Abstract
A hole-patterned electrode liquid crystal (LC) lens with electrically switching coaxial bi-focus and single focus modes of tuning is demonstrated. The proposed LC lens mainly consists of a two LC layer (TLCL) structure with different thicknesses to achieve higher focusing power than the conventional hole-patterned electrode LC lens with the same aperture size. In the TLCL structure, one LC layer, doped with 3 wt % RM257, was photopolymerized to achieve a fixed focusing power of 18.5 Diopter. Due to polarization dependence in TLCL lenses, an additional 90° twisted nematic (TN) cell was used to change the incident polarization in order to switch lens functions on or off. As a result, a fixed focusing power of 18.5 Diopter was achieved when voltages of 10 Vrms were applied to the 90° TN cell. In addition, the switching capabilities of the bi-focus and single focus modes were achieved when operating individually with applied voltages from 20 Vrms to 90 Vrms, and higher voltages of over 90 Vrms, respectively. The maximum focusing power in the fabricated TLCL lens is 30.9 Diopter.
Highlights
Owing to the key characteristics of optical birefringence and dielectric anisotropy, liquid crystals (LCs) are usually used to fabricate numerous electro-optical devices such as tunable LC lenses, displays, phase modulators, and optical gratings, among others [1,2,3,4]
The operation principle of tunable LC lenses is mostly electrically driven in order to reorient LC molecules to achieve ideal gradient refractive index distributions, so that incident light passing through them modifies its wave front to focus or defocus
We demonstrate that a hole-patterned electrode LC lens is capable of electrically tuning focuses and switching between single and bi-focal modes
Summary
Owing to the key characteristics of optical birefringence and dielectric anisotropy, liquid crystals (LCs) are usually used to fabricate numerous electro-optical devices such as tunable LC lenses, displays, phase modulators, and optical gratings, among others [1,2,3,4]. LC lenses [10], cholesteric LC lenses [11], and circular hole-patterned LC lenses [12,13,14] Among these types of LC lens, the hole-patterned electrode LC lens possesses the features of tunable focus, a wide lens aperture size range, and easy fabrication. The hole-patterned electrode LC lens has been widely investigated and developed in numerous fields including imaging systems [15,16,17], 3D displays [18,19,20], and biological applications [21,22]. Higher focusing power in the single focal mode is available for this proposed LC lens compared with the conventional hole-patterned electrode with the same aperture size. After determining the suitable thickness of the two LC layers, this TLCL LC lens is characterized by a free disclination line and high focusing power
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