Emerging light fields from liquid crystal microlenses

Liquid crystal (LC) microlenses have a variable focal length with a change in applied voltage. These lenses have suitable dimensions and focal length variations for a wide range of applications where the absence of moving parts is favored. In this article we present the three-dimensional imaging of the emerging light fields from these lenses for the first time. This novel technique is evaluated as a measure of the optical performance of the microlenses. It is compared with the results obtained on an interferometer custom built for the investigation of the optical properties of micro-optics. These combined results make this the most detailed investigation of the optical properties of liquid crystal microlenses to date. The results are centered on a microlens with a diameter of 60 μm at the lower (0.09) and higher (0.11) numerical apertures achievable with these lenses. In previous studies on LC microlens cells the main area of investigation was the focal length ranges available for particular applications. Images have been taken with these lenses and interference patterns between the extraordinary and ordinary rays propagating through the cells have been presented to show the lensing properties of the cells. However, a detailed examination of their optical properties show that although this type of lenses can produce images at certain voltages they act as diffraction limited lenses only over a short voltage range. It is also shown that the optical properties can be improved by variation of the driving frequency of the applied voltage.