an image reconstructing apparatus wherein the object under examination is irradiated in at least one direction to provide projection data , and the provided projection data is optically processed to form a reconstructed image representing the internal information of the object . an image associated with the projection data is formed and stored in the storage medium . the stored image is optically read out of the storage medium . the read out stored image which corresponds to one direction of irradiation is integrated at a time to produce sum data . the sum data and projection data corresponding to the same direction of irradiation are compared to form correction data . an image associated with the correction data is formed and optically superposed on the stored image in the storage medium corresponding to the same direction of irradiation , to produce the reconstructed image .