Optical lens

Abstract

The application discloses an optical lens, which comprises, in sequence from an object side to an imaging surface along an optical axis, a first lens with negative optical power, the image side of which is a concave surface; a second lens with positive optical power, the object side of which is a concave surface and the image side of which is a convex surface; a third lens with positive optical power, the object side of which is a convex surface and the image side of which is a concave surface; a liquid lens with optical power, which presents different focal lengths according to different applied voltages; a fourth lens with negative optical power, the object side of which is a concave surface and the image side of which is a concave surface; a fifth lens with positive optical power, the object side of which is a convex surface and the image side of which is a convex surface; and a sixth lens with positive optical power, the object side of which is a convex surface and the image side of which is a concave surface. The optical lens provided by the application has the advantages of fast focusing, small volume, high image quality and the like.

Description

Technical Field

[0001] This invention relates to the field of imaging lens technology, and in particular to an optical lens. Background Technology

[0002] In recent years, with the development of the automation industry, machine vision has experienced explosive growth, and the application fields of industrial lenses have become increasingly widespread. Due to their characteristics of high resolution, high definition, and good stability, industrial lenses are widely used in fields such as dimensional measurement, defect detection, and image acquisition.

[0003] To achieve good image acquisition and analysis capabilities, these industrial lenses typically require high-resolution imaging to capture the image features of the subject and high relative illumination to ensure uniform illumination. Simultaneously, to ensure good imaging performance at different working distances, the lens needs to acquire images at varying distances through focusing. However, traditional lens focusing methods rely on mechanical motion. For example, a motor is installed inside the lens to drive lens elements or lens groups to move laterally along the optical axis, changing the optical spacing between lens elements or between the lens and the camera sensor, thereby compensating for the shift in focus caused by changes in working distance. However, these mechanically focusing lenses suffer from slow focusing speeds, the need for manual focusing, and large size, making them unsuitable for applications with high real-time requirements. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide an optical lens that has at least the advantages of fast autofocus, small size, and high image quality.

[0005] The present invention achieves the above objectives through the following technical solutions.

[0006] This invention provides an optical lens comprising, along the optical axis from the object side to the imaging plane, the following components in sequence: a first lens with negative optical power, the image side of which is concave; a second lens with positive optical power, the object side of which is concave and the image side of which is convex; a third lens with positive optical power, the object side of which is convex and the image side of which is concave; a liquid lens with optical power, the liquid lens exhibiting different focal lengths depending on the applied voltage; a fourth lens with negative optical power, the object side of which is concave and the image side of which is concave; a fifth lens with positive optical power, the object side of which is convex and the image side of which is convex; and a sixth lens with positive optical power, the object side of which is convex and the image side of which is concave.

[0007] In some embodiments, the object-side surface of the first lens is convex.

[0008] In some embodiments, the object-side surface of the first lens is concave.

[0009] In some embodiments, an aperture is provided inside the liquid lens.

[0010] In some embodiments, a filter is provided between the sixth lens and the imaging surface.

[0011] In some embodiments, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are made of glass lenses.

[0012] In some embodiments, the object distance OBJ of the optical lens satisfies: 60 mm ≤ OBJ ≤ 800 mm; the driving voltage U of the liquid lens satisfies: 28 V < U < 65 V; the effective focal length fe of the liquid lens satisfies: |fe| > 50 mm; the effective focal length F of the optical lens satisfies: 5.5 mm < F < 6.5 mm.

[0013] In some embodiments, the overall optical length TTL of the optical lens satisfies: TTL < 21 mm.

[0014] In some embodiments, the maximum field of view FOV of the optical lens satisfies: 50° < FOV < 70°.

[0015] In some embodiments, the image height IH corresponding to the maximum field of view of the optical lens satisfies: 6.0 mm < IH < 7.0 mm.

[0016] In some embodiments, the chief ray angle of incidence CRA of the optical lens satisfies: 15° < CRA < 19.5°.

[0017] In some embodiments, the overall optical length TTL of the optical lens and the optimal effective focal length f of the optical lens satisfy: 2.9 < TTL / f < 3.6.

[0018] In some embodiments, the effective focal length f1 of the first lens and the optimal effective focal length f of the optical lens satisfy: -1.7 < f1 / f < -1.1.

[0019] In some embodiments, the effective focal length f3 of the third lens and the optimal effective focal length f of the optical lens satisfy: 1.1 < f3 / f < 1.7.

[0020] In some embodiments, the effective focal length f4 of the fourth lens and the optimal effective focal length f of the optical lens satisfy: -0.75 < f4 / f < -0.5.

[0021] In some embodiments, the effective focal length f6 of the sixth lens and the optimal effective focal length f of the optical lens satisfy: 1.5 < f6 / f < 2.2.

[0022] In some embodiments, the radius of curvature R6 of the image side of the third lens and the optimal effective focal length f of the optical lens satisfy: 1.7 < R6 / f < 2.7; the radius of curvature R18 of the image side of the sixth lens and the optimal effective focal length f of the optical lens satisfy: 6.1 < R18 / f < 16.2.

[0023] In some embodiments, the radius of curvature R3 of the object side of the second lens and the radius of curvature R4 of the image side of the second lens satisfy: 2.3 < (R3 + R4) / (R3 - R4) < 3.6.

[0024] In some embodiments, the sagittal height Sag18 of the clear aperture of the image side of the sixth lens and the clear aperture diameter DT62 of the image side of the sixth lens satisfy: 0 < Sag18 / DT62 < 0.05.

[0025] In some embodiments, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens and the optimal effective focal length f of the optical lens satisfy: 2.5 < (f1 + f2 + f3) / f < 3.6.

[0026] In some embodiments, the air spacing CT45 on the optical axis between the fourth lens and the fifth lens and the air spacing CT56 on the optical axis between the fifth lens and the sixth lens satisfy: 0.4 < CT45 / CT56 < 1.9.

