CN113703138B

CN113703138B - Optical lens

Info

Publication number: CN113703138B
Application number: CN202111251746.6A
Authority: CN
Inventors: 章彬炜; 王义龙; 曾昊杰; 曾吉勇
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Jiangxi Lianyi Optics Co Ltd
Priority date: 2021-10-27
Filing date: 2021-10-27
Publication date: 2022-03-29
Anticipated expiration: 2041-10-27
Also published as: CN113703138A

Abstract

The invention provides an optical lens, which comprises eight lenses in total, and sequentially comprises the following components from an object side to an imaging surface: a diaphragm; the first lens with positive focal power has a convex object-side surface and a concave image-side surface; a second lens having a negative optical power; a third lens with focal power, wherein the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a concave surface; a fourth lens having a refractive power, an image-side surface of which is concave; a fifth lens element with positive refractive power having a concave object-side surface and a convex image-side surface; a sixth lens element with negative refractive power having a convex object-side surface and a concave image-side surface; a seventh lens having positive optical power; and the object side surface of the eighth lens with negative focal power is a concave surface, and the image side surface of the eighth lens is a concave surface. The optical lens satisfies: TTL/ImgH is more than 1.0 and less than 1.2. Through this application for optical lens has the advantage of high pixel and has big light ring and the high advantage of imaging quality.

Description

Optical lens

Technical Field

The invention relates to the technical field of lens imaging, in particular to an optical lens.

Background

At present, a camera lens has become a standard configuration of an electronic device (such as a smart phone and a camera), and even the camera lens has become an index of primary consideration when a consumer purchases the electronic device. In recent years, with the development of design level and manufacturing technology, the size, weight and performance of the imaging lens have been reduced.

The higher the mobile phone is, the higher the pixels of the mobile phone are, the smaller the size of the chip pixel points matched with the camera is, and the information obtained by photographing is increased.

However, the optical lens generally has the technical defects of low pixel, small f-number, low measurement accuracy, low molding quality and the like.

Disclosure of Invention

Accordingly, an object of the present invention is to provide an optical lens, which can at least overcome at least one of the above-mentioned drawbacks in the prior art, so as to meet the design requirements of the optical lens of the electronic device.

An optical lens, comprising eight lenses in total, sequentially from an object side surface to an image plane along an optical axis:

a diaphragm;

the first lens with positive focal power has a convex object-side surface and a concave image-side surface;

a second lens having a negative optical power;

a third lens with focal power, wherein the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a concave surface;

a fourth lens having a refractive power, an image-side surface of which is concave;

a fifth lens element with positive refractive power having a concave object-side surface and a convex image-side surface;

a sixth lens element with negative refractive power having a convex object-side surface and a concave image-side surface;

a seventh lens having positive optical power;

and the object side surface of the eighth lens with negative focal power is a concave surface, and the image side surface of the eighth lens is a concave surface.

Wherein, a distance TTL between an object side surface of the first lens element and an image plane of the optical lens along an optical axis and a half ImgH of an image height corresponding to a maximum field angle of the optical lens satisfy the following conditional expression: TTL/ImgH is more than 1.0 and less than 1.2. The optical lens is favorable for realizing a larger imaging height and a shorter optical total length, so that the miniaturization of the optical lens is favorable for realizing and the imaging quality is favorable for improving.

In some embodiments, the effective focal length f of the optical lens and the maximum half field angle Semi-FOV of the optical lens satisfy: 2.0mm < f × tan (Semi-FOV) < 2.2 mm. The large image plane characteristic can be realized, so that the photosensitive element with larger size can be matched, the optical lens has the characteristics of high pixel and high definition, and the imaging quality of the optical lens is improved.

In some embodiments, the first lens is a glass aspheric lens, and the second lens, the third lens, the fourth lens, the sixth lens, the seventh lens and the eighth lens are plastic aspheric lenses.

In some embodiments, the first lens element, the fifth lens element and the second lens element are both glass aspheric lens elements, and the second lens element, the third lens element, the fourth lens element, the sixth lens element, the seventh lens element and the eighth lens element are all plastic aspheric lens elements.

