Image reading device

Abstract

To provide an image reading device which performs shading correction at a more appropriate timing than prior arts.SOLUTION: In an image reading device, with a light source turned off upon activating the image reading device, reflected light from a reference board is detected by a line sensor and a reference black data value for each chip is acquired. When an operation section receives a read start command for a document, reflected light from the reference board is detected by the line sensor with the light source turned off, and a black data value for each chip is acquired. It is determined whether or not a ratio of the black data value for each chip to the reference black data value is equal to or greater than a predetermined reference value. If the ratio is equal to or greater than the reference value regarding for least one of a plurality of chips, a shading correction section is caused to perform shading correction.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to an image reading device, and more particularly to an image reading device using a line sensor configured with a plurality of optical sensor chips. [Background technology]

[0002] Conventionally, there is known an image reading device that reads an original document, which is equipped with a contact image sensor (CIS) that reads the original document using a line sensor that moves in the sub-scanning direction along the underside of the glass surface of the original document placing table while scanning in the main scanning direction.

[0003] The analog image signal output from the CIS passes through an analog front end (AFE) and is converted into a digital image signal. The CIS line sensor is composed of multiple chips (optical sensor chips) arranged in the main scanning direction. In general, the AFE is provided near the center of the CIS line sensor.

[0004] A known problem with image reading devices using such a CIS is that image quality may deteriorate, such as with uneven density, due to a sudden increase in thermal noise (dark current noise) caused by a rise in temperature of the AFE and CIS. In particular, heat generated by the AFE can cause degradation in image quality near the center of the line sensor to be more noticeable than at the ends of the line sensor.

[0005] Generally, in an image reading device, when the output signal level varies from chip to chip due to the influence of noise such as thermal noise, shading correction is performed to correct the level difference of the output signals of each chip in the line sensor to a predetermined reference level.

[0006] For example, known techniques include white shading correction, which corrects the white signal to a reference level obtained by reading reflected light from a white reference board at the start of an image reading operation, and black shading correction, which corrects the black signal to a reference level obtained by reading reflected light from a white reference board with the reading light source turned off.

[0007] A conventional technique for such shading correction is disclosed in which an image reading device reads the output signal from the OB pixel section (light-shielding section) of each chip as a first OB signal at the beginning of a job, performs shading correction in response to a job start signal, and then performs shading correction again when the black offset level difference between adjacent channels reaches a predetermined level based on the monitored OB signal (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2003-163796 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, the level of the black signal due to the temperature rise of the AFE and CIS varies over time, and varies significantly especially immediately after the start-up of the image reading device, and the rate of variation also differs significantly depending on each chip.

[0010] Therefore, conventional methods of performing shading correction at the beginning of a job or in response to a job start signal have not been able to sufficiently suppress the effects of image quality degradation caused by fluctuations in the black signal level due to temperature increases in the AFE and CIS.

[0011] This disclosure has been made in consideration of the above circumstances, and has an object to provide an image reading device that performs shading correction at more appropriate timing than conventional devices. [Means for solving the problem]

[0012] This disclosure relates to an image reading device that reads an original document and generates image data, the image reading device comprising an original document placement table on which the original document is placed, a reference plate provided on the original document placement table, a light source that illuminates the original document placed on the original document placement table, an operation unit that receives commands from a user, and a plurality of chips arranged in a main scanning direction, a line sensor that scans in the main scanning direction to detect reflected light from the original document and acquire image data when the operation unit receives a command to start reading the original document, a memory that stores the image data, and a shading correction unit that performs shading correction in the line sensor to correct variations in the levels of signals from the plurality of chips based on a predetermined reference black data value, and and a control unit that controls the shading correction unit, wherein the control unit detects reflected light from the reference plate with the line sensor with the light source turned off when the image reading device is started up, and obtains the reference black data value for each chip, and when the operation unit receives a command to start reading the original, detects reflected light from the reference plate with the line sensor with the light source turned off, and obtains the black data value for each chip, and determines whether the ratio between the black data value and the reference black data value for each chip is equal to or greater than a predetermined reference value, and if the ratio for at least one of a plurality of the chips is equal to or greater than the reference value, causes the shading correction unit to perform the shading correction. Effect of the Invention

