Photoelectric automatic focusing system based on interference

The principle and the method of a new automatic focusing system are present ed in this paper. The system is constructed relying on the relationship bet ween laser wave interference patterns and defocusing displacement. A CCD li near array receives interference patterns in the form of light intensity, w hich are converted into digital signals afterwards. Then the computer contr ols a stepping motor to complete auto-focusing process according to the dig ital results. The system has been applied in a kind of film resolution test ing instrument and it shows that it has the advantage of high accuracy, hig h speed and wide applications. (C) 2001 Published by Elsevier Science Ltd.