JP5222028B2 - Image processing apparatus, image forming apparatus, and image processing method - Google Patents

Description

The present invention relates to a method for correcting image data .

  2. Description of the Related Art Conventionally, image forming apparatuses that perform image formation by irradiating a photosensitive drum with laser light have been used. When such a laser optical system is used, the writing position of the scanning line exposed on the photosensitive drum may be shifted, the magnification may be distorted, or the latent image may be caused by assembly accuracy such as mechanical accuracy or assembly error during assembly. May be tilted, curved, or distorted. Of these methods, correction of the writing position and magnification has conventionally been performed by detecting an error and electrically correcting it. However, since such electrical correction is difficult for the inclination and distortion of the scanning line, conventionally, correction using high-quality optical components is performed so as to prevent such inclination and distortion. For this reason, an apparatus having an expensive configuration is required, and further fine fine adjustment is required at the time of assembly, leading to an increase in man-hours, resulting in an increase in production cost.

  With respect to the above problem, Patent Document 1 detects registration at a plurality of positions in at least three locations in the main scanning direction, and corrects distortions such as inclination and curvature in the main scanning direction calculated from the detected registration. As described above, a method for changing image data has been proposed. Here, also for the correction of one pixel or less in the sub-scanning direction, the writing position is similarly detected from the registration detection result, and the image data is changed so as to correct the detected writing position in the sub-scanning direction. By forming an image of the changed image data in this way, it is possible to correct the position of the scanning line, such as tilt and distortion, without using expensive optical components or through a precise adjustment process, and it is inexpensive. A high-quality image forming apparatus can be provided.

JP 2004-170755 A (page 13, FIG. 1)

  However, in the case of the configuration shown in Patent Document 1, it is necessary to provide at least three registration detection units in at least three locations in the main scanning direction, and there is a problem that the cost of the apparatus itself is greatly increased.

  Further, in Patent Document 1, the inclination / distortion of the scanning line is derived from the detection result of the registration pattern and correction is performed on the image data. However, depending on the shape of the inclination and distortion of the scanning line, correction in the main scanning direction is performed. In some cases, the position cannot be corrected optimally due to the density.

The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to realize high-quality image formation by reducing the curvature of a scanning line by correcting image data .

In order to achieve the above object, an image processing apparatus according to claim 1 comprises:
A photosensitive member for forming a latent image; a light source for emitting a light beam for forming a latent image on the photosensitive member; and the light beam so that the light beam moves on the photosensitive member in a main scanning direction. An image processing apparatus for generating image data for an image forming apparatus having deflection means for deflecting a beam,
Changing means for changing a scan line of image data of a target pixel in accordance with a curve in a sub-scan direction of a scan line drawn in the main scan direction by the light beam on the photoconductor;
Correction means for correcting image data of pixels that are adjacent to the pixels of the image data in which the scan line has been changed in the sub-scanning direction and that indicate pixels that are white to image data that indicates dots having a size of less than one pixel;
Using a pulse width table, and a pulse width modulation means for converting the image data corrected by the image data other than the corrected image data by correcting means and the correction means to the pulse width data for controlling the light source Have
The pulse width table is a table in which image data and pulse width data are associated with each other,
Said pulse width modulating means is characterized by using said different pulse width table by the corrected image data and image data other than the image data corrected by the correction means by said correcting means.

According to the present invention, it is possible to reduce the curve of the scanning line and realize high-quality image formation by correcting the image data .

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

(First embodiment)
<Device configuration>
As an example of an image forming apparatus to which the present invention is applicable, two types of copying machines 100 and 200 shown in FIGS. 1 and 2 will be described. 1 and 2 are diagrams illustrating the internal configuration of the copying machines 100 and 200 according to the first embodiment. Note that the image forming apparatus according to the present invention is not limited to such a copying machine, and the present invention can also be applied to a printer, a fax machine, or a multifunction machine having both functions.

  In the copying machine 100 shown in FIG. 1, in the reader unit 11, a document G placed on a document table glass 13 is irradiated by a light source, and the reflected light forms an image on a CCD sensor through an optical system. The CCD sensor generates red, green, and blue component signals for each line sensor by a group of red, green, and blue CCD line sensors arranged in three rows. These reading optical system units scan the document in the direction of the arrow to convert the document into an electric signal data string for each line. The image signal obtained by the CCD sensor is subjected to image processing by a reader image processing unit (not shown) and then sent to the printer unit 12.

