JP2016200758A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology that can suppress a ghost occurring in a single transfer material.SOLUTION: There is provided an image forming apparatus comprising: an image carrier; charging means that charges a surface of the image carrier; exposure means that forms an electrostatic latent image on the surface of the image carrier; developing means that develops the electrostatic latent image; and a light emission control means that controls light emission of the exposure means, and transfers a developed developer image to a transfer material, the image forming apparatus including: latent image forming means that consists of a dot gain for each of a plurality of dots arranged in matrix in a main scanning direction and a sub scanning direction of the exposure means and creates latent image data for each of the dots; and ghost correction means that corrects the dot gain in a dot of a reference source for each of the dots in the latent image data on the basis of the dot gain in the dot of the reference source and a dot gain in a dot of a reference destination backward in the sub scanning direction by the amount corresponding to one rotation of the developing means from a dot of the reference source.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus such as a printer or a copying machine.

  As one of the image forming apparatuses, for example, there is an apparatus that applies electrophotographic technology. In such an apparatus, an image carrier such as a photosensitive drum and a photosensitive drum surface arranged in order in the rotation direction of the photosensitive drum are arranged on a predetermined surface. A charging unit that is charged to a potential of a negative polarity, an exposure unit that forms an electrostatic latent image by exposing the charged photosensitive drum surface to an image, and a developer carrier such as a developing roller. A developing unit for attaching a developer (toner) to form a developer image, a transfer unit for transferring the developer image onto a transfer material such as paper, a fixing unit for fixing the developer image on the transfer material, and the like It is composed of The exposure unit includes a latent image forming unit that forms latent image data from image data and a light emission control unit that controls light emission of image exposure.

In particular, the developing unit includes a developing roller, a regulating roller, a supply roller, and the like, and a toner layer controlled to a predetermined thickness is formed on the developing roller. The developing roller is pressed against the photosensitive drum, and the rotation is controlled so that the contact surface between the developing roller and the photosensitive drum is in the same direction. As described above, the electrostatic latent image on the surface of the photosensitive drum is developed with the toner on the developing roller. To do. The supply roller, also called a reset roller, is pressed against the developing roller and is controlled to rotate so that the contact surface between the developing roller and the supply roller faces each other. Supply. The regulating roller is pressed by the developing roller, and is controlled to rotate so that the contact surface between the developing roller and the regulating roller faces. The toner supplied from the developing roller to the photosensitive drum has a desired layer thickness and charging. The toner on the developing roller is regulated to obtain a layer.
Further, in a color image forming apparatus, for example, the developing unit includes four color developing devices of Y (yellow), M (magenta), C (cyan), and K (black), and development performed by the developing devices of the respective colors. A color image is printed by transferring the agent image onto the same transfer material.

  In the image forming apparatus having such a configuration, for example, although the solid image data shown in FIG. 4 is printed, a length corresponding to one rotation of the developing roller from the printing start position is shown in FIG. The print area P2 having a lighter print density than the print area P1 may be printed after the print area P1 having a high print density (hereinafter, this type of ghost is referred to as “negative”. Ghost "). Further, even when printing the same solid image data, as shown in FIG. 6, the print density is darker than the print area P3 after the print area P3 having a light print density corresponding to a length corresponding to one rotation of the developing roller. The print area P4 may be printed (hereinafter, this type of ghost is referred to as “positive ghost”).

  In addition, the white arrow shown in FIGS. 4-6 is the feeding direction of the transfer material, and the white or black circle is a mark for clearly indicating each region. Further, the circumferential length of the developing roller and the corresponding image length are different in dimension because the circumferential speed of the developing roller and the circumferential speed of the photosensitive drum are different. Therefore, in the present specification, “a position corresponding to one rotation of the developing roller on the image” is appropriately described as “a circumferential position for one rotation of the developing roller”.

  When printing the solid image data described above, one of the causes of the density in the print density is the excess or deficiency of the charge amount in the toner supplied from the developing roller to the photosensitive drum. That is, it is desirable that the toner charge amount is originally charged and saturated by one rotation of the developing roller, but it is actually difficult, and the charge amounts at the first and second rotations are slightly different from each other. There are many. The excess or deficiency of the charge amount in the first and second rotations is expressed as a negative ghost or a positive ghost. In order to solve this problem, fast charge rise characteristics and overcharge prevention of the toner itself have been proposed through trial and error, but have not yet been fully satisfied.

  In addition to the improvement of the toner itself, there is also proposed a technique for supplying new toner after the toner rotated once on the developing roller is once peeled off from the developing roller, that is, after resetting. However, since only a part of the toner is replaced, there is a problem that a ghost is generated in a solid image or a solid solid image.

  Furthermore, the occurrence of negative ghosts and positive ghosts is not limited to printing only solid images on the same transfer material. For example, as shown in FIGS. Even in a solid image having a halftone area of halftone dots, negative ghost and positive ghost are generated. Details will be described below.

  As shown in FIG. 7, when an image in which the white area P6 is formed in the printing area P5 having a length corresponding to one rotation of the developing roller is printed, as shown in FIG. A printing area P1 having a length corresponding to one rotation of the developing roller from the start position and a printing area P7 corresponding to one rotation of the developing roller from the white area P6 are areas having a high printing density. At this time, the print area P2 following the print area P1 is an area having a lighter print density than the print area P1, as in FIG. As a result, the print area P7 printed in the print area P2 becomes conspicuous, and in particular, the print area P7 is visually recognized as a ghost. However, the print areas P1 and P7 have the same density.

