CN210270347U

CN210270347U - Optical imaging lens

Info

Publication number: CN210270347U
Application number: CN201921405204.8U
Authority: CN
Inventors: 刘青天; 上官秋和; 李雪慧
Original assignee: Xiamen Leading Optics Co Ltd
Current assignee: Xiamen Leading Optics Co Ltd
Priority date: 2019-08-28
Filing date: 2019-08-28
Publication date: 2020-04-07
Anticipated expiration: 2029-08-28

Abstract

The utility model relates to a camera lens technical field relates to an optical imaging camera lens especially. The utility model discloses an optical imaging lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens; the first lens is a convex-concave lens with positive refractive index; the second lens is a convex-concave lens with negative refractive index; the third lens has a convex-concave lens with negative refractive index; the fourth lens is a convex-flat lens with positive refractive index; the fifth lens is a concave lens with negative refractive index; the sixth lens is a convex lens with positive refractive index; the seventh lens is a concave-convex lens with positive refractive index; the eighth lens is a convex lens with positive refractive index; the fifth lens and the sixth lens are cemented to each other. The utility model has the advantages of large image surface; the resolution ratio is high, the resolution power uniformity is good, the contrast ratio is high, and the requirement of high-contrast images can be met at night; the distortion is small; and infrared defocusing is small.

Description

Optical imaging lens

Technical Field

The utility model belongs to the technical field of the camera lens, specifically relate to an optical imaging camera lens.

Background

With the continuous progress of the technology, in recent years, the optical imaging lens is also rapidly developed, and is widely applied to various fields such as smart phones, tablet computers, video conferences, vehicle-mounted monitoring, security monitoring and the like. As outdoor sports become popular, more and more optical imaging lenses are used in outdoor sports for motion capture, and thus, the demand for the optical imaging lenses is higher and higher. However, the existing optical imaging lens for outdoor sports has many defects, such as poor night vision effect, low resolution, more noise at night and poor contrast; the lens with low distortion has a small image surface and an image height phi <7 mm; the lens with a large image surface has large distortion, the optical distortion is more than 8%, and the distortion of a shot object is serious; the low distortion lens with a large image surface has poor infrared confocal performance and large infrared defocusing, and cannot meet the increasing requirements.

Disclosure of Invention

An object of the utility model is to provide an optical imaging lens is used for solving the technical problem that above-mentioned exists.

In order to achieve the above object, the utility model adopts the following technical scheme: an optical imaging lens sequentially comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens from an object side to an image side along an optical axis; the first lens element to the eighth lens element each include an object-side surface facing the object side and allowing the imaging light to pass therethrough and an image-side surface facing the image side and allowing the imaging light to pass therethrough;

the first lens element with positive refractive index has a convex object-side surface and a concave image-side surface;

the second lens element with negative refractive index has a convex object-side surface and a concave image-side surface;

the third lens element with negative refractive index has a convex object-side surface and a concave image-side surface;

the fourth lens element with positive refractive index has a convex object-side surface and a flat image-side surface;

the fifth lens element with negative refractive index has a concave object-side surface and a concave image-side surface;

the sixth lens element with positive refractive index has a convex object-side surface and a convex image-side surface; the image side surface of the fifth lens and the object side surface of the sixth lens are mutually cemented;

the seventh lens element with positive refractive power has a concave object-side surface and a convex image-side surface;

the eighth lens element with positive refractive index has a convex object-side surface and a convex image-side surface;

the optical imaging lens has only eight lenses with refractive indexes.

Further, the optical diaphragm is arranged between the fourth lens and the fifth lens.

Furthermore, the diaphragm is tightly attached to the image side surface of the fourth lens.

Further, the optical imaging lens further satisfies: D22/R22 is less than or equal to 1.77, wherein D22 is the clear aperture of the image side surface of the second lens, and R22 is the curvature radius of the image side surface of the second lens.

Further, the optical imaging lens further satisfies: nd2>1.9, where nd2 is the refractive index of the second lens at d-line.

Further, the optical imaging lens further satisfies: -120mm < R71< -10mm, wherein R71 is the radius of curvature of the object-side face of the seventh lens.

Further, the optical imaging lens further satisfies: vd6 is more than or equal to 46, vd5 is less than or equal to 18, and vd6-vd5 is more than 28, wherein vd5 and vd6 are the dispersion coefficients of the fifth lens and the sixth lens at the d line respectively.

Further, any adjacent two lenses of the first lens to the eighth lens have different refractive indexes.