According to the optical lens provided by the invention, through reasonably matching the combination of the lens shape and the focal power among the lenses, the size of the whole optical lens is effectively reduced, the effect of clear imaging of the large aperture is realized while the optical lens is miniaturized, the optical lens has the advantages of miniaturization, high imaging quality and large aperture, has good applicability to portable electronic equipment, and can effectively improve the shooting experience of a user.

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 system according to a first embodiment of the present invention;

FIG. 2 is a field curvature graph of an optical lens according to a first embodiment of the present invention;

FIG. 3 is a diagram illustrating a distortion curve of an optical lens according to a first embodiment of the present invention;

FIG. 4 is a graph illustrating axial chromatic aberration of an optical lens according to a first embodiment of the present invention;

FIG. 5 is a vertical axis chromatic aberration diagram of an optical lens according to a first embodiment of the present invention;

FIG. 6 is a schematic structural diagram of an optical lens system according to a second embodiment of the present invention;

FIG. 7 is a field curvature graph of an optical lens according to a second embodiment of the present invention;

FIG. 8 is a distortion graph of an optical lens in a second embodiment of the present invention;

FIG. 9 is a graph of axial chromatic aberration of an optical lens according to a second embodiment of the present invention;

FIG. 10 is a vertical axis chromatic aberration diagram of an optical lens according to a second embodiment of the present invention;

FIG. 11 is a schematic structural diagram of an optical lens assembly according to a third embodiment of the present invention;

FIG. 12 is a field curvature graph of an optical lens according to a third embodiment of the present invention;

fig. 13 is a distortion graph of an optical lens in a third embodiment of the present invention;

FIG. 14 is a graph illustrating axial chromatic aberration of an optical lens according to a third embodiment of the present invention;

FIG. 15 is a vertical axis chromatic aberration diagram of an optical lens according to a third embodiment of the present invention;

FIG. 16 is a schematic structural diagram of an optical lens system according to a fourth embodiment of the present invention;

fig. 17 is a field curvature graph of an optical lens in a fourth embodiment of the present invention;

fig. 18 is a distortion graph of an optical lens in a fourth embodiment of the present invention;

FIG. 19 is a graph showing axial chromatic aberration of an optical lens according to a fourth embodiment of the present invention;

fig. 20 is a vertical axis chromatic aberration diagram of an optical lens according to a fourth 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

In order to make the objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. 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.

It should be noted that in this specification, the expressions first, second, third, etc. are used only to distinguish one feature from another, and do not represent any limitation on the features. Thus, the first lens discussed below may also be referred to as the second lens or the third lens without departing from the teachings of the present invention.

In the drawings, the thickness, size, and shape of the lens have been slightly exaggerated for convenience of explanation. In particular, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shape of the spherical surface or the aspherical surface is not limited to the shape of the spherical surface or the aspherical surface shown in the drawings. The figures are purely diagrammatic and not drawn to scale.

It will be further understood that the terms "comprises," "comprising," "has," "having," "includes" and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears after a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present invention, "may" be used to mean "one or more embodiments of the present invention. Also, the term "exemplary" is intended to refer to an example or illustration.

The invention provides an optical lens, which comprises eight lenses in total, and sequentially comprises the following components from an object side to an imaging surface:

a diaphragm;

a second lens having a negative optical power;

a seventh lens having positive optical power;

The distance TTL from the object side surface of the first lens element to the imaging surface of the optical lens on the optical axis and the half ImgH of the image height corresponding to the maximum field angle of the optical lens satisfy the following conditional expression: TTL/ImgH is more than 1.0 and less than 1.2. The optical lens is favorable for realizing a larger imaging height and a shorter optical total length, so that the miniaturization of the optical lens is favorable for realizing and the imaging quality is favorable for improving.

In some embodiments, the effective focal length f of the optical lens and the maximum half field angle Semi-FOV of the optical lens satisfy the following conditional expression: 2.0mm < f × tan (Semi-FOV) < 2.2 mm. The large image plane characteristic can be realized, so that the photosensitive element with larger size can be matched, the optical lens has the characteristics of high pixel and high definition, and the imaging quality of the optical lens is improved.