  On the other hand, when a positive ghost occurs when the image shown in FIG. 7 is printed, as shown in FIG. 9, a printing area P3 having a length corresponding to one rotation of the developing roller from the printing start position, and a white area P6 to the developing roller. The print area P8 corresponding to one rotation of the print area is an area having a low print density. At this time, the print area P4 following the print area P3 is an area having a darker print density than the print area P3, as in FIG. As a result, the print area P8 printed in the print area P4 becomes conspicuous, and in particular, the print area P8 is visually recognized as a ghost. However, even when a positive ghost is generated, the print areas P3 and P8 have the same density.

  The occurrence of such print areas P2 and P4 is that the toner on the developing roller corresponding to the white area P6 among the toner on the developing roller remains on the developing roller without being used for development on the photosensitive drum. This is because the toner on the developing roller corresponding to these areas (printing areas P1, P3) is used for development on the photosensitive drum. The toner remaining on the developing roller is collected by the supply roller, and at the same time, new toner is supplied to the developing roller (reset). On the other hand, since only new toner is supplied onto the developing roller in which the toner is used, even in the areas after the printing areas P1 and P3 that have a length corresponding to one rotation of the developing roller from the printing start position, The print areas P7 and P8 and the print areas P2 and P4 are printed with different densities.

  Furthermore, as shown in FIG. 10, a halftone printing area P10 with halftone dots is formed following the area where the white area P6 is formed in the solid printing area P9 narrower than the equivalent of one rotation of the developing roller. When printing an image, the effect of the solid print area P9 occurs in the halftone print area P10. That is, when a negative ghost occurs, as shown in FIG. 11, the halftone print area P10 following the solid print area P9 has a print density lower than that of the halftone print area P10, that is, the original print density of the halftone image data. A halftone print region P11 having a lighter print density than that occurs. At this time, the halftone printing area P11 is an area corresponding to one rotation of the developing roller from the printing area P9. Further, the halftone printing area P12 corresponding to one rotation of the developing roller from the white area P6 is the same or substantially the same, equivalent or similar (hereinafter collectively referred to as “same”) as the halftone printing area P10. Print density.

  On the other hand, when a positive ghost occurs when the image shown in FIG. 10 is printed, as shown in FIG. 12, the print density in the halftone print area P14 following the solid print area P13 is higher than that in the halftone print area P14. A dark print area, that is, a halftone print area P15 having a darker print density than the original print density of the halftone image data is generated. Also at this time, the halftone printing area P15 is an area corresponding to one rotation of the developing roller from the printing area P13. Further, the halftone printing area P16 corresponding to one rotation of the developing roller from the white area P6 has the same printing density as the halftone printing area P14.

  As a technique for solving a ghost that occurs when printing such a specific pattern, there is an image forming apparatus described in Patent Document 1, for example. In the image forming apparatus described in Patent Document 1, after the development of the inspection pattern, the developing roller has an entire width of the developing roller and develops a belt-like image at least equal to or larger than the circumferential length of the developing roller. Thus, the toner is uniformly consumed to prevent the occurrence of a ghost accompanying the development of the inspection pattern.

JP 2005-62244 A

  However, the technique described in Patent Document 1 is a technique for preventing the influence of the first image printing on the transfer material from affecting the next second image printing. There is a problem that ghosts (negative ghosts and positive ghosts) generated in an image printed on a material cannot be suppressed.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique capable of suppressing ghosts generated in the same transfer material.

(1) The present invention for solving the above-described problems includes an image carrier, a charging means for charging the surface of the image carrier, which is arranged in the rotation direction of the image carrier, and a charged image carrier. An exposure unit that forms an electrostatic latent image by exposing the surface of the body to an image; a developing unit that develops the electrostatic latent image with a developer; and a light emission control unit that controls light emission of the exposure unit. An image forming apparatus for transferring a developer image developed by an agent to a transfer material,
Based on image data, it comprises dot gains for each of a plurality of dots arranged in a matrix in the main scanning direction of the exposure unit and the sub-scanning direction of the exposure unit orthogonal to the main scanning direction. Latent image forming means for generating latent image data;
For each dot of the latent image data, based on a dot gain in a reference source dot and a dot gain in a reference destination dot corresponding to one rotation of the developing unit in the sub-scanning direction from the reference source dot. And a ghost correction unit that corrects the dot gain of the reference source dot.

(2) In the image forming apparatus according to (1), the light emission control unit performs light emission control of the exposure unit at least twice for each dot of the latent image data. Consisting of means,
The light emission of the exposure means at least twice by the light emission control means
A first light emission according to a dot gain for each dot generated by the latent image forming means;
And second light emission according to a correction level for correcting the dot gain of the reference source dot generated by the ghost correction unit based on the dot gain of the reference destination dot.

