JP2019097029A - Image forming device - Google Patents

Abstract

To provide an image forming device capable of accurately reading a test pattern.SOLUTION: An image forming device comprises: reading means that reads an image of a document to be conveyed at a reading position; a first roller provided upstream of the reading position, in the document conveyance direction, and for conveying the document toward the reading position; a second roller provided downstream of the reading position, in the transport direction, and for conveying the document having passed the reading position downstream; and control means for controlling the first roller and the second roller and curving the document in the direction of the reading means between the first roller and the second roller. The control means, when reading the document in which a test pattern for adjustment control is formed, makes the amount of curving larger than when reading the document on which the test pattern is not formed.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a technique for performing adjustment control of an image forming apparatus with high accuracy.

  In an electrophotographic image forming apparatus, time-dependent changes, environmental changes, and density fluctuations (or tint fluctuations) due to replacement of consumables may occur. Therefore, the image forming apparatus performs density correction as one of adjustment control. Patent Document 1 discloses a configuration for performing density correction using a reading unit that reads an image of a document. Further, Patent Document 2 discloses a configuration in which test patterns are formed on a plurality of recording media, and image forming conditions such as gradation correction are adjusted based on the read results of the test patterns. Further, Patent Document 3 discloses a configuration for reducing the user's workload by using an automatic document feeder (ADF) when reading test patterns formed on a plurality of recording media.

Patent No. 3143484 Japanese Patent Laid-Open No. 2002-59626 Japanese Patent Application Publication No. 2007-329929

  When the document on which the test pattern is formed is read by the reading unit, if the document has minute floating or waviness, it affects the result of reading the test pattern, and the accuracy of adjustment control may deteriorate.

  The present invention provides an image forming apparatus capable of accurately reading a test pattern.

  According to one aspect of the present invention, the image forming apparatus is provided with a reading unit that reads an image of a document to be conveyed at a reading position, and is provided upstream of the reading position in the conveyance direction of the document and directed to the reading position. A first roller for conveying the document, a second roller provided downstream of the reading position in the conveying direction, for conveying the document having passed the reading position toward the downstream, and Control means for controlling the roller and the second roller to bend the document in the direction of the reading means between the first roller and the second roller, the control means adjusting When reading the document on which a test pattern for control is formed, the amount of bending is made larger than when reading the document on which the test pattern is not formed. To.

  According to the present invention, test patterns can be read with high accuracy.

FIG. 1 is a block diagram of an image forming apparatus. FIG. 2 is a block diagram of a printer control unit. Explanatory drawing of gradation correction control. 6 is a flowchart of tone correction table generation processing. FIG. 6 is a view showing an example of a screen displayed on a display unit. The figure which shows a test pattern. Explanatory drawing of the conveyance state of the original in the reading position vicinity of an original. Explanatory drawing of conveyance control of a document. FIG. 7 is a view showing an example of forming a test pattern on a recording medium.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. The following embodiment is an exemplification, and the present invention is not limited to the contents of the embodiment. Further, in each of the following drawings, components that are not necessary for the description of the embodiment will be omitted from the drawings.

First Embodiment
FIG. 1 is a block diagram of an image forming apparatus according to the present embodiment. The image forming apparatus includes a reader unit A and a printer unit B. The reader unit A includes an image reading unit 200 and an automatic document feeding unit (ADF) 100. When reading an image of a document placed on the document tray 30, which is fed by the ADF 100, the scanner unit 209 is moved to a position directly below the platen glass 201 and stands by until the document reaches the reading position. The ADF 100 brings the sheet feeding roller 1 into contact with the document surface of the document bundle S to rotate the sheet feeding roller 1. Thus, the topmost original of the original bundle is fed to the conveyance path. The separation roller 2 and the separation pad 8 regulate that documents other than the one document on the topmost sheet are conveyed overlappingly from the document bundle S. One original document separated by the separation roller 2 and the separation pad 8 is abutted against the resist roller 3. As a result, the skew in the conveyance of the document is eliminated. A pre-reading roller 4 is provided downstream of the registration roller 3. The pre-reading roller 4 conveys the document toward the space between the platen glass 201 and the platen roller 5 provided near the reading position. The platen roller 5 is provided to bring the document into contact with the platen glass 201 at the reading position. The document having passed between the platen glass 201 and the platen roller 5 is conveyed further downstream by the reading roller 6. The discharge roller 7 discharges the document to the outside of the apparatus. The read sensor 14 detects an original on the upstream side of the reading position. The timing at which the document reaches the reading position is determined based on the timing at which the read sensor 14 detects the document.