In some embodiments, the distance CT12 between the first lens and the second lens on the optical axis and the central thickness CT1 of the first lens and the central thickness CT2 of the second lens satisfy the following conditional expression: 0.14 < CT12/(CT1+ CT2) < 0.46. The distance between the first lens and the second lens on the optical axis and the central thickness of the first lens and the second lens are reasonably controlled, the requirement of the AOA technology (high-precision optical alignment technology) on the gap between the first lens and the second lens is favorably met during assembly of the first lens, the yield of the optical lens can be improved, and the production cost is reduced.

In some embodiments, the radius of curvature R21 of the object-side surface of the second lens and the radius of curvature R22 of the image-side surface of the second lens satisfy the following conditional expression: -2.0 < (R21+ R22)/(R21-R22) < 3.0. The off-axis aberration can be corrected, and the light rays can have proper incidence and emergent angles on the second lens, which is beneficial to increasing the area of an imaging surface.

In some embodiments, the radius of curvature R31 of the object-side surface of the third lens and the radius of curvature R32 of the image-side surface of the third lens satisfy the following conditional expression: -10.0 < (R31+ R32)/(R31-R32) < 5.0. The deflection degree of light when passing through the third lens can be reduced, so that aberration is reduced, and the imaging quality of the optical lens is improved.

In some embodiments, the distance CT34 between the third lens and the fourth lens on the optical axis and the central thicknesses CT3 and CT4 of the third lens and the fourth lens satisfy the following conditional expressions: 0.2 < CT34/(CT3+ CT4) < 0.7. The distance between the third lens and the fourth lens on the optical axis and the central thickness of the third lens and the fourth lens are reasonably controlled, so that the distortion contribution amount is favorably controlled within a reasonable range.

In some embodiments, the distance CT56 between the fifth lens and the sixth lens on the optical axis and the central thicknesses CT5 and CT6 of the fifth lens and the sixth lens satisfy the following conditional expressions: 0.03 < CT56/(CT5+ CT6) < 0.1. The distance between the fifth lens and the sixth lens on the optical axis and the central thickness of the fifth lens and the sixth lens are reasonably controlled, so that the distortion contribution amount is favorably controlled within a reasonable range.

In some embodiments, the distance CT67 on the optical axis of the sixth lens and the seventh lens and the central thickness CT6 of the sixth lens and the central thickness CT7 of the seventh lens satisfy the following conditional expressions: 0.1 < CT67/(CT6+ CT7) < 0.55. The distance between the sixth lens and the seventh lens on the optical axis and the central thickness of the sixth lens and the seventh lens are reasonably controlled, so that the distortion contribution amount is favorably controlled within a reasonable range.

In some embodiments, the combined focal length f13 of the first to third lenses and the effective focal length f of the optical lens satisfy the following conditional expression: f13/f is more than 0.9 and less than 1.1. By the arrangement of enhancing the powers of the first lens, the second lens and the third lens, the light beam on the axis is more converged, which is advantageous for the miniaturization of the fourth lens and the fifth lens arranged at the rear end of the third lens.

In some embodiments, the sago 61 of the sixth lens object-side surface and the effective aperture DM61 of the sixth lens object-side surface satisfy the following conditional: -0.15 < SAG61/DM61 < -0.01. The opening angle of the object side surface of the sixth lens is larger, so that deflection of peripheral light rays is reduced, and imaging quality is improved.

In some embodiments, the radius of curvature R71 of the object-side surface of the seventh lens and the radius of curvature R72 of the image-side surface of the seventh lens satisfy the following conditional expression: -2.0 < (R71+ R72)/(R71-R72) < 3.0. The aberration generated by the optical system under the large aperture can be corrected, so that the refractive power of the optical system in the direction vertical to the optical axis is uniformly configured, the distortion and the aberration generated by the first lens and the sixth lens can be effectively corrected, the seventh lens is prevented from being excessively bent, and the difficulty in forming and manufacturing the seventh lens is reduced.

