We have developed a simple optical method based on measurements of phase retardation[1] versus out-of-plane cell rotation angle and data analyzed by extended Jones matrix method to obtain pretilt angles of inverse twisted nematic (ITN) and tilted homeotropic liquid crystal (LC) cells. In our Jones-matrix calculations, we have assumed a constant pretilt angle as the LC-director tilt angles throughout the ITN cell as well as the tilted homeotropic cell. We have compared the measured pretilt angles of the ITN cell with those of an accompanying tilted homeotropic (ATH) cell. The results showed increasing discrepancies between them with increasing rubbing depth for LC alignments. However, these discrepancies could be explained by assuming that the surface-LC tilt angle of the ITN cell was equal to the measured pretilt angle of the ATH cell to generate a convex-type LC-director-deformation profile within the ITN cell based on Oseen-Frank elastic continuum theory with infinite anchoring energies. The average of the LC-director tilt angles over this profile was equivalent to the measured pretilt angle of the ITN cell.

For the first time we report direct measurements on asymmetric pretilt angles of OCB cell (pi‐cell) with results in good agreement with the pretilt angles measured on accompanying tilted homogenous cells fabricated by using same material and processing steps. Our method has potential applications to monitor the changing in pretilt angles of fresh made or aged pi‐cells.

No abstract

We have developed a simple optical method and analyzed data by extended Jones matrix method to obtain pretilt angles of invesed twist nematic (ITN) and tilted homeotropic liquid crystal (LC) cells. We have compared the measured pretilt angles of the ITN cell with those of an accompanying tilted homeotropic (ATH) cell. The results showed increasing discrepancies between them with increasing rubbing depth for LC alignments. However, these discrepancies could be explained by assuming that the surface-LC tilt angle of the ITN cell was equal to the measured pretilt angle of the ATH cell to generate a LC director-deformation profile within the ITN cell based on Oseen-Frank elastic continuum theory with infinite anchoring energy. The average of the LC tilt angles over this profile was equivalent to the measured pretilt angle of the ITN cell. Author KeywordsLiquid crystal deformation, inverse twisted nematic (ITN), pretilt angle of ITN cell P-106 / S.-Y. Wang SID 2014 DIGEST • 1387

Laser speckle contrast imaging (LSCI) can generate retinal blood flow maps inexpensively and non-invasively. These flow maps can be used to identify various eye disorders associated with reduced blood flow. Despite early success, one of the major obstacles to clinical adoption of LSCI is poor repeatability of the modality. Here, we propose an LSCI registration pipeline that registers contrast maps to correct for rigid movements. Post-registration, intra(same)-day and inter(next)-day repeatability are studied using various quantitative metrics. We have studied LSCI repeatability intra-day by using the coefficient of variation. Using the processing pipelines and custom hardware developed, similar repeatability was observed when compared to previously reported values in the literature. Inter-day repeatability analysis indicates no statistical evidence (p = 0.09) of a difference between flow measurements performed on two independent days. Further improvements to hardware, environmental controls, and participant control must be made to provide higher confidence in the repeatability of blood flow. However, this is the first time that repeatability across two different days (inter-day) using multiple exposure speckle imaging (MESI) has been analyzed and reported.