Spherical mirror having a decoupled aspheric
The technology provides decoupling an aspheric optical element from a birdbath optical element in a near-eye display (NED) device. One or more aspheric lens are used with a spherical birdbath reflective mirror in a projection light engine of a NED device. A projection light engine provides image light (or other information), by way of the spherical birdbath reflective mirror and at least one aspheric lens, to a near-eye display of the NED device. The spherical birdbath reflective mirror collimates and reflects the image light to an exit pupil external to the projection light engine. Decoupling the aspheric optical element from the spherical birdbath reflective mirror may enable high modulation transfer function (MTF) and improved manufacturability of the projection light engine. The NED device having aspheric optical elements decoupled from a birdbath optical element may be positioned by a support structure in a head-mounted display (HMD) or head-up display (HUD).
1. An apparatus comprising:
a display to provide an image light, wherein the display includes a microdisplay;
a beam splitter to beam split the image light, wherein the beam splitter is a type of beam splitter selected from a group consisting of cube, plate, wire-grid polarizer and internally refractive;
a spherical mirror to receive the image light from the beam splitter, wherein the spherical mirror reflects and collimates the image light;
an aspheric meniscus lens, separate from the beam splitter and decoupled and spaced from the spherical mirror, to correct image distortion in the image light caused by surface errors on the spherical mirror, wherein the aspheric meniscus lens includes an aspheric meniscus doublet disposed between the beam splitter and an external exit pupil;
a quarter wave retarder disposed between the aspheric meniscus lens and the beam splitter, wherein the image light passes through the aspheric meniscus lens and the quarter wave retarder after reflecting off the spherical mirror;
a doublet disposed between the spherical mirror and the beam splitter; and
a color select filter disposed between the beam splitter and the external exit pupil.
2. The apparatus of claim 1 , wherein the aspheric meniscus lens includes a first and second aspheric meniscus lens,
wherein the spherical mirror reflects and collimates the image light to the external exit pupil, and
wherein the first and second aspheric meniscus lens are disposed between the spherical mirror and the external exit pupil.
3. The apparatus of claim 1 ,
wherein the aspheric meniscus lens is disposed between the spherical mirror and the beam splitter.
4. The apparatus of claim 3 , further comprising:
an illumination unit including at least one light source,
wherein the microdisplay outputs the image light by reflecting light from the at least one light source.
5. The apparatus of claim 1 , further comprising:
at least one polarizer to polarize the image light,
wherein the microdisplay is a self-emissive microdisplay.
6. The apparatus of claim 1 , wherein the apparatus is included in projection light engine of a near-eye display device, the near-eye display device includes the projection light engine and a near-eye display that includes a waveguide.
7. The apparatus of claim 6 , wherein the projection light engine is included in a housing, wherein the projection light engine outputs the image light at the external exit pupil that is external to the housing.
8. A method comprising:
directing image light from an image source along a first optical path to a reflective mirror the image source including a microdisplay;
beam splitting, by a beam splitter, the image light, wherein the beam splitter is positioned in the first optical path;
collimating and reflecting the image light, by the reflective mirror, along a second optical path to an exit pupil outside a housing of the reflective mirror;
receiving the image light, by a spherical doublet disposed between the reflective mirror and the beam splitter along the first optical path;
prepolarizing the image light, by a prepolarizer disposed between the microdisplay and the spherical doublet along the first optical path; and
correcting, by an aspheric meniscus lens, an image distortion of the image light caused by surface errors on the reflective mirror, the aspheric meniscus lens disposed along the second optical path, the aspheric meniscus lens being decoupled and spaced from other elements, the image light passing through the aspheric meniscus lens after reflecting off of the reflective mirror.
9. The method of claim 8 , comprising:
receiving, at an input of a diffractive waveguide, the image light from the first optical path.
10. The method of claim 8 , further comprising:
polarizing the image light in at least one of the first optical path and the second optical path,
wherein polarizing the image light is performed at least in part by a polarizing beam splitter,
wherein the aspheric meniscus lens includes a first aspheric lens and a second aspheric lens, and
wherein the first aspheric lens and the second aspheric lens are disposed along the second optical path between the polarizing beam splitter and the exit pupil.
11. The method of claim 8 , further comprising:
polarizing the image light in at least one of the first optical path and the second optical path,
wherein polarizing the image light is performed at least in part by a polarizing beam splitter, and
wherein the aspheric meniscus lens is disposed along the second optical path between the reflective mirror and the polarizing beam splitter.
12. The method of claim 11 , wherein directing the image light along the first optical path to the reflective mirror comprises:
correcting a field of the image light from the microdisplay; and
reflecting the image light to the prepolarizer.
13. The method of claim 12 wherein directing the image light along the first optical path to the reflective mirror comprises:
outputting the image light, by the spherical doublet, to the polarizing beam splitter.
14. The apparatus of claim 1 ,
wherein the aspheric meniscus lens is disposed between the beam splitter and the external exit pupil.
15. An apparatus comprising:
a display to provide an image light, wherein the display includes a microdisplay;
a beam splitter to beam split the image light;
a reflective surface to reflect the image light from the microdisplay to the beam splitter;
a spherical doublet disposed between the reflective surface and the beam splitter;
a prepolarizer disposed between the spherical doublet and the microdisplay;
a field corrector disposed between the microdisplay and the reflective surface;
a spherical mirror to receive the image light from the beam splitter, wherein the spherical mirror reflects and collimates the image light; and
an aspheric meniscus lens to correct image distortion in the image light caused by surface errors on the spherical mirror, wherein the aspheric meniscus lens is disposed between the spherical mirror and the beam splitter, and wherein the aspheric meniscus lens is separate from the beam splitter and decoupled and spaced from the spherical mirror.
16. The apparatus of claim 15 , wherein the apparatus is included in projection light engine of a near-eye display device, the near-eye display device includes the projection light engine and a near-eye display that includes a waveguide.
17. The apparatus of claim 16 , wherein the projection light engine is included in a housing, wherein the projection light engine outputs the image light at an exit pupil that is external to the housing.
18. The apparatus of claim 15 , further comprising:
at least one polarizer to polarize the image light.
19. The apparatus of claim 15 , wherein the microdisplay is a self-emissive microdisplay.
20. The apparatus of claim 15 , wherein the beam splitter is a polarizing beam splitter.