USRE50141EActiveUtilityPatentIndex 72
Image-forming apparatus

Assignee: CANON KKPriority: Jun 12, 2014Filed: Feb 4, 2021Granted: Sep 24, 2024
Est. expiryJun 12, 2034(~7.9 yrs left)· nominal 20-yr term from priority
Inventors:KAWANA TAKASHI ISHIHARA KAZUYUKI TAKAYAMA YUUJI UCHIDATE HIKARU TANAKA YOSHIHIKO FUKUHARA HIROYUKI KUROKAWA SHUICHI
H04N 1/04H04N 1/02885H04N 1/1135H04N 1/053G03G 2215/0429G03G 15/04018G03G 15/043
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Claims
Abstract

An image-forming apparatus includes a light-irradiation unit configured to move a spot of laser light on a surface of a photosensitive member at a non-constant scanning velocity in a main scanning direction to form a latent image on the photosensitive member, an image data correcting unit configured to correct a length in the main scanning direction of image data by inserting one or more image data pieces into the image data, the number of the image data pieces increasing as the scanning velocity increases, and/or extracting one or more image data pieces from the image data, the number of the image data pieces increasing as the scanning velocity decreases, and a brightness correcting unit configured to correct a brightness of the laser light so that an emission brightness increases as the scanning velocity increases and/or the emission brightness decreases as the scanning velocity decreases.
Claims

exact text as granted — not AI-modified
What is claimed is: 
     
       1. An image forming apparatus including a photosensitive member, and a light-irradiation unit configured to form a latent image on the photosensitive member by scanning, with laser light, a plurality of sections in a main scanning direction at a non-constant scanning velocity, the image forming apparatus comprising:
 an image data changing unit configured to extract a pixel piece smaller in size than one pixel from image data or insert the pixel piece into the image data according to which of the sections in the main scanning direction data corresponds to among image data for scanning with the laser light; and   a brightness changing unit configured to change an emission brightness of the laser light according to which of the sections in the main scanning direction the laser light corresponds to,   wherein, in a first section in the main scanning direction, the image data changing unit changes a number of pixel pieces corresponding to the first section to a first number and the brightness changing unit changes an emission brightness of laser light corresponding to the first section to a first emission brightness,   wherein, in a second section, in which a scanning velocity is faster than that in the first section, in the main scanning direction, the image data changing unit changes a number of pixel pieces corresponding to the second section to a second number and the brightness changing unit changes an emission brightness of laser light corresponding to the second section to a second emission brightness, and   wherein the first number is smaller than the second number, and the second emission brightness is larger than the first emission brightness.   
     
     
       2. The image forming apparatus according to  claim 1 , wherein a scanning velocity of the laser light is increased from a center to an end in the main scanning direction. 
     
     
       3. The image forming apparatus according to  claim 1 , further comprising:
 an emission period changing unit configured to change an emission period of the laser light per pixel according to which of the sections in the main scanning direction the laser light corresponds to,   wherein the emission period changing unit changes an emission period of laser light corresponding to the first period to a first period and changes an emission period of laser light corresponding to the second period to a second period, and   wherein the second period is shorter than the first period.   
     
     
       4. The image forming apparatus according to  claim 3 , wherein, in the second section, the emission period changing unit changes the emission period of the laser light corresponding to the second period to the second period shorter than the first period corresponding to the second number of pixel pieces changed by the image data changing unit, and the brightness changing unit changes the emission brightness of the laser light corresponding to the second section to a third emission brightness larger than the second emission brightness. 
     
     
       5. The image forming apparatus according to  claim 3 , wherein in a case where a lowest scanning velocity among scanning velocities of the laser light is represented by Vmin, a highest scanning velocity among the scanning velocities is represented by Vmax, a rate of change in the scanning velocity is represented by C, a brightness in the center in the main scanning direction is represented by P 3 , and a brightness in the end in the main scanning direction is represented by P 3 ′, the following condition is satisfied:
   C=((Vmax−Vmin)/Vmin)*100
 
   and 
   (P3′/P3)&gt;(100+C)/100.
 
 
     
     
       6. The image forming apparatus according to  claim 1 , wherein the image data changing unit extracts the pixel piece in the first section that is near the center in the main scanning direction and inserts the pixel piece in the second section that is near the end in the main scanning direction. 
     
     
       7. The image forming apparatus according to  claim 1 , wherein in a case where the image data changing unit inserts the pixel piece, the image data changing unit inserts a pixel piece of same data as a pixel piece adjacent to a position at which the pixel piece is inserted on an upstream side in the main scanning direction. 
     
     
       8. The image forming apparatus according to  claim 1 , wherein the image data changing unit changes the image data so that widths of pixels of the latent image are substantially equal. 
     
     
       9. The image forming apparatus according to  claim 1 , wherein in a case where a lowest scanning velocity among scanning velocities of the laser light is represented by Vmin, a highest scanning velocity among the scanning velocities is represented by Vmax, and a rate of change in the scanning velocity C is expressed by
   C=((Vmax−Vmin)/Vmin)*100,
   
       the rate of change in the scanning velocity C is 20% or more. 
     
