Optical Imaging for Telephoto Applications Featuring a Lens Design Optimized For Thermal Compensation

Abstract

Temperature fluctuations in optical imaging systems often affect picture resolution. The quality of the optical element varies due to the high temperature, resulting in focus shift. An optical system for severe temperatures ranging from - 40° to +80° is examined in this paper. To investigate physical and geometrical aberration, a five-element telephoto lens system with the following specifications is used: The entrance pupil diameter (EPD) is 25 mm, the visible wavelength is 486, 587, 656 nm, the field of angle is 0, 7, 10, the F- number is 4, and the semi field of view (FOV) is 10. This preliminary system performance measured and observed picture quality using modulation transfer function (MTF) and spot diagram (SPO). For a spatial frequency of 20 lp/mm, the MTF is 0.5, and the spot diagram reveals that the rays are not converging in the optical axis. This system attained an MTF value of >0.8 (80% accuracy) after optimization. Also, by using Automatic design, the error function or merit function is lowered from 1407.08 to 13.93, and further reduced to 6.77 by incorporating Aspheric surface for element surfaces 1 and 3. We were able to develop a high resolution optical system without modifying the glass material and the overall length of the system.