[0013] According to this disclosure, an image reading device is realized that performs shading correction at a more appropriate timing than conventional methods by determining whether or not to perform shading correction based on the ratio between the black data value obtained when a command to start reading a document is received and the reference black data value obtained when the device is started. [Brief description of the drawings]

[0014] [Figure 1] 1 is a perspective view showing an external appearance of a digital multifunction peripheral according to a first embodiment of the present disclosure. [Diagram 2] 2 is a cross-sectional view showing a mechanical configuration of a main body portion of the digital multifunction peripheral shown in FIG. [Diagram 3] 2 is a block diagram showing an electrical configuration of the digital multifunction peripheral shown in FIG. 1. [Figure 4] FIG. 4 is an exploded perspective view showing a schematic configuration of an image reading unit of the digital multifunction peripheral shown in FIG. 4(A) shows the configuration of the glass surface of the document placement table for reading a document, and FIG. 4(B) shows the configuration of a reading mechanism that optically reads the document. [Diagram 5] FIG. 5 is an explanatory diagram showing a schematic configuration of the CIS unit shown in FIG. [Figure 6] 4 is a flowchart showing an example of a document reading process of the digital multifunction peripheral shown in FIG. [Figure 7] 7 is a graph showing an example of black data values ​​of some chips constituting the line sensor of the CIS unit shown in Fig. 4. Fig. 7(A) shows a graph of the change over time in black data values ​​of chips 1 to 8 from start-up, and Fig. 7(B) shows a graph of the change over time in black data values ​​of chips 3 to 6 from start-up. [Figure 8] 11 is a flowchart showing an example of a document reading process of a digital multifunction peripheral according to a second embodiment of the present disclosure. [Figure 9] 13 is a graph showing an example of a fluctuation rate of black data values ​​of chips constituting a line sensor of a CIS unit according to a second embodiment of the present disclosure. [Figure 10] FIG. 11 is a block diagram showing an electrical configuration of a digital multifunction peripheral according to a third embodiment of the present disclosure. [Figure 11] 11 is a flowchart showing an example of a document reading process of a digital multifunction peripheral according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Further, preferred embodiments of this disclosure will be described.

[0016] In this disclosure, an "image reading device" is a device that reads an original image and outputs image data, such as a scanner having a scanning function or an MFP (Multifunctional Peripheral) that also has functions other than scanning.

[0017] In the image reading device according to this disclosure, the control unit may cause the shading correction unit to perform the shading correction, and then replace the black data value acquired when the operation unit receives a command to start reading the document with a new reference black data value.

[0018] In this way, the black data value acquired when a command to start reading the document is received is replaced with a new reference black data value, thereby realizing an image reading device that performs shading correction at a more appropriate timing than conventional methods.

[0019] In the image reading device disclosed herein, the control unit may detect reflected light from the reference plate using the line sensor with the light source turned off when the device is started up, and obtain the reference black data value of a predetermined judgment chip among the multiple chips, and when the operation unit receives a command to start reading the original, detect reflected light from the reference plate using the line sensor with the light source turned off, and obtain the black data value of the judgment chip, determine whether the ratio between the black data value of the judgment chip and the reference black data value is equal to or greater than a predetermined reference value, and if the ratio is equal to or greater than the reference value, cause the shading correction unit to perform the shading correction.

[0020] The "predetermined chip for judgment" is the chip having the largest fluctuation rate of black data value due to the influence of heat generated by the AFE or the like. The number of chips for judgment is not limited to one, and two or more chips may be used as the chips for judgment. In this case, for example, when the ratio between the black data value and the reference black data value of at least one of the two or more chips for judgment is equal to or greater than a predetermined reference value, shading correction may be performed.

[0021] In this way, it is not necessary to determine the fluctuation rate of the black data value for all chips that make up the line sensor, and it is determined whether or not shading correction should be performed based on the ratio between the black data value obtained for the chip used for judgment that has a large fluctuation rate of the black data value and the reference black data value, thereby making it possible to realize an image reading device that performs shading correction at a more appropriate timing than before.