     
       10. The image forming apparatus according to  claim 1 , further comprising:
 a constant current circuit configured to output a first current,   wherein the laser light is emitted by supplying, to the light-irradiation unit, a third current obtained by subtracting a second current output by the brightness changing unit from the first current, and   wherein the brightness changing unit changes the second current according to a scanning velocity in the main scanning direction.   
     
     
       11. The image forming apparatus according to  claim 1 , further comprising:
 a constant current circuit configured to output a first current,   wherein the laser light is emitted by supplying, to the light-irradiation unit, a third current obtained by adding a second current drawn by the brightness changing unit to the first current, and   wherein the brightness changing unit changes the second current according to a scanning velocity in the main scanning direction.   
     
     
       12. The image forming apparatus according to  claim 1 , further comprising:
 a rotational polygon mirror configured to reflect the laser light,   wherein the laser light reflected by the rotational polygon mirror is applied onto the photosensitive member without being transmitted through a lens having an fθ characteristic.   
     
     
       13. An image forming apparatus including a photosensitive member, and a light-irradiation unit configured to form a latent image on the photosensitive member by scanning, with laser light, a plurality of sections in a main scanning direction at a non-constant scanning velocity, the image forming apparatus comprising:
 an image data changing unit configured to extract pixel piece smaller in size than one pixel from image data or insert the pixel piece into the image data according to which of the sections in the main scanning direction data corresponds to among image data for scanning with the laser light; and   a brightness changing unit configured to change an emission brightness of the laser light according to which of the sections in the main scanning direction the laser light corresponds to,   wherein, in a plurality of sections in the main scanning direction, the image data changing unit extracts or inserts the pixel piece from or into image data corresponding to the plurality of sections and the brightness changing unit changes an emission brightness of laser light corresponding to the plurality of sections.   
     
     
       14. An image forming apparatus including a photosensitive member, and a light-irradiation unit configured to form a latent image on the photosensitive member by scanning, with laser light, a plurality of sections in a main scanning direction without transmitting the laser light through a lens having an fθ characteristic, the image forming apparatus comprising:
 an image data changing unit configured to extract pixel piece smaller in size than one pixel from image data or insert the pixel piece into the image data according to which of the sections in the main scanning direction data corresponds to among image data for scanning with the laser light; and 
 a brightness changing unit configured to change an emission brightness of the laser light according to which of the sections in the main scanning direction the laser light corresponds to, 
 wherein, in a plurality of sections in the main scanning direction, the image data changing unit extracts or inserts the pixel piece from or into image data corresponding to the plurality of sections and the brightness changing unit changes an emission brightness of laser light corresponding to the plurality of sections. 
 
     
     
       15. An image forming apparatus including a photosensitive member, and a light-irradiation unit configured to form a latent image on the photosensitive member by scanning, with laser light, a plurality of sections in a main scanning direction at a non-constant scanning velocity according to image data indicating a density of an image, the image forming apparatus comprising:
 a pixel width correcting unit configured to extract a pixel piece smaller in size than one pixel from the image data or insert the pixel piece into the image data according to which of the sections in the main scanning direction data corresponds to among image data for scanning with the laser light; and   a density correcting unit configured to change a density of the image data according to which of the sections in the main scanning direction data corresponds to among the image data,   wherein, in a first section in the main scanning direction, a number of pixel pieces corresponding to the first section is changed to a first number and a density of image data corresponding to the first section is changed to a first density,   wherein, in a second section, in which a scanning velocity is faster than a scanning velocity in the first section, in the main scanning direction, a number of pixel pieces corresponding to the second section is changed to a second number and a density of image data corresponding to the second section is changed to a second density, and   wherein the second number is smaller than the first number, and the second density is higher than the first density.    
     
     
       16. The image forming apparatus according to claim 15, wherein halftone processing is performed on the image data of which the density is changed, and
 wherein image data on which the halftone processing has not been performed is changed.    
     
     
       17. The image forming apparatus according to claim 15, wherein the density of the image data is changed using a density correction value.  
     
     
       18. The image forming apparatus according to  claim 17 , wherein the density correction value corresponding to the first section is a first value to correct the density to the first density, and the density correction value corresponding to the second section is a second value to correct the density of the image data to the second density higher than the first density.  
     
     
       19. The image forming apparatus according to claim 17, wherein the density correction value stored in a storage unit is read.  
     
     
       20. The image forming apparatus according to  claim 15 , wherein the image data indicating the density of the image is multi-valued data.  
     
     
       21. The image forming apparatus according to  claim 15 , wherein the scanning velocity of the laser light is increased from a center of the photosensitive member to an end of the photosensitive member in the main scanning direction.  
     
     
       22. The image forming apparatus according to claim 15, wherein the pixel piece is inserted in the first section that is near a center of the photosensitive member in the main scanning direction and extracts the pixel piece in the second section that is near an end of the photosensitive member in the main scanning direction.  
     