(3) The present invention for solving the above-described problems is the image forming apparatus according to (2), further comprising a detecting unit that detects an ambient environment where the image forming apparatus is installed, and a surrounding detected by the detecting unit. And storage means for storing the correction polarity corresponding to the environment and the dot gain correction level of the reference source dot corresponding to the correction polarity as table data,
The ghost correction unit is obtained by referring to the storage unit according to the surrounding environment detected by the detection unit and the dot gain of the reference destination dot corresponding to one rotation before the developing unit. In the image forming apparatus, the second light emission is controlled based on a correction polarity and a correction level.

According to the present invention of (1) described above, the ghost correcting means is used for latent image data for each dot comprising dot gains for a plurality of dots arranged in a matrix in the main scanning direction and the sub-scanning direction. The dot gain in the reference source dot is corrected based on the dot gain in the reference source dot and the dot gain in the reference destination dot corresponding to one rotation of the developing unit before the reference source dot.
Therefore, the amount of developer from the developing unit when developing the electrostatic latent image drawn on the image carrier is different, and the amount of charge of the developer supplied in the next one rotation of the developer unit is different. However, since it is possible to correct the developing ability of the electrostatic latent image due to the variation in the charge amount of the developer, it is possible to prevent the occurrence of ghosts caused by the developing means.

  According to the invention of (2) described above, the light emission control means controls the light emission of the exposure means at least twice for each dot of the latent image data, and the dot gain for each dot generated by the latent image forming means. Development by the first light emission according to the correction and the second light emission according to the correction level for correcting the dot gain of the reference source dot generated by the ghost correction means based on the dot gain of the reference destination dot. Since the latent image for correcting the occurrence of the ghost due to the means is drawn on the image carrier, an effect that the ghost correction means can be formed with a simple structure can be obtained.

  According to the invention of (3) described above, since the detecting means for detecting the surrounding environment where the image forming apparatus is installed is provided, the correction polarity corresponding to the surrounding environment detected by the detecting means by the storage means And the correction level are stored as table data, and the ghost correction unit refers to the storage unit according to the dot gain in the reference destination dot corresponding to one rotation of the developing unit, and sets the obtained correction polarity and correction level. Based on this, since the second light emission is controlled, an effect that the ghost correcting means can be formed with a simple structure can be obtained.

  Other effects of the present invention will become apparent from the description of the entire specification.

1 is a diagram for explaining a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a diagram for explaining a detailed configuration of a latent image forming unit according to the first embodiment. FIG. 4 is a diagram for explaining a schematic configuration of dot gain correction in the image forming apparatus according to the first embodiment. It is a figure which shows a solid image. FIG. 5 is a diagram illustrating an example of a negative ghost when the solid image illustrated in FIG. 4 is printed. FIG. 5 is a diagram illustrating an example of a positive ghost when the solid image illustrated in FIG. 4 is printed. It is a figure which shows the white solid image in which a white area | region is formed in the area | region of the length equivalent to 1 rotation of a developing roller. FIG. 8 is a diagram illustrating an example of a negative ghost when the image illustrated in FIG. 7 is printed. It is a figure which shows an example of the positive ghost at the time of printing the image shown in FIG. FIG. 6 is a diagram showing an image in which a halftone image area with halftone dots is formed following a solid white image area that is narrower than that corresponding to one rotation of the developing roller. FIG. 11 is a diagram illustrating an example of a negative ghost when the image illustrated in FIG. 10 is printed. It is a figure which shows an example of the positive ghost at the time of printing the image shown in FIG.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. However, in the following description, the same components are denoted by the same reference numerals, and repeated description is omitted.

  FIG. 1 is a diagram for explaining a schematic configuration of an image forming apparatus according to an embodiment of the present invention. Hereinafter, the image forming apparatus according to the present embodiment will be described in detail with reference to FIG. However, FIG. 1 illustrates an exposure unit that forms an electrostatic latent image by exposing a part of each component, that is, a charged photosensitive drum surface, for image formation included in the image forming apparatus of the present embodiment. FIG. 2 is a diagram showing a developing unit that forms a developer image on the electrostatic latent image with a developer (toner) on a developer carrying member (developing roller). In the following description, the case where the present invention is applied to a monochrome image forming apparatus will be described. However, the present invention is not limited to a monochrome image forming apparatus and can be applied to a color image forming apparatus. . In the color image forming apparatus, for example, the developing unit includes four color sub-developing units of Y (yellow), M (magenta), C (cyan), and K (black), and the developer developed in each sub-developing unit. A color image is printed by transferring the image onto the same transfer material. Therefore, the present invention can also be applied to a color image forming apparatus by applying the configuration of the developing unit described later to each of the Y, M, C, and K sub-developing units.

  The image forming apparatus according to this embodiment includes a photosensitive drum 4, a charging unit (not shown) that is arranged in a moving direction of the photosensitive drum 4 and charges the surface of the photosensitive drum 4 to a predetermined potential, and an image of the surface of the charged photosensitive drum 4. The exposure unit 5 includes a well-known LED array that forms an electrostatic latent image by exposure, and a developing unit that forms a toner image from the electrostatic latent image with toner on the developing roller 2. The exposure unit 5 includes a latent image forming unit 6 that forms latent image data from image data, and a light emission control unit that controls light emission of the LED. The toner on the developing roller 2 is regulated so as to obtain a desired toner layer in both the layer thickness and the charge amount, and then the charged toner is conveyed to a region facing the photosensitive drum 4, and is exposed to the photosensitive drum 4 by the exposure unit 5. The electrostatic latent image formed on the outer peripheral surface is developed.

