JP5608621B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus and an image forming apparatus including the image reading apparatus, and more particularly to a technique for dealing with unnecessary radiation.

  Electromagnetic interference (EMI: Electro-Magnetic Interference) is a phenomenon in which a malfunction (for example, malfunction) occurs in a device due to an electromagnetic wave radiated from an electronic device called unwanted radiation.

  As a device that can cope with unnecessary radiation, there are a measuring unit that measures the radiated radio wave of the transmission line used by the communication device, and a comparison unit that compares the measured value of the radiated radio wave measured by the measuring unit with a preset reference value. A radiation information management device has been proposed in which the comparison unit notifies the communication device of the comparison result when the measured value exceeds the reference value (see, for example, Patent Document 1).

JP 2005-318557 A

  When the image signal output from the image pickup device (for example, CCD sensor) of the image reading apparatus is analog, the image signal becomes a radiation source of unnecessary radiation. The level of the analog image signal is unstable due to variations in the amount of light emitted from the light source to the image sensor. The causes of the variation in the amount of light are the illuminance variation for each light source, the illuminance variation due to the temperature characteristics of the light source, the illuminance decrease due to the aging of the light source, the reflectivity of the reflective optical system due to the mirror dirt and the variation in the reflectivity of each mirror. Variation and the like.

  When the variation in the amount of light from the light source to the image sensor is a condition for increasing the amount of light, the level of unnecessary radiation caused by the analog image signal increases. Since the variation in the amount of light occurs due to the above-described cause, the range of the variation in the amount of light cannot be specified. For this reason, there is a possibility that the level of unnecessary radiation due to the analog image signal may exceed a regulation value defined by standards such as IEC (International Electrotechnical Commission) and CISPR (Comite international Special des Perturbations Radioelectriques).

  In order to prevent the fluctuation of the level of the analog image signal from affecting the image quality of the image read by the image reading device, the image signal is changed from analog to digital after the fluctuation is corrected in the peripheral circuit. Converted. The lower limit of the illuminance of the light source is set so that the image quality after the correction does not fall below a predetermined standard in consideration of the variation in the amount of light from the light source to the image sensor.

  Incidentally, some image reading apparatuses include a carriage that can move in the sub-scanning direction, an image sensor in addition to a light source and an optical system. In this type, since the light source, the optical system, and the image sensor are arranged on the carriage, there is a drawback that it is difficult to make the image reading apparatus compact, but there is an advantage that the accuracy of the optical system can be easily maintained.

  However, in the above type, since the image sensor is arranged on the carriage, the cable connecting the image sensor and the peripheral circuit becomes relatively long. Therefore, it is conceivable that the level of unnecessary radiation in which the analog image signal output from the image sensor becomes a radiation source increases.

  An object of the present invention is to provide an image reading apparatus and an image forming apparatus capable of suppressing the level of unnecessary radiation caused by an analog image signal output from an image sensor.

  An image reading apparatus according to one aspect of the present invention that achieves the above object includes a light source that irradiates light on a document, and an image that receives light reflected from the document and outputs an analog image signal indicating an image of the document. A first peripheral circuit for supplying a digital control signal including a clock signal to the image sensor and an analog output signal including the analog image signal output from the image sensor; A second peripheral circuit that performs the above processing; a first wiring that is connected to the image sensor and the first peripheral circuit and transmits the digital control signal; and the image sensor and the second peripheral circuit; And a second wiring for transmitting the analog output signal, a first electromagnetic wave radiated from the first wiring, and a level for measuring a level of the second electromagnetic wave radiated from the second wiring. And the difference between the level of the first electromagnetic wave and the level of the second electromagnetic wave measured by the level measuring unit and the level measuring unit is supplied to the light source so as to be within a predetermined range. A first power control unit that controls power.

  In one aspect of the present invention, the first electromagnetic wave radiated from the first wiring to which the digital control signal including the clock signal is transmitted and the second wiring to which the analog output signal including the analog image signal is transmitted. The level of the second electromagnetic wave is measured by the level measuring unit. Then, the first power control unit is supplied to the light source so that the difference between the level of the first electromagnetic wave measured by the level measurement unit and the level of the second electromagnetic wave is within a predetermined range. To control the power.

