JP5767910B2 - Document reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a document reading apparatus and an image forming apparatus including the same, and more particularly to correction of image data indicating an image of a document read by the document reading apparatus.

  A document reading apparatus such as a scanner has a function of correcting image data when the document is read and image data indicating an image of the document is generated. As such correction, in order to ensure a dynamic range, gain correction for adjusting the analog image signal output from the image sensor to the full AD conversion range, illumination non-uniformity, and the center and peripheral portions of the lens And shading correction for a phenomenon in which the brightness varies depending on the position of the pixel due to a difference in the degree of light condensing.

  As an example of a document reading apparatus having a function of correcting image data, means for comparing the image signal level of each color when an optical image of a white reference plate is formed on a color image sensor with a set value, and this means Has been proposed that includes a means for controlling the lighting voltage of the light source so that the comparison of the two matches, and a means for correcting the image signal output from the color image sensor in accordance with the change in the lighting voltage ( For example, see Patent Document 1).

  As another example of a document reading apparatus having a function of correcting image data, temperature variation detection for detecting temperature variations of an R light source, a G light source, and a B light source immediately after scanning of a document is stopped Means, storage means for storing the relationship between the temperature variation detected by the means and the output of the image sensor as a correction value, and correction means for correcting the output of the image data in accordance with the correction value stored in the means. Have been proposed (see, for example, Patent Document 2).

  As still another example of a document reading apparatus having a function of correcting image data, temperature data of each pixel of the CCD is acquired prior to reading the document, and the image data obtained by reading the document is converted to the temperature. A technique for correcting the black level using data has been proposed (see, for example, Patent Document 3).

JP-A-1-149672 JP 2001-333283 A JP-A-6-350925

  In gain correction and shading correction, before reading a document, light is emitted from a light source to a white reference plate extending in the main scanning direction, and data of light reflected by the white reference plate is obtained. Correction is performed for each main scanning line. For this reason, in the method of reading a document by moving the document relatively in the sub-scanning direction, gain correction and shading correction can be used if an event occurs in which the light amount from the light source fluctuates from the start to the end of the movement. Can not do it. In other words, gain correction and shading correction handle events that occur while scanning a document and affect the scanned document image (for example, fluctuations in the voltage and current supplied to the light source, and fluctuations in the light source temperature). Can not do it.

  According to the present invention, in a method of reading a document by relatively moving the document in the sub-scanning direction, correction for an event that occurs during reading of the document and affects the image of the read document can be performed on the image data. An object of the present invention is to provide a document reading apparatus and an image forming apparatus including the same.

  The document reading apparatus according to the present invention that achieves the above object divides the document into a plurality of lines along the main scanning direction, reads the document while relatively moving the document in the sub-scanning direction, An imaging unit for outputting image data including pixel data indicating pixels constituting an image of a document, and event data indicating an event that occurs in a predetermined element among elements used when the document is read by the imaging unit A measurement unit that executes an operation for measuring the movement from the start to the end of the movement, a storage unit that stores correction data corresponding to the event in advance, and the imaging unit reads the plurality of lines in order. The correction value for each line is determined using the event data and the correction data for each line measured by the measurement unit, and the line corresponding to each line is determined. For arsenide, and a correction section that corrects the pixel data by using the correction value at each line.

  In the document reading apparatus according to the present invention, among the elements (for example, the power source and the light source) used when the document is read by the imaging unit, events (for example, power supply voltage and current fluctuation, light source) The operation of measuring event data indicating (temperature fluctuations) is performed from the start to the end of relative movement of the document in the sub-scanning direction. The correction value for each line is determined using event data and correction data for each line measured when a plurality of lines are read in sequence. Then, for the pixels corresponding to each line, the pixel data is corrected using the correction value in each line. Therefore, according to the document reading apparatus of the present invention, in a method of reading a document by relatively moving the document in the sub-scanning direction, correction for an event that occurs during reading of the document and affects the image is performed. Can be executed.

