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CN-114258507-B - Folding camera lens design

CN114258507BCN 114258507 BCN114258507 BCN 114258507BCN-114258507-B

Abstract

A folded camera having a total track length (total TRACK LENGTH, TTL), an aperture value of less than 1.2, and a large field of view, e.g., at least 60 degrees. Such a folded camera may comprise N lens elements, where n≥7, an image sensor and an optical path folding element for providing a folded optical path between an object and a lens, where an aperture stop of the lens is located closer to a first surface of the first lens element facing the object than a distance d, which satisfies d/ttl=0.2.

Inventors

  • Gale sabertai
  • Ephraim Gordenburg
  • Roy Roddick
  • Nadaf Gulinsky

Assignees

  • 核心光电有限公司

Dates

Publication Date
20260505
Application Date
20210714
Priority Date
20200722

Claims (20)

  1. 1. A folding camera, comprising: a) A lens having an effective focal length (EFFECTIVE FOCAL LENGTH, EFL) and comprising N lens elements L i along a lens optical axis, wherein N is greater than or equal to 7, wherein a first lens element L faces an object side, each lens element L i comprising a respective front surface S 2i-1 and a respective rear surface S 2i , the lens element surfaces being labeled S k , wherein 1≤k≤2N, wherein each lens element surface S k has a clear height CH (S k ) and a clear aperture CA (S k ); b) A lens barrel for carrying the lens; c) An image sensor, and D) An optical path folding element (opticalpath folding element, OPFE) for folding a first optical path parallel to a plane containing the image sensor to a second optical path perpendicular to the first optical path and parallel to the lens optical axis; Wherein the folded camera has a total track length (totaltracklength, TTL), wherein an aperture stop of the lens is located closer to a first surface of the first lens element facing the object than a distance d, the distance d satisfying d/ttl=0.2, and wherein the camera has an aperture value (f number, f/#) of <1.2, and wherein a clear aperture value CA (S 2N ) of a last surface of the last lens element L N is greater than a clear aperture value CA (S k ) of a lens element surface S k , wherein 1≤k≤2n-1.
  2. 2. The folded camera of claim 1, wherein the aperture value is <1.1.
  3. 3. The folded camera of claim 1, wherein the aperture value is less than or equal to 1.0.
  4. 4. The folded camera of claim 1, further comprising an optical element, wherein the optical element is positioned between the lens and the image sensor.
  5. 5. The folded camera of claim 1, wherein the camera has a pair of angular fields of view (FOV) of greater than 60 degrees.
  6. 6. The folded camera of claim 1, wherein at least some of the lens elements are cut lens elements having a width W Li that is greater than a height H Li , wherein the height H Li is measured in a direction parallel to the first optical path, and wherein the W Li is measured in a direction perpendicular to the first optical path and perpendicular to the second optical path.
  7. 7. The folded camera of claim 1, wherein at least some of the lens elements have a width W Li and a height H Li that satisfy the width W Li /the height H Li >1.1.
  8. 8. The folded camera of claim 1, wherein at least some of the lens elements have a width W Li and a height H Li that satisfy the width W Li /the height H Li >1.2.
  9. 9. The folding camera of claim 1, wherein the barrel has a barrel height of 5.5 millimeters (mm) or less.
  10. 10. The folded camera of claim 1, wherein the image sensor has a sensor diagonal SD, the sensor diagonal being >6 millimeters (mm).
  11. 11. The folded camera of claim 1, wherein the light path folding element has a height H O , the lens has a height H L , and wherein the height H O > the height H L , wherein the height H O and the height H L are measured in a direction parallel to the first light path.
  12. 12. The folding camera as in claim 1, wherein an optical path folding element height H O > a barrel height H LB , wherein the optical path folding element height H O and the barrel height H LB are measured in a direction parallel to the first optical path.
  13. 13. The folded camera of claim 1, wherein the camera has a height H C determined by a height H O of the light path folding element, and wherein the height H O and the height H C are measured in a direction parallel to the first light path.
  14. 14. The folded camera of claim 1, wherein f i >5 times the effective focal length (5 xEFL) is 1≤i≤3.
  15. 15. The folded camera of claim 1, wherein a lens element L 5 has a maximum optical power among all lenses, |f5| < |fi|, for i+.5.
  16. 16. The folded camera of claim 1, wherein f 5 < the Effective Focal Length (EFL).
  17. 17. The folded camera of claim 1, wherein a lens subsystem comprising the lens elements L 4 and L 5 has positive refractive power.
  18. 18. The folded camera of claim 1, wherein the focal length f 4 of the lens element L 4 and the focal length f 5 of the lens element L 5 satisfy |the focal length f 4 | <4 times the focal length f 5 (4xf 5 ).
  19. 19. The folded camera of claim 1, wherein the focal length f 4 of the lens element L 4 and the focal length f 5 of the lens element L 5 satisfy |the focal length f 4 | <3 times the focal length f 5 (3xf 5 .
  20. 20. The folded camera of claim 1, wherein the lens includes at least one air gap between the lens elements, the air gap meeting STD <0.020, wherein STD is a normalized gap standard deviation.

