The physical properties of liquid crystals determine their usefulness in applications like displays (computer monitors, cell phones, etc.). With clever algorithms it is possible to obtain many of these properties like switching speed, rotational viscosity, threshold voltage, etc. through the application of various drive waveforms to a small thin cell containing liquid crystal material sandwiched between two glass plates. We used a Xilinx FPGA driving a DAC to provide these drive waveforms, using direct digital synthesis (DDS) techniques for fine frequency control. The same FPGA also interfaces to an ADC that returns the current response of the LC sample. This response contains all the information needed to obtain many physical properties of the material. A USB interface transfers waveform and response data to and from the PC and provides control of the instrument functions.

In addition to developing the FPGA code, we also provided a PC user interface written in C# as a starting point for the clients’ own software development efforts. We also developed a circuit model of the system using Mathematica, and invented a new method of obtaining certain physical parameters based on insights from that model.