  The scanner unit 209 reads an image of a document conveyed on the platen glass 201 at a reading position. Specifically, the light source 203 of the scanner unit 209 irradiates light toward the document conveyed at the reading position via the platen glass 201. Reflected light from the document is received by the CCD sensor unit 210 via the mirrors 204, 205, 206 and the lens 207. The CCD sensor unit 210 outputs image information corresponding to the image of the document to the reader image processing unit 211 based on the reflected light from the document. The reader image processing unit 211 outputs the RGB image signal to the printer control unit 109 based on the image information from the CCD. The image reading unit 200 can also read the document placed on the document table glass 202 while moving the scanner unit 209 in the arrow a direction (sub scanning direction). The reference white plate 219 is provided to create reference data of white level in the shading correction process.

  Subsequently, the printer unit B will be described. The printer unit B includes image forming units 120, 130, 140, and 150. The image forming units 120, 130, 140 and 150 have photosensitive members 121, 131, 141 and 151, respectively. The image forming units 120, 130, 140, and 150 form toner images of yellow (Y), magenta (M), cyan (C), and black (Bk), respectively. The configurations of the image forming units 120, 130, 140, and 150 are the same except for the color of the toner to be used, and therefore, the configuration of the image forming unit 120 will be representatively described below. The charger 122 charges the surface of the photosensitive member 121 to a predetermined potential. The exposure unit 110 exposes the photosensitive member 121 under the control of the printer control unit 109. As a result, an electrostatic latent image is formed on the photosensitive member 121. The developing device 123 develops the electrostatic latent image on the photosensitive member 121 with toner to form a toner image. The transfer blade 124 discharges from the back surface of the transfer belt 111 and transfers the toner image on the photosensitive member 121 onto the recording medium conveyed on the transfer belt 111. A full-color toner image is formed on the recording medium by overlappingly transferring the toner images of the photosensitive members 121, 131, 141, and 151 onto the recording medium. Thereafter, the recording medium is conveyed to the fixing device 114. The fixing unit 114 heats and presses the recording medium to fix the toner image on the recording medium. After fixing the toner image, the recording medium is discharged out of the apparatus. In addition, surface electrometers 125, 135, 145, 155 for measuring the surface electric potential are provided at opposing positions of the respective photosensitive members 121, 131, 141, 151. Surface potentiometers 125, 135, 145, 155 are used to adjust the contrast potential.

  FIG. 2 shows a control configuration of the image forming apparatus including the printer control unit 109. The image forming apparatus is generally controlled by the CPU 301. The memory 302 includes a ROM and a RAM, and stores control programs and various data. The RGB image signal processed by the reader unit A is input to the color processing unit 303 of the printer control unit 109. The color processing unit 303 outputs an image signal represented by YMCK based on the image signal represented by RGB from the reader unit A using the LUTid 304.

  The tone control unit 311 includes a UCR unit 305 and a tone correction unit 306. The UCR unit 305 is a circuit that limits the sum of image signal levels by regulating the integrated value of the image signal in each pixel. If the sum exceeds the specified value, the UCR unit 305 executes under color removal processing (UCR) to replace a predetermined amount of YMC signals with K signals, and reduces the sum of image signal levels. The tone correction unit 306 compensates for the non-linear characteristics of the printer unit B, and inputs so that the tone value (pixel value) indicated by the input image signal and the density of the formed image have a linear relationship. The tone value of the image signal to be converted is converted and output. The relationship between the gradation value indicated by the input image signal and the gradation value to be output is indicated by LUTa 306 a. The signal output from the gradation control unit 311 is dithered by the dither processing unit 307, pulse width modulated by the PWM unit 308, and a PWM signal is generated. The laser driver 309 causes the semiconductor laser 310 of the exposure unit 110 to emit light based on the PWM signal.

