CN113933973B - Optical lens and imaging apparatus - Google Patents
Optical lens and imaging apparatus Download PDFInfo
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- CN113933973B CN113933973B CN202111536199.6A CN202111536199A CN113933973B CN 113933973 B CN113933973 B CN 113933973B CN 202111536199 A CN202111536199 A CN 202111536199A CN 113933973 B CN113933973 B CN 113933973B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/0005—Optical objectives specially designed for the purposes specified below having F-Theta characteristic
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
- G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
- G02B13/0045—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having five or more lenses
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Abstract
The invention provides an optical lens and imaging equipment, belonging to the field of optical imaging; the optical lens comprises six lenses, and sequentially comprises the following components from an object side to an imaging surface along an optical axis: a first lens having a negative optical power; a second lens having a positive optical power; a third lens having a positive optical power; a diaphragm; a fourth lens having a positive optical power; a fifth lens having a negative optical power; a sixth lens having positive optical power; the optical lens satisfies the conditional expression: TTL/CT2 is more than 3.2 and less than 3.5, TTL/CT5 is more than 4.5 and less than 6, wherein CT2 represents the central thickness of the second lens, CT5 represents the central thickness of the fifth lens, TTL represents the total optical length of the optical lens, and the optical lens has the characteristics of large aperture, high resolving power and positive F-Theta distortion so as to meet the requirements of the oblique photogrammetry technology of the unmanned aerial vehicle. The imaging device includes an optical lens and an imaging element that converts an optical image into an electrical signal.
Description
Technical Field
The present invention relates to the field of optical imaging technologies, and in particular, to an optical lens and an imaging device.
Background
Traditional aerial photography can only be followed the vertical angle and shot ground object, and oblique photography is then through carrying on many camera lenses at same platform, from different angles such as perpendicular, side looking simultaneously and gather the image, has effectively compensatied traditional aerial photography's limitation, can alternate shooting angle and composition rapidly, breaks through the restriction of topography and shooting angle, makes aerial photography have more the flexibility.
The unmanned aerial vehicle oblique photography measurement technology is a high and new technology developed in recent years, and the three-dimensional data of the oblique photography technology can truly reflect the attributes of the appearance, the position, the height and the like of a ground object; by means of the unmanned aerial vehicle, image data can be rapidly acquired, and full-automatic three-dimensional modeling is achieved; the oblique photography data is measurable image data with spatial position information, and can simultaneously output multiple results such as DSM, DOM, TDOM, DLG and the like. At present, the oblique photogrammetry technology of unmanned aerial vehicles has been approved and applied by more and more industries, and therefore, the performance requirement on aerial photography lenses is higher and higher.
The oblique photogrammetry technology of unmanned aerial vehicle requires high to the optical lens who carries on, requires its light transmission ability reinforce at first, can adapt to external environment's light and shade change, requires the camera lens to have higher formation of image definition simultaneously, can effectively distinguish the detail of ground environment, requires the camera lens simultaneously can have good resolving power to the object at image edge to satisfy oblique photogrammetry's special requirement. However, most lenses in the existing market cannot well meet the requirements, so that it is urgent to develop an optical lens with large aperture, high resolution and positive F-Theta distortion which can be matched with the oblique photogrammetry technology of the unmanned aerial vehicle.
Disclosure of Invention
Based on the optical lens, the invention provides the optical lens which at least has the characteristics of large aperture, high resolving power and positive F-Theta distortion so as to meet the requirements of the oblique photogrammetry technology of the unmanned aerial vehicle.
The embodiment of the invention realizes the aim through the following technical scheme.
In a first aspect, an embodiment of the present invention provides an optical lens system, which includes six lenses, in order from an object side to an image plane along an optical axis:
the lens comprises a first lens with negative focal power, a second lens and a third lens, wherein the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;
the second lens is provided with positive focal power, and the object side surface and the image side surface of the second lens are convex surfaces;
a third lens having a positive optical power, the third lens having a convex object-side surface and a concave or convex image-side surface at a paraxial region;
a diaphragm;
the fourth lens is provided with positive focal power, and the object side surface and the image side surface of the fourth lens are convex surfaces;
a fifth lens element having a negative optical power, the fifth lens element having a concave object-side surface and a concave image-side surface;
the sixth lens has positive focal power, and both the object-side surface and the image-side surface of the sixth lens are convex surfaces;
the second lens, the fourth lens and the fifth lens are all spherical glass lenses, and the first lens, the third lens and the sixth lens are all aspheric glass lenses;
the optical lens satisfies the conditional expression:
3.2＜TTL/CT2＜3.5；
4.5＜TTL/CT5＜6；
wherein CT2 denotes a center thickness of the second lens, CT5 denotes a center thickness of the fifth lens, and TTL denotes an optical total length of the optical lens.
