JP5617364B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In the technique described in Patent Document 1, correction information for correcting image information is created based on density information of an image obtained by forming and reading a test image having a predetermined density by an image forming apparatus. It has been proposed to perform image formation by correcting image information with correction information at the time of formation.

  In addition, in the technique described in Patent Document 2, the toner retention amount near both ends tends to be smaller than that near the center due to mechanical reasons. However, it has been proposed to correct density unevenness by correcting the amount of laser light applied to the end of the photosensitive drum.

JP-A-11-112809 JP 2000-141758 A

  An object of the present invention is to suppress image defects caused by correction of density unevenness.

The information processing apparatus according to claim 1 is configured to measure a density of an image formed on a recording medium and a predetermined density based on a measurement result by the measurement means of an image in a predetermined density range. A light amount correction calculating unit that calculates correction information for correcting the amount of light emitted when forming an image so as to correct density unevenness in the region, and an image in the density region other than the density region by the measuring unit. Based on the measurement result, image information correction calculating means for calculating correction information for correcting image information representing an image to be imaged so as to correct density unevenness in a density area other than the density area, and the light amount and an image forming means for forming an image by correcting the density unevenness by using the correction information calculated by the respective correction calculation unit and the image information correction calculation means, the light amount correction calculation means, before Calculation of correction information for correcting the light quantity so as to correct the density unevenness of the low density area based on the measurement result of the measuring means of the image in which the predetermined density area is a predetermined low density area. To do .

The invention according to claim 2, in the invention described in claim 1, wherein the light amount correction calculation means, on the basis of the measurement result by the measuring means of the low-density region of the image, the density unevenness of the low concentration range After calculating the correction information for correcting the light quantity so as to correct, the image information correction calculating means reflects the correction information calculated by the light quantity correction calculating means in the density area other than the low density area. Correction information for correcting the image information is calculated on the basis of a measurement result obtained by the measuring means.

According to a third aspect of the present invention, there is provided a measuring means for measuring the density of an image formed on a recording medium, and irradiation when forming an image so as to correct density unevenness based on a measurement result of the measuring means. Based on the measurement result of the measurement means, the light quantity correction calculating means for correcting the light quantity of the light to be corrected and the image information representing the image to be imaged are corrected so as to correct the density unevenness. Image information correction calculating means for calculating correction information for correcting the image, and image forming means for correcting density unevenness using each correction information calculated by each of the light quantity correction calculating means and the image information correction calculating means to form an image And the light amount correction calculating means calculates correction information based on the measurement result of the measuring means of the image in a low resolution range where the correction resolution by the image information correction calculating means is predetermined. And, the image information correcting calculation means, said calculating the correction information based on the measurement result of the measuring means of the image in other than the low-resolution area, wherein the image forming means, the density unevenness by using the correction information calculated It is characterized in that an image is formed by correction.

According to a fourth aspect of the present invention, in the invention according to the third aspect , the light amount correction calculation means is a measurement result of the measurement means of the image in a low resolution region in which the correction resolution by the image information correction calculation means is predetermined. After the correction information is calculated based on the correction information, the image information correction calculation unit corrects the correction information based on the measurement result of the measurement unit of the image outside the low resolution region reflecting the correction information calculated by the light amount correction calculation unit. It is characterized by calculating.

According to a fifth aspect of the present invention, a computer is caused to function as a light amount correction calculating unit and an image information correction calculating unit constituting the image forming apparatus according to any one of the first to fourth aspects. It is said.

  According to the first and sixth aspects of the present invention, light density correction is performed for a predetermined density area, and other density areas are generated by correcting density unevenness as compared with a case where a configuration for correcting image information is not provided. There is an effect that an image defect can be suppressed.

  According to the second aspect of the present invention, there is an effect that correction can be performed using a correction method having a higher correction resolution for each density region.

  According to the third aspect of the invention, there is an effect that the time for forming a sample image for measuring density unevenness and the consumption of toner can be suppressed.

  According to the fourth aspect of the present invention, the density unevenness correction is performed as compared with the case where the low resolution area in which the correction resolution is predetermined performs light amount correction and the other resolution areas do not have a configuration for correcting image information. It is possible to suppress image defects caused by the above.