  The processing in the tone correction unit 306 will be described with reference to FIG. In FIG. 3, a region I indicates the characteristics of the reader unit A. The II region indicates the characteristics of the LUTa 306 a used by the tone correction unit 306. Region III indicates the characteristics of the printer unit B. The IV region indicates the relationship between the image density of the document and the image density formed by the printer unit B. In order to compensate for the non-linearity in the printer unit B in the III region, as shown in the II region, the tone correction unit 306 converts the tone value. The characteristics of the printer unit B shown in the area III can be measured by forming a test pattern on a recording medium without causing the tone correction unit 306 to operate, and reading the recording medium. The LUTa 306a is generated by exchanging the input and the output in the characteristic of the region III. In the present embodiment, the number of output gradations is 256 gradations (8 bits), but the gradation control unit 311 processes digital signals with 10 bits, and therefore the number of gradations in FIG. It has become.

  FIG. 4 is a flowchart of LUTa 306a generation processing as calibration. FIG. 5A shows an example of a screen displayed on the display unit when the user selects calibration execution. As shown in FIG. 5A, a button for executing printing is displayed. At the same time, as a guide to the user, the display "Print for performing calibration" is displayed. When the user presses a button for performing printing shown in FIG. 5A, the process of FIG. 4 is started. First, in S10, the CPU 301 forms a test pattern on a recording medium. At this time, the CPU 301 causes the dither processing unit 307 to input the output of the UCR unit 305 without executing the tone correction by the tone correction unit 306.

  FIG. 6 shows an example of a test pattern. The test pattern includes 10 gradation patches for each of yellow (Y), magenta (M), cyan (C) and black (K). For example, 10 gradation patches are 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100 when the maximum density is 100%, respectively. It is formed at a concentration of%. When a test pattern (chart) is formed on the recording medium in S1, the CPU 301 displays, for example, a screen as illustrated in FIG. 5B on the display unit. This screen is provided with a button for reading a test pattern. At the same time, as guidance for the user, “Please set in the ADF to read the chart.” Is displayed. When the user places the recording medium on which the test pattern is formed on the document tray 30 of the ADF 100 and presses the test pattern reading button according to the displayed guidance, the process of S11 in FIG. 4 is started. . In S11, the reader unit A reads a test pattern formed on the recording medium. The read result of the test pattern is input to the printer control unit 109 of the printer unit B as an RGB image signal. The color processing unit 303 of the printer control unit 109 converts the RGB image signal into an image signal indicating the density of each YMCK. Thus, in S12, the CPU 301 detects the density of each patch of the test pattern. In step S13, the CPU 301 determines the characteristics of the printer unit B shown in area III of FIG. 3 based on the detected density value of each patch and the gradation value used to form each patch, and generates the LUTa 306a. Do.

  FIG. 7 shows the state of a document when reading the document in the reader unit A. In FIG. 7, the position in the transport direction, which corresponds to the upper vertex portion in the solid triangle, indicates the reading position. At the time of copying in which the image of the original is read using the ADF 100 and the read image is formed on the recording medium, the original is conveyed as shown by the broken arrow in FIG. 7A. FIG. 7A corresponds to a state in which the transport speed of the document at the reading position is not changed from the front end to the rear end of the document. In this case, the state of the document between the rollers is close to the shortest course, although a slight curve is drawn. However, in this path, the contact area of the document on the platen glass 201 at the reading position is small, and slight slippage or wrinkles of the document cause the platen glass 201 to move as shown by the dotted and dashed lines in FIG. The manuscript may float. In the reading position, when the document floats off the platen glass 201, the reading focal length may change, which may affect the density value to be read.