  In the printer unit 12, the photosensitive drum 4 as an image carrier for carrying an electrostatic latent image corresponding to an image on the surface rotates at a predetermined angular velocity. Then, the surface of the photosensitive drum 4 is uniformly charged by a charger 8 as a charging means. Next, an electrostatic latent image according to the image data is formed on the photosensitive drum 4 by exposing and scanning the laser beam L with an exposure device 40 as an exposure unit that is ON / OFF controlled according to the image data from the reader unit 11. It is formed. The developing device 3 as a developing unit forms a developer image by causing toner as a developer to fly to the electrostatic latent image formed on the surface of the photosensitive drum 4. The visualized toner image is transferred onto an intermediate transfer member 5 as transfer means that is rotationally driven while being pressed against the photosensitive drum 4 with a predetermined pressing force. Thereafter, the toner image is transferred to the recording material 6 fed from the paper feeding unit, the toner image on the recording material 6 after the transfer is fixed in the fixing device 7, and then the recording material 6 is discharged out of the apparatus. .

  A copying machine 200 shown in FIG. 2 is a tandem type image forming apparatus, and unlike the copying machine 100 shown in FIG. 1, the process cartridges 20Y, 20M, 20C, and 20K corresponding to the respective colors are arranged. Since the configuration is the same as that of the copying machine 100 shown in FIG. 1 except that a plurality of process cartridges are provided, the same components are denoted by the same reference numerals and description thereof is omitted.

  The chargers 8Y, 8M, 8C, and 8K included in the process cartridges 20Y to 20K are roller chargers. By applying a bias, the surfaces of the photosensitive drums 4Y, 4M, 4C, and 4K are uniformly negatively charged. Charge. The image data is converted into laser light through a laser driver and a laser light source included in an exposure device 40 as exposure means, and the laser light is reflected by a polygon mirror and uniformly charged to each of the photosensitive drums 4Y to 4K. Irradiated on top. The photosensitive drums 4Y to 4K on which the latent images are formed by scanning with the laser light rotate in the direction of the arrow shown in the drawing.

  Each of the process cartridges 20Y to 20K is provided with a yellow toner developer 3Y, a magenta toner developer 3M, a cyan toner developer 3C, and a black toner developer 3K.

  Here, taking the process cartridge 20Y as an example, the image forming process will be specifically described. The surface of the photosensitive drum 4Y of the process cartridge 20Y is uniformly charged by the charger 8Y (for example, −500 V in this embodiment). Next, exposure scanning is performed by the exposure device 40Y that is ON / OFF controlled according to the image data of the first color, and the electrostatic latent image of the first color (about −150 V in the present embodiment) is exposed. It is formed on the drum 4Y. The electrostatic latent image of the first color is developed and visualized by a yellow toner developing device 3Y containing yellow toner (-polarity) of the first color. This visualized first toner image is pressed against the photosensitive drum 4Y and is intermediately transferred at the nip portion with the intermediate transfer body 5 that is rotationally driven at a speed approximately equal to the peripheral speed of the photosensitive drum 4Y. Primary transfer is performed on the body 5. The toner remaining on the photosensitive drum 4Y without being transferred to the intermediate transfer body 5 at the time of primary transfer is scraped off by a cleaning blade 9Y pressed against the photosensitive drum 4Y and collected in a waste toner container (not shown). .

  The same process is performed on the other process cartridges 20M, 20C, and 20K. Toner images of different colors for each process cartridge are sequentially transferred and stacked on the intermediate transfer member 5, and then supplied from the paper supply unit. Secondary transfer is performed collectively on the recording material 6 that has been made paper. After the transfer, the recording material 6 undergoes a fixing process by a fixing device 7 and is discharged outside the apparatus to form a full color print.

