US 5,838,403 A · Liquid crystal display system with internally reflecting waveguide for backlighting and non-Lambertian diffusing

Abstract

Systems and methods for providing an LCD with a collimated backlight and a non-Lambertian diffuser are described. An LCD system includes: an illumination source for producing light; a collimating waveguide optically connected to the illumination source, the collimating waveguide including a top surface, an incident end and a plurality of substantially parallel optical elements for redirecting light from the incident end to, and through, the top surface, each of the plurality of substantially parallel optical elements including a first facet that is nonparallel to the top surface and a second facet that is nonparallel to the top surface; a reflector optically connected to the light source and optically connected to the collimating waveguide, the reflector (1) at least partially surrounding the illumination source, and (2) reflecting light from said illumination source to said incident end by direct reflection; a liquid crystal display optically connected to the collimating waveguide; and a non-Lambertian diffuser optically connected to the liquid crystal display for directing light from said liquid crystal display. The light from the reflector is directly incident upon the incident end. The systems and methods provide advantages in that the light from the LCD is bright and homogenous.

Claims67

Dependent claims

An apparatus, comprising:

an illumination source for producing light;
a first collimating waveguide optically connected to said illumination source, said first collimating waveguide including a top surface, an incident end and a first plurality of substantially parallel optical elements for redirecting light from said incident end to, and through, said top surface by total internal reflection, each of said first plurality of optical elements including a concave first facet that is nonparallel to said top surface and a second facet that is nonparallel to said top surface, said second facet being concave with respect to said top surface;
a second collimating waveguide optically connected to said first collimating waveguide, said second collimating waveguide including an upper surface and a second plurality of optical elements for redirecting light from said top surface through said upper surface;
a diffuser for homogenizing light optically connected to said second collimating waveguide;
and
a reflector optically connected to said light source and optically connected to said first distributed wedge collimating waveguide, said reflector (1) at least partially surrounding said illumination source, and (2) reflecting light from said illumination source to said incident end by direct reflection.

3 more elements

A backlight comprising:

a collimating waveguide having a light input end, a top surface, a bottom surface, and opposing sides;
said bottom surfaces converging toward said top surface in a direction along said backlight away from said light input end;
said bottom surface comprising a plurality of straight facets having a density .rho. distributed along said bottom surface in a direction along said backlight away from said light input end and extending at least part way between said opposing sides;
each said straight facet having a straight facet bottom surface which converges toward said top surface in a direction along said backlight away from said light input end at an angle less than approximately 5.degree.;
each said straight facet bottom surface of each said straight facet being parallel to each said straight facet bottom surface of each other said straight facet;
said collimating waveguide reflecting light rays entering said light input end in accordance with total internal reflection and at an angle greater than a total internal reflection critical angle;
said facets causing light entering said light input end and having an angle near said total internal reflection critical angle to exit said top surface at an angle nearly tangential to said top surface and of approximately 2.gamma.;
a second collimating waveguide optically coupled to said collimating waveguide, said second collimating waveguide including an upper surface and a second plurality of facets for redirecting light exiting said top surface through and out said upper surface at an angle substantially greater than 2.gamma. and approximately normal to said top surface;
a non-Lambertian diffuser optically coupled to said second collimating waveguide for directing light exiting said second collimating waveguide.

6 more elements

Dependencies are inferred from the claim text.

Liquid crystal display system with internally reflecting waveguide for backlighting and non-Lambertian diffusing

Life of this patent

Liquid crystal display system with internally reflecting waveguide for backlighting and non-Lambertian diffusing

Life of this patent

Abstract

Claims67