Ghost image mitigation in see-through displays with pixel arrays
A head-mounted apparatus include an eyepiece that include a variable dimming assembly and a frame mounting the eyepiece so that a user side of the eyepiece faces a towards a user and a world side of the eyepiece opposite the first side faces away from the user. The dynamic dimming assembly selectively modulates an intensity of light transmitted parallel to an optical axis from the world side to the user side during operation. The dynamic dimming assembly includes a variable birefringence cell having multiple pixels each having an independently variable birefringence, a first linear polarizer arranged on the user side of the variable birefringence cell, the first linear polarizer being configured to transmit light propagating parallel to the optical axis linearly polarized along a pass axis of the first linear polarizer orthogonal to the optical axis, a quarter wave plate arranged between the variable birefringence cell and the first linear polarizer, a fast axis of the quarter wave plate being arranged relative to the pass axis of the first linear polarizer to transform linearly polarized light transmitted by the first linear polarizer into circularly polarized light, and a second linear polarizer on the world side of the variable birefringence cell.
1. A system comprising:
an eyepiece comprising:
a dynamic dimming assembly configured to selectively modulate an intensity of light transmitted through the dynamic dimming assembly, the dynamic dimming assembly comprising:
a variable birefringence cell,
a first linear polarizer arranged on a first side of the variable birefringence cell,
a quarter wave plate arranged between the variable birefringence cell and the first linear polarizer, the quarter wave plate having a fast axis,
an array of pixel electrodes arranged between the variable birefringence cell and the quarter wave plate, and
a second linear polarizer on a second side of the variable birefringence cell; and
a see-through display comprising a plurality of waveguides, wherein each of the waveguides corresponds to at least one of a different respective color of light or a different respective depth of virtual content for presentation by the see-through display, and wherein the first linear polarizer is disposed between the see-through display and the variable birefringence cell,
wherein the fast axis of the quarter wave plate and a pass axis of the first linear polarizer are aligned relative to each other so that light from the see-through display incident on the dynamic dimming assembly that is transmitted by the first linear polarizer is circularly polarized by the quarter waveplate, reflected by the pixel electrodes, and absorbed by the first linear polarizer.
2. The system of claim 1 , wherein the each of the waveguides corresponds to a different respective color of light for presentation by the see-through display.
3. The system of claim 1 , wherein the each of the waveguides corresponds to a different respective depth of virtual content for presentation by the see-through display.
4. The system of claim 1 , wherein the first linear polarizer is configured to linearly polarize ambient light and transmit the linearly polarized ambient light to the quarter wave plate.
5. The system of claim 4 , wherein the quarter wave plate is configured to circularly polarize the linearly polarized ambient light received from the first linear polarizer, and transmit the circularly polarized ambient light to the variable birefringence cell.
6. The system of claim 1 , wherein the dynamic dimming assembly comprises an optical retarder disposed between the variable birefringence cell and the second linear polarizer.
7. The system of claim 6 , wherein the optical retarder comprises a second quarter wave plate.
8. The system of claim 7 , wherein the dynamic dimming assembly comprises a third quarter wave plate, wherein the first linear polarizer is disposed between the third quarter wave plate and the variable birefringence cell.
9. The system of claim 8 , wherein the dynamic dimming assembly comprises a fourth quarter wave plate, wherein the fourth quarter wave plate is disposed between the see-through display and the variable birefringence cell.
10. The system of claim 6 , wherein the optical retarder comprises an A-plate with a retardation greater than a retardation of the quarter wave plate.
11. The system of claim 6 , wherein a difference between a retardation of the optical retarder and a retardation of the quarter wave plate corresponds to a residual retardation of the variable birefringent cell in a minimum birefringence state.
12. The system of claim 1 , further comprising an anti-reflective layer, wherein the anti-reflective layer is disposed between the see-through display and the dynamic dimming assembly.
13. The system of claim 1 , further comprising an anti-reflective layer, wherein the dynamic dimming assembly is disposed between the anti-reflective layer and the see-through display.
14. The system of claim 1 , further comprising an index-matched layer disposed between the see-through display and the variable dimming assembly.
15. The system of claim 14 , wherein the index-matched layer has a refractive index that is the same as a refractive index of a portion of the eyepiece nearest the index-matching layer.
16. The system of claim 15 , wherein the index-matched layer comprises at least one of a gel or an optical adhesive.
17. A headset for an augmented reality system, wherein the headset comprises the system of claim 1 .