[0027] In some embodiments, the overall optical length TTL of the optical lens and the image height IH corresponding to the maximum field angle of the optical lens satisfy: 2.6 < TTL / IH < 3.4.

[0028] In some embodiments, the image height IH corresponding to the maximum field angle of the optical lens, the optimal effective focal length f of the optical lens and the maximum field angle FOV of the optical lens satisfy: 0.96 < (IH / 2) / (f × tan(FOV / 2)) < 1.03.

[0029] In some embodiments, the maximum field angle FOV of the optical lens and the f-number FNO of the optical lens satisfy: 10 < FOV / FNO < 13.5.

[0030] In some embodiments, the back focal length BFL of the optical lens and the optimal effective focal length f of the optical lens satisfy: 0.7 < BFL / f < 1.1.

[0031] In some embodiments, the effective focal length f2 of the second lens and the optimal effective focal length f of the optical lens satisfy: 2.6 < f2 / f < 3.5.

[0032] In some embodiments, the effective focal length f5 of the fifth lens and the optimal effective focal length f of the optical lens satisfy: 0.8 < f5 / f < 1.1.

[0033] In some embodiments, the combined focal length f123 of the first lens, the second lens, and the third lens and the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens satisfy: 0.3 < f123 / f456 < 0.6.

[0034] In some embodiments, the combined focal length f123 of the first lens, the second lens, and the third lens and the optimal effective focal length f of the optical lens satisfy: 0.9 < f123 / f < 1.4.

[0035] In some embodiments, the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens and the optimal effective focal length f of the optical lens satisfy: 2.1 < f456 / f < 2.9.

[0036] In some embodiments, the radius of curvature R13 of the object side surface of the fourth lens and the effective focal length f4 of the fourth lens satisfy: 1.5 < R13 / f4 < 2.1; the radius of curvature R13 of the object side surface of the fourth lens and the radius of curvature R14 of the image side surface of the fourth lens satisfy: -1.2 < R13 / R14 < -0.7.

[0037] In some embodiments, the radius of curvature R14 of the image side surface of the fourth lens and the optimal effective focal length f of the optical lens satisfy: 1.0 < R14 / f < 1.5; the radius of curvature R14 of the image side surface of the fourth lens and the radius of curvature R15 of the object side surface of the fifth lens satisfy: 0.1 < R14 / R15 < 0.6.

[0038] In some embodiments, the radius of curvature R17 of the object side surface of the sixth lens and the optimal effective focal length f of the optical lens satisfy: 1.2 < R17 / f < 1.8; the radius of curvature R16 of the image side surface of the fifth lens and the radius of curvature R17 of the object side surface of the sixth lens satisfy: -0.8 < R16 / R17 < -0.4.

[0039] In some embodiments, the sum ∑CT of the central thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens and the optimal effective focal length f of the optical lens satisfy: 1.2 < ∑CT / f < 1.8.

[0040] In some embodiments, the half-aperture DT32 of the image-side surface of the third lens and the half-aperture DT41 of the object-side surface of the fourth lens satisfy: 1.3 <DT32 / DT41<1.9。

[0041] In some embodiments, the air gap CT12 between the first lens and the second lens on the optical axis, the air gap CT23 between the second lens and the third lens on the optical axis, and the air gap CT3E between the third lens and the liquid lens on the optical axis satisfy: 0.9 < (CT12 + CT23) / CT3E < 2.1.

[0042] In some embodiments, the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens and the effective focal length f6 of the sixth lens satisfy: 1.1 <f456 / f6<1.7。

[0043] In some embodiments, the half-aperture DT11 of the object side of the first lens, the image height IH corresponding to the maximum field of view of the optical lens, and the maximum field of view FOV of the optical lens satisfy: 1.4 < 2 × DT11 / IH / tan(FOV / 2) < 2.1.

[0044] In some embodiments, the center thickness CT1 of the first lens and the center thickness CT2 of the second lens satisfy: 3.3 <CT2 / CT1<5.5。

[0045] Compared with the prior art, the optical lens provided by the present invention has at least the following beneficial effects:

[0046] (1) The optical lens provided by the present invention adopts a combination of six conventional lenses and one liquid lens. By reasonably allocating the liquid lens and the focal length relationship of each lens, the optical lens has good imaging ability at different object distances and good thermal stability. At the same time, by reasonably configuring the thickness, spacing and surface shape of each lens, the optical lens has advantages such as small total length, high relative illumination, large image plane, high resolution and autofocus.

[0047] (2) The optical lens provided by the present invention expands the original fixed working distance industrial lens into an autofocus lens with an adjustable working distance within a certain range (working object distance is 60mm-800mm) by applying liquid lens to the optical path design, which greatly expands the application range of the optical lens and improves the detection efficiency of the optical lens.

[0048] (3) The optical lens provided by the present invention can adjust the focus position of the entire optical system in real time by controlling the driving voltage of the liquid lens, so as to achieve the purpose of fast focusing at different working distances and make the optical lens have high resolution at different object distances.

[0049] (4) The optical lens provided by the present invention uses liquid lens to achieve autofocus, and the lens does not shift during the focusing process, which makes the overall stability of the optical lens better. Attached Figure Description

[0050] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0051] Figure 1 This is a schematic diagram of the structure of an optical lens provided in the first embodiment of the present invention.

[0052] Figure 2 The field curvature curve of the optical lens provided in the first embodiment of the present invention.

[0053] Figure 3 The F-Tanθ distortion curve of the optical lens provided in the first embodiment of the present invention.

[0054] Figure 4 The transverse chromatic aberration curve of the optical lens provided in the first embodiment of the present invention.

[0055] Figure 5 The axial aberration curve of the optical lens provided in the first embodiment of the present invention.

[0056] Figure 6 The MTF curve of the optical lens provided in the first embodiment of the present invention.

[0057] Figure 7 The relative illumination curve of the optical lens provided in the first embodiment of the present invention.

[0058] Figure 8 This is a schematic diagram of the structure of an optical lens provided in the second embodiment of the present invention.

