The present invention provides an image scanner comprising an automatic document feeder and a moveable light source. The image scanner uses a sensing device to detect the position of a lid, and uses a switch mechanism to control the power output of a motor. When the lid is at an “on” position, the power output of the motor will be transmitted to the automatic document feeder to scan opaque documents. When the lid is at an “off ” position, the power output of the motor will be transmitted to the light source to scan transparent documents. The transparent documents can be scanned without additional locating devices to locate transparent documents thus making the image scanner multi-functional and easy to use.