A tunable optical IRIS based on electromagnetic actuation for a high-performance mini/micro camera

This paper presents a tunable iris based on electromagnetic actuation for a tiny high-performance camera in mobile devices such as smart phones and pads. To investigate the effect of a magnetic field on a ferrofluid, the contact angle modification and transportation of a sessile ferrofluid droplet are tested using a neodymium magnet and electric coil. The variation of the contact angle of the ferrofluid droplet is 21.3° for the neodymium magnet and 18.1° for the electric coil based on electromagnetic induction. And the transportation of the ferrofluid droplet is also demonstrated using the neodymium magnet and electric coil. As the concept proof, the pretest of a tunable iris operated by electromagnetic actuation is conducted by using a hollow cylinder cell. In the initial state, the ferrofluid is in the relax state, so the cylinder cell shows the largest aperture (4.06 mm). When an electrical current is applied to an electric coil wound around the outside of the cylinder cell, the ferrofluid initially placed in the hydrophobic sidewall inside the cylinder cell is actuated and pulled to the center. The aperture under the current is modified from 4.06 mm at 0 A to 3.2 mm at 2 A. Finally, the envisioned tunable iris consisted of two connected circular microchannels is realized using a MEMS technology. The iris size is 9×9×2 mm³, and the variation of the aperture diameter is from 1.72 mm at 0 A to 1.09 mm at 2.6 A.