  The first electromagnetic wave is unnecessary radiation in which the clock signal included in the digital control signal input to the image sensor is a radiation source, and the second electromagnetic wave is an analog image signal included in the analog output signal output from the image sensor. Unwanted radiation that becomes a radiation source. The level of unnecessary radiation due to the clock signal does not depend on the illuminance of the light source, but the level of unnecessary radiation due to the analog image signal depends on the illuminance of the light source. In addition, since the clock signal is stable, the level of unnecessary radiation where the clock signal is a radiation source is stable. According to one aspect of the present invention, the power supplied to the light source so that the level of unwanted radiation from the analog image signal is within a predetermined range with reference to the level of unwanted radiation from the clock signal. Is controlling. Therefore, it is possible to suppress the level of unnecessary radiation due to the analog image signal output from the image sensor. The predetermined range is, for example, an upper limit value (or a margin) that is allowed as a level of unnecessary radiation from the analog image signal so that the level of unnecessary radiation generated in the image reading device does not exceed a regulation value. In order to prevent this, it means a range that does not exceed a value slightly lower than the upper limit value.

  In addition, according to one aspect of the present invention, the reference level is set to a level of unnecessary radiation from the clock signal, so that it is not necessary to set the reference level in the manufacturing process of the image reading apparatus.

  Further, according to one aspect of the present invention, the power supplied to the light source is set so that the difference between the level of unnecessary radiation due to the clock signal and the level of unnecessary radiation due to the analog image signal is within a predetermined range. I have control. As a result, the light amount of the light source is feedback-controlled, so that the illuminance of the light source can be regulated within a predetermined range. Therefore, it can contribute to stabilization of the image quality of the read image.

  In the above configuration, the light source and the image sensor are provided with moving means that can move in the sub-scanning direction, and the first peripheral circuit and the second peripheral circuit are included in objects to be moved by the moving means. Not.

  In this configuration, since the image sensor can move in the sub-scanning direction and the first peripheral circuit and the second peripheral circuit do not move, the first wiring and the second wiring become long. For this reason, the level of the 1st electromagnetic wave and the 2nd electromagnetic wave becomes comparatively large. As described above, according to one aspect of the present invention, it is possible to suppress the level of unnecessary radiation caused by the analog image signal output from the imaging device. Therefore, one aspect of the present invention is an image reading apparatus of the above type. It is especially effective for.

  In the above configuration, the level measurement unit is provided at a position closer to the first wiring than the second wiring, and includes a first antenna that receives the first electromagnetic wave, and the first wiring. A second antenna that is provided near the second wiring and receives the second electromagnetic wave.

  In this configuration, since the first antenna is provided at a position close to the first wiring, the first antenna has unnecessary radiation due to the clock signal (first electromagnetic wave) and unnecessary radiation due to the analog image signal (second radiation). Of electromagnetic waves), unnecessary radiation due to clock signals can be mainly received. On the other hand, since the second antenna is provided at a position close to the second wiring, the second antenna is mainly unnecessary for the analog image signal among the unnecessary radiation due to the clock signal and the unnecessary radiation due to the analog image signal. Can receive radiation. Therefore, according to this configuration, it is possible to improve the measurement accuracy of the level of unwanted radiation due to the clock signal and the level of unwanted radiation due to the analog image signal. Therefore, for example, it is possible to improve the accuracy with which the level of unnecessary radiation generated in the image reading apparatus does not exceed the regulation value.

  In the above configuration, the first wiring is disposed between the first antenna and the second antenna, and the first wiring is accommodated on the first antenna side, and the second wiring is accommodated on the second antenna side. Equipped with a flat cable.

  According to this configuration, the first antenna can be disposed close to the first wiring while being separated from the second wiring, and the second antenna can be disposed near the second wiring. However, it can be arranged away from the first wiring. Therefore, it is possible to improve the measurement accuracy of the level of unwanted radiation due to the clock signal and the level of unwanted radiation due to the analog image signal.

  In the above configuration, when the level of the second electromagnetic wave measured by the level measurement unit is higher than the level of the first electromagnetic wave instead of the first power control unit, the level of the first electromagnetic wave is The power supplied to the light source is controlled so that the difference from the level of the second electromagnetic wave is within a predetermined range, and the level of the second electromagnetic wave is higher than the level of the first electromagnetic wave. When low, a second power control unit that does not execute the control is provided.

  According to this configuration, only when the level of the second electromagnetic wave (unwanted radiation due to the analog image signal) is higher than the level of the first electromagnetic wave (unwanted radiation due to the clock signal), the difference between the levels of these electromagnetic waves is determined in advance. The power supplied to the light source is controlled so as to be within a predetermined range.

  Since the clock signal is stable, the level of unnecessary radiation due to the clock signal is stable. For this reason, the unnecessary radiation generated in the image reading apparatus may exceed the regulation value when the level of unnecessary radiation due to the analog image signal is higher than the level of unnecessary radiation due to the clock signal. According to this configuration, when the level of unwanted radiation due to the analog image signal is lower than the level of unwanted radiation due to the clock signal, the level difference between these electromagnetic waves is supplied to the light source so as to be within a predetermined range. Do not process to control the power. Thereby, it becomes possible to reduce the burden of the 2nd electric power control part.

