The presently disclosed subject matter is generally related to the field of digital cameras.
Dual-aperture zoom cameras (also referred to as dual-cameras), in which one camera (also referred to as “sub-camera”) has a Wide FOV (“Wide sub-camera”) and the other has a narrow FOV (“Tele sub-camera”), are known.
International patent publication WO 2016/024192, which is incorporated herein by reference in its entirety, discloses a “folded camera module” (also referred to simply as “folded camera”) that reduces the height of a compact camera. In the folded camera, an optical path folding element (referred to hereinafter as “OPFE”) e.g. a prism or a mirror (otherwise referred to herein collectively as “reflecting element”) is added in order to tilt the light propagation direction from perpendicular to the smart-phone back surface to parallel to the smart-phone back surface. If the folded camera is part of a dual-aperture camera, this provides a folded optical path through one lens assembly (e.g. a Tele lens). Such a camera is referred to herein as “folded-lens dual-aperture camera”. In general, the folded camera may be included in a multi-aperture camera, for example together with two “non-folded” (upright) camera modules in a triple-aperture camera.
A small height of a folded camera is important to allow a host device (e.g. a smartphone, tablets, laptops or smart TV) that includes it to be as thin as possible. The height of the camera is often limited by the industrial design. In contrast, increasing the optical aperture of the lens results in an increase in the amount of light arriving at the image sensor and improves the optical properties of the camera.
Therefore, there is a need for, and it would be advantageous to have a folded camera in which the height of the lens optical aperture is maximal for a given camera height and/or for a lens module height.
In exemplary embodiments, there are provided high optical performance lenses (or “lens assemblies”) with a large front clear aperture (CA), a large first surface CA and relatively small clear apertures for all other lens elements. The lens elements are listed in order from an object side (first lens element L1) to an image side (last lens element Li). In each embodiment, the last lens element clear aperture is smaller than the diagonal length of an image sensor (also referred to herein as “sensor diagonal length” or “SDL”) included with the lens in a digital camera. In the following Tables, all dimensions are given in millimeters. All terms and acronyms have their ordinary meaning as known in the art.
In some embodiments, there are provided folded lens assemblies for a folded camera, comprising: a plurality of lens elements that include, in order for an object side to an image side, a first lens element L1 with a clear aperture CA(S1) and a second lens element L2 with a clear aperture CA(S3), wherein CA(S1)/CA(S3)>1.2 and wherein the lens assembly has a ratio between an image sensor diagonal length SDL and a clear aperture of a last lens element surface CA(S2N), SDL/CA(S2N)>1.5.
In some embodiments, the first lens element has positive refractive power and the second lens element has negative refractive power, and the plurality of lens elements further includes a third lens element with positive refractive power and a fourth lens element with negative refractive power.
In some embodiments, the first lens element has positive refractive power and the second lens element has negative refractive power, and the plurality of lens elements further includes a third lens element with positive refractive power and a fourth lens element with positive refractive power. In some embodiments, the first lens element has positive refractive power and the second lens element has negative refractive power, and the plurality of lens elements further includes a third lens element with negative refractive power and a fourth lens element with positive refractive power.
In some embodiments, the plurality of lens elements further includes a fifth lens element with negative refractive power.
In some embodiments, the lens assembly has a total track length (TTL) and a back focal length (BFL) with a ratio BFL/TTL>0.35.
In some embodiments, an optical window is positioned in a path defining the BFL and the TTL.
In some embodiments, there are provided folded lens assemblies for a folded camera, comprising: a plurality N of lens elements that include, in order for an object side to an image side, a first lens element L1 with a clear aperture CA(S1), wherein all clear apertures of all other lens elements L2 to LN of the plurality N of lens elements are no larger than CA(S1), wherein the folded camera includes an image sensor having a sensor diagonal length SDL and wherein CA(S1)<SDL<1.5×CA(S1).
Non-limiting examples of embodiments disclosed herein are described below with reference to figures attached hereto that are listed following this paragraph. The drawings and descriptions are meant to illuminate and clarify embodiments disclosed herein, and should not be considered limiting in any way. Like elements in different drawings may be indicated by like numerals. Elements in the drawings are not necessarily drawn to scale. In the drawings:
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding. However, it will be understood by those skilled in the art that the presently disclosed subject matter may be practiced without these specific details. In other instances, well-known methods have not been described in detail so as not to obscure the presently disclosed subject matter.
