Canon BJC 6000 Service Manual - Page 87
Automatic Printing Position Alignment Function, Automatic Printing Position Alignment
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BJC-6000 Part 4: Technical Reference 2.3 Automatic Printing Position Alignment Function This printer features the automatic printing position alignment function so that the difference between the installed left and right BJ cartridges in vertical/horizontal printing position and bi-directional printing position will be automatically adjusted. After the automatic printing position adjustment patterns are printed, each under slightly different conditions, Automatic Printing Position Alignment is performed through the reflection of the patterns by the print position sensor, comprised of a red LED and a photosensor, which is installed on the carriage. The variations in the photosensor output are used to calculate the optimum printing position compensation value. Based on the compensation value obtained, the printer corrects for the difference in vertical/horizontal printing position and bi-directional printing position between the right and left cartridges. The Auto Printing Position Alignment starts with the calibration of LED and photosensor sensitivity to correct variations between them. Then the difference in vertical printing position between the left and right cartridges will be compensated for, followed by the adjustment of bi-directional printing position for each printing mode, and then the adjustment of the horizontal printing position to the accuracy of ±1 pixel, after which finer adjustments will automatically be conducted. The adjustment patterns will be printed in both black and cyan, as a red LED is used as the light source. For automatic printing position alignment, you must use B5 or larger paper. LED Photosensor Paper Standard dot Mis-aligned dot Shifted in - direction Printing positions coincide Shifted in + direction Figure 4-12 Automatic Printing Position Alignment CAUTION Do not perform automatic printing position alignment with the front cover open, as external light may make accurate measurements impossible. For this reason, during servicing, do not perform automatic printing position adjustment with the front cover open or upper cover removed. 4-15