In recent years, an image forming apparatus that prints an image (hereinafter, referred to as an erasable image), such as a character or a picture, on a recording medium, for example, on a sheet using an erasable color material has been proposed. In addition, an image erasing apparatus that erases an erasable image printed on a sheet has been proposed. A user can reuse a single sheet multiple times by repeating forming an erasable image on the sheet and erasing the erasable image on the sheet. Therefore, it is possible to contribute to resource saving by using the above apparatuses.
Repeating the cycle of the image formation and the image erasing is based on the assumption of the erasing of an image printed on the sheet. When erasing an erasable image, it is generally thought that erasable images printed in advance on a plurality of sheets are erased at a time. When erasing the images on the plurality of sheets at a time, it is efficient to set the plurality of sheets in a paper feed unit of the image erasing apparatus and execute erasing processing automatically by turning on an erase start switch.
On the other hand, in document management (management of a sheet on which an image is printed), there is a management method in which an image printed on the sheet cannot be erased unless a predetermined storage period has passed even if the image is erasable. In this management method, a case may be considered in which a sheet within the storage period is accidentally included in a large amount of sheets to be erased.
However, it is not practical to check the image content of each of the large amount of sheets to be erased, and to determine whether or not each sheet is a sheet within the storage period.