[0059] Figure 9 The field curvature curve of the optical lens provided in the second embodiment of the present invention.

[0060] Figure 10 The F-Tanθ distortion curve of the optical lens provided in the second embodiment of the present invention.

[0061] Figure 11 The transverse chromatic aberration curve of the optical lens provided in the second embodiment of the present invention.

[0062] Figure 12The axial aberration curve of the optical lens provided in the second embodiment of the present invention.

[0063] Figure 13 The MTF curve of the optical lens provided in the second embodiment of the present invention.

[0064] Figure 14 The relative illumination curve of the optical lens provided in the second embodiment of the present invention.

[0065] Figure 15 This is a schematic diagram of the structure of an optical lens provided in the third embodiment of the present invention.

[0066] Figure 16 The field curvature curve of the optical lens provided in the third embodiment of the present invention.

[0067] Figure 17 The F-Tanθ distortion curve of the optical lens provided in the third embodiment of the present invention.

[0068] Figure 18 The transverse chromatic aberration curve of the optical lens provided in the third embodiment of the present invention.

[0069] Figure 19 The axial aberration curve of the optical lens provided in the third embodiment of the present invention.

[0070] Figure 20 The MTF curve of the optical lens provided in the third embodiment of the present invention.

[0071] Figure 21 The relative illumination curve of the optical lens provided in the third embodiment of the present invention. Detailed Implementation

[0072] To better understand the invention, various aspects of the invention will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of embodiments of the invention and are not intended to limit the scope of the invention in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0073] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of the invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0074] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0075] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the subject is called the object-side surface of the lens, and the surface of each lens closest to the imaging plane is called the image-side surface of the lens.

[0076] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not individual elements in the list. Additionally, when describing embodiments of the invention, the word "may" is used to mean "one or more embodiments of the invention." And the term "exemplary" is intended to refer to an example or illustration.

[0077] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0078] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0079] The present invention proposes an optical lens, which comprises, in sequence along the optical axis from the object side to the imaging plane: a first lens, a second lens, a third lens, a liquid lens, a fourth lens, a fifth lens, and a sixth lens, wherein the optical centers of each lens are located on the same straight line.

[0080] Specifically, the first lens has negative optical power, its object-side surface is either convex or concave, and its image-side surface is concave; the second lens has positive optical power, its object-side surface is concave, and its image-side surface is convex; the third lens has positive optical power, its object-side surface is convex, and its image-side surface is concave; the fourth lens has negative optical power, its object-side surface is concave, and its image-side surface is concave; the fifth lens has positive optical power, its object-side surface is convex, and its image-side surface is convex; the sixth lens has positive optical power, its object-side surface is convex, and its image-side surface is concave; the liquid lens can exhibit different focal lengths depending on the applied voltage, and the liquid lens is equipped with an aperture stop.

[0081] In some embodiments, the liquid lens, from the object side to the imaging surface, sequentially includes a first surface, a second surface, a third surface, a fourth surface, a fifth surface, and a sixth surface. An aperture is provided at the sixth surface to narrow the range of light emitted from the forward optical system. The first, second, fourth, fifth, and sixth surfaces are all planar, while the third surface is curved and can have different radii of curvature depending on the applied driving voltage, thereby allowing the liquid lens to have different optical powers. More specifically, when the optical lens starts working, a certain starting voltage is applied to the liquid lens according to the current working object distance. At this time, the third surface in the liquid lens will have a certain radius of curvature, and the liquid lens will have a corresponding focal length. Together with the other six lenses, it can make the optical lens in the best imaging state. When the working object distance of the optical lens changes within the preset working range, the driving voltage applied to the liquid lens will be automatically adjusted to change the radius of curvature of the third surface, and thus the focal length of the liquid lens will also change accordingly. That is, according to the different working object distances required by the optical lens, the driving voltage applied to the liquid lens can be automatically adjusted to make the liquid lens have a corresponding focal length, and thus the optical lens can have a suitable focal length (the overall focal length of the optical lens is adjusted within a small range), realizing the function of autofocus, so that the optical lens has high resolution at different working object distances.

[0082] In an embodiment of the present invention, when the object distance OBJ of the optical lens satisfies: 60 mm ≤ OBJ ≤ 800 mm, the driving voltage U applied to the liquid lens satisfies: 28 V < U < 65 V, the effective focal length fe of the liquid lens satisfies: |fe| > 50 mm, and the effective focal length F of the optical lens satisfies: 5.5 mm < F < 6.5 mm. That is, when the optical lens operates at an object distance within a certain range, the driving voltage applied to the liquid lens will be automatically adjusted within a certain range. At the same time, the automatic adjustment of the driving voltage will cause a corresponding change in the curvature radius of the third surface of the liquid lens, and the corresponding change in the curvature radius of the third surface will correspondingly change the optical power of the liquid lens, making it have a certain range of positive or negative optical power, thereby causing a small change in the focal length of the optical lens. More preferably, when the object distance OBJ of the optical lens satisfies: 60 mm ≤ OBJ ≤ 800 mm, the driving voltage U applied to the liquid lens satisfies: 28 V < U < 65 V, the curvature radius R9 of the third surface in the liquid lens satisfies: R9 ∈ (-∞, -5) & (3, +∞), the effective focal length fe of the liquid lens satisfies: fe ∈ (-∞, -92) & (55, +∞), and the effective focal length F of the optical lens satisfies: 5.5 mm < F < 6.5 mm. That is, at different object distances (60 mm ≤ OBJ ≤ 800 mm), by changing the driving voltage on the liquid lens (28 V < U < 65 V), the curvature radius of the liquid lens can be changed, and then the liquid lens can present different focal lengths (|fe| > 50 mm) to meet the requirement that the optical lens has a relatively clear imaging quality at different object distances, that is, the fast autofocus function of the optical lens at different object distances can be achieved.

