Holographic multi-combiner for head-up display

• US 4,688,879 A
• Filed: 07/08/1985
• Issued: 08/25/1987
• Est. Priority Date: 07/08/1985
• Status: Expired due to Fees

• Current Assignee: Kaiser Optical Systems, Inc. (Endress+Hauser AG)
• Original Assignee: Kaiser Optical Systems, Inc. (Endress+Hauser AG)
• Inventors: Fairchild, Ronald C.
• Primary Examiner(s): ARNOLD, BRUCE
• Application Number:
  US06/752,734
• Time in Patent Office: 778 Days
• Field of Search: 350/3.7, 350/172, 350/174
• US Class Current: 340/908
• CPC Class Codes: G02B 2027/0116 comprising devices for correcting chromatic aberration
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 27/0103 comprising holographic elements
• CPC Class Codes: G02B 27/1093 for use with monochromatic radiation only, e.g. devices for splitting a single laser source
• CPC Class Codes: G02B 5/32 Holograms used as optical elements

Abstract

A head-up display which combines an internal image, produced by a cathode ray tube image source, at substantially a wavelength of light λ, with an external image, using a holographic optical element. The holographic optical element consists of two or more holographic optical subelements in series, each satisfying the Bragg condition with respect to wavefronts at the wavelength λ from a particular direction. While wavefronts satisfying these conditions are reflected to the observer'"'"'s field of view, all others are transmitted through the holographic subelements. The holographic optical subelements largely overlap in the direction of their illumination by the internal image source, and may slightly overlap in the direction their images are to be presented to the observer. Wavelength λ is chosen at the peak of the phosphor response curve of the cathode ray tube image source.

Claims

1. A head-up display supported in an aircraft cockpit having a windshield, including a display information source having a light output at a predetermined wavelength and a combiner supported in the pilot'"'"'s field of view through the cockpit windshield, the combiner being operative to reflect the source output to the pilot and consisting of a plurality of HOE combiner subelements each constructed to reflect the predetermined wavelength, supported relative to the source and the pilot so that a portion of the light reaching one of the subelements from the source intersects the subelement at substantially the Bragg angle and is reflected to the pilot'"'"'s eye and another portion of the light reaching said one subelement intersects the subelement at an angle substantially different from the Bragg angle and is transmitted through said subelement and at least part of such transmitted light intersects another of the subelements at substantially the Bragg angle and is reflected from such other subelement to the pilot'"'"'s eye, whereby the pilot perceives an image of the source formed by light reflected from more than one subelement.

2. The head-up display of claim 1, wherein said combiner subelements are planar.

3. The head-up display of claim 1, wherein the display information source is a cathode ray tube.

4. A head-up display supported in an aircraft cockpit having a windshield, including a display information source having a light output at a predetermined wavelength, lens means for collimating the light from the source, and a combiner supported in the pilot'"'"'s field of view through the cockpit windshield, the combiner being operative to reflect the collimated source output to the pilot and consisting of a plurality of HOE combiner subelements each constructed to reflect the predetermined wavelength, supported relative to the lens means and the pilot so that a portion of the light reaching one of the subelements from the lens means intersects the subelement at substantially the Bragg angle and is reflected to the pilot'"'"'s eye and another portion of the light reaching said one subelement intersects the subelement at an angle substantially different from the Bragg angle and is transmitted through said subelement and at least part of such transmitted light intersects another of the subelements at substantially the Bragg angle and is reflected from such other subelement to the pilot'"'"'s eye, whereby the pilot perceives an image of the source formed by light reflected from more than one subelement.

5. The head-up display of claim 4, wherein said combiner subelements are planar.

6. The head-up display of claim 5, wherein said combiner subelements are mutually parallel.

7. The head-up display of claim 4, wherein the display information source is a cathode ray tube.

8. A head-up display supported in an aircraft cockpit having a windshield, including a display information source having a light output at a predetermined wavelength, reflecting means for reflecting the light output, lens means for collimating ther reflected light, and a combiner supported in the pilot'"'"'s field of view through the cockpit windshield, the combiner being operative to reflect the collimated light to the pilot and consisting of two parallel planar HOE combiner subelements each constructed to reflect the predetermined wavelength, supported relative to the lens means and the pilot so that a portion of the light reaching the subelement closer to the lens means intersects the subelement at substantially the Bragg angle and is reflected to the pilot'"'"'s eye and another portion of the light reaching the subelement closer to the lens means intersects the subelement at an angle substantially different from the Bragg angle and is transmitted through said subelement and at least part of such transmitted light intersects the other subelement at substantially the Bragg angle and is reflected from such other subelement to the pilot'"'"'s eye, whereby the pilot perceives an image of the source formed by light reflected from two subelements.