In this paper, we present a heterodyne interferometer using photorefractive cubic crystal Bi_(12)SiO_(20)(BSO) in a two-wave mixing configuration. The combination of heterodyne detection with the photorefractive process results in a well proven nosie insensitive technique with a large etendue (ability to work on roguh surfaces). In our case, by using a low gain and fast time response PRC such as BSO, the low frequency (less than kHz) and large amplitude noise that creates decorrelation and large phase shift of the speckle signal can be compensated. The heterodyne technique allows automatic absolute calibration of the displacement.
展开▼
