Measurement method of glass thickness and refractive index based on spectral interference technology

Based on spectral interference technique, a method for simultaneously measuring the thickness and refractive index of a glass was proposed. This method used the Michelson optical path to solve the interference signal received by the spectrometer through a Fourier transform algorithm to obtain the modulation period of the spectral interference fringe. The modulation period was determined according to the optical path difference formed between the measuring arm and the reference arm before and after the glass sample to be tested was placed in the measuring arm, and the geometric thickness and refractive index of the glass sample can be obtained. The method did not need mechanical scanning delay line and adopted the improved phase extraction algorithm in the Fourier domain, which improved the anti-interference ability of the measurement system and the detection speed was fast. The experimental results show that the thickness measurement accuracy of the glass sample is better than±1μm, and the refractive index measurement accuracy is ±5×10^-4.