Optical assembly for a compact wide field of view digital camera with low first lens diameter to image diagonal ratio
An optical assembly for a point action camera or other compact digital camera having a wide field of view, includes multiple lens elements, including at least one lens element that has an aspheric lens surface. The optical assembly is configured to provide a field of view in excess of 120 degrees. The optical assembly includes a ratio of a diameter of a first lens element at the object end of the optical assembly to an image diagonal is less than approximately 3.
1. A digital point action camera, comprising:
(a) an optical assembly, comprising from object end to image end:
a first optical group including two or more lens elements configured to collect and reduce a field angle of light incident at a field of view in excess of 120 degrees;
a second optical group including a doublet;
a third optical group including two or more lens elements, wherein at least one lens element of the third optical group includes an aspheric surface that is configured to correct higher order astigmatism; and
a fourth optical group configured to deliver a telecentric cone to an image sensor; and wherein the optical assembly further comprises an aperture stop between said second and third optical groups,
wherein a ratio of a diameter of a first lens element at the object end of the optical assembly to an image diagonal is less than approximately 3,
wherein the optical assembly comprises a depth of focus that is greater than 20 microns; and
(b) an image sensor disposed approximately at a focal plane of the optical assembly; and
(c) a digital camera housing including electronics and a user interface, and containing said optical assembly and said image sensor in optically effective relative disposition.
2. The digital point action camera of claim 1 , wherein a diameter of a convexo-concave or meniscus lens of said first optical group is less than 30 mm.
3. The digital point action camera of claim 1 , wherein a diameter of a convexo-concave or meniscus lens of said first optical group is less than 25 mm.
4. The digital point action camera of claim 1 , wherein the optical assembly comprises less than five microns of lateral chromatic aberration.
5. The digital point action camera of claim 1 , comprising a ratio of total track length to effective focal length of the optical assembly (hereinafter “TTL/EFL”) that is less than 10.
6. The digital point action camera of claim 5 , wherein the total track length TTL of the optical assembly is less than 8 cm.
7. The digital point action camera of claim 1 , wherein said TTL/EFL ratio is less than 8.
8. The digital point action camera of claim 1 , wherein the fourth optical group comprises two spaced apart lens elements.
9. The digital point action camera of claim 8 , wherein the fourth optical group comprises a convexo-planar, convexo-quasi-planar or convexo-concave lens element.
10. The digital point action camera of claim 9 , wherein the fourth optical group further comprises a second convexo-planar, convexo-quasi planar or convexo-concave lens element.
11. The digital point action camera of claim 1 , wherein said first optical group comprises a convexo-concave or meniscus lens.
12. The digital point action camera of claim 11 , wherein said first optical group further comprises a doublet.
13. The digital point action camera of claim 12 , wherein said doublet of said first optical group comprises a biconcave lens coupled to a biconvex lens.
14. The digital point action camera of claim 11 , wherein the first optical group further comprises a second convexo-concave or meniscus lens.
15. The digital point action camera of claim 14 , wherein said first optical group further comprises a doublet.
16. The digital point action camera of claim 1 , wherein the third optical group further comprises a doublet.
17. The digital point action camera of claim 16 , wherein said doublet of said third optical group comprises a biconcave lens coupled to a biconvex lens.
18. The digital point action camera of claim 1 , wherein said doublet of said second optical group comprises a convexo-concave lens coupled to a biconvex, convexo-quasi-convex or convexo-planar lens.
19. The digital point action camera of claim 1 , wherein axial chromatic aberration of the optical assembly is less than 0.025 microns.
20. The digital point action camera of claim 19 , wherein the axial chromatic aberration of the optical assembly is defined across a spectral band between 465 nm to 650 nm.