JP5329783B2 - Image forming apparatus, control method thereof, and control program - Google Patents

Description

  The present invention relates to an image forming apparatus, a control method thereof, and a control program.

  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 problems of the prior art, with respect to such tilt or warp of the optical science system of the scanning line is performed and accurate fine adjustment of the time correction or assembly by expensive optical components An object is to realize high-quality image formation without any problems.

In order to achieve the above object, an apparatus according to the present invention provides:
An image carrier that carries an electrostatic latent image according to image data on the surface;
Charging means for charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image by scanning the surface of the charged image carrier with light according to image data;
Developing means for developing the electrostatic latent image formed on the surface of the image carrier with a developer;
Transfer means for transferring the developer image formed on the surface of the image carrier to a recording material to form an image on the recording material;
An image forming apparatus having
The image data input to the exposure unit is 1 according to the pixel position in the main scanning direction of the scanning line so as to correct the inclination or distortion of the scanning line when the image carrier is scanned by the exposure unit. Image correction means for performing correction to offset the pixel position in the sub-scanning direction with an offset amount in pixel units;
Storage means for storing a plurality of exposure amount patterns for controlling the exposure amount of the exposure means during the smoothing process;
Smoothing processing means for performing smoothing in the main scanning direction on the image data corrected by the image correction means using the exposure amount pattern stored in the storage means;
Have
The smoothing processing means includes
From said plurality of exposure pattern stored in the storage unit, select the exposure pattern in accordance with the image forming condition, on the basis of the main scanning direction of density change at the pixel position where the offset amount is changed, the selection Control the direction in which the exposure dose pattern is used ,
With respect to the image data corrected by the image correction means, pixel positions where the offset amount has changed along the main scanning direction, and the intermediate points between two adjacent pixel positions are respectively determined, and a plurality of determined intermediate points Among these, smoothing is performed using the selected exposure amount pattern for each region between adjacent intermediate points .

In order to achieve the above object, the method according to the present invention comprises:
An image carrier that carries an electrostatic latent image according to image data on the surface;
Charging means for charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image by scanning the surface of the charged image carrier with light according to image data;
Developing means for developing the electrostatic latent image formed on the surface of the image carrier with a developer;
Transfer means for transferring the developer image formed on the surface of the image carrier to a recording material to form an image on the recording material;
An image forming apparatus control method comprising:
The image data input to the exposure unit is 1 according to the pixel position in the main scanning direction of the scanning line so as to correct the inclination or distortion of the scanning line when the image carrier is scanned by the exposure unit. An image correction step for performing correction to offset the pixel position in the sub-scanning direction by an offset amount in pixel units;
A smoothing process step of performing smoothing in the main scanning direction on the image data corrected in the image correction step using an exposure amount pattern stored in a storage unit included in the image forming apparatus;
Including
The storage means stores a plurality of exposure amount patterns for controlling the exposure amount of the exposure means during the smoothing process in the smoothing process step,
In the smoothing process,
From said plurality of exposure pattern stored in the storage unit, select the exposure pattern in accordance with the image forming condition, on the basis of the main scanning direction of density change at the pixel position where the offset amount is changed, the selection Control the direction in which the exposure dose pattern is used ,
With respect to the image data corrected in the image correction step, pixel positions at which the offset amount has changed along the main scanning direction, and the intermediate points between two adjacent pixel positions are respectively determined, and a plurality of determined intermediate points Among these, smoothing is performed using the selected exposure amount pattern for each region between adjacent intermediate points .

