Self-calibrated global rainbow refractometry: a dual-wavelength approach

Calibration of the relationship between the scattering angle and the CCD pixel is a key part of achieving accurate measurements of rainbow refractometry. A novel self-calibrated global rainbow refractometry system based on illumination by two lasers of different wavelengths is proposed. The angular calibration and refractive index measurement of two wavelengths can be completed simultaneously without extra measurement devices. The numerical and experimental results show the feasibility and high precision of the self-calibration method, which enables the rainbow refractometry to be implemented in a more powerful and convenient way. The self-calibrated rainbow system is successfully applied to measure the refractive indices of ethanol-water solutions with volume concentrations of 10% to 60%.