JP4984525B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus.

  In recent years, in an electrophotographic image forming apparatus, the thickness of the charge transport layer of the photoconductor is increased in order to increase the life of the photoconductor that carries an electrostatic latent image. In such a thickened photoconductor, when laser light is applied when the charge transport layer is thick when it is new, the charge generated in the charge generation layer diffuses until it reaches the surface of the photoconductor. As a result, the latent image becomes blurred and thin lines are difficult to reproduce. On the other hand, if the charge transport layer is shaved and the thickness of the charge transport layer is reduced by overlapping image formation, the charge generated in the charge generation layer does not diffuse and a sharp latent image can be obtained. The reproducibility is improved compared to when the photoconductor is new.

In order to increase the reproducibility of fine lines when the photoconductor is new, there is a method of increasing the development performance and increasing the density of the fine lines. In this case, however, a problem arises that lines other than the fine lines become thick. In addition, this method has a problem that in a photographic image, the density becomes too high to achieve good gradation reproduction. As a technique for improving the reproducibility of thin lines, for example, there are techniques disclosed in Patent Document 1 and Patent Document 2. The techniques disclosed in these patent documents improve the reproducibility of fine lines by detecting the fine lines and performing smoothing on the extracted fine lines.
JP-A-5-91299 JP-A-6-169399

  The techniques disclosed in Patent Document 1 and Patent Document 2 have a smoothing effect when the resolution of the output image is lower than the resolution of the input image. However, when the output image has a high resolution of 600 dpi or the like, if the smoothing is performed with the technique of Patent Document 1 or Patent Document 2, the line becomes too thick and a high-definition image cannot be obtained. End up.

  The present invention has been made under the background described above, and an object thereof is to improve the reproducibility of fine lines while preventing the fine lines from becoming too thick.

The present invention also provides an image carrier including a photosensitive layer having photoconductivity, input means for inputting image data representing an image, and analyzing an image represented by the image data input to the input means, A specifying means for specifying a first pixel other than a white pixel that does not constitute a thin line in the image and a second pixel other than a white pixel that constitutes a thin line in the sub-scanning direction in the image; and the input means The image carrier is exposed in accordance with an image represented by the image data input to the image carrier, and an electrostatic latent image corresponding to the image is formed on the image carrier. For the pixel specified in (2), an area corresponding to the first pixel is exposed with a first exposure amount to form an electrostatic latent image corresponding to the first pixel, and specified by the specifying means as the second pixel. The pixel corresponding to the second pixel Is exposed at a second exposure amount greater than the first exposure amount, and is exposed at a region corresponding to one pixel adjacent to the region exposed at the second exposure amount in the main scanning direction, and at the second exposure amount. An image forming apparatus comprising: an exposure unit that exposes an area of one pixel adjacent to a region opposite to the main scanning direction with an exposure amount smaller than the second exposure amount to form an electrostatic latent image. I will provide a.

The present invention also provides an image carrier including a photosensitive layer having photoconductivity, input means for inputting image data representing an image, and analyzing an image represented by the image data input to the input means, A first pixel other than a white pixel that does not constitute a thin line having an angle with respect to the main scanning direction in the image, and a white pixel that constitutes a thin line having an angle with respect to the main scanning direction in the image Specifying means for specifying a second pixel other than the image data, and exposing the image carrier in accordance with an image represented by the image data input to the input means to display an electrostatic latent image corresponding to the image as the image carrier The pixel specified as the first pixel by the specifying unit is formed so that an electrostatic latent image of the first region is formed at a position corresponding to the first pixel. The image carrier is exposed, and the second pixel is specially specified by the specifying means. For the pixels which are, the electrostatic latent image of the wider first region second region exposing the image carrying body so as to be formed in a position corresponding to the second pixel, adjacent the for during the second pixels to the image forming apparatus having an exposing unit for exposing the front Kizo carrying member as an electrostatic latent image of the first region and a narrow region than said second region is formed I will provide a.

  According to the present invention, it is possible to improve the reproducibility of a fine line while preventing the fine line from becoming too thick.

[First Embodiment]
[Configuration of the embodiment]
FIG. 1 is a block diagram illustrating a configuration of a main part of an image forming apparatus 1 according to an embodiment of the present invention. As illustrated in FIG. 1, each unit of the image forming apparatus 1 is connected to a bus 101, and communication is performed between the units via the bus 101.

