Evaluation of the key design parameters of liquid crystal tunable lenses for depth-from-focus algorithm.

Liquid crystal (LC) tunable lenses have been extensively studied and used in various applications, however, most of them have been evaluated regardless of their optical imaging quality, in particular, concerning their intrinsic diffuse scattering. In this paper, we investigate the impact of such impairments when LC lenses are used as tunable elements in a depth-from-focus algorithm (DfF). We attempt to analyze these effects in order to design LC lenses that mitigate their impact on the imaging quality. For this purpose, we designed various lenses to evaluate several parameters such as optical, electrical, manufacturing, etc., according to their implementations in a near-pixel DfF architecture.

Low aberrations symmetrical adaptive modal liquid crystal lens with short focal lengths.

We describe the design, fabrication, and characterization of modal liquid crystal lenses (MLCLs) with a symmetrical electrode structure using a resistive composite polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS). We achieved MLCLs with shorter focal lengths (up to 1cm), shorter apertures (1 to 5mm), and lower aberrations compared to other MLCLs. We demonstrate a very uniform conductivity distribution in the PEDOT-PSS layers over a wide resistivity range (100kOmega/sq-10MOmega/sq) combined with a symmetrical electrode structure, enabling us to manufacture MLCLs with short f-numbers, large depths of focus, and low aberrations.

Electrically tunable liquid-crystal wave plate using quadripolar electrode configuration and transparent conductive polymer layers.

We present the realization of an electrically tunable wave plate, which uses a nematic liquid-crystal (LC) phase retarder that allows fast and continuous control of the polarization state. This device is built using a quadripolar electrode design and transparent conductive polymer layers in order to obtain a uniform electric field distribution in the interelectrode area. With this realization, we obtain a high degree of control of the orientation of the electric field and, consequently, of the LC director. Indeed, this modulator outperforms classical bipolar LC cells in both optical path variation (>4 microm) and LC rotation speed (0.4 degrees/micros).