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US 6,643,031 B1Granted
Image processing apparatus
AssigneesKabushiki Kaisha Toshiba, Toshiba Tec Kabushiki Kaisha
InventorsGaku Takano, Hiroki Kanno
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Abstract
For an image signal having density equal to or larger than a predetermined threshold value, this invention realizes stable reproduction by reducing intermediate transition regions by increasing the intervals between pixels in the pixel arrangement of a non-image portion. For an image density signal whose density is smaller than the threshold value, the invention uses half-tone processing with higher resolution to thereby improve the image quality. This improves the reproducibility of pixel structures such as dots and line patterns at high densities, improves the stability of tone reproduction against environments, and improves the image quality.
Claims18
An image forming method comprising the steps of:
- reading an image signal in units of pixels;
- generating a first driving signal corresponding to an image portion and a non-image portion in one pixel based on the read image signal of each pixel;
- generating a second driving signal for clustering non-image portions of a plurality of pixels, on the basis of the read image signal of each pixel and an image signal of a peripheral pixel;
- detecting whether the read image signal of each pixel has a density not less than a predetermined density;
- selectively outputting the first driving signal if the image signal of the detected pixel has a density not less than the predetermined density;
- selectively outputting the second driving signal if the image signal of the detected pixel has a density not more than the predetermined density;
- outputting a laser beam on the basis of the selectively output first or second driving signal;
- forming a latent image on a photosensitive body with the laser beam;
- and
- forming an image by developing the formed latent image with toner.
7 more elements
An image forming apparatus comprising:
- reading means for reading an image signal in units of pixels;
- first generating means for generating a first driving signal corresponding to an image portion and a non-image portion in one pixel based on the image signal of each pixel read by said reading means;
- second generating means for generating a second driving signal for clustering non-image portions of a plurality of pixels on the basis of the image signal of each pixel read by said reading means and an image signal of a peripheral pixel;
- detecting means for detecting whether the image signal of each pixel read by said reading means has a density not less than a predetermined density;
- first output means for selectively outputting the first driving signal generated by said first generating means if the image signal of the pixel detected by said detecting means has a density not less than the predetermined density, and selectively outputting the second driving signal generated by said second generating means if the image signal of the pixel detected by said detecting means has a density not more than the predetermined density;
- second output means for outputting a laser beam on the basis of the first or second driving signal selectively output by said first output means;
- forming means for forming a latent image on a photosensitive body with the output laser beam from said second output means;
- and
- developing means for forming an image by developing with toner the latent image formed by said forming means.
6 more elements
An image processing apparatus comprising:
- detecting means for detecting whether a density of an image signal of an input pixel is not less than a predetermined density;
- first converting means for converting the image signal into image signals of an image portion and a non-image portion for each pixel on the basis of the density of the image signal of each input pixel and a pixel position of each input pixel;
- second converting means for converting the image signal into image signals of an image portion and a non-image portion for each pixel, on the basis of the density of the image signal of each input pixel and the pixel position of each input pixel, thereby clustering image signals of non-image portions of a plurality of pixels;
- and
- output means for selectively outputting the image signal from said second converting means if said detecting means detects that the density of the image signal of the input pixel is not less than the predetermined density, and selectively outputting the image signal from said first converting means if said detecting means detects that the density of the image signal of the input pixel is not more than the predetermined density.
2 more elements
An image processing apparatus comprising:
- detecting means for detecting whether a density of an image signal of an input pixel is not less than a predetermined density;
- first storage means for storing first basic dither information of a dither matrix used to cluster non-image portions of a plurality of pixels;
- second storage means for storing second basic dither information of a dither matrix used to cluster image portions of a plurality of pixels;
- first output means for selecting the first basic dither information stored in said first storage means if the density of the image signal of the pixel detected by said detecting means is not less than the predetermined density, selecting the second basic dither information stored in said second storage means if the density of the image signal of the pixel detected by said detecting means is not more than the predetermined density, and outputting dither information, based on the first or second basic dither information selected and a pixel position of the input pixel, as a threshold value;
- second output means for quantizing the image signal of the input pixel by the threshold value from said first output means and outputting the quantized image signal;
- first generating means for generating coordinate information in a main scan direction and coordinate information in a sub-scan direction based on the pixel position of the input pixel;
- second generating means for generating a reference position signal in the pixel from the coordinate information in the main scan direction and the coordinate information in the sub-scan direction generated by said first generating means;
- third output means for outputting an image density signal of a pixel to be processed after pixel value shifting, from the coordinate information in the main scan direction and the coordinate information in the sub-scan direction generated by said first generating means and the image density signal quantized by said second output means;
- and
- fourth output means for outputting as the reference position signal in the pixel generated by said second generating means and the image density signal of the pixel to be processed after pixel value shifting output from said third output means.
7 more elements
An image processing apparatus comprising:
- a plurality of converting means for converting each input pixel of a two-dimensional image in a main scan direction and a sub-scan direction into an image density signal;
- a plurality of generating means provided in one-to-one correspondence with said plurality of converting means to generate a driving signal on the basis of the image density signal from a corresponding converting means;
- and
- output means for selecting the driving signal from one of said generating means at each main scan period of each input pixel of the image, and periodically changing a main-scan-direction initial phase, selected whenever scan is performed, in the sub-scan direction and outputting the phase,
- wherein said converting means include converting means for converting an input pixel corresponding to a high-density portion into an image density signal in a saturated range and converting means for converting an input pixel corresponding to a high-density portion into an image density signal in an unsaturated range.
2 more elements
An image processing apparatus comprising:
- a plurality of converting means for converting each input pixel of a two-dimensional image in a main scan direction and a sub-scan direction into an image density signal;
- a plurality of generating means provided in one-to-one correspondence with said plurality of converting means to generate a driving signal on the basis of the image density signal from a corresponding converting means;
- and
- output means for selecting the driving signal from one of said generating means at each main scan period of each input pixel of the image, and periodically changing a main-scan-direction initial phase, selected whenever scan is performed, in the sub-scan direction and outputting the phase,
- wherein said converting means include converting means for converting an input pixel corresponding to a high-density portion into an image density signal in a saturated range, converting means for converting an input pixel corresponding to a high-density portion into an image density signal in an unsaturated range, converting means for converting an input pixel corresponding to a low-density portion into zero or an image density signal in a range within which no image is formed, and converting means for converting an input pixel corresponding to a low-density portion into an image density signal in a range within which an image is formed.
2 more elements
Dependencies are inferred from the claim text.