  An image forming apparatus according to another aspect of the present invention includes the image reading device, and the second peripheral circuit is a circuit having a function of converting the analog image signal into a digital image signal, and the image reading device. An image forming unit that forms an image indicated by the digital image signal output from the image on a sheet.

  Since the image forming apparatus according to another aspect of the present invention includes the image reading apparatus according to one aspect of the present invention, the operations and effects of the image reading apparatus according to one aspect of the present invention described above can be obtained.

  According to the present invention, it is possible to suppress the level of unnecessary radiation due to the analog image signal output from the image sensor.

1 is a diagram illustrating an outline of an internal structure of an image forming apparatus that can include an image reading apparatus according to an embodiment of the present disclosure. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus illustrated in FIG. 1. 1 is a block diagram illustrating a configuration of an image reading apparatus according to an embodiment. It is a figure which shows the positional relationship of a 1st wiring, a 2nd wiring, a 1st antenna, and a 2nd antenna. It is a figure which shows the relationship between the illumination intensity of a light source, the unnecessary radiation by a clock signal, and an analog image signal by a specific numerical value. 6 is a flowchart illustrating an operation of the image reading apparatus according to the present embodiment. It is a flowchart explaining the operation | movement of the modification of this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of the internal structure of an image forming apparatus 1 that can include an image reading apparatus according to an embodiment of the present invention. The image forming apparatus 1 can be applied to, for example, a digital multi-function peripheral having a copy, printer, scanner, and facsimile function. The image forming apparatus 1 includes an apparatus main body 100, a document reading unit 200 disposed on the apparatus main body 100, a document feeding unit 300 disposed on the document reading unit 200, and an operation disposed on the upper front surface of the apparatus main body 100. A display unit 400 is provided.

  The document feeder 300 functions as an automatic document feeder, and can continuously send a plurality of documents placed on the document placement unit 301 to the document reading unit 200.

  A document reading unit 200 includes a carriage 201 equipped with a light source and a CCD (Charge Coupled Device) sensor, a document table 203 formed of a transparent member such as glass, a document reading slit 205, and a reference document (reference white plate) 206 for shading correction. Is provided. When reading a document placed on the document table 203, the document is read by the CCD sensor while moving the carriage 201 in the longitudinal direction of the document table 203. On the other hand, when reading a document fed from the document feeding unit 300, the carriage 201 is moved to a position facing the document reading slit 205, and the document fed from the document feeding unit 300 is scanned. Reading is performed by the CCD sensor through the reading slit 205. The CCD sensor outputs the read original as image data.

  The apparatus main body 100 includes a sheet storage unit 101, an image forming unit 103, and a fixing unit 105. The sheet storage unit 101 is disposed at the lowermost part of the apparatus main body 100 and includes a sheet tray 107 that can store a bundle of sheets. In the bundle of sheets stored in the sheet tray 107, the uppermost sheet is sent out toward the sheet conveyance path 111 by driving the pickup roller 109. The sheet is conveyed to the image forming unit 103 through the sheet conveyance path 111.

  The image forming unit 103 forms a toner image on the conveyed paper. The image forming unit 103 includes a photosensitive drum 113, an exposure unit 115, a developing unit 117, and a transfer unit 119. The exposure unit 115 generates light modulated according to image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.), and is uniformly charged. Irradiate the circumferential surface of the photosensitive drum 113. As a result, an electrostatic latent image corresponding to the image data is formed on the peripheral surface of the photosensitive drum 113. In this state, a toner image corresponding to image data is formed on the peripheral surface by supplying toner from the developing unit 117 to the peripheral surface of the photosensitive drum 113. This toner image is transferred by the transfer unit 119 to the sheet conveyed from the sheet storage unit 101 described above.

  The sheet on which the toner image is transferred is sent to the fixing unit 105. In the fixing unit 105, heat and pressure are applied to the toner image and the paper, and the toner image is fixed on the paper. The paper is discharged to the stack tray 121 or the paper discharge tray 123.

  The operation display unit 400 includes an operation key unit 401 and a display unit 403. The display unit 403 has a touch panel function, and displays a screen including soft keys. The user operates the soft keys while viewing the screen to make settings necessary for executing functions such as copying.

  The operation key unit 401 is provided with operation keys including hard keys. Specifically, a start key 405, a numeric key 407, a stop key 409, a reset key 411, a function switching key 413 for switching between a copy, a printer, a scanner, and a facsimile are provided.