In some embodiments, the sagittal height SAG71 of the seventh lens object-side surface and the effective aperture DM71 of the seventh lens object-side surface satisfy the following conditional expression: -0.08 < SAG71/DM71 < -0.03. The opening angle of the object side surface of the seventh lens is larger, so that deflection of peripheral light rays is reduced, and imaging quality is improved.

In some embodiments, the sagittal height SAG72 of the seventh lens image-side and the sagittal height SAG81 of the eighth lens object-side satisfy the following conditional: 0.4 < SAG72/SAG81 < 0.6. The effect of increasing the image height and reducing the total length can be generated, and the light and thin requirements on the market are met while the advantage of high pixel is met.

In some embodiments, the focal length f8 of the eighth lens and the effective focal length f of the optical lens satisfy the following conditional expression: -0.8 < f8/f < -0.7. The optical lens can have higher imaging quality and lower sensitivity.

In some embodiments, the first lens element is a glass aspheric lens, and the second lens element, the third lens element, the fourth lens element, the fifth lens element, the sixth lens element, the seventh lens element and the eighth lens element are plastic aspheric lens elements.

The use of aspheric lenses has at least three advantages:

1. the lens has better imaging quality;

2. the structure of the lens is more compact;

3. the total optical length of the lens is shorter.

The surface shape of the aspheric lens in each embodiment of the invention satisfies the following equation:

，

wherein z is the distance rise from the aspheric surface vertex when the aspheric surface is at the position with the height h along the optical axis direction, c is the paraxial curvature of the surface, k is the quadric coefficient, A_2iIs the aspheric surface type coefficient of 2i order.

In the following embodiments, the thickness, the curvature radius, and the material selection of each lens in the optical lens are different, and specific differences can be referred to in the parameter tables of the embodiments.

First embodiment

Referring to fig. 1, fig. 1 is a schematic structural diagram of an optical lens according to a first embodiment of the present disclosure.

In this embodiment, as illustrated in fig. 1, the optical lens includes, in order from an object side to an image side along an optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter G1.

The first lens L1 is a glass aspheric lens with positive power, and has a convex object-side surface S1 and a concave image-side surface S2;

the second lens element L2 is a plastic aspheric lens with negative power, and has a convex object-side surface S3 and a concave image-side surface S4;

the third lens element L3 has a plastic aspheric lens with positive power, with an object-side surface S5 being convex at the paraxial region and an image-side surface S6 being concave at the paraxial region;

the fourth lens element L4 has a negative aspheric surface with a convex object-side surface S7 at paraxial region and a concave image-side surface S8 at paraxial region;

the fifth lens element L5 has a plastic aspheric lens with positive power, a concave object-side surface S9 at the paraxial region, and a convex image-side surface S10 at the paraxial region;

the sixth lens element L6 has a negative aspheric surface with a convex object-side surface S11 at paraxial region and a concave image-side surface S12 at paraxial region;

the seventh lens element L7 has a plastic aspheric lens with positive power, with an object-side surface S13 being convex at the paraxial region and an image-side surface S14 being concave at the paraxial region;

the eighth lens element L8 has a plastic aspheric lens with positive power, with an object-side surface S15 concave at the paraxial region and an image-side surface S16 concave at the paraxial region.

The design parameters of the optical lens provided in this embodiment are shown in table 1, where R represents the radius of curvature, d represents the optical surface distance, and n_dD-line refractive index, V, of the material_dRepresents the abbe number of the material.

TABLE 1

The surface type coefficients of the aspheric surfaces in the optical lens provided by the first embodiment of the present invention are shown in table 2.

TABLE 2

In the present embodiment, graphs of curvature of field, distortion, axial chromatic aberration, and vertical axis chromatic aberration of the optical lens are shown in fig. 2, 3, 4, and 5, respectively.

The field curvature curve of fig. 2 indicates the degree of curvature of the meridional image plane and the sagittal image plane, the horizontal axis indicates the offset amount (unit: mm), and the vertical axis indicates the half field angle (unit: °). As can be seen from fig. 2, the field curvature of the meridional image plane and the sagittal image plane is controlled within ± 0.2mm, which indicates that the field curvature of the optical lens is better corrected.

