Wearable heads-up display with optical path fault detection

1. A wearable heads-up display, comprising:

a power source;

a plurality of laser sources;

a lightguide having at least one optical path defined therein;

at least one photodetector positioned proximate to a perimeter of the lightguide to detect a first intensity of a portion of a test light emitted from the at least one optical path; and

a laser safety circuit communicatively coupled to the power source and the at least one photodetector, the laser safety circuit to provide a control to reduce or shut off a supply of electrical power from the power source to the plurality of laser sources in response to an output signal from the at least one photodetector indicating that the detected first intensity is below a first threshold.

2. The wearable heads-up display of claim 1 , wherein the plurality of laser sources are visible laser sources, and wherein at least one of the visible laser sources generates the test light.

3. The wearable heads-up display of claim 1 , wherein the plurality of laser sources includes a plurality of visible laser sources and at least one infrared laser source, and wherein the at least one infrared laser source generates the test light.

4. The wearable heads-up display of claim 1 , further comprising a display engine to provide controls that modulate outputs of the plurality of laser sources according to display data, wherein the laser safety circuit is communicatively coupled to the display engine, the laser safety circuit to provide a notification to the display engine in response to the output signal from the at least one photodetector indicating that the detected first intensity is below the first threshold.

5. The wearable heads-up display of claim 1 , further comprising an in-coupler positioned at an input region of the lightguide to couple light into the input region.

6. The wearable heads-up display of claim 5 , further comprising at least one scan mirror positioned to receive an aggregated beam formed from outputs of the plurality of laser sources and redirect the aggregated beam to the in-coupler.

7. The wearable heads-up display of claim 5 , wherein the at least one optical path extends from the input region to the perimeter of the lightguide.

8. The wearable heads-up display of claim 5 , further comprising an out-coupler positioned at an output region of the lightguide to direct light out of the output region.

9. The wearable heads-up display of claim 8 , wherein the lightguide has a second optical path defined therein, and wherein the second optical path is in optical communication with the input region.

10. The wearable heads-up display of claim 9 , further comprising an exit pupil expander positioned at a fold region of the lightguide that is intermediate between the input region and the output region, the exit pupil expander in optical communication with the at least one optical path and the second optical path, the exit pupil expander to redirect at least a portion of light propagating along the second optical path to the at least one optical path.

11. The wearable heads-up display of claim 10 , further comprising a second photodetector positioned proximate to the perimeter of the lightguide to detect a second intensity of a portion of the test light that is emitted from the second optical path.

12. The wearable heads-up display of claim 11 , wherein the second optical path extends from the input region to the perimeter of the lightguide.

13. The wearable heads-up display of claim 11 , wherein the laser safety circuit is communicatively coupled to the second photodetector, the laser safety circuit to provide a control to reduce or shut off the supply of electrical power from the power source to the plurality of laser sources in response to an output signal from the second photodetector indicating that the detected second intensity is below a second threshold.

14. The wearable heads-up display of claim 13 , further comprising a display engine to provide controls that modulate outputs of the plurality of laser sources according to display data, wherein the laser safety circuit is communicatively coupled to the display engine to provide a notification to the display engine in response to the output signal from the at least one photodetector indicating that the detected first intensity is below the first threshold and/or the output signal from the second photodetector indicating that the detected second intensity is below the second threshold.

15. The wearable heads-up display of claim 1 , further comprising a support frame having a frame front and at least one temple coupled to the frame front, wherein the frame front carries at least one lens, and wherein the lightguide is integrated with the at least one lens.

16. The wearable heads-up display of claim 15 , wherein the at least one photodetector is embedded in a portion of the frame front circumscribing the at least one lens.

17. The wearable heads-up display of claim 15 , wherein the at least one temple is coupled to the frame front by a hinge and is movable between an open position and a folded position by the hinge, wherein the at least one temple carries the plurality of laser sources, wherein a support frame optical path is defined from the temple to the lightguide when the temple is in the open position and undefined when the temple is in the folded position, and wherein the lightguide is optically coupled to the plurality of laser sources when the support frame optical path is defined.

