Folded lens system with five refractive lenses

Patent metadata

Field	Value
Publication number	US-11194133-B2
Application number	US-201916593895-A
Country	US
Kind code	B2
Filing date	Oct 4, 2019
Priority date	Mar 28, 2016
Publication date	Dec 7, 2021
Grant date	Dec 7, 2021

Abstract

Compact folded lens systems are described that may be used in small form factor cameras. Lens systems are described that may include five lens elements with refractive power, with a light folding element such as a prism, located between a first lens element on the object side of the lens system and a second lens element, that redirects the light refracted from the first lens element from a first axis onto a second axis on which the other lens elements and a photosensor are arranged. The lens systems may include an aperture stop located behind the front vertex of the lens system, for example at the first lens element, and an optional infrared filter, for example located between the last lens element and a photosensor.

First claim

What is claimed is:

1. A lens system, comprising:
a plurality of elements arranged along a folded optical axis of the lens system, wherein the plurality of elements includes, in order along the folded optical axis from an object side to an image side:
a first lens element on a first portion of the folded optical axis having a convex object-side surface in a paraxial region, and positive refractive power;
a light folding element configured to redirect light from the first lens element to a second portion of the folded optical axis, wherein no other lens element is positioned between the first lens element and the light folding element on the first portion of the folded optical axis;
a second lens element on the second portion of the folded optical axis having a concave image-side surface in the paraxial region;
a third lens element on the second portion of the folded optical axis;
a fourth lens element on the second portion of the folded optical axis; and
a fifth lens element on the second portion of the folded optical axis having a concave image-side surface in the paraxial region.

2. The lens system as recited in claim 1 , wherein the first lens element has positive refractive power, the second lens element has negative refractive power, and the third lens element has positive refractive power.

3. The lens system as recited in claim 1 , wherein the lens system further comprises an aperture stop located between the object side of the lens system and the light folding element.

4. The lens system as recited in claim 1 , wherein the lens system provides a 35 mm equivalent focal length in the range of 50-85 mm and less than 6.5 mm of Z-height measured from a front vertex of the lens system to a rear vertex of the folding element.

5. The lens system as recited in claim 1 , wherein the first, third and fifth lens elements are formed of optical materials with Abbe number Vd>40, and the second lens element is formed of an optical material with Abbe number Vd<30.

6. The lens system as recited in claim 1 , wherein the first and fifth lens elements are formed of optical materials with Abbe number Vd>40, and the second lens element is formed of an optical material with Abbe number Vd<35.

7. The lens system as recited in claim 1 , wherein both the object-side and image-side surfaces of the second lens element are aspheric.

8. The lens system as recited in claim 1 , wherein both the object-side and image-side surfaces of the fifth lens element are aspheric.

9. The lens system as recited in claim 1 , wherein the lens system satisfies one or more of the relationships:
0.3<| f/f 1|<1
0.5<| f/f 2|<2, or
0.5<| f/f 3|<2
where f is effective focal length of the lens system, f1 is focal length of the first lens element, f2 is focal length of the second lens element, and f3 is focal length of the third lens element.

10. The lens system as recited in claim 1 , wherein at least one of the plurality of lens elements is formed of lightweight polymer or plastic material.

11. The lens system as recited in claim 1 , wherein the light folding element is a prism.

12. The lens system as recited in claim 11 , wherein an image side surface of the first lens element is flat/plano, and wherein the image side surface of the first lens element is in contact with the object side surface of the prism.

13. The lens system as recited in claim 1 , wherein effective focal length of the lens system is within a range of 5.5 millimeters to 11 millimeters.

14. A camera, comprising:
a photosensor configured to capture light projected onto a surface of the photosensor; and
a folded lens system configured to refract light from an object field located in front of the camera to form an image of a scene at an image plane at or near the surface of the photosensor, wherein the lens system comprises five refractive lens elements arranged along a folded optical axis of the camera from an object side to an image side and a light folding element located between a first and second lens element from the object side and configured to redirect light from a first axis onto a second axis;
wherein the folded lens system satisfies one or more of the relationships:
0.3<| f/f 1|<1
0.5<| f/f 2|<2, or
0.5<| f/f 3|<2

where f is effective focal length of the folded lens system, f1 is focal length of the first lens element from the object side, f2 is focal length of the second lens element from the object side, and f3 is focal length of a third lens element from the object side.

15. The camera as recited in claim 14 , wherein the folded lens system provides a 35 mm equivalent focal length in the range of 50-85 mm.

16. The camera as recited in claim 14 , wherein Z-height of the folded lens system measured from a front vertex of the lens system to a rear vertex of the folding element is less than 6.5 mm.

17. The camera as recited in claim 14 , wherein effective focal length of the lens system is within a range of 5.5 millimeters to 11 millimeters, and wherein the photosensor is between 4 millimeters and 8 millimeters in a diagonal dimension.

18. The camera as recited in claim 14 , wherein the photosensor is configured to move on one or more axes relative to the lens system to adjust focus of the camera.

19. A device, comprising:
one or more processors;
one or more cameras; and
a memory comprising program instructions executable by at least one of the one or more processors to control operations of the one or more cameras;
wherein at least one of the one or more cameras is a camera comprising:
a photosensor configured to capture light projected onto a surface of the photosensor; and
a folded lens system configured to refract light from an object field located in front of the camera to form an image of a scene at an image plane proximate to the surface of the photosensor, wherein the lens system comprises five refractive lens elements arranged along a folded optical axis of the lens system from an object side to an image side and a light folding element configured to redirect light from a first lens element on the object side to a second portion of the folded optical axis, and wherein a second lens element of the five refractive lens elements in order along the folded optical axis from the object side to the image side has a concave image-side surface in a paraxial region of the second lens element;
wherein the light folding element is a prism, wherein an image side surface of the first lens element is flat/plano in a paraxial region of the first lens element, and wherein the image side surface of the first lens element is in contact with an object side surface of the prism.

20. The device as recited in claim 19 , wherein the folded lens system provides a 35 mm equivalent focal length in the range of 50-85 mm and less than 6.5 mm of Z-height measured from a front vertex of the lens system to a rear vertex of the folding element.

Assignees

• Apple Inc

Inventors

• Yao Yuhong
• Shinohara Yoshikazu

Classifications

• G02B13/0065 Primary

  having a beam-folding prism or mirror · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title

• G02B13/0045

  having five or more lenses · CPC title