US Patent 10391794 Defect detection for print media

A duplex sheet printer comprising a first and second sheet quality detection device for determining a suitability of a sheet for printing. The first sheet quality detection device applies a first sheet rejection threshold to which sensed sheets are compared, while the second sheet quality detection device applies a second sheet rejection threshold different from the first. The controller designates sheets in the printing system to be sensed by one of the sheet quality detection devices in accordance with the sheet's media type or the sheet being on a simplex or duplex pass. Different rejection criteria are thus applied to the sheets without adjustment of a sheet quality detection device, resulting in high speed printing.