COMPOSITIONS OF ATHERMALIZED THREE-COMPONENT INFRARED OBJECTIVES

Abstract

Devices of infrared equipment are often operating under complicated environmental conditions. First of all it concerns temperature range which can reach ±60 °С in accordance with the requirements. Proceeding from this condition one of the most important tasks for designing objectives if the infrared devices is to preserve their main characteristics during temperature fluctuations. Temperature changes in internal part of the objective leads to changes in design values of the optical system and it leads consequently to thermal defocusing and appearance of aberrations in image that entails sharp decrease in frequency and energy characteristics of the system. The paper considers a problem on compensation of temperature field influence on image quality of focusing units operating in infrared spectral range when there is uniform temperature distribution in the system.

It is expedient to remove dependences of infrared objective characteristics on temperature at the designing stage of focusing unit while using an athermalization method. The paper examines application results of the developed methodology for passive optical athermalization for designing infrared triplet objectives and reveals their advantages in comparison with non-athermalized analogues. Schemes of thermal-independent three-component objectives operating in in the long-distance infrared range of the spectrum 8–14 mkm with matrix photo-receivers have been proposed in the paper. The paper provides results of the analysis on influence of temperature field changes on image quality as non-athermalized so athermalized infrared objectives as well. Combinations of optical materials and characteristics of optical systems for creation of athermalized objectives with long-distance infrared spectrum range have been recommended in the paper. The paper presents an optical system of the triplet which is calculated on the basis of the developed athermalization methodology.