The distortion curve in fig. 3 shows f-tan θ distortion at different image heights on the image forming plane, the abscissa shows f-tan θ distortion (unit:%), and the ordinate shows half field angle (unit:%). As can be seen from fig. 3, the optical distortion at different image heights on the image plane is controlled within ± 2%, which indicates that the distortion of the optical lens is well corrected.

The axial chromatic aberration curve of fig. 4 represents the aberration on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from fig. 4, the offset of the axial chromatic aberration is controlled within ± 0.03mm, which indicates that the optical lens can effectively correct the axial chromatic aberration.

The vertical axis chromatic aberration in fig. 5 indicates a chromatic aberration at different image heights on the image forming plane for each wavelength with respect to the center wavelength (0.55 μm), the horizontal axis indicates a vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis indicates a normalized angle of view. As can be seen from FIG. 5, the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength are controlled within + -1 μm, which shows that the optical lens can effectively correct the aberration of the fringe field and the secondary spectrum of the whole image plane.

Second embodiment

Referring to fig. 6, fig. 6 is a schematic structural diagram of an optical lens system according to a second embodiment of the present invention.

In this embodiment, as shown in fig. 6, the optical lens includes, in order from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter G1.

the second lens element L2 has a negative aspheric surface with a concave object-side surface S3 at paraxial region and a concave image-side surface S4;

the fourth lens element L4 has a negative aspheric surface with a concave object-side surface S7 and a concave image-side surface S8 at the paraxial region;

the seventh lens element L7 has a plastic aspheric lens with positive power, and has a convex object-side surface S13 at paraxial region and a convex image-side surface S14;

The design parameters of the optical lens provided in this embodiment are shown in table 3, where R represents the radius of curvature, d represents the optical surface distance, and n_dD-line refractive index, V, of the material_dRepresents the abbe number of the material.

TABLE 3

The second embodiment of the present invention provides an optical lens having aspheric surface coefficients as shown in table 4.

TABLE 4

In the present embodiment, graphs of curvature of field, distortion, axial chromatic aberration, and vertical axis chromatic aberration of the optical lens are shown in fig. 7, 8, 9, and 10, respectively.

The field curvature curve of fig. 7 indicates the degree of curvature of the meridional image plane and the sagittal image plane, the horizontal axis indicates the offset amount (unit: mm), and the vertical axis indicates the half field angle (unit: °). As can be seen from fig. 7, the field curvature of the meridional image plane and the sagittal image plane is controlled within ± 0.1mm, which indicates that the field curvature of the optical lens is better corrected.

The distortion curve in fig. 8 shows f-tan θ distortion at different image heights on the image forming plane, the abscissa shows f-tan θ distortion (unit:%), and the ordinate shows half field angle (unit:%). As can be seen from fig. 8, the optical distortion at different image heights on the image plane is controlled within ± 2%, which indicates that the distortion of the optical lens is well corrected.

The axial chromatic aberration curve of fig. 9 represents aberration on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from fig. 9, the offset of the axial chromatic aberration is controlled within ± 0.03mm, which indicates that the optical lens can effectively correct the axial chromatic aberration.

In fig. 10, the vertical axis chromatic aberration represents the chromatic aberration at different image heights on the image forming plane for each wavelength with respect to the center wavelength (0.55 μm), the horizontal axis represents the vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis represents the normalized angle of view. As can be seen from fig. 10, the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ± 1 μm, which indicates that the optical lens can effectively correct the aberration of the fringe field and the secondary spectrum of the entire image plane.

Third embodiment

Referring to fig. 11, fig. 11 is a schematic structural diagram of an optical lens system according to a third embodiment of the present invention.

In this embodiment, as illustrated in fig. 11, the optical lens includes, in order from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter G1.

the second lens element L2 has a negative aspheric surface with a concave object-side surface S3 at the paraxial region and a convex image-side surface S4 at the paraxial region;

the seventh lens element L7 is a plastic aspheric lens with positive power, and has a concave object-side surface S13 and a convex image-side surface S14;

The design parameters of the optical lens provided in this embodiment are shown in table 5, where R represents the radius of curvature, d represents the optical surface distance, and n_dD-line refractive index, V, of the material_dRepresents the abbe number of the material.

