Image reading apparatus

An image reading apparatus comprising:

• a transmission type projection screen through which an image projected on an inner surface side of the projection screen is readable from an outer surface side thereof;
• a projection optical system for projecting an image onto the inner surface side of the projection screen;
• a reading unit movable in a projection optical path between the projection screen and the projection optical system for reading image information in an image reading mode;
• a light shield in the projection optical path between the projection screen and the projection optical system, said light shield being movable to a position where an ambient light incident from the outer surface side of the projection screen, reflected by the projection optical system and entered into the reading unit, is blocked;
• a motor for moving the light shield;
• and
• a controller for controlling the motor to move the light shield to the position corresponding to a position of the reading unit in the image reading mode where the ambient light is blocked,
• wherein the reading unit has a length over a main scanning direction of the projection screen and is moved in a sub-scanning direction orthogonal to the main scanning direction, and
• wherein the light shield has a length over the main scanning direction and is moved in parallel with the projection screen in the sub-scanning direction.