  A start key 405 is a key for starting operations such as copying and facsimile transmission. A numeric keypad 407 is a key for inputting numbers such as the number of copies and a facsimile number. A stop key 409 is a key for stopping a copying operation or the like halfway. A reset key 411 is a key for returning the set contents to the initial setting state.

  The function switching key 413 includes a copy key, a transmission key, and the like, and is a key for switching between a copy function and a transmission function. When the copy key is operated, an initial copy screen is displayed on the display unit 403. When the transmission key is operated, an initial screen for facsimile transmission and mail transmission is displayed on the display unit 403.

  FIG. 2 is a block diagram showing a configuration of the image forming apparatus 1 shown in FIG. The image forming apparatus 1 has a configuration in which an apparatus main body 100, a document reading unit 200, a document feeding unit 300, an operation display unit 400, a control unit 500, and a communication unit 600 are connected to each other by a bus. Since the apparatus main body 100, the document reading unit 200, the document feeding unit 300, and the operation display unit 400 have already been described, description thereof will be omitted.

  The control unit 500 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU executes control necessary for operating the image forming apparatus 1 on the above-described components of the image forming apparatus 1 such as the apparatus main body 100. The ROM stores software necessary for controlling the operation of the image forming apparatus 1. The RAM is a main memory of the image forming apparatus 1 and is used for temporary storage of data generated during execution of software, storage of application software, and the like. The RAM is, for example, a DRAM (Dynamic Random Access Memory).

  The communication unit 600 includes a facsimile communication unit 601 and a network I / F unit 603. The facsimile communication unit 601 includes an NCU (Network Control Unit) for controlling connection of a telephone line with a destination facsimile and a modulation / demodulation circuit for modulating / demodulating a signal for facsimile communication. The facsimile communication unit 601 is connected to the telephone line 605.

  A network I / F unit 603 is connected to a LAN (Local Area Network) 607. A network I / F unit 603 is a communication interface circuit for executing communication with a terminal device such as a personal computer connected to the LAN 607.

  The configuration of the image reading apparatus according to this embodiment will be described. FIG. 3 is a block diagram illustrating a configuration of the image reading apparatus 3 according to the present embodiment. The document reading unit 200 illustrated in FIG. 1 functions as the image reading device 3. The image reading apparatus 3 includes a fixed portion that does not move and a movable portion that can move in the sub-scanning direction D. The movable part is a carriage 201, which can be moved in the sub-scanning direction D by the moving means 10.

  A light source 11, an image sensor 12, a reflection optical system 13, an inverter 14, and the like are arranged on the carriage 201. The light source 11 irradiates the document 15 placed on the document table 203 and the reference document 206 with light L. The light source 11 is, for example, a cold cathode tube lamp or an LED. In the present embodiment, a cold cathode tube lamp will be described as an example.

  The image sensor 12 is a line sensor that receives the light L reflected from the document 15 and outputs an analog image signal S2 indicating an image of the document 15. As the image sensor 12, a CCD sensor or a CMOS sensor can be used. In the present embodiment, a CCD sensor will be described as an example.

  The reflection optical system 13 includes a plurality of mirrors and the like, and has a function of guiding the reflected light to the image sensor 12 by reflecting the light L emitted from the light source 11 onto the document 15 by the document 15.

  The fixed part includes a moving means 10, a first peripheral circuit 16, a second peripheral circuit 17, a level measuring unit 18, a power control unit 19, and a power source 20.

  The moving unit 10 enables the carriage 201 to move in the sub-scanning direction D. The moving means 10 includes a rail (not shown) for guiding the carriage 201 in the sub-scanning direction D, a motor (not shown) for supplying power for moving the carriage 201 along the rail, and the like.

  The first peripheral circuit 16 generates a digital control signal to be supplied to the image sensor 12. This control signal includes a clock signal S1 used to transfer charges in the CCD sensor which is the image sensor 12. The first peripheral circuit 16 and the image sensor 12 are connected by a first wiring 21. The first wiring 21 transmits a digital control signal.

  The second peripheral circuit 17 receives an analog output signal output from the image sensor 12. This output signal includes an analog image signal S2. The second peripheral circuit 17 has an analog front-end function, and performs predetermined processing (for example, converting an image signal from analog to digital) on the analog image signal S2 output from the image sensor 12. The second peripheral circuit 17 and the image sensor 12 are connected by a second wiring 22. The second wiring 22 transmits an analog output signal.

