Method and system for fiber scanning projector with angled eyepiece
A method of displaying an image to a viewer includes operating a fiber scanning projector to produce a scanned light beam incident on an incoupling diffractive optical element (DOE) coupled to a waveguide. A portion of the light beam is reflected via a reflective back surface of the incoupling DOE. The reflected portion of the scanned light beam is incident on a reflective optical element, which reflects the light beam back to the incoupling DOE. The returning light beam is then diffracted by the incoupling DOE to produce a second pass first diffracted light beam. The second pass first diffracted light beam is propagated within the planar waveguide via total internal reflection (TIR) to an outcoupling DOE, which directs a portion of the second pass first diffracted light beam toward an eye of a viewer to display the image to the user.
1. A wearable display system comprising:
a fiber scanner including:
an optical fiber; and
a scanning mechanism configured to scan a tip of the optical fiber along an emission trajectory, the emission trajectory defining an optical axis;
a collimating optical element positioned along the optical axis and configured to:
receive a divergent input light beam emitted from the tip of the optical fiber incident thereon in an on-axis configuration; and
reflect a portion of the divergent input light beam to produce a collimated light beam; and
an eyepiece positioned in front of the tip of the optical fiber, the eyepiece including:
a planar waveguide oriented such that a normal of the planar waveguide is tilted at a first angle with respect to the optical axis; and
an incoupling diffractive optical element (DOE) coupled to a first lateral region of the planar waveguide that is intercepted by the optical axis, the incoupling DOE configured to:
as the divergent input light beam emitted from the tip of the optical fiber is incident on the incoupling DOE on a first pass through the planar waveguide toward the collimating optical element, produce a first negative first order diffracted light beam that fails total internal reflection (TIR) condition of the planar waveguide; and
as the collimated light beam produced by reflection from the collimating optical element is incident on the incoupling DOE on a second pass, produce a second negative first order diffracted light beam that meets the TIR condition of the planar waveguide.
2. The wearable display system of claim 1 wherein the eyepiece further includes an outcoupling DOE coupled to a second lateral region of the planar waveguide displaced from the first lateral region, the outcoupling DOE configured to diffract a portion of the second negative first order diffracted light beam out of the planar waveguide toward an eye of a viewer.
3. The wearable display system of claim 1 wherein the collimating optical element comprises a concave mirror.
4. The wearable display system of claim 1 wherein the tip of the optical fiber is positioned on a first side of the eyepiece, and the collimating optical element is positioned on a second side of the eyepiece opposite from the first side.
5. The wearable display system of claim 1 wherein the incoupling DOE is metallized, and wherein the tip of the optical fiber and the collimating optical element are positioned on a same side of the eyepiece.
6. The wearable display system of claim 1 further comprising a mirror positioned along the optical axis on a first side of the eyepiece, wherein the tip of the optical fiber and the collimating optical element are positioned on a second side of the eyepiece opposite from the first side.
7. The wearable display system of claim 1 wherein the emission trajectory of the tip of the optical fiber is forms a two-dimensional convex surface.
8. The wearable display system of claim 1 wherein the emission trajectory of the tip of the optical fiber forms a one-dimensional arc.
9. The wearable display system of claim 1 wherein the tip of the optical fiber comprises an angled facet.
10. The wearable display system of claim 1 wherein the divergent input light beam is imagewise modulated.
11. The wearable display system of claim 1 wherein the optical fiber comprises a non-polarization-maintaining optical fiber, and the divergent input light beam is unpolarized.
12. A wearable display system comprising:
a fiber scanner comprising:
an optical fiber having a distal end and configured for projection of a light beam from the distal end, an optical axis of the fiber scanner being defined as co-axial with the light beam as projected from the optical fiber when the optical fiber is not deflected; and
a scanning mechanism configured to deflect the optical fiber to scan the light beam to produce a scanned light beam that forms an image;
an eyepiece comprising:
a planar waveguide oriented non-perpendicular to the optical axis of the fiber scanner; and
an incoupling diffractive optical element (DOE) coupled to the planar waveguide, the incoupling DOE being configured to diffract the scanned light beam incident on the incoupling DOE on a first pass to produce a first pass first diffracted light beam that fails total internal reflection (TIR) condition of the planar waveguide; and
a collimating optical element configured to reflect a portion of the scanned light beam that passes through the incoupling DOE on the first pass to produce a reflected portion of the scanned light beam incident on the incoupling DOE on a second pass, and
wherein the incoupling DOE is configured to diffract the reflected portion of the scanned light beam on the second pass to produce a second pass first diffracted light beam that meets the TIR condition of the planar waveguide.
13. The wearable display system of claim 12 wherein the eyepiece further includes an outcoupling DOE coupled to the planar waveguide, the outcoupling DOE being configured to direct at least a portion of the second pass first diffractive light beam out of the planar waveguide toward an eye of a viewer.
14. The wearable display system of claim 12 wherein the collimating optical element is configured so that the reflected portion of the scanned light beam is collimated by the collimating optical element, which comprises a concave mirror.
15. The wearable display system of claim 12 further comprising an outcoupling DOE coupled to the planar waveguide.
16. The wearable display system of claim 12 wherein the collimating optical element comprises a concave mirror.
17. The wearable display system of claim 12 wherein a tip of the optical fiber is positioned on a first side of the eyepiece and the collimating optical element is positioned on a second side of the eyepiece opposite from the first side.
18. The wearable display system of claim 12 wherein:
the incoupling DOE is metallized; and
a tip of the optical fiber and the collimating optical element are positioned on a same side of the eyepiece.
19. The wearable display system of claim 12 wherein a tip of the optical fiber comprises an angled facet.
20. The wearable display system of claim 12 wherein the optical fiber comprises a non-polarization-maintaining optical fiber and the light beam is unpolarized.