FIG. 3 is a diagram illustrating the internal configuration of the image processing unit included in the reader unit 11. The luminance signal of the original image read by the CCD 301 is input to the A / D conversion unit 302 and converted into a digital signal. The digital luminance signal is sent to the shading unit 303, and shading correction is performed for unevenness in the amount of light due to variations in the sensitivity of each CCD element. By correcting the shading, the measurement reproducibility of the CCD is improved. The luminance signal corrected by the shading unit 303 is further subjected to LOG conversion by the LOG conversion unit 304. Subsequently, the LOG-converted signal is sent to the γLUT 305 and converted by the γ-LUT 305 created so that the ideal density characteristic of the printer device matches the output image density characteristic processed according to the γ characteristic. Is done. The converted image signal is transmitted to the image memory 310 of the printer unit 12 and stored therein.

The exposure apparatus 40 according to this embodiment will be described with reference to FIGS. The exposure apparatus 40 includes a laser drive unit 45, a rotary polygon mirror motor 41, a rotary polygon mirror 42, an optical system f-θ lens 43, and a reflection mirror 44. The laser L emitted from the laser driving unit 45 is reflected by the reflecting surface of the rotating polygon mirror 42 installed on the rotating polygon mirror motor 41, and the optical system f-θ lens 43 has a constant linear velocity on the exposure surface. , And further reflected by the reflection mirror 44 and reaches the photosensitive drum 4. At this time, the locus of the reflected laser L is desirably drawn as an ideal straight line as shown in FIG.

  However, each component of the exposure apparatus 40 mounted without any adjustment in particular has an inherent inclination or distortion, and when the exposure operation is performed as it is, the scanning line is as shown in FIG. Do not draw an ideal straight line. That is, the exposed scanning line scans on the photosensitive drum 4 with the influence of the inherent inclination and distortion as shown in FIG. Conventionally, in order to scan the exposure scanning line on the photosensitive drum 4 without causing such inclination and distortion, expensive optical components have been used when assembling the exposure apparatus 40 or precise fine adjustment has been performed on the apparatus itself. . In this embodiment, without using such expensive parts or performing precise fine adjustment, it is possible to cancel the inclination and distortion of the inherent scanning line of the laser optical system, and to obtain inexpensive and good image quality. An image processing unit 46. The image processing unit 46 includes a profile storage unit 47 that stores profile data representing distortion and tilt of the exposure apparatus, and an image correction unit 48 as an image forming unit that deforms input image data based on the stored profile data. Including. Furthermore, a smoothing processing unit 49 is included as a smoothing processing unit for controlling the laser driving unit 45 to smooth the stepped portion included in the image data after the deformation.

<Correction control>
Data correction processing for compensating for image deformation due to design errors in the shape or position of the optical system of an image forming apparatus such as a copying machine will be described below. This data correction process can be divided into the following five.
(1) Measurement and storage of profile of optical system including exposure apparatus (2) Transfer of profile data to image forming apparatus (3) Generation of first correction data from profile data (4) First correction at the time of image formation Processing of image data using data (5) Smoothing processing

Therefore, the above five processes will be described separately.
(1) Scanning line profile measurement As the first stage of data correction processing to compensate for image deformation caused by the optical system, a profile such as tilt and distortion inherent to the laser optical system is measured during the manufacture of the laser optical system. To do.
At this point, as shown in FIG. 7, the position in the sub-scanning direction at each division point when the scanning line is divided into n in the main scanning direction (n is at least 3 or more, here n = 10 as an example) is defined as a profile point. To do.

  The measured profile data is stored in the laser optical system unit by holding a storage medium such as EPROM. Alternatively, as a simple configuration, data is encrypted and stored in a unit such as a barcode and attached to the unit body of the laser optical system.

(2) Transfer of Profile Data to Image Forming Apparatus The stored profile data is read from the EPROM of the laser optical system unit to the image forming apparatus main body at the time of assembly. Even if the customer replaces the laser optical system unit after shipment, the profile data corresponding to the replaced laser optical system unit is stored in the profile storage unit 47 from the EPROM held in the unit after the unit replacement. To do.

  Alternatively, a configuration may be adopted in which an operator reads barcode data encrypted by using an encryption reading device such as a barcode reader and reflects it on the image forming apparatus main body at the time of assembly. In this case, the service person reads the barcode attached to the unit to be replaced with a barcode reader or substitutes a numerical value, and similarly stores the profile data corresponding to the laser optical system unit in the profile storage unit 47. .

