| 摘要 |
PURPOSE:To enable automatic focusing, by receiving the light beam reflected from the white part of an original to be transmitted with a reading element through a lens and outputting a signal to move the lens in the direction where the average of the output signal increases from a processing unit. CONSTITUTION:The output waveform of a reading element 4 is lower than the threshold Vth when a focus is not matched and the output voltage of a white level differs on the right and left unless the focus of an optical system consisting of a light source 1, an original 2' for focusing, a lens 3 and the element 4 is not matched. A processing unit 5 detects that the output waveform is lower than the prescribed threshold Vth and outputs the signal for moving the lens 3 in the optical axis direction to a focusing device 6. However, the unit 5 outputs the signal for adjusting the angle of inclination of the axis of the lens 3 to the device 6 when the output waveform such as (c) is not obtained simply by moving the lens in the optical axis direction 7. The prescribed waveform is obtained by repeating such adjustment. In other words, the focusing is accomplished automatically. |