TABLE 5

The third embodiment of the present invention provides an optical lens having aspheric surface coefficients as shown in table 6.

TABLE 6

In the present embodiment, graphs of curvature of field, distortion, axial chromatic aberration, and vertical axis chromatic aberration of the optical lens are shown in fig. 12, 13, 14, and 15, respectively.

The field curvature curve in fig. 12 indicates the degree of curvature of the meridional image plane and the sagittal image plane, the horizontal axis indicates the offset amount (unit: mm), and the vertical axis indicates the half field angle (unit: °). As can be seen from fig. 12, the field curvature of the meridional image plane and the sagittal image plane is controlled within ± 0.1mm, which indicates that the field curvature of the optical lens is better corrected.

The distortion curve in fig. 13 shows f-tan θ distortion at different image heights on the image forming plane, the abscissa shows f-tan θ distortion (unit:%), and the ordinate shows half field angle (unit:%). As can be seen from fig. 13, the optical distortion at different image heights on the image plane is controlled within ± 2%, indicating that the distortion of the optical lens is well corrected.

The axial chromatic aberration curve of fig. 14 represents the aberration on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from fig. 14, the offset of the axial chromatic aberration is controlled within ± 0.03mm, which indicates that the optical lens can effectively correct the axial chromatic aberration.

In fig. 15, the vertical axis chromatic aberration represents the chromatic aberration at different image heights on the image forming plane for each wavelength with respect to the center wavelength (0.55 μm), the horizontal axis represents the vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis represents the normalized angle of view. As can be seen from fig. 15, the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ± 1 μm, which indicates that the optical lens can effectively correct the aberration of the fringe field and the secondary spectrum of the entire image plane.

Fourth embodiment

Referring to fig. 16, fig. 16 is a schematic structural diagram of an optical lens according to a fourth embodiment of the present invention.

In this embodiment, as illustrated in fig. 16, the optical lens includes, in order from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter G1.

the third lens element L3 has a negative aspheric surface with a convex object-side surface S5 at paraxial region and a concave image-side surface S6 at paraxial region;

the fourth lens element L4 has a plastic aspheric lens with positive power, with an object-side surface S7 being convex at the paraxial region and an image-side surface S8 being concave at the paraxial region;

the fifth lens L5 is a glass aspheric lens with positive power, with its object-side surface S9 being concave at the paraxial region and its image-side surface S10 being convex at the paraxial region;

The design parameters of the optical lens provided in this embodiment are shown in table 7, where R represents the radius of curvature, d represents the optical surface distance, and n_dD-line refractive index, V, of the material_dRepresents the abbe number of the material.

TABLE 7

The surface shape coefficients of the aspherical surfaces of the optical lens in this embodiment are shown in table 8.

TABLE 8

In the present embodiment, graphs of curvature of field, distortion, axial chromatic aberration, and vertical axis chromatic aberration of the optical lens are shown in fig. 17, 18, 19, and 20, respectively.

The field curvature curve in fig. 17 indicates the degree of curvature of the meridional image plane and the sagittal image plane, the horizontal axis indicates the offset amount (unit: mm), and the vertical axis indicates the half field angle (unit: °). As can be seen from fig. 17, the field curvature of the meridional image plane and the sagittal image plane is controlled within ± 0.2mm, which indicates that the field curvature of the optical lens is better corrected.

The distortion curve in fig. 18 shows f-tan θ distortion at different image heights on the image forming plane, the abscissa shows f-tan θ distortion (unit:%), and the ordinate shows half field angle (unit:%). As can be seen from fig. 18, the optical distortion at different image heights on the image plane is controlled within ± 2%, indicating that the distortion of the optical lens is well corrected.

