| 摘要 |
PURPOSE:To obtain an image reader providing a function for executing necessary adjustment of a light source according to an actuated state by installing a voltage supply means for selectively impressing either a voltage which is connected and disconnected at a 1st frequency out of an audible area or a voltage which is disconnected and connected at a 2nd frequency in the audible area on the light source. CONSTITUTION:When a program is started, the value of 50 is inputted in the counter A and the counter B of a CPU 21 respectively and the voltage whose disconnecting and connecting frequency is 20kHz and whose duty ratio is 0.5 is impressed on a halogen lamp 1. When a button for starting the read of an image is pushed, the value of 250 is inputted in the counters A and B respectively and the switching of a FET 24 is performed in 2MHz/250+250=4,000Hz, then the voltage whose disconnecting and connecting frequency is 4kHz in the audible area and whose duty ratio is 0.5 is impressed on the halogen lamp 1. Since a machinery system starts to be actuated just thereafter oscillation noise is absorbed by the noise of a device of the machinery system, so that there is no problem even if the frequency is lowered. Thus, the harsh oscillation noise can be prevented and a stage for adjusting the illuminance of the light source which does not hinder the read of the image can be obtained. |