Description

Folding camera lens design RELATED APPLICATIONS The present application claims priority from U.S. provisional patent application No.63/054,862 filed 7/22 in 2020, the entire contents of which are incorporated herein by reference. Technical Field The present invention relates to the field of digital cameras, and more particularly to folded optical designs in such digital cameras. Definition of the definition In the present application, for the optical and other characteristics mentioned throughout the specification and the drawings, the following symbols and abbreviations are used, all of which are known in the art: Total track length (Total TRACK LENGTH, TTL) the maximum distance between a point of the front surface S 1 of a first lens element L 1 and an image sensor measured in a direction parallel to the optical axis of a lens (or lens assembly) when a camera system comprising the lens is focused to a finite distance object distance. Back focal length (Back focal length, BFL) the smallest distance between a point of the rear surface S 2N of the last lens element L N of a lens (or lens assembly) and an image sensor, measured in a direction parallel to the first optical axis, when a camera system comprising lenses is focused to a finite distance object. Effective focal length (EFFECTIVE FOCAL LENGTH, EFL) the distance between a back principal point P 'and a back focus F' of a lens assembly of lens elements L 1 to L N. -Aperture value (f-number, f/#) ratio of EFL to an entrance pupil diameter (entrance pupil diameter). Background Two-phase or three-phase transmission (or a general multi-phase transmission) for a mobile device such as a smart phone is known. In a typical three-camera, one camera has a field of view (FOV) FOVUW, the other camera has a Wide field of view (WIDE FIELD of view) FOVW that is narrower than FOVUW, and the other camera has a tele field of view (TELE FIELD of view) FOVT that is narrower than FOVW. These cameras are also referred to herein as ultra wide angle (or UW) cameras, wide angle (or W) cameras, and tele (or T) cameras, respectively. In general, a wide angle camera is considered to be the primary camera of a smartphone. The aperture value ("f/#") of a camera lens is the ratio of the Effective Focal Length (EFL) to the camera entrance pupil diameter D, f/# = EFL/D. The entrance pupil (entrance pupil) is the optical image of an aperture stop "seen" through the front aperture of the lens system. The front aperture (front aperture) is the object-side aperture of the lens. The main camera of a smart phone requires low f/#, because it has 3 main advantages of good low light sensitivity, strong "natural" foreground effect, and high image resolution, as will be discussed next: 1. The low sensitivity is a major performance defect of today's mobile device compatible cameras compared to, for example, digital Single Lens Reflex (DSLR) cameras. For example, halving the f/# of the camera (for the same EFL) increases the aperture area by a factor of 4, which means that the light entering the camera is increased by a factor of 4. This difference is particularly important when capturing low light scenes. 2. The scene (Bokeh) refers to the aesthetic quality of the blur produced by the out-of-focus segment of an image, and it is a very desirable function for today's smartphones. The foreground effect is inversely proportional to the depth of field (DOF) of the image, where DOF-f/#. Low f/# is beneficial to support strong "natural" foreground effects. Because f/# in current smart phone cameras does not provide enough "natural" foreground, the need for strong foreground is met by "manual" foreground, i.e., applying blur to out-of-focus image segments artificially. 3. Image sensors with ever increasing pixel resolution are entering mobile device equipment, exceeding 100 megapixels for the first time in 2019. This (as well as other factors) is achieved by shrinking the size of individual pixels, i.e., increasing spatial pixel frequency. In order to convert pixel resolution to image resolution, a camera lens must support the spatial pixel frequency k Pixel of the sensor. For a well-designed (diffraction-limited) camera lens, the resolvable spatial frequency k Lens of the lens is inversely proportional to f/# with k Lens -1/f/#, i.e., a lower f/# corresponds to a higher image resolution (assuming an image sensor with sufficient spatial pixel frequency). The latest high-end smartphones are equipped with a main wide-angle camera with f/# of approximately f/1.9 (Hua is P40 Pro) and f/1.8 (Apple iphone 11Pro Max). One of the main challenges of low f/# cameras is lens design to correct the strong aberrations that are introduced by the large front aperture required, for example for chromatic aberration correction. This is typically solved by a more complex lens design comprising a large number of lens elements. However, this typically results in a larger Total Track Length (TTL) and a larger camera module heig