CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. provisional patent application No. 62/889,633 filed August 21, 2019, which is incorporated herein by reference in its entirety.

FIELD

Embodiments disclosed herein relate to optical lenses, and more particularly, to miniature lens assemblies.

BACKGROUND

Digital camera modules are now standard in a variety of host devices. Such host devices include cellular telephones (smartphones), personal data assistants (PDAs), computers, and so forth. Cameras in smartphones in particular require a compact imaging lens system for good quality imaging and with a small total track length (TTL) relative to the size of the image sensor in such cameras. The image sensor size can always be expressed by the sensor diagonal, SDL.

SUMMARY

In various exemplary embodiments, there are disclosed lens assemblies comprising: from an object side to an image side, seven lens elements numbered L1-L7, an optical window and an image sensor having a sensor diagonal length (SDL), wherein an exemplary lens assembly has a total track length TTL that includes the optical window, an effective focal length (EFL) and a field of view (FOV), wherein TTL/EFL < 1.100, wherein TTL/SDL < 0.64, wherein FOV< 90 degrees, wherein a normalized thickness standard deviation constant T STD and a central thickness CT of at least three of the seven lens elements complies with T STD / CT <0.065, and wherein a focal length fi of lens element LI fulfills fi/EFL<0.95. In an embodiment, D/2 is an aperture radius and wherein a sign of z(r) from z(0.85*D/2) to z(D/2) is positive for surfaces LOi, LIi of LI and surfaces LCh, LI 2 of L2, and negative for surfaces LO4, LI4 of L4, LO5, LI5 of L5 LO6, LI6 of L6 and LO7, LI7 of L7.

In some embodiments, ach element has a clear aperture (CA) and wherein a CA of lens elements L3 or L4 is the smallest of all CAs in the lens assembly.

In some embodiments, TTL/EFL < 1.090.

In some embodiments, TTL/EFL < 1.083.

In some embodiments, TTL/ SDL < 0.63.

In some embodiments, TTL/ SDL < 0.61.

In some embodiments, lens element LI is convex on the object side.

In some embodiments, the lens elements have, starting with lens element LI , a power sign sequence of positive-negative-positive-negative-positive-positive-negati ve.

In some embodiments, the CT of at least 6 of the 7 lens elements complies CT/TTL<0.07.

In some embodiments, the T STD of at least 5 of the 7 lens elements complies with T_STD /CT<0.11.

In some embodiments, the T STD of at least 5 of the 7 lens elements complies with T STD /CT<0.10.

In some embodiments, T STD /CT<0.05.

In some embodiments, fi/EFL<0.9.

In some embodiments, fi/EFL <0.85;

In some embodiments, a focal length fs of lens element L5 fulfills |f5/EFL|>4.0.

In some embodiments, focal length fs of lens element L5 fulfills |fs/EFL|>6.0.

In some embodiments, focal length fs of lens element L5 fulfills |fs/EFL|>8.0.

In some embodiments, a focal length fs of lens element L6 fulfills f6/EFL|>l 5.0.

In some embodiments, a focal length fs of lens element L6 fulfills f6/EFL|>30.0.

In some embodiments, a focal length fs of lens element L6 fulfills f6/EFL|>45.0.

In some embodiments, a normalized gap standard deviation constant G STD of a gap between lens elements LI and L2 complies with G STD < 0.015.

In some embodiments, a normalized gap standard deviation constant G STD of a gap between lens elements LI and L2 complies with G STD < 0.01. In some embodiments, a normalized gap standard deviation constant G STD of a gap between lens elements LI and L2 complies with G STD < 0.007.

