PURPOSE:To eliminate a shift of position in the main scan direction at a joint of each partial scan by having coincidence between the phase of a modulated clock used for partial scans at and after the 2nd stage and the modulated clock used at the first stage. CONSTITUTION:A scan region is divided into plural, e.g., two partial scan regions for wide-range scan. The following modulated clock is used to eliminate a shift of position in the main scan direction at a joint of each partial scan. That is, reference signal trains CK1-CK4 having the same frequency and phases different successively are first generated. Then a scan start point detection signal 1 is detected for the scan region of the first stage. The signal train CK2 which has the 1st rise after the rise of the signal 1 is selected and used as a modulated clock 1 of a first stage scan region I . Then the train CK3 is selected in the same way when a scan start point detection signal 2 of a scan region IIis detected. This signal train is used to count the time up to the start of scan of the region II, and then the train CK3 is switched to the phase of the train CK2 which is selected at the first stage. This phase is used to the modulated clock of the region II.
展开▼
