Multifocal method using Liquid Crystal

1. Multifocal method using Liquid Crystal Xuan Wang Oct, 28th

2. Multifocal method using Liquid Crystal • High-speed switchable lens enables the development of a volumetric stereoscopic display. Love, Gordon D., et al. Optics express 17.18 (2009): 15716-15725. • A multi-plane optical see-through head mounted display design for augmented reality applications. Liu, Shuxin, Yikai Su et al. Journal of the Society for Information Display 24.4 (2016): 246-251. • Fast-response switchable lens for 3D and wearable displays. Lee, Yun-Han, Fenglin Peng, and Shin-Tson Wu. Optics express 24.2 (2016): 1668-1675.

3. High-speed switchable lens • High-speed switchable lens enables the development of a volumetric stereoscopic display They present a new stereoscopic display system using a high-speed, switchable lens integrated with computer display. The lens is placed in front of the eye and is synchronized to the graphic display such that each depth region in the simulated scene is presented when the lens is in the appropriate state. In this way, they construct a temporally multiplexed image with correct focus cues.

4. High-speed switchable lens • Key Element • 1 Polarizer • 2 Birefringent lenses • 2 Liquid Crystal Modulators

5. High-speed switchable lens • Lens Performance The four focal states are shown. The distance: (a) 285 mm (b) 375 mm (c) 590 mm (d) 970mm

6. High-speed switchable lens • Setup

7. High-speed switchable lens • Results

8. High-speed switchable lens • A multi-plane optical see-through head mounted display design for augmented reality applications They presented a design for an optical see-through HMD utilizing multiplane display technology. Polymer-stabilized liquid crystal scattering shutters were used in projecting slices of a 3D scene. A proof-of-concept two-plane optical see-through HMD prototype is demonstrated.

9. High-speed switchable lens • Polymer-stabilized liquid crystal scattering shutter

10. High-speed switchable lens • Setup

11. High-speed switchable lens • Results

12. Fast-response switchable lens • Fast-response switchable lens for 3D and wearable displays They presented a focus-switching device for 3D head mounted displays. A twisted nematic (TN) cell liquid crystal is used as polarization switch to control the optical path length through the system. Different polarization state leads to different path length in the proposed optical system, which in turn results in different focal length. They also proposed some configuration to cascade such device structures together to generate more different focuses for 3D displays.

13. Fast-response switchable lens • Key Element The LC device used here is a 90°twisted nematic (TN) cell. This is an electrically tunable achromatic half-wave (λ/2) plate. For a linearly polarized input light, say p-wave, the output light can be converted to s-wave if the applied voltage is off (V = 0) or it remains p-wave if V>>Vth (threshold voltage).

14. Fast-response switchable lens • Experimental setup The total path length from L1 to L2 for the red route is d1 = 43 cm. The total path length from L1 to L2 for the blue route is d2 = 48 cm

15. Fast-response switchable lens • Results

16. Fast-response switchable lens • Features • Response time • The rise time and the decay time to be 4.3 ms and 1.0 ms, respectively. Note that the response time was not optimized due to the limited TN cells they have. (the rise time and the decay time can reach 2.8 ms and 0.6 ms theoretically) • Voltage • The power they use is an AC voltage(1kHz) of only 10V, which is safe for human. • Low chromatic aberration • PBS, TN and retardation plates are all achromatic

17. Fast-response switchable lens • Configuration

18. Thank you!