Electrically tunable liquid crystal lens with suppressed axial chromatic aberration

We demonstrate an electrically tunable dual-switching liquid crystal lens with suppressed axial chromatic aberration. A liquid crystal (LC) switch twisted vertical alignment (TVA) mode is utilized in the lens. By using a chiral nematic LC with a proper cell thickness-to-helical pitch ratio (d/p) and a thick cell gap, the lens provides a low director rotation rate, and the focal length dispersion at different wavelengths is reduced. The image quality of the LC lenses with different d/p ratios is investigated. The axial chromatic aberration can be reduced up to 30% when the d/p ratio is 0.5 ± 0.05. Comparing with a traditional liquid crystal lens without a twisted-nematic structure (i.e., d/p = 0), the contrast ratio of the image obtained from a lens with a twist structure (d/p = 0.5 ± 0.05) increases by 15%. The static voltage response from a LC cell shows that the suppressed chromatic aberration results from the suppressed wavelength dispersion of phase retardation-voltage relation of the TVA mode.