PROJECTION DISPLAY

• US 20140218801A1
• Filed: 08/13/2012
• Published: 08/07/2014
• Est. Priority Date: 08/17/2011
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: Simmonds, Michael David, Valera, Mohmed Salim
• Granted Patent: US 9,400,387 B2
• Time in Patent Office: Days
• US Class Current: 359/567
• CPC Class Codes: G02B 2027/0112 comprising device for genereting colour display
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 5/18 Diffraction gratings holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area

Abstract

The present invention provides a projection display (10) for projecting a colour image to a viewer (12) overlaid on a real world scene viewed through the display. The display comprises an image generator (16) for generating image bearing chromatic light for injection into a waveguide assembly (28) at a first range of field angles (44) and a second range of field angles (46). The waveguide assembly comprises a first waveguide (30) having a first input diffraction region (32) arranged to couple image bearing chromatic light in the first range of field angles into the first waveguide to propagate by total internal reflection; and a second waveguide (40) having a second input diffraction region (42) arranged to couple image bearing chromatic light in the second range of field angles into the second waveguide to propagate by total internal reflection. The first and second waveguides have first and second output diffraction regions (48, 50) arranged to output image bearing chromatic light from the respective waveguides for projecting a colour image in the first and second range of field angles to a viewer overlaid on a real world scene viewed through the waveguide assembly.

Claims

1. A projection display for projecting a colour image to a viewer overlaid on a real world scene viewed through the display, the display comprising:

an image generator for generating image bearing chromatic light for injection into a waveguide assembly at a first range of field angles and a second range of field angles;

the waveguide assembly comprising;

a first waveguide having a first input diffraction region arranged to couple image bearing chromatic light in the first range of field angles into the first waveguide to propagate by total internal reflection;

a second waveguide having a second input diffraction region arranged to couple image bearing chromatic light in the second range of field angles into the second waveguide to propagate by total internal reflection;

the first and second waveguides having first and second output diffraction regions arranged to output image bearing chromatic light from the respective waveguides for projecting a colour image in the first and second range of field angles to a viewer overlaid on a real world scene viewed through the waveguide assembly.

2. A projection display as claimed in claim 1, wherein the first input diffraction region is arranged to be generally transmissive to image bearing chromatic light in the second range of field angles allowing the light in the second range of field angles to pass through the first waveguide to the second waveguide.

3. A projection display as claimed in claim 1, wherein the first input diffraction region is arranged to couple into the first waveguide at least one wavelength of the image bearing chromatic light across the full extent of the first range of field angles and the first output diffraction region is arranged to output light of said at least one wavelength from the first waveguide across the full extent of the first range of field angles.

4. A projection display as claimed in claim 1, wherein the second input diffraction region is arranged to couple into the second waveguide at least one wavelength of the image bearing chromatic light across the full extent of the second range of field angles and the second output diffraction region is arranged to output light of said at least one wavelength from the second waveguide across the full extent of the second range of field angles.

5. A projection display as claimed in claim 1, the first input diffraction region is arranged to couple into the first waveguide at least one wavelength of the image bearing chromatic light across the full extent of the first range of field angles and the first output diffraction region is arranged to output light of said at least one wavelength from the first waveguide across the full extent of the first range of field angles, wherein the second input diffraction region is arranged to couple into the second waveguide at least one wavelength of the image bearing chromatic light across the full extent of the second range of field angles and the second output diffraction region is arranged to output light of said at least one wavelength from the second waveguide across the full extent of the second range of field angles and wherein image bearing chromatic light of a wavelength different from said at least one wavelength is coupled into and output from the first and the second waveguides across less than the full extent of the first range of field angles and the second range of field angles such that the image output from the waveguide assembly can be viewed over a larger range of field angles for light of said at least one first wavelength and a smaller range of field angles for light of said different wavelengths.

6. A projection display as claimed in claim 5, wherein the difference between the larger range of field angles and the smaller range of field angles corresponds generally to the peripheral vision of a human viewer and the smaller range of field angles corresponds generally to the full colour perception of a human viewer.

7. A projection display as claimed in claim 5, wherein said at least one wavelength corresponds generally to green light and said different wavelengths correspond generally to red and blue light.

8. A projection display as claimed in claim 1, wherein the first range of field angles is from 0°

perpendicular to the plane of the of the waveguide assembly to between +10° and

+30°

to the perpendicular and the second range of field angles is from 0°

perpendicular to the plane of the of the waveguide assembly to between −

10° and

−

30°

to the perpendicular.

9. A projection display as claimed in claim 1, wherein the image generator is arranged to generate an input pupil of image bearing chromatic light for expansion in first and second generally orthogonal dimensions by the waveguide assembly and for outputting an expanded exit pupil from the assembly, and wherein the first and second waveguides comprise respectively first expansion diffraction regions for expanding the input pupil in the first dimension and second expansion diffraction regions for expanding the input pupil in the second dimension, said first and second output diffraction regions forming one of said first expansion diffraction regions or said second expansion diffraction regions.

10. A projection display as claimed in claim 9, wherein the first range of field angles and the second range of field angles are ranges in at least one of the first dimension or the second dimension.

11. A projection display as claimed in claim 10, wherein the first dimension corresponds generally with a horizontal dimension with respect to the viewer and the second dimension corresponds generally with a vertical dimension with respect to the viewer, and the first and the second range of field angles are angles in the horizontal dimension such that the total range of field angles output from the waveguide assembly is larger in the horizontal dimension than in the vertical dimension.

12. A projection display as claimed in claim 1, wherein the image generator comprises a light processor for generating image bearing light and a lens for directing said image bearing light towards the waveguide assembly over the first and the second range of field angles.

13. A projection display as claimed in claim 1, wherein the image generator is arranged to split an input pupil of image bearing chromatic light into the first range of field angles for injection into the first waveguide and the second range of field angles for injection into the second waveguide, the first input diffraction region is located to receive image bearing chromatic light in the first range of field angles from the image generator and the second input diffraction region is located to receive image bearing chromatic light in the second range of field angles from the image generator.

14. A projection display as claimed in claim 13, wherein the first and second input diffraction regions are located to allow light in the second range of field angles to be received by the second input diffraction region without passing through the first input diffraction region.

15. (canceled)