  The ROM 103 stores a program executed by the CPU 102. The CPU 102 reads a program stored in the ROM 103, executes the program using the RAM 104 as a work area, and controls each unit of the image forming apparatus 1. The storage unit 105 includes a hard disk device and stores various data such as image data.

  The image input unit 108 includes a scanner mechanism that optically reads a document and an ADF (Auto Document Feeder) that transports the document to the scanner mechanism. The documents set in the ADF are conveyed one by one on the platen glass provided in the scanner mechanism. The scanner mechanism irradiates the document conveyed on the platen glass by the ADF with light. Then, the light reflected by the document is read by a CCD (Charge Coupled Device), and image data representing the read document is generated. This image data is stored in the storage unit 105.

  The input unit 106 includes various keys such as a numeric keypad and an arrow key for operating the image forming apparatus 1. When the user operates these keys, various instructions are input to the image forming apparatus 1 and various settings of the image forming apparatus 1 are performed. The display unit 107 includes a display device such as a liquid crystal display, for example, and displays a menu screen, various messages, and the like for operating the image forming apparatus 1 under the control of the CPU 102.

  The communication unit 110 is connected to a LAN (Local Area Network: not shown) and functions as a communication interface for communicating with a computer device (not shown) such as a personal computer connected to the LAN. The communication unit 110 receives image data sent via the LAN and format data representing a format for forming an image represented by the image data. The received data is stored in the storage unit 105.

  The image processing unit 111 performs image processing such as gradation correction, screen processing, and fine line correction processing on the image represented by the input image data. Then, Y (Yellow), M (Magenta), C (Cyan), and K (black) image signals are generated from the image-processed image and output to the image forming unit 109. Details of the image processing unit 111 will be described later.

  The image forming unit 109 includes an image forming engine (not shown) that forms a toner image on a recording sheet by electrophotography. This image forming engine employs an intermediate transfer system, and includes an image forming unit that forms toner images of colors of Y (Yellow), M (Magenta), C (Cyan), and K (black). Each image forming unit forms an electrostatic latent image on the photoconductor in accordance with the corresponding color image signal output from the image processing unit 111, and then attaches toner on the photoconductor to form each color toner image of YMCK. Form. Then, after the toner image is transferred to the intermediate transfer belt, the toner image transferred to the intermediate transfer belt is transferred to the recording sheet conveyed from the paper tray. The toner image transferred to the recording sheet is fixed by applying heat and pressure, and then the recording sheet on which the toner image is formed is discharged out of the image forming apparatus 1.

[Configuration of Image Processing Unit 111]
Next, the configuration of the image processing unit 111 and parts related to the image processing unit 111 will be described. FIG. 2 is a block diagram illustrating the configuration of the image processing unit 111 and parts related to the image processing unit 111. Multi-valued color image data is input to the interface unit 111A. The interface unit 111A interprets input image data and generates a bitmap image G1 of each color of Y, M, C, and K. This bitmap image G1 is output to the fine line extraction unit 111B.

  The fine line extraction unit 111B analyzes the input bitmap image G1, and detects a fine line having an angle with respect to the main scanning direction and having a predetermined width or less. Then, tag information for controlling the laser beam output from the light source unit 230 is added to the pixels constituting the detected thin line. Then, the image G2 to which the Tag information is added is output to the digital filter unit 111C. Note that the thin line extraction unit 111B may detect a thin line having a width of one pixel or a thin line having a width of two pixels.

  The digital filter unit 111C performs edge enhancement processing on the image G2 output from the thin line extraction unit 111B in order to improve the sharpness of the output image. Then, the image G3 subjected to the edge enhancement process is output to the TRC unit 111D.

  A TRC (Tone Reproduction Curve) unit 111D prevents density fluctuations occurring during an image forming job or density fluctuations caused by changes in the image forming unit 109 from affecting the image formed on the recording sheet. Further, density correction processing is performed on the image G3 output from the digital filter unit 111C. The TRC unit 111D outputs the image G4 subjected to density correction to the screen unit 111E.

  The screen unit 111E performs screen processing on the multi-value bitmap image G4 output from the TRC unit 111D, and converts the multi-value image of each color of YMCK into a binary image G5. Here, the screen unit 111E adds Tag information to pixels corresponding to pixels to which Tag information is added in each color image of YMCK. The screen unit 111E outputs the binary image G5 of each color to the ROS control unit 111F.