  Here, in the case of copying, blurring can be suppressed to an unnoticeable level due to the sharpness of image processing or the like, and it is less likely to become a problem even if it becomes slightly darker. However, in order to accurately adjust the image forming apparatus, it is necessary to read the test pattern with high accuracy. For this purpose, when reading a document on which a test pattern is formed, the document is transported such that the contact area between the document and the platen glass 201 becomes large, as shown by the broken line in FIG. 7B. , The original document is prevented from floating from the platen glass 201. The shape (path) of the document between the pre-reading roller 4 and the post-reading roller 6 via the platen roller 5 is curved and is also called a loop shape. Further, in the state of the document indicated by the broken line in FIG. 7B, the amount of bending is larger than the state indicated by the broken line in FIG. That is, the length in the conveyance direction of the document existing between the pre-reading roller 4 and the post-reading roller 6 is longer in FIG. 7B than in FIG. 7A. The state of FIG. 7B is expressed as the loop amount is larger (the amount of bending is larger) than the state of FIG. 7A. In the present embodiment, when reading a test pattern, the rotational speeds of the pre-reading roller 4 and the post-reading roller 6 are controlled to make the loop amount larger than that in the normal copying operation.

  Specifically, at the time of normal copying, the rotational speeds of the pre-reading roller 4 and the post-reading roller 6 are set to the same V1. The dotted line in FIG. 8B indicates the state of the original during normal copying, that is, when the test pattern is not read. On the other hand, when reading the test pattern, the rotational speed of the pre-reading roller 4 is set to V1 equal to that at copying, but the rotational speed of the post-reading roller 6 is set to V2 slower than V1. Therefore, the loop amount of the document until the leading end of the document reaches the roller 6 after reading is the same at the time of normal copying and at the time of reading of the test pattern. However, since the rotational speed of the post-reading roller 6 is made slower than the rotational speed of the pre-reading roller 4 when reading the test pattern, after the leading edge of the document reaches the post-reading roller 6, the loop amount is It becomes bigger than the time of copying. Then, when reading the test pattern, the CPU 301 sets the rotational speed of the post-reading roller 6 to the same V1 as the pre-reading roller 4 when the state of the document becomes the state shown by the solid line in FIG. The timing of changing the rotational speed of the post-reading roller 6 from V2 to V1 is determined by the elapsed time after the leading edge of the document reaches the post-reading roller 6. That is, when a predetermined time passes after the leading edge of the document reaches the post-reading roller 6, the CPU 301 changes the rotational speed of the post-reading roller 6 from V2 to V1.

  For example, if the diameter of the pre-reading roller 4 and the post-reading roller 6 is 8 mm and normal copying is performed with V1 being 183 rpm, the length of the document between the pre-reading roller 4 and the reading position, the reading position and reading The lengths of the original with the rear roller 6 were 30 mm and 25 mm, respectively. In this case, V2 is set to 181 rpm, and the rotational speed of the post-reading roller 6 is changed to V1 about 1.2 seconds after the leading end of the document reaches the post-reading roller 6. As a result, the length of the document between the pre-reading roller 4 and the reading position and the length of the document between the reading position and the post-reading roller 6 become 30.5 mm and 25.5 mm, respectively, and the loop amount is increased. be able to.

  As described above, it is possible to control the loop amount by adjusting the rotational speed difference between the pre-reading roller 4 and the post-reading roller 6 and the duration in which the speed difference is provided. Then, at the time of reading the test pattern, the test pattern can be read with high accuracy by making the loop amount larger than when not reading the test pattern. In the present embodiment, the test pattern is for gradation control, but the present invention is not limited to the reading of the test pattern for gradation correction, and any adjustment control of the image forming apparatus is possible. The present invention can be applied to reading of test patterns to be used. For example, a test pattern for correcting density unevenness or inclination in a direction orthogonal to the document conveyance direction, or a test pattern for correcting driving unevenness of an image forming apparatus or circumferential pitch unevenness of an image forming member, etc. The present invention can be applied.

