Image reading apparatus

An image reading apparatus comprising:

• a platen glass plate on which an original is to be placed;
• an original positioning portion which determines a position of the original to be placed on the platen glass plate;
• a pressure plate which is rotatably provided so as to open and close the platen glass plate and which holds the original placed on the platen glass plate;
• a light source which illuminates the original placed on the platen glass plate;
• a line image sensor which includes a plurality of light receiving portions arranged side by side in a main scanning direction and which receives a light reflected from the original illuminated by the light source to generate image data;
• a sensor which detects that an angle formed by the pressure plate and the platen glass plate is equal to or less than a predetermined angle;
• an original size detector which is disposed at a detecting position which is away from the original positioning portion by a predetermined distance in a sub-scanning direction orthogonal to the main scanning direction;
• an original image reading start instructing unit which outputs an image reading start instruction for starting an image reading operation of reading an image of the original when the original image reading start instructing unit is depressed by a user;
• a memory which stores a size of the original;
• and
• a controller which, in a case in which the controller receives the image reading start instruction from the original image reading start instructing unit in a state in which it is detected from a detection result of the sensor that the angle of the pressure plate is greater than the predetermined angle, when the size of the original is not stored in the memory, determines the size of the original based on a detection result of the line image sensor and a detection result of the original size detector.