  The ROS (Raster Output Scanner) control unit 111F outputs the binary image G5 of each color of YMCK output from the screen unit 111E and the APC signal S1 for performing APC (Auto Power Control) control of the ROS unit 200 to the ROS unit. Based on the SOS (Start Of Scan) signal S2 output from the signal 200, the signal is output to the ROS unit 200.

  The ROS unit 200 is provided in an image forming unit for each color of YMCK included in the image forming unit 109, and includes a laser control unit 210, a laser driving unit 220, a light source unit 230, a monitor unit 300, and a synchronization sensor unit 310. ing. In FIG. 2, only one ROS unit is illustrated among four ROS units corresponding to the four colors of YMCK in order to prevent the drawing from becoming complicated.

  The laser controller 210 receives the binary image G5 output from the screen unit 111E and the APC signal S1. The laser control unit 210 outputs the input binary image G5 to the laser driving unit 220. Further, the laser control unit 210 controls the light amount setting signal S3 for controlling the light amount of the laser light output from the light source unit 230 based on the APC signal S1 output from the ROS control unit 111F and a monitor signal S4 described later. Is output.

  The laser driving unit 220 controls the light source unit 230 so that an electrostatic latent image corresponding to the input binary image G5 is formed on the photoreceptor 400. Specifically, the drive signal S5 instructing the output of the laser beam is generated according to the input binary image and Tag information. Then, the current value of the generated drive signal is determined according to the light amount setting signal S 3, and the drive signal S 5 having the determined current value is output to the light source unit 230.

  The light source unit 230 is a device that irradiates the photoreceptor 400 with laser light. The light source unit 230 outputs laser light in accordance with the drive signal S5 output from the laser drive unit 220, and exposes the photoreceptor 400. The light source unit 230 controls the amount of laser light to be output in accordance with the current value of the drive signal S5 output from the laser drive unit 220. When the light source unit 230 outputs laser light to the photoreceptor 400, an electrostatic latent image is formed on the photoreceptor 400.

The monitor unit 300 includes a sensor that detects the laser beam output from the light source unit 230. When the monitor unit 300 detects the laser beam, the monitor unit 300 outputs a monitor signal S4 indicating the intensity of the laser beam.
The synchronization sensor unit 310 includes a sensor that transmits laser light. This sensor is provided on the optical path of the laser beam output from the light source unit 230, detects the start of the main scan based on the transmission of the laser beam, and indicates that the scan has started. ) The signal S2 is output to the ROS control unit 111F.

  The photoconductor 400 is a stacked (function-separated) OPC (Organic Photoconductor) photoconductor, and is charged by a charger (not shown) that charges the photoconductor 400 to a constant potential. FIG. 3 is a diagram illustrating a cross section of the photoreceptor 400. In FIG. 3, in order to make the configuration of the photoconductor 400 easy to understand, the size of the photoconductor and the thickness of each layer constituting the photoconductor are different from the actual size. As shown in FIG. 3, the photoreceptor 400 includes a cylindrical conductive support 400A, on which an undercoat layer 400B, a charge generation layer 400C, and a charge transport layer 400D are stacked. The undercoat layer 400B is provided on the surface of the conductive support so as not to inject charges from the conductive support side. The charge generation layer 400C is laminated on the undercoat layer 400B, and generates positive and negative charge carriers when irradiated with light while the photoreceptor 400 is charged. The charge transport layer 400D is stacked on the charge generation layer 400C and transports carriers generated in the charge generation layer.

[Operation of the embodiment]
Next, the operation of this embodiment will be described. When multi-valued image data is transmitted from the computer device connected to the LAN to the image forming apparatus 1, the image data is received by the communication unit 110. The image data received by the communication unit 110 is temporarily stored in the storage unit 105 and then supplied to the image processing unit 111 by the CPU 102.

  In the image processing unit 111, the supplied image data is input to the interface unit 111A. The interface unit 111A interprets input multi-valued image data, generates a bitmap image G1 represented by the image data for each color of Y, M, C, and K, and generates the generated bitmap image G1 as a thin line extraction unit. To 111B.