[0083] In some embodiments, the overall optical length TTL of the optical lens and the optimal effective focal length f of the optical lens satisfy: 2.9 < TTL / f < 3.6. Satisfying the above conditional formula can effectively compress the overall length of the optical lens and is beneficial to the miniaturization of the optical lens.

[0084] In some embodiments, the effective focal length f1 of the first lens and the optimal effective focal length f of the optical lens satisfy: -1.7 < f1 / f < -1.1. Satisfying the above conditional formula can make the first lens have an appropriate negative optical power, which is beneficial to collecting as many large-angle incident light rays as possible, and at the same time can avoid introducing more aberrations, which is beneficial to reducing the difficulty of aberration correction of the subsequent optical system and improving the imaging quality of the optical lens.

[0085] In some embodiments, the effective focal length f3 of the third lens and the optimal effective focal length f of the optical lens satisfy: 1.1 < f3 / f < 1.7. Meeting the above conditional formula can make the third lens have an appropriate positive optical power, which is beneficial to balancing the negative optical power at the front end of the optical lens, enabling light rays with a large field angle to smoothly enter the rear end of the optical lens, reducing the sensitivity of the optical lens, and improving the imaging quality of the optical lens.

[0086] In some embodiments, the effective focal length f4 of the fourth lens and the optimal effective focal length f of the optical lens satisfy: -0.75 < f4 / f < -0.5. Meeting the above conditional formula can make the fourth lens have an appropriate negative optical power, which is beneficial to increasing the imaging area of the optical lens and realizing the large target surface imaging characteristic of the optical lens.

[0087] In some embodiments, the effective focal length f6 of the sixth lens and the optimal effective focal length f of the optical lens satisfy: 1.5 < f6 / f < 2.2. Meeting the above conditional formula can make the sixth lens have an appropriate positive optical power, which is beneficial to suppressing the angle of the marginal field incident on the imaging surface, so as to effectively transmit more light beams to the imaging surface and improve the imaging quality.

[0088] In some embodiments, the radius of curvature R6 of the image side of the third lens and the optimal effective focal length f of the optical lens satisfy: 1.7 < R6 / f < 2.7. Meeting the above conditional formula can reasonably control the surface shape of the image side of the third lens, which is beneficial to reducing the distortion generated by the front-end lens and the difficulty of distortion correction of the subsequent lens, and improving the imaging quality of the optical lens.

[0089] In some embodiments, the radius of curvature R18 of the image side of the sixth lens and the optimal effective focal length f of the optical lens satisfy: 6.1 < R18 / f < 16.2. Meeting the above conditional formula can reasonably set the concave surface shape of the image side of the sixth lens, which is beneficial to converging the marginal field light rays into the imaging surface and increasing the relative illumination of the optical lens.

[0090] In some embodiments, the radius of curvature R3 of the object side of the second lens and the radius of curvature R4 of the image side of the second lens satisfy: 2.3 < (R3 + R4) / (R3 - R4) < 3.6. Meeting the above conditional formula can reasonably control the shapes of the object side and the image side of the second lens, which is beneficial to controlling the light ray trend, reducing the aberration of the optical lens, and improving the imaging quality of the optical lens.

[0091] In some embodiments, the sagittal height Sag18 of the clear aperture on the image side of the sixth lens and the clear aperture diameter DT62 of the image side of the sixth lens satisfy: 0 < Sag18 / DT62 < 0.05. By satisfying the above conditional formula, the sagittal height of the image side of the sixth lens and the clear aperture diameter of the image side can be reasonably controlled within a reasonable range, which is beneficial to controlling the trend of light rays in the marginal field of view, highlighting the detailed information of the central field of view of the optical lens, and improving the resolution of the optical lens.

[0092] In some embodiments, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens and the optimal effective focal length f of the optical lens satisfy: 2.5 < (f1 + f2 + f3) / f < 3.6. By satisfying the above conditional formula, the optical power of the first lens to the third lens can be reasonably configured, which is beneficial to improving the imaging quality of the optical lens while ensuring the compact structure of the optical lens.

[0093] In some embodiments, the air spacing CT45 on the optical axis between the fourth lens and the fifth lens and the air spacing CT56 on the optical axis between the fifth lens and the sixth lens satisfy: 0.4 < CT45 / CT56 < 1.9. By satisfying the above conditional formula, the distances of the fourth lens and the fifth lens, as well as the fifth lens and the sixth lens on the optical axis can be reasonably configured, which is beneficial to meeting the requirements of the processability and manufacturability of the optical lens.

[0094] In some embodiments, the overall optical length TTL of the optical lens and the image height IH corresponding to the maximum field angle of the optical lens satisfy: 2.6 < TTL / IH < 3.4. By satisfying the above conditional formula, while meeting the miniaturization of the optical lens, it can ensure that light converges better on the imaging surface, which is beneficial to achieving large-format imaging of the optical lens.

[0095] In some embodiments, the image height IH corresponding to the maximum field angle of the optical lens, the optimal effective focal length f of the optical lens and the maximum field angle FOV of the optical lens satisfy: 0.96 < (IH / 2) / (f × tan(FOV / 2)) < 1.03. By satisfying the above conditional formula, the optical distortion of the optical lens can be better controlled, and the resolution of the optical lens can be improved.

[0096] In some embodiments, the maximum field angle FOV of the optical lens and the f-number FNO of the optical lens satisfy: 10 < FOV / FNO < 13.5. By satisfying the above conditional formula, it is beneficial for the optical lens to obtain more scene information and meet the requirements of large-range detection.

[0097] In some embodiments, the back focal length (BFL) of the optical lens and the optimal effective focal length (f) of the optical lens satisfy: 0.7 < BFL / f < 1.1. Meeting the above conditional formula is conducive to achieving miniaturization of the optical lens while enabling the optical lens to have an appropriate back focal length, facilitating the assembly of the optical lens.

