Patent ID: 7526241

Claim:
An image forming apparatus forming a full-color image with a plurality of primary color toners, the apparatus comprising: a plurality of image forming members each to form a plurality of test patches; an image transfer member to receive the plurality of test patches from each one of the plurality of image forming members; a plurality of sensors to detect the plurality of test patches carried on the image transfer member; a calculator to perform a logical operation relative to detection signals output by the plurality of sensors; an edge extractor to detect edges and generate edge signals based upon an output signal of the calculator; a counter to count clock pulses with respect to the edge signals generated by the edge extractor to determine a length of each of the plurality of test patches detected; and a misregistration corrector to calculate time lags among the detection signals based on count values counted by the counter for the plurality of test patches detected and to correct misregistration of the full-color image based on the calculated time lags.