Optical display apparatus, method, and applications

1. A see-through optical head-worn display (HWD) apparatus, comprising:

an image generating component;

a tilted primary mirror having a non-flat, freeform, front optical surface; and

a tilted secondary mirror having a non-flat, freeform, front optical surface,

wherein the apparatus has an external pupil, and wherein the non-flat, freeform, front optical surfaces of the tilted primary mirror and the tilted secondary mirror have concave curvatures.

2. The apparatus of claim 1 , wherein the external pupil is an aperture stop located at the entrance pupil of an observer viewing the image.

3. The apparatus of claim 1 , wherein the image generating component is an OLED microdisplay.

4. The apparatus of claim 1 , wherein at least one of the mirrors' surfaces has a photochromic or an electrochromic coating.

5. The apparatus of claim 1 , wherein the primary mirror and the secondary mirror form a two-mirror optical system, and

wherein the primary mirror is a semi-transparent/semi-reflective optical component, and the secondary mirror has a 100% reflective freeform front optical surface.

6. The apparatus of claim 5 , wherein at least one of the mirrors' surfaces has a photochromic or an electrochromic coating.

7. The apparatus of claim 5 , wherein the primary mirror has a non-flat, freeform, rear optical surface.

8. The apparatus of claim 1 , further comprising a flat surface, semi-transparent/semi-reflective optical component.

9. The apparatus of claim 5 , wherein the image generating component, primary mirror, and secondary mirror are fitted within a spherical volume having a radius that is equal to or less than 14 millimeters (mm).

10. The apparatus of claim 1 , characterized by a field of view (FOV) between 20-30 degrees.

11. The apparatus of claim 1 , further comprising an eyeglass frame to which the image generating component, the primary mirror, and the secondary mirror are coupled.

12. The apparatus of claim 1 , further comprising a head-wearable structure to which the image generating component, the primary mirror, and the secondary mirror are coupled.

13. A method for designing and making a see-through optical head-worn display (HWD) apparatus of claim 1 for displaying an image generated by or on an image generating component of the apparatus, comprising:

a) determining an apparatus specification;

b) selecting a field of view and an aperture stop size for the apparatus;

c) positioning the aperture stop at an entrance pupil of an observing optical system;

d) designing a rotationally symmetric, spherical optical system;

e) determining an aberration content of the apparatus over the full field of view;

f) identifying a dominant aberration comprising one of coma and astigmatism, and

i) if coma: determining whether the coma is more field constant or more field dependent, and

if more field constant: adding a coma term to the optical surface nearest to the aperture stop, or

if more field dependent: adding a spherical aberration term to the optical surface furthest from the aperture stop; or

ii) if astigmatism: determining whether the astigmatism is more field constant or more field dependent, and

if more field constant: adding an astigmatism term to the optical surface nearest to the aperture stop, or

if more field dependent: adding a coma term to the optical surface furthest from the aperture stop;

g) optimizing the optical system design;

h) determining whether the aberration content of the optimized design decreased, and

iii) if no: determining whether the apparatus meets the determined specification, and

if yes: design is complete, or

if no: determining whether the limiting aberration is more field constant or more field dependent, and

if more field constant: adding the next higher-order aberration term to the surface nearest to the aperture stop, or

if more field dependent: adding the next higher-order aberration term to the surface furthest from the aperture stop;

i) repeating steps (g) through (h); or

iv) if yes: repeating steps (e) through (h).

14. A see-through optical head-worn display (HWD) apparatus, comprising:

an image generating component;

a tilted tertiary mirror having a non-flat, freeform, front optical surface;

a tilted secondary mirror having a non-flat, freeform, front optical surface;

a primary mirror comprising a flat surface, semi-transparent/semi-reflective optical component; and

an external pupil;

wherein the primary mirror, the secondary mirror, and the tertiary mirror form a three-mirror optical system;

wherein the non-flat, freeform, front optical surfaces of the tertiary mirror and the secondary mirror have concave curvatures and

wherein the secondary mirror and the tertiary mirror have 100% reflective freeform front optical surfaces.

15. The apparatus of claim 14 , wherein at least one of surfaces of the primary mirror, the secondary mirror, or the tertiary mirror has a photochromic or an electrochromic coating.

16. The apparatus of claim 14 , wherein the image generating component, primary mirror, secondary mirror and tertiary mirror are fitted within a spherical volume having a diameter that is equal to or less than 32.5 millimeters (mm).