Variable pixel density display system with mechanically actuated image projector
Head-mounted virtual and augmented reality display systems include a light projector with one or more emissive micro-displays having a first resolution and a pixel pitch. The projector outputs light forming frames of virtual content having at least a portion associated with a second resolution greater than the first resolution. The projector outputs light forming a first subframe of the rendered frame at the first resolution, and parts of the projector are shifted using actuators, such that physical positions of light output for individual pixels occupy gaps between the old locations of light output for individual pixels. The projector then outputs light forming a second subframe of the rendered frame. The first and second subframes are outputted within the flicker fusion threshold. Advantageously, an emissive micro-display (e.g., micro-LED display) having a low resolution can form a frame having a higher resolution by using the same light emitters to function as multiple pixels of that frame.
1. A head-mounted display system comprising:
an array of light emitters associated with a first resolution, wherein the array of light emitters is configured to output light forming frames of virtual content to be directed to a user of the head-mounted display system;
one or more actuators; and
one or more processors, the one or more processors configured to:
receive a rendered frame of virtual content, the rendered frame comprising at least a portion associated with a second resolution, wherein the second resolution is higher than the first resolution;
cause the array of light emitters to output light forming a first subframe of the rendered frame;
after causing the array of light emitters to output light forming the first subframe of the rendered frame, adjust, via the one or more actuators, positions associated with light output from the array of light emitters; and
after adjusting the positions associated with light output from the array of light emitters, cause the array of light emitters to output light forming a second subframe of the rendered frame, wherein the second subframe overlaps and is laterally shifted relative to the first subframe.
2. The head-mounted display of claim 1 , wherein the portion associated with the second resolution is associated with a foveal region of the user's eye.
3. The head-mounted display of claim 2 , wherein the one or more processors are configured to determine that light forming the portion falls within a threshold angular distance of a fovea of the user.
4. The head-mounted display of claim 2 , wherein the one or more processors are configured to cause:
for the second subframe, light emitters to update emitted light forming the portion; and
for the first subframe, light emitters to not update emitted light forming parts of the rendered frame outside of the portion.
5. The head-mounted display of claim 1 , wherein the array of light emitters has an associated emitter size, wherein the emitter size is less than a pixel pitch, and wherein a total number of subframes of the rendered frame is determined based on a size associated with the pixel pitch and the emitter size.
6. The head-mounted display of claim 5 , wherein the one or more processors are configured to cause the array of light emitters to successively output light forming the total number of subframes.
7. The head-mounted display of claim 6 , wherein the one or more processors are configured to time multiplex the rendered frame by causing the one or more actuators to shift parts of a light projection system for each subframe.
8. The head-mounted display of claim 7 , wherein the one or more processors are configured to cause the one or more actuators to shift the parts of the light projection system such that geometric positions associated with the array of light emitters are tiled within respective inter-emitter regions.
9. The head-mounted display of claim 7 , wherein the one or more processors are configured to cause the one or more actuators to shift the parts of the light projection system according to a movement pattern, and wherein the movement pattern is a continual movement pattern.
10. The head-mounted display of claim 1 , wherein the first subframe and the second subframe each comprise pixels associated with respective portions of the rendered frame.
11. The head-mounted display of claim 1 , wherein the head-mounted display comprises a plurality of arrays of light emitters.
12. The head-mounted display system of claim 11 , further comprising:
an X-cube prism, wherein each of the arrays of light emitters face a different side of the X-cube prism.
13. The head-mounted display of claim 11 , wherein each of the arrays of light emitters is configured to direct light into dedicated associated projection optics.
14. The head-mounted display of claim 11 , wherein the arrays of light emitters are attached to a common back plane.
15. The head-mounted display of claim 1 , wherein the one or more actuators are configured to shift projection optics to adjust the positions associated with light output from the array of light emitters.
16. The head-mounted display of claim 1 , wherein the one or more actuators are piezoelectric motors.
17. The head-mounted display of claim 1 , wherein the one or more actuators are configured to shift the array of light emitters along two axes.
18. The head-mounted display of claim 1 , wherein the array of light emitters is configured to emit light of a plurality of component colors.
19. The head-mounted display of claim 18 , wherein each light emitter comprises a stack of constituent light generators, and wherein each constituent light generator emits light of a different color.
20. The head-mounted display of claim 1 , further comprising:
an eyepiece configured to receive light from the array of light emitters and to direct the received light to the user, wherein the eyepiece comprises a waveguide assembly comprising one or more waveguides, each waveguide comprising:
an in-coupling optical element configured to incouple light from the array of light emitters into the waveguide; and
an out-coupling optical element configured to outcouple incoupled light out of the waveguide.