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US 12,210,308 B2Granted
Method for correcting positional shift of image
AssigneeCanon Kabushiki Kaisha
InventorKeisuke Ishizumi
Life of this patent
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Abstract
An image forming apparatus receives light from an intermediate transfer member or a correction pattern. The pattern includes an overlapping pattern on which a first monochromatic toner image is formed as a lower layer and a second monochromatic toner image having a smaller area than the first monochromatic toner image is formed as an upper layer. The image forming apparatus controls a plurality of image forming units to form the overlapping pattern such that a dynamic range becomes less than 1.0 and greater than 0.5.
Claims20
An image forming apparatus comprising:
- a plurality of image forming units each having an image carrier, an exposure unit configured to form an electrostatic latent image by exposing a surface of the image carrier, and a developing unit configured to form a toner image by developing, with toner, the electrostatic latent image formed on the surface of the image carrier by the exposure unit;
- an intermediate transfer member on which a plurality of toner images of different colors are transferred from the plurality of image forming units;
- a sensor configured to detect a correction pattern in order to correct a positional shift of an image formed on the intermediate transfer member;
- and
- a controller configured to control the plurality of image forming units based on a detection result of the sensor, wherein
- the sensor includes:
- a light emitting element configured to irradiate the intermediate transfer member with light,
- a light receiving element configured to receive light reflected by either the intermediate transfer member or the correction pattern from the light outputted from the light emitting element, and
- the correction pattern includes:
- an overlapping pattern on which a first monochromatic toner image is formed as a lower layer and a second monochromatic toner image having a smaller area than the first monochromatic toner image is formed as an upper layer, and
- the controller controls the plurality of image forming units to form the overlapping pattern such that a dynamic range D, which is calculated from a first received light amount V1 obtained by the light receiving element receiving light reflected from the first monochromatic toner image, a second received light amount V2 obtained by the light receiving element receiving light reflected from the second monochromatic toner image, a received light amount V1′ of a case where a tone value of the first monochromatic toner image is 100%, and a received light amount V2′ of a case where a tone value of the second monochromatic toner image is 100%, becomes less than 1.0 and greater than 0.5, where D=(V1−V2)/(V1′−V2′).
8 more elements
An image forming apparatus comprising:
- a plurality of image forming units each having an image carrier, an exposure unit configured to form an electrostatic latent image by exposing a surface of the image carrier, and a developing unit configured to form a toner image by developing, with toner, the electrostatic latent image formed on the surface of the image carrier by the exposure unit;
- an intermediate transfer member on which a plurality of toner images of different colors are transferred from the plurality of image forming units;
- a sensor configured to detect a correction pattern in order to correct a positional shift of an image formed on the intermediate transfer member;
- and
- a controller configured to control the plurality of image forming units based on the detection result of the sensor, wherein
- the sensor includes:
- a light emitting element configured to irradiate the intermediate transfer member with light, and
- a light receiving element configured to receive light reflected by either the intermediate transfer member or the correction pattern from light outputted from the light emitting element,
- the correction pattern includes:
- an overlapping pattern on which a first monochromatic toner image is formed as a lower layer and a second monochromatic toner image having a smaller area than the first monochromatic toner image is formed as an upper layer,
- a first received light amount obtained by the light receiving element receiving light reflected from the first monochromatic toner image is greater than a threshold and a second received light amount obtained by the light receiving element receiving light reflected from the second monochromatic toner image is less than the threshold,
- a tone value of either one of the first monochromatic toner image and the second monochromatic toner image is formed at less than 100%,
- the controller adjusts an exposure amount by the exposure unit by applying a dither pattern on image data that is the source of the overlapping pattern, and
- a number of lines of the dither pattern used for forming the overlapping pattern and a number of lines of a dither pattern used for forming a user image that has been arbitrarily prepared by a user are different.
11 more elements
Dependencies are inferred from the claim text.