In some embodiments, the optical lens satisfies the conditional expression:
0.9＜f/IH＜1；
f/ENPD＜1.81；
wherein f represents the effective focal length of the optical lens, IH represents half of the maximum diameter of the effective pixel area of the optical lens on the imaging plane, and ENPD represents the entrance pupil diameter of the optical lens.
In some embodiments, the optical lens satisfies the conditional expression:
-3.6＜R3/R4＜-2.5；
|R6|/R5＞2.5；
1.6＜R3/TTL＜2.4；
|R6|/TTL＞1；
wherein R3 represents a radius of curvature of the object-side surface of the second lens, R4 represents a radius of curvature of the image-side surface of the second lens, R5 represents a radius of curvature of the object-side surface of the third lens, and R6 represents a radius of curvature of the image-side surface of the third lens.
In some embodiments, the optical lens satisfies the conditional expression:
2.3mm-1＜TTL/(IH*f)＜2.55mm-1；
wherein IH represents a half of a maximum diameter of an effective pixel area of the optical lens on an imaging plane, and f represents an effective focal length of the optical lens.
In some embodiments, the optical lens satisfies the conditional expression:
-1.3＜f4/f5＜-1；
wherein f4 denotes an effective focal length of the fourth lens, and f5 denotes an effective focal length of the fifth lens.
In some embodiments, the optical lens satisfies the conditional expression:
(CRA)max＜21°；
wherein (CRA) max represents a maximum value of an incident angle of a chief ray of the optical lens in a full field of view on an image plane.
In some embodiments, the optical lens satisfies the conditional expression:
2.6＜Vd4/Vd5＜2.8；
0.8＜Nd4/Nd5＜0.9；
wherein Vd4 denotes an abbe number of the fourth lens, Vd5 denotes an abbe number of the fifth lens, Nd4 denotes a refractive index of the fourth lens, and Nd5 denotes a refractive index of the fifth lens.
In some embodiments, the optical lens satisfies the conditional expression:
-18°＜|ϕ5|-arctan[D5/(R52-D52)1/2] ＜18°；
-18°＜|ϕ6|-arctan[D6/(R62-D62)1/2] ＜18°；
-25°＜| ϕ11|-arctan[D11/(R112-D112)1/2] ＜25°；
-5°＜| ϕ12|-arctan[D12/(R122-D122)1/2] ＜5°；
wherein ϕ 5 denotes a face center angle of an object-side surface of the third lens at the effective half aperture, ϕ 6 denotes a face center angle of an image-side surface of the third lens at the effective half aperture, ϕ 11 denotes a face center angle of an object-side surface of the sixth lens at the effective half aperture, ϕ 12 denotes a face center angle of an image-side surface of the sixth lens at the effective half aperture; d5 denotes an effective half aperture of an object-side surface of the third lens, D6 denotes an effective half aperture of an image-side surface of the third lens, D11 denotes an effective half aperture of an object-side surface of the sixth lens, and D12 denotes an effective half aperture of an image-side surface of the sixth lens; r5 denotes a radius of curvature of an object-side surface of the third lens, R6 denotes a radius of curvature of an image-side surface of the third lens, R11 denotes a radius of curvature of an object-side surface of the sixth lens, and R12 denotes a radius of curvature of an image-side surface of the sixth lens.
In some embodiments, the optical lens satisfies the conditional expression:
-1.8＜f1/f＜-1.5；
4.5＜f2/f＜6；
8＜f3/f＜9.5；
1.2＜f4/f＜1.5；
-1.4＜f5/f＜-1；
1.7＜f6/f＜2.3；
wherein f1 denotes an effective focal length of the first lens, f2 denotes an effective focal length of the second lens, f3 denotes an effective focal length of the third lens, f4 denotes an effective focal length of the fourth lens, f5 denotes an effective focal length of the fifth lens, f6 denotes an effective focal length of the sixth lens, and f denotes an effective focal length of the optical lens.