  Further, a supply roller 1 is arranged as a developer supply body so as to face the peripheral side surface of the developing roller 2, and ideally, all the toner rotated once on the developing roller 2 is peeled off once ( The new toner is supplied from (Reset). The developing roller 2 is also provided with a regulating roller 3 on the downstream side of the supply roller 1 so as to oppose the peripheral side surface thereof. The developing roller 2 is supplied to the developing roller 2 by the regulating roller 3. The toner is regulated so as to have a desired toner layer in both layer thickness and charge amount. At this time, the toner adhering to the regulating roller 3 is scraped off and collected by the collection blade 7.

  As is apparent from FIG. 1, the supply roller 1, the developing roller 2, and the regulating roller 3 are formed of a roller body, and are in a direction opposite to the rotation direction (counterclockwise direction in FIG. 1) of the photosensitive drum 4 (FIG. 1). 1 (clockwise in FIG. 1). The developing roller 2 has a configuration in which a surface layer 2a having elasticity is formed on the outer periphery of a conductive rigid body 2b such as stainless steel having a central axis serving as a rotation center. The supply roller 1 has a configuration in which, for example, a toner supply layer 1a made of conductive nylon or the like is formed on the outer periphery of a conductive rigid body 1b such as stainless steel having a central axis serving as a rotation center. Further, a predetermined bias is supplied to the developing roller 2 and the supply roller 1 from a well-known bias power source (not shown). At this time, the developing roller 2 is pressed against the photosensitive drum 4, and the rotation is controlled so that the contact surface between the developing roller 2 and the photosensitive drum 4 is in the same direction. The supply roller 1 is pressed against the developing roller 2, and the developing roller 2 is pressed. The rotation is controlled so that the contact surface between the roller 2 and the supply roller 1 is in the facing direction. Further, the regulating roller 3 is pressed by the developing roller 2, and the contacting surface between the developing roller 2 and the regulating roller 3 faces. The rotation is controlled so that

  Further, the developing unit of the present embodiment includes a well-known stirring and conveying roller (not shown) and the like, and is configured to replenish toner to the supply roller 1. In addition, a known eraser lamp for erasing residual charges on the photosensitive drum 4 and a developer image formed on the photosensitive drum 4 are transferred onto a transfer material such as paper around the photosensitive drum 4. A well-known transfer unit (not shown) is arranged. Furthermore, the image forming apparatus according to the present exemplary embodiment includes a well-known fixing unit (not shown) that fixes the transferred developer image on the transfer material, a well-known conveyance unit (not shown) that conveys the transfer material, and the like. Yes.

  Next, FIG. 2 is a diagram for explaining a detailed configuration of the latent image forming unit of the present embodiment, FIG. 3 is a diagram for explaining a schematic configuration of dot gain correction in the image forming apparatus of the present embodiment, Hereinafter, ghost correction using dot gain correction of each dot in the image forming apparatus of the present embodiment will be described in detail with reference to FIGS. However, in the following description, when one dot of the electrostatic latent image is formed on the photosensitive drum 4, the maximum number of lighting (number of lines) of the LEDs that are turned on for a predetermined time is four times (four lines). However, the number of times the LED is turned on is not limited to four. Also, the number of times the LED used for ghost correction is turned on may be two or more. Further, in the present specification, the data input by the print instruction is image data, and data indicating the lighting intensity of the first line 12 after known correction such as γ correction is performed on the image data. The latent image data, the data indicating the lighting intensity of the second and third lines 13 and 14 of the enhancement correction corresponding to each dot of the latent image data, the fourth of the ghost correction corresponding to each dot of the enhancement correction data and latent image data. Data indicating the lighting intensity of the line 15 (including no lighting (lighting off)) is referred to as ghost correction data.

  As shown in FIG. 3, in the image forming apparatus of this embodiment, the electrostatic latent image is written by four lines for each dot. Specifically, LED lighting per dot is configured by four lines from the first line 12 to the fourth line 15 in detail. That is, for each dot, one dot of the electrostatic latent image drawn on the photosensitive drum 4 is drawn by four times of light emission of the LED that performs writing. The lighting intensity of the LEDs on lines 12-15 is controlled. At this time, the first line 12 as the first light emission is configured such that the light emission amount (light emission intensity) is controlled based on the latent image data. Further, for example, thin lines or the like tend to be printed thinly with respect to other portions in normal printing, that is, printing based on latent image data. Accordingly, the second line 13 and the third line 14 are provided in order to perform writing with enhancement correction so that the print density is higher than the latent image data. Furthermore, the image forming apparatus according to the present invention has a configuration in which a fourth line 15 for performing writing for correction is provided as the second light emission based on the latent image data before one rotation of the developing roller 2. ing. Note that the ghost correction line is not limited to one line (fourth line 15), that is, one LED lighting, and a ghost correction line may be formed by two or more lines. . By forming the ghost correction line with two or more lines, it is possible to control the gradation at the time of ghost correction more finely.