(3) Calculation of First Correction Data A process for correcting the tilt and distortion of the laser optical system during image formation will be described with reference to FIG. FIG. 6 is a flowchart for explaining the flow of the correction process, and each process is realized by a processor (not shown) provided in the image forming apparatus executing a predetermined program.

  In step S64, based on the profile data of n scanning lines, first correction data is calculated from the amount of deviation from each point and the ideal coordinates.

  Here, the calculation flow of the first correction data will be described with reference to FIGS. In step S81 of FIG. 8A, first, as shown in FIG. 8B, the scanning lines divided by n pieces of n profile point data are approximated over the entire main scanning area. Here, in the present embodiment, linear approximation between two adjacent points is used. Next, in step S82, the main scanning write position is set as a reference point among the approximate points in the entire main scanning area obtained in step S81.

  In step S83, an approximate point is checked from the reference point in the main scanning direction. If the difference ΔV in the sub-scanning direction from the reference point exceeds one pixel, the main scanning position of that point (point A) is offset in step S84. Points. In step S86, point A is reset as a new reference point.

  By performing the above steps S83 to S86 over the entire main scanning region, the coordinates (X points) of the position (offset point) for performing offset in units of one pixel in the sub-scanning direction for correcting the inclination and distortion of the scanning line. Is obtained (FIG. 8C). The coordinate information of the X offset points thus obtained and the information on the offset amount from the reference line at each offset point are stored in the profile storage unit 47 as the first correction data.

(4) the image correcting unit 48 according to the first correction data in machining step S65 of the image data using the first correction data at the time of image formation, for machining of the input image data (first correction).

  Here, the processing of image data using the first correction data will be described with reference to FIGS. 9A and 9B. FIG. 9A is a line buffer and is constituted by a RAM. In this embodiment, when the main scanning direction width is 297 mm and 600 dpi, correction data for about 7000 dots is written in the RAM. In the present embodiment, the correction data is composed of, for example, 8 bits, and forms an offset line buffer 91 for the first correction with a signed binary number.

  FIG. 9B is a diagram showing an offset line buffer 91 for the first correction.

In FIG. 9B, 92 is input image data, and 91 is an offset line buffer for processing the image data here. First, the coordinate information and offset amount information of the first correction data calculated in step S84 are read into the offset line buffer 91 for the first correction. That is, an offset amount Y _n is set for the coordinate X _{n of the} offset point, and is replaced by image data at a position shifted in the sub-scanning direction from the original position by the number of lines Y _n (from the shifted position on the memory). Read out). As a result, corrected bitmap data 93 is created. In the example of FIG. 9B, the offset point X ₁ is not offset because it is defined as the offset amount Y ₀ = 0. However, since the offset point X ₂ is defined by the offset amount Y ₂ = −1, the pixel is read from the previous address in the sub-scanning direction by one pixel on the memory. By performing this processing for each offset point X _n , the bitmap data 92 indicating the horizontal straight line in FIG. 9B is rearranged into a straight line rising to the right as shown in the bitmap data 93.

(5) Smoothing Process In step S66 of FIG. 6, a smoothing process (second correction) is performed on the corrected bitmap data rearranged by the first correction in step S65. The flow of this processing will be described with reference to FIG. 10A, B and Figure 15 to D.

  FIG. 10A is a diagram showing a line buffer, which is constituted by a RAM. In this embodiment, when the main scanning direction width is 297 mm and 600 dpi, correction data for about 7000 dots is written in the RAM. In this embodiment, the smoothed data is composed of, for example, 8 bits, and constitutes a smoothing line buffer 101.

FIG. 10B shows a flowchart of the smoothing process executed by the smoothing processor 49. In step S101 of FIG. 10B, first, the bitmap data Img (x) of the main scanning coordinate x at the offset point _Xn of the first correction data calculated in step S84 and the bitmap data Img of the previous pixel in the main scanning direction are calculated. Compare (x-1). If Img (x) <Img (x−1) (for example, the lower step in FIG. 15A), the region X _{n +} between the next offset point X _{n + 1} and the offset point X _n in step S102. _{1 to Xn} are defined as a smoothing region S (1). In step S103, Img (x)> Img (x-1) if it was (e.g. upper step of Fig. 15A), the area X of the offset point X _n-1 and the offset point X _n before in step S104 _{n-1 to Xn} are calculated and set as the smoothed region S (-1).