     
       23. The image forming apparatus according to claim 15, wherein in a case where the pixel piece is inserted, a pixel piece is inserted of same data as a pixel piece adjacent to a position at which the pixel piece is inserted on an upstream side in the main scanning direction.  
     
     
       24. The image forming apparatus according to claim 15, wherein emission timing of the laser light is corrected so that widths of pixels of the latent image are substantially equal in the main scanning direction.  
     
     
       25. The image forming apparatus according to  claim 15 , wherein in a case where a lowest scanning velocity among scanning velocities of the laser light is represented by Vmin, a highest scanning velocity among the scanning velocities is represented by Vmax, and a rate of change in the scanning velocity C is expressed by
   C(%)=((Vmax−Vmin)/Vmin)*100,
   the rate of change in the scanning velocity C is 20% or more.    
     
     
       26. An image forming apparatus including a photosensitive member, and a light-irradiation unit configured to form a latent image on the photosensitive member by scanning, with laser light, a plurality of positions in a main scanning direction at a non-constant scanning velocity according to image data indicating a density of an image, the image forming apparatus comprising:
 a pixel width correcting unit configured to extract a pixel piece smaller in size than one pixel from the image data or insert the pixel piece into the image data according to a position in the main scanning direction; and   a density correcting unit configured to change image data to change a density according to which of the positions in the main scanning direction data corresponds to among the image data, and   wherein, at a first position in the main scanning direction, a number of pixel pieces corresponding to the first position is changed to a first number and a density of image data corresponding to the first position is changed to a first density,   wherein, at a second position, at which a scanning velocity is faster than a scanning velocity at the first position, in the main scanning direction, a number of pixel pieces corresponding to the second position is changed to a second number and a density of image data corresponding to the second position is changed to a second density, and   wherein the second number is smaller than the first number, and the second density is higher than the first density.    
     
     
       27. An image forming apparatus including a photosensitive member, and a light-irradiation unit configured to form a latent image on the photosensitive member by scanning, with laser light, a plurality of positions in a main scanning direction at a non-constant scanning velocity according to image data indicating a density of an image, the image forming apparatus comprising:
 a pixel width correcting unit configured to extract a pixel piece smaller in size than one pixel from the image data or insert the pixel piece into the image data according to a position in the main scanning direction,   wherein, in a case where a density of image data at a first position in the main scanning direction is a first density and a density of image data at a second position, at which a scanning velocity is faster than a scanning velocity at the first position, in the main scanning direction is a second density equal to the first density,   at the first position, a number of pixel pieces corresponding to the first position is changed to a first number, and at the second position, a number of pixel pieces corresponding to the second position is changed to a second number, and   wherein the second number is smaller than the first number, the first density becomes a third density, and the second density becomes a fourth density higher than the third density.    
     
     
       28. The image forming apparatus according to  claim 27 , wherein the first density and the second density are largest densities.  
     
     
       29. An image forming apparatus including a photosensitive member, and a light-irradiation unit configured to form a latent image on the photosensitive member by scanning, with laser light, a plurality of positions in a main scanning direction at a non-constant scanning velocity according to image data indicating an image density of an image, the image forming apparatus comprising:
 a pixel width correcting unit configured to extract a pixel piece smaller in size than one pixel from the image data or insert the pixel piece into the image data according to a position in the main scanning direction,   wherein, in a case where image data at a first position in the main scanning direction has a first density and image data at a second position, in the main scanning direction, to be scanned at a scanning velocity higher than a scanning velocity at the first position has a second density equal to the first density,   a number of pixel pieces of one pixel corresponding to the first position is changed to a first number at the first position, a number of pixel pieces of one pixel corresponding to the second position is changed to a second number at the second position, the second number is smaller than the first number, and   a first exposure amount of the laser light emitted to the first position on the photosensitive member is equal to a second exposure amount of the laser light emitted to the second position on the photosensitive member.    
     
     
       30. The image forming apparatus according to  claim 29 , wherein the first density and the second density are largest densities.  
     
     
       31. The image forming apparatus according to claim 29, further comprising a brightness correcting unit configured to change an emission brightness of the laser light according to which of the positions in the main scanning direction the laser light corresponds to,
 wherein an emission brightness of laser light corresponding to the first position is changed to a first emission brightness, and an emission brightness of laser light corresponds to the second position is changed to a second emission brightness larger than the first emission brightness, and   wherein the laser light is changed so that the first exposure amount is equal to the second exposure amount.    
     
     
       32. The image forming apparatus according to claim 29, wherein image data is changed to change a density according to which of the positions in the main scanning direction data corresponds to, among the image data,
 wherein the image data corresponding to the first position is changed so as to have a first density, and the image data corresponding to the second position is changed so as to have a second density,   the second density is higher than the first density, and   the image data is changed so that the first exposure amount is equal to the second exposure amount.
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