Abstract
We propose and demonstrate a novel method to measure dynamic refractive index distributions using a combination of total internal reflection (TIR) and dual-channel simultaneous phase-shifting interferometry (DCSPSI). First, a right-angle prism is introduced into the DCSPSI system, the reflection phase variation induced by TIR, which contains the refractive index information of tested sample, can be achieved by the spatial carrier-frequency phase-shifting algorithm from a pair of interferograms with the phase shifts of π/2 captured by DCSPSI system. Second, based on the relationship between the reflection phase variation and the refractive index, the 2D refractive index distribution can be calculated easily. Importantly, the proposed TIR-DCSPSI method will supply a useful tool for dynamic refractive index distribution measurement of dynamic process, such as the droplet evaporation, mutual solubilization and diffusion of different droplets, cell culture, colloid curing, etc.
Highlights
Refractive index distribution measurement of dynamic process is an important content for studying physical changes such as evaporation of solution, mutual solubilization of different liquids, diffusion process, etc
To verify the validity of proposed total internal reflection (TIR)- dual-channel simultaneous phase-shifting interferometry (DCSPSI) method, three samples, e.g. deionized water, ethylene glycol and 80% glycerol-water mixture are chosen as the tested objects in an airtight laboratory with temperature of 25 °C and relative humidity of 60%
By combining TIR technique and our homemade DCSPSI system, we propose a novel TIR-DCSPSI method to achieve dynamic refractive index distribution during dynamic process
Summary
Refractive index distribution measurement of dynamic process is an important content for studying physical changes such as evaporation of solution, mutual solubilization of different liquids, diffusion process, etc. Though the SPSI method can effectively restrain the noise by multi-frame phase-shifting interferograms, the synchronization problem of multiple CCD cameras makes the system complex, and the corresponding synchronization error reduces the accuracy To solve those problems, a dual-channel simultaneous phase-shifting interferometry (DCSPSI) is proposed[24], in which a pair of interferograms with the spatial phase shift of π/2 is captured simultaneously at one-time single exposure, so the phase retrieval of dynamic process can be achieved with two-step phase-shifting algorithm. By combining total internal reflection (TIR) technique and our homemade dual-channel simultaneous phase-shifting interferometry (DCSPSI) system, we proposed a novel TIR-DCSPSI method to achieve dynamic 2D refractive index distribution during dynamic process.
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