Design And Development For Precise Measurement System Of Optical Phase Retardation Of Different Wavelength Wave-Plates Using Single Wavelength Laser

The development of optical precision measurement instrument is important guarantee for morden optical technology. Optical phase retardation measurement is very fundamental and important in physical optics and optical instrumentation.Wave-plates are typical polarization optical elements and widely used as phase retardation devices in photoelasticity, polarimetry, all fiber optical current transducer, optical communications, and remote sensing polarization imaging system, etc. The accuracy of phase retardation provided by a wave-plate significantly affects the performances of the instrument and the system employing the wave-plate. Many classical and advanced methods have been proposed and used for measuring the phase retardation given by a wave-plate. But there are wavelength bandwidth limitations which measuring the wave-plate with the same wavelength in most of these methods. Accordingly, we propose a new method of cross-wavelength measurement to provide high precision phase retardation measurement at any wavelength by actually measuring the phase retardation using few or just one laser line. Four parts are introduced respectively, that is the optical modulation compensation unit, the mechanical structure and the control unit, the photoelectric detection unit and the software of data processing unit. The measurement theory of the integrated system is also analysed. After the experiments study and the optimization of development, transformation of the system of commercialization is achieved.1. Modulated-polarization light producted by electric light modulator and attached with cosine signal is used to accurately determine the orthogonal zeros of the system. A Babinet-Soleil compensator is employed to measure the optical phase retardation. The advantage is that it can precisely locate the zeros using modulated-polarized light.2. The system should be calibrated before measurement. We use different wavelengths for calibration for fitting a curve by least square method. Linear relationship between apparatus constant and laser wavelength is found to propose a wavelength cross-measurement algorithm for measuring the phase retardation at any wavelength. The results of wave-plate measurements using both direct laser lines and cross-wavelength measurement are presented and compared. The average accuracy of less than 0.2% and a relative accuracy of less than 0.3% are obtained. The proposed system can offer an accuracy of measurementλ/1000 for laser line measurements.3. After the system optimization, we have also presented a new commercial cross-wavelength measurement device which uses only one laser and allows the system to measure the phase retardation of a wave-plate at any wavelength.