  In the above configuration, the predetermined element includes a power source of a light source that irradiates light to the original when the original is read by the imaging unit, and the event data is supplied from the power source to the light source. Including data indicating a variation amount of voltage or current, wherein the correction data includes data capable of specifying a correction value of a gradation with respect to the variation amount, and the measurement unit is a voltage supplied from the power source to the light source. Alternatively, the current measurement is performed from the start to the end of the movement, and the correction unit determines the correction value in each line for the gradation using the event data and the correction data, For the pixel corresponding to the line, the gradation of the pixel is corrected using the correction value in each line.

  When the voltage (or current) supplied from the power source to the light source fluctuates during reading of the original, the illuminance of the light source fluctuates, which affects the read original image. Although voltage (or current) fluctuation is an unpredictable event, according to this configuration, image data can be corrected for voltage (or current) fluctuation that occurs during reading of a document.

  In the above configuration, the predetermined element includes a light source that emits light to the original when the original is read by the imaging unit, and the event data is data indicating an amount of temperature variation of the light source. The correction data includes data that can specify a correction value of a gradation with respect to the amount of variation, and the measurement unit performs measurement of the temperature of the light source from the start to the end of the movement, and the correction The unit determines the correction value in each line for gradation using the event data and the correction data, and uses the correction value in each line for the pixel corresponding to each line. The gradation of the pixel is corrected.

  When the temperature of the light source varies, the illuminance of the light source varies. For this reason, if the temperature of the light source fluctuates during reading of the original, the read original image is affected. Although the variation in the temperature of the light source is an unpredictable event, according to this configuration, the image data can be corrected with respect to the variation in the temperature of the light source that occurs during the reading of the document.

  An image forming apparatus according to the present invention includes the above-described document reading device and an image forming unit that forms an image of the document indicated by the image data including the pixel data corrected by the correction unit on a sheet. .

According to the image forming apparatus of the present invention, an image can be formed on a sheet using image data obtained by the document reading apparatus of the present invention.
An original reading apparatus according to the present invention divides an original into a plurality of lines along the main scanning direction, and reads the original while moving the original relatively in the sub-scanning direction to form an image of the original An image pickup unit that outputs image data including pixel data indicating pixels to be read, a control unit that causes the image pickup unit to read a white reference plate for a predetermined time before starting reading the document, and the image pickup unit Event data indicating an event that occurs in a predetermined element among elements used when reading a document , and changes in the predetermined time, and image data output from the imaging unit due to the change measuring but the operation of measuring the event data that changes, run from the start to the end of the movement, and to perform the operation of measuring the event data in the reading of the white reference plate A correction data calculation unit that calculates correction data using image data output from the imaging unit and the event data generated by the measurement unit by reading the white reference plate, and the correction data A storage unit that stores the correction data calculated by the calculation unit, and the event data for each line measured by the measurement unit when the imaging unit reads the plurality of lines in sequence. A correction unit that determines the correction value for each line separately using the correction data, and corrects the pixel data for the pixel corresponding to each line using the correction value for each line; .
In the above configuration, the predetermined element includes a direct current power source of a light source that irradiates light to the original when the original is read by the imaging unit, and the event data is supplied from the power source to the light source. The correction data includes data that can specify a gradation correction value for the amount of fluctuation, and the measurement unit is supplied from the power source to the light source. The voltage or current measurement is performed from the start to the end of the movement, and the correction unit determines the correction value in each line for gradation using the event data and the correction data, For the pixel corresponding to each line, the gradation of the pixel is corrected using the correction value in each line.

  According to the present invention, in a method of reading an original by relatively moving the original in the sub-scanning direction, correction for an event that occurs during reading of the original and affects an image of the read original is added to the image data. Can be executed.

1 is a diagram showing an outline of an internal structure of an image forming apparatus to which a document reading apparatus according to a first embodiment and a second embodiment of the present invention can be applied. 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 main part of a document reading apparatus according to a first embodiment of the present invention. It is a time chart which shows an example of the relationship between the digitally converted image data and event data. 6 is a flowchart for explaining the operation of the document reading apparatus according to the first embodiment. It is a time chart which shows an example of execution of amendment by a amendment part. It is a block diagram which shows the principal part of the original document reading apparatus concerning 2nd Embodiment of this invention. 10 is a flowchart for explaining the operation of the document reading apparatus according to the second 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 to which the document reading apparatus according to the first and second embodiments of the present invention can be applied. The image forming apparatus 1 can be applied to, for example, a digital multifunction machine having functions of a copy, a printer, a scanner, and a facsimile. 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. Part 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.