The axial chromatic aberration curve of fig. 19 represents the aberration on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from fig. 19, the offset of the axial chromatic aberration is controlled within ± 0.03mm, which indicates that the optical lens can effectively correct the axial chromatic aberration;

in fig. 20, the vertical axis chromatic aberration represents the chromatic aberration at different image heights on the image forming plane for each wavelength with respect to the center wavelength (0.55 μm), the horizontal axis represents the vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis represents the normalized angle of view. As can be seen from fig. 20, the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ± 1 μm, which indicates that the optical lens can effectively correct the aberration of the fringe field and the secondary spectrum of the entire image plane.

Referring to table 9, table 9 shows the optical characteristics of the optical lens in the above four embodiments, including the effective focal length F, F #, the distance TTL from the object-side surface of the first lens element to the image plane of the optical lens, the field angle FOV of the optical lens, and the related values corresponding to each of the aforementioned conditional expressions.

TABLE 9

In each of the above embodiments, the thickness, the curvature radius, and the material of each lens in the optical lens are different, and specific differences can be referred to the parameter tables in the embodiments. The above-mentioned embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, 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 equivalents, and all such changes, substitutions, combinations or simplifications are intended to be included in the scope of the present invention.

In summary, the optical lens provided by the embodiment of the invention effectively reduces the size of the whole optical lens by reasonably matching the lens shape and the focal power combination among the lenses, realizes the effect of clear imaging of the large aperture while realizing miniaturization, has the advantages of miniaturization, high aperture and high imaging quality, has good applicability to portable electronic equipment, and can effectively improve the shooting experience of users.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present 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 patent shall be subject to the appended claims.

Claims

1. An optical lens system having eight lenses in total, comprising, in order from an object side to an image plane along an optical axis:

a diaphragm;

a second lens having a negative optical power;

a seventh lens having positive optical power;

an eighth lens element with negative refractive power having a concave object-side surface and a concave image-side surface;

the distance TTL from the object side surface of the first lens element to the imaging surface of the optical lens on the optical axis and the half ImgH of the image height corresponding to the maximum field angle of the optical lens satisfy that: TTL/ImgH is more than 1.0 and less than 1.2;

the effective focal length f of the optical lens and the maximum half field angle Semi-FOV of the optical lens meet the following conditions: 2.0mm < f × tan (Semi-FOV) < 2.2 mm.

2. An optical lens as claimed in claim 1, characterized in that the radius of curvature R21 of the object-side surface of the second lens and the radius of curvature R22 of the image-side surface of the second lens satisfy: -2.0 < (R21+ R22)/(R21-R22) < 3.0.

3. An optical lens as claimed in claim 1, characterized in that the radius of curvature R31 of the object-side surface of the third lens and the radius of curvature R32 of the image-side surface of the third lens satisfy: -10.0 < (R31+ R32)/(R31-R32) < 5.0.

4. An optical lens according to claim 1, wherein a distance CT34 between the third lens and the fourth lens on the optical axis satisfies, with a central thickness CT3 of the third lens and a central thickness CT4 of the fourth lens: 0.2 < CT34/(CT3+ CT4) < 0.7.

5. An optical lens according to claim 1, wherein a distance CT56 between the fifth lens and the sixth lens on the optical axis satisfies, with a central thickness CT5 of the fifth lens and a central thickness CT6 of the sixth lens: 0.03 < CT56/(CT5+ CT6) < 0.1.

6. An optical lens according to claim 1, wherein a distance CT67 on an optical axis between the sixth lens and the seventh lens and a central thickness CT6 of the sixth lens and a central thickness CT7 of the seventh lens satisfy the following conditional expressions: 0.1 < CT67/(CT6+ CT7) < 0.55.

7. An optical lens as claimed in claim 1, characterized in that the radius of curvature R71 of the object-side surface of the seventh lens and the radius of curvature R72 of the image-side surface of the seventh lens satisfy: -2.0 < (R71+ R72)/(R71-R72) < 3.0.

8. An optical lens according to claim 1, characterized in that a combined focal length f13 of the first to third lenses and an effective focal length f of the optical lens satisfy the following conditional expression: f13/f is more than 0.9 and less than 1.1.

9. An optical lens according to claim 1, wherein the focal length f8 of the eighth lens and the effective focal length f of the optical lens satisfy the following conditional expression: -0.8 < f8/f < -0.7.