[0022] In the image reading device according to this disclosure, a timer for measuring time may be further provided, and when the operation unit receives a command to start reading the document, the control unit may use the timer to determine whether or not a predetermined judgment time has elapsed since startup of the image reading device, and if it is within the judgment time, cause the shading correction unit to perform the shading correction.

[0023] In this way, since the rate of fluctuation in black data values ​​is large within a specified judgment time (e.g., 300 seconds) from the time the device is started up, by performing shading correction within the judgment time, it is possible to realize an image reading device that performs shading correction at a more appropriate timing than conventional methods.

[0024] In the image reading device disclosed herein, when the judgment time has elapsed, the control unit may determine whether or not this is the first read start command after the judgment time has elapsed, and if it is the first read start command, cause the shading correction unit to perform the shading correction.

[0025] In this way, even if the judgment time has elapsed, if it is the first reading start command, shading correction is performed, thereby making it possible to realize an image reading device that performs shading correction at a more appropriate timing than conventional devices.

[0026] In the image reading device disclosed herein, if the control unit receives an instruction to start reading after the determination time has elapsed and this is not the first time, it may turn on the light source and cause the line sensor to detect reflected light from the original document and acquire image data without performing the shading correction.

[0027] In this way, when the reading start command is issued for the second or subsequent times after the lapse of the determination time, shading correction is not performed, thereby making it possible to realize an image reading device that performs shading correction at a more appropriate timing than conventional devices.

[0028] The present disclosure will be described in further detail below with reference to the accompanying drawings. Note that the following description is illustrative in all respects and should not be construed as limiting the present disclosure.

[0029] [Embodiment 1] The schematic configuration of a digital multifunction peripheral 1, which is an embodiment of an image reading device according to the present disclosure, will be described with reference to FIGS.

[0030] FIG. 1 is a perspective view showing the appearance of a digital multifunction peripheral 1 according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view showing the mechanical configuration of the main body of the digital multifunction peripheral 1 shown in FIG.

[0031] The digital multifunction device 1 is a device such as a multifunction device or MFP (Multifunctional Peripheral) that digitally processes image data and has a copying function, a scanner function, and a facsimile function.

[0032] The digital multifunction peripheral 1 executes scanning, printing and copying jobs based on instructions from a user received via the operation unit 103 or communication unit 55 .

[0033] <Digital MFP 1 Configuration> Here, the internal configuration of the digital multifunction peripheral 1 shown in FIG. 2 will be briefly described.

[0034] The digital multifunction machine 1 prints color images using the colors black (K), cyan (C), magenta (M), and yellow (Y) on printing paper. Therefore, the digital multifunction peripheral 1 is internally configured to have four each of the developing devices 12, photosensitive drums 13, drum cleaning devices 14, and chargers 15.

[0035] In order to form four types of toner images corresponding to the four colors, four image stations Pa, Pb, Pc, and Pd are configured corresponding to black, cyan, magenta, and yellow, respectively.

[0036] The digital multifunction peripheral 1 may be one that prints monochrome images using a single color (for example, black) on printing paper.

[0037] In each of the image stations Pa, Pb, Pc, and Pd, a toner image is formed in the following manner.

[0038] The drum cleaning device 14 removes and collects residual toner from the surface of the photoconductor drum 13 . Thereafter, the charger 15 uniformly charges the surface of the photosensitive drum 13 to a predetermined potential. An optical scanning device 11 then exposes the uniformly charged surface to light to form an electrostatic latent image on the surface. Thereafter, developer unit 12 develops the electrostatic latent image. As a result, a toner image of each color is formed on the surface of each photoconductor drum 13.

[0039] The intermediate transfer belt 21 moves in a circular motion in the direction of the arrow C. The toner images of each color on the surface of each photoconductor drum 13 are transferred in sequence onto the intermediate transfer belt 21 and overlapped, forming a color toner image on the intermediate transfer belt 21. The belt cleaning device 22 removes and collects residual toner from the intermediate transfer belt 21 as it moves around.

