Folded camera lens designs
Digital cameras, optical lens modules for such digital cameras and methods for assembling lens elements in such lens modules. In various embodiments, the digital cameras comprise an optical lens module including N≥3 lens elements L i , each lens element comprising a respective front surface S 2i-1 and a respective rear surface S 2i . In various embodiments the first lens element toward the object side, L 1 and its respective front surfaces S 1 have optical and/or mechanical properties, such as a clear aperture, a clear height and a mechanical height that are larger than respective properties of following lens elements and surfaces. This is done to achieve a camera with large aperture stop, given a lens and/or camera height.
1. A digital camera, comprising:
a) N lens elements having a symmetry along a first optical axis, wherein N is equal to or greater than 3;
b) an image sensor;
c) an optical path folding element (OPFE) operative to provide a folded optical path from a first optical path to a second optical path; and
d) a barrel with a cavity in which the plurality of lens elements are held, wherein a height of cavity measured along the first optical path is variable along the first optical axis,
wherein the cavity comprises a first portion in which a first lens element L 1 of the N lens elements is located and a second portion in which at least the last lens element L N of the other lens elements closest to the sensor is located,
wherein a height of the first portion of the cavity H 1 is greater than the height of the second portion of the cavity H 2 , so that H 1 >1.1×H 2 ,
wherein each lens element of the N lens elements comprises a respective front surface S 2i-1 and a respective rear surface S 2i , the lens element surfaces marked S k where 1≤k≤2N,
wherein each lens element surface S k has a clear height value CH(S k ), and
wherein clear height value CH(S 1 ) of surface S 1 is greater than a clear height value of each of surfaces S 2 to S 2N .
2. The digital camera of claim 1 , wherein the N lens elements have an axial symmetry.
3. The digital camera of claim 1 , wherein the digital camera has a total track length TTL and a focal back length BFL and wherein BFL≥0.3×TTL.
4. The digital camera of claim 1 , wherein lens element L 1 is made of glass.
5. The digital camera of claim 1 , wherein lens element L 1 is made of plastic.
6. The digital camera of claim 1 , wherein lens element L 1 is made of plastic for any 2≤i≤N.
7. The digital camera of claim 1 , wherein the N lens elements form a front aperture lens module.
8. The digital camera of claim 1 , wherein at least some of the lens elements have a width W L greater than their height H L .
9. The digital camera of claim 1 , wherein a height of cavity, measured along an axis orthogonal to the first optical axis, is variable along the first optical axis.
10. The digital camera of claim 1 , wherein lens element L 1 has a portion that is not completely surrounded by the cavity and wherein walls of the cavity align a center of lens element L 1 with the first optical axis.
11. The digital camera of claim 8 , wherein lens element L N is located outside the barrel.
12. The digital camera of claim 10 , wherein lens element L N has a portion that is not completely surrounded by the cavity and wherein walls of the cavity align a center of lens element L N with the first optical axis.
13. The digital camera of claim 10 , wherein at least one of an extremity of the walls and an extremity of lens element L 1 is shaped so that the extremity of the walls acts a stop for at least a portion of lens element L 1 , thereby aligning a center of lens element L 1 with the first optical axis.
14. The digital camera of claim 12 , wherein a first portion of lens element L 1 is located in the cavity between the extremity of the walls and a second portion of lens element L 1 is located outside the barrel and wherein a thickness of the second portion of lens element L 1 along the first optical axis is greater than a thickness of the first portion of lens element L 1 along the first optical axis.
15. The digital camera of claim 12 , wherein a cross-section of the extremity of the walls has a stepped shape.
16. The digital camera of claim 12 , wherein a cross-section of the extremity of lens element L 1 has a stepped shape.
17. The digital camera of claim 12 , wherein a cross-section of the extremity of the walls has a sloping shape.
18. The digital camera of claim 12 , wherein the extremity of the walls comprises a chamfer.
19. The digital camera of claim 10 , further comprising a cover for covering and protecting lens element L 1 .
20. The digital camera of claim 19 , wherein the cover has an extreme point beyond lens element L 1 .
21. The digital camera of claim 19 , wherein the cover blocks light from entering a mechanical part of lens element L 1 .
22. The digital camera of claim 1 , wherein each lens elements of the N lens elements comprises a respective front surface S 2i-1 and a respective rear surface S 2i , the lens element surfaces marked S k where 1≤k≤2N, wherein each respective lens element surface S k has a clear aperture value CA(S k ), wherein CA(S 1 ) is greater than CA(S k ) for 2≤k≤2N and wherein CA(S 2N )≤CA(S 1 ).
23. The digital camera of claim 22 , wherein CA(S 1 )<7 mm.
24. The digital camera of claim 1 , wherein CH(S 1 )<7 mm.