Folded lens system with five refractive lenses

Patent metadata

Field	Value
Publication number	US-11604337-B2
Application number	US-202117542252-A
Country	US
Kind code	B2
Filing date	Dec 3, 2021
Priority date	Mar 28, 2016
Publication date	Mar 14, 2023
Grant date	Mar 14, 2023

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;
a light folding element configured to redirect light from the first lens element to a second portion of the folded optical axis;
a second lens element on the second portion of the folded optical axis;
a third lens element on the second portion of the folded optical axis having a convex object-side surface in the paraxial region;
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;

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

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 second lens element has a concave image-side surface in the paraxial region, and wherein the fifth lens element has a concave image-side surface in the paraxial region.

4. 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.

5. The lens system as recited in claim 1 , wherein the lens system has less than 6 mm of Z-height measured from a front vertex of the lens system to a rear vertex of the light folding element.

6. 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.

7. The lens system as recited in claim 6 , wherein the second lens element is formed of an optical material with Abbe number Vd<30.

8. The lens system as recited in claim 6 , wherein the second lens element is formed of an optical material with Abbe number Vd<35.

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

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

11. 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

−0.5<| f/f 3|<2

where f is effective focal length of the lens system, f1 is focal length of lens 1 , f2 is focal length of lens 2 , and f3 is focal length of lens 3 .

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

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

14. The lens system as recited in claim 13 , 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.

15. 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 of the five refractive lens elements in order from the object side to the image side and configured to redirect light from a first axis onto a second axis;
wherein the first lens element and a fifth lens element of the five refractive lens elements, in order from the object side to the image side, 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.

16. The camera as recited in claim 15 , 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.

17. The camera as recited in claim 15 , wherein the photosensor is configured to move on one or more axes relative to the lens system to adjust focus of the camera.

18. The camera as recited in claim 15 , 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.

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 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 of the five refractive lens elements in order from the object side to the image side and configured to redirect light from a first axis onto a second axis;
wherein the first lens element and a fifth lens element of the five refractive lens elements, in order from the object side to the image side, 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.

20. The device as recited in claim 19 , wherein the lens system further comprises at least one aperture stop located between a front vertex of the lens system and the light folding element.

Assignees

• Apple Inc

Inventors

• Yao Yuhong
• Shinohara Yoshikazu

Classifications

• G02B13/0045

  having five or more lenses · CPC title

• G02B27/0025

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

• G02B13/0065 Primary

  having a beam-folding prism or mirror · CPC title