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Digital Image Registration Control Technology (IReCT)

Ultra-high-precision image correction utilizing Digital Image Registration Control Technology

IReCT (Image Registration Control Technology) is a digital image registration control technology used in color multifunction devices and color printers which enables the correction of image misregistration at the ultra-high precision of 2,400dpi.

In the xerography process, a color image is reproduced by superimposing four colors of toner: cyan, magenta, yellow, and black. Thus, in order to achieve high image quality, it is necessary to minimize the occurrence of misalignment of individual colors (“color misregistration”), which makes color misregistration correction important.
Previously, color misregistration was generally corrected by mechanically changing the location of image writing. However, there were some problems with this mechanical method: the mechanism used was large and complicated and required time to operate, and the level of precision of correction was low.

With IReCT, color misregistration information of an image is first read by optical sensors and processed at high speeds, and image processing is then performed on the image data (in the form of a digital signal) at the high precision of 2,400 dpi in order to correct the color misregistration. As a result, we succeeded in not only simplifying the structure of the machine and achieving high-speed correction but also providing high-precision print images with minimal color misregistration.

*
dpi (dots per inch): the number of image dots contained within the space of one inch

Digital correction
Fig. 1: Digital correction

Structure of IReCT
Fig. 2: Schematic diagram of IReCT

High-precision correction of front-to-back misregistration

Misregistration of an image in relation to the paper has an immense impact on the quality of the printed output. In order to solve this problem, the possible range of correction was expanded for some production printers to enable high-precision correction of front-to-back misregistration. Also, we have made correction of front-to-back misregistration on various paper types possible by allowing the following six parameters to be set independently for each side of the sheet (Fig. 3): image position adjustment (1) (2), which adjusts the position of the image by adjusting the timing of printing, magnification adjustment (3) (4), which adjusts the length and width of the image by correcting the magnification ratio, and perpendicularity adjustment (5) and skew adjustment (6), which correct rhombic distortion and rotation of the image by performing skew correction.

Correction parameters for front-to-back misregistration
Fig. 3: Correction parameters for front-to-back misregistration

Correction of cyclical color misregistration

In some of our production printers, a function that detects the rotational phase information of photoreceptor drums has been combined with IReCT in order to allow digital correction of cyclical color misregistration that results from fluctuation in the rotational speeds of the four color photoreceptor drums.
First, information on misregistration between each of the four colors is read by an optical sensor while the relative rotational phases of the four photoreceptor drums are maintained constant using motor control. This information is used to create correction profiles for color misregistration that change with each phase to reduce the amount of cyclical fluctuation. Then, the appropriate amount of digital correction is performed for each rotational phase of the photoreceptor drums based on the image data and the phase information. Because of this, it becomes possible to perform color misregistration correction at a higher level of precision than was possible using the previous method of correction by controlling the speed of each photoreceptor drum.

Schematic diagram of cyclical color misregistration using IReCT
Fig. 4: Schematic diagram of cyclical color misregistration using IReCT

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