Liquid Crystal Microlens Arrays Using Patterned Polymer Networks

4 Liquid Crystal Microlens Arrays Using Patterned Polymer Networks 

As described previously, polymer patterning techniques can be used to define LC microlenses. However, it is relatively difficult to control lens shapes with such technique, and the lens surface thus formed is rather rough as a result of the random phase separation between the LC and the prepolymer. Therefore, obtaining microlens arrays with high optical performance while keeping the fabrication process simple remains a challenging task. 

In comparison with other tunable microlenses, this fabrication method can obtain an ideal spherical shape and glazed surface for each microlens. Consequently, imaging quality and optical efficiency were much improved. 

Procedures for fabricating polymer network liquid crystal microlens arrays. Source Ren, H.W., Y.H. Fan, and S.T. Wu. 2004. Optics Letters, 29(14), 1608-1615. With permission.) 

To obtain homogeneous LC alignment, the inner surface of the top substrate was coated with a polyimide layer and rubbed in one direction. The LC mixture was heated above its dear point and then slowly cooled to room temperature. The sealed cell was then exposed to UV light at 10 mW/cm intensity for 60 min to form the needed polymer networks. The UV curing was conducted at room temperature. 

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