Wearable pupil-forming display apparatus

1. A wearable display apparatus comprising:

(a) an image generator that forms a 2D image;

(b) a partially transmissive mirror having a curved reflective surface;

(c) a beam splitter disposed to reflect light toward the curved mirror surface; and

(d) an optical image relay that is configured to conjugate the formed 2D image at the image generator to a curved focal surface of the partially transmissive mirror, wherein the curved focal surface is defined between the curved reflective surface of the partially transmissive mirror and the beam splitter, wherein the optical image relay comprises:

(i) a prism having an input surface, an output surface, and a folding surface extending between the input and output surfaces and configured for folding an optical path for light generated by the image generator, wherein an aperture stop for the relay lies within the prism;

(ii) at least a first plano-aspheric lens in optical contact against the prism input surface and configured to guide light from the image generator toward the folding surface;

wherein the relay, curved mirror, and beam splitter are configured to form an exit pupil for viewing the 2D image superimposed on a portion of a visible object scene.

2. The apparatus of claim 1 wherein the wearable display apparatus is configured to form a binocular, 3-dimensional image.

3. The apparatus of claim 1 wherein the optical image relay further comprises a second plano-aspheric lens in optical contact against the prism output surface and configured to direct the light to the curved focal surface.

4. The apparatus of claim 3 further comprising a singlet and a doublet for shaping the beam of image-bearing light directed toward the prism.

5. The apparatus of claim 1 further comprising a field lens that directs an image-bearing light beam from the image generator toward the first plano-aspheric lens.

6. The apparatus of claim 1 having a field of view (FOV) wherein a ratio of horizontal:vertical FOV dimensions equals or exceeds 1.5 and wherein the horizontal FOV equals or exceeds 50 degrees, and wherein the optical path is folded within the prism so that a portion of the system optical axis between the image generator and the prism is parallel to a line between left and right pupils of a viewer.

7. The apparatus of claim 1 wherein the curved surface is conic.

8. The apparatus of claim 1 wherein the curved surface is spherical.

9. The apparatus of claim 1 wherein the beam splitter is a polarization beam splitter.

10. The apparatus of claim 9 further comprising a quarter wave plate in the path of light between the polarization beam splitter and the curved mirror.

11. The apparatus of claim 1 wherein the beam splitter is a wire grid polarization beam splitter.

12. The apparatus of claim 11 wherein the quarter wave plate is cylindrically curved.

13. The apparatus of claim 1 wherein the image generator is an electroluminescent display that is disposed to direct an image-bearing light beam in a direction parallel to a line between left and right pupils of a viewer.

14. The apparatus of claim 1 wherein the folding surface is at least 10% transmissive and further comprising an eye-tracking sensor in the path of light that reflects from an iris of the viewer and transmits through the folding surface.

15. A wearable display apparatus having a left-eye optical system and a right-eye optical system, wherein each optical system defines a corresponding exit pupil for a viewer along a view axis and comprises:

(a) an electroluminescent image generator that is energizable to direct image-bearing light for a 2D image from an emissive surface;

(b) a curved reflective surface disposed along the view axis and partially transmissive, wherein the curved reflective surface defines a curved intermediate focal surface;

(c) a beam splitter disposed along the view axis and oriented to reflect light toward the curved reflective surface; and

(d) an optical image relay that is configured to optically conjugate the formed 2D image at the image generator with the intermediate focal surface, wherein the optical image relay comprises:

(i) a prism having an input surface facing toward the emissive surface of the image generator, an output surface facing toward the intermediate focal plane, and a folding surface extending between the input and output surfaces and configured for folding an optical path for light generated by the image generator, wherein an aperture stop for the relay lies within the prism;

(ii) a first plano-aspheric lens in optical contact against the prism input surface and configured to guide the image-bearing light from the image generator toward the folding surface;

(iii) a second plano-aspheric lens in optical contact against the prism output surface and configured to direct the light from the folding surface toward the curved intermediate focal surface;

wherein the relay, curved mirror, and beam splitter are configured to form the exit pupil for viewing the generated 2D image superimposed on a portion of a visible object scene.

16. The apparatus of claim 15 further comprising a cylindrically curved quarter wave plate in the path of light between the beam splitter and the curved reflective surface.

17. The apparatus of claim 15 wherein the folding surface is partially transmissive and further comprising an eye-tracking sensor in the path of light that reflects from an iris of the viewer and transmits through the folding surface.

18. A method for forming an image for a viewer of a wearable display apparatus, the method comprising:

a) forming an eyebox for display, from an intermediate image formed on a curved aerial surface, by disposing a beam splitter to reflect light from the curved aerial surface toward a partially transmissive curved surface, wherein the curved aerial surface is a focal surface for the partially transmissive curved surface;

b) configuring an optical image relay to conjugate the curved aerial surface with a two-dimensional image generator, wherein the optical image relay is configured to:

(i) direct modulated light from the image generator along an optical path; and

(ii) focus the light through an aperture stop that lies within a turning prism, wherein the turning prism has an input surface, an output surface, and a folding surface extending between the input and output surfaces and is configured for folding the optical path to direct the modulated light to focus along the curved aerial surface; and

c) providing one or more signals to the image generator for providing modulated light output, wherein the relay, curved mirror, and beam splitter are configured to form an exit pupil within the eyebox for viewing the two-dimensional image superimposed on a portion of an object scene that is visible through the partially transmissive curved surface.

19. The method of claim 18 wherein configuring the optical image relay comprises providing at least one aspheric corrector coupled to the input surface of the prism.

20. The method of claim 18 further comprising obtaining an image of the viewer's iris from light transmitted through the folding surface.

21. The method of claim 18 further comprising adjusting a focal surface position for the modulated light using a piezoelectric actuator.