It is appreciated that certain features of the presently disclosed subject matter, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the presently disclosed subject matter, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.
The term “processing unit” as disclosed herein should be broadly construed to include any kind of electronic device with data processing circuitry, which includes for example a computer processing device operatively connected to a computer memory (e.g. digital signal processor (DSP), a microcontroller, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc.) capable of executing various data processing operations.
Furthermore, for the sake of clarity the term “substantially” is used herein to imply the possibility of variations in values within an acceptable range. According to one example, the term “substantially” used herein should be interpreted to imply possible variation of up to 10% over or under any specified value. According to another example, the term “substantially” used herein should be interpreted to imply possible variation of up to 5% over or under any specified value. According to a further example, the term “substantially” used herein should be interpreted to imply possible variation of up to 2.5% over or under any specified value.
The path of the optical rays from an object (not shown) to image sensor 104 defines an optical path (see optical paths 105 and 106, which represent portions of the optical path).
OPFE 101 may be a prism or a mirror. As shown in
In particular, in some examples, OPFE 101 can be inclined at substantially 45° with respect to optical axis 103. In
In some known examples, image sensor 104 lies in a X-Y plane substantially perpendicular to optical axis 103. This is however not limiting and the image sensor 104 can have a different orientation. For example, and as described in WO 2016/024192, image sensor 104 can be in the XZ plane. In this case, an additional OPFE can be used to reflect the optical rays towards image sensor 104.
According to some examples, image sensor 104 has a rectangular shape. According to some examples, image sensor 104 has a circular shape. These examples are however not limiting.
In various examples camera 100 may be mounted on a substrate 109, e.g. a printed circuit board (PCB), as known in the art. Two sub-cameras, for example a Wide sub-camera 130 and a Tele sub-camera 100 may be included in a digital camera 170 (also referred to as dual-camera or dual-aperture camera). A possible configuration is described with reference to
Wide sub-camera 130 can include an aperture 132 (indicating object side of the camera) and an optical lens module 133 (or “Wide lens module”) with a symmetry (and optical) axis 134 in the Y direction, as well as a Wide image sensor 135. The Wide lens module is configured to provide a Wide image. The Wide sub-camera has a Wide field of view (FOVW) and the Tele sub-camera has a Tele field of view (FOVT) narrower than FOVW. Notably, in some examples, a plurality of Wide sub-cameras and/or a plurality of Tele sub-cameras can be incorporated and operative in a single digital camera.
According to one example, the Wide image sensor 135 lies in the X-Z plane, while image sensor 104 (which is in this example is a Tele image sensor) lies in a X-Y plane substantially perpendicular to optical axis 103.
In the examples of
The processing unit may include hardware (HW) and software (SW) specifically dedicated for operating with the digital camera. Alternatively, a processor of an electronic device (e.g. its native CPU) in which the camera is installed can be adapted for executing various processing operations related to the digital camera (including, but not limited to, processing the Tele image and the Wide image into an output image).
Attention is now drawn to
Lens module 200 includes a plurality of N lens elements Li (wherein “i” is an integer between 1 and N). L1 is the lens element closest to the object side and LN is the lens element closest to the image side, i.e. the side where the image sensor is located. This order holds for all lenses and lens elements disclosed herein. Lens elements Li can be used e.g. as lens elements of camera 100 represented in
In the examples of
In the examples of
Optical rays (after their reflection by a reflecting element, such as OPFE 101) pass through lens elements Li and form an image on an image sensor 202. In the examples of
Each lens element Li comprises a respective front surface S2i−1 (the index “2i−1” being the number of the front surface) and a respective rear surface S2i (the index “2i” being the number of the rear surface), where “i” is an integer between 1 and N. This numbering convention is used throughout the description. Alternatively, as done throughout this description, lens surfaces are marked as “Sk”, with k running from 1 to 2N. The front surface and the rear surface can be in some cases aspherical. This is however not limiting.
As used herein the term “front surface” of each lens element refers to the surface of a lens element located closer to the entrance of the camera (camera object side) and the term “rear surface” refers to the surface of a lens element located closer to the image sensor (camera image side).