  Next, in step S105, the white image area (Img (x) = 0) adjacent to the offset point and the smoothed area S obtained in steps S102 and 104 are supplemented with dots less than one pixel. Smoothing processing is performed (for example, FIG. 15B).

  Here, in this embodiment, pixels are formed by using 16-division PWM per pixel. That is, smoothing processing is performed using 16 levels of exposure corresponding to the pulse width.

  Normally, at the time of image formation, the input image signal value is configured to modulate the pulse width according to a preset pulse width table as shown in FIG. The pulse width table as shown in FIG. 11 actually depends on the input image signal and the shape of the electrostatic latent image on the photosensitive drum formed when the photosensitive drum is exposed accordingly.

  Here, using FIG. 12, the relationship between the input image signal and the electrostatic latent image formed on the photosensitive drum by the exposure amount varied by pulse width modulation is schematically represented. When a pulse width modulation table as shown in FIG. 11 is used and three types of image signals as shown in FIG. 12 (a) are input, an image is shown for each pixel as shown in (b). Exposure is performed with a pulse width corresponding to the signal. Here, FIG. 12B schematically shows the lighting time of the pulse by the length in one pixel, and does not show the arrangement of lighting in one pixel. In this case, the electrostatic latent image formed on the photosensitive drum is as shown in FIG. 12C, and as a result, the image forming apparatus outputs an image as shown in FIG. 12D.

  In other words, when there is data in a pixel adjacent to the own pixel and when there is no data in the adjacent pixel and the own pixel is an isolated dot, the output image is different even if exposure is performed with the same pulse width. Originally, it is desirable to perform exposure with an appropriate exposure amount according to the adjacent pixel and the own pixel by changing the pulse width for each pixel according to the arrangement of the input image signal. However, since the configuration is complicated and the cost is high, a pulse width table that can be applied to both the case where there is an adjacent pixel and the case where it is an isolated pixel is usually adopted. Alternatively, the pixel arrangement / growth pattern of the pseudo halftone process is configured so as to place importance on either the adjacent pixel or the isolated pixel so that there is no problem with the output image.

  Here, the section of the length | S | obtained in steps S102 and 104 is subjected to smoothing processing using pulse width modulation, but one pixel formed for smoothing processing. Less than dots are always guaranteed to have another latent image in the adjacent area. Therefore, in this embodiment, in order to form dots of less than one pixel formed by the smoothing process, a pulse width table for smoothing process different from the pulse width table for normal image formation is provided. FIG. 13 shows a pulse width table for normal image formation and a pulse width table used for the second correcting means of this embodiment.

  FIG. 14 shows a block diagram of the present embodiment. The overall processing flow of this embodiment will be described with reference to FIG.

  After the input image signal 1401 is subjected to pseudo halftone processing by the halftone processing unit 1402, the first correction circuit 1403 performs the first correction according to the offset amount calculated by the offset amount calculation circuit 1405 based on the scanning line profile 1404. The correction process is performed. Thereafter, the second correction circuit 1406 performs a smoothing process, which is a second correction process, on the section of the length | S | obtained in steps S102 and S104. At this time, the second correction pulse width table 1407 as shown in FIG. 13 is used and output as an output image signal 1409. It should be noted that correction processing is performed on a region other than the section | S | by using a pulse width table 1408 for normal image formation.

  In this embodiment, since the pulse width table as shown in FIG. 13 optimized for the smoothing process, which is the second correction means, is used in advance, the area exposed at each pulse width is subjected to the smoothing process. There is an advantage that it is not necessary to optimize in accordance with the latent image formed again.

  Here, when the sign of the smoothing section S is positive, a dot of less than one pixel is formed in the forward order of the pulse width table, and when the sign of the smoothing section S is negative, the dot of less than one pixel is formed in the reverse order of the pulse width table. .

  In this embodiment, the smoothing line buffer and the offset line buffer are described in different configurations for ease of explanation, but actually, the same line buffer is used for each purpose. It is possible.

