Heads-up display combiner utilizing a cholesteric liquid crystal element

• US 4,900,133 A
• Filed: 10/27/1988
• Issued: 02/13/1990
• Est. Priority Date: 10/27/1988
• Status: Expired due to Term

• Current Assignee: Kaiser Electronics Co., Ltd.
• Original Assignee: Kaiser Electronics Co., Ltd.
• Inventors: Berman, Arthur L.
• Primary Examiner(s): Heyman, John S.
• Assistant Examiner(s): Mai, Huy K.
• Application Number:
  US07/263,149
• Time in Patent Office: 474 Days
• Field of Search: 350/346, 350/345, 350/352, 350/174, 350/334, 350/169, 350/171, 350/3.7, 350/3.5, 350/298
• US Class Current: 349/11
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 27/01 Head-up displays
• 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
• CPC Class Codes: G02B 5/3016 involving passive liquid crystal elements optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528

Abstract

A heads-up display (HUD) system employs a cholesteric liquid crystal combiner, an image source, and collimating optics to combine a generated image with an image in an observer'"'"'s field of view. The cholesteric liquid crystal combiner has a bandwidth, B, around a primary wavelength of maximum reflection, and the image source projects its images within bandwidth B for high efficiency of reflection. Outside bandwidth B the cholesteric combiner has a high efficiency of transmission. Images from the image source are projected upon the combiner which reflects the images toward the observer, together with images from the outside environment in the line-of-sight of the observer. Collimating optics are used to focus the projected images at a distance away from the observer.

Claims

1. An apparatus for positioning images in an observer'"'"'s line-of-sight, wherein projected images from an image source are reflected by a liquid crystal element acting as a combiner to combine the projected images with images in the line-of-sight of the observer, comprising:

an image source, having selected primary wavelengths, for projecting symbology; and

a liquid crystal element reflective to images at said selected primary wavelengths, and transmissive to images at all other wavelengths.

2. An apparatus for positioning an image in an observer'"'"'s line-of-sight, wherein a projected image, from an image source, having a first rotary sense if projected in an image source plane, and reflected by a liquid crystal element placed at the intersection of a line-of-sight plane and said image source plane, the liquid crystal element acting as a combiner to combine the projected image with an image in the line-of-sight plane, comprising:

an image source, having a primary wavelength range, for projecting an image; and

a first liquid crystal element reflective to an image having said first rotary sense within said primary wavelength range, and transmissive to an image having a second rotary sense, opposite said first rotary sense within said primary wavelength range and to an image at all wavelengths outside said primary wavelength range.

3. The apparatus as claimed in claim 2, further comprising means in said image source plane for collimating said projected image in said image source plane.

4. The apparatus as claimed in claim 2, further comprising a second liquid crystal element proximate said first liquid crystal element, in said image source and line-of-sight planes, and opposite said image source from said first liquid crystal element, reflective to an image having said second rotary sense within said primary wavelength range, and transmissive to an image having said first rotary sense within said primary wavelength range and to an image at any wavelength outside said primary wavelength range, which is capable of reflecting said projected image within said primary wavelength range without reversal of said image'"'"'s rotary sense, for combining said projected image with an image in said line-of-sight plane.

5. The apparatus as claimed in claim 2, further comprising a second liquid crystal element proximate said first liquid crystal element, in said image source and line-of-sight planes, and opposite said image source form said first liquid crystal element, reflective to an image having said first rotary sense within said primary wavelength range, and transmissive to an image having said second rotary sense within said primary wavelength range and to an image at any wavelength outside said primary wavelength range, which is capable of reflecting said projected image within said primary wavelength range without reversal of said image'"'"'s rotary sense, for combining said projected image with an image in said line-of-sight plane, and further comprising a half-wavelength filter located between said first and second liquid crystal elements for reversing the rotary sense of a projected image transmitted therethrough.

