Patent ID: 6273570
Filing Date: 2001-08-14
Classification: H04N

Abstract:
A high contrast-ratio liquid crystal projection display apparatus, comprising:a housing having a bottom surface extending parallel to a Y-axis and perpendicular to a Z-axis;a projection screen forming a front surface of the housing and angled downward relative to the Z-axis;a main fold mirror positioned above a projection module and angled downward relative to the Z-axis to reflect image bearing light toward the projection screen; andsaid projection module supported by the bottom surface and projecting the image bearing light toward the main fold mirror, the projection module comprising:a light source propagating light along an optical axis;a first aspherical Fresnel lens diffracting the light at a first angle relative to the optical axis;a liquid crystal display positioned substantially parallel to the first aspherical Fresnel lens and transmitting the light received at the first angle to form the image bearing light; anda second aspherical Fresnel lens positioned substantially parallel to the liquid crystal display and diffracting the image bearing light at a second angle relative to the optical axis, wherein the image bearing light exiting the second aspherical Fresnel lens, reflected off the main fold mirror, and displayed on the projection screen has a contrast ratio that ranges from at least 200:1 to about 1,500:1.