Heat dissipation for head-mountable device
A head-mountable device can provide passive cooling that utilizes surfaces of an optical assembly to allow heat to be managed in a manner that does not detrimentally impact the visual information displayed to the user. Lenses can be coated with a transparent and thermally conductive material, such as silver nanowire. Such a thermal layer can provide superior thermal conductivity, transmittance, flexibility, flat transmission, low cost, and angular color stability. The thermal layer can passively manage heat by increasing the surface area across which heat can be efficiently dissipated.
1. A head-mountable device comprising:
a frame; and
an optical module coupled to the frame, the optical module comprising:
a waveguide;
a display element configured to project light onto the waveguide;
a lens positioned on a side of the waveguide;
a first thermal layer on a first side of the lens facing the waveguide and comprising silver nanowires, the first thermal layer being separated from the lens by a gap; and
a second thermal layer on a second side of the lens, the second thermal layer defining an outermost end of the optical module and comprising silver nanowires for conducting heat from the frame across an outer surface of the lens.
2. The head-mountable device of claim 1 , wherein:
the lens is a first lens;
the head-mountable device further comprises a second lens; and
the waveguide is positioned between the first lens and the second lens.
3. The head-mountable device of claim 2 , the head-mountable device further comprising:
a third thermal layer on a first side of the second lens; and
a fourth thermal layer on a second side of the second lens.
4. The head-mountable device of claim 1 , further comprising an arm extending away from the frame, wherein the display element is within the arm.
5. The head-mountable device of claim 1 , wherein the lens has a thermal conductivity that is less than 1 W·m −1 ·K −1 .
6. The head-mountable device of claim 1 , wherein:
the optical module is a first optical module; and
the head-mountable device further comprises a second optical module coupled to the frame.
7. An optical module for a head-mountable device, the optical module comprising:
a waveguide;
an inner lens separated from a first side of the waveguide by a first gap;
an outer lens separated from a second side of the waveguide by a second gap, the inner lens and the outer lens each comprising a first material;
a first thermal layer on an inner side of the inner lens and defining an innermost end of the optical module; and
a second thermal layer on an outer side of the outer lens and defining an outermost end of the optical module, the first and second thermal layers comprising a second material that conducts heat more efficiently than the first material.
8. The optical module of claim 7 , wherein:
the first material has a first thermal conductivity; and
the second material has a second thermal conductivity that is at least 100 times greater than the first thermal conductivity.
9. The optical module of claim 8 , wherein:
the first thermal conductivity is less than 1 W·m −1 ·K −1 ; and
the second thermal conductivity is greater than 400 W·m −1 ·K −1 .
10. The optical module of claim 7 , further comprising:
a frame;
an arm extending away from the frame; and
a display element within the arm and configured to project light onto the waveguide.
11. The optical module of claim 7 , wherein the second material is silver forming nanowires of the first and second thermal layers.
12. The optical module of claim 7 , further comprising:
a third thermal layer on an outer side of the inner lens; and
a fourth thermal layer on an inner side of the outer lens.
13. A head-mountable device comprising:
a frame;
arms extending from opposite sides of the frame;
electrical components in each of the arms; and
an optical module for providing a view to an external environment, the optical module being supported by the frame, being thermally coupled to the electrical components, and comprising:
a waveguide;
an inner lens separated from a first side of the waveguide by a first gap;
an outer lens separated from a second side of the waveguide by a second gap, the inner lens and the outer lens each comprising a first material;
a first thermal layer on an inner side of the inner lens and defining an innermost end of the optical module; and
a second thermal layer on an outer side of the outer lens and defining an outermost end of the optical module, the first and second thermal layers comprising a second material that conducts heat more efficiently than the first material, the first and second thermal layers comprising a conductive material having a thermal conductivity of greater than 100 W·m −1 ·K −1 .
14. The head-mountable device of claim 13 , further comprising a display element within one of the arms and configured to project light onto the waveguide.
15. The head-mountable device of claim 13 , the head-mountable device further comprising:
a third thermal layer on an inner side of the outer lens; and
a fourth thermal layer on an inner side of the outer lens.
16. The head-mountable device of claim 13 , wherein the inner lens and the outer lens each has a thermal conductivity that is less than 1 W·m −1 ·K −1 .
17. The head-mountable device of claim 13 , wherein:
each of the first and second thermal layers has a first thermal conductivity; and
the inner lens and the outer lens each has a second thermal conductivity, wherein the first thermal conductivity is at least 100 times greater than the second thermal conductivity.
18. The head-mountable device of claim 13 , wherein the conductive material has a thermal conductivity of greater than 400 W·m −1 ·K −1 .
19. The head-mountable device of claim 13 , wherein the conductive material is silver forming nanowires.