Optical systems with solid transparent substrate
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 optical system comprising:
a solid transparent substrate comprised of a transparent first material having a refractive index n 1 ;
a concave mirror positioned to a first side of the substrate, the concave mirror having a central opening;
a convex mirror positioned to a second side of the substrate and opposite the central opening;
a solid transparent second material having a refractive index n 2 , positioned to the second side of the substrate; and
a transparent third material having a refractive index n 3 with n 3 <n 1 and n 3 <n 2 , the third material positioned between the substrate and the second material, the substrate and third material forming a first interface, and the third material and second material forming a second interface;
wherein the optical system projects image-forming rays from a first conjugate to a second conjugate; and the image-forming rays propagate along optical paths that originate from the first conjugate, enter the substrate through the central opening, reflect off the convex mirror, reflect off the concave mirror, refract at the first interface between the substrate and the third material, and then refract at the second interface between the third material and the second material.
2. The optical system of claim 1 wherein the third material is a solid transparent third material.
3. The optical system of claim 1 wherein n 1 −n 3 ≥0.1 and n 2 −n 3 ≥0.1.
4. The optical system of claim 1 wherein n 1 ≥1.50, n 2 ≥1.50, and n 3 ≤1.45.
5. The optical system of claim 1 wherein values of n 1 and n 2 are closer to each other than to a value of n 3 .
6. The optical system of claim 1 wherein the third material comprises silicone.
7. The optical system of claim 1 wherein the third material comprises an adhesive.
8. The optical system of claim 1 wherein the second material is one of acrylic or Zeonex.
9. The optical system of claim 1 wherein the optical system is contained in a contact lens, and the second material is part of the contact lens.
10. The optical system of claim 1 wherein the optical system is contained in a contact lens, and a refractive index of the contact lens is substantially equal to n 2 .
11. The optical system of claim 1 wherein the first interface and the second interface are both curved.
12. The optical system of claim 1 wherein the second interface is planar.
13. The optical system of claim 1 wherein the optical system is a precursor for assembly into a contact lens, and a surface of the second material opposite the second interface has a same shape as an exterior surface of the contact lens.
14. The optical system of claim 1 wherein the optical system is a precursor for assembly into a contact lens, and the second material is shaped with a protrusion.
15. The optical system of claim 1 further comprising a light baffle system comprising a source baffle, an exit baffle and a side baffle.
16. The optical system of claim 1 wherein the optical system is small enough to be mounted in a contact lens.
17. The optical system of claim 1 further comprising:
a source baffle located between (a) a first group of optical paths between the central opening and the convex mirror and (b) a second group of optical paths between the convex mirror and the concave mirror.
18. The optical system of claim 1 further comprising:
an exit baffle located between (a) a first group of optical paths between the convex mirror and the concave mirror, and (b) a second group of optical paths between the concave mirror and the first refractive interface.
19. The optical system of claim 1 further comprising:
a side baffle located outside a sidewall of the substrate.
20. The optical system of claim 1 wherein the concave mirror and convex mirror contact the substrate.