[0098] In some embodiments, the effective focal length (f2) of the second lens and the optimal effective focal length (f) of the optical lens satisfy: 2.6 < f2 / f < 3.5. Meeting the above conditional formula can endow the second lens with an appropriate positive optical power, which is conducive to converging light rays and enabling the light rays to transition smoothly, reducing the sensitivity of the optical lens, and at the same time facilitating the balancing of aberrations introduced by the first lens, thereby improving the imaging quality of the optical lens.

[0099] In some embodiments, the effective focal length (f5) of the fifth lens and the optimal effective focal length (f) of the optical lens satisfy: 0.8 < f5 / f < 1.1. Meeting the above conditional formula can endow the fifth lens with an appropriate positive optical power, which is conducive to optimizing various aberrations in each field of view of the optical lens and improving the imaging quality of the optical lens.

[0100] In some embodiments, the combined focal length (f123) of the first lens, the second lens, and the third lens and the combined focal length (f456) of the fourth lens, the fifth lens, and the sixth lens satisfy: 0.3 < f123 / f456 < 0.6. Meeting the above conditional formula, by reasonably setting the ratio of the focal lengths of the front and rear lens groups of the liquid lens, it is possible to match with the variable-focus liquid lens to achieve the fast autofocus characteristic of the optical lens and ensure that the optical lens can achieve a high resolution at different object distances.

[0101] In some embodiments, the combined focal length (f123) of the first lens, the second lens, and the third lens and the optimal effective focal length (f) of the optical lens satisfy: 0.9 < f123 / f < 1.4. Meeting the above conditional formula, by reasonably setting the proportion of the focal length of the lens group before the liquid lens, it is conducive to the smooth transition of light rays, enabling the light rays to enter the aperture and the liquid lens at a relatively gentle angle as much as possible, reducing the influence of the liquid lens on the system sensitivity and relative illuminance, and ensuring that the optical lens has a high imaging quality at different object distances.

[0102] In some embodiments, the combined focal length (f456) of the fourth lens, the fifth lens, and the sixth lens and the optimal effective focal length (f) of the optical lens satisfy: 2.1 < f456 / f < 2.9. Meeting the above conditional formula, by reasonably setting the proportion of the focal length of the lens group after the liquid lens, the aberrations brought by the front lens group and the liquid lens can be effectively corrected, enabling the optical lens to have better imaging quality at different object distances.

[0103] In some embodiments, the radius of curvature R13 of the object side surface of the fourth lens and the effective focal length f4 of the fourth lens satisfy: 1.5 < R13 / f4 < 2.1; the radius of curvature R13 of the object side surface of the fourth lens and the radius of curvature R14 of the image side surface of the fourth lens satisfy: -1.2 < R13 / R14 < -0.7. Satisfying the above conditional expressions can reasonably control the shapes and optical powers of the object side surface and the image side surface of the fourth lens, which is beneficial to balancing the aberration of the front lens group and improving the imaging quality of the optical lens.

[0104] In some embodiments, the radius of curvature R14 of the image side surface of the fourth lens and the optimal effective focal length f of the optical lens satisfy: 1.0 < R14 / f < 1.5; the radius of curvature R14 of the image side surface of the fourth lens and the radius of curvature R15 of the object side surface of the fifth lens satisfy: 0.1 < R14 / R15 < 0.6. Satisfying the above conditional expressions can reasonably control the radii of curvature of the image side surface of the fourth lens and the object side surface of the fifth lens, which is beneficial to optimizing the field curvature of the optical lens and improving the imaging quality of the optical lens.

[0105] In some embodiments, the radius of curvature R17 of the object side surface of the sixth lens and the optimal effective focal length f of the optical lens satisfy: 1.2 < R17 / f < 1.8; the radius of curvature R16 of the image side surface of the fifth lens and the radius of curvature R17 of the object side surface of the sixth lens satisfy: -0.8 < R16 / R17 < -0.4. Satisfying the above conditional expressions can reasonably control the radii of curvature of the image side surface of the fifth lens and the object side surface of the sixth lens, which is beneficial to converging the light rays in the edge field of view and improving the field curvature of the optical lens, thereby improving the imaging quality of the optical lens.

[0106] In some embodiments, the sum ∑CT of the central thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens and the optimal effective focal length f of the optical lens satisfy: 1.2 < ∑CT / f < 1.8. Satisfying the above conditional expressions can reasonably control the central thicknesses of the first lens to the sixth lens, ensure that the optical lens can clearly image within a predetermined working object distance, improve the processability of the lens, and reduce the production cost.

[0107] In some embodiments, the clear aperture radius DT32 of the image side surface of the third lens and the clear aperture radius DT41 of the object side surface of the fourth lens satisfy: 1.3 < DT32 / DT41 < 1.9. Satisfying the above conditional expressions can reasonably control the clear aperture radii of the image side surface of the third lens and the object side surface of the fourth lens within a suitable range, which helps to reduce the focusing difficulty of the liquid lens and improve the imaging quality of the edge field of view of the optical lens.

[0108] In some embodiments, the air spacing CT12 on the optical axis between the first lens and the second lens, the air spacing CT23 on the optical axis between the second lens and the third lens, and the air spacing CT3E on the optical axis between the third lens and the liquid lens satisfy: 0.9 < (CT12 + CT23) / CT3E < 2.1. By satisfying the above conditional expression, the distances between the first lens and the second lens, the second lens and the third lens, and the third lens and the liquid lens on the optical axis are limited within a reasonable range, which can maintain a reasonable arrangement of each lens within the optical lens and improve the production yield.

[0109] In some embodiments, the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens and the effective focal length f6 of the sixth lens satisfy: 1.1 < f456 / f6 < 1.7. By satisfying the above conditional expression, the focal length ratio between the rear lens group and the sixth lens can be reasonably controlled, which is beneficial to ensuring a reasonable distribution of the optical power of the lens and reducing the aberration of the optical lens, thereby improving the imaging quality of the optical lens.