As explained below, a clear height value CH(Sk) can be defined for each surface Sk for 1≤k≤2N), and a clear aperture value CA(Sk) can be defined for each surface Sk for 1≤k≤2N). CA(Sk) and CH(Sk) define optical properties of each surface Sk of each lens element.
As shown in
The definition of CH(Sk) does not depend on the object currently imaged, since it refers to the optical rays that “can” form an image on the image sensor. Thus, even if the currently imaged object is located in a black background that does not produce light, the definition does not refer to this black background since it refers to any optical rays that “can” reach the image sensor to form an image (for example optical rays emitted by a background that would emit light, contrary to a black background).
For example,
In
Attention is drawn to
As shown in
Detailed optical data and surface data are given in tables below for ten lens (or lens assembly) examples (embodiments) numbered as Ex1, Ex2, . . . Ex 10. The ten lens assembly embodiments Ex1 to Ex10 are also shown in, respectively,
Tables 1, 4, 7, 10, 13, 16, 19, 22, 25 and 28 provide respectively a summary of lens properties for each of examples 1-10. For each lens, the following parameters are described:
Effective focal length (EFL), in millimeters (mm).
Total track length (TTL), in mm, defined as the distance from the first surface S1 of the first lens element to the image sensor. In some embodiments, an optical window is positioned in, and included in the TTL.
f number f/#, (unitless number).
Image sensor diagonal length (SDL), in mm.
Back focal length (BFL), in mm, which is the distance from the last surface of the last lens element S2N to the image sensor. In some embodiments, an optical window is positioned in, and included in the BFL.
Ratio between the TTL and the EFL, TTL/EFL.
Ratio between the BFL and the EFL, BFL/EFL.
Ratio between the clear aperture (CA) of the first surface S1 of the first lens element and the clear aperture of the first surface S3 of the second lens element, CA(S1)/CA(S3).
Focal length of each lens element, fi.
Tables 2, 5, 8, 11, 14, 17, 20, 23, 26 and 29 provide respectively a description of the surfaces of each element for each of embodiments Ex 1, Ex2, . . . Ex 10. For each lens element and each surface, the following parameters are described:
Surface type (see below).
The lens element number L and surface number.
The surface radius in mm, infinity means flat surface.
The thickness between surface i to surface i+1.
The surface refraction index Nd.
The surface abbe number Vd.
The surface half diameter D/2.
Tables 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30 provide respectively a further description of aspheric surfaces of each lens element in each of embodiments Ex 1, Ex2, . . . Ex 10.
a) Q type 1 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, rmax is one half of the surfacs clear aperture, and An are the polynomial coefficients shown in lens data tables.
b) Even aspheric surfaces formula:
The equation of the surface profiles of each surface Sk (for k between 1 and 2N) is expressed by:
where “z” is the position of the profile of the surface Sk measured along optical axis 103 (coinciding with the Z axis, wherein z=0 corresponds to the intersection of the profile of the surface Sk with the Z axis), “r” is the distance from optical axis 103 (measured along an axis which is perpendicular to optical axis 103), “K” is the conic coefficient, c=1/R where R is the radius of curvature, and An (n from 1 to 7) are coefficients given in Tables 2 and 4 for each surface Sk. The maximum value of r, “max r”, is equal to D/2.
c) Flat surface;
The values provided for these examples are purely illustrative and according to other examples, other values can be used.
In the tables below, the units of the radius of curvature (“R”), the lens element thickness (“T”) and the clear aperture are expressed in millimeters.
Line “0” of Tables 1, 3 and 5 and 7 describes parameters associated to the object (not visible in the figures); the object is being placed at 1 km from the system, considered to be an infinite distance.
Lines “1” to “8” of Tables 1 to 4 describe respectively parameters associated to surfaces S1to S8. Lines “1” to “10” of Tables 5 to 8 describe respectively parameters associated with surfaces S1to S10.
Lines “9”, “10” and “11” of Tables 1 and 3, and lines “11”, “12” and “13” in Tables 5 and 7 describe respectively parameters associated with surfaces 205a, 205b of optical element 205 and of a surface 202a of the image sensor 202.
