We have developed an instrument that measures fast transient birefringence and polymer chain orientation angle in complex fluids. This instrument uses a dual-crystal transverse Electro-Optic modulator with second crystal's modulation voltage applied 180$DGR out of phase from that of the first crystal. The precise measurement of birefringence using this instrument strictly depends on three separate signals. These are the dc, first and second harmonic voltages. The harmonics are relatively noise-free while the dc signal is subject to appreciable noise. Therefore, wavelet based noise reduction techniques have been used to denoise the measured dc signal. The de-noised signal was recombined with the harmonic signals to obtain retardation and birefringence measurements using a high precision 1/16 wave plate in a rotating mount to simulate a birefringence sample.
展开▼