  The document reading unit 200 includes a carriage 201 on which a light source and the like are mounted, a document table 203 made of a transparent member such as glass, an imaging element (not shown), and a document reading slit 205. When reading a document placed on the document table 203, the document is read by the image 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 image sensor through the reading slit 205. The image 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 modulated light corresponding 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 to the peripheral 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 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 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 unit 400 have already been described, description thereof is omitted.

  The control unit 500 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an image memory, and the like. The CPU executes control necessary for operating the image forming apparatus 1 on the hardware constituting the image forming apparatus 1. The ROM stores software necessary for controlling the operation of the image forming apparatus 1. The RAM is used for temporary storage of data generated during execution of software, storage of application software, and the like. The image memory temporarily stores image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.).

  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) that controls connection of a telephone line with a destination facsimile, and a modulation / demodulation circuit that modulates / demodulates 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.

  FIG. 3 is a block diagram showing the main part of the document reading apparatus 2a according to the first embodiment of the present invention. The document reading device 2a functions as the document reading unit 200 (FIG. 1). The document reading device 2 a includes an imaging unit 10, a measurement unit 20, an analog / digital conversion processing unit 30, and a correction processing unit 40.

  The imaging unit 10 includes a light source 11 and an imaging element 12. The imaging unit 10 irradiates the original with white light from the light source 11, receives light reflected from the original with the imaging element 12, and outputs image data D 1 indicating an image of the original. The imaging unit 10 divides the document into a plurality of lines along the main scanning direction, and reads the document while relatively moving the document in the sub-scanning direction.

  The image data D1 includes first line data, second line data,..., Last line data. The line data is data obtained when the image pickup unit 10 reads one line of the main scan. The line data is pixel data indicating the first pixel in the main scanning direction, pixel data indicating the second pixel, pixel data indicating the third pixel,..., Pixel data indicating the last pixel in one line. Composed and composed. The pixel data is, for example, gradation data.

  When reading a document placed on the document table 203 (FIG. 1), the document is fixed. On the other hand, when reading a document fed from the document feeding unit 300 (FIG. 1), the document is It is moved in the sub-scanning direction. For this reason, “the document is moved relatively in the sub-scanning direction” is described.

  The imaging device 12 is a linear image sensor configured by, for example, a CCD sensor or a CMOS sensor. The image data D1 output from the image sensor 12 is sent to the analog-digital conversion circuit 31 of the analog-digital conversion processing unit 30 as channel 1 data.

  The light source 11 is, for example, a white fluorescent lamp or a white LED. The power source of the light source 11 is, for example, a DC power source 13 that generates a DC voltage of 24V. The DC voltage generated by the DC power supply 13 inevitably causes an event in which the voltage fluctuates due to various causes. When the voltage varies, the illuminance of the light source 11 varies. The DC power supply 13 is an example of a predetermined element among elements used when the document is read by the imaging unit 10.

  The positive electrode of the DC power supply 13 is connected to the light source 11 and is connected to the analog / digital conversion unit 32 of the analog / digital conversion processing unit 30 through the wiring 14. A measuring unit 20 is connected to the wiring 14. The measuring unit 20 performs an operation of acquiring event data D2 indicating an event (amount of voltage fluctuation) occurring in a predetermined element (DC power supply 13) among elements used when the document is read by the imaging unit 10. This is executed from the start to the end of relative movement of the document in the sub-scanning direction.

  The measuring unit 20 includes a capacitor 21 and a voltage dividing circuit 22 and measures a fluctuation component of a voltage supplied to the light source 11. The capacitor 21 is connected to the wiring 14 and cuts the DC component of the voltage detected from the wiring 14. Resistors 15 and 16 are connected to the wiring 14 between the capacitor 21 and the analog-digital conversion circuit 32. The resistor 15 is connected to the power source 17, and the resistor 16 is grounded. The resistor 15 and the resistor 16 constitute a voltage dividing circuit 22.

