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Angular dependence determination of LCD light shutters using Poincare sphere

Introduction. Dealing with problems of the propagation of polarized light through birefringent layers it is often necessary to determine the shape and the sense of rotation of the ellipseUtilizing standard light propagation equations results in rather complex calculationsPoincare sphere represent

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Angular dependence determination of LCD light shutters using Poincare sphere

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    1. Angular dependence determination of LCD light shutters using Poincare sphere Author: Andrej Vrecko Mentor: Dr. Janez Pir

    2. Introduction Dealing with problems of the propagation of polarized light through birefringent layers it is often necessary to determine the shape and the sense of rotation of the ellipse Utilizing standard light propagation equations results in rather complex calculations Poincare sphere representation It allows us to understand the origin of viewing-angle problems in LCDs Angular dependence of crossed polarizers Angular dependence of optical light shutter Compensated optical light shutter

    3. Characterization of the state of polarization by Stokes parameters To characterize the polarization ellipse three independent quantities are necessary (a1, a2 and d or a, b and ?) It is convenient to characterize the state of polarization by Stokes parameters

    4. Poincare sphere The following relations hold:

    5. Reference axes for Obliquely Incident Light Approximation of low birefringence y-z plane is the plane of incidence The plane perpendicular to k0 contains four important parameters

    6. Effect of birefringent material and transmission of incoming beam Additional slab of birefringent material Pure rotation about fast axiss representation point Q for an angle:

    7. Steps for calculating transmission Calculate position of fast axis of birefringent layers and the polarizer's and analyzer's transmission axis with respect to each s direction. Determine the rotation due to a birefringent layer. Rotate the state of polarization around calculated position of fast axis. Calculate the transmission.

    8. Crossed polarizers Polarizers and analyzers representation points depend on the viewing angle

    9. Crossed polarizers angular dependence High angularly dependent characteristics

    10. Description of the optical light shutter angular dependence Two state devices Different technical requirements Much higher driving voltages (high switching speed) than LCD screens Superior optical performances Solutions in LCD display industry not applicable Homeotropic LC orientation

    11. Negative birefringent c-plate and 1800 cell We developed the solution for manufacturing the negative birefringent c-plate compensation layer We also developed a novel concept of the LCD light shutter (1800 cell)

    12. Approximation 1800 cell a novel concept We can make advantage of the boundary a-plates

    13. Explanation with the use of Poincare sphere F: final state of polarization after the exit boundary plate To eliminate the light leakage final polarization must be opposite to the transmission axis of the analyzer A If there was no residual retardation (a-plates ~ 30 nm) final polarization would be at point P

    14. Angular dependence of uncompensated and compensated optical light shutter Result: optical light shutter with great angular dependence

    15. Conclusion Characterization of the state of polarization by Stokes parameters Poincare sphere representation for obliquely incident light Angular characterization of crossed polarizers Description of the optical light shutter angular dependence using Poincare sphere 1800 cell (patent) Negative birefringent plate (patent) In this way we succeded to develop optical light shutter with great angular characteristics

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