Hybrid fresnel lens with reduced artifacts
A lens defined by a first lens surface and a second lens surface opposite to the first lens surface is disclosed. A first portion of the first lens surface is defined by a smooth surface profile function, and a second portion of the first lens surface is defined by a Fresnel surface profile function. The second portion of the first lens surface is around the first portion of the first lens surface. Also disclosed is a display device that includes the lens and an array of light emitting devices coupled with the lens for outputting light through the lens.
1. A display device, comprising:
a lens, defined by a first lens surface and a second lens surface opposite to the first lens surface, wherein:
a first portion of the first lens surface is defined by a smooth surface profile function;
a second portion of the first lens surface is defined by a Fresnel surface profile function;
the second portion of the first lens surface is around the first portion of the first lens surface;
the first portion and the second portion of the first lens surface are defined by a sum of two surface profile functions;
a first surface profile function of the two surface profile functions defines a smooth surface profile across the first portion and the second portion of the first lens surface;
the smooth surface profile defined by the first surface profile function corresponds to an aspheric curve; and
a second surface profile function of the two surface profile functions defines:
a smooth surface profile across the first portion of the first lens surface; and
a Fresnel surface profile across the second portion of the first lens surface; and
an array of light emitting devices coupled with the lens for outputting light through the lens.
2. The display device of claim 1 , wherein the array of light emitting devices is configured to output light and transmit the light through the lens toward an eye of a user when the display device is worn on a head of the user.
3. The display device of claim 1 , wherein the first lens surface of the lens is positioned toward the array of light emitting devices and the second lens surface of the lens is positioned away from the array of light emitting devices.
4. The display device of claim 1 , wherein the display device is a head-mounted display device.
5. A lens, defined by a first lens surface and a second lens surface opposite to the first lens surface, wherein:
a first portion of the first lens surface is defined by a smooth surface profile function;
a second portion of the first lens surface is defined by a Fresnel surface profile function;
the first portion and the second portion of the first lens surface are defined by a sum of two surface profile functions;
a first surface profile function of the two surface profile functions defines a smooth surface profile across the first portion and the second portion of the first lens surface;
the smooth surface profile defined by the first surface profile function corresponds to an aspheric curve; and
a second surface profile function of the two surface profile functions defines:
a smooth surface profile across the first portion of the first lens surface; and
a Fresnel surface profile across the second portion of the first lens surface.
6. The lens of claim 5 wherein:
a width of the first portion of the first lens surface is at least 10% of a width of the lens.
7. The display device lens of claim 5 wherein:
a derivative of the first surface profile function is continuous across of the first portion and the second portion of the first lens surface; and
a derivative of the second surface profile function is continuous across the first portion of the first lens surface.
8. The lens of claim 5 wherein:
the smooth surface profile, of the second surface profile function, across the first portion of the first lens surface is flat.
9. The lens of claim 5 wherein:
a derivative of the second surface profile function has discontinuities across the second portion of the first lens surface.
10. The lens of claim 5 wherein:
the lens is configured to focus light impinging on the first lens surface.
11. The lens of claim 5 wherein:
the second portion includes an annular region, around the first portion, of the first lens surface.
12. The lens of claim 5 wherein:
the first portion of the first lens surface is a single contiguous region of the first lens surface; and
the second portion of the first lens surface is a single contiguous region of the first lens surface.
13. The lens of claim 5 wherein:
the second portion of the first lens surface extends from the first portion of the first lens surface.
14. The lens of claim 13 , wherein:
a derivative of the second surface profile function adjacent to a junction between the first portion of the first lens surface and the second portion of the first lens surface is zero.
15. The lens of claim 5 wherein:
the first portion and the second portion of the first lens surface are rotationally symmetric.
16. The lens of claim 5 wherein:
the first portion and the second portion of the first lens surface are reflectionally symmetric without being rotationally symmetric.
17. The lens of claim 5 wherein:
the smooth surface profile defined by the first surface profile function corresponds to a spherical curve.
18. The lens of claim 5 wherein:
the second surface is a flat surface.
19. The lens of claim 5 , wherein the second portion of the first lens surface is around the first portion of the first lens surface.