  The fine line extraction unit 111B analyzes the multi-valued bitmap image G1 output from the interface unit 111A and measures an angle with respect to the main scanning direction (for example, the angle of the fine line with respect to the main scanning direction is 30 to 60 degrees). Detects a thin line (hatched line). Then, the fine line extraction unit 111B adds Tag information to the pixels constituting the fine line having an angle in the main scanning direction. For example, as illustrated in FIG. 4, tag information is added to each pixel of a thin line having an angle with respect to the main scanning direction. On the other hand, even if the pixel constitutes a thin line, the pixel constituting the thin line along the main scanning direction as shown in FIG. 5 and the pixel constituting the thin line along the sub-scanning direction as shown in FIG. Tag information is not added.

  The fine line extraction unit 111B outputs the generated image G2 to the digital filter unit 111C when the generation of the image to which the tag information is added is completed. The image G2 output from the thin line extraction unit 111B is subjected to edge enhancement processing by the digital filter unit 111C, and then density-corrected by the TRC unit 111D. The image G4 whose density has been corrected by the TRC unit 111D is subjected to screen processing by the screen unit 111E. Thereby, a binary image G5 of each color of YMCK is generated. When the generation of the binary image G5 is completed, the screen unit 111E outputs the generated binary image G5 and the APC signal S1 to the ROS unit 200 based on the SOS signal S2 output from the synchronization sensor unit 310.

  In the ROS unit 200 provided for each color of YMCK, the APC signal S1 and the corresponding color image are input to the laser control unit 210. The laser control unit 210 generates a light amount setting signal S3 for controlling the light amount of the laser light based on the input APC signal S1 and the monitor signal S4 output from the monitor unit 300. Then, the generated light amount setting signal S3 and the input binary image G5 are output to the laser driving unit 220.

  The laser drive unit 220 generates a drive signal S5 instructing output of laser light according to the input binary image and Tag information. Then, the current value of the generated drive signal S5 is determined according to the light amount setting signal S3, and the drive signal S5 having the determined current value is output to the light source unit 230. Specifically, for pixels to which tag information is not added, a drive signal is generated corresponding to the pixels. For example, as illustrated in FIG. 7, tag information is not added to the thin line along the main scanning direction of the laser light output from the light source unit 230. In this case, the laser driver 220 generates the drive signal S5 having the waveform shown in FIG. 7 corresponding to the pixel width. Further, as shown in FIG. 8, Tag information is not added to the fine line along the sub-scanning direction of the laser light output from the light source unit 230. In this case, the laser driver 220 generates the drive signal S5 having the waveform shown in FIG.

  On the other hand, as shown in FIG. 9, Tag information is added to the thin line pixels having an angle with respect to the main scanning direction. As shown in FIG. 9, the laser drive unit 220 generates the drive signal S5 so that one pixel is added in the main scanning direction in the electrostatic latent image for the pixels to which the Tag information is added.

  The light source unit 230 outputs a laser beam to the photosensitive member 400 in accordance with the drive signal S5 output from the laser drive unit 220. Here, as shown in FIG. 7, for the fine lines along the main scanning direction, the laser beam is continuously output in the main scanning direction according to the drive signal shown in FIG. 7, and as shown in FIG. The electrostatic latent image becomes a straight line. Further, as shown in FIG. 8, for thin lines along the sub-scanning direction, dot-like static lines as shown in FIG. 11 correspond to the pixels constituting the thin lines in accordance with the drive signals shown in FIG. Laser light is irradiated so that the electrostatic latent image is continuous in the sub-scanning direction to form a thin line electrostatic latent image. In this case, as shown in FIG. 11, although the fine line in the electrostatic latent image is not a clean straight line but has irregularities, the fine line is a continuous straight line. In this way, in the case of fine lines along the main scanning direction and the sub-scanning direction, the electrostatic latent image representing the thin line becomes a continuous straight line, and the potential of the electrostatic latent image on the photosensitive member is sufficient to develop the toner image. Because of the potential, the thin line is developed as a line.

  Further, as shown in FIG. 9, for the thin line having an angle with respect to the main scanning direction, a laser beam is output corresponding to the drive signal corrected for one pixel as shown in FIG. As shown in FIG. 4, a thin line electrostatic latent image with a corrected line width is formed on the photoreceptor 400. When the electrostatic latent image is formed as a slanted thin line by making the dotted electrostatic latent image obliquely continuous without performing any correction on the drive signal S5, the electrostatic latent image does not become a continuous straight line. As shown in FIG. Then, since the electrostatic latent image does not have a sufficient potential for developing the toner image at the point where the point is in contact with the point, the developed toner image is not continuous but is cut off. However, in the present embodiment, as shown in FIG. 12, for the slanted thin line, a thin line electrostatic latent image with a corrected line width is formed on the photoconductor 400, so that the main scanning direction is corrected. The oblique diagonal lines increase the line width, and when the photosensitive member 400 is exposed, the electrostatic latent image is continuous, and the potential of the electrostatic latent image is sufficient to develop the toner image.