  The level measuring unit 18 measures the levels of the first electromagnetic wave E1 radiated from the first wiring 21 and the second electromagnetic wave E2 radiated from the second wiring 22. The first electromagnetic wave E1 radiated from the first wiring 21 is unnecessary radiation using the clock signal S1 as a radiation source. The second electromagnetic wave E2 radiated from the second wiring 22 is unnecessary radiation using the analog image signal S2 as a radiation source. The level measurement unit 18 includes a first antenna 23, a second antenna 24, and a level calculation unit 25.

  The first antenna 23 is provided at a position closer to the first wiring 21 than the second wiring 22, and receives the first electromagnetic wave E <b> 1 radiated from the first wiring 21. The second antenna 24 is provided at a position closer to the second wiring 22 than the first wiring 21, and receives the second electromagnetic wave E <b> 2 radiated from the second wiring 22. The level calculation unit 25 calculates each of the levels of the first electromagnetic wave E1 received by the first antenna 23 and the second electromagnetic wave E2 received by the second antenna 24.

  FIG. 4 is a diagram illustrating a positional relationship between the first wiring 21, the second wiring 22, the first antenna 23, and the second antenna 24. The first wiring 21 and the second wiring 22 are accommodated in a flat cable 26. The first wiring 21 is accommodated on one side of the two sides along the longitudinal direction of the flat cable 26. The second wiring 22 is accommodated on the other side of the two sides along the longitudinal direction of the flat cable 26.

  The first wiring 21 is a wiring group including a wiring 21a through which the clock signal S1 is transmitted. The second wiring 22 is a wiring group including a wiring 22a through which the analog image signal S2 is transmitted. The outermost wiring on one side of the flat cable 26 is assigned as the wiring 21a through which the clock signal S1 is transmitted. The outermost wiring on the other side of the flat cable 26 is assigned as the wiring 22a through which the analog image signal S2 is transmitted.

  The flat cable 26 is disposed between the first antenna 23 and the second antenna 24. The first antenna 23 is disposed on the first wiring 21 side, and the second antenna 24 is disposed on the second wiring 22 side.

  Returning to the description of FIG. The power source 20 supplies power to the inverter 14 and becomes the power source 20 of the light source 11. The output of the power supply 20 is variable.

  The power control unit 19 functions as a first power control unit, and the first electromagnetic wave E1 received by the first antenna 23 calculated by the level calculation unit 25 and the second electromagnetic wave received by the second antenna 24. A signal indicating the level of the electromagnetic wave E2 is input. Based on this signal, the power control unit 19 determines the difference between the level of the first electromagnetic wave E1 radiated from the first wiring 21 and the level of the second electromagnetic wave E2 radiated from the second wiring 22, The output of the power source 20 (that is, the power supplied to the light source 11) is controlled so as to be within a predetermined range. The predetermined range is, for example, an upper limit value (or a margin) that is allowed as a level of unwanted radiation from the analog image signal S2 so that the level of unwanted radiation generated in the image reading device 3 does not exceed a regulation value. Is a range that does not exceed a value slightly lower than the upper limit value).

  The level of the first electromagnetic wave E1 radiated from the first wiring 21 (unwanted radiation by the clock signal S1) does not depend on the illuminance of the light source 11, but the second electromagnetic wave radiated from the second wiring 22 It will be described that the level of E2 (unwanted radiation by the analog image signal S2) depends on the illuminance of the light source 11. FIG. 5 shows the relationship between the illuminance of the light source 11 and unnecessary radiation by the clock signal S1 and the analog image signal S2 by specific numerical values. The frequency of unwanted radiation due to the clock signal S1 is 79.09 MHz, and the frequency of unwanted radiation due to the analog image signal S2 is 65.88 MHz.

  The level of unnecessary radiation by the clock signal S1 is 17.0 decibels when the illuminance of the light source 11 is 23,400 lux, and 16.8 decibels when the illuminance of the light source 11 is 30,000 lux. The difference is -0.2 dB. Even if the illuminance of the light source 11 increases, the level of unnecessary radiation hardly changes. On the other hand, the level of unnecessary radiation by the analog image signal S2 is 18.3 decibels when the illuminance of the light source 11 is 23,400 lux, and 20 when the illuminance of the light source 11 is 30,000 lux. .3 dB, and the difference is +2.0 dB. As the illuminance of the light source 11 increases, the level of unnecessary radiation increases. From the above, it can be seen that the level of unnecessary radiation due to the clock signal S1 does not depend on the illuminance of the light source 11, but the level of unnecessary radiation due to the analog image signal S2 depends on the illuminance of the light source 11.

