Lens assembly including a silicone fresnel lens
A lens assembly and a method of making the assembly are described. The lens assembly includes a first lens and a second lens slidably coupled with the first lens. The second lens includes a silicone material and has a Fresnel pattern surface. Also described is a display device including the lens assembly and an array of light emitting devices coupled with the lens assembly for outputting light through the lens assembly.
1. A lens assembly, comprising:
a first lens; and
a second lens that includes silicone material and has a surface with a Fresnel pattern, wherein the second lens is slidably coupled with the first lens so that the first lens slides relative to the second lens in a direction that is substantially parallel to an optical axis of the first lens or the second lens.
2. The lens assembly of claim 1 , wherein:
the first lens includes polymethylmethacrylate (PMMA).
3. The lens assembly of claim 1 , wherein:
the second lens includes a plurality of guides that are slidably coupled with the first lens.
4. The lens assembly of claim 3 , wherein:
a plurality of through-holes are defined in the first lens; and
the plurality of through-holes are configured to mate with the plurality of guides.
5. The lens assembly of claim 4 , further comprising:
a lock configured for conditionally preventing a sliding motion of the second lens relative to the first lens.
6. The lens assembly of claim 1 , wherein:
the first lens includes a plurality of guides that are slidably coupled with the second lens.
7. The lens assembly of claim 6 , wherein:
a plurality of through-holes are defined in the second lens; and
the plurality of through-holes are configured to mate with the plurality of guides.
8. The lens assembly of claim 7 , further comprising:
a lock configured for conditionally preventing a sliding motion of the second lens relative to the first lens.
9. The lens assembly of claim 6 , further comprising:
an actuator configured to move the first lens and/or the second lens so as to change a distance between the first lens and the second lens.
10. The lens assembly of claim 1 , wherein:
the first lens is rotationally symmetric; and
the second lens is rotationally symmetric.
11. The lens assembly of claim 1 , wherein:
the Fresnel pattern is defined by a surface profile function; and
a derivative of the surface profile function has one or more discontinuities.
12. A display device, comprising:
the lens assembly of claim 1 ; and
an array of light emitting devices coupled with the lens assembly for outputting light through the lens assembly.
13. The display device of claim 12 , wherein the display device is a head-mounted display device.
14. The display device of claim 13 , wherein the array of light emitting devices is configured to output light and transmit the light through the lens assembly toward an eye of a user when the display device is worn on a head of the user.
15. A method for making a lens assembly, the method comprising:
providing a first lens;
providing a second lens that includes silicone material and has a surface with a Fresnel pattern; and
slidably coupling the first lens with the second lens so that the first lens slides relative to the second lens in a direction that is substantially parallel to an optical axis of the first lens or the second lens.
16. The method of claim 15 , further comprising:
mechanically coupling the first lens and/or the second lens with an actuator configured to change a distance between the first lens and the second lens.
17. The method of claim 15 , further comprising:
changing a distance between the first lens and the second lens to obtain a particular magnification for the lens assembly.
18. The method of claim 17 , further comprising:
fixing the distance between the first lens and the second lens.
19. The method of claim 18 , wherein:
the first lens and the second lens are slidably coupled with a plurality of guides and a plurality of corresponding through-holes; and
fixing the distance between the first lens and the second lens includes engaging one or more locks to prevent a sliding motion of at least one guide of the plurality of guides relative to a corresponding through-hole of the plurality of through-holes.
20. The method of claim 15 , wherein:
providing the second lens includes:
providing, in a mold having a first Fresnel pattern, a silicone material comprising silicone; and
curing the silicone material in the mold to form a Fresnel lens, wherein the cured silicone material has a second Fresnel pattern that corresponds to the first Fresnel pattern.