Color image forming apparatus having function of obtaining color information of patch
AssigneeCanon Kabushiki Kaisha
InventorsMasatake Usui, Hiroshi Kita, Shun-ichi Ebihara, Ken Yokoyama
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Abstract
An image forming apparatus uses the difference in time taken for each patch to reach a color sensor, which occurs upon reversing the conveyance direction of a printing material. Due to this difference in time, the temperature of the printing material in detection by the color sensor differs among the respective patches. The error of a colorimetric value due to thermochromism is reduced by placing a patch with a colorimetric value which has a low temperature dependence so as to be detected earlier, and a patch with a colorimetric value which has a high temperature dependence so as to be detected later.
Claims7
An image forming apparatus including a fixing unit configured to heat and fix a toner image transferred onto a printing material, comprising:
- a switchback mechanism configured to reverse a conveyance direction of a printing material on which the toner image is fixed;
- and
- a colorimetry unit which is located in a vicinity of a conveyance path conveying the printing material, the conveyance direction of which is reversed by the switchback mechanism, and is configured to obtain pieces of color information of patches of a plurality of colors, formed on the printing material, from light reflected by the patches of the plurality of colors upon irradiating the patches of the plurality of colors with light,
- wherein an average of a variation in the color information of a patch, formed in a first region on the printing material, in response to a predetermined change in temperature is larger than an average of a variation in the color information of a patch, formed in a second region on the printing material, in response to the predetermined change in temperature, and
- the first region and the second region are on a leading edge side and a rear edge side, respectively, at a time of passage through the fixing unit when the printing material is divided into two regions in a direction perpendicular to the conveyance direction.
An image forming apparatus including a fixing unit configured to heat and fix a toner image transferred onto a printing material, comprising:
- a switchback mechanism configured to reverse a conveyance direction of a printing material on which the toner image is fixed;
- and
- a colorimetry unit which is located in a vicinity of a conveyance path conveying the printing material, the conveyance direction of which is reversed by the switchback mechanism, and is configured to obtain pieces of color information of patches of a plurality of colors, formed on the printing material, from light reflected by the patches of the plurality of colors upon irradiating the patches of the plurality of colors with light,
- wherein when a variation in the color information of each patch, formed on the printing material, in response to a predetermined change in temperature is approximated by a linear function in an order of formation of the patches, the linear function has a negative gradient.
Dependencies are inferred from the claim text.