  The operation of the image reading apparatus according to the present embodiment will be described with reference mainly to FIGS. FIG. 6 is a flowchart for explaining this operation. When the operator turns on a power switch (not shown) of the image forming apparatus 1, the image forming apparatus 1 is activated, the fixing unit 105 and the like are activated, and a standby state is entered. At this time, the carriage 201 moves to the position of the reference document 206, power from the power source 20 is supplied to the light source 11 via the inverter 14, and the light source 11 is turned on (step S1).

  The level measuring unit 18 measures the level of the first electromagnetic wave E1 (unwanted radiation by the clock signal S1) and the level of the second electromagnetic wave E2 (unwanted radiation by the analog image signal S2) (step S2). More specifically, a digital control signal including a clock signal S <b> 1 sent to the image sensor 12 is transmitted to the first wiring 21. As a result, the first electromagnetic wave E <b> 1 radiated from the first wiring 21 is received by the first antenna 23 and sent to the level calculation unit 25. The level calculation unit 25 calculates the level of the first electromagnetic wave E1 radiated from the first wiring 21. On the other hand, an analog output signal including the analog image signal S <b> 2 output from the image sensor 12 is transmitted to the second wiring 22. As a result, the second electromagnetic wave E <b> 2 radiated from the second wiring 22 is received by the second antenna 24 and sent to the level calculation unit 25. The level calculation unit 25 calculates the level of the second electromagnetic wave E2 radiated from the second wiring 22.

  The power control unit 19 determines whether or not the difference between the level of the first electromagnetic wave E1 and the level of the second electromagnetic wave E2 calculated by the level calculation unit 25 is within a predetermined range (step S3). .

  When the power control unit 19 does not determine that the difference is within a predetermined range (No in step S3), the power control unit 19 controls the output of the power source 20 (step S4). More specifically, when the level of the second electromagnetic wave E2 radiated from the second wiring 22 is higher than the level of the first electromagnetic wave E1 radiated from the first wiring 21, the output of the power supply 20 is lowered. Thus, the power supplied to the light source 11 is controlled to be lowered. Thereby, since the illuminance of the light source 11 is lowered, the level of the analog image signal S2 can be lowered, and the level of the second electromagnetic wave E2 radiated from the second wiring 22 can be lowered.

  On the other hand, when the level of the second electromagnetic wave E2 radiated from the second wiring 22 is lower than the level of the first electromagnetic wave E1 radiated from the first wiring 21, the output of the power supply 20 is increased. Thus, control is performed to increase the power supplied to the light source 11. Thereby, since the illumination intensity of the light source 11 goes up, it can prevent that the illumination intensity of the light source 11 falls too much.

  The reason why it is possible to increase the power supplied to the light source 11 is as follows. The level of the first electromagnetic wave E1 is stable, and the level of the first electromagnetic wave E1 is set to a level that satisfies the regulation value defined by the standard. Therefore, when the level of the second electromagnetic wave E2 is lower than the level of the first electromagnetic wave E1, the level of the second electromagnetic wave E2 also satisfies the regulation value. Therefore, there is no need to further reduce the level of the second electromagnetic wave E2. In addition, if the level of the second electromagnetic wave E2 is less than the level of the first electromagnetic wave E1, there is a margin for increasing the level of the second electromagnetic wave E2 within the range of the regulation value. Can be increased.

  After the power control unit 19 controls the output of the power supply 20 (step S4), the process returns to step S2.

  When the power control unit 19 determines that the difference is within a predetermined range (Yes in step S3), the second peripheral circuit 17 uses the analog image signal S2 to perform various initial settings (for example, input gain adjustment, (Shading correction) is performed (step S5). The control unit 500 determines whether or not the document 15 is set on the document table 203 and the start key 405 (FIG. 1) is operated. That is, control unit 500 determines whether or not an instruction to start reading a document has been issued (step S6).

  When the control unit 500 does not determine that an instruction to start reading a document has been given (No in step S6), the level measuring unit 18 executes step S2 after a predetermined interval (step S7).

  When the control unit 500 determines that an instruction to start reading a document has been given (Yes in step S6), the control unit 500 causes the document reading device 200 functioning as the image reading device 3 to start a reading operation of the document 15. (Step S8).

  The main effects of this embodiment will be described. In the present embodiment, the second wiring 22 through which the first electromagnetic wave E1 radiated from the first wiring 21 through which the digital control signal including the clock signal S1 is transmitted and the analog output signal including the analog image signal S2 is transmitted. The level measuring unit 18 measures the level of the second electromagnetic wave E2 radiated from. Then, the power control unit 19 supplies the light source 11 so that the difference between the level of the first electromagnetic wave E1 and the level of the second electromagnetic wave E2 measured by the level measurement unit 18 is within a predetermined range. Control the power supplied.