  When the smoothing process is completed, the pulse width data is transmitted to the printer in step S67 of FIG.

<Overall flow>
FIG. 15 shows an image of the image correction so far. FIG. 15A is an image diagram obtained by performing the first correction. When the second correction is performed on the image of FIG. 15A, the image shown in FIG. 15B is obtained. When the corrected image data of FIG. 15B is laser-exposed, a latent image is formed with an image as shown in FIG. 15C, and when this latent image is formed, an image as shown in FIG. 15D is obtained. In addition, the ▼ mark in the figure is the offset point where the first correction is performed.

<Effects of First Embodiment>
As described above, when recording the image data offset according to the scanning line profile unique to the laser optical system, the second correction for smoothing the vicinity of the offset region is used for the second correction. Is performed using a pulse width table optimized for the above. It is not necessary to optimize the area exposed at each pulse width according to the latent image formed again during the smoothing process. As a result, it is possible to provide a good image with corrected main scanning tilt and main scanning distortion at low cost without using expensive parts or performing special fine adjustment during assembly.

(Second Embodiment)
In the first embodiment, smoothing processing is performed using a pulse width table optimized for the second correction unit in advance, as a second correction unit, in addition to the pulse width table optimized for normal image formation. The configuration is to be performed. However, in an electrophotographic image forming apparatus, development conditions and transfer conditions differ depending on image forming conditions such as temperature and humidity, so even if a latent image is formed under the same conditions, dots are always reproduced in the same way. Not necessarily. In particular, when dots of less than one pixel are formed, dot reproduction varies depending on the above conditions, and as a result, there is a concern that the smoothing process performed by the second correction unit is not optimally performed. Therefore, in this embodiment, even if such a change in image forming conditions occurs, an effect of smoothing processing using minute dots is obtained stably. Since other configurations and operations are the same as those in the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  In the present embodiment, a plurality of pulse width tables are stored in advance as shown in FIG. 16 according to the absolute water content calculated based on temperature and humidity data obtained from an environmental sensor (not shown). In FIG. 16, as an example, three types of pulse width tables are held according to the absolute water content information.

  Next, FIG. 17 shows a correction flowchart in the present embodiment. In the first embodiment, the same parts as those of the second correction process described with reference to FIG. 10B are denoted by the same reference numerals, and description thereof is omitted.

If it is confirmed in step S102 or S104 that the dot needs to be smoothed, in step 175, the absolute moisture in the image forming apparatus based on the temperature / humidity data obtained from the environmental sensor provided in the image forming apparatus. Calculate the amount. Then, one is selected from a plurality of pulse width tables as shown in FIG. 16 according to the absolute water content. In step S105, the smoothing process, which is the second correction process, is performed on the smoothed section | S | obtained in steps 102 and 104 in accordance with the selected pulse width table.
In the present embodiment, in addition to the effects of the first embodiment, even when the image forming apparatus fluctuates due to environmental conditions, the second correction effect can be optimized according to the fluctuations. Can be provided.

(Third embodiment)
In the second embodiment, a plurality of pulse width tables are held in advance, and the optimum pulse width table used for the second correction unit is selected according to the environmental conditions obtained from the environmental sensor. In this case, in order to optimize the second correction unit with high accuracy according to the environmental conditions, it is necessary to hold a large number of pulse width tables in advance for each environmental condition, and there is a concern that the configuration becomes complicated. Is done. In the present embodiment, one basic pulse width table is held, a correction coefficient is calculated according to the environmental conditions, and a correction coefficient is calculated in the basic pulse width table, thereby generating a pulse width table that is optimal for the environmental conditions. Since other configurations and operations are the same as those in the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 18 shows a flowchart of correction in the present embodiment. Portions similar to those in FIG. 10B in the first embodiment are assigned the same reference numerals and description thereof is omitted.

  If it is confirmed in step S102 or S104 that the dot needs to be smoothed, the absolute moisture content inside the image forming apparatus is calculated based on the temperature and humidity data obtained from the environmental sensor in step 185, and the pulse width table is calculated. A correction coefficient to be corrected is calculated. In step 186, the correction pulse width table is generated by calculating the calculated correction coefficient in the pulse width table. Then, the smoothing process as the second correction process is performed on the smoothed section | S | obtained in steps 102 and 104 using the generated pulse width table.