In some embodiments, SDL =12mm and FOV < 82.1 degrees. BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples of embodiments disclosed herein are described below with reference to figures attached hereto that are listed following this paragraph. Identical structures, elements or parts that appear in more than one figure are generally labeled with a same numeral in all the figures in which they appear. The drawings and descriptions are meant to illuminate and clarify embodiments disclosed herein and should not be considered limiting in any way. In the drawings:

FIG. 1 shows an exemplary embodiment of a lens assembly disclosed herein. DETAILED DESCRIPTION

FIG. 1 shows an embodiment of an optical lens system disclosed herein and numbered 100 Embodiment 100 comprises in order from an object side to an image side a plurality of lens elements (here exemplarily seven lens elements numbered L1-L7) with a common optical axis 102 The lens further comprises three aperture stops marked SI and two blocking surfaces S8 and

S9. Lens element surfaces are marked “Si”, with S2 marking an object side surface of first lens element LI and SI 8 marking an image side of lens element L7. Lens 100 further comprises an optional glass window 104 disposed between surface SI 8 and an image sensor 106 for image formation of an object. Image sensor 106 has a size characterized by an image sensor diagonal SDL.

The TTL is defined as the distance from the Si to the image sensor. FIG. 1 also shows a back focal length (BFL), defined as the distance from the last surface of the last lens element S2N to the image sensor. For convenience in some equations and relations presented below, lens element surfaces are also marked “LOi” on the object side surface of lens element number i and “Lli” on the image side surface of lens element number i.

Surface types

Surface types are defined in Table 1 and the coefficients for the surfaces are in Table 2: a) Plano: flat surfaces, no curvature b) Q type 1 (QT1) surface sag formula: where {z, r} are the standard cylindrical polar coordinates, c is the paraxial curvature of the surface, k is the conic parameter, r _norm is generally one half of the surface’s clear aperture, and A _n are the polynomial coefficients shown in lens data tables z - axis is positive towards image.

In this specification, the term “RMOi” refers to the aperture radius of a surface LOi. The term “RMIi” refers to the aperture radius of a surface LIi.

In this specification, the term “normal thickness” (NT) is a function of r marked NTi(r), and refers to the distance between the two surfaces of a lens element at coordinate r along the normal vector of the surface closer to object. Several functions and constants are defined per normal thickness: For r=0, NTi(r=0) is defined as the central thickness (CT) of lens element i (CTi)

A “thickness average” (T_AVGi) constant is given by: where k is a discrete variable that runs from 0 to N, where N is an integer >10 (for this and all other functions and constants below).

A normalized thickness standard deviation (T STDi) constant is given by: where k is a discrete variable that runs from 0 to N, and where T_AVGi is defined as in (Eq.2).

In this specification, a “gap” or an “air gap” refers to the space between consecutive lens elements. Several functions and constants per gap are defined:

A “Gapi(r)” function (for r = 0, an “on-axis gap” OA Gapi) is defined as the thickness Lli Gapi(r) = OA Gapi + z(r) of LIi - z(r) of LOi+i, where z(r) is it standard polar coordinate z. OA_Gapi(r=0) of Lli is the air thickness which is the air gap for r=0.

A “gap average” (G_AVGi) constant is given by: where k is a discrete variable that runs from 0 to N, where N is an integer >10, and where Rmim is the minimum aperture radius value of surfaces {RMIi, RMOi+i};

A normalized gap standard deviation (G STDi) constant is given by: and G AVGiis defined as in (Eq.4). * Reference wavelength is 587.6 nm (d - line)

* Units are in mm except for index and Abbe #. HFOV indicates half field of view

Table 1

5

Table 2

Table 2 (continued) Table 3 below summarizes the design characteristics and parameters as they appear in the example listed above. These characteristics help to achieve the goal of a compact lens (i.e. small TTL) with a large image height (i.e. large SDL) and small F number (F#):

“AA”: AAi º TTL/EFL < 1.100, AA ₂ º TTL/EFL < 1.090, AA ₃ º TTL/EFL < 1.083; “BB”: BBi º TTL/SDL < 0.64, BB ₂ º TTL/ SDL < 0.63, BB ₃ º TTL/ SDL < 0.61;

“CC”: Lens 1 is convex on object side; “DD”: the CA of Lens 3 or Lens 4 is the smallest of all element CAs; “EE”: power sign sequence: +-+-++-;

Table 3

In summary, various lens assembly embodiments disclosed herein have or fulfill different design characteristics and parameters listed in the Tables above. While this disclosure describes a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of such embodiments may be made. In general, the disclosure is to be understood as not limited by the specific embodiments described herein, but only by the scope of the appended claims.