18. A wearable heads-up display, comprising:

a first laser source;

a second laser source;

a power source;

a lightguide having a first optical path and a second optical path defined therein;

a first in-coupler positioned to receive a first laser light output by the first laser source and couple the first laser light into the first optical path;

a second in-coupler positioned to receive a second laser light output by the second laser source and couple the second laser light into the second optical path;

a photodetector positioned proximate to a perimeter of the lightguide to detect an intensity of a portion of the first laser light emitted from the first optical path; and

a laser safety circuit communicatively coupled to the power source and the photodetector, the laser safety circuit to provide a control to reduce or shut off a supply of electrical power from the power source to the second laser source in response to an output signal from the photodetector indicating that the detected intensity is below a threshold.

19. The wearable heads-up display of claim 18 , wherein the first laser source is an infrared laser source, and wherein the second laser source is a visible laser source.

20. The wearable heads-up display of claim 19 , further comprising at least one scan mirror positioned to receive an aggregated beam formed from the first laser light output and the second laser light output and redirect the aggregated beam to the first in-coupler and the second in-coupler.

21. The wearable heads-up display of claim 20 , wherein the first in-coupler is in stack with the second in-coupler.

22. The wearable heads-up display of claim 21 , wherein the first in-coupler is responsive to light from the infrared laser source but unresponsive to light from the visible laser source, and wherein the second in-coupler is responsive to light from the visible laser source but unresponsive to light from the infrared laser source.

23. The wearable heads-up display of claim 18 , further comprising an out-coupler positioned to couple at least a portion of the second laser light output out of the lightguide.

24. The wearable heads-up display of claim 23 , wherein the lightguide has a third optical path defined therein, and wherein the out-coupler is in optical communication with the third optical path.

25. The wearable heads-up display of claim 24 , further comprising an exit pupil expander positioned to redirect at least a portion of the second laser light output propagating along the second optical path into the third optical path.

26. The wearable heads-up display of claim 18 , further comprising a support frame having a frame front and at least one temple coupled to the frame front, wherein the frame front carries at least one lens, and wherein the lightguide and in-couplers are integrated with the at least one lens.

27. The wearable heads-up display of claim 26 , wherein the photodetector is embedded in a portion of the frame front circumscribing the at least one lens.

28. The wearable heads-up display of claim 26 , wherein the at least one temple is coupled to the frame front by a hinge and is movable between an open position and a folded position by the hinge, wherein the at least one temple carries the first laser source and the second laser source, wherein a support frame optical path is defined from the temple to the lightguide when the temple is in the open position and undefined when the temple is in the folded position, and wherein the in-couplers are optically coupled to the respective laser sources when the support frame optical path is defined.

29. A wearable heads-up display, comprising:

a power source;

a first laser source;

a second laser source;

a lightguide having a first optical path, a second optical path, and a third optical path defined therein;

a first in-coupler positioned to receive a first laser light output by the first laser source and couple the first laser light into the first optical path and the second optical path;

a second in-coupler positioned to receive a second laser light output by the second laser source and couple the second laser light into the third optical path;

a first photodetector positioned proximate to a perimeter of the lightguide to detect a first intensity of a portion of the first laser light emitted from the first optical path;

a second photodetector positioned proximate to the perimeter of the lightguide to detect a second intensity of a portion of the first laser light emitted from the second optical path; and

a laser safety circuit communicatively coupled to the first photodetector, the second photodetector, and the power source, the laser safety circuit to provide a control to reduce or shut off a supply of electrical power from the power source to the second laser source in response to an output signal from the first photodetector indicating that the detected first intensity is below a first threshold and/or an output signal from the second photodetector indicating that the detected second intensity is below a second threshold.

30. The wearable heads-up display of claim 29 , wherein the first laser source is an infrared laser source, and wherein the second laser source is a visible laser source.

31. The wearable heads-up display of claim 29 , further comprising an out-coupler in optical communication with the third optical path, the out-coupler to couple at least a portion of the second laser light out of the lightguide.

32. The wearable heads-up display of claim 29 , further comprising at least one scan mirror positioned to receive the second laser light from the second laser source and redirect the second laser light to the second in-coupler.