Second Embodiment
Subsequently, a second embodiment will be described focusing on differences from the first embodiment. In the first embodiment, the loop amount is controlled by the rotational speed difference between the pre-reading roller 4 and the post-reading roller 6 and the duration in which the speed difference is provided. In the present embodiment, as shown in FIG. 8C, the loop amount is controlled by the rotation start timing of the post-reading roller 6. Specifically, when reading the test pattern, after the leading edge of the document reaches the post-reading roller 6 or after a predetermined period has elapsed after the leading edge of the document reaches the post-reading roller 6 After the reading, the rotation of the roller 6 is started at a predetermined timing. Therefore, the loop amount of the document is increased until the rotational speed of the post-reading roller 6 reaches the same V1 as the pre-reading roller 4. As described above, the loop amount can also be controlled by the timing at which the rotation of the post-reading roller 6 is started.

Third Embodiment
As described in the first and second embodiments, the loop amount can be controlled by controlling the rotation of the post-reading roller 6. However, since the loop amount is increased only after the leading edge of the document reaches the roller 6 after reading, the reading accuracy for the area of the document passing the reading position may be deteriorated before the loop amount increases. Similarly, when the trailing end of the document passes through the pre-reading roller 4, the loop amount can be reduced. Therefore, the test pattern passes through the reading position while the loop amount is small by not forming a test pattern in a predetermined range from the front end of the document and in a predetermined range from the rear end in the document conveyance direction. You can prevent. That is, as shown in FIG. 9, the margin X is provided on the leading end side of the document conveyance direction, and the margin Y is provided on the trailing end side. The length of the margin X in the transport direction is equal to or greater than the distance between the post-reading roller 6 and the reading position. Here, the distance between the post-reading roller 6 and the reading position can be a length in the conveyance direction of the document existing between the post-reading roller 6 and the reading position in a target loop amount. For example, when the loop amount reaches a predetermined amount, the position behind the position of the document at the reading position can be set as the formation start position of the test pattern on the front end side of the document. Similarly, the length of the margin Y in the transport direction is equal to or greater than the distance between the pre-reading roller 4 and the reading position. Here, the distance between the pre-reading roller 4 and the reading position can be a length in the conveyance direction of the document existing between the pre-reading roller 4 and the reading position in a target loop amount. For example, when the rear end of the document is at the position of the pre-reading roller 4, the position on the front side of the position of the document at the reading position can be set as the formation end position of the test pattern on the rear end side of the document. In FIG. 9, although the margins are provided on the front end side and the rear end side in the transport direction, the margins are provided around the test pattern, that is, on the front end, rear end, right side and left side in the transport direction. can do. At this time, the length of the margin is made larger than the larger one of the distance between the post-reading roller 6 and the reading position and the distance between the pre-reading roller 4 and the reading position. Thus, the same test pattern can be used regardless of the document transport direction.

Fourth Embodiment
Also in this embodiment, the loop amount is controlled by controlling the rotation of the post-reading roller 6 as in the first and second embodiments. Here, there are various types of recording media on which the test pattern is formed, and the rigidity differs depending on the state of the fiber and the type and amount of the additive. Therefore, the time for providing the rotational speed difference and speed difference between the post-reading roller 6 and the pre-reading roller 4 for setting an appropriate loop amount, and the timing of starting the rotation of the post-reading roller 6 differ depending on the type of recording medium. Therefore, in the present embodiment, the time for providing the rotational speed difference and the speed difference between the post-reading roller 6 and the pre-reading roller 4 and the timing for starting the rotation of the post-reading roller 6 are changed according to the type of recording medium. The type of recording medium on which the test pattern is formed can be specified by the image forming apparatus according to which paper feed stage the paper is fed from. Further, the relationship between the recording medium and the time for providing the rotational speed difference and speed difference between the post-reading roller 6 and the pre-reading roller 4 and the timing for starting the rotation of the post-reading roller 6 is stored in the memory 302, for example. deep. With this configuration, even when test patterns are formed on various recording media, the test patterns can be read with high accuracy.

