| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing an error in positional deviation detection due to eccentricity of a photoreceptor drum to form high-quality images to which color shift correction is made with high accuracy, without reducing productivity.SOLUTION: An image forming apparatus includes at least photoreceptor drums 7, an intermediate transfer body 8, test pattern forming means for forming test patterns on the intermediate transfer body 8, writing permission instruction means, writing instruction means, a sensor for detecting the positional deviation amount of the test patterns, color shift amount calculation means, and image data correction means for performing coordinate conversion of images in respective colors so as to correct the obtained color shift amount. A writing instruction signal is issued at a timing of the reception of a detection request signal, or at a timing at which a period has elapsed from the time at which the immediately previous test pattern is formed, the period being obtained by adding a predetermined rotation period to an integral multiple of one rotation period of the photoreceptor drum; and the test patterns are formed on the basis of a writing permission signal and the writing instruction signal. |
