LCD with reduced canopy reflection

• US 5,715,028 A
• Filed: 11/07/1996
• Issued: 02/03/1998
• Est. Priority Date: 06/07/1995
• Status: Expired due to Term

• Current Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Original Assignee: OIS Optical Imaging Systems, Inc. (KOCH Industries Incorporated)
• Inventors: Abileah, Adiel, Xu, Gang, Brinkley, Patrick F.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/744,950
• Time in Patent Office: 453 Days
• Field of Search: 349/117, 349/96, 349/102, 349/74
• US Class Current: 349/117
• CPC Class Codes: G02F 1/133502 Antiglare, refractive index matching layers
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n

Abstract

A liquid crystal display and corresponding method are provided for reducing display image reflections off of a reflection point on an external medium (e.g. cockpit canopy or automotive windshield). A retarder is provided on the front side of the display so that the polarization direction of the display image is substantially parallel to the plane of incidence when the image reaches the reflection point. Additionally, the angle of incidence Θ_i is substantially matched to the Brewster angle Θ_p in order to maximize the reduction of reflection at the reflection point. The retarder has a retardation value of from about 220-320 nm according to certain embodiments, and is a 1/2 λ retarder according to preferred embodiments.

Claims

1. A liquid crystal display for directly transmitting an image to a viewer, the display comprising:

a liquid crystal layer;

front and rear linear polarizers sandwiching said liquid crystal layer therebetween;

the display being oriented so as to allow the viewer to directly view a transmitted image via a front surface of the display; and

a retarder disposed adjacent to a front surface of the front polarizer having a retardation value and a retardation axis selected for reducing image reflections off of an external medium.

2. The display of claim 1, wherein a retardation value (RV) of said retarder is approximately defined by ##EQU2## where "d" is a thickness of said retarder, "Δ

n" a birefringent value of said retarder, and "φ

" an angle defined between (i) a line or vector normal to the front surface of the display and (ii) a line or vector between a reflection point on the external medium and the front surface of the display.

3. A method of reducing liquid crystal display image reflections off of a reflection point on a substantially transparent external medium, the method comprising the steps of:

providing a liquid crystal display including a liquid crystal layer, at least a front polarizer or analyzer, and at least one retarder;

outputting an image from a front surface of the display toward a viewer so that the viewer directly views the image;

choosing a retardation value of the retarder for reducing reflections off of the substantially transparent external medium; and

positioning the retarder on or adjacent the display so that the retarder is disposed between the liquid crystal layer and the external medium so as to reduce image reflections off of the substantially transparent external medium.

4. The method of claim 3, wherein the external medium is one of a cockpit canopy and an automobile windshield.

5. The method of claim 4, including the step of positioning the retarder adjacent the front polarizer so that the retarder is located between the external medium and the front polarizer.