[0110] In some embodiments, the clear aperture semi-diameter DT11 of the object side of the first lens, the image height IH corresponding to the maximum field angle of the optical lens, and the maximum field angle FOV of the optical lens satisfy: 1.4 < 2×DT11 / IH / tan(FOV / 2) < 2.1. By satisfying the above conditional expression, the balance among the front port diameter of the optical lens, the image plane, and the field angle size can be ensured, and the imaging quality of the optical lens can be improved.

[0111] In some embodiments, the central thickness CT1 of the first lens and the central thickness CT2 of the second lens satisfy: 3.3 < CT2 / CT1 < 5.5. By satisfying the above conditional expression, the proportion of the central thickness of the first lens and the second lens can be reasonably set, which is beneficial to reducing the difficulty of aberration correction of the rear lens and improving the imaging quality of the optical lens.

[0112] In some embodiments, the chief ray angle of incidence CRA of the optical lens satisfies: 15° < CRA < 19.5°. By satisfying the above conditional expression, the incident light can enter the image sensor at an appropriate angle, which is beneficial to improving the photosensitive performance of the image sensor and the imaging quality of the optical lens.

[0113] As an embodiment, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens can be made of all-glass lenses or a combination of glass and plastic lenses, and both can achieve good imaging effects. In this application, in order to improve the imaging quality of the lens, each lens is made of glass lenses.

[0114] The present invention will be further described below with reference to several embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the optical lens are different; for specific differences, please refer to the parameter tables of each embodiment. The following embodiments are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Any changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention.

[0115] First Embodiment

[0116] Please see Figure 1 The diagram shows a schematic of the structure of an optical lens 100 provided in the first embodiment of the present invention. The optical lens 100 includes, along the optical axis from the object side to the imaging surface S21, a first lens L1, a second lens L2, a third lens L3, a liquid lens E1, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a filter G1, and the optical centers of each lens are located on the same straight line.

[0117] The first lens L1 has negative optical power, with its object-side surface S1 being concave and its image-side surface S2 being concave. The second lens L2 has positive optical power, with its object-side surface S3 being concave and its image-side surface S4 being convex. The third lens L3 has positive optical power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens L4 has negative optical power, with its object-side surface S13 being concave and its image-side surface S14 being concave. The fifth lens L5 has positive optical power, with its object-side surface S15 being convex and its image-side surface S16 being convex. The sixth lens L6 has positive optical power, with its object-side surface S17 being convex and its image-side surface S18 being concave. The object-side surface S19 and image-side surface S20 of the filter G1 are both planar.

[0118] Meanwhile, the liquid lens E1, from the object side to the imaging surface, sequentially includes a first surface S7, a second surface S8, a third surface S9, a fourth surface S10, a fifth surface S11, and a sixth surface S12. The aperture stop is located at the sixth surface S12. The first, second, and fourth surfaces S7, S8, S10, S11, and S12 are all planar, while the third surface S9 is curved and can have different radii of curvature depending on the applied driving voltage, thus allowing the liquid lens E1 to have different optical powers. For example, when the working object distance OBJ of the optical lens satisfies 60mm ≤ OBJ ≤ 800mm, the driving voltage U applied to the liquid lens satisfies 28V < U < 65V, and the effective focal length fe of the liquid lens satisfies |fe| > 50mm.

[0119] The relevant parameters of each lens element in the optical lens 100 provided in this embodiment are shown in Table 1.

[0120] Table 1

[0121]

[0122] In this embodiment, when the working object distance OBJ of the optical lens satisfies: 60mm≤OBJ≤800mm, the driving voltage U applied to the liquid lens satisfies: 32V≤U≤48V, the radius of curvature R9 of the third surface satisfies: R9∈(-∞, -182.1]&[172.63, +∞), and the effective focal length fe of the liquid lens satisfies: fe∈(-∞, -9.89]&[9.38, +∞). At this time, the effective focal length F of the optical lens satisfies: 5.87mm≤F≤6.14mm. More specifically, when the optical lens is at its optimal working object distance of 120mm, the voltage applied to the liquid lens is 40.5V (this voltage is the starting voltage), the radius of curvature of the third surface in the liquid lens is 1387.232mm, the effective focal length of the liquid lens is 25531.954mm, and the optimal effective focal length of the optical lens is 6.00mm. The relevant parameters of the optical lens 100 provided in this embodiment at the optimal working distance, minimum working distance, and maximum working distance are shown in Table 2.

[0123] Table 2

[0124] Optimal working distance Minimum working distance Maximum working distance OBJ(mm) 120.00 60.00 800.00 F(mm) 6.00 5.87 6.14 U(V) 40.50 48.00 32.00 fe(mm) 25531.954 172.63 -182.10 R9 (mm) 1387.232 9.38 -9.89

[0125] Figure 2 The field curvature curve of the optical lens 100 in this embodiment is shown, which represents the degree of curvature of light of different wavelengths in the meridional and sagittal image planes. The horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the field curvature of the meridional and sagittal image planes is controlled within ±0.05 mm, indicating that the optical lens can effectively correct the field curvature.

[0126] Figure 3 The T-Fanθ distortion curve of the optical lens 100 in this embodiment is shown, which represents the distortion at different field-of-view angles on the imaging plane. The horizontal axis represents the distortion value (unit: %), and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the distortion value is controlled within -3%, indicating that the optical lens can correct distortion well.

[0127] Figure 4The diagram shows the transverse chromatic aberration curve of the optical lens 100 in this embodiment. It represents the chromatic aberration of each wavelength relative to the center wavelength (0.64 μm) at different image heights on the imaging plane. The horizontal axis represents the transverse chromatic aberration value of each wavelength relative to the center wavelength (unit: μm), and the vertical axis represents the normalized field of view. As can be seen from the figure, the transverse chromatic aberration of the longest and shortest wavelengths is controlled within ±0.6 μm, indicating that the optical lens can effectively correct chromatic aberration at the edge of the field of view and the secondary spectrum of the entire image plane.