Compared with the prior art, the invention has the beneficial effects that: the optical lens adopts six glass lenses, and has the beneficial effects of large aperture, high resolving power, positive F-Theta distortion and the like while realizing good imaging quality through reasonable configuration of the surface types of the lenses and reasonable collocation of focal power; and all use glass lens, can guarantee the dependability quality of camera lens to a great extent, make it be applicable to the more harsh technical field of environment.
In a second aspect, an embodiment of the present invention further provides an imaging apparatus, which includes the optical lens described above and an imaging element, where the imaging element is configured to convert an optical image formed by the optical lens into an electrical signal.
Compared with the prior art, the invention has the beneficial effects that: this imaging device adopts above-mentioned optical lens, has big light ring, high resolution power, the characteristics of positive F-Theta distortion to satisfy the demand of unmanned aerial vehicle oblique photography measurement technique.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic structural diagram of an optical lens assembly according to a first embodiment of the present invention;
FIG. 2 is a field curvature diagram of an optical lens according to a first embodiment of the present invention;
FIG. 3 is a schematic diagram of F-Theta distortion of an optical lens according to a first embodiment of the present invention;
FIG. 4 is a schematic diagram of an MTF curve of an optical lens according to a first embodiment of the present invention;
FIG. 5 is a schematic structural diagram of an optical lens assembly according to a second embodiment of the present invention;
FIG. 6 is a diagram illustrating curvature of field of an optical lens according to a second embodiment of the present invention;
FIG. 7 is a schematic diagram of F-Theta distortion of an optical lens according to a second embodiment of the present invention;
fig. 8 is a schematic MTF curve of an optical lens according to a second embodiment of the present invention.
Description of the main element symbols:
the following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Several embodiments of the invention are presented in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The invention provides an optical lens, which comprises six lenses in total, and sequentially comprises the following components from an object side to an imaging surface along an optical axis:
the first lens has negative focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;
the second lens has positive focal power, and both the object side surface and the image side surface of the second lens are convex surfaces;
the third lens has positive focal power, the object side surface of the third lens is convex, and the image side surface of the third lens is concave or convex at a paraxial region;
a diaphragm;
the fourth lens has positive focal power, and both the object side surface and the image side surface of the fourth lens are convex surfaces;
the fifth lens has negative focal power, and the object side surface and the image side surface of the fifth lens are both concave surfaces;
the sixth lens has positive focal power, and both the object side surface and the image side surface of the sixth lens are convex surfaces;
the second lens, the fourth lens and the fifth lens are all spherical glass lenses, and the first lens, the third lens and the sixth lens are aspheric glass lenses; the optical lens fully uses glass lenses, so that the reliability and quality of the lens can be ensured to a great extent, and the optical lens can be applied to the technical field which is harsh to the environment.
Further, the optical lens satisfies the following conditional expression:
3.2＜TTL/CT2＜3.5；（1）
4.5＜TTL/CT5＜6；（2）
wherein CT2 denotes a center thickness of the second lens, CT5 denotes a center thickness of the fifth lens, and TTL denotes an optical total length of the optical lens. Satisfying conditional expressions (1) to (2), the effect of correcting curvature of field is achieved by increasing the center thickness of the second lens.
Further, the optical lens satisfies the following conditional expression:
0.9＜f/IH＜1；（3）
f/ENPD＜1.81；（4）
wherein f represents the effective focal length of the optical lens, IH represents half of the maximum diameter of the effective pixel area of the optical lens on the imaging plane, and ENPD represents the entrance pupil diameter of the optical lens. Satisfying above-mentioned conditional expression (3), showing that the camera lens has great imaging surface, can satisfy the imaging demand of big target surface chip. Satisfying the above conditional expression (4), by placing the diaphragm between the third lens and the fourth lens, the optical lens can be made to have a larger aperture and have good imaging in a bright and dark environment.