  The voltage of the DC power supply 13 is cut by the capacitor 21 to have only a fluctuation component (AC component). Thereby, event data D2 indicating a fluctuation component of the voltage of the DC power supply 13 is generated. The voltage of the event data D2 is lowered by the voltage dividing circuit 22 to a voltage range (for example, 0 to 3.3 V) that can be processed by the analog-digital conversion circuit 32. The event data D2 is sent to the analog-digital conversion circuit 32 as channel 2 data.

  The analog / digital conversion processing unit 30 includes analog / digital conversion circuits 31 and 32 and a parallel-serial conversion circuit 33. The image data D1 output from the image sensor 12 is an analog signal. This analog signal is converted into a digital signal by the analog-digital conversion circuit 31. The event data D2 flowing through the wiring 14 is also an analog signal. This analog signal is converted into a digital signal by an analog-digital conversion circuit 32.

  FIG. 4 is a time chart showing an example of the relationship between the digitally converted image data D1 and event data D2. The sub-scanning synchronization signal SG1 is a signal indicating a section in which an image is valid in the sub-scanning direction. An image in which the sub-scanning synchronization signal SG1 is in the low state is valid, and an image in the high state is invalid.

  The image data D1 indicating the image of the document is synchronized with the main scanning synchronization signal SG2, and the first line data, the second line data, the third line data,. Are sent to the parallel-serial conversion circuit 33 in the order of the line data.

  The image valid section signal SG3 is a signal indicating a section in which an image is valid in one main scanning line. An image in which the image valid section signal SG3 is in the low state is valid, and an image in the high state is invalid.

  When the first line is read by the imaging unit 10, the voltage fluctuation value indicated by the sampled event data D2 is, for example, -0.2V. This indicates that when the reference voltage of the DC power supply 13 is 24.0V, for example, the voltage of the DC power supply 13 when the first line is read is 23.8V. When the second and third lines are read by the imaging unit 10, the voltage fluctuation value indicated by the sampled event data D2 is, for example, + 0.1V. This indicates that the voltage of the DC power source 13 is 24.1V when the second and third lines are read. When the fourth line is read by the imaging unit 10, the voltage fluctuation value indicated by the sampled event data D2 is, for example, 0.0V. This indicates that the voltage of the DC power supply 13 when the fourth line is read is 24.0V.

  The parallel-serial conversion circuit 33 converts the image data D1 converted into a digital signal by the analog-digital conversion circuit 31 and the event data D2 converted into a digital signal by the analog-digital conversion circuit 32 from parallel data to serial data. . In this serial data, event data D2 (+ 0.1V) corresponding to the first line data, event data D2 (-0.2V) corresponding to the first line data, second line data, and second line data. ) Event data D2 (+ 0.1V) corresponding to the third line data, third line data, event data D2 (0.0V) corresponding to the fourth line data, fourth line data,. The last line data is transmitted in the order of event data D2 corresponding to the last line data.

  The correction processing unit 40 will be described. The correction processing unit 40 is an ASIC (Application Specific Integrated Circuit) including a serial-parallel conversion circuit 41, a distribution circuit 42, a correction data calculation unit 43, a storage unit 44, and a correction unit 45.

  The serial-parallel conversion circuit 41 converts the serial data output from the parallel-serial conversion circuit 33 into parallel data. As a result, the image data D1 and the event data D2 returned in parallel are sent to the distribution circuit 42.

  The distribution circuit 42 switches whether the image data D1 and the event data D2 are transferred to the correction data calculation unit 43 or the correction unit 45.

  The correction data calculation unit 43 uses the event data D2 to calculate correction data D3 corresponding to the event. The correction data D3 includes data that can specify the correction value of the gradation with respect to the fluctuation amount of the voltage of the DC power supply 13. The correction data D3 is stored in the storage unit 44. The storage unit 44 has a delay function and corrects a shift in line timing between the correction data and the image data to be corrected. The correction unit 45 uses the event data D2 and the correction data D3 for each line measured by the measurement unit 20 when the imaging unit 10 reads a plurality of lines in order, and the correction value for each line. The pixel data is corrected using the correction value in each line for the pixels corresponding to each line. Details of processing in the correction data calculation unit 43 and the correction unit 45 will be described later.

