Liquid refractive index measurement based on liquid crystal on silicon

In this paper, a method for measuring the liquid refractive index based on liquid crystal on silicon (LCoS) is presented. The liquid measuring chamber is composed of two optical lenses, an inlet, and an outlet. By filling the liquid with different refractive indices, the liquid measuring chamber has different focal lengths according to geometric optics. As a reflective micro-display device, the LCoS is another key component, in which the liquid crystal (LC) molecules are arranged in a nematic phase. The programming function of the LCoS, based on the interaction of incident light and the LC molecules in the LCoS, enables the LCoS to form as a digital lens. By using the measuring chamber in the optical system and adjusting the focal lengths of the digital lens, which is loaded on the LCoS, the refractive index of the liquid can be calculated accurately when the sensor receives the focused spot. The experimental results verify the feasibility of our proposed method.