6. An apparatus for positioning images in an observer'"'"'s line-of-sight, comprising:

an image source for producing an image within a primary wavelength range, located in an image source plane, and further for projecting said image upon a line-of-sight plane;

collimating means in said image source plane for collimating said projected image; and

a first cholesteric liquid crystal element located at the intersection of said image source plane and said line-of-sight plane reflective to an image having said first rotary sense within said primary wavelength range and transmissive to an image having a second rotary sense, opposite said first rotary sense, within said primary wavelength range, and to an image having either said first or said second rotary senses at any wavelength outside said primary wavelength range, for combining said projected image with an image in said line-of-sight plane.

7. A method for positioning an image in an observer'"'"'s line-of-sight, comprising the steps of:

positioning in a line-of-sight plane a liquid crystal element reflective to an image having a first rotary sense within a selected range of wavelengths, transmissive to an image having a second rotary sense opposite said first rotary sense within said selected range of wavelengths and transmissive to an image having either said first or said second rotary senses outside said selected range of wavelengths; and

projecting an image within said selected range of wavelengths to be combined with an image in said line-of-sight plane from an image source such that said projected image is reflected by said liquid crystal element toward the observer in said line-of-sight plane together with said image in said line-of-sight plane.

8. A method for positioning an image in an observer'"'"'s line-of-sight, comprising the steps of:

positioning in a line-of-sight plane a first liquid crystal element reflective to an image having a first rotary sense within a selected range of wavelengths, transmissive to images having a second rotary sense opposite said first rotary sense within said selected range of wavelengths and transmissive to images having either said first or said second rotary senses outside said selected range of wavelengths;

positioning proximate said first liquid crystal element and in said line-of-sight plane a second liquid crystal element having high reflectivity to an image within said selected range of wavelengths and having said second rotary sense and high transmissivity to images within said selected range of wavelengths and having said first rotary sense and to images outside said selected range of wavelengths; and

projecting an image within said selected range of wavelengths comprising components in equal amounts of said first and second rotary senses to be combined with an image in said line-of-sight plane from an image source such that a component of said projected image having said first rotary sense is reflected by said first liquid crystal element toward the observer in said line-of-sight plane together with said image in said line-of-sight plane, and such that that component of said projected image having said second rotary sense is transmitted through said first liquid crystal element without reversal of said component'"'"'s rotary sense to said second liquid crystal element which reflects said component having said second rotary sense without reversal of said component'"'"'s rotary sense to said first liquid crystal element which transmits said component without reversal of said component'"'"'s rotary sense toward the observer in said line-of-sight plane together with said image in said line-of-sight plane.

9. A method for positioning an image in an observer'"'"'s line-of-sight, comprising the steps of:

positioning in a line-of-sight plane first and second liquid crystal elements proximate one another, each reflective to an image having a first rotary sense within a selected range of wavelengths and transmissive to an image having a second rotary sense opposite said first rotary sense within said selected range of wavelengths and to an image having either said first or said second rotary senses outside said selected range of wavelengths;

positioning between said first and second liquid crystal elements a half-wavelength filter; and

projecting an image within said selected range of wavelengths comprising components in equal amounts of said first and second rotary senses to be combined with an image in said line-of-sight plane from an image source such that a first component of said projected image having said first rotary sense is reflected by said first liquid crystal element toward the observer in said line-of-sight plane together with said image in said line-of-sight plane, and such that a second component of said projected image having said second rotary sense is transmitted by said first liquid crystal element, without reversal of said second component'"'"'s rotary sense, to said-wavelength filter, which reverses said second component'"'"'s rotary sense, from said first rotary sense to said second rotary sense, and transmits said second component to said second liquid crystal element which reflects said second component, without reversal of said second component'"'"'s rotary sense, into said line-of-sight plane and to said half-wave-length filter which reverses said second component'"'"'s rotary sense, from said second rotary sense to said first rotary sense, and which transmits said second component to said first liquid crystal element which transmits said second component, without reversal of said second component'"'"'s rotary sense, toward the observer in said line-of-sight plane together with said image in said line-of-sight plane.