  The operation of the document reading apparatus 2a according to the first embodiment will be described. FIG. 5 is a flowchart for explaining this operation. When the operator sets a document on the document table 203 or the document feeding unit 300 shown in FIG. 1 and operates the start key 405, the control unit 500 shown in FIG. 10, the white reference plate is read for a predetermined time (for example, a time corresponding to the start and end of reading one original) (step S 1). The white reference plate is used for shading correction.

  The image data D1 output from the image sensor 12 and the event data D2 generated during the execution of the reading of the white reference plate are converted from analog signals to digital signals by the analog-to-digital conversion circuits 31 and 32, respectively. . These signals are converted into serial data by the parallel-serial conversion circuit 33 and sent to the serial-parallel conversion circuit 41 of the correction processing unit 40. The serial-parallel conversion circuit 41 converts the transmitted serial data into parallel data. The parallel-converted image data D1 and event data D2 are sent to the distribution circuit 42. Since the distribution circuit 42 is connected to the correction data calculation unit 43 in advance by the control unit 500, the image data D1 and the event data D2 are sent to the correction data calculation unit 43.

  The correction data calculation unit 43 calculates correction data D3 by using the image data D1 and event data D2 obtained by reading the white reference plate (step S2). The calculation of the correction data D3 will be specifically described. For example, the gradation of the pixel obtained when the fluctuation component of the voltage of the DC power supply 13 is 0.0 V (in other words, the voltage of the DC power supply 13 is the reference voltage 24.0 V) is M, and the voltage of the DC power supply 13 is The gradation of the pixel obtained when the fluctuation component of + 0.1V (in other words, the voltage of the DC power supply 13 is 24.1V) is M + 3, and the fluctuation component of the voltage of the DC power supply 13 is + 0.2V (in other words, For example, the gradation of the pixel obtained when the voltage of the DC power supply 13 is 24.2 V) is M + 6, and the fluctuation component of the voltage of the DC power supply 13 is −0.1 V (in other words, the voltage of the DC power supply 13 is 23.9V) when the gradation of the pixel obtained is M-3 and the fluctuation component of the voltage of the DC power supply 13 is -0.2V (in other words, the voltage of the DC power supply 13 is 23.8V). It is assumed that the gradation of the pixel obtained in (5) is M-6.

  The correction data calculation unit 43 calculates correction data D3 using the above fluctuation component and gradation data. Here, the correction data D3 is “formula: correction value = −30X” (X is a fluctuation component). For example, when the fluctuation component is +0.1 V, the correction value is −3. Note that as the correction data D3, a lookup table indicating the correspondence relationship between the above-described variation component and gradation may be created.

  The correction data calculation unit 43 stores the correction data D3 in the storage unit (step S3). Then, the control unit 500 causes the imaging unit 10 to start reading a document (step S4).

  As in the case of reading the white reference plate described above, the image data D1 output from the image sensor 12 by the reading of the document and the event data D2 generated during the reading are respectively converted into the analog-digital conversion circuit 31, At 32, an analog signal is converted to a digital signal. These signals are converted into serial data by the parallel-serial conversion circuit 33 and sent to the serial-parallel conversion circuit 41 of the correction processing unit 40. The serial-parallel conversion circuit 41 converts the sent serial data into parallel data. The parallel-converted image data D1 and event data D2 are sent to the distribution circuit 42. Since the distribution circuit 42 is connected to the correction unit 45 in advance by the control unit 500, the image data D1 and the event data D2 are sent to the correction unit 45. The correction unit 45 reads the correction data D3 stored in the storage unit 44. The correction unit 45 corrects the image data D1 (step S5).

  FIG. 6 is a time chart showing an example of execution of correction by the correction unit 45. The fluctuation component when the first line is read by the imaging unit 10 is, for example, −0.2V, and the fluctuation component when the second line is read is, for example, + 0.1V.