  According to the fifth aspect of the present invention, there is an effect that the time for forming a sample image for measuring density unevenness and the consumption of toner can be suppressed.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a schematic configuration for correcting density unevenness of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a diagram illustrating an example of density unevenness and a correction amount with respect to a sheet width direction (main scanning direction) position when image information is corrected for a density range of 30%. (A) is a diagram showing a density change when the correction value of the image information is changed by 1 in the low density area, and (B) is a density change when the correction value of the image information is changed by 1 in the high density area. FIG. It is a figure which shows the correction sensitivity with respect to a density range. 6 is a flowchart illustrating an example of a processing flow when correcting density unevenness in the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 10 according to an embodiment of the present invention. In this embodiment, an image forming apparatus that forms a color image will be described as an example.

  As shown in FIG. 1, in the image forming apparatus 10, an endless belt-like intermediate transfer belt 12 is supported by a plurality of rolls 14 with a predetermined tension.

  Further, on the intermediate transfer belt 12, along the belt running direction X, images of colors corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). The image forming mechanisms 16Y, 16M, 16C, and 16K are formed in this order. In the following description, reference numerals corresponding to the respective colors are omitted unless otherwise specified.

  Each image forming mechanism 16 includes a photosensitive drum 18 having a rotation shaft supported rotatably on an apparatus main body (not shown). Further, around each photosensitive drum 18, along the rotation direction of each photosensitive drum 18 (counterclockwise direction in FIG. 1), a cleaning unit 20, a static eliminator (not shown), a charger 22, and an exposure device. 24, a developing device 26, and a primary transfer roll 28 are arranged in this order.

  That is, after the toner remaining on the photosensitive drum 18 is removed by the cleaning unit 20, the charge on the photosensitive member is discharged by the charge eliminator for discharging, and charged by the charger 22, and the photosensitive drum is charged by the exposure device 24. A latent image is formed by irradiating the surface 18 with light modulated in accordance with the image. The latent image formed by the exposure device 24 is developed by the developing device 26, so that a toner image is formed on the photosensitive drum 18. The toner image formed on the photosensitive drum 18 is transferred onto the intermediate transfer belt 12 by the primary transfer roll 28. At this time, the toner images formed by the image forming mechanisms 16 are transferred onto the intermediate transfer belt 12 so as to overlap each other, whereby a color image is formed on the intermediate transfer belt 12. Note that sub-scanning is performed by the photosensitive drum 18, and main scanning is performed by the exposure device 24.

  The image forming apparatus 10 also detects the density of each color toner image of Y, M, C, and K formed on the intermediate transfer belt 12 and measures the density distribution (density unevenness) of the image. The density sensor 30 is disposed downstream of the black image forming mechanism 16K in the belt conveyance direction (X direction in FIG. 1). As the density sensor 30, for example, a reflection type photosensor arranged in a large number in the main scanning direction can be applied.

  On the other hand, a sheet as an image formation target is accommodated in a sheet feeding unit (not shown), fed out one by one, conveyed along a predetermined path, and sent to the press contact position of the secondary transfer roll 32. Then, after the color images on the intermediate transfer belt 12 are collectively transferred to the sheet by the secondary transfer roll 32, the sheet on which the color image is formed by being subjected to fixing processing (heating, pressing, etc.) by the fixing device 34 is obtained. It is conveyed so as to be discharged from the image forming apparatus 10.

  Next, a configuration for correcting density unevenness of the image forming apparatus 10 according to the embodiment of the present invention will be described. FIG. 2 is a block diagram showing a schematic configuration for correcting density unevenness of the image forming apparatus 10 according to the embodiment of the present invention.

  The image forming apparatus 10 according to the embodiment of the present invention includes a density unevenness correction unit 40 that corrects density unevenness.

  The density unevenness correction unit 40 includes an image information correction unit 42, a light amount correction unit 44, and a correction control unit 46 in order to correct density unevenness caused by various factors.

  In addition, image information representing an image to be imaged is input to the correction control unit 46 and a measurement result of density unevenness measured by the density sensor 30 is input.

  The correction control unit 46 calculates the correction information by the light amount correction unit 44 and the image information correction unit 42 based on the measurement result obtained by measuring the sample image for each density region formed in advance by the density sensor 30, and calculates each of the calculated values. Based on the correction information, the exposure device 24 is controlled so as to correct the density unevenness.

