Electrically tunable achromatic liquid crystal bifocal lens.

In this Letter, a longitudinally achromatic liquid crystal bifocal lens (LABLs) is proposed. The relative intensities of the two foci can be electrically controlled, with applied voltages of 0 and 15 V corresponding to focal positions of f = 150 mm and f = 250 mm, respectively. The LABLs are composed of three individual lenses targeting 445 nm, 520 nm, and 638 nm, respectively. Each individual lens achieves a transmittance exceeding 95% at the corresponding target wavelength and has an aperture of approximately 5 mm. The integrated LABLs experimentally demonstrate tunable focal lengths and effective suppression of chromatic aberration. These features make the proposed device promising for applications in industrial machine vision, astronomical telescope systems, spectral imaging, and virtual and augmented reality (VR and AR) displays.