In the field of augmented reality/virtual reality head-mounted displays or eyeglasses, electro-optical tunable lenses have great potential to resolve the issue of accommodation-convergence conflicts and to correct vision problems. A high-quality tunable lens with a large field of view is highly desired for these near-to-eye applications. Recently, gradient refractive index tunable liquid crystal lenses with a concentric ring electrode design and segmented phase profile have received attention due to their compactness, low-voltage requirement, and ability to provide a large aperture size while maintaining a fast-switching speed. However, this design can result in degradation of optical quality, causing haze from the phase reset boundaries and electrode discontinuity. We analyze the cause of haze and presents solutions to reduce these effects, and we experimentally validate them.
An optical imaging system’s image quality can deteriorate due to uncorrected astigmatism and defocus. An approach to correct these issues is proposed, which involves a non-mechanical, electronically adjustable system. This system consists of three liquid crystal-based cylindrical lenses, which adjust optical power depending on applied voltage values. The advantages of this system include a simple and low-cost structure, large aperture size, low-voltage drive, and compact design. This non-mechanical solution has great potential for various applications, such as wavefront correction for large telescopes, microscopy, augmented reality/virtual reality, and prescription eyeglasses. Design, fabrication, and optical characterization of the proposed device are discussed.
Continuous tunable lenses have significant prospect to replace conventional bulky fixed power lens system. However, lightweight, fast response, large aperture (⪆1 cm) tunable lens system remained an active challenge in the field of adaptive optics. While many approaches have been reported so far, very few can be realized for practical application of optics that requires large aperture size tunable lenses. Gradient Refractive Index (GRIN) liquid crystal lenses are one of approach which gives good control over the continuous tunability, however, large aperture device suffers from very low switching speed. In this paper, without compromising the switching speed, we are reporting 5 cm aperture size GRIN liquid crystal based continuous tunable focus lens. Reported approach implements Fresnel lens like parabolic shaped segmented phase profile instead of continuous phase, which is obtained from segmented voltage distribution. The designed lens is flat, fast switching (⪅500 ms), thin (⪅ 2 mm), light weight (⪅ 10 gm), low voltage driven (⪅ 5 V), also tunable continuously between positive to negative power. Such compact system with good optical quality scopes for potential application in eyeglasses to solve presbyopia, accomodation-convergence mismatch issue in emerging head mounted display technology, and many other imaging systems.
There is a need for a tunable lens technology in AR/VR head mounted displays to solve the accommodation-convergence mismatch issue. Liquid crystal lens technology is one of the promising approaches to achieve a simple, low cost and compact design. However, it is challenging to make a lens with a 5 cm aperture with the required variable power range of 0 D to 2.50 D, with an acceptable switching speed. In the device considered here, we use multiple cell design with segmented phase profile to achieve a tunable focus ability with switching speed under 500 ms. To simplify the electronics of the device, inner-ring resistor network have been used between concentric electrodes. Previously, the effect of the electrode gaps has been studied and the improvement with floating electrodes demonstrated for lower power and smaller aperture (2 cm) LC lenses. In this paper, the effect of the fringing electric fields associated with the discrete electrodes are explored through modeling and imaging characterization, and an improved fabrication process are detailed.
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