In production systems it is often necessary to use visual control of the produced units. Nowadays, such control is carried out by trained operators. For Ejnar Jensen & Son, TI/Industrial Automation has developed a line-scan vision in-spection unit, Jenscan, which enables automatic, contact-free, quality control of linen. Ejnar Jensen & Son, Roenne, Denmark is a large manufacturer and exporter of folders and stackers for use in industrial laundries. With a speed of 30 metres per minute sheets and tea towels are inspected in order to reveal spots and holes. Depending on previous sorting criterias the sheets and towels will be approved or sorted out, folded and stacked. The resolution of the system is 3x3 mm with a scanning width of 4 metres. The detection width can be divided into 1 to 6 parallel running lanes. The detection area for spots and holes can be adjusted individually for each lane, from the minimum level upwards. The paper attaches importance to the experience made from specifying, developing and testing the system. Trends of development according to knowledge based vision systems for on line quality control will be discussed.