Optimal focal length search and design of a compact zoom lens based on a telecentric intermediate image

The design of a compact zoom lens requires a designer’s most abundant and professional skills and experience, which increases the difficulty of zoom lens miniaturization. In this paper, an automatic optimal focal length search method for a catadioptric zoom lens is proposed. After 7 h of searching for the initial structure and further optimization, a 3 × compact zoom lens based on a telecentric intermediate image is obtained, which is applicable for 1/4 inch (6.35 mm) CMOS, with a focal length range of − 4.8 ∼ − 14 m m and a F-number range of 2.7–8.0. The depth and total length are within 6 mm and 30 mm, separately. The proposed method helps to reduce researchers’ difficulty in designing compact zoom lenses and can provide some reference for the development of the mobile zoom lens industry.