Image reading apparatus and control method to perform a determination of whether a medium overlaps another medium based on the light quantity being above or below a threshold after changing the light quantity from a first light quantity to a second light quantity

A method of controlling an image reading apparatus, the image reading apparatus including a feeder that feeds a medium in a feeding direction, a multi-feed detector that detects overlapping of the medium and another medium being fed along a transport route at a multi-feed detection location, a reader that reads an image on the medium being fed, the reader being disposed downstream of the multi-feed detection location in the feeding direction, and a medium detector that detects presence or absence of the medium at a medium detection location positioned on the transport route between the feeder and the multi-feed detection location, the medium detector including a light transmitter that emits light with a light quantity to the medium detection location, the light quantity being variable, and a light receiver that receives the light that traveled across the transport route, the image reading apparatus being configured to perform a process based on detection results of the multi-feed detector and the medium detector, the method comprising:

• a first step of, when the medium detector detects that a state where the medium is absent is switched to a state where the medium is present with the light quantity set to a first light quantity, switching the light quantity from the first light quantity to a second light quantity, the second light quantity being larger than the first light quantity;
• a second step of, when a quantity of the light received by the light receiver exceeds a threshold in response to switching of the light quantity from the first light quantity to the second light quantity, determining whether the medium overlaps the another medium, based on the detection result of the multi-feed detector;
• and
• a third step of, when the quantity of the light received by the light receiver does not exceed the threshold in response to the switching of the light quantity from the first light quantity to the second light quantity, skipping determination of whether the medium overlaps the another medium.