Design Of The Optical System Applied In Intenal Drum CTP

With the development of computer and laser technology, digital pre-printing flow process becomes simpler and simpler, and it's a natural trend to replace the CTF (Computer To Film) with CTP (Computer To Plate). Of all kinds of CTP, internal drum CTP uses a small and light rotating mirror as scanning component for its long optical path. And it's more suitable for the photosensitive plate-making. What's more, the application of a purple semi-conductor laser improves the resolution and scanning speed of internal drum CTP in recording printing plates.This dissertation is mainly about the research on the optical system applied in internal drum laser plate-making machine, which include following aspects: Firstly, the significance and purpose of this dissertation are given. We present the development and current situation of CTP at home and abroad ,compare performance parameters of some typical versions.Secondly, we make an introduction of each performance parameter of CTP, and propose the value of each performance parameter in our CTP and optical system.Thirdly, the whole optical system is designed, including the beam expander, spatial filter and focusing objective lens, according to the performance parameters. The image quality evaluation of such optical system is given with the tolerance analysis.Finally, we analyze the error produced during scanning process, obtain the relationship between the spot position in the image plane and the deviation of each component as well as the deviation of scanning lines from ideal lines. We also calculate the tolerance of each component.