25-fold increase in lens power of a KTN varifocal lens by employing an octagonal structure

We successfully improved the variable lens power range of a KTN varifocal lens by changing the lens structure. An octagonal structure was proposed based on the concept that an increase in the curvature of the electric field lines is important in terms of increasing the lens power. The optimum lens structure was investigated using the finite element method, and we concluded that the optimum angle between the electrodes and the optical axis was 26.5°, because this provided both minimum wave aberration and increased lens power. We also found by simulation that the octagonal lens contained both convex and concave lens parts. In addition, the simulation revealed that the concave lens parts corrected the wave aberrations induced by the convex lens parts. Our experimental results agreed well with the simulation results. Our octagonal structure achieved a 2.5 times greater lens power than the conventional rectangular structure.