Birefringence imaging

Many transparent materials are optically anisotropic i.e. the refractive index varies with the polarisation orientation of the light. The variation, birefringence, can reveal the underlying anisotropy of the material, whether this anisotropy is caused by the structure of the material or by applied stress. Several methods have been developed to measure the birefringence, although only two imaging microscope techniques, the 'rotating polariser technique' and the 'Polscope', capable of separating the magnitude of the anisotropy (#delta# or vertical bar sin#delta# vertical bar), its orientation (#phi#) and its transmission (l_0) are in common use today. In this thesis the rotating polariser technique has been completely revised, with a new and easily accessible user interface as a result. Calibration routines and several analytical tools have been developed. The technique is now capable of measuring the change in birefringence during phase transitions to very high a degree of precision. Examples of the use of the technique in the study of phase transition are presented. The shifted wavelength rotating polariser (SWRP) method has been developed, as the first fully automated method, to enable the measurements of higher order birefringence. The improved rotating polariser technique has been applied to conoscopic images, showing for the first time the separation of vertical bar sin#delta# vertical bar and #phi# in such images and has been used in the analysis of collagen in bone and in tendons. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:D213849 / BLDSC - British Library Document Supply CentreGBUnited Kingdo