Optical thickness measurement of stacked glass based on balanced cross-correlation

We propose a method of measuring the optical thickness of stacked glass using an absolute distance measurement based on the principle optical balanced cross correlation. The optical balanced cross correlation system is mainly composed of a nonlinear crystal, which is used to generate two second-harmonic sub-pulses. The balanced cross correlation signal will be generated while the measurement pulses and the reference pulses are overlap by scanning the repetition rate. The signal is used as an error signal to lock the repetition rate of the laser by controlling the cavity length. In this study, multiple glasses are pasted one by one with different thickness and the thickness of each glass is measured with sub millimeter precision.