  The image information correction unit 42 corrects the image information in order to correct the density unevenness measured by the density sensor 30. That is, correction information for correcting image information corresponding to the density unevenness measured by the density sensor 30 is calculated, and the image information is corrected using the correction information, thereby correcting the density unevenness. For example, the correction amount of the image information corresponding to the position in the main scanning direction is calculated from the measurement result of the density sensor 30 and determined by a lookup table or the like, and the image information is corrected using the lookup table.

  The light quantity correction unit 44 corrects the light quantity in order to correct the density unevenness measured by the density sensor 30. That is, correction information for correcting the amount of light corresponding to the density unevenness measured by the density sensor 30 is calculated, and the amount of light irradiated from the exposure device 24 to the photosensitive drum 18 is corrected using the correction information. Thus, density unevenness is corrected. For example, the correction amount of the light amount corresponding to the position in the main scanning direction is calculated from the measurement result of the density sensor 30 and determined by a lookup table or the like, and the light amount irradiated from the exposure device 24 is corrected using the lookup table. To do.

  As described above, in this embodiment, the image information correction unit 42 and the light amount correction unit 44 are provided to correct the density unevenness. However, since the density unevenness varies depending on the density range, a sample image is formed for each density range. Then, it is necessary to correct the density unevenness by measuring the density of the sample image with the density sensor 30.

  Here, when forming a sample image for measuring density unevenness, when calculating correction information for correcting image information by the image information correction unit 42, a sample image for each density region is formed. The correction information can be determined, but when calculating the correction information for correcting the light amount by the light amount correction unit 44, in order to calculate the correction information, a sample image in which the light amount is changed for each density region is used. It needs to be formed and takes more time than correcting the image information, and also consumes more toner, etc. In this respect, it is preferable to correct the image information.

  However, when the image information correction unit 42 corrects the image information, if the correction amount increases, the correction value is added to the image information representing the gradation, so that the gradation is compressed, and the correction amount increases. The number of gradations will decrease.

  Furthermore, when image information is corrected in a predetermined low density region, streaks occur as image defects due to correction. For example, in an example of density unevenness and correction amount with respect to a position in the paper width direction (main scanning direction) when image information is corrected for a sample image with a density range of 30%, as shown in FIG. A streak occurs at the indicated position.

  Here, as a result of analyzing the streaks generated in the predetermined low density region, it was found that the correction sensitivity (the density change with respect to the change of the image information) when correcting the image information is different for each density range. . Specifically, when correcting the image information, the density change when the correction value is changed by 1 differs between the low density area and the high density area, and the correction value in the low density area as shown in FIG. The density change when the correction value is changed by 1 in the high density region is smaller than the density change when the value is changed by 1, as shown in FIG. Therefore, when correcting image information, it has been found that the correction sensitivity with respect to the correction amount is lower and the correction resolution is higher in the high density region than in the low density region.

  Similarly, when correcting the light quantity, the density change when the light quantity correction value is changed by 1 also differs for each density area. In this case, the correction sensitivity is lower in the low density area than in the high density area. Low and high correction resolution.

  Specifically, as shown in FIG. 5, when the image information is corrected and when the light amount is corrected, the correction sensitivity differs for each density region, and the low density region (for example, Cin 20 to 50%). (Especially 30%, etc.), the correction sensitivity is lower when the light amount is corrected than when the image information is corrected. Therefore, the correction resolution is higher when the light amount is corrected, and the image information is corrected in other density regions. Since the correction sensitivity is lower, the correction resolution is higher when the image information is corrected. FIG. 5 shows the results of examining the correction sensitivity when the image information is corrected and the correction sensitivity when the light amount is corrected for each density region of each color of Y, M, C, and K.

  Therefore, in the present embodiment, the correction control unit 46 sets the sample image in a predetermined density range (a predetermined low density range where the correction sensitivity of the light amount is low, or a predetermined resolution range where the correction resolution of the light amount is high). After the correction information for correcting the light amount is calculated by the light amount correction unit 44 based on the density unevenness, the correction information based on the correction information by the light amount correction unit 44 is reflected on the basis of the density unevenness of the sample image in the other density region. When the image information correction unit 42 calculates correction information for correcting image information and forms an image, exposure is performed using the calculated correction information (light amount correction information and image information correction information). By controlling the device 24, an image is formed.