  When the formation of the electrostatic latent image is completed, the image forming apparatus 1 forms a toner image of each color of YMCK by attaching toner on the photoreceptor 400. Then, after the toner image is transferred to the intermediate transfer belt, the toner image transferred to the intermediate transfer belt is transferred to the recording sheet conveyed from the paper tray. The toner image transferred to the recording sheet is fixed by applying heat and pressure, and then the recording sheet on which the toner image is formed is discharged out of the image forming apparatus 1.

  As described above, according to the present embodiment, fine lines are corrected only for oblique thin lines, and correction is not performed for fine lines along the main scanning direction and sub-scanning direction, so that a good image can be obtained. it can. Further, in the present embodiment, since correction for adding pixels to an image is not performed, lines in an image formed on a recording sheet do not become too thick.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. This embodiment is different from the first embodiment in that the current of the drive signal S5 for controlling the light source unit 230 is controlled in accordance with the thickness of the charge transport layer of the photoreceptor 400. FIG. 14 is a block diagram illustrating the configuration of the image processing unit 111 according to the present embodiment and the portion related to the image processing unit 111. In FIG. 14, parts having the same configuration as in the first embodiment are denoted by the same reference numerals, and in the following description, description of parts having the same configuration as in the first embodiment is omitted.

  The film thickness detection unit 500 supplies a current to the photoconductor 400 and detects the current value of the current flowing through the photoconductor 400. Then, a film thickness signal S6 indicating the detected current value is output to the CPU 102. When the current value of the current passed through the photoconductor 400 is constant, the photoconductor 400 is used to reduce the film thickness, and the current flowing through the photoconductor 400 changes when the thickness of the charge transport layer 400D of the photoconductor 400 changes. . Therefore, the thickness of the charge transport layer 400D can be obtained by measuring the current value of the current flowing through the photoconductor 400. The CPU 102 obtains the thickness of the charge transport layer 400D based on the inputted film thickness signal S6, and outputs film thickness information indicating the obtained thickness of the photosensitive layer to the thin line extraction unit 111B.

  The fine line extraction unit 111B according to the present embodiment analyzes the input bitmap image G1 and detects a fine line. Then, tag information for controlling the amount of laser light output from the light source unit 230 is added to the pixels constituting the thin line. Specifically, the thin line extraction unit 111B determines whether or not the film thickness represented by the input film thickness information is equal to or greater than a predetermined film thickness. When the thin line extraction unit 111B determines that the film thickness is equal to or greater than the predetermined film thickness, the thin line extraction unit 111B adds tag information to the pixels constituting the thin line. On the other hand, when it is determined that the film thickness is less than the predetermined film thickness, tag information is not added even to a pixel determined to form a thin line. Even if the film thickness is equal to or greater than the predetermined film thickness, tag information is not added to a pixel that does not constitute a thin line.

  The screen unit 111E performs screen processing on the image to which the tag information is added by the thin line extraction unit 111B, and generates a binary image of each color of YMCK. Here, the screen unit 111E adds Tag information to pixels corresponding to pixels to which Tag information is added in each color image of YMCK.

  The laser drive unit 220 generates a drive signal S5 that instructs the output of laser light in accordance with the input binary image. Then, the current value of the generated drive signal S5 is determined according to the light amount setting signal S3 and the Tag information added to the binary image, and the drive signal S5 having the determined current value is output to the light source unit 230.

[Operation of the embodiment]
Next, the operation of this embodiment will be described. When multi-valued image data is transmitted from the computer device connected to the LAN to the image forming apparatus 1, the image data is received by the communication unit 110. The image data received by the communication unit 110 is temporarily stored in the storage unit 105. When the CPU 102 finishes storing the image data in the storage unit 105, the CPU 102 controls the film thickness detection unit 500 to pass a current through the photosensitive member 400. The film thickness detection unit 500 detects the current value of the current flowing through the photosensitive member 400 and outputs a film thickness signal S6 indicating the detected current value to the CPU 102.

  The CPU 102 obtains the thickness of the charge transport layer 400D of the photoreceptor 400 based on the input film thickness signal S6. Then, the CPU 102 outputs film thickness information indicating the obtained thickness of the charge transport layer 400D to the thin line extraction unit 111B.