  As shown in FIG. 2, the latent image forming unit 6 of the present embodiment generates latent image data indicating the lighting intensity of the first line 12 in each dot of the electrostatic latent image based on the image data. A latent image data forming unit 8 is provided as image forming means. The latent image data forming unit 8 of the present embodiment also performs known correction such as γ correction when generating latent image data from image data. In addition, the latent image forming unit 6 performs, based on the latent image data, for example, the second line 13 and the third line 14 that perform enhancement correction to make the print density of a portion such as a thin line darker than the latent image data. An enhancement unit 9 is provided for generating enhancement correction data indicating the lighting intensity. The latent image data generated by the latent image data forming unit 8 is for each of a plurality of dots arranged in a matrix in the main scanning direction of the exposure unit 5 and the sub-scanning direction of the exposure unit 5 orthogonal to the main scanning direction. It is data consisting of the dot gain.

In addition, the latent image forming unit 6 based on each latent image data, latent image data (dot gain) at a dot (hereinafter referred to as a reference destination dot) corresponding to one rotation of the developing roller 2 from each dot. , A ghost correction unit (ghost correction means) 10 that generates light emission control data (ghost correction data) for controlling the lighting intensity of the fourth line 15 of each dot serving as a reference source is provided. The generation of the ghost correction data by the ghost correction unit 10 is determined based on the dot gain of the reference destination dot that is a dot corresponding to one rotation of the developing roller.
1. Set the dot gain when LED writing is equivalent to “OFF” to A
2. When the LED writing is equivalent to “ON”, set the dot gain to B
3. Correction level α is α ≧ 0 (zero)
If
In the case of a negative ghost, B is controlled to satisfy [B = (1 + α) × A],
In the case of positive ghost, A is controlled to satisfy [A = (1 + α) × B].

  In addition, the ghost correction unit 10 according to the present embodiment determines a ghost polarity (negative ghost or positive ghost) to be corrected and a correction level α for each dot of the latent image data, and sets it as ghost correction data. The determination of the ghost polarity and the correction level α is performed based on the installation environment of the image forming apparatus measured by a known temperature / humidity sensor (not shown) included in the image forming apparatus of the present embodiment. However, the detection of the installation environment for determining the polarity of the ghost is not limited to the combination of only the temperature and humidity measured by the temperature and humidity sensor. In addition, the detection of the installation environment by the ghost correction unit 10 of the present embodiment is not limited to each print instruction of image data, and may be performed every preset time.

  In particular, the ghost correction unit 10 of the present embodiment is configured to include table data (not shown) that stores the ghost polarity and the correction level α corresponding to the temperature and humidity measured by the temperature and humidity sensor. The ghost correction unit 10 refers to the table data for each image print instruction, and generates data of a correction level α including correction polarity according to the installation environment at the time of printing of the image forming apparatus as ghost correction data. In the image forming apparatus according to the present embodiment, since the ghost is corrected by turning on the fourth line 15, the ghost correction data is a reference destination that is a dot corresponding to one rotation of the developing roller 2. Whether to correct the dot gain of the reference source dot for which the LED writing is ON (lit) or the reference source dot for which the LED write is OFF (dark), or which part of the dot gain to correct This is polarity data to be determined and lighting intensity data of the fourth line 15 for each latent image data. The table data for storing the ghost polarity and the correction level α is stored in a storage unit (storage means) made up of a well-known nonvolatile memory element provided separately from the ghost correction unit 10, and the ghost correction unit 10. May be referred to.

  That is, the ghost correction unit 10 according to the first embodiment performs latent image data (dot gain) on each dot (reference destination dot) corresponding to one rotation of the developing roller 2 from each dot (reference source dot) of the latent image data. Detects whether the LED is OFF (extinguished) or ON (lit). Next, the ghost correction unit 10 refers to the table data based on the installation environment measured by the temperature / humidity sensor and the LED ON / OFF detection result, and the lighting intensity of the fourth line 15 of the reference source dot To decide. However, when viewed from the reference source data, there may be no image exposure data before the development roller 2 corresponding to one rotation. For example, the developing roller 2 rotates slightly before the electrostatic latent image is developed, but there is no image exposure data during this period. Also, there is no image exposure data between transfer materials during continuous printing. However, even in this case, the rotation of the developing roller 2 and the supply of the developer to the developing roller 2 are continuously performed. Therefore, the ghost correcting unit 10 determines that the developer is not consumed by the developing roller 2, that is, the dot gain of the reference destination is 0 (zero) and is equivalent to the case where the LED is turned off.

  Further, the latent image forming unit 6 of the present embodiment includes the latent image data generated by the latent image data forming unit 8, the enhancement correction data generated by the enhancement unit 9, and the ghost correction generated by the ghost correction unit 10. A light emission control unit (light emission control means) 11 that generates light emission control data in the first to fourth lines 12 to 15 of each dot based on the data is provided. At this time, the output from the light emission control unit 11 becomes the final dot gain when the latent image is drawn on the peripheral side surface of the photosensitive drum 4, that is, the corrected dot gain.

  In other words, in the ghost correction caused by the developing roller 2 by the image forming apparatus of the present embodiment, the ghost correction unit 10 controls the light emission intensity of the LED in the fourth line 15 serving as a ghost correction line, thereby generating a ghost region. The dot gain of each dot is corrected to prevent the occurrence of ghost. However, in the image forming apparatus of the present embodiment, the dot gain of each dot of the electrostatic latent image drawn on the peripheral side surface of the photosensitive drum 4 is only corrected to increase.

