Folded telephoto camera lens system

Patent metadata

Field	Value
Publication number	US-11112582-B2
Application number	US-201916586798-A
Country	US
Kind code	B2
Filing date	Sep 27, 2019
Priority date	Mar 7, 2014
Publication date	Sep 7, 2021
Grant date	Sep 7, 2021

Abstract

A folded telephoto lens system may include multiple lenses with refractive power and a light path folding element. Light entering the camera through lens(es) on a first path is refracted to the folding element, which changes direction of the light on to a second path with lens(es) that refract the light to form an image plane at a photosensor. At least one of the object side and image side surfaces of at least one of the lens elements may be aspheric. Total track length (TTL) of the lens system may be 14.0 mm or less. The lens system may be configured so that the telephoto ratio (TTL/f) is less than or equal to 1.0. Materials, radii of curvature, shapes, sizes, spacing, and aspheric coefficients of the optical elements may be selected to achieve quality optical performance and high image resolution in a small form factor camera.

First claim

What is claimed is:

1. A telephoto lens system, comprising:
a plurality of optical elements arranged along a first optical axis and a second optical axis of the lens system and configured to:
refract light from an object field along the first optical axis;
redirect the light on to the second optical axis; and
refract the light on the second optical axis to form an image at an image plane;

wherein the plurality of optical elements includes, in order along the first and second optical axes from an object side of the lens system to an image side of the lens system:
a first lens element with positive refractive power having a convex object side surface;
a second lens element with negative refractive power;
a light path folding element configured to redirect the light at a particular surface of the light path folding element from the first optical axis on to the second optical axis;
a third lens element located along the second optical axis, the third lens element with negative refractive power and having a concave image-side surface; and
a fourth lens element with positive refractive power.

2. The telephoto lens system as recited in claim 1 , wherein at least one surface of at least one of the lens elements is aspheric.

3. The telephoto lens system as recited in claim 1 , wherein at least one of the lens elements is composed of a first plastic material, and wherein at least one other of the lens elements is composed of a second plastic material with different optical characteristics than the first plastic material.

4. The telephoto lens system as recited in claim 1 , wherein at least one of the plurality of optical elements is configured to translate or move along a respective optical axis to adjust focus of the image at the image plane.

5. The telephoto lens system as recited in claim 1 , wherein telephoto ratio (TTL/f) of the lens system is within a range of 0.8 to 1.0, where f is effective focal length of the lens system and TTL is total track length of the lens system.

6. The telephoto lens system as recited in claim 1 , wherein effective focal length f of the lens system is within a range of 8 millimeters to 14 millimeters, and wherein focal ratio of the lens system is within a range of 2.4 to 10.

7. The telephoto lens system as recited in claim 1 , wherein effective focal length f of the lens system is 14 millimeters, and wherein focal ratio of the lens system is 2.8.

8. The telephoto lens system as recited in claim 1 , further comprising an aperture stop located between the first lens element and the second lens element.

9. The telephoto lens system as recited in claim 1 , further comprising an aperture stop located between the second lens element and a reflecting surface of the light path folding element.

10. The telephoto lens system as recited in claim 1 , further comprising an aperture stop that is adjustable to provide a focal ratio of the telephoto lens system that is within a range of 2.4 to 10.

11. The telephoto lens system as recited in claim 1 , wherein the fourth lens element is positive meniscus shape and has a concave image side surface.

12. The telephoto lens system as recited in claim 1 , wherein the fourth lens element is a biconvex lens.

13. The telephoto lens system as recited in claim 1 , wherein the lens system has effective focal length f, wherein the first lens element is a biconvex lens, and wherein focal length f1 of the first lens element satisfies the condition:
0.4<| f 1/ f|< 0.8.

14. The telephoto lens system as recited in claim 1 , wherein the lens system has effective focal length f, and wherein the first lens element has vertex radii of curvature R1 and R2 and satisfies the condition:
0≤| R 1/ R 2|<6.1.

15. The telephoto lens system as recited in claim 1 , wherein the lens system has effective focal length f, and wherein the second lens element has negative focal length f2, vertex radii of curvature R3 and R4, and satisfies the conditions:
(0.5<| f 2/ f|< 1.5, and 0.02<| R 3 R 4|<3.3).

16. The telephoto lens system as recited in claim 1 , wherein the light path folding element is one of a mirror or a prism.

17. A lens system, comprising:
a plurality of optical elements including, in order along a folded optical axis from an object side of the lens system to an image side of the lens system:
a first lens element with positive refractive power having a convex object side surface;
a second lens element with negative refractive power;
a light path folding element configured to redirect light from a first optical path of the folded optical axis on to a second optical path of the folded optical axis;
a third lens element with negative refractive power and having a concave image-side surface; and
a fourth lens element with positive refractive power, wherein the fourth lens element is a biconvex lens;

wherein telephoto ratio (TTL/f) of the lens system is within a range of 0.8 to 1.0, where f is effective focal length of the lens system and TTL is total track length of the lens system.

18. The lens system as recited in claim 17 , wherein the effective focal length f of the lens system is within a range of 8 millimeters to 14 millimeters, and wherein focal ratio of the lens system is within a range of 2.4 to 10.

19. The lens system as recited in claim 17 , wherein at least one of the lens elements is configured to translate or move along a respective optical axis to adjust focus of the lens system.

20. The lens system as recited in claim 17 , wherein the lens system further includes an aperture stop located between the first lens element and a reflecting surface of the light path folding element.

Assignees

• Apple Inc

Inventors

• Mercado Romeo I

Classifications

• H04N23/56

  provided with illuminating means · CPC title

• G02B9/36

  arranged + -- + · CPC title

• G02B13/0065

  having a beam-folding prism or mirror · CPC title

• G03B9/02

  Diaphragms · CPC title

• G03B30/00

  Camera modules comprising integrated lens units and imaging units, specially adapted for being embedded in other devices, e.g. mobile phones or vehicles · CPC title