| Description |
Refractive errors of vision are very common in all human beings, namely myopia, hyperopia, presbyopia, and astigmatism. Worldwide, over 1 billion people were estimated to suffer from presbyopia with around 410 million of them suffering from near vision loss. The result of refractive errors is blurred vision, affecting our ability to focus on near or far objects. The utilization of conventional fixed, uniform, or graded power eyeglasses is generally unsatisfactory as fixed power eyepieces cannot provide any accommodation restoration. In this dissertation, we demonstrate compact tunable-focus liquid lenses suitable for ophthalmic adaptive eyeglasses. These lightweight, low footprint tunable-focus lenses augment the accommodation range of vision, thus restoring normal vision function. First, a tunable-focus large aperture liquid lens is constructed using shape memory alloy (SMA) springs as actuators. The lens mainly consists of a shallow liquid-filled cylindrical cavity bound by a thin compressible annular rim and encapsulated by a flexible circular membrane on the top of the rim and a rigid circular plate at the rim bottom. The lens optical power is adjusted by a controlled compression of the annular rim in vertical direction via actuation of the three shape memory alloy (SMA) springs. Second, we report a compact tunable-focus liquid lens with large aperture actuated by piezo-electric bimorph actuators. The lens consists of a rigid annular sealing rim encapsulated by two membranes forming a sealed chamber with a fixed volume of high index optical fluid filled in it. When a normal force is applied to the bottom piston via piezo-electric bimorph actuators, the shape of the top membrane is changed, causing the change of focal length. We did the simulation using Python to improve the lens optical quality, and lens parameters were determined from the simulation. While simulation and fabrication of the tunable-focus liquid lens using piezo-electric bimorph actuators, we noticed the effect of tension over lens membrane to determine lens optical power and optical quality. This gave us the idea of implementing tunable-focus liquid lens by changing the tension of the membrane. The theory, simulation, fabrication, and experimentation for these three different lenses are discussed in this dissertation. |
