PURPOSE: To enable reading of image information by using a reader having a simple mechanism by constituting the titled body in such a manner as to attain an open position to expose an accumulation type fluorescent material layer when an accumulation type fluorescent material sheet is relatively drawn out of a light shielding member.

CONSTITUTION: A projecting part 1a which projects in the transverse direction of the accumulation type fluorescent material sheet 1 is formed at the rear end of said sheet. This accumulation type fluorescent material sheet 1 is so formed that the projecting part 1a of the sheet can be drawn out to the position corresponding to the inside wall surface 2c on the lateral side of the aperture 2a of the light shielding member 2. The accumulation type fluorescent material sheet 1 attains the pen position where the entire part of the image recording region thereof is exposed to the outside of the light shielding member 2 when the projecting part 1a comes into contact with the inside wall surface 2c. The entire part of the accumulation type fluorescent material sheet 1 is, therefore, exposed when the sheet 1 is drawn out of the light shielding member 2 and, therefore, the reading of the image information is executed when the entire surface thereof is irradiated with excitation light.