processing by the control unit,
The second operation mode is an image reading apparatus in which the compression by the image compression unit is completed in conjunction with the compression process by the control unit. The image reading apparatus according to claim 4,
A communication unit that communicates with an external device;
In the second operation mode, the image is read and compressed by the first reading unit and the second reading unit according to an instruction from the external device, and the compressed image is transferred to the external device via the communication unit. An image reading apparatus that is in an operation mode. The image reading apparatus according to claim 4,
The second operation mode is an image reading apparatus that operates with reduced power consumption.

Images