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The purpose of the invention is to provide a light guide of a variety of forms having a uniform distribution of brightness in the plane and a planer light source device for a liquid crystal display device which uses such light guide. The light guide comprises a first surface which is a surface to wh

The purpose of the invention is to provide a light guide of a variety of forms having a uniform distribution of brightness in the plane and a planer light source device for a liquid crystal display device which uses such light guide. The light guide comprises a first surface which is a surface to which a natural polarization light is incident and a second surface other than the first surface which is an exit surface of a specific polarization light into which, said natural polarization light is modulated, wherein;

대표청구항 ▼

[ What is claimed is:] [1.]1. A planar light guide, comprising:a polarization separator having a planar light entrance surface upon which unpolarized light that travels in a propagation direction is incident at a generally a right angle;said polarization separator having a planar light exit surface

[ What is claimed is:] [1.]1. A planar light guide, comprising:a polarization separator having a planar light entrance surface upon which unpolarized light that travels in a propagation direction is incident at a generally a right angle;said polarization separator having a planar light exit surface that extends perpendicular to said light entrance surface and parallel to said propagation direction, and from which polarized light exits said polarization separator;said polarization separator having a plurality of planar light-refracting interfaces that are located below said light exit surface;said light-refracting interfaces comprising a plurality of planes that are inclined to said light exit surface;said light-refracting interfaces being formed by a physical engagement of a first and a second sheet of light-transparent material that extend parallel to said light exit surface;said first and second sheets of material having different index of refractions;said refracting interfaces being formed by a first series of isosceles triangle columns whose apices are directed upward toward said light exit surface, each triangle column within said first series of triangle columns alternating with a second series of isosceles triangle columns whose apices are directed downward and away from said light exit surface;with height lines that equally divide said apices extending perpendicular to said light exit surface, and with opposite equal length sides of each triangle column extending at an angle of .theta..sub.B, +/-20-degrees relative to said propagation direction;said angle .theta..sub.B being an angle that satisfies Brewster condition; anda difference between the said index of refraction of said two materials being between 0.001 and 1.0.