  Hereinafter, based on FIGS. 4-12, the ghost correction | amendment operation | movement by the ghost correction | amendment part 10 of this embodiment is demonstrated in detail. However, as shown in the above-mentioned problem section, even when the solid image shown in FIG. 4 is printed, that is, when the image data is a solid image, the printed image obtained by printing is the toner on the developing roller 2. Depending on the amount of charge, there may be a ghost image of either the negative ghost shown in FIG. 5 or the positive ghost shown in FIG. However, since the ghost correction unit 10 determines whether the negative ghost or the positive ghost is generated based on the detection result of the temperature / humidity sensor, in the following description, the negative ghost is determined. The ghost correction operation will be described separately for the case of the positive ghost. The lighting operation of the fourth line 15 will be described in detail. However, the arrow L shown in FIGS. 4 to 12 is the print length corresponding to one rotation of the developing roller 2.

(Negative ghost correction)
The ghost correction unit 10 detects the temperature and humidity from the temperature / humidity sensor, the dot gain of each dot (reference source dot) of the latent image data generated by the latent image data forming unit 8, and the latent image data. The table data is searched based on the dot gain in the dot corresponding to one rotation of the developing roller 2 (reference destination dot) from each dot. Therefore, when the negative ghost shown in FIG. 5 occurs, printing is started when the dot gain of the dot corresponding to one rotation of the developing roller 2 from the printing area P1 (reference destination dot indicated by L1 in the drawing) is referred to. Since there is no image exposure data because it is before, that is, LED writing is OFF (extinguishment), the developer is not consumed on the developing roller 2. Therefore, the ghost correcting unit 10 sets the dot gain of each reference destination dot to 0 (zero). As a result, the ghost correction data in which the LED does not emit light in the fourth line 15 of the dot serving as the reference source corresponding to the print region P1 is obtained.

  On the other hand, when reference is made to the dot gain in the dots corresponding to one rotation of the developing roller 2 from the printing area P2 (indicated by L21 and L22 in the figure), the printing areas P1 and P2 are solid printing, and LED writing is ON. Since it is (lit), the developer on the developing roller 2 is consumed. Therefore, the ghost correction data for each dot in the printing region P2 generated by the ghost correction unit 10 becomes ghost correction data for causing the LEDs of the fourth line 15 to emit light with the light emission intensity (correction level α) corresponding to the table data. That is, the dot gain of the light emission control data for each dot in the print region P2 is increased. As a result, since the print density of each dot in the print area P2 is increased, the ghost shown in the print area P2 shown in FIG. 5 is corrected, and the solid image shown in FIG. 4 is printed. However, the light emission of the fourth line 15 may be light emission having a predetermined light emission intensity.

  Further, as shown in FIG. 7, when printing of an image in which a white area P6 is formed on a solid image is instructed, the negative ghost shown in FIG. 8 is obtained. As in the case of printing the solid image shown in FIG. 4, the ghost correction unit 10 generates ghost correction data. On the other hand, since the dot gain of the dot in the white region P6 shown in FIG. 8 is 0 (zero), the dot gain in the reference destination dot (indicated by arrow L6) that is the dot corresponding to one rotation of the developing roller 2 Regardless of this, the ghost correction unit 10 generates ghost correction data for each dot in the white region P6, where the dot gain is 0 (zero), that is, the LED in the fourth line 15 does not emit light. On the other hand, since the dot gain of each dot in the printing area P7 becomes a dot gain corresponding to solid printing, the ghost correction unit 10 corresponds to one rotation of the developing roller 2 for each dot in the printing area P7. A dot (indicated by an arrow L76) in the white region P6 that is a dot is referred to. At this time, since the dot gain of each dot in the white area P6 is 0 (zero), the ghost correction unit 10 does not emit the LED in the fourth line 15 for each dot in the print area P7. Is generated. As a result, only the fourth line 15 of only each dot in the print area P2 emits light, and only the print density of the print area P2 becomes dark, so that the ghost shown in the print area P2 shown in FIG. 8 is corrected, and FIG. A print image in which a white region P6 is formed is printed on the solid image shown.

  As shown in FIG. 10, the halftone print area P10 of the halftone dot is formed following the area where the white area P6 is formed in the solid print area P9 narrower than the equivalent of one rotation of the developing roller 2. When printing is instructed, the negative ghost shown in FIG. 11 is obtained. In the print areas P6 and P9, the ghost correction unit 10 generates ghost correction data as in the case of printing the image shown in FIG. On the other hand, among the two halftone printing areas P10 shown in FIG. 11, in the halftone printing area P10 on the side adjacent to the printing area P9, the LED writing ON (lighted) dots are in the printing area P9 described above. Similar to the dots, the ghost correction unit 10 generates ghost correction data that does not light the fourth line 15. Further, among the two halftone printing areas P10 shown in FIG. 11, in the halftone printing area P10 adjacent to the printing area P9, the LED writing OFF (lights off) dot (dot gain is 0 (zero)). As for the dots), the ghost correction unit 10 generates ghost correction data that does not light the fourth line 15 in the same manner as the dots in the print region P6 shown in FIG.

