The Thermal Analysis And Compensation Of The Long Zoom Lens

With the development of modern technology, the photoelectric tracking measurement system of observation and tracking ability request is higher and higher, and then design of optical system is more and more complex. So zoom structure more and more applied in the photoelectric tracking measurement system. Zoom optical system of the detection precision is high, and its structure is complex. Especially, long focal length zoom system is vulnerable to the influence of the temperature. So thermal analysis and thermal compensati on for optical system can improve the imaging quality and the temperature stability of the system. This paper mainly analyzes the temperature effect of long focal length zoom optical system, and to do temperature compensation for the optical system design.First, the basic theory of temperature effect is studied. The temperature analysis of basic principle, and list the formula for calculating optical parameters when the temperature is changing are studied. Then the evaluation method for temperature effect is studied. The temperature effect of the zoom optical system is evaluated form the MTF, focal length and parfocalization features.Secondly, the temperature compensation way is studied. The traditional design methods for athermalization are summarized, and several emerging ways of athermalization compensation are illustrated. The most important thing is that a new thought of temperature compensation is come up. The method is surface displacement compensation formula. The formula can guide the optical system of athermalization.Then, some a long focal length of the zoom optical system is analyzed. After this analysis the optical performance of the system from the above three aspects is evaluated. The evaluation finds that the optical system is greatly infl uenced by temperature. The greater the temperature deviation from the normal temperature range from-30 ℃ to +60℃, the more changing of the optical performance of the system. The MTF is decreased, the focal is changed and the optical system cannot parfoal.So the compensation of this optical system design is necessary. According to the surface displacement compensation formula, the method that mechanical and electrical compensation and mechanical passive compensation mixed together is proposed. After the compensation of this optical system design, the optical performance of the system is evaluated again. This evaluation found something. The MTF is greater than 0.25 when the short, medium and long focal. The focal length meets the design index. And zoom system has reached the parfocalization. The temperature effect of the optical system has weakened. The hybrid compensation method has good temperature compensation effect for long focal length of this zoom optical system.