  In the present embodiment, in addition to the effects of the second embodiment, there is no need to hold a plurality of pulse width tables, and it is possible to simplify the configuration and provide a good image.

(Other embodiments)
Although the embodiments of the present invention have been described in detail above, the present invention may be applied to a system constituted by a plurality of devices or may be applied to an apparatus constituted by one device.

  In the present invention, a control program for realizing the functions of the above-described embodiments is supplied directly or remotely to a system or apparatus, and the processor of the system or apparatus reads and executes the supplied program code. Is also achieved. Accordingly, the program code itself installed in the computer in order to realize the functional processing of the present invention by the computer is also included in the technical scope of the present invention.

  In that case, as long as it has a function of a control program, the form of the program is not limited, such as an object code, a program executed by an interpreter, script data supplied to the OS, and the like.

  Examples of the recording medium for supplying the control program include a floppy (registered trademark) disk, a hard disk, an optical disk, and a magneto-optical disk. Further, there are MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD-R) and the like.

  In addition, there is a usage method in which a browser of a client PC is used to connect to an Internet site and a program according to the present invention itself or a file including an automatic installation function is downloaded to a recording medium such as a hard disk. It can also be realized by dividing the program code constituting the program according to the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program for realizing the functional processing of the present invention on a computer is also included in the scope of the present invention. Further, the program according to the present invention may be encrypted and stored in a storage medium such as a CD-ROM and distributed to users. This is realized by having a user who has cleared a predetermined condition download key information to be decrypted from a homepage via the Internet, execute the encrypted program by using the key information, and install it on a computer. It is also possible.

  Further, the functions of the above-described embodiments can be realized by an OS or the like running on the computer based on an instruction of the program and performing part or all of the actual processing.

  Furthermore, when the program according to the present invention is written in the memory provided in the function expansion unit of the PC and the CPU or the like provided in the function expansion unit performs part or all of the actual processing based on the program, Included in the category.

1 is a schematic cross-sectional view of an image forming apparatus as a first embodiment according to the present invention. 1 is a schematic cross-sectional view of an image forming apparatus as a first embodiment according to the present invention. It is a flowchart regarding the image signal processing unit in the first embodiment. It is a schematic diagram of the laser optical system of a prior art. It is a schematic diagram of the laser optical system of 1st Embodiment. It is a flowchart of a 1st embodiment. It is a schematic diagram which shows a scanning line profile. It is a flowchart which calculates 1st correction data. It is a figure explaining the approximation process of a scanning line profile. It is a figure explaining the process which derives an offset point. It is a figure shown about the structure of the buffer memory used for 1st correction | amendment. It is the schematic which shows 1st correction | amendment. It is a figure shown about the structure of the buffer memory used for 1st correction | amendment. It is a flowchart which shows the flow of 2nd correction | amendment. It is a figure which shows the pulse width table used by normal image formation. It is a schematic diagram which shows the relationship between the arrangement | positioning of an input image signal, and the exposed electrostatic latent image. It is a figure which shows the pulse width table used in 1st Embodiment. 1 is a block diagram of an image forming apparatus as a first embodiment according to the present invention. It is a figure which shows the example of an image of correction | amendment of 1st Embodiment. It is a figure which shows the example of an image of correction | amendment of 1st Embodiment. It is a figure which shows the example of an image of correction | amendment of 1st Embodiment. It is a figure which shows the example of an image of correction | amendment of 1st Embodiment. It is a figure which shows the pulse width table used in 2nd Embodiment. It is a flowchart which shows the 2nd correction | amendment of 2nd Embodiment. It is a flowchart which shows the 2nd correction | amendment of 3rd Embodiment.

