Multiple image forming apparatus

• US 4,987,410 A
• Filed: 12/18/1989
• Issued: 01/22/1991
• Est. Priority Date: 01/25/1988
• Status: Expired due to Fees

• Current Assignee: Kaiser Aerospace & Electronics Corporation (Rtx Corporation)
• Original Assignee: Kaiser Aerospace & Electronics Corporation (Rtx Corporation)
• Inventors: Lewis, Thomas M., Berman, Arthur L.
• Primary Examiner(s): Brier, Jeffery A.
• Application Number:
  US07/455,896
• Time in Patent Office: 400 Days
• Field of Search: 340/705, 340/716, 340/717, 340/702, 340/795, 340/784, 340/980, 340/794, 350/33 D, 350/331 R, 350/335, 350/337, 350/350 S, 350/347 R, 350/347 E, 350/347 V, 350/388, 350/391, 350/169, 350/171, 350/172, 350/174, 353/28, 353/30, 353/31, 353/34, 358/61, 358/232, 358/250, 358/253
• US Class Current: 345/9
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/0165 associated with a head-down display
• CPC Class Codes: G02B 27/01 Head-up displays
• 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
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence
• CPC Class Codes: G02F 2201/343 cholesteric liquid crystal reflector
• CPC Class Codes: G09B 9/326 the image being transformed by optical means
• CPC Class Codes: G09G 3/002 to project the image of a two-dimensional display, such as an array of light emitting or modulating elements or a CRT

Abstract

A head-up display (HUD)/head-down display (HDD) system capable of projecting multi-color images employs cholesteric liquid crystal elements, two-state liquid crystal devices, an image source, a beam splitter, and a combiner to, in sequence, generate HUD and HDD images. An LCD and cholesteric liquid crystal element operate together to selectively transmit or block portions of an image incident thereon. The switching frequency of the LCD-cholesteric liquid crystal element is above the flicker-fusion frequency, such that both the HUD and HDD displays appear to the observer to be simultaneously and continuously operating.

Claims

1. An apparatus for directing a plurality of images from an image source, which generates a first and a second image having a first and a second wavelength, along a first and a second optical path, comprising:

means for converting incident radiation of the first wavelength to a first polarization;

means for converting incident radiation of the second wavelength to a second polarization;

a beam splitter, disposed along the first and second optical paths, for transmitting a first portion of said converted incident radiation along said first optical path and reflecting a second portion of said converted radiation along said second optical path, said transmitted first portion has radiation of said first wavelength polarized in said first polarization and said second wavelength polarized in said second polarization,

said reflected second portion has radiation of said first wavelength polarized in a third polarization, orthogonal to said first polarization, and said second wavelength polarized in a fourth polarization, orthogonal to said second polarization;

a first shutter means, disposed along said first optical path and responsive to a first filter signal, for reflecting said first wavelength and passing said second wavelength of said transmitted first portion of said converted radiation;

a second shutter means, disposed along said first optical path and responsive to a second filter signal, for reflecting said second wavelength and passing said first wavelength of said transmitted first portion;

a third shutter means, disposed along said second optical path and responsive to a third filter signal, for reflecting said first wavelength and passing said second wavelength of said reflected second portion of said converted radiation;

a fourth shutter means, disposed along said second optical path and responsive to a fourth filter signal, for reflecting said second wavelength and passing said first wavelength of said reflected second portion; and

a timing device for providing said first, second, third and fourth filter signals to selectively pass desired images of said first and second wavelength along said first and second optical paths.

2. An apparatus for directing a plurality of images from an image source, which generates a first and a second image having a first and a second wavelength, along a first and a second optical path, comprising:

a first and a second cholesteric element respectively having a primary wavelength at the first and second wavelength wherein incident radiation from the first and second images is particularly circularly polarized in a predetermined handedness, said first and second cholesteric elements disposed along the first and second optical paths;

a beam splitter, disposed at a junction of said first and second optical paths, for transmitting a first portion of said particularly polarized radiation along said first optical path and for reflecting a second portion of said particularly polarized radiation having an orthogonal polarization along said second optical path;

a first and a second cholesteric means, disposed along said first optical path and responsive to an assertion of a respective filter signal, for changing said particular circular polarization to said orthogonal polarization, said first cholesteric changing means operative on said first wavelength and said second cholesteric changing means operative on said second wavelength;

a first cholesteric filter, disposed along said first optical path, for reflecting incident radiation of said first wavelength having said orthogonal polarization;

a second cholesteric filter, disposed along said first optical path, for reflecting incident radiation of said second wavelength having said orthogonal polarization;

a third and a fourth cholesteric means, disposed along said second optical path and responsive to an assertion of a respective filter signal, for changing said orthogonal polarization to said particular polarization, said third cholesteric changing means operative on said first wavelength and said fourth cholesteric changing means operative on said second wavelength;

a third cholesteric filter, disposed along said second optical path, for reflecting incident radiation of said first wavelength having said orthogonal polarization;

a fourth cholesteric filter, disposed along said second optical path, for reflecting incident radiation of said second wavelength having said orthogonal polarization; and

a timing device, coupled to said cholesteric changing means and to the image source, for independently providing said filter signals to said first, second, third and fourth cholesteric changing means which permits any combination of the first and second images to be received at an end of either optical path.

