| 摘要 |
An image forming apparatus comprises a pickup roller for picking up paper from a paper supply part and supplying the paper directly to a transfer nip (that is, the contact formed between a photoconductive drum and a transferring roller), a laser scanning unit for scanning a certain light onto the photoconductive drum, a paper sensor for detecting the top end of the paper being picked up and supplied by the pickup roller, a paper entry sensor for detecting the entry of the paper into the transfer nip, and a controller for updating a scanning point of the laser scanning unit based on the time from the detection of the top end of the paper by the paper sensor to the time the paper entry sensor detects entry of the top end of the paper into the transfer nip. Using this apparatus, an actual time for transferring the paper from the point of detecting the top end of the paper to the point of entrance of the paper into the transfer nip, is calculated, a shift amount with respect to a top margin stored to a controller is calculated based on the calculated information, the top margin value is updated by compensating the shift amount, and upon the error compensation, a light is scanned onto a following sheet of the paper by applying the updated top margin value, thereby processing an image. Accordingly, the top margin can be constantly maintained.
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