Further, the optical lens satisfies the following conditional expression:
-3.6＜R3/R4＜-2.5；（5）
|R6|/R5＞2.5；（6）
1.6＜R3/TTL＜2.4；（7）
|R6|/TTL＞1；（8）
wherein R3 denotes a radius of curvature of an object-side surface of the second lens element, R4 denotes a radius of curvature of an image-side surface of the second lens element, R5 denotes a radius of curvature of an object-side surface of the third lens element, R6 denotes a radius of curvature of an image-side surface of the third lens element, and TTL denotes a total optical length of the optical lens. The relative position of the pupil image of the second lens image side secondary reflection ghost image on the focal plane and the relative position of the pupil image of the third lens image side secondary reflection ghost image on the focal plane can be changed by satisfying the conditional expressions (5) to (8), the pupil image of the ghost image can be far away from the focal plane by controlling the curvature radius, the relative energy value of the ghost image is effectively reduced, and the quality of a lens imaging picture is improved.
Further, the optical lens satisfies the following conditional expression:
2.3mm-1＜TTL/(IH*f)＜2.55mm-1；（9）
wherein, TTL represents the total optical length of the optical lens, IH represents a half of the maximum diameter of the effective pixel area of the optical lens on the imaging plane, and f represents the effective focal length of the optical lens. The condition formula (9) is satisfied, the total length and the effective focal length of the lens can be compressed while the image plane of the lens is enlarged, the design of the lens is more miniaturized, and the lens is convenient to carry on a terminal device.
Further, the optical lens satisfies the following conditional expression:
-1.3＜f4/f5＜-1；（10）
wherein f4 denotes an effective focal length of the fourth lens, and f5 denotes an effective focal length of the fifth lens. The condition formula (10) is satisfied, and the effect of eliminating chromatic aberration is achieved by reasonably distributing the positive and negative focal powers of the two lenses.
Further, the optical lens satisfies the following conditional expression:
(CRA)max＜21°；（11）
wherein (CRA)maxRepresents the maximum value of the incident angle of the chief ray of the full field of view of the optical lens on the image plane. The CRA of the lens can be matched with the CRA of the chip photosensitive element better by meeting the conditional expression (11), and the chip photosensitive efficiency is improved.
Further, the optical lens satisfies the following conditional expression:
2.6＜Vd4/Vd5＜2.8；（12）
0.8＜Nd4/Nd5＜0.9；（13）
wherein Vd4 denotes an abbe number of the fourth lens, Vd5 denotes an abbe number of the fifth lens, Nd4 denotes a refractive index of the fourth lens, and Nd5 denotes a refractive index of the fifth lens. Satisfying conditional expressions (12) to (13), elimination of chromatic aberration is facilitated by increasing the abbe number difference and the refractive index difference between the fourth lens L4 and the fifth lens L5.
Further, the optical lens satisfies the following conditional expression:
-18°＜|ϕ5|-arctan[D5/(R52-D52)1/2]＜18°；（14）
-18°＜|ϕ6|-arctan[D6/(R62-D62)1/2]＜18°；（15）
-25°＜| ϕ11|-arctan[D11/(R112-D112)1/2]＜25°； （16）
-5°＜| ϕ12|-arctan[D12/(R122-D122)1/2] ＜5°； （17）
wherein ϕ 5 denotes a face center angle of an object-side surface of the third lens at the effective half aperture, ϕ 6 denotes a face center angle of an image-side surface of the third lens at the effective half aperture, ϕ 11 denotes a face center angle of an object-side surface of the sixth lens at the effective half aperture, ϕ 12 denotes a face center angle of an image-side surface of the sixth lens at the effective half aperture; d5 denotes an effective half aperture of an object-side surface of the third lens, D6 denotes an effective half aperture of an image-side surface of the third lens, D11 denotes an effective half aperture of an object-side surface of the sixth lens, and D12 denotes an effective half aperture of an image-side surface of the sixth lens; r5 denotes a radius of curvature of an object-side surface of the third lens, R6 denotes a radius of curvature of an image-side surface of the third lens, R11 denotes a radius of curvature of an object-side surface of the sixth lens, and R12 denotes a radius of curvature of an image-side surface of the sixth lens. The conditional expressions (14) to (17) are satisfied, so that the change trend of the focal power from the center to the edge of the third lens and the sixth lens is closer to a cosine function, and the defocusing curves of all the fields are more converged when the temperature changes, which is beneficial to improving the temperature performance of the lens.
