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 two or more spaced apart lens elements;
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
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 MTF at Nyquist frequency approximately 200 line pairs per millimeter above 0.35 and a MTF at half Nyquist frequency approximately 100 line pairs per millimeter above 0.55; 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 camera of claim 1 , wherein a stray light irradiance ratio is below 1/10,000.
3. The digital camera of claim 1 , wherein a stray light power ratio is below 1/100.
4. The digital camera of claim 1 , wherein axial chromatic aberration is less than 0.025 microns.
5. The digital camera of claim 4 , wherein the axial chromatic aberration is defined by a spectral band between 465 nm to 650 nm.
6. The digital camera of claim 1 , wherein a diameter of a convexo-concave or meniscus lens of said first optical group is less than 30 mm.
7. The digital camera of claim 1 , wherein a diameter of a convexo-concave or meniscus lens of said first optical group is less than 25 mm.
8. The digital camera of claim 1 , comprising less than five microns of lateral chromatic aberration.
9. The digital 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 12.
10. The digital camera of claim 9 , wherein the total track length TTL is less than 10 cm.
11. The digital camera of claim 1 , wherein said first optical group comprises a convexo-concave or meniscus lens.
12. The digital camera of claim 11 , wherein said first optical group further comprises a biconcave lens.
13. The digital camera of claim 1 , wherein the third optical group further comprises a doublet.