Eyebox expansion and exit pupil replication in wearable heads-up display having integrated eye tracking and laser projection
Systems, devices, and methods that integrate eye tracking capability into scanning laser projector (“SLP”)-based wearable heads-up displays are described. An infrared laser diode is added to an RGB SLP and an infrared photodetector is aligned to detect reflections of the infrared light from features of the eye. A holographic optical element (“HOE”) may be used to combine visible light, infrared light, and environmental light into the user's “field of view.” The HOE may be heterogeneous and multiplexed to apply positive optical power to the visible light and zero or negative optical power to the infrared light.
1. A wearable heads-up display (“WHUD”) comprising:
a support frame that in use is worn on a head of a user;
a laser module carried by the support frame, the laser module including an infrared laser diode to output an infrared light and at least one visible light laser diode to output a visible light;
a scan mirror carried by the support frame and aligned with an output of the laser module to receive both the infrared light and the visible light output by the laser module, the scan mirror to controllably reflect both the infrared light and the visible light;
an optical splitter aligned to:
receive both the infrared light and the visible light from the scan mirror;
transmit the infrared light therethrough without influencing the infrared light; and
separate the visible light into angle-separated copies;
a wavelength-multiplexed holographic optical element (“HOE”) carried by the support frame and positioned within a field of view of at least one eye of the user when the support frame is worn on the head of the user, the wavelength-multiplexed HOE aligned to receive both the infrared light and the angle-separated copies of the visible light from the optical splitter and to redirect both the infrared light and the angle-separated copies of the visible light towards the at least one eye of the user when the support frame is worn on the head of the user, wherein the wavelength-multiplexed-HOE includes a first hologram that is responsive to the angle-separated copies of the visible light and unresponsive to the infrared light and a second hologram that is responsive to the infrared light and unresponsive to the angle-separated copies of the visible light, and wherein the wavelength-multiplexed HOE is substantially transparent to environmental light; and
an infrared detector carried by the support frame and aligned to receive at least a portion of infrared light reflected from the at least one eye of the user when the support frame is worn on the head of the user.
2. The WHUD of claim 1 wherein the support frame has a general shape and appearance of a pair of eyeglasses.
3. The WHUD of claim 1 wherein the wavelength-multiplexed HOE comprises at least two distinct layers of holographic material, a first layer of holographic material that includes the first hologram and a second layer of holographic material that includes the second hologram.
4. The WHUD of claim 1 wherein the wavelength-multiplexed HOE comprises a single volume of holographic material that includes both the first hologram and the second hologram.
5. The WHUD of claim 1 wherein the at least one visible light laser diode in the laser module includes at least one visible light laser diode selected from the group consisting of: a red laser diode, a green laser diode, a blue laser diode, and any combination of a red laser diode, a green laser diode, and/or a blue laser diode.
6. The WHUD of claim 1 wherein the exit pupil replication optic is at least partially formed of cold optical material.
7. The WHUD of claim 1 wherein each angle-separated copy of the visible light is a respective copy of a same image.
8. The WHUD of claim 1 wherein the optical splitter expands an eyebox of the WHUD.
9. The WHUD of claim 1 wherein the exit pupil replication optic includes multiple surfaces positioned and oriented to direct the angle-separated copies of the visible light towards the wavelength-multiplexed HOE at respectively different angles.
10. The WHUD of claim 1 wherein the first hologram applies a first optical power to the angle-separated copies of visible light and the second hologram applies a second optical power to the infrared light, the second optical power different from the first optical power.
11. The WHUD of claim 10 wherein the first optical power is a positive optical power and the first optical power is greater than the second optical power.
12. The WHUD of claim 11 wherein the second optical power is less than or equal to zero.