Further, the optical imaging lens further satisfies: ALT <20mm, ALG <11mm, ALT/ALG <2, wherein ALT is the total of eight lens thicknesses of the first lens to the eighth lens on the optical axis, and ALG is the total of air gaps of the first lens to an imaging plane on the optical axis.

The utility model has the advantages of:

the utility model adopts eight lenses, and through corresponding design of each lens, the transfer function is high, the resolution ratio is high, the contrast ratio is high (when the infrared 125lp/mm can be realized, the central MTF is more than 49%, the edge MTF is more than 40%), and the requirement that the high-contrast image can be shot at night is satisfied; the image surface is large (the image height phi can be larger than 8 mm); distortion becomes low (optical distortion can be less than 3%); good infrared confocal (infrared defocus IR shift can be less than 3 μm).

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a first embodiment of the present invention;

FIG. 2 is a graph of the MTF of the visible light 486-;

FIG. 3 is a graph of MTF at 850nm in the first embodiment of the present invention;

FIG. 4 is a defocus plot of 486-656nm of visible light in accordance with a first embodiment of the present invention;

fig. 5 is a graph of infrared 850nm defocus curve of the first embodiment of the present invention;

fig. 6 is a schematic view of curvature of field and distortion according to a first embodiment of the present invention;

fig. 7 is a schematic structural diagram of a second embodiment of the present invention;

FIG. 8 is the MTF graph of 486-;

FIG. 9 is an infrared 850nm MTF graph according to the second embodiment of the present invention;

FIG. 10 is a defocus plot of 486-;

fig. 11 is a graph of infrared 850nm defocus curve of the second embodiment of the present invention;

fig. 12 is a schematic view of curvature of field and distortion according to a second embodiment of the present invention;

fig. 13 is a schematic structural view of a third embodiment of the present invention;

FIG. 14 is the MTF graph of 486-;

FIG. 15 is an infrared 850nm MTF graph according to a third embodiment of the present invention;

FIG. 16 is a defocus plot of 486-;

fig. 17 is a graph of infrared 850nm defocus curve of the third embodiment of the present invention;

fig. 18 is a schematic view of curvature of field and distortion according to a third embodiment of the present invention;

fig. 19 is a table of values of important parameters according to three embodiments of the present invention.

Detailed Description

To further illustrate the embodiments, the present invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. With these references, one of ordinary skill in the art will appreciate other possible embodiments and advantages of the present invention. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.

The present invention will now be further described with reference to the accompanying drawings and detailed description.

The term "a lens element having positive refractive index (or negative refractive index)" means that the paraxial refractive index of the lens element calculated by Gaussian optics theory is positive (or negative). The term "object-side (or image-side) of a lens" is defined as the specific range of imaging light rays passing through the lens surface. The determination of the surface shape of the lens can be performed by the judgment method of a person skilled in the art, i.e., by the sign of the curvature radius (abbreviated as R value). The R value may be commonly used in optical design software, such as Zemax or CodeV. The R value is also commonly found in lens data sheets (lens data sheets) of optical design software. When the R value is positive, the object side is judged to be a convex surface; and when the R value is negative, judging that the object side surface is a concave surface. On the contrary, regarding the image side surface, when the R value is positive, the image side surface is judged to be a concave surface; when the R value is negative, the image side surface is judged to be convex.

The utility model provides an optical imaging lens, which comprises a first lens to an eighth lens from an object side to an image side along an optical axis in sequence; the first lens element to the eighth lens element each include an object-side surface facing the object side and passing the image light, and an image-side surface facing the image side and passing the image light.

The first lens element with positive refractive index has a convex object-side surface and a concave image-side surface.

The second lens element with negative refractive index has a convex object-side surface and a concave image-side surface.

The third lens element with negative refractive index has a convex object-side surface and a concave image-side surface.

The fourth lens element with positive refractive power has a convex object-side surface and a flat image-side surface.

The fifth lens element with negative refractive index has a concave object-side surface and a concave image-side surface.

The sixth lens element with positive refractive index has a convex object-side surface and a convex image-side surface; the image side surface of the fifth lens and the object side surface of the sixth lens are mutually cemented.

The seventh lens element with positive refractive power has a concave object-side surface and a convex image-side surface. The seventh lens element has a positive refractive index, which is beneficial to the MTF optimization.

The eighth lens element with positive refractive power has a convex object-side surface and a convex image-side surface.

