| 摘要 |
PURPOSE:To improve focusing control accuracy by eliminating the influence of noises and false signals that the output signal of a line sensor contains when representing the high frequency components of the output signal of the line sensor as its absolute value and integrating this absolute value to decide focusing. CONSTITUTION:Projection image information incident on the image sensor is read out as a time-series output within a read time, the full-wave rectified signal D of the high frequency component obtained by filtering the output signal is integrated within a range t1-t2 except the leading and trailing edges of an effective output signal for an effective picture element of an image sensor, and the integral value is used to decided focusing. The full-wave rectified signal D of the high frequency component of the time-series output signal of the image sensor is all integrated to include the influence of noises and false signals C1 and C2. but the integration is limited to the range t1-t2 of the effective output signal which contains neither the false signal C1 or C2, so that the majority of the influence of the noises is removed and the influence of the false signals C1 and C2 is removed completely. This integral value becomes a signal indicating the contrast of an image and a projection lens is moved to the position where the contrast signal is maximum to obtain the focusing. |
