Optical device and associated methods

1. An optical device, comprising:

a transparent, rigid substrate having substantially planar opposing first and second surfaces;

a first replicated refractive surface on the first surface of the substrate in a first material; and

a second replicated refractive surface on the second surface of the substrate, the second replicated refractive surface being made of a second material, different from the first material, wherein the material and curvature of the first replicated surface, the material and curvature of the second replicated surface, and a material of the substrate are each configured to reduce the thermal sensitivity of the optical device relative to an optical device using first and second materials or having curvatures of the first and second replicated refractive surfaces alone.

2. The optical device as claimed in claim 1 , wherein the first and second surfaces of the substrate are substantially parallel.

3. The optical device as claimed in claim 1 , where the material and curvature of the first replicated surface and the material and curvature of the second replicated surface are configured to reduce the chromatic dispersion of the optical device relative to an optical device using first and second materials.

4. The optical device as claimed in claim 1 , further comprising:

another transparent substrate adjacent the transparent substrate;

a third replicated refractive surface on a first surface of the another substrate in a third material; and

a fourth replicated refractive surface on a second surface, opposite the first surface, of the another substrate and in a fourth material, the first to fourth replicated refractive surfaces being aligned along an optical axis.

5. The optical device as claimed in claim 4 , wherein the first surface of the another substrate is secured to the second surface of the substrate.

6. The optical device as claimed in claim 4 , wherein the first and fourth materials are the same.

7. The optical device as claimed in claim 4 , wherein the first and second surfaces of the substrate and the first and second surfaces of the another substrate are all substantially planar.

8. The optical device as claimed in claim 4 , wherein at least one of the first and second refractive surfaces is aspheric and at least one of the third and fourth refractive surfaces is aspheric.

9. The optical device as claimed in claim 4 , further comprising an image sensor configured to receive light output from the fourth replicated refractive surface.

10. The optical device as claimed in claim 9 , wherein light output from the fourth replicated refractive surface is directly incident on the image sensor.

11. The optical device as claimed in claim 1 , where the material and curvature of the first replicated surface and the material and curvature of the second replicated surface are configured to reduce the chromatic dispersion of the optical device relative to an optical device using first and second materials or having curvatures of the first and second replicated refractive surfaces alone.

12. The optical device as claimed in claim 1 , wherein the first replicated refractive surface and the second replicated refractive surface are formed on the substrate while the substrate is part of a wafer.

13. A method of forming an optical device, the method comprising:

providing a plurality of first surfaces in a first material having a first coefficient of optothermal expansion;

providing a plurality of second surfaces in a second material having a second coefficient of optothermal expansion on corresponding first surfaces, the second surfaces having a radius of curvature, thereby forming a plurality of optical devices;

designing the first and second surfaces to reduce at least one of the coefficient of optothermal expansion and chromatic dispersion for the optical device having the first and second surfaces relative to an optical device using first and second materials or having first and second surfaces alone; and

singulating the plurality of optical devices to form the optical device.

14. The method as claimed in claim 13 , wherein the plurality of first surfaces are on a substantially planar portion of a rigid substrate.

15. The method as claimed in claim 14 , wherein designing includes a thickness of the rigid substrate as a parameter.

16. The method as claimed in claim 14 , further comprising providing an anti-reflective coating between the rigid substrate and the plurality of first surfaces.