Adjustable Tilt Angle of Liquid Microlens With Four Coplanar Electrodes

We present a novel method to adjust the beam tilt angle and tune the axial focus of an electrowetting on dielectric liquid microlens encapsulated by parylene film. The lens system consists of four control electrodes with two immiscible spherical liquid lenses of different refractive indexes encapsulated by a flexible polymer. To tilt the incident beam, the lateral position and curvature of the inner lens were modulated by ac voltage applied to the electrodes. The measured lateral position and curvature of the inner lens allowed us to estimate the position of the focal point. The tunability of the tilt angle was increased by ±2.13° at an applied voltage of $45.3~V_{\mathrm {rms}}$ when using thin dielectric layers. The resolvable image was 80% and 68% of the aperture diameter for 20 and 50 L&S/mm, respectively, assuming that the critical modulation transfer function value was 50% for quality imaging.