Dual axis internal optical beam tilt for eyepiece of an HMD
An eyepiece includes a display module for providing display light, a concave end reflector, and a viewing region including a partially reflective surface to redirect at least a portion of the display light out of an eye-ward side of the eyepiece along an emission path. The partially reflective surface is obliquely angled with an offset from 45 degrees relative to the eye-ward side to cause the emission path to have a first oblique angle in a horizontal dimension relative to a first normal vector of the eye-ward side. The concave end reflector is tilted such that a second normal vector from a center point of the concave end reflector is obliquely angled relative to a top or bottom surface of the eyepiece to cause the emission path to have a second oblique angle in a vertical dimension relative to the first normal vector of the eye-ward side.
1. An eyepiece, comprising:
a display module for providing display light along a forward propagation path within the eyepiece;
a concave end reflector disposed at an opposite end of the eyepiece from the display module to reflect the display light back along a reverse propagation path within the eyepiece; and
a viewing region disposed between the display module and the concave end reflector and including a partially reflective surface, the partially reflective surface to redirect at least a portion of the display light traveling along the reverse propagation path out of an eye-ward side of the eyepiece along an emission path,
wherein the partially reflective surface is obliquely angled with an offset from 45 degrees relative to the eye-ward side to cause the emission path to have a first oblique angle in a horizontal dimension relative to a first normal vector of the eye-ward side,
wherein the concave end reflector is tilted such that a second normal vector from a center point of the concave end reflector is obliquely angled relative to a top or bottom surface of the eyepiece to cause the emission path to have a second oblique angle in a vertical dimension relative to the first normal vector of the eye-ward side,
wherein the horizontal dimension is orthogonal to the vertical dimension, the vertical dimension intersects through the top and bottom surfaces of the eyepiece, and the horizontal dimension intersects through the display module and the concave end reflector.
2. The eyepiece of claim 1 , wherein the top and bottom surfaces are flat and planar.
3. The eyepiece of claim 2 , wherein the eye-ward side of the eyepiece is flat and planar and substantially perpendicular to the top and bottom surfaces.
4. The eyepiece of claim 3 , wherein the eyepiece is configured to be coupled to a head mounted display that holds the eyepiece level above an eye of a user and angles an end of the eyepiece proximate to the display module towards a temple region of the user such that the user looks straight forward and up to align the eye with the emission path of the display light.
5. The eyepiece of claim 4 , wherein the first oblique angle is 6 degrees ±3 degrees, the offset from 45 degrees of the partially reflective surface is 2 degrees ±1 degree, the second oblique angle is 7 degrees ±3 degrees, and the second normal vector from the center point of the concave end reflector is obliquely angled relative to the top or bottom surface of the eyepiece by 2 degrees ±1 degree.
6. The eyepiece of claim 1 , wherein the display module comprises:
a lamp source to generate lamp light; and
a display panel positioned to be illuminated by the lamp light and to selectively reflect the lamp light as the display light,
wherein the display panel is tilted to reduce ghost images due to back reflections of the display light reaching the display panel.
7. The eyepiece of claim 6 , wherein the display panel is tilted to be obliquely angled relative to the eye-ward side of the eyepiece.
8. The eyepiece of claim 7 , wherein the display panel is tilted clockwise about an axis that is substantially parallel to an axis that extends from the display module to the concave end reflector and is substantially parallel to the eye-ward side.
9. The eyepiece of claim 6 , wherein the display module further comprises:
an in-coupling beam splitter disposed between the lamp source and the display panel to redirect the display light received from the display panel along the forward propagation path within the eyepiece.
10. The eyepiece of claim 9 , wherein the in-coupling beam splitter comprises a polarizing beam splitter, the eyepiece further comprising: a light relay section coupled between the viewing region and the display module through which the forward propagation path extends;
a linear polarizer disposed within the forward propagation path between the display module and the partially reflective surface, wherein the linear polarizer is oriented to filter out a first linear polarization that is substantially passed through the in-coupling beam splitter and to pass a second linear polarization that is substantially reflected by the in-coupling beam splitter.
11. The eyepiece of claim 10 , wherein the light relay section has first section with a first cross-section size that coupled to the display module and a section with a second cross-section size larger than the first cross-section size that extends to the viewing region.
12. The eyepiece of claim 11 , wherein the light relay section and the viewing region of the eyepiece are made of two plastic pieces with oblique mating interfaces between which the partially reflective surface is disposed.
13. A head mounted display (“HMD”) for providing display light to an eye of a user, the HMD comprising:
an eyepiece including:
a display module for generating display light;
a concave end reflector disposed at an opposite end of the eyepiece from the display module; and
a viewing region disposed between the display module and the concave end reflector and including a partially reflective surface, the partially reflective surface to pass at least a portion of the display light traveling along a forward propagation path and to redirect at least a portion of the display light traveling along the reverse propagation path out of an eye-ward side of the eyepiece along an emission path,
a frame assembly to support the eyepiece for wearing on a head of the user with the viewing region positioned above the eye of the user,
wherein the partially reflective surface is obliquely angled with an offset from 45 degrees relative to the eye-ward side to cause the emission path to have a first oblique angle in a horizontal dimension relative to a first normal vector of the eye-ward side,
wherein the concave end reflector is tilted such that a second normal vector from a center point of the concave end reflector is obliquely angled relative to a top or bottom surface of the eyepiece to cause the emission path to have a second oblique angle in a vertical dimension relative to the first normal vector of the eye-ward side,
wherein the horizontal dimension is orthogonal to the vertical dimension, the vertical dimension intersects through the top and bottom surfaces of the eyepiece, and the horizontal dimension intersects through the display module and the concave end reflector.
14. The HMD of claim 13 , wherein the eye-ward side of the eyepiece is flat and planar and substantially perpendicular to the top and bottom surfaces.
15. The HMD of claim 14 , wherein the frame assembly is configured to hold the eyepiece level above an eye of a user and angles an end of the eyepiece proximate to the display module towards a temple region of the user such that the user looks straight forward and up to align the eye with the emission path of the display light.
16. The HMD of claim 13 , wherein the display module comprises:
a lamp source to generate lamp light; and
a display panel positioned to be illuminated by the lamp light and to selectively reflect the lamp light as the display light,
wherein the display panel is tilted to reduce ghost images due to back reflections of the display light reaching the display panel.
17. The HMD of claim 16 , wherein the display panel is tilted to be obliquely angled relative to the eye-ward side of the eyepiece.
18. The HMD of claim 17 , wherein the display panel is tilted clockwise about an axis that is substantially parallel to an axis that extends from the display module to the concave end reflector and is substantially parallel to the eye-ward side.
19. The HMD of claim 16 , wherein the display module further comprises an in-coupling beam splitter,
wherein the in-coupling beam splitter comprises a polarizing beam splitter, the eyepiece further comprising: a light relay section coupled between the viewing region and the display module through which the forward propagation path extends;
a linear polarizer disposed within the forward propagation path between the display module and the partially reflective surface, wherein the linear polarizer is oriented to filter out a first linear polarization that is substantially passed through the in-coupling beam splitter and to pass a second linear polarization that is substantially reflected by the in-coupling beam splitter.
20. The HMD of claim 19 , wherein the light relay section and the viewing region of the eyepiece are made of two plastic pieces with oblique mating interfaces between which the partially reflective surface is disposed.