The optical imaging lens has only eight lenses with refractive indexes. The utility model adopts eight lenses, and through the corresponding design of each lens, the lens has the advantages of high transmission, high resolution and high contrast, and meets the requirement that high-contrast images can be shot at night; the image surface is large; the distortion becomes low; good infrared confocal performance.

Preferably, the diaphragm is arranged between the fourth lens and the fifth lens, a symmetrical structure of the front four and the rear four is adopted, the overall light is relatively gentle, and the tolerance and the manufacturability are strong.

More preferably, the diaphragm is tightly attached to the image side surface of the fourth lens, the interval tolerance is well controlled, and the mass production performance is good.

Preferably, the optical imaging lens further satisfies: D22/R22 is not more than 1.77, wherein D22 is the clear aperture of the image side surface of the second lens, and R22 is the curvature radius of the image side surface of the second lens, so that the processing is convenient on the premise of low distortion function.

Preferably, the optical imaging lens further satisfies: nd2>1.9, wherein nd2 is the refractive index of the second lens in the d line, further optimizes the image quality, reduces the outer diameter of the lens and effectively reduces the optical distortion.

Preferably, the optical imaging lens further satisfies: -120mm < R71< -10mm, wherein R71 is the radius of curvature of the object side of the seventh lens, which diverges light rays and effectively avoids large-angle ghost images.

Preferably, the optical imaging lens further satisfies: vd6 is more than or equal to 46, vd5 is less than or equal to 18, and vd6-vd5 is more than 28, wherein vd5 and vd6 are dispersion coefficients of the fifth lens and the sixth lens at the d line respectively, and high-low dispersion materials are combined to effectively control chromatic aberration, optimize image quality and improve system performance.

Preferably, in the first lens to the eighth lens, the refractive indexes of any two adjacent lenses are different, so that a balance system is further realized, the system performance is improved, and better visible and infrared confocal performance is realized.

Preferably, the optical imaging lens further satisfies: ALT <20mm, ALG <11mm, ALT/ALG <2, wherein ALT is the total of eight lens thicknesses of the first lens to the eighth lens on the optical axis, and ALG is the total of air gaps of the first lens to an imaging plane on the optical axis. The system length of the optical imaging lens is further shortened, the processing and the manufacturing are easy, and the system configuration is optimized.

The optical imaging lens of the present invention will be described in detail with reference to specific embodiments.

Implement one

As shown in fig. 1, an optical imaging lens includes, in order along an optical axis I, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a stop, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a protective glass 9, and an image plane 10 from an object side a1 to an image side a 2; the first lens element 1 to the eighth lens element 8 each include an object-side surface facing the object side a1 and passing the image light, and an image-side surface facing the image side a2 and passing the image light.

The first lens element 1 has a positive refractive index, the object-side surface 11 of the first lens element 1 is convex, and the image-side surface 12 of the first lens element 1 is concave.

The second lens element 2 has a negative refractive index, and an object-side surface 21 of the second lens element 2 is convex and an image-side surface 22 of the second lens element 2 is concave.

The third lens element 3 has a negative refractive index, and an object-side surface 31 of the third lens element 3 is convex and an image-side surface 32 of the third lens element 3 is concave.

The fourth lens element 4 has a positive refractive index, the object-side surface 41 of the fourth lens element 4 is a convex surface, and the image-side surface 42 of the fourth lens element 4 is a flat surface.

The fifth lens element 5 has a negative refractive index, and an object-side surface 51 of the fifth lens element 5 is concave and an image-side surface 52 of the fifth lens element 5 is concave.

The sixth lens element 6 with positive refractive index has a convex object-side surface 61 of the sixth lens element 6 and a convex image-side surface 62 of the sixth lens element 6; the image-side surface 52 of the fifth lens element 5 and the object-side surface 61 of the sixth lens element 6 are cemented to each other.

The seventh lens element 7 has a positive refractive index, and an object-side surface 71 of the seventh lens element 7 is concave and an image-side surface 75 of the seventh lens element 7 is convex.

The eighth lens element 8 has a positive refractive index, and an object-side surface 81 of the eighth lens element 8 is convex and an image-side surface 82 of the eighth lens element 8 is convex.

In this embodiment, the stop is closely attached to the image side surface 42 of the fourth lens 4, but in other embodiments, the stop may be disposed between other lenses.

The detailed optical data of this embodiment are shown in Table 1-1.

Table 1-1 detailed optical data for example one

Please refer to fig. 19 for the values of the conditional expressions according to this embodiment.