  The first electromagnetic wave E1 is unnecessary radiation in which the clock signal S1 included in the digital control signal input to the image sensor 12 serves as a radiation source, and the second electromagnetic wave E2 is included in the analog output signal output from the image sensor 12. The analog image signal S2 to be generated is unnecessary radiation that becomes a radiation source. Since the clock signal S1 is stable, the level of unnecessary radiation that causes the clock signal S1 to be a radiation source is stable. According to the present embodiment, the level of unwanted radiation from the analog image signal S2 is supplied to the light source 11 with reference to the level of unwanted radiation from the clock signal S1. The power is controlled. Therefore, it is possible to suppress the level of unnecessary radiation due to the analog image signal S2 output from the image sensor 12.

  In addition, according to the present embodiment, the reference level is set to the level of unnecessary radiation from the clock signal S1, so that it is not necessary to set the reference level in the manufacturing process of the image reading apparatus 3.

  Furthermore, according to the present embodiment, the power supplied to the light source 11 so that the difference between the level of unwanted radiation due to the clock signal S1 and the level of unwanted radiation due to the analog image signal S2 is within a predetermined range. Is controlling. Thereby, since the light quantity of the light source 11 is feedback-controlled, the illuminance of the light source 11 can be regulated within a predetermined range. Therefore, it can contribute to stabilization of the image quality of the read image.

  In the present embodiment, since the image pickup device 12 is movable in the sub-scanning direction D and the first peripheral circuit 16 and the second peripheral circuit 17 are not moved, the image reading device 3 is used. The second wiring 22 becomes longer. For this reason, the level of the 1st electromagnetic wave E1 and the 2nd electromagnetic wave E2 becomes comparatively large. As described above, according to the present embodiment, it is possible to suppress the level of unnecessary radiation caused by the analog image signal S2 output from the image pickup device 12, and this is particularly effective for the image reading apparatus 3 of the above type. Note that the present invention can also be applied to an image reading apparatus in which the image sensor 12 does not move in the sub-scanning direction D.

  In the present embodiment, since the first antenna 23 is provided at a position close to the first wiring 21, the first antenna 23 generates unnecessary radiation (first electromagnetic wave E1) and analog image signal due to the clock signal S1. Of the unwanted radiation (second electromagnetic wave E2) caused by S2, unwanted radiation caused mainly by the clock signal S1 can be received. On the other hand, since the second antenna 24 is provided at a position close to the second wiring 22, the second antenna 24 mainly includes unnecessary radiation due to the clock signal S1 and unnecessary radiation due to the analog image signal S2. Unwanted radiation by the analog image signal S2 can be received. Therefore, it is possible to improve the measurement accuracy of the level of unwanted radiation due to the clock signal S1 and the level of unwanted radiation due to the analog image signal S2. Therefore, for example, it is possible to improve the accuracy with which the level of unnecessary radiation generated in the image reading device 3 does not exceed the regulation value.

  According to the present embodiment, as shown in FIG. 4, the first wiring 21 and the second antenna 24 are arranged between the first antenna 23 and the second antenna 24, and the first wiring 23 is provided on the first antenna 23 side. The flat cable 26 which accommodated the 2nd wiring 22 in each is provided. Accordingly, the first antenna 23 can be disposed close to the first wiring 21 while being separated from the second wiring 22, and the second antenna 24 can be disposed near the second wiring 22. While being arranged, it can be arranged away from the first wiring 21. Therefore, it is possible to improve the measurement accuracy of the level of unwanted radiation due to the clock signal S1 and the level of unwanted radiation due to the analog image signal S2.

  A modification of this embodiment will be described. In the modification, the power control unit 19 shown in FIG. 3 functions as a second power control unit described below. The second power control unit receives signals indicating the levels of the first electromagnetic wave E1 and the second electromagnetic wave E2 calculated by the level calculation unit 25. Based on this signal, the power control unit 19 performs the following processes (1) and (2).

  (1) When the level of the second electromagnetic wave E2 is higher than the level of the first electromagnetic wave E1, the difference between the level of the first electromagnetic wave E1 and the level of the second electromagnetic wave E2 falls within a predetermined range. As described above, the output of the power source 20 (that is, the power supplied to the light source 11) is controlled.

  (2) When the level of the second electromagnetic wave E2 is lower than the level of the first electromagnetic wave E1, the control of (1) is not executed.

  The operation of the modification will be described. FIG. 7 is a flowchart for explaining this operation. The difference from the flowchart shown in FIG. 6 is that step S9 is added between step S2 and step S3.