  For each pixel data d included in the first line data, the correction unit 45 corrects the gradation of each pixel using “Expression: gradation after correction = gradation before correction + correction value”. As described above, the correction value is “formula: correction value = −30X” (X is a fluctuation component).

  The correction value of the first line data is +6. This means that when the first line is read, the voltage supplied to the light source 11 is 0.2V lower than the reference voltage 24.0V, so that the gradation is increased by 6. For example, in the case of 1024 gradations, if the gradation of the first pixel data d1 before correction is 500, the gradation of the first pixel data d1 after correction is 506, and the second pixel data before correction. If the gradation of d2 is 501, the gradation of the second pixel data d2 after correction is 507,..., if the gradation of the last pixel data dn before correction is 490, after correction The gradation of the last pixel data dn is 496.

  The correction value of the second line data is -3. This means that, when reading the second line, the voltage supplied to the light source 11 is 0.1V higher than the reference voltage 24.0V, so that the gradation is lowered by 3. The correction unit 45 corrects the gradation of each pixel data included in the second line data using the correction value −3.

  Similarly, the correction unit 45 corrects the gradation of the pixel data constituting each line data with respect to the last line data from the third line data.

  As described above, the correction unit 45 uses the event data D2 and the correction data D3 to determine a correction value for each line for the gradation, and for each pixel corresponding to each line, the correction value for each line is determined. Used to correct the gradation of the pixel.

  The image data D1 corrected by the correcting unit 45 is subjected to predetermined image processing by an image processing unit (not shown) and sent to the image forming unit 103 shown in FIG. The image forming unit 103 executes a process for forming the image indicated by the image data D1 on a sheet (step S6). Then, the sheet on which the image is formed is discharged to the stack tray 121 or the discharge tray 123.

  The main effects of the first embodiment will be described. The imaging unit 10 divides the document into a plurality of lines along the main scanning direction, reads the document while relatively moving the document in the sub-scanning direction, and outputs image data D1 indicating an image of the document. When the voltage supplied from the DC power source 13 to the light source 11 varies during reading of the document, the illuminance of the light source 11 varies, which affects the scanned image of the document. Voltage fluctuations are unpredictable events.

  In the document reading apparatus 2a according to the first embodiment, the operation of measuring event data D2 indicating the fluctuation of the voltage supplied to the light source 11 is executed from the start to the end of the relative movement of the document in the sub-scanning direction ( In other words, it is executed during the reading period of the document). A correction value for each line is determined using event data D2 and correction data D3 for each line measured when the plurality of lines are read in sequence. Then, for the pixels corresponding to each line, the pixel data d is corrected using the correction value in each line. Therefore, according to the document reading apparatus 2a according to the first embodiment, in a method of reading a document by moving the document relatively in the sub-scanning direction, correction for an event that occurs during reading of the document and affects the image is performed. Can be executed on the image data D1.

  In the first embodiment, a change in voltage supplied from the DC power source 13 to the light source 11 is used as an event, but a change in current supplied from the DC power source 13 to the light source 11 can also be used as an event. In this case, a measurement unit that measures the current supplied to the light source 11 is provided in place of the measurement unit 20 shown in FIG.

  A second embodiment of the present invention will be described with a focus on differences from the first embodiment. FIG. 7 is a block diagram showing a main part of a document reading device 2b according to the second embodiment of the present invention. The same elements as those constituting the document reading apparatus 2a according to the first embodiment shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted. The document reading device 2 b functions as the document reading unit 200.

  In the second embodiment, attention is focused on the fact that when the light source 11 is continuously lit, the temperature of the light source 11 increases and the illuminance decreases. The variation in the temperature of the light source 11 is an example of an event.

  The document reading device 2b does not include the measurement unit 20 that measures the voltage variation shown in FIG. 3, but instead includes the measurement unit 50 that measures the temperature of the light source 11.

