Attenuation of light transmission artifacts in wearable displays
A wearable display system includes an eyepiece stack having a world side and a user side opposite the world side, wherein during use a user positioned on the user side views displayed images delivered by the system via the eyepiece stack which augment the user's view of the user's environment. The wearable display system also includes an angularly selective film arranged on the world side of the of the eyepiece stack. The angularly selective film includes a polarization adjusting film arranged between pair of linear polarizers. The linear polarizers and polarization adjusting film significantly reduces transmission of visible light incident on the angularly selective film at large angles of incidence without significantly reducing transmission of light incident on the angularly selective film at small angles of incidence.
1. A wearable display system, comprising:
an eyepiece stack having a world side and a user side opposite the world side, wherein during use a user positioned on the user side views displayed images delivered by the wearable display system via the eyepiece stack which augment the user's field of view of the user's environment; and
an angularly selective film arranged on the world side of the of the eyepiece stack, the angularly selective film comprising a polarization adjusting film arranged between a pair of linear polarizers,
wherein, for unpolarized light in a wavelength range from 420 nm to 680 nm, the angularly selective film has a transmission efficiency of 40% or more at angles of incidence less than 350 and has a transmission efficiency of 1% or less for at least one angle of incidence greater than 35°, wherein for a D65 source, the angularly selective film shifts a (0.33, 0.33) CIE 1931 white point less than (+/−0.2, +/−0.2) for unpolarized light with an angle of incidence between −32° and +32°.
2. The wearable display system of claim 1 , wherein for unpolarized light in a wavelength range from 420 nm to 680 nm, the angularly selective film has a transmission efficiency greater than 45% at angles of incidence between −32° and +32°.
3. The wearable display system of claim 1 , wherein pass axes of the pair of linear polarizers are crossed.
4. The wearable display system of claim 1 , wherein the polarization adjusting film rotates a polarization state of light transmitted by a first linear polarizer of the pair of linear polarizers on the world side of the polarization adjusting film.
5. The wearable display system of claim 4 , wherein an amount of rotation of the polarization state varies depending on an angle of incidence of light transmitted by the first linear polarizer of the pair of linear polarizers.
6. The wearable display system of claim 5 , wherein the light transmitted having angles of incidence of 350 or more is rotated less than the light transmitted having angles of incidence less than 35°.
7. The wearable display system of claim 1 , wherein unpolarized light of wavelength in a range from 420 nm to 680 nm incident of the angularly selective film with an angle of incidence between 35° and 65° has a transmission efficiency less than 0.5%.
8. The wearable display system of claim 1 , wherein the polarization adjusting film comprises at least one layer of a birefringent material.
9. The wearable display system of claim 8 , wherein the at least one layer of birefringent material comprises a C-plate.
10. The wearable display system of claim 9 , wherein the at least one layer of birefringent material comprises a pair of quarter wave plates, the quarter wave plates being disposed on opposite sides of the C-plate.
11. The wearable display system of claim 10 , wherein the each of the pair of quarter wave plates is arranged relative to a corresponding one of the linear polarizers to form a circular polarizer.
12. The wearable display system of claim 9 , wherein the at least one layer of birefringent material comprises at least one quarter wave plate.
13. The wearable display system of claim 1 , wherein the polarization adjusting film is a first polarization adjusting film and the angularly selective film further comprises a second polarization adjusting film and a third linear polarizer, the second polarization adjusting film being arranged between the pair of linear polarizers and the third linear polarizer.
14. The wearable display system of claim 13 , wherein the first and second polarization adjusting films are each composed of one or more layers of birefringent materials.
15. The wearable display system of claim 14 , wherein the one or more layers of birefringent materials of the first and second polarization adjusting films each comprises a C-plate.
16. The wearable display system of claim 15 , wherein the one or more layers of birefringent materials of the first and second polarization adjusting films each comprise a pair of quarter wave plates arranged on opposite sides of the corresponding C-plate.
17. The wearable display system of claim 1 , wherein the angularly selective film comprises two or more stages, each stage comprising a polarization adjusting film arranged between a pair of linear polarizers.
18. The wearable display system of claim 17 , wherein adjacent stages share a linear polarizer.
19. The wearable display system of claim 1 , wherein the angularly selective film further comprises a liquid crystal layer having variable optical properties.