  The CPU 102 outputs the film thickness information to the thin line extraction unit 111B, and then supplies the image data stored in the storage unit 105 to the image processing unit 111. The operation from when the image data is input to the image processing unit 111 to when the multi-value bitmap image G1 of each color of YMCK is output to the thin line extraction unit 111B is the same as the operation of the first embodiment.

  The fine line extraction unit 111B detects the fine line by analyzing the multi-valued bitmap image G1 output from the interface unit 111A. Here, the thin line extraction unit 111B determines whether or not the film thickness represented by the film thickness information input from the CPU 102 is equal to or greater than a predetermined film thickness. When the thin line extraction unit 111B determines that the film thickness is equal to or greater than the predetermined film thickness, the thin line extraction unit 111B adds tag information to the pixels constituting the thin line. For example, when the thin line extraction unit 111B detects a thin line having a width of one pixel shown in FIG. 15, the thin line extraction unit 111B adds Tag information to each pixel constituting the thin line. On the other hand, when it is determined that the film thickness is less than the predetermined film thickness, tag information is not added even to a pixel determined to form a thin line.

  When the addition of the tag information ends, the fine line extraction unit 111B outputs the image G2 with the added tag information to the digital filter unit 111C. The image G2 output from the thin line extraction unit 111B is subjected to edge enhancement processing by the digital filter unit 111C, and then density-corrected by the TRC unit 111D. The image G4 whose density has been corrected by the TRC unit 111D is subjected to screen processing by the screen unit 111E. Thereby, a binary image G5 to which Tag information is added for each color of YMCK is generated. When the generation of the binary image G5 is completed, the digital filter unit 111C outputs the binary image G5 to which the tag information is added and the APC signal S1 based on the SOS signal S2 output from the synchronization sensor unit 310. Output to 200.

  In the ROS unit 200 provided for each color of YMCK, the APC signal S1 and the corresponding color image are input to the laser control unit 210. The laser control unit 210 generates a light amount setting signal S3 for controlling the light amount of the laser light based on the input APC signal S1 and the monitor signal S4 output from the monitor unit 300. Then, the generated light amount setting signal S3 and the binary image G5 to which the Tag information is added are output to the laser driving unit 220.

  The laser drive unit 220 generates a drive signal S5 that instructs the output of the laser light according to the binary image G5 to which the Tag information is added. Then, the current value of the generated drive signal S5 is determined according to the light amount setting signal S3 and the Tag information added to the binary image, and the drive signal S5 having the determined current value is output to the light source unit 230. For example, with respect to the fine line along the sub-scanning direction, when tag information is not added to the pixels constituting the fine line (when the charge transport layer 400D is thin and less than the predetermined film thickness), it is shown in FIG. As described above, the current value of the drive signal S5 for forming the electrostatic latent image of the thin line is set as the first current value. On the other hand, when Tag information is added to the pixels constituting the thin line (when the charge transport layer 400D is thick and is greater than or equal to the predetermined film thickness), as shown in FIG. 15, the electrostatic latent image of the thin line The current value of the drive signal S5 for forming the second current value is higher than the first current value.

  The light source unit 230 outputs a laser beam to the photosensitive member 400 in accordance with the drive signal S5 output from the laser drive unit 220. Here, when the current value of the drive signal S5 is the first current value, the light amount of the laser light output from the light source unit 230 is the predetermined first light amount. On the other hand, when the current value of the drive signal S5 is the second current value, since the current value of the drive signal S5 is higher than the first current value, the light amount of the laser light output from the light source unit 230 is greater than the first light amount. The second light quantity is high. As described above, when the charge transport layer of the photoconductor 400 is thick, the amount of laser light output to form a thin line increases, so that the potential of the electrostatic latent image develops the toner image. This is a sufficient potential. As described above, according to this embodiment, the electrostatic latent image of the fine line is not blurred without correcting the image, and the fine line is reproduced even when the photoconductor 400 is new.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, For example, you may implement the present invention, changing the above-mentioned embodiment as follows.

  In the first embodiment described above, when the resolution of the output image is higher than the resolution of the input image (for example, when the resolution of the input image is 600 dpi and the resolution of the output image is 1200 dpi), diagonal lines The pixels between the pixels may be complemented with pixels smaller than the pixels of the input image as shown in FIG. According to this aspect, the oblique line does not need to be thick. If the pulse width modulation in the main scanning direction of the laser beam applied to the photosensitive member can be performed, the pulse width modulation in the main scanning direction of the laser beam is performed to obtain the electrostatic latent image shown in FIG. It may be.

