Chapter 2
Elastomeric Membrane Lens
A lens made of liquid but with at least one elastomeric membrane as its flexible boundary or all-soft elastomeric material is referred to as an elastic memb rane lens. When the volume of the lens is changed or redistributed, the shape of the lens surface profile can be changed accordingly. As a result, the reshaping of the lens surface causes the focal length of the lens to change without physical motion. The change of the lens surface is exhibited in a manner analogous to that of a human eye. The development of elastic membrane lens has been going for more than four decades. The earliest patent regarding the liquid lens with variable focal length was issued in 1968 (1). Since then, various actuation approaches, such as syringe (2–6), servo motor (7–9), piezoelectric (10–13), artificial muscle (14), and voice coil actuator (VCA) (15, 16) have been proposed to deform the shape of the lens surface.
In this chapter, we will first introduce the device structures and properties of the elastic membrane lenses. Next, we will compare the merits and demerits of each approach. The applications of the elastic membrane lenses will also be described. Finally, the remaining technical challenges of the membrane liquid lenses will be summarized.
2.1 Polydimethylsiloxane (PDMS) Membrane
In an elastomeric membrane lens, the elastic (or distensible) membrane is a key part of the lens. An ideal membrane material should have following properties:
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