In lines “i” of Tables 1, 3 and 5 (with i between 1 and 10 in tables 1 and 3 and i between 1 and 12 in Table 5), the thickness corresponds to the distance between surface Si and surface Si+1, measured along the optical axis 103 (which coincides with the Z axis).
In line “11” of Tables 1, 3 (line “13” in Tables 5 and 7), the thickness is equal to zero, since this corresponds to the last surface 202a.
Sign of refractive elements:
The following list and Table 33 summarize the design characteristics and parameters as they appear in the examples listed above. These characteristics helps to achieve the goal of a compact folded lens with large lens assembly aperture:
“AA”: AA1≡BFL/TTL>0.35, AA2≡BFL/TTL>0.4, AA3≡BFL/TTL>0.5;
“BB”: BB1≡CA(S1)/CA(S3)>1.2, BB2≡CA(S1)/CA(S3)>1.3, BB3≡CA(S1)/CA(S3)>1.4;
“CC”: CC1≡T(AS to S3)/TTL>0.1, CC2≡T(AS to S3)/TTL>0.135, CC3≡T(AS to S3)/TTL>0.15;
“DD”: At least two gaps that comply with DD1≡STD<0.020, DD2≡STD<0.015, DD3STD<0.010;
“EE”: At least 3 gaps that comply with EE1≡STD<0.035, EE2≡STD<0.025, EE3≡STD<0.015;
“FF”: At least 4 gaps that comply with FF1≡STD<0.050, FF2≡STD<0.035, FF3≡STD<0.025;
“GG”: GG1≡SDUCA(S2N)>1.5, GG2≡SDUCA(S2N)>1.55, GG3≡SDL/CA(S2N)>1.6;
“HH”: a power sign sequence;
“II”: At least 1 gap that complies with II1≡STD<0.01 and OA_Gap/TTL<1/80, II2≡STD<0.015 and OA_Gap/TTL<1/65;
“JJ”: JJ1: Abbe number sequence of lens elements L1, L2 and L3 can be respectively larger than 50, smaller than 30 and larger than 50;
JJ2: Abbe number sequence of lens elements L1, L2 and L3 can be respectively larger than 50, smaller than 30 and smaller than 30;
“KK”: KK1≡|f2/f1|>0.4 and Abbe number sequence of lens elements L1, L2 and L3 can be respectively larger than 50, smaller than 30 and smaller than 30; KK2≡|f2/f1|<0.5 and Abbe number sequence of lens elements L1, L2 and L3 can be respectively larger than 50, smaller than 30 and larger than 50; and
“LL”: LL1≡f1/EFL<0.55, LL2≡f1/EFL<0.45;
“MM”: MM1≡|f2/f1|<0.9, MM2|f2/f1|<0.5; and
“NN”: NN1≡TTL/EFL<0.99, NN2≡TTL/EFL<0.97, NN3≡TTL/EFL<0.95.
“OO”: At least two gaps that comply with OO1≡STD>0.020, OO2≡STD>0.03, OO3≡STD>0.040;
“PP”: At least 3 gaps that comply with PP1≡STD>0.015, PP2≡STD >0.02, PP3STD>0.03;
“QQ”: At least 4 gaps that comply with QQ1≡STD >0.015, QQ2≡STD>0.02, QQ3≡STD>0.03;
“RR”: At least 3 OA_Gaps that comply with RR1≡TTL/Min_Gap>50, RR2≡TTL/Min_Gap>60, RR3≡TTL/Min_Gap>100.
Unless otherwise stated, the use of the expression “and/or” between the last two members of a list of options for selection indicates that a selection of one or more of the listed options is appropriate and may be made.
It should be understood that where the claims or specification refer to “a” or “an” element, such reference is not to be construed as there being only one of that element.
All patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present disclosure.
This application is a 371 National Phase application from international application PCT/IB2019/053662 filed May 4, 2019 and claims the benefit of priority from U.S. Provisional patent applications No. 62/671,086 filed May 14, 2018 and 62/755,826 filed Nov. 5, 2018, both of which are incorporated herein by reference in their entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2019/053662 | 5/4/2019 | WO | 00 |
Number | Date | Country | |
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62755726 | Nov 2018 | US | |
62671086 | May 2018 | US |