Head up display (HUD) using a light pipe
A head up display can be used in compact environments. The head up display includes a combiner system including at least one light pipe and a waveguide. The at least one light pipe includes a turning grating or mirror array for providing light into the waveguide from the light pipe. An additional light pipe can also be provided. The combiner system can be headworn or stand-alone and can provide dual axis pupil expansion.
1. A head up display, comprising:
an input port having a first input face and a second input face perpendicular to the first input face, and comprising a first grating on the first input face;
a first light pipe coupled to the input port and having a first elongated face extending in a first direction and coplanar with the second input face of the input port, the first light pipe configured to expand a pupil in the first direction and comprising at least one turning grating and comprising a second grating on the second input face; and
a waveguide combiner configured to expand the pupil in a second direction perpendicular to the first direction and comprising an output grating,
wherein the first grating is reciprocal to the output grating so that light entering the first grating and light exiting the output grating travels in the same direction, and the second grating is reciprocal to the at least one turning grating so that light entering the second grating and light exiting the at least one turning grating travels in the same direction.
2. The head up display of claim 1 , wherein light enters the first light pipe from the input port at the first elongated face.
3. The head up display of claim 2 , wherein the first light pipe has a second elongated face opposite the first elongated face, the second elongated face comprising the second grating.
4. The head up display of claim 1 , wherein the first light pipe comprises at least one mirror array.
5. The head up display of claim 1 , wherein the first light pipe comprises four elongated surfaces, wherein two of the elongated surfaces comprise mirror symmetric gratings.
6. The head up display of claim 1 , further comprising:
an additional light pipe having a graded partial reflector positioned adjacent the first light pipe.
7. The head up display of claim 6 , further comprising an input grating disposed on elongated surface of the additional light pipe.
8. The head up display of claim 7 wherein the first light pipe comprises two high efficiency mirror gratings.
9. The head up display of claim 1 , wherein the output grating is in an XY plane and the first grating is in the XY plane, and
wherein the light travels down the first light pipe in an X direction in an XYZ coordinate system.
10. A method of providing information to a user, the method comprising:
providing light from an image source in a first direction via a first grating;
directing the light from the image source in a second direction perpendicular to the first direction with a second grating;
providing the light from the second grating to a first light pipe;
propagating a spiral light ray down the first light pipe;
expanding a pupil in a third direction different from and coplanar with the second direction with the first light pipe; and
providing the light from the first light pipe to a waveguide combiner using a turning grating;
wherein the first grating is reciprocal to an output grating of the waveguide combiner so that the light entering the first grating and the light exiting the output grating travels in the same direction, and the second grating is reciprocal to the turning grating so that the light entering the second grating and light exiting the turning grating travels in the same direction.
11. The method of claim 10 , wherein the first light pipe comprises the turning grating and the turning grating is associated with a surface between the first light pipe and the waveguide combiner.
12. The method of claim 10 , further comprising:
diffracting light out of the waveguide combiner and expanding the pupil in a fourth direction perpendicular to the third direction.
13. The method of claim 10 , wherein the second grating is the turning grating and the first light pipe further comprises the first grating, wherein the waveguide combiner comprises the output grating, wherein the turning grating is complementary to the first grating and the output grating.
14. The method of claim 10 , further comprising:
providing the light from the first light pipe to a second light pipe disposed between the first light pipe and the waveguide combiner.
15. A head up display system, comprising:
at least one light pipe comprising an input grating and a turning grating that is a reciprocal grating to the input grating so that light entering the input grating and light exiting the turning grating travels in the same direction; and
a waveguide combiner, wherein the at least one light pipe propagates light between the input grating and the turning grating via mirror reflection and into the waveguide combiner from the light pipe via the turning grating, the waveguide combiner comprises an output grating that is a reciprocal grating to a first grating of an input port so that the light entering the input port via the first grating and the light exiting the waveguide combiner via the output grating travels in the same direction.
16. The head up display system of claim 15 , further comprising an additional light pipe.
17. The head up display system of claim 16 , wherein the additional light pipe comprises a turning grating on a surface parallel to a main surface of the waveguide combiner.
18. The head up display system of claim 15 , wherein the light pipe expands a pupil in a first direction and the waveguide combiner expands the pupil in a second direction.
19. The head up display system of claim 15 , wherein the input grating is in an XZ plane and the turning grating is in the XZ plane, and
wherein the light travels down the light pipe in an X direction in an XYZ coordinate system.