Converting natural light into light with planar polarisation in video image projectors

摘要

The converter includes a source (1) natural white light and a divider (3). The divider splits the beam into a reflected beam and a transmitted beam. The two beams consist of either s- or p-polarised light. The two planes of polarisation are orthogonal with respect to one another. A rotator (6) turns the plane of polarisation of one beam parallel to the other. A device combines the two emerging beams with the same polarisation. The beam divider is a stack of parallel plates of two distinct optical media which alternate with refractive index (nl,nm). The thickness of each plate is much greater than the wavelengths of coherence of the light coming from the source. The angle of incidence (theta) of the beam on the second plate (102) is eta /> eta b = arctg(nl/nm). eta b is the Brewster angle of incidence on the second plate (102) made up of material with second index.