In order to achieve the above object, a program according to the present invention provides:
An image carrier that carries an electrostatic latent image according to image data on the surface;
Charging means for charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image by scanning the surface of the charged image carrier with light according to image data;
Developing means for developing the electrostatic latent image formed on the surface of the image carrier with a developer;
Transfer means for transferring the developer image formed on the surface of the image carrier to a recording material to form an image on the recording material;
An image forming apparatus control program comprising:
The image data input to the exposure unit is 1 according to the pixel position in the main scanning direction of the scanning line so as to correct the inclination or distortion of the scanning line when the image carrier is scanned by the exposure unit. An image correction step for performing correction to offset the pixel position in the sub-scanning direction by an offset amount in pixel units;
A smoothing process step of performing smoothing in the main scanning direction on the image data corrected in the image correction step using an exposure amount pattern stored in a storage unit included in the image forming apparatus;
Is executed by the processor of the image forming apparatus,
The storage means stores a plurality of exposure amount patterns for controlling the exposure amount of the exposure means during the smoothing process in the smoothing process step,
In the smoothing process,
From said plurality of exposure pattern stored in the storage unit, select the exposure pattern in accordance with the image forming condition, on the basis of the main scanning direction of density change at the pixel position where the offset amount is changed, the selection Control the direction in which the exposure dose pattern is used ,
With respect to the image data corrected in the image correction step, pixel positions at which the offset amount has changed along the main scanning direction, and the intermediate points between two adjacent pixel positions are respectively determined, and a plurality of determined intermediate points Among these, smoothing is performed using the selected exposure amount pattern for each region between adjacent intermediate points .

  According to the present invention, it is possible to realize high-quality image formation without performing correction by an expensive optical component or precise fine adjustment at the time of assembly with respect to inclination or distortion of the scanning line of the optical system. it can.

  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. Except for having a plurality of process cartridges, the configuration is the same as that of the copying machine 100 shown in FIG.

  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 developing device 3Y including 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 Process Therefore, the above five processes will be described separately below.

(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. For example, when straight line image data is input to the exposure apparatus, a curved toner image formed on the photosensitive drum is read, and the reverse calculation is performed from the curve. That is, curved image data (scanning line) that needs to be input to the exposure apparatus in order to form a completely straight toner image on the photosensitive drum is obtained.
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 profile data consists of a set and the profile point data formula or point data indicating a trajectory of the scanning line.

  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.

Based on the profile data of n number of scanning lines in step S6 4, it calculates a first correction data from the shift amount from each point and 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 process will be described with reference to FIGS. 10A, 10B and 12.

  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 101 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 94 and the coordinate x−1 immediately before in the main scanning direction. The bitmap data Img (x-1) is compared. If Img (x) <Img (x−1) (eg, the lower step in FIG. 12A), in step 102, the intermediate point X _fm between the next offset point X _{n + 1} and the offset point X _n and the offset An intermediate point _Xbm between the point _Xn and the previous offset point _Xn-1 is calculated. In step 103, the regions X _{fm to} X _bm sandwiched between the intermediate points are set as the smoothed region S (1). In step 104, if Img (x)> Img (x-1) (for example, the upper step in FIG. 12A), in step 105, the intermediate between the previous offset point _Xn-1 and offset point _Xn. calculating a point _{X bm,} an offset point _{X n} and the next intermediate point _{X fm} between the offset point _{X n + 1.} The region _X bm _{to X fm} sandwiched at their midpoint in step 106 and smoothed region S (-1). Next, in step 107, the region S obtained in steps 103 and 106 is smoothed using dots of less than one pixel (for example, FIG. 12B).

  Here, in this embodiment, since the pixel is formed using 16 division PWM per pixel, the smoothing process is performed using 16 levels corresponding to the pulse width. FIG. 11 shows the correspondence (exposure amount pattern) between the coordinates in the main scanning direction in the smoothing region S and the pulse width at that position. By using the exposure amount pattern table shown in FIG. 11, dots of less than one pixel are formed in the smoothing region S. Here, for the smoothing region S (1), the exposure amount pattern is arranged in the normal order (the pulse width is changed from large to small), and for the smoothing region S (-1), the exposure amount pattern is arranged in the reverse order (pulse width). Is changed from small to large), and smoothing processing is performed.

  The configuration of the smoothing line buffer 101 is the same as that of the offset line buffer 91. Therefore, in the present embodiment, the configuration is described as another configuration, but in practice, the same line buffer may be used. Is possible.

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

<Overall flow>
FIG. 12 shows an image of the image correction so far. FIG. 12A is an image diagram obtained by performing the first correction. When the second correction is performed on the image of FIG. 12A, the image shown in FIG. 12B is obtained. When the corrected image data in FIG. 12B is laser-exposed, a latent image is formed as an image as shown in FIG. 12C, and when this latent image is formed, an image as shown in FIG. 12D is obtained. In addition, the ▼ mark in the figure is the offset point where the first correction is performed.

