Design on Hybrid Diffractive and Refractive Long-Focal Objective

Diffractive optical elements (DOE) have the special property of minus dispersion which can be used in the optical system instead of lens to improve its performance, lighten its weight, and reduce its volume effectively. Based on a conventional refractive long-length objective, a lightweight Hybrid Diffractive - Refractive (HDR) long-length objective was designed with the CODE V software. The optical parameters of the system were that focal length was 100 mm, full field-of-view was 6.2°, diameter is 20mm., and its wavelength range is from 486.1 mm to 656.27 mm. The surface profile parameter of the diffractive optical element was calculated accurately. The mean MTF approached to 0.6 at the frequency of 50 lp/mm. The aberration characteristics of the conventional refractive and the designed HRD optical system were compared such as spot diagram, MTF curve, distortion and field curvature. The results show that the image quality of the HDR system is significantly improved, and can meet the demands at the situation with high accuracy.