A distance image acquisition unit captures a low-resolution image of an object placed on a document board, and an object detection unit corrects the low-resolution image and generates a low-resolution corrected image. A camera image acquisition unit captures a high-resolution image of the object placed on the document board, and an image processing unit corrects the high-resolution image and generates a high-resolution corrected image. A display unit displays the low-resolution corrected image until the high-resolution corrected image is generated, and displays the high-resolution corrected image when the high-resolution corrected image is generated.