  The measurement unit 50 includes a thermistor 51 and a resistor 52 connected in series. The resistor 52 is connected to the power supply 53, and the thermistor 51 is grounded. A wiring 54 serving as an output of the measurement unit 50 is connected to a wiring connecting the thermistor 51 and the resistor 52. The wiring 54 is connected to the analog / digital conversion circuit 32. As a result, event data D <b> 2 indicating the temperature data of the light source 11 measured by the measurement unit 50 is input to the analog-digital conversion circuit 32.

  The correction processing unit 40 of the second embodiment does not include the distribution circuit 42, the correction data calculation unit 43, the storage unit 44, and the correction unit 45 shown in FIG. 3, but includes a storage unit 46 and a correction unit 47 instead. In the storage unit 46, correction data D3 indicating the correlation of the change in illuminance with the change in the temperature of the light source 11 is stored in advance. The correction data D3 is acquired in the development stage of the document reading device 2b, for example.

  For example, when the temperature of the light source 11 rises once, and the gradation of the pixel decreases by 10, the correction data D3 becomes “Expression: Correction Value = + 10 (T−t1)”. t1 is the temperature of the light source 11 when the imaging unit 10 reads the first line. T is the temperature of the light source 11 when the imaging unit 10 reads each line from the second line to the last line. For example, when the temperature of the light source rises by 0.1 ° C. with respect to t1, the correction value becomes 1. Note that the correction data D3 may be a look-up table showing the correspondence between the temperature change of the light source 11 and the gradation.

  The correction unit 47 uses the event data D2 and the correction data D3 for each line measured by the measurement unit 50 when the imaging unit 10 reads a plurality of lines in order, and the correction value for each line. The pixel data is corrected using the correction value in each line for the pixels corresponding to each line. Details of the processing in the correction unit 47 will be described later.

  The operation of the document reading apparatus 2b according to the second embodiment will be described. FIG. 8 is a flowchart for explaining this operation. In the document reading device 2b, the correction data D3 is acquired at the development stage of the document reading device 2b, and the correction data D3 is stored in the storage unit 46 in advance. Therefore, in the operation of the document reading device 2b, the processing corresponding to steps S1 to S3 shown in FIG. 5 is not executed.

  When the operator sets a document on the document table 203 or the document feeding unit 300 shown in FIG. 1 and operates the start key 405, the control unit 500 shown in FIG. 2 causes the imaging unit 10 to start reading the document (step) S11). The image data D1 output from the image sensor 12 by the reading of the document and the event data D2 generated during the execution are converted from analog signals to digital signals by the analog-digital conversion circuits 31 and 32, respectively. These signals are converted into serial data by the parallel-serial conversion circuit 33 and sent to the serial-parallel conversion circuit 41 of the correction processing unit 40. The serial-parallel conversion circuit 41 converts the transmitted serial data into parallel data. The image data D1 and event data D2 converted into parallel are sent to the correction unit 47. The correction unit 47 reads the correction data D3 stored in the storage unit 46. The image data D1 is corrected by the correction unit 47 (step S12).

  The correction unit 47 corrects the image data D1 by using “Expression: gradation after correction = gradation before correction + correction value” and “expression: correction value = + 10 (T−t1)” described above. Since the temperature t1 of the light source 11 when reading the first line is a reference, correction is not performed on each pixel data constituting the first line data. The temperature T of the light source 11 when reading the second line is, for example, t1 + 0.2 ° C. In this case, the correction value of the second line data is +2. For example, in the case of 1024 gradations, for each pixel data constituting the second line data, if the gradation of the first pixel data before correction is 500, the gradation of the first pixel data after correction is If the gradation of the second pixel data before correction is 501 and the gradation of the second pixel data after correction is 503, ..., the gradation of the last pixel data before correction is If it is 490, the gradation of the last pixel data after correction is 492.

  Similarly, the correction unit 47 corrects the gradation of the pixel data constituting each line data for the third line data to the last line data.

  As described above, the correction unit 47 uses the event data D2 and the correction data D3 to determine a correction value for each line for the gradation, and for each pixel corresponding to each line, the correction value for each line is determined. Used to correct the gradation of the pixel.

  The image data D1 corrected by the correcting unit 47 is subjected to predetermined image processing by an image processing unit (not shown) and sent to the image forming unit 103 shown in FIG. The image forming unit 103 executes processing for forming an image indicated by the image data D1 on a sheet (step S13). Then, the sheet on which the image is formed is discharged to the stack tray 121 or the discharge tray 123.

