Observation of retardation waviness
During this experiment, it was observed that under certain rubbing conditions, a periodic change in the retardation distribution occurs. The figure below illustrates this phenomenon. The magnitude of the retardation is represented by the height of the yellow bars. It can be seen that the retardation changes periodically in one direction. This periodic change in retardation is called “waviness” in this paper. This waviness was observed when the birefringence was measured while moving the sample at intervals of about 0.2 mm. The cause of the waviness and whether or not it can be used as a criterion for judging whether rubbing is good or bad is not yet known. However, some people believe that there should be some correlation between the swell and the display characteristics. We have confirmed that the ABR-10A has good measurement reproducibility, so we can conclude that it is a difference in measurement resolution.
The following four tables summarize the relationship between the strength of the rubbing and the pitch of the swell. It can be seen that the pitch of the swell changes depending on the rubbing conditions.
The next page shows the results of a study of changes over time.