Tunable lenses, lenses that can adjust their power without lens assembles. These lenses are made by entrapping liquids in clear elastic membranes and actuated mechanically (by pressure) or electronically (bellow actuators). These lenses have been out there for quite a while but their full potential is not yet realized due to aberration inducing spherical profile, single axis tuning and limited actuation cycles.
Aberration problem can be solved by actuating the membrane at aspheric profile. This is done by using two liquid enclosures, one to actuate and another to provide a path for aspheric curve. The complete mechanism and obtained results are shown in the illustrated figure. The aberrations have been reduced significantly owing to complex machined profiles. First of its kind aspheric curves were obtained in tunable optics, paving the way for mainstream usage to replace complex lens assemblies.
Multi-axis tuning is done by a multi way triggering method with radial and axial actuation to focus anywhere along a given volume just like our eyes. This is done by embedding a tunable lens in a spherical profile. Axial focus is obtained by actuating tunable lens and radial focus is obtained by voltage difference between sphere surface and lens surface. A micro solenoid grid is formed to support the actuation or threads can be used for low power low accuracy applications wherein threads physically locate the focal points by tension and relaxation. Such lenses are a vital part for VR domains as these lenses can act as human eye and so a true VR experience like “focus on and object but still aware of surrounding can be implemented with ease.”
The flexible membrane was developed in situ and was engineered for better actuation cycles and optical properties. The uncured silicon RTV was mixed with low density PDMS to eliminate free radicals and replace them with organic bonds. Then the mixture was cured at high pressure and room temperature which resulted in lower grain boundaries. A clear silicon sheet was obtained. Further, silicone gel can be infused as an optical additive to increase the internal surface area exposed to ambient light.
A light field hologram generation mechanism is now worked upon using micro arrays of such tunable lenses to create a 3D Light Holographic field. This can potentially revolutionize the entire 3D experience. Such a holographic field can also form a way to ultrafast additive manufacturing approaches as material can simultaneously cure at many nucleation sites at one time.