3. An apparatus for directing a plurality of images from an image source, which generates a first and a second image having a first and a second wavelength, along a first and a second optical path, comprising:

means for converting incident radiation of the first wavelength to a first polarization;

means for converting incident radiation of the second wavelength to a second polarization;

a beam splitter, disposed along the first and second optical paths, for transmitting a first portion of said converted incident radiation along said first optical path and reflecting a second portion of said converted radiation along said second optical path, said transmitted first portion has radiation of said first wavelength polarized in said first polarization and said second wavelength polarized in said second polarization,

said reflected second portion has radiation of said first wavelength polarized in a third polarization, and said second wavelength polarized in a fourth polarization;

a first shutter means, disposed along said first optical path and responsive to a first filter signal, for reflecting said first wavelength and passing said second wavelength of said transmitted first portion of said converted radiation;

a second shutter means, disposed along said first optical path and responsive to a second filter signal, for reflecting said second wavelength and passing said first wavelength of said transmitted first portion;

a third shutter means, disposed along said second optical path and responsive to a third filter signal, for reflecting said first wavelength and passing said second wavelength of said reflected second portion of said converted radiation;

a fourth shutter means, disposed along said second optical path and responsive to a fourth filter signal, for reflecting said second wavelength and passing said first wavelength of said reflected second portion; and

a timing device for providing said first, second, third and fourth filter signals to selectively pass desired images of said first and second wavelength along said first and second optical paths.

4. Apparatus for forming at least first and second images to be respectively viewed at first and second viewing positions, the apparatus comprising:

imaging means for alternately producing the first and second images;

polarizing means for selectively providing the first and second images with a first and a second circular polarization, respectively;

means for directing the first and second images onto at least first and second paths, the directing means including means for reversing the circular polarization of the first and second images directed onto the first path;

filter mans positioned in each of the first and second paths to reflect images having the first circular polarization and to transmit, substantially unattenuated, images having the second circular polarization on to the first and second viewing positions.

5. The apparatus of claim 4, wherein the imaging means includes means for forming the first and second images in a bandwidth around a predetermined primary wavelength.

6. The apparatus of claim 5, wherein the polarizing means comprises a first cholesteric means for imparting the first and second images with the first circular polarization.

7. The apparatus of claim 6, wherein the polarizing means includes a means, operable in synchronism with the imaging means, for converting the first circular polarization of the second images to the second circular polarization, and transmitting the first images unchanged.

8. The apparatus of claim 7, wherein the filter means includes second cholesteric liquid crystal means reflective to images within a bandwidth having the second circular polarization.

9. The apparatus of claim 8, wherein the directing means includes mirror means operable to reflect the first and second images onto the first path, and to transmit the first and second image onto the second path.

10. The apparatus of claim 4, wherein the polarizing means, and each of the filter means includes a cholesteric liquid crystal means reflective to images within a bandwidth having the second circular polarization.

11. The apparatus of claim 10, wherein the polarizing means includes a liquid crystal means operable in synchronism with the imaging means, for converting the first circular polarization of the second images to a second circular polarization, and transmitting the first images unchanged.

12. The apparatus of claim 4, including additional filter means positioned in association with the polarizing means to reflect images from the imaging means having the first circular polarization and to transmit, substantially unattenuated, images having the second circular polarization.

13. The apparatus of claim 12, wherein the polarizing means includes controllable liquid crystal means operable in a first mode to receive and transmit, substantially unchanged, images from the filter means, and in a second mode to transmit received images having the first circular polarization as images having the second circular polarization.

14. The apparatus of claim 13, including control means coupled to the controllable liquid crystal means and operable in synchronism with the imaging means to alternately place the controllable liquid crystal means in the first and the second mode as the imaging means produces the first and second images, respectively.

15. Apparatus for communicating at least first and second images to corresponding first and second viewing positions, the apparatus comprising:

imaging means for alternately producing the first and second images;

first cholesteric crystal means reflective to images within a bandwidth having a second circular polarization for transmitting the first and second images with a first circular polarization;

liquid crystal means operable in synchronism with the imaging means, for converting the circular polarization of the second images to the second circular polarization, and transmitting the first images unchanged;

means for directing the first and second images onto at least first and second paths, the directing means including means for converting images directed onto the first path having first or second circular polarizations to second or first circular polarizations, respectively;

second and third cholesteric means reflective to images with the bandwidth having the second circular polarization, positioned in each of the first and second paths to reflect images having the first circular polarization and to transmit, substantially unattenuated, images having the second circular polarization on to the first and second viewing positions, respectively.

16. The apparatus of claim 15, wherein the first and second circular polarizations are left and right hand circular polarizations, respectively.

17. The apparatus of claim 15, wherein the imaging means produces the first and second images in an alternating frequency that is substantially flicker-free to a viewer at the first or the second viewing position.