Other Embodiments
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Can also be realized. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

  200: image reading unit 4: 4: pre-reading roller 6: 6: post-reading roller 301: CPU

Claims (13)

Reading means for reading an image of a conveyed document at a reading position;
A first roller provided on the upstream side of the reading position in the conveyance direction of the original, and configured to convey the original toward the reading position;
A second roller provided downstream of the reading position in the transport direction and transporting the document having passed the reading position toward the downstream side;
Control means for controlling the first roller and the second roller to bend the document in the direction of the reading means between the first roller and the second roller;
Equipped with
When reading the document on which a test pattern for adjustment control is formed, the control means makes the amount of curvature larger than when reading the document on which the test pattern is not formed. apparatus. It further comprises a third roller provided between the first roller and the second roller,
The document is conveyed between the third roller and the glass,
The image forming apparatus according to claim 1, wherein the reading unit irradiates light toward the document through the glass and reads an image of the document by receiving reflected light from the document. apparatus.   The control means controls the rotational speed of the second roller, and the timing at which the rotational speed of the second roller is changed after the leading end of the document has reached the position conveyed by the second roller. The image forming apparatus according to claim 1, wherein the amount of curvature is controlled.   The control means rotates the first roller at a first rotational speed, rotates the second roller at a second rotational speed slower than the first rotational speed, and the leading end of the document is conveyed by the second roller. 4. The image forming apparatus according to claim 3, wherein the rotational speed of the second roller is changed to the first rotational speed after reaching the predetermined position.   When the recording medium on which the test pattern is formed is read as the document, the control means sets the second rotation speed and the rotation speed of the second roller to the first rotation speed according to the type of the recording medium. 5. The image forming apparatus according to claim 4, wherein the timing of change is determined.   The control means does not rotate the second roller until the leading end of the document reaches the position conveyed by the second roller, and the leading end of the document reaches the position conveyed by the second roller The image forming apparatus according to claim 1, wherein the amount of bending is controlled by controlling a timing at which the rotation of the second roller is started later.   The control means rotates the first roller at a first rotational speed, and the rotational speed of the second roller is equal to the first rotational speed after the leading end of the document reaches a position conveyed by the second roller. 7. The image forming apparatus according to claim 6, wherein rotation of the second roller is started so as to be.   When the recording medium on which the test pattern is formed is read as the document, the control means determines the timing to start the rotation of the second roller according to the type of the recording medium. Or the image forming apparatus according to 7.   When reading the document on which the test pattern is not formed, the control means causes the second roller to be at the first rotational speed before the leading end of the document reaches a position conveyed by the second roller. The image forming apparatus according to claim 4, wherein the image forming apparatus is rotated. It further comprises an image forming means for forming the test pattern on a recording medium,
The image forming unit is characterized in that the test pattern is formed on the recording medium by providing a margin larger than the distance between the second roller and the reading position on the leading end side of the recording medium in the transport direction. The image forming apparatus according to any one of claims 1 to 9. It further comprises an image forming means for forming the test pattern on a recording medium,
The image forming unit is characterized in that the test pattern is formed on the recording medium by providing a margin equal to or more than the distance between the first roller and the reading position on the rear end side of the recording medium in the transport direction. The image forming apparatus according to any one of claims 1 to 10, wherein It further comprises an image forming means for forming the test pattern on a recording medium,
The image forming unit may set a margin larger than the larger one of the first distance between the first roller and the reading position and the second distance between the second roller and the reading position in the test pattern. The image forming apparatus according to any one of claims 1 to 9, wherein the test pattern is formed on the recording medium by being provided in the periphery. A reading unit configured to irradiate light through the glass toward the document conveyed between the first roller and the glass, and to read an image of the document by receiving reflected light from the document;
A second roller provided upstream of the first roller in the document transport direction, for transporting the document toward the first roller;
A third roller provided downstream of the first roller in the transport direction and transporting the document having passed through the first roller toward the downstream side;
When reading the document on which a test pattern for adjustment control is formed, the second roller and the second roller are arranged such that the contact area between the glass and the document is larger than when reading the document on which the test pattern is not formed. Control means for controlling the third roller;
An image forming apparatus comprising: