Abstract
Purpose :
Polarization-independent tunable modulators for broadband visible light have wide applications in vision care, including treatment of amblyopia, light-responsive smart sunglasses, variable attenuator for ophthalmic optical systems, etc. There are stringent requirements on these tunable modulators such as low operation voltage (<24 volts), high contrast ratio (>100), fast response (~ subsecond), polarization independent, and broadband (400-700nm). To meet all these requirements with a single device is quite challenging. Previous technologies using electrochromatic, photochromatic, and liquid crystal materials do not satisfy all these requirements simultaneously. Recently we have developed two new techniques towards this goal by using different liquid crystal mixtures.
Methods :
In one approach, we used a dual-frequency cholesteric liquid crystal host doped with silica nanoparticles and the mixture can dynamically self-organize into a helical configuration and exhibit multi-stability, that is, homeotropic, focal conic, and planar states, depending on the frequency applied at sustained low voltage. In another approach, we chose to use a cholesteric liquid crystal with dichroic dye. By tuning the amplitude of the applied voltage, the orientations of the liquid crystal droplets are also stable at multiple states, and the scattering and absorption properties of the mixture are modulated correspondingly. A model eye setup has been built to demonstrate the performance of both modulators.
Results :
For the first device, the amplitude of the field is fixed to be 14.4Vrms but the frequency is changed from 40k Hz to 80k Hz, and the transmission can be continuously tuned. It is very interesting that the contrast of the image also changes continuously under the influence of the electrical field. This could be very useful in optometry since the contrast can be a more sensitive parameter for early diagnosis of vision impairment. For the second device, a record high contrast above 300 has been achieved with a voltage around 20 Vrms. Both devices are polarization-independent and broadband with a response time near 150 milliseconds.
Conclusions :
The new liquid crystal eyewear has unprecedented optical performance with potential applications for treatment of amblyopia and light-responsive smart sunglasses
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.