Referring to fig. 2 and 3, it can be seen from the figures that the transfer function is high, the resolution is high, the contrast is high, the central MTF is greater than 49% and the edge MTF is greater than 40% at 125lp/mm in the infrared region, the confocal properties of visible light and infrared light are good, the infrared offset is less than 3 μm, the field curvature and distortion images are shown in (a) and (B) of fig. 6, the distortion is small, the optical distortion is less than 3%, and the imaging quality is high.

In this embodiment, the focal length f of the optical imaging lens is 5.8mm, the aperture value FNO is 2.0, the field angle FOV is 70 °, the image plane size Φ is 8mm, and the distance TTL between the object-side surface 11 of the first lens 1 and the imaging surface 10 on the optical axis I is 29.84 mm.

Example two

As shown in fig. 7, in this embodiment, the surface convexoconcave and the refractive index of each lens are the same as those of the first embodiment, and only the optical parameters such as the curvature radius of the surface of each lens and the thickness of the lens are different.

The detailed optical data of this embodiment is shown in Table 2-1.

TABLE 2-1 detailed optical data for example two

Referring to fig. 8 and 9, it can be seen that the image resolution of the present embodiment is high in transfer function, high in resolution, and high in contrast, and when the infrared light is 125lp/mm, the central MTF is greater than 49%, the edge MTF is greater than 40%, and the confocal property between visible light and infrared light is shown in fig. 10 and 11, and it can be seen that the confocal property between visible light and infrared light is good, the infrared offset is less than 3 μm, and the field curvature and distortion diagram is shown in (a) and (B) of fig. 12, it can be seen that the distortion is small, the optical distortion is less than 3%, and the imaging quality is high.

EXAMPLE III

As shown in fig. 13, the lens elements of this embodiment have the same surface irregularities and refractive index as those of the first embodiment, and only the optical parameters such as the curvature radius of the surface of each lens element and the lens thickness are different.

The detailed optical data of this embodiment is shown in Table 3-1.

TABLE 3-1 detailed optical data for EXAMPLE III

Referring to fig. 14 and 15, the image resolution of the present embodiment can be seen from the figures, which show that the transfer function is high, the resolution is high, the contrast is high, the central MTF is greater than 49% and the edge MTF is greater than 40% at 125lp/mm in the infrared, the confocal properties of visible light and infrared light are good, the infrared offset is less than 3 μm, the field curvature and distortion are shown in (a) and (B) of fig. 18, the distortion is small, the optical distortion is less than 3%, and the imaging quality is high.

In this embodiment, the focal length f of the optical imaging lens is 5.8mm, the aperture value FNO is 2.0, the field angle FOV is 70 °, the image plane size Φ is 8mm, and the distance TTL between the object-side surface 11 of the first lens 1 and the imaging surface 10 on the optical axis I is 29.85 mm.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. An optical imaging lens characterized in that: the optical lens assembly sequentially comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens from the object side to the image side along an optical axis; the first lens element to the eighth lens element each include an object-side surface facing the object side and allowing the imaging light to pass therethrough and an image-side surface facing the image side and allowing the imaging light to pass therethrough;

the optical imaging lens has only eight lenses with refractive indexes.

2. The optical imaging lens according to claim 1, characterized in that: and the diaphragm is arranged between the fourth lens and the fifth lens.

3. The optical imaging lens according to claim 2, characterized in that: the diaphragm is tightly attached to the image side surface of the fourth lens.

4. The optical imaging lens of claim 1, further satisfying: D22/R22 is less than or equal to 1.77, wherein D22 is the clear aperture of the image side surface of the second lens, and R22 is the curvature radius of the image side surface of the second lens.

5. The optical imaging lens of claim 1, further satisfying: nd2>1.9, where nd2 is the refractive index of the second lens at d-line.

6. The optical imaging lens of claim 1, further satisfying: -120mm < R71< -10mm, wherein R71 is the radius of curvature of the object-side face of the seventh lens.

7. The optical imaging lens of claim 1, further satisfying: vd6 is more than or equal to 46, vd5 is less than or equal to 18, and vd6-vd5 is more than 28, wherein vd5 and vd6 are the dispersion coefficients of the fifth lens and the sixth lens at the d line respectively.

8. The optical imaging lens according to claim 1, characterized in that: in the first to eighth lenses, any adjacent two lenses have different refractive indices.

9. The optical imaging lens of claim 1, further satisfying: ALT <20mm, ALG <11mm, ALT/ALG <2, wherein ALT is the total of eight lens thicknesses of the first lens to the eighth lens on the optical axis, and ALG is the total of air gaps of the first lens to an imaging plane on the optical axis.