[0040] The printing paper is picked up from one of the four feed trays 18 by a pickup roller 33, and is fed to the secondary transfer device 23 via a paper transport path R1. Alternatively, the sheet is fed from a manual feed tray 19 by a pickup roller (not shown) and fed to the secondary transfer device 23 via a paper transport path R1.

[0041] A registration roller 34 is disposed on the paper transport path R1 to temporarily stop the print paper and align the leading edge of the print paper. Also provided are transport rollers 35 for promoting the transport of the printing paper.

[0042] Between the transfer roller 23 a of the secondary transfer device 23 and the intermediate transfer belt 21 , a nip area is formed. The registration rollers 34 temporarily stop the printing paper, and then transport the printing paper to the nip area in accordance with the timing of the transfer of the toner image.

[0043] When the printing paper passes through the nip, the color toner image formed on the surface of the intermediate transfer belt 21 is transferred to the printing paper.

[0044] After passing through the nip area, the printing paper is sandwiched between the heating roller 24 and the pressure roller 25 of the fixing device 17 and is heated and pressurized. This heat and pressure fixes the color toner image onto the printing paper.

[0045] Next, the print paper that has passed through the fixing device 17 is discharged via discharge rollers 36a or 36b onto a discharge tray 39a or 39b.

[0046] The destination of the print paper is controlled by the control unit 100, which will be described later, and the transport path is switched by a switching mechanism (not shown) so that the print paper is guided to either of the discharge trays 39a and 39b.

[0047] The mechanism for switching the transport path of the print paper is well known in the technical field of image forming apparatuses, and therefore will not be illustrated in detail.

[0048] Next, the electrical configuration of the digital multifunction peripheral 1 will be briefly described with reference to FIG.

[0049] FIG. 3 is a block diagram showing the electrical configuration of the digital multifunction peripheral 1 shown in FIG. As shown in FIG. 3, the digital multifunction peripheral 1 includes a communication unit 55, a control unit 100, a printing unit 102, an operation unit 103, a display unit 104, a storage unit 105, an image reading unit 111, a conveying unit 112 and an image processing unit 113.

[0050] The communication unit 55 is a circuit and firmware of a communication interface that transmits and receives communication data to and from external devices and receives, for example, a command to execute a print job from an external computer.

[0051] The control unit 100 controls the digital multifunction peripheral 1 in an integrated manner, and is made up of at least one CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read only memory), various interface circuits, and the like.

[0052] The control unit 100 controls the overall operation of the digital multifunction peripheral 1, and monitors and controls all loads such as the detection of each sensor, motors, clutches, and fixing lamps. The number of control units 100 is not limited to one, and the operation of the digital multifunction peripheral 1 may be controlled by a plurality of control units 100.

[0053] The printing unit 102 prints a print image on a printing sheet by electrophotography. 2, the optical scanning device 11, the developing device 12, the photoconductor drum 13, the drum cleaning device 14, and the charger 15. The printing unit 102 also includes electrical components related to the intermediate transfer belt 21, the fixing device 17, the paper transport path R1, the feed tray 18, and the discharge trays 39a and 39b.

[0054] The operation unit 103 is composed of a liquid crystal display and a touch panel, and is a part that displays information on the liquid crystal display and receives instructions from the user via the touch panel.

[0055] The display unit 104 is a part that displays various types of information. The display unit 104 is, for example, a CRT display, a liquid crystal display, an EL display, or the like, and is a display device such as a monitor or line display for displaying electronic data such as the processing state of the operating system and application software. The control unit 100 displays the operation and status of the digital multifunction peripheral 1 through the display unit 104 .

[0056] The storage unit 105 includes a RAM 104a and a ROM 104b, and is a non-volatile storage means such as a hard disk drive (HDD) or a flash storage unit, and stores various data and programs.

[0057] The RAM 104a is a storage unit (Random Access Memory) accessible by the control unit 100, and provides a working storage unit for temporarily storing data. The RAM 104a stores, for example, a capacitance threshold value of the touch panel and a database of various types of images.

[0058] The ROM 104b is a read only memory accessible by the control unit 100, and stores data necessary for the control unit 100 to control programs. The ROM 104b stores various data that are the basis for setting the image reading function, the touch panel function, and the like.

[0059] The RAM 104a and the ROM 104b are connected to the control unit 100 via a bus, and stores programs for operating the control unit 100 and develops the programs in the memory. These are merely examples of configurations, and the system may be configured with multiple CPUs or boards.

[0060] The image reading unit 111 detects and optically reads an original placed on a platen or an original conveyed from an original tray, and generates image data. The image reading unit 111 includes a CIS unit 1110 , an LED 1113 , and a shading correction unit 1114 .

[0061] FIG. 4 is an exploded perspective view showing a schematic configuration of the image reading unit 111 of the digital multifunction peripheral 1 shown in FIG.

[0062] FIG. 4A shows the configuration of the glass surface of the document placement table for reading the document. As shown in FIG. 4A, there are provided an original reading glass 1115 for reading an original conveyed by an ADF (Automatic Document Feeder) and an original placement glass 1116 for placing an original on an original placement table.

[0063] FIG. 4B shows the configuration of a reading mechanism that optically reads the document placed under the glass surface of FIG. 4A. As shown in FIG. 4B, the CIS unit 1110 is configured to be movable in the sub-scanning direction on a rail 1117 by a drive belt 1118 and a drive gear 1119. When reading an original conveyed by the ADF, the CIS unit 1110 is held stationary under the original reading glass 1115, and the conveyed original is sequentially read by the line sensor.

[0064] The CIS unit 1110 includes a plurality of CMOS sensors 1111 arranged in the main scanning direction, and an AFE that adjusts analog image data output from the CMOS sensors 1111, converts it into digital image data, and outputs it.

[0065] FIG. 5 is an explanatory diagram showing a schematic configuration of the CIS unit 1110 shown in FIG. In the example of FIG. 5, the CIS unit 1110 is configured from a line sensor made up of 12 CMOS sensor chips (chip 1 to chip 12) arranged in the main scanning direction, and an AFE provided near chip 4.

[0066] The LED 1113 is a light source for reading the document. Moreover, with the LED 1113 turned off, the CIS unit 1110 detects reflected light from a predetermined white reference plate to obtain a reference black data value for shading correction.

[0067] The shading correction section 1114 is a section that performs shading correction on the image data output from the CIS unit 1110 and outputs the corrected image data to the image processing section 113 .

[0068] The transport unit 112 transports documents set on the document table, the ADF, and a predetermined tray to the image reading unit 111.

[0069] The image processing unit 113 is a part that converts the image data read from the original by the image reading unit 111 into an appropriate electrical signal based on job commands such as printing input from the operation unit 103, and processes the signal so that it is suitable for output such as enlargement / reduction.

[0070] The control unit 100 controls the conveying unit 112 to convey the document. Then, the image of the document is read by the image reading unit 111 , and the image is processed by the image processing unit 113 , after which image data representing the image of the document is stored in the storage unit 105 . Further, the control unit 100 controls the printing unit 102 to print an image of a document indicated by the image data in the storage unit 105 on a printing paper by the printing unit 102.

[0071] The above is an outline of the configuration of the digital multi-function machine 1.

[0072] <Flow of document reading process of digital multi-function machine 1 according to Embodiment 1 of this disclosure> Next, based on FIGS. 6 to 8, the flow of the document reading process of the digital multi-function machine 1 according to Embodiment 1 of this disclosure will be described.

[0073] FIG. 6 is a flowchart showing an example of the document reading process of the digital multi-function machine 1 shown in FIG. 1.

[0074] In step S1 of FIG. 6, after the apparatus is started up, in step S1, the control unit 100 reads the reflected light from a predetermined white reference plate by the CIS unit 1110 with the LED 1113 turned off, and causes the reference black data value for shading correction to be acquired (step S1). Here, as the timing for acquiring the reference black data value, for example, any time between 0 seconds (immediately after startup) and 300 seconds (the time until the fluctuation of the black data value is generally stabilized) may be used.

[0075] Next, in step S2, the control unit 100 determines whether or not the operation unit 103 has received a reading start command (step S2).

[0076] When the operation unit 103 has received a reading start command (when the determination in step S2 is Yes), in step S3, the control unit 100 reads the reflected light from a predetermined white reference plate by the CIS unit 1110 with the LED 1113 turned off, and causes the black data value to be acquired (step S3).

[0077] In the subsequent step S4, the control unit 100 determines whether or not the fluctuation rate of the black data value is equal to or greater than a predetermined reference value (step S4). Here, the fluctuation rate is the ratio obtained by dividing the black data value of each chip constituting the line sensor of the CIS unit 1110 by the reference black data value.

[0078] FIG. 7 is a graph showing an example of black data values ​​of some chips constituting the line sensor of the CIS unit 1110 shown in FIG. Here, the "black data value" is a value obtained by taking the value of the pixel at the center of one chip in the main scanning direction as a representative value. The black data value may also be the average value, minimum value, or maximum value of multiple pixels in one chip. The same applies to the other figures.

[0079] Fig. 7(A) shows a graph of the change over time from startup of the black data values ​​of chips 1 to 8. Fig. 7(B) shows a graph of the change over time from startup of the black data values ​​of chips 3 to 6.

[0080] As shown in FIG. 7(B), it can be seen that the changes in chips 4 and 6 are larger than the changes in chips 3 and 5 immediately after startup.

[0081] If the rate of change in the black data value is equal to or greater than a predetermined reference value (if the determination in step S4 is Yes), in step S5, the control unit 100 causes the shading correction unit 1114 to execute shading correction (step S5).

[0082] In the next step S6, the control unit 100 replaces the black data value acquired in step S3 with a new reference black data value (step S6).

[0083] After the start of the startup, when the operation unit 103 receives a second or subsequent reading start command, the fluctuation rate is determined in step S4 based on the reference black data value replaced in step S6.

[0084] Thereafter, in step S7, the control unit 100 causes the image reading unit 111 to read the document (step S7), and then ends the process.

[0085] On the other hand, if the fluctuation rate of the black data value is less than the predetermined reference value in step S4 (if the determination in step S4 is No), in step S7, the control unit 100 causes the image reading unit 111 to read the document.

[0086] On the other hand, when the possibility of image quality deterioration due to heat generation is low and the fluctuation rate of the black data value is small, shading correction is not performed before the start of reading. Generally, shading correction takes 3 to 4 seconds, so compared to conventional technology in which shading correction is always performed at the beginning of a job, when there is a low possibility of image quality degradation due to heat generation, the image reading device of embodiment 1 of this disclosure can start reading the document immediately after receiving a reading start command.

[0087] In this way, by determining whether or not shading correction should be performed based on the ratio between the black data value obtained when a command to start reading the document is received and the reference black data value obtained when the device is started up, a digital multifunction device 1 can be realized that performs shading correction at a more appropriate timing than before.

[0088] [Embodiment 2] <Flow of document reading process of digital multifunction peripheral 1 according to embodiment 2 of the present disclosure> Next, a flow of document reading processing by the digital multifunction peripheral 1 according to the second embodiment of the present disclosure will be described with reference to FIGS.

[0089] The schematic configuration of the digital multifunction peripheral 1 according to the second embodiment is the same as that of the first embodiment (FIGS. 1 to 5), and therefore a description thereof will be omitted.

[0090] FIG. 8 is a flowchart showing an example of a document reading process of the digital multifunction peripheral 1 according to the second embodiment of the present disclosure. The processes in steps S11 to S13 and S15 to S17 in FIG. 8 correspond to the processes in steps S1 to S3 and S5 to S7 in FIG. 6 of the first embodiment, respectively, and therefore will not be described. Here, the determination in step S14 in FIG. 8, which is different from that in the first embodiment, will be described.

[0091] In step S13 of FIG. 8, after acquiring the black data value (step S13), in the following step S14, the control unit 100 determines whether or not the fluctuation rate of the black data value of a predetermined chip is equal to or greater than a predetermined reference value (step S14).

[0092] FIG. 9 is a graph showing an example of the fluctuation rate of the black data value of the chip constituting the line sensor of the CIS unit 1110 according to the second embodiment of this disclosure. The horizontal axis in FIG. 9 indicates the number of pixels in the main scanning direction, and the vertical axis indicates the fluctuation rate of the black data value (black data value / reference black data value).

[0093] In FIG. 9, the fluctuation rate of the black data value (black data value / reference black data value) is smallest at 1, and the further away from 1 the fluctuation rate becomes larger. Moreover, the main scanning width is 5184 pixels, and the number of pixels per chip is 432 pixels. In the example of FIG. 9, it can be seen that the fluctuation rate is about 1.1 near the pixel number of about 1728 (chip 4), and the fluctuation rate is next about 0.95 near the pixel number of about 2592 (chip 6). This is thought to be due to the effect of heat generated by the AFE provided near the chip 4 as shown in FIG.

[0094] Therefore, in the second embodiment, for chip 4 which is assumed to have a large fluctuation rate, it is determined whether or not the fluctuation rate of the black data value is equal to or greater than a predetermined reference value.

[0095] In this way, there is no need to determine the fluctuation rate of the black data value for all chips 1 to 12 that make up the line sensor, and it is determined whether or not shading correction should be performed based on the ratio between the black data value obtained for chip 4, which has a large fluctuation rate of black data as the chip for judgment, and the reference black data value, thereby realizing a digital multifunction printer 1 that performs shading correction at a more appropriate timing than before.

[0096] [Embodiment 3] <Flow of document reading process of digital multifunction peripheral 1 according to embodiment 3 of this disclosure> Next, a flow of document reading processing by the digital multifunction peripheral 1 according to the third embodiment of the present disclosure will be described with reference to FIGS.

[0097] FIG. 10 is a block diagram showing an electrical configuration of the digital multifunction peripheral 1 according to the third embodiment of the present disclosure. The schematic configuration of the digital multifunction peripheral 1 according to the third embodiment is the same as that of the first embodiment (FIGS. 1 to 5), except that a timer 106 is provided.

[0098] The timer 106 is a part that measures and counts time, and obtains the time from, for example, a built-in clock or via a wired / wireless network. In the third embodiment, the timer 106 is used to measure the elapsed time from the start-up of the device.

[0099] FIG. 11 is a flowchart showing an example of a document reading process of the digital multifunction peripheral 1 according to the third embodiment of the present disclosure.

[0100] In step S21 of FIG. 10, the control unit 100 determines whether or not the operation unit 103 has received a reading start command (step S21).

[0101] When the operation unit 103 receives a reading start command (when the determination in step S21 is Yes), in step S22, the control unit 100 determines whether or not it is within 300 seconds from the start-up of the device (step S22).

[0102] If it is within 300 seconds since the start-up of the device (if the determination in step S22 is Yes), in step S24, the control unit 10 causes the shading correction unit 1114 to execute shading correction (step S24).

[0103] Thereafter, in step S25, the control unit 100 causes the image reading unit 111 to read the document (step S25), and then ends the process.

[0104] On the other hand, if it is not within 300 seconds from the start-up of the device in step S22 (if the determination in step S22 is No), in step S23, the control unit 100 determines whether or not this is the first reading after 300 seconds have elapsed since the start-up of the device (step S23).

[0105] If this is the first reading after 300 seconds have elapsed since the start-up of the device (if the determination in step S23 is Yes), in step S24, the control unit 10 causes the shading correction unit 1114 to execute shading correction.

[0106] On the other hand, if it is not the first reading after 300 seconds have elapsed since the start-up of the apparatus (if the determination in step S23 is No), in step S25, the control unit 100 causes the image reading unit 111 to read the document.

[0107] As shown in the graphs in Figures 7(A) and (B), after 300 seconds have passed since startup, the fluctuations in the black data values ​​of each chip become roughly stable. Therefore, if 300 seconds have passed since the device was started up and this is not the first reading, shading correction is not performed.

[0108] In this manner, since the rate of fluctuation of the black data value is large within a specified judgment time from the start of the device, shading correction is performed if it is within the judgment time, and even if the judgment time has passed, shading correction is performed if it is the first reading start command, thereby realizing a digital multifunction device 1 that performs shading correction at a more appropriate timing than before.

