Optical systems for cameras incorporating lens elements formed separately and subsequently bonded to low CTE substrates
View Patent ↗Systems and methods in accordance with embodiments of the invention implement optical systems incorporating lens elements formed separately and subsequently bonded to low coefficient of thermal expansion substrates. Optical systems in accordance with various embodiments of the invention can be utilized in single aperture cameras, and multiple-aperture array cameras. In one embodiment, a robust optical system includes at least one carrier characterized by a low coefficient of thermal expansion to which at least a primary lens element formed from precision molded glass is bonded.
1. A camera array, comprising:
a processor;
memory; and
an optical system comprising:
a carrier substrate supporting a plurality of lens elements bonded to the carrier substrate including at least one glass lens element;
a primary lens element proximate to a scene to be imaged and having a first coefficient of thermal expansion;
a secondary lens element proximate to an image sensor and having a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion;
wherein the image sensor is aligned with the back focal lengths of the plurality of lens elements;
wherein at least one lens element differs between lens stacks that image different color channels.
2. The camera array of claim 1 , wherein the first coefficient of thermal expansion is lower than the second coefficient of the thermal expansion.
3. The camera array of claim 1 , wherein the carrier substrate is a glass material having a relatively low coefficient of thermal expansion such that optical characteristics of the glass remain consistent with variations in temperature.
4. The camera array of claim 1 , wherein the at least one glass lens element has a lower coefficient of thermal expansion relative to a coefficient of thermal expansion of a polymer material used for the secondary lens element.
5. The camera array of claim 1 , further comprising an aperture-defining mask disposed on the carrier substrate.
6. The camera array of claim 5 , wherein the aperture defining mask creates virtual lens barrels providing optical isolation between lens stacks.
7. The camera array of claim 5 , wherein the mask has a thickness that is approximately on the order of magnitude of the thickness of the lens element.
8. The camera array of claim 1 , wherein at least one lens element is distanced from the carrier substrate by an air gap.
9. The camera array of claim 1 , wherein at least one lens element is distanced from the carrier substrate by a material having different optical characteristics.
10. The camera array of claim 1 , wherein the primary lens element is plano-convex and the secondary lens element is plano-concave.
11. The camera array of claim 1 , wherein the primary lens element was formed using precision glass molding and the secondary lens element was formed using injection molding to form plastic elements.
12. The camera array of claim 1 , wherein the primary lens element is a meniscus lens and the secondary lens element is a biconcave lens.
13. The camera array of claim 12 , wherein a gap separates the meniscus lens and the biconcave lens from the glass substrate.
14. The camera array of claim 1 , wherein the carrier substrate is a glass substrate with integrated aperture stops.
15. The camera array of claim 1 , wherein all of the optical elements differ between lens stacks that image different color channels.
16. The camera array of claim 1 , wherein the glass substrate is fabricated so as to include embedded color filters.
17. The camera array of claim 1 , wherein the optical system further comprises a color filter for each constituent lens stack in the carrier substrate.
18. The camera array of claim 1 , wherein the plurality of lens elements comprise lens elements fabricated from certain cavities associated with certain substrate thicknesses within overall batch variation and adhesives with differently sized spacer-beads to increase homogeneity of the fabricated optical system.
19. A camera array comprising:
a processor;
memory; and
an optical system comprising:
a glass carrier substrate supporting a plurality of lens elements bonded to the carrier substrate;
a glass lens element proximate to a scene to be imaged and having a first coefficient of thermal expansion;
a polymer lens element proximate to an image sensor and having a second coefficient of thermal expansion that is higher than the first coefficient of thermal expansion;
wherein the image sensor is aligned with the back focal lengths of the plurality of lens elements;
wherein at least one lens element differs between lens stacks that image different color channels.