  Among the dots in the halftone print area P11, the dots in which LED writing is ON (lighted) are dots corresponding to one rotation of the developing roller 2 (indicated by an arrow L119), similarly to the dots in the print area P2 in FIG. Is a solid print area P9, the ghost correction unit 10 generates ghost correction data for causing the LEDs of the fourth line 15 to emit light at a light emission intensity (correction level α) corresponding to the table data. On the other hand, the ghost correction unit 10 generates ghost correction data that does not illuminate the fourth line 15 for the dots in which the LED writing is OFF (extinguish) among the dots in the halftone print region P11.

  Further, among the dots in the halftone print area P12, the LED write ON (lighted) dots are not emitted from the LED in the fourth line 15 by the ghost correction unit 10 in the same manner as the dots in the print area P7 in FIG. Generate ghost correction data. In addition, among the dots in the halftone print area P12, the ghost correction unit 10 generates ghost correction data that does not light the fourth line 15 for the LED writing OFF (lights off). As in the printing area P7 of FIG. 8, this is because the dot (indicated by the arrow L126) corresponding to one rotation of the developing roller 2 from each dot in the halftone printing area P12 is the dot in the white area P6, that is, the dot gain. This is because the dot is 0 (zero).

  Furthermore, in the halftone print area P10 that follows the halftone print area P11 in the two halftone print areas P10, the dot corresponding to one rotation of the developing roller 2 from the print dot is a print dot. That is, the ghost correction unit 10 generates fuzzy ghost correction data based on the dot gain of each dot of the reference source and the reference destination. However, as is clear from FIG. 11, in the halftone print region P10, there are more dots with LED writing OFF (lights off) than with dots with LED writing ON (lights up) (data rate less than 50%). In addition, the dot before the LED writing is turned on (lit) and the dot corresponding to one rotation of the developing roller 2 also increases the number of the LED writing off (lights off). Accordingly, in the halftone printing area P10 following the halftone printing area P11, the ghost correction unit 10 becomes ghost correction data that does not light the fourth line 15 for the LED writing OFF (extinguishment) dots. The probability of generating ghost correction data for emitting LEDs of four lines 15 is extremely low (25% probability when the data rate is 50%), and fuzzy ghost correction data is produced, but the amount of toner used for development is small For this reason, it is practically impossible to determine a ghost.

  As a result of the above description, the fourth line 15 of the LED writing ON (lit) dot in the halftone print area P11 emits light, and the print density in the halftone print area P11 becomes dark, so that the ghost shown in FIG. 11 is corrected. The image shown in FIG. 10 is printed.

(Positive ghost correction)
During the solid printing, when the positive ghost shown in FIG. 6 is generated, the dot (indicated by L3 in the drawing) before the one rotation of the developing roller 2 from the printing area P3 is before the start of printing, so there is no image exposure data. That is, since the LED writing is OFF (extinguishment), the developer is not consumed by the developing roller 2. Therefore, the ghost correcting unit 10 sets the dot gain of each reference destination dot to 0 (zero). Here, in the table data corresponding to the temperature and humidity in the installation environment where the positive ghost is generated, the developer is consumed by the dot gain of the reference destination dot being 0 (zero), that is, the dot corresponding to one time before the developing roller 2. If not, the ghost correction unit 10 generates ghost correction data for emitting the fourth line 15 in the reference source dot. Therefore, the ghost correction unit 10 generates ghost correction data for causing the LEDs in the fourth line 15 to emit light for each dot in the print region P3. However, it becomes ghost correction data for causing the LEDs of the fourth line 15 to emit light at the light emission intensity (correction level α) corresponding to the table data. The light emission of the fourth line 15 may be light emission having an arbitrary light emission intensity set in advance.

  On the other hand, when reference is made to the dot gain in the dots corresponding to one rotation of the developing roller 2 from the printing area P4 (indicated by L43 and L44 in the figure), the printing areas P3 and P4 are solid printing, and LED writing is ON. Since it is (lit), the developer on the developing roller 2 is consumed. Therefore, the ghost correction unit 10 generates ghost correction data in which the LED of the fourth line 15 does not emit light. As a result, the print density of each dot in the print region P3 becomes dark, so that the ghost shown in the print region P3 shown in FIG. 6 is corrected, and the solid image shown in FIG. 4 is printed.

  When the positive ghost shown in FIG. 9 occurs in the print image in which the white area P6 is formed in the solid image shown in FIG. 7, the solid image shown in FIG. 6 is printed in the print areas P3 and P4. Similarly to the time, the ghost correction unit 10 generates ghost correction data. Further, since the dot gain of the dots in the white region P6 is 0 (zero), the ghost correction unit 10 has a dot gain of 0 (zero) for each dot in the white region P6, as in the case of the negative ghost occurrence. Ghost correction data in which the LED in the fourth line 15 does not emit light is generated. On the other hand, since the dot gain of each dot in the printing area P8 is a dot gain corresponding to solid printing, the ghost correction unit 10 corresponds to one rotation of the developing roller 2 for each dot in the printing area P8. A dot (indicated by an arrow L86) in the white region P6 that is a dot is referred to. At this time, since the dot gain of each dot in the white region P6 is 0 (zero), the ghost correction unit 10 applies the fourth line 15 to each dot in the print region P8 as in the correction for the print region P3. The ghost correction data for causing the LED in FIG. As a result, the fourth line 15 of only each dot in the print areas P3 and P8 emits light, and the print density of the print areas P3 and P8 becomes dark, so that the ghost shown in the print areas P3 and P8 shown in FIG. 9 is corrected. A print image in which the white region P6 is formed is printed on the solid image shown in FIG.