[0128] Figure 5 The diagram shows the axial aberration curve of the optical lens 100 in this embodiment, which represents the aberration of each wavelength on the optical axis at the imaging plane. The horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the axial aberration offset is controlled within ±0.05 mm, indicating that the optical lens can effectively correct axial aberration.

[0129] Figure 6 The modulation transfer function (MTF) curve of the optical lens 100 in this embodiment is shown, which represents the lens imaging modulation at different spatial frequencies in each field of view. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. As can be seen from the figure, the MTF value of this embodiment is above 0.3 throughout the entire half-image height, exhibiting good imaging quality and good detail resolution in both low-frequency and high-frequency conditions.

[0130] Figure 7 The diagram shows the relative illumination curve of the optical lens 100 in this embodiment, which represents the relative illumination value at different image heights on the imaging plane. The horizontal axis represents the half field of view (unit: °), and the vertical axis represents the relative illumination value (unit: %). As can be seen from the figure, the relative illumination value of the optical lens is still greater than 75% at the maximum half field of view, indicating that the optical lens has good relative illumination.

[0131] Second Embodiment

[0132] Please see Figure 8 The diagram shows a schematic of the structure of an optical lens 200 provided in the second embodiment of the present invention. The structure of the optical lens 200 is roughly the same as that of the optical lens 100 in the first embodiment. The main differences are that the curvature radius, thickness, spacing between lenses, and materials of each lens are different.

[0133] The relevant parameters of each lens element in the optical lens 200 provided in this embodiment are shown in Table 3.

[0134] Table 3

[0135]

[0136] In this embodiment, when the working object distance OBJ of the optical lens satisfies: 60mm≤OBJ≤800mm, the driving voltage U applied to the liquid lens satisfies: 32.4V≤U≤48.7V, the radius of curvature R9 of the third surface satisfies: R9∈(-∞, -10.12]&[8.78, +∞), and the effective focal length fe of the liquid lens satisfies: fe∈(-∞, -186.79]&[162.02, +∞). At this time, the effective focal length F of the optical lens satisfies: 5.76mm≤F≤6.06mm. More specifically, when the optical lens is at the optimal working object distance of 249.03mm, the voltage applied to the liquid lens is 35.8V (this voltage is the starting voltage), the radius of curvature of the third surface in the liquid lens is -17.090mm, and the effective focal length of the liquid lens is -312.025mm. The optimal effective focal length of the optical lens is 5.99mm. The relevant parameters of the optical lens 200 provided in this embodiment at the optimal working distance, minimum working distance, and maximum working distance are shown in Table 4.

[0137] Table 4

[0138] Optimal working distance Minimum working distance Maximum working distance OBJ(mm) 249.03 60.00 800.00 F(mm) 5.99 5.76 6.06 U(V) 35.80 48.70 32.40 fe(mm) -312.025 162.02 -186.79 R9 (mm) -17.090 8.78 -10.12

[0139] Figures 9 to 14 The diagram shows the field curvature curve, T-Fanθ distortion curve, transverse chromatic aberration curve, axial aberration curve, MTF curve, and relative illumination curve of the optical lens 200 in this embodiment. Figure 9 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within ±0.08mm, indicating that the optical lens can effectively correct field curvature; from Figure 10 As can be seen, the distortion value is controlled within -2.5%, indicating that the optical lens can effectively correct distortion; from Figure 11 As can be seen, the transverse chromatic aberration of the longest and shortest wavelengths is controlled within ±0.4μm, indicating that the optical lens can effectively correct chromatic aberration at the edges of the field of view and the second-order spectrum of the entire image plane; from Figure 12 As can be seen, the axial aberration offset is controlled within ±0.05mm, indicating that the optical lens can effectively correct axial aberration; from Figure 13 As can be seen, the MTF value of this embodiment is above 0.3 throughout the entire half-image height, demonstrating good imaging quality and detail resolution in both low and high frequency conditions; from Figure 14 As can be seen, the relative illumination value of the optical lens is still greater than 80% at the maximum half field of view, indicating that the optical lens has good relative illumination.

[0140] Third Embodiment

[0141] Please see Figure 15The figure shows a schematic diagram of the structure of the optical lens 300 provided in the third embodiment of the present invention. The structure of the optical lens 300 is roughly the same as that of the optical lens 100 in the first embodiment. The main differences are that the curvature radius, thickness, spacing between lenses, and materials of each lens are different.

[0142] The relevant parameters of each lens element in the optical lens 300 provided in this embodiment are shown in Table 5.

[0143] Table 5

[0144]

[0145] In this embodiment, when the working object distance OBJ of the optical lens satisfies: 60mm≤OBJ≤800mm, the driving voltage U applied to the liquid lens satisfies: 34.3V≤U≤49.5V, the radius of curvature R9 of the third surface satisfies: R9∈(-∞, -13.06]&[7.96, +∞), and the effective focal length fe of the liquid lens satisfies: fe∈(-∞, -236.41]&[144.07, +∞). At this time, the effective focal length F of the optical lens satisfies: 5.81mm≤F≤6.10mm. More specifically, when the optical lens is at the optimal working object distance of 155.67mm, the voltage applied to the liquid lens is 39.98V (this voltage is the starting voltage), the radius of curvature of the third surface in the liquid lens is -165.996mm, the effective focal length of the liquid lens is -3004.38mm, and the optimal effective focal length of the optical lens is 5.99mm. The relevant parameters of the optical lens 300 provided in this embodiment at the optimal working distance, minimum working distance, and maximum working distance are shown in Table 6.