<Effects of First Embodiment>
As seen above, the image data offset according to the scanning line profile such as the inherent tilt and distortion of the laser optical system measured in advance is sandwiched between the midpoints of the offset positions on both sides. The smoothing process is performed by replacing the region that is between the offset region and the offset position with a smoothing pattern. 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, the smoothing process is performed by adjusting the exposure amount. However, in an electrophotographic image forming apparatus, the exposure amount may be adjusted to the same exposure amount due to differences in image forming conditions such as environmental conditions such as temperature and humidity around the image forming unit and deterioration of the developer. Differences may appear in dot reproducibility. In particular, when dots of less than one pixel are formed, there is a great concern that dot reproduction varies due to environmental conditions including at least one of the temperature and humidity around the image forming unit or deterioration of the developer. Therefore, in the present embodiment, when smoothing processing is performed using such minute dots, control is performed so that the effect of smoothing processing can be stably obtained by considering the image forming conditions.

  This embodiment shows an application example of the smoothing process in step S66 in the flowchart of FIG. 6 described in the first embodiment. FIG. 13 shows a flowchart of the smoothing process in the present embodiment.

In step 131 of FIG. 13, 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 94 and the coordinate x−1 immediately before in the main scanning direction. The bitmap data Img (x-1) is compared. If Img (x) <Img (x−1), in step 132, the intermediate point _Xfm between the next offset point _{Xn + 1} and the offset point _Xn , the offset point _Xn, and the previous offset point _Xn. The intermediate point X _bm with ₋₁ is calculated, and the regions X _{fm to} X _bm sandwiched between them at step 133 are defined as the smoothed region S (1). In step 134, if Img (x)> Img (x-1), in step 135, an intermediate point _Xbm between the previous offset point _Xn-1 and offset point _Xn and an offset point _Xn And an intermediate point X _fm between the offset point X _{n + 1} and the next offset point X _{n + 1} are calculated, and regions X _{bm to} X _fm sandwiched between them are set as a smoothed region S (−1) in step 136. Next, in step 137, the regions S (1) and S (-1) obtained in steps 133 and 136 are smoothed using dots of less than one pixel.

  In the first embodiment, in step S104, a smoothing image is formed using dots of less than one pixel with respect to the smoothing region S. At that time, the exposure amount pattern shown in FIG. The dots are formed in the range of the smoothing region S and the smoothing process is performed.

In contrast, in the present embodiment, as shown in FIGS. 14A to 14D, a plurality of exposure amount patterns are held in advance. Then, based on the environmental conditions obtained from the environmental sensor in step S137 or the recording material transfer number obtained from the number counter of the process cartridge, a plurality of smoothing patterns as shown in FIGS. Select the best pattern from the list. Other configurations are the same as those in the first embodiment.
In the present embodiment, even if the scanning line profile is a laser optical system having inclination and distortion, it is possible to correct the inclination and distortion and form a good image as in the first embodiment. Even when the image forming apparatus changes due to environmental conditions, durability conditions, and the like, the effect of the smoothing process can be optimized according to the change, so that a good image can be provided.

(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 showing the smoothing pattern used by 2nd correction | amendment. 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 the schematic which shows the 2nd correction | amendment of 2nd Embodiment. It is a figure showing the some smoothing pattern used by the 2nd correction | amendment of 2nd 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 (5)