  A positive ghost image is formed on an image in which a halftone print area P10 having a halftone dot is formed following an area in which a white area P6 is formed in a solid print area P9 narrower than one rotation of the developing roller 2 shown in FIG. When this occurs, the image shown in FIG. 12 is printed. In this case, the developer is used only at the dot (indicated by arrow L1513) that corresponds to one rotation of the developing roller 2 from each dot in the halftone print area P15. That is, the developer is not consumed at each dot (indicated by arrows L13, L14, and L166, respectively) from the dots in the print area P13, the print area P14, and the print area P16, corresponding to one rotation of the developing roller 2 (dots L13, L14, and L166, respectively). The gain becomes 0 (zero). However, in the halftone print area P14 following the halftone print area P15, development is performed from each dot of the halftone print area P14, similarly to the halftone print area P10 following the halftone print area P11 at the time of the negative ghost correction described above. It is assumed that the developer is not consumed in the dots corresponding to one rotation of the roller 2.

  Therefore, the ghost correction unit 10 causes the LED in the fourth line 15 to emit light for each dot in the print region P13 and each dot in which the LED writing is turned on (lit) in the halftone print regions P14 and P16. Generate data. As a result, the fourth line 15 of print dots in the print area P13 and the halftone print areas P14 and P16 emits light, and the print density in the print area P13 and the halftone print areas P14 and P16 becomes dark. The ghost in the area P13 and the halftone print areas P14 and P16 is corrected, and the image shown in FIG. 10 is printed.

  As described above, in the image forming apparatus of the present embodiment, the ghost correction polarity and the correction level are determined based on the detection result of the installation environment including the temperature and humidity sensor, and the developing roller 2 is determined from the reference source dot. With reference to the dot gain of the reference dot corresponding to one rotation before, the presence or absence of consumption of the developer before the rotation of the developing roller 2 is estimated from the reference source dot, and the reference source is based on the estimation result This is a configuration for correcting the dot gain of the dots. Therefore, when developing the electrostatic latent image drawn on the photosensitive drum, the toner development from the developing roller to the photosensitive drum is caused by the difference in toner charge amount between the first rotation of the developing roller and the second and subsequent rotations. Even if the capacities are different, the developing capability of the electrostatic latent image can be corrected, so that it is possible to prevent the occurrence of a ghost attributed to the developing roller.

  Note that the image forming apparatus according to the present embodiment is not limited to ghost correction due to an increase in print density due to the fourth line. For example, a function for adjusting the density of the print density of the entire known print image is used. Thus, the configuration may be such that the latent image data and the enhancement correction data are corrected so that the print density of the area having a high print density at the time of positive ghost is lightly printed.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment of the invention. However, the invention is not limited to the embodiment of the invention, and various modifications can be made without departing from the scope of the invention. It can be changed.

DESCRIPTION OF SYMBOLS 1 Supply roller 2 Developing roller 3 Control roller 4 Photosensitive drum 5 Exposure part 6 Latent image formation part 7 Collecting blade 8 Latent image data formation part 9 Enhance part 10 Ghost correction part 11 Light emission control part 12-15 1st-4th line

Claims (3)

An image carrier, a charging unit arranged in the rotation direction of the image carrier and charging the surface of the image carrier, and image exposure of the charged image carrier surface to form an electrostatic latent image An exposure unit; a development unit that develops the electrostatic latent image with a developer; and a light emission control unit that controls light emission of the exposure unit, and transfers the developer image developed by the developer to a transfer material. An image forming apparatus,
Based on image data, it comprises dot gains for each of a plurality of dots arranged in a matrix in the main scanning direction of the exposure unit and the sub-scanning direction of the exposure unit orthogonal to the main scanning direction. Latent image forming means for generating latent image data;
For each dot of the latent image data, based on a dot gain in a reference source dot and a dot gain in a reference destination dot corresponding to one rotation of the developing unit in the sub-scanning direction from the reference source dot. An image forming apparatus comprising: a ghost correcting unit that corrects a dot gain in the reference source dot. The light emission control means comprises means for controlling the light emission of the exposure means at least twice for each dot of the latent image data,
The light emission of the exposure means at least twice by the light emission control means
A first light emission according to a dot gain for each dot generated by the latent image forming means;
And a second light emission according to a correction amount for correcting a dot gain of the reference source dot generated by the ghost correction unit based on a dot gain of the reference destination dot. The image forming apparatus according to 1. A detection unit configured to detect a surrounding environment in which the image forming apparatus is installed; a correction polarity corresponding to the surrounding environment detected by the detection unit; and a dot gain of the reference source dot corresponding to the correction polarity Storage means for storing the correction level as table data,
The ghost correction unit is obtained by referring to the storage unit according to the surrounding environment detected by the detection unit and the dot gain of the reference destination dot corresponding to one rotation before the developing unit. The image forming apparatus according to claim 2, wherein the second light emission is controlled based on a correction polarity and a correction level.