The Wider View
The bright and beautiful image from the liquid crystal display however, was not equally accessible to all. For the viewer looking from an angle to the display, the contrast, grayscale, and color presented by the twisted nematic screen was not at all the same as when viewed head on; and the more oblique the viewing angle, the greater the discrepancies. For computer monitors and notebook screens, perhaps this viewing angle problem is not all that important, but for the family watching television in the living room, a viewing angle of at least 80° is a commercial necessity, and for the crew and passengers on commercial aircraft, the instruments readings of the pilot and co-pilot should be the same, otherwise the consequences could be dire indeed.
The imperfect wide viewing angle image is basically due to the different optical path taken by the light to the oblique viewer’s eye, which will cause a different phase retardation from that of the head-on view. The direction of vibration of the electric vector (E) of a light beam is perpendicular to its direction of propagation; linearly polarized light, upon entering an anisotropic medium having different dielectric constants in different directions, will be phase retarded depending on the angle that the transverse vibrations of the E-vector makes with the directions of different indices of refraction in the medium. For the different incident angles and subsequent longer optical paths of oblique angle viewing, the phase ...