  Next, processing related to density unevenness correction of the image forming apparatus 10 according to the embodiment of the present invention configured as described above will be described. FIG. 6 is a flowchart illustrating an example of a processing flow when correcting the density unevenness of the image forming apparatus 10 according to the embodiment of the present invention. Note that the following processing may be started at the time of activation, when a predetermined time has elapsed, or may be started by an instruction from the user.

  In step 100, a sample image in a predetermined density range (for example, a low density range such as Cin 30% or a density range of Cin 20 to 30%) is formed, and the process proceeds to step 102. In the present embodiment, since there are four colors of C, M, Y, and K, a sample image having a predetermined density range is formed for each color, and the following processing is performed for each color. As the sample image, for example, a sample image such as a band-shaped image having a predetermined width in the main scanning direction may be applied, or a sample image of another shape may be applied.

  In step 102, the density of the formed sample image is measured by the density sensor 30, and the process proceeds to step 104. That is, the result obtained by measuring the density of the sample image formed in step 100 by the density sensor 30 is taken into the density unevenness correction unit 40.

  In step 104, correction information for correcting the light amount is calculated by the light amount correction unit 44, and the process proceeds to step 106. That is, the density information is calculated from the measurement result of the density sensor 30 taken into the density unevenness control unit 40, and correction information indicating the light amount correction amount is calculated by the light amount correction unit 44 so as to cancel the density distribution. . For example, the correction information may be determined by calculating a light amount correction value for the position in the main scanning direction and using a lookup table or the like.

  In step 106, a sample image in another density region is formed using the light quantity correction information, and the process proceeds to step 108. That is, a sample image in another density region is formed by reflecting the correction information calculated by the light amount correction unit 44 in step 104. At this time, when forming a sample image in another density area, the image is formed reflecting the correction information of the light amount. Therefore, density unevenness may be promoted depending on the density area. Correction information for correcting image information including density unevenness is calculated by the following process.

  In step 108, the density unevenness in each density range is measured by the density sensor 30, and the process proceeds to step 110. That is, the result obtained by measuring the density of the sample image formed in step 106 by the density sensor 30 is taken into the density unevenness correction unit 40.

  In step 110, correction information for correcting the image information is calculated by the image information correction unit 42, and the process proceeds to step 112. That is, the density information is calculated from the measurement result of the density sensor 30 taken into the density unevenness control unit 40, and correction information representing the correction amount of the image information is calculated by the image information correction unit 42 so as to cancel the density distribution. Is done. For example, the correction value of the image information for the position in the main scanning direction may be calculated and determined using a lookup table or the like. Here, when density unevenness is promoted by the light amount correction as described above, it is corrected by the image information. At this time, since the correction resolution when correcting the image information is in the density region, the density unevenness is corrected in detail, and image defects (for example, density unevenness, streaks, etc.) are suppressed.

  In step 112, image formation is performed using light quantity correction information and image information correction information. That is, using the light amount correction information calculated by the light amount correction unit 44 and the image information correction information corrected by the image information correction unit 42, density unevenness is corrected and an image is formed. As a result, an image in which uneven density is suppressed is formed.

  As described above, the image forming apparatus 10 according to the present embodiment forms a sample image of a predetermined density range, measures the density, calculates correction information for correcting the light quantity, and then calculates the correction information. Use this to form a sample image of another density range, measure the density, calculate correction information for correcting the image information, and perform image formation using each calculated correction information, thereby correcting the light amount When calculating the information, it is only necessary to form a sample image in a predetermined density range, so that time for forming a sample image in another density range and consumption of toner are suppressed. In addition, although the correction resolution differs depending on each correction method (light amount correction and image information correction), density unevenness is corrected using a correction method with a high correction resolution, so image defects caused by correction of density unevenness are suppressed. Is done.

  In the above embodiment, the predetermined low density area corrects the light amount, and the other density areas correct the image information. However, the correction resolution when correcting the image information is low. The amount of light may be corrected in the resolution area, and the image information may be corrected in other correction resolution areas.