  The main effects of the second embodiment will be described. When the temperature of the light source 11 varies, the illuminance of the light source 11 varies. For this reason, if the temperature of the light source 11 fluctuates during reading of the original, the read original image is affected. The fluctuation of the temperature of the light source 11 is an unpredictable event.

  In the document reading device 2b according to the second embodiment, the operation of measuring event data D2 indicating the temperature variation of the light source 11 is executed from the start to the end of the relative movement of the document (in other words, during the document reading period). Run). A correction value for each line is determined using event data D2 and correction data D3 for each line measured when a plurality of lines are read in sequence. Then, for the pixels corresponding to each line, the pixel data is corrected using the correction value in each line. Therefore, according to the document reading apparatus 2b according to the second embodiment, in a method of reading a document by relatively moving the document in the sub-scanning direction, correction for an event that occurs during reading of the document and affects the image is performed. Can be executed on the image data D1.

  In the first and second embodiments, the image data D1 and the event data D2 are converted from parallel data to serial data by the analog-digital conversion processing unit 30, and the serial data is converted to parallel data by the correction processing unit 40. doing. However, the image data D1 and the event data D2 may be transferred from the analog / digital conversion processing unit 30 to the correction processing unit 40 without being converted into serial data. In this case, the parallel-serial conversion circuit 33 and the serial-parallel conversion circuit 41 can be omitted.

  As an event, a change in the voltage supplied to the light source 11 and a change in the temperature of the light source 11 have been described as examples. However, the event applied to the present invention is not limited thereto. That is, there is a possibility of fluctuation during reading of the original, and this is an event that affects the read original image, and an event that can be measured as an analog signal is an event applied to the present invention. For example, vibration that occurs when the document feeding unit 300 (FIG. 1) automatically feeds a document using a motor may be used as an event. When a spread spectrum clock generator (SSCG) is used as the clock generation device of the document reading apparatus, the jitter of the clock generated thereby may be used as an event.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2a, 2b Document reader 10 Imaging part 20 Measuring part 44 Storage part 45 Correction part 46 Storage part 47 Correction part 50 Measuring part D1 Image data D2 Event data D3 Correction data

Claims (3)

An image including pixel data indicating pixels constituting an image of the document by dividing the document into a plurality of lines along the main scanning direction, reading the document while moving the document relatively in the sub-scanning direction An imaging unit for outputting data;
A control unit that causes the imaging unit to read a white reference plate for a predetermined time before starting reading the document;
Event data indicating an event that occurs in a predetermined element among elements used when the document is read by the imaging unit , changes within the predetermined time, and is changed from the imaging unit by the change. A measurement unit that performs an operation of measuring event data in which output image data is changed from the start to the end of the movement, and performs an operation of measuring the event data in reading of the white reference plate;
A correction data calculation unit that calculates correction data using the image data output from the imaging unit and the event data generated by the measurement unit by reading the white reference plate;
A storage unit storing the correction data calculated by the correction data calculation unit;
Using the event data and the correction data for each line measured by the measurement unit when the imaging unit reads the plurality of lines in order, correction values for each line are separately set. And a correction unit that corrects the pixel data using the correction value in each line for the pixels corresponding to each line. The predetermined element includes a direct current power source of a light source that irradiates light to the original when the original is read by the imaging unit,
The event data includes data indicating the amount of variation in voltage or current supplied from the power source to the light source,
The correction data includes data that can specify a gradation correction value for the amount of variation,
The measurement unit performs measurement of voltage or current supplied from the power source to the light source from the start to the end of the movement,
The correction unit determines the correction value in each line for gradation using the event data and the correction data, and sets the correction value in each line for the pixel corresponding to each line. The document reading device according to claim 1, wherein the document reading device is used to correct gradation of the pixel. The document reading device according to claim 1 or 2,
An image forming apparatus comprising: an image forming unit that forms an image of the document indicated by the image data including the pixel data corrected by the correcting unit on a sheet.

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