33. The wearable heads-up display of claim 29 , further comprising a display engine to provide controls that modulate the output of the second laser source according to display data, wherein the laser safety circuit is communicatively coupled to the display engine, the laser safety circuit to provide a notification to the display engine in response to the output signal from the first photodetector indicating that the detected first intensity is below the first threshold and/or the output signal from the second photodetector indicating that the detected second intensity is below the second threshold.

34. The wearable heads-up display of claim 29 , further comprising a support frame having a frame front and at least one temple coupled to the frame front, wherein the frame front carries at least one lens, and wherein the lightguide and in-couplers are integrated with the at least one lens.

35. The wearable heads-up display of claim 34 , wherein the photodetectors are embedded in a portion of the frame front circumscribing the at least one lens.

36. The wearable heads-up display of claim 34 , wherein the at least one temple is coupled to the frame front by a hinge and is movable between an open position and a folded position by the hinge, wherein the at least one temple carries the first laser source and the second laser source, wherein a support frame optical path is defined from the temple to the lightguide when the temple is in the open position and undefined when the temple is in the folded position, and wherein the in-couplers are optically coupled to the respective laser sources when the support frame optical path is defined.

37. A wearable heads-up display, comprising:

a power source;

a laser module including at least one laser source;

a lightguide having at least one optical path defined therein;

an in-coupler positioned to receive a display light output by the laser module and couple the display light into the at least one optical path;

at least one light source to output a test light that is directed into the lightguide through a first portion of a surface of the lightguide;

a photodetector positioned proximate to a perimeter of the lightguide to detect an intensity of a portion of the test light emitted from within the lightguide; and

a laser safety circuit communicatively coupled to the power source and the photodetector, the laser safety circuit to provide a control to reduce or shut off a supply of electrical power from the power source to the laser module in response to an output signal from the photodetector indicating that the detected intensity is below a threshold.

38. The wearable heads-up display of claim 37 , wherein the at least one light source is a laser diode or a light emitting diode.

39. The wearable heads-up display of claim 38 , wherein the at least one light source is an infrared light source.

40. The wearable heads-up display of claim 38 , further comprising a support frame having a frame front and at least one temple coupled to the frame front, wherein the frame front carries at least one lens, and wherein the lightguide and in-coupler are integrated with the lens.

41. The wearable heads-up display of claim 40 , wherein the at least one light source and photodetector are embedded in a portion of the frame front circumscribing the at least one lens.

42. A method of safely operating a wearable heads-up display having a field of view, a lightguide positioned within the field of view, a plurality of laser sources, a power source, and a support frame, the method comprising:

at select times during use of the wearable heads-up display, testing the wearable heads-up display for optical path faults, the testing comprising:

generating a test light;

directing the test light along a support frame optical path to the lightguide; and

detecting an intensity of a portion of the test light that is emitted at a perimeter of the lightguide from an optical path within the lightguide; and

in response to detecting an intensity of the portion of the test light that is below a threshold, reducing or shutting off a supply of electrical power from the power source to the plurality of laser sources.

43. The method of claim 42 , further comprising projecting one or more display images to a display space within the field of view, wherein each projection of a display image comprises:

forming a display light from a combination of laser light generated by the plurality of laser sources;

directing the display light along the support frame optical path to the lightguide; and

coupling the display light into the lightguide.

44. The method of claim 43 , wherein each projection of a display image is preceded by testing the wearable heads-up display for optical path faults.

45. The method of claim 43 , wherein projecting the one or more display images to the display space within the field of view is interspersed with testing the wearable heads-up display for optical path faults.

46. The method of claim 43 , wherein reducing the supply of electrical power from the power source to the plurality of laser sources comprises limiting the supply of electrical power to the plurality of laser sources such that an optical power density of the display light does not exceed the maximum permissible exposure for a Class 1 laser.

47. The method of claim 42 , wherein the test light is visible light.

48. The method of claim 47 , wherein at least one of the plurality of laser sources outputs the test light.

49. The method of claim 42 , wherein the test light is infrared light.