Abstract
ABSTRACT We describe in this paper a special polarimeter for measuring linear birefringence in transparent optical samples. The polarimeter employs two photoelastic modulators that operate at different frequencies (50 KHz and 60 KHz). The resulting electronic signal at the detector is processed using two methods: demodulation by lock-in amplifiers or using Fourier analysis of a digitized waveform. We compare the re sults obtained by using the two signal processing methods in this special polarimeter and discuss how each method benefits selected applications. Keywords : special polarimeter, photoelastic modulator, birefringence, wave plate, stretched polymer, on-line monitor 1. INTRODUCTION In recent years, we have developed several models of Exicor ® linear birefringence measurement systems for different industrial and research needs. 1 These Exicor models are based on the working principle that we established for the configuration of single photoelastic modulator (PEM) and two detecting channels.
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