“…Similar observations have also been reported by others that the phase retardation in the deep area may accumulate relatively fast in some locations of cartilage samples. 15,26 However, in some other reported literature, 14,16,20 low birefringence has been found in deep zone at normal incidence. The difference in the results shows that the quantification of birefringence in the deep zone is quite sensitive, and it may depend on the types of samples, topographical locations, illumination angles, etc.…”