An image carrier that carries an electrostatic latent image according to image data on the surface;
Charging means for charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image by scanning the surface of the charged image carrier with light according to image data;
Developing means for developing the electrostatic latent image formed on the surface of the image carrier with a developer;
Transfer means for transferring the developer image formed on the surface of the image carrier to a recording material to form an image on the recording material;
An image forming apparatus having
The image data input to the exposure unit is 1 according to the pixel position in the main scanning direction of the scanning line so as to correct the inclination or distortion of the scanning line when the image carrier is scanned by the exposure unit. Image correction means for performing correction to offset the pixel position in the sub-scanning direction with an offset amount in pixel units;
Storage means for storing a plurality of exposure amount patterns for controlling the exposure amount of the exposure means during the smoothing process;
Smoothing processing means for performing smoothing in the main scanning direction on the image data corrected by the image correction means using the exposure amount pattern stored in the storage means;
Have
The smoothing processing means includes
From said plurality of exposure pattern stored in the storage unit, select the exposure pattern in accordance with the image forming condition, on the basis of the main scanning direction of density change at the pixel position where the offset amount is changed, the selection Control the direction in which the exposure dose pattern is used ,
With respect to the image data corrected by the image correction means, pixel positions where the offset amount has changed along the main scanning direction, and the intermediate points between two adjacent pixel positions are respectively determined, and a plurality of determined intermediate points An image forming apparatus characterized in that smoothing is performed by using the selected exposure amount pattern for each region between adjacent intermediate points .   The image forming apparatus according to claim 1, wherein the image forming condition is at least one of a temperature and a humidity around the developing unit.   The image forming apparatus according to claim 1, wherein the image forming condition is a number of sheets transferred to the recording material. An image carrier that carries an electrostatic latent image according to image data on the surface;
Charging means for charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image by scanning the surface of the charged image carrier with light according to image data;
Developing means for developing the electrostatic latent image formed on the surface of the image carrier with a developer;
Transfer means for transferring the developer image formed on the surface of the image carrier to a recording material to form an image on the recording material;
An image forming apparatus control method comprising:
The image data input to the exposure unit is 1 according to the pixel position in the main scanning direction of the scanning line so as to correct the inclination or distortion of the scanning line when the image carrier is scanned by the exposure unit. An image correction step for performing correction to offset the pixel position in the sub-scanning direction by an offset amount in pixel units;
A smoothing process step of performing smoothing in the main scanning direction on the image data corrected in the image correction step using an exposure amount pattern stored in a storage unit included in the image forming apparatus;
Including
The storage means stores a plurality of exposure amount patterns for controlling the exposure amount of the exposure means during the smoothing process in the smoothing process step,
In the smoothing process,
From said plurality of exposure pattern stored in the storage unit, select the exposure pattern in accordance with the image forming condition, on the basis of the main scanning direction of density change at the pixel position where the offset amount is changed, the selection Control the direction in which the exposure dose pattern is used ,
With respect to the image data corrected in the image correction step, pixel positions at which the offset amount has changed along the main scanning direction, and the intermediate points between two adjacent pixel positions are respectively determined, and a plurality of determined intermediate points A control method for an image forming apparatus , wherein smoothing is performed using the selected exposure amount pattern for each of regions between adjacent intermediate points . An image carrier that carries an electrostatic latent image according to image data on the surface;
Charging means for charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image by scanning the surface of the charged image carrier with light according to image data;
Developing means for developing the electrostatic latent image formed on the surface of the image carrier with a developer;
Transfer means for transferring the developer image formed on the surface of the image carrier to a recording material to form an image on the recording material;
An image forming apparatus control program comprising:
The image data input to the exposure unit is 1 according to the pixel position in the main scanning direction of the scanning line so as to correct the inclination or distortion of the scanning line when the image carrier is scanned by the exposure unit. An image correction step for performing correction to offset the pixel position in the sub-scanning direction by an offset amount in pixel units;
A smoothing process step of performing smoothing in the main scanning direction on the image data corrected in the image correction step using an exposure amount pattern stored in a storage unit included in the image forming apparatus;
Is executed by the processor of the image forming apparatus,
The storage means stores a plurality of exposure amount patterns for controlling the exposure amount of the exposure means during the smoothing process in the smoothing process step,
In the smoothing process,
From said plurality of exposure pattern stored in the storage unit, select the exposure pattern in accordance with the image forming condition, on the basis of the main scanning direction of density change at the pixel position where the offset amount is changed, the selection Control the direction in which the exposure dose pattern is used ,
With respect to the image data corrected in the image correction step, pixel positions at which the offset amount has changed along the main scanning direction, and the intermediate points between two adjacent pixel positions are respectively determined, and a plurality of determined intermediate points A control program for an image forming apparatus , wherein smoothing is performed by using the selected exposure amount pattern for each of regions between adjacent intermediate points .

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