APPARATUS FOR DETERMINING WHETHER A SHEET IS OF A FIRST TYPE OR A SECOND TYPE

An apparatus for determining whether a sheet is of a first type or a second type, the sheet including two marks printed on opposite halves of the sheet. The apparatus includes a thickness detector for detecting a thickness of the sheet to detect parts greater than a predetermined thickness, an image input unit for imaging the two marks of the sheet, a judging unit for determining a check condition when any part thicker than the predetermined thickness is located between the two marks and extend between lengthwise edges of the sheet, a comparison unit for comparing the images of the two marks of the sheet imaged by the image input unit when the judging unit determines the check condition and for providing a result signal representative of whether the two marks correspond to each other, and a determining unit for determining in response to the result signal that the sheet is of the first type when the two marks correspond to each other and of the second type when the two marks do not correspond to each other.