Fundamentals of ellipsometry and automatic ellipsometers are introduced briefly

and a sample machine of new type automatic null ellipsometer has been designed and constructed. Some techniques that can be used in measurement of LCD thin films are analyzed

then we point out that due to its properties of non-destructive

high-accuracy and high-speed

automatic ellipsometer is very suited for on-line monitoring of LCD thin film system. Owing to its advantages

ellipsometry and automatic ellipsometers can be used in many other fields and will gain good results.