CTP machines are generally divided into inner drum type, outer drum type, flat type, and curve type. Among these four types, the most used ones are inner drums and outer drums; among them, high-end CTP platesetters with relatively good performance use the outer drum type. CTP technology has thermal imaging technology and photosensitive imaging technology, the most widely used, the most stable thermal imaging technology. The most advanced and most mature thermal imaging technology for CTP machines is Kodak's “Square Spot” thermal imaging technology.