[0109] Preferred aspects of the present disclosure include any combination of the above-mentioned aspects. In addition to the above-mentioned embodiment, various modifications of this disclosure are possible. These modifications should not be interpreted as not belonging to the scope of this disclosure. This disclosure should include all modifications within the scope of the claims and the equivalent meanings. [Explanation of symbols]

[0110] 1: digital multifunction device, 11: optical scanning device, 12: developing device, 13: photoconductor drum, 14: drum cleaning device, 15: charging device, 17: fixing device, 18: feeding tray, 19: manual feed tray, 21: intermediate transfer belt, 22: belt cleaning device, 23: secondary transfer device, 23a: transfer roller, 24: heating roller, 25: pressure roller, 33: pickup roller, 34: registration roller, 35: transport roller, 36a, 36b: discharge roller, 39a, 39b: discharge tray, 55: communication unit, 100: control unit, 102: printing unit, 103: operation unit, 104: display unit, 104a: RAM, 104b: ROM, 105: storage unit, 111: image reading unit, 112: transport unit, 113: image processing section, 1110: CIS unit, 1111: CMOS sensor, 1112: AFE, 1113: LED, 1114: shading correction section, 1115: document reading glass, 1116: document placement glass, 1117: rail, 1118: drive belt, 1119: drive gear, C: arrow direction, Pa, Pb, Pc, Pd: image station, R1: paper transport path

Claims

1. An image reading device that reads an original and generates image data, a document placement table on which the document is placed; A reference plate provided on the document placement table; a light source that illuminates the document placed on the document placement table; An operation unit that receives commands from a user; a line sensor that is composed of a plurality of chips arranged in a main scanning direction, and that scans in the main scanning direction when the operation unit receives a command to start reading the document, detects reflected light from the document, and acquires image data; A memory for storing the image data; a shading correction unit that performs shading correction in the line sensor to correct variations in the levels of signals from the plurality of chips based on a predetermined reference black data value; a control unit that controls the light source, the line sensor, the memory, and the shading correction unit, the control unit detects reflected light from the reference plate by the line sensor in a state in which the light source is turned off when the image reading device is started, and acquires the reference black data value for each chip; when the operation unit receives a command to start reading the document, the line sensor detects reflected light from the reference plate in a state in which the light source is turned off, and obtains a black data value for each chip; an image reading device characterized by determining whether a ratio between the black data value and the reference black data value for each chip is equal to or greater than a predetermined reference value, and causing the shading correction unit to perform the shading correction when the ratio for at least one of the multiple chips is equal to or greater than the reference value.

2. 2. The image reading device according to claim 1, wherein the control unit causes the shading correction unit to perform the shading correction, and then replaces the black data value acquired when the operation unit receives a command to start reading the document with the new reference black data value.

3. the control unit detects reflected light from the reference plate by the line sensor with the light source turned off when the device is started up, and acquires the reference black data value of a predetermined chip for judgment among the plurality of chips; When the operation unit receives a command to start reading the document, the line sensor detects reflected light from the reference plate in a state where the light source is turned off, and obtains a black data value of the determination chip; 2. The image reading device according to claim 1, further comprising: a determining unit that determines whether a ratio between the black data value of the judgment chip and the reference black data value is equal to or greater than a predetermined reference value; and, if the ratio is equal to or greater than the reference value, causes the shading correction unit to perform the shading correction.

4. Further comprising a timer for measuring time, when the operation unit receives a command to start reading the document, the control unit determines whether or not a predetermined determination time has elapsed since the start of the image reading device, using the timer; The image reading apparatus according to claim 1 , wherein if the determined time is within the judgment time, the shading correction unit is caused to perform the shading correction.

5. 5. The image reading device according to claim 4, wherein, when the determination time has elapsed, the control unit determines whether or not the command to start reading is the first command after the determination time has elapsed, and, when the command to start reading is the first command, causes the shading correction unit to perform the shading correction.

6. The image reading device according to claim 5, wherein the control unit, when the first reading start command is not received after the determination time has elapsed, turns on the light source and causes the line sensor to detect reflected light from the document and acquire image data without performing the shading correction.

Images