  In an image forming apparatus that employs an OPC photoconductor, the surface of the photoconductor becomes worn as image formation is performed, and a sharper latent image can be obtained from a new photoconductor. Will be improved. As described above, when a sharp latent image can be obtained, if the image correction described in the first embodiment is performed, the correction with respect to the oblique line becomes excessive and the oblique line becomes thick. Therefore, the number of output images (the number of recording sheets on which images are formed) is counted, and the image correction method may be varied according to the number of output images. For example, until the number of output images reaches a predetermined number, the pixels are complemented as shown in FIG. 16, and when the number of output images exceeds the predetermined number, it is shown in FIG. As described above, the pixels may be complemented.

  In the first embodiment, the digital filter unit 111C may correct the image so as to enhance the high frequency component of the image. In the first embodiment, the image density may be corrected using a look-up table (LUT).

  In the second embodiment, the film thickness of the charge transport layer 400D may be detected in four stages, and the Tag information may be 2-bit data so that the detected four stages can be expressed. The laser driving unit 220 may control the current value of the driving current in four steps according to the 2-bit Tag information. For example, if the film thickness indicated by the film thickness information is equal to or greater than the first thickness, the fine line extraction unit 111B adds Tag information “00 (A pattern)”. If the film thickness indicated by the film thickness information is less than the first thickness and greater than or equal to the second thickness (first thickness> second thickness), “01 (B pattern) "Is added. If the film thickness indicated by the film thickness information is less than the second thickness and greater than or equal to the third thickness (second thickness> third thickness), “10 (C pattern) ", And when the film thickness indicated by the film thickness information is less than the third thickness, tag information" 11 (D pattern) "is added. When the tag information “00 (A pattern)” is added, the laser driving unit 220 sets the current value of the drive signal S5 as the fourth current value as shown in FIG. When tag information “(B pattern)” is added, the current value of the drive signal S5 is set as the third current value. When the tag information “10 (C pattern)” is added, the laser driving unit 220 sets the current value of the drive signal S5 as the second current value as shown in FIG. When Tag information “(D pattern)” is added, the current value of the drive signal S5 is set as the first current value. Thus, if the current value that determines the amount of laser light is finely controlled according to the film thickness of the charge transport layer 400D, the thin line can be reproduced more stably.

  In the second embodiment described above, when Tag information is added to a pixel, the waveform of the drive current is overshooted for the pixel to which Tag information is added as shown in FIG. Also good.

  In the second embodiment described above, pixels in the background portion around the thin line may be detected, and tag information may be added to the detected pixels. Then, for a pixel to which Tag information is added (a pixel that is not originally exposed), the current value of the drive signal of the pixel portion is controlled as shown in FIG. 20 so that weak exposure is performed. You may make it do.

  In the screen unit 111E, the reproducibility of the thin line may be optimized by switching the screen threshold for the pixels to which the Tag information is added.

  In the second embodiment described above, the thickness of the charge transport layer 400D is not determined, tag information is added to the pixels forming the fine line, and tag information is not added to the pixels not forming the thin line. Good.

  In the second embodiment described above, the fine line extraction unit 111B may add Tag information to the pixels constituting the fine line without referring to the film thickness information. Then, the film thickness information is supplied to the laser driving unit 220, and when the laser driving unit 220 determines that the film thickness indicated by the film thickness information is equal to or greater than the predetermined film thickness, the pixel information of the pixel to which the Tag information is added. The current value of the drive signal S5 for forming the electrostatic latent image is set as the second current value, and the current value of the drive signal S5 for forming the electrostatic latent image of the pixel to which no tag information is added is the first current. A value may be used.

