Ultra-Slim Zoom Lens Design for a 3X Mobile Camera Sung-Chan Park and Yong-Joo Jo J. Korean Phys.Soc. 52,1048 [doi: 10.3938/jkps.52.1048 | PDF Download] This study presents an ultra-slim zoom lens with a zoom ratio of 3$\times$ for a mobile camera by using a prism. The lens modules and the ray aberrations are applied to the initial design for a four-group inner-focus zoom system. An initial design with a focal length range of 4.4 to 12.76 mm is derived by assigning appropriate first-order quantities and lower-order aberrations to each module along with the constraints required for optimum solutions. By using an optimization design method rather than analytic approaches, we separately designed a real lens for each group at given conjugates and then combined them to establish an actual zoom system. The combination of the separately designed groups results in a system that satisfies the basic properties of the zoom system consisting of the original lens modules. In order to fold the ray path, we directly inserted the right-angle prism without any lens in front of the first group. This configuration resulted in a more compact zoom system with a depth of 7 mm. The finally designed zoom lens has an f-number of 3.5 to 4.5 and is expected to fulfill the requirements for an ultra-slim mobile zoom camera.