  The power control unit 19 determines whether the level of the second electromagnetic wave E2 is higher than the level of the first electromagnetic wave E1 with respect to the level of the first electromagnetic wave E1 and the level of the second electromagnetic wave E2 calculated by the level calculation unit 25. Judgment is made (step S9).

  When the power control unit 19 does not determine that the level of the second electromagnetic wave E2 is higher than the level of the first electromagnetic wave E1 (No in Step S9), that is, the second electromagnetic wave E2 radiated from the second wiring 22 When it is determined that the level is lower than the level of the first electromagnetic wave E1 radiated from the first wiring 21, the process proceeds to step S5.

  When the power control unit 19 determines that the level of the second electromagnetic wave E2 is higher than the level of the first electromagnetic wave E1 (Yes in step S9), the process proceeds to step S3.

  The effect of the modification will be described. According to the modification, only when the level of the second electromagnetic wave E2 (unwanted radiation by the analog image signal S2) is higher than the level of the first electromagnetic wave E1 (unwanted radiation by the clock signal S1), the level of these electromagnetic waves The power supplied to the light source 11 is controlled so that the difference falls within a predetermined range.

  Since the clock signal S1 is stable, the level of unnecessary radiation due to the clock signal S1 is stable. For this reason, the unnecessary radiation generated in the image reading device 3 may exceed the regulation value when the level of unnecessary radiation due to the analog image signal S2 is higher than the level of unnecessary radiation due to the clock signal S1. According to the modification, when the level of unwanted radiation due to the analog image signal S2 is lower than the level of unwanted radiation due to the clock signal S1, the light source is set so that the difference between these electromagnetic wave levels is within a predetermined range. 11 is not performed to control the power supplied to 11. As a result, it is possible to reduce the burden on the power control unit 19 that functions as the second power control unit.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image reader 11 Light source 12 Image pick-up element 15 Document 16 1st peripheral circuit 17 2nd peripheral circuit 18 Level measurement part 19 Power control part (1st power control part, 2nd power control part)
20 power supply 21 first wiring 22 second wiring 23 first antenna 24 second antenna 25 level calculation unit 26 flat cable D sub-scanning direction E1 first electromagnetic wave E2 second electromagnetic wave L light S1 clock signal S2 analog Image signal

Claims (6)

A light source for illuminating the document;
An image sensor that receives light reflected from the document and outputs an analog image signal indicating an image of the document;
A first peripheral circuit for supplying a digital control signal including a clock signal to the image sensor;
A second peripheral circuit that receives an analog output signal including the analog image signal output from the image sensor and performs predetermined processing on the analog image signal;
A first wiring that is connected to the image sensor and the first peripheral circuit and transmits the digital control signal;
A second wiring that is connected to the image sensor and the second peripheral circuit and transmits the analog output signal;
A level measuring unit for measuring levels of the first electromagnetic wave radiated from the first wiring and the second electromagnetic wave radiated from the second wiring;
A first control unit configured to control power supplied to the light source such that a difference between the level of the first electromagnetic wave measured by the level measuring unit and the level of the second electromagnetic wave is within a predetermined range. And an electric power control unit. A moving means for moving the light source and the image sensor in a sub-scanning direction;
The image reading apparatus according to claim 1, wherein the first peripheral circuit and the second peripheral circuit are not included in an object to be moved by the moving unit.   The level measuring unit is provided at a position closer to the first wiring than the second wiring, and receives the first antenna that receives the first electromagnetic wave, and the second antenna than the first wiring. The image reading apparatus according to claim 1, further comprising: a second antenna provided at a position near the wiring and receiving the second electromagnetic wave.   A flat cable disposed between the first antenna and the second antenna and accommodating the first wiring on the first antenna side and the second wiring on the second antenna side; An image reading apparatus according to claim 3.   Instead of the first power control unit, when the level of the second electromagnetic wave measured by the level measurement unit is higher than the level of the first electromagnetic wave, the level of the first electromagnetic wave and the second electromagnetic wave When the power supplied to the light source is controlled so that the difference from the electromagnetic wave level is within a predetermined range, and the level of the second electromagnetic wave is lower than the level of the first electromagnetic wave, The image reading apparatus according to claim 1, further comprising a second power control unit that does not execute control. The image reading apparatus according to any one of claims 1 to 5, comprising:
The second peripheral circuit is a circuit having a function of converting the analog image signal into a digital image signal,
An image forming apparatus comprising: an image forming unit that forms an image indicated by the digital image signal output from the image reading apparatus on a sheet.

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