Design of general type zoom fish-eye lens for dome-screen projector

To match the projecting images on dome screens from different types and specs of mainstream digital engineering projectors,a basic design method for a general projection fisheye zoom lens was presented.First,based on the characteristics and universality of the projection fisheye lens,the optical structure used in the final system was defined.By configuring the initial parameters of moving unit bestly,the moving path of compensating group was linearized to construct synchronously two cam curves to be standard helical lines.Then,image surface position was kept steady during a zooming process by controlling the spherical aberration of front fixed group and the focal length of back fixed group.The final design indicates that the optical system can always keep a full field angle of view of 160° and a F# of 2.0 as it uses two moving components that contain a positive zooming group and a negative compensating group.By controlling parameters reasonably,the system can match prisms of different effective optical thicknesses from 16.5 mm to 26 mm in several kinds of digital projector engines,and also can match digital engineering projectors by using 1LCD,3LCD and 1DMD technologies with the chip sizes from 16-24 cm(0.63-0.95 in) and the length-width ratio of chip in 16∶9 and 4∶3 when the image shift is within ±0.03 mm.The design can fulfill the requirements of common and general projections with its simpler structure and good technology.