Further, the optical lens satisfies the conditional expression:
-1.8＜f1/f＜-1.5；（18）
4.5＜f2/f＜6；（19）
8＜f3/f＜9.5；（20）
1.2＜f4/f＜1.5；（21）
-1.4＜f5/f＜-1；（22）
1.7＜f6/f＜2.3；（23）
wherein f1 denotes an effective focal length of the first lens, f2 denotes an effective focal length of the second lens, f3 denotes an effective focal length of the third lens, f4 denotes an effective focal length of the fourth lens, f5 denotes an effective focal length of the fifth lens, f6 denotes an effective focal length of the sixth lens, and f denotes an effective focal length of the optical lens. The conditional expressions (18) to (23) are satisfied, and the aberration of the system can be better corrected and the imaging quality of the lens can be improved through reasonable combination of the focal powers of the lenses.
The aspheric surface shape of the imaging lens in the embodiments of the present invention satisfies the following equation:
wherein the content of the first and second substances,zindicating the distance of the curved surface from the apex of the curved surface in the direction of the optical axis,cthe curvature of the apex of the curved surface is shown,Kthe coefficients of the quadric surface are represented,hthe distance from the optical axis to the curved surface is shown,B、C、D、E、Frespectively representing the fourth, sixth, eighth, tenth and twelfth order surface coefficients.
The invention is further illustrated below in the following examples. In various embodiments, the thickness, the curvature radius, and the material selection of each lens in the wide-angle lens are different, and the specific differences can be referred to in the parameter tables of the various embodiments. The following examples are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited only by the following examples, and any other changes, substitutions, combinations or simplifications which do not depart from the innovative points of the present invention should be construed as being equivalent substitutions and shall be included within the scope of the present invention.
First embodiment
Fig. 1 is a schematic structural diagram of an optical lens according to a first embodiment of the present invention, the optical lens sequentially includes, from an object side to an image plane along an optical axis: a first lens L1, a second lens L2, a third lens L3, a stop STO, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a filter L7;
the first lens element L1 has negative power, and has a convex object-side surface S1 and a concave image-side surface S2;
the second lens L2 has positive focal power, and both the object side surface S3 and the image side surface S4 are convex surfaces;
the third lens element L3 has positive power, with the object side S5 being convex and the image side S6 being concave at the paraxial region;
the stop STO is disposed between the third lens L3 and the fourth lens L4;
the fourth lens L4 has positive power, and both the object-side surface S7 and the image-side surface S8 are convex;
the fifth lens L5 has negative power, and both the object-side surface S9 and the image-side surface S10 are concave;
the sixth lens L6 has positive power, and both the object-side surface S11 and the image-side surface S12 are convex;
the second lens L2, the fourth lens L4 and the fifth lens L5 are all glass spherical lenses, and the first lens L1, the third lens L3 and the sixth lens L6 are glass spherical lenses. The filter L7 is provided between the sixth lens L6 and the image plane S15.
Please refer to table 1-1, which shows the related parameters of each lens in the optical lens system according to the first embodiment of the present invention.
TABLE 1-1
The first embodiment of the present invention provides an optical lens having aspheric surface coefficients as shown in tables 1-2.
Tables 1 to 2
Referring to fig. 2, fig. 3 and fig. 4, a field curvature graph, an F-Theta distortion graph and an MTF graph of the optical lens in the present embodiment are respectively shown.
The field curvature curve of fig. 2 indicates the degree of curvature of the meridional image plane and the sagittal image plane. In fig. 2, the horizontal axis represents the offset amount (unit: mm) and the vertical axis represents the angle of view (unit: degree). As can be seen from fig. 2, the maximum curvature of field of the meridional image plane and the sagittal image plane is controlled to ± 0.1 mm or less in the full field angle, which indicates that the curvature of field of the optical lens is well corrected.
The F-Theta distortion curve of fig. 3 represents F-Theta distortion values for different field angles on the imaging plane. In FIG. 3, the horizontal axis represents the F-Theta distortion value (unit:%), and the vertical axis represents the angle of view (unit: degree). As can be seen from FIG. 3, the F-Theta distortion value at the maximum field angle is close to 30%, which shows that the F-Theta distortion of the optical lens at the marginal field is a positive increase, and the marginal field can contain more image information.
The MTF curves of fig. 4 represent paraxial MTFs for different spatial frequencies. In fig. 4, the horizontal axis represents spatial frequency (unit: cycle/mm), and the vertical axis represents MTF values. As can be seen from fig. 4, the paraxial MTF value at the maximum spatial frequency is still 0.6 or more, which indicates that the paraxial aberration of the optical lens is well corrected.