Explanation of symbols

3 Developing device 4 Photosensitive drum 5 Intermediate transfer member 6 Recording material 7 Fixing device 8 Charger 9 Cleaner 20 Process cartridge 41 Rotating polygon mirror motor 42 Rotating polygon mirror 43 f-θ lens 44 Reflecting mirror 91 Offset line buffer 101 For smoothing Line buffer

Claims (7)

A photosensitive member for forming a latent image; a light source for emitting a light beam for forming a latent image on the photosensitive member; and the light beam so that the light beam moves on the photosensitive member in a main scanning direction. An image processing apparatus for generating image data for an image forming apparatus having deflection means for deflecting a beam,
Changing means for changing a scan line of image data of a target pixel in accordance with a curve in a sub-scan direction of a scan line drawn in the main scan direction by the light beam on the photoconductor;
Correction means for correcting image data of pixels that are adjacent to the pixels of the image data in which the scan line has been changed in the sub-scanning direction and that indicate pixels that are white to image data that indicates dots having a size of less than one pixel;
Using a pulse width table, the image data corrected by the image data and the correction means other than the image data corrected by said correction means, and pulse width modulation means for converting the pulse width data for controlling the light source Have
The pulse width table is a table in which image data and pulse width data are associated with each other,
It said pulse width modulation means, the image processing apparatus characterized by the use of different pulse width table by the corrected image data by correcting image data other than image data and the correction means by said correcting means.   The pulse width modulation means includes
    For image data other than the image data corrected by the correcting means, there are a case where a pixel adjacent to the target pixel exists, a case where a pixel adjacent to the target pixel does not exist, and a case where the target pixel is an isolated pixel. Use the first pulse width table corresponding to any of
    For the image data corrected by the correction means, the second pulse width table corresponding to the case where a pixel adjacent to the target pixel exists is used.
The image processing apparatus according to claim 1.   The pulse width indicated by each pulse width data included in the second pulse width table is equal to or less than the pulse width indicated by the corresponding pulse width data included in the first pulse width table.
The image processing apparatus according to claim 2. Holding means for holding a plurality of pulse width tables respectively corresponding to different temperatures and humidity,
The pulse width modulation means includes
For the image data corrected by the correction unit, the pulse width data is selected using a pulse width table selected from the plurality of pulse width tables held by the holding unit according to environmental conditions in the image forming apparatus. the image processing apparatus according to any one of claims 1 to 3, characterized in that to convert to. The pulse width modulation means includes
For the image data corrected by the correcting means, the pulse width table is corrected by a correction coefficient calculated according to the environmental conditions in the image forming apparatus, and the pulse width table is corrected using the corrected pulse width table. the image processing apparatus according to any one of claims 1 to 3, characterized in that into data. A photoreceptor for forming a latent image;
A light source that emits a light beam for forming a latent image on the photoreceptor;
Deflecting means for deflecting the light beam so that the light beam moves in the main scanning direction on the photosensitive member;
Changing means for changing a scan line of image data of a target pixel in accordance with a curve in a sub-scan direction of a scan line drawn in the main scan direction by the light beam on the photoconductor;
Correction means for correcting image data of pixels that are adjacent to the pixels of the image data in which the scan line has been changed in the sub-scanning direction and that indicate pixels that are white to image data that indicates dots having a size of less than one pixel;
Using a pulse width table, and a pulse width modulation means for converting the image data corrected by the image data other than the corrected image data by correcting means and the correction means to the pulse width data for controlling the light source Have
The pulse width table is a table in which image data and pulse width data are associated with each other,
It said pulse width modulation means, the image forming apparatus characterized by the use of different pulse width table by the corrected image data by correcting image data other than image data and the correction means by said correcting means. A photosensitive member for forming a latent image; a light source for emitting a light beam for forming a latent image on the photosensitive member; and the light beam so that the light beam moves on the photosensitive member in a main scanning direction. An image processing method for generating image data for an image forming apparatus having deflection means for deflecting a beam,
A changing step of changing a scanning line of image data of a pixel of interest according to a curve in a sub-scanning direction of a scanning line drawn in the main scanning direction by the light beam on the photoconductor;
A correction step of correcting the image data of the pixel that is adjacent to the pixel of the image data in which the scanning line is changed in the sub-scanning direction and that indicates white and that has a size of less than one pixel. When,
Pulse width modulating means, using a pulse width table, converts the corrected image data in the correction step image data and the correction process other than the corrected image data in the pulse width data for controlling the light source A pulse width modulation process,
The pulse width table is a table in which image data and pulse width data are associated with each other,
The pulse width modulation process, an image processing method characterized by using different pulse width table by the corrected image data in the correction step and the image data other than the corrected image data in the correction step.

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