Femtoprojector optical systems, used in eye-mounted display
A variety of femtoprojector optical systems are described. Each of them can be made small enough to fit in a contact lens using plastic injection molding, diamond turning, photolithography and etching, or other techniques. Most, but not all, of the systems include a solid cylindrical transparent substrate with a curved primary mirror formed on one end and a secondary mirror formed on the other end. Any of the designs may use light blocking, light-redirecting, absorbing coatings or other types of baffle structures as needed to reduce stray light.
1. An eye-mounted display comprising:
a contact lens mountable on a user's eye; and
one or more femtoprojectors in the contact lens, at least one of the femtoprojectors comprising:
an image source that produces an image; and
a femtoprojector optical system comprising:
a convex first mirror facing the image source, where image-forming rays from the image source are incident on and reflected by the first mirror and stray rays from the image source are not incident on the first mirror;
a concave second mirror having a center opening to accommodate the image source, the second mirror having a lateral dimension that is larger than the first mirror and also larger than the image source, the second mirror facing the first mirror and further reflecting the image-forming rays from the first mirror, the first mirror and the second mirror cooperating to project the image from the image source; wherein the image source, the first mirror and the second mirror are axially aligned along a common axis, and a distance along the common axis from the image source to the second mirror is less than a distance from the second mirror to the first mirror; and
a light baffle system that includes an obscuration adjacent to and surrounding the first mirror, the obscuration blocking stray rays from the image source that are not reflected by the first mirror.
2. The eye-mounted display of claim 1 where an optical path for imaging-forming rays from the image source to a retina of the user's eye does not include any air gaps.
3. The eye-mounted display of claim 1 where the contact lens contains a cylindrical hole; and a structure containing the image source, first mirror, second mirror and obscuration fits into the cylindrical hole.
4. The eye-mounted display of claim 3 where the light baffle system further includes a side baffle that is external to the second mirror and blocks stray rays emitted from the image source at oblique angles, and the side baffle is positioned on an interior of the cylindrical hole.
5. The eye-mounted display of claim 3 where the structure includes a planar exterior surface facing the user's eye.
6. The eye-mounted display of claim 1 where the contact lens has a thickness of not more than 2 mm.
7. The eye-mounted display of claim 1 where all of the femtoprojectors have a magnification of not more than 5× from the image source to a retina of the user's eye.
8. The eye-mounted display of claim 1 where at least one femtoprojector has a full field of view of at least five degrees.
9. The eye-mounted display of claim 8 where at least one femtoprojector has a full field of view of at least fifteen degrees.
10. The eye-mounted display of claim 1 where the one or more femtoprojectors comprises two or more femtoprojectors, the images projected by the femtoprojectors forming a composite image on a retina of the user's eye.
11. The eye-mounted display of claim 10 where the femtoprojectors project images onto the retina at different resolutions.
12. The eye-mounted display of claim 10 where some of the stray rays form a halo, and none of the halos from any of the femtoprojectors are projected to a fovea of the user's eye.
13. The eye-mounted display of claim 1 where the light baffle system further includes a source baffle that is outside the image source but inside the second mirror, the source baffle reducing a divergence of rays from the image source.
14. The eye-mounted display of claim 1 where the image source emits rays according to a Lambertian distribution.
15. The eye-mounted display of claim 1 where the image source is an array of individually addressable emitters.
16. The eye-mounted display of claim 15 where the image source is an array of individually addressable light emitting diodes.
17. The eye-mounted display of claim 1 where the image source has a maximum lateral dimension of not more than 500 microns.
18. The eye-mounted display of claim 17 where the image source is an array of individually addressable emitters, and the emitter-to-emitter pitch is not more than 3 microns.
19. The eye-mounted display of claim 1 further comprising a turning mirror, where the femtoprojector is horizontally positioned within the contact lens, and the turning mirror direct image-forming rays towards the user's retina.