Polarized heads up display

• US 5,212,471 A
• Filed: 03/25/1991
• Issued: 05/18/1993
• Est. Priority Date: 10/27/1989
• Status: Expired due to Fees

• Current Assignee: Hughes Aircraft Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: McDonald, Mark E.
• Primary Examiner(s): Weldon, Ulysses
• Assistant Examiner(s): Luu, Matthew
• Application Number:
  US07/674,809
• Time in Patent Office: 785 Days
• Field of Search: 350/174, 350/403, 350/3.7, 350/396, 340/705, 340/980, 356/350, 358/88, 358/92, 455/619, 359/70, 359/71, 359/63, 359/48, 359/13, 359/14, 359/630, 359/613
• US Class Current: 345/7
• CPC Class Codes: B60K 35/23 Head-up displays [HUD] optical aspects of head-up displays G02B27/01
• CPC Class Codes: G02B 2027/012 comprising devices for attenuating parasitic image effects
• CPC Class Codes: G02B 2027/0194 with combiner of laminated type, for optical or mechanical aspects
• CPC Class Codes: G02B 27/0018 with means for preventing ghost images anti-reflection coatings G02B1/11
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00

Abstract

A head-up display for vehicle including a windshield having first and second opposing air interfaces for partially reflecting imaging illumination at a predetermined air interface to produce a primary virtual image viewable by the operator of the vehicle, and a half-wave retarder interposed between the first and second air interfaces of the windshield for rotating the linear polarization of illumination transmitted therethrough. An imaging illumination source provides linearly polarized imaging illumination to the first air interface of the windshield at an angle which is selected to enhance the reflection of S-polarized light and the transmission of P-polarized light, with the polarization being selected so as to provide S-polarized imaging illumination at the predetermined beam splitting air interface.

Claims

1. A head-up display for a vehicle, comprising:

a substantially transparent substrate having first and second opposing air interfaces for partially reflecting imaging illumination at a beamsplitter region on a selected one of said air interfaces to produce a primary virtual image viewable by the operator of the vehicle;

image source means for directing linearly polarized imaging illumination to said beam-splitter region at an angle which enhances reflection of a first predetermined linear polarization and transmission of a second linear polarization, the polarization state of said imaging illumination depending on the air interface selected to produce the primary image occurs; and

means interposed between said first and second opposing air interfaces and adjacent said beamsplitter region for rotating the linear polarization of imaging illumination transmitted therethrough.

2. The head-up display of claim 1 wherein said substantially transparent substrate comprises a laminar vehicle windshield and wherein said polarization rotating means comprises a half-wave retarder embedded between the layers of said windshield.

3. The head-up display of claim 2 wherein said beamsplitter region is on said first air interface, and wherein said image source means provides S-polarized imaging illumination.

4. The head-up display of claim 2 wherein said beamsplitter region is on said second air interface, and wherein said image source provides P-polarized imaging illumination.

5. The head-up display of claim 2 wherein said windshield comprises glass and wherein said imaging illumination is incident on said glass windshield at an angle within the range of about 47 to 72 degrees relative to normal.

6. A head-up display for a vehicle comprising:

a vehicle windshield having inside and outside air interfaces for partially reflection imaging illumination at a beamsplitter region on a selected one of said air interfaces to produce a primary virtual image viewable by the operator of said vehicle;

image source means for directing linearly polarized imaging illumination to said beam-splitter region at an angle which enhances reflection of a first predetermined linear polarization and transmission of a second linear polarization, the polarization state of said polarized imaging illumination depending on the air interface selected to produce said primary virtual image; and

a half-wave retarder embedded in said windshield adjacent said beamsplitter region for rotating the linear polarization of imaging illumination transmitted therethrough.

7. The head-up display of claim 6 wherein said beamsplitter region is on the inside windshield air interface, and wherein said image source means provides S-polarized imaging illumination.

8. The head-up display of claim 6 wherein said predetermined air interface is on the outside windshield air interface, and wherein said image source provides P-polarized imaging illumination.

9. The head-up display of claim 6 wherein said imaging illumination is incident on said glass windshield at an angle within the range of about 47 to 72 degrees relative to normal.