[0146] Table 6

[0147] Optimal working distance Minimum working distance Maximum working distance OBJ(mm) 155.67 60.00 800.00 F(mm) 5.99 5.81 6.10 U(V) 39.98 49.50 34.30 fe(mm) -3004.380 144.07 -236.41 R9 (mm) -165.996 7.96 -13.06

[0148] Figures 16 to 21 The diagram shows the field curvature curve, T-Fanθ distortion curve, transverse chromatic aberration curve, axial aberration curve, MTF curve, and relative illumination curve of the optical lens 300 in this embodiment. Figure 16 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within ±0.06mm, indicating that the optical lens can effectively correct field curvature; from Figure 17 As can be seen, the distortion value is controlled within -4%, indicating that the optical lens can effectively correct distortion; from Figure 18 As can be seen, the transverse chromatic aberration of the longest and shortest wavelengths is controlled within ±0.6μm, indicating that the optical lens can effectively correct chromatic aberration at the edges of the field of view and the second-order spectrum of the entire image plane; from Figure 19As can be seen, the axial aberration offset is controlled within ±0.04mm, indicating that the optical lens can effectively correct axial aberration; from Figure 20 As can be seen, the MTF value of this embodiment is above 0.3 throughout the entire half-image height, demonstrating good imaging quality and detail resolution in both low and high frequency conditions; from Figure 21 As can be seen, the relative illumination value of the optical lens is still greater than 80% at the maximum half field of view, indicating that the optical lens has good relative illumination.

[0149] Please refer to Table 7, which shows the optical characteristics of the optical lenses provided in the above four embodiments at the optimal working object distance, including the working object distance OBJ of the optical lens, the optimal effective focal length f, the total optical length TTL, the maximum field of view FOV, the image height IH corresponding to the maximum field of view IH, the aperture value Fno, the driving voltage U of the liquid lens, and the effective focal length fe of the liquid lens. It also includes the relevant values ​​corresponding to each conditional expression in the above-mentioned conditional expressions.

[0150] Table 7

[0151]

[0152]

[0153]

[0154] In summary, the optical lens provided by this invention has at least the following advantages:

[0155] (1) The optical lens provided by the present invention adopts a combination of six glass lenses and one liquid lens. By reasonably allocating the liquid lens and the focal length relationship of each lens, the optical lens has good imaging ability at different object distances and good thermal stability. At the same time, by reasonably configuring the thickness of each lens, the spacing between each lens and the surface shape of each lens, the optical lens has advantages such as small total length, high relative illumination, large image plane, high resolution and autofocus.

[0156] (2) The optical lens provided by the present invention expands the original fixed working distance focusing industrial lens into an autofocus lens with an adjustable working distance within a certain range (working object distance is 60mm-800mm) by applying liquid lens to the optical path design, which greatly expands the application range of the optical lens and improves the detection efficiency of the optical lens.

[0157] (3) The optical lens provided by the present invention can adjust the focus position of the entire optical system in real time by controlling the driving voltage of the liquid lens, so as to achieve the purpose of fast focusing at different working distances and make the optical lens have high resolution at different object distances.

[0158] (4) The optical lens provided by the present invention uses liquid lens to achieve autofocus, and the lens does not shift during the focusing process, which makes the overall stability of the optical lens better.

[0159] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0160] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. An optical lens comprising six lenses and one liquid lens, characterized in that, It sequentially includes from the object side to the imaging surface along the optical axis: A first lens with negative optical power, and the image side of the first lens is concave; A second lens with positive optical power, the object side of the second lens is concave, and the image side of the second lens is convex; A third lens with positive optical power, the object side of the third lens is convex, and the image side of the third lens is concave; A liquid lens with optical power, and the liquid lens presents different focal lengths according to different applied voltages; A fourth lens with negative optical power, the object side of the fourth lens is concave, and the image side of the fourth lens is concave; A fifth lens with positive optical power, the object side of the fifth lens is convex, and the image side of the fifth lens is convex; A sixth lens with positive optical power, the object side of the sixth lens is convex, and the image side of the sixth lens is concave; Wherein, the total optical length TTL of the optical lens and the optimal effective focal length f of the optical lens satisfy: 2.9 < TTL / f < 3.6; The effective focal length f6 of the sixth lens and the optimal effective focal length f of the optical lens satisfy: 1.5 < f6 / f < 2.

2.

2. The optical lens according to claim 1, characterized in that, The effective focal length f1 of the first lens and the optimal effective focal length f of the optical lens satisfy: -1.7 < f1 / f < -1.

1.

3. The optical lens according to claim 1, characterized in that, The effective focal length f3 of the third lens and the optimal effective focal length f of the optical lens satisfy: 1.1 < f3 / f < 1.

7.

4. The optical lens according to claim 1, characterized in that, The effective focal length f4 of the fourth lens and the optimal effective focal length f of the optical lens satisfy: -0.75 < f4 / f < -0.

5.

5. The optical lens according to claim 1, characterized in that, The total optical length TTL of the optical lens and the image height IH corresponding to the maximum field angle of the optical lens satisfy: 2.6 < TTL / IH < 3.

4.

6. The optical lens according to claim 1, characterized in that, The radius of curvature R6 of the image side of the third lens and the optimal effective focal length f of the optical lens satisfy: 1.7 < R6 / f < 2.7; the radius of curvature R18 of the image side of the sixth lens and the optimal effective focal length f of the optical lens satisfy: 6.1 < R18 / f < 16.

2.

7. The optical lens according to claim 1, characterized in that, The radius of curvature R3 of the object side of the second lens and the radius of curvature R4 of the image side of the second lens satisfy: 2.3 < (R3 + R4) / (R3 - R4) < 3.

6.

8. The optical lens according to claim 1, characterized in that, The sagittal height Sag18 of the clear aperture semi-diameter of the image side of the sixth lens and the clear aperture semi-diameter DT62 of the image side of the sixth lens satisfy: 0 < Sag18 / DT62 < 0.

05.

9. The optical lens according to claim 1, characterized in that, The effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens and the optimal effective focal length f of the optical lens satisfy: 2.5 < (f1 + f2 + f3) / f < 3.

6.

10. The optical lens according to claim 1, characterized in that, The air spacing CT45 on the optical axis between the fourth lens and the fifth lens and the air spacing CT56 on the optical axis between the fifth lens and the sixth lens satisfy: 0.4 < CT45 / CT56 < 1.9.

Images