Compact light path and package for liquid crystal projection displays
First Claim
1. 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; and
said 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; and
a 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.
12 Assignments
0 Petitions
Accused Products
Abstract
An LCD projection display (120) houses a projection module (10) in which light propagates through an LCD module (38) at a shallow angle (62) that improves the contrast ration of and intentionally Keystones the image bearing light. The Keystoned light is reflected by a fold mirror (64) that is mounted at a 52° upward angle, which introduces more intentional Keystoning. A projection lens (16) is mounted coaxial to a tilted optical axis (12), but the Keystoned image bearing light is refracted about 10° off the optical axis and follows a Keystoning axis (70) through the projection lens. The light propagating from the projection lens is reflected by a main fold mirror (122) that is mounted at a 57° angle from the vertical to project the image bearing light onto a 10° slanted projection screen (98). Central light rays (102), image margin light rays (106), and the axial light rays (125) propagate unequal distances from the projection lens to the projection screen and are, therefore, unequally magnified to compensate for the Keystoning introduced by the LCD module. The steep mounting angle of the main fold mirror allows positioning it higher and more forward in the display, which reduces first surface reflections from ambient lighting and allows a significantly reduced depth dimension for the display.
-
Citations
17 Claims
-
1. 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; and
said 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; and
a 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.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
10.The apparatus of claim 1 in which at least one of the first and second aspherical Fresnel lenses have a center that is offset from the optical axis.
-
-
10. A high contrast-ratio liquid crystal projection display method, comprising:
-
providing a housing having a bottom surface extending parallel to a Y-axis and perpendicular to a Z-axis;
forming a projection screen on a front surface of the housing, the projection screen angled downward relative to the Z-axis;
positioning a main fold mirror above a projection module and angled downward relative to the Z-axis for reflecting image bearing light toward the projection screen;
supporting said projection module by the bottom surface;
propagating light along an optical axis of the projection module;
diffracting the light at a first angle relative to the optical axis with a first aspherical Fresnel lens;
positioning a liquid crystal display substantially parallel to the first aspherical Fresnel lens for transmitting the light received at the first angle and forming the image bearing light; and
diffracting the image bearing light at a second angle relative to the optical axis with a second aspherical Fresnel lens positioned substantially parallel to the liquid crystal display such that the image bearing light exiting the second aspherical Fresnel lens reflects off the main fold mirror and is displayed on the projection screen at a contrast ratio that ranges from at least 200;
1 to about 1,500;
1.
-
- 11. The method of claim 11 in which at least one of the first and second aspherical Fresnel lenses have a center that is offset from the optical axis.
Specification
-
- Resources
-
Current AssigneeA Division Of Planar Systems Clarity
-
Original AssigneeClarity Visual Systems, Inc. (Leyard Optoelectronic Co., Ltd.)
-
InventorsFogarty, John P., Clifton, Benjamin R.
-
Primary Examiner(s)DOWLING, WILLIAM C
-
Application NumberUS09/425,316Time in Patent Office663 DaysField of Search353/69, 353/70, 353/74, 353/77, 353/78, 353/98, 353/99, 353/119, 353/121US Class Current353/74CPC Class CodesH04N 9/3141 Constructional details ther...