1 is a block diagram of a main part of an image forming apparatus according to a first embodiment of the present invention. 2 is a block diagram illustrating configurations of an image processing unit 111 and a ROS unit 200 according to the embodiment. FIG. 2 is a diagram illustrating a cross section of a photoreceptor 400. FIG. It is the figure which illustrated the pixel which comprises the slanting thin line with respect to the main scanning direction. It is the figure which illustrated the pixel which comprises the thin line along the main scanning direction. It is the figure which illustrated the pixel which comprises the thin line along a subscanning direction. It is the figure which illustrated the thin line along the main scanning direction, and the waveform of drive signal S5. It is the figure which illustrated the waveform of thin line drive signal S5 along a subscanning direction. It is the figure which illustrated the slanting thin line with respect to the main scanning direction, and the waveform of drive signal S5. It is the figure which illustrated the electrostatic latent image of the fine line along the main scanning direction. It is the figure which illustrated the electrostatic latent image of the fine line along the subscanning direction. It is the figure which illustrated the electrostatic latent image of the slanting thin line with respect to the main scanning direction. It is the figure which illustrated the electrostatic latent image of the diagonal fine line at the time of not correcting a drive signal. It is the block diagram which showed the structure of the image process part 111 and ROS part 200 concerning 2nd Embodiment of this invention. It is the figure which illustrated the waveform of drive signal S5. It is the figure which illustrated the electrostatic latent image of the corrected slender fine line. It is the figure which illustrated the electrostatic latent image of the corrected slender fine line. It is the figure which showed the modification of the waveform of drive signal S5. It is the figure which showed the modification of the waveform of drive signal S5. It is the figure which showed the modification of the waveform of drive signal S5.

Explanation of symbols

102 ... CPU, 103 ... ROM, 104 ... RAM, 105 ... storage unit, 106 ... input unit, 107 ... display unit, 108 ... image input unit, 109 ... Image forming unit 110 ... Communication unit 111 ... Image processing unit 111A ... Interface unit 111B ... Thin line extraction unit 111C ... Digital filter unit 111D ... TRC unit 111E: Screen unit, 111F ... ROS control unit, 200 ... ROS unit, 210 ... Laser control unit, 220 ... Laser drive unit, 230 ... Light source unit, 300 ... Monitor , 310... Synchronous sensor unit, 400... Photoreceptor, 500.

Claims (3)

An image carrier provided with a photosensitive layer having photoconductivity;
Input means for inputting image data representing an image;
Analyzes the image image data represents input to the input means, a first pixel other than white pixels not constitute a thin line during the image, the white constituting the sub-scanning direction of the thin line during the image Specifying means for specifying a second pixel other than the pixel;
Means for exposing the image carrier in accordance with an image represented by image data input to the input means, and forming an electrostatic latent image corresponding to the image on the image carrier, wherein the specifying means For the pixel specified as the first pixel, an area corresponding to the first pixel is exposed with a first exposure amount to form an electrostatic latent image corresponding to the first pixel, and the specifying unit performs the second operation. For a pixel specified as a pixel, an area corresponding to the second pixel is exposed with a second exposure amount larger than the first exposure amount, and the region exposed with the second exposure amount is exposed in the main scanning direction. An area corresponding to one pixel adjacent to one another and an area adjacent to one pixel in the direction opposite to the main scanning direction with respect to the area exposed with the second exposure amount are exposed with an exposure amount smaller than the second exposure amount. And an exposure unit that forms an electrostatic latent image. An image carrier provided with a photosensitive layer having photoconductivity;
Input means for inputting image data representing an image;
Analyzing the image represented by the image data input to the input means, the first pixel other than the white pixel that does not constitute a thin line having an angle with respect to the main scanning direction in the image, and the main pixel in the image A specifying means for specifying a second pixel other than a white pixel constituting a thin line having an angle with respect to the scanning direction;
Means for exposing the image carrier in accordance with an image represented by the image data input to the input means to form an electrostatic latent image corresponding to the image on the image carrier, wherein the specifying means For the pixel specified as the first pixel, the image carrier is exposed so that an electrostatic latent image of the first region is formed at a position corresponding to the first pixel, and the specifying means For the pixel specified as the second pixel, the image carrier is exposed so that an electrostatic latent image of a second region wider than the first region is formed at a position corresponding to the second pixel. And an exposure unit that exposes the image carrier so that an electrostatic latent image of the first region and a region narrower than the second region is formed between the adjacent second pixels. An image forming apparatus. Image forming means for developing the electrostatic latent image to form an image on a recording sheet;
Counting means for counting the number of recording sheets on which images are formed by the image forming means,
The specifying means does not specify the first pixel and the second pixel when the number counted by the counting means is less than a predetermined number, and the number counted by the counting means is a predetermined number. The image forming apparatus according to claim 2, wherein if the number is greater than or equal to the number, the first pixel and the second pixel are identified.

Images