Numerical simulation for meniscus shape and optical performance of a MEMS-based liquid micro-lens

Abstract

It is very difficult to fabricate tunable optical systems having an aperture below 1000 micrometers with the conventional means on macroscopic scale. Krogmann et al. (J. Opt. A 8, S330-S336, 2006) presented a MEMS-based tunable liquid micro-lens system with an aperture of 300 micrometers. The system exhibited a tuning range of back focal length between 2.3mm and infinity by using the electrowetting effect to change the contact angle of the meniscus shape on silicon with a voltage of 0-45 V. However, spherical aberration was found in their lens system. In the present study, a numerical simulation is performed for this same physical configuration by solving the Young-Laplace equation on the interface of the lens liquid and the surrounding liquid. The resulting meniscus shape produces a back focal length that agrees with the experimental observation excellently. To eliminate the spherical aberration, an electric field is applied on the lens. The electric field alters the Young-Laplace equation and thus changes the meniscus shape and the lens quality. The numerical result shows that the spherical aberration of the lens can be essentially eliminated when a proper electric field is applied.

Electrowetting lenses for compensating phase and curvature distortion in arrayed laser systems

“…While we have measured the lens quality without applied voltage, we do not expect a significant change in quality during tuning. The change in spherical aberration with lens tuning was modeled numerically based on the methods of [21]. We calculated the spherical aberration to be small in every tuning condition, increasing from −0.017 λ in the resting state to −0.011 λ with 5 V applied.…”

Simulation of electrowetting lens and prism arrays for wavefront compensation

“…The effect of gravity on the lenses has been simulated. At large diameters, greater than 6 mm, for a typical silicone oil and water mixture, gravity distorts the perfectly spherical surface achievable with electrowetting by only λ ∕17 [21,22]. At small diameters (< few millimeters), gravity has minimal effects on the spherical surfaces for liquids of similar density (oil and water), and response speeds improve with smaller volumes.…”

Wide-angle nonmechanical beam steering using liquid lenses

“…We used pressuredriven liquid lenses due to their large aperture, since electrowetting components are limited in size and by gravitational effects. Electrowetting lenses are governed by surface tension and effects of gravity are generally negligible for mm-size optics [41][42][43]. Specific size limits will be determined by the density mismatch of the two liquids used in the devices.…”