Second embodiment
Fig. 4 is a schematic structural diagram of an optical lens according to a second embodiment of the present invention, in which the optical lens in this embodiment is substantially the same as the optical lens in the first embodiment, except that the curvature radius and the thickness of each lens are different; it should be noted that the image-side surface S6 of the third lens element is convex at the paraxial region, and the relevant parameters of each lens element are shown in table 2-1.
The second embodiment of the present invention provides an optical lens system having the parameters of each lens shown in table 2-1.
TABLE 2-1
The second embodiment of the present invention provides an optical lens having aspheric surface coefficients as shown in table 2-2.
Tables 2 to 2
Please refer to fig. 6, fig. 7, and fig. 8, which respectively show a curvature of field curve graph, an F-Theta distortion graph, and an MTF graph of the optical lens in the present embodiment.
The field curvature curve of fig. 6 indicates the degree of curvature of the meridional image plane and the sagittal image plane. In fig. 6, the horizontal axis represents the offset amount (unit: mm) and the vertical axis represents the angle of view (unit: degree). As can be seen from fig. 6, the maximum curvature of field of the meridional image plane and the sagittal image plane is controlled to ± 0.1 mm or less in the full field angle, which indicates that the curvature of field of the optical lens is well corrected.
The F-Theta distortion curve of fig. 7 represents F-Theta distortion values for different field angles on the imaging plane. In FIG. 7, the horizontal axis represents the F-Theta distortion value (unit:%) and the vertical axis represents the angle of view (unit: degree). As can be seen from FIG. 7, the F-Theta distortion value at the maximum field angle is close to 30%, indicating that the F-Theta distortion of the optical lens at the marginal field is a positive growth, and the marginal field can contain more image information.
The MTF curves of fig. 8 represent paraxial MTFs for different spatial frequencies. In fig. 8, the horizontal axis represents spatial frequency (unit: cycle/mm), and the vertical axis represents MTF values. As can be seen from fig. 8, the paraxial MTF value at the maximum spatial frequency is still 0.6 or more, which indicates that the paraxial aberration of the optical lens is well corrected.
Table 3 shows the corresponding optical characteristics in the above embodiments, including the effective focal length F, total optical length TTL, field angle FOV, F # of the optical lens, and the corresponding values for each conditional expression.
TABLE 3
In conclusion, the optical lens provided by the invention adopts six glass lenses, and has the characteristics of large aperture, high resolving power and positive F-Theta distortion while realizing good imaging quality through reasonable configuration of the surface types of the lenses and reasonable collocation of focal power; and all use glass lens, can to a great extent guarantee the reliability quality of camera lens, make it can be applicable to the harsher field of environment to satisfy the demand of unmanned aerial vehicle oblique photography measurement technique.
Third embodiment
The present embodiment provides an imaging apparatus including the image pickup lens (e.g., optical lens 100) in any of the above embodiments, and an imaging element provided outside the imaging plane S15, the imaging element converting an optical image formed by the optical lens 100 into an electrical signal.
Further, the imaging element may be a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and may also be a CCD (Charge Coupled Device) image sensor.
Further, the imaging device may be a unmanned aerial vehicle oblique photography lens or the like.
The imaging device provided by the embodiment comprises the optical lens, and various aberrations of the imaging system are better corrected by combining the glass spherical surface with the aspheric surface of the optical lens, so that the imaging device provided by the embodiment has the characteristics of large aperture, high resolving power, positive F-Theta distortion and the like.
The above examples are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present invention should be subject to the appended claims.
Claims (10)
1. An optical lens system comprising six lenses, sequentially arranged along an optical axis from an object side to an image plane, comprising:
the lens comprises a first lens with negative focal power, a second lens and a third lens, wherein the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;
the second lens is provided with positive focal power, and the object side surface and the image side surface of the second lens are convex surfaces;
a third lens having a positive optical power, the third lens having a convex object-side surface and a concave or convex image-side surface at a paraxial region;
a diaphragm;
the fourth lens is provided with positive focal power, and the object side surface and the image side surface of the fourth lens are convex surfaces;
a fifth lens element having a negative optical power, the fifth lens element having a concave object-side surface and a concave image-side surface;
the sixth lens has positive focal power, and both the object-side surface and the image-side surface of the sixth lens are convex surfaces;
the second lens, the fourth lens and the fifth lens are all spherical glass lenses, and the first lens, the third lens and the sixth lens are all aspheric glass lenses;
the optical lens satisfies the conditional expression:
3.2＜TTL/CT2＜3.5；
4.5＜TTL/CT5＜6；
wherein CT2 represents a central thickness of the second lens, CT5 represents a central thickness of the fifth lens, and TTL represents a total optical length of the optical lens.
2. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression:
0.9＜f/IH＜1；
f/ENPD＜1.81；
wherein f represents the effective focal length of the optical lens, IH represents half of the maximum diameter of the effective pixel area of the optical lens on the imaging plane, and ENPD represents the entrance pupil diameter of the optical lens.
3. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression:
-3.6＜R3/R4＜-2.5；
|R6|/R5＞2.5；
1.6＜R3/TTL＜2.4；
|R6|/TTL＞1；
wherein R3 represents a radius of curvature of the object-side surface of the second lens, R4 represents a radius of curvature of the image-side surface of the second lens, R5 represents a radius of curvature of the object-side surface of the third lens, and R6 represents a radius of curvature of the image-side surface of the third lens.
4. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression:
2.3mm-1＜TTL/(IH*f)＜2.55mm-1；
wherein IH represents a half of a maximum diameter of an effective pixel area of the optical lens on an imaging plane, and f represents an effective focal length of the optical lens.
5. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression:
-1.3＜f4/f5＜-1；
wherein f4 denotes an effective focal length of the fourth lens, and f5 denotes an effective focal length of the fifth lens.
6. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression:
(CRA)max＜21°；
wherein (CRA)maxAnd the maximum value of the incident angle of the chief ray of the full field of view of the optical lens on the image plane is represented.
7. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression:
2.6＜Vd4/Vd5＜2.8；
0.8＜Nd4/Nd5＜0.9；
wherein Vd4 denotes an abbe number of the fourth lens, Vd5 denotes an abbe number of the fifth lens, Nd4 denotes a refractive index of the fourth lens, and Nd5 denotes a refractive index of the fifth lens.
8. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression:
-18°＜|ϕ5|-arctan[D5/(R52-D52)1/2]＜18°；
-18°＜|ϕ6|-arctan[D6/(R62-D62)1/2]＜18°；
-25°＜| ϕ11|-arctan[D11/(R112-D112)1/2]＜25°；
-5°＜| ϕ12|-arctan[D12/(R122-D122)1/2] ＜5°；
wherein ϕ 5 denotes a face center angle of an object-side surface of the third lens at the effective half aperture, ϕ 6 denotes a face center angle of an image-side surface of the third lens at the effective half aperture, ϕ 11 denotes a face center angle of an object-side surface of the sixth lens at the effective half aperture, ϕ 12 denotes a face center angle of an image-side surface of the sixth lens at the effective half aperture; d5 denotes an effective half aperture of an object-side surface of the third lens, D6 denotes an effective half aperture of an image-side surface of the third lens, D11 denotes an effective half aperture of an object-side surface of the sixth lens, and D12 denotes an effective half aperture of an image-side surface of the sixth lens; r5 denotes a radius of curvature of an object-side surface of the third lens, R6 denotes a radius of curvature of an image-side surface of the third lens, R11 denotes a radius of curvature of an object-side surface of the sixth lens, and R12 denotes a radius of curvature of an image-side surface of the sixth lens.
9. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression:
-1.8＜f1/f＜-1.5；
4.5＜f2/f＜6；
8＜f3/f＜9.5；
1.2＜f4/f＜1.5；
-1.4＜f5/f＜-1；
1.7＜f6/f＜2.3；
wherein f1 denotes an effective focal length of the first lens, f2 denotes an effective focal length of the second lens, f3 denotes an effective focal length of the third lens, f4 denotes an effective focal length of the fourth lens, f5 denotes an effective focal length of the fifth lens, f6 denotes an effective focal length of the sixth lens, and f denotes an effective focal length of the optical lens.
10. An imaging apparatus comprising the optical lens according to any one of claims 1 to 9 and an imaging element for converting an optical image formed by the optical lens into an electric signal.
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| CN110955031A (en) * | 2019-12-23 | 2020-04-03 | 福建福光天瞳光学有限公司 | 2.8mm wide-angle optical system and imaging method thereof |
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