  In the above embodiment, the image forming apparatus that includes the image forming mechanism 16 corresponding to each color of C, M, Y, and K and forms a color image is applied. However, the present invention is not limited to this. An image forming apparatus that forms a black and white image with the image forming mechanism may be applied, or another type of image forming apparatus may be applied.

  In the above embodiment, the light quantity correction information is calculated and then the sample image is formed using the light quantity correction information, and the light quantity is corrected from the measurement result of the density of the formed sample image. However, the present invention is not limited to this. In a predetermined low density region (for example, Cin 30%), correction by the light amount correction unit 44 is performed. In other density regions, the correction control unit 46 may switch the correction method so that the correction by the image information correction unit 42 is performed without reflecting the light amount correction information.

  In the above-described embodiment, the density sensor 30 is provided at a position for measuring the density of the toner image transferred to the intermediate transfer body to measure the density unevenness. However, the present invention is not limited to this. Alternatively, the density unevenness of the toner image on the photosensitive drum 18 may be measured by providing it at a position where the density of the toner image formed on each photosensitive drum 18 is measured, or an image formed on the paper. It is also possible to measure the density unevenness of the image formed on the paper by providing it at the position where the density of the image is measured.

  Moreover, although the process of steps 104 and 110 in the process of FIG. 6 in the above embodiment has been described as the process performed by the density unevenness correction unit 40 as hardware, it is not limited to this, and is executed by a computer, for example. It is good also as processing which software performs as a program to carry out.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming mechanism 24 Exposure apparatus 30 Density sensor 40 Density unevenness correction part 42 Image information correction part 44 Light quantity correction part

Claims (5)

Measuring means for measuring the density of the image formed on the recording medium;
Correction information for correcting the amount of light emitted when forming an image so as to correct the density unevenness of the predetermined density range based on the measurement result of the image of the predetermined density range by the measuring unit. A light amount correction calculating means for calculating;
For correcting image information representing an image to be formed so as to correct density unevenness in a density area other than the density area based on a measurement result of the image in the density area other than the density area. Image information correction calculating means for calculating correction information;
Image forming means for correcting density unevenness using each correction information calculated by each of the light amount correction calculating means and the image information correction calculating means to form an image;
Equipped with a,
The light quantity correction calculating means adjusts the light quantity so as to correct density unevenness in the low density area based on a measurement result by the measuring means of an image in which the predetermined density area is set to a predetermined low density area. An image forming apparatus that calculates correction information for correction . The light intensity correction calculation unit, before SL based on a measurement result by the measuring means of the low-density region of the image, said to correct density unevenness in the low concentration range, and calculates the correction information for correcting the amount of light Thereafter, the image information correction calculation unit corrects the image information based on a measurement result of the image in the density region other than the low density region reflecting the correction information calculated by the light amount correction calculation unit. The image forming apparatus according to claim 1 , wherein correction information for calculating the correction information is calculated . Measuring means for measuring the density of the image formed on the recording medium;
A light amount correction calculating unit that calculates correction information for correcting the light amount of light emitted when forming an image so as to correct density unevenness based on the measurement result of the measuring unit;
Image information correction calculating means for calculating correction information for correcting image information representing an image to be imaged so as to correct density unevenness based on the measurement result of the measuring means;
Image forming means for correcting density unevenness using each correction information calculated by each of the light amount correction calculating means and the image information correction calculating means to form an image;
With
The light amount correction calculation unit calculates correction information based on a measurement result of the measurement unit of an image in a low resolution region in which a correction resolution by the image information correction calculation unit is predetermined, and the image information correction calculation unit An image forming apparatus that calculates correction information based on a measurement result of the measurement unit for an image in a region other than a low resolution region, and the image forming unit corrects density unevenness using the calculated correction information to form an image. After the light amount correction calculation means calculates correction information based on the measurement result of the measurement means of the image in the low resolution region where the correction resolution by the image information correction calculation means is predetermined, the image information correction calculation means The image forming apparatus according to claim 3, wherein the correction information is calculated based on a measurement result of the measurement unit for an image in a region other than the low resolution region reflecting the correction information calculated by the light amount correction calculation unit . An image forming program for causing a computer to function as a light